CROSS-REFERENCES TO RELATED APPLICATIONS

[0001] The present application claims the benefit of U.S. Provisional Patent Application No. 62/149,335, filed April 17, 2015 which application is incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] 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.

SUMMARY OF THE INVENTION

[0003] A tilting ball variator (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.

[0004] A CVP includes 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. The invention pertains to 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,

[0005] 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 (>lGPa), 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.

[0006] Currently, CVT and Infinitely Variable Transmissions (IVT) often use some form of mechanical clamping mechanism, typically comprising 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.

[0007] 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.

[0008] 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.

[0009] Provided herein is a continuously variable ball planetary transmission having passive 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 drive ring and a second drive ring and a traction fluid; at least one axial force mechanism in contact with at least one of the first drive ring or the second drive ring through one or more cam bearings; at least one enclosed rotating cavity optionally comprising bleed holes; at least one clamping element (a piston/ring), adjacent to and at least partially within the rotating cavity, in

approximate contact with the axial force mechanism; and hydraulic fluid within the rotating cavity, wherein the hydraulic fluid is subject to centrifugal force as a result of rotational speeds of the continuously variable ball planetary. 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 of the continuously variable ball planetary, exerts pressure against the clamping element. In some embodiments of the continuously variable ball planetary, the hydraulic pressure applied to the clamping element is combined with a cam clamp load provided by the at least one axial force mechanism to apply axial loading to at least one of the first drive ring or the second drive ring to increase pressure against the tilting traction planets. In some embodiments, the increased axial force is applied to the first drive ring and/or second drive ring to counteract hydrodynamic lift between the tilting traction planets and the first drive ring and/or second drive ring. In some embodiments, a clamping element (piston/ring) applies a variable hydraulic clamping force to at least one axial force mechanism. In some embodiments, the variable hydraulic clamping force is produced by centrifugal force generated by the hydraulic fluid exerted on the clamping element (piston/ring) resulting from a rotational speed of the clamping element . In some embodiments, the variable hydraulic clamping force is a squared function of the rotational speed of the clamping element. In some embodiments, the radial locations of the optional bleed holes in at least one enclosed, rotating cavity, determines a gain of the clamping force with respect to the squared speed of the clamping element. In some embodiments, the cam bearing is configured for relative rotation with respect to the first drive ring, the relative rotation corresponding to an operating torque of the CVT, and wherein the bleed holes are arranged to be blocked by the cam bearing under high torque operation. In some embodiments, the cam bearing uncovers the bleed holes under low torque operation. In some embodiments of the continuously variable ball planetary, the clamping force is defined as: dp ,

— = ρω r

dr ^'

wherein;

F _D = clamping force; ω = angular velocity in radians/second; r ₂ = maximum radius of the piston face; Γι = inner radius of the piston, R ₀ = inner radius of hydraulic fluid (bleed hole radius / exit radius of fluid, p = fluid density, and π = mathematical constant. In some embodiments Ro = Γι. In some embodiments of the continuously variable ball planetary, the clamping force may be determined by other formulae comprising similar and /or different variables known to those skilled in the art. In some embodiments, the radial locations of the optional bleed holes 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 is within about 0 and 30. In some embodiments, the bleed hole is inside the diameter of the piston. In some embodiments of the continuously variable ball planetary, the diameter of the optional bleed holes is within about 0.20 mm and 8.0 mm.

[0010] Provided herein is a method of generating passive centrifugal hydraulic clamping force in a continuously variable ball planetary comprising applying an additive passive centrifugal axial hydraulic clamping force to a first clamping element (piston/ring), at any rotational speed, causing the clamping element to engage a first axial force mechanism in contact with a first drive ring through a cam bearing. In some embodiments of the method, the centrifugal clamping force applied by the first clamping element (piston/ring) is combined with a clamp load from the first axial force mechanism to increase pressure between the first drive ring and the rotating traction planets. In some embodiments of the method, the centrifugal clamping force applied by the first clamping element (piston/ring) is combined with a clamp load from a preload nut to increase pressure between the first drive ring and the rotating traction planets. In some embodiments of the method, the continuously variable ball planetary is in overdrive. In some embodiments, the axial force mechanism is a cam. In some embodiments, the cam is single- sided, or double-sided. In some embodiments, the cam is uni-directional or bi-directional. In some embodiments the axial force mechanism is a single cam (on the input or output ring) or a dual cam (on the input ring and output ring). In other embodiments the axial force mechanism is a roller load cam. In some embodiments, the clamping element is an axially sliding element, (e.g. : a stepped ring), in intimate, sealed contact with a rotating cavity having optional bleed holes positioned radially, adjacent the diametral face of the clamping element, and ideally in the approximate radial center of either a first or a second drive ring face, (in a single cam

