Braking device

Abstract

A braking device 30 comprises: a first supply source 34A that includes an electric cylinder 40 that supplies brake fluid to a wheel cylinder 211; a second supply source 34B that includes an electric cylinder 40 that supplies brake fluid to a wheel cylinder 212; a switching unit 35; and a processing circuit 71 that, when an abnormality occurs in only one of the plurality of supply sources 34A, 34B, executes retraction processing in which a piston of the supply source in which the abnormality is occurring is moved to the initial position of the piston by setting the state of the switching unit 35 to a communication state and causing the brake fluid to be supplied from the supply source having no abnormality to the supply source in which the abnormality is occurring.

Description

Brake device

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

[0002] The brake 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 piston.

[0003] The above brake 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 brake 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.

[0004] Japanese Unexamined Patent Application Publication No. 2021-37939

[0005] In the brake device as described above, an abnormality may occur in the first electric cylinder while adjusting the hydraulic pressure of the first wheel cylinder. In this case, in the first electric cylinder, there is a possibility that the state where the piston has moved in the forward direction from the initial position is maintained.

[0006] In the brake device, it is possible to adjust the hydraulic pressure of the plurality of wheel cylinders by opening the shut-off valve to communicate the first wheel cylinder and the second wheel cylinder and then operating the second electric cylinder. However, when the piston of the first electric cylinder has not returned to the initial position, the amount of the brake fluid supplied from the second electric cylinder that flows into the cylinder of the first electric cylinder cannot be grasped. As a result, there is a possibility that the hydraulic pressure of the plurality of wheel cylinders cannot be appropriately controlled.

[0007] 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 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 blocked, and a processing circuit that, when an abnormality occurs in only one of the supply sources, controls the switching unit to set it to the communication state and supplies brake fluid from a supply source among the multiple supply sources that is not experiencing an abnormality, thereby performing a retraction process that retracts the piston of the supply source experiencing the abnormality to an initial position which is the retraction end within the movable range of the piston.

[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.

[0009] Figure 1 is a schematic diagram showing a vehicle equipped with a braking device according to an embodiment. Figure 2 is a schematic cross-sectional view showing the schematic configuration of electric cylinders provided by multiple supply sources in the braking device of Figure 1. Figure 3 is a flowchart showing a series of processes executed by the control device of the braking device of Figure 1. Figure 4 is a diagram showing how brake fluid is supplied from a supply source that is not malfunctioning to a supply source that is malfunctioning during reverse operation. Figure 5 is a diagram showing how a supply source that is not malfunctioning and a reservoir are in communication during reverse operation. Figure 6 is a diagram showing the relationship between the amount of piston forward movement and the braking pressure when one supply source adjusts the braking pressure of one wheel cylinder, and the relationship between the amount of piston forward movement and the braking pressure when one supply source adjusts the braking pressure of two wheel cylinders. Figure 7 is a flowchart showing a series of processes executed by the control device of the braking device of Figure 1 to determine the control of the supply sources. Figure 8 is a diagram showing the relationship between the amount of piston forward movement and the braking pressure of the wheel cylinder when forward movement control is performed during reverse operation.

[0010] An embodiment of the braking device will be described with reference to Figures 1 to 7. Figure 1 shows a vehicle 10 equipped with a braking device 30. The vehicle 10 is equipped with a plurality of wheels and a plurality of friction brakes 20 corresponding to each of the plurality of wheels.

[0011] The multiple wheels include a first wheel 11, a second wheel 12, a third wheel 13, and a fourth wheel 14. For example, the first wheel 11 and the second wheel 12 are the front wheels of the vehicle 10, while the third wheel 13 and the fourth wheel 14 are the rear wheels of the vehicle 10.

[0012] Each of the multiple friction brakes 20 comprises a wheel cylinder, a rotating body 22, and a friction part 23. The rotating body 22 rotates integrally with the corresponding wheels 11-14. The friction brake 20 generates braking force on the corresponding wheels 11-14 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.

[0013] 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". The wheel cylinder corresponding to the third wheel 13 will be referred to as "wheel cylinder 213". The wheel cylinder corresponding to the fourth wheel 14 will be referred to as "wheel cylinder 214".

[0014] <Configuration of the braking device> The braking device 30 comprises a first braking unit 31, a second braking unit 60, and a control device 70. <First braking unit> The first 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 first braking unit 31 comprises a reservoir 32, a supply passage 33, a first supply source 34A, a second supply source 34B, and a switching unit 35.

