JPH0840243A - Antiskid brake device for vehicle - Google Patents

Abstract

PURPOSE:To shorten the brake distance, securing the optimum brake power at all times, by holding the brake pressure in order when the calculation value of the wheel speed exceeds a plurality of threshold values, starting the decompression of the brake pressure, and relatively reducing the decompression quantity when the brake pressure holding time is long. CONSTITUTION:A control unit 24 receives each detection signal supplied from a brake switch 25, steering angle sensor 26, and the wheel speed sensors 27-30, and outputs the brake hydraulic signal into each valve unit 20, 21, 23 of a brake control system 15, and carries out the ABS control for each wheel 1-4 in parallel. In this case, if the calculation value of the wheel speed exceeds the prescribed first threshold value, the brake pressure is held. Further, if the calculation value of the wheel speed exceeds the second threshold value set to the slip increase side in comparison with the case of the first threshold value, the reduction of the brake pressure is started. Further, when the brake pressure holding time is long, the dcompression quantity is reduced in comparison with the case having the shorter holding time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle antiskid brake device.

[0002]

2. Description of the Related Art A vehicle anti-skid brake system is
Basically, the braking pressure (brake oil pressure) applied to the wheels is controlled to increase or decrease so that the wheels decelerate at the target deceleration or at the target slip ratio or slip amount. Accordingly, this is referred to as ABS control) to prevent the wheels from being locked or skid during braking, and to stop the vehicle for a short braking distance without losing directional stability. In this case, the ABS control is performed when the wheel deceleration exceeds a predetermined threshold value and increases, or when the wheel slip rate or slip amount exceeds a predetermined threshold value and increases. It is usually started.

Here, the wheel deceleration is generally calculated by differentiating the wheel speed, and the control start threshold value for this wheel deceleration is set to, for example, about -3 G (value converted into gravitational acceleration). .

The slip ratio is calculated from the vehicle speed and the wheel speed by the following equation. As the vehicle speed, the maximum value of the rotational speeds of the four wheels of the vehicle is generally used as the pseudo vehicle speed.

Slip rate = {(vehicle body speed-wheel speed) /
Vehicle speed} × 100% Then, the control start threshold value for this slip ratio is
For example, it is set to about 15%. Further, the slip amount is a deviation obtained by subtracting the wheel speed from the vehicle body speed, and the control start threshold value for this slip amount is, for example, 5 km.
It is set to about / h.

On the other hand, it has been conventionally proposed to change the control start threshold value of the ABS control according to the situation. For example, in the anti-skid brake device disclosed in Japanese Patent Laid-Open No. 5-85335, the brake is applied. After lowering the control start threshold value of the ABS control as the pedal is depressed, that is, after changing the control start threshold value to the side where the ABS control is easily entered, the control start threshold value is gradually returned to the original value. As a result, while satisfying the requirement for early start of ABS control when the brake pedal is pressed quickly, avoiding early start of ABS control when the brake pedal is pressed slowly, the driver can The brake pedal is operated while grasping the situation.

In recent ABS control, there is an extremely strong demand for shortening the braking distance. From this point of view, it is considered that the ABS control is started from the braking pressure holding state. Holds the braking pressure at that time when the deceleration of the wheel and / or the slip ratio or the slip amount of the wheel calculated from the wheel speed exceeds a predetermined first threshold value, and When the deceleration and / or the slip ratio or slip amount of the wheel exceeds a second threshold value set on the slip increase side of the threshold value, the braking pressure is reduced.

Further, for example, Japanese Patent Laid-Open No. 1-273758.
As disclosed in the publication, the time from the start of braking to the start of ABS control is measured, and when this time is long, the traveling road surface is determined to be a high μ road with a high friction coefficient μ, and the braking pressure is reduced. There is also known an anti-skid control device in which the traveling road surface is determined to be a low μ road having a low friction coefficient μ when the measurement time is short and the braking pressure is rapidly reduced when the measurement time is short.

[0009]

By the way, as described above, when the ABS control is started from the holding state of the braking pressure, the deceleration of the wheel and / or Alternatively, the slip ratio or slip amount of the wheels does not reach the second threshold value (pressure reduction start threshold value), and the braking pressure holding state is maintained for a long time. In such a case, since the brake hydraulic pressure is not higher than necessary, it is desirable to limit the pressure reduction in order to shorten the braking distance.

In view of the above-mentioned circumstances, according to the present invention, when the ABS control is started from the holding state of the braking pressure, the locking or skid of the wheels is prevented and the optimum braking force is secured to shorten the braking distance. An object of the present invention is to provide an anti-skid brake device for a vehicle.

[0011]

An anti-skid brake device for a vehicle according to the present invention comprises a wheel speed detecting means for detecting a wheel rotation speed, a braking pressure adjusting means for adjusting a wheel braking pressure, and the wheel speed detecting means. In the anti-skid brake device for a vehicle, which comprises an anti-skid control means for operating the braking pressure adjusting means based on the wheel speed detected by the means to periodically increase and decrease the braking pressure, the wheel speed detecting means detects the wheel speed. When the calculated value calculated based on the determined wheel speed exceeds a predetermined first threshold value, the braking pressure is maintained by the braking pressure adjusting means, and is set on the slip increasing side from the first threshold value. When the calculated value exceeds the determined second threshold value, the braking pressure adjusting means starts reducing the braking pressure, and
When the holding time of the braking pressure is long, the pressure reducing amount reducing means for reducing the pressure reducing amount is provided as compared with when the holding time is short.

The calculated value calculated based on the wheel speed is the deceleration of the wheel and / or the slip amount of the wheel.

According to one aspect of the present invention, the reduction of the reduced pressure amount comprises increasing the second threshold value.

When the holding time of the braking pressure is longer than the predetermined time, it is determined that the friction coefficient μ of the traveling road surface is high μ.

[0015]

When the ABS control is started from the braking pressure holding state and the braking pressure holding time is long on the high μ road, the brake pedal is stepped near the lock limit and the pressure is gradually increased. Is being done.

According to the first aspect of the present invention, the brake pedal is stepped near the lock limit by providing the reduced pressure amount reducing means for reducing the reduced pressure amount when the holding time of the braking pressure is long and short. It is possible to secure the braking force when the vehicle is on and reduce the braking distance.

Further, in the invention of claim 3, since the decompression amount reducing means of claim 1 comprises means for increasing the second threshold value which is the decompression start threshold value, it is difficult to start the reduction of the braking pressure. Therefore, the amount of reduced pressure is reduced.

[0018]

Embodiments of the present invention will be described below with reference to the drawings.

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 3 and 4 are drive wheels, and the output torque of the engine 5 is an automatic transmission. 6
Is transmitted to the left and right rear wheels 3 and 4 via the propeller shaft 7, the differential device 8 and the left and right drive shafts 9 and 10.

Each of the wheels 1 to 4 includes a disc 11a to 14a that rotates integrally with the wheel and a brake including a caliber 11b to 14b that receives the supply of brake hydraulic pressure and brakes the rotation of the disc 11a to 14a. Device 11-
14 are provided respectively, and these brake devices 11 to 11 are provided.
A brake control system 15 for actuating 14 is provided.

