braking device

Abstract

A brake device 20 is configured to include: an electric cylinder 51 that discharges brake fluid having a hydraulic pressure corresponding to driving by the electric motor 513 from an output port 516; a master cylinder 31 configured to discharge brake fluid from a main chamber Rm by the movement of a master piston 43 accompanied by an increase in hydraulic pressure in a servo chamber Rs, and to flow brake fluid into the main chamber Rm by the movement of the master piston 43 accompanied by a decrease in hydraulic pressure in the servo chamber Rs; a first flow path 331 connecting the main chamber Rm and a wheel cylinder 11 for a front wheel; a sixth flow path 58 connecting the output port 516 and the wheel cylinder 11 for a rear wheel; a fifth flow path 55 connecting the sixth flow path 58 and the servo chamber Rs;and a differential pressure control valve 551 provided in the fifth flow path 55 and adjusting a differential pressure between a first hydraulic pressure, which is a hydraulic pressure in the sixth flow path 58, and a second hydraulic pressure, which is a hydraulic pressure in the servo chamber Rs;

Description

Technical area

[0001] The present invention relates to a braking device. State of the art

[0002] A braking device is known from the related prior art which generates different frictional braking forces on a front wheel and a rear wheel by adjusting the hydraulic pressure of a brake fluid supplied to a front wheel cylinder and a rear wheel cylinder. A braking device disclosed in PTL 1, for example, comprises a main unit that supplies brake fluid to a master cylinder of the front wheel and a control unit that supplies the brake fluid to a cylinder of the rear wheel and to the main unit.

[0003] The main unit comprises a main piston that defines a servo chamber and a main chamber. When brake fluid is supplied to the servo chamber, the main piston moves within the main unit in a direction that reduces the volume of the main chamber. As a result, the brake fluid is directed from the main chamber to the master cylinder of the front wheel.

[0004] The pressure control unit comprises an electric pump that delivers the brake fluid, a first electromagnetic valve that adjusts the brake fluid delivered by the electric pump to a first hydraulic pressure, and a second electromagnetic valve that adjusts the brake fluid delivered by the electric pump to a second hydraulic pressure. The pressure control unit supplies the brake fluid adjusted to the first hydraulic pressure to the rear wheel cylinder and the brake fluid adjusted to the second hydraulic pressure to the servo chamber. The friction control unit ensures that the friction braking force generated at the front wheel is less than the friction braking force generated at the rear wheel by making the second hydraulic pressure lower than the first hydraulic pressure. Citation list for patent literature

[0005] PTL 1: JP2019-137202A Brief description of the invention: Technical problem

[0006] The braking device described above must control the electric pump, the first electromagnetic valve, and the second electromagnetic valve when generating the friction braking force at the front and rear wheels. In other words, the braking device described above must control multiple targets when generating the friction braking force at the front and rear wheels. Solution to the problem

[0007] The following describes a means of solving the above problem and its impact on operations.

[0008] A braking device for solving the above problem is a braking device for a vehicle comprising a first wheel cylinder, a second wheel cylinder, a first wheel generating a friction braking force corresponding to a hydraulic pressure in the first wheel cylinder, and a second wheel generating a friction braking force corresponding to a hydraulic pressure in the second wheel cylinder, wherein the braking device comprises an electric cylinder with an electric motor as a power source and an output port for dispensing brake fluid at a hydraulic pressure corresponding to the drive by the electric motor;a master cylinder with a main piston defining a servo chamber and a main chamber, configured such that brake fluid flows out of the main chamber by a movement of the main piston accompanied by an increase in hydraulic pressure in the servo chamber, and brake fluid flows into the main chamber by a movement of the main piston accompanied by a decrease in hydraulic pressure in the servo chamber; a first fluid path connecting the main chamber and the first wheel cylinder; a second fluid path connecting the outlet port and the second wheel cylinder; a third fluid path connecting the second fluid path and the servo chamber;and a differential pressure control valve, provided and configured in the third fluid path to adjust a differential pressure between a first hydraulic pressure, which is a hydraulic pressure in the second fluid path, and a second hydraulic pressure, which is the hydraulic pressure in the servo chamber.

[0009] The brake system controls the electric cylinder and the differential pressure control valve to generate the friction braking force for the first and second wheels. Specifically, the brake system supplies the second wheel cylinder with brake fluid via the second fluid path, which is adjusted to the first hydraulic pressure by the electric cylinder. The brake system delivers the brake fluid, which is adjusted to the second hydraulic pressure by the differential pressure control valve, to the servo chamber of the master cylinder via the third fluid path. The brake fluid corresponding to the hydraulic pressure in the servo chamber is then supplied from the main chamber of the master cylinder to the first wheel cylinder via the first fluid path. In this way, the brake system can generate different friction braking forces on the first and second wheels by controlling the electric cylinder and the differential pressure control valve. Brief description of the drawings Fig. Figure 1 is a schematic representation of a vehicle with a braking device. Fig. Figure 2 is a flowchart illustrating the process of a operation carried out by a control unit. Fig. Figure 3 contains time diagrams (a) to (c) illustrating the transition of the target braking force, the regenerative braking force and the wheel cylinder pressure when the vehicle is to be braked. Fig. Figure 4 is a diagram that illustrates the relationship between the braking force of the front wheel and the braking force of the rear wheel. Description of the exemplary implementations

[0010] An exemplary embodiment of a braking device is described below with reference to the drawings.

[0011] Fig. Figure 1 shows a plurality of wheels FL, FR, RL, and RR, a plurality of friction braking mechanisms 10, a braking device 20, and a regenerative braking device 60. The plurality of wheels FL, FR, RL, and RR includes two front wheels FL and FR and two rear wheels RL and RR. In the exemplary embodiment, the two front wheels FL and FR correspond to a "first wheel," and the two rear wheels RL and RR correspond to a "second wheel." <Konfiguration des Reibungsbremsmechanismus>

[0012] A friction braking mechanism 10 is provided for one wheel. Each of the multiple friction braking mechanisms 10 comprises a wheel cylinder 11, to which brake fluid is supplied, a rotating disc 12 that rotates integrally with a wheel, and a friction material 13 that is pressed against the rotating disc 12. The friction braking mechanism 10 is configured such that it can press the friction material 13 more strongly against the rotating disc 12 when the hydraulic pressure in the wheel cylinder 11 is increased. The friction braking mechanism 10 generates a friction braking force that corresponds to the hydraulic pressure in the wheel cylinder 11.