configuration). The clamping element is immediately adjacent, to and in contact with the first or second drive ring through a cam bearing. In some embodiments of a single cam

configuration, the hydraulic pressure within the cavity created by centrifugal force, acting on the hydraulic fluid in the cavity, exerts a force on the adjacent clamping element which exceeds the pre-loaded clamping force, causing the clamping element to slide axially off of a hard stop on the face of the rotating cavity and apply a greater axial force or clamping force to the drive ring of the CVP than would have otherwise been available from the axial force mechanism alone. In some embodiments the clamping elements are axially sliding elements, (e.g. : a stepped ring), in intimate, sealed contact with rotating cavities comprising optional bleed holes positioned radially, adjacent the diametral face of more two clamping elements, and ideally in the approximate radial center of both a first and a second drive ring face, (such as in a dual cam configuration). The clamping elements are immediately adjacent, to and in contact with the first and second drive ring through a cam bearing. In some embodiments of a dual cam

configuration, the hydraulic pressure within the cavities created by centrifugal force, acting on the hydraulic fluid in the cavity, exerts a force on the adjacent clamping element which exceeds the pre-loaded clamping force, causing the clamping element to slide axial off of a hard stop on the face of the rotating cavity and apply a greater axial force or clamping force to the input drive ring and output drive ring of the CVP than would have been available from the axial force mechanisms alone.

[0011] Provided herein is a method of generating passive centrifugal hydraulic clamping force in a continuously variable ball planetary comprising applying an additive passive centrifugal axial hydraulic clamping force to a second clamping element (piston/ring), at rotational speed, causing the clamping element to engage an second axial force mechanism in contact with a second drive ring through a cam bearing. In some embodiments of the method, the centrifugal clamping force applied by the second clamping element (piston/ring) is combined with a cam clamp load from the second axial force mechanism to increase pressure between the second drive ring and the rotating traction planets. In some embodiments of the method, the centrifugal clamping force applied by the second clamping element (piston/ring) is combined with a cam clamp load from the second axial force mechanism to increase pressure between the second drive ring and the rotating traction planets.

[0012] Provided herein is a method of generating passive centrifugal clamping force between rotating traction planets and a first drive ring and a second drive ring for a continuously variable ball planetary comprising applying an additive passive centrifugal axial hydraulic clamping force to a first clamping element (piston/ring) and a second clamping element (piston/ring), at rotational speed, causing the first and second clamping elements to engage a first axial force mechanism and a second axial force mechanism in contact with the first drive ring and the second drive ring through cam bearings. In some embodiments of the method, the centrifugal clamping force applied by the first clamping element (piston/ring) and the second clamping element (piston/ring) is combined with a system preload from the first axial force mechanism and the second axial force mechanism to increase pressure between the first drive ring, the second drive ring, and the rotating traction planets. In some embodiments of the method, a side of the variator with higher revolutions per minute would be an active speed-dependent clamp side. In some embodiments of the method, a non-active cam driver would react to the active clamp load and the pressure from the fluid within the variator to become the active cam driver. Or stated another way, if the non-active cam is for example, ring 2, [assuming the system is in overdrive], and the input [Rl] is at a low torque state, and if the hydraulic clamp mechanism on R2 is producing a higher clamp force due to its speed, then it reacts to become the active clamp device.

[0013] In any one of the previously described transmissions or methods, the centrifugal clamping force is generated by hydraulic pressure applied to a clamping element, whereby said hydraulic pressure generates an additive force in excess of a cam clamp load generated by the first or second axial force mechanism, in the continuously variable ball planetary.

[0014] In any one of the previously described transmissions or methods, the combined clamping force of the clamping element and the axial force mechanism exceeds a predetermined value of the cam clamp load of a ball-and-cam axial force mechanism to produce a useful increase in total clamping force at low torque/high speed.

