JPS6142659B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention compares the wheel speed of a vehicle with an approximate vehicle body speed that approximates the vehicle body speed, and generates a slip signal when the wheel speed becomes smaller than the approximate vehicle body speed by a predetermined amount or more. The present invention relates to an anti-skid control circuit.

A conventional anti-skid control circuit that controls each wheel or wheel group of a vehicle having multiple wheels is equipped with a wheel speed sensor that detects the wheel speed on each wheel or wheel group. form an approximate vehicle speed that approximates the vehicle speed to An approximate vehicle speed is formed that approximates the vehicle speed, such approximate vehicle speed is compared with each wheel speed, and when the wheel speed is smaller than the approximate vehicle speed by a predetermined amount or more, that is,
When the slip rate or slip value exceeds a predetermined value, a slip signal is generated, and the acceleration/deceleration of each wheel is determined, and when this acceleration/deceleration exceeds a predetermined reference value, an acceleration signal or a deceleration signal is generated; A control signal for controlling the braking force is generated based on these slip signals, acceleration signals, or deceleration signals.

In the above anti-skid control circuit, when forming an approximate vehicle speed from the wheel speed, the wheel speed is used as the vehicle speed until the wheel deceleration reaches a predetermined value, and when the wheel deceleration exceeds the predetermined value, The wheel speed at that time is set as an initial value, and is then decreased by a predetermined slope to form an approximate vehicle speed. However, when a predetermined deceleration occurs in the wheels, a considerable amount of braking is applied to the wheels, and a slip rate of several percent, for example, occurs in the wheels. The value is lower than the speed by an amount corresponding to a slip rate of several percent.

Therefore, when forming an approximate vehicle speed from multiple wheel speeds, if each wheel is heavily braked and the slip rate of all wheels has advanced to some extent, the approximate vehicle speed will not match the true vehicle speed. Compared to this, the speed becomes smaller by the amount corresponding to this slip ratio. Also, when sufficient braking is not applied to one of the wheels or wheel groups and the slip ratio is almost zero, the approximate vehicle speed that is formed is Approximately equal to the true vehicle speed.

However, in conventional anti-skid control circuits, the difference between the approximate vehicle speed and the true vehicle speed is ignored, and a slip signal is generated when the wheel speed becomes less than the approximate vehicle speed by a fixed predetermined amount. Therefore, if the predetermined amount is set assuming that each wheel is sufficiently braked, the predetermined amount may be too small if sufficient braking cannot be applied to any wheel or wheel group. If a predetermined amount is set assuming that a slip signal occurs before sufficient braking is applied, and conversely, that any wheel or group of wheels is not sufficiently braked, then each wheel The disadvantage is that the wheels slip too much when sufficient braking is applied.

The present invention has been made in view of the above-mentioned drawbacks of the conventional anti-skid control circuit, and an object of the present invention is to provide an anti-skid control circuit that always performs appropriate brake control on all wheels.

According to the present invention, the present invention provides a wheel speed sensor that detects the wheel speed for each wheel or wheel group of a vehicle having a plurality of wheels, and a wheel speed sensor that detects the wheel speed so that the acceleration/deceleration of the wheel determined from the wheel speed is set to a predetermined reference value. a first comparator that generates an acceleration signal or a deceleration signal when the wheel speed exceeds an approximate vehicle speed; a second comparator that generates a slip signal when the wheel speed becomes smaller than an approximate vehicle speed that approximates the vehicle body speed by a predetermined amount; and a control circuit that receives the output signal of the second comparator and generates a control signal for controlling the braking force of the wheel or wheel group, and the approximate vehicle speed is determined by the wheel speed detected by each of the wheel speed sensors. In the anti-skid control circuit, the anti-skid control circuit is formed based on the wheel speed and the wheel speed. A switching signal generator is provided that generates a switching signal when the difference from the approximate vehicle speed exceeds a predetermined value, and when any of the wheels or wheel groups is not under control and switching signals from all switching signal generators are provided. This is achieved by an anti-skid control circuit characterized in that, when a slip signal occurs, the predetermined amount for generating the slip signal in each of the second comparators is switched to a smaller amount.

