JP2591157B2 - Anti-skid control device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an anti-skid control device for controlling a brake fluid pressure so as to prevent a brake slip of a wheel.

(Prior Art) The anti-skid control device is designed such that when the wheel speed during braking has a predetermined slip relationship with the vehicle speed (for example, when the road surface friction coefficient of the wheel exceeds an ideal slip ratio at which the road surface friction coefficient is maximized),
The brake fluid pressure is reduced so as to prevent slip (lock) of the wheel.

By the way, detecting the vehicle speed (actual vehicle speed) directly requires an expensive Doppler radar or the like, which is not practical. Therefore, a pseudo vehicle speed is generated from the wheel speed using a technique disclosed in Japanese Patent Application Laid-Open No. 60-285163, for example. This is used as the vehicle speed. This technology uses the wheel speed V _W1 of the right front wheel (non-drive wheel),
Wheel speed V _W2 of the left front wheel (non-driving wheel), the average Figure 6 from the wheel speed V _W3 (a) of the two-wheel and after (driving wheel) (V _C is the actual vehicle speed as shown by reference) those such as In some cases, the pseudo vehicle speed is calculated as follows. That is, since the highest one of the wheel speeds V _W1 , V _W2 , V _W3 is closest to the actual vehicle speed, this is selected high as shown by V _W in FIG. V _W acceleration α
_W (negative deceleration) is calculated as shown in FIG.

Then, at t ₀ ~t ₅ deceleration alpha _W becomes the reference value b ₂ or more,
Since the select high wheel speed V _W is not intended simulates the actual vehicle speed V _C, obtaining the calculation speed V _i of a predetermined decrease gradient relative to the select high wheel speed V _W at this time. Gradient, the first is scheduled slope that has been determined in advance from the point V _{b (0),} 2 round of the gradient obtained by connecting the point V _{b (0)} and the point V _{b (1),} also the third time after In the same manner as the second time, the gradient is determined with the point _{Vb (0)} as a starting point. In addition, V _i to match the select high wheel speed V _W at the time of the lapse of a certain period of time ΔT in order to avoid the weighting of the calculation error.

The select-high this way of calculating the vehicle speed V _i and the select high wheel speed V _W obtained from higher to be close to the actual vehicle speed V _C, this to as a sixth diagram (d) Medium V _iW And the pseudo vehicle speed _ViW .

(0005) Thus, depression of the thus than produce a pseudo vehicle speed based on the highest wheel speed in any case unconditionally an accelerator pedal up to instant t _1, as shown in FIG. 7 The driving wheels generate an acceleration slip (wheel spin) and the wheel speed V _W3 is the actual vehicle speed V
Around top _C, from then instant t ₃ when the wheel speed V _W3 under the control of the depression of the instant t ₂ after the brake pedal is sharply reduced together with the non-drive wheel speed V _W1, V _W2, pseudo vehicle speed V _iW is Figure 7 It looks like this.

Therefore, the pseudo vehicle speed V _iW becomes too higher than the actual vehicle speed V _C, it is compared to perform determination of the brake slip and this wheel speed, cause misjudgment and slipped though not slipping, unnecessary The braking distance becomes longer due to the reduction in the brake fluid pressure, or in the worst case, the braking becomes impossible.

In order to solve this problem, it is conceivable to generate the pseudo vehicle speed only from the wheel speeds of the non-drive wheels that do not cause a drive slip. However, in this case, the following problem occurs. That is, when the wheel is recovering its rotation by reducing the brake fluid pressure by the anti-skid control, it is inevitable that the re-pressure increase timing will be advanced due to the fluctuation of the wheel speed due to the unevenness of the road surface, and therefore, from the own wheel speed The wheels that are subjected to anti-skid control based on the created pseudo vehicle speed will gradually decrease the pseudo vehicle speed and the wheel speed. The fluctuation of the wheel speed due to the unevenness of the road surface occurs almost in synchronization between the non-driving wheels and between the driving wheels. If the pseudo vehicle speed is generated only from the wheel speeds of the non-driving wheels as described above, However, in both cases, the wheel speeds decrease rapidly, and as a result, the pseudo vehicle speed decreases, and it is difficult to expect accurate anti-skid control.