[0015] The reservoir 32 stores brake fluid and is open to the atmosphere. The supply passage 33 is a brake fluid passage connecting the reservoir 32 to the wheel cylinders 211 and 212. The supply passage 33 branches into two on its way from the connection point with the reservoir 32 to the wheel cylinders 211 and 212. That is, the supply passage 33 includes one main passage 33a connected to the reservoir 32 and two branch passages 33b and 33c connected to the main passage 33a. The connection point between the main passage 33a and the branch passages 33b and 33c is referred to as "branching point P0".

[0016] The wheel cylinder 211 is connected to the branched passage 33b, and the wheel cylinder 212 is connected to the branched passage 33c. Hereafter, the branched passage 33b connected to the wheel cylinder 211 will be referred to as the "first fluid passage" and the branched passage 33c connected to the wheel cylinder 212 will be referred to as the "second fluid passage".

[0017] A first hydraulic pressure sensor 37A is connected to the branch channel 33b to detect the brake fluid pressure in the branch channel 33b. A second hydraulic pressure sensor 37B is connected to the branch channel 33c to detect the brake fluid pressure in the branch channel 33c. The multiple hydraulic pressure sensors 37A and 37B are sensors that detect 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".

[0018] The first supply source 34A and the second supply source 34B each 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 branching passage 33b. The first supply source 34A is configured to supply brake fluid to the wheel cylinder 211 via the branching passage 33b. In this respect, 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". Hereafter, the connection point of the first supply source 34A in the branching passage 33b will be referred to as "connection point P1".

[0019] The second supply source 34B is connected to the branching channel 33c. The second supply source 34B is configured to supply brake fluid to the wheel cylinder 212 via the branching channel 33c. In this respect, 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". Hereafter, the connection point of the second supply source 34B in the branching channel 33c will be referred to as "connection point P2".

[0020] The switching unit 35 is configured to switch between a communication state in which the wheel cylinder 211 and the wheel cylinder 212 are connected, and a disconnection state in which the communication between the wheel cylinder 211 and the wheel cylinder 212 is blocked. For example, the switching unit 35 has a first system shut-off valve 51, a second system shut-off valve 52, and an atmospheric release valve 53. The first system shut-off valve 51, the second system shut-off valve 52, and the atmospheric release valve 53 are normally open solenoid valves. In other words, when the power supply to the solenoid is stopped, the first system shut-off valve 51, the second system shut-off valve 52, and the atmospheric release valve 53 open as shown in Figure 1. On the other hand, when the solenoid is energized, the first system shut-off valve 51, the second system shut-off valve 52, and the atmospheric release valve 53 close.

[0021] The first system shut-off valve 51 is installed in the branch passage 33b. More specifically, it is located between branch point P0 and connection point P1 in the branch passage 33b. The second system shut-off valve 52 is installed in the branch passage 33c. More specifically, it is located between branch point P0 and connection point P2 in the branch passage 33c. The atmospheric release valve 53 is located in the main passage 33a.

[0022] The state of the switching unit 35 when both of the two system shut-off valves 51 and 52 are closed corresponds to the "shut-off state". The state of the switching unit 35 when both of the two system shut-off valves 51 and 52 are open and the atmospheric release valve 53 is closed corresponds to the "connected state".

[0023] Referring to Figure 2, the configuration of the electric cylinder 40 for multiple supply sources 34A and 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.

[0024] 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".

[0025] 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". Of the movable range RA, the retraction end, i.e., the end in the retraction direction Zb, is described as the "initial position Psf". When no braking pressure Pwc is generated in 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.

[0026] 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 channel 33.

[0027] 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".

[0028] 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 backward 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.

[0029] 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).

[0030] <Second Braking Unit> As shown in Figure 1, the second braking unit 60 operates to generate braking force on the third wheel 13 and the fourth wheel 14. For example, the second braking unit 60 is configured to allow individual adjustment of the braking pressure Pwc of the wheel cylinder 213 and the braking pressure Pwc of the wheel cylinder 214. For example, the second braking unit 60 is equipped with a supply source that can supply brake fluid by driving an electric motor. An example of a supply source for the second braking unit 60 is an electric cylinder or an electric pump.

[0031] <Control device> The control device 70 includes a processing circuit 71 that controls the first braking unit 31 and the second braking unit 60. 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 first braking unit 31 and the second braking unit 60.

