Brake system

Abstract

Provided is a brake system (1) wherein a first brake system (50) is provided with a first main hydraulic pressure path (51) and a switching valve (56) provided in the first main hydraulic pressure path (51). A second brake system (60) is provided with a third main hydraulic pressure path (61). A connecting hydraulic pressure path (71) leads from the first main hydraulic pressure path (51) to the third main hydraulic pressure path (61). When energized, the switching valve (56) assumes a state in which the first main hydraulic pressure path (51) and the connecting hydraulic pressure path (71) do not communicate with each other. When not energized, the switching valve (56) assumes a state in which the first main hydraulic pressure path (51) and the connecting hydraulic pressure path (71) communicate with each other. In this configuration, even when a first brake unit (10) is not actuated, hydraulic braking pressure can be applied to a wheel brake of the first brake unit (10).

Description

Brake system

[0001] The present invention relates to a brake system.

[0002] One brake system has a hydraulic pressure generating device that generates brake hydraulic pressure by driving an electric motor in accordance with the stroke of the brake pedal, and two brake systems connected to the hydraulic pressure generating device, and applies brake hydraulic pressure to both brake systems from one hydraulic pressure generating device (see, for example, Patent Document 1).

[0003] JP 2012-210879 A

[0004] From the viewpoint of fail-safety and the like, there is a demand for a brake system 100, as shown in Figure 6, which includes two brake units 10, 20 each having a hydraulic pressure generator 12, 22, brake system 50, 60, and electronic control device 14, 24, and which independently controls both brake units 10, 20. In this brake system 100, two wheel brakes B1, B2 on the front wheels FR, FL are connected to one brake unit 10, and two wheel brakes B3, B4 on the rear wheels RR, RL are connected to the other brake unit 20.

[0005] In the above-described brake system 100, if the electronic control device 14 or hydraulic pressure generating device 12 of one of the brake units 10 does not operate, braking force will be obtained only by the two wheel brakes B3, B4 connected to the other brake unit 20.

[0006] The present invention aims to solve the above-mentioned problems and provide a brake system that can apply brake fluid pressure to the two wheel brakes of the first brake unit even when the electronic control device or hydraulic pressure generating device of the first brake unit of the two brake units is not operating.

[0007] To solve the above problem, the present invention provides a brake system including a first brake unit, a second brake unit, and a connecting hydraulic line connecting the first brake unit and the second brake unit. The first brake unit includes a first hydraulic pressure generating device that generates brake hydraulic pressure in response to the amount of operation of a brake operator, a first brake system, and a first electronic control device that controls the first hydraulic pressure generating device and the first brake system. The first brake system includes a first main hydraulic line from the first hydraulic pressure generating device to a first wheel brake, a second main hydraulic line from the first main hydraulic line to a second wheel brake, and a changeover valve provided in the first main hydraulic line. The second main hydraulic line communicates with the first main hydraulic line on the first wheel brake side relative to the changeover valve. The second brake unit includes a second hydraulic pressure generating device that generates brake hydraulic pressure in response to the amount of operation of the brake operator, a second brake system, and a second electronic control device that controls the second hydraulic pressure generating device and the second brake system. The second brake system includes a third main hydraulic line extending from the second hydraulic pressure generator to a third wheel brake and a fourth main hydraulic line extending from the third main hydraulic line to a fourth wheel brake, and the connecting hydraulic line extends from the first main hydraulic line to the third main hydraulic line. When energized, the changeover valve establishes communication between the first hydraulic pressure generator side and the first wheel brake side of the first main hydraulic line, and does not establish communication between the first main hydraulic line and the connecting hydraulic line. When deenergized, the changeover valve does not establish communication between the first hydraulic pressure generator side and the first wheel brake side of the first main hydraulic line, and establishes communication between the first main hydraulic line and the connecting hydraulic line.