The brake control system 15 includes a booster 17 for increasing the stepping force of a brake pedal 16 by a driver, and a master cylinder 1 for generating a brake hydraulic pressure according to the stepping force increased by the booster 17.
8 and. The front wheel brake hydraulic pressure supply line 19 from the master cylinder 18 is branched into two paths, and the front wheel branch brake hydraulic pressure lines 19a and 19b are connected to the calibers 11 of the brake devices 11 and 12 for the left and right front wheels 1 and 2.
a, 12a, one branch brake hydraulic line 1 for the front wheel, which is connected to the brake device 11 for the left front wheel 1
9a is provided with a first valve unit 20 including an electromagnetic on-off valve 20a and an electromagnetic relief valve 20b, and is connected to the other front wheel branch brake hydraulic line 19b leading to the brake device 12 for the right front wheel 2. Similarly to the first valve unit 20, the second valve unit 21 including an electromagnetic on-off valve 21a and an electromagnetic relief valve 21b is also provided.
Is provided.

Relief valve 20 of the first valve unit 20
The brake oil discharged from b and the brake oil discharged from the relief valve 21b of the second valve unit 21 are stored in the common reservoir 31 and are pumped up from the reservoir 31 by the pump 32 operated during the ABS control. Are supplied to the front wheel brake hydraulic pressure supply line 19. The brake oil in the reservoir 31 passes through a drain line (not shown) to the reservoir tank 18a of the master cylinder 18.
Is returned to.

On the other hand, the brake hydraulic pressure supply line 22 for the rear wheel from the master cylinder 18 is provided with an electromagnetic opening / closing valve 23a and an electromagnetic relief valve 23b, like the first and second valve units 20 and 21. The third valve unit 23 is provided.

This rear wheel brake hydraulic pressure supply line 22
Is branched into two paths on the downstream side of the third valve unit 23, and these rear wheel branch brake hydraulic lines 22a, 2
2b are connected to the calibers 13b and 14b of the brake devices 13 and 14 for the left and right rear wheels 3 and 4, respectively.

Relief valve 23 of the third valve unit 23
The brake oil discharged from b is stored in the reservoir 33, and the brake oil pumped up from the reservoir 33 by the pump 34 operated during the ABS control is supplied to the rear wheel brake hydraulic pressure supply line 22. . The brake oil in the reservoir 33 is also returned to the reservoir tank 18a of the master cylinder 18 via a drain line (not shown).

The brake control system 15 includes a brake device 11 for the left front wheel 1 via a first valve unit 20.
The first channel for variably controlling the brake hydraulic pressure of the
Brake device 1 for right front wheel 2 via valve unit 21
A second channel for variably controlling the brake hydraulic pressure of No. 2 and a third channel for variably controlling the brake hydraulic pressure of both brake devices 13, 14 for the left and right rear wheels 3, 4 via the third valve unit 23 are provided. The first to third channels are configured to be controlled independently of each other.

The brake control system 15 includes a first
~ Control unit 24 for controlling the third channel
The control unit 24 is provided with a brake signal from a brake switch 25 for detecting ON / OFF of the brake pedal 16, a steering angle signal from a steering angle sensor 26 for detecting a steering angle of the steering wheel, and rotation of each wheel. It receives the wheel speed signals from the wheel speed sensors 27 to 30 respectively detecting the speeds, and outputs brake hydraulic pressure control signals corresponding to these signals to the first to third valve units 20, 21, 23.
To the front and rear wheels 1 and 2 and the rear wheels 3 and 4 on the left and right to control the braking, that is, AB
The S control is performed in parallel for each of the first to third channels.

The control unit 24 makes a first determination based on the wheel speed detected by each wheel speed sensor 27-30.
-Opening / closing valves 20a, 21a, 23a and relief valves 20b, 21b in the third valve units 20, 21, 23,
By controlling the opening and closing of the front and rear wheels 23b and 23b respectively, the front wheels 1 and 2 and the rear wheels 3 and 4 are controlled by the brake hydraulic pressure according to the locked state.
It is designed to apply braking force to.

In the ABS non-controlled state, a brake hydraulic pressure control signal is output from the control unit 24, and the first to third valve units 20, 2 as shown in the figure.
Relief valves 20b, 21b, 23b in Nos. 1 and 23 are held closed, respectively, and each valve unit 20, 2
Since the on-off valves 20a, 21a and 23a of the valves 1 and 23 are held open, the brake hydraulic pressure generated in the master cylinder 18 in response to the stepping force of the brake pedal 16 is applied to the front wheel brake hydraulic pressure supply line 19 and the rear wheel brake. It is supplied to the brake devices 11 to 14 of the left and right front wheels 1, 2 and the rear wheels 3, 4 via the hydraulic pressure supply line 22, and the control force corresponding to these brake hydraulic pressure is applied to the front wheels 1, 2 and the rear wheels 3, 4. It will be given directly.

Next, an outline of the brake control performed by the control unit 24 will be described.

The control unit 24 controls the wheel speeds Vw1 to Vw indicated by the signals from the wheel speed sensors 27 to 30.
4, the decelerations DVw1 to DVw4 and the accelerations AVw1 to AVw4 for each wheel are calculated.

Explaining the method of calculating the acceleration or deceleration, the control unit 24 calculates the difference between the previous value of the wheel speed and the current value and the sampling cycle Δ.
After dividing by t (for example, 7 ms), a value obtained by converting the result into gravitational acceleration is updated as the current acceleration and deceleration.

Further, the control unit 24 executes a predetermined rough road judging process to judge whether or not the traveling road surface is a bad road. Explaining the outline of this rough road determination, for each wheel corresponding to each channel, the number of times that the wheel acceleration or wheel deceleration is equal to or higher than a predetermined rough road determination threshold value during a predetermined period is counted. When the number of times is less than or equal to the predetermined value, the rough road flag Fak is set to 0, and when the number of times is larger than the predetermined value, the rough road flag Fak is set to 1.

The control unit 24 has a third
The rear wheels 3 and 4 which represent the wheel speed for the channel and the acceleration / deceleration are selected, but both wheel speeds are taken into consideration in consideration of the detection error of the both wheel speed sensors 29 and 30 of the rear wheels 3 and 4 at the time of slip. The lower one of the wheel speeds is selected as the rear wheel speed, and the acceleration and deceleration obtained from the wheel speed are selected as the rear wheel acceleration and the rear wheel deceleration.

Further, the control unit 24 calculates the road surface friction coefficient of each of the three channels at predetermined micro time intervals, and in parallel with this, calculates the pseudo vehicle body speed Vr of the vehicle.

The control unit 24 controls the rear wheel speeds obtained from the signals from the wheel speed sensors 29, 30 and the wheel speeds of the left and right front wheels 1, 2 detected by the wheel speed sensors 27, 28 and the pseudo vehicle body speed Vr. From 1st to 3rd
The slip amount for each channel is calculated, but in this embodiment, the non-slip ratio represented by the following equation is used.

Non-slip rate = (wheel speed / pseudo vehicle body speed) × 100% Therefore, the pseudo vehicle body speed Vr (hereinafter simply referred to as the vehicle body speed Vr
The deviation of the wheel speed with respect to () will increase, and the non-slip rate decreases, and the slip tendency of the wheel increases.

Next, the control unit 24
~ Various control threshold values used to control the third channel are set, and lock determination processing for each channel is performed using these control threshold values, and the first to third valve units 20,
A phase determination process for defining the control amount for 21, 23 and a cascade determination process are performed.

