Vehicle Brake Systems

Abstract

Provided is a vehicle brake system capable of executing anti-lock brake control even when a hydraulic pressure control device is not operating. A hydraulic pressure generation device (1) is provided with master cut valves (7a, 7b) that open and close main hydraulic pressure paths (1a, 1b) leading from a master cylinder (10) to a hydraulic pressure control device (2), communication paths (3a, 3b) that lead from a slave cylinder (30) to the main hydraulic pressure paths (1a, 1b), cutoff valves (8a, 8b) that open and close the communication paths (3a, 3b), and a control device (4). When the hydraulic pressure control device (2) is not operating, the control device (4) causes brake fluid pressure to be generated from the slave cylinder (30) and controls the master cut valves (7a, 7b) and the cutoff valves (8a, 8b) for both the first main hydraulic pressure path (1a) and the second main hydraulic pressure path (1b) in accordance with wheel slippage to perform anti-lock brake control.

Description

[Technical Field]

[0001] The present invention relates to a brake system for a vehicle. [Background technology]

[0002] Conventionally, a vehicle brake system has been known that includes a master cylinder that generates brake fluid pressure according to the force applied to the brake pedal, a slave cylinder that generates brake fluid pressure by driving an electric actuator, and a fluid pressure control device that helps stabilize the vehicle's behavior by controlling the brake fluid pressure acting on the wheel brakes (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-210879 Summary of the Invention [Problem to be solved by the invention]

[0004] The vehicle brake system of Patent Document 1 is configured to control the brake fluid pressure acting on the wheel brakes by a fluid pressure control device, and therefore cannot perform antilock brake control when the fluid pressure control device is not in operation.

[0005] SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide a vehicle brake system that can perform antilock brake control even when the hydraulic pressure control device is not in operation. [Means for solving the problem]

[0006] To achieve the above object, the present invention provides a vehicle brake system including a hydraulic pressure generating device having a master cylinder that generates brake hydraulic pressure in response to the amount of operation of a brake operator and a slave 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 wheel brakes using the brake hydraulic pressure from the hydraulic pressure generating device. The hydraulic pressure generating device includes a master cutoff valve that opens and closes a main hydraulic pressure passage leading from the master cylinder to the hydraulic pressure control device, a communication passage leading from the slave cylinder to the main hydraulic pressure passage downstream of the master cutoff valve, a shutoff valve that opens and closes the communication passage, and a control device that controls operation of the slave cylinder, the master cutoff valve, and the shutoff valve. The main hydraulic pressure passage includes a first main hydraulic pressure passage leading to at least one of the plurality of wheel brakes, and a second main hydraulic pressure passage leading to the remaining wheel brakes. The master cutoff valve, the communication passage, and the shutoff valve are provided in the first main hydraulic pressure passage and the second main hydraulic pressure passage, respectively. The control device is characterized in that when the hydraulic control device is not operating, brake hydraulic pressure is generated from the slave cylinder, and the control device performs anti-lock brake control by controlling the master cut valve and the shut-off valve for each of the first main hydraulic pressure line and the second main hydraulic pressure line depending on the wheel slip condition.

[0007] In the vehicle brake system of the present invention, when the hydraulic pressure control device is not in operation, the control device controls the slave cylinder, master cut valve, and shutoff valve of the hydraulic pressure generator, thereby enabling antilock brake control to be performed. Therefore, even if the hydraulic pressure control device fails, for example, antilock brake control can be performed depending on the wheel slippage.

[0008] It is also preferable that the master cut valve is a normally open on-off valve, and the shutoff valve is a normally closed on-off valve.

[0009] According to this configuration, the antilock brake control can be performed when the hydraulic pressure control device is not in operation with a simple system configuration using a normally open on-off valve and a normally closed on-off valve, thereby reducing costs.

[0010] Preferably, the master cylinder has two pressure chambers and is configured to be able to output hydraulic pressures generated in the two pressure chambers to the first main hydraulic line and the second main hydraulic line, respectively.Furthermore, it is preferable that the slave cylinder has two slave cylinder pressure chambers and is configured to be able to output hydraulic pressures generated in the two slave cylinder pressure chambers to the first main hydraulic line and the second main hydraulic line, respectively.

[0011] According to this configuration, when the hydraulic pressure control device is not in operation, antilock brake control can be preferably achieved for each of the first main hydraulic pressure path and the second main hydraulic pressure path by the brake hydraulic pressure generated in the two slave cylinder pressure chambers. Therefore, a vehicle brake system can be obtained that has excellent brake fluid transmission performance and can suitably achieve antilock brake control when the hydraulic pressure control device is not in operation.

[0012] Furthermore, when increasing the brake fluid pressure in at least one of the first main hydraulic line and the second main hydraulic line during the antilock brake control, it is preferable to close the master cut valve of the hydraulic line to be increased and open the shut-off valve of the hydraulic line to be increased, and to apply the brake fluid pressure generated in the slave cylinder to the hydraulic line to be increased.

[0013] According to this configuration, during antilock brake control when the hydraulic pressure control device is not in operation, the master cut valve, the shutoff valve, and the slave cylinder can be controlled to preferably increase the pressure in the hydraulic pressure path that is the target of pressure increase.

[0014] Furthermore, when reducing the brake fluid pressure in at least one of the first main hydraulic line and the second main hydraulic line during the antilock brake control, it is preferable to close the master cut valve of the hydraulic line to be reduced, open the shut-off valve of the hydraulic line to be reduced, and drive and control the piston of the slave cylinder in the direction of reduction by the electric actuator.

[0015] According to this configuration, during antilock brake control when the hydraulic pressure control device is not in operation, the master cut valve, the shutoff valve, and the slave cylinder can be controlled to suitably reduce the pressure in the hydraulic pressure path that is the target of pressure reduction.

[0016] Furthermore, when maintaining the brake fluid pressure of at least one of the first main hydraulic line and the second main hydraulic line during the antilock brake control, it is preferable to close the master cut valve of the hydraulic line to be maintained and to close the shut-off valve of the hydraulic line to be maintained.

[0017] According to this configuration, during antilock brake control when the hydraulic pressure control device is not in operation, the master cut valve, the shutoff valve, and the slave cylinder can be controlled to suitably maintain the hydraulic pressure path to be maintained.

[0018] Furthermore, when reducing the brake fluid pressure in at least one of the first main hydraulic line and the second main hydraulic line during the antilock brake control, it is preferable to open the master cut valve of the hydraulic line to be reduced, close the shut-off valve of the hydraulic line to be reduced, and return the brake fluid to the master cylinder side through the open master cut valve.

[0019] With this configuration, during anti-lock brake control when the hydraulic control device is not operating, the brake fluid in the hydraulic line to be reduced in pressure can be returned to the master cylinder side, making it possible to reduce the pressure in one hydraulic line while increasing the pressure in the other hydraulic line.

[0020] In addition, it is preferable that the brake fluid pressure control device further includes a return passage that connects the wheel brake to the atmospheric pressure side of the master cylinder or to a reservoir tank, and an on-off valve that opens and closes the return passage. In this case, when reducing the brake fluid pressure in at least one of the first main hydraulic line and the second main hydraulic line during the antilock brake control, it is preferable that the master cut valve and the shutoff valve in the hydraulic line to be reduced are closed and the on-off valve is opened.

[0021] With this configuration, during antilock brake control when the hydraulic pressure control device is not operating, the brake fluid can be returned to the atmospheric pressure side of the master cylinder or to the reservoir tank through the return flow path. In other words, even when the brake operator is operated and brake fluid pressure generated in the master cylinder is acting on the first main hydraulic pressure line and the second main hydraulic pressure line, the pressure in at least one of the first main hydraulic pressure line and the second main hydraulic pressure line can be reduced.

[0022] Preferably, the first main hydraulic pressure line is connected to the wheel brake on the front wheel side of the front and rear wheels of the vehicle, and the second main hydraulic pressure line is connected to the wheel brake on the rear wheel side.

[0023] With this configuration, the front and rear wheels can be subjected to antilock brake control separately, and braking force distribution between the front and rear of the vehicle can be optimally achieved according to the vehicle type.

[0024] In addition, the control device is preferably capable of executing fluid suction control for suctioning brake fluid into the slave cylinder during the antilock brake control, and when it is necessary to execute fluid suction control, it is preferable that the control device closes the shutoff valve and drives the piston of the slave cylinder in a pressure reducing direction by the electric actuator.

[0025] In this configuration, during antilock brake control when the hydraulic pressure control device is not in operation, when the shutoff valve is closed and the slave piston is driven in the decompression direction, the slave cylinder's pressure chamber becomes negative pressure, causing brake fluid to be sucked into the slave cylinder from the upstream device. This fluid suction control allows brake fluid to be replenished into the slave cylinder pressure chamber for re-pressurization, ensuring sufficient brake fluid for pressure increase. This results in a brake system that can increase hydraulic pressure to a high range without increasing the size of the slave cylinder. [Effects of the Invention]

[0026] The vehicle brake system of the present invention can perform antilock brake control when the hydraulic pressure control device is not in operation. [Brief explanation of the drawings]

[0027] [Figure 1] 1 is a hydraulic circuit diagram showing a vehicle brake system according to a first embodiment of the present invention. [Figure 2] 2 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. FIG. [Figure 3] 2 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. FIG. [Figure 4] 3 is a diagram showing the flow of brake fluid during antilock brake control when automatic brake control is in operation and the hydraulic pressure control device is not in operation in the vehicle brake system according to the first embodiment of the present invention. FIG. [Figure 5] 3 is a diagram showing the flow of brake fluid during antilock brake control when automatic brake control is in operation and the hydraulic pressure control device is not in operation in the vehicle brake system according to the first embodiment of the present invention. FIG. [Figure 6] 3 is a diagram showing the flow of brake fluid during fluid suction control when automatic brake control is in operation and the hydraulic pressure control device is not in operation in the vehicle brake system according to the first embodiment of the present invention. FIG. [Figure 7] 3 is a diagram showing the flow of brake fluid during fluid suction control when automatic brake control is in operation and the hydraulic pressure control device is not in operation in the vehicle brake system according to the first embodiment of the present invention. FIG. [Figure 8] 3 is a diagram showing the flow of brake fluid during fluid suction control when automatic brake control is in operation and the hydraulic pressure control device is not in operation in the vehicle brake system according to the first embodiment of the present invention. FIG. [Figure 9] 3 is a diagram showing the flow of brake fluid during antilock brake control when the brake pedal is being operated and the hydraulic pressure control device is not in operation in the vehicle brake system according to the first embodiment of the present invention. FIG. [Figure 10] 3 is a diagram showing the flow of brake fluid during antilock brake control when the brake pedal is being operated and the hydraulic pressure control device is not in operation in the vehicle brake system according to the first embodiment of the present invention. FIG. [Figure 11] 3 is a diagram showing the flow of brake fluid during antilock brake control when the brake pedal is being operated and the hydraulic pressure control device is not in operation in the vehicle brake system according to the first embodiment of the present invention. FIG. [Figure 12] FIG. 5 is a hydraulic circuit diagram showing a vehicle brake system according to a second embodiment of the present invention. [Figure 13] 10 is a diagram showing the flow of brake fluid in a pressure reduction mode of antilock brake control when the brake pedal is being operated and the hydraulic pressure control device is not in operation in a vehicle brake system according to a second embodiment of the present invention. FIG. [Figure 14] 10 is a diagram showing the flow of brake fluid in a pressure reduction mode of antilock brake control when the brake pedal is being operated and the hydraulic pressure control device is not in operation in a vehicle brake system according to a second embodiment of the present invention. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0028] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings shown below, the same components are designated by the same reference numerals, and redundant description will be omitted. The vehicle brake system 100 of the present invention can be installed in hybrid vehicles that also use a motor, electric vehicles and fuel cell vehicles that are powered only by a motor, and vehicles that are powered only by an engine (internal combustion engine).

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

[0030] The vehicle brake system 100 includes a hydraulic pressure generator 1 that generates brake hydraulic pressure according to the stroke amount (actuation amount) of a brake pedal BP (brake operator), and a hydraulic pressure control device 2 that is connected to the hydraulic pressure generator 1 and controls the brake hydraulic pressure acting on each wheel cylinder W of the wheel brake. The vehicle brake system 100 is composed of two bases (two blocks) consisting of a base 1A on which the components of the hydraulic pressure generator 1 are attached, and a base 1B on which the components of the hydraulic pressure control device 2 are attached.

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

[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 pseudo operation reaction force to the brake pedal BP. The slave cylinder 30 generates brake fluid pressure using an electric motor 36 as an electric actuator as a drive source. As will be described later, the slave cylinder 30 operates to increase the brake fluid pressure of the wheel brakes during normal brake control when there is no risk of the wheel brakes locking, during anti-lock brake control, and during automatic brake control that assists in stabilizing the vehicle behavior. In other words, the slave cylinder 30 is responsible for increasing the brake fluid pressure of the wheel brakes in general, and also functions as a control device that performs anti-lock brake control in place of the hydraulic pressure control device when the hydraulic pressure control device 2 is not in operation.

[0033] The master cylinder 10 includes two pistons 12a and 12b inserted into a first cylinder bore 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. Also, 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 has two bottom-side pressure chambers 14a and 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 brake fluid to the master cylinder 10. The hydraulic pressure generated in the master cylinder 10 can be output to a first main hydraulic line 1a and a second main hydraulic line 1b, which will be described later. The hydraulic pressure generated in the bottom pressure chamber 14a is output to the first main hydraulic line 1a, and the hydraulic pressure generated in the opening pressure chamber 14b is output to the second main hydraulic line 1b. The first main hydraulic line 1a is connected to the front wheel brakes of the front and rear wheels of the vehicle. The second main hydraulic line 1b is connected to the rear wheel brakes.

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

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

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

[0037] A reservoir tank communication passage 1e is connected to the back pressure chamber 26 in which the coil spring 23 is disposed. The reservoir tank communication passage 1e is connected to the reservoir tank 15 (atmospheric pressure side) via the master cylinder 10 and a supply port 15b.

[0038] In the stroke simulator 20, the brake fluid pressure applied in 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 pseudo operation reaction force to the brake pedal BP.

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

[0040] A first slave cylinder supply passage 1h is connected to the bottom pressure chamber 34a. The first slave cylinder supply passage 1h is in communication with the reservoir tank 15 via the master cylinder 10 and a supply port 15a. A first communication passage 3a, which is in communication with the first main hydraulic pressure passage 1a, is also connected to the bottom pressure chamber 34a. A first shutoff valve 8a is provided in the first communication passage 3a.

