JPS5940656B2 - anti skid device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an anti-skid device that prevents the wheels of a vehicle from skidding, and in particular, uses a radar vehicle speed sensor, such as a Doppler ground speed detection device, as a device for detecting ground speed. This relates to an anti-skid device that detects ground speed.

The conventional anti-skid device, as shown in FIG. 1, is a ground speed signal V detected by a Doppler ground speed sensor 1 and a wheel speed signal VW detected by a wheel speed sensor 2. Each is input to the comparator 3, and the slip rate S is calculated as S-(V-Vw)/V in the comparator 3, and the slip rate S is set in advance.

When S≧So, that is, ■≦(1-8o)・■, a hydraulic control signal 4 is generated to reduce the brake hydraulic pressure.
Skid control is performed by generating a command signal to restore brake oil pressure when the condition S<So is satisfied.

In this case, the method of installing a Doppler ground speed detection device and detecting the ground speed V using the Doppler radar is to It has the great advantage of being able to accurately determine the slip ratio.

That is, as shown in the explanatory diagram of slip ratio detection in FIG. 2, since it is possible to detect a speed approximately equal to the actual running speed vA indicated by the dashed-dotted line as the ground speed ■, for example, one of the rear wheels at the braking point A When the wheel speed Vw of the wheels decreases, the ratio of the ground speed ■ and the wheel speed Vw becomes the set value, and the set slip rate S.

(Figure 2 shows the case where the setting is ◯:Vw-3:2.

), extreme skid control can be performed in order to release the brake hydraulic pressure of the nearly locked rear wheels.

However, the above-mentioned disadvantage of the Doppler radar is, for example, when a vehicle is exposed to water on a road (hereinafter referred to as a flooded road).

), the water spray is transmitted by the rotational force of the wheels and is rolled up against the ground in the same direction as the vehicle's traveling direction, and the Dotsuplar radar detects the speed relative to the water spray as the ground speed. Because of this, the ground speed may be detected to be much lower than the actual ground speed.

In this case, as shown in the explanatory diagram in Figure 3, the ground speed ■ is significantly lower than the actual vehicle speed vA by 7, and the slip rate is detected based on the detected ground speed ■, so the slip rate is made smaller than the actual one. was detected, and the brake hydraulic pressure is released at point C.
There was a risk that the wheels would be unable to perform proper skid control due to the delay.

The present invention has been made in view of the above, and in order to perform anti-skid control appropriately when a radar vehicle speed sensor detects a ground speed lower than the actual speed, for example in a flooded waterway, etc.
When the wheel speed of any wheel exceeds a predetermined average deceleration of the vehicle due to deceleration after a difference occurs between the ground speed and the average vehicle speed, a speed correction circuit is installed to correct the wheel speed to the average deceleration. The output of this speed correction circuit is used as a ground speed signal to calculate the slip ratio.

The present invention will be explained below with reference to the drawings.

FIG. 4 is a block diagram of an embodiment of the present invention.

In FIG. 4, 7 is a speed correction circuit, which is composed of a selection circuit 5 and a deceleration setting circuit 6.

Other symbols are the same as in FIG. Selection circuit 5
are the ground speed signal V detected by the Dotsupura ground speed sensor 1 and the wheel speed signal ■ detected by the wheel speed sensor 2.
and then select the one with the higher speed.

The output of this selection circuit 5 is sent to a deceleration setting circuit 6, which is constituted by, for example, a charging/discharging circuit, and the deceleration setting circuit 6 generates an output signal that decreases at a predetermined degree of decrease.

Comparator 3 converts the output of this deceleration setting circuit 6 into the first conventional example.
The slip rate is detected by regarding it as the output of the Doppler ground speed sensor shown in the figure.

FIG. 5 is a block diagram of one embodiment of the selection circuit 5 in FIG. 4, and shows a digital type.

fl indicates a signal input with a frequency proportional to the ground speed detected by the Doppler ground speed sensor 1, and f2 indicates a signal input with a frequency proportional to the wheel speed detected by the wheel speed sensor 2.

Now, for the sake of simplicity, it is assumed that fl and f2 are signals of the same frequency for the same speed.

