Braking device

Abstract

To suppress the decrease in the controllability of the hydraulic pressure of multiple wheel cylinders based on the operation of the other supply source when a malfunction occurs in only one of the two supply sources. [Solution] The braking device 30 includes a first supply source 34A having an electric cylinder 40 that supplies brake fluid to a wheel cylinder 211, a second supply source 34B having an electric cylinder 40 that supplies brake fluid to a wheel cylinder 212, a switching unit 35, and a processing circuit 71. The processing circuit 71 shuts off the supply when all of the multiple supply sources 34A and 34B are functioning normally, and operates the multiple supply sources 34A and 34B by controlling the amount of forward movement. The processing circuit 71 connects the supply sources when an abnormality occurs in only one of the multiple supply sources 34A and 34B, and operates the normal supply source by controlling the switching unit 35.

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 wheel cylinders.

Background Art

[0002] The braking device disclosed in Patent Document 1 includes a first electric cylinder that supplies brake fluid to a first wheel cylinder via a first liquid passage, and a second electric cylinder that supplies brake fluid to a second wheel cylinder via a second liquid passage. The plurality of electric cylinders are configured to supply brake fluid to the corresponding wheel cylinders by moving the pistons in the forward direction from the initial positions. The initial position is the most rearward position within the movable range of the pistons.

[0003] The above braking device further includes a communication passage that connects the first liquid passage and the second liquid passage, and a shut-off valve installed in the communication passage. When all of the plurality of electric cylinders are normal, the control unit of the braking device closes the shut-off valve to block the communication between the first wheel cylinder and the second wheel cylinder. In this state, the control unit controls the hydraulic pressure of the first wheel cylinder by operating the first electric cylinder and controls the hydraulic pressure of the second wheel cylinder by operating the second electric cylinder.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the braking system described above, a malfunction may occur in the first electric cylinder while the hydraulic pressure of the first wheel cylinder is being adjusted. In this case, the piston in the first electric cylinder may remain in a position where it has moved forward from its initial position.

[0006] In the braking system, it is possible to adjust the hydraulic pressure of multiple wheel cylinders by opening the shut-off valve to connect the first and second wheel cylinders and then operating the second electric cylinder. However, if the piston of the first electric cylinder does not return to its initial position, it is impossible to determine the amount of brake fluid supplied from the second electric cylinder that flows into the cylinder of the first electric cylinder. As a result, there is a risk that the hydraulic pressure of multiple wheel cylinders cannot be properly controlled. [Means for solving the problem]

[0007] The 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 comprises: a first supply source having a first electric cylinder that supplies brake fluid to the first wheel cylinder by the movement of a piston in the forward direction within the cylinder driven by an electric motor; a second supply source having a second electric cylinder that supplies brake fluid to the second wheel cylinder by the movement of a piston in the forward direction within the cylinder driven by an electric motor; a switching unit that can switch between a communication state in which the first wheel cylinder and the second wheel cylinder are in communication and a disconnection state in which communication between the first wheel cylinder and the second wheel cylinder is disconnected; a first control unit that, when all of the multiple supply sources are normal, operates the multiple supply sources by controlling the switching unit to the disconnection state and by forward amount control that makes the correlation value of the forward amount, which is the amount of movement of the piston in the forward direction from the initial position, follow a target value; and a second control unit that, when an abnormality occurs in only one of the multiple supply sources, operates the other supply source by controlling the switching unit to the communication state and by hydraulic pressure control that makes the hydraulic pressure of the multiple wheel cylinders follow a target value of the hydraulic pressure. [Effects of the Invention]

[0008] The above braking device has the effect of suppressing the decrease in the controllability of the hydraulic pressure of multiple wheel cylinders based on the operation of the other supply source when a malfunction occurs in only one of the two supply sources. [Brief explanation of the drawing]

[0009] [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 cross-sectional view showing the schematic configuration of the electric cylinders provided by multiple power sources in the braking device of Figure 1. [Figure 3] Figure 3 is a block diagram showing the functional configuration of the control device for the braking system shown in Figure 1. [Figure 4] Figure 4 is a flowchart showing a series of processes executed in the braking device of Figure 1 when a braking request is made under conditions where all of the multiple power sources are functioning normally. [Figure 5] Figure 5 is a flowchart showing a series of processes executed in the braking device of Figure 1 when a braking request is made under the condition that a malfunction occurs in only one of the multiple supply sources. [Figure 6] Figure 6 shows the relationship between piston advance and braking pressure when one power source adjusts the braking pressure of one wheel cylinder, and the relationship between piston advance and braking pressure when one power source adjusts the braking pressure of two wheel cylinders. [Figure 7] Figure 7 is a flowchart showing a portion of the series of processes that are executed in the braking device of the second embodiment when a braking request is made while an abnormality occurs in only one of the multiple supply sources. [Modes for carrying out the invention]

[0010] (First Embodiment) A first embodiment of the braking device will be described with reference to Figures 1 to 5. Figure 1 illustrates a vehicle 10 equipped with a braking system 30. The vehicle 10 comprises a plurality of wheels and a plurality of friction brakes 20 corresponding to each of the plurality of wheels. In Figure 1, only the first wheel 11 and the second wheel 12 are shown among the plurality of wheels.

[0011] Each friction brake 20 comprises a wheel cylinder, a rotating body 22, and a friction part 23. The rotating body 22 rotates integrally with the corresponding wheels 11 and 12. The friction brake 20 generates braking force on the corresponding wheels 11 and 12 by pressing the friction part 23 against the rotating body 22. The force pressing the friction part 23 against the rotating body 22 increases with higher hydraulic pressure in the wheel cylinder. In other words, the friction brake 20 can generate greater braking force as the hydraulic pressure in the wheel cylinder increases.

[0012] Hereafter, the hydraulic pressure of the wheel cylinder will be referred to as "braking pressure Pwc". The wheel cylinder corresponding to the first wheel 11 will be referred to as "wheel cylinder 211". The wheel cylinder corresponding to the second wheel 12 will be referred to as "wheel cylinder 212".

[0013] <Configuration of the braking system> The braking system 30 comprises a braking unit 31 and a control device 70. <Brake part> The braking unit 31 can adjust the braking force generated by the first wheel 11 and the second wheel 12 by controlling the braking pressure Pwc of the wheel cylinder 211 and the braking pressure Pwc of the wheel cylinder 212. The braking unit 31 includes a reservoir 32, a supply passage 33, a first supply source 34A, a second supply source 34B, and a switching unit 35.

[0014] Reservoir 32 stores brake fluid and is also open to the atmosphere. The supply passage 33 is a brake fluid passage connecting the reservoir 32 and the wheel cylinders 211, 212. The supply passage 33 branches into two on the way from the connection point with the reservoir 32 toward the wheel cylinders 211, 212. That is, the supply passage 33 includes one main passage 33a connected to the reservoir 32 and two branch passages 33b, 33c connected to the main passage 33a. The connection point between the main passage 33a and the branch passages 33b, 33c is described as "branch point P0".

