Braking control device

Abstract

To provide a braking control device that can shorten a time elapsing after a driver starts to operate a brake pedal until braking force is generated in a wheel.SOLUTION: An upstream-side control part 50 of a braking control device 30, when a detected value by a first stroke sensor 43 is above a braking determined value, executes braking processing in which brake liquid is supplied from a liquid chamber Re to a wheel cylinder 20 by moving a slave piston 492 in an advancing direction Za, and pre-charge processing in which the slave piston 492 is moved in the advancing direction Za from an initial position, before executing the braking processing.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a brake control device that generates braking force on vehicle wheels by adjusting hydraulic pressure in wheel cylinders. [Background technology]

[0002] Patent Document 1 describes an example of a braking control device that includes a stroke sensor that detects the amount of brake pedal operation, an electric cylinder that applies braking force to the wheels by supplying brake fluid to the wheel cylinder, and a control unit that controls the electric cylinder.

[0003] In the braking control device, the electric cylinder includes a slave cylinder having a fluid chamber filled with brake fluid, a piston that moves forward and backward within the slave cylinder, and an electric motor that drives the piston. The fluid chamber has an input port connected to a reserve tank and an output port connected to a wheel cylinder. When the brake pedal is not operated, the piston is located in an initial position, which is the most retracted position. When the piston is located in the initial position, the input port is open. In other words, when the piston is located in the initial position, the fluid chamber is connected to the reserve tank.

[0004] When the brake pedal is operated, the piston moves forward from its initial position. Even though the piston starts to move forward from its initial position, brake fluid is not supplied from the fluid chamber to the wheel cylinder while the input port is open. As a result, no braking force is generated at the wheel. After that, as the piston continues to move forward, it closes the input port, and brake fluid is supplied from the fluid chamber to the wheel cylinder in response to the piston's forward movement. As a result, braking force is generated at the wheel. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-188037 Summary of the Invention [Problem to be solved by the invention]

[0006] In the electric cylinder described above, there may be a delay between when the driver starts to operate the brake pedal and when braking force is actually generated at the wheels. [Means for solving the problem]

[0007] The means for solving the above problems and their effects will be described below. The brake control device that solves the above problem is a brake control device that generates a braking force on a wheel of a vehicle by adjusting the hydraulic pressure in a wheel cylinder, and includes a reserve tank that stores brake fluid, a slave cylinder having a fluid chamber defined therein, a slave piston that is slidable within the slave cylinder, and an electric motor that drives the slave piston, and supplies brake fluid from the fluid chamber to the wheel cylinder by moving the slave piston in a forward direction, a sensor that detects parameters that change in response to the driver's brake operation, and a control unit that controls the electric cylinder, An input port is formed in the slave cylinder to connect the fluid chamber with the reserve tank, and the slave piston opens the input port when located in an initial position and closes the input port by moving in the forward direction from the initial position, and the control unit performs a braking process to supply brake fluid from the fluid chamber to the wheel cylinder by moving the slave piston in the forward direction when the detection value of the sensor is equal to or greater than a braking judgment value, and a pre-charge process to move the slave piston in the forward direction from the initial position before performing the braking process.

[0008] The brake control device performs a pre-charge process before performing a braking process. This allows the brake control device to start the braking process with the slave piston positioned further forward than the initial position. Therefore, the brake control device can shorten the period from when the driver starts braking until braking force is generated at the wheels. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of a braking control device. [Figure 2] FIG. 2 is a flowchart illustrating the flow of processing executed by the upstream control unit to control the electric cylinder. [Figure 3] 3(a) to 3(c) are time charts when the driver operates the brake operating member. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of a braking control device will be described with reference to the drawings. <Vehicle> As shown in FIG. 1, the vehicle includes a plurality of wheels 10 (11-14), a plurality of wheel cylinders 20 (21-24) corresponding to the plurality of wheels 10, and a braking control device 30 that generates braking force at the wheels 10 by adjusting the hydraulic pressure of the plurality of wheel cylinders 20.

