JP2019209792A - Four-wheel-drive vehicle control apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device for a four-wheel drive vehicle in which straight running stability and startability are not impaired even if output characteristic variations occur in an electronically controlled coupling. According to a control device (70) of a vehicle (10) of the present embodiment, a pair of left and right electronically controlled couplings (34L) that receive a transmission torque command value indicating the same transmission torque when traveling straight ahead in a four-wheel drive mode, When there is a difference in the transmission torque of 34R, a difference in the changing speed is generated based on the difference in the changing speed of the differential rotation between the ring gear 52a of the pair of left and right electronically controlled couplings 34L and 34R and the rear wheels 16L and 16R. The transmission torque command value is corrected so that it does not exist. As a result, the output characteristics of the pair of left and right electronically controlled couplings 34L and 34R are made uniform, so that it is possible to prevent the straight traveling stability, the starting performance, or the turning stability of the vehicle 10 from being impaired. [Selection diagram] Fig. 3

Description

  The present invention relates to a control device for a four-wheel drive vehicle including a pair of left and right electronic control couplings.

  A pair of left and right main drive wheels to which transmission torque is transmitted from a drive force source, a torque transmission device for transmitting power from the drive force source to a pair of left and right sub drive wheels, and the pair of left and right sub drive wheels are provided in series. There is known a control device for a four-wheel drive vehicle including a pair of left and right electronically controlled couplings that change transmission torque transmitted from an input side rotation member to an output side rotation member in accordance with a transmission torque command value. . For example, a control device for a four-wheel drive vehicle described in Patent Document 1 is this.

  In the control device for a four-wheel drive vehicle described in Patent Document 1, a control current is supplied to a pair of left and right electronic control couplings arranged in series with each of the left and right rear wheels, that is, the auxiliary drive wheels, The transmission torque is controlled individually. As a result, it is possible to efficiently control the straight running stability, startability, etc. of the four-wheel drive vehicle.

JP 2009-150484 A

  However, the electronically controlled coupling configured by the wet multi-plate clutch has variations in output characteristics due to individual differences, temperature characteristics, or changes with time of the wet multi-plate clutch. Therefore, in the control device for a four-wheel drive vehicle described in Patent Document 1, for example, a difference between the transmission torque transmitted from the pair of left and right electronic control couplings to the left and right rear wheels with respect to the transmission torque command value from the control device. Therefore, there is a possibility that the straight running stability and startability of the four-wheel drive vehicle may be impaired.

  The present invention has been made against the background of the above circumstances, and the object of the present invention is a four-wheel drive in which straight-line stability and startability are not impaired even if output characteristics vary in the electronically controlled coupling. It is in providing the control apparatus of a vehicle.

  The gist of the present invention is provided in a power transmission path between a pair of left and right main driving wheels to which transmission torque is transmitted from a driving force source, and the pair of left and right auxiliary driving wheels. A torque transmission device capable of connecting / disconnecting the power transmission path and the pair of left and right auxiliary drive wheels are provided in series, and transmission torque transmitted from the input side rotating member to the output side rotating member according to a transmission torque command value is transmitted. A control device for a four-wheel drive vehicle including a pair of left and right electronic control couplings to be changed, each of which transmits a transmission torque command value for commanding an equal transmission torque to the pair of left and right electronic control couplings when traveling straight ahead. The pair of left and right electronic controls is obtained based on the difference in the change speed of the rotational speed difference between the input side rotation member and the force side rotation member of the pair of left and right electronic control couplings obtained when commanded. It is to correct the transfer torque command value for Ppuringu.

  According to the control device for a four-wheel drive vehicle of the present invention, when the four-wheel drive vehicle travels straight, there is a difference between the transmission torques of the pair of left and right electronic control couplings that respectively receive transmission torque command values indicating equal transmission torque. When this occurs, the difference in the change speed, for example, the change in the change speed becomes small, based on the change in the change speed in the difference in the rotation speed between the input side rotation member and the output side rotation member of the pair of left and right electronic control couplings. Thus, the transmission torque command value is corrected. As a result, the output characteristics of the pair of left and right electronically controlled couplings are aligned, so that it is possible to prevent the straight running stability, startability, and the like of the four-wheel drive vehicle from being impaired.

It is a figure explaining the schematic structure of each part regarding the vehicle to which this invention is applied, and is a figure explaining the principal part of the control system and control function for controlling each part. It is a figure which shows an example of the time chart which shows the change of the rotation speed of a rear wheel when a transmission torque command value is supplied to a pair of left and right electronic control couplings. It is a flowchart explaining the principal part of the control action of the electronic controller for controlling the output characteristic of a pair of left and right electronic control couplings. It is a flowchart explaining the principal part of the control action of the electronic control apparatus for controlling the output characteristic of the left-right paired electronic control coupling of the other Example of this invention.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the following embodiments, the drawings are appropriately simplified or modified, and the dimensional ratios, shapes, and the like of the respective parts are not necessarily drawn accurately.

  FIG. 1 is a diagram illustrating a schematic configuration of a vehicle 10 to which the present embodiment is applied, and also illustrates a main part of a control system and a control function for controlling each unit. The vehicle 10 is a four-wheel drive vehicle and includes, for example, an engine 12 as a driving force source. The engine 12 is an internal combustion engine such as a gasoline engine or a diesel engine. The vehicle 10 transmits the power of the engine 12, that is, the driving torque of the engine 12, so-called transmission torque, to the front wheels 14 </ b> L and 14 </ b> R (referred to as front wheels 14 unless otherwise specified) and the transmission torque of the engine 12. And a second power transmission path for transmitting to the rear wheels 16L and 16R (referred to as the rear wheel 16 if not particularly distinguished). The front wheels 14 are main drive wheels that serve as drive wheels to which transmission torque is transmitted from the engine 12 via the first power transmission path in the two-wheel drive state and the four-wheel drive state. The rear wheel 16 is a sub-drive wheel that becomes a driven wheel when in a two-wheel drive state, and a drive wheel that transmits transmission torque from the engine 12 via the second power transmission path when in a four-wheel drive state. is there. Therefore, the vehicle 10 is an FF-based front and rear wheel drive vehicle.

