JPH0976895A - Traction controlling method and controller thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To bring an estimated vehicle body speed close to an actual vehicle body speed by performing traction control while setting the estimated vehicle body speed to a wheel speed when fluctuation in the wheel speed due to application of a brake fluid pressure is the predetermined value or less. SOLUTION: A testing brake fluid pressure is impressed to a wheel cylinder 12 for wheels by an action of an open/close valve in a fluid pressure unit 20 for the predetermined time during traction control, and this impression is carried out to one wheel, and then, its wheel speed is found. It is determined whether the wheel grips or not by finding fluctuation in wheel speeds after/before application of a brake and a wheel acceleration. When the wheel grips, the fluctuation in the wheel speed and the wheel acceleration range within the predetermined values, and traction control is carried out while an estimated vehicle body speed is set to the wheel speed. In this way, the estimated vehicle body speed is brought close to an actual vehicle body speed, so that a speed reduction feeling or a lack of acceleration can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a traction control system (TCS) for all-wheel drive vehicles.

[0002]

2. Description of the Related Art Conventionally, when obtaining an estimated vehicle speed in traction control of an all-wheel drive vehicle, all the wheels may overspin, so that all the wheel speeds may not match the actual vehicle speed. is there. Therefore, for example, an accelerometer (hereinafter referred to as a G sensor) is installed in the vehicle body, and the estimated vehicle body speed is estimated by obtaining the vehicle body acceleration from the signal of the G sensor.

[0003]

Problems to be Solved by the Invention Conventionally, there are the following problems. <A> With the conventional method using the G sensor, an accurate vehicle speed cannot be obtained due to, for example, the inclination of the vehicle body or an error in the sensor. Therefore, there was a feeling of deceleration or insufficient acceleration in the traction control. For example, if the estimated vehicle body speed calculated using the G sensor is lower than the actual vehicle body speed, it means that a slip is apparently occurring even if the slip is not occurring, which is required by the traction control. Acceleration is impeded above.

[0004]

[Purpose of the present invention]

<A> The present invention is to bring the estimated vehicle speed closer to the actual vehicle speed in the traction control of the all-wheel drive vehicle. <B> The present invention is to solve the feeling of deceleration and insufficient acceleration in traction control of an all-wheel drive vehicle.

[0005]

SUMMARY OF THE INVENTION The present invention is a traction control method for performing traction control by comparing the wheel speed of an all-wheel drive vehicle with an estimated vehicle speed, and obtains the wheel speed of at least one wheel. After applying the brake fluid pressure for a predetermined time to, after determining the wheel speed of the wheel,
A traction control method characterized in that a fluctuation in wheel speed of the wheel due to application of brake fluid pressure is obtained, and if the fluctuation in the wheel speed is within a predetermined value, the estimated vehicle speed is set to the wheel speed to perform traction control. Or, if the brake fluid pressure is applied to at least one wheel for a predetermined time, the wheel acceleration of the wheel is obtained after the brake fluid pressure is applied, and if the wheel acceleration of the wheel due to the application of the brake fluid pressure is within a predetermined value, it is estimated. A traction control method for performing traction control by changing a vehicle speed to a wheel speed, or a traction control device for performing traction control by comparing a wheel speed of an all-wheel drive vehicle with an estimated vehicle speed. A wheel cylinder that applies pressure to brake each wheel, an open / close control valve that controls the brake fluid pressure applied to the wheel cylinder, and a vehicle for each wheel. And a wheel speed sensor for measuring the speed,
An electronic control device for controlling the opening / closing of the opening / closing control valve, wherein the electronic control device obtains a wheel speed of at least one wheel, applies a brake fluid pressure to the wheel for a predetermined time, and applies the brake fluid pressure to the wheel of the wheel. The traction control is characterized in that the speed is calculated, the fluctuation of the wheel speed of the wheel due to the brake fluid pressure is calculated, and when the fluctuation of the wheel speed is within a predetermined value, the estimated vehicle speed is set to the wheel speed to perform the traction control. Device, or a wheel cylinder that applies brake fluid pressure to brake each wheel, an opening / closing control valve that controls the brake fluid pressure applied to the wheel cylinder, and a wheel speed sensor that measures the wheel speed of each wheel, An electronic control device for controlling the opening / closing of the opening / closing control valve, wherein the electronic control device applies the brake fluid pressure to at least one wheel for a predetermined time, and after applying the brake fluid pressure,
A traction control device is characterized in that a wheel acceleration of the wheel is obtained, and when the wheel acceleration of the wheel due to application of a brake fluid pressure is within a predetermined value, the estimated vehicle speed is set to the wheel speed to perform traction control.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. <A> Traction control device (FIG. 1) There are various methods for traction control, such as fuel control and ignition timing control. A brake traction control device will be described as an example. Brake traction control, for example, when the accelerator pedal is depressed to increase the rotation of the wheels, and as a result, the wheels overspin and the coefficient of friction between the wheels and the ground decreases, for example, brake the wheels to control the rotation speed. It reduces the friction and increases the frictional resistance coefficient. Therefore, the electronic control device receives a signal from the wheel speed sensor 13, detects the rotation speed of the wheel, obtains the estimated vehicle body speed and the wheel speed, and calculates the degree of overspin. When the overspin exceeds a predetermined threshold value, the opening / closing valve of the hydraulic unit 20 is operated to apply the brake hydraulic pressure to the wheel cylinder 12 of the wheel to reduce the overspin. The electronic control unit is a dedicated hardware device,
Further, it has a hardware configuration of a general computer such as an input device, an output device, a storage device, and an arithmetic device.