[0011] <Brake control device> The braking control device 30 includes an upstream pressure device 40, a downstream pressure device 60, a first fluid path 81, and a second fluid path .

[0012] <Upstream pressure device> The upstream pressurizing device 40 is connected to the wheel cylinders 21 and 22 of the front wheels 11 and 12 via a first fluid passage 81. Similarly, the upstream pressurizing device 40 is connected to the wheel cylinders 23 and 24 of the rear wheels 13 and 14 via a second fluid passage 82.

[0013] The upstream pressurizing device 40 includes a reserve tank 41, a brake operating member 42, a first stroke sensor 43, and a stroke simulator 44. The upstream pressurizing device 40 also includes a master cylinder 45, a third fluid path 461, a fourth fluid path 462, a first control valve 471, a second control valve 472, a reaction pressure sensor 48, an electric cylinder 49, and an upstream control unit 50.

[0014] The reserve tank 41 is a tank that stores brake fluid. The brake operation member 42 is, for example, a brake pedal. The brake operation member 42 is operated by the driver when the driver wishes to brake the vehicle. The first stroke sensor 43 detects the amount of operation of the brake operation member 42 by the driver. The amount of operation corresponds to an example of a "parameter" that changes in accordance with the driver's brake operation, and the first stroke sensor 43 corresponds to an example of a "first sensor." The stroke simulator 44 generates a reaction force in accordance with the amount of operation of the brake operation member 42.

[0015] <Master cylinder> Master cylinder 45 includes a main cylinder 451, a cover cylinder 452, a master piston 453, an input piston 454, a master spring 456, and an input spring 457. In the following description, the left side of master cylinder 45 in FIG. 1 is the front side, and the right side of master cylinder 45 in FIG. 1 is the rear side.

[0016] The interior of the main cylinder 451 is divided into a master chamber Rm, a first fluid chamber R1, and a servo chamber Rs by a master piston 453. The master chamber Rm is located near the front end of the master cylinder 45. The first fluid chamber R1 is located rearward of the master chamber Rm. The servo chamber Rs is located rearward of the first fluid chamber R1. A first fluid path 81 is connected to the master chamber Rm. A second fluid path 82 is connected to the servo chamber Rs.

[0017] A second fluid chamber R2 and a third fluid chamber R3 are defined inside the cover cylinder 452 by an input piston 454. In the master cylinder 45, the second fluid chamber R2 is located rearward of the servo chamber Rs. The third fluid chamber R3 is located rearward of the second fluid chamber R2. The second fluid chamber R2 is connected to the first fluid chamber R1 by a third fluid path 461. The second fluid chamber R2 is connected to the reserve tank 41 via the third fluid path 461 and a fourth fluid path 462 connected to the third fluid path 461. A reaction pressure sensor 48 is provided in the third fluid path 461. The reaction pressure sensor 48 detects the reaction pressure, which is the fluid pressure in the first fluid chamber R1.

[0018] The master piston 453 is housed in the master cylinder 45 in contact with the inner wall of the main cylinder 451. Therefore, when the master piston 453 moves forward or rearward, the master piston 453 slides against the inner wall of the main cylinder 451. The rear end of the master piston 453 extends to the second fluid chamber R2.

[0019] The input piston 454 is housed in the master cylinder 45 in contact with the inner wall of the cover cylinder 452. Therefore, when the input piston 454 moves forward or rearward, the input piston 454 slides against the inner wall of the cover cylinder 452. In the second fluid chamber R2, a gap exists between the tip of the input piston 454 and the rear end of the master piston 453. The rear end of the input piston 454 is connected to the brake operating member 42. The input piston 454 moves forward in accordance with the amount of operation of the brake operating member 42.