Here, the outline of the phase determination processing will be described. The control unit 24 compares the respective threshold values set according to the running state of the vehicle with the wheel acceleration / deceleration and the non-slip ratio to obtain the ABS. Phase 0 indicating a non-controlled state, Phase I that is a pressure increasing state during ABS control, Phase that is a holding state after pressure increasing
II, phase III which is a depressurized state, phase IV which is a rapidly depressurized state, and phase V which is a holding state after depressurization are selected.

The lock determination process will be described. For example, in the lock determination process for the first channel for the left front wheel, the control unit 24
First, the current value of the continuation flag Fcn1 for the first channel is set as the previous value, and then the vehicle body speed Vr and the wheel speed Vw1 are set to predetermined conditions (for example, Vr <5 km / h, V
w1 <7.5 km / h) is determined, and when these conditions are satisfied, the continuation flag Fcn1 and the lock flag Flok1 are reset to 0, respectively, and if not satisfied, the lock flag Flok1 is reset. Is set to 1 or not.

If the lock flag Flok1 is not set to 1, the lock flag Flok1 is set to 1 under a predetermined condition (for example, when the wheel deceleration becomes -3G).

On the other hand, in the control unit 24, when the lock flag Flok1 is set to 1, for example, the phase flag P1 of the first channel is set to 5 indicating the phase V, and the non-slip ratio S1 is 5 which will be described later. -1 When the continuation flag Fcn1 is larger than the non-slip rate threshold value Bsz, 1 is set. The lock determination process is similarly performed for the second and third channels.

In the above-described cascade determination process, particularly on a low friction road surface such as ice burn, even if a small brake pressure is applied to the wheels, it is easy to lock the wheels. This is a determination, and the cascade flag Fcs is set to 1 when a predetermined condition in which cascade lock is likely to occur is satisfied.

Thus, the control unit 24 is
A brake pressure signal corresponding to the phase instructed by each phase flag P1 is output to each of the first to third valve units 20, 21 and 23 for each channel.
Accordingly, the first to third valve units 20, 21, 2
Branch brake pressure line 19 for front wheels on the downstream side of 3
a, 19b and the branch brake pressure line 22a for the rear wheels,
The brake pressure of 22b is increased or decreased, or is maintained at the pressure level after the increase or decrease. next,
A method for calculating the road surface friction coefficient (road surface μ) will be described.

First, the road surface friction coefficient Mu of the first channel
When calculating 1, the road surface friction coefficient Mu1 is calculated on the basis of the wheel speed Vw1 of the front wheels 1 and its acceleration Vg. However, the acceleration Vg after acceleration is sufficient by using a timer of 500 ms and a timer of 100 ms. Not grow 50
The acceleration Vg is calculated by the following equation from the change of the wheel speed Vw1 every 100 ms until the lapse of 0 ms in 100 ms.

Vg = K1 × [Vw1 (i) −Vw1 (i-100)] After the lapse of 500 ms when the acceleration Vg becomes sufficiently large, the acceleration is calculated by the following equation from the change of the wheel speed every 500 ms for 500 ms. Vg is calculated.

Vg = K2 × [Vw1 (i) −Vw1 (i-500)] In the above formula, Vw1 (i) is the current wheel speed,
Vw1 (i-100) is the wheel speed 100 ms before, Vw
1 (i-500) is the wheel speed before 500 ms, K1, K
2 is a predetermined constant. The road surface friction coefficient Mu1
Is calculated by three-dimensional interpolation from the μ table shown in FIG. 2 using the wheel speed Vw1 obtained as described above and its acceleration Vg. However, the road surface μ = 1.0 to 2.5 corresponds to low friction, the road surface μ = 2.5 to 3.5 corresponds to medium friction, and the road surface μ = 35 to 5.0 corresponds to high friction. .

Next, the road surface friction coefficient Mu of the second channel
When calculating 2, the wheel speed Vw2 is used for the same calculation as described above, and the surface friction coefficient Mu3 of the third channel is set equal to the smaller one of the road surface friction coefficient Mu1 and the road surface friction coefficient Mu2. . However, the road surface μ detected by three dedicated road surface μ sensors corresponding to the first to third channels
May be applied.

Next, the calculation processing of the pseudo vehicle body speed Vr will be described with reference to the flowchart of FIG. The following vehicle speed Vr means a pseudo vehicle speed.

First, the control unit 24 reads various data (S20), then calculates the maximum wheel speed Vwm from the wheel speeds Vw1 to Vw4 indicated by the signals from the sensors 27 to 30 (S21), and then Maximum wheel speed V
The maximum wheel speed change amount Δwm per sampling period Δt of wm is calculated (S22).

Next, the control unit 24 sets S2
3 in the friction state value Mu (first
~ Minimum road friction value of channel 3) The vehicle body speed correction value CVr is read out, and it is determined in S24 whether the maximum wheel speed change amount ΔVwm is equal to or less than the vehicle body speed correction value CVr.

As a result of the determination, the wheel speed change amount ΔVwm
When it is determined that is equal to or smaller than the vehicle body speed correction value CVr (S24: YES), the value obtained by subtracting the vehicle body speed correction value CVr from the previous value of the vehicle body speed Vr is replaced with the current value in S25. Therefore, the vehicle body speed Vr is the vehicle body speed correction value CV.
It will decrease with a predetermined gradient according to r.

On the other hand, the control unit 24 uses S2
4, the wheel speed change amount ΔVwm is the vehicle body speed correction value C.
When it is determined that it is larger than Vr (S24: NO), that is, when the maximum wheel speed Vwm shows an excessive change,
In S26, the pseudo vehicle body speed Vr to the maximum wheel speed Vw
It is determined whether the value obtained by subtracting m is greater than or equal to the predetermined value Vo.

That is, the maximum wheel speed Vwm and the vehicle body speed V
It is determined whether or not there is a large difference with r. When there is a large difference (S26: YES), the value obtained by subtracting the vehicle body speed correction value CVr from the previous value of the vehicle body speed Vr is replaced with the current value in S25.

Further, when there is no large difference between the maximum wheel speed Vwm and the vehicle body speed Vr (S26: NO), the control unit 24 replaces the maximum wheel speed Vwm with the vehicle body speed Vr in S27. Thus
The vehicle body speed Vr of the vehicle is updated every sampling period Δt according to the wheel speeds Vw1 to Vw4.

Next, the process of setting various control threshold values will be described with reference to the flowchart of FIG. 5 and FIGS. The control threshold value setting process is executed independently for each channel, but here, the control threshold value setting process for the first channel for the left front wheel will be described.

The control unit 24 reads various data in S30, and then in S31, the frictional state value Mu and the vehicle body speed Vr are calculated from the table preset with the vehicle speed range and the road surface μ as parameters as shown in FIG. The driving condition parameter according to is selected. For example, when the friction state value Mu is 1, which is indicated by the low friction road surface, and the vehicle body speed Vr is in the medium speed range, the LM2 for the medium speed low friction road surface is selected as the traveling state parameter. The friction state value M
u is determined from the minimum one of the friction coefficients Mu1 to Mu3. In FIG. 6, Mu = 1 indicates a low friction state, M
u = 2 corresponds to a medium friction state, and Mu = 3 corresponds to a high friction state.

