JP3308640B2 - Anti-skid brake system for vehicles - Google Patents

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 suppressing an excessive braking force during braking of a vehicle, and more particularly to an improved pressure reduction control of a high-friction road-side brake hydraulic pressure at the time of running on a split road and at the end thereof. About things.

[0002]

2. Description of the Related Art As a vehicle brake system, an anti-skid brake device has been put to practical use in which the locking or skid state of wheels during braking is prevented. This type of anti-skid brake device controls a wheel speed sensor that detects wheel speeds of four wheels, an electromagnetic control valve that adjusts brake oil pressure, and an electromagnetic control valve based on the wheel speed detected by the wheel speed sensor. A control device. This control device obtains the acceleration / deceleration of the wheel based on, for example, the detected wheel speed, and when the wheel deceleration becomes equal to or less than a predetermined value, reduces the braking pressure by controlling the pressure of the electromagnetic control valve to decrease the braking pressure. When the wheel speed increases and the wheel acceleration reaches a predetermined value, the braking pressure is increased by controlling the pressure of the control valve.

[0003] Such a series of braking pressure control (hereinafter referred to as AB
S control) is continued until the vehicle stops, for example, to prevent the wheels from being locked or skid during sudden braking, and to stop the vehicle at a short braking distance while ensuring the directional stability of the vehicle. Becomes by the way,
When running on a split road surface where one side of the road surface is in a low friction state and the other side of the road surface is in a high friction state and braking is performed, the slip amount of the wheel on the low friction road surface is reduced by the wheel on the high friction road surface. Significantly larger than the slip amount of
The ABS control is executed only for the braking pressure of the brake device of the wheel on the low friction road surface, the braking force of the brake device of the wheel on the high friction road surface becomes excessive, and the vehicle easily spins.

Therefore, from the viewpoint of securing running stability when traveling on a slip road surface and preventing spinning, in order to suppress an increase in the braking pressure of the brake device on the high friction road surface side in the braking state, the braking pressure is increased at predetermined intervals. The technique of forcibly reducing the pressure has been put to practical use. For example, U.S. Pat.No. 4,374,421 discloses a technique corresponding to the forcible pressure reduction for the above-described split road surface measures, in which when running on a split road surface, the ABS control is started for the braking pressure on the low friction road surface side. At first, the braking pressure on the high friction road surface side is maintained at first,
After that, there has been proposed a technique of gradually increasing the vehicle speed gradually as the vehicle speed increases.

Further, in the prior art, even when the traveling on the slip road surface is completed, the forcible pressure reduction is continued until the next pressure reduction by the ABS control is executed.

[0005]

SUMMARY OF THE INVENTION During the ABS control,
If the forced decompression is suddenly terminated at the time when the split road surface traveling is completed, there is a problem that the braking force is suddenly changed due to a sudden change in the brake oil pressure, and the rate of change of the deceleration (deceleration G) is increased. Therefore, if the forced decompression is continued even after the end of the split road running as in the prior art, the brake hydraulic pressure is excessively reduced, which is not preferable. An object of the present invention is to provide an anti-skid brake device for a vehicle that can secure an appropriate braking force while suppressing a sudden change in the braking force at the end of split road surface traveling.

[0006]

According to a first aspect of the present invention, there is provided an anti-skid brake system for a vehicle, comprising: a wheel speed detecting unit for detecting a rotation speed of a wheel; a hydraulic pressure adjusting unit for adjusting a brake oil pressure; and a wheel speed detecting unit. An anti-skid brake device for a vehicle, comprising: anti-skid control means for operating hydraulic pressure adjusting means based on the detected wheel speed, wherein a friction state of a road surface is detected based on the wheel speed detected by the wheel speed detecting means. Road surface friction state detection means, split road surface detection means for detecting a split road surface based on the road surface friction state detected by the road surface friction state detection means, and split road surface detection detected by the split road surface detection means, During the control of the brake hydraulic pressure of the wheels on the low friction road surface side by the anti-skid control means, A first pressure reduction control means for forcibly reducing the brake oil pressure of the wheel every first predetermined time; and a control target of the first pressure reduction control means during the control by the anti-skid control means and after the split road surface traveling. And a second pressure reduction control means for forcibly reducing the applied brake oil pressure a predetermined number of times at every second predetermined time longer than the first predetermined time.

According to a second aspect of the present invention, in the anti-skid brake device of the first aspect, the pressure reduction by the anti-skid control means is performed on the brake oil pressure to be controlled during the control by the second pressure reduction control means. In this case, a prohibiting means for prohibiting the forcible decompression by the second decompression control means is provided.

[0008]

According to the first aspect of the present invention, there is provided an anti-skid brake device for a vehicle.
Split road surface detecting means, first pressure reducing control means,
Pressure reducing control means, and when the vehicle is traveling on a split road surface, the brake oil pressure on the high friction road surface is forcibly reduced at every first predetermined time during control by the anti-skid control means. The oil pressure is forcibly reduced by a predetermined number of times at every second predetermined time longer than the first predetermined time. Therefore, while the running of the split road surface is suppressed, the brake oil pressure of the wheels on the high friction road surface side is restrained from excessively increasing and the running stability is ensured, while the sudden change of the brake oil pressure before and after the end of the split road surface running is suppressed, and the deceleration ( The deceleration G) can be changed smoothly.