Hereinafter, details of the present invention will be explained based on illustrated embodiments.

FIG. 1 shows a block diagram of an anti-skid control circuit of an embodiment in which the present invention is applied to an automobile. In the figure, 1a and 1b represent wheel speed sensors mounted on the right front wheel and the left front wheel, and 1c represents the wheel speed sensor mounted on the propeller shaft. represents the wheel speed sensor. The wheel speed sensors 1a, 1b, and 1c generate pulses with a frequency proportional to the rotational speed of the wheels, and among these, the wheel speed sensor 1c generates a pulse with a frequency proportional to the average wheel rotational speed of both rear wheels. The outputs of the wheel speed sensors 1a, 1b, 1c are supplied to wheel speed calculation units 2a, 2b, 2c, respectively, where the wheel speeds are calculated, and the outputs are sent to acceleration/deceleration calculation comparators 3a, 3b, 3, respectively.
c, approximate vehicle speed generators 4a, 4b, 4c, slip calculation comparators 6a, 6b, 6c, and switching signal generators 15a, 15b, 15c.

In the acceleration/deceleration comparators 3a, 3b, and 3c, the outputs of the wheel speed calculators 2a, 2b, and 2c are differentiated with respect to time, respectively, and the deceleration of the wheels is determined to be equal to or higher than a predetermined deceleration reference value (for example, -1.5 g). Then, a deceleration signal -b is generated, and when the acceleration of the wheel exceeds a predetermined acceleration reference value (for example, 0.5 g), an acceleration signal +b is generated. Acceleration/deceleration calculation comparator 3a,
The deceleration signals -b of 3b and 3c are respectively applied to approximate vehicle speed generators 4a, 4b, 4c and the first control circuits 7a, 7b, 7c whose details are shown in FIG.
are supplied to the input terminals, and the respective acceleration signals +b
is supplied to the second input terminals of the control circuits 7a, 7b, 7c.

Approximate vehicle speed generators 4a, 4b, 4c receive the outputs of wheel speed calculators 2a, 2b, 2c, and determine the deceleration of the wheels at a predetermined deceleration reference value (in this embodiment -
1.5g (of course not limited to this) and the deceleration signal -b is not generated yet, the outputs of the wheel speed calculators 2a, 2b, 2c are generated as they are, and when the deceleration signal -b is generated, After that, a speed signal that linearly decreases at a predetermined slope is generated, and when the outputs of the wheel speed calculators 2a, 2b, 2c become higher than this speed signal,
It functions to generate that output as it is.

Approximate vehicle speed generators 4a, 4b,
The outputs of 4c are each supplied to the selection circuit 5,
Here, the highest of these outputs, ie, the approximate vehicle speed, is selected. Such selection outputs of the selection circuit 5 are sent to slip calculation comparators 6a, 6b,
6c, the above-mentioned wheel speed calculators 2a, 2b, 2c
It is supplied for calculation and comparison with the output of , and is further supplied to switching signal generators 15a, 15b, and 15c. Two standard rates are set for each of the slip calculation comparators 6a, 6b, and 6c,
These are switched by the output signal of the OR gate 10 for controlling the slip rate. The two standard rates are, for example, 15% and 10%, and are compared with the value obtained by subtracting the percentage of the wheel speed relative to the approximate vehicle speed from 100 (slip rate), and if this slip rate is greater than the standard rate, the slip calculation comparison is performed. vessels 6a, 6b, 6
c generates a slip signal. These standard rates are switched by the output signal of the OR gate 10, and when the output signal of the OR gate 10 is "1", the larger 15% is selected, and when it is "0", the smaller 10% is selected. % is selected. The outputs of the slip calculation comparators 6a, 6b, 6c are supplied to the third input terminals of control circuits 7a, 7b, 7c, respectively.

