JP3040497B2 - 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 a vehicle which performs anti-skid control for controlling a slip ratio of a drive wheel by controlling a brake fluid pressure.

[0002]

2. Description of the Related Art Conventionally, in order to prevent a wheel from being locked or skid due to an excessive braking force during braking, a slip ratio of each wheel is calculated and the slip ratio is separately set. There is known an anti-skid control for controlling a braking force of each wheel to obtain a target slip ratio.

[0003] This kind of anti-skid brake device is
For example, as disclosed in Japanese Patent Publication No. 56-22736,
A wheel speed sensor that detects the rotation speed of the wheel, and an electromagnetic control valve that adjusts the brake fluid pressure, according to a speed change rate (acceleration or deceleration) based on the wheel speed detected by the wheel speed sensor during braking The vehicle body speed of the vehicle is reduced, and the braking effect is enhanced by repeating a control cycle of the brake fluid pressure for maintaining, reducing or subsequently increasing the brake fluid pressure so that the slip ratio of the wheel becomes a predetermined value. .

Further, an anti-skid brake in which the duration of the rapid pressure increase stage is controlled in accordance with the amount of increase in the braking pressure applied to the wheels in the previous anti-skid control cycle, thereby providing appropriate braking performance. A control device is disclosed in Japanese Patent Publication No. 57-4544. In the anti-skid brake control device disclosed in the above-mentioned Japanese Patent Publication No. 57-4544, a duty valve arranged in a brake fluid pressure control system in accordance with a change in the braking pressure of the wheels in the previous anti-skid control cycle. To control the pressure applied to the wheels by controlling the pressure on the secondary side of the valve, that is, the output side, to control the pressure applied to the wheels. Can be said to be improved.

[0005]

The braking pressure applied to the wheels is the brake fluid pressure on the secondary side of the duty valve. The pressure on the secondary side of the valve is the pressure on the primary side of the valve, that is, the brake pedal. Is affected by the original pressure of the brake fluid pressure applied to the master cylinder. As the source pressure increases, the pressure on the secondary side of the valve also increases. Then, the pressure on the primary side of the valve changes according to the operation of the brake pedal. Therefore, in order to accurately control the braking pressure applied to the wheels, it is necessary to control the duty of the valve in consideration of the fluctuation of the brake fluid pressure on the primary side of the valve or the operation state of the brake pedal.

According to the present invention, it is possible to provide excellent braking performance irrespective of fluctuations in the brake fluid pressure on the primary side of a brake fluid pressure control valve of an anti-skid brake control hydraulic mechanism. It is an object of the present invention to provide an anti-skid brake device that can be used.

[0007]

According to the present invention, there is provided an anti-skid brake device for a vehicle configured to achieve the above object, wherein a master cylinder generates a larger brake fluid pressure as the operation amount of the brake pedal increases in accordance with the operation of the brake pedal. When,
By controlling the opening and closing of a valve member provided in the middle of a hydraulic circuit that communicates with a wheel cylinder that applies a braking force to wheels by the supply of the brake hydraulic pressure, the brake hydraulic pressure for driven wheel or drive wheel braking is increased. An anti-skid control means for controlling a slip ratio of a driven wheel or a drive wheel by controlling the pressure, and a pressure increase of a control cycle by the anti-skid control means according to a magnitude of a brake fluid pressure generated in response to a brake pedal operation. Gain changing means for changing a control gain in a step, wherein the gain changing means is configured such that when the brake fluid pressure is taken on a horizontal axis and the control gain is taken on a vertical axis, the control gain is changed at a start end and an end.
It is characterized in that the control gain in the pressure increasing stage is changed according to a map characteristic showing a mountain-shaped diagram that is small and large at the center .

[0008] In a preferred aspect, the gain changing means includes:
When the brake fluid pressure generated in response to the operation of the brake pedal is high, the control gain in the pressure increasing step is reduced. The gain changing means may be configured to decrease the control gain in the pressure increasing step when the brake fluid pressure generated in response to the operation of the brake pedal is low. The gain changing means does not change the pressure increase gain by the brake fluid pressure when the brake fluid pressure generated in response to the operation of the brake pedal takes an intermediate value.

