JPS6142661B2 - - 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 a plurality of wheel speeds, if a considerable amount of braking is applied to each wheel and the slip rate of all wheels has advanced to some extent, the approximate vehicle speed that is formed 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 Almost 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 body speed that approximates the vehicle body speed; Each includes 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 based on the wheel speed detected by each of the wheel speed sensors. In the anti-skid control circuit, the second comparator is capable of switching the predetermined amount to a smaller amount in response to a switching command, receives control signals from each of the control circuits, and receives control signals from each of the control circuits. This is achieved by an anti-skid control circuit provided with a discriminator that detects generation of a control signal from the control circuit and issues the switching command.

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 according to 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 a 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 and slip calculation comparators 6a, 6b, 6c.

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
Supplied for calculation and comparison with the output of Two reference rates are set in each of the slip calculation comparators 6a, 6b, and 6c, and these are switched by the output signal of the OR gate 10 for controlling the slip rate. For example, the two base rates are 15%
is 10%, and is compared with the value obtained by subtracting the percentage of the wheel speed relative to the approximate vehicle body speed from 100 (slip rate). If this slip rate is greater than the reference rate, the slip calculation comparators 6a, 6b, and 6c determine the slip rate. Generate a 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. Slip calculation comparator 6
The outputs of a, 6b, and 6c are controlled by control circuits 7a and 7a, respectively.
It is supplied to the third input terminals of 7b and 7c.

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 deceleration calculation comparator 3a is supplied to the AND gate 72 and the off-delay timer 72, and the off-delay timer 77 is connected to the first input terminal of the OR gate 79 for controlling the supply valve. . Further, the acceleration signal +b from the acceleration/deceleration calculation comparator 3a is supplied to the brake rise pulse generator 70, the logical NOT input terminal of the AND gate 78 (indicated by a circle, and the same applies hereinafter), and the third input terminal of the OR gate 79. . Brake lift pulse generator 70
is composed of an off-delay timer 73, a pulse generator 74, and AND gates 75 and 76, and increases the brake pressure stepwise for a predetermined time set by the off-delay timer 73 after the acceleration signal +b disappears. Generates a pulse signal for 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 AND gate 7 described above.
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 78 are supplied to an OR gate 80 for controlling supply and discharge valves. The setting time of the off delay timer 71 is sufficiently long, and in normal control, the off delay timer 71 is configured to remain on 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 even when the brake is not sufficiently 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 not gates 9a, 9b, respectively.
Connected to 9c. Knot gate 9a, 9b, 9
The output terminal of c is connected to the above-mentioned slip rate control OR gate 10, and the output terminal of this OR gate 10 is connected to the above-mentioned slip calculation comparators 6a, 6b, 6c.
connected to. Discriminator or off delay timer 8
The delay times of a, 8b, and 8c are set to be sufficiently long, and once 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 shown by the dashed line E. The two-dot chain line T indicates the true vehicle speed. As mentioned above, the approximate vehicle speed signal E 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, 4c, so that the approximate vehicle speed signal E becomes smaller in a certain period of time as shown in FIG. 3A. does not change linearly, and the output signals of the wheel speed calculators 2a, 2b, 2c
It matches Va, Vb, and 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.

Eventually, at time _t1 , the slip rate of the right front wheel with respect to the approximate vehicle speed E exceeds 15%, so a slip signal λ is generated from the slip calculation comparator 6a as shown in FIG. 3B, and this is output as the output signal SRa. It is obtained from the control circuit 7a. That is, the second
As shown in the figure, the slip signal λ is supplied to the off-delay timer 71 and the AND gate 78, and becomes the output SRa of the OR gate 80, which is the output of the OR gate 79.
It is also supplied to the fourth input terminal of. 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, the output signal SRa of the OR gate 80 is supplied to the OFF delay timer 8a as shown in FIG. As shown, the output becomes "0", but since the slip signal λ has not yet been generated from the slip calculation comparators 6b and 6c, and therefore the outputs SRb and SRc of the OR gate 30 have not yet been generated, the outputs Ob and Oc of the NOT gates 9b and 9c have not yet been generated. remains “1”. Therefore, the output of the slip rate control OR gate 10 is "1", and the set slip rate of each slip calculation comparator 6a, 6b, 6c remains at the larger 15%. In addition, as mentioned above, each off-delay timer 8a, 8 as a discriminator
The set delay times of b and 8c are sufficiently long,
Once the output becomes "1", it remains at "1" during the normal anti-skid control.