[0008] In the brake system of the present invention, when the selector valve is in a de-energized state, brake fluid pressure generated by the second fluid pressure generator is transmitted to the third main fluid pressure line and also from the connecting fluid pressure line to the first main fluid pressure line through the selector valve. As a result, even when the first electronic control device or the first fluid pressure generator of the first brake unit is not operating, brake fluid pressure is applied to the two wheel brakes of the first brake unit, and braking force can be generated in both wheel brakes of the first brake unit.

[0009] In the brake system described above, it is preferable that the first wheel brake and the second wheel brake are provided on the left and right front wheels, respectively, and the third wheel brake and the fourth wheel brake are provided on the left and right rear wheels, respectively. With this configuration, even if the first electronic control device or the first hydraulic pressure generating device of the first brake unit is not activated, a large braking force is generated in the wheel brakes of the left and right front wheels, allowing the vehicle to be braked stably.

[0010] In the above-described brake system, it is preferable that the first brake system includes a first inlet valve that opens and closes the first main hydraulic line, a second inlet valve that opens and closes the second main hydraulic line, return hydraulic lines extending from the first main hydraulic line and the second main hydraulic line to a reservoir tank, and an outlet valve that opens and closes the return hydraulic line.

[0011] In this configuration, by opening the inlet valve and closing the outlet valve, the brake fluid pressure generated by the hydraulic pressure generator is transmitted to the wheel brakes (during normal braking or when pressure is increased under anti-lock brake control). Furthermore, by closing the inlet valve and opening the outlet valve, the brake fluid pressure transmitted to the wheel brakes is reduced (when pressure is reduced under anti-lock brake control). Furthermore, by closing both the inlet valve and the outlet valve, the brake fluid pressure transmitted to the wheel brakes is maintained (when pressure is maintained under anti-lock brake control).

[0012] In the above-described brake system, it is preferable that the drive amount of the second hydraulic pressure generating device is set to be larger when the switching valve is in a de-energized state than when the switching valve is in a powered state. It is also preferable that the drive amount of the second hydraulic pressure generating device is set to be larger based on the amount of hydraulic fluid required when the switching valve is in a powered state. With this configuration, even when the electronic control device and hydraulic pressure generating device of the first brake unit are not operating, brake hydraulic pressure equivalent to that under normal conditions can be applied to both wheel brakes of the first brake unit by only the second hydraulic pressure generating device of the second brake unit.

[0013] In the brake system described above, the first rear wheel is provided with the third wheel brake and the first electric brake, and the second rear wheel is provided with the fourth wheel brake and the second electric brake. The second brake system is also provided with a third inlet valve that opens and closes the third main hydraulic line, and a fourth inlet valve that opens and closes the fourth main hydraulic line. When the switching valve is in a de-energized state, the third inlet valve and the fourth inlet valve are closed, and the first electric brake and the second electric brake are activated.

[0014] In this way, when the first electronic control device and the first hydraulic pressure generating device of the first brake unit are not operating and the switching unit is in a de-energized state, the brake hydraulic pressure generated by the second hydraulic pressure generating device is not transmitted to the third main hydraulic pressure line but is entirely transmitted to the first main hydraulic pressure line. This allows for increased braking force of the wheel brakes provided on the two front wheels. Also, the two rear wheels can be braked by the first electric brake and the second electric brake.

[0015] In the above-described brake system, when the changeover valve is configured as a three-way valve, two brake systems can be connected while reducing the number of electromagnetic valves.

[0016] In the brake system described above, the first hydraulic pressure generating device and the second hydraulic pressure generating device are configured to generate brake fluid pressure by moving pistons in cylinders using an electric motor. The cylinders of the first hydraulic pressure generating device are connected to the first main hydraulic pressure line, and the cylinders of the second hydraulic pressure generating device are connected to the third main hydraulic pressure line. During normal braking, brake fluid pressure is applied from the first hydraulic pressure generating device to the first wheel brake and the second wheel brake, and brake fluid pressure is applied from the second hydraulic pressure generating device to the third wheel brake and the fourth wheel brake.

