JP2008223869A - Initial stop position setting method of electric motor in differential gear with differential limiting mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To properly set an initial stop position of an electric motor to operate a friction multiple plate clutch of a differential gear with a differential limiting mechanism by eliminating the influence of the temperature change. <P>SOLUTION: In setting the initial stop position of the electric motor to operate the friction multiple plate clutch to exert the differential limiting mechanism in the differential mechanism, the initial stop position MposO is set as a sum of an oil temperature dependent term f(To) changing corresponding to the oil temperature in the differential mechanism and an oil temperature independent term MposBase so that the proper initial stop position can be set to compensate the change even when the clearance of the friction multiple plate clutch fluctuates owing to the expansion and contraction of a part followed by the oil temperature change. Thereby the engagement responsibility owing to the increase of the friction multiple plate clutch can be prevented from lowering or brake drag can be prevented owing to the clearance decrease. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a differential mechanism that distributes the output of an internal combustion engine to left and right drive wheels as a driving force; a friction multi-plate clutch as a differential limiting mechanism that limits the differential operation of the differential mechanism; and a first cam A plate and a second cam plate, and a ball housed in a cam groove formed so as to oppose each of the cam plates, and converts the rotational force of the electric motor into a linear pushing force to increase friction. A ball cam mechanism for engaging the plate clutch; a rotation angle sensor for detecting the actual motor rotation angle of the electric motor; and instructing the target motor rotation angle to the electric motor, and setting the actual motor rotation angle of the electric motor to the target motor rotation angle The present invention relates to a method for setting an initial stop position of an electric motor in a differential device with a differential limiting mechanism that includes a control device that controls to match.

Such a differential device with a differential limiting mechanism is known from Patent Document 1 below.
JP 2005-249080 A

  By the way, in this type of differential device with a differential limiting mechanism, in order to accurately control the differential limiting torque, the clearance of the friction multi-plate clutch, that is, the initial stop position of the electric motor that engages the friction multi-plate clutch. However, since the clearance varies due to the expansion and contraction accompanying the temperature change of the parts constituting the friction multi-plate clutch, the appropriate initial stop position of the electric motor also varies.

  Therefore, if the initial stop position of the electric motor is set to a fixed position, when the clearance increases, the rotation angle of the electric motor until the friction multi-plate clutch is engaged increases, and the responsiveness decreases or the clearance decreases. There is a problem that the frictional multi-plate clutch is engaged and an unintended differential limiting torque is generated.

  The present invention has been made in view of the above-described circumstances, and appropriately sets an initial stop position of an electric motor that operates a friction multi-plate clutch of a differential device with a differential limiting mechanism, without the influence of temperature change. For the purpose.

  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 is limited. A friction multi-plate clutch as a differential limiting mechanism, and a first cam plate and a second cam plate, and a ball housed in a cam groove formed so as to face each of the cam plates. A ball cam mechanism for converting the rotational force of the motor into a linear pushing force and engaging the frictional multi-plate clutch; a rotational angle sensor for detecting the actual motor rotational angle of the electric motor; and instructing the target motor rotational angle to the electric motor And a control device that controls the actual motor rotation angle of the electric motor to match the target motor rotation angle, wherein the control device includes oil in the differential mechanism. And the target motor rotation angle corresponding to the initial stop position, which is the stop position of the electric motor when no differential limiting force is applied to the differential mechanism, is changed according to the oil temperature change, An electric motor initial stop position setting method in a differential device with a differential limiting mechanism is proposed.

  According to the second aspect of the present invention, in addition to the configuration of the first aspect, the target motor rotation angle corresponding to the initial stop position is a clearance between the friction multi-plate clutch and the pushing portion of the ball cam mechanism. Is set to be maintained in a fixed relationship regardless of the oil temperature change, and the control device sets the fluctuation amount of the target motor rotation angle corresponding to the initial stop position due to the oil temperature change using the oil temperature as a parameter. Correcting means for correcting the basic target motor rotation angle, which is a constant eigenvalue for each of the differential mechanisms, with the variation amount, thereby obtaining a target motor rotation angle corresponding to the initial stop position. An initial stop position setting method for an electric motor in a differential device with a differential limiting mechanism is proposed.