On the other hand, when the bad road flag Fak is set to 1 indicating the bad road condition, the running condition parameter corresponding to the vehicle body speed Vr is selected as shown in FIG. In this case, for example, when the vehicle body speed Vr belongs to the medium speed range, the HM for the medium speed and low friction road surface is used as the traveling state parameter.
2 is forced to be selected. That is, the road surface μ tends to be estimated to be small due to the large fluctuation of the wheel speed during traveling on a rough road.

After selecting the running condition parameters, the control unit 24 reads the various control threshold values corresponding to the running condition parameters from the control threshold value setting table shown in FIG. 7 in S32.

Here, as various control thresholds, AB
7 shows a 0-2 deceleration threshold value B ₀₂ (first threshold value in claim 1) for determining the transition from the phase 0 indicating the S non-control state to the phase II indicating the holding state after pressure increase, and FIG. As shown in FIG. 1, 1-2 intermediate deceleration threshold value B ₁₂ for judging transition from phase I, which is a pressure increasing state during ABS control, to phase II, which is a holding state after pressure increasing, and a pressure reducing state from phase II. 2-3 intermediate non-slip ratio threshold value Bsg (second threshold value in claim 1) for determining the transition to phase III, which is the transition determination from phase III to phase V, which is the holding state after depressurization 3-5 Intermediate deceleration threshold B
₃₅ , 5-1 for judging transition from phase V to phase I
The non-slip rate threshold value Bsz and the like are set for each running state parameter. The 0-2 deceleration threshold value B ₀₂ is set to -3G.

In this case, the deceleration threshold value which greatly influences the control force is such that the friction performance is high in order to achieve a high level of both braking performance when the road surface μ is large and control response when the road surface μ is small. The smaller the level of the state value Mu, that is, the smaller the road surface μ, the closer to 0G. Here, when the control unit 24 selects LM2 for medium speed / low friction road surface as the traveling state parameter, as shown in the column of LM2 in the control threshold setting table of FIG. Speed threshold B ₁₂ , 2-3 intermediate non-slip ratio threshold Bsg, 3
-5 Intermediate deceleration threshold value B ₃₅ , 5-1 Non-slip rate threshold value Bsz, -0.5G, 90%, 0G, 90%
Each value of is read out.

Next, the control unit 24 sets S3
At 3, it is determined whether or not the frictional state value Mu is set to 3, which indicates a high friction road surface, and when Yes is determined, at S34, it is determined whether or not the rough road flag Fak is set to 0. As a result of the determination, the rough road flag F
When ak is 0, the process proceeds to S35, in which it is determined whether the absolute value of the steering angle θ detected by the steering angle sensor 26 is smaller than 90 °, and the absolute value of the steering angle θ is smaller than 90 °. If not, in S36, the control threshold value is corrected according to the steering angle θ. This control threshold correction processing is shown in FIG.
It is performed based on the control threshold value correction table illustrated in FIG.

That is, in the control threshold value correction table of FIG. 8, in order to secure the steerability when the steering wheel operation amount is large when the road is not a bad road with low friction, medium friction and high friction, The value obtained by adding 5% to each of the 3 intermediate non-slip ratio threshold Bsg and the 5-1 intermediate non-slip ratio threshold Bsz is the final 2-3 non-slip ratio threshold Bs.
g and the final 5-1 non-slip rate threshold value Bsz, and other intermediate threshold values are set as they are as the final threshold value.

On a rough road with a high friction (flag Fak = 1), in order to ensure the running performance when the steering wheel operation amount is small, 2-3 intermediate non-slip ratio threshold values Bsg and 5-
The values obtained by subtracting 5% from the 1 intermediate slip ratio threshold Bsz are set as the final 2-3 non-slip ratio threshold Bsg and the final 5-1 non-slip ratio threshold Bsz. Next, when the determination result in S35 is NO,
Each of the above intermediate threshold values is directly set as the final threshold value.

On the other hand, the control unit 24 uses S3
If it is determined that the rough road flag Fak is set to 1 in step 4, the process proceeds to step S37, and the relation between the rough road flag Fak and the steering angle θ is 2 based on the control threshold value correction table of FIG. -3 Intermediate non-slip ratio threshold Bs
g and the 5-1 non-slip rate threshold value Bsz are respectively corrected to obtain the final 2-3 intermediate non-slip rate threshold value Bs.
g and the final 5-1 non-slip rate threshold value Bsz are set. Then, in step S38, based on the control threshold value correction table of FIG.
The correction processing for setting the intermediate deceleration value obtained by subtracting 1.0G from the threshold B ₁₂ as the final 1-2 deceleration threshold B ₁₂ performs.

This is because the wheel speed sensors 27 to 30 are likely to make erroneous detections at the time of determining a bad road, so that the response of the control is delayed and a good braking force is secured.
Incidentally, other intermediate threshold values are set as they are as final threshold values. Furthermore, the control unit 24
When it is determined in S33 that the frictional state value Mu is not 3, the process proceeds to S35. The control thresholds are set for the second and third channels as in the case of the first channel.

Next, regarding the control signal output processing for determining the above-mentioned phase and outputting the braking control signal of each phase to the valve unit, taking the first channel as an example, the flowcharts of FIGS. 9 to 13 and FIGS. The description will be made with reference to 18. Note that this process is a process that is repeated, for example, every 4 ms.

First, various data are read (S40 in FIG. 9), and then it is determined in S41 whether or not the brake switch 25 is ON. If the determination is NO, the process returns through S42 and the above determination is YES. If it is, the vehicle body speed Vr is a predetermined value C1 (for example, 5.0 km / h) in S43.
Below, and the wheel speed Vw1 is a predetermined value (for example, 7.5).
km / h) Judge whether it is less than or equal to. If the determination is YES, it is in a sufficiently decelerated state, and there is no need for ABS control, so the process returns via S42, but the determination in S43 is No.
If so, the process proceeds to S44.

At S42, the phase flag P1, the lock flag Flok1, the continuation flag Fcn1, and the flag F are set to 0.
Respectively, and then returns to S40.

Next, in S44, the lock flag Flok is set.
It is determined whether 1 is 0 or not, and the flag F is set before the ABS control is started.
When lok1 is 0, the process proceeds to S45 and the wheel speed Vw
When the deceleration DVw1 of 1 (provided that DVw1 ≦ 0) is equal to or less than a predetermined value D ₀ , that is, the 0-2 deceleration threshold B ₀₂ (for example, −3G), and the determination is YES Shifts to S46. On the other hand, when the determination in S44 is NO, the process proceeds to S49.

Next, if the determination in S45 is YES, S
The lock flag Flok1 is set to 1 in 46, then the flag P1 is set to 2 in S47, and the process proceeds to phase II (holding phase after pressure increase), and then preset in S48 for phase II. The braking control signal is output to the first valve unit 20, and then the process returns.

After the ABS control is started, the flag Flok1 is set to 1. Therefore, the process proceeds from S44 to S49, and it is determined whether the flag P1 is 2. If the flag P1 is 2, the process proceeds to S50, When P1 is not 2, the process proceeds to S54.