[0017] In the above-described brake system, the second electronic control unit may be configured to switch the switching valve between an energized state and a de-energized state based on operation detection of the first brake unit. In this configuration, for example, when the second electronic control unit detects a malfunction of the first brake unit, the second electronic control unit can de-energize the switching valve, thereby applying brake fluid pressure from the second hydraulic pressure generator to both wheel brakes of the first brake unit.

[0018] In the brake system of the present invention, even if the electronic control device or hydraulic pressure generating device of the first brake unit of the two brake units is not operating, brake hydraulic pressure can be applied to the two wheel brakes of the first brake unit to brake the vehicle.

[0019] FIG. 1 is a configuration diagram showing a brake system according to an embodiment of the present invention. FIG. 1 is a configuration diagram showing a brake system according to an embodiment of the present invention during normal brake operation. FIG. 2 is a configuration diagram showing a case where the first electronic control device and the first hydraulic pressure generating device of the first brake unit are not operating in the brake system according to an embodiment of the present invention. FIG. 3 is a graph showing changes in brake hydraulic pressure generated by a hydraulic pressure generating device in the brake system according to an embodiment of the present invention. FIG. 4 is a configuration diagram showing a case where brake hydraulic pressure is applied only to the wheel brakes of the first brake unit in a state where the first electronic control device and the first hydraulic pressure generating device of the first brake unit are not operating in the brake system according to an embodiment of the present invention.

[0020] An embodiment of the present invention will be described in detail with reference to the drawings as appropriate. In this embodiment, a brake system of the present invention applied to a four-wheeled vehicle will be described as an example. As shown in FIG. 1 , the brake system 1 is a by-wire brake system that is activated when a prime mover (such as an engine or an electric motor) is started. The brake system 1 can be installed in hybrid vehicles that also use a motor, electric vehicles and fuel cell vehicles that are powered solely by a motor, and vehicles that are powered solely by an engine (internal combustion engine).

[0021] The brake system 1 includes a first brake unit 10 to which a first wheel brake B1 and a second wheel brake B2 are connected, a second brake unit 20 to which a third wheel brake B3 and a fourth wheel brake B4 are connected, and a connecting hydraulic pressure line 71. In this embodiment, the first wheel brake B1 brakes the left front wheel FL, and the second wheel brake B2 brakes the right front wheel FR. The third wheel brake B3 brakes the left rear wheel RL, and the fourth wheel brake B4 brakes the right rear wheel RR. As described above, the brake system 1 of this embodiment has an H-pipe brake structure. In this embodiment, a first electric brake EB1 functioning as a parking brake is provided on the left rear wheel RL, and a second electric brake EB2 functioning as a parking brake is provided on the right rear wheel RR.

[0022] The first brake unit 10 includes a first base body 11, a first hydraulic pressure generator 12, a first brake system 50, a first reservoir tank 13, and a first electronic control device 14. The first base body 11 is a metal block mounted on the vehicle. A plurality of flow paths are formed inside the first base body 11.

[0023] The first hydraulic pressure generating device 12 is an electric actuator that generates brake hydraulic pressure in accordance with the stroke amount (operation amount) of the brake pedal P (brake operator). The first hydraulic pressure generating device 12 is attached to the first base body 11. The first hydraulic pressure generating device 12 uses an electric motor 12a as a drive source to move a piston 12b within a cylinder 12c, thereby generating brake hydraulic pressure.

[0024] The first reservoir tank 13 is a container for supplying brake fluid to the first hydraulic pressure generating device 12, and is attached to the first base body 11. Brake fluid is supplied from the first reservoir tank 13 to the cylinder 12c of the first hydraulic pressure generating device 12 through a flow path in the first base body 11.

[0025] The first brake system 50 has a first main hydraulic pressure line 51, a second main hydraulic pressure line 52, and a first return hydraulic pressure line 53 formed in the first base body 11. The first main hydraulic pressure line 51 is a flow path leading from the first hydraulic pressure generator 12 to the wheel cylinder of the first wheel brake B1. The second main hydraulic pressure line 52 is a flow path leading from the first main hydraulic pressure line 51 to the wheel cylinder of the second wheel brake B2. The first main hydraulic pressure line 51 is connected to the cylinder 12c of the first hydraulic pressure generator 12, and brake hydraulic pressure is applied from the first hydraulic pressure generator 12 to the first main hydraulic pressure line 51 and the second main hydraulic pressure line 52.

[0026] The first return fluid path 53 is a flow path that leads from the first main hydraulic path 51 and the second main hydraulic path 52 to the first reservoir tank 13. The first return fluid path 53 includes a first branch fluid path 54 that branches off from the first main hydraulic path 51 and a second branch fluid path 55 that branches off from the second main hydraulic path 52. The first branch fluid path 54 and the second branch fluid path 55 merge to form a single fluid path. That is, the first return fluid path 53 includes the first branch fluid path 54 and the second branch fluid path 55 that communicate with the first main hydraulic path 51 and the second main hydraulic path 52, respectively, and a fluid path that leads from the junction of the first branch fluid path 54 and the second branch fluid path 55 to the first reservoir tank 13. Brake fluid released from the first wheel brake B1 and the second wheel brake B2 flows into the first return fluid path 53. The brake fluid released to the first return fluid path 53 is returned to the first reservoir tank 13 via the first return fluid path 53.

[0027] A changeover valve 56 is provided in the first main hydraulic line 51 on the first hydraulic pressure generator 12 side of the branch point with the first branch hydraulic line 54. In this embodiment, the changeover valve 56 is configured as a two-position, three-port, three-way solenoid valve. The ports of the changeover valve 56 are respectively connected to the first hydraulic pressure generator 12 side of the first main hydraulic line 51, the first wheel brake B1 side of the first main hydraulic line 51, and a connecting hydraulic line 71, which will be described later. The second main hydraulic line 52 is connected to the first main hydraulic line 51 on the first wheel brake B1 side of the changeover valve 56.

[0028] As shown in Fig. 2, when the switching valve 56 is energized, the first main hydraulic pressure line 51 communicates with the first hydraulic pressure generator 12 side and the first wheel brake B1 side, and the first main hydraulic pressure line 51 does not communicate with the connecting hydraulic pressure line 71. When normal brake control and anti-lock brake control are performed in a brake system 1 that is operating normally, the switching valve 56 is energized. As shown in Fig. 1, when the switching valve 56 is not energized, the first main hydraulic pressure line 51 does not communicate with the first hydraulic pressure generator 12 side and the first wheel brake B1 side, and the first main hydraulic pressure line 51 communicates with the connecting hydraulic pressure line 71. When the brake system 1 is not energized, or when the first hydraulic pressure generator 12 or the first electronic control unit 14 is not operating normally, the switching valve 56 is de-energized.

[0029] A first inlet valve 51a is provided in the first main hydraulic line 51 between the branch point of the second main hydraulic line 52 and the branch point of the first branch hydraulic line 54. The first inlet valve 51a is a normally open solenoid valve that opens and closes the first main hydraulic line 51. A first outlet valve 54a is provided in the first branch hydraulic line 54. The first outlet valve 54a is a normally closed solenoid valve that opens and closes the first branch hydraulic line 54.

[0030] A second inlet valve 52a is provided in the second main hydraulic pressure line 52, closer to the first hydraulic pressure generator 12 than the branch point with the second branch hydraulic pressure line 55. The second inlet valve 52a is a normally open solenoid valve that opens and closes the second main hydraulic pressure line 52. A second outlet valve 55a is provided in the second branch hydraulic pressure line 55. The second outlet valve 55a is a normally closed solenoid valve that opens and closes the second branch hydraulic pressure line 55.

