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Title:
HYDRAULIC AND CENTRIFUGAL CLAMPING FOR HIGH-SPEED CONTINUOUSLY VARIABLE PLANETARY OPERATION
Document Type and Number:
WIPO Patent Application WO/2018/071376
Kind Code:
A1
Abstract:
Provided is a ball planetary variator (CVP) having a hydraulic centrifugal clamping mechanism and a method for controlling the clamp force thereof including: sensing a CVP input speed and a CVP output speed: determining a current CVP ratio: sensing engine torque and speed; calculating a required clamp load force for the CVP based on the current CVP ratio, the engine torque, and the engine speed; calculating a current cam load clamp force for the CVP based on the engine torque; calculating a current centrifugal clamp load force for the CVP based on the current CVP ratio and the engine speed; calculating a required active clamp load force for the CVP based on the required clamp load force, the current cam load clamp force and the current centrifugal clamp load force; and commanding a pressure setpoint of the hydraulic centrifugal clamping mechanism based on the required active clamp load force.

Inventors:
DAVID, Jeffrey, M. (1808 Spider Lily View, Cedar Park, TX, 78613, US)
HORAK, Joseph, J. (1401 Northridge Drive, Austin, TX, 78723, US)
MILLER, Travis, J. (2930 Grand Oaks Loop #202, Cedar Park, TX, 78613, US)
NELMS, Ryan, D. (1506 Payne Avenue, Unit BAustin, TX, 78757, US)
PETERS, Sebastian, J. (610 Wildbriar Court, Cedar Park, TX, 78613, US)
MCLEMORE, T., Neil (613 Garner Park Drive, Georgetown, TX, 78628, US)
Application Number:
US2017/055868
Publication Date:
April 19, 2018
Filing Date:
October 10, 2017
Export Citation:
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Assignee:
DANA LIMITED (3939 Technology Drive, Po Box 1000Maumee, OH, 43537, US)
International Classes:
F16H61/664; F16H15/28; F16H59/14; F16H59/36; F16H59/40; F16H59/42; F16H59/44; F16H59/46; F16H59/68
Foreign References:
US20160290451A12016-10-06
JP3711688B22005-11-02
EP0959269A21999-11-24
US9086145B22015-07-21
US8469856B22013-06-25
US8870711B22014-10-28
Attorney, Agent or Firm:
EVANS, Stephen, P. et al. (Marshall & Melhorn, LLCFour Seagate - 8th Floo, Toledo OH, 43604, US)
Download PDF:
Claims:
WHAT IS CLAIMED IS:

1. A method for controlling clamp force in a ball planetary variator (CVP) having a hydraulic centrifugal clamping mechanism, said CVP operably coupled to an engine of a vehicle, the method comprising:

sensing a CVP input speed and a CVP output speed;

determining a current CVP ratio based on the CVP input speed and the CVP output speed;

sensing an engine torque and an engine speed;

calculating a required clamp load force for the CVP based on the current CVP ratio, the engine torque, and the engine speed;

calculating a current cam load clamp force for the CVP based on the engine torque;

calculating a current centrifugal clamp load force for the CVP based on the current CVP ratio and the engine speed;

calculating a required active clamp load force for the CVP based on the required clamp load force, the current cam load clamp force and the current centrifugal clamp load force; and

commanding a pressure setpoint of the hydraulic centrifugal clamping mechanism based on the required active clamp load force.

2. The method of Claim 1 , wherein commanding a pressure setpoint of the hydraulic centrifugal clamping mechanism further comprises controlling a variable bleed solenoid valve coupled to the hydraulic centrifugal clamping mechanism.

3. The method of claim 1 , wherein commanding a pressure setpoint of the hydraulic centrifugal clamping mechanism further comprises controlling an operating pressure of a rotary hydraulic fluid cavity of the hydraulic centrifugal clamping mechanism.

4. A method for controlling clamp force in a ball planetary variator (CVP) having a hydraulic centrifugal clamping mechanism, said CVP operably coupled to an engine of a vehicle, the method comprising:

sensing a CVP input speed and a CVP output speed;

determining a current CVP ratio based on the CVP input speed and the CVP output speed;

sensing a first traction ring speed and a second traction ring speed; calculating a current slip state of the CVP based at least in part on a comparison between the current CVP ratio and a commanded CVP ratio;

comparing the current slip state of the CVP to a target slip state; and commanding a pressure setpoint of the hydraulic centrifugal clamping mechanism based on a required active clamp load force.

5. The method of Claim 4, wherein commanding a pressure setpoint of the hydraulic centrifugal clamping mechanism further comprises controlling a variable bleed solenoid valve coupled to the hydraulic centrifugal clamping mechanism.

6. The method of Claim 4, wherein commanding a pressure setpoint of the hydraulic centrifugal clamping mechanism further comprises

commanding a decrease in an applied pressure when the current CVP slip state is less than the target slip state.

7. The method of Claim 4, wherein commanding a pressure setpoint of the hydraulic centrifugal clamping mechanism further comprises

commanding an increase in an applied pressure when the current CVP slip state is greater than the target slip state.

8. A method for operating a vehicle equipped with an electric hybrid powertrain having an engine, a first motor/generator, a second motor/ generator, and a ball planetary variator (CVP) having a hydraulic centrifugal clamping mechanism, said CVP operably coupled to the engine, the first motor/generator, and the second motor/generator, the method comprising controlling the electric hybrid powertrain by:

receiving a signal indicative of a vehicle speed;

determining if the vehicle is stopped based on the vehicle speed;

commanding a pressure setpoint of the hydraulic centrifugal clamping mechanism based on the vehicle speed; and

commanding the engine to shut off based on the vehicle speed.

9. The method of Claim 8, wherein commanding a pressure setpoint of the hydraulic centrifugal clamping mechanism further comprises

commanding a release of pressure to the hydraulic centrifugal clamping mechanism.

10. The method of Claim 9, wherein the engine is operably coupled to a first traction ring assembly of the CVP, the first motor/generator is operably coupled to a carrier assembly of the CVP, and the second motor/generator is operably coupled to a second traction ring of the CVP.

11. A computer-implemented control system for controlling clamp force in a ball planetary variator (CVP) having a hydraulic centrifugal clamping mechanism, said CVP operably coupled to an engine of a vehicle, the computer-implemented control system comprising:

a digital processing device comprising an operating system configured to perform executable instructions and a memory device;

a computer program including the instructions executable by the digital processing device, the computer program comprising a software module configured to control the hydraulic centrifugal clamping mechanism and the CVP; and a plurality of sensors comprising:

a current CVP input speed sensor configured to sense a CVP input speed and provide the CVP input speed to the software module; a current CVP output speed sensor configured to sense a CVP output speed and provide the CVP output speed to the software module, wherein the software module determines a current CVP ratio based on the CVP input speed and the CVP output speed;

an engine torque sensor configured to sense an engine torque and provide the engine torque to the software module; and

an engine speed sensor configured to sense an engine speed and provide the engine speed to the software module,

wherein the software module is configured to calculate:

a required clamp load force for the CVP based on the current CVP ratio, the engine torque, and the engine speed;

a current cam load clamp force for the CVP based on the engine torque;

a current centrifugal clamp load force for the CVP based on the current CVP ratio and the engine speed; and

a required active clamp load force for the CVP based on the required clamp load force, the current cam load clamp force and the current centrifugal clamp load force, and

wherein the software module is configured to command a pressure setpoint of the hydraulic centrifugal clamping mechanism based on the required active clamp load force.

12. The computer-implemented control system of Claim 11 , wherein the software module further comprises a calibration map, the calibration map configured to store values of the required clamp load force based on the current CVP ratio, the engine torque, and the engine speed.

13. The computer-implemented control system of Claim 11 , wherein commanding a pressure setpoint of the hydraulic centrifugal clamping mechanism further comprises controlling a variable bleed solenoid valve coupled to the hydraulic centrifugal clamping mechanism.

14. A continuously variable ball planetary transmission having a hydraulic centrifugal clamping mechanism, the continuously variable ball planetary comprising:

a plurality of tilting traction planets mounted on a carrier, the traction planets in contact with a first traction ring and a second traction ring and a hydraulic fluid;

an axial force mechanism comprising:

a cam ring aligned coaxially with the first traction ring, a plurality of cam bearing balls in contact with the cam ring and the first traction ring, and

a cam bearing retainer operably coupled to each of the cam bearing balls;

a cam driver configured to transmit a rotational power to the cam ring; a hydraulic piston coaxial with and in contact with the cam ring, the hydraulic piston coaxial with and enclosed within the cam driver;

an enclosed, rotating cavity arranged between the cam driver and the hydraulic piston; and

a hydraulic fluid contained within the enclosed cavity, wherein the hydraulic fluid is subject to centrifugal force as a result of rotational speeds of the continuously variable ball planetary.

15. The continuously variable ball planetary transmission of Claim 14, further comprising a plurality of pressure regulating valves coupled to the cam driver, each pressure regulating valve in fluid communication with the hydraulic fluid.

16. The continuously variable ball planetary transmission of Claim 15, wherein the plurality of pressure regulating valves further comprises a sub- plurality of pressure relief valves configured to limit the hydraulic pressure from exceeding a maximum pressure.

17. The continuously variable ball planetary transmission of Claim 15, wherein the plurality of pressure regulating valves are ball valves configured to close at a predetermined operating speed. 18. The continuously variable ball planetary transmission of Claim 15, wherein the plurality of pressure regulating valves are configured to provide a first operating region, a second operating region and a third operation, wherein the first operating region corresponds to a minimum hydraulic pressure, the second operating region corresponds to a variable hydraulic pressure, and the third operating region corresponds to a maximum hydraulic pressure.