At S50, it is determined whether or not the slip ratio S1 is equal to or less than the 2-3 slip ratio threshold value Bsg. Since it is determined as NO at the beginning, the process shifts from S50 to S48. The slip ratio S1 is the threshold value Bs
When it becomes g or less, the process proceeds from S50 to S51. This S
In 51, the flag P1 is set to 3 and the process moves to phase III (phase of pressure reduction).

Next, in S52, the timer T for counting the elapsed time after the start of the phase III is reset and then started, and then in S53, the braking control signal for the phase III is output to the first valve unit 20. Is
Then return. However, the subroutine of S53 will be described later with reference to FIGS.

If the result of the determination in S49 is that the flag P1 is not 2, the process proceeds from S49 to S54 and the flag P1 is set to 3
If the determination is YES, the process proceeds to S55, and if the determination is NO, the process proceeds to S59 in FIG.

In S55, it is determined whether or not the deceleration DVw1 is equal to the 3-5 intermediate deceleration threshold value B ₃₅ , and it is determined to be NO at the beginning, so the process proceeds from S55 to S53. By repeating the above, when the deceleration DVw1 becomes equal to the threshold value B ₃₅ , the process proceeds to S56, the flag P1 is set to 5 in S56, and the process proceeds to the phase V (holding phase after depressurization). Next, in S57, S
The flag F used in the subroutine 53 is reset to 0.

Next, in S58, a braking control signal preset for phase V is output to the first valve unit 20, and then the process returns.

Next, if the determination in S54 is NO,
In S59 of 0, it is determined whether or not the flag P1 is 5, and if the determination is YES, the process proceeds to S60, and if NO, the process proceeds to S67. When the flag P1 is 5, S60
In, it is determined whether the slip ratio S1 is 5-1 slip ratio threshold Bsg or more.

At the beginning, it is determined to be NO, so S6
The transition from 0 to S58 in FIG. 9 is repeated. And
In phase V, the non-slip rate S1 increases and S
When the determination result in 60 is YES, the process proceeds to S61, in which the flag P1 is set to 1 and the phase I (pressure increase phase) is entered, and the continuation flag Fcn1 is set to 1.
Is set to

Next, in S62, the rapid pressure increase time Tpz of the initial rapid pressure increase executed at the beginning of the phase I (pressure increase phase) is calculated. This rapid pressure increase time Tpz is S7.
It is set as a value proportional to the pressure increase time Ti of the previous cycle calculated and stored at 0. Next, in S63, the timer T1 that counts the elapsed time after the start of the phase I is reset and then started, and then in S64, it is determined whether the count time T1 of the timer T1 is equal to or less than the rapid pressure increase time Tpz set in S62. If it is determined that the sudden pressure increase time Tpz is the first time or less, the process proceeds from S64 to S65, and a braking control signal preset for the initial rapid pressure increase of phase I is output to the first valve unit 20 in S65. , Then return.

Next, after shifting to phase I, the determination in S59 is NO, so the flow shifts from S59 to S67.
In 67, it is determined whether or not the flag P1 is 1, and the flag P
When 1 is 1, the deceleration DVw1 is 1 in S68.
-2 It is determined whether or not the intermediate deceleration threshold value B _{12 is} less than or equal to, and the determination is NO at the beginning, so S68 to S64
Transition to S64 and before the rapid pressure increase time Tpz elapses from S64 to S
The process of shifting to 65 is repeated. While repeating this,
After the transition to phase I, when the rapid pressure increase time Tpz elapses,
Since the determination in S64 is NO, the process proceeds from S64 to S65, where a braking control signal preset for the slow pressure increase in phase I is output to the second valve unit 20, and then the process returns.

Next, when the determination in S68 is YES, S
The flag P1 is set to 2 in 69, and then S70.
At time t1, the pressure increase time T is calculated based on the time measured by the timer T1.
i (phase I period) is calculated and stored, and then the process proceeds to S48.

In this way, after the ABS control is started, the phase II, the phase III, the phase V, the phase I, the phase II, the phase III, ... Are executed in this order over a plurality of cycles, and the determination in S43 is YES. If the brake switch 25 is turned off, ABS
The control ends (see FIG. 15).

Next, the subroutine of S53 of FIG. 9 will be described with reference to the flowcharts of FIGS. 11 to 13 and FIGS. 14 to 16.

As shown in FIG. 16, the depressurization in the phase III of the first cycle is carried out by opening the relief valve 20b intermittently in five times from the first time to the fifth time. The reduced pressure amount is set by the opening time of the valve 20b.

In the table of decompression level / decompression amount shown in FIG. 14, decompression start time of each decompression, decompression level,
The reduced pressure amount of each reduced pressure is described.

The decompression levels DL, DM, DS, DVS are
It is set from the reduced pressure conversion DV calculated by the following equation.

DV = Slip amount Sm + kc × Absolute value of wheel deceleration Note that in the above equation, the slip amount Sm is equal to (vehicle body speed Vr
-Wheel speed Vw) and kc are predetermined constants.

When k3≤DV, the reduced pressure level = L
D, (large decompression level) When k2 ≦ DV <k3, decompression level = DM, (during decompression level) When k1 ≦ DV <k2, decompression level = DS, (small decompression level) When DV <k1, decompression Level = DVS, (small decompression level) For example, k3 = 0.25Vr, k2 = 0.10V
r, k1 = 0.05 Vr.

In this way, the pressure reduction conversion DV is calculated from the slip amount Sm and the wheel speed deceleration, and this pressure reduction conversion DV is calculated.
And the vehicle speed Vr from the decompression level DL, DM, DS, D
The VS is determined, the decompression amount is determined from the decompression level based on the map of FIG. 14, and the decompression is executed by outputting the braking control signal for opening the relief valve 20b for the decompression amount time at each decompression.

In the flowchart of FIG. 11, first, the pressure reduction conversion DV and the pressure reduction level are calculated in S80, then it is determined in S81 whether the continuation flag Fcn1 is 0, the flag Fcn1 is 0, and the first In the phase III of the cycle, the flow shifts to S82, the determination of the flag F is executed in S82 to S84, and when the flag F is 0 for the first time, the flow shifts to S86, and the control signal for the first pressure reduction is output.

This initial decompression is a decompression of a predetermined amount (for example, decompression time 8 ms, decompression time 16 ms when road surface μ is high) regardless of the decompression level, and a control signal for opening the relief valve 20b for 8 ms or 16 ms is used. Then, the flag F is set to 1 in S87, and the process returns.

When the flag F is 1, the process proceeds from S82 to S88, the depressurization amount of the second depressurization is calculated based on the depressurization level and the map of FIG. 14, and then in S89, the timer started in S52. Time T of T is 8
It is determined whether or not ms is reached, and when T = 8 ms is reached, S9
At 0, a control signal for opening the relief valve 20b for the time corresponding to the pressure reduction amount is output, and then at S91, the flag F is opened.
Set to 2 and return. That is, the second decompression is
It is executed subsequent to the first depressurization of a predetermined amount.

When the road surface μ is high, the depressurization amount of the second depressurization is +3 ms as described in [Note] in FIG.
Only the increase is corrected.