[0020] The master spring 456 is disposed in the master chamber Rm of the main cylinder 451. The master spring 456 biases the master piston 453 rearward. In other words, the master spring 456 is compressed when the master piston 453 moves forward.

[0021] The input spring 457 is disposed in the second fluid chamber R2 of the cover cylinder 452. The input spring 457 biases the input piston 454 rearward. That is, the input spring 457 is compressed when the input piston 454 moves forward.

[0022] In the master cylinder 45, the master chamber Rm is connected to the reserve tank 41. More specifically, a portion of the master chamber Rm near the rear end is connected to the reserve tank 41 via a port formed in the main cylinder 451. When the master piston 453 is located in its most retracted initial position, the port is opened, and the master chamber Rm is hydraulically connected to the reserve tank 41. When the master piston 453 moves forward from the initial position, the port is closed, and the master chamber Rm and the reserve tank 41 are hydraulically isolated from each other. In this state, brake fluid flows out of the master chamber Rm into the first fluid path 81 as the master piston 453 moves forward.

[0023] The third fluid chamber R3 is always connected to the reserve tank 41. Therefore, when the input piston 454 moves forward, brake fluid flows into the third fluid chamber R3 from the reserve tank 41. On the other hand, when the input piston 454 moves rearward, brake fluid flows out from the third fluid chamber R3 to the reserve tank 41.

[0024] The first control valve 471 is a normally closed solenoid valve, and the second control valve 472 is a normally open solenoid valve. The first control valve 471 is provided on the third fluid path 461 closer to the second fluid chamber R2 than the connection point between the fourth fluid path 462 and the third fluid path 461. The second control valve 472 is provided on the fourth fluid path 462 near the connection point between the third fluid path 461 and the third fluid path 461. When the electric cylinder 49 is operating normally, the first control valve 471 is opened, and the second control valve 472 is closed.

[0025] <Electric cylinder> The electric cylinder 49 has a slave cylinder 491, a slave piston 492 that can slide within the slave cylinder 491, an electric motor 493 that drives the slave piston 492, and a direct-acting conversion mechanism 494 that converts the rotation of the output shaft of the electric motor 493 into direct-acting of the slave piston 492.

[0026] A fluid chamber Re into which brake fluid is introduced is defined by a slave piston 492 inside the slave cylinder 491. An electric motor 493 is capable of generating a driving force that slides the slave piston 492 inside the slave cylinder 491. Therefore, the position of the slave piston 492 inside the slave cylinder 491 is changed by the electric motor 493. The volume of the fluid chamber Re changes in accordance with the change in the position of the slave piston 492. In the following description, the movement direction of the slave piston 492 that reduces the volume of the fluid chamber Re is referred to as the "forward direction Za," and the movement direction of the slave piston 492 opposite the forward direction Za that increases the volume of the fluid chamber Re is referred to as the "rearward direction Zb." The position of the slave piston 492 where the volume of the fluid chamber Re is maximum is referred to as the "initial position." In other words, the initial position is the position where the slave piston 492 has moved the furthest in the rearward direction Zb.

[0027] The slave cylinder 491 has two ports, an input port 495 and an output port 496, which communicate between the fluid chamber Re and the outside. The slave piston 492 has a through hole 497. The through hole 497 is formed at a position where it communicates with the input port 495 when the slave piston 492 is located at the initial position. As a result, when the slave piston 492 is located at the initial position, the fluid chamber Re of the slave cylinder 491 is connected to the fourth fluid path 462 via the input port 495 and the through hole 497. In other words, the fluid chamber Re of the slave cylinder 491 is connected to the reserve tank 41 via the input port 495 and the through hole 497. The input port 495 is open when the slave piston 492 is located at the initial position, and is closed by the slave piston 492 when the slave piston 492 moves a predetermined amount in the forward direction Za from the initial position. The predetermined amount is the amount by which the slave piston 492 has moved in the forward direction Za from the initial position to a position where the input port 495 and the through-hole 497 are not in communication with each other. On the other hand, the output port 496 of the slave cylinder 491 is connected to the second fluid path 82. The output port 496 is always open, regardless of the position of the slave piston 492.