Pulse counter A1 and pulse counter B reach logic level "'1" when they both count inputs of the same number of pulses.
This is a counter that generates a signal.

Assuming that fl, which corresponds to the ground speed, is now showing a lower speed, pulse counter B reaches the set pulse number first and outputs a signal of level ``1'' first.

As a result, the flip-flop FF receives an input at the reset terminal R, generates an output "1" at the output terminal Q, and outputs "1" from the output terminal Q.
becomes the output "0".

Therefore, the output of the AND circuit ANDI becomes "0", and the AND circuit AND2 outputs the same frequency signal as the frequency f2 corresponding to the wheel speed.

Further, the OR circuit OR1 generates an output "1" at the moment the output from the pulse counter B becomes "1", and resets both the pulse counters A and B.

As a result, pulse counters A and B start comparing f, , f2 again from this point.

FIG. 6 shows a configuration diagram of an embodiment of the deceleration setting circuit 6 in FIG. 4. The input IN enters the comparator COMP and is compared with the output OUT. When the frequency is high), the comparator COMP generates a logic level "1" output and charges the capacitor C through the diode D and the small resistance resistor R2.

Since R2C is set to a very small value, it sufficiently follows changes in the input IN, resulting in an analog voltage proportional to the input.

■CO is a voltage/frequency converter that generates a frequency proportional to this voltage, and when the input IN and output OUT become the same frequency, the output of the comparator COMP becomes "0", and therefore the capacitor C is not charged, and a large It is discharged through the resistor R1 of resistance value, so that it is always an analog voltage proportional to the input.

However, when the input suddenly decreases, the capacitor C is discharged through the resistor R1, so the voltage does not decrease suddenly and R
, -C, the output frequency also follows this.

Note that this time constant is preferably set to correspond to a deceleration value of 0.9 to 1.1 g.

The differences in anti-skid control in flooded waterways between the device of the present invention configured as described above and the conventional device are explained in the second section. Third
This will be described with reference to FIG.

FIG. 7 shows the temporal change state of each speed signal in the case of the method of the present invention. The curve shown in FIG. 3 corresponds to the one-dot chain line vA, the actual ground speed, the curve 2, the ground speed curve detected by the Dotsupura ground speed sensor, and the two-dot chain line showing the controlled wheel speed. A curve M shown by indicates an output signal (hereinafter referred to as corrected ground speed) from the deceleration setting circuit 6 in FIG. 4 according to the embodiment of the present invention.

The ground speed detected by Dotsuplar radar is much lower than the actual ground speed in flooded waterways, and the conventional method
The slip rate was calculated from this ground speed signal and wheel speed signal, and when the slip rate exceeded the set slip rate, a signal was issued to reduce the brake oil pressure.The controlled wheel speed is shown in Figure 3 by the curve . As shown in Figure 3, the control was downward, and the release point C of the brake hydraulic pressure was delayed.

On the other hand, according to the embodiment shown in FIG. 4, either the Dotsupura ground speed signal or the wheel speed signal, whichever is higher, is selected, and a signal that limits the deceleration of the selected speed signal is used as a new corrected ground speed. Since the system uses this signal as a signal and calculates the slip rate using this signal and the wheel speed signal, it is controlled as shown in curve M in Figure 7.Also, the brake oil pressure is reduced when the wheel speed is relatively high. A signal can be issued and the slip rate can be controlled appropriately.

On the other hand, when the Dotsupura ground speed sensor 1 detects a value close to the actual vehicle speed vA (Fig. 2) when not driving through a flooded waterway, the selection circuit 5 shown in Fig. 4 selects the ground speed signal ■. However, since a speed signal without deceleration correction is output, the slip ratio can be calculated as before.

FIG. 8 is a configuration diagram showing another embodiment of the present invention, which includes:
Instead of setting the deceleration set value at a constant value, if the detected ground speed is lower than the wheel speed by a certain set value, it is determined that the water is flooded, and the deceleration set value is set further than the preset constant value. This is a case where the force is lowered (for example, 0.6 to 0.8G).

As for the configuration, a comparator 7 and a brake switch 8 are added compared to the embodiment shown in FIG.

