JPH1170868A - Antiskid control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an antiskid control device with a good pedal feeling by regulating the time to limit the movement of a brake pedal. SOLUTION: It is decided whether all the holding valves 21 to 24 are not opened or opened for the period for a specific time, in the antiskid control time, and when it is decided all the holding valves 21 to 24 are not opened, one wheel of plural wheels 1 to 4 is selected, and either one of the holding valves 21 to 24 corresponding to the wheel cylinders 11 to 14 of the selected wheel is to be opened. Consequently, a brake pedal 27 can be stepped on before the driver receives the plate feeling. And pressure reduction valve 31 to 34 corresponding to the wheel cylinders 11 to 14 to open the holding valves 31 to 34 are to be opened when the holding valves 31 to 34 are opened. Consequently, the pressures of the wheel cylinders 11 to 14 are prevented from increasing by opening the holding valves 21 to 24.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anti-skid control device for adjusting a wheel slip that occurs during braking of a vehicle.

[0002]

2. Description of the Related Art Conventionally, an anti-skid control device performs an anti-skid control to avoid a wheel lock by obtaining a slip ratio from a vehicle speed and a wheel speed for each wheel and maintaining a slip state of the vehicle in an appropriate state. ing. The anti-skid control device includes a master cylinder that generates brake fluid pressure in response to a driver's operation of a brake pedal, and a plurality of wheel cylinders that generate brake fluid pressure on each wheel based on the brake fluid pressure generated in the master cylinder. Have. The anti-skid control device controls the slip state of the vehicle by controlling the brake fluid pressure (hereinafter, referred to as W / C pressure) in the wheel cylinder.

[0003] Specifically, the anti-skid control device includes:
When the slip ratio increases and the wheels tend to lock, the brake fluid pressure (hereinafter referred to as W / C pressure) is reduced by releasing the brake fluid in each wheel cylinder to the reservoir, and the locking tendency is released by the reduced pressure. The anti-skid control is performed by controlling the W / C pressure to be maintained when the vehicle is headed for, and increasing the W / C pressure at a predetermined timing when the locking tendency is released.

[0004]

In the above-described apparatus, the W / C pressure is increased based on the brake fluid pressure generated by the master cylinder. A predetermined holding valve provided in a pipe connecting the cylinder and the wheel cylinder is closed so that brake hydraulic pressure generated in the master cylinder is not transmitted to the wheel cylinder.

However, when the holding valve is shut off, the movement of the brake pedal is limited. If the time during which the movement of the brake pedal is limited becomes long,
There is a problem in that the driver feels as if the brake pedal cannot be depressed (hereinafter, referred to as "plate feeling"), thereby deteriorating the pedal feel. The present invention has been made in view of the above circumstances, and has as its object to provide a good pedal feel anti-skid control device by adjusting the time during which the movement of the brake pedal is restricted.

[0006]

Means for Solving the Problems In order to achieve the above object, the present inventors have studied a control method of an anti-skid control device. The anti-skid control device performs anti-skid control by independently increasing, maintaining, and reducing the W / C pressure corresponding to each wheel.

FIG. 9 shows a time chart of the anti-skid control together with the operation amount of the brake pedal.
9A shows a comparison between the vehicle body speed and the wheel speed, FIG. 9B shows an opening / closing timing of the holding valve,
(C) shows the opening and closing timing of the pressure reducing valve, and (d) shows W /
(E) returns the brake fluid released to the reservoir to the master cylinder without using a pump,
(F) returns the brake fluid released to the reservoir toward the master cylinder using a pump,
It shows the operation amount of the brake pedal in a so-called system with a pump.

As shown in FIG. 1, when the anti-skid control starts, the pressure reduction and the holding control are sequentially performed. Accordingly, during this time, the holding valve is always shut off, so that the brake fluid pressure generated in the master cylinder is not transmitted to the wheel cylinder. As described above, when the holding valve is shut off, the movement of the brake pedal is restricted, so that the driver receives the gap between the boards. Therefore, if the holding valve is not shut off for a long time, the driver Is not affected by the feeling of plate, and is considered not to deteriorate the pedal feel.

Based on the above study, the present invention employs the following technical means. In the invention described in claim 1, the anti-skid control means is configured to inhibit the flow of the brake fluid in all of the plurality of pipes during the anti-skid control for a first predetermined time (KT1) or more. , At least one of the plurality of wheels (1 to 4) is selected, and the holding valves (21 to 24) corresponding to the wheel cylinders (11 to 14) of the selected wheels are set in the communicating state. The brake fluid is allowed to flow between the master cylinder (16) and the wheel cylinders (11 to 14).

In this manner, the master cylinder (16) and the wheel cylinder (1) for reducing the pressure are used for the first predetermined time (KT1) or more, which is earlier than the time when the driver can feel the plate feeling.
When the flow of the brake fluid between 1 to 14) is prohibited, the holding valve (21 to 21) corresponding to the wheel cylinder (11 to 14) in at least one of the plurality of wheels (1 to 4). 24) to allow the brake fluid to flow between the master cylinder (16) and the wheel cylinders (11 to 14), the brake pedal (27) can be provided before the driver feels a flat feeling. ) Can be performed. This allows
A good anti-skid control device for the pedal feel can be obtained.

