JPH1148953A - Braking force controller of vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent pressure within a wheel cylinder from temporarily being lower than master cylinder pressure by connecting a wheel cylinder and a master cylinder after a brake booster and the wheel cylinder of non-controlled object wheel on the side of a front wheel. SOLUTION: When a drift out suppression control is started during a brake assist control, brake pressure of left and right front wheels is surely prevented from temporarily and remarkably lowering and deceleration of a vehicle is surely prevented from temporarily and remarkably lowering due to this lowering, just after a transition from the brake assist control to a drift out suppression control is performed because wheel cylinders of the left and right front wheels are connected with a hydrobooster 16 for prescribed time in a state that pressure reducing valves of the left and right front wheels to be non-controlled wheels of a behavior control are closed. When an emergency brake operation is performed by a driver under the circumstances in which the behavior control of the vehicle is executed, the brake assist control is not executed because an affirmative discrimination is performed.

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 master cylinder,
The present invention relates to a braking force control device that controls a wheel cylinder pressure using a brake booster and a high pressure source as a hydraulic pressure source.

[0002]

2. Description of the Related Art In a vehicle such as an automobile, a normal control for controlling the pressure in a wheel cylinder using a master cylinder as a hydraulic pressure source, and a wheel using a high pressure source as a hydraulic pressure source by interrupting communication between the master cylinder and the wheel cylinder. Brake assist control, which controls the pressure in the cylinder, and the behavior of the vehicle, by interrupting the communication between the master cylinder and the wheel cylinder of the wheel to be controlled and controlling the pressure in the wheel cylinder of the wheel to be controlled using the high pressure source as the hydraulic pressure source 2. Description of the Related Art A braking force control device that performs stabilizing behavior control has been conventionally known.

As one of such braking force control devices, for example, Japanese Patent Application No. Hei 8-10954 filed by the applicant of the present invention.
As described in the specification 8 and the drawings, when the behavior control is started during the brake assist control, the working fluid in the wheel cylinder of the wheel not controlled by the behavior control is released to the reservoir, and A braking force control device has been proposed in which the brake assist control is terminated and the control is shifted to the behavior control by connecting the wheel cylinder and the master cylinder after the pressure is reduced.

According to the braking force control device configured as described above, when the behavior control is started during the brake assist control, the pressure in the wheel cylinder of the wheel not controlled by the behavior control is reliably reduced. In addition, when shifting from the brake assist control to the behavior control, it is possible to reliably prevent the high-pressure working fluid from flowing back from the wheel cylinder of the non-control target wheel to the master cylinder.

[0005]

However, in the braking force control device according to the above-mentioned application, the behavior control started during the brake assist control is performed, for example, to decelerate the vehicle and to apply the yaw moment in the turning assist direction to the vehicle. In the mode in which the left and right rear wheels are braked and at least one of the left and right front wheels is not braked to give the brake control, the brake assist control is terminated and the process is shifted to the behavior control. Is temporarily reduced to a pressure lower than the master cylinder pressure, so that the deceleration of the vehicle is temporarily greatly reduced, and the occupant of the vehicle has a problem that the driver feels strange.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems in the conventional braking force control device for performing the brake assist control and the behavior control. In the mode in which the wheels are braked and at least one of the left and right front wheels is not braked, the pressure in the wheel cylinder of the front wheel-side non-control target wheel is temporarily reduced when the brake assist control is ended and the process is shifted to the behavior control. It is to prevent the vehicle deceleration from temporarily dropping significantly by preventing the pressure from dropping to a pressure lower than the master cylinder pressure.

[0007]

According to the present invention, the main object as described above is the structure of the above-mentioned claim 1, that is, the normal control for controlling the wheel cylinder pressure using the master cylinder as a hydraulic pressure source, A brake assist control that cuts off the communication between the master cylinder and the wheel cylinder and controls the pressure in the wheel cylinder using a high pressure source as a hydraulic pressure source, and a high pressure source that cuts off the communication between the master cylinder and the wheel cylinder of the wheel to be controlled. When the behavior control is started during the brake assist control as a vehicle braking force control device that performs a behavior control that stabilizes the behavior of the vehicle by controlling the pressure in the wheel cylinder of the control target wheel as a hydraulic pressure source When the behavior control is a mode in which the left and right rear wheels are braked and at least one of the left and right front wheels is not braked, After disconnecting the communication between the pressure source and the wheel cylinder of the front wheel side non-control target wheel and connecting the brake booster to the front wheel side non-control target wheel cylinder, the wheel cylinder is connected to the master cylinder. This is achieved by a vehicle braking force control device having the above-described configuration.

