JP2008232215A - Differential device with differential limiting mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress turbulence of vehicular behavior by generating a differential limiting force for a differential mechanism without delay while a vehicle is turning. <P>SOLUTION: When travelling around a corner, a control device for controlling a differential limiting action of the differential mechanism estimates a time Tc to "intersect" when a rotation speed of an inside turning driving wheel exceeds a rotation speed of an outside turning driving wheel from rotation speed difference and rotation acceleration difference of the inside and outside turning driving wheels and outputs a drive instruction to an electric motor of the differential mechanism at the time point when this prediction time Tc becomes equal to or shorter than a predetermined value. Thus, it is possible to output the drive instruction at an earlier time point (time t2') compared with a case that the drive instruction is output to the electric motor at the time point (time t2) when it "intersects" actually. Hence, it is possible to prevent transmission of the driving torque to the outside turning driving wheel and to prevent a travelling locus of the vehicle from swelling to outside by limiting differential action of the differential mechanism before developing an idling inclination as ground contact load of the inside turning driving wheel is reduced at the time of turning around the corner and by transmitting driving torque to the outside turning driving wheel. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a differential mechanism that distributes the output of an internal combustion engine as a driving force to left and right drive wheels, a friction multi-plate clutch as a differential limiting mechanism that limits the differential operation of the differential mechanism, and a friction multi-plate The present invention relates to a differential device with a differential limiting mechanism that includes an actuator that applies an engagement force to a clutch, a drive source that drives the actuator, and a control device that outputs a drive command to the drive source.

Since the differential device with a differential limiting mechanism can transmit driving force to the other of the left and right drive wheels by limiting the differential operation of the differential device even when one of the left and right drive wheels is idle, It is possible to improve the escape performance when a vehicle is stacked on a road or a snowy road. As this kind of differential device with a differential limiting mechanism, a differential limiting force is generated by operating an actuator with hydraulic pressure (see Patent Document 1 below), or a differential limiting force is generated by operating an actuator with an electric motor. The thing to generate (refer the following patent document 2) is proposed.
Japanese Patent Publication No. 7-21304 JP 2005-249080 A

  By the way, when the vehicle is turning, the ground load on the outer driving wheel tends to increase due to the centrifugal force acting on the vehicle body, and the ground load on the inner driving wheel tends to decrease. In particular, the vehicle turns while accelerating. In this case, slip (idling) of the turning inner drive wheel with reduced grounding load with respect to the road surface may increase, and the traveling locus of the vehicle may swell outward.

  In such a case, if the differential device has a differential limiting mechanism, the differential limiting mechanism is activated when the state of “inner driving wheel speed> outer driving wheel speed” is reached, so that the turning inner drive It is possible to prevent the running trajectory of the vehicle from bulging outward by suppressing the idling of the wheel and transmitting the driving force to the turning outer driving wheel and generating a yaw moment in a direction assisting the turning.

  However, the detection delay of the “inner driving wheel speed> outer driving wheel speed” state or the “inner driving wheel speed> outer driving wheel speed” state accompanying the calculation for performing the moving average processing of the wheel speed detected by the wheel speed sensor There is a possibility that the traveling locus of the vehicle cannot be reliably prevented from bulging outward due to the delay in the generation of the differential limiting force due to the actuation delay of the actuator after the detection of.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to suppress a disturbance in vehicle behavior by generating a differential limiting force in a differential mechanism without delay when the vehicle turns.

  In order to achieve the above object, according to the first aspect of the present invention, a differential mechanism that distributes the output of the internal combustion engine as a driving force to the left and right drive wheels, and the differential operation of the differential mechanism are limited. Differential limiting mechanism comprising: a friction multi-plate clutch as a differential limiting mechanism; an actuator that applies an engagement force to the friction multi-plate clutch; a drive source that drives the actuator; and a control device that outputs a drive command to the drive source In the mechanism-equipped differential device, the control device determines the rotational speed of the turning inner drive wheel from the difference between the rotational speeds of the left and right drive wheels and the rotational acceleration difference of the left and right drive wheels during turning. A differential device with a differential limiting mechanism is proposed, in which a time until the rotation speed is exceeded is predicted, and a drive command is output to the drive source when the predicted time becomes a predetermined value or less.