[0013] A vehicle has a plurality of wheel cylinders 11. In the exemplary embodiment, among the plurality of wheel cylinders 11, the wheel cylinders 11 for the front wheels FL and FR correspond to a “first wheel cylinder” and the wheel cylinders 11 for the rear wheels RL and RR to a “second wheel cylinder”. <Konfiguration der Bremsvorrichtung>

[0014] The brake device 20 adjusts a friction braking force generated in the vehicle by supplying brake fluid to the wheel cylinders 11 of the plurality of friction braking mechanisms 10. The brake device 20 comprises a brake actuation element 21, a hydraulic pressure generating device 22, a brake adjusting device 23, and a storage tank 24.

[0015] The brake actuation element 21 can be operated by the driver of the vehicle. An example of a brake actuation element 21 is a brake pedal. The storage tank 24 stores the brake fluid. The interior of the storage tank 24 is open to the atmosphere.

[0016] The hydraulic pressure generating device 22 is configured to generate hydraulic pressure depending on the actuation amount of the brake actuating element 21. The hydraulic pressure generating device 22 comprises a main unit 30 and a friction brake section 50. The main unit 30 can supply brake fluid to the brake actuator 23. The friction brake section 50 can supply brake fluid to both the main unit 30 and the brake actuator 23. <haupteinrichtung>

[0017] The main device 30 comprises a master cylinder 31, a stroke simulator 32, a plurality of flow paths 331, 332 and 333 connected to the master cylinder 31, and a plurality of control valves 341 and 342 that control the flow of brake fluid. The stroke simulator 32 can generate a reaction force corresponding to the actuation amount of the brake actuation element 21.

[0018] The master cylinder 31 consists of a master cylinder 41 and a cover cylinder 42. The master cylinder 31 includes a master piston 43 and an input piston 44. The master cylinder 31 includes a main spring 45, which preloads the master piston 43, and an input spring 46, which preloads the input piston 44. The master piston 43 and the input piston 44 can move relative to the master cylinder 41 and the cover cylinder 42.

[0019] The main cylinder 41 of the main cylinder 31 has a plate-shaped bottom wall 411 and a first circumferential wall 412 extending from the bottom wall 411 along an axis of the bottom wall 411. The main cylinder 41 further comprises a second circumferential wall 413 extending from a rear end of the first circumferential wall 412 along an axis of the first circumferential wall 412, and a first annular wall 414 extending from a rear end of the second circumferential wall 413 towards an axis of the second circumferential wall 413. Both the first circumferential wall 412 and the second circumferential wall 413 are tubular in shape. A hole is formed in the first annular wall 414 into which a rear end section of the main piston 43, described later, is inserted. The inner diameter of the first circumferential wall 412 is smaller than the inner diameter of the second circumferential wall 413.

[0020] A main chamber Rm is formed in the main cylinder 41 by the bottom wall 411, the first circumferential wall 412, and the main piston 43. In the following, a left side in the main cylinder 31 is described. Fig. 1, i.e., a direction of movement of the main piston 43 to reduce the volume of the main chamber Rm is referred to as the "front," and a direction opposite to the front is referred to as the "back." The back is also a direction to increase the volume of the main chamber Rm.

[0021] In the main cylinder 41, a first fluid chamber R1 is bounded by the second circumferential wall 413 and the main piston 43, and a servo chamber Rs is bounded by the second circumferential wall 413, the first annular wall 414, and the main piston 43. The main chamber Rm is formed near the front end of the main cylinder 31. The first fluid chamber R1 is located downstream of the main chamber Rm. The servo chamber Rs is located downstream of the first fluid chamber R1. Inside the main cylinder 41, the main chamber Rm, the first fluid chamber R1, and the servo chamber Rs are not connected to each other. The cross-sectional area of ​​the main chamber Rm is equal to the cross-sectional area of ​​the servo chamber Rs. The cross-sectional area of ​​the servo chamber Rs is the cross-sectional area of ​​the servo chamber Rs in the state in which the main piston 43 is located.

[0022] The cover cylinder 42 of the main cylinder 31 comprises a tubular third circumferential wall 421 and a second annular wall 422, which extends from a rear end of the third circumferential wall 421 towards an axis of the third circumferential wall 421. The third circumferential wall 421 is attached to the first annular wall 414 such that its axis coincides with the axis of the second circumferential wall 413 of the main cylinder 41. The second annular wall 422 is provided with a hole into which a rear end section of the inlet piston 44, described later, is inserted.

[0023] In the cover cylinder 42, a second fluid chamber R2 is formed by the third circumferential wall 421, the second annular wall 422, and the first annular wall 414 of the main cylinder 41. In the main cylinder 31, the second fluid chamber R2 is formed downstream of the servo chamber Rs.

[0024] The main piston 43 is located in the main cylinder 31 in surface contact with an inner circumferential surface of the first circumferential wall 412, an inner circumferential surface of the second circumferential wall 413, and an inner circumferential surface of the first annular wall 414 of the main cylinder 41. When the main piston 43 moves in an axial direction, it therefore slides on the inner circumferential surface of the first circumferential wall 412, the inner circumferential surface of the second circumferential wall 413, and the inner circumferential surface of the first annular wall 414. The rear end section of the main piston 43 projects further rearward relative to the first annular wall 414 and is located in the second fluid chamber R2. An area of ​​the rear end section of the main piston 43 (an area that absorbs a force in the axial direction due to hydraulic pressure in the second fluid chamber R2) is equal to a cross-sectional area of ​​the first fluid chamber R1.The cross-sectional area of ​​the first fluid chamber R1 is a cross-sectional area of ​​the first fluid chamber R1 in a state in which the main piston 43 is housed.

[0025] The inlet piston 44 is located in the main cylinder 31 in surface contact with an inner circumferential surface of the second annular wall 422 of the cover cylinder 42. As the inlet piston 44 moves axially, it slides on the inner circumferential surface of the second annular wall 422. The rear end section of the inlet piston 44 projects further rearward relative to the second annular wall 422. The area of ​​the front end section of the inlet piston 44 is equal to the area of ​​the rear end section of the main piston 43. The brake actuating element 21 is coupled to the rear end section of the inlet piston 44. Therefore, the inlet piston 44 moves in the direction of approach to the main piston 43 according to the actuation force of the brake actuating element 21. Furthermore, a gap is formed between the inlet piston 44 and the main piston 43 in the second fluid chamber R2.

[0026] The main spring 45 is located in the main chamber Rm of the main cylinder 41. The master spring 45 pushes the main piston 43 backwards. Therefore, the master spring 45 is elastically compressed when the main piston 43 moves forwards.

