JP2006297973A - Torque distribution control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the precision of torque distribution control by effectively judging slipping. <P>SOLUTION: A center differential gear 3 transmits motive power from an engine 1 to a driving system of the front wheel side and a driving system of the rear wheel side. A center clutch 5 sets a torque distribution ratio transmitted to each of the driving systems variably by limiting the differentiation of the driving system of the front wheel side and the driving system of the rear wheel side in accordance with its own engaging force. A detection part 19 respectively and directly detects fore-and-aft forces Fx working on wheels 4. A control part 18 determines the existence of the slipping of the wheels 4 in accordance with the fore-and-aft force of the front wheel and the fore-and-aft force of the rear wheel and controls the engaging force of the center clutch 5 in accordance with this determination result. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a torque distribution control device.

2. Description of the Related Art Conventionally, there is known a torque distribution control device that suppresses slip generated in a wheel by variably controlling a torque distribution ratio transmitted to each wheel (see, for example, Patent Documents 1 and 2). In this type of device, the torque distribution ratio of the front and rear wheels or the torque distribution ratio of the left and right wheels is controlled by adjusting the engagement force of the transfer clutch and limiting the differential of the differential gear (differential device). In order to suppress wheel slip, it is effective to set the engagement force of the transfer clutch to be larger than the current value according to the rotation difference between the wheels, and to control the front and rear wheels or the left and right wheels to be directly connected. is there. In such an apparatus, the wheel speed of each wheel is detected by a vehicle speed sensor in order to specify the rotation difference between the wheels.
Japanese Patent Application Laid-Open No. 06-99762 Japanese Patent Application Laid-Open No. 11-1129

  As a method for detecting slip generated in a wheel, a method using a vehicle speed pulse output according to the rotational speed of the wheel is well known. However, this detection method has a disadvantage that detection accuracy is low particularly in a low speed region, leading to erroneous determination of slip.

  Accordingly, an object of the present invention is to improve the accuracy of torque distribution control by effectively determining slip.

  In order to solve this problem, the present invention provides a torque distribution control device. The torque distribution control device includes a first differential device that transmits power from a drive source to one drive system and another drive system different from the one drive system, and a first differential device according to its own engagement force. By limiting the differential by one differential device, a first clutch that variably sets a distribution ratio of transmission torque transmitted to one drive system and the other drive system, and driven by one drive system And a detection unit that directly detects each of the longitudinal forces acting on the wheels, and a longitudinal force of the wheels driven by one of the drive systems. And a controller that determines the presence or absence of slipping of the wheel based on the longitudinal force of the wheel driven by the other drive system, and that controls the engagement force of the first clutch based on the determination result. .

  Here, in the present invention, the control unit calculates a difference between the longitudinal force of the wheel driven by one drive system and the longitudinal force of the wheel driven by the other drive system, and calculates the calculated value and a predetermined value. It is preferable to determine the presence or absence of wheel slip by comparing the determination value. In this case, it is desirable that the control unit calculates the calculated value after performing weighting based on the current torque distribution ratio.

  In the present invention, when the calculated value is larger than the determination value, the control unit determines that the wheel is slipping, and the first clutch is configured such that the engagement force of the first clutch is larger than the current value. It is preferable to control the clutch. In this case, the control unit may control the first clutch such that one drive system and the other drive system are directly connected to each other.

  In the present invention, it is preferable that one drive system is a drive system that drives left and right front wheels, and the other drive system is a drive system that drives left and right rear wheels. On the other hand, one drive system is a drive system that drives the left front wheel, and the other drive system is a drive system that drives the right front wheel, or one drive system drives the left rear wheel. The other drive system may be a drive system that drives the right rear wheel.

  Furthermore, in the present invention, the torque distribution control device is interposed in one drive system or the other drive system, and the power from the first differential device is transmitted to one of the left and right wheels and the other. Torque transmitted to one wheel and the other wheel by limiting the differential by the second differential device that transmits to the other wheel and the second differential device according to its own engagement force And a second clutch that variably sets the distribution ratio. In this case, the control unit determines whether or not the wheel slips based on the longitudinal force of one wheel and the longitudinal force of the other wheel, and controls the engagement force of the second clutch based on the determination result. It is preferable to do.

  According to the present invention, since the longitudinal force acting on the wheel is directly detected, it is possible to accurately determine whether or not the wheel slips. And the slip which arises on a wheel can be effectively suppressed by controlling the engaging force of a clutch based on this judgment result. In the present invention, since the longitudinal force is directly detected by the detection unit, the longitudinal force can be specified with higher accuracy than the method of detecting this value by estimation or the like. As a result, according to the present invention, slip determination can be performed with higher accuracy.

  FIG. 1 is a schematic diagram of a vehicle to which the torque distribution control device according to the present embodiment is applied. Power from a crankshaft (not shown) of the engine 1 that is a drive source is transmitted to a center differential (hereinafter simply referred to as “center differential”) 3 via an automatic transmission 2. The power transmitted to the center differential 3 is transmitted to the front wheel side through one drive system, and is transmitted to the rear wheel side through the other drive system different from this. As a result, driving torque is applied to the left and right front wheels 4fl and 4fr and the left and right rear wheels 4rl and 4rr, and driving force is applied to these wheels 4fl to 4rr. In this specification, when the left front wheel 4fl and the right front wheel 4fr are collectively referred to, the term “front wheel 4f” is used. When the left rear wheel 4rl and the right rear wheel 4rr are collectively referred to, the term “rear wheel 4r” is used. Use. In addition, the term “wheel 4” is used when referring to all of the left front wheel 4fl, the right front wheel 4fr, the left rear wheel 4rl, and the right rear wheel 4rr, or when indicating an arbitrary and independent wheel.

  The center differential 3 is a compound planetary gear type differential device, and a transmission output shaft 2a of the automatic transmission 2 is inserted in a freely rotatable state from the front (engine 1 side). The power from the transmission output shaft 2a is transmitted to the drive system on the rear wheel side via the first sun gear 3a, the first pinion 3b, the second pinion 3c, and the second sun gear 3d. The power from the transmission output shaft 2a is also transmitted to the drive system on the front wheel side via the first sun gear 3a and the carrier 3e. This center differential 3 distributes the transmission torque transmitted to the drive system on the front wheel side and the drive system on the rear wheel side in accordance with a reference torque distribution ratio set for itself. The reference torque distribution ratio can be set to a predetermined value by appropriately setting the meshing pitch circle radius between the first and second sun gears 3a and 3d and the first and second pinions 3b and 3c. Yes (for example, front wheel: rear wheel = 35: 65). Further, the rotational difference between the front wheel 4f and the rear wheel 4r generated during turning is absorbed by the planetary rotation of the pinion member 3f in which the first and second pinions 3b and 3c are integrally formed.

  A hydraulic multi-plate center clutch 5 is provided between two output elements of the center differential 3, that is, between the second sun gear 3d and the carrier 3e. A hydraulic device (not shown) is connected to the center clutch 5 through a flow path in which a solenoid valve 6 is interposed. By performing duty control of the solenoid valve 6, the engagement force of the center clutch 5 is obtained. Is adjusted. The differential of the center differential 3 is limited in accordance with the engagement force of the center clutch 5, whereby the distribution ratio of the transmission torque transmitted to the front wheel side drive system and the rear wheel side drive system (hereinafter referred to as “front and rear”). "Torque distribution ratio") is set variably. Specifically, when the engagement force of the center clutch 5 is “0”, that is, when the clutch is disengaged, the differential by the center differential 3 is allowed. In this case, the front-rear torque distribution ratio is the above-described reference torque distribution ratio. When the engagement force of the center clutch 5 is greater than “0”, the differential by the center differential 3 is limited, and the front-rear torque distribution ratio is distributed more to the front wheels than the reference torque distribution ratio. When the engagement force of the center clutch 5 is maximum, the front and rear drive systems are directly connected to each other. In this case, the front / rear torque distribution ratio is the front / rear torque distribution ratio that is most biased to the front wheels.

  In the drive system on the rear wheel side, the power from the center differential 3 is transmitted through a rear differential (hereinafter simply referred to as “rear differential”) via a rear drive shaft 7, a propeller shaft 8 and a drive pinion shaft 9 connected to the second sun gear 3d. ) 10. The power from the rear differential 10 is transmitted to the left rear wheel 4rl and the right rear wheel 4rr via the axle 11.

  The rear differential 10 is a bevel gear type differential device. A hydraulic multi-plate rear clutch 12 is provided between the two output elements of the rear differential 10, that is, between the differential case 10a and one side gear 10b. Similar to the center clutch 5 described above, the engagement force of the rear clutch 12 is adjusted by controlling the duty of the solenoid valve 13 for the rear clutch. The differential of the rear differential 10 is limited in accordance with the engagement force of the rear clutch 12, and accordingly, the distribution ratio of the transmission torque transmitted to the left rear wheel 4rl and the right rear wheel 4rr (hereinafter referred to as “left-right torque distribution ratio”). Is variably set. Specifically, in the state where the engagement force of the rear clutch 12 is “0”, that is, the clutch is released, the left-right torque distribution ratio is equal (left rear wheel: right rear wheel = 50: 50). When the engagement force of the rear clutch 12 becomes larger than “0”, the differential by the rear differential 10 is limited, and the left-right torque distribution ratio is increased from the high-speed wheel side to the low-speed wheel side by an increase in engagement force compared to the left-right equivalent distribution ratio. The distribution ratio becomes biased. When the engagement force of the rear clutch 12 is maximum, the rear wheel drive system is directly connected to the left and right. In this case, the left-right torque distribution ratio corresponds to the ratio between the value obtained by multiplying the vertical load acting on the left rear wheel 4rl by the road surface friction coefficient and the value obtained by multiplying the vertical load acting on the right rear wheel 4rr by the road surface friction coefficient. To do.

  On the other hand, in the drive system on the front wheel side, the power from the center differential 3 is transmitted through the front differential (hereinafter referred to as “front differential”) via the transfer drive gear 14, the transfer driven gear 15 and the front drive shaft 16 fixedly attached to the carrier 3e. ). The front differential 17 is omitted in FIG. 1 and is a bevel gear type differential device, similar to the rear differential 10 described above. The power from the front differential 17 is transmitted to the left front wheel 4fl and the right front wheel 4fr via the axle 11.

  FIG. 2 is a block configuration diagram functionally showing the control unit 18 according to the present embodiment. As the control unit 18, a microcomputer mainly composed of a CPU, a ROM, a RAM, and an input / output interface can be used. The control unit 18 performs a calculation related to the torque distribution ratio according to the control program stored in the ROM. Then, the control unit 18 outputs the control amount (control signal) calculated by this calculation to the actuator (the solenoid valve 6 in this embodiment). Detection signals from various sensors including the detection unit 19 are input to the control unit 18 in order to perform torque distribution control described later.

  FIG. 3 is an explanatory diagram of the acting force. The detection unit 19 detects the acting force acting on the wheel 4. For convenience of explanation, FIG. 2 shows only one block corresponding to the detection unit 19, but actually the detection unit 19 is provided corresponding to each wheel 4. The acting forces that can be detected by the detector 19 are a longitudinal force Fx, a lateral force Fy, and a vertical force Fz. The longitudinal force Fx is a component force generated in the direction parallel to the wheel center plane (x-axis) among the frictional forces generated on the ground contact surface of the wheel 4, and the lateral force Fy is a direction perpendicular to the wheel center plane (y This is the component force generated on the shaft. On the other hand, the vertical force Fz is a force acting in the vertical direction (z-axis), that is, a so-called vertical load. Of these acting forces Fx, Fy, Fz, the longitudinal force Fx is important in the present embodiment. Each detection unit 19 is mainly configured by a strain gauge and a signal processing circuit that processes an electrical signal output from the strain gauge and generates a detection signal corresponding to the acting force. Based on the knowledge that the stress generated in the axle 11 is proportional to the acting force, the acting force relating to each wheel 4 is directly detected by embedding a strain gauge in each axle 11. The specific configuration of the detection unit 19 is disclosed in, for example, Japanese Patent Application Laid-Open No. 04-331336 and Japanese Patent Application Laid-Open No. 10-318862, and should be referred to if necessary.

  When the control unit 18, which is a microcomputer, is functionally grasped, the control unit 18 executes the following functions. First, based on the detection result of the detector 19, the longitudinal force acting on the front wheel 4f (hereinafter referred to as “front wheel longitudinal force”) Ff_x and the longitudinal force acting on the rear wheel 4r (hereinafter referred to as “rear wheel”). Fr_x) is calculated. Secondly, the presence or absence of slip of the wheel 4 is determined based on the calculated longitudinal forces Ff_x and Fr_x. Thirdly, the engagement force of the center clutch 5 is controlled based on this determination result.

  FIG. 4 is a flowchart showing a torque distribution control routine according to the present embodiment. This routine is called at predetermined intervals and executed by the control unit 18. First, in step 1, the longitudinal force Fx detected for each of the wheels 4fl to 4rr is read. In step 2, a front wheel longitudinal force Ff_x and a rear wheel longitudinal force Fr_x are calculated. The front wheel front / rear force Ff_x is calculated as an average value of the front / rear force Fx acting on the left front wheel 4fl and the right front wheel 4fr. The rear wheel front / rear force Fr_x acts on the left rear wheel 4rl and the right rear wheel 4rr, respectively. It is calculated as an average value of the longitudinal force Fx. In addition to such a calculation method, the front / rear forces Ff_x and Fr_x may be calculated as the sum of the lateral forces Fy of the left and right wheels, or the front / rear force Fx of one of the left and right wheels 4 is representative. May be used.

  When the processing up to step 2 is completed, it is next determined whether or not slip has occurred in the front wheel 4f or the rear wheel 4r. In a four-wheel drive vehicle in which power is transmitted to the front and rear wheels 4f and 4r, the distribution of the longitudinal force Fx acting on the front wheels 4f and the rear wheels 4r basically corresponds to the longitudinal torque distribution ratio. However, when a slip occurs in one of the wheels 4, the longitudinal force (absolute value) acting on the wheel 4 is smaller than that in a non-slip state. Therefore, at the time of a slip, the distribution ratio between the front wheel front / rear force Ff_x and the rear wheel front / rear force Fr_x is offset from the front / rear torque distribution ratio. Therefore, the presence or absence of slip can be determined by specifying this offset.

  In the slip determination, a difference (absolute value) ΔFx1 (hereinafter referred to as “first calculated value”) between the front wheel longitudinal force Ff_x and the rear wheel longitudinal force Fr_x is compared with a predetermined first determination value ΔFxth1 set in advance. (Step 3). The first determination value ΔFxth1 is set in advance with a minimum value of the first calculated value ΔFx1 that can be determined that a slip has occurred in one of the wheels 4 through experiments and simulations. However, in the case where the current front-rear torque distribution ratio is biased toward the front wheel 4f or the rear wheel 4r, the first calculated value ΔFx may be equal to or greater than the first determination value ΔFxth1 even during non-slip. Therefore, in the process shown in step 3, as a premise for calculating the first calculated value ΔFx1, first, a predetermined gain k1, Set k2. Then, with these gains k1 and k2, weighting is performed so that the first calculated value ΔFx1 at the time of non-slip becomes approximately 0, and then the first calculated value ΔFx is calculated (ΔFx1 = | Ff_x · k1− Fr_x · k2 |). The correspondence relationship between the gains k1, k2 and the front-rear torque distribution ratio is created in advance as a map through experiments and simulations, and is stored at a predetermined address in the ROM of the control unit 18. If an affirmative determination is made in step 3, that is, if slip occurs in the front wheel 4f or the rear wheel 4r (ΔFx1 ≧ ΔFxth1), the process proceeds to step 4. On the other hand, if a negative determination is made in step 3, that is, if no slip has occurred in the front wheel 4f and the rear wheel 4r (ΔFx1 <ΔFxth1), the process proceeds to step 5.

  In step 4, the duty control of the solenoid valve 6 is performed so that the engagement force of the center clutch 5 is larger than the current value by a predetermined step value. When the current value of the engagement force is a maximum value that can be regarded as a state in which the drive systems on the front and rear wheels are directly connected to each other, the duty control of the solenoid valve 6 is not performed in this step 4 (that is, The engagement force remains at the maximum value). On the other hand, in step 5, normal control of the center clutch 5 is executed. In this normal control, for example, the motion state of the vehicle is determined based on the acting force of the wheel 4 (for example, the longitudinal force Fx), thereby controlling the torque distribution ratio for the front and rear wheels 4f and 4r. Details regarding the normal control are disclosed in, for example, Japanese Patent Application Laid-Open No. 05-338458, so refer to them if necessary.

  As described above, according to the present embodiment, since the longitudinal force Fx acting on each wheel 4 is directly detected, the presence or absence of slip occurring on one wheel 4 based on the longitudinal force Fx of the front and rear wheels 4f and 4r. Can be accurately determined. When the front wheel 4f or the rear wheel 4r slips, the engagement force of the center clutch 5 is increased from the current value. As a result, the center clutch 5 is controlled so that the front-wheel-side drive system and the rear-wheel-side drive system tend to be directly connected to each other, so that slip generated on the wheels 4 can be suppressed. Further, in the present embodiment, the slip determination is performed based on the longitudinal force Fx of the wheel 4 instead of the conventional method based on the rotational speed of the wheel 4. When a vehicle speed pulse is detected as the rotational speed of the wheel 4, the detection accuracy is particularly poor in a low speed range, but such inconvenience is solved by making a slip determination based on the longitudinal force as in this embodiment. be able to. As a result, the accuracy of slip determination can be improved, and the accuracy of torque distribution control can be improved. Further, in the present embodiment, the longitudinal force Fx is accurately detected as compared with a so-called indirect method in which this value is detected by estimation or the like because the longitudinal force Fx is directly detected by the detection unit 19. Can be identified. Therefore, by performing control based on the detection result of the detection unit 19, more accurate slip determination can be performed.

  In the present embodiment, when the engagement force of the center clutch 5 is increased in consideration of control stability, this is performed step by step using a step value. However, in addition to this method, when it is determined that slip has occurred in the wheel 4, the center clutch 5 is connected so that the front wheel side drive system and the rear wheel side drive system are directly connected to each other. The engagement force may be controlled to the maximum value. Further, when the engagement force is increased or decreased using the step value, it is not necessary to set the step value to a constant value. That is, this value is made variable so that the step value increases stepwise or continuously as the slip degree increases, that is, as the difference between the first calculated value ΔFx and the first determination value ΔFxth1 increases. It may be set. Such a change in the control method can be similarly applied to a second embodiment described later.

(Second Embodiment)
FIG. 5 is a flowchart showing a torque distribution control routine according to the second embodiment. The control procedure of this embodiment is different from that of the first embodiment in that in addition to the front-rear torque distribution control, the left-right torque distribution control of the rear wheels 4r is performed. Note that in the second embodiment, the same components as those described in the first embodiment are denoted by the same reference numerals, and description thereof is omitted. First, in steps 11 to 15, torque distribution control of the front and rear wheels 4 f and 4 r is executed as in steps 1 to 5 shown in FIG. 4.

  In step 16 following step 14 or step 15, it is determined whether or not slip has occurred in one of the left and right rear wheels 4rl, 4rr. The longitudinal force Fx acting on the left rear wheel 4rl and the right rear wheel 4rr is basically equivalent. However, when slip occurs in one of the left and right rear wheels 4rl and 4rr, the longitudinal force (absolute value) acting on the slipping wheel 4 is smaller than that in non-slip. Therefore, in step 16, a difference (absolute value) ΔFx2 (hereinafter referred to as “second calculated value”) between the longitudinal force Fx of the left rear wheel 4rl and the longitudinal force Fx of the right rear wheel 4rr is set in advance. Compare with the second determination value ΔFxth2. The second determination value ΔFxth2 is set in advance as a minimum value of the second calculated value ΔFx2 that can be determined that slip has occurred in one of the left and right rear wheels 4rl and 4rr, through experiments and simulations. Yes. If an affirmative determination is made in step 16, that is, if slip occurs in one of the left and right rear wheels 4rl and 4rr (ΔFx2 ≧ ΔFxth2), the process proceeds to step 17. On the other hand, if a negative determination is made in step 16, that is, if no slip has occurred in the left and right rear wheels 4rl and 4rr (ΔFx2 <ΔFxth2), the process proceeds to step 18.

  In step 17, the duty control of the solenoid valve 13 is performed so that the engagement force of the rear clutch 12 is larger than the current value by a predetermined step value. If the current value of the engagement force is the maximum value that allows the drive systems on the left and right rear wheels to be regarded as being directly connected to each other, the duty control of the solenoid valve 13 is not performed in this step 17 (that is, The engagement force remains at the maximum value). On the other hand, in step 18, normal control of the rear clutch 12 is executed. In this normal control, for example, the torque distribution ratio with respect to the left and right rear wheels 4rl and 4rr is controlled based on the acting force acting on the wheel 4 (for example, the longitudinal force Fx). Details regarding the normal control are disclosed in, for example, Japanese Patent Application Laid-Open No. 05-338458, so refer to them if necessary.

  As described above, according to the present embodiment, the same effects as those of the first embodiment can be obtained, and the presence / absence of slip occurring on one of the wheels 4 can be determined based on the longitudinal force Fx of the left and right rear wheels 4rl and 4rr. Can do. When slip occurs in the left rear wheel 4rl or the right rear wheel 4rr, the engagement force of the rear clutch 12 is increased from the current value, and the drive system on the left rear wheel side and the drive system on the right rear wheel side are increased. Is controlled to a direct connection. As a result, torque is moved from the high-speed slip wheel 4 to the low-speed grip wheel 4 in the left and right wheels 4. For this reason, for example, it is possible to improve the maneuverability on the road surfaces having different road surface friction coefficients between the left and right wheels 4, so-called split μ road surfaces.

