Vehicle brake system

Abstract

The invention provides a vehicle brake system capable of executing anti-lock brake control even when a hydraulic control device is not operated. A hydraulic pressure generation device (1) is provided with: main shutoff valves (7a, 7b) for opening and closing a main hydraulic pressure path leading from a main cylinder (10) to a hydraulic pressure control device (2); communication paths (3a, 3b) leading from the auxiliary cylinder (30) to the main hydraulic paths (7a, 7b); shutoff valves (8a, 8b) that open and close the communication paths (3a, 3b); and a control device (4). The control device (4) is configured so that, when the hydraulic pressure control device (2) is not operating, brake hydraulic pressure is generated from the assist cylinder (30) and, in accordance with the slip of the wheels, main shut-off valves (7a, 7b) and shut-off valves (8a, 8b) are controlled in the first main hydraulic pressure path (1a) and the second main hydraulic pressure path (1b), respectively, to perform anti-lock brake control.

Description

Technical Field

[0001] The present invention relates to a braking system for a vehicle. Background Art

[0002] In the prior art, a vehicle braking system is known to include: a master cylinder that generates brake fluid pressure corresponding to the depression force of the brake pedal; an auxiliary cylinder that generates brake fluid pressure by driving an electric actuator; and a hydraulic control device that assists in stabilizing the vehicle's behavior by controlling the brake fluid pressure acting on the wheel brakes (for example, refer to Patent Document 1). [Prior art literature] [Patent Document]

[0003] Patent Document 1: Japanese Patent Application Publication No. 2012-210879 Summary of the Invention [Technical problem to be solved by the invention]

[0004] The vehicle brake system of Patent Document 1 adopts a configuration in which the brake fluid pressure acting on the wheel brakes is controlled by the hydraulic control device. Therefore, when the hydraulic control device is not in operation, anti-lock brake control cannot be performed.

[0005] The technical problem of the present invention is to solve the above-mentioned problem and provide a vehicle brake system capable of executing anti-lock brake control even when a hydraulic control device is not in operation. [Technical solutions for solving technical problems]

[0006] To solve the above-mentioned technical problems, the present invention provides a vehicle brake system comprising: a hydraulic pressure generating device having a master cylinder that generates brake hydraulic pressure in response to the amount of operation of a brake operating member and an auxiliary cylinder that generates brake hydraulic pressure by driving an electric actuator; and a hydraulic pressure control device that controls the brake hydraulic pressure acting on the wheel brakes using the brake hydraulic pressure from the hydraulic pressure generating device. The hydraulic pressure generating device comprises: a master cut valve that opens and closes a main hydraulic pressure path from the master cylinder to the hydraulic pressure control device; a communication path that connects the auxiliary cylinder to the main hydraulic pressure path downstream of the master cut valve; a shutoff valve that opens and closes the communication path; and a control device that controls the operation of the auxiliary cylinder, the master cutoff valve, and the shutoff valve. The main hydraulic pressure path comprises a first main hydraulic pressure path that communicates with at least one of the plurality of wheel brakes and a second main hydraulic pressure path that communicates with the remaining wheel brakes. The master cutoff valve, the communication path, and the shutoff valve are provided in the first and second main hydraulic pressure paths, respectively. The control device is characterized in that when the hydraulic control device is not in operation, brake hydraulic pressure is generated from the auxiliary cylinder and according to the slip situation of the wheel, the main stop valve and the shut-off valve are controlled respectively according to the first main hydraulic path and the second main hydraulic path to perform anti-lock braking control.

[0007] In the vehicle brake system of the present invention, when the hydraulic control device is inoperative, anti-lock braking control can be executed by controlling the slave cylinder, master cutoff valve, and shutoff valve of the hydraulic pressure generating device via the control device. Therefore, even if the hydraulic control device fails, anti-lock braking control can be executed based on wheel slip.

[0008] Furthermore, it is preferable that the main stop valve is a normally open on-off valve, and the shutoff valve is a normally closed on-off valve.

[0009] According to this configuration, anti-lock brake control can be executed when the hydraulic control device is not operating by a simple system configuration using a normally open on-off valve and a normally closed on-off valve, thereby reducing costs.

[0010] The master cylinder preferably includes two pressure chambers and is configured to output the hydraulic pressure generated in the two pressure chambers to the first main hydraulic path and the second main hydraulic path, respectively. Furthermore, the auxiliary cylinder preferably includes two auxiliary cylinder pressure chambers and is configured to output the hydraulic pressure generated in the two auxiliary cylinder pressure chambers to the first main hydraulic path and the second main hydraulic path, respectively.

[0011] According to this configuration, when the hydraulic control device is not in operation, anti-lock braking control can be appropriately achieved in each of the first main hydraulic path and the second main hydraulic path using the brake hydraulic pressure generated in the two assist cylinder pressure chambers. Therefore, it is possible to obtain a vehicle brake system that is excellent in the transfer performance of the brake fluid and can appropriately implement anti-lock brake control when the hydraulic control device is not in operation.

[0012] In addition, preferably, in the anti-lock braking control, when the brake hydraulic pressure of at least one of the first main hydraulic path and the second main hydraulic path is boosted, the main stop valve of the hydraulic path of the boosted object is closed and the shut-off valve of the hydraulic path of the boosted object is opened, so that the brake hydraulic pressure generated by the auxiliary cylinder acts on the hydraulic path of the boosted object.

[0013] According to this configuration, during anti-lock brake control when the hydraulic control device is not in operation, the master cut valve, the shutoff valve, and the assist cylinder are controlled to appropriately increase the pressure in the hydraulic path to be pressurized.

[0014] In addition, preferably, in the anti-lock braking control, when the brake hydraulic pressure of at least one of the first main hydraulic path and the second main hydraulic path is reduced in pressure, the main stop valve of the hydraulic path of the pressure reducing object is closed and the shut-off valve of the hydraulic path of the pressure reducing object is opened, and the piston of the auxiliary cylinder is driven and controlled in the pressure reducing direction through the electric actuator.

[0015] According to this configuration, during anti-lock brake control when the hydraulic control device is not in operation, the master cut valve, the shutoff valve, and the assist cylinder are controlled to appropriately depressurize the hydraulic path to be depressurized.

[0016] In addition, preferably, in the anti-lock braking control, when the brake hydraulic pressure of at least one of the first main hydraulic path and the second main hydraulic path is maintained, the main cut valve of the hydraulic path to be maintained is closed and the shutoff valve of the hydraulic path to be maintained is closed.

[0017] According to this configuration, during the anti-lock brake control when the hydraulic control device is not in operation, the master cut valve, the shutoff valve, and the assist cylinder are controlled, and the hydraulic path to be held can be appropriately held.

[0018] In addition, preferably, in the anti-lock braking control, when the brake hydraulic pressure of at least one of the first main hydraulic path and the second main hydraulic path is reduced in pressure, the main stop valve of the hydraulic path of the pressure-reducing object is opened and the shut-off valve of the hydraulic path of the pressure-reducing object is closed, and the brake fluid is returned to the master cylinder side through the opened main stop valve.

[0019] According to this configuration, during antilock brake control when the hydraulic control device is not in operation, the brake fluid in the hydraulic path to be depressurized can be returned to the master cylinder. Therefore, one hydraulic path can be depressurized while the other hydraulic path can be pressurized.

[0020] Furthermore, it is preferred that the system include a return flow path leading from the wheel brake to the atmospheric pressure side of the master cylinder or a reservoir tank, and an on-off valve for opening and closing the return flow path. In this case, it is preferred that, during the anti-lock braking control, when reducing the brake fluid pressure in at least one of the first main hydraulic path and the second main hydraulic path, the master cut valve and the shutoff valve of the hydraulic path to be reduced in pressure are closed, and the on-off valve is opened.

[0021] With this configuration, during anti-lock braking control when the hydraulic control device is inoperative, brake fluid can be returned to the atmospheric pressure side of the master cylinder or to the reservoir tank via the return flow path. In other words, even when the brake operating member is operated and the brake fluid pressure generated by the master cylinder acts on the first and second main hydraulic paths, at least one of the first and second main hydraulic paths can be depressurized.

[0022] Furthermore, it is preferable that the first main hydraulic path communicate with the wheel brake on the front wheel side of the front and rear wheels of the vehicle, and the second main hydraulic path communicate with the wheel brake on the rear wheel side.

[0023] In this configuration, anti-lock braking control can be performed on the front wheels and the rear wheels separately, and appropriate braking force distribution between the front and rear of the vehicle can be achieved according to the vehicle type.