  The first power transmission path includes a transmission 18, a front differential 20, left and right front wheel axles 22L, 22R (referred to as front wheel axle 22 unless otherwise specified), and the like. The front differential 20 acts as a front-wheel transmission torque distribution unit that distributes transmission torque transmitted to the front wheels 14. The two power transmission paths are a transfer 26 that is a front and rear wheel transmission torque distribution device that distributes the transmission torque of the engine 12 to the rear wheels 16, and a transmission that transmits the transmission torque of the engine 12 distributed by the transfer 26 to the rear wheels 16. A propeller shaft 28 which is a torque transmission shaft is provided. The second power transmission path includes a rear wheel transmission torque distribution unit 30 that distributes a transmission torque input from the propeller shaft 28 to the left and right rear wheels 16L and 16R, and left and right rear wheel axles 32L and 32R (particularly distinction). If not, the rear wheel axle 32 is provided).

  The transmission 18 constitutes a part of a common power transmission path among the first power transmission path between the engine 12 and the front wheel 14 and the second power transmission path between the engine 12 and the rear wheel 16. doing. The transmission 18 is, for example, a known planetary gear type multi-stage transmission in which a plurality of shift stages having different gear ratios γ (= transmission input rotation speed Nin / transmission output rotation speed Nout) are selectively established. Is a known continuously variable transmission that can be continuously changed steplessly, or a known synchronous mesh type parallel twin-shaft transmission.

  As shown in FIG. 1, the transfer 26 includes a first rotating member 38, a second rotating member 40 formed with a ring gear 40 a that meshes with a driven pinion 28 a formed at an end of the propeller shaft 28 on the front wheel 14 side, A meshing-type first clutch 24 that selectively connects and disconnects power transmission between the first rotating member 38 and the second rotating member 40 is provided. When power transmission between the first rotating member 38 and the second rotating member 40 is connected by the first clutch 24, part of the transmission torque output from the engine 12 to the front wheel 14 is the rear wheel 16, that is, the propeller shaft 28. Distributed to.

  The first rotating member 38 is a cylindrical member through which the front wheel axle 22R penetrates the inner peripheral side thereof, and is supported by the differential case 20c and the transfer case 26c so as to be rotatable around the first axis C1, for example. An outer peripheral meshing tooth (not shown) that meshes with an inner peripheral meshing tooth (not shown) formed in the differential case 20c is formed at the end of the first rotating member 38 on the front wheel 14L side. A first clutch tooth 38b that always meshes with an inner peripheral tooth 42a of a cylindrical movable sleeve 42 provided in the first clutch 24 is formed at the end of the first rotating member 38 opposite to the front wheel 14L side. Yes.

  The second rotating member 40 is a cylindrical member through which the front wheel axle 22R penetrates the inner peripheral side, and is supported by the transfer case 26c so as to be rotatable around the first axis C1, for example. The aforementioned ring gear 40a is formed at the end of the second rotating member 40 on the front wheel 14R side, and the inner periphery of the movable sleeve 42 is formed at the end of the second rotating member 40 opposite to the front wheel 14R side. Second clutch teeth 40b that can mesh with the teeth 42a are formed.

  The first clutch 24 selectively transmits power between the engine 12 connected to the first rotating member 38 via the differential case 20 c and the transmission 18 and the propeller shaft 28 connected to the second rotating member 40. It is a meshing clutch as a torque transmission device that connects and disconnects. The first clutch 24 includes a first clutch tooth 38b formed on the first rotating member 38, a second clutch tooth 40b formed on the second rotating member 40, a first clutch tooth 38b and a first axis C1 direction. And a movable sleeve 42 formed with inner peripheral teeth 42a that are always meshed so as to be relatively movable and can mesh with the second clutch teeth 40b. Further, the first clutch 24 includes a first actuator 44 that moves the movable sleeve 42 in the direction of the first axis C1 between a meshing position that meshes with the second clutch teeth 40b and a non-meshing position that does not mesh with the second clutch teeth 40b. ing. The first actuator 44 includes, for example, a first clutch electric actuator that includes a first clutch electromagnetic coil and a ball cam and can be electrically controlled, and a meshing clutch operated by the first clutch electric actuator. ing. Although not shown, the first clutch 24 preferably has a relative rotational difference between the first rotating member 38 and the second rotating member 40 when the inner peripheral teeth 42a of the movable sleeve 42 mesh with the second clutch teeth 40b. There may be provided a synchronization mechanism for reducing. FIG. 1 shows a state where the first clutch 24 is released.

  The rear wheel transmission torque distribution unit 30 transmits a transmission torque distributed from the transfer 26 to the rear wheel 16 while allowing the differential rotation of the left and right rear wheel axles 32L and 32R, and the differential mechanism 46 and the propeller. A meshing-type second clutch 50 that selectively connects and disconnects power transmission with the shaft 28 is provided. The transmission torque distributed from the transfer 26 is transmitted from the propeller shaft 28 to the differential mechanism 46 via the second clutch 50.

  As shown in FIG. 1, the differential mechanism 46 has a pair of left and right electronic control couplings 34L and 34R. The differential mechanism 46 transmits to the rear electronic control coupling 34L for adjusting the transmission torque transmitted to the rear wheel 16L corresponding to the left wheel of the rear wheels 16, and to the rear wheel 16R corresponding to the right wheel of the rear wheel 16. A right electronic control coupling 34R for adjusting the transmission torque to be transmitted, and a central axle 48 having the left electronic control coupling 34L and the right electronic control coupling 34R connected to both ends. Although not illustrated, the left electronic control coupling 34L and the right electronic control coupling 34R include, for example, a coupling electric actuator that includes a coupling electromagnetic coil and a ball cam and can be electrically controlled, and the coupling electric actuator. A wet multi-plate clutch whose frictional force is adjusted is provided. In the left electronic control coupling 34L and the right electronic control coupling 34R, the transmission torque transmitted to the rear wheels 16L and 16R is adjusted by the magnetic force generated by energizing the coupling electromagnetic coil. In other words, the left electronic control coupling 34L and the right electronic control coupling 34R include, for example, an electronic control device to be described later based on a transmission torque command value corresponding to the magnitude of the transmission torque of the rear wheels 16L and 16R required for traveling. The control currents I3 and I4 corresponding to the transmission torque command value are respectively supplied from the 70 to the coupling electromagnetic coils to the pair of left and right electronic control couplings 34L and 34R.

