JP3146954B2 - Vehicle braking force control device - Google Patents

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, and more particularly to a braking force control device suitable for suppressing and reducing undesired behaviors such as spin and drift-out during turning. According to.

[0002]

2. Description of the Related Art As one of braking force control devices for controlling the behavior of spin and the like when turning a vehicle such as an automobile, for example, as described in JP-A-6-24304,
2. Description of the Related Art A yaw rate feedback type braking force control device that controls a braking force so that an actual yaw rate of a vehicle becomes a target yaw rate calculated based on a running state of the vehicle is conventionally known.

According to such a braking force control device, since the braking force is controlled so that the actual yaw rate becomes equal to the target yaw rate, even if spin or drift-out occurs during turning, the unstable behavior is reduced. The turning behavior of the vehicle can be stabilized as compared to a case where such braking force control is not performed.

[0004]

The behavior control by the braking force control device must be executed even when the driver is performing a braking operation if the behavior of the vehicle becomes unstable. Therefore, the behavior control is performed using the accumulator as a pressure source during the behavior control, and the supply source of the pressure supplied to the wheel cylinder is switched so that the braking is performed by the master cylinder pressure that changes according to the pedaling force on the brake pedal during the braking operation by the driver. Hydraulic circuits are conceivable.

In the braking force control device provided with such a hydraulic circuit, if the residual pressure in the wheel cylinder is high when the pressure source is switched from the accumulator to the master cylinder due to the end of the behavior control, The residual pressure may flow back to the master cylinder. In general, the master cylinder is configured into two systems, a front wheel system and a rear wheel system, for the purpose of fail-safe, and has two pressurizing chambers for the front wheel and the rear wheel separated by a free piston, and the free piston is operated by a brake pedal. It is connected to the driven main piston by connecting means such as a rod.

Therefore, when the residual pressure in the wheel cylinder flows back to the master cylinder at the end of the behavior control, a large force acts on the connecting means due to a sudden change in the pressure acting on the free piston, thereby increasing the durability of the connecting means. Getting worse. Also, in the case where the connecting means such as a rod is not provided, when the residual pressure in the wheel cylinder flows backward to the master cylinder, the free piston moves rapidly, so that
Master cylinder reliability is adversely affected.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems in the conventional braking force control apparatus, and a main problem of the present invention is that when the behavior control is completed, the residual pressure in the wheel cylinder becomes the master pressure. It is also to prevent the force acting on the free piston from abruptly changing even when flowing back to the cylinder, thereby preventing deterioration of the durability of the connecting means and deterioration of the reliability of the master cylinder.

[0008]

SUMMARY OF THE INVENTION According to the present invention, there is provided, in accordance with the present invention, a master cylinder having first and second pressurized chambers defined by a free piston. A passage means for communicating and connecting the pressurizing chamber of the master cylinder and the wheel cylinder of each wheel, and a switching valve provided in the passage means, which allows communication between the master cylinder and the wheel cylinder; A first state in which the communication between the pressure source generating the predetermined high pressure and the wheel cylinder is interrupted, a communication between the master cylinder and the wheel cylinder is interrupted, and the pressure source and the wheel cylinder are communicated and connected. A switching valve for switching to a second state, and control means for switching the switching valve to the first or second state according to a traveling state of the vehicle. And when the control means switches the switching valve from the second state to the first state, communication between the first pressurizing chamber and the wheel cylinder and the second pressurizing chamber and the wheel This is achieved by a braking force control device for a vehicle, comprising means for delaying one of the communication with the cylinder with respect to the other.

According to this configuration, when the control means switches the switching valve from the second state to the first state, the communication between the first pressurizing chamber and the wheel cylinder and the communication between the second pressurizing chamber and the second pressurizing chamber are performed. One of the communication with the wheel cylinder is delayed with respect to the other, so that when the other pressurizing chamber is in communication with the wheel cylinder, the communication between the one pressurizing chamber and the wheel cylinder is in a disconnected state, and the free piston is Since one of the pressurizing chambers is hydraulically locked, even if the residual pressure in the wheel cylinder flows back to the other pressurizing chamber of the master cylinder, a large force is applied to the connecting means connected to the free piston. And the sudden movement of the free piston is reliably prevented.

[0010]

According to a preferred aspect of the present invention, in the structure of the first aspect, the first pressurizing chamber generates a braking pressure for the front wheels and generates a braking pressure for the front wheels. The second pressurizing chamber is configured to communicate with a wheel cylinder of the rear wheel and communicate with the wheel cylinder of the rear wheel.

According to another preferred solution of the means for solving the problems of the present invention, in the configuration of the preferred embodiment described above, the communication between the second pressurizing chamber and the wheel cylinder of the rear wheel is performed by the first load. The communication between the pressure chamber and the wheel cylinder of the front wheel is configured to be delayed.

[0012]

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.

In FIG. 1, a braking device 10 includes a master cylinder 14 for pumping brake oil from first and second ports in response to a depression operation of a brake pedal 12 by a driver, and an oil pressure in the master cylinder. And a hydraulic booster 16 for increasing the brake oil to a pressure (regulator pressure) corresponding to the pressure. Master cylinder 1
The first port 4 is a brake hydraulic control conduit 18 for the front wheels.
The brake hydraulic control devices 20 and 22 for the left and right front wheels
The second port is connected to a three-port two-position switching type electromagnetic control valve 28 for the right and left rear wheels by a rear wheel brake hydraulic control conduit 26 having a proportional valve 24 on the way. The control valve 28 is connected by a conduit 30 to a brake hydraulic control device 32 for the left rear wheel and a brake hydraulic control device 34 for the right rear wheel.