Next, when the flag F = 2, the flow shifts from S83 to S92 to judge whether the time T of the timer T is 40 ms, and repeats returning for T <40 ms until T = 40 ms. Then, in S93, the pressure reduction amount of the third pressure reduction is calculated based on the pressure reduction level and the map of FIG. 14, and then in S94, a control signal for opening the relief valve 20b for the time of the pressure reduction amount is output, and then S95
Then, the flag F is set to 3, and the process returns. In other words, the third depressurization is 40m after the start of timer T
It is executed from the time when s has elapsed. Note that [Note] in FIG.
As described in (1), when the road surface μ is low, the decompression amount of the decompression for the third time and thereafter is increased and corrected by +2 ms.

Next, when the flag F = 3, the flow shifts from S84 to S96 to determine whether the time T of the timer T is 80 ms, and repeats returning for T <80 ms until T = 80 ms. , S97, the decompression amount of the fourth decompression is calculated based on the decompression level and the map of FIG. 14, then the control signal for opening the relief valve 20b for the time of the decompression amount is output in S98, and the flag is output in S99. Set F to 4 and return. That is,
The fourth depressurization is executed when 80 ms has elapsed after the start of the timer T start.

Next, when the flag F = 4, the process proceeds from S85 to S100 and the time measured by the timer T is 120 ms.
If T = 120 ms, the pressure reduction amount for the fifth deceleration is calculated based on the pressure reduction level and the map of FIG. 14, and then S102. At, the control signal for opening the relief valve 20b for the time corresponding to the pressure reduction amount is output, and then at S103, the flag F is reset to 0 and the process returns. That is, the fifth depressurization is executed when 120 ms have elapsed after the start of the timer T start.

As a result of the determination in S81, the continuation flag Fcn1
Is 1, that is, Phase III after the second cycle
If so, the process proceeds to S104 of FIG.

In S104 to S106, the flag F is determined, and when the flag F is initially 0, the process proceeds to S107 and the depressurization amount of the initial depressurization is calculated. However, after the second cycle, as shown in FIG. 14, the decompression amount of the first decompression is also calculated based on the decompression level and the map of FIG. Next, in S108, a control signal for opening the relief valve 20b for the time corresponding to the pressure reduction amount is output,
Next, in step S109, the flag F is set to 1, and the process returns. When the road surface μ is high, the decompression amount of the initial decompression is increased and corrected by +3 ms.

Next, when the flag F is 1, the process proceeds from S104 to S110, and the time T counted by the timer T is 40 ms.
If T = 40 ms, the pressure reduction amount of the second pressure reduction is calculated based on the pressure reduction level and the map of FIG. 14, and then S112. At, a control signal for opening the relief valve 20b is output for the time corresponding to the pressure reduction amount, and then the flag F is set to 2 in S113, and then the process returns. In other words, the second depressurization is executed when 40 ms has elapsed after the start of the timer T start. When the road surface μ is low, the decompression amount for the second and subsequent decompressions is increased and corrected by +2 ms.

Next, when the flag F = 2, S105
To S114, the time T of the timer T is 80 m
It is determined whether or not s, and the process is repeatedly returned for T <80 ms. When T = 80 ms, 3 is obtained in S115.
The depressurization amount of the second depressurization is calculated based on the depressurization level and the map of FIG. 14, then a control signal for opening the relief valve 20b for the time of the depressurization amount is output in S116, and then the flag F is set to 3 in S117. Return after setting. That is, the third depressurization is executed when 80 ms has elapsed after the start of the timer T start.

Next, when the flag F = 3, S106
To S118, the measured time T of the timer T is 120
It is determined whether or not it is ms and returns for T <120 ms. When T = 120 ms, the pressure reduction amount of the fourth pressure reduction is calculated in S119 based on the pressure reduction level and the map of FIG. In S120, a control signal for opening the relief valve 20b for the time corresponding to the pressure reduction amount is output, and then in S121, the flag F is reset to 0 and the process returns. That is, the fourth depressurization is executed when 120 ms has elapsed after the start of the timer T.

Here, as a measure against the case where the road surface μ suddenly changes from high μ to low μ, the subroutine of FIG. 13 is executed in parallel with the subroutines of FIG. 11 and FIG.

By the determination in S130, the timer T repeats returning before the time T counted by 40 ms has elapsed. Then, in S131, it is determined whether 40 ms ≦ T <80 ms. If the determination is Yes, The process proceeds to S132.

In S132, it is determined whether or not the pressure reduction level is DL. When the pressure reduction level is DL and the degree of pressure reduction is high, a control signal for continuously opening the relief valve 20b for continuous pressure reduction is output in S133. And then return. If the pressure reduction level is lowered by the continuous pressure reduction and the determination in S132 is NO, a control signal for stopping the continuous pressure reduction is output in S134, and then the process returns.

Next, when T ≧ 80 ms, the process proceeds from S131 to S135, in S135, it is determined whether the pressure reduction level is DL, and when the pressure reduction level is DL and the demand for pressure reduction is large, in S136, continuously. A control signal for continuously opening the relief valve 20b to reduce the pressure is output, and then the process returns. When the pressure reduction level is lowered by the continuous pressure reduction and the determination in S135 is NO, S1 is set.
Move to 37.

In S137, it is determined whether or not the pressure reduction level is DM, and when the pressure reduction level is DM and the degree of pressure reduction is still high, a control signal for continuously opening the relief valve 20b to continuously reduce the pressure is sent in S138. It is output and then returns. When the pressure reduction level is lowered by the continuous pressure reduction and the determination in S137 is NO, a control signal for stopping the continuous pressure reduction is output in S139, and then the process returns.

Next, regarding the operation of the ABS control described above, the ABS control for the first channel will be taken as an example.
This will be described with reference to the time chart of FIG.

In this embodiment, as described above, AB
The 0-2 deceleration threshold value B ₀₂ for determining the transition from the phase 0 indicating the S non-control state to the phase II indicating the holding state after pressure increase, that is, the first threshold value is set to -3G, As shown in the table of FIG. 7, the 2-3 intermediate non-slip ratio threshold value Bsg for determining the transition from the phase II to the phase III indicating the reduced pressure state is 8 depending on the running state parameter.
It is set in the range of 5 to 95%.

In the ABS non-controlled state during deceleration, the braking pressure generated by the depression operation of the brake pedal 16 gradually increases, and the rate of change of the wheel speed Vw1 of the left front wheel 1 (deceleration DVw1) is -3G (first Threshold value), the lock flag Flok1 of the first channel is set to 1, and the ABS control is started from the time ta.

In the first cycle immediately after the start of the control, the frictional state value Mu is set to a value corresponding to the road surface frictional state, and various control threshold values are set according to the running state parameter.

Next, the non-slip ratio S1, the wheel deceleration DVw1, and the wheel acceleration AVw1 obtained from the wheel speed Vw1 are compared with various control threshold values, the phase 0 is changed to the phase II, and the braking pressure is increased. It will be maintained at the level immediately after.

When the non-slip ratio S1 falls below the 2-3 intermediate slip ratio threshold value Bsg (second threshold value), the phase II shifts to III, and the relief valve 20b is turned ON with the pressure reducing characteristic as described above. It is turned off and the time tb
Thus, the braking pressure decreases at a predetermined gradient, the braking force gradually decreases, and the rotational force of the front wheels 1 begins to recover. Further, the braking pressure continues to be reduced, and the wheel deceleration DVw1 becomes equal to the threshold value B ₃₅ (0
When it falls to G), the phase shifts from phase III to V, and from that time tc the braking pressure is maintained at the level after the pressure reduction.

