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 second brake system (60) is provided with a second main hydraulic pressure path (61). A first connecting hydraulic pressure path (71) leads from the first main hydraulic pressure path (51) to the second main hydraulic pressure path (61), and a second connecting hydraulic pressure path (72) leads from the second main hydraulic pressure path (61) to the first main hydraulic pressure path (51). When not energized, a first switching valve (56) causes the first main hydraulic pressure path (51) and the first connecting hydraulic pressure path (71) to communicate with each other. When non energized, a second switching valve (66) allows the second main hydraulic pressure path (61) and the second connecting hydraulic pressure path (72) to communicate with each other. In this configuration, even when one brake unit is not actuated, hydraulic braking pressure can be generated in both brake units.

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-safes and the like, there is a demand for a brake system 100, as shown in Figure 8, which includes two brake units 10, 20, each having a hydraulic pressure generator 12, 22, brake systems 50, 60, and electronic control devices 14, 24, and which independently controls both brake units 10, 20. In such a brake system 100, if the electronic control device 14 or hydraulic pressure generator 12 of one brake unit 10 does not operate, braking force will be obtained only by the two wheel brakes B2, B4 connected to the other brake unit 20.

[0005] The present invention aims to solve the above-mentioned problems and provide a brake system that can generate brake fluid pressure in both brake units even if the electronic control device or fluid pressure generating device of one of the two brake units is not operating.

[0006] To solve the above problem, the present invention provides a brake system including a first brake unit, a second brake unit, and first and second connecting hydraulic lines connecting the first and second brake units. 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 third main hydraulic line from the first main hydraulic line to a third wheel brake, and a first switch valve provided in the first main hydraulic line. 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 second main hydraulic line extending from the second hydraulic pressure generator to the second wheel brake, a fourth main hydraulic line extending from the second main hydraulic line to the fourth wheel brake, and a second selector valve provided in the second main hydraulic line. A first connecting hydraulic line extends from the first main hydraulic line to the second main hydraulic line, and a second connecting hydraulic line extends from the second main hydraulic line to the first main hydraulic line. When energized, the first selector valve establishes communication between the first hydraulic pressure generator side of the first main hydraulic line and the first wheel brake side, and does not establish communication between the first main hydraulic line and the first connecting hydraulic line. When deenergized, the first selector valve does not establish communication between the first hydraulic pressure generator side of the first main hydraulic line and the first wheel brake side, and establishes communication between the first main hydraulic line and the first connecting hydraulic line. When energized, the second selector valve establishes a state in which the second hydraulic pressure generator side of the second main hydraulic pressure line communicates with the second wheel brake side, and the second main hydraulic pressure line does not communicate with the second connecting hydraulic pressure line.When de-energized, the second selector valve does not establish a state in which the second hydraulic pressure generator side of the second main hydraulic pressure line communicates with the second wheel brake side, and the second main hydraulic pressure line communicates with the second connecting hydraulic pressure line.

[0007] In the brake system of the present invention, when the first selector valve is energized and the second selector valve is de-energized, brake fluid pressure generated by the first hydraulic pressure generator is transmitted to the first main hydraulic pressure line and also transmitted from the second connecting hydraulic pressure line to the second main hydraulic pressure line via the second selector valve. This makes it possible to generate braking force in the wheel brakes on the first brake unit side and the wheel brakes on the second brake unit side even when the second electronic control device and the second hydraulic pressure generator of the second brake unit are not operating.

[0008] In the brake system of the present invention, when the second selector valve is energized and the first selector valve is de-energized, the brake fluid pressure generated by the second fluid pressure generator is transmitted to the second main fluid pressure line and also transmitted from the first connecting fluid pressure line to the first main fluid pressure line via the first selector valve. This makes it possible to generate braking force in the wheel brakes on the second brake unit side and the wheel brakes on the first brake unit side even when the first electronic control device and the first fluid pressure generator of the first brake unit are not operating.

[0009] In this way, in the brake system of the present invention, even if the electronic control device or hydraulic pressure generating device of one of the two brake units is not operating, brake hydraulic pressure can be applied to the wheel brakes connected to both brake units.