[0031] The first electronic control unit 14 has a housing that houses a control board, and is attached to the first base body 11. The first electronic control unit 14 controls the operation of the first hydraulic pressure generating unit 12 and the opening and closing of each valve in the first brake system 50 based on information obtained from various sensors such as a pressure sensor and a stroke sensor, pre-stored programs, etc.

[0032] The first brake unit 10 is capable of executing anti-lock brake control. During anti-lock brake control, the switching valve 56 is energized, communicating the first hydraulic pressure generator 12 side of the first main hydraulic pressure line 51 with the first wheel brake B1 side. During normal braking and during pressure increase during anti-lock brake control, as shown in FIG. 2 , the first inlet valve 51a and the second inlet valve 52a are open, and the first outlet valve 54a and the second outlet valve 55a are closed. This allows brake fluid generated by the first hydraulic pressure generator 12 to be transmitted to the two wheel brakes B1 and B2. During pressure decrease during anti-lock brake control, the first inlet valve 51a and the second inlet valve 52a are energized to close, and the first outlet valve 54a and the second outlet valve 55a are energized to open. This allows brake fluid to escape from the two wheel brakes B1 and B2 to the first return hydraulic line 53, reducing the brake fluid pressure transmitted to the two wheel brakes B1 and B2. During the holding mode of the antilock brake control, the first inlet valve 51 a and the second inlet valve 52 a are energized and closed, and the first outlet valve 54 a and the second outlet valve 55 a are closed, thereby maintaining the brake fluid pressure transmitted to the two wheel brakes B1 and B2.

[0033] The second brake unit 20 has the same configuration as the first brake unit 10 described above, and includes a second base 21, a second hydraulic pressure generating device 22, a second brake system 60, a second reservoir tank 23, and a second electronic control device 24. The second hydraulic pressure generating device 22 generates brake hydraulic pressure according to the stroke amount of the brake pedal P by moving a piston 22b within a cylinder 22c using an electric motor 22a.

[0034] The second brake system 60 has a third main hydraulic pressure line 61 that runs from the second hydraulic pressure generator 22 to the third wheel brake B3, and a fourth main hydraulic pressure line 62 that runs from the third main hydraulic pressure line 61 to the fourth wheel brake B4. The second brake system 60 is not provided with a switching valve. The second brake system 60 also has a second return hydraulic pressure line 63 that runs from the third main hydraulic pressure line 61 and the fourth main hydraulic pressure line 62 to the second reservoir tank 23. The second return hydraulic pressure line 63 has a third branch hydraulic pressure line 64 that branches off from the third main hydraulic pressure line 61, and a fourth branch hydraulic pressure line 65 that branches off from the fourth main hydraulic pressure line 62. The third branch hydraulic pressure line 64 and the fourth branch hydraulic pressure line 65 merge to form a single hydraulic pressure line. That is, the second return hydraulic line 63 has a third branch hydraulic line 64 and a fourth branch hydraulic line 65 which are connected to the third main hydraulic line 61 and the fourth main hydraulic line 62, respectively, and a hydraulic line which leads from the confluence of the third branch hydraulic line 64 and the fourth branch hydraulic line 65 to the second reservoir tank 23.

[0035] A third inlet valve 61a is provided in the third main hydraulic pressure line 61, and a third outlet valve 64a is provided in a third branch hydraulic pressure line 64 of the second return hydraulic pressure line 63. A fourth inlet valve 62a is provided in the fourth main hydraulic pressure line 62, and a fourth outlet valve 65a is provided in the fourth branch hydraulic pressure line 65. Similar to the first brake unit 10, the second brake unit 20 can perform anti-lock brake control by the second electronic control device 24 controlling the operation of the second hydraulic pressure generator 22 and the opening and closing of each valve in the second brake system 60.

