Braking device

Abstract

To enable the acquisition of the reference position of the piston in the electric cylinder while controlling the braking pressure of the first wheel cylinder and the second wheel cylinder. [Solution] The braking device 30 includes a first supply source 40A that supplies brake fluid to the first wheel cylinder 211 via a first fluid passage 33, and a second supply source 40B that supplies brake fluid to the second wheel cylinder 212 via a second fluid passage 34. The control device 300 supplies brake fluid from the electric cylinder 60 of one of the multiple supply sources 40A, 40B to both the multiple wheel cylinders 211, 212, while simultaneously performing movement control to move the piston of the electric cylinder 60 of the other supply source to a reference position. The control device 300 acquires a position-related value as a reference-related value that relates to the position of the piston when the piston of the electric cylinder 60 of the other supply source is in the reference position as a result of the execution of the movement control.

Description

Technical Field

[0001] The present invention relates to a brake device that applies braking force to a vehicle by adjusting the brake pressures of a first wheel cylinder and a second wheel cylinder.

Background Art

[0002] Patent Document 1 discloses a brake device provided with an electric cylinder that serves as a supply source of brake fluid to wheel cylinders. When the control unit of the brake device detects, for example, that a vehicle door is opened and a driver has boarded the vehicle, the control unit executes an acquisition process for acquiring the reference position of the piston in the electric cylinder.

[0003] In the acquisition process, the control unit drives the electric motor of the electric cylinder so that the piston retreats to the rearmost position. When the control unit can confirm that the piston has reached the rearmost position, the control unit drives the electric motor so that the piston advances by a predetermined amount. Then, upon confirming that the piston has moved by the predetermined amount from the rearmost position, the control unit stores the position of the piston at that time as the reference position of the piston.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of Invention

Problems to be Solved by the Invention

[0005] Depending on how the vehicle driver uses the vehicle, before the control unit acquires the reference position of the piston of the electric cylinder as described above, a brake request may be generated by the driver's braking operation or the like. In this case, since the control unit has not been able to acquire the reference position, the control unit may not be able to appropriately adjust the brake pressure of the wheel cylinders.

Means for Solving the Problems

[0006] 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 comprises a first fluid passage, which is a brake fluid passage connected to the first wheel cylinder; a second fluid passage, which is a brake fluid passage connected to the second wheel cylinder; a first electric cylinder configured to discharge brake fluid into the first fluid passage by advancing a piston driven by an electric motor; a second electric cylinder configured to discharge brake fluid into the second fluid passage by advancing a piston driven by an electric motor; a communication passage, which is a brake fluid passage connecting the first fluid passage and the second fluid passage; and a control device for controlling the first electric cylinder and the second electric cylinder. The control device supplies brake fluid from one of the plurality of electric cylinders to both of the plurality of wheel cylinders, and performs movement control to move the piston of the other of the plurality of electric cylinders to a reference position set to be further back than the position of the piston when braking pressure for the wheel cylinder begins to be generated, within the range of motion of the piston, and acquires a position-related value, which is a state quantity related to the position of the piston when the piston of the other electric cylinder is in the reference position as a reference position-related value. [Effects of the Invention]

[0007] The above-described control device has the effect of controlling the braking pressure of the first wheel cylinder and the second wheel cylinder while simultaneously obtaining the reference position of the piston in the electric cylinder. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a schematic diagram showing a vehicle equipped with a braking system according to an embodiment. [Figure 2] Figure 2 is a schematic cross-sectional view showing the electric cylinder of the braking device shown in Figure 1. [Figure 3]Figure 3 is a flowchart showing the braking process performed by the control device included in the braking system shown in Figure 1. [Figure 4] Figure 4 is a flowchart showing the details of the movement control in Figure 3. [Modes for carrying out the invention]

[0009] One embodiment of the braking device will be described with reference to Figures 1 to 4. <Vehicle Configuration> 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, the first wheel 11 and the second wheel 12 are shown among the plurality of wheels.

[0010] Each friction brake 20 comprises a wheel cylinder, a rotating body 22, and a friction part 23. The hydraulic pressure of the wheel cylinder is referred to as the "braking pressure." 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 increasing braking pressure of the wheel cylinder. In other words, the friction brake 20 can generate greater braking force as the braking pressure increases.

[0011] Hereafter, the wheel cylinder corresponding to the first wheel 11 will be referred to as the "first wheel cylinder 211," and the braking pressure of the first wheel cylinder 211 will be referred to as the "first braking pressure Pw1." The wheel cylinder corresponding to the second wheel 12 will be referred to as the "second wheel cylinder 212," and the braking pressure of the second wheel cylinder 212 will be referred to as the "second braking pressure Pw2."

[0012] <Configuration of the braking system> The braking system 30 comprises a braking unit 31 and a control device 300. The braking unit 31 includes a reservoir 32, a first fluid passage 33, a second fluid passage 34, a first supply source 40A, a second supply source 40B, a switching unit 50, a reservoir fluid passage 36, and a reservoir shut-off valve 37.