[0015] The wheel cylinder 211 is connected to the branch passage 33b, and the wheel cylinder 212 is connected to the branch passage 33c. Hereinafter, among the supply passage 33, the branch passage 33b connected to the wheel cylinder 211 may be referred to as the "first fluid passage", and the branch passage 33c connected to the wheel cylinder 212 may be referred to as the "second fluid passage".

[0016] A first hydraulic pressure sensor 37A for detecting the brake fluid pressure in the branch passage 33b is connected to the branch passage 33b. A second hydraulic pressure sensor 37B for detecting the brake fluid pressure in the branch passage 33c is connected to the branch passage 33c. The plurality of hydraulic pressure sensors 37A, 37B are sensors for detecting the braking pressure Pwc and output a detection signal to the control device 70. The brake fluid pressure based on the detection signal of the first hydraulic pressure sensor 37A is described as "first braking pressure detection value PwcS1". The brake fluid pressure based on the detection signal of the second hydraulic pressure sensor 37B is described as "second braking pressure detection value PwcS2".

[0017] The first supply source 34A and the second supply source 34B have an electric cylinder 40. The configuration of the electric cylinder 40 will be described later. The first supply source 34A is connected to the branch passage 33b. The first supply source 34A can supply brake fluid to the wheel cylinder 211 via the branch passage 33b. In this regard, the wheel cylinder 211 corresponds to the "first wheel cylinder". The electric cylinder 40 of the first supply source 34A corresponds to the "first electric cylinder". Hereinafter, the connection point of the first supply source 34A in the branch passage 33b is described as "connection point P1".

[0018] The second supply source 34B is connected to the branch flow path 33c. The second supply source 34B can supply brake fluid to the wheel cylinder 212 via the branch flow path 33c. In this regard, the wheel cylinder 212 corresponds to the "second wheel cylinder". The electric cylinder 40 of the second supply source 34B corresponds to the "second electric cylinder". Hereinafter, the connection point of the second supply source 34B in the branch flow path 33c will be referred to as "connection point P2".

[0019] The switching unit 35 is configured to be switchable between a communication state in which the wheel cylinder 211 and the wheel cylinder 212 communicate with each other and a cutoff state in which the communication between the wheel cylinder 211 and the wheel cylinder 212 is cut off. For example, the switching unit 35 includes a first system cutoff valve 51, a second system cutoff valve 52, and an atmosphere release valve 53. The first system cutoff valve 51, the second system cutoff valve 52, and the atmosphere release valve 53 are normally open solenoid valves. That is, when the energization of the solenoid is stopped, the first system cutoff valve 51, the second system cutoff valve 52, and the atmosphere release valve 53 open as shown in FIG. 1. On the other hand, when the solenoid is energized, the first system cutoff valve 51, the second system cutoff valve 52, and the atmosphere release valve 53 close.

[0020] The first system cutoff valve 51 is installed in the branch flow path 33b. Specifically, it is disposed between the branch point P0 and the connection point P1 in the branch flow path 33b. The second system cutoff valve 52 is installed in the branch flow path 33c. Specifically, it is disposed between the branch point P0 and the connection point P2 in the branch flow path 33c. The atmosphere release valve 53 is disposed in the main flow path 33a.

[0021] The state of the switching unit 35 when both of the two system cutoff valves 51, 52 are closed corresponds to the "cutoff state". The state of the switching unit 35 when both of the two system cutoff valves 51, 52 are open and the atmosphere release valve 53 is closed corresponds to the "communication state".

[0022] Referring to FIG. 2, the configuration of the electric cylinders 40 of the plurality of supply sources 34A, 34B will be described. The electric cylinder 40 includes a cylinder 41, a piston 42, an electric motor 43, a conversion mechanism 44, and a motor angle sensor 45. The piston 42 is provided in a state that allows it to reciprocate within the cylinder 41. The conversion mechanism 44 converts the rotation of the output shaft of the electric motor 43 into the linear movement of the piston 42.

[0023] Inside the cylinder 41, a hydraulic chamber Re for storing brake fluid is partitioned by the peripheral wall of the cylinder 41 and the piston 42. The position of the piston 42 inside the cylinder 41 can be changed by driving the electric motor 43. Hereafter, the direction of linear movement of the piston 42 when reducing the volume of the hydraulic chamber Re will be described as the "forward direction Za". The opposite direction of the forward direction Za will be described as the "reverse direction Zb". The reverse direction Zb is also the direction of linear movement of the piston 42 when increasing the volume of the hydraulic chamber Re. When the piston 42 moves in the forward direction Za, it will be described as "the piston 42 moves forward", and when the piston 42 moves in the reverse direction Zb, it will be described as "the piston 42 moves backward".

[0024] The electric cylinder 40 does not have a return spring that biases the piston 42 in the retraction direction Zb. The range in which the piston 42 can be moved by the electric cylinder 40 is described as the "movable range RA of the piston 42". Within the movable range RA, the retraction end, i.e., the position furthest back in the retraction direction Zb, is described as the "initial position Psf". When no braking pressure Pwc is generated by the wheel cylinders 211 and 212, the piston 42 is in the initial position Psf. When the piston 42 is in the initial position Psf, further movement of the piston 42 in the retraction direction Zb is restricted by the restricting member.

[0025] The cylinder 41 has an output port 41P that connects the hydraulic chamber Re to the outside. The output port 41P is always open. The output port 41P is in communication with the supply passage 33.

[0026] The motor angle sensor 45 outputs a detection signal to the control device 70 corresponding to the change in the rotation angle of the output shaft of the electric motor 43. Hereafter, the rotation angle of the electric motor 43 based on the detection signal of the motor angle sensor 45 will be referred to as "motor rotation angle θmt".

[0027] When the motor rotation angle θmt increases due to the drive of the electric motor 43, the piston 42 moves in the forward direction Za. As a result, the brake fluid in the hydraulic chamber Re is discharged to the branch passages 33b and 33c via the output port 41P. This supplies brake fluid to the wheel cylinders 211 and 212, increasing the braking pressure Pwc. On the other hand, when the motor rotation angle θmt decreases due to the drive of the electric motor 43, the piston 42 moves in the reverse direction Zb. As a result, the brake fluid in the branch passages 33b and 33c flows into the hydraulic chamber Re via the output port 41P. In this case, brake fluid flows out of the wheel cylinders 211 and 212, decreasing the braking pressure Pwc.

