JP2016002776A - Vehicular braking system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent occurrence of a self-lock in a normal-open valve used as a shutoff valve in a by-wire brake.SOLUTION: A differential pressure detection part 201 detects differential pressure on the basis of detection values of first and second hydraulic pressure sensors Pp, Pm. A shutoff pressure setup part 202 sets shutoff pressure that is maximum differential pressure enabling a master cut valve 60a (60b) to close. A comparison part 203 compares between the differential pressure detected by the differential pressure detection part 201 and the shutoff pressure set by the shutoff pressure setup part 202. In a case where the state of the former being larger than the latter continuing for a given period of time or more in the comparison, a backup control part 204 performs backup control. That is, in the case where the state of the former being larger than the latter continues for the given period or more, an operation of a motor 72 is decreased than in the case of otherwise, thus stopping a power supply to cause the master cut valve 60a (60b) to open.

Description

  The present invention relates to a vehicle braking system.

  In a so-called by-wire brake used as a braking device for a vehicle, a shut-off valve called a master cut valve is provided in a communication path between a master cylinder and a slave cylinder that is an actuator that drives the by-wire brake. (See Patent Document 1 and the like). The master cut valve is a normally open valve that is energized and closed when the driver operates the brake pedal. When the driver steps on the brake pedal, the hydraulic pressure (hydraulic pressure) of the master cylinder is It is not transmitted downstream from the cut valve (slave cylinder side). Instead, the slave cylinder is driven on the basis of the stroke amount of the brake pedal detected by the brake pedal stroke sensor, and operates as a by-wire brake.

JP 2014-19243 A

However, the master cut valve is kept normally open by the biasing force of the built-in spring. If the hydraulic pressure on the slave cylinder side downstream of the master cut valve becomes larger than the urging force of the spring, self-lock, which is a phenomenon that the master cut valve cannot be opened, may occur. When the self-lock occurs, a residual pressure is generated on the downstream side (slave cylinder side) from the master cut valve, and problems such as deterioration of fuel consumption due to brake drag occur.
An object of the present invention is to appropriately operate a normally open valve used as a shut-off valve in a by-wire brake.

The present invention shuts off a path between the master cylinder and the actuator by closing a master cylinder, an actuator that communicates with the master cylinder and generates a hydraulic pressure, and closes the hydraulic pressure on the master cylinder side. A normally open valve that operates in the valve opening direction, a first hydraulic pressure sensor that detects a hydraulic pressure on the actuator side from the normally open valve, and a hydraulic pressure that is detected by at least the first hydraulic pressure sensor is the normally open valve. A first control unit that performs control to reduce the operation of the actuator and to open the normally open valve when the pressure is not less than a predetermined cutoff pressure that can maintain the closed state of It is provided with the braking system for vehicles characterized by comprising.
According to this invention, generation | occurrence | production of the inappropriate operation | movement of a normally open valve can be prevented beforehand.

In the present invention, a second hydraulic pressure sensor that detects a hydraulic pressure on the master cylinder side from the normally open valve is provided, and the first control unit detects the hydraulic pressure detected by the second hydraulic pressure sensor and the first hydraulic pressure sensor. When the differential pressure from the hydraulic pressure detected by the hydraulic pressure sensor becomes equal to or higher than a predetermined pressure, the operation of the actuator may be reduced and the normally open valve may be opened.
According to this invention, generation | occurrence | production of the inappropriate operation | movement of a normally open valve can be prevented beforehand.

In the present invention, a cutoff pressure setting unit that sets the cutoff pressure according to the drive voltage of the normally open valve may be provided.
According to the present invention, it is possible to prevent inadvertent control by the first control unit.

In the present invention, when the actuator is in the initial position and the normally open valve is in a non-energized state, the hydraulic pressure detected by the first hydraulic pressure sensor is the open pressure of the normally open valve. When this is the case, a second control unit may be provided that performs a control to reduce the operation of the actuator and to open the normally open valve as compared to when it is not.
According to the present invention, it is possible to eliminate the occurrence of inappropriate operation of the normally open valve.

