AU2020285746A1

AU2020285746A1 - Control system for vehicle

Info

Publication number: AU2020285746A1
Application number: AU2020285746A
Authority: AU
Inventors: Yoshihisa Hamanaka; Atsushi Kimura; Masayuki Kobayashi
Original assignee: IJTT Co Ltd
Current assignee: IJTT Co Ltd
Priority date: 2019-05-31
Filing date: 2020-02-26
Publication date: 2021-12-02
Also published as: JP7071945B2; ZA202110893B; JP2020196298A; WO2020240953A1

Abstract

Provided is a vehicle control system capable of suppressing a shock torque generated in a drive system component of a font wheel.　This control system (100) for a vehicle (1) is provided with: a transfer (10) having a multiplate clutch (11); and a control device (50) that controls fastening force of the multiplate clutch (11) according to a speed difference between the front and rear wheels (2, 3), wherein the control device (50) controls, during vehicle traveling, the multiplate clutch (11) so that an increase in the fastening force of the multiplate clutch (11) is suppressed when the angular acceleration (α) of the front wheel (2) has reached a predetermined threshold (αT) or less.

Description

CONTROL SYSTEM FOR VEHICLE BACKGROUND

Technical Field

[0001] The present invention relates to a control system for a vehicle.

Background Art

[0002] As a control system for a vehicle, such one is known that has a transfer having a multi-plate clutch that switches between all-wheel drive and rear-wheel drive and variably distributes a part of driving force transmitted to rear wheel side to front wheel side, and a control device for controlling engaging force of the multi-plate clutch.

[0003] Generally, the control device is configured to control the engaging force of the multi-plate clutch according to a speed difference between front and rear wheels.

Citation List Patent Literature

[0004]

[PTL 1] WO 2008/096438

SUMMARY Technical Problem

[0005] However, in the above control system, for example, when the vehicle is running on a low roadd and then only the front wheels first enter a high road from the low roada, drive torque transmitted to the front wheels increases suddenly, and a load (shock torque) may be generated in drive system components such as an axle for the front wheel.

[0006] Therefore, it is an object of the present invention to solve the above-mentioned problems and to provide a control system for a vehicle that can restrain shock torque generated in drive system components for a front wheel.

Solution to Problem

[0007] According to one aspect of the present invention, a control system for a vehicle is provided that comprises: a transfer having a multi-plate clutch that switches between all-wheel drive and rear-wheel drive and variably distributes a part of driving force transmitted to a rear wheel side to a front wheel side; and a control device for controlling engaging force of the multi-plate clutch according to a speed difference between a front wheel and a rear wheel, wherein the control device controls the multi-plate clutch such that when an angular acceleration of the front wheel becomes equal to or less than a predetermined threshold value while the vehicle is running, an increase of the engaging force of the multi-plate clutch is restrained.

[0008] Preferably, the control device controls the multi-plate clutch such that when the angular acceleration of the front wheel becomes equal to or less than the threshold value while the vehicle is running, the engaging force of the multi-plate clutch becomes zero.

[0009] Preferably, the threshold value is set to a negative value.

[0010] According to a control system for a vehicle according to the present invention, it is possible to restrain shock torque generated in drive system components for a front wheel.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] FIG. 1 is a left side view of a vehicle during running on a low [road; FIG. 2 is a left side view of a vehicle when entering a high road from a low road; FIG. 3 is an overall diagram of a control system for a vehicle; FIG. 4 is a cross-sectional view of a transfer; FIG. 5 is a cross-sectional view taken along the line A-A of FIG. 4; FIG. 6 is a time chart showing an example of a control state of a control device, in which (a) represents rotation speed of front and rear wheels, (b) represents speed difference between front and rear wheels, (c) represents engaging force of the multi-plate clutch, and (d) represents drive torque transmitted to front wheel; and FIG. 7 is a time chart showing an example of a control state of a control device, in which (a) is an enlarged view of part VII in FIG. 6, and (b) shows an angular acceleration corresponding to the rotation speed of the front wheel shown in (a).

DESCRIPTION OF THE EXAMPLE EMBODIMENTS

[0012] Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that each direction in the embodiment described later corresponds to each direction of a vehicle according to the present embodiment.

[0013] As shown in FIGS. 1 and 2, a cab-over type truck is used for a vehicle 1. However, the vehicle 1 may be a vehicle other than the cab-over type truck. Reference numeral 2 indicates a front wheel of the vehicle 1, and reference numeral 3 indicates a rear wheel of the vehicle 1. Further, reference numeral RLow indicatesa low p road having a low friction coefficient ([) in respect of the front and rear wheels 2 and 3, and reference numeral RHi indicates a high road having a high friction coefficient ([) in respect to the front and rear wheels 2 and 3.