[0027] The inlet spring 46 is located in the second fluid chamber R2 of the cover cylinder 42. The inlet spring 46 pushes the inlet piston 44 backwards. Therefore, the inlet spring 46 is elastically compressed when the inlet piston 44 moves forwards.

[0028] In the main cylinder 31, the main chamber Rm is connected to the storage tank 24. In particular, a section near the rear end of the main chamber Rm is connected to the storage tank 24 via an opening formed in the first circumferential wall 412 of the main cylinder 41. Therefore, the main chamber Rm and the storage tank 24 are not connected to each other when the main piston 43 extends from a Fig. The main piston 43 moves forward from its initial position as shown in Figure 1. Consequently, the hydraulic pressure in the main chamber Rm increases as the main piston 43 moves forward. For example, if the hydraulic pressure in the servo chamber Rs increases, the main piston 43 is moved forward by the hydraulic pressure in the servo chamber Rs. Accordingly, the hydraulic pressure in the main chamber Rm increases.

[0029] The first flow path 331 connects the main chamber Rm and the brake actuator 23. Specifically, the first flow path 331 connects the main chamber Rm and the wheel cylinders 11 for the front wheels FL and FR. In this respect, the first flow path 331 corresponds to a “first fluid path”. The second fluid path 332 connects the first fluid chamber R1 and the second fluid chamber R2. The third flow path 333 connects the storage tank 24 and the second flow path 332.

[0030] The first control valve 341 is a normally closed electromagnetic valve. The second control valve 342 is a normally open electromagnetic valve. The first control valve 341 is located in the second fluid path 332 between a connection point with the third fluid path 333 and the second fluid chamber R2. The second control valve 342 is located in the third fluid path 333. When a control device 80 of the brake device 20 is in operation, the first control valve 341 opens and the second control valve 342 closes.

[0031] The stroke simulator 32 is arranged between the first fluid chamber R1 and the first control valve 341 in the second fluid path 332. The stroke simulator 32 includes, for example, a piston (not shown) that is biased from a rear surface by a spring. In this case, the stroke simulator 32 generates pressure in the brake fluid in response to the displacement of the piston when the inner piston is moved against the spring bias by the brake fluid flowing in from the second flow path 332. In particular, when the input piston 44 is moved forward by actuation of the brake actuating element 21 in a state where the first control valve 341 is open and the second control valve 342 is closed, the volume of the second fluid chamber R2 decreases by the volume of the input piston 44 entering the second fluid chamber R2.Therefore, the brake fluid flowing from the second fluid chamber R2 to the second fluid path 332 flows into the stroke simulator 32. Consequently, the stroke simulator 32 generates the same pressure in the second fluid chamber R2 and the first fluid chamber R1, which are connected by the second fluid path 332. Since the area of ​​the rear end section of the main piston 43, which projects into the second fluid chamber R2, is equal to the cross-sectional area of ​​the first fluid chamber R1, the main piston 43 is not moved axially by this pressure when the same pressure is generated in the second fluid chamber R2 and the first fluid chamber R1. <reibungsbremsabschnitt>

[0032] The friction brake section 50 includes an electric cylinder 51. The friction brake section 50 can adjust the hydraulic pressure in the multiple wheel cylinders 11 when the electric cylinder 51 is actuated.

[0033] The friction brake section 50 comprises a fourth flow path 54, a fifth flow path 55, and a sixth flow path 58. The fourth flow path 54 connects the electric cylinder 51 and the storage tank 24. The fifth flow path 55 connects the servo chamber Rs of the master cylinder 31 and the sixth flow path 58. The sixth flow path 58 connects the brake actuator 23 and the electric cylinder 51. Specifically, the sixth flow path 58 connects the wheel cylinders 11 for the rear wheels RL and RR to the electric cylinder 51. In this respect, the sixth flow path 58 corresponds to a "second fluid path" and the fifth flow path 55 to a "third fluid path".

[0034] The electric cylinder 51 is arranged between the fourth flow path 54 and the sixth flow path 58. The fourth flow path 54 is connected to an inlet port 515 of the electric cylinder 51. The sixth flow path 58 is connected to an outlet port 516 of the electric cylinder 51. The fifth flow path 55 is equipped with a differential pressure control valve 551 and a check valve 552. The differential pressure control valve 551 is an electromagnetic valve that adjusts the differential pressure between a section of the fifth flow path 55 that is closer to the servo chamber Rs than the differential pressure control valve 551, and a section of the fifth flow path 55 that is closer to the electric cylinder 51 than the differential pressure control valve 551. That is, the differential pressure control valve 551 can adjust the amount of brake fluid supplied to the servo chamber Rs.

[0035] In the following, a hydraulic pressure in the section of the fifth flow path 55 that is closer to the electric cylinder 51 than the differential pressure control valve 551 is referred to as the "first hydraulic pressure," and a hydraulic pressure in the section of the fifth flow path 55 that is closer to the servo chamber Rs than the differential pressure control valve 551 is referred to as the "second hydraulic pressure." The first hydraulic pressure is a hydraulic pressure in the sixth flow path 58, and the second hydraulic pressure is the hydraulic pressure in the servo chamber Rs.

[0036] The check valve 552 is arranged in parallel to the differential pressure control valve 551 in the fifth flow path 55. The check valve 552 allows the flow of brake fluid from the servo chamber Rs to the sixth fluid path 58 and restricts the flow of brake fluid from the sixth fluid path 58 to the servo chamber Rs. In particular, the check valve 552 allows the flow of brake fluid to the sixth fluid path 58 when the second hydraulic pressure is greater than the first hydraulic pressure. Conversely, when the second hydraulic pressure is less than the first hydraulic pressure, the check valve 552 restricts the flow of brake fluid to the servo chamber Rs. <Konfiguration eines elektrischen Zylinders>

[0037] The electric cylinder 51 comprises a cylinder 511, a piston 512, an electric motor 513, and a conversion mechanism 514. The piston 512 is slidably arranged within the cylinder 511. The electric motor 513 is an energy source for the electric cylinder 51. The conversion mechanism 514 converts a rotary motion of an output shaft of the electric motor 513 into a linear motion of the piston 512.