[0028] The amount of movement of the piston 42 from the initial position Psf to the forward direction Za is referred to as "the amount of forward movement of the piston 42 STp". When the motor rotation angle θmt increases due to the driving of the electric motor 43, the amount of forward movement STp increases. When the motor rotation angle θmt decreases due to the driving of the electric motor 43, the amount of forward movement STp decreases. When the piston 42 returns to the initial position Psf, the amount of forward movement STp becomes 0 (zero).

[0029] <Control device> As shown in Figure 1, the control device 70 includes a processing circuit 71 that controls the braking unit 31. An example of the processing circuit 71 is an electronic control device. In this case, the processing circuit 71 has a CPU 72 and a memory 73. The memory 73 stores various control programs executed by the CPU 72. The CPU 72 executes the control programs in the memory 73, thereby controlling the braking unit 31.

[0030] Referring to Figure 3, the functional configuration of the processing circuit 71 will be explained. The processing circuit 71 functions as a set of functional units for operating the braking unit 31, with the CPU 72 executing the control program for the memory 73. The set of functional units includes a first control unit 101, a second control unit 102, an abnormality determination unit 103, and a forward movement amount acquisition unit 104.

[0031] <First Control Unit> The first control unit 101 controls the braking pressure Pwc of the wheel cylinders 211 and 212 by activating the multiple supply sources 34A and 34B when all of the multiple supply sources 34A and 34B are functioning normally. Specifically, the first control unit 101 shuts off the switching unit 35 by closing all of the multiple system shut-off valves 51 and 52. At this time, the first control unit 101 may also close the atmospheric release valve 53. Then, the first control unit 101 controls the braking pressure Pwc of the wheel cylinder 211 by activating the first supply source 34A. The first control unit 101 controls the braking pressure Pwc of the wheel cylinder 212 by activating the second supply source 34B.

[0032] Here, there is a correspondence between the forward movement STp of the piston 42 of the electric cylinder 40 and the consumption amount, which is the amount of brake fluid supplied from the supply source to the wheel cylinder. There is also a correspondence between the braking pressure Pwc of the wheel cylinder and the consumption amount. Furthermore, there is a correspondence between the forward movement STp of the piston 42 and the motor rotation angle θmt. Therefore, it can be said that there is a correspondence between the forward movement STp and the motor rotation angle θmt and the braking pressure Pwc. Thus, the first control unit 101 can set the target value of the motor rotation angle θmt as a correlation value of the target value of the forward movement STp, based on the required braking pressure PwcRq, which is the required value of the braking pressure Pwc. Hereafter, the target value of the motor rotation angle θmt will be referred to as the "target motor rotation angle".

[0033] Therefore, the first control unit 101 sets a target braking pressure PwcTr1, which is the target value of the braking pressure Pwc of the wheel cylinder 211, and a target braking pressure PwcTr2, which is the target value of the braking pressure Pwc of the wheel cylinder 212, based on the above-mentioned required braking pressure PwcRq. The first control unit 101 sets the motor rotation angle θmt corresponding to the target braking pressure PwcTr1 as the target motor rotation angle θmtTr1 of the electric motor 43 of the first power source 34A. The target motor rotation angle θmtTr1 is the correlation value of the target value of the forward movement amount STp of the piston 42 of the first power source 34A. Then, the first control unit 101 operates the first power source 34A by executing feedback control to make the motor rotation angle θmt of the electric motor 43 of the first power source 34A follow the target motor rotation angle θmtTr1.

[0034] Similarly, the first control unit 101 sets the motor rotation angle θmt corresponding to the target braking pressure PwcTr2 to the target motor rotation angle θmtTr2 of the electric motor 43 of the second power source 34B. The target motor rotation angle θmtTr2 is the correlation value of the target value of the forward movement amount STp of the piston 42 of the second power source 34B. The first control unit 101 then operates the second power source 34B by performing feedback control to make the motor rotation angle θmt of the electric motor 43 of the second power source 34B follow the target motor rotation angle θmtTr2.

[0035] Hereafter, the feedback control that makes the motor rotation angle θmt follow the target motor rotation angles θmtTr1 and θmtTr2, as described above, will be referred to as "forward movement control". <Second Control Unit> The second control unit 102 controls the braking pressure Pwc of the multiple wheel cylinders 211, 212 by activating the other supply source if an abnormality occurs in only one of the multiple supply sources 34A, 34B. Specifically, the second control unit 102 opens both of the two system shut-off valves 51, 52 and closes the atmospheric release valve 53, thereby setting the switching unit 35 to a communication state. Then, the second control unit 102 activates the supply source among the multiple supply sources 34A, 34B that is not experiencing an abnormality. Hereafter, the supply source that is not experiencing an abnormality may also be referred to as a "normal supply source".

[0036] The second control unit 102 sets a target braking pressure PwcTr, which is the target value for the braking pressure Pwc of the multiple wheel cylinders 211, 212, based on the requested braking pressure PwcRq. The second control unit 102 then operates a normal power supply by performing feedback control to make the braking pressure Pwc of the multiple wheel cylinders 211, 212 follow the target braking pressure PwcTr. For example, the second control unit 102 selects one of the first braking pressure detection value PwcS1 and the second braking pressure detection value PwcS2. In this case, the processing circuit 71 may select the first braking pressure detection value PwcS1 if the first power supply 34A is normal, and select the second braking pressure detection value PwcS2 if the second power supply 34B is normal. The processing circuit 71 then drives the electric motor 43 of a normal power source so that the selected braking pressure detection value PwcS follows the target braking pressure PwcTr.

[0037] Hereafter, the feedback control that makes the braking pressure Pwc of multiple wheel cylinders 211, 212 follow the target braking pressure PwcTr as described above will be referred to as "hydraulic control". <Abnormality determination section> The abnormality determination unit 103 determines whether an abnormality has occurred in each of the supply sources 34A and 34B. "Supply source abnormality" here includes the inability to control the electric cylinder 40. Such abnormalities can occur due to failures of the electric motor 43, the driver circuit of the electric motor 43, the motor angle sensor 45, the hydraulic pressure sensors 37A and 37B, the processing circuit 71, and the CPU 72. In this embodiment, the braking device 30 has one processing circuit 71 and one CPU 72. However, the braking device may be configured to include multiple processing circuits and multiple CPUs to correspond to each of the multiple supply sources.

[0038] <Advance amount acquisition part> The forward movement amount acquisition unit 104 acquires the forward movement amount STp of the piston 42 of the supply source 34A, 34B at the time the abnormality occurred, as the forward movement amount STpA, when the first control unit 101 determines that an abnormality has occurred in only one of the supply sources 34A, 34B while the multiple supply sources 34A, 34B are operating under forward movement amount control. For example, the forward movement amount acquisition unit 104 acquires the motor rotation angle θmt of the electric motor 43 of the supply source where the abnormality occurred, at the time the abnormality occurred, as the motor rotation angle θmtA. Then, the forward movement amount acquisition unit 104 acquires the value obtained by converting the motor rotation angle θmtA to a forward movement amount STp, as the forward movement amount STpA.