As shown in detail in FIG. 10, a cylinder bore 102 is provided in the cylinder housing 100 of the master cylinder 14, and the cylinder bore 102 has a first pressurizing piston 104 and a second pressurizing piston ( A free piston 106 is fitted in a liquid-tight manner and slidably in the left-right direction in the figure. Each piston 104 and 10
A first pressurizing chamber 108 and a second pressurizing chamber 110 are formed in front of (to the left as viewed in FIG. 10), respectively. The first pressurizing piston 104 is connected to the brake pedal 12 via a rod, a reaction mechanism, etc., not shown in FIG.
The first pressurizing chamber 108 and the second pressurizing chamber 110 generate hydraulic pressure in response to depression of the brake pedal 12.

The first pressure piston 104 and the second pressure piston 106 are sealed by cup seals 112 and 114 for maintaining liquid tightness, respectively. The relative position between the two is regulated by the separation limit regulating member 118. The first compression coil spring 116 is
4 and 106 are biased in a direction to separate them from each other.
The first separation limit regulating member 118 includes a shaft portion 118A, a large diameter head portion 118B formed at one end of the shaft portion, and a stepped large diameter valve holding formed at the other end of the shaft portion 118A. The portion 118C is formed.

The head portion 118B is the second pressurizing piston 1
06 is movably accommodated in a bottomed hole 120 formed in the hole 06, and the movement is regulated by engaging with the open end of the hole 120. On the other hand, the valve holding portion 118C is movably accommodated in the bottomed hole 122 of the first pressurizing piston 104, and its movement is regulated by engaging with the lid member 124. Therefore, the first pressurizing piston 1 by the urging force of the first compression coil spring 116
The separation distance between the pressure piston 04 and the second pressure piston 106 is regulated by the first separation limit regulating member 118.

At the bottom of the hole 122 of the first pressurizing piston 104, a communication hole 128 for connecting the first pressurizing chamber 108 and the through hole 126 is provided.
8 is a communication hole 128, a through hole 126, a cylinder chamber 130,
It is connected to the reservoir 36 through the port 132. Also, the valve holding portion 11 of the first separation limit regulating member 118
8C, a rubber valve element 134 for opening and closing the communication hole 128 is provided.
Is fixed, and the valve element 134 is
6 urges the communication hole 128 in a direction to close it.

Similarly, the second pressurizing piston 106 includes a block 138 fixed to the front end of the cylinder housing 100.
The second compression coil spring 140 and the second separation limit regulating member 142 regulate the relative position with respect to the front end of the cylinder housing and the block 138. The second compression coil spring 140 is connected to the pressure piston 106
Are biased in a direction to separate from the block 138.
The second separation limit regulating member 142 includes a shaft portion 142A, a large diameter head portion 142B formed at one end of the shaft portion, and a stepped large diameter valve holding formed at the other end of the shaft portion 142A. The portion 142C is formed.

The head portion 142B is movably housed in a bottomed hole 144 formed in the block 138,
The movement is regulated by engaging with the open end of 4. On the other hand, the valve holding portion 142C is movably accommodated in the bottomed hole 146 of the second pressurizing piston 106, and its movement is regulated by engaging with the lid member 148. Therefore, the separation distance between the block 138 and the second pressure piston 106 due to the urging force of the second compression coil spring 140 is regulated by the second separation limit regulating member 142.

At the bottom of the hole 146 of the second pressurizing piston 106, a communication hole 152 for connecting the second pressurizing chamber 110 and the through hole 150 is provided.
0 is connected to the reservoir 36 through the communication hole 152, the through hole 150, and the port 156. The communication hole 15 is provided in the valve holding portion 142C of the second separation limit regulating member 142.
2, a rubber valve element 158 that opens and closes is fixed.
The valve element 158 is connected to the communication hole 15 by a compression coil spring 160.
2 is closed.

Further, the first pressurizing chamber 108 is connected to a front-wheel brake hydraulic control conduit 18 through a port 162 provided in the cylinder housing 100, and the second pressurizing chamber 110 is also connected to the cylinder housing 100. 100 is connected to a brake hydraulic control conduit 26 for a rear wheel through a port 164 provided in the vehicle 100.

In the master cylinder configured as described above, when the brake pedal 12 is depressed, the first pressurizing piston 104 is driven to the left in the drawing, and the valve of the first separation limit regulating member 118 is moved. The element 134 approaches the communication hole 128. When the first pressurizing piston 104 is further driven, the valve element 134 closes the communication hole 128, and a hydraulic pressure is generated in the first pressurizing chamber 108.

When the hydraulic pressure is generated in the first pressurizing chamber 108, the second pressurizing piston 106 is also driven to the left in the drawing, and the valve element 158 of the second separation limit regulating member 142 is opened. Approach 152. When the second pressurizing piston 106 is further driven, the valve element 158 closes the communication hole 152, and a hydraulic pressure is generated in the second pressurizing chamber 110. The hydraulic pressure generated in the first pressurizing chamber 108 and the second pressurizing chamber 110 is supplied to the brake hydraulic control conduit 18 for the front wheels and the brake hydraulic control conduit 2 for the rear wheels via ports 162 and 164, respectively.
6.

