TRANSMISSION WITH L1-L2 SHIFTING DURING ENGINE BRAKING

Abstract

Gearbox (10) for use with a motor (15), the gearbox (10) comprising: a stationary element (17); a drive element (14) that is connected to the motor (15); a plurality of gear sets (20, 30, 40, 50), each having a plurality of nodes (S1-4, R1-4, CM1-4), with a toothed ring, a sun gear, and a support element; a first coupling (C1) which, when applied, connects a node (S1) of one of the wheelsets (20) to the stationary element (17) to the To engage 1st gear in reduction mode (L1 mode); a second clutch (C2) which, when applied, connects a node (S4) from another of the wheelsets (50) to the stationary element (17) to produce the 2nd gear in reduction mode (L2 mode); a selectable one-way coupling (SOWC) (12) connected between nodes (R2, CM3) of two wheelsets (30, 40); and a control unit (25), programmed, in response to a requested shift from L1 mode to L2 mode during engine braking, to disengage the first clutch (C1) and thereby enter a neutral mode of the transmission (10), disengage the SOWC (12) when a slip level of the first clutch (C1) exceeds a first calibrated slip limit, re-engage the first clutch (C1) when a slip level of the SOWC (12) exceeds a second calibrated slip limit, thereby establishing a 1st gear freewheel mode and engaging the second clutch (C2) to establish the L2 mode and resume engine braking.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a transmission for shifting between a 1st gear with reduction (L1) and a 2nd gear with reduction (L2) during engine braking. BACKGROUND

[0002] A selectable one-way clutch is a torque-transmitting device capable of establishing a mechanical connection between rotating drive parts and driven parts of a power-transmitting device. A typical selectable one-way clutch is configured to hold torque in one or two rotational directions using torque-holding elements, such as spring-loaded struts. The struts, which are rotatably mounted between adjacent races, can be selectively forced into a corresponding strut recess of one of the races by rotation of a selector rail. Engagement of the struts holds torque in both rotational directions, while pressing the struts into the strut recesses of the selectable one-way clutch in one rotational direction allows for overrun or freewheeling.Due to the non-slip, direct, continuous engagement of the individual spring struts in the races, selectable one-way clutches are typically only used at low speeds.

[0003] From US 2002 / 0 033 312 A1 a transmission control system is known which, in the event that during a gear change from one gear to another gear the inertia phase control time is less than a predetermined time period or the effective gear ratio at the time of inertia phase end detection is outside a range, controls the operating fluid pressure in a time management mode to prevent a shift shock.

[0004] Furthermore, DE 11 2009 002 179 T5 describes a method for controlling a powertrain. The method includes monitoring a transmission output speed, monitoring an engine output speed, and monitoring an engine braking request. If the engine braking request is present, a target engine output speed is determined based on the transmission output speed. The engine speed is commanded to the target engine output speed. If the engine braking request is present, the slip speed of a selectable one-way clutch is determined based on the transmission output speed and the engine output speed. The slip speed of the selectable one-way clutch is used to further command the engine speed to generate a slip speed of the selectable one-way clutch of zero. If the slip speed of the selectable one-way clutch is zero, the selectable one-way clutch is also engaged. SUMMARY

[0005] A transmission is disclosed herein for use with an engine. The transmission includes a selectable one-way clutch (SOWC) and a controller programmed to momentarily release the SOWC during braking while the transmission is operating in a first-gear low-range mode (L1 mode). By momentarily releasing the SOWC, the transmission can be shifted to a second-gear low-range mode (L2), with engine braking possible in both L1 and L2 modes.

[0006] An exemplary configuration of the transmission includes a stationary element, an input member connectable to a motor, an output member, and gear sets, each having a plurality of nodes including a ring gear, a sun gear, and a carrier member. The transmission further includes first and second clutches and a controller. When the first clutch is applied, it connects a node of one of the gear sets to the stationary element to establish the L1 mode. When the second clutch is applied, it connects a node of another of the gear sets to the stationary element to establish the L2 mode. The SOWC is connected between the nodes of two of the gear sets.

[0007] The controller is programmed to disengage the first clutch in response to a requested shift from L1 to L2 mode during active engine braking, thereby entering a neutral mode of the transmission. The controller then disengages the second clutch when a slip level of the first clutch exceeds a first calibrated slip limit. The controller reapplies the first clutch when a slip level of the SOWC exceeds a second calibrated slip limit, thereby entering a 1st gear coasting mode, and reapplies the second clutch to enter L2 mode and resume engine braking.