According to the first aspect of the invention, even when the behavior control is started during the brake assist control, the behavior control brakes the left and right rear wheels and does not brake at least one of the left and right front wheels. In the mode, after the communication between the high-pressure source and the wheel cylinder of the front wheel side non-control target wheel is interrupted for a predetermined time and the brake booster is connected to the wheel cylinder of the front wheel side non-control target wheel, the wheel cylinder And the master cylinder are connected.

Therefore, when the behavior control is started during the brake assist control, regardless of the mode of the behavior control, the working fluid in the wheel cylinder of the wheel to be controlled is released to the reservoir and Since the amount of reduction in the pressure in the wheel cylinder of the non-control target wheel on the front wheel side is reduced as compared with the case of connecting the wheel cylinder and the master cylinder after reducing the pressure in the cylinder,
The pressure in the wheel cylinder of the uncontrolled wheel on the front wheel side is prevented from temporarily dropping to a pressure lower than the master cylinder pressure, thereby reliably preventing the deceleration of the vehicle from temporarily dropping significantly. You.

[0010]

According to a preferred aspect of the present invention, in the configuration according to the first aspect, when the behavior control is started during the brake assist control, the behavior control is performed in the right and left directions. When the mode is not the mode in which the wheels are braked and at least one of the left and right front wheels is not braked, the working fluid in the wheel cylinder of the uncontrolled wheel is released to the reservoir to reduce the pressure in the wheel cylinder, and then the wheel cylinder and the master cylinder Is connected, the brake assist control is terminated and the operation is shifted to the behavior control (preferred mode 1).

According to another preferred embodiment of the present invention, when the vehicle is in the drift-out state, the left and right rear wheels are braked as the behavior control and the left and right front wheels are not braked. In this way, the vehicle is decelerated and drift-out suppression control that gives the vehicle a yaw moment in the turning assist direction is performed. When the drift-out suppression control is started during the brake assist control, the high pressure source and the left and right front wheel cylinders are started for a predetermined time. After connecting the brake booster to the left and right front wheel cylinders, the left and right front wheel cylinders are connected to the master cylinder (preferred embodiment 2).

According to another preferred embodiment of the present invention, in the configuration of the preferred embodiment 1, when the vehicle is in a spin state, at least the turning outer front wheel is braked and at least the turning inner front and rear wheels are controlled as behavior control. When the spin suppression control is started by applying the yaw moment in the spin suppression direction to the vehicle by not braking the vehicle, and the spin suppression control is started during the brake assist control, the working fluid in the wheel cylinder of the wheel not controlled by the spin suppression control Is released to the reservoir to reduce the pressure in the wheel cylinder, and then the wheel cylinder and the master cylinder are connected to terminate the brake assist control and shift to the spin suppression control (preferred mode 3).

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the accompanying 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. In FIG. 1, the solenoids of the electromagnetically driven valves are not shown.

In FIG. 1, reference numeral 10 denotes a hydraulic braking device. The braking device 10 includes a master cylinder 14 for pumping brake oil in response to a depression operation of a brake pedal 12 by a driver, and a master cylinder. And a hydraulic booster 16 for increasing the brake oil to a pressure (regulator pressure) corresponding to the oil pressure inside. The master cylinder 14 has a brake hydraulic control conduit 18 for the front wheels.
Is connected to the other end of the brake hydraulic control conduit 18, a brake hydraulic control conduit 20 FL for the left front wheel and a brake hydraulic control conduit 20 FR for the right front wheel. In the middle of the conduits 20FL and 20FR, three-port two-position switching electromagnetic control valves 22FL and 22FR are provided, respectively, and the other ends of these conduits control the braking force of the left front wheel and the right front wheel, respectively. Wheel cylinder 24FL and 24FR
Is connected.