[0028] <Upstream control section> The upstream control unit 50 is an electronic control device that includes one or more processors that execute various controls and a memory that stores control programs and data. The upstream control unit 50 corresponds to the "first control unit." The upstream control unit 50 can communicate with the downstream control unit 70, which will be described later, via an in-vehicle communication network. The upstream control unit 50 controls the electric cylinder 49, the first control valve 471, and the second control valve 472 based on detection signals input from various sensors, such as the first stroke sensor 43 and the reaction force pressure sensor 48.

[0029] When the upstream pressurizing device 40 is normal, the upstream control unit 50 opens the first control valve 471 and closes the second control valve 472. In this state, the second fluid chamber R2 is hydraulically connected to the stroke simulator 44 and is hydraulically cut off from the reserve tank 41. When the brake operating member 42 is operated in this state, the stroke simulator 44 transmits a pedal feeling to the brake operating member 42.

[0030] The upstream control unit 50 acquires a first detection value S1 indicating the amount of operation of the brake operation member 42 based on the detection signal of the first stroke sensor 43. Subsequently, the upstream control unit 50 determines whether the first detection value S1 is equal to or greater than a braking determination value SBth. The braking determination value SBth is a value for determining whether the user has operated the brake operation member 42. If the first detection value S1 is equal to or greater than the braking determination value SBth, that is, if the upstream control unit 50 determines that the user has operated the brake operation member 42, the upstream control unit 50 executes a braking process to supply brake fluid to the wheel cylinder 20 by driving the electric cylinder 49. On the other hand, if the first detection value S1 is less than the braking determination value SBth, that is, if the upstream control unit 50 determines that the user has not operated the brake operation member 42, the upstream control unit 50 does not execute the braking process.

[0031] In the braking process, the upstream control unit 50 calculates a target value of the hydraulic pressure in the wheel cylinder 20 based on the first detection value S1 of the first stroke sensor 43. At this time, the upstream control unit 50 may calculate the target value of the hydraulic pressure in the wheel cylinder 20 by taking into account the reaction pressure, which is the detection value of the reaction pressure sensor 48, in addition to the first detection value S1. The upstream control unit 50 then moves the slave piston 492 of the electric cylinder 49 in the forward direction Za so that the hydraulic pressure in the wheel cylinder 20 reaches the target value. In this way, the upstream control unit 50 causes brake fluid to flow from the fluid chamber Re of the electric cylinder 49 through the output port 496. The brake fluid flowing out of the fluid chamber Re is supplied to the second hydraulic passage 82 and the servo chamber Rs. When brake fluid is supplied to the servo chamber Rs, the master piston 453 moves forward. This causes brake fluid to flow from the master chamber Rm to the first hydraulic passage 81. In this way, the upstream control unit 50 controls the electric cylinder 49, the first control valve 471, and the second control valve 472 to supply brake fluid to the first fluid path 81 and the second fluid path 82. As a result, the fluid pressure in the wheel cylinder 20 increases, and braking force is generated on the wheel 10. In other words, the electric cylinder 49 can be said to be an "electric pressure device" that can electrically increase the fluid pressure in the wheel cylinder 20.

[0032] The upstream control unit 50 also reduces noise components contained in the detection signal of the first stroke sensor 43 by applying low-pass filtering to the detection signal of the first stroke sensor 43. The low-pass filtering may use a filter that cuts out high-frequency components, or may use a moving average method. In the following description, the detection signal of the first stroke sensor 43 before low-pass filtering is referred to as the first raw value SR1, and the detection signal of the first stroke sensor 43 after low-pass filtering is referred to as the first filtered value SF1. In other words, the first detection value S1 in this embodiment includes the first raw value SR1 and the first filtered value SF1.

