JPH0624913B2 - Anti-skid controller - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anti-skid control device that prevents wheel lock, and more particularly to an anti-skid control device that does not perform inappropriate operation due to vehicle vibration during operation.

[Prior Art] Conventionally, an anti-skid control device has been known for the purpose of preventing the wheels from being locked and the steering performance of the vehicle being impaired when the vehicle brakes. This anti-skid control device prevents the wheels from being locked during the braking operation by adjusting the braking force of the braking device according to the slip state of the wheels.

This anti-skid control device detects the rotation speed of the wheel, and if the amount of change in the wheel speed (hereinafter referred to as rotation acceleration) becomes a value smaller than the reduction reference value, the braking force is determined as the wheel is locking. There is something that lowers. That is, when the wheels are locked, the wheel rotation speed decreases at a very large rate, so that the slip state of the wheels is detected and the braking force is adjusted.

By the way, when the braking force is increased or decreased as described above, vibration is generated in the suspension system, and this vibration causes positive and negative rotational speed changes in the wheels. Then, in the anti-skid control device that simply adjusts the braking force based on the value of the wheel rotational acceleration, the change in the wheel rotational acceleration due to this vibration causes an unnecessary reduction in the braking force and increases the braking distance.

In order to solve such a drawback, the reduction reference value is lowered according to the increase amount of the wheel speed due to the reduction of the braking force so that the reduction of the braking force does not occur due to the rotational acceleration change due to the vibration of the suspension system. (For example, JP-A-60-154947).

[Problems to be Solved by the Invention] However, such an anti-skid control device does not sufficiently consider the change in the vibration cycle of the suspension system.

Therefore, if the vibration cycle of the suspension system changes due to a change in vehicle weight, suspension replacement, or the like, sufficient performance may not be exhibited.

For example, when the vehicle weight increases and the vibration cycle of the suspension system becomes long, the decrease reference value ends decreasing before the acceleration change due to the vibration of the suspension system subsides. Degradation occurs. Alternatively, when the vehicle weight is reduced and the vibration cycle is shortened, the anti-skid control device works effectively because the reduction reference value is reduced even after the acceleration change due to the vibration of the suspension system has subsided. Absent.

Also. In order to mount the conventional anti-skid control device on a vehicle, it is necessary to set the reduction time of the reduction reference value or the like according to the vehicle weight, suspension characteristics and the like. Therefore, the conventional anti-skid control device lacks versatility.

[Means for Solving Problems] An object of the present invention is to solve the above problems.
As illustrated in the figure, the following configuration was adopted.

That is, the gist of the present invention is to provide an anti-skid control that adjusts the braking force of the braking device according to the slip state of the wheels when the braking device that generates the braking force according to the braking operation of the vehicle driver is operated. In the device, a rotational acceleration detecting means for detecting a rotational acceleration of a wheel, and when the detected rotational acceleration becomes smaller than a preset reduction reference value, the braking force of the brake device is reduced, and then the braking force of the braking force is reduced. When the rotational acceleration exceeds the reduction reference value due to the decrease, a braking force adjusting means for increasing the braking force of the brake device, and a reference in which the detected rotational acceleration is set to a value larger than the reduction reference value in advance. When the change value is exceeded, the time measuring means for measuring the elapsed time until the rotational acceleration becomes equal to or less than the reference change value, and the time measuring means. According to the elapsed time, a change time setting means for setting a change time at which the decrease reference value should be changed to a predetermined value smaller than a normal value such that the longer the elapsed time becomes, the longer the elapsed time, and the elapsed time by the time measuring means. After the time is measured, if the rotational acceleration decreases to a change acceleration set in advance to a value smaller than the reference change value and larger than the decrease reference value, then the change time set by the change time setting means is set. An anti-skid control device is provided with: a reduction reference value changing means for changing the reduction reference value to a predetermined value smaller than usual until the time elapses.

[Operation] As described above, the anti-skid control device of the present invention operates when the brake device that generates a braking force in accordance with the brake operation of the vehicle driver is actuated, that is, when the vehicle is braked, and the braking force adjusting means causes the rotational acceleration. When the rotational acceleration detected by the detecting means becomes smaller than the reduction reference value, the braking force of the brake device is reduced, and when the rotation acceleration exceeds the reduction reference reference value due to the reduction of the braking force, the braking force of the brake device is increased.

