JPH04293654A - Antiskid braking device for vehicle - Google Patents

Abstract

PURPOSE:To perform control in response to the change of the traveling state by setting the deceleration threshold value as the starting condition of antiskid control in response to operation states, e.g. brake pedal depression quantity, braking liquid pressure or depressing force. CONSTITUTION:A control unit 24 sets the braking liquid pressure level P1 in response to the phase value set for each wheel and outputs the braking pressure control signals according to the control quantity to the first through third valve units 20, 21, 23 respectively. The braking pressure of front wheel branch braking pressure lines 19a, 19b and rear wheel branch braking pressure lines 22a, 22b on the downstream side of the first through third valve units 20, 21, 23 is controlled to be increased, decreased or maintained at the pressure level after the increase or decrease. The control unit 24 is inputted with various data including the depression state of a brake pedal at individual wheel speeds W1-W4 and braking pressure, i.e., braking liquid pressure.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anti-skid brake system for a vehicle that performs anti-skid control to control the slip rate of wheels by controlling brake fluid pressure.

0002

[Background Art] Conventionally, in order to prevent the wheels from locking or skidding due to excessive braking force and impairing braking performance during braking, the slip ratio of each wheel is calculated and the slip ratio is set separately. Anti-skid control is known in which the braking force of each wheel is controlled to achieve a target slip ratio.

[0003] This type of anti-skid brake device is
For example, as disclosed in Japanese Patent Publication No. 56-22736, it is equipped with a wheel speed sensor that detects the rotational speed of the wheel and an electromagnetic control valve that adjusts the brake fluid pressure. The vehicle body speed is reduced according to the speed change rate (acceleration or deceleration) based on the wheel speed, and the brake fluid pressure is maintained, reduced, or increased as appropriate so that the wheel slip rate becomes a predetermined value. This is to control the braking pressure and increase the braking effect.

[0004] Japanese Patent Application Laid-Open No. 60-259559 also discloses an example of an anti-skid control device. When starting this anti-skid control, a threshold value for whether or not to start anti-skid control is set for the above-mentioned slip rate or other factors, and when that threshold is exceeded, anti-skid control is started. It is supposed to start and control brake fluid pressure.

[0005]

In conventional anti-skid control, the set threshold value is fixed and the vehicle is always started under the same conditions. However, the occurrence of wheel locking changes depending on driving conditions. In order to obtain appropriate braking performance of the vehicle in response to such changes in conditions, it is desirable to change the starting conditions for anti-skid control as appropriate depending on the operating state of the brake pedal.

The object of the present invention is to provide an anti-skid brake device which is constructed from the above-mentioned viewpoint and can stably improve braking performance regardless of changes in driving conditions.

[0007]

[Means for Solving the Problems] An anti-skid brake device for a vehicle configured to achieve the above object controls the brake fluid pressure for braking the wheels when it is determined that the wheels are in a locked state. anti-skid control means for controlling the slip rate of the wheels; and threshold setting means for setting a threshold value of wheel deceleration for starting control by the anti-skid control means in accordance with the amount of depression of the brake pedal. , a deceleration detection means for detecting the deceleration of the wheel, and a lock determination means for determining that the wheel is in a locked state when the detected deceleration of the wheel exceeds the threshold value corresponding to the amount of depression of the brake pedal. It is characterized by having the following.

[0008] In a preferred embodiment, the lock determining means is configured such that the deceleration of the wheel reaches the threshold when the brake pedal depression speed is smaller than a predetermined value or when the brake pedal depression amount is maintained at a substantially constant value. If the value exceeds this value, it is determined that the wheels are in a locked state. Further, the threshold value setting means determines the wheel deceleration for starting the control by the anti-skid control means in response to the brake fluid pressure as braking pressure or the magnitude of the brake pedal depression force instead of the amount of depression of the brake pedal. and the lock determination means determines that the wheels are in a locked state when the deceleration of the wheels exceeds the threshold corresponding to the brake fluid pressure or the magnitude of the brake pedal depression force. It can also be configured to do so.

[0009]

[Operation] According to the present invention, when it is determined that the wheels are in a locked state, the anti-skid control means
The brake fluid pressure as the braking pressure for the wheels, that is, the driving wheel and the driven wheel, is controlled so that the slip ratio of the wheel becomes a predetermined target value.

