JP2019211044A - Control device of four-wheel drive vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device of a four-wheel drive vehicle capable of grasping output characteristics of a pair of left and right electronically controlled couplings while turning. According to a control device 70 of a vehicle 10 of the present embodiment, based on differential rotational accelerations dωdl / dt and dωdr / dt between an input side rotating member, that is, a ring gear 52a and an output side rotating member, that is, rear wheels 16L and 16R. Since the friction coefficients μl and μr of the pair of left and right electronically controlled couplings 34L and 34R are estimated, the output characteristics of the pair of left and right electronically controlled couplings 34L and 34R are grasped based on the estimated friction coefficients μl and μr. be able to. As a result, during turning, the control for correcting the transmission torque command value is executed in order to make the output characteristics of the pair of left and right electronically controlled couplings 34L and 34R uniform, for example, so that the turning stability of the four-wheel drive vehicle is impaired. Can be suppressed. [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 driving force source; and a pair of left and right auxiliary driving wheels to which a part of transmission torque is transmitted from the driving force source via a power transmission member in a four-wheel drive state; A pair of left and right electronic control couplings that are provided in series with the pair of left and right sub-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 four-wheel drive vehicle is known. 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 on the left and right of the rear wheel, that is, the auxiliary drive wheel, and the transmission torque of the left and right rear wheels is increased. Each is controlled. Thereby, the turning stability of the four-wheel drive vehicle can be efficiently controlled.

JP 2017-001447 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, transmission transmitted from the pair of left and right electronic control couplings to the left and right rear wheels with respect to the control current from the control device, that is, the transmission torque command value. Since a difference occurs in torque, the turning stability of the four-wheel drive vehicle may be impaired. Therefore, in order to correct the transmission torque command value supplied to the pair of left and right electronic control couplings, for example, so as not to impair the turning stability of the four-wheel drive vehicle, It is necessary to grasp the output characteristics.

  The present invention has been made against the background of the above circumstances, and its object is to control a four-wheel drive vehicle capable of grasping the output characteristics of a pair of left and right electronically controlled couplings during turning. To provide an apparatus.

  The gist of the present invention is that a pair of left and right main drive wheels to which transmission torque is transmitted from a driving force source and a part of transmission torque from the driving force source through a power transmission member in a four-wheel drive state. A pair of left and right auxiliary drive wheels and a pair of left and right auxiliary drive wheels that are provided in series, and that change the transmission torque transmitted from the input side rotation member to the output side rotation member in accordance with the transmission torque command value. A control device for a four-wheel drive vehicle including a plurality of electronically controlled couplings, wherein the pair of left and right electronically controlled couplings are released to drive only the main drive wheels during turning. When a transmission torque command value for commanding equal transmission torque is commanded to the pair of left and right electronic control couplings, either one of the pair of left and right electronic control couplings slips. It is to estimate the friction coefficient of the pair of the electronic controlled coupling based on the change rate of the rotational speed difference between the input side rotating member and the output rotary member when it becomes on purpose.

  According to the control device for a four-wheel drive vehicle of the present invention, the pair of left and right pairs is controlled based on the change speed of the differential rotation between the input-side rotation member and the output-side rotation member during turning in the two-wheel drive state. Since the coefficient of friction of the electronically controlled coupling is estimated, the output characteristics of the pair of left and right electronically controlled couplings can be grasped during the turning based on the estimated coefficient of friction. Accordingly, for example, by executing control for correcting the transmission torque command value in order to align the output characteristics of the pair of left and right electronic control couplings, it is possible to prevent the turning stability of the four-wheel drive vehicle from being impaired. Can do.

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 the characteristic of the friction coefficient by the relationship between the differential rotational acceleration of a pair of left and right electronically controlled coupling, and a clutch fastening force. 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.

  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 second power transmission path transmits the transmission torque of the engine 12 distributed by the transfer 26, which is a front and rear wheel transmission torque distribution device that distributes the transmission torque of the engine 12 to the rear wheels 16, to the rear wheels 16. A propeller shaft 28 serving as a transmission 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. By increasing the transmission torque command value, a clutch pressing force, so-called clutch engagement force Wc, which is a force for engaging the pair of left and right electronic control couplings 34L and 34R 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.

