Title of Invention	ELECTRICALLY VARIABLE TRANSMISSION WITH AN AXIALLY-MOVEABLE SELECTABLE ONE-WAY CLUTCH ASSEMBLY
Abstract	An electrically variable transmission (EVT) includes two shafts and a selectable one-way clutch (SOWC) having a first and second ring. The SOWC selectively connects the shafts, and is applied by moving the first ring and a blocking device in an axial direction into frictional contact with the second ring. A hydraulic piston applies the SOWC and a return spring releases it. The SOWC freewheels in both directions, or holds torque in one or both directions, depending on how the blocking device is rotated. A method for reducing losses in an EVT includes axially moving a second ring and blocking device of a SOWC into contact with a first ring, rotating the blocking device using frictional contact with the first ring, locking rotation of the first ring to apply the SOWC, and moving the second ring and blocking device an axial distance from the first ring to release the SOWC.

Title of Invention

ELECTRICALLY VARIABLE TRANSMISSION WITH AN AXIALLY-MOVEABLE SELECTABLE ONE-WAY CLUTCH ASSEMBLY

Abstract

An electrically variable transmission (EVT) includes two shafts and a selectable one-way clutch (SOWC) having a first and second ring. The SOWC selectively connects the shafts, and is applied by moving the first ring and a blocking device in an axial direction into frictional contact with the second ring. A hydraulic piston applies the SOWC and a return spring releases it. The SOWC freewheels in both directions, or holds torque in one or both directions, depending on how the blocking device is rotated. A method for reducing losses in an EVT includes axially moving a second ring and blocking device of a SOWC into contact with a first ring, rotating the blocking device using frictional contact with the first ring, locking rotation of the first ring to apply the SOWC, and moving the second ring and blocking device an axial distance from the first ring to release the SOWC.