According to the present invention, in determining the locked state of the wheels, a threshold value of the wheel deceleration corresponding to the amount of depression of the brake pedal is set, and preferably this threshold value is set as the amount of depression of the brake pedal. The control unit is equipped with a map corresponding to this map, and the wheel deceleration detected using this map is compared with a threshold value corresponding to the current amount of brake pedal depression. Therefore, the value of the wheel deceleration that corresponds to the amount of brake pedal depression set as a threshold value has a critical meaning that there is a high risk of locking when the amount of depression reaches a certain value. determined experimentally. Therefore, the brake pedal depression amount that gives the threshold value is a virtual maximum brake pedal depression amount, and a map of the threshold value of the wheel deceleration is created in relation to this virtual maximum brake pedal depression amount. When the virtual maximum depression amount increases,
The deceleration threshold increases.

The lock determining means detects the amount of depression of the brake pedal, calculates the current wheel deceleration from the wheel speed, and compares this deceleration with a threshold value for the amount of depression of the brake pedal by referring to a map. compare. and,
When the current wheel deceleration exceeds the threshold value, the lock determination means determines that the wheels are in a locked state, and starts controlling the slip rate by the anti-skid control means.

[0012] In order to ensure accurate control, the lock state should be determined when the speed at which the brake pedal is depressed is not so high, or when the amount of depression does not change much and is held almost constant. preferred above. In addition, when determining the lock state, we experimentally created a threshold map by focusing on the brake fluid pressure as braking pressure or the force on the brake pedal instead of the amount of brake pedal depression, and based on this map. It can also be determined whether the obtained wheel deceleration is greater than a threshold value corresponding to the brake fluid pressure or pedal force.

[0013]

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. 1 is a system diagram of a hydraulic circuit for controlling brakes of an engine and wheels of a vehicle to which anti-skid control according to the present invention is applied.

As shown in FIG. 1, in the vehicle according to this embodiment, the left and right front wheels 1 and 2 are driven wheels, and the left and right rear wheels are driving wheels, and the output torque of an engine 5 is transmitted from an automatic transmission 6 to a propeller. shaft 7, differential device 8 and left and right drive shafts 9,
10, the signal is transmitted to the left and right rear wheels 3 and 4. Each of the wheels 1 to 4 is provided with discs 11a to 14a that rotate integrally with the wheels 1 to 4, and is supplied with braking pressure.
Brake devices 11 to 14 each including calipers 11b to 14b are provided to brake the rotation of the brake devices 11 to 14, and a brake control system 15 is provided to perform a braking operation on these brake devices 11 to 14.

This brake control system 15 includes a booster 17 that increases the force on the brake pedal 16 by the driver, and a master cylinder 18 that generates braking pressure in accordance with the increased pedal force by the booster 17. have The front wheel brake pressure supply line 19 led from the master cylinder 18 branches into two routes, and these front wheel branch brake pressure lines 19a and 19b supply the brake devices 11 and 12 for the left and right front wheels 1 and 2. caliper 11
a, 12a, respectively, and the left front wheel 1
A first valve unit 2 consisting of an electromagnetic on-off valve 20a and an electromagnetic relief valve 20b is connected to one front wheel branch braking pressure line 19a leading to the brake device 11.
0 is installed, and the first branch braking pressure line 19b for the other front wheel leading to the brake device 12 of the right front wheel 2 is also
Similarly to the valve unit 20, a second valve unit 21 is installed, which includes an electromagnetic on-off valve 21a and a relief valve 21b, which is also electromagnetic.

On the other hand, the rear wheel braking pressure supply line 22 led from the master cylinder 18 has the first and second
Similar to the valve units 20 and 21, an electromagnetic on-off valve 2
3a and a similarly electromagnetic relief valve 23b is installed, and this rear wheel braking pressure supply line 22 is branched into two routes downstream of the third valve unit 23. These rear wheel branch braking pressure lines 22a, 22b are connected to the calipers 13b, 14 of the brake devices 13, 14 on the left and right rear wheels 3, 4.
b, respectively.