  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, Signals representing Wfr, Wrl, and Wrr (rpm) 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 ωcin (rpm) of the input side rotation member and the rotation speed ωcout (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, a ring gear 52a, and the electronic control unit 70 uses a signal representing the rotation speed Nrr (rpm) of the ring gear 52a detected by the rotation speed sensor 94 as a signal representing the rotation speed ωcin of the input side rotation member. To be supplied. The output side rotating member is, for example, the rear wheel 16, and a signal representing the rotational speeds Wrl and Wrr of the rear wheels 16L and 16R detected by the wheel speed sensor 90 is electronic as a signal representing the rotational speed ωcout of the output side rotating member. Each is supplied to the control device 70.

  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 traveling state determination unit, that is, a traveling state determination unit 100, a torque command value control unit, that is, a torque command value control unit 102, and a rotational speed detection unit, that is, a rotation. Speed detection unit 104, differential rotation state determination unit or differential rotation state determination unit 106, differential rotation acceleration calculation unit or differential rotation acceleration calculation unit 108, friction coefficient estimation unit or friction coefficient estimation unit 110, output characteristic determination unit or output characteristic determination Unit 112 and torque command value correction means, that is, a torque 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 and the steering angle θ detected by the steering sensor 88, for example, whether the vehicle 10 is turning or not. Determine whether. For example, the traveling state determination unit 100 determines that the steering angle θ of the vehicle 10 is larger than a predetermined constant steering angle θath obtained experimentally or design in advance, and the vehicle speed V of the vehicle 10 is experimentally or design in advance. It is determined that the vehicle is turning when the vehicle speed is higher than the predetermined constant vehicle speed Vth.

  Moreover, the traveling state determination unit 100 determines whether or not the vehicle 10 is in a disconnected state. For example, the traveling state determination unit 100 is in a two-wheel drive state in which the first clutch 24, the second clutch 50, the left electronic control coupling 34L, and the right electronic control coupling 34R are released while the vehicle is traveling. Determine whether or not.

  The torque command value control unit 102 controls a transmission torque command value supplied to the pair of left and right electronic control couplings 34L and 34R, that is, control currents I3 and I4. In the present embodiment, for example, when the transmission torque command value is corrected while the vehicle 10 is in a disconnected state and turning, the behavior of the vehicle 10 during turning in the two-wheel drive mode is affected in order to determine the correction amount. The left and right electronically controlled couplings 34L and 34R are commanded with transmission torque command values indicating constant transmission torques equal to each other, that is, control currents I3 and I4, which are controlled within a range where there is no turning, that is, an increase range in which turning can be continued. When the same transmission torque command value is supplied to the pair of left and right electronic control couplings 34L and 34R by the torque command value control unit 102 while the vehicle 10 is in a disconnected state and turning, the rotational speed of the turning inner wheel of the vehicle 10 is Since the rotational speed is relatively slower than the rotational speed of the outer turning wheel, a difference in rotational speed occurs between the inner turning wheel and the outer turning wheel, and slipping or slipping occurs in one of the pair of left and right electronically controlled couplings 34L and 34R.

  The rotational speed detector 104 detects the rotational speed ωcin of the input side rotational member and the rotational speeds ωcoutl and ωcoutr of the output side rotational member of the pair of left and right electronic control couplings 34L and 34R. Specifically, the rotational speed detection unit 104 detects the rotational speed Nrr of the ring gear 52a by the rotational speed sensor 94 as the rotational speed ωcin of the input side rotational member of the pair of left and right electronic control couplings 34L and 34R. Further, the rotation speed detection unit 104 detects the rotation speed Wrl of the rear wheel 16L by the wheel speed sensor 90 as the rotation speed ωcoutl 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 wheel speed sensor 90 detects the rotation speed Wrr of the rear wheel 16R as the rotation speed ωcoutr of the rotating member.

  The differential rotation state determination unit 106 determines whether one of the pair of left and right electronic control couplings 34L and 34R is in a slip state. Specifically, the differential rotation state determination unit 106 determines whether the rotational speed difference between the rotational speed ωcin of the input side rotational member and the rotational speeds ωcoutl and ωcoutr of the output side rotational member, that is, one of the differential rotational speeds ωdl and ωdr. Then, it is determined whether or not it is larger than a predetermined differential rotation determination value ωth obtained experimentally in advance. The differential rotation ωdl is the difference in rotational speed between the rotational speed ωcin of the input side rotational member and the rotational speed ωcoutl of the output side rotational member. The differential rotational ωdr is the rotational speed ωcin of the input side rotational member and the rotational speed ωcin of the output side rotational member. This is the difference in rotational speed from the rotational speed ωcoutr.

