JPH0536775Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to an anti-skid control device that prevents wheels from locking by controlling brake fluid pressure.

(Prior art) When braking a vehicle, the rotational state of the wheels or propeller shaft, that is, the deceleration or slip rate of the wheels, is detected, and the brake fluid pressure is adjusted according to the detected value to maintain a certain slip rate of the wheels. Anti-skid control devices are already known which attempt to control the vehicle body to obtain maximum deceleration and lateral stability.

Here, this anti-skid control device includes a wheel speed sensor that detects the speed of each wheel of the vehicle and sends a speed signal corresponding to the wheel speed, a brake switch that detects whether the brake is on or off, and a brake fluid pressure in the brake pipe. It has a modulator that controls each modulator and a drive circuit that sends a drive signal to operate each modulator, and detects a tendency for the wheels to lock during braking based on the output signal from each wheel speed sensor. If this is detected, as shown in Figure 6, the brake fluid pressure is suddenly released to a predetermined pressure V1 to avoid slipping, and then the brake fluid pressure is reduced to a constant pressure.
The brake fluid pressure is increased in steps for each Va, that is, the brake fluid pressure is released for a set time Z, and then
The brake fluid pressure is charged for a certain period of time t, and then the fluid pressure is held for a certain period of time T, and this brake fluid pressure filling and hydraulic pressure holding are repeated, and as mentioned above, the maximum reduction of the vehicle body is The objective is to simultaneously obtain speed and lateral stability, that is, to shorten the braking distance of the vehicle while preventing the vehicle from turning on snowy roads.

(Problems to be Solved by the Invention) As described above, when a vehicle equipped with the above-mentioned anti-skid control device applies the brakes while driving on a low μ road such as a snowy road and the wheels tend to lock, the above-mentioned Control such as this, that is, control in which the brake fluid pressure is set to V1 by setting it to V1 for a set time Z, and then the brake fluid pressure is set to V1 for a fixed time t, and is increased in steps with a hold time T in between. is carried out, and when driving on low μ roads such as snowy roads,
There is no problem with the above control, which focuses on avoiding turning of the vehicle body rather than braking distance, but it is suitable for low μ roads with relatively high road resistance such as corrugated roads, gravel roads, uneven roads, and ground roads. That is, when driving on a rough road, it is desirable to shorten the braking distance by slightly locking the wheels and braking while dragging gravel or the like. However, if the brakes are applied while the vehicle is bouncing due to the unevenness of the road while driving on the so-called rough road mentioned above, the wheels may float and become locked, even if the wheels are not slipping. As a result, the computer that controls the anti-skid control device determines that the wheel is slipping, and the above-mentioned brake fluid pressure is interrupted for a set time Z, and then the brake fluid pressure is held for a hold time T. A certain period of time t in between
As a result, braking distance is increased significantly, which can be dangerous and even dangerous. Ta.

An object of the present invention is to provide an anti-skid control device that can shorten the braking distance when driving on rough roads with relatively high road resistance, such as corrugated roads, gravel roads, bumpy roads, and dirt roads.

(Means for Solving the Problems) In order to achieve the above object, the anti-skid control device of the present invention detects the speed of each wheel of the vehicle as shown in FIG. 1, and sends a speed signal corresponding to the wheel speed. A wheel speed sensor 30 that sends out a brake, a brake switch 15 that detects whether the brake is on or off,
A modulator 8 that controls the brake fluid pressure of each brake pipe, and each drive circuit 18 that sends a drive signal that operates each modulator 8.
detects a locking tendency of the wheels during braking based on the output signal from each wheel speed sensor 30, and when a locking tendency of the wheels is detected, the brake fluid pressure is adjusted for a set time Z. Anti-skid control that sends a brake fluid pressure release signal to release the brake fluid pressure, and then sends a brake fluid pressure filling signal to the drive circuit 18 to increase the brake fluid pressure in steps at fixed time intervals t with a hold time T in between. The anti-skid control device includes a means 100 and prevents the wheels from locking through brake fluid pressure control by the anti-skid control means 100, comprising: a calculating means 62 for calculating a fluctuation frequency of the speed signal when the brake is off; and a comparison means 63 which compares the output of the brake fluid with a predetermined value and, if the output is equal to or higher than the predetermined value, determines that the road is rough and sends out a rough road signal; , a brake fluid pressure change signal generation means 69 that generates a brake fluid pressure change signal that is extended from the fixed application time t after the second step, and a brake on signal that receives the brake on signal after receiving the rough road signal. In this case, switching means 68 sends a signal from the brake fluid pressure change signal generating means 69 to the drive circuit 18 instead of the brake fluid pressure filling signal after sending the brake fluid pressure release signal. It is characterized by comprising a controller 17 consisting of the following.

(Function) According to the present invention, the output from each wheel speed sensor 30 is input to the calculation means 62, and the output from each wheel speed sensor 30 is inputted to the calculation means 62.
The fluctuation frequency of the wheel speed when the brake is off is calculated and inputted to the comparison means 63. If the fluctuation frequency is equal to or higher than a predetermined value that can be considered as a rough road by the comparison means 63, a rough road signal is detected. is input to the switching means 68. On the other hand, switching means 68
A brake signal from the brake switch 15 is also inputted to the brake switch 15, and when a brake-on signal is received after receiving a bad road signal, the brake signal is sent from the anti-skid control means 100 to the drive circuit 18 that drives each modulator 8 when the wheels tend to lock. Ru. The drive signal after the conventional brake fluid pressure release signal that releases the brake fluid pressure for a set time Z is set for a fixed time t with a brake fluid pressure hold time T in between.
Instead of a brake fluid pressure filling signal that increases in steps every time, the charging time αt of the first step of the brake fluid pressure is changed to a constant charging time t from the second step onwards.
Brake fluid pressure change signal generation means 69 for generating a brake fluid pressure change signal that is longer
The brake fluid pressure change request signal is now sent from the brake system, and anti-skid control that can shorten the braking distance is performed.

(Example) Examples of the present invention will be described below with reference to the drawings. FIG. 2 is a schematic configuration diagram of an anti-skid control device for a four-wheel drive vehicle without a center differential showing an embodiment of the present invention. A transfer 3 that is directly connected to the propulsion shaft 2, and a master cylinder 20 to each wheel cylinder 4, 5 of the front and rear wheels.
A pair of brake pipes (also referred to as diagonal pipes) 6, 7 arranged in an
a, 18b, and two left and right speed sensors 30a, 30b supported by the axle housing on both sides of the front differential 10, which detect the rotational speed of each left and right front wheel FW, and the rotational speed of each left and right rear wheel RW. , and two left and right speed sensors 30c and 30d supported by the axle housing on both sides of the rear differential 70, an acceleration/deceleration sensor (hereinafter simply referred to as G sensor) 13, and a brake pedal 14.
The brake switch 15 detects the operation (on/off) of the brake in conjunction with the ignition switch 16, which operates when the ignition switch 16 is turned on.
30b, 30c, 30d, 13 and the drive circuit 18a, in response to signals from the brake switch 15.
A controller 17 is provided to send a signal to 18b. Here, speed sensors 30a, 30b, 30c,
30d and the G sensor 13 are of a known structure, and the modulators 8a and 8b are hydraulic or pneumatic type that control the brake fluid pressure using hydraulic pressure or pneumatic pressure by operating a solenoid, or modulators 8a and 8b are of a hydraulic or pneumatic type that control the brake fluid pressure by operating a solenoid. These are of a known structure such as an electric type that directly controls the control, and detailed explanations thereof will be omitted.

The controller 17 is a microcomputer configured to achieve the same functions as the calculation means 62, the comparison means 63, the switching means 68, the brake fluid pressure change signal generation means 69, and the well-known anti-skid control means 100 in FIG. Furthermore, a program that can achieve the above functions is written in the ROM in the controller 17, and each setting value and data table are stored and processed. ROM
A flowchart of the program written in is shown in Figure 3.

