Vehicle brake system

Abstract

The vehicle brake system can reduce the number of parts, reduce the cost, avoid large-scale structural elements of the system, and improve the pressure boosting performance of brake hydraulic pressure at the same time. A vehicle brake system is provided with a hydraulic pressure generation device (1) having an assist cylinder (30) for generating brake hydraulic pressure by driving an electric actuator (36), and a hydraulic pressure control device (2) for controlling the brake hydraulic pressure acting on a wheel brake on the basis of the brake hydraulic pressure from the hydraulic pressure generation device (1). A hydraulic pressure control device (2) is provided with: a pressure regulating valve (R) that is provided in a hydraulic pressure passage that communicates with a wheel brake and that can regulate the difference in brake hydraulic pressure between the hydraulic pressure generation device (1) side and the wheel brake side, an open passage (C), a pump (45), and a supply unit (15); brake fluid discharged from a wheel brake flows into the open passage (C); a pump (45) that sucks the brake fluid in the open passage (C) and discharges the brake fluid to the hydraulic passage; the supply unit (15) is provided on the upstream side of the assist cylinder (30) and is capable of storing brake fluid. The open passage (C) communicates with the supply unit (15).

Description

Technical Field

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

[0002] In the prior art, a vehicle braking system is known (for example, refer to Patent Document 1), which includes a master cylinder, a slave cylinder, and a hydraulic control device, wherein the master cylinder generates a brake hydraulic pressure corresponding to the pedaling force of the brake pedal; the slave cylinder generates the brake hydraulic pressure by being driven by an electric actuator; and the hydraulic control device assists in stabilizing the vehicle behavior by controlling the brake hydraulic pressure acting on the wheel brakes. Prior art literature Patent Literature

[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 structure in which brake fluid is sucked into a pump through a suction valve and brake fluid discharged from an outlet valve is temporarily stored in a reservoir. Therefore, the number of parts is large, resulting in increased costs. Furthermore, in general, vehicle brake systems utilize high-performance motors to drive pumps to enhance brake fluid pressure boosting performance, which can lead to increased size of system components.

[0005] The technical problem of the present invention is to provide a vehicle braking system that can solve the above problems, reduce the number of parts and components, lower costs, avoid the enlargement of the system's structural elements, and at the same time improve the boosting performance of the brake hydraulic pressure. [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 and a hydraulic pressure control device. The hydraulic pressure generating device includes an auxiliary cylinder that generates brake fluid pressure through the drive of an electric actuator. The hydraulic pressure control device controls the brake fluid pressure applied to the wheel brakes based on the brake fluid pressure from the hydraulic pressure generating device. The hydraulic pressure control device comprises a pressure regulating valve, an open passage, a pump, and a supply unit. The pressure regulating valve is disposed in the hydraulic passage connected to the wheel brakes and is capable of adjusting the brake fluid pressure difference between the hydraulic pressure generating device and the wheel brakes. Brake fluid discharged from the wheel brakes flows into the open passage. The pump draws brake fluid from the open passage and discharges it into the hydraulic passage. The supply unit is disposed upstream of the auxiliary cylinder and is capable of supplying brake fluid to the auxiliary cylinder. The open passage is characterized by being connected to the supply unit.

[0007] In the vehicle brake system of the present invention, the pump can directly draw brake fluid from the supply unit during operation. Furthermore, brake fluid discharged from the wheel brakes can be directly returned to the supply unit through an open passage. This eliminates the need for a suction valve upstream of the pump or a separate reservoir for storing brake fluid discharged from the wheel brakes. Consequently, the number of components in the vehicle brake system can be reduced, leading to lower costs. Furthermore, since there is no suction valve upstream of the pump, there is no resistance to the brake fluid passing through the suction valve. This improves the pressure-boosting performance of the brake fluid acting on the wheel brakes. This eliminates the need for a high-performance motor to drive the pump, enabling the miniaturization of system components.

[0008] Furthermore, by configuring the supply portion as a reservoir tank for supplying brake fluid to the assist cylinder, it is possible to achieve smooth flow of brake fluid within the system.

[0009] Furthermore, in the case of a master cylinder that generates brake fluid pressure in response to the amount of operation of a brake operating member, the reservoir tank is preferably connected to the master cylinder so as to supply brake fluid to the master cylinder. This configuration allows brake fluid to be supplied from a single reservoir tank to the slave cylinder via the master cylinder, thereby reducing the number of system components.

[0010] In addition, the hydraulic pressure generating device preferably includes a master cylinder and a main hydraulic passage, wherein the master cylinder is connected to the supply unit and generates brake hydraulic pressure in response to the amount of operation of the brake operating member, and the main hydraulic passage leads from the master cylinder to the hydraulic control device. In addition, the hydraulic pressure generating device preferably includes a master shutoff valve, a connecting passage, and a shutoff valve, wherein the master shutoff valve is provided in the main hydraulic passage for switching between the application of the master cylinder's brake hydraulic pressure to the hydraulic control device and the application of the auxiliary cylinder's brake hydraulic pressure to the hydraulic control device, the connecting passage leads from the auxiliary cylinder to the main hydraulic passage, and the shutoff valve is used to open and close the connecting passage. Furthermore, the hydraulic control device preferably includes an output hydraulic passage as the hydraulic passage and a wheel hydraulic passage, wherein the output hydraulic passage is connected to the main hydraulic passage, and the wheel hydraulic passage leads to the wheel brakes. In this case, the pressure regulating valve preferably adjusts the brake hydraulic pressure difference between the output hydraulic passage and the wheel hydraulic passage, and the pump draws brake fluid from the open passage and discharges brake fluid to the wheel hydraulic passage.

[0011] This structure allows the master shutoff valve to switch the connection between the master and auxiliary cylinders and the wheel brakes, while the shutoff valve can shut off the connection from the auxiliary cylinder. This allows the hydraulic pressure acting on the wheel brakes to be controlled in a variety of states without requiring a complex structure, enabling efficient hydraulic control tailored to system and vehicle conditions. Furthermore, since efficient hydraulic control can be achieved without having a complex structure, it is possible to suppress an increase in the size of the system.

[0012] In addition, preferably, the auxiliary cylinder operates during normal braking control when the wheel brakes have no risk of locking, during anti-lock braking control, and during automatic braking control to assist in stabilizing the behavior of the vehicle, and is capable of increasing the pressure on the hydraulic control device side of the main cut-off valve in the main hydraulic passage.

[0013] According to this structure, the assist cylinder can be used to increase the brake fluid pressure during normal braking control, anti-lock braking control, and automatic braking control, thereby improving the pressure increase response. In addition, compared with pressure increase by pump drive, it also has the advantage of low operating noise.

[0014] Furthermore, preferably, the pump directly draws brake fluid from the supply portion through the open passage to assist in pressurizing the wheel hydraulic passage only during normal braking control when there is no risk of locking of the wheel brakes and when the assist cylinder fails.

[0015] In this structure, in addition to boosting the brake fluid pressure using the assist cylinder, the pump can also be used to boost the brake fluid pressure. This allows normal braking control to be performed using the assist cylinder's boost pressure, while also allowing the pump to increase the brake fluid pressure when a higher boost pressure is required. This allows for sufficient boost pressure to be achieved without excessively increasing the assist cylinder's boost pressure capability. This contributes to the miniaturization of the assist cylinder. Furthermore, since the pump can be driven to assist in pressurizing the wheel hydraulic passage when the assist cylinder fails, brake assist with brake hydraulic pressure boosting is possible even when the assist cylinder fails, resulting in excellent boosting performance during failure. Furthermore, since the driving frequency of the pump is reduced, the durability of the pump can also be improved. Furthermore, because the pump is driven in a controlled manner, brake fluid discharged from the wheel brakes during anti-lock braking control due to pressure reduction is not drawn into the pump but directly returned to the supply unit. This eliminates the problem of excessive pressure buildup caused by the pump.