  The differential rotation acceleration calculation unit 108 calculates the change speeds of the differential rotations ωdl and ωdr between the rotation speed ωcin of the input side rotation member of the pair of left and right electronic control couplings 34L and 34R and the rotation speeds ωcoutl and ωcoutr of the output side rotation member, respectively. calculate. The speed of change is the time rate of change of the differential rotation between the rotational speed ωcin of the input side rotating member and the rotational speeds ωcoutl and ωcoutr of the output side rotating member, that is, expressed by the angular acceleration of the differential rotations ωdl and ωdr. Differential rotational accelerations dωdl / dt and dωdr / dt (referred to as differential rotational acceleration dωd / dt unless otherwise specified). The differential rotational acceleration dωd / dt between the pair of left and right electronically controlled couplings 34L and 34R varies depending on the clutch engagement force Wc, the turning radius R of the vehicle 10, the vehicle speed V, and the like.

  The friction coefficient estimation unit 110 estimates the friction coefficients μl and μr of the pair of left and right electronically controlled couplings 34L and 34R based on the differential rotation accelerations dωdl / dt and dωdr / dt calculated by the differential rotation acceleration calculation unit 108, respectively. To do. Specifically, the force F expressed as a value of multiplication of the weight W and the acceleration α can be expressed as a frictional force F by a value of multiplication of the weight W and the friction coefficient μ. Assuming that W is replaced with the clutch engagement force Wc and the acceleration α is replaced with the differential rotational accelerations dωdl / dt and dωdr / dt, the friction coefficient estimation unit 110 is based on the differential rotational accelerations dωdl / dt and dωdr / dt. Friction coefficients μl and μr are estimated, respectively. The friction coefficient μl is the friction coefficient of the left electronic control coupling 34L, and the friction coefficient μr is the friction coefficient of the right electronic control coupling 34R. The friction coefficient estimation unit 110 estimates the friction coefficients μl and μr, for example, by comparing with an assumed relationship map between the differential rotational acceleration dωd / dt and the clutch engagement force Wc obtained experimentally in advance.

  Based on the friction coefficients μl and μr estimated by the friction coefficient estimation unit 110, the output characteristic determination unit 112 determines whether there is an abnormality in the output characteristics of the pair of left and right electronic control couplings 34L and 34R. For example, when the friction coefficients μl and μr estimated by the friction coefficient estimation unit 110 deviate from the assumed value of the assumed μ characteristic shown in the assumed relation map, and both the left and right electronic control couplings 34L and 34R When the friction coefficients μl and μr of the two are larger than the predetermined difference, the output characteristic determination unit 112 determines that the output characteristics of the pair of left and right electronic control couplings 34L and 34R are abnormal. The predetermined difference in the friction coefficient is a constant determination obtained experimentally or design in advance in order to determine a case where the friction coefficients μl and μr of the pair of left and right electronically controlled couplings 34L and 34R greatly deviate from each other. It refers to the friction coefficient μth.

  FIG. 2 is a diagram showing the characteristic of the friction coefficient μ according to the relationship between the differential rotational acceleration dωd / dt of the pair of left and right electronically controlled couplings 34L and 34R and the clutch engagement force Wc. A straight line “a” in FIG. 2 indicates an assumed μ characteristic obtained experimentally in advance as an example of the assumed relationship map. For example, when the differential rotational acceleration dωd1 / dt when the clutch engaging force Wc1 is used, the friction coefficient μ1 is an assumed value of the assumed μ characteristic. A straight line b in FIG. 2 indicates a high μ characteristic in which the differential rotational acceleration dωd2 / dt is larger than the differential rotational acceleration dωd1 / dt and the friction coefficient μ2 is larger than the assumed value μ1 when the clutch engagement force Wc1 is applied. A straight line c in FIG. 2 indicates a low μ characteristic in which the differential rotational acceleration dωd3 / dt is smaller than the differential rotational acceleration dωd1 / dt and the friction coefficient μ3 is smaller than the assumed value μ1 when the clutch engagement force Wc1 is applied. That is, the friction coefficients μl and μr estimated by the friction coefficient estimation unit 110 exceed a certain assumed allowable range μro obtained experimentally or design in advance based on the assumed μ characteristics, for example, When the high μ characteristic or the low μ characteristic deviates from the assumed value, the output characteristic determination unit 112 determines that the output characteristics of the pair of left and right electronic control couplings 34L and 34R are abnormal.

  The torque command value correction unit 114 corrects the transmission torque command value when the output characteristic determination unit 112 determines that the output characteristics of the pair of left and right electronic control couplings 34L and 34R are abnormal. Specifically, the torque command value correction unit 114 is configured to assume the friction coefficients μl and μr of the pair of left and right electronic control couplings 34L and 34R in order to align the output characteristics of the pair of left and right electronic control couplings 34L and 34R. The μ characteristic of the pair of left and right electronically controlled couplings 34L and 34R is assumed to eliminate the deviation of the characteristic from the assumed value and the deviation between the friction coefficient μl and the friction coefficient μr, that is, the difference of the characteristic difference of the μ characteristic. The transmission torque command value is corrected so that the clutch engagement force Wc with respect to the differential rotational acceleration dωd / dt is changed.

  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 a 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 a disconnected state. If the determination in S10 is affirmative, that is, if the vehicle 10 is in a disconnected state, S20 corresponding to the traveling state determination unit 100 is executed. If the determination in S10 is negative, that is, if the vehicle 10 is not in a disconnected state, this routine is terminated.

  In S20 corresponding to the traveling state determination unit 100, it is determined whether or not the vehicle 10 is turning. If the determination in S20 is affirmative, that is, if the steering angle θ of the vehicle 10 is greater than the predetermined constant steering angle θath and the vehicle speed V of the vehicle 10 is greater than the predetermined constant vehicle speed Vth, the torque command S30 corresponding to the value control unit 102 is executed. If the determination in S20 is negative, that is, if the steering angle θ of the vehicle 10 is smaller than the predetermined constant steering angle θath and the vehicle speed V of the vehicle 10 is smaller than the predetermined constant vehicle speed Vth, this routine is executed. Is terminated.

  In S30 corresponding to the torque command value control unit 102, the 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 are controlled based on the transmission torque command value. In this embodiment, transmission torque command values indicating transmission torques that are equal to each other and controlled in a range that does not affect the behavior of the vehicle 10 are supplied to the pair of left and right electronic control couplings 34L and 34R, respectively. When the torque command value control unit 102 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 104 is executed.

  In S40 corresponding to the rotational speed detection unit 104, the rotational speed detection unit 104 causes the rotational speed ωcin of the ring gear 52a, which is the input side rotational member of the pair of left and right electronic control couplings 34L, 34R, and the rear wheel 16L of the output side rotational member, The rotational speeds ωcoutl and ωcoutr of 16R are detected. When the rotation speed detection unit 104 detects the rotation speed ωcin of the input side rotation member and the rotation speeds ωcoutl and ωcoutr of the output side rotation member, S50 corresponding to the differential rotation state determination unit 106 is executed.

  In S50 corresponding to the differential rotation state determination unit 106, it is determined whether any one of the pair of left and right electronic control couplings 34L and 34R is in the slip state. If the determination in S50 is affirmative, that is, one of the differential rotations ωdl and ωdr between the rotational speed ωcin of the input side rotating member and the rotational speeds ωcoutl and ωcoutr of the output side rotating member is a constant differential rotational determination value. When it is larger than ωth, S60 corresponding to the friction coefficient estimating unit 110 is executed. When the determination in S50 is negative, that is, when the difference rotations ωdl and ωdr between the rotation speed ωcin of the input side rotation member and the rotation speeds ωcoutl and ωcoutr of the output side rotation member are smaller than a certain difference rotation determination value ωth. This routine is terminated.

  In S60 corresponding to the friction coefficient estimator 110, based on the differential rotational accelerations dωdl / dt and dωdr / dt calculated by the differential rotational acceleration calculator 108, the friction coefficients μl of the pair of left and right electronic control couplings 34L and 34R, μr is estimated. When the friction coefficient estimation unit 110 estimates the friction coefficients μl and μr, S70 corresponding to the output characteristic determination unit 112 is executed.

  In S70 corresponding to the output characteristic determination unit 112, based on the friction coefficients μl and μr estimated by the friction coefficient estimation unit 110, it is determined whether or not there is an abnormality in the output characteristics of the pair of left and right electronic control couplings 34L and 34R. Determined. When the determination in S70 is affirmative, that is, when the friction coefficients μl and μr deviate from the assumed value of the assumed μ characteristic, and the friction coefficients μl and μr of both the pair of left and right electronic control couplings 34L and 34R are predetermined. When the difference is larger than the difference, S80 corresponding to the torque command value correction unit 114 is executed. When the determination in S70 is negative, that is, when the friction coefficients μl and μr have not deviated from the assumed value of the assumed μ characteristic, and the friction coefficients μl and μr of both the pair of left and right electronic control couplings 34L and 34R are If it is smaller than the predetermined difference, this routine is terminated.

  In S80 corresponding to the torque command value correction unit 114, when the output characteristic determination unit 112 determines that the output characteristics of the pair of left and right electronic control couplings 34L and 34R are abnormal, 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, based on the differential rotational accelerations dωdl / dt and dωdr / dt between the input side rotating member, that is, the ring gear 52a, and the output side rotating members, that is, the rear wheels 16L and 16R. Thus, the friction coefficients μl and μr of the pair of left and right electronic control couplings 34L and 34R are estimated, and the output characteristics of the pair of left and right electronic control couplings 34L and 34R are grasped based on the estimated friction coefficients μl and μr. be able to. As a result, the turning stability of the four-wheel drive vehicle is impaired by executing the control for correcting the transmission torque command value in order to align the output characteristics of the pair of left and right electronic control couplings 34L and 34R, for example, during turning. Can be suppressed.

  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 rotation member on the input side 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, 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 used as a signal representing the rotational speed ωcin of the rotating member on the input side. May be supplied.

  In the above-described embodiment, the rotating member on the output side of the pair of left and right electronic control couplings 34L and 34R is the rear wheel 16, but is not limited thereto, and may be the rear wheel axle 32, for example. . That is, even if the signals representing the respective rotational speeds of the rear wheel axles 32L and 32R detected by the rotational speed sensor 94 are supplied to the electronic control unit 70 as signals representing the rotational speeds ωcoutl and ωcoutr of the output side rotating member, respectively. Good.

  Further, in the above-described embodiment, the storage unit that stores the rotation speed of each unit detected by the rotation speed detection unit 104 and the transition of the differential rotation acceleration of each unit calculated by the differential rotation acceleration calculation unit 108 in a predetermined period is stored. It may be functionally equipped. Accordingly, for example, the friction coefficient estimation unit 110, based on the transition of the differential rotational accelerations dωdl / dt and dωdr / dt calculated by the differential rotational acceleration calculation unit 108 in a predetermined period, a pair of left and right electronic control couplings 34L and 34R. The coefficient of friction μl and μr may be estimated respectively.

  In the above-described embodiment, the differential rotational accelerations dωdl / dt and dωdr / dt are calculated by the differential rotational acceleration calculation unit 108. However, the present invention is not limited to this. For example, by providing an acceleration sensor in the vehicle, It may be detected by the acceleration sensor.

  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 (4-wheel drive vehicle)
12: Engine (drive power source)
14: Front wheel (main drive wheel)
16: Rear wheel (sub drive wheel, rotating member on the output side)
34L, 34R: A pair of left and right electronic control couplings 52a: Ring gear (input side rotating member)
70: Electronic control device (control device)
dωd / dt: Differential rotation acceleration (change speed of differential rotation)

Claims (1)

A pair of left and right main drive wheels to which transmission torque is transmitted from a driving force source; and a pair of left and right auxiliary driving wheels to which a part of transmission torque is transmitted from the driving force source via a power transmission member in a four-wheel drive state; A pair of left and right electronically controlled couplings that are provided in series with the pair of left and right auxiliary drive wheels, respectively, 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 four-wheel drive vehicle,
A pair of left and right electronically controlled couplings is used to transmit a transmission torque command value for commanding an equal transmission torque during a two-wheel drive state in which the pair of left and right electronically controlled couplings are released to drive only the main drive wheels. When either of the pair of left and right electronic control couplings is in a slip state, based on the change speed of the differential rotation between the input side rotating member and the output side rotating member A control device for a four-wheel drive vehicle, wherein the friction coefficient of the pair of left and right electronically controlled couplings is estimated.

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