In this phase V, the non-slip rate S1
Becomes 5-1 non-slip rate threshold value Bsz or more, the continuation flag Fcn1 is set to 1, and the ABS control shifts from the time td to the second cycle. At this time, the phase is forcibly shifted to the phase I, and immediately after the shift to the phase I, the opening / closing valve 20a, as described above, has the rapid pressure increase time T set with the pressure increase time Ti of the previous cycle as a parameter.
During pk, the relief valve 20b is closed and the on-off valve 20a is 1
The opening and closing valve 20 is opened at a duty ratio of 00% to increase the braking pressure steeply, and after the rapid pressure increase time Tpz has elapsed.
a is turned on / off at a predetermined duty ratio, and the braking pressure gradually increases with a gentler gradient. Thus, immediately after the shift to the second cycle, the braking pressure is reliably increased, and a good braking pressure is secured.

On the other hand, even after the second cycle, the appropriate friction state value Mu is determined, and the friction state value Mu is determined.
Since various control threshold values corresponding to the traveling state parameters corresponding to the vehicle speed Vr and the vehicle body speed Vr are selected from the control threshold value setting table in FIG. 7, precise control of the braking pressure according to the traveling state is performed.

After that, phase V in the second cycle
In, for example, when it is determined that the slip ratio S1 is larger than the threshold value Bsz, the phase I of the third cycle is performed.

In the ABS control of this embodiment, FIG.
, The continuation flag Fcn1 is 0, that is, the first flag
In the depressurizing phase of the cycle, in S86, the depressurizing amount of the initial depressurizing is set to a predetermined amount (the opening time of the relief valve 20b is 8 m).
s, but 16 ms when high μ) is set and the pressure reduction is executed. Therefore, the minimum required amount is not affected by the unstable slip ratio and wheel speed deceleration at the start of ABS control. The first decompression of can be executed.

Next, with reference to the flow charts shown in FIGS. 17 and 18, the decompression amount reduction processing which is a characteristic part of the present invention will be described. In the figure, flag F _D = 1
Indicates that the wheel deceleration has exceeded the 0-2 deceleration threshold value B ₀₂ (first threshold value = -3G) and has shifted to phase II (holding brake hydraulic pressure), and flag F _D = 2 Indicates that the phase II state (holding state) is for a predetermined time (for example, 30 m
s) indicates a continuous state, the flag F _D = 3 indicates a normal depressurized state (phase III) when the holding time is shorter than a predetermined time (30 ms), and the flag F _D = 4 indicates a predetermined holding time. The reduced decompression state (Phase III) when the time is longer than (30 ms), the flag F _D = 0,
Indicates that none of the above conditions exist.

First, in S140 to S143 of FIG. 17, it is determined which state the flag F _D indicates.
Initially, since F _D = 0, the determination results of S140 to S143 are all NO, and the process proceeds to S144. S144
Then, it is determined whether or not the wheel deceleration exceeds the 0-2 deceleration threshold value B ₀₂ (first threshold value = -3G). While this determination result is NO, the routine returns, but the determination result is When YES, the brake oil pressure is maintained in S145, and S14
At 6, the flag F _D is set to 1 and the process returns.

When the flag F _D is set to 1, the determination result of S142 becomes YES in the next control cycle.
In S147, it is determined whether or not the ABS control is completed. If the ABS control is not completed (S147: N
O), the process proceeds to S148 and the holding state is maintained for a predetermined time (30 m
s) Determine whether or not it has continued. Then, if the determination result is NO, in S149, the non-slip ratio of the wheels is
Whether it is lower than the 2-3 intermediate non-slip ratio Bsg (second threshold value) for determining the transition from phase II to phase III, that is, the wheel slip ratio {= (1-non-slip ratio) × 100%} exceeds the second threshold value, and returns while the determination result of S149 is NO, but if the determination result of S149 is YES, S15
Proceed to 0, set flag F _D to 3, and return. It should be noted that when the ABS control is completed while holding (S
(147: YES), the flag F _D is reset to 0 in S151, and the process returns.

When the flag F _D is set to 3, the determination result in S140 is YES in the next control cycle,
In S152, it is determined whether or not the ABS control is completed. If the ABS control is not completed (S152: N
O), in S153, according to the table for setting the control threshold values shown in FIG. 7, the table for setting the correction values for the control threshold values shown in FIG. 8, and the pressure reduction / pressure reduction amount table shown in FIG. The brake hydraulic pressure reduction control is executed and the process returns (normal control). When it is determined in S152 that the ABS control is completed (S152: YE
S) and S154 reset the flag F _D to 0 and return.

On the other hand, when it is determined in S148 that the holding state has continued for the predetermined time (30 ms) (S14
8: YES), the flag F _D is reset to 2 in S155, and the process returns. Then, when the flag F _D is set to 2, the determination result of S143 is YES in the next control cycle.
Therefore, the process proceeds to S156 in FIG. 18 and it is determined whether the ABS control is finished. If the ABS control is not finished (S156: NO), the program proceeds to S157 and the wheel non-slip ratio is 2 -3 Whether it is lower than the intermediate non-slip rate Bsg (second threshold value), that is, whether the wheel slip rate {= (1-non-slip rate) × 100%} exceeds the second threshold value. It is determined whether or not the determination result of S157 is N.
While O is returned, the determination result of S157 is Y.
When it becomes ES, the process proceeds to S158, sets the flag F _D to 4 and returns. When the ABS control is completed during holding (S156: YES), the flag F _D is reset to 0 in S159 and the process returns.

When the flag F _D is set to 4, the determination result of S141 becomes YES in the next control cycle.
It progresses to S160 of FIG. 18 and it is judged whether ABS control is complete | finished, and if ABS control is not complete (S16).
0: NO), and in S161, a process of reducing the pressure reduction amount than usual is executed. The pressure reduction amount reduction processing when the flag F _D is set to 4 is performed by reducing the pressure reduction time of the first cycle in the pressure reduction / pressure reduction amount table shown in the table of FIG. 14, that is, the relief valve in the first cycle. This is achieved by reducing the opening time of 21b (corresponding to the pulse width of the signal applied to the relief valve 21b) as shown in the table of FIG. In FIG. 19, the decompression time of the first decompression in the first cycle is 1 ms with respect to the decompression time of the first decompression in FIG.
Each of the values of the second to fifth decompression times is subtracted from the values of the second to fifth decompression times of FIG. 14 by 4 ms.

As described above, in S161, the table for setting the control threshold values shown in FIG. 7, the table for setting the correction values for the control threshold values shown in FIG. 8, and the decompression / decompression amount shown in FIG. The brake pressure reduction control according to the table is executed, and it is determined in the next S162 whether or not the first cycle has been completed, and the routine returns while the determination result in S162 is NO. Then, if it is determined that the first cycle has ended (S162: YES), the flag F _D is set to 3. Therefore, after the second cycle, the values in the table of FIG. 14 are used as they are. When it is determined in S160 that the ABS control is completed (S1
(60: YES), the flag F _D is reset to 0 in S164, and the process returns.

As described above, in this embodiment, when it is determined that the holding state of the brake oil pressure has continued for the predetermined time (30 ms), the pressure reduction amount is reduced by reducing the pressure reduction time of the first cycle. On the high μ road, the braking force is secured when the brake pedal is stepped near the lock limit and the pressure is gradually increased, and the braking distance can be shortened. It should be noted that the high μ road may be determined when the brake oil pressure is maintained for a predetermined time (30 ms).