According to a second aspect of the present invention, an anti-skid brake system is provided with a prohibition unit, and the pressure reduction by the anti-skid control unit is performed on the brake oil pressure to be controlled during the control by the second pressure reduction control unit. In such a case, by forcibly reducing the pressure by the second pressure reducing control means, it is possible to prevent the brake hydraulic pressure from excessively decreasing and secure the braking force.

[0010]

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, left and right front wheels 1 and 2 are driven wheels, left and right rear wheels 3 and 4 are driving wheels, and the output torque of an engine 5 is Propeller shaft 7, differential device 8, and left and right drive shafts 9,10
And transmitted to the left and right rear wheels 3 and 4 via the. Each of the wheels 1 to 4 is provided with a disc 11a to 14a which rotates integrally with the wheel, and a brake device 11 to which calipers 11b to 14b which brake the rotation of the discs 11a to 14a when braking pressure is supplied. A brake control system for operating these brake devices 11 to 14 is provided respectively.
15 are provided.

The brake control system 15 includes a booster 17 for increasing the depression force of the brake pedal 16 by the driver.
And a master shilling 18 for generating a braking pressure corresponding to the stepping force increased by the booster 17. Front-wheel braking pressure supply line 19 from this master shilling 18
Is branched into two paths, and these front wheel branch braking pressure lines 19
a and 19b are respectively connected to calipers 11a and 12a of brake devices 11 and 12 of left and right front wheels 1 and 2, respectively.
A first valve unit 20 comprising an electromagnetic on-off valve 20a and an electromagnetic relief valve 20b is provided on one of the front-branch branch braking pressure lines 19a leading to the brake device 12 for the right front wheel 2. Branch braking pressure line 19 for the other front wheel
Similarly to the first valve unit 20, b also has a second valve unit 21 including an electromagnetic on-off valve 21a and an electromagnetic relief valve 21b.

On the other hand, the first and second valve units 20 and 2 are connected to the rear wheel braking pressure supply line 22 from the master cylinder 18.
Similarly to 1, a third valve unit 23 including an electromagnetic on-off valve 23a and an electromagnetic relief valve 23b is provided. The rear wheel braking pressure supply line 22 is branched into two paths on the downstream side of the third valve unit 23, and these rear wheel branch braking pressure lines 22a, 22b are connected to the brake devices 13 for the left and right rear wheels 3, 4. , 14 are connected to calipers 13b, 14b, respectively. The brake control system 15 includes a first channel for variably controlling the braking pressure of the brake device 11 of the left front wheel 1 via the first valve unit 20, and a brake channel 12 for the right front wheel 2 via the second valve unit 21. A left and right rear wheel via a second channel for variably controlling the braking pressure and a third valve unit 23;
There is provided a third channel for variably controlling the braking pressure of both the brake devices 13 and 14, and the first to third channels are controlled independently of each other.

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

The control unit 24 controls the first to first wheels based on the wheel speeds indicated by the wheel speed signals from the wheel speed sensors 27 to 30.
On-off valves 20a, 21a, 23 in the third valve units 20, 21, 23
a and the relief valves 20b, 21b, 23b are controlled by duty control to apply braking force to the front wheels 1, 2 and the rear wheels 3, 4 with a braking pressure according to the slip state. I have. In addition, the first to third valve units
The brake oil discharged from each of the relief valves 20b, 21b, 23b at 20, 21, and 23 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 braking pressure control signal is not output from the control unit 24, and the relief valves 20b, 21b, 23b in the first to third valve units 20, 21, 23 as shown in FIG. Since the open / close valves 20a, 21a, 23a of the units 20, 21, 23 are held open, respectively, the braking pressure generated in the master cylinder 18 in accordance with the depressing force of the brake pedal 16 increases the braking pressure for the front wheels. Left and right front wheels 1 and 2 via a pressure supply line 19 and a rear wheel braking pressure supply line 22.
The braking force is supplied to the braking devices 11 to 14 of the rear wheels 3 and 4, and the braking force according to these braking pressures is directly applied to the front wheels 1 and 2 and the rear wheels 3 and 4.

Next, an outline of the brake control performed by the control unit 24 will be described. Control unit 24
Are the wheel speeds Vw1 to Vw1 indicated by the signals from the wheel speed sensors 27 to 30.
Based on Vw4, decelerations DVw1 to DVw4 and accelerations AVw1 to AVw4 are calculated for each wheel. The calculation method of the acceleration or the deceleration will be described. The control unit 24 divides the difference between the current value of the wheel speed and the previous value of the wheel speed by the sampling period Δt (for example, 7 ms), and converts the result into a gravitational acceleration. Is updated as the current acceleration or deceleration.

