Actuator for multi-mode clutch module

A transmission clutch module including inner and outer races, a plurality of race engaging pawls and an actuator ring incorporates an actuator having a rotatable spool header adapted to rotate an attached actuator lever between at least two angular positions. The actuator lever moves the actuator ring to selectively block the pawls so inner and outer races may freewheel relative to one another in at least one operating mode. The actuator may be electric or hydraulic powered, and may be spring-biased to a default position in event of power failure. An elongated axially moveable plunger is secured to and supported within a piston at a first end, and has a radially extending pin at its second end. A fixed spool sleeve to which the spool header is supported includes a helical slot through which the pin extends. As the plunger moves reciprocally, the pin undergoes both translational and rotational movement.

FIELD OF DISCLOSURE

The present disclosure relates generally to overrunning clutches for automotive transmissions, and more particularly to multiple mode clutch actuators employed in operation of such transmissions.

BACKGROUND OF DISCLOSURE

An automotive vehicle typically includes an internal combustion engine containing a rotary crankshaft configured to transfer motive power from the engine through a driveshaft to turn the wheels. A transmission is interposed between engine and driveshaft components to selectively control torque and speed ratios between the crankshaft and driveshaft. In a manually operated transmission, a corresponding manually operated clutch may be interposed between the engine and transmission to selectively engage and disengage the crankshaft from the driveshaft to facilitate manual shifting among available transmission gear ratios.

On the other hand, if the transmission is automatic, the transmission will normally include an internal plurality of automatically actuated clutches adapted to dynamically shift among variously available gear ratios without requiring driver intervention. Pluralities of clutches, also called clutch modules, are incorporated within such transmissions to facilitate the automatic gear ratio changes.

In an automatic transmission for an automobile, anywhere from three to ten forward gear ratios may be available, not including a reverse gear. The various gears may be structurally comprised of inner gears, intermediate gears such as planet or pinion gears supported by carriers, and outer ring gears. Specific transmission clutches may be associated with specific sets of the selectable gears within the transmission to facilitate the desired ratio changes.

Because automatic transmissions include pluralities of gear sets to accommodate multiple gear ratios, friction drag is a constant issue; the drag arises from mechanical interactions of the various parts employed. Much effort has been directed to finding ways to reduce friction drag within automatic transmission components and systems.

For example, one of the clutch modules of an automatic transmission associated with first (low) and reverse gear ratios may be normally situated at the front of the transmission and closely adjacent the engine crankshaft. The clutch may have an inner race and an outer race disposed circumferentially about the inner race. One of the races, for example the inner race, may be drivingly rotatable in only one direction. The inner race may be selectively locked to the outer race via an engagement mechanism such as, but not limited to, a roller, a sprag, or a pawl, as examples. In the one direction, the inner race may be effective to directly transfer rotational motion from the engine to the driveline.

Within the latter system, the outer race may be fixed to an internal case or housing of an associated planetary member of the automatic transmission. Under such circumstances, in a first configuration the inner race may need to be adapted to drive in one rotational direction, but freewheel in the opposite direction, in a condition referred to as overrunning. Those skilled in the art will appreciate that overrunning may be particularly desirable under certain operating states, as for example when a vehicle is traveling downhill. Under such circumstance, a driveline may occasionally have a tendency to rotate faster than its associated engine crankshaft. Providing for the inner race to overrun the outer race may avoid damage to the engine and/or transmission components.

In a second configuration, such as when a vehicle may be in reverse gear, the engagement mechanisms may be adapted for actively engaging in both rotational directions of the inner race, thus not allowing for the overrunning condition in the non-driving direction.

Above certain thresholds of rotational speed, the need for interaction of the engagement mechanisms, particularly those associated with the first (low) and/or reverse gear ratios, may become unnecessary. Thus, rather than contributing to drag, for example at highway speeds, there is substantial motivation to reduce and/or avoid interaction of the engagement mechanisms with any of the clutch parts, particularly those associated with the low/reverse clutch module.

SUMMARY OF DISCLOSURE

In accordance with one aspect of the disclosure, an actuator for a multi-mode clutch module is disclosed. The clutch module comprises an inner race; a fixed outer race disposed concentrically about the inner race, and a plurality of engagement mechanisms circumferentially disposed between the inner and outer races. Each engagement mechanism is adapted to provide a locked position, wherein, via the actuator, the mechanism locks the inner race to the outer race in a driving rotational direction, and an unlocked position that allows the inner race to freewheel in an opposite, non-driving, rotational direction.