For this reason, as described above, the pseudo vehicle speed is usually created based not only on the wheel speed of the non-drive wheel but also on the wheel speed of the drive wheel. This is because it supports a larger load than the wheels, so that the brake sharing of the front wheels is larger than that of the rear wheels, and the pressure reduction of the front wheels should be suppressed.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-described problem by generating a pseudo vehicle speed based on the wheel speed of a non-driven wheel when an accelerated slip of a driven wheel occurs.

(Means for Solving the Problems) For this purpose, the present invention obtains a simulated vehicle speed based on the higher one of the wheel speed of a non-drive wheel and the wheel speed of a drive wheel. An anti-skid control device for reducing a brake fluid pressure of a wheel in the above-described braking slip state to prevent a braking slip, comprising: an acceleration slip detecting means for detecting an acceleration slip of a driving wheel at the start of the anti-skid; At the time, only the wheel speed of the non-driving wheel is switched to a state in which the pseudo vehicle speed is used as the calculation data, and at the start of the anti-skid of the driving wheel, the higher of the wheel speed of the non-driving wheel and the wheel speed of the driving wheel is pseudo. Wheel speed selection means for returning to a state in which the vehicle speed is used as calculation data.

(Operation) The anti-skid control device determines that the wheel speed of the anti-skid control device is greater than or equal to the pseudo vehicle speed determined based on the higher one of the non-driving wheel speed and the driving wheel speed during braking with the brake fluid pressure generated. The brake fluid pressure of the wheel in the brake slip state is reduced to prevent the brake slip of the wheel.

By the way, if the driving wheel is generating an acceleration slip at the start of the anti-skid, the wheel speed selecting means receives a signal from the acceleration slip detecting means for detecting the acceleration slip and determines only the wheel speed of the non-driving wheel with the calculation data of the pseudo vehicle speed. I do. Therefore, the pseudo vehicle speed is not generated based on the wheel speeds of the driving wheels causing the acceleration slip, and the pseudo vehicle speed becomes higher than the actual vehicle speed, and the braking distance becomes longer due to unnecessary pressure reduction of the brake fluid pressure. , Can be prevented from becoming impossible to brake.

In addition, the above-mentioned wheel speed selecting means may use the driving wheel acceleration slip at the start of the anti-skid to temporarily calculate only the wheel speed of the non-driving wheel as the reference vehicle speed data. Since the acceleration slip has subsided, the wheel speed of the non-driven wheels and the wheel speed of the driven wheels will return to the state where the higher vehicle speed is used as the calculation data of the pseudo vehicle speed. By calculating the pseudo vehicle speed only from the wheel speeds of the non-driving wheels, it is possible to avoid the adverse effect that the pseudo vehicle speed becomes inaccurate.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is an overall system diagram showing an embodiment of the anti-skid control device of the present invention, in which 1 is a right front wheel (non-drive wheel),
1a is the wheel cylinder, 2 is the left front wheel (non-drive wheel),
2a is the wheel cylinder, 3 is the right rear wheel (drive wheel), 3a
Denotes a wheel cylinder, 4 denotes a rear left wheel (drive wheel), and 4a denotes the wheel cylinder. 5 is an engine,
Reference numeral 6 denotes a transmission, 7 denotes a propeller shaft, 8 denotes a differential gear, and 9 and 10 denote rear axles, respectively.
It is assumed that the vehicle can be driven by driving 3 and 4.

The brake system is one of the two-system master cylinder 11
11a is connected to the right front wheel cylinder 1a by a pipe 12, the left cylinder wheel 2a is connected to a left front wheel cylinder 2 by a pipe 13, the other system 11b is connected to the right rear wheel 3a by a pipe 14, and the pipe 14 is connected. , 15, a so-called front-back split type hydraulic brake device connected to the left rear wheel cylinder 4a. The brake device is operated by the master cylinder hydraulic pressure generated by the depression of the brake pedal 16 and output from the two systems 11a and 11b of the master cylinder 11, and the vehicle can be decelerated.

A total of three anti-skid control means are provided for the right front wheel 1, the left front wheel 2, and the two rear wheels 3, 4, which are provided with conduits 12, 13,
It is composed of actuators 17a, 17b, 17c respectively inserted into and an anti-skid control circuit 18 for controlling their operation.