19. The continuously variable ball planetary transmission of Claim 14, wherein the cam driver is provided with a plurality of fluid channels in fluid communication with the rotary hydraulic fluid cavity, and wherein the cam retainer ring further comprises a plurality of axial extensions located around an outer periphery of the cam retainer ring, wherein each axial extension is located in proximity to each of the fluid channels.

20. The continuously variable ball planetary transmission of Claim 19, wherein the plurality of axial extensions are configured to variably cover the plurality of fluid channels during operation of the continuously variable ball planetary.

21. The continuously variable ball planetary transmission of Claim 14, wherein the cam driver is provided with a plurality of fluid channels in fluid communication with the rotary hydraulic fluid cavity, and wherein the cam retainer ring further comprises a plurality of plungers located radially about an outer periphery of the cam retainer ring and aligned with the plurality of fluid channels, wherein each plunger is coupled to a spring that is adapted to press the plunger onto the cam driver.

22. The continuously variable ball planetary transmission of Claim 21 , wherein the plurality of plungers are configured to variably cover the plurality of fluid channels during operation of the continuously variable ball planetary.

23. The continuously variable ball planetary transmission of Claim 14, wherein the hydraulic piston is provided with a first plurality of fluid channels in fluid communication with the rotary hydraulic fluid cavity; and wherein the cam ring is provided with a second plurality of fluid channels aligned with the first plurality of fluid channels and with the plurality of cam bearing balls.

24. The continuously variable ball planetary transmission of Claim 23, wherein the plurality of cam bearing balls are configured to variably cover the second plurality of fluid channels during operation of the continuously variable ball planetary.

25. A computer-implemented control system for controlling clamp force in a ball planetary variator (CVP) having a hydraulic centrifugal clamping mechanism, said CVP operably coupled to an engine of a vehicle, the computer-implemented control system comprising:

a digital processing device comprising an operating system configured to perform executable instructions and a memory device;

a computer program including the instructions executable by the digital processing device, the computer program comprising a software module configured to control the hydraulic centrifugal clamping mechanism and the CVP; and a plurality of sensors comprising:

a current CVP input speed sensor configured to sense a CVP input speed and provide the CVP input speed to the software module; a current CVP output speed sensor configured to sense a CVP output speed and provide the CVP output speed to the software module, wherein the software module determines a current CVP ratio based on the CVP input speed and the CVP output speed;

a first traction ring speed sensor configured to sense a first traction ring speed and provide the first traction ring to the software module; and

a second traction ring speed sensor configured to sense a second traction ring speed and provide the second traction ring speed to the software module,

wherein the software module is configured to:

calculate a current slip state of the CVP based at least in part on a comparison between the current CVP ratio and a commanded CVP ratio,

compare the current slip state of the CVP to a target slip state, and

command a pressure setpoint of the hydraulic centrifugal clamping mechanism based on a required active clamp load force.

26. The computer-implemented system of Claim 25, wherein the software module further comprises a calibration map, the calibration map configured to store values of the target slip state based on the current CVP ratio, an engine torque, and an engine speed.

27. The computer-implemented system of Claim 26, wherein commanding a pressure setpoint of the hydraulic centrifugal clamping mechanism further comprises controlling a variable bleed solenoid valve coupled to the hydraulic centrifugal clamping mechanism.

28. The computer-implemented system of Claim 25, wherein commanding a pressure setpoint of the hydraulic centrifugal clamping mechanism further comprises commanding a decrease in an applied pressure when the current CVP slip state is less than the target slip state.

29. The computer-implemented system of Claim 25, wherein commanding a pressure setpoint of the hydraulic centrifugal clamping mechanism further comprises commanding an increase in an applied pressure when the current CVP slip state is greater than the target slip state.

Description:
HYDRAULIC AND CENTRIFUGAL CLAMPING FOR HIGH-SPEED CONTINUOUSLY VARIABLE PLANETARY OPERATION

RELATED APPLICATION

The present application claims the benefit of U.S. Provisional Application No. 62/406,588 filed on October 11 , 2016, which is incorporated herein by reference in its entirety.

BACKGROUND

Automatic and manual transmissions are commonly used on

automobiles. Such transmissions have become more and more complicated since the engine speed has to be adjusted to limit fuel consumption and the emissions of the vehicle. A vehicle having a driveline including a tilting ball variator allows an operator of the vehicle or a control system of the vehicle to vary a drive ratio in a stepless manner. A variator is an element of a

Continuously Variable Transmission (CVT) or an Infinitely Variable

Transmission (IVT). Transmissions that use a variator can decrease the transmission's gear ratio as engine speed increases. This keeps the engine within its optimal efficiency while gaining ground speed, or trading speed for torque during hill climbing, for example. Efficiency in this case can be fuel efficiency, decreasing fuel consumption and emissions output, or power efficiency, allowing the engine to produce its maximum power over a wide range of speeds. That is, the variator keeps the engine turning at constant RPMs over a wide range of vehicle speeds.

A tilting ball variator, or a Continuously Variable Planetary (CVP), is a form of traction drive based on a planetary gearing principle. In a traction drive, flat-surfaced rollers contact with other flat-surfaced rollers without teeth, and transfer power. This is accomplished using a lubricant called 'traction oil' or "traction fluid" to create an elasto-hydrodynamic film.

A CVP can include a first drive ring, a second drive ring, and a plurality of variator balls, also referred to as traction planets, disposed between the first drive ring and the second drive ring. The plurality of traction planets is simultaneously tilted, which adjusts an axis angle of each of the traction planets, for example, by moving a carrier, on which the plurality of traction planets are rotatably disposed. The plurality of traction planets are in driving engagement with the first drive ring and the second drive ring through one of a boundary layer type friction and an elasto-hydrodynamic film where the increased moment of inertia and weight of large traction planets decrease the effectiveness of the elasto-hydrodynamic boundary layer friction coupling between the traction planets and drive rings. Loss of effective frictional coupling leads to decreases in efficiency and performance of the overall CVT. There remains a need to develop devices and methods relating to generating clamping force in certain types of transmissions necessary to maintain effective passive frictional coupling between the traction planets and drive rings.

In the case of a tilting ball variator, having less than ideal conforming flat surfaces and high contact pressures, the bodies suffer elastic strains at the contact patch. Such strain creates a load-bearing area, which provides an almost parallel gap for the fluid to flow through. The motion of the contacting bodies generates a flow induced pressure (>1GPa), over a short duration (=10-3 sec) which acts as the bearing force over the contact area. At such high pressure regimes, the viscosity of the fluid rises considerably and behaves like an elastic solid. At full elastohydrodynamic lubrication the generated lubricant film completely separates the surfaces while still efficiently transferring torque. Hydrodynamic lift at the traction planets, can become significant at high speeds, reducing the traction coefficient, leading to gross slippage between the traction planets and rings, and reductions in efficiency. In fact, all traction variators have losses which appear as a speed or slip loss across the variator.

Currently, CVTs and IVTs often use some form of mechanical clamping mechanism, typically including a ball-and-cam mechanism to generate axial clamping forces necessary to facilitate the transmission of torque between or among transmission components via traction or friction, often referred to as clamping force mechanisms or generators. At high torques and low speeds, a standard ball-and-cam clamping force mechanism determines the clamp load. Examples of ball-and-cam clamping force mechanism are found in United States Patent No. 9,086,145, which is hereby incorporated by reference. Clamping force generators typically fall into three general categories: Non-Torque Reactive; Torque Reactive, and Active/Programmable. Non- Torque Reactive clamping means are generally defined as ratio dependent, speed dependent and fixed (fully preloaded). Torque Reactive clamping means are generally defined by axial forces due to: external influences or loads; torque reaction on floating elements; screws and cams; or passive hydraulic; and Active/Programmable clamping means wherein hydraulic or other means are actively applied to a clamping means to create axial clamping forces. Depending on the configuration used, the clamping force mechanism used in a transmission with a Continuously Variable Ball Planetary (CVP) variator provides a load to the input and/or output ring to ensure adequate clamping force between the drive ring(s) and the traction planets.

Unfortunately, traditional clamping force mechanisms are limited in their ability to provide high clamping loads at high speeds and low torque. There remains a need for a system that can deliver consistently high clamping forces at high speeds in a CVP. A hydraulic clamping system could provide significant advantages over traditional clamping force mechanisms in that it could theoretically reduce required preloading between the input, output and planets, and improve overall efficiency of the system.

SUMMARY

Provided herein is a method for controlling clamp force in a ball planetary variator (CVP) having a hydraulic centrifugal clamping mechanism, said CVP operably coupled to an engine of a vehicle, the method including: sensing a CVP input speed and a CVP output speed; determining a current CVP ratio based on the CVP input speed and the CVP output speed; sensing an engine torque and an engine speed; calculating a required clamp load force for the CVP based on the current CVP ratio, the engine torque, and the engine speed; calculating a current cam load clamp force for the CVP based on the engine torque; calculating a current centrifugal clamp load force for the CVP based on the current CVP ratio and the engine speed; calculating a required active clamp load force for the CVP based on the required clamp load force, the current cam load clamp force and the current centrifugal clamp load force; and commanding a pressure setpoint of the hydraulic centrifugal clamping mechanism based on the required active clamp load force.

Provided herein is a method for controlling clamp force in a ball planetary variator (CVP) having a hydraulic centrifugal clamping mechanism, said CVP operably coupled to an engine of a vehicle, the method including: sensing a CVP input speed and CVP output speed; determining a current CVP ratio based on the CVP input speed and the CVP output speed; sensing a first traction ring speed and a second traction ring speed; calculating a current slip state of the CVP based at least in part on a comparison between the current CVP ratio and a commanded CVP ratio; comparing the current slip state of the CVP to a target slip state, and commanding a pressure setpoint of the hydraulic centrifugal clamping mechanism based on a required active clamp load force.