[0024] Furthermore, the control device is preferably capable of executing a fluid suction control for absorbing brake fluid in the assist cylinder during the anti-lock braking control. When the fluid suction control is required, the shutoff valve is closed and the electric actuator is used to drive and control the piston of the assist cylinder in a decompression direction.

[0025] In this structure, during anti-lock braking control when the hydraulic control device is inactive, driving the slave piston in the decompression direction with the shutoff valve closed creates a negative pressure in the slave cylinder's pressure chamber, drawing brake fluid from the upstream device into the slave cylinder. This fluid suction control replenishes the slave cylinder's pressure chamber with brake fluid for re-pressurization, ensuring the required brake fluid for pressure increase. This provides a braking system that can increase pressure to a high hydraulic pressure range while avoiding increasing the size of the slave cylinder. [Effects of the Invention]

[0026] The vehicle brake system of the present invention can execute anti-lock brake control when the hydraulic control device is not in operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a hydraulic circuit diagram showing a vehicle brake system according to a first embodiment of the present invention. Figure 2 This is a diagram showing the flow of brake fluid during normal brake control in the vehicle brake system according to the first embodiment of the present invention. Figure 3 This is a diagram showing the flow of brake fluid during automatic brake control in the vehicle brake system according to the first embodiment of the present invention. Figure 4 This is a diagram showing the flow of brake fluid during anti-lock brake control when automatic brake control is in operation and the hydraulic control device is inoperative in the vehicle brake system according to the first embodiment of the present invention. Figure 5 This is a diagram showing the flow of brake fluid during anti-lock brake control when automatic brake control is in operation and the hydraulic control device is inoperative in the vehicle brake system according to the first embodiment of the present invention. Figure 6 This is a diagram showing the flow of brake fluid during fluid suction control when the automatic brake control is in operation and the hydraulic control device is inoperative in the vehicle brake system according to the first embodiment of the present invention. Figure 7 This is a diagram showing the flow of brake fluid during fluid suction control when the automatic brake control is in operation and the hydraulic control device is inoperative in the vehicle brake system according to the first embodiment of the present invention. Figure 8 This is a diagram showing the flow of brake fluid during fluid suction control when the automatic brake control is in operation and the hydraulic control device is inoperative in the vehicle brake system according to the first embodiment of the present invention. Figure 9 This is a diagram showing the flow of brake fluid during anti-lock brake control when the brake pedal is operated and the hydraulic control device is not in operation in the vehicle brake system according to the first embodiment of the present invention. Figure 10 This is a diagram showing the flow of brake fluid during anti-lock brake control when the brake pedal is operated and the hydraulic control device is not in operation in the vehicle brake system according to the first embodiment of the present invention. Figure 11 This is a diagram showing the flow of brake fluid during anti-lock brake control when the brake pedal is operated and the hydraulic control device is not in operation in the vehicle brake system according to the first embodiment of the present invention. Figure 12 This is a hydraulic circuit diagram showing a vehicle brake system according to a second embodiment of the present invention. Figure 13This is a diagram showing the flow of brake fluid in the decompression mode of anti-lock brake control when the brake pedal is being operated and the hydraulic control device is not operating in the vehicle brake system according to the second embodiment of the present invention. Figure 14 This is a diagram showing the flow of brake fluid in the decompression mode of anti-lock brake control when the brake pedal is being operated and the hydraulic control device is not operating in the vehicle brake system according to the second embodiment of the present invention. DETAILED DESCRIPTION

[0028] Below, with appropriate reference to the attached Figure 1 In the following drawings, the same components are denoted by the same reference numerals and overlapping descriptions are omitted. The vehicle brake system 100 of the present invention can be installed in a hybrid vehicle using a motor in combination, an electric vehicle / fuel cell vehicle using only a motor as a power source, or a vehicle using only an engine (internal combustion engine) as a power source.

[0029] (First embodiment) like Figure 1 As shown, the vehicle brake system 100 includes both a by-wire brake system that operates when a prime mover (engine, electric motor, etc.) is started and a hydraulic brake system that operates when the prime mover is stopped.

[0030] Vehicle brake system 100 includes a hydraulic pressure generator 1 that generates brake fluid pressure in response to the stroke (amount of movement) of a brake pedal BP (brake operating element); and a hydraulic pressure control device 2 connected to hydraulic pressure generator 1 to control the brake fluid pressure acting on each wheel cylinder W of the wheel brakes. Vehicle brake system 100 is constructed from two base bodies (two blocks): a base 1A, to which the components of hydraulic pressure generator 1 are mounted, and a base 1B, to which the components of hydraulic pressure control device 2 are mounted.

[0031] The base 1A includes a master cylinder 10, a stroke simulator 20, and an assist cylinder 30. Alternatively, the base 1A may be divided into two parts, with the master cylinder 10 and the stroke simulator 20 provided on one divided base and the assist cylinder 30 provided on the other divided base.

[0032] The master cylinder 10 functions as an input device that generates brake fluid pressure according to the stroke of the brake pedal BP. The stroke simulator 20 applies a simulated operational reaction force to the brake pedal BP. The assist cylinder 30 generates brake fluid pressure using an electric motor 36 as an electric actuator as a driving source. As described later, the assist cylinder 30 is activated during normal braking control (preventing the wheel brakes from locking), anti-lock braking control, and automatic braking control (assisting with vehicle stabilization) to boost the brake fluid pressure of the wheel brakes. Specifically, the assist cylinder 30 is responsible for boosting the brake fluid pressure of all wheel brakes and, when the hydraulic control device 2 is inoperative, serves as a control device for executing anti-lock braking control, replacing the hydraulic control device.

[0033] The master cylinder 10 includes two pistons 12 a and 12 b inserted into a first cylinder hole 11 of the base body 1A. A bottom-side pressure chamber 14a is formed between the bottom surface of the first cylinder bore 11 and the bottom-side piston 12a. Furthermore, an opening-side pressure chamber 14b is formed between the bottom-side piston 12a and the opening-side piston 12b. In other words, the master cylinder 10 comprises two pressure chambers: the bottom-side pressure chamber 14a and the opening-side pressure chamber 14b. A reservoir tank 15 for storing brake fluid is attached to the master cylinder 10. The reservoir tank 15 has supply ports 15a and 15b for supplying the brake fluid to the master cylinder 10. The hydraulic pressure generated by the master cylinder 10 is configured to be output to both the first main hydraulic path 1a and the second main hydraulic path 1b, described below. The hydraulic pressure generated by the bottom-side pressure chamber 14a is output to the first main hydraulic path 1a, while the hydraulic pressure generated by the open-side pressure chamber 14b is output to the second main hydraulic path 1b. The first main hydraulic path 1a communicates with the front wheel brakes of the vehicle. The second main hydraulic path 1b communicates with the rear wheel brakes.

[0034] The tip of the rod R1 of the brake pedal BP is connected to the piston 12b on the open side. The two pistons 12a and 12b slide within the first cylinder bore 11 in response to the force applied to the brake pedal BP, pressurizing the brake fluid in the bottom-side pressure chamber 14a and the open-side pressure chamber 14b. A stroke sensor 16 is mounted on the master cylinder 10 to detect the amount of operation (depression) of the brake pedal BP.

[0035] The stroke simulator 20 includes a piston 22 inserted into the second cylinder hole 21 of the base body 1A, a cover member 24 closing the opening of the second cylinder hole 21 , and a coil spring 23 accommodated between the piston 22 and the cover member 24 .

[0036] A pressure chamber 25 is formed between the bottom surface of the second cylinder hole 21 and the piston 22. The pressure chamber 25 communicates with the opening-side pressure chamber 14b of the first cylinder hole 11 via a first branch hydraulic path 1c, a second branch hydraulic path 1d, and a second main hydraulic path 1b.

[0037] The reservoir communication path 1e is connected to the back pressure chamber 26 where the coil spring 23 is arranged. The reservoir communication path 1e communicates with the reservoir 15 (atmospheric pressure side) via the master cylinder 10 and the supply port 15b.

[0038] In the stroke simulator 20, the brake fluid pressure applied by the opening-side pressure chamber 14b causes the piston 22 to move against the biasing force of the coil spring 23. The biased piston 22 then applies a simulated operational reaction force to the brake pedal BP.