[0015] Provided herein is a method of manufacturing a continuously variable planetary transmission comprising a variator with passive centrifugal clamping means, the variator comprising: a plurality of tilting traction planets mounted on a carrier, the traction planets in contact with a first drive ring and a second drive ring; at least one axial force mechanism; at least one enclosed, rotating cavity ; at least one clamping element (piston/ring), adjacent to and at least partially within the rotating cavity, in approximate contact with the axial force mechanism and hydraulic fluid within the rotating cavity, wherein the hydraulic fluid is subject to centrifugal force as a result of rotational speeds of the continuously variable ball planetary; wherein at least one rotating cavity, generates hydraulic pressure at any rotational speeds and exerts a force on at least one clamping element adequate to fully engage at least one axial force mechanism, wherein the force generated on the first and/or second drive ring is greater than a torque controlled ramp force provided by at least one axial force mechanism alone. In some embodiments of the continuously variable planetary transmission, the rotating cavity comprises bleed holes.

[0016] Provided herein is a method of controlling passive centrifugal hydraulic clamping force in a continuously variable ball planetary comprising applying an additive passive centrifugal axial hydraulic clamping force to a first clamping element, at any rotational speed, causing the clamping element to engage an first axial force mechanism in contact with a first drive ring through a cam bearing. In some embodiments, the centrifugal hydraulic clamping force applied by the first clamping element is combined with a cam clamp load from the first axial force mechanism to increase pressure between the first drive ring and the rotating traction planets. In some embodiments, the continuously variable ball planetary is in overdrive.

[0017] Provided herein is a method of controlling passive centrifugal hydraulic clamping force in a continuously variable ball planetary comprising applying an additive passive centrifugal axial hydraulic clamping force to a second clamping element, at any rotational speed, causing the clamping element to engage a second axial force mechanism in contact with a second drive ring through a cam bearing. In some embodiments, the centrifugal hydraulic clamping force applied by the second clamping element is combined with a cam clamp load from the second axial force mechanism to increase pressure between the second drive ring and the rotating traction planets.

[0018] Provided herein is a method of controlling passive centrifugal hydraulic clamping force between rotating traction planets and a first drive ring and a second drive ring for a continuously variable ball planetary comprising applying an additive passive centrifugal axial hydraulic clamping force to a first clamping element and a second clamping element, at high rotational speed, causing the first and second clamping elements to engage an first axial force mechanism and a second axial force mechanism in contact with the first drive ring and the second drive ring through cam bearings. In some embodiments, the centrifugal hydraulic clamping force applied by the first clamping element and the second clamping element is combined with a cam clamp load from the first axial force mechanism and the second axial force mechanism to increase pressure between the first drive ring, the second drive ring, and the rotating traction planets. In some embodiments, the clamping element with the higher revolutions per minute is the active speed-dependent clamping device. In some embodiments, a non-active cam driver would react to the active clamp load and the pressure from the fluid within the variator to become the active cam driver. In some embodiments, the centrifugal clamping force is controlled by hydraulic pressure applied to a clamping element, whereby said hydraulic pressure generates an additive force in excess of a cam clamp load generated by the first or second axial force mechanism, in the continuously variable ball planetary. In some embodiments, the combined clamping force of the clamping element and the axial force mechanism exceeds the design value of the cam clamp load of a ball-and-cam axial force mechanism to produce a useful increase in total clamping force at low torque/high speed.

INCORPORATION BY REFERENCE

[0019] 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

[0020] The novel features of the invention are set forth with particularity in the appended claims. A better understanding of the features and advantages of the present invention will be obtained by reference to the following detailed description that sets forth illustrative

embodiments, in which the principles of the invention are utilized, and the accompanying drawings of which:

[0021] Figure 1 is a side sectional view of a ball-type variator [0022] Figure 2 depicts a block diagram of a passive centrifugal clamping mechanism illustrating a cross-section of rotating cavity containing hydraulic fluid and a clamping element.

[0023] Figure 3 depicts a representative isometric view of a planetary ball variator comprising optional fluid output or bleed ports.

[0024] Figure 4 depicts a representative cross-section view of a planetary ball variator in Figure 3 with a representative depiction of a rotating cavity for hydraulic fluid and a clamping element.

[0025] Figure 5 depicts a detail representative section view of Figure 4, showing one half of a CVP.

[0026] 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.

[0027] Figure 7 depicts a representative isometric view of another planetary ball variator with an integrated speed wheel in the cam driver; notched captures between the cam driver and cam ring to transfer torque; and optional fluid output, or bleed ports.