[0010] In the brake system described above, when the third main hydraulic line communicates with the first main hydraulic line on the first hydraulic pressure generator side relative to the first selector valve, and when the second selector valve is energized and the first selector valve is de-energized, brake hydraulic pressure generated by the second hydraulic pressure generator is transmitted from the first connecting hydraulic line to the first wheel brake side of the first main hydraulic line through the first selector valve. As a result, when the first electronic control device and the first hydraulic pressure generator of the first brake unit are not operating, braking forces are generated in three wheel brakes: the first wheel brake, the second wheel brake, and the fourth brake. Also, in the brake system described above, when the fourth main hydraulic line communicates with the second main hydraulic line on the second hydraulic pressure generator side relative to the second selector valve, and when the first selector valve is energized and the second selector valve is de-energized, brake hydraulic pressure generated by the first hydraulic pressure generator is transmitted from the second connecting hydraulic line to the second wheel brake side of the second main hydraulic line through the second selector valve. As a result, when the second electronic control device and the second hydraulic pressure generating device of the second brake unit are not activated, braking force is generated in the three wheel brakes, i.e., the first wheel brake, the second wheel brake, and the third wheel brake. With the above-mentioned configuration, the brake hydraulic pressure transmitted to the three wheel brakes can be made larger than when the brake hydraulic pressure generated by the hydraulic pressure generating device of one brake unit is transmitted to four wheel brakes.

[0011] 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. In the above configuration, even if the electronic control device or hydraulic pressure generating device of one of the brake units is not operating, braking force is generated in the wheel brakes of both the left and right front wheels, so that the vehicle can be braked stably with a large braking force.

[0012] In the brake system described above, the first brake system preferably includes a first inlet valve that opens and closes the first main hydraulic line, a first return hydraulic line from the first main hydraulic line to a first reservoir tank, and a first outlet valve that opens and closes the first return hydraulic line.The second brake system preferably includes a second inlet valve that opens and closes the second main hydraulic line, a second return hydraulic line from the second main hydraulic line to a second reservoir tank, and a second outlet valve that opens and closes the second return hydraulic line.

[0013] 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).

[0014] In the above-described brake system, it is preferable to simplify and downsize the fluid path structure of the brake system by providing the first switching valve between the first inlet valve and the first return fluid path, and providing the second switching valve between the second inlet valve and the second return fluid path.

[0015] In the above-described brake system, it is preferable that the drive amount of the first hydraulic pressure generating device is set to be larger when the second switching valve is in a de-energized state than when the second switching valve is in a powered state. Also, it is preferable that the drive amount of the second hydraulic pressure generating device is set to be larger when the first switching valve is in a powered state than when the first switching valve is in a powered state. It is preferable that the first hydraulic pressure generating device is set to increase its drive amount based on the amount of fluid required when the second switching valve is in a powered state. It is also preferable that the second hydraulic pressure generating device is set to increase its drive amount based on the amount of fluid required when the first switching valve is in a powered state.

[0016] With this configuration, even if the electronic control device or hydraulic pressure generating device of one brake unit is not operating, the hydraulic pressure generating device of the other brake unit alone can apply brake hydraulic pressure equivalent to that under normal conditions to the wheel brakes connected to both brake units.

[0017] In the above-described brake system, when the first changeover valve and the second changeover valve are configured as three-way valves, it is possible to connect two brake systems while reducing the number of electromagnetic valves.

[0018] 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 electric motors. 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 second 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 third wheel brake, and brake fluid pressure is applied from the second hydraulic pressure generating device to the second wheel brake and the fourth wheel brake.

[0019] In the brake system described above, the first electronic control unit may be configured to switch the second switching valve between an energized state and a de-energized state, and the second electronic control unit may be configured to switch the first switching valve between an energized state and a de-energized state. The first electronic control unit may be configured to switch the second switching valve between an energized state and a de-energized state based on operation detection of the second brake unit. The second electronic control unit may be configured to switch the first switching valve between an energized state and a de-energized state based on operation detection of the first brake unit.