The operation of this device will be explained below according to the program.

When the program starts, the first step is step 1.
The flag is set to 0 in step 2, and in step 2, each sensor, that is, wheel speed sensor 30a, 30b, 30c, 30d and G
Read the output value from sensor 13 and proceed to step 3
In step 3, it is determined whether the brake switch 15 is on, that is, whether the brake pedal 14 is depressed. If the brake pedal 14 is depressed, the process proceeds to step 4, and if it is not depressed, the process proceeds to step 5. In step 5, the variable frequency of each wheel is detected by each wheel speed sensor 30a, 30a.
It is calculated based on the output values from 0b, 30c, and 30d, and the process proceeds to step 6, where it is determined whether the fluctuating frequency is equal to or greater than a predetermined value.
Here, the waveform of the wheel speed when driving on a so-called rough road with relatively high road resistance, such as a corrugated road, a gravel road, an uneven road, and a dirt road, is a substantially sinusoidal wave with a short period, or a short periodic wave with jagged edges on the waveform. It is known that the waveform is approximately a sine wave, and the frequency at that time, that is, when the road is rough, is set as a predetermined value, so if the calculated fluctuation frequency is equal to or higher than the predetermined value, it is determined that the road is rough. Then proceed to step 7, set the flag to 1 in step 7, then return to step 2,
On the other hand, if it is smaller than the predetermined value, it is determined that the road is not rough and the process proceeds to step 8, where the flag is set to 0, and then the process returns to step 2.
Note that the predetermined value referred to here is a value determined experimentally, and in this embodiment, it is set to 13 to 14 Hz. Then, when returning to step 2, the process proceeds to step 2 and step 3 in the same manner as described above, and in step 3, the brake switch 15 is turned on.
That is, if it is determined that the brake pedal 14 is being depressed, the process proceeds to step 4, where it is determined whether or not there is a slipping wheel, and if there is no slipping wheel (when there is no wheel heading toward lock). In this case, there is no need to perform anti-skid control, so the process returns to step 2. On the other hand, if there is a slip wheel (if there is a wheel heading toward lock), the process advances to step 9, in which the well-known anti-skid control is performed, and then In order to prevent the vehicle body from turning, a drive signal is applied to both modulators 8a and 8b, and the hydraulic pressure in the brake pipes 6 and 7 is removed for a set time Z. Then, as shown in FIG. 4, the brake fluid pressure suddenly drops significantly from V2 to V1. Then step
In step 10, it is determined whether the aforementioned flag is 0, that is, whether the road is rough. If the flag is 0 here, it is assumed that the road is not bad and the process proceeds to step 11, where the conventional normal brake fluid pressure control is performed to avoid turning rather than shorten the braking distance. Control (6th
(see figure), and then returns to step 2. On the other hand, if the flag is not 0, that is, 1
In this case, it is assumed that the road is rough and the process proceeds to step 12. In step 12, anti-skid control for rough roads,
In other words, in order to perform control to shorten the braking distance by slightly locking the wheels while dragging gravel, etc., control is performed in which only the brake fluid pressure filling time for the first step is made longer than the fixed filling time for the second and subsequent steps. Execute. That is, as shown in FIG. 4, hydraulic pressure control is performed such that the first opening time of the valve for charging brake fluid pressure is longer αt than the conventional constant opening time t from the second time onward. . When such control is performed, the brake fluid pressure returns to the ideal control fluid pressure more quickly than conventional control, and the deceleration rate is also lower than that of the conventional control fluid pressure, as shown by the solid line in FIG. This increases faster than the deceleration, making it possible to shorten the braking distance. Incidentally, in this example, t=8~
It is set to 15 mm seconds and αt = 12 to 22.5 mm seconds (approximately 1.5 times t). Once the control for rough roads has been performed in this way, the process returns to step 2.