  The left electronic control coupling 34L on the rear wheel 16L side is provided in series with the rear wheel 16, and when the transmission torque command value is increased, the transmission torque transmitted to the rear wheel 16L increases, and the rear wheel 16R side The right electronic control coupling 34R is provided in series with the rear wheel 16, and is configured to increase the transmission torque transmitted to the rear wheel 16R side when the transmission torque command value is increased. Thereby, the transmission torque distribution of the left and right rear wheels 16 can be continuously controlled by controlling the pair of left and right electronic control couplings 34L and 34R.

  As shown in FIG. 1, the rear wheel transmission torque distribution unit 30 includes a first rotating member 52 provided in the rear wheel transmission torque distribution unit 30 so as to be rotatable about the second axis C2, and a second axis. And a second rotating member 54 that is integrally fixed to the central axle 48 of the differential mechanism 46 so as to be rotatable around C2. The second clutch 50 is a meshing dog clutch that selectively connects and disconnects power transmission between the first rotating member 52 and the second rotating member 54. The first rotating member 52 is a cylindrical member through which the central axle 48 penetrates on the inner peripheral side thereof, and the rear wheel 16L side end portion of the first rotating member 52 that is the cylindrical member is disposed at the rear wheel of the propeller shaft 28. A ring gear 52a that meshes with the drive pinion 28b formed at the end on the 16 side is formed. A first clutch tooth 52b that can mesh with an inner peripheral tooth 56a of a cylindrical movable sleeve 56 provided in the second clutch 50 is formed at the end opposite to the rear wheel 16L side of the first rotating member 52. Has been. The second rotating member 54 is a disk member fixed to the central axle 48, and second clutch teeth 54 a that are always meshed with the inner peripheral teeth 56 a of the movable sleeve 56 are formed on the outer peripheral portion of the second rotating member 54. ing.

  As shown in FIG. 1, the second clutch 50 transmits power between the propeller shaft 28 connected to the first rotating member 52 and the central axle 48 of the differential mechanism 46 connected to the second rotating member 54. It is a meshing clutch as a torque transmission device that selectively connects and disconnects. The second clutch 50 includes a first clutch tooth 52b formed on the first rotating member 52, a second clutch tooth 54a formed on the second rotating member 54, a second clutch tooth 54a and the second axis C2 direction. And a movable sleeve 56 formed with inner peripheral teeth 56a that are always meshed so as to be relatively movable and can mesh with the first clutch teeth 52b. The second clutch 50 includes a second actuator 58 that moves the movable sleeve 56 in the second axis C2 direction between a meshing position that meshes with the first clutch teeth 52b and a non-meshing position that does not mesh with the first clutch teeth 52b. ing. The second actuator 58 includes, for example, a second clutch electric actuator that includes a second clutch electromagnetic coil and a ball cam and can be electrically controlled, and a meshing clutch operated by the second clutch electric actuator. ing. Although not shown in the drawing, the second clutch 50 preferably has a relative rotational difference between the first rotating member 52 and the second rotating member 54 when the inner peripheral teeth 56a of the movable sleeve 56 mesh with the first clutch teeth 52b. There may be provided a synchronization mechanism for reducing. FIG. 1 shows a state where the second clutch 50 is released.

  The vehicle 10 has different gear ratios between the front wheel axle 22 and the rear wheel axle 32. Specifically, the vehicle 10 has a front wheel axle side gear ratio γf represented by a ratio of the rotational speed Nfp (rpm) of the driven pinion 28a in the first clutch 24 and the rotational speed Nfr (rpm) of the ring gear 40a, and the first The rear wheel axle side gear ratio γr represented by the ratio of the rotational speed Nrp (rpm) of the drive pinion 28b and the rotational speed Nrr (rpm) of the ring gear 52a in the two-clutch 24 has different gear ratios. ing. For example, the front wheel axle side gear ratio γf and the rear wheel axle side gear ratio γr are formed such that the rotational speed Nfr of the ring gear 40a is lower than the rotational speed Nrr of the ring gear 52a with respect to the rotational speed of the propeller shaft 28. . When the front wheel axle side gear ratio γf and the rear wheel axle side gear ratio γr are different from each other and the vehicle speed V of the vehicle 10 increases to a predetermined vehicle speed or higher, for example, input of a pair of left and right electronically controlled couplings 34L and 34R is performed. A slip occurs due to a difference in rotational speed between the rotational speed Nrr of the side rotating member, for example, the ring gear 52a, and the rotational speeds Wrl, Wrr (rpm) of the output side rotating member, for example, the rear wheel 16. When the vehicle starts in the four-wheel drive mode capable of four-wheel drive traveling, the pair of left and right electronically controlled couplings 34L and 34R starts to slip, for example, from the one having the lower friction coefficient μ.

  In the vehicle 10 configured as described above, when the first clutch 24, the second clutch 50, the left electronic control coupling 34L, and the right electronic control coupling 34R are respectively engaged, the engine 12 and the left and right front wheels 14L. , 14R and the left and right rear wheels 16L, 16R are in a four-wheel drive state in which transmission torque is transmitted. Further, when the first clutch 24, the second clutch 50, the left electronic control coupling 34L, and the right electronic control coupling 34R are respectively released, the transmission torque is transmitted from the engine 12 to the left and right front wheels 14L, 14R. It will be in a wheel drive state. In the two-wheel drive state, the first clutch 24, the second clutch 50, the left electronic control coupling 34L, and the right electronic control coupling 34R are released, so that the propeller shaft 28 is moved to the left and right front wheels 14L, 14R. In addition, a disconnection state in which the left and right rear wheels 16L and 16R are disconnected is brought about. In the four-wheel drive state, since the first clutch 24, the second clutch 50, the left electronic control coupling 34L, and the right electronic control coupling 34R are engaged, the propeller shaft 28 is connected to the left and right front wheels 14L, 14R and the left and right rear wheels 16L, 16R are connected. In the disconnected state, the rotational speeds Wfl and Wfr (rpm) of the front wheels 14 are slightly faster than the rotational speeds Wrl and Wrr of the rear wheels 16 due to the front wheel axle side gear ratio γf and the rear wheel axle side gear ratio γr.

  The vehicle 10 includes, for example, an electronic control unit 70 that controls the distribution of transmission torque of the front and rear wheels 14 and 16. The electronic control unit 70 includes, for example, a so-called microcomputer having a CPU, a RAM, a ROM, an input / output interface, and the like. The CPU uses a temporary storage function of the RAM and follows a program stored in the ROM in advance. Various controls of the vehicle 10 are executed by performing signal processing.