On the other hand, when the depression of the brake pedal 12 is released, the fluid pressures in the first pressurizing chamber 108 and the second pressurizing chamber 110 decrease rapidly. That is, the first pressurizing piston 104 and the second pressurizing piston 106 are returned to the initial positions by the compression coil springs 116 and 140, respectively, the communication holes 128 and 152 are opened, and the first pressurizing chamber 1 is opened.
08 and the hydraulic pressure in the second pressure chamber 110 are released to the reservoir 36 via ports 132 and 156, respectively.

In FIG. 1, the braking device 10 has an oil pump 40 which pumps up brake oil stored in a reservoir 36 and supplies it to the high-pressure conduit 38 as high-pressure oil. The high pressure conduit 38 is connected to the hydro booster 16 and to the switching valve 44,
An accumulator 46 for accumulating high-pressure oil discharged from the oil pump 40 as accumulator pressure is connected in the middle of 8. As shown, the switching valve 44 is also a three-port two-position switching type electromagnetic switching valve.
It is connected to the.

The brake hydraulic pressure control devices 20 and 22 for the front left and right wheels respectively include wheel cylinders 48FL and 48FR for controlling the braking force on the corresponding wheels, three-port two-position switching type electromagnetic control valves 50FL and 50FR, and a reservoir. Low pressure conduit 5 as return passage connected to 36
Normally open electromagnetic open / close valves 54FL and 54FR and a normally closed electromagnetic open / close valve 56FL provided in the middle of the regulator pressure supply conduit 53 for the left and right front wheels connected between the control valve 2 and the switching valve 44. And 56FR. On-off valve 5 each
The regulator pressure supply conduit 53 for the left and right front wheels between the 4FL, 54FR and the on-off valves 56FL, 56FR is connected to the connection conduits 58FL, 5FL.
The control valves 50FL and 50FR are connected by 8FR.

The brake hydraulic control device 32 for the left and right rear wheels,
Reference numeral 34 denotes a normally-open electromagnetic on-off valve 60RL, 60 provided between the control valve 28 and the low-pressure conduit 52 in the middle of the conduit 30.
RR and normally closed solenoid-operated on-off valves 62RL, 62RR, and wheel cylinders 64RL, 64RR for controlling braking force on the corresponding wheels, respectively.
RL and 64RR are connected to the conduit 30 between the on-off valves 60RL and 60RR and the on-off valves 62RL and 62RR by connecting conduits 66RL and 66RR, respectively.

The control valves 50FL and 50FR are respectively a brake hydraulic control conduit 18 for the front wheels and a wheel cylinder 48FL.
And 48FR and wheel cylinder 48FL
, 48FR and the connection conduits 58FL and 58FR, the first position shown in the figure, the brake hydraulic control conduit 18 and the wheel cylinders 48FL and 48FR are disconnected, and the wheel cylinders 48FL and 48FR are connected to the connection conduit 58FL.
, And 58FR.

A regulator pressure supply conduit 68 for the left and right rear wheels is connected between the switching valve 44 and the left and right rear wheel control valve 28, and the control valves 28 are connected to the brake oil pressure control conduits 26 for the rear wheel, respectively. The on-off valves 60RL, 60RR are connected in communication with each other, and the on-off valves 60RL, 60RR are connected to the regulator pressure supply conduit 68.
The communication between the brake oil pressure control conduit 26 and the on-off valves 60RL, 60RR is interrupted, and the on-off valves 60RL, 60RR and the regulator pressure supply conduit 6 are disconnected.
8 is switched to a second position for communicating with the second position.

The control valves 50FL, 50FR, and 28 function as master cylinder pressure shut-off valves, and when these control valves are at the first position shown in the figure, the wheel cylinders 48FL, 48FR
FR, 64RL, 64RR are connected in communication with conduits 18, 26,
By supplying the master cylinder pressure to each wheel cylinder, the braking force of each wheel is controlled according to the amount of depression of the brake pedal 12 by the driver, and the control valves 50FL, 50FL
When 0FR, 28 is in the second position, each wheel cylinder is shut off from the master cylinder pressure.

The switching valve 44 has a wheel cylinder 48F.
L, 48FR, 64RL, 64RR serve to switch the hydraulic pressure supplied between the accumulator pressure and the regulator pressure, the control valves 50FL, 50FR, 28 are switched to the second position and the on-off valves 54FL, 54FR. , 60RL, 60RR and the opening / closing valves 56FL, 56FR, 62RL, 62RR are in the positions shown in the figure, and when the switching valve 44 is maintained at the first position shown in the figure, the wheel cylinders 48FL, 48FR, 64R
When the regulator pressure is supplied to L and 64RR, the pressure in each wheel cylinder is controlled by the regulator pressure, so that the braking pressure of the wheel is controlled by the amount of depression of the brake pedal 12 regardless of the braking pressure of the other wheels. It is controlled in the pressure increasing mode by the corresponding regulator pressure.

Even if each valve is switched to the pressure increasing mode by the regulator pressure, when the pressure in the wheel cylinder is higher than the regulator pressure, the oil in the wheel cylinder flows backward, and the control mode is the pressure increasing mode. Nevertheless, the actual braking pressure decreases.