[0039] <Normal braking procedure> Referring to Figure 4, a series of processes are executed when a braking request occurs from vehicle 10 under the condition that all of the multiple supply sources 34A and 34B are functioning normally.

[0040] When a braking request occurs, the processing circuit 71 starts a series of processes as shown in Figure 4. In step S11, the processing circuit 71 determines whether the state of the switching unit 35 is in the off state or not. If the state of the switching unit 35 is in the off state (S11: YES), the processing circuit 71 proceeds to step S15. On the other hand, if the state of the switching unit 35 is in the connected state (S11: NO), the processing circuit 71 proceeds to step S13.

[0041] In step S13, the processing circuit 71 functions as the first control unit 101 and sets the state of the switching unit 35 to the shut-off state. That is, the processing circuit 71 closes the two system shut-off valves 51 and 52. Then, the processing circuit 71 proceeds to step S15.

[0042] In step S15, the processing circuit 71, functioning as the first control unit 101, sets a plurality of target braking pressures PwcTr1 and PwcTr2 based on the requested braking pressure PwcRq. In the subsequent step S17, the processing circuit 71, functioning as the first control unit 101, sets the motor rotation angle θmt corresponding to the target braking pressure PwcTr1 as the target motor rotation angle θmtTr1. The processing circuit 71 sets the motor rotation angle θmt corresponding to the target braking pressure PwcTr2 as the target motor rotation angle θmtTr2.

[0043] Then, in step S19, the processing circuit 71, functioning as the first control unit 101, operates the first power source 34A by controlling the amount of forward movement so that the motor rotation angle θmt of the electric motor 43 of the first power source 34A follows the target motor rotation angle θmtTr1. The processing circuit 71 also operates the second power source 34B by controlling the amount of forward movement so that the motor rotation angle θmt of the electric motor 43 of the second power source 34B follows the target motor rotation angle θmtTr2.

[0044] In the next step S21, the processing circuit 71 functions as an abnormality determination unit 103 to determine whether or not an abnormality has occurred in the multiple supply sources 34A and 34B. For example, the processing circuit 71 determines that an abnormality has occurred in the first supply source 34A if the deviation between the braking pressure Pwc of the wheel cylinder 211 and the target braking pressure PwcTr1 exceeds the allowable range. The processing circuit 71 determines that an abnormality has occurred in the second supply source 34B if the deviation between the braking pressure Pwc of the wheel cylinder 212 and the target braking pressure PwcTr2 exceeds the allowable range.

[0045] If the processing circuit 71 determines that an abnormality has occurred in at least one of the multiple supply sources 34A and 34B (S21: YES), the processing circuit 71 terminates the series of processes shown in Figure 4. Then, the processing circuit 71 starts executing the series of processes shown in Figure 5, which will be described later. On the other hand, if the processing circuit 71 determines that no abnormality has occurred in any of the multiple supply sources 34A and 34B (S21: NO), the processing circuit 71 moves the process to step S23.

[0046] In step S23, the processing circuit 71, functioning as the first control unit 101, determines whether or not a braking request has occurred. If a braking request has occurred (S23: YES), the processing circuit 71 proceeds to step S15. That is, the processing circuit 71 continues to control the first supply source 34A and the second supply source 34B by forward amount control. On the other hand, if no braking request has occurred (S23: NO), the processing circuit 71 terminates the control of the first supply source 34A and the second supply source 34B by forward amount control. The processing circuit 71 then completes the series of processes shown in Figure 4.

[0047] <Braking procedures in case of abnormal conditions> Referring to Figure 5, a series of processes are executed when a braking request is made by the vehicle 10 while an abnormality is occurring in only one of the multiple supply sources 34A and 34B.

[0048] If a braking request is issued while the processing circuit 71 has determined that an abnormality has occurred in at least one of the multiple supply sources 34A, 34B, the processing circuit 71 starts the series of processes shown in Figure 5. In step S41, the processing circuit 71 functions as an abnormality determination unit 103 to determine whether an abnormality has occurred in only one of the multiple supply sources 34A, 34B. If the processing circuit 71 determines that an abnormality has occurred in only one of the multiple supply sources (S41: YES), the processing circuit 71 proceeds to step S43. On the other hand, if the processing circuit 71 determines that an abnormality has occurred in both of the multiple supply sources 34A, 34B (S41: NO), the processing circuit 71 terminates the series of processes shown in Figure 5. In this case, the processing circuit 71 sets the state of the switching unit 35 to a communication state and opens the atmospheric release valve 53. Furthermore, if the braking device 30 includes other braking components besides the braking unit 31, the processing circuit 71 generates braking force in the vehicle 10 by activating the other braking components.

[0049] In step S43, the processing circuit 71 determines whether the state of the switching unit 35 is in a connected state or not. If the state of the switching unit 35 is in a connected state (S43: YES), the processing circuit 71 proceeds to step S47. On the other hand, if the state of the switching unit 35 is in a disconnected state (S43: NO), the processing circuit 71 proceeds to step S45.

[0050] In step S45, the processing circuit 71 functions as the second control unit 102, thereby changing the state of the switching unit 35 to a communication state. Then, the processing circuit 71 proceeds to step S47. That is, the processing from step S47 onward is performed with both of the two system shut-off valves 51 and 52 open, while the atmospheric release valve 53 is closed.

[0051] In step S47, the processing circuit 71 determines whether the control of the supply source has just switched from forward amount control to hydraulic control. If the processing circuit 71 was operating multiple supply sources 34A and 34B by forward amount control immediately before the start of the series of processes shown in Figure 5, it determines that the control has just switched from forward amount control to hydraulic control (S47: YES). Then, the processing circuit 71 proceeds to step S51. On the other hand, if the control of the supply source was hydraulic control before the start of the series of processes shown in Figure 5, the processing circuit 71 determines that the control has not just switched from forward amount control to hydraulic control (S47: NO). Then, the processing circuit 71 proceeds to step S71.

[0052] In step S51, the processing circuit 71 functions as the second control unit 102 and sets the braking pressure detection value PwcS when the state of the switching unit 35 is in a communication state to the initial value of the target braking pressure PwcTr. For example, if the first supply source 34A is a normal supply source, the processing circuit 71 sets the first braking pressure detection value PwcS1 to the initial value of the target braking pressure PwcTr. If the second supply source 34B is a normal supply source, the processing circuit 71 sets the second braking pressure detection value PwcS2 to the initial value of the target braking pressure PwcTr.

[0053] In the subsequent step S53, the processing circuit 71 functions as a forward movement amount acquisition unit 104 and acquires the forward movement amount STp of the piston 42 of one of the multiple supply sources 34A, 34B at the time an abnormality occurs in that one supply source, as the forward movement amount STpA at the time of occurrence. Here, the processing circuit 71 acquires the value obtained by converting the motor rotation angle θmt of the electric motor 43 of the supply source where the abnormality occurred to the forward movement amount STp of the piston 42, from the motor rotation angle θmt at the time the abnormality occurred, as the forward movement amount STpA at the time of occurrence.

[0054] In the subsequent step S55, the processing circuit 71 functions as a second control unit 102, and by operating a normal supply source through hydraulic pressure control, causes the braking pressure Pwc of the multiple wheel cylinders 211, 212 to follow the target braking pressure PwcTr.

[0055] In this case, the processing circuit 71 sets the control gain Gc of the hydraulic control to a value corresponding to the initial forward movement STpA obtained in step S53. The "control gain Gc" here is the gain of the feedback control. If the feedback control is PID control, the processing circuit 71 sets at least one of the gains from the proportional control gain, the integral control gain, and the differential control gain to a value corresponding to the initial forward movement STpA. For example, the processing circuit 71 increases the control gain Gc at the start of hydraulic control as the initial forward movement STpA is larger.

[0056] As this hydraulic control is performed, the discrepancy between the braking pressure Pwc of the multiple wheel cylinders 211, 212 and the target braking pressure PwcTr gradually decreases. Therefore, the processing circuit 71 changes the control gain Gc described above so that its value decreases as the discrepancy between the braking pressure Pwc and the target braking pressure PwcTr decreases.

[0057] If the processing circuit 71 is performing this hydraulic pressure control, it proceeds to step S57. In step S57, the processing circuit 71 determines whether the target braking pressure PwcTr is substantially equal to the required braking pressure PwcRq. An example of the required braking pressure PwcRq is the braking pressure corresponding to the target value of the braking force of the vehicle 10. If the difference between the target braking pressure PwcTr and the required braking pressure PwcRq is within a predetermined error range, the target braking pressure PwcTr is considered substantially equal to the required braking pressure PwcRq. If the difference exceeds the predetermined error range, the target braking pressure PwcTr is considered not equal to the required braking pressure PwcRq. If the processing circuit 71 determines that the target braking pressure PwcTr is substantially equal to the required braking pressure PwcRq (S57: YES), the processing circuit 71 proceeds to step S73. On the other hand, if the processing circuit 71 determines that the target braking pressure PwcTr is not equal to the required braking pressure PwcRq (S57: NO), the processing circuit 71 proceeds to step S59.

[0058] In step S59, the processing circuit 71, functioning as a second control unit 102, performs a gradual change process to modify the target braking pressure PwcTr so that the target braking pressure PwcTr gradually approaches the requested braking pressure PwcRq. For example, in the gradual change process, the processing circuit 71 modifies the target braking pressure PwcTr so that the target braking pressure PwcTr changes at a predetermined speed.

[0059] In the following step S61, the processing circuit 71 determines whether or not a braking request has occurred. If a braking request has occurred (S61: YES), the processing circuit 71 proceeds to step S55. That is, the processing circuit 71 continues to operate the normal supply source with hydraulic control. On the other hand, if no braking request has occurred (S61: NO), the processing circuit 71 terminates the operation of the normal supply source. Then, the processing circuit 71 completes the series of processes shown in Figure 5.

[0060] In step S71, the processing circuit 71, functioning as the second control unit 102, sets the requested braking pressure PwcRq to the target braking pressure PwcTr. Then, the processing circuit 71 proceeds to step S73.

[0061] In step S73, the processing circuit 71 functions as a second control unit 102, and by operating a normal supply source through hydraulic pressure control, causes the braking pressure Pwc of the multiple wheel cylinders 211, 212 to follow the target braking pressure PwcTr.

[0062] The hydraulic pressure control in step S55 described above is for when the target braking pressure PwcTr deviates from the required braking pressure PwcRq, whereas the hydraulic pressure control in step S73 is for when the target braking pressure PwcTr is equal to the required braking pressure PwcRq. When the processing circuit 71 is executing the hydraulic pressure control in step S73, it may vary the control gain Gc of the hydraulic pressure control according to the deviation between the braking pressure Pwc of the multiple wheel cylinders 211, 212 and the target braking pressure PwcTr. Alternatively, the processing circuit 71 may maintain the control gain Gc of the hydraulic pressure control at the value at the point when the target braking pressure PwcTr becomes equal to the required braking pressure PwcRq.

[0063] In the following step S75, the processing circuit 71 determines whether or not a braking request has occurred. If a braking request has occurred (S75: YES), the processing circuit 71 proceeds to step S71. That is, the processing circuit 71 continues to operate the normal supply source with hydraulic control. On the other hand, if no braking request has occurred (S75: NO), the processing circuit 71 terminates the operation of the normal supply source. Then, the processing circuit 71 terminates the series of processes shown in Figure 5.

[0064] <Operation and Effects of This Embodiment> (1-1) When all of the multiple supply sources 34A and 34B are functioning normally, the processing circuit 71 is shut off by the control of the switching unit 35 and operates the multiple supply sources 34A and 34B individually by forward amount control. In this situation where multiple supply sources 34A and 34B are operating, an abnormality may occur in only one of the multiple supply sources 34A and 34B. If an abnormality occurs in an operating supply source, the processing circuit 71 may not be able to determine the forward amount STp of the piston 42 of that supply source. Consider a comparative example in which the processing circuit 71 operates a normal supply source by forward amount control even in such a situation.

[0065] In this comparative example, the processing circuit 71 is kept in communication by the control of the switching unit 35. Then, the processing circuit 71 operates the normal supply source with forward amount control. In this case, a portion of the brake fluid supplied from the normal supply source to the supply channel 33 flows into the cylinder 41 of the supply source where the abnormality is occurring. Moreover, if the forward amount STp of the piston 42 of the supply source where the abnormality is occurring is unknown, it is difficult for the processing circuit 71 to determine the amount of brake fluid supplied from the normal supply source to the supply channel 33 that flows into the cylinder 41 of the supply source where the abnormality is occurring. For this reason, in the comparative example, the processing circuit 71 cannot determine the amount of brake fluid that was supplied to the multiple wheel cylinders 211, 212, and therefore there is a risk that the processing circuit 71 will not be able to properly control the braking pressure Pwc of the multiple wheel cylinders 211, 212.

[0066] Therefore, in the braking device 30, if the processing circuit 71 determines that an abnormality has occurred in only one of the multiple supply sources 34A, 34B, it switches the control of the normal supply source from forward movement control to hydraulic pressure control. That is, the processing circuit 71 is put into a communication state by the control of the switching unit 35 and operates the normal supply source by hydraulic pressure control. As a result, the processing circuit 71 can appropriately control the braking pressure Pwc of the multiple wheel cylinders 211, 212 even if the forward movement STp of the piston 42 of the supply source where the abnormality has occurred is unknown.

[0067] Therefore, the braking device 30 can suppress a decrease in the controllability of the braking pressure Pwc of the multiple wheel cylinders 211, 212 based on the operation of the other supply source when an abnormality occurs in only one of the multiple supply sources 34A, 34B.

[0068] (1-2) When multiple supply sources 34A and 34B are operating under forward amount control, if an abnormality occurs in only one of the supply sources 34A and 34B, the processing circuit 71 will connect them under the control of the switching unit 35 and then switch the control of the normal supply source from forward amount control to hydraulic control.

[0069] Consider a comparative example in which the required braking pressure PwcRq is set to the target braking pressure PwcTr immediately after switching the control of a normal supply source from forward amount control to hydraulic pressure control. If the discrepancy between the detected braking pressure PwcS and the required braking pressure PwcRq is relatively large immediately before the switch, in this comparative example, the braking pressure Pwc may change significantly before and after the switch. If the braking pressure Pwc changes significantly while the vehicle 10 is in motion, the deceleration of the vehicle 10 will change significantly, which may cause discomfort to the occupants of the vehicle 10.

[0070] Therefore, in the braking device 30, the processing circuit 71 sets the brake pressure detection value PwcS at the time the switching unit 35 is activated to the initial value of the target brake pressure PwcTr and starts hydraulic control. As a result, the processing circuit 71 can suppress large changes in the brake pressure Pwc before and after the control switch. Consequently, the braking device 30 can suppress large changes in the deceleration of the vehicle 10 caused by the switch in control from forward amount control to hydraulic control.

[0071] (1-3) After the processing circuit 71 starts hydraulic control by setting the detected braking pressure PwcS at the time the switching unit 35 puts it into a shut-off state as the initial value of the target braking pressure PwcTr, it gradually changes the target braking pressure PwcTr toward the requested braking pressure PwcRq. As a result, the braking device 30 can appropriately control the braking force of the vehicle 10 even when the control is switched from forward control to hydraulic control.

[0072] (1-4) When the control of a normal supply source switches from forward movement control to hydraulic control, the larger the first forward movement STp1, which is the forward movement STp of the piston 42 of the supply source experiencing an abnormality at the time of the switch, the greater the amount of brake fluid supplied by the normal supply source to the supply passage 33 that flows into the cylinder 41 of the supply source experiencing the abnormality. As a result, immediately after the control of the normal supply source switches from forward movement control to hydraulic control, the braking pressure Pwc of the multiple wheel cylinders 211, 212 is unlikely to increase.

[0073] Therefore, the processing circuit 71 increases the control gain Gc at the start of hydraulic control as the first forward amount STp1 increases. This allows the processing circuit 71 to increase the amount of brake fluid supplied from a normal supply source to the supply passage 33 immediately after the start of hydraulic control. As a result, the processing circuit 71 can move the piston 42 of the supply source where an abnormality has occurred to the initial position Psf earlier. This allows the processing circuit 71 to suppress the delay in the increase of the braking pressure Pwc of the multiple wheel cylinders 211, 212.

[0074] (1-5) If the control gain Gc of the hydraulic control remains large, the processing circuit 71 may have difficulty converging the braking pressure Pwc to the target braking pressure PwcTr when operating a normal supply source by hydraulic control. In other words, the hunting of the braking pressure Pwc may continue for a long time. Therefore, when the hydraulic control is being performed, the processing circuit 71 reduces the control gain Gc as the discrepancy between the braking pressure Pwc and the target braking pressure PwcTr decreases. As a result, the processing circuit 71 reduces the control gain Gc as the discrepancy decreases during the execution of hydraulic control. Consequently, the processing circuit 71 can suppress the hunting of the braking pressure Pwc from continuing for a long time.

[0075] (Second Embodiment) A second embodiment of the braking device will be described with reference to Figures 6 and 7. In the following description, we will mainly explain the differences between the control content and the first embodiment when an abnormality occurs in only one of the multiple supply sources. Components that are the same as or equivalent to those in the first embodiment will be denoted by the same reference numerals, and redundant explanations will be omitted.

[0076] <Second Control Unit> The second control unit 102 activates a functioning supply source by hydraulic control when it determines that an abnormality has occurred in only one of the multiple supply sources 34A and 34B.

[0077] When a normal supply source is supplying brake fluid to the supply passage 33 via hydraulic pressure control, the brake fluid supplied by the normal supply source flows into the cylinder 41 of the supply source experiencing an abnormality. As a result, the hydraulic pressure in the hydraulic chamber Re within the cylinder 41 of the supply source experiencing the abnormality increases, causing the forward movement STp of the piston 42 to decrease. In other words, the piston 42 moves in the backward direction Zb toward the initial position Psf.

[0078] Therefore, the second control unit 102 estimates the forward movement STp of the piston 42 of the malfunctioning supply source when a normal supply source is being operated by hydraulic control. Based on this estimation, the second control unit 102 then determines whether or not the piston 42 of the malfunctioning supply source has moved to its initial position Psf. The method for this determination will be described later.

[0079] If the second control unit 102 determines that the piston 42 of the supply source experiencing an abnormality has moved to its initial position Psf, it switches the control of the normal supply source from hydraulic control to forward movement control. In this forward movement control, the second control unit 102 sets the target motor rotation angle θmtTrA as the correlation value of the target forward movement STp of the piston 42 of the normal supply source. The method for setting the target motor rotation angle θmtTrA will be described later.

[0080] Then, the second control unit 102 operates the normal power supply source by controlling the amount of forward movement so that the motor rotation angle θmt of the normal power supply source's electric motor 43 follows the target motor rotation angle θmtTrA. However, even when operating the normal power supply source by controlling the amount of forward movement, the second control unit 102 maintains the state of the switching unit 35 in a connected state.

[0081] <Determination process to determine whether the piston of the supply source experiencing the malfunction has returned to its initial position.> Refer to Figure 6 to explain an example of the determination process. The dashed line in Figure 6 illustrates the normal relationship MP1, which is the relationship between the forward movement STp of the piston 42 and the braking pressure Pwc when the switching unit 35 is in the shut-off state. The solid line in Figure 6 illustrates the single-system relationship MP2, which is the relationship between the forward movement STp of the piston 42 of a supply source and the braking pressure Pwc when a single supply source adjusts the braking pressure Pwc of multiple wheel cylinders 211, 212.

[0082] When the first control unit 101 operates multiple supply sources 34A and 34B individually by forward movement control, the forward movement STp of the piston 42 corresponding to the braking pressure Pwc at that time can be derived based on the normal relationship MP1 in Figure 6.

[0083] When the supply source is operating normally by hydraulic control, the second control unit 102 determines whether the relationship between the first forward amount STp1, which is the forward amount STp of the piston 42 of the normal supply source, and the braking pressure Pwc has become the single-system relationship MP2.