  Various input signals detected by various sensors provided in the vehicle 10 are supplied to the electronic control unit 70. For example, a signal indicating the engine rotation speed Ne (rpm) of the engine 12 detected by the rotation speed sensor 80, a signal indicating the vehicle speed V (km / h) detected by the vehicle speed sensor 82, and the accelerator opening sensor 84 are detected. A signal representing the accelerator opening Acc (%), a signal representing the throttle valve opening θth (%) detected by the throttle valve opening sensor 86, and the like are supplied. Further, the electronic control unit 70 includes a signal representing the steering angle θ detected by the steering sensor 88, and the wheel speeds of the front wheels 14L and 14R and the rear wheels 16L and 16R detected by the wheel speed sensor 90, that is, the rotational speed Wfl, A signal representing Wfr, Wrl, Wrr (rpm) and a signal representing acceleration G in the front-rear direction of the four-wheel drive vehicle 10 detected by the acceleration sensor 92 are input to the electronic control unit 70. Further, the electronic control unit 70 is supplied with a 4WD switching signal indicating a request for switching to a four-wheel drive state from a driver detected by a 4WD switching switch (not shown), a turbine rotational speed Nt (rpm), and the like.

  Various signals other than the above are supplied to the electronic control unit 70. For example, the electronic control unit 70 is supplied with signals representing the rotation speed Ncin (rpm) of the input side rotation member and the rotation speed Ncout (rpm) of the output side rotation member of the pair of left and right electronic control couplings 34L and 34R. . The input side rotation member is, for example, the ring gear 52a, and the signal representing the rotation speed Nrr of the ring gear 52a detected by the rotation speed sensor 94 is a signal representing the rotation speed of the ring gear 52a, that is, the rotation speed Ncin of the input side rotation member. It is supplied to the electronic control unit 70. The output side rotating member is, for example, the rear wheel 16, and signals indicating the rotational speeds Wrl and Wrr of the rear wheels 16L and 16R detected by the wheel speed sensor 90 are the rotation speeds of the rear wheels 16L and 16R, that is, output side rotation. The rotation speeds Ncoutl and Ncoutr of the members are supplied to the electronic control unit 70, respectively.

  Various output signals are supplied from the electronic control device 70 to each device provided in the vehicle 10. For example, an engine output control command signal Se for output control of the engine 12, a hydraulic control command signal Sp for hydraulic control related to the shift of the transmission 18, and the like are output. Further, the electronic control unit 70 engages the first control current I1 supplied to the first clutch electromagnetic coil of the first actuator 44 to engage the first clutch 24, and the second clutch 50. A second control current I2 supplied to the second clutch electromagnetic coil of the second actuator 58 is output. Further, from the electronic control unit 70, a coupling electric actuator for coupling (not shown) provided in the left electronic control coupling 34L for controlling the transmission torque transmitted between the rear wheel 16L and the central axle 48 is used. In order to control the third control current I3 supplied to the electromagnetic coil and the transmission torque transmitted between the rear wheel 16R and the central axle 48, a coupling electric actuator (not shown) provided in the right electronic control coupling 34R is provided. A fourth control current I4 supplied to the coupling electromagnetic coil is output. Further, the electronic control device 70 outputs a shift range signal indicating a shift range of a shift device (not shown), a steering braking signal, and the like.

  As shown in FIG. 1, the electronic control unit 70 includes, as main parts of the control function, a travel state determination unit, that is, a travel state determination unit 100, a travel control unit, that is, a travel control unit 102, and a clutch state determination unit, that is, a clutch state determination unit 104. , Rotation speed detection means or rotation speed detection section 106, torque command value control means or torque command value control section 108, storage means or storage section 110, output characteristic determination means or output characteristic determination section 112, torque command value correction means or torque The command value correction unit 114 is functionally provided.

  The traveling state determination unit 100 determines the traveling state of the vehicle 10. Specifically, the vehicle speed V detected by the vehicle speed sensor 82, the accelerator opening Acc detected by the accelerator opening sensor 84, the throttle valve opening θth detected by the throttle valve opening sensor 86, and the wheel speed sensor 90 Based on the detected rotational speeds Wfl, Wfr, Wrl, Wrr of the front and rear wheels 14, 16, the steering angle θ detected by the steering sensor 88, the acceleration G detected by the acceleration sensor 92, etc. It is determined whether the vehicle 10 is stopped or whether the vehicle 10 is in steady running. In the steady running, for example, the vehicle speed V is larger than a predetermined constant vehicle speed value Vth obtained experimentally or design in advance, and the steering angle θ of the vehicle 10 is predetermined constant obtained experimentally or design in advance. The term refers to a straight running steady state in which the transmission torque of the vehicle 10, for example, the transmission torque of the front and rear wheels 14, 16 is smaller than a predetermined constant transmission torque value obtained experimentally or design in advance.

  The traveling state determination unit 100 determines whether the vehicle 10 is in a four-wheel drive state, for example, when the vehicle 10 starts straight from a stopped state. Specifically, the running state determination unit 100 executes vehicle start control that sets the vehicle 10 to a four-wheel drive state when the vehicle 10 starts moving straight from a stopped state, and the vehicle speed V is experimentally or designed in advance. It is determined whether or not the vehicle is in a state smaller than a predetermined constant vehicle speed value Vthb that has been obtained.

  For example, when there is a request to switch the vehicle 10 from the two-wheel drive state, that is, the disconnected state to the four-wheel drive state, that is, the connected state, the traveling control unit 102 receives the first clutch 24, the second clutch 50, and the pair of left and right electronic devices. Control for engaging the control couplings 34L and 34R is executed. Further, when there is a request to switch the vehicle 10 from the connected state to the disconnected state, the traveling control unit 102 releases the first clutch 24, the second clutch 50, and the pair of left and right electronic control couplings 34L, 34R. The control to be executed is executed. Furthermore, when starting the vehicle 10 from the stop state, the travel control unit 102 performs vehicle start control so that the vehicle 10 is in a four-wheel drive state, that is, a connected state. The travel control unit 102 controls the rear wheel transmission torque distribution unit 30 so that the transmission torque transmitted to the rear wheels 16L and 16R is distributed to the same value in the vehicle start time control.

