The present disclosure relates generally to overrunning clutches for automotive transmissions, and more particularly to multiple mode clutch actuators employed in the operation of such transmissions.
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 clutch units adapted to dynamically shift among variously available gear ratios without requiring driver intervention. Pluralities of such clutch units, 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.
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 in one mode be drivingly rotatable in only one direction. The inner race may he 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 he fixed to an internal case or driven housing of an associated planetary member of the automatic transmission. Under such circumstances, in a first configurational mode 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 mode, 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 an overrunning condition in either direction, for example,
Because automatic transmissions include pluralities of gear sets accommodate multiple gear ratios, reliability of actuators used for automatically switching clutch modules between and/or among various available operating modes is a consistent design concern. One particular issue relates to the impact of G-forces on actuator assemblies and their associated components. In some instances, such structures can become unintentionally dislodged during travel over bumpy roads, for example. Therefore, efforts continue to be directed to finding ways to assure actuator reliability at competitive costs,
In accordance with le aspect of the disclosure, an actuator assembly for use with a multi-mode clutch module is disclosed. The clutch module has an inner race and an outer race, and a plurality of pawls circumferentially positioned between the inner and outer races. The actuator assembly includes an actuator cam ring having a torque arm and configured to move between at least two angular positions to selectively control movements of the pawls for locking and unlocking the races together.
In accordance with another aspect of the disclosure, the actuator assembly includes a reciprocal actuator including a housing, a translatable plunger having one end secured within the housing, the plunger having a free end.
In accordance with yet another aspect of the disclosure, a bellcrank is pivotally affixed to the outer race, the bellcrank having a first lever configured to receive the free end of the plunger, and a second lever containing a slot and configured to engage the torque arm for moving the actuator cam ring between the two angular positions.
In accordance with yet another aspect of the disclosure, the bellcrank includes a third lever having a mass relatively greater than either of the first and second levers. The mass of the third lever is configured to provide an inertial resistance to any uncommanded rotation of the bellcrank which can occur under externally induced G-forces.
In accordance with still another aspect of the disclosure, the actuator assembly moves the actuator cam ring to selectively block the pawls so that the inner race may lock to the outer race in a first rotational direction in one clutch operating mode, and freewheel relative to the outer race in the same clutch operating mode.
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.
Referring to
A splined interior hub 14 may be adapted for transfer of power from an engine (not shown) to a vehicular driveline (not shown). Referring now also to
Controlled movements of the pawls 18 may be achieved via an actuator cam ring 20 having radially arranged cam surfaces 21 configured to selectively block or unblock movement of otherwise spring-loaded pawls 18. For this purpose, the actuator cam ring 20 is rotatable between at least two angular limits, as further detailed below.
The actuator assembly 10 includes a reciprocal actuator 22, which may be powered by an electric solenoid or hydraulic source, supported within a housing 24 from which a plunger 30 extends. One end (not shown) of the plunger 30 is attached to a piston armature (not shown), and is supported for reciprocal movement within the housing 24 relative to a stator (not shown) that is fixedly supported within the housing 24. An opposite free end 32 of the plunger 30 is adapted to interact with a bellcrank 40, rotatably supported on a pivot pin 42 secured to and axially extending from the outer race 12. The bellcrank 40 has a slot 50, for interaction with a torque arm 52 fixed to and axially extending from the actuator cam ring 20. As such, the torque arm 52 is configured to cooperatively engage the slot 50 of the bellcrank to effect desired movement of the actuator cam ring 20, as described below. Those skilled in the art will appreciate that the slot 50 could alternatively be located in the actuator cam ring 20. For purposes of this disclosure, the alternative arrangements of the slot 50 may be deemed equivalent.
Referring now also to
Those skilled in the art will appreciate that the counterclockwise angular movement of the actuator cam ring 20 occurs against a biasing spring force of at least one circumferential cam return spring 23 (
The limited angular rotation of the actuator cam ring 20 is effective to selectively control movement of the pawls 18 with respect to any given operating mode of the clutch module 8. For example, in this disclosure the plurality of pawls 18 are arranged in distinct interleaved sets of two, pawls 18A and 18B, each pawl having a heel end 26 and an opposite toe end 28, with the respective sets of pawls 18A and 189 being asymmetrically shaped, and reversely identical. The heel ends 26 are configured to interact with the cam surfaces 21 of the actuator cam ring 20. Axially oriented, circumferentially spaced cogs 29 are provided on the outside periphery of the interior driven hub 14 to be selectively engaged by toe ends 28 of the pawls. As such, the pawls 18A and 18B are adapted to normally interact with the cogs 29 under the force of pawl springs 34, unless blocked by cam surfaces 21 of the actuator cam ring 20, for supporting desired rotary movements of the inner race 16 about the axis A-A.
