JPH11152020A - Brake control system of vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent control from being finished by mistake immediately after the start of control, in a brake control system which feeds a wheel cylinder with the output hydraulic pressure of a master cylinder through a hydraulic pump to perform brake assist control. SOLUTION: This brake control system is equipped with first on-off valves SC1 and SC2 opening or closing a main hydraulic passage MF; a hydraulic pump HP1 connecting a discharge side among the first on-off valves SC1, SC2 and wheel cylinders Wfr, Wf1, Wrr, Wrf and discharging a boosted brake fluid to these wheel cylinders; an auxiliary hydraulic passage Mfc connecting an inlet side of the hydraulic pump HP1, to a master cylinder C; a second on-off valve S11 opening or closing the auxiliary hydraulic passage Mfc, and a hydraulic pressure sensor PS detecting hydraulic pressure in the master cylinder MC. On the basis of the detected result of the hydraulic pressure sensor PS, whether the necessity of starting brake assist control is judged, and when the start of control is judged necessary, the first and second on-off valves as well as the hydraulic pump are controlled to control the brake assist, and on the basis of the detected result of the hydraulic pressure sensor MS, the necessity of ending the brake assist control is judged. Moreover, after the starting of this brake assist control is judged necessary, no end of the brake assist control is to be judged until the setting time elapses.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is to assist a driver in operating a brake pedal by automatically increasing a braking force when the brake pedal is depressed at a rapid speed or when the brake pedal is depressed deeply. The present invention relates to a vehicle brake control device having a brake assist control function.

[0002]

2. Description of the Related Art During traveling of a vehicle, for example, during emergency braking, a brake pedal is depressed at a rapid speed. However, the pedaling force is insufficient or it is difficult to maintain the pedaling force, so that an appropriate braking force may not be obtained. In light of this, recently,
It has been proposed to add a brake assist control function,
Already installed in some commercial vehicles. This brake assist control automatically increases the braking force when the brake pedal is depressed at a rapid speed to assist the driver in operating the brake pedal. Generally, the boosting function of the vacuum booster is used. Control is being done.

Here, for the purpose of completely or partially saving the vacuum booster, there is a technology for performing brake assist control using a pump for anti-skid control or traction control (Japanese Patent Laid-Open No. 8-230634). Are known. Specifically, this is a wheel cylinder, a master cylinder, a main hydraulic pressure path connecting the master cylinder to the wheel cylinder, a first on-off valve for opening and closing the main hydraulic pressure path, and a first on-off valve. A hydraulic pump that connects the discharge side between the hydraulic cylinder and the wheel cylinder and discharges brake fluid that has been pressurized to the wheel cylinder, an auxiliary hydraulic path that connects the suction side of the hydraulic pump to the master cylinder, and an auxiliary hydraulic path And a second on-off valve for opening and closing the valve. Furthermore, a pressure sensor for detecting the output hydraulic pressure of the master cylinder is provided,
When the output hydraulic pressure of the master cylinder is equal to or higher than a predetermined hydraulic pressure and the rate of increase in the output hydraulic pressure of the master cylinder exceeds a predetermined ratio, the brake assist control is performed by controlling the hydraulic pump and the first and second on-off valves. Is started, and the brake assist control is ended when the output hydraulic pressure of the master cylinder is equal to or lower than a predetermined hydraulic pressure.

[0004]

Since the brake assist control is performed by sucking the brake fluid of the master cylinder by a hydraulic pump, the master cylinder hydraulic pressure during the control when the master cylinder hydraulic pressure is not controlled is controlled. It is a lower value than. This phenomenon is particularly noticeable immediately after the start of the control, and the master cylinder hydraulic pressure may become lower than the threshold value for determining the end of the control (that is, the predetermined hydraulic pressure).

In the above-described system, when the master cylinder hydraulic pressure is equal to or lower than a predetermined hydraulic pressure, the brake assist control is unconditionally terminated. In the above-described case, the control is erroneously terminated immediately after the start of the control. Cannot assist the brake pedal operation of the driver.

Therefore, the present invention avoids erroneous termination of control immediately after the start of control in a brake control device that performs brake assist control by supplying output hydraulic pressure of a master cylinder to a wheel cylinder by a hydraulic pump. That
Its technical issues.

[0007]

In order to solve the above-mentioned technical problems, a vehicle brake control device according to the present invention is provided with a wheel cylinder mounted on wheels of a vehicle to apply a braking force, and A master cylinder for generating a hydraulic pressure in response to an operation of a brake pedal, a main hydraulic path connecting the master cylinder to the wheel cylinder, a first on-off valve for opening and closing the main hydraulic path, 1
A hydraulic pump that connects a discharge side between the on-off valve and the wheel cylinder and discharges brake fluid that has been boosted to the wheel cylinder; and an auxiliary hydraulic pressure that connects a suction side of the hydraulic pump to the master cylinder. Path, a second opening / closing valve for opening and closing the auxiliary hydraulic path, hydraulic pressure detecting means for detecting the output hydraulic pressure of the master cylinder, and a start of the brake assist control based on the detection result of the hydraulic pressure detecting means. Start determining means for determining whether or not braking is required, and when the start determining means determines that control start is required, the first and / or second on-off valve and the hydraulic pump are controlled to perform the brake assist control. Control means; end judging means for judging whether or not to end the brake assist control based on the detection result of the hydraulic pressure detecting means; and judgment by the start judging means that the brake assist control needs to be started. Until the set time has elapsed after it has been,
An end prohibition unit for causing the end determination unit to determine whether the brake assist control has ended is provided.

