Driving force transmission device

Abstract

The present application relates to a drive force transmission device. The drive force transmission device includes: a multiplate clutch that transmits a drive force using a frictional force generated between a plurality of clutch plates; a housing (5) that houses the multiplate clutch; a piston that presses the multiplate clutch using a hydraulic pressure of working oil supplied to a hydraulic chamber provided in the housing (5); a hydraulic unit (6) configured to supply the working oil to the hydraulic chamber; and a control device (7) configured to control the hydraulic unit (6), the control device (7) being configured to correct a control amount of the hydraulic unit (6) in accordance with a result of estimation based on a temperature of operation of the hydraulic unit (6).

Description

TECHNICAL FIELD

[0001] The present application relates to a drive force transmission device that is installed on a vehicle to transmit a drive force of a drive source of the vehicle to a wheel side. BACKGROUND

[0002] In some four-wheel drive vehicles that include, for example, front wheels as main drive wheels and rear wheels as auxiliary drive wheels, a drive force of a drive source such as an engine is transmitted to the rear wheels via a drive force transmission device that includes a multi-plate clutch. In such a drive force transmission device, lubricating oil is used to lubricate frictional sliding between clutch plates of the multi-plate clutch in order to suppress wear of the clutch plates and heating of the clutch plates.

[0003] Japanese Unexamined Patent Application Publication No. 2009-97662 (JP 2009-97662 A) describes a drive force transmission device that is configured to estimate a temperature of a torque coupling that includes a multi-plate clutch based on an outside air temperature, correct a control target value of the torque coupling based on the estimated temperature, and correct an outside air temperature value used to estimate the temperature of the torque coupling based on a time elapsed from a stop of an engine to a restart of the engine and a temperature of engine coolant in order to reduce a possibility that a transmitted drive force increases to an unnecessarily large value due to an increase in viscosity of lubricating oil, particularly at low temperatures. SUMMARY

[0004] In recent years, due to advances in electronic control of vehicles such as traction control for suppressing free rotation of wheels and stability control for suppressing side slip during cornering, high precision is required to control a drive force to be transmitted to auxiliary drive wheels of a four-wheel drive vehicle compared to the related art.

[0005] The present application provides a drive force transmission device that is capable of improving precision of a drive force transmitted by a multi-plate clutch.

[0006] One aspect of the present application relates to a drive force transmission device that includes a multi-plate clutch that transmits a drive force using a frictional force generated between a plurality of clutch plates, a housing that houses the multi-plate clutch, a piston that presses the multi-plate clutch using a hydraulic pressure of working oil supplied to a hydraulic chamber provided in the housing, a hydraulic unit configured to supply the working oil to the hydraulic chamber, and a control device configured to control the hydraulic unit. The control device corrects a control amount of the hydraulic unit in accordance with a result of temperature estimation based on an operation of the hydraulic unit.

[0007] With the drive force transmission apparatus according to the present application, it is possible to improve the accuracy of drive force transmitted through the plurality of clutches. BRIEF DESCRIPTION OF DRAWINGS

[0008] Features, advantages, and technical and industrial significance of exemplary embodiments of the present application will be described below with reference to the accompanying drawings, wherein the same reference numerals in different drawings denote the same element, and wherein:

[0009] Figure 1 is a schematic view showing an example of a schematic configuration of a four-wheel drive vehicle on which a drive apparatus according to an embodiment of the present application is mounted;

[0010] Figure 2 is a cross-sectional view showing an example of a configuration of the drive apparatus;

[0011] Figure 3A shows an appearance of an example of the hydraulic unit;

[0012] Figure 3B shows an example of the hydraulic unit as seen along an arrow A in Figure 3A , which shows an internal structure of the hydraulic unit with a broken line;

[0013] Figure 4 is a cross-sectional view showing an example of a configuration of the first electromagnetic valve;

[0014] Figure 5A is a perspective view showing the fourth housing member;

[0015] Figure 5B is a perspective view showing the fifth housing member;

[0016] Figure 6 is a graph showing a first temperature characteristic;

[0017] Figure 7 is a graph showing a second temperature characteristic;

[0018] Figure 8 is a graph showing a third temperature characteristic; and

[0019] Figure 9 is a flowchart showing a specific example of a process executed by the control apparatus according to the second embodiment. DETAILED DESCRIPTION

[0020] The first embodiment of the present application will be described with reference to Figures 1 to 8 The embodiments described below are provided as specific examples of embodying the present application. The technical scope of the present application is not limited to the embodiments.

[0021] Figure 1is a schematic view showing an example of a schematic configuration of a four-wheel drive vehicle on which a drive device according to a first embodiment of the present application is mounted. The four-wheel drive vehicle 1 includes right and left front wheels 101 and 102 as main drive wheels that are driven by a driving force of an engine 11 as a main drive source, and right and left rear wheels 103 and 104 as auxiliary drive wheels that are driven by a drive device 10 including a drive motor 2 as an auxiliary drive source. A wheel speed sensor is attached to each of the right and left front wheels 101 and 102 and the right and left rear wheels 103 and 104.