In the described configuration, the driven housing of the clutch module 8 includes the outer race 12. The actuator 22 (
As depicted and disclosed herein, the pawls 18 are elongated hardened steel members circumferentially positioned about the axis A-A of the clutch module 8. Alternatively, the pawls maybe forgings or other manufactured structures, otherwise generally adapted to handle required engagement loads between the inner and outer races 16. 12, as necessary.
In view of the foregoing, it will be appreciated that the actuator 22 ultimately controls movement of the actuator cam ring 20 which, in turn, rotates between the two angular positions. Actual positioning of the pawls 18A and 18B is in turn controlled by the cam surfaces 21 against forces of the pawl springs 34.
Referring now specifically to
Alternatively, when the actuator cam ring 20 is in the second of its two angular positions (
As disclosed, each individual pawl 18A, 18B is urged radially inwardly against the cogs 29 of the inner race 16 via a single spring 34. Although only a leaf-style spring is depicted, alternative spring types or even other biasing arrangements may be employed. For example, coil springs could be used; e.g., one for each pair of opposed pawls 18A, 18B.
The structures herein described may have alternative configurations, although not shown or described herein. For example, the actuator 22 may be actuated hydraulically instead of electrically. In addition, the biasing system for returning the actuator cam ring 20 may utilize a spring structure other than a conventional-style coil spring (
For purposes of this disclosure, the bellcrank actuator assembly 10 includes at least the following components:
Referring now to
The second lever 46 is configured to interact with the previously described torque arm 52 (FIG, 5) which extends through the slot 50, as described in relation to the actuator cam ring 20. In the disclosed embodiment, the slot 50 extends symmetrically within, and has an identical orthogonal orientation as, the described second lever 46. A third lever 54, however, does not directly interact with any of the noted components, but rather incorporates an inertial mass 56 to counteract anticipated G-forces of the type induced on the bellcrank during rough travel, as for example as would be encountered on bumpy roads. The term G-forces as used herein refers to multiples of the force of gravity, also known as units of gravitational force, or G-units.
The physical size of the inertial mass 56 may be increased or reduced, as desired, by extending or shortening along either of its axial and/or radial dimensions, for any specific anticipated G-force encounters. In some situations, anticipated road force loads may be up to 20 times the force of gravity. Those skilled in the art will appreciate that such loads can tend to cause unintentional, uncommanded dislodgements of the bellcrank actuator assembly 10, i.e. rotation of the bellcrank 40 from an intended and/or previously commanded position. Use of a calculated predetermined inertial mass 56 will be effective to counter such an unintentional G-force reaction.
Finally, although the actuator assembly 10 has been described with respect to the provision of only two clutch modes, those skilled in the art will appreciate that the plunger 30 could be arranged to have an intermediate position which could facilitate an additional, or third mode such as a free-free mode, for example. In addition, although each of the three levers 44, 46, and 54 is depicted to have orthogonal relationships with respect to each other about the aperture 41, other angular orientations and/or shapes may be suitable, depending on space limitations and/or other factors.
The above-described embodiment of the clutch module 8 utilizes a single actuator assembly 10 which produces two distinct modes, as has been particularly described in reference to
Referring initially to
The use of dual bellcrank actuator assemblies 100A and 100B can provide functionality beyond that offered by the clutch module 8, which employs only a single bellcrank actuator assembly 10. In the clutch module 80, the two sets of pawls 118A and 118B are controlled by two distinct actuator cam rings 120A and 120B to achieve a total of four modes, as opposed to just the two modes offered by the clutch module 8. For this purpose, those skilled in the art will appreciate that the cam ring 120A may be controlled by the actuator assembly 100A, while the cam ring 120B may be separately controlled by the actuator assembly 100B.
Various individual features of the clutch modules 8 and 80 operate analogously. For example, within the clutch module 8, movements of the pawls 18A, 18B caused by movements of respective heel ends 26 resulting from contact thereof by the free end 32 of the plunger 30, though not shown in
Referring now also to
Finally referring now to
respectively. For achieving these respective modes, the actuator assembly 100A is energized while the actuator assembly 100B is de-energized in the one-way mode of
Those skilled in the art will appreciate that numerous other embodiments may be available under the disclosure and claims as presented herein. For example, although the outer race 12, 112 has been described herein as a driven race, while the inner race 16, 116 has been described as a driving race, the two races could be arranged with opposite functionalities in alternative embodiments of the clutch module 8, 80.
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 actuator assembly offers a unique approach to managing movements of pawls adapted to engage the inner and outer races of clutch modules used in automatic transmissions. Use of a bellcrank in accordance with this disclosure may offer additional design opportunities for clutch modules utilized in automatic transmissions.
This Application is a non-provisional patent application claiming priority under 35 USC § 119(e) to U.S. Provisional Patent Application Ser. No. 62/147,694 filed on Apr. 15, 2015.
Filing Document | Filing Date | Country | Kind |
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PCT/US2016/026589 | 4/8/2016 | WO | 00 |
Number | Date | Country | |
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62147694 | Apr 2015 | US |