JP2008273384A - Braking force control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a brake boosting control device to generate wheel cylinder pressure in response to brake operating force in high precision by precisely detecting pressure generated by the brake pedal operating force of a driver. <P>SOLUTION: This braking force control device is furnished with a first decompression means to carry out decompression motion by reducing brake fluid of a wheel cylinder by making a gate valve GVOP in a valve opening state when hydraulic pressure of the wheel cylinder is higher than a master cylinder upon a decompression demand from an anti-lock brake control in simultaneously controlling a brake assist control and the anti-lock brake control; and a second decompression means to carry out the decompression motion by driving a pump PMPP by making the gate valve in the valve opening state, a holding valve in a valve closing state and a decompression valve in a valve opening state. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention provides a brake assist control for supplying a brake fluid pressure higher than a pressure corresponding to a braking operation by the driver when the driver performs a braking operation, and an anti-lock for preventing the wheels from being locked during braking. The present invention relates to a brake control device that performs brake control.

  Conventionally, when a driver's emergency braking operation is detected, or when the driver's braking operation cannot obtain sufficient braking force intended by the driver due to brake fade, the pressure corresponding to the driver's braking operation is used. A braking device that supplies a high braking fluid pressure is also known. Brake assist control (hereinafter referred to as BA control) is a brake control that can generate a braking force intended by the driver by supplying a brake fluid pressure higher than the pressure corresponding to the driver's braking operation. It is called.

  Anti-lock brake control (hereinafter referred to as ABS control) is also a well-known technique for appropriately operating the wheel cylinder pressure of a wheel when the wheel slip becomes excessive during braking. Therefore, even in the BA control, it is possible to generate a large braking force without generating excessive slip on the wheel by combining with the ABS control.

  In the BA control and ABS control, as described in, for example, Patent Document 1, in the middle of a brake circuit connecting the master cylinder and the wheel cylinder, a gate valve for controlling these conductive states, and the wheel cylinder side from the gate valve. Is connected to the holding valve for controlling the conduction state to the wheel cylinders for one system and two wheels communicating with each other, the pump, the suction valve for controlling the conduction state between the master cylinder and the suction hole of the pump, and the suction hole of the pump. This is realized in an apparatus including a reservoir and a pressure reducing valve that controls a conduction state between the reservoir and the wheel cylinder.

  In the above device, when the BA control is started, the intake valve is opened and the pump is activated, so that the brake fluid on the master cylinder side is pumped by the pump, and the gate valve is closed at this time. The wheel cylinder pressure can be increased according to the discharge amount of the pump when the holding valve is opened and the pressure reducing valve is closed. That is, it is possible to supply a braking hydraulic pressure higher than the pressure corresponding to the braking operation by the driver.

  Further, from the BA control state, when the intake valve is closed, the holding valve is closed, and the pressure reducing valve is opened, the wheel cylinder and the reservoir are connected, and the brake fluid flows to the reservoir. Depressurization is possible. If the wheel slip becomes excessive during braking and the wheel cylinder needs to be depressurized, the depressurizing means can be used to control the wheel slip. By such means, ABS control during BA control can be realized.

  The brake fluid that has flowed into the reservoir due to the pressure reduction of the wheel cylinder is guided to the suction hole of the communicating pump by the pressure reducing means, and is pumped by the pump. At this time, since the gate valve and the holding valve are both closed during the pressure reducing means, the high pressure oil passage between the gate valve, the holding valve and the pump discharge hole is blocked. . When the brake fluid in the reservoir is pumped by the pump while the high pressure oil passage is shut off, the pressure in the high pressure oil passage further increases. In the technique described in Patent Document 1, a relief valve is built in the gate valve, and when the hydraulic pressure in the high pressure oil passage becomes a predetermined relief pressure compared to the master cylinder pressure, The structure allows the flow of brake fluid toward the master cylinder, preventing excessive pressure increase in the high-pressure oil passage.

  However, in the technique described in Patent Document 1, in order to prevent an excessive pressure increase in the high-pressure oil passage, means for incorporating a relief valve in the gate valve is taken. The size itself increases.

Therefore, in the technique disclosed in Patent Document 2, instead of the configuration in which the relief valve is built in, a linear solenoid valve that can change the relief pressure in the gate valve is used as a relief means, and an excessive increase in the high pressure oil passage is used. Prevents pressure.
Japanese Patent Laid-Open No. 11-20640 JP 2006-51592 A

  However, since the technique described in Patent Document 2 does not require a relief valve, it is necessary to employ a linear solenoid valve even if the cost and increase in size associated with incorporating the relief valve can be avoided. This linear solenoid valve is costly and does not solve the problem that the valve itself becomes large. This is because, for example, in order to ensure the relationship between the opening degree and the current, the solenoid itself is increased in size and it is necessary to ensure controllability.

  The present invention has been made in view of the above-described problems, and an object thereof is to provide a braking force control device capable of simultaneously controlling BA control and ABS control with an inexpensive configuration.

In order to achieve the above object, in the present invention, a master cylinder that generates a hydraulic pressure corresponding to a driver's braking operation,
A pump having a suction hole capable of communicating with the master cylinder;
A suction valve for controlling a conduction state between the master cylinder and the suction hole of the pump;
A wheel cylinder capable of communicating with both the master cylinder and the discharge hole of the pump;
In the middle of a brake circuit connecting the master cylinder and the wheel cylinder, a gate valve for controlling the conduction state of these,
Holding valves for controlling the conduction state to the wheel cylinders for one system and two wheels communicating with each other on the wheel cylinder side from the gate valve;
A reservoir capable of communicating with both the wheel cylinder and the suction hole of the pump;
A pressure reducing valve for controlling a conduction state between the wheel cylinder and the reservoir;
The gate valve is closed, the intake valve is opened, the holding valve is opened, the pressure reducing valve is closed, and the pump is driven to assist the braking force generated by the master cylinder. Brake assist means for executing brake assist control;
Including a process for controlling a conduction state with the master cylinder, the wheel cylinder, the pump, and the reservoir, and a process for bringing the pump into an operating state, and the hydraulic pressure of the wheel cylinder is increased or decreased to avoid wheel lock. Anti-lock brake means for executing anti-lock brake control for pressure control;
In a braking force control device comprising:
When the anti-lock brake means is under the brake assist control and the hydraulic pressure of the wheel cylinder is higher than the hydraulic pressure of the master cylinder, the anti-lock brake means responds to the pressure reduction request by the anti-lock brake control. First depressurizing means for depressurizing the wheel cylinder with the valve opened;
When the brake assist control is in progress and the hydraulic pressure of the wheel cylinder is lower than the hydraulic pressure of the master cylinder, the gate valve is opened in response to a pressure reduction request by the antilock brake control, And a second pressure reducing means for performing a pressure reducing operation of the wheel cylinder with the suction valve closed, the holding valve closed, and the pressure reducing valve opened.

  That is, when the oil passage constituted between the gate valve, the holding valve and the discharge side of the pump is a high pressure oil passage, the hydraulic pressure in the high pressure oil passage during the brake assist control is By executing the first pressure reducing means, the gate valve is opened to reduce the pressure. Thereby, the hydraulic pressure in the high-pressure oil passage does not become higher than the hydraulic pressure at the time of the pressure reduction request of the antilock brake control, that is, the wheel lock pressure. Therefore, excessive hydraulic pressure is not applied to the high-pressure oil passage, and the brake assist control and the antilock brake control can be simultaneously controlled without expensive relief means such as a relief valve or a solenoid valve.

