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Title:
ONE WAY CLUTCH WITH ENHANCED RATCHETING PROPERTIES
Document Type and Number:
WIPO Patent Application WO/2018/157236
Kind Code:
A1
Abstract:
The present disclosure relates generally to strut-type overrunning coupling devices. More specifically, the present disclosure is directed to a one-way clutch configured to provide a first or latched mode having the struts engaged with ratchet teeth to establish a one-way torque path, a second or ratcheting mode having the struts ratcheting over the ratchet teeth, and a third or uncoupled mode having the struts moved, via centrifugal forces, to a position displaced from the ratchet teeth.

Inventors:
CIOC, Adrian (203 Weldrick Road West, Richmond Hill, Ontario L4C 5J2, CA)
Application Number:
CA2018/000048
Publication Date:
September 07, 2018
Filing Date:
March 02, 2018
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
MAGNA POWERTRAIN INC. (50 Casmir Court, Concord Ontario, L4K 4J5, CA)
International Classes:
F16D41/16; F16D43/04; F16H29/12
Domestic Patent References:
WO2016170429A12016-10-27
Foreign References:
US5205386A1993-04-27
US20150354640A12015-12-10
US5853073A1998-12-29
US20080264692A12008-10-30
US6481551B12002-11-19
Attorney, Agent or Firm:
DICKINSON WRIGHT LLP (199 Bay Street, Suite 2200Toronto, Ontario M5L 1G4, CA)
Download PDF:
Claims:
CLAIMS

What is claimed:

1. A one-way clutch, comprising:

an inner race disposed about an axis and having ratchet teeth;

an outer race disposed about the axis and defining a strut pocket; and

a strut assembly mounted in the strut pocket and including a pivotal strut and a spring acting on the strut, wherein the strut is pivotably moveable between a first position engaged with one of the ratchet teeth, a second position ratcheting over the ratchet teeth, and a third position disengaged from ratcheting engagement with the ratchet teeth, wherein the spring is arranged to bias the strut toward the first position, and wherein the strut moves from the second position into the third position in response to the rotary speed of the outer race exceeding a predetermined threshold speed value.

2. The bi-directional clutch assembly of Claim 1 wherein the strut includes a pivot segment pivotably connected inside the strut pocket and a leg segment extending from the pivot segment along a strut axis, and wherein the leg segment of the strut terminates at a tip segment having a camming surface extending at an acute angle relative to the strut axis for contacting the ratchet teeth of the inner race when the strut is in the second position during rotation of the second race to cause the leg segment to be mechanically rejected out of engagement with the ratchet teeth in opposition to the spring.

3. The bi-directional clutch assembly of Claim 2 wherein the acute angle is less than or equal to 45 degrees.

4. The bi-directional clutch assembly of Claim 2 wherein a latch valley is defined circumferentially between each of the ratchet teeth, and wherein each of the ratchet teeth has an outer diameter surface positioned radially outward from the latch valley, a blend radius extending from the outer diameter, and a latch section between the blend radius and the latch valley, and wherein the camming surface of the strut is positioned generally in radial alignment with the blend radius when the strut is in the second position during rotation of the second race to cause the leg segment to be mechanically rejected out of engagement with the ratchet teeth in opposition to the spring during rotation of the second race.

5. The bi-directional clutch assembly of Claim 4 wherein the tip segment of the strut further has a terminal end surface extending generally perpendicularly to the strut axis.

6. The bi-directional clutch assembly of Claim 5 wherein the second race has a stop surface defining part of the strut pocket, wherein the leg segment of the strut has a backside surface facing the stop surface, and wherein the strut is pivotable between the first position in which the terminal end surface engages the latch section of one of the teeth to inhibit rotation of the second race relative to the first race, the second position in which the camming surface is generally radially aligned with the blend radius causing the ratcheting of the strut over the ratchet teeth, and the third position in which the backside surface of the strut is positioned adjacent the stop surface of the second race.

7. A one-way clutch, comprising: a first race disposed about an axis and having ratchet teeth;

a second race disposed about the axis and defining a strut pocket;

a strut disposed in the pocket and including a pivot segment being pivotably connected inside the pocket, and a leg segment extending from the pivot segment along a strut axis, the leg segment configured to be pivoted radially toward and away from the ratchet teeth of the inner race;

a spring positioned between the outer race and the leg segment of the strut and biasing the strut toward the ratchet teeth;

the leg segment of the strut terminating at a tip segment having a camming surface extending at an acute angle relative to the strut axis for contacting the ratchet teeth of the outer race in response to a rotary speed of the second race exceeding a predetermined threshold speed value causing the camming surface to be partially radially spaced from the ratchet teeth such that the leg segment is mechanically rejected out of engagement with the ratchet teeth during rotation of the second race.

8. The bi-directional clutch assembly of Claim 7 wherein the acute angle is less than or equal to 45 degrees.

9. The bi-directional clutch assembly of Claim 7 wherein a latch valley is defined between each of the ratchet teeth, and wherein each of the ratchet teeth has an outer diameter surface positioned radially out from the latch valley, a blend radius extending from the outer diameter, and a latch section extending between the blend radius and the latch valley, and wherein the camming surface of the strut is positioned in radial alignment with the blend radius when the rotary speed of the second race exceeds the threshold speed value to cause the strut to be mechanically rejected out of engagement with the ratchet tooth.

10. The bi-directional clutch assembly of Claim 9 wherein the tip segment of the strut further has a terminal end surface extending generally perpendicularly to the strut axis.

1 1. The bi-directional clutch assembly of Claim 10 wherein the second race has a stop surface defining part of the strut pocket, wherein the leg segment of the strut has a backside surface facing the stop surface, and wherein the strut is pivotable between a tucked position wherein the backside surface of the strut is positioned adjacent the stop surface of the second race, a ratcheting position wherein the camming surface is radially aligned with the blend radius, and a deployed position in which the terminal end surface engages the latch section of one of the teeth to inhibit rotation of the second race relative to the first race.