[0032] <Normal Braking Control> Braking control when no abnormality occurs in the first braking unit 31 will be described. The braking control described here may also be referred to as "normal braking control". In normal braking control, the processing circuit 71 closes both of the two system shut-off valves 51 and 52 to shut off the switching unit 35. At this time, the processing circuit 71 may also close the atmospheric release valve 53.

[0033] 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 and the motor rotation angle θmt of the electric motor 43. Therefore, it can be said that there is a correspondence between the forward movement STp and motor rotation angle θmt and the braking pressure Pwc. Thus, the processing circuit 71 can set the target value of the motor rotation angle θmt as the correlation value of the target value of the forward movement STp based on the required value of the braking pressure Pwc. Hereafter, the target value of the motor rotation angle θmt will be referred to as "target motor rotation angle θmtTr".

[0034] When the state of the switching unit 35 is turned off, the processing circuit 71 activates the multiple supply sources 34A and 34B. At this time, the processing circuit 71 sets a target motor rotation angle θmtTr that corresponds to the required value of the braking pressure Pwc of the wheel cylinder 211. Then, the processing circuit 71 adjusts the amount of brake fluid supplied from the first supply source 34A to the wheel cylinder 211 by performing feedback control so that the motor rotation angle θmt of the electric motor 43 of the first supply source 34A follows the target motor rotation angle θmtTr.

[0035] Similarly, the processing circuit 71 sets a target motor rotation angle θmtTr that corresponds to the required value of the braking pressure Pwc of the wheel cylinder 212. The processing circuit 71 then adjusts the amount of brake fluid supplied from the second supply source 34B to the wheel cylinder 212 by performing feedback control so that the motor rotation angle θmt of the electric motor 43 of the second supply source 34B follows the target motor rotation angle θmtTr.

[0036] Hereafter, the feedback control that makes the motor rotation angle θmt follow the target motor rotation angle θmtTr as described above will be referred to as "forward movement control". <If an abnormality occurs in only one of the multiple supply sources> While the processing circuit 71 is controlling the multiple supply sources 34A and 34B by normal braking control, an abnormality may occur in only one of the multiple supply sources. In this case, the supply source where the abnormality has occurred will not be able to control the forward movement STp of the piston 42.

[0037] In this context, "abnormality of the power source" includes the inability to control the electric cylinder 40. Such abnormalities can occur due to failure of the electric motor 43, failure of the driver circuit of the electric motor 43, failure of the motor angle sensor 45, failure of the hydraulic pressure sensors 37A and 37B, failure of the processing circuit 71, and failure of 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 have multiple processing circuits and multiple CPUs to correspond to each of the multiple power sources.

[0038] Referring to Figures 3 to 5, an example of a handling procedure for when an abnormality occurs in only one of the multiple supply sources 34A and 34B during normal braking control will be explained. For example, the processing circuit 71 repeatedly executes the series of processes shown in Figure 3.

[0039] In step S11, the processing circuit 71 determines whether an abnormality has occurred in only one of the multiple supply sources 34A and 34B. If the processing circuit 71 determines that an abnormality has occurred in only one of the supply sources (S11: YES), the processing circuit 71 proceeds to step S13. On the other hand, if the processing circuit 71 determines that all of the multiple supply sources 34A and 34B are normal (S11: NO), the processing circuit 71 terminates the series of processes shown in Figure 3. Also, if the processing circuit 71 determines that an abnormality has occurred in all of the multiple supply sources 34A and 34B (S11: NO), the processing circuit 71 terminates the series of processes shown in Figure 3.

[0040] In step S13, the processing circuit 71 determines whether the vehicle 10 is stopped or not. For example, if the duration of the vehicle 10's driving speed being 0 (zero) is longer than a predetermined time, the vehicle 10 is considered to be stopped. On the other hand, if the duration is less than the predetermined time, or if the driving speed is not 0 (zero), the vehicle 10 is considered not to be stopped. If the processing circuit 71 determines that the vehicle 10 is stopped (S13: YES), the processing circuit 71 proceeds to step S15. On the other hand, if the processing circuit 71 determines that the vehicle 10 is not stopped (S13: NO), the processing circuit 71 terminates the series of processes shown in Figure 3.

[0041] In step S15, the processing circuit 71 activates the second braking unit 60 to perform an increase process that increases the braking force generated by the third wheel 13 and the fourth wheel 14. At this time, the processing circuit 71 should increase the braking force generated by the third wheel 13 and the fourth wheel 14 so that the vehicle 10 can remain stopped even if the braking force generated by the first wheel 11 and the second wheel 12 becomes 0 (zero). Once the processing circuit 71 has increased the braking force generated by the third wheel 13 and the fourth wheel 14 through this increase process, it proceeds to step S17.

