Patent Application
20130248317
The present disclosure relates a drive disconnect clutch for providing torque to a secondary drive shaft in an all-wheel drive vehicle, specifically, a drive disconnect clutch providing synchronization with frictional engagement of clutch plates and a locked connection with expanding wedge plates.
For providing torque to a secondary drive shaft of an all-wheel drive vehicle, U.S. Pat. No. 7,150,694 is an example of using a clutch in a power transfer unit (PTU), which adds to the mass and size of the PTU. U.S. Pat. No. 7,150,694 and U.S. Pat. No. 7,309,301 are examples of using a transfer (typically wet) clutch in a differential to control torque to a secondary drive shaft. Pressurized fluid must be continuously supplied to keep the clutches in a closed mode, adding to the power usage associated with usage of the clutches. U.S. Pat. No. 6,520,885 is an example of using a roller or dog clutch to control torque to a secondary drive shaft. However, a vehicle must be at a stand still to use of such clutches.
According to aspects illustrated herein, there is provided a drive disconnect clutch assembly, including: an input component arranged to receive torque from a motor; an output gear; and a clutch. The clutch includes: a piston plate; at least one clutch plate; at least one wedge plate; and respective friction material disposed between the at least one clutch plate and the at least one wedge plate. The piston plate is arranged to: displace a first distance in a first axial direction to clamp the at least one clutch plate and the at least one wedge plate to lock rotation of the input component to rotation of the output gear; and displace further in the first axial direction to displace the at least one wedge plate to lock respective rotations of the input component and the output gear via contact of the at least one wedge plate with the input component and the output gear.
According to aspects illustrated herein, there is provided a drive disconnect clutch, including: an input component arranged for driving connection to a motor; an output gear; and a clutch. The clutch includes: a piston plate; at least one clutch plate; at least one wedge plate; and respective friction material disposed between the at least one clutch plate and the at least one wedge plate. In a synchronizing mode, the at least one wedge plate is rotationally connected to the input component and the at least one wedge plate is rotatable with respect to the output gear. In the synchronizing mode, the piston plate is arranged to displace a first distance in a first axial direction to clamp the at least one clutch plate and the at least one wedge plate to lock rotation of the input component to rotation of the output gear. In a locked mode, the piston plate is arranged to displace further in the first axial direction such that: the at least one wedge plate is rotated with respect to the input component; and the at least one wedge plate is compressively engaged with the input component and the output gear to lock rotation of the input component to rotation of the output gear.
According to aspects illustrated herein, there is provided a drive disconnect clutch, including: an input component arranged to receive torque from a motor and including an outer circumference formed by a first plurality of flat sides; an output gear; and a clutch including: a piston plate; at least one clutch plate; at least one wedge plate including an inner circumference formed by a second plurality of flat sides in contact with the first plurality of flat sides; a key plate including a plurality of radially displaceable keys; and respective friction material disposed between the at least one clutch plate and the at least one wedge plate. While the plurality of radially displaceable keys rotationally locks the at least one wedge plate and the input component, the piston plate is arranged to displace a first distance in a first axial direction to clamp the at least one clutch plate and the wedge plate to lock rotation of the input component to rotation of the output gear. The piston plate is arranged to displace further in the first axial direction such that: the plurality of radially displaceable keys retract to enable rotation of the at least one wedge plate with respect to the input component; the first plurality of flat sides slide along the second plurality of flat sides; an inner circumference of the wedge plate is in compressive engagement with the input component; and an outer circumference of the wedge plate is in compressive engagement with the output gear.
Various embodiments are disclosed, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, in which:
At the outset, it should be appreciated that like drawing numbers on different drawing views identify identical, or functionally similar, structural elements of the disclosure. It is to be understood that the disclosure as claimed is not limited to the disclosed aspects.
Furthermore, it is understood that this disclosure is not limited to the particular methodology, materials and modifications described and as such may, of course, vary. It is also understood that the terminology used herein is for the purpose of describing particular aspects only, and is not intended to limit the scope of the present disclosure.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this disclosure belongs. It should be understood that any methods, devices or materials similar or equivalent to those described herein can be used in the practice or testing of the disclosure.
The adverbs “axially,” “radially,” and “circumferentially” are with respect to an orientation parallel to axis 81, radius 82, or circumference 83, respectively. The adverbs “axially,” “radially,” and “circumferentially” also are regarding orientation parallel to respective planes.
Drive disconnect clutch assembly 100 includes input, or input component (final drive ring gear), 108, arranged to receive torque from the motor, for example via final drive pinion shaft 103, output, or output component, 104, and clutch 110. Output 104 transmits torque to SDS via shaft 105. Gear 108 transmits torque to LFA and RFA via differential gear set 107. Clutch 110 includes piston plate 112, at least one clutch plate 114, at least one wedge plate 116, backing plate 117, and respective friction material 118 disposed between the at least one clutch plate and the at least one wedge plate. In an example embodiment, the friction material is fixed to the at least one wedge plate, but in other embodiments (not shown), the friction material may be fixed to the at least one clutch plate. In the example illustrated by the figures, assembly 100 includes three plates 114 and three plates 116; however, it should be understood that assembly 100 is not limited to a particular number of plates 114 or plates 116 or a particular ratio of plates 114 to plates 116. To simplify the presentation, the discussion that follows is directed to “plates 114,” “clutch plates,” “plates 116,” and “wedge plates”; however, it should be understood that the discussion is applicable to configurations including only one clutch plate or wedge plate, or only one each clutch plate and wedge plate.