[0041] A second slave cylinder supply passage 1i is connected to the opening-side pressure chamber 34b. The second slave cylinder supply passage 1i branches off from a reservoir tank communication passage 1e and communicates with the reservoir tank 15 via the reservoir tank communication passage 1e. A second communication passage 3b that communicates with the second main hydraulic pressure passage 1b is also connected to the opening-side pressure chamber 34b. A second shutoff valve 8b serving as a shutoff valve and a second pressure sensor P2 are provided in the second communication passage 3b.

[0042] The slave cylinder 30 includes a drive transmission unit 35 and an electric motor 36. The electric motor 36 is an electric servo motor whose drive is controlled by a control device 4, which will be described later. The drive transmission unit 35 is a mechanism that 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 configured by, 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 part 35, the rod 35a of the drive transmission part 35 moves forward and backward. The tip of the rod 35a abuts against the slave piston 32b. The slave pistons 32a, 32b slide within the third cylinder bore 31 upon receiving input from the rod 35a, and pressurize the brake fluid within the bottom pressure chamber 34a and the opening pressure chamber 34b.

[0043] The control device 4 includes, for example, a housing attached to the side of the base body 1B and a control board housed in the housing. The control device 4 controls the operation of the electric motor 36 and the opening and closing of each valve based on information obtained from the stroke sensor 16 and various sensors, pre-stored programs, etc. The control device 4 is a dedicated control device for the hydraulic pressure generator 1. In addition to normal brake control, the control device 4 performs antilock brake control when the hydraulic control device 2 is not in operation (including when the hydraulic control device 2 is not in operation due to a malfunction). Specifically, the control device 4 performs antilock brake control by controlling the operation of the first master cut valve 7a, the second master cut valve 7b, the first shutoff valve 8a, the second shutoff valve 8b, and the slave cylinder 30 according to the wheel slippage state. In this case, the control device 4 can perform antilock brake control for each of the first main hydraulic pressure line 1a and the second main hydraulic pressure line 1b.

[0044] The control device 4 also has a function of performing fluid suction control. The fluid suction control is a control for ensuring brake fluid in the slave cylinder 30. That is, the fluid suction control is a control for actively suctioning brake fluid into the bottom-side pressure chamber 34a and the opening-side pressure chamber 34b of the slave cylinder 30 through the first slave cylinder supply line 1h and the second slave cylinder supply line 1i. The fluid suction control is executed when it is necessary to replenish brake fluid to the slave cylinder 30, for example, when the brake fluid pressure is increased in the slave cylinder 30 during antilock brake control by the hydraulic pressure control device 2. The fluid suction control is also executed, for example, when the hydraulic pressure generated in the slave cylinder 30 reaches the hydraulic pressure required by the driver and brake fluid is to be reserved in advance in preparation for subsequent pressurization. The control device 4 also performs the fluid suction control when the hydraulic pressure generating device 1 performs antilock brake control when the hydraulic pressure control device 2 is not operating (for example, when the hydraulic pressure control device 2 fails).

[0045] Next, each hydraulic passage formed in the base body 1A will be described. Within the base body 1A, there are provided a first main hydraulic passage 1a and a second main hydraulic passage 1b as main hydraulic passages leading to the master cylinder 10, and a first branch hydraulic passage 1c branching from the second main hydraulic passage 1b.

[0046] The first main hydraulic line 1a is a hydraulic line that starts from the bottom pressure chamber 14a of the first cylinder bore 11. A first pressure sensor P1 is provided in the first main hydraulic line 1a. The first pressure sensor P1 detects the brake hydraulic pressure generated in the master cylinder 10. A pipe Ha that leads to the base 1B of the hydraulic control device 2 is connected to an outlet port that is the end point of the first main hydraulic line 1a.

[0047] The second main hydraulic passage 1b is a hydraulic passage that starts from the pressure chamber 14b on the opening side of the first cylinder bore 11. A pipe Hb that leads to the base 1B of the hydraulic control device 2 is connected to an outlet port that is the end point of the second main hydraulic passage 1b.

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

[0049] The second branch hydraulic line 1d is a hydraulic line that connects the second main hydraulic line 1b to the first branch hydraulic line 1c. The second branch hydraulic line 1d is connected to a portion of the first branch hydraulic line 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 line 1d. The check valve 6 is connected in parallel to the simulator valve 5. The check valve 6 only allows the flow of brake fluid from the pressure chamber 25 side to the first cylinder bore 11 side.

[0050] A first master cut valve 7a serving as a master cut valve is provided in the first main hydraulic line 1a. The first master cut valve 7a is an on-off valve (ON / OFF valve) made up of a normally open solenoid valve, and opens and closes the first main hydraulic line 1a. A second master cut valve 7b serving as a master cut valve is provided in the second main hydraulic line 1b. The second master cut valve 7b is an on-off valve (ON / OFF valve) made up of a normally open solenoid valve, and opens and closes the second main hydraulic line 1b.

[0051] A first communication passage 3a is connected to the first main hydraulic passage 1a downstream of the first master cut valve 7a. A first shutoff valve 8a in the first communication passage 3a is an on-off valve (ON / OFF valve) made of a normally closed solenoid valve that opens and closes the first communication passage 3a. A second communication passage 3b is connected to the second main hydraulic line 1b downstream of the second master cut valve 7b. A second shutoff valve 8b in the second communication passage 3b is an on-off valve (ON / OFF valve) made of a normally closed solenoid valve, and opens and closes the second communication passage 3b. A second pressure sensor P2 in the second communication passage 3b detects the brake fluid pressure generated in the slave cylinder 30. The information acquired by the first pressure sensor P1 and the second pressure sensor P2 is output to the control device 4.

[0052] When the first master cut valve 7a is in the open state shown in Figure 1 and the first shut-off valve 8a is in the closed state, the upstream side (master cylinder 10 side) and downstream side (hydraulic pressure control device 2 side) of the first main hydraulic line 1a are connected, and the first main hydraulic line 1a and the first communication line 3a are blocked. When the first master cut valve 7a is in the closed state shown in Figure 1 and the first shut-off valve 8a is in the open state, the upstream and downstream sides of the first main hydraulic line 1a are blocked, and the first communication line 3a is connected to the downstream side of the first main hydraulic line 1a.

[0053] Similarly, when the second master cut valve 7b is in the open state shown in Figure 1 and the second shut-off valve 8b is in the closed state, the upstream side (master cylinder 10 side) and downstream side (hydraulic pressure control device 2 side) of the second main hydraulic line 1b are connected, and the second main hydraulic line 1b and the second communication line 3b are blocked. When the second master cut valve 7b is in the closed state shown in Figure 2 and the second shut-off valve 8b is in the open state, the upstream and downstream sides of the second main hydraulic line 1b are blocked, and the second communication line 3b is connected to the downstream side of the second main hydraulic line 1b.

[0054] The hydraulic pressure control device 2 can appropriately control the brake hydraulic pressure applied to each wheel cylinder W. 1, the hydraulic pressure control device 2 is disposed between the hydraulic pressure generating device 1 and each wheel cylinder W. The hydraulic pressure 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 body 1B of the hydraulic pressure control device 2. Pipes Ha and Hb connected to the output ports of the base body 1A of the hydraulic pressure generating device 1 are connected to the inlet ports 4a and 4b. Each wheel cylinder W is connected to the output ports of the base body 1B of the hydraulic pressure control device 2 via a pipe. The brake output system K1 communicates with the first main hydraulic pressure line 1a, and the brake output system K2 communicates with the second main hydraulic pressure line 1b.

[0056] The brake output system K1 includes a regulator R as a pressure adjusting valve, a control valve means V, an intake valve 47, a reservoir 48, a pump 45, and a third hydraulic pressure sensor P3. The brake output system K2 has the same configuration as the brake output system K1, so the following description will be given in detail of the brake output system K1.