[0028] Figure 8 depicts a representative cross-section view of a planetary ball variator in Figure 7 with a representative depiction of a rotating cavity for hydraulic fluid and a clamping element.

[0029] Figure 9 depicts a detail representative cross-section view of Figure 7 showing one half of a CVP.

[0030] Figure 10 depicts a detail representative cross-section view of Figure 7 illustrating only the main shaft, cam driver, clamping element and cam ring.

[0031] Figures 11-A, 11-B and 11-C depict side, front ISO and rear ISO cross-section views of Figure 7 illustrating only the cam driver, clamping element and cam ring.

[0032] Figure 12 depicts a detail section view of the interface of the cam driver, clamping element and cam ring of Figure 7.

[0033] Figure 13 depicts another detail section view illustrating a lip capture feature of the clamping element utilized to capture and distribute hydraulic fluid to the piston within the variator.

DETAILED DESCRIPTION OF THE INVENTION

[0034] A continuously variable ball planetary variator produces a passive 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.

[0035] The cross-section of a typical CVP is shown in FIG. 1. Such a CVP, as described throughout this specification, comprises a number of balls, or traction planets 997, two discs with a conical surface contact with the traction planets, as input 995 and output 996, and an idler 999. The traction planets are mounted on axes 998, themselves held in a cage or carrier allowing changing of the ratio by tilting the balls' axes. Other types of ball CVTs also exist, like the one produced by Milner, but are slightly different.

[0036] 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 is changed between input and output. When the axis is horizontal the ratio is one, when the axis is tilted the distance between the axis and the contact point change, modifying the overall ratio. All the traction planets' axes are tilted at the same time with a mechanism included in the cage.

[0037] As used herein, the terms "input ring", and "output ring" may alternately be referred to as a first or second "drive ring".

[0038] 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 inventive 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 may take a variety of forms, which in certain instances will be readily apparent to a person of ordinary skill in the relevant technology.

[0039] 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 1011 A and bearing 101 IB) will be referred to collectively by a single label (for example, bearing 1011).

[0040] 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 may be 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 may operate in both tractive and frictional applications. For example, in the embodiment where a CVT is used for a bicycle application, the CVT operates at times as a friction drive and at other times as a traction drive, depending on the torque and speed conditions present during operation.

[0041] Provided herein is a continuously variable ball planetary transmission having passive centrifugal clamping means, as illustrated in FIG. 4, the continuously variable ball planetary 100 comprising: a plurality of tilting traction planets 997 mounted on a carrier 114, the traction planets in contact with a first drive ring 995 and a second drive ring 996 and traction fluid; at least one axial force mechanism 102 in contact with at least one of the first drive ring or the second drive ring through a cam bearing 107; at least one enclosed rotating cavity 108 optionally comprising bleed holes 104a; at least one clamping element 106 (a piston/ring), 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 CVT 100. In some embodiments, the clamping element 106 is a ring or a piston.

[0042] 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.

[0043] 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.

[0044] In some embodiments of the continuously variable ball planetary, the hydraulic pressure applied to the clamping element is combined with a cam clamp load provided by the at least one axial force mechanism 109 to apply axial loading to at least one of the first drive ring 995 or the second drive ring 996 to increase pressure against the tilting traction planets 997.

[0045] In some embodiments, the increased axial force is applied to the first drive ring and/or second drive ring to counteract hydrodynamic lift between the tilting traction planets and the first drive ring and/or second drive ring. During operation of the CVT 100, the axial force generated by the axial force mechanism 109 is variable with torque and speed. Under certain operating conditions, for example, at high speeds, the axial force generated by the axial force mechanism 109 may be insufficient to transmit the desired torque. An additional axial force may be applied by passive means through the hydraulic centrifugal force applied to the clamping element 2.

[0046] In some embodiments, a clamping element 2 (piston/ring) applies a variable hydraulic clamping force to at least one axial force mechanism 102. In some embodiments, the variable hydraulic clamping force is produced by centrifugal force generated by the hydraulic fluid in the fluid cavity 3 exerted on the clamping element 2 (piston/ring) resulting from a rotational speed of the clamping element, causing it to move off of the hard stop 1. In some embodiment, an optional O-ring 9 exists between the cavity and the clamping element.

[0047] As illustrated in FIG. 2, in some embodiments 10, the variable hydraulic clamping force 4 is a squared function of the rotational speed 8 of the clamping element 2.

[0048] 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.

[0049] In some embodiments, the cam bearing is configured for relative rotation with respect to the first drive ring, the relative rotation corresponding to an operating torque of the CVT, and wherein the bleed holes are arranged to be blocked by the cam bearing under high torque operation.

[0050] In some embodiments, the cam bearing uncovers the bleed holes under low torque operation.

[0051] As further illustrated in FIG. 2, in some embodiments of the continuously variable ball planetary, the clamping force is defined as: dp

ρω Ϊ

c!F, di

p{r) 2πτ p{ r)

~dr ^~

, wherein;

F _D = clamping force; ω = angular velocity in radians/second; r ₂ = maximum radius of the piston face; ΙΊ = inner radius of the piston, R ₀ = inner radius of hydraulic fluid (bleed hole radius / exit radius of fluid, p = fluid density, and π = mathematical constant.

[0052] In some embodiments R ₀ = ΐ

[0053] In some embodiments of the continuously variable ball planetary, the clamping force may be determined by other formulae comprising similar and /or different variables known to those skilled in the art.

[0054] 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 1 10.0 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.

[0055] In some embodiments of the continuously variable ball planetary, the number of the optional bleed holes 104a is within about 0 and 30.

[0056] In some embodiments, the bleed hole is inside the diameter of the piston. [0057] In some embodiments of the continuously variable ball planetary, 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 comprise plugs 104b.

[0058] As illustrated in FIG. 6, 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.

[0059] In a further illustration as depicted in FIG. 3, the CVP 100 comprises a cam driver 101, a cam ring 102, a cam bearing race 103, optional bleed holes 104a, bleed hole plugs 104b and a main shaft 105.

[0060] Still further, as illustrated in FIGS. 4 and 5, the cross-sectional view reveals the inner structure of an illustrative CVP 100 comprising the relative placement of hydraulic ports 1 lOa/b, 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.

[0061] 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%, 2,5%, 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.

[0062] Provided herein is a method of generating passive centrifugal hydraulic clamping force in a continuously variable ball planetary comprising applying an additive passive centrifugal axial hydraulic clamping force to a first clamping element (piston/ring), at any rotational speed, causing the clamping element 106 to engage a first axial force mechanism 102 in contact with a first drive ring 995 through the cam bearing 107.

[0063] In some embodiments of the method, the centrifugal clamping force applied by the first clamping element 106 (piston/ring) is combined with a clamp load from the first axial force mechanism 102 to increase pressure between the first drive ring 995 and the rotating traction planets 997.

[0064] In some embodiments of the method, the centrifugal clamping force applied by the first clamping element 106 (piston/ring) is combined with a clamp load from a preload nut 109 to increase pressure between the first drive ring 995 and the rotating traction planets 997. [0065] In some embodiments of the method, the continuously variable ball planetary 100, 200 is in overdrive.

[0066] In some embodiments of the CVP transmission, the axial force mechanism is a cam 102. In some embodiments, the cam is single-sided, or double-sided. In some embodiments, the cam is uni-directional or bi-directional. In some embodiments the axial force mechanism is a single cam (on the input or output ring, 995, 996) or a dual cam (on the input ring and output ring). In other embodiments the axial force mechanism is a roller load cam.

[0067] In some embodiments of the CVP transmission, the clamping element is an axially sliding element, (e.g.: a stepped ring), in intimate, sealed contact with a rotating cavity having optional bleed holes 104a positioned radially, adjacent the diametral face of the clamping element, and ideally in the approximate radial center of either a first or a second drive ring face, (in a single cam configuration). The clamping element is immediately adjacent, to and in contact with the first or second drive ring through cam bearings.

[0068] In some embodiments of the CVP transmission comprising a single cam configuration, the hydraulic pressure within the cavity created by centrifugal force, acting on the hydraulic fluid in the cavity, exerts a force on the adjacent clamping element which exceeds the pre-loaded clamping force, causing the clamping element to slide axially off of a hard stop on the face of the rotating cavity and apply a greater axial force or clamping force to the drive ring of the CVP than would have otherwise been available from the axial force mechanism alone.

[0069] In some embodiments of the CVP transmission the clamping elements are axially sliding elements, (e.g.: a stepped ring), in intimate, sealed contact with rotating cavities comprising optional bleed holes positioned radially, adjacent the diametral face of more two clamping elements, and ideally in the approximate radial center of both a first and a second drive ring face, (such as in a dual cam configuration). The clamping elements are immediately adjacent, to and in contact with the first and second drive ring through cam bearings.

[0070] In some embodiments of a dual cam configuration CVP transmission, the hydraulic pressure within the cavities created by centrifugal force, acting on the hydraulic fluid in the cavity, exerts a force on the adjacent clamping element which exceeds the pre-loaded clamping force, causing the clamping element to slide axial off of a hard stop on the face of the rotating cavity and apply a greater axial force or clamping force to the input drive ring and output drive ring of the CVP than would have been available from the axial force mechanisms alone, as previously illustrated and described in FIG. 2.

[0071] In still other embodiments of a CVP transmission 200, 300, 400, 500, 600 and 700 comprising passive hydraulic clamping, such as illustrated in FIGS. 8 - 13, the CVP comprises a Cam Driver 201, a Cam Ring 202, a Cam Bearing Race 203, Bleed Holes 204a and Plugs 204b, a Main Shaft 205, a Piston / Ring 206, a Cam Bearing 207, a Rotary Hydraulic Fluid Cavity 208, a Pre-load Nut 209, Hydraulic Fluid Input Ports (external) 210a, Hydraulic Fluid Input Port (internal) 210b, Torque Transfer Notches (integrated into the Cam Driver) 211, an Integrated Speed Wheel 212, O-Rings (optional) 213, a Carrier / Stator 214, a Cam Bearing track 217, a Piston Support Notch 218, a Piston Ring Hydraulic Fluid Capture Lip 219, an Idler Bearing 220, a Cam Driver Mounting Hub 221, an Idler Inner Race 222, and the standard CVP components comprising an Input Ring 995, an Output Ring 996, Traction Planets (Balls) 997, Planet Axles 998 and Idler 999.

[0072] Provided herein is a method of generating passive centrifugal hydraulic clamping force in a continuously variable ball planetary comprising applying an additive passive centrifugal axial hydraulic clamping force to a second clamping element (piston/ring), at rotational speed, causing the clamping element to engage an second axial force mechanism in contact with a second drive ring through the cam bearings.

[0073] In some embodiments of the method, the centrifugal clamping force applied by the second clamping element (piston/ring) is combined with a cam clamp load from the second axial force mechanism to increase pressure between the second drive ring and the rotating traction planets.

[0074] In some embodiments of the method, the centrifugal clamping force applied by the second clamping element (piston/ring) is combined with a cam clamp load from the second axial force mechanism to increase pressure between the second drive ring and the rotating traction planets.

[0075] Provided herein is a method of generating passive centrifugal clamping force between rotating traction planets and a first drive ring and a second drive ring for a continuously variable ball planetary comprising applying an additive passive centrifugal axial hydraulic clamping force to a first clamping element (piston/ring) and a second clamping element (piston/ring), at rotational speed, causing the first and second clamping elements to engage a first axial force mechanism and a second axial force mechanism in contact with the first drive ring and the second drive ring through the cam bearings.

[0076] In some embodiments of the method, the centrifugal clamping force applied by the first clamping element (piston/ring) and the second clamping element (piston/ring) is combined with a system preload from the first axial force mechanism and the second axial force mechanism to increase pressure between the first drive ring, the second drive ring, and the rotating traction planets. [0077] In some embodiments of the method, a side of the variator with higher revolutions per minute would be an active speed-dependent clamp side.

[0078] In some embodiments of the method, a non-active cam driver would react to the active clamp load and the pressure from the fluid within the variator to become the active cam driver. Or stated another way, if the non-active cam is for example, ring 2, [assuming the system is in overdrive], and the input [Rl] is at a low torque state, and if the hydraulic clamp mechanism on R2 is producing a higher clamp force due to its speed, then it reacts to become the active clamp device. For example, assuming the following conditions where: a hydraulic clamp unit was on the R2 side; the input torque is 70 Nm; the input speed 5000 RPM; and the SR (speed ratio) is 1.8, then output would be 9000 RPM. The clamp load due to Rl cam ramps would be ~11,000 N, then the hydraulic clamp force from R2 would be greater than 37,000 N and hence would be the 'active' clamping device. If the device was on Rl, then one should get a minimum -12,000 N, which is still larger than the Rl cam ramps.

[0079] In any one of the previously described methods, the centrifugal clamping force is generated by hydraulic pressure applied to a clamping element, whereby said hydraulic pressure generates an additive force in excess of a cam clamp load generated by the first or second axial force mechanism, in the continuously variable ball planetary.