The control valves 50FL, 50FR, 28 are switched to the second position, and the on-off valves 54FL, 54FR, 60RL,
When the switching valve 44 is switched to the second position in a state where the 60RR and the opening / closing valves 56FL, 56FR, 62RL, 62RR are at the positions shown in the figure, the wheel cylinders 48FL, 48FR, 64R
By supplying the accumulator pressure to the L and 64RR, the pressure in each wheel cylinder is controlled at an accumulator pressure higher than the regulator pressure, so that regardless of the amount of depression of the brake pedal 12 and the braking pressure of the other wheels, The braking pressure of the wheels is controlled in an accumulator pressure increasing mode.

Further, with the control valves 50FL, 50FR, 28 switched to the second position, the on-off valves 54FL, 54FR, 6
0RL and 60RR are switched to the second position, and the on-off valve 56F
When L, 56FR, 62RL, and 62RR are controlled to the illustrated state, the pressure in each wheel cylinder is maintained regardless of the position of the switching valve 44, and the control valves 50FL, 50FR, and 28 are switched to the second position. Open / close valve 54FL, 54FR, 6
0RL, 60RR and open / close valve 56FL, 56FR, 62RL, 62
When the RR is switched to the second position, the pressure in each wheel cylinder is reduced irrespective of the position of the switching valve 44, whereby the wheel is irrespective of the amount of depression of the brake pedal 12 and the braking pressure of the other wheels. The braking pressure is controlled in the pressure reduction mode.

Switching valve 44, control valves 50FL, 50FR, 2
8. The on-off valves 54FL, 54FR, 60RL, and 60RR and the on-off valves 56FL, 56FR, 62RL, and 62RR are controlled by an electric control device 70 as described later in detail. The electric control device 70 includes a microcomputer 72 and a drive circuit 74.
Although the microcomputer 72 is not shown in detail in FIG. 1, for example, the central processing unit (C)
PU), a read only memory (ROM), a random access memory (RAM), and an input / output port device, which are generally connected to each other by a bidirectional common bus. Good.

A signal indicating the vehicle speed V from the vehicle speed sensor 76, a signal indicating the lateral acceleration Gy of the vehicle body from a lateral acceleration sensor 78 substantially provided at the center of gravity of the vehicle body, a yaw rate sensor 80 A signal indicating the yaw rate γ of the vehicle body, a signal indicating the steering angle θ from the steering angle sensor 82, a signal indicating the longitudinal acceleration Gx of the vehicle body from the longitudinal acceleration sensor 84 provided substantially at the center of gravity of the vehicle body, the wheel speed sensors 86FL From 86RR, the wheel speeds (peripheral speeds) Vwfl, Vwfr,
Signals indicating Vwrl and Vwrr, brake switch (SW)
From 88, a signal indicating whether or not the brake switch is in the ON state is input. The lateral acceleration sensor 78, the yaw rate sensor 80, and the like detect lateral acceleration and the like with the left turning direction of the vehicle as positive, and
Reference numeral 4 indicates that the longitudinal acceleration is detected by setting the acceleration direction of the vehicle to be positive.

The ROM of the microcomputer 72 stores the control flow of FIGS. 2 to 6 and the maps of FIGS. 7 to 9 as described later, and the CPU executes the following processing based on the parameters detected by the various sensors described above. Various calculations are performed as described above to determine the spin state amount SS for determining the turning behavior of the vehicle.
And a drift-out state quantity DS, the turning behavior of the vehicle is estimated based on these state quantities, and the braking behavior of each wheel is controlled based on the estimation result to control the turning behavior.

Next, the vehicle behavior control routine will be described with reference to the flowcharts shown in FIGS. The control according to the flowcharts shown in FIGS. 2 and 3 is started by closing an ignition switch (not shown) and is repeatedly executed at predetermined time intervals.

First, at step 10, the vehicle speed sensor 7
6, a signal indicating the vehicle speed V detected is read, and in step 20, the deviation Gy of the lateral acceleration Gy and the product V * γ of the vehicle speed V and the yaw rate γ is calculated as Gy−V * γ. That is, the skid acceleration Vyd of the vehicle is calculated, and in step 30, the skid acceleration Vyd is integrated to calculate the skid speed Vy of the vehicle body.
The slip angle β of the vehicle body is calculated as the ratio Vy / Vx of the vehicle body slip speed Vy to the vehicle body front-rear speed Vx (= vehicle speed V).

In step 40, the spin amount SV is calculated as the linear sum K1 * β + K2 * Vyd of the vehicle slip angle β and the skid acceleration Vyd, using K1 and K2 as positive constants, respectively. In step 50, the yaw rate is calculated. The turning direction of the vehicle is determined based on the sign of γ, and the spin state amount SS is calculated as SV when the vehicle is turning left and −SV when the vehicle is turning right. When the calculation result is a negative value, the spin state amount SS is calculated. The amount is set to zero. The spin amount SV may be calculated as a linear sum of the slip angle β of the vehicle body and its differential value βd.

In step 60, the target yaw rate γ is calculated according to the following equation 1 using Kh as a stability factor.
c is calculated, and the reference yaw rate γt is calculated according to the following equation 2 using T as a time constant and s as a Laplace operator. Incidentally, the target yaw rate γc may be calculated in consideration of the lateral acceleration Gy of the vehicle in consideration of a dynamic yaw rate.