In accordance with another aspect, the multi-mode clutch module includes an actuator ring having two positions, one position locking a first, driving directional, rotational motion of the inner race, but allowing the inner race to freewheel in an opposed second direction.

In accordance with another aspect, the actuator ring of the clutch module incorporates a second position that assures the locking of the inner race in both directions of rotational motion with respect to the outer race.

In yet another aspect, the engagement mechanisms may be adapted to centrifugally disengage from the races at a specific rotational speed of the inner race.

These and other aspects and features of the present disclosure may be better appreciated by reference to the following detailed description and accompanying drawings.

It should be understood that the drawings are not to scale, and that the disclosed embodiments are illustrated only diagrammatically and in partial views. It should also be understood that this disclosure is not limited to the particular embodiments illustrated herein.

DETAILED DESCRIPTION

Referring toFIG. 1, a clutch module10may be adapted to be utilized as a sub-unit of an automatic transmission (not shown). Such a transmission may be employed in a front-wheel driven automobile, for example. The clutch module10may include an exterior case or housing12, as well as an interior driven hub14adapted for transfer of power from an engine (not shown) to a vehicular driveline (not shown).

Axially oriented, circumferentially spaced cogs16are provided on the outside periphery of the interior driven hub14. Referring now also toFIG. 2, an inner race20is formed as two plates20A and20B spaced along an axis “A-A”. The cogs16are adapted for supporting rotary movement of the plates along the axis. For this purpose, the plates20A and20B have circumferentially spaced detents18on their inside peripheries; the detents are adapted to engage the cogs16.

With specific reference now toFIG. 2, an outer race22is situated between the two inner race plates20A and20B. Although the inner race plates20A and20B are specifically displayed in this disclosure as ring structures, other configurations may be suitable for use within the scope of this disclosure. The outer race22is rotationally fixed with respect to the interior of the exterior case or housing12as shown within the multi-mode clutch module10, and an actuator ring24is situated between the outer race22and the plate20B of the inner race20. The actuator ring24is adapted to be rotated over a small angle about the axis A-A between two circumferentially spaced positions, as further described below. Within its interior periphery, the actuator ring24incorporates a strategically situated array of circumferentially spaced recesses, herein called slots26, defined by and situated between projections, herein called teeth28. The slots26and teeth28are adapted to interact with pawls30, as now described.

As depicted and disclosed herein, the pawls30are elongated hardened steel members circumferentially positioned about the axis A-A of the clutch module10. Alternatively, the pawls maybe forgings or other manufactured structures, otherwise generally adapted to handle required loads of engagement between the inner and outer races20,22, as necessary for any particular clutch design. To accommodate interactions in both directions of relative rotation between the inner race20and the outer race22, the pawls are arranged in sets of opposed pairs,30A and30B, as shown. The actuator ring24is adapted to selectively block interactions of the pawls30A and30B between the inner race20and the outer race22, as further described below.

A hydraulic actuator32(FIGS. 1,2, and3) is secured to the module housing12, and includes an actuator lever34, which in turn moves an actuator tab40(FIGS. 2 and 3). The axially projecting actuator tab40is formed on a peripheral edge of the actuator ring24; the ring24rotates between two angularly spaced positions, as noted above. Referring now more specifically toFIG. 3, the inner race plates20A and20B, the outer race22, and the actuator ring24are shown assembled within the cross-sectioned partial view of the clutch module10. Axially extending rivets42(FIG. 2) are used to secure the two inner race plates20A and20B together. The rivets42extend through apertures43(FIG. 3) in each of the plates20A and20B to hold the two plates rigidly together, and to assure against any relative rotation between respective plates. In lieu of the rivets42, other structural fasteners may be employed within the scope of this disclosure to secure the inner race plates20A,20B together.

In view of the foregoing, it will be appreciated that the actuator32controls movement of the actuator tab40which, in turn, rotates the actuator ring24between the two angular positions. Actual positioning of the pawls30A and30B, axially retained between the riveted inner race plates20A and20B, is directly controlled by the actuator ring24against forces of pawl springs44, as further described below.