Eventually, at time t ₂ , the wheel speed of the left front wheel becomes
Since Vb also exceeds a slip rate of 15% with respect to the approximate vehicle speed E, an output signal SRb as shown in FIG. 3B is generated from the control circuit 7b, and a signal SHb for controlling the supply valve is also generated. The brake pressure on the wheel cylinders is switched from increasing to decreasing. On the other hand, since the output signal SRb is also supplied to the off delay timer 8b, the not gate 9
The output Ob of the not gate 9c becomes "0" as shown in FIG.
remains at "1", the output of the slip rate control OR gate 10 remains at "1", and the set slip rate of each slip calculation comparator 6a, 6b, 6c is set to the larger 15%. Yes, it is.

Eventually, when the wheel speed Va recovers and its acceleration exceeds a predetermined reference value, for example 0.5g, at time _t3 , the acceleration/deceleration calculation comparator 3a outputs an acceleration signal +
b is generated and applied to the logical NOT input terminal of the AND gate 78, so the output SRa of the OR gate 80 becomes "0" at time _t3 as shown in FIG. 3B.
becomes. On the other hand, the acceleration signal +b is the OR gate 79
Since the output SHa of the OR gate 79 is still "1". Therefore, the brake pressure for the wheel cylinder of the right wheel, which is controlled by the outputs SHa and SRa, is switched from being lowered to being kept constant. In addition, the output
Even if SRa becomes "0", the output of the off-delay timer 8a is still "1", so the output Oa of the not gate 9a remains "0".

Next, at time _t4 , when the wheel speeds Vc of both rear wheels, which have been difficult to brake, exceed a slip rate of 15% relative to the approximate vehicle speed E, the control circuit 7c outputs a signal as shown in FIG. 3B. Since an output signal SRc is generated and a signal SHc for controlling the supply valve is also generated, the brake pressure applied to the wheel cylinders of both rear wheels is switched from increasing to decreasing. On the other hand, since the output signal SRc is also supplied to the off-delay timer 8c, the output Oc of the not gate 9c is
As shown in FIG.
Sc becomes "0" as shown in FIG. 3D, and the set slip rate of each slip calculation comparator 7a, 7b, 7c is switched to the smaller 10%. Since the delay time of each off-delay timer 8a, 8b, 8c is set to be long enough as described above, the signal
Even if any or all of SRa, SRb, and SRc disappear, the output of the OR gate 10 remains "0", and thereafter each slip calculation comparator 6a,
The set slip rates for 6b and 6c remain at the smaller 10%.

That is, in the embodiment illustrated in FIG. 3, as the brake pressure decreases, the wheel speed of each wheel gradually decreases.
Va, Vb, Vc recover at times t ₃ , t ₅ and t ₆ respectively
At this time, the output signals SRa, SRb, and SRc become "0" again, but the output Sc of the OR gate 10 is kept at "0" even after that due to the sufficiently long delay time of the off-delay timers 8a, 8b, and 8c. In the illustrated embodiment, after the slip ratio of each slip calculation comparator 6a, 6b, 6c is switched to the smaller 10%, the slip signal λ from the comparators 6b, 6c disappears.

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 -b is generated before the first slip signal λ is generated, this deceleration signal -b is supplied to the OR gate 79 via the off delay timer 77.
The output signal SHa, SHb, or SHc of the control circuit 7a, 7b, or 7c that receives b becomes "1", and only the solenoid 13a, 13b, or 13c of the supply valve is energized, and as a result, the brake is applied to the wheel cylinder of the corresponding wheel. Pressure is held constant. 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.
Therefore, the delay time of the off-delay timer 77 is determined taking such things into consideration.