The control unit 24 executes a predetermined rough road determination process to determine whether or not the traveling road surface is a rough road. This rough road determination processing is executed as follows. For example, if the number of times that the deceleration or acceleration of the rear wheels 3, 4 exceeds a predetermined upper limit or lower limit within a predetermined time is within a set value, the bad road flag Fak is maintained at 0 to indicate the acceleration and deceleration. If the number of times that the value exceeds the upper limit value and the lower limit value within a certain period of time is equal to or greater than a set value, it is determined that the traveling road surface is a bad road, and the bad road flag Fak is set to 1. Further, the control unit 24 selects the rear wheels 3, 4 representing the wheel speed and acceleration / deceleration for the third channel. In the present embodiment, the smaller one of the two wheel speeds is selected as the rear wheel speed in consideration of the detection error of the two wheel speed sensors 29, 30 of the rear wheels 3, 4 at the time of slip. The acceleration and the deceleration obtained from the speed are selected as the rear wheel acceleration and the rear wheel deceleration.

Further, the control unit 24 estimates a road surface friction coefficient for each channel, and calculates a pseudo vehicle speed in parallel with the estimation. The control unit 24 controls the rear wheel speeds obtained from the signals from the wheel speed sensors 29 and 30, the wheel speeds of the left and right front wheels 1 and 2 indicated by the signals from the wheel speed sensors 27 and 28, and the pseudo vehicle speed. Then, the slip rates for the first to third channels are calculated respectively. In this case, the slip rates are calculated by the following relational expression. Slip ratio = (wheel speed / pseudo-vehicle speed) × 100 Therefore, as the deviation of the wheel speed from the pseudo-vehicle speed increases, the slip rate decreases and the tendency of the wheels to slip increases.

Next, the control unit 24
Various control threshold values used for control of the third channel are respectively set, and the lock determination process for each channel is performed using these control threshold values, and the first to third valve units 2 are set.
A phase determination process for defining a control amount for 0, 21, and 23 and a cascade determination process are performed.

Here, the lock determination processing will be described. For example, in the lock determination processing 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 pseudo vehicle speed Vr and the wheel speed Vw1 are set under predetermined conditions (for example, Vr <5Km / H, Vw1 <
7.5Km / H) is determined, and when these conditions are satisfied, the continuation flag Fcn1 and the lock flag F
lok1 is reset to 0, respectively, and if not satisfied, it is determined whether or not the lock flag Flok1 is set to 1. 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 pseudo vehicle speed Vr is higher than the wheel speed Vw1).

On the other hand, when the control unit 24 determines that the lock flag Flok1 is set to 1, for example, the phase value P1 of the first channel is set to 5 indicating the phase V, and the slip ratio S1 is 90%. When it is larger than 1, the continuation flag Fcn1 is set to 1.
Note that the lock determination process is similarly performed on the second and third channels.

To explain the outline of the phase determination processing, the control unit 24 compares the respective control thresholds set according to the running state of the vehicle with the wheel acceleration / deceleration and the slip ratio to determine whether the ABS is in the non-control state. Phase 0 indicating a pressure increasing state during ABS control, Phase II indicating a holding state after pressure increasing, Phase III indicating a depressurizing state, Phase IV indicating a rapid depressurizing state, and holding state after depressurizing Phase V is selected.

In the cascade determination process, especially on a low friction road surface such as an ice burn, the wheels are likely to lock even with a small braking pressure. The cascade flag Fcs is set to 1 when a predetermined condition in which cascade lock is likely to occur is satisfied.

In this manner, the control unit 24 sets the control amount according to the phase value P1 set for each channel, and then applies the braking pressure control signal according to the control amount to the first to third valve units 20. , 21, and 23 respectively. As a result, the first to third valve units 20, 21,
The braking pressure of the front-wheel branch braking pressure lines 19a, 19b and the rear-wheel branch braking pressure lines 22a, 22b downstream of 23 is increased or reduced, or maintained at the increased or reduced pressure level. .

The processing for estimating the road surface friction coefficient is, for example, as follows.
The first channel is performed as follows based on the flowchart of FIG. Note that the reference symbol Si (i = 1,
(2, 3,...) Indicate each step. The control unit 24 reads various data (S
1) Next, it is determined whether or not the ABS flag Fabs is set to 1 (that is, whether or not the ABS control is being performed) (S2). The ABS flag Fabs is, for example,
Lock flag Flok1, Flok2, Flok3 of the third channel
Is set to 1 when any one of them is set to 1, and reset to 0 when the brake switch 25 switches from ON to OFF. When it is determined that the ABS flag Fabs is not set to 1, in S3, 3 indicating a high friction road surface is set as the friction coefficient value Mu1.

