JP2000247220A - Brake controller for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To keep the difference of fluid pressure or to hold the fluid pressure in a case when the fluid pressures of a plurality of wheel cylinders supplied from a hydraulic pump are different from one another in a brake controller for controlling the brake assist by supplying the output fluid pressure of a master cylinder to the wheel cylinders from the hydraulic pump. SOLUTION: This brake controller comprises a first shut-off valve SC for opening and closing a main hydraulic path MF, a hydraulic pump HP of which a discharge side is connected between the first shut-off valve and a plurality of wheel cylinders for discharging the brake fluid in the pressure rising of the wheel cylinders, an auxiliary hydraulic path Mfc for connecting an intake side of the hydraulic pump to a master cylinder, an intake valve SI for opening and closing the auxiliary hydraulic path, and the second shut-off valves PC1, 2 for controlling the supply of the fluid pressure to the wheel cylinders. The fluid pressure is detected for every wheel cylinder, and the second shut-off valves are independently controlled when the detected fluid pressures are different from one another.

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's operation of 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 composed of two wheel cylinders, a master cylinder, a main hydraulic passage connected to the master cylinder, a first shutoff valve for opening and closing the main hydraulic passage, and a first on-off valve. A hydraulic pump that connects the discharge side to the main hydraulic path on the wheel cylinder side and discharges the brake fluid that has been boosted to the wheel cylinder, an auxiliary hydraulic path that connects the suction side of the hydraulic pump to the master cylinder, A suction valve for opening and closing the hydraulic passage, two branch hydraulic passages for branching the main hydraulic passage into two and connecting brake fluid to two wheel cylinders, and a branch provided in each branch hydraulic passage. A second shutoff valve for opening and closing the communication of the hydraulic pressure path; and a bypass passage having a check ball that bypasses the second shutoff valve and allows only the flow from the wheel cylinder side to the master cylinder side. . Two sets (two systems) of the above-described configuration excluding the master cylinder are provided, and each system is connected to one master cylinder to control four wheels of the vehicle.

In this brake assist control, the communication between the wheel cylinder and the master cylinder via the main hydraulic pressure path is closed by closing the first shut-off valve. Simultaneously, the suction valve is opened, the hydraulic pump is driven, and the brake pump supplies brake fluid from the master cylinder to the wheel cylinder via the auxiliary hydraulic pressure path to perform brake assist control. The brake fluid pressure supplied to each wheel cylinder is adjusted by adjusting the closing timing of the second shut-off valve provided in each branch hydraulic pressure passage, or by controlling the branch hydraulic pressure separately from the second shut-off valve. By setting the relief through a discharge valve provided on the road, the setting can be made for each wheel cylinder.

[0005]

However, in the above-described vehicle, when a hydraulic pressure difference is provided between two wheel cylinders in the same system during the brake assist control, for example, one wheel runs on a low μ road such as on ice. However, when the other wheel travels on a high μ road such as a dry road surface, the following problem occurs. The first problem is that when there is a hydraulic pressure difference between the two wheel cylinders, it is difficult to maintain the hydraulic pressure of the high-pressure wheel cylinder and increase the pressure of the low-pressure wheel cylinder. The check valve provided in the bypass passage bypassing the second shut-off valve is opened and closed by a pressure difference between the master cylinder side and the wheel cylinder side of the second shut-off valve,
If the hydraulic pressure on the master cylinder side is lower than the hydraulic pressure on the wheel cylinder side, the brake hydraulic pressure in the wheel cylinder will decrease via the bypass passage. In particular, when the second control valve (provided in the branch hydraulic pressure passage communicating with the low pressure side wheel cylinder) is opened in order to increase the pressure of the low pressure side wheel cylinder, the hydraulic pressure of the second shutoff valve on the master cylinder side is increased. Since the pressure is reduced, the brake fluid pressure is reduced via the bypass passage of the second shut-off valve on the high pressure side to maintain the pressure.
The second problem is that it is difficult to increase the hydraulic pressure of the two wheel cylinders while maintaining a predetermined hydraulic pressure difference from a state where there is a hydraulic pressure difference between two wheel cylinders in the same system. When the respective second shut-off valves are opened to increase the hydraulic pressures of the two wheel cylinders, the two wheel cylinders communicate with each other via the branch hydraulic pressure path (and the main hydraulic pressure path), and thereby the brake fluid is released. Flows to equalize the hydraulic pressure. That is, the brake fluid flows from the high-pressure wheel cylinder to the low-pressure wheel cylinder.

Accordingly, the present invention relates to a brake control device for supplying brake fluid output from a master cylinder to a plurality of wheel cylinders by a hydraulic pump and performing brake assist control capable of adjusting hydraulic pressure for each wheel cylinder. It is an object of the present invention to be able to maintain a hydraulic pressure difference therebetween and to maintain a hydraulic pressure to be supplied to a wheel cylinder.