As described above, the switching signal generators 15a, 15b, 15c receive the outputs of the wheel speed calculators 2a, 2b, 2c and the output of the selection circuit 5, and output the outputs of the selection circuit 5, that is, approximate vehicle speed and wheel speed. are compared, and when the difference therebetween exceeds a set value ΔV, for example 5 km/h, a negative switching signal "0" is generated. Therefore, the difference between them is △
If it is below V, a positive output signal "1" is generated. Note that in this embodiment, the switching signal generator 15
Although a speed difference ΔV, that is, a slip value is set for a, 15b, and 15c, a slip rate may be set instead. However, in any case, this slip value or slip rate,
That is, the slip amount is determined by the slip calculation comparator 6a,
The slip amount is set smaller than the slip amount set in 6b and 6c. For example, switching signal generator 15
The set values of a, 15b, and 15c may be set to 5%. In other words, the switching signal generators 15a, 15
The amount of slip set in b and 15c is the standard for determining whether the brake is applied sufficiently, and the amount of slip set in the slip calculation comparators 6a, 6b and 6c is used to determine that the brake is applied too much. It is considered as a standard.

Next, details of the control circuits 7a, 7b, and 7c will be explained with reference to FIG. Since these circuits have exactly the same configuration, only the control circuit 7a will be explained.

As mentioned above, the deceleration signal -b from the acceleration/deceleration calculation comparator 3a is supplied to the AND gate 72 and the off delay timer 77.
is connected to the first input terminal of the supply valve control OR gate 79. Further, the acceleration signal +b from the acceleration/deceleration calculation comparator 3a is supplied to the brake rise pulse generator 7.
0, the logic negation input terminal of the AND gate 78 (indicated by a circle, the same applies hereafter), and the third input terminal of the OR gate 79
Supplied to the input terminal. The brake rise pulse generator 70 has an off delay timer 73 and a pulse generator 7
4, and AND gates 75 and 76, and after the acceleration signal +b disappears, the off delay timer 7
A pulse signal is generated to increase the brake pressure stepwise for a predetermined period of time set by 3. Such a pulse signal is supplied to the second input terminal of OR gate 79.

Slip signal λ from slip calculation comparator 6a
is the off-delay timer 71 and the above-mentioned AND gate 7.
8, and the output of the off-delay timer 71 is supplied to the other input terminal of the AND gate 72 mentioned above.
The outputs of the AND gates 72 and 73 are supplied to an OR gate 80 for controlling supply valves and discharge valves. The set time of the off delay timer 71 is sufficiently long, and in normal control, the off delay timer 71 is configured to maintain the on state longer than the time from when the first slip signal λ disappears after the brake is applied until the next slip signal λ is generated. By using the off delay timer 71 and the AND gate 72, after the brake is applied, the first brake release signal is generated by the slip signal λ, and thereafter either the slip signal λ or the deceleration signal -b is generated. This circuit constitutes a judgment circuit that generates a brake release signal even if this occurs. Such a judgment circuit is provided because the deceleration signal -b is easily generated as noise due to unevenness of the road surface during the transient movement of the wheels after the brake is applied, and the deceleration signal -b is easily generated as noise even when the brake is not fully applied. This is to avoid the risk of releasing the brake, and to generate the first brake release signal using a slip signal that is generated only after the brake is sufficiently applied.

Output signals of OR gates 79, 80 SHa, SHb,
SHc, SRa, SRb, SRc are amplifiers 11a, 11b, 11c and 12a, 1 as shown in FIG.
2b, 12c, and amplifiers 11a, 11
The outputs of b, 11c and 12a, 12b, 12c are supplied by solenoids 13a, 13b, 1 of the supply valve, respectively.
3c and discharge valve solenoids 14a, 14b, 1
4c. The supply valve and the discharge valve have a known structure even if not shown, and each solenoid 1
3a, 13b, 13c and 14a, 14b, 14
When c is not excited, that is, OR gate 7
When the output signals of 9 and 80 are "0", the master cylinder is operated and the brake pressure to the wheel cylinder of the wheel is increased, the supply valve solenoids 13a, 13b, 13c are energized, and the discharge valve solenoids 14a, 13c are energized. 14b and 14c are not excited, that is, when the output signal of the OR gate 79 is "1" and the output signal of the OR gate 80 is "0", the brake pressure to the wheel cylinder of the wheel is held constant, and the supply valve and discharge valve are Valve solenoids 13a, 13b, 13c and 14a, 14
When b and 14c are both excited, that is, when the output signals of the OR gates 79 and 80 are "1", the brake pressure to the wheel cylinder of the wheel is reduced.