[0036] The brake system 1 of this embodiment includes a connecting hydraulic line 71 that extends from the first main hydraulic line 51 to the third main hydraulic line 61. The connecting hydraulic line 71 is formed by flow paths within the first base 11 and the second base 21, and piping provided between the first base 11 and the second base 21. One end of the connecting hydraulic line 71 is connected to the switching valve 56. The other end of the connecting hydraulic line 71 communicates with the third main hydraulic line 61 on the second hydraulic pressure generator 22 side relative to the third inlet valve 61a.

[0037] In the brake system 1 of this embodiment, the drive amount of the second hydraulic pressure generating device 22 is set to be larger when the selector valve 56 is in a de-energized state than when the selector valve 56 is in a conductive state (see FIG. 4 ). Specifically, the drive amount of the second hydraulic pressure generating device 22 is controlled so that the amount of fluid required (required fluid amount) is supplied from the second hydraulic pressure generating device 22 so that the brake fluid pressures applied to the two wheel brakes (required brake fluid pressures) when the selector valve 56 is in a conductive state are equal to the brake fluid pressures applied to the four wheel brakes (required brake fluid pressures) when the selector valve 56 is in a de-energized state.

[0038] Next, brake control in the brake system 1 of this embodiment will be described. During normal braking, as shown in FIG. 2 , the selector valve 56 of the first brake unit 10 is energized. This connects the first hydraulic pressure generator 12 side of the first main hydraulic pressure line 51 to the first wheel brake B1 side. Brake fluid pressure generated by the first hydraulic pressure generator 12 is transmitted to the first wheel brake B1 and also to the second wheel brake B2 via the second main hydraulic pressure line 52. Brake fluid pressure generated by the second hydraulic pressure generator 22 is transmitted to the third wheel brake B3 via the third main hydraulic pressure line 61 and to the fourth wheel brake B4 via the fourth main hydraulic pressure line 62. Thus, during normal braking, the first hydraulic pressure generator 12 generates braking forces on the two wheel brakes B1 and B2 on the front wheels FR and FL, and the second hydraulic pressure generator 22 generates braking forces on the two wheel brakes B3 and B4 on the rear wheels RR and RL.

[0039] During normal braking, as shown in FIG. 3 , a malfunction may occur in the first brake unit 10, causing at least one of the first electronic control device 14 and the first hydraulic pressure generator 12 to malfunction and de-energizing the selector valve 56. In this case, the selector valve 56 returns to its initial position (de-energized state), preventing communication between the first hydraulic pressure generator 12 side of the first main hydraulic line 51 and the first wheel brake B1 side, and instead providing communication between the first main hydraulic line 51 and the connecting hydraulic line 71. In this state, brake hydraulic pressure generated by the second hydraulic pressure generator 22 is transmitted to the two wheel brakes B3 and B4 on the rear wheels RR and RL. Furthermore, brake hydraulic pressure generated by the second hydraulic pressure generator 22 is also transmitted to the two wheel brakes B1 and B2 on the front wheels FR and FL via the third main hydraulic line 61, the connecting hydraulic line 71, the selector valve 56, the first main hydraulic line 51, and the second main hydraulic line 52. In this way, even when the first electronic control device 14 and the first hydraulic pressure generating device 12 of the first brake unit 10 are not operating, braking force is generated by the second hydraulic pressure generating device 22 of the second brake unit 20 on the two wheel brakes B1, B2 on the front wheels FR, FL side and the two wheel brakes B3, B4 on the rear wheels RR, RL side.

[0040] The drive amount of the second hydraulic pressure generating device 22 is larger when the switching valve 56 is in a non-energized state (when the first electronic control device 14 and the first hydraulic pressure generating device 12 are not operating) than when the switching valve 56 is in an energized state (during normal braking operation) (see FIG. 4). As a result, even when the second hydraulic pressure generating device 22 applies brake hydraulic pressure to four wheel brakes, the same brake hydraulic pressure as in normal operation is applied to each wheel brake.