[0007]

In order to solve the above-mentioned technical problem, a vehicle brake control device according to the first aspect of the present invention includes a wheel cylinder mounted on each wheel of a vehicle and applying a braking force to a wheel cylinder. On the other hand, a master cylinder that boosts and outputs the brake fluid according to the operation amount of the brake pedal,
A main hydraulic passage communicating with the master cylinder, a first shutoff valve for opening and closing the main hydraulic passage, and a discharge side connected to the main hydraulic passage closer to the wheel cylinder than the first shutoff valve. A hydraulic pump for discharging the brake fluid pressurized to the wheel cylinder, an auxiliary hydraulic path connecting the suction side of the hydraulic pump to the master cylinder, a suction valve for opening and closing the auxiliary hydraulic path, a first shutoff A plurality of branch hydraulic pressure paths for connecting the main hydraulic pressure path closer to the wheel cylinder than the valve and the wheel cylinder, and a brake control means for switching the first shut-off valve and the suction valve and for driving and controlling the hydraulic pump; When a predetermined condition is satisfied when the brake pedal is operated, the first shutoff valve is closed by the braking control means, the suction valve is opened, and the drive pump is driven to output the output of the hydraulic pump. Apply brake fluid pressure to the wheel A second shutoff valve disposed in each of the branch hydraulic pressure paths for opening and closing the branch hydraulic pressure path, and a wheel cylinder closer to the wheel cylinder than the second shutoff valve. And a first hydraulic pressure detecting means for detecting each hydraulic pressure in the branch hydraulic pressure path, wherein the braking control means performs switching control of the second shut-off valve, and the switching control is performed by automatically controlling the hydraulic pump. At the time of pressure and when there is a difference between the detection pressures of the first hydraulic pressure detection means, each of the second shut-off valves is independently controlled.

With this configuration, during the brake assist control (during the automatic pressurization of the hydraulic pump), the hydraulic pressure of each wheel cylinder is detected by the first hydraulic pressure detecting means. By independently controlling the second shut-off valve for adjusting the increase and decrease of the hydraulic pressure for each wheel cylinder, the hydraulic pressure difference for each wheel cylinder can be maintained. Further, the main hydraulic pressure path in which the first shutoff valve is provided and the auxiliary hydraulic pressure path in which the suction valve is provided communicate with the master cylinder, respectively.
It is not necessary to provide the first shut-off valve and the suction valve independently.
In other words, there are three ports, a port communicating with the master cylinder, a port communicating with the main hydraulic pressure path, and a port communicating with the auxiliary hydraulic pressure path, and the brake fluid from the master cylinder is supplied to the main hydraulic pressure path and the auxiliary hydraulic pressure path. It is also possible to use a switching valve means that can selectively supply the same.

Preferably, the vehicle brake control device of the present invention detects the hydraulic pressure in the main hydraulic pressure passage or the branch hydraulic pressure passage closer to the master cylinder than the second shut-off valve. The second hydraulic pressure detecting means, and the braking control means, when at least one of the detected pressures of the first hydraulic pressure detecting means is higher than the detected pressure of the second hydraulic pressure detecting means, Preferably, each of the two shut-off valves is independently controlled.

With this configuration, the second hydraulic pressure detecting means detects the hydraulic pressure of the second shut-off valve on the master cylinder side, so that both sides of the second shut-off valve are accurately connected to the first hydraulic pressure detecting means. It is possible to realize a high hydraulic pressure contrast. In addition, the hydraulic pressure detection by the second hydraulic pressure detecting means includes at least one hydraulic pressure in the main hydraulic pressure passage closer to the wheel cylinder than the first shutoff valve or the branch hydraulic pressure passage closer to the master cylinder than the second shutoff valve. Preferably, a pressure sensor is arranged. Also, the master cylinder pressure immediately before the start of the brake assist control, the discharge pressure of the hydraulic pump based on the rotation speed of the hydraulic pump, etc., and the fluid supplied to the wheel cylinder based on the opening time of each second shut-off valve, etc. It is also possible to estimate the hydraulic pressure detection in consideration of the pressure.

Preferably, as set forth in claim 3, the second shut-off valve of the vehicle brake control device of the present invention includes a bypass passage that allows only a flow from the wheel cylinder side to the master cylinder side, The brake control means maintains the hydraulic pressure in the branch hydraulic pressure path in which the detection pressure of the first hydraulic pressure detection means is higher than the detection pressure of the second hydraulic pressure detection means, and the first hydraulic pressure If it is necessary to control the opening of the second shut-off valve of the branch hydraulic pressure path in which the detection pressure of the detection means is lower than the detection pressure of the second hydraulic pressure detection means, the bypass passage is closed after a predetermined time has elapsed. It may be configured to open the second shut-off valve in order to compensate for the amount of liquid flowing through.

