JPH04197864A - Antiskid brake device for vehicle - Google Patents

Abstract

PURPOSE:To prevent cascade lock from being produced securely by prohibiting pressure increasing control of braking pressure in a pressure increasing phase following a pressure decreasing phase or holding phase after reducing pressure when a coefficient of friction on a ground during ABS control is small. CONSTITUTION:A brake control system 15 makes braking control, i. e., ABS control for slippage of wheels 1 to 4 by outputting braking pressure control signals according to output signals from a brake switch 25 and wheel speed sensors 26 to 29 for respective wheels to valve units 20, 21, and 23 by a control unit 24. The ABS control increases and decreases brake hydraulic pressure periodically according to cycles including pressure increasing phase, pressure decreasing phase, and holding phase after reducing pressure. In this case, a coefficient of friction on a ground is estimated based on the wheel speed and, when it is small, the pressure increasing control is prohibited after phase is moved from the holding phase or pressure decreasing phase to the pressure increasing phase.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an anti-skid brake device that suppresses excessive braking force when braking a vehicle, and in particular to an anti-skid brake device that suppresses excessive braking force when braking a vehicle. The present invention relates to an anti-skid brake system for a vehicle that periodically controls the increase and decrease of the brake.

(Prior Art) A vehicle brake system is sometimes equipped with an anti-skid brake device for the purpose of preventing wheel locking or skidding during braking.

Generally, this type of anti-skid brake device is equipped with a wheel speed sensor that detects the rotational speed of the wheel, and an electromagnetic control valve that adjusts the brake oil pressure, and has a predetermined value based on the wheel speed detected by the wheel speed sensor during braking. The pseudo-vehicle speed of the vehicle is reduced according to the speed change rate (deceleration) of When the braking pressure is lowered and the rotational speed of the wheels recovers due to the reduction in the braking pressure until the wheel speed returns to a predetermined relationship with the pseudo vehicle speed, the control valve is controlled to increase the pressure. It is designed to increase braking pressure. By continuously performing a series of braking pressure controls (hereinafter referred to as ABS control), for example, until the vehicle comes to a stop, the speed of the vehicle decreases according to a predetermined gradient, causing sudden This prevents the wheels from locking or skidding during braking, making it possible to stop the vehicle in a short braking distance without losing directional stability.

By the way, in this type of ABS control, in order to ensure reliable control performance, the above-mentioned pseudo vehicle speed is reduced assuming a high friction road surface. On a road surface with a small road surface friction coefficient, there is a problem in that the influence of changes in braking pressure becomes acute and the wheels tend to lock.

For such problems, for example, Japanese Patent Application Laid-Open No. 58-194
As described in Japanese Patent No. 647, there is a system that reduces the rate at which the pseudo vehicle speed is subsequently reduced when the depressurization time reaches a set time or more.

According to this, if the pressure is depressurized for a long time (when this occurs, the pseudo vehicle speed will be reduced due to the slope corresponding to the low-friction road surface, so it is necessary to control the braking pressure appropriately according to the road surface condition. becomes possible.

(Problems to be Solved by the Invention) However, even in the conventional technology described in the above publication, the following problems may occur.

In other words, in this type of ABS control, when the wheel speed exceeds the pseudo vehicle speed, the pseudo vehicle speed is updated in accordance with the wheel speed. On road surfaces where the
The wheels may become locked before the wheel speed returns to the pseudo vehicle speed, and the pseudo vehicle speed may not be updated due to a decrease in the wheel speed caused by this.

If such a phenomenon continues to occur, the pseudo vehicle speed will decrease according to the predetermined deceleration, as shown in Figure 9, and the difference between the actual vehicle speed (actual vehicle speed) and the vehicle in question will decrease. The error increases over time, and there is a large difference (VED) between the actual vehicle speed and the pseudo vehicle speed at the end of ABS control.
) may occur.

SUMMARY OF THE INVENTION In view of the above-mentioned circumstances in an anti-skid brake system for a vehicle, it is an object of the present invention to prevent the occurrence of so-called cascade lock.

(Means for solving the problem) First, the invention of claim 1 of the present application (hereinafter referred to as the first invention)
The anti-skid brake device for a vehicle according to the above includes a wheel speed detection means for detecting the rotational speed of the wheels, a hydraulic pressure adjustment means for adjusting the brake oil pressure, and an anti-skid brake device for the vehicle based on the wheel speed detected by the wheel speed detection means. A pseudo vehicle speed calculating means for calculating a pseudo vehicle speed compares the pseudo vehicle speed calculated by the calculating means during braking with the wheel speed, and based on the comparison result, the brake oil pressure is adjusted to a pressure increasing phase, a pressure decreasing phase, and a control means for operating the hydraulic pressure adjusting means to periodically increase or decrease according to a cycle including a holding phase after pressure reduction, the road surface friction coefficient being determined based on the wheel speed detected by the wheel speed detecting means. A road surface friction coefficient estimating means for estimating, and when the road surface friction coefficient estimated by this estimating means is small, at least the control means when transitioning from a holding phase after pressure reduction to a pressure increase phase or from a pressure reduction phase to a pressure increase phase. The present invention is characterized in that a pressure increase prohibiting means for prohibiting pressure increase control is provided.