[0043]

Γ c = V * θ / (1 + Kh * V ² ) * H

## EQU2 ## γt = γc / (1 + T * s)

In step 70, the drift-out amount DV is calculated according to the following equation (3). Note that the drift-out amount DV may be calculated according to the following Expression 4 using H as a wheel base.

[0045]

## EQU3 ## DV = (γt−γ)

## EQU4 ## DV = H * (γt−γ) / V

In step 80, the turning direction of the vehicle is determined based on the sign of the yaw rate γ, and the drift-out state amount DS is calculated as DV when the vehicle is turning left, and as -DV when the vehicle is turning right. When the calculation result is a negative value, the drift-out state amount is set to zero.

In step 90, the spin state amount SS
The slip ratio target value Rssfo of the front outside wheel is calculated from the map corresponding to the graph shown in FIG. 7 on the basis of the graph shown in FIG. 7, and in step 100, the target value corresponding to the graph shown in FIG. A target slip ratio Rsall of the entire vehicle is calculated from the map.

In step 110, Ksri is set as the distribution ratio of the inside turning rear wheel, and the target slip ratios Rsfo, Rsfi, Rsro of the turning outside front wheel, the turning inside front wheel, the turning outside rear wheel, and the turning inside rear wheel according to the following equation (5). , Rsri are calculated.

Rsfo = Rssfo Rsfi = 0 Rsro = (Rsall-Rssfo) * (100-Ksri) / 1
00 Rsri = (Rsall-Rssfo) * Ksri / 100

In step 120, the turning inner and outer wheels are specified by determining the turning direction of the vehicle based on the sign of the yaw rate γ, and the final target slip ratios Rsi (i = fr, i = fr, fl, rr, rl) are calculated. That is, when the final target slip ratio Rsi is a left turn and a right turn of the vehicle, the following equations 6 and 7 are respectively given.
Is required in accordance with

[0050]

Rsfr = Rsfo Rsfl = Rsfi Rsrr = Rsro Rsrl = Rsri

Rsfr = Rsfi Rsfl = Rsfo Rsrr = Rsri Rsrl = Rsro

In step 130, it is determined whether or not all final target slip rates Rsi are 0, that is, whether or not behavior control is unnecessary. After the flag F is reset to 0 in 140, the process returns to step 10, and if a negative determination is made, the flag F is set to 1 in step 150.

In step 160, the target wheel speed Vwti of each wheel is calculated according to the following equation 8 using Vb as a reference wheel speed (for example, the wheel speed of the front wheel inside the turn).

Vwti = Vb * (100-Rsi) / 100

In step 170, Vwid is the wheel acceleration (differential value of Vwi) of each wheel, and Ks is a positive constant coefficient, and the target slip amount SP of each wheel is calculated according to the following equation (9).
i is calculated, and in step 180, the duty ratio Dri of each wheel is obtained from the map corresponding to the graph shown in FIG.
Is calculated.

SPi = Vwi−Vwti + Ks * (Vwid−Gx)

Further, in step 190, the switching valve 44
Is switched to the second position, the accumulator pressure is introduced, and a control signal is output to the control valves 28, 50FR to 50RL of the respective wheels corresponding to the wheels for which the final target slip Rsi is not zero. The control valve is set to switch to the second position. By outputting a control signal corresponding to the duty ratio Dri to the open / close valve of each wheel, the supply and discharge of the accumulator pressure to and from the wheel cylinders 48FR to 48RL are controlled, thereby controlling the braking pressure of each wheel.

In this case, when the duty ratio Dri is a value between the negative reference value and the positive reference value, the upstream open / close valve is switched to the second position and the downstream open / close valve is set to the first position. By holding the position, the pressure in the corresponding wheel cylinder is held, and when the duty ratio is equal to or more than the positive reference value, the upstream and downstream open / close valves are controlled to the positions shown in FIG. By supplying the accumulator pressure to the corresponding wheel cylinder, the pressure in the wheel cylinder is increased. When the duty ratio is equal to or less than the negative reference value, the upstream and downstream open / close valves are in the second position. , The brake oil in the corresponding wheel cylinder is supplied to the low-pressure conduit 52.
To reduce the pressure in the wheel cylinder.

When the pressure in the wheel cylinder is increased, the upstream open / close valve is opened / closed according to the duty ratio. When the pressure in the wheel cylinder is reduced, the downstream open / close valve is opened / closed according to the duty ratio. It is opened and closed. As a result, the increasing / decreasing gradient of the pressure in the wheel cylinder becomes greater as the duty ratio increases.

Next, a flag setting routine, that is, a behavior control end processing routine according to the illustrated embodiment will be described with reference to flowcharts shown in FIGS.
The control according to the flowcharts shown in FIGS. 4 and 5 is executed by interruption every predetermined time.

First, in step 210, it is determined whether or not the final target slip ratio Rsfr of the right front wheel is 0. If a negative determination is made, the process proceeds to step 280, and if an affirmative determination is made, From the time when the final target slip ratio Rsfr becomes 0 in step 220, T1
(Positive constant) It is determined whether or not the time has elapsed. When an affirmative determination is made in this step, the routine proceeds to step 250, and when a negative determination is made, the routine proceeds to step 230.