[0039] The assist cylinder 30 has two slave pistons 32a and 32b inserted into the third cylinder bore 31 of the base body 1A, and two pressure chambers: a bottom-side pressure chamber 34a and an open-side pressure chamber 34b. Specifically, the third cylinder bore 31 is divided into the bottom-side pressure chamber 34a and the open-side pressure chamber 34b. The bottom-side pressure chamber 34a is formed between the bottom surface of the third cylinder bore 31 and the bottom-side slave piston 32a. The open-side pressure chamber 34b is formed between the bottom-side slave piston 32a and the open-side slave piston 32b. The two slave pistons 32a and 32b slide within the third cylinder bore 31 in response to input from the rod 35a, pressurizing the brake fluid in the bottom-side pressure chamber 34a and the open-side pressure chamber 34b.

[0040] The bottom-side pressure chamber 34a is connected to a first auxiliary cylinder supply path 1h. This path communicates with the reservoir tank 15 via the master cylinder 10 and the supply port 15a. Furthermore, the bottom-side pressure chamber 34a is connected to a first communication path 3a, which communicates with the first main hydraulic path 1a. A first shutoff valve 8a, serving as a shutoff valve, is provided on the first communication path 3a.

[0041] The second auxiliary cylinder supply path 1i is connected to the opening-side pressure chamber 34b. This second auxiliary cylinder supply path 1i branches off from the reservoir communication path 1e and communicates with the reservoir tank 15 via the reservoir communication path 1e. Furthermore, the second communication path 3b, which communicates with the second main hydraulic path 1b, is connected to the opening-side pressure chamber 34b. The second communication path 3b is provided with a second shutoff valve 8b, serving as a shutoff valve, and a second pressure sensor P2.

[0042] The assist cylinder 30 includes a drive transmission unit 35 and an electric motor 36. The electric motor 36 is an electric servo motor driven and controlled by the control device 4 described later. The drive transmission unit 35 converts the rotational drive force of the output shaft of the electric motor 36 into a linear axial force. The drive transmission unit 35 is composed of, for example, a ball screw mechanism. When the output shaft of the electric motor 36 rotates and the rotational driving force is input to the drive transmission unit 35, the rod 35a of the drive transmission unit 35 moves forward and backward. The distal end of the rod 35a contacts the driven piston 32b. The slave pistons 32 a and 32 b receive input from the rod 35 a and slide in the third cylinder bore 31 , respectively, to pressurize the brake fluid in the bottom-side pressure chamber 34 a and the opening-side pressure chamber 34 b .

[0043] The control device 4 comprises, for example, a housing mounted on a side surface of the base 1B and a control board housed within the housing. The control device 4 controls the operation of the electric motor 36 and the opening and closing of the various valves based on information obtained from the stroke sensor 16 and various sensors, or based on pre-stored programs. The control device 4 is a dedicated control device for the hydraulic pressure generating device 1. In addition to normal braking control, the control device 4 also performs anti-lock braking control when the hydraulic control device 2 is inoperative (including when the hydraulic control device 2 fails). Specifically, the control device 4 controls the operation of the first master cut valve 7a, the second master cut valve 7b, the first stop valve 8a, the second stop valve 8b, and the assist cylinder 30 based on wheel slip, thereby performing anti-lock braking control. In this case, the control device 4 can perform anti-lock braking control for both the first main hydraulic path 1a and the second main hydraulic path 1b.

[0044] The control device 4 also has a function for performing fluid suction control. This control is used to secure brake fluid within the slave cylinder 30. Specifically, the control actively draws brake fluid into the bottom-side pressure chamber 34a and the opening-side pressure chamber 34b of the slave cylinder 30 via the first slave cylinder supply path 1h and the second slave cylinder supply path 1i. The control is performed when it is desired to replenish brake fluid into the slave cylinder 30, for example, when the slave cylinder 30 is pressurizing the brake fluid during anti-lock braking control by the hydraulic control device 2. Furthermore, the control is also performed to secure brake fluid in advance for subsequent pressurization, for example, when the generated hydraulic pressure in the slave cylinder 30 has reached the hydraulic pressure required by the driver. Furthermore, the control device 4 also performs the fluid suction control when the anti-lock brake control is executed by the hydraulic pressure generating device 1 when the hydraulic pressure control device 2 is not in operation (for example, when the hydraulic pressure control device 2 has failed).

[0045] Next, each hydraulic path formed in the base body 1A will be described. A first main hydraulic path 1 a and a second main hydraulic path 1 b as main hydraulic paths communicating with the master cylinder 10 , and a first branch hydraulic path 1 c branching from the second main hydraulic path 1 b are provided in the base body 1A.

[0046] The first main hydraulic path 1a is a hydraulic path originating from the bottom-side pressure chamber 14a of the first cylinder bore 11. A first pressure sensor P1 is provided in the first main hydraulic path 1a. The first pressure sensor P1 detects the brake hydraulic pressure generated by the master cylinder 10. A pipe Ha leading to the base body 1B of the hydraulic control device 2 is connected to the outlet port at the end of the first main hydraulic path 1a.

[0047] The second main hydraulic path 1b is a hydraulic path starting from the opening-side pressure chamber 14b of the first cylinder bore 11. A pipe Hb leading to the base 1B of the hydraulic control device 2 is connected to the outlet port serving as the terminal of the second main hydraulic path 1b.

[0048] The first branch hydraulic path 1c is a hydraulic path leading from the second main hydraulic path 1b to the pressure chamber 25 of the stroke simulator 20. The first branch hydraulic path 1c is provided with a simulator valve 5. The simulator valve 5 is a normally closed solenoid valve that opens and closes the first branch hydraulic path 1c.

[0049] The second branch hydraulic path 1d is a hydraulic path from the second main hydraulic path 1b to the first branch hydraulic path 1c. The second branch hydraulic path 1d communicates with a portion of the first branch hydraulic path 1c that is closer to the pressure chamber 25 than the simulator valve 5. A check valve 6 is provided in the second branch hydraulic path 1d. The check valve 6 is connected in parallel with the simulator valve 5. This check valve 6 only allows brake fluid to flow from the pressure chamber 25 to the first cylinder bore 11.

[0050] A first master stop valve 7a, serving as a main stop valve, is provided on the first main hydraulic path 1a. The first master stop valve 7a is an on / off valve (on / off valve) comprised of a normally open solenoid valve, and opens and closes the first main hydraulic path 1a. A second master stop valve 7b, serving as a main stop valve, is provided on the second main hydraulic path 1b. The second master stop valve 7b is an on / off valve (on / off valve) comprised of a normally open solenoid valve, and opens and closes the second main hydraulic path 1b.

[0051] The first communication path 3a is connected downstream of the first master stop valve 7a in the first main hydraulic path 1a. The first shutoff valve 8a of the first communication path 3a is an on-off valve (on-off valve) composed of a normally closed solenoid valve that opens and closes the first communication path 3a. The second communication path 3b is connected downstream of the second master cutoff valve 7b in the second main hydraulic path 1b. A second shutoff valve 8b in the second communication path 3b is an on-off valve (on-off valve) comprised of a normally closed solenoid valve, which opens and closes the second communication path 3b. A second pressure sensor P2 in the second communication path 3b detects the brake fluid pressure generated by the assist cylinder 30. Information acquired by the first pressure sensor P1 and the second pressure sensor P2 is output to the control device 4 .

[0052] The first main stop valve 7a is Figure 1 In the open valve state shown and the first shut-off valve 8a is in the closed valve state, the upstream side (master cylinder 10 side) and the downstream side (hydraulic control device 2 side) of the first main hydraulic path 1a are connected, and the first main hydraulic path 1a and the first communicating path 3a are shut off. The first main stop valve 7a is Figure 1 In the closed state shown and the first shutoff valve 8a in the open state, the upstream and downstream sides of the first main hydraulic path 1a are shut off, and the first communication path 3a communicates with the downstream side of the first main hydraulic path 1a.

[0053] Likewise, when the second main stop valve 7b is Figure 1 In the open valve state shown and the second shut-off valve 8b is in the closed valve state, the upstream side (master cylinder 10 side) and the downstream side (hydraulic control device 2 side) of the second main hydraulic path 1b are connected, and the second main hydraulic path 1b and the second communicating path 3b are shut off. The second main stop valve 7b is Figure 2 In the closed state shown and the second shutoff valve 8b in the open state, the upstream and downstream sides of the second main hydraulic path 1b are shut off, and the second communication path 3b communicates with the downstream side of the second main hydraulic path 1b.

