JPH0858552A - Anti-skid brake device for vehicle - Google Patents

Abstract

PURPOSE: To prevent respective wheels from being apt to be locked by limiting pressure intensification of the other control channels, when a specified control channel is during pressure reducing among a plurality of control channels variably controlling brake pressure of respective wheels so as to perform anti-skid control. CONSTITUTION: A control unit 24 gives braking force to right and left front wheels 2, 1 and rear wheels 4, 3 at the brake oil pressure in response to the lock state, by respectively controlling the respective opening/closing valves 20a-23a and the respective relief valves 20b-23b of a plurality of valve units 20, 21, 23 based on the respective detected signals from a plurality of wheel speed sensors 27-30. Then a plurality of control channels for variably controlling the brake pressure of the respective wheels 1-4 so as to perform anti-skid control are set. In this case, when a specified control channel is during pressure reducing, the other control channels are limited for pressure intensification.

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 device for preventing wheel skids by properly braking wheels during vehicle braking.

[0002]

2. Description of the Related Art Conventionally, there is known an anti-skid brake device for preventing the wheels from being locked due to an excessive braking pressure when the vehicle is being braked and losing the braking performance and steering performance.

This type of anti-skid brake system is
An electromagnetic control valve installed in the brake hydraulic system to adjust the braking pressure, a wheel speed sensor that detects the rotational speed of the wheel, and the wheel speed detected by these sensors detects that the wheel is going to lock. In this case, the electromagnetic control valve is pressure-reduced to reduce the braking pressure, and when the rotational speed of the released wheel increases due to the reduction of the braking pressure, the electromagnetic control valve is pressure-increase controlled to reduce the braking pressure. A control unit that periodically increases or decreases the braking pressure by increasing the pressure is provided. Then, the control unit sets, for example, the fastest wheel speed of the wheel speeds of the four wheels detected by the wheel speed sensor as the pseudo vehicle body speed, and calculates the slip ratio from the pseudo vehicle body speed and the wheel speed. Then, when the slip ratio reaches the target slip ratio (pressure reduction threshold value), the pressure reduction of the braking pressure is started.

By continuing such a series of braking pressure control (hereinafter referred to as ABS control as necessary) until just before the vehicle stops, for example, the wheels are locked or skid during sudden braking. It is possible to prevent the vehicle from stopping and to stop the vehicle with a short braking distance while ensuring the directional stability of the vehicle.

The ABS control device as described above generally has a first control channel for controllably applying a brake hydraulic pressure to the left front wheel, a second control channel for controllably applying a brake hydraulic pressure to the right front wheel, and a left and right control channel. A third control channel for controllably applying the brake hydraulic pressure to the rear wheels is provided, and the control unit independently controls the brake hydraulic pressures of the control channels during braking.

As the braking pressure control, the control phase (pressure increasing phase, pressure reducing phase, holding phase) is determined based on the change in wheel speed for each control channel, and the brake hydraulic pressure is increased in accordance with each determined phase. Pressure, decompression,
Retention takes place. More specifically, for example, when it is determined that the slip ratio of the wheels is large and there is a tendency to lock, it is determined to be the decompression phase and the brake hydraulic pressure is decompressed. If the hydraulic pressure is maintained, and if the slip ratio falls to a predetermined value in this maintained state, it is determined to be the pressure increase phase and the brake hydraulic pressure is increased. Thereafter, the cycle of pressure reduction, holding and pressure increase is repeated to set the slip ratio to the target slip ratio. The control is performed to converge to.

By the way, in the ABS control as described above, there may occur a case where all the control channels are synchronously increased or decreased in pressure in the same manner. In such a case, the deceleration of the vehicle changes greatly, which causes the vehicle body to vibrate back and forth, which gives an occupant a discomfort. Also, if all control channels are depressurized simultaneously,
The braking force of each wheel is reduced at the same time, the deceleration of the vehicle suddenly decreases, and the driver feels uncomfortable due to a sudden change in deceleration.

