Control device of all-wheel drive vehicle

Abstract

To provide a control device of an all-wheel drive vehicle of a torque split type, the control device being capable of promoting initial running of a differential (hypoid gear).SOLUTION: When it is determined that initial running of a rear differential 47 including a hypoid gear 47a has not been completed and a vehicle operation state satisfies a predetermined initial running promotion control execution condition, a TCU 70 performs initial running promotion control of increasing a fastening power of a transfer clutch 41.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a control system for an all-wheel drive vehicle. [Background technology]

[0002] Conventionally, for example, all-wheel drive (AWD) vehicles (or four-wheel drive (4WD) vehicles) have been put to practical use, which have driving wheels that are directly driven by an engine and driven wheels that are connected to the engine via a transfer clutch, and are configured so that torque distribution to the driven wheels can be adjusted by controlling the fastening force of the transfer clutch according to the driving conditions, etc.

[0003] In such a coupling-type all-wheel drive vehicle using a transfer clutch (torque-split all-wheel drive vehicle), the torque distribution ratio between the driving wheels and the driven wheels can be varied between 100 (driving wheels) : 0 to 50:50 (driven wheels) by adjusting (releasing to engaging) the engagement pressure (engagement force) of the transfer clutch. For example, in the case of a FF base, the front / rear torque distribution ratio can be varied between 100 (front) : (rear) 0 to 50:50.

[0004] In addition, torque (driving force) generated by an engine or the like is converted by a transmission and then transmitted to the drive wheels of the vehicle via a differential. The differential includes hypoid gears and the like, and reduces the rotation speed of the drive shaft, and when the vehicle turns, distributes the driving force to the inner and outer wheels while allowing a speed difference (rotation difference) between the inner wheel (inner wheel for turning) and the outer wheel (outer wheel for turning), thereby improving the maneuverability of the vehicle (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2003-28279 A Summary of the Invention [Problem to be solved by the invention]

[0006] Incidentally, the gears (particularly hypoid gears) that make up the differential have not been broken in or settled into their tooth surfaces when they are new, such as when they are assembled or shipped from the factory. Therefore, after starting to use the vehicle, until the initial break-in of the differential (particularly the hypoid gear tooth surfaces) is completed (until initial habituation occurs), the temperature rise due to heat generation in the differential (particularly the gear sliding parts) is large, and if high-load operating conditions (such as towing) continue continuously, the temperature is likely to become high.

[0007] Furthermore, when the differential (hypoid gear) gets hot, and the oil also gets hot, the oil viscosity decreases and the oil film breaks down, causing abnormal wear and scoring on the gear teeth. It can also lead to premature deterioration of the oil, which reduces lubricating performance, and high temperature deterioration of plastic and rubber parts, shortening their lifespan.

[0008] On the other hand, for example, in a torque-split all-wheel drive vehicle based on a front-wheel drive vehicle, there is a problem that the initial break-in of the rear differential (hypoid gear) is difficult to progress because torque distribution to the rear side (rear wheels) is eliminated (or reduced) during steady-state driving, etc.

[0009] The present invention has been made to solve the above problems, and has an object to provide a control device for an all-wheel drive vehicle that is capable of promoting the initial break-in of the differential (hypoid gear) in a torque split type all-wheel drive vehicle. [Means for solving the problem]

[0010] A control device for an all-wheel drive vehicle according to one embodiment of the present invention comprises a transfer clutch that adjusts the torque transmitted to the slave drive wheels depending on the clamping force, a differential including a hypoid gear and distributing the torque transmitted via the transfer clutch to the left and right wheels while allowing a rotational difference between the left and right wheels, and a control unit that controls the clamping force of the transfer clutch based on the driving state of the vehicle, and is characterized in that when the control unit determines that the initial break-in of the differential has not been completed and that the driving state of the vehicle satisfies predetermined conditions for executing the initial break-in promotion control, it executes initial break-in promotion control to increase the clamping force of the transfer clutch.

[0011] According to an aspect of the present invention, the control device for an all-wheel drive vehicle increases the fastening force of the transfer clutch when the initial break-in of the differential including the hypoid gear is not yet completed and the vehicle operating state is determined to satisfy a predetermined initial break-in promotion control execution condition, thereby increasing the torque input (transmitted) to the differential (hypoid gear) and promoting the initial break-in of the differential (hypoid gear). Effect of the Invention

[0012] According to the present invention, it is possible to promote the initial break-in of the differential (hypoid gear) in a torque split type all-wheel drive vehicle. [Brief description of the drawings]

[0013] [Figure 1] 1 is a block diagram showing a configuration of a control device for an all-wheel drive vehicle according to an embodiment, and an all-wheel drive vehicle equipped with the control device; [Diagram 2] 5 is a flowchart showing a processing procedure of initial break-in promotion control performed by a control device for an all-wheel drive vehicle according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In addition, unless otherwise necessary, the same reference numerals will be used for the same or corresponding parts in the drawings. In addition, the same reference numerals will be used for the same elements in each drawing, and duplicated explanations will be omitted.