[0042] In step S17, the processing circuit 71 performs a retraction process to move the piston 42 of the supply source where the abnormality has occurred back to its initial position Psf. The retraction process will be described in detail with reference to Figures 4 and 5. Figures 4 and 5 illustrate the case in which only the first supply source 34A among the multiple supply sources 34A and 34B has an abnormality. In other words, in the example shown in Figures 4 and 5, the first supply source 34A is the supply source where the abnormality has occurred, while the second supply source 34B is the supply source where the abnormality has not occurred. Hereafter, the supply source where the abnormality has not occurred may also be referred to as the "normal supply source".

[0043] As shown in Figure 4, during the reversing process, the processing circuit 71 closes the atmospheric release valve 53 while opening both of the two system shut-off valves 51 and 52. That is, the processing circuit 71 sets the state of the switching unit 35 to a communication state. Next, the processing circuit 71 supplies brake fluid to the supply passage 33 from the second supply source 34B, which is a normal supply source among the multiple supply sources. The brake fluid supplied from the second supply source 34B flows through the supply passage 33 as shown by arrow Y1 in Figure 4 and flows into the cylinder 41 of the first supply source 34A, which is a supply source where an abnormality has occurred. As a result, the hydraulic pressure in the hydraulic chamber Re inside the cylinder 41 of the first supply source 34A increases, causing the piston 42 to move in the reversing direction Zb. This reduces the amount of forward movement STp of the piston 42, causing the piston 42 to approach its initial position Psf. Hereafter, as explained using Figure 4, the process of supplying brake fluid from a normal supply source to a supply source experiencing an abnormality will be referred to as the "supply process."

[0044] The processing circuit 71 monitors the amount of forward movement STp of the piston 42 of the second supply source 34B. The processing circuit 71 can obtain the amount of forward movement STp of the piston 42 of the second supply source 34B by converting the motor rotation angle θmt of the electric motor 43 of the second supply source 34B into the amount of forward movement STp. When the amount of forward movement STp of the piston 42 reaches a specified amount of forward movement, the processing circuit 71 stops the movement of the piston 42 in the forward direction Za and terminates the supply process. The processing circuit 71 then operates the switching unit 35 so that the inside of the cylinder 41 of the second supply source 34B and the reservoir 32 are in communication. For example, as shown in Figure 5, the processing circuit 71 opens the atmospheric release valve 53 and the second system shut-off valve 52. On the other hand, the processing circuit 71 maintains a state in which the inside of the cylinder 41 of the first supply source 34A and the reservoir 32 are not in communication by closing the first system shut-off valve 51. In this state, the processing circuit 71 drives the electric motor 43 so that the piston 42 of the second supply source 34B moves in the backward direction Zb. As a result, brake fluid is supplied from the reservoir 32 into the cylinder 41 of the second supply source 34B, as shown by the arrow Y2 in Figure 5. Hereafter, as explained using Figure 5, the process of flowing brake fluid from the reservoir 32 into the cylinder 41 of a normal supply source will be referred to as the "recovery process".

[0045] And when the processing circuit 71 determines that the piston 42 of the second supply source 34B has returned to the initial position Psf, the processing circuit 71 stops driving the electric motor 43 and returns the state of the switching unit 35 to the state shown in FIG. 4. That is, the processing circuit 71 ends the recovery process. After that, the processing circuit 71 alternately repeats the supply process and the recovery process until the end condition of the backward movement process is satisfied.

[0046] Incidentally, since the backward movement process in the case where an abnormality occurs in the second supply source 34B while the first supply source 34A is normal is the same as described above, a detailed description thereof will be omitted. Returning to FIG. 3, when the processing circuit 71 is executing the backward movement process in step S17, the process proceeds to step S19. In step S19, the processing circuit 71 determines whether or not the piston 42 of the supply source in which an abnormality has occurred has returned to the initial position Psf by executing the backward movement process. The determination process as to whether or not the piston 42 has returned to the initial position Psf will be described later. When the processing circuit 71 determines that the piston 42 has returned to the initial position Psf (S19: YES), the processing circuit 71 can determine that the end condition of the backward movement process is satisfied, and thus the process proceeds to step S23. On the other hand, when the processing circuit 71 determines that the piston 42 has not returned to the initial position Psf (S19: NO), the processing circuit 71 proceeds to step S21.

