KR100751229B1 - Brake control system for a vehicle - Google Patents

Abstract

The present invention relates to a vehicle brake control system having an auxiliary braking force control function of a brake that automatically increases the braking force when the brake pedal is pressed quickly or deeply, thereby assisting the driver's brake operation. It relates to a vehicle brake control system for improving the feeling of pedaling.

According to the present invention, the control of the auxiliary braking force of the brake is performed on / off of the motor at a set current duty ratio to prevent the brake pressure of the master cylinder from escaping to the hydraulic pump inlet side to prevent the brake pedal from being turned off. At the end of the auxiliary braking force control, the pressure difference between the wheel cylinder and the master cylinder is reduced in advance, and the brake pressure of the reduced wheel cylinder is returned to the master cylinder, thereby lowering the impact on the brake pedal and improving the feeling of the brake pedal.

Description

Brake control system for a vehicle

1 is a brake hydraulic pressure circuit diagram of a conventional vehicle brake control system.

2 is a brake hydraulic pressure circuit diagram of a vehicle brake control system according to an exemplary embodiment of the present invention.

FIG. 3 is a control flowchart illustrating an initial pressure control pattern when controlling an auxiliary braking force of a brake in the brake hydraulic circuit diagram of FIG. 1.

FIG. 4 is a control flowchart illustrating an ending pressure control pattern when controlling auxiliary braking force of a brake in the brake hydraulic circuit diagram of FIG. 1.

* Description of the symbols for the main functions of the drawings *

MC: Master cylinder SC1, SC2: Normally open cut valve

SI1, SI2: Normally closed inlet valve PC1 ~ PC4: Normally open inlet valve

PC5 ~ PC8: Normally closed outlet valve PS: Pressure sensor

MF: Main Hydraulic Pressure Line MFc: Auxiliary Hydraulic Pressure Line

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle brake control system, and more particularly, to a vehicle brake control system having an auxiliary braking force control function of a brake that automatically increases a braking force when a brake pedal is pressed quickly or deeply to assist a driver in brake operation. .

In general, brake assist control of brakes is based on the anti-lock brake system (ABS) or traction control system when the driver fails to produce sufficient braking force in an emergency braking situation. It supplies auxiliary braking force by operating hydraulic modulator used in Ccontrol System (hereinafter referred to as TCS).

1 is a simplified brake hydraulic circuit diagram of a conventional vehicle brake control system. As shown in FIG. 1, a liquid pressure line MF is connected between the master cylinder MC and the wheel cylinder W, and a normal open to open and close the liquid pressure line MF on the liquid pressure line MF. The valve SC is installed. In addition, an auxiliary hydraulic line (MFC) is connected between the suction side of the hydraulic pump (HP) and the master cylinder (MC), and a normal closed valve (SIc) for opening and closing the auxiliary hydraulic line (MFc) on the auxiliary hydraulic line (MFc). ) Is installed. At this time, the normal open valve SC, the normal closed valve SI and the motor M for operating the hydraulic pump are driven by the electronic control unit ECU. Notation PC1 is an inlet valve, PC2 is an outlet valve, WS is a wheel speed sensor, CV1 and CV2 are check valves.

Referring to the operation of FIG. 1, when the starting condition of the auxiliary braking force control of the brake is satisfied, such as a driver operating the brake pedal rapidly, the electronic control unit ECU first generates the auxiliary braking force. By closing the normal closing valve (SI), the brake fluid with the brake pressure boosted in the master cylinder is introduced into the suction side of the hydraulic pump (HPC) through the auxiliary hydraulic pressure line (MFC) according to the brake pedal operation. Then, by driving the motor (M) to operate the hydraulic pump (HP) to provide an auxiliary braking force to the wheel cylinder (W) to assist the braking force.

However, when the normal closing valve is opened and the hydraulic pump is operated, the brake pressure of the master cylinder is sucked into the suction side of the hydraulic pump momentarily, which does not generate brake reaction force on the brake pedal, so the driver feels that the brake pedal is severely turned off. Will receive.

In addition, when the driver's brake pedal pedal speed falls below a certain speed or the brake pedal pressure rise rate is lower than a predetermined rate, the electronic brake unit (ECU) is satisfied. Opens the normal open valve (SC), closes the normal close valve (SI), stops the motor (M) and terminates the auxiliary braking force control of the brake.