[0016] Furthermore, it is preferred that a control device be provided for controlling the hydraulic pressure generating device and the hydraulic pressure control device. In this case, it is preferred that, during normal braking control in which there is no risk of locking of the wheel brakes, the control device drive and control the electric actuator in response to the amount of operation of the brake operating member, switch the master cut valve, and further open the cut valve so that the brake hydraulic pressure of the assist cylinder is applied to the hydraulic pressure control device.

[0017] With this configuration, the assist cylinder can be used to boost the brake fluid pressure during normal brake control, thereby achieving brake control with good boost responsiveness according to the amount of operation of the brake operating element.

[0018] Furthermore, preferably, when auxiliary pressurization of the wheel hydraulic pressure passage is required during the normal brake control, the control device sets the valve opening pressure of the pressure regulating valve to a target pressure and drives and controls the pump.

[0019] With this structure, during normal braking control, when a higher pressure boost is required, the pump can increase the brake fluid pressure in the wheel fluid pressure passage. This allows sufficient pressure boosting performance to be achieved without excessively increasing the pressure boosting performance of the assist cylinder.

[0020] Furthermore, the system preferably includes a control device and a control valve unit, wherein the control device controls the hydraulic pressure generating device and the hydraulic pressure control device, and the control valve unit switches between connecting and disconnecting the hydraulic pressure passage from the wheel hydraulic passage to the wheel brake, and connecting and disconnecting the hydraulic pressure passage from the wheel brake to the release passage. In this case, the control device preferably controls the control valve unit to execute anti-lock braking control, switching the brake fluid pressure acting on the wheel brakes between a reduced pressure state, a maintained pressure state, or a pressurized state. Furthermore, during the reduced pressure operation of the anti-lock braking control, the control device preferably controls the brake fluid discharged from the wheel brakes to be directly returned to the supply unit through the release passage, without driving or controlling the pump.

[0021] This structure allows for appropriate anti-lock braking control using the hydraulic control device. Furthermore, during anti-lock braking control, brake fluid discharged through the control valve unit due to pressure reduction is not drawn into the pump but directly returned to the supply unit, eliminating the problem of excessive pressure buildup caused by the pump.

[0022] Furthermore, it is preferred that a control device be provided for controlling the hydraulic pressure generating device and the hydraulic pressure control device. In this case, it is preferred that the control device be capable of executing a fluid suction control for sucking brake fluid into the assist cylinder during anti-lock braking control. When the fluid suction control is required, the shutoff valve is closed and the piston of the assist cylinder is driven in a decompression direction via the electric actuator.

[0023] In this structure, during anti-lock brake control, when the shutoff valve closes during fluid suction and the slave piston is driven in the decompression direction, the hydraulic chamber of the slave cylinder reaches negative pressure, and brake fluid is drawn into the slave cylinder from the supply unit. This fluid suction control replenishes the hydraulic chamber with brake fluid for re-pressurization, ensuring the appropriate amount of brake fluid required for pressure increase. This provides a braking system that can appropriately boost pressure to a high hydraulic range while avoiding an increase in the size of the slave cylinder. Furthermore, since brake fluid discharged into the open passage due to wheel brake decompression returns to the supply unit through the circulation passage, the appropriate amount of brake fluid required for fluid suction can be ensured.

[0024] Furthermore, it is preferred that a control device be provided for controlling the hydraulic pressure generating device and the hydraulic pressure control device. In this case, it is preferred that the control device be capable of executing automatic braking control to assist in stabilizing vehicle behavior. When the automatic braking control is required, the control device drives and controls the electric actuator, switches the main shutoff valve, and further opens the shutoff valve, so that the brake hydraulic pressure of the assist cylinder is applied to the hydraulic pressure control device.

[0025] In this configuration, the assist cylinder can be used to increase the brake fluid pressure during automatic brake control, thereby achieving automatic brake control with good pressure increase responsiveness.

[0026] Furthermore, it is preferred that a control device is provided for controlling the hydraulic pressure generating device and the hydraulic pressure control device. In this case, it is preferred that, when the assist cylinder fails and auxiliary pressurization of the wheel hydraulic passage is required, the control device sets the valve opening pressure of the pressure regulating valve to a target pressure and drives and controls the pump.

[0027] According to this structure, the pump can be driven to assist in pressurizing the wheel hydraulic passage when the assist cylinder fails. Therefore, even when the assist cylinder fails, brake assist with boosting the brake hydraulic pressure can be achieved. Therefore, the boosting performance during failure is excellent.

[0028] In addition, preferably, the main hydraulic passage includes a first main hydraulic passage and a second main hydraulic passage, wherein the first main hydraulic passage leads to at least one of the plurality of wheel brakes, and the second main hydraulic passage leads to the remaining wheel brakes. In this case, preferably, the master cylinder has two hydraulic chambers and is configured to output the hydraulic pressure generated by the master cylinder to the first main hydraulic passage and the second main hydraulic passage, respectively. In addition, preferably, the auxiliary cylinder has one hydraulic chamber and is configured to output the hydraulic pressure generated by the auxiliary cylinder to the first main hydraulic passage and the second main hydraulic passage, respectively. In addition, preferably, the main shut-off valve, the connecting passage, and the shut-off valve are respectively provided in the first main hydraulic passage and the second main hydraulic passage.

[0029] In this structure, when the brake operating element is operated with the master cut valve open, the brake hydraulic pressure generated in one hydraulic chamber can be transmitted to different wheel brakes. This provides a vehicle brake system applicable to hydraulic circuits having multiple wheel brakes. Effects of the Invention

[0030] The vehicle braking system of the present invention can reduce the number of components, lower costs, and improve the boosting performance of the brake hydraulic pressure. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a hydraulic circuit diagram showing a vehicle brake system according to a first embodiment of the present invention. Figure 2 1 and 2 are diagrams showing the operation of each component during brake control of 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 normal 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 under assist pressure during normal brake control 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 under pressure reduction control during anti-lock braking control in the vehicle brake system according to the first embodiment of the present invention. Figure 6 1 is a diagram showing the flow of brake fluid under fluid suction control during anti-lock brake control in the vehicle brake system according to the first embodiment of the present invention. Figure 7 This is a time chart showing the timing of fluid suction control during anti-lock brake control in the vehicle brake system according to the first embodiment of the present invention. Figure 8This 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 9 1 is a diagram showing the flow of brake fluid during backup control 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 under auxiliary pressure during backup control in the vehicle brake system according to the first embodiment of the present invention. Figure 11 This is a hydraulic circuit diagram showing a vehicle brake system according to a second embodiment of the present invention. DETAILED DESCRIPTION

[0032] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following drawings, the same components are denoted by the same reference numerals, and repeated descriptions are omitted. The vehicle brake system 100 of the present invention can be installed in a hybrid vehicle that also uses a motor, an electric vehicle and a fuel cell vehicle that use only a motor as a power source, or a vehicle that uses only an engine (internal combustion engine) as a power source.

[0033] (First embodiment) like Figure 1 As shown, the vehicle brake system 100 comprises a dual system: 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. In the hydraulic brake system, if the assist cylinder 30 fails, brake assist can be achieved through auxiliary pressure application, which will be described later.

[0034] Vehicle brake system 100 includes a hydraulic pressure generator 1 and a hydraulic pressure control unit 2. Hydraulic pressure generator 1 generates brake fluid pressure in response to the stroke (amount of movement) of brake pedal BP (brake operating member). Hydraulic pressure control unit 2 is connected to hydraulic pressure generator 1 and controls the brake fluid pressure applied to each wheel cylinder W of the wheel brakes. Vehicle brake system 100 is comprised of three bases (three modules): base 1A and base 1B, on which the components of hydraulic pressure generator 1 are mounted, and base 1C, on which the components of hydraulic pressure control unit 2 are mounted.