Therefore, for example, Japanese Patent Laid-Open No. 4-110263.
In the vehicle anti-skid brake device disclosed in the publication, the braking force of each control channel is controlled so that the pressure reducing phases do not match in all control channels, thereby solving the above problem.

[0009]

However, in the case where three control channels are provided as described above, if control is performed so that the pressure reduction phases do not match in all control channels, two control channels are in the pressure reduction phase. However, no pressure reduction is performed in the remaining one control channel, which causes a problem that the wheels of the control channel are easily locked.

Further, particularly on a high μ road having a high friction coefficient μ on the road surface, a relatively large braking force is applied during braking,
A large load (front load) is applied to the front wheels. Therefore, when pressure is reduced in the control channel of the rear wheels in this state, the front load is released and the grip force of the front wheels on the road surface is reduced. Therefore, there is a problem that when the pressure increase is started in the control channel of the front wheels, the front wheels tend to be locked.

Further, when the left and right front wheels are braked and a load is applied to the left and right front wheels, if the pressure is reduced by the control channel of one of the front wheels, for example, the left front wheel, the other front wheel,
That is, the load on the right front wheel is released, and it becomes easier to lock. Therefore, the pressure reduction is also started in the control channel of the right front wheel,
There was also a problem that the braking force became insufficient due to the repetition of this.

An object of the present invention is to provide an antiskid brake device for a vehicle which can effectively solve the above-mentioned problems.

[0013]

According to a first aspect of the present invention, a plurality of control channels for variably controlling wheel braking pressure to perform antiskid control are provided, and each control channel has a wheel rotation. The wheel speed detecting means for detecting the speed, the braking pressure adjusting means for adjusting the braking pressure of the wheel, and the braking pressure adjusting means are operated based on the wheel speed detected by the wheel speed detecting means to cycle the braking pressure. In a vehicle anti-skid brake device that is provided with anti-skid control means for selectively reducing and increasing pressure, when a specific control channel of the plurality of control channels is being depressurized, another control channel is increased. It is characterized in that a pressure increase limiting means for limiting the pressure is provided.

According to one aspect of the invention described in claim 1, when the control channels are provided for the front wheels and the rear wheels respectively, and the pressure reduction is started in the control channel on the rear wheel side, the pressure increase limit is set. The means limits the pressure increase of the control channel on the front wheel side for a predetermined time (claim 2).

The pressure increase restriction by the pressure increase restriction means is executed on a high μ road having a high road surface friction coefficient μ. (Claim 3).

According to a fourth aspect of the present invention, a plurality of control channels are provided for variably controlling the wheel braking pressure to perform anti-skid control, and each control channel has a wheel speed for detecting a wheel rotation speed. Detecting means, braking pressure adjusting means for adjusting the braking pressure of the wheels, and the braking pressure adjusting means are operated based on the wheel speed detected by the wheel speed detecting means to periodically reduce and increase the braking pressure. In a vehicle anti-skid brake device provided with anti-skid control means, when a specific control channel of the plurality of control channels is being depressurized, depressurization limiting means for limiting depressurization of other control channels It is characterized by having.

According to one aspect of the invention described in claim 4, when the control channel is provided for each of the left and right front wheels, and the control channel on one front wheel side is being depressurized, the depressurization limiting means is provided. It is characterized in that the pressure reduction of the other front wheel side control channel is limited (claim 5).

The decompression limiting means allows the initial decompression and makes it difficult to decompress thereafter (claim 6).

[0019]

In the invention described in claims 1 and 2, when a specific control channel (rear wheel side control channel) is being depressurized, another control channel (front wheel side control channel) is By providing the pressure increase limiting means for limiting the pressure increase, when the rear wheel control channel is depressurized, the front load is released, the grip force of the front wheel on the road surface is reduced, and the front wheel becomes locked. Can be prevented.