Full Text	ELECTRICALLY VARIABLE TRANSMISSION WITH AN AXIALLY-MOVEABLE SELECTABLE ONE-WAY CLUTCH ASSEMBLY CLAIM OF PRIORITY [0001] This application claims priority to U.S. Provisional Patent Application No. 60/975,949, filed on September 28, 2007, which is hereby incorporated by reference in its entirety. TECHNICAL FIELD [0002] The present invention relates generally to an electrically variable transmission (EVT) with a selectable one-way clutch (SOWC) assembly having an axially-moveable portion for establishing one of three different clutch operating states. BACKGROUND OF THE INVENTION [0003] An EVT utilizes differential gearing and one or two electric motor/generators, also referred to as "motors" for simplicity, to allow adjustment of a speed ratio of a transmission input over a transmission output. An EVT may be particularly useful in a hybrid electric vehicle when used in conjunction with an electric energy storage device, such as a battery. An EVT may be able to save fuel relative to certain conventional automatic transmissions, in part because the EVT uses the energy- conserving action of the electric motors rather than the energy-dissipating action of a hydraulic torque converter. Additionally, an EVT provides the ability to continuously vary a transmission ratio, as well as the ability to recover energy during a braking event or slowing of the vehicle and to store this captured energy within the energy storage device. Finally, an EVT can assist a smaller and generally more efficient engine in propelling the vehicle. [0004] An EVT may have a single range, also referred to as a "mode", wherein the input speed, the output speed, and one or more motor speeds are a linear combination of one another. For example, the output speed may be one third of the sum of twice the speed of the input and the speed of one electric motor. Alternately, an EVT may have multiple ranges/modes to reduce the motor power required for adjusting the transmission speed ratio and a transmission or transfer of power from the input to the output. [0005] The multiple ranges/modes described above are activated by the engagement of selectable torque-transmitting devices or clutches. For example, a two- mode EVT may have one range for high transmission speed ratios, which is activated by the engagement of one clutch, and another range for low transmission speed ratios, which is activated by engagement of another clutch. Since each of these ranges is continuously variable, the EVT may be designed so that shifting between the two ranges may be accomplished with the transmission operating at a particular speed ratio which is common to both ranges. Therefore, the shift event may be made synchronously, that is, with zero relative speed across the clutches during the shift event. The shift event is then simply a torque transfer between one clutch and another clutch without the necessity of slipping between the clutches, while the electric motors control the speed ratio through the transmission both before and after the shift event. SUMMARY OF THE INVENTION [0006] Accordingly, an EVT is constructed with a SOWC that is operable for connecting first and second members or shafts of the EVT. The SOWC has a pair of rings, and is actuated or applied by moving one ring in an axial direction to select between multiple ranges or SOWC operating modes. The different transmission operating modes achieved through selection of the different SOWC operating modes reduce the motor power required for adjusting the transmission speed ratio through the range required for optimal engine efficiency over a wide range of vehicle operating conditions. Multiple ranges are also useful for reducing the amount of mechanical energy from the engine that must be converted to electrical energy and back into mechanical energy, for reducing the losses which come from these conversions, and therefore for improving fuel economy if greater losses are not incurred from the devices necessary for operating in multiple ranges. [0007] According to one embodiment, an electric motor can be connected to one or both of the first and second shafts to control a relative speed of the first and second rings. The SOWC includes a blocking device that moves through frictional contact with the first ring, with the blocking device at least partially determining a transition of the SOWC from a transmission of torque in one rotational direction to a transmission of torque in both rotational directions. The SOWC can be configured to include two sets of struts oriented in opposite directions, and the blocking device can include a plurality of windows aligned with respect to the struts to establish one of a plurality of different clutch operating modes, including holding torque in one, both, or neither rotational direction, depending one which set or sets of struts are blocked by the blocking device. [0008] A SOWC is provided for use with an EVT, and includes a first and a second ring, a plurality of strut pieces each configured for holding torque in one of a first and a second rotational direction to establish one of a plurality of different clutch operating modes, and a blocking device. The blocking device has a plurality of windows, and moves through frictional contact with the second ring to align the windows. The SOWC is applied by moving the second ring in an axial direction with respect to an axis of rotation of the first ring and the second ring. [0009] A method is also provided for reducing losses due to drag within an EVT. The method provides a SOWC having an axially-moveable second ring, a rotatable first ring, and an axially-moveable and selectively rotatable blocking device, and applies an apply force to the second ring to move the second ring into contact with the blocking device. The blocking device is then moved in an axial direction to establish frictional contact between the blocking device and the first ring. The frictional contact rotates the blocking device to align the blocking device and the first ring. The method includes locking the rotation of the first ring in at least one direction when the desired alignment is established, thus applying the SOWC, and releasing the SOWC by moving the second ring and the blocking device a predetermined axial distance away from the first ring. [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 a schematic cross sectional view of an electrically-variable transmission (EVT) having a selectable one-way clutch (SOWC) according to the invention; [0012] FIGURE 2 is an exploded perspective side view of a SOWC usable with the EVT shown in Figure 1; [0013] FIGURE 3A is a table describing multiple clutch operating modes according to the invention; [0014] FIGURE 3B is a schematic fragmentary cross sectional side view of the SOWC of the invention in a first operating mode; [0015] FIGURE 3C is a schematic fragmentary cross sectional side view of the SOWC of Figures 2 and 3B in a second operating mode; [0016] FIGURE 3D is a schematic fragmentary cross sectional side view of the SOWC of Figures 2, 3B, and 3C showing a different aspect of the second operating mode of Figure 3C; [0017] FIGURE 3E is a schematic fragmentary cross sectional side view of the SOWC of Figures 2, 3B, 3C, and 3D in a third operating mode; [0018] FIGURE 4A is a graphical illustration of differential clutch speed versus clutch operating mode during an application of the SOWC shown in Figure 2; and [0019] FIGURE 4B is a graphical illustration of differential clutch speed versus clutch operating mode during a release of the SOWC shown in Figure 2. DESCRIPTION OF THE PREFERRED EMBODIMENTS [0020] Referring to the drawings wherein like reference numbers correspond to like or similar components throughout the several figures, and beginning with Figure 1, a transmission 10, shown in one embodiment as an electrically variable transmission (EVT), has a selectable one-way clutch 18, hereinafter referred to simply as the SOWC 18, with an axis of rotation 11 (see Figure 2). The SOWC 18 is shown as a mechanical diode-type one-way clutch device, but it may also take the form of a sprag clutch, a roller clutch, or another style of one-way clutch within the scope of the invention. The transmission 10 has a stationary outer housing or case 13 that is constructed or cast from a ferrous or a nonferrous material, and within which the SOWC 18 is enclosed. The SOWC 18 includes a first race or ring 20, second race or ring 22, and a selector plate/ring or a blocking device 50, each of which will be described in detail below with reference to Figure 2. [0021] The SOWC 18 also includes an actuator 16, such as a hydraulic apply piston or other hydraulically-actuated device, that is moveable in response to a force imparted by pressurized hydraulic fluid 23 (see Figure 2). The fluid 23 of Figure 2 may be delivered to the SOWC 18 by a pump (not shown) as needed through one or more fluid channels (not shown), as will be understood by those of ordinary skill in the art. The transmission 10 has a first rotatable shaft 12A that is connected to an electric motor/generator 17, and the transmission 10 further includes a second rotatable shaft 12B. The SOWC 18 is operable for transferring torque from a power source, such as an engine (not shown) and/or the electric motor/generator 17, to the drive wheels of a vehicle (not shown) by selectively transferring torque between the first and second rotatabfe shafts 12A and 12B, respectively, as needed, and/or between one of the rotatable shafts 12A, 12B and a stationary member of the transmission 10, such as the case 13. [0022] In accordance with the invention, the transmission 10 may successfully shift gears using the SOWC 18 under all necessary operating conditions, including some random output torque fluctuations that may be caused by rough roads. The SOWC 18 does not cause significant drag and does not require a high-volume, high- pressure supply of oil for actuation in the manner of conventional wet plate clutches. Using the SOWC 18, therefore, the transmission 10 will gain a substantial further advantage by lowering the losses occurring within the transmission 10, thus optimizing fuel economy while reducing emissions. [0023] A portion of the SOWC 18, such as the second ring 22, is splined or otherwise operatively connected to the first rotatable shaft 12A so that the second ring 22 is configured for or is capable of axial motion along the first rotatable shaft 12A. Another portion of the SOWC 18, such as the first ring 20, is splined to the second rotatable shaft 12B of the transmission 10, so that the first ring 20 resists axial motion. The SOWC 18 connects the first and second rotating shafts 12A, 12B, respectively, and so may be called a "rotating clutch", while an otherwise similarly configured clutch 19 connects the second rotating shaft 12B with the non-rotating case 13 or another stationary member, and so may be called a "stationary clutch". [0024] Referring to Figure 2 as one possible embodiment of the SOWC 18, the first ring 20 includes a circular central bore 39, and includes a plurality of radially-inward projecting teeth or splines (not shown) which are configured to engage or mate with slots or grooves of a rotatable body, such as the first rotatable shaft 12A, to thereby rotate in conjunction therewith. Likewise, the second ring 22 has a circular central bore 24 through which a rotatable and/or groundable hub portion (not shown) extends. To enable the transfer of torque from the first rotatable shaft 12A (see Figure 1) to the second ring 22, the second ring 22 may be operatively connected to a reaction gear of a compound planetary gear set (not shown), or the hub portion (not shown) may be directly splined to the central bore 24, depending on the application, as