  The clutch state determination unit 104 determines whether or not the pair of left and right electronic control couplings 34L and 34R are operating normally. For example, it is determined whether or not a failure occurs in the pair of left and right electronic control couplings 34L and 34R based on the operating states of the electric actuator for coupling by energization and the wet multi-plate clutch. When the coupling electric actuator and the wet multi-plate clutch are operating normally, the clutch state determination unit 104 indicates that the pair of left and right electronic control couplings 34L and 34R are operating normally and a failure occurs. Judge that it is not.

  The rotation speed detection unit 106 detects the rotation speed Ncin of the input side rotation member and the rotation speeds Ncoutl and Ncoutr of the output side rotation member of the pair of left and right electronic control couplings 34L and 34R. Specifically, the rotation speed detection unit 106 detects the rotation speed Nrr of the ring gear 52a by the rotation speed sensor 94 as the rotation speed Ncin of the input side rotation member of the pair of left and right electronic control couplings 34L and 34R. Further, the rotation speed detection unit 106 detects the rotation speed Wrl of the rear wheel 16L by the wheel speed sensor 90 as the rotation speed Ncoutl of the output side rotation member of the left electronic control coupling 34L, and outputs the output side of the right electronic control coupling 34R. The rotational speed Wrr of the rear wheel 16R is detected by the wheel speed sensor 90 as the rotational speed Ncoutr of the rotating member.

  The torque command value control unit 108 controls transmission torque command values supplied to the pair of left and right electronic control couplings 34L and 34R, that is, control currents I3 and I4. In this embodiment, for example, when correcting the transmission torque command value during steady running of the vehicle 10, a range that does not affect the behavior of the vehicle 10 during steady running in the four-wheel drive mode in order to determine the correction amount, that is, A transmission torque command value indicating a constant transmission torque controlled within an increase range in which steady running can be continued, that is, control currents I3 and I4 are supplied to the left and right electronic control couplings 34L and 34R.

  The storage unit 110 stores changes in the rotation speed of each unit detected by the rotation speed detection unit 106 during a predetermined period. Specifically, in the present embodiment, the storage unit 110 includes the rotational speed Ncin of the ring gear 52a that is an input side rotation member of the pair of left and right electronic control couplings 34L and 34R and the rear wheels 16L and 16R that are output side rotation members. The rotation speeds Ncoutl and Ncoutr are stored in a predetermined period, that is, the difference between the rotation speed Ncin of the ring gear 52a and the rotation speeds Ncoutl and Ncoutr of the rear wheels 16L and 16R, so-called differential speed change speed difference. . For example, when the vehicle 10 is in steady running, the predetermined period of time is determined by the torque command value control unit 108 supplying equal transmission torque command values to the pair of left and right electronic control couplings 34L and 34R. This is a period until the rotational speeds Ncoutl and Ncoutr of the output side rotating members such as the rear wheels 16L and 16R of the pair of electronically controlled couplings 34L and 34R coincide with the rotational speed Ncin of the input side rotational member such as the ring gear 52a. For example, when the vehicle 10 is in a stopped state, the predetermined period is a period from when the vehicle starts moving straight in four-wheel drive until the so-called slip occurs in the left and right electronic control couplings 34L and 34R. .

  In the present embodiment, when the vehicle 10 is in steady running in the four-wheel drive mode, the storage unit 110 can continue the range in which the behavior of the vehicle 10 is not affected by the torque command value control unit 108, that is, steady running can be continued. Changes in the rotational speed Ncin of the ring gear 52a and the rotational speeds Ncoutl and Ncoutr of the rear wheels 16L and 16R in the predetermined period after the transmission torque command value indicating the transmission torque in the increased range is supplied to the electronic control couplings 34L and 34R, respectively. Is stored.

  Based on the difference in the change speed of the rotational speed difference between the rotational speed Ncin of the input side rotational member and the rotational speeds Ncoutl and Ncoutr of the output side rotational member stored in the storage unit 110, the output characteristic determination unit 112 It is determined whether or not there is a difference between the output characteristics of the electronic control couplings 34L and 34R. Specifically, during the steady running of the vehicle 10, in the pair of left and right electronic control couplings 34L, 34R to which the transmission torque command value is supplied, the respective increments of the rotational speeds Ncoutl, Ncoutr of the rear wheels 16L, 16R, In other words, a so-called deviation indicated by a difference between the rotational speeds Ncoutl and Ncoutr and the rotational speed Ncin of the ring gear 52a in the steady running increases to a predetermined constant rotational speed Nth set in advance. In some cases, the output characteristic determination unit 112 determines that there is a difference between the output characteristics of the pair of left and right electronic control couplings 34L and 34R. The predetermined difference of the increase time, the so-called divergence time difference, is a constant determination obtained in advance experimentally or design in order to determine a case where the increase time of both the pair of left and right electronic control couplings 34L and 34R is greatly deviated. It means time tath.

  FIG. 2 is an example of a time chart showing changes in the rotational speeds Ncoutl and Ncoutr of the rear wheels 16L and 16R when a transmission torque command value is supplied to the pair of left and right electronic control couplings 34L and 34R. Specifically, FIG. 2 shows changes in the rotational speeds Ncoutl and Ncoutr of the rear wheels 16L and 16R when there is a difference in the output characteristics of the pair of left and right electronic control couplings 34L and 34R. This shows a change in which the rotational speeds Ncoutl and Ncoutr of the rear wheels 16L and 16R increase to a constant rotational speed Nth after the transmission torque command value is supplied to the control couplings 34L and 34R. In FIG. 2, for example, a transmission torque command value indicating a transmission torque in a range that does not affect the behavior of the vehicle 10 is supplied to the pair of left and right electronic control couplings 34 </ b> L and 34 </ b> R. The counter shown in FIG. 2 counts up until both the rotational speeds Ncoutl and Ncoutr of the rear wheels 16L and 16R increase to a constant rotational speed Nth. The CP output shown in FIG. 2 indicates whether or not the transmission torque is transmitted from the pair of left and right electronic control couplings 34L and 34R to the rear wheels 16L and 16R. When the CP output is ON, transmission torque is transmitted from the pair of left and right electronic control couplings 34L, 34R to the rear wheels 16L, 16R. When the CP output is OFF, the pair of left and right electronic control couplings 34L, 34R No transmission torque is transmitted to the rear wheels 16L, 16R. The pair of left and right electronically controlled couplings 34L and 34R are controlled such that the CP output is turned off when the rotational speeds Ncoutl and Ncoutr of the rear wheels 16L and 16R increase to a constant rotational speed Nth. The rotational speed shown in FIG. 2 indicates changes in the rotational speeds Ncoutl and Ncoutr of the rear wheels 16L and 16R. Specifically, the amount of increase in the rotational speeds Ncoutl and Ncoutr of the rear wheels 16L and 16R, that is, the rear wheels 16L. , The difference between the rotational speeds Ncoutl and Ncoutr of 16R and the rotational speed Ncin of the ring gear 52a, that is, a change in deviation. The rotation speed Nn indicates the rotation speed of the rear wheel 16 during steady running when the transmission torque command value is not supplied to the pair of left and right electronic control couplings 34L and 34R.