A method for operating a vehicle equipped with an electric hybrid powertrain having an engine, a first motor/generator, a second motor/ generator, and a ball planetary variator (CVP) having a hydraulic centrifugal clamping mechanism, said CVP operably coupled to the engine, the first motor/generator, and the second motor/generator, the method including:

controlling the electric hybrid powertrain by: receiving a signal indicative of a vehicle speed; determining if the vehicle is stopped based on the vehicle speed; commanding a pressure setpoint of the hydraulic centrifugal clamping mechanism based on the vehicle speed; and commanding the engine to shut off based on the vehicle speed.

A computer-implemented control system for controlling clamp force in a ball planetary variator (CVP) having a hydraulic centrifugal clamping

mechanism, said CVP operably coupled to an engine of a vehicle, the computer-implemented control system including: a digital processing device including an operating system configured to perform executable instructions and a memory device; a computer program including the instructions

executable by the digital processing device, the computer program comprising a software module configured to control the hydraulic centrifugal clamping mechanism and the CVP; and a plurality of sensors. The plurality of sensors include: a current CVP input speed sensor configured to sense a CVP input speed and provide the CVP input speed to the software module; a current CVP output speed sensor configured to sense a CVP output speed and provide the CVP output speed to the software module, wherein the software module determines a current CVP ratio based on the CVP input speed and the CVP output speed; an engine torque sensor configured to sense an engine torque and provide the engine torque to the software module; and an engine speed sensor configured to sense an engine speed and provide the engine speed to the software module. The software module is configured to calculate: a required clamp load force for the CVP based on the current CVP ratio, the engine torque, and the engine speed; a current cam load clamp force for the CVP based on the engine torque; a current centrifugal clamp load force for the CVP based on the current CVP ratio and the engine speed; and a required active clamp load force for the CVP based on the required clamp load force, the current cam load clamp force and the current centrifugal clamp load force, and wherein the software module is configured to command a pressure setpoint of the hydraulic centrifugal clamping mechanism based on the required active clamp load force.

A continuously variable ball planetary transmission having a hydraulic centrifugal clamping mechanism, the continuously variable ball planetary having a plurality of tilting traction planets mounted on a carrier, the traction planets in contact with a first traction ring and a second traction ring and a hydraulic fluid; an axial force mechanism; a cam driver configured to transmit a rotational power to the cam ring; a hydraulic piston coaxial and in contact with the cam ring, the hydraulic piston coaxial with, and enclosed within the cam driver; an enclosed, rotating cavity arranged between the cam driver and the hydraulic piston; and a hydraulic fluid contained within the enclosed cavity, wherein the hydraulic fluid is subject to centrifugal force as a result of rotational speeds of the continuously variable ball planetary. The axial force mechanism including a cam ring aligned coaxially with the first traction ring, a plurality of cam bearing balls in contact with the cam ring and the first traction ring, and a cam bearing retainer operably coupled to each of the cam bearing balls.

A computer-implemented control system for controlling clamp force in a ball planetary variator (CVP) having a hydraulic centrifugal clamping

mechanism, said CVP operably coupled to an engine of a vehicle, the computer-implemented control system including :a digital processing device comprising an operating system configured to perform executable instructions and a memory device; a computer program including the instructions executable by the digital processing device, the computer program including a software module configured to control the hydraulic centrifugal clamping mechanism and the CVP; and a plurality of sensors. The plurality of sensors include a current CVP input speed sensor configured to sense a CVP input speed and provide the CVP input speed to the software module; a current CVP output speed sensor configured to sense a CVP output speed and provide the CVP output speed to the software module, wherein the software module determines a current CVP ratio based on the CVP input speed and the CVP output speed; a first traction ring speed sensor configured to sense a first traction ring speed and provide the first traction ring to the software module; and a second traction ring speed sensor configured to sense a second traction ring speed and provide the second traction ring speed to the software module. The software module is configured to calculate a current slip state of the CVP based at least in part on a comparison between the current CVP ratio and a commanded CVP ratio, compare the current slip state of the CVP to a target slip state, and command a pressure setpoint of the hydraulic centrifugal clamping mechanism based on a required active clamp load force.

INCORPORATION BY REFERENCE

All publications, patents, and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication, patent, or patent application was specifically and individually indicated to be incorporated by reference.

BRIEF DESCRIPTION OF THE DRAWINGS

Novel features of the preferred embodiments are set forth with particularity in the appended claims. A better understanding of the features and advantages of the present embodiments will be obtained by reference to the following detailed description that sets forth illustrative embodiments, in which the principles of the preferred embodiments are utilized, and the accompanying drawings of which:

Figure 1 is a side sectional view of a ball-type variator.

Figure 2 is a plan view of a carrier member that is used in the variator of Figure 1.

Figure 3 is an illustrative view of different tilt positions of the ball-type variator of Figure 1.

Figure 4 is a block diagram of a powertrain having an infinitely or continuously variable transmission (IVT) controlled by a transmission controller and used in a vehicle.

Figure 5 depicts a block diagram of a centrifugal clamping mechanism illustrating a cross-section of rotating cavity containing hydraulic fluid and a clamping element.

Figure 6 depicts a representative graph of the centrifugal force (N) generated vs. RPM of the planetary ball variator at different radial bleed hole locations, controlling the amount of fluid to push the piston.

Figure 7 depicts a representative cross-section view of an exemplary planetary ball variator in Fig. 3 with a representative depiction of a rotating cavity for hydraulic fluid and a clamping element.

Figure 8 depicts a representative isometric view of a planetary ball variator including optional fluid output or bleed ports.

Figure 9 depicts a detail representative section view of Figure 7, showing one half of a CVP.

Figure 10 is a cross-section view of a hydraulic centrifugal clamping mechanism that is implementable in the CVP of Figures 1-3.

Figures 1 A-B are schematic views of a pressure relief valve used in the hydraulic centrifugal clamping mechanism of Figure 10.

Figures 12A-B are schematic views of a pressure regulating valve used in the hydraulic centrifugal clamping mechanism of Figure 10.

Figure 13 is a chart depicting a relationship between axial force and speed of the hydraulic centrifugal clamping mechanism of Figure 10.

Figure 14 is a cross-sectional view of a hydraulic centrifugal clamping mechanism that is implementable in the CVP of Figures 1-3. Figure 15 is an isometric view of certain components of the hydraulic centrifugal clamping mechanism of Figure 14.

Figure 16 is a detail view A of certain components of the hydraulic centrifugal clamping mechanism of Figure 14.

Figure 17 is a cross-sectional view of another hydraulic centrifugal clamping mechanism that is implementable in the CVP of Figures 1-3.

Figure 18 is an isometric view of certain components of the hydraulic centrifugal clamping mechanism of Figure 17.

Figure 19 is a cross-sectional view of yet another hydraulic centrifugal clamping mechanism that is implementable in the CVP of Figures 1-3.

Figure 20 is a detail view B of certain components of the hydraulic centrifugal clamping mechanism of Figure 19.

Figure 21 is a chart depicting a relationship between axial clamping force and applied hydraulic pressure on a representative hydraulic piston provided on the hydraulic centrifugal clamping mechanisms disclosed herein.

Figure 22 is a flow chart depicting a control process for a hydraulic centrifugal clamping mechanism.

Figure 23 is a flow chart depicting another control process for a hydraulic centrifugal clamping mechanism.

Figure 24 is a schematic diagram of an electric hybrid powertrain having a planetary ball variator equipped with a hydraulic centrifugal clamping mechanism.

Figure 25 is a flow chart depicting a control process for a hydraulic centrifugal clamping mechanism.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A continuously variable ball planetary variator produces a centrifugal hydraulic clamping force that exceeds the design value of a cam clamp load of a ball-and-cam mechanism at design speed, reducing or counteracting the hydrodynamic lift between the planetary traction planets, input and output drive rings, and improving output torque and efficiency. Provided herein are configurations of CVTs based on ball-type variators, also known as CVP, for continuously variable planetary. Basic concepts of a ball-type Continuously Variable Transmissions are described in United States Patent No. 8,469,856 and 8,870,711 incorporated herein by reference in their entirety. Such a CVT, adapted herein as described throughout this

specification, includes a number of balls (planets, spheres) 1 , depending on the application, two ring (disc) assemblies with a conical surface contact with the balls, as input (first) ring 2 and output (second) ring 3, and an idler (sun) assembly 4 as shown on FIG. 1. The balls are mounted on tiltable axles 5, themselves held in a carrier (stator, cage) assembly having a first carrier member 6 operably coupled to a second carrier member 7. The first carrier member 6 rotates with respect to the second carrier member 7, and vice versa. In some embodiments, the first carrier member 6 can be substantially fixed from rotation while the second carrier member 7 is configured to rotate with respect to the first carrier member, and vice versa. In some embodiments, the first carrier member 6 is provided with a number of radial guide slots 8. The second carrier member 7 is provided with a number of radially offset guide slots 9. The radial guide slots 8 and the radially offset guide slots 9 are adapted to guide the tiltable axles 5. The axles 5 are adjusted to achieve a desired ratio of input speed to output speed during operation of the CVT. In some

embodiments, adjustment of the axles 5 involves control of the position of the first carrier member and the second carrier member to impart a tilting of the axles 5 and thereby adjusts the speed ratio of the variator. Other types of ball CVTs also exist, like the one produced by Milner, but are slightly different.