[0013] Reservoir 32 stores brake fluid and is also open to the atmosphere. The first fluid passage 33 and the second fluid passage 34 are each passages through which brake fluid flows. The first fluid passage 33 is connected to the first wheel cylinder 211. The second fluid passage 34 is connected to the second wheel cylinder 212. A first hydraulic pressure sensor 35A, which detects the brake fluid pressure in the first fluid passage 33, is connected to the first fluid passage 33. A second hydraulic pressure sensor 35B, which detects the brake fluid pressure in the second fluid passage 34, is connected to the second fluid passage 34. Each of the first hydraulic pressure sensor 35A and the second hydraulic pressure sensor 35B outputs a detection signal to the control device 300 according to the detection result. Hereafter, the detected value of the first braking pressure Pw1 based on the detection signal of the first hydraulic pressure sensor 35A will be referred to as "first braking pressure detection value Pw1S". The detected value of the second braking pressure Pw2 based on the detection signal of the second hydraulic pressure sensor 35B will be referred to as "second braking pressure detection value Pw2S".

[0014] The first fluid source 40A is connected to the first fluid passage 33. The first fluid source 40A can supply brake fluid to the first wheel cylinder 211 via the first fluid passage 33. The second fluid source 40B is connected to the second fluid passage 34. The second fluid source 40B can supply brake fluid to the second wheel cylinder 212 via the second fluid passage 34. Each of the first fluid source 40A and the second fluid source 40B has an electric cylinder 60. The configuration of the electric cylinder 60 will be described later.

[0015] The switching unit 50 is configured to switch between a connected state, which connects the first fluid passage 33 and the second fluid passage 34, and a blocked state, which blocks the connection between the first fluid passage 33 and the second fluid passage 34. For example, the switching unit 50 has a connecting passage 51, which is a passage through which brake fluid flows, a first system shut-off valve 52, and a second system shut-off valve 53. Of the two ends of the connecting passage 51, the first end is connected to the first fluid passage 33, and the second end is connected to the second fluid passage 34.

[0016] The first system shutoff valve 52 and the second system shutoff valve 53 are installed in series in the communication passage 51. Of the two system shutoff valves 52 and 53, the shutoff valve that shuts off the connection between the first fluid passage 33 and the communication passage 51 is the first system shutoff valve 52, while the shutoff valve that shuts off the connection between the second fluid passage 34 and the communication passage 51 is the second system shutoff valve 53. Each of the first system shutoff valve 52 and the second system shutoff valve 53 is a normally open solenoid valve. Therefore, when energization is stopped in both the first system shutoff valve 52 and the second system shutoff valve 53, the first system shutoff valve 52 and the second system shutoff valve 53 open as shown in Figure 1. As a result, the first fluid passage 33 and the second fluid passage 34 communicate with each other via the communication passage 51. That is, the state of the switching unit 50 in which both the first system shutoff valve 52 and the second system shutoff valve 53 are open corresponds to the "communication state".

[0017] On the other hand, when electric power is supplied to the first system shutoff valve 52, the first system shutoff valve 52 closes. When electric power is supplied to the second system shutoff valve 53, the second system shutoff valve 53 closes. When at least one of the first system shutoff valve 52 and the second system shutoff valve 53 is closed, the communication between the first fluid passage 33 and the second fluid passage 34 via the communication passage 51 is shut off. That is, the state of the switching unit 50 in which both the first system shutoff valve 52 and the second system shutoff valve 53 are closed corresponds to the "shutoff state".

[0018] The reservoir fluid passage 36 is a brake fluid passage that communicates the portion of the communication passage 51 between the first system shutoff valve 52 and the second system shutoff valve 53 with the reservoir 32. A reservoir shutoff valve 37 is installed in the reservoir fluid passage 36. The reservoir shutoff valve 37 is a normally open solenoid valve. Therefore, when energization to the reservoir shutoff valve 37 is stopped, the reservoir shutoff valve 37 opens as shown in Figure 1, so that the communication passage 51 communicates with the reservoir 32 via the reservoir fluid passage 36. On the other hand, when electric power is supplied to the reservoir shutoff valve 37, the reservoir shutoff valve 37 closes, so that the communication between the communication passage 51 and the reservoir 32 is shut off.

[0019] The reservoir cutoff valve 37 has a first solenoid and a second solenoid. When electric power is supplied to at least one of the first solenoid and the second solenoid, the reservoir cutoff valve 37 is closed. On the other hand, when energization to both the first solenoid and the second solenoid is stopped, the reservoir cutoff valve 37 is opened.

[0020] <Electric Cylinder> The electric cylinder 60 will be described with reference to Figure 1 and Figure 2. The electric cylinder 60 includes a cylinder 61, a piston 62, an electric motor 63, and a conversion mechanism 64. The piston 62 is provided in a state capable of reciprocating within the cylinder 61. The conversion mechanism 64 converts the rotation of the output shaft of the electric motor 63 into linear movement of the piston 62.