will be understood by those of ordinary skill in the art. [0025] The second ring 22 is shaped or configured to capture a plurality of torque-holding wedges, strut pieces, or struts 34 and a first ring 20 is shaped or configured to include a plurality of angled strut pockets 36 for receiving the struts 34, with two sets of the struts 34 and pockets 36 oriented differently in order to hold torque in a particular direction, as will be explained later hereinbelow. The blocking device 50 is positioned between the respective first and second rings 20 and 22, and is configured with a plurality of alternating windows 54 and blocking sections 55 arranged circumferentially around the blocking device 50. The alternating windows 54 and blocking sections 55 are positioned relative to the struts 34 so that by rotating the blocking device 50 relative to the second ring 22, all of the struts 34 that are oriented or facing in one direction or the other direction may be blocked or otherwise prevented from engaging the first ring 20. [0026] An optional centering spring 38 is fitted between the second ring 22 and the blocking device 50 and is adapted for aligning each of the alternating windows 54 of the blocking device 50 with a different one of the struts 34. One end of the centering spring 38 may be press-fitted to the blocking device 50 through a mating hole 35 formed or bored therein, and at another end to the second ring 22 through a mating hole 31 formed or bored therein. The centering spring 38 is positioned or routed external to any interface formed between the second ring 22 and the blocking device 50 when the second ring 22 contacts the blocking device 50, as described in more detail below. [0027] The second ring 22 is configured with a plurality of strut wells 32, which in the embodiment shown in Figure 2 may be configured as through-openings through the second ring 22, i.e., from a front face 22A of the second ring 22 completely through to a rear face 22B of the second ring 22. Half of the strut wells 32 are oriented in one direction, and the remaining strut wells 32 are oriented or aligned in the opposite direction. In this manner, approximately half of the struts 34 are allowed to "lock" or engage with the angled strut pockets 36 of the first ring 20 at any given time to lock torque in a corresponding rotational direction. The different orientation of the struts 34 allows some struts 34 to be deployed in an axial direction (arrow A) while the remaining struts 34 are depressed by the blocking sections 55 of the blocking device 50, so that the rotation of the first ring 20 may be locked or held in one rotational direction or the other rotational. [0028] The blocking device 50 has three effective positions relative to the second ring 22: a first position allowing those of the struts 34 that are oriented or facing in one common direction to engage the first ring 20 and lock it in one rotational direction relative to the second ring 22, a second position allowing those of the struts 34 that oriented or facing in the other common direction to engage the first ring 20 and lock it in the other rotational direction relative to the second ring 22, and a third position which may be assisted by the centering spring 38, the third position allowing all of the struts 34 of either orientation to engage the first ring 20 and lock it in both directions relative to the first ring 22, provided that the actuator 16 has moved the second ring 22 in close enough proximity to the first ring 20. [0029] The SOWC 18 further includes the actuator 16 also shown in Figure 1, such as a hydraulic apply piston responsive to pressurized hydraulic fluid 23, that may be operatively connected to or formed integrally with an apply ring 26. The second ring 22 and the blocking device 50 together make up an axially-moveable portion 21 of the SOWC 18, i.e., a portion of the SOWC 18 that is moveable in an axial direction in response to an apply force in the direction of arrow A. The apply ring 26 has a plurality of axially-projecting teeth 26A that are mutually spaced around a circumference of the apply ring 26. The teeth 26A have an upper surface 27, and are each separated by a lower surface or valley 28. As the strut wells 32 of the second ring 22 are through- openings as described above, i.e., they each extend axially through the second ring 22 from the front face 22A to the rear face 22B, movement of the apply ring 26 in the direction of arrow A allows the teeth 26A to enter a corresponding strut well 32 positioned adjacent thereto. [0030] The axial movement of the apply ring 26 in response to an apply force in the direction of arrow A acts as a force on a strut spring 37 that is positioned in each of the strut wells 32 between the upper surface 27 of each tooth 26A and the strut 34. If this force acting on each of the strut springs 37 is not opposed by a blocking surface 55 of the blocking device 50 positioned between a strut 34 and a mating angled strut pocket 36 in the first ring 20, the spring force imparted by the strut spring 37 will force each strut 34 into a mating angled pocket 36 of the first ring 20. If this force is so opposed, the strut spring 37 will compress, providing a potential force for rapidly deploying the strut 34 when the blocking device 50 is again moved. [0031] Once the blocking device 50 is placed in direct contact with the second ring 22, a continued application of force in the direction of arrow A will eventually move the blocking device 50 into contact with the first ring 20. Frictional forces imparted by the rotational motion of the first ring 20, and by any intervening fluid film from the pressurized hydraulic fluid 23 present between the first ring 20 and the blocking device 50, will tend to drag the blocking device 50 in the same rotational direction. This drag will ultimately position the blocking device 50 in such a manner as to cover one commonly oriented set of struts 34 with the blocking surfaces 55, and to free the other commonly oriented set of struts 34 to move or deploy through the windows 54 into the angled strut wells 36 of the first ring 20. That is, the blocking device 50 will rotate to cover the set of struts 34 oriented so as to immediately attempt to the lock the first ring 20 with respect to the second ring 22 as the struts 34 and the strut springs 37 are actuated by the apply ring 26. [0032] A return mechanism 58 is provided within the SOWC 18, with the return mechanism 58 being configured as a spring or another suitable device providing a sufficient return force for moving the blocking device 50 and the second ring 22 in the direction of arrow R a sufficient distance for disengaging the struts 34 from the first ring 20. Therefore, when an apply force in the direction of arrow A is discontinued or removed, such as by temporarily interrupting a supply of pressurized hydraulic fluid 23 to the actuator 16, the return force in the direction of arrow R allows the SOWC 18 to disengage and to "freewheel" until engagement of the SOWC 18 in one or both directions is desired. [0033] Referring to Figure 3A, various clutch operating modes are shown for the SOWC 18 (see Figures 1 and 2), with each mode defining a direction of torque holding with respect to the SOWC 18. In Mode 1, pressure to the actuator 16 (see Figure 2) is turned off, and the SOWC 18 is allowed to "freewheel", i.e., torque is not held in either rotational direction. Mode 1 permits the first ring 20 to rotate or spin unimpeded with respect to the second ring 22. In Modes 2A and 3, pressure to the actuator 16 is turned on, and torque is locked or held in one rotational direction. Modes 2A and 2B are identical in operation, except for the direction in which torque is held. For example, in Mode 2A the first ring 20 may be permitted to freewheel or rotate unimpeded in a forward rotational direction, and to lock or be prevented from rotating in the reverse rotational direction, while Mode 2B would likewise permit the reverse rotation of the first ring 20, holding torque in the forward direction. Finally, in Mode 3 the SOWC 18 is locked, i.e., torque is held in both rotational directions. Each of the operating modes described generally above as applied to the SOWC 18 are shown in detail in the fragmentary cross-sectional side views of Figures 3B, 3C, and 3D, respectively. [0034] In each of Figures 3B, 3C, and 3D, the angled strut pockets 36 of Figure 2 are shown as the angled strut pockets 36A and 36B to differentiate their different torque- holding orientation. Each of the strut pockets 36A, 36B has a substantially vertical locking surface 40 and an angled surface 41. The struts 34 of Figure 1 are represented by their respective orientation as 34A, 34B. The vertical locking surface 40 is configured and/or shaped to oppose a strut 34A, 34B as needed to thereby prevent rotation of the first ring 20 in one direction when either of Modes 2A, 2B, or 3 are selected (see Figure 3A). Likewise, the sloped surface 41 is configured and/or shaped to allow a strut 34A, 34B to be depressed by the blocking device 50 into a mating strut well 32A, 32B to permit relative rotation of one of the respective first and second rings 20, 22 (see Figure 2). When the SOWC 18 is locked in one direction and is transmitting torque, the separation of the ends of the struts 34 in the axial direction may create a force that tends to separate the first ring 20 from the second ring 22, so that upon the SOWC 18 locking in one direction, the friction force on the blocking device 50 is reduced, and the blocking device 50 is rotated by the centering spring 35 (see Figure 2) into the center position shown in Figure 3E. Alternately, the centering spring 35 may assist friction force on the blocking device 50 so that as the first ring 20 rotates slightly relative to the second ring 22 to lock via a commonly oriented set of the struts 34, the blocking device 50 also rotates slightly relative to the second ring 22, thus uncovering the other commonly oriented set of struts 34. In this position, all of the struts 34 are aligned with the windows 54 in the blocking device 50, and may therefore engage the first ring 20. [0035] As shown in Figures 3B through 3E, a sensor (S) 29 can sense, detect, or otherwise determine the relative speed of the rings 20, 22 for use in controlling the SOWC 16. The second ring 22 may be rotating or grounded, such as to the stationary transmission housing or casing 13 (see Figure 1), and first ring 20 is always allowed to rotate. The first ring 20 may be connected to motor/generator 17 (see Figure 1), which is in communication with a motor controller (not shown) that is configured to synchronize the rotational speeds of the first and second rings 20, 22 to facilitate actuation of the SO WC 18. However, in the event the second ring 22 is not grounded and therefore is also rotating, the motor/generator 17 would be likewise connected to the second ring 22 and in communication with the controller (not shown), as will be understood by those of ordinary skill in the art. [0036] In Figure 3B, and representing Mode 1 or a "freewheeling" mode, the blocking device 50 is separated from the first ring 20 by the return mechanism 58 (see Figure 2), thus forcing the struts 34 out of engagement with each respective mating strut pocket 36. The apply force represented by the arrow A, as shown also in Figure 2, is zero or off, allowing the previously described return force (arrow R) to move or separate the blocking device 50 and the second ring 22 from the first ring 20. The initial distance of separation (d1) is sufficient for ensuring that no portion of any of the struts 34A, 34B may contact the first ring 20. The SOWC 18 therefore freewheels in either direction, as represented by arrows 1 and 