That is, when the vehicle is being braked, the braking force generated by the brake device by the braking operation of the vehicle driver is large, and when the rotation speed of the wheels is rapidly reduced, the wheels may slip and lock, so that the anti-skid of the present invention may be performed. In the control device, the braking force adjusting means determines such a slip state of the wheel during vehicle braking by determining whether or not the rotational acceleration of the wheel is smaller than the reduction reference value, and the rotational acceleration of the wheel is smaller than the reduction reference value. If the rotational speed of the vehicle is rapidly decreasing, the braking force of the brake device is reduced to prevent the wheels from locking. Further, if the braking force of the brake device is reduced, it is possible to suppress a sudden decrease in the rotation speed, but if this state is continued as it is, the braking force will become too small this time. The braking force adjusting means increases the braking force of the braking device when the rotational acceleration of the rear wheels after the braking force is reduced exceeds the reduction reference value.

As a result, in the anti-skid control device of the present invention, once the rotational acceleration of the wheels falls below the reduction reference value during the operation of the brake device, thereafter, the rotation acceleration of the wheels converges to the reduction reference value. Since the braking force is increased or decreased, the vehicle can be braked with the optimum braking force.

By the way, when the braking force increase / decrease control is performed in this way,
Since positive and negative acceleration is applied to the vehicle body in the traveling direction,
Vibration occurs in the suspension system that supports the vehicle body. When the suspension system vibrates in this way, it appears as a change in the rotational acceleration of the wheel as described above. Therefore, when the slip state of the wheel is determined from the rotational acceleration of the wheel as described above, it is actually Even though the wheels have not slipped, it is determined that a large slip has occurred on the wheels, and the braking force is reduced. Further, as described above, the vibration cycle generated in the suspension system is
Since it changes according to the vehicle weight, suspension characteristics, etc., the cycle of changes in the rotational acceleration of the wheels also changes depending on the vehicle weight and suspension characteristics.

Therefore, in the anti-skid control device of the present invention,
The change in the rotational acceleration of the wheels and the cycle thereof due to the vibration of the suspension system are detected by the time measuring means.

That is, when the suspension system vibrates, the rotational acceleration of the wheels also changes correspondingly. Therefore, in the timing means, it is determined whether or not the rotational acceleration of the wheels exceeds the reference change value set in advance to a value larger than the decrease reference value. Detects the change in the rotational acceleration of the wheel due to the vibration of the suspension system. Further, if the cycle is large, the time for which the rotational acceleration of the wheel exceeds the reference change value becomes long, and if the cycle is short, the rotational acceleration of the wheel is increased. Since the time period over which the reference change value is exceeded becomes short, the vibration period of the suspension system is detected by measuring the elapsed time during which the rotational acceleration of the wheel exceeds the reference change value.

Further, next, in the anti-skid control device of the present invention, when the time measuring means detects the change in the rotational acceleration of the vehicle due to the vibration of the suspension system and measures the elapsed time corresponding to the vibration cycle, the change time setting means However, depending on the elapsed time, the change time should be changed to a predetermined value which is smaller than the normal value so that the longer the elapsed time is, the longer the elapsed time is, and further, after the elapsed time is measured by the time measuring means, When the rotational acceleration decreases to the change acceleration set to a value smaller than the reference change value and larger than the decrease reference value, the decrease reference value changing means then waits until the change time set by the change time setting means elapses. Meanwhile, the decrease reference value is changed to a predetermined value smaller than usual.

That is, when the elapsed time is measured by the time measuring means, the rotational acceleration changes periodically with the vibration of the suspension system, so after the elapsed time is measured, the rotational acceleration of the wheel decreases in the direction of the decrease reference value. Do it. Then, at this time, if the reduction reference value is set to the same value as that in the normal time, the rotational acceleration becomes smaller than the reduction reference value, and the braking force adjusting means reduces the braking force. Further, in this case, the time when the rotational acceleration becomes smaller than the reduction reference value, in other words, the time when the braking force adjusting means reduces the braking force becomes longer as the vibration period of the suspension system becomes longer.

Therefore, in the anti-skid control device of the present invention, after the elapsed time is measured by the time measuring means, the braking force adjusting means reduces the braking force due to the change in the rotational acceleration of the wheels due to the vibration of the suspension system. When the rotational acceleration of the vehicle is reduced to the change acceleration by the reference value changing means, the decrease reference value is changed to a predetermined value smaller than the normal time, and the change time is changed by the change time setting means. The longer the elapsed time is, the longer the time is set in accordance with the result (elapsed time) measured by the time measuring means corresponding to the cycle.