  The phrase “maintained in a certain relationship” in claim 2 is “an electric motor in which the actual motor rotation angle does not follow the target motor rotation angle when the target motor rotation angle is increased in the direction in which the pressing force increases. This means that it is always maintained in the clearance between the friction multi-plate clutch and the pushing portion of the ball cam mechanism when the motor rotation angle is returned from the drive position, or simply “maintained at a constant value”.

  The electronic control unit U of the embodiment corresponds to the control device of the present invention, the oil temperature dependent term f (To) of the embodiment corresponds to the correcting means of the present invention, and the zero point Mpos0 of the embodiment is Corresponding to the target motor rotation angle of the present invention, the oil temperature independent term MposBase of the embodiment corresponds to the basic target motor rotation angle of the present invention.

  According to the configuration of the first aspect, when setting the initial stop position of the electric motor for operating the friction multi-plate clutch that causes the differential mechanism to exhibit the differential limiting function, the target motor rotation angle corresponding to the initial stop position is set. Therefore, even if the clearance of the friction multi-plate clutch fluctuates due to the expansion and contraction of parts caused by the oil temperature change, the fluctuation is compensated for and the appropriate initial stop position of the electric motor is compensated. Can be set. Accordingly, it is possible to prevent a decrease in engagement response due to an increase in the clearance of the friction multi-plate clutch and a drag due to a decrease in the clearance.

  According to the second aspect of the present invention, the target motor rotation angle corresponding to the initial stop position is maintained in a constant relationship regardless of the oil temperature change in the gap between the friction multi-plate clutch and the push portion of the ball cam mechanism. Therefore, it is possible to reliably prevent the frictional multi-plate clutch engagement responsiveness from being lowered and dragging due to the oil temperature change. Moreover, the fluctuation amount of the target motor rotation angle corresponding to the initial stop position due to the oil temperature change is set with the oil temperature as a parameter, and the basic target motor rotation angle, which is a constant eigenvalue for each differential mechanism, is corrected by the fluctuation amount. Since the target motor rotation angle corresponding to the initial stop position is obtained, it is not necessary to engage the friction multi-plate clutch each time the initial stop position is set, and the steering torque varies due to the engagement of the friction multi-plate clutch. Can prevent discomfort.

  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 of FIG. 3, FIG. 8 is a sectional view taken along line 8-8 of FIG. 4, FIG. 9 is a block diagram of a control system of the electric motor, and FIG. FIG. 11 is an explanatory diagram of an acquisition method of an oil temperature independent term MposBase based on a manual acquisition request, and FIG. 12 is an explanation of the rotation angle of the electric motor at the time of starting and initial stop position setting after starting. FIGS. 13A and 13B are explanatory diagrams of the operation of the initial stop position control of the electric motor.

  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 an LSD (differential limit) control unit 91 and a motor control unit 92. For example, the LSD control unit 91 to which the wheel speed signal is input from the electronic control unit of the antilock brake device calculates the target differential torque to be generated by the differential mechanism D based on the acceleration / deceleration, turning direction, yaw rate, etc. of the vehicle. The target differential torque is converted into a target motor rotation angle of the electric motor 79. A motor to which a deviation between the target motor rotation angle of the electric motor 79 output by the LSD control unit 91 and the actual motor rotation angle of the electric motor 79 detected by the rotation angle sensor 65 (see FIG. 4) composed of an incremental encoder is input. The control unit 92 feedback-controls the actual motor rotation angle of the electric motor 79 via the motor driver 93 so that the deviation converges to zero.

  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.

  By the way, in order to improve the engagement response of the friction multi-plate clutch 52 as much as possible, the initial stop position, which is the stop position of the electric motor 79 when the differential limiting force is not applied to the differential mechanism D, is changed to the clutch plate 41. It is desirable to set the clearance between the two as small as possible within a range where the clutch disks 42 do not contact. However, since the clearance fluctuates due to the thermal expansion of the parts accompanying the temperature change of the differential mechanism D, it is difficult to reduce the clearance only by setting the initial stop position of the electric motor 79 uniformly. A method for controlling the initial stop position of the electric motor 79 for solving this problem will be described below.

  First, a method for setting an initial stop position (hereinafter also referred to as a zero point) of the electric motor 79 will be described based on the flowchart of FIG. This routine is executed at a cycle of 1 msec while the system is energized.