The control valve 2 is provided in the middle of the hydro booster 16.
6 is connected to one end of a regulator pressure supply conduit 28 having a brake hydraulic control conduit 30RL for the left rear wheel and a brake hydraulic control conduit 3 for the right rear wheel.
0RR is connected. The other ends of the conduits 30RL and 30RR are connected to wheel cylinders 24RL and 24RR that control the braking force of the left rear wheel and the right rear wheel, respectively. A non-return bypass conduit 32 is connected to the conduit 28 near the control valve 26 to allow only oil flow from the hydro booster 16 to the conduits 30RL and 30RR.

One end of a high-pressure conduit 36 having a control valve 34 in the middle thereof is connected to the regulator pressure supply conduit 28, and the other end of the high-pressure conduit 36 is connected to an oil pump 38 driven by a motor (not shown). It is connected to the.
In the illustrated embodiment, the control valve 26 is a normally-open electromagnetic on-off valve, and the control valve 34 is a normally-closed electromagnetic on-off valve. When the control valve 26 is opened and closed, the control valves 34 are closed and opened substantially simultaneously.

The oil pump 38 pumps up the brake oil stored in the reservoir 40 and supplies it to the high-pressure conduit 36 as high-pressure oil. The high pressure conduit 36 is a relief conduit 42
And the relief conduit 42 has a relief valve (not shown) that opens when the pressure in the hydrobooster 16 becomes excessive. The high-pressure conduit 36 is connected to the reservoir 40 by a relief conduit 46 having a relief valve 44 in the middle. Further, an accumulator 48 for accumulating high-pressure oil discharged from an oil pump 38 as accumulator pressure is connected to the high-pressure conduit 36.

In the middle of the conduits 20FL and 20FR, normally open solenoid valves (pressure increasing valves) 50FL and 50FR are provided, respectively. Return conduit 5 connected to reservoir 40
A connection conduit 54FL for the front left wheel and a connection conduit 54FR for the front right wheel are connected between the connection pipe 2 and the conduits 20FL and 20FR, respectively. In the middle of the connecting conduits 54FL and 54FR, normally closed solenoid on-off valves (pressure reducing valves) 56FL and 56FR are provided, respectively. The conduits 20FL and 20FR near the solenoid on-off valves 50FL and 50FR have wheel cylinders 2 respectively.
Non-return bypass conduits 58FL and 58 allowing only oil flow from 4FL and 24FR toward master cylinder 14
FR is connected.

Similarly, solenoid-operated on-off valves (pressure increasing valves) 50RL and 50RR are provided in the middle of the conduits 30RL and 30RR. A connection pipe 54RL for the left rear wheel and a connection pipe 54RR for the right rear wheel are connected between the return pipe 52 and the pipes 30RL and 30RR, respectively. Connecting conduit 54RL
The normally closed electromagnetic on-off valves (pressure reducing valves) 56RL and 56RR are provided in the middle of the RRs. Non-return bypass conduits 58RL and 58RR that allow only oil flow from the wheel cylinders 24RL and 24RR toward the hydro booster 16 are connected to the conduits 30RL and 30RR near the electromagnetic on-off valves 50RL and 50RR, respectively.

As shown in FIG. 1, control valves 22FL and 22FR are connected to brake hydraulic control conduits 20FL and 2FL, respectively.
A first position allowing the communication of 0FR, the communication between the brake oil pressure control conduits 20FL and 20FR and the conduit 36F,
The position is switched to a second position where the regulator pressure supply conduit 28 and the wheel cylinders 24FL and 24FR are connected to each other via 36FL and 36FR.

In particular, in the illustrated embodiment, the control valve 2
2FL and 22FR are set to the first position when the drive current is not supplied to the corresponding solenoid, in other words, normally, whereby the master cylinder pressure is supplied to the wheel cylinders 24FL and 24FR. Similarly, the control valves 26 and 34 are normally at the first position shown in FIG. 1, and the regulator pressure is supplied to the wheel cylinders 24RL and 24RR. Therefore, at normal times, the pressure in the wheel cylinder of each wheel, that is, the braking force,
Is increased or decreased according to the pedaling force of the vehicle.