The gain changing means may be configured to change the control gain in the pressure increasing step in accordance with the amount of depression of the brake pedal or the magnitude of the depression force, which is an amount related to the brake fluid pressure. The above anti-skid brake device is
A pressure sensor for detecting a brake hydraulic pressure generated by operating the brake pedal may be further provided.

[0010]

According to the present invention, the anti-skid control means controls the brake fluid pressure for braking the driven wheel or the driven wheel, thereby controlling the slip ratio of the driven wheel or the driven wheel. In this case, specifically, the anti-skid control means is constituted by a control unit for controlling the brake device provided in the hydraulic control mechanism of the brake device, and a hydraulic control valve that is duty-controlled by a signal from the control unit. Can be. The primary side of the hydraulic control valve communicates with a master cylinder, and an operation force of a brake pedal is applied to the master cylinder. Further, the brake fluid pressure on the secondary side of the hydraulic control valve gives a braking force to the wheels. The control unit controls the hydraulic pressure on the secondary side of the hydraulic control valve to control the duty ratio of the hydraulic control valve so as to achieve the target slip ratio determined in consideration of various conditions. In this case, in the present invention, in determining the duty ratio, taking into account that the brake fluid pressure on the secondary side of the hydraulic control valve is affected by the pressure on the primary side,
The control gain in the pressure increasing stage of the control cycle in the anti-skid control is changed according to the primary pressure, that is, the brake fluid pressure that generates the pressure corresponding to the operation of the brake pedal.

When the brake fluid pressure on the primary side is large, the pressure increasing gain is reduced. Also, when the brake fluid pressure on the primary side is small, the pressure increasing gain is reduced. In this way, the brake fluid pressure applied to the wheels, that is, the braking pressure, can be controlled without being affected by the fluctuation of the brake fluid pressure on the primary side of the hydraulic control valve.

[0012]

Embodiments of the present invention will be described below in detail with reference to the drawings. Schematic view of a vehicle structure 1 is blurring of the engine and the wheels of a vehicle anti-skid control is applied according to the present invention - is a system diagram of a key control hydraulic circuit.

As shown in FIG. 1, in the vehicle according to this embodiment, front wheels 1 and 2 are driven wheels on the left and right, driving wheels are left and right, and the output torque of the engine 5 is transmitted from the automatic transmission 6 to the propeller. Shaft 7, differential device 8 and left and right drive shafts 9,
The power is transmitted to the right and left rear wheels 3 and 4 via the transmission 10. Each of the wheels 1 to 4 receives the disks 11a to 14a that rotate integrally with the wheels 1 to 4 and the supply of the braking pressure, and receives these disks 11a to 14a.
Brake devices 11 to 14 each including a caliper 11b to 14b for braking the rotation of the vehicle are provided, and a brake control system 15 for performing a brake operation of these brake devices 11 to 14 is 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 cylinder 18 for generating a braking pressure corresponding to the depression force increased by the booster 17. Have. The front-wheel braking pressure supply line 19 guided from the master cylinder 18 branches into two paths, and these front-wheel branch braking pressure lines 19a and 19b are connected to the brake devices 11 and 12 of the left and right front wheels 1 and 2, respectively. Caliper 11
a, 12a and the left front wheel 1
A first valve unit 2 composed of an electromagnetic open / close valve 20a and an electromagnetic relief valve 20b is connected to one of the front-branch branch braking pressure lines 19a communicating with the brake device 11 of the first embodiment.
0, and the first front wheel branch braking pressure line 19b which communicates with the brake device 12 of the right front wheel 2
Like the valve unit 20, the electromagnetic on-off valve 21a
And a second valve unit 21 which is also comprised of an electromagnetic relief valve 21b.

On the other hand, the first and second brake pressure supply lines 22 guided from the master cylinder 18
Like the valve units 20 and 21, the electromagnetic on-off valve 2
A third valve unit 23 comprising a solenoid valve 3a and an electromagnetic relief valve 23b is also installed. The rear wheel braking pressure supply line 22 branches into two paths downstream of the third valve unit 23. Then, these rear wheel branch braking pressure lines 22a, 22b are connected to the calipers 13b, 14 of the brake devices 13, 14 in the left and right rear wheels 3, 4.
b.

A control unit 24 for controlling the brake control system 15 is provided. The control unit 24 is provided with a brake signal from a brake switch 25 for detecting ON / OFF of the brake pedal 16,
Wheel speed sensor 26 for detecting the rotation speed of each wheel
And the wheel speed signals from the first to third valve units 20 to 29.
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 slipping.
That is, anti-skid control is performed. That is, based on the wheel speed indicated by the wheel speed signals from the wheel speed sensors 27 to 30, the control unit 24 controls the first to third valve units 20, 21,.
By controlling the opening / closing valves 20a, 21a, 23a and the relief valves 20b, 21b, 23b in duty ratio control, the front wheels 1, 2 and the rear wheels 3, 4 are controlled by the braking pressure according to the slip state. Power is provided. In addition, each relief valve 20b in the first to third valve units 20, 21, and 23,
The brake oil discharged from the cylinders 21b and 23b is supplied to the master cylinder 18 via a drain line (not shown).
Is returned to the reservoir tank 18a.

In the non-anti-skid control state, no braking pressure control signal is output from the control unit 24, and therefore, as shown in the drawing, the relief valves 20b, 2b,
1b and 23b are held closed, and the on-off valves 20a, 21a and 23a of the units 20, 21 and 23 are held open, respectively.
The braking pressure generated in the master cylinder 18 in response to the pedaling force of the brake pedal 6 is applied to the left and right front wheels 1 and 2 and the rear wheels 3 and 4 via the front wheel braking pressure supply line 19 and the rear wheel braking pressure supply line 22. A braking force is supplied to the front wheels 1 and 2 and the rear wheels 3 and 4 in accordance with these braking pressures.

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

Further, the control unit 24 estimates a road surface friction coefficient, and calculates a pseudo vehicle speed of the vehicle using the road surface friction coefficient. The control unit 24 controls the rear wheel speeds obtained from the signals from the wheel speed sensors 28 and 29 and the wheel speed sensors 26 and 2.
The slip ratio is calculated based on the following relational expression from the wheel speeds of the left and right front wheels 1 and 2 indicated by the signal from 7 and the pseudo vehicle body speed.

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

Further, the control unit 24 as a start condition for starting the anti-skid control determines the locked state of each wheel based on the wheel deceleration or the slip ratio, and determines whether the first to third valve units 2 are in the locked state.
A phase determination process for determining the control amount of the brake fluid pressure for 0, 21, and 23 is performed.
In this case, the control unit 24 has a value of brake fluid pressure level P ₁ that is set in advance corresponding to each phase, therefore, automatically brake fluid pressure is determined corresponding the phase is determined. The control unit 24 includes a phase 0 indicating a non-anti-skid control state, a phase I indicating an increased pressure state during anti-skid control, a phase II indicating a holding state after the increased pressure, Decompression phase
III, a phase IV indicating a rapid decompression state and a phase V indicating a holding state after decompression are selected.

In this case, when the phases III and IV relating to the pressure reduction are selected, the first to third valve units 20 and 21 are selected according to the depressing speed of the brake pedal 16.
The control gains of the duty control for and 23 are changed. Then, the control unit 24, the brake fluid after having set the pressure level P _1, the brake pressure control signal first to third valve units 20 in accordance with the control amount corresponding to the phase value set for each wheel, 2
1 and 23, respectively. As a result,
The braking pressure of the front wheel branch braking pressure lines 19a, 19b and the rear wheel branch braking pressure lines 22a, 22b on the downstream side of the third valve units 20, 21, 23 is increased or decreased, or increased or decreased. The anti-skid control is performed by repeatedly executing a control cycle such as maintaining the pressure.