[0020] In this configuration, for example, when the first electronic control device detects a malfunction of the second brake unit, the first electronic control device de-energizes the second switching valve, thereby allowing brake fluid pressure to be applied from the first hydraulic pressure generator to the wheel brakes of the second brake unit. Also, when the second electronic control device detects a malfunction of the first brake unit, the second electronic control device de-energizes the first switching valve, thereby allowing brake fluid pressure to be applied from the second hydraulic pressure generator to the wheel brakes of the first brake unit.

[0021] In the brake system of the present invention, even if the electronic control device or hydraulic pressure generating device of one of the two brake units is not operating, brake hydraulic pressure can be applied to the wheel brakes connected to both brake units, thereby obtaining balanced braking force.

[0022] 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. 1 is a configuration diagram showing a case where the second electronic control device and the second hydraulic pressure generating device of the second brake unit do not operate in the brake system according to an embodiment of the present invention. FIG. 1 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 do not operate in the brake system according to an embodiment of the present invention. FIG. 2 is a graph showing changes in brake hydraulic pressure generated by a hydraulic pressure generating device in a brake system according to an embodiment of the present invention. FIG. 2 is a configuration diagram showing a case where the second electronic control device and the second hydraulic pressure generating device of the second brake unit do not operate in the brake system according to another embodiment of the present invention. FIG. 3 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 do not operate in the brake system according to another embodiment of the present invention.

[0023] 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).

[0024] The brake system 1 includes a first brake unit 10 connected to a first wheel brake B1 and a third wheel brake B3, and a second brake unit 20 connected to a second wheel brake B2 and a fourth wheel brake B4. In this embodiment, the first wheel brake B1 brakes the left front wheel FL, and the third wheel brake B3 brakes the right rear wheel RR. The second wheel brake B2 brakes the right front wheel FR, and the fourth wheel brake B4 brakes the left rear wheel RL. As described above, the brake system 1 of this embodiment has an X-pipe brake structure. In this embodiment, electric brakes EB that function as parking brakes are provided on the left rear wheel RL and the right rear wheel RR, respectively.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] The first brake system 50 has a first main hydraulic pressure line 51, a third 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 third main hydraulic pressure line 52 is a flow path leading from the first main hydraulic pressure line 51 to the wheel cylinder of the third wheel brake B3. 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 third main hydraulic pressure line 52.

[0029] The first return fluid path 53 is a flow path that leads from the first main hydraulic path 51 and the third 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 third branch fluid path 55 that branches off from the third main hydraulic path 52. The first branch fluid path 54 and the third 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 third branch fluid path 55 that communicate with the first main hydraulic path 51 and the third main hydraulic path 52, respectively, and a fluid path that leads from the junction of the first branch fluid path 54 and the third branch fluid path 55 to the first reservoir tank 13. Brake fluid released from the first wheel brake B1 and the third wheel brake B3 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.

[0030] A first selector 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 return hydraulic line 53. In this embodiment, the first selector valve 56 is configured as a two-position, three-port, three-way solenoid valve. The ports of the first selector 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 first connecting hydraulic line 71, which will be described later. The third main hydraulic line 52 is connected to the first main hydraulic line 51 on the first hydraulic pressure generator 12 side of the first selector valve 56.

[0031] As shown in Fig. 2 , when energized, the first selector valve 56 connects the first hydraulic pressure generator 12 side of the first main hydraulic line 51 to the first wheel brake B1 side, and does not connect the first main hydraulic line 51 to the first connecting hydraulic line 71. When normal brake control and anti-lock brake control are performed in a brake system 1 that is operating normally, the first selector valve 56 is energized. As shown in Fig. 1 , when de-energized, the first selector valve 56 does not connect the first hydraulic pressure generator 12 side of the first main hydraulic line 51 to the first wheel brake B1 side, and connects the first main hydraulic line 51 to the first connecting hydraulic line 71. In addition to when energization to the brake system 1 is turned off, when the first hydraulic pressure generator 12 or the first electronic control unit 14 is not operating normally, energization to the first selector valve 56 is stopped.

[0032] A first inlet valve 51a is provided in the first main hydraulic line 51 between the branch point of the third main hydraulic line 52 and the first switching valve 56. 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.

[0033] A third inlet valve 52a is provided in the third main hydraulic line 52, closer to the first hydraulic pressure generator 12 than the branch point with the third branch hydraulic line 55. The third inlet valve 52a is a normally open solenoid valve that opens and closes the third main hydraulic line 52. A third outlet valve 55a is provided in the third branch hydraulic line 55. The third outlet valve 55a is a normally closed solenoid valve that opens and closes the third branch hydraulic line 55.

[0034] 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.

[0035] The first brake unit 10 is capable of executing anti-lock brake control. During anti-lock brake control, the first 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 third inlet valve 52a are open, and the first outlet valve 54a and the third outlet valve 55a are closed. This allows brake fluid generated by the first hydraulic pressure generator 12 to be transmitted to the first wheel brake B1 and the third wheel brake B3. During pressure decrease during anti-lock brake control, the first inlet valve 51a and the third inlet valve 52a are energized to close them, and the first outlet valve 54a and the third outlet valve 55a are energized to open them. This allows brake fluid to escape from the first wheel brake B1 and the third wheel brake B3 to the first return hydraulic line 53, reducing the brake fluid pressure transmitted to the first wheel brake B1 and the third wheel brake B3. During the holding state of the antilock brake control, the first inlet valve 51 a and the third inlet valve 52 a are energized and closed, and the first outlet valve 54 a and the third outlet valve 55 a are closed, thereby maintaining the brake fluid pressure transmitted to the first wheel brake B1 and the third wheel brake B3.

[0036] 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.

[0037] The second brake system 60 has a second main hydraulic pressure line 61 that runs from the second hydraulic pressure generator 22 to the second wheel brake B2, and a fourth main hydraulic pressure line 62 that runs from the second main hydraulic pressure line 61 to the fourth wheel brake B4. The second brake system 60 also has a second return hydraulic pressure line 63 that runs from the second 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 includes a second branch hydraulic pressure line 64 that branches off from the second 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 second 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 second branch hydraulic line 64 and a fourth branch hydraulic line 65 which are connected to the second main hydraulic line 61 and the fourth main hydraulic line 62, respectively, and a hydraulic line which leads from the confluence of the second branch hydraulic line 64 and the fourth branch hydraulic line 65 to the second reservoir tank 23.

[0038] A second inlet valve 61 a is provided in the second main hydraulic pressure line 61, and a second outlet valve 64 a is provided in the second branch hydraulic pressure line 64 of the second return hydraulic pressure line 63. A fourth inlet valve 62 a is provided in the fourth main hydraulic pressure line 62, and a fourth outlet valve 65 a is provided in the fourth branch hydraulic pressure line 65. Similar to the first brake unit 10, the second brake unit 20 can perform antilock 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.

[0039] A second selector valve 66 is provided in the second main hydraulic pressure line 61 on the second hydraulic pressure generator 22 side of the branch point with the second branch hydraulic pressure line 64. Ports of the second selector valve 66 are connected to the second hydraulic pressure generator 22 side of the second main hydraulic pressure line 61, the second wheel brake B2 side of the second main hydraulic pressure line 61, and a second connecting hydraulic pressure line 72, which will be described later. The fourth main hydraulic pressure line 62 is connected to the second main hydraulic pressure line 61 on the second hydraulic pressure generator 22 side of the second selector valve 66.

[0040] As shown in FIG. 2 , when energized, the second selector valve 66 connects the second hydraulic pressure generator 22 side of the second main hydraulic line 61 to the second wheel brake B2 side, and does not connect the second main hydraulic line 61 to the second connecting hydraulic line 72. When normal brake control and anti-lock brake control are performed in a brake system 1 that is operating normally, the second selector valve 66 is energized. As shown in FIG. 1 , when de-energized, the second selector valve 66 connects the first hydraulic pressure generator 12 side of the second main hydraulic line 61 to the second wheel brake B2 side, and connects the second wheel brake B2 side of the second main hydraulic line 61 to the second connecting hydraulic line 72. When energization to the brake system 1 is turned off, or when the second hydraulic pressure generator 22 or the second electronic control unit 24 is not operating normally, energization to the second selector valve 66 is stopped.

[0041] The brake system 1 of this embodiment is provided with a first connecting hydraulic line 71 connecting the first main hydraulic line 51 to the second main hydraulic line 61, and a second connecting hydraulic line 72 connecting the second main hydraulic line 61 to the first main hydraulic line 51. One end of the first connecting hydraulic line 71 is connected to the first selector valve 56. The other end of the first connecting hydraulic line 71 is connected to the second main hydraulic line 61 on the second wheel brake B2 side of the second selector valve 66. One end of the second connecting hydraulic line 72 is connected to the second selector valve 66. The other end of the second connecting hydraulic line 72 is connected to the first main hydraulic line 51 on the first hydraulic pressure generator 12 side of the first selector valve 56. The first connecting hydraulic line 71 and the second connecting hydraulic line 72 are formed by flow paths within the first base 11 and the second base 21, piping provided between the first base 11 and the second base 21, etc.

[0042] In the brake system 1 of this embodiment, the drive amount of the first hydraulic pressure generating device 12 is set to be larger when the second selector valve 66 is in a de-energized state than when the second selector valve 66 is in a conductive state (see FIG. 5 ). Specifically, the drive amount of the first hydraulic pressure generating device 12 is controlled so that the amount of fluid required (required fluid amount) is supplied from the first hydraulic pressure generating device 12 so that the brake fluid pressure (required brake fluid pressure) applied to each wheel brake (two wheel brakes in this embodiment) when the second selector valve 66 is in a conductive state is equal to the brake fluid pressure (required brake fluid pressure) applied to each wheel brake (three wheel brakes in this embodiment) when the second selector valve 66 is in a de-energized state.

[0043] Furthermore, the drive amount of the second hydraulic pressure generating device 22 is set to be larger when the first selector valve 56 is in a non-energized state than when the first selector valve 56 is in a powered state. Specifically, the drive amount of the second hydraulic pressure generating device 22 is controlled so that the amount of fluid (required fluid amount) required for the brake fluid pressure (required brake fluid pressure) applied to each wheel brake (two wheel brakes in this embodiment) when the first selector valve 56 is in a powered state to be equal to the brake fluid pressure (required brake fluid pressure) applied to each wheel brake (three wheel brakes in this embodiment) when the first selector valve 56 is in a powered state is supplied from the second hydraulic pressure generating device 22.

[0044] Next, brake control in the brake system 1 of this embodiment will be described. During normal braking, as shown in FIG. 2 , the first selector valve 56 of the first brake unit 10 is energized, and the second selector valve 66 of the second brake unit 20 is energized. This establishes communication between the first hydraulic pressure generator 12 side of the first main hydraulic pressure line 51 and 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 transmitted to the third wheel brake B3 via the third main hydraulic pressure line 52. Furthermore, the second hydraulic pressure generator 22 side of the second main hydraulic pressure line 61 is also energized between the second wheel brake B2 side and the second wheel brake B2 side. Brake fluid pressure generated by the second hydraulic pressure generator 22 is transmitted to the second wheel brake B2 and also transmitted to the fourth wheel brake B4 via the fourth main hydraulic pressure line 62. In this way, during normal braking operation, the first hydraulic pressure generating device 12 generates braking force on the first wheel brake B1 and the third wheel brake B3, and the second hydraulic pressure generating device 22 generates braking force on the second wheel brake B2 and the fourth wheel brake B4.

[0045] 3 , during normal braking, a malfunction may occur in the second brake unit 20, causing at least one of the second electronic control device 24 and the second hydraulic pressure generator 22 to fail to operate, resulting in the second selector valve 66 being de-energized. In this case, the position of the second selector valve 66 returns to its initial state (de-energized state), so that the second hydraulic pressure generator 22 side of the second main hydraulic pressure line 61 is not communicated with the second wheel brake B2 side and the fourth wheel brake B4 side, and the second main hydraulic pressure line 61 is communicated with the second connecting hydraulic pressure line 72. In this state, brake hydraulic pressure generated by the first hydraulic pressure generator 12 is transmitted to the first wheel brake B1 and the third wheel brake B3, and is also transmitted to the second wheel brake B2 from the first main hydraulic pressure line 51 through the second connecting hydraulic pressure line 72, the second selector valve 66, and the second main hydraulic pressure line 61. In this way, even when the second electronic control device 24 and the second hydraulic pressure generating device 22 of the second brake unit 20 are not operating, braking force is generated in the first wheel brake B1, the second wheel brake B2, and the third wheel brake B3 by the first hydraulic pressure generating device 12 of the first brake unit 10.

[0046] The drive amount of the first hydraulic pressure generating device 12 is greater when the second selector valve 66 is in a non-energized state (when the second electronic control device 24 and the second hydraulic pressure generating device 22 are not operating) than when the second selector valve 66 is in an energized state (during normal braking operation) (see FIG. 5). As a result, even when the first hydraulic pressure generating device 12 applies brake hydraulic pressure to the three wheel brakes B1, B2, B3, brake hydraulic pressure equivalent to that applied during normal operation is applied to each of the wheel brakes B1, B2, B3.

[0047] 4 , during normal braking, 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 of the first brake unit 10 to fail to operate, and the first selector valve 56 to become de-energized. In this case, the position of the first selector valve 56 returns to its initial state (de-energized state), so that the first hydraulic pressure generator 12 side of the first main hydraulic pressure line 51 does not communicate with the first wheel brake B1 side, and the first main hydraulic pressure line 51 communicates with the first connecting hydraulic pressure line 71. In this state, brake hydraulic pressure generated by the second hydraulic pressure generator 22 is transmitted to the second wheel brake B2 and the fourth wheel brake B4, and is also transmitted from the second main hydraulic pressure line 61 to the first connecting hydraulic pressure line 71, the first selector valve 56, and the first main hydraulic pressure line 51 to the first wheel brake B1. 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 in the first wheel brake B1, the second wheel brake B2 and the fourth wheel brake B4 by the second hydraulic pressure generating device 22 of the second brake unit 20.

[0048] The drive amount of the second hydraulic pressure generating device 22 is larger when the first selector 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 first selector valve 56 is in an energized state (during normal braking operation) (see FIG. 5). As a result, even when the second hydraulic pressure generating device 22 applies brake hydraulic pressure to the three wheel brakes B1, B2, B4, brake hydraulic pressure equivalent to that applied during normal operation is applied to each of the wheel brakes B1, B2, B4.

[0049] In the brake system 1 configured as described above, during normal braking operation, the first hydraulic pressure generator 12 applies brake hydraulic pressure to the first wheel brake B1 and the third wheel brake B3, as shown in Figure 2. The second hydraulic pressure generator 22 applies brake hydraulic pressure to the second wheel brake B2 and the fourth wheel brake B4. In this way, the brake system 1 can control both brake units 10, 20 independently.

[0050] 3, in the brake system 1 of this embodiment, even if the second electronic control device 24 or the second hydraulic pressure generator 22 of the second brake unit 20 is not operating, brake hydraulic pressure can be applied to the second wheel brake B2 connected to the second brake unit 20. As a result, even if the second electronic control device 24 or the second hydraulic pressure generator 22 of the second brake unit 20 is not operating, braking force can be generated in the three wheel brakes B1, B2, B3. In particular, large braking force is generated by the first wheel brake B1 and the second wheel brake B2 provided on both the left and right front wheels FL, FR, allowing for stable braking of the vehicle.

[0051] 4, in the brake system 1 of this embodiment, even if the first electronic control device 14 or the first hydraulic pressure generator 12 of the first brake unit 10 does not operate, brake hydraulic pressure can be applied to the first wheel brake B1 connected to the first brake unit 10. As a result, even if the first electronic control device 14 or the first hydraulic pressure generator 12 of the first brake unit 10 does not operate, braking forces can be generated in the three wheel brakes B1, B2, and B4. In particular, large braking forces are generated in the first wheel brake B1 and the second wheel brake B2 provided on both the left and right front wheels, allowing the vehicle to be braked stably.