For the right-hand wheel, as already mentioned, the brake pressure on the wheel cylinder of the wheel is reduced and the wheel speed increases so that its acceleration exceeds the reference value, and an acceleration signal +b is generated. Incidentally, at the time points _t5 and _t6 , the outputs SRb and SRc become "0" as shown in FIG. 3B. Since the acceleration signal +b is supplied to the OR gate 79 in the control circuit 7a, 7b or 7c, the solenoid 13a, 13 of the supply valve
As a result of energizing b or 13c, the brake pressure is held constant. Then, when the acceleration of this wheel becomes less than the reference value and the acceleration signal +b disappears, the brake raising pulse generator 70 composed of the off delay timer 73, the pulse generator 74, and the AND gates 75 and 76 The control circuit 7 generates pulses for increasing the brake pressure stepwise.
Output signal SHa, SHb or from a, 7b or 7c
Occurs as SHc.

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 generation 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 when the desired running speed of the vehicle is eventually achieved, 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. Then, when sufficient braking force is applied to all wheels, that is, when slip has sufficiently progressed on all wheels (time t ₄ in the illustrated embodiment), the settings of slip calculation comparators 6a, 6b, and 6c are adjusted. Since the slip rate is switched to the smaller 10%, an appropriate brake release signal will always be obtained after the brake is applied.

When the same braking force is applied to all wheels after the brake is activated, slip signals λ are obtained from the slip calculation comparators 6a, 6b, and 6c almost simultaneously, and the output Sc of the OR gate 10 becomes "0". The set slip rate can be switched to the smaller 10%.

As described above, immediately after the brake is applied, when no sufficient brake is applied to any wheel and the approximate vehicle speed E is approximately equal to the true vehicle speed T, a slip signal is generated with a large slip rate, Alternatively, a slip signal can be generated with a large slip ratio even when sufficient braking is not applied to any wheel, so that sufficient braking force is applied to all wheels and the approximate vehicle speed E becomes the true vehicle speed. Since the slip signal is generated at a small slip rate after the point when the slip rate becomes considerably smaller than T, each wheel is controlled to always have the optimum slip rate in any case, and the braking distance is further shortened than before. be done.

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, when the slip rate of any wheel progresses and a slip signal λa, λb or λc is generated from the slip calculation comparator 6a, 6b or 6c, the AND gate in each control circuit 7a, 7b, 7c is activated. 72 becomes conductive to the deceleration signal -b, and when the deceleration of any wheel exceeds a predetermined reference value and the deceleration signal -b is generated, this causes the brake to be applied to the wheel cylinder of the corresponding wheel. A signal to reduce the pressure is obtained from the AND gate 72 as SRa, SRb or SRc.
When the deceleration of all wheels exceeds a predetermined reference value, slip calculation comparators 6a, 6b, 6
The set slip reference rate of c is switched from a large value to a small value.

In the configuration shown in FIG. 4, as long as the first slip signal is not generated for any wheel after the brake is applied, even if the deceleration signal -b is generated for all wheels, the slip calculation comparators 6a, 6b, The set slip rate of 6c is not switched to a smaller value, and even if the brake force is not applied sufficiently and the deceleration signal -b as noise is generated from all wheels, a brake release signal is generated. Never. That is, unless the slip rate of at least one wheel exceeds the set 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 slip calculation comparators 6a,
The signals for switching the set slip rates of 6b and 6c are formed based on the first slip signal after the brake is applied, but in the example of Fig. 5, either the deceleration signal -b or the slip signal λ comes first. A switching signal for the set slip rate is obtained based on the signal generated during the slip rate. It is clear that even with such a switching signal, the effects of the above-described 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...Not Gate, 10...Or Gate.

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. In the second comparator,
The predetermined amount can be switched to a smaller amount in response to a switching command, and the switching command is issued upon receiving a control signal from each of the control circuits and detecting that a control signal has been generated from all the control circuits. Anti-skid control circuit equipped with a discriminator.