Further, as set forth in claim 4, the predetermined time of claim 3 is set until the detection pressure of the second hydraulic pressure detection means becomes higher than the detection pressure of the first hydraulic pressure detection means. Then, the second shutoff valve may be opened to compensate for the amount of liquid flowing through the bypass passage.

These can specifically solve the first problem of the prior art described above. When the pressure difference is provided between the wheel cylinders in the same system during the brake assist control, the high pressure side is reduced. May be able to maintain the hydraulic pressure of the wheel cylinder. That is, when the pressure on the master cylinder side of the second shut-off valve becomes smaller than the pressure on the wheel cylinder side, the brake fluid in the wheel cylinder flows out to the master cylinder side via the bypass passage. In particular, when the second shut-off valve provided in the branch hydraulic pressure passage communicating with the low pressure side wheel cylinder is opened to increase the pressure, this flow becomes remarkable in the high pressure side wheel cylinder, and as a result, the high pressure side wheel The hydraulic pressure in the cylinder will be reduced.
Further, the brake fluid is supplemented after the hydraulic pressure on the master cylinder side of the second shut-off valve, which is increased in pressure by the fluid pump, becomes higher than the hydraulic pressure on the wheel cylinder side.
Backflow from the wheel cylinder side to the master cylinder side can be prevented through the shut-off valve. The amount of the brake fluid to be compensated is determined by the pressure detected by the first and second hydraulic pressure detecting means,
This can be handled by estimating the outflow amount of the brake fluid from the flow diameter of the bypass passage.

Preferably, as set forth in claim 5, the brake control means of the vehicle brake control device of the present invention is arranged such that the detected pressure of the first hydraulic pressure detecting means is higher than the detected pressure of the second hydraulic pressure detecting means. When it is necessary to control the opening of the second shut-off valve of the branch hydraulic pressure path which is also high pressure, the detection pressure of the first hydraulic pressure detection means is higher than the detection pressure of the second hydraulic pressure detection means. It is preferable that the second shut-off valve of the low-pressure branch hydraulic pressure path be closed.

This configuration specifically addresses the second problem of the prior art described above. If there is a pressure difference between the wheel cylinders during the brake assist control, the high pressure side wheel cylinder and And / or to prevent the brake fluid from flowing from the high pressure side wheel cylinder to the low pressure side wheel cylinder via the branch hydraulic pressure path (and the main hydraulic pressure path) when a pressure increase request is issued to the low pressure side wheel cylinder. What you get. When a differential pressure is required between the wheel cylinders, the road surface of the wheel on which the low-pressure wheel cylinder is mounted
Low μ road surface due to ice, water, gravel, etc. Therefore, even when a pressure increase request is made to the wheel cylinder on the low pressure side, the pressure increase to this wheel cylinder is slightly delayed, and its effect is smaller than the decrease in the braking force of the whole system in the same system due to the spillage of the brake fluid. In view of the above, the pressure difference between the wheel cylinders can be maintained by giving priority to increasing the pressure on the wheel cylinders on the high pressure side.

[0016]

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

FIG. 1 shows the overall configuration of an embodiment of a braking control device according to the present invention, in which wheels FL, FR, RL.
RR wheel cylinders Wfl, Wfr, Wrl,
Wrr is mounted. The wheel FL indicates the front left wheel when viewed from the driver's seat, and hereinafter the wheel FR is the front right wheel.
Wheel RL indicates a rear left wheel, and wheel RR indicates a rear right wheel.

In the present embodiment, the master cylinder MC is double-pressed via the vacuum booster VB in response to the operation of the brake pedal BP, and the brake fluid in the low-pressure reservoir LRS is boosted to increase the wheels FR, RL. The master cylinder hydraulic pressure is output to the hydraulic system on the vehicle side and the hydraulic system on the wheels FL and 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 hydraulic system on the side of the wheels FR and RL, and the second pressure chamber Mcb is connected to the wheel F
It is connected to the brake hydraulic system on the L, RR side. As described above, the hydraulic system according to the present embodiment is divided into two systems, and the diagonal piping (X piping) is configured.

In the brake hydraulic system on the side of the wheels FR and RL, the first pressure chamber MCa is connected to the wheel cylinders W through the main hydraulic path MF and the branch hydraulic paths MFr and MF1, respectively.
fr, Wrl. In the main hydraulic path MF, a normally open 2-port 2-position solenoid valve shut-off valve SC1 (referred to as a cut-off valve, hereinafter referred to as SC * when representing two systems of shut-off valves) Is interposed. The shut-off valve SC * of this embodiment is a linear solenoid type, and is controlled so that the differential pressure across the shut-off valve SC * changes in proportion to the solenoid drive current. Further, the first pressure chamber MCa is connected to check valves CV5 and CV described later via an auxiliary hydraulic pressure path MFc.
6 are connected. The auxiliary hydraulic pressure passage MFc is provided with a normally closed 2-port 2-position solenoid on-off valve suction valve S11 (hereinafter referred to as Sl * when representing two suction valves).

In the branch hydraulic pressure paths MFr and MFl, normally open two-port two-position solenoid valves PC1 and PC2 (hereinafter, referred to as PC2) are respectively provided.
Opening / closing valves PC1, PC2) are interposed.
In addition, bypass passages BP1 and BP2, in which check valves CV1 and CV2 are interposed in parallel with these, respectively, are opened and closed valves PC1 and P2.
It is provided so as to bypass C2. Check valve CV1,
CV2 permits the flow of the brake fluid in the direction of the master cylinder MC and limits the flow of the brake fluid in the direction of the wheel cylinders Wfr and Wrl.
1, CV2 and shut-off valve SC in the open position (the state shown in FIG. 1)
1 causes the brake fluid in the wheel cylinders Wfr, Wrl to flow through the master cylinder MC and thus the low-pressure reservoir LRS.
It is configured to be returned to. Here, when the brake pedal BP is released, the wheel cylinder Wf
The hydraulic pressure in r and Wrl can quickly follow the hydraulic pressure drop on the master cylinder MC side. Further, the wheel cylinder Wfr,
Branch hydraulic pressure paths RFr, Rf on the discharge side that are connected to Wrl
1 is a normally closed 2-port 2-position solenoid valve PC5, P
C6 (hereinafter simply referred to as on-off valves PC5 and PC6) is interposed, and the discharge hydraulic pressure line RF where the branch hydraulic pressure lines RFr and RFl join is connected to the reservoir RS1.

In the brake hydraulic system for the wheels FR and RL, the on-off valves PC1 and PC2 and the on-off valves PC5 and PC5 are used.
Each modulator is constituted by PC6. Further, on the upstream side of the on-off valves PC1, PC2, the branch hydraulic pressure paths MFr,
A hydraulic pump HP1 is connected to a hydraulic passage MFp that is connected to the MFl.
Is provided with a check valve CV5 or CV5 on its suction side.
The reservoir RS1 is connected via V6. Also,
The discharge side of the hydraulic pump HP1 is connected to the on-off valves PC1 and PC2 via the check valve CV7, respectively. The hydraulic pump HP1 is driven by one electric motor M together with the hydraulic pump HP2, and is configured to introduce brake fluid from the suction side, increase the pressure to a predetermined pressure, and output the pressure from the discharge side. The reservoir RS1 is provided independently of the low-pressure reservoir LRS of the master cylinder MC, has a piston Pi and a spring Sp, and is configured to be able to store brake fluid of a capacity necessary for various controls described later. I have.

The master cylinder MC is connected between the check valve CV5 and the check valve CV6 on the suction side of the hydraulic pump HP1 via the auxiliary hydraulic passage MFc. The check valve CV5 prevents the flow of the brake fluid to the reservoir RS1, and allows the flow in the reverse direction.
V7 regulates the flow of the brake fluid sucked and discharged through the hydraulic pump HP1 in a certain direction, and is usually integrally formed in the hydraulic pump HP1. Here, when the suction valve SI1 is in the closed position shown in FIG. 1, the communication between the master cylinder MC and the suction side of the hydraulic pump HP1 is cut off, and in the closed position, the master cylinder MC and the hydraulic pump HP1 are closed.
1 are switched so that the suction side communicates.

In parallel with the shutoff valve SC1, the master cylinder M
The flow of brake fluid from C to the on-off valves PC1 and PC2 is restricted. When the brake fluid pressure on the on-off valves PC1 and PC2 side becomes larger than the brake fluid pressure on the master cylinder MC by a predetermined pressure difference or more, the master A release valve RV1 that allows the flow of the brake fluid in the direction of the cylinder MC and a check valve AV1 that allows the flow of the brake fluid in the direction of the wheel cylinders Wfr and Wrl and prohibits the flow in the opposite direction are interposed. Here, when the pressurized brake fluid discharged from the hydraulic pump HP1 becomes larger than the output hydraulic pressure of the master cylinder MC by a predetermined differential pressure or more by the relief valve RV1, the brake fluid is returned to the master cylinder MC, The pressure is adjusted so that the brake fluid pressure in the fluid pressure path MF does not rise above a predetermined pressure. Further, due to the presence of the check valve AV1, the brake fluid pressure in the wheel cylinders Wfr and Wrl can be increased by depressing the brake pedal BP even when the shut-off valve SC1 is in the closed position. 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.

Similarly, in the brake hydraulic system on the side of the wheels FL and RR, similarly to the reservoir RS2, the damper DP2 and the proportioning valve PV2, the processing valve SC2 of the normally open type 2-port 2-position solenoid valve, and the normally open valve SC2. 2 port 2
Suction valve SI2 of position solenoid on-off valve, normally closed 2-port 2-position solenoid on-off valve PC7, PC8, normally open 2-port 2-position solenoid on-off valve PC3, PC4, check valve CV3, CV4, C
V8 to CV10, relief valve RV2, bypass passage B
P3, BP4 and a check valve AV2 are provided. The hydraulic pump HP2 is driven by the motor M to operate the hydraulic pump HP1.
And after starting the motor M, the two hydraulic pumps HP
1, HP2 are driven continuously. The shutoff valve SC *,
The drive of the suction valve SI * and the on-off valves PC1 to PC8 is controlled by the electronic control unit ECU, and a control mode such as anti-skid control is executed.

Wheel speed sensors WS1 to WS4 are provided on the wheels FR, RL, FL, RR, respectively, and these are connected to the electronic control unit ECU to control the rotation speed of each wheel,
That is, a pulse signal having a pulse number proportional to the wheel speed is input to the electronic control unit ECU. Further, a brake switch BS or the like, which is turned on when the brake pedal BP is depressed, is connected to the electronic control unit ECU. In the present embodiment, the electronic control unit ECU
Is connected to a hydraulic pressure sensor PS, and a signal representing the master cylinder hydraulic pressure is input to the electronic control unit ECU. In addition to these, the wheel cylinder Wf
r, Wrl, Wfl, Wrr are respectively provided with hydraulic pressure sensors PSfr, PSrl. PSfl,
PSrr is provided, and a hydraulic pressure sensor PSMF1 is provided on the side of the branch hydraulic pressure passages MFr, MFl from the shut-off valve SC1 of the main hydraulic pressure passage MF. Similarly, a hydraulic pressure sensor PSMF2 is provided in the brake hydraulic system on the wheels FL and RR. Hydraulic pressure sensors PSfr, PSrl, PSf
1, PSrr, PSMF1, and PSMF2 are connected to the electronic control unit ECU, and are configured to input signals representing the respective fluid pressures to the electronic control unit ECU.

The electronic control unit ECU of the present embodiment comprises a processing unit (CP) interconnected via a bus.
U), a memory (ROM, RAM), an input port, an output port, etc., and a microcomputer (not shown). Output signals from the wheel speed sensors WS1 to WS4, the brake switch BS, and the like are configured to be input to the CPU from input ports via amplifier circuits (not shown). The output port is configured to output a control signal to each of the electromagnetic on-off valves described later via a drive circuit (not shown). Electronic control unit EC
In U, the memory (ROM) stores programs to be used for various processes, the CPU executes the programs while an ignition switch (not shown) is closed, and the memory (RAM) stores the programs necessary for executing the programs. Temporarily store variable data.

In the brake hydraulic system having the above configuration, during normal braking operation, each solenoid valve is in the state shown in FIG. 1, and the motor M is stopped. When the brake pedal BP is depressed in this state, the master cylinder MC
The master cylinder hydraulic pressure is output from the first and second pressure chambers MCa and MCb to the hydraulic systems of the wheels FR and RL and the wheels FL and RR, respectively, and the shutoff valve SC * and the on-off valves PC1 to PC1 to open positions are provided. Through PC8, the wheel cylinder Wf
r, Wrl, Wfl, Wrr. Further, at the time of the brake assist control, the shutoff valve SC * is set to the closed position and the suction valve SI * is set to the open position, and the motor M is driven. This will be described later with reference to FIG.

For example, the mode shifts to the anti-skid control during the braking operation. For example, when it is determined that the wheels FR are in a locking tendency, the opening and closing valve P
C1 is set to the closed position, and the on-off valve PC5 is set to the open position. Here, the wheel cylinder Wfr is an on-off valve P
The brake fluid in the wheel cylinder Wfr flows into the reservoir RS1 and is reduced in pressure by communicating with the reservoir RS1 via C5. The wheels FR and RL and the wheels FL and RR
Since the hydraulic system on the wheel side has the same configuration, the hydraulic system on the wheels FR and RL side will be representatively described below.

When the wheel cylinder Wfr enters the pulse pressure increasing mode, the open / close valve PC5 is set to the closed position and the open / close valve PC1 is set to the closed position. To the wheel cylinder Wfr. In addition, on-off valves PC1,
By simultaneously setting the PC5 to the closed position, the brake fluid in the wheel cylinder Wfr is held at the pressure. Then, the on-off valve PC1 is intermittently controlled, and the wheel cylinder W
The brake fluid in fr is repeatedly increased in pressure and maintained, increases in a pulsed manner, and is gradually increased. Wheel cylinder W
When the rapid pressure increase mode is set for fr, the on / off valve PC1 is set to the open position after the on / off valve PC5 is set to the closed position, and the master cylinder MC supplies the master cylinder hydraulic pressure. Then, when the brake pedal BP is released and the master cylinder hydraulic pressure becomes lower than the hydraulic pressure of the wheel cylinder Wfr, the brake fluid in the wheel cylinder Wfr flows through the check valve CV1 and the shut-off valve SC1 in the open position into the master cylinder. Return to MC, and eventually to low pressure reservoir LRS. In this way, independent braking force control is performed for each wheel.

The control operation according to this embodiment having the above configuration will be described. When an ignition switch (not shown) is closed, execution of a program corresponding to the flowcharts of FIGS. 2 and 3 starts, and a series of processes such as brake assist control and ABS control are performed by the electronic control unit ECU.
FIG. 2 shows the entire braking control operation. Initially, in step 101, initialization is performed, and various calculated values are cleared. Next, at step 102, the wheel speed sensor WS
In addition to the detection signals of 1 to WS4 being read, the detection signal (master cylinder Pmc) of the hydraulic pressure sensor PS is read. In the present embodiment, the master cylinder hydraulic pressure Pmc detected by the hydraulic pressure sensor PS is used as the brake operation amount, but the stroke of the brake pedal BP may be used.

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 Vm ** (** indicates each wheel FR etc.) of each wheel is calculated, and these are differentiated to obtain the wheel acceleration DV ** of each wheel. Then, Step 10
In 5, the maximum value of the wheel speed Vw ** of each wheel is calculated as the estimated vehicle speed Vso at the position of the center of gravity of the vehicle (Vs
o = MAX (Vw **)). Also, the wheel speed V of each wheel
An estimated vehicle speed Vso ** is obtained for each wheel based on w **, and if necessary, normalization is performed to reduce an error based on a difference between inner and outer wheels when the vehicle turns. Further, the estimated vehicle speed Vso is differentiated, and the estimated vehicle acceleration DVso at the position of the center of gravity of the vehicle is calculated.

In step 106, the actual slip ratio of each wheel is determined based on the wheel speed Vm ** of each wheel and the estimated vehicle speed Vso ** (or the normalized estimated vehicle speed) obtained in steps 104 and 105. Sa **
= (Vso **-Vw **) / Vso **. Next, in step 107, the road surface friction coefficient μ is determined based on the estimated vehicle acceleration DVso at the position of the center of gravity of the vehicle.
Is required. Further, as means for detecting the road surface friction coefficient μ, various means such as a sensor for directly detecting the road surface friction coefficient can be used.

Subsequently, at step 108, ABS / brake assist control is performed, which will be described later. Then, by the hydraulic servo control in step 109, the pump M and various solenoid valves are controlled, and the braking force on each wheel is controlled.

FIG. 3 shows A in step 108 of FIG.
Of the specific processing contents of BS / brake assist control,
4 illustrates control according to the present invention. First, in step 201, it is determined whether the brake assist control is being performed. Step 2 if brake assist is in progress
Go to 02. In step 202, it is determined whether the ABS control is being performed. Step 2 if ABS control is in progress
03, and if the ABS control is not being performed, the process proceeds to step 204. In step 203, it is determined whether the ABS control has been completed. In step 204, it is determined whether the ABS control has been started. Step 201 to step 20
In the determination and control up to 4, it is determined whether or not the control start condition and the control end requirement of the generally known ABS control and brake assist control are satisfied.

Here, if it is determined in step 203 that the ABS control has not been completed,
When the BS control is started, in step 205, the wheel cylinder W is set in consideration of various calculation results from step 102 to step 107 and the road surface condition.
The brake fluid pressure to be supplied to fr, Wrl, Wrl, Wrr is calculated, and on-off valves PC1 to PC8 are calculated based on the calculation results.
Control.

Next, at step 206, it is determined whether there is a hydraulic pressure difference between the wheel cylinders in the same hydraulic system. Specifically, in the hydraulic system on the wheels FR, RL side, it is determined whether there is a pressure difference between the wheel cylinders Wfr, Wrl by comparing the detection of the hydraulic sensors PSfr, PSrl. If there is a pressure difference in step 206, the process proceeds to step 207.

In step 207, it is determined whether there is a pressure increase request on the low pressure side. In the detection of the hydraulic pressure sensors PSfr and PSrl compared in step 206, it is determined whether or not a pressure increase request has been issued to the wheel cylinders Wfr and Wrl indicating low pressure. If there is a low pressure side pressure increase request, the process proceeds to step 208. In step 208, it is determined whether there is a pressure increase request on the high pressure side. In step 208, similarly to step 207, it is determined whether or not there has been a pressure increase request for the wheel cylinders Wfr, Wrl indicating high pressure, among the detections of the hydraulic pressure sensors PSfr, PSrl compared in step 206. If it is determined in step 208 that a pressure increase request has been made on the high pressure side, the process proceeds to step 209.
On the other hand, if it is determined in step 208 that there has been no pressure increase request on the high pressure side, the process proceeds to step 210.

In step 209, the pressure increase output request to the low pressure side wheel cylinders Wfr and Wrl is forcibly changed to the pressure holding output request, and the low pressure side pressure is delayed.
On the other hand, in step 210, it is determined whether there is a hydraulic pressure holding request for the wheel cylinders Wfr, Wrl on the high pressure side. If there is a hydraulic pressure holding request in step 210,
Proceed to step 211. In step 211, a pressure increase output is requested to the wheel cylinders Wfr, Wrl on the high pressure side for which the request for maintaining the hydraulic pressure has been issued after a predetermined time has elapsed. Here, it is possible to provide a separate timer for the elapse of the predetermined time, but the detection of the hydraulic pressure sensor PSMF1 and the detection of the hydraulic pressure sensor PSfr
(Or the detection of the hydraulic pressure sensor PSrl) may be compared with each other, and the control may wait until the detection of the hydraulic pressure sensor PSMF1 becomes larger.

As described above, the hydraulic system on the wheels FR and RL has been described, but the hydraulic system on the wheels FL and RR can be similarly controlled.

In the above-described embodiment, the hydraulic pumps HP1 and HPMF are controlled by the hydraulic sensors PSMF1 and PSMF2.
Although the pressure on the discharge side of P2 is directly detected, it is not always necessary to provide the hydraulic pressure sensors PSMF1 and PSMF2. That is, the hydraulic path MFp and the hydraulic path MFp
To the wheel cylinders Wfr, Wrl and the branch hydraulic passages MFr, MFl with respect to the shutoff valve SC1 of the main hydraulic passage MF communicating with the main hydraulic passage MF.
The total volume on the master cylinder MC side of the on-off valves PC1 and PC2 is extremely smaller than the discharge capacity of the hydraulic pumps HP1 and HP2, and if the on-off valves PC1 and PC2 are closed, the hydraulic pumps HP1 and HP2 In view of the fact that the discharge fluid can push back and open the relief valve RV1 and return to the master cylinder MC side by slightly rotating the hydraulic pressure sensor P
It is also possible to estimate the flow rate of the brake fluid flowing when the on-off valves PC1 and PC2 are opened based on the detection of S.

FIG. 4 shows another embodiment corresponding to FIG. In the embodiment shown in FIG. 4, the three-port two-position solenoid valve EV1 and EV2 (hereinafter, referred to as “EV1” and “EV2”)
EV * is used to indicate a two-system solenoid on-off valve) is employed instead of the shutoff valve SC * and the suction valve SI * shown in FIG. FIG. 4 shows a normal control state in which the brake fluid is supplied and discharged between the master cylinder MC and the wheel cylinders Wfr, Wrl, etc., via the main fluid passage MF without driving the hydraulic pumps HP1, HP2. I have. On the other hand, brake assist control is performed and the hydraulic pumps HP1 and HP2
To drive the master cylinder M through the auxiliary liquid passage MFc.
In the case of supplying and discharging the brake fluid between C and the wheel cylinders Wfr, Wrl, etc., it is possible to switch between EV * s.

In FIGS. 1 and 4, the shut-off valve SC
*, Suction valve SI *, solenoid on-off valve EV * and on-off valve PC *
All use an electromagnetic valve, but it is possible to use a switching valve or the like without using a solenoid without being limited to the electromagnetic valve.

[0043]

According to the present invention, there is provided a brake control device for performing a brake assist control capable of adjusting a hydraulic pressure for each wheel cylinder by supplying an output hydraulic pressure of a master cylinder to a plurality of wheel cylinders by a hydraulic pump. It is possible to maintain the hydraulic pressure difference between the wheel cylinders and maintain the hydraulic pressure to be supplied to the wheel cylinders.

[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 flowchart showing an entire vehicle braking control according to the embodiment of the present invention.

FIG. 3 is a flowchart showing details of ABS control and brake assist control of FIG. 2;

FIG. 4 is a diagram showing another embodiment corresponding to FIG. 1;

[Explanation of symbols]

FR, FL, RR, RL Wheel Wfr, Wfl, Wrr, Wrl Wheel cylinder BP Brake pedal MC Master cylinder MF Main hydraulic pressure path MFr, MF1 Branch hydraulic pressure path SC1, SC2 Shutoff valves (first shutoff valves) HP1, HP2 Hydraulic pump MFc Auxiliary hydraulic pressure path SI1, SI2 Second on-off valve PS Hydraulic pressure sensor PSfr, PSrl, PSfl, PSrr Hydraulic pressure sensor (first hydraulic pressure detection sensor) PSMF1, PSMF2 Hydraulic pressure sensor (Second hydraulic pressure sensor) Pressure detection sensor) PC1 to PC4 On / off valve (second shutoff valve) PC5 to PC8 On / off valve ECU Electronic control unit BP1, BP2, BP3, BP4 Bypass passage

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Hiraku Kato 2-1-1 Asahi-cho, Kariya-shi, Aichi Prefecture Inside Aisin Seiki Co., Ltd. (72) Inventor Kenji Tanaka 2-1-1 Asahi-cho, Kariya-shi, Aichi Prefecture 3D046 BB00 BB25 BB28 CC02 DD04 EE01 FF09 HH16 JJ16 LL23 LL29 LL37 LL43

Claims (5)

[Claims] 1. A wheel cylinder mounted on each wheel of a vehicle for applying a braking force, a master cylinder for boosting and outputting brake fluid to the wheel cylinder in accordance with an operation amount of a brake pedal, and communicating with the master cylinder. A main hydraulic pressure path to be connected, a first shut-off valve for opening and closing the main hydraulic pressure path,
A hydraulic pump that connects a discharge side to the main hydraulic pressure path closer to the wheel cylinder than the first shutoff valve and discharges a boosted brake fluid to the wheel cylinder, and a suction side of the hydraulic pump An auxiliary hydraulic pressure path connected to a master cylinder, a suction valve for opening and closing the auxiliary hydraulic pressure path, and a communication connection between the main hydraulic pressure path closer to the wheel cylinder than the first shutoff valve and the wheel cylinder. A plurality of branch hydraulic paths, a brake control means for controlling switching of the first shut-off valve and the suction valve and driving of the hydraulic pump, and when a predetermined condition is satisfied when operating the brake pedal; The brake control means causes the first shutoff valve to be in the closed position and the suction valve to be in the open position, and drives the drive pump to supply the output brake fluid pressure of the hydraulic pump to the wheel cylinder. A second shut-off valve disposed in each of the branch hydraulic pressure paths to open and close the branch hydraulic pressure path, and the wheel cylinder being located closer to the wheel cylinder than the second shut-off valve. First hydraulic pressure detecting means for detecting each hydraulic pressure in the side branch hydraulic pressure path, wherein the braking control means performs switching control of the second shut-off valve, and the switching control includes When the hydraulic pump is automatically pressurized and the first
And a control unit for controlling each of the second shut-off valves independently when there is a difference between the detected pressures of the hydraulic pressure detecting means. 2. The pressure sensor according to claim 1, further comprising a second hydraulic pressure detecting means for detecting a hydraulic pressure in the main hydraulic pressure passage or the branch hydraulic pressure passage closer to the master cylinder than the second shutoff valve. And
The brake control means independently controls each of the second shut-off valves when at least one of the detection pressures of the first hydraulic pressure detection means is higher than the detection pressure of the second hydraulic pressure detection means. And a braking control device for a vehicle. 3. The system according to claim 2, wherein the second shut-off valve further includes a bypass passage allowing only a flow from the wheel cylinder side to the master cylinder side, and the braking control means includes: The pressure detected by the pressure detecting means is equal to the second pressure.
The hydraulic pressure of the branch hydraulic pressure path, which is higher than the detection pressure of the hydraulic pressure detection means, is maintained, and the detection pressure of the first hydraulic pressure detection means is equal to the detection pressure of the second hydraulic pressure detection means. If it is necessary to open the second shut-off valve of the branch hydraulic pressure passage having a lower pressure than that of the branch hydraulic passage, the second shut-off valve is opened to compensate for the amount of liquid flowing through the bypass passage after a predetermined time has elapsed. A braking control device for a vehicle. 4. The pressure detection device according to claim 3, wherein the second shutoff valve is opened to compensate for an amount of liquid flowing through the bypass passage, and the detection pressure of the second hydraulic pressure detection means is equal to the first hydraulic pressure detection. A braking control device for a vehicle, which is started after the pressure becomes higher than the detection pressure of the means. 5. The branch hydraulic pressure path according to claim 2, wherein the braking control means has a detection pressure of the first hydraulic pressure detection means higher than a detection pressure of the second hydraulic pressure detection means. When it is necessary to control the opening of the second shut-off valve, the branch hydraulic pressure path in which the detection pressure of the first hydraulic pressure detection means is lower than the detection pressure of the second hydraulic pressure detection means A second control valve for closing the vehicle.