[0047] In step S21, the processing circuit 71 determines whether or not the condition for forced termination of the backward movement process is satisfied. The processing circuit 71 determines that the condition for forced termination is satisfied when at least one of a plurality of conditions (A1) and (A2) shown below is satisfied. On the other hand, the processing circuit 71 determines that the condition for forced termination is not satisfied when none of the plurality of conditions (A1) and (A2) is satisfied.

[0048] (A1) The start of the vehicle 10 is requested. (A2) It is required to execute other braking processes than the reverse process. When the processing circuit 71 determines that the forced termination condition is not satisfied (S21: NO), the processing circuit 71 transfers the process to step S17. That is, the processing circuit 71 continues to execute the reverse process. On the other hand, when the processing circuit 71 determines that the forced termination condition is satisfied (S21: YES), the processing circuit 71 ends the reverse process and temporarily ends the series of processes shown in FIG. 3.

[0049] In step S23, the processing circuit 71 ends the reverse process and executes an air release process of communicating the plurality of wheel cylinders 211 and 212 with the reservoir 32. In the air release process, the processing circuit 71 stops driving the electric motors 43 of the plurality of supply sources 34A and 34B, and then opens the air release valve 53 and the two system cutoff valves 51 and 52. Then, the processing circuit 71 temporarily ends the series of processes shown in FIG. 3. After the end of the series of processes, the processing circuit 71 closes the air release valve 53 while opening the two system cutoff valves 51 and 52.

[0050] <Determination process of whether the piston of the supply source with an abnormality has returned to the initial position> Referring to FIG. 6, an example of the determination process will be described. The broken line in FIG. 6 illustrates the normal relationship MP1 between the forward movement amount STp of the piston 42 and the braking pressure Pwc when the state of the switching unit 35 is in the cutoff state. The solid line in FIG. 6 shows the one-system relationship MP2 between the forward movement amount STp of the piston 42 of the supply source and the braking pressure Pwc when adjusting the braking pressure Pwc of the plurality of wheel cylinders 211 and 212 with one supply source.

[0051] When the processing circuit 71 is executing the reverse process, it determines whether the relationship between the first forward movement amount STp1, which is the forward movement amount STp of the piston 42 of the normal supply source, and the braking pressure Pwc has become the one-system relationship MP2.

[0052] When reversing is being performed, the piston 42 approaches its initial position Psf in the supply source where the abnormality has occurred. 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.

[0053] Therefore, the processing circuit 71 determines whether the relationship between the first forward 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 processing circuit 71 obtains the value obtained by converting the motor rotation angle θmt of the electric motor 43 of a normal power source into the forward amount STp of the piston 42 as the first forward amount STp1. The processing circuit 71 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 processing circuit 71 sets the point indicated by the first forward amount STp1 and the braking pressure detection value obtained in this way as the state point PA1. Then, when the state point PA1 is located on the line representing the single-system relationship MP2, the processing circuit 71 determines that the relationship between the first forward amount STp1 and the braking pressure Pwc has become the single-system relationship MP2. In other words, the processing circuit 71 determines that the piston 42 has moved to its initial position Psf in the supply source where the abnormality has occurred.

[0054] <Switching Control of Supply Sources> Referring to Figure 7, a series of processes performed by the processing circuit 71 to determine the control of the electric cylinders 40 of supply sources 34A and 34B will be explained. The processing circuit 71 repeatedly performs this series of processes at predetermined control cycles.

[0055] In step S41, the processing circuit 71 determines whether all of the multiple supply sources 34A and 34B are functioning normally. If the processing circuit 71 determines that all of the multiple supply sources 34A and 34B are functioning normally (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 at least one of the multiple supply sources 34A and 34B (S41: NO), the processing circuit 71 proceeds to step S45.

[0056] In step S43, the processing circuit 71 selects the forward amount control described above as the control of the supply sources 34A and 34B. Then, the processing circuit 71 temporarily terminates the series of processes shown in Figure 7. In this case, the processing circuit 71 controls the braking pressure Pwc of the wheel cylinder 211 by activating the first supply source 34A through the forward amount control. The processing circuit 71 also controls the braking pressure Pwc of the wheel cylinder 212 by activating the second supply source 34B through the forward amount control.

[0057] In step S45, the processing circuit 71 determines whether an abnormality has occurred in only one of the multiple supply sources 34A and 34B. If the processing circuit 71 determines that an abnormality has occurred in only one of the supply sources (S45: YES), the processing circuit 71 proceeds to step S49. On the other hand, if the processing circuit 71 determines that an abnormality has occurred in both of the multiple supply sources 34A and 34B (S45: NO), the processing circuit 71 proceeds to step S47.