[0084] When brake fluid is supplied to the supply channel 33 from a normal supply source, the piston 42 approaches the initial position Psf in the supply source where an abnormality is occurring. As a result, as shown by arrow Y3 in Figure 6, the state point PA1, which is the point that shows the relationship between the first forward amount STp1 and the braking pressure Pwc, moves.

[0085] Therefore, the second control unit 102 determines whether the relationship between the first forward movement amount STp1 and the braking pressure Pwc has become the single-system relationship MP2, based on the position of the state point PA1 relative to the line representing the single-system relationship MP2. For example, the second control unit 102 obtains the value obtained by converting the motor rotation angle θmt of the electric motor 43 of a normal power source into the forward movement amount STp of the piston 42 as the first forward movement amount STp1. The second control unit 102 also obtains the first braking pressure detection value PwcS1 or the second braking pressure detection value PwcS2 as the braking pressure detection value. In the graph shown in Figure 6, the second control unit 102 sets the point indicated by the first forward movement amount STp1 and the braking pressure detection value obtained in this way as the state point PA1. Then, the processing circuit 71 determines that the relationship between the first forward movement amount STp1 and the braking pressure Pwc has become the single-system relationship MP2 when the state point PA1 is located on the line representing the single-system relationship MP2. In other words, the second control unit 102 determines that the piston 42 of the supply source where the abnormality occurred has moved to its initial position Psf.

[0086] <Setting process for target motor rotation angle θmtTrA> The second control unit 102 sets the requested motor rotation angle θmtRq as the initial value of the target motor rotation angle θmtTrA. This is because, when the piston 42 of the supply source where an abnormality has occurred due to hydraulic control moves to the initial position Psf, the relationship between the first forward amount STp1 and the braking pressure Pwc becomes the single-system relationship MP2. Therefore, even if the initial value in the forward amount control is set to the requested motor rotation angle θmtRq, the control target value will not change abruptly when switching from hydraulic control to forward amount control.

[0087] The requested motor rotation angle θmtRq is set based on the single-system time relationship MP2 shown in Figure 6. Specifically, the second control unit 102 derives the forward movement amount STp corresponding to the requested braking pressure PwcRq at that time based on the single-system time relationship MP2. Then, the second control unit 102 converts the derived forward movement amount STp into a motor rotation angle θmt and sets the value obtained by this conversion to the requested motor rotation angle θmtRq.

[0088] <Braking procedures in case of abnormal conditions> Referring to Figure 7, the processing circuit 71 executes a series of processes when a braking request is made by the vehicle 10 while an abnormality occurs in only one of the multiple supply sources 34A and 34B. Here, we will mainly explain the parts of this series of processes that differ from those of the first embodiment described above.

[0089] If the processing circuit 71 is operating a normal supply source by the hydraulic pressure control in step S73 of Figure 5, the processing circuit 71 proceeds to step S81. In step S81, the processing circuit 71, by functioning as the second control unit 102, obtains the first forward amount STp1, which is the current forward amount STp of the piston 42 of the normal supply source, and the braking pressure detection value PwcS. For example, if the normal supply source is the first supply source 34A, the processing circuit 71 obtains the first braking pressure detection value PwcS1 as the braking pressure detection value PwcS.

[0090] In the subsequent step S83, the processing circuit 71, functioning as the second control unit 102, determines whether the piston 42 of the supply source experiencing an abnormality has moved to its initial position Psf. For example, the processing circuit 71 determines whether the piston 42 has moved to its initial position Psf based on the first forward amount STp1 and the braking pressure detection value PwcS acquired in step S81, and the single-system relationship MP2. If the processing circuit 71 determines that the piston 42 has moved to its initial position Psf (S83: YES), the processing circuit 71 proceeds to step S85. On the other hand, if the processing circuit 71 determines that the piston 42 has not moved to its initial position Psf (S83: NO), the processing circuit 71 proceeds to step S75 in Figure 5. In this case, the processing circuit 71 does not switch the control of the normal supply source from hydraulic pressure control to forward amount control.

[0091] In step S85, the processing circuit 71, functioning as the second control unit 102, operates the normal supply source by controlling the amount of forward movement based on the target motor rotation angle θmtTrA. Because the piston 42 of the supply source experiencing an abnormality has moved to its initial position Psf due to hydraulic pressure control, the relationship between the first amount of forward movement STp1 and the braking pressure Pwc is in the single-system relationship MP2. Therefore, the processing circuit 71 sets the requested motor rotation angle θmtRq to the target motor rotation angle θmtTrA and drives the electric motor 43 of the normal supply source based on the target motor rotation angle θmtTrA. Then, the processing circuit 71 proceeds to step S87.

[0092] In step S87, the processing circuit 71 determines whether or not a braking request has occurred. If a braking request has occurred (S87: YES), the processing circuit 71 proceeds to step S85. That is, the processing circuit 71 continues to operate the normal supply source with forward amount control. On the other hand, if no braking request has occurred (S87: NO), the processing circuit 71 terminates the operation of the normal supply source. Then, the processing circuit 71 terminates the series of processes shown in Figure 7.

[0093] <Operation and Effects of This Embodiment> In this embodiment, in addition to the effects equivalent to those of the first embodiment (1-1) to (1-5) described above, the following further effects can be obtained.

[0094] (2-1) The electric cylinder 40 adjusts the braking pressure Pwc by driving the electric motor 43. Therefore, when the motor rotation angle θmt increases or decreases, there is a delay in the change of the braking pressure detection value in response to the change in the motor rotation angle θmt. For this reason, the controllability when operating the electric cylinder 40 based on the motor rotation angle θmt is higher than the controllability when operating the electric cylinder 40 based on the braking pressure detection value.

[0095] Therefore, even if an abnormality occurs in only one of the multiple supply sources 34A, 34B, the processing circuit 71 determines that the piston 42 of the abnormal supply source has moved to its initial position Psf, and switches the control of the normal supply source from hydraulic control to forward movement control. As a result, the braking device 30 can improve the controllability of the braking pressure Pwc of the multiple wheel cylinders 211, 212 by operating the normal supply source when an abnormality occurs in only one supply source.

[0096] (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.

[0097] In the above-described embodiments, the processing circuit 71, i.e., the second control unit 102, changes the control gain Gc of the hydraulic pressure control according to the difference between the braking pressure Pwc and the target braking pressure PwcTr when it starts operating a normal supply source by the hydraulic pressure control described above, but it is not limited to this. For example, the processing circuit 71 may set the control gain Gc to become smaller as the detected braking pressure value PwcS increases.

[0098] In the above-described embodiments, the processing circuit 71, i.e., the second control unit 102, does not need to vary the control gain Gc according to the generation advance amount STpA obtained in step S53 of Figure 5.