[0008] A related method for shifting from L1 mode to L2 mode during engine braking includes detecting a requested shift from L1 to L2 mode during engine braking and then disengaging a first clutch to enter a neutral mode of the transmission. As mentioned above, the first clutch, when applied, connects a node of one of the gear sets to the stationary member to establish the L1 mode. The method includes disengaging the SOWC when a slip level of the first clutch exceeds a first calibrated slip limit, the SOWC being connected between nodes of two of the gear sets. The first clutch is reapplied via the controller when a slip level of the SOWC exceeds a second calibrated slip limit, thereby establishing a 1st gear coasting mode.The controller then applies the second clutch to connect a node of another of the gear sets to the stationary member, thereby establishing L2 mode and resuming engine braking.

[0009] The above features, as well as other features and advantages of the present disclosure, will be apparent from the following detailed description of the best modes for carrying out the disclosure when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic diagram of an exemplary multi-speed transmission having a selectable one-way clutch and a controller programmed to release the selectable one-way clutch in accordance with the method disclosed herein. Fig. 2 is a schematic side view of the selectable one-way clutch and the control of Fig. 1. Fig. 3 is a time diagram of the changing amplitude of the various control parameters during an exemplary L1 to L2 switching of the Fig. 1 shown gearbox. Fig. 4 is a flowchart illustrating an exemplary method for releasing the selectable one-way clutch of the Fig. 1 and Fig. 2 during the Fig. 3, whereby the method enables engine braking in the L1 and L2 modes. DETAILED DESCRIPTION

[0010] Referring to the drawings, wherein like reference numerals refer to like or similar components throughout the several views, an exemplary automatic multi-speed transmission 10 is shown in Fig. 1. The transmission 10 includes a selectable one-way clutch (SOWC) 12, an exemplary embodiment of which is described below with reference to Fig. 2. The automatic disengagement of the SOWC 12 is controlled via a controller (C) 25 according to a method 100 to facilitate the shift from 1st gear (L1) in low range mode to 2nd gear in low range mode (L2) during engine braking. As is known in the art, engine braking occurs when engine and friction can act as resistance to a powertrain, such as when a driver releases pressure from an accelerator pedal. Engine braking is therefore a way to slow a vehicle without using the friction brakes. The benefits of engine braking are therefore extended from L2 mode to L1 mode via operation of the controller 25 and method 100.

[0011] As described below with reference to Fig. 3 and Fig. 4, the controller 25 is programmed with control logic and includes the steps of the method 100. Execution of the method 100 in response to input signals (arrow 11) enables the controller 25 to command disengagement of the SOWC 12 via a set of clutch control signals (arrow 13) while the transmission 10 is still operating in the L1 mode. Therefore, during engine braking in the L1 mode, the controller 25 can temporarily release an engine load acting on the struts or other torque-retaining elements of the SOWC 12, thereby enabling the shift to the L2 mode, followed by resumption of engine braking in the L2 mode.

[0012] The Fig. The control unit 25 schematically illustrated in Figure 1 may be embodied as one or more digital computers with a processor (P) and a physical, non-transitory memory (M), such as an optical, magnetic, flash, or other read-only memory. The control unit 25 may also include sufficient random access memory, electrically erasable, programmable read-only memory, and the like, as well as a high-speed clock, analog-to-digital and digital-to-analog circuits and input / output circuits and devices, as well as suitable signal conditioning and buffer circuits.

[0013] In a non-limiting exemplary embodiment, the transmission 10 includes Fig. 1, the respective input and output members 14 and 16. The input member 14 receives a drive torque (arrow TI) generated by an internal combustion engine (E) 15. A plurality of gear sets, such as the planetary gear sets 20, 30, 40, and 50, transmit the drive torque (arrow TI) in different ratios to the output member 16 to ultimately drive one or more drive axles (not shown). The SOWC 12, which includes a one-way clutch element F1 and a selectable clutch element S1, thus enables elements of the gear sets 30, 40, and 50 to rotate or connect a stationary member 17 and prevent rotation depending on the operating mode.