[0014] As shown in FIG. 3, the vehicleIisa4WDvehicle (four-wheel drive vehicle) or an AWD vehicle (all-wheel drive vehicle) based on an FR vehicle (front engine/ rear drive vehicle). Rotational driving force from an engine E mounted on a front part of the vehicle is transmitted to a propeller shaft 4 via a transmission T/M and a transfer 10 (described later). The rotational driving force transmitted to the propeller shaft 4 is transmitted to the rear wheels 3 via a differential gear (not shown) housed in a differential case 5. Further, the rotational driving force from the transmission T / M is selectively transmitted to an input shaft 6 of a differential gear for driving the front wheels via the transfer 10.

[0015] The front wheels 2 and the rear wheels 3 are provided with wheel speed sensors S for detecting their respective rotation speeds (number of revolutions per unit time). As the wheel speed sensor S, a wheel speed sensor of existing anti-lock braking system (ABS) is used. However, the wheel speed sensor S may not be limited to the wheel speed sensor of ABS.

[0016] A control system 100 for the vehicle 1 includes a transfer 10 having a multi-plate clutch 11, and an electronic control unit (ECU) 50 as a control device for controlling engaging force of the multi-plate clutch 11.

[0017] The multi-plate clutch 11 is configured to switch between all-wheel drive to drive the front wheels 2 and the rear wheels 3, and rear wheel drive to drive the rear wheels 3 only, and to variably distribute a part of the driving force transmitted to the rear wheels 3 side to the front wheels 2 side.

[0018] In the present embodiment, a driving force distribution ratio between the front wheel 2 side and the rear wheel 3 side is set such that the driving force on the front wheel 2 side and the driving force on the rear wheel 3 side are the same size (front wheel side: rear wheel side = 5: 5) when the driving force is maximally distributed to the front wheel 2 side during all-wheel drive. Further, in case of rear-wheel drive, the driving force distribution ratio is set such that the driving force on the front wheel 2 side is zero (front wheel side: rear wheel side = 0: 10). However, the driving force distribution ratio may be arbitrary. For example, the driving force distribution ratio may be set such that the driving force on the rear wheel 3 side is larger than that on the front wheel 2 side (for example, front wheel side: rear wheel side = 4: 6) when the driving force is distributed to the front wheel 2 side to the maximum during all-wheel drive.

[0019] As shown in FIG. 4, the transfer 10 includes a housing 12 provided on the transmission T / M, afirst shaft 13 rotatably provided in the housing 12, and an inner rotating member 14 provided on the first shaft 13. Further, the transfer 10 includes a first sprocket 15 rotatably provided on the first shaft 13, an outer rotating member 16 provided on the first sprocket 15, a multi-plate clutch 11 for connecting the inner rotating member 14 to the outer rotating member 16 so that they can be adjacent to each other, and an actuator 17 for driving the multi-plate clutch 11. Further, the transfer 10 includes a second shaft 18 rotatably provided in the housing 12, a second sprocket 19 provided on the second shaft 18, and a chain 20 hung on the first sprocket 15 and the second sprocket 19.

[0020] A front end part of the first shaft 13 is connected to an output shaft (not shown) of the transmission T/M. Further, a rear end part of the first shaft 13 is connected to the propeller shaft 4 (see FIG. 3). On the other hand, a front end part of the second shaft 18 is connected to an input shaft 6 (see FIG. 3) of the differential gear for driving the front wheels.

[0021] The actuator 17 includes a cam mechanism 21 fixed to the housing 12, a driving device 22 for driving the cam mechanism 21, and a pressing member 23 interposed between the cam mechanism 21 and the multi-plate clutch 11.

[0022] As shown in FIGS. 4 and 5, the cam mechanism 21 has a sector gear (fan-shaped gear) 24 that rotates about a central axis C of the first shaft 13. The cam mechanism 21 is configured to change a rotation by the sector gear 24 into an axial movement to move the pressing member 23 in front and rear directions.

[0023] The driving device 22 is comprised of a DC motor with an encoder. A worm gear 25 is provided on a drive shaft 22a of the driving device 22. The worm gear 25 is meshed with the sector gear 24 of the cam mechanism 21. That is, the driving device 22 rotates the sector gear 24 by changing the rotation angle (phase) of the drive shaft 22a. As a result, the pressing member 23 is moved in front and rear directions via the cam mechanism 21, and the engaging force of the multi-plate clutch 11 is increased or decreased.

[0024] The actuator 17 may be of any type, and for example, a DC motor without an encoder, a servo motor, a stepping motor, a hydraulic motor, or an electromagnet may be used as the driving device 22.

[0025] ECU 50 includes CPU, ROM, RAM, storage devices, input/output ports and the like. The driving device 22 and the wheel speed sensors S are electrically connected to the ECU 50. Although not shown, various sensors are electrically connected to the ECU 50 such as a vehicle speed sensor for detecting a speed of the vehicle 1, an accelerator opening sensor for detecting an accelerator opening, and an engine rotation sensor for detecting an engine speed.

[0026] The ECU 50 controls the engaging force of the multi-plate clutch 11 through the actuator 17 by controlling a rotation angle (phase) of the drive shaft 22a of the driving device 22.

[0027] Although details will be described later, the ECU 50 of the present embodiment controls the engaging force of the multi-plate clutch 11 according to a speed difference between the front wheels 2 and the rear wheels 3 (see FIG. 1). Further, the ECU 50 controls the multi-plate clutch 11 such that when an angular acceleration of the front wheel 2 becomes equal to or less than a predetermined threshold value while the vehicle is running, an increase of the engaging force of the multi-plate clutch 11 is restrained, in particular the engaging force of the multi-plate clutch 11 becomes zero. The threshold value is set to a negative value of the angular acceleration generated when the front wheel 2 enters the high road RHi from the low road RLw (see FIG. 2).

[0028] Detail of control by the ECU 50 will be described with reference to FIGS. 6 and 7. FIGS. 6 and 7 are time charts showing an example of control status of the ECU 50.

[0029] FIG. 6(a) shows the rotation speed n (rpm) of the front and rear wheels 2 and 3, FIG. 6(b) shows the speed difference An (rpm) between the front and rear wheels 2 and 3, FIG. 6 (c) shows the engaging force F (N) of the multi-plate clutch 11, and FIG. 6(d) shows the drive torque T (N- m) transmitted to the front wheels 2. In FIG. 6(a), a solid line nF represents the rotation speed of the front wheel 2, and a dotted line nL represents the rotation speed of the rear wheel 3.

[0030] On the other hand, FIG. 7(a) is an enlarged view of the rotation speed nF of the front wheel 2 shown in part VII of FIG. 6(a), and FIG. 7(b) shows the angular acceleration a corresponding to the rotation speed nFOf the front wheel 2 shown in FIG. 7(a).

[0031] Further, in these figures, time tl represents a time when the front wheel 2 enters the high p road RHi from the low [t road RLw (see FIG. 2). Further, a period before the time tI represents a period during when the vehicle 1 is running on the low roadd before the front wheel 2 enters the high road RHi from the low road RLw (see FIG. 1). A period after the time tl represents a period after the front wheel 2 has entered the high road RHi and before the rear wheel 3 has entered the high road RHi.

[0032] As shown in FIGS. 6(a) and 6(b), the ECU 50 calculates, while the vehicle 1 is running, the speed difference An (An = nL-nF) between the front and rear wheels 2 and 3 based on the rotation speed nF of the front wheel 2 and the rotation speed nL of the rear wheel 3 transmitted from the wheel speed sensor S.

[0033] Further, the ECU 50 controls the engaging force F of the multi-plate clutch 11 according to the calculated speed difference An between the front and rear wheels 2 and 3. In the present embodiment, the ECU 50 controls the multi-plate clutch 11 such that the larger the speed difference An between the front and rear wheels 2 and 3 is, the larger the engagement force F of the multi-plate clutch 11 is.

[0034] Further, as shown in FIGS. 7(a) and 7(b), the ECU 50 of the present embodiment calculates, while the vehicle 1 is running, the angular acceleration a of the front wheel 2 based on the rotational speed nFOf the front wheel 2. The angular acceleration a of the front wheel 2 is calculated as a differential value of the rotational speed nFOf the front wheel 2.

[0035] By the way, during running on the low [t road before the time tl in the illustrated example, the front and rear wheels 2 and 3 slip on the low road RLw and the multi-plate clutch 11 is engaged (ON). The ECU 50 controls the engaging force F of the multi-plate clutch 11 such that the speed difference An between the front and rear wheels 2 and 3 becomes zero, and allows the vehicle 1 to run on the low road RLw by all-wheel drive.

[0036] On the other hand, at time tI, when the front wheel 2 enters the high road RHi from the low roadd RLow, the front wheel 2 that has slipped on the low roadd RLw suddenly grips on the high road RHi, and the rotation speed NF of the front wheel 2 suddenly drops. As a result, the speed difference An between the front and rear wheels 2 and 3 increases, and the angular acceleration a of the front wheel 2 decreases equal to or less than the negative threshold value UT.

[0037] At this time, the ECU 50 determines that the front wheel 2 has entered the high road RHi, interrupts the control of the multi-plate clutch 11 according to the speed difference An, and controls the engaging force F of the multi-plate clutch 11 to zero. As a result, driving manner is switched to rear-wheel drive from all-wheel drive.

[0038] Incidentally, in period after the time tl in the illustrated example, the rotation speed NL of the rear wheel 3 hardly decreases since the rear wheel 3 has not yet entered the high [road RHi from the low [t road RLw. Therefore, the ECU 50 continues the control to make the engaging force F of the multi-plate clutch 11 zero, and drives the vehicle 1 by the rear wheel drive.

[0039] By the way, in a general ECU, as shown by an alternate long and short dash line F' in FIG. 6(c), even when the front wheel 2 only first enters the high road RHi from the low road

RLow when running on the low roadd by all-wheel drive, the control of the multi-plate clutch 11 according to the speed difference An is still continued.

[0040] However, in this control, as shown by the alternate long and short dash line T' in FIG. 6(d), the drive torque T' to the front wheel 2 may suddenly increase. As a result, a load (shock torque) due to inertia may be generated on the drive system components such as the axle of the front wheel 2 and the drive shaft.

[0041] Generally, for this shock torque, for example, measures are taken to increase fatigue strength of the drive system components. However, due to width and height of the vehicle, it may not be possible to increase the fatigue strength of the drive train components.

[0042] As another measure, such a method is conceivable that the driving force distribution ratio is set so that the driving force maximally distributed to the front wheel side during all-wheel drive is smaller (for example, front wheel side: rear wheel side = 2: 8). However, this method has a problem that running performance of the vehicle during all-wheel drive is lowered.

[0043] On the other hand, in the present embodiment, as shown in FIG. 7, it is detected that the front wheel 2 has entered the high road RHi from the low road RLw by the angular acceleration a of the front wheel 2, and then the engaging force F of the multi-plate clutch 11 is controlled to zero. As a result, it is possible to instantly switch from all-wheel drive to rear-wheel drive, and it is possible to eliminate the drive torque T to the front wheels 2.

[0044] Therefore, in the present embodiment, it is possible to restrain the sudden increase in the drive torque T to the front wheel 2 and restrain the shock torque generated in the drive system components such as the axle of the front wheel 2.

[0045] Further, according to the present embodiment, fatigue of the components can be restrained without increasing the fatigue strength of the drive system components such as the axle of the front wheel 2. Therefore, it is particularly advantageous in case that the fatigue strength of the drive system components cannot be increased due to the vehicle width and the vehicle height.

[0046] Further, according to the present embodiment, shock torque of the drive system components can be restrained without setting the driving force distribution ratio so that the driving force maximally distributed to the front wheel side during all-wheel drive is smaller (for example, front wheel side: rear wheel side = 2: 8). Therefore, the driving force distribution ratio on the front wheel 2 side can be set high (for example, front wheel side: rear wheel side = 5: ) to improve the running performance of the vehicle 1 during all-wheel drive.

[0047] On the other hand, the above-mentioned basic embodiment can be a modification or a combination thereof as follows. In the following description, the same reference numerals are used for the same components as those in the above embodiment, and detailed description thereof will be omitted.

[0048] (First modification) Although not shown, while the vehicle is running, the ECU 50 may control the engaging force T to a value larger than zero when the angular acceleration a of the front wheels 2 becomes equal to or less than the threshold value U if increase in the engaging force of the multi-plate clutch 11 can be restrained.

[0049] (Second modification) The ECU 50 may acquire the angular acceleration of the front wheel 2 from the angular acceleration sensor mounted on the ABS or the like without calculating the angular acceleration of the front wheel 2 based on the rotation speed of the front wheel 2.

[0050] (Third modification) In a third modification, when the brakes of the front wheel 2 and the rear wheel 3 are operating, or when the angular acceleration of the rear wheel 3 is equal to or less than a predetermined threshold value, the ECU 50 does not execute the control for reducing the engaging force of the multi-plate clutch 11, even when the angular acceleration becomes equal to or less than the threshold value. According to the third modification, when the angular acceleration of the front wheel 2 is reduced by operation of the brake, it is possible to prevent the front wheel 2 from being mistakenly recognized as having entered the high road RHi from the low roadd RLw.

Claims

WHAT IS CLAIMED IS:

1. A control system for a vehicle, comprising: a transfer having a multi-plate clutch that switches between all-wheel drive and rear-wheel drive and variably distributes a part of driving force transmitted to a rear wheel side to a front wheel side; and a control device for controlling engaging force of the multi-plate clutch according to a speed difference between a front wheel and a rear wheel, wherein the control device controls the multi-plate clutch such that when an angular acceleration of the front wheel becomes equal to or less than a predetermined threshold value while the vehicle is running, an increase of the engaging force of the multi-plate clutch is restrained.

2. The control system for the vehicle according to claim 1, wherein: the control device controls the multi-plate clutch such that when the angular acceleration of the front wheel becomes equal to or less than the threshold value while the vehicle is running, the engaging force of the multi-plate clutch becomes zero.

3. The control system for the vehicle according to claim 1 or 2, wherein: the threshold value is set to a negative value.