However, when the brake pressure of the wheel cylinder is relatively higher than the brake pressure of the master cylinder and the normal open valve SC is opened to its original state at the end of the control of the auxiliary braking force of the brake, the pressure difference between the wheel cylinder and the master cylinder The pressure of the wheel cylinder suddenly flows into the master cylinder, hitting the brake pedal.

Due to the phenomenon at the beginning and end of the auxiliary braking force control of the brake, there is a problem that the driver feels a bad feeling of the brake pedal.

The present invention is to solve the above problems, an object of the present invention to provide a brake control system for a vehicle for improving the driver's pedaling feeling in the control of the auxiliary braking force of the brake.

The vehicle brake control system of the present invention for achieving the above object is a normal open-type cut valve for opening and closing each wheel cylinder, the master cylinder, the liquid pressure line connecting the master cylinder and the wheel cylinder, and the liquid pressure line And a hydraulic pump installed at the discharge side of the wheel cylinder to boost and discharge the brake pressure to the wheel cylinder, a motor for operating the hydraulic pump, an auxiliary hydraulic line connecting the suction side of the hydraulic pump to the master cylinder; And a normal closed inlet valve for opening and closing the auxiliary hydraulic line, an inlet valve and an outlet valve respectively provided at the inlet and outlet sides of the wheel cylinder, the normal open cut valve, the normal closed inlet valve, the inlet valve, and the outlet valve. And a control means for controlling the driving of the hydraulic pump, wherein the control means controls the braking force according to the driver's brake pedal operation. The normal open cut valve is closed and the normal closed inlet valve is opened so that the brake fluid of the master cylinder flows into the suction side of the hydraulic pump through the auxiliary hydraulic pressure line when controlling the braking force of the brake to assist the brake. Drive a motor for operating the hydraulic pump, characterized in that to maintain the reaction force of the brake pedal by making the off-time longer than the on time of the motor.

The control means closes the normal closed inlet valve, stops the motor, and opens the normal open cut valve at the end of the auxiliary braking force control of the brake, wherein the brake of the wheel cylinder is opened through the inlet valve and the outlet valve. After the pressure is reduced, the normal open cut valve is opened to reduce the impact applied to the brake pedal by the brake pressure of the wheel cylinder returned to the master cylinder.

In addition, in the control method of the vehicle brake system of the present invention, the normal open cut valve is closed so that the brake fluid of the master cylinder flows into the suction side of the hydraulic pump through the auxiliary hydraulic pressure line during the control of the auxiliary braking force of the brake. The normal closed inlet valve is opened, and the motor is driven with an off time longer than the on time of the motor so as to maintain the reaction force of the brake pedal, and when the auxiliary braking force control of the brake is finished, the normal closed inlet valve is The motor is stopped and the normal open cut valve is opened, and the inlet valve and the outlet valve are reduced to reduce the shock applied to the brake pedal by the brake pressure of the wheel cylinder returned to the master cylinder. Through the brake pressure of the wheel cylinder After the pressure is reduced, the normal-open cut valve is opened.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

2 is a brake hydraulic pressure circuit diagram of a vehicle brake control system according to an exemplary embodiment of the present invention. As shown in FIG. 2, the brake control system according to the embodiment of the present invention includes a master cylinder MC that generates brake pressure by the operation of the vacuum booster VB by the pressing of the brake pedal BP. .                     

This master cylinder (MC) has two chambers (MCP, MCS), the first chamber (MCP) and front wheel right wheel to control the brake hydraulic pressure transmitted from the master cylinder (MC) to the wheel cylinder (WFR, WRL) A normal open cut valve SC1 is provided in the liquid pressure line MF between the wheel cylinders WFR and WRL provided at the FR and the rear wheel left wheel RL, respectively. In addition, the normal open inlet valves PC1 and PC2 are provided in the hydraulic lines MFr and MFl between the normal open cut valve SC1 and the wheel cylinders WFR and WRL. These normal open inlet valves PC1 and PC2 are provided with check valves CV1 and CV2 in parallel, respectively. The brake fluid in the wheel cylinders WFR and WRL is returned to the master cylinder MC through the cut valves SC1 via the check valves CV1 and CV2.