The output of the OR gate 80 is further divided into discriminators 8a, 8b, each configured with an off-delay timer,
8c, these discriminators 8a, 8b, 8c
The output terminals of are the above-mentioned AND gates 9a and 9a, respectively.
It is connected to the logical negation input terminals of 9b and 9c.
The output terminals of the AND gates 9a, 9b, 9c are connected to the above-mentioned OR gate 10 for controlling the slip rate.
The output terminal of this OR gate 10 is connected to the above-mentioned slip calculation comparators 6a, 6b, and 6c. The delay times of the discriminators, ie, the off-delay timers 8a, 8b, and 8c, are set to be sufficiently long, and once they are turned on, they remain on during anti-skid control.

The anti-skid control circuit according to the embodiment of the present invention is constructed as described above.Next, the operation of this circuit will be explained.

Although not shown in the diagram, when the brake pedal is pressed and the master cylinder is activated while the car is running, the brake mechanisms of both front and rear wheels, the road conditions in which they come into contact, and the differences in the coefficient of friction between the tires and the road surface cause the wheels to move. Outputs of speed calculators 2a, 2b, 2c
It is assumed that Va, Vb, and Vc each change over time as shown in FIG. 3A. Along with these, the selection circuit 5 generates an approximate vehicle speed signal as indicated by Vn. The dashed line T indicates the true vehicle speed.
As mentioned above, the approximate vehicle speed signal Vn is the maximum output among the outputs of the approximate vehicle speed generators 4a, 4b, and 4c, but the speed signals generated linearly are If the output signal is larger, this output signal is directly generated from the approximate vehicle speed generators 4a, 4b, and 4c, so that the approximate vehicle speed signal Vn changes over a certain period of time as shown in FIG. 3A. does not change linearly,
In the illustrated example, the output signal of the wheel speed calculator 2c
Matches Vc.

Immediately after the brake is applied, that is, before time _t1 in FIG. 3, sufficient braking is not yet applied to any of the wheels, and the deceleration signal -b from the acceleration/deceleration calculators 3a, 3b, and 3c is also a slip calculation comparison. The slip signals λ are not generated from the devices 6a, 6b, 6c, so the output signals of the OR gates 79, 80 are "0", and the solenoids 13a, 13b, 13c and 14a, 14 of the supply valve and discharge valve
b and 14c are not excited, and the brake pressure to the wheel cylinder of the wheel increases.

At the beginning of braking, each wheel speed
Va, Vb, and Vc are all approximately equal to the approximate vehicle speed Vn, but at time t ₁ , the wheel speed of the right front wheel becomes Va.
is smaller than the approximate vehicle speed Vn by more than △V, that is, smaller than the broken line Vp shown in FIG. 3A,
Negative pulse signal from switching signal generator 15a
Ca is generated as shown in FIG. 3B. As a result, the output Oa of the AND gate 9a becomes "0" as shown in FIG. 3C, and the input to one input terminal of the OR gate 10 becomes "0". Since the switching signal has not yet been generated from the control circuits 7b and 7c, and therefore the brake control signals SRa, SRb, and SRc have not been generated from the control circuits 7b and 7c, the outputs of the AND gates 9b and 9c are "1". Therefore, the output of the OR gate 10 remains "1", and each slip calculation comparator 6
The set slip rate for a, 6b, and 6c is 15, which is the larger one.
% remains.