[0033] <Downstream pressure device> The downstream pressure device 60 is a unit that can individually adjust the pressure in the plurality of wheel cylinders 20. The downstream pressure device 60 includes a front wheel pressure unit 61, a rear wheel pressure unit 62, a second stroke sensor 63, and a downstream control unit 70.

[0034] The front-wheel pressure unit 61 generates braking force on the front wheels 11, 12 by adjusting the hydraulic pressure in the wheel cylinders 21, 22 of the front wheels 11, 12. The rear-wheel pressure unit 62 generates braking force on the rear wheels 13, 14 by adjusting the hydraulic pressure in the wheel cylinders 23, 24 of the rear wheels 13, 14. The second stroke sensor 63 is a sensor that detects the amount of operation of the brake operating member 42, similar to the first stroke sensor 43, but is a separate sensor from the first stroke sensor 43. The second stroke sensor 63 corresponds to the "second sensor." The detection signal of the second stroke sensor 63 is input to the downstream control unit 70 but not to the upstream control unit 50.

[0035] The downstream control unit 70 is also configured as an electronic control device, similar to the upstream control unit 50. The downstream control unit 70 corresponds to the "second control unit." The downstream control unit 70 controls the front wheel side pressurizing unit 61 and the rear wheel side pressurizing unit 62 based on the second detection value S2 of the second stroke sensor 63.

[0036] The downstream control unit 70 acquires a second detection value S2 indicating the amount of operation of the brake operating member 42 based on the detection signal of the second stroke sensor 63. The downstream control unit 70 executes an auxiliary braking process, for example, when the second detection value S2 is equal to or greater than the braking determination value SBth and the electric cylinder 49 is not functioning normally. The auxiliary braking process is a process for controlling the front-wheel pressurizing unit 61 and the rear-wheel pressurizing unit 62 to adjust the hydraulic pressure in the wheel cylinders 21 to 24. In the auxiliary braking process, the downstream control unit 70 calculates a target value for the hydraulic pressure in the wheel cylinder 20 based on at least the second detection value S2. Then, the downstream control unit 70 controls the front-wheel pressurizing unit 61 and the rear-wheel pressurizing unit 62 so that the hydraulic pressure in the wheel cylinder 20 becomes the target value.

[0037] The downstream control unit 70 also applies low-pass filtering to the detection signal of the second stroke sensor 63 to reduce noise components contained in the detection signal of the second stroke sensor 63. In the following description, the detection signal of the second stroke sensor 63 after low-pass filtering is referred to as the second filtered value SF2. In this embodiment, the second detection value S2 includes the second filtered value SF2. The downstream control unit 70 transmits the second filtered value SF2 to the upstream control unit 50 at predetermined intervals, regardless of whether or not the auxiliary braking process is executed.

[0038] <Precharge processing in the upstream control unit> As described above, in the electric cylinder 49, the input port 495 is open when the slave piston 492 is located at the initial position. The input port 495 is closed by the slave piston 492 when the slave piston 492 moves in the forward direction Za from the initial position. The amount of brake fluid flowing from the fluid chamber Re to the second fluid path 82 when the slave piston 492 moves in the forward direction Za with the input port 495 open is less than the amount of brake fluid flowing from the fluid chamber Re to the second fluid path 82 when the slave piston 492 moves in the forward direction Za with the input port 495 closed. In other words, when the slave piston 492 moves forward with the input port 495 open, the increase in hydraulic pressure in the wheel cylinder 20 is small, and therefore the braking force generated on the wheel 10 is small. Therefore, due to the structure of the electric cylinder 49, when the slave piston 492 moves forward from the initial position after the driver starts operating the brake operating member 42, there is a possibility that a delay occurs before a braking force is generated on the wheel 10.