[0021] Inside the cylinder 61, a hydraulic chamber Re that stores brake fluid is defined by the peripheral wall of the cylinder 61 and the piston 62. The position of the piston 62 inside the cylinder 61 can be changed by driving the electric motor 63. Hereinafter, the direction of linear movement of the piston 62 when reducing the volume of the hydraulic chamber Re is referred to as "forward movement direction Za". The direction opposite to the forward movement direction Za is referred to as "retreat direction Zb". The retreat direction Zb is also the direction of linear movement of the piston 62 when increasing the volume of the hydraulic chamber Re. The movement of the piston 62 in the forward movement direction Za is described as "the piston 62 moves forward", and the movement of the piston 62 in the retreat direction Zb is described as "the piston 62 retreats".

[0022] The electric cylinder 60 does not have a return spring that biases the piston 62 in the retreat direction Zb. The range in which the piston 62 can be moved by the electric cylinder 60 is referred to as "movable range RA of the piston 62". Of the movable range RA, the end on the retreat side, that is, the position farthest in the retreat direction Zb, is referred to as "most retracted position Pf".

[0023] Although not shown in Figure 2, when the piston 62 reaches its furthest retracted position Pf, the rear end of the piston 62 comes into contact with the stopper. In this state, further retraction of the piston 62 is restricted by the stopper. If the electric motor 63 continues to drive to retract the piston 62 even when the piston 62 is in contact with the stopper, the motor current, which is the current flowing through the electric motor 63, increases. Therefore, based on the change in motor current, the control device 300 can determine whether or not the piston 62 has reached its furthest retracted position Pf. In addition to the change in motor current, the determination of whether or not the piston has reached its furthest retracted position Pf can also be made using the rotational speed of the motor.

[0024] The cylinder 61 is provided with an output port 61p that connects the hydraulic chamber Re to the outside. The output port 61p is always open. The output port 61p of the electric cylinder 60 of the first supply source 40A is connected to the first fluid passage 33. The output port 61p of the electric cylinder 60 of the second supply source 40B is connected to the second fluid passage 34.

[0025] The electric motor 63 has a motor angle sensor 63S. The motor angle sensor 63S outputs a detection signal to the control device 300 in accordance with the change in the rotation angle of the output shaft of the electric motor 63. Specifically, the motor angle sensor 63S of the first power source 40A outputs a detection signal to the first controller 310 of the control device 300, which will be described later. The motor angle sensor 63S of the second power source 40B outputs a detection signal to the second controller 320 of the control device 300, which will be described later. Hereafter, the rotation angle of the electric motor 63 based on the detection signal of the motor angle sensor 63S will be referred to as "motor rotation angle θmt".

[0026] When the motor rotation angle θmt increases due to the drive of the electric motor 63, the piston 62 moves forward. As a result, brake fluid from the hydraulic chamber Re is discharged through the output port 61p. This supplies brake fluid to the wheel cylinders 211 and 212, increasing the braking pressures Pw1 and Pw2. On the other hand, when the motor rotation angle θmt decreases due to the drive of the electric motor 63, the piston 62 moves backward. As a result, brake fluid flows into the hydraulic chamber Re through the output port 61p. In this case, brake fluid flows out from the wheel cylinders 211 and 212, decreasing the braking pressures Pw1 and Pw2.

[0027] In this embodiment, the electric cylinder 60 of the first power source 40A corresponds to the "first electric cylinder," and the electric cylinder 60 of the second power source 40B corresponds to the "second electric cylinder."

[0028] <Sensor> As shown in Figure 1, the vehicle 10 has multiple sensors 81, 82, and 83. The detection signals from these sensors 81 to 83 are input to the control device 300. The multiple sensors 81 to 83 include a braking sensor, a wheel speed sensor, and an acceleration sensor. The braking sensor detects the amount of brake pedal operation by the driver of the vehicle 10. The wheel speed sensor detects the rotational speed of the corresponding wheels 11 and 12. The acceleration sensor detects the longitudinal acceleration of the vehicle 10.

[0029] The control variable based on the detection signal from the braking sensor is described as "braking control variable Ba". The rotational speed based on the detection signal from the wheel speed sensor is described as "wheel speed Vw". The longitudinal acceleration based on the detection signal from the acceleration sensor is described as "longitudinal acceleration Gx".

[0030] <Control device> The control device 300 will be described with reference to Figure 1. The control device 300 comprises a first controller 310 and a second controller 320. Each of the first controller 310 and the second controller 320 is configured to send and receive information and commands via a control communication line 330. An example of the control communication line 330 is a CAN bus. "CAN" is an abbreviation for "Controller Area Network".

[0031] The first controller 310 is a processing circuit that controls the energization of the electric cylinder 60 of the first power source 40A, the first system shut-off valve 52 of the switching unit 50, and the first solenoid of the reservoir shut-off valve 37. An example of a processing circuit is an electronic control device. In this case, the first controller 310 has a CPU 311, a first memory 312, and a second memory 313. The first memory 312 stores the control program executed by the CPU 311. The second memory 313 stores the calculation results of the CPU 311. The first controller 310 can control its controlled objects by having the CPU 311 execute the control program in the first memory 312.

[0032] The second controller 320 is a processing circuit that controls the energization of the electric cylinder 60 of the second power source 40B, the second system shut-off valve 53 of the switching unit 50, and the second solenoid of the reservoir shut-off valve 37. An example of a processing circuit is an electronic control device. In this case, the second controller 320 has a CPU 321, a first memory 322, and a second memory 323. The first memory 322 stores the control program executed by the CPU 321. The second memory 323 stores the calculation results of the CPU 321. The second controller 320 can control its controlled objects by having the CPU 321 execute the control program in the first memory 322.

[0033] <Processing during vehicle power system startup> When the driver sits in the driver's seat and turns on the vehicle 10's operating switch, the vehicle 10's power system starts up. Then the braking system 30 also starts up. When the braking system 30 starts up, the control device 300 executes a start-up process. In one example of the start-up process, the first controller 310 obtains the reference rotation angle θmB of the electric motor 63 of the electric cylinder 60 of the first power source 40A. The second controller 320 also obtains the reference rotation angle θmB of the electric motor 63 of the electric cylinder 60 of the second power source 40B. The reference rotation angle θmB is the motor rotation angle θmt when the piston 62 is in the reference position Pb. If the state quantities related to the position of the piston 62 when the piston 62 is in the reference position are called "reference position related values", then the reference rotation angle θmB corresponds to a "reference position related value".

[0034] Here, the reference position Pb is, for example, the position where the piston 62 is in standby when the vehicle 10 is not braking. Therefore, if the position of the piston 62 at which braking pressure in the wheel cylinder begins to be generated within the movable range RA of the piston 62 is defined as the "generation position", then the reference position Pb is located in the backward direction Zb from the generation position. In the braking device 30, the furthest retracted position Pf is set to the reference position Pb.

[0035] In one example of the startup process, each of the multiple controllers 310 and 320 drives the electric motor 63 so that the motor rotation angle θmt becomes small. As a result, each of the multiple controllers 310 and 320 retracts the piston 62 to its furthest retracted position Pf. When each of the multiple controllers 310 and 320 confirms that the piston 62 is in the furthest retracted position Pf, it acquires the motor rotation angle θmt at that time as the reference rotation angle θmB. In other words, each of the multiple controllers 310 and 320 stores the motor rotation angle θmt when the piston 62 is in the furthest retracted position Pf as the reference rotation angle θmB in the second memory 313 and 323.

[0036] Furthermore, when the power system of the vehicle 10 is shut down, the contents of the second memories 313 and 323 are erased. Therefore, in the braking system 30, each time the braking system 30 is started, multiple controllers 310 and 320 acquire the reference rotation angle θmB of the electric motor 63.

[0037] <Individual braking pressure control> The individual braking pressure control performed by the control device 300 will now be described. When a braking request occurs under the condition that the reference rotation angle θmB of the electric motor 63 has been acquired for any of the multiple power sources 40A and 40B, the control device 300 performs individual braking pressure control.

[0038] In individual braking pressure control, the control device 300 sets the switching unit 50 to a shut-off state. Specifically, the first controller 310 closes the first system shut-off valve 52. The second controller 320 closes the second system shut-off valve 53. In this state, the first controller 310 adjusts the first braking pressure Pw1 by operating the electric cylinder 60 of the first power source 40A. The second controller 320 adjusts the second braking pressure Pw2 by operating the electric cylinder 60 of the second power source 40B.

[0039] As described above, the electric cylinder 60 has a reference position Pb set as the position where the piston 62 is in standby when not braking. In the braking device 30, for example, the rearmost retracted position Pf is set as the reference position Pb. The amount of movement of the piston 62 from the rearmost retracted position Pf to the forward direction Za is the "amount of forward movement of the piston 62 STp". In this case, there is a correspondence between the amount of forward movement of the piston 62 STp 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 of the wheel cylinder and the consumption amount. Furthermore, there is a correspondence between the amount of forward movement of the piston 62 STp and the relative rotation angle θmR, which is the relative motor rotation angle with respect to the reference rotation angle θmB. Therefore, it can be said that there is a correspondence between the amount of forward movement STp and the relative rotation angle θmR and the braking pressure.

[0040] The first controller 310 uses a map showing the relationship between the first braking pressure Pw1 and the relative rotation angle θmR to derive the relative rotation angle θmR corresponding to the target value of the first braking pressure Pw1, and sets this relative rotation angle θmR as the target motor rotation angle θmtTr1. The first controller 310 then operates the electric cylinder 60 of the first power source 40A by performing feedback control to make the relative rotation angle θmR of the electric motor 63 of the first power source 40A follow the target motor rotation angle θmtTr1.