Further time passes, and at time _t2 , the wheel speed Vb of the left front wheel becomes smaller than the approximate vehicle speed Vn by more than △V, and a negative direction pulse signal Cb is generated from the switching signal generator 15b as shown in FIG. 3B. do. As a result, the output Ob of the AND gate 9b becomes
As shown in , the input to the other input terminal of the OR gate 10 becomes "0", but since the switching signal has not yet been generated from the switching signal generator 15c, the output of the AND gate 9c is “1”
It is. Therefore, the output of the OR gate 10 remains "1", and the set slip rate of each slip calculation comparator 6a, 6b, 6c is set to the larger one.
It remains at 15%.

Note that between time t ₁ and t ₂ , the wheel speed Va of the right front wheel has a slip rate of 15% with respect to the approximate vehicle speed Vn.
Therefore, the slip signal λ is generated from the slip calculation comparator 6A, and this is obtained from the control circuit 7a as the output signal SRa. That is, as shown in FIG.
and the AND gate 78, and the OR gate 8
This results in an output SRa of 0, which is also supplied to the fourth input terminal of the OR gate 79. As a result, the output signal SHa is also obtained from the OR gate 79, the solenoids 13a and 14a of the supply valve and discharge valve are energized, and the brake pressure applied to the wheel cylinder of the right front wheel is switched from increasing to decreasing.

On the other hand, as shown in FIG.
The output of this timer 8a that becomes "1" is applied to the logic NOT input terminal of the AND gate 9a, but the switching signal Ca of "0" has already been switched to one input terminal of the AND gate 9a. Since the signal is supplied from the signal generator 14a, the output of the AND gate 9a does not change and is "0".

As mentioned above, the set delay time of each off-delay timer 8a, 8b, 8c as a discriminator is sufficiently long, and once the output becomes "1", in normal anti-skid control, the control It is kept at "1" in the middle. Therefore, even if the switching signal Ca as a negative direction pulse disappears at time _t4 as shown in FIG. 3B, the AND gate 9
The output of a is kept at "0" as it is.

Next, at time _t3 , when the wheel speed Vc of both rear wheels, which is difficult to brake, becomes smaller than the approximate vehicle speed Vn by △V or more, that is, by 5 Km/H or more, a negative direction pulse is generated from the switching signal generator 15c.
Cc occurs as shown in FIG. 3B, and as a result, the output Oc of the AND gate 9c changes from "1" to "0" as shown in FIG. 3C, and as a result, all input terminals of the OR gate 10 The input of the OR gate 10 becomes "0", and the output Sc of the OR gate 10 changes from "1" to "0" as shown in FIG. 3C. As a result, the set slip rate of each slip calculation comparator 6a, 6b, 6c is switched to the smaller one, 10%.

Note that after this, there is a period in which the outputs Cb and Cc of the switching signal generators 15b and 15c become "1" as shown in FIG. A slip signal λ is generated from the gates 6b and 6c, and the outputs of the off-delay timers 8b and 8c, which are "1", are applied to the logical NOT input terminals of the AND gates 9b and 9c. Furthermore, the delay times of the off-delay timers 8b and 8c are set in normal anti-skid control so that once they are turned on, they remain on during the control. Therefore, after time _t3 , even if any switching signal generator 1
Switching signals Ca, Cb, Cc from 5a, 15b, 15c
Even if the output of the OR gate 10 disappears, the output of the OR gate 10 remains "0", and from now on, the set slip rate of each slip calculation comparator 6a, 6b, 6c is set to the smaller one.
It remains at 10%.

When the deceleration signal -b is generated after the first slip signal λ is generated after the brake is applied, the output “1” of the off-delay timer 71 is supplied to one input terminal of the AND gate 72. Therefore, the output signal in each control circuit 7a, 7b, 7c
SHa, SHb, SHc and SRa, SRb, SRc are “1”
Therefore, the brake pressure to the wheel cylinder of each wheel is reduced. Furthermore, if the deceleration signal H-b is generated before the first slip signal λ is generated, it is supplied to the OR gate 79 via the off-delay timer 77, so that the deceleration signal H-b is not received. The output signal SHa, SHb or SHc of the control circuit 7a, 7b or 7c becomes "1", and only the solenoid 13a, 13b or 13c of the supply valve is energized, so that the brake pressure to the wheel cylinder of the corresponding wheel is constant. is maintained. The reason why the deceleration signal -b is supplied to the OR gate 79 via the off-delay timer 77 is that after the deceleration signal -b disappears, the brake pressure is not immediately increased, but the brake pressure is held constant for a certain period of time. This is to prevent the wheels from moving into lock position. Therefore, the delay time of the off-delay timer 77 is determined taking such things into consideration.