  If the ignition switch is not turned ON at this time in step S1 and the internal combustion engine E is in a state before starting, the zero point of the electric motor 79 is not set. When the ignition switch is ON in step S1 and there is a request for manual acquisition of the zero point in step S2, that is, when the actuator A is assembled at the factory or when the actuator A is replaced for maintenance. If it is necessary to obtain a zero point, the following steps S3 to S7 are executed.

  That is, after the target motor rotation angle (motor command value) and the actual motor rotation angle (output of the rotation angle sensor 65) of the electric motor 79 are both reset to zero in step S3, the target motor rotation angle is set in the negative direction (the friction multiplate). When the clutch 52 is gradually increased (in the direction in which the clutch 52 is disengaged), the first and second cam plates 67 and 68 of the ball cam mechanism 72 move so as to approach each other. The rotation angle cannot follow the target motor rotation angle, and the deviation between the two increases gradually. When the deviation exceeds a threshold value (for example, 45 deg), it is determined that the ball cam mechanism 72 has reached the end, and the electric motor 79 is stopped at that position (see position a in FIG. 11 and FIG. 13A). In this way, the electric motor 79 is reversely rotated to return the ball cam mechanism 72 to the abutting position and completely disengage the friction multi-plate clutch 52, thereby engaging the clutch plates 41 ... and the clutch disks 42 ... The biting by can be released.

  Subsequently, when the target motor rotation angle is gradually increased in the positive direction (the direction in which the frictional multi-plate clutch 52 is engaged), the first and second cam plates 67 and 68 of the ball cam mechanism 72 are mutually moved by the positive rotation of the electric motor 79. And the clutch plates 41 of the friction multi-plate clutch 52 and the clutch discs 42 are engaged and compressed in a close contact direction. When the clutch plates 41 and the clutch disks 42 reach a limit position where they cannot be compressed any more, the actual motor rotation angle cannot follow the target motor rotation angle, and the deviation between the two gradually increases. When the deviation exceeds a threshold (for example, 60 deg), it is determined that the friction multi-plate clutch 52 is completely engaged, and the electric motor 79 is stopped at that position (position b in FIG. 11 and FIG. 13B). reference).

  Subsequently, the electric motor 79 is driven in the reverse direction (direction in which the frictional multi-plate clutch 52 is disengaged) by a set return angle (for example, 255 deg), and that position is stored as an initial stop position (zero point) (FIG. 11). C position and FIG. 13C).

  The set return angle for reversely rotating the electric motor 79 is set experimentally. In other words, an experimental load cell is temporarily arranged between the second cam plate 68 and the inner wall surface 20a of the actuator cover 20, and the electric motor 79 is reversely rotated from the position where the friction multi-plate clutch 52 is engaged to thereby load the load cell. Is monitored, and the reverse rotation angle of the electric motor 79 when the load becomes zero is set as the set return angle.

  Incidentally, there is the following relationship between the oil temperature To of the differential mechanism D and the initial stop position (zero point) of the electric motor 79. Each term in the following equation is based on the rotation angle of the electric motor 79.

Zero point Mpos0 = Oil temperature dependent term f (To) + Oil temperature independent term MposBase
Here, the oil temperature dependence term f (To) is an unknown function having the oil temperature To as a parameter, and based on data obtained experimentally in advance by a unit evaluation bench test or the like of the actuator A, table interpolation or an approximate expression Or the like.

  When the above equation is solved for the oil temperature independent term MposBase, the following equation is obtained.

Oil temperature independent term MposBase = zero point Mpos0−oil temperature dependent term f (To)
Here, the zero point Mpos0 of the first term on the right side can be obtained by the step S3 (refer to the position c in FIG. 11), and the oil temperature dependent term f (To) of the second term on the right side is obtained from the experimental data as described above. Can be obtained on the basis.

  Therefore, the oil temperature To of the oil of the differential mechanism D is acquired in step S4, the value is calculated by substituting the oil temperature To in the oil temperature dependence term f (To) in step S5, and in step S6, the value is calculated. By subtracting the value of the oil temperature dependent term f (To) obtained in step S6 from the value of the zero point Mpos0 obtained in step S3, the value of the oil temperature independent term MposBase can be calculated. In step S7, the value of the oil temperature independent term MposBase is stored in the nonvolatile memory of the electronic control unit U.