When the control valves 22FL and 22FR are switched to the second position, the control valves 26 and 34 are at the first position, and the on-off valves of each wheel are at the positions shown in FIG. 24FL, 24FR, 24RL, 24RR
Is supplied with a regulator pressure. Therefore, also in this case, the braking force of each wheel is increased or decreased substantially according to the depression force of the brake pedal.

On the other hand, control valves 22FL, 22FR, 26,
34 is switched to the second position.
When in the position shown in FIG.
Since accumulator pressure is supplied to FL, 24FR, 24RL, and 24RR, the braking force of each wheel is increased or decreased by opening and closing the on-off valve of each wheel regardless of the depression force of the brake pedal.

Particularly, the pressure in the wheel cylinder is controlled by the on-off valve 5.
0FL, 50FR, 50RL, 50RR and open / close valve 56FL, 56
When FR, 56RL, 56RR are at the first position shown in FIG. 1, the pressure is increased (pressure increase mode), and the on-off valves 50FL, 50FL
When FR, 50RL, 50RR is switched to the second position and on-off valves 56FL, 56FR, 56RL, 56RR are in the first position shown in FIG. 1 (holding mode), on-off valves 50FL, 50FR, 50RL, 50RR and on-off valve 56F
When L, 56FR, 56RL, 56RR are switched to the second position, the pressure is reduced (pressure reduction mode).

Control valves 22FL, 22FR, 26, 34, on-off valves 50FL, 50FR, 50RL, 50RR and on-off valves 56FL,
The 56FR, 56RL, and 56RR are controlled by an electric control device 70 as described later in detail. Electric control device 7
Reference numeral 0 denotes a microcomputer 72 and a drive circuit 74. The microcomputer 72 is not shown in detail in FIG.
, A read only memory (ROM), a random access memory (RAM), and an input / output port device, which may be of a general configuration connected to each other by a bidirectional common bus.

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 provided substantially 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) Vwi (i = fl, f
r, rl, rr) and a signal indicating the depression stroke S of the brake pedal 12 from the stroke sensor 88 are 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 the longitudinal acceleration sensor 84 detects longitudinal acceleration with the acceleration direction of the vehicle as positive.

The ROM of the microcomputer 72 stores various control flows and maps as described later, and the CPU performs various calculations as described later based on the parameters detected by the various sensors described above. The turning behavior is determined, and when the vehicle is in the spin state or the drift-out state, the target slip ratio of each wheel for stabilizing the turning behavior is calculated, whereby the electric control device 70 calculates the braking force of each wheel. Control is performed based on the target slip ratio to stabilize the behavior.

When the driver's depressing speed of the brake pedal 12 is equal to or higher than a predetermined value, the electric control device 70 determines that emergency braking has been performed and the master cylinder 1
The brake assist (abbreviated as BA if necessary) for controlling the pressure in the wheel cylinder of each wheel by interrupting the communication between the wheel cylinder 4 and the wheel cylinder of each wheel and using the accumulator pressure as a hydraulic pressure source.

Further, when the vehicle is in a spin state during the brake assist control, the electric control device 70 applies a braking force to the turning outer front wheel to apply a yaw moment in the spin suppressing direction to the vehicle, thereby suppressing the spin. Along with
After depressurizing the wheel cylinders 24 of the wheels not controlled by the behavior control, that is, the wheels other than the turning outer front wheel for a predetermined time to depressurize the wheel cylinders 24 of those wheels, the wheel cylinders 24FL and 24FR of the left and right front wheels and the master cylinder 14 And connect.

On the other hand, when the vehicle drifts out during the brake assist control, the electric control device 70 applies a braking force to the left and right rear wheels to decelerate the vehicle and apply a yaw moment in the turning assist direction to the vehicle. To suppress drift-out and reduce the pressure of the left and right front wheels 5
6FL and 56FR are closed and the accumulator 48
The communication between the hydraulic booster 16 and the left and right front wheel cylinders 24FL, 24FR is cut off and the communication between the left and right front wheel cylinders 24FL, 24FR is cut off.

Next, a braking force control routine in the illustrated embodiment will be described with reference to a 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.

First, at step 10, the vehicle speed sensor 7
6, a signal indicating the vehicle speed V detected is read, and in step 20, it is determined whether or not the behavior control of the vehicle is necessary according to the routine shown in the flowchart of FIG. When it is determined that the behavior control is unnecessary, the process returns to step 10. When it is determined that the behavior control is necessary, step 40 is performed.
Proceed to.

In step 40, it is determined whether or not the brake assist control is being performed at the time when the determination in step 20 changes from the behavior control unnecessary to the behavior control necessary, and a negative determination is made. Sometimes step 15
If the determination is affirmative, the process proceeds to step 50. The brake assist control is executed according to a routine according to a flowchart shown in FIG.

In step 50, it is determined whether or not the required behavior control is drift-out suppression control.
When a negative determination is made, the process proceeds to step 110, and when an affirmative determination is made, the pressure reducing valves 56FL, 56FR of the left and right front wheels are closed in step 60, and the control valves 22FL, 22FR are turned on in step 70. The control is switched, the control valve 26 is opened, and the control valve 34 is closed, whereby the control source hydraulic pressure is set to the regulator pressure.

In step 80, the count value T1 of the timer is incremented by .DELTA.T (for example, a positive constant corresponding to the cycle time in the flowchart shown in FIG. 2), and in step 90, the count value T1 of the timer is incremented. It is determined whether or not the value is equal to or more than the reference value T1c (positive constant).
0, and when an affirmative determination is made, step 100 is executed.
At this time, the count value T1 of the timer is reset to 0 and the control valves 22FL and 22FR are turned off.

In step 110, the pressure increasing valve 50 of the non-controlled wheel for behavior control is closed and the pressure reducing valve 56 is opened. In step 120, the count value T2 of the timer is incremented by ΔT. In step 130, it is determined whether or not the count value T2 of the timer is equal to or greater than T2C (positive constant). If a negative determination is made, the process directly proceeds to step 150, and if a positive determination is made, At step 140, the count value T of the timer
2 is reset to 0, and the booster valve 5 for the uncontrolled wheel for behavior control
0 is opened, the pressure reducing valve 56 is closed, and the control valve 22FL or 22FR of the front wheel on the inside of turning is turned off.

In step 150, necessary behavior control, that is, spin suppression control or drift-out suppression control is executed in accordance with the behavior control routine according to the flowchart shown in FIG. 4, thereby stabilizing the unstable behavior of the vehicle. Be transformed into

In step 21 of the behavior required control determination routine according to the flowchart shown in FIG. 3, the deviation G between the lateral acceleration Gy and the product V * γ of the vehicle speed V and the yaw rate γ is determined.
The deviation of the lateral acceleration, ie, the side slip acceleration Vyd of the vehicle is calculated as y−V * γ, and the side slip acceleration Vyd is integrated to calculate the side slip speed Vy of the vehicle, and further, the longitudinal speed Vx of the vehicle (= vehicle speed V). The slip angle β of the vehicle body is calculated as the ratio Vy / Vx of the side slip speed Vy of the vehicle body to Vy.

In step 22, the spin amount SV is calculated as the linear sum K1 * β + K2 * Vyd of the slip angle β and the skid acceleration Vyd using K1 and K2 as positive constants, respectively. In step 23, 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 turns left and −SV when the vehicle turns right. When the calculation result is a negative value, the spin state amount is calculated as −SV. It is set to 0. 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 24, the target yaw rate γc is calculated according to the following equation (1) using Kh as a stability factor, H as a wheelbase, Rg as a steering gear ratio, T as a time constant, and s as Laplace. The reference yaw rate γt according to the following equation 2 as an operator
Is calculated. 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.

[0042]

Γ c = V * θ / (1 + Kh * V ² ) * H / Rg

Γt = γc / (1 + T * s)

In step 25, the drift value DV is calculated according to the following equation (3). The drift value DV may be calculated according to the following equation (4).

[0044]

Equation 3 DV = (γt−γ)

## EQU4 ## DV = H * (γt−γ) / V

In step 26, the turning direction of the vehicle is determined on the basis of the sign of the yaw rate γ, and the drift-out state amount DS is calculated as DV when the vehicle turns left, and as -DV when the vehicle turns right. When the result is a negative value, the drift-out state amount is set to zero.