A control unit 24 for controlling the brake control system 15 is provided, and the control unit 24 receives a brake signal from a brake switch 25 for detecting ON/OFF of the brake pedal 16;
Wheel speed sensor 26 that detects the rotational speed of each wheel
-29, and outputs a braking pressure control signal according to these signals to the first to third valve units 20,
By outputting signals to 21 and 23, respectively, braking control is performed against slips of the left and right front wheels 1 and 2 and the rear wheels 3 and 4.
That is, anti-skid control is performed. That is, the control unit 24 controls the first to third valve units 20, 21, 2 based on the wheel speeds indicated by the wheel speed signals from the respective wheel speed sensors 27 to 30.
By controlling the opening/closing valves 20a, 21a, 23a and the relief valves 20b, 21b, 23b in No. 3 by duty ratio control, the front wheels 1, 2 and the rear wheels 3, 4 are controlled with braking pressure according to the slip state. It is designed to provide power. Note that each relief valve 20b, 2 in the first to third valve units 20, 21, 23
The brake oil discharged from 1b and 23b is returned to the reservoir tank 18a of the master cylinder 18 via a drain line (not shown).

In the non-anti-skid control state, the control unit 24 does not output a braking pressure control signal, so the relief valves 20b, 2 in the first to third valve units 20, 21, 23 are activated as shown in the figure.
1b, 23b are held closed, and the on-off valves 20a, 21a, 23a of each unit 20, 21, 23 are held open, so that the brake pedal 1
The braking pressure generated in the master cylinder 18 in response to the pedal force of the driver 6 is applied to the left and right front wheels 1 and 2 and the rear wheel 3 via the front wheel brake pressure supply line 19 and the rear wheel brake pressure supply line 22.
, 4, and braking forces corresponding to these braking pressures are generated at the front wheels 1, 2 and the rear wheels 3, 4.

The control unit 24 performs brake control according to the following procedure. As shown in FIG. 2, the control unit 24 calculates the acceleration and deceleration of each wheel based on the wheel speeds indicated by the signals from the sensors 26 to 29. When calculating the acceleration or deceleration, the control unit 24 divides the difference between the previously detected wheel speed value and the current detected value by a predetermined sampling period Δt (for example, 7 ms), converts the result into gravitational acceleration, and calculates the current value. It is adopted as the acceleration or deceleration of This deceleration is necessary for use as one of the parameters when setting the starting conditions for anti-skid control.

Furthermore, the control unit 24 estimates the road surface friction coefficient and uses this road surface friction coefficient to calculate the pseudo body speed of the vehicle. The control unit 24 controls the rear wheel speed obtained from the signals from the wheel speed sensors 28 and 29 and the respective wheel speed sensors 26 and 2.
The slip ratio is calculated from the wheel speeds of the left and right front wheels 1 and 2 indicated by the signal from 7 and the pseudo vehicle body speed based on the following relational expressions.

Slip rate=(wheel speed/pseudo vehicle speed)×100 As the deviation of the wheel speed from the pseudo vehicle speed increases, the slip ratio decreases, and the tendency of the wheel to slip increases. The control unit 24 starts anti-skid control when the slip rate exceeds a predetermined threshold.

Further, as a starting condition for starting anti-skid control, the control unit 24 determines the locked state of each wheel based on the wheel deceleration or slip rate, and controls the first to third valve units 20.
, 21, and 23. A phase determination process is performed to determine the control amount of brake fluid pressure for , 21, and 23. In this case, the control unit 24 controls the pressure level P1 of the brake fluid pressure set in advance corresponding to each phase.
Therefore, when the phase is determined, the corresponding brake fluid pressure is automatically determined. The control unit 24 controls phase 0, which indicates a non-antiskid control state, and phase I, which indicates a pressure increase state during antiskid control, depending on the wheel acceleration/deceleration, slip rate, etc.
, Phase II showing a holding state after pressure increase, Phase III showing a pressure reducing state, Phase IV showing a sudden pressure reducing state, and Phase V showing a holding state after pressure reducing.

The control unit 24 sets the brake fluid pressure level P1 according to the phase value set for each wheel, and then sends a brake pressure control signal to the first to third valve units according to the control amount. 20, 21, and 23, respectively. As a result, the braking pressure of the front wheel branch braking pressure lines 19a, 19b and the rear wheel branch braking pressure lines 22a, 22b on the downstream side of the first to third valve units 20, 21, 23 increases or decreases, or Control is performed such as increasing the pressure or maintaining the pressure at the pressure level after decreasing the pressure.