[0080] In any one of the previously described methods, the combined clamping force of the clamping element and the axial force mechanism exceeds a predetermined value of the cam clamp load of a ball-and-cam axial force mechanism to produce a useful increase in total clamping force at low torque/high speed. As an example, if one were to increase the cam mu to better match some minimum traction coefficient to improve efficiency, wherein the cam mu is 0.08, then at 400 Nm of input torque, 5000 RPM input and 1.8 SR, the clamp load due to the cams would be -35,000 N, while the hydraulic clamp on R2 (if that's where the device went) should be >37,000 N.

[0081] Provided herein is a method of manufacturing a continuously variable planetary transmission comprising a variator with passive centrifugal clamping means, the variator comprising: a plurality of tilting traction planets mounted on a carrier, the traction planets in contact with a first drive ring and a second drive ring; at least one axial force mechanism; at least one enclosed, rotating cavity ; at least one clamping element (piston/ring), adjacent to and at least partially within the rotating cavity, in approximate contact with the axial force mechanism and hydraulic fluid within the rotating cavity, wherein the hydraulic fluid is subject to centrifugal force as a result of rotational speeds of the continuously variable ball planetary; wherein at least one rotating cavity, generates hydraulic pressure at any rotational speeds and exerts a force on at least one clamping element adequate to fully engage at least one axial force mechanism, wherein the force generated on the first and/or second drive ring is greater than a torque controlled ramp force provided by at least one axial force mechanism alone.

[0082] In some embodiments of the continuously variable planetary transmission, the rotating cavity comprises bleed holes.

[0083] Provided herein is a method of controlling passive centrifugal hydraulic clamping force in a continuously variable ball planetary comprising applying an additive passive centrifugal axial hydraulic clamping force to a first clamping element, at any rotational speed, causing the clamping element to engage an first axial force mechanism in contact with a first drive ring through a cam bearing.

[0084] In some embodiments, the centrifugal hydraulic clamping force applied by the first clamping element is combined with a cam clamp load from the first axial force mechanism to increase pressure between the first drive ring and the rotating traction planets.

[0085] In some embodiments, the continuously variable ball planetary is in overdrive.

[0086] Provided herein is a method of controlling passive centrifugal hydraulic clamping force in a continuously variable ball planetary comprising applying an additive passive centrifugal axial hydraulic clamping force to a second clamping element, at any rotational speed, causing the clamping element to engage a second axial force mechanism in contact with a second drive ring through a cam bearing.

[0087] In some embodiments, the centrifugal hydraulic clamping force applied by the second clamping element is combined with a cam clamp load from the second axial force mechanism to increase pressure between the second drive ring and the rotating traction planets.

[0088] Provided herein is a method of controlling passive centrifugal hydraulic clamping force between rotating traction planets and a first drive ring and a second drive ring for a continuously variable ball planetary comprising applying an additive passive centrifugal axial hydraulic clamping force to a first clamping element and a second clamping element, at high rotational speed, causing the first and second clamping elements to engage an first axial force mechanism and a second axial force mechanism in contact with the first drive ring and the second drive ring through cam bearings.

[0089] In some embodiments, the centrifugal hydraulic clamping force applied by the first clamping element and the second clamping element is combined with a cam clamp load from the first axial force mechanism and the second axial force mechanism to increase pressure between the first drive ring, the second drive ring, and the rotating traction planets. [0090] In some embodiments, the clamping element with the higher revolutions per minute is the active speed-dependent clamping device.

[0091] In some embodiments, a non-active cam driver would react to the active clamp load and the pressure from the fluid within the variator to become the active cam driver.

[0092] In some embodiments, the centrifugal clamping force is controlled by hydraulic pressure applied to a clamping element, whereby said hydraulic pressure generates an additive force in excess of a cam clamp load generated by the first or second axial force mechanism, in the continuously variable ball planetary.

[0093] In some embodiments, the combined clamping force of the clamping element and the axial force mechanism exceeds the design value of the cam clamp load of a ball-and-cam axial force mechanism to produce a useful increase in total clamping force at low torque/high speed.

[0094] While preferred embodiments of the present invention 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 invention. It should be understood that various alternatives to the embodiments of the invention described herein may be employed in practicing the invention. It is intended that the following claims define the scope of the invention and that methods and structures within the scope of these claims and their equivalents be covered thereby.