The process of estimating the road surface friction coefficient is specifically performed as follows in accordance with, for example, the flowchart of FIG. The control unit 24 reads various data in step S1, and determines in step S2 whether the anti-skid flag F _ABS is set to 1. That is, it is determined whether the anti-skid control is being performed. The anti-skid flag F _ABS is set to 1 when the above parameters such as the slip ratio and deceleration exceed predetermined threshold values, and when the brake switch 25 is switched from ON to OFF. Are reset to 0. When the control unit 24 determines that the anti-skid flag F _ABS has not been set to 1, the process proceeds to step S3 and sets 3 indicating a high friction road surface as the friction coefficient value MU.

When the control unit 24 determines in step S2 that the anti-skid flag F _ABS is set to 1, that is, when it is determined that the anti-skid control is being performed, the control unit 24 proceeds to step S4 to execute the operation in the previous cycle. deceleration DW ₁ is -20g (g is the gravitational acceleration)
Together to determine whether less or not, when it is determined that YES in terms of acceleration AW ₁ in same prior cycle proceeds to step S6 determines whether the larger 10 g, N
When it is determined to be O, step S6 is executed and the coefficient of friction M
A value ₁ indicating a low friction road surface is set as U1.

Further, the control unit 24, when the deceleration DW ₁ in step S4 is determined to be not smaller than -20g moves to step S7 by skipping step S6, whether the acceleration AW ₁ is greater than 20g while the determination, sets 3 as a friction coefficient value MU ₁ executes step S8, when the result of determination is YES,
When the result of determination is NO sets 2 showing a middle friction road surface as a friction coefficient value MU ₁ executes step S9.

On the other hand, the process of calculating the pseudo vehicle speed is specifically performed as follows according to the flowchart of FIG. That is, the control unit 24
On reading the various data T1, in step T2 and determines the highest wheel speed W _MX out of the wheel speed W ₁ to _W-4 indicated by the signal from the sensor 26 to 29, the wheel speed W in step T3 _The amount of change in wheel speed ΔW _MX per sampling period Δt of _MX is calculated.

[0027] Then, the control unit 24 reads the vehicle speed correction value C _VR corresponding to the friction coefficient value MU from the map shown in FIG. 4 executes step T4, the vehicle speed correction value C _VR in step T5 Then, it is determined whether or not the wheel speed change amount ΔW _MX is small. When it is determined that the wheel speed change amount ΔW _MX is smaller than the vehicle speed correction value C _VR , step T6 is executed to subtract a value obtained by subtracting the vehicle speed correction value C _VR from the previous value of the pseudo vehicle speed V _R. This time replace with the value. Therefore, the pseudo vehicle speed V _R decreases at a predetermined gradient according to the vehicle speed correction value C _VR .

On the other hand, the control unit 24
In step T5, the wheel speed change amount ΔW_MXIs the vehicle speed correction value
C_VRWhen it is judged that it is larger, that is, the above-mentioned highest wheel
Speed W _MXIndicates an excessive change, the process proceeds to Step T7.
Is the pseudo vehicle speed V_RFrom maximum wheel speed W_MXIs the value obtained by subtracting
Predetermined value V_DIt is determined whether it is greater than. That is,
High wheel speed W_MXAnd pseudo vehicle speed V_RThere is a big gap between
It is determined whether it is. And the big difference
If not, the above-described step T6 is executed to execute the pseudo vehicle speed V
_RFrom the previous value of the vehicle speed correction value C_VRNow subtract the value
Replace with times value.

Further, the control unit 24, when a large gap occurs between the highest wheel speed W _MX and the pseudo vehicle body speed V _R is the maximum wheel speed W _MX pseudo vehicle body speed V _R by performing the step T8 replace. In this way, the estimated vehicle speed V _R of the vehicle is gradually updated every sampling period Δt according to the wheel speeds W ₁ to _W-4.