[0038] Inside cylinder 511, a hydraulic chamber Re, into which the brake fluid is introduced, is bounded by a circumferential wall of the cylinder 511 and the piston 512. The position of the piston 512 within the cylinder 511 can be changed by driving the electric motor 513. Hereinafter, a direction of movement of the piston 512 to decrease the volume of the hydraulic chamber Re is referred to as the "forward direction Za," and a direction opposite to the forward direction Za is referred to as the "retraction direction Zb." The retraction direction Zb is a direction of movement of the piston 512 to increase the volume of the hydraulic chamber Re.

[0039] The inlet port 515 and the outlet port 516 are formed in the circumferential wall of the cylinder 511 as connecting openings between the hydraulic chamber Re and the outside world. A through-hole 517 is formed in the piston 512. If the position of the piston 512 in a state where there is no braking request for the vehicle is defined as the ready position, the through-hole 517 allows the inlet port 515 and the hydraulic chamber Re to communicate with each other when the piston 512 is in the ready position or in a position shifted relative to the ready position in the retraction direction Zb. Accordingly, the hydraulic chamber Re of the cylinder 511 is connected to the fourth flow path 54 via the inlet port 515 and the through-hole 517 when the piston 512 is in the ready position.This means that the hydraulic chamber Re of cylinder 511 is connected to the storage tank 24 via the inlet port 515 and the through-bore 517. The inlet port 515 is open when the piston 512 is in the ready position and is closed by the piston 512 when the piston 512 moves from the ready position in the forward direction Za. Thus, when the inlet port 515 is closed by the piston 512, the hydraulic pressure in the hydraulic chamber Re increases when the piston 512 moves in the forward direction Za.

[0040] The outlet port 516 of the cylinder 511 is connected to the brake actuator 23 and the fifth flow path 55 via the sixth flow path 58. The outlet port 516 is always open, regardless of the position of the piston 512. Therefore, if the inlet port 515 is closed by the piston 512, when the piston 512 moves in the forward direction Za, the brake fluid in the hydraulic chamber Re is drained from the outlet port 516 to the outside of the cylinder 511.

[0041] The electric cylinder 51 provided in the brake device 20 does not contain a spring that biases the piston 512 in the retraction direction Zb. The electric cylinder 51 may contain a spring that biases the piston 512 in the retraction direction Zb.

[0042] The friction brake section 50 comprises a release flow path 56 and a release valve 57 located in the release flow path 56. The release flow path 56 is a flow path that connects the storage tank 24 and the wheel cylinder 11 to bypass the electric cylinder 51. A first end section of the release flow path 56 is connected to the fourth flow path 54, and a second end section of the release flow path 56 is connected to the sixth flow path 58. Specifically, the release flow path 56 connects a section between the storage tank 24 and the inlet port 515 in the fourth flow path 54 and a section between the outlet port 516 and the brake actuator 23 in the sixth flow path 58.

[0043] The release valve 57 is a normally closed electromagnetic valve. Therefore, if the opening of the drain valve 57 is not controlled, the drain flow path 56 is closed. <bremsenstellglied>

[0044] The brake actuator 23 is capable of individually adjusting the hydraulic pressures in the multiple wheel cylinders 11. The brake actuator 23 comprises a front wheel pressure control unit 231 and a rear wheel pressure control unit 232. The front wheel pressure control unit 231 generates a friction braking force at the front wheels FL and FR by adjusting the hydraulic pressure in the wheel cylinders 11 for the front wheels FL and FR. The rear wheel pressure control unit 232 generates a friction braking force at the rear wheels RL and RR by adjusting the hydraulic pressure in the wheel cylinders 11 for the rear wheels RL and RR. Hereinafter, the hydraulic pressure in the wheel cylinders 11 for the front wheels FL and FR is also referred to as the front wheel cylinder pressure, and the hydraulic pressure in the wheel cylinders 11 for the rear wheels RL and RR is also referred to as the rear wheel cylinder pressure. <Erfassungssystem der Bremsvorrichtung>

[0045] As in Fig. 1 and Fig. As shown in Figure 2, a detection system of the brake device 20 comprises a plurality of sensors. A detection signal from the sensor is input into the control unit 80 of the brake device 20. The multiple sensors include several hydraulic pressure sensors 351, 352 and 353 as well as a stroke sensor SE1.

[0046] The main hydraulic pressure sensor 351 detects the hydraulic pressure in the main chamber Rm. The master hydraulic pressure sensor 351 is, for example, located in the first flow path 331. The input hydraulic pressure sensor 352 detects the hydraulic pressure in the second fluid chamber R2. The input hydraulic pressure sensor 352 is, for example, connected at a position between the first control valve 341 and the second fluid chamber R2 in the second fluid path 332. The control pressure sensor 353 is a pressure sensor that detects the hydraulic pressure of the brake fluid delivered by the electric cylinder 51. The control pressure sensor 353 is, for example, located near the output port 516 of the electric cylinder 51. As an example, Fig. 1. A configuration in which the control pressure sensor 353 is connected between the control valve 57 and the output port 516 in the release flow path 56. The stroke sensor SE1 detects an actuation amount of the brake actuation element 21. <Steuereinrichtung der Bremsvorrichtung>

[0047] The brake device 20 includes the control unit 80. The control unit 80 is, for example, an electronic control unit with a CPU and memory. The memory stores a control program to be executed by the CPU. The control unit 80 controls the hydraulic pressure generating unit 22 and the brake actuator 23 by having the CPU execute the control program. That is, the control unit 80 controls the various electromagnetic valves 341, 342, 551, 57 and the electric motor 513 of the hydraulic pressure generating unit 22, as well as the front wheel pressure control unit 231 and the rear wheel pressure control unit 232 of the brake actuator 23. The control unit 80 communicates with the regenerative braking device 60 to exchange various types of information.

[0048] The control unit 80 functions as a target braking force derivation unit 81, a friction braking force derivation unit 82, and a friction control unit 83, with the CPU executing the control program. The target braking force derivation unit 81, the friction braking force derivation unit 82, and the friction control unit 83 are functional units for the operation of the hydraulic pressure generating unit 22.

[0049] The target braking force derivation unit 81 derives a target braking force, which is a braking force required for the vehicle. That is, when the brake actuating element 21 is actuated, the target braking force derivation unit 81 derives a target braking force value that corresponds to the actuation amount of the brake actuating element 21. For example, the target braking force derivation unit 81 increases the target braking force with increasing actuation amount. The target braking force derivation unit 81 also derives the target braking force when the vehicle needs to be decelerated in a situation where no braking operation is performed. The target braking force derivation unit 81 transmits the target braking force to the regenerative braking device 60. The target braking force derivation unit 81 receives an actual regeneration braking force from the regenerative braking device 60, which the regenerative braking device 60 actually generates at the front wheels FL and FR.The received actual regeneration braking force is a regenerative braking force generated by the regenerative braking device 60 on the front wheels FL and FR.