12. A bi-directional clutch assembly comprising:

a first race presenting a plurality of first ratchet teeth;

a second race presenting a plurality of second ratchet teeth and a plurality of strut pockets;

a passive one-way clutch including a plurality of passive struts pivotably supported by the second race in the strut pockets for pivoting into engaging relationships with the first ratchet teeth during rotation of the second race in a first direction;

a selectable one-way reverse clutch including at least one active strut supported by the first race and selectively pivotable from an unlocked position wherein the active strut is disengaged from the second ratchet teeth to a locked position for engaging one of the plurality of second ratchet teeth during rotation of the second race in a second direction opposite the first direction; and

the plurality of passive struts arranged to pivot between a first position engaged with the first ratchet teeth, a second position ratcheting relative to the first ratchet teeth, and a third position disengaged from ratchet engagement relative to the first ratchet teeth in response to a rotary speed of the second race exceeding a predetermined threshold value.

13. The bi-directional clutch assembly of Claim 12 wherein the passive struts are biased by a spring toward their engaged position, and wherein centrifugal loads applied to the passive struts in response to rotation of the second race causes movement of the struts toward the third position.

14. The bi-directional clutch assembly of Claim 13 wherein each passive strut has a tip segment moved to a tucked position displaced from the first ratchet teeth when the struts are in the third position.

15. The bi-directional clutch assembly of Claim 13 wherein each of the passive struts includes a pivot segment pivotably connected inside the strut pocket and a leg segment extending from the pivot segment along a strut axis, and wherein the leg segment of the strut terminates at a tip segment having a camming surface extending at an acute angle relative to the strut axis for contacting the ratchet teeth of the first race when the strut is in the second position during rotation of the second race to cause the leg segment to be mechanically rejected out of engagement with the ratchet teeth of the first race in opposition to the spring.

Description:
ONE WAY CLUTCH WITH ENHANCED RATCHETING PROPERTIES

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Patent Application

Serial No. 62/465,887 filed on March 02, 2017, and titled "One Way Clutch With Enhanced Ratcheting Properties," the entire disclosure of which is hereby incorporated by reference.

FIELD OF THE INVENTION

[0002] The present disclosure relates generally to strut-type overrunning coupling devices. More specifically, the present disclosure is directed to a one-way clutch configured to provide a first or latched mode wherein the struts are engaged with ratchet teeth to establish a one-way torque path, a second or ratcheting mode wherein the struts ratchet over the ratchet teeth, and a third or uncoupled mode wherein the struts move, via centrifugal forces, to a position displaced from the ratchet teeth.

BACKGROUND OF THE INVENTION

[0003] This section provides background information related to the present disclosure which is not necessarily prior art.

[0004] Automatic transmissions provide a plurality of forward and reverse speed or gear ratios by selectively actuating one or more clutches and/or brakes to establish a torque- transmitting drive connection between a transmission input and a transmission output for supplying motive power (i.e., drive torque) from a powertrain to a driveline in a motor vehicle. One type of brake or clutch widely used in automatic transmission is an overrunning coupling device, commonly referred to as a one-way clutch (OWC), which overruns when one of its races (in radial coupling configuration) or one of its drive plates (in axial coupling configurations) rotates in a first (i.e., freewheel) direction relative to the other race or drive plate, and engages or locks in a second (i.e., lockup) direction. Such conventional one-way clutches provide no independent control over their modes of operation, that is to say whether they lockup or freewheel in both directions and are commonly referred to as passive one-way clutches. Thus, basic one-way clutches provide a "locked" mode in one rotary direction and a "freewheel" mode in the opposite direction based on the direction that the drive torque is being applied to the input race or drive plate.

[0005] There are however, requirements in modern automatic transmissions where a "controllable" overrunning coupling device, commonly referred to as a selectable oneway clutch (SOWC), can be selectively controlled to provide additional functional modes of operation. Specifically, a selectable one-way clutch may further be capable of providing a freewheel mode in both rotary directions until a command signal (i.e., from the transmission controller) causes a power-operated actuator to shift the coupling device into its lockup mode. Thus, a selectable one-way clutch may be capable of providing a drive connection between an input member and an output member in one or both rotational directions and it may also be operable to freewheel in one or both directions. It is also known in modern automatic transmissions to integrate a passive one-way clutch and a selectable one-way clutch into a combined coupling device, commonly referred to as a bi-directional clutch.

[0006] As noted, current OWC solutions provide engagement in one direction and ratcheting in the opposite direction with movement of the struts to a ratcheting position due to centrifugal forces. However, currently there are no simple solutions directed to preventing unintended clutch engagement at high relative speeds between the inner and outer members.

[0007] Thus, a need exists to continue development of new and improved overrunning coupling devices that advance the art and provide enhanced functionality. SUMMARY OF THE INVENTION

[0008] This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.

[0009] It is an aspect of the present disclosure to provide a one-way coupling device having a speed-dependent strut "tuck-in" feature configured to move the struts to a decoupled position relative to the ratchet teeth.

[0010] It is a further aspect of the present disclosure to provide a unique strut tip profile that is configured to interact with a mating ratchet tooth profile for rejecting the strut out of engagement in response to the strut tip not being fully located in a locking portion of the ratchet tooth.

[0011] It is yet another aspect to provide the one-way coupling device as a standalone one-way clutch or as a passive one-way clutch integrated into a bi-directional clutch assembly also having a controllable one-way clutch.

[0012] In accordance with one non-limiting embodiment, a passive one-way clutch includes an outer race pivotably supporting a plurality of passive struts, an inner race having outer ratchet teeth, and a speed-dependent disconnect mechanism for moving the passive struts from a ratcheting position into a tucked position relative to the ratchet teeth as a result of the centrifugal loading applied to the struts. The passive struts include a tip profile configured to reject the struts from engagement with the ratchet teeth if the strut tip is not fully positioned within a latching valley portion of the ratchet teeth.

[0013] In accordance with yet another non-limiting embodiment, a one-way clutch is provided including an inner race disposed about an axis and having ratchet teeth. An outer race is disposed about the axis and defines a strut pocket. A strut assembly is mounted in the strut pocket. The strut assembly includes a pivotable strut and a spring acting on the strut. The strut is pivotable between a first position engaged with one of the ratchet teeth, a second position ratcheting over the ratchet teeth, and a third position disengaged from ratcheting engagement with the ratchet teeth. The spring is arranged to bias the strut toward the first position. The strut moves from the second position into the third position in response to the rotary speed of the outer race exceeding a predetermined threshold speed value.

[0014] In accordance with yet another non-limiting embodiment, a one-way clutch is provided including a first race disposed about an axis and having ratchet teeth. A second race is disposed about the axis and defines a strut pocket. A strut is disposed in the pocket and includes a pivot segment being pivotably connected inside the pocket. A leg segment extends from the pivot segment along a strut axis. The leg segment is configured to be pivoted radially toward and away from the ratchet teeth of the inner race. A spring is positioned between the outer race and the leg segment of the strut and biases the strut toward the ratchet teeth. The leg segment of the strut terminates at a tip segment having a camming surface extending at an acute angle relative to the strut axis for contacting the ratchet teeth of the outer race in response to a rotary speed of the second race exceeding a predetermined threshold speed value, thus causing the camming surface to be partially radially spaced from the ratchet teeth such that the leg segment is mechanically rejected out of engagement with the ratchet teeth during rotation of the second race.

[0015] In accordance with yet another non-limiting embodiment, a bi-directional clutch assembly is provided including a first race presenting a plurality of first ratchet teeth, and a second race presenting a plurality of second ratchet teeth and a plurality of strut pockets. A passive one-way clutch includes a plurality of passive struts pivotably supported by the second race in the strut pockets for pivoting into engaging relationships with the first ratchet teeth during rotation of the second race in a first direction. A selectable one-way reverse clutch includes at least one active strut supported by the first race and selectively pivotable from an unlocked position wherein the active strut is disengaged from the second ratchet teeth to a locked position for engaging one of the plurality of second ratchet teeth during rotation of the second race in a second direction opposite the first direction. The plurality of passive struts are arranged to pivot between a first position engaged with the first ratchet teeth, a second position ratcheting relative to the first ratchet teeth, and a third position disengaged from ratchet engagement relative to the first ratchet teeth in response to a rotary speed of the second race exceeding a predetermined threshold value.

[0016] Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The drawings described herein are for illustrative purposes only of selected embodiments and are not intended to limit the scope of the present disclosure. The inventive concepts associated with the present disclosure will be more readily understood by reference to the following description in combination with the accompanying drawings wherein:

[0018] FIG. 1 is an exploded perspective view of a bi-directional clutch assembly configured to include a passive one-way clutch and a selectable one-way clutch having an electromechanical actuator; [0019] FIGS. 2 A is a sectional view of a bi-directional clutch assembly configured with a constant backlash arrangement between the struts of the passive and selectable one-way clutches;

[0020] FIGS. 2B and 2C are generally similar to FIG. 2A and more clearly indicates a plurality of sets of diametrically opposed passive sets associated with one non- limiting constant backlash configuration;

[0021] FIGS. 2D and 2E illustrate another alternative version of a bi-directional clutch assembly configured with a plurality of sets of passive struts in another embodiment of a constant backlash arrangement of the bi-directional clutch assembly;

[0022] FIG. 3 is a side view of an alternative version of a passive one-way clutch with each of the passive struts shown positioned in one of several possible operative positions;

[0023] FIG. 4 is an enlarged partial view of the passive one-way clutch shown in

FIG. 3 with the passive strut located in an engaged position relative to a ratchet tooth on the inner race; and

[0024] FIG. 5 is another enlarged partial view illustrating the passive strut located in a latch rejecting position relative to a ratchet tooth on the inner race.

DESCRIPTION OF THE ENABLING EMBODIMENTS

[0025] Example embodiments will now be described more fully with reference to the accompanying drawings. In general, each embodiment is directed to an overrunning coupling device (i.e. brake and/or clutch) having at least a passive one-way locking device including a moveable locking component (i.e. sprag, strut, etc.). However, the example embodiments are only provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well- known processes, well-known device structures, and well-known technologies are not described in detail.

[0024] Referring to the Figures, wherein like numerals indicate corresponding parts throughout the several views, a bi-directional clutch assembly 20 is generally shown. As will be detailed, bi-directional clutch assembly 20 generally includes a stationary outer race, a rotatable inner race, a passive one-way clutch having a plurality of passive struts, and a selectable one-way clutch having at least one active strut assembly and an electromagnetic actuator. The clutch assembly 20 includes an outer race 22 that extends annularly about an axis A. The outer race 22 includes an outer ring segment 24 and an inner ring segment 26 that are spaced radially from one another and interconnected via a radial web segment 27. The outer ring segment 24 presents a plurality of outer lugs 28 that extend radially outwardly for mating with a first component. The first component can be a stationary component (such as a housing of a transmission) or a rotary component (such as a shaft). The outer ring segment 24 further presents a pair of protrusions 30 that extend radially outwardly. Each of the protrusions 30 defines a radially extending actuator pocket 32 and a strut pocket 33. It should be appreciated that more or fewer protrusions 30 could be utilized. The inner ring segment 26 presents a plurality of inner ramp surfaces, hereinafter referred to as inner ratchet teeth 34, that extend radially inwardly and are evenly distributed or spaced from one another about the axis A to define an inner tooth degree spacing 0i. [0025] The clutch assembly 20 further includes an inner race 36 that also extends annularly about the axis A. The inner race 36 has an outer rim 38 and an inner rim 40 that are spaced radially from one another. The outer rim 38 is disposed radially between the outer and inner ring segments 24, 26 of the outer race 22, and the inner rim 40 is disposed radially inwardly from the inner ring segment 26 of the outer race 22. The inner rim 40 of the inner race 36 presents a plurality of inner lugs 42 that extend radially inwardly for mating with a second component (typically a rotary component). Commonly, lugs 42 interconnect a shaft or clutch plates for rotation with inner race 36. Further, the outer rim 38 of the inner race 36 presents a plurality of outer ramp surfaces, hereinafter referred to as outer ratchet teeth 44, that extend radially outwardly and are evenly distributed or spaced from one another about the axis A to define an outer tooth spacing angle 0 2 .

[0026] The passive one-way forward clutch includes a plurality of locking elements or passive struts 46 that are pivotally supported in strut apertures formed in the inner race 36 for pivoting between a locking position and an unlocking position. In the locking position, as exemplarily highlighted by circles in FIGS. 2C and 2E, the passive struts 46 engage the inner ratchet teeth 34 of the outer race 22 to define a forward engagement position for connecting the outer and inner races 22, 36 to one another during counter-clockwise rotation of the inner race 36 relative to the outer race 22. Therefore, the forward engagement position established by one or more of the passive struts 46 prevents relative displacement of the outer and inner races 22, 36 in the counter-clockwise direction. However, the passive struts 46 still allow relative displacement, i.e., overrun, in the clockwise direction when located in the locking position since they ratchet over the ramped profile of the inner ratchet teeth 34 and are radially spaced from the inner ratchet teeth 34 of the outer race 22 to establish the unlocking position. As best shown in FIG. 1, the passive struts 46 are biased towards the locking position by a biasing member 47, such as a spring or the like.

[0027] As shown in FIG. 1, the selectable one-way reverse clutch includes an active strut assembly 48 received by each of the strut pockets 33 of the outer ring segment 24. Each of the active strut assemblies 48 includes an active strut 50 that is selectively pivotal between a locked and an unlocked position. In the locked position, the active strut 50 lockingly engages the outer ratchet teeth 44 of the inner race 36 during clockwise movement of the inner race 22 relative to the outer race 22 to define a reverse engagement position thereby locking the outer and inner races 22, 36 to one another. However, the active strut 50 still allows relative displacement, i.e., overrun, in the counter-clockwise direction. In the unlocked position, the active strut 50 is radially spaced from the outer ratchet teeth 44, allowing the inner and outer races 22, 36 to rotate relative to one another. Furthermore, as best illustrated in Figure 1, each of the active strut assemblies 48 includes an armature 60 that is disposed adjacent to the active strut 50 for providing the pivotal movement of the active strut 50.

[0028] The selectable one-way reverse clutch also includes electromagnetic actuators 51, each including a coil assembly 52 mounted in the actuator pocket 32 and radially spaced from the active strut 50 and armature 60. The coil assembly 52 includes a core 54 of a magnetically permeable material, a bobbin 56 disposed about the core 54, and a coil 58 wrapped about the bobbin 56. Furthermore, the armature 60 is disposed between the active strut 50 and the coil 58 for pivoting toward the core 54 and thus providing the pivotal movement of the active strut 50 in response to energization of the coil 58.

[0029] More specifically, when voltage and/or current are applied to the coil 58, the coil 58 becomes an electromagnet producing an electric field (or flux). The flux flows outwards in all directions and transfers through the small air gap between the armature 60 and core 54 in the center of the coil assembly 52. The core 54 becomes magnetized, therefore attracting the armature 60 towards the core 54. The resulting motion forces the active strut 50 to mechanically deploy due to the linkage between the active strut 50 and the armature 60. On deployment, the active strut 50 moves from its unlocked position to its locked position where it locates itself against one of the outer ratchet teeth 44 of the inner race 36 to define the reverse engagement position, effectively locking the inner race 36 from rotating in that direction. Disengagement occurs as voltage and/or current is removed from the coil assembly 52, wherein the armature 60 is demagnetized and free from the coil assembly 52. A biasing spring (not shown) is positioned between the active strut 50 and the outer race 22, causing the active strut 50 to move back to its unlocked position during disengagement.

[0030] The combination of the passive and active struts 46, 50 provide for a bidirectional configuration of the clutch assembly 20 that allows engagement in two opposite directions (clockwise and counter-clockwise). It should be appreciated that the arrangement of the armature 60, active strut 50, and coil assembly 52 can act to apply a locking force not only in a radial direction (as shown in FIGS. 1 , and 2A-2E) but also in an axial direction, depending on the layout and/or requirements of the clutch assembly 20. Radial stacked clutch assembly designs offer packaging advantages over their axial counterparts in situations where axial space is tight, e.g., in automatic transmissions. Further, radially applied clutches transmit driving torque directly outwards to be grounded against the transmission housing without the fear of forces being directed axially which could cause problems for the sizing of other system components to compensate for axial force. [0031] To maintain functionality, it is desirable to maintain a consistent amount of backlash between the forward and reverse engagement positions of the passive and active struts 46, 50 so that the clutch assembly 20 is free to disengage in one direction before engaging in the opposite direction. Backlash is defined as travel in the opposite direction from a current forward or reverse engagement position that is required to release a first strut (i.e., passive or active strut) before the second (e.g., other) strut is in position to engage its respective teeth in the opposite direction. In other words, bi-directional backlash is the amount of rotational movement that is available between the forward engagement position and the reverse engagement position. Once again, the forward engagement position is defined by an engagement of the passive strut(s) with the inside ratchet teeth of the outer race and the reverse engagement position is defined by an engagement of the active strut(s) with the outside ratchet teeth of the inner race. If no backlash was available between the forward and reverse engagement positions, it is possible for both the passive and active struts/sprags to be engaged at the same time, thus preventing their disengagement and any relative movement between the inner and outer races whether it is intended or not. In contrast, with too much backlash, the engagement of the passive and active struts with the respective ratchet teeth in both directions may be perceived as rough and unrefined, detrimentally affecting the NVH characteristics of the transmission.

[0032] In accordance with an aspect of the subject disclosure, and with reference to FIGS. 2A-2E, clutch assembly 20' is configured to provide a constant amount of backlash between the forward and reverse engagement positions. Specifically, as will be described in more detail below, the active struts 50 of the clutch assembly 20' are circumferentially spaced from the inner struts 46 such that the active struts 50 never engage the outer ratchet teeth 44 on the inner race 36 as the passive struts 46 engage the inner ratchet teeth 34 on the outer race 22. To maintain constant backlash, engagement in one direction is optimally designed to occur midpoint between two consecutive possible engagements in the opposite direction.

[0033] Initially, as shown in FIGS. 2A-2E, the bi-directional clutch assembly 20' includes a plurality of passive struts 46 that are unevenly circumferentially spaced from one another along the inner race 36 to establish an indexed relationship among the plurality of passive struts 46. As highlighted in FIGS. 2C and 2E, this indexed relationship establishes a staggered engagement of sequential ones of the passive struts 46 with the inner ratchet teeth 34 of the outer race 22. Put another way, the indexed relationship among the passive struts 46 provides that only some of the passive struts 46 are engaged at any one time (with engaged passive struts highlighted by the circles) with sequential passive struts 46 being disposed in a ready to engage position. While all of the passive struts 46 could be engaged at the same time to increase the torque capability of the passive one-way forward clutch, such an arrangement increases the forward backlash and thus is detrimental to the function of the forward clutch as it results in an increase in NVH. The unevenly circumferentially spaced relationship of the passive struts 46 provides for greater engagement precision between the passive struts 46 and the inner ratchet teeth 44 which leads to decreased forward backlash for the passive one-way forward clutch.

[0034] As best illustrated by FIGS. 2A-2E, in a preferred and non-limiting arrangement of the bi-directional clutch assembly 20', the passive one-way clutch includes six passive struts 46 that are pivotably supported by inner race 36. However, it should be appreciated that more or fewer passive struts 46 could alternatively be utilized. In this preferred arrangement, as best illustrated by FIGS. 2B-2E, the indexed relationship among the passive struts 46 can be accomplished by grouping the passive struts into a plurality of sets 62a, 62b, 62c, 62d, 62e of evenly circumferentially spaced passive struts 46. For example, as best illustrated by FIGS. 2B and 2C, in a non-limiting example the passive struts 46 are grouped into multiple sets of diametrically opposed passive struts 62a, 62b, 62c, with each one of the passive struts 46 in the sets 62a, 62b, 62c disposed 180 degrees from each other. Alternatively, as best illustrated by FIGS. 2D and 2E, in another non-limiting example, the passive struts 46 can be grouped into multiple sets of passive strut trios 62d, 62e, with each set 62d, 62e including a trio of passive struts disposed 120 degrees apart from one another.

[0035] Depending on the application, it is desirable to have improved engagement precision (less backlash) which can be achieved by positioning the sets 62a, 62b, 62c, 62d, 62e of passive struts in a circumferentially indexed manner. For example, in each exemplary arrangement of the sets 62a, 62b, 62c, 62d, 62e of passive struts, and as illustrated in FIGS. 2B- 2E, a first set 62a, 62d of the sets of passive struts are a reference, or un-indexed, set of passive struts and then each sequential set 62b, 62c, 62d of passive struts is circumferentially indexed towards a preceding set of the passive struts by a forward indexing angle. As will be described in more detail below, the forward indexing angle is equal to the inner tooth degree spacing Qi (i.e., number of degrees between adjacent inner ratchet teeth) divided by the number of sets of passive struts.

[0036] For example, in the non-limiting embodiment shown in FIGS. 2A-2E, the outer race 22 exemplarily includes sixty (60) inner ratchet teeth 34 with each of the inner ratchet teeth 34 spaced by six (6) degrees from one another (i.e., the inner tooth degree spacing θι). With reference to FIGS. 2B and 2C, when the sets of passive struts 62a, 62b, 62c are comprised of a pair of diametrically opposed passive struts, the sets of diametrically opposed passive struts 62a, 62b, 62c are indexed so that only a single pair of diametrically opposed passive struts are engaged with the inner ratchet teeth 34 of the outer race 22 at any one time. In order to avoid simultaneous engagement of all sets 62a, 62b, 62c of passive struts with the inner ratchet teeth 34 of the outer race 22, a first pair of diametrically opposed passive struts 62a is considered the "reference" or un-indexed set and the sequential or second pair of diametrically opposed passive struts 62b is positioned circumferentially indexed (i.e. staggered) towards the reference first pair 62a by the forward indexing angle, in this case 2 degrees (i.e., 6 degrees of inner tooth spacing between two consecutive teeth divided by three sets of diametrically opposed passive struts = a 2 degree forward indexing angle). Similarly, the next sequential or third set 62c of diametrically opposed passive struts is circumferentially indexed towards the second set 62b by the forward indexing angle, i.e., 2 degrees. Accordingly the three sets of diametrically opposed passive struts pairs 62a, 62b, 62b can engage the inner ratchet teeth 34 during every two degrees of rotation in the first direction.

[0037] As best illustrated in FIG. 2C, the aforementioned indexing disposes each sequential set 62b, 62c of passive struts at a spacing angle Bs relative to the preceding set of passive struts by an equidistant angle (equal to 360 degrees divided by the number of passive struts 46) minus the forward indexing angle. For example, if the six passive struts 36 were designed to collectively engage the inner ratchet teeth 34 at the same time, each of the six passive struts 36 would be equidistantly spaced from one another by an equidistant angle of 60 degrees. However, in this instance, each sequential set 62b, 62c of passive struts is indexed towards a preceding set of passive struts by the forward indexing angle of 2 degrees. Accordingly, each sequential set 62b, 62c of passive struts is disposed at a spacing angle 0s of 58 degrees, leaving the remaining angle BR which extends between the last of the sequential sets 62c of diametrically opposed passive struts and the reference set 62a of diametrically opposed passive struts to be 64 degrees (i.e., 180 degrees minus 2 x 58 degrees).

[0038] In the other non-limiting embodiment, and with reference to FIGS. 2D and

2E, the indexed relationship between the sets of passive struts is further explained using the same number of passive struts 46 and inner ratchet teeth 34, but with the sets of passive strut trios 62d, 62e having a tri-engagement configuration. As will be explained below, such an arrangement leads to increased torque capacity over the sets of diametrically opposed passive strut pairs with slightly less engagement precision. Specifically, as described previously, the plurality of sets 62d, 62e of passive struts trios are made up of groups of three passive struts 46 each equi distantly spaced one hundred and twenty degrees (120) from one another. In this arrangement, only one trio of passive struts is engaged with the inner ratchet teeth 34 of the outer race 22 at one time. Once again, the first set 62d of passive strut trios is classified as a first or "reference" set and a second or sequential set 62e of passive strut trios group is circumferentially indexed (i.e., staggered) towards the first set 62d of passive strut trios by the forward indexing angle, in this case 3 degrees (i.e., 6 degrees of inner tooth spacing between two consecutive teeth divided by two sets of passive strut trios = a 3 degree forward indexing angle). Accordingly the two sets of passive struts trios 62d, 62e can each engage the inner ratchet teeth 34 during every three degrees of rotation in the first direction. This arrangement achieves greater torque capacity over use of the sets comprised of pairs of diametrically opposed passive struts via a triple engagement of the passive struts 46 with the inner ratchet teeth 34 of the outer race 22 while providing slightly more backlash (i.e., a 3 degree forward indexing angle vs. a 2 degree forward indexing angle). [0039] As best illustrated in FIG. 2E, the aforementioned indexing disposes the sequential set 62e of passive strut trios at a spacing angle 0s relative to the preceding (and in this case reference) set 62d of passive strut trios by an equidistant angle (equal to 360 degrees divided by the number of passive struts 46) minus the forward indexing angle. In this instance, the sequential set 62e of passive strut trios is indexed towards the preceding (and reference) set 62d of passive strut trios by the forward indexing angle of 3 degrees. Accordingly, the sequential set 62e of passive strut trios is disposed at a spacing angle 0s of 57 degrees, leaving the remaining angle OR which extends between the sequential set 62e of passive strut trios and the reference set 62d of passive strut trios to be 63 degrees (i.e., 120 degrees minus 57 degrees).

[0040] As will be appreciated, the actual angle values described previously can change depending on the required angular backlash, the number of passive struts 46 employed, the number of inner ratchet teeth 34, and the desired type of engagement (e.g., single, dual, triple, or quadruple engagement).

[0041] As previously mentioned, the bi-directional clutch assembly 20' also includes a selectable one-way reverse clutch which includes at least one active strut 50 that is selectively pivotable from an unlocked position to a locked position. In the locked position, the active strut 50 engages one of the plurality of outer ratchet teeth 44 during rotation of the inner race 36 in a second direction opposite the first direction to define the reverse engagement position. As best illustrated in FIGS. 2A-2E, in a non-limiting embodiment the bi-directional clutch assembly 20' includes a plurality of active struts 50, preferably two active struts 50, which are collectively pivotable from the unlocked position to the locked position. However, additional active struts 50 can be utilized without departing from the scope of the subject disclosure. Similar to the plurality of passive struts 46, the plurality of active struts 50 are also circumferentially indexed relative to one another to reduce and optimize the reverse backlash for the bi-directional clutch assembly 20'. Accordingly, while the bi-directional clutch assembly 20 of FIGS. 2A-2E includes two electrically-actuated active struts, only one active strut is engaged with a respective one of the ratchet teeth at any one time (i.e., single engagement) with the other active strut 50 being disposed in a ready to engage position.

[0042] Similar to the indexing of the passive struts 46, a first one of the plurality of active struts 50 is a reference, or non-indexed, active strut 50 and each sequential active strut 50' is circumferentially indexed towards the preceding active strut 50 by a reverse indexing angle. As will be described in the following exemplary arrangements, the reverse indexing angle is equal to the outer tooth degree spacing 0 2 (i.e., number of degrees between adjacent outer ratchet teeth 44) divided by the number of active struts 50. For example, as illustrated in FIGS. 2A-2E, in the non-limiting example of the bi-directional clutch assembly 20', the inner race 22 includes ninety (90) outside ratchet teeth 44 for being engaged by the active struts 50 of the outer race 22. Accordingly, each of the outside ratchet teeth 44 is spaced by four degrees from one another (i.e., the outer tooth degree spacing Θ2) Further, since there are two electrically-actuated active struts 50, the sequential active strut 50' is indexed towards the reverse indexing angle, in this case two degrees (i.e., the outer tooth degree spacing Θ2 of four degrees divided by two active struts). Accordingly, engagement between the active struts 50 and outside ratchet teeth 44 can occur during every two degrees of rotation of the inner race 36. In other words, the active struts 50 do not engage the inner race 36 simultaneously but rather only when one active strut 50 is disposed in the reverse engagement position with the other active strut preferably spaced halfway between two consecutive outer ratchet teeth 44. [0043] In a preferred arrangement, this reverse indexing angle (e.g., reverse clutch backlash) is equal to, or a multiple of, the forward indexing angle (e.g., forward clutch backlash) to prevent lock-up or binding of the forward and reverse transmission clutches during operation. As an example, if the forward indexing angle (e.g., forward clutch backlash) is 2 degrees, the reverse indexing angle (e.g., reverse clutch backlash) can be 2, 4, 8 degrees and so on. Likewise, if the forward indexing angle (e.g., forward clutch backlash) is 1.5 degrees, the reverse indexing angle (e.g., reverse clutch backlash) can be 1.5, 3.0, 4.5, 6.0 degrees and so on. This relationship between the forward and reverse indexing angles can be applied in both directions such that the forward clutch backlash can be equal to, or a multiple of, the reverse clutch backlash. For example, if the reverse indexing angle (e.g., reverse clutch backlash) is 2 degrees, the forward indexing angle (e.g., forward clutch backlash) can be 2, 4, 8 degrees and so on. As a non-limiting example, with reference to the arrangement of the bi-directional clutch assembly 20' including a plurality of sets of diametrically opposed passive struts 62a, 62b, 62c, the forward indexing angle is equal to 2 degrees and the reverse indexing angle of the active struts 50 is also 2 degrees.