Next, the anti-skid control for the front wheels will be described with reference to FIGS. The control unit 24 reads various data prior to the anti-skid control (step Q1). In the non-anti-skid control state, when a wheel lock state or a slip state is detected due to the wheel deceleration, the slip ratio, etc. exceeding respective threshold values due to the depression operation of the brake pedal 16, the anti-skid control is performed. Is started. For example, when the wheel deceleration threshold value is set to -3.0 g, as shown in FIG.
When W ₁ reaches -3.0Gg, satisfies one of the conditions for starting the anti-skid control.

The control in step Q2 unit 24 depression speed of the brake pedal 16 to determine whether it is less than a predetermined value, sets the value of the depression speed flag F _s in accordance with the determination result (step Q3, Q4 )
. In this case, if the stepping speed is equal to or less than a predetermined value, 1 is set.
Otherwise, set to 0. Next, the control unit 24 determines whether or not the anti-skid control is being performed (step Q5). If the anti-skid control is not set, the control unit 24 proceeds to the return as it is. If it is determined that the anti-skid control has been started, the control unit 24
Then, it is determined whether or not the control cycle of the brake fluid pressure is the first cycle and the pressure reducing step of the cycle is performed (step Q6). Brake fluid pressure control after anti-skid control is started, it is determined whether the first cycle, the determination is YES, that is, in the first cycle immediately after start of control, the friction coefficient value MU ₁ as described above the high-friction road surface Since it is set to 3 as shown, the control unit 24 sets a threshold value corresponding to a high friction road surface.

The control unit 24, the slip ratio S ₁ that when starting the anti-skid control is calculated from the wheel speed W _1, deceleration DW _1, it compares the acceleration AW ₁ and the threshold. In this case, when the initial slip ratio threshold value B ₁ is being set for example to 90%, when the slip ratio S ₁ is showing a 96%, the control unit 24, the brake fluid as shown in FIG. 7 (b) The pressure phase value P ₁ is changed from 0 to 2. Therefore, the brake fluid pressure, that is, the braking pressure, is as shown in FIG.
It is maintained at the level immediately after the pressure increase. Then, for example, when the slip ratio S ₁ is decreased from 90%, the control unit 24 changes the phase value P ₁ from 2 to 3. Thus, the first cycle pressure reduction step is started. As described above, the determination of the pressure reduction stage in the first brake fluid pressure control cycle after the start of the anti-skid control can be detected by monitoring the change in the slip ratio.

Next, when it is determined that the pressure reduction phase of the first cycle, the control unit 24, whether the value of the depression speed flag F _s is 1, i.e., a trigger for starting the anti-skid control It is determined whether the depressing speed of the brake pedal 16 is equal to or lower than a predetermined value (step Q7). If this determination is YES,
If the depressing speed is lower than the predetermined value, it is further determined whether or not the current depressing amount of the brake pedal 16 is maintained substantially constant, in other words, whether or not the stroke variation of the brake pedal 16 is within a predetermined range. (Step Q8). If it is determined that the amount of depression of the brake pedal 16 is substantially constant, the control unit 24 selects a map A for determining a control gain in the step of reducing the brake fluid pressure (step Q9). As shown in FIG. 8, the characteristic of the control gain given by the map A tends to decrease slightly when the brake pedal depressing speed increases from 0, and then takes a minimum value at a predetermined value of the depressing speed. Starts to increase as the stepping speed increases. Then, the control unit 24 obtains a control gain in the pressure reduction step corresponding to the depressing speed of the brake pedal from the map A.
(Step Q10).

Then, the duty ratio of the relief valve 20b of the first valve unit 20 is calculated based on the pressure reduction control gain (step Q11). In this case, the final duty ratio is obtained by adding a correction by the pressure reduction control gain to the basic duty ratio. However, since the specific calculation procedure itself is known and does not constitute a characteristic part of the present invention, The detailed description is omitted. The control unit 24 drives the relief valve 20b in accordance with the duty ratio calculated in step Q11 to execute duty control (step Q12). This duty control constitutes a part of the brake fluid pressure control by the anti-skid control.

If the determination in step Q7 is NO, that is,
If the stepping speed of the brake pedal is higher than the predetermined value, or the determination in step Q7 is YES, but the determination in step Q8 is NO, that is, the amount of stepping on the brake pedal after entering the anti-skid control varies. In this case, the control unit 24 selects the map B when obtaining the pressure reduction control gain (step S1).
Q13). As shown in FIG. 9, the characteristic of the pressure reduction control gain of the map B is such that the control gain value increases as the stepping speed of the brake pedal increases. In this case, the pressure reduction control gain is set based on the map B, the duty ratio of the relief valve 20b is calculated in the same procedure as described above, and the duty of the relief valve 20b is controlled (steps Q11 and Q12).

Further, when the determination in step Q6 is NO, that is, when the anti-skid control is not the first brake hydraulic pressure control cycle, the control unit 24 executes the normal procedure without referring to the map A or the map B. To set the control gain (Step Q1
4) The duty ratio of the relief valve 20b is controlled by calculating the duty ratio (steps Q11 and Q12).

As described above, the relief valve 20 is operated in accordance with the duty ratio determined according to the stepping speed as described above.
By ON / OFF of b, with Wachi braking force Do push brake fluid decreases at a predetermined gradient from the time t _b, as shown in FIG. 7 (c) is gradually decreased, the rotational speed of the front wheel 1 is recovered Begin to. In this example, since the to obtain the pressure reduction control gain according to depression speed of the brake pedal as described above, it varies according to the pressure gradient is depression speed from the time t _b. When the stepping speed is high, the value of the pressure reduction control gain increases, so that the pressure reduction gradient also increases, so that the braking pressure decreases early and the wheel rotation speed recovers. Therefore, the brake fluid pressure rises sharply due to the sudden depression of the brake pedal, and the anti-skid control is started, so that the wheels are likely to be locked. Thus, the wheel lock can be effectively prevented. Conversely, when the depression speed of the brake pedal is low, the brake fluid pressure is slowly increased by the depression of the brake pedal 16, and the braking force is also moderately exerted. Therefore, in this case, the control gain is reduced to limit the reduction of the braking force in the pressure reduction stage. However, even if the stepping speed of the brake pedal 16 is low, the case where the stepping amount of the brake pedal 16 after entering the anti-skid control is maintained substantially constant is another case. It is considered that such a brake pedal operation is often performed when the road surface friction coefficient is small.However, when traveling on a road surface where the friction coefficient is small, if the brake fluid pressure drop during the pressure reduction stage is insufficient, the wheel Locks that occur before the speed has fully recovered may cause so-called cascade locks. In the control of the present example, the cascade lock as described above is activated when the operation speed of the brake pedal is small so that the brake pedal depressing speed is slow and then the anti-skid control is performed. Judging that the pressure is likely to occur, the pressure reduction control gain is set to a large value. As a result, it is possible to accelerate the reduction of the brake fluid pressure in the pressure reduction stage and to speed up the recovery of the wheel speed. As a result, it is possible to effectively suppress the occurrence of the cascade lock.

In the case where the above-described brake fluid pressure reduction control is performed, the braking pressure is further reduced and the front wheel 1
Deceleration DW ₁ and acceleration AW calculated from the wheel speed W1
_{When 1} becomes 0, the control unit 24 changes the phase value P ₁ from 3 to 5. Accordingly, as shown in FIG. 7 (c), so that the brake pressure from the time t _a is maintained at the level of post-vacuum.

The state of phase V continues and the slip ratio S ₁
Exceeds 90%, the control unit 24
The anti-skid control passes from the time t _d in the second cycle. In that case, control unit 2
_No. 4 forcibly changes the phase value P ₁ to 1. In the anti-skid control as phase value P ₁ is shown in As the 1 second. 7 (c), into the pressure increase phase. The control unit 24 controls the brake fluid pressure applied to the wheels to increase at a predetermined rate by opening the on-off valve 20a and closing the relief valve 20b by duty control.

After the second cycle, as shown in the flow chart of FIG.
An appropriate friction coefficient value MU ₁ according to W ₁ , acceleration AW _1, etc.
There together is determined, the control thresholds corresponding to these friction coefficient values MU ₁ is to be selected, the control of dense braking pressure according to the running condition is performed. FIG. 10 is a flowchart illustrating an example of the pressure increase control of the present example. The control unit 24 stores data such as the wheel speed, the amount of depression of the brake pedal, and the brake fluid pressure on the primary side of the opening / closing valve 20a (detected by a pressure sensor (not shown) (not shown), not shown) in the same manner as in the flow chart at the pressure reduction stage in FIG. Is read (step R1), and it is determined whether or not the anti-skid control is being performed (step R2). If it is the anti-skid control in, it is determined whether become pressure increase phase of the anti-skid control cycle (step R3), in the case of pressure increase step-off valve 2 from the map C in FIG. 11
The pressure increase gain in the anti-skid control for calculating the duty ratio of the on-off valve, which is given in relation to the primary side brake fluid pressure of 0a, is obtained (step R4). As shown in FIG. 11 , the pressure increase gain takes a small value when the brake fluid pressure is low and high, and is set to a normal value when it takes an intermediate value of the brake fluid pressure. If the brake fluid pressure on the primary side is large, the brake fluid pressure on the secondary side of the on-off valve 20a tends to be high. Therefore, if the pressure increase gain is set without considering the brake fluid pressure on the primary side, the secondary side The pressure increase gradient of the brake fluid pressure tends to be higher than usual, which promotes the locking tendency of the wheels. Therefore, when the brake fluid pressure on the primary side is high, it is set smaller than usual.

When the brake fluid pressure on the primary side is small, the depression amount of the brake pedal 16 is small. The anti-skid control performed in such a state indicates that the coefficient of road surface friction is small. . In such a state, if the normal pressure increasing gain is set, the increasing gradient of the braking pressure becomes unnecessarily high and locking tends to occur. Therefore, the pressure increasing gain is set to be small.

As described above, the control unit 24
Calculates the duty ratio of the on-off valve 20a by adjusting the pressure increasing gain (step R5), and controls the duty of the on-off valve 20a in accordance with the duty ratio to thereby control the brake fluid pressure on the secondary side of the on-off valve 20a. Then, the braking pressure applied to the wheels is controlled (step R6). In this case, immediately after the shift to the phase 1, the on-off valve 20b of the first valve unit 20 is relatively large during the initial rapid pressure increase time T _PZ set based on the duration of the phase V in the first cycle. The duty ratio is set, and the braking pressure is increased at a steep gradient as shown in FIG. After the initial rapid pressure increase time T _PZ ends, the on-off valve 20a is turned on / off according to a predetermined duty ratio, and the braking pressure gradually increases according to a gradient that is gentler than the gradient.

According to the present embodiment, regardless of the duty ratio of the rapid pressure increase stage during the time T _PZ and the subsequent gentle pressure increase stage, the duty ratio is calculated according to the brake fluid pressure on the primary side of the on-off valve 20a. A pressure increase gain for controlling the on-off valve 20a is set. The control is also performed for the other wheel W ₂ to _W-4. In the above control, the on-off valve 20a
The primary side brake fluid pressure is detected by a pressure sensor,
Although the pressure increase gain is determined in accordance with the detected value, it is not always necessary to directly detect the primary side brake fluid pressure. As described above, the brake fluid pressure on the primary side of the on-off valve 20a fluctuates according to the depressed state of the brake pedal 16, so that the depressed amount of the brake pedal 16 is detected and the pressure increase gain is set based on the detected amount. May be. Further, a configuration may be adopted in which the pressure applied to the brake pedal 16, that is, the pedaling force is detected, and the pressure increasing gain is set according to the pedaling force.