When the brake pressure on the wheel cylinder of a wheel is reduced and the wheel speed increases so that its acceleration exceeds a reference value, an acceleration signal +b is generated. Since the acceleration signal +b is supplied to the OR gate 79 in the control circuit 7a, 7b or 7c, the solenoid 13a, 13b or 13c of the supply valve is energized, so that the brake pressure is kept constant. Then, when the acceleration of this wheel becomes less than the reference value and the acceleration signal +b disappears, the off delay timer 73,
Pulse generator 74 and AND gates 75, 76
Brake raising pulse generator 70 configured by
As a result, a pulse for increasing the brake pressure stepwise is generated as an output signal SHa, SHb or SHc from the control circuit 7a, 7b or 7c.

That is, even if the acceleration signal +b disappears, the output of the timer 73 is "1" for the predetermined time set in the off-delay timer 73, and the acceleration signal +b is not applied to the logic NOT input terminal of the AND gate 75. Therefore, the output of the AND gate 75 becomes "1", which is applied to the input terminal of the other AND gate 76, and the pulse of the pulse generator 74 is applied to the other input terminal of the AND gate 76. , a pulse synchronized with the pulse of the pulse generator 74 is obtained from the AND gate 76,
This passes through the OR gate 79 and the control signal SHa,
Solenoid 13a of the supply valve as SHb or SHc,
As a result of being supplied to 13b or 13c, this solenoid is energized intermittently and the brake pressure to the wheel cylinder of the wheel is increased stepwise.
Then, when the deceleration signal -b or the slip signal λ is generated (the set delay time of the off-delay timer 73 is sufficiently long and its output is still "1"), the control signal SHa, SHb or SHc is intermittently As a result, the brake pressure applied to the wheel cylinder of the wheel is reduced. Below, acceleration signal +b, deceleration signal -b
In response to the occurrence of the slip signal λ, the operations of holding the brake pressure constant, increasing the brake pressure stepwise, and decreasing the brake pressure are repeated, and eventually, when the desired running speed of the vehicle is obtained, the anti-skid control ends.

The anti-skid control circuit according to the embodiment of the present invention operates as described above. Immediately after the brake is applied, the slip calculation comparators 6a, 6b, and 6c are set at the larger slip rate of 15%, so the selection circuit 5 An appropriate slip signal, that is, brake relaxation, is generated for each wheel with respect to the output of the approximate vehicle body speed generator 4c, which is formed based on the output of the wheel with the smallest braking force (Vc in the illustrated embodiment). signal is obtained. Sufficient braking force acts on both wheels. That is, even if the slip signal λ has not yet been generated, the slip calculation comparator 6 is activated when the slip has sufficiently progressed in each wheel (time t ₃ in the illustrated embodiment).
Set the slip rate of a, 6b, 6c to the smaller 10
%, an appropriate brake release signal can always be obtained after the brake is applied.

After brake activation, the same braking force is applied to all wheels, and when the speed becomes smaller than the approximate vehicle speed Vn by a predetermined speed △V, that is, 5 km/h or more, the switching signal Ca is generated from the switching signal generators 15a, 15b, and 15c almost at the same time. , Cb, Cc are obtained, or gate 1
When the output Sc of 0 becomes "0", the set slip rate is switched to the smaller 10%.