When the control unit 24 determines in S2 that the ABS flag Fabs is set to 1, that is, determines that the ABS control is being performed,
In S4, the wheel deceleration DVw1 during the previous cycle is -20.
It is determined whether or not the wheel acceleration AVw1 during the previous cycle is greater than 10G in S5. If the result of the determination is Yes, it is determined in S6 whether or not the wheel acceleration AVw1 in the previous cycle is greater than 10G. As the friction coefficient value Mu1, 1 indicating a low friction road surface is set. On the other hand, the control unit 24 determines in step S4 that the wheel deceleration DVw1 is -2.
If it is determined that the wheel acceleration is not smaller than 0 G, the process skips S5 and proceeds to S7 to determine whether or not the wheel acceleration AVw1 is larger than 20G. If the determination result is Yes, 3 is set as the friction coefficient value Mu1. On the other hand, when it is determined as No, in S9, 2 indicating the middle friction road surface is set as the friction coefficient value Mu1. The road surface friction coefficient is similarly estimated for the second and third channels.

Next, the calculation process of the pseudo vehicle speed Vr will be described with reference to the flowchart of FIG. First, the control unit 24 reads various data (S2
0), then the wheel speeds Vw1 to Vw1 indicated by the signals from the sensors 27 to 30
The maximum wheel speed Vwm is calculated from Vw4 (S21), and then the maximum wheel speed change amount ΔVwm per sampling period Δt of the maximum wheel speed Vwm is calculated (S22). Next, the control unit 24 reads the vehicle speed correction value CVr corresponding to the representative friction coefficient value Mu (the minimum value of the first to third channels) from the map shown in FIG.
The maximum wheel speed change amount ΔVwm is equal to the vehicle speed correction value CVr
It is determined whether or not:

As a result of the determination, when it is determined that the wheel speed change amount ΔVwm is equal to or less than the vehicle speed correction value CVr, the program proceeds to S2
5, the vehicle speed correction value C from the previous value of the pseudo vehicle speed Vr.
The value obtained by subtracting Vr is replaced with the current value. Therefore, the pseudo vehicle speed Vr decreases at a predetermined gradient corresponding to the vehicle speed correction value CVr. On the other hand, the control unit 24
In S24, the wheel speed change amount ΔVwm is equal to the vehicle speed correction value CV.
When it is determined that it is greater than r, that is, when the maximum wheel speed Vwm shows an excessive change, it is determined in S26 whether a value obtained by subtracting the maximum wheel speed Vwm from the pseudo vehicle speed Vr is equal to or more than a predetermined value V0. That is, it is determined whether or not there is a large difference between the maximum wheel speed Vwm and the pseudo vehicle speed Vr. If there is no large difference, in S27, the value obtained by subtracting the vehicle speed correction value CVr from the previous value of the pseudo vehicle speed Vr is replaced with the current value.

Further, when a large gap occurs between the maximum wheel speed Vwm and the pseudo vehicle speed Vr, the control unit 24 replaces the maximum wheel speed Vwm with the pseudo vehicle speed Vr in S27. In this way, the pseudo vehicle body speed Vr of the vehicle is updated for each sampling cycle Δt according to each wheel speed Vw1 to Vw4.

Next, the process of setting various control thresholds will be described with reference to the flowchart of FIG. The control threshold setting process is executed independently for each channel. Here, the control threshold setting process for the left front wheel first channel will be described. The control unit 24 reads various data in S31,
Next, in S32, as shown in FIG. 6, a representative friction coefficient value Mu obtained from the wheel speeds Vw1 to Vw4 from a table in which the vehicle speed range and the road surface friction coefficient are set as parameters.
And a running state parameter corresponding to the pseudo vehicle speed Vr. Here, as the representative friction coefficient value Mu, the minimum value among the friction coefficient values Mu1 to Mu3 of the first to third channels is used. For example, when the representative friction coefficient value Mu is 1 indicating a low friction road surface and the pseudo vehicle body speed Vr belongs to the medium speed region, the LM for the medium speed low friction road surface is used as the traveling state parameter.
2 will be selected.

The rough road flag Fak is set to 1 indicating a rough road state.
When it is set to, as shown in FIG. 6, a traveling state parameter corresponding to the pseudo vehicle speed Vr is selected. In this case, for example, when the pseudo vehicle speed Vr belongs to the medium speed range, the running state parameter H for the medium speed low friction road surface is used.
M2 is forcibly selected. This is because the road surface friction coefficient tends to be estimated to be small during running on a rough road due to large fluctuations in wheel speed.

After the selection of the traveling state parameters, the control unit 24 reads various control threshold values corresponding to the traveling state parameters from the control threshold value setting table shown in FIG. 7 in S33. Here, as shown in FIG. 7, the various control thresholds include a 1-2 intermediate deceleration threshold B for determining switching from phase I to phase II.
12, 2- for judging switching from phase II to phase III
3 Intermediate slip ratio threshold value Bsg, 3-5 intermediate deceleration threshold value B3 for determining switching from phase III to phase V
5. 5-1 for determining switching from phase V to phase I
A slip ratio threshold value Bsz and the like are set for each traveling state parameter.