[0050] The friction braking force derivation unit 82 derives a target friction braking force based on the target braking force and the actual regeneration braking force. This target friction braking force is a total value derived from the target friction braking force generated at the front wheels FL and FR and the target friction braking force generated at the rear wheels RL and RR. Specifically, if the actual regeneration braking force is equal to or greater than the target braking force, it is unnecessary to generate the friction braking force, and therefore the friction braking force derivation unit 82 sets the target friction braking force to "0". Conversely, if the actual regeneration braking force is less than the target braking force, the friction braking force must be generated, and the friction braking force derivation unit 82 therefore derives a value greater than "0" as the target friction braking force.For example, if the actual regeneration braking force is lower than the target braking force, the friction braking force derivation unit 82 derives a larger value as target friction braking force, because the difference between the target braking force and the actual regeneration braking force is increased.

[0051] The friction control unit 83 controls the electric cylinder 51 and the differential pressure control valve 551 based on the target friction braking force. That is, the friction control unit 83 calculates an initial hydraulic pressure to be generated by the electric cylinder 51 based on a target value corresponding to the target friction braking force. The friction control unit 83 then drives the electric motor 513 of the electric cylinder 51. At this point, the friction control unit 83 drives the electric motor 513 such that the amount of movement of the piston 512 in the forward direction Za from the ready position increases as the target friction braking force increases.

[0052] If the first hydraulic pressure is "0", the friction control unit 83 sets "0" as the differential pressure setpoint, i.e., the setpoint for the differential pressure between the first and second hydraulic pressures. Conversely, if the first hydraulic pressure is greater than "0", the friction control unit 83 sets "0" or a value greater than "0" as the differential pressure setpoint. For example, if the first hydraulic pressure is greater than "0", the friction control unit 83 sets a predetermined differential pressure as the differential pressure setpoint. The predetermined differential pressure can be a fixed preset value or a variable value. If the predetermined differential pressure is a variable value, it can be varied using the micron value (µ-value) of the road surface on which the vehicle travels and similar parameters.

[0053] The friction control unit 83 adjusts the excitation quantity to the solenoid coil of the differential pressure control valve 551, generating an electromagnetic force in the differential pressure control valve 551 that corresponds to the set differential pressure setpoint. When the second hydraulic pressure is changed by actuating the differential pressure control valve 551, the hydraulic pressure in the servo chamber Rs changes. Consequently, the main piston 43 in the master cylinder 31 moves in accordance with the change in hydraulic pressure in the servo chamber Rs. This, in turn, changes the hydraulic pressure in the main chamber Rm, which is connected to the wheel cylinders 11 for the front wheels FL and FR. The hydraulic pressure in the main chamber Rm is equal to the hydraulic pressure in the servo chamber Rs, i.e., the second hydraulic pressure. In this way, the friction control unit 83 generates the friction braking force at the front wheels FL and FR as a function of the second hydraulic pressure. <Regenerative Bremsvorrichtung>

[0054] The regenerative braking device 60 comprises a motor-generator 61 for the front wheels FL and FR and a regeneration control unit 62 that controls the motor-generator 61. By operating the motor-generator 61 as an electric motor, a driving force is transmitted from the motor-generator 61 to the front wheels FL and FR. Conversely, by functioning as a generator, the motor-generator 61 generates a regenerative braking force on the front wheels FL and FR, which corresponds to an amount of energy produced by the motor-generator 61.

[0055] The regeneration control unit 62 controls the motor-generator 61. The regeneration control unit 62 derives a maximum regenerative braking force, which is the maximum value of the regenerative braking force that the motor-generator 61 can generate at the front wheels FL and FR at any given time. For example, the regeneration control unit 62 derives the maximum regenerative braking force based on the rotational speeds of the front wheels FL and FR, the state of charge and temperature of a vehicle battery that supplies power to the motor-generator 61, and similar factors. After receiving information about the target braking force from the control unit 80 of the brake device 20, the regeneration control unit 62 compares the target braking force with the maximum regenerative braking force.If the target braking force is equal to or less than the maximum regenerative braking force, the regeneration control unit 62 controls the power generation of the motor-generator 61 so that the regenerative braking force equals the target braking force. Conversely, if the target braking force is greater than the maximum regenerative braking force, the regeneration control unit 62 controls the power generation of the motor-generator 61 so that the regenerative braking force equals the maximum regenerative braking force. The regeneration control unit 62 transmits information about the actual regenerative braking force generated at the front wheels FL and FR to the control unit 80. <bremsverarbeitung>

[0056] The sequence of processing carried out by the control unit 80 when the vehicle brakes is described by means of Fig. 2 described.

[0057] As in Fig. As shown in Figure 2, the control unit 80 determines whether braking is requested (S11) based on a detection signal from the lift sensor SE1 or similar. If the vehicle's deceleration is requested by another control unit, the control unit 80 determines that braking is requested, even if the brake actuator 21 is not actuated. If braking is not requested (S11: NO), the control unit 80 terminates processing. If, however, braking is requested (S11: YES), the control unit 80 derives a target braking force (S12). For example, if the brake actuator 21 is actuated, the control unit 80 derives the target braking force based on a detection signal from the lift sensor SE1 or similar.If the vehicle's deceleration is requested by another control unit, control unit 80 derives a target braking force value that corresponds to a requested value for deceleration.

[0058] The control unit 80 transmits the target braking force to the regeneration control unit 62 (S13) and receives an actual regeneration braking force from the regeneration control unit 62 (S14).

[0059] When the regeneration control unit 62 receives the target braking force transmitted by the control unit 80 in step S13, it compares the maximum regenerative braking force with the target braking force to derive an actual regeneration braking force that can be generated at the front wheels FL and FR. The regeneration control unit 62 then controls the motor generator 61 to generate the actual regeneration braking force at the front wheels FL and FR. Furthermore, the regeneration control unit 62 transmits the actual regeneration braking force to the control unit 80. In this way, the actual regeneration braking force transmitted by the regeneration control unit 62 is received by the control unit 80 in step S14.

[0060] The control unit 80 then determines whether the actual regeneration braking force is equal to the target braking force (S15). If the actual regeneration braking force is equal to the target braking force (S15: YES), i.e., if the target braking force can be covered solely by the regenerative braking force, a target friction braking force is set to "0" (S16). The control unit 80 then switches to step S18, which is described later. If, on the other hand, the actual regeneration braking force and the target braking force are not equal (S15: NO), i.e., the target braking force cannot be covered solely by the regeneration braking force, the target friction braking force is derived from the difference between the target braking force and the actual regeneration braking force (S17).

