Power transmission device

Abstract

The present invention provides a drive force transmission device that can suppress a decrease in responsiveness even when the friction clutch is worn out. [Solution] The drive force transmission device 10 includes a friction clutch 20, a mechanism 10A having a pressing mechanism 3 that presses the friction clutch 20 with a piston 30, and a motor 4 that operates the pressing mechanism 3, and a control device 81 that controls the mechanism 10A. The control device 81 stores the transmission torque increase start angle, which is the rotation angle of the motor 4 when the transmission torque of the friction clutch 20 begins to increase from a state in which the piston 30 is not pressing the friction clutch 20, and performs a correction process to correct the transmission torque increase start angle. In the correction process, the rotation angle of the motor 4 is measured when the motor torque generated by the motor 4 is a predetermined value when the vehicle is stopped, and the transmission torque increase start angle is corrected based on the measured value of the rotation angle and the initial rotation angle value, which is the rotation angle of the motor 4 when the motor torque is a predetermined value.

Description

[Technical Field]

[0001] The present invention relates to a drive force transmission device that uses the rotation of a motor to operate a piston and press a friction clutch. [Background technology]

[0002] Conventionally, a device is known for regulating the transmission of the driving force of a vehicle's power source, in which a piston is operated by the rotation of a motor to press a friction clutch (see, for example, Patent Documents 1 and 2).

[0003] The control device for controlling the torque distribution device described in Patent Document 1 controls the motor by referring to a control map that shows the relationship between the motor rotation angle and the motor current. The control device also performs learning control to correct the control map when the ignition is turned off and after driving a predetermined distance. In this learning control, the control map is corrected based on the current value in the current stabilization region where the change in motor current in response to a change in the motor rotation angle is within a predetermined value, and the motor rotation angle when a motor current of a predetermined value is supplied to the motor.

[0004] The control device for the drive force transmission device described in Patent Document 2 controls the motor by referring to a control map that shows the relationship between a target torque value, which is the target torque value to be transmitted to the output rotating member, and a command current value, which is the command value of the motor current supplied to the motor. The control device also calculates the torque value actually transmitted from the input rotating member to the output rotating member based on the output signal of the strain sensor, and corrects the control map if the calculated torque value differs from the target torque value so that they match. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2016-061414 [Patent Document 2] Japanese Patent Publication No. 2014-184922 [Overview of the project] [Problems that the invention aims to solve]

[0006] In a power transmission device that uses the rotation of a motor to operate a piston and press a friction clutch, it is desirable to keep the piston close to the friction clutch when the friction clutch is in an open state and not transmitting power, in order to improve responsiveness. However, as the friction clutch wears down, its axial thickness changes, increasing the piston's free-travel distance when the friction clutch transitions from an open state to an engaged state, thus reducing responsiveness. Therefore, the present invention aims to provide a power transmission device that can suppress the decrease in responsiveness even when the friction clutch is worn.

[0007] Furthermore, in recent years, the control of driving force has become more sophisticated in order to improve vehicle dynamics and safety performance, and there is a demand for further improvement in the controllability of transmitted torque in driving force transmission devices that transmit driving force from the drive source to the wheel side. Therefore, a further objective of the present invention is to provide a driving force transmission device that can achieve high precision in transmitted torque. [Means for solving the problem]

[0008] To achieve the above objective, the present invention provides a drive force transmission device that transmits the driving force of a vehicle by the friction clutch, comprising: a mechanism having a friction clutch having a plurality of friction members, a pressing mechanism that presses the friction clutch with a piston, and a motor that operates the pressing mechanism, and a control device that controls the mechanism, wherein the pressing mechanism is configured such that when the motor rotates in the forward direction, the piston moves forward toward the friction clutch, and when the motor rotates in the reverse direction, the piston moves backward toward the direction away from the friction clutch, and the control device controls the state when the piston is not pressing the friction clutch and the motor rotates in the forward direction The present invention provides a drive force transmission device that stores in a memory unit the transmission torque increase start angle, which is the rotation angle of the motor at which the transmission torque of the friction clutch begins to increase due to rotation, and performs a correction process to correct the transmission torque increase start angle, the memory unit also stores an initial rotation angle value, which is the rotation angle of the motor when the motor torque generated by the motor is a predetermined value in the initial state after the manufacture of the mechanism, and the correction process includes measuring the rotation angle of the motor when the motor torque generated by the motor is a predetermined value when the vehicle is stopped, and correcting the transmission torque increase start angle based on the measured rotation angle value and the initial rotation angle value. [Effects of the Invention]

[0009] According to the power transmission device of the present invention, it is possible to suppress a decrease in responsiveness even when the friction clutch is worn out. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic diagram illustrating the general configuration of a vehicle equipped with a power transmission device according to the first embodiment of the present invention. [Figure 2] This is a schematic diagram illustrating a general example of the configuration of a drive force distribution device. [Figure 3] This is a cross-sectional view of a portion of the drive force transmission device along the vehicle width direction and the vertical direction. [Figure 4]This is a cross-sectional view of the driving force transmission device taken along line A-A in Figure 3. [Figure 5] This is a cross-sectional view of the driving force transmission device taken along line B-B in Figure 4. [Figure 6] (a) is a plan view of an outer clutch plate. (b) is a plan view of an inner clutch plate. [Figure 7] This is a graph showing an example of changes in the motor rotation angle and motor torque when performing the pressing step, retraction step, and advance step. [Figure 8] This is a graph showing an example of a change in motor current when the motor is rotated in the forward direction to change the motor rotation angle. [Figure 9] This is a graph for explaining the reason and significance of obtaining the subtraction value according to the difference between the initial value and the current value of the averaged motor rotation angle in the second arithmetic processing of the correction step. [Figure 10] This is a graph showing an example of the relationship between the motor rotation angle and the motor current when the lubricating oil is at a low temperature and at a normal temperature. [Figure 11] This is a graph showing an example of changes in the motor rotation angle and motor torque when performing the pressing step, retraction step, and advance step in a modified example of the correction operation. [Figure 12] This is a schematic configuration diagram showing an example of the configuration of a test apparatus for acquiring correspondence information between clutch torque and motor torque in the initial state of the driving force transmission device. [Figure 13] (a) is a measurement result obtained in the first stage process of the process of generating the correspondence information. (b) is a measurement result obtained in the second stage process of the process of generating the correspondence information. [Figure 14] This is a graph showing the relationship between the clutch torque and the motor torque obtained as the correspondence information. [Figure 15] This is a graph showing an example of a change in the motor rotation angle in the correction operation of the second embodiment. [Figure 16] This is a graph showing an example of the relationship between the reference angle and the average value of the respective measurement results of the first to third gradually increasing states and gradually decreasing states. [Figure 17]This graph shows an example of the relationship between the reference angle and the average values ​​of the measurement results for the 1st to 3rd increasing and decreasing states. [Figure 18] This flowchart shows an example of a procedure performed by the control unit of a control device. [Modes for carrying out the invention]

[0011] [First Embodiment] A first embodiment of the present invention will be described with reference to the drawings. The embodiments described below are shown as preferred specific examples for carrying out the present invention, and some parts specifically illustrate various technically preferable technical matters, but the technical scope of the present invention is not limited to these specific embodiments.

[0012] Figure 1 is a schematic diagram showing a general configuration example of a four-wheel drive vehicle 1 equipped with a drive force transmission device 10 according to the first embodiment of the present invention. The four-wheel drive vehicle 1 includes an engine 111 as a drive source that generates driving force according to the amount the accelerator pedal 110 is pressed (accelerator opening), a transmission 112 that changes the output of the engine 111, left and right front wheels 121, 122 as main drive wheels to which the driving force of the engine 111, which has been changed by the transmission 112, is always transmitted, and left and right rear wheels 123, 124 as auxiliary drive wheels to which the driving force of the engine 111 is transmitted according to the driving state of the four-wheel drive vehicle 1.

[0013] Wheel speed sensors 101 to 104 are respectively positioned on the left and right front wheels 121 and 122 and the left and right rear wheels 123 and 124. An accelerator pedal sensor 105 is positioned on the accelerator pedal 110 to detect the amount of depression of the accelerator pedal 110. The engine 111 starts when the start switch 113 is pressed by the driver and stops when the start switch 113 is pressed again. In addition to the engine 111, a high-output electric motor or a so-called hybrid system combining an engine and an electric motor may also be used as the drive source.

[0014] Furthermore, the four-wheel drive vehicle 1 is equipped with a front differential 13, a rear differential 14, a propeller shaft 15 between the front differential 13 and the rear differential 14, left and right front drive shafts 16, 17, and left and right rear drive shafts 18, 19. The power transmission device 10 is combined with the rear differential 14.

[0015] The driving force from the engine 111 is transmitted to the left and right front wheels 121 and 122 via the transmission 112, the front differential 13, and the left and right front drive shafts 16 and 17. The front differential 13 includes a pair of side gears 131 and 132 connected to the left and right front drive shafts 16 and 17 respectively so as not to rotate relative to each other, a pair of pinion gears 133 and 134 that mesh with the pair of side gears 131 and 132 with their gear axes perpendicular to each other, a pinion gear shaft 135 that supports the pair of pinion gears 133 and 134, a differential case 136 that houses these components, and a ring gear 137 fixed to the differential case 136.