[0014] The gearbox 10 from Fig. 1 may be configured as an exemplary 9-speed transmission, as illustrated. In such an embodiment, the transmission 10 may include a plurality of clutches, including rotating clutches C57R, C4, and C6789 and brake clutches CB38, CB29, and CB123456. The nomenclature CB123456, as used herein, represents a brake clutch (CB) that engages each of the 1st-6th gear ratios to connect a gear member or node of a particular gear set to a stationary member 17, e.g., a housing of the transmission 10. In the same nomenclature, the absence of a B corresponds to a rotating clutch. Thus, the particular clutch in which a given clutch is engaged can be determined from the naming rule; for example, CB29 is engaged in 2nd and 9th gear ratios.

[0015] Each gear set 20, 30, 40, and 50 includes multiple gear elements or nodes. For example, gear set 20 includes nodes S1, CM1, and R1, representing a sun gear, carrier elements, and ring gears. Gear set 30 includes nodes S2, CM2, and R2, representing a sun gear, carrier elements, and ring gears. Likewise, gear sets 40 and 50 include ring gears, carriers, and sun gears, i.e., R3 and R4, CM3 and CM4, and S3 and S4.

[0016] In the example of Fig. 1, node CM2 of gear set 30 is directly and continuously connected to node R1 of gear set 20. Likewise, node R4 of gear set 50 is directly and continuously connected to node R3 of gear set 40, and node R3 is in turn continuously and directly connected to node CM1 of gear set 20.

[0017] Clutch C6789 selectively connects the input member to node CM4 of gear set 50. Clutch C57R selectively connects the input member to node S3 of gear set 40. Likewise, clutch C4 selectively connects node S4 of gear set 50 to node CM3 of gear set 40.

[0018] With respect to the various brake clutches of this embodiment, clutches CB29 and CB38 selectively connect nodes S4 of gear set 50 and S3 of gear set 40 to stationary member 17. Clutch CB123456 selectively connects node S1 of gear set 20 to stationary member 14. Clutches CB123456 and CB29 are referred to as first and second clutches C1 and C2, respectively, and are described below with reference to Fig. 3 and Fig. 4 controlled.

[0019] The speed sensors S I and S Ocan be connected to the input and output members 14 and 16. One or more speed sensors of the center gear S M may be connected to a corresponding element of the center gear, e.g., to element 23, which in various embodiments connects the SOWC to nodes CM3 and R2 or node S3. Thus, the input signals (arrow 11) may include the measured speeds of the input, center gear, and output elements, with the speeds being indicated as arrows N, respectively. 14 , N M , and N 16 Other input signals (arrow 11) may include a low gear setting from a park position, reverse gear, neutral position, PRNDL lever, so that the controller 25 can detect a requested L1-L2 mode shift via sensing a position of such a PRNDL lever, as is known in the art.

[0020] Referring to Fig. 2 is the SOWC 12 of Fig. 1 in an engaged state during engine braking. The SOWC 12 includes first and second races 21 and 27, a rotating member 23 positioned between the races 21 and 27, and a rotatable shift rail 26. The first and second races 21 and 27 are connected to the stationary member 17 and are thus grounded or held in place. An engine braking force (arrow F EB) acts on the rotating member 23, thus preventing rotation of the shift rail 26 when engine braking is active. While engine braking is in L1 mode, the SOWC 12 is locked in both directions of rotation by displacing the respective forward and reverse struts 31F and 31R into the strut recesses 32W of the first race 21 and the rotating member 23. The springs 33, as is known in the art, bias the struts 31R and 31F in an extended position, as shown. Since the engine braking force (arrow F EB ) a hydraulic or electromechanical shift rail force (arrow F SP ), which acts in an opposite direction to the engine braking force (arrow F EB), the shift rail 26 cannot press these reverse gear struts 31R into the strut recesses 32W of the second race 27. As a result, engine braking is usually not permitted in L1 mode, since the SOWC 12 cannot shift from L1 mode, ie, due to the engine braking force (arrow F EB ) loaded struts 31F and 31R.