[0052] While the present invention has been described above with reference to an embodiment, it is not limited to the embodiment and can be modified as appropriate without departing from the spirit of the present invention. In the brake system 1 of this embodiment, as shown in FIG. 1 , the third main hydraulic line 52 communicates with the first main hydraulic line 51 on the first hydraulic pressure generator 12 side relative to the first selector valve 56, and the fourth main hydraulic line 62 communicates with the second main hydraulic line 61 on the second hydraulic pressure generator 22 side relative to the second selector valve 66. However, as in a brake system 1A shown in FIG. 6 , the third main hydraulic line 52 may communicate with the first main hydraulic line 51 on the first wheel brake B1 side relative to the first selector valve 56, and the fourth main hydraulic line 62 may communicate with the second main hydraulic line 61 on the second wheel brake B2 side relative to the second selector valve 66.

[0053] 6 , in the brake system 1A described above, when the second selector valve 66 is de-energized during normal braking, the brake fluid pressure generated by the first fluid pressure generator 12 is transmitted to the first wheel brake B1 and the third wheel brake B3, and is also transmitted to the second wheel brake B2 and the fourth wheel brake B4 from the first main fluid pressure line 51 through the second connecting fluid pressure line 72, the second selector valve 66, the second main fluid pressure line 61, and the fourth main fluid pressure line 62. In this way, in the brake system 1A, braking forces are generated in the four wheel brakes B1, B2, B3, and B4 by the first fluid pressure generator 12 of the first brake unit 10 even when the second electronic control device 24 and the second fluid pressure generator 22 of the second brake unit 20 are not operating.

[0054] 7, in the brake system 1A described above, when the first selector valve 56 is de-energized during normal braking, the brake fluid pressure generated by the second fluid pressure generator 22 is transmitted to the second wheel brake B2 and the fourth wheel brake B4, and is also transmitted to the first wheel brake B1 and the third wheel brake B3 from the second main fluid pressure line 61 through the first connecting fluid pressure line 71, the first selector valve 56, the first main fluid pressure line 51 and the third main fluid pressure line 52. In this way, in the brake system 1A, braking forces are generated in the four wheel brakes B1, B2, B3 and B4 by the second fluid pressure generator 22 of the second brake unit 20 even when the first electronic control device 14 and the first fluid pressure generator 12 of the first brake unit 10 are not operating.

[0055] 1 may be configured to detect the operating state of the second brake unit 20, and the second electronic control unit 24 may be configured to detect the operating state of the first brake unit 10. Furthermore, the first electronic control unit 14 may be configured to switch the second selector valve 66 between an energized state and a de-energized state, and the second electronic control unit 24 may be configured to switch the first selector valve 56 between an energized state and a de-energized state. In this configuration, the second selector valve 66 is not de-energized during normal braking, but if the first electronic control unit 14 detects a malfunction in the operation of the second brake unit 20, the first electronic control unit 14 may de-energize the second selector valve 66, thereby allowing the first hydraulic pressure generator 12 to apply brake hydraulic pressure to the second wheel brake B2 of the second brake unit 20. Furthermore, during normal braking operation, the first switching valve 56 is not in a non-energized state, but if the second electronic control device 24 detects a malfunction in the operation of the first brake unit 10, the second electronic control device 24 will put the first switching valve 56 in a non-energized state, thereby allowing brake fluid pressure to be applied from the second hydraulic pressure generating device 22 to the first wheel brake B1 of the first brake unit 10.

[0056] In the brake system 1 of this embodiment, the first switching valve 56 and the second switching valve 66 are configured as three-way valves, but a single switching valve may be configured by combining a plurality of electromagnetic valves.