  According to the present invention, it is possible to prevent an inappropriate operation from occurring in a normally open valve used as a shut-off valve in a by-wire brake.

It is a lineblock diagram showing the outline of the brake system for vehicles concerning one embodiment of the present invention. It is explanatory drawing which shows schematic structure of the master cut valve of the braking system for vehicles concerning one Embodiment of this invention. It is a block diagram which shows the electrical connection of ECU of the braking system for vehicles concerning one Embodiment of this invention.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
[Schematic configuration of vehicle braking system 10]
FIG. 1 is a configuration diagram illustrating an outline of a vehicle braking system 10 according to the present embodiment.
The vehicle braking system 10 is a device for generating a friction braking force of the vehicle. The vehicular braking system 10 is communicated with an input device 14 including a master cylinder 34 that converts a pedal force input by a driver by operating a brake pedal 12 into a hydraulic pressure (hydraulic pressure) of the brake fluid, and the master cylinder. The slave cylinder device 16 serving as an actuator for driving the by-wire brake by generating the brake fluid pressure in accordance with the brake fluid pressure generated at 34 or independently of the brake fluid pressure, and the vehicle behavior stabilizing device (VSA (registered trademark) device or the like) 18 and disc brake mechanisms 30a to 30d. The slave cylinder device 16 includes first and second slave pistons 77a and 77b that receive the driving force of the motor 72 and generate brake fluid pressure.

The pipes 22a to 22f are provided with brake fluid pressure sensors Pm, Pp, and Ph that detect the brake fluid pressure of each part. The VSA device 18 also includes a brake fluid pressurizing pump 73.
The slave cylinder device 16 (via the VSA device 18) is provided on the left rear wheel, and a wheel cylinder 32FR that generates a friction braking force by hydraulic pressure by a disc brake mechanism 30a provided on the right front wheel of the vehicle (not shown). A wheel cylinder 32RL for generating friction braking force by hydraulic pressure on the disc brake mechanism 30b, a wheel cylinder 32RR for generating friction braking force by hydraulic pressure on the disc brake mechanism 30c provided on the right rear wheel, and a left front wheel. The disc brake mechanism 30d is connected to a wheel cylinder 32FL that generates a friction braking force by hydraulic pressure.

[Basic operation of vehicle braking system 10]
Next, the basic operation of the vehicle braking system 10 will be described.
In the vehicle braking system 10, when the driver steps on the brake pedal 12 during normal operation of a control system (such as ECU 200 described later) that controls the slave cylinder device 16 and the by-wire, a so-called by-wire type brake is applied. The system becomes active. Specifically, in the vehicle braking system 10 during normal operation, when the driver steps on the brake pedal 12 (detected by a brake pedal stroke sensor (not shown)), the first cutoff valve 60a and the second cutoff valve respectively called master cut valves are detected. The slave cylinder device 16 drives the motor 72 while the shutoff valve 60b shuts off the communication between the master cylinder 34 and the disc brake mechanisms 30a to 30d (wheel cylinders 32FR, 32RL, 32RR, 32FL) that brake each wheel. The disc brake mechanisms 30a to 30d are operated using the brake hydraulic pressure generated by the above to brake each wheel.

  During normal operation, the master cut valve (first shutoff valve) 60a and the master cut valve (second shutoff valve) 60b are shut off, while the third shutoff valve 62 is opened, and the brake fluid is supplied to the master cylinder. 34 flows into the stroke simulator 64, and even if the first shut-off valve 60a and the second shut-off valve 60b are shut off, the brake fluid moves, and a stroke occurs when the brake pedal 12 is operated, resulting in a pedal reaction force. It becomes like this.