<B> Hydraulic Unit (FIG. 2) The hydraulic unit 20 is a circuit for brake fluid, and, for example, the master cylinder 11 and the wheel cylinder 12 of each wheel are provided with an independent main hydraulic passage 21. It is connected.
An inlet valve 3 which is a normally open solenoid valve on the way of the main hydraulic pressure passage 21.
1 is incorporated.

The return passage 22 is connected to the main hydraulic passage 21 before and after the inlet valve 31. A normally closed outlet valve 32, an auxiliary reservoir 33, an auxiliary pressure source and a damping chamber 36 are provided in the return flow path 22. The auxiliary pressure source includes a hydraulic pump 34 and a motor 35.

A traction valve 37 is provided upstream of the confluence of the main reservoir 33 of the main hydraulic pressure passage 21 and the return passage 22. Traction valve 37 and master cylinder 1
An auxiliary flow path 23 is connected to the main hydraulic pressure flow path 21 between No. 1 and the return flow path 22 between the auxiliary pressure source and the outlet valve 32. An auxiliary valve 38 is provided along the auxiliary flow path 23.

<C> Operation of hydraulic unit during normal braking The hydraulic pressure generated in the master cylinder 11 by the brake operation is applied to the wheel cylinder 12 of the wheel via the traction valve 37 and the inlet valve 31 of the main hydraulic pressure passage 21. Supplied. When the brake is released, the brake fluid is the main fluid pressure passage 21.
In reverse, and is returned to the master cylinder 11.

<D> Operation of hydraulic unit during traction operation For example, when an all-wheel drive vehicle is started or accelerated on a road surface having a low friction coefficient (hereinafter referred to as a low μ road), wheels tend to overspin. When this is detected, the traction valve 37 closes and the auxiliary pressure device operates to activate the hydraulic pump 34.
Brake fluid pressure from inlet valve 31 and traction valve 3
It is generated in the main hydraulic pressure passage 21 between 7 and 7. The generated brake fluid pressure is supplied to the wheel cylinder 12 of the drive wheel by the opening / closing operation of the inlet valve 31 and the outlet valve 32, and traction control is performed.

The traction control will be described below. <A> Start of Traction Control When the brake traction control is started, the electronic control unit obtains the acceleration of the wheel from the signal of the G sensor 14, for example, and integrates it to calculate the estimated vehicle speed. At the same time, a signal is received from the wheel speed sensor 13 of each wheel to calculate the wheel speed of each wheel. Next, find the slip state of each wheel,
When the slip ratio exceeds the threshold value, the wheels are decelerated so that the friction resistance coefficient between the wheels and the road surface becomes high, and the brake traction control is performed.

<B> Application of Test Brake Fluid Pressure During Traction Control (FIG. 3) During the traction control, a test brake fluid pressure is applied to the wheel cylinders 12 of the wheels. It is preferable that the test brake fluid pressure and the application time do not substantially affect the speed of the vehicle body. The applied wheels are applied to at least one wheel, and, for example, the one having the smallest wheel speed is selected. The brake fluid pressure is, for example, pulsed, the fluid pressure is 10 bar, and the time is 100 ms.