[0061] The control unit 80 derives a first hydraulic pressure and a second hydraulic pressure based on the target friction braking force specified in step S16 or S17 and controls the operation of the friction braking section 50 (S18). That is, the control unit 80 adjusts the first hydraulic pressure and the second hydraulic pressure by controlling the electric cylinder 51 and the differential pressure control valve 551. The control unit 80 then terminates the process. <Betriebsweisen und Wirkungen>

[0062] The transition of the regenerative braking force and the front wheel cylinder pressure and the rear wheel cylinder pressure with respect to a change in the target braking force is described with reference to (a) to (c) of Fig. 3 and Fig. 4 described. The pressure of the front wheel cylinder correlates with the second hydraulic pressure, and the pressure of the rear wheel cylinder correlates with the first hydraulic pressure. Therefore, in Fig. 3. The transition in pressure of the front wheel cylinder to the transition in the second hydraulic pressure, and the transition in pressure of the rear wheel cylinder to the transition in the first hydraulic pressure. Several in Fig. The three depicted time points each correspond to several in Fig. 4 times shown.

[0063] As in Fig. As shown in Figure 3, the target braking force begins to increase when braking is requested at a first time t11. If the target braking force is small, especially if it is equal to or less than the maximum regenerative braking force, the target braking force can only be covered by the regenerative braking force. Therefore, the regenerative braking force increases in a similar way to the target braking force during the period between the first time t11 and the next second time t12, while the friction braking force of the front wheel and the friction braking force of the rear wheel remain at zero. The regenerative braking force is a braking force generated only at the front wheels FL and FR. Therefore, as shown in Figure 3, the regenerative braking force increases... Fig. Figure 4 shows only the front wheel braking force of the front wheel and rear wheel braking forces during the period between the first time t11 and the second time t12.

[0064] At the second time point t12, the target braking force becomes equal to the maximum regenerative braking force, since the target braking force is increased. In the Fig. In the example shown, the target braking force increases after the second time point t12. Therefore, in the period after the second time point t12, the target braking force can no longer be covered solely by the regenerative braking force. Therefore, in the period after the second time point t12, when the target braking force increases, the pressure in the rear wheel cylinder is increased to boost the friction braking force.

[0065] Specifically, a target friction braking force is derived from the difference between the target braking force and an actual regeneration braking force. In this case, the electric cylinder 51 and the differential pressure control valve 551 are controlled based on the target friction braking force. In the electric cylinder 51, the piston 512 is moved in the forward direction Za by driving the electric motor 513. This causes brake fluid to be discharged from the output port 516 of the electric cylinder 51, thereby increasing the initial hydraulic pressure. Consequently, the wheel cylinder pressure in the rear wheel increases, and thus the friction braking force of the rear wheel also increases.

[0066] In the friction brake section 50, the hydraulic pressure of the brake fluid supplied from the electric cylinder 51 increases until the predetermined differential pressure is set as the differential pressure setpoint for the differential pressure control valve 551. Therefore, the differential pressure control valve 551 restricts the supply of brake fluid from the output port 516 of the electric cylinder 51 to the servo chamber Rs in the master cylinder 31 when the difference in hydraulic pressure between the first and second hydraulic pressures is equal to or less than the predetermined differential pressure. That is, the second hydraulic pressure is not increased. Since the hydraulic pressure in the main chamber Rm of the master cylinder 31 is not increased in this case, the pressure in the front wheel cylinders 11 also does not increase. Consequently, the friction braking force of the front wheel does not increase.For example, the predetermined differential pressure is set according to a pressure in the front wheel cylinders in order to generate a braking force as friction braking force of the front wheels FL and FR that corresponds to the regenerative braking force.

[0067] If the magnitude of the differential pressure between the first hydraulic pressure and the second hydraulic pressure is equal to or less than the predetermined differential pressure, only the first hydraulic pressure and the second hydraulic pressure increase. Consequently, as shown in Fig. Figure 4 shows that after the second time point t12 the braking force of the rear wheel is maintained, while the braking force of the front wheel is maintained.

[0068] In the Fig. In the example shown, the target friction braking force also increases after the second time point t12. At a third time point t13, the differential pressure between the first and second hydraulic pressures reaches the predetermined differential pressure. In this case, to maintain the differential pressure between the first and second hydraulic pressures at the predetermined differential pressure, some of the brake fluid discharged from the output port 516 of the electric cylinder 51 is supplied to the servo chamber Rs via the differential pressure control valve 551. Accordingly, the second hydraulic pressure also increases. After the third time point t13, when the piston 512 in the electric cylinder 51 is moved forward in the Za direction, both the first and second hydraulic pressures increase, while the differential pressure between the first and second hydraulic pressures is maintained.

[0069] When the second hydraulic pressure, i.e., the hydraulic pressure in the servo chamber Rs, increases in the master cylinder 31, the hydraulic pressure in the main chamber Rm increases by driving the main piston 43 in accordance with the increase in the hydraulic pressure in the servo chamber Rs. Since, in this case, the brake fluid is directed from the main chamber Rm to the wheel cylinders 11 for the front wheels FL and FR, the pressure in the front wheel cylinders 11 increases. As a result, the frictional braking force of the front wheels increases.

[0070] In the Fig. In the example shown, the target friction braking force increases until a subsequent fourth time point t14. Therefore, in the period between the third time point t13 and the fourth time point t14, both the pressure in the rear wheel cylinder and the pressure in the front wheel cylinder increase, while a pressure difference between the rear and front wheel cylinders is maintained. Accordingly, both the friction braking force of the rear wheel and the friction braking force of the front wheel increase, while a braking force difference between the friction braking force of the rear wheel and the friction braking force of the front wheel is maintained.

[0071] In this way, the brake device 20 can adjust the magnitudes of the frictional braking force of the front wheel and the frictional braking force of the rear wheel by controlling the electric cylinder 51 and the differential pressure control valve 551. If an electric pump were used as the source for generating the hydraulic pressure instead of the electric cylinder 51, an expensive pump such as a gear pump would have to be used instead of an electric pump, or a variety of electromagnetic valves would have to be used to adjust the hydraulic pressure. That is, since the brake device 20 uses the electric cylinder 51, which is less expensive than the electric pump, and includes an electromagnetic valve required for adjusting the hydraulic pressure, the system can be constructed simply and inexpensively.

