ROTARY-TYPE SELECTABLE ONE-WAY CLUTCH

CLAIM OF PRIORITY AND CROSS-REFERENCE TO RELATED APPLICATION [0001] This application claims the benefit of and priority to U.S. Provisional

Patent Application No. 61/028,557, filed on February 14, 2008, which is hereby incorporated by reference in its entirety.

TECHNICAL FIELD

[0002] The present invention relates to a selectable one-way clutch (SOWC) assembly having various rotatable races or plates, including a pocket plate, a notch plate, and a selector ring or slide plate, with the SOWC assembly being shiftable via a hydraulic piston when the three plates are rotating.

BACKGROUND OF THE INVENTION

[0003] In various mechanical devices, and particularly within automatic vehicle transmissions, specialized overrunning or one-way clutches are used to produce a oneway driving connection between the input and output members of the transmission. In particular, a one-way clutch has a pair of members, races, or plates capable of transmitting torque when the rotation of one plate with respect to the other is in one direction, with the clutch "overrunning" or freewheeling when the rotational direction is reversed.

[0004] The relative shape and/or orientation of the plates may vary depending on the particular clutch design. Certain one-way clutches have input and output races or plates that are oriented in a radially-concentric manner with respect to each other. Alternately, the confronting or mating faces of the plates have a planar orientation or relationship. The mechanical means used to lock a typical one-way clutch are varied, but commonly consist of torque -transmitting elements such as rollers, sprags, rockers, or struts that are positioned between the plates. Depending on the particular type or style of one-way clutch and the direction of rotation, each plate may contain unique surface

features suitable for engaging one or more of the struts in order to selectively enable various clutch operating modes.

[0005] In a basic one-way clutch, the operating mode is determined by the direction of the torque being applied to an input race or plate of the clutch. However, the increased complexity of power transmitting mechanisms has led to a class of selectable one-way clutches. A selectable one-way clutch or SOWC is similar to a one-way clutch in operation, as described above. As the name implies, a SOWC is capable of producing a driving connection between the input and output plates in one or both rotational directions, and/or is able to freewheel in one or both rotational directions as needed. In a conventional SOWC, one of the two plates is indexed or grounded to a stationary member, such as a transmission case or center support, and therefore can be less than optimal when used in certain applications.

SUMMARY OF THE INVENTION

[0006] Accordingly, a SOWC assembly is provided having a selector ring or a slide plate, a pocket race or plate, and a notch race or plate, each being rotatable with respect to the others. The SOWC assembly is a two-mode device which can be selectively locked in either rotational direction to thereby establish one of the two operating modes when the pocket plate, slide plate, and the notch plate are rotating at approximately the same speed. That is, the SOWC assembly can be engaged without indexing or grounding either of the pocket or notch plates to a stationary member of the transmission in the conventional manner.

[0007] In addition to the pocket plate, the slide plate, and the notch plate, the

SOWC assembly includes an annular piston having a ramped surface feature that is specially adapted for actuating the SOWC assembly. In one embodiment, fluid pressure can be used to move the annular piston in a first axial direction toward the pocket plate to apply the annular piston. An axial portion of the slide plate, such as a knob or an arm, is trapped by the ramped surface feature. Continued rotation of the plates rotates the slide plate sufficiently so as to shift the SOWC from a first or forward operating mode into a second or a reverse operating mode. The axial motion of the piston is thus translated into

rotational movement of the slide plate. Likewise, release or disengagement of the annular piston shifts the SOWC back into the first or forward operating mode. [0008] The pocket plate can be configured with a through-hole or slot with first and second ends. The knob portion of the slide plate is moved to the second end of the slot whenever the piston is applied. That is, the knob portion rides over the ramped surface feature so that the knob portion rotates as the piston is applied, thereby selecting an "engaged" or first operating mode of the SOWC assembly, i.e., the reverse mode. A second of the two operating modes, i.e., the forward mode, is selected as the piston is released or moves away from the pocket plate. To facilitate movement of the knob portion, a biasing spring or other suitable device can bias the knob portion against the first end of the slot once a return spring moves the piston in a second axial direction. [0009] Within the SOWC assembly, an annular plate, plate, or dam is positioned between the piston and the slide plate to restrict travel of the piston toward the slide plate whenever the piston is applied, thus minimizing impingement of the slide plate if the piston is moved too far during its application. A guide pin can be inserted into each of the piston and the dam, and allowed to freely move in and out of the dam. The guide pin maintains a relative position of the piston and the slide plate as the piston and the slide plate rotate at a relatively high rate of speed and accelerate.