The outputs of the ground speed sensor 1 and the wheel speed sensor 2 at the moment when the brake switch signal is generated from the brake switch 8, that is, at the moment when the brake pedal is depressed, are input to the comparator 7, where the ground speed ■ and the wheel speed are calculated. When the relationship V < a - VW holds true between the speed
A signal of logic level "1" is output, and the deceleration setting value in the deceleration setting circuit 6 is switched from a high value to a low value by this signal.

Other operations are the same as in Figure 4.

FIG. 9 is a block diagram of an embodiment of the deceleration setting circuit 6 in FIG. 8, in which a resistor R3 and a switch sW are further added compared to FIG. 6.

The switch SW is an electronic switch whose opening/closing is controlled by the output of the comparator 7 shown in FIG.
W is closed, and the capacitor C is discharged by a parallel-connected resistor circuit consisting of two resistors R and R3. However, when a signal of level "1" is generated from the comparator 7, the electronic switch SW is activated. The circuit becomes open and discharge is caused only by the resistor R1, so that the resistance value becomes a dog, the time constant becomes large, and the deceleration setting value of the deceleration setting circuit 6 becomes small.

FIG. 10 is a diagram showing temporal changes in various speeds when the embodiment shown in FIG. 8 is adopted, and the symbols attached to the curves are the same as in the case of FIG. 7.

As described above, according to the present invention, even if a radar vehicle speed sensor such as a Doppler radar ground speed sensor detects a ground speed lower than the actual ground speed, the brake oil pressure reduction control point can be made appropriate. have

[Brief explanation of drawings]

Fig. 1 is a block diagram explaining the general configuration of the anti-skid device, Figs. 2 and 3 are explanatory diagrams of slip ratio detection, Fig. 4 is a block diagram of an embodiment of the present invention, and Fig. 5 6 is an embodiment of the selection circuit used in the present invention, FIG. 6 is an embodiment of the deceleration setting circuit used in the present invention, and FIG.
Figure 8: Diagram showing temporal changes in various speeds when the embodiment is adopted.
The figure shows another embodiment of the present invention, FIG. 9 shows an embodiment of the deceleration setting circuit in FIG. 8, and FIG. 10 shows temporal changes in various speeds when the embodiment of FIG. 8 is adopted. It is a diagram. Explanation of symbols, 1... Dotsupura ground speed sensor,
2... Wheel speed sensor, 3, 7... Comparator, 4... Brake oil pressure reduction control signal, 5...
...Selection circuit, 6...Deceleration setting circuit,
I: Speed correction circuit, 8: Brake switch.

Claims (1)

[Scope of Claims] 1. A radar vehicle speed sensor that detects the ground speed of a vehicle is provided, and a slip rate is calculated from a ground speed signal detected by the sensor and a wheel speed signal detected by a wheel speed detection sensor when braking the vehicle. , in a device that controls braking oil pressure when the slip rate reaches a set slip rate, the vehicle is decelerated from a time when there is a difference between the ground speed and the average wheel speed, and the detected wheel speed is set in advance. The vehicle includes a speed correction circuit that outputs a signal corrected to the average deceleration when the average deceleration exceeds the average deceleration, and the signal output from the speed correction circuit is used as a ground speed signal to calculate the slip ratio. anti-skid device. 2. The speed correction circuit includes a selection circuit that selects a speed signal having a larger speed value from among the ground speed signal and the wheel speed signal, and a selection circuit that selects a speed signal having a larger speed value from the ground speed signal and the wheel speed signal, and a selection circuit that selects a speed signal having a larger speed value from the ground speed signal and the wheel speed signal, and a selection circuit that selects a speed signal having a larger speed value from the ground speed signal and the wheel speed signal, and a selection circuit that selects a speed signal having a larger speed value from the ground speed signal and the wheel speed signal. 2. The anti-skid control device according to claim 1, further comprising a deceleration setting circuit for setting the deceleration of the speed signal to the average deceleration in the case of a vehicle. 3 The deceleration setting circuit includes a comparator that outputs an output when the difference between the speed value of the ground speed signal and the speed value of the wheel speed signal is not less than a certain value, and the deceleration setting circuit that outputs the average deceleration according to the output of the comparator. 3. The anti-skid device according to claim 2, further comprising a switching circuit for switching to a deceleration smaller than the speed.