[0057] In the following description, the hydraulic path from the inlet port to the regulator R will be referred to as the "output hydraulic path A," and the hydraulic path from the regulator R to the outlet port will be referred to as the "wheel hydraulic path B." Furthermore, the hydraulic path branching off from the output hydraulic path A to the pump 45 will be referred to as the "suction path C," and the hydraulic path from the pump 45 to the wheel hydraulic path B will be referred to as the "discharge path D." Furthermore, the hydraulic path from the wheel hydraulic path B to the suction path C will be referred to as the "open path E." Furthermore, "upstream side" means the master cylinder MC side, and "downstream side" means the wheel brake (wheel cylinder W) side.

[0058] The regulator R can adjust the brake fluid pressure difference between the output hydraulic pressure line A and the wheel hydraulic pressure line B, and has the function of switching between a state in which the flow of brake fluid is permitted and a state in which the flow of brake fluid is blocked. The regulator R also has the function of adjusting the brake fluid pressure in the wheel hydraulic pressure line B to a predetermined fluid pressure when the flow of brake fluid in the output hydraulic pressure line A is blocked. The regulator R is equipped with a cut valve 41 and a check valve 42.

[0059] The cut valve 41 is a normally open linear solenoid valve interposed between the output hydraulic pressure line A and the wheel hydraulic pressure line B. The cut valve 41 switches between a state in which the flow of brake fluid from the output hydraulic pressure line A to the wheel hydraulic pressure line B is permitted and a state in which the flow of brake fluid is blocked. In other words, the cut valve 41 is configured to be able to adjust the valve opening pressure by controlling the power supply to the solenoid (it also functions as a relief valve).

[0060] When the brake fluid pressure in the wheel hydraulic pressure line B exceeds the brake fluid pressure in the output hydraulic pressure line A and the hydraulic pressure difference between the brake fluid pressure in the output hydraulic pressure line A and the brake fluid pressure in the wheel hydraulic pressure line exceeds the force that tries to close the valve, which is controlled by energizing the solenoid, the cut valve 41 releases the brake fluid pressure in the wheel hydraulic pressure line B to the output hydraulic pressure line A side to adjust it.

[0061] The check valve 42 is connected in parallel to the cut valve 41. The check valve 42 is a one-way valve that allows the flow of brake fluid from the output hydraulic pressure line A to the wheel hydraulic pressure line B. The check valve 42 is provided integrally with a normally open solenoid valve that constitutes the regulator R.

[0062] The control valve means V switches between communication and blocking of the fluid path leading from the wheel hydraulic pressure path B to the wheel brakes (wheel cylinders W), and communication and blocking of the fluid path leading from the wheel brakes to the release path E. The control valve means V increases, maintains, or reduces the brake fluid pressure acting on each wheel cylinder W. For this purpose, the control valve means V is configured with an inlet valve 43, an outlet valve 44, and a check valve 43a.

[0063] The inlet valve 43, outlet valve 44, and check valve 43a are arranged in two hydraulic pressure paths leading to each wheel cylinder W of the two wheel brakes. The inlet valve 43 is a normally-open linear solenoid valve, and the differential pressure between the upstream and downstream of the inlet valve 43 (the valve opening pressure of the inlet valve 43) can be adjusted according to the value of the drive current flowing through the coil of the inlet valve 43. The inlet valve 43 is normally open, allowing hydraulic pressure to be applied from the slave cylinder 30 to the wheel cylinder W. Furthermore, when the wheels are about to lock, the inlet valve 43 is controlled by the control device 9 to close, thereby cutting off (maintaining) the brake hydraulic pressure applied to the wheel cylinder W.

[0064] The outlet valve 44 is a normally closed solenoid valve disposed between the wheel cylinder W and the release 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 opens, the brake fluid acting on the wheel cylinder W is released to the release path E, and the pressure of the brake fluid acting on the wheel cylinder W is reduced.

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

[0066] Intake valve 47 is a normally closed solenoid valve provided in suction path C, and switches between an open state and a closed state of suction path C. An electromagnetic coil for driving the valve element of suction valve 47 is electrically connected to control device 9, and based on a command from control device 7, the valve opens when the electromagnetic coil is excited and closes when the electromagnetic coil is de-energized.

[0067] The reservoir 48 is provided in the open path E and has the function of temporarily storing the brake fluid that is released when the outlet valve 44 is opened. In addition, a check valve 49 is interposed between the reservoir 48 and the pump 45, which only allows the brake fluid to flow from the reservoir 48 side to the pump 45 side.

[0068] The pump 45 has an intake side connected to an intake passage C (open passage E) and an outlet side connected to a discharge passage D. The pump 45 is driven by the motor M to draw in brake fluid from a reservoir 48 and discharge the pressurized brake fluid into the wheel hydraulic pressure passage B via the discharge passage D. When the cut valve 41 of the regulator R is closed and the intake valve 47 is open, the pump 45 draws in brake fluid stored in the master cylinder 10, the output hydraulic pressure passage A, and the intake passage C and discharges it into the discharge passage D. The amount of brake fluid discharged by the pump 45 depends on the rotation speed of the motor M.

[0069] The control device 9 includes a housing attached to the side of the base body 1B, for example, and a control board housed in 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, pre-stored programs, etc.

[0070] Next, the operation of the vehicle brake system 100 will be described with reference to FIGS. In the vehicle brake system 100 shown in Fig. 1, when the system is started, the simulator valve 5 of the first branch hydraulic line 1c of the hydraulic pressure generator 1 is opened. When the brake pedal BP is depressed, the first master cut valve 7a and the second master cut valve 7b of the hydraulic pressure generator 1 are excited to operate and close. Note that the system may be configured so that when the system is started, the first master cut valve 7a and the second master cut valve 7b of the hydraulic pressure generator 1 are excited to operate and close. Furthermore, the first shutoff valve 8a and the second shutoff valve 8b are excited and actuated, and are opened.

[0071] This connects the downstream side of the first main hydraulic line 1a to the first communication line 3a, and connects the downstream side of the second main hydraulic line 1b to the second communication line 3b, thereby isolating the master cylinder 10 from each wheel cylinder W and connecting the slave cylinder 30 to each wheel cylinder W.

[0072] In the following explanation, the thick double white lines shown in the diagrams of the hydraulic circuit indicate the fluid path along which the brake fluid pressure generated in the master cylinder 10 acts, and the thick solid lines indicate the fluid path along which the brake fluid pressure generated in the slave cylinder 30 acts. In addition, the thick dashed lines indicate the fluid path through which the brake fluid is released from the wheel cylinder W when the antilock brake control is reduced, and the thick dashed lines with small intervals indicate the fluid path through which the brake fluid pressure is maintained when the antilock brake control is maintained. 4 to 11 do not show the brake fluid paths of the fluid pressure control device 2. In FIGS. 4 to 11, brake fluid pressure acts on the same flow paths as the fluid paths indicated by the thick solid lines in FIG.

[0073] (Normal brake control) Figure 2 shows the flow of brake fluid during normal brake control. During normal brake control, when the brake pedal BP is depressed and there is no risk of the wheels locking, the stroke sensor 16 detects the amount of depression, and the control device 4 drives the electric motor 36 of the slave cylinder 30. This generates brake fluid pressure in the slave cylinder 30.