  The electric motor 79 of the embodiment corresponds to the drive source of the present invention, the electronic control unit U of the embodiment corresponds to the control device of the present invention, and the expected crossing time Tc of the embodiment is the prediction of the present invention. Corresponds to time.

  According to the first aspect of the present invention, the control device for controlling the engagement force of the friction multi-plate clutch that restricts the differential operation of the differential mechanism is configured so that the rotational speed difference and the rotation of the inner and outer driving wheels during turning are determined. Since the time until the rotational speed of the inner driving wheel exceeds the rotational speed of the outer driving wheel from the difference in acceleration is predicted, a drive command is output to the actuator drive source when this predicted time falls below a predetermined value. Compared with the case where the drive command is output to the drive source of the actuator when the rotational speed of the turning inner drive wheel actually exceeds the rotation speed of the turning outer drive wheel, the friction multi-plate clutch can be engaged earlier. it can. As a result, the differential operation of the differential mechanism is limited before the ground load on the turning inner drive wheel decreases and tends to run idle during turning, and the driving force is transmitted to the turning outer drive wheel to It is possible to prevent swelling outward.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  1 to 13 show an embodiment of the present invention. FIG. 1 is a rear view of an internal combustion engine for an automobile, FIG. 2 is an enlarged sectional view of a differential mechanism and an actuator, and FIG. 2 is an enlarged view of part 4 of FIG. 3 showing the structure of the actuator, FIG. 5 is an enlarged view of part 5 of FIG. 3 showing the structure of the friction multi-plate clutch, and FIG. 6 is a sectional view taken along line 7-7 in FIG. 3, FIG. 8 is a sectional view taken along line 8-8 in FIG. 4, FIG. 9 is a block diagram of a control system of the electric motor, and FIG. 10 is electronic control. 11 is a flowchart for explaining the processing contents of the unit, FIG. 11 is a diagram for explaining the moving average of the rotational speed of the drive wheels, FIG. 12 is a time chart for explaining the action of driving force distribution during turning (conventional example), and FIG. It is a time chart (embodiment) explaining the effect | action of this driving force distribution.

  As shown in FIG. 1, an internal combustion engine E mounted horizontally on the front body of a front engine / front drive automobile has a transmission T integrally coupled to a left side surface thereof, and a difference between the rear surface of the transmission T and the rear surface thereof. A moving mechanism D is provided. A half shaft 11 (intermediate shaft) extends rightward from a differential mechanism D arranged to be shifted leftward from the vehicle body center line, and a right axle that drives a right drive wheel (not shown) to the halfshaft 11. 12 is connected, and a left drive wheel (not shown) is driven via a left axle 13 extending in the left direction from the differential mechanism D. The right end of the half shaft 11 is supported by a stay 10 fixed to the engine block 22.

  As is clear from FIG. 2, the housing 14 that houses the differential mechanism D covers the housing body 15 that is formed integrally with the casing of the transmission T and the left end opening of the housing body 15. And a cover plate 17 fixed by a plurality of bolts 16. A plurality of actuators A, which are separately attached to the right side of the differential mechanism D, are an actuator case 18 that fits into the right end opening of the housing body 15 of the differential mechanism D, and a plurality of actuators A so as to cover the right end opening of the actuator case 18. The actuator cover 20 is fixed by a plurality of bolts 19... And is fixed to the engine block 22 by a plurality of bolts 21 penetrating the actuator case 18. The differential mechanism D and the actuator A constitute a differential device.

  The differential mechanism D housed in the housing 14 includes a first case 24 on the right side supported by the roller body 23 on the housing body 15 and a second case 26 on the left side supported by the roller bearing 25 on the cover plate 17. Are connected by a plurality of bolts 27, and an axle drive gear 29 driven by the transmission T is fixed to the outer periphery of the first case 24 by a plurality of bolts 30.

  Next, the structure of the differential mechanism D will be described with reference to FIGS. 3 and 5 to 7.

  The differential mechanism D housed in the housing 14 includes four pinion shafts 31 integrated so as to intersect in a cross shape. The pinion shafts 31 having a circular cross section are formed with chamfers 31a at their ends, and the chamfers 31a are fitted into four support grooves 24a formed on the inner peripheral surface of the first case 24. To do. Four pinions 32 are rotatably supported on the four pinion shafts 31. Spacers 33 are arranged between the pinions 32 and the inner peripheral surface of the first case 24, and the radial positions of the pinions 32 are regulated by these spacers 33.

  The outer periphery of the half shaft 11 inserted into the first case 24 is splined to the right side gear 34 </ b> R and is prevented from coming off by a snap ring 35. Further, the right end of the left axle 13 inserted through the second case 26 and inserted into the first case 24 is splined to the clutch inner 37 and is prevented from coming off by a snap ring 38. A left side gear 34 </ b> L is integrally formed on the right side surface of the clutch inner 37. The left and right side gears 34L and 34R mesh with the four pinions 32.

  A clutch outer 40 is integrally formed on the inner periphery of the first case 24 so as to face the outer periphery of the clutch inner 37, and a plurality of clutch plates (five in the embodiment) are provided on the inner peripheral surface of the clutch outer 40. 41 ... are spline-fitted to the outer peripheral portion of the clutch inner 37, and the inner peripheral portions of a plurality of (6 in the embodiment) clutch discs 42 are spline-fitted to the outer peripheral surface of the clutch inner 37. The clutch plates 41 and the clutch disks 42 are alternately arranged so that the friction materials 43 attached to both surfaces of the clutch disks 42 contact the clutch plates 41.

  The outer peripheral portion of the pressure plate 44 is spline-fitted to the inner peripheral surface of the clutch outer 40, and the left side surface of the pressure plate 44 is opposed to the right side surface of the clutch disk 42 located at the rightmost end. A plurality (four in the embodiment) of lever lever storage recesses 24b extending in the radial direction are formed on the inner surface of the first case 24 facing the right side surface of the pressure plate 44, and each lever lever storage recess 24b is formed. A fulcrum 45a at the radially outer end of the lever lever 45 is slidably engaged with the radially outer end.

  Inside the actuator case 18, the first hollow shaft 47 is fitted to the outer periphery of the half shaft 11 via a needle bearing 46 (see FIG. 1) so as to be relatively rotatable and axially movable. Inside the first case 24, the right end of the second hollow shaft 48 is engaged with the left end of the first hollow shaft 47 so that the right end of the second hollow shaft 48 is not rotatable relative to the left end, and the right end of the third hollow shaft 49 is connected to the left end of the second hollow shaft 48. Engages with concaves and convexes so that relative rotation is impossible. A diameter-expanded portion 48a having a diameter increased along the inner peripheral surface of the first case 24 is formed on the left end side of the second hollow shaft 48, and the diameter of the third hollow shaft 49 is set to the maximum diameter of the diameter-expanded portion 48a. Match.

  A plurality (six in the embodiment) of through holes 48b are formed in the enlarged diameter portion 48a of the second hollow shaft 48, and the four extended portions 24c projecting from the inner surface of the first case 24 are penetrated. It penetrates the hole 48b loosely and protrudes to the inside of the enlarged diameter portion 48a. The tip of each extending portion 24c comes into contact with the back surface of the right side gear 34R via the friction washer 50. The back surface of the left side gear 34 </ b> L, that is, the left side surface of the clutch inner 37 abuts against the inner surface of the second case 26 via the friction washer 51.