2. [0037] Referring to Figure 3C, which represents Mode 2A or torque-holding in a reverse direction, the apply pressure (arrow A) is turned on, thus forcing the apply ring 26 to move axially in the direction of arrow A. This moves the axially-moveable portion 21 of the SOWC 18, and the distance of separation (d2) between the actuator ring 26 and the first ring 20 is less than the initial distance of separation (d1) shown in Figure 3B. The blocking device 50 blocks the struts 34A, with the strut springs 37 forcing any previously depressed strut 34B into engagement with the first ring 20. The struts 34B "lock' via interference with a vertical locking surface 40 of each angled strut well 36B into which the struts 34B are forced or moved. The orientation of the struts 34B within the angled strut wells 36B therefore ensures that torque is held or prevented in the reverse position by allowing the first ring 20 to rotate in the direction of arrow 2, but by preventing the first ring 20 from rotating in the direction of arrow 1 (see Figure 3B). [0038] Referring to Figure 3D, which represents Mode 2B or torque-holding in a forward direction, the apply pressure (arrow A) remains on, still forcing the apply ring 26 to move in the direction of arrow A. The blocking device 50 blocks the struts 34B, with strut springs 37 forcing any previously depressed strut 34A into engagement with the first ring 20. The struts 34A "lock" via interference with a vertical locking surface 40 of each well 36A into which the struts 34A are forced or moved. The orientation of the struts 34A within the wells 36B therefore ensures that torque is held or prevented in the reverse position by preventing the first ring 20 from rotating in the direction of arrow 2. [0039] Turning to Figure 3E, which represents Mode 3 or torque-holding in both rotational directions, the apply pressure (arrow A) remains on, still forcing the apply ring 26 to move in the direction of arrow A. The SOWC 18 stops, with zero relative motion between the inner and second rings 20 and 22, respectively. Drag on the blocking device 50 therefore disappears. Absent such drag forces, the centering ring 38 (see Figure 2) is allowed to force or pull the blocking device 50 into a desired alignment with the second ring 22, with the strut springs 37 allowed to move any previously depressed struts 34A, 34B into engagement with the first ring 20. The struts 34A and 34B therefore "lock" the torque via interference with a vertical locking surface 40 of each well 36A, 36B into which the struts 34A, 34B are respectively forced or moved. The orientation of the struts 34A, 34B within the angled strut wells 36A, 36B therefore ensures that torque is held or pre\ ented in both the forward and reverse positions by preventing the first ring 20 from rotating in the direction of arrows 1 and 2 (see Figure 3B). [0040] As shown in Figure 4A, while in Mode 1, i.e., "freewheeling", in order to apply the SOWC 18, a controller (not shown) cycles or synchronizes the first and second rings 20, 22, respectively, so that a differential speed Δs therebetween approaches approximately zero revolution per minute, as represented by the point 61. A signal communicated at point 61 precipitates a change from Mode 1 to Mode 2 when a speed sensor (not shown) detects that the direction of Δs, which changes at point 62, reaches a non-negative quantity, i.e., at point 64, at which point the SOWC 18 of Figure 2 is "shifted" or changed to either of Mode 2A or Mode 2B, depending on the rotational direction of first ring 20, and thus holding torque in the respective reverse or forward rotational direction. [0041] Because of the inherent time delay in making a physical shift by movement of the blocking device plate 50 (see Figures 2 and 3B through 3E), a slight time lag At occurs before Mode 2 is fully realized at point 65. While the direction of Δs is positive, the SOWC 18 continues freewheeling. While in Mode 2, when the direction of Δs turns negative, i.e., at point 68, the clutch 18 locks. When the speed sensor (not shown) detects zero differential clutch speed and zero speed change, the SOWC 18 changes to Mode 3 so that rotational motion is prevented in both directions, as shown in Figure 2D, thereby freeing or releasing the electric motor/generator 17 (see Figure 1) to change speeds as necessary. Because of the time delay in making the physical shift by actuation of the blocking device 50, a slight time lag At occurs before Mode 3 is fully realized at point 69. [0042] Referring to Figure 4B, a similar speed curve is shown describing the release of the SOWC 18, beginning with dual-directional torque holding of Mode 3. To initiate a release of the SOWC 18, a mode change is signaled from Mode 3 to Mode 2 at point 71. Prior to a mode change to Mode 2, the SOWC 18 is momentarily loaded in the direction opposite that of the impending clutch release in the opposite direction, and then in Mode 2A or 2B, the clutch 18 is unloaded so that the SOWC 18 may be easily released. When the speed sensor (not shown) detects that the quantity Δs is positive, the operating mode is changed to "freewheel in both directions", i.e., Mode 1 at point 72, which is the initial state of Figure 4A as previously described hereinabove. [0043] 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. CLAIMS 1. A transmission comprising: a first shaft; a second shaft; a selectable one-way clutch (SOWC) having an axis of rotation, a first ring, and an axially-moveable second ring, the SOWC being operable for selectively moving the second ring in an axial direction to connect the first shaft to the second shaft; and an electric motor connected to at least one of the first shaft and the second shaft; wherein the electric motor is operable for controlling a relative speed between the first ring and the second ring of the SOWC. 2. The transmission of claim 1, wherein the SOWC is applied by moving the second ring in an axial direction with respect to the axis of rotation toward the first ring until the second ring is locked to the first ring. 3. The transmission of claim 2, wherein the SOWC includes at least one blocking device configured for moving through frictional contact with the first ring, the blocking device at least partially determining a transition of the SOWC from a transmission of torque in one rotational direction to a transmission of torque in both rotational directions. 4. The transmission of claim 3, wherein the SOWC includes a plurality of strut pieces and the blocking device includes a plurality of windows, and wherein moving through frictional contact aligns the plurality of windows with respect to the plurality of strut pieces in a predetermined manner for establishing one of a plurality of different clutch operating modes, including a first operating mode comprising a freewheeling of the SOWC in both of the rotational directions, a second operating mode comprising a holding of torque in one rotational direction, and a third operating mode for holding torque in both rotational directions. 5. The transmission of claim 1, further comprising an apply mechanism capable of motion along an axis parallel to the axis of rotation of one of the first shaft and the second shaft, and a return mechanism operable for applying a return force on the apply mechanism; wherein the SOWC is actuatable using the apply mechanism and is releasable using the return spring mechanism. 6. The transmission of claim 5, wherein the apply mechanism is a hydraulic piston. 7. A selectable one-way clutch (SOWC) for use with a vehicle transmission, the SOWC comprising: a first ring; a second ring; a plurality of strut pieces each configured for holding torque in one of a first and a second rotational direction to establish one of a plurality of different clutch operating modes; and a blocking device having a plurality of windows, the blocking device being configured for moving through frictional contact with the first ring to thereby align the plurality of windows in a predetermined manner for establishing one of the plurality of different clutch operating modes; wherein the SOWC is applied by moving the second ring in an axial direction with respect to an axis of rotation of the first ring and the second ring. 8. The SOWC of claim 7, wherein the plurality of different clutch operating modes includes a freewheeling of the SOWC in two rotational directions, a holding of torque in one rotational direction, and a holding of torque in both rotational directions. 9. The SOWC of claim 7, further comprising a centering spring that is fitted between the second ring and the blocking device; wherein the centering spring aligns each of the plurality of windows of the blocking device with a different one of the plurality of strut pieces. 10. The SOWC of claim 1, further comprising a hydraulic piston for moving the second ring in the axial direction with respect to the axis of rotation of the first ring and the second ring. 11. The SOWC of claim 7, wherein half of the plurality of strut pieces are configured for holding torque in the first rotational direction and half of the plurality of strut pieces are configured for holding torque in the second rotational direction. 12. A method for reducing losses due to clutch drag within a vehicle transmission, the method comprising: providing a selectable one-way clutch (SOWC) having a rotatable first ring, an axially moveable second ring, and an axially moveable and selectively rotatable blocking device; applying an apply force to the second ring to move the second ring in an axial direction and into contact with the blocking device; moving the blocking device in the axial direction to establish a frictional contact between the blocking device and the first ring; rotating the blocking device using the frictional contact with the first ring to thereby establish a desired alignment between the blocking device and the first ring; preveting a rotation of the first ring in at least one direction when the desired alignment is established, thereby applying the SOWC; and moving the second ring and the blocking device a predetermined axial distance away from the first ring to thereby release the SOWC. 13. The method of claim 12, wherein moving the second ring and the blocking device includes applying a return force to the second ring while reducing the force a sufficient level below a level of the return force. 14. The method of claim 12, further comprising providing the selectable one-way clutch (SOWC) with a plurality of strut pieces; wherein applying the SOWC includes blocking half of the plurality of strut pieces using the blocking device. 15. The method of claim 12, further comprising providing the SOWC with an apply ring; wherein moving the blocking device in the axial direction includes applying a pressurized supply of fluid to thereby move the apply ring into contact with the second ring. An electrically variable transmission (EVT) includes two shafts and a selectable one-way clutch (SOWC) having a first and second ring. The SOWC selectively connects the shafts, and is applied by moving the first ring and a blocking device in an axial direction into frictional contact with the second ring. A hydraulic piston applies the SOWC and a return spring releases it. The SOWC freewheels in both directions, or holds torque in one or both directions, depending on how the blocking device is rotated. A method for reducing losses in an EVT includes axially moving a second ring and blocking device of a SOWC into contact with a first ring, rotating the blocking device using frictional contact with the first ring, locking rotation of the first ring to apply the SOWC, and moving the second ring and blocking device an axial distance from the first ring to release the SOWC.