In addition, the invention of claim 2 of the present application (hereinafter referred to as the second invention)
The anti-skid brake device for a vehicle according to the above includes a wheel speed detection means for detecting the rotational speed of the wheels, a hydraulic pressure adjustment means for adjusting the brake oil pressure, and an anti-skid brake device for the vehicle based on the wheel speed detected by the wheel speed detection means. A pseudo vehicle speed calculating means for calculating a pseudo vehicle speed compares the pseudo vehicle speed calculated by the calculating means during braking with the wheel speed, and based on the comparison result, the brake oil pressure is adjusted to a pressure increasing phase, a pressure decreasing phase, and a control means for operating the hydraulic pressure adjusting means to periodically increase or decrease according to a cycle including a holding phase after pressure reduction, the road surface friction coefficient being determined based on the wheel speed detected by the wheel speed detecting means. A road surface friction coefficient estimation means to estimate, and an increase by the control means when the road surface friction coefficient estimated by this estimation means is small and the pressure is shifted from the holding phase after pressure reduction to the pressure increase phase or from the pressure reduction phase to the pressure increase phase. The present invention is characterized in that it includes a pressure increase prohibition means for prohibiting pressure control, and a pressure increase prohibition canceling means for canceling the operation of the pressure increase prohibition means when the wheels are not accelerating.

The anti-skid brake device for a vehicle according to the invention of claim 3 of the present application (hereinafter referred to as the third invention) includes: a wheel speed detection means for detecting the rotational speed of the wheels; a hydraulic pressure adjustment means for adjusting the brake oil pressure; A pseudo vehicle speed calculating means for calculating a pseudo vehicle speed of the vehicle based on the wheel speed detected by the wheel speed detecting means, and comparing the pseudo vehicle speed and the wheel speed calculated by the calculating means during braking, and a control means for operating the oil pressure adjusting means so that the brake oil pressure is periodically increased or decreased according to a cycle including a pressure increase phase, a pressure reduction phase, and a holding phase after pressure reduction based on the comparison result. road surface friction coefficient estimating means for estimating a road surface friction coefficient based on the wheel speed detected by the wheel speed detecting means; and when the road surface friction coefficient estimated by this estimating means is small, pressure is increased from at least a holding phase after pressure reduction. a pressure increase inhibiting means for prohibiting pressure increase control by the control means when transitioning from a phase or a pressure reduction phase to a pressure increase phase, and a ratio of rear wheel speed to the pseudo vehicle speed is greater than a predetermined value, and after The present invention is characterized in that a pressure increase inhibition canceling means is provided for canceling the operation of the pressure increase inhibition means when the wheels are not accelerating.

(Function) According to the first to third inventions, when the road surface friction coefficient is small during ABS control, the pressure increase inhibiting means controls the pressure increase during the pressure decrease phase or the pressure increase phase following the pressure decrease holding phase. Since pressure increase control of the braking pressure by the means is prohibited, the rotational speed of the wheels continues to increase and exceeds the wheel speed or the pseudo vehicle body speed.

As a result, even on a low-friction road surface such as an icy road, the pseudo vehicle speed is reliably updated, and the occurrence of cascade lock is reliably prevented.

Further, according to the second invention, when the wheel is not accelerating, for example, when the wheel speed, which has once increased due to a reduction in braking pressure, decreases due to road resistance, the operation of the pressure increase inhibiting means is released. Therefore, occurrence of braking failure is also prevented.

Furthermore, according to the third invention, for the rear wheels whose wheel speeds change slowly, the operation of the pressure increase inhibiting means takes into account the ratio of the rear wheel speed to the pseudo vehicle speed, that is, the slip state of the rear wheels. This prevents erroneous judgments.

(Example) Examples of the present invention will be described below.

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 3.4 are driving wheels, and the output torque of an engine 5 is transmitted from an automatic transmission 6. The power is transmitted to the left and right rear wheels 3.4 via the propeller shaft 7, the differential gear 8, and the left and right drive shafts 9.10.

Each of the wheels 1 to 4 has a disc 1la to 14a that rotates integrally with the wheels 1 to 4, and a caliper 1lb that receives braking pressure and brakes the rotation of these discs 1a to 14a. -14b and the like are provided, and a brake control system 15 is provided to perform a braking operation on these brake devices 11=14.

This brake control system 15 includes a booster 17 that increases the depression force of the brake pedal 16 by the driver, and a master cylinder 18 that generates braking pressure in accordance with the depression force increased by the booster 17. . The front wheel brake pressure supply line 19 led from the master cylinder 18 is branched into two routes, and these front wheel branch brake pressure lines 1.9a and 19b are connected to the left and right front wheels 1.9a and 19b.
caliper of the brake device 11.12 in 2,
12a, and one front wheel branch braking pressure line 19a leading to the brake device 11 of the left front wheel l has a first branch braking pressure line 19a consisting of an electromagnetic on-off valve 20a and an electromagnetic relief valve 20b. A valve unit 20 is installed, and the other front wheel branch braking pressure line 19b leading to the brake device 12 of the right front wheel 2 is also equipped with an electromagnetic on-off valve 21a and an electromagnetic on-off valve 21a, similar to the first valve unit 20 described above. A second valve unit 21 consisting of a relief valve 21b is installed.