According to the invention described in claims 4 and 5,
When a specific control channel is being depressurized, the depressurization limiting means for restricting depressurization of the other control channel is provided so that when the control channel of one front wheel is depressurized, the load of the other front wheel is released. It is possible to prevent the braking force from becoming insufficient due to the ease of locking, the start of pressure reduction, and the repetition of this. Then, in that case, as described in claim 6, by allowing the initial pressure reduction, for example, the first pressure reduction in each cycle, it is possible to prevent insufficient pressure reduction.

[0021]

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 driving 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 that includes 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 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 includes 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 brake hydraulic pressure supply line 22 for rear wheels
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 has 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-control state, a brake hydraulic pressure control signal is output from the control unit 24, and the first to third valve units 20 and 2 are output 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 judgment processing 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 calculates the rear wheel speed obtained from the signals from the wheel speed sensors 29 and 30, and the wheel speeds of the left and right front wheels 1 and 2 detected by the wheel speed sensors 27 and 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 speed) × 100% Therefore, the pseudo vehicle speed Vr (hereinafter simply referred to as the vehicle 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 in accordance with the running state of the vehicle with the wheel acceleration / deceleration and the non-slip rate. 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 determining process will be described. For example, in the lock determining 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, the wheels are easily locked. 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 of 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 equation, 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), and 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). 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 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. In this way, 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 the selection of the running condition parameter, the control unit 24 reads each control threshold value corresponding to the running condition parameter from the control threshold value setting table shown in FIG. 7 in S32.

Here, as various control threshold values, 0-2 deceleration threshold value B ₀₂ for judging transition from phase 0 (ABS non-control state) to phase II (holding state after pressure increase), That is, in addition to the ABS control start threshold value,
As shown in FIG. 1, 1-2 intermediate deceleration threshold B ₁₂ for determining the transition from phase I to phase II, 2-3 intermediate non-slip ratio threshold Bsg for determining the transition from phase II to phase III. , 3-5 intermediate deceleration threshold value B ₃₅ for judging transition from phase III to phase V, 5-1 non-slip ratio threshold value Bsz for judging transition from phase V to phase I, etc. It is set for each parameter.

In this case, the deceleration threshold value which has a great influence on the control force is such that the braking performance when the road surface μ is large and the control responsiveness when the road surface μ is small are compatible with each other at a high level. 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 of 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 secure 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 in S41, it is determined 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
The deceleration DVw1 of 1 (provided that DVw1 ≦ 0) is a predetermined value Do, that is, the 0-2 deceleration threshold value B described above.
₀₂ (for example, -3G) or less is determined, and the determination is Y
If ES, the process proceeds to S46. On the other hand, when the determination in S44 is NO, the process proceeds to S49.

Next, when 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 or not the flag P1 is 2. If the flag P1 is 2, the process proceeds to S50 and the flag is set. 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.

When the flag P1 is not 2 as a result of the determination in S49, 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, the braking control signal preset for phase V is output to the first valve unit 20, and then the process returns.

Next, when the determination in S54 is NO, the process shown in FIG.
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.

Since it is determined to be NO at the beginning, 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, at S62, the rapid pressure increase time Tpz of the initial rapid pressure increase executed at the beginning of the phase I (phase of pressure increase) 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 the shift 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 (vehicle body speed Vr
-Wheel speed Vw) and kc are predetermined constants.

When k3≤DV, the pressure reduction 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 flag 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 to output the control signal for the first pressure reduction.

This initial pressure reduction is a pressure reduction of a predetermined amount (for example, pressure reduction time 8 ms, pressure reduction time 16 ms when the road surface μ is high) regardless of the pressure reduction 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 determine 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 judge 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 pressure reduction amount of the initial pressure reduction 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 FIGS. 11 and 12.