[0058] In step S47, the processing circuit 71 stops controlling the multiple supply sources 34A and 34B. Then, the processing circuit 71 temporarily terminates the series of processes shown in Figure 7. In this case, the processing circuit 71 adjusts the braking force generated by the vehicle 10 by activating the second braking unit 60.

[0059] In step S49, the processing circuit 71 determines whether the piston 42 of the supply source where the abnormality occurred has returned to its initial position Psf. The determination method here is the same as the determination method described above. If the processing circuit 71 determines that the piston 42 has returned to its initial position Psf (S49: YES), the processing circuit 71 proceeds to step S53. On the other hand, if the processing circuit 71 determines that the piston 42 has not returned to its initial position Psf (S49: NO), the processing circuit 71 proceeds to step S51.

[0060] In step S51, the processing circuit 71 selects hydraulic control as the control method for the electric cylinder 40 of the normal supply source. Hydraulic control is a control method that makes the braking pressure Pwc follow the target braking pressure PwcTr, which is the target value of the braking pressure Pwc. Then, the processing circuit 71 temporarily terminates the series of processes shown in Figure 7.

[0061] In hydraulic pressure control, the processing circuit 71 selects one of the first braking pressure detection value PwcS1 and the second braking pressure detection value PwcS2. For example, the processing circuit 71 may select the first braking pressure detection value PwcS1 if the first supply source 34A is functioning normally, and select the second braking pressure detection value PwcS2 if the second supply source 34B is functioning normally. The processing circuit 71 then drives the electric motor 43 of the functioning supply source so that the selected braking pressure detection value follows the target braking pressure PwcTr.

[0062] In step S53, the processing circuit 71 selects forward movement control as the control of the electric cylinder 40 of the normal power source. The "forward movement control" selected here is a control that makes the motor rotation angle θmt of the electric motor 43 of the normal power source follow the target motor rotation angle θmtTr. Then, the processing circuit 71 temporarily terminates the series of processes shown in Figure 7.

[0063] <Operation and Effects of This Embodiment> (1) When the processing circuit 71 controls the braking pressure Pwc of multiple wheel cylinders 211 and 212 by operating multiple supply sources 34A and 34B after setting the state of the switching unit 35 to the shut-off state, it determines whether or not an abnormality has occurred in the supply sources 34A and 34B. If the processing circuit 71 determines that an abnormality has occurred in only one of the multiple supply sources 34A and 34B, it executes the reverse process. In the reverse process, the processing circuit 71 sets the state of the switching unit 35 to the shut-off state and supplies brake fluid to the supply passage 33 from a normal supply source.

[0064] Brake fluid supplied from a normal supply source to the supply channel 33 flows into the cylinder 41 of the supply source where the malfunction is occurring. As a result, the hydraulic pressure in the hydraulic chamber Re of the cylinder 41 increases, causing the piston 42 to retract toward its initial position Psf.

[0065] After the piston 42 returns to its initial position Psf due to the retraction process, the piston 42 of the faulty supply source remains in the initial position Psf. The processing circuit 71 then adjusts the braking pressure Pwc of the two wheel cylinders 211 and 212 by setting the switching unit 35 to a communication state and activating the normal supply source. When the piston 42 of the faulty supply source is in the initial position Psf, the brake fluid supplied from the normal supply source is not supplied to the faulty supply source, but is supplied to the multiple wheel cylinders 211 and 212. As a result, the braking device 30 can suppress the decrease in the controllability of the braking pressure Pwc of the multiple wheel cylinders 211 and 212 based on the operation of the other supply source when a fault occurs in only one of the multiple supply sources 34A and 34B.

[0066] (2) When the processing circuit 71 is performing the retraction process, it determines whether the piston 42 of the supply source where the abnormality occurred has retracted to the initial position Psf. The processing circuit 71 then determines that the piston 42 has retracted to the initial position Psf and terminates the retraction process. As a result, after the retraction process is completed, the braking device 30 can accurately control the braking pressure Pwc of the multiple wheel cylinders 211 and 212 by operating a normal supply source.