Full Text

ELECTRICALLY VARIABLE TRANSMISSION WITH AN AXIALLY-MOVEABLE
SELECTABLE ONE-WAY CLUTCH ASSEMBLY
CLAIM OF PRIORITY
[0001] This application claims priority to U.S. Provisional Patent Application
No. 60/975,949, filed on September 28, 2007, which is hereby incorporated by
reference in its entirety.
TECHNICAL FIELD
[0002] The present invention relates generally to an electrically variable
transmission (EVT) with a selectable one-way clutch (SOWC) assembly having an
axially-moveable portion for establishing one of three different clutch operating states.
BACKGROUND OF THE INVENTION
[0003] An EVT utilizes differential gearing and one or two electric
motor/generators, also referred to as "motors" for simplicity, to allow adjustment of a
speed ratio of a transmission input over a transmission output. An EVT may be
particularly useful in a hybrid electric vehicle when used in conjunction with an electric
energy storage device, such as a battery. An EVT may be able to save fuel relative to
certain conventional automatic transmissions, in part because the EVT uses the energy-
conserving action of the electric motors rather than the energy-dissipating action of a
hydraulic torque converter. Additionally, an EVT provides the ability to continuously
vary a transmission ratio, as well as the ability to recover energy during a braking event
or slowing of the vehicle and to store this captured energy within the energy storage
device. Finally, an EVT can assist a smaller and generally more efficient engine in
propelling the vehicle.
[0004] An EVT may have a single range, also referred to as a "mode", wherein
the input speed, the output speed, and one or more motor speeds are a linear
combination of one another. For example, the output speed may be one third of the

sum of twice the speed of the input and the speed of one electric motor. Alternately, an
EVT may have multiple ranges/modes to reduce the motor power required for adjusting
the transmission speed ratio and a transmission or transfer of power from the input to
the output.
[0005] The multiple ranges/modes described above are activated by the
engagement of selectable torque-transmitting devices or clutches. For example, a two-
mode EVT may have one range for high transmission speed ratios, which is activated
by the engagement of one clutch, and another range for low transmission speed ratios,
which is activated by engagement of another clutch. Since each of these ranges is
continuously variable, the EVT may be designed so that shifting between the two
ranges may be accomplished with the transmission operating at a particular speed ratio
which is common to both ranges. Therefore, the shift event may be made
synchronously, that is, with zero relative speed across the clutches during the shift
event. The shift event is then simply a torque transfer between one clutch and another
clutch without the necessity of slipping between the clutches, while the electric motors
control the speed ratio through the transmission both before and after the shift event.
SUMMARY OF THE INVENTION
[0006] Accordingly, an EVT is constructed with a SOWC that is operable for
connecting first and second members or shafts of the EVT. The SOWC has a pair of
rings, and is actuated or applied by moving one ring in an axial direction to select
between multiple ranges or SOWC operating modes. The different transmission
operating modes achieved through selection of the different SOWC operating modes
reduce the motor power required for adjusting the transmission speed ratio through the
range required for optimal engine efficiency over a wide range of vehicle operating
conditions. Multiple ranges are also useful for reducing the amount of mechanical
energy from the engine that must be converted to electrical energy and back into
mechanical energy, for reducing the losses which come from these conversions, and

therefore for improving fuel economy if greater losses are not incurred from the
devices necessary for operating in multiple ranges.
[0007] According to one embodiment, an electric motor can be connected to one
or both of the first and second shafts to control a relative speed of the first and second
rings. The SOWC includes a blocking device that moves through frictional contact with
the first ring, with the blocking device at least partially determining a transition of the
SOWC from a transmission of torque in one rotational direction to a transmission of
torque in both rotational directions. The SOWC can be configured to include two sets
of struts oriented in opposite directions, and the blocking device can include a plurality
of windows aligned with respect to the struts to establish one of a plurality of different
clutch operating modes, including holding torque in one, both, or neither rotational
direction, depending one which set or sets of struts are blocked by the blocking device.
[0008] A SOWC is provided for use with an EVT, and includes a first and a
second ring, a plurality of strut pieces each configured for holding torque in one of a
first and a second rotational direction to establish one of a plurality of different clutch
operating modes, and a blocking device. The blocking device has a plurality of
windows, and moves through frictional contact with the second ring to align the
windows. The SOWC is applied by moving the second ring in an axial direction with
respect to an axis of rotation of the first ring and the second ring.
[0009] A method is also provided for reducing losses due to drag within an
EVT. The method provides a SOWC having an axially-moveable second ring, a
rotatable first ring, and an axially-moveable and selectively rotatable blocking device,
and applies an apply force to the second ring to move the second ring into contact with
the blocking device. The blocking device is then moved in an axial direction to
establish frictional contact between the blocking device and the first ring. The
frictional contact rotates the blocking device to align the blocking device and the first
ring. The method includes locking the rotation of the first ring in at least one direction
when the desired alignment is established, thus applying the SOWC, and releasing the

SOWC by moving the second ring and the blocking device a predetermined axial
distance away from the first ring.
[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 a schematic cross sectional view of an electrically-variable
transmission (EVT) having a selectable one-way clutch (SOWC) according to the
invention;
[0012] FIGURE 2 is an exploded perspective side view of a SOWC usable with
the EVT shown in Figure 1;
[0013] FIGURE 3A is a table describing multiple clutch operating modes
according to the invention;
[0014] FIGURE 3B is a schematic fragmentary cross sectional side view of the
SOWC of the invention in a first operating mode;
[0015] FIGURE 3C is a schematic fragmentary cross sectional side view of the
SOWC of Figures 2 and 3B in a second operating mode;
[0016] FIGURE 3D is a schematic fragmentary cross sectional side view of the
SOWC of Figures 2, 3B, and 3C showing a different aspect of the second operating mode
of Figure 3C;
[0017] FIGURE 3E is a schematic fragmentary cross sectional side view of the
SOWC of Figures 2, 3B, 3C, and 3D in a third operating mode;
[0018] FIGURE 4A is a graphical illustration of differential clutch speed versus
clutch operating mode during an application of the SOWC shown in Figure 2; and
[0019] FIGURE 4B is a graphical illustration of differential clutch speed versus
clutch operating mode during a release of the SOWC shown in Figure 2.
DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Referring to the drawings wherein like reference numbers correspond to
like or similar components throughout the several figures, and beginning with Figure 1, a
transmission 10, shown in one embodiment as an electrically variable transmission
(EVT), has a selectable one-way clutch 18, hereinafter referred to simply as the SOWC
18, with an axis of rotation 11 (see Figure 2). The SOWC 18 is shown as a mechanical
diode-type one-way clutch device, but it may also take the form of a sprag clutch, a roller
clutch, or another style of one-way clutch within the scope of the invention. The
transmission 10 has a stationary outer housing or case 13 that is constructed or cast from
a ferrous or a nonferrous material, and within which the SOWC 18 is enclosed. The
SOWC 18 includes a first race or ring 20, second race or ring 22, and a selector plate/ring
or a blocking device 50, each of which will be described in detail below with reference to
Figure 2.
[0021] The SOWC 18 also includes an actuator 16, such as a hydraulic apply
piston or other hydraulically-actuated device, that is moveable in response to a force
imparted by pressurized hydraulic fluid 23 (see Figure 2). The fluid 23 of Figure 2 may
be delivered to the SOWC 18 by a pump (not shown) as needed through one or more
fluid channels (not shown), as will be understood by those of ordinary skill in the art.
The transmission 10 has a first rotatable shaft 12A that is connected to an electric
motor/generator 17, and the transmission 10 further includes a second rotatable shaft
12B. The SOWC 18 is operable for transferring torque from a power source, such as an
engine (not shown) and/or the electric motor/generator 17, to the drive wheels of a
vehicle (not shown) by selectively transferring torque between the first and second
rotatabfe shafts 12A and 12B, respectively, as needed, and/or between one of the
rotatable shafts 12A, 12B and a stationary member of the transmission 10, such as the
case 13.
[0022] In accordance with the invention, the transmission 10 may successfully
shift gears using the SOWC 18 under all necessary operating conditions, including
some random output torque fluctuations that may be caused by rough roads. The
SOWC 18 does not cause significant drag and does not require a high-volume, high-
pressure supply of oil for actuation in the manner of conventional wet plate clutches.