By the determination at S130, the timer T repeats returning before the time T counted by 40 ms has elapsed, and then at 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 routine proceeds from S131 to S135, where it is determined whether the pressure reduction level is DL or not, and if the pressure reduction level is DL and the demand for pressure reduction is large, then 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 for continuous pressure reduction is given 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 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) reaches -3G. At this time, 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 traveling 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, the phase shifts from phase II to III, the relief valve 20b is turned on / off with the pressure reducing characteristic as described above, and from that time tb. 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. When the wheel pressure deceleration DVw1 continues to decrease to the threshold value B ₃₅ (0G), the phase III shifts to V and the braking pressure is maintained at the reduced pressure level from time tc. .

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.

The routine of FIG. 17 is an interrupt routine executed at a predetermined timing, and determines the contents of hydraulic control in the next rapid pressure increase phase based on the operation of the wheels in the rapid pressure increase phase.

When the ABS control is being performed, the control unit 24 determines in S140 of FIG. 17 whether or not it is in the rapid pressure increase phase. When in the rapid pressure increase phase, it is further determined in S142 whether or not the traveling road is a bad road.

Next, the control unit 24 sets S1
At 42, the acceleration or deceleration G ₁ of the wheel is detected 8 ms after the start of pressure increase. Then, in S143, the minimum wheel acceleration or deceleration G ₂ within a predetermined time (104 ms in this example) from the start of the pressure increase phase is calculated. When calculating the minimum wheel acceleration / deceleration, the control unit 24 compares the stored value with the newly detected value, and repeats the procedure of storing the smaller one. Next, the control unit 24 calculates the difference G _T between the acceleration / deceleration G ₁ and G ₂ . Then, the control content of the sudden pressure increase in the next brake hydraulic pressure control cycle is determined by the magnitude of the difference G _T. The content of this control is determined by the value of the flag RATE. The value of the flag RATE is set to 1 to 4 according to the difference G _T.

FIG. 18 shows the relationship between the value of the flag RATE and the control in the rapid pressure increase phase. In the case of the first channel, the brake hydraulic pressure is controlled by controlling the duty ratio of the valve unit 20 with respect to the on-off valve 20a. In this example, one duty cycle is set to 40 ms, so
When an ON signal of 40 ms is input to the opening / closing valve 20a, the opening / closing valve 20a is fully opened. The numerical value of ms in FIG. 18 indicates the opening time of the on-off valve 20a. The larger the numerical value, the longer the opening time, the more the hydraulic pressure supplied from the timer cylinder 18, the steeper the pressure increase gradient. FIG.
As shown in, the larger the value of the flag RATE, the longer the valve opening time, that is, the larger the duty ratio, the larger the pressure increase gradient, and the steeper the rise of the hydraulic pressure in the rapid pressure increase phase. In this embodiment, the duty ratio is also changed according to the value of the friction coefficient of the road surface, and the duty ratio is controlled to increase as the road surface becomes higher in friction. This is because, as the road surface friction coefficient increases, the wheel lock limit increases, so that the brake hydraulic pressure can be rapidly changed without causing wheel lock, and quick braking is possible.

Further, the fact that the control is performed on a high friction road surface means that the driver's brake depression is large and the base pressure of the brake pressure is high, and the difference in the brake hydraulic pressure is relatively small in any braking condition. Become. Therefore, stable braking operation is possible if the initial pressure increase state is not changed rapidly. Therefore, the flag R
The pressure increase gradient is not changed regardless of the value of ATE.

In braking in the rapid pressure increase phase, the control unit 24 determines that the difference G _T is 0.3 in S145.
It is determined whether or not it is smaller than G (G is gravitational acceleration). When the difference G _T is smaller than 0.3 G, S146
Then, 1 is added to the flag RATE. The initial flag RAT
E is set to a value of 1 to 4.