In this case, the deceleration threshold value which has a large effect on the braking force is determined so that the braking performance when the road surface friction coefficient is large and the control responsiveness when the road surface friction coefficient is small are compatible at a high level. , As the level of the representative friction coefficient value Mu decreases, that is, as the road surface friction coefficient decreases.
It is set to approach G. Here, when LM2 for a medium-speed low-friction road surface is selected as the traveling state parameter, as shown in the column of LM2 in the control threshold value setting table in FIG.
1-2 intermediate deceleration threshold value B12, 2-3 intermediate slip rate threshold value Bsg, 3-5 intermediate deceleration threshold value B35, 5-
As one slip ratio threshold value Bsz, -0.5G, 90
%, 0G, and 90% are read out.

Next, the control unit 24 executes S33
In, it is determined whether or not the representative friction coefficient value Mu is set to 3 indicating a high friction road surface. If it is determined to be Yes, it is determined in S34 whether or not the rough road flag Fak is set to 1. As a result of the determination, the rough road flag F
If ak is not set to 1, the process proceeds to S35, where it is determined whether the absolute value of the steering angle θ indicated by the steering angle signal is smaller than 90 °, and the absolute value of the steering angle θ is not smaller than 90 °. At this time, in S36, a correction process of the control threshold value according to the steering angle θ is performed. This correction process of the control threshold value is performed by the process shown in FIG.
This 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 steering performance when the steering wheel operation amount is large, the 2-3 intermediate slip ratio threshold value Bsg and the 5-1 intermediate slip ratio threshold value are set. The values obtained by adding 5% to the threshold values Bsz are set as the final 1-2 slip ratio threshold Bsg and the final 5-1 slip ratio threshold Bsz, and the other intermediate thresholds are left as they are. Set as the final threshold. When the result of the determination in S35 is Yes, each of the intermediate thresholds is set as the final threshold as it is.

On the other hand, the control unit 24 executes S34
When it is determined that the rough road flag Fak is set to 1, the process proceeds to S37, and the steering angle θ is set in the same manner as in S35.
It is determined whether or not the absolute value of is smaller than 90 °, and when it is determined as Yes, in S38, based on the control threshold value correction table of FIG. -5 from the slip ratio threshold value Bsz
% Is set as the final 2-3 intermediate slip ratio threshold value Bsg and the final 5-1 slip ratio threshold value Bsz. A correction process of setting a value obtained by subtracting 1.0 G from the intermediate deceleration threshold value B12 as the final 1-2 deceleration threshold value B12 is performed.

This is because, when a bad road is determined, the wheel speed sensors 27 to 30 are likely to make an erroneous detection, so that the response of the control is delayed to secure a good braking force. The other intermediate thresholds are set as final thresholds. When the control unit 24 determines in S37 that the absolute value of the steering angle θ is not smaller than 90 °, the control unit 24 proceeds to S39 and performs a correction process of the control threshold value according to only the rough road. Further, the control unit 24
When it is determined that the representative friction coefficient value Mu is not 3 in S33, the process proceeds to S35. It should be noted that control threshold values are set for the second and third channels in the same manner as in the case of the first channel.

Next, the decompression control for split road surface measures executed by the control unit 24 will be described with reference to the flowchart of FIG. This control is performed during braking on a split road when the left and right front wheels 1,
This is control for the first or second channel on the high friction road surface side of the second brake devices 11, 12, and is executed during execution of the ABS control for the first or second channel corresponding to the low friction road surface side. . Here, the split road surface is a road surface in which the road surface friction state on one side of the road surface is different from the road surface friction state on the other side of the road surface.When braking during traveling on the split road surface, the wheels on the low friction road surface are skid. ABS control is started for the brake device on the low friction road surface side because the vehicle tends to be in the state,
ABS control is not easily started for the brake device on the high friction road surface side, and the brake hydraulic pressure increases, the braking force becomes excessive, and the running stability tends to decrease. Control is executed.

When reading of various data is executed (S5)
0), a determination is made in S51 as to whether the running road surface is a split road surface. This determination is based on the friction coefficient value Mu.
When 1, Mu2 are equal, it is determined that the vehicle is not on a split road surface. When the friction coefficient values Mu1, Mu2 are not equal, it is determined that the vehicle is on a split road surface. If the result of the determination is that the vehicle is not on a split road surface, the counter I is cleared (S52), the timer T is cleared (S53),
The initial flag Fi is reset (S54).

On the other hand, when the vehicle is on a split road surface, S
In 55, it is determined whether or not the split road surface determination is the first time based on the first time flag Fi. In the case of the first time, in S56, forcible pressure reduction for the split road surface measure is executed. This forced decompression is performed for a predetermined time (for example, 8 m
During the period s), the operation is performed by operating the relief valve 20b or the relief valve 21b of the high friction road surface side channel at a predetermined duty ratio. Next, a counter I for counting the number of times of forced decompression is incremented by 1 (S57), and a timer T is started to determine the timing of the next forced decompression (S58).
Next, the first-time flag Fi is set to 1 (S59), and thereafter, the process returns.