In step 230, it is determined whether or not the brake operation by the driver is being performed by determining whether or not the brake switch 88 is on. If the determination is affirmative, the process proceeds to step 240. In this case, the duty ratio Drfr is set to 0%, and if a negative determination is made, the routine proceeds to step 265. If a sensor for detecting the pressure in the master cylinder is provided, it is determined whether or not the braking operation by the driver is being performed. May be performed.

In step 250, it is determined whether or not a time T2 (a positive constant larger than T1) has elapsed from the time when the final target slip ratio Rsfr becomes zero. When an affirmative determination is made in this step, the flag F1 is reset to 0 in step 300, and when a negative determination is made, the routine proceeds to step 260. In step 260, it is determined whether or not the driver has performed a braking operation. If a negative determination is made, in step 265, the duty ratio Drfr is set to 100%.
Is set, and when an affirmative determination is made, step 2
At 70, the duty ratio Drfr is set to 50%, and thereafter, at step 280, the flag F1 is set to 1.

Steps 310 to 400 are executed for the left front wheel in the same manner as steps 210 to 300, except that the front right wheel is replaced by the front left wheel and the flag F1 is replaced by the flag F2.

In steps 410 to 500, the right front wheel is replaced by the right rear wheel, the flag F1 is replaced by the flag F4, and in step 470, the duty ratio Drfr is 5%.
Steps 210 to 30 except that
This is executed for the right rear wheel in the same manner as 0. Step 4
If a positive determination is made in step 50, step 49
It is determined whether or not a time T3 (a positive constant greater than T2) has elapsed from the time when the final target slip ratio Rsrr has become 0 at 0, and if a positive determination has been made at this step, The process proceeds to step 500, and if a negative determination is made, the process proceeds to step 465.

Steps 510 to 600 are executed for the left rear wheel in the same manner as steps 410 to 500, except that the right rear wheel is replaced with the left rear wheel and the flag F4 is replaced with the flag F5. In step 610, it is determined whether or not the flags F4 and F5 are 0.
When an affirmative determination is made, the flag F3 is reset to 0 in step 620, and when a negative determination is made, the flag F3 is set to 1 in step 630.

As understood from the above description, in this flag setting routine, the duty ratio is set for a predetermined time from the time when the final target slip ratio Rsi becomes 0, that is, the time when the behavior control of each wheel is completed. Dri is set to the value shown in Table 1 below (unit is%). Flags F1 and F2
, F3, respectively, when any one of the right front wheel, the left front wheel, and the left and right rear wheels is under the behavior control (Rsi is not 0) and is under the behavior control end processing according to the flowcharts shown in FIGS. Set to 1.

[0065]

[Table 1] Elapsed time = 0 to T1 Elapsed time = T1 to T2 Elapsed time = T2 to T3 Dri braking non-braking braking non-braking (no braking judgment) Drfr 0 100 50 100 ----- Drfl 0 100 50 100 --- Drrr 0 100 5 100 100 Drrl 0 100 5 100 100

Next, a valve control routine at the end of the behavior control in this embodiment will be described with reference to the flowchart shown in FIG. The control by this routine is also executed by interruption every predetermined time.

At step 710, it is determined whether or not the flag F is 1, and when a positive determination is made, at step 720, the switching valve 44 is switched to the ON position (second position). Is supplied, the accumulator pressure is supplied.
The regulator pressure is supplied by switching the switching valve 44 to the off position (the first position) in the step (1).

In step 740, the flag F1 is set to 1
Is determined, and when an affirmative determination is made, the control valve 50FR is switched to the ON position (the second position) in step 750, whereby the communication between the wheel cylinder and the master cylinder is cut off. When a negative determination is made, the control valve 50FR is determined in step 760.
Is switched to the off position (first position), whereby the wheel cylinder and the master cylinder are connected to each other.

In step 770, the flag F2 is set to 1
Is determined, and if a positive determination is made, the control valve 50FL is switched to the ON position (second position) in step 780, and if a negative determination is made, the process proceeds to step 790. Then, the control valve 50FL is switched to the off position (first position).

In step 800, the flag F3 is set to 1
The control valve 28 is switched to the ON position (the second position) in step 810 when an affirmative determination is made, and in a step 820 when a negative determination is made. Then, the control valve 28 is switched to the off position (first position).

In step 830, flags F and F1
, F2 and F3 are all 1 or not. If a negative determination is made, the on-off valves of the respective wheels are driven according to the duty ratio Dri in step 840, and an affirmative determination is made. Since the control of the braking force is not required when it is performed, the opening and closing valves of each wheel are controlled to the first positions shown in FIG. 1 in step 850.

The drive control of the on-off valve in accordance with the duty ratio Dri is, for example, Drfr
Is a positive value, pressure increase control is performed.
With the 6FR closed, the on-off valve 54FR is opened and closed according to the duty ratio Drfr. When the duty ratio Drfr is a negative value, pressure reduction control is performed.
With the FR closed, the on-off valve 56FR has a duty ratio D
rfr and the holding control is performed when the duty ratio Drfr is 0, so that the on-off valves 54FR and 56FR
Are maintained in the valve closed state.

Thus, according to this embodiment, when the turning behavior of the vehicle is in a stable state, an affirmative determination is made in step 130, and the flag F is reset to 0 in step 140. Returning to step 10, the behavior control in steps 160 to 190 is not executed in this case, whereby the braking pressure of each wheel is controlled in accordance with the amount of depression of the brake pedal 12 by the driver.