[0010] The above features and advantages, and other features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] FIGURE 1 is an exploded schematic perspective view of a SOWC assembly in accordance with the invention;

[0012] FIGURE IA is a schematic illustration of a transmission having the

SOWC assembly of Figure 1;

[0013] FIGURE 2 is a schematic perspective view of a portion of the SOWC assembly shown of Figure 1 in a first operating mode;

[0014] FIGURE 3 is a schematic partial perspective view of a portion of the

SOWC assembly shown in Figures 1 and 2;

[0015] FIGURE 4 is a schematic perspective view of the SOWC assembly of

Figure 1 in a second operating mode; and

[0016] FIGURE 5 is a schematic side cross-sectional view of an inner portion of the SOWC assembly of Figures 1-4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] With reference to the Figures, wherein like reference numerals refer to like or similar components throughout the several figures, and beginning with Figure 1, a selectable one-way clutch (SOWC) assembly 11 has an axis of rotation 13. Therefore, the term "axial" and "axial direction" as used herein refers to the relative position of a given feature or movement with respect to the axis 13. The SOWC assembly 11 also includes a first race or a notch plate 16, a selector ring or slide plate 18, and a second race or a pocket plate 20. The notch plate 16 has internal teeth or splines 17, while the pocket plate 20 has external teeth or splines 21. The slide plate 18 has an axial extension or an axial knob portion 30 for selecting the two modes of the SOWC assembly 11, as described below.

[0018] Although not shown in Figure 1 for simplicity, it will be understood by those of ordinary skill in the art that a notch plate such as the notch plate 16 of Figure 1 is a rotatable race having a series of interspaced notches or wells formed in a surface 19, with each well (not shown) configured for retaining a mating, spring-biased torque holding piece, commonly referred to as a strut (not shown). Depending on the rotational position of the slide plate 18, various struts can be selectively blocked or unblocked by the slide plate 18, deploying through mating windows (not shown) in the slide plate 18 when unblocked and into a mating pocket (not shown) formed in a surface 31 of the pocket plate 20. Once the struts (not shown) are positioned within their respective pockets (not shown), rotation of the SOWC assembly 11 in one or both rotational directions is prevented by the struts (not shown). As used herein, the first operating mode or forward mode allows some of the struts to hold torque in a clockwise direction,

i.e., in the direction of engine torque, while the second operating mode or reverse mode allows other struts to hold torque in the counterclockwise direction, i.e., in a the direction opposite that of the engine torque.

[0019] The SOWC assembly 11 includes an annular apply piston 26 having a ramped surface feature 50 (see Figures 2-4) adapted to engage the slide plate 18 when the piston 26 is applied to establish the second operating mode, as will be described below. In one embodiment, the piston 26 can be hydraulically-actuated using fluid pressure (arrow F) provided by a pressurized fluid source (P) 80, although other mechanical, electrical, or electro-mechanical actuation methods may be used within the scope of the invention. The source 80 can be commanded by a controller 60 having an appropriate shift algorithm (not shown), with the controller 60 being part of an overall transmission controller or a separate device as desired. The SOWC assembly 11 can also include an annular dam 22 that is sufficiently shaped or configured to allow a return spring 24 or other suitable return device to be seated therein. The dam 22 also acts to limit the travel or range of motion of the piston 26 whenever the piston 26 is being applied, as will be discussed below.

[0020] The return spring 24 can be any device adapted for providing a sufficient return force for moving the piston 26 in an axial direction with respect to the axis or rotation 13 of the SOWC assembly 11 when the piston 26 is not applied or is disengaged to establish the first or forward operating mode, as will be explained below. In the exemplary embodiment shown in Figure 1 , the return spring 24 is configured as an annular spring cage or a series of interspaced helical coil springs, although other spring devices may be used within the scope of the invention. Various retaining clips or rings 12, 14, 23, and 25 may also be used to help secure the different parts of the SOWC assembly 11 to each other and/or to secure the SOWC assembly 11 within the transmission 10 (see Figure IA), with the SOWC assembly 11 being splined within an outer clutch housing, drum, or center support 28 having external splines 29 for engagement with a stationary member (not shown), such as a transmission housing. [0021] Referring to Figure IA, the SOWC assembly 11 of Figure 1 can be used to selectively establish different operating modes in a transmission 10 having a rotatable

first member 71 and a rotatable second member 72. The first member 71 has an input torque Ti, referring to an inlet torque into the SOWC assembly 11 , and is operatively connected to the notch plate 16 of the SOWC assembly 11. The output member 72 has an output torque To, i.e., an output torque from the SOWC 11 , and is operatively connected to the pocket plate 20. The entire SOWC assembly 11 is positioned in or supported by the drum or center support 28, as will be understood by those of ordinary skill in the art. The SOWC assembly 11 therefore holds torque in one or the other rotational direction, depending on which of the two operating modes is selected, and thus can transfer the input torque Ti from the notch plate 16 and the first member 71 to the pocket plate 20 and output member 72, as needed, which then rotates with the output torque To.