Next, similarly, S50 and the subsequent steps are executed.
After the initial flag Fi is set, the determination result of S55 is:
Since the result is No, the flow shifts from S55 to S60, and it is determined whether or not the count time of the timer T has reached 128 ms.
Before 28 ms, return via S67,
When 128 ms has elapsed, the flow shifts from S60 to S61 to determine whether the flag Fa is 1 or not. This flag Fa
Is set via S68 and S69, initially, the flag Fa = 0, and S61 to S6
Then, as in S56, the second forcible pressure reduction is executed (S62), and then the counter I is incremented, the timer T is cleared, and the timer T is started (S64 to S66). ), Then return.

In this manner, forcible decompression is performed every 128 ms, and after performing the forcible decompression six times or more, S
The result of the determination at 67 is Yes, and the flow shifts to S68, where it is determined whether the pressure reduction by the ABS control for the brake oil pressure on the high friction road surface side has been executed. This determination is made as Yes during or immediately after the control unit 24 outputs the braking pressure control signal to the relief valve 20b or the relief valve 21b of the high friction road surface side channel. When the pressure reduction by the ABS control is not being executed, the process returns as it is. However, when the pressure reduction by the ABS control is executed with the counter I being 6 or more, the process proceeds from S68 to S69 and the flag Fa is set to 1 and thereafter To return.

When the process proceeds to S61 at the first forcible decompression timing after the setting of the flag Fa, the determination result is Yes, and the process proceeds to S63. After the flag Fa is reset to 0 in S63, S62 is skipped. S64
Then, S64 to S66 are executed. In other words, until the counter I = 6, the forced decompression for the split road surface countermeasures is executed at least six times at 128 ms intervals regardless of whether or not the decompression by the ABS control is executed. The traveling stability can be ensured by suppressing the rise of the vehicle speed. When the decompression by the ABS control is executed after the execution of the forced decompression six times or more, the next forced decompression is omitted.
It is possible to reliably prevent the brake oil pressure from excessively decreasing, the braking force from decreasing, and the deceleration (deceleration G) from becoming too small. However, in the present embodiment, the forced decompression following the omitted forced decompression is performed, but the forced decompression after the omitted forced decompression may be omitted. .

Next, the pressure reduction control at the end of the split road surface executed by the control unit 24 will be described with reference to FIG.
0 will be described. This pressure reduction control is similar to the pressure reduction control for the split road surface countermeasures, and the first channel or the low friction road surface side channel 1 This control is executed at the end of the split road surface during the ABS control for the brake oil pressure of the second channel. The change in the brake oil pressure at the end of the split road surface traveling is smoothed, and the rate of change of the deceleration (deceleration G) is reduced. Control. First, various data are read (S80), and then it is determined whether or not the traveling road surface is a split road surface (S81).
This determination is made based on the friction coefficient values Mu1 and Mu2. If the friction coefficient values Mu1 and Mu2 are not equal to each other on a split road surface, a flag Fs indicating that the vehicle is traveling on the split road surface is set in S82, and the process returns.

Meanwhile, when the split road surface is resolved, the determination result in S81 becomes No, and the flow shifts to S83, where it is determined whether the flag Fs is 1 or not. When it is determined that the vehicle is not on the split road surface for the first time this time, that is, when the vehicle is no longer on the split road surface on the previous time on the split road surface, the flag Fs is 1, and the process proceeds from S83 to S84,
The counter I for counting the number of times of forcible pressure reduction is set to 2, then the flag Fs is reset in S85, and the timer T is started. Next, in S86, it is determined whether or not the counter I is 0. Since the counter I is 2 immediately after the split road surface is resolved, the determination result is
No, the process shifts from S86 to S87, and it is determined whether or not the count time T of the timer T has reached 256 ms.

At first, since T is less than 256 ms,
The process proceeds from S87 to S92, and it is determined whether or not the pressure reduction of the ABS control for the brake oil pressure corresponding to the high friction road surface side has been performed (S92).
Is determined based on the braking pressure control signal in the same manner as S68.
As long as the pressure reduction of the ABS control is not executed, the process returns as it is, and thereafter, as described above, S80 to S83, S8
6, S87 is executed, and the count time T of the timer T is 2
When the time reaches 56 ms, the flow shifts from S87 to S88, and forcible pressure reduction is performed. This forced decompression
Similar to S56 in FIG. 9, the process is performed by operating the relief valve 20b or the relief valve 21b of the high friction road surface side channel at a predetermined duty ratio for a predetermined time (for example, 8 ms).

Next, the counter I is decremented by 1 (S89), and the timer T is cleared (S90).
Next, a timer T is started in order to measure the timing of the next pressure reduction (S91), and the process returns. next,
Similarly, S80 and subsequent steps are executed, but the next 256 ms
Until the timing of S87, the process proceeds from S87 to S92, and returns to S92 until the depressurization of the ABS control is not executed. The above is repeated, and at the next timing of 256 ms, the second forced operation is performed in S88. The decompression is performed. As a result, the counter I becomes 0, so that the next time the determination result in S86 is Yes, the process returns from S86, and no forcible decompression is performed thereafter.