Next, the control unit 24 sets S1
At 47, it is determined whether or not the acceleration / deceleration difference G _T is larger than 0.8 G. If this determination is YES, it is considered that the brake hydraulic pressure is controlled within an appropriate range.
Therefore, the control unit 24 determines that the flag RA
Do not change the value of TE. If this determination is NO, the control unit 24 determines the flag R in S148.
Subtract 1 from the value of ATE. When the rough road determination in S141 is YES, it is difficult to obtain accurate wheel acceleration because the wheel acceleration fluctuates. Therefore, it is difficult to properly grasp the control result of the brake hydraulic pressure at that time. Therefore, in this case, the value of the flag RATE is not changed (S149).

The flag RAT corresponding to the pressure increasing gradient of the initial rapid pressure increase is similarly applied to the second and third channels.
The E value is determined.

Next, referring to the flow chart shown in FIG. 19, a pressure increase limiting routine in the front wheel side control channel when the pressure reduction is started in the rear wheel side control channel will be described.

First, in S1, it is determined whether or not the road surface is high μ, and if it is high μ (S1: YES), it is determined in the next S2 whether or not ABS control is being performed. And ABS
If the pressure is being controlled (S2: YES), it is determined in S3 whether or not the pressure reduction has been started in the rear wheel control channel. If the pressure reduction has not been started (S3: NO), the process proceeds to S6. A table in which each control threshold value shown in FIG. 7 is set, a table in which each control threshold value correction value shown in FIG. 8 is set,
Normal ABS control is executed according to the pressure reduction / pressure reduction amount table shown in FIG. 14 and the sudden pressure increase amount table shown in FIG.

On the other hand, if the pressure reduction is started in the rear wheel side control channel (S3: YES), the pressure increase in the front wheel side control channel is limited in S4. The limitation of the pressure increase is, for example, the rapid pressure increase time in the rapid pressure increase amount table shown in FIG. 18, that is, the opening time of the open / close valve 21a (open / close valve 21
20), which corresponds to the pulse width of the signal applied to a), as shown in FIG. That is, in FIG. 20, the rapid pressure increase time is subtracted by 2 ms from each value of the rapid pressure increase time in FIG. Next, in S5, it is determined whether or not a predetermined time has elapsed, and until the predetermined time has elapsed (S5: NO), the process returns to S4 and the pressure increase restriction is continued. Then, when the predetermined time has elapsed (S5: YES), the process returns to the normal ABS control of S6.

When pressure is reduced in the rear wheel control channel due to the restriction of pressure increase in the front wheel control channel, the front load is released, the grip force of the front wheel on the road surface is reduced, and the front wheel tends to lock. Can be prevented.

Next, with reference to the flow chart shown in FIG. 21, a depressurization limiting routine in the other front wheel control channel when the pressure is being depressurized in one front wheel control channel will be described.

First, in S11, it is checked whether or not the ABS control is in progress. If the ABS control is in progress (S11: YES), S1
At 2, it is determined whether or not the control channel of one front wheel (for example, the left front wheel) is being depressurized, and if it is being depressurized (S1S1
22: YES), and in the next S13, it is determined whether or not the control channel of the other front wheel (for example, the right front wheel) has started depressurization. Then, when the determination result of at least one of S12 and S13 is NO, the process proceeds to S16, and a table in which each control threshold value shown in FIG. 7 is set, and a correction value of each control threshold value shown in FIG. 8 is set. Normal ABS control is executed according to the above table, the pressure reduction / pressure reduction amount table shown in FIG. 14, and the sudden pressure increase amount table shown in FIG.