[0041] The second controller 320 uses a map showing the relationship between the second braking pressure Pw2 and the relative rotation angle θmR to derive the relative rotation angle θmR corresponding to the target value of the second braking pressure Pw2, and sets this relative rotation angle θmR as the target motor rotation angle θmtTr2. The second controller 320 then operates the electric cylinder 60 of the second power source 40B by performing feedback control to make the relative rotation angle θmR of the electric motor 63 of the second power source 40B follow the target motor rotation angle θmtTr2.

[0042] <Braking process> Referring to Figure 3, the braking process performed by the control device 300 will be explained. In the control device 300, the braking process is repeatedly executed at predetermined control cycles.

[0043] In step S11, the first controller 310 of the control device 300 determines whether or not a braking request has occurred. If the first controller 310 determines that a braking request has occurred (S11: YES), the process proceeds to step S13. On the other hand, if the first controller 310 determines that no braking request has occurred (S11: NO), the current braking process is terminated.

[0044] In step S13, the control device 300 determines whether the reference rotation angle θmB has been acquired for any of the multiple electric cylinders 60 at the time the braking request is made. If the reference rotation angle θmB has been acquired for any of the multiple electric cylinders 60 at the time the braking request is made (S13: YES), the process proceeds to step S15. On the other hand, if the reference rotation angle θmB has not been acquired for at least one of the multiple electric cylinders 60 at the time the braking request is made (S13: NO), the process proceeds to step S17. In other words, even if the reference rotation angle θmB is acquired for any of the multiple electric cylinders 60 by the execution of the movement control described later while the braking request is ongoing, the process proceeds to step S17 instead of step S15.

[0045] In step S15, the control device 300 adjusts the first braking pressure Pw1 and the second braking pressure Pw2 by the individual braking pressure control described above. Then, the braking process is temporarily terminated.

[0046] In step S17, the control device 300 adjusts the first braking pressure Pw1 and the second braking pressure Pw2 by movement control. Details of the movement control will be described later. Then, the braking process is temporarily terminated.

[0047] <Movement control> Referring to Figure 4, the details of the movement control in step S17 described above will be explained. In step S41, the first controller 310 of the control device 300 sets a target braking pressure PwTr, which is a common target value for braking pressures Pw1 and Pw2. For example, when the driver is operating the brake pedal, the first controller 310 sets the target braking pressure PwTr to a value that increases as the braking operation amount Ba increases. If another on-board control device requests deceleration of the vehicle 10, the first controller 310 sets the target braking pressure PwTr to a value corresponding to the request of the other on-board control device.

[0048] In the next step S43, the control device 300 sets the state of the switching unit 50 to a connected state. Specifically, the first controller 310 opens the first system shut-off valve 52 by stopping the power supply to the first system shut-off valve 52. The second controller 320 opens the second system shut-off valve 53 by stopping the power supply to the second system shut-off valve 53. At this time, if the reservoir shut-off valve 37 is open, the first controller 310 or the second controller 320 closes the reservoir shut-off valve 37.

[0049] In the following step S45, the first controller 310 determines whether or not it has already acquired the reference rotation angle θmB of the electric cylinder 60 of the first power source 40A (i.e., the first electric cylinder). If the first controller 310 has already acquired the reference rotation angle θmB of the electric cylinder 60 of the first power source 40A (S45: YES), the process proceeds to step S61. On the other hand, if the first controller 310 has not yet acquired the reference rotation angle θmB of the first power source 40A (S45: NO), the process proceeds to step S47.

[0050] In step S47, the second controller 320 operates the electric cylinder 60 of the second power source 40B (i.e., the second electric cylinder) based on the target braking pressure PwTr. For example, the second controller 320 operates the electric cylinder 60 of the second power source 40B so that the detected second braking pressure Pw2S follows the target braking pressure PwTr. That is, if the difference between the target braking pressure PwTr and the detected second braking pressure Pw2S is within an acceptable range, the second controller 320 maintains the motor rotation angle θmt of the electric motor 63 of the second power source 40B. If the detected second braking pressure Pw2S is smaller than the target braking pressure PwTr, the second controller 320 drives the electric motor 63 so that the motor rotation angle θmt increases. If the second braking pressure detection value Pw2S is greater than the target braking pressure PwTr, the second controller 320 drives the electric motor 63 so that the motor rotation angle θmt decreases.