Specifically, the process for estimating the road surface friction coefficient is performed as follows, for example, according to the flowchart shown in FIG. The control unit 24 reads various data in step S3, and determines whether the anti-skid flag FABS is set to 1 in step S2. In other words, it is determined whether anti-skid control is being performed. This anti-skid flag FABS is set to 1 when the above-mentioned parameters such as slip rate and deceleration exceed predetermined threshold values, and when the brake switch 25 is switched from ON to OFF. It is set to be reset to 0. Then, the control unit 24 determines that the anti-skid flag FABS is 1.
If it is determined that the
Proceed to step 3 and set the friction coefficient value MU1 to 3, which indicates a high friction road surface.

The control unit 24 also sets the anti-skid flag FABS in step S2 above.
When it is determined that is set to 1, that is, when it is determined that anti-skid control is being performed, the process proceeds to step S4, and it is determined whether the deceleration DW1 during the previous cycle is smaller than -20 g (g is gravitational acceleration). At the same time, YE
When the determination is S, the process proceeds to step S6, and it is also determined whether the acceleration AW1 during the previous cycle is greater than 10 g. When the determination is NO, step S6 is executed and the friction coefficient value MU1 is set as the low friction road surface. 1 showing
Set.

Further, when the control unit 24 determines in step S4 that the deceleration DW1 is not smaller than -20g, it skips step S5 and moves to step S7, where it determines whether the acceleration AW1 is larger than 20g. However, when the determination is YES, step S8 is executed and 3 is set as the friction coefficient value MU, while when the determination is NO, step S9 is executed and the friction coefficient value MU is set to 2 indicating a medium friction road surface.

On the other hand, the process of calculating the pseudo vehicle speed is specifically performed as follows according to the flowchart of FIG. That is, the control unit 24 reads various data in step T1, and then adjusts the wheel speeds W1 to W1 indicated by the signals from the sensors 26 to 29 in step T2.
The highest wheel speed WMX is determined from W4, and at step T3, the amount of change in wheel speed ΔWMX per sampling period Δt of the wheel speed WMX is calculated.

Next, the control unit 24 executes step T4 to read out the vehicle speed correction value CVR corresponding to the friction coefficient value MU from the map shown in FIG.
In step T5, it is determined whether the wheel speed change amount ΔWMX is smaller than the vehicle body speed correction value CVR. When it is determined that the wheel speed change amount ΔWMX is smaller than the vehicle speed correction value CVR, step T6 is executed to replace the value obtained by subtracting the vehicle speed correction value CVR from the previous value of the pseudo vehicle speed VR with the current value. . Therefore, the pseudo vehicle speed VR decreases at a predetermined slope according to the vehicle speed correction value CVR.

On the other hand, when the control unit 24 determines in step T5 that the wheel speed change amount ΔWMX is larger than the vehicle speed correction value CVR, that is, when the maximum wheel speed WMX shows an excessive change, the control unit 24 proceeds to step T7. Move from pseudo vehicle speed VR to maximum wheel speed WMX
It is determined whether the value obtained by subtracting is larger than a predetermined value VD. That is, it is determined whether there is a large difference between the maximum wheel speed WMX and the pseudo vehicle speed VR. Then, when there is no large difference, the above step T6
is executed to replace the value obtained by subtracting the vehicle speed correction value CVR from the previous value of the pseudo vehicle speed VR with the current value.

Furthermore, when a large difference occurs between the maximum wheel speed WMX and the pseudo vehicle body speed VR, the control unit 24 executes step T8 to adjust the maximum wheel speed W.
Replace MX with pseudo vehicle speed VR. In this way, the pseudo body speed VR of the vehicle is set to each wheel speed W1 to W4.
It is updated every sampling period Δt in accordance with .