Next, a pressure reduction amount reducing process in another embodiment of the present invention will be described with reference to the flow chart shown in FIG. In the present embodiment, when the holding state of the brake hydraulic pressure continues for a predetermined time (30 ms), the value of the 2-3 intermediate non-slip ratio Bsg (second threshold value) for determining the transition from phase II to phase III is set. By reducing
That is, when viewed as the slip ratio threshold value, by increasing the value, it is difficult to start depressurization and the depressurization amount is reduced.

First, in S170, the flag F _D is set to 1
Is set to. At first, F _D =
Since it is 0, the determination result of S170 is NO, and S1
Proceed to 71. In S171, it is determined whether or not the wheel deceleration exceeds the 0-2 deceleration threshold value (first threshold value = -3G). While this determination result is NO, the routine returns, but the determination result is YES. When it becomes, the brake hydraulic pressure is maintained in S172, the flag F _D is set to 1 in S173, and the process returns.

When the flag F _D is set to 1, the determination result of S170 becomes YES in the next control cycle.
In step S174, it is determined whether the ABS control is completed. If the ABS control is not completed (S174: N
O), the process proceeds to S175 and the holding state is maintained for a predetermined time (30 m
s) Determine whether or not it has continued. If the determination result is NO, the non-slip ratio of the wheel is 2 in S176.
-3 Whether or not it is lower than the intermediate non-slip ratio Bsg (second threshold value), that is, the wheel slip ratio {= (1-
It is determined whether or not (non-slip ratio) × 100%} exceeds the second threshold value, and the routine returns while the determination result of S176 is NO, but if the determination result of S176 is YES,
Progressing to S177, the table in which each control threshold value shown in FIG. 7 is set, the table in which each control threshold value correction value shown in FIG. 8 is set, and the pressure reduction according to the pressure reduction / pressure reduction amount table shown in FIG. Start control.

On the other hand, when the holding state continues for the predetermined time (30 ms) (S175: YES), the process proceeds to S178, and the 2-
The third intermediate non-slip rate threshold value Bsg (second threshold value) is changed as shown in FIG. That is, in FIG. 21, the 2-
Each value of the third intermediate non-slip rate threshold value Bsg is subtracted by 2% from each value of the 2-3 intermediate non-slip rate threshold value Bsg in FIG. Therefore, when viewed as the slip ratio threshold value, 2% is added by 2 and the second threshold value is changed so that the pressure reduction is difficult to start.
Then, in S176, it is determined whether or not the non-slip rate of the wheels is lower than the 2-3 intermediate non-slip rate Bsg (second threshold value), that is, the slip rate of the wheels exceeds the second threshold value. If the determination result of S176 is NO, the process returns. However, if the determination result of S176 is YES, the process proceeds to S177, a table in which each control threshold value shown in FIG. The pressure reduction control is started according to the table in which the correction values of the respective control threshold values shown in FIG. Note that S17
When it is determined in 4 that the ABS control is completed (S174: YES), the flag F _D is reset to 0 in S179 and the process returns.

As described above, also by changing the value of the 2-3 intermediate non-slip ratio threshold value Bsg so that the pressure reduction is less likely to be started, the same effect as that of the above-described embodiment can be obtained.

In the above embodiment, the first threshold value is set for the deceleration of the wheel speed, and the second threshold value is set for the non-slip ratio of the wheel. The threshold value may be set for the deceleration of the wheel speed, similarly to the first threshold value. In that case, the first set to -3G
With respect to the threshold value, a standard second threshold value is normally set to, for example, -4G, and in S178 of FIG.
The second threshold may be changed to -5G, for example.

Further, the second threshold value may be set with respect to the wheel slip rate {= (1-non-slip rate) × 100%}, and both the first and second threshold values are set. It may be set for the slip amount of the wheel (= pseudo vehicle body speed-wheel speed). In that case, the first threshold is, for example, 5
The ordinary standard second threshold value may be set to, for example, 7 km / h, and the second threshold value may be changed to, for example, 9 km / h in S178 of FIG.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an anti-skid brake device for a vehicle according to an embodiment.

[Fig.2] Diagram of μ table

FIG. 3 is a flowchart of a pseudo vehicle speed calculation process.

FIG. 4 is a diagram of a map of vehicle body speed correction values.

FIG. 5 is a flowchart of control threshold setting processing.

FIG. 6 is a diagram of a table in which driving state parameters are set.

FIG. 7 is a diagram of a table in which various control thresholds are set.

FIG. 8 is a diagram of a table in which correction values of various control threshold values are set.

FIG. 9 is a part of a flowchart of control signal output processing

FIG. 10: Remaining part of flowchart of control signal output processing

11 is a part of a flowchart of a control signal output subroutine of S53 of FIG.

12 is the rest of the flowchart of the control signal output subroutine of S53 of FIG.

13 is a flowchart of a control signal output subroutine executed in parallel with FIG. 11 and FIG.

[Fig. 14] Diagram of decompression level / decompression amount table

FIG. 15 is an operation time chart of the anti-skid brake device.

16 is an operation time chart of Phase III in the first cycle of FIG.

FIG. 17 is a part of a flowchart showing a pressure reduction amount reduction process.

FIG. 18 is the rest of the flowchart showing the pressure reduction amount reduction processing.

FIG. 19 is a diagram of a decompression level / decompression amount table used in place of the table of FIG. 14 in the decompression amount reduction processing.

FIG. 20 is a flowchart showing a second threshold value changing process according to another embodiment.

FIG. 21 is a diagram of a table in which various control threshold values are set, which are used instead of the table of FIG.

[Explanation of symbols]

 1, 2 front wheels 3, 4 rear wheels 11-14 brake device 15 brake control system 27-30 wheel speed sensor 20, 21, 23 1st-3rd valve unit 20a, 21a, 23a open / close valve 20b, 21b, 23b relief valve 24 control unit

Claims (4)

[Claims] 1. A wheel speed detecting means for detecting a rotation speed of a wheel, a braking pressure adjusting means for adjusting a braking pressure of the wheel, and the braking pressure adjusting means based on the wheel speed detected by the wheel speed detecting means. In a vehicle anti-skid brake device having an anti-skid control means for activating the brake pedal to periodically increase or decrease the braking pressure, a calculated value calculated based on the wheel speed detected by the wheel speed detecting means is a predetermined value. When the first threshold value is exceeded, the braking pressure is maintained by the braking pressure adjusting means, and the calculated value exceeds the predetermined second threshold value that is set on the slip increase side with respect to the first threshold value. When the holding time of the braking pressure is long, the amount of pressure reduction is reduced compared to when the holding time of the braking pressure is long. Antiskid brake apparatus for a vehicle, wherein a provided. 2. The anti-skid brake device for a vehicle according to claim 1, wherein the calculated value is a wheel deceleration and / or a wheel slip amount. 3. The anti-skid brake device for a vehicle according to claim 1, wherein the reduction of the pressure reduction amount is performed by increasing the second threshold value. 4. The antiskid brake device for a vehicle according to claim 1, wherein when the holding time of the braking pressure is longer than a predetermined time, it is determined that the friction coefficient μ of the road surface is high μ. .