The present disclosure relates to a clutch assembly having a ball cam actuator.
The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art.
Traditional automatic transmissions use friction clutches in the form of either band clutches or multi-plate friction clutches. Friction clutches work by pressing two plates together. Friction between clutch elements allows the transfer of energy by allowing one plate to spin faster than the other or to slip. Automatic transmissions use friction clutches so that changing gear doesn't require engine power to drop. While changing gear, an automatic transmission can disconnect one clutch as it engages another. When ambient temperature drops below zero, however, and particularly at temperatures approaching −40° F. the hydraulic fluid pressure required to actuate friction clutches requires increased pump capacity, which may not be available in smaller engine and vehicle designs.
Dog clutches can be used in place of friction clutches and are commonly used in manual transmissions. Dog clutches are interference in lieu of slip clutches. Power is transmitted by a tooth of one side pressing on a tooth of the other side. Dog clutches cannot slip therefore they are either engaged or disengaged. Dog clutches suffer little parasitic loss and are simple and compact. Synchronizer dog clutches commonly employed in manual transmissions synchronize the speed of two components prior to engagement of those two components. Known synchronizers include a conical sleeve integrally connected to a blocker or dog ring. The sleeve has a set of teeth and is rotationally fixed to a first component and is longitudinally translatable along an axis of rotation to engage a set of teeth located on a second component. Longitudinal movement of the sleeve toward the direction of the second component initially causes a frusto-conical surface of the blocker ring to engage a matching frusto-conical surface on the second component prior to engagement of the teeth. Engagement of these two surfaces is a clutching action which causes the second component to be speed synchronized with the blocker ring and sleeve and thus the first component.
Known dog clutch synchronizers and their conical sleeves and one-way ball bearing clutches are limited in that they only provide engagement in one direction. In an application such as engagement of a final drive planetary gear set with a differential, known dog rings do not provide the necessary structure to allow functioning under load in opposite directions of displacement.
According to several aspects, a ball cam actuated dog clutch assembly for a motor vehicle includes a clutch sleeve having multiple ball bearings retained by the clutch sleeve. A clutch hub has multiple helical grooves created in an outer facing wall. The clutch hub is positioned partially within the clutch sleeve having each of the helical grooves receiving a portion of one of the ball bearings. Rotation of the clutch hub causes axial translation of the clutch sleeve in a selected one of a first direction or an opposite second direction by translation of the ball bearings within the helical grooves.
According to further aspects, the clutch sleeve includes a plurality of gear teeth positioned at a first end aligned for meshed engagement with gear teeth of a drive assembly.
According to further aspects, the clutch sleeve includes the multiple ball bearings disposed at a second end.
According to further aspects, the clutch assembly further includes a bushing sleeve having a spline.
According to further aspects, the clutch sleeve further includes a splined face which is slidably connected with the spline of the bushing sleeve, wherein the clutch sleeve is axially slidable in each of the first direction and the second direction along the spline.
According to further aspects, a clip member is located at a free end of the spline acting to provide a positive stop for the clutch sleeve.
According to further aspects, a biasing member is positioned in contact with each of an end face of the clutch sleeve and a contact face of the bushing sleeve, the biasing member normally biasing the clutch sleeve in the first direction.
According to further aspects, the clutch hub and the clutch sleeve are coaxially aligned on a longitudinal axis, the rotation of the clutch hub defining an axial rotation with respect to the longitudinal axis and the translation of the clutch sleeve in either of the first or the second directions being parallel to the longitudinal axis.
According to further aspects, in an open position of the clutch assembly, each of the ball bearings directly contacts a groove end face of the helical grooves formed in a first end of the clutch hub.
According to further aspects, a length of each of the helical grooves is predetermined and defines a total axial displacement in each of the first direction and the opposite second direction of the clutch sleeve resulting from axial rotation of the clutch hub.
According to further aspects, the clutch sleeve includes a circumferential slot created in an inner facing wall proximate to an end of the clutch sleeve, the ball bearings positioned partially within the slot and individually retained and spaced by a cage assembly.
According to further aspects, the slot is positioned proximate to an end face of the end, providing clearance between an inner wall end face and an opposite end of the clutch hub, allowing free sliding motion of the clutch hub within the clutch sleeve.
According to further aspects, the helical grooves are each created in an outward facing cylindrical wall of the clutch hub; and each of the ball bearings occupy only a partial depth of the helical grooves, with approximately 50% or more of the ball bearings extending out of the helical grooves.