The working principle of such a CVP of FIG. 1 is shown on FIG. 2. The

CVP itself works with a traction fluid. The lubricant between the ball and the conical rings acts as a solid at high pressure, transferring the power from the input ring, through the balls, to the output ring. By tilting the balls' axes, the ratio can be changed between input ring and output ring. When the axis is horizontal the ratio is one, illustrated in FIG. 3, when the axis is tilted the distance between the axis and the contact point change, modifying the overall ratio. All the balls' axes are tilted at the same time with a mechanism included in the carrier and/or idler. The embodiments disclosed here are related to the control of a variator and/or a CVT using generally spherical planets each having a tiltable axis of rotation that can be adjusted to achieve a desired ratio of input speed to output speed during operation. In some embodiments, adjustment of said axis of rotation involves angular misalignment of the planet axis in a first plane in order to achieve an angular adjustment of the planet axis in a second plane that is substantially perpendicular to the first plane, thereby adjusting the speed ratio of the variator. The angular misalignment in the first plane is referred to here as "skew", "skew angle", and/or "skew condition". In some embodiments, a control system coordinates the use of a skew angle to generate forces between certain contacting components in the variator that will tilt the planet axis of rotation. The tilting of the planet axis of rotation adjusts the speed ratio of the variator. It should be noted that a skew shifted CVT having radially offset guide slots 9, for example, has an inherent characteristic that when rotated in opposite direction of design intent, the slot angle feedback mechanism becomes positive and will drive planet axles towards full OD and lock the unit. Therefore, it is desirable to implement a method of control to prevent lock up in the CVP during operation.

As used here, the terms "operationally connected," "operationally coupled", "operationally linked", "operably connected", "operably coupled", "operably linked," and like terms, refer to a relationship (mechanical, linkage, coupling, etc.) between elements whereby operation of one element results in a corresponding, following, or simultaneous operation or actuation of a second element. It is noted that in using said terms to describe the embodiments, specific structures or mechanisms that link or couple the elements are typically described. However, unless otherwise specifically stated, when one of said terms is used, the term indicates that the actual linkage or coupling will take a variety of forms, which in certain instances will be readily apparent to a person of ordinary skill in the relevant technology.

For description purposes, the term "radial" is used here to indicate a direction or position that is perpendicular relative to a longitudinal axis of a transmission or variator. The term "axial" as used here refers to a direction or position along an axis that is parallel to a main or longitudinal axis of a transmission or variator. For clarity and conciseness, at times similar components labeled similarly (for example, bearing 101 A and bearing 1011 B) will be referred to collectively by a single label (for example, bearing 10 1).

It should be noted that reference herein to "traction" does not exclude applications where the dominant or exclusive mode of power transfer is through "friction." Without attempting to establish a categorical difference between traction and friction drives here, generally these are understood as different regimes of power transfer. Traction drives usually involve the transfer of power between two elements by shear forces in a thin fluid layer trapped between the elements. The fluids used in these applications usually exhibit traction coefficients greater than conventional mineral oils. The traction coefficient (μ) represents the maximum available traction forces which would be available at the interfaces of the contacting components and is a measure of the maximum available drive torque. Typically, friction drives generally relate to transferring power between two elements by frictional forces between the elements. For the purposes of this disclosure, it should be understood that the CVTs described here will operate in both tractive and frictional applications. As a general matter, the traction coefficient μ is a function of the traction fluid properties, the normal force at the contact area, and the velocity of the traction fluid in the contact area, among other things. For a given traction fluid, the traction coefficient μ increases with increasing relative velocities of

components, until the traction coefficient μ reaches a maximum capacity after which the traction coefficient μ decays. The condition of exceeding the maximum capacity of the traction fluid is often referred to as "gross slip condition".

As used herein, "creep", "ratio droop", "slip" or "slip state" is the discrete local motion of a body relative to another and is exemplified by the relative velocities of rolling contact components such as the mechanism described herein. In traction drives, the transfer of power from a driving element to a driven element via a traction interface requires creep. Usually, creep in the direction of power transfer is referred to as "creep in the rolling direction." Sometimes the driving and driven elements experience creep in a direction orthogonal to the power transfer direction, in such a case this component of creep is referred to as "transverse creep." For description purposes, the terms "prime mover", "engine," and like terms, are used herein to indicate a power source. Said power source may be fueled by energy sources including hydrocarbon, electrical, biomass, solar, geothermal, hydraulic, and/or pneumatic to name but a few. Although typically described in a vehicle or automotive application, one skilled in the art will recognize the broader applications for this technology and the use of alternative power sources for driving a transmission including this technology.

As used herein, and unless otherwise specified, the term "about" or "approximately" means an acceptable error for a particular value as determined by one of ordinary skill in the art, which depends in part on how the value is measured or determined. In certain embodiments, the term "about" or

"approximately" means within 1 , 2, 3, or 4 standard deviations. In certain embodiments, the term "about" or "approximately" means within 30%, 25%, 20%, 15%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1 %, 0.5%, 0.1%, or 0.05% of a given value or range. In certain embodiments, the term "about" or "approximately" means within 40.0 mm, 30.0 mm, 20.0 mm, 10.0mm 5.0 mm 1.0 mm, 0.9 mm, 0.8 mm, 0.7 mm, 0.6 mm, 0.5 mm, 0.4 mm, 0.3 mm, 0.2 mm or 0.1 mm of a given value or range.

Those of skill will recognize that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the embodiments disclosed herein, including with reference to the transmission control system described herein, for example, may be implemented as electronic hardware, software stored on a computer readable medium and executable by a processor, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention. For example, various illustrative logical blocks, modules, and circuits described in connection with the embodiments disclosed herein may be implemented or performed with a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a

microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such

configuration. Software associated with such modules may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, a hard disk, a removable disk, a CD-ROM, or any other suitable form of storage medium known in the art. An exemplary storage medium is coupled to the processor such the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. The processor and the storage medium may reside in an ASIC. For example, in some embodiments, a controller for use of control of the IVT includes processor (not shown).

For description purposes, the terms "electronic control unit", "ECU", "Driving Control Manager System" or "DCMS" are used interchangeably herein to indicate a vehicle's electronic system that controls subsystems monitoring or commanding a series of actuators on an internal combustion engine to ensure optimal engine performance. It does this by reading values from a multitude of sensors within the engine bay, interpreting the data using multidimensional performance maps (called lookup tables), and adjusting the engine actuators accordingly. Before ECUs, air-fuel mixture, ignition timing, and idle speed were mechanically set and dynamically controlled by mechanical and pneumatic means.

In some embodiments, the control systems described herein includes a digital processing device, or use of the same. In further embodiments, the digital processing device includes one or more hardware central processing units (CPU) that carry out the device's functions. In still further embodiments, the digital processing device further comprises an operating system configured to perform executable instructions. In some embodiments, the digital processing device is optionally connected a computer network. In further embodiments, the digital processing device is optionally connected to the Internet such that it accesses the World Wide Web. In still further

embodiments, the digital processing device is optionally connected to a cloud computing infrastructure. In other embodiments, the digital processing device is optionally connected to an intranet. In other embodiments, the digital processing device is optionally connected to a data storage device.

In accordance with the description herein, suitable digital processing devices include, by way of non-limiting examples, server computers, desktop computers, laptop computers, notebook computers, sub-notebook computers, netbook computers, netpad computers, set-top computers, media streaming devices, handheld computers, Internet appliances, mobile smartphones, tablet computers, personal digital assistants, and vehicles. Those of skill in the art will recognize that many smartphones are suitable for use in the system described herein. Those of skill in the art will also recognize that select televisions, video players, and digital music players with optional computer network connectivity are suitable for use in the system described herein.

Suitable tablet computers include those with booklet, slate, and convertible configurations, known to those of skill in the art.

In some embodiments, the digital processing device includes an operating system configured to perform executable instructions. The operating system is, for example, software, including programs and data, which manages the device's hardware and provides services for execution of applications. In some embodiments, the device includes a storage and/or memory device. The storage and/or memory device is one or more physical apparatuses used to store data or programs on a temporary or permanent basis. In some embodiments, the device is volatile memory and requires power to maintain stored information. In some embodiments, the device is non-volatile memory and retains stored information when the digital processing device is not powered. In further embodiments, the non-volatile memory comprises flash memory. In some embodiments, the nonvolatile memory comprises dynamic random-access memory (DRAM). In some embodiments, the non-volatile memory comprises ferroelectric random access memory (FRAM). In some embodiments, the non-volatile memory comprises phase-change random access memory (PRAM). In other embodiments, the device is a storage device including, by way of non-limiting examples, CD-ROMs, DVDs, flash memory devices, magnetic disk drives, magnetic tapes drives, optical disk drives, and cloud computing based storage. In further embodiments, the storage and/or memory device is a combination of devices such as those disclosed herein.

In some embodiments the control system disclosed herein includes one or more non-transitory computer readable storage media encoded with a program including instructions executable by the operating system of an optionally networked digital processing device. In further embodiments, a computer readable storage medium is a tangible component of a digital processing device. In still further embodiments, a computer readable storage medium is optionally removable from a digital processing device. In some embodiments, a computer readable storage medium includes, by way of non- limiting examples, CD-ROMs, DVDs, flash memory devices, solid state memory, magnetic disk drives, magnetic tape drives, optical disk drives, cloud computing systems and services, and the like. In some cases, the program and instructions are permanently, substantially permanently, semi-permanently, or non-transitorily encoded on the media.