[0035] The base body 1A includes a master cylinder 10 and a stroke simulator 20 . The base body 1B also includes an assist cylinder 30 . The master cylinder 10 functions as an input device that generates brake fluid pressure in response 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 a motor 36 as an electric actuator as a driving source. As will be described later, the assist cylinder 30 operates during normal braking control (where there is no risk of wheel brakes locking), anti-lock braking control, and automatic braking control to assist in stabilizing vehicle behavior, boosting the brake fluid pressure on the hydraulic control device 2 side. In other words, the assist cylinder 30 is responsible for the overall boosting of the brake fluid pressure on the hydraulic control device 2 side.

[0036] 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 hole 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. The master cylinder 10 is additionally provided with a reservoir tank 15 as a supply unit capable of supplying brake fluid to the master cylinder 10 and the assist cylinder 30. The reservoir tank 15 has supply ports 15a and 15b for supplying brake fluid to the master cylinder 10. The hydraulic pressure generated by the master cylinder 10 is configured to be outputtable to each of a first master hydraulic passage 1 a and a second master hydraulic passage 1 b described later.

[0037] 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 receive the force applied to the brake pedal BP and slide within the first cylinder bore 11, 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.

[0038] The stroke simulator 20 includes a piston 22 , a cover member 24 , and a coil spring 23 . The piston 22 is inserted into the second cylinder hole 21 of the base body 1A. The cover member 24 blocks the opening of the second cylinder hole 21 . The coil spring 23 is accommodated between the piston 22 and the cover member 24 .

[0039] 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 described below.

[0040] The reservoir communication passage 1e is connected to the back pressure chamber 26 in which the coil spring 23 is arranged. The reservoir communication passage 1e communicates with the reservoir 15 (atmospheric pressure side) via the master cylinder 10 and the supply port 15b.

[0041] In the stroke simulator 20, the brake fluid pressure pressurized 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 simulated operational reaction force to the brake pedal BP.

[0042] The auxiliary cylinder 30 includes a slave piston 32 a , an electric motor 36 , and a drive transmission portion 35 , wherein the slave piston 32 a is inserted into the third cylinder hole 31 of the base body 1B. A pressure chamber 34 a is formed between the bottom surface of the third cylinder hole 31 and the slave piston 32 a.

[0043] The auxiliary cylinder supply passage 1g1 is connected to the pressure chamber 34a. The auxiliary cylinder supply passage 1g1 communicates with the supply passage 1g of the base body 1B via a pipe Hc connected to the connection port 2c of the base body 1B. The supply passage 1g branches from the reservoir communication passage 1e within the base body 1B. Consequently, the pressure chamber 34a of the auxiliary cylinder 30 communicates with the reservoir tank 15 via the auxiliary cylinder supply passage 1g1, the pipe Hc, the supply passage 1g, and the reservoir communication passage 1e.

[0044] The electric motor 36 of the assist cylinder 30 is an electric servo motor that is driven and controlled by a control device 4 to be described later. The drive transmission unit 35 is a mechanism that converts the rotational drive force of the output shaft of the motor 36 into an axial force in a linear direction. The drive transmission unit 35 is composed of, for example, a ball screw mechanism. When the output shaft of the 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 32a. The slave piston 32 a receives input from the rod 35 a and slides in the third cylinder hole 31 , thereby pressurizing the brake fluid in the pressure chamber 34 a .

[0045] The control device 4 is mounted, for example, on the side of the base 1B, and houses a control board within its 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, as well as pre-stored programs. The control device 4 is a dedicated control device for the hydraulic pressure generating device 1. The control device 4 also has a function for executing fluid suction control. Fluid suction control actively draws brake fluid into the pressure chamber 34a of the assist cylinder 30 via the assist cylinder supply passage 1g1 to maintain the brake fluid within the assist cylinder 30. For example, during anti-lock braking control, fluid suction control is executed when it is necessary to secure brake fluid for pressurization in the assist cylinder 30. Furthermore, fluid suction control is executed when, for example, the hydraulic pressure generated in the assist cylinder 30 reaches the hydraulic pressure required by the driver (this state is referred to as a "steady state") to secure brake fluid in preparation for subsequent pressurization.

[0046] Next, each hydraulic passage formed in the base body 1A will be described. Provided within the base body 1A are a first main hydraulic passage 1 a and a second main hydraulic passage 1 b as main hydraulic passages communicating with the master cylinder 10 , and a first branch hydraulic passage 1 c branching from the second main hydraulic passage 1 b .

[0047] The first master hydraulic passage 1a is a hydraulic passage originating from the bottom-side pressure chamber 14a of the first cylinder bore 11. A first pressure sensor P1 is provided in the first master hydraulic passage 1a. The first pressure sensor P1 detects the brake fluid 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 terminus of the first master hydraulic passage 1a.

[0048] The second main hydraulic passage 1b is a hydraulic passage 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, which is the terminal of the second main hydraulic passage 1b.

[0049] The first branch hydraulic passage 1c is a hydraulic passage leading from the second main hydraulic passage 1b to the pressure chamber 25 of the stroke simulator 20. The first branch hydraulic passage 1c is provided with a simulator valve 5. The simulator valve 5 is a normally closed electromagnetic valve for opening and closing the first branch hydraulic passage 1c.

[0050] The second branch hydraulic passage 1d is a hydraulic passage that connects the second main hydraulic passage 1b to the first branch hydraulic passage 1c. The second branch hydraulic passage 1d communicates with a portion of the first branch hydraulic passage 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 passage 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 side to the first cylinder bore 11 side.

[0051] A first main hydraulic passage 1a1, which communicates with the first main hydraulic passage 1a, and a second main hydraulic passage 1b1, which communicates with the second main hydraulic passage 1b, are provided within the base body 1B. The first main hydraulic passage 1a1 communicates with the first main hydraulic passage 1a via a pipe Ha connected to the connection port 2a. Furthermore, the second main hydraulic passage 1b1 communicates with the second main hydraulic passage 1b via a pipe Hb connected to the connection port 2b.

[0052] A first master cut valve 7a, serving as a master cut valve, is provided in the first main hydraulic passage 1a1. This first master cut valve 7a is a normally open solenoid valve that opens and closes the first main hydraulic passage 1a1. A second master cut valve 7b, serving as a master cut valve, is provided in the second main hydraulic passage 1b1. This second master cut valve 7b is a normally open solenoid valve that opens and closes the second main hydraulic passage 1b1.

[0053] Furthermore, a first communication passage 3 a and a second communication passage 3 b are provided in the base body 1B as communication passages leading from the assist cylinder 30 to the first main hydraulic passage 1 a 1 and the second main hydraulic passage 1 b 1 . The first communication passage 3a is a hydraulic passage that leads from the pressure chamber 34a of the third cylinder bore 31 to the first main hydraulic passage 1a1. It communicates with the common communication passage 3c, which is connected to the pressure chamber 34a. The terminal end of the first communication passage 3a is connected to the downstream side of the first master cut valve 7a. A first cutoff valve 8a is provided in the first communication passage 3a, serving as a cutoff valve for opening and closing the first communication passage 3a. The first cutoff valve 8a is a normally closed solenoid valve.

[0054] The second communication passage 3b similarly connects the pressure chamber 34a of the third cylinder bore 31 to the second main hydraulic passage 1b1. It communicates with the common communication passage 3c, which is connected to the pressure chamber 34a. The terminal end of the second communication passage 3b is connected to the downstream side of the second master shutoff valve 7b. A second shutoff valve 8b is provided in the second communication passage 3b, serving as a shutoff valve for opening and closing the second communication passage 3b. The second shutoff valve 8b is a normally closed solenoid valve.

[0055] When the first master cut valve 7a is in Figure 1 When the first shutoff valve 8a is in the open state shown and the first shutoff valve 8a is in the closed state, the upstream side (master cylinder 10 side) and the downstream side (hydraulic control device 2 side) of the first main hydraulic passage 1a1 are connected, and the first main hydraulic passage 1a1 and the first communication passage 3a are cut off. When the first master cut valve 7a is in Figure 3 When the first shutoff valve 8a is in the closed state shown and the first shutoff valve 8a is in the open state, the upstream and downstream sides of the first main hydraulic passage 1a1 are blocked, and the first communication passage 3a communicates with the downstream side of the first main hydraulic passage 1a1.