That is, if the pressure reduction of the ABS control is not executed after the end of the split road surface, the forced decompression of 8 ms is executed only twice in a cycle of 256 ms. By the way, if the pressure reduction of the ABS control is executed after the start of this control, the process returns after the counter I is cleared in S93. That is, when the depressurization of the ABS control is executed, the forcible depressurization of S88 is not executed thereafter.

Next, the operation of the above-described ABS control will be described by taking the ABS control for the first channel as an example.
This will be described with reference to the time chart of FIG. In the ABS non-control state at the time of deceleration, the brake pressure generated in the master cylinder 18 is gradually increased by the depression operation of the brake pedal 16, and as shown in FIG. 11 (c), the wheel speed Vw1 of the left front wheel 1 changes. When the amount (deceleration DVW1) reaches -3G, the lock flag Flok1 of the first channel is set to 1 as shown in FIG.
Shift to BS control.

In the first cycle immediately after the start of this control, since the friction coefficient value Mu1 is set to 3 indicating a high friction road surface (see S2 and S3 in FIG. 2), the rough road flag Fak
Is zero and the pseudo vehicle speed Vr calculated from the wheel speed Vw1 belongs to, for example, a middle speed range, HM2 for a middle speed and high friction road surface is selected as a running condition parameter, and various controls are performed based on the running condition parameter. A threshold is set. That is, various control threshold values preset in the column of HM2 in the control threshold value setting table of FIG. 7 are read.

Next, the slip ratio S obtained from the wheel speed Vw1
1. The wheel deceleration DVw1 and the wheel acceleration AVw1 are compared with various control thresholds. In this case, the phase value P1 is changed from 0 to 2 as shown in FIG. Is maintained at the level immediately after the pressure increase, as shown in FIG. And the slip ratio S1 is 2
When the value falls below the −3 intermediate slip ratio threshold value Bsg (90%), the phase value P1 is changed from 2 to 3.
At this time, the relief valve 20b of the first valve unit 20 is turned ON / OFF according to a predetermined duty ratio, and the braking pressure decreases at a predetermined gradient from time tb as shown in FIG. As a result, the braking force gradually decreases, and the rotational force of the front wheels 1 starts to recover. When the brake pressure is further reduced and the wheel deceleration DVw1 drops to the 3-5 intermediate deceleration threshold B35 (0G), the phase value P1 is changed from 3 to 5, as shown in FIG. Then, the braking pressure is maintained at the reduced level from time tc.

When the state of the phase V continues and the slip ratio S1 exceeds the 5-1 slip ratio threshold value Bsz (90%), as shown in FIG.
l is set to 1. As a result, the ABS control in the first channel shifts to the second cycle from time td. At this time, the phase value P1 is forcibly changed to 1. Immediately after the transition to the phase I, the on-off valve 20a of the first valve unit 20 is set to the 100% duty ratio in accordance with the initial rapid pressure increase time Tpz set based on the duration of the phase V in the first cycle. As shown in FIG. 3E, the braking pressure is increased at a steep gradient. After the initial rapid increase time Tpz has elapsed, the on-off valve 20a is turned ON / OFF according to a predetermined duty ratio. The braking pressure gradually increases with a gentler gradient. Thus, immediately after the transition to the second cycle, the braking pressure is reliably increased, and a good braking pressure is secured.

On the other hand, after the second cycle, FIG.
As shown in the flowchart, an appropriate friction coefficient value Mu1 is determined in accordance with the wheel deceleration DVw1 and the wheel acceleration AVw1 in the previous cycle, and corresponds to a traveling state parameter corresponding to these friction coefficient values and the vehicle speed Vr. Since the control threshold value to be performed is selected from the control threshold value setting table of FIG. 8, a precise control of the braking pressure according to the traveling state is performed. Thereafter, in the state of the phase V in the second cycle, for example, when it is determined that the slip ratio S1 is larger than the 5-1 slip ratio threshold value Bsz,
The phase value P1 is set to 1, and the process shifts to the third cycle. Further, as described with reference to FIG. 5, the control threshold value is corrected in accordance with the magnitude of the steering angle θ at the time of determining a rough road, and the representative friction coefficient value Mu is also determined at the time of determining a non-rough road condition or determining a rough road. Is not 3, which indicates a high friction road surface, the control threshold value is similarly corrected when the steering angle θ shows a relatively large value, so that the braking pressure can be controlled more precisely according to the running state. become.

Next, regarding the pressure reduction control for the split road surface countermeasure shown in FIG. 9, the wheel speed of the wheel on the high friction road surface side and the brake oil pressure are shown by dotted lines in FIG. Thus, the rate of increase in brake oil pressure is reduced.
Then, when the deceleration of the wheel becomes -0.3 G, the ABS control for the brake device of the wheel is started, and in the same manner as the above-mentioned ABS control, the ABS control of the brake hydraulic pressure holding, pressure reduction, holding, and pressure increase patterns Is executed. FIG.
FIG. 5 shows a brake oil pressure on the high friction road surface side and a brake pressure control signal in the split road surface countermeasure pressure reduction control, and the pressure reduction by the ABS control is executed after the forced pressure reduction is performed six times or more. Since the forced pressure reduction immediately after the pressure reduction by the ABS control is omitted, an excessive decrease in the brake oil pressure can be suppressed, and an excessive decrease in the braking force can be prevented.

As described above, in the pressure reduction control for the split road surface countermeasures, the pressure increase rate of the brake hydraulic pressure of the wheels on the high friction road surface side is reduced by executing the forced decompression six times or more, and the control of the wheel is controlled. Suppress excessive power,
A decrease in running stability and generation of spin can be reliably prevented. 6
When the pressure reduction by the ABS control is executed after the forced pressure reduction of at least one time, the forced pressure reduction immediately after the pressure reduction by the ABS control is omitted, so that the brake hydraulic pressure excessively decreases, that is, the braking force decreases. It can be prevented from being done too much. In the decompression control for the split road surface countermeasures, forcible decompression is performed at a cycle of 128 ms for a period of 8 ms.
The period of s is an example, and is not limited to this. When the period and the period are changed, the minimum number of times of forcible pressure reduction performed “six or more times” is also appropriately changed. .

By the pressure reduction control at the end of the split road surface shown in FIG.
In order to execute the forced decompression of 8 ms twice in the cycle of
As shown in FIG. 12, since the brake oil pressure changes smoothly without sudden increase, the rate of change of the deceleration (deceleration G) can be suppressed to a small value. In addition, after the pressure reduction by the ABS control is performed, the forcible pressure reduction is stopped, so that an excessive decrease in the brake oil pressure is prevented, the braking force is secured, and the deceleration G can be secured. In the decompression control at the end of the split road surface, forcible decompression is performed at a cycle of 256 ms for eight times.
Although the deceleration in the period of ms is performed twice, these numerical values are merely examples, and the present invention is not limited thereto. A shorter cycle or period may be used, and the pressure is reduced three or more times. You may do so.

[Brief description of the drawings]

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

FIG. 2 is a flowchart of a road surface friction coefficient estimation process.

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

FIG. 4 is a diagram of a map of a vehicle speed correction value.

FIG. 5 is a flowchart of a control threshold value setting process.

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

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

FIG. 8 is a chart of a table in which correction values of various control thresholds are set.

FIG. 9 is a flowchart of pressure reduction control for a split road surface measure.

FIG. 10 is a flowchart of pressure reduction control at the end of a split road surface.

FIG. 11 is an operation time chart of the anti-skid brake device.

FIG. 12 is a time chart of brake hydraulic pressure related to pressure reduction control for split road surface measures and pressure reduction control at the end of the split road surface.

[Explanation of symbols]

 1, 2 front wheel 3, 4 rear wheel 11-14 brake device 15 brake control system 27-30 wheel speed sensor 20, 21, 23 first to third valve unit 20a, 21a, 23a on-off valve 20b, 21b, 23b relief valve 24 control unit

──────────────────────────────────────────────────の Continued on the front page (72) Inventor Reihiro Watanabe 3-1 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Inside Mazda Co., Ltd. (72) Keizumi Masu 3-1 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Naru (56) References JP-A-1-197158 (JP, A) JP-A-4-176766 (JP, A) JP-A-1-164667 (JP, A) (58) Fields investigated (Int) .Cl. ⁷ , DB name) B60T ^7/ 12-8/96

Claims (2)

(57) [Claims] 1. Anti-skid control for operating a wheel speed detecting means for detecting a rotation speed of a wheel, a hydraulic adjusting means for adjusting a brake oil pressure, and a hydraulic adjusting means based on a wheel speed detected by the wheel speed detecting means. Means for detecting the friction state of the road surface based on the wheel speed detected by the wheel speed detection means, and the road surface friction state detected by the road surface friction state detection means. A split road surface detecting means for detecting a split road surface based on the road surface friction state, and a brake oil pressure of a wheel on a low friction road surface side when traveling on the split road surface detected by the split road surface detecting means and by the anti-skid control means. During the control, the brake pressure of the wheels on the high friction road surface side is forcibly reduced every first predetermined time via the hydraulic pressure adjusting means. (1) During the control by the anti-skid control means and after the end of the split road running, the brake oil pressure controlled by the first pressure-reducing control means is increased by a second predetermined time longer than a first predetermined time. And a second pressure reduction control means for forcibly reducing pressure every predetermined number of times. 2. During the control by the second pressure reduction control means,
2. The control device according to claim 1, further comprising a prohibition unit that prohibits forced decompression by the second decompression control unit when pressure reduction by the anti-skid control unit is performed on the brake hydraulic pressure to be controlled. Anti-skid brake device for vehicles.