[0072] During the period between the fourth time point t14 and the next fifth time point t15, the target braking force is constant. Therefore, if the maximum regenerative braking force is constant, the friction braking force of the front wheel and the friction braking force of the rear wheel are also constant. During the friction braking section 50, the position of piston 512 in the electric cylinder 51 is maintained.

[0073] At the fifth time point t15, the target braking force begins to decrease. Therefore, the target friction braking force decreases while the regenerative braking force is maintained. In this case, in the friction brake section 50, the piston 512 in the electric cylinder 51 is moved in the retraction direction Zb, while the differential pressure setpoint for the differential pressure control valve 551 is maintained. The first hydraulic pressure decreases due to the actuation of the electric cylinder 51. If the first hydraulic pressure is greater than the second hydraulic pressure, the brake fluid does not flow from the servo chamber Rs via the check valve 552 into the sixth flow path 58. Therefore, of the first hydraulic pressure and the second hydraulic pressure, only the first hydraulic pressure decreases. Consequently, in the period from the fifth time point t15 to the next sixth time point t16, the pressure in the front wheel cylinder does not decrease, but the pressure in the rear wheel cylinder does.In other words, only the braking force of the rear wheel decreases.

[0074] At the sixth time point t16, the pressure in the front wheel cylinder and the pressure in the rear wheel cylinder are equal. Therefore, in the period after the sixth time point t16, when the first hydraulic pressure decreases according to the movement of the piston 512 of the electric cylinder 51 in the retraction direction Zb, the second hydraulic pressure is slightly higher than the first hydraulic pressure. Consequently, the brake fluid flows from the servo chamber Rs via the check valve 552 to the sixth flow path 58, and thus the second hydraulic pressure also decreases according to the decrease in the first hydraulic pressure. As a result, in the period after the sixth time point t16, both the pressure in the front wheel cylinder and the pressure in the rear wheel cylinder decrease. Consequently, both the friction braking force of the front wheel and the friction braking force of the rear wheel decrease.

[0075] At the seventh point in time, t17, the pressure in both the front and rear wheel cylinders reaches zero. Therefore, after the seventh point in time, t17, the target braking force is only covered by the regenerative braking force. This means that after the seventh point in time, t17, the regenerative braking force decreases in a similar way to the target braking force.

[0076] At an eighth time point t18, the target braking force becomes "0". Therefore, the regenerative braking force also becomes "0".

[0077] In the Fig. In the example shown, a period in which a braking force is generated in the vehicle is defined as the braking period, a period in which the regenerative braking force is generated in the vehicle as the regenerative braking period, and a period in which the frictional braking force is generated in the vehicle as the frictional braking period. In this case, both the braking period and the regenerative braking period are periods between the first time point t11 ​​and the eighth time point t18. That is, the braking time and the regenerative braking time are identical. The frictional braking period, on the other hand, is a period from the second time point t12 to the seventh time point t17. That is, the frictional braking time is shorter than the braking time.

[0078] The friction braking period comprises an initial increase period in which only the friction braking force of the rear wheel is increased, and a second increase period in which both the friction braking force of the front wheel and the friction braking force of the rear wheel are increased following the initial increase period. The friction braking period comprises an initial decrease period in which only the friction braking force of the rear wheel is decreased, and a second decrease period in which both the friction braking force of the front wheel and the friction braking force of the rear wheel are decreased following the initial decrease period.

[0079] The first increase period encompasses the start of the friction braking period and only increases the first hydraulic pressure. The second increase period, however, increases both the first and second hydraulic pressures. The length of the second increase period can be zero, depending on the required braking force. For example, if the required braking force can be covered by the regenerative braking force and the friction braking force of the rear wheel, the length of the second increase period is zero.

[0080] The first reduction period is a period in which only the first hydraulic pressure is reduced until the pressure differential between the first and second hydraulic pressures is eliminated. When the frictional braking force of the front wheel is "0", i.e., when the first hydraulic pressure equals atmospheric pressure, the first hydraulic pressure is reduced to atmospheric pressure. In this case, the duration of the next reduction period is "0". The second reduction period is a period in which both the first and second hydraulic pressures are reduced.

[0081] In the Fig. In the example shown, the first increase period is the period from the second time point t12 to the third time point t13, and the second increase period is the period from the third time point t13 to the fourth time point t14. The first decrease period is the period from the fifth time point t15 to the sixth time point t16, and the second decrease period is the period from the sixth time point t16 to the seventh time point t17.

[0082] In this embodiment, the following effects can also be achieved. (1) A comparative example is considered in which the check valve 552 is not provided. In this comparative example, the second hydraulic pressure can be greater than the first hydraulic pressure when the piston 512 of the electric cylinder 51 is driven in the retraction direction Zb as the friction braking force is reduced. To reduce the second hydraulic pressure, the differential pressure setpoint for the differential pressure control valve 551 is therefore reduced, but depending on the design of the differential pressure control valve 551 and the hydraulic pressure difference between the first and second hydraulic pressures, a delay in opening the differential pressure control valve 551 may occur. In this respect, in the brake device 20 according to the exemplary embodiment, when the second hydraulic pressure is greater than the first hydraulic pressure, the brake fluid flows from the servo chamber Rs via the check valve 552 towards the sixth flow path 58.Therefore, the braking device 20 can prevent the occurrence of a delay when the second hydraulic pressure decreases as the friction braking force decreases. (2) If the target braking force is increased, the brake device 20 can adjust the second hydraulic pressure so that it is less than the first hydraulic pressure, but it cannot adjust the second hydraulic pressure so that it is greater than the first hydraulic pressure. In other words, the brake device 20 can set the pressure in the front wheel cylinder to be less than the pressure in the rear wheel cylinder, but it cannot set the pressure in the front wheel cylinder to be greater than the pressure in the rear wheel cylinder. However, the vehicle has a regenerative braking device 60 that is capable of generating a regenerative braking force on the front wheels FL and FR. Therefore, the brake device 20 can make the front wheel braking force greater than the rear wheel braking force. <modifikationen>

[0083] The exemplary embodiment can be modified and implemented as follows. The exemplary embodiment and the following modifications can be combined within a technically consistent range.

[0084] The distribution ratio between regenerative braking force and friction braking force can be changed as needed. For example, when braking is required, both the regenerative braking force and the friction braking force can be increased, instead of only the regenerative braking force.