On the other hand, the rear wheel braking pressure supply line 22 led from the master cylinder 18 includes an electromagnetic on-off valve 23a and an electromagnetic relief valve similarly to the first and second valve units 20.21. 23b is installed, and this rear wheel braking pressure supply line 22 is branched into two routes on the downstream side of the third valve unit 23, and these rear wheel branch lines The braking pressure lines 22a, 22b are the calipers of the brake devices 13, 1.4 on the left and right rear wheels 3, 4]3b.

14b, respectively. That is, the brake control system 15 in this embodiment includes a first channel that variably controls the braking pressure of the brake device 11 on the left front wheel l by the operation of the first valve unit 20, and a first channel that variably controls the braking pressure of the brake device 11 on the left front wheel l by the operation of the second valve unit 21. a second channel that variably controls the braking pressure of the brake device 12 in the left and right rear wheels 3 and 4 through the operation of the third valve unit 23; are provided, and these first to third channels are controlled independently of each other.

The brake control system 15 includes the first to
A control unit 24 that controls the third channel is provided, and this control unit 24 receives a brake signal from a brake switch 25 that detects 0N10FF of the brake pedal 16, and a wheel speed that detects the rotational speed of each wheel. Wheel speed signals from sensors 26 to 29 are input, and a braking pressure control signal corresponding to these signals is input to the first
~By outputting to the third valve unit 20, 21, and 23, the braking control for slipping of the left and right front wheels 1.2 and the rear wheels 3, 4, that is, the ABS control is performed in the first
~It is designed to be performed in parallel for each third channel. That is, the control unit 24 controls the first to third valve units 20, 21, 23 based on the wheel speeds indicated by the wheel speed signals from the respective wheel speed sensors 26 to 29.
On-off valves 20a, 21a, 23a and relief valve 2 in
0b.

By controlling the opening and closing of the wheels 2 lb and 23b by duty control, respectively, braking force is applied to the front wheels 1, 2 and the rear wheels 3, 4 with a braking pressure according to the state of slip. Note that the first to third valve units 2
Each relief valve 20b, 21b at 0,21.23.

The brake oil discharged from 23b is returned to the reservoir tank 18a of the master cylinder 18 via a drain line (not shown).

In the ABS non-control state, the control unit 24 does not output a braking pressure control signal, so as shown in the figure, the first to third valve units 20,
Relief valves 20b, 21b at 21.23.

23b are each held closed, and each unit 20°2
1.23 on-off valves 20a, 21a, and 23a are held open, and the braking pressure generated in the master cylinder 18 in response to the depression force of the brake pedal 16 is transferred to the front wheel braking pressure supply line 19 and the rear wheel. It is supplied to the brake devices 11 to 14 in the left and right front wheels 1, 2 and rear wheels 3.4 through the wheel braking pressure supply line 22, and braking force corresponding to these braking pressures is applied to the front wheels 1, 2 and the rear wheels. Rings 3 and 4
It will be given directly to.

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

That is, the control unit 24 controls the sensor 2
Acceleration and deceleration for each wheel are calculated based on the wheel speeds indicated by signals from 6 to 29. Here, to explain how to calculate acceleration or deceleration, the control unit 24 divides the difference between the current value and the previous value of the wheel speed by the sampling period Δt (for example, 7 m s), and then divides the result based on the gravity The value converted to acceleration is updated as the current acceleration or deceleration.

Furthermore, the control unit 24 executes a predetermined rough road determination process to determine whether the road surface the vehicle is traveling on is a rough road or not. This rough road determination process is executed, for example, as follows. In other words,
For example, if the number of times the deceleration or acceleration of the rear wheels 3, 4 exceeds a predetermined upper limit or lower limit within a certain period of time is within a set value, the control unit 24 maintains the rough road flag Fa at 0, and and the value indicating deceleration is
If the number of times the upper and lower limits are exceeded within a certain period of time is greater than or equal to the set value, it is determined that the road surface is rough, and a rough road flag F is set to 1.

The control unit 24 controls the rear wheels 3 and 4 to represent the wheel speed and acceleration/deceleration for the third channel.
Select. In this embodiment, the smaller of the two wheel speeds is selected as the rear wheel speed in consideration of the detection error of the two wheel speed sensors 28 and 29 of the rear wheels 3 and 4 at the time of slipping. The acceleration and deceleration determined from the wheel speed are selected as the rear wheel deceleration and rear wheel acceleration.

Furthermore, the control unit 24 estimates the road surface friction coefficient for each channel and calculates the pseudo body speed of the vehicle in parallel.