  Hereinafter, the best embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a system configuration diagram of a braking force control apparatus according to an embodiment of the present invention. The braking force control apparatus of the present embodiment includes a first system P including a left front wheel FL and a right rear wheel RR, and a second system S including a right front wheel FR and a left rear wheel RL. These two systems are identical in configuration. For this reason, in the following description, the configuration and operation of the first system P will be described. That is, in the following description, the configuration and operation of the second system may be considered by converting P (system) into S (system), FL into FR, and RR into RL.

  The braking force control apparatus according to the first embodiment is controlled by a control unit (hereinafter, ECU). The braking force control device includes a brake pedal BP, and the brake pedal BP is connected to the vacuum booster BB. The vacuum booster BB increases the driver's braking force, thereby generating hydraulic pressure in the master cylinder MC. The master cylinder MC is a tandem type having two hydraulic chambers, and communicates with the first system P and the second system S, respectively.

  A hydraulic pressure sensor PSM is disposed in the hydraulic pressure passage H0P of the first system P. The hydraulic pressure in the hydraulic pressure passage H0P, that is, the hydraulic pressure generated by the master cylinder MC is converted into an electric signal and supplied to the ECU. The master cylinder hydraulic pressure PMC is detected by ECU.

  A high pressure oil passage H1P is connected to the hydraulic pressure passage H0P via a gate valve GVOP. The gate valve GVOP is a normally open type electromagnetic valve that maintains the valve open state in an uncontrolled state and shuts off the communication state between the hydraulic pressure passage H0P and the high pressure oil passage H1P when a drive signal is supplied from the ECU. . A check valve CVP is arranged in parallel with the gate valve GVOP. The check valve CVP is a one-way valve that allows only the flow of brake fluid from the high-pressure oil passage H1P to the hydraulic passage H0P.

  The high pressure oil passage H1P communicates with the wheel cylinder hydraulic passages H2FL and H2RR via the holding valves SIFL and SIRR, respectively. The holding valves SIFL and SIRR maintain the valve open state in an uncontrolled state, and when the drive signal is supplied from the ECU, the normally open valve shuts off the communication state between the high pressure oil passage H1P and the wheel cylinder hydraulic pressure passages H2FL and H2RR. Type solenoid valve.

  Check valves CVFL and CVRR are arranged in parallel with the holding valves SIFL and SIRR, respectively. The check valves CVFL and CVRR are one-way valves that allow only the flow of brake fluid from the wheel cylinder hydraulic pressure paths H2FL and H2RR to the high pressure oil path H1P. The wheel cylinder hydraulic pressure paths H2FL and H2RR communicate with the wheel cylinders WCFL and WCRR, respectively.

  In addition, hydraulic pressure sensors PSFL and PSRR are arranged on each wheel. The hydraulic pressure generated by each wheel cylinder is converted into an electrical signal and supplied to the ECU, and the wheel cylinder hydraulic pressure PWCFL (RR) is supplied to the ECU. To detect.

  At the same time, wheel speed sensors VWFL and VWRR are installed on each wheel, and a pulse signal is output at a cycle corresponding to the wheel speed VW. The output signals of the wheel speed sensors VWFL and VWRR are supplied to the ECU, and the wheel speed VWFL (RR) is detected by the ECU.

  The wheel cylinder hydraulic pressure paths H2FL and H2RR communicate with the pressure reducing path H3P via pressure reducing valves SOFL and SORR. The pressure reducing valves SOFL and SORR are normally closed solenoid valves that open the wheel cylinder hydraulic pressure paths H2FL and H2RR and the pressure reducing path H3P when a drive signal is supplied from the ECU while the valve is closed in an uncontrolled state. It is.

  The decompression path H3P communicates with the reservoir RSVP. The reservoir RSVP incorporates a piston and a spring therein, and can store brake fluid by elastically deforming the spring.

  The reservoir RSVP communicates with the suction path HPP via the one-way valve CVRP. The suction path HPP communicates with the suction side of the pump PMPP. The discharge side of the pump PMPP communicates with the high-pressure oil passage H1P. The suction path HPP communicates with the hydraulic pressure path H0P via the suction valve GVIP. The suction valve GVIP is a normally closed electromagnetic valve that maintains a closed state in an uncontrolled state and opens the hydraulic pressure passage H0P and the suction passage HPP when a drive signal is supplied from the ECU.

  The pump PMPP is driven by the motor MOT by the ECU command supply, so that the brake fluid stored in the reservoir PSVP or the brake fluid that flows from the hydraulic pressure passage H0P by opening the suction valve GVIP is supplied to the high-pressure oil passage H1P. Can be sent to.

  In BA control, when the driver's emergency braking operation is detected, or when the driver's braking operation cannot obtain sufficient braking force as intended by the driver due to brake fade, etc., the wheel cylinder fluid pressure is adjusted to the master cylinder fluid pressure. The pressure is higher than the pressure to assist the driver's braking operation. In this assist control, the gate valve GVOP is closed to shut off the hydraulic pressure passage H0P and the high-pressure oil passage H1P, and the suction valve GVIP is opened to open the hydraulic pressure passage H0P and the suction passage HPP. The wheel cylinder hydraulic pressure can be made higher than the master cylinder hydraulic pressure by driving the MOT and sending the brake fluid flowing into the suction passage HPP by the pump PMPP to the high-pressure oil passage H1P.

  Further, when the slip of the wheel becomes excessive during BA control, ABS control for appropriately controlling the wheel cylinder hydraulic pressure of the wheel is performed. The principle of ABS control is well known. Briefly, based on the input from each wheel speed sensor VWFL, VWFR, VWRL, VWRR, the wheel slip at the time of braking is calculated. After the wheel cylinder hydraulic pressure of the wheel is reduced to avoid wheel lock, the pressure is increased / decreased and held as appropriate so that the wheel speed becomes the most effective slip for braking.

  In the braking force control apparatus of the first embodiment, when the BA control is started, the wheel cylinder hydraulic pressure becomes higher than the master cylinder hydraulic pressure, and a slip exceeding the ABS control start threshold may occur in any wheel. is there. When the ECU recognizes an ABS control request during BA control, the ECU executes BA control and ABS control simultaneously. Hereinafter, this state is referred to as ABS control during BA control.

  As described above, even during the BA control, when the wheel slips, it is necessary to ensure the pressure reduction by the ABS control. Therefore, even during BA control, the suction valve GVIP is closed or the valve opening time and cycle are controlled so that the hydraulic pressure in the suction passage HPP becomes a predetermined negative pressure. That is, when the brake fluid is discharged from the pressure reducing valve by the ABS control, the brake fluid flows into the reservoir RSVP. Since the brake fluid that has flowed in is almost atmospheric pressure, it cannot be said that the brake fluid that has flowed into the reservoir RSVP is necessarily sucked if the suction path HPP is at about atmospheric pressure. Then, even if it is going to discharge brake fluid by the next decompression control, the reservoir RSVP cannot store the brake fluid and the ABS control cannot be executed properly.

  Therefore, the brake fluid flowing into the reservoir RSVP is always sucked by the pump PMPP by controlling the suction path HPP to have a predetermined negative pressure. As a result, the brake fluid stored in the reservoir RSVP does not remain indefinitely, and the pressure reduction control can always be executed.

  FIG. 2 is a flowchart of a control routine executed by the ECU to perform ABS control during BA control. FIG. 2 is executed for each control cycle, and processing is performed for each wheel. At the same time, the time chart shown in FIG. 3 shows a waveform operation example of wheel speed, master cylinder, wheel cylinder hydraulic pressure waveform, and differential pressure between wheel cylinder pressure and master cylinder pressure in the ABS control during BA control.

  Note that the time intervals in FIG. 3 are shown mainly with emphasis on the timing of pressure reduction. Further, in FIG. 3, for the sake of explanation, an example regarding the FL wheel and the RR wheel that are the first system is shown, but even if this is replaced with the second system, the FL wheel and the RR wheel in FIG. Even if the vertical relationship is considered in reverse, the establishment of the ABS control during the BA control does not change.

  First, it is determined in step 101 in FIG. 2 whether or not BA control is being performed. If it is determined that BA control is being performed, step 102 is executed.

  In step 102, the pump PMPP is driven by driving the motor MOT by the ECU command supply. The motor MOT is driven continuously so as to coincide with the target rotational speed set as appropriate at the same time as the BA control is started, and the motor MOT is already driven in the ABS control during BA control. Good.

  In FIG. 3, a BA control request is generated at time t1, steps 103 → 107 → 109 are executed, the gate valve GVOP is closed, the suction valve GVIP is opened, the hydraulic pressure passage H0P and the suction passage HPP. Is opened, the brake fluid flows into the suction passage HPP, and the inflow brake fluid is discharged to the high-pressure oil passage H1P by the pump PMPP.

  The brake fluid that has flowed into the high pressure oil passage H1P flows into the wheel cylinder fluid pressure passages H2FL, H2RR, and as a result, the wheel cylinder pressures PWCFL, PWCRR are led to a higher pressure than the master cylinder pressure PMC. Hereinafter, this state is referred to as pump-up pressure increase. The pressure increase amount of the pump up pressure increase can be controlled by the valve opening time of the suction valve GVIP or the rotational speed of the motor MOT that drives the pump PMPP.

  Next, in step 103, it is determined whether or not ABS control is being performed. In FIG. 3, the pseudo vehicle speed VI is created based on inputs from the wheel speed sensors VWFL, VWFR, VWRL, and VWRR. The ABS control starts when the wheel speed of any of the four wheels falls below the ABS intervention threshold calculated to a value that gives a predetermined slip amount with respect to the pseudo vehicle speed VI. If ABS control is being performed, step 104 is executed, and if ABS control is not being performed, step 107 is executed.

  In step 107, the gate valve GVOP is closed, and then step 108 is executed. In step 108, it is determined whether there is a holding request. The holding request is generated when the maximum value of the assist amount corresponding to the driver's braking operation is exceeded in BA control. If it is determined that there is no holding request, step 109 is executed, the suction valve GVIP is opened, and the wheel cylinder pump-up pressure is continued. On the other hand, if it is determined that there is a holding request, the suction valve GVIP is closed in step 110, and holding is performed by blocking the inflow of brake fluid from the hydraulic pressure passage H0P to the pump suction hole.

  On the other hand, if it is determined in step 103 that the ABS control is being performed, step 104 is executed. In step 104, it is determined whether there is a pressure reduction request. If there is a pressure reduction request, step 105 is performed. Is executed.

  In step 105, the ABS pressure reduction control during BA control shown in FIG. 4 is performed. In PWCXX and PWCYY in FIG. 4, XX represents a calculation wheel, and YY represents the other wheel communicating with the calculation wheel in the same system. For example, in the case of the X piping as in the first embodiment, YY = RR when XX = FL. Hereinafter, the FL wheel will be described as an example (when XX = FL and YY = RR), but even if this is replaced with another system, the feasibility of the ABS control during BA control does not change.

[ABS decompression control during BA control]
FIG. 4 is a flowchart showing the ABS pressure reduction control process during BA control.
In step 201, it is determined whether or not the differential pressure PWCMC between the wheel cylinder pressure PWCFL and the master cylinder pressure PMC is equal to or lower than a predetermined hydraulic pressure α1. As a result, the region where the pressure difference can be reliably reduced by the gate valve GVOP can be adjusted by the offset amount α1 in the determination in step 201 for the region where the differential pressure PWCMC is small.

  If it is determined in step 201 that the differential pressure between the wheel cylinder pressure PFL and the master cylinder hydraulic pressure PMC is equal to or less than the predetermined hydraulic pressure α1, step 202 is executed. On the other hand, if it is determined that the differential pressure between the wheel cylinder pressure PFL and the master cylinder pressure PMC is not less than or equal to the predetermined hydraulic pressure α1, step 203 is executed.

  In step 202, it is determined whether the slip calculated by the ECU based on the input from each wheel speed sensor VWFL, VWFR, VWRL, VWRR is equal to or greater than a predetermined value β1. If it is determined in step 202 that the slip is equal to or greater than the predetermined value β1, step 203 is executed. On the other hand, when the slip is smaller than the predetermined value β1, step 204 is executed.

  On the other hand, in step 203, for example, when the processing wheel is a front left (FL) wheel, the wheel cylinder pressure (PWCRR) of the other wheel (RR) communicating with one system is higher than the master cylinder pressure PMC. Determine if there is. If the wheel cylinder pressure (PWCRR) of the other wheel (RR) communicating with one system is higher than the master cylinder pressure PMC, step 205 is executed. Conversely, if it is on the low pressure side, step 208 is executed.

  In step 204, it is determined whether or not the wheel cylinder pressure (PWCFL) of the corresponding wheel (front left) is higher than the wheel cylinder pressure (PWCRR) of the other wheel (rear right) connected in one system. As a determination method, for example, a determination method based on the magnitude relation between the respective wheel cylinder hydraulic pressures can be considered.

  If the wheel cylinder pressure (PWCFL) of the corresponding wheel (front left) is higher than the wheel cylinder pressure (PWCRR) of the other wheel (rear right) in one system in step 204, step 206 is executed. Is executed. Specifically, when the gate valve GVOP is opened, the intake valve GVIP is closed, and the holding valve SIFL is opened, the brake fluid that generates the wheel cylinder pressure of the relevant wheel (front left) Using the pressure difference between the cylinder pressure (PWCFL) and the master cylinder hydraulic pressure PMC, the wheel cylinder pressure is reduced through the flow of the wheel cylinder hydraulic pressure path H2FL, high pressure oil path H1P, and hydraulic pressure path H0P. The

  On the other hand, if the wheel cylinder pressure (PWCFL) of the corresponding wheel (front left) is lower than the wheel cylinder pressure (PWCRR) of the other wheel (right rear) in one system in step 204, Step 205 is executed.

  In step 205, the holding valve SIFL is closed, and the pressure reducing valve SOFL is opened, so that the wheel cylinder pressure flows out through the wheel cylinder hydraulic pressure path H2FL, the pressure reducing path H3P, and the reservoir RSVP, and the wheel cylinder pressure is reduced. The Further, in one system, the other holding valve SIRR is closed, and the wheel cylinder hydraulic pressure path H2RR and the high pressure oil path H1P are shut off.

  In step 207, high pressure oil passage overpressure prevention means is executed. The high pressure oil passage over-pressure prevention means prevents the brake fluid decompressed from the wheel cylinder from excessively flowing into the high pressure oil passage H1P by the pump PMPP, and will be described in detail later.

  In step 208, the holding valve SIFL is closed, the pressure reducing valve SOFL is opened, and the gate valve GVOP is opened. In this state, both wheel wheel cylinder pressures (PWCFL, PWCRR) of one communicating system are both lower than the master cylinder hydraulic pressure PMC, and the gate valve GVOP is opened.

  Next, the flow of the decompression control will be described using the example of the ABS control waveform during BA control in the first embodiment shown in FIG.

  At time t2 in FIG. 3, the slip amount of the right rear wheel speed VWRR falls below the ABS intervention threshold value, ABS control is started, and first a pressure reduction request for avoiding lock is generated. At this time, in step 201 in the BA pressure-reducing ABS pressure reduction control process (XX = RR, YY = FL in FIG. 4) for the right rear wheel RR, the pressure is lower than the other wheel FL of the same system. 203. In step 203, since the wheel cylinder pressure PWCFL is higher than the master cylinder pressure PMC, the routine proceeds to step 205. In step 205, the RR wheel holding valve SIRR is closed and the pressure reducing valve SORR is opened, so that pressure reduction according to the pressure reduction request value is executed.

  At this time, the brake fluid flowing out from the wheel cylinder WCRR of the right rear wheel RR by opening the pressure reducing valve SORR is discharged to the high pressure oil passage H1P via the reservoir RSVP and the pump PMPP. At this time, since the gate valve GVOP and the holding valve SIRR are closed and the holding valve SIFL is opened, the brake fluid flowing into the high pressure oil passage H1P passes through the holding valve SIFL as it is to the wheel cylinder passage H2FL of the left front wheel. As a result, the pressure increases more than intended by the BA control or ABS control means.

  Therefore, after execution of step 205, step 207 is executed, and the high pressure oil passage H1P is obtained by the process of opening the gate valve for the balanced valve opening time tvb calculated by the high pressure oil passage overpressure prevention means as shown in FIG. Keep the brake fluid level in balance. Details of this processing will be described later.

  When the slip amount of the left front wheel speed VWFL falls below the ABS intervention threshold at time t3 in FIG. 3, a pressure reduction request is generated. At this time, in the ABS pressure-reducing control process during BA control in FIG. 4 for the left front wheel FL (XX = FL, YY = RR in FIG. 4), Step 201 → 202 → 204 → 206, the gate valve GVOP is opened, and The suction valve GVIP is closed and the holding valve SIFL is opened, and the pressure is reduced according to the pressure reduction request value.

  At this time, the right rear wheel RR, which is the other wheel of the same system, is decompressed at time t2, the holding valve SIRR is closed, and the right rear wheel wheel cylinder hydraulic pressure path H2RR and the high pressure oil path H1P are Since it is shut off, even if the gate valve GVOP is opened, the wheel cylinder WCRR of the right rear wheel RR does not depressurize.

  Next, at time t4, the slip amount of the front left wheel speed VWFL falls below the pressure reduction threshold value of the ABS control, and a pressure reduction request is generated. The ABS control decompression threshold is calculated with a predetermined slip amount for the simulated vehicle body speed VI created based on the input from each wheel speed sensor VWFL, VWFR, VWRL, VWRR, and more than the ABS intervention threshold. When the slip amount threshold is set small, and the wheel speed falls below this threshold, a pressure reduction request is generated for the corresponding wheel.

  At this time, in the ABS pressure reduction control process during BA control in FIG. 4 (XX = FL, YY = RR in FIG. 4), the same steps as above, step 201 → 202 → 204 → 206, the gate valve GVOP is opened, and The suction valve GVIP is closed, the holding valve SIFL is opened, and pressure reduction according to the pressure reduction request value is executed (hereinafter, pressure reduction control using the gate valve GVOP is referred to as first pressure reduction means). However, if the wheel slip is further increased by the pressure reduction at time t4, such as between time t4 and t5, a further pressure reduction request is generated.

  However, in this region, the differential pressure between the wheel cylinder pressure PWCFL and the master cylinder pressure PMC is small, and the pressure reduction by the gate valve GVOP opening cannot be performed satisfactorily, and the controllability of the wheel cylinder hydraulic pressure to perform ABS control Deteriorates.

  Therefore, at time t5, in step 201, the condition that the differential pressure between the wheel cylinder pressure PWCFL and the master cylinder pressure PMC is not greater than a predetermined value (α1) is not satisfied, and step 203 is executed. In step 203, one wheel cylinder pressure PWCRR of the same system is not equal to or higher than the master cylinder pressure, so step 208 is executed, the gate valve GVOP is opened, the holding valve SIFL is closed, and the pressure reducing valve SOFL is opened. Thus, the wheel cylinder pressure PWCFL is reduced as required for pressure reduction (hereinafter, pressure reduction control using the pressure reduction valve SOFL is referred to as second pressure reduction means).

  That is, at the timing of time t5, the main pressure reducing control valve of the wheel cylinder pressure PWCFL is switched from the gate valve GVOP to the pressure reducing valve SOFL, and the controllability of the wheel cylinder hydraulic pressure can be ensured.

  At time t6, the slip amount of the right rear wheel speed VWRR falls below the ABS control decompression threshold value, and a decompression request is generated. In the ABS pressure-reducing control process during BA control in FIG. 4 (XX = RR, YY = FL in FIG. 4), Step 201 → 203. Since it is determined in step 203 that one wheel cylinder pressure PWCFL of the same system is equal to or higher than the master cylinder pressure, step 205 is executed. In step 205, the holding valve SIRR in the right rear RR that is the relevant wheel is closed, the pressure reducing valve SORR is opened, and the wheel cylinder pressure PWCRR is reduced as required for pressure reduction.

  At time t7, the slip amount of the left front wheel speed VWFL falls below the ABS control decompression threshold value, and a decompression request is generated. The operation at this time is the same as that at time t4. However, when the slip suddenly increases as in subsequent times t7 to t8, the switching may be slow in the control switching determination based on the differential pressure described above as the operation at time t5.

  For this reason, when the slip amount of the left front wheel speed VWFL falls below the pressure reducing means switching threshold value β1 at time t8, the control is switched regardless of the determination result of the control switching determination based on the differential pressure. The depressurizing means switching threshold value β1 is set so that the slip amount is larger than the ABS depressurizing threshold value. Then, in the ABS pressure-reducing control process during BA control of FIG. 4 at time t8 (XX = FL, YY = RR in FIG. 4), step 201 → 202, slip amount ≧ β1 at 202, and step 203 is executed. . Since the processing after step 203 is the same as that at time t5, it is omitted.

  At time t9, the slip amount of the left front wheel speed VWFL falls below the ABS depressurization threshold value, and a depressurization request is generated. The operation at this time is the same as that at the time t4, but the vertical relationship between the wheel cylinder pressure PWCFL and the wheel cylinder pressure PWCRR is reversed at the time t10 by reducing the pressure.

  Immediately before time t9, the gate valve GVOP is closed, the left front wheel holding valve SIFL is opened, and the right rear wheel holding valve SIRR is closed. The wheel cylinder pressure PWCFL is reduced by opening the GVOP. However, when the gate valve GVOP is further opened in response to the pressure reduction request at t10, the hydraulic pressure in the high pressure oil passage H1P that decreases simultaneously with the wheel cylinder pressure PWCFL becomes lower than the wheel cylinder pressure PWCRR. As a result, the brake fluid in the right rear wheel wheel cylinder hydraulic path H2RR flows out through the check valve CVRR installed in parallel with the holding valve SIRR, and the wheel cylinder pressure PWCRR is the hydraulic pressure in the high pressure oil path H1P, that is, the front The wheel cylinder pressure PWCFL is unintentionally reduced, and the individual hydraulic pressure controllability necessary for ABS control is lost.

  The above problem can be solved by matching the hydraulic pressure of the high-pressure oil passage H1P to the higher one of the wheel cylinders WCFL, WCRR, and is realized by the processing of step 204 in FIG. .

  In response to the pressure reduction request for the left front wheel at time t10, in the ABS pressure reduction control process during BA control in FIG. 4 (XX = FL, YY = RR in FIG. 4), Step 201 → 202 → 203 → 204. On the condition that the wheel cylinder pressure PWCFL is higher than the other wheel cylinder pressure PWCRR of the same system, the wheel cylinder pressure PWCFL is greater than the other wheel cylinder pressure PWCRR of the same system at time t10. Therefore, step 205 is executed.

  In step 205, the pressure reduction control of the left front wheel is performed by opening the pressure reducing valve SIFL, and the processing is described in the explanation of the pressure increasing control means described later, but the other holding valve SIRR of the same system is opened. By controlling the valve, the hydraulic pressure in the high pressure oil passage H1P is set to the wheel cylinder pressure PWCRR. That is, at time t10, the main pressure reducing control valve for the wheel cylinder pressure PWCFL is switched from the gate valve GVOP to the pressure reducing valve SOFL, and the main pressure reducing control valve for the wheel cylinder pressure PWCRR is changed from the pressure reducing valve SORR to the gate valve GVOP. Switch.

  At time t11, the slip amount of the right rear wheel speed VWRR falls below the pressure reduction threshold for ABS control, and a pressure reduction request is generated. At this time, in the ABS pressure-reducing control process during BA control in FIG. 4 (XX = RR, YY = FL in FIG. 4), Step 201 → 202 → 204, the gate valve GVOP is opened, and the intake valve GVIP is closed. Is done. That is, at time t10, the main pressure reduction control valve of the wheel cylinder pressure PWCRR is switched to the gate valve GVOP, so the pressure reduction is performed at the gate GVOP.

  Further, when step 205 is performed, step 207 is executed, and the high pressure oil passage overpressure preventing means calculates the equilibrium valve opening time tvb and opens the gate valve for the calculated time, Prevents pressure increase on the other side of the same system.

  FIG. 5 is a flowchart of the high pressure oil passage overpressure preventing means. The process shown in FIG. 5 is performed for each system P, S of the brake. In the description, processing relating to the P system will be described as an example.

  In step 301 of FIG. 5, the pressure reducing valve opening time tv by ABS control is read, and in step 302, the pressure reducing valve outflow brake fluid amount ΔQ is estimated. The pressure reducing valve outflow brake fluid amount ΔQ can be determined by the relationship between the pre-reducing wheel cylinder pressure PWC0 of the pressure reducing valve and the valve opening time tv. In the ECU, the pressure reducing valve outflow brake fluid amount ΔQ is determined by the calculation means referring to a preset conversion table or the calculation means based on a preset arithmetic expression. The ECU uses the calculation means to estimate the pressure reducing valve outflow brake fluid amount ΔQ based on the pre-reduced wheel cylinder pressure PWC0 and the valve opening time tv.

  Next, at step 303, an equilibrium valve opening time tvb for allowing the pressure reducing valve outflow brake fluid amount ΔQ to flow out from the high pressure oil passage H1P through the gate valve GVOP is calculated. The equilibrium valve opening time tvb can also be determined in relation to the pressure reducing valve outflow brake fluid amount ΔQ and the wheel cylinder pressure PFL. In the above-mentioned relationship, the ECU has the equilibrium valve opening time tvb according to the pressure reducing valve outflow brake fluid amount ΔQ and the conversion table set in advance according to the pressure difference PWCMC between the hydraulic pressure of the high pressure oil passage H1P and the master cylinder pressure PMC. It is determined by a calculation means that refers to the above or a calculation means based on a preset arithmetic expression.

  The ECU uses the calculation means to calculate the equilibrium valve opening time tvb based on the pressure reducing valve outflow brake fluid amount ΔQ and the differential pressure PWCMC between the master cylinder pressure PMC. The ECU opens the gate valve for the balanced valve opening time tvb according to the calculated balanced valve opening time tvb.

  Here, the reason why the high pressure oil passage excessive pressure is prevented from flowing out from the gate valve will be described. In order to avoid an excessively high pressure in the high-pressure oil passage H1P, the brake fluid discharged to the high-pressure oil passage H1P may be reduced or the excessively discharged brake fluid may be discharged. That is, it is possible to either throttle the suction valve GVIP on the suction side of the pump PMPP or to let it flow out from the gate valve GVOP.

  However, in the control of the wheel cylinder pressure that is higher than the master cylinder pressure and on the high pressure side, since the holding operation is performed by the suction valve GVIP (see step 410 in the flowchart described later), the excessive pressure increase prevention means is executed by the suction valve GVIP. This is because two commands are output to the suction valve GVIP, causing competition and making control impossible.

[ABS pressure increase control during BA control]
Next, when the ABS control during BA control in this embodiment is executed, there is no pressure reduction request in Step 104 of FIG. 2, and the ABS pressure increase control during BA control of Step 106 is performed as shown in FIGS. It explains using.

  FIG. 6 is an example of a control flowchart when the ABS pressure increasing control is performed during BA control. As in FIG. 4, in PWCXX and PWCYY in FIG. 6, XX represents a calculation wheel, and YY represents the other wheel communicating with the calculation wheel in the same system. For example, in the case of X piping as in the embodiment, YY = RR is obtained when XX = FL. Hereinafter, the left front wheel will be described as an example (in the case of XX = FL and YY = RR), but even if this is replaced with another system, the feasibility of the ABS control during BA control does not change.

  First, in step 401 of FIG. 6, it is determined whether or not a pressure increase request has occurred. If a pressure increase request has occurred, step 402 is executed. On the other hand, if there is no pressure increase request, it is already determined in step 104 that there is no pressure reduction request, and therefore it is a holding request. In this case, step 408 is executed.

  In step 402, if it is determined that the differential pressure between the wheel cylinder pressure PFL and the master cylinder hydraulic pressure PMC is equal to or higher than the predetermined hydraulic pressure α2, step 404 is executed, and conversely, the wheel cylinder pressure PFL and the master cylinder hydraulic pressure. If it is determined that the pressure difference from the PMC is not equal to or higher than the predetermined hydraulic pressure α2, step 403 is executed.

  Step 403 is, for example, if the wheel being processed is a front left (FL) wheel, is the wheel cylinder pressure (PWCRR) of the other wheel (RR) communicating with one system higher than the master cylinder pressure PMC? Judge whether. If the wheel cylinder pressure PWCRR of the other wheel (RR) communicating with one system is higher than the master cylinder pressure PMC, step 405 is executed. Conversely, if it is on the low pressure side, step 407 is executed.

  On the other hand, in Step 404, it is determined whether or not the wheel cylinder pressure PWCFL of the corresponding wheel (front left) is higher than the wheel cylinder pressure PWCRR of the other wheel (back right) communicating with one system. This determination is based on the same determination as in step 204.

  When the wheel cylinder pressure PWCFL of the corresponding wheel (front left) is higher than the wheel cylinder pressure PWCRR of the other wheel (right rear) communicating with one system in step 404, step 406 is executed, The wheel cylinder pressure PWCFL can be increased by setting the gate valve GVOP to the closed state, the intake valve GVIP to the open state, and the pump-up pressure increasing state.

  If it is determined in step 404 that the wheel cylinder pressure PWCFL of the corresponding wheel (front left) is lower than the wheel cylinder pressure PWCRR of the other wheel (right rear) communicating with one system, step 405 Is executed.

  In step 405, the holding valve SIFL is opened and the pressure reducing valve SOFL is closed. Thus, the pressure can be increased by flowing into the wheel cylinder WCFL using the differential pressure between the wheel cylinder pressure PWCFL of the corresponding wheel and the hydraulic pressure of the high pressure oil passage H1P.

  Step 407 is executed when it is determined that any of the wheel cylinders WCFL, WCRR in the same system is smaller than the master cylinder pressure PMC (it may be considered small). In this case, the principle of step 405 Similarly, the holding valve SIFL is opened, the pressure reducing valve SOFL is closed to increase the pressure, and the gate valve GVOP is opened.

  Next, the flow of pressure increase control will be described using the example of the ABS control waveform during BA control in the present embodiment of FIG.

  FIG. 7 shows an operation example in which the same operation as that in FIG. 3 is performed, and shows how to divide the time mainly with an emphasis on the timing of pressure increase. Also, in FIG. 7, as in FIG. 3, for convenience of explanation, an example regarding the FL wheel and the RR wheel that are the first system is shown, but even if this is replaced with the second system, the FL wheel in FIG. Even if the vertical relationship between the wheel and the RR wheel is considered in reverse, the establishment of the ABS control during the BA control does not change.

  A BA control request is generated at time t1 in FIG. 7 (this is the same time as time t1 in FIG. 3), and the wheel cylinder pressures PWCFL and PWCRR are led to a higher pressure than the master cylinder pressure PMC by the pump-up pressure increase. Thereafter, the control shifts to the ABS control during the BA control at time t2 in FIG. 3, and the pressure reduction control is performed at times t3 and t4. When the slip is recovered by this pressure reduction control, the slip rate is optimized by the ABS control means. In order to control this, pressure increase control is performed.

  In the pressure increase generated in the left front wheel at time t12, in the ABS pressure reduction control process during BA control in FIG. 6 (XX = FL, YY = RR in FIG. 6), a pressure increase request is determined in step 401, and step 402 In step 402, it is determined that the differential pressure between the wheel cylinder pressure PFL and the master cylinder hydraulic pressure PMC is equal to or higher than the predetermined hydraulic pressure α2, and step 404 is executed.

  Next, in step 404, since it is determined that the pressure is high, step 406 is executed, the gate valve GVOP is closed, and the intake valve GVIP is opened, and the pump-up pressure increasing state is reached, and the pressure is increased. .

  In the pressure increase occurring at the right rear wheel at time t13, in the ABS pressure-reducing control process during BA control in FIG. 6 (XX = RR, YY = FL in FIG. 6), Step 401 → Step 402. It is determined that the differential pressure between the wheel cylinder pressure PFL and the master cylinder hydraulic pressure PMC is not equal to or higher than the predetermined hydraulic pressure α2, and step 205 is executed.

  In step 405, the holding valve SIRR is opened and the pressure reducing valve SORR is closed, and the pressure is increased using the differential pressure between the wheel cylinder pressure PWCRR and the hydraulic pressure in the high pressure oil passage H1P.

  In the pressure increase occurring at the left front wheel at time t14, the ABS pressure reduction control process during BA control in FIG. 6 (XX = FL, YY = RR in FIG. 6) is performed in advance (time t5 in FIG. 3) Wheel cylinder pressure PFL is lower than master cylinder pressure PMC. Therefore, step 402 → 403, and then in step 403, it is determined that the wheel cylinder pressure PWCRR of the other wheel (RR) communicating with one system is lower than the master cylinder pressure PMC, and step 407 is executed. As a result, in step 407, the holding valve SIFL is opened and the pressure reducing valve SOFL is closed, and the pressure is increased using the differential pressure between the wheel cylinder pressure PWCRR and the master cylinder pressure PMC.

  In the pressure increase generated at the left front wheel at time t15, the differential pressure between the wheel cylinder pressure PWCRR and the master cylinder pressure PMC in the ABS pressure reduction control process during the BA control in FIG. 6 (XX = FL, YY = RR in FIG. 6). Therefore, the pressure increase method executed at time t14 cannot increase the pressure, and the controllability of the wheel cylinder hydraulic pressure for performing the ABS control deteriorates.

  Therefore, in step 402, it is determined that the differential pressure between the wheel cylinder pressure PFL and the master cylinder hydraulic pressure PMC is equal to or higher than the predetermined hydraulic pressure α2, and the pump-up pressure increase is performed again by executing steps 404 → 406. This makes it possible to increase the pressure. That is, at this timing, the main pressure increase control valve of the wheel cylinder pressure PWCFL is switched from the holding valve SIFL to the suction valve GVIP (motor MOT).

  At time t16, the right rear wheel wheel cylinder pressure PWCRR exceeds the left front wheel wheel cylinder pressure PWCFL. This timing is the same as the time t10 shown in the time chart of FIG. In the pressure increase that occurs at this time, in the ABS pressure reduction control process during BA control in FIG. 6 (XX = RR, YY = FL in FIG. 6), Step 401 → 402 → 404. The gate valve GVOP is closed.

  On the other hand, at the same time t16 (time t10 shown in the time chart of FIG. 3), step 205 is performed in the left rear wheel processing in the ABS pressure reduction control during BA control of FIG. 4, and the holding valve SIFL is closed. The pressure reducing valve SOFL is opened to perform pressure reduction.

  For this reason, in the pressure increase occurring at the left front wheel at time t11, in the ABS pressure reduction control process during BA control in FIG. 6 (XX = FL, YY = RR in FIG. 6), steps 401 → 402 → 403 → 405 are obtained. By opening the holding valve SIFL and closing the pressure reducing valve SOFL, the pressure is increased by utilizing the differential pressure between the wheel cylinder pressure PWCFL and the hydraulic pressure of the high pressure oil passage H1P.

  That is, at time t17, the main pressure reduction control valve of the wheel cylinder pressure PWCFL is switched from the gate valve GVOP to the pressure reduction valve SOFL as described above with reference to the operation at time t10 in FIG. The pressure reducing control valve is switched from the pressure reducing valve SORR to the gate valve GVOP. At the same time, the main pressure increasing control valve of the wheel cylinder pressure PWCFL is switched from the suction valve GVIP (motor MOT) to the holding valve SIFL, and the wheel cylinder pressure PWCRR The main pressure increase control valve is switched from the holding valve SIRR to the suction valve GVIP (motor MOT).

  Next, when there is no pressure increase request in step 401 in FIG. 6, that is, the operation of the holding request will be described. Hereinafter, the left front wheel will be described as an example (in the case of XX = FL and YY = RR), but even if this is replaced with another system, the feasibility of the ABS control during BA control does not change.

  If there is no pressure increase request in step 401, step 408 is executed. In step 408, it is determined whether or not the wheel cylinder pressure PWCFL of the corresponding wheel (front left) is higher than the master cylinder pressure PMC. If the wheel cylinder pressure PWCFL of the relevant wheel (front left) is higher than the master cylinder pressure PMC, step 409 is executed. If the wheel cylinder pressure PWCFL of the relevant wheel (front left) is less than the master cylinder pressure PMC, step 409 is executed. 411 is executed.

  In step 409, it is determined whether or not the wheel cylinder pressure PWCFL of the corresponding wheel (front left) is higher than the wheel cylinder pressure PWCRR of the other wheel (right rear) communicating with one system. This determination is based on the same determination as in step 204.

  If it is determined in step 409 that the wheel cylinder pressure PWCFL of the corresponding wheel (front left) is higher than the wheel cylinder pressure PWCRR of the other wheel (back right) communicating with one system, the pressure reducing valve SOFL Is closed, and the suction valve GVP is closed to stop the pressure increase due to the pump-up pressure increase and maintain the wheel cylinder pressure PWCFL.

  On the other hand, if the wheel cylinder pressure PWCFL of the relevant wheel (front left) is judged to be lower than the wheel cylinder pressure PWCRR of the other wheel (right rear) communicating with one system, the holding valve SIFL is closed. By closing the pressure reducing valve SOFL, the flow of brake fluid from the high pressure oil passage H1P to the wheel cylinder hydraulic pressure passage H2FL and the flow of brake fluid from the wheel cylinder hydraulic pressure passage H2FL to the pressure reduction passage H3P are blocked. Hold the wheel cylinder pressure PWCFL.

  As described above, in the first embodiment, unlike the conventional technique, an expensive relief valve or solenoid valve is not used for the relief means of the high-pressure oil passage. Control and ABS control can be controlled simultaneously.

  In the first embodiment, the wheel cylinder pressure is detected by the hydraulic pressure sensor. However, the wheel cylinder pressure sensor may be removed from the first embodiment. There is a known technique for estimating the wheel cylinder pressure of each wheel based on the detected value of the master cylinder pressure sensor, the drive signal of each control valve, and the pump drive state, and this estimated value is replaced with the wheel cylinder pressure of each wheel in the first embodiment. Think about it.

Hereinafter, effects related to the creation of the technical idea based on the first embodiment will be listed below.
(1) Brake assist control that assists the braking force generated by the master cylinder by driving the pump with the gate valve closed, the intake valve open, the holding valve open, and the pressure reducing valve closed Hydraulic pressure of the wheel cylinder so as to avoid wheel lock, including brake assist means for executing the following, a process for controlling the conduction state between the master cylinder, the wheel cylinder, the pump, and the reservoir, and a process for turning the pump on. In the braking force control device having the anti-lock brake means for executing the anti-lock brake control for increasing / decreasing the pressure, the ECU is in the brake assist control and the hydraulic pressure of the wheel cylinder is the hydraulic pressure of the master cylinder. When the pressure is higher, in response to a pressure reduction request by anti-lock brake control, the gate valve is opened and the wheel cylinder is depressurized. When the pressure reduction means and brake assist control are in progress, and the hydraulic pressure of the wheel cylinder is lower than the hydraulic pressure of the master cylinder, the gate valve is opened and the intake valve is in response to the pressure reduction request by the antilock brake control. In the closed state, the holding valve in the closed state, and the pressure reducing valve in the open state, and the second pressure reducing means for performing the pressure reducing operation of the wheel cylinder.

  That is, when the oil passage constituted between the gate valve, the holding valve and the discharge side of the pump is a high pressure oil passage, the hydraulic pressure in the high pressure oil passage during the brake assist control is By executing the first pressure reducing means, the gate valve is opened to reduce the pressure. Thereby, the hydraulic pressure in the high-pressure oil passage does not become higher than the hydraulic pressure at the time of the pressure reduction request of the antilock brake control, that is, the wheel lock pressure. Therefore, excessive hydraulic pressure is not applied to the high-pressure oil passage, and the brake assist control and the antilock brake control can be simultaneously controlled without expensive relief means such as a relief valve or a solenoid valve.

(2) When the first pressure reducing means is executed, if the pressure difference between the hydraulic pressure of the wheel cylinder and the hydraulic pressure of the master cylinder becomes a predetermined value or less, the second pressure reducing means is switched.
Therefore, even if the differential pressure between the hydraulic pressure of the wheel cylinder and the hydraulic pressure of the master cylinder is reduced and the pressure reduction by the first pressure reducing means becomes difficult, the second pressure reducing means can Therefore, the pressure reducing operation can be surely performed in response to the pressure reducing request from the antilock brake control.

(3) The ECU has a slip calculating means for calculating a wheel slip amount equivalent value of each wheel, and when the first pressure reducing means is executed, if the wheel slip amount equivalent value becomes a predetermined value or more, the second pressure reducing means. It was decided to switch to.
For example, when the wheel slip amount equivalent value suddenly increases, the determination described in (2) above cannot ensure responsiveness, or the determination in (2) above may occur due to wheel cylinder hydraulic pressure detection error. There may be a delay. Since it is ABS control during brake assist control, the brake pedal is depressed by the driver in principle, and it is considered that a certain level of fluid pressure is generated in the master cylinder. At this time, since the reservoir is at almost atmospheric pressure, the hydraulic pressure in the reservoir is lower than the hydraulic pressure in the master cylinder. Therefore, the pressure reduction speed can be secured, and the response can be improved.

  (4) Of the wheel cylinders for one system and two wheels communicating on the wheel cylinder side from the gate valve, the wheel cylinder with high hydraulic pressure is judged as the high pressure side wheel cylinder, and the wheel cylinder with low hydraulic pressure is designated as the low pressure side wheel cylinder. The ECU includes a judging means for judging, and the ECU permits the execution of the first pressure reducing means only for the high-pressure side wheel cylinder, and for the low-pressure side wheel cylinder, regardless of the relationship of the hydraulic pressure between the master cylinder and the wheel cylinder. Therefore, the second decompression means is always executed.

  That is, if the gate valve is opened in response to the pressure reduction request of the low pressure side wheel cylinder, the hydraulic pressure of the high pressure side wheel cylinder is also lowered. Therefore, in the low pressure side wheel cylinder, the hydraulic pressure of the two wheel cylinders in one system can be independently controlled by always reducing the pressure from the pressure reducing valve by the second pressure reducing means.

  (5) The pressure reducing valve effluent amount calculating means for calculating the amount of the pressure reducing valve effluent flowing out of the wheel cylinder by the second pressure reducing means, and necessary for allowing the pressure reducing valve effluent amount to flow out from the gate valve. The balance valve opening time calculation means for calculating the valve opening time, which is the correct valve opening time, and the wheel cylinder with high hydraulic pressure among the wheel cylinders for one system and two wheels communicating with the wheel cylinder side from the gate valve is connected to the high pressure side. Determination means for determining a wheel cylinder having a low hydraulic pressure as a low-pressure wheel cylinder, and the ECU performs a balanced valve opening time when the second pressure reducing means is executed in the low-pressure wheel cylinder. In the meantime, an over-pressure increase preventing means for opening the gate valve is provided.

  When the pressure is reduced from the low pressure side wheel cylinder by the first pressure reducing means, the brake fluid in the low pressure side wheel cylinder flows into the reservoir. Since this reservoir communicates with the suction hole of the pump, there is a possibility that the amount that flows into the reservoir will be discharged to the high-pressure side wheel cylinder and become higher than intended. Therefore, the amount of the pressure reducing valve effluent that has flowed out of the low-pressure side wheel cylinder can be prevented from flowing into the high-pressure side wheel cylinder by allowing it to flow out from the gate valve only during the balanced valve opening time.

  (6) When the ECU is under brake assist control and the hydraulic pressure of the wheel cylinder is higher than the hydraulic pressure of the master cylinder, the intake valve is opened in response to the pressure increase request by the antilock brake means. When the brake assist control is being performed and the hydraulic pressure of the wheel cylinder is lower than the hydraulic pressure of the master cylinder, the increase by antilock brake control is performed. In response to a pressure request, there is provided a second pressure increasing means for increasing the pressure of the wheel cylinder with the gate valve opened, the suction valve closed, the holding valve opened, and the pressure reducing valve closed. It was.

  Therefore, it is possible to reliably respond to the pressure increase request of the antilock brake control during the brake assist control.

  (7) Of the wheel cylinders for one system and two wheels communicating on the wheel cylinder side from the gate valve, the wheel cylinder with high hydraulic pressure is judged as the high pressure side wheel cylinder, and the wheel cylinder with low hydraulic pressure is designated as the low pressure side wheel cylinder. The ECU includes a judging means for judging, and the ECU permits execution of the first pressure-increasing means only for the high-pressure side wheel cylinder, and for the low-pressure side wheel cylinder, the ECU relates to the hydraulic pressure relationship between the master cylinder and the wheel cylinder. Instead, the second pressure increasing means is always executed.

  When increasing the pressure of the low pressure side wheel cylinder, the pressure can be increased by utilizing a differential pressure from the hydraulic pressure of the high pressure side wheel cylinder. When increasing the pressure of the high pressure side wheel cylinder, it can be increased by a pump. Thereby, the hydraulic pressure of two wheel cylinders of one system can be controlled independently with one pump.

1 is a braking force control apparatus according to a first embodiment. 3 is a control flowchart executed in the first embodiment. It is an example of the control waveform assumed in Example 1, and is a timing chart which pays attention to pressure reduction timing. 3 is a control flowchart executed during pressure reduction control in the first embodiment. 3 is a flowchart of a high-pressure oil passage over-pressure prevention unit in the first embodiment. It is an example of the control waveform assumed in Example 1, and is a timing chart which pays attention to the pressure increase timing. 3 is a control flowchart executed during pressure increase and holding control in the first embodiment.

Explanation of symbols

MC master cylinder
PSM master cylinder hydraulic pressure sensor
WCFL, WCFR, WCRL, WCRR Wheel cylinder for each wheel
PSFL, PSFR, PSRL, PSRR Wheel Cylinder Pressure Sensor for Each Wheel
VWFL, VWFR, VWRL, VWRR Wheel speed sensor for each wheel
GVOP, GVOS each system gate valve
GVIP, GVIS each system intake valve
SIFL, SIFR, SIRL, SIRR each wheel holding valve
SOFL, SOFR, SORL, SORR Each wheel pressure reducing valve
RSVP, RSVS each system reservoir
PMPP and PMPS pumps
MOT pump drive motor
ECU control unit

Claims (7)

A master cylinder that generates hydraulic pressure corresponding to the driver's braking operation;
A pump having a suction hole capable of communicating with the master cylinder;
A suction valve for controlling a conduction state between the master cylinder and the suction hole of the pump;
A wheel cylinder capable of communicating with both the master cylinder and the discharge hole of the pump;
In the middle of a brake circuit connecting the master cylinder and the wheel cylinder, a gate valve for controlling the conduction state of these,
Holding valves for controlling the conduction state to the wheel cylinders for one system and two wheels communicating with each other on the wheel cylinder side from the gate valve;
A reservoir capable of communicating with both the wheel cylinder and the suction hole of the pump;
A pressure reducing valve for controlling a conduction state between the wheel cylinder and the reservoir;
The gate valve is closed, the intake valve is opened, the holding valve is opened, the pressure reducing valve is closed, and the pump is driven to assist the braking force generated by the master cylinder. Brake assist means for executing brake assist control;
Including a process for controlling a conduction state with the master cylinder, the wheel cylinder, the pump, and the reservoir, and a process for bringing the pump into an operating state, and the hydraulic pressure of the wheel cylinder is increased or decreased to avoid wheel locking. Anti-lock brake means for executing anti-lock brake control for pressure control;
In a braking force control device comprising:
When the anti-lock brake means is under the brake assist control and the hydraulic pressure of the wheel cylinder is higher than the hydraulic pressure of the master cylinder, the anti-lock brake means responds to the pressure reduction request by the anti-lock brake control. First depressurizing means for depressurizing the wheel cylinder with the valve opened;
When the brake assist control is being performed and the hydraulic pressure of the wheel cylinder is lower than the hydraulic pressure of the master cylinder, the gate valve is opened in response to a pressure reduction request by the antilock brake control, A second pressure reducing means for performing a pressure reducing operation of the wheel cylinder with the suction valve closed, the holding valve closed, and the pressure reducing valve opened;
A braking force control device comprising: The braking force control apparatus according to claim 1, wherein
Braking force control characterized in that, when the first pressure reducing means is executed, when the pressure difference between the hydraulic pressure of the wheel cylinder and the hydraulic pressure of the master cylinder falls below a predetermined value, switching to the second pressure reducing means is performed. apparatus. The braking force control apparatus according to claim 1 or 2,
The anti-lock brake control means has a slip calculation means for calculating a wheel slip amount equivalent value of each wheel, and when the wheel slip amount equivalent value is equal to or greater than a predetermined value when the first pressure reducing means is executed, A braking force control device that switches to the second pressure reducing means. The braking force control device according to any one of claims 1 to 3,
Of the wheel cylinders for one system and two wheels communicating with each other on the wheel cylinder side from the gate valve, a wheel cylinder having a high hydraulic pressure is determined as a high pressure side wheel cylinder, and a wheel cylinder having a low hydraulic pressure is determined as a low pressure side wheel cylinder. With judgment means,
The anti-lock brake control means permits the execution of the first pressure reducing means only for the high pressure side wheel cylinder, and the hydraulic pressure relationship between the master cylinder and the wheel cylinder for the low pressure side wheel cylinder. Regardless of this, the braking force control apparatus is characterized in that the second pressure reducing means is always executed. In the braking force control device according to claim 4,
Pressure reducing valve effluent amount calculating means for calculating a pressure reducing valve effluent amount that is the amount of brake fluid flowing out from the wheel cylinder by the second pressure reducing means;
An equilibrium valve opening time calculating means for calculating an equilibrium valve opening time which is a valve opening time required to flow out the amount of the pressure reducing valve effluent from the gate valve;
With
The anti-lock brake means has an overpressure prevention means for opening the gate valve during the equilibrium valve opening time when the second pressure reducing means is executed in the low pressure wheel cylinder. A braking force control device. In the braking force control device according to any one of claims 1 to 5,
When the anti-lock brake means is in the brake assist control and the hydraulic pressure of the wheel cylinder is higher than the hydraulic pressure of the master cylinder, the anti-lock brake means First pressure increasing means for increasing pressure by the brake assist means with the intake valve opened;
When the brake assist control is in progress and the hydraulic pressure of the wheel cylinder is lower than the hydraulic pressure of the master cylinder, the gate valve is opened in response to a pressure increase request by the antilock brake control. A second pressure increasing means for performing a pressure increasing operation of the wheel cylinder with the suction valve closed, the holding valve opened, and the pressure reducing valve closed;
A braking force control device comprising: In the braking force control device according to claim 6,
Of the wheel cylinders for one system and two wheels communicating with each other on the wheel cylinder side from the gate valve, a wheel cylinder having a high hydraulic pressure is determined as a high pressure side wheel cylinder, and a wheel cylinder having a low hydraulic pressure is determined as a low pressure side wheel cylinder. With judgment means,
The anti-lock brake control means permits execution of the first pressure increasing means only for the high pressure side wheel cylinder, and for the low pressure side wheel cylinder, the hydraulic pressure between the master cylinder and the wheel cylinder is controlled. The braking force control apparatus characterized in that the second pressure increasing means is always executed regardless of the relationship.

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