According to the first aspect of the invention, it is forcibly determined that the brake assist control is to be terminated until the set time elapses after it is determined that the brake assist control needs to be started. It is possible to prevent the control from erroneously ending due to a drop in the output hydraulic pressure.

According to a first aspect of the present invention, as set forth in the second aspect of the present invention, the hydraulic pressure change rate calculating means for calculating a change rate of the output hydraulic pressure of the master cylinder based on a detection result of the hydraulic pressure detecting means, It is preferable that the apparatus further comprises a time setting means for setting the set time based on a change rate of the output hydraulic pressure of the master cylinder when the start determination means determines that the brake assist control needs to be started. According to this configuration, it is possible to further prevent the control from being erroneously terminated immediately after the control is started.

According to a second aspect of the present invention, as set forth in the third aspect of the present invention, the time setting means sets the set time to be shorter when the rate of increase in the output hydraulic pressure of the master cylinder is smaller than when the rate of increase is larger. It is preferable to set the length to be long.

In a preferred embodiment, the apparatus further comprises a hydraulic pressure increase rate calculating means for calculating an increase rate of the output hydraulic pressure of the master cylinder based on a detection result of the hydraulic pressure detecting means, Only when the increase rate of the output hydraulic pressure of the master cylinder calculated by the increase rate calculating means is equal to or less than a predetermined rate, the start determining means determines that the brake assist control needs to be started and the set time elapses until the set time elapses. It is preferable to configure the end determination unit to determine whether the brake assist control is to be ended.

When the increase rate of the output hydraulic pressure of the master cylinder is large, the decrease in the master cylinder hydraulic pressure due to the suction of the hydraulic pump is smaller than the increase in the master cylinder hydraulic pressure due to the operation of the brake pedal. There is almost no drop in hydraulic pressure. On the other hand, when the rate of increase in the output hydraulic pressure of the master cylinder is small, the decrease in the master cylinder hydraulic pressure due to the suction of the hydraulic pump is greater than the increase in the master cylinder hydraulic pressure due to the brake pedal operation. The drop in cylinder fluid pressure is large. Therefore, when the rate of increase in the output hydraulic pressure of the master cylinder is small, the end prohibition time is set longer than when the output hydraulic pressure of the master cylinder is large, or as set forth in claim 4, If the end prohibition time is provided only when the increase rate of the output hydraulic pressure is equal to or less than the predetermined rate, it is possible to further prevent the control from being erroneously ended immediately after the control is started.

According to a first aspect of the present invention, as set forth in the fifth aspect of the present invention, the end determining means determines that the brake assist control is terminated when the output hydraulic pressure of the master cylinder detected by the hydraulic pressure detecting means is equal to or lower than a predetermined value. It is preferable to configure so that it is necessary.

According to a first aspect of the present invention, as set forth in the sixth aspect of the present invention, the brake of the wheel cylinder is interposed between the first on-off valve and the wheel cylinder, and the brake of the wheel cylinder is provided in accordance with an output of the brake control means. It is preferable to further include a modulator for adjusting the hydraulic pressure.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of a braking control device according to the present invention, wherein an engine EG includes a throttle control device TH.
In the internal combustion engine provided with the fuel injection device FI, the throttle control device TH controls the main throttle opening of the main throttle valve MT according to the operation of the accelerator pedal AP. Further, the sub-throttle valve ST of the throttle control device TH is driven to control the sub-throttle opening in accordance with the output of the electronic control unit ECU, and the fuel injection device FI is driven to control the fuel injection amount. It is configured. The engine EG of the present embodiment is connected to wheels DL and DR at the rear of the vehicle via a shift control device GS and a differential gear DF to form a so-called rear-wheel drive system. It is not limited to.

Next, regarding the braking system, the wheels NL, N
Wheel cylinders Wfl, Wf for R, DL, DR respectively
r, Wrl, Wrr are mounted, and a brake fluid pressure control device PC is connected to these wheel cylinders Wfl and the like. Wheel NL indicates a driven wheel on the front left side as viewed from the driver's seat, wheel NR indicates a driven wheel on the front right side, and wheel DL
Indicates a driving side on the rear left side, and wheels DR indicate driving wheels on the rear right side. The brake fluid pressure control device PC is configured as shown in FIG. 2, which will be described later.

The wheels NL, NR, DL, DR are provided with wheel speed sensors WS1 to WS4, which are connected to the electronic control unit ECU, and which control the rotational speed of each wheel, that is, the number of pulses proportional to the wheel speed. Is input to the electronic control unit ECU. A hydraulic pressure sensor PS for detecting an output brake hydraulic pressure (hereinafter, referred to as master cylinder hydraulic pressure) Pmc of the master cylinder MC is connected to the electronic control unit ECU, and a signal representing the master cylinder hydraulic pressure Pmc is transmitted to the electronic control unit ECU. It is configured to be inputted to. Further, a brake switch BS which is turned on when the brake pedal BP is depressed, a front wheel steering angle sensor (not shown) for detecting a steering angle θf of the wheels NL and NR in front of the vehicle, and a lateral sensor for detecting a lateral acceleration Gy of the vehicle. An electronic control unit EC includes an acceleration sensor (not shown) and a yaw rate sensor (not shown) for detecting the vehicle yaw rate γ.
U is connected.

The electronic control unit ECU of the present embodiment comprises processing units CP connected to each other via a bus.
A microcomputer MCP including a U, a memory ROM, a RAM, an input port IPT, an output port OPT, and the like is provided. Output signals from the wheel speed sensors WSl to WS4, the hydraulic pressure sensor PS, the brake switch BS, the front wheel steering angle sensor, the yaw rate sensor, the lateral acceleration sensor, and the like are input to the processing unit CPU from the input port IPT via the amplifier circuit AMP. It is configured to: Further, a control signal is output from the output port OPT to the throttle control device TH and the brake fluid pressure control device PC via the drive circuit ACT.

In the microcomputer MCP,
The memory ROM stores programs used for various processes including the flowcharts shown in FIGS. 3 to 8, the processing unit CPU executes the programs while an ignition switch (not shown) is closed, and the memory RAM executes the programs. Temporarily stores the variable data required for the execution of For each control such as throttle control,
Alternatively, a plurality of microcomputers may be configured by appropriately combining related controls, and the microcomputers may be electrically connected to each other.

This shows a brake fluid pressure control device BC.
In response to the operation of the brake pedal BP, the master cylinder MC is boosted via the vacuum booster VB, and the brake fluid in the master reservoir LRS is pressurized and the wheels F
The master cylinder pressure is output to the hydraulic system on the R, RL and wheel FL, RR side. The master cylinder MC is a tandem type master cylinder, and two pressure chambers are connected to respective brake hydraulic systems. That is, the first pressure chamber MCa is connected to the brake fluid pressure system on the wheels FR and RL, and the second pressure chamber MCb is connected to the wheels FL and R.
It is connected to the brake hydraulic system on the R side.

In the brake hydraulic system for the wheels FR and RL, the first pressure chamber MCa is connected to the wheel cylinders Wfr and Wrl via a main hydraulic passage MF and branch hydraulic passages MFr and MFl, respectively. I have. In the main hydraulic path MF,
A normally opened two-port two-position first electromagnetic on-off valve SC1 (functioning as a so-called cutoff valve, hereinafter simply referred to as on-off valve SC1) is provided. Further, the first pressure chamber MCa is connected to a check valve C described later via an auxiliary hydraulic pressure path MFc.
V5 and CV6. The aforementioned hydraulic pressure sensor PS is connected to the auxiliary hydraulic pressure passage MFc, and detects the master cylinder hydraulic pressure Pmc. As a sensor for detecting the operation state of the brake pedal BP, a stroke sensor for detecting the stroke of the brake pedal BP may be used instead of the hydraulic pressure sensor PS.

The branch hydraulic pressure paths MFr and MFl are provided with normally open two-port two-position solenoid valves PC1 and PC2 (hereinafter simply referred to as valve PC1 and PC2). Further, check valves CV1 and CV2 are arranged in parallel with these, respectively. The check valves CV1 and CV2 allow only the flow of the brake fluid in the direction of the master cylinder MC, and the brake fluid in the wheel cylinders Wfr and Wrl passes through the check valves CV1 and CV2 and the on-off valve SC1. The master cylinder MC is returned to the master cylinder reservoir LRS. Therefore, when the brake pedal BP is released, the wheel cylinder Wf
The fluid pressure in r and Wrl can quickly follow the fluid pressure drop on the master cylinder MC side. Further, the wheel cylinder Wfr,
Discharge-side branch hydraulic pressure passages RFr, R connected to Wrl
Fl, normally closed 2-port 2-position solenoid on-off valve PC
5, PC6 (hereinafter simply referred to as on-off valves PC5, PC6)
Is disposed, and the discharge hydraulic pressure line RF where the branch hydraulic pressure lines RFr and RFl join is connected to the auxiliary reservoir RS1.

The auxiliary reservoir RS1 has a check valve CV6,
The suction side of the hydraulic pump HP1 is connected via CV5,
The discharge side is connected to the upstream side of the on-off valves PC1 and PC2 via the check valve CV7 and the hydraulic path MFp. The hydraulic pump HP1 is driven by a single electric motor M together with the hydraulic pump HP2, introduces brake fluid from the suction side, increases the pressure to a predetermined pressure, and outputs it from the discharge side. The auxiliary reservoir RS1 is connected to the master reservoir LR of the master cylinder MC.
It is provided independently of S, and can be called an accumulator, and has a piston and a spring, and is configured to be able to store a predetermined volume of brake fluid.

The master cylinder MC is connected in communication between a check valve CV5 and a check valve CV6 on the suction side of the hydraulic pump HP1 via an auxiliary hydraulic passage MF. Check valve CV5
Is for blocking the flow of the brake fluid to the auxiliary reservoir RS1 and allowing the flow in the reverse direction. The check valves CV6 and CV7 regulate the flow of the brake fluid discharged through the hydraulic pump HP1 in a certain direction, and are usually integrally formed in the hydraulic pump HP1. Thus, the on-off valve SI1 shuts off communication between the master cylinder MC and the suction side of the hydraulic pump HP1 at the normal closed position shown in FIG. 2, and opens and closes the master cylinder MC and the hydraulic pump H at the open position.
It is switched so that the suction side of P1 communicates.

A relief valve RV1 and a check valve AV1 are arranged in parallel with the on-off valve SC1. The relief valve RV1 is connected from the master cylinder MC to the on-off valves PC1, P
Restrict the flow of brake fluid in the C2 direction,
1, when the brake fluid pressure on the PC2 side becomes larger than the master cylinder fluid pressure by a predetermined pressure difference or more, the master cylinder MC
This allows the flow of brake fluid in the direction, whereby the discharge brake fluid of the hydraulic pump HP1 is regulated to a predetermined pressure. The check valve AV1 is connected to the wheel cylinder Wfr,
This allows the flow of the brake fluid in the Wrl direction and prohibits the flow in the reverse direction. Due to the presence of the check valve AV1, even when the on-off valve SC1 is in the closed position, when the brake pedal BP is depressed, the wheel cylinder Wf
The brake fluid pressure in r and Wrl is increased. In addition, a damper DP1 is disposed on the discharge side of the hydraulic pump HP1, and a proportioning valve PV1 is interposed in a hydraulic path leading to the wheel cylinder Wrl on the rear wheel side.

On the other hand, in the brake fluid pressure system on the wheels FL and RR, similarly, a normally open 2-port 2-position solenoid valve SC2 (first opening / closing valve) including a reservoir RS2, a damper DP2, and a proportioning valve PV2. Valve), normally closed 2-port 2-position solenoid valve SI2 (second on-off valve), normally-open 2-port 2-position solenoid valve PC3, PC
4. Normally closed 2-port 2-position solenoid valve PC7, PC
8, check valves CV3, CV4, CV8 to CV10, a relief valve RV2, and a check valve AV2. The hydraulic pump HP2 is driven by the electric motor M to
Driven with P1.

The above-mentioned electric motor M, on-off valves SC1, SC
2, SI1, SI2 and on-off valves PC1 to PC8 are
Drive control is performed by the above-described electronic control unit ECU, and various controls such as brake assist control, anti-skid control, braking steering control (oversteer or understeer suppression control), front / rear braking force distribution control, and traction control, which will be described later, are performed.

In the present embodiment configured as described above, a series of processes such as braking steering control, brake assist control, anti-skid control, and the like are performed by the electronic control unit ECU, and an ignition switch (not shown) is opened. Then, the execution of the program corresponding to the flowcharts of FIGS. 3 to 8 starts.

FIG. 4 shows the operation of the braking control. First, at step 101, the microcomputer MCP is initialized and various calculated values are cleared. Then step 1
At 02, the detection signals of the wheel speed sensors WS1 to WS4 are read, and the detection signal of the hydraulic pressure sensor PS (master cylinder hydraulic pressure Pmc) is read. Also,
The detection signal of the front wheel steering angle sensor (the steering angle θf), the detection signal of the yaw rate sensor (the actual yaw rate γ), and the detection signal of the lateral acceleration sensor (that is, the actual lateral acceleration Gya) are read.

Next, the routine proceeds to step 103, where the master cylinder hydraulic pressure Pmc is differentiated, and a master cylinder hydraulic pressure change rate DPmc is obtained. Then, in step 104, the wheel speed Vw ** (** represents each wheel) of each wheel is calculated, and the wheel speed Vw ** of each wheel is differentiated to obtain the wheel acceleration DVw ** of each wheel. Is calculated. Next, at step 105, based on the wheel speed Vw ** of each wheel, the estimated vehicle speed Vso at the position of the center of gravity of the vehicle is Vso = MAX.
(Vw **), and an estimated vehicle speed Vso ** at each wheel position is obtained. Furthermore, if necessary, normalization is performed on each wheel position vehicle speed Vso ** in order to reduce an error based on a difference between the inner and outer wheels when the vehicle turns. Further, the vehicle body deceleration (hereinafter referred to as vehicle body deceleration) DVso in the front-rear direction at the position of the center of gravity of the vehicle is calculated by differentiating the vehicle speed Vso at the position of the center of gravity. Here, for convenience of description, the vehicle body deceleration is used, but if the sign is reversed, the vehicle body acceleration is used.)

Next, at step 106, the wheel speed Vw * of each wheel obtained at steps 103 and 104 described above.
* And the estimated vehicle speed Vso ** at each wheel position (or the normalized estimated vehicle speed at each wheel position), the actual slip ratio Sa ** of each wheel is Sa ** = (Vso ** − Vw). **) / Vso **
Is required. Next, at step 107, based on the vehicle body deceleration DVso and the actual lateral acceleration Gya at the position of the center of gravity, the road surface friction coefficient μ is approximately μ = (DVso ² + Gya).
² ) Estimated as ^1/2 . The road surface friction coefficient μ ** at each wheel position may be calculated based on the road surface friction coefficient μ and the estimated value of the wheel cylinder hydraulic pressure Pw ** of each wheel.

Subsequently, brake assist control is performed in step 108, which will be described later. Then, the process proceeds to a step 109, wherein various control modes such as anti-skid control are set, and a target slip ratio to be provided for the various control modes is set as described later. Next, by the hydraulic servo control in step 110, the brake hydraulic pressure control device PC is controlled to control the braking force on each wheel. In particular, in the brake assist control, the driving of the electric motor M and the on-off valves SC1, SC2, SI1, SI2 is controlled.

Next, referring to FIG. 4, step 10 in FIG.
8 will be described in detail.

First, at step 201, it is determined whether or not the brake assist control flag FL is the flag F1 or the flag F2.
Here, the flag F1 indicates that the start specifying control is being performed, and the flag F2 indicates that this control is being performed. At step 202, it is determined whether or not the BA control start condition is satisfied. If so, the process proceeds to step 203, where the control flag FL is set to the start specific control in-progress flag F1. Here, the condition for starting the brake assist control is determined by the detected hydraulic pressure Pm of the hydraulic pressure sensor PS.
c is greater than or equal to a predetermined value, and the detected fluid pressure change rate D
Whether or not the brake assist control needs to be started is determined based on whether or not Pmc is equal to or higher than a predetermined ratio, and specifically, whether or not it falls within a hatched area in FIG.

Subsequently, from step 203 to step 20
Proceeding to 4, the start specific control calculation is performed. That is, the control end prohibition time Ti, the duty Dis of the on-off valve SI * used for the start specifying control, and the execution time Ts of the start specifying control are set. Specifically, the control end prohibition time Ti
Using the graph shown in FIG. 0, the increase rate DPmc of the master cylinder hydraulic pressure at the present time (that is, at the time when it is determined that the control start is necessary)
Is set based on That is, as shown by the solid line in FIG. 10, the control end prohibition time Ti is set longer when the increase rate DPmc of the master cylinder hydraulic pressure is small than when it is large, and the increase rate DPmc of the master cylinder hydraulic pressure is large. It is set so that it becomes shorter gradually. On the other hand, as shown by the dashed line in FIG. 10, the control end prohibition time Ti is set to the master cylinder hydraulic pressure increase rate DPmc.
May be set only when is less than or equal to a predetermined ratio. That is,
If the increase rate DPmc of the master cylinder fluid pressure exceeds a predetermined rate, the control end prohibition time Ti may be set to zero.

The duty Dis of the on-off valve SI *
Is a predetermined duty (for example, 15%) according to the master cylinder hydraulic pressure Pmc and the change rate DPmc of the master cylinder hydraulic pressure.
%, 30%, 50%, 75%) are selected from a set map (not shown). Further, the execution time Ts of the start specifying control is determined by, for example, the hydraulic pump HP in consideration of the consumption amount Vc of the wheel cylinder and the duty of the on-off valve SI *.
It is set to the smaller of the estimated discharge time Tv calculated based on the discharge amount Vp of 1 (HP2) and the fixed time Tc (for example, 1 sec).

Then, the process proceeds to a step 205, wherein the duty of the opening / closing valve SI * for the specific start control is set to the value selected in the step 204, and the duty of the opening / closing valve SC * is set to 100%. Then, step 20
At 6, it is determined whether the above-mentioned execution time Ts has elapsed since the start of the brake assist control. If the execution time Ts has not elapsed, the process returns to the main routine of FIG.
07, and after the control flag FL is set to F2,
It returns to the main routine of FIG.

On the other hand, if it is determined in step 201 that the control flag FL is the start-specific control-in-progress flag F1 or the main control-in-progress flag F2, the process proceeds to step 208, in which it is determined whether the brake assist control end condition is satisfied. You. This control termination determination will be described later. If it is determined in step 208 that the termination condition is not satisfied, the process proceeds to step 209, and it is determined whether the control flag FL is the start-specific-control-in-progress flag F1. If so, the processing of steps 205 to 207 is executed again. Step 2
If it is determined in step 09 that the control flag FL is not F1, the control flag FL is the flag F2 during the main control, and the process proceeds to steps 210 to 213 to execute the processing of the main control.

First, at step 210, a vehicle deceleration Δg corresponding to a predetermined hydraulic pressure for brake assist control is added to a vehicle deceleration Gm corresponding to the master cylinder hydraulic pressure Pmc, and the target deceleration G of the vehicle is obtained. * Is set. That is, the target deceleration G * according to the operation state of the brake pedal BP is set. Then, the process proceeds to a step 211, wherein a difference between the target deceleration G * of the vehicle and the vehicle deceleration DVso at the position of the center of gravity used as the actual deceleration is calculated.
This deceleration deviation ΔG is set as a control deviation, and
Calculates the brake assist control amount. That is,
As shown in FIG. 11, based on the deceleration deviation ΔG, the on-off valve S
The duty of I * and SC * (the ratio of energization time) is set.

More specifically, on the pressure increasing side (the deceleration deviation ΔG is positive), the duty Di of the on-off valve SI * is set to be proportional to the deceleration deviation, and the duty Dc of the on-off valve SC * is set to 100. % And a substantially closed position. On the other hand, on the pressure reduction side (the deceleration deviation ΔG is negative),
The duty Dc of the on-off valve SC * is set to be proportional to the deceleration deviation, and the duty Dc of the on-off valve SI * is set.
i is set to a constant value near 0%, and is set to a substantially closed position. Further, a predetermined limit is imposed on the duty Di of the on-off valve SI *. That is, even if the deceleration deviation ΔG is large, the duty Di of the on-off valve SI * is set to the predetermined upper limit Du.
It is set so as not to exceed p. This is because an excessive amount of brake fluid is supplied from the master cylinder MC to the hydraulic pump HP
As a result, the sinking of the brake pedal BP and the fluctuation of the output signal of the hydraulic pressure sensor PS can be suppressed as much as possible.

Subsequently, the routine proceeds to step 213, where a brake assist braking force distribution control amount calculation is performed. This is to maintain the stable braking state by adjusting the braking force distribution between the wheels even during the brake assist control, and the target slip ratio of each wheel is set.

On the other hand, if it is determined in step 208 that the brake assist control end condition is satisfied, the routine proceeds to step 214, where the control flag FL is set to the end specifying control in-progress flag F3. Next, in step 215, an end specifying control operation is executed. That is, from a map (not shown) in which a predetermined duty is set according to the change rate (decrease rate) DPmc of the master cylinder fluid pressure, the duty Dce of the on-off valve SC * provided for the end specifying control.
Is selected. In the map, the duty is
The value is increased when the decrease rate of the master cylinder hydraulic pressure is large. Further, the execution time Te of the end specifying control is set to a fixed time (for example, 0.2 sec).

Then, the process proceeds to a step 216, wherein the duty of the on-off valve SC * for the end specifying control is set to the value selected in the step 215, and the duty of the on-off valve SI * is set to 0%. Next, at step 217, the execution time Te after the brake assist control ends.
Is determined. If not, the process returns to the main routine of FIG.
After the control flag FL is set to F0,
Return to the main routine.

On the other hand, when it is determined in step 202 that the BA control start condition is not satisfied (ie, during the end specifying control or not in control), the process proceeds to step 219, and the control flag FL is changed to the end specifying control flag F3. It is determined whether the answer is NO, and if so, steps 216 to 218 are executed again, and then the process returns to the main routine of FIG. Step 2
If it is determined in step 19 that the control flag FL is not the end-specifying-control-in-progress flag F3, it means that control is not being performed.
Return to the main routine.

Next, referring to FIG. 5, step 20 in FIG.
8 will be described in detail.

First, in step 401, after the start of the brake assist control (ie, after it is determined that the brake assist control needs to be started), the control end prohibition time Ti (FIG.
It is determined whether or not (set in step 204) has elapsed. If not, the routine proceeds to step 402, where the brake assist control end flag is forcibly turned off.
That is, the end of the brake assist control is prohibited until the predetermined time Ti elapses after the start of the brake assist control.

On the other hand, if it is determined in step 401 that the control termination prohibition time Ti has elapsed, the termination determination is permitted and the processing of steps 403 to 406 is executed. That is, it is determined in step 403 whether or not the brake switch BS is off. Otherwise, the process proceeds to step 404, in which it is determined whether or not the vehicle speed Vso at the position of the center of gravity is equal to or lower than a predetermined speed. Otherwise, the process proceeds to step 405, where the master cylinder hydraulic pressure Pmc is set to the predetermined lower limit Pa (for example, 1
(MPa) or less; otherwise, the process proceeds to step 406, where it is determined whether the master cylinder hydraulic pressure Pmc is equal to or greater than a predetermined upper limit Pb (for example, 15 MPa) corresponding to the lock pressure on a high μ road surface. You. Otherwise, the process proceeds to step 402, where the brake assist control end flag is turned off, and it is determined whether the control is to be ended. On the other hand, when it is determined in step 403 that the brake switch BS is off, or in step 404, the vehicle speed V
If so is determined to be equal to or lower than the predetermined speed Vk, or if it is determined in step 405 that the master cylinder hydraulic pressure Pmc is equal to or lower than the predetermined lower limit Pa, or to step 406
If it is determined that the master cylinder hydraulic pressure Pmc is equal to or higher than the predetermined upper limit value Pb, the routine proceeds to step 407, where the brake assist control end flag is turned on, and it is determined that the control end is necessary.

FIG. 6 is a timing chart for explaining the above-mentioned brake assist control. The characteristic (A) shows the detected master cylinder hydraulic pressure Pmc of the hydraulic pressure sensor PS, which substantially corresponds to the depression force of the brake pedal BP. The solid line shows an example of the characteristic during the brake assist control, and the two-dot chain line shows the characteristic when the brake assist control is not performed. The brake fluid pressure of the wheel cylinder during the brake assist control is indicated by a broken line. (B) shows the control mode of the brake assist control, in which the start specifying control, the gain down control, the main control, and the end specifying control are performed in this order from the left side of FIG.
Therefore, other than these, the brake assist is not controlled.
The characteristic (C) shows the change (drop amount) of the master cylinder hydraulic pressure Pmc caused by the brake assist control, and the characteristic (D) shows the dependence on the output of the hydraulic pressure sensor PS during the brake assist control. The characteristic of (E) is the deceleration deviation ΔG
(F) shows the change in duty of the on-off valves SI * and SC *.

In the figure, when the master cylinder hydraulic pressure Pmc detected by the hydraulic pressure sensor PS is equal to or higher than a predetermined value, the rate of change D
At point a at which Pmc becomes a predetermined ratio or more, the start specific control of the brake assist control starts, and until the point b after the execution time Ts, the duty Dis of the on-off valve SI * becomes a constant value based on the aforementioned map. Is set. When the start specifying control ends at the point b, the gain-down control is performed thereafter, and the duty Di of the on-off valve SI * is limited to 50% of that during the main control until the point c after the execution time Td has elapsed. Where a
From the point until the above-mentioned predetermined time Ti (see FIG. 10) elapses, as apparent from the characteristics (A) and (C), the drop amount of the master cylinder hydraulic pressure is particularly large, and the master cylinder hydraulic pressure Pmc May be less than or equal to a predetermined lower limit value Pb (see FIG. 5), and it may be erroneously determined that control termination is necessary. Therefore, in the present embodiment, as shown in FIG. 5, control termination is forcibly prohibited from the point a until the predetermined time Ti (see FIG. 10) elapses.

Thereafter, this control is performed up to the point f, the duty Di of the on-off valve SI * and the duty SC * of the on-off valve SC *.
c is set so as to be proportional to the deceleration deviation ΔG, based on which the on / off valves SI * and SC * are controlled to open and close. That is,
As shown by the broken line in (A), the wheel cylinder hydraulic pressure is
The hydraulic pressure is raised by a predetermined pressure relative to the master cylinder hydraulic pressure indicated by the two-dot chain line. However, the master cylinder pressure Pmc during the brake assist control is lower than the master cylinder pressure indicated by the two-dot chain line because the brake fluid in the master cylinder MC is sucked into the hydraulic pump HP as shown by the solid line. Become.

During this control, for example, the brake pedal B
When the pedaling force of P is weakened, the deceleration deviation ΔG becomes a negative value (that is, acceleration), and when the depression force of the brake pedal increases at point e, the deceleration deviation ΔG increases. As the deceleration deviation ΔG increases, the duty Di of the on-off valve SI * increases. However, if the duty Di increases as indicated by the broken line in (F), the amount of brake fluid sucked into the hydraulic pump HP increases accordingly. , (A), the master cylinder fluid pressure sharply decreases as indicated by the broken line, and the pedaling force of the brake pedal BP decreases extremely, giving the driver an uncomfortable feeling. For this reason, the duty Di of the on-off valve SI * is set so as not to exceed the upper limit value Dup, and a restriction is added as shown by a solid line near point e in FIG. When it is determined at point f that the detected master cylinder hydraulic pressure Pmc of the hydraulic pressure sensor PS is less than the predetermined value, the end specifying control is performed, and during the execution time Te, the duty Dce of the on-off valve SC * is set in the aforementioned map. , The brake assist control ends.

Finally, the hydraulic servo control in step 109 in FIG. 3 will be described in detail with reference to FIGS. 7 and 8.
Here, the drive control of the on-off valves SI * and SC * and the slip ratio servo control of the wheel cylinder hydraulic pressure for each wheel are performed.

First, at step 301, it is determined whether or not the mode is the braking steering control mode. If so, the routine proceeds to step 302, where the preset target slip ratio Sv ** for the braking steering control is set to the target slip of each wheel. If the target slip ratio St ** of each wheel is set to 0, the process proceeds to step 304. In step 304, it is determined whether or not the brake assist braking force distribution control is being performed. If so, in step 305, the slip ratio correction amount ΔSb ** for the brake assist braking force distribution control is added to the target slip ratio St **. After the addition, the process proceeds to step 306. Otherwise, the process directly proceeds to step 30.
Proceed to 6. In step 306, the target slip ratio St **
Slip ratio correction amount ΔSd for longitudinal braking force distribution control
**, slip ratio correction amount ΔSr ** for traction control,
The target slip ratio St ** is updated by adding the slip ratio correction amount ΔSs ** for anti-skid control. Note that ΔS
The values of d **, ΔSr **, and ΔSs ** are set to 0 when the corresponding control is not performed.

Then, in step 307, the slip ratio deviation ΔSt ** is calculated for each wheel, and in step 308, the vehicle body acceleration deviation ΔDVso ** is calculated.
Specifically, in step 307, the difference between the target slip rate St ** of each wheel and the actual slip rate Sa ** is calculated to determine a slip rate deviation ΔSt ** (ΔSt ** = St **).
-Sa **). In step 308, the difference between the vehicle deceleration DVso at the position of the center of gravity of the vehicle and the wheel acceleration DVw ** of the wheel to be controlled is calculated, and the vehicle deceleration deviation ΔD
Vso ** is required. At this time, the actual slip ratio Sa ** of each wheel and the vehicle body deceleration deviation ΔDVso ** are calculated differently depending on the control mode such as anti-skid control, traction control, etc., but the description thereof will be omitted.

Then, the routine proceeds to step 309, where the slip ratio deviation ΔSt ** is compared with the predetermined value Ka. If the difference is equal to or larger than the predetermined value Ka, the integrated value of the slip ratio deviation ΔSt ** is updated in step 311. That is, the current slip ratio deviation ΔS
The value obtained by multiplying t ** by the gain GI ** is added to the previous slip ratio deviation integrated value IΔSt **, and the current slip ratio deviation integrated value IΔSt ** is obtained. Slip ratio deviation | ΔSt *
When * | is smaller than the predetermined value Ka, the slip ratio deviation integrated value IΔSt ** is cleared (0) in step 310. Next, in steps 312 to 314, the slip ratio deviation integrated value IΔSt ** is equal to or less than the upper limit Kb and the lower limit K
c is limited to a value greater than or equal to
When the value is lower than the lower limit value Kc, the value is set to Kc, and the process proceeds to step 316.

In step 316, one parameter Y used for brake fluid pressure control in each control mode is set.
** is calculated as Gs ** · (ΔSt ** + IΔSt **). Further, in step 317, another parameter X ** to be provided for the brake fluid pressure control is calculated as Gd ** · ΔDVso **. The gains Gs ** and Gd ** are fixed gains set in advance.

Thereafter, the routine proceeds to step 318, where the hydraulic mode is set for each wheel in accordance with the control map shown in FIG. 12 based on the parameters X ** and Y **. In FIG. 12, a rapid decompression region, a pulse decompression region, a holding region,
Each region of the pulse pressure increasing region and the rapid pressure increasing region is set, and it is determined which region corresponds to the values of the parameters X ** and Y **. In the non-control state, the hydraulic mode is not set (the solenoid is off).

If the area determined this time in step 318 is switched from pressure increase to pressure reduction or pressure reduction to pressure increase with respect to the area determined last time, the fall or rise of the brake fluid pressure is made smooth. Since it is necessary, the pressure increase / decrease compensation processing is performed in step 319. For example, when switching from the rapid pressure reduction mode to the pulse pressure increase mode,
Sudden pressure increase control is performed, and the time is determined based on the duration of the immediately previous rapid pressure reduction mode. Then, step 3
At 20, the control mode for each wheel is set in relation to the other wheels. For example, rear row select control is performed, and hydraulic pressure control is performed on the rear wheels RR and RL based on the low-speed wheels.