[0021] To address such a control problem, the controller 25 receives input signals (arrow 11) and selectively commands the momentary release of an input clutch or first gear clutch, for example, the first clutch C1 shown in Fig. 1, via the control signals (arrow 13). This control measure reduces the load on the spring struts 31R by Fig. 2 briefly the engine braking force (arrow F EB ). This causes the shift rail force (arrow F SP ), which increases the engine braking force (arrow F EP) no longer counteracts the spring force, the spring struts 31R are released from continuous engagement with the rotating element 23. The spring struts 31R are pressed into the spring strut recesses 32W of the second race 27, thereby compressing the springs 33. This control measure enables a rapid shift of the transmission 10 into the L2 operating mode from the L1 mode. Engine braking in the L2 mode can then begin, enabling engine braking in both the L1 and L2 modes.

[0022] Referring to Fig. 3 describes a timing diagram 60 an exemplary L1-L2 circuit of the transmission 10 of Fig. 1 during engine braking. The amplitude (A) and time (t) are plotted on the corresponding vertical and horizontal axes. Line ΔN C1 represents the slip of an input clutch to the gearbox 10 to put the gearbox 10 in neutral, for example the first clutch C1 of Fig. 1, also marked as coupling CB123456. Line ΔN 12 represents the slip level of the SOWC 12, that is, the speed difference of the SOWC 12, where a slip of zero means a locked SOWC 12. The timing diagram 60 also includes a drive speed (line N 14 ), for example, a turbine speed when using a hydrodynamic torque converter, where the gradual decrease in input speed indicates the state of active engine braking. Clutch pressure commands P C1 and P C2 represent the pressure commands of the controller 25 to the respective first and second clutches C1 and C2 of Fig. 1. All speed variables can be directly controlled via the drive, output, speed sensors of the center gearbox S I , S O , S M as speeds are measured (arrows N 14 , N 16 , N M), as mentioned above, and / or at any node of the transmission 10, using the known gear ratios of the transmission elements 20, 30, 40, and 50, as is known in the art.

[0023] The different lines in Fig. 3 will continue to be used with reference to Fig. 4, which illustrate one embodiment of the method 100. Step S102 involves detecting a driver-requested or self-requested L1-L2 shift of the transmission 10. Step S102 may include processing the input signals (arrow 11) to determine a position of a PRNDL lever, or within the logic of the controller 25, to determine whether the transmission 10 is currently in L1 mode and the current speed and / or torque conditions permit a shift to L2 mode. The method 100 remains at step S102 until a requested L1-L2 shift is detected, at which point the controller 25 proceeds to step S104.

[0024] At step S104, the controller 25 commands a momentary release of the first clutch C1, ie, the clutch CB123456 in the exemplary transmission 10 of Fig. 1. The identity of the first clutch C1 may vary with the configuration of the transmission 10. However, the first clutch C1 is an input clutch of the transmission 10, the release of which establishes a neutral state by effectively separating the engine 15 from the input member 14 of the transmission 10. In Fig. 3, the first clutch C1 is released at approximately t1, as indicated by the sharp drop in the clutch pressure command P C1 displayed. The method 100 then proceeds to step S106.

[0025] Step S106 involves comparing a measured or calculated slip of the first clutch C1 with a first calibrated slip limit. That is, in Fig. 3 starts approximately at t1 line ΔN C1 to increase until immediately before t4. The method 100 proceeds to step S108 as soon as line ΔN C1 rises above the first calibrated slip limit.

[0026] Step S108 includes disengaging the SOWC 12 in response to exceeding the first calibrated slip limit in step S106. Step S108 may vary with the particular control strategy used to pressurize the SOWC 12. For example, a given pressure control solenoid may be placed in an off state to cause the SOWC 12 to release oil to complete the commanded disengagement. Optionally, step S108 may include requesting positive engine torque to disengage the SOWC 12. For example, between t2 and t3, the controller 25 may determine that the first clutch C1 is fully disengaged and, as a result, as part of the control signals (arrow 13) or other control signals, transmit a request to an engine control module (not shown) to request a momentary increase in engine torque from the engine 15 in Fig. 1. The method 100 proceeds to step S110 once the release of the SOWC 12 has been instructed.

[0027] At step S110, the controller 25 next determines whether the SOWC 12 has slipped beyond a second calibrated slip limit. Slip of the SOWC 12, ie, line ΔN 12 from Fig. 3, should rise shortly after release of SOWC 12, with the rise of line ΔN 12 indicates the release of the SOWC 12. The controller 25 monitors line ΔN 12 to an increase in the slip limit and then proceeds to step S112 when line ΔN 12 exceeds the second calibrated slip limit.