  When there is no request for manual acquisition of the zero point in step S2 and the ignition switch has been previously turned off in step S8, that is, when the internal combustion engine E is started this time, the electric motor 79 is driven in reverse rotation in step S9, and the ball cam mechanism. 72 is returned to the end, that is, to the position d in FIG.

  If the previous ignition switch is not OFF in step S8, that is, after the internal combustion engine E is started, it is determined in step S10 whether or not to set a zero point during the traveling of the vehicle.

The zero point is set during traveling when the following three conditions (1), (2), and (3) are all satisfied.
(1) Steering angle is less than a predetermined value
(2) Difference in rotation speed between right drive wheel and left drive wheel
(3) The driving force generated in the drive wheels is a predetermined value or less. The predetermined value of the steering angle in (1) is, for example, ± 5 °. This predetermined value is set in a range where the driver does not feel the side force generated from the slip angle of the wheel as a steering reaction force.

  The predetermined value of the rotational speed difference between the right driving wheel and the left driving wheel in (2) is, for example, 5 rpm. Even if the steering angle is small, on the split μ road such as a one-wheel icing road, the left and right wheels slip, resulting in a difference in the number of rotations of the left and right wheels. In this state, differential limiting torque is generated. Then, the driver may feel as a change in steering torque. Therefore, the predetermined value is set in a range where the driver does not feel the fluctuation of the steering torque.

  The predetermined value of the driving force generated in the driving wheel in (3) is, for example, 300 N in terms of the force by which the tire kicks the road surface, that is, the value obtained by dividing the tire torque by the tire radius. If differential limiting torque is generated with a large driving force generated on the driving wheels, the vehicle behavior including the steering torque is likely to change. Therefore, the predetermined value is within a range in which the driver does not feel a change in the vehicle behavior (specifically, Is set to a driving force corresponding to the rolling resistance of the tire). The drive torque generated in the drive wheels takes into account the gear position information and brake information to the engine torque retrieved from the output map of the internal combustion engine E based on the engine speed, intake negative pressure, and differential state of the variable valve mechanism. Can be calculated.

  If any of the conditions (1), (2) and (3) is not satisfied in step S10, it is determined in step S11 whether or not to set a zero point while the vehicle is stopped.

The condition for setting the zero point during the stop is when all of the following three conditions (1), (2), and (3) are satisfied.
(1) Vehicle speed is zero (or smaller than a predetermined value)
(2) Gear position is N position or P position (for automatic transmission)
(3) Brake is operating (Brake switch is ON)
Thus, when it is determined in step S10 that the zero point should be set during traveling, and in step S11, when it is determined that the zero point should be set during stop, steps S12 to S12 are performed. In S15, the zero point of the electric motor 79 is set.

  That is, the oil temperature To of the oil of the differential mechanism D is acquired in step S12, and the value is calculated by substituting the oil temperature To in the oil temperature dependency term f (To) in step S13. In step S14, the value is calculated. By adding the value of the oil temperature dependent term f (To) and the value of the oil temperature independent term MposBase stored in the non-volatile memory in step S7, a new value of the zero point Mpos0 considering the current oil temperature Is calculated. In step S15, the electric motor 79 is driven toward the e position in FIG. 12, which is a new zero point Mpos0.

  As is clear from FIG. 12, when the internal combustion engine E is started, the electric motor 79 is once returned to the abutting position (d position), and then the value of the oil temperature dependence term f (To) and the oil temperature which is a fixed value at that time. The electric motor 79 is driven toward the zero point Mpos0 (e position) obtained by adding the value of the independent term MposBase. After the start of the internal combustion engine E, when a predetermined condition of the zero point setting during stoppage or during travel is satisfied, the oil temperature dependence term f (To) at that time is a fixed value. The zero point (e position) is sequentially updated using the zero point Mpos0 obtained by adding the value of the temperature independent term MposBase.

  After the execution of the routine of the flowchart of FIG. 10 described above, the shift to the differential limiting control is performed, but the position (actual motor rotation angle) of the electric motor 79 when the differential limiting force after starting of the internal combustion engine E is not applied is initially stopped. The operation for adjusting to the target motor rotation angle corresponding to the position (zero point) is performed in the differential limiting control.