[0056] Likewise, when the second master cut valve 7b is in Figure 1 When the second shutoff valve 8b is in the open state shown and the second shutoff valve 8b is in the closed state, the upstream side (master cylinder 10 side) and the downstream side (hydraulic control device 2 side) of the second main hydraulic passage 1b1 are connected, and the second main hydraulic passage 1b1 and the second communicating passage 3b are cut off. When the second master cut valve 7b is in Figure 3 When the second shutoff valve 8b is in the closed state shown and the second main hydraulic passage 1b1 is in the open state, the upstream and downstream sides of the second main hydraulic passage 1b1 are blocked, and the second communication passage 3b communicates with the downstream side of the second main hydraulic passage 1b1.

[0057] The common communication passage 3 c is provided with a second pressure sensor P2 for detecting 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 .

[0058] The hydraulic control device 2 can appropriately control the brake hydraulic pressure acting on each wheel cylinder W. like Figure 1 As shown, the hydraulic control device 2 is arranged between the hydraulic pressure generating device 1 and each wheel cylinder W. The hydraulic control device 2 has a brake output system K1 and a brake output system K2, wherein the brake output system K1 is used to brake two of the four wheel brakes, and the brake output system K2 is used to brake the other two wheel brakes.

[0059] Two inlet ports 4a and 4b are provided on the base 1C of the hydraulic control device 2. Pipes Hd and He are connected to the inlet ports 4a and 4b, and these pipes Hd and He are connected to the output port of the base 1B of the hydraulic pressure generating device 1. Each wheel cylinder W is connected to the output port of the base 1C of the hydraulic control device 2 via a pipe. The brake output system K1 communicates with the first main hydraulic passages 1 a , 1 a 1 , and also communicates with the second main hydraulic passages 1 b , 1 b 1 . The base body 1C is provided with an inlet and outlet port 4c. The inlet and outlet port 4c is connected to a pipe Hf from the hydraulic pressure generating device 1 side.

[0060] The brake output system K1 includes a pressure reducing valve (regulator) R as a pressure regulating valve, a control valve unit V, a pump 45 , a third hydraulic pressure sensor P3 , and a control device 9 . In addition, since the brake output system K2 has the same structure as the brake output system K1 , in the following description, the brake output system K1 will be described in detail.

[0061] In the following description, the hydraulic path from the inlet port to the pressure-reducing valve R is referred to as the "output hydraulic path A," and the hydraulic path from the pressure-reducing valve R to the outlet port is referred to as the "wheel hydraulic path B." Furthermore, the hydraulic path from the wheel hydraulic path B to the suction side of the pump 45 and the inflow / outflow port 4 c is referred to as the "opening path C," and the hydraulic path from the pump 45 to the wheel hydraulic path B is referred to as the "discharge hydraulic path D."

[0062] Pressure-reducing valve R adjusts the brake fluid pressure difference between the output hydraulic passage A and the wheel hydraulic passage B, switching between allowing and blocking brake fluid flow. Furthermore, when brake fluid flow in output hydraulic passage A is blocked, pressure-reducing valve R regulates the brake fluid pressure in wheel hydraulic passage B to below a specified value. Pressure-reducing valve R includes a shutoff valve 41 and a check valve 42.

[0063] The shutoff valve 41 is a normally open linear solenoid valve interposed between the output hydraulic passage A and the wheel hydraulic passage B. It switches between allowing and blocking the flow of brake fluid from the output hydraulic passage A to the wheel hydraulic passage B. Specifically, the shutoff valve 41 is configured to adjust the valve opening pressure by controlling the energization of the solenoid (also functioning as a relief valve).

[0064] During the auxiliary pressure increase control during normal braking control (described later) and during the auxiliary pressure increase control when the assist cylinder 30 fails, the shutoff valve 41 is closed by the control of the control device 9. Furthermore, when the brake fluid pressure in the wheel fluid pressure passage B exceeds the brake fluid pressure in the output fluid pressure passage A, and the pressure difference between the brake fluid pressure in the output fluid pressure passage A and the brake fluid pressure in the wheel fluid pressure passage exceeds the force intended to close the valve, which is controlled by energizing the solenoid, the shutoff valve 41 releases the brake fluid pressure in the wheel fluid pressure passage B to the output fluid pressure passage A for regulation.

[0065] The check valve 42 is connected in parallel with the shutoff valve 41. The check valve 42 is a one-way valve that allows the brake fluid to flow from the output hydraulic passage A to the wheel hydraulic passage B. The check valve 42 is integrally provided in the normally open electromagnetic valve constituting the pressure reducing valve R.

[0066] The control valve unit V switches the hydraulic passage from the wheel hydraulic passage B to the wheel brake (wheel cylinder W) between connection and disconnection, and the hydraulic passage from the wheel brake to the release passage C between connection and disconnection. The control valve unit V increases, maintains, or reduces the brake hydraulic pressure acting on each wheel cylinder W. Therefore, the control valve unit V is configured to include an inlet valve 43, an outlet valve 44, and a check valve 43a.

[0067] An inlet valve 43, an outlet valve 44, and a check valve 43a are each located in the two hydraulic passages leading to the wheel cylinders of the two wheel brakes. The inlet valve 43 is a normally open linear solenoid valve that adjusts the pressure differential between the upstream and downstream sides of the inlet valve 43 (the opening pressure of the inlet valve 43) based on 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 assist cylinder 30 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, cutting off (maintaining) the brake hydraulic pressure applied to the wheel cylinders W.

[0068] Outlet valve 44 is a normally closed solenoid valve disposed between the wheel cylinder W and the open passage C. Outlet valve 44 is normally closed, but is opened under the control of control device 9 when the wheel is about to lock. When outlet valve 44 is opened, brake fluid acting on the wheel cylinder W is released into the open passage C, reducing the pressure of the brake fluid acting on the wheel cylinder W.

[0069] 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, even when the inlet valve 43 is closed, the check valve 43a allows brake fluid to flow from the wheel cylinder W side to the assist cylinder 30 side.

[0070] The suction side of pump 45 is connected to open passage C, and the discharge side of pump 45 is connected to discharge hydraulic passage D. Pump 45 is driven by motor M, drawing brake fluid from open passage C and directly from reservoir 15 through pipe Hf, which serves as a connecting passage to open passage C. Pump 45 then discharges the pressurized brake fluid through discharge hydraulic passage D to wheel hydraulic passage B. During normal brake control and when the assist cylinder 30 fails, pump 45 is limitedly driven under the control of control device 9 to assist in pressurizing the brake hydraulic passage of wheel hydraulic passage B. That is, pump 45 is not driven during anti-lock brake control or automatic brake control. Furthermore, the amount of brake fluid discharged by pump 45 depends on the rotational speed of motor M.

[0071] The control device 9 is mounted, for example, on the side of the base 1C, and houses a control board within its housing. The control device 9 controls the operation of the pump 45 (motor M) and the opening and closing of various valves based on information obtained from various sensors and pre-stored programs. The control device 9 is a dedicated control device for the hydraulic control device 2. The control device 9 also has a brake assist function. Specifically, during normal braking control and during backup control due to failure of the assist cylinder 30, it drives the pump 45 to assist in pressurizing the brake fluid pressure acting on the wheel brakes. In this case, the pump 45 draws brake fluid directly from the reservoir 15 via the pipe Hf and the open passage C. When executing the auxiliary pressurization control, the control device 9 sets the valve opening pressure of the pressure reducing valve R (shutoff valve 41) to the target pressure and controls the pump 45.