[0099] In the second embodiment described above, the processing circuit 71, i.e., the second control unit 102, may determine whether the piston 42 of the supply source experiencing the abnormality has moved to the initial position Psf using a method different from the method described in the second embodiment. For example, if the processing circuit 71 can obtain the motor rotation angle θmt of the electric motor 43 of the supply source experiencing the abnormality, it may determine whether the piston 42 has moved to the initial position Psf based on the motor rotation angle θmt.

[0100] In the above-described embodiments, the processing circuit 71, i.e., the second control unit 102, may set a value different from the brake pressure detection value PwcS at the time the state of the switching unit 35 is set to the communication state for the target brake pressure PwcTr at the start of hydraulic pressure control. For example, the processing circuit 71 may set the required brake pressure PwcRq at that time for the target brake pressure PwcTr at the start of hydraulic pressure control.

[0101] The electric cylinder may have a stroke sensor capable of detecting the forward movement STp of the piston 42. In this case, the processing circuit 71 may drive the electric motor 43 in forward movement control such that the forward movement detection value, which is the value detected by the stroke sensor, follows the target value of the forward movement.

[0102] The electric cylinder may have a return spring that is not strong enough to return the piston 42 to its initial position Psf by the biasing force of the spring alone. In the above embodiments, the initial position Psf was set to the furthest retracted end of the movable range RA of the piston 42, but this is not limited to this. For example, the initial position Psf may be set to a position that is a predetermined amount forward from the furthest retracted end of the movable range RA of the piston 42. The processing circuit 71 may then perform forward movement control based on this initial position Psf.

[0103] However, when switching from hydraulic control to forward movement control, it is preferable to switch the control when the piston 42 of the supply source experiencing the malfunction has moved to its furthest retracted end. This is because forward movement control uses the relationship between the forward movement STp of the piston 42 and the braking pressure Pwc, and if the piston 42 of the supply source experiencing the malfunction has moved to its furthest retracted end in the connected state, the relationship between the forward movement STp and the braking pressure Pwc is determined by the single-system relationship MP2, making it easier to derive the target value for forward movement control.

[0104] Conversely, if forward movement control is performed when the piston 42 of the faulty supply source has not moved to its furthest backward position, the relationship between the forward movement STp and the braking pressure Pwc changes depending on the forward movement STp of the faulty supply source piston 42. This reduces the accuracy of forward movement control. Furthermore, in this case, if one attempts to improve the accuracy of forward movement control, it becomes necessary to correct the relationship between the forward movement STp and the braking pressure Pwc according to the forward movement STp of the faulty supply source piston 42, making forward movement control complicated.

[0105] The braking system may be configured such that a first supply source can supply brake fluid to two wheel cylinders. In this case, the two wheel cylinders correspond to the "first wheel cylinders." The braking system may also be configured such that a second supply source can supply brake fluid to two wheel cylinders. In this case, the two wheel cylinders correspond to the "second wheel cylinders."

[0106] The first braking unit of the braking device may be configured to include a third supply source, if it includes a first supply source and a second supply source. For example, the third supply source may be installed between the first and second supply sources and the first and second wheel cylinders. In this case, even if the first and second supply sources are not operating, the braking pressure Pwc of the first and second wheel cylinders is adjusted by the operation of the third supply source. For example, the third supply source may be configured to have an electric pump that discharges brake fluid.

[0107] The processing circuit of the control device 70 may include multiple processing circuits. For example, the processing circuit may include a first processing circuit that controls the first supply source 34A, a second processing circuit that controls the second supply source 34B, and a third processing circuit that controls the switching unit 35.

[0108] 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.

[0109] (Other technological ideas) The technical concepts that can be understood from the above-mentioned multiple embodiments and modifications are described below. [Note 1] In the hydraulic pressure control, the second control unit preferably gradually changes the target value of the hydraulic pressure from the initial value to a hydraulic pressure corresponding to the required braking force of the vehicle.

[0110] [Note 2] In the hydraulic pressure control, the second control unit preferably reduces the control gain as the difference between the hydraulic pressure of the plurality of wheel cylinders and the target value of the hydraulic pressure decreases.

[0111] 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]

[0112] 10... Vehicles 20… Friction brakes 211,212… Wheel cylinders 30...braking device 34A…1st supply source 34B…Second supply source 35…Switching section 40…Electric Cylinder 41...Cylinder 42... Piston 43… Electric motor 70...Control device 71…Processing circuit 101...First Control Unit 102...Second Control Unit 103...Abnormality determination section 104…Advance amount acquisition section

Claims

1. Applicable to vehicles equipped with a first wheel cylinder and a second wheel cylinder, A first supply source having a first electric cylinder that supplies brake fluid to the first wheel cylinder by driving an electric motor which causes a piston to move forward within the cylinder, A second supply source having a second electric cylinder that supplies brake fluid to the second wheel cylinder by driving an electric motor, causing a piston to move forward within the cylinder, A switching unit that can switch between a communication state in which the first wheel cylinder and the second wheel cylinder are connected and a disconnection state in which communication between the first wheel cylinder and the second wheel cylinder is blocked, A first control unit operates the multiple supply sources by controlling the switching unit to shut them off when all of the multiple supply sources are functioning normally, and by forward amount control to make the correlation value of the forward amount, which is the amount of movement of the piston in the forward direction from the initial position, follow a target value. The system includes a second control unit that, when an abnormality occurs in only one of the multiple supply sources, controls the switching unit to connect the supply sources and operates the other supply source by controlling the hydraulic pressure of the multiple wheel cylinders to follow a target value of that hydraulic pressure. Braking device.

2. If, while the first control unit is operating the multiple supply sources by the forward amount control, an abnormality occurs in only one of the multiple supply sources, the second control unit sets the hydraulic pressure of one of the multiple wheel cylinders, when it is in the communication state by the control of the switching unit, to the initial value of the target hydraulic pressure and starts the hydraulic pressure control. The braking device according to claim 1.

3. The initial position is the retracted end of the piston within the movable range of the supply source where the abnormality is occurring, among the plurality of supply sources. During the execution of the hydraulic pressure control, if the piston of one of the supply sources experiencing the abnormality moves to the initial position, the second control unit switches the control of the supply sources that are not experiencing the abnormality from hydraulic pressure control to forward movement control, which adjusts the correlation value of the forward movement amount of the piston of that supply source to follow a target value. A braking device according to claim 1 or claim 2.

4. The first control unit operates the plurality of supply sources by the forward movement control, and if an abnormality occurs in only one of the plurality of supply sources, the forward movement amount of the piston of the supply source at the time the abnormality occurred is acquired by a forward movement amount acquisition unit, which is used to acquire the forward movement amount at the time of the abnormality. The second control unit, in the hydraulic pressure control, increases the control gain at the start of the hydraulic pressure control as the amount of forward movement at the time of generation increases. The braking device according to claim 1.

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