[0022] Referring to Figure 2, a portion of the SOWC assembly 11 of Figure 1 is shown as it appears when the piston 26 is fully applied in the direction of arrow A. Such a fully applied position provides a second or reverse operating mode of the SOWC assembly 11. The knob portion 30 of the slide plate 18 protrudes through a through-hole or a slot 33 formed or otherwise provided in the pocket plate 20. The slot 33 has a first end 82 and a second end 81. The knob portion 30 is shown at the limit of its range of motion within the slot 33, and adjacent to the first end 82 of the slot 33. [0023] In accordance with the invention, the piston 26 is formed or provided with a notch or a ramped surface feature 50, as will be described in more detail below with reference to Figure 3. The ramped surface feature 50 allows the piston 26 to trap or engage the knob portion 30 to thereby force or move the knob portion 30 to the first end 82 of the slot 33, which is the position shown in Figure 2. A biasing spring 42 acts on each of the knob portion 30 and a post 43 formed integrally with or operatively connected to the notch plate 20. Force applied by the piston 26 in the direction of arrow A acts to overcome any biasing force provided by the biasing spring 42. [0024] Referring to Figure 3, a more detailed view is provided of the ramped surface feature 50 of the piston 26 relative to the positioning of the knob portion 30. The ramped surface feature 50 has a first angled surface 61 and a second angled surface 62 that are machined into or formed integrally with the piston 26 along a surface 95 thereof,

with the surface 95 being a surface of piston 26 that is immediately adjacent to the notch plate 20. The junction of the surfaces 61 and 62 form a substantially V-shaped profile or valley, as indicated by arrow B, in which the knob portion 30 is ultimately engaged or trapped during rotation of the notch plate 20 as the piston 26 is applied in an axial direction, i.e., in the direction of arrow A of Figure 2.

[0025] In the position shown in Figure 3, the return spring 24 (see Figure 1) is fully compressed, and an extension or arm portion 47 of the biasing spring 42 applies a reaction force on the knob portion 30, thus providing a potential return force that is realized once the piston 26 is released or when the SOWC assembly 11 is shifted or transitioned back to the first or forward operating mode. The knob portion 30 of the slide plate 18 toward the first end 82 of the slot 33. Torque is thus held by the SOWC assembly 11 (see Figure 1 ) in the desired direction, here the counterclockwise direction or a default forward direction that is opposite the direction of the input torque, as long as the piston 26 continues to apply a sufficient force in the direction of arrow A. [0026] Referring to Figure 4, the SOWC assembly 11 of Figure 1 is shown as it appears when the piston 26 is fully disengaged or released in the direction of arrow R. Such a fully released position may provide a first operating mode of the SOWC assembly 11, i.e., a default forward mode. Fluid pressure F (see Figure 1) is interrupted or discontinued, and therefore the return spring 24 is able to overcome any remaining apply force in the direction of arrow A (see Figures 2 and 3). The piston 26 is forced or moved a distance "d" away from the pocket plate 20 in the direction of arrow R by the return spring 24. A spring force provided by the biasing spring 42, and in particular by the extension portion or arm portion 47 thereof, reacts against the post 43 to force the knob portion 30 of the slide plate 18 away from the first end 82 and back toward the second end 81 of the slot 33. The knob portion 30 is thus disengaged from the ramped surface feature 50.

[0027] Referring to Figure 5, the SOWC assembly 11 of Figure 1 is shown with the piston 26 in the fully disengaged or OFF position, i.e., in the position or mode corresponding to Figure 4 as described above. The return spring 24 thus forces the piston 26 away from the pocket plate 20 in the direction of arrow R. An apply cavity 70 is

provided between the piston 26 and the center support 28, with the apply cavity 70 being in fluid communication with the fluid source 80 (see Figure 1), such as a hydraulic pump, through one or more fluid passages 77. Fluid admitted to the apply cavity 70 can thereby move the piston 26 in the direction of arrow A, such that the knob portion 30 of the slide plate 18 ultimately engages the ramped surface feature 50 (see Figure 3) and compresses or energizes the biasing spring 42 as described above.

[0028] The respective relative positions of each of the piston 26 and the slide plate 18 remain consistent, as they rotate at relatively high speeds and/or as they accelerate. In order to ensure the constant relative positioning of the piston 26 with respect to the slide plate 18, and vice versa, a guide pin 90 can be inserted into the piston 26 and adapted to freely move in and out of an opening 91 formed or provided in the dam 22. Also, maximum travel of the piston 26 is restricted by the presence of the dam 22, thereby preventing inadvertent interference with or damage to the slide plate 18 by the piston 26 as the piston 26 is applied.

[0029] While the best modes for carrying out the invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims.