JP2000211489A - Traction control device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To display a stable traction function, even when a vehicle suddenly starts after left and right drive wheels stop on a road surface of different coefficient of frictions and a vehicle stop holding function is operated. SOLUTION: In this control device, a cut valve 1, hold valves 2L, 2R and decay valves 3L, 3R are arranged within a channel communicating a master cylinder to wheel cylinders of left and right drive wheels, a circuit for traction control (TCS unit) is connected to a channel between the cut valve 1 and the hold valves 2L, 2R, the cut valve 1 is closed when the drive wheels slip and braking force can be worked on a wheel cylinder on the slip wheel side by hydraulic pressure from the traction control circuit side. In this case, when slip is generated at one side drive wheel of the left and right wheels and a traction control is started, the hold valves 2 (2L, 2R) of a non-control drive wheel on the other side are closed and at the same time, the decay valves 3 (3L, 3R) are opened for prescribed time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a traction control device for a vehicle having an anti-lock control function and a vehicle stop holding function, after the left and right driving wheels stop on a road surface having a different friction coefficient and the vehicle stop holding function is activated. The present invention relates to a traction control device for a vehicle that can exhibit a stable traction function even when the vehicle starts suddenly.

[0002]

2. Description of the Related Art Conventionally, a traction control device for a vehicle for preventing a slip of a driving wheel when starting a vehicle,
A braking force holding device (vehicle stop holding device) that can automatically hold the stopped state when the vehicle stops is known (for example, Japanese Patent Application Laid-Open No. 8-40239, Japanese Patent Application Laid-Open No. 64-7895).
No. 7). More recently, a brake device or the like combining the above-described traction control device and a braking force holding device has been developed to improve operability.

[0003]

By the way, in a vehicle equipped with a brake control device having a traction control function and a stop holding function, when the left and right driving wheels are on a road surface having different friction coefficients, the vehicle stops and stops and holds. If the vehicle starts suddenly after the device is operated, the stop holding device detects the vehicle start operation and releases the brake pressure contained in the wheel cylinder. Immediately thereafter, if a slip occurs on the drive wheels on the low μ road surface side before the brake pressure on the left and right drive wheels has sufficiently decreased, the traction control device will operate.

The traction control device drives an electromagnetic valve (hold valve, decay valve) and a traction pump (TCS pump) of a hydraulic unit for antilock control / traction control, and applies a drive to a slipping wheel. Only the brake pressure is supplied, and in the drive wheels where no slip occurs, the hold valve is closed to shut off the brake fluid pressure supplied from the TCS pump.
However, if the traction control is started immediately after the sudden start as described above, the brakes on the drive wheels that are not slipping are
Since the hold valve is closed by the traction control before the key pressure is sufficiently reduced, the brake pressure at that time is recontained. In particular, in a vehicle equipped with an LSPV equipped with a proportioning valve for adjusting the brake fluid pressure of the front and rear driving wheels, the pressure drop of the non-slip driving wheels is particularly delayed.

For this reason, in the above-described state, the brake force should be applied only to the slip-generating drive wheels, but the brake is simultaneously applied to the left and right drive wheels due to insufficient pressure reduction of the non-slip drive wheels. Pressure will be generated,
There was a problem that traction control performance deteriorated.
That is, the purpose of traction control is to distribute the excess drive torque of the slip drive wheels to the non-slip drive wheels so that the left and right drive forces are balanced, but the residual brake pressure is applied to the non-slip drive wheels. Is generated, interference occurs between the driving torque and the braking torque distributed from the slip drive wheels, causing a problem that acceleration performance deteriorates and vehicle vibration occurs.

Accordingly, the present invention provides a vehicle which, when the left and right driving wheels are on a road surface having a different friction coefficient, stops after the vehicle stops and the stop holding device is operated, starts suddenly, and the driving wheels on the road surface having a low friction coefficient slip. When the traction control is started, not only the hold valve of the non-slip drive wheel is closed but also the decay valve is opened at the same time, so that the brake pressure of the non-slip drive wheel is sufficiently reduced. It is an object of the present invention to provide a vehicle traction control capable of suppressing the occurrence of torque interference and preventing the traction control performance from deteriorating even when the vehicle starts suddenly during operation, and solving the above problems.

In the present invention, when the vehicle suddenly starts and a slip occurs on one side of the left and right drive wheels, the traction control device is operated, and the drive wheel in which the slip is generated is supplied from the pump via an open hold valve. The brake valve supplied by the pump is supplied by closing the hold valve on the drive wheel where the supplied brake fluid pressure is supplied and no slip occurs.
Shut off hydraulic pressure. The brake fluid pressure is sufficiently released by further opening the decay valve on the drive wheel in which no slip has occurred, and then the normal traction control state is returned. Thus, at the start of the traction control, not only the hold valve of the non-slip drive wheel is closed, but also the decay valve is opened at the same time, so that the brake pressure can be sufficiently reduced. It is possible to suppress the occurrence of torque interference and prevent the traction control performance from deteriorating.

[0008]

For this reason, the technical solution adopted by the present invention is to provide a cut valve in a flow path communicating a master cylinder and a wheel cylinder of left and right driving wheels.
A hold valve and a decay valve are arranged, a traction control circuit is connected to a flow path between the cut valve and the hold valve, the cut valve is closed at the time of driving wheel slip, and a hydraulic pressure from the traction control circuit side is used. In a traction control device for a vehicle, which can apply a braking force to a wheel cylinder on a slip wheel side, when slippage occurs in one of the left and right wheels and traction control is started, the other non-controlled drive wheel on the other side is driven. A traction control device for a vehicle, wherein the decay valve is opened for a predetermined time at the same time as the closing of the pressure valve.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a hydraulic circuit configuration diagram of a vehicle traction control device having an antilock control function and a vehicle stop holding function according to an embodiment of the present invention, in which the drive wheels are left and right rear wheels. In the figure, each valve provided in the hydraulic circuit is controlled by a known electronic control device (not shown). FIG. 2 is a flowchart of the operation of the solenoid valves (hold valve, decay valve) at the time of traction control, and it is natural that the present traction control device can be applied to a front-wheel drive, four-wheel drive type vehicle.

In the figure, M is a master cylinder, 1 is a cut valve, 2L is a left rear wheel hold valve, 3L is a left rear wheel decay valve, 2R is a right rear wheel hold valve, and 3R is a right rear wheel. Decay valve for wheels, BL is left rear wheel brake cylinder, BR is right rear wheel brake cylinder,
Reference numeral 4 denotes a reservoir. Brake cylinders BL and BR for left and right rear wheels are connected to respective pipelines between the hold valves 2L and 2R and the decay valves 3L and 3R as shown in the figure. The suction port of the anti-skid hydraulic pump 5 is provided in a pipe line between the pump and the reservoir 4, and the discharge port of the anti-skid hydraulic pump 5 is connected to the cut valve 1 and the hold valve 2L via a check valve 5A. , 2R to form a hydraulic circuit.

A traction control unit (hereinafter, referred to as a TCS unit) to be described later is connected to a pipeline between the cut valve 1 and the hold valves 2L and 2R of the hydraulic circuit. The TCS unit includes a hydraulic pressure generating means 7, an accumulator 8, a TCS pump 9, and a normally-open two-position switching valve 1.
0, a relief valve 11. The hydraulic pressure generating means 7 is connected to the discharge side of the TCS pump 9, and the suction side of the TCS pump 9 is connected to the accumulator 8.
The two-position switching valve 10 and the relief valve 11 are connected in parallel with the CS pump 9. The hydraulic pressure generating means 7 has a pressurizing piston 7b which divides the inside of the main body cylinder 7a into a first liquid chamber 72 and a second liquid chamber 73. The pressurizing piston 7b is in a liquid-tight state inside the cylinder 7a. And slidably provided. The pressure piston 7b is constantly urged to the left in the figure by a pressure spring 71 disposed in the second liquid chamber 73.

The hydraulic pressure generating means 7 introduces the brake fluid discharged from the TCS pump 9 into the first liquid chamber 72 at the time of traction control, and pushes the pressure piston 7b to the pressure spring 71.
Has the function of moving the brake fluid in the second fluid chamber 73 rightward in the drawing against the urging force of the second fluid chamber 73 and supplying it to the anti-skid hydraulic circuit. It is connected to the hold valves 2L and 2R. Further, the accumulator 8 is used for controlling the hydraulic pressure generating means 7 during non-traction control.
For accumulating the brake fluid in the first fluid chamber 72 in the accumulator. A piston 8a is slidably disposed in the accumulator in a liquid-tight manner. Being energized. The spring load between the pressure spring 71 in the hydraulic pressure generating means 7 and the accumulator spring 81 in the accumulator is set to be larger in the pressure spring 71 than in the accumulator spring 81. The TCS pump 9 operates during traction control, and the accumulator 8
Is pumped up and supplied to the hydraulic pressure generating means 7. At this time, the two-position switching valve 10 is closed. Further, the relief valve 11 has a function of releasing the hydraulic pressure when the discharge pressure of the TCS pump 9 increases.

Therefore, in the hydraulic circuit of the TCS unit, the pressurizing piston 7b in the hydraulic pressure generating means is urged leftward in the figure by the pressurizing spring 71 as shown in FIG. The brake fluid in the first fluid chamber 72 in the pressure generating means presses the accumulator piston 8a to the right in the drawing against the accumulator spring 81, so that a pressure is accumulated in the accumulator chamber.
At this time, the second fluid chamber 73 of the fluid pressure generating means 7 is filled with the brake fluid in communication with the above-described antilock control fluid pressure circuit.

Next, the operation of the traction control device having the above configuration will be described. [During Normal Braking] During normal braking, the hold valves and decay valves 2L and 2R are in the state shown in the figure. The hydraulic pressure generated in the master cylinder M by depressing the brake pedal is transmitted from the discharge port of the master cylinder to the cut valve 1, the left and right hold valves 2L, 2R.
Are supplied to the left and right rear wheel brake cylinders BL and BR via the brake pedal, and the brakes are operated. When the brake pedal is released, the brake fluid supplied to the left and right brake cylinders BL and BR returns to the master cylinder M through the same path,
The brake is released.

[At the time of anti-skid control] When a brake pedal is depressed to apply a brake to the vehicle, a hydraulic pressure is generated in the master cylinder M. This hydraulic pressure is supplied to the left and right rear wheel brake cylinders BL and BR via the cut valve 1 and the hold valves 2L and 2R, and applies a braking force to the left and right rear wheels.
When a drive wheel speed sensor (not shown) detects a tendency to lock the drive wheels during braking, the electronic control circuit controls the opening and closing of each of the hold valves 2L, 2R and the decay valves 3L, 3R according to the locked state of the drive wheels. And the anti-skid hydraulic pump 5 is driven. For example, when the right rear wheel tends to lock, a brake pressure reduction command is output from the electronic control unit, the hold valve 2R is closed to shut off the oil passage between the master cylinder M and the right rear wheel brake cylinder, and at the same time, the decay valve 3R is opened. Right rear wheel brake cylinder BR
The brake fluid in the right rear wheel brake cylinder is discharged to the reservoir 4 and the brake fluid pressure is reduced. Then, the brake fluid discharged to the reservoir 4 is
The fluid is recirculated to the master cylinder M by the anti-skid hydraulic pump 5 that operates simultaneously with the start of the hydraulic control. When the signal for holding the brake is output, the hold valve 2R and the decay valve 3R of the corresponding drive wheel are closed, the communication with the master cylinder M and the reservoir 4 is cut off, and the brake fluid pressure in the brake cylinder is maintained at the current fluid pressure. Is done. When re-pressurization is necessary, the hold valve 2R is opened and the decay valve 3R is closed. In addition,
The hydraulic control of the left and right rear wheel brake cylinders is performed independently in accordance with the state of each drive wheel.

At the time of traction control, when a driving wheel speed sensor (not shown) detects that the driving wheels have slipped due to sudden start when the vehicle starts, a signal is input to a known electronic control device, and traction control is performed. Be executed.

The electronic control circuit includes the hold valves 2L and 2R and the decay valve 3 according to the slip state of the drive wheels.
L, 3R and the anti-skid hydraulic pump 5 are controlled. Now, when a slip control signal for the right and left rear wheels is output from the electronic control unit, the cut valve 1 is closed to cut off the communication between the master cylinder M and the left and right rear wheel brake cylinders, and the two-position switching valve 10 is operated to increase the hydraulic pressure. The communication between the generating means 7 and the accumulator 8 is cut off. At the same time, the TCS pump 9 starts operating, and sucks the brake fluid from the accumulator 8. The sucked brake fluid is supplied to the first fluid chamber 72 of the fluid pressure generating means, moves the pressure piston 7b rightward against the pressure spring 71, and holds the brake fluid in the second fluid chamber 73. The power is supplied to the left and right rear wheels via the valves 2L and 2R, and the drive wheels are braked to reduce the drive slip. Also, during the slip control, the electronic control unit controls the hold valves 2L, 2R, the decay valve 3L,
Each of the 3Rs is controlled, and the braking force holding, the pressure reduction, and the re-pressurization are repeated according to the slip state of each drive wheel. As described above, the drive slip can be controlled to an optimum state. When the drive slip is almost eliminated, the electronic control unit detects this and stops the drive of the TCS pump 9, and at the same time, the two-position switching valve 10, the cut valve 1
Is switched to the illustrated state.

[At the time of stop holding control] When it is detected that the vehicle has once stopped at an intersection or the like, the cut valve 1 is closed by a command from the electronic control unit and the master cylinder M is closed.
And cut off the communication with the left and right rear wheel brake cylinders.
The position switching valve 10 operates to cut off the communication between the hydraulic pressure generating means 7 and the accumulator 8, and at the same time, the TCS pump 9 starts operating, pumping up the brake fluid from the accumulator 8 and causing the first hydraulic pressure of the hydraulic pressure generating means to change. It is supplied to the chamber 72. As a result, the pressurizing piston 7b moves rightward against the pressurizing spring 71, and the brake fluid in the second fluid chamber is supplied to the left and right rear wheels via the left and right hold valves 2L and 2R, and the brake is applied to the drive wheels. It is set to the stop holding state. This stop holding state is released by starting operation of the accelerator or the like.

By the way, when the vehicle stops when the left and right driving wheels are on a road surface having a different coefficient of friction, and after the above-mentioned stop holding device is operated, the stop holding device detects the start operation of the vehicle. The two-position switching valve 10 is closed, the TCS pump 9 is stopped, and the cut valve 1 is opened to release the brake fluid pressure sealed in the left and right rear wheel brake cylinders. Immediately thereafter, if a slip occurs on the drive wheels on the low μ road surface side before the brake pressure on the left and right drive wheels has sufficiently decreased, traction control will be started.
Here, the traction control device is a two-position switching valve 10 and T
The CS pump 9 is driven to supply the brake pressure only to the driving wheels where slippage has occurred, and to the driving wheels where no slippage has occurred, the hold valve used in the antilock control is closed and supplied from the pump. The applied brake pressure.

However, as described above, when the traction control is started immediately after the sudden start, the traction control is started on the non-slip drive wheel side before the brake pressure is sufficiently reduced, and the hold valve is activated. Because of the closing, the brake pressure will be confined again in that state. For this reason, there is a problem that the brake pressure is simultaneously generated on the left and right driving wheels, and the traction control performance is deteriorated, while the braking force should be applied only to the slip generating driving wheels. . Therefore, in order to eliminate such a state, in the present traction control device,
On the non-slip driving wheel side, the hold valve is closed and the decay valve is opened to prevent the brake pressure from being re-enclosed.

Hereinafter, the control flowchart will be described with reference to FIG. This program is started when the vehicle stops when the left and right drive wheels are on the road surface having different friction coefficients and the vehicle is suddenly started after the stop holding device described above is operated. First, in step S1, it is determined whether traction control (ASR control) is in operation. If the traction control has been started, the process proceeds to step S2, in which the decay valve on the non-slip driving wheel (non-control wheel) side is opened,
Proceed to step S3. The hold valve on the side of the non-slip driving wheel (non-control wheel) is closed at the same time as the start of traction control. In step S3, it is determined whether or not a predetermined time has elapsed from the start of the control. If the predetermined time has elapsed, it is determined in step S4 that the brake fluid pressure on the drive wheel that has not slipped has been sufficiently released, and the decay is performed. The valve is closed, and the process further proceeds to step S5 to perform normal traction control.

When the traction control is not operating in step S1, the process proceeds to step S6, and when the predetermined time has not elapsed from the start of the control in step S3, the control after step S5 is performed.
As described above, the hold valve of the non-controlled drive wheel must be kept closed while the traction control is operating. However, the decay valve requires a predetermined time (until the residual pressure disappears) or It is sufficient to open the drive wheel only until the drive wheel generates an acceleration slip and enters the traction control. As described above, according to the present invention, the brake pressure can be sufficiently reduced by not only closing the hold valve of the non-controlled driving wheel but also opening the decay valve at the same time when the traction control is started. Even when the vehicle suddenly starts, the occurrence of torque interference can be suppressed and the traction control performance can be prevented from deteriorating.

[0023]

As described in detail above, according to the present invention,
Even if the vehicle stops and suddenly starts when the left and right drive wheels are on a road surface with different friction coefficients, the brake fluid pressure on the non-slip drive wheel is opened by opening the decay valve on the non-slip drive wheel for a predetermined time. Can be sufficiently released, so that an excellent effect of suppressing occurrence of torque interference and preventing deterioration of traction control performance can be achieved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a traction control device having an antilock control function and a stop holding function as an embodiment according to the present invention.

FIG. 2 is a control flowchart for a non-controlled drive wheel during traction control.

[Explanation of symbols]

 Reference Signs List 1 cut valve 2L, 2R hold valve 3L, 3R decay valve 4 reservoir 5 anti-skid hydraulic pump 7 hydraulic pressure generating means 7a cylinder 7b pressurizing piston 71 pressurizing spring 72 first liquid chamber 73 second liquid chamber 8 accumulator 9 TCS pump 10 2-position switching valve 11 Relief valve M Master cylinder BL, BR Left and right rear wheel brake cylinder

Claims (1)

[Claims] 1. A cut valve 1, a hold valve 2L, 2R, and a decay valve 3L, 3R are arranged in a flow path connecting a master cylinder and a wheel cylinder of a left and right driving wheel. A traction control circuit (TCS unit) is connected to the flow path between the traction control circuit and the cut valve 1 is closed when a drive wheel slips, and a brake force is applied to the wheel cylinder on the slip wheel side by the hydraulic pressure from the traction control circuit side. In a traction control device for a vehicle, when the traction control is started due to the occurrence of a slip on one of the left and right wheels, the hold valve 2 of the other uncontrolled drive wheel is closed and the decay valve 3 is turned on for a predetermined time. A traction control device for a vehicle, wherein the traction control device is opened.