When the turning behavior of the vehicle is in an unstable state, a negative determination is made in step 130, and the flag F is set to 1 in step 150. Target wheel speed V
wti is calculated, and in steps 170 to 190, the braking force is controlled so that the wheel speed of each wheel becomes the target wheel speed Vwti, whereby the turning behavior of the vehicle is stabilized.

In other words, the spin state amount is calculated based on the slip angle β of the vehicle body and the like, and the drift-out state amount is calculated based on the actual yaw rate γ and the like, and both the spin state amount and the drift-out state amount are calculated. Based on this, the braking force of each wheel is controlled, thereby reducing their unstable behavior in both the spin state and the drift-out state.

When the behavior of the vehicle becomes stable and the final target slip ratios Rsi of all wheels become zero and the behavior control ends, the behavior control end processing is performed according to the flowcharts shown in FIGS. Is performed. This behavior control termination processing is performed for the front wheel for the time T2, but is continued for the rear wheel after the time T2 elapses until the time T3 elapses.

In particular, when the vehicle is only in the spin state, or when the vehicle is in the spin state and also in the drift-out state (when the vehicle is traveling on a trajectory outside the target turning trajectory but the slip angle of the vehicle body is large). The target slip ratios SPi of the outer front wheels and the left and right rear wheels become a certain value, and when the behavior of the vehicle becomes stable, the target slip ratios of these wheels become zero. Therefore, when the control for suppressing the spin state or the control for suppressing both the spin state and the drift-out state ends, the front wheel behavior control end processing ends at the time when the time T2 elapses, and the wheel cylinder of the front wheel ends. 48FR and 48FL and the first pressurizing chamber 108 of the master cylinder 14 are connected to each other, and after a lapse of time T3, the rear wheel behavior control ending process ends.
The wheel cylinders 64RR and 64RL of the left and right rear wheels and the second pressurizing chamber 110 of the master cylinder 14 are connected for communication.

Therefore, when the wheel cylinders of the left and right front wheels and the first pressurizing chamber of the master cylinder are connected with each other,
Since the second pressurizing chamber 110 of the master cylinder is in a state of being disconnected from the wheel cylinders of the left and right rear wheels and is in a hydraulically locked state, the first separation limit regulating member 11
8 exerts excessive stress on the second pressurizing piston 106
Does not move suddenly, thereby improving the reliability of the master cylinder.

When the wheel cylinders of the left and right rear wheels and the second pressurizing chamber 110 of the master cylinder are connected for communication after the elapse of the time T3, the behavior control end processing is performed in the process up to that time. Since the residual pressure in the wheel cylinders of the left and right rear wheels has been sufficiently reduced since the operation has been performed for a sufficiently long time, even if the residual pressure flows into the second pressurizing chamber, the second separation limit regulating member 142 is excessively large. The second pressurizing piston 106 is not suddenly driven due to a large stress.

Further, when the vehicle is only in the drift-out state, the target slip ratios SPfr and SPrl of the left and right rear wheels are set.
Only when the behavior control ends, the left and right rear wheel cylinders 66RR and 66RL and the master cylinder 1
4 is connected to the second pressurizing chamber 110, but also in this case, the left and right rear wheel behavior control end processing is performed for a sufficiently long time, and the residual pressure in the wheel cylinder is low. Even if the first pressurizing chamber 108 is not hydraulically locked, the residual pressure in the wheel cylinders of the left and right rear wheels will be reduced to the first pressurizing chamber 1.
No excessive stress is applied to the second separation limit regulating member 142 when flowing into the flow passage 08, and the second pressurizing piston 106 is not suddenly moved.

Also in this case, if necessary, the wheel cylinders of the left and right rear wheels and the second pressurizing chamber 11 of the master cylinder are used.
When the control valves 50FR and 50FL for the left and right front wheels are switched to the second position when the communication between the first and second front wheels is performed, the first pressurizing chamber 108 is disconnected from the wheel cylinders for the left and right front wheels. The pressurization chamber may be hydraulically locked.

Further, according to the illustrated embodiment, when the behavior of the vehicle becomes stable and the final target slip ratios Rsi of all the wheels become zero and the behavior control ends, the switching valve 44 is switched to the state shown in FIG. It is returned to the first position shown, whereby a regulator pressure (pressure corresponding to the master cylinder pressure) is introduced into the wheel cylinders of each wheel. In the conventional behavior control device, the regulator pressure or the master cylinder pressure is introduced into the wheel cylinders of each wheel at the same time as the termination of the behavior control, so that the braking operation is performed by the driver and the pedaling force on the brake pedal is high. When the master cylinder pressure is high, a relatively high hydraulic pressure is rapidly introduced into the wheel cylinders, and the high master cylinder pressure is rapidly supplied to the wheel cylinders simultaneously with the switching of the pressure source. There is a possibility that the behavior of the vehicle will be disturbed due to the rise. Therefore, the hunting of the behavior control may occur in which the behavior control ends, the behavior of the vehicle is disturbed, the behavior control is restarted, and the behavior control ends.