[0072] Next, refer to Figures 2 to 10 The operation of the vehicle brake system 100 will be described. Figure 2 In the diagram, "ACT" indicates action, and the "(Open)" and "(Closed)" following "ACT" indicate the valve's open or closed state. "Suction" indicates that suction control is sometimes executed. "-" indicates inaction. "X" indicates inaction during a failure. exist Figure 1 In the illustrated vehicle brake system 100 , when the system is activated, the first master cut valve 7 a and the second master cut valve 7 b of the hydraulic pressure generating device 1 are energized and activated (ACT), and are respectively closed. In addition, the first stop valve 8a and the second stop valve 8b are energized and operated (ACT), and are opened respectively.

[0073] As a result, the downstream side of the first main hydraulic passage 1a1 communicates with the first communication passage 3a, and the downstream side of the second main hydraulic passage 1b1 communicates with the second communication passage 3b. As a result, the master cylinder 10 is disconnected from the wheel cylinders W, and the assist cylinder 30 communicates with the wheel cylinders W. In addition, when the system is started, the simulator valve 5 of the first branch hydraulic passage 1 c of the hydraulic pressure generating device 1 is opened. In the following description, the thick, white, hollow double lines shown in the hydraulic circuit diagram represent the hydraulic pathway through which the brake fluid pressure generated by the master cylinder 10 is currently acting, and the thick, solid lines represent the hydraulic pathway through which the brake fluid pressure generated by the slave cylinder 30 is currently acting. Furthermore, the thick, dashed lines represent the hydraulic pathway through which the brake fluid pressure discharged from the pump 45 is currently acting, and the dashed lines, which are thinner and spaced closer together than the thick, dashed lines, represent the hydraulic pathways for the brake fluid discharged from the wheel cylinders W during decompression, the brake fluid suctioned by the pump 45, and the brake fluid suctioned by the slave cylinder 30.

[0074] (Conventional brake control) Figure 3 This diagram shows the flow of brake fluid during normal braking control. During normal braking control, where there is no risk of wheel locking, 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. In addition, the brake hydraulic pressure generated by the master cylinder 10 by operating the brake pedal BP is not transmitted to the wheel cylinders W but is transmitted to the stroke simulator 20 through the second main hydraulic passage 1 b and the first branch hydraulic passage 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 hydraulic pressure detected by the first pressure sensor P1) corresponding to the amount of operation of the brake pedal BP. Based on this comparison result, the control device 4 controls the speed, drive time, and other parameters of the electric motor 36. In this way, the brake hydraulic pressure, which has been boosted in response to the amount of operation of the brake pedal BP, is input into the hydraulic control device 2 via the common communication passage 3c, the first communication passage 3a, the second communication passage 3b, the first main hydraulic passage 1a1, and the second main hydraulic passage 1b1.

[0076] The brake fluid pressure input to the hydraulic control device 2 flows through the pressure reducing valve R of the output fluid pressure passage A to the wheel fluid pressure passage B, 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 of the brake pedal BP. If the 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 drives the pump 45 to perform assist pressure increase control to increase the brake hydraulic pressure in the wheel hydraulic passage B.

[0078] In auxiliary pressure control, such as Figure 4 As shown, the control unit 9 energizes the pressure-reducing valve R, causing it to operate (ACT), closing the valve. Furthermore, the motor M drives the pump 45, pressurizing the brake fluid drawn from the open passage C and discharging it through the discharge fluid passage D into the wheel fluid passage B. Consequently, the brake fluid corresponding to high-pressure areas such as emergency braking is transmitted to the wheel cylinders W via the inlet valve 43. Furthermore, the driving currents for the pressure-reducing valve R and the motor M can be appropriately set based on the required hydraulic pressure corresponding to the amount of brake pedal BP operation.

[0079] Furthermore, when the brake pedal BP is released, the control device 9 drives the electric motor 36 of the assist cylinder 30 in reverse. This reduces the hydraulic pressure generated in the assist cylinder 30, and the pressure in the pressure chamber 34a of the assist cylinder 30 becomes negative. Consequently, the brake fluid pressure transmitted to the wheel cylinder W returns to the assist cylinder 30 via the wheel hydraulic passage B, the output hydraulic passage A, the first main hydraulic passage 1a1, the second main hydraulic passage 1b1, the first communication passage 3a, the second communication passage 3b, and the common communication passage 3c. This return of brake fluid ensures a sufficient supply of brake fluid in preparation for subsequent pressurization.

[0080] (Anti-lock Braking Control) When a wheel is about to lock, anti-lock braking control is performed by appropriately selecting whether to reduce, increase, or maintain a constant level of the brake fluid pressure acting on the wheel cylinder W. The control unit 9 determines whether to select a decompression mode, a pressure increase mode, or a holding mode based on the wheel speed obtained from a wheel speed sensor (not shown).

[0081] While the brake pedal BP is depressed, that is, when the brake hydraulic pressure generated by the assist cylinder 30 acts on the hydraulic control device 2 , if the wheels are about to lock, the control device 9 starts anti-lock braking control. When the decompression mode is selected in the anti-lock brake control, such as Figure 5As shown, the control device 9 energizes the inlet valve 43 and the outlet valve 44. This causes the inlet valve 43 to close, and the outlet valve 44 to open. This releases the brake fluid in the wheel hydraulic passage B, which leads to the wheel cylinder W, from the outlet valve 44 into the open passage C. This reduces the brake fluid pressure acting on the wheel cylinder W. The brake fluid released into the open passage C is directly returned to the reservoir tank 15 via the pipe Hc.

[0082] Furthermore, when the boost mode is selected during anti-lock braking control, the control device 9 demagnetizes the inlet valve 43 and the outlet valve 44. This demagnetizes the inlet valve 43 and 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 passage B.

[0083] Furthermore, 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. This causes the inlet valve 43 and outlet valve 44 to close, and the brake fluid is thus confined within the closed flow path through the inlet valve 43, outlet valve 44, and wheel cylinder W. As a result, the brake fluid pressure acting on the wheel cylinder W remains constant.

[0084] (Fluid suction control during anti-lock brake control) The fluid suction control is a control that draws brake fluid from the reservoir 15 to ensure that brake fluid is in the pressure chamber 34a of the assist cylinder 30. Furthermore, except for special braking operations such as emergency braking or when anti-lock brake control is frequently and continuously performed, a necessary amount of brake fluid is ensured in the pressure chamber 34a during normal braking control (brake control with the first and second stop valves 8a and 8b open).

[0085] Next, refer to Figure 6 and Figure 7 The timing diagram illustrates the flow of brake fluid and the timing of suction control during suction control. exist Figure 7 The timing chart shows the fluid suction control when the control device 4 determines that the maximum stroke STL of the slave piston 32a of the assist cylinder 30 cannot meet the required fluid pressure corresponding to the amount of operation of the brake pedal BP. The maximum stroke STL can be set, for example, to the distance the slave piston 32a moves from its initial position to a position immediately adjacent to the bottom of the third cylinder bore 31 during pressurization.

[0086] If it is determined that the maximum stroke amount STL cannot meet the driver's required hydraulic pressure, the driven piston 32a is temporarily returned to the pressure reducing direction and then pressurized again to increase the pressure beyond the maximum stroke amount STL. The return amount STB at this time can be calculated based on a map (not shown), for example.

[0087] Specifically, after the brake pedal BP is depressed at time 0, fluid suction control begins at time T1 when the stroke of the slave piston 32a reaches its maximum stroke STL. The control device 4 then controls the first and second stop valves 8a and 8b to close. The control device 4 then reverses the motor 36 in the decompression direction (return direction) by a return amount STB. This causes the slave piston 32a to return in the decompression direction, maintaining the hydraulic pressure in the wheel cylinder W. The pressure in the pressure chamber 34a is reduced to a negative pressure state. Consequently, brake fluid is drawn from the reservoir 15 into the slave cylinder 30 through the reservoir communication passage 1e, the supply passage 1g, and the slave cylinder supply passage 1g1. In this case, the amount of brake fluid drawn is based on the return amount STB and is sufficient to supplement the pressure.