On the other hand, if the pressure reduction is started in the other front wheel control channel (S13: YES), the pressure reduction in the other front wheel control channel is limited in S14. This restriction of the pressure reduction is performed by the pressure reduction time in the pressure reduction / pressure reduction amount table shown in FIG. 14, that is, the opening time of the relief valve 21b (corresponding to the pulse width of the signal applied to the relief valve 21b), for example, as shown in FIG. In a variety of ways. That is, in FIG. 22, the first and fifth depressurizations of the first cycle are permitted with the same depressurization time as in FIG.
All the values of the fourth depressurization time are set to zero, and the brake hydraulic pressure during that time is maintained. Further, even after the second cycle, the first and fourth depressurizations are allowed with the same depressurization time as in FIG. 14, but the respective values of the second and third depressurization times are all set to zero, and during that time. Brake oil pressure is maintained.

Next, in S15, it is judged whether or not the pressure reducing phase in the control channel for one of the front wheels has ended, and until the pressure reducing phase ends (S15: NO), S1
Returning to step 4, the restriction of pressure reduction in the control channel of the other front wheel is continued. Then, when a predetermined time elapses (S
5: YES), and returns to the normal ABS control of S6. Then, when the pressure reducing phase of the control channel for one of the front wheels ends (S15: YES), the process returns to the normal ABS control of S16.

Due to the restriction of the pressure reduction in the control channel of the other front wheel as described above, when the pressure reduction is performed in the control channel of the one front wheel, the load of the other front wheel is released, the lock easily occurs, and the pressure reduction is started. It is possible to prevent the braking force from being insufficiently repeated.

[Brief description of drawings]

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

[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 flowchart showing an initial rapid pressure increase gradient setting routine.

FIG. 18 is a diagram of a table in which opening / closing valve opening times are set in the routine of FIG.

FIG. 19 is a flowchart of a pressure increase limiting routine in a front wheel control channel.

FIG. 20 is a diagram of a table used in place of the table of FIG. 18 when increasing pressure is restricted.

FIG. 21 is a flowchart of a pressure reduction limiting routine in the other front wheel control channel.

22 is a diagram of a decompression level / decompression amount table used in place of the table of FIG. 14 when decompression is restricted.

[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 (6)

[Claims] 1. A plurality of control channels for variably controlling a wheel braking pressure to perform anti-skid control, each wheel being provided with a wheel speed detecting means for detecting a wheel rotation speed and a wheel braking pressure. A braking pressure adjusting means and an anti-skid control means for periodically reducing and increasing the braking pressure by operating the braking pressure adjusting means based on the wheel speed detected by the wheel speed detecting means. In a vehicle anti-skid brake device that is provided, when a specific control channel of the plurality of control channels is being depressurized, it is provided with a pressure increase limiting means for limiting the pressure increase of another control channel. A featured vehicle anti-skid brake system. 2. The control channel is provided for each of the front wheels and the rear wheels, and when pressure reduction is started in the control channel on the rear wheel side, the pressure increase limiting means limits the pressure increase of the control channel on the front wheel side for a predetermined time. The antiskid brake device for a vehicle according to claim 1, wherein: 3. The antiskid brake device for a vehicle according to claim 1, wherein the pressure increase restriction by the pressure increase restriction means is executed on a high μ road having a high road friction coefficient μ. 4. A plurality of control channels for variably controlling wheel braking pressure to perform anti-skid control are provided, and wheel speed detecting means for detecting wheel rotation speed and wheel braking pressure are provided in each control channel. And a anti-skid control means for periodically reducing and increasing the braking pressure by operating the braking pressure adjusting means based on the wheel speed detected by the wheel speed detecting means. In a vehicle anti-skid brake device that is provided, when a specific control channel among the plurality of control channels is being depressurized, it is provided with depressurization limiting means for limiting depressurization of other control channels. Anti-skid brake system for vehicles 5. The control channel is provided for each of the left and right front wheels, and when the control channel on one front wheel side is being depressurized, the depressurization limiting means limits the depressurization on the control channel on the other front wheel side. The anti-skid brake device for a vehicle according to claim 4, which is characterized in that. 6. The anti-skid brake device for a vehicle according to claim 4, wherein the depressurization limiting means allows the initial depressurization and makes subsequent depressurization difficult.