[0044] As previously described, when the passive struts 46 engage the inner ratchet teeth 34 of the outer race 22, this defines a forward engagement position for connecting the outer and inner races 22, 36 to one another during counter-clockwise rotation of the inner race 36 relative to the outer race 22. This forward engagement position established by one or more of the passive struts 46 prevents relative displacement of the outer and inner races 22, 36 in the counter-clockwise direction. To maintain constant functionality for the bi-directional clutch assembly 20', it is desirable to maintain a consistent amount of backlash between the forward and reverse engagement positions (i.e., forward-to-reverse backlash) of the passive and active struts 46, 50 so that the clutch assembly 20' is free to disengage in one direction before engaging in the opposite direction. In other words, forward-to-reverse backlash is the amount of rotational movement that is available between the forward engagement position and the reverse engagement position. Backlash less than 0.5 degrees can bind the clutch due to elastic deformation caused during loading. In contrast, backlash exceeding 1.5 degrees has a negative influence on NVH. In a preferred arrangement of the bi-directional clutch assembly 20', the forward-to-reverse backlash is between 0.75 and 1.25 degrees, and preferably approximately 1.0 degree. This arrangement permits a constant amount of predetermined forward-to-reverse backlash to be introduced into the clutch assembly. Providing for such evenly distributed backlash improves bi-directional clutch functionality when switching between the engagement of the passive and active struts 46, 50 and thus ensures consistent disengagement when required.

[0045] The basic theory for the integration of a mechanism providing backlash control is that engagement in one direction should be designed to occur between two possible engagements in the opposite direction. With reference to the above disclosed alternative embodiments, the number of struts, inner and outer ratchet teeth and type of engagement (single, double, triple or quad) provides a desired combination of torque capacity and backlash.

[0046] Referring now to FIGS. 3-5, a passive one-way clutch 100 is generally shown to include an outer race 102 extending annularly about an axis A, an inner race 104 also extending annularly about the axis A, and a plurality of passive strut assemblies 106. Outer race 102 defines a series of contoured strut pockets 108 each having a pivot pocket section 110, a tuck-in pocket section 112, and a spring retainer pocket section 114. Each strut assembly 106 includes a strut 120 and a biasing spring 122. Each strut 120 is configured to include a cylindrical pivot segment 124 retained in a corresponding pivot pocket section 100, an elongated leg segment 126 retained in tuck-in pocket section 112, and a tip segment 128. Each biasing spring 122 is retained in spring retainer pocket section 114 and engages leg segment 126 of a corresponding strut 120.

[0047] For purposes of illustration only, a first strut 120a is shown with its tip segment locking engaged within a ratchet tooth, one of a series of ratchet teeth 130, formed on inner race 104. A second strut 120b is shown with its tip segment riding along or "ratcheting" over another ratchet tooth. A third strut 120c is shown with its leg segment fully retracted into tuck-in pocket section 112 such that its tip segment is decoupled from any type of engagement with ratchet teeth 130. Finally, a fourth strut 120d is shown, similar to first strut 120a, in a fully engaged or deployed position relative to inner race 104. Pivotal movement of struts 120 between a first or engaged position of strut 120a, a second or ratcheting position of strut 120b, and a third or tucked position of strut 120c is a result of the centrifugal forces applied thereto upon rotation of outer race 102, as will be detailed hereinafter. Note that biasing spring 122a is shown permitted to bias strut 120a into its fully deployed and engaged position, biasing spring 122b is shown partially compressed to establish the ratcheting position of strut 120b, and biasing spring 122c is shown fully compressed to locate strut 120c in its decoupled position. Biasing spring 122d functions to locate strut 120d in its fully deployed position. As previously disclosed, backlash can be controlled with struts 120 arranged to permit one or more to be engaged with corresponding ratchet teeth 130.

[0048] The present disclosure is also directed to an improved profile for tip segment 128 of struts 120 which is configured to interact with ratchet teeth 130 on inner race 104. Specifically, and as best seen in FIGS. 4 and 5, the leg segment 126 of each strut 120 extends from the pivot segment 124 along a strut axis S. Furthermore, strut 120 is shown with its tip segment 128 having a contoured edge profile defining a first locking surface 140, a second locking surface 142, a camming surface 144 interconnecting first and second locking surfaces 140, 142, and a terminal end surface 146. In the example embodiment, the terminal end surface 146 extends generally perpendicularly to the strut axis S. It should be appreciated that all or part of the terminal end surface 146 may extend slightly non-perpendicularly to the strut axis S. As illustrated, the camming surface 144 extends radially inwardly at an acute angle 03 relative to the strut axis S. In the example embodiment, the angle is approximately 45 degrees. Each ratchet tooth 130 includes a latch valley 150 defined by a ratchet section 152 and a latch section 154 interconnected by a bottom section 156. Each tooth 130 also includes an outer diameter surface 158. A blend radius 160 interconnects outer surface 158 to latch section 154 of each ratchet tooth 130. FIG. 4 illustrates strut 120 biased by biasing spring 122 into its engaged position such that tip segment 128 is lockingly retained in latch valley 150 of one of ratchet teeth 130. More particular, in this arrangement, the terminal end surface 146 engages the latch section 154 of the tooth 130. In contrast, FIG. 5 illustrates strut 120 biased by biasing spring 122 such that camming section 144 on tip segment 128 is radially aligned with, and engages blended radius 160 of ratchet tooth 130.