[0088] At time T2, when the return amount STB completes, the control device 4 opens the first and second stop valves 8a and 8b. Furthermore, the control device 4 drives the electric motor 36 forward again in the pressurizing direction for the remaining stroke. This further boosts the brake fluid pressure in the wheel cylinders W, reaching the brake fluid pressure corresponding to the driver's desired pressure at time T3.

[0089] After this, when the brake pedal BP is released, the control device 4 controls the first and second stop valves 8a, 8b to close in order to terminate the fluid suction control, and reversely drives the electric motor 36 in the decompression direction (return direction). Consequently, brake fluid is sucked from the reservoir 15 into the assist cylinder 30 through the reservoir communication passage 1e, the supply passage 1g, and the assist cylinder supply passage 1g1, and the fluid suction control terminates at time T4.

[0090] On the other hand, when it is determined that the hydraulic pressure required by the driver can be satisfied by the maximum stroke amount STL (time T4), the motor 36 is driven in the forward direction within the range of the maximum stroke amount STL regardless of the return amount STB. Figure 7 The following example shows the motor 36 being driven forward to its maximum stroke STL (time T5). In this case, when the brake pedal BP is released, the control device 4 also controls the first stop valve 8a and the second stop valve 8b to be closed, and the motor 36 is driven in the reverse direction in the decompression direction (return direction), supplying brake fluid to the assist cylinder 30 and terminating the fluid suction control (time T6).

[0091] (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 vehicle behavior. Figure 8As shown, similar to the normal brake control, the control device 4 drives the assist cylinder 30 and opens the first and second stop valves 8a and 8b to transmit the brake fluid pressure generated by the assist cylinder 30 to the hydraulic control device 2 .

[0092] In the hydraulic control device 2, the control device 9 demagnetizes the pressure reducing valve R to an open state, demagnetizes the inlet valve 43 to an open state, and demagnetizes the outlet valve 44 to a closed state. Consequently, the brake hydraulic pressure generated by the assist cylinder 30 is transmitted from the output hydraulic passage A of the hydraulic control device 2 through the wheel hydraulic passage B to the wheel cylinder W, thereby braking the wheel. Furthermore, since the inlet valve 43 is energized to a closed state and the outlet valve 44 is energized to an open state, the brake fluid pressure acting on the wheel cylinder W can be released from the outlet valve 44 to the open passage C. In this case, the brake fluid released to the open passage C also returns from the open passage C to the reservoir tank 15 through the pipe Hf.

[0093] (Backup Brake Control) The backup brake control is a backup mode control in which, when the assist cylinder 30 fails (when the hydraulic pressure generating device 1 fails), the brake hydraulic pressure generated by the master cylinder 10 is directly applied to the wheel cylinders W. Furthermore, the backup brake control can perform brake assist by boosting the brake hydraulic pressure in the wheel hydraulic passage B through auxiliary pressurization using the pump 45 of the hydraulic control device 2.

[0094] During backup brake control, the components of the hydraulic pressure generator 1 and the hydraulic control unit 2 are temporarily restored to their pre-system activation states. This opens the first and second master cut valves 7a and 7b, establishing communication between the upstream and downstream sides of the first and second main hydraulic passages 1a1 and 1b1, respectively. Furthermore, the simulator valve is closed, isolating the master cylinder 10 from the stroke simulator 20. Furthermore, in the hydraulic control unit 2, the pressure reducing valve R and inlet valve 43 are opened, while the outlet valve 44 is closed.

[0095] Therefore, when the brake pedal BP is depressed, the brake fluid pressure generated in the master cylinder 10 is transmitted to the hydraulic control device 2 via the first and second master fluid pressure passages 1a, 1a1, 1b, 1b1. Consequently, the brake fluid pressure is directly transmitted to each wheel cylinder W via the output fluid pressure passage A and the wheel fluid pressure passage B.

[0096] During the auxiliary pressure control, the control device 9 energizes the pressure reducing valve R, causing it to operate (ACT), closing the valve. Furthermore, the motor M drives the pump 45, pressurizing the brake fluid drawn from the open passage C and discharging it from the discharge fluid passage D to the wheel fluid passage B. This increases the brake fluid pressure acting on the wheel cylinder W.

[0097] During auxiliary pressure control, the third hydraulic pressure sensor P3 detects the driver's required hydraulic pressure. Then, the control device 9 drives the pump 45 for a predetermined time to increase the brake fluid pressure to the required hydraulic pressure through a control program based on the vehicle type and other characteristics pre-set in the control device 9.

[0098] Furthermore, during the above-described normal brake control, if a hydraulic abnormality occurs in either the brake output system K1 or the brake output system K2, the control device 4 can control the closing of the first stop valve 8a or the second stop valve 8b of the abnormal system. In this case, the control device 4 controls the opening of the first stop valve 8a or the second stop valve 8b of the normal system. For example, the control device 4 can determine an abnormality based on the following detection values: the detection value of the second pressure sensor P2 when one of the first stop valve 8a and the second stop valve 8b is closed and the auxiliary cylinder 30 is driven; the detection value of the second pressure sensor P2 when the other of the first stop valve 8a and the second stop valve 8b is closed and the auxiliary cylinder 30 is driven; and the detection value of the second pressure sensor P2 when both are closed and the auxiliary cylinder 30 is driven.

[0099] According to the vehicle brake system 100 of the present embodiment described above, the pump 45 can directly draw brake fluid from the reservoir tank 15 during operation. Furthermore, brake fluid discharged from the wheel cylinders W of the wheel brakes can be directly returned to the reservoir tank 15 via the open passage C. This eliminates the need for a suction valve upstream of the pump 45, nor does it require a separate reservoir for storing brake fluid discharged from the wheel cylinders W. Consequently, the number of components in the vehicle brake system 100 can be reduced, leading to cost savings. Furthermore, since there is no intake valve upstream of pump 45, there is no resistance to the brake fluid passing through the intake valve. This improves the performance of boosting the brake fluid pressure acting on the wheel brakes. Consequently, there is no need for a high-performance motor M to drive pump 45, enabling the miniaturization of system components.

[0100] Furthermore, since the supply unit capable of storing the brake fluid is the reservoir tank 15 that supplies the brake fluid to the assist cylinder 30 , the brake fluid can be smoothly circulated within the system.

[0101] Furthermore, since the reservoir tank 15 is connected so as to be able to supply brake fluid to the master cylinder 10 , brake fluid can be supplied from one reservoir tank 15 to the assist cylinder 30 via the master cylinder 10 , thereby reducing the number of system components.

[0102] Furthermore, the connection between the master cylinder 10 and the auxiliary cylinder 30 can be switched using the first and second master cut valves 7a and 7b, while the connection from the auxiliary cylinder 30 can be cut off using the first and second cut valves 8a and 8b. This allows the brake hydraulic pressure of the wheel cylinders W acting on the wheel brakes to be controlled in a variety of states without requiring a complex structure, thereby achieving efficient hydraulic control tailored to system and vehicle conditions. Furthermore, since efficient hydraulic control can be achieved without having a complicated structure, it is possible to suppress an increase in the size of the system.

[0103] Furthermore, since the assist cylinder 30 boosts the brake fluid pressure during normal braking control, anti-lock braking control, and automatic braking control, the boost response is good. Furthermore, compared to boosting the pressure by driving the pump 45 , there is also the advantage of less operating noise.

[0104] Furthermore, in addition to boosting the brake fluid pressure by the assist cylinder 30, the pump 45 can also boost the brake fluid pressure. Therefore, while normal braking control is performed by boosting the assist cylinder 30, the pump 45 can also be used to increase the brake fluid pressure when a higher boost is required. This allows sufficient boosting performance to be achieved without excessively increasing the boosting performance of the assist cylinder 30. This contributes to the miniaturization of the assist cylinder 30. Furthermore, since the pump 45 is driven to assist in pressurizing the wheel hydraulic passage B when the assist cylinder 30 fails, brake assist with brake hydraulic pressure boosting is achieved even when the assist cylinder 30 fails, resulting in excellent boosting performance during failure.