Using the SOWC 18, therefore, the transmission 10 will gain a substantial further
advantage by lowering the losses occurring within the transmission 10, thus optimizing
fuel economy while reducing emissions.
[0023] A portion of the SOWC 18, such as the second ring 22, is splined or
otherwise operatively connected to the first rotatable shaft 12A so that the second ring 22
is configured for or is capable of axial motion along the first rotatable shaft 12A.
Another portion of the SOWC 18, such as the first ring 20, is splined to the second
rotatable shaft 12B of the transmission 10, so that the first ring 20 resists axial motion.
The SOWC 18 connects the first and second rotating shafts 12A, 12B, respectively, and
so may be called a "rotating clutch", while an otherwise similarly configured clutch 19
connects the second rotating shaft 12B with the non-rotating case 13 or another stationary
member, and so may be called a "stationary clutch".
[0024] Referring to Figure 2 as one possible embodiment of the SOWC 18, the
first ring 20 includes a circular central bore 39, and includes a plurality of radially-inward
projecting teeth or splines (not shown) which are configured to engage or mate with slots
or grooves of a rotatable body, such as the first rotatable shaft 12A, to thereby rotate in
conjunction therewith. Likewise, the second ring 22 has a circular central bore 24
through which a rotatable and/or groundable hub portion (not shown) extends. To enable
the transfer of torque from the first rotatable shaft 12A (see Figure 1) to the second ring
22, the second ring 22 may be operatively connected to a reaction gear of a compound
planetary gear set (not shown), or the hub portion (not shown) may be directly splined to
the central bore 24, depending on the application, as will be understood by those of
ordinary skill in the art.
[0025] The second ring 22 is shaped or configured to capture a plurality of
torque-holding wedges, strut pieces, or struts 34 and a first ring 20 is shaped or
configured to include a plurality of angled strut pockets 36 for receiving the struts 34,
with two sets of the struts 34 and pockets 36 oriented differently in order to hold torque
in a particular direction, as will be explained later hereinbelow. The blocking device 50
is positioned between the respective first and second rings 20 and 22, and is configured
with a plurality of alternating windows 54 and blocking sections 55 arranged

circumferentially around the blocking device 50. The alternating windows 54 and
blocking sections 55 are positioned relative to the struts 34 so that by rotating the
blocking device 50 relative to the second ring 22, all of the struts 34 that are oriented or
facing in one direction or the other direction may be blocked or otherwise prevented from
engaging the first ring 20.
[0026] An optional centering spring 38 is fitted between the second ring 22 and
the blocking device 50 and is adapted for aligning each of the alternating windows 54 of
the blocking device 50 with a different one of the struts 34. One end of the centering
spring 38 may be press-fitted to the blocking device 50 through a mating hole 35 formed
or bored therein, and at another end to the second ring 22 through a mating hole 31
formed or bored therein. The centering spring 38 is positioned or routed external to any
interface formed between the second ring 22 and the blocking device 50 when the second
ring 22 contacts the blocking device 50, as described in more detail below.
[0027] The second ring 22 is configured with a plurality of strut wells 32, which
in the embodiment shown in Figure 2 may be configured as through-openings through the
second ring 22, i.e., from a front face 22A of the second ring 22 completely through to a
rear face 22B of the second ring 22. Half of the strut wells 32 are oriented in one
direction, and the remaining strut wells 32 are oriented or aligned in the opposite
direction. In this manner, approximately half of the struts 34 are allowed to "lock" or
engage with the angled strut pockets 36 of the first ring 20 at any given time to lock
torque in a corresponding rotational direction. The different orientation of the struts 34
allows some struts 34 to be deployed in an axial direction (arrow A) while the remaining
struts 34 are depressed by the blocking sections 55 of the blocking device 50, so that the
rotation of the first ring 20 may be locked or held in one rotational direction or the other
rotational.
[0028] The blocking device 50 has three effective positions relative to the second
ring 22: a first position allowing those of the struts 34 that are oriented or facing in one
common direction to engage the first ring 20 and lock it in one rotational direction
relative to the second ring 22, a second position allowing those of the struts 34 that
oriented or facing in the other common direction to engage the first ring 20 and lock it in

the other rotational direction relative to the second ring 22, and a third position which
may be assisted by the centering spring 38, the third position allowing all of the struts 34
of either orientation to engage the first ring 20 and lock it in both directions relative to the
first ring 22, provided that the actuator 16 has moved the second ring 22 in close enough
proximity to the first ring 20.
[0029] The SOWC 18 further includes the actuator 16 also shown in Figure 1,
such as a hydraulic apply piston responsive to pressurized hydraulic fluid 23, that may be
operatively connected to or formed integrally with an apply ring 26. The second ring 22
and the blocking device 50 together make up an axially-moveable portion 21 of the
SOWC 18, i.e., a portion of the SOWC 18 that is moveable in an axial direction in
response to an apply force in the direction of arrow A. The apply ring 26 has a plurality
of axially-projecting teeth 26A that are mutually spaced around a circumference of the
apply ring 26. The teeth 26A have an upper surface 27, and are each separated by a
lower surface or valley 28. As the strut wells 32 of the second ring 22 are through-
openings as described above, i.e., they each extend axially through the second ring 22
from the front face 22A to the rear face 22B, movement of the apply ring 26 in the
direction of arrow A allows the teeth 26A to enter a corresponding strut well 32
positioned adjacent thereto.
[0030] The axial movement of the apply ring 26 in response to an apply force in
the direction of arrow A acts as a force on a strut spring 37 that is positioned in each of
the strut wells 32 between the upper surface 27 of each tooth 26A and the strut 34. If this
force acting on each of the strut springs 37 is not opposed by a blocking surface 55 of the
blocking device 50 positioned between a strut 34 and a mating angled strut pocket 36 in
the first ring 20, the spring force imparted by the strut spring 37 will force each strut 34
into a mating angled pocket 36 of the first ring 20. If this force is so opposed, the strut
spring 37 will compress, providing a potential force for rapidly deploying the strut 34
when the blocking device 50 is again moved.
[0031] Once the blocking device 50 is placed in direct contact with the second
ring 22, a continued application of force in the direction of arrow A will eventually move
the blocking device 50 into contact with the first ring 20. Frictional forces imparted by