The control unit 24 includes the wheel speed sensor 28.
The left and right front wheels 1, indicated by the rear wheel speed determined from the signal from 29 and the signals from the respective wheel speed sensors 26, 27,
The slip ratios for the first to third channels are calculated from the wheel speed and pseudo vehicle speed in step 2. In this case, the following relational expression, slip ratio = (wheel speed/pseudo vehicle speed) x 100, is calculated. The slip rate is calculated using In other words, the larger the deviation of the wheel speed from the pseudo vehicle speed, the smaller the slip rate becomes, and the greater the tendency of the wheel to slip.

Subsequently, the control unit sets various control threshold values used to control the first to third channels.

Here, the outline of the control threshold setting process will be described. This control threshold setting process is performed, for example, as follows. That is, the control unit 24 selects the control threshold corresponding to the friction coefficient value and the pseudo vehicle body speed from various control thresholds set in advance according to the vehicle speed range and the road surface friction coefficient, and also sets these control thresholds to the above-mentioned control threshold. Correction is made according to the judgment result of the rough road judgment process. Here, the control threshold value is, for example, 0 for determining the transition from phase 0 indicating the ABS non-control state to phase ■ indicating the holding state after pressure increase.
-2 deceleration threshold &2, 1-2 deceleration threshold BI2 for determining transition from phase I indicating pressure increase state to phase ■ above
, 2-3 deceleration threshold % for determining transition from the above phase ■ to phase ■ indicating a depressurized state, and 3-3 deceleration threshold % for determining transition from this phase ■ to phase ■ indicating a holding state after depressurization.
5 deceleration threshold &, 5-1 slip rate threshold % for determining pressure increase from phase V to phase ■, initial slip rate threshold B1 for the first cycle, etc., depending on the vehicle speed range and road friction coefficient. It is set. In this case, the deceleration threshold, which has a large effect on the braking force, is set at the level of the friction coefficient value in order to achieve a high level of both braking performance when the road surface friction coefficient is large and control responsiveness when the road surface friction coefficient is small. It is set so that the smaller the road surface friction coefficient becomes, the closer the road surface friction coefficient becomes to the OG.

Further, control threshold values are similarly set for the second and third channels.

The control unit 24 is configured to perform lock determination processing for each channel, phase determination processing for defining control amounts for the first to third valve units 20, 21, and 23, and cascade determination processing. It has become.

Here, the lock determination process will be explained as follows. For example, in the lock determination process for the first channel for the left front wheel, the control unit 24 first sets the continuation flag F[ for the first channel.
, set the current value of ON+ as the previous value, and then set the pseudo vehicle speed ■8 and wheel speed W1 under predetermined conditions (for example,
V < 5 Km/H, W, < 7.5 Km/H
), and when these conditions are satisfied, the continuation flag F is set. l and lock flag F1. )K
Each of I is reset to 0, and if not satisfied, it is determined whether the lock flag F is set to I or not. If the lock flag F is not set to 1, the lock flags Fl and XI are set to 1 under a predetermined condition (for example, when the pseudo vehicle speed V3 is greater than the wheel speed W1).

On the other hand, the control unit 24 controls the lock flag Fl.
j) When determining that Kl is set to 1,
For example, the phase value P1 of the first channel is set to 5 indicating phase V, and the slip rate S1 is 90%.
When the value is greater than 1, the continuation flag F is set to 1.

Note that lock determination processing is similarly performed for the second and third channels.

Further, to explain the outline of the phase determination process, the control unit 24 indicates the ABS non-control state by comparing each control threshold value set according to the driving state of the vehicle with the wheel acceleration/deceleration and slip rate. Phase 0, Phase T indicating pressure increase state during ABS control
, phase (2) indicating a holding state after pressure increase, phase (2) indicating a reduced pressure state, phase (2) indicating a sudden pressure reduction state, and phase (2) indicating a holding state after pressure reduction are selected.

Then, the control unit 24 sets a control amount according to the phase value set for each channel, and then transmits a braking pressure control signal according to the control amount to the first to third valve units h20, 21.23. Output for each. As a result, the first to third valve units 20, 2
Branch braking pressure line 19 for front wheels on the downstream side of 1.23
a, 19b and rear wheel branch braking pressure lines 22a, 22
The braking pressure b is increased or decreased, or is maintained at the pressure level after the pressure increase or decrease.

Specifically, the estimation process of the road surface friction coefficient is performed by e.g.
The process is performed as follows according to the flowchart in the figure.

That is, the control unit 24 reads various data in step S1, and then controls the ABS in step S2.
It is determined whether flag F6 is set to 1 or not.

In other words, it is determined whether ABS control is in progress. This ABS flag FABs is, for example, the lock flag F1. of the first to third channels. I) K1. FLOPK2. F
It is set to 1 when any one of the LDKs 3 is set to 1, and is reset to O when the brake switch 25 is changed from ON to OFF. Then, the control unit 24
When it is determined that the BS flag F is not set to l, the process proceeds to step S, where the friction coefficient value MU is set to 3, which indicates a high friction road surface.