[0074] In addition, the brake fluid pressure generated in the master cylinder 10 by operating the brake pedal BP is not transmitted to each wheel cylinder W, but is transmitted to the stroke simulator 20 through the second main fluid pressure line 1b and the first branch fluid pressure line 1c. 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 brake pedal BP to stroke. As a result, a pseudo operation reaction force is applied to the brake pedal BP.

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

[0076] The brake fluid pressure input to the hydraulic pressure control device 2 is passed through a regulator R in the output hydraulic pressure line A to a wheel hydraulic pressure line B, and is transmitted directly to a wheel cylinder W through an inlet valve 43. This causes the wheels (not shown) to be braked.

[0077] The control device 4 compares the brake fluid pressure generated in the slave cylinder 30 (the fluid pressure detected by the second pressure sensor P2) with the required fluid pressure corresponding to the amount of operation of the brake pedal BP. If the comparison result indicates that an increase in the brake fluid pressure to a high fluid pressure range, such as for emergency braking, is required, the control device 4 can instruct the control device 9 to drive the pump 45 and perform auxiliary pressure control so as to increase the brake fluid pressure in the wheel hydraulic pressure path B. In this case, the drive currents of the regulator R and the motor M can be set appropriately based on the required fluid pressure corresponding to the amount of operation of the brake pedal BP.

[0078] When the brake pedal BP is released, the control device 4 drives the electric motor 36 of the slave cylinder 30 in the reverse direction. This reduces the hydraulic pressure generated in the slave cylinder 30, and reduces the pressure in the bottom-side pressure chamber 34a and the open-side pressure chamber 34b of the slave cylinder 30. As a result, the brake fluid pressure that was transmitted to the wheel cylinder W is returned to the slave cylinder 30 via the wheel hydraulic pressure line B, the output hydraulic pressure line A, the first main hydraulic pressure line 1a, the second main hydraulic pressure line 1b, the first communication line 3a, and the second communication line 3b. This return of the brake fluid ensures that there is sufficient brake fluid in preparation for subsequent pressurization.

[0079] (Anti-lock brake control by hydraulic pressure control device) Antilock brake control by the hydraulic pressure control device 2 is performed when the wheels are about to lock up, and is realized by appropriately selecting a state in which the brake hydraulic pressure acting on the wheel cylinder W is reduced, increased, or maintained constant. The control device 9 determines whether to select the reduction mode, pressure increase mode, or pressure maintenance mode based on the wheel speed obtained from a wheel speed sensor (not shown).

[0080] While the brake pedal BP is being depressed, that is, while the brake fluid pressure generated in the slave cylinder 30 is acting on the fluid pressure control device 2, if the wheels are about to lock, the control device 9 starts 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. This closes the inlet valve 43 and opens the outlet valve 44. This causes the brake fluid in the wheel hydraulic pressure path B leading to the wheel cylinder W to escape from the outlet valve 44 to the release path E. This reduces the brake hydraulic pressure acting on the wheel cylinder W. The brake fluid escaped to the release path E flows into the reservoir 48. The brake fluid that has flowed into the reservoir 48 is then sucked in by and returned to the hydraulic pressure generator 1 side through the discharge path D, the wheel hydraulic pressure path B, and the output hydraulic pressure path A.

[0081] Furthermore, when the pressure increase mode is selected in the antilock brake control, the control device 9 de-energizes the inlet valve 43 and the outlet valve 44. This opens the inlet valve 43 and closes the outlet valve 44. This increases the brake fluid pressure acting on the wheel cylinder W through the wheel fluid pressure path B by the brake fluid pressure generated in the slave cylinder 30.

[0082] Furthermore, when the hold mode is selected in the antilock brake control, the control device 9 magnetizes the inlet valve 43 and de-magnetizes the outlet valve 44. This closes the inlet valve 43 and the outlet valve 44. In this way, the brake fluid is trapped in the flow path closed 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 brake control) When the control device 4 determines that the wheels should be braked while the driver is not depressing the brake pedal BP, automatic brake control is executed to assist in stabilizing the behavior of the vehicle. In automatic brake control, as in normal brake control, as shown in Fig. 3, the control device 4 drives the slave cylinder 30, opens the first shutoff valve 8a and the second shutoff valve 8b, and transmits the brake fluid pressure generated in the slave cylinder 30 to the fluid pressure control device 2.

[0084] In the hydraulic pressure control device 2, the controller 9 demagnetizes the regulator R to open it, demagnetizes the inlet valve 43 to open it, and demagnetizes the outlet valve 44 to close it. As a result, the brake hydraulic pressure generated in the slave cylinder 30 is transmitted from the output hydraulic pressure path A of the hydraulic pressure control device 2 to the wheel hydraulic pressure path B to the wheel cylinder W, thereby braking the wheels.

[0085] The brake fluid pressure acting on the wheel cylinder W can be released from the outlet valve 44 to the release path E by energizing the inlet valve 43 to close the valve and energizing the outlet valve 44 to open the valve. In this case, too, the brake fluid released to the release path E is temporarily stored in the reservoir 48, and then sucked in by the pump 45 and returned to the hydraulic pressure generator 1 side through the discharge path D, the wheel hydraulic pressure path B, and the output hydraulic pressure path A.

[0086] If the wheels are about to lock during such automatic brake control, the hydraulic pressure control device 2 executes antilock brake control in the same manner as the antilock brake control described above. The automatic brake control is also executed when the hydraulic pressure control device 2 is not in operation, for example, when there is a malfunction of the hydraulic pressure control device 2. The antilock brake control when the automatic brake control is executed when the hydraulic pressure control device 2 is not in operation will be described later.

[0087] (Fluid absorption control in anti-lock brake control) The fluid suction control is a control for suctioning brake fluid from the reservoir tank 15 in order to ensure brake fluid in the bottom pressure chamber 34a and the opening pressure chamber 34b of the slave cylinder 30. Note that the bottom pressure chamber 34a and the opening pressure chamber 34b ensure the amount of brake fluid required for normal brake control (when the first shutoff valve 8a and the second shutoff valve 8b are open), except for special braking such as sudden braking or when anti-lock brake control is frequently and continuously performed.

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

[0089] If it is determined that the brake fluid required for pressure increase cannot be supplied by the maximum stroke amount of the slave pistons 32a, 32b, the slave pistons 32a, 32b are temporarily returned in the pressure reducing direction to re-pressurize the brake fluid. The return amount at this time can be calculated, for example, based on a map preset in the control device 4. When re-pressurizing the brake fluid in this manner, the control device 4 de-energizes the first shutoff valve 8a and the second shutoff valve 8b to control them to a closed state.

[0090] When the control device 4 drives the electric motor 36 to rotate in the direction of pressure reduction (return direction), the slave pistons 32a, 32b are returned in the direction of pressure reduction, and the bottom-side pressure chamber 34a and the opening-side pressure chamber 34b are reduced in pressure to a negative pressure while maintaining the hydraulic pressure in the wheel cylinder W. As a result, brake fluid is sucked into the slave cylinder 30 from the reservoir tank 15 through the first slave cylinder supply line 1h and the second slave cylinder supply line 1i. The amount of brake fluid sucked into the slave cylinder 30 corresponds to the amount of return of the slave pistons 32a, 32b.

[0091] When the return amount of the slave pistons 32a, 32b reaches the target value, the control device 4 controls the first shutoff valve 8a and the second shutoff valve 8b to be open. Then, the control device 4 drives the electric motor 36 to rotate forward again in the pressurizing direction. As a result, the brake fluid pressure to the wheel cylinders W is increased again to the brake fluid pressure corresponding to the fluid pressure required by the driver.

[0092] Thereafter, when the brake pedal BP is released, the control device 4 drives the electric motor 36 to rotate in the reverse direction (return direction) to reduce the pressure, causing the brake fluid to be sucked into the slave cylinder 30 from the reservoir tank 15 through the first slave cylinder supply line 1h and the second slave cylinder supply line 1i, and the fluid suction control ends.

[0093] (Anti-lock brake control when hydraulic pressure control device is not operating) Next, a case where automatic brake control is executed when the hydraulic pressure control device 2 is not in operation (for example, when the hydraulic pressure control device 2 fails) will be described. If the wheels are about to lock while the hydraulic pressure control device 2 is not in operation and automatic brake control is being executed, the control device 4 executes antilock brake control.

[0094] During antilock brake control when the hydraulic control device 2 is not operating and automatic brake control is being performed, if the control device 4 selects, for example, a pressure reduction mode for the brake output system K2, as shown in Figure 4, the control device 4 de-energizes the second master cut valve 7b to open it, and de-energizes the second shut-off valve 8b to close it.

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

[0096] Furthermore, in antilock brake control when the hydraulic control device 2 is not operating and automatic brake control is being executed, if the control device 4 selects, for example, the holding mode of the brake output system K2, as shown in Figure 5, the control device 4 energizes the second master cut valve 7b to close it, and deenergizes the second shut-off valve 8b to close it.

[0097] In this way, the brake fluid is confined within 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, thereby maintaining a constant brake fluid pressure in the brake output system K2.

[0098] In addition, during anti-lock brake control when the hydraulic control device 2 is not operating and automatic brake control is being performed, if the control device 4 selects, for example, a pressure reduction mode for both brake output systems K1 and K2, it is also possible to reduce the pressure by driving the slave cylinder 30. In this case, the first master cut valve 7a and the second master cut valve 7b are energized and closed by the control device 4, and the first shutoff valve 8a and the second shutoff valve 8b are energized and opened by the control device 4. Then, the electric motor 36 is driven to rotate in the pressure reducing direction (return direction) in the reverse direction.

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

[0100] Such pressure reduction by driving the slave cylinder 30 can also be performed when the following pressure reduction mode and pressure holding mode are selected. Specifically, this can be performed when the control device 4 selects the pressure reduction mode for one of the brake output systems K1, K2 and the pressure holding mode for the other system.

[0101] For example, when the control device 4 selects the pressure reduction mode of the brake output system K1 and the pressure retention mode of the brake output system K1, the first master cut valve 7a and the second master cut valve 7b are energized and closed, the first shutoff valve 8a is energized and opened, and the second shutoff valve 8b is deenergized and closed. Then, the control device 4 drives the electric motor 36 to rotate in the pressure reduction direction (return direction) in the reverse direction.

[0102] In this way, the brake fluid acting on the wheel cylinder W of the brake output system K1 is returned to the bottom pressure chamber 34a of the slave cylinder 30 through the first main hydraulic pressure line 1a and the first communication line 3a. Meanwhile, the brake fluid is confined within 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 acting on the wheel cylinder W of the brake output system K1 is reduced, and the brake fluid pressure of the brake output system K2 is maintained constant.

[0103] Next, we will explain the antilock brake control when the brake pedal BP is operated while the hydraulic pressure control device 2 is not in operation. Similar to the antilock brake control described above, the antilock brake control when the hydraulic pressure control device 2 is not in operation and the brake pedal BP is being operated is also executed when the wheels are about to lock. Note that the first master cut valve 7a and the second master cut valve 7b are energized by the control device 4, and are both closed.

[0104] During antilock brake control while the hydraulic pressure control device 2 is not operating and the brake pedal BP is being operated, if the control device 4 selects, for example, a pressure reduction mode for both the brake output systems K1 and K2, the control device 4 energizes the first shutoff valve 8a and the second shutoff valve 8b to open them, as shown in Figure 9. Then, the electric motor 36 is driven to rotate in the reverse direction in the pressure reduction direction (return direction). As a result, the brake fluid in the brake output system K1 is returned from the first main hydraulic pressure path 1a through the first communication path 3a to the bottom pressure chamber 34a of the slave cylinder 30, and the brake fluid in the brake output system K2 is returned from the second main hydraulic pressure path 1b through the second communication path 3b to the open pressure chamber 34b of the slave cylinder 30.

[0105] As a result, when the brake pedal BP is operated, the brake fluid pressure acting on the wheel cylinders W of the brake output systems K1 and K2 is reduced.

[0106] Furthermore, during antilock brake control when the hydraulic control device 2 is not operating and the brake pedal BP is being operated, if the control device 4 selects, for example, a holding mode for the brake output system K2, the control device 4 de-energizes the second shut-off valve 8b and closes it, as shown in Figure 10.

[0107] In this way, the brake fluid is confined within 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, thereby maintaining a constant brake fluid pressure in the brake output system K2.

[0108] Furthermore, during antilock brake control when the hydraulic control device 2 is not operating and the brake pedal BP is being operated, if the control device 4 selects, for example, the hold mode for both the brake output systems K1 and K2, the control device 4 de-energizes the first shut-off valve 8a and the second shut-off valve 8b, closing them as shown in FIG. 11.

[0109] In this way, the brake fluid is confined in the flow path closed by the first master cut valve 7a, the first shutoff valve 8a, and the wheel cylinder W of the brake output system K1, and 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 pressures in the brake output systems K1 and K2 are each maintained constant.

[0110] (Liquid suction control when the hydraulic pressure control device 2 is not operating) The following describes a case where fluid suction control is performed during antilock brake control when the hydraulic pressure control device 2 is not operating and automatic brake control is being executed. In this case, fluid suction control is performed in a mode in which both the first shutoff valve 8a and the second shutoff valve 8b are de-energized and closed.

[0111] An example of a mode in which both the first shutoff valve 8a and the second shutoff valve 8b are de-energized is a mode in which both the brake output systems K1 and K2 are de-energized, as shown in Fig. 6. When the de-energization mode is selected for both the brake output systems K1 and K2, the control device 4 de-energizes the first master cut valve 7a and the second master cut valve 7b to open them, and de-energizes the first shutoff valve 8a and the second shutoff valve 8b to close them.

[0112] In this way, the brake fluid in the brake output systems K1, K2 is released to the first main hydraulic pressure line 1a and the second main hydraulic pressure line 1b on the hydraulic pressure generating device 1 side through the wheel hydraulic pressure line B and the output hydraulic pressure line A of the hydraulic pressure control device 2. Then, the brake fluid released to the first main hydraulic pressure line 1a and the second main hydraulic pressure line 1b passes through the first master cut valve 7a and the second master cut valve 7b, flows into the master cylinder 10, and is returned to the reservoir tank 15.

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

[0114] In addition, as another mode in which both the first shutoff valve 8a and the second shutoff valve 8b are de-energized, for example, a case in which the pressure reduction mode of the brake output system K1 is selected and the pressure holding mode of the brake output system K2 is selected is shown in Fig. 7. When the brake output system K1 is in the pressure reduction mode, the control device 4 de-energizes the first master cut valve 7a to open it, and de-energizes the first shutoff valve 8a to close it. When the pressure holding mode of the brake output system K2 is selected, the control device 4 energizes the second master cut valve 7b to close it, and de-energizes the second shutoff valve 8b to close it.

[0115] In this way, the brake fluid acting on the wheel cylinder W of the brake output system K1 is released to the first main hydraulic line 1a on the hydraulic pressure generating device 1 side through the wheel hydraulic line B and the output hydraulic line A of the hydraulic control device 2, as described above, passes through the first master cut valve 7a, flows into the master cylinder 10, and is returned to the reservoir tank 15. Furthermore, the brake fluid is trapped 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 in the brake output system K2 is maintained constant.

[0116] In this state, the control device 4 drives the electric motor 36 to rotate in the reverse direction (return direction) to reduce the pressure in the bottom-side pressure chamber 34a and the opening-side pressure chamber 34b, thereby 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 sucked into the slave cylinder 30 from the reservoir tank 15 through the first slave cylinder supply line 1h and the second slave cylinder supply line 1i.

[0117] Another mode in which both the first shutoff valve 8a and the second shutoff valve 8b are de-energized is, for example, when both the brake output systems K1 and K2 are in the hold mode, as shown in Fig. 8. When both the brake output systems K1 and K2 are in the hold mode, the control device 4 de-energizes the first master cut valve 7a and the second master cut valve 7b to open them, and de-energizes the first shutoff valve 8a and the second shutoff valve 8b to close them.

[0118] In this state, similarly to the above, the electric motor 36 is driven to rotate in the reverse direction (return direction) by the control device 4, and brake fluid is sucked into the bottom side pressure chamber 34a and the opening side pressure chamber 34b, which are now in a negative pressure state.

[0119] According to the vehicle brake system 100 of this embodiment described above, even when the hydraulic pressure control device 2 is not operating, antilock brake control can be performed by controlling the slave cylinder 30 of the hydraulic pressure generating device 1, the first master cut valve 7a, the second master cut valve 7b, the first shut-off valve 8a, and the second shut-off valve 8b by the control device 4. Therefore, even if the hydraulic pressure control device 2 fails, for example, antilock brake control can be performed based on the wheel slip condition to prevent the wheels from locking.

[0120] Furthermore, the first master cut valve 7a and the second master cut valve 7b are normally open valves, and the first shutoff valve 8a and the second shutoff valve 8b are normally closed valves. Therefore, with this simple system configuration, antilock brake control can be performed when the hydraulic control device 2 is not operating, thereby reducing costs.

[0121] In addition, when the hydraulic control device 2 is not in operation, antilock brake control can be preferably achieved by transmitting the brake hydraulic pressure generated in the bottom pressure chamber 34a and the opening pressure chamber 34b of the slave cylinder 30 to the respective wheel brakes of the first main hydraulic pressure line 1a and the second main hydraulic pressure line 1b.

[0122] Furthermore, during anti-lock brake control when the hydraulic control device 2 is not operating and automatic brake control is in progress, by controlling the first master cut valve 7a, the second master cut valve 7b, the first shut-off valve 8a, the second shut-off valve 8b and the slave cylinder 30, it is possible to suitably reduce the pressure in the hydraulic lines that are to be reduced in pressure, suitably increase the pressure in the hydraulic lines that are to be increased in pressure, and further suitably maintain the pressure in the hydraulic lines that are to be maintained in pressure.

[0123] Furthermore, during antilock brake control when the hydraulic control device 2 is not operating, the first master cut valve 7a and second master cut valve 7b of the hydraulic line to be reduced in pressure are opened, and the first shut-off valve 8a and second shut-off valve 8b of the hydraulic line to be reduced in pressure are closed, thereby allowing the brake fluid to be returned to the master cylinder 10 side through the open first master cut valve 7a and second master cut valve 7b. This allows the hydraulic line to be reduced in pressure in an appropriate manner.

[0124] Furthermore, the first main hydraulic line 1a is connected to the front wheel brakes of the front and rear wheels of the vehicle, and the second main hydraulic line 1b is connected to the rear wheel brakes. This allows the front and rear wheels to be anti-lock braked separately when the hydraulic control device 2 is not in operation. In other words, it is possible to achieve an optimal distribution of braking force between the front and rear of the vehicle depending on the vehicle model.

[0125] (Second embodiment) Next, a vehicle brake system according to a second embodiment will be described with reference to Figures 12 and 13. This embodiment differs from the first embodiment in that a first return flow path 1a1 communicating with the first main hydraulic pressure path 1a and a second return flow path 1b1 communicating with the second main hydraulic pressure path 1b are arranged opposite to each other.

[0126] The first return flow path 1a1 branches off from the first main hydraulic pressure path 1a downstream of the first master cut valve 7a and leads to the first slave cylinder supply path 1h. A first on-off valve 13a is provided in the first return flow path 1a1. The first on-off valve 13a is an on-off valve (ON / OFF valve) made up of a normally closed solenoid valve.

[0127] The second return flow path 1b1 branches off from the second main hydraulic pressure path 1b downstream of the second master cut valve 7b and leads to the first return flow path 1a1. A second on-off valve 13b is provided in the second return flow path 1b1. The second on-off valve 13b is an on-off valve (ON / OFF valve) made up of a normally closed solenoid valve.

[0128] The first on-off valve 13a and the second on-off valve 13b are opened and closed under the control of the control device 4. Specifically, the first on-off valve 13a and the second on-off valve 13b are opened when the pressure reduction mode is selected in the anti-lock brake control while the hydraulic pressure control device 2 is not operating and the brake pedal BP is being operated.

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

[0130] Next, a description will be given of antilock brake control when the hydraulic pressure control device 2 is not in operation and the brake pedal BP is being operated. In this embodiment, the brake fluid can be returned to the reservoir tank 15 through the first return flow path 1a1 and the second return flow path 1b1.

[0131] In antilock brake control when the hydraulic pressure control device 2 is not operating and the brake pedal BP is being operated, for example, if the control device 4 selects a mode for reducing the pressure in the brake output system K1, as shown in Figure 13, the control device 4 de-energizes the first shut-off valve 8a to close it, and energizes the first opening / closing valve 13a to open it.

[0132] In this way, the brake fluid acting on the wheel cylinder W of the brake output system K1 is released from the first main hydraulic pressure path 1a to the first return flow path 1a1, and then flows into the master cylinder 10 through the first slave cylinder supply path 1h and is returned to the reservoir tank 15.

[0133] As a result, the brake fluid pressure acting on the wheel cylinder W of the brake output system K1 is reduced while the brake pedal BP is being operated.

[0134] Furthermore, in antilock brake control when the hydraulic control device 2 is not operating and the brake pedal BP is being operated, if the control device 4 selects a mode for reducing the pressure in the brake output systems K1, K2, as shown in FIG. 14, the control device 4 de-energizes the first shut-off valve 8a and the second shut-off valve 8b to close them, and energizes the first opening / closing valve 13a and the second opening / closing valve 13b to open them.

[0135] In this manner, the brake fluid acting on the wheel cylinder W of the brake output system K1 is released from the first main hydraulic pressure path 1a to the first return flow path 1a1, and then flows into the master cylinder 10 through the first slave cylinder supply path 1h and is returned to the reservoir tank 15. On the other hand, the brake fluid acting on the wheel cylinder W of the brake output system K2 is released from the second main hydraulic pressure path 1b to the second return flow path 1b1, and then flows into the master cylinder 10 from the first return flow path 1a1 through the first slave cylinder supply path 1h and is returned to the reservoir tank 15.

[0136] As a result, even when the brake pedal BP is operated, the brake fluid pressure acting on the wheel cylinders W of the brake output systems K1 and K2 is reduced.

[0137] The vehicle brake system 100A of this embodiment described above provides the same effects as those described in the first embodiment. In addition, the vehicle brake system 100A of this embodiment can preferably reduce the pressure in the hydraulic pressure path to be reduced by returning the brake fluid to the master cylinder 10 side through the first return flow path 1a1 or the second return flow path 1b1 during antilock brake control when the hydraulic pressure control device 2 is not in operation. In other words, even when the brake fluid pressure generated in the master cylinder 10 by operating the brake pedal BP acts on the first main hydraulic pressure path 1a and the second main hydraulic pressure path 1b, the brake fluid can be returned to the master cylinder 10 side through the first return flow path 1a1 and the second return flow path 1b1.

[0138] In this embodiment, the terminal end of the first return flow path 1a1 is connected to the first slave cylinder supply path 1h, but this is not limited thereto, and the terminal end may be connected to the reservoir tank communication path 1e. Also, the terminal end may be configured to return the fluid directly to the reservoir tank 15.

[0139] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments and can be modified as appropriate within the scope of the invention. For example, in the first and second embodiments, the master cylinder 10 is shown to have two bottom-side pressure chambers 14a and opening-side pressure chambers 14b, but this is not limited to this and the master cylinder 10 may have one pressure chamber from which the first main hydraulic line 1a and the second main hydraulic line 1b are branched through a common hydraulic line.

[0140] Furthermore, in the first and second embodiments, the slave cylinder 30 has two pressure chambers, a bottom-side pressure chamber 34a and an opening-side pressure chamber 34b. However, the present invention is not limited to this. The slave cylinder 30 may have one pressure chamber, which is branched into the first communication passage 3a and the second communication passage 3b through a common hydraulic path.

[0141] In the first embodiment, the hydraulic pressure generating device 1 and the hydraulic pressure control device 2 are configured with two bases 1A and 1B, but this is not limiting, and the base 1A may be divided into two bases to configure the hydraulic pressure generating device 1. Furthermore, the hydraulic pressure generating device 1 and the hydraulic pressure control device 2 may be configured together on a single base.

[0142] Furthermore, in the first and second embodiments, two control devices 4, 9 are provided, but this is not limited to this, and the hydraulic pressure generating device 1 and the hydraulic pressure control device 2 may be controlled by one control device. [Explanation of symbols]

[0143] 1. Hydraulic pressure generator 1a First main hydraulic line (main hydraulic line) 1b Second main hydraulic line (main hydraulic line) 1a1 First return flow path (return flow path) 1b1 Second return flow path (return flow path) 2. Hydraulic control device 3a First series passage (communicating passage) 3b Second communication path (communication path) 4,9 Control device 7a First master cut valve (master cut valve) 7b Second master cut valve (master cut valve) 8a First shutoff valve (shutoff valve) 8b Second shutoff valve (shutoff valve) 10 Master cylinder 14a Bottom pressure chamber (pressure chamber) 14b Opening side pressure chamber (pressure chamber) 30 slave cylinder 34a Bottom pressure chamber (slave cylinder pressure chamber) 34b Opening side pressure chamber (slave cylinder pressure chamber) 36 Electric motor (electric actuator) 100,100A vehicle brake system BP Brake pedal (brake operator)

Claims

1. a hydraulic pressure generating device including a master cylinder that generates brake hydraulic pressure in accordance with the amount of operation of a brake operator and a slave cylinder that generates brake hydraulic pressure by driving an electric actuator; a hydraulic pressure control device that controls brake hydraulic pressure acting on wheel brakes using brake hydraulic pressure from the hydraulic pressure generating device, The hydraulic pressure generating device is a master cut valve that opens and closes a main hydraulic passage that leads from the master cylinder to the hydraulic control device; a communication passage that leads from the slave cylinder to the main hydraulic passage downstream of the master cut valve; a shutoff valve that opens and closes the communication passage; and a control device that controls the operation of the slave cylinder, the master cutoff valve, and the shutoff valve, the main hydraulic pressure line includes a first main hydraulic pressure line communicating with at least one of the plurality of wheel brakes, and a second main hydraulic pressure line communicating with the remaining wheel brakes, the master cut valve, the communication passage, and the shutoff valve are provided in the first main hydraulic passage and the second main hydraulic passage, respectively; The control device A vehicle brake system characterized in that when the hydraulic pressure control device is not operating, brake hydraulic pressure is generated from the slave cylinder, and the master cut valve and the shut-off valve are controlled for each of the first main hydraulic pressure line and the second main hydraulic pressure line depending on the wheel slippage condition, thereby performing anti-lock brake control.

2. 2. The vehicle brake system according to claim 1, wherein the master cut valve is a normally open on-off valve, and the shutoff valve is a normally closed on-off valve.

3. the master cylinder has two pressure chambers and is configured to be able to output hydraulic pressures generated in the two pressure chambers to the first main hydraulic line and the second main hydraulic line, respectively; 2. The vehicle brake system according to claim 1, wherein the slave cylinder includes two slave cylinder pressure chambers, and is configured to be able to output hydraulic pressures generated in the two slave cylinder pressure chambers to the first main hydraulic line and the second main hydraulic line, respectively.

4. 2. The vehicle brake system according to claim 1, wherein, when increasing the brake fluid pressure in at least one of the first main hydraulic line and the second main hydraulic line during the antilock brake control, the master cut valve of the hydraulic line to be increased is closed, and the shut-off valve of the hydraulic line to be increased is opened, so that the brake fluid pressure generated in the slave cylinder is applied to the hydraulic line to be increased.

5. 2. The vehicle brake system according to claim 1, wherein, when reducing the brake fluid pressure in at least one of the first main hydraulic pressure line and the second main hydraulic pressure line during the antilock brake control, the master cut valve of the hydraulic pressure line to be reduced is closed, the shut-off valve of the hydraulic pressure line to be reduced is opened, and the piston of the slave cylinder is driven and controlled in the direction of reduction by the electric actuator.

6. 2. The vehicle brake system according to claim 1, wherein, when maintaining brake fluid pressure in at least one of the first main hydraulic pressure line and the second main hydraulic pressure line during the antilock brake control, the master cut valve of the hydraulic pressure line to be maintained is closed and the shut-off valve of the hydraulic pressure line to be maintained is closed.

7. 2. A vehicle brake system as described in claim 1, characterized in that when the brake fluid pressure in at least one of the first main hydraulic pressure line and the second main hydraulic pressure line is reduced during the antilock brake control, the master cut valve of the hydraulic pressure line to be reduced is opened, and the shut-off valve of the hydraulic pressure line to be reduced is closed, and the brake fluid is returned to the master cylinder side through the opened master cut valve.

8. a return flow path leading from the wheel brake to the atmospheric pressure side of the master cylinder or to a reservoir tank; an on-off valve that opens and closes the return flow path, 2. The vehicle brake system according to claim 1, wherein, when the brake fluid pressure in at least one of the first main hydraulic pressure line and the second main hydraulic pressure line is reduced during the antilock brake control, the master cut valve and the shut-off valve in the hydraulic pressure line to be reduced are closed and the on-off valve is opened.

9. 2. The vehicle brake system according to claim 1, wherein the first main hydraulic line is connected to the wheel brakes on the front wheels of the vehicle, and the second main hydraulic line is connected to the wheel brakes on the rear wheels.

10. The control device a fluid suction control for suctioning brake fluid into the slave cylinder during the antilock brake control; 2. The vehicle brake system according to claim 1, wherein when it is necessary to perform the liquid suction control, the shutoff valve is closed and the piston of the slave cylinder is driven and controlled in a direction of reducing pressure by the electric actuator.

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