In some embodiments, the control system disclosed herein includes at least one computer program, or use of the same. A computer program includes a sequence of instructions, executable in the digital processing device's CPU, written to perform a specified task. Computer readable instructions may be implemented as program modules, such as functions, objects, Application Programming Interfaces (APIs), data structures, and the like, that perform particular tasks or implement particular abstract data types. In light of the disclosure provided herein, those of skill in the art will recognize that a computer program may be written in various versions of various languages. The functionality of the computer readable instructions may be combined or distributed as desired in various environments. In some embodiments, a computer program comprises one sequence of instructions. In some

embodiments, a computer program comprises a plurality of sequences of instructions. In some embodiments, a computer program is provided from one location. In other embodiments, a computer program is provided from a plurality of locations. In various embodiments, a computer program includes one or more software modules. In various embodiments, a computer program includes, in part or in whole, one or more web applications, one or more mobile applications, one or more standalone applications, one or more web browser plug-ins, extensions, add-ins, or add-ons, or combinations thereof

Referring now to FIG. 4, in some embodiments, a vehicle is equipped with a powertrain 50 having a torsional damper 51 between an engine 52 and an infinitely or continuously variable transmission (CVT) 53 to avoid transferring torque peaks and vibrations that could damage the CVT 53 (also referred to as a variator). In some embodiments, the CVT 53 includes a variator of the type described in reference to Figures 1-3. In some embodiments, the CVT 53 is coupled to a driveline 54 that includes a number of fixed ratio gearing or other means to couple a rotational power output from the CVT 53 to drive wheels of a vehicle (not shown). In some configurations this damper is optionally coupled with a clutch for the starting function or to allow the engine 52 to be decoupled from the transmission. In other embodiments, a torque converter (not shown), is used to couple the engine 52 to the CVT 53. Other types of CVT's (apart from ball-type traction drives) are optionally used as the variator in this layout. In addition to the configurations above where the variator is used directly as the primary transmission, other architectures are possible. Various powerpath layouts are introduced by adding a number of gears, clutches and simple or compound planetaries. In such configurations, the overall transmission will provide several operating modes; a CVT, an IVT, a combined mode and so on. A control system, a transmission controller 55, for use in an infinitely or continuously variable transmission is implemented. It should be appreciated that the transmission controller 55 is optionally configured as an electromechanical device having a number of sensors, actuators, and computer- implemented software modules configured to monitor and control the powertrain 50.

Referring now to FIG. 5, in some embodiments, a centrifugal clamping mechanism 75 is configurable on the CVP of Figures 1-3 and the powertrain of Figure 4. The centrifugal clamping mechanism 75 includes a variable hydraulic clamping force Fd 79 that is produced by centrifugal force generated by the hydraulic fluid in the fluid cavity 78 exerted on the clamping element 77

(piston/ring). The variable hydraulic clamping force 79 is applied to the clamping element 77, causing it to move off of a component configured to be a hard stop 76. In some embodiments, an optional O-ring 84 exists between the cavity 78 and the clamping element 77. In some embodiments, the centrifugal clamping mechanism 75, the variable hydraulic clamping force 79 is a squared function of the rotational speed 83 of the clamping element 77. In some embodiments, the fluid cavity 78 is a volume having an outer diameter 80 and an inner diameters 82.

Referring now to FIG. 6, in some embodiments of the CVP, the centrifugal clamping mechanism 75 is optionally provided with a means for hydraulic fluid to exit the fluid cavity 78. As used herein, "bleed holes" are openings provided in the centrifugal clamping mechanism 75 to provide a path for fluid to flow out of the fluid cavity 78. As depicted graphically in the chart of Figure 6, the variable hydraulic clamping force 79 is characterized by the following relationship:

dp

parr

wherein; FD = clamping force (79); ω = angular velocity (83) in radians/second;

r2 = maximum radius of the piston face (80); r1 = inner radius of the piston (81); R0 = inner radius of hydraulic fluid (82) (bleed hole radius / exit radius of fluid); p = fluid density; and π = mathematical constant. In some embodiments R0 = r1. In some embodiments of the continuously variable ball planetary, the variable hydraulic clamping force 79 may be determined by other formulae including similar and /or different variables known to those skilled in the art.

Referring now to FIGS. 7-9, in some embodiments, a continuously variable ball planetary (CVP) 100 includes a number of tilting traction planets, or balls 997 mounted on a carrier 14. The traction planets are in contact with a first traction ring 995 and a second traction ring 996. It should be appreciated that the continuously variable ball planetary 00 is configured in a similar manner as the variator of Figures 1-3. The CVP 100 includes a first axial force mechanism 102A in contact with the first traction ring 995 through a cam bearing 107. In some embodiments, the CVP 100 is provided with a second axial force mechanism 102B in contact with the second traction ring 996. It should be appreciated and the first axial force mechanism 102A and the second axial force mechanism 102B are configured to be ball-and-cam axial force generator devices. For example, the first axial force mechanism 102A and the second axial force mechanism 102B are configured to provide an axial force to the first traction ring 995 and the second traction ring 996, respectively, that is proportional to the amount of torque transmitted on the first traction ring 995 and the second traction ring 996. In some embodiments, at least one enclosed rotating cavity 108 is optionally provided with a set of bleed holes 104a. The CVP 100 includes a first clamping element 106 that is adjacent to and at least partially within the rotating cavity 108, in approximate contact with the axial force mechanism 102 and hydraulic fluid within the rotating cavity. The hydraulic fluid is subject to rotational forces during operation of the CVP 100. In some embodiments, the clamping element 106 is a ring or a piston. In some embodiments of the continuously variable ball planetary, the hydraulic pressure within the cavity, generated by centrifugal force as a result of high rotational speeds continuously variable ball planetary, exerts pressure against the clamping element. As used herein, and unless otherwise specified, the terms "traction fluid", "traction oil" and "hydraulic fluid" mean a fluid intended for the purpose of lubrication and or preventing seizure and abrasion between the discs and traction planets by preventing them from coming into direct contact with each other. These fluids flow between the discs and planets, lubricating the surfaces for protection and transmitting power between them. This potential to transmit power is referred to as the traction coefficient. In certain embodiments, the term "hydraulic fluid" means a fluid used to convey power or generate a force, such as a clamping force. Hydraulic systems like those described herein work most efficiently if the hydraulic fluid used has zero compressibility. In some applications and embodiments, the terms are used interchangeably.

In some embodiments of the CVP 100, the hydraulic pressure applied to the clamping element 106 is combined with a cam clamp load provided by the first axial force mechanism 102A to apply axial loading to at least one of the first traction ring 995 or the second traction ring 996 to increase contacting pressure against the tilting traction planets 997.

During operation of the CVP 100, the axial force generated by the axial force mechanism 102A is variable with torque and speed. Under certain operating conditions, for example, at high speeds, the axial force generated by the first axial force mechanism 102A may be insufficient to transmit the desired torque. An additional axial force may be applied by through the hydraulic centrifugal force applied to the clamping element 106. In some embodiments, a clamping element 106 applies a variable hydraulic clamping force to the first axial force mechanism 102A. In some embodiments, the radial locations of the optional bleed holes 104a in at least one enclosed, rotating cavity 108, determines a gain of the clamping force with respect to the squared speed of the clamping element. In some embodiments, the cam bearing 107 is

configured for relative rotation with respect to the first traction ring, the relative rotation corresponding to an operating torque of the CVP 100, and wherein the bleed holes 04a are arranged to be blocked by the cam bearing 107 under certain operating conditions, such as high torque operation. In some

embodiments, the cam bearing uncovers the bleed holes other operating conditions, such as low torque operation. In some embodiments, the radial locations of the optional bleed holes 104a are within a range of about 0.1 mm and 200.0 mm, 10.0 mm and 175.0 mm, 20.0 mm and 150.0 mm, 30.0 mm and 130.0 mm, 30.0 mm and 120.0 mm, 30.0 mm and 110.0 mm, 30.0 mm and 100.0 mm, 30.0 mm and 90.0 mm, 30.0 mm and 80.0 mm, 30.0 mm and 75.0 mm, 30.0 mm and 70.0 mm, 30.0 mm and 65.0 mm, 30.0 mm and 60.0 mm, 30.0 mm and 55.0 mm, 30.0 mm and 50.0 mm, 30.0 mm and 45.0 mm, 30.0 mm and 40.0 mm, 35.0 mm and 80.0 mm, 40.0 mm and 80.0 mm, 45.0 mm and 80.0 mm, 50.0 mm and 80.0 mm, 55.0 mm and 80.0 mm, 60.0 mm and 80.0 mm, 65.0 mm and 80.0 mm, 70.0 mm and 80.0 mm, 35.0 mm and 75.0 mm, 40.0 mm and 70.0 mm, 45.0 mm and 65.0 mm, 40.0 mm and 60.0 mm, 35.0 mm and 70.0 mm, 35.0 mm and 65.0 mm, 35.0 mm and 60.0 mm, 40.0 mm and 75.0 mm, and 40.0 mm and 65.0 mm from the axial centerline of rotation.

In some embodiments of the continuously variable ball planetary, the number of the optional bleed holes 104a is within about 0 and 30.

In some embodiments, the bleed hole is inside the diameter of the clamping element 106.

In some embodiments, the bleed hole is outside the diameter of the clamping element 106.

In some embodiments of the CVP 100, the diameter of the optional bleed holes 104a is within about 0.20 mm and 8.0 mm. In some embodiments, the optional bleed holes 104a further include plugs 04b.

As illustrated in FIGS. 8 and 9, the radial location and diameters of the bleed holes has a dramatic effect on the centrifugal force exerted by the piston 106 on the cam ring 102, depending on the diameter of the CVP 100. In a further illustration as depicted in FIG.8, the CVP 100 includes a cam driver 101 , the first axial force mechanism 102, a cam bearing race 103, optional bleed holes 104a, bleed hole plugs 104b and a main shaft 105.