[0105] Furthermore, since the driving frequency of pump 45 is reduced, the durability of pump 45 is also improved. Furthermore, since pump 45 is driven in a limited manner, during anti-lock braking control, brake fluid discharged from wheel cylinders W due to decompression is not drawn into pump 45 but directly returned to reservoir tank 15. Consequently, there is no problem of excessive pressure increase caused by pump 45.

[0106] Furthermore, during normal braking control, the control device 4 drives and controls the pump 45 of the assist cylinder 30 in response to the amount of operation on the brake pedal BP, and switches the first and second master cut valves 7a and 7b so that the brake hydraulic pressure from the assist cylinder 30 is applied to the hydraulic control device 2. Furthermore, the first and second cut valves 8a and 8b are further opened. This allows the assist cylinder 30 to boost the brake hydraulic pressure during normal braking control, thereby achieving braking control with excellent pressure boost responsiveness in response to the amount of operation on the brake pedal BP.

[0107] Furthermore, during anti-lock braking control, the first and second stop valves 8a and 8b are closed during fluid suction, and the slave piston 32a is driven in the decompression direction to perform fluid suction control. When the slave piston 32a is driven in the decompression direction, the pressure chamber 34a of the assist cylinder 30 reaches a negative pressure, and brake fluid is drawn from the reservoir 15 into the assist cylinder 30. This fluid suction control replenishes the pressure chamber 34a with brake fluid for re-pressurization, thereby ensuring the appropriate amount of brake fluid required for pressure increase. This provides a braking system that can appropriately boost pressure to a high hydraulic pressure range while avoiding an increase in the size of the assist cylinder 30. Furthermore, since brake fluid discharged into the open passage C due to decompression by the wheel brakes returns to the reservoir 15 through the circulation passage, the appropriate amount of brake fluid required for suction can be ensured.

[0108] Furthermore, when the brake pedal BP is operated while the first and second master cut valves 7a and 7b are open, the brake fluid pressure generated in one pressure chamber 34a of the assist cylinder 30 can be transmitted to the wheel cylinders W of different wheel brakes. This provides a vehicle brake system 100 applicable to hydraulic circuits having multiple wheel brakes.

[0109] (Second embodiment) Reference Figure 11 A vehicle brake system according to a second embodiment will be described. This embodiment differs from the first embodiment in that three-way valves are used as the first and second master cut valves 7a and 7b, and in that an assist cylinder 30 having two hydraulic chambers is used.

[0110] like Figure 11 As shown, vehicle brake system 100A is composed of two bases (three modules): base 1A and base 1C. Base 1A is equipped with components of a hydraulic pressure generating device 1, while base 1C is equipped with components of a hydraulic pressure control device 2. Hydraulic pressure generating device 1 includes a master cylinder 10, a stroke simulator 20, and an auxiliary cylinder 30.

[0111] The assist cylinder 30 has two slave pistons 32a1 and 32b1 inserted into the third cylinder bore 31 of the base body 1A. The third cylinder bore 31 is divided into a bottom-side pressure chamber 34a1 and an opening-side pressure chamber 34b1. The bottom-side pressure chamber 34a1 is formed between the bottom surface of the third cylinder bore 31 and the bottom-side slave piston 32a1. The opening-side pressure chamber 34b1 is formed between the bottom-side slave piston 32a1 and the opening-side slave piston 32b1. The two slave pistons 32a1 and 32b1 slide within the third cylinder bore 31 in response to input from the rod 35a, pressurizing the brake fluid in both the bottom-side pressure chamber 34a1 and the opening-side pressure chamber 34b1.

[0112] The bottom-side pressure chamber 34a1 is connected to the first auxiliary cylinder supply passage 1h. This passage communicates with the reservoir tank 15 via the master cylinder 10 and the supply port 15a. Furthermore, the bottom-side pressure chamber 34a1 is connected to the first communication passage 3a1, which communicates with the first main hydraulic passage 1a. A first shutoff valve 8a is provided in the first communication passage 3a1.

[0113] The second auxiliary cylinder supply passage 1i is connected to the open-side pressure chamber 34b1. This second auxiliary cylinder supply passage 1i branches off from the reservoir communication passage 1e and communicates with the reservoir 15 via the reservoir communication passage 1e. Furthermore, the open-side pressure chamber 34b1 is connected to a second communication passage 3b1, which communicates with the second main hydraulic passage 1b. A second shutoff valve 8b and a second pressure sensor P2 are provided in this second communication passage 3b1.

[0114] A first master cut valve 7a1 serving as a master cut valve is provided at a connection portion between the first master hydraulic passage 1a and the first communication passage 3a1. The first master cut valve 7a1 is a 2-position 3-way solenoid valve. When the first master cut valve 7a1 is in Figure 11 In the illustrated first position, the upstream side (master cylinder 10 side) and the downstream side (hydraulic control device 2 side) of the first main hydraulic passage 1a are in communication, and the first main hydraulic passage 1a and the first communication passage 3a1 are blocked. On the other hand, when the first master cut valve 7a1 is in the second position, the upstream and downstream sides of the first main hydraulic passage 1a are blocked, and the first communication passage 3a1 communicates with the downstream side of the first main hydraulic passage 1a.

[0115] A second master cut valve 7b1 serving as a master cut valve is provided at a connection portion between the second master hydraulic passage 1b and the second communication passage 3b1. The second master cut valve 7b1 is a 2-position 3-way solenoid valve. When the second master cut valve 7b1 is in Figure 11In the first position shown, the upstream side (master cylinder 10 side) and the downstream side (hydraulic control device 2 side) of the second main hydraulic passage 1b are connected, and the second main hydraulic passage 1b and the second communication passage 3b1 are blocked. On the other hand, when the second master cut valve 7b1 is in the second position, the upstream and downstream sides of the second main hydraulic passage 1b are blocked, and the second communication passage 3b1 communicates with the downstream side of the second main hydraulic passage 1b.

[0116] The vehicle brake system 100A of the present embodiment described above achieves the same operational advantages as the first embodiment. Specifically, when the pump 45 is operating, brake fluid can be directly drawn from the reservoir tank 15, and brake fluid discharged from the wheel cylinders W of the wheel brakes can be directly returned to the reservoir tank 15 via the open passage C. This eliminates the need for a suction valve upstream of the pump 45, nor does it require a separate reservoir for storing brake fluid discharged from the wheel cylinders W. Consequently, the number of components in the vehicle brake system 100 can be reduced, leading to lower costs. Furthermore, since no suction valve is provided on the upstream side of the pump 45, no resistance is generated when the brake fluid passes through the suction valve.

[0117] While the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments and can be appropriately modified within the scope of the present invention. For example, in the first and second embodiments described above, the master cylinder 10 has a structure including two bottom-side pressure chambers 14 a and two opening-side pressure chambers 14 b . However, the present invention is not limited thereto and a structure including one pressure chamber may be employed.

[0118] Furthermore, in the first embodiment described above, the hydraulic pressure generating device 1 and the hydraulic pressure control device 2 are configured by three base bodies 1A, 1B, and 1C. However, the present invention is not limited thereto, and the base bodies 1A and 1B may be combined into a single base body to form the hydraulic pressure generating device 1. Furthermore, the hydraulic pressure generating device 1 and the hydraulic pressure control device 2 may be integrated into a single base body.

[0119] Furthermore, in the first and second embodiments described above, examples are shown in which two control devices 4 and 9 are provided. However, the present invention is not limited thereto, and a configuration in which one control device controls the hydraulic pressure generating device 1 and the hydraulic pressure control device 2 may be employed.

[0120] In addition, in the embodiment, the fluid storage tank 15 is shown as the supply unit, but is not limited to this. A hydraulic passage such as an open passage C that can store brake fluid, a piping Hf, and a fluid reservoir that can store brake fluid can be provided on the open passage C and the piping Hf as a supply unit for supplying brake fluid to the auxiliary cylinder 30. Alternatively, a tank for supplying brake fluid to the master cylinder 10 and a tank for supplying brake fluid to the assist cylinder 30 may be provided separately, and a main tank capable of supplying brake fluid to both tanks may be provided upstream thereof, with the main tank serving as the supply unit. Description of Reference Numerals

[0121] 1: Hydraulic pressure generating device; 1a, 1a1: First main hydraulic passage (main hydraulic passage); 1b, 1b1: Second main hydraulic passage (main hydraulic passage); 2: Hydraulic pressure control device; 3a, 3a1: First communication passage (communication passage); 3b, 3b1: Second communication passage (communication passage); 3c: Common communication passage (communication passage); 7a, 7a1: First master cutoff valve (master cutoff valve); 7b, 7b1: Second master cutoff valve (master cutoff valve); 8a: First stop valve (stop valve); 8b: Second stop valve (stop valve); 10: Master cylinder; 15: Fluid reservoir (supply unit); 30: Auxiliary cylinder; 36: Electric motor (electric actuator); 43: Inlet valve; 44: Outlet valve; 45: Pump; A: Output hydraulic passage; B: Wheel hydraulic passage; C: Open passage; Hf: Piping (circulation passage); R: Pressure reducing valve (pressure regulating valve); V: Control valve unit; 100, 100A: Vehicle braking system.

Claims

1. A vehicle braking system comprising a hydraulic pressure generating device and a hydraulic pressure control device, wherein: The hydraulic pressure generating device has an auxiliary cylinder that generates brake hydraulic pressure through the drive of an electric actuator. The hydraulic control device controls the brake hydraulic pressure acting on the wheel brakes according to the brake hydraulic pressure from the hydraulic pressure generating device. It is characterized by: The hydraulic control device includes a pressure regulating valve, an opening passage, a pump, and a supply unit, wherein: The pressure regulating valve is provided in a hydraulic passage communicating with the wheel brake and is capable of regulating a brake hydraulic pressure difference between the hydraulic pressure generating device side and the wheel brake side; The brake fluid discharged from the wheel brake flows into the open passage; The pump sucks the brake fluid from the open passage and discharges the brake fluid from the hydraulic passage; The supply unit is provided on the upstream side of the assist cylinder and is capable of supplying brake fluid to the assist cylinder. The open passage communicates with the supply portion.

2. The vehicle braking system according to claim 1, characterized in that The supply unit is a fluid reservoir that supplies brake fluid to the assist cylinder.

3. The vehicle braking system according to claim 2, characterized in that: A master cylinder is provided for generating brake hydraulic pressure in response to an operation amount of a brake operating member. The reservoir tank is connected to the master cylinder so as to be able to supply brake fluid to the master cylinder.

4. The vehicle braking system according to claim 1, wherein: The hydraulic pressure generating device includes a master cylinder, a main hydraulic passage, a main shut-off valve, a communication passage and a shut-off valve, wherein: The master cylinder is connected to the supply portion and generates brake hydraulic pressure in response to an operation amount of a brake operating member; The main hydraulic passage leads from the master cylinder to the hydraulic control device; The master cut valve is provided in the main hydraulic passage and is used to switch between a state in which the brake hydraulic pressure of the master cylinder is applied to the hydraulic control device and a state in which the brake hydraulic pressure of the auxiliary cylinder is applied to the hydraulic control device. The communication passage leads from the auxiliary cylinder to the main hydraulic passage; The stop valve is used to open and close the communication passage. The hydraulic control device includes an output hydraulic passage and a wheel hydraulic passage as the hydraulic passage, wherein the output hydraulic passage is connected to the main hydraulic passage, and the wheel hydraulic passage leads to the wheel brake. The pressure regulating valve is capable of adjusting the brake fluid pressure difference between the output fluid pressure passage side and the wheel fluid pressure passage side. The pump sucks the brake fluid in the open passage and discharges the brake fluid to the wheel hydraulic passage.

5. The vehicle braking system according to claim 4, characterized in that The assist cylinder is operated during normal braking control when there is no risk of locking of the wheel brakes, anti-lock braking control, and automatic braking control to assist in stabilizing vehicle behavior, and can increase the pressure on the hydraulic control device side of the master cut valve in the main hydraulic passage.

6. The vehicle braking system according to claim 4, characterized in that The pump directly draws brake fluid from the supply portion through the open passage to assist in pressurizing the wheel hydraulic passage only during normal braking control when there is no risk of locking of the wheel brakes and when the assist cylinder fails.

7. The vehicle braking system according to claim 4, characterized in that: A control device is provided, which controls the hydraulic pressure generating device and the hydraulic pressure control device, During normal braking control with no risk of locking of the wheel brakes, the control device drives and controls the electric actuator in response to the operation amount of the brake operating member, switches the main shut-off valve, and further opens the shut-off valve so that the brake hydraulic pressure of the auxiliary cylinder is applied to the hydraulic control device.

8. The vehicle braking system according to claim 7, characterized in that: During the normal brake control, when auxiliary pressurization of the wheel hydraulic pressure passage is required, the control device sets the valve opening pressure of the pressure regulating valve to a target pressure and drives and controls the pump.

9. The vehicle braking system according to claim 4, characterized in that A control device and a control valve unit are provided, wherein: The control device controls the hydraulic pressure generating device and the hydraulic pressure control device, The control valve unit is used to switch between connecting and disconnecting the hydraulic passage from the wheel hydraulic passage to the wheel brake, and connecting and disconnecting the hydraulic passage from the wheel brake to the release passage. The control device can execute anti-lock braking control by controlling the control valve unit to switch the brake fluid pressure acting on the wheel brake to a reduced pressure state, a maintained pressure state, or a pressurized pressure state. During pressure reduction in the anti-lock brake control, the control device controls the brake fluid discharged from the wheel brake to directly return to the supply portion through the open passage without driving and controlling the pump.

10. The vehicle braking system according to claim 9, characterized in that: A control device is provided to control the hydraulic pressure generating device and the hydraulic pressure control device, The control device is capable of executing a fluid suction control for sucking brake fluid into the assist cylinder during anti-lock brake control. When liquid suction control is required, the control device closes the stop valve and drives the piston of the auxiliary cylinder in the pressure reducing direction through the electric actuator.

11. The vehicle braking system according to claim 4, characterized in that A control device is provided to control the hydraulic pressure generating device and the hydraulic pressure control device, The control device is capable of executing automatic braking control to assist in stabilizing vehicle behavior, When the automatic brake control is required, the control device drives and controls the electric actuator, switches the master cut valve, and further opens the cut valve so that the brake hydraulic pressure of the assist cylinder is applied to the hydraulic control device.

12. The vehicle braking system according to claim 4, characterized in that A control device is provided to control the hydraulic pressure generating device and the hydraulic pressure control device, When the assist cylinder fails and auxiliary pressurization of the wheel hydraulic passage is required, the control device sets the valve opening pressure of the pressure regulating valve to a target pressure and drives and controls the pump.

13. The vehicle braking system according to claim 4, characterized in that The main hydraulic passage includes a first main hydraulic passage and a second main hydraulic passage, wherein: The first main hydraulic passage leads to at least one wheel brake among the plurality of wheel brakes, and the second main hydraulic passage leads to the remaining wheel brakes. The master cylinder has two hydraulic chambers and is configured to output the hydraulic pressure generated by the master cylinder to the first master hydraulic passage and the second master hydraulic passage, respectively. The auxiliary cylinder has a hydraulic chamber and is configured to output the hydraulic pressure generated by the auxiliary cylinder to the first main hydraulic passage and the second main hydraulic passage respectively. 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.

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