JPS5930585B2 - Anti-skid device for vehicles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an anti-skid device for a vehicle that can control the braking force of the wheels to an optimum value so as to prevent the wheels from locking during braking of the vehicle.

Generally, in order to control the braking force of a vehicle to an optimal value, a wheel rotation speed detector is provided, and the deceleration of the wheel is detected from the output of the detector, and the deceleration of the wheel is larger than a predetermined set value. When this occurs, it is determined that this is a sign that the wheels are about to lock up, and the braking pressure on the wheels is reduced.

FIG. 1 is a block diagram of a conventional anti-skid device of this type. In the figure, 1 is a wheel rotation speed detector that generates a signal with a frequency proportional to the rotation speed of the wheel; 2//'i wheel rotation speed; An f-V converter converts the output signal of the detector 1 into a DC voltage corresponding to the wheel rotation speed; 3 is a differentiating circuit;
An output voltage corresponding to the reduced acceleration of the wheel is generated.

4 is a comparator, 5 is an amplification device that amplifies the output signal of the comparator 4, and 6 is a solenoid valve installed inside the braking force control device 7. When the solenoid valve 6 is excited, the braking force is increased at a predetermined speed. This is to reduce the pressure.

Next, the operation of the conventional device configured as described above will be explained using the operation explanatory diagram shown in FIG.

In FIG. 2, 8 is a diagram showing the vehicle speed, and 9 is a diagram showing the wheel speed, which correspond to the output of the f--■ converter 2 in FIG.

2 is a diagram showing the reduced acceleration of a 10-wheel wheel, and corresponds to the output of the differential circuit 3 in FIG. 1.

11 is a diagram showing braking pressure, and 12 is a diagram showing control braking pressure.

Therefore, as the braking pressure increases during braking, the slip ratio of the wheel speed to the vehicle body speed increases, and when the braking pressure reaches the ideal braking pressure or higher, the wheel deceleration increases and reaches the deceleration setting value of the comparator 4. At point A, the comparator 4 generates a braking force reduction signal.

After the braking force reduction signal is current-amplified by the amplifier 5, the solenoid valve 6 in the braking force control device γ is energized, and when the solenoid valve 6 is energized, the braking force starts to be depressurized at a predetermined speed. The pressure reduction of the braking force is continued until the point B where the wheel deceleration reaches the set deceleration of the comparator 4 or less due to the decrease in the braking force.

When the excitation of the solenoid valve 6 is cut off at point B, the control braking pressure 12 gradually starts increasing pressure toward the braking pressure 11. While repeating this operation, the wheel speed is decelerated to a slip ratio of around 20 relative to the vehicle body speed. It was something to do.

However, such a control system has the following problems.

The set deceleration of comparator 4 is a value that is taken as a sign that the wheels are about to lock, and is generally selected around -1.4G (G: power acceleration), but it is difficult to adapt it to all the various conditions during braking. Met.

For example, as shown in the operation diagram in Figure 3, when the gear position of the transmission between the wheel engine and the wheels is low, the moment of inertia of the wheel system becomes larger than when the gear position is high. There were cases in which the wheel deceleration slightly exceeded the set deceleration and its duration became long.

In this situation, the control braking pressure is much lower than the ideal braking pressure, so if the braking pressure is gradually increased from point B, where the braking force reduction signal is released, the area of low braking pressure becomes longer and the wheel speed decreases. The disadvantage is that the slip ratio relative to the vehicle speed is low and the braking distance is significantly extended.

Furthermore, if the set deceleration of the comparator 4 is increased in order to prevent such braking force from becoming too loose, the wheel deceleration will continue to be below the set value and the wheels will lock at the 0 point in the rear cylinder 3 diagram. There were drawbacks.

In any case, it has been difficult to provide a system that does not cause the wheels to lock under various conditions during braking and does not extend the braking distance compared to when the wheels lock and brake. .

The present invention solves the above-mentioned drawbacks and provides an effective device that can be applied under various conditions, and will be described below with reference to an embodiment of the present invention shown in FIG.

In FIG. 4, 13 is a time limit circuit that is activated by the output signal of the comparator 4 to generate a fixed time pulse, and 14 is a pseudo vehicle speed generation circuit that includes a diode 15, a capacitor 16, a constant current discharge circuit 17, and a slip rate setting resistor 18. .19.

20 is a comparator, 21 is an AND circuit, and 22 is an OR circuit.

Here, the output voltage corresponding to the wheel rotation speed generated in the fV converter 2 is passed through the diode 15 to the capacitor 1.
6 is stored.

Further, the charge of the capacitor 16 is discharged by a constant current discharge circuit 17.

Resistors 18 and 19 are voltage dividing resistors whose values are selected so as not to affect the discharge of capacitor 16, and their outputs are led to comparator 20.

Note that for convenience of explanation, the diode 15 is assumed to be an ideal diode.

FIG. 5 is an explanatory diagram of the operation of FIG. 4, and 23 is a diagram showing the pseudo vehicle speed, which corresponds to the potential of the capacitor 16 in FIG. 4.

24 is a diagram showing the potential divided by the voltage dividing resistors 18 and 19, 25 is the output signal of the comparator 4, diagram 26 is the output signal of the time limit circuit 13, and 27 is a diagram showing the output signal of the comparator 20. be.