[0016] The driving force from the engine 111 is transmitted to the left and right rear wheels 123 and 124 via the propeller shaft 15 and the rear differential 14. The rear differential 14 includes a pair of side gears 141 and 142 connected to the left and right rear drive shafts 18 and 19 respectively so as not to rotate relative to each other, a pair of pinion gears 143 and 144 that mesh with the pair of side gears 141 and 142 with their gear shafts perpendicular to each other, a pinion gear shaft 145 that supports the pair of pinion gears 143 and 144, a differential case 146 that houses these components, and a ring gear 147 fixed to the differential case 146.

[0017] The ring gear 137 of the front differential 13 meshes with a pinion gear 151 located at the vehicle-front end of the propeller shaft 15. The ring gear 147 of the rear differential 14 meshes with a pinion gear 152 located at the vehicle-rear end of the propeller shaft 15. The power transmission device 10 is arranged to transmit power between the differential case 146 of the rear differential 14 and one of the side gears 141. When the power transmission device 10 transmits power between the differential case 146 of the rear differential 14 and one of the side gears 141, the differential rotation of the pair of side gears 141 and 142 is restricted. In other words, in this embodiment, the power transmission device 10 functions as a differential limiting device.

[0018] The drive force transmission device 10 includes a mechanism 10A housed in a case 7 in combination with the rear differential 14, a motor 4 that operates the mechanism 10A, and a control unit 8 connected to the motor 4. The drive force transmission device 10, the rear differential 14, and the case 7 constitute a drive force distribution device 100 that distributes the input drive force to the drive shafts 18 and 19. The configuration and operation of the drive force distribution device 100, including the drive force transmission device 10, will be described in detail below. In the following description, the rear differential 14 will be simply referred to as the differential 14, and the four-wheel drive vehicle 1 will be simply referred to as the vehicle 1.

[0019] Figure 2 is a schematic diagram illustrating a general configuration example of the drive force distribution device 100. In the following description, "left side" and "right side" refer to the left and right sides of the vehicle 1 in the vehicle width direction. As shown in Figure 2, the left drive shaft 18 has an intermediate shaft 180, an inboard constant velocity joint 181 connected to the differential 14, and an outboard constant velocity joint 182 connected to the hub unit 125 of the left rear wheel 123. The right drive shaft 19 has an intermediate shaft 190, an inboard constant velocity joint 191 connected to the differential 14, and an outboard constant velocity joint 192 connected to the hub unit 126 of the right rear wheel 124. The inboard constant velocity joints 181 and 191 are sliding constant velocity universal joints, such as tripod-type constant velocity joints. The outboard constant velocity joints 182 and 192 are fixed constant velocity universal joints, such as ball-type constant velocity joints.

[0020] Of the pair of side gears 141 and 142 of the differential 14, the left side gear 141 has the outer coupling member 181a of the constant velocity joint 181 attached to it so as not to rotate relative to it. The right side gear 142 has the outer coupling member 191a of the constant velocity joint 191 attached to it so as not to rotate relative to it.

[0021] The power transmission device 10 comprises, as its main components, a clutch mechanism 2 having a friction clutch 20, a pressing mechanism 3 that presses the friction clutch 20 with a piston 30, a motor 4 that operates the pressing mechanism 3, a reduction mechanism 5 that reduces the rotation of the output rotating shaft 41 of the motor 4, and a control unit 8 having a control device 81 that controls the motor 4. The clutch mechanism 2, the pressing mechanism 3, and the reduction mechanism 5 constitute the mechanical part 10A of the power transmission device 10.

[0022] The pressing mechanism 3 includes a piston 30, a pair of cam plates 31 and 32 facing each other along the axial direction, a plurality of cam balls 33 positioned between the pair of cam plates 31 and 32, an annular retainer 34 that holds the plurality of cam balls 33, and a thrust bearing 35 positioned between one of the cam plates 32 and the piston 30. When the output rotating shaft 41 of the motor 4 rotates, its rotational force is amplified by the reduction mechanism 5, causing the pair of cam plates 31 and 32 to rotate relative to each other, and the piston 30 to press against the friction clutch 20.

[0023] Case 7 has a first case member 71 and a second case member 72, and the first case member 71 and the second case member 72 are fastened together by a plurality of bolts 73. The clutch mechanism 2, the pressing mechanism 3, and the reduction mechanism 5 of the drive force transmission device 10 are housed in the first case member 71 together with the stem portion 181b of the outer joint member 181a of the constant velocity joint 181.

[0024] The power transmission device 10 can switch between a state in which power is transmitted between the differential case 146 and the left side gear 141 by the clutch mechanism 2, and a state in which power is not transmitted between them. The differential case 146 is an input rotating member that inputs power to the power transmission device 10, and the left side gear 141 is an output rotating member to which the power transmission device 10 outputs power. When the clutch mechanism 2 is activated and power is transmitted between the differential case 146 and the left side gear 141 by the clutch mechanism 2, the relative rotation between the differential case 146 and the left side gear 141 is restricted, and this also restricts the relative rotation between the differential case 146 and the right side gear 142. On the other hand, when the clutch mechanism 2 is not activated, the left side gear 141 and the right side gear 142 can rotate relative to each other due to the rotation of the pair of pinion gears 143 and 144.

[0025] Figure 3 is a cross-sectional view of the drive force transmission device 10, including the mechanism 10A, differential 14, case 7, and constant velocity joints 181 and 191, in the vehicle width direction and vertical direction. Figure 4 is a cross-sectional view of the drive force transmission device 10 along line AA in Figure 3. Figure 5 is a cross-sectional view along line BB in Figure 4, showing the clutch mechanism 2, pressing mechanism 3, and reduction mechanism 5.

[0026] In Figures 3 and 5, the rotation axis O of the differential case 146 is shown by a dashed line. The outer coupling members 181a and 191a of the pair of side gears 141 and 142 and constant velocity joints 181 and 191 are rotatable relative to the differential case 146 about the rotation axis O. Hereinafter, the direction parallel to the rotation axis O will be referred to as the axial direction.

[0027] The differential case 146 has a cylindrical portion 146a that supports both ends of the pinion gear shaft 145, a left wall portion 146b and a right wall portion 146c, a left cylindrical portion 146d extending axially from the inner diameter end of the left wall portion 146b, and a right cylindrical portion 146e extending axially from the inner diameter end of the right wall portion 146c. A bearing 61 is positioned between the right cylindrical portion 146e and the second case member 72.

[0028] The left side gear 141 has a gear portion 141a that meshes with a pair of pinion gears 143 and 144, and a cylindrical portion 141b that is inserted inside the left cylindrical portion 146d of the differential case 146. The stem portion 181b of the outer coupling member 181a is fitted inside the cylindrical portion 141b in a manner that prevents relative rotation. Similarly, the right side gear 142 has a gear portion 142a that meshes with a pair of pinion gears 143 and 144, and a cylindrical portion 142b that is inserted inside the right cylindrical portion 146e of the differential case 146. The stem portion 191b of the outer coupling member 191a is fitted inside the cylindrical portion 142b in a manner that prevents relative rotation.

[0029] In the clutch mechanism 2, the intermittent state of the driving force changes continuously according to the rotation angle of the motor 4 as the friction clutch 20 is pressed axially by the piston 30. The friction clutch 20 is a multi-plate clutch having multiple outer clutch plates 201 and inner clutch plates 202 as friction members, and more specifically, it is a wet multi-plate clutch in which the frictional sliding between the multiple outer clutch plates 201 and the inner clutch plates 202 is lubricated by lubricating oil. When the friction clutch 20 is pressed axially, the driving force is transmitted by the frictional force generated by the frictional contact between the multiple outer clutch plates 201 and the multiple inner clutch plates 202. The magnitude of the driving force transmitted by the friction clutch 20, i.e., the transmitted torque, increases as the friction clutch 20 is pressed more strongly.

[0030] The clutch mechanism 2 includes a clutch drum 21 that rotates integrally with a plurality of outer clutch plates 201, and a clutch hub 22 that rotates integrally with a plurality of inner clutch plates 202. The clutch drum 21 integrally includes an outer cylindrical portion 211 having a spline engagement portion 210 on its inner circumference that engages the plurality of outer clutch plates 201 in an axially movable manner, an annular wall portion 212 aligned axially with the friction clutch 20, a connecting portion 213 that is non-rotatably connected to the cylindrical portion 141b of the left side gear 141, and a connecting portion 214 that connects the wall portion 212 and the connecting portion 213. A bearing 62 is positioned between the wall portion 212 of the clutch drum 21 and the first case member 71.

[0031] The clutch hub 22 integrally comprises an inner cylindrical portion 221 having a spline engagement portion 220 on its outer circumference into which a plurality of inner clutch plates 202 engage in an axially movable manner, a connecting portion 222 connected to the left cylindrical portion 146d of the differential case 146 in a manner that prevents relative rotation, and a connecting portion 223 connecting the inner cylindrical portion 221 and the connecting portion 222. A washer 63 is positioned between the connecting portion 214 of the clutch drum 21 and the connecting portion 223 of the clutch hub 22.

[0032] One of the pair of cam plates 31 and 32, cam plate 31, is fixed to the first case member 71, dividing the space inside the case 7 into a first housing space 701 and a second housing space 702. The clutch mechanism 2, the pressing mechanism 3, and the reduction mechanism 5 are housed in the first housing space 701. The differential 14 is housed in the second housing space 702. The other cam plate 32 rotates relative to the first cam plate 31 by the output rotation of the motor 4, which is reduced by the reduction mechanism 5.

[0033] Hereinafter, one cam plate 31 will be referred to as the fixed cam plate 31, and the other cam plate 32 will be referred to as the rotating cam plate 32. Between the fixed cam plate 31 and the left cylindrical portion 146d of the differential case 146, a bearing 64 is positioned to rotatably support the differential case 146. The fixed cam plate 31 integrally comprises a disc-shaped disc portion 311, an outer projection 312 (see Figure 4) provided to project radially from the outer diameter end of the disc portion 311, and a cylindrical inner projection 313 provided to project axially toward the clutch mechanism 2 from the inner diameter end of the disc portion 311. The disc portion 311 is fixed to the first case member 71 by a plurality of bolts 74. The outer projection 312 is fitted into a recess 710 formed in the first case member 71. The rotating cam plate 32 is positioned on the outer circumference of the inner projection 313 of the fixed cam plate 31.

[0034] The pressing mechanism 3 is configured such that when the motor 4 rotates in the forward direction, the piston 30 moves forward toward the friction clutch 20, and when the motor 4 rotates in the reverse direction, the piston 30 moves backward toward the friction clutch 20. In this embodiment, the rotational force of the motor 4 causes the rotating cam plate 32 to rotate relative to the fixed cam plate 31, and a plurality of cam balls 33 roll in a plurality of arc-shaped rolling grooves 310, 320 formed in the fixed cam plate 31 and the rotating cam plate 32, respectively, thereby causing the piston 30 to press against the friction clutch 20. The rolling grooves 310, 320 are formed with an inclination such that the axial depth gradually changes, and as the cam balls 33 roll in the rolling grooves 310, 320, the rotating cam plate 32 moves axially relative to the fixed cam plate 31.

[0035] The piston 30 has an annular projection 301 at its inner circumference end, and a return spring 65 is positioned between this annular projection 301 and the connection portion 223 of the clutch hub 22. The return spring 65 is a disc spring and biases the piston 30 toward the rotating cam plate 32. The return spring 65 has oil holes 650 formed at multiple locations in the circumferential direction. When the motor 4 rotates in the reverse direction, the biasing force of the return spring 65 causes the piston 30 to separate from the friction clutch 20.

[0036] As shown in Figure 2, the motor 4 includes a motor case 40, a rotor 42 that rotates integrally with the output rotating shaft 41, a stator 43 fixed to the motor case 40, and a multi-turn encoder 44 which acts as a rotation angle detector for detecting the rotation angle of the output rotating shaft 41 relative to the motor case 40. The multi-turn encoder 44 is an absolute type capable of detecting the absolute rotation angle of the output rotating shaft 41 relative to the motor case 40 in a range of 360° or more, and outputs a signal containing information about the rotation angle of the output rotating shaft 41 to the control device 81.

[0037] The control unit 8 includes a control device 81, an inverter 82 that generates motor current supplied to the motor 4 by switching multiple switching elements, and a current sensor 83 that detects the magnitude of the motor current. The motor 4 is, for example, a three-phase AC motor, and the inverter 82 supplies three-phase AC motor current to the windings of the stator 43 of the motor 4. The signal indicating the detection result (current value) of the current sensor 83 is input to the control device 81. The control device 81 includes a control unit 811 having a CPU (processing unit), and a storage unit 812 configured with non-volatile memory. The storage unit 812 stores information such as programs executed by the control unit 811.

[0038] The control device 81 controls the motor 4 so that an appropriate differential limiting force is generated according to the vehicle state detected by multiple on-board sensors. These on-board sensors include wheel speed sensors 101-104 and an accelerator pedal sensor 105. The control device 81 outputs a PWM signal to the inverter 82 so that a motor current of a magnitude corresponding to the differential limiting force to be generated, i.e., the driving force to be transmitted by the clutch mechanism 2, is supplied from the inverter 82 to the motor 4.

[0039] Motor 4 generates motor torque corresponding to the current supplied from control unit 8, and rotates the rotating cam plate 32 relative to the fixed cam plate 31 via reduction mechanism 5. The motor torque is substantially proportional to the motor current. The rotation of the output rotating shaft 41 of motor 4 is reduced by the reduction mechanism 5 and transmitted to the rotating cam plate 32. The pressing mechanism 3 presses the friction clutch 20 toward the wall portion 212 of the clutch drum 21 with a pressing force of a magnitude corresponding to the motor torque generated by motor 4.

[0040] The reduction mechanism 5 includes a reduction gear 51 having a large-diameter gear portion 511 and a small-diameter gear portion 512, and a counter gear 52 having a gear portion 521 that meshes with the small-diameter gear portion 512 of the reduction gear 51 and the rotating cam plate 32 of the pressing mechanism 3. The large-diameter gear portion 511 of the reduction gear 51 meshes with the output rotating shaft 41 of the motor 4. The reduction gear 51 is supported by a support pin 75 attached to the first case member 71. The counter gear 52 has a shaft portion 522 in its center, which is inserted into a support hole 312a formed in the outer projection 312 of the fixed cam plate 31 and is prevented from coming out by a retaining ring 53.

[0041] The frictional sliding of the multiple outer clutch plates 201 and inner clutch plates 202 of the friction clutch 20 is lubricated by lubricating oil L (see Figure 3). In this embodiment, the lubricating oil L is sealed in the case 7. Leakage of the lubricating oil L from the case 7 is prevented by an oil seal 66 located between the first case member 71 and the outer joint member 181a of the constant velocity joint 181, and by an oil seal 67 located between the second case member 72 and the outer joint member 191a of the constant velocity joint 191. The lubricating oil L is mainly contained in the second containment space 702. When the vehicle 1 is stopped, the oil level of the lubricating oil L is below the lowest point in the vertical direction of the friction clutch 20, as shown in Figure 3.

[0042] As the ring gear 147 rotates together with the differential case 146, the ring gear 147 scrapes up the lubricating oil L in the second storage space 702. A portion of the scraped and scattered lubricating oil L enters the oil passage 711 (see Figure 3) formed in the first case member 71 and is supplied from the oil passage 711 to the first storage space 701. The lubricating oil L supplied to the first storage space 701 lubricates the clutch mechanism 2, the pressing mechanism 3, and the reduction mechanism 5. The lubricating oil L that flows downward from the first storage space 701 returns to the second storage space 702 through the discharge hole 311a formed at the lower end of the disc portion 311 of the fixed cam plate 31.

[0043] Figure 6(a) is a plan view of the outer clutch plate 201. The outer clutch plate 201 integrally comprises a ring-shaped metal disc portion 201a and a plurality of spline projections 201b protruding from the outer peripheral end of the disc portion 201a. The plurality of spline projections 201b engage with the spline engagement portion 210 of the clutch drum 21. The outer clutch plate 201 also has a plurality of missing teeth portions 201c in a part of the circumferential direction where the spline projections 201b are not formed. These missing teeth portions 201c facilitate the axial flow of lubricating oil L between the outer clutch plate 201 and the outer cylindrical portion 211 of the clutch drum 21.

[0044] Figure 6(b) is a plan view of the inner clutch plate 202. The inner clutch plate 202 integrally comprises a ring-shaped metal disc portion 202a and a plurality of spline projections 202b protruding from the inner circumference end of the disc portion 202a. The plurality of spline projections 202b engage with the spline engagement portion 220 of the clutch hub 22. The inner clutch plate 202 has a plurality of missing teeth portions 202c in which the spline projections 202b are not formed in a part of the circumferential direction, and these missing teeth portions 202c facilitate the axial flow of lubricating oil L between the inner clutch plate 202 and the inner cylindrical portion 221 of the clutch hub 22.

[0045] Furthermore, the inner clutch plate 202 has a friction material 202d on the portion facing the disc portion 201a of the outer clutch plate 201 in the axial direction, which has a lubricating oil retaining function that impregnates and retains lubricating oil L. The friction material 202d is made of, for example, paper friction material, nonwoven fabric, or porous material, and is attached to both sides of the disc portion 202a. As the lubricating oil L is impregnated into the friction material 202d, the frictional sliding between the outer clutch plate 201 and the inner clutch plate 202 becomes smoother, and overheating is suppressed.

[0046] When frictional force is generated between multiple outer clutch plates 201 and multiple inner clutch plates 202, and a clutch is engaged to transmit driving force by the friction clutch 20, the control device 81 rotates the motor 4 in the forward direction to move the piston 30 toward the wall portion 212 of the clutch drum 21, sandwiching the multiple outer clutch plates 201 and inner clutch plates 202 between the wall portion 212 and the piston 30. The wall portion 212 functions as a receiving portion that receives the pressing force of the piston 30 from the pressing mechanism 3.

[0047] On the other hand, when the friction clutch 20 is in an open state and does not transmit driving force, the piston 30 is moved away from the wall portion 212 of the clutch drum 21. However, if the piston 30 is moved too far away from the wall portion 212 of the clutch drum 21, the free-travel distance of the piston 30 before frictional force is generated between the multiple outer clutch plates 201 and the inner clutch plate 202 when engaging the friction clutch 20 will be longer, and it will take longer to engage. In other words, the responsiveness of the friction clutch 20 will decrease. Also, if the position of the piston 30 is close to the wall portion 212, the multiple inner clutch plates 202 and the outer clutch plate 201 will rub against each other, generating drag torque.

[0048] Hereinafter, when the motor 4 is rotated in the forward direction to generate frictional force in the friction clutch 20, the rotation angle of the motor 4 at the point when the multiple outer clutch plates 201 and multiple inner clutch plates 202 come into contact and the transmitted torque of the friction clutch 20 begins to increase is referred to as the 0 (zero) point. In other words, the rotation angle of the motor 4 at the point when the gap between the multiple outer clutch plates 201 and multiple inner clutch plates 202 closes and the multiple outer clutch plates 201 and multiple inner clutch plates 202 begin to come into contact is referred to as the 0 (zero) point. The position of the piston 30 when the rotation angle of the motor 4 is the 0 point is referred to as the touch point. This 0 point corresponds to the "transmitted torque increase start angle" of the present invention.

[0049] The control device 81 stores zero-point information in the memory unit 812, and when the clutch mechanism 2 is released, it sets the rotation angle of the motor 4 to zero and places the piston 30 in standby position at the touch point. Furthermore, when the clutch mechanism 2 is moved from the released state to the engaged state, the control device 81 rotates the motor 4 in the forward direction from the zero-point position. This improves the responsiveness of the friction clutch 20. In addition, when the start switch 113 is pressed by the driver, the control device 81 controls the motor 4 to set the rotation angle of the motor 4 to zero.

[0050] The initial zero position of the drive force transmission device 10 can be measured, for example, at the factory where the drive force transmission device 10 is manufactured, in its initial state after the manufacture of the mechanism 10A (before shipment from the factory), and stored in the memory unit 812 of the control device 81. This zero position can be measured, for example, based on the detection results of the multi-turn encoder 44 and current sensor 83 when the piston 30 is moved towards the friction clutch 20 from a state where the piston 30 is not pressing against the friction clutch 20. In other words, when the rotation angle of the motor 4 exceeds the zero position, the piston 30 receives a force in the direction of being pushed back from the friction clutch 20, so the torque and motor current generated by the motor 4 increase to counteract this force. The rotation angle of the motor 4 when the motor current begins to increase can be set as the zero position.

[0051] However, if the friction material 202d of the multiple inner clutch plates 202 wears down due to subsequent use of the drive force transmission device 10, the actual zero point position changes. Even if the motor 4 is rotated to the zero point position stored in the initial state and the piston 30 is positioned at the touch point corresponding to that zero point, a delay in the rise of the transmission torque transmitted by the friction clutch 20 occurs.

[0052] Therefore, in this embodiment, with the power transmission device 10 mounted on the vehicle 1, the control device 81 performs a correction operation to correct the zero point. This correction operation is performed, for example, immediately after the engine stops when the vehicle 1 is stopped and the start switch 113 is pressed. The control device 81 may perform the correction operation each time the vehicle 1's start switch 113 is pressed and the vehicle 1's engine stops, or it may perform the correction operation when the engine stops after the vehicle 1 has been driven for a predetermined period (for example, several days) since the previous correction operation was performed.

[0053] Next, with reference to Figures 7 to 10, a specific example of the correction operation will be described. The correction operation includes a pressing step in which the motor 4 is rotated in the forward direction to press the friction clutch 20 with the piston 30 and bring the multiple outer clutch plates 201 and multiple inner clutch plates 202 into contact with each other; a retraction step in which, after the pressing step, the motor 4 is rotated in the reverse direction to retract the piston 30; an advance step in which, after the retraction step, the motor 4 is rotated in the forward direction at a lower speed than in the pressing step while measuring the current value of the motor current supplied to the motor 4; and a correction step which is a correction process that calculates a new zero point based on the current value of the motor current measured in the advance step and corrects the zero point. In the retraction step, the motor 4 is rotated at a higher speed than in the pressing step and the advance step.

[0054] Figure 7 is a graph showing an example of the changes in motor rotation angle and motor torque during the pressing step, retraction step, and forward step. The horizontal axis of the graph is the time axis, and the vertical axis shows the motor rotation angle and motor torque. The motor rotation angle is the rotation angle of the motor 4 detected by the multi-turn encoder 44, and the motor torque is the torque generated by the motor 4 due to the motor current supplied from the control unit 8. Since the motor torque is substantially proportional to the motor current, the motor torque can be calculated from the detection result of the current sensor 83. On the horizontal axis of the graph, t0 indicates the time when the motor 4 begins to rotate in the positive direction during the pressing step. θ0 on the vertical axis indicates the zero point of the motor rotation angle.

[0055] As shown in Figure 7, there is a corresponding relationship between the motor rotation angle and the motor torque. As the motor rotation angle increases, the piston 30 moves forward and presses against the friction clutch 20, causing the multiple outer clutch plates 201 and the multiple inner clutch plates 202 to press more strongly, and thus increasing the motor torque.

[0056] Here, one possible method for the control device 81 to determine the zero point of the motor 4 from the motor torque and motor rotation angle is to set the motor rotation angle at which the increase in motor torque relative to the motor rotation angle becomes large as the zero point. However, in the free-running phase before the piston 30 moves forward and the gap between the multiple outer clutch plates 201 and the multiple inner clutch plates 202 closes and the motor torque begins to increase, the motor torque may fluctuate due to sliding resistance and catching between the piston 30, the multiple outer clutch plates 201 and the multiple inner clutch plates 202 and the clutch drum 21 and clutch hub 22 as they move axially. Therefore, it is difficult to accurately capture the motor rotation angle at which the motor torque begins to increase as the gap between the multiple outer clutch plates 201 and the multiple inner clutch plates 202 closes. In other words, even if the motor torque temporarily increases, it is difficult to determine whether that increase is due to the sliding resistance when the piston 30, the multiple outer clutch plates 201, and the multiple inner clutch plates 202 move, or to the contact between the multiple outer clutch plates 201 and the multiple inner clutch plates 202. Furthermore, the motor torque when the piston 30 presses against the friction clutch 20 to close the gap is also affected by the amount and temperature of the lubricating oil interposed between the multiple outer clutch plates 201 and the multiple inner clutch plates 202. Unless the influence of these factors on the motor torque is suppressed, the zero point will fluctuate each time a correction operation is performed, making it impossible to control the motor 4 with high precision.

[0057] Therefore, in this embodiment, the control device 81 corrects the zero point by a correction operation including a pressing step, a retraction step, and an advance step. The pressing step is a step to bring a plurality of outer clutch plates 201 and a plurality of inner clutch plates 202 into contact with each other and discharge the lubricating oil L interposed between the outer clutch plates 201 and the inner clutch plates 202. In the pressing step, the friction clutch 20 is pressed with a pressing force such that a portion of the lubricating oil L contained in the friction material 202d attached to the inner clutch plate 202 is squeezed out by compression. This makes it possible to suppress the influence of the lubricating oil L on the result of the correction operation. In other words, it is possible to suppress the result of the correction operation from changing depending on the amount of lubricating oil L interposed between the outer clutch plates 201 and the inner clutch plates 202 when the correction operation is executed.

[0058] In the retraction step following the pressing step, the rotation angle of the motor 4 is returned to near zero, and the piston 30 is retracted. At this time, the control device 81 does not return the rotation angle of the motor 4 to zero, and when the retraction step is completed, the piston 30 is on the friction clutch 20 side of the touch point position. This zero point is the zero point corrected in the previous correction operation. By not returning the rotation angle of the motor 4 to zero in the retraction step, the entry of lubricating oil L between the outer clutch plate 201 and the inner clutch plate 202 is suppressed, and the time required for the correction operation is shortened. In addition, in this embodiment, the control device 81 performs the correction operation when the vehicle 1 is stopped, so this also suppresses the entry of lubricating oil L between the outer clutch plate 201 and the inner clutch plate 202.

[0059] In the correction step, the new zero point after correction is calculated by the first to third calculation processes described below. The first calculation process is to find the averaged motor rotation angle, which is the average of the rotation angles of the motor 4 when the motor current is within a predetermined range in the forward step. The second calculation process is to find the zero point current value, which is the difference between the initial value of the averaged motor rotation angle (the value obtained when the drive force transmission device 10 was manufactured) and the current value of the averaged motor rotation angle (the value obtained in the first calculation process immediately before performing the second calculation process), and then subtract the obtained difference value from the current value of the averaged motor rotation angle. The third calculation process is to find a weighted average value, which is the weighted average obtained by taking into account the calculation values ​​from multiple past correction operations.

[0060] In this embodiment, during the pressing step, a motor current greater than the upper limit of a predetermined range in the first calculation process is supplied to the motor 4. Furthermore, in this embodiment, in the third calculation process, the current zero point value obtained in multiple past correction operations is taken into account and a weighted average is calculated, and the resulting weighted average is set as the new zero point. The first to third calculation processes will be described in more detail below.

[0061] Figure 8 is a graph showing an example of the change in motor current when the motor 4 is rotated in the forward direction and the motor rotation angle is changed. The horizontal axis of the graph represents the motor rotation angle, and the vertical axis represents the motor current. The current values ​​I1 and I2 shown on the vertical axis are the lower and upper limits of the predetermined range in the first calculation process, with a range of ±ΔI relative to the reference value I0 of the motor current. This predetermined range is set to a linear region in which the motor current increases at approximately a constant rate with respect to the motor rotation angle. As shown in Figure 8, the motor rotation angle corresponding to the current value I1 is θ1, and the motor rotation angle corresponding to the current value I2 is θ2.

[0062] The reference value I0 for the motor current is set to correspond to the value of the motor torque generated by the motor 4 when the pressing force of the friction clutch 20 by the piston 30 increases as the motor 4 rotates further in the forward direction from the zero point. In other words, the value of the motor torque when the motor current is the reference value I0 is a predetermined value of the motor torque generated by the motor 4 when the pressing force of the friction clutch 20 by the piston 30 increases as the motor 4 rotates further in the forward direction from the zero point.

[0063] Equation (1) is an example of an arithmetic formula for the averaging process in the first calculation. In equation (1), n ​​is the number of samplings in which the control device 81 samples the motor rotation angle and motor current while the motor rotation angle changes from θ1 to θ2, and θi (i=1~n) is the motor rotation angle at each sampling. θavr in equation (1) is the averaged motor rotation angle obtained in the first calculation.

number

[0064] In the second calculation process, the value of the averaged motor rotation angle after assembly of the drive force transmission device 10, obtained at the factory where the drive force transmission device 10 is manufactured, is used as the initial value of the averaged motor rotation angle. The value of the averaged motor rotation angle obtained in the first calculation process of the correction operation when the drive force transmission device 10 is installed in the vehicle 1 after leaving the factory is used as the current value of the averaged motor rotation angle. A difference value is calculated according to the difference between the initial value and the current value of the averaged motor rotation angle. Then, the calculated difference value is subtracted from the current value of the averaged motor rotation angle obtained in the first calculation process to calculate the zero-point current value.

[0065] Figure 9 is a graph for explaining the reason and significance of obtaining the subtraction value according to the difference between the initial value of the averaged motor rotation angle and the current value in the second arithmetic processing. The horizontal axis and vertical axis of this graph represent the motor rotation angle and the motor current, respectively, similarly to the graph of Figure 8. Further, in the graph of Figure 9, the relationship between the motor rotation angle and the motor current at the initial stage after assembly of the driving force transmission device 10 in the factory is shown by a thin line, and the relationship between the motor rotation angle and the motor current at the time of executing the correction operation after use of the driving force transmission device 10 in a state of being mounted on the vehicle 1 is shown by a thick line.

[0066] As shown in Figure 9, when wear or hardening of the friction material 202d of the inner clutch plate 202 progresses due to the use of the driving force transmission device 10 in the state of being mounted on the vehicle 1, the rise of the motor current is delayed. Further, after the rise of the motor current, the increase rate of the motor current with respect to the motor rotation angle becomes large. In Figure 9, the rotation angle of the motor 4 when the plurality of outer clutch plates 201 and the inner clutch plates 202 start to come into contact with each other in the initial state is represented by θ 10 , and the rotation angle of the motor 4 when the plurality of outer clutch plates 201 and the inner clutch plates 202 start to come into contact with each other in a state where wear or hardening of the friction material 202d has progressed is represented by θ 11 . In Figure 9, the initial value of the averaged motor rotation angle in the initial state of the driving force transmission device 10 is represented by θ 20 , and the averaged motor rotation angle in a state where wear or hardening of the friction material 202d has progressed is represented by θ 21 .

[0067] As shown in Figure 9, in a state where wear or hardening of the friction material 202d has progressed due to the use of the driving force transmission device 10, Δθ2, which is the difference between θ 11 and θ 21 , is smaller than Δθ1, which is the difference between θ in the initial state of the driving force transmission device 10 10 and θ 20 . The difference between θ 20 and θ 21 serves as an index value indicating the deterioration state of the friction clutch 20, and the difference between θ 20 and θ 21The larger the difference, the smaller the value of Δθ2. Therefore, in the second calculation process, the initial value of the averaged motor rotation angle (θ 20 (equivalent to) and the current value (θ 21 The difference is calculated based on the difference between (equivalent to) and . This allows for a more accurate determination of the zero point, taking into account the wear and hardening of the friction material 202d.

[0068] Equation (2) is an example of an calculation formula for determining the difference value Δθ. In equation (2), θini represents the initial value of the averaged motor rotation angle, and θcur represents the current value of the averaged motor rotation angle (θavr). Also, K1 in equation (2) represents a predetermined constant determined in advance through experiments or other means. The memory unit 812 of the control device 81 stores the initial value of the averaged motor rotation angle measured at the factory where the drive force transmission device 10 is manufactured.

number

[0069] The initial value of the averaged motor rotation angle is the rotation angle of motor 4 when the motor torque generated by motor 4 in the initial state is the predetermined value described above, and corresponds to the "initial rotation angle value" of the present invention. The current value of the averaged motor rotation angle is the measured value of the rotation angle of motor 4 when the motor torque generated by motor 4 is the predetermined value described above while vehicle 1 is stopped, and corresponds to the "measured rotation angle value" of the present invention. In this embodiment, the zero point (transmission torque increase start angle) is corrected based on the current value of the averaged motor rotation angle (measured rotation angle value) and the initial value of the averaged motor rotation angle (initial rotation angle value).

[0070] In the second calculation, the difference Δθ obtained by equation (2) is subtracted from the averaged motor rotation angle (θcur) obtained in the first calculation to obtain the zero-point current value. Equation (3) is the calculation formula for obtaining the zero-point current value (0Pcur).

number

[0071] In the third calculation process, to prevent the zero point from changing significantly due to a single correction operation, the current zero point value obtained from each of the previous multiple correction operations is taken into account and a weighted average is calculated. Equation (4) is an example of the calculation formula for the weighted average (Wavr) when the current zero point value from previous correction operations up to m operations ago is weighted average. 0Pcur in Equation (4) j (j=0~m) represents the current zero point value for the current and past m correction operations, respectively. 0Pcur0 is the current zero point value obtained in the second calculation process immediately preceding the third calculation process. Pcur1 is the current zero point value for the previous correction operation. Kw j This is a weighting coefficient, and its value decreases as you go back through past correction actions.

number

[0072] In the correction step, the control device 81 sets the weighted average value (Wavr) obtained by equation (4) as a new zero point. This zero point is stored in the non-volatile memory of the control device 81 and is used to control the motor 4 when generating frictional force in the friction clutch 20 until the next correction operation is performed.

[0073] Furthermore, the current zero point value obtained in the second calculation process immediately preceding the third calculation process and the current zero point values ​​from the previous m correction operations may be simply averaged to obtain a new zero point. Also, if the current zero point value has changed significantly beyond a predetermined limit range compared to the zero point value obtained in the correction step of the previous correction operation (the transmission torque increase start angle obtained in the previous correction step), the current zero point value may be changed to fit within the limit range. This process is intended to suppress the reflection of abnormal values ​​in the transmission torque increase start angle caused by accidental events, such as foreign objects getting stuck in the spline engagement portion 210 that the outer clutch plate 201 engages with, or the spline engagement portion 220 that the inner clutch plate 202 engages with. The limit range is set to a value such that the current zero point value does not exceed the limit range when no accidental events occur.

[0074] Furthermore, the third calculation process may be omitted, and the current zero point value (0Pcur) obtained in the second calculation process may be used as the new zero point. Also, the control device 81 may perform all of the first to third calculation processes when the vehicle 1 stops and the start switch 113 is pressed to stop the engine, but some of the first to third calculation processes may be performed when the vehicle restarts after the start switch 113 is pressed again. Performing some of the calculation processes when the vehicle restarts makes it possible to avoid the power supply to the control device 81 being cut off during the execution of the correction step.

[0075] Incidentally, since the viscosity of the lubricating oil L changes with temperature, it is desirable to change the predetermined range in the first calculation process according to the temperature of the lubricating oil L. In other words, for example, when the lubricating oil L is at a low temperature, its viscosity increases and it becomes difficult to flow, so it is desirable to shift the predetermined range in the first calculation process toward a higher current compared to when the lubricating oil L is at room temperature or a high temperature. The temperature of the lubricating oil L may be determined, for example, by measuring the temperature of the lubricating oil L that flows out from between the outer cylindrical portion 211 of the clutch drum 21 and the inner cylindrical portion 221 of the clutch hub 22 during the pressing step using a temperature sensor, or it may be determined by estimation calculation based on the integrated value of the motor current, etc.

[0076] Figure 10 is a graph showing an example of the relationship between motor rotation angle and motor current when the lubricating oil L is at a low temperature and at room temperature. When the lubricating oil L is at a low temperature, the motor current increases even if the motor rotation angle is the same. For this reason, as shown in Figure 10, the lower and upper limits of the predetermined range in the first calculation process are increased. Specifically, the current values ​​I1 and I2 are set as the lower and upper limits, respectively, with a range of ±ΔI relative to the value obtained by multiplying the reference value I0 of the motor current by a predetermined temperature coefficient Tc. This allows for more accurate correction of the zero point.

[0077] [Example of correction operation 1] Here, we will describe Modification 1 of the correction operation. In Modification 1, the method of calculating the difference value Δθ in the second calculation process among the first to third calculation processes described above is different. In the second calculation process in Modification 1, this difference value Δθ is obtained by equation (5).

number

[0078] In equation (5), K2 is a predetermined constant determined in advance through experiments or other means. 0Ppre is the zero point value obtained in the processing of the correction step of the previous correction operation (the torque increase start angle obtained in the processing of the previous correction step). 0Pini is the zero point value in the initial state measured at the factory where the drive force transmission device 10 is manufactured (initial zero point value). That is, in this modified example, in the correction step, the difference value Δθ is calculated according to the difference between the previous zero point value obtained in the processing of the previous correction step and the initial zero point value. The initial zero point value is stored in the storage unit 812 of the control device 81.

[0079] The Δθ obtained by equation (5) is used as the subtraction to be subtracted from θcur in equation (3) above, and the 0Pcur (current value at point 0) obtained by equation (3) is used in the calculation of the weighted average in equation (4) above. In other words, in this modified example, the torque increase start angle is corrected based on the value obtained by subtracting the subtraction Δθ obtained by equation (5) from the current value (θcur) of the averaged motor rotation angle. The weighted average value (Wavr) obtained by equation (4) is used to control the motor 4 when generating frictional force in the friction clutch 20 until the next correction operation is performed.

[0080] [Modified Correction Operation 2] Figure 11 is a graph showing an example of the changes in motor rotation angle and motor torque when performing the pressing step, retraction step, and forward step in Modification 2 of the correction operation. In this Modification 2, the forward step is repeated multiple times (three times in the example shown in Figure 11), and a correction step is performed after each forward step. Before the second and subsequent forward steps, a retraction step is performed in which the motor 4 is rotated in the reverse direction to retract the piston 30.

[0081] In Modification 2, the zero point is corrected based on the calculation results of multiple correction steps. In this case, the zero points obtained as calculation results of multiple correction steps may be averaged to create a new zero point, or the median of the zero points obtained in each of the multiple correction steps may be used as the new zero point. According to Modification 2, although the time required for the correction operation is longer, it becomes possible to determine the zero point more accurately.

[0082] (Effects of the first embodiment) According to the first embodiment described above, it is possible to suppress a decrease in responsiveness even when the friction clutch 20 is worn out.

[0083] [Second Embodiment] Next, a second embodiment of the present invention will be described. The power transmission device according to the second embodiment is configured similarly to the power transmission device 10 of the first embodiment described with reference to Figures 1 to 6, and the control device 81 performs a correction process to correct the transmission torque increase start angle based on the rotation angle measurement value and the initial rotation angle, but the specific processing content differs from that of the first embodiment. In addition, in the second embodiment, the control device 81 stores relationship information showing the relationship between the rotation angle of the motor 4 and the motor torque in the storage unit 812. The control device 81 measures the rotation angle of the motor 4 and the motor torque when the vehicle 1 is stopped, and performs a correction process to correct the relationship information based on the measurement results. The relationship information shows the relationship between the motor's rotation angle and motor torque when the motor 4 rotates in the positive direction above the transmission torque increase start angle.

[0084] In the second embodiment, correspondence information showing the relationship between the clutch torque transmitted by the friction clutch 20 and the motor torque generated by the motor 4 is stored in the storage unit 812 of the control device 81, and the control device 81 controls the motor 4 based on the relationship information and the correspondence information. The correspondence information is acquired in the initial state after the manufacture of the mechanism unit 10A, for example, using a test device at the factory that manufactures the drive force transmission device 10, and stored in the storage unit 812.

[0085] Figure 12 is a schematic diagram showing an example configuration of a test apparatus 9 for acquiring correspondence information between clutch torque and motor torque in the initial state for each of the factory-produced mechanical parts 10A. The test apparatus 9 includes a drive device 91, a load device 92, a torque sensor 93, and an information processing device 94. The drive device 91 uses, for example, an electric motor as a drive source and rotates a drive shaft 911 that is connected to the clutch hub 22 in a way that prevents relative rotation. The drive device 91 can increase or decrease the torque applied to the drive shaft 911. The load device 92 is configured, for example, with a generator and a resistor and generates rotational resistance on a load shaft 921 that is connected to the clutch drum 21 in a way that prevents relative rotation. In this test configuration, the drive shaft 911 is the input rotating member, and the load shaft 921 is the output rotating member.

[0086] The torque sensor 93 is attached to the load shaft 921 and detects the clutch torque transmitted from the drive shaft 911 to the load shaft 921 by the friction clutch 20. The information processing device 94 generates corresponding information based on the clutch torque detected by the torque sensor 93 and the motor rotation angle detected by the multi-turn encoder 44. The generated corresponding information is stored in the storage unit 812 of the control device 81. Alternatively, the functions of the information processing device 94 may be assigned to the control device 81. In this case, the control device 81 acquires the clutch torque information detected by the torque sensor 93, generates the corresponding information, and stores it in the storage unit 812.

[0087] The process for generating correspondence information consists of two stages: a first stage in which the clutch torque is gradually changed while the drive shaft 911 is rotated and the correspondence between the clutch torque and the motor rotation angle is measured; and a second stage in which the drive shaft 911 is stopped and the motor rotation angle is gradually changed while the correspondence between the motor torque and the drive shaft 911 is measured. The first stage is a measurement that simulates the driving state of vehicle 1, and the second stage is a measurement that simulates the stopped state of vehicle 1.

[0088] Figure 13(a) shows the measurement results obtained in the first stage of processing. In the first stage, the motor rotation angle is adjusted so that the clutch torque matches each of several preset values, and the motor rotation angle when the clutch torque matches each of the preset values ​​is stored. In the example shown in Figure 13(a), 16 values ​​from Tc(0) to Tc(15) are preset as clutch torque settings, and the motor rotation angles when the clutch torque matches each of Tc(0) to Tc(15) are shown as θ(0) to θ(15). Tc(0) is the clutch torque value when the piston 30 moves forward and the multiple outer clutch plates 201 and multiple inner clutch plates 202 begin to press against each other, and θ(0) corresponding to Tc(0) is the initial value of the transmission torque increase start angle, which is the initial value of the 0 point (transmission torque increase start angle) of the motor rotation angle in the initial state. This information of the transmission torque increase start angle initial value is stored in the storage unit 812 and used in the correction process to correct the transmission torque increase start angle. Tc(15) is a value equivalent to the rated torque of the friction clutch 20.

[0089] Figure 13(b) shows the measurement results obtained in the second stage of processing. In the second stage, the motor 4 is controlled so that the motor rotation angle matches each of θ(0) to θ(15) obtained in the first stage, and the motor torque when the motor rotation angle matches each of θ(0) to θ(15) is stored as Tm(0) to Tm(15). Then, by associating Tc(0) to Tc(15) with Tm(0) to Tm(15), correspondence information showing the relationship between clutch torque and motor torque is obtained.

[0090] In this embodiment, i is a natural number greater than or equal to 1, and Tc(1) to Tc(15) are generalized as T(i), θ(1) to θ(15) are generalized as θ(i), and Tm(1) to Tm(15) are generalized as Tm(i). In this embodiment, there are 16 sample points for clutch torque, and the maximum value of i is 15, but the number of sample points for clutch torque is not limited to this, and should be at least 1. However, it is preferable to have multiple sample points for clutch torque, and it is even more preferable to have, for example, 4 or more points.

[0091] Figure 14 is a graph showing the relationship between clutch torque and motor torque obtained as correspondence information, with the horizontal axis representing clutch torque and the vertical axis representing motor torque. The black dots in the graph of Figure 14 represent the coordinate points (Tc(i), Tm(i)). As shown in this graph, clutch torque and motor torque are approximately directly proportional, but due to variations in the characteristics of the motor 4 and the sliding resistance of each part in the mechanism 10A, for example, the relationship is not perfectly proportional, and the ratio of Tc(i) to Tm(i) fluctuates depending on the motor rotation angle. Furthermore, the relationship between clutch torque and motor torque also differs depending on the individual drive force transmission device 10 that is manufactured. In this embodiment, the control device 81 uses the correspondence information between clutch torque and motor torque to control the motor 4, thereby enabling the transmission of appropriate driving force according to the vehicle state from the input rotating member to the output rotating member with high precision, and improving the accuracy of the transmitted torque.

[0092] In this embodiment, the control device 81 measures the motor torque while rotating the motor 4 in the forward direction in the initial state, and stores the motor angle when the motor torque reaches a predetermined reference torque as the initial value of the provisional reference angle in the storage unit 812. The reference torque is set in a linear region in which the motor torque increases at a substantially constant rate as the motor 4 rotates. This process is performed, for example, between the first and second stages of the process for generating corresponding information, and the motor 4 is rotated in the forward direction until the clutch torque becomes greater than the maximum value of the motor torque (Tm(15)) in the second stage.

[0093] In this embodiment, as in the first embodiment, the control device 81 performs a correction operation to correct the zero point (the angle at which the transmission torque starts to rise) while the drive force transmission device 10 is mounted on the vehicle 1. In this embodiment, in addition to correcting the zero point, the control device 81 also corrects the relationship information showing the relationship between the motor rotation angle and the motor torque. The information of the initial value of the provisional reference angle stored in the storage unit 812 in the initial state is used in these correction processes.

[0094] Figure 15 is a graph showing an example of the change in motor rotation angle during the correction operation of this embodiment. In this graph, the horizontal axis is the time axis and the vertical axis is the motor rotation angle. After the vehicle 1 stops, the control device 81 rotates the motor 4 in the positive direction to press the friction clutch 20, causing the mechanism 10A to perform a pressing operation that brings the multiple outer clutch plates 201 and the multiple inner clutch plates 202 into contact with each other. In Figure 15, the start time of the pressing operation is indicated by t0. In the pressing operation, similar to the pressing step of the first embodiment, the friction clutch 20 is pressed with a pressing force such that a portion of the lubricating oil L contained in the friction material 202d attached to the inner clutch plate 202 is squeezed out by compression.

[0095] In the correction operation, the control device 81 generates multiple instances of a gradual increase state in which the motor torque gradually increases as the motor 4 rotates in the forward direction, and multiple instances of a gradual decrease state in which the motor torque generated by the motor 4 gradually decreases as the motor 4 rotates in the reverse direction. In the example shown in Figure 15, three gradual increase states and three gradual decrease states are generated. In Figure 15, the start times of the first gradual increase state, the first gradual decrease state, the second gradual increase state, the second gradual decrease state, the third gradual increase state, the third gradual decrease state, and the end time of the third gradual decrease state are indicated by t1 to t7, respectively. The occurrence times of each gradual increase state (t2-t1, t4-t3, t6-t5) and each gradual decrease state (t3-t2, t5-t4, t7-t6) are common.

[0096] In the gradual increase state, the control device 81 rotates the motor 4 in the forward direction at a slower speed than during the pressing operation while measuring the motor current. In the gradual decrease state, the control device 81 rotates the motor 4 in the reverse direction at a slower speed than during the pressing operation while measuring the motor current.

[0097] The control device 81 performs correction processing of related information and correction processing of the transmission torque increase start angle by the following processes 1 to 8. The process of the first step is to acquire the motor angle when the motor torque becomes the above reference torque when the motor 4 rotates in the positive direction during the pressing operation as a provisional reference angle. In Figure 15, this provisional reference angle is shown as a white dot.

[0098] Furthermore, when determining the initial value of the provisional reference angle and the provisional reference angle, an averaging process may be performed in the same manner as the calculation of the averaged motor rotation angle described in the first embodiment. That is, a predetermined range with a width of ±ΔT relative to the reference torque may be set, and the motor rotation angles sampled during the period from the lower limit to the upper limit of this predetermined range may be averaged to obtain the initial value of the provisional reference angle and the provisional reference angle.

[0099] The second step involves calculating the reference angles θr(1) to θr(15) based on the provisional reference angle obtained in the first step, using the following equation (6). In equation (6), the reference angles θr(1) to θr(15) are expressed as θr(i) (1≦i≦15).

number

[0100] The third step involves rotating the motor 4 in the forward and reverse directions while measuring the motor rotation angle during multiple (three in this embodiment) increasing and decreasing states, and measuring the motor torque when the motor rotation angle is θr(1) to θr(15). In Figure 15, θr(1) to θr(15) are shown on the vertical axis of the graph, and the coordinate points for when the motor rotation angle is θr(1) to θr(15) in the increasing and decreasing states are shown as black circles. Hereinafter, the reference motor torque, which is the measurement result of the motor torque when the motor rotation angle is θr(1) to θr(15), will be referred to as Tmr(1) to Tmr(15).

[0101] The fourth step involves averaging the values ​​of Tmr(1) to Tmr(15) in the first, second, and third increasing states and the values ​​of Tmr(1) to Tmr(15) in the decreasing state for each of θr(1) to θr(15). Specifically, the control device 81 averages Tmr(1) in the first increasing state and Tmr(1) in the first decreasing state to obtain Tmr1(1), and averages Tmr(2) in the first increasing state and Tmr(2) in the first decreasing state to obtain Tmr1(2). This process is also performed for Tmr(3) to Tmr(15) to obtain their respective average values, Tmr1(1) to Tmr1(15). Furthermore, the control device 81 performs the same process for the second and third increasing and decreasing states, and calculates the average values ​​of the reference motor torques for the second increasing and decreasing states, Tmr2(1) to Tmr2(15), and the average values ​​of the reference motor torques for the third increasing and decreasing states, Tmr3(1) to Tmr3(15).

[0102] Figure 16 is a graph showing an example of the relationship between the reference angles θr(1) to θr(15) and the average values ​​of the reference motor torques for the first, second, and third increasing and decreasing states, respectively: Tmr1(1) to Tmr1(15), Tmr2(1) to Tmr2(15), and Tmr3(1) to Tmr3(15). In this graph, the characteristic line showing the relationship between the motor rotation angle and motor torque in the initial state is shown as a solid line, the characteristic line showing the relationship between the motor rotation angle and the average values ​​of the reference motor torques Tmr1(1) to Tmr1(15) for the first increasing and decreasing states is shown as a dashed line, the characteristic line showing the relationship between the motor rotation angle and the average values ​​of the reference motor torques Tmr2(1) to Tmr2(15) for the second increasing and decreasing states is shown as a dashed line, and the characteristic line showing the relationship between the motor rotation angle and the average values ​​of the reference motor torques Tmr3(1) to Tmr3(15) for the third increasing and decreasing states is shown as a dashed line.

[0103] As shown in Figure 16, the more the friction material 202d wears or compresses, the slower the rise of motor torque relative to the motor rotation angle becomes, and after the rise in motor torque, the rate of increase of motor torque relative to the motor rotation angle becomes larger.

[0104] The fifth step involves averaging the average values ​​of the reference motor torques in the first, second, and third increasing and decreasing states, respectively, for each of θr(1) to θr(15), Tmr1(1) to Tmr1(15), Tmr2(1) to Tmr2(15), and Tmr3(1) to Tmr3(15), along the vertical axis of the graph shown in Figure 16. Specifically, the control device 81 averages Tmr1(1), Tmr2(1), and Tmr3(1) for θr(1) to obtain Tmravg(1), and averages Tmr1(2), Tmr2(2), and Tmr3(2) for θr(2) to obtain Tmravg(2). This process is also performed for θr(3) to θr(15) to obtain their respective average values, Tmravg(1) to Tmravg(15). In other words, in this embodiment, the measurement results in the increasing state and the measurement results in the decreasing state are averaged, and then the measurement results from multiple increases and decreases are averaged to obtain Tmravg(1) to Tmravg(15).

[0105] Alternatively, Tmravg(1) to Tmravg(15), obtained by averaging Tmr1(1) to Tmr1(15), Tmr2(1) to Tmr2(15), and Tmr3(1) to Tmr3(15), may be temperature-corrected using the estimated temperature of the friction clutch 20. In this case, for example, a temperature coefficient corresponding to the estimated temperature of the lubricating oil L is multiplied by Tmravg(1) to Tmravg(15) to calculate new temperature-corrected Tmravg(1) to Tmravg(15).

[0106] Figure 17 is a graph showing an example of the relationship between θr(1)~θr(15) and Tmravg(1)~Tmravg(15). The control device 81 stores the relationship between θr(1)~θr(15) and Tmravg(1)~Tmravg(15) as a θTm map showing the relationship between motor rotation angle and motor torque. In the following sixth step, the θTm map is referenced by linear interpolation between the coordinate points of the graph shown by the black circles.

[0107] The sixth step involves applying the Tm(1) to Tm(15) stored in the initial state to the θTm map to determine the corresponding reference angles θm(1) to θm(15). This provides a motor rotation angle corresponding to the motor torque, taking into account wear of the friction clutch 20 due to the use of the drive force transmission device 10. θm(1) to θm(15) are acquired values ​​obtained from the measurement results of the motor rotation angle and motor torque in a single correction process performed by the control device 81. The control device 81 may control the mechanism 10A during vehicle 1's operation after restart based on the relationship between Tm(1) to Tm(15) and θm(1) to θm(15) obtained in the sixth step, but in this embodiment, the seventh step is performed further.

[0108] The processing in the seventh step involves averaging the current values ​​(acquired values) of the conforming reference angles θm(1) to θm(15) obtained in the immediately preceding sixth step with the conforming reference angles θm(1) to θm(15) obtained in the sixth step during the correction processing performed after at least one engine stop in the past, to obtain the average conforming reference angle, which is the conforming average motor angle θmavr(1) to θmavr(15). This is then stored in the storage unit 812 as relational information showing the relationship between Tm(1) to Tm(15) and θmavr(1) to θmavr(15).

[0109] In this way, the control device 81 reflects the average value obtained by averaging the acquired values ​​from multiple correction processes into the relational information. The number of past correction processes to be reflected in the relational information is not particularly limited, but for example, it can be two. In this case, the average value obtained by averaging the acquired values ​​from three correction processes will be reflected in the relational information.

[0110] Furthermore, in the processing of the seventh step, the control device 81, for each of the current values ​​of the conforming reference angles θm(1) to θm(15), modifies the current acquired values ​​of the conforming reference angles θm(1) to θm(15) to fit within a predetermined limit range if the acquired value obtained by one correction process exceeds a predetermined limit range compared to the conforming average motor angles θmavr(1) to θmavr(15) of the related information before the correction process. This limiting process for the conforming reference angles θm(1) to θm(15) is a process to suppress the reflection of abnormal values ​​in the related information caused by accidental events, such as foreign objects getting stuck in the spline engagement portion 210 that the outer clutch plate 201 engages with, or the spline engagement portion 220 that the inner clutch plate 202 engages with. This limit range is set to a value of such magnitude that the limiting process is not performed under normal circumstances when no accidental events occur.

[0111] The eighth step is a process to correct the transmission torque increase start angle. In this embodiment, based on the processing results of the first to sixth steps, one of the conforming reference angles θm(1) to θm(15) is used as the rotation angle measurement value, θ(0) obtained in the initial state is used as the initial value of the transmission torque increase start angle, and one of θ(0) to θ(15) obtained in the initial state is used as the initial rotation angle to correct the transmission torque increase start angle. However, the rotation angle measurement value and the initial rotation angle value must correspond to one common motor torque (for example, θm(12)) among the motor torques Tm(0) to Tm(15) obtained in the second step of the process that generates correspondence information in the initial state. The rotation angle measurement value is, for example, θm(12), and the rotation angle initial value is, for example, θ(12). However, it is not limited to this, and the rotation angle measurement value and the rotation angle initial value may be θm(11), θ(11), or θm(13), θ(13), respectively.

[0112] In the eighth step, the torque increase start angle is calculated using the following equation (7), with i being a natural number, as described above.

number

number

[0113] Thus, the control device 81 determines the transmission torque increase start angle by subtracting a difference value corresponding to the difference between the initial rotation angle and the initial transmission torque increase start angle from the rotation angle measurement value. This difference value is "(θ(i)-θ(0))" in equation (7) and "K3(θ(i)-θ(0))" in equation (8).

[0114] When the control device 81 disengages the clutch mechanism 2, it sets the rotation angle of the motor 4 to 0 point (the angle at which the transmitted torque starts to increase) and positions the piston 30 at the touch point. When the control device 81 changes the clutch mechanism 2 from the disengaged state to the engaged state, it rotates the motor 4 in the forward direction from the 0 point position.

[0115] Incidentally, the control device 81 performs a correction process, including the processing of the first to eighth steps, when the start switch 113 is pressed and the engine stops. However, if, for example, the internal gap increases due to wear of the friction clutch 20, or if the lubricating oil L is hot and its viscosity is low, it may take longer than usual for each of the increasing and decreasing states to occur, and it may not be possible to generate the specified number of increasing and decreasing states (for example, 3 times) before the power supply to the control device 81 is cut off. In such cases, the control device 81 reduces the number of occurrences of the increasing and decreasing states to less than the specified number, and in the processing of the fourth step, it averages the Tmr(1) to Tmr(15) for the increasing state and Tmr(1) to Tmr(15) for the decreasing state for the actual number of occurrences. In other words, if the number of occurrences of each of the increasing and decreasing states is n times (n is a natural number of 1 or more) which is less than the specified number due to the time limit, the control device 81 averages the measurement results of each of the n increasing and decreasing states and corrects the related information. In the fifth step, the average values ​​of the reference motor torques for n gradually increasing and gradually decreasing states are averaged. For example, if the actual number of times the gradually increasing and gradually decreasing states occur is 2 (n=2), Tmr1(i) and Tmr2(i) are averaged to obtain Tmravg(i). If the actual number of times the gradually increasing and gradually decreasing states occur is 1 (n=1), Tmr1(i) is used as is to obtain Tmravg(i).

[0116] Figure 18 is a flowchart showing an example of the procedure executed by the control unit 811 of the control device 81 for this process. In this flowchart, "reciprocating motion" refers to the operation of controlling the motor 4 to generate one increasing and decreasing state, and "number of reciprocating motions" refers to the number of times the reciprocating motion is completed. "Specified number of times" refers to the number of times the increasing and decreasing states occur in a normal correction process without circumstances such as high viscosity of lubricating oil L (3 times in this embodiment). The "upper limit of reciprocating motion time" is a time limit value that includes a certain amount of buffer time, calculated by subtracting the time required for the correction process calculation from the time during which power is supplied to the control device 81 after the engine stops.

[0117] The control unit 811 repeatedly executes the flowchart process shown in Figure 18 at a predetermined control cycle. In this flowchart process, the control unit 811 determines whether the number of round trips has reached a predetermined number (step S1), and if the number of round trips has reached a predetermined number, it executes the processes of steps 1 to 8 (step S2). On the other hand, if the number of round trips has not reached a predetermined number, it determines whether the elapsed time since engine stoppage has exceeded the upper limit of round trip operation time (step S3). If the result of the determination in step S3 is Yes, it determines whether at least one round trip operation has been completed, that is, whether the number of round trips is 1 or more (step S4). If the result of the determination in step S4 is Yes, it executes the process of step S2. If the result of the determination in step S3 or step D4 is No, it continues the round trip operation (step S5). Thus, in this embodiment, the control unit 811 of the control device 81 executes the processes of steps 1 to 8 on the condition that at least one round trip operation has been completed.

[0118] (Effects of the second embodiment) As with the first embodiment described above, it is possible to suppress a decrease in responsiveness even when the friction clutch 20 is worn. Furthermore, according to this embodiment, relational information showing the relationship between the motor rotation angle and the motor torque is stored in the region where the motor rotation angle is greater than the zero point, and this relational information is corrected, so it is possible to adjust the torque transmitted by the friction clutch 20 with greater precision. Moreover, according to this embodiment, the control device 81 uses the correspondence information between the clutch torque and the motor torque together with the relational information to control the motor 4, so that the magnitude of the driving force to be transmitted by the friction clutch 20 according to the driving state of the vehicle 1 is determined as the clutch torque, the motor torque corresponding to the determined clutch torque is determined by referring to the correspondence information, and the motor rotation angle corresponding to the determined motor torque is determined by referring to the relational information, so that an appropriate driving force according to the driving state of the vehicle 1 can be transmitted by the friction clutch 20. When referring to the relational information, the control device 81 interpolates a plurality of operating points represented by (Tm(i),θmavr(i)) to determine the motor torque corresponding to the clutch torque.

[0119] (Note) The present invention has been described above based on embodiments, but these embodiments do not limit the invention as defined in the claims. It should also be noted that not all combinations of features described in the embodiments are necessarily essential for solving the problem of the invention. Furthermore, the present invention can be implemented by omitting some components, or by adding or substituting components, without departing from its spirit.

[0120] The configuration of a vehicle equipped with the power transmission device of the present invention is not limited to that shown in Figure 1, and the power transmission device of the present invention can be used in vehicles having various drivetrain configurations. For example, a power distribution device including the power transmission device of the present invention may be used on the front wheel side of a two-wheel drive vehicle that distributes the driving force of a drive source to the left and right front wheels. In this case, the power distribution device 100 is positioned between the left and right front wheels 121 and 122 instead of the front differential 13. Furthermore, a power distribution device including the power transmission device of the present invention may be positioned to correspond to either or both of the drive source on the front wheel side and the drive source on the rear wheel side of a four-wheel drive vehicle that has drive sources on both the front and rear wheel sides.

[0121] Furthermore, although the above embodiment describes a case where the power transmission device functions as a differential limiting device, the invention is not limited to this. For example, the power transmission device of the present invention may be placed between the rear differential and the propeller shaft, and the power transmission device may be used to adjust the power transmitted to the rear wheels. Alternatively, the power transmission device of the present invention may be placed between the rear differential and either the left or right rear wheel. [Explanation of Symbols]

[0122] 1…Four-wheel drive vehicle 10…Drive force transmission device 20… Friction clutch 201...Outer clutch plate (friction component) 202... Inner clutch plate (friction component) 202d…Friction material 3…Pressing mechanism 30... Piston 4…motor 81...Control device 812...Storage section L…Lubricating oil

Claims

1. A drive force transmission device comprising a friction clutch having multiple friction members, a pressing mechanism that presses the friction clutch with a piston, a mechanism having a motor that operates the pressing mechanism, and a control device that controls the mechanism, wherein the drive force of a vehicle is transmitted by the friction clutch, The pressing mechanism is configured such that when the motor rotates in the forward direction, the piston advances toward the friction clutch, and when the motor rotates in the reverse direction, the piston retracts toward the friction clutch. The control device stores in a memory unit the transmission torque increase start angle, which is the rotation angle of the motor at which the transmission torque of the friction clutch begins to increase due to the motor's rotation in the forward direction from a state in which the piston is not pressing against the friction clutch, and performs a correction process to correct the transmission torque increase start angle. The storage unit stores an initial rotation angle value, which is the rotation angle of the motor when the motor torque generated by the motor is a predetermined value in the initial state after the manufacture of the mechanism. The correction process includes measuring the rotation angle of the motor when the motor torque generated by the motor is at a predetermined value while the vehicle is stopped, and correcting the transmission torque increase start angle based on the measured rotation angle value and the initial rotation angle value. Power transmission device.

2. The predetermined value is the value of the motor torque generated by the motor when the motor rotates further in the forward direction from the angle at which the transmission torque starts to increase, thereby increasing the pressing force of the friction clutch by the piston. The drive force transmission device according to claim 1.

3. The storage unit stores the initial value of the transmission torque increase start angle, which is the initial value of the transmission torque increase start angle in the initial state. In the correction process, the control device subtracts a difference value corresponding to the difference between the initial rotation angle and the initial transmission torque increase start angle from the measured rotation angle to determine the transmission torque increase start angle. The drive force transmission device according to claim 2.

4. The control device stores relationship information in the storage unit that shows the relationship between the rotation angle of the motor and the motor torque. The correction process includes measuring the rotation angle and motor torque of the motor when the vehicle is stopped, and correcting the related information based on the measurement results. The drive force transmission device according to claim 1.

5. In the correction process, the control device measures the rotation angle and motor torque of the motor in a gradually increasing state where the motor torque generated by the motor gradually increases as the motor rotates in the forward direction, and in a gradually decreasing state where the motor torque generated by the motor gradually decreases as the motor rotates in the reverse direction, and corrects the relationship information by averaging the measurement results in the gradually increasing state and the measurement results in the gradually decreasing state. The drive force transmission device according to claim 4.

6. The control device, in the correction process, generates the increasing state and the decreasing state multiple times, and corrects the related information by averaging the measurement results of each of the multiple increasing states and the decreasing states. The drive force transmission device according to claim 5.

7. In the correction process, if the number of occurrences of the increasing state and the decreasing state is less than a specified number due to the time limit (n times, where n is a natural number of 1 or more), the control device corrects the related information by averaging the measurement results of the n increasing states and decreasing states. The drive force transmission device according to claim 6.

8. The control device modifies the acquired values ​​obtained from the measurement results of the motor's rotation angle and motor torque during a single correction process if the acquired values ​​have changed significantly beyond a predetermined limit range compared to the relationship information before the single correction process, so that the acquired values ​​fall within the limit range. The drive force transmission device according to any one of claims 4 to 7.

9. The control device reflects the average value obtained by averaging the acquired values ​​from each of the multiple correction processes into the relational information. The drive force transmission device according to claim 8.

10. The storage unit stores correspondence information indicating the relationship between the clutch torque transmitted by the friction clutch and the motor torque generated by the motor. The control device controls the motor based on the relational information and the corresponding information. The drive force transmission device according to claim 4.

11. The control device, before generating the increasing and decreasing states, rotates the motor in the forward direction to press the friction clutch, causing the mechanism to perform a pressing operation that brings the plurality of friction members into contact with each other. The drive force transmission device according to any one of claims 5 to 7.

Images