Next, a control procedure for determining the start of anti-skid control will be explained with reference to FIGS. 5 and 6. The control unit 24 performs step Q
In step 1, input various data. This includes the wheel speeds W1 to W4, the depression state of the brake pedal, and the braking pressure, that is, the brake fluid pressure. Next, it is determined whether anti-skid control is currently being performed (step Q2). If anti-skid control is not being performed, it is further determined whether the brake pedal depression speed is slow and below a predetermined value (step Q3).
. If this determination is YES, that is, if the brake pedal depression speed is below a predetermined value, it is further determined whether the brake pedal depression amount is approximately constant and the change is within a predetermined range (step Q4). If this determination is YES, that is, if the brake pedal depression amount is approximately constant, it is further determined whether the brake fluid pressure, that is, the braking pressure, is approximately constant and its fluctuation is within a predetermined range (step Q5). When the brake fluid pressure is approximately constant, in this example, it is further determined whether the driver's operational pressure, that is, the pedal force applied to the brake pedal is approximately constant and the change is within a predetermined range. (Step Q6). If this determination is also YES, that is, if the pedal force is substantially constant, the control unit 24 determines whether the current operating state is in the locked state. In this case, the control unit 24 is provided with a map of the threshold value of the wheel deceleration corresponding to the amount of depression of the brake pedal 16, and the threshold value and the current value of the amount of depression of the brake pedal are determined based on this map. Determination is made by comparing with wheel deceleration. When creating a threshold map, it is important to consider that when braking is performed by depressing the brake pedal under normal driving conditions, there is a high possibility that a lock condition will occur if the amount of depressing increases and the deceleration increases further. The critical point was determined experimentally and set as the deceleration threshold for the amount of brake pedal depression. Therefore, the threshold value in this map can be understood as the deceleration of the wheels at the hypothetical maximum depression amount of the brake pedal 16 at which no lock condition occurs on the road surface in question. The control unit 24 reads out the threshold value of the current wheel deceleration based on the current amount of brake pedal depression (step Q7), and determines whether the current wheel deceleration is larger than the threshold value (step Q8).

[0032] Then, if the current wheel deceleration exceeds the threshold value for the brake pedal depression amount, anti-skid control is started (step Q9).
. In this example, if any of the determinations in steps Q3 to Q6 is NO, the control unit 24 sets the threshold for the wheel deceleration to -3.0 g (step Q10). In this case, the wheel deceleration is −
If the weight does not exceed 3.0g, it is not determined that the wheels are in a locked state (step Q10), so until then,
Anti-skid control is never initiated. Next, anti-skid control for the front wheels will be explained.

In the non-anti-skid control state during deceleration, when the brake pedal 16 is depressed, the amount B1 of the brake pedal depression exceeds a predetermined value, and the amount of change B2 in the braking pressure generated in the master cylinder 18, that is, the brake fluid pressure, exceeds the predetermined value. is exceeded and the amount of change in pedal force B3 is equal to or greater than a predetermined value, the wheel deceleration threshold is set to a lower value of −1.5g, so for example, as shown in FIG. 7(a), When the amount of change in the wheel speed W1 of the left front wheel 1, that is, the deceleration DW1, reaches -1.5 g, the time t
A will shift to anti-skid control. Furthermore, if any of the brake pedal depression amount B1, the brake fluid pressure change amount B2, or the pedal force change amount B3 does not exceed a predetermined value set for each, the threshold value of the wheel deceleration is -3. Since the anti-skid control is set to .0g, anti-skid control is started when the deceleration DW1 reaches -3.0g.

In the first cycle immediately after the start of this control, since the friction coefficient value MU1 is set to 3 indicating a high friction road surface, the control unit 24 sets various control threshold values corresponding to the high friction road surface. will be set. The control unit 24 then calculates the slip rate S1 calculated from the wheel speed W1 and the deceleration DW.
1. Compare the acceleration AW1 with the various control thresholds described above. In this case, if the initial slip rate threshold B1 is set to 90%, for example, then the slip rate S
When 1 indicates 96%, the control unit 24
changes the phase value, that is, the level value P1, from 0 to 2, as shown in FIG. 7(b). Therefore, the braking pressure is maintained at the level immediately after the pressure increase, as shown in FIG. 7(c). For example, the slip rate S1
When P1 drops below 90%, the control unit 24 changes the phase value P1 from 2 to 3. As a result, the relief valve 20b of the first valve unit 20 is turned ON/OFF according to a predetermined duty rate, and as shown in FIG. 7(c), the braking pressure decreases at a predetermined gradient from time tb. As a result, the braking force gradually decreases, and the rotational force of the front wheels 1 begins to recover accordingly.

Further, the braking pressure continues to be reduced, and the deceleration DW1 and acceleration AW1 obtained from the wheel speed W1 of the front wheel 1 are reduced.
respectively become 0, the control unit 24 changes the phase value P1 from 3 to 5. Therefore, as shown in FIG. 7(c), the braking pressure is maintained at the level after the pressure reduction from the time ta. When the state of phase V continues and the slip ratio S1 exceeds 90%, the control unit 24 shifts the anti-skid control to the second cycle from the time td. In that case, the control unit 24 forcibly changes the phase value P1 to 1.