Further, when the control unit 24 determines that the ABS flag F is set to 1 in step & above, that is, when determining that ABS control is in progress,
Proceeding to step S4, it is determined whether or not the deceleration DW during the previous cycle is smaller than 120G, and if it is determined as YES, the process proceeds to step & to determine whether the acceleration AW during the previous cycle is also larger than IOG. If the result is NO, step & is executed to set the friction coefficient value MU, and l indicating a low-friction road surface.

On the other hand, the control unit 24 performs the step S4 described above.
When it is determined that the deceleration DW is not smaller than 120G, step & is skipped and the process goes to step S, where it is determined whether the acceleration AW is larger than 20G, and when the determination is YES, step & is executed. and set 3 as the friction coefficient value MU, while when the determination is NO, execute step & to set the friction coefficient value MU,
2 is set to indicate a medium friction road surface.

On the other hand, the process of calculating the pseudo vehicle speed is specifically performed as follows according to the flowchart shown in FIG.

That is, the control unit 24 performs steps T,
After reading various data, proceed to step T.

The wheel speed W1 indicated by the signals from the sensors 26 to 29 is
The highest wheel speed WMx is determined from W4, and at step T3, the wheel speed change amount ΔWMX per sampling period Δt of the wheel speed WMx is calculated.

Next, the control unit 24 executes step T4 to read out the vehicle body speed correction value CvR corresponding to the friction coefficient value MU representing the friction coefficient value for each channel from the map shown in FIG. It is determined whether the wheel speed change amount ΔMMX is smaller than the vehicle speed correction value CVR. When it is determined that the wheel speed change amount △W is smaller than the vehicle speed correction value C□, step T6 is executed to subtract the vehicle speed correction value C from the previous value of the pseudo vehicle speed v, R. Replace the value with the current value.

Therefore, the pseudo vehicle speed V3 decreases at a predetermined slope according to the vehicle speed correction value C.

On the other hand, the control unit 24 performs the steps T,
When it is determined that the wheel speed change amount ΔWMx is larger than the vehicle speed correction value CvR, that is, when the maximum wheel speed W shows an excessive change, the process moves to step T7 and the maximum wheel speed WMX is changed from the pseudo vehicle speed vR. It is determined whether the value obtained by subtracting is larger than a predetermined value v0. In other words, it is determined whether there is a large difference between the maximum wheel speed W and the pseudo vehicle speed vR. When there is no large difference, step T6 is executed to set the pseudo vehicle speed v,
The value obtained by subtracting the vehicle speed correction value CvR from the previous value of l is replaced with the current value.

In addition, when a large difference occurs between the maximum wheel speed W and the pseudo vehicle speed V8, the control unit 24 controls the
Step T is executed to replace the maximum wheel speed WMx with the pseudo vehicle speed vR.

In this way, the pseudo body speed vR of the vehicle is updated every sampling period Δt according to each wheel speed W1 to W4.

The cascade determination process, which is a characteristic part of the present invention, is performed as follows for the first channel, for example, according to the flowchart shown in FIG.

That is, the control unit 24 first executes step U1 to read various data, and then determines in step U2 whether or not the current value of the phase value is set to l indicating the pressure increase state, and selects YES. When it is determined that this is the case, the process proceeds to step U3, where it is determined whether or not the previous value of the phase value is set to 3, which indicates a reduced pressure state.

When the determination is No, the process proceeds to step U4, where it is determined whether the previous value of the phase value P1 was 5, which indicates the holding state after pressure reduction. And the above step Ua,
When it is determined YES in U4, step U
, and determines whether the current value of the continuation flag FQ)Nl is O. When it is determined No, that is, the continuation flag F
When COTII is l, the process proceeds to step U6, where it is determined whether the previous value of the flag FCxNl is O. That is, it is determined whether the first channel has transitioned from the first cycle to the second cycle immediately after the start of control. When the determination is YES, the control unit 24 next executes step U and determines whether the continuation flag F of the first channel for the right front wheel is set to O. In other words, it is determined whether the first channel first shifts to the second cycle. and,
When the determination is YES, step U8 is executed and the value of the cascade flag Fc of the first channel is set to 1. As a result, when the first channel first shifts to the second cycle, the cascade flag F1 is forcibly set to 1 regardless of the value of the friction coefficient value MU.

Further, the control unit 24 performs the steps U,
When the determination is No, that is, when it is determined that the control cycle is the second cycle or later, the process proceeds to step U, where it is determined whether the friction coefficient value MU is 1 or not. When it is determined YES, that is, when it is determined that the road surface is low friction, it is determined in step U1° whether or not the front wheels l are decelerating, and when it is determined that the front wheels l are not decelerating, step Ull is executed. The value of the cascade flag FCAsl is set to 1, and when it is determined that the deceleration is occurring, step U12 is executed and the cascade flag F is set. Clear the value of 4 to O.