In step 27, the spin state amount SS
The slip ratio target value Rssfo of the front wheel outside the turning is calculated from the map corresponding to the graph shown in FIG. 6 on the basis of the graph shown in FIG. A target slip ratio Rsall of the entire vehicle is calculated from the map.

In step 29, Ksri is defined as the distribution ratio of the inside wheel at the inside of the turn and the front wheel at the outside of the turn is calculated according to the following equation (5).
The target slip ratios Rsfo, Rsfi, Rsro, and Rsri of the turning inside front wheel, turning outside rear wheel, and turning inside rear wheel are calculated.

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

In step 30, the turning direction of the vehicle is determined based on the sign of the yaw rate γ, whereby the inner and outer turning wheels are specified, and the final target slip ratio 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

[0049]

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

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

In step 31, it is determined whether or not any final target slip ratio Rsi is positive (whether or not all Rsi are not 0), that is, whether or not behavior control is necessary. When the determination is made and the affirmative determination is made, the process proceeds to step 40, and when the negative determination is made, the process proceeds to step 10
Return to

In step 151 of the behavior control routine according to the flowchart shown in FIG. 4, the target wheel speed Vwti of the turning front wheel is calculated in accordance with the following equation 8 using the wheel speed of the inside front wheel as the reference wheel speed Vb. .

Vwti = Vb * (100-Rsi) / 100

In step 152, the target slip amount SPi of the wheel is calculated in accordance with the following equation 9 with Vwid being the wheel acceleration (differential value of Vwi) of the wheel and Ks being a positive constant coefficient. In Figure 8
Is calculated from the map corresponding to the graph shown in FIG.

SPi = Vwi-Vwti + Ks * (Vwid-Gx)

In step 154, the control valve 22FL,
22FR, 26, and 34 are switched to the second position and the accumulator pressure is introduced as the control source hydraulic pressure,
By outputting a control signal corresponding to the duty ratio Dri to the opening / closing valve of the corresponding wheel, supply / discharge of the accumulator pressure to / from the corresponding wheel cylinders 24FR to 24RL is controlled, thereby controlling the braking pressure of each wheel. You.

In this case, when the duty ratio Dri is 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 discharged to the return conduit 52, and the pressure in the wheel cylinder is reduced.

Next, the BA control routine in the illustrated embodiment will be described with reference to the flowchart shown in FIG. The control according to the flowchart shown in FIG. 5 is also started by closing an ignition switch (not shown), and is repeatedly executed at predetermined time intervals.

First, in step 210, it is determined whether or not the vehicle behavior control is being performed. If the determination is affirmative, the process proceeds to step 260. If the determination is negative, the process proceeds to step 220. And the stroke S of the brake pedal detected by the stroke sensor 88
Is read.

In step 230, for example, the stepping speed Vp of the brake pedal is calculated as a time differential value of the stroke S of the brake pedal, and whether or not the stepping speed Vp is higher than a reference value Vpc (positive constant) is determined. Is determined, and when an affirmative determination is made, step 27 is executed.
0, and when a negative determination is made, step 240
Proceed to.

In step 240, it is determined whether or not the flag F is 1, that is, whether or not the brake assist control is being performed. If a negative determination is made, steps 250 to 280 are executed. Step 21 without doing
0, and when an affirmative determination is made, step 250 is reached.
Proceed to.

In step 250, it is determined whether or not the brake assist control release condition such as the brake pedal depression speed Vp is less than a predetermined value or a stop lamp switch (not shown) is off. Is determined, and when a positive determination is made, step 26
At 0, the brake assist control is canceled and the flag F is reset to 0. When a negative determination is made, the brake assist control is executed at step 270, and the flag F is set to 1 at step 280. Is done.

Since the brake assist control in step 270 is well known in the art, a detailed description thereof will be omitted, but the brake assist control is performed, for example, using a pressure not shown in the drawing. A time differential value ΔPm of the master cylinder pressure Pm detected by the sensor is calculated, and the control valves 26 and 34 are in a state in which the control valves 22FL and 22FR are turned on, and the duty ratio corresponding to the time differential value ΔPm equal to or more than the reference value is obtained. The on / off control is performed in accordance with the ratio, whereby the pressure in each wheel cylinder is controlled so that the rate of increase in the pressure in the wheel cylinder of each wheel is greater than the rate of increase in the master cylinder pressure Pm.