[0051] Furthermore, the first controller 310 performs a retraction process of the electric cylinder 60 of the first power source 40A (i.e., the first electric cylinder). In the retraction process, the first controller 310 drives the electric motor 63 to retract the piston 62 of the first power source 40A, that is, to decrease the motor rotation angle θmt of the electric motor 63. At this time, the first controller 310 drives the electric motor 63 so that the rotational speed dθmt of the electric motor 63 follows the target rotational speed dθmtTr. The target rotational speed dθmtTr is the target value of the rotational speed dθmt. For example, the target rotational speed dθmtTr is set to a rotational speed dθmt that can prevent the retraction speed of the piston 62 from becoming too large.

[0052] In the next step S51, the first controller 310 determines whether the piston 62 in the electric cylinder 60 of the first power source 40A (i.e., the first electric cylinder) has reached the reference position Pb. If the first controller 310 determines that the piston 62 has not reached the reference position Pb (S51: NO), the series of processes shown in Figure 4 are terminated. On the other hand, if the first controller 310 determines that the piston 62 has reached the reference position Pb (S51: YES), the process moves on to step S53.

[0053] In step S53, the first controller 310 acquires the current motor rotation angle θmt of the electric motor 63 of the first power source 40A as the reference rotation angle θmB. Then, the series of processes shown in Figure 4 are completed.

[0054] In step S61, the first controller 310 operates the electric cylinder 60 of the first power source 40A (i.e., the first electric cylinder) based on the target braking pressure PwTr. For example, the first controller 310 operates the electric cylinder 60 of the first power source 40A so that the first braking pressure detection value Pw1S follows the target braking pressure PwTr.

[0055] Furthermore, the second controller 320 performs a retraction process for the electric cylinder 60 of the second power source 40B (i.e., the second electric cylinder). In the retraction process, the second controller 320 drives the electric motor 63 to retract the piston 62 of the second power source 40B, that is, to decrease the motor rotation angle θmt of the electric motor 63. At this time, the second controller 320 drives the electric motor 63 so that the rotation speed dθmt of the electric motor 63 follows the target rotation speed dθmtTr. The control method for the electric cylinders 60 of the multiple power sources 40A and 40B in step S61 is substantially the same as the control method for the electric cylinders 60 of the multiple power sources 40A and 40B in step S47. Therefore, the details of the processing content in step S61 are omitted.

[0056] In the next step, S65, the second controller 320 determines whether the piston 62 in the electric cylinder 60 of the second power source 40B (i.e., the second electric cylinder) has reached the reference position Pb. If the second controller 320 determines that the piston 62 has not reached the reference position Pb (S65: NO), the series of processes shown in Figure 4 is terminated. On the other hand, if the second controller 320 determines that the piston 62 has reached the reference position Pb (S65: YES), the process moves on to step S67.

[0057] In step S67, the second controller 320 acquires the current motor rotation angle θmt of the electric motor 63 of the second power source 40B as the reference rotation angle θmB. Then, the series of processes shown in Figure 4 are completed.

[0058] Furthermore, if movement control is initiated in response to a braking request, the reference rotation angle θmB of the electric motor 63 is acquired at any of the multiple power sources 40A and 40B during the execution of movement control. Even after the acquisition of the reference rotation angle θmB is complete, as long as the current braking request continues to occur, the adjustment of multiple braking pressures Pw1 and Pw2 by movement control will continue. Alternatively, instead of continuing the adjustment of multiple braking pressures Pw1 and Pw2 by movement control, the system may transition to adjusting multiple braking pressures Pw1 and Pw2 by individual braking pressure control.

[0059] <Operation and Effects of This Embodiment> (1) The braking unit 31 is equipped with a plurality of electric cylinders 60. When the first fluid passage 33 and the second fluid passage 34 are in communication via the communication passage 51, brake fluid can be supplied to both of the plurality of wheel cylinders 211 and 212 by the operation of at least one of the plurality of electric cylinders 60.

[0060] Therefore, if a braking request occurs in a situation where the reference rotation angle θmB of the electric motor 63 has not been obtained for at least one of the multiple electric cylinders 60, the control device 300 performs movement control. In movement control, brake fluid is supplied from one of the multiple electric cylinders 60 to both of the multiple wheel cylinders 211 and 212. This adjusts the first braking pressure Pw1 and the second braking pressure Pw2. When the first braking pressure Pw1 and the second braking pressure Pw2 are adjusted by one of the multiple electric cylinders 60, the other electric cylinder 60 moves its piston 62 to the reference position Pb. Then, the motor rotation angle θmt of the electric motor 63 when the piston 62 of the other electric cylinder 60 is in the reference position Pb is obtained as the reference rotation angle θmB.

[0061] Therefore, the control device 300 can obtain the reference rotation angle θmB of the electric motor 63 while controlling the first braking pressure Pw1 and the second braking pressure Pw2 by performing movement control. (2) The movement control includes a first movement control and a second movement control. The first movement control is a control that retracts the piston 62 at the first supply source 40A to a reference position Pb while supplying brake fluid from the electric cylinder 60 of the second supply source 40B to a plurality of wheel cylinders 211, 212. The second movement control is a control that retracts the piston 62 at the second supply source 40B to a reference position Pb while supplying brake fluid from the electric cylinder 60 of the first supply source 40A to a plurality of wheel cylinders 211, 212.