In the pressure reduction stage of the anti-skid control cycle, there is little need to change the control gain in accordance with the brake fluid pressure on the primary side of the on-off valve 20a. In the pressure reduction stage, the on-off valve 20a is closed, and the relief pressure 20b is duty-controlled to control the braking pressure.
Therefore, in the pressure reduction stage, there is no influence of the fluctuation of the brake fluid pressure on the primary side of the on-off valve 20a.

[0045]

As described above, according to the present invention, the control gain at the pressure increasing stage in the anti-skid control cycle is determined according to the brake fluid pressure generated in response to the operation of the brake pedal. Thus, the braking pressure applied to the wheels can be accurately controlled without affecting the operation of the brake pedal. Therefore, appropriate anti-skid control can be performed according to the present invention. For example, when the brake fluid pressure on the primary side suddenly rises due to sudden depression of the brake pedal and the anti-skid control is started, this influence is exerted on the brake fluid pressure applied to the secondary side wheels, and the wheels are locked. Although it becomes easier, the balance can be achieved by reducing the pressure increasing gain in the pressure increasing step in response to the sudden increase in the brake fluid pressure, so that the wheel lock can be effectively prevented.

When the brake pressure on the primary side is small, the depression amount of the brake pedal 16 is small. The anti-skid control performed in such a state indicates that the coefficient of road surface friction is small. . In such a state, if the normal pressure increasing gain is set, the increasing gradient of the braking pressure becomes unnecessarily high and locking tends to occur. Therefore, the pressure increasing gain is set to be small. Thereby, even when the road surface friction coefficient is small, the tendency to lock can be effectively prevented.

[Brief description of the drawings]

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

FIG. 2 is a flowchart showing a process of estimating a road surface friction coefficient;

FIG. 3 is a flowchart showing a process of calculating a pseudo vehicle body speed;

FIG. 4 is an explanatory diagram of a map used in the calculation processing;

FIG. 5 is a flowchart showing the contents of anti-skid control;

FIG. 6 is a flowchart showing the contents of anti-skid control;

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

FIG. 8 is a graph showing a relationship between an initial pressure reduction control gain and a brake pedal depressing speed in anti-skid control;

FIG. 9 is a graph showing a relationship between an initial pressure reduction control gain and a brake pedal depression speed in anti-skid control.

FIG. 10 is a flowchart showing a gain setting procedure in a pressure increasing stage in an anti-skid control cycle.

FIG. 11 is a graph showing a relationship between a pressure increase gain and a brake fluid pressure in anti-skid control.

[Explanation of symbols]

 1, 2, front wheel 3, 4 rear wheel 20, 21, 23 valve unit 24 control unit 26-39 wheel speed sensor.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-136962 (JP, A) JP-A-3-136693 (JP, A) JP-A-4-135958 (JP, A) JP-A-62-162 74756 (JP, A) JP-A-62-149546 (JP, A) JP-A-2-141356 (JP, A) JP-A 64-63448 (JP, A) JP-A-3-287440 (JP, A) JP-A-4-121260 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B60T 8/32-8/58

Claims (2)

(57) [Claims] 1. A master cylinder which generates a larger brake fluid pressure as the operation amount of the brake pedal is larger, and a wheel cylinder which applies a braking force to a wheel by supplying the brake fluid pressure. Anti-skid control means for controlling the slip ratio of the driven wheel or the drive wheel by controlling the brake fluid pressure for braking the driven wheel or the drive wheel by opening and closing control of a valve member provided in the middle of the communicating hydraulic circuit; and A gain changing means for changing a control gain in a pressure increasing stage of a control cycle by the anti-skid control means in accordance with a magnitude of a brake fluid pressure generated in response to a brake pedal operation; When the horizontal axis represents the brake fluid pressure and the vertical axis represents the control gain , the control gain is
Small at the beginning and end, large at the center
An anti-skid brake device for a vehicle, wherein a control gain in a pressure increasing stage is changed according to a map characteristic showing a simple mountain-shaped diagram. 2. The anti-skid brake device according to claim 1, further comprising a pressure sensor for detecting the brake fluid pressure.