The time when the driver can feel the plate feeling is the first time.
Beyond the predetermined time (KT1), a second predetermined time (KT1)
2) Assuming that the time has elapsed, if any of the holding valves (21 to 24) is in a communicating state within this time, the driver does not feel a plate feeling. Therefore, the plurality of wheels (1 to 4) are set only when the flow of the brake fluid is not allowed to flow in all of the plurality of pipelines during the second predetermined time (KT2). ), At least one wheel is selected, and the holding valve (21-2) corresponding to the wheel cylinder (11-14) of the selected wheel is selected.
4) may be set to a communication state.

According to the third aspect of the present invention, the time for which the holding valves (21 to 24) are in the communicating state is changed according to the pressure of the wheel cylinders (11 to 14) on the selected wheel. And If the selected valve keeps the pressure of the wheel cylinders (11 to 14) at a predetermined pressure and the holding valve is kept in communication for a long time, the pressure of the wheel cylinders (11 to 14) increases greatly. Would. Therefore, according to the pressure of the wheel cylinder (11 to 14) at the selected wheel, the holding valve (2)
By changing the time during which the communication states of the wheel cylinders 1 to 24) are changed, it is possible to prevent the pressure of the wheel cylinders (11 to 14) from being greatly increased.

In the invention described in claim 4, the anti-skid control means sets the pressure reducing valves (31-34) corresponding to the selected wheels together with the holding valves (21-24) in communication with each other and selects the anti-skid control means. Wheel cylinder (11-
It is characterized in that the brake fluid is allowed to flow between the pipeline corresponding to (14) and the reservoir (37, 39).

As described above, if the pressure reducing valves (31-34) are brought into communication with the holding valves (21-24),
By setting the holding valves (21 to 24) in the communicating state, the pressure of the wheel cylinders (11 to 14) does not increase, and it is possible to prevent the driver from feeling flat.
In the invention described in claim 5, the anti-skid control means selects a wheel which has passed the most time since the previous pressure increase control was performed, among the plurality of wheels (1 to 4). It is characterized by becoming.

The wheel which has passed the most time since the previous pressure increase control has been performed has been running for a long time since the previous pressure increase output was executed, and therefore the W / C pressure was not so high and increased. It seems that there is room to press. Therefore, by selecting such a wheel, anti-skid control can be more appropriately performed. Further, as shown in claim 6,
If the wheel with the lowest slip ratio is selected, the wheel can be more specifically prevented from slipping. And Claim 7
As shown in (2), a wheel having the smallest sum of the time during which the pressure increase output was performed may be selected from the previous pressure decrease output to the present. That is, it is considered that the W / C pressure is lower in the wheel with the shortest sum of the time during which the boosting output is performed than in the other wheels, so that the desired boosting control can be performed while preventing the wheel from slipping. It can be carried out.

[0016]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a first embodiment of the present invention. FIG. 1 is a schematic diagram illustrating a configuration of an anti-skid control device to which the present invention is applied. As shown in FIG. 1, a front right wheel 1, a front left wheel 2, a rear right wheel 3, and a rear left wheel 4
Are respectively provided with wheel speed sensors 5 to 8 of an electromagnetic pickup type or an electric resistance element (MRE) type, and generate a pulse signal according to the rotation of each wheel 1 to 4.

Wheel cylinders 11 to 14 are disposed on the wheels 1 to 4, respectively. The brake fluid pressure from the master cylinder 16 is supplied through holding valves 21 to 24 as valve means and hydraulic lines. It is sent to each wheel cylinder 11-14. Note that the master cylinder 16 is
7, a brake fluid pressure is generated, and the depression state of the brake pedal 27 is detected by a stop switch 29.

Further, the wheel cylinders 11, 14 are connected to a reservoir 37 via pressure reducing valves 31, 34, and the wheel cylinders 32, 33 are connected to a reservoir 39 via pressure reducing valves 32, 33. Each of the holding valves 21 to 24 and the pressure reducing valves 31 to 34 is an electromagnetic two-position valve having a communication position and a shutoff position. The holding valve 21
Bypass valves 41 to 44 are provided upstream and downstream of ２４24 by check valves 41 a to 44 a, which allow only pressure oil flowing from the wheel cylinders 11 to 14 to the master cylinder 16 to flow through the holding valves 21 to 24. ing. Further, the reservoirs 37 and 39 and the master cylinder 16 are connected to the check valve 4.
They are connected by hydraulic lines via 7 and 49, and only the flow of the pressure oil from the reservoirs 37 and 39 to the master cylinder 16 is permitted.

The detection signals of the wheel speed sensors 5 to 8 and the stop switch 29 are input to an electronic control circuit (hereinafter referred to as ECU) 50. The ECU 50 includes a CPU, R
A known microcomputer having an OM, a RAM, and an I / O generates a signal for controlling each of the holding valves 21 to 24 and the pressure reducing valves 31 to 34 based on the detection signal. This control signal is composed of a pressure increase output, a hold output, and a pressure decrease output generated for each of the wheels 1 to 4. Here, the operation of the holding valves 21 to 24 and the pressure reducing valves 31 to 34 corresponding to each output will be described by taking the right front wheel 1 as an example.

To generate a pressure increase output to the right front wheel 1 means to generate a control signal so that the holding valve 21 is set to the communication position and the pressure reducing valve 31 is set to the shut-off position. Thereby, the brake fluid pressure generated by the master cylinder 16 is supplied to the wheel cylinder 11 as it is. To generate a holding output at the right front wheel 1 means to generate a control signal so that both the holding valve 21 and the pressure reducing valve 31 are in the shut-off position.
As a result, the brake fluid pressure of the wheel cylinder 11 is maintained. If the brake pedal 27 is released during the continuation of the holding output, the pressure oil flows through the bypass pipe 41 and the brake fluid pressure of the wheel cylinder 11 is reduced.

To generate a pressure reducing output to the right front wheel 1 means to generate a control signal so that the holding valve 21 is set to the shut-off position and the pressure reducing valve 31 is set to the communication position. Thereby, the pressure oil of the wheel cylinder 11 flows into the reservoir 37, and the brake fluid pressure is reduced. Note that the ECU 50
The same output is performed for the other wheels 2-4. In addition, in each control signal of the reduced pressure output, the increased pressure output, and the holding output,
The state of the control signal may be changed depending on which output control signal was used last time.

Next, the processing executed by the ECU 50 will be described in detail with reference to the flowcharts of FIGS. ECU5
0 executes the main routine shown in FIG. 2 when the ignition switch is turned on. Note that the ECU 50 executes this main routine for each of the wheels 1 to 4 in a time-sharing manner. When the processing is started, first, in step 1000, an initialization processing is executed. By this initialization processing, initialization processing such as memory clear, flag reset, etc. is performed, and in the subsequent step 2000, a predetermined time Ta has elapsed in order to execute a transition arithmetic processing every predetermined time Ta (for example, 5 ms). By determining whether or not this is the case, it waits for the predetermined time Ta to elapse.

If the answer is Yes in step 2000, the process proceeds to step 3000, where each wheel speed sensor 5
The wheel speed VW ** of each of the wheels 1 to 4 is calculated based on the rotation speed signals from. Here, “**” indicates each wheel 1
4 is a generic term for the symbols FR, RL, RR, and FL, that is, “VW **” is VWFR, VWRL, VWRR,
VWFL, which indicates wheel speeds for the right front wheel 1, the left rear wheel 2, the right rear wheel 3, and the left front wheel 4, respectively.

In the following step 4000, step 30
By differentiating the wheel speed VW ** obtained in 00, the wheel acceleration dVW ** of each of the wheels 1 to 4 is calculated.
Then, in step 5000, the vehicle speed (estimated vehicle speed) is calculated based on the maximum speed VWmax among the wheel speeds VW ** of the wheels 1-4 obtained in step 3000. This processing is performed by, for example, the wheel speed V of each wheel 1-4.
The maximum speed VWmax of WFR to VWRL is a deceleration limit value obtained by subtracting a predetermined value from the vehicle speed VB (n-1) from an acceleration limit value Vα obtained by adding a predetermined value to the vehicle speed VB (n-1) obtained last time. Judge whether it is within the range up to Vβ,
If the maximum speed VWmax is within the range from the acceleration limit values Vα to Vβ, the maximum speed VWmax is directly used as the vehicle speed V.
B, and the maximum speed VWmax is equal to the acceleration limit value Vα.
Is exceeded, the acceleration limit value Vα is set as the vehicle body speed VB, and if it is below the maximum speed VWmax deceleration speed limit value Vβ, the deceleration limit speed Vβ is set as the vehicle body speed VB.

In step 6000, step 5
The vehicle body deceleration dVB is calculated by differentiating the vehicle body speed VB obtained at 000. Then, a slip ratio SW ** for each of the wheels 1 to 4 is calculated based on the obtained vehicle speed VB and wheel speed VB **. Thereafter, in step 8000, the slip ratio SW in each of the wheels 1 to 4
The control mode of each of the actuators 21 to 24 is calculated for each of the wheels 1 to 4 based on ** and the wheel acceleration dVW **. The details of this process will be described with reference to the flowchart of the four-wheel control mode calculation shown in FIG.

Then, in step 9000, the holding valve is determined to be open, and a request for opening the holding valve and the pressure reducing valve is made for the wheels meeting predetermined conditions. The details of this process will be described with reference to the flowchart of FIG. Thereafter, in step 10000, processing according to each control mode selected in step 8000 and step 9000 is executed, and solenoid driving of the holding valves 21 to 24 and the pressure reducing valves 31 to 34 is performed. The details of this process will be described with reference to the flowchart of each wheel output control shown in FIGS.

Next, the details of step 8000 in FIG. 2 will be described with reference to the flowchart shown in FIG. This routine includes holding valves 21 to 24 in each of wheels 1 to 4.
And a control mode setting process for the pressure reducing valves 31 to 34, which is executed four times in total for the FR wheel 1, the FL wheel 2, the RR wheel 3, and the RL wheel 4. The setting of the control mode is performed in order to determine the control condition of how many milliseconds and in what state the pressure increase output, the pressure decrease output, and the hold output in each of the wheels 1 to 4 are performed. The details of each control mode will be described later.

First, at step 210, it is determined whether or not the stop switch 26 is ON, that is, whether or not the vehicle is being braked. Until the stop switch 26 is turned on, the process proceeds to step 220, where the control flag of the wheel is reset, and the control mode of the holding valves 21 to 24 and the pressure reducing valves 31 to 34 of the wheel is set to the pressure increasing mode. And terminate the processing. Here, the pressure increase mode is a mode in which the above-described pressure increase output is continuously generated. That is, the brake fluid pressure generated by the master cylinder 16 in the normal brake during vehicle braking is directly applied to the wheel cylinder 11.
~ 14.

On the other hand, when the stop switch 26 is turned on, the routine proceeds to step 240, where it is determined whether or not the control flag is set. In other words, immediately after the stop switch 26 is turned on, the control flag is in the reset state.
Go to step 50, the slip ratio SW of the wheel being determined
It is determined whether ** is larger than the target slip ratio KS0 (for example, 20%).

If No in step 250,
Proceeding to step 220, the control-in-progress flag is reset, the control mode of the wheel is set to the pressure increasing mode, and the process is terminated. If Yes in step 250, the process proceeds to step 260, in which the control flag is set, and
Go to 0. Next, in step 270, it is determined whether or not the slip ratio SW ** of the wheel is larger than a predetermined slip ratio KS1. This predetermined slip ratio KS1 is
Smaller than the target slip ratio KS0, for example, KS1 =
If it is 20%, KS1 = 15%.

If the answer is Yes in step 270, the process proceeds to step 280, in which the wheel acceleration dVW * of the wheel concerned is obtained.
It is determined whether or not * is smaller than zero acceleration (0G), that is, whether the wheel is in a state of being controlled in the deceleration direction or in a state of being reversed from the deceleration direction to the acceleration direction. If Yes in step 280, step 29
The process proceeds to 0, and the pressure reducing mode is set as the control mode of the holding valves 21 to 24 and the pressure reducing valves 31 to 34, and the process is ended. If No in Step 280, Step 30
The process proceeds to 0, and the holding mode is set as the control mode of the holding valves 21 to 24 and the pressure reducing valves 31 to 34, and the process is ended.

Here, the depressurization mode is a mode in which the above-described holding output and the depressurizing output are alternately and repeatedly generated (for example, by switching every 15 ms), and the holding mode continuously generates the above-described holding output. Mode. That is,
When the wheel acceleration dVW ** is 0 G or less and the wheel is being locked, the brake fluid pressure of the wheel cylinders 11 to 14 is gradually reduced by the pressure reduction mode, and the wheel acceleration dVW ** exceeds 0 G and slippage occurs. When the brake fluid pressure is gradually being eliminated, the brake fluid pressure is held in the holding mode. In the depressurization mode, the control mode setting determines the change cycle of the depressurized output and the held output.

Specifically, if the number of times of pressure increase output in the previous pressure increase mode is large (or if the pressure increase output time is long), the duty ratio of the pressure reduction output is increased. On the other hand, if No in step 270, the process proceeds to step 310 to determine whether or not the control mode of the pulse pressure increasing mode has been executed a predetermined number of times. Here, the pulse pressure increasing mode means that the pressure of the wheel cylinder pressure of the brake device is changed in a predetermined cycle by alternately changing the pressure of the holding valves 21 to 24 and the pressure reducing valves 31 to 34 by the pressure increasing output and the holding output. This is a mode in which the pressure is gradually increased in accordance with the pressure increase pattern. In this control mode setting, a change cycle and the like are determined, and the pressure increase and decrease are provided.

Specifically, the change cycle of the pressure increasing mode and the like are as follows:
It is determined by the number of times of pressure reduction output in the previous pressure reduction mode (or the accumulated time of pressure reduction output). For example, if the accumulated time of the reduced pressure output during the previous reduced pressure mode is long, it is assumed that the W / C pressure can be increased to some extent and abruptly, and the change cycle to the output of the current increased pressure mode is accelerated. Also,
If the accumulated time of the decompression output during the previous decompression mode is short,
The change period of the pressure increase output in the current pressure increase mode is delayed. As a result, the pressure increase output timing in the pressure increase mode changes, but it is possible to estimate the schedule of the pressure increase output during the pressure increase mode based on the change cycle determined in this way.

If Yes in step 310, it is assumed that the slip of the wheel is completely suppressed and the wheel does not slip even if the hydraulic control is terminated.
Proceeding to step 220, the control-in-progress flag is reset,
The control mode of the holding valves 21 to 24 and the pressure reducing valves 31 to 34 is set to the pressure increasing mode, and the process ends. That is, it returns to the normal brake. If No in step 310, the process proceeds to step 320, in which the control of the pulse increasing mode is kept set, and the process ends.

Next, the details of step 9000 in FIG. 2 will be described with reference to the flowchart shown in FIG.
This routine determines a case where the driver may feel a feeling of flatness in the future, selects the most suitable wheel for opening the holding valves 21 to 24, and sets the holding valve for the selected wheel. A request to open the pressure reducing valves 31 to 34 (hereinafter, a request to open the pressure reducing valves 31 to 34 at the same time as opening the holding valves 21 to 24 and setting a request to open the pressure reducing valves 31 to 34) is set. (Referred to as a pressure-reducing valve opening request).

First, at step 410, the holding valve 21 for a predetermined time KT1 or more for all four wheels from the time when the pressure-increase output to any one of the wheel cylinders 11 to 14 was last performed.
24 to determine whether or not an output has been made. That is, if the holding valves 21 to 24 are not further opened for more than the predetermined time KT1, the brake fluid in the master cylinder 16 is not consumed.
The brake fluid inside does not move to the wheel cylinder side, and the driver feels that the driver can not depress the brake pedal,
This is because the pedal feel deteriorates. Then, if Yes in step 410, the process proceeds to step 420,
If so, the process ends.

It should be noted that as an affirmative determination in step 410, all four wheels are set to the decompression mode or the holding mode, and in this state, the predetermined time KT1
When the elapsed time has elapsed, at least one of the four wheels is set to the pressure increasing mode, but a case where a predetermined time KT1 has elapsed from the previous pressure increasing output based on the change cycle to the pressure increasing output may be considered.

In step 420, after a predetermined time KT1 has elapsed since the last time any one of the holding valves 21 to 24 was opened, four more time passes until a predetermined time KT2 elapses.
It is determined whether or not the holding valves 21 to 24 are to be opened for any of the wheels. In other words, if the time during which the holding valves 21 to 24 are not opened exceeds the predetermined time KT1 and the predetermined time KT2 further elapses, it is assumed that the above-described time period for feeling the plate feeling is reached. If the holding valves 21 to 24 are not opened with respect to the wheels, the pedal feel will be deteriorated.

For this reason, if Yes in step 420, the process proceeds to step 430, where the holding valves 21 to 24 and the pressure reducing valve 3
Select wheels to open 1-34. This wheel selection is performed based on whether or not each of the wheels is such that the brake fluid can flow into the reservoirs 37 and 39 by opening the pressure reducing valves 31 to 34. The wheels of the system in which the amount of the brake fluid flowing into the reservoirs 37 and 39 is the smallest among the wheels 1 to 4 are selected. This is because it is considered that the reservoirs 37 and 39 corresponding to the wheels of this system have room for storing the brake fluid. If No in step 420, the process is terminated because the pedal feel does not deteriorate.

When a wheel is selected in step 430, the process proceeds to step 440, in which a valve opening request is set for the selected wheel according to the state of the selected wheel, and the process ends. . Specifically, the setting of the valve opening request is performed by selecting whether only the holding valve opening request is set, or whether the pressure reducing valve opening request is set together with the holding valve opening request. That is, when only the holding valve opening request is set, the holding output is set in the pulse pressure increasing mode, or the W / C pressure is not substantially zero. In these cases, it is necessary to maintain the W / C pressure,
The W / C pressure is prevented from being reduced by not opening the pressure reducing valves 31 to 34. On the other hand, the case where the pressure reducing valve opening request is set together with the holding valve opening request is when the holding mode is set and the W / C pressure is substantially zero, or when the pressure reducing mode is set. In this case, since it is not necessary to maintain the W / C pressure, a request to open the pressure reducing valve is set together with the request to open the holding valve.

It should be noted that whether the W / C pressure is substantially zero or not is determined by W
The determination is made by directly detecting the / C pressure using a pressure sensor or the like, or estimating the W / C pressure from the vehicle deceleration before the pressure reduction. For example, when estimating the W / C pressure based on the vehicle deceleration before the pressure reduction, it is determined whether or not the W / C pressure is substantially zero based on the pressure reduction time and the pressure reduction curve.

As described above, when the determination of the valve opening is completed, FIG.
Then, the process proceeds to step 10000 to execute the four-wheel output control process. Hereinafter, the details of step 10000 are shown in FIG.
This will be described based on the flowchart shown in FIG. In this routine, the solenoid drive corresponding to each of the pressure increase output, the pressure decrease output, and the hold output is performed in accordance with the previously set control mode of each of the wheels 1 to 4 while giving priority to the result of the valve opening request determination in step 9000. Set the pattern. Note that this routine is performed for FR wheel 1, FL wheel 2, RR
The process is executed four times for the wheel 3 and the RL wheel 4 in total.

First, one wheel is set from each of the wheels 1 to 4 and processing is performed for that wheel. If the pressure increase mode has been set for that wheel, the routine proceeds to step 510,
Set the solenoid drive pattern for boost pressure output. If the pulse pressure increase mode has been set for the set wheel, the process proceeds to step 520, and it is determined whether or not it is the pressure increase output timing for that wheel. The pressure increase output timing is determined according to the change cycle set in step 310 and the like. If it is the boost pressure output timing, the process proceeds to step 510, where the solenoid drive pattern for the boost output is set. If it is not the boost output timing, the process proceeds to step 530 to set the solenoid drive pattern for the hold output.

If the holding mode has been set for the set wheel, the routine proceeds to step 530, where the solenoid drive pattern for the holding output is set. Then, when the solenoid drive pattern in the holding output is set in step 530, the process proceeds to step 540, and the processing of the pressure reducing valve open output determination is executed. FIG. 6 shows a flowchart of the process of determining the pressure-reducing valve opening output, and details of step 540 will be described.

In this routine, when opening the holding valves 21 to 24 corresponding to the selected wheel, it is determined whether or not all the pressure reducing valves 31 to 34 corresponding to the selected wheel are also opened. That is, it is determined whether or not the pressure reducing valves 31 to 34 are to be opened according to the valve opening request set in the illustrated step 440. Step 61
If it is 0, it is determined in step 440 whether or not the pressure reducing valve opening request is set. Then, in step 610, Ye
If s, the process proceeds to step 620, and if No, the process ends.

At step 620, the current pressure reducing valves 31 to 3
Then, it is determined whether or not it is the output timing to open No. 4. That is, the time during which the pressure reducing valves 31 to 34 are opened is set in advance. For example, since the setting is made such that the pressure reducing valves 31 to 34 are continuously opened during the TR1 time, the pressure reducing valves 31 to 34 are operated during the TR1 time. It is determined that it is the output timing to open, and when the TR1 time has elapsed, it is determined that the output timing is not to open the pressure reducing valves 31 to 34. Therefore, if the state in which all the holding valves 21 to 24 are closed for the time KT1 continues,
Thereafter, during time TR1, the pressure reducing valves 31 to 34 are opened. However, the time TR1 does not need to be a constant, and may be changed according to the W / C pressure.

Then, if Yes in step 620, the flow advances to step 630 to set the pressure-reducing valve opening output pattern and ends the processing. If No, the processing ends as it is. As described above, when the pressure reducing valve open output pattern is set, the pressure reducing valve open output pattern is given priority over the solenoid driving pattern in the previously set holding output, and the solenoid for forcibly opening the pressure reducing valves 31 to 34 is set. It becomes a driving pattern.

As described above, when the process of determining the output of the pressure reducing valve in step 540 is completed, the process proceeds to step 550 to execute the process of determining the output of holding the valve. FIG. 7 shows a flowchart of the process of determining the holding valve opening output, and details of step 550 will be described. In this routine, the holding valves 21 to 24
It is determined whether or not to open. That is, in response to the valve opening request set in step 440 described above, the holding valves 21 to 24
It is determined whether or not to open.

In step 710, it is determined whether or not the holding valve opening request has been set in step 440. If Yes in step 710, the process proceeds to step 720, and if No, the process ends. In step 720, it is determined whether or not it is the output timing to open the holding valves 21 to 24 at present. That is, the holding valves 21 and 2
4 is set in advance, for example, the time TH1
Is set to open the holding valves 21 to 24 continuously, it is determined that it is the output timing to open the holding valves 21 to 24 during the time TH1, and after the time TH1, the holding valves 21 to 24 are opened. It is determined that it is not the output timing to open. Therefore, if the state in which all the holding valves 21 to 24 are closed continues for the time KT1, the holding valves 21 to 24 will be opened thereafter for the time TH1. However, the time TH1 does not need to be a constant, and may be changed according to the W / C pressure.

If Yes in step 720, the flow advances to step 730 to set a pressure-reducing valve opening output pattern, and ends the processing. If No, the processing ends as it is. As described above, when the holding valve opening output pattern is set, the holding valve opening output pattern is prioritized over the solenoid driving pattern in the holding output set earlier, so that the holding valves 21 to 24 are forcibly opened. Such a solenoid drive pattern is obtained.

Further, if the decompression mode has been set for the set wheel, the process proceeds to step 560, and it is determined whether or not it is presently the decompression output timing for that wheel. The decompression output timing is determined according to the change cycle set in step 290. If it is not the pressure reduction timing, the process proceeds to step 530 to set the solenoid drive pattern for the holding output, and if it is the pressure reduction timing, the process proceeds to step 570 to set the solenoid drive pattern for the pressure reduction output.

When the solenoid drive pattern for the holding output is set in step 530, the routine proceeds to step 540, where the above-described pressure-reducing valve opening output determination is performed, and then the routine proceeds to step 550. When the solenoid drive pattern for the reduced pressure output is set in step 570, the process proceeds to step 550. Then, in step 550, the above-described holding valve open output determination is performed.

Here, when the solenoid driving pattern for the pressure reduction output is set, the reason why the pressure reducing valve opening output determination in step 540 is not performed is that the pressure reducing valves 31 to 34 are opened in the solenoid driving pattern for the pressure reduction output. In this case, the pressure reducing valves 31 to 34 are opened at the timing of the normal pressure reducing output.

When the solenoid drive pattern corresponding to each control mode is set in this way, step 5
Proceeding to 80, it is determined whether the setting of the solenoid drive pattern has been completed for all four wheels. And step 58
If Yes at 0, the process proceeds to step 590, where each holding valve 21 is set in accordance with the previously set solenoid driving pattern.
-24 and the solenoids provided in each of the pressure reducing valves 31-34 are driven to move the two-position valve to a valve position corresponding to each output. If No in step 580, the process proceeds to step 600, where the next wheel different from the wheel that has been currently processed is set, and the process for that wheel is performed.

As described above, before the driver feels a plate feeling,
By opening the selected holding valves 21 to 24, the driver can depress the brake pedal 27. FIG. 8 shows a time chart when the anti-skid control based on such processing is performed. However, in FIG. 8, for the sake of simplicity, the time chart shows only the wheels selected in step 430 in the above control. 8A shows a comparison between the vehicle speed and the wheel speed, FIG. 8B shows an opening / closing timing of the holding valves 21 to 24 at the selected wheel, and FIG. 8C shows a pressure reducing valve at the selected wheel. 3
(D) shows the W / C pressure, and (e) returns the brake fluid released to the reservoir toward the master cylinder without using a pump. (F) shows the operation amount of the brake pedal in a system with a pump in which the brake fluid released to the reservoir is returned to the master cylinder using a pump. .

As shown in FIG. 8A, when the wheel speed becomes lower than the vehicle speed, pressure reduction control is started, and the pressure reduction mode is set at step 290. After that, when the wheel speed is restored and the tendency to lock is avoided, the holding mode is set. While the pressure reducing mode and the holding mode are set, the holding valve is set as shown in FIG. The state where 21 to 24 are closed continues.

However, even in such a case, the state in which the holding valves 21 to 24 are closed continues for the time KT1, and
Further, if the holding valves 21 to 24 are not scheduled to be opened during the time KT2, as described above, the time KT2
As time elapses, the optimal wheel is selected and the corresponding holding valves 21 to 24 are opened. That is, one of the holding valves 21 to 24 is opened after the time KT1 elapses and before the time KT2 elapses further, so that the brake pedal 27 can be depressed before the driver feels a feeling of board feeling.

The holding valve 2 corresponding to the selected wheel
As shown in FIG. 8C, the pressure reducing valves 31 to 34 corresponding to the wheels are also opened at the same time as 1 to 24 are opened. That is, as shown in FIG. 8D, since the W / C pressure has become substantially zero by the previously executed pressure reduction control, the W / C
Since there is no need to maintain the pressure, the holding valves 21 to 24 are opened and the pressure reducing valves 31 to 34 are opened to prevent the W / C pressure from increasing. When the holding mode is set and the W / C pressure is held at a predetermined pressure, only the holding valve opening request is set in step 440, whereby the W / C pressure is set.
The / C pressure is not reduced.

As described above, by opening the holding valves 21 to 24 before the driver feels a plate feeling, a good anti-skid control device for the pedal feel can be obtained. Further, by opening the holding valves 21 to 24 and also opening the pressure reducing valves 31 to 34, the W / C is opened by opening the holding valves 21 to 24 regardless of whether the holding mode or the pressure reducing mode is set. The pressure can be prevented from increasing.

In the above embodiment, step 430 is executed.
When the wheels are selected, among the wheels 1 to 4, the wheels of the system in which the amount of the brake fluid flowing into the reservoirs 37 and 39 is small are selected, but the amount of the brake fluid flowing into the reservoirs 37 and 39 is selected. Can be directly detected from the amount of movement of the pistons of the reservoirs 37 and 39, or indirectly detected from the sum of the time during which the pressure reduction output is executed.

Further, in the wheel selection in step 430, the wheel in which the depressurization mode is currently set may be selected. The fact that the pressure reducing mode is set means that the pressure reducing valves 31 to 34 may be opened, so that if the holding valves 21 to 24 are opened and the pressure reducing valves 31 to 34 are opened, the pressure of the wheel cylinders 11 to 14 is increased. This is because it is possible to avoid giving the driver a feeling of flatness without any problem.

Further, in the wheel selection in step 430, the wheel having the oldest pressure increase output or the wheel having the smallest wheel slip ratio may be selected. This is because even if the pressure is increased for the wheel, it is considered that the wheel does not slip. In addition, when selecting a wheel in which the depressurization mode is currently set or selecting a wheel having the smallest wheel slip ratio, it is not limited to the case where the so-called pumpless system shown in FIG. 1 is applied.
The present invention can also be applied to a system with a pump.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration of an anti-skid control device according to the present invention.

FIG. 2 is a flowchart showing a main routine of the anti-skid control device shown in FIG.

FIG. 3 is a flowchart of a control mode calculation process in FIG.