Referring now specifically toFIG. 3, it will be noted that the two inner race plates20A and20B, are adapted to rotate within the case or housing12. If the actuator ring24is in the first of its two specific angular positions, one set of the pawls, e.g. pawls30B, will lock the inner race20(i.e., plates20A and20B) to the outer race22, to drivingly rotate in one direction, for example counterclockwise. In the opposite rotational direction, e.g. clockwise, the pawls30A will be unlocked whenever the clutch module10in an automatic first or drive gear configuration so as to permit freewheeling of the inner race20relative to the outer race22.

Alternatively, when the actuator ring24is in the second of its two angular positions, both sets of pawls30A and30B, will lock the inner race to the outer race in either rotational direction to accommodate a reverse or manual first gear configuration; i.e. when in a mode during which no overrunning is desirable. In both configurations of the multi-mode clutch, it will be noted that the outer race22remains non-rotatable relative to the exterior case or housing12. For accommodating desired engagement with the pawls30A and30B, the inner circumference of the outer race22(FIG. 2; see bottom portion thereof) contains circumferentially spaced notches36, each defined by and situated between pairs of radially inwardly projecting cogs38.

Referring now toFIGS. 4A and 5A, first and second angular positions of the actuator tab40are depicted, respectively. InFIG. 4A, the actuator tab40is shown in a first (angularly rightward) selectable position, representative of the first described one-way clutch mode. In the latter configuration, the actuator ring24is positioned so that toe ends50of the pawls30A are blocked by teeth28from engagement with the notches36, and hence with the cogs38on the interior of the outer race22. As such the inner race20is enabled to freewheel relative to the outer race22, and to thus provide for an overrunning condition when the inner race20is rotating clockwise as shown. Conversely, however, the position of the actuator ring24allows of the toe ends52of the pawls30B to engage the actuator slots26of the actuator ring24, and to thereby directly engage the cogs38of the outer race22to lock the inner and outer races,20and22together whenever the inner race20undergoes a driving, or counterclockwise (CCW) rotational movement, as indicated by arrow.

InFIG. 5A, the actuator tab40is shown in a second (angularly leftward) selectable position, representative of a manual first or reverse gear mode. In the latter configuration, the actuator ring24is positioned so that the toe ends50,52of both sets of the pawls30A and30B engage the actuator slots26of the actuator ring24, and interact with the outer race22as described above to lock the inner race20to the outer race22, irrespective of the rotational direction of the inner race20.

Continuing reference now to bothFIGS. 4A and 5A, the pawls30A and30B are asymmetrically shaped, and reversely identical. Each pair of the opposed pawls is movably retained within its own bowtie-shaped pawl aperture60(FIG. 3) of the respective inner race plates20A and20B. Each individual pawl30A,30B is urged radially outwardly via a single spring44. Each spring has a base45, and a pair of spring arms46and48. The spring arms46bear against the bottoms of the pawls30A, while the spring arms48bear against the bottoms of the pawls30B, each to urge respective toe ends50,52into engagement with the cogs38of the outer race22.

Although the use of a leaf-style spring is depicted and described herein, an alternative type of spring or even other biasing arrangements may be employed. For example, a pair of coil springs could be used; e.g., one for each of the pair of opposed pawls30A,30B.

Opposite each toe end50and52, each pawl30A and30B has a heel end54and56, respectively (FIGS. 4A and 5A). As already described, the slots26in the interior circumference of the actuator ring24can be selectively positioned so that each toe end50,52engages a notch36(FIG. 2) of the outer race22to permit the toe ends to engage outer race cogs38(FIG. 2) in the interior circumference of the outer race22to physically lock the inner and outer races together.

Operationally, radially inwardly depending actuator ring teeth28are adapted to selectively block such toe ends50,52of the pawls30from being urged radially outwardly by respective spring arms46,48and into notches36. The interaction of the teeth28with such toe ends50,52defines the mechanism that permits the earlier described freewheeling of the inner race20relative to the outer race22as, for example, in the case of the above-described configuration for manual first or reverse gear.

In the immediate disclosure, the heel ends54and56may be designed to contain more mass than the toe ends50,52, so that at a particular threshold rotational speed of the inner race20, the heel ends will tend to swing radially outwardly under centrifugal forces of rotation. This action will cause the toe ends50,52to become disengaged from notches36of the outer race22. As such, the inner race20will become disengaged from the outer race22. Under such forces, the toe ends of pawls30A will bear down against the spring arms46, while the toe ends52of pawls30B will respectively bear against spring arms48. In each case, the differential in mass between heel and toe ends must be designed to 1) overcome the resistive forces imposed by the respective spring arms46,48of the springs44, and 2) achieve such centrifugal force induced load against the respective spring arms46,48at a specific rotational speed threshold.