Then, in step 321, the on-off valves SI * and SC * are opened and closed based on the duty Di of the on-off valve SI * and the duty Dc of the on-off valve SC * set in steps 205, 212 and 216 of FIG. (Ie, duty driving), and the electric motor M is also driven. Further, the solenoids of the on-off valves PC1 to PC8 are driven according to the above-mentioned hydraulic pressure control mode and the pressure increase / decrease compensation processing, and the braking force of each wheel is controlled.

[0061]

According to the present invention, it is forcibly determined that the brake assist control is to be terminated or not until the set time elapses after it is determined that the brake assist control needs to be started. It is possible to prevent the control from being erroneously terminated due to a drop in the hydraulic pressure.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of an embodiment of a braking control device of the present invention.

FIG. 2 is a configuration diagram illustrating an example of a brake fluid pressure control device of FIG. 1;

FIG. 3 is a flowchart showing an entire vehicle braking control according to the embodiment of the present invention.

FIG. 4 is a flowchart showing details of the brake assist control of FIG. 3;

FIG. 5 is a flowchart showing details of an end determination in FIG. 4;

FIG. 6 is a timing chart showing a fluctuation state of a master cylinder hydraulic pressure, a brake assist control mode, a deceleration deviation, a duty of each on-off valve, and the like in one embodiment of the present invention.

FIG. 7 is a flowchart showing details of hydraulic servo control in FIG. 3;

FIG. 8 is a flowchart showing details of hydraulic servo control in FIG. 3;

FIG. 9 is a graph showing a start area of the brake assist control according to the embodiment of the present invention.

FIG. 10 is a graph showing a relationship between an increasing rate of a master cylinder hydraulic pressure and a control end prohibition time in one embodiment of the present invention.

FIG. 11 is a graph showing the relationship between the deceleration deviation and the duty of the first and second on-off valves in one embodiment of the present invention.

FIG. 12 is a graph showing a relationship between a parameter used for brake hydraulic pressure control and a hydraulic mode in one embodiment of the present invention.

[Explanation of symbols]

 NR, NL, DR, DL Wheel Wfr, Wfl, Wrr, Wrl Wheel cylinder BP Brake pedal MC Master cylinder MF Main hydraulic path SC1, SC2 First open / close valve HP1, HP2 Hydraulic pump MFc Auxiliary hydraulic path SI1, SI2 Second on-off valve PS Hydraulic pressure sensor (hydraulic pressure detecting means) PC1 to PC8 On-off valve (modulator) ECU Electronic control unit

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takayuki Ito 2-1-1 Asahi-cho, Kariya-shi, Aichi Pref. Aisin Seiki Co., Ltd.

Claims (6)

[Claims] 1. A wheel cylinder mounted on wheels of a vehicle to apply a braking force, a master cylinder generating hydraulic pressure in response to an operation of a brake pedal on the wheel cylinder, and connecting the master cylinder to the wheel cylinder. A main hydraulic pressure path, a first on-off valve for opening and closing the main hydraulic pressure path, and a brake fluid which is connected to a discharge side between the first on-off valve and the wheel cylinder, and is pressurized with respect to the wheel cylinder. A hydraulic pump that discharges, and an auxiliary hydraulic pressure path that connects the suction side of the hydraulic pump to the master cylinder,
In a vehicle brake control device provided with a second on-off valve for opening and closing the auxiliary hydraulic pressure path, a hydraulic pressure detecting means for detecting an output hydraulic pressure of a master cylinder;
Start determination means for determining whether or not to start brake assist control based on the detection result of the hydraulic pressure detection means; and when the start determination means determines that control start is required, the first and / or second Braking control means for controlling the opening / closing valve and the hydraulic pump to perform the brake assist control; end determining means for determining whether or not to end the brake assist control based on the detection result of the hydraulic pressure detecting means; And a stop prohibiting means for causing the end determining means to determine whether the brake assist control is to be ended or not until a set time elapses after the means has determined that the brake assist control needs to be started. . 2. The brake assist control according to claim 1, wherein a hydraulic pressure change rate calculating means for calculating a change rate of an output hydraulic pressure of the master cylinder based on a detection result of the hydraulic pressure detecting means, and the start determining means. A vehicle braking control device, further comprising: time setting means for setting the set time based on a change ratio of the output hydraulic pressure of the master cylinder when it is determined necessary. 3. The time setting unit according to claim 2, wherein the time setting means sets the set time longer when the rate of increase in the output hydraulic pressure of the master cylinder is small than when the rate of increase is large. Vehicle braking control device. 4. The apparatus according to claim 1, further comprising a hydraulic pressure increase rate calculating means for calculating an increase rate of the output hydraulic pressure of the master cylinder based on a detection result of the hydraulic pressure detecting means, Only when the increase rate of the output hydraulic pressure of the master cylinder calculated by the hydraulic pressure increase rate calculating means is equal to or less than a predetermined rate, until the set time elapses after the start determining means determines that the brake assist control needs to be started. A brake control device for a vehicle configured to cause the end determination unit to determine whether the brake assist control has ended. 5. The end determination unit according to claim 1, wherein the termination determination unit determines that the brake assist control needs to be terminated when the output hydraulic pressure of the master cylinder detected by the hydraulic pressure detection unit is equal to or less than a predetermined value. Control device for a vehicle that is running. 6. The modulator according to claim 1, further comprising a modulator interposed between the first on-off valve and the wheel cylinder, the modulator for adjusting a brake fluid pressure of the wheel cylinder in accordance with an output of the braking control means. A vehicle braking control device, comprising: