JPH0939768A - Vehicle braking force control device - Google Patents

Abstract

(57) An object of the present invention is to prevent an impact from occurring in a master cylinder or the like when the wheel cylinder is connected to the master cylinder at the end of braking force control. A wheel cylinder (38FL, etc.) is connected to a master cylinder (14) when the vehicle is in a normal state,
A braking force control device for a vehicle that controls a braking force by connecting a wheel cylinder to an accumulator (36) or a reservoir (30) as a high pressure source when the vehicle is in a predetermined state. When the deviation between the wheel cylinder pressure (Pwi) and the master cylinder pressure (Pm) exceeds a predetermined range when the vehicle changes from the predetermined state to the normal state, the wheel cylinder pressure is controlled so that the deviation is within the predetermined range. Connect the rear wheel cylinder to the master cylinder.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a braking force control device for a vehicle such as an automobile. More specifically, the wheel cylinder is connected to a master cylinder when the vehicle is in a normal state, and the wheel cylinder has a high pressure when the vehicle is in a predetermined state. The present invention relates to a braking force control device that controls a braking force by being connected to a power source or a reservoir.

[0002]

2. Description of the Related Art As one of braking force control devices for controlling a braking force so that an actual wheel speed becomes a target wheel speed in a vehicle such as an automobile, as disclosed in, for example, Japanese Patent Laid-Open No. 2-70561. , Estimate the steering state from the deviation between the actual yaw rate of the vehicle body and the target yaw rate during turning of the vehicle,
Controls the difference in braking force between the left and right wheels according to the steering state,
Conventionally, a braking force control device configured to improve the stability of the vehicle when turning is known.

According to such a behavior control device, it is possible to prevent the steered state from becoming excessively oversteered or excessively understeered during turning, which makes it possible to prevent the vehicle from spinning or drifting out. Unnecessary turning behavior can be reduced.

[0004]

In the braking force control device described in the above publication, it is necessary to make the braking force of each wheel higher than the master cylinder pressure corresponding to the pedaling force of the driver on the brake pedal. In some cases, it is necessary to connect the wheel cylinder to a high pressure source to control the braking pressure, and connect the wheel cylinder to the master cylinder when the control of the braking force of each wheel is completed. However, if the differential pressure between the wheel cylinder pressure and the master cylinder pressure is large at the stage when the control of the braking force is completed, a shock occurs in the master cylinder etc. when the wheel cylinder is connected to the master cylinder. Sometimes.

The present invention has been made in view of the above-mentioned problems in the conventional braking force control device, and the main problem of the present invention is to terminate the wheel cylinder pressure and the master cylinder pressure at the end of the braking force control. By connecting the wheel cylinder to the master cylinder when the pressure difference between the master cylinder and the wheel cylinder becomes small, it is possible to prevent the master cylinder and the like from being impacted.

[0006]

SUMMARY OF THE INVENTION According to the present invention, the main problem described above is that the wheel cylinder is connected to the master cylinder when the vehicle is in a normal state, and the wheel cylinder is a high pressure source or a reservoir when the vehicle is in a predetermined state. In a braking force control device for a vehicle that controls the braking force by connecting to a vehicle, when the vehicle goes from a predetermined state to a normal state, the deviation between the wheel cylinder pressure and the master cylinder pressure falls within a predetermined range. A braking force control device for a vehicle (structure according to claim 1) having means for connecting the wheel cylinder to the master cylinder at a different stage.
Alternatively, in a vehicle braking force control device for controlling a braking force by connecting a wheel cylinder to a master cylinder when the vehicle is in a normal state and connecting the wheel cylinder to a high pressure source or a reservoir when the vehicle is in a predetermined state, A means for detecting the cylinder pressure Pw, a means for detecting the master cylinder pressure Pm, and a deviation calculating means for obtaining a deviation between the wheel cylinder pressure Pw and the master cylinder pressure Pm when the vehicle goes from a predetermined state to a normal state. When the deviation is outside the predetermined range and Pw <Pm, the wheel cylinder is connected to a high pressure source to increase the wheel cylinder pressure, and the deviation is outside the predetermined range and Pw> Pm. Sometimes a first connecting means for connecting the wheel cylinder to the reservoir to reduce the wheel cylinder pressure, and And a second connecting means for connecting the wheel cylinder to the master cylinder when the deviation is within a predetermined range, the second connecting means holding the wheel cylinder pressure and the wheel cylinder. Achieved by a braking force control device for a vehicle (configuration according to claim 2), characterized in that it is configured to repeatedly switch to a connection state in which is connected to the master cylinder and to gradually reduce the time ratio of the holding state. To be done.

According to the above-mentioned structure of the first aspect, when the vehicle goes from the predetermined state to the normal state, the wheel cylinder is at a stage where the deviation between the wheel cylinder pressure and the master cylinder pressure is within a predetermined range. Is connected to the master cylinder, it is possible to reliably prevent the impact on the master cylinder and the like due to the pressure difference between the wheel cylinder pressure and the master cylinder pressure.

According to the second aspect of the present invention, the deviation between the wheel cylinder pressure Pw and the master cylinder pressure Pm when the vehicle goes from the predetermined state to the normal state is outside the predetermined range and Pw <Pm. In some cases, the wheel cylinder pressure is increased by connecting the wheel cylinder to the high pressure source by the first connecting means, and when the deviation is outside the predetermined range and Pw> Pm, the first connecting means controls the wheel cylinder. Is connected to the reservoir to reduce the wheel cylinder pressure, and when the deviation is within a predetermined range, the second connecting means connects the wheel cylinder to the master cylinder, and the second connecting means holds the wheel cylinder pressure. When the holding state is repeated and the holding state is repeatedly switched to the connecting state in which the wheel cylinder is connected to the master cylinder. Since the target ratio is gradually reduced, the pressure deviation can be reliably and relatively quickly determined even when the deviation between the wheel cylinder pressure and the master cylinder pressure when the vehicle is in the normal state rather than the predetermined state is out of the predetermined range. The wheel cylinder is securely and relatively quickly connected to the master cylinder, and the degree of connection between the wheel cylinder and the master cylinder gradually increases even if the pressure deviation falls within a predetermined range. Therefore, it is possible to reliably prevent the impact on the master cylinder and the like.

According to the present invention, in order to effectively achieve the above-mentioned main problems, in the structure of claim 1 or 2,
The means for detecting the wheel cylinder pressure Pw is configured to estimate the wheel cylinder pressure based on the operating conditions of the first and second connecting means (claim 3).

According to the third aspect of the present invention, since the wheel cylinder pressure is estimated based on the operating conditions of the first and second connecting means, a pressure sensor or the like for detecting the wheel cylinder pressure of each wheel is required. Instead, wheel cylinder pressure is required.

According to the present invention, in order to effectively achieve the above-mentioned main object, in the structure of claim 3, means for momentarily actuating the second connecting means and the second Is configured to correct the estimated wheel cylinder pressure based on the fluctuation of the master cylinder pressure Pm when the connection means of the above is momentarily operated (configuration of claim 4).

According to the structure of claim 4, the estimated value of the wheel cylinder pressure is corrected based on the fluctuation of the master cylinder pressure Pm when the wheel cylinder is momentarily connected to the master cylinder by the second connecting means. Therefore, the wheel cylinder pressure can be obtained more accurately than when the correction is not performed.

[0013]

According to a preferred mode of the problem solving means of the present invention, in the configuration of claim 1 or 2, it is determined that the state in which the turning behavior of the vehicle is unstable is a predetermined state, A state in which the turning behavior of the vehicle is stable is determined to be a normal state.

According to another preferred mode of the means for solving the problems of the present invention, in the structure of claim 1, when the deviation between the wheel cylinder pressure and the master cylinder pressure is within a predetermined range. The means for connecting the wheel cylinder to the master cylinder is configured to repeatedly switch between a holding state in which the wheel cylinder pressure is held and a connected state in which the wheel cylinder is connected to the master cylinder and to gradually reduce the time ratio of the holding state. It

According to another preferred aspect of the problem solving means of the present invention, in the structure of claim 4, the wheel cylinder pressure is the master cylinder before the wheel cylinder is momentarily connected to the master cylinder. Pressure, the master cylinder pressure immediately after the wheel cylinder is momentarily connected to the master cylinder, or the maximum value of the master cylinder pressure when the wheel cylinder is momentarily connected to the master cylinder,
It is configured to be corrected based on the master cylinder pressure after a predetermined time has elapsed from the moment when the wheel cylinder was momentarily connected to the master cylinder.

[0016]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a first embodiment of the present invention;

FIG. 1 is a schematic configuration diagram showing a hydraulic circuit and an electric control device of one embodiment of a braking force control device according to the present invention.

Referring to FIG. 1, the braking device 10 has a master cylinder 14 for pumping brake oil from the first and second ports in response to the driver's depression of the brake pedal 12, and the first port Is connected to the brake hydraulic pressure control devices 18 and 20 for the left and right front wheels by the brake hydraulic pressure control conduit 16 for the front wheels, and the second port is connected by the brake hydraulic pressure control conduit 24 for the rear wheels having a proportional valve 22 in the middle. Brake hydraulic control device 2
6 and 28. Further, the braking device 10 pumps the brake oil stored in the reservoir 30 and supplies it as high-pressure oil to the high-pressure conduit 32.
have. The high-pressure conduit 32 is connected to each brake hydraulic pressure control device 18, 20, 26, 28, and an accumulator 36 is connected in the middle thereof.

Each brake hydraulic control device 18, 20, 2
6 and 28 are wheel cylinders 38FL, 38FR, 38RL, and 38RR that control the braking force for the corresponding wheels.
And 3 port / 2 position switching type electromagnetic control valve 40FL,
40FR, 40RL, 40RR and normally open electromagnetic on-off valves 44FL, 44FR, 44RL, 44RR and normally closed electromagnetic valves provided between the low pressure conduit 42 connected to the reservoir 30 and the high pressure conduit 32. Open / close valve 46FL, 46FR, 46RL, 46
RR and. Open / close valves 44FL, 44FR, 4 respectively
4RL, 44RR and on-off valves 46FL, 46FR, 46RL, 46RR
The high pressure conduit 32 between and is a connecting conduit 48FL, 48FR, 48
Control valves 40FL, 40FR, 40RL, 40 by RL, 48RR
Connected to RR.

The control valves 40FL and 40FR are respectively the brake hydraulic control conduit 16 for the front wheels and the wheel cylinder 38FL.
And 38FR are connected for communication and the wheel cylinder 38FL
, 38FR and the connecting conduits 48FL and 48FR in the first position shown in the figure, and the brake hydraulic control conduit 16 and the wheel cylinders 38FL and 38FR in communication and the wheel cylinders 38FL and 38FR and the connecting conduit 48FL.
And 48FR are switched to a second position where they are connected for communication. Similarly, 40RL and 40RR are the brake hydraulic pressure control conduit 24 for the rear wheels and the wheel cylinder 3 respectively.
8RL and 38RR are communicatively connected and the wheel cylinder 3
8RL and 38RR and connecting conduits 48RL and 48RR, the first position shown in the figure, and the brake hydraulic pressure control conduit 2
4 and the wheel cylinders 38RL and 38RR are disconnected from each other, and the wheel cylinders 38RL and 38RR are connected to the connecting conduit 4.
8RL and 48RR are switched to a second position where they are connected for communication.

In the situation where the control valves 40FL, 40FR, 40RL, 40RR are in the second position, the on-off valves 44FL, 44FR, 4
4RL, 44RR and on-off valves 46FL, 46FR, 46RL, 46
When the RR is controlled to the illustrated state, the wheel cylinder 38
FL, 38FR, 38RL, 38RR are control valves 40FL, 40FR,
40RL, 40RR and connecting conduits 48FL, 48FR, 48RL,
It is communicatively connected to the high-pressure conduit 32 via 48RR, which increases the pressure in the wheel cylinder. Conversely, when the control valve is in the second position, the on-off valves 44FL, 44FR,
44RL and 44RR are closed and open / close valves 46FL, 46FR and 46
When RL and 46RR are opened, the wheel cylinder is connected in communication with the low-pressure conduit 42 via the control valve and the connecting conduit, which reduces the pressure in the wheel cylinder. Further, when the control valve is in the second position, the on-off valves 44FL, 4FL
4FR, 44RL, 44RR and on-off valves 46FL, 46FR, 46
When RL and 46RR are closed, the wheel cylinder is shut off from both the high-pressure conduit 32 and the low-pressure conduit 42, so that the pressure in the wheel cylinder is maintained as it is.

Thus, the braking device 10 includes the control valve 40FL,
When 40FR, 40RL, 40RR are in the first position, the wheel cylinders 38FL, 38FR, 38RL, 38RR generate a braking force according to the amount of depression of the brake pedal 12 by the driver, and the control valves 40FL, 40FR, 40RL, 40RR are generated.
When any of the RRs is in the second position, the on-off valves 44FL, 44FR, 44RL, 44RR and the on-off valve 46FL of the corresponding wheel are
By controlling opening / closing of 46FR, 46RL, and 46RR, the braking force of the wheel can be controlled regardless of the depression amount of the brake pedal 12 and the braking force of other wheels.

Control valves 40FL, 40FR, 40RL, 40RR,
Open / close valves 44FL, 44FR, 44RL, 44RR and open / close valve 46
FL, 46FR, 46RL, and 46RR are controlled by the electric controller 50 as will be described later in detail. The electric control device 50 comprises a microcomputer 52 and a drive circuit 54, which is not shown in detail in FIG. 1, but is, for example, a central processing unit (CPU).
, A read only memory (ROM), a random access memory (RAM), and an input / output port device, which may be connected to each other by a bidirectional common bus.

The input / output port device of the microcomputer 52 has a signal indicating a vehicle speed V from a vehicle speed sensor 56, a signal indicating a lateral acceleration Gy of the vehicle body from a lateral acceleration sensor 58 provided substantially at the center of gravity of the vehicle body, and a yaw rate sensor 60. Signal indicating the yaw rate γ of the vehicle body, a signal indicating the steering angle θ from the steering angle sensor 62, a signal indicating the wheel speeds VFL to VRR of the left and right front wheels and left and right rear wheels, respectively, from the wheel speed sensors 64FL to 64RR, and pressure sensors 66 and 68. The pressure Pm in the master cylinder 14 and the pressure P in the accumulator, respectively.
A signal indicating a is input.

Further, the ROM of the microcomputer 52 stores a control flow and a map which will be described later, and the CPU performs various calculations as will be described later on the basis of the parameters detected by the various sensors described above to determine the turning behavior of the vehicle. The spin value SV for determination is obtained, the turning behavior of the vehicle is estimated and controlled based on the spin value, and at the end of the turning behavior control, the pressure in the wheel cylinder of each wheel is substantially equal to the pressure in the master cylinder. It is designed to control the value.

Next, turning behavior control of the vehicle in the embodiment will be described with reference to the flowchart shown in FIG. The control according to the flowchart shown in FIG. 2 is started by closing an ignition switch (not shown) and is repeatedly executed at predetermined time intervals. Further, steps 120 to 220 are executed in time series for the left and right front wheels.

First, in step 10, the vehicle speed sensor 5
A signal or the like indicating the vehicle speed V detected in 6 is read, and in step 20, the lateral acceleration Gy is deviated from the product V * γ of the vehicle speed V and the yaw rate γ as a deviation Gy-V * γ. That is, the lateral slip acceleration Vyd of the vehicle is calculated, and the lateral slip velocity Vy of the vehicle body is calculated by integrating the deviation Vyd of the lateral acceleration, and the longitudinal velocity Vx of the vehicle body is calculated.
(= Vehicle speed V) The ratio Vy of the side slip speed Vy of the vehicle body
The vehicle body slip angle β is calculated as / Vx. Further, the slip angular velocity βd of the vehicle body is calculated as the differential value of the slip angle β of the vehicle body.

At step 30, the spin value SV is calculated as the linear sum a * β + b * βd of the slip angle β and the slip angular velocity βd of the vehicle body, where a and b are positive constants, respectively, and at step 40, the spin value SV is calculated. Based on the absolute value of the value SV, the target slip ratio Rsfo of the front wheel on the outside of the turning is calculated from the map corresponding to the graph shown in FIG. In step 50, the wheel cylinders 38F for the left and right front wheels are followed according to the flowchart shown in FIG.
The pressure Pwi (i = FL, FR) in L and 38FR is estimated, and in step 60, the pressure Pwi in the wheel cylinders of the left and right front wheels is corrected according to the flowchart shown in FIG.

At step 80, the target slip ratio R
Whether or not sfo is 0 is determined, that is, whether or not the turning behavior of the vehicle is stable and behavior control is unnecessary is determined, and if a positive determination is made, the process proceeds to step 120, and negative. When the determination is made, the process proceeds to step 90.
In step 90, the target wheel speed Vwt of the front wheel on the outer side of the turning wheel is calculated according to the following equation 1 with Vb as the reference wheel speed, that is, the wheel speed of the front wheel on the inner turning wheel side.

## EQU1 ## Vwt = Vb * (1-Rsfo)

In step 100, the duty ratio D
r is calculated according to Equation 2 below. In the following Equation 2, Vout is the wheel speed of the front wheel on the outside of the turning, and Kp and Kd are proportional constants of the proportional term and the derivative term in the wheel speed feedback control.

## EQU2 ## Dr = Kp * (Vout-Vwt) + Kd * d (V
out −Vwt) / dt

In step 110, a control signal is output to the control valve 50FL or 50FR for the front wheel on the outside of the turning direction so that the control valve is switched to the second position and the opening / closing valve for the front wheel on the outside of the turning path is also set. On the other hand, the control signal corresponding to the duty ratio Dr is output to control the supply / discharge of the accumulator pressure to / from the wheel cylinder 48FL or 48FR of the front wheel on the outside of the turning, thereby controlling the braking pressure on the front wheel on the outside of the turning.

In this case, when the duty ratio Dr is between the negative reference value and the positive reference value, the upstream side opening / closing valve of the turning outer front wheel is set to the second position and the downstream side opening / closing valve is set. Is held at the first position, the pressure in the corresponding wheel cylinder is held, and when the duty ratio is equal to or greater than the positive reference value, the upstream and downstream on-off valves of the turning outer front wheel are shown in FIG. When the duty ratio is equal to or less than the negative reference value, the upstream side of the turning outside front wheel is increased by controlling the accumulated position to supply the accumulator pressure to the corresponding wheel cylinder. Brake oil in the corresponding wheel cylinders is discharged to the low-pressure conduit 52 by switching and setting the open / close valves on the downstream side and the downstream side to the second position. Pressure eel in the cylinder is reduced.

In step 120, it is judged whether or not the previous command value (target slip ratio) is 0.
When a negative determination is made, the flag Fe is set to 1 in step 130. In step 140, it is determined whether or not the flag Fe is 1, and when the determination is affirmative, the process proceeds to step 160, and when the determination is negative, the control valve 40 is determined in step 150.
FL, 40FR and open / close valves 44FL, 44FR, 46FL, 46FR
Is set to the position shown in FIG. 1, whereby the wheel cylinders 38FL and 38FR are connected to the master cylinder 14.

In step 160, it is judged whether or not the pressure Pwi in the wheel cylinder is higher than the master cylinder pressure Pm. If a negative judgment is made, in step 170 the pressure deviation Pm- Pwi is the standard value P
It is determined whether or not it is less than e1 (a positive constant), and when a negative determination is made, in step 180, the control valves 40FL and 4FL are set with the duty ratio Dr set to 1.
By switching 0FR to the second position, the pressure in the wheel cylinder is increased, and when a positive determination is made, connection control is performed in step 190 according to the routine shown in FIG.

When a positive determination is made in step 160, the pressure deviation Pwi- in step 200.
It is determined whether Pm is less than the reference value Pe2 (a positive constant), and if a negative determination is made, step 210
In the state where the duty ratio Dr is set to 1, the control valves 40FL, 40FR, the open / close valves 44FL, 4FR, the open / close valve 46
By switching FL and 46FR to the second position, the pressure in the wheel cylinder is reduced, and when an affirmative determination is made, connection control is performed in step 220 according to the routine shown in FIG.

The reference value Pe2 may be the same as the reference value Pe1, but the impact generated in the master cylinder is Pwi.
Since the case of <Pwi> Pm is higher than the case of <Pm,
The reference value Pe2 is preferably set to a value smaller than the reference value Pe1.

In step 300 of the connection control in step 190 or 220, it is determined whether the flag Fm is 1 or not. If a positive determination is made, the process proceeds to step 320 and a negative determination is made. When the operation is performed, the timer is reset to 0 and the flag Fm is set to 1 in step 310.

At step 320, it is judged whether or not the count value T of the timer exceeds 5 * Tr with Tr as a positive constant. When a positive judgment is made, at step 330 the flag Fe is detected. And Fm are reset, the duty ratio Dm for connecting the wheel cylinder to the master cylinder is set to 1, and when a negative determination is made, the count value T of the timer is incremented by the sampling time Ts and the duty ratio Dm. Is set according to the following Equation 3. Step 35
At 0, a control signal for connecting the wheel cylinder to the master cylinder with a duty ratio Dm is output to the control valve and the on-off valve.

## EQU3 ## Dm = 1-exp (-T / Tr)

Next, the pressure estimation routine and the pressure correction routine in the wheel cylinders in steps 50 and 60 will be described with reference to the flow charts shown in FIGS. 6 and 7, respectively.

In step 51 of the flow chart shown in FIG. 6, it is judged whether the master cylinder pressure Pm is being introduced, that is, whether the wheel cylinder is connected to the master cylinder. If a negative determination is made, the process proceeds to step 53. If an affirmative determination is made, in step 52, the filter coefficient R is set according to the following equation 4 with Tn as a positive constant, and The pressure Pwi is corrected according to the following equation 5.

[0041]

(4) R = (Ts / Tn) * Dm

[Equation 5] Pwi = (1-R) * Pwi + Pm * R

In step 53, it is judged whether or not the pressure in the wheel cylinder is increased. When a negative judgment is made, the routine proceeds to step 55, and when an affirmative judgment is made, the routine proceeds to step 54. The filter coefficient R is set in accordance with the following equation 6 using Tu as a positive constant, and the pressure Pwi in the wheel cylinder is given by the following equation 7.
Is corrected according to.

[0043]

## EQU6 ## R = (Ts / Tu) * Dr

[Equation 7] Pwi = (1-R) * Pwi + Pa * R

In step 55, it is judged whether or not the pressure in the wheel cylinder is reduced. If a negative judgment is made, the routine proceeds to step 60, and if a positive judgment is made, the routine proceeds to step 56. The filter coefficient R is set according to the following equation 8 with Td as a positive constant, and the pressure Pwi in the wheel cylinder is given by the following equation 9.
Is corrected according to.

[0045]

## EQU8 ## R = (Ts / Td) * Dr

[Equation 9] Pwi = (1-R) * Pwi

In step 61 of the flow chart shown in FIG. 7, the wheel cylinder is the master cylinder 14.
It is judged whether or not it is not connected to the terminal. If a negative judgment is made, the routine proceeds to step 68, and if a positive judgment is made, the count value C1 of the timer is incremented by the sampling time Ts in step 62. .
In step 63, it is determined whether or not the count value C1 of the timer exceeds the reference value C1a (a positive constant). If a negative determination is made, the process proceeds to step 69,
When the affirmative determination is made, it is determined in step 64 whether or not the master cylinder pressure Pm0 before the output of the pulse-like connection command is detected, and when the negative determination is made, the master cylinder pressure Pm0 is determined in step 65. The cylinder pressure Pm0 is detected.

In step 66, it is judged whether or not the absolute value of the deviation between the wheel cylinder pressure Pwi and the master cylinder pressure Pm0 is less than the reference value Pth (a positive constant).
When a positive determination is made, in step 67, a command signal for connecting the wheel cylinder to the master cylinder in a pulsed manner is output, the count value C1 of the timer is reset to 0, and the flag Fm is set to 1. When a negative determination is made, the count value C1 of the timer is reset to 0 and the master cylinder pressure Pm0 is cleared at step 68.

In step 69, it is judged whether or not the flag Fm is 1, and when a positive judgment is made, the count value C2 of the timer is incremented by the sampling time Ts in step 70 and a negative judgment is made. When the step is performed, the count value C2 of the timer is reset to 0 in step 71.

In step 72, it is judged whether or not the count value C2 of the timer exceeds the reference value C2a (a positive constant). If a negative judgment is made, step 7 is executed.
If the affirmative determination is made in step 5, it is determined in step 73 whether or not the master cylinder pressure Pm1 immediately after the wheel cylinder is pulse-connected to the master cylinder has been detected, and a negative determination is made. When is performed, the master cylinder pressure Pm1 is detected in step 74.

In step 75, it is judged whether or not the count value C2 of the timer exceeds the reference value C2b (a positive constant). If a negative judgment is made, the routine proceeds to step 80 and the affirmative judgment is made. When the control is performed, the master cylinder pressure Pm2 is detected in step 76, and the count value C2 of the timer and the flag Fm are reset to zero. In step 77, the correction value Pc of the wheel cylinder pressure is calculated according to the following equation 10,
In step 78, the wheel cylinder pressure Pwi is calculated according to the following equation 11 using Kc as a correction coefficient,
At step 79, the pressures Pm0 to Pm2 are cleared,
Then, the process proceeds to step 80.

[0051]

[Formula 10] Pc = Pm1− (Pm0 + Pm2) / 2

[Equation 11] Pwi = Pwi + Kc * Pc

Thus, in the illustrated embodiment, the slip angle β and the slip angular velocity βd of the vehicle body are calculated in step 20, the spin value SV is calculated as the linear sum of these in step 30, and step 40
At step 50, the target slip ratio Rsfo of the front wheel on the outside of the turning, which is the braking force control wheel, is calculated according to the absolute value of the spin value SV, the pressure Pwi in the wheel cylinder is estimated at step 50, and at step 60. The pressure Pwi is corrected, and it is determined in step 80 whether or not the turning behavior of the vehicle is stable.

When the turning behavior of the vehicle is in an unstable state such as spin, a negative determination is made in step 80, and the target wheel speed V of the front wheel on the outside of the turning is determined in step 90.
wt is calculated, and in step 100 the target wheel speed Vwt
The duty ratio Dr for achieving the above is calculated, and in step 110, the wheel speed of the front wheel on the outside of the turning is determined to be the target wheel speed Vwt.
The braking force is controlled so that the anti-spin moment is applied to the vehicle to stabilize the turning behavior of the vehicle.

When the turning behavior of the vehicle becomes stable, an affirmative decision is made in step 80, whereby steps 120 to 220 are executed. In particular, immediately after the turning behavior of the vehicle becomes stable rather than unstable, a negative determination is made in step 120 and an affirmative determination is made in step 140 to determine the wheel cylinder pressure Pwi. Steps 170 to 190 or steps 200 to 220 are executed according to the magnitude relationship with the master cylinder pressure Pm.

For example, when the wheel cylinder pressure Pwi is lower than the master cylinder pressure Pm by Pe1 or more, step 17
A negative determination is made at 0, and the wheel cylinder pressure is increased by connecting the wheel cylinder to the accumulator 36 at step 180. When the deviation between the wheel cylinder pressure and the master cylinder pressure becomes less than Pe1 by this control, an affirmative determination is made in step 170, and the connection control is performed in step 190 according to the routine shown in FIG.

When the wheel cylinder pressure Pwi is higher than the master cylinder pressure Pm by Pe2 or more, step 200
At step 210, the wheel cylinder pressure is reduced by connecting the wheel cylinder to the reservoir 30 at step 210. When the deviation between the wheel cylinder pressure and the master cylinder pressure becomes less than Pe2 by this control, an affirmative determination is made in step 200,
In step 220, connection control is performed according to the routine shown in FIG.

In the connection control routine of step 190 or 220, first, a negative determination is made in step 300, step 310 is executed, then a negative determination is made in step 300, and step 320 is executed. In this case, steps 340 and 350 are repeatedly executed until a positive determination is made, in other words, as shown in FIG. 8A, until the duty ratio Dm becomes substantially 1, whereby the control valves 40FL, 40FR. And open / close valves 44FL, 44FR
Is repeatedly switched between a state in which the wheel cylinder pressure is maintained and a connection state in which the wheel cylinder is connected to the master cylinder, as shown schematically in FIG. 8B, and the time ratio of the held state is gradually reduced. Therefore, the degree of connection between the wheel cylinder and the master cylinder is gradually increased.

If a positive determination is made in step 320, the duty ratio Dm in step 330.
Is set to 1 and the flag Fe is reset to 0, so that a negative determination is made in steps 120 and 140, and each control valve and the on-off valve are maintained in the states shown in step 150.

Therefore, according to the illustrated embodiment, in the graph of FIG. 9 in which the master cylinder pressure Pm is the horizontal axis and the wheel cylinder pressure Pwi is the vertical axis, the wheel cylinder pressure is lower than the straight line Pwi = Pm-Pe1. In the case of, the wheel cylinder is first connected to the accumulator to increase the pressure, and the wheel cylinder is connected to the master cylinder so that the connection degree gradually increases when the wheel cylinder is above the straight line Pwi = Pm-Pe1. On the contrary, in the graph of FIG. 9, when the wheel cylinder pressure is above the straight line Pwi = Pm + Pe2, first, the wheel cylinder is connected to the reservoir to reduce the pressure, and the straight line Pwi = Pm +
The wheel cylinder is connected to the master cylinder so that the degree of connection gradually increases at a stage below Pe2.

When the turning behavior of the vehicle continues to be stable, a positive determination is made in step 120 and a negative determination is made in step 140. Therefore, in this case, steps 90 to 110 are performed. The behavior control is not executed and the wheel cylinder is maintained in a state of being connected to the master cylinder, whereby the braking pressure of each wheel is controlled according to the depression amount of the brake pedal 12 by the driver.

In the illustrated embodiment, when the wheel cylinder pressure Pwi is in the state where the master cylinder pressure Pm is introduced into the wheel cylinder according to the estimation routine of FIG. And the duty ratio Dm and the master cylinder pressure Pm
When the pressure in the wheel cylinder is increased, the duty ratio Dr and the pressure P in the accumulator are calculated in step 54 according to equations 6 and 7.
When the pressure in the wheel cylinder is reduced, it is calculated according to the duty ratio Dr according to the equations (8) and (9) in step 56. Therefore, the pressure in each wheel cylinder is obtained by estimation without the need for a pressure sensor to detect them.

Further, in the embodiment shown in FIG. 10, the pressure correction routine in the wheel cylinder (FIG. 7) is executed,
, The master cylinder pressure Pm0 before the wheel cylinder is pulse-connected to the master cylinder,
The master cylinder pressure Pm1 immediately after the wheel cylinder is pulse-connected to the master cylinder, and the master cylinder pressure Pm2 after a predetermined time has elapsed from the time when the wheel cylinder is pulse-connected to the master cylinder, are detected. Based on the equations (10) and (11), the wheel cylinder pressure Pwi is corrected.

Therefore, the estimation error of the wheel cylinder internal pressure estimated according to the estimation routine of FIG. 6 is reduced, whereby the wheel cylinder internal pressure is accurately estimated, and in this case, the connection between the wheel cylinder and the master cylinder is pulsed. This connection ensures that the master cylinder is not impacted.

In the above embodiment, only the braking force of the left and right front wheels is controlled according to the turning behavior of the vehicle, but the braking force of all four wheels depends on the turning behavior of the vehicle. May be controlled in such a case, in which case steps 50 and 60
And steps 120 to 220 may be executed in time series for all four wheels in the order of, for example, the left front wheel, the right front wheel, the left rear wheel, and the right rear wheel, and in that case, the wheel cylinder pressure is detected for all four wheels. The number of pressure sensors and the number of wire harnesses can be reduced as compared with the case where a pressure sensor that operates is provided, thereby simplifying the structure of the braking force control device and reducing costs.

In the above embodiment, the wheel cylinder is connected to the master cylinder when the turning behavior of the vehicle is stable, and the wheel cylinder is connected to the accumulator or the reservoir when the turning behavior of the vehicle is unstable. According to the present invention, the wheel cylinders are connected to the master cylinder when the vehicle is in a normal state, and the wheel cylinders are connected to a high pressure source or a reservoir when the vehicle is in a predetermined state. Therefore, it may be applied to any braking force control device that controls the braking force.

Although the present invention has been described in detail above with reference to specific embodiments, the present invention is not limited to the above-described embodiments, and various other embodiments are also possible within the scope of the present invention. It will be apparent to those skilled in the art that

For example, in the illustrated embodiment, the pressures in the wheel cylinders of the left and right front wheels are estimated according to the routines of FIGS. 6 and 7, but the pressures in the wheel cylinders of the respective wheels are the pressures. It may be detected by a sensor, whereby steps 50 and 60 may be omitted.

Further, in the illustrated embodiment, even when the wheel cylinder internal pressure Pwi is smaller than the master cylinder pressure Pm, the deviation is less than Pe1 until step 18
When the wheel cylinder pressure is increased from 0 and the pressure deviation becomes less than the reference value, the connection control in step 190 is executed. However, if Pwi <Pm, the deviation Steps 300-350 regardless of size
The wheel cylinder may be connected to the master cylinder by a routine similar to.

Further, in the illustrated embodiment, the pressure Pm1
Is detected as the master cylinder pressure at the time point C2a has elapsed from the start of the pulsed connection of the wheel cylinder to the master cylinder, and the pressure Pm1 is the pressure until the predetermined time C2b has elapsed from the start of the pulsed connection. It may be detected as the maximum value of the master cylinder pressure in the meantime.

[0070]

As is apparent from the above description, according to the structure of claim 1 of the present invention, when the vehicle is in the normal state from the predetermined state, the deviation between the wheel cylinder pressure and the master cylinder pressure is predetermined. Since the wheel cylinder is connected to the master cylinder when it is within the range, it is possible to ensure that the master cylinder, etc. is impacted due to the differential pressure between the wheel cylinder pressure and the master cylinder pressure. Can be prevented.

According to the second aspect of the present invention, when the deviation between the wheel cylinder pressure Pw and the master cylinder pressure Pm when the vehicle goes from the predetermined state to the normal state is outside the predetermined range and Pw <Pm. The wheel cylinder pressure is increased by connecting the wheel cylinder to the high pressure source by the first connecting means, and when the deviation is out of the predetermined range and Pw> Pm, the wheel cylinder is stored by the first connecting means. When the deviation is within a predetermined range, the wheel cylinder is connected to the master cylinder by the second connecting means, and the second connecting means holds the wheel cylinder pressure. State and the connected state in which the wheel cylinder is connected to the master cylinder are repeatedly switched, and the hold state is timed. Is gradually reduced, the pressure deviation can be reliably and relatively quickly set within a predetermined range even when the deviation between the wheel cylinder pressure and the master cylinder pressure when the vehicle is in a normal state rather than a predetermined state is outside the predetermined range. The wheel cylinder can be reliably and relatively quickly connected to the master cylinder, and the degree of connection between the wheel cylinder and the master cylinder gradually increases even if the pressure deviation is within a predetermined range. Controlled as
As a result, it is possible to reliably prevent the impact on the master cylinder and the like.

According to the third aspect of the invention, since the wheel cylinder pressure is estimated based on the operating conditions of the first and second connecting means, a pressure sensor or the like for detecting the wheel cylinder pressure of each wheel is required. Therefore, the wheel cylinder pressure can be obtained without using the wheel cylinder pressure, and the structure of the braking force control device can be simplified and the cost can be reduced as compared with the case where a pressure sensor for detecting the wheel cylinder pressure is provided for each wheel.

Further, according to the structure of claim 4, the estimated value of the wheel cylinder pressure is corrected based on the fluctuation of the master cylinder pressure Pm when the wheel cylinder is momentarily connected to the master cylinder by the second connecting means. Therefore, the wheel cylinder pressure can be more accurately obtained as compared with the case where such a correction is not performed, and thereby it is possible to appropriately prevent the impact on the master cylinder and the like.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a hydraulic circuit and an electric control device of one embodiment of a braking force control device according to the present invention.

FIG. 2 is a flowchart showing a part of a braking force control routine in the embodiment configured as a behavior control device.

FIG. 3 is a flowchart showing a remaining part of a braking force control routine in the embodiment configured as a behavior control device.

4 is a flowchart showing a connection control routine of the flowchart shown in FIG.

FIG. 5 is a graph showing the relationship between the absolute value of the spin value SV and the target slip ratio Rsfo.

FIG. 6 is a flowchart showing a wheel cylinder pressure estimation routine in the illustrated embodiment.

FIG. 7 is a flowchart showing a wheel cylinder pressure correction routine in the illustrated embodiment.

FIG. 8 is a graph showing a change (A) in the duty ratio Dm and a change (B) in the connection state between the wheel cylinder and the master cylinder.

FIG. 9 is a graph showing the relationship between master cylinder pressure Pm and wheel cylinder pressure Pwi, and pressure increase / decrease and gradual connection to the master cylinder.

FIG. 10: Pulse connection and master cylinder pressures Pm0, Pm
It is a graph which shows the relationship between the detection timing of 1 and Pm2.

[Explanation of symbols]

 10 ... Braking device 14 ... Master cylinder 18, 20, 26, 28 ... Brake hydraulic pressure control device 34 ... Oil pump 38FL, 38FR, 38RL, 38RR ... Wheel cylinder 40FL, 40FR, 40RL, 40RR ... Control valve 44FL, 44FR, 44RL, 44RR ... Open / close valve 46FL, 46FR, 46RL, 46RR ... Open / close valve 50 ... Electric control device 56 ... Vehicle speed sensor 58 ... Lateral acceleration sensor 60 ... Yaw rate sensor 62 ... Steering angle sensor 64FL-64RR ... Wheel speed sensor 66, 68 ... Pressure Sensor

Claims (4)

[Claims] 1. A braking force control device for a vehicle which controls a braking force by connecting a wheel cylinder to a master cylinder when the vehicle is in a normal state and connecting the wheel cylinder to a high pressure source or a reservoir when the vehicle is in a predetermined state. When the vehicle goes from a predetermined state to a normal state, a means for connecting the wheel cylinder to the master cylinder is provided when the deviation between the wheel cylinder pressure and the master cylinder pressure is within a predetermined range. A braking force control device for a vehicle, which is characterized by: 2. A braking force control device for a vehicle for controlling a braking force by connecting a wheel cylinder to a master cylinder when the vehicle is in a normal state and connecting the wheel cylinder to a high pressure source or a reservoir when the vehicle is in a predetermined state. In the above, a means for detecting the wheel cylinder pressure Pw, a means for detecting the master cylinder pressure Pm, and a deviation between the wheel cylinder pressure Pw and the master cylinder pressure Pm when the vehicle goes from a predetermined state to a normal state Deviation calculating means, when the deviation is out of a predetermined range and Pw <Pm, the wheel cylinder is connected to a high pressure source to increase the wheel cylinder pressure, and the deviation is out of the predetermined range and Pw When> Pm, the first connecting means for connecting the wheel cylinder to the reservoir to reduce the wheel cylinder pressure. And a second connecting means for connecting the wheel cylinder to the master cylinder when the deviation is within a predetermined range, and the second connecting means holds the wheel cylinder pressure and the holding state. A braking force control device for a vehicle, wherein the braking force control device for a vehicle is configured to be repeatedly switched to a connection state in which a wheel cylinder is connected to the master cylinder and to gradually reduce a temporal ratio of a holding state. 3. The vehicle braking force control device according to claim 1 or 2, wherein the means for detecting the wheel cylinder pressure Pw determines the wheel cylinder pressure based on the operating conditions of the first and second connecting means. A braking force control device for a vehicle, which is configured to estimate. 4. A braking force control device for a vehicle according to claim 3, wherein:
Means for momentarily actuating the second connecting means, and correcting the estimated wheel cylinder pressure based on the fluctuation of the master cylinder pressure Pm when the second connecting means is momentarily actuated. A braking force control device for a vehicle, which is configured as described above.