Still referring to FIGS. 7-9, in some embodiments, an inner structure of the CVP 100 includes the relative placement of hydraulic ports 10a/b to the cam bearings 107, the rotary hydraulic cavity 108, an optional O-ring 113 and the preload nut 109, with respect to the other variator components already described. Passing now to FIG. 10, in some embodiments, a hydraulic centrifugal clamping mechanism 200 is adapted to be used in the CVP 100. The hydraulic centrifugal clamping mechanism 200 includes a cam driver 201 coupled to a cam ring 202. In some embodiments, a cam bearing retainer ring 203 is adapted to guide a number of cam bearings 207. The cam bearings 207 are in contact with the first traction ring 995. In some embodiments, the hydraulic centrifugal clamping mechanism 200 includes a hydraulic piston 206 arranged to be in contact with a rotary hydraulic fluid cavity 208. The rotary hydraulic fluid cavity 208 is filled with a hydraulic fluid during operation of the CVP 100. In some embodiments, the hydraulic fluid is routed to the rotary hydraulic fluid cavity 208 through passages internal to the main shaft of the CVP 100 (not shown). In some embodiments, the cam driver 201 includes a number of torque transfer notches 211 and a cam driver extension 212. An O-ring 213 is adapted to provide a seal between the hydraulic piston 206 and the cam driver 201. In some embodiments of the hydraulic centrifugal clamping mechanism 200, the cam driver 201 is provided with a channel 218 to provide fluid communication between the rotary hydraulic fluid cavity 208 and an array of pressure regulating valves 219.

Referring now to FIGs. 11A-B, and still referring to FIG. 10, in some embodiments, the array of pressure regulating valves 219 is optionally configured with a pressure relief valve 220. The pressure relief valve 220 is optionally configured as a typical ball check valve having a ball 221 engaged with a spring 222. The pressure relief valve 220 is provided with an inlet port 223 and an outlet port 224 whereby hydraulic fluid can flow during operation. Figure 11 A depicts the pressure relief valve 220 in a closed position and Figure 11 B depicts the pressure relief valve 220 in an open position. When the pressure relief valve 220 is in a closed position, the ball 221 is in contact with a surface 225. The surface 225 is typically conformal with the ball 22 . In the closed position, hydraulic fluid is prevented from flowing from the inlet port 223 to the output port 224. When hydraulic fluid pressure applies a force to the ball 221 greater than the force provided by the spring 222, the pressure relief valve 220 opens. In the opened position, the ball 221 is moved away from the surface 225 thereby providing a path between the input port 223 and the outlet port 224 for the hydraulic fluid.

Referring now to FIGs. 12A-B, and still referring to FIG. 10, in some embodiments, the array of pressure regulating valves 219 is optionally configured with a pressure regulating valve 230. The pressure regulating valve 230 is optionally configured as a typical ball valve having a ball 231 engaged with a spring 232. The pressure regulating valve 230 is provided with an inlet port 233 and an outlet port 234 whereby hydraulic fluid can flow during operation. Figure 12B depicts the pressure regulating valve 230 in a closed position and/or a position having a minimum flow and Figure 12A depicts the pressure regulating valve 230 in an open position. When the pressure regulating valve 230 is in an open position, the ball 231 is in contact with a surface 235. The surface 235 is typically conformal with the ball 231. In the open position, hydraulic fluid is allowed to flow from the inlet port 233 to the output port 234. When a centrifugal force on the ball 231 greater than the force provided by the spring 232, the pressure regulating valve 230 closes or reduces flow. In the closed or reduced flow position, the ball 231 is moved away from the surface 235 and contacting surface 236 to thereby close or reduce the flow path between the input port 233 and the outlet port 234 for the hydraulic fluid. It should be noted that the orientation of the pressure regulating valve 230 in the hydraulic centrifugal clamping mechanism 200 is in a way to provide an open position for low speed operation, and a closed or reduced flow position for high speed operation.

Referring now to FIG. 3, and still referring to FIG. 10, the hydraulic centrifugal clamping mechanism 200 provides a speed dependent axial force during operation of the CVP 100. In some embodiments, the spring rates of the spring 222 and the spring 232, among other design parameters of the valves 220 and 230, are configurable to provide a desired axial force for certain operating conditions. The graph depicted in Figure 13 is of axial force on the planet (y-axis) as a function of the rotary speed of the piston 206 (x-axis). A first vertical line represents a first speed threshold value 240, a second vertical line represents a second speed threshold value 241. A first operating region is characterized as the operating region between zero speed and the first speed threshold value 240. In the first operating region, the hydraulic pressure in the rotary hydraulic fluid cavity 208 is comparatively low because the pressure regulating valve 230 is in an open position while the pressure relief valve 220 is in a closed or reduced flow position. A second operating region is

characterized as the operating region between the first speed threshold value 240 and the second speed threshold value 241. In the second operating region, the pressure regulating valve 230 closes and allows pressure to build up in the rotary hydraulic fluid cavity 208 while the pressure relief valve 220 remains open. A third operating region is characterized as the operating region having speeds higher than the second speed threshold value 241. In the third operating region, the pressure relief valve 220 is in an open position to maintain a maximum pressure in the rotary hydraulic fluid cavity 208 as well as the pressure regulating valve 230.

Provided herein is a continuously variable ball planetary transmission having a hydraulic centrifugal clamping means, the continuously variable ball planetary comprising: a plurality of tilting traction planets mounted on a carrier, the traction planets in contact with a first traction ring and a second traction ring and a hydraulic fluid; an axial force mechanism comprising: a cam ring aligned coaxially with the first traction ring; a plurality of cam bearing balls in contact with the cam ring and the first traction ring; and a cam bearing retainer operably coupled to each of the cam bearing balls; a cam driver configured to transmit a rotational power to the cam ring; a hydraulic piston coaxial and in contact with the cam ring, the hydraulic piston coaxial with, and enclosed within the cam driver; an enclosed, rotating cavity arranged between the cam driver and the hydraulic piston; hydraulic fluid contained within the enclosed cavity, wherein the hydraulic fluid is subject to centrifugal force as a result of rotational speeds of the continuously variable ball planetary; and a plurality of pressure regulating valves coupled to the cam driver, each pressure regulating valve in fluid communication with the hydraulic fluid. In some embodiments of the

continuously variable ball planetary, an axial force applied to first traction ring is a combination of an axial force originating from a hydraulic pressure applied to the hydraulic piston and/or an axial force originating from the axial force mechanism. In some embodiments of the continuously variable ball planetary, the hydraulic pressure is regulated by the array of pressure regulating valve. In some embodiments of the continuously variable ball planetary, the plurality of pressure regulating valves further comprises a first plurality of pressure relief valves, wherein the pressure relief valves are configured to limit the hydraulic pressure from exceeding a maximum pressure. In some embodiments of the continuously variable ball planetary, the plurality of pressure regulating valves are ball valves configured to close at a predetermined operating speed. In some embodiments of the continuously variable ball planetary, the plurality of pressure regulating valves are configured to provide three operating regions, wherein a first operating region corresponds to a minimum hydraulic pressure, a second operating region corresponds to a variable hydraulic pressure, and a third operating region corresponds to a maximum hydraulic pressure.

Moving now to FIGs. 14-16, in some embodiments, a hydraulic centrifugal clamping mechanism 250 includes a cam driver 251 coupled to a cam ring 252. A hydraulic piston 253 couples to the cam ring 252. The hydraulic piston 253 is configured to apply an axial force to the cam ring 252, where the axial force is generated from a rotary hydraulic fluid cavity 254 formed between the cam driver 251 and the hydraulic piston 253. In some embodiments, the hydraulic centrifugal clamping mechanism 250 includes a set of cam bearing balls 255 supported in a cam retainer ring 256. The cam bearing balls 255 are in contact with, and guided by, ramped surfaces formed on the cam ring 252 and the first traction ring 995. In some embodiments, the cam retainer ring 256 is provided with an array of axial extensions 257 formed around an outer periphery of the cam retainer ring 256. The axial extensions 257 are configured to cover a portion of the cam driver 251. In some

embodiments, the cam driver 251 is provided with an array of fluid channels 258 arranged to provide a fluid path between the rotary hydraulic fluid cavity 254 and the outer periphery of the cam driver 251. Upon assembly of the hydraulic centrifugal clamping mechanism 250, each of the fluid channels 258 is aligned with one of the axial extensions 257. During operation, the cam retainer ring 256 rotates with respect to the cam driver 251 proportional to the transmitted torque and speed of the cam driver 251 and the first traction ring 995. The relative rotation of the cam retainer ring 256 with respect to the cam driver 251 coincides with a change in the relative position of the axial extensions 257 with respect to the fluid channels 258 to thereby open and close the fluid path created in the fluid channels 258. As depicted in the view A of FIG. 16, during off-cam operation, the axial extension 257 cover the fluid channels 258 to thereby seal or close the path of fluid out of the rotary hydraulic fluid cavity 254. As used herein, "off-cam operation" or "off-cam condition" refers to an operating condition when the cam bearing ball is located at a valley of the ramp, which is often associated with a low torque operation. The pressure within the rotary hydraulic fluid cavity 254 is regulated by the movement of the axial extensions 257 with respect to the fluid channels 258. It should be appreciated, that the rotary hydraulic fluid cavity 254 is configured to receive a supply of hydraulic fluid from a pressurized source of hydraulic fluid located within the CVP. In some embodiments, a pump is used to circulate hydraulic fluid from a reservoir to the hydraulic fluid cavity 254. In some embodiments, hydraulic fluid is routed through a number of channels in the main shaft of the CVP and directed as appropriate through various seals and channels to other components in the CVP.