[0067] (3) The processing circuit 71 performs a retraction process if an abnormality occurs in only one of the multiple supply sources 34A and 34B. The processing circuit 71 then determines whether the relationship between the first forward amount STp1 and the braking pressure Pwc has become the single-system relationship MP2. If the processing circuit 71 determines that the relationship between the first forward amount STp1 and the braking pressure Pwc has become the single-system relationship MP2, it determines that the piston 42 of the supply source where the abnormality occurred has retracted to the initial position Psf. In other words, the processing circuit 71 can determine whether the piston 42 has retracted to the initial position Psf even if it cannot determine the motor rotation angle θmt of the electric motor 43 of the supply source where the abnormality occurred.

[0068] (4) 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.

[0069] Therefore, the processing circuit 71 operates the electric cylinder 40 of a normal supply source by hydraulic control before the piston 42 of the supply source experiencing an abnormality retracts to its initial position Psf. On the other hand, after the piston 42 has retracted to its initial position Psf, the processing circuit 71 operates the electric cylinder 40 of the normal supply source by 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 a normal supply source when an abnormality occurs in only one of the multiple supply sources 34A, 34B.

[0070] (5) When the processing circuit 71 determines that the piston 42 of the supply source where the abnormality has occurred has retracted to the initial position Psf and terminates the retraction process, it executes an atmospheric release process. In the atmospheric release process, the processing circuit 71 connects the inside of the cylinders 41 of the multiple supply sources 34A and 34B to the reservoir 32. This allows the processing circuit 71 to match the hydraulic pressure inside the cylinders 41 of the supply sources 34A and 34B to atmospheric pressure. In other words, even if the amount of brake fluid in the cylinder 41 of a normal supply source becomes slightly insufficient due to the execution of the retraction process, the atmospheric release process replenishes the brake fluid in that cylinder 41. Also, even if the amount of brake fluid in the cylinder 41 of the supply source where the abnormality has occurred becomes excessive due to the execution of the retraction process, the atmospheric release process discharges the excess brake fluid in that cylinder 41 to the reservoir 32. Therefore, during subsequent vehicle braking, the processing circuit 71 can appropriately control the braking pressure Pwc of the multiple wheel cylinders 211 and 212 by activating a normal supply source.

[0071] <Examples of Modifications> The above embodiment can be implemented with the following modifications. The above embodiment and the following examples of modifications can be combined with each other to the extent that they do not contradict each other technically.

[0072] - The processing circuit 71 may operate a normal supply source by hydraulic pressure control even after the relationship between the first forward amount STp1 and the braking pressure Pwc becomes the single-system relationship MP2. - The processing circuit 71 may also perform forward amount control during reverse processing. The forward amount control in this case will be explained in Figure 8.

[0073] This method is preferably implemented on the premise that the control device 70 can acquire the detection signal from the motor angle sensor 45 of the supply source where an abnormality is occurring. The processing circuit 71 of the control device 70 acquires the relationship MP3 between the forward movement amount STp of the piston 42 and the braking pressure Pwc when adjusting the braking pressure Pwc of two wheel cylinders 211 with one normal supply source, based on the motor rotation angle θmt based on the motor angle sensor 45 of the supply source where an abnormality is occurring. As shown by the dashed line in Figure 8, the relationship MP3 is located between the normal relationship MP1 and the single-system relationship MP2. The processing circuit 71 then performs forward movement control based on the relationship MP3. Specifically, the processing circuit 71 derives a target value for the forward movement amount based on the target value of the braking pressure and the relationship MP3. The processing circuit 71 acquires the value obtained by converting the target value of the forward movement amount into the motor rotation angle θmt as the target rotation angle. The processing circuit 71 then performs feedback control so that the motor rotation angle θmt, based on the detection signal from the motor angle sensor 45 of a normal power source, follows the target rotation angle.

[0074] The processing circuit 71 may determine whether the piston 42 of the supply source experiencing an abnormality has retracted to its initial position Psf using a method different from the method described in the above embodiment. For example, if the detection signal from the motor angle sensor 45 of the supply source experiencing an abnormality is input to the processing circuit 71, the processing circuit 71 may determine whether the piston 42 has retracted to its initial position Psf using the motor rotation angle θmt based on the detection signal from the motor angle sensor 45.

[0075] Even if the piston 42 of the faulty supply source returns to its initial position Psf, if a normal supply source is supplying brake fluid to the supply passage 33, the detected braking pressure value will start to increase. Therefore, the processing circuit 71 may determine that the piston 42 of the faulty supply source has retracted to its initial position Psf when the amount of increase in the detected braking pressure value due to the execution of the reversing process exceeds a threshold.