In this way, in the present invention, when braking while driving on a rough road, the anti-skid control for driving on rough roads, that is, only the application time of the first step of brake fluid pressure is made longer than the fixed application time after the second step. Since the control is carried out, it is possible to shorten the braking distance which is desired when driving on rough roads.

In the above embodiment, there are four wheel speed sensors.
The application of the modulator to a so-called 4-sensor, 2-channel 4-wheel drive vehicle without a center differential has been described as an example. This is particularly effective since the braking distance on rough roads is longer than that of a so-called 4-sensor, 4-channel 4-wheel drive vehicle, but the modulator can also be applied to 4-sensor, 4-channel 4-wheel drive vehicles, and can also be applied to 4-wheel drive vehicles with a center differential.

(Effects) As described above, according to the present invention, the fluctuation frequency of the wheel speed when the brake is off is calculated, and if the calculated value is equal to or higher than a predetermined value that can be considered as a rough road, the brake fluid pressure is released during anti-skid control. Since the charging time for the first step of the subsequent brake fluid pressure filling operation is made longer than the constant charging time for the second and subsequent steps, it is possible to significantly shorten the braking distance when driving on rough roads. .

[Brief explanation of the drawing]

Fig. 1 is an overall block diagram of the present invention, Fig. 2 is a schematic block diagram of an anti-skid control device showing an embodiment of the present invention, and Fig. 3 is a flowchart of the program stored in the controller in Fig. 2. Chaat, 4th
The figure is a diagram of the change in brake fluid pressure over time using the device of the present invention, Figure 5 is a diagram of the change in deceleration over time to compare the braking performance of the device of the present invention and the conventional device, and Figure 6 is a diagram of the brake fluid pressure with the conventional device. FIG. 3 is a diagram of changes in hydraulic pressure over time. 6, 7... Brake piping, 8, 8a, 8b...
Modulator, 14... Brake pedal, 15...
...Brake switch, 17...Controller, 1
8, 18a, 18b...drive circuit, 30, 30
a, 30b, 30c, 30d...Wheel speed sensor, 62...Calculation means, 63...Comparison means, 68
...Switching means, 69...Brake fluid pressure change signal generation means, 100...Anti skid control means, FW, RW...Wheels, T...Hold time,
t... fixed time (fixed filling time after the second step), Z... set time, αt... filling time of the first step.

Claims (1)

[Scope of utility model registration request] a wheel speed sensor that detects the speed of each wheel of the vehicle and sends a speed signal corresponding to the wheel speed; a brake switch that detects whether the brake is on or off;
It has a modulator that controls the brake fluid pressure of each brake pipe, and a drive circuit that sends a drive signal that operates each modulator, and locks the wheels during braking based on the output signal from each wheel speed sensor. If the wheel lock tendency is detected, a brake fluid pressure release signal is sent to release the brake fluid pressure for a set time Z, and then the brake fluid pressure is held for a set time T. The anti-skid control means includes an anti-skid control means for sending a brake fluid pressure filling signal to the drive circuit to increase the brake fluid pressure in steps at fixed time intervals t, and prevents the wheels from locking by controlling the brake fluid pressure by the anti-skid control means. In the device, a calculating means for calculating a fluctuation frequency of the speed signal when the brake is off, and comparing an output from the calculating means with a predetermined value,
When the output is equal to or greater than the predetermined value, the comparison means determines that the road is rough and sends out a rough road signal, and the brake fluid pressure charging time αt of the first step is set to a constant charging time t from the second step onwards. a brake fluid pressure change request signal generation means for generating a brake fluid pressure change request signal that is extended longer; and when a brake on signal is received after receiving the rough road signal, the brake fluid pressure release signal is sent. Anti-skid control characterized by comprising a controller comprising switching means for sending a signal from the brake fluid pressure change signal generation means to the drive circuit in place of the brake fluid pressure change signal. Device.