  In the second embodiment described above, torque distribution control is performed with the left and right rear wheels 4rl and 4rr as control targets. However, by providing the front differential 17 with a hydraulic multi-plate rear clutch that restricts the differential between the left and right front wheels 4fl and 4fr, the torque distribution control may be performed on the left and right front wheels 4fl and 4fr as control targets. Further, in the present embodiment, the left / right torque distribution ratio control and the front / rear torque distribution ratio control are performed, respectively, but in the present invention, only the left / right torque distribution ratio control may be performed independently. In this case, the vehicle to be controlled may be a vehicle driven by front wheels or rear wheels as well as a four-wheel drive vehicle.

  In the first or second embodiment described above, the detection unit 19 is configured to detect a force acting in three directions as an acting force by embedding the detection unit 19 in the axle 11. For example, the detection unit 19 may be provided on a member that holds the wheel 4, for example, a hub or a hub carrier, and the acting force acting in the necessary component force direction is not limited thereto. It is sufficient if a six component force meter that detects the six component forces including the moments around these three directions may be used. Even with such a configuration, there is no problem as a matter of course, since at least the acting force required in the control can be detected.

Schematic of a vehicle to which a torque distribution control device is applied The block block diagram which shows the control part concerning 1st Embodiment functionally Illustration of acting force The flowchart which shows the torque distribution control routine concerning 1st Embodiment. The flowchart which shows the torque distribution control routine concerning 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 2 Automatic transmission 3 Center differential 4 Wheel 5 Center clutch 6 Solenoid valve 7 Rear drive shaft 8 Propeller shaft 9 Drive pinion shaft 10 Rear differential 11 Axle 12 Rear clutch 13 Solenoid valve 14 Transfer drive gear 15 Transfer driven gear 16 Front drive shaft 17 Front differential 18 Control unit 19 Detection unit

Claims (8)

In the torque distribution control device,
A first differential device that transmits power from a drive source to one drive system and another drive system different from the one drive system;
The distribution ratio of the transmission torque transmitted to the one drive system and the other drive system is variably set by limiting the differential by the first differential device in accordance with its own engagement force. One clutch,
A detection unit that directly detects each of the longitudinal forces acting on the wheels, with the wheels driven by the one drive system and the wheels driven by the other drive system as detection targets;
Based on the longitudinal force of the wheel driven by the one drive system and the longitudinal force of the wheel driven by the other drive system, the presence or absence of slipping of the wheel is determined, and the determination result And a controller for controlling the engagement force of the first clutch.   The control unit calculates a difference between a longitudinal force of the wheel driven by the one drive system and a longitudinal force of the wheel driven by the other drive system, and the calculated value and a predetermined determination 2. The torque distribution control device according to claim 1, wherein the presence / absence of slippage of the wheel is determined by comparing with a value.   3. The torque distribution control device according to claim 2, wherein the control unit calculates the calculated value after performing weighting based on a current torque distribution ratio. 4.   When the calculated value is greater than the determination value, the control unit determines that the wheel is slipping, and the first clutch is configured such that the engagement force of the first clutch is greater than the current value. 4. The torque distribution control device according to claim 2, wherein the clutch is controlled.   5. The torque distribution control device according to claim 4, wherein the control unit controls the first clutch such that the one drive system and the other drive system are directly connected to each other. .   6. The drive system according to claim 1, wherein the one drive system is a drive system that drives left and right front wheels, and the other drive system is a drive system that drives left and right rear wheels. The described torque distribution control device.   The one drive system is a drive system that drives the left front wheel, and the other drive system is a drive system that drives the right front wheel, or the one drive system is a drive that drives the left rear wheel. 6. The torque distribution control device according to claim 1, wherein the other drive system is a drive system for driving the right rear wheel. The second drive system is interposed in the one drive system or the other drive system, and transmits power from the first differential device to one wheel and the other wheel of the left and right wheels. Differentials of
By limiting the differential by the second differential device in accordance with its own engagement force, a distribution ratio of transmission torque transmitted to the one wheel and the other wheel is variably set. A clutch,
The controller determines whether or not the wheel slips based on the longitudinal force of the one wheel and the longitudinal force of the other wheel, and based on the determination result, determines whether the second clutch is engaged. 7. The torque distribution control device according to claim 6, wherein the resultant force is controlled.

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