On the other hand, in the vehicular braking system 10, when the driver steps on the brake pedal 12 in an abnormal state where the slave cylinder device 16 or the like is inoperative, the existing hydraulic brake system becomes active. Specifically, in the vehicle braking system 10 at the time of abnormality, when the driver steps on the brake pedal 12, the master cut valve 60a and the master cut valve are opened, and the third cutoff valve 62 is closed. As a state, the brake hydraulic pressure generated in the master cylinder 34 is transmitted to the disc brake mechanisms 30a to 30d (wheel cylinders 32FR, 32RL, 32RR, 32FL), and the disc brake mechanisms 30a to 30d (wheel cylinders 32FR, 32RL, 32RR, 32FL) is actuated to brake each wheel. That is, in this case, the vehicle braking system 10 can be operated as a conventional brake.
Since the configurations and operations of the other input device 14, slave cylinder device 16, and VSA device 18 are well known, detailed description thereof is omitted.

[Configuration of master cut valve]
FIG. 2 is an explanatory diagram showing a schematic configuration of the master cut bubble. As described above, the master cut valve 60a and the master cut valve 60b (both have the same configuration) are normally open valves that are closed when the driver steps on the brake pedal 12 or the like. The master cut valve 60a (60b) includes an upstream pipe 22a1 (22d1) on the master cylinder 34 side (upstream side of the brake fluid) of the pipe 22a (22d) and a slave cylinder 16 side (downstream side of the brake fluid). ) And downstream piping 22a2 (22d2).

  In the master cut valve 60a (60b), there are a movable core 101 movable in the vertical direction in FIG. 2 and a valve element 102 provided at the tip of the movable core 101 to open and close the master cut valve 60a (60b). And are provided. That is, the movable core 101 opens and closes the master cut valve 60a (60b) by moving in the axial direction. Further, a spring 103 is provided inside the master cut valve 60a (60b), and this spring 103 moves the movable core 101 to the arrow 111 in FIG. 2 so that the master cut valve 60a (60b) is opened by the valve element 102. Energized in the direction. Further, the master cut valve 60a (60b) is provided with an exciting coil 104 for driving the valve element 102. Reference numeral 105 denotes a valve seat that receives the valve element 102.

  When the exciting coil 104 is not driven without being energized, the master cut valve 60a (60b) is normally opened by the spring 103 urging the valve element 102 toward the arrow 111 side. In the master cut valve 60a (60b), the hydraulic pressure on the master cylinder 34 side acts in the valve opening direction. On the other hand, when the exciting coil 104 is energized, the valve element 102 moves in the direction of the arrow 112 in FIG. 2 against the elastic force of the spring 103 by electromagnetic force, and the master cut valve 60a (60b) is closed.

  Here, the difference in fluid pressure between the master cylinder 34 (upstream of the brake fluid) and the slave cylinder 16 (downstream of the brake fluid) will be simply referred to as “differential pressure” below. When the master cut valve 60a (60b) is in a non-energized state, the master cut valve 60a is self-opened by an open pressure (maximum differential pressure that can open the master cut valve 60a (60b) in the non-energized state). (60b) can be opened to operate the vehicle braking system 10 as a conventional brake as described above.

  However, even if the master cut valve 60a (60b) is in a non-energized state (even if the driver releases the brake pedal 12), the self-sealing force due to the fluid pressure on the slave cylinder 16 side (downstream side) The master cut valve 60a (60b) falls into a self-locking state (the valve element 102 is locked in the direction of the arrow 112), which is a state in which the master cut valve 60a (60b) cannot self-open even when energization is stopped. In this self-locking state, the brake fluid pressure remains on the slave cylinder 16 side (downstream of the brake fluid), so that inconveniences such as deterioration of fuel consumption due to brake dragging occur in the vehicle.

Since self-locking is not a component failure, when hydraulic pressure is generated on the master cylinder 34 side (upstream side) by the driver's operation of the brake pedal 12, if the differential pressure decreases and becomes lower than the release pressure, the master The cut valve 60a (60b) can be opened. However, in this case, if the control of the hydraulic pressure of the by-wire brake is continued in the self-locking state, the hydraulic pressure on the slave cylinder 16 side (downstream side) increases when the brake pedal 12 is operated. The possibility of self-opening of the master cut valve 60a (60b) by the operator's operation is greatly reduced.
Therefore, in the following, a description will be given of the contents of control for canceling the state when the occurrence of the self-lock is high or when the occurrence of the self-lock is detected.

