Braking device

Abstract

To enable the identification of the causes of abnormal detection pressure. [Solution] The braking device 40 includes a first supply source 421, a second supply source 422, a first pressure sensor 441, a second pressure sensor 442, a switching unit 60, and a processing circuit 71. The processing circuit 71 performs the following: a first abnormality determination process which determines whether or not an abnormality has occurred in the first detected pressure and whether or not an abnormality has occurred in the second detected pressure when the switching unit 60 is in a shut-off state and brake fluid is supplied to the supply sources 421 and 422; a second abnormality determination process which determines whether or not an abnormality has occurred in at least one of the first detected pressure and the second detected pressure when the switching unit 60 is in a communication state and brake fluid is supplied to the supply sources 421 and 422; and an abnormality identification process which identifies the abnormal part based on the determination result of the first abnormality determination process and the determination result of the second abnormality determination process.

Description

Technical Field

[0001] The present invention relates to a braking device that generates braking force on a vehicle by adjusting the hydraulic pressure of a wheel cylinder.

Background Art

[0002] Patent Document 1 discloses a system including a first braking unit that adjusts the braking pressure of a first wheel cylinder and a second braking unit that adjusts the braking pressure of a second wheel cylinder. Each of the plurality of braking units includes a supply source of brake fluid and a sensor that detects the braking pressure. When the detected pressure of the sensor of one of the plurality of braking units is abnormal, the control device of the above system determines that an abnormality has occurred in the sensor. The control device connects a first liquid passage communicating with the first wheel cylinder and a second liquid passage communicating with the second wheel cylinder. When the vehicle brakes, the control device supplies brake fluid from two supply sources based on the detected pressure of the sensor of the other braking unit among the plurality of braking units.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When brake fluid is supplied from the supply source to the wheel cylinder in a situation where brake fluid leaks from the liquid passage or the wheel cylinder to the outside, even if the sensor is normal, the detected pressure of the sensor will deviate from the hydraulic pressure corresponding to the supply amount of the brake fluid of the supply source. Therefore, in the above system, even when brake fluid leakage occurs, it is determined that an abnormality in the detected pressure has occurred. However, the subsequent countermeasures are different between the case where an abnormality occurs in the sensor and the case where brake fluid leakage occurs. [Means for solving the problem]

[0005] A braking device for solving the above problems is applied to a vehicle equipped with a first wheel cylinder and a second wheel cylinder. The braking device includes a first supply source that adjusts the first braking pressure, which is the hydraulic pressure of the first wheel cylinder, by supplying brake fluid to the first wheel cylinder via a first fluid passage; a second supply source that adjusts the second braking pressure, which is the hydraulic pressure of the second wheel cylinder, by supplying brake fluid to the second wheel cylinder via a second fluid passage; a first pressure sensor that detects the first braking pressure as a first detection pressure; a second pressure sensor that detects the second braking pressure as a second detection pressure; a switching unit that can switch between a communication state in which the first fluid passage and the second fluid passage are in communication and a disconnection state in which communication between the first fluid passage and the second fluid passage is blocked; and a processing circuit that controls the first supply source, the second supply source and the switching unit. The processing circuit performs a first abnormality determination process that determines whether an abnormality has occurred in the first detected pressure while brake fluid is supplied to the first supply source when the switching unit is in the shut-off state, and determines whether an abnormality has occurred in the second detected pressure while brake fluid is supplied to the second supply source; a second abnormality determination process that determines whether an abnormality has occurred in at least one of the first detected pressure and the second detected pressure while the switching unit is in the communication state and brake fluid is supplied to at least one of the first supply source and the second supply source; and an abnormality identification process that identifies the abnormal part based on the determination result of the first abnormality determination process and the determination result of the second abnormality determination process. [Effects of the Invention]

[0006] The above braking device has the effect of being able to identify the cause of abnormalities in the detected pressure. [Brief explanation of the drawing]

[0007] [Figure 1]Figure 1 is a schematic diagram showing a vehicle equipped with a braking system according to the first embodiment. [Figure 2] Figure 2 is a table showing the correspondence between the result of the judgment process and the cause of the abnormality in the braking device shown in Figure 1. [Figure 3] Figure 3 is a flowchart showing a series of processes performed by the control device included in the braking system shown in Figure 1. [Figure 4] Figure 4 is a flowchart showing the series of processes for determining abnormalities in the detected pressure during the first abnormality detection process. [Figure 5] Figure 5 is a flowchart showing the series of processes when executing the second abnormality detection process. [Figure 6] Figure 6 is a flowchart showing the series of processes when executing the second abnormality determination process in the braking device of the second embodiment. [Figure 7] Figure 7 is a flowchart showing a series of processes when executing the first abnormality determination process in the braking device of the third embodiment. [Figure 8] Figure 8 is a flowchart showing a series of processes performed by the control unit in the modified braking system. [Modes for carrying out the invention]

[0008] (First Embodiment) A first embodiment of the braking device will be described with reference to Figures 1 to 5. <Overall vehicle configuration> Figure 1 shows a vehicle 10 equipped with the braking device 40 of this embodiment. The vehicle 10 further comprises a braking operating member 11, a plurality of wheels, a plurality of friction brakes 20, and a plurality of sensors.

[0009] The braking operation member 11 is a member operated by the driver of the vehicle 10 to adjust the deceleration of the vehicle 10 when braking force is generated. An example of the braking operation member 11 is the brake pedal. Multiple wheels include at least one first wheel 12 and at least one second wheel 13. In the example shown in Figure 1, the vehicle 10 has one first wheel 12 and one second wheel 13. In this case, an example of the first wheel 12 is the left front wheel, and an example of the second wheel 13 is the right front wheel.

[0010] Multiple friction brakes 20 are individually provided for multiple wheels 12, 13. Each friction brake 20 has a wheel cylinder, a rotating body 22, and a friction part 23. The rotating body 22 rotates integrally with the wheels 12, 13. Therefore, by pressing the friction part 23 against the rotating body 22, braking force is generated on the wheels 12, 13. The force pressing the friction part 23 against the rotating body 22 increases with higher hydraulic pressure in the wheel cylinder. Therefore, the friction brake 20 can generate a greater braking force as the hydraulic pressure in the wheel cylinder increases.

[0011] Hereafter, the hydraulic pressure inside the wheel cylinder will be referred to as "braking pressure". The wheel cylinder of the friction brake 20 corresponding to the first wheel 12 will be referred to as "first wheel cylinder 221". The wheel cylinder of the friction brake 20 corresponding to the second wheel 13 will be referred to as "second wheel cylinder 222". The braking pressure of the first wheel cylinder 221 will be referred to as "first braking pressure Pw(1)". The braking pressure of the second wheel cylinder 222 will be referred to as "second braking pressure Pw(2)".

[0012] Multiple sensors each output detection signals to a control device 70, which will be described later. The multiple sensors include, for example, a brake sensor 31 and multiple wheel speed sensors 32. The brake sensor 31 detects the amount of operation of the driver's braking operation member 11. The multiple wheel speed sensors 32 are individually provided for the multiple wheels 12, 13. The wheel speed sensors 32 detect the rotational speed of the corresponding wheel.

[0013] <Configuration of the braking system> As shown in Figure 1, the braking device 40 comprises a plurality of braking units, a switching unit 60, and a control device 70.

[0014] <Brake Unit> The plurality of brake units includes a first brake unit 411 and a second brake unit 412. The first brake unit 411 adjusts the first braking pressure Pw(1). The second brake unit 412 adjusts the second braking pressure Pw(2).

[0015] The first brake unit 411 has a first supply source 421, a first liquid passage 431, and a first pressure sensor 441. The second brake unit 412 has a second supply source 422, a second liquid passage 432, and a second pressure sensor 442.

[0016] The first liquid passage 431 and the second liquid passage 432 are liquid passages through which the brake fluid flows. The first liquid passage 431 is a liquid passage connecting the first supply source 421 and the first wheel cylinder 221. The second liquid passage 432 is a liquid passage connecting the second supply source 422 and the second wheel cylinder 222.

[0017] The first supply source 421 adjusts the first braking pressure Pw(1) by supplying brake fluid to the first wheel cylinder 221 via the first liquid passage 431. The second supply source 422 adjusts the second braking pressure Pw(2) by supplying brake fluid to the second wheel cylinder 222 via the second liquid passage 432.

[0018] The first pressure sensor 441 detects the first braking pressure Pw(1). For example, the first pressure sensor 441 is connected to the first liquid passage 431. In this case, the first pressure sensor 441 outputs a detection signal corresponding to the hydraulic pressure of the first liquid passage 431 to the control device 70. The hydraulic pressure based on the detection signal of the first pressure sensor 441 corresponds to the "first detected pressure PwS(1)", which is the detected pressure of the first braking pressure Pw(1).

[0019] The second pressure sensor 442 detects the second braking pressure Pw(2). For example, the second pressure sensor 442 is connected to the second liquid passage 432. In this case, the second pressure sensor 442 outputs a detection signal corresponding to the hydraulic pressure of the second liquid passage 432 to the control device 70. The hydraulic pressure based on the detection signal of the second pressure sensor 442 corresponds to the "second detected pressure PwS(2)", which is the detected pressure of the second braking pressure Pw(2).