According to the illustrated embodiment, at the end of the behavior control, it is determined whether or not the braking operation by the driver has been performed for a predetermined time. The duty ratio Dri of the opening / closing valve 54FR on the side is reduced, thereby preventing a sudden change in the braking force of each wheel. That is, as shown in Table 1 above, when the final target slip ratio Rsi becomes zero, the duty ratio Dri is set to 100% during non-braking, so that the residual pressure of the wheel cylinder is quickly increased. It is released, but 0% when the elapsed time (elapsed time from when the final target slip ratio Rsi becomes 0) is 0 to T1 during braking.
(Hold), and when the elapsed time is between T1 and T2, the front wheel is set to 50% and the rear wheel is set to 5%, whereby the pressure in the wheel cylinder of each wheel is gradually controlled to the regulator pressure (master cylinder pressure). By doing so, a sudden change in the braking force is reliably prevented.

In this case, the reason why the duty ratios Drrr and Drrl of the rear wheels are set to a value smaller than that of the front wheels is that the influence on the disturbance of the behavior of the vehicle caused by the sudden change of the braking force is greater than that of the rear wheels. Is higher.

In the above, the present invention has been described in detail with respect to a specific embodiment. However, the present invention is not limited to the above embodiment, and various other embodiments are included within the scope of the present invention. It will be clear to those skilled in the art that is possible.

For example, in the above-described embodiment, the communication between the second pressure chamber 110 and the wheel cylinder of the rear wheel is delayed with respect to the communication between the first pressure chamber 108 and the wheel cylinder of the front wheel. However, the first pressurizing chamber 108
And the front wheel cylinder communicates with the second pressure chamber 11.
It may be delayed for communication between 0 and the wheel cylinder of the rear wheel.

In the above embodiment, the braking force of each wheel is controlled by the wheel speed feedback. However, the braking force of each wheel is controlled by the pressure feedback on the pressure in the wheel cylinder. May be done.

In the above embodiment, the drift-out state is determined based on the drift-out state quantity calculated based on the yaw rate deviation. However, the drift-out state is determined based on the actual yaw rate or the yaw rate deviation. The reference steering angle may be determined from the lateral acceleration or the like, and the determination may be made based on a deviation between the reference steering angle and the actual steering angle.

[0089]

As is apparent from the above description, according to the present invention, when the control means switches the switching valve from the second state to the first state, the first pressurizing chamber and the wheel cylinder are switched. And one of the communication between the second pressurizing chamber and the wheel cylinder is delayed with respect to the other, so that the communication between the one pressurizing chamber and the wheel cylinder is performed when the other pressurizing chamber is communicated with the wheel cylinder. Is shut off and the free piston is hydraulically locked by one pressurizing chamber, so even if the residual pressure in the wheel cylinder flows back to the other pressurizing chamber of the master cylinder, It is possible to reliably prevent a large force from acting on the connecting means connected to the free piston or to suddenly move the free piston, thereby deteriorating the durability of the connecting means and reducing the reliability of the master cylinder. It can be a reduction in reliably prevented.

[Brief description of the 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 illustrating a first half of a behavior control routine according to the embodiment;

FIG. 3 is a flowchart illustrating a second half of a behavior control routine according to the embodiment.

FIG. 4 is a flowchart illustrating a first half of a behavior control end processing routine according to the embodiment;

FIG. 5 is a flowchart illustrating a second half of a behavior control end processing routine according to the embodiment;

FIG. 6 is a flowchart showing a valve control routine at the end of behavior control in the embodiment.

FIG. 7 is a graph showing a relationship between a spin state amount SS and a slip ratio target value Rssfo of a turning outer front wheel.

FIG. 8 is a graph showing a relationship between a drift-out state quantity DS and a slip rate target value Rsall of the entire vehicle.

FIG. 9 shows a target slip amount SPi and a duty ratio D of each wheel.
6 is a graph showing the relationship between ri.

FIG. 10 is an enlarged partial sectional view showing the master cylinder shown in FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Braking device 14 ... Master cylinder 16 ... Hydro booster 20, 22, 32, 34 ... Brake hydraulic pressure control device 28, 50FL, 50FR ... Control valve 44 ... Switching valve 44FL, 44FR, 64RL, 64RR ... Wheel cylinder 70 ... Electric type Control device 104: first pressurizing piston 106: second pressurizing piston 108 ... first pressurizing chamber 110 ... second pressurizing chamber 118 ... first separation limit regulating member 142 ... second separation limit Control member

Continuation of the front page (56) References JP-A-7-9973 (JP, A) JP-A-1-119461 (JP, A) JP-A-7-132815 (JP, A) JP-A-6-24304 (JP) , A) (58) Field surveyed (Int. Cl. ⁷ , DB name) B60T ^7/ 12-8/96

Claims (1)

(57) [Claims] 1. A master cylinder having first and second pressurizing chambers separated by a free piston, and a passage means for connecting and connecting the pressurizing chamber of the master cylinder and a wheel cylinder of each wheel. A switching valve provided in the passage means, wherein a first state in which communication between the master cylinder and the wheel cylinder is allowed and communication between the pressure source generating a predetermined high pressure and the wheel cylinder is interrupted, A switching valve that shuts off communication between the master cylinder and the wheel cylinder and switches to a second state in which the pressure source and the wheel cylinder are connected for communication, and the switching valve according to a running state of the vehicle. And a control means for switching to the first or second state, wherein the control means switches the switching valve from the second state to the first state. A means for delaying one of the communication between the first pressurizing chamber and the wheel cylinder and the communication between the second pressurizing chamber and the wheel cylinder with respect to the other. Braking force control device for a vehicle.