  The third hollow shaft 49 is formed with four U-shaped notches 49a that open to the left end side at 90 ° intervals. The third hollow shaft 49 can move in the axial direction while avoiding interference between the four pinion shafts 31 and the spacers 33 fitted to the outer periphery thereof by the notches 49a. And the press part 49b which presses the power point 45b provided in the radial direction inner end of the lever lever 45 is formed in the left end of the 3rd hollow shaft 49. As shown in FIG. An action point 45 c that abuts against the right side surface of the pressure plate 44 is provided at an intermediate portion of the lever lever 45.

  In this way, the friction multi-plate clutch 52 for fastening the left axle 13 to the differential case 28 by the clutch inner 37, the clutch outer 40, the clutch plate 41, the clutch disk 42, the pressure plate 44, and the lever lever 45. Is configured.

  Next, the structure of the actuator A that engages the friction multi-plate clutch 52 through the first to third hollow shafts 47, 48, and 49 will be described with reference to FIGS.

  A flange member 61 is slidably fitted to the right end of the first hollow shaft 47 extending inside the actuator case 18 and the actuator cover 20, and a spring seat 63 and a flange locked to the first hollow shaft 47 by a clip 62. A coil spring 64 is disposed in a compressed state between the back surface of the member 61.

  On the half shaft 11 between the flange member 61 and the inner wall surface 20a of the actuator cover 20, a first cam plate 67 and a second cam plate 68 are supported via needle bearings 69 and 70 so as to be rotatable and axially movable. Is done. The first cam plate 67 contacts the flange member 61 via the thrust bearing 85, and the second cam plate 68 contacts the inner wall surface 20 a of the actuator cover 20 via the thrust bearing 86. Inclined cam grooves 67a..., 68a... Are formed on the opposing surfaces of the first and second cam plates 67 and 68, and the balls 71 are accommodated in the cam grooves 67a. The first and second cam plates 67 and 68 and the balls 71 constitute a ball cam mechanism 72.

  A first shaft 73 is supported on the actuator case 18 via a ball bearing 74 and a needle bearing 75, and a second shaft 76 is supported via ball bearings 77 and 78. The first gear 80 provided on the first shaft 73 connected in series to the output shaft 79 a of the electric motor 79 supported on the actuator case 18 is the second and third gears 81 and 82 provided on the second shaft 76. Mesh with the second gear 81. In addition, fourth and fifth gears 83 and 84 are formed on the outer circumferences of the first and second cam plates 67 and 68, respectively. The fourth gear 83 meshes with the second gear 81 of the second shaft 76, and The fifth gear 84 meshes with the third gear 82 of the second shaft 76. The gear ratio between the second gear 81 and the fourth gear 83 and the gear ratio between the third gear 82 and the fifth gear 84 are slightly different.

  As shown in FIG. 9, the electronic control unit U that controls the operation of the electric motor 79 of the actuator A includes a standard yaw rate calculation unit 91, a subtraction unit 92, an LSD (differential limit) operation determination unit 93, a differential A limit torque map 94, a torque / motor rotation angle conversion unit 95, a drive torque estimation calculation unit 96, a drive torque positive / negative determination unit 97, and a drive wheel speed state determination unit 98 are provided.

  The vehicle speed and the steering angle are input to the reference yaw rate calculation unit 91, the yaw rate is input to the subtraction means 92, the brake operation signal, the vehicle speed and the yaw rate are input to the LSD operation determination unit 93, and the drive torque estimation calculation unit 96 The engine speed, intake negative pressure, transmission main shaft speed, and transmission shift position are input, and each wheel speed is input to the drive wheel speed state determination unit 98.

  Next, the operation of the embodiment of the present invention having the above configuration will be described.

  The differential mechanism D exhibits a differential limiting function in addition to the normal differential function, and the differential limiting torque generated by the differential limiting function is generated by the operation of the actuator A.

  First, the normal differential function of the differential mechanism D will be described.

  When the driving force of the internal combustion engine E is input to the axle drive gear 29 of the differential mechanism D via the transmission T, the differential case 28 coupled to the axle drive gear 29 with bolts 30. When the vehicle is in a straight traveling state, the four pinions 32 are not rotated with respect to the pinion shafts 31 and are not rotated with respect to the pinions 32, but the left side gear 34L meshed with the pinions 32 and the right axle meshed with the left axle 13 and the pinions 32. The side gear 34R and the integral half shaft 11 rotate at the same speed, and the driving force is evenly distributed to the left and right driving wheels.

  For example, when the vehicle is in a left turn state, the left axle 13 connected to the left drive wheel is decelerated and the half shaft 11 connected to the right drive wheel is accelerated, so that a differential rotation occurs between the left and right side gears 34L and 34R. Although generated, the differential rotation is absorbed by the rotation of the pinions 32 meshed with the left and right side gears 34L, 34R. Similarly, when the vehicle is in a right turn state, the left axle 13 connected to the left drive wheel is accelerated and the half shaft 11 connected to the right drive wheel is decelerated, so that the difference between the left and right side gears 34L and 34R. Although rotation occurs, the differential rotation is absorbed by the rotation of the pinions 32 meshed with the left and right side gears 34L, 34R.

  Next, the differential limiting function generated by the operation of the actuator A will be described.

  When the electric motor 79 of the actuator A is driven, the rotation of the first gear 80 of the first shaft 73 coupled to the output shaft 79a is transmitted to the second gear 81 and the second shaft 76 rotates. When the second shaft 76 rotates, the first cam plate 67 rotates through the second gear 81 and the fourth gear 83, and the second cam plate 68 rotates through the third gear 82 and the fifth gear 84. However, since the gear ratio between the second gear 81 and the fourth gear 83 and the gear ratio between the third gear 82 and the fifth gear 84 are slightly different, the first and second cam plates of the ball cam mechanism 72 are different. 67 and 68 rotate relative to each other. As a result, the relative positions of the cam grooves 67a of the first and second cam plates 67, 68 change from the state shown in FIG. 8A to the state shown in FIG. 1. The second cam plates 67 and 68 are driven in directions away from each other.

  The second cam plate 68 that has received a rightward load generated by the ball cam mechanism 72 is prevented from moving rightward by the actuator cover 20. Accordingly, the first cam plate 67 that has received the leftward load generated by the ball cam mechanism 72, that is, the pressing force for engaging the friction multi-plate clutch 52, moves to the left, and the first cam plate 67 passes through the thrust bearing 85 and the flange member 61. 1 Press the hollow shaft 47 in the left direction.

  When a leftward pressing force is applied to the first hollow shaft 47 by the actuator A, the second hollow shaft 48 and the third hollow shaft 49 coupled to the first hollow shaft 47 move to the left, and the third hollow shaft 49 The pressing portions 49b provided at the left end press the force points 45b of the four lever levers 45. As a result, the lever levers 45 swing around the fulcrum 45a, and the action point 45c presses the pressure plate 44 to the left, so that the clutch plates 41 and the clutch disks 42 are in close contact with each other, and the clutch The inner 37 and the clutch outer 40 are coupled together.

  Since the distance L1 between the fulcrum 45a and the force point 45b of the lever lever 45 is set larger than the distance L2 between the fulcrum 45a and the action point 45c, the pressing force F1 input to the lever lever 45 is increased by L1 / L2. The pressure plate 44 can be pressed with the boosted pressing force F2, so that a sufficient pressing force can be applied to the friction multi-plate clutch 52 even if the electric motor 79 of the actuator A is downsized.

  When the friction multi-plate clutch 52 is engaged in this way, the left axle 13 integrated with the clutch inner 37 is integrated with the differential case 28, whereby the left axle 13 and the half shaft 11, that is, the left axle 13. The right axle 12 is integrated so as not to rotate relative to each other, and the differential function of the differential mechanism D is limited so that it can be escaped from soft ground such as muddy, or the stability during high-speed straight running is increased. Can do. At this time, by controlling the current driving the electric motor 79 to change the pressing force generated by the actuator A and causing the friction multi-plate clutch 52 to generate a predetermined slip, the differential mechanism D has an arbitrary magnitude. Differential limiting torque can be exhibited.

  As described above, the pressing force of the frictional multi-plate clutch 52 generated by the actuator A can be axially moved to the outer periphery of the half shaft 11 without passing through the half shaft 11 to which the driving force of the internal combustion engine E is transmitted. Since it transmits via the 1st-3rd hollow shafts 47, 48, and 49 arrange | positioned so that relative rotation is possible, it is the frictional force which acts on the spline coupling part of the half shaft 11 by transmitting the driving force of the internal combustion engine E. The pressing force generated by the actuator A is not reduced, and the friction multi-plate clutch 52 can be stably engaged.

  Next, control of the electric motor 79 of the actuator A of the differential mechanism D will be described.

  In the block diagram of FIG. 9, the reference yaw rate calculation unit 91 calculates a reference yaw rate that is a target yaw rate to be generated in the vehicle based on the vehicle speed and the steering angle, and the subtraction unit 92 subtracts the actual yaw rate from the reference yaw rate. Calculate the deviation.

  The drive torque estimation calculation unit 96 calculates the total drive torque transmitted to the drive wheels based on the engine speed, intake negative pressure, transmission main shaft speed, and transmission shift position, and the drive torque positive / negative determination unit 97. Determines whether the sign of the drive torque is positive (not in the engine brake state). When the sign of the drive torque is positive, the drive wheel speed state determination unit 98 determines the estimated time until the rotation speed of the turning inner drive wheel exceeds the rotation speed of the turning outer drive wheel based on each wheel speed at a predetermined value. It is determined whether or not the following has occurred.

  Hereinafter, based on the flowchart of FIG. 10, the operation of the drive wheel speed state determination unit 98 will be described in detail. This routine is executed with a period of 10 msec.

  First, in step S1, the latest rotation speed WL of the left drive wheel and the latest rotation speed WR of the right drive wheel are read, and in step S2, the latest rotation speeds WL and WR of the left and right drive wheels Td (for example, the drive system) The moving average at 80 msec) corresponding to the resonance period is calculated, the average rotational speed of the left driving wheel is VL, and the average rotational speed of the right driving wheel is VR. Thus, the average rotational speeds VL and VR of the left and right drive wheels are obtained by subjecting the rotational speeds WL and WR, which are the raw data detected by the sensor, to moving average processing over the drive system resonance period of 80 msec. 8 samples are included, and fluctuations in the rotational speeds WL and WR, which are raw data, can be averaged to improve accuracy (see FIG. 11).

  In the subsequent step S3, the processing period 10 msec is added to the difference between the current values VL (n) and VR (n) of the average rotational speeds VL and VR of the left and right drive wheels and the previous values VL (n−1) and VR (n−1). The rotational accelerations AL and AR of the left and right drive wheels are calculated by multiplying the frequency NF (100 Hz).

AL = {VL (n) −VL (n−1)} × NF
AR = {VR (n) −VR (n−1)} × NF
In subsequent step S4, the actual yaw rate is compared with the reference yaw rate, and if the relationship of actual yaw rate <reference yaw rate is established, that is, the vehicle is in an understeer state, and the traveling locus of the vehicle during turning may swell outward. If there is, the expected intersection time Tc is calculated by the following equation in step S5.

Tc = (VR−VL) / (AL−AR)
In general, during the turning of the vehicle, the rotational speed of the outer driving wheel with the larger moving distance is higher than the rotational speed of the inner driving wheel with the smaller moving distance. If the vehicle is tilted, the turning inner drive wheel is likely to be lifted off the road surface to be in an idling state, so that a reverse phenomenon occurs in which the rotation speed of the turning inner drive wheel is higher than the rotation speed of the turning outer drive wheel. The intersection of the rotational speed line of the turning inner drive wheel and the rotational speed line of the turning outer drive wheel at this time is defined as “intersection” (see FIG. 12).