  At time t1 shown in FIG. 2, the torque command value control unit 108 supplies a transmission torque command value indicating a constant transmission torque equal to each other, that is, the third control current I3, to the left electronic control coupling 34L, and the fourth control current I4. Are respectively supplied to the right electronic control coupling 34R. A time t2 shown in FIG. 2 is a time during which the rotational speed Ncoutr of the rear wheel 16R increases to a constant rotational speed Nth after the transmission torque command value is supplied, and a time t3 shown in FIG. 2 is supplied with the transmission torque command value. This is the time during which the rotational speed Ncoutl of the rear wheel 16L increases to a constant rotational speed Nth. The time difference Td between the time t3 and the time t2 shown in FIG. 2 is the difference in the increase time. When the time t3 and the time t2 greatly deviate and the time difference Td between the time t3 and the time t2 becomes larger than a predetermined constant time tath, that is, the input side rotating member of the pair of left and right electronic control couplings 34L and 34R When the difference in the change speed of the differential rotation with the output-side rotating member becomes larger than a predetermined value, the output characteristic determination unit 112 determines that there is a difference in the output characteristics of the pair of left and right electronic control couplings 34L and 34R. To do.

  Further, when the vehicle 10 starts in the four-wheel drive mode, the output characteristic determination unit 112 calculates the rotation speed Ncin of the input-side rotation member and the rotation speeds Ncoutl and Ncoutr of the output-side rotation member stored in the storage unit 110. Based on the transition, it is determined whether or not there is a difference between the output characteristics of the pair of left and right electronic control couplings 34L and 34R. Specifically, the output characteristic determination unit 112 receives the rotation torques Ncoutl and Ncoutr of the rear wheels 16L and 16R and the ring gear after the transmission torque command values equal to each other are supplied to the pair of left and right electronic control couplings 34L and 34R, respectively. When the deviation from the rotational speed Ncin of 52a increases and the slip occurs in the pair of left and right electronic control couplings 34L and 34R, that is, when the slip occurrence time Tsl and Tsr have a predetermined time difference, that is, the pair of left and right When the difference in the change speed of the differential rotation between the input side rotation member and the output side rotation member of the electronic control couplings 34L and 34R becomes larger than a predetermined value, the output characteristics of the pair of left and right electronic control couplings 34L and 34R It is determined that there is a difference. The slip occurrence time Tsl is the time from when the transmission torque command value is supplied to the left electronic control coupling 34L until the slip occurs in the left electronic control coupling 34L. The slip occurrence time Tsr is the right electronic control coupling. This is the time from when the transmission torque command value is supplied to 34R until the slippage occurs in the right electronic control coupling 34R. The predetermined time difference refers to a predetermined determination time tbth obtained experimentally or design in advance in order to determine a case where the time difference between the slip occurrence time Tsl and the slip occurrence time Tsr is greatly deviated.

  The torque command value correction unit 114 corrects the transmission torque command value when the output characteristic determination unit 112 determines that there is a difference between the output characteristics of the pair of left and right electronic control couplings 34L and 34R. Specifically, the torque command value correction unit 114 corrects the transmission torque command value so that the time difference Td is eliminated in order to align the output characteristics of the pair of left and right electronic control couplings 34L and 34R, and the torque command value The corrected transmission torque command value, that is, the control currents I3 and I4 are supplied from the control unit 108 to the pair of left and right electronic control couplings 34L and 34R. For example, in the case of the pair of left and right electronic control couplings 34L and 34R shown in FIG. 2, in order to make the time difference Td zero, the torque command value correction unit 114 transmits the transmission torque command value to the left electronic control coupling 34L. After the supply torque command value is corrected so as to shorten the time for which the rotation speed Ncoutl of the rear wheel 16L increases to the constant rotation speed Nth, or the transfer torque command value is supplied to the right electronic control coupling 34R. The transmission torque command value is corrected so as to lengthen the time during which the rotational speed Ncoutr of the rear wheel 16R increases to the constant rotational speed Nth. That is, the torque command value correction unit 114 corrects the transmission torque command value to control the control currents I3 and I4 supplied to the pair of left and right electronic control couplings 34L and 34R to rotate the rear wheels 16L and 16R. The numbers Ncoutl and Ncoutr are aligned.

  FIG. 3 is a flowchart for explaining a main part of the control operation of the electronic control unit 70 for controlling the output characteristics of the pair of left and right electronic control couplings 34L and 34R, and is repeatedly executed.

  In step (hereinafter, step is omitted) S10 corresponding to the traveling state determination unit 100, it is determined whether or not the vehicle 10 is in steady traveling in the four-wheel drive mode. If the determination in S10 is affirmative, that is, the vehicle speed V of the vehicle 10 is greater than a predetermined constant vehicle speed value Vth, the steering angle θ of the vehicle 10 is smaller than the constant steering angle θath, and the transmission torque of the vehicle 10 such as the front and rear wheels 14 , 16 is a straight running steady state in which the transmission torque is smaller than a predetermined constant transmission torque value, S20 corresponding to the clutch state determination unit 104 is executed. If the determination in S10 is negative, that is, if the vehicle 10 is not in steady running, this routine is terminated.

  In S20 corresponding to the clutch state determination unit 104, it is determined whether or not the pair of left and right electronic control couplings 34L and 34R are operating normally. If the determination in S20 is affirmative, that is, if no failure has occurred in the pair of left and right electronic control couplings 34L and 34R, S30 corresponding to the torque command value control unit 108 is executed. If the determination in S20 is negative, that is, if a failure has occurred in the pair of left and right electronic control couplings 34L and 34R, this routine is terminated.