On the other hand, when the control unit 24 determines in step U that the value of the friction coefficient MU is not 1, the control unit 24 moves to step UI3 and determines whether the value of the friction coefficient MU is 3 or not. Then, when the value of the friction coefficient value M U+ is not 3, that is, when it is determined that it is 2 indicating a medium friction road surface, step U14 is executed and the first
Opening/closing valve 2 of the first valve unit 20 in the channel
It is determined whether the cumulative sum of the duty ON times of 0a, that is, the pressure increase execution time t, has reached a predetermined value T, (for example, 25 m5), and the time t is determined. 2 reaches a predetermined value T0, step U1. Then, the deceleration DW is set to a predetermined value G,
(for example, -4G). When the determination is YES, step LLa is executed to set the value of the cascade flag F(jJ+ to 1. This is because the initial value of the brake oil pressure is set when the brake pedal 16 is locked with a small depression amount. This is to avoid insufficient pressure increase due to this.

When the control unit 24 determines in step u+g that the deceleration DW is not larger than the predetermined value T0, it executes step U17 to determine whether or not the front wheel l is decelerating, and when it determines YES Step Ufg is executed to clear the value of cascade flag F, , 1 to 0.

Furthermore, the control unit 24 performs the step U described above.
2. When it is determined NO in U, respectively,
Execute step U19 to set the cascade flag FCASI
The value of is cleared to 0.

Note that similar cascade determination processing is performed on the second channel for the right front wheel.

On the other hand, the cascade determination process for the third channel for the rear wheels follows the flowchart shown in FIG.

That is, the control unit 24 first executes step v1 to read various data, and then determines in step v2 whether or not the current value of the phase value P is set to 1 indicating a pressure increase state. When the determination is YES, the process proceeds to step V, where it is determined whether the previous value of the phase value P3 has been set to 3, which indicates a reduced pressure state. If the determination is NO, the process proceeds to step V, where the previous value of the phase value P3 is determined to be 5, which indicates the holding state after pressure reduction.
Determine whether or not it was. And the above step V3
．． When the determination is YES in V4, step 5 is executed and the continuation flag F is set. ) It is determined whether the current value of N3 is O or not, and when the determination is No, that is, when the continuation flag FO )N3 is 1, the process advances to step V6 and the flag F is determined. , 13 is 0 or not. That is, it is determined whether the third channel has transitioned from the first cycle to the second cycle immediately after the start of control. When the determination is YES, step V is executed to set the value of the cascade flag FCA53 of the third channel to 1. As a result, when the third channel first shifts to the second cycle, the cascade flag F is set regardless of the value of the friction coefficient value MU. AS3 will be forced to be set to 1.

Further, the control unit 24 performs the step v6 described above.
When it is determined NO in step 3, that is, when it is determined that it is the second cycle or later, the process proceeds to Step Knob (2) and it is determined whether the value of the friction coefficient value MU is 1 or not. When it is determined to be YES, that is, when it is determined that the road surface is low friction, it is determined in step v9 whether or not the rear wheels 3.4 are decelerating, and when it is determined that the rear wheels 3.4 are not decelerating, step V1o is executed. and cascade flag FCASI
The value of I is set to 1, and when it is determined that the vehicle is decelerating, the slip rate 83 of the third channel is set to a predetermined value S in step V1. (For example, 98%) or more is determined, and if the determination is YES, step 12 is executed to clear the value of the cascade flag FcAs3 to O.

On the other hand, when the control unit 24 determines in step (2) that the friction coefficient value MU is not 1, the control unit 24 proceeds to step V13 and determines whether the friction coefficient value MU is 3 or not. Then, when the value of the friction coefficient value MUs is not 3, that is, when it is determined that it is 2 indicating a medium friction road surface, step v14 is executed and the on-off valve 23 of the third valve unit 23 in the third channel is
The cumulative sum of the duty ON times of a, that is, the pressure increase execution time t. 2 is the predetermined value T. (for example, 25 m, s), and when the time tDZ reaches a predetermined value T0, proceed to step v11 to determine the rear wheel deceleration DWR.
is larger than a predetermined value G0 (for example, -4G). Then, if the determination is YES, step ■
16 to set the value of cascade flag FcA33 to 1.

When the control unit 24 determines in step V1B that the rear wheel deceleration DWR is not greater than the predetermined value T0, it executes step v17 to
．． 4 is decelerating, and if it is determined as YES, the slip ratio & is set to a predetermined value of 5 in step via.
It is determined whether or not the above is true, and if the determination is YES, step V(g) is executed to clear the value of the cascade flag F.4 to O.

Furthermore, the control unit 24 performs the step V described above.
, , V, respectively, execute step U2o and set the cascade flag FCAS.
The value of 3 is cleared to 0.

Next, the operation of this embodiment will be explained using ABS control for the first channel as an example.

That is, in the ABS non-control state during deceleration, the master cylinder 18 is activated by depressing the brake pedal 16.
The braking pressure generated in
As shown in , the wheel speed W of the left front wheel 1.

When the amount of change in , that is, the deceleration DW, reaches 13G, the lock flag FIj)K+ in the first channel is set to 1, as shown in FIG. will be transferred. In the first cycle immediately after the start of this control, since the friction coefficient value MU is set to 3 indicating a high friction road surface as described above, the control unit 24 sets various control thresholds corresponding to the high friction road surface. will be set.

Then, the control unit 24 controls the wheel speed W1.
Slip rate S1, deceleration DW, acceleration A calculated from
W, and the various control threshold values described above are compared. In this case, assuming that the initial slip rate threshold S1 is set to 90%, for example, when the slip rate S1 indicates 96%, the control unit 24, as shown in FIG.
Change the phase value P1 from 0 to 2. Therefore, the braking pressure is maintained at the level immediately after the pressure increase, as shown in FIG. 2(e). For example, when the slip ratio S1 falls below 90%, the control unit 24 changes the phase value P1 from 2 to 3. As a result, the relief valve 20b of the first valve unit 20 is 0N10FF according to a predetermined duty rate, and as shown in FIG. As the braking force gradually decreases, the rotational force of the front wheel l begins to recover.

When the braking pressure continues to be reduced and the deceleration DW and acceleration AW calculated from the wheel speed Wl of the front wheel l become 0, the control unit 24 changes the phase value P1 from 3 to 5. Therefore, as shown in FIG. 6(e), the braking pressure is maintained at the level after the pressure reduction from that time.

Then, the state of phase ■ continues and the slip rate S1 becomes 9.
When it exceeds 0%, the control unit 24
As shown in FIG. 3(b), the continuation flag Fat is set to 1. As a result, the ABS control in the first channel will shift to the second cycle from the relevant time. In that case, the control unit 24 forcibly changes the phase value P to I.

Immediately after the transition to phase E, the on-off valve 20b of the first valve unit 20 operates at 100% duty according to the initial surge pressure time T, which is set based on the duration of phase V in the first cycle. As a result, the braking pressure is increased at a steep gradient, as shown in FIG. 2(e). In addition, the initial surge pressure time TP
7, the opening/closing valve 20a is turned ON/OFF according to a predetermined duty rate, and the braking pressure gradually increases according to a gentler slope than the above-mentioned slope.

On the other hand, in the second and subsequent cycles, as shown in the flowchart of FIG. 2, the deceleration DW in the previous cycle,
An appropriate friction coefficient value MU is determined according to the vehicle speed, acceleration AW, etc., and a control threshold value is selected according to these friction coefficient values MU, so precise braking is performed according to the driving condition. The pressure will be controlled.

In the state of phase V in the second cycle, the control unit 24 controls, for example, when the slip rate S1 is 5-5.
When it is determined that the 1-slip rate is greater than the threshold value, the phase value P1 is set to 1 and a transition is made to the third cycle.

Among the first to third channels, for example, the first
Assuming the channel first transitions to the second cycle,
The control unit 24 sets the value of the cascade flag FCJJ+ for the first channel to 1 (the fifth
(see Figure, steps U6-U6). Therefore, Fig. 8 (
As shown in e), the increase in braking pressure is suppressed even though it is in Phase I, which indicates a pressure increase state.
As shown in FIG. 4A, the rotation speed of the left front wheel l continues to increase, and the wheel speed W1 exceeds the pseudo vehicle speed vR. As a result, the pseudo vehicle speeds v and l are updated to match the wheel speed W1, and are then reduced at a predetermined slope depending on the value of the friction coefficient value MU. Then, in a predetermined state in which the wheel speed W1 of the left front wheel 1 begins to decrease, the control unit 24 sets the cascade flag F. Clear the value of Ail to 0. Therefore, the braking pressure increases as shown in FIG. 2(e).

This prevents the braking pressure from dropping excessively when the pressure is reduced (and thus also avoids deterioration in braking performance).

Furthermore, when transitioning from the second cycle to the third cycle, if the value of the friction coefficient MU in this first channel is set to l indicating a low friction road surface, the control unit 24 sets the cascade flag FCA51.
Set the value of to l. Therefore, in this case as well, the increase in braking pressure is stopped, and the rotational speed of the left front wheel l continues to increase in the same manner as above, causing the wheel speed W1 to exceed the pseudo vehicle speed vR. As a result, the pseudo vehicle speed V
R is updated to match the wheel speed W1, and
Thereafter, the friction coefficient value MU is reduced at a predetermined slope depending on the value of the friction coefficient value MU, so that the actual vehicle speed does not deviate greatly.

Note that even when switching from phase (2) to phase (2), if the above conditions are satisfied, the increase in braking pressure will be suppressed.

(Effects of the Invention) As described above, according to the anti-skin braking device for a vehicle according to the present invention, when the road surface friction coefficient is small during ABS control, the pressure increase phase following the pressure reduction phase or the holding phase after pressure reduction, When r-1, the pressure increase prohibiting means prohibits the control means from increasing the braking pressure, so the wheel rotational speed continues to rise and the wheel speed exceeds the pseudo vehicle speed. It turns out. As a result, even on a low-friction road surface such as an icy road, the pseudo vehicle speed is reliably updated, and the occurrence of cascade lock is reliably prevented.