Thus, in either of the first or reverse gear configurations of the clutch module10, and at rotational speeds of the inner race20in excess of a threshold of 500 RPM, for example, the pawls30A and30B of the clutch module10are adapted to become disengaged under centrifugal forces imposed thereon by a predetermined speed of rotation. At such threshold speed, the centrifugal forces will be sufficient to overcome the radially opposing forces of the spring arms46,48, and the toe ends50,52of the pawls will disengage. As such, this disclosure offers an effective way to reduce and/or avoid parasitic drag loads within the clutch module.

Referring now more particularly toFIGS. 4B and 5B, the interior operating structure of the actuator32is shown in detail. The actuator32includes an actuator lever34rotatable between the two angular limits of rotation, as previously described in reference toFIGS. 2 and 3. The lever34extends into a slot41of the actuator tab40, as best viewed inFIG. 2.

FIG. 4Bdepicts the lever34in a one-way clutch mode position corresponding toFIG. 4A. Conversely,FIG. 5Bdepicts the lever34in its opposite position in which the inner and outer races are locked in both directions, corresponding toFIG. 5A. The actuator32includes an exterior housing62affixed to the clutch module housing12, and to which is secured a rotatable spool header64from which the moveable lever34radially extends into the slot41. The rotatable spool header64is axially mounted on a non-rotatable spool sleeve86that may be secured to the housing62via socket bolts66.

As apparent inFIGS. 4B and 5B, the spool header64is rotatably mounted on the spool sleeve86for providing limited angular movement of the lever34between the one-way clutch and locked mode positions already described. A separate retainer68is configured to axially secure the rotatable spool header64to the spool sleeve86. As such, the retainer68is fixedly secured to the fixed spool sleeve86.

Within the housing62of the actuator32, shown herein as a hydraulic actuator, an actuator piston70is adapted to move slidably, along an axis B-B parallel to axis A-A, between the one-way clutch and locked mode positions. For this purpose, hydraulic ports (not shown) in communication with the housing62accommodate flows of hydraulic fluid (not shown) into and out of the housing in a manner to move the piston axially between the two positions. InFIG. 4B, the hydraulic fluid urges the piston end wall72toward the housing end wall76in direction of arrow, as shown.

Conversely, inFIG. 5B, hydraulic fluid urges the piston end wall72away from the housing end wall76, as shown by the opposing arrow depicted in the latter view. An actuator plunger80is secured to the piston end wall72via a securement boss82attached to the end wall72via a radial locking ring84. The actuator plunger80is adapted to be translated axially along, as well as rotated about, axis B-B, in a manner described below.

The spool header64is supported for rotatable movement on the exterior circumference of the fixed spool sleeve86. The interior circumference of the spool sleeve86supports an end portion78of the actuator plunger80that extends into the spool header64. It will be noted that the spool sleeve86includes a radial flange88adapted to axially retain a set of washers and bushings92between the open cylindrical end71of the actuator piston, the latter being situated opposite the piston end wall72. Those skilled in the art will appreciate that the set of washers and bushings92may be appropriately selected and/or dimensionally adjusted so as to accommodate any required axial tolerances of the actuator piston and spool sleeve parts for proper operation.

A default return spring90may be radially interposed between the actuator piston70and the actuator plunger80. As such, the spring90is positioned to be axially trapped between the piston end wall72and the radial flange88. In the disclosed embodiment, the spring90is adapted to become fully extended (FIG. 4B) in the one-way clutch mode position, which acts as a default position in case of hydraulic failure. Conversely, in the same embodiment the spring90becomes compressed under the force of hydraulic pressure in the locked clutch mode position.

As noted, the actuator plunger80is both axially translated and rotationally moved via the hydraulic forces to rotate the spool header64. For causing rotation of the spool header64, the rotationally fixed spool sleeve86, which circumferentially supports the spool header64to which the actuator lever34is secured, incorporates a helical slot94. The helical slot94accommodates an actuator pin100fixedly secured to the free end96of the actuator plunger80, i.e. the end opposite the securement boss82. The pin100projects radially outwardly of the center of the rotatable plunger80, and extends through the helical slot94.