[0041] In the brake system 1 described above, during normal braking operation, the first hydraulic pressure generator 12 applies brake hydraulic pressure to the first wheel brake B1 and the second wheel brake B2, and the second hydraulic pressure generator 22 applies brake hydraulic pressure to the third wheel brake B3 and the fourth wheel brake B4, as shown in Figure 2. In this way, the brake system 1 can control both brake units 10, 20 independently.

[0042] 3, even when the first electronic control device 14 or the first hydraulic pressure generator 12 of the first brake unit 10 is not operating, brake hydraulic pressure can be applied not only to the two wheel brakes B3 and B4 on the rear wheels RR and RL, but also to the two wheel brakes B1 and B2 on the front wheels FR and FL connected to the first brake unit 10. As a result, even when the first electronic control device 14 or the first hydraulic pressure generator 12 of the first brake unit 10 is not operating, a large braking force is generated in the wheel brakes B1 and B2 provided on the left and right front wheels FR and FL, allowing the vehicle to be braked stably.

[0043] Although the above describes an embodiment of the present invention, the present invention is not limited to the above embodiment and can be modified as appropriate without departing from the spirit and scope of the present invention. For example, as shown in FIG. 5 , the third inlet valve 61a and the fourth inlet valve 62a may be closed when the first electronic control device 14 and the first hydraulic pressure generator 12 of the first brake unit 10 are not operating and the switching valve 56 is not energized. In this configuration, the brake hydraulic pressure generated by the second hydraulic pressure generator 22 is not transmitted to the third main hydraulic pressure line 61 but is entirely transmitted to the first main hydraulic pressure line 51. This increases the braking force of the two wheel brakes B1 and B2 on the front wheels FR and FL. In the brake control described above, the first electric brake EB1 is activated to brake the left rear wheel RL, and the second electric brake EB2 is activated to brake the right rear wheel RR.

[0044] 1 may be configured to detect the operating state of the first brake unit 10 and to switch the switching valve 56 between an energized state and a de-energized state. In this configuration, the switching valve 56 is not de-energized during normal braking, but if the second electronic control unit 24 detects a malfunction in the operation of the first brake unit 10, the second electronic control unit 24 de-energizes the switching valve 56, thereby allowing the second hydraulic pressure generator 22 to apply brake hydraulic pressure to the two wheel brakes B1, B2 of the first brake unit 10.

[0045] In the brake system 1 of this embodiment, the switching valve 56 is configured as a three-way valve, but a single switching valve may be configured by combining a plurality of electromagnetic valves.

[0046] In this embodiment, the first wheel brake B1 brakes the front wheel FL, the second wheel brake B2 brakes the front wheel FR, the third wheel brake B3 brakes the rear wheel RL, and the fourth wheel brake B4 brakes the rear wheel RR, but the wheels that are braked by each wheel brake are not limited.

[0047] REFERENCE SIGNS LIST 1 Brake system 10 First brake unit 11 First base 12 First hydraulic pressure generating device 12a Electric motor 12b Piston 12c Cylinder 13 First reservoir tank 14 First electronic control device 20 Second brake unit 21 Second base 22 Second hydraulic pressure generating device 22a Electric motor 22b Piston 22c Cylinder 23 Second reservoir tank 24 Second electronic control device 50 First brake system 51 First main hydraulic line 51a First inlet valve 52 Second main hydraulic line 52a Second inlet valve 53 First return hydraulic line 54 First branch hydraulic line 54a First outlet valve 55 Second branch hydraulic line 55a Second outlet valve 56 Switching valve 60 Second brake system 61 Third main hydraulic line 61a Third inlet valve 62 Fourth main hydraulic line 62a Fourth inlet valve 63 Second return fluid path 64 Third branch fluid path 64a Third outlet valve 65 Fourth branch fluid path 65a Fourth outlet valve 71 Connecting fluid pressure path B1 First wheel brake B2 Second wheel brake B3 Third wheel brake B4 Fourth wheel brake EB1 First electric brake EB2 Second electric brake FL Left front wheel FR Right front wheel RL Left rear wheel RR Right rear wheel P Brake pedal