Further, the brake fluid is provided with normal closed outlet valves PC5 and PC6 on the outlet side of the wheel cylinders WFR and WRL. The low pressure accumulator RS1 temporarily storing the brake fluid discharged from the wheel cylinders WFR, WRL and the brake fluid stored in the low pressure accumulator RS1 are forced to the outlet side of the normal closed outlet valves PC5 and PC6. A hydraulic pump HP1 and a motor M for reflux are provided.

Meanwhile, a normal open inlet valve SI1 is provided between the suction side of the hydraulic pump HP1 and the auxiliary hydraulic line MFc between the first chamber MCP of the master cylinder MC. The check valves CV5 and CV6 are respectively provided on two hydraulic lines branched by the auxiliary hydraulic line MFc. Accordingly, when the inlet valve SI1 is closed, the auxiliary hydraulic line MFc between the master cylinder MC and the hydraulic pump HP1 is blocked, and when the inlet valve SI1 is opened, the master cylinder MC and the hydraulic pump are closed. Auxiliary hydraulic pressure line MFc between HP1 is connected. At this time, the check valve CV5 prevents the brake fluid from flowing into the low pressure accumulator RS1.

On the other hand, in the hydraulic circuit of the front wheel left wheel FL and the rear wheel right wheel RR, the respective components are configured in the same way as the hydraulic circuit of the front wheel right wheel FR and the rear wheel left wheel RL. For reference, reference numerals DP1 and DP2 are high pressure accumulators.

Inlet valves PC1 to PC4 and outlet valves PC5 to PC8 in the cut valves SC1 and SC2, inlet valves SI1 and SI2, and respective wheel cylinders WFR, WRL, WFL, and WRR in FIG. The hydraulic pumps HP1 and HP2 are operated by an electronic control unit ECU which performs a control mode such as an ABS mode.

The wheel speed sensors WS1 to WS4 respectively provided on the front left and right wheels FL and FR and the rear left and right wheels RL and RR are electrically connected to the electronic control unit ECU to provide the detected rotation speed of the wheels. do.

In addition, the brake switch BS, which is turned on when the brake pedal BP is pressed and turned off when the brake is released, is electrically connected to the electronic control unit ECU. In addition, a pressure sensor PS for detecting the pressure of the master cylinder MC is electrically connected to the electronic control unit ECU.

FIG. 3 is a control flowchart illustrating an initial pressure control pattern when controlling an auxiliary braking force of a brake in the brake hydraulic circuit diagram of FIG. 1. 3, the value of the pressure sensor PS for detecting the pressure of the master cylinder MC is read (100). Then, the auxiliary braking force control start condition of the brake is determined based on the read pressure of the master cylinder MC (110). At this time, when the pressure value of the read master cylinder MC is larger than the preset pressure value and the pressure change rate is larger than the preset ratio, it is determined as the auxiliary braking force control start condition of the brake.

If it is determined in the operation mode 110 that the auxiliary braking force control start condition of the brake is opened, the inlet valves SI1 and SI2 are opened and the normal open cut valves SC1 and SC2 are closed (120). Thus, the auxiliary hydraulic pressure line MFc is opened so that the brake fluid of the master cylinder MC flows into the hydraulic pumps HP1 and HP2 through the auxiliary hydraulic pressure line.

In addition, the hydraulic pumps HP1 and HP2 are operated to drive the motor M to increase the brake hydraulic pressure of each wheel cylinder WFR, WRL, WFL, and WRR (130). For example, by controlling the motor M with a preset current duty ratio such as 3 scan time on / 7 scan time off, the brake pressure of the master cylinder is momentarily released to the suction side of the hydraulic pumps HP1 and HP2. Prevents exit and improves brake pedal feel.

Hereinafter, the control operation at the end of the auxiliary braking force control of the brake will be described.

FIG. 4 is a control flowchart illustrating an ending pressure control pattern when controlling auxiliary braking force of a brake in the brake hydraulic circuit diagram of FIG. 1. Referring to FIG. 4, the value of the pressure sensor PS for detecting the pressure of the master cylinder MC is read (200). Then, based on the read pressure value of the master cylinder MC, the brake braking force control termination condition of the brake is determined (210). At this time, when the pressure value of the read master cylinder MC is smaller than the preset pressure value and the pressure change rate is smaller than the preset ratio, it is determined as the termination condition of the auxiliary braking force control of the brake.