Since the actuators 17a, 17b, and 17c are the same, the corresponding parts are indicated by the same reference numerals with different suffixes a, b, and c, and only the right front wheel actuator 17a will be described in detail below. Actuator 17a is an inflow valve (EV
A valve 19a, a discharge valve (AV valve) 20a, a pump 21a, an accumulator 22a, and a check valve 23a are connected as shown in the figure. The EV valve 19a and the AV valve 20a are individually controlled by an EV1 signal and an AV1 signal from the anti-skid control circuit 18, and the pump 21a is appropriately driven by a common motor 24 together with the pumps 21b and 21c in the other actuators 17b and 17c. This driving is controlled by the MR signal from the anti-skid control circuit 18. With the EV1 signal opening the EV valve 19a at the L level and the AV1 signal closing the AV valve 20a at the L level,
The brake fluid pressure to the wheel cylinder 1a is increased until it reaches the same value as the master cylinder fluid pressure. In this state, EV
When the 1 signal changes to the H level and the EV valve 19a is also closed, the brake fluid pressure to the wheel cylinder 1a is held. Next, in this state, the AV1 signal changes to the H level to open the AV valve 20a, and additionally, the transistor 25 is turned on by the H level MR signal,
When the motor 24 is energized by the power supply + E to drive the pump 21a, the brake fluid pressure of the wheel cylinder 1a is returned to the master cylinder 11 and reduced. The following table summarizes the operations described above.

The anti-skid control circuit 18 includes a circuit portion 18a that emits the EV1 signal and the AV1 signal based on a signal from a wheel speed sensor 26a that detects the rotation speed of the right front wheel 1, and a wheel speed that detects the rotation speed of the left front wheel 2. A circuit portion 18b for generating an EV2 signal and an AV2 signal for the left front wheel actuator 17b based on a signal from the sensor 26b, and a wheel for detecting a rotation speed of the propeller shaft 7, which is an average rotation speed of the rear two wheels 3, 4. Speed sensor 26
EV for rear wheel actuator 17c based on signal from c
The circuit portion 18c for generating the three signals and the AV3 signal, the pseudo vehicle speed generation circuit 27, the target wheel speed generation circuit 28, and the logical sum of the AV1, AV2, and AV3 signals (H level) common to these circuit portions 18a, 18b, and 18c. It comprises an OR gate 29 and a retrievable timer 30 which is triggered every time the output of the OR gate rises and issues an H level MR signal for a predetermined time.

Since the circuit portions 18a, 18b, 18c have the same configuration,
Corresponding portions are indicated by the same reference numerals having different suffixes a, b, and c, and only the circuit portion 18a will be described in detail. 31a is a wheel speed detection circuit, calculates the right front wheel rotational speed (pulse) signal and the peripheral speed of the right front wheel turning radius (wheel speed) V _W1 from the wheel speed sensor 26a. The wheel speed V _W1 is input to the wheel acceleration detection circuit 32a and is used for calculating the wheel acceleration α _W1 (deceleration is negative). The wheel acceleration alpha _W1 is compared comparator 33a, 34a in the deceleration base value b ₁ and the acceleration reference value a _1, the comparator 33
a outputs an H level signal when the wheel deceleration α _W1 becomes larger than the reference value b ₁ , and the comparator 34a outputs the wheel acceleration α _W1
There outputs an H level signal when it comes to large acceleration than the reference value a _1. The comparator 35a compares the wheel speed _VW1 with the target wheel speed generation circuit 28.
Compared to the later-described target wheel speed from (V _iW × 0.85), the wheel speed V _W1 is comparators 35a between: the target wheel speed outputs an H level signal. The OR gate 36a ORs the H level outputs of the comparators 33a to 35a to generate an H level EV1 signal,
This signal is supplied to the EV valve 19a via the amplifier 37a. The AND gate 38a takes the logical product of the H level output of the comparator 35a and the L level signal from the comparator 34a to generate an H level AV1 signal, and supplies this signal to the AV valve 20a via the amplifier 39a.

Pseudo vehicle speed generating circuit 27 as the configuration of FIG. 2, the wheel speed V _W1
~ V _W3 , MR signal and AV ₃ signal for driving wheel are input respectively,
Based on these, it is assumed that the pseudo vehicle speed _ViW is calculated as described later. For this reason, the circuit 27 includes a select high switch 41 for selecting the higher one of the front wheel speeds V _W1 and V _W2 and a self-draw switch 42 for selecting the lower one. The inner wheel difference correction circuit 43 corrects the select high front wheel speed from the switch 41 by the inner wheel difference correction circuit 43 during the anti-skid control in which the MR signal is at the H level.
When the anti-skid control in which the MR signal is at the L level is not executed, the signal is input to the select high switch 44 as it is. The select high switch 44 is the non-drive wheel speed _VWF because the larger of the select high front wheel speed via the inner wheel difference correction circuit 43 and the select low front wheel speed from the switch 42 is closer to the actual vehicle speed.
Select high switch 45 and select switch 46
To enter. Select high switch 45 is non-drive wheel speed _VWF
Since the larger one of the drive wheel speeds _VW3 is close to the actual vehicle speed, it is input to the select switch 46 as the select high wheel speed _VWH . The select switch provided the select high wheel speed V _WH from the switch 45 for the calculation of the pseudo vehicle speed V _iW contacts as normally solid line position, the non-drive wheel speed V _WF and H level during contact of the control signals S ₁ as a dotted line position The value is input to a pseudo vehicle speed calculation circuit 47 so as to be used for calculating the pseudo vehicle speed _ViW .

The pseudo vehicle speed calculating circuit 47 is a well-known circuit which calculates the pseudo vehicle speed _ViW based on the wheel speed selected by the select switch 46 as shown in FIGS. 6 (b), 6 (c) and 6 (d). In addition to inputting the vehicle speed to the wheel spin determination value calculation circuit 48,
It is input to the target wheel speed generation circuit 28 in FIG. Circuit 48 is
From experiments, acceleration slip (wheel spin) of drive wheels 3 and 4
_Is determined by an operation of _ViW × 1.05 + 4 km / h, and this is input to the comparator 49. Comparator 49 is driven wheel speed V
_W3 is supplied to another input, which is the wheel spin determination value V
_{When iW} × 1.05 + 4 km / h or more, the output is set to the H level by discriminating the wheel spin of the driving wheels 3 and 4. This H level output is connected to one input of the OR gate 50 on the one hand, and to the NOT gate 51 on the other hand.
Then, the signal is supplied to the other input of the OR gate via the retriggerable timer 52. Retriggerable timer 52 rise of the output of the NOT gate 51, i.e. the seventh third output set time T ₁ in the output from the time the wheel spins resolved that falls H of the comparator 49, as shown in diagram corresponding to FIG. Level. Therefore, OR gate 50 is an AND gate 53 the output during wheel spin during the subsequent setting time T ₁ of the drive wheel 3, 4 in the H level
To one input.

Rise of MR signals to other input of an AND gate 53, i.e. the retriggerable timer also outputs an H level signal during the set time T ₂ as in Figure 3 than the instantaneous t ₃ when started antiskid in any one wheel Supply output from 54. And AND
The remaining one input of the gate 53 provides an output of the flip-flop circuit 55, when the flip-flop circuit rises of AV ₃ signals, i.e. anti-skid start of the driving wheels instant t ₄
And the output is set to L level, and the output is set to H level when the output of the NOT gate 56 to which the MR signal is input rises, that is, at the end of the anti-skid of all the wheels. The output of the three-input AND gate 53 is supplied to one input of an OR gate 57, and the other input of the OR gate 57 is supplied to the output of a NOT gate 59 for inverting the MR signal. The output of OR gate 57 is used as a control signals S ₁ to the select switch 46.

Target wheel speed generating circuit 28 of FIG. 1 from the pseudo vehicle speed V _iW,
Target wheel speed _ViW × to obtain an ideal slip ratio of 0.15 that maximizes the road surface friction coefficient (minimizes the braking distance)
0.85 is obtained and supplied to the comparators 35a to 35c to determine wheel lock.

 The operation of the above embodiment will now be described.

First, the operation of the pseudo vehicle speed generation circuit 27 is instantaneously performed as shown in FIG.
The driving wheel speed V _W3 causes wheel spin with acceleration up to t ₁ , and the non-driving wheel speeds V _W1 and V _W2 lock at the instant t ₃ with braking after the instant t ₂ to start anti-skid control (MR signal Will be described). Since up to instant t ₃ the MR signal is anti-skid control is not executed in the L level, NOT gates 59
Is supplied to a select switch 46 via an OR gate 57, and the select switch 46 outputs the non-driving wheel speed.
_VWF is supplied to the circuit 47 to contribute to the calculation of the pseudo vehicle speed _ViW .