[0028] Step S112 involves re-applying the first clutch C1, which is indicated by the increase in the clutch pressure command (line P C1 ) to the first clutch C1 in Fig. 3, is displayed shortly after t6. Successful completion of step S112 results in a 1-gear freewheel mode, where free rotation occurs via the SOWC 12 in one direction. The method 100 then proceeds to step S114.

[0029] At step S114, the controller 25 next instructs the application of the second clutch C2, ie clutch CB29 in the embodiment of the Fig. 1, or another 2nd gear clutch in another embodiment of the transmission 10. The application of the second clutch C2 is indicated by the rise of the line P C2 from Fig. 3 can be seen shortly after t7. Successful completion of step S114 results in L2 mode with engine braking.

[0030] Using the method 100 described above, engine braking is made available in first gear of the transmission 10, yet the fuel efficiency, packaging, mass, and cost advantages of a selectable one-way clutch instead of a conventional friction clutch are obtained. This extends engine braking from second gear to first gear. Other potential limitations are also addressed, such as eliminating the conventional requirement that the transmission 10 be engaged in first gear until positive engine torque is requested.

Claims

[1] A transmission (10) for use with an engine (15), the transmission (10) comprising: a stationary element (17); a drive element (14) connected to the motor (15); a plurality of gear sets (20, 30, 40, 50), each having a plurality of nodes (S1-4, R1-4, CM1-4), with a ring gear, a sun gear, and a carrier element; a first coupling (C1) which, when applied, connects a node (S1) of one of the wheel sets (20) to the stationary element (17) to 1st gear in reduction mode (L1 mode); a second clutch (C2) which, when applied, connects a node (S4) of another of the gear sets (50) to the stationary member (17) to establish the 2nd gear in the reduction mode (L2 mode); a selectable one-way coupling (SOWC) (12) connected between nodes (R2, CM3) of two wheel sets (30, 40); and a controller (25) programmed, in response to a requested shift from L1 mode to L2 mode during engine braking, to release the first clutch (C1) and thereby enter a neutral mode of the transmission (10), release the SOWC (12) when a slip level of the first clutch (C1) exceeds a first calibrated slip limit, reapply the first clutch (C1) when a slip level of the SOWC (12) exceeds a second calibrated slip limit, thereby establishing a 1st gear coasting mode and apply the second clutch (C2) to establish L2 mode and resume engine braking. [2] The transmission (10) of claim 1, wherein the plurality of gear sets includes first, second, third, and fourth gear sets, the first clutch (C1) connects a node (S1) of the first gear set (20) to the stationary member (17), the SOWC (12) is connected between nodes (R2, CM3) of the second and third gear sets (30, 40), and the second clutch (C2) connects the fourth gear set (50) to the stationary member (17). [3] Transmission (10) according to claim 2, wherein the transmission (10) is an automatic 9-speed transmission (10). [4] The transmission (10) of claim 3, wherein the first clutch (C1) connects a sun gear (S1) of the first gear set (20) to the stationary member (17), the second clutch (C2) connects a sun gear (S4) of the fourth gear set (50) to the stationary member (17), and the SOWC (12) is connected between a ring gear (R2) of the second gear set (30) and a carrier member (CM3) of the third gear set (40). [5] Transmission (10) according to claim 1, further comprising a plurality of speed sensors (S I , S M , S O ) positioned relative to the transmission (10) and serving to measure the rotational speeds of the input member (14), an output member (16) and a mid-gear member of the transmission (10), the controller (25) being programmed to calculate the slip levels using the measured rotational speeds. [6] The transmission (10) of claim 1, wherein the controller (25) is programmed to release the SOWC (12) by reducing a pressure command to the SOWC (12). [7] The transmission (10) of claim 6, wherein the SOWC (12) includes a pair of races (21, 27), a plurality of struts (31R, 31F), and a shift rail (26) for depressing the struts (31R, 31F) into the strut recesses (32W) of one of the races (21, 27), and wherein reducing the pressure on the SOWC (12) causes rotation of the shift rail (26) sufficient to force the struts (31R, 31F) into the strut recesses (32W). [8] The transmission of claim 6, wherein the controller (25) is programmed to request additional output torque from the engine (15) to facilitate disengagement of the SOWC (12).

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