the rotational motion of the first ring 20, and by any intervening fluid film from the
pressurized hydraulic fluid 23 present between the first ring 20 and the blocking device
50, will tend to drag the blocking device 50 in the same rotational direction. This drag
will ultimately position the blocking device 50 in such a manner as to cover one
commonly oriented set of struts 34 with the blocking surfaces 55, and to free the other
commonly oriented set of struts 34 to move or deploy through the windows 54 into the
angled strut wells 36 of the first ring 20. That is, the blocking device 50 will rotate to
cover the set of struts 34 oriented so as to immediately attempt to the lock the first ring 20
with respect to the second ring 22 as the struts 34 and the strut springs 37 are actuated by
the apply ring 26.
[0032] A return mechanism 58 is provided within the SOWC 18, with the return
mechanism 58 being configured as a spring or another suitable device providing a
sufficient return force for moving the blocking device 50 and the second ring 22 in the
direction of arrow R a sufficient distance for disengaging the struts 34 from the first ring
20. Therefore, when an apply force in the direction of arrow A is discontinued or
removed, such as by temporarily interrupting a supply of pressurized hydraulic fluid 23 to
the actuator 16, the return force in the direction of arrow R allows the SOWC 18 to
disengage and to "freewheel" until engagement of the SOWC 18 in one or both directions
is desired.
[0033] Referring to Figure 3A, various clutch operating modes are shown for the
SOWC 18 (see Figures 1 and 2), with each mode defining a direction of torque holding
with respect to the SOWC 18. In Mode 1, pressure to the actuator 16 (see Figure 2) is
turned off, and the SOWC 18 is allowed to "freewheel", i.e., torque is not held in either
rotational direction. Mode 1 permits the first ring 20 to rotate or spin unimpeded with
respect to the second ring 22. In Modes 2A and 3, pressure to the actuator 16 is turned
on, and torque is locked or held in one rotational direction. Modes 2A and 2B are
identical in operation, except for the direction in which torque is held. For example, in
Mode 2A the first ring 20 may be permitted to freewheel or rotate unimpeded in a
forward rotational direction, and to lock or be prevented from rotating in the reverse
rotational direction, while Mode 2B would likewise permit the reverse rotation of the first

ring 20, holding torque in the forward direction. Finally, in Mode 3 the SOWC 18 is
locked, i.e., torque is held in both rotational directions. Each of the operating modes
described generally above as applied to the SOWC 18 are shown in detail in the
fragmentary cross-sectional side views of Figures 3B, 3C, and 3D, respectively.
[0034] In each of Figures 3B, 3C, and 3D, the angled strut pockets 36 of Figure 2
are shown as the angled strut pockets 36A and 36B to differentiate their different torque-
holding orientation. Each of the strut pockets 36A, 36B has a substantially vertical
locking surface 40 and an angled surface 41. The struts 34 of Figure 1 are represented by
their respective orientation as 34A, 34B. The vertical locking surface 40 is configured
and/or shaped to oppose a strut 34A, 34B as needed to thereby prevent rotation of the
first ring 20 in one direction when either of Modes 2A, 2B, or 3 are selected (see Figure
3A). Likewise, the sloped surface 41 is configured and/or shaped to allow a strut 34A,
34B to be depressed by the blocking device 50 into a mating strut well 32A, 32B to
permit relative rotation of one of the respective first and second rings 20, 22 (see Figure
2). When the SOWC 18 is locked in one direction and is transmitting torque, the
separation of the ends of the struts 34 in the axial direction may create a force that tends
to separate the first ring 20 from the second ring 22, so that upon the SOWC 18 locking
in one direction, the friction force on the blocking device 50 is reduced, and the blocking
device 50 is rotated by the centering spring 35 (see Figure 2) into the center position
shown in Figure 3E. Alternately, the centering spring 35 may assist friction force on the
blocking device 50 so that as the first ring 20 rotates slightly relative to the second ring
22 to lock via a commonly oriented set of the struts 34, the blocking device 50 also
rotates slightly relative to the second ring 22, thus uncovering the other commonly
oriented set of struts 34. In this position, all of the struts 34 are aligned with the
windows 54 in the blocking device 50, and may therefore engage the first ring 20.
[0035] As shown in Figures 3B through 3E, a sensor (S) 29 can sense, detect, or
otherwise determine the relative speed of the rings 20, 22 for use in controlling the
SOWC 16. The second ring 22 may be rotating or grounded, such as to the stationary
transmission housing or casing 13 (see Figure 1), and first ring 20 is always allowed to
rotate. The first ring 20 may be connected to motor/generator 17 (see Figure 1), which is

in communication with a motor controller (not shown) that is configured to synchronize
the rotational speeds of the first and second rings 20, 22 to facilitate actuation of the
SO WC 18. However, in the event the second ring 22 is not grounded and therefore is
also rotating, the motor/generator 17 would be likewise connected to the second ring 22
and in communication with the controller (not shown), as will be understood by those of
ordinary skill in the art.
[0036] In Figure 3B, and representing Mode 1 or a "freewheeling" mode, the
blocking device 50 is separated from the first ring 20 by the return mechanism 58 (see
Figure 2), thus forcing the struts 34 out of engagement with each respective mating strut
pocket 36. The apply force represented by the arrow A, as shown also in Figure 2, is zero
or off, allowing the previously described return force (arrow R) to move or separate the
blocking device 50 and the second ring 22 from the first ring 20. The initial distance of
separation (d1) is sufficient for ensuring that no portion of any of the struts 34A, 34B may
contact the first ring 20. The SOWC 18 therefore freewheels in either direction, as
represented by arrows 1 and 2.
[0037] Referring to Figure 3C, which represents Mode 2A or torque-holding in a
reverse direction, the apply pressure (arrow A) is turned on, thus forcing the apply ring
26 to move axially in the direction of arrow A. This moves the axially-moveable portion
21 of the SOWC 18, and the distance of separation (d2) between the actuator ring 26 and
the first ring 20 is less than the initial distance of separation (d1) shown in Figure 3B.
The blocking device 50 blocks the struts 34A, with the strut springs 37 forcing any
previously depressed strut 34B into engagement with the first ring 20. The struts 34B
"lock' via interference with a vertical locking surface 40 of each angled strut well 36B
into which the struts 34B are forced or moved. The orientation of the struts 34B within
the angled strut wells 36B therefore ensures that torque is held or prevented in the reverse
position by allowing the first ring 20 to rotate in the direction of arrow 2, but by
preventing the first ring 20 from rotating in the direction of arrow 1 (see Figure 3B).
[0038] Referring to Figure 3D, which represents Mode 2B or torque-holding in a
forward direction, the apply pressure (arrow A) remains on, still forcing the apply ring 26
to move in the direction of arrow A. The blocking device 50 blocks the struts 34B, with

strut springs 37 forcing any previously depressed strut 34A into engagement with the first
ring 20. The struts 34A "lock" via interference with a vertical locking surface 40 of each
well 36A into which the struts 34A are forced or moved. The orientation of the struts
34A within the wells 36B therefore ensures that torque is held or prevented in the reverse
position by preventing the first ring 20 from rotating in the direction of arrow 2.
[0039] Turning to Figure 3E, which represents Mode 3 or torque-holding in both
rotational directions, the apply pressure (arrow A) remains on, still forcing the apply ring
26 to move in the direction of arrow A. The SOWC 18 stops, with zero relative motion
between the inner and second rings 20 and 22, respectively. Drag on the blocking device
50 therefore disappears. Absent such drag forces, the centering ring 38 (see Figure 2) is
allowed to force or pull the blocking device 50 into a desired alignment with the second
ring 22, with the strut springs 37 allowed to move any previously depressed struts 34A,
34B into engagement with the first ring 20. The struts 34A and 34B therefore "lock" the
torque via interference with a vertical locking surface 40 of each well 36A, 36B into
which the struts 34A, 34B are respectively forced or moved. The orientation of the struts
34A, 34B within the angled strut wells 36A, 36B therefore ensures that torque is held or
pre\ ented in both the forward and reverse positions by preventing the first ring 20 from
rotating in the direction of arrows 1 and 2 (see Figure 3B).
[0040] As shown in Figure 4A, while in Mode 1, i.e., "freewheeling", in order to
apply the SOWC 18, a controller (not shown) cycles or synchronizes the first and second
rings 20, 22, respectively, so that a differential speed Δs therebetween approaches
approximately zero revolution per minute, as represented by the point 61. A signal
communicated at point 61 precipitates a change from Mode 1 to Mode 2 when a speed
sensor (not shown) detects that the direction of Δs, which changes at point 62, reaches a
non-negative quantity, i.e., at point 64, at which point the SOWC 18 of Figure 2 is
"shifted" or changed to either of Mode 2A or Mode 2B, depending on the rotational
direction of first ring 20, and thus holding torque in the respective reverse or forward
rotational direction.
[0041] Because of the inherent time delay in making a physical shift by
movement of the blocking device plate 50 (see Figures 2 and 3B through 3E), a slight