[0085] The friction brake section 50 must not contain the check valve 552. In this case, when the friction brake force is reduced, the control device 80 preferably changes the differential pressure setpoint for the differential pressure control valve 551 to avoid a condition in which the second hydraulic pressure is excessively greater than the first hydraulic pressure ( ).

[0086] In the exemplary embodiment above, the first flow path 331 is connected to the wheel cylinders 11 for the front wheels FL and FR, and the sixth flow path 58 is connected to the wheel cylinders 11 for the rear wheels RL and RR. In a modification, the first flow path 331 can be connected to the wheel cylinders 11 for the rear wheels RL and RR, and the sixth flow path 58 to the wheel cylinders 11 for the front wheels FL and FR. In this case, the control device 80 can adjust the wheel cylinder pressure so that the pressure in the front wheel is greater than the pressure in the rear wheel. Therefore, the control device 80 can adjust the friction braking force so that the friction braking force of the front wheel is greater than that of the rear wheel.

[0087] The vehicle can include the regenerative braking device 60 for the rear wheels RL and RR, which generates a regenerative braking force on the rear wheels RL and RR.

[0088] The vehicle can be equipped without the regenerative braking device 60. Even in this case, the braking device 20 can adjust the friction braking force of the front wheel and the friction braking force of the rear wheel by controlling the electric cylinder 51 and the differential pressure control valve 551.

[0089] The control unit 80 is not limited to a device containing a CPU and a ROM and performing software processing. That is to say, the control unit 80 can have any of the following configurations (a) to (c). (a) The control device 80 contains one or more processors that perform various types of processing in accordance with a computer program. The processor comprises a CPU and memory, such as RAM and ROM. The memory stores program code or an instruction configured to cause the CPU to perform processing. The memory, i.e., a computer-readable medium, includes any available medium accessible to a general-purpose or specialized computer. (b) The control device 80 comprises one or more dedicated hardware circuits that perform various types of processing. Examples of dedicated hardware circuits are application-specific integrated circuits, i.e., ASICs and FPGAs. ASIC is an abbreviation for "Application Specific Integrated Circuit" and FPGA is an abbreviation for "Field Programmable Gate Array". (c) The control device 80 comprises a processor that performs some of the different processing operations in accordance with a computer program and a special hardware circuit that performs the rest of the different processing operations. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP 2019-137202A

[0005] < / modifikationen> < / bremsverarbeitung> < / bremsenstellglied> < / reibungsbremsabschnitt> < / haupteinrichtung>

Claims

[1] Brake device (20) to be fitted to a vehicle having a first wheel cylinder, a second wheel cylinder, a first wheel (FL, FR) that generates a friction braking force corresponding to a hydraulic pressure in the first wheel cylinder, and a second wheel (RL, RR) that generates a friction braking force corresponding to a hydraulic pressure in the second wheel cylinder, wherein the brake device (20) comprises: an electric cylinder (51) comprising an electric motor (513) as a power source and an output port (516) for dispensing brake fluid having a hydraulic pressure equivalent to being driven by the electric motor (513); a master cylinder (31) having a main piston (43) defining a servo chamber (Rs) and a main chamber (Rm), and configured such that the brake fluid flows out of the main chamber (Rm) by a movement of the main piston (43) which is accompanied by an increase in hydraulic pressure in the servo chamber (Rs) and the brake fluid flows into the main chamber (Rm) by a movement of the main piston (43) which is accompanied by a decrease in hydraulic pressure in the servo chamber (Rs); a first fluid path (331) connecting the main chamber (Rm) and the first wheel cylinder; a second fluid path (58) connecting the outlet port and the second wheel cylinder; a third fluid passage (55) connecting the second fluid path (58) and the servo chamber (Rs); and a differential pressure control valve (551) provided in the third fluid path (55) and configured to adjust a differential pressure between a first hydraulic pressure, which is a hydraulic pressure in the second fluid passage (58), and a second hydraulic pressure, which is the hydraulic pressure in the servo chamber (Rs). [2] Brake device (20) according to claim 1, further comprising: a check valve (552) which is provided in parallel to the differential pressure control valve (551), wherein The check valve (552) allows brake fluid to flow from the servo chamber (Rs) towards the second fluid path (58) and restricts brake fluid flow from the second fluid path (58) towards the servo chamber (Rs). [3] Brake device (20) according to claim 1 or 2, further comprising: a control device (80) configured to control the electric cylinder (51) and the differential pressure control valve (551), wherein The control device (80) adjusts the first hydraulic pressure by controlling the electric cylinder (51), and adjusts the second hydraulic pressure to be equal to or less than the first hydraulic pressure by controlling the differential pressure control valve (551). [4] Brake device (20) according to claim 3, wherein the first wheel (FL, FR) is a front wheel, the first wheel cylinder is a wheel cylinder for the front wheel, the second wheel (RL, RR) is a rear wheel and the second wheel cylinder is a wheel cylinder for the rear wheel and The control device (80) adjusts the friction braking force generated at the rear wheel by adjusting the first hydraulic pressure, and adjusts the friction braking force generated at the front wheel by adjusting the second hydraulic pressure. [5] Braking device (20) according to claim 4, wherein the vehicle has a regenerative braking device (60) which generates a regenerative braking force at the front wheel, and the control device (80) adjusts the second hydraulic pressure to be equal to or less than the first hydraulic pressure when the regeneration braking force is generated at the front wheel. [6] Brake device (20) according to claim 3, wherein In a situation where a target friction braking force, which is a target value of the friction braking forces for the vehicle, is increased, the control device (80) increases the first hydraulic pressure while maintaining a condition in which the second hydraulic pressure is less than the first hydraulic pressure. [7] Braking device (20) according to claim 5, wherein the control unit (80) only the first hydraulic pressure is increased from the first hydraulic pressure and the second hydraulic pressure when the friction braking forces are increased in a situation where the differential pressure between the first hydraulic pressure and the second hydraulic pressure is equal to or less than a predetermined differential pressure, and Both the first hydraulic pressure and the second hydraulic pressure are increased when the friction braking force is increased in a situation where the differential pressure is greater than the predetermined differential pressure. [8] Braking device (20) according to claim 3, wherein in a situation where a target friction braking force, which is a target value of the friction braking forces for the vehicle, is reduced, the control device (80) reduces only the first hydraulic pressure from the first hydraulic pressure and the second hydraulic pressure if the first hydraulic pressure is greater than the second hydraulic pressure, and reduces both the first hydraulic pressure and the second hydraulic pressure if the first hydraulic pressure is equal to or less than the second hydraulic pressure.

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