FIG. 4 is a flowchart of a four-wheel output mode determination process in FIG. 2;

FIG. 5 is a flowchart of a four-wheel output control process in FIG. 2;

FIG. 6 is a flowchart of a pressure reducing valve opening output determination in FIG.

FIG. 7 is a flowchart of a holding valve opening output determination in FIG.

FIG. 8 is a time chart showing an operation based on the processing of the anti-skid control device in FIG. 1;

FIG. 9 is a time chart showing an operation based on processing of a conventional anti-skid control device.

[Explanation of symbols]

1 ... right front wheel, 2 ... left front wheel, 3 ... right rear wheel, 4 ... left rear wheel, 5
-8: Wheel speed sensor, 11-14: Wheel cylinder,
21 to 24, 31 to 34 ... two-position valve, 27 ... brake pedal, 29 ... stop switch, 50 ... ECU.

Claims (7)

[Claims] 1. A plurality of wheel cylinders (11 to 14) for applying a wheel braking force to each of a plurality of wheels (1 to 4) at the time of vehicle braking, and brake fluid directed to the plurality of wheel cylinders at the time of vehicle braking. A master cylinder (16) for providing the following, a plurality of pipelines communicating the master cylinder and each of the plurality of wheel cylinders, and a slip state detecting means (7000) for detecting a slip state of the plurality of wheels. Anti-skid control means for performing anti-skid control by adjusting brake fluid pressure applied to the plurality of wheel cylinders based on a detection result of the slip state detection means; provided in each of the plurality of pipelines; A plurality of holding valves (21 to 21) controlled by the control means
24), wherein the anti-skid control means performs, during the anti-skid control, pressure reduction control for reducing the brake fluid pressure of one of the plurality of wheel cylinders or holding control for holding the brake fluid pressure. The holding valve corresponding to the depressurized / held wheel cylinder is shut off to inhibit the flow of the brake fluid between the master cylinder and the depressurized wheel cylinder, and the brake fluid pressure of any of the plurality of wheel cylinders is reduced. When performing the pressure increase control to increase the pressure, the holding valve corresponding to the wheel cylinder to be increased in pressure is in a communicating state to allow the flow of the brake fluid between the master cylinder and the wheel cylinder to be increased in pressure. The anti-skid control means includes: A first determination means (410) for determining whether or not the flow of the brake fluid in all of the plurality of pipelines is prohibited for a fixed time (KT1) or more, wherein an affirmative determination is made by the first determination means. When formed, the anti-skid control means selects at least one of the plurality of wheels, and sets the holding valve corresponding to a wheel cylinder of the selected wheel to a communication state, and An anti-skid control device wherein the flow of brake fluid between a master cylinder and a wheel cylinder is allowed. 2. In the anti-skid control, during the anti-skid control, the anti-skid control may be performed in any one of the plurality of conduits during a second predetermined time (KT2) after the first predetermined time is exceeded. Second determining means (420) for determining whether there is a schedule for allowing the flow of the brake fluid
When the negative determination is made by the second determination means, the anti-skid control means selects at least one of the plurality of wheels, and selects a wheel cylinder of the selected wheel. The anti-skid control device according to claim 1, wherein the corresponding holding valve is in a communicating state to allow a flow of brake fluid between the master cylinder and the wheel cylinder. 3. The anti-skid control means changes a time for bringing the holding valve corresponding to a wheel cylinder in the selected wheel into a communicating state in accordance with a pressure of the wheel cylinder in the selected wheel. The anti-skid control device according to claim 1, wherein: 4. A reservoir (37, 39) for releasing brake fluid in the plurality of pipelines during the pressure reduction control, and a plurality of pressure reducing valves for controlling flow of brake fluid from the plurality of pipelines to the reservoir. When performing the pressure reduction control, the anti-skid control means controls the pressure reduction valve corresponding to the wheel cylinder to reduce the pressure, and corresponds to the wheel cylinder to reduce the pressure. When permitting the flow of the brake fluid between the pipeline and the reservoir and performing the holding control or the pressure increasing control, the pressure reducing valve corresponding to the wheel cylinder for increasing and holding the pressure is controlled, and The flow of brake fluid between the pipeline corresponding to the wheel cylinder to be depressurized and the reservoir is prohibited, and an affirmative determination is made by the first determination unit. In this case, the anti-skid control means puts the pressure reducing valve corresponding to the selected wheel into a communicating state, and sets a brake between the pipeline corresponding to the wheel cylinder of the selected wheel and the reservoir. 4. The method according to claim 1, wherein the liquid is allowed to flow.
The anti-skid control device according to any one of the above. 5. The anti-skid control means is configured to select, from the plurality of wheels, a wheel that has passed the most time since the previous pressure increase control was performed. An anti-skid control device according to any one of claims 1 to 4. 6. The anti-skid control unit according to claim 1, wherein the anti-skid control unit selects a wheel having a smallest slip ratio among the plurality of wheels. Anti-skid control device. 7. The anti-skid control means is configured to select, from the plurality of wheels, a wheel having the shortest pressure increase time since the previous pressure reduction control was performed. 5. The anti-skid control device according to any one of 1 to 4.