The extremity of the actuator pin100defines a channel tracking end102which engages and slides axially within a separate axially extending channel104(FIG. 4B) formed on the interior of the spool header64. The channel104is positioned immediately adjacent the helical slot94, and the actuator pin100extends fully radially from the plunger80through the slot94and into the channel104. Since the channel104is tracked by the end96of the actuator pin100, those skilled in the art will appreciate that when the actuator plunger80is axially translated between the one-way and locked clutch mode positions via hydraulic forces, the plunger80is forced to rotate via the helical slot94which is fixed relative to the housing62. This action will in turn cause the spool header64to rotate relative to the housing62, thereby forcing the lever34to swivel between one-way and locked clutch mode positions.

As a result of the actuator operation described, the actuator32thus operates to swivel the lever32between one-way and locked clutch mode positions described. Movement of the lever32within the slot41of the actuator tab40is then effective to angularly rotate the actuator ring24between the positions described in context ofFIGS. 1-3. Among other aspects, those skilled in the art will appreciate that when the spool header64and its associated actuator lever34move clockwise the actuator ring24will move counterclockwise. Conversely, when the lever34moves counterclockwise, the actuator ring will move clockwise.

For purposes of both manufacturing economy and weight management, the spool sleeve86, the spool header64and the retainer68may be formed of a plastic material, instead of metal. For example, the plastic Nylon 66 as a Zytel (registered trademark) resin manufactured by DuPont can be economically and effectively utilized in an environment saturated with hydraulic fluids. For example, a hydraulic actuator32employing such parts was effectively tested over 1 million cycles of movement on the plunger80under a maximum pressure load of 20 bars. All other parts of the actuator32may be conventionally formed of metal, for example aluminum for weight management considerations.

The structures herein described may have alternative configurations, though not shown. The actuator32could for example be actuated electrically instead of hydraulically. In addition, a biasing system involving a structure other than a conventional-style coil spring90could be used as a default return spring. Further, the piston70and the plunger80could be alternatively formed as one element, thereby eliminating need for the separate radial locking ring84, even though in the latter case, the piston70including its end wall72would not only move axially with, but would also rotate with, the plunger80. Although these modifications constitute only three examples, numerous other examples are applicable within the context of this disclosure.

A method of making a multi-mode clutch module10, including an actuator32having a spool header and lever34may include steps of providing a pair of inner race plates20A and20B to form an inner race, and a separate annular structure to form an outer race22, with the race plates including reversely oriented pawl apertures60. The actuator ring24and individual pawls30A,30B are also provided; the pawls may be inserted into the pawl apertures60of a first,20A, of the pair of inner race plates20, and after positioning the outer race22and the actuator ring24, the second inner race plate20B is assembled so as to sandwich the outer race22and actuator ring24between the two inner race plates20along the common axis A-A, while assuring that the pawls30are retained within each set of their aligned pawl apertures60. The assembled inner race20, pawls30, outer race22and actuator ring24may then be inserted into the clutch module housing12in a manner such that the outer race22is non-rotatably secured to the housing12, and such that in operation each of the pawls30is adapted to disengage from the actuator ring24and the outer race22under centrifugal force at a predetermined rotational speed of the inner race20.

The method of making the multi-mode clutch module may also incorporate pawls30that comprise elongated hardened steel members having heel ends54and toe ends52, with the heel ends54containing more mass than the toe ends52for achieving the described centrifugal action.

INDUSTRIAL APPLICABILITY

The clutch module, including the actuator, of this disclosure may be employed in a variety of vehicular applications, including but not limited to, automobiles, trucks, off-road vehicles, and other machines of the type having engines, automatic transmissions, and drivelines.

The disclosed clutch module offers a unique approach to avoiding parasitic drag associated with pawls generally employed to engage inner and outer races of clutches in automatic transmissions. Each pawl may be individually and movably situated between a pair of riveted rotatable inner races, each pawl having its axially oriented lateral ends captured within and/or between pairs of opposed notches for permitting limited angular motion.

To the extent that the heel ends of each pawl are designed to contain more mass, the heel ends may be appropriately weighted so that the toe ends of the pawls may become disengaged from their associated outer race notches at predetermined threshold rotational speeds of the inner race. This approach provides for a relatively simple and reliable reduction of parasitic drag above speeds not requiring continued engagement or interaction of inner and outer race members in, for example, a first (low) and reverse clutch module of an automatic transmission.