<C> Change of estimated vehicle speed (FIG. 3) When the test brake fluid pressure is applied to the wheel, if the wheel grips the road surface (not slips), the wheel speed fluctuates and the wheel speed changes. Acceleration falls within the specified range.
Therefore, it is possible to determine whether or not the wheel is gripped by obtaining the wheel speed variation and the wheel acceleration before and after applying the brake.

For example, the wheel acceleration of the lowest wheel speed is within a normal acceleration range (0 G to 0.6 G) for a predetermined time (0.2 s to
0.6 s), if the brake pressure is applied in a pulsed manner, the acceleration of the vehicle to which the brake pressure is applied hardly changes as long as the vehicle grips, but the wheel speed and the wheel acceleration become normal when overspin occurs. It fluctuates over the acceleration range.

Therefore, if the wheel is gripped, the wheel speed becomes the actual vehicle speed, so that the wheel speed is replaced with the estimated vehicle speed to continue the traction control. When slipping, changes in wheel speed and acceleration fluctuate. In that case, the estimated G-sensor 1 will continue without reviewing the estimated vehicle speed.
Calculate the estimated vehicle speed by integrating 4.

[0017]

According to the present invention, the following effects can be obtained. <B> When the estimated vehicle body speed is estimated to be lower than the actual vehicle body speed during traction control, the estimated vehicle body speed can be corrected to the actual vehicle body speed, so that the feeling of deceleration and insufficient acceleration can be improved.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a brake traction control device.

FIG. 2 Brake hydraulic circuit diagram for traction control

FIG. 3 is a wheel speed variation graph when the estimated vehicle speed is smaller than the actual vehicle speed.

Claims (4)

[Claims] 1. A traction control method for performing traction control by comparing a wheel speed of an all-wheel drive vehicle with an estimated vehicle body speed, wherein a wheel speed of at least one wheel is obtained, and a brake fluid pressure is applied to the wheel for a predetermined time. After applying the brake fluid pressure, the wheel speed of the wheel is obtained, and the variation of the wheel speed of the wheel due to the application of the brake fluid pressure is obtained. If the variation of the wheel speed is within a predetermined value, the estimated vehicle body speed is calculated as A traction control method characterized by performing traction control at high speed. 2. A traction control method for performing traction control by comparing the wheel speed of an all-wheel drive vehicle with an estimated vehicle speed, wherein a brake fluid pressure is applied to at least one wheel for a predetermined time, and after applying the brake fluid pressure, A traction control method, wherein wheel acceleration of the wheel is obtained, and when the wheel acceleration of the wheel due to application of brake fluid pressure is within a predetermined value, the estimated vehicle speed is set to the wheel speed to perform traction control. 3. A traction control device for performing traction control by comparing the wheel speed of an all-wheel drive vehicle with an estimated vehicle speed, and a wheel cylinder for applying brake fluid pressure to brake each wheel, and a wheel cylinder for applying the brake fluid pressure to each wheel. An opening / closing control valve for controlling the brake fluid pressure, a wheel speed sensor for measuring the wheel speed of each wheel, and an electronic control device for opening / closing the opening / closing control valve, wherein the electronic control device has at least one wheel. The speed is obtained, the brake fluid pressure is applied to the wheel for a predetermined time, the wheel speed of the wheel is obtained after the application of the brake fluid pressure, and the variation of the wheel speed of the wheel due to the brake fluid pressure is obtained. A traction control device, which performs traction control by setting an estimated vehicle speed to a wheel speed when the value is within a predetermined value. 4. A traction control device for performing traction control by comparing a wheel speed of an all-wheel drive vehicle with an estimated vehicle speed, and a wheel cylinder for applying a brake fluid pressure to each wheel to apply a brake to the wheel cylinder. An opening / closing control valve for controlling the brake fluid pressure, a wheel speed sensor for measuring the wheel speed of each wheel, and an electronic control device for controlling the opening / closing of the opening / closing control valve are provided. After applying the brake fluid pressure for a time, the wheel acceleration of the wheel is obtained after applying the brake fluid pressure, and when the wheel acceleration of the wheel due to the application of the brake fluid pressure is within a predetermined value, the estimated vehicle speed is set to the wheel speed and the traction is performed. Traction control device characterized by performing control.