[0020] The multiple power sources 421, 422 include, for example, an electric cylinder 50. The electric cylinder 50 has a cylinder 51, a piston 52, an electric motor 53, a conversion mechanism 54, and a motor angle sensor. The motor angle sensor of the first power source 421 is referred to as "motor angle sensor 551". The motor angle sensor of the second power source 422 is referred to as "motor angle sensor 552". The piston 52 is provided in a slidable manner within the cylinder 51. The conversion mechanism 54 converts the rotation of the output shaft of the electric motor 53 into the linear movement of the piston 52.

[0021] Inside the cylinder 51, a hydraulic chamber Re for storing brake fluid is partitioned by the peripheral wall of the cylinder 51 and the piston 52. The position of the piston 52 inside the cylinder 51 can be changed by driving the electric motor 53. Hereafter, the direction of linear movement of the piston 52 when reducing the volume of the hydraulic chamber Re will be referred to as the "forward direction Za," while the opposite direction to the forward direction Za will be referred to as the "reverse direction Zb." The reverse direction Zb is also the direction of linear movement of the piston 52 when increasing the volume of the hydraulic chamber Re.

[0022] The cylinder 51 has an output port 51p that connects the hydraulic chamber Re to the outside. The output port 51p is always open. The first fluid passage 431 is connected to the output port 51p of the electric cylinder 50 of the first supply source 421. The second fluid passage 432 is connected to the output port 51p of the electric cylinder 50 of the second supply source 422.

[0023] The motor angle sensors 551 and 552 output detection signals to the control device 70 in accordance with the change in the rotation angle of the electric motor 53. Hereafter, the rotation angle of the electric motor 53 based on the detection signals of the motor angle sensors 551 and 552 will be referred to as "motor rotation angle θmt".

[0024] When the motor rotation angle θmt increases due to the drive of the electric motor 53, the piston 52 moves in the forward direction Za. As a result, the brake fluid in the hydraulic chamber Re is discharged into the fluid passages 431 and 432 via the output port 51p. This supplies brake fluid to the wheel cylinders 221 and 222, so the braking pressures Pw(1) and Pw(2) increase. On the other hand, when the motor rotation angle θmt decreases due to the drive of the electric motor 53, the piston 52 moves in the backward direction Zb. As a result, the brake fluid in the fluid passages 431 and 432 flows into the hydraulic chamber Re via the output port 51p. In this case, brake fluid flows out from the wheel cylinders 221 and 222, so the braking pressures Pw(1) and Pw(2) decrease.

[0025] <Switching section> The switching unit 60 is configured to be switchable between a connected state in which the first liquid passage 431 and the second liquid passage 432 are connected, and a blocked state in which the connection between the first liquid passage 431 and the second liquid passage 432 is blocked.

[0026] For example, the switching unit 60 includes a connecting fluid passage 61 that connects the first fluid passage 431 and the second fluid passage 432, and a shut-off valve 62 installed in the connecting fluid passage 61. An example of the shut-off valve 62 is a normally open solenoid valve controlled by the control device 70. In this case, when the shut-off valve 62 is open, the first fluid passage 431 and the second fluid passage 432 communicate with each other via the connecting fluid passage 61. On the other hand, when the shut-off valve 62 is closed, communication between the first fluid passage 431 and the second fluid passage 432 is blocked by the shut-off valve 62. That is, the state of the switching unit 60 when the shut-off valve 62 is open is the communication state. On the other hand, the state of the switching unit 60 when the shut-off valve 62 is closed is the shut-off state.

[0027] When the switching unit 60 is in the shut-off state, the brake fluid supplied from the first supply source 421 is supplied to the first wheel cylinder 221 via the first fluid passage 431. The portion through which the brake fluid supplied from the first supply source 421 flows is referred to as the "first system." The first system includes the first supply source 421, the first fluid passage 431, and the first wheel cylinder 221. Similarly, when the switching unit 60 is in the shut-off state, the brake fluid supplied from the second supply source 422 is supplied to the second wheel cylinder 222 via the second fluid passage 432. The portion through which the brake fluid supplied from the second supply source 422 flows is referred to as the "second system." The second system includes the second supply source 422, the second fluid passage 432, and the second wheel cylinder 222.

[0028] <Control device> The control device 70 includes a processing circuit 71. An example of the processing circuit 71 is an electronic control device. In this case, the processing circuit 71 includes a CPU 72, a first memory 73, and a second memory 74. The first memory 73 stores a control program executed by the CPU 72. The second memory 74 stores the calculation results of the CPU 72, etc. By the CPU 72 executing the control program in the first memory 73, the processing circuit 71 controls the first power source 421, the second power source 422, and the switching unit 60.

[0029] The processing circuit 71 shuts off the switching unit 60 by closing the shut-off valve 62, and then adjusts the first braking pressure Pw(1) and the second braking pressure Pw(2). The processing circuit 71 sets the first target pressure PwTr(1), which is the target value of the first braking pressure Pw(1). Then, the processing circuit 71 operates the first supply source 421 so that the first detected pressure PwS(1) follows the first target pressure PwTr(1). For example, the processing circuit 71 derives the amount of brake fluid consumed Qf(1), which is the amount of brake fluid to be supplied to the first wheel cylinder 221 in order to increase the first braking pressure Pw(1) to the first target pressure PwTr(1). The processing circuit 71 sets the motor rotation angle θmt to the target rotation angle θmtTr so that the amount of brake fluid supplied by the first supply source 421 is equal to the amount of brake fluid consumed Qf(1). The processing circuit 71 drives the electric motor 53 so that the motor rotation angle θmt becomes the target rotation angle θmtTr. This allows the processing circuit 71 to make the first detected pressure PwS(1) follow the first target pressure PwTr(1).

[0030] Similarly, the processing circuit 71 sets the second target pressure PwTr(2), which is the target value of the second braking pressure Pw(2). Then, the processing circuit 71 operates the second supply source 422 so that the second detected pressure PwS(2) follows the second target pressure PwTr(2). For example, the processing circuit 71 derives the amount of brake fluid consumed Qf(2), which is the amount of brake fluid to be supplied to the second wheel cylinder 222 in order to increase the second braking pressure Pw(2) to the second target pressure PwTr(2). The processing circuit 71 sets the motor rotation angle θmt to the target rotation angle θmtTr so that the amount of brake fluid supplied by the second supply source 422 is equal to the amount of brake fluid consumed Qf(2). The processing circuit 71 drives the electric motor 53 so that the motor rotation angle θmt becomes the target rotation angle θmtTr. This allows the processing circuit 71 to make the second detection pressure PwS(2) follow the second target pressure PwTr(2).

[0031] <Functional Section> The processing circuit 71 has a function to diagnose whether or not an abnormality has occurred in the detected pressures PwS(1) and PwS(2). Furthermore, if the processing circuit 71 diagnoses that an abnormality has occurred in the detected pressures PwS(1) and PwS(2), it has a function to identify the abnormal part, which is the part where the abnormality has occurred. Specifically, the processing circuit 71 determines whether an abnormality has occurred in the pressure sensors 441, 442 or the motor angle sensors 551, 552, or whether brake fluid leakage is occurring from the electric cylinder 50 or the wheel cylinders 221, 222 or the fluid passages 431, 432.

[0032] The processing circuit 71 functions as a set of functional units for performing such abnormality diagnosis, with the CPU 72 executing the control program for the first memory 73. These functional units include a first abnormality determination unit 101, a second abnormality determination unit 102, and an abnormality identification unit 103.

[0033] <First abnormality determination section> The first abnormality determination unit 101 performs the following two determination processes (A1) and (A2) when the switching unit 60 is in a shut-off state. The first abnormality determination unit 101 determines whether an abnormality has occurred in the first system or whether the second abnormality has occurred.

[0034] (A1) A process to determine whether or not an abnormality has occurred in the first detected pressure PwS(1) while brake fluid is being supplied to the first supply source 421. (A2) A process to determine whether or not an abnormality has occurred in the second detection pressure PwS(2) while brake fluid is being supplied to the second supply source 422.

[0035] An example of the above judgment process (A1) is described in detail below. The first abnormality determination unit 101 sets a first target pressure PwTr(1). Based on the first target pressure PwTr(1), the first abnormality determination unit 101 generates a first braking pressure Pw(1) by supplying brake fluid from the first supply source 421 to the first wheel cylinder 221.

[0036] Next, the first abnormality determination unit 101 derives the amount of brake fluid supplied by the first supply source 421, Qs, when the first braking pressure Pw(1) is generated. For example, when brake fluid is discharged from the electric cylinder 50 of the first supply source 421, there is a correlation between the increase in the motor rotation angle θmt and the amount of brake fluid supplied, Qs. Therefore, based on this correlation, the first abnormality determination unit 101 derives the supply amount Qs such that the value increases as the increase in the motor rotation angle θmt increases. In this case, the first abnormality determination unit 101 may use a map that shows the relationship between the motor rotation angle θmt and the amount of brake fluid supplied by the first supply source 421.

[0037] The first abnormality determination unit 101 sets the first determination pressure Pwth(1) based on the derived supply amount Qs. The first determination pressure Pwth(1) is a predicted value of the first braking pressure Pw(1) under the assumption that brake fluid is supplied from the first supply source 421 to the first wheel cylinder 221 as described above, under the condition that no brake fluid leakage occurs. Therefore, the first abnormality determination unit 101 sets the first determination pressure Pwth(1) such that the value increases as the supply amount Qs increases.

[0038] The first abnormality determination unit 101 determines that an abnormality has occurred in the first detected pressure PwS(1) if the magnitude of the difference between the first detected pressure PwS(1) and the first determined pressure Pwth(1) is greater than or equal to the abnormality determination value ΔPwth(1). On the other hand, the first abnormality determination unit 101 determines that no abnormality has occurred in the first detected pressure PwS(1) if the magnitude of the difference is less than the abnormality determination value ΔPwth(1). The abnormality determination value ΔPwth(1) is the criterion for determining whether the discrepancy between the first detected pressure PwS(1) and the first determined pressure Pwth(1) is large or not. In other words, "an abnormality has occurred in the first detected pressure PwS(1)" in the first abnormality determination process means that the discrepancy between the first detected pressure PwS(1) and the first determined pressure Pwth(1) is large.

[0039] An example of the above judgment process (A2) is described in detail below. The first abnormality determination unit 101 sets the second target pressure PwTr(2). Based on the second target pressure PwTr(2), the first abnormality determination unit 101 generates the second braking pressure Pw(2) by supplying brake fluid from the second supply source 422 to the second wheel cylinder 222.

[0040] Next, the first abnormality determination unit 101 derives the supply amount Qs of brake fluid from the second supply source 422 when the second braking pressure Pw(2) is generated. The method for deriving the supply amount Qs of the second supply source 422 here is the same as the method for deriving the supply amount Qs of the first supply source 421 in the determination process (A1) described above.

[0041] The first abnormality determination unit 101 sets the second determination pressure Pwth(2) based on the derived supply amount Qs. The second determination pressure Pwth(2) is a predicted value of the second braking pressure Pw(2) under the assumption that brake fluid is supplied to the second wheel cylinder 222 from the second supply source 422 as described above, under the condition that no brake fluid leakage has occurred. Therefore, the first abnormality determination unit 101 sets the second determination pressure Pwth(2) such that the value increases as the supply amount Qs increases.

[0042] The first abnormality determination unit 101 determines that an abnormality has occurred at the second detection pressure PwS(2) if the magnitude of the difference between the second detection pressure PwS(2) and the second determination pressure Pwth(2) is greater than or equal to the abnormality determination value ΔPwth(2). On the other hand, the first abnormality determination unit 101 determines that no abnormality has occurred at the second detection pressure PwS(2) if the magnitude of the difference is less than the abnormality determination value ΔPwth(2). The abnormality determination value ΔPwth(2) is the criterion for determining whether the discrepancy between the second detection pressure PwS(2) and the second determination pressure Pwth(2) is large or not. In other words, "an abnormality has occurred at the second detection pressure PwS(2)" in the first abnormality determination process means that the discrepancy between the second detection pressure PwS(2) and the second determination pressure Pwth(2) is large.

[0043] <Second abnormality determination section> The second abnormality determination unit 102 performs the following determination process (B1) when the switching unit 60 is in communication and brake fluid is supplied to at least one of the first supply source 421 and the second supply source 422.

[0044] (B1) A process to determine whether or not an abnormality has occurred in at least one of the two detected pressures PwS(1) and PwS(2) by comparing the first detected pressure PwS(1) and the second detected pressure PwS(2).

[0045] The following describes in detail an example of a determination performed by the second abnormality determination unit 102. The second abnormality detection unit 102 connects the switching unit 60 and supplies brake fluid from both the first supply source 421 and the second supply source 422. At this time, the second abnormality detection unit 102 should set the first target pressure PwTr(1) and the second target pressure PwTr(2) to the same braking pressure. Then, the second abnormality detection unit 102 activates the first supply source 421 based on the first target pressure PwTr(1). The second abnormality detection unit 102 activates the second supply source 422 based on the second target pressure PwTr(2).

[0046] Next, the second abnormality determination unit 102 determines whether or not there is a discrepancy between the first detected pressure PwS(1) and the second detected pressure PwS(2). For example, the second abnormality determination unit 102 determines that an abnormality has occurred in either the first detected pressure PwS(1) or the second detected pressure PwS(2) if the magnitude of the difference between the first detected pressure PwS(1) and the second detected pressure PwS(2) is greater than or equal to the sensor abnormality determination value ΔPwAth. On the other hand, the second abnormality determination unit 102 determines that no abnormality has occurred in either the first detected pressure PwS(1) or the second detected pressure PwS(2) if the magnitude of the difference is less than the sensor abnormality determination value ΔPwAth. Hereafter, determining that an abnormality has occurred in either the first detected pressure PwS(1) or the second detected pressure PwS(2) will be referred to as "detection pressure abnormality". Furthermore, determining that no abnormalities have occurred in either the first detection pressure PwS(1) or the second detection pressure PwS(2) will be described as "normal detection pressure."

[0047] <Anomaly Identification Unit> The abnormality identification unit 103 identifies the abnormal part based on the determination result from the first abnormality determination unit 101 and the determination result from the second abnormality determination unit 102.

[0048] Referring to Figure 2, the abnormality identification process by the abnormality identification unit 103 will be explained. For example, the abnormality identification unit 103 determines that no abnormality has occurred in the braking device 40 if the pattern of the determination result by the first abnormality determination unit 101 and the determination result by the second abnormality determination unit 102 is the first pattern PT1. The first pattern PT1 is the combination shown below.

[0049] The first abnormality determination unit 101 determines that no abnormality has occurred in either the first detected pressure PwS(1) or the second detected pressure PwS(2). In other words, both the first detected pressure PwS(1) and the second detected pressure PwS(2) are normal.

[0050] The determination result by the second abnormality determination unit 102 is that the detected pressure is normal. For example, the abnormality identification unit 103 determines that an abnormality has occurred in the first pressure sensor 441 or the first motor angle sensor 551 if the pattern of the determination result by the first abnormality determination unit 101 and the determination result by the second abnormality determination unit 102 is the second pattern PT2. The second pattern PT2 is the combination shown below.

[0051] The determination result by the first abnormality determination unit 101 indicates that an abnormality has occurred only in the first detection pressure PwS(1) out of the first detection pressure PwS(1) and the second detection pressure PwS(2). The determination result by the second abnormality determination unit 102 is that the detected pressure is abnormal.

[0052] For example, the abnormality identification unit 103 determines that a brake fluid leak has occurred in the first system if the pattern of the determination result by the first abnormality determination unit 101 and the determination result by the second abnormality determination unit 102 is the third pattern PT3. If a brake fluid leak has occurred in the first system, it can be assumed that a brake fluid leak has occurred in at least one of the first supply source 421, the first fluid passage 431, and the first wheel cylinder 221.

[0053] The third pattern, PT3, consists of the following combinations. The determination result by the first abnormality determination unit 101 indicates that an abnormality has occurred only in the first detection pressure PwS(1) out of the first detection pressure PwS(1) and the second detection pressure PwS(2).

[0054] The determination result by the second abnormality determination unit 102 is that the detected pressure is normal. For example, the abnormality identification unit 103 determines that an abnormality has occurred in the second pressure sensor 442 or the second motor angle sensor 552 if the pattern of the determination result by the first abnormality determination unit 101 and the determination result by the second abnormality determination unit 102 is the fourth pattern PT4. The fourth pattern PT4 is the combination shown below.

[0055] The determination result by the first abnormality determination unit 101 indicates that an abnormality has occurred only in the second detection pressure PwS(2) out of the first detection pressure PwS(1) and the second detection pressure PwS(2). The determination result by the second abnormality determination unit 102 is that the detected pressure is abnormal.

[0056] For example, the abnormality identification unit 103 determines that a brake fluid leak has occurred in the second system if the pattern of the determination result by the first abnormality determination unit 101 and the determination result by the second abnormality determination unit 102 is the fourth pattern PT4. If a brake fluid leak has occurred in the second system, it can be assumed that a brake fluid leak has occurred in at least one of the second supply source 422, the second fluid passage 432, and the second wheel cylinder 222.

[0057] The fifth pattern, PT5, consists of the following combinations. The determination result by the first abnormality determination unit 101 indicates that an abnormality has occurred only in the second detection pressure PwS(2) out of the first detection pressure PwS(1) and the second detection pressure PwS(2).

[0058] The determination result by the second abnormality determination unit 102 is that the detected pressure is normal. <Anomaly Diagnosis Processing> Referring to Figure 3, a series of processes performed by the processing circuit 71 to identify the abnormal part will be described. This series of processes constitutes the abnormality diagnosis process. The processing circuit 71 executes the abnormality diagnosis process when predetermined execution conditions are met.

[0059] The predetermined execution conditions include, for example, that the vehicle 10 is parked. The processing circuit 71 can determine that the vehicle 10 is parked if at least one of the following is true: that a parking brake force is being applied to the vehicle 10, and that the rotation of the axle is being restricted by the parking lock mechanism.

[0060] As shown in Figure 3, in step S11, the processing circuit 71 functions as a first abnormality determination unit 101 and performs a first abnormality determination process. The first abnormality determination process is a process that determines whether or not an abnormality has occurred in the first detected pressure PwS(1) when the switching unit 60 is in a shut-off state and brake fluid is being supplied to the first supply source 421, and determines whether or not an abnormality has occurred in the second detected pressure PwS(2) when brake fluid is being supplied to the second supply source 422.

[0061] In other words, the first abnormality determination process includes abnormality determination of the first detected pressure PwS(1) (S111) and abnormality determination of the second detected pressure PwS(2) (S113). Details of these abnormality determinations will be described later with reference to Figure 4. When the processing circuit 71 executes the first abnormality determination process, it moves the process to step S17.

[0062] In step S17, the processing circuit 71 functions as a second abnormality determination unit 102 and executes a second abnormality determination process. The second abnormality determination process determines whether or not an abnormality has occurred in at least one of the first detected pressure PwS(1) and the second detected pressure PwS(2), under the conditions that the switching unit 60 is in communication and brake fluid is supplied to at least one of the first supply source 421 and the second supply source 422. The second abnormality determination process will be described later with reference to Figure 5. After executing the second abnormality determination process, the processing circuit 71 proceeds to step S19.

[0063] In step S19, the processing circuit 71 functions as an abnormality identification unit 103 and performs abnormality identification processing. Based on the results of the first abnormality determination processing and the second abnormality determination processing, the abnormality identification processing identifies whether the sensor is malfunctioning or whether a brake fluid leak has occurred. After that, the processing circuit 71 terminates the abnormality diagnosis processing.

[0064] Note that in Figure 3, the second abnormality determination process in step S17 is executed after the first abnormality determination process in step S11, but this is not limited to this. For example, the first abnormality determination process may be executed after the second abnormality determination process.

[0065] <First abnormality detection process> Referring to Figure 4, the abnormality determination of the Nth detection pressure PwS(N) in the first abnormality determination process will be explained. In the abnormality determination of the first detection pressure PwS(1), "N" is set to 1. In the abnormality determination of the second detection pressure PwS(2), "N" is set to 2.

[0066] In step S21, the processing circuit 71 performs a process to generate braking pressure Pw(N). In this generation process, the processing circuit 71 sets the Nth target pressure PwTr(N). Based on the Nth target pressure PwTr(N), the processing circuit 71 supplies brake fluid from the Nth supply source.

[0067] In the subsequent step S23, the processing circuit 71 derives the supply amount Qs of brake fluid from the Nth supply source when the braking pressure Pw(N) is generated by the generation process in step S21. For example, the processing circuit 71 derives the supply amount Qs such that the value increases as the increase in the motor rotation angle θmt of the electric motor 53 of the electric cylinder 50 of the Nth supply source increases.

[0068] In the next step S25, the processing circuit 71 sets the Nth decision pressure Pwth(N) based on the supply amount Qs derived in step S23. The processing circuit 71 sets the Nth decision pressure Pwth(N) such that its value increases as the supply amount Qs increases.

[0069] In the following step S27, the processing circuit 71 derives the magnitude of the difference between the Nth detected pressure PwS(N) and the Nth judgment pressure Pwth(N) as the pressure difference ΔPw(N). Then, in step S29, the processing circuit 71 determines whether the pressure difference ΔPw(N) is greater than or equal to the abnormal judgment value ΔPwth(N). If the pressure difference ΔPw(N) is greater than or equal to the abnormal judgment value ΔPwth(N) (S29: YES), the processing circuit 71 proceeds to step S33. On the other hand, if the pressure difference ΔPw(N) is less than the abnormal judgment value ΔPwth(N) (S29: NO), the processing circuit 71 proceeds to step S31.

[0070] In step S31, the processing circuit 71 determines that there is no abnormality in the Nth detection pressure PwS(N), that is, the Nth detection pressure PwS(N) is normal. Then, the processing circuit 71 proceeds to step S39.

[0071] In step S33, the processing circuit 71 determines that an abnormality has occurred in the Nth detection pressure PwS(N). In the following step S35, the processing circuit 71 determines whether the Nth detection pressure PwS(N) is greater than or equal to the Nth determination pressure Pwth(N). If the Nth detection pressure PwS(N) is greater than or equal to the Nth determination pressure Pwth(N) (S35: YES), the processing circuit 71 proceeds to step S37. On the other hand, if the Nth detection pressure PwS(N) is less than or equal to the Nth determination pressure Pwth(N) (S35: NO), the processing circuit 71 proceeds to step S39.

[0072] In step S37, the processing circuit 71 sets the prohibition flag FLG(N) to ON. The prohibition flag FLG(N) is a flag used to determine whether or not to prohibit the execution of the second abnormality determination process. After that, the processing circuit 71 terminates the series of processes shown in Figure 4.

[0073] Furthermore, if the prohibition flag FLG(N) is set to ON, it can be confirmed that the pressure sensor is malfunctioning. Therefore, the processing circuit 71 does not execute the second malfunction determination process. In other words, the processing circuit 71 prohibits the switching unit 60 from being in a connected state.

[0074] In step S39, the processing circuit 71 sets the prohibition flag FLG(N) to off. In this case, the processing circuit 71 allows the execution of the second abnormality determination process. That is, the processing circuit 71 allows the switching unit 60 to be opened. After that, the processing circuit 71 completes the series of processes shown in Figure 4.

[0075] <Second abnormality detection process> Referring to Figure 5, the second abnormality detection process will be explained. In step S51, the processing circuit 71 determines whether the execution conditions for the second abnormality determination process are met. For example, if both the prohibition flags FLG(1) and FLG(2) are set to off, the processing circuit 71 determines that the execution conditions are met (S51: YES). In this case, the processing circuit 71 proceeds to step S55. On the other hand, if at least one of the prohibition flags FLG(1) and FLG(2) is set to on, the processing circuit 71 determines that the execution conditions are not met (S51: NO). Then, the processing circuit 71 terminates the series of processes shown in Figure 5.

[0076] In step S55, the processing circuit 71 supplies brake fluid from both the first supply source 421 and the second supply source 422. For example, the processing circuit 71 sets a first target pressure PwTr(1) and a second target pressure PwTr(2). In this case, it is preferable that the processing circuit 71 sets the first target pressure PwTr(1) and the second target pressure PwTr(2) so that they are equal to each other. Then, the processing circuit 71 drives the electric motor 53 of the electric cylinder 50 of the first supply source 421 based on the first target pressure PwTr(1). The processing circuit 71 operates the electric motor 53 of the electric cylinder 50 of the second supply source 422 based on the second target pressure PwTr(2). When the processing circuit 71 finds that the motor rotation angle θmt of the electric motor 53 of the first supply source 421 is maintained at a value corresponding to the first target pressure PwTr(1), and that the motor rotation angle θmt of the electric motor 53 of the second supply source 422 is maintained at a value corresponding to the second target pressure PwTr(2), the processing circuit 71 proceeds to step S57.

[0077] In step S57, the processing circuit 71 performs a communication process that switches the switching unit 60 from the closed state to the open state by opening the shut-off valve 62. Then, the processing circuit 71 proceeds to step S65.

[0078] In step S65, the processing circuit 71 determines whether the magnitude of the difference between the first detected pressure PwS(1) and the second detected pressure PwS(2) is less than or equal to the sensor abnormality determination value ΔPwAth. If the magnitude of the difference is less than or equal to the sensor abnormality determination value ΔPwAth (S65: YES), the processing circuit 71 proceeds to step S67. On the other hand, if the magnitude of the difference is greater than the sensor abnormality determination value ΔPwAth (S65: NO), the processing circuit 71 proceeds to step S69.

[0079] In step S67, the processing circuit 71 determines that the detected pressure is normal. Subsequently, the processing circuit 71 completes the series of processes shown in Figure 5. In step S69, the processing circuit 71 determines that the detected pressure is abnormal. Subsequently, the processing circuit 71 completes the series of processes shown in Figure 5.

[0080] <Processing after identifying the abnormal area> If the processing circuit 71 identifies the abnormal part as a sensor, it keeps the switching unit 60 in a connected state. Then, when the vehicle 10 is braked, the processing circuit 71 adjusts the first braking pressure Pw(1) and the second braking pressure Pw(2) using the detection results of the pressure sensor and motor angle sensor, which have been determined to be normal.

[0081] On the other hand, if the processing circuit 71 identifies the abnormal area as the first system, it determines that a brake fluid leak is occurring in the first system and keeps the switching unit 60 in the shut-off state. Then, when the vehicle 10 is braked, the processing circuit 71 adjusts the second braking pressure Pw(2) by prohibiting the supply of brake fluid from the first supply source 421 and supplying brake fluid to the second supply source 422.

