The present disclosure relates generally to overrunning clutches for automotive transmissions, and more particularly to multiple mode clutches employed in 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 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.
In accordance with one aspect of the disclosure, 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 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 cam plate 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 cam 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 are 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.
Referring to
Axially oriented, circumferentially spaced cogs 16 are provided on the outside periphery of the interior driven hub 14. Referring now also to
With specific reference now to
As disclosed, the pawls 30 are elongated hardened steel members circumferentially positioned about the axis A-A of the clutch module 10. Alternatively, the pawls maybe forgings or other manufactured structures, otherwise generally adapted to handle required loads of engagement as necessary for any particular clutch design. The pawls are situated so as to interact with both the inner race 20 and the outer race 22, and are arranged in sets of opposed pairs, 30A and 30B. The actuator cam 24 is adapted to control interactions of the pawls 30A and 30B between the inner race 20 and the outer race 22, as further described below.
A hydraulic actuator 32 (
In view of the foregoing, it will be appreciated that the actuator 32 ultimately controls the actuator tab 40 which, in turn, moves the actuator cam 24 between two distinct angular positions. Thus, the positioning of the pawls 30A and 30B, as axially retained between the riveted inner race plates 20A and 20B, is directly controlled by the actuator cam 24 against forces of springs 44, as further described below.
Referring now specifically to
Alternatively, when the actuator cam 24 is in the second of its two angular positions, both sets of pawls 30A and 30B, 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 race 22 remains non-rotatable relative to the exterior case or housing 12. For accommodating interactions with the pawls 30A and 30B, the inner circumference of the outer race 22 (
Referring now to
In
Continuing reference now to both
Opposite each toe end 50 and 52, each pawl 30A and 30B has a heel end 54 and 56, respectively (
Operationally, radially inwardly depending actuator cam teeth 28 are adapted to selectively block such toe ends 50, 52 of the pawls 30 from being urged radially outwardly by respective spring arms 46, 48 and into notches 36. The interaction of the cam teeth 28 with such toe ends 50, 52 defines the mechanism that permits the earlier described freewheeling of the inner race 20 relative to the outer race 22 as, for example, in the case of the above-described configuration for manual first or reverse gear.
In the immediate disclosure, the heel ends 54 and 56 are designed to contain more mass than the toe ends 50, 52, so that at a particular threshold rotational speed of the inner race 20, the heel ends will tend to swing radially outwardly under centrifugal forces of rotation. This action will cause the toe ends 50, 52 to become disengaged from notches 36 of the outer race 22. As such, the inner race 20 will become disengaged from the outer race 22. Under such forces, the toe ends of pawls 30A will bear down against the spring arms 46, while the toe ends 52 of pawls 30B will respectively bear against spring arms 48. 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 arms 46, 48 of the springs 44, and 2) achieve such centrifugal force induced load against the respective spring arms 46, 48 at a specific rotational speed threshold.
Thus, in either of the first or reverse gear configurations of the clutch module 10, and at rotational speeds of the inner race 20 in excess of a threshold of 500 RPM, for example, the pawls 30A and 30B of the clutch module 10 are 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 arms 46, 48, and the toe ends 50, 52 of the pawls will disengage. As such, this disclosure offers an effective way to reduce and/or avoid parasitic drag loads within the clutch module.
A method of making a multi-mode clutch module may include steps of providing a pair of ring plates to form an inner race, and a separate ring structure to form an outer race, with the ring plates including reversely identical pawl apertures. An actuator cam and individual pawls are also provided; the pawls may be inserted into the pawl apertures of a first of the pair of ring plates, and after positioning the outer race and the actuator cam, the second ring plate is assembled so as to sandwich the outer race and actuator cam between the two ring plates along a common axis, while assuring that the pawls are retained within each set of then aligned pawl apertures. The assembled inner race, pawls, outer race and actuator cam are inserted into a transmission clutch housing in a manner such that the outer race is non-rotatably secured to the housing, and such that in operation each of the pawls is adapted to disengage from the actuator plate and the outer race under centrifugal forces at a predetermined rotational speed of the inner race.
The method of making the multi-mode clutch module may also incorporate pawls that comprise elongated hardened steel members having heel ends and toe ends, with the heel ends containing more mass than the toe ends.
The clutch module 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.
Filing Document | Filing Date | Country | Kind |
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PCT/US2014/013127 | 1/27/2014 | WO | 00 |
Publishing Document | Publishing Date | Country | Kind |
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WO2014/120595 | 8/7/2014 | WO | A |
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20150176662 | Lee | Jun 2015 | A1 |
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20150204392 | Kimes | Jul 2015 | A1 |
Number | Date | Country |
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101096982 | Jan 2008 | CN |
102224355 | Oct 2011 | CN |
2004-144218 | May 2004 | JP |
2004144218 | May 2004 | JP |
WO 2009132056 | Oct 2009 | WO |
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WO 2010-056497 | May 2010 | WO |
WO 2014-120595 | Aug 2014 | WO |
Entry |
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International Search Report Application No. PCT/US2014/013127; reported on May 8, 2014. |
European Search Report Application No. EP 14 746273 reported on Oct. 13, 2016. |
Chinese Office Action for related Application No. 2014800051976 dated Nov. 8, 2016. |
Number | Date | Country | |
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20150354640 A1 | Dec 2015 | US |
Number | Date | Country | |
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61758356 | Jan 2013 | US |