[0057] 1 Brake system 1A Brake system (another embodiment) 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 Third main hydraulic line 52a Third inlet valve 53 First return hydraulic line 54 First branch hydraulic line 54a First outlet valve 55 Third branch hydraulic line 55a Third outlet valve 56 First switching valve 60 Second brake system 61 Second main hydraulic line 61a Second inlet valve 62 Fourth main hydraulic line 63 Second return hydraulic line 64 Second branch hydraulic line 64a Second outlet valve 65 Fourth branch hydraulic line 65a Fourth outlet valve 66 Second switching valve 71 First connecting hydraulic line 72 Second connecting hydraulic line B1 First wheel brake B2 Second wheel brake B3 Third wheel brake B4 Fourth wheel brake FL Left front wheel FR Right front wheel RL Left rear wheel RR Right rear wheel P Brake pedal EB Electric brake

Claims

1. A brake system comprising a first brake unit, a second brake unit, and a first connecting hydraulic pressure line and a second connecting hydraulic pressure 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 pressure line from the first hydraulic pressure generating device to a first wheel brake, a third main hydraulic pressure line from the first main hydraulic pressure line to a third wheel brake, and a first changeover valve provided in the first main hydraulic pressure line, 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 second main hydraulic pressure line from the second hydraulic pressure generating device to the second wheel brake, and a fourth main hydraulic pressure line from the second main hydraulic pressure line to a fourth wheel brake, a second changeover valve provided in the second main hydraulic pressure path, the first connecting hydraulic pressure path leading from the first main hydraulic pressure path to the second main hydraulic pressure path, the second connecting hydraulic pressure path leading from the second main hydraulic pressure path to the first main hydraulic pressure path, when energized, the first changeover valve connects the first hydraulic pressure generator side of the first main hydraulic pressure path to the first wheel brake side and does not connect the first main hydraulic pressure path to the first connecting hydraulic pressure path, when de-energized, the first changeover valve does not connect the first hydraulic pressure generator side of the first main hydraulic pressure path to the first wheel brake side and connects the first main hydraulic pressure path to the first connecting hydraulic pressure path, when energized, the second changeover valve connects the second hydraulic pressure generator side of the second main hydraulic pressure path to the second wheel brake side and does not connect the second main hydraulic pressure path to the second connecting hydraulic pressure path, A brake system characterized in that, when not energized, the second switching valve does not communicate between the second hydraulic pressure generating device side and the second wheel brake side of the second main hydraulic pressure path, and communicates between the second main hydraulic pressure path and the second connecting hydraulic pressure path.

2. A brake system as described in claim 1, characterized in that the third main hydraulic line communicates with the first main hydraulic line on the first hydraulic pressure generating device side of the first switching valve, and the fourth main hydraulic line communicates with the second main hydraulic line on the second hydraulic pressure generating device side of the second switching valve.

3. A brake system as claimed in claim 1, characterized in that the first wheel brake and the second wheel brake are provided on the left and right front wheels, respectively.

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

5. A brake system as claimed in claim 4, characterized in that the first switching valve is provided between the first inlet valve and the first return fluid path, and the second switching valve is provided between the second inlet valve and the second return fluid path.

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

7. A brake system as described in claim 6, wherein the first hydraulic pressure generating device is set to increase the amount of drive based on the amount of fluid required when the second switching valve is in a non-energized state, and the second hydraulic pressure generating device is set to increase the amount of drive based on the amount of fluid required when the first switching valve is in a non-energized state.

8. A brake system as claimed in claim 1, characterized in that the first changeover valve and the second changeover valve are constituted by three-way valves.

9. 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 path, and the cylinder of the second hydraulic pressure generating device is connected to the second main hydraulic pressure path.

10. A brake system as described in claim 1, wherein the first electronic control device is capable of switching between an energized state and a non-energized state of the second switching valve, and the second electronic control device is capable of switching between an energized state and a non-energized state of the first switching valve.

11. A brake system as described in claim 10, wherein the first electronic control device switches between an energized state and a non-energized state of the second switching valve based on operation detection of the second brake unit, and the second electronic control device switches between an energized state and a non-energized state of the first switching valve based on operation detection of the first brake unit.

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