  In S30 corresponding to the torque command value control unit 108, the transmission torque command values to be supplied to the pair of left and right electronic control couplings 34L and 34R, that is, control currents I3 and I4 are controlled based on the transmission torque command value. In the present embodiment, a transmission torque command value indicating a transmission torque controlled in a range that does not affect the behavior of the vehicle 10 is supplied to the pair of left and right electronic control couplings 34L and 34R. When the torque command value control unit 108 supplies the transmission torque command value controlled to the pair of left and right electronic control couplings 34L and 34R, S40 corresponding to the rotation speed detection unit 106 and the storage unit 110 is executed. The

  In S40 corresponding to the rotational speed detection unit 106 and the storage unit 110, the rotational speed detection unit 106 causes the rotational speed Ncin of the ring gear 52a that is the input side rotational member of the pair of left and right electronic control couplings 34L and 34R and the output side rotational member of the output side rotational member. The rotational speeds Ncoutl and Ncoutr of the rear wheels 16L and 16R are detected, and the detected changes in the rotational speed Ncin of the ring gear 52a and the rotational speeds Ncoutl and Ncoutr of the rear wheels 16L and 16R in a predetermined period are stored in the storage unit 110. . The rotational speed detection unit 106 detects the rotational speed Ncin of the ring gear 52a and the rotational speeds Ncoutl and Ncoutr of the rear wheels 16L and 16R, and the storage unit 110 detects the rotational speed Ncin of the ring gear 52a and the rotational speeds Ncoutl of the rear wheels 16L and 16R. When the transition of Ncoutr in a predetermined period is stored, S50 corresponding to the output characteristic determination unit 112 is executed.

  In S50 corresponding to the output characteristic determination unit 112, the left and right electronic control couplings 34L, based on the transition of the rotation speed Ncin of the ring gear 52a and the rotation speeds Ncoutl and Ncoutr of the rear wheels 16L and 16R stored in the storage unit 110, It is determined whether or not there is a difference in the output characteristics of 34R. When the output characteristic determining unit 112 determines that the output characteristics of the pair of left and right electronic control couplings 34L and 34R are different, that is, the respective increments of the rotational speeds Ncoutl and Ncoutr of the rear wheels 16L and 16R are constant rotational speeds. If there is a divergence time difference larger than the predetermined determination time tath in each increase time increasing to Nth, S60 corresponding to the torque command value correction unit 114 is executed. When the output characteristic determination unit 112 determines that there is no difference between the output characteristics of the pair of left and right electronic control couplings 34L and 34R, that is, the respective increments of the rotational speeds Ncoutl and Ncoutr of the rear wheels 16L and 16R are constant rotational speeds. When the difference in divergence time of each increase time increasing to Nth is smaller than the fixed determination time tath, this routine is terminated.

  In S60 corresponding to the torque command value correction unit 114, the transmission torque command value is corrected. That is, in order to align the output characteristics of the pair of left and right electronic control couplings 34L and 34R, the corrected torque command value is supplied from the torque command value control unit 108 to the pair of left and right electronic control couplings 34L and 34R. To. When the torque command value correction unit 114 corrects the transmission torque command value, this routine is terminated.

  Thus, according to the control device 70 of the vehicle 10 of the present embodiment, a pair of left and right electronic control couplings 34L each receiving a transmission torque command value indicating equal transmission torque when traveling straight in the four-wheel drive mode, When a difference occurs in the transmission torque of 34R, a difference in the change speed is generated based on the difference in the change speed of the differential rotation between the ring gear 52a of the pair of left and right electronically controlled couplings 34L, 34R and the rear wheels 16L, 16R. The transmission torque command value is corrected so as not to occur. As a result, the output characteristics of the pair of left and right electronic control couplings 34L and 34R are aligned, so that it is possible to prevent the straight traveling stability, startability, or turning stability of the vehicle 10 from being impaired.

  In addition, according to the control device 70 of the vehicle 10 of the present embodiment, the torque command value correction unit 114 is configured so that the rotational speed Ncin of the ring gear 52a is supplied after the transmission torque command value is supplied to the pair of left and right electronic control couplings 34L and 34R. The transmission torque command value is corrected based on the time until the difference between the rotational speeds Ncoutl and Ncoutr of the rear wheels 16L and 16R reaches a predetermined constant rotational speed Nth. As a result, the torque command value correction unit 114 can correct the transmission torque command value more accurately. Therefore, the transmission torque of the pair of left and right electronic control couplings 34L and 34R is corrected more accurately, and the pair of left and right electronic control couplings is corrected. The output characteristics of the electronically controlled couplings 34L and 34R, that is, the rotational speeds Ncoutl and Ncoutr of the rear wheels 16L and 16R with respect to the transmission torque command value are aligned. Accordingly, it is possible to further suppress the straight travel stability, startability, or turning stability of the vehicle 10 from being impaired.

  Next, another embodiment of the present invention will be described. In addition, the same code | symbol is attached | subjected to the part which is common in above-mentioned Example 1, and description is abbreviate | omitted.

  FIG. 4 is a flowchart for explaining a main part of the control operation of the electronic control device 70 for controlling the output characteristics of the pair of left and right electronic control couplings 34L and 34R of the present embodiment, and is repeatedly executed.

  In S210 corresponding to the traveling state determination unit 100, when the vehicle 10 starts straight from the stopped state, it is determined whether or not the vehicle 10 is in the four-wheel drive state. If the determination in S210 is affirmative, that is, vehicle start control is executed when the vehicle 10 starts and the vehicle speed V is smaller than a predetermined constant vehicle speed value Vthb, the rotation speed detection unit 106 and the storage unit S220 corresponding to 110 is executed. When the determination in S210 is negative, that is, when the vehicle 10 is started, vehicle start control is not executed and the vehicle 10 is not in a four-wheel drive state, or the vehicle speed V is greater than a predetermined constant vehicle speed value Vthb. If so, the routine is terminated.

  In S220 corresponding to the rotational speed detection unit 106 and the storage unit 110, the rotational speed detection unit 106 causes the rotational speed Ncin of the ring gear 52a that is the input side rotational member of the pair of left and right electronic control couplings 34L and 34R and the output side rotational member of the output side rotational member. The rotation speeds Ncoutl and Ncoutr of the rear wheels 16L and 16R are detected, and the detected rotation speed Ncin of the ring gear 52a and the rotation speeds Ncoutl and Ncoutr of the rear wheels 16L and 16R in a predetermined period, specifically, the ring gear 52a The transition of the deviation between the rotational speed Ncin and the rotational speeds Ncoutl and Ncoutr of the rear wheels 16L and 16R is stored in the storage unit 110. The rotational speed detection unit 106 detects the rotational speed Ncin of the ring gear 52a and the rotational speeds Ncoutl and Ncoutr of the rear wheels 16L and 16R, and the storage unit 110 detects the rotational speed Ncin of the ring gear 52a and the rotational speeds Ncoutl of the rear wheels 16L and 16R. When the deviation transition of Ncoutr in a predetermined period is stored, S230 corresponding to the output characteristic determination unit 112 is executed.