[0049] As designed, strut tip 128 is configured to be mechanically "rejected" from engagement with tooth valley 150 of ratchet teeth 130 if the position of strut tip 128 is not radially deep enough within teeth valley 150 - that is to say - if strut 120 is not completely located in its deployed and fully engaged position (FIG. 4). In operation, the depth of strut tip 128 within tooth valley 150 depends on several factors including the relative rotary speed between strut 120 (and outer race 102) and inner race 104, and the spring force exerted on strut 120 by biasing spring 122. [0050] In the non-limiting embodiment shown, outer race 102 always rotates in a predefined direction, say counterclockwise (CCW), and its speed can vary between zero (stationary) and a maximum established via a particular clutch application. When outer race 102 is rotating, the centrifugal forces generated act on struts 120 to force them to pivot about their rotational axes (within pivot pocket section 110 of strut pocket 108) and forcibly compress biasing spring 122 within spring retainer pocket section 114. Once a predetermined tucking speed threshold for outer race 102 is exceeded, struts 120 will be located in their tucked position such that a backside surface 170 of leg segment 126 will engage a stop surface 172 within tuck- in pocket section 112 of strut pocket 108 such that strut tip section 128 is displaced to a position completely disengaged or "decoupled" from any of ratchet teeth 130. The tucking speed threshold for outer race 102 required for complete tuck-in of struts 120 is dependent on several factors including, without limitations, the strut pitch diameter, the spring force of biasing spring 122, the profile of leg segment 126 and tip section 128 of strut 120, and the total mass of strut 120. This threshold value can be easily adjusted or calibrated by simply changing the spring load provided by springs 122.

[0051] Inner race 104 can rotate in both directions relative to outer race 102. In one direction - say the clockwise (CW) direction - struts 120 will ratchet over ratchet teeth 130 to establish the freewheeling clutch mode. In contrast, rotation of inner race 104 in the CCW direction causes struts 120 to engage ratchet teeth 130 and establish the locked clutch mode when inner race 104 attempts to rotate faster than outer race 102.

[0052] Under certain operating conditions, and depending on the relative speed differential between inner race 104 and outer race 102 - provided that the outer race 102 speed is less than the predetermined threshold value - it is imperative to prevent struts 120 from engaging inner race 104 to inhibit undesired shock loads from being developed within clutch 100. To prevent this, camming section 144 on strut tip 128 is arranged to cam against radius 160 of ratchet tooth 130. As such, if tip segment 128 of strut 120 is not fully engaged within tooth valley 150, contact between strut camming section 144 and blend radius 160 will result in strut 120 being mechanically rejected out of engagement (FIG. 5) in opposition to the biasing of spring 122. More particularly, as shown in FIG. 5, in this position, the strut tip 128 is radially spaced from the tooth valley 150 such that the camming section 144 is partially positioned radially outward of the tooth outer diameter surface 158, and partially radially aligned with the blend radius 160 of ratchet tooth 130. This causes the leg segment 126 of the strut 120 to be mechanically rejected out of engagement with the ratchet tooth 130 in opposition to the biasing spring 122 during rotation of the second race 102. It should be appreciated that the acute angle Θ3 at which the camming section 144 extends may be chosen based on the size and arrangement of the blended radius 160. In the example embodiment, utilizing less than or equal to a 45 degree actuate angle Θ3 ensures that a mechanical rejection of the strut 120 is provided during contact against the blended radius 160. On the other hand, as set forth in FIG. 4, when the strut tip section 128 is fully deployed, the terminal end surface 146 engages the latch section 154 of the tooth 130 to inhibit rotation of the second race 102.

[0053] The position of strut 120 relative to tooth valley 150 of ratchet tooth 130 depends on the relative speed between races 102, 104, the tooth and strut tip profiles, and the spring force of spring 122. Specifically, it is a matter of a first time (Ti) required for strut 120 to angularly move from its ratcheting position whereat its tip segment engages outer surface 158 of tooth 150 until it is in its deployed and fully engaged position within tooth valley 150. Ti depends on the mass of strut 120 and the spring force of spring 122. If we consider a second time (T 2 ) that is required for tip segment 128 of strut 120 to travel between OD surface 158 on two consecutive teeth 130, this time period is dependent on the relative speed between inner race 104 and outer race 102. Thus, if (Ti < T 2 ), strut 120 will always engage. However, if (Ti > T 2 ), strut 120 will be rejected from ratchet tooth 130.

[0054] In summary, the strut profile works with the inner race tooth profile in such a way that, when inner race 104 rotates CCW, struts 120 will ratchet and will not engage inner race 104 unless the inner race 104 has a rotary speed below a certain threshold (i.e. less than 700 rpm). In this way, torque spikes are prevented. Also, above the threshold rotary speed of outer race (i.e. greater than 1700 rpm), struts 120 are centrifugally moved into their tucked position. Thus, torque transmittal is permitted under certain conditions, while prohibiting strut engagement if the relative speed between the two rotating members is not within a predefined safe limit. Components can be net-shaped, including strut pockets in outer race 102 and struts 120.

[0055] Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail.

[0056] The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms "a," "an," and "the" may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms "comprises," "comprising," "including," and "having," are inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed.

[0057] When an element or layer is referred to as being "on," "engaged to,"

"connected to," or "coupled to" another element or layer, it may be directly on, engaged, connected or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being "directly on," "directly engaged to," "directly connected to," or "directly coupled to" another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., "between" versus "directly between," "adjacent" versus "directly adjacent," etc.). As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

[0058] Although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another region, layer or section. Terms such as "first," "second," and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the example embodiments.

[0059] Spatially relative terms, such as "inner," "outer," "beneath," "below,"

"lower," "above," "upper," and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. Spatially relative terms may be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as "below" or "beneath" other elements or features would then be oriented "above" the other elements or features. Thus, the example term "below" can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

[0060] It should be appreciated that the foregoing description of the embodiments has been provided for purposes of illustration and the aforementioned teachings for providing a centrifugally-actuated decoupling arrangement could be utilized on other one-way clutch assembly configurations. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varies in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of disclosure.