[0039] Therefore, in this embodiment, before executing the braking process, the upstream control unit 50 executes a pre-charge process in which the slave piston 492 is moved in the forward direction Za from its initial position. In the pre-charge process, the upstream control unit 50 moves the slave piston 492 in the forward direction Za until it closes the input port 495. Whether the slave piston 492 has moved to a position where it closes the input port 495 may be determined based on, for example, a signal detected by a rotation angle sensor (not shown) that detects the rotation angle of the electric motor 493. Alternatively, this may be determined based on a signal detected by a stroke sensor (not shown) that detects the stroke amount of the slave piston 492.

[0040] The upstream control unit 50 uses the first raw value SR1 before low-pass filtering to determine whether to perform the pre-charge process, and the first filtered value SF1 after low-pass filtering to determine whether to perform the braking process. In other words, the upstream control unit 50 uses the first raw value SR1, which is likely to reflect the driver's tendency to brake, to determine whether to perform the pre-charge process, thereby enabling the pre-charge process to be performed early. Furthermore, the upstream control unit 50 uses the first filtered value SF1, in which noise components are reduced, to determine whether to perform the braking process with high accuracy.

[0041] Furthermore, the upstream control unit 50 uses only the first detection value S1 of the first stroke sensor 43 to determine whether to perform the pre-charge process, and uses the first detection value S1 of the first stroke sensor 43 and the second detection value S2 of the second stroke sensor 63 to determine whether to perform the braking process. In other words, the upstream control unit 50 uses only the first detection value S1, which is acquired at a shorter interval than the second detection value S2, to determine whether to perform the pre-charge process, thereby enabling the pre-charge process to be performed early. Furthermore, the upstream control unit 50 uses both the first detection value S1 and the second detection value S2 to determine whether to perform the braking process, thereby accurately determining whether to perform the braking process.

[0042] As described above, the upstream control unit 50 executes the pre-charge process when the first raw value SR1 is equal to or greater than the pre-charge determination value SCth. On the other hand, the upstream control unit 50 executes the braking process when both the first filter value SF1 and the second filter value SF2 are equal to or greater than the braking determination value SBth. In this embodiment, the pre-charge determination value SCth is a value smaller than the braking determination value SBth. When the first raw value SR1 is equal to or greater than the pre-charge determination value SCth, it can be determined that the driver has started braking, and therefore the upstream control unit 50 executes the pre-charge process. On the other hand, when both the first filter value SF1 and the second filter value SF2 are equal to or greater than the braking determination value SBth, it can be determined that the driver is requesting deceleration of the vehicle, and therefore the upstream control unit 50 executes the braking process.

[0043] The first stroke sensor 43 outputs a detection signal containing noise even when the driver is not operating the brake operating member 42. For this reason, it is preferable that the upstream control unit 50 not execute the precharge process when the driver is not operating the brake operating member 42. Therefore, it is preferable that the precharge determination value SCth is not too small. On the other hand, if the precharge determination value SCth is equal to or greater than the braking determination value SBth, the precharge process is not executed before the braking process. For this reason, the precharge determination value SCth is set to a value smaller than the braking determination value SBth.

[0044] Furthermore, the driver may cancel the operation of the brake operation member 42 immediately after starting to operate the brake operation member 42. That is, after the first raw value SR1 becomes equal to or greater than the pre-charge determination value SCth, the first raw value SR1 may become less than the pre-charge determination value SCth without the first filter value SF1 becoming equal to or greater than the braking determination value SBth. In this case, it is preferable that the upstream control unit 50 executes a return process to return the slave piston 492 to its initial position rather than continuing the pre-charge process. However, even if the driver does not cancel the operation of the brake operation member 42, the first raw value SR1 may become less than the pre-charge determination value SCth due to the influence of noise. In this case, unlike when the driver cancels the operation of the brake operation member 42, it is preferable not to execute the return process.

[0045] Therefore, it is preferable that the upstream control unit 50 does not immediately execute the restoration process when the first raw value SR1 becomes less than the precharge determination value SCth after starting the precharge process. For example, the upstream control unit 50 may execute the restoration process when the first raw value SR1 remains less than the precharge determination value SCth for a predetermined determination period after starting the precharge process.

[0046] Next, the flow of the process executed by the upstream control unit 50 will be described with reference to Fig. 2. This process is repeatedly executed at every predetermined control period. As shown in FIG. 2, the upstream control unit 50 acquires a first raw value SR1 based on the detection signal of the first stroke sensor 43 (S11). Next, the upstream control unit 50 calculates a first filter value SF1 based on the detection signal of the first stroke sensor 43 (S12). Thereafter, the upstream control unit 50 acquires a second filter value SF2 transmitted from the downstream control unit 70 at predetermined communication intervals (S13). The second filter value SF2 is a value calculated by the downstream control unit 70 based on the detection signal of the second stroke sensor 63. The execution period of this process by the upstream control unit 50 is shorter than the communication period of the second filter value SF2 by the downstream control unit 70. Therefore, even if the acquired first filter value SF1 changes between this process in one execution period and this process in the next execution period, the acquired second filter value SF2 may not change.

[0047] Then, the upstream control unit 50 determines whether both the first filter value SF1 and the second filter value SF2 are equal to or greater than the braking determination value SBth (S14). If at least one of the first filter value SF1 and the second filter value SF2 is less than the braking determination value SBth (S14: NO), the upstream control unit 50 determines whether the first raw value SR1 is equal to or greater than the pre-charge determination value SCth (S15). If the first raw value SR1 is less than the pre-charge determination value SCth (S15: NO), the upstream control unit 50 temporarily ends this process.

[0048] On the other hand, if the first raw value SR1 is equal to or greater than the precharge determination value SCth (S15: YES), the upstream control unit 50 executes the precharge process (S16). That is, the upstream control unit 50 moves the slave piston 492 of the electric cylinder 49 from the initial position in the forward direction Za, thereby causing the slave piston 492 to close the input port 495. Thereafter, the upstream control unit 50 ends this process.

[0049] In step S14, if both the first filter value SF1 and the second filter value SF2 are equal to or greater than the braking determination value SBth (S14: YES), the upstream control unit 50 executes braking processing (S15). That is, the upstream control unit 50 supplies brake fluid to the wheel cylinder 20 by moving the slave piston 492 in the forward direction Za based on the target value of the hydraulic pressure of the wheel cylinder 20. Thereafter, the upstream control unit 50 ends this processing.

[0050] <Actions and Effects of This Embodiment> 3(a), (b), and (c), the transitions of the detected value, the position of the slave piston 492 of the electric cylinder 49, and the hydraulic pressure in the wheel cylinder 20 when the driver operates the brake operating member 42 will be described in this embodiment and the comparative example. The transition of the second filter value SF2 shown in FIG. 3(a) is the transition of the second filter value SF2 acquired by the upstream control unit 50. In addition, in FIGS. 3(b) and 3(c), the transitions of the position of the slave piston 492 and the hydraulic pressure in the wheel cylinder 20 in the embodiment are shown by solid lines, and the transitions of the position of the slave piston 492 and the hydraulic pressure in the wheel cylinder 20 in the comparative example are shown by dashed dotted lines.

[0051] 3, when the driver starts operating the brake operating member 42 at a first timing t11, the first raw value SR1, the first filtered value SF1, and the second filtered value SF2 gradually increase. Because the first raw value SR1 is a value before low-pass filtering, and the first filtered value SF1 is a value after low-pass filtering, the first filtered value SF1 increases with a delay relative to the first raw value SR1. Furthermore, the second filtered value SF2 is transmitted from the downstream control unit 70 at predetermined communication intervals after being subjected to low-pass filtering in the downstream control unit 70. Therefore, the second filtered value SF2 that can be acquired by the upstream control unit 50 increases in a