[0022] The driving force of the engine 11 is transmitted from a transmission 12 to a differential device 13, and the driving force is distributed from the differential device 13 to the right and left front wheels 101 and 102 via right and left drive shafts 141 and 142, respectively. The driving force is transmitted from the drive device 10 to the right and left rear wheels 103 and 104 via right and left drive shafts 151 and 152, respectively. The main drive source can be a high-output electric motor, and can be a so-called hybrid type in which an engine and a high-output electric motor are combined with each other.

[0023] The drive device 10 includes the drive motor 2, a reduction mechanism 3 that reduces the rotational speed of an output shaft 20 of the drive motor 2, a driving force distribution mechanism 4 that distributes and outputs the driving force input from the drive motor 2 via the reduction mechanism 3, a housing 5 that houses these components, a hydraulic unit 6 that supplies working oil to the driving force distribution mechanism 4, and a control device 7 that controls the drive motor 2 and the hydraulic unit 6. Among them, the driving force distribution mechanism 4, the housing 5, the hydraulic unit 6, and the control device 7 constitute a driving force transmission device 100 that transmits the driving force of the drive motor 2 to the right and left drive shafts 151 and 152.

[0024] Figure 2 is a cross-sectional view showing an example of a configuration of the drive device 10. Figure 2 The left side of corresponds to the left side of the four-wheel drive vehicle 1 in the vehicle left-right direction. Figure 2 The right side of corresponds to the right side of the four-wheel drive vehicle 1 in the vehicle left-right direction. The housing 5 includes first to fifth housing members 51 to 55 that are formed by die casting and made of an aluminum alloy. The housing members 51 to 55 are fixed to each other by a plurality of bolts. The housing 5 is fixed to a vehicle body of the four-wheel drive vehicle 1.

[0025] The drive motor 2 is an electric motor to which a motor current is supplied from the control device 7, and includes an output shaft 20 provided in a hollow tube shape, a rotor 21 that rotates together with the output shaft 20, a stator 22 provided at an outer periphery of the rotor 21, and a rotation sensor 23 that detects a rotation of the output shaft 20. The rotor 21 includes a rotor core 211 and a plurality of permanent magnets 212 fixed to the rotor core 211. The stator 22 includes a stator core 221 and windings 222 for a plurality of phases wound around the stator core 221. A first output rotary member 41 of the drive force distribution mechanism 4 is inserted through an inside of the output shaft 20. For example, a three-phase alternating current (AC) motor current is supplied from the control device 7 to the windings 222 for the plurality of phases to rotate the rotor 21 relative to the stator 22 with a torque matching a magnitude of the motor current.

[0026] The reduction mechanism 3 is configured to include a tubular pinion 31 that is fitted to an outer periphery of an end portion of the output shaft 20 of the drive motor 2, a reduction gear 32 that includes a large-diameter gear portion 321 and a small-diameter gear portion 322, and a ring gear 33 that is engaged with the small-diameter gear portion 322. The pinion 31 is spline-fitted to the output shaft 20 to rotate together with the output shaft 20. A gear portion 311 provided at an outer periphery of the pinion 31 is engaged with the large-diameter gear portion 321 of the reduction gear 32. A drive force of the drive motor 2 is input from the ring gear 33 to an input rotary member 40 of the drive force distribution mechanism 4.

[0027] The drive force distribution mechanism 4 includes the input rotary member 40 that receives the drive force of the drive motor 2 via the reduction mechanism 3, a first output rotary member 41 and a second output rotary member 42 that are provided coaxially with the input rotary member 40 so as to be capable of relative rotation, a first multi-plate clutch 43 that is provided between the input rotary member 40 and the first output rotary member 41, a second multi-plate clutch 44 that is provided between the input rotary member 40 and the second output rotary member 42, a first pressing mechanism 45 that presses the first multi-plate clutch 43, and a second pressing mechanism 46 that presses the second multi-plate clutch 44.

[0028] Further, in the present embodiment, the first clutch hub 47 is interposed between the first multi-plate clutch 43 and the first output rotation member 41, and the second clutch hub 48 is interposed between the second multi-plate clutch 44 and the second output rotation member 42. The first output rotation member 41 is splined to the first clutch hub 47 to rotate together with the first clutch hub 47. The second output rotation member 42 is splined to the second clutch hub 48 to rotate together with the second clutch hub 48. A thrust bearing 49 is provided between the first clutch hub 47 and the second clutch hub 48.

[0029] A plurality of first output clutch plates 432 can be splined to the first output rotation member 41 with the first clutch hub 47 omitted. A plurality of second output clutch plates 442 can be splined to the second output rotation member 42 with the second clutch hub 48 omitted.

[0030] The input rotation member 40, the first output rotation member 41, and the second output rotation member 42 are rotatable relative to each other about a rotation axis O extending in the vehicle left-right direction. Each of the first multi-plate clutch 43 and the second multi-plate clutch 44 is a wet multi-plate clutch in which frictional sliding between clutch plates to be discussed later is lubricated with lubricating oil sealed in the housing 5. Rolling bearings 551 to 559 that smooth rotation of the respective parts and sealing members 561 to 563 that suppress leakage of lubricating oil and entry of foreign matter are provided at appropriate positions in the drive device 10. In the following, a direction parallel to the rotation axis O will be referred to as an "axial direction".

[0031] The input rotation member 40 includes a first clutch drum 401 provided at an outer periphery of the first clutch hub 47, a second clutch drum 402 provided at an outer periphery of the second clutch hub 48, a center plate 403 provided between the first clutch drum 401 and the second clutch drum 402, and a plurality of bolts 404. The bolts 404 couple the first clutch drum 401, the second clutch drum 402, and the center plate 403 so that the first clutch drum 401, the second clutch drum 402, and the center plate 403 are not rotatable relative to each other and fix these components to the ring gear 33. One of the bolts 404 is shown in Figure 2

[0032] ​The first multiplate clutch 43 includes a plurality of first input clutch plates 431 that rotate together with the first clutch drum 401 and a plurality of first output clutch plates 432 that rotate together with the first clutch hub 47. The first input clutch plates 431 and the first output clutch plates 432 are alternately arranged along the axial direction. The first input clutch plates 431 are movable in the axial direction and are not relatively rotatable with respect to the first clutch drum 401 by being splined to the first clutch drum 401. The first output clutch plates 432 are movable in the axial direction and are not relatively rotatable with respect to the first clutch hub 47 by being splined to the first clutch hub 47.

[0033] The first multiplate clutch 43 transmits a driving force from the first clutch drum 401 to the first clutch hub 47 using a frictional force generated between the first input clutch plates 431 and the first output clutch plates 432. Frictional sliding between the first input clutch plates 431 and the first output clutch plates 432 is lubricated with lubricating oil introduced through a plurality of lubricating oil introduction holes 470 provided in the first clutch hub 47.

[0034] The second multiplate clutch 44 includes a plurality of second input clutch plates 441 that rotate together with the second clutch drum 402 and a plurality of second output clutch plates 442 that rotate together with the second clutch hub 48. The second input clutch plates 441 and the second output clutch plates 442 are alternately arranged along the axial direction. The second input clutch plates 441 are movable in the axial direction and are not relatively rotatable with respect to the second clutch drum 402 by being splined to the second clutch drum 402. The second output clutch plates 442 are movable in the axial direction and are not relatively rotatable with respect to the second clutch hub 48 by being splined to the second clutch hub 48.

[0035] The second multiplate clutch 44 transmits a driving force from the second clutch drum 402 to the second clutch hub 48 using a frictional force generated between the second input clutch plates 441 and the second output clutch plates 442. Frictional sliding between the second input clutch plates 441 and the second output clutch plates 442 is lubricated with lubricating oil introduced through a plurality of lubricating oil introduction holes 480 provided in the second clutch hub 48.

[0036] The first pressing mechanism 45 includes a ring-shaped piston 451 that receives hydraulic pressure supplied from the hydraulic unit 6; a thrust roller bearing 452 that is provided side by side with the piston 451 in the axial direction; a pressing member 453 that receives a pressing force of the piston 451 via the thrust roller bearing 452; a pressing plate 454 that is provided on the inner side of the first clutch drum 401; and a return spring 455 that contacts the pressing member 453.

[0037] A portion of the piston 451 in the axial direction is housed in a first hydraulic chamber 550 that is provided in a ring shape in the fifth housing member 55. The piston 451 presses the first multiple disk clutch 43 using the pressure of the working oil supplied to the first hydraulic chamber 550 from the hydraulic unit 6. The pressing member 453 integrally includes a ring-shaped portion 453a provided in a circular ring shape and a plurality of columnar pressing protrusions 453b that project in the axial direction from the ring-shaped portion 453a toward the first multiple disk clutch 43. The pressing protrusions 453b are inserted through the respective through holes 401a provided in the first clutch drum 401. The distal end portions of the pressing protrusions 453b contact the pressing plate 454. The return spring 455 contacts the ring-shaped portion 453a to bias (i.e., push) the pressing member 453 toward the fifth housing member 55.

[0038] The second pressing mechanism 46 includes a ring-shaped piston 461 that receives hydraulic pressure supplied from the hydraulic unit 6; a thrust roller bearing 462 that is provided side by side with the piston 461 in the axial direction; a pressing member 463 that receives a pressing force of the piston 461 via the thrust roller bearing 462; a pressing plate 464 that is provided on the inner side of the second clutch drum 402; and a return spring 465 that contacts the pressing member 463.

[0039] A portion of the piston 461 in the axial direction is housed in a second hydraulic chamber 540 that is provided in a ring shape in the fourth housing member 54. The piston 461 presses the second multiple disk clutch 44 using the pressure of the working oil supplied to the second hydraulic chamber 540 from the hydraulic unit 6. The pressing member 463 integrally includes a ring-shaped portion 463a provided in a circular ring shape and a plurality of columnar pressing protrusions 463b that project in the axial direction from the ring-shaped portion 463a toward the second multiple disk clutch 44. The pressing protrusions 463b are inserted through the respective through holes 402a provided in the second clutch drum 402. The distal end portions of the pressing protrusions 463b contact the pressing plate 464. The return spring 465 contacts the ring-shaped portion 463a to bias (i.e., push) the pressing member 463 toward the fourth housing member 54.

[0040] Figure 3A The appearance of an example of the hydraulic unit 6 is shown. Figure 3B The hydraulic unit 6 as seen along the arrow A in Figure 3A , and Figure 3B The internal structure of this hydraulic unit 6 is shown in broken lines. The hydraulic unit 6 includes: a housing member 61; an electric motor 62 that drives a pump, the electric motor 62 generating a torque that matches the current supplied from the control device 7; a hydraulic pump 63 that is rotationally driven by the electric motor 62; a safety valve 64; a first electromagnetic valve 65 and a second electromagnetic valve 66; and a connector 67 for electrical connection with the control device 7.

[0041] The housing member 61 is formed by die casting and made of an aluminum alloy, and is fixed to the fourth housing member 54 by bolts (not shown). The electric motor 62 is a three-phase motor to which currents for U-phase, V-phase, and W-phase are supplied from the control device 7, and generates a torque of a size that matches the supplied phase currents to drive the hydraulic pump 63. In addition, the electric motor 62 includes a rotation sensor. The control device 7 is able to detect the rotational speed of the electric motor 62 using a signal from the rotation sensor.

[0042] The hydraulic pump 63 sucks working oil from the reservoir 60 (see Figure 2 ) provided in the housing member 61 to discharge the working oil. In the present embodiment, the hydraulic pump 63 is an external gear pump, and includes a drive gear 631 that rotates using the torque of the electric motor 62, and a driven gear 632 that meshes with the drive gear 631 to rotate, as shown in Figure 3B In Figure 3B , the direction of rotation of the drive gear 631 is indicated by an arrow B. The hydraulic pump 63 is not limited to an external gear pump, and can be, for example, an internal gear pump or a vane pump. The safety valve 64 is a fixed throttle valve that returns a portion of the discharged working oil to the reservoir 60.

[0043] The first electromagnetic valve 65 is provided in a path that extends from the hydraulic pump 63 to the first hydraulic chamber 550. The second electromagnetic valve 66 is provided in a path that extends from the hydraulic pump 63 to the second hydraulic chamber 540. The first electromagnetic valve 65 is a pressure control valve that adjusts the pressure of the working oil supplied to the first hydraulic chamber 550. The second electromagnetic valve 66 is a pressure control valve that adjusts the pressure of the working oil supplied to the second hydraulic chamber 540. The valve opening degree of each of the first electromagnetic valve 65 and the second electromagnetic valve 66 varies according to the current supplied from the control device 7.

[0044] Figure 4is a cross-sectional view showing an example of the configuration of the first electromagnetic valve 65. The second electromagnetic valve 66 is also similarly configured. The first electromagnetic valve 65 includes: a tubular sleeve 81 housed in a housing hole 610 provided in the case member 61; a spool 82 as a valve element that is movable in an axial direction in a valve hole 810 provided in the sleeve 81; and an electromagnetic solenoid 83 that protrudes from the case member 61. In Figure 4 In the figure, the center axis C of the valve hole 810 is indicated by alternate long and short dashes, the state in which the spool 82 is moved to one side in the axial direction is shown on the lower side of the figure with respect to the center axis C, and the state in which the spool 82 is moved to the other side in the axial direction is shown on the upper side of the figure with respect to the center axis C.

[0045] The sleeve 81 is provided with: a supply port 811 to which working oil discharged from the hydraulic pump 63 is supplied; an output port 812 from which working oil is output to the first hydraulic chamber 550; and a discharge port 813 connected to the reservoir 60. The spool 82 is provided with first to fourth convex regions 821 to 824 that face the inner peripheral surface of the valve hole 810 via minute clearances. The end portion of the sleeve 81 on the opposite side of the electromagnetic solenoid 83 is closed by a cap 84. A coil spring 85 is provided in a compressed state between the cap 84 and the spool 82.

[0046] The electromagnetic solenoid 83 includes: an electromagnetic coil 831 that generates a magnetic force using electric current supplied from the control device 7; a plunger 832 that presses the spool 82 toward the cap 84 using the magnetic force of the electromagnetic coil 831; a solenoid housing 833 that houses the electromagnetic coil 831 and the plunger 832; and a shaft 834 interposed between the plunger 832 and the spool 82. The spool 82 is positioned at a position at which the pressing force of the plunger 832 received via the shaft 834 and the spring force received from the coil spring 85 are balanced with each other.

[0047] When the electric current supplied to the electromagnetic coil 831 changes, the position of the spool 82 in the valve hole 810 changes to change the area of the flow path for working oil between the supply port 811 and the output port 812 and the area of the flow path for working oil between the output port 812 and the discharge port 813. Thus, the pressure of the working oil output from the output port 812 changes. In other words, the control device 7 is able to control the pressure of the working oil in the first hydraulic chamber 550 by increasing and decreasing the electric current supplied to the first electromagnetic valve 65. Similarly, the control device 7 is able to control the pressure of the working oil in the second hydraulic chamber 540 by increasing and decreasing the electric current supplied to the second electromagnetic valve 66.

[0048] When the working oil is supplied from the hydraulic unit 6 to the first hydraulic chamber 550, the piston 451 of the first pressing mechanism 45 presses the first multi-plate clutch 43 toward the center plate 403 with a pressing force that matches the pressure of the working oil. The driving force (clutch torque) transmitted from the input rotary member 40 to the first output rotary member 41 through the first multi-plate clutch 43 varies in accordance with the pressure of the working oil supplied to the first hydraulic chamber 550.

[0049] When the working oil is supplied from the hydraulic unit 6 to the second hydraulic chamber 540, the piston 461 of the second pressing mechanism 46 presses the second multi-plate clutch 44 toward the center plate 403 with a pressing force that matches the pressure of the working oil. The driving force (clutch torque) transmitted from the input rotary member 40 to the second output rotary member 42 through the second multi-plate clutch 44 varies in accordance with the pressure of the working oil supplied to the second hydraulic chamber 540.

[0050] Figure 5A is a perspective view illustrating the fourth housing member 54. Figure 5B is a perspective view illustrating the fifth housing member 55. Figure 5A The right side of Figure 5A corresponds to the front side in the vehicle front-rear direction. Figure 5B The left side of Figure 5B corresponds to the front side in the vehicle front-rear direction. Figure 5A and Figure 5B The upper side of Figure 5A and Figure 5B corresponds to the upper side in the vertical direction.

[0051] In Figure 5A and Figure 5B , the first oil passage 501 and the second oil passage 502 are illustrated with dotted lines, in which the working oil is guided from the hydraulic unit 6 to the first hydraulic chamber 550 through the first oil passage 501, and the working oil is guided from the hydraulic unit 6 to the second hydraulic chamber 540 through the second oil passage 502. In Figure 2 , the first oil passage 501 and the second oil passage 502 are schematically illustrated as cross-hatched lines.

[0052] The first oil passage 501 includes a first oil hole 541 and a second oil hole 542 provided in the fourth housing member 54, and a third oil hole 551 and a fourth oil hole 552 provided in the fifth housing member 55. The first oil hole 541 has an introduction port 501a coupled to the hydraulic unit 6, and working oil output from the first electromagnetic valve 65 is introduced through the introduction port 501a, and the first oil hole 541 extends from the introduction port 501a toward the front side of the vehicle. The second oil hole 542 communicates with the first oil hole 541, and extends toward the right side of the vehicle. The third oil hole 551 communicates with the second oil hole 542, further extends toward the right side of the vehicle, and communicates with a lower end portion of the fourth oil hole 552. The fourth oil hole 552 communicates with the third oil hole 551, and extends upward. An upper end portion of the fourth oil hole 552 serves as a discharge port 501b that is open in the first hydraulic chamber 550.

[0053] The second oil passage 502 includes a fifth oil hole 543 to a seventh oil hole 545 provided in the fourth housing member 54. The fifth oil hole 543 has an introduction port 502a coupled to the hydraulic unit 6, and working oil output from the second electromagnetic valve 66 is introduced through the introduction port 502a, and the fifth oil hole 543 extends from the introduction port 502a toward the front side of the vehicle. The sixth oil hole 544 intersects the fifth oil hole 543 and the seventh oil hole 545, and extends in the vehicle left-right direction. The seventh oil hole 545 extends in the vehicle front-rear direction in parallel to the fifth oil hole 543. An end portion at the front side in the vehicle front-rear direction of the seventh oil hole 545 serves as a discharge port 502b that is open in the second hydraulic chamber 540. First end portions of the sixth oil hole 544 and the seventh oil hole 545 are respectively closed by spherical plug bodies 572 and 573 (see Figure 2 ).

[0054] The lubricating oil that lubricates the first and second multiple disk clutches 43 and 44 and the working oil that operates the first and second squeeze mechanisms 45 and 46 are separated so as not to mix with each other. As shown in Figure 5A the lower end portion of the fourth housing member 54 serves as an oil reservoir 546 in which the lubricating oil accumulates, and the first oil hole 541, the second oil hole 542, and the fifth oil hole 543 to the seventh oil hole 545 are provided in the vicinity of the oil reservoir 546. Further, the first oil hole 541, the second oil hole 542, and the fifth oil hole 543 to the seventh oil hole 545 are provided below the oil surface of the lubricating oil in the stationary time when the rotation of the input rotation member 40 and the first and second output rotation members 41 and 42 is stopped. Therefore, when the temperature of the lubricating oil is raised by the frictional heat generated by the first and second multiple disk clutches 43 and 44, the heat is conducted through the fourth housing member 54 to raise the temperature of the working oil.

[0055] Generally, the pressure of the working oil output from the output port of the electromagnetic valve including the valve element (spool) operated by the electromagnetic solenoid fluctuates depending on the temperature of the working oil even when the current supplied to the electromagnetic solenoid and the pressure of the working oil supplied to the supply port of the electromagnetic valve are constant. Therefore, it is desirable to correct the control amount of the hydraulic unit 6 depending on the temperature of the working oil. In the present embodiment, the control device 7 performs temperature estimation based on the operation of the hydraulic unit 6, and corrects the control amount of the hydraulic unit 6 based on the result of the temperature estimation. Specifically, the amount of current supplied to the first electromagnetic valve 65 and the second electromagnetic valve 66 is corrected. The control process performed by the control device 7 will be described in detail below.

[0056] Figure 6 is a graph representing a first temperature characteristic indicating a relationship between the exciting current Ie for the electromagnetic coil 831 of the electromagnetic solenoid 83 of the first electromagnetic valve 65 and the extrusion force P generated by the piston 451 of the first extrusion mechanism 45 in a case where the pressure of the working oil supplied to the supply port 811 is constant and the temperature Te1 of the working oil is -40°C, 0°C, 40°C, and 100°C. As indicated in Figure 6 , the extrusion force P increases approximately in proportion to the exciting current Ie, and the extrusion force P is greater in a case where the temperature Te1 of the working oil is low than in a case where the temperature Te1 of the working oil is high.

[0057] Figure 7 is a graph representing a second temperature characteristic indicating a relationship between the rotational speed V of the electric motor 62 and the temperature Te1 of the working oil in a case where the phase current Ip supplied to the electric motor 62 is 10 A, 15 A, and 20 A. The higher the temperature Te1 of the working oil, the lower the viscous drag (i.e., the viscous resistance) of the working oil, and the lower the load for driving the hydraulic pump 63. Therefore, even when the phase current is constant, the higher the temperature Te1 of the working oil, the higher the rotational speed V of the electric motor 62. Therefore, the control device 7 is able to estimate the temperature Te1 of the working oil based on the magnitude of the phase current and the rotational speed V of the electric motor 62.

[0058] The control device 7 stores the first temperature characteristic indicated in Figure 6 and the second temperature characteristic indicated in Figure 7 as mapping information in a non-volatile memory. The control device 7 estimates the temperature Te1 of the working oil based on the second temperature characteristic, and corrects the exciting current Ie based on the estimated temperature Te1 and the first temperature characteristic so that the necessary extrusion force P can be obtained. Therefore, fluctuation in the extrusion force P due to a change in the temperature Te1 of the working oil can be suppressed. In addition to the correction of the exciting current Ie, the phase current of the electric motor 62 can also be corrected as the control amount for the hydraulic unit 6.

[0059] Furthermore, in the present embodiment, the control device 7 controls the hydraulic unit 6 so as to suppress fluctuations in the clutch torque, that is, fluctuations in the torque transmitted through the first multi-plate clutch 43 and the torque transmitted through the second multi-plate clutch 44, caused by changes in the temperature of the lubricating oil. For this control, the control device 7 stores in the nonvolatile memory Figure 8 The third temperature characteristic indicated in is used as mapping information.

[0060] Figure 8 It is a graph showing a third temperature characteristic, which indicates the relationship between the temperature Te2 of the lubricating oil and the clutch torque Tq for each rotational speed difference △N per unit time between the input rotating member 40 and the first output rotating member 41 when the squeezing force P of the piston 451 is constant for the first multi-plate clutch 43. Figure 8 The relationship between the lubricating oil temperature Te2 and the clutch torque Tq is shown for rotational speed differences ΔN of 2 rpm, 10 rpm, 50 rpm, 100 rpm, and 300 rpm. The control device 7 stores a third temperature characteristic for multiple values ​​of the pressing force P. The rotational speed of the input rotating member 40 can be calculated based on the rotational speed of the drive motor 2 and the reduction ratio of the reduction mechanism 3. For example, the rotational speed of the first output rotating member 41 can be calculated based on the rotational speed of the right rear wheel 103.

[0061] like Figure 8 As indicated in FIG. , clutch torque Tq increases as lubricating oil temperature Te2 decreases and as rotational speed difference ΔN increases. As previously discussed, heat from the lubricating oil is transferred to the operating oil, and therefore, it is assumed that there is no significant deviation between lubricating oil temperature Te2 and operating oil temperature Te1. By referring to the third temperature characteristic, while considering that lubricating oil temperature Te2 and operating oil temperature Te1 are consistent with each other, and controlling hydraulic unit 6 so that the driving force to be transmitted to first output rotating member 41 matches the clutch torque of first multi-plate clutch 43, the accuracy of the driving force transmitted to first output rotating member 41 via first multi-plate clutch 43 can be improved. Furthermore, control device 7 can also improve the accuracy of the driving force transmitted to second output rotating member 42 via second multi-plate clutch 44 in a similar manner.

[0062] The functions and effects of the first embodiment will now be described. In the first embodiment described above, the control device 7 performs temperature estimation based on the operation of the hydraulic unit 6 and corrects the control amount of the hydraulic unit 6 based on the results of the temperature estimation. Consequently, it is possible to improve the accuracy of the driving force transmitted to the first output rotary member 41 via the first multi-plate clutch 43 and the driving force transmitted to the second output rotary member 42 via the second multi-plate clutch 44.

[0063] Next, a second embodiment of the application will be described. In the first embodiment, the hydraulic unit 6 is controlled while it is assumed that the temperature Te2 of the lubricating oil and the temperature Tei of the working oil agree with each other as an example. However, in the second embodiment, the temperature of the working oil is estimated when the engine 11 is started, that is, when the ignition is turned on, and the temperature of the lubricating oil is estimated based on the estimated temperature of the working oil. It is assumed that the degree of agreement between the temperature of the lubricating oil and the temperature of the working oil is particularly high when the engine 11 is started, that is, when the ignition is turned on. Thereafter, the temperature of the lubricating oil in each of the first and second multi-plate clutches 43 and 44 is estimated based on the heat generation amount (that is, the amount of heat generated) and the heat release amount (that is, the amount of heat released) of the corresponding one of the first and second multi-plate clutches 43 and 44.

[0064] Figure 9 is a flowchart showing a specific example of a process performed by the control device 7 according to the second embodiment. The control device 7 repeatedly performs the process shown in the flowchart in each predetermined control cycle (for example, 5 ms). Although Figure 9 A process for controlling the driving force transmitted through the first multi-plate clutch 43 is shown, but a similar process is performed also for the second multi-plate clutch 44.

[0065] In the process shown in the flowchart, the control device 7 first determines whether the engine 11 has just been started, more specifically, whether the time from the time when the ignition is turned on is equal to or shorter than a predetermined time (step S1). In the case where the result of the determination indicates that the engine 11 has just been started (S1: YES), the temperature of the working oil is estimated based on the operation of the hydraulic unit 6 in the same manner as in the first embodiment (step S2).

[0066] Next, the control device 7 calculates the elapsed time from the last stop until the engine 11 is restarted (hereinafter referred to as "engine-off time") (step S3), and calculates an estimated value of the temperature of the lubricating oil in the first multi-plate clutch 43 (hereinafter referred to as "estimated lubricating oil temperature value") based on the temperature of the working oil estimated in step S2 and the engine-off time calculated in step S3 (step S4). Specifically, when the engine-off time is longer than a predetermined value, the temperature of the working oil estimated in step S2 is used as the estimated lubricating oil temperature value without change, while when the engine-off time is equal to or shorter than the predetermined value, the estimated lubricating oil temperature value is calculated based on the temperature of the working oil at the time of the last stop of the engine 11 and taking into account the engine-off time and the outside air temperature.

[0067] In the case where the result of the determination in step S1 indicates that the engine 11 is not just started (S1: No), the control device 7 calculates the heat generation amount of the first multi-plate clutch 43 based on the driving force transmitted through the first multi-plate clutch 43 and the rotational speed difference value ΔN (step S5), and then estimates the temperature of the working oil based on the operation of the hydraulic unit 6 (step S6). Next, the control device 7 calculates the estimated lubricating oil temperature value using the following expression (1) (step S7).

[0068] Tmp = Tmp1 + K1 x H - K2 x (Tmp1 - Te1)... (1)

[0069] In this expression, Tmp is the estimated lubricating oil temperature value in the current control cycle, Tmp1 is the estimated lubricating oil temperature value in the previous control cycle, K1 and K2 are each a conversion coefficient, H is the heat generation amount calculated in step S5, and Te1 is the temperature of the working oil estimated in step S6.

[0070] In the above expression (1), the term K2 x (Tmp1 - Te1) indicates the heat release amount. That is, the lubricating oil is contained in the casing 5, and the working oil is present in the first and second oil paths 501 and 502 provided in the casing 5 and in the reservoir 60 contained in the housing member 61 outside the casing 5. Therefore, the working oil is more easily affected by the outside air temperature and the air received when the vehicle is running than the lubricating oil, and the heat release amount of the lubricating oil can be estimated by multiplying the difference obtained by subtracting the temperature of the working oil from the temperature of the lubricating oil by a predetermined coefficient.

[0071] Next, the control device 7 stores the estimated lubricating oil temperature value calculated in step S4 or step S7 as a variable for use in the calculation in the next control cycle (step S8). Further, the control device 7 controls the hydraulic unit 6 by referring to the first to third temperature characteristics as in the first embodiment based on the estimated lubricating oil temperature value calculated in step S4 or step S7 (step S9).

[0072] With the second embodiment, it is possible to further improve the accuracy of the driving force transmitted to the first output rotational member 41 through the first multi-plate clutch 43 and the driving force transmitted to the second output rotational member 42 through the second multi-plate clutch 44.

[0073] While the present application has been described on the basis of the embodiments, the embodiments do not limit the present application. It should be noted that not all combinations of the features described with respect to the embodiments are necessary to solve the problems of the present application.

[0074] The present application can be modified as appropriate without departing from the scope of the present application. For example, in the above-described embodiment, the front wheels 101 and 102 are driven by the engine, and the rear wheels 103 and 104 are driven by the drive device 10. However, the configuration of the vehicle is not limited thereto, and the drive device 10 according to the present application is applicable to vehicles having various configurations. For example, the present application is also applicable to a four-wheel drive vehicle in which the driving force of the engine is distributed to the right and left front wheels and the right and left rear wheels.

[0075] In the above-described embodiment, the drive device 10 includes two multi-plate clutches (the first multi-plate clutch 43 and the second multi-plate clutch 44). However, the driving force transmitted via one multi-plate clutch can be distributed to the left and right wheels by a differential device.

[0076] In the above-described embodiment, the housing member 61 of the hydraulic unit 6 is separate from the housing 5, and the hydraulic unit 6 is provided outside the housing 5. However, the present application is not limited thereto. For example, some or all of the first solenoid valve 65 and the second solenoid valve 66, the hydraulic pump 63, and the electric motor 62 can be housed in the housing 5.

Claims

1. A drive force transmission device characterized by Comprising: a multi-plate clutch that transmits driving force using frictional force generated between a plurality of clutch plates; a housing (5) that houses the multi-plate clutch; a piston that presses the multi-plate clutch using hydraulic pressure of working oil supplied to a hydraulic chamber provided in the housing (5); a hydraulic unit (6) configured to supply the working oil to the hydraulic chamber; and a control device (7) configured to control the hydraulic unit (6), the control device (7) being configured to correct a control amount for the hydraulic unit (6) in accordance with a result of estimation based on a temperature of the hydraulic unit (6) in operation, wherein the hydraulic unit (6) includes a hydraulic pump (63), an electric motor (62) that drives the hydraulic pump (63), and a solenoid valve that adjusts hydraulic pressure of the working oil supplied from the hydraulic pump (63) to the hydraulic chamber; the solenoid valve includes a solenoid and a valve element, wherein the valve element is operated by the solenoid; and the control device (7) is configured to correct at least an amount of current supplied to the solenoid as the control amount, wherein frictional sliding of the clutch plates of the multi-plate clutch is lubricated by lubricating oil sealed in the housing (5); and the housing (5) is provided with an oil passage that guides the working oil from the hydraulic unit (6) to the hydraulic chamber, wherein the control device (7) is configured to control the hydraulic unit (6) by: estimating a temperature of the working oil based on operation of the hydraulic unit (6); calculating a period of engine stop from a last time of engine stop until a restart of the engine; estimating a temperature of the lubricating oil from the temperature of the working oil and the period of engine stop, and referencing a temperature characteristic that indicates a relationship between the temperature of the lubricating oil and driving force transmitted by the multi-plate clutch. the control device (7) is configured to estimate the temperature of the lubricating oil from the temperature of the working oil estimated based on operation of the hydraulic unit (6) at the time of start, and thereafter estimate the temperature of the lubricating oil based on an amount of heat generation and an amount of heat release of the multi-plate clutch.

2. The driving force transmission device according to claim 1, characterized by, ​

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