[0054] The hydraulic control device 2 can appropriately control the brake hydraulic pressure applied to each wheel cylinder W. like Figure 1 As shown, the hydraulic control device 2 is disposed between the hydraulic pressure generating device 1 and each wheel cylinder W. The hydraulic control device 2 includes a brake output system K1 for braking two of the four wheel brakes and a brake output system K2 for braking the other two wheel brakes.

[0055] Two inlet ports 4a and 4b are provided on the base 1B of the hydraulic control device 2. These inlet ports 4a and 4b are connected to pipes Ha and Hb, which are connected to the output port of the base 1A of the hydraulic pressure generating device 1. Each wheel cylinder W is connected to the output port of the base 1B of the hydraulic control device 2 via a pipe. The brake output system K1 communicates with the first main hydraulic path 1 a , and the brake output system K2 communicates with the second main hydraulic path 1 b .

[0056] The brake output system K1 includes a pressure reducing valve R as a pressure regulating valve, a control valve mechanism V, a suction valve 47 , a reservoir 48 , a pump 45 , and a third hydraulic pressure sensor P3 . The hydraulic control device 2 also includes a control device 9 . In addition, since the brake output system K2 and the brake output system K1 have the same structure, in the following description, the brake output system K1 is described in detail.

[0057] In the following description, the fluid path from the inlet port to the pressure-reducing valve R is referred to as the "output hydraulic path A," and the fluid path from the pressure-reducing valve R to the outlet port is referred to as the "wheel hydraulic path B." Furthermore, the hydraulic path branching from the output hydraulic path A to the pump 45 is referred to as the "intake path C," and the hydraulic path from the pump 45 to the wheel hydraulic path B is referred to as the "discharge path D." Furthermore, the hydraulic path from the wheel hydraulic path B to the intake path C is referred to as the "open path E." The "upstream side" refers to the master cylinder MC side, and the "downstream side" refers to the wheel brake (wheel cylinder W) side.

[0058] The pressure-reducing valve R adjusts the brake fluid pressure difference between the output hydraulic path A and the wheel hydraulic path B, switching between a state in which the brake fluid is allowed to flow and a state in which the brake fluid is blocked. Furthermore, when the brake fluid flow in the output hydraulic path A is blocked, the pressure-reducing valve R adjusts the brake fluid pressure in the wheel hydraulic path B to a predetermined pressure. The pressure-reducing valve R includes a shutoff valve 41 and a check valve 42.

[0059] The shutoff valve 41 is a normally open linear solenoid valve interposed between the output hydraulic path A and the wheel hydraulic path B. The shutoff valve 41 switches between a state in which brake fluid is permitted to flow from the output hydraulic path A to the wheel hydraulic path B and a state in which brake fluid is prevented from flowing from the output hydraulic path A to the wheel hydraulic path B. Specifically, the shutoff valve 41 is configured to adjust the valve opening pressure by controlling the energization of the solenoid (constructed to also function as a relief valve).

[0060] When the brake hydraulic pressure of wheel hydraulic path B exceeds the brake hydraulic pressure of output hydraulic path A, and the hydraulic difference between the brake hydraulic pressure of output hydraulic path A and the brake hydraulic pressure of wheel hydraulic path exceeds the force of the closing valve controlled by energizing the solenoid, the shut-off valve 41 opens the brake hydraulic pressure of wheel hydraulic path B to the output hydraulic path A side for adjustment.

[0061] The check valve 42 is connected in parallel with the cutoff valve 41. The check valve 42 allows the brake fluid to flow from the output hydraulic path A to the wheel hydraulic path B. The check valve 42 is integrally provided with a normally open solenoid valve constituting the pressure reducing valve R.

[0062] The control valve mechanism V switches the flow of fluid from the wheel hydraulic path B to the wheel brakes (wheel cylinders W) between open and closed, and the flow of fluid from the wheel brakes to the open path E between open and closed. The control valve mechanism V increases, maintains, or reduces the brake fluid pressure acting on each wheel cylinder W. Therefore, the control valve mechanism V is configured to include an inlet valve 43, an outlet valve 44, and a check valve 43a.

[0063] An inlet valve 43, an outlet valve 44, and a check valve 43a are provided on each of the two hydraulic paths leading to the wheel cylinders W of the two wheel brakes. The inlet valve 43 is a normally open linear solenoid valve. The pressure differential between the upstream and downstream sides of the inlet valve 43 (the valve opening pressure of the inlet valve 43) can be adjusted based on the value of the driving current flowing through the coil of the inlet valve 43. The inlet valve 43 is normally open, allowing the hydraulic pressure from the assist cylinder 30 to be supplied to the wheel cylinders W. Furthermore, when the wheels are about to lock, the inlet valve 43 is closed under the control of the control device 9, thereby blocking (maintaining) the brake hydraulic pressure supplied to the wheel cylinders W.

[0064] The outlet valve 44 is a normally closed solenoid valve disposed between the wheel cylinder W and the open path E. The outlet valve 44 is normally closed, but is opened under the control of the control device 9 when the wheel is about to lock. When the outlet valve 44 is opened, the brake fluid acting on the wheel cylinder W is released to the open path E, reducing the pressure of the brake fluid acting on the wheel cylinder W.

[0065] A check valve 43a is connected in parallel with the inlet valve 43. The check valve 43a is a valve that only allows brake fluid to flow from the wheel cylinder W side to the assist cylinder 30 side (the master cylinder 10 side). Therefore, when the inlet valve 43 is closed, the check valve 43a also allows brake fluid to flow from the wheel cylinder W side to the assist cylinder 30 side.

[0066] The intake valve 47 is a normally closed solenoid valve provided in the intake path C, switching between an open state and a closed state. The solenoid coil for driving the valve core of the intake valve 47 is electrically connected to the control device 9. In response to commands from the control device 7, the valve is opened when the solenoid coil is energized and closed when the solenoid coil is deenergized.

[0067] The reservoir 48 is provided in the open path E and has the function of temporarily storing the brake fluid discharged by opening the outlet valve 44. In addition, a one-way valve 49 is provided between the reservoir 48 and the pump 45 to allow only the brake fluid to flow from the reservoir 48 side to the pump 45 side.

[0068] The pump 45 has its suction side connected to the suction path C (open path E) and its discharge side connected to the discharge path D. Driven by the motor M, the pump 45 draws brake fluid from the reservoir 48 and discharges the pressurized brake fluid through the discharge path D to the wheel hydraulic path B. Furthermore, when the shutoff valve 41 of the pressure reducing valve R is closed and the suction valve 47 is open, the pump 45 draws brake fluid from the master cylinder 10, the output hydraulic path A, and the suction path C, and discharges it to the discharge path D. The amount of brake fluid discharged by the pump 45 depends on the rotational speed of the motor M.

[0069] The control device 9 includes, for example, a housing mounted on a side surface of the base 1B and a control board housed within the housing. The control device 9 controls the operation of the pump 45 (motor M) and the opening and closing of each valve based on information obtained from various sensors or pre-stored programs.

[0070] Next, refer to Figures 2 to 8 The operation of the vehicle brake system 100 will be described. exist Figure 1 In the illustrated vehicle brake system 100, when the system is started, the simulator valve 5 of the first branch hydraulic path 1c of the hydraulic pressure generator 1 is opened. The first and second master stop valves 7a and 7b of the hydraulic pressure generator 1 are energized and activated when the brake pedal BP is depressed, respectively closing the valves. Alternatively, a configuration may be employed in which, when the system is started, the first and second master stop valves 7a and 7b of the hydraulic pressure generator 1 are energized and activated, respectively closing the valves. In addition, the first stop valve 8a and the second stop valve 8b are energized and operated to open the valves.

[0071] Thus, the downstream side of the first main hydraulic path 1a communicates with the first communication path 3a, and the downstream side of the second main hydraulic path 1b communicates with the second communication path 3b.

[0072] In the following description, the hollow bold double lines shown in the diagrams of the hydraulic circuit represent the fluid paths through which the brake fluid pressure generated by the master cylinder 10 acts, and the bold solid lines represent the fluid paths through which the brake fluid pressure generated by the slave cylinder 30 acts. Furthermore, the bold dashed lines represent the fluid paths through which the brake fluid is discharged from the wheel cylinders W during anti-lock brake control decompression, and the bold dashed lines with narrow intervals represent the flow paths through which the brake fluid pressure is maintained during anti-lock brake control. In addition, Figures 4 to 11 In the embodiment, the brake fluid path of the hydraulic control device 2 is omitted. Figures 4 to 11 In, to and by Figure 2 The same flow path as the fluid path shown by the thick solid line acts on the brake hydraulic pressure.

[0073] (Normal brake control) Figure 2 This diagram shows the flow of brake fluid during normal braking control. During normal braking control, where the wheels do not lock, when the brake pedal BP is depressed, the depression amount is detected by the stroke sensor 16, and the control device 4 drives the electric motor 36 of the assist cylinder 30. This generates brake fluid pressure in the assist cylinder 30.

[0074] Furthermore, the brake hydraulic pressure generated in the master cylinder 10 by operation of the brake pedal BP is not transmitted to the wheel cylinders W but is transmitted to the stroke simulator 20 via the second main hydraulic path 1 b and the first branch hydraulic path 1 c . Then, the brake fluid pressure in the pressure chamber 25 of the stroke simulator 20 increases, and the piston 22 moves against the biasing force of the coil spring 23, thereby allowing the stroke of the brake pedal BP.

[0075] The control device 4 compares the brake hydraulic pressure generated by the assist cylinder 30 (the hydraulic pressure detected by the second pressure sensor P2) with the required hydraulic pressure (the first pressure sensor P1) corresponding to the amount of operation of the brake pedal BP. The control device 4 then controls the rotational speed and drive time of the electric motor 36 based on the comparison result. In this way, the assist cylinder 30 generates a brake hydraulic pressure corresponding to the amount of operation of the brake pedal BP. The brake hydraulic pressure boosted by the assist cylinder 30 is input to the hydraulic control device 2 via the first communication path 3a, the second communication path 3b, the first main hydraulic path 1a, and the second main hydraulic path 1b.

[0076] The brake fluid pressure input to the hydraulic control device 2 communicates with the wheel fluid pressure path B via the pressure reducing valve R of the output fluid pressure path A and is directly transmitted to the wheel cylinder W via the inlet valve 43 . This brakes the wheels (not shown).

[0077] Furthermore, the control device 4 compares the brake hydraulic pressure generated by the assist cylinder 30 (the hydraulic pressure detected by the second pressure sensor P2) with the required hydraulic pressure corresponding to the amount of operation on the brake pedal BP. If this comparison indicates that the brake hydraulic pressure needs to be increased to a high hydraulic pressure range, such as for emergency braking, the control device 4 can instruct the control device 9 to drive the pump 45, thereby performing assist pressure control to increase the brake hydraulic pressure in the wheel hydraulic path B. In this case, the driving current of the pressure reducing valve R or the motor M can be appropriately set based on the required hydraulic pressure corresponding to the amount of operation on the brake pedal BP.

[0078] When the brake pedal BP is released, the electric motor 36 of the assist cylinder 30 is reversely driven by the control device 4. This reduces the generated hydraulic pressure in the assist cylinder 30 and reduces the pressure in the bottom-side pressure chamber 34a and the opening-side pressure chamber 34b of the assist cylinder 30. Consequently, the brake fluid pressure transmitted to the wheel cylinder W returns to the assist cylinder 30 via the wheel hydraulic path B, the output hydraulic path A, the first main hydraulic path 1a, the second main hydraulic path 1b, the first communication path 3a, and the second communication path 3b. This return of brake fluid ensures a sufficient supply of brake fluid for subsequent pressurization.

[0079] (Anti-lock brake control of hydraulic control device) Anti-lock braking control by the hydraulic control device 2 is executed when the wheels are about to lock by appropriately selecting whether to reduce, increase, or maintain the brake fluid pressure acting on the wheel cylinders W. The control device 9 determines whether to select a decompression mode, a pressure increase mode, or a pressure hold mode based on the wheel speeds obtained from wheel speed sensors (not shown).

[0080] While the brake pedal BP is being depressed, that is, when the brake hydraulic pressure generated by the assist cylinder 30 is acting on the hydraulic control device 2 , if the wheels are about to fall into a locked state, the control device 9 starts the anti-lock brake control. When the pressure reduction mode is selected in the anti-lock brake control, the control device 9 energizes the inlet valve 43 and the outlet valve 44. Consequently, the inlet valve 43 is closed and the outlet valve 44 is open. Consequently, the brake fluid in the wheel hydraulic path B, which communicates with the wheel cylinder W, is discharged from the outlet valve 44 to the open path E. This reduces the brake fluid pressure acting on the wheel cylinder W. The brake fluid discharged into the open path E flows into the reservoir 48. The brake fluid flowing into the reservoir 48 is then drawn in and returned to the hydraulic pressure generating device 1 through the discharge path D, the wheel hydraulic path B, and the output hydraulic path A.

[0081] When the pressure-boosting mode is selected during anti-lock braking control, the control device 9 demagnetizes the inlet valve 43 and the outlet valve 44. This opens the inlet valve 43 and closes the outlet valve 44. Consequently, the brake fluid pressure generated by the assist cylinder 30 boosts the brake fluid pressure acting on the wheel cylinder W via the wheel hydraulic pressure path B.

[0082] When the hold mode is selected during anti-lock braking control, the control device 9 energizes the inlet valve 43 and deenergizes the outlet valve 44. Consequently, the inlet valve 43 and the outlet valve 44 are both closed. This confines the brake fluid within the flow path enclosed by the inlet valve 43, the outlet valve 44, and the wheel cylinder W. As a result, the brake fluid pressure is maintained constant.

[0083] (Automatic Braking Control) When the driver does not step on the brake pedal BP, the control device 4 determines that the wheels should be braked, and performs automatic braking control to assist in stabilizing the behavior of the vehicle. Figure 3 As shown, similar to normal brake control, the assist cylinder 30 is driven by the control device 4 and the first and second stop valves 8a and 8b are in an open state, and the brake hydraulic pressure generated by the assist cylinder 30 is transmitted to the hydraulic control device 2 side.

[0084] In the hydraulic control device 2, the control device 9 demagnetizes the pressure reducing valve R and opens it, demagnetizes the inlet valve 43 and opens it, and demagnetizes the outlet valve 44 and closes it. Consequently, the brake fluid pressure generated by the assist cylinder 30 is transmitted from the output fluid pressure path A of the hydraulic control device 2 through the wheel fluid pressure path B to the wheel cylinder W, braking the wheels.

[0085] Furthermore, by energizing the inlet valve 43 to a closed state and the outlet valve 44 to an open state, the brake fluid pressure acting on the wheel cylinder W can be discharged from the outlet valve 44 to the open path E. In this case, the brake fluid discharged to the open path E is also temporarily stored in the reservoir 48, then sucked into the pump 45, and returned to the hydraulic pressure generating device 1 through the discharge path D, the wheel hydraulic pressure path B, and the output hydraulic pressure path A.

[0086] When such automatic braking control is performed, if the wheels are about to fall into a locked state, the anti-lock braking control is executed by the hydraulic control device 2 in the same manner as the above-mentioned anti-lock braking control. Automatic braking control is also performed when the hydraulic control device 2 is not in operation, for example, when the hydraulic control device 2 fails. Anti-lock braking control when the automatic braking control is performed when the hydraulic control device 2 is not in operation will be described later.

[0087] (Fluid suction control in anti-lock brake control) The fluid suction control is a control for sucking brake fluid from the reservoir tank 15 to ensure that brake fluid is maintained in the bottom-side pressure chamber 34a and the open-side pressure chamber 34b of the assist cylinder 30. Furthermore, the bottom-side pressure chamber 34a and the open-side pressure chamber 34b ensure a sufficient amount of brake fluid for normal braking (brake control with the first and second stop valves 8a and 8b open), except for special braking operations such as emergency braking or frequent, continuous anti-lock braking operations.

[0088] For example, the fluid suction control is performed when the control device 4 determines that the required hydraulic pressure corresponding to the amount of operation of the brake pedal BP cannot be provided by the maximum stroke of the slave pistons 32a, 32b of the assist cylinder 30. Here, the maximum stroke can be set, for example, as the distance the slave pistons 32a, 32b move from their initial positions to a position immediately before contact with the bottom of the third cylinder bore 31 during pressurization.

[0089] If it is determined that the brake fluid required for pressure increase cannot be supplied by the maximum stroke of the slave pistons 32a and 32b, the slave pistons 32a and 32b are temporarily returned in the decompression direction before re-pressurization. The return amount in this case can be calculated, for example, based on a map pre-set in the control device 4. Furthermore, during this re-pressurization, the control device 4 de-energizes the first and second stop valves 8a and 8b, controlling them to a closed state.

[0090] When the electric motor 36 is driven in the reverse direction (return direction) by the control device 4, the slave pistons 32a and 32b return in the decompression direction, maintaining the hydraulic pressure in the wheel cylinder W. This reduces the pressure in the bottom-side pressure chamber 34a and the opening-side pressure chamber 34b, creating a negative pressure state. Consequently, brake fluid is drawn from the reservoir 15 through the first and second slave cylinder supply paths 1h and 1i into the slave cylinder 30. The amount of brake fluid drawn into the slave cylinder 30 corresponds to the amount of brake fluid returned by the slave pistons 32a and 32b.

[0091] When the return amount corresponding to the return amount of the movable pistons 32a and 32b reaches the target value, the control device 4 controls the first and second stop valves 8a and 8b to open. The control device 4 then drives the electric motor 36 to rotate forward again in the pressurizing direction. This further boosts the brake fluid pressure in the wheel cylinders W to the fluid pressure corresponding to the driver's desired pressure.

[0092] When the brake pedal BP is released, the control device 4 reversely rotates the electric motor 36 in the pressure reducing direction (return direction). This causes brake fluid to be drawn from the reservoir 15 through the first and second auxiliary cylinder supply paths 1h and 1i into the auxiliary cylinder 30, terminating the fluid suction control.

[0093] (Anti-lock brake control when the hydraulic control device is not in operation) Next, we will describe the case where automatic braking control is executed when the hydraulic control device 2 is inoperative (e.g., when the hydraulic control device 2 fails). When the hydraulic control device 2 is inoperative and the wheels are about to lock during automatic braking control, the control device 4 executes anti-lock braking control.

[0094] During the anti-lock brake control when the hydraulic control device 2 is not in operation and the automatic brake control is being executed, when the control device 4 selects the decompression mode of the brake output system K2, for example, Figure 4 As shown, the control device 4 de-energizes the second master stop valve 7 b to open the valve, and de-energizes the second stop valve 8 b to close the valve.

[0095] In this way, the brake fluid acting on the wheel cylinder W of the brake output system K2 is discharged to the second main hydraulic path 1b on the hydraulic pressure generating device 1 through the wheel hydraulic path B and the output hydraulic path A of the hydraulic control device 2. The brake fluid discharged to the second main hydraulic path 1b flows into the master cylinder 10 through the second master cutoff valve 7b and returns to the reservoir 15. As a result, the brake fluid pressure acting on the wheel cylinder W of the brake output system K2 is reduced.

[0096] In addition, during the anti-lock brake control when the hydraulic control device 2 is not in operation and the automatic brake control is being executed, when the control device 4 selects the holding mode of the brake output system K2, for example, Figure 5 As shown, the control device 4 sets the second main stop valve 7b to an energized state and closed, and sets the second stop valve 8b to a de-energized state and closed.

[0097] Thus, the brake fluid is confined in the flow path closed by the second master cut valve 7b, the second shutoff valve 8b, and the wheel cylinder W of the brake output system K2. As a result, the brake fluid pressure of the brake output system K2 is maintained constant.

[0098] Furthermore, during antilock brake control when the hydraulic control device 2 is inactive and automatic brake control is being executed, if the control device 4 selects a pressure reduction mode for both brake output systems K1 and K2 , pressure reduction can also be performed by driving the assist cylinder 30 . In this case, the control device 4 energizes the first and second main stop valves 7a and 7b to close them, and energizes the first and second stop valves 8a and 8b to open them. The control device 4 then drives the electric motor 36 in the reverse direction (return direction) in the pressure reducing direction.

[0099] In this way, the brake fluid acting on the wheel cylinders W of the brake output systems K1 and K2 returns through the first main hydraulic path 1a, the second main hydraulic path 1b, the first communication path 3a, and the second communication path 3b to the bottom-side pressure chamber 34a and the opening-side pressure chamber 34b of the assist cylinder 30. As a result, the brake fluid pressure acting on the wheel cylinders W of the brake output systems K1 and K2 is reduced.

[0100] Specifically, the control device 4 can select the decompression mode for one of the brake output systems K1 and K2 and the holding mode for the other.

[0101] When the control device 4 selects, for example, the decompression mode or the holding mode of the brake output system K1, the first and second master stop valves 7a and 7b are energized and closed, the first stop valve 8a is energized and opened, and the second stop valve 8b is de-energized and closed. The control device 4 then drives the electric motor 36 in the reverse direction (return direction) of the decompression direction.

[0102] In this way, the brake fluid acting on the wheel cylinder W of the brake output system K1 returns to the bottom-side pressure chamber 34a of the assist cylinder 30 through the first main hydraulic path 1a and the first communication path 3a. On the other hand, the brake fluid is confined in the flow path closed by the second master stop valve 7b, the second shutoff valve 8b, and the wheel cylinder W of the brake output system K2. As a result, the brake hydraulic pressure acting on the wheel cylinder W of the brake output system K1 is reduced, and the brake hydraulic pressure of the brake output system K2 is maintained constant.

[0103] Next, we will describe the anti-lock braking control performed when the brake pedal BP is operated while the hydraulic control device 2 is inactive. Similar to the aforementioned anti-lock braking control, the anti-lock braking control performed when the hydraulic control device 2 is inactive and the brake pedal BP is being operated is executed when the wheels are about to lock. Furthermore, the control device 4 energizes the first and second master stop valves 7a and 7b, respectively, and closes them.

[0104] In the anti-lock brake control when the hydraulic control device 2 is not in operation and the brake pedal BP is being operated, when the control device 4 selects the decompression mode of both the brake output systems K1 and K2, for example, Figure 9 As shown, the control device 4 energizes the first and second stop valves 8a, 8b, and opens them. The electric motor 36 is then driven in the reverse direction (return direction) to reduce pressure. This causes the brake fluid in the brake output system K1 to return from the first main hydraulic path 1a through the first communication path 3a to the bottom-side pressure chamber 34a of the assist cylinder 30, while the brake fluid in the brake output system K2 to return from the second main hydraulic path 1b through the second communication path 3b to the open-side pressure chamber 34b of the assist cylinder 30.

[0105] Thus, in a state where the brake pedal BP is operated, the brake fluid pressures acting on the wheel cylinders W of the brake output systems K1 and K2 are respectively reduced.

[0106] In addition, during the anti-lock brake control when the hydraulic control device 2 is not in operation and the brake pedal BP is being operated, when the control device 4 selects the holding mode of the brake output system K2, for example, Figure 10 As shown, the second stop valve 8b is de-energized and closed by the control device 4 .

[0107] Thus, the brake fluid is confined in the flow path closed by the second master cut valve 7b, the second shutoff valve 8b, and the wheel cylinder W of the brake output system K2. As a result, the brake fluid pressure of the brake output system K2 is maintained constant.

[0108] In addition, during the anti-lock brake control when the hydraulic control device 2 is not in operation and the brake pedal BP is being operated, when the control device 4 selects the holding mode of both the brake output systems K1 and K2, for example, Figure 11 As shown, the first stop valve 8a and the second stop valve 8b are de-energized by the control device 4 and are closed.

[0109] In this way, the brake fluid is confined within the flow path enclosed by the first master cut valve 7a, the first shutoff valve 8a, and the wheel cylinder W of the brake output system K1, while the brake fluid is confined within the flow path enclosed by the second master cut valve 7b, the second shutoff valve 8b, and the wheel cylinder W of the brake output system K2. As a result, the brake hydraulic pressures of the brake output systems K1 and K2 are each maintained constant.

[0110] (Liquid Suction Control When the Hydraulic Control Device 2 Is Not Operating) The following describes a case where the fluid suction control is performed during anti-lock braking control when the hydraulic control device 2 is inactive and automatic braking control is in progress. The fluid suction control in this case is performed in a mode where both the first and second stop valves 8a and 8b are de-energized and closed.

[0111] As a mode in which both the first stop valve 8a and the second stop valve 8b are in a non-excited state, for example Figure 6 As shown, a mode for decompressing both the brake output systems K1 and K2 can be listed. When the decompression mode is selected for both the brake output systems K1 and K2, the control device 4 de-energizes the first and second master stop valves 7a and 7b, respectively, to open the valves, and de-energizes the first and second stop valves 8a and 8b, respectively, to close the valves.

[0112] In this way, the brake fluid in the brake output systems K1 and K2 is discharged to the first main hydraulic path 1a and the second main hydraulic path 1b on the hydraulic pressure generating device 1 through the wheel hydraulic path B and the output hydraulic path A of the hydraulic control device 2, respectively. The brake fluid discharged to the first main hydraulic path 1a and the second main hydraulic path 1b then flows into the master cylinder 10 through the first master stop valve 7a and the second master stop valve 7b, respectively, and returns to the reservoir 15.

[0113] On the other hand, the electric motor 36 is driven to rotate in the reverse direction (return direction) by the control device 4 , and the slave pistons 32 a and 32 b are temporarily returned in the decompression direction. As a result, the bottom-side pressure chamber 34a and the opening-side pressure chamber 34b are depressurized to a negative pressure state, and brake fluid is drawn from the reservoir 15 through the first and second auxiliary cylinder supply paths 1h and 1i into the auxiliary cylinder 30. The amount of brake fluid drawn into the auxiliary cylinder 30 corresponds to the amount of return of the slave pistons 32a and 32b.

[0114] In addition, as a mode in which both the first stop valve 8a and the second stop valve 8b are in a non-excited state, for example, Figure 7 As shown, the decompression mode is selected for the brake output system K1, while the holding mode is selected for the brake output system K2. When the brake output system K1 is in the decompression mode, the control device 4 de-energizes the first master stop valve 7a and opens it, while the first shutoff valve 8a is de-energized and closed. Furthermore, when the holding mode is selected for the brake output system K2, the control device 4 energizes the second master stop valve 7b and closes it, while the second shutoff valve 8b is de-energized and closed.

[0115] In this way, the brake fluid acting on the wheel cylinder W of the brake output system K1 is discharged to the first main hydraulic path 1a on the hydraulic generating device 1 side through the wheel hydraulic path B and the output hydraulic path A of the hydraulic control device 2 in the same way as described above, flows into the master cylinder 10 through the first master stop valve 7a, and returns to the fluid reservoir 15. Furthermore, the brake fluid is confined in the flow path closed by the second master cut valve 7b, the second shutoff valve 8b, and the wheel cylinder W of the brake output system K2. As a result, the brake fluid pressure of the brake output system K2 is maintained constant.

[0116] In this state, the electric motor 36 is driven in the reverse direction (return direction) by the control device 4, reducing the pressure in the bottom-side pressure chamber 34a and the opening-side pressure chamber 34b to a negative pressure state. As a result, brake fluid is drawn from the reservoir 15 through the first assist cylinder supply path 1h and the second assist cylinder supply path 1i into the assist cylinder 30.

[0117] In addition, as a mode in which both the first stop valve 8a and the second stop valve 8b are in a non-excited state, for example, Figure 8 As shown, the case where both the brake output systems K1 and K2 are in the holding mode can be exemplified. When both the brake output systems K1 and K2 are in the holding mode, the control device 4 de-energizes the first master stop valve 7a and the second master stop valve 7b to open them, and de-energizes the first stop valve 8a and the second stop valve 8b to close them.

[0118] In this state, similarly to the above, the control device 4 drives the electric motor 36 in reverse rotation in the decompression direction (return direction), and the brake fluid is absorbed into the bottom side pressure chamber 34a and the opening side pressure chamber 34b in the negative pressure state.

[0119] According to the vehicle brake system 100 of the present embodiment described above, even when the hydraulic control device 2 is inoperative, the control device 4 controls the auxiliary cylinder 30, the first master stop valve 7a, the second master stop valve 7b, the first stop valve 8a, and the second stop valve 8b of the hydraulic pressure generating device 1, thereby enabling anti-lock braking control. Therefore, even if the hydraulic control device 2 fails, for example, anti-lock braking control can be executed in response to wheel slip without locking the wheels.

[0120] Furthermore, the first and second master stop valves 7a and 7b are normally open on-off valves, while the first and second stop valves 8a and 8b are normally closed on-off valves. Therefore, with this simple system configuration, anti-lock braking control can be performed when the hydraulic control device 2 is not in operation, thereby reducing costs.

[0121] In addition, when the hydraulic control device 2 is not in operation, the brake hydraulic pressure generated by the bottom side pressure chamber 34a and the open side pressure chamber 34b of the auxiliary cylinder 30 can be transmitted to the wheel brakes of the first main hydraulic path 1a and the second main hydraulic path 1b respectively, thereby enabling appropriate anti-lock braking control.

[0122] In addition, in the anti-lock braking control in which the hydraulic control device 2 is not in operation and the automatic braking control is in progress, by controlling the first master stop valve 7a, the second master stop valve 7b, the first stop valve 8a, the second stop valve 8b and the auxiliary cylinder 30, the hydraulic path of the decompression object can be appropriately decompressed, the hydraulic path of the pressurization object can be appropriately pressurized, and the hydraulic path of the maintenance object can be appropriately maintained.

[0123] Furthermore, during anti-lock braking control when the hydraulic control device 2 is not in operation, the first and second master stop valves 7a, 7b of the hydraulic path to be depressurized are opened, and the first and second stop valves 8a, 8b of the hydraulic path to be depressurized are closed. This allows brake fluid to be returned to the master cylinder 10 through the opened first and second master stop valves 7a, 7b. This allows the hydraulic path to be depressurized to be appropriately depressurized.

[0124] Furthermore, the first main hydraulic path 1a communicates with the front wheel brakes, while the second main hydraulic path 1b communicates with the rear wheel brakes. This allows for separate anti-lock braking control of the front and rear wheels when the hydraulic control device 2 is inactive. This allows for optimal front-to-rear braking force distribution tailored to the vehicle's vehicle type.

[0125] (Second embodiment) Next, refer to Figure 12 、 Figure 13 The vehicle brake system of the second embodiment is described below. This embodiment differs from the first embodiment in that a first return flow path 1a1 communicating with the first main hydraulic path 1a and a second return flow path 1b1 communicating with the second main hydraulic path 1b correspond to each other.

[0126] Downstream of the first master stop valve 7a, a first return flow path 1a1 branches from the first main hydraulic path 1a to the first assist cylinder supply path 1h. A first on-off valve 13a is provided midway along the first return flow path 1a1. The first on-off valve 13a is an on-off valve (on-off valve) comprised of a normally closed solenoid valve.

[0127] Downstream of the second master stop valve 7b, a second return flow channel 1b1 branches from the second main hydraulic path 1b to the first return flow channel 1a1. A second on-off valve 13b is provided midway along the second return flow channel 1b1. Second on-off valve 13b is an on-off valve (on-off valve) comprised of a normally closed solenoid valve.

[0128] The first on-off valve 13a and the second on-off valve 13b are opened and closed by the control of the control device 4. Specifically, when the pressure reducing mode is selected in the anti-lock brake control while the hydraulic control device 2 is inactive and the brake pedal BP is being operated, the first on-off valve 13a and the second on-off valve 13b are opened.

[0129] The first on-off valve 13a is opened by the control device 4 during the decompression mode of the anti-lock braking control of the brake output system K1. The second on-off valve 13b is opened by the control device 4 during the decompression mode of the anti-lock braking control of the brake output system K2.

[0130] Next, the anti-lock brake control when the hydraulic control device 2 is not in operation and the brake pedal BP is being operated will be described. In this embodiment, the brake fluid can be returned to the reservoir 15 through the first return flow path 1a1 and the second return flow path 1b1.

[0131] In the anti-lock brake control when the hydraulic control device 2 is not in operation and the brake pedal BP is being operated, for example, when the control device 4 selects a mode for reducing the pressure on the brake output system K1, as shown in FIG. Figure 13 As shown, the control device 4 de-energizes the first stop valve 8a to close the valve, and energizes the first on-off valve 13a to open the valve.

[0132] Thus, the brake fluid acting on the wheel cylinder W of the brake output system K1 is discharged from the first main hydraulic path 1 a to the first return flow path 1 a 1 , flows into the master cylinder 10 through the first assist cylinder supply path 1 h , and returns to the reservoir 15 .

[0133] Thus, in a state where the brake pedal BP is operated, the brake fluid pressure acting on the wheel cylinder W of the brake output system K1 is reduced.

[0134] In addition, during the anti-lock brake control when the hydraulic control device 2 is not in operation and the brake pedal BP is being operated, for example, when the control device 4 selects a mode for reducing the pressure on the brake output systems K1 and K2, as shown in FIG. Figure 14 As shown, the control device 4 de-energizes the first and second stop valves 8a and 8b to close the valves, and energizes the first and second on-off valves 13a and 13b to open the valves.

[0135] In this manner, the brake fluid acting on the wheel cylinder W of the brake output system K1 is discharged from the first main hydraulic path 1a to the first return flow path 1a1, flows into the master cylinder 10 through the first auxiliary cylinder supply path 1h, and returns to the reservoir 15. Meanwhile, the brake fluid acting on the wheel cylinder W of the brake output system K2 is discharged from the second main hydraulic path 1b to the second return flow path 1b1, and flows from the first return flow path 1a1 to the master cylinder 10 through the first auxiliary cylinder supply path 1h, and returns to the reservoir 15.

[0136] Thus, while the brake pedal BP is operated, the brake fluid pressures acting on the wheel cylinders W of the brake output systems K1 and K2 are also reduced.

[0137] The vehicle brake system 100A of the present embodiment described above achieves the same operational advantages as those described in the first embodiment. Furthermore, in the vehicle brake system 100A of the present embodiment, during antilock braking control when the hydraulic control device 2 is inoperative, brake fluid is returned to the master cylinder 10 via the first return flow path 1a1 or the second return flow path 1b1, thereby appropriately reducing the pressure in the hydraulic paths to be reduced. In other words, even when the brake fluid pressure generated by the master cylinder 10 acts on the first and second main hydraulic paths 1a and 1b due to operation of the brake pedal BP, the brake fluid can be returned to the master cylinder 10 via the first and second return flow paths 1a1 and 1b1.

[0138] In this embodiment, the terminal end of the first return flow passage 1a1 is connected to the first assist cylinder supply path 1h, but the present invention is not limited thereto and may be connected to the tank communication path 1e. Alternatively, the return flow may be directly to the tank 15.

[0139] While the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments and can be appropriately modified within the scope of the present invention. For example, in the first and second embodiments, the master cylinder 10 is shown to have two pressure chambers, namely, a bottom-side pressure chamber 14a and an open-side pressure chamber 14b. However, the present invention is not limited thereto and may have one pressure chamber configured to branch from the pressure chamber into a first main hydraulic path 1a and a second main hydraulic path 1b through a common hydraulic path.

[0140] In addition, in the first and second embodiments, the auxiliary cylinder 30 is shown to have two pressure chambers, namely the bottom side pressure chamber 34a and the open side pressure chamber 34b, but is not limited to this. It can also have one auxiliary cylinder pressure chamber, which is constructed to branch from the auxiliary cylinder pressure chamber into a first connecting path 3a and a second connecting path 3b through a common hydraulic path.

[0141] Furthermore, in the first embodiment, the hydraulic pressure generating device 1 and the hydraulic pressure control device 2 are shown as being composed of two base bodies 1A and 1B. However, the present invention is not limited thereto and the hydraulic pressure generating device 1 may be composed of two base bodies, the base body 1A being divided. Alternatively, the hydraulic pressure generating device 1 and the hydraulic pressure control device 2 may be unified into a single base body.

[0142] Furthermore, in the first and second embodiments, two control devices 4 and 9 are shown, but the present invention is not limited thereto, and a single control device may control the hydraulic pressure generating device 1 and the hydraulic pressure control device 2 . [Explanation of Reference Numerals]

[0143] 1: Hydraulic generating device; 1a: first main hydraulic path (main hydraulic path); 1b: Second main hydraulic path (main hydraulic path); 1a1: first return flow channel (return flow channel); 1b1: Second return flow channel (return flow channel); 2: Hydraulic control device; 3a: first communication path (communication path); 3b: second communication path (communication path); 4, 9: control device; 7a: First main stop valve (main stop valve); 7b: Second main stop valve (main stop valve); 8a: First shut-off valve (shut-off valve); 8b: Second shut-off valve (shut-off valve); 10: Master cylinder; 14a: bottom side pressure chamber (pressure chamber); 14b: Open side pressure chamber (pressure chamber); 30: auxiliary cylinder; 34a: bottom side pressure chamber (auxiliary cylinder pressure chamber); 34b: Opening side pressure chamber (auxiliary cylinder pressure chamber); 36: Electric motor (electric actuator); 100, 100A: vehicle braking system; BP: Brake pedal (brake operating part)

Claims

1. A vehicle braking system comprising: a hydraulic pressure generating device including a master cylinder for generating brake hydraulic pressure according to an operation amount of a brake operating member and an auxiliary cylinder for generating brake hydraulic pressure by driving an electric actuator; and a hydraulic control device that controls the brake hydraulic pressure acting on the wheel brakes using the brake hydraulic pressure from the hydraulic pressure generating device; It is characterized in that The hydraulic pressure generating device includes: a main stop valve that opens and closes a main hydraulic path from the master cylinder to the hydraulic control device; a communication path that leads from the auxiliary cylinder to the main hydraulic path on the downstream side of the main stop valve; a stop valve that opens and closes the communication path; and a control device that controls the operation of the auxiliary cylinder, the main stop valve, and the stop valve. The main hydraulic path includes a first main hydraulic path communicating with at least one of the plurality of wheel brakes and a second main hydraulic path communicating with the remaining wheel brakes. The main stop valve, the communication path and the shutoff valve are respectively provided in the first main hydraulic path and the second main hydraulic path. When the hydraulic control device is not in operation, the control device generates brake hydraulic pressure from the auxiliary cylinder, and controls the main cut-off valve and the shut-off valve according to the first main hydraulic path and the second main hydraulic path respectively to perform anti-lock braking control according to the slip situation of the wheel.

2. The vehicle braking system according to claim 1, wherein: The main stop valve is a normally open on-off valve, and the shut-off valve is a normally closed on-off valve.

3. The vehicle braking system according to claim 1, wherein: The master cylinder has two pressure chambers and is configured to output hydraulic pressure generated in the two pressure chambers to the first main hydraulic path and the second main hydraulic path, respectively. The assist cylinder includes two assist cylinder pressure chambers, and is configured to be capable of outputting hydraulic pressure generated in the two assist cylinder pressure chambers to the first main hydraulic path and the second main hydraulic path, respectively.

4. The vehicle braking system according to claim 1, wherein: In the anti-lock braking control, when the brake hydraulic pressure of at least one of the first main hydraulic path and the second main hydraulic path is boosted, the main stop valve of the hydraulic path of the boosted object is closed and the shut-off valve of the hydraulic path of the boosted object is opened, so that the brake hydraulic pressure generated by the auxiliary cylinder acts on the hydraulic path of the boosted object.

5. The vehicle braking system according to claim 1, wherein: In the anti-lock braking control, when the brake hydraulic pressure of at least one of the first main hydraulic path and the second main hydraulic path is reduced in pressure, the main stop valve of the hydraulic path of the pressure reducing object is closed and the shut-off valve of the hydraulic path of the pressure reducing object is opened, and the piston of the auxiliary cylinder is driven and controlled in the pressure reducing direction through the electric actuator.

6. The vehicle braking system according to claim 1, wherein: In the antilock brake control, when maintaining the brake hydraulic pressure in at least one of the first main hydraulic path and the second main hydraulic path, the master cut valve of the hydraulic path to be maintained is closed, and the shutoff valve of the hydraulic path to be maintained is closed.

7. The vehicle braking system according to claim 1, wherein: In the anti-lock braking control, when the brake hydraulic pressure of at least one of the first main hydraulic path and the second main hydraulic path is reduced in pressure, the main stop valve of the hydraulic path of the pressure-reducing object is opened and the shut-off valve of the hydraulic path of the pressure-reducing object is closed, and the brake fluid is returned to the master cylinder side through the opened main stop valve.

8. The vehicle braking system according to claim 1, wherein: have: a return flow passage leading from the wheel brake to the atmospheric pressure side of the master cylinder or a reservoir; and an on-off valve, which opens and closes the return flow channel, In the antilock brake control, when reducing the brake fluid pressure in at least one of the first main fluid pressure path and the second main fluid pressure path, the master cut valve and the shutoff valve of the fluid pressure path to be reduced are closed, and the on-off valve is opened.

9. The vehicle braking system according to claim 1, wherein: The first main hydraulic path communicates with the wheel brake on the front wheel side of the front and rear wheels of the vehicle, and the second main hydraulic path communicates with the wheel brake on the rear wheel side.

10. The vehicle braking system according to claim 1, wherein: The control device is capable of performing a fluid suction control for absorbing brake fluid on the assist cylinder during the anti-lock brake control. When the liquid suction control is required, the shutoff valve is closed and the piston of the assist cylinder is driven and controlled in the pressure reducing direction by the electric actuator.

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