That is, is the voltage of the capacitor 16 V during normal driving? - is f-
The output voltage of the capacitor 16 is the same as the output voltage of the V converter 2, and when the wheel rapidly decelerates during braking and the degree of deceleration is greater than the degree to which the charge of the capacitor 16 is discharged by the constant current discharge circuit 17, the voltage of the capacitor 16 is f The voltage value of the capacitor 16 becomes higher than the voltage of the -V converter 2, and the voltage value of the capacitor 16 represents the pseudo vehicle speed.

Therefore, the energization time constant of the capacitor 16 is selected to be a value corresponding to the maximum deceleration caused by the friction of the wheels with the road surface -1.0 G (G: gravitational acceleration).

The time limit circuit 13 is a constant time pulse generator that is activated and generated by the output of the comparator 4 (i.e., the generation of code 25 in FIG. 5), and can be constructed from an ordinary monostable multivibrator. The time required to prevent excessive depressurization of power is selected, for example, about 100 (ms).

The braking force reduction signal is transmitted to the braking force control device γ via the amplifier 5 when an output signal is generated to the AND circuit 21 or when a slip signal is generated that is output to the comparator 20 by the function of the OR circuit 22. The signal is transmitted to the solenoid valve 6 inside.

The signal is output by logical product of the output signal of the AND circuit 21, the comparator 4, and the output signal of the time limit circuit 13.

During braking, the wheel deceleration increases as the braking pressure increases, and at point D shown in FIG. Occur.

On the other hand, the time limit circuit 13 is also activated by the generation of the comparator 25, and generates a fixed time pulse as shown in the diagram 26.

Since the braking force reduction signal is generated by the logical product of the comparator 4 and the timer circuit 13, when the signal generation time of the comparator 4 is shorter than the constant time pulse of the timer circuit 13, the output signal of the comparator 4 becomes the braking force reduction signal as it is,
The control is similar to that of the conventional device, and if the generation time of the output signal of the comparator 4 is longer than the fixed time pulse of the time limit circuit 13, the braking force reduction signal is released by the action K of the AND circuit 21 at point E shown in FIG. be done.

Thereafter, the braking force gradually increases from point E, which has the effect of preventing excessive depressurization of the braking force.

However, under various conditions, such as when the friction coefficient of the road surface is low, if the braking force reduction signal is limited by the time width of the fixed-time pulse, the control braking pressure will not decrease to the ideal braking pressure, as shown in Figure 5. Wheel speed 9 as shown by the dashed line
may move in the locking direction.

In such a state, the wheel rotation speed 9 is equal to the pseudo vehicle body speed 23.
At point F, where the slip speed reaches the set slip speed 24 or less, the comparator 20 generates a slip signal 27 and starts reducing the braking force.

The control force reduction signal from the comparator 20 continues at the G point when the wheel rotational speed reaches a set slip ratio or less with respect to the pseudo vehicle speed due to the pressure reduction of the braking force, thereby preventing the wheels from locking.

In addition, in the above embodiment, the pressure reduction of the braking force by the slip signal detects the acceleration of the wheel, and the wheel speed accelerates.
It is also possible to cancel the braking force reduction signal at the point, and the amount of deceleration of the wheel speed with respect to the vehicle body speed, that is, the slip amount may be used instead of the slip ratio of the wheel speed with respect to the vehicle body speed.

As explained above, the present invention provides a fixed-time pulse generation circuit that is activated upon generation of the deceleration detection signal in order to prevent excessive depressurization of the braking force due to the deceleration detection signal.
The braking force deceleration signal based on the deceleration detection signal is limited, and a pseudo vehicle speed generation circuit is provided to compare the wheel rotation speed and the pseudo vehicle body speed, and determine whether the wheel rotation speed is compared to the pseudo vehicle speed and set to a predetermined value. To provide an anti-skid device which prevents wheels from locking and does not extend braking distance by generating a slip signal and adding a braking force release signal based on the slip signal when decelerating.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a conventional device, FIGS. 2 and 3 are diagrams explaining the operation of the conventional device, FIG. 4 is a configuration diagram showing an embodiment of the present invention, and FIG. 5 is an explanation of the operation of FIG. 4. It is a diagram. In the figure, 1 is a wheel rotation speed detector, 2 is an f-V converter,
3t/'i differentiator circuit, 4 is a comparator, 5 is an amplifier,
7 is a braking force control device, 13 is a time limit circuit, 14 is a pseudo vehicle speed generation circuit, 20 is a comparator, 21 is an AND circuit,
22 is an OR circuit. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A vehicle rotation speed detector that detects the rotation speed of the vehicle, detects the deceleration of the wheels based on the output of the wheel rotation speed detector, and when the wheel deceleration reaches a predetermined value or more, outputs a deceleration signal. a deceleration detection circuit that generates a deceleration signal; a time limit circuit that is activated by the generation of the deceleration signal and generates a fixed-time pulse; a pseudo vehicle speed generation circuit that receives input from the output of the wheel rotation speed detector and generates a simulated vehicle speed; a slip detection circuit that compares the output of the pseudo vehicle speed generation circuit with the output of the wheel rotation speed detector and generates a slip signal when the slip amount or slip ratio of the wheels reaches a predetermined value or more; A braking force control device includes a braking force reducing mechanism that acts in a direction to reduce the braking force generated by the braking device, and means for reducing the braking force by a logical product of the deceleration signal and the fixed time pulse, and a slip signal. An anti-skid device for a vehicle, characterized in that it is provided with means for reducing the pressure of braking force.