As for a typical wet clutch arrangement, clutch plates 114 are keyed to the input such that the clutch plates are axially displaceable and rotationally connected to the input. By “rotationally connected” we mean that two or more components are directly or indirectly connected such that respective rotations of the components are locked. That is, the components rotate in unison. Slots 137 are used to key, or spline, the clutch plates to the input.
In the disengaged mode, the piston plate is positioned such that the piston plate does not clamp the clutch plates and the wedge plates. Further, as described below, the wedge plates are rotationally locked with the output component. Thus, the clutch plates and the input are rotatable with respect to the wedge plates and the output component and torque is not transmitted from the input to the output.
The clamping of the clutch plates and wedge plates enables torque from the motor and input component to be transmitted to the output, for example, as further described infra, to synchronize energy, or rotational speeds, of the input component and the output component, as well as other components connected to the output component, such as shaft 105 and secondary drive shaft SDS.
As further described infra, in a locked mode, following the synchronizing mode, the piston plate is arranged to displace further in direction D1 to displace the wedge plate keys to lock rotation of the wedge plates with rotation of the input component and the output. Specifically, the wedge plates are expanded and wedged between the input component and the output. Once the wedge plates are displaced to lock the rotation of the input component and the output, torque can be transferred from the input component to the output via the wedge plates. Thus, the clutch plates are no longer needed for torque transfer, and as further described infra, the piston can be displaced in direction D2, opposite D1, to relieve axial pressure on the clutch plates and enable the clutch plates to disengage from the wedge plates. Advantageously, the amount of force applied to the piston, for example, in the form of pressurized hydraulic fluid, during closed operation of the clutch (to maintain torque transfer from the input component to the output gear) is reduced. For example, rather than applying an amount of force needed to radially retract the wedge keys and clamp the wedge plates and clutch plates, only the lesser amount of force needed to retract the wedge keys is applied to the piston.
Clutch 110 includes key plate 122 rotationally connected to the output component. During the disengaged mode and the displacement of the piston in the synchronizing mode, the key plate is engaged with the wedge plates to rotationally lock the wedge plates and the output component. During the locked mode, the piston plate is arranged to displace the key plate to enable relative rotation between the wedge plates and the output component such that the wedge plates contact the input. This contact rotationally locks the wedge plates, the input component, and the output, enabling torque transmission from the input component to the output by the wedge plates without the use of the clutch plates.
In the synchronizing mode, the wedge plates are rotatable with respect to the input, that is, respective outer circumferences OC1 of the wedge plates and inner circumference IC1 of the input are separated by radial distance RD1.
In an example embodiment, the output component includes outer circumference OC2 with flat surfaces 128 and the wedge plate includes inner circumference IC2 with flat surfaces 130. Pairs of mated surfaces 128 and 130, for example 128A and 130A, are at an acute angle with respect to a radius R passing through the surfaces. That is the surfaces form complementary ramps with respect to circumferential directions C1 and C2. In the disengaged and synchronizing modes, surfaces 128 and 130 are engaged such that plates 116 are in maximally radially inward positions (distance RD1 is present).
In the locked mode, as further described infra, enabling the wedge plates to rotate with respect to the output component, for example, withdrawing the keys from the slots, causes the wedge plates to compressively engage the input component and the output (distance RD1 is removed) to lock respective rotations of the input component and the output.
In the locked mode, the wedge plates are no longer fixed by keys 126 and the wedge plates rotate with respect to the output component, for example, in direction C1, due to contact with the clutch plates. Respective surfaces 128 then slide along respective surfaces 130. That is, the frictional engagement of the wedge plates with the clutch plates urges the wedge plates in direction C1. Due to the ramp configuration described above, as surfaces 128 slide along surfaces 130, surfaces 128 are pushed radially outward, pushing 1C2 of the wedge plates radially outward. In turn, as further described infra, OC1 also expands radially outward. It should be understood that movement of the wedge plates in direction C2, opposite C1, from the synchronizing position results in the same radially outward displacement of the wedge plates described above.
Thus the wedge plates are in compressive engagement with the input component and the output to rotationally lock the input component and the output component and to transmit torque from the input component to the output. By “compressive engagement,” we mean that the wedge plates exert a pressure, for example in a radial direction, on the input component and/or the output, or the input component and the output exert a pressure, for example in a radial direction, on the wedge plates. In an example embodiment, the rotation of the wedge plates with respect to the output component is typically small, for example, two or three degrees. However, it should be understood that other amounts of relative rotation between the wedge plates and the output component are possible.