[About backup control]
FIG. 3 is a block diagram showing electrical connection of the ECU 200. The ECU (Electronic Control Unit) 200 is a so-called ESB (Electric Servo Brake) -ECU, and controls the by-wire brake operation by the vehicle braking system 10. In particular, the ECU 200 includes a brake fluid pressure sensor (first fluid pressure) that detects a fluid pressure on the slave cylinder 16 side (downstream side) from the master cut valve 60a (60b) among the brake fluid pressure sensors Pm, Pp, Ph. Sensors Pp and the detected value of the brake hydraulic pressure sensor (second hydraulic pressure sensor) Pm for detecting the hydraulic pressure on the master cylinder 34 side (upstream side) from the master cut valve 60a (60b) are input. The ECU 200 also includes a drive circuit 211 that drives the motor 72 of the slave cylinder 16 serving as an actuator that drives the by-wire brake, and a drive circuit 212 that drives the excitation coil 104 of the master cut valve 60a (60b). ing.

  In the ECU 200, the first control unit 205 determines that at least the hydraulic pressure on the slave cylinder 16 side (downstream side) detected by the first hydraulic pressure sensor Pp is equal to or higher than the cutoff pressure that can maintain the closed state of the master cut valve 60a (60b). Judge whether or not. When the pressure is higher than the shut-off pressure, the operation of the motor 72 is reduced (or stopped) than when it is not, and the energization to the exciting coil 104 is stopped to open the master cut valve 60a (60b). Perform backup control to shift to the mode.

  More specifically, the first control unit 205 includes a differential pressure detection unit 201, a cutoff pressure setting unit 202, a comparison unit 203, and a backup control unit 204. The differential pressure detection unit 201 detects the differential pressure based on the detection values of the first hydraulic pressure sensor Pp and the second hydraulic pressure sensor Pm. The cut-off pressure setting unit 202 sets a predetermined pressure (cut-off pressure) that is the maximum differential pressure that can be closed by the magnetic field generated by the excitation coil 104 by the master cut valve 60a (60b). The comparison unit 203 compares the differential pressure detected by the differential pressure detection unit 201 with the cutoff pressure set by the cutoff pressure setting unit 202. Then, the comparison unit 203 compares the differential pressure detected by the differential pressure detection unit 201 with the cutoff pressure set by the cutoff pressure setting unit 202, and when the former is larger than the latter for a predetermined time or more, The backup control unit 204 performs backup control. That is, the backup control unit 204 reduces (or stops) the operation of the motor 72 when the state in which the former is greater than the latter continues for a predetermined time or more, and the energization to the excitation coil 104 is not performed. Is stopped and backup control for shifting to the backup mode for opening the master cut valve 60a (60b) is performed. In the backup mode, when the operation of the motor 72 is stopped, the energization to the excitation coil 104 is stopped, and the master cut valve 60a (60b) is opened, the vehicular braking system 10 uses the conventional brake. Works as.

That is, when a differential pressure equal to or higher than the shut-off pressure is generated during the control (a state where the hydraulic pressure on the master cylinder 34 side (upstream side) is high), the master cut valve 60a (60b) is opened once, and the brake fluid becomes When the pressure flows from the cylinder 34 side (upstream side) to the slave cylinder 16 side (downstream side) and the differential pressure decreases, the master cut valve 60a (60b) is closed. If the amount of brake fluid flowing from the upstream side to the downstream side during opening of the master cut valve 60a (60b) is greater than a certain amount, the fluid pressure on the slave cylinder 16 side (downstream side) increases, and thereafter Self-locking may occur after the valve is closed.
Therefore, when the pressure difference (when the hydraulic pressure on the slave cylinder 16 side (downstream side) is high) is greater than the shutoff pressure for a predetermined time or longer, the mode is shifted to the backup mode to prevent the occurrence of self-lock. can do.

Further, the cutoff pressure setting unit 202 that sets the cutoff pressure can set the cutoff pressure variously according to the drive voltage of the master cut valve 60a (60b) by the drive circuit 212.
For example, when the driving voltage of the master cut valve 60a (60b) is high, the cutoff pressure increases. In this case, the cutoff pressure set by the cutoff pressure setting unit 202 can be reduced to prevent self-locking. it can.
Further, when the drive voltage of the master cut valve 60a (60b) is low, the shut-off pressure becomes low. In this case, the shut-off pressure set by the shut-off pressure setting unit 202 is increased to unnecessarily shift to the backup mode. This can be prevented.

In the second controller 221, the slave cylinder 16 serving as a by-wire brake actuator is in an initial position (the stroke of the slave cylinder 16 is 0), and the hydraulic pressure on the slave cylinder 16 side (downstream side) is When the pressure is reduced to the maximum, the following judgment is made. That is, the second control unit 221 determines that the master cut valve 60a (60b) is in a non-energized state and the fluid pressure on the slave cylinder 16 side (downstream side) detected by the first fluid pressure sensor Pp is the open pressure ( When the master cut valve 60a (60b) is in a non-energized state, it is determined whether or not it is equal to or higher than the maximum differential pressure at which the master cut valve 60a (60b) can be opened. When the condition is satisfied, since the self-lock is generated, the operation of the motor 72 is reduced (or stopped), and the energization to the excitation coil 104 is stopped and the master cut valve is turned off. Backup control for shifting to the backup mode for opening 60a (60b) is performed. Also in this case, the vehicle braking system 10 operates as the conventional brake.
In this case, by reducing (or stopping) the operation of the motor 72 and controlling in a direction to open the master cut valve 60a (60b), the differential pressure is reduced and the occurrence of self-locking is eliminated. Can do.

10 Vehicle braking system 16 Slave cylinder (actuator)
34 Master cylinder 60a, 60b Master cut valve (normally open valve)
202 Blocking pressure setting unit 205 First control unit 221 Second control unit Pp First hydraulic pressure sensor Pm Second hydraulic pressure sensor

Claims (4)

A master cylinder;
An actuator that communicates with the master cylinder and generates a hydraulic pressure;
A normally open valve that shuts off the path between the master cylinder and the actuator by closing the valve, and the hydraulic pressure on the master cylinder side acts in the valve opening direction;
A first hydraulic pressure sensor for detecting a hydraulic pressure on the actuator side from the normally open valve;
When at least the hydraulic pressure detected by the first hydraulic pressure sensor is equal to or higher than a predetermined cutoff pressure that can maintain the normally open valve closed state, the operation of the actuator is reduced as compared with the case where the hydraulic pressure is not so, A first control unit that performs control to open the normally open valve;
A vehicle braking system comprising: A second hydraulic pressure sensor for detecting the hydraulic pressure on the master cylinder side from the normally open valve;
The first control unit reduces the operation of the actuator when a differential pressure between a hydraulic pressure detected by the second hydraulic pressure sensor and a hydraulic pressure detected by the first hydraulic pressure sensor is equal to or higher than a predetermined pressure. The vehicular braking system according to claim 1, wherein the normally open valve is opened.   The vehicle braking system according to claim 1, further comprising a cutoff pressure setting unit that sets the cutoff pressure in accordance with a drive voltage of the normally open valve.   When the hydraulic pressure detected by the first hydraulic pressure sensor is equal to or higher than the opening pressure of the normally open valve when the actuator is in the initial position and the normally open valve is in a non-energized state, 4. The apparatus according to claim 1, further comprising a second control unit that performs control to reduce the operation of the actuator and to open the normally open valve as compared with the case where the actuator is not. Vehicle braking system.

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