Provided herein is a continuously variable ball planetary transmission having a hydraulic centrifugal clamping means, the continuously variable ball planetary comprising: a plurality of tilting traction planets mounted on a carrier, the traction planets in contact with a first traction ring and a second traction ring and a hydraulic fluid; an axial force mechanism comprising: a cam ring aligned coaxially with the first traction ring; a plurality of cam bearing balls in contact with the cam ring and the first traction ring; and a cam bearing retainer operably coupled to each of the cam bearing balls; a cam driver configured to transmit a rotational power to the cam ring; a hydraulic piston coaxial and in contact with the cam ring, the hydraulic piston coaxial with, and enclosed within the cam driver; a rotary hydraulic fluid cavity arranged between the cam driver and the hydraulic piston; hydraulic fluid contained within the enclosed cavity, wherein the hydraulic fluid is subject to centrifugal force as a result of rotational speeds of the continuously variable ball planetary; wherein the cam driver is provided with a plurality of fluid channels in fluid communication with the rotary hydraulic fluid cavity; and wherein the cam retainer ring further comprises a plurality of axial extensions located around an outer periphery of the cam retainer ring, wherein each axial extension is located in proximity to each of the fluid channels. In some embodiments of the continuously variable ball planetary, an axial force applied to first traction ring is a combination of an axial force originating from a hydraulic pressure applied to the hydraulic piston and/or an axial force originating from the axial force mechanism. In some embodiments of the continuously variable ball planetary, the plurality of axial extensions are configured to cover the plurality of fluid channels during low torque operation. In some embodiments of the continuously variable ball planetary, the plurality of axial extensions are configured to uncover the plurality of fluid channels during high torque operation. In some embodiments of the continuously variable ball planetary, the plurality of axial extensions are configured to variably cover the plurality of fluid channels during operation of the continuously variable ball planetary.

Referring now to FIGS. 17 and 18, in some embodiments, a hydraulic centrifugal clamping mechanism 260 includes a cam driver 261 coupled to a cam ring 262. A hydraulic piston 263 couples to the cam ring 262. The hydraulic piston 263 is configured to apply an axial force to the cam ring 262, where the axial force is generated from a rotary hydraulic fluid cavity 264 formed between the cam driver 261 and the hydraulic piston 263. In some embodiments, the hydraulic centrifugal clamping mechanism 260 includes a set of cam bearing balls 266 supported in a cam retainer ring 265. The cam bearing balls 266 are in contact with, and guided by, ramped surfaces formed on the cam ring 262 and the first traction ring 995. In some embodiments, the cam retainer ring 265 is provided with an array of plungers 267 each coupled to a spring 268. The array of plunger 267 are located radially about the cam retainer ring 265. The springs 268 are adapted to press the plungers 267 onto the cam driver 261. The cam driver 261 is provided with a first array of fluid channels 269 configured to provide a fluid path between the rotary hydraulic fluid cavity 264 and a second array of fluid channels 270. In some

embodiments, the second array of fluid channels 270 are aligned to contact each plunger 270. In some embodiments, the first array of fluid channels 269 are provided with a set of plugs 271. During operation, the cam retainer ring 265 rotates with respect to the cam driver 261 proportional to the transmitted torque and speed of the cam driver 261 and the first traction ring 995. The relative rotation of the cam retainer ring 265 with respect to the cam driver 261 coincides with a change in the relative position of the plungers 267 with respect to the second array of fluid channels 270. For operation at "on-cam"

conditions, the cam driver 261 rotates with respect to the cam retainer ring 265 to thereby open the fluid channel 270 and exhaust the pressure built in the rotary hydraulic fluid cavity 264. As used herein, the term "on-cam condition" or "on-cam operation" refers to an operating condition when the cam bearing ball is located on a portion of the ramp, which is often associated with non-zero torque transmission through the CVP. For off-cam conditions, the fluid channel 270 is covered by the plunger 267, hydraulic pressure within the rotary hydraulic fluid cavity 264 is regulated by the axial movement of the plunger 267 with respect to the spring 268. For example, the spring 268 is configured to provide a maximum pressure threshold within the rotary hydraulic fluid cavity 264. It should be appreciated, that the rotary hydraulic fluid cavity 254 is configured to receive a supply of hydraulic fluid from a pressurize source of hydraulic fluid located within the CVP. In some embodiments, hydraulic fluid is routed through a number of channels in the main shaft of the CVP and directed as appropriate through various seals and channels to other components in the CVP.

Provided herein is a continuously variable ball planetary transmission having a hydraulic centrifugal clamping means, the continuously variable ball planetary comprising: a plurality of tilting traction planets mounted on a carrier, the traction planets in contact with a first traction ring and a second traction ring and a hydraulic fluid; an axial force mechanism comprising: a cam ring aligned coaxially with the first traction ring; a plurality of cam bearing balls in contact with the cam ring and the first traction ring; and a cam bearing retainer operably coupled to each of the cam bearing balls; a cam driver configured to transmit a rotational power to the cam ring; a hydraulic piston coaxial and in contact with the cam ring, the hydraulic piston coaxial with, and enclosed within the cam driver; a rotary hydraulic fluid cavity arranged between the cam driver and the hydraulic piston; hydraulic fluid contained within the enclosed cavity, wherein the hydraulic fluid is subject to centrifugal force as a result of rotational speeds of the continuously variable ball planetary; and wherein the cam driver is provided with a plurality of fluid channels in fluid communication with the rotary hydraulic fluid cavity; wherein the cam retainer ring further comprises a plurality of plungers located radially about an outer periphery of the cam retainer ring, wherein each plunger is coupled to a spring that is adapted to press the plunger onto the cam driver, wherein the plurality of plungers are aligned with the plurality of fluid channels. In some embodiments of the continuously variable ball planetary, an axial force applied to first traction ring is a

combination of an axial force originating from a hydraulic pressure applied to the hydraulic piston and/or an axial force originating from the axial force mechanism. In some embodiments of the continuously variable bail planetary, the plurality of plungers are configured to cover the plurality of fluid channels during low torque operation. In some embodiments of the continuously variable ball planetary, the plurality of plungers are configured to uncover the plurality of fluid channels during high torque operation. In some embodiments of the continuously variable ball planetary, the plurality of plungers are configured to variably cover the plurality of fluid channels during operation of the continuously variable ball planetary.

Referring now to FIGS. 19 and 20, in some embodiments, a hydraulic centrifugal clamping mechanism 280 includes a cam driver 281 coupled to a cam ring 282. A hydraulic piston 283 couples to the cam ring 282. The hydraulic piston 283 is configured to apply an axial force to the cam ring 282, where the axial force is generated from a rotary hydraulic fluid cavity 284 formed between the cam driver 281 and the hydraulic piston 283. In some embodiments, the hydraulic centrifugal clamping mechanism 280 includes a set of cam bearing balls 286 supported in a cam retainer ring 285. The cam bearing balls 286 are in contact with, and guided by, ramped surfaces 289a, 289b (FIG. 20) formed on the cam ring 282 and the first traction ring 995. In some embodiments, the hydraulic piston 283 is formed with a first array of fluid channels 287 configured to be in fluid communication with the rotary hydraulic fluid cavity 284. The cam ring 282 is formed with a second array of fluid channels 288 configured to align with the first array of fluid channels 287. The second array of fluid channels 288 are arranged on the cam ring 282 at one end of the ramped surfaces 289a, 289b. For example, upon assembly, the second array of fluid channels 288 are covered by the cam bearing balls 286. During operation, the cam bearing balls 286 move with respect to the cam ring 282 proportional to the transmitted torque and speed of the cam ring 282 and the first traction ring 995. The relative rotation of the cam ring 282 with respect to the cam bearing balls 286 coincides with a change in the relative position of the cam bearing balls 286 with respect to the fluid channels 288 to thereby open and close the fluid path created in the fluid channels 288. As depicted in the view B of FIG. 20, during off-cam operation, the cam bearing balls 286 cover the fluid channels 288 to thereby seal or close the path of fluid out of the rotary hydraulic fluid cavity 284. The pressure within the rotary hydraulic fluid cavity 284 is regulated by the movement of the cam bearing balls 286 with respect to the fluid channels 288. It should be appreciated, that the rotary hydraulic fluid cavity 284 is configured to receive a supply of hydraulic fluid from a pressurize source of hydraulic fluid located within the CVP. In some embodiments, hydraulic fluid is routed through a number of channels in the main shaft of the CVP and directed as appropriate through various seals and channels to other components in the CVP.