MR signal rises at instant t _3, when one even antiskid control of the two front wheels is started, the output of the NOT gate 59 is L
Level, and the control signal S ₁ of the select switch 46 is AND
The level is determined by the gate 53. When the MR signal rises at the instant t _3, the retriggerable timer from now on in the set time T ₂
54 sets the corresponding input of the AND gate 53 to H level. Further, the flip-flop circuit 55 is reset at the end of the previous anti-skid, and the corresponding input of the AND gate 53 is set at the H level to keep the output at the H level. On the other hand, OR gate 50 is a wheel spin during and after the set time T ₁ in AND drive wheel
The corresponding input of the gate 53 is set to H level. Therefore, during the anti-skid control start instant t ₃ thereafter until the instant t _5, AND gate 5
3 the control signals S ₁ of wheel spin detection therefore select switch 46 to H level, contributing to the non-drive wheel speed V _WF in the calculation of the pseudo vehicle speed V _iW. For this reason, the driving wheel speed V _W3 at the time of occurrence of the wheel spin does not contribute to the calculation of the pseudo vehicle speed _ViW , and the pseudo vehicle speed can be obtained by the circuit 47 as shown by a two-dot chain line in FIG. _iW it is possible to solve the larger problem than the actual vehicle speed under the influence of the drive wheel speed V _W3.

The output of the OR gate 50 does not cause the wheel spin even the same anti-skid control in is at the L level, the control signals S ₁ to the solid line position of contact of the selection switch 46 a L level. As a result, the highest one of the wheel speeds of all the wheels is used for the calculation of the pseudo vehicle speed _ViW as before, but since the wheel spin does not occur, the pseudo vehicle speed is calculated.
V _iW is never higher than the actual vehicle speed.

Also, instant t ₄ after the anti-skid control of the drive wheel 3, 4 is started, or after a set time T ₂ from the instantaneous t ₃ will correspond two inputs of the AND gate 53 is L level, even in these cases the total The highest one of the wheel speeds is used for calculating the pseudo vehicle speed. Therefore, it is possible to prevent the above-described problem caused by calculating the pseudo vehicle speed based on only the non-drive wheel speed _VWF .

Next, the anti-skid control of the right front wheel 1 of the apparatus shown in FIG. 1 will be described based on an operation example of FIG. When the brake fluid pressure is generated in the depression of the brake pedal 16 instantaneously t _0,
Wheel speed V _W1 decreases, and wheel deceleration α _W1 occurs. At the instant t ₁ when the wheel deceleration α _W1 exceeds the reference value b ₁ ,
The level output starts the EV1 signal and closes the EV valve 19a. As a result, the brake fluid pressure P _W is maintained at the value at this time despite the increase in the brake pedal depression force, and the first skid cycle is started.

Also reduces the wheel speed V _W1 This holding pressure, finally the output of the comparator 35a instantaneously t ₂ becomes lower than the target wheel speed V _iW × 0.85 also rising, AV1 signal I L level output coupled with the comparator 34a Rises and opens the AV valve 20a. Therefore instant t ₂ subsequent brake fluid pressure is reduced, it is possible to recover the rotation of the front wheel 1. At this time, the MR signal rises, and the H level is maintained during the anti-skid control by the retriggerable timer 30, so that the motor 24 is driven and the above-described pressure reduction is enabled.

When the rotation of the front wheel 1 is restored and the wheel speed V _W1 increases, a wheel acceleration α _W1 is generated. instant t ₃ when α _W1 ≧ a ₁
In between ~t _4, comparator 34a is output to the H level, closing the AV valve 20a at the L level AV1 signals. Therefore, brake fluid pressure P _W
The pressurized coercive, alpha _W1 <instant t ₄ after became a _1, the comparator 34a
EV valve 19a due to the fall of the output (rising of EV1 signal)
Open to increase the brake fluid pressure _PW .

Decreased Kamata wheel speed V _W1 with increase of the brake fluid pressure P _W, it becomes the next skid cycle than the instantaneous t ₅ that the deceleration alpha _W1 exceeds the reference value b _1, repeating the above anti-skid control in each skid cycle . Therefore, the brake hydraulic pressure P _W is maintained at a value near the lock hydraulic pressure P _{L at} which the braking efficiency is maximized, and anti-skid control is performed on the front wheels 1 in such a manner as to minimize the braking distance. Become.