Thus, according to this embodiment, when the turning behavior of the vehicle is in a stable state and the emergency braking operation is not being performed, a negative determination is made in step 31.
In steps 210, 230, and 240, a negative determination is made. Therefore, in this case, step 150 (151 to 151) is performed.
The behavior control according to 154) and the brake assist control at step 270 are not executed, whereby the braking pressure of each wheel is controlled according to the depression force on the brake pedal 12 by the driver.

When the driver performs an emergency brake operation in a situation where the turning behavior of the vehicle is stable, a negative determination is made in step 31 and the behavior control is not executed. A positive determination is made at 230, and a brake assist control is performed at step 270, whereby the vehicle is effectively decelerated.

On the other hand, when the turning behavior of the vehicle is in an unstable state but the driver has not performed the emergency braking operation, an affirmative determination is made in step 210, and the brake assist in step 270 is performed. No control is performed, but an affirmative determination is made in step 20 and a negative determination is made in step 40, whereby the behavior control is performed in step 150, thereby stabilizing the turning behavior of the vehicle. Is done.

That is, in steps 21 to 23, the spin state amount SS is calculated based on the slip angle β of the vehicle body and the like. In steps 24 to 26, the drift out state amount DS is calculated based on the actual yaw rate γ and the like. The braking force of each wheel is controlled on the basis of both the spin state amount and the drift-out state amount in steps 27 to 31 and steps 151 to 154, and thereby, in any of the spin state and the drift-out state Their unstable behavior is reduced.

For example, when the vehicle is in the spin state, a braking force is applied to the turning outer front wheel and the turning outer rear wheel to apply a yaw moment in the spin reducing direction to the vehicle, thereby reducing the spin state. When the vehicle is in a drift-out state, different braking forces are applied to the left and right rear wheels, thereby decelerating the vehicle and applying a yaw moment in the turning assist direction to the vehicle, thereby reducing the drift-out state. You.

If the vehicle is spinning during the brake assist control, an affirmative determination is made in step 210 and the brake assist control is canceled in step 260. An affirmative determination is made in steps 20 and 40, and a negative determination is made in step 50,
In steps 110-140, the pressure in the wheel cylinder of these wheels is rapidly reduced by closing the pressure-intensifying valves and opening the pressure-reducing valves of the non-controlled wheels of the T2c time behavior control. By executing the spin suppression control in the above, the spin state of the vehicle is reduced.

Further, if the vehicle drifts out during the brake assist control, also in this case, step 210 is executed.
In step 260, the brake assist control is released, and in steps 20 and 40, a positive determination is made. However, in this case, an affirmative determination is also made in step 50, and
In steps 100 to 100, the pressure reducing valves of the left and right front wheels are closed, the T1c time control valve 22 is maintained in the ON state, the control valve 26 is opened, and the control valve 34 is closed. Wheel cylinder is hydro booster 1
6 and the drift-out suppression control is executed in step 150 to reduce the drift-out state of the vehicle.

Therefore, as shown in FIG. 9, regardless of whether the behavior control is the spin suppression control or the drift-out suppression control, when the behavior control is started during the brake assist control, a predetermined value is obtained. In the conventional braking force control device in which the pressure increasing valve of the non-controlled wheel of the time behavior control is closed and the pressure reducing valve is opened, the non-controlled wheel is temporarily stopped immediately after the transition from the brake assist control to the behavior control. Is greatly reduced to the master cylinder pressure Pm or less, and the deceleration of the vehicle is temporarily greatly reduced.

On the other hand, according to the embodiment shown in FIG.
As shown in FIG. 0, when the drift-out suppression control is started during the brake assist control, the left and right front wheels, which are the non-control wheels of the behavior control, are closed for a predetermined period of time while the pressure reducing valves are closed. Since the wheel cylinders of the front wheels are connected to the hydro booster 16, the braking pressures of the left and right front wheels temporarily decrease significantly immediately after the shift from the brake assist control to the drift-out suppression control, and the deceleration of the vehicle due to this is reduced. Can be reliably prevented from temporarily dropping significantly.