As described above, immediately after the brakes are applied, sufficient brakes are not applied to any of the wheels, and the approximate vehicle speed Vn is almost equal to the true vehicle speed T.
When wheel speeds Va, Vb, and Vc are within △V from this, a slip signal is generated at a large slip rate, or a slip signal is generated at a large slip rate even when sufficient braking is not applied to any of the wheels. so that sufficient braking force is applied to all wheels to maintain the approximate vehicle speed.
Since the slip signal is generated at a small slip rate after the predetermined speed △V becomes smaller than Vn, each wheel is controlled so that it is always at the optimum slip rate in any case, and the braking distance is longer than before. is further shortened.

According to the invention, in particular the switching signal generator 15a,
15b and 15c are provided, and all wheel speeds Va,
When Vb and Vc become smaller than the approximate vehicle speed Vn by more than a predetermined speed △V, the output of the OR gate 10 is set to "0" and the slip calculation comparators 6a, 6b, 6
Since the set slip rate of c is switched from a large value to a small value, almost ideal slip control can be performed. That is, the slip calculation comparators 6a, 6b, 6 are calculated based on the slip signal and deceleration signal indicating excessive braking.
Rather than switching the set slip rate of c,
Since the switching signal generators 15a, 15b, and 15c detect whether or not the brake is sufficiently applied to any wheel, the above-mentioned set slip rate is switched, so that more fine-grained slip control can be performed. . This means that if the slip calculation comparator 6
This is because if the set slip ratios of wheels a, 6b, and 6c were to be switched, the set slip ratios would be switched at the point when all the wheels are over-braked.

Although the embodiments of the present invention have been described above, the present invention is of course not limited to these embodiments and can be modified in various ways based on the technical idea of the present invention.

For example, in the above embodiment, the first brake release signal after the brake is applied is generated by the slip signal, but instead of this, the fourth brake release signal is generated by the slip signal.
A configuration as shown in the figure may be used. That is, the output terminals of the slip calculation comparators 6a, 6b, and 6c are connected to an OR gate 90, and the output terminal of this OR gate 90 is connected to the OFF delay timer 7 in the above embodiment.
1, and the output terminal of this off-delay timer 71 is connected to the AND gate 72 in each control circuit 7a, 7b, 7c.
Connect to one input terminal of the The outputs of this AND gate 72 are designated as the above-mentioned SRa, SRb, and SRc. Therefore, the control circuits 7a, 7b,
The off-delay timer 71, AND gate 78, and OR gate 80 in 7c are omitted.

In the configuration shown in FIG. 4, as the slip rate of one of the wheels progresses, the slip signal λa, λb, or λc is output to the slip calculation comparator 6a, 6b, or 6c.
, the AND gate 72 in each control circuit 7a, 7b, 7c becomes conductive to the deceleration signal -b, and if the deceleration of one of the wheels exceeds a predetermined reference value, the deceleration signal -b is activated. When this occurs, a signal is obtained from the AND gate 72 as SRa, SRb, or SRc to reduce the brake pressure to the wheel cylinder of the corresponding wheel.

In the configuration shown in FIG. 4, after the brake is applied, as long as the first slip signal is not generated for any wheel, even if the deceleration signal -b is generated for any wheel, the off delay timers 8a, 8b, The input to 8c will never be "1", and even if the brake force is not sufficiently applied and the deceleration signal -b as noise is generated from all wheels, a brake release signal will be generated. There isn't. That is,
The slip rate of at least one wheel is set to a standard rate of 15
%, a brake release signal is not generated, so stable anti-skid control is guaranteed. This is because if the slip rate of at least one wheel exceeds 15%, a considerable amount of braking force must be applied to the other wheels after the brake is applied.

Furthermore, although FIG. 5 shows a modification other than the above embodiment, in this configuration, the control circuit 7
a, 7b, 7c output signals SHa, SHb, SHc and
SRa, SRb, SRc are or gates 92a, 92b,
92c, and these or gates 92a, 92
The outputs of the off-delay timers 8a and 92c are
8b and 8c. That is, the OR gate 80 in the off delay timers 8a, 8b, 8c and the control circuits 7a, 7b, 7c in the above embodiment
OR gates 92a, 92b,
92c is further connected, and this OR gate 92a,
The output terminal of the OR gate 79 in the control circuits 7a, 7b, 7c is connected to the other input terminal of the control circuits 92b, 92c.