time lag At occurs before Mode 2 is fully realized at point 65. While the direction of Δs
is positive, the SOWC 18 continues freewheeling. While in Mode 2, when the direction
of Δs turns negative, i.e., at point 68, the clutch 18 locks. When the speed sensor (not
shown) detects zero differential clutch speed and zero speed change, the SOWC 18
changes to Mode 3 so that rotational motion is prevented in both directions, as shown in
Figure 2D, thereby freeing or releasing the electric motor/generator 17 (see Figure 1) to
change speeds as necessary. Because of the time delay in making the physical shift by
actuation of the blocking device 50, a slight time lag At occurs before Mode 3 is fully
realized at point 69.
[0042] Referring to Figure 4B, a similar speed curve is shown describing the
release of the SOWC 18, beginning with dual-directional torque holding of Mode 3. To
initiate a release of the SOWC 18, a mode change is signaled from Mode 3 to Mode 2 at
point 71. Prior to a mode change to Mode 2, the SOWC 18 is momentarily loaded in the
direction opposite that of the impending clutch release in the opposite direction, and then
in Mode 2A or 2B, the clutch 18 is unloaded so that the SOWC 18 may be easily
released. When the speed sensor (not shown) detects that the quantity Δs is positive, the
operating mode is changed to "freewheel in both directions", i.e., Mode 1 at point 72,
which is the initial state of Figure 4A as previously described hereinabove.
[0043] 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.

CLAIMS
1. A transmission comprising:
a first shaft;
a second shaft;
a selectable one-way clutch (SOWC) having an axis of rotation, a first
ring, and an axially-moveable second ring, the SOWC being operable for selectively
moving the second ring in an axial direction to connect the first shaft to the second
shaft; and
an electric motor connected to at least one of the first shaft and the
second shaft;
wherein the electric motor is operable for controlling a relative speed
between the first ring and the second ring of the SOWC.
2. The transmission of claim 1, wherein the SOWC is applied by
moving the second ring in an axial direction with respect to the axis of rotation toward
the first ring until the second ring is locked to the first ring.
3. The transmission of claim 2, wherein the SOWC includes at least
one blocking device configured for moving through frictional contact with the first ring,
the blocking device at least partially determining a transition of the SOWC from a
transmission of torque in one rotational direction to a transmission of torque in both
rotational directions.
4. The transmission of claim 3, wherein the SOWC includes a
plurality of strut pieces and the blocking device includes a plurality of windows, and
wherein moving through frictional contact aligns the plurality of windows with respect to
the plurality of strut pieces in a predetermined manner for establishing one of a plurality
of different clutch operating modes, including a first operating mode comprising a

freewheeling of the SOWC in both of the rotational directions, a second operating mode
comprising a holding of torque in one rotational direction, and a third operating mode
for holding torque in both rotational directions.
5. The transmission of claim 1, further comprising an apply
mechanism capable of motion along an axis parallel to the axis of rotation of one of the
first shaft and the second shaft, and a return mechanism operable for applying a return
force on the apply mechanism;
wherein the SOWC is actuatable using the apply mechanism and is
releasable using the return spring mechanism.
6. The transmission of claim 5, wherein the apply mechanism is a
hydraulic piston.
7. A selectable one-way clutch (SOWC) for use with a vehicle
transmission, the SOWC comprising:
a first ring;
a second ring;
a plurality of strut pieces each configured for holding torque in one of a
first and a second rotational direction to establish one of a plurality of different clutch
operating modes; and
a blocking device having a plurality of windows, the blocking device
being configured for moving through frictional contact with the first ring to thereby align
the plurality of windows in a predetermined manner for establishing one of the plurality
of different clutch operating modes;
wherein the SOWC is applied by moving the second ring in an axial
direction with respect to an axis of rotation of the first ring and the second ring.

8. The SOWC of claim 7, wherein the plurality of different clutch
operating modes includes a freewheeling of the SOWC in two rotational directions, a
holding of torque in one rotational direction, and a holding of torque in both rotational
directions.
9. The SOWC of claim 7, further comprising a centering spring that
is fitted between the second ring and the blocking device;
wherein the centering spring aligns each of the plurality of windows of the
blocking device with a different one of the plurality of strut pieces.
10. The SOWC of claim 1, further comprising a hydraulic piston for
moving the second ring in the axial direction with respect to the axis of rotation of the
first ring and the second ring.
11. The SOWC of claim 7, wherein half of the plurality of strut pieces
are configured for holding torque in the first rotational direction and half of the
plurality of strut pieces are configured for holding torque in the second rotational
direction.
12. A method for reducing losses due to clutch drag within a vehicle
transmission, the method comprising:
providing a selectable one-way clutch (SOWC) having a rotatable first
ring, an axially moveable second ring, and an axially moveable and selectively rotatable
blocking device;
applying an apply force to the second ring to move the second ring in an
axial direction and into contact with the blocking device;
moving the blocking device in the axial direction to establish a frictional
contact between the blocking device and the first ring;

rotating the blocking device using the frictional contact with the first ring
to thereby establish a desired alignment between the blocking device and the first ring;
preveting a rotation of the first ring in at least one direction when the
desired alignment is established, thereby applying the SOWC; and
moving the second ring and the blocking device a predetermined axial
distance away from the first ring to thereby release the SOWC.
13. The method of claim 12, wherein moving the second ring and the
blocking device includes applying a return force to the second ring while reducing the
force a sufficient level below a level of the return force.
14. The method of claim 12, further comprising providing the
selectable one-way clutch (SOWC) with a plurality of strut pieces;
wherein applying the SOWC includes blocking half of the plurality of
strut pieces using the blocking device.
15. The method of claim 12, further comprising providing the SOWC
with an apply ring;
wherein moving the blocking device in the axial direction includes
applying a pressurized supply of fluid to thereby move the apply ring into contact with
the second ring.

An electrically variable transmission (EVT) includes two shafts and a
selectable one-way clutch (SOWC) having a first and second ring. The SOWC
selectively connects the shafts, and is applied by moving the first ring and a blocking
device in an axial direction into frictional contact with the second ring. A hydraulic
piston applies the SOWC and a return spring releases it. The SOWC freewheels in
both directions, or holds torque in one or both directions, depending on how the
blocking device is rotated. A method for reducing losses in an EVT includes axially
moving a second ring and blocking device of a SOWC into contact with a first ring,
rotating the blocking device using frictional contact with the first ring, locking rotation
of the first ring to apply the SOWC, and moving the second ring and blocking device
an axial distance from the first ring to release the SOWC.

Documents:

http://ipindiaonline.gov.in/patentsearch/GrantedSearch/viewdoc.aspx?id=1qiNoB1oilAg+0TqE/27CA==&loc=wDBSZCsAt7zoiVrqcFJsRw==

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Patent Number

270628

Indian Patent Application Number

1535/KOL/2008

PG Journal Number

02/2016

Publication Date

08-Jan-2016

Grant Date

05-Jan-2016

Date of Filing

05-Sep-2008

Name of Patentee

GM GLOBAL TECHNOLOGY OPERATIONS, INC.

Applicant Address

300 GM RENAISSANCE CENTER DETROIT, MICHIGAN

Inventors:

#	Inventor's Name	Inventor's Address
1	ALAN G. HOLMES	6520 HADLEY HILLS COURT CLARKSTON, MICHIGAN 48348

PCT International Classification Number

F16H3/72; F16H3/44

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	60/975,949	2007-09-28	U.S.A.