[0076] - If the volume of the cylinder 41 of the electric cylinder 40 is relatively large, during the retraction process, the piston 42 of the supply source experiencing an abnormality can be moved back to its initial position by moving the piston 42 in the forward direction Za once until the forward amount STp of the piston 42 of the normal supply source reaches a specified forward amount. In such cases, the processing circuit 71 may not release the multiple wheel cylinders 211, 212 to the atmosphere during the retraction process. In other words, the processing circuit 71 does not need to perform the above recovery process during the retraction process.

[0077] 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 so that the forward movement detection value, which is the value detected by the stroke sensor, follows the target value of the forward movement.

[0078] - The electric cylinder may have a return spring with such force that the spring biasing force alone is insufficient to return the piston 42 to its initial position Psf. - The braking device may be configured such that the first supply source can supply brake fluid to the two wheel cylinders. In this case, the two wheel cylinders correspond to the "first wheel cylinder". - The braking device may be configured such that the second supply source can supply brake fluid to the two wheel cylinders. In this case, the two wheel cylinders correspond to the "second wheel cylinder".

[0079] - The first braking unit of the braking device may be configured to include a third supply source, in addition to the first and second supply sources. 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. Furthermore, the reverse operation may be assisted by this third supply source. For example, the third supply source may be configured to have an electric pump that discharges brake fluid.

[0080] 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 and a second processing circuit that controls the second supply source 34B.

[0081] The processing circuit 71 may be configured as a circuit including one or more dedicated hardware circuits, such as one or more processors that operate according to a computer program, or 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, and the memory stores program code or instructions configured to cause the CPU to execute the processes. The memory, i.e., storage medium, includes any available medium that can be accessed by a general-purpose or dedicated computer.

[0082] 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."

[0083] <Other Technical Concepts> The following describes the technical concepts that can be understood from the above embodiments and modified examples. (Note 1) The device comprises a first fluid passage that guides brake fluid supplied from the first supply source to the first wheel cylinder, and a second fluid passage that guides brake fluid supplied from the second supply source to the second wheel cylinder, wherein when the state of the switching unit is the communication state, the first fluid passage and the second fluid passage are in communication, and when the state of the switching unit is the blocked state, communication between the first fluid passage and the second fluid passage is blocked.

[0084] (Note 2) The system is equipped with a reservoir that stores brake fluid and is open to the atmosphere, and the processing circuit preferably disconnects the communication between the plurality of wheel cylinders and the reservoir when the reverse processing is being performed, and performs an open-to-the-atmosphere processing that connects the plurality of wheel cylinders and the reservoir after the completion of the reverse processing.

Claims

1. A braking device applicable to a vehicle equipped with a first wheel cylinder and a second wheel cylinder, comprising: a first supply source having a first electric cylinder that supplies brake fluid to the first wheel cylinder by the drive of an electric motor causing 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 the drive of 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 in communication and a disconnection state in which communication between the first wheel cylinder and the second wheel cylinder is blocked; and a processing circuit that, when an abnormality occurs in only one of the multiple supply sources, controls the switching unit to set it to the communication state and supplies brake fluid from one of the supply sources that is not experiencing an abnormality, thereby performing a retraction process that retracts the piston of the supply source experiencing the abnormality to an initial position which is the retraction end within the movable range of the piston.

2. The braking device according to claim 1, wherein the processing circuit terminates the retraction process when it determines that the piston of the supply source where the abnormality has occurred has retracted to the initial position while the retraction process is being performed.

3. The braking device according to claim 2, wherein the amount of movement of the piston in the forward direction from the initial position is the amount of forward movement, and the processing circuit determines that the piston of the supply source where the abnormality occurred has moved to the initial position when the retraction process is executed, and the relationship between the first amount of forward movement, which is the amount of forward movement of the piston of the supply source where the abnormality has not occurred, and the hydraulic pressure of the plurality of wheel cylinders becomes a single-system relationship, which is the relationship between the amount of forward movement of the piston of the supply source and the hydraulic pressure when the hydraulic pressure of the plurality of wheel cylinders is adjusted by a single supply source.

4. The braking device according to any one of claims 1 to 3, wherein the processing circuit operates a supply source in which no abnormality has occurred by controlling the hydraulic pressure of a plurality of wheel cylinders to follow a target value of the hydraulic pressure during the reversing process, and after the piston of the supply source in which the abnormality has occurred has moved to the initial position due to the execution of the reversing process, the brake device in which no abnormality has occurred operates by controlling the amount of movement of the piston of the supply source in which no abnormality has occurred in the forward direction from the initial position to follow a target value of the amount of movement.

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