Provided herein is a continuously variable ball planetary transmission having hydraulic centrifugal clamping means, the continuously variable ball planetary comprising: a plurality of tilting traction planets mounted on a carrier, the traction planets in contact with a first traction ring and a second traction ring and a hydraulic fluid; an axial force mechanism comprising: a cam ring aligned coaxially with the first traction ring; a plurality of cam bearing balls in contact with the cam ring and the first traction ring; and a cam bearing retainer operably coupled to each of the cam bearing balls; a cam driver configured to transmit a rotational power to the cam ring; a hydraulic piston coaxial and in contact with the cam ring, the hydraulic piston coaxial with, and enclosed within the cam driver; a rotary hydraulic fluid cavity arranged between the cam driver and the hydraulic piston; hydraulic fluid contained within the enclosed cavity, wherein the hydraulic fluid is subject to centrifugal force as a result of rotational speeds of the continuously variable ball planetary; wherein the hydraulic piston is provided with a first plurality of fluid channels in fluid communication with the rotary hydraulic fluid cavity; wherein the cam ring is provided with a second plurality of fluid channels aligned with the first plurality of fluid channels, the second plurality of fluid channels aligned with the plurality of cam bearing balls. In some embodiments of the continuously variable ball planetary, an axial force applied to first traction ring is a combination of an axial force originating from a hydraulic pressure applied to the hydraulic piston and/or an axial force originating from the axial force mechanism. In some embodiments of the continuously variable ball planetary, the plurality of cam bearing balls are configured to cover the second plurality of fluid channels during low torque operation. In some embodiments of the continuously variable ball planetary, the plurality of cam bearing balls are configured to uncover the second plurality of fluid channels during high torque operation. In some embodiments of the continuously variable ball planetary, the plurality of cam bearing balls are configured to variably cover the second plurality of fluid channels during operation of the continuously variable ball planetary.

Referring now to FIGS. 21-23, in the embodiments described herein having a hydraulic piston having an inner diameter and an outer diameter, and configured to apply a force to a cam member, a pressurized hydraulic fluid source is optionally provided to fill the fluid cavity 78 or the rotary hydraulic fluid cavity 108, for example. The magnitude of this force is calculated as shown in the following relationship, and depicted in the graph of Figure 21 :

Faxial piston ~ ^apply * -^piston ~ ^apply * π Ό ~ r i )

r 0 = piston outer diameter

Γ [ = piston inner diameter

In some embodiments, the magnitude of the force on the hydraulic piston is actively controlled by an electric valve, for example, a variable bleed solenoid valve configured to be in fluid communication with the source of pressurized hydraulic fluid and in electrical communication with the

transmission controller 55, for example. In some embodiments, the

transmission controller 55 is optionally configured to include an open loop clamp force setpoint control method where test stand data is used to generate open loop clamping force schedules as a function of torque, speed, and ratio to provide the appropriate clamping plus a margin of safety. This is translated to a required apply piston pressure setpoint and then the requested pressure can be achieved with typical closed loop pressure feedback. In some

embodiments, the transmission controller 55 is optionally configured to include closed loop clamp force control methods where an additional CVP performance metric is used to generate the pressure setpoint to the apply piston.

Referring specifically now to FIG. 22, in some embodiments, a control process 300 is implemented in the transmission controller 55, for example, by way of a software module to control a hydraulic piston pressure, for example, in the fluid cavity 78 or the rotary hydraulic fluid cavity 108, among others. The control process 300 begins at a start state 301 and proceeds to a block 302 where a number of input signals are received. The input signals are indicative of a current CVP ratio, an engine torque, an engine speed, among other operating parameters. The input signals can be received from sensors provided on the vehicle o transmission. The sensors may include temperature, speed, torque, pressure and position sensors among others. The control process 300 proceeds to a block 303 where a required clamp load force is determined by using a calibrateable look-up table, for example. The control process 300 proceeds to a block 304 where a current cam load clamp force is calculated based at least in part on the input signals. The control process 300 proceeds to a block 305 where a current hydraulic centrifugal clamp load force is calculated by at least in part on a speed signal. The control process 300 proceeds to an evaluation block 306 where a current required active clamp load force is compared to the current cam load clamp force and the current hydraulic centrifugal clamp load force based at least in part on the results of the block 303, the block 304, and the block 305. If the evaluation block 306 returns a true result indicating that the current clamp load is insufficient, the process proceeds to a block 307 where the hydraulic piston is enabled and a piston pressure setpoint is determined by dividing the result of the block 303 by the area of the hydraulic piston. The block 307 is optionally configured to pass the piston pressure setpoint to other modules of the transmission controller 55 to control the piston pressure to the setpoint. If the evaluation block 306 returns a false result indicating that the current clamp load is sufficient, the process returns to block 303.

Provided herein is a computer-implemented method for clamp force in a ball planetary variator (CVP) having a hydraulic centrifugal clamping

mechanism, said CVP operabiy coupled to an engine of the vehicle, the vehicle comprising a plurality of sensors and a computer-implemented system comprising a digital processing device comprising an operating system configured to perform executable instructions and a memory device, and a computer program including the instructions executable by the digital processing device, wherein the computer program comprises a software module configured to control the hydraulic centrifugal clamping mechanism and the CVP, the method comprising controlling the clamp force by: the software module receiving a plurality of signals from one or more sensors reflecting vehicle parameters sensed by the one or more sensors, the vehicle parameters comprising a current CVP speed ratio, an engine torque, and an engine speed; calculating a required clamp load force for the CVP based on the current CVP ratio, the engine torque, and the engine speed; calculating a current cam load clamp force for the CVP based on the engine torque; calculating a current centrifugal clamp load force for the CVP based on the current CVP ratio and the engine speed; calculating a required active clamp load force for the CVP based on the required clamp load force, the current cam load clamp force and the current centrifugal clamp load force; and commanding a pressure setpoint of the hydraulic centrifugal clamping mechanism based on the required active clamp load force. In some embodiments of the computer-implemented method, the software module further comprises a calibration map, the calibration map configured to store values of the required clamp load force based on the current CVP ratio, the engine torque, and the engine speed. In some

embodiments of the computer-implemented method, commanding a pressure setpoint of the hydraulic centrifugal clamping mechanism further comprises controlling a variable bleed solenoid valve, the variable bleed solenoid valve coupled to the hydraulic centrifugal clamping mechanism. Referring specifically now to FIG. 23, in some embodiments, a control process 310 is implemented in the transmission controller 55 to provide closed- loop control of a hydraulic piston pressure. In some embodiments, the hydraulic piston pressure is the operating pressure of the rotary hydraulic fluid cavity 108, for example. The control process 310 begins at a start state 311 and proceeds to a block 312 where a number of signals are received. The signals are indicative of a current CVP ratio, a commanded CVP ratio, a CVP input speed, a CVP output speed, among other operating parameters. The control process 310 proceeds to a block 313 where a current CVP slip state is determined. The control process 310 proceeds to an evaluation block 314 where the current CVP slip state is compared to a target slip state. In some embodiments, the target slip state is a parameter stored in a calibrateable look up table or map based on operating condition of the CVP. If the evaluation block 314 returns a true result indicating that the current CVP slip state is less than the target slip state, the control process 300 proceeds to a block 315 where a command to decrease the piston pressure is sent to other modules of the transmission controller 55 to achieve a lower pressure in the hydraulic fluid cavity. If the evaluation block 314 returns a false result indicating that the current CVT slip state is greater than the target slip state, the control process 300 is proceeds to a block 316 where a command is sent to other modules of the transmission controller 55 to achieve a higher pressure in the hydraulic fluid cavity. The control process 300 proceeds back to the block 313 from the block 315 and the block 316.

Referring now to FIG. 24, in some embodiments, an electric hybrid powertrain 350 includes a variator 351 of the type described herein having a first traction ring assembly 352 and a second traction ring assembly 353 in contact with a number of tilting balls supported in a carrier assembly 354. In some embodiments, the variator 351 is provided with a first sun member 355 and a second sun member 356 located radially inward of the first traction ring assembly 352 and the second traction ring assembly 353. In some

embodiments, the variator 351 is provided with a hydraulic piston having an inner diameter and an outer diameter, and configured to apply a force to a cam member of one of the first traction ring assembly 352 or the second traction ring assembly 353. The electric hybrid powertrain 350 is adapted to have a pressurized hydraulic fluid source, which is optionally provided to fill the fluid cavity 78 or the rotary hydraulic fluid cavity 108, for example. The electric hybrid powertrain 350 includes an engine 357 operably coupled to the first traction ring assembly 352. The electric hybrid powertrain 350 includes a first motor/generator 358 operably coupled to the carrier assembly 354. The electric hybrid powertrain 350 includes a second motor/generator 359 operably coupled to the second traction ring assembly 353.

Referring now to FIG. 25, in some embodiments, a control process 400 is implementable in the electric hybrid powertrain 350 as part of a hybrid control strategy. The control process 400 begins at a start state 401 and proceeds to a block 402 where a number of signals are received such as vehicle speed, variator input speed, variator output speed, variator ratio, hydraulic clamp pressure, among others. The signals may be sent from sensors provided on the vehicle and/or transmission. The sensors may include pressure, speed, torque temperature and position sensors among others. The control process 400 proceeds to an evaluation block 403. When the evaluation block 403 returns a false result, indicating that the vehicle speed is not zero, then the control process 400 returns to the block 402. When the evaluation block 403 returns a true result, indicating that the vehicle speed is zero, among other conditions such as the engine is shutdown, the control process 400 proceeds to a block 404 where a command is sent to release the hydraulic clamp pressure in a predetermined schedule, such as a ramped pressure release over a predetermined time. The control process 400 proceeds to a block 405 where a command is sent to shut off the engine. The control process 400 proceeds to an end state 406. During operation of the electric hybrid powertrain 350, a vehicle is able to accelerate from a stopped position with the engine speed at zero by using the first motor/generator 358 and/or the second motor/generator 359. With the hydraulic clamp pressure released on the first traction ring assembly 352, the second traction ring assembly 353 is allowed to spin with no losses in the variator 351 because the mechanical path the first traction ring assembly 352 is decoupled. While preferred embodiments have been shown and described herein, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. Numerous variations, changes, and substitutions will now occur to those skilled in the art without departing from the preferred embodiments. It should be understood that various alternatives to the embodiments described herein may be employed in practice. It is intended that the following claims define the scope of the preferred embodiments and that methods and structures within the scope of these claims and their equivalents be covered thereby.