If it is determined in the operation mode 210 that the auxiliary braking force control termination condition of the brake is closed, the inlet valves SI1 and SI2 are closed and the motor M is stopped (220). At this time, the cut valves SC1 and SC2 are kept closed.

In order to reduce the brake pressure for a predetermined time (for example, 21 msec), the inlet valves P1 to P4 are closed for a predetermined time and the outlet valves P5 to P8 are opened (230 and 240).

After a predetermined time has elapsed, the inlet valves P1 to P4 are opened again so that the brake pressure of each wheel cylinder WFR, WRL, WFL, WRR can be returned to the master cylinder MC side, and the outlet valves P5 to P8. ) Closes (250).

Thereafter, the cut valves SC1 and SC2 are opened (260) to return the brake pressure of each wheel cylinder WFR, WRL, WFL, WRR to the master cylinder MC through the liquid pressure line MF. Accordingly, the pressure difference between the wheel cylinders WFR, WRL, WFL, WRR and the master cylinder MC is reduced in a predetermined value, thereby reducing the phenomenon of hitting the brake pedal by the pressure difference, thereby improving the feeling of the brake pedal. .

As described above in detail, the present invention controls the motor on / off at the initial control of the braking force of the brake at a set current duty ratio, thereby preventing the brake pressure of the master cylinder from temporarily escaping to the suction side of the hydraulic pump so that the brake pedal is turned off. It is effective to improve the brake pedal feeling by not lifting.

In addition, the present invention is to reduce the pressure difference between the wheel cylinder and the master cylinder in advance at the end of the auxiliary braking force control of the brake, and to reduce the shock applied to the brake pedal by reducing the brake pressure of the reduced wheel cylinder to the master cylinder to improve the feeling of the brake pedal It works.

Claims (3)

Each wheel cylinder, a master cylinder, a main liquid pressure line connecting the master cylinder and the wheel cylinder, a normal open cut valve for opening and closing the main liquid pressure line, and installed on the discharge side of the wheel cylinder to the wheel cylinder A hydraulic pump for boosting and discharging the brake pressure, a motor for operating the hydraulic pump, an auxiliary hydraulic line connecting the suction side of the hydraulic pump and a master cylinder, a normal closed inlet valve for opening and closing the auxiliary hydraulic line; And control means for driving and controlling the inlet and outlet valves provided at the inlet and outlet sides of the wheel cylinder, the normal open cut valve, the normal closed inlet valve, the inlet valve, the outlet valve, and the hydraulic pump, respectively. The control means closes the normal-open cut valve so that the brake fluid of the master cylinder flows into the suction side of the hydraulic pump through the auxiliary hydraulic pressure line when controlling the auxiliary braking force of the brake for assisting the braking force according to the driver's brake pedal operation. And the normal closed inlet valve is opened to drive a motor for operating the hydraulic pump, the off-time longer than the on time of the motor to maintain the reaction force of the brake pedal. . The method of claim 1, wherein the control means closes the normal closed inlet valve, stops the motor, and opens the normal open cut valve at the end of the auxiliary braking force control of the brake, through the inlet valve and the outlet valve. A brake control system for a vehicle, characterized in that to reduce the impact applied to the brake pedal by the brake pressure of the wheel cylinder returned to the master cylinder by reducing the brake pressure of the wheel cylinder and then opening the normally open cut valve. . The method of claim 1, wherein the normal open cut valve is closed so that the brake fluid of the master cylinder flows into the suction side of the hydraulic pump through the auxiliary hydraulic pressure line during the control of the auxiliary braking force of the brake, The normal closed inlet valve is opened, Driving the motor by making the off time longer than the on time of the motor to maintain the reaction force of the brake pedal, At the end of the auxiliary braking force control of the brake, the normal closed inlet valve is closed. Stop the motor, The normal open cut valve is opened, and the brake pressure of the wheel cylinder is reduced through the inlet valve and the outlet valve to reduce the shock applied to the brake pedal by the brake pressure of the wheel cylinder returned to the master cylinder. The control method of the brake system for a vehicle, characterized in that for opening the cut-off valve after opening.

Images