Claims

1. A brake system comprising a first brake unit, a second brake unit, and a connecting hydraulic line connecting the first brake unit and the second brake unit, wherein the first brake unit comprises: a first hydraulic pressure generating device which generates brake hydraulic pressure in response to an amount of operation of a brake operator; a first brake system; and a first electronic control device which controls the first hydraulic pressure generating device and the first brake system, wherein the first brake system comprises: a first main hydraulic line from the first hydraulic pressure generating device to a first wheel brake; a second main hydraulic line from the first main hydraulic line to a second wheel brake; and a changeover valve provided in the first main hydraulic line, wherein the second main hydraulic line is connected to the first main hydraulic line on the first wheel brake side of the changeover valve, and wherein the second brake unit comprises: a second hydraulic pressure generating device which generates brake hydraulic pressure in response to an amount of operation of the brake operator; a second brake system; and a second electronic control device which controls the second hydraulic pressure generating device and the second brake system, wherein the second brake system comprises: a third main hydraulic pressure line extending from the second hydraulic pressure generator to a third wheel brake; and a fourth main hydraulic pressure line extending from the third main hydraulic pressure line to a fourth wheel brake, wherein the connecting hydraulic pressure line extends from the first main hydraulic pressure line to the third main hydraulic pressure line, wherein when energized, the changeover valve establishes communication between the first hydraulic pressure generator side and the first wheel brake side of the first main hydraulic pressure line and does not establish communication between the first main hydraulic pressure line and the connecting hydraulic pressure line, and wherein when de-energized, the changeover valve does not establish communication between the first hydraulic pressure generator side and the first wheel brake side of the first main hydraulic pressure line and establishes communication between the first main hydraulic pressure line and the connecting hydraulic pressure line.

2. A brake system as described in claim 1, wherein the first wheel brake and the second wheel brake are provided on the left and right front wheels, respectively, and the third wheel brake and the fourth wheel brake are provided on the left and right rear wheels, respectively.

3. A brake system as claimed in claim 1, characterized in that the first brake system comprises: a first inlet valve for opening and closing the first main hydraulic line; a second inlet valve for opening and closing the second main hydraulic line; a return hydraulic line extending from the first main hydraulic line and the second main hydraulic line to a reservoir tank; and an outlet valve for opening and closing the return hydraulic line.

4. A brake system as claimed in claim 1, characterized in that the drive amount of the second hydraulic pressure generating device is set to be greater when the switching valve is in a non-energized state than when the switching valve is in a powered state.

5. A brake system as claimed in claim 4, characterized in that the second hydraulic pressure generating device is set to increase the amount of drive based on the amount of hydraulic fluid required when the switching valve is in a non-energized state.

6. A brake system as described in claim 2, wherein a first rear wheel is provided with the third wheel brake and a first electric brake, and a second rear wheel is provided with the fourth wheel brake and a second electric brake, and the second brake system comprises a third inlet valve which opens and closes the third main hydraulic line, and a fourth inlet valve which opens and closes the fourth main hydraulic line, and when the changeover valve is in a non-energized state, the third inlet valve and the fourth inlet valve are closed, and the first electric brake and the second electric brake are activated.

7. A brake system according to claim 1, characterized in that the changeover valve is constituted by a three-way valve.

8. A brake system as claimed in claim 1, wherein the first hydraulic pressure generating device and the second hydraulic pressure generating device are configured to generate brake hydraulic pressure by moving a piston within a cylinder using an electric motor, and the cylinder of the first hydraulic pressure generating device is connected to the first main hydraulic pressure passage, and the cylinder of the second hydraulic pressure generating device is connected to the third main hydraulic pressure passage.

9. A brake system as claimed in claim 1, characterized in that the second electronic control device is capable of switching the switching valve between an energized state and a non-energized state.

10. A brake system as claimed in claim 9, characterized in that the second electronic control device switches the switching valve between a conductive state and a non-conductive state based on detection of the operation of the first brake unit.