When an emergency brake operation is performed by the driver in a situation where the behavior control of the vehicle is being executed, an affirmative determination is made in step 210.
No brake assist control is performed, so that the behavior control is not adversely affected by the brake assist control.

Although the present invention has been described in detail with reference to specific embodiments, the present invention is not limited to the above-described embodiments, and various other embodiments may be 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 spin state amount SS indicating the degree of spin of the vehicle and the drift state amount DS indicating the degree of drift out of the vehicle are calculated, and these state amounts are reduced. Although the target slip ratio of each wheel is calculated and the braking pressure is controlled so that the slip ratio of each wheel becomes the target slip ratio, the behavior of the vehicle is stabilized. The behavior control may be performed in any mode as long as it includes a mode in which at least the left and right rear wheels are braked and at least one of the left and right front wheels is not braked in order to stabilize the behavior of the vehicle.

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

[0074]

As is apparent from the above description, according to the present invention, even when the behavior control is started during the brake assist control, the behavior control is performed right and left as in the drift-out suppression control, for example. In the mode in which the wheels are braked and at least one of the left and right front wheels is not braked, the communication between the high-pressure source and the wheel cylinder of the uncontrolled wheel on the front wheel side is interrupted for a predetermined time, and the brake booster and the uncontrolled object on the front wheel side are disconnected. After the wheel cylinder of the wheel is connected, the connection of the wheel cylinder and the master cylinder reduces the amount of decrease in the pressure in the wheel cylinder of the wheel to be uncontrolled on the front wheel side. Prevents the pressure in the wheel cylinder of the target wheel from temporarily dropping to a pressure lower than the master cylinder pressure, thereby decelerating the vehicle There can be reliably prevented that the passenger of the vehicle is reliably prevented from being lowered temporarily increase may feel a sense of incongruity.

[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 braking force control routine according to the embodiment.

FIG. 3 is a flowchart illustrating a behavior required control determination routine according to the embodiment.

FIG. 4 is a flowchart illustrating a behavior control routine according to the embodiment.

FIG. 5 is a flowchart illustrating a BA (brake assist) control routine of the embodiment.

FIG. 6 is a graph showing a relationship between a spin state amount SS and a slip ratio target value Rssfo of a front wheel on the outside of turning;

FIG. 7 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. 8 shows a target slip amount SPi and a duty ratio D of each wheel.
6 is a graph showing the relationship between ri.

FIG. 9 is a time chart showing an operation when drift-out suppression control is started during brake assist control in a conventional braking force control device.

FIG. 10 is a time chart showing an operation when drift-out suppression control is started during brake assist control in the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Braking device 14 ... Master cylinder 16 ... Hydro booster 22FL, 22FR, 26, 34 ... Control valve 24FL, 24FR, 24RL, 24RR ... Wheel cylinder 38 ... Oil pump 48 ... Accumulator 70 ... Electric control device 86FL-86RR ... Wheel Speed sensor 88 ... Stroke sensor

Claims (1)

[Claims] 1. A normal control for controlling the pressure in a wheel cylinder using a master cylinder as a hydraulic pressure source, and controlling the pressure in the wheel cylinder using a high pressure source as a hydraulic pressure source by interrupting communication between the master cylinder and the wheel cylinder. Brake assist control and behavior control for stabilizing the behavior of the vehicle by interrupting the communication between the master cylinder and the wheel cylinder of the wheel to be controlled and controlling the pressure in the wheel cylinder of the wheel to be controlled using the high pressure source as the hydraulic pressure source When the behavior control is started during the brake assist control and the behavior control is in a mode in which the left and right rear wheels are braked and at least one of the left and right front wheels is not braked. Disconnecting the communication between the high-pressure source and the wheel cylinder of the uncontrolled wheel on the front wheel for a predetermined time, After connecting the data and the front-wheel side of the non-controlled wheel of the wheel cylinder, vehicle braking force control apparatus characterized by being configured to connect the with the wheel cylinder the master cylinder.