[0082] Similarly, if the processing circuit 71 identifies the abnormal area as the second system, it determines that a brake fluid leak is occurring in the second system and keeps the switching unit 60 in the shut-off state. Then, when the vehicle 10 is braked, the processing circuit 71 adjusts the first braking pressure Pw(1) by prohibiting the supply of brake fluid from the second supply source 422 and supplying brake fluid to the first supply source 421.

[0083] <Operation and Effects of This Embodiment> (1-1) The processing circuit 71 performs a first abnormality determination process when the switching unit 60 is in the shut-off state. In the first abnormality determination process, the processing circuit 71 determines whether or not an abnormality has occurred in the first detected pressure PwS(1) while brake fluid is being supplied from the first supply source 421. The processing circuit 71 determines whether or not an abnormality has occurred in the second detected pressure PwS(2) while brake fluid is being supplied from the second supply source 422.

[0084] Here, an abnormality in the Nth detection pressure PwS(N) means that the Nth detection pressure PwS(N) deviates from the Nth judgment pressure Pwth(N). The Nth judgment pressure Pwth(N) is the braking pressure corresponding to the supply amount Qs of brake fluid from the Nth supply source. An abnormality in the first detection pressure PwS(1) can occur not only when there is an abnormality in the first pressure sensor 441 or the first motor angle sensor 551, but also when brake fluid is leaking from the first system. An abnormality in the second detection pressure PwS(2) can occur not only when there is an abnormality in the second pressure sensor 442 or the second motor angle sensor 552, but also when brake fluid is leaking from the second system.

[0085] Therefore, in the braking device 40, the processing circuit 71 performs a second abnormality determination process in addition to the first abnormality determination process. In the second abnormality determination process, the processing circuit 71 determines whether an abnormality has occurred in at least one of the first detected pressure PwS(1) and the second detected pressure PwS(2), under the conditions that the switching unit 60 is in communication and brake fluid is supplied to the multiple supply sources 421, 422. For example, the processing circuit 71 determines whether there is a discrepancy between the first detected pressure PwS(1) and the second detected pressure PwS(2).

[0086] Then, the processing circuit 71 performs an abnormality identification process to identify the abnormal part based on the determination result of the first abnormality determination process and the determination result of the second abnormality determination process. For example, if the processing circuit 71 determines in the first abnormality determination process that an abnormality has occurred in the first detected pressure PwS(1), and the processing circuit 71 determines in the second abnormality determination process that there is a discrepancy between the first detected pressure PwS(1) and the second detected pressure PwS(2), then the processing circuit 71 can diagnose that the first pressure sensor 441 or the first motor angle sensor 551 is abnormal, and that there is no brake fluid leakage in the first system. Furthermore, if the processing circuit 71 determines in the first abnormality determination process that an abnormality has occurred in the first detected pressure PwS(1), and also determines in the second abnormality determination process that there is no discrepancy between the first detected pressure PwS(1) and the second detected pressure PwS(2), then the processing circuit 71 can diagnose that the first pressure sensor 441 and the first motor angle sensor 551 are functioning normally, and that a brake fluid leak has occurred in the first system. In other words, by executing the first and second abnormality determination processes, the processing circuit 71 can identify whether the cause of the abnormality in detected pressure is an abnormality in the pressure sensor or motor angle sensor, or a brake fluid leak. Therefore, the processing circuit 71 can identify the cause of the abnormality in detected pressure. In addition, the processing circuit 71 can appropriately control the switching unit 60 according to the location where the abnormality occurs.

[0087] (1-2) In the first abnormality determination process, the processing circuit 71 determines that an abnormality has occurred at the Nth detection pressure PwS(N) if it determines that there is a large discrepancy between the Nth detection pressure PwS(N) and the Nth determination pressure Pwth(N). Furthermore, if the processing circuit 71 determines that an abnormality has occurred at the Nth detection pressure PwS(N), it determines whether the Nth detection pressure PwS(N) is greater than the Nth determination pressure Pwth(N).

[0088] If a brake fluid leak occurs, the Nth detection pressure PwS(N) should be smaller than the Nth judgment pressure Pwth(N). In other words, if the Nth detection pressure PwS(N) is larger than the Nth judgment pressure Pwth(N), the cause of the abnormality in the Nth detection pressure PwS(N) is not a brake fluid leak in the Nth system.

[0089] Therefore, in the braking device 40, the processing circuit 71 determines that an abnormality has occurred in the Nth detected pressure PwS(N), and if the Nth detected pressure PwS(N) is greater than the Nth determined pressure Pwth(N), it does not execute the second abnormality determination process. In other words, the processing circuit 71 can diagnose that an abnormality has occurred in the pressure sensor or motor angle sensor without having to execute the second abnormality determination process. That is, the processing circuit 71 can suppress the unnecessary execution of the second abnormality determination process.

[0090] (Second Embodiment) A second embodiment of the braking device will be described with reference to Figure 6. Note that the second embodiment differs from the first embodiment in the content of the second abnormality determination process. In the following description, the differences from the first embodiment will be primarily explained, and identical component components are denoted by the same reference numerals to avoid redundant explanations.

[0091] When the shut-off valve 62 is open, the orifice diameter of the shut-off valve 62 is referred to as the "diameter of the switching section 60". The larger the system of the switching section 60, the easier it is for brake fluid to flow between the first fluid passage 431 and the second fluid passage 432 via the connecting fluid passage 61 when the state of the switching section 60 is switched from the shut-off state to the open state.

[0092] The first embodiment is suitable for cases where the diameter of the switching section 60 is large, and the first braking pressure Pw(1) and the second braking pressure Pw(2) become equal immediately after switching the state of the switching section 60 from the shut-off state to the open state. On the other hand, if the diameter of the switching section 60 is small, and a predetermined time is required for the first braking pressure Pw(1) and the second braking pressure Pw(2) to become equal after switching the state of the switching section 60 from the shut-off state to the open state, it is preferable to identify the cause of the abnormality using the second embodiment of the braking device described below.

[0093] In the second embodiment, the second abnormality determination process is executed using the result of the first abnormality determination process. Therefore, the second abnormality determination process is executed after the first abnormality determination process has been executed. For example, if the first abnormality determination process determines that an abnormality has occurred in either the first detected pressure PwS(1) or the second detected pressure PwS(2), the second abnormality determination process is executed.

[0094] Referring to Figure 6, the second abnormality determination process performed in the braking device 40 of this embodiment will be described. The processing circuit 71 functions as the second abnormality determination unit 102 and executes the processes of the multiple steps S211 to S227 shown in Figure 6.

[0095] In step S211, the processing circuit 71 determines whether the execution conditions for the second abnormality determination process are met, similar to step S51 in Figure 5. If the execution conditions are met (S211: YES), the processing circuit 71 proceeds to step S213. On the other hand, if the execution conditions are not met (S211: NO), the processing circuit 71 terminates the series of processes shown in Figure 6.

[0096] In step S213, the processing circuit 71 identifies a normal detection pressure PwS from among the first detection pressure PwS(1) and the second detection pressure PwS(2). The normal detection pressure PwS is the detection pressure from among the first detection pressure PwS(1) and the second detection pressure PwS(2) that was determined not to be abnormal in the first abnormality determination process. On the other hand, the detection pressure from among the first detection pressure PwS(1) and the second detection pressure PwS(2) that was determined to be abnormal in the first abnormality determination process is sometimes called an "abnormal detection pressure".

[0097] In the following step S215, the processing circuit 71 sets the first target pressure PwTr(1) and the second target pressure PwTr(2) so that they are equal to each other.

[0098] Then, in step S217, the processing circuit 71 activates the first power source 421 based on the first target pressure PwTr(1). The processing circuit 71 activates the second power source 422 based on the second target pressure PwTr(2). When the motor rotation angle θmt of the electric motor 53 of the first power source 421 is maintained at a value corresponding to the first target pressure PwTr(1), and the motor rotation angle θmt of the electric motor 53 of the second power source 422 is maintained at a value corresponding to the second target pressure PwTr(2), the processing circuit 71 proceeds to step S219.

[0099] In step S219, the processing circuit 71 performs a communication process that switches the switching unit 60 from a closed state to a connected state by opening the shut-off valve 62. In step S221, the processing circuit 71 derives the change gradient dPwS of the normal detection pressure PwS when the switching unit 60 is switched from the shut-off state to the connected state. For example, the processing circuit 71 derives the rate of change of the normal detection pressure PwS based on the change in the normal detection pressure PwS from the time the switching unit 60 is switched from the shut-off state to the connected state. Then, the processing circuit 71 derives the absolute value of the derived rate of change of the normal detection pressure PwS as the change gradient dPwS.

[0100] In the subsequent step S223, the processing circuit 71 determines whether the derived change gradient dPwS is greater than or equal to a predetermined gradient dPwSth. The predetermined gradient dPwSth is a criterion for determining whether the rate of change of the normal detection pressure PwS caused by the switching unit 60 being in a connected state is large or not. If the change gradient dPwS is greater than or equal to the predetermined gradient dPwSth (S223: YES), the processing circuit 71 proceeds to step S225. On the other hand, if the change gradient dPwS is less than the predetermined gradient dPwSth (S223: NO), the processing circuit 71 proceeds to step S227.

[0101] In step S225, the processing circuit 71 determines that the detected pressure is normal. Subsequently, the processing circuit 71 completes the series of processes shown in Figure 6. In step S227, the processing circuit 71 determines that the detected pressure is abnormal. Subsequently, the processing circuit 71 completes the series of processes shown in Figure 6.

[0102] <Operation and Effects of This Embodiment> If the processing circuit 71 determines in the first abnormality determination process that an abnormality has occurred in only one of the first detection pressure PwS(1) and the second detection pressure PwS(2), it executes the second abnormality determination process. In the second abnormality determination process, the processing circuit 71 identifies the detection pressure that was determined not to have an abnormality in the first abnormality determination process as the normal detection pressure PwS.

[0103] The processing circuit 71 keeps the switching unit 60 in the shut-off state and supplies brake fluid from both the first supply source 421 and the second supply source 422. At this time, the processing circuit 71 makes the first target pressure PwTr(1) and the second target pressure PwTr(2) equal. Then, the processing circuit 71 switches the switching unit 60 from the shut-off state to the open state.

[0104] Here, we will explain the case where the normal detection pressure PwS is the first detection pressure PwS(1). In this case, if brake fluid leakage occurs in the second system, the second braking pressure Pw(2) will be lower than the first braking pressure Pw(1). Therefore, when the switching unit 60 is in a connected state, brake fluid flows from the first fluid passage 431 to the second fluid passage 432 via the connecting fluid passage 61. As a result, the first detection pressure PwS(1), which is the normal detection pressure PwS, decreases.

[0105] On the other hand, if no brake fluid leak occurs, the supply of brake fluid from the first supply source 421 as described above increases the first braking pressure Pw(1) to near the first target pressure PwTr(1). The supply of brake fluid from the second supply source 422 as described above increases the second braking pressure Pw(2) to near the second target pressure PwTr(2). The first target pressure PwTr(1) is equal to the second target pressure PwTr(2). Therefore, the difference between the first braking pressure Pw(1) and the second braking pressure Pw(2) is relatively small. As a result, even if the switching section 60 is in a connected state, flow of brake fluid through the connecting fluid passage 61 is unlikely to occur. Consequently, the first detected pressure PwS(1), which is the normal detected pressure PwS, does not change much.

[0106] Therefore, in the braking device 40 of this embodiment, the processing circuit 71 derives the change gradient dPwS of the normal detected pressure PwS when the switching unit 60 is switched from the shut-off state to the open state. The processing circuit 71 can determine that the pressure sensor or motor angle sensor is not abnormal and that brake fluid leakage is occurring if the change gradient dPwS is greater than or equal to a predetermined gradient dPwSth. On the other hand, the processing circuit 71 can determine that the pressure sensor or motor angle sensor is abnormal and that brake fluid leakage is not occurring if the change gradient dPwS is less than the predetermined gradient dPwSth.

[0107] The processing circuit 71 performs an abnormality identification process after performing a second abnormality determination process. In the abnormality identification process, the processing circuit 71 identifies the abnormal part based on the determination result of the first abnormality determination process and the determination result of the second abnormality determination process.

[0108] Let's explain the case where the first detected pressure PwS(1) is the normal detected pressure PwS. For example, the processing circuit 71 determines in the first abnormality determination process that an abnormality has occurred in the second detected pressure PwS(2). If there is no discrepancy between the first detected pressure PwS(1) and the second detected pressure PwS(2) when the state of the switching unit 60 switches to the communication state in the second abnormality determination process, the processing circuit 71 can determine that no abnormality has occurred in either the first detected pressure PwS(1) or the second detected pressure PwS(2). In other words, the processing circuit 71 can determine that the second pressure sensor 442 is normal, but that brake fluid leakage is occurring in the second system.

[0109] On the other hand, if a discrepancy occurs between the first detected pressure PwS(1) and the second detected pressure PwS(2) when the state of the switching unit 60 switches to the communication state in the second abnormality determination process, the processing circuit 71 determines that there is a detection pressure abnormality. In other words, the processing circuit 71 can determine that the second pressure sensor 442 or the second motor angle sensor 552 is abnormal and that there is no brake fluid leakage in the second system.

[0110] Furthermore, the case where the second detection pressure PwS(2) is the normal detection pressure PwS is the same as the case where the first detection pressure PwS(1) is the normal detection pressure PwS. Therefore, the explanation of how to identify the abnormal part when the second detection pressure PwS(2) is the normal detection pressure PwS will be omitted.

[0111] In the second embodiment, the braking device 40 makes the first target pressure PwTr(1) and the second target pressure PwTr(2) equal in the second abnormality determination process. As a result, if there is a discrepancy between the first damping pressure Pw(1) and the second damping pressure Pw(2), the normal detection pressure PwS changes immediately after the state of the switching unit 60 switches from the shut-off state to the communication state. On the other hand, if there is no discrepancy between the first damping pressure Pw(1) and the second damping pressure Pw(2), the normal detection pressure PwS does not change much even when the state of the switching unit 60 switches from the shut-off state to the communication state.

[0112] Therefore, by using the gradient of the change in the normal detection pressure PwS when the state of the switching unit 60 switches from the shut-off state to the communication state, the processing circuit 71 can identify the cause of the abnormality. For example, even if the diameter of the switching unit 60 is small and the time required for the first damping pressure Pw(1) and the second damping pressure Pw(2) to become equal after the state of the switching unit 60 switches from the shut-off state to the communication state is relatively long, the processing circuit 71 can quickly identify the cause of the abnormality.

[0113] (Third embodiment) A third embodiment of the braking device will be described with reference to Figure 7. Note that the third embodiment differs from the above-described embodiments in the content of the first abnormality determination process. In the following description, the differences from the above-described embodiments will be mainly explained, and the same reference numerals will be used for components identical to those in the above-described embodiments to avoid redundant explanations.

[0114] Referring to Figure 7, the first abnormality determination process performed by the braking device 40 of this embodiment will be described. The processing circuit 71 functions as the first abnormality determination unit 101 and executes the processes of the multiple steps S311 to S335 shown in Figure 7.

[0115] In step S311, the processing circuit 71 sets the first target pressure PwTr(1) and the second target pressure PwTr(2) so that they are equal to each other.

[0116] Then, in step S313, the processing circuit 71 activates the first power source 421 based on the first target pressure PwTr(1). The processing circuit 71 activates the second power source 422 based on the second target pressure PwTr(2). When the motor rotation angle θmt of the electric motor 53 of the first power source 421 is maintained at a value corresponding to the first target pressure PwTr(1), and the motor rotation angle θmt of the electric motor 53 of the second power source 422 is maintained at a value corresponding to the second target pressure PwTr(2), the processing circuit 71 proceeds to step S315.

[0117] In step S315, the processing circuit 71 determines whether the first detected pressure PwS(1) and the second detected pressure PwS(2) are substantially equal. For example, if the difference between the first detected pressure PwS(1) and the second detected pressure PwS(2) falls within the error range, the processing circuit 71 can consider the first detected pressure PwS(1) and the second detected pressure PwS(2) to be substantially equal. When the first detected pressure PwS(1) and the second detected pressure PwS(2) are substantially equal, it can be determined that both pressure sensors 441, 442 and both motor angle sensors 551, 552 are functioning correctly, and that no brake fluid leakage is occurring in the braking device 40. Therefore, if the processing circuit 71 determines that the first detected pressure PwS(1) and the second detected pressure PwS(2) are substantially equal (S315: YES), the processing circuit 71 terminates the series of processes shown in Figure 6. On the other hand, if the processing circuit 71 determines that the first detected pressure PwS(1) and the second detected pressure PwS(2) are inconsistent (S315: NO), the processing circuit 71 proceeds to step S317.

[0118] In step S317, the processing circuit 71 determines whether the second detection pressure PwS(2) is greater than the first detection pressure PwS(1). If the second detection pressure PwS(2) is greater than the first detection pressure PwS(1) (S317: YES), the processing circuit 71 proceeds to step S319. On the other hand, if the second detection pressure PwS(2) is less than or equal to the first detection pressure PwS(1) (S317: NO), the processing circuit 71 proceeds to step S331.

[0119] In step S319, the processing circuit 71 determines whether the second detected pressure PwS(2) is substantially equal to the second target pressure PwTr(2). If the magnitude of the difference between the second detected pressure PwS(2) and the second target pressure PwTr(2) falls within an acceptable range, the second detected pressure PwS(2) can be considered substantially equal to the second target pressure PwTr(2). If the processing circuit 71 determines that the second detected pressure PwS(2) is substantially equal to the second target pressure PwTr(2) (S319: YES), the processing circuit 71 proceeds to step S321. On the other hand, if the processing circuit 71 determines that the second detected pressure PwS(2) deviates from the second target pressure PwTr(2) (S319: NO), the processing circuit 71 proceeds to step S335.

[0120] In step S321, the processing circuit 71 determines whether the first value, which is the value obtained by subtracting the first detection pressure PwS(1) from the second detection pressure PwS(2), is greater than or equal to the deviation determination value ΔPwSth. The deviation determination value ΔPwSth is the criterion for determining whether the deviation between the second detection pressure PwS(2) and the first detection pressure PwS(1) is large or not. If the first value is greater than or equal to the deviation determination value ΔPwSth (S321: YES), the processing circuit 71 proceeds to step S323. On the other hand, if the first value is less than the deviation determination value ΔPwSth (S321: NO), the processing circuit 71 terminates the series of processes shown in Figure 7. In this case, the processing circuit 71 can determine that no abnormality has occurred in either the first detection pressure PwS(1) or the second detection pressure PwS(2), that is, that both the first detection pressure PwS(1) and the second detection pressure PwS(2) are normal.

[0121] In step S323, the processing circuit 71 determines that an abnormality has occurred in the first detection pressure PwS(1). Subsequently, the processing circuit 71 completes the series of processes shown in Figure 7. In step S331, the processing circuit 71 determines whether the first detected pressure PwS(1) is substantially equal to the first target pressure PwTr(1). If the magnitude of the difference between the first detected pressure PwS(1) and the first target pressure PwTr(1) falls within an acceptable range, the first detected pressure PwS(1) can be considered substantially equal to the first target pressure PwTr(1). If the processing circuit 71 determines that the first detected pressure PwS(1) is substantially equal to the first target pressure PwTr(1) (S331: YES), the processing circuit 71 proceeds to step S333. On the other hand, if the processing circuit 71 determines that the first detected pressure PwS(1) deviates from the first target pressure PwTr(1) (S331: NO), the processing circuit 71 proceeds to step S323.

[0122] In step S333, the processing circuit 71 determines whether the second value, which is the value obtained by subtracting the second detection pressure PwS(2) from the first detection pressure PwS(1), is greater than or equal to the above-mentioned deviation determination value ΔPwSth. If the second value is greater than or equal to the deviation determination value ΔPwSth (S333: YES), the processing circuit 71 proceeds to step S335. On the other hand, if the second value is less than the deviation determination value ΔPwSth (S333: NO), the processing circuit 71 terminates the series of processes shown in Figure 7. In this case, the processing circuit 71 can determine that no abnormality has occurred in either the first detection pressure PwS(1) or the second detection pressure PwS(2), that is, both the first detection pressure PwS(1) and the second detection pressure PwS(2) are normal.

[0123] In step S335, the processing circuit 71 determines that an abnormality has occurred in the second detection pressure PwS(2). Subsequently, the processing circuit 71 terminates the series of processes shown in Figure 7. In the braking device 40 of this embodiment, the processing circuit 71 executes the series of processes shown in Figure 7 when the state of the switching unit 60 is in the shut-off state. This allows the processing circuit 71 to determine whether or not an abnormality has occurred in the first detected pressure PwS(1) while brake fluid is being supplied to the first supply source 421. The processing circuit 71 can also determine whether or not an abnormality has occurred in the second detected pressure PwS(2) while brake fluid is being supplied to the second supply source 422.

[0124] (Example of change) The above embodiments can be implemented with the following modifications. The above embodiments and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0125] In the above embodiments, the processing circuit 71 (i.e., the first abnormality determination unit 101) is configured to execute the first abnormality determination process when the vehicle 10 is parked, but it is not limited to this configuration.

[0126] For example, in the first embodiment described above, the processing circuit 71 may execute the first abnormality determination process when a braking force is generated at the first wheel 12 while the vehicle 10 is in motion. In this case, the processing circuit 71 can determine whether or not an abnormality has occurred in the first detected pressure PwS(1) even while the vehicle 10 is in motion. Similarly, the processing circuit 71 may execute the first abnormality determination process when a braking force is generated at the second wheel 13 while the vehicle 10 is in motion. In this case, the processing circuit 71 can determine whether or not an abnormality has occurred in the second detected pressure PwS(2) even while the vehicle 10 is in motion.

[0127] For example, in the third embodiment described above, the processing circuit 71 may execute the first abnormality determination process when the first wheel 12 and the second wheel 13 generate the same amount of braking force while the vehicle 10 is in motion.

[0128] The processing circuit 71 (i.e., the second abnormality determination unit 102) may execute the second abnormality determination process on the condition that it has determined in the first abnormality determination process that an abnormality has occurred in only one of the first detected pressure PwS(1) and the second detected pressure PwS(2).

[0129] In the above embodiments, the processing circuit 71 (i.e., the second abnormality determination unit 102) is configured to perform the second abnormality determination process when the vehicle 10 is parked, but it is not limited to this. That is, the processing circuit 71 may also perform the second abnormality determination process when the vehicle 10 is in motion. In this case, the processing circuit 71 may be configured to prohibit switching the state of the switching unit 60 to the communication state when the difference between the first target pressure PwTr(1) and the second target pressure PwTr(2) is greater than or equal to a threshold.

[0130] In the second abnormality determination process of the first embodiment, the magnitude of the difference between the first detected pressure PwS(1) and the second detected pressure PwS(2) is used to determine whether or not an abnormality has occurred in the detected pressure. In the second abnormality determination process of the second embodiment, the gradient of change in the normal detected pressure PwS when the state of the switching unit 60 is switched from the shut-off state to the communication state is used to determine whether or not an abnormality has occurred in the detected pressure.

[0131] Here, in the second abnormality determination process, similar to the first abnormality determination process, it is possible to determine whether or not an abnormality has occurred in the detected pressure by using the magnitude of the difference between the detected pressure and the determined pressure. In such a modified example, it is preferable to execute the first abnormality determination process before the second abnormality determination process to identify the normal detected pressure PwS, and then execute the second abnormality determination process using the magnitude of the difference between the normal detected pressure PwS and the determined pressure.

[0132] In other words, in step S411, the processing circuit 71 determines whether the magnitude of the difference between the first target pressure PwTr(1) and the second target pressure PwTr(2) is greater than or equal to the threshold ΔPwBth. If the magnitude of the difference is greater than or equal to the threshold ΔPwBth (S411: YES), the processing circuit 71 terminates the series of processes shown in Figure 8. That is, the processing circuit 71 does not execute the second abnormality determination process. On the other hand, if the magnitude of the difference is less than the threshold ΔPwBth (S411: NO), the processing circuit 71 proceeds to step S13. The flow of processing from step S13 onward is the same as in the first embodiment described using Figure 3. Therefore, further explanation is omitted.

[0133] When the first fluid passage 431 and the second fluid passage 432 are connected under conditions where there is a large discrepancy between the second target pressure PwTr(2) and the first target pressure PwTr(1), brake fluid flows between the first fluid passage 431 and the second fluid passage 432. As a result, the lower of the first braking pressure Pw(1) and the second braking pressure Pw(2) increases, which may cause the wheel to lock up due to the braking force applied to that pressure. Consequently, the behavior of the vehicle 10 may become unstable. In this modified brake device 40, the switching unit 60 does not enter a connected state when there is a large discrepancy between the second target pressure PwTr(2) and the first target pressure PwTr(1). Thus, even though the modified brake device is configured to perform the second abnormality determination process while the vehicle 10 is running, the instability of the vehicle 10's behavior can be suppressed by keeping the switching unit 60 in a connected state.

[0134] In the first and second embodiments described above, if the processing circuit 71 determines that an abnormality has occurred in the first detection pressure PwS(1) through the first abnormality determination process, it may execute the second abnormality determination process even if the first detection pressure PwS(1) is greater than the first determination pressure Pwth(1). Similarly, if the processing circuit 71 determines that an abnormality has occurred in the second detection pressure PwS(2) through the first abnormality determination process, it may execute the second abnormality determination process even if the second detection pressure PwS(2) is greater than the second determination pressure Pwth(2).

[0135] In the first embodiment described above, the first abnormality determination process may include only one of the abnormality determination of the first detected pressure PwS(1) (step S111 in Figure 3) and the abnormality determination of the second detected pressure PwS(2) (step S113 in Figure 3). For example, if it is determined that the first detected pressure PwS(1) is normal, the processing circuit 71 may perform the abnormality determination of the first detected pressure PwS(1) in the first abnormality determination process, but not perform the abnormality determination of the second detected pressure PwS(2).

[0136] In the first embodiment described above, the processing circuit 71 (i.e., the second abnormality determination unit 102) may increase the first braking pressure Pw(1) and the second braking pressure Pw(2) by supplying brake fluid from only one of the first supply source 421 and the second supply source 422.

[0137] The first abnormality determination process may be the process shown below. Specifically, the processing circuit 71 (i.e., the first abnormality determination unit 101) drives the electric motor 53 of the nth power source by feedback control that takes the deviation between the nth target pressure PwTr(N) and the nth detected pressure PwS(N) as input. At this time, if the nth detected pressure PwS(N) does not converge to the nth target pressure PwTr(N) even after a predetermined time has elapsed from the start of this feedback control, the processing circuit 71 determines that an abnormality has occurred in the nth detected pressure PwS(N). If the nth detected pressure PwS(N) converges to the nth target pressure PwTr(N) within the predetermined time elapsed from the start of the above process, the processing circuit 71 determines that no abnormality has occurred in the nth detected pressure PwS(N).

[0138] The second abnormality determination process may be the process shown below. Specifically, the processing circuit 71 (i.e., the second abnormality determination unit 102) sets the first target pressure PwTr(1) and the second target pressure PwTr(2) to equal magnitudes. The processing circuit 71 activates the first supply source 421 based on the first target pressure PwTr(1) and activates the second supply source 422 based on the second target pressure PwTr(2). In this state, the processing circuit 71 opens the switching unit 60. If the processing circuit 71 determines that the first detected pressure PwS(1) and the second detected pressure PwS(2) are equal, it can determine that the pressure sensor and motor angle sensor are normal, but that brake fluid leakage is occurring. Conversely, if the processing circuit 71 determines that the first detected pressure PwS(1) and the second detected pressure PwS(2) are different, it can determine that the pressure sensor or motor angle sensor is malfunctioning, but that there is no brake fluid leak.

[0139] The processing circuit 71 may execute the first abnormality determination process after executing the second abnormality determination process. The vehicle to which the braking system 40 is applied may be a vehicle equipped with a plurality of first wheel cylinders 221. Similarly, the vehicle to which the braking system 40 is applied may be a vehicle equipped with a plurality of second wheel cylinders 222.

[0140] The first and second supply sources may differ from the configuration shown in Figure 1, as long as they can supply brake fluid to the wheel cylinders via a fluid passage. For example, the first and second supply sources may be configured to include pumps driven by electric motors.

[0141] The switching unit may have a configuration different from the switching unit 60 shown in Figure 1, as long as it can switch between a connected state and a disconnected state. For example, the switching unit may have a configuration that includes multiple solenoid valves.

[0142] The control device 70 may be configured to include multiple processing circuits. For example, the control device 70 may be configured to include a first processing circuit that functions as a first abnormality determination unit 101, a second processing circuit that functions as a second abnormality determination unit 102, and a second processing circuit that functions as an abnormality identification unit 103.

[0143] The processing circuit 71 may be configured as a circuit including one or more processors that operate according to a computer program, one or more dedicated hardware circuits such as dedicated hardware that performs at least some of the various processes, or a combination thereof. Examples of dedicated hardware include application-specific integrated circuits (ASICs). The processor includes a CPU and memory such as RAM and ROM, where the memory stores program code or instructions configured to cause the CPU to perform the processes. The memory, i.e., storage medium, includes any available medium that can be accessed by a general-purpose or dedicated computer.

[0144] <Other technological ideas> This section describes the technical concepts that can be understood from the above-mentioned multiple embodiments and modifications. [Note 1] The first abnormality determination process includes a process for determining whether or not an abnormality has occurred in the second detected pressure. The aforementioned processing circuit is In the first abnormality determination process, with brake fluid being supplied to the second supply source, if the magnitude of the difference between the second detection pressure and the second determination pressure corresponding to the amount of brake fluid supplied by the second supply source is greater than or equal to a threshold, it is determined that an abnormality has occurred in the second detection pressure. When the first abnormality determination process determines that an abnormality has occurred in the second detection pressure, it is preferable not to execute the second abnormality determination process if the second detection pressure is greater than the second determination pressure.

[0145] [Note 2] It is preferable that the processing circuit executes the second abnormality determination process if it determines in the first abnormality determination process that an abnormality has occurred in only one of the first detection pressure and the second detection pressure.

[0146] [Note 3] In the second abnormality determination process, the processing circuit performs the following: Of the first and second detected pressures, the detected pressure that is determined to be abnormal in the first abnormality determination process is identified as the abnormal detected pressure, and the detected pressure that is determined to be abnormal in the first abnormality determination process is identified as the normal detected pressure. It is preferable to determine whether or not an abnormality has occurred in the abnormal detection pressure based on the change in the normal detection pressure, while the switching unit is in the communication state and brake fluid is supplied to at least one of the first supply source and the second supply source.

[0147] [Note 4] The processing circuit, in the abnormality identification process, If the first abnormality determination process determines that an abnormality has occurred in the first detected pressure, and the second abnormality determination process determines that an abnormality has occurred in either the first detected pressure or the second detected pressure, then the first pressure sensor is determined to be abnormal. If the first abnormality determination process determines that an abnormality has occurred in the second detected pressure, and the second abnormality determination process determines that an abnormality has occurred in either the first detected pressure or the second detected pressure, then the second pressure sensor is determined to be abnormal. If the first abnormality determination process determines that an abnormality has occurred at the first detection pressure, while the second abnormality determination process determines that no abnormality has occurred at either the first or second detection pressure, then it is determined that brake fluid leakage has occurred in at least one of the first supply source, the first fluid passage, and the first wheel cylinder. In the first abnormality determination process, it is determined that an abnormality has occurred in the second detection pressure, while in the second abnormality determination process, it is determined that no abnormality has occurred in either the first or second detection pressure. In such cases, it is preferable to determine that brake fluid leakage has occurred in at least one of the second supply source, the second fluid passage, and the second wheel cylinder.

[0148] In this specification, the expression "at least one" means "one or more" of the desired options. For example, if there are two options, the expression "at least one" means "only one option" or "both of the two options." As another example, if there are three or more options, the expression "at least one" means "only one option" or "a combination of two or more arbitrary options." [Explanation of Symbols]

[0149] 10... Vehicles 221…First wheel cylinder 222... Second wheel cylinder 40...braking device 411, 412… Braking Unit 421…1st supply source 422…Second supply source 431...1st liquid path 432…Second liquid path 441...First pressure sensor 442...Second pressure sensor 551...First motor angle sensor 552...Second motor angle sensor 60... Switching section 70...Control device 71…Processing circuit 101...First abnormality determination section 102...Second abnormality determination section 103... Anomaly Identification Unit

Claims

1. Applicable to vehicles equipped with a first wheel cylinder and a second wheel cylinder, A first supply source that adjusts the first braking pressure, which is the hydraulic pressure of the first wheel cylinder, by supplying brake fluid to the first wheel cylinder via a first fluid passage, A second supply source adjusts the second braking pressure, which is the hydraulic pressure of the second wheel cylinder, by supplying brake fluid to the second wheel cylinder via a second fluid passage. A first pressure sensor that detects the first braking pressure as the first detection pressure, A second pressure sensor that detects the second braking pressure as the second detection pressure, A switching unit that can switch between a connected state in which the first liquid passage and the second liquid passage are connected, and a blocked state in which the connection between the first liquid passage and the second liquid passage is blocked, The system comprises a processing circuit that controls the first supply source, the second supply source, and the switching unit, The aforementioned processing circuit is When the switching unit is in the shut-off state, a first abnormality determination process performs at least one of the following: determining whether an abnormality has occurred in the first detection pressure while brake fluid is being supplied to the first supply source, and determining whether an abnormality has occurred in the second detection pressure while brake fluid is being supplied to the second supply source. A second abnormality determination process determines whether or not an abnormality has occurred in at least one of the first detected pressure and the second detected pressure, under the condition that the switching unit is in the communication state and brake fluid is supplied to at least one of the first supply source and the second supply source, An abnormality identification process is performed to identify the abnormal part based on the determination result of the first abnormality determination process and the determination result of the second abnormality determination process. Braking device.

2. The first abnormality determination process includes a process for determining whether the first detected pressure is abnormal, The aforementioned processing circuit is In the first abnormality determination process, with brake fluid being supplied to the first supply source, if the magnitude of the difference between the first detection pressure and the first determination pressure corresponding to the amount of brake fluid supplied by the first supply source is greater than or equal to a threshold, it is determined that an abnormality has occurred in the first detection pressure. If the first abnormality determination process determines that an abnormality has occurred in the first detected pressure, and the first detected pressure is greater than the first determined pressure, the second abnormality determination process is not executed. The braking device according to claim 1.

3. The processing circuit is configured to execute the second abnormality determination process after executing the first abnormality determination process. When the processing circuit determines in the first abnormality determination process that an abnormality has occurred in the first detected pressure and that no abnormality has occurred in the second detected pressure, The aforementioned processing circuit is In the second abnormality determination process, the first target pressure and the second target pressure are made equal, the first supply source is controlled to bring the first braking pressure closer to the first target pressure, the second supply source is controlled to bring the second braking pressure closer to the second target pressure, and then, when the switching unit is switched from the shut-off state to the open state, if the gradient of change of the second detected pressure is greater than or equal to a predetermined gradient, it is determined that no abnormality has occurred in the first detected pressure. In the abnormality identification process, if the second abnormality determination process determines that no abnormality has occurred in the first detected pressure, it is determined that brake fluid leakage has occurred in at least one of the first supply source, the first fluid passage, and the first wheel cylinder. The braking device according to claim 1.

4. The processing circuit prohibits switching the switching unit to the communication state when the difference between the first target pressure, which is the target value of the first braking pressure, and the second target pressure, which is the target value of the second braking pressure, is greater than or equal to a threshold. The braking device according to claim 1.

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