In the embodiment described above, the off delay timers 8a, 8
The first control signals applied to signals b and 8c were formed based on the first slip signal after the brake was applied, but in the example of FIG. This signal is used to control the off-delay timers 8a, 8b, and 8c. It is clear that even with such a signal, the effects of the above embodiment can be obtained.

Further, in the above embodiment, the slip calculation comparators 6a, 6b, and 6c receive the output of the selection circuit 5 and the output of the wheel speed calculation units 2a, 2b, and 2c, respectively, and calculate the slip rate. Although the slip signal is generated when the value exceeds a predetermined reference value, a multiplier and a comparator may be used instead. In this case, the multiplier of the multiplier is switched between a large value and a small value, the output of the selection circuit 5 is supplied to this multiplier, and the output of the multiplier and the wheel speed calculators 2a, 2b, 2c are The output is compared with the output by a comparator, and when the output of the multiplier is larger than the output of the wheel speed calculators 2a, 2b, and 2c, a slip signal is generated from the comparator. For example, following the example above, the multiplier is 0.85
and 0.90, and these are switched by the output of the OR gate 10.

In addition, in the above embodiment, the slip calculation comparator 6
In a, 6b, and 6c, two standard rates of 15% and 10% are set, but instead of this, two standard values, for example, 15 Km/h and 10 Km/h may be set. In this case, when the output of the wheel speed calculators 2a, 2b, 2c becomes lower than the output of the selection circuit 5 by more than a reference value, a slip signal is generated from the slip calculation comparators 6a, 6b, 6c.

Further, in the above embodiment, the case where it is applied to an automobile has been explained, but the present invention can of course be applied to a two-wheeled motor vehicle, and in this case, in the circuit of the embodiment, one system, for example, 1c, 2c ,3c,4c,6
c, 7c, 8c, 9c, 11c, 12c, 13
The control system configured by c and 14c can be omitted.

As described above, the anti-skid control circuit of the present invention can always perform appropriate brake control on all wheels, and can shorten the braking distance compared to the conventional one.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an anti-skid control circuit for an automobile according to an embodiment of the present invention, Fig. 2 is a detailed circuit diagram of a part of the control circuit, and Fig. 3 is a graph for explaining the operation of the control circuit. , FIG. 4 is a block diagram showing a part of a first modification of the embodiment, and FIG. 5 is a block diagram showing a part of a second modification of the embodiment. In the figure, 1a, 1b, 1c...wheel speed sensor, 3a, 3b, 3c...acceleration/deceleration calculation comparator, 4a, 4b, 4c...approximate vehicle body speed generator, 5...selection circuit, 6a, 6b, 6c...Slip operation comparator, 7a, 7b, 7c...Control circuit, 8a, 8b, 8c...Discriminator, 9a, 9b,
9c...and gate, 10...or gate, 1
5a, 15b, 15c...Switching signal generator.

Claims (1)

[Claims] 1 A wheel speed sensor detects the wheel speed for each wheel or wheel group of a vehicle having multiple wheels, and generates an acceleration signal or deceleration signal when the acceleration/deceleration of the wheel determined from the wheel speed exceeds a predetermined reference value. a first comparator that generates a slip signal when the wheel speed becomes smaller than an approximate vehicle speed that approximates the vehicle body speed by a predetermined amount; a second comparator that generates a slip signal; an anti-skid control circuit, each comprising a control circuit that generates a control signal for controlling the braking force of the wheel or wheel group; and the approximate vehicle speed is formed based on the wheel speed detected by each of the wheel speed sensors. , for each wheel or wheel group, a discriminator that determines whether the wheel or wheel group is under control based on the control signal, and a difference between the wheel speed and the approximate vehicle body speed is a predetermined value. A switching signal generator is provided which generates a switching signal when the switching signal is exceeded, and when any of the wheels or wheel groups is not under control and switching signals are generated from all switching signal generators, each of the second comparators An anti-skid control circuit characterized in that the predetermined amount for generating the slip signal is switched to a small amount.