[0062] When the first braking pressure Pw1 and the second braking pressure Pw2 are controlled by movement control, the control device 300 executes the first movement control when a braking request occurs, and during the execution of the first movement control, the reference rotation angle θmB of the electric motor 63 of the first power source 40A is acquired. After that, the control transitions from the first movement control to the second movement control. Then, during the execution of the second movement control, the reference rotation angle θmB of the electric motor 63 of the second power source 40B is acquired.

[0063] Therefore, by performing motion control, the control device 300 can sequentially acquire the reference rotation angle θmB of the multiple electric motors 63 while controlling the first braking pressure Pw1 and the second braking pressure Pw2.

[0064] (3) In the braking device 30, the reference rotation angle θmB of the electric motor 63 of the electric cylinder 60 is acquired while adjusting multiple braking pressures Pw1 and Pw2 during movement control. Therefore, the control device 300 can start adjusting the braking pressures Pw1 and Pw2 by individual braking pressure control at an early stage.

[0065] (4) If individual braking pressure control is performed without obtaining the reference rotation angle θmB, the controllers 310 and 320 cannot grasp the forward movement STp of the piston 62 which corresponds to the relative rotation amount of the electric motor 63 with respect to the reference rotation angle θmB. As a result, the controllers 310 and 320 cannot set appropriate values ​​for the target motor rotation angles θmtTr1 and θmtTr2 according to the target values ​​of the braking pressures Pw1 and Pw2. Therefore, the controllers 310 and 320 cannot properly control the braking pressures Pw1 and Pw2.

[0066] In this regard, in the braking device 30, individual braking pressure control is not performed when the reference rotation angle θmB has not been acquired. Specifically, the control device 300 sets the state of the switching unit 50 to a communication state and closes the reservoir shut-off valve 37, and then supplies brake fluid from one of the multiple electric cylinders 60 to the multiple wheel cylinders 211, 212. At this time, the control device 300 operates one of the multiple electric cylinders 60 so that the detected braking pressure values ​​Pw1S, Pw2S follow the target braking pressure PwTr. As a result, the control device 300 can improve the controllability of the braking pressures Pw1, Pw2 when the reference rotation angle θmB has not been acquired, compared to when individual braking pressure control is performed.

[0067] (5) In movement control, when moving the piston 62 to the reference position Pb in one of the multiple electric cylinders 60, the electric motor 63 is driven so that its rotational speed dθmt follows the target rotational speed dθmtTr. This prevents the retraction speed of the piston 62 from becoming too large. As a result, when the control device 300 retracts the piston 62 by movement control, the collision noise and impact when the piston 62 comes into contact with the stopper can be reduced.

[0068] (6) When a braking request occurs in any of the multiple power sources 40A and 40B while the reference rotation angle θmB of the electric motor 63 has been acquired, individual braking pressure control is performed. Since the reference rotation angle θmB of the electric motor 63 has already been acquired, in individual braking pressure control, the first controller 310 can set an appropriate relative rotation angle θmR to the target motor rotation angle θmtTr1 according to the target value of the first braking pressure Pw1. The second controller 320 can also set an appropriate relative rotation angle θmR to the target motor rotation angle θmtTr2 according to the target value of the second braking pressure Pw2. Therefore, the control device 300 can accurately adjust the first braking pressure Pw1 and the second braking pressure Pw2 by performing individual braking pressure control.

[0069] <Example of changes> The above embodiment can be implemented with the following modifications. The above embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0070] In movement control, when moving the piston 62 to the reference position Pb, it is not necessary to set a target rotational speed dθmtTr for the rotational speed dθmt of the electric motor 63. The reference position Pb does not have to be the fully retracted position Pf, as long as it is a position of the piston 62 that does not generate braking pressure. In other words, any position between the generation position and the fully retracted position Pf may be set as the reference position Pb.

[0071] • The position in which vehicle 10 waits when not braking does not need to coincide with the reference position Pb. In the above embodiment, the reference rotation angle θmB was obtained by acquiring the rotation angle of the electric motor 63 when the piston 62 was in the reference position Pb, but this method is not limited to this. For example, if the electric cylinder 60 is equipped with a displacement sensor that detects the position of the piston 62, the value detected by the displacement sensor when the piston 62 is in the reference position Pb may be acquired as a reference position-related value.

[0072] The electric cylinder 60 may have a return spring that is not strong enough to return the piston 62 to its rearmost position Pf by biasing force alone. The braking device may be configured such that the first supply source 40A can supply brake fluid to the two wheel cylinders even when the switching unit 50 is set to the shut-off state. In this case, the two wheel cylinders are connected to the first fluid passage 33. In this respect, the two wheel cylinders correspond to the "first wheel cylinder".

[0073] The braking device may be configured such that the second supply source 40B can supply brake fluid to the two wheel cylinders even when the switching unit 50 is set to the shut-off state. In this case, the two wheel cylinders are connected to the second fluid passage 34. In this respect, the two wheel cylinders correspond to the "second wheel cylinders".

[0074] The braking unit does not necessarily have to include a reservoir 32. In this case, the switching unit may be configured to include a single system shut-off valve. Preferably, the system shut-off valve is a normally open solenoid valve having a first solenoid whose energization is controlled by a first controller 310 and a second solenoid whose energization is controlled by a second controller 320. When power is supplied to at least one of the first solenoid and the second solenoid, the system shut-off valve is closed.

[0075] The control device 300 may be configured as a circuit including one or more processors that operate according to a computer program, one or more dedicated hardware circuits that perform 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.

[0076] <Other technological ideas> The technical concepts that can be understood from the above embodiments and modified examples are described below. [Note 1] The aforementioned reference position is preferably the position furthest back within the range of motion of the piston.

[0077] [Note 2] The aforementioned movement control is, A first movement control that moves the piston of the first electric cylinder to the reference position while supplying brake fluid from the second electric cylinder to both of the plurality of wheel cylinders, The system includes a second movement control that moves the piston of the second electric cylinder to the reference position while supplying brake fluid from the first electric cylinder to both of the plurality of wheel cylinders, Preferably, when a braking request occurs, the control device executes the first movement control, acquires the reference position-related value of the piston of the first electric cylinder during the execution of the first movement control, then transitions the control from the first movement control to the second movement control, and acquires the reference position-related value of the piston of the second electric cylinder during the execution of the second movement control.

[0078] [Note 3] A shut-off valve is installed in the aforementioned communication passage and, when open, connects the first liquid passage and the second liquid passage, while when closed, it blocks communication between the first liquid passage and the second liquid passage. In the movement control, it is preferable that the control device opens the shut-off valve and then operates the plurality of electric cylinders.

[0079] [Note 4] The control device is capable of performing individual braking pressure control, which involves closing the shut-off valve, adjusting the braking pressure of the first wheel cylinder by operating the first electric cylinder, and adjusting the braking pressure of the second wheel cylinder by operating the second electric cylinder. The control device is If a braking request occurs while the reference position-related value can be obtained in any of the aforementioned multiple electric cylinders, the individual braking pressure control will be executed. If a braking request occurs while the reference position-related value of at least one of the plurality of electric cylinders has not been acquired, it is preferable to perform the movement control.

[0080] [Note 5] The control device is configured to acquire the reference rotation angle, which is the rotation angle of the electric motor when the piston is in the reference position, as the reference position-related value. The rotation angle of the electric motor with respect to the aforementioned reference rotation angle is the relative rotation angle. In the individual braking pressure control, the control device preferably sets the relative rotation angle corresponding to the target value of the braking pressure as the target rotation angle, and drives the electric motor so that the relative rotation angle follows the target rotation angle.

[0081] 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]

[0082] 10... Vehicles 20… Friction brakes 211…First wheel cylinder 212... Second wheel cylinder 30...braking device 33...1st liquid path 34…Second liquid path 40A…1st supply source 40B…Second supply source 50... Switching section 51...Communication path 52, 53… System shut-off valves 60…Electric Cylinder 62... Piston 63… Electric motor 300... Control device 310,320… controllers

Claims

1. Applicable to vehicles equipped with a first wheel cylinder and a second wheel cylinder, A first fluid passage, which is a brake fluid passage connected to the first wheel cylinder, The second fluid passage, which is a brake fluid passage connected to the second wheel cylinder, A first electric cylinder is configured to discharge brake fluid into the first fluid passage by driving an electric motor to advance a piston, A second electric cylinder is configured to discharge brake fluid into the second fluid passage by driving an electric motor to advance a piston, A connecting passage which is a brake fluid passage that connects the first fluid passage and the second fluid passage, The system comprises a control device for controlling the first electric cylinder and the second electric cylinder, The control device is While supplying brake fluid from one of the multiple electric cylinders to both of the multiple wheel cylinders, movement control is performed to move the piston of the other of the multiple electric cylinders to a reference position set to be retracted within the piston's range of motion, beyond the position of the piston when braking pressure in the wheel cylinder begins to be generated. The position-related value, which is a state quantity related to the position of the piston of the other electric cylinder when the piston is positioned at the reference position as a result of the execution of the movement control, is acquired as the reference position-related value. Braking device.

2. The control device, in the motion control, operates one of the multiple electric cylinders so that the braking pressure of the multiple wheel cylinders follows a target value of the braking pressure. The braking device according to claim 1.

3. In the movement control, the control device drives the electric motor of the electric cylinder that moves the piston to the reference position among the plurality of electric cylinders so that the rotational speed of the electric motor of the electric cylinder follows a target value of that rotational speed. The braking device according to claim 1 or claim 2.

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