In an example embodiment, the wedge plates are discontinuous in the circumferential directions by virtue of a radially disposed space 135 separating circumferential ends 136 of the wedge plate by circumferential distance CD. In the locked mode, the piston plate, via the output component, element 127, and plate 122, is arranged to increase CD to expand the wedge plate radially outward. That is, space 135 enables the wedge plate to expand radially outward in response to rotation of the output and the sliding contact of surfaces 128 and 130 to contact the input.
Advantageously, once the wedge plates are radially expanded to compressively engage the input component and the output, that is, the wedge plates are wedged between the input component and the output, the wedge plates are able to transmit torque and the clutch plates are no longer needed to transmit torque. Therefore, the force on the piston, for example, pressurized hydraulic fluid, can be reduced as described above. Thus, the energy requirement of assembly 100 is reduced, since it is no longer necessary to provide pressurized fluid to clamp the clutch plates. As long as torque is being transmitted from the input component to the wedge plates in direction C1, the wedge plates remain locked to the input component and the output.
As noted above, the wedge plates remain engaged with input component and the output component as long as torque from the motor is present on the input component (drive mode). In a coast mode, torque from the motor is withdrawn from the input component (for example, an accelerator for the motor is released) and the wheels associated with axle SA are rotating and applying torque to shaft 105. The torque from the axle causes the output to rotate in direction C2, which in turn, causes the wedge plates to rotate in direction C2 with respect to the input component. As noted above, as long as the keys are withdrawn by the piston, rotation in direction C2 also causes the wedge plates to radially expand and lock the input component with the output gear. That is, as the surfaces slide toward the position associated with the synchronizing mode (keys aligned with slots 124) the wedge plates radially contract, but as the surfaces slide past the position, the surfaces cause the wedge plates to again expand. Thus, as long as the keys remain retracted, the wedge plates continue to transmit torque in alternating drive and coast modes without the need for clamping the wedge plates.
In an example embodiment, clutch 110 includes resilient element 138 engaged with keys 126 and urging keys 126 radially outward, for example, urging the keys into slots 124 during the disengaged and synchronizing modes. For example, when the piston plate displaces in direction D1 against the wedge plate key, the action of the piston plate displaces the keys radially inward against the force of the resilient element to enable rotation of the wedge plates with respect to the output component. If the piston is retracted such that the piston no longer urges the keys radially inward, element 138 urges the keys radially outward. In the locked mode, the keys are urged against surfaces 128, but cannot enter slots 124 due to the misalignment of the keys and slots 124.
To disengage the clutch (disengaged mode), the piston is withdrawn and the keys contact surfaces 128 as described above. Then, when a transition from torque in direction C1 to torque in direction C2 occurs (or vice versa) and the wedge plates circumferentially shift, slots 126 align with the keys and element 138 pushes the keys into slots 126, locked the output component and the wedge plates. The re-alignment of slots 126 and the keys enables OC1 to contract radially inward so that distance RD1 is again formed, as described above. Therefore, the wedge plate rotates with the output component, the wedge plate rotates independently of the input, and the clutch plates are unclamped. Thus, no torque is transmitted through assembly 100.
Advantageously, assembly 100 does not increase the size of a state-of-the-art bevel gear differential assembly with a disconnect clutch such as clutch 110.
Clutch 110 synchronizes the energy of stationary components during initial clutch lock up, for example in the synchronizing mode. For example, when clutch 100 is disengaged, torque from the motor is not supplied to the “downstream” components such as the output, shaft 105, and shaft SDS and these components are at rest. Thus, as described supra, to begin clutch 110 lockup, an axial force is applied by the piston plate forcing the respective friction material into contact with clutch plates 114 on opposite axial sides of the wedge plates. The axial friction force functions in clutch 110, for example, as for a typical automatic transmission wet clutch until the entire driveline (including down stream components) has reached a synchronized speed, or a point near the synchronized speed such that noise, vibration, harshness (NVH) is satisfactory. Thus, in the synchronizing mode described supra, clamping the clutch plates and wedge plates in clutch 110 transmits torque from the motor such that the downstream components are brought from rest positions to respective rotational speeds synchronized with the input to assembly 100.
In the locked mode described supra, when the driveline has reached the synchronized speed, or the point near the synchronized speed, clutch 110, via the compressive engagement of the wedge plates with the input component and the output, transmits full driveline torque requirements to the secondary drive shaft. Thus, an abrupt transfer of torque, with an associated and undesirable jolt is avoided by first synchronizing the driveline and then engaging the wedge plates.
Although a particular configuration of clutch plates and wedge plates is shown, it should be understood that assembly 100 is not limited to the configuration shown. Other numbers of clutch plates or wedge plates are possible in order to satisfy surface area requirements for torque transfer.
It will be appreciated that various of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.
This application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Patent Application No. 61/615,655 filed Mar. 26, 2012, which application is incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61615655 | Mar 2012 | US |