[0036] Immediately after the transition to phase 1, the on-off valve 20b of the first valve unit 20 is increased by 100% according to the initial surge pressure time TPZ set based on the duration of phase V in the first cycle. %, and the braking pressure is increased at a steep gradient as shown in FIG. 7(c). In addition, after the initial surge pressure time TPZ ends, the on-off valve 20a
is turned ON/OFF according to a predetermined duty rate, and the braking pressure gradually increases according to a gentler slope than the above-mentioned slope.

On the other hand, from the second cycle onward, as shown in FIG.
As shown in the flowchart, an appropriate friction coefficient value MU1 is determined according to the deceleration DW1, acceleration AW1, etc. in the previous cycle, and a control threshold value is selected according to these friction coefficient values MU1. Therefore, the braking pressure is precisely controlled according to the driving condition.

The above control is similarly performed for the other wheels W2 to W4. In the above example, on the assumption that the brake pedal depression speed, brake pedal depression amount, brake fluid pressure, and depression force are within predetermined ranges, the deceleration corresponding to the brake pedal depression amount is assumed to be the starting condition for anti-skid control. Although threshold values are set, it is also possible to determine the locked state when one or more, or two or more, exceed a predetermined value.

Furthermore, in the above example, a map is created by setting a threshold value corresponding to the amount of depression of the brake pedal, but it is also possible to create a map using brake fluid pressure or depression force as a parameter and refer to this map. It is also possible to enter a locked state by In this case, the procedure is the same as that described for the brake pedal depression amount, so detailed explanation thereof will be omitted.

[0040]

As described above, in the present invention, the deceleration threshold value as a starting condition for anti-skid control is set depending on the driving situation at the time, for example, the amount of depression of the brake pedal, the brake fluid pressure, or the depression force. Therefore, appropriate anti-skid control can be performed in response to changes in driving conditions such as the state in which the brake pedal is depressed.

[Brief explanation of drawings]

[Fig. 1] Overall schematic configuration diagram of a vehicle equipped with an anti-skid brake device according to the present invention

[Fig. 2] Flowchart diagram showing the estimation process of the road surface friction coefficient,

[Fig. 3] Flowchart diagram showing the calculation process of pseudo vehicle speed,

FIG. 4 is an explanatory diagram of a map used in the calculation process,

[Figure 5]
Flow chart diagram showing the contents of anti-skid control,

[Fig. 6] Flowchart diagram showing the contents of anti-skid control,

FIG. 7 is a time chart showing changes in various variables related to anti-skid control of the present embodiment.

[Explanation of symbols]

1, 2 Front wheel 3, 4 Rear wheel 20, 21, 23 Valve unit 24 Control unit 26-39 Wheel speed sensor.

Claims (3)

[Claims] 1. Anti-skid control means for controlling the slip rate of the wheels by controlling brake fluid pressure for braking the wheels when it is determined that the wheels are in a locked state;
threshold setting means for setting a threshold value of wheel deceleration for starting control by the anti-skid control means in accordance with the amount of depression of the brake pedal; and deceleration detection means for detecting the deceleration of the wheels. an anti-skid device for a vehicle, comprising lock determination means for determining that the wheel is in a locked state when the detected deceleration of the wheel exceeds the threshold value corresponding to the amount of depression of the brake pedal. Brake device. 2. The lock determination means is configured to determine whether the deceleration of the wheel is below the threshold value when the brake pedal depression speed is smaller than a predetermined value or when the brake pedal depression amount is maintained at a substantially constant value. 2. The anti-skid brake device according to claim 1, wherein the anti-skid brake device determines that the wheels are in a locked state when the threshold is exceeded. 3. The threshold setting means is configured to start the control by the anti-skid control means in response to the brake fluid pressure as braking pressure or the magnitude of the brake pedal depression force instead of the amount of depression of the brake pedal. The lock determination means sets a threshold value for wheel deceleration, and the lock determination means locks the wheel when the wheel deceleration exceeds the threshold value corresponding to the brake fluid pressure or the brake pedal depression force. The anti-skid brake device according to claim 1, wherein the anti-skid brake device determines that the brake is in a locked state.