According to further aspects, each helical groove starts at a first end partially extending through a first end face of the clutch hub, and extends to a groove end face positioned approximately 50% of a distance between the first end face and an opposite second end face of the clutch hub.
Further aspects, advantages and areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.
The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses.
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According to several aspects, the final drive unit 16 defines a planetary gear set having a ring gear 22. A ring gear extension member 24 is integrally connected to and axially extends from the ring gear 22. Gear teeth of the ring gear extension member 24 can be meshed with gear teeth of a clutch sleeve 26 defining a clutch assembly closed position, which will be described in greater detail in reference to
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To mechanically couple the clutch sleeve 26 to the clutch hub 32, the clutch sleeve 26 further includes a plurality of ball bearings 58 (only one of which is visible in this view), which are retained at a second end 60 of the clutch sleeve. A cage assembly 62 is provided which individual retains the ball bearings 58 at the second end 60. In the open position shown for the clutch assembly 36, each of the ball bearings 58 directly contacts a groove end face 64 of a plurality of helically curved or helical grooves 66 (only one of which is visible in this view) located at a first end 68 of the clutch hub 32. The ball bearings 58 can rotate and/or slidably displace within the helical grooves 66 when not in direct contact with the groove end face 64. The clutch sleeve 26 is axially displaced as the ball bearings 58 displace within the helical grooves 66. A length “C” of each of the helical grooves 66 is predetermined to establish a total axial displacement in the direction “A” and the opposite direction “B” of the clutch sleeve 26 which results from axial rotation of the clutch hub 32. As previously noted, the clutch hub 32 is rotatably supported by the bushing 34, and is also prevented from being axially displaced in either the direction “A” or the opposite direction “B” by a clip 70.
Axial rotation of the clutch hub 32 results from meshed rotation of a gear 72 which according to several aspects is a spur gear whose teeth mesh with gear teeth 74 of the clutch hub 32. The gear 72 is rotated by an actuator member which according to several aspects defines an actuator motor 76 connected by a motor shaft 78 to the gear 72. The motor shaft 78 can extend through a shaft bore 80 created in an end wall 82 of the case 12, which also supports the actuator motor 76. A seal or multiple seals, not shown, can be positioned in the shaft bore 80 to rotationally seal the motor shaft 78. According to several aspects, the actuator motor 76 is provided as a DC brushless motor, however other motor designs can also be used within the scope of the present disclosure. According to further aspects, the actuator motor 76 may be sealed and positioned within the case 12, proximate to an inside facing surface of the end wall 82. According to still further aspects, the actuator motor 76 is selectively operable to rotate in opposite rotational directions such that the clutch hub 32 can be rotated in either of opposite rotational directions. This permits the clutch sleeve 26 to be axially displaced in either the direction “A” or the opposite direction “B” to engage or disengage the ring gear extension member 24 even under torsional load. Operation of the actuator motor 76 can be controlled by a transmission control system (not shown) also used to control operation of other transmission control functions.
When the actuator motor 76 is supported off the end wall 82 a longitudinal and rotational axis 84 of the motor shaft 78 is oriented parallel to and offset from the longitudinal axis 38, to allow connection to the clutch hub 32 through the spur gear 72. From the open position of the clutch assembly 36 shown, the actuator motor 76 is energized to rotate the clutch hub 32 and to thereby axially displace the clutch sleeve 26 in the direction “B” until the gear teeth 54 of the clutch sleeve 26 mesh with the gear teeth 52 of the ring gear extension member 24. This meshed engagement defines a clutch closed position shown and described in greater detail in reference to
Because the ball bearings 58 are retained in an axially fixed relationship to the clutch sleeve 26 and are displaced within the helical grooves 66 formed in the clutch hub 32, axial rotation of the clutch hub 32 with the clutch hub 32 being fixed against displacement in a direction of the longitudinal axis 38 converts the rotational force of the clutch hub 32 to a force having an axial component (parallel to the longitudinal axis 38) acting against the ball bearings 66. Because the ball bearings 58 are in direct contact with the walls of the helical grooves 66 the ball bearings 66 are forced to displace within the helical grooves 66, thereby axially displacing the clutch sleeve 26. The biasing member 46 and the helical shape of the helical grooves 66 allow the clutch assembly 36 to open automatically using only the applied force of the biasing member 46 after the clutch assembly 36 is unloaded (e.g., with the vehicle in a park position) and in the event of a failed actuator motor 76.
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The description of the invention is merely exemplary in nature and variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.