  As described above, the initial stop position (zero point) of the electric motor 79 is set in consideration of the oil temperature of the oil in the differential mechanism D. Therefore, the clearance of the friction multi-plate clutch 52 is increased by the expansion and contraction of the parts accompanying the temperature change. Even if it fluctuates, the optimum zero point can always be set accordingly, and the engagement response of the friction multi-plate clutch 52 is ensured while ensuring the necessary minimum clearance while preventing the friction multi-plate clutch 52 from dragging. Can increase the sex.

  Further, except when manual acquisition is requested (see step S3), it is not necessary to engage the frictional multi-plate clutch 52 for setting the zero point. It is possible to prevent the driver from feeling uncomfortable due to fluctuations in the steering torque transmitted to the steering wheel due to the engagement of the plate clutch 52.

  Further, since the zero point is set while the vehicle is stopped or in a specific running state of the vehicle, even if the friction multi-plate clutch 52 is engaged for some reason during the process, the steering transmitted to the steering wheel is transmitted. The driver's discomfort can be eliminated by minimizing torque fluctuations.

  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 incremental encoder employed in the rotation angle sensor 65 in the embodiment can only detect a rotation angle within 360 deg and cannot distinguish between 1 rotation + Adeg and 2 rotation + Adeg, so steps S3 and S9 in the flowchart of FIG. Then, the electric motor 79 is once returned to the abutting position and then advanced to the initial stop position while counting the number of rotations. However, if an absolute encoder capable of discriminating between one rotation + Adeg and two rotations + Adeg is employed, the electric motor 79 can be directly advanced to the initial stop position without once returning to the butting position.

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 Flowchart for explaining the operation of the embodiment Explanatory drawing of the acquisition method of oil temperature independent term MposBase based on a manual acquisition request Explanatory drawing of rotation angle of electric motor at initial stop position setting at start and after start Action explanatory diagram of initial stop position control of electric motor

Explanation of symbols

52 Friction multi-plate clutch 65 Rotation angle sensor 67 First cam plate 67a Cam groove 68 Second cam plate 67b Cam groove 71 Ball 72 Ball cam mechanism 79 Electric motor D Differential mechanism E Internal combustion engine f (To) Oil temperature dependent term (correction) means)
Mpos0 Initial stop position, zero point (target motor rotation angle)
MposBase Oil temperature independent term (basic target motor rotation angle)
U Electronic control unit (control device)

Claims (2)

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);
The first cam plate (67) and the second cam plate (68), and the balls (71) stored in the cam grooves (67a, 67b) formed so as to face each other of the cam plates (67, 68). A ball cam mechanism (72) for converting the rotational force of the electric motor (79) into a linear pressing force and engaging the friction multi-plate clutch (52);
A rotation angle sensor (65) for detecting the actual motor rotation angle of the electric motor (79);
A control device (U) for instructing the target motor rotation angle to the electric motor (79) and controlling the actual motor rotation angle of the electric motor (79) to coincide with the target motor rotation angle;
In a differential device with a differential limiting mechanism comprising:
The control device (U) detects the oil temperature in the differential mechanism (D), and is a stop position of the electric motor (79) when no differential limiting force is applied to the differential mechanism (D). A method for setting an initial stop position of an electric motor in a differential device with a differential limiting mechanism, wherein the target motor rotation angle corresponding to the initial stop position is changed according to a change in oil temperature. The target motor rotation angle corresponding to the initial stop position is maintained at a constant relationship regardless of the oil temperature change in the gap between the frictional multi-plate clutch (52) and the pushing portion of the ball cam mechanism (72). Set to
The control device (U) includes correction means (f (To)) for setting a variation amount of the target motor rotation angle (Mpos0) corresponding to the initial stop position due to a change in oil temperature, using the oil temperature as a parameter. The target motor rotation angle (Mpos0) corresponding to the initial stop position is obtained by correcting the basic target motor rotation angle (MposBase), which is a constant eigenvalue for each moving mechanism (D), with the variation amount. An initial stop position setting method for an electric motor in a differential device with a differential limiting mechanism according to claim 1.

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