  The equation for defining the expected intersection time Tc, Tc = (VR−VL) / (AL−AR), is based on the assumption that the rotational accelerations AL and AR of the current turning outer drive wheel and the turning inner drive wheel are maintained. Represents the time until the difference between the average rotational speeds VL and VR of the turning outer drive wheel and the turning inner drive wheel becomes zero.

However, if any of the following three conditions is satisfied, the process ends without calculating the expected intersection time Tc.
・ When intersection determination has already been set (to reduce processing load)
・ When at least one of AL and AR is negative (because it is determined that acceleration is not in progress)
-When AL = AR (to avoid an operation error due to the denominator of division being 0)
In the following step S6,
Ts + Td / 2 ≧ Tc
Is established, an intersection determination which is one of the conditions for starting the differential limiting operation is set in step S7. In the above equation, Ts is a delay time from when the operation command is output to the electric motor 79 until the actuator A actually starts to operate. Td / 2 is half the period Td for performing the moving average process. The reason is that in FIG. 11, the moving average (that is, the average rotational speed VL, VR) calculated at time t is considered to represent the rotational speed Td / 2 before time t.

  In step S4, the actual yaw rate is compared with the standard yaw rate. If the relationship of actual yaw rate <standard yaw rate is not established, the intersection determination is cleared in step S8.

Returning to the block diagram of FIG. 9, the LSD operation determination unit 93
・ Vehicle speed is more than specified value (30km / h ～ 40km / h) ・ Vehicle is turning ・ Brake is OFF
・ Sign of drive torque is positive (not in engine brake state)
-When the five conditions for which the intersection determination has been set are satisfied, a determination is made to execute the differential limiting operation.

  The condition “the vehicle speed is equal to or higher than the predetermined value” is because a torque steer phenomenon is likely to occur when the differential limiting operation is executed at a low vehicle speed. The condition “the vehicle is turning” is determined by the actual yaw rate being equal to or greater than a predetermined value. When the left and right wheels are on road surfaces with different friction coefficients (so-called split μ roads), the left and right This is to exclude the phenomenon in which a difference in rotational speed occurs in the wheel from the phenomenon in which the turning inner drive wheel is lifted off the road surface. The condition of “brake off” is that the differential limiting operation is not performed when the brake pedal is depressed even when the vehicle is in an acceleration state. This is to prevent disturbing the behavior.

  When the LSD operation determination unit 93 determines the execution of the differential limiting operation as described above, the differential to be generated by the operation of the actuator A from the yaw rate deviation (deviation of the actual yaw rate with respect to the reference yaw rate) in the differential limiting torque map 94. The limit torque is searched, and the torque / motor rotation angle conversion unit 95 converts the differential limit torque into the rotation angle of the electric motor 79 and drives the electric motor 79 to generate the differential limit torque.

  As a result, when the vehicle is turning, the turning inner driving wheel is lifted by the centrifugal force, making it difficult for the driving torque to be transmitted to the turning outer driving wheel. The drive torque is transmitted to the turning outer drive wheel by the movement restricting operation to generate a yaw moment inward in the turning direction, and the vehicle trajectory can be prevented from expanding outward to stabilize the vehicle behavior.

  At this time, instead of starting the differential limiting operation when the average rotation speed of the turning inner drive wheel exceeds (intersects) the average rotation speed of the turning outer drive wheel, the time when the intersection occurs is predicted, By starting the differential limiting operation prior to the predicted intersection, it is possible to prevent a delay from occurring in the start of the differential limiting operation and further stabilize the vehicle behavior.

  The time chart of FIG. 12 corresponds to the conventional example, and during the steady turning of the vehicle before time t1, the rotational speed of the turning outer drive wheel exceeds the rotation speed of the turning inner drive wheel. At this time, the driving torque of the turning inner drive wheel slightly exceeds the driving torque of the turning outer drive wheel is due to the influence of the preset torque of the friction multi-plate clutch 52. When a transition is made from steady turning to acceleration turning at time t1, the turning inner drive wheel floats off the road surface due to the centrifugal force, and at time t2, the rotation speed of the turning inner drive wheel exceeds the rotation speed of the turning outer drive wheel. When the “crossing” occurs, a drive command is output to the electric motor 79 of the actuator A to execute the differential limiting operation. However, since there is a response delay after the drive command is output to the electric motor 79 until the actual rotation angle of the electric motor 79 changes, the drive torque of the turning outer drive wheel rises late, from time t2 to time t3. There is a problem that the state in which the rotational speed of the turning inner drive wheel exceeds the rotational speed of the turning outer drive wheel continues until the traveling locus of the vehicle swells outward.

  The time chart of FIG. 13 corresponds to the embodiment, and at time t2 ′ before a “crossing” in which the rotational speed of the turning inner drive wheel exceeds the rotational speed of the turning outer drive wheel actually occurs at time t2. In anticipation of the occurrence of “crossing”, a drive command is output to the electric motor 79 of the actuator A to execute the differential limiting operation. As a result, even if there is a response delay in the electric motor 79, a drive command can be output to the electric motor 79 of the actuator A by a predetermined time (Ts + Td / 2) prior to the “intersection” predicted at the expected intersection time Tc. Therefore, the response torque from when the drive command is output to the electric motor 79 until the actual rotation angle of the electric motor 79 changes is compensated for, so that the drive torque of the driving wheel on the outside of the turn is quickly raised, and the traveling locus of the vehicle is outside. The vehicle behavior can be stabilized by reliably preventing the vehicle from inflating. The thin line in FIG. 13 indicates the characteristics of the conventional example described in FIG.

  As mentioned above, although embodiment of this invention was explained in full detail, this invention can perform a various design change in the range which does not deviate from the summary.

  For example, the structures of the differential mechanism D and the actuator A are not limited to those in the embodiment, and any structures can be adopted.

Rear view of automotive internal combustion engine Enlarged sectional view of differential mechanism and actuator FIG. 2 is an enlarged view of part 3 of the differential mechanism. 4 is an enlarged view of part 4 in FIG. 3 showing the structure of the actuator. FIG. 3 is an enlarged view of part 5 showing the structure of the friction multi-plate clutch 6-6 sectional view of FIG. Sectional view along line 7-7 in FIG. Sectional view taken along line 8-8 in FIG. Block diagram of electric motor control system Flow chart explaining processing contents of electronic control unit Explanatory diagram of moving average of rotational speed of drive wheels Time chart explaining the effect of driving force distribution during turning (conventional example) Time chart for explaining the operation of driving force distribution during turning (embodiment)

Explanation of symbols

52 Friction multi-plate clutch 79 Electric motor (drive source)
A Actuator D Differential mechanism E Internal combustion engine Tc Estimated crossing time (expected time)
U Electronic control unit (control device)

Claims (1)

A differential mechanism (D) for distributing the output of the internal combustion engine (E) to the left and right drive wheels as a drive force;
A friction multi-plate clutch (52) as a differential limiting mechanism for limiting the differential operation of the differential mechanism (D);
An actuator (A) for applying an engagement force to the friction multi-plate clutch (52);
A drive source (79) for driving the actuator (A);
A control device (U) for outputting a drive command to the drive source (79);
In a differential device with a differential limiting mechanism comprising:
The control device (U) determines the rotation speed of the turning inner drive wheel from the rotation speed difference of the left and right drive wheels and the rotation acceleration difference of the left and right drive wheels during rotation. A differential device with a differential limiting mechanism, characterized by predicting a time (Tc) until the time is exceeded and outputting a drive command to the drive source (79) when the predicted time (Tc) becomes a predetermined value or less. .

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