As a result, according to the anti-skid control device of the present invention,
Only when the rotational acceleration of the wheel is lower than the normal reduction standard value due to the vibration of the suspension system, the reduction standard value is surely changed to a predetermined value smaller than the normal value, and the braking force adjusting means is not suitable due to the vibration of the suspension system. It is possible to prevent the execution of the various braking force reduction control.

[Embodiment] An embodiment of the present invention will be described with reference to the drawings. The present invention is not limited to this, and includes various embodiments without departing from the scope of the invention.

FIG. 2 is a schematic configuration diagram of the anti-skid control device of the present embodiment, and shows only the configuration of the brake system for the left front wheel of the front engine rear drive vehicle. The right front wheel or the left and right rear wheels has the same configuration as the left front wheel, and therefore description thereof will be omitted.

The configuration of this embodiment will be described.

The anti-skid control device is connected to a master cylinder 20 that generates a brake hydraulic pressure according to the amount of depression of the brake pedal 10, a supply pipe 30 connected to a pressure chamber (not shown) of the master cylinder 20, and a supply pipe 30. Brake pipe 60 and brake pipe 6 having two throttles 40 and 50
A two-position valve 70 connected to 0, a brake pipe 80 connected to one port of the two-position valve 70, and a wheel cylinder 90 connected to the brake pipe 80 and performing a braking operation.

A hydraulic pump 100 for increasing the brake hydraulic pressure is provided between the two throttles 40 and 50 at the branch pipe 110,
The branch pipe 110 is connected through the check valve 120.
Connected to the hydraulic pump 100 to store the pressure oil discharged from the hydraulic pump 100, the hydraulic pump 100, and the two-position valve 7 described above.
0 is provided with a reservoir tank 160 connected by a branch pipe 150 via a throttle 140.

Furthermore, the switching valve 180 connected to the supply pipe 30 via the branch pipe 170, and the branch pipe 2 connecting the output port of the switching valve 180 to the brake pipe 80 via the check valve 190.
00, a branch pipe 220 that connects the supply pipe 30 and the branch pipe 200 via a check valve 210 is provided.

Here, the two-position valve 70 is a one-solenoid type solenoid operated directional control valve which is switched to a valve position a by a spring force when a signal is not input and to a valve position b when a drive signal is input. The two brake pipes 60 and 80 are communicated with each other at a, and the brake pipe 60 and the branch pipe 150 are communicated at each valve position b. Further, the switching valve 180 is a one-solenoid type switching valve, and the two branch pipes 170, 20 are formed by spring force.
Two branch pipes 17 depending on the valve position c communicating 0 and the drive signal.
And a valve position d for shutting off the communication of 0,200.

The check valve 120 is directed from the branch pipe 110 toward the brake pipe 60, and the check valve 190 is the switching valve 180.
In the direction from the branch pipe 200 to the check valve 210,
To the branch pipe 220.

Further, the brake pedal 10 includes the brake pedal 1
A brake switch 230 for detecting the depression of 0 and a wheel speed sensor 240 for detecting the rotation of the rotating shaft are provided on the rotating shaft of the wheel (not shown).

The brake switch 230 and the wheel speed sensor 24 described above
0 is connected to the electronic control circuit 300, and the electronic control circuit 300 controls the two-position valve 70, the hydraulic pump 100, and the switching valve 180 described above based on the detection signals of these sensors and the like.

The electronic control circuit 300 is a well-known CPU 310, ROM
320, RAM 330, an input / output circuit 340 for inputting / outputting to / from the outside, and a common bus 350 interconnecting these.
Etc.

The operation of this embodiment will be described.

First, during normal braking operation, the electronic control unit 300
Does not output a signal from the 2-position valve 70 and the switching valve 180. Therefore, the two-position valve 70 becomes the valve position a,
The brake pipe 60 and the brake pipe 80 are communicated with each other. Further, the switching valve 180 is at the valve position c, and the branch pipe 170 and the branch pipe 200 communicate with each other. Therefore, the pressure oil generated in the master cylinder 20 due to the depression of the brake pedal 10 is
By the two flow passages of the supply pipe 30, the brake pipe 60, the two-position valve 70, the brake pipe 80, and the supply pipe 30, the branch pipe 170, the switching valve 180, the check valve 190, and the branch pipe 200. , To the wheel cylinder 90. Then, when the brake pedal 10 is opened, two flow passages are provided, a flow passage leading to the supply pipe 30 via the two-position valve 70 and a flow passage leading to the supply pipe 30 via the check valve 210 and the branch pipe 220. The pressure oil in the wheel cylinder 90 returns to the master cylinder 20.

Next, a case where the antiskid control device operates will be described. In the present embodiment, when the brake switch 230 is turned on, the anti-skid control device is activated and the switching valve 180 is brought to the valve position d by the signal from the electronic control circuit 300.

Then, when it is determined by the electronic control circuit 300 that the braking hydraulic pressure generated in the wheel cylinder 90 needs to be reduced based on the wheel speed detected by the wheel speed sensor 240 and the amount of change thereof (wheel acceleration), Electronic control circuit 3
00 outputs a signal to the 2-position valve 70 to set the valve position b.
Therefore, the pressure oil generated in the wheel cylinder 90 is sent to the reservoir tank 160 via the brake pipe 80, the two-position valve 70, the throttle 140, and the branch pipe 150. At the same time, the electronic control circuit 300 outputs an operation signal to the hydraulic pump 100, so that the hydraulic oil accumulated in the reservoir tank 160 is pumped out by the hydraulic pump 100, and a part of the hydraulic oil is accumulated in the damper 130 via the branch pipe 110. Then, it is returned to the master cylinder 20 via the check valve 120 and the like. At this time, since the switching valve 180 is at the valve position d and the check valve 210 is closed, the hydraulic pressure on the master cylinder side is shut off. As a result, the oil pressure of the wheel cylinder 90 drops.

Then, when the electronic control circuit 300 determines from the above wheel speed, wheel acceleration, etc. that the braking hydraulic pressure generated in the wheel cylinder 90 needs to be increased, the electronic control circuit 300 drives the two-position valve 70. The output of the signal is stopped and the valve position a is set. Therefore, the master cylinder 20
Is sent to the wheel cylinder 90 to increase the braking oil pressure of the wheel cylinder 90. Further, at this time, if the oil pressure of the damper 130 is higher than the pressure passing through the throttle 40, the pressure oil of the damper 130 is also changed to the wheel cylinder 90.
Sent to. As a result, the braking hydraulic pressure of the wheel cylinder 90 rises.

In this embodiment, when the wheel speed V is smaller than a speed reference described later and the wheel acceleration dV is smaller than a reduction reference value Gs described later during the operation of the anti-skid control device, the braking hydraulic pressure described above is reduced. The depressurization operation is performed, and the pressure increase operation is performed other than that to prevent the wheels from being locked.
Then, when the wheel acceleration dV exceeds the reference change value G0, the decrease reference value Gs is lowered to prevent an inappropriate pressure reducing operation due to vibration of the suspension system due to repeated increase and decrease of the braking hydraulic pressure.

The operation of the antiskid control device of this embodiment will be further described with reference to the flowcharts of FIGS. 3 and 4. It should be noted that these processes are executed by activating a program stored in the ROM 330 in the electronic control unit 300 at predetermined time intervals.

FIG. 3 shows the basic control of the antiskid control device of this embodiment. This basic control is the same as the conventionally performed anti-skid control, except for the vibration countermeasure process (step 440) described later, and thus will be briefly described.

This control calculates the wheel speed V and the wheel acceleration dV from the output signal of the wheel speed sensor 240 (step 40).
0, 410), the vehicle body speed Vb is estimated from the wheel speed V and the wheel acceleration dV (step 420).
The speed reference Vs is calculated based on b (step 43).
0).

Subsequently, step 440 is a vibration countermeasure process for changing the reduction reference value Gs so that the present embodiment does not perform an inappropriate operation due to the vibration of the suspension system, which will be described in detail later.

When the vibration countermeasure process (step 440) is finished, it is checked whether or not the brake switch 230 is turned on (step 450). If the brake switch 230 is turned off, the process is finished as it is, and if it is turned on, the antiskid operation is performed. It is determined whether or not (step 460). At this location, the wheel speed V and the like are calculated regardless of the presence or absence of the braking operation. Therefore, when it is detected that the brake switch 230 is turned on, the anti-skid operation can be executed immediately.

When it is determined that the brake switch 230 is on (step 450), the braking hydraulic pressure is adjusted (steps 460 to 490). That is, when the wheel speed V is smaller than the speed reference Vs (step 460) and the wheel acceleration dV is smaller than the decrease reference value Gs (step 470), the braking hydraulic pressure generated in the wheel cylinder 90 by the above operation is determined. Decrease (step 480), otherwise increase the braking hydraulic pressure (step 490)
Of.

The vibration countermeasure process will be described with reference to FIG.

In this vibration countermeasure process, the wheel acceleration dV is the reference change value G.
By changing the time T for decreasing the decrease reference value Gs according to the time t that exceeds 0, an inappropriate operation is prevented from occurring due to the change in the wheel acceleration dV due to the vibration of the suspension system.

That is, when the control shifts to this processing, first, the wheel acceleration d
It is determined whether V is the reference change value G0 or more (step 500). If dV ≧ G0, the counter A indicating the time t when the wheel acceleration dV exceeds the reference change value G0 is incremented by one unit (step 510).
The counter B indicating the time T during which the decrease reference value Gs is decreased is cleared (step 520), and the time T during which the decrease reference value Gs is decreased based on the time t indicated by the counter A is set according to the relationship shown in FIG. Request (Step 53
0), control is passed to step 540. That is, dV ≧ G
While the state of 0 continues, each time the vibration countermeasure process is executed, the counter A is sequentially incremented in step 510, and in step 530, the value of the counter A and the execution interval (time of the vibration countermeasure process). ), The duration t of dV ≧ G0 is obtained, and the time T for decreasing the decrease reference value Gs is obtained from the duration t according to the relationship shown in FIG. On the other hand, if dV <G0,
Control is passed to step 540 without executing anything. The fifth
The relationships shown in the figure are stored in the ROM 320 of the electronic control unit 300.

In step 540, it is determined whether or not the correction is performed so as to reduce the decrease reference value Gs. Here, the wheel acceleration dV
When <0 and the brake switch 230 is on, it is determined that the reduction reference value Gs is to be reduced. When it is determined in step 540 that the reduction reference value Gs is to be reduced, the anti-skid control device reduces the reduction reference value Gs to G1 for a predetermined time T in steps 550 to 580.

In step 550, the time f (B) during which the decrease reference value Gs obtained from the value of the counter B and the execution interval (time) of the vibration countermeasure process is decreasing, and the decrease reference value Gs set above are decreased. When the time T is compared and B ≦ T, the counter B is incremented by one unit (step 560), the decrease reference value Gs is set to G1 described later (step 570), and the counter A is cleared (step 570). 580), and this processing ends. On the other hand, if B> T in step 550, the reduction reference value G in step 590.
This process is terminated by setting s to G2 described later.

If it is determined in step 540 that the correction for reducing the decrease reference value Gs is not performed, then in step 590, the decrease reference value Gs is set to G2 described below, and this processing ends. Here, G2 assigned to Gs in step 590 is a reference value used when there is no influence of vibration of the suspension system, and G1 assigned to Gs in step 570.
Is a reference value used when there is an influence of vibration of the suspension system. G1 is set sufficiently low so that the wheel acceleration dV does not fall below this value due to the influence of vibration of the suspension system.

FIG. 6 and FIG. 7 show an operation example of the antiskid control device of this embodiment configured as described above.

6 and 7, the conditions of the suspension system and the like are the same, but only the vehicle weight is different. FIG. 6 is a time chart showing the operation when the vehicle body weight is relatively light, for example, when the vehicle-mounted object is only the driver, and FIG. 7 is when the vehicle body weight is relatively heavy, for example, up to the vehicle limit. It is a time chart which shows operation when an in-vehicle thing is carried.

First, FIG. 6 will be described.

At time S0, when the brake pedal 10 is depressed, the braking hydraulic pressure of the wheel cylinder 90 rises and the wheel speed V increases.
Is reduced. When the wheel acceleration dV falls below the reduction reference value Gs at the time point S1, the braking hydraulic pressure is reduced (see steps 470 and 480 in FIG. 3), and the wheel speed V gradually increases. The decrease reference value Gs changes between time S1 and time S2, but this is for stably reducing the brake oil pressure by giving hysteresis to the pressure decrease condition of the brake oil pressure. Further, the amplitude of the wheel acceleration dV generated thereafter is due to the vibration of the suspension system due to the reduction of the braking hydraulic pressure.

When the braking hydraulic pressure is reduced as described above and the wheel acceleration dV rises and exceeds the reference change value G0, the time t when the wheel acceleration dV exceeds the reference change value G0 by the counter A as described above in this embodiment. (FIG. 6, t1, t2, t3) was measured, and the time T (T1, T2, T,
3) Decrease the decrease reference value Gs. In this way, inappropriate depressurization operation due to vibration of the suspension system is prohibited.

Further, even when the vehicle-mounted weight increases and the vibration cycle of the suspension system becomes longer as shown in FIG. 7, the time t () when the wheel acceleration dV exceeds the reference change value G0 as in the case of FIG. (Fig. 7, t4, t5) is measured, and the reduction reference value Gs is decreased by the time T (T4, T4, T5) corresponding thereto, thereby prohibiting an inappropriate depressurizing operation due to vibration of the suspension system. Of.

On the other hand, in the conventional anti-skid control device, the decrease time of the decrease reference value Gs is the preset period Ts, and its change is as shown by the broken lines in FIGS. 6 and 7. That is, in the conventional anti-skid control device, since the change in vehicle weight is not taken into consideration, when it is about the same as the vehicle weight used for setting the decrease time Ts of the decrease reference value Gs, as shown in FIG. Improper depressurization due to vibration of the suspension system can be prohibited. However, when the vehicle weight is significantly different from that used for setting the lowering time Ts as shown in FIG. 7, it is not possible to prohibit an inappropriate depressurizing operation due to the vibration of the suspension system. Period Te
Thus, the braking pressure is unnecessarily reduced and the braking distance is extended.

As described above, in this embodiment, the decrease time of the decrease reference value Gs is changed according to the time when the wheel acceleration dV exceeds the reference change value G0. Therefore, even if the vibration characteristics of the suspension system change due to changes in the vehicle weight or the like, it is possible to prohibit an inappropriate decompression operation due to the vibration of the suspension system. Further, as described above, in the antiskid control device of this embodiment, the characteristics of the suspension system and the like do not influence the antiskid operation. Therefore,
The anti-skid control device of the present embodiment does not need to set various values according to the vehicle weight, suspension characteristics, etc., and the same effect can be obtained regardless of the type of vehicle installed.

Although the reference change value G0 is a constant value in the present embodiment, it may be changed according to the wheel speed, the time from the start of braking, and the like. Further, in the present embodiment, the reduced reduction reference value Gs is set to the constant value G1, but it may be changed according to the wheel speed, the elapsed time from the start of the reduction of the reduction reference value Gs, and the like.

[Advantages of the Invention] By adopting the above-described configuration, the present invention prohibits an inappropriate depressurization operation due to the vibration of the suspension system even if the vibration characteristics of the suspension system change due to changes in vehicle weight and the like. can do.

Further, as described above, the anti-skid control device of the present invention can be mounted on the vehicle without setting various values according to the vehicle weight, suspension characteristics, etc., because the characteristics of the suspension system etc. do not affect the anti-skid operation. . That is, since the anti-skid control device of the present invention is extremely versatile, it can be easily mounted on any vehicle.

[Brief description of drawings]

FIG. 1 is a block diagram of the present invention, FIG. 2 is a block diagram of an embodiment of the present invention, FIGS. 3 and 4 are flow charts for explaining the operation thereof, and FIG. 5 shows the relationship used therein. Diagrams, FIGS. 6 and 7 are time charts for explaining the operation. 10 ... Brake pedal, 20 ... Master cylinder, 7
0 ... 2-position valve, 90 ... Wheel cylinder, 100 ...
… Hydraulic pump, 230 …… Brake switch, 240…
... Wheel speed sensor, 300 ... Electronic control circuit

Claims (1)

[Claims] Claim: What is claimed is: 1. An anti-skid control device for adjusting a braking force of a braking device according to a slip state of a wheel when a braking device that generates a braking force in response to a braking operation of a vehicle driver is operated. A rotational acceleration detecting means for detecting acceleration, and when the detected rotational acceleration becomes smaller than a preset reduction reference value, the braking force of the brake device is reduced, and then the rotational acceleration is reduced by the reduction of the braking force. When the decrease reference value is exceeded, a braking force adjusting means for increasing the braking force of the brake device, and when the detected rotational acceleration exceeds a reference change value set in advance to a value larger than the decrease reference value, After that, according to the elapsed time measured by the time measuring means and the elapsed time until the rotational acceleration becomes equal to or less than the reference change value, the elapsed time is measured. Change time setting means for setting a change time for changing the decrease reference value to a predetermined value smaller than usual so that the longer the longer time is, and the time after the elapsed time is measured by the time measuring means, When the rotational acceleration decreases to a change acceleration that is set to a value smaller than the reference change value and larger than the decrease reference value in advance, then the change time set by the change time setting means elapses until the change An anti-skid control device comprising: a reduction reference value changing means for changing the reduction reference value to a predetermined value smaller than usual.