Further, according to the second invention, when the wheel is not accelerating, for example, when the wheel speed, which has once increased due to a reduction in braking pressure, decreases due to road resistance, the operation of the pressure increase inhibiting means is released. Therefore, occurrence of braking failure is also prevented.

Furthermore, according to the third invention, for the rear wheels whose wheel speeds change slowly, the operation of the pressure increase inhibiting means takes into account the ratio of the rear wheel speed to the pseudo vehicle speed, that is, the slip state of the rear wheels. This prevents erroneous judgments.

[Brief explanation of the drawing]

The drawings show an embodiment according to the present invention, and Fig. 1 is a general schematic diagram of a vehicle equipped with an anti-skid brake device according to the present invention, and Fig. 2 is a flowchart showing a process for estimating the coefficient of road friction. , FIG. 3 is a flowchart showing the pseudo vehicle speed calculation process, FIG. 4 is an explanatory diagram of a map used in the calculation process, FIGS. 5 and 6 are flowcharts showing the cascade determination process, and FIG. FIG. 8 is a time chart showing the operation of this embodiment. Further, FIG. 9 is an explanatory diagram of conventional problems. 1.2...front wheel, 3,4...rear wheel, 20,21.2
3... Valve unit (hydraulic adjustment means), 24...
Control unit (control means, pseudo vehicle speed calculation means, road surface friction coefficient estimation means, pressure increase prohibition means, pressure increase prohibition canceling means), 26 to 29... wheel speed sensors (wheel speed detection means). Procedural amendment January 14, 1992

Claims (3)

[Claims] (1) A wheel speed detection means that detects the rotational speed of the wheels, a hydraulic pressure adjustment means that adjusts the brake oil pressure, and a pseudo body speed that calculates the pseudo body speed of the vehicle based on the wheel speed detected by the wheel speed detection means. Comparing the vehicle speed calculation means with the pseudo vehicle speed calculated by the calculation means during braking and the wheel speed,
and control means for operating the hydraulic pressure adjusting means so that the brake hydraulic pressure is periodically increased or decreased according to a cycle including a pressure increase phase, a pressure decrease phase, and a holding phase after pressure reduction based on the comparison result. The skid brake device includes: a road surface friction coefficient estimating means for estimating a road surface friction coefficient based on the wheel speed detected by the wheel speed detecting means; and when the road surface friction coefficient estimated by the estimating means is small, at least An anti-skid vehicle characterized in that a pressure increase inhibiting means for prohibiting pressure increase control by the control means when transitioning from a holding phase after pressure reduction to a pressure increase phase or from a pressure reduction phase to a pressure increase phase is provided. Brake device. (2) A wheel speed detection means for detecting the rotational speed of the wheels, a hydraulic pressure adjustment means for adjusting the brake oil pressure, and a pseudo body speed for calculating the pseudo body speed of the vehicle based on the wheel speed detected by the wheel speed detection means. Comparing the vehicle speed calculation means with the pseudo vehicle speed calculated by the calculation means during braking and the wheel speed,
and control means for operating the hydraulic pressure adjusting means so that the brake hydraulic pressure is periodically increased or decreased according to a cycle including a pressure increase phase, a pressure decrease phase, and a holding phase after pressure reduction based on the comparison result. The skid brake device includes road surface friction coefficient estimating means for estimating a road surface friction coefficient based on the wheel speed detected by the wheel speed detecting means; pressure increase inhibiting means for inhibiting pressure increase control by the control means when transitioning from the subsequent holding phase to the pressure increasing phase or from the pressure decreasing phase to the pressure increasing phase; and a pressure increasing inhibiting means for inhibiting the pressure increasing control when the wheels are not accelerating An anti-skid brake device for a vehicle, characterized in that it is provided with a prohibition release means for canceling the operation. (3) A wheel speed detection means for detecting the rotation speed of the wheels, a hydraulic pressure adjustment means for adjusting the brake oil pressure, and a pseudo body speed for calculating the pseudo body speed of the vehicle based on the wheel speed detected by the wheel speed detection means. Comparing the vehicle speed calculation means with the pseudo vehicle speed calculated by the calculation means during braking and the wheel speed,
and control means for operating the hydraulic pressure adjusting means so that the brake hydraulic pressure is periodically increased or decreased according to a cycle including a pressure increase phase, a pressure decrease phase, and a holding phase after pressure reduction based on the comparison result. The skid brake device includes: a road surface friction coefficient estimating means for estimating a road surface friction coefficient based on the wheel speed detected by the wheel speed detecting means; and when the road surface friction coefficient estimated by the estimating means is small, at least A pressure increase inhibiting means for prohibiting pressure increase control by the control means when transitioning from a holding phase after pressure reduction to a pressure increase phase or from a pressure decrease phase to a pressure increase phase, and a ratio of rear wheel speed to the pseudo vehicle speed is predetermined. 1. An anti-skid brake system for a vehicle, characterized in that an anti-skid brake device for a vehicle is provided with an inhibition canceling means for canceling the operation of the pressure increase inhibiting means when the rear wheel is not accelerating.