The same anti-skid control is performed for the other front wheels 2 and the rear two wheels 3 and 4. However, when a common pseudo vehicle speed _ViW is obtained, when the wheel spin of the drive wheels 3 and 4 occurs, the wheel speed V _W3 is used. Since the wheel speeds V _W1 , V _W2 (non-drive wheel speed V _WF ) of the non-drive wheels ₁ and ₂ are used, the pseudo vehicle speed _ViW becomes higher than the actual vehicle speed, and the braking distance is extended due to unnecessary decompression. ,
It is possible to prevent the braking from becoming impossible.

The pseudo vehicle speed generating circuit 27 may be configured as shown in FIG. 5 instead of FIG. 2, and the flip-flop circuit 55 may be set. That is, in this example, the AND gate 61 is connected to the set input of the flip-flop circuit 55, and the AND gate 61
A retrigable timer 62 is connected to one input and a NOR gate 63 is connected to the other input. Retriggerable timer 62 is rising of AV ₃ signals, that is, during the set time from the start of pressure reduction of the driving wheels 3, 4 H
A level signal is output, and the NOR gate 63 outputs an H level signal at the start of pressure increase of the drive wheels 3 and 4 in which both the EV ₃ signal and the AV ₃ signal are at L level. Therefore, the AND gate 61 sets the pressure-increasing flip-flop circuit 55 after the first pressure reduction of the driving wheels 3 and 4.

(Effect of the Invention) As described above, the anti-skid control device of the present invention is configured to obtain the pseudo vehicle speed based only on the wheel speed of the non-drive wheel during the acceleration slip of the drive wheel. It is no longer based on a pseudo vehicle speed higher than the actual vehicle speed based on it. Unnecessary decompression is performed by anti-skid control based on such a pseudo vehicle speed, and the braking distance is extended,
It is possible to prevent the braking from becoming impossible.

Also, after the start of the anti-skid of the driving wheel, since it is clear that the driving wheel does not accelerate and slip, the pseudo vehicle speed is determined based on the higher one of the non-driving wheel speed and the driving wheel speed as usual. It is possible to avoid the above-described adverse effect of obtaining the pseudo vehicle speed based on the non-driving wheel speed.

[Brief description of the drawings]

FIG. 1 is an overall system diagram showing an embodiment of the anti-skid control device of the present invention, FIG. 2 is an electronic circuit diagram of a pseudo vehicle speed generating circuit in the example, FIG. 3 is an operation waveform diagram of the circuit, FIG. FIG. 5 is an operation waveform diagram showing an anti-skid control operation for the right front wheel of the device shown in FIG. 1, FIG. 5 is an electronic circuit diagram showing another example of the pseudo vehicle speed generation circuit, and FIGS. FIG. 6 is a waveform diagram of the pseudo vehicle speed calculation operation of FIG. 1 right front wheel (non-drive wheel) 2 left front wheel (non-drive wheel) 3,4 rear wheel (drive wheel) 1a-4a wheel cylinder 7 propeller shaft 8 differential gear 11 … 2 master cylinders 16… Brake pedals 17a, 17b, 17c… Actuator 18… Anti-skid control circuits 19a, 19b, 19c… EV valves 20a, 20b, 20c… AV valves 21a, 21b, 21c… ... Pumps 22a, 22b, 22c ... Accumulators 24 ... Pump drive motors 26a, 26b, 26c ... Wheel speed sensors 27 ... Simulated vehicle speed generation circuit 28 ... ... Target wheel speed generation circuit 30 ... ... Retriggerable timer 31a, 31b, 31c …… wheel speed detection circuit 32a, 32b, 32c …… wheel acceleration detection circuit 41,44,45 …… select high switch 42 …… select low switch 43 …… inner wheel difference correction circuit, 46 …… select switch 47 …… Simulated vehicle speed calculation circuit 48 …… Wheel spin determination value calculation circuit 49 …… Comparators 52,5 4,65 …… Retriggerable timer 55 …… Flip-flop circuit

Claims (1)

(57) [Claims] A quasi-vehicle speed is determined based on a higher one of a wheel speed of a non-driving wheel and a wheel speed of a driving wheel. An anti-skid control device for reducing a pressure to prevent a braking slip; an acceleration slip detecting means for detecting an acceleration slip of a driving wheel at the start of the anti-skid; Wheel speed that switches to a state in which the vehicle speed calculation material is used, and returns to a state in which the higher of the non-drive wheel wheel speed and the drive wheel wheel speed is used as the vehicle speed calculation material at the start of driving wheel anti-skid. An anti-skid control device comprising a selection unit.