JP2004203286A - Vehicle differential rotation control device - Google Patents

Abstract

An object of the present invention is to reliably and promptly avoid interference with an anti-lock brake system by a simple control logic, and to stably control the rotational speed ratio of the left and right wheels over a wide range.
A hydraulic passage is provided between output shafts (10L, 10R) of a differential device (2) and axles (11L, 11R), and communicates with a discharge port and a suction port of each of the hydraulic pumps (3L, 3R). 15 and 16 are connected by a bypass passage 17 provided with an opening valve 18. When the ABS is not operating, the opening valve 18 is closed, and the displacement of the pump is variably controlled so that the rotational speed ratio of the left and right wheels becomes the target rotational speed ratio based on the vehicle operating state, so that the rotational speed ratio of the left and right wheels is wide. During the ABS operation, the release valve 18 is opened to freely rotate the hydraulic pumps 3L and 3R to prevent interference with the ABS. Then, when the ABS is changed from the operation to the non-operation, the opening valve 18 is gradually closed, and the control is smoothly shifted to the normal control while reducing the impact when the bypass passage 17 is closed.
[Selection diagram] Fig. 1

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a differential rotation control device for a vehicle that stably controls a rotation speed ratio of left and right wheels over a wide range while avoiding interference with an antilock brake system.
[0002]
[Prior art]
BACKGROUND ART Conventionally, various types of devices for distributing torque to left and right wheels of a vehicle have been devised and put into practical use. A typical example is to provide a coupling between the left and right wheels that can variably control the transmission torque capacity, and to control the coupling to adjust the torque movement and the amount of torque movement. Multi-plate clutches are widely used.
[0003]
Such devices are disclosed in, for example, Japanese Patent No. 2641724 and Japanese Patent No. 2826580. In the devices disclosed in these patent documents, a mechanical type that transmits power from a power source to left and right wheels is used. A gear pair for forcibly making the left and right shafts differential is installed separately from the differential device, and the amount of torque movement between the left and right by the gear pair is adjusted by a hydraulic multi-plate clutch.
[0004]
[Patent Document 1]
Japanese Patent No. 2641724 [0005]
[Patent Document 2]
Japanese Patent No. 2,826,580
[Problems to be solved by the invention]
However, in the devices disclosed in Patent Literature 1 and Patent Literature 2, the controllable upper limit of the rotational speed ratio of the left and right wheels is determined by the gear ratio of the gear pair, and the controllable width is limited by the mechanical configuration. Not only that, but also in order to maintain the rotation speeds of the left and right wheels at the target rotation speed, feedback control for increasing or decreasing the torque is required, which complicates the system.
[0007]
In particular, in a vehicle equipped with an anti-lock brake system (ABS), it is necessary to avoid interference of the ABS with the brake operation of the wheels. This may hinder smooth cooperative control, and may cause a sense of incongruity.
[0008]
The present invention has been made in view of the above circumstances, and it is possible to reliably and quickly avoid interference with the antilock brake system with a simple control logic, and to stably control the rotational speed ratio of the left and right wheels over a wide range. It is an object of the present invention to provide a differential rotation control device for a vehicle that can perform the rotation.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides two hydraulic pumps which are respectively connected to left and right axles, and at least one of which is a variable displacement pump, communicates a discharge port and a suction port of each of the two hydraulic pumps. Two hydraulic passages that form a closed circuit, an opening valve that opens and closes a bypass passage that bypasses the two hydraulic passages, and a rotation of the left and right axles by closing the opening valve when the antilock brake system is not operating. The two hydraulic pumps were reversibly operated by a pump and a motor by changing the pump displacement of the variable displacement pump so that the number ratio became a rotation speed ratio according to the operation state, and the antilock brake system was operated. Means for opening the release valve to freely rotate the two hydraulic pumps.
[0010]
At this time, when the anti-lock brake system returns from the operation to the non-operation state, it is preferable to close the release valve gradually, or to close the release valve after adjusting the discharge amounts of the two hydraulic pumps to be equal, The impact caused by the closing of the passage is reduced, and the control can be smoothly returned to the normal control.
[0011]
Further, when the anti-lock brake system is activated, it is desirable to open the release valve and adjust the discharge amounts of the two hydraulic pumps to be equal, and when the anti-lock brake system is deactivated from activated, It is possible to quickly return to the normal control while alleviating the impact caused by closing the bypass passage.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 to 4 relate to a first embodiment of the present invention, FIG. 1 is an explanatory view showing a configuration of a differential rotation control device, FIG. 2 is an explanatory view of a variable displacement hydraulic pump, and FIG. FIG. 4 is a characteristic diagram showing the relationship between the number ratio and the displacement ratio of the left and right pumps. FIG. 4 is a flowchart showing control processing of the hydraulic pump by the controller.
[0013]
The differential rotation control device according to the present invention controls the rotation speed ratio between the left and right wheels by using two hydraulic pumps (motors) that perform a pump and a motor operation reversibly with at least one being a variable displacement type. Can be arbitrarily distributed, and FIG. 1 shows an example in which the present invention is applied to driving wheels. In the figure, reference numeral 1 denotes a power transmission shaft for transmitting a driving force transmitted from an engine (not shown) via a transmission, and a differential device 2 is connected to the power transmission shaft 1. And a differential rotation control device 4 mainly including the hydraulic pumps 3L and 3R.
[0014]
The differential device 2 has a well-known mechanical configuration, and a crown gear 7 fixedly provided outside a rotatable differential case 6 meshes with a drive pinion gear 5 coupled to a rear end of the power transmission shaft 1. The side gears 9, 9 are engaged with the pinion gears 8, 8, which are supported by the differential case 6 and rotate integrally. The left and right output shafts 10 </ b> L, 10 </ b> R are fixedly attached to the side gears 9, 9, and extend left and right through the differential case 6.
[0015]
The left and right output shafts 10L and 10R of the differential device 2 are connected to the pump shafts of the left and right hydraulic pumps 3L and 3R, respectively, and further connected to the left and right axles 11L and 11R via the pump shafts. Left and right drive wheels 12L, 12R are fixedly mounted on the shaft ends of the left and right axles 11L, 11R.
[0016]
The left and right hydraulic pumps 3L and 3R include, for example, vane pumps and piston pumps, and at least one of them is a variable displacement pump, and the discharge port and the suction port of each other are connected by a hydraulic passage forming a closed circuit. That is, the discharge port of the left hydraulic pump 3L communicates with the suction port of the right hydraulic pump 3R via the hydraulic passage 15, and the discharge port of the right hydraulic pump 3R and the suction port of the left hydraulic pump 3L communicate with each other. They are communicated via a passage 16.
[0017]
The hydraulic passage 15 and the hydraulic passage 16 are connected to each other via a bypass passage 17, and an opening valve 18 is provided in the bypass passage 17. The opening valve 18 is normally closed, and is opened when an ABS (anti-lock brake system) is operated to equalize the pressure in the hydraulic passages 15 and 16 as described later, and the left and right hydraulic pumps 3L and 3L are opened. This is to enable the 3R to freely rotate and prevent interference with the brake control by the ABS.
[0018]
Note that the left and right hydraulic pumps 3L, 3R are not arranged in series between the output shafts 10L, 10R of the differential device 2 and the axles 11L, 11R, and a gear train fixed to each of the output shafts 10L, 10R. It may be arranged in parallel with the differential device 2 via a chain or the like. When the differential rotation control device 4 is applied to the driven wheels, the differential device 2 becomes unnecessary, and the pump shafts of the hydraulic pumps 3L and 3R are connected to the respective axles of the left and right driven wheels.
[0019]
FIG. 2 shows a configuration example of the hydraulic pumps 3L and 3R. In FIG. 2, both of them are variable displacement hydraulic pumps using a vane pump in which a rotor 21 having a vane 20 rotates in a circular cam ring 22. . In this variable displacement hydraulic pump, the amount of eccentricity of a cam ring 22 with respect to the center of rotation of a rotor 21 serving as a pump shaft is varied by an actuator 23. For example, the rotation of an actuator 23 such as a motor is supported by a fulcrum 22a of the cam ring 22. , The pump displacement (discharge volume) can be varied.
[0020]
The actuators 23, 23 of the left and right hydraulic pumps 3L, 3R and the opening valve 18 of the bypass passage 17 are connected to a controller 50 mainly composed of a microcomputer or the like, and are driven and opened / closed by a signal from the controller 50. You. The controller 50 also includes ABS control for preventing directional locking, securing directional stability, and shortening the braking distance by preventing wheels from being locked during sudden braking or braking on slippery roads such as icy roads. An ABS signal indicating an ABS operating state is input from the ABS control unit 51, and various parameters indicating a vehicle operating state, for example, a steering angle of a steering wheel, wheel speeds of four front and rear wheels, an accelerator Parameters such as an opening, an engine speed, a longitudinal acceleration, and a lateral acceleration are input.
[0021]
When the ABS signal from the ABS control unit 51 is OFF (ABS is not operated), the controller 50 keeps the open valve 18 of the bypass passage 17 in the closed state so that the rotational speed ratio between the left and right wheels becomes the target rotational speed ratio. The left and right hydraulic pumps 3L, 3R are controlled. In this control, a control target value (target rotational speed ratio) with respect to the rotational speed ratio of the left and right wheels during traveling is set based on one or more of various parameters representing the vehicle driving state, and the target rotational speed ratio is obtained. Thus, the displacement of the pump is variably controlled via the actuators 23, 23.
[0022]
That is, while the vehicle is traveling, the hydraulic pumps 3L and 3R rotate at the same speed as the wheels. Therefore, if the displacement per rotation of the left hydraulic pump 3L is VL and the rotational speed of the left wheel is NL, the hydraulic pumps The discharge flow rate QL of 3L is represented by the following equation (1). Similarly, assuming that the displacement volume per rotation of the right hydraulic pump 3R is VR and the rotation speed of the right wheel is NR, the discharge flow rate QR of the hydraulic pump 3R is expressed by the following equation (2).
QL = VL × NL (1)
QR = VR × NR (2)
[0023]
Here, since the left hydraulic pump 3L and the right hydraulic pump 3R are configured such that their respective discharge ports and suction ports are connected by closed-circuit hydraulic passages 15 and 16, the left and right hydraulic pumps 3L and 3L are connected to each other. The relationship (QL = QR) that the discharge flow rates of the 3Rs are the same holds, and the following formula (3) holds from the above formulas (1) and (2).
VL × NL = VR × NR (3)
[0024]
Then, when the equation (3) is modified with respect to the rotational speed ratio NR / NL of the left and right wheels, the following equation (3 ′) is obtained. As shown in FIG. A characteristic in which the left and right wheel rotational speed ratio NR / NL changes linearly can be obtained.
VL / VR = NR / NL (3 ′)
[0025]
Therefore, when the displacement of one of the left and right hydraulic pumps is increased by a predetermined ratio, the hydraulic pump on the opposite side acts as a motor, and the rotational speed of the opposite wheel can be increased by the same ratio. That is, by variably controlling the displacement of the pump, one axle 11L or 11R can be decelerated, while the other axle 11R or 11L can be increased in speed and relatively rotated via the differential device 2 to achieve power transmission. The driving force transmitted from the shaft 1 and distributed to the left and right by the differential device 2 can be arbitrarily redistributed to the left and right axles 11L and 11R in accordance with the rate of the acceleration / deceleration.
[0026]
As described above, of the left and right hydraulic pumps 3L and 3R, one can be a variable displacement hydraulic pump and the other can be a fixed displacement hydraulic pump. The ability to change the displacement of both is advantageous in terms of control width and control adaptability, and it is desirable that both the left and right hydraulic pumps 3L, 3R be variable displacement hydraulic pumps.
[0027]
On the other hand, when the ABS signal input from the ABS control unit 51 is turned on (ABS operation), the controller 50 opens the open valves 18 of the bypass passages 17 of the left and right hydraulic pumps 3L and 3R, and the hydraulic pumps 3L and 3R are opened. Rotation is free, and interference with ABS brake control is prevented. Then, when the ABS operation is stopped, the displacement of the left and right hydraulic pumps 3L and 3R is set to a target value, and then the opening valve 18 is closed while reducing the impact caused by opening and closing the bypass passage 17. Performs the processing and shifts to normal control.
[0028]
Hereinafter, control processing of the hydraulic pumps 3L and 3R by the controller 50 will be described with reference to the flowchart shown in FIG.
[0029]
As described above, during the execution of the normal control, the bypass passages 17 of the left and right hydraulic pumps 3L, 3R are closed by the open valves 18, and the displacements of the respective pumps are controlled so as to have the target rotational speed ratio according to the operation state. Have been. When an ABS signal is input from the ABS control unit 51 in this control state, the process proceeds to step S1, where it is checked whether the ABS signal is ON.
[0030]
As a result, when the ABS signal is ON, that is, when the ABS is activated, the process proceeds from step S1 to step S2, where the opening valve 18 of the bypass passage 17 is opened immediately, and the rotation of the left and right hydraulic pumps 3L, 3R is made freely. Avoid interference with the left and right wheel brake control by ABS. Then, while maintaining the open valve 18 in the open state, the process returns to step S1, and the monitoring of the ABS signal is continued.
[0031]
Thereafter, when the ABS is deactivated and the ABS signal is turned off, the process proceeds from step S1 to step S3 to set a target pump displacement ratio VL / VR for controlling the left / right rotational speed ratio according to the operation state. At S4, the opening valve 18 is gradually closed. For example, as shown in the drawing, the opening valve 18 is closed while the opening of the bypass valve 17 is reduced while the closing speed from the fully open position and the valve closing speed near the position where the fully closed position is reached are relatively slowed. Is closed, and after the open valve 18 is fully closed, the process proceeds from step S4 to step S5 to return to the normal control.
[0032]
As described above, in the normal control when the ABS is not operated, the rotation speed can be controlled to an arbitrary rotation speed ratio by changing the pump displacement using a variable displacement hydraulic pump, and the actual rotation speed ratio can be adjusted to the target rotation speed. When the ratio deviates from the number ratio, the torque by the hydraulic pressure automatically acts in the direction approaching the target rotational speed ratio, so that stable control can be realized with extremely simple control logic.
[0033]
In other words, in the technology in which torque is controlled as in a conventional device using a hydraulic clutch and a gear pair, feedback control for increasing or decreasing the torque is necessary in order to set the rotation speeds of the left and right wheels to the target rotation speed. In the differential rotation control device 4 according to the present invention, there is no need for feedback control, and a wide control range and stable traveling control can be realized with extremely simple control logic.
[0034]
Also, between the two hydraulic pumps, the differential rotational energy flows from the pump whose rotation is to be reduced to the pump whose rotation is to be increased. There is an advantage that energy loss is small and the efficiency is high as compared with the one that requires.
[0035]
On the other hand, when the ABS is operated, the left and right hydraulic pumps 3L, 3R can be freely rotated immediately by opening the open valve 18 of the bypass passage 17, and interference with the ABS can be reliably and promptly avoided. In addition, when the ABS is deactivated from the operation and returns to the normal control, the displacement ratio of the left and right hydraulic pumps 3L, 3R is set to the target value for controlling the left and right rotation speed ratio according to the operation state. After the setting, the opening valve 18 is gradually closed, so that the impact accompanying the closing of the bypass passage 17 can be reduced and the control can be smoothly shifted to the normal control. That is, smooth emphasis control can be realized with simple control logic reliably and quickly avoiding interference with the ABS.
[0036]
Next, a second embodiment of the present invention will be described. FIG. 5 is a flowchart showing control processing of the hydraulic pump by the controller.
[0037]
In the second mode, in the return process from the ABS operation, the displacement volumes corresponding to the left and right wheel speed ratios at the time of releasing the ABS are set to the left and right hydraulic pumps 3L and 3R that have been rotating freely until then. After adjusting the discharge amounts of the hydraulic pumps 3L and 3R to be equal to each other, the opening valve 18 of the bypass passage 17 is closed, so that the impact at the time of closing the bypass passage 17 is reduced, and the control is smoothly shifted to the normal control. Things.
[0038]
Therefore, in the second embodiment, as shown in FIG. 5, when the ABS signal input from the ABS control unit 51 is turned on during the execution of the normal control, whether the ABS signal is turned on in step S11 as in the first embodiment. If the ABS signal is ON, that is, if the ABS is activated, the process proceeds from step S11 to step S12 to immediately open the opening valve 18 of the bypass passage 17, and then returns to step S11 to monitor the ABS signal. To continue.
[0039]
Thereafter, when the ABS signal is turned off, the process proceeds from step S11 to step S13 to measure the wheel speeds of the left and right wheels based on the signal of the wheel speed sensor, and calculates the rotational speed ratio NR / NL of the left and right wheels in step S14. . Next, proceeding to step S15, the displacement ratio VL / VR of the left and right hydraulic pumps 3L, 3R corresponding to the calculated rotational speed ratio NR / NL of the left and right wheels is set, and each hydraulic pressure is set at the displacement ratio VL / VR. Adjustment is made so that the discharge amounts of the pumps 3L and 3R become equal.
[0040]
Then, in step S16, the opening valve 18 of the bypass passage 17 is closed, and in step S17, the control returns to the normal control. After the return to the normal control, the target pump displacement ratios of the left and right hydraulic pumps 3L, 3R are set so that the rotational speed ratio of the left and right wheels becomes the target rotational speed ratio according to the operation state.
[0041]
In the second embodiment, when returning from the ABS operation, before the opening valve 18 of the bypass passage 17 is closed, the discharge flow rates of the left and right hydraulic pumps 3L and 3R are adjusted in advance so as to be equal. Not only can the shock at the time of closing of 17 be reduced to smoothly shift to the normal control, but also the occurrence of unnecessary yaw moment can be prevented and the vehicle behavior can be stabilized.
[0042]
Next, a third embodiment of the present invention will be described. FIG. 6 is a flowchart showing the control processing of the hydraulic pump by the controller.
[0043]
In the third embodiment, during the ABS operation, the bypass passages 17 of the left and right hydraulic pumps 3L, 3R are opened, and the discharge flow rates of the left and right hydraulic pumps 3L, 3R are made equal while monitoring the left and right wheel speeds. By controlling the displacement of the pump to follow, the shock at the time of closing the bypass passage 17 is reduced, and when the ABS becomes inactive, the control is quickly shifted to the normal control.
[0044]
For this reason, in the third embodiment, as shown in FIG. 6, when the ABS signal input from the ABS control unit 51 is turned on during execution of the normal control, it is checked in step S21 whether or not the ABS signal is turned on. When the signal is ON, that is, when the ABS is activated, the process proceeds from step S21 to step S22, where the opening valve 18 of the bypass passage 17 is opened immediately. In step S23, the wheel speeds of the left and right wheels are determined based on the signal of the wheel speed sensor. measure.
[0045]
Next, proceeding to step S24, the rotational speed ratio NR / NL of the left and right wheels is calculated, and in step S25, the displacement ratio VL of the left and right hydraulic pumps 3L, 3R corresponding to the calculated left / right rotational speed ratio NR / NL. / VR is set, and the displacements of the hydraulic pumps 3L, 3R are adjusted to be equal at the displacement ratio VL / VR, and then the process returns to step S21 to maintain the open valve 18 of the bypass passage 17 in the open state. Then, the monitoring of the ABS signal and the left and right wheel speeds is continued.
[0046]
When the ABS signal is turned off, the process proceeds from step S21 to step S26 to immediately close the opening valve 18 of the bypass passage 17, and returns to the normal control in step S27. After the return to the normal control, the target pump displacement ratios of the left and right hydraulic pumps 3L, 3R are set so that the rotational speed ratio of the left and right wheels becomes the target rotational speed ratio according to the operation state.
[0047]
In the third embodiment, since the discharge flow rates of the left and right hydraulic pumps 3L and 3R are adjusted in advance at the time of the ABS operation, the opening valve 18 can be closed immediately when the ABS is changed from the operation to the non-operation. It is possible to immediately return to the normal control without causing an impact in the bypass passage 17.
[0048]
【The invention's effect】
As described above, according to the present invention, it is possible to reliably and quickly avoid interference with the antilock brake system with a simple control logic, and to stably control the rotational speed ratio of the left and right wheels over a wide range. , Smooth cooperative control with the anti-lock brake system can be realized.
[Brief description of the drawings]
FIG. 1 is an explanatory view showing a configuration of a differential rotation control device according to a first embodiment of the present invention. FIG. 2 is an explanatory view of a variable displacement hydraulic pump. FIG. FIG. 4 is a characteristic diagram showing the relationship between the ratio and the displacement ratio of the left and right pumps. FIG. 4 is a flowchart showing control processing of the hydraulic pump by the controller. FIG. 5 is a hydraulic pump by the controller according to the second embodiment of the present invention. FIG. 6 is a flowchart showing control processing of a hydraulic pump by a controller according to a third embodiment of the present invention.
3L, 3R hydraulic pump 4 Differential rotation control device 11L, 11R Axles 15, 16 Hydraulic passage 17 Bypass passage 18 Opening valve 50 Controller 51 ABS control unit

Claims (4)

Two hydraulic pumps respectively connected to the left and right axles, at least one of which is a variable displacement pump;
Two hydraulic passages that form a closed circuit by communicating the discharge port and the suction port of the two hydraulic pumps with each other;
An opening valve that opens and closes a bypass passage that bypasses the two hydraulic passages;
When the anti-lock brake system is not operating, the release valve is closed and the pump displacement of the variable displacement pump is varied so that the rotational speed ratio of the left and right axles becomes a rotational speed ratio according to the operating state. Means for reversibly operating the two hydraulic pumps and the motor so as to open the release valve and freely rotate the two hydraulic pumps when the anti-lock brake system is operated. Differential rotation control device. 2. The differential rotation control device for a vehicle according to claim 1, wherein the release valve is gradually closed when the anti-lock brake system returns from the operation state to the non-operation state. 2. The vehicle according to claim 1, wherein when the anti-lock brake system returns from the operation state to the non-operation state, the discharge valves of the two hydraulic pumps are adjusted to be equal to each other, and then the release valve is closed. Differential rotation control device. 2. The differential rotation control device for a vehicle according to claim 1, wherein when the anti-lock brake system is activated, the release valve is opened to adjust the discharge amounts of the two hydraulic pumps to be equal.

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