[0015] First, the configuration of a control device for an all-wheel drive vehicle according to an embodiment will be described with reference to Fig. 1. Fig. 1 is a block diagram showing the configuration of a control device for an all-wheel drive vehicle and an all-wheel drive vehicle (AWD vehicle) 1 equipped with the control device. The AWD vehicle 1 according to this embodiment is an AWD vehicle equipped with a continuously variable transmission (CVT) 30. In particular, the AWD vehicle 1 is a FF (Front engine Front drive) based torque split AWD vehicle.

[0016] The engine 20 may be of any type, but may be, for example, a horizontally opposed, direct-injection, four-cylinder gasoline engine. In the engine 20, air taken in through an air cleaner (not shown) is throttled by an electronically controlled throttle valve (hereinafter, also simply referred to as a "throttle valve") 85 provided in an intake pipe, passes through an intake manifold, and is taken in by each cylinder formed in the engine 20. Here, the amount of air taken in through the air cleaner is detected by an air flow meter. Furthermore, the throttle valve 85 is provided with a throttle opening sensor 83 that detects the opening of the throttle valve 85. An injector that injects fuel is attached to each cylinder. Also, each cylinder is provided with an ignition plug that ignites the mixture, and an igniter-integrated coil that applies high voltage to the ignition plug. In each cylinder of the engine 20, the mixture of the taken in air and the fuel injected by the injector is ignited by the ignition plug and combusted. Exhaust gas after combustion is discharged through an exhaust pipe.

[0017] In addition to the air flow meter and throttle opening sensor 83 described above, a cam angle sensor 81 for identifying the cylinders of the engine 20 is attached near the camshaft of the engine 20. Also, a crank angle sensor 82 for detecting the position of the crankshaft is attached near the crankshaft of the engine 20. These sensors are connected to an engine control unit (hereinafter referred to as "ECU") 80, which will be described later. Also connected to the ECU 80 are various sensors, such as an accelerator opening sensor 84 for detecting the amount of depression of the accelerator pedal, i.e., the opening degree of the accelerator pedal, and a water temperature sensor for detecting the temperature of the cooling water for the engine 20.

[0018] An output shaft (crankshaft) 21 of the engine 20 is connected to a torque converter 22 having a clutch function and a torque amplification function, and a continuously variable transmission 30 that converts and outputs the driving force from the engine 20 via a forward / reverse switching mechanism 31.

[0019] The torque converter 22 is mainly composed of a pump impeller 23, a turbine runner 24, and a stator 25. The pump impeller 23 connected to the output shaft 21 generates a flow of oil, and the turbine runner 24 arranged opposite the pump impeller 23 receives power from the engine 20 via the oil to drive the output shaft. The stator 25 located between them rectifies the discharge flow (return) from the turbine runner 24 and returns it to the pump impeller 23, thereby generating a torque amplification effect.

[0020] The torque converter 22 also has a lock-up clutch 26 that directly connects the input and output. When the lock-up clutch 26 is not engaged (non-lock-up state), the torque converter 22 amplifies the driving force of the engine 20 and transmits it to the continuously variable transmission 30, and when the lock-up clutch 26 is engaged (lock-up state), the torque converter 22 directly transmits the driving force of the engine 20 to the continuously variable transmission 30. The rotation speed (turbine rotation speed) of the turbine runner 24 that constitutes the torque converter 22 is detected by a turbine rotation sensor 79. The detected turbine rotation speed is output to a transmission control unit (hereinafter referred to as "TCU") 70, which will be described later.

[0021] The forward / reverse switching mechanism 31 switches between normal and reverse rotation of the drive wheels (forward and reverse of the AWD vehicle 1). The forward / reverse switching mechanism 31 mainly includes a double pinion type planetary gear train (not shown), a forward clutch, and a reverse brake. The forward / reverse switching mechanism 31 is configured to be able to switch the transmission path of the engine output by controlling the respective states of the forward clutch and the reverse brake.

[0022] The continuously variable transmission 30 has a primary shaft 32 connected to the turbine shaft of the torque converter 22 via a forward / reverse switching mechanism 31, and a secondary shaft 37 arranged in parallel to the primary shaft 32. A primary pulley 34 is provided on the primary shaft 32. The primary pulley 34 has a fixed sheave 34a joined to the primary shaft 32 and a movable sheave 34b opposed to the fixed sheave 34a and attached to the primary shaft 32 so as to be slidable in the axial direction of the primary shaft 32, and is configured to be able to change the cone surface spacing of the sheaves 34a and 34b, i.e., the pulley groove width. On the other hand, a secondary pulley 35 is provided on the secondary shaft 37. The secondary pulley 35 has a fixed sheave 35a joined to the secondary shaft 37 and a movable sheave 35b opposed to the fixed sheave 35a and attached to the secondary shaft 37 so as to be slidable in the axial direction of the secondary shaft 37, and is configured to be able to change the pulley groove width.

[0023] A chain 36 for transmitting a driving force is stretched between the primary pulley 34 and the secondary pulley 35. The gear ratio is continuously changed by changing the groove width of the primary pulley 34 and the secondary pulley 35 to change the ratio (pulley ratio) of the winding diameter of the chain 36 to each of the pulleys 34, 35. Here, if the winding diameter of the chain 36 around the primary pulley 34 is Rp and the winding diameter of the chain 36 around the secondary pulley 35 is Rs, the gear ratio i is expressed as i=Rs / Rp. Therefore, the gear ratio i can be calculated by dividing the primary pulley rotation speed Np by the secondary pulley rotation speed Ns (i=Np / Ns).

[0024] Here, a hydraulic chamber 34c is formed in the primary pulley 34 (movable sheave 34b). Meanwhile, a hydraulic chamber 35c is formed in the secondary pulley 35 (movable sheave 35b). The groove widths of the primary pulley 34 and the secondary pulley 35 are set and changed by adjusting the primary hydraulic pressure introduced into the hydraulic chamber 34c of the primary pulley 34 and the secondary hydraulic pressure introduced into the hydraulic chamber 35c of the secondary pulley 35.

[0025] The secondary shaft 37 of the continuously variable transmission 30 is connected to a counter shaft 39 via a reduction gear 38 consisting of a pair of gears (reduction drive gear, reduction driven gear), and the driving force converted by the continuously variable transmission 30 is transmitted to the counter shaft 39 via the reduction gear 38. The counter shaft 39 is connected to a front drive shaft 43 via a counter gear 40 consisting of a pair of gears (counter drive gear, counter driven gear). The driving force transmitted to the counter shaft 39 is transmitted to a front differential (hereinafter also referred to as "front diff") 44 via the counter gear 40 and the front drive shaft 43.

[0026] The front differential 44 is, for example, a bevel gear type differential device to which the driving force is input via a hypoid gear 44a. The driving force from the front differential 44 is transmitted to the left front wheel 10FL via a left front wheel drive shaft 45L and to the right front wheel 10FR via a right front wheel drive shaft 45R.

[0027] Meanwhile, a transfer clutch 41 for adjusting the driving force transmitted to the rear differential 47 is provided behind the counter gear 40 (counter drive gear) on the counter shaft 39. The fastening force (i.e., torque distribution rate to the rear wheels (subordinate drive wheels) 10RL, 10RR) of the transfer clutch 41 is controlled according to the driving state of the four wheels (e.g., slip state of the front wheels 10FL, 10FR), engine torque, etc. Thus, the driving force transmitted to the counter shaft 39 is distributed according to the fastening force of the transfer clutch 41, and is also transmitted to the rear wheels 10RL, 10RR. That is, the transfer clutch 41 adjusts the torque transmitted to the rear wheels 10RL, 10RR according to the fastening force.

[0028] More specifically, the rear end of the countershaft 39 is connected to a propeller shaft 46 extending toward the rear of the vehicle via a transfer gear 42 consisting of a pair of gears (transfer drive gear, transfer driven gear). Therefore, the driving force transmitted to the countershaft 39 and adjusted (distributed) by the transfer clutch 41 is transmitted from the transfer gear 42 (transfer driven gear) via the propeller shaft 46 to a rear differential (hereinafter also referred to as "rear differential") 47.

[0029] The rear differential 47 is, for example, a bevel gear type differential device to which driving force is input via a hypoid gear 47a. A left rear wheel drive shaft 48L and a right rear wheel drive shaft 48R are connected to the rear differential 47. Driving force from the rear differential 47 is transmitted to the left rear wheel 10RL via the left rear wheel drive shaft 48L and to the right rear wheel 10RR via the right rear wheel drive shaft 48R. That is, the rear differential 47 includes the hypoid gear 47a, and distributes torque transmitted via the transfer clutch 41 to the left and right rear wheels 10RL and 10RR while allowing a rotation difference between the left and right rear wheels 10RL and 10RR.

[0030] With the driving force transmission system of the powertrain configured as described above, for example, when the select lever is operated to the D range, the engine output is input to the primary shaft 32 of the continuously variable transmission 30. The driving force converted by the continuously variable transmission 30 is output from the secondary shaft 37 and transmitted to the front drive shaft 43 via the reduction gear 38, the counter shaft 39, and the counter gear 40. The driving force is then distributed to the left and right by the front differential 44, and transmitted to the left and right front wheels 10FL, 10FR. Therefore, the left and right front wheels 10FL, 10FR are always driven when the AWD vehicle 1 is in a traveling state.

[0031] Meanwhile, a portion of the driving force transmitted to the countershaft 39 is transmitted to a propeller shaft 46 via a transfer clutch 41 and a transfer gear 42. When a predetermined clutch torque is applied to the transfer clutch 41, the driving force distributed in accordance with the clutch torque is output to the propeller shaft 46. The driving force is also transmitted to the rear wheels 10RL, 10RR via a rear differential 47. This allows the AWD vehicle 1 to function as a FF-based torque split AWD vehicle.

[0032] Each of the wheels 10FR-10RR (hereinafter, all the wheels 10FR-10RR may be collectively referred to as wheels 10) is provided with a brake 11FR-11RR (hereinafter, all the brakes 11FR-11RR may be collectively referred to as brake 11) for braking the wheels 10FR-10RR. Also, each of the wheels 10FR-10RR is provided with a wheel speed sensor 12FR-12RR (hereinafter, all the wheel speed sensors 12FR-12RR may be collectively referred to as wheel speed sensor 12) for detecting the wheel rotation speed.

[0033] The wheel speed sensor 12 is a non-contact sensor that detects changes in a magnetic field caused by a rotor (gear rotor or magnetic rotor) that rotates together with the wheel 10. For example, a semiconductor type that detects rotor rotation using a Hall element or MR element is preferably used.

[0034] In addition, this AWD vehicle 1 is equipped with a VDC control unit (hereinafter referred to as "VDCU") 50 that prevents skidding and ensures excellent driving stability, for example, when entering a corner at an excessive speed or when the vehicle posture (behavior) becomes unstable due to sudden steering.

[0035] The hydraulic pressure for shifting the continuously variable transmission 30, that is, the above-mentioned primary hydraulic pressure and secondary hydraulic pressure, are controlled by a valve body (control valve) 60. The valve body 60 adjusts the hydraulic pressure discharged from the oil pump 62 by opening and closing an oil passage formed in the valve body 60 using a spool valve and a solenoid valve (electromagnetic valve) that operates the spool valve, and supplies the hydraulic pressure to the hydraulic chamber 34c of the primary pulley 34 and the hydraulic chamber 35c of the secondary pulley 35. Similarly, the valve body 60 adjusts the hydraulic pressure discharged from the oil pump 62 by opening and closing an oil passage formed in the valve body 60 using a spool valve and a solenoid valve (electromagnetic valve) 61 that operates the spool valve, and supplies the hydraulic pressure for engaging / releasing each clutch to the transfer clutch 41. Here, as the solenoid valve 61 that adjusts the hydraulic pressure to be supplied to the transfer clutch 41, for example, a duty solenoid that can control the drive amount according to the duty ratio of the applied voltage is used.

[0036] The shift control of the continuously variable transmission 30 is executed by the TCU 70. That is, the TCU 70 adjusts the hydraulic pressure supplied to the hydraulic chamber 34c of the primary pulley 34 and the hydraulic chamber 35c of the secondary pulley 35 by controlling the drive of a solenoid valve (electromagnetic valve) constituting the above-mentioned valve body 60, thereby changing the gear ratio of the continuously variable transmission 30. Similarly, the TCU 70 adjusts the hydraulic pressure supplied to the transfer clutch 41 by controlling the drive of a solenoid valve 61 constituting the above-mentioned valve body 60, thereby adjusting the distribution ratio of the driving force transmitted to the rear wheels 10RL, 10RR.

[0037] As described above, the shift control of the continuously variable transmission 30 and the engagement / disengagement control (driving force distribution control) of the transfer clutch 41 are executed by the TCU 70. The TCU 70 is connected to the ECU 80, which comprehensively controls the engine 20, the VDCU 50, a meter control unit (hereinafter referred to as "MCU") 90, a driving support device 93, and the like, for example, via a CAN (Controller Area Network) 100 so as to be able to communicate with each other. The CAN 100 is also configured to be able to connect an external diagnostic device 95, for example, via a connector.

[0038] The TCU 70, ECU 80, VDCU 50, MCU 90, and driving assistance device 93 are each configured to include a microprocessor that performs calculations, an EEPROM that stores programs and the like for causing the microprocessor to execute each process, a RAM that stores various data such as calculation results, a backup RAM whose stored contents are maintained by a battery, and an input / output I / F, etc.

[0039] The ECU 80 includes an injector driver that drives the injector, an output circuit that outputs an ignition signal, a motor driver that drives an electric motor that opens and closes an electronically controlled throttle valve 85, and the like.

[0040] The ECU 80 identifies the cylinder from the output of the cam angle sensor 81, and obtains the engine speed from the change in the rotational position of the crankshaft detected by the output of the crank angle sensor 82. The ECU 80 also obtains various information such as the intake air amount, the accelerator pedal opening, the air-fuel ratio of the mixture, and the water temperature based on the detection signals input from the various sensors described above. The ECU 80 then comprehensively controls the engine 20 by controlling the fuel injection amount, the ignition timing, and various devices such as the throttle valve 85 based on the various information obtained. The ECU 80 also obtains the output torque of the engine 20 based on, for example, the intake air amount and the engine speed. The output torque of the engine 20 may be calculated on the TCU 70 side.

[0041] Furthermore, the ECU 80 transmits various types of information, such as the engine speed, engine torque (output torque), accelerator pedal opening, and engine water temperature (cooling water temperature), to the TCU 70 via the CAN 100.

[0042] The VDCU 50 is connected to four wheel speed sensors 12FL-12RR, a steering angle sensor 16, a longitudinal acceleration (longitudinal G) sensor 55, a lateral acceleration (lateral G) sensor 56, and a brake switch 57. As described above, the wheel speed sensors 12FL-12RR detect the rotation of the gears attached to the centers of the wheels 10FL-10RR using a magnetic pickup or the like to detect the rotation of the wheels 10FL-10RR (including the number of rotations of the wheels 10FL-10RR). The longitudinal acceleration sensor 55 detects the longitudinal acceleration (hereinafter simply referred to as "acceleration") acting on the AWD vehicle 1, and the lateral acceleration sensor 56 detects the lateral acceleration acting on the AWD vehicle 1. The steering angle sensor 16 detects the turning angle of the front wheels 10FL, 10FR, which are the steered wheels (i.e., the steering angle of the steering wheel 15), by detecting the rotation angle of the pinion shaft.

[0043] The VDCU 50 drives the brake actuator according to the amount of operation (depression) of the brake pedal to brake the vehicle, and detects the vehicle behavior using various sensors (e.g., the wheel speed sensor 12, the steering angle sensor 16, the acceleration sensors 55, 56, the yaw rate sensor, etc.), and suppresses skidding by automatic pressurization brake control and torque control of the engine 20 to ensure vehicle stability during cornering. That is, the VDCU 50 prevents skidding and ensures excellent driving stability, for example, when the vehicle enters a corner at an overspeed or when the vehicle attitude (behavior) is disturbed due to a sudden steering operation. More specifically, the VDCU 50 detects the vehicle attitude (behavior) using the above sensors, etc., and automatically controls the vehicle according to the driving situation by applying the brakes to the front wheels 10FL, 10FR on the outside of the corner if it determines that the vehicle is oversteering, and by contrast, by determining that the vehicle is understeering, it reduces the engine output and applies the brakes to the rear wheels 10RL, 10RR on the inside of the corner. In addition to the above VDC (side slip prevention) function, the VDCU50 also has an ABS (anti-lock brake) function and a TCS (traction control) function.

[0044] The VDCU 50 transmits the detected wheel speed of each wheel 10 (the number of rotations of each wheel 10), the steering angle, the longitudinal acceleration, the lateral acceleration, and braking information (braking information) to the TCU 70 via the CAN 100.

[0045] The driving support device 93 has a function of detecting the external environment of the vehicle (for example, the driving environment in front of the vehicle) and issuing an alarm for an obstacle ahead and performing automatic braking (automatic braking function / pre-crash braking function).The driving support device 93 also has a function of supporting the driver's driving operation by performing automatic following control (automatic following driving) and warning control for the detected preceding vehicle.

[0046] The driving assistance device 93 processes image data captured by, for example, a stereo camera 94 consisting of a pair of cameras that captures images in front of the vehicle, and detects, for example, the driving environment (external environment) outside the vehicle, such as the conditions of the road, preceding vehicles, obstacles, etc.

[0047] The driving support device 93 processes the image data and detects lanes (driving lanes) based on road dividing lines (white lines) drawn on the road on which the vehicle is traveling. Based on the detected lanes, the driving support device 93 detects, for example, the presence or absence of a curve, the distance to the curve, the radius (curvature) of the curve, and the width of the road. The driving support device 93 also extracts the preceding vehicle from the captured image by edge extraction, pattern recognition processing, etc., and determines the inter-vehicle distance from the preceding vehicle by a triangulation method based on the difference in the position of the preceding vehicle in the left and right captured images, and determines the relative speed (whether the preceding vehicle has decelerated, etc.) from the amount of change from the distance determined in the previous frame.

[0048] Then, the driving support device 93 transmits the detected external environment information to the TCU 70 via the CAN 100. Note that information on the driving route, such as the radius (curvature) of a curve, may be acquired from, for example, a car navigation system.

[0049] The MCU 90 is connected to a touch screen 91 disposed, for example, in a meter visor (combination meter) or on the top of a dashboard. The touch screen 91 includes a display unit 91a (corresponding to a presentation means described in the claims) including a liquid crystal display (LCD) or the like that is a display device that displays the status and various information of the vehicle and the engine 20, and an operation screen, and an operation (input) unit 91b (corresponding to an input receiving means described in the claims) including a touch panel or the like that detects a touch operation (input) by a user (driver, etc.). When the driver, etc. performs a touch operation on the information displayed on the display unit 91a (liquid crystal display), the operation (input) unit 91b (touch panel) detects the touch operation and the operation by the driver, etc. is received.

[0050] In particular, when the MCU 90 receives presentation information transmitted from the TCU 70, it drives the display unit 91a to present (display text, etc.) information, etc., for confirming with the driver whether or not to execute the initial break-in promotion control. Note that voice, etc. may be output at the same time. The MCU 90 also acquires input from the driver, such as an instruction to execute the initial break-in promotion control or an instruction not to execute the initial break-in promotion control, received by the operation (input) unit 91b. Then, the MCU 90 transmits the acquired information to the TCU 70.

[0051] When the hypoid gear 47a or a unit including the hypoid gear 47a (i.e., the rear differential 47) is replaced with a new one, the external diagnostic device 95 transmits reset information to the TCU 70 via the CAN 100 to reset (initialize) the integrated value (sum of products) of the multiplication value of the number of rotations of the hypoid gear 47a since the start of use and the torque input to the hypoid gear 47a.

[0052] For example, when the vehicle dealer replaces the hypoid gear 47a or the rear differential 47 including the hypoid gear 47a with a new one, the integrated value is reset using the external diagnostic device 95. When the TCU 70 receives reset information, the TCU 70 resets (i.e., initializes) the integrated value stored in the memory.

[0053] In addition to the turbine rotation sensor 79 described above, the TCU 70 is connected to an oil temperature sensor 76 that detects the oil temperature of the continuously variable transmission 30, an output shaft rotation sensor 77 that detects the rotation speed of the secondary shaft (output shaft) 37, a range switch 78 that detects the selected position of the shift lever, etc.

[0054] As described above, the TCU 70 receives information such as the wheel speed (the number of rotations of each wheel 10), steering angle, longitudinal acceleration, lateral acceleration, and braking information from the VDCU 50 via the CAN 100, and also receives information such as the engine speed, engine torque (output torque), accelerator pedal opening, and engine water temperature from the ECU 80. The TCU 70 also receives information such as curve curvature and automatic following driving from the driver assistance device 93 via the CAN 100 (note that the information such as the curve curvature may be received from a car navigation system). The TCU 70 also receives information input by the driver from the MCU 90 via the CAN 100. Furthermore, the TCU 70 receives reset information for resetting the integrated value from the external diagnostic device 95 via the CAN 100. Meanwhile, the TCU 70 transmits presentation information (for example, information for confirming with the driver whether or not to execute the initial break-in promotion control) to the MCU 90 via the CAN 100.

[0055] The TCU 70 automatically and steplessly changes the gear ratio according to the driving conditions of the AWD vehicle 1 (e.g., accelerator opening and vehicle speed) in accordance with a shift map. The shift map is stored in an EEPROM or the like in the TCU 70. The TCU 70 also executes transfer clutch control (driving force distribution control) (i.e., controls the fastening force of the transfer clutch 41) based on various information (vehicle driving conditions, etc.) acquired from the various sensors described above. That is, the TCU 70 functions as a control unit as described in the claims.

[0056] In particular, the TCU 70 has a function of promoting the initial break-in of the rear differential 47 (hypoid gear 47a) in a torque split type all-wheel drive vehicle (AWD vehicle) 1. In the TCU 70, this function is realized by a microprocessor executing a program stored in an EEPROM or the like.

[0057] Therefore, the TCU 70 determines whether the initial break-in of the rear differential 47 (hypoid gear 47a) has been completed based on whether the integrated value (Σ(number of rotations of the hypoid gear 47a × input torque), i.e., total energy) of the multiplication of the number of rotations (number of meshes) of the rear differential 47 (hypoid gear 47a) since the start of use and the torque input to the rear differential 47 (hypoid gear 47a) is greater than or equal to a predetermined threshold value.

[0058] That is, the TCU 70 determines that the initial break-in of the rear differential 47 (hypoid gear 47a) is not yet complete when the integrated value (sum of products) of the multiplication value of the number of rotations of the rear differential 47 (hypoid gear 47a) since the start of use and the torque input to the rear differential 47 (hypoid gear 47a) is less than a predetermined threshold value. On the other hand, the TCU 70 determines that the initial break-in of the rear differential 47 (hypoid gear 47a) is complete when the integrated value (sum of products) is equal to or greater than a predetermined threshold value. The predetermined threshold value may be map data (lookup table).

[0059] At this time, the number of rotations (number of meshes) of the rear differential 47 (hypoid gear 47a) can be obtained from, for example, the engine speed, the output shaft speed, or the wheel speed. Also, the torque input to the rear differential 47 (hypoid gear 47a) can be obtained according to the output torque of the engine 20 and the speed ratio (gear ratio) of the continuously variable transmission 30. Note that, for example, the vehicle weight may be taken into consideration when calculating the torque input to the rear differential 47 (hypoid gear 47a).

[0060] The TCU 70 also determines whether or not a predetermined condition (initial run-in promotion control execution condition) for executing the initial run-in promotion control (described in detail later) is satisfied. More specifically, the TCU 70 determines that the predetermined initial run-in promotion control execution condition is satisfied when, for example, the traveling road is a straight road or a substantially straight road (the curvature of the traveling road is equal to or less than a predetermined value) and the vehicle speed is within a predetermined speed range. Note that, instead of or in addition to the above conditions, the TCU 70 may determine that the predetermined initial run-in promotion control execution condition is satisfied when, for example, the vehicle is automatically following the vehicle ahead on a highway (a highway for automobiles).

[0061] Furthermore, the TCU 70 transmits information to the MCU 90 to confirm with the driver whether or not to execute the initial break-in promotion control, and displays the information on the display unit 91a of the touch screen 91. Meanwhile, the TCU 70 acquires from the MCU 90 an input from the driver (input accepted by an operation (input) unit 91b of the touch screen 91) indicating whether or not to execute the initial break-in promotion control (approval).

[0062] Then, when the initial break-in of the rear differential 47 (hypoid gear 47a) is not completed, the vehicle operating state satisfies a predetermined initial break-in promotion control execution condition, and an input from the driver indicating that the initial break-in promotion control is to be executed (agreement) is received, the TCU 70 executes the initial break-in promotion control. That is, the TCU 70 increases the fastening force of the transfer clutch 41 (engages the transfer clutch 41).

[0063] Furthermore, when the rear differential 47 including the hypoid gear 47a is replaced with a new one and reset information is received from the external diagnostic device 95, the TCU 70 resets (initializes) the integrated value (sum of products) of the multiplication value of the number of rotations of the rear differential 47 (hypoid gear 47a) and the torque input to the rear differential 47 (hypoid gear 47a), which is stored in the memory. Note that when the ECU 80 is replaced, the integrated value is carried over. In other words, the data is transferred via the external diagnostic device 95.

[0064] Next, the operation of the control device for an all-wheel drive vehicle will be described with reference to Fig. 2. Fig. 2 is a flowchart showing the procedure of the initial break-in promotion control performed by the control device for an all-wheel drive vehicle. This process is executed repeatedly at a predetermined timing mainly by the TCU 70.

[0065] In step S100, it is determined whether or not the initial break-in of the rear differential 47 (hypoid gear 47a) has not been completed. If the initial break-in of the rear differential 47 (hypoid gear 47a) has already been completed, the process is terminated (i.e., normal control is executed). On the other hand, if the initial break-in of the rear differential 47 (hypoid gear 47a) has not been completed, the process proceeds to step S102. The method of determining whether or not the initial break-in of the rear differential 47 (hypoid gear 47a) has been completed is as described above, and therefore a detailed description thereof will be omitted here.

[0066] In step S102, it is determined whether or not a predetermined condition for executing the initial break-in promotion control is satisfied. If the predetermined condition for executing the initial break-in promotion control is not satisfied, the process is temporarily terminated. On the other hand, if the predetermined condition for executing the initial break-in promotion control is not satisfied, the process proceeds to step S104. Note that the predetermined condition for executing the initial break-in promotion control is as described above, and therefore a detailed description thereof will be omitted here.

[0067] In step S104, information is presented to the driver to confirm whether or not to execute the initial break-in promotion control.

[0068] Next, in step S106, it is determined whether or not an input (operation) to execute the initial break-in promotion control has been accepted. If an input (operation) to execute the initial break-in promotion control has not been accepted, the process is temporarily terminated. On the other hand, if an input (operation) to execute the initial break-in promotion control has been accepted, the process proceeds to step S108.

[0069] In step S108, the initial break-in promotion control is executed. That is, the engagement force of the transfer clutch 41 is increased (engaged). Then, the process temporarily exits from this process.

[0070] As described above in detail, according to this embodiment, when the initial break-in of the rear differential 47 (hypoid gear 47a) is not yet completed and it is determined that the driving state of the vehicle satisfies a predetermined initial break-in promotion control execution condition, the fastening force of the transfer clutch 41 is increased (fastened). Therefore, the torque input (transmitted) to the differential 47 (hypoid gear 47a) is increased, and the initial break-in of the rear differential 47 (hypoid gear 47a) can be promoted. As a result, in the torque split type all-wheel drive vehicle 1, it is possible to promote the initial break-in of the rear differential 47 (hypoid gear 47a).

[0071] According to this embodiment, the initial break-in promotion control is executed when an input from the driver to execute the initial break-in promotion control is received. That is, the initial break-in promotion control is executed with the driver's consent. Therefore, the driver can be made aware that the initial break-in promotion control is being executed, and the driver can be prevented from feeling uncomfortable.

[0072] According to this embodiment, when the traveling road is a straight or substantially straight road and the vehicle speed is within a predetermined speed range, it is determined that the predetermined condition for executing the initial break-in promotion control is satisfied. Therefore, during steady driving where the transfer clutch 41 is (normally) released, the fastening force of the transfer clutch 41 can be increased (i.e., the input torque to the rear differential 47 can be increased), and the initial break-in of the rear differential 47 can be promoted.

[0073] According to this embodiment, if the integrated value of the product of the number of rotations of the rear differential 47 (hypoid gear 47a) since the start of use and the torque input to the rear differential 47 (hypoid gear 47a) is less than a predetermined threshold value, it is determined that the initial break-in of the rear differential 47 (hypoid gear 47a) is not yet completed. Therefore, it is possible to more accurately determine whether the initial break-in of the rear differential 47 (hypoid gear 47a) is not yet completed.

[0074] Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment and various modifications are possible. For example, the initial break-in control execution conditions are not limited to the above embodiment and can be changed as desired according to requirements, etc. In addition, the mileage, etc. may be taken into consideration when determining whether the initial break-in has been completed.

[0075] Incidentally, when the front and rear wheel diameters (tire diameters) are different, or when the rotation speeds of the front and rear wheels are not the same due to, for example, axle loads, wheel air pressure, etc., engaging the transfer clutch generates an internal circulating torque according to the difference in rotation between the front and rear wheels. For this reason, it is possible to further promote the initial break-in by, for example, lowering the air pressure of the front wheels below that of the rear wheels, or by using a device capable of adjusting the vehicle height (for example, air suspension) to raise the vehicle height on the rear side (rear wheel side), thereby making the front wheel diameter smaller than the rear wheel diameter and increasing the torque to the rear wheels.

[0076] Furthermore, the TCU 70 may prohibit the ECU 80 from operating the engine 20 at a high load (limit the maximum torque) when the initial break-in of the rear differential 47 (hypoid gear 47a) has not yet been completed. Then, the TCU 70 may permit the ECU 80 to operate the engine 20 at a high load when the initial break-in of the rear differential 47 (hypoid gear 47a) has been completed.

[0077] In the above embodiment, a hydraulic type is used as the transfer clutch 41, but for example, an electromagnetic type (electromagnetic clutch) or the like may be used.

[0078] In the above embodiment, a chain-type continuously variable transmission (CVT) is used, but instead of the chain-type continuously variable transmission, for example, a belt-type continuously variable transmission, a toroidal-type continuously variable transmission, etc. may be used. Also, a manual transmission (MT), a stepped automatic transmission (step AT), DCT, etc. may be used.

[0079] In addition, in the above embodiment, an AWD vehicle 1 using a gasoline engine 20 as a driving force source has been described as an example, but the present invention can also be applied to, for example, an HEV (hybrid vehicle) or PHEV using an engine and an electric motor as a driving force source, and an EV (electric vehicle) using an electric motor as a driving force source.

[0080] Furthermore, in the above embodiment, the ECU 80 that controls the engine 20 and the TCU 70 that controls the continuously variable transmission 30 are configured as separate pieces of hardware, but they may also be configured as integrated hardware. [Explanation of symbols]

[0081] 1 Front-wheel drive (AWD) vehicles 10FL,10FR,10RL,10RR wheels 12FL, 12FR, 12RL, 12RR Wheel speed sensor 20 Engine 22 Torque converter 30 Continuously variable transmission 41 Transfer clutch 44 Front differential 44a Hypoid gear 47 Rear differential 47a Hypoid gear 50 VDCU 60 Valve body (control valve) 70 TCU 76 Oil temperature sensor 77 Output shaft rotation sensor 78 Range switch 79 Turbine rotation sensor 80 ECU 81 Cam angle sensor 82 Crank angle sensor 83 Throttle opening sensor 84 Accelerator opening sensor 85 Electronically controlled throttle valve 90 MCU 91 Touchscreen 91a Display section 91b Operation (input) section 93 Driving assistance devices 95 External diagnostic equipment 100 CAN

Claims

1. a transfer clutch that adjusts the torque transmitted to the slave drive wheels in accordance with the fastening force; a differential including a hypoid gear and distributing torque transmitted via the transfer clutch to the left and right wheels while allowing a rotation difference between the left and right wheels; a control unit that controls the engagement force of the transfer clutch based on a driving state of the vehicle, A control device for an all-wheel drive vehicle, characterized in that the control unit executes initial break-in promotion control to increase the tightening force of the transfer clutch when it determines that the initial break-in of the differential has not been completed and that the driving state of the vehicle satisfies predetermined conditions for executing initial break-in promotion control.

2. a presentation means for presenting information to a driver to confirm whether or not to execute the initial break-in promotion control; and an input receiving means for receiving an input from a driver indicating whether or not to execute the initial break-in promotion control.

2. The control device for an all-wheel drive vehicle according to claim 1, wherein the control unit further executes the initial break-in promotion control when an input to execute the initial break-in promotion control is received.

3. Further comprising a driving assistance device that detects an external environment of the vehicle including a road condition; 3. The control device for an all-wheel drive vehicle according to claim 2, wherein the control unit determines that the predetermined initial break-in promotion control execution condition is satisfied when the driving road is a straight road or a substantially straight road and the vehicle speed is within a predetermined speed range.

4. 4. The control device for an all-wheel drive vehicle as described in claim 3, wherein the control unit determines that the initial break-in of the differential is not complete when an integrated value of the product of the number of rotations of the differential since the start of use and the torque input to the differential is less than a predetermined threshold value.

5. 5. The control device for an all-wheel drive vehicle according to claim 4, wherein the differential is a rear differential which distributes the torque transmitted via the transfer clutch to the left and right rear wheels.

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