  In S230 corresponding to the output characteristic determination unit 112, the pair of left and right electronic control cups is based on the transition of the deviation between the rotation speed Ncin of the ring gear 52a and the rotation speeds Ncoutl and Ncoutr of the rear wheels 16L and 16R stored in the storage unit 110. It is determined whether or not the difference between the slip generation times Tsl and Tsr until the slips occur in the rings 34L and 34R has deviated more than a predetermined determination time tbth. When it is determined that the difference between the slip occurrence times Tsl and Tsr is larger than the predetermined determination time tbth, S240 corresponding to the torque command value correction unit 114 is executed in the same manner as S60 described above. When it is determined that the difference between the slip occurrence times Tsl and Tsr is smaller than the predetermined determination time tbth, this routine is terminated.

  Thus, according to the control device 70 of the vehicle 10 of the present embodiment, when the vehicle 10 starts straight from the stopped state, the transmission torque command value is supplied to the pair of left and right electronic control couplings 34L and 34R. To the time from when the deviation between the rotational speed of the rear wheels 16L and 16R and the rotational speed of the ring gear 52a increases to cause slippage in the pair of left and right electronic control couplings 34L and 34R, that is, the slip occurrence times Tsl and Tsr. If there is a predetermined time difference, the transmitted torque command value is corrected by the torque command value correction unit 114. As a result, for example, when the output characteristics of the pair of left and right electronic control couplings 34L and 34R vary, the torque command value correction unit 114 corrects the transmitted torque command value to thereby correct the pair of left and right electronic control couplings. Output characteristics for the transmission torque command values of 34L and 34R are aligned. Therefore, it is possible to suppress the straight running stability, startability, or turning stability of the vehicle 10 from being impaired.

  The preferred embodiments of the present invention have been described in detail with reference to the drawings. However, the present invention is not limited to these embodiments, and may be implemented in other modes.

  For example, in the above-described embodiment, the present invention is applied to a vehicle including the engine 12 as a driving force source. However, the present invention is not limited to this, and the present invention is not limited to this. Can also be applied.

  In the above-described embodiment, the input side rotation member of the pair of left and right electronic control couplings 34L and 34R is the ring gear 52a. However, the present invention is not limited to this, and for example, the pair of left and right electronic control couplings 34L and 34R The central axle 48 serving as the input shaft, the second rotating member 54, the first rotating member 52, the propeller shaft 28, or the like may be used. That is, a signal representing the rotational speed of the central axle 48, the second rotating member 54, the first rotating member 52 or the propeller shaft 28 by the rotational speed sensor 94 is sent to the electronic control unit 70 as a signal representing the rotational speed Ncin of the input side rotating member. It may be supplied.

  In the above-described embodiment, the output side rotation member of the pair of left and right electronic control couplings 34L and 34R is the rear wheel 16. However, the present invention is not limited thereto, and may be the rear wheel axle 32, for example. That is, signals representing the respective rotational speeds of the rear wheel axles 32L and 32R detected by the rotational speed sensor 94 may be supplied to the electronic control unit 70 as signals representing the rotational speeds Ncoutl and Ncoutr of the output side rotating member. .

  In the above-described embodiment, the output characteristic determination unit 112 increases the rear wheels 16L and 16R that increase after the transmission torque command value is supplied to the pair of left and right electronic control couplings 34L and 34R during the steady running of the vehicle 10. Whether or not there is a difference in output characteristics between the pair of left and right electronic control couplings 34L and 34R is determined on the basis of the difference in increase time during which the rotation speeds Ncoutl and Ncoutr increase to the constant rotation speed Nth. However, the output characteristic determination unit 112 determines that the rotational speeds Ncoutl and Ncoutr of the rear wheels 16L and 16R that increase after the transmission torque command value is supplied to the pair of left and right electronic control couplings 34L and 34R for a certain time, for example, the time of FIG. It may be determined whether there is a difference between the output characteristics of the pair of left and right electronic control couplings 34L and 34R based on the difference between the increase values at time t2. In short, based on the change speed difference between the rotational speeds Ncoutl and Ncoutr of the rear wheels 16L and 16R, that is, the difference in change speed of the differential rotation between the input side rotation member and the output side rotation member of the pair of left and right electronic control couplings 34L and 34R, It is determined whether there is a difference in output characteristics.

  As mentioned above, although the Example of this invention was described in detail based on drawing, what was mentioned above is one embodiment to the last, and it does not illustrate each other, but this invention is a person skilled in the art within the range which does not deviate from the meaning. It can be implemented in a mode with various changes and improvements based on knowledge.

10: Vehicle 12: Engine (drive power source)
14: Front wheel (main drive wheel)
16: Rear wheel (sub drive wheel, output side rotating member)
34L, 34R: A pair of left and right electronic control couplings 50: Second clutch (torque transmission device)
52a: Ring gear (input side rotating member)
70: Electronic control device (control device)
Ncin: rotational speed of the input side rotating member Ncout: rotational speed of the output side rotating member

Claims (1)

A pair of left and right main drive wheels to which transmission torque is transmitted from a driving force source;
A torque transmission device provided in a power transmission path between the driving force source and a pair of left and right auxiliary driving wheels, and capable of connecting and disconnecting the power transmission path;
A pair of left and right electronic control couplings that are provided in series with the pair of left and right auxiliary drive wheels and change transmission torque transmitted from the input side rotation member to the output side rotation member in accordance with a transmission torque command value. A control device for a wheel drive vehicle,
The input side rotating member and the force side of the pair of left and right electronic control couplings, which are obtained when the pair of left and right electronic control couplings are each commanded to transmit torque command values that command equal transmission torque during straight traveling A control device for a four-wheel drive vehicle, wherein a transmission torque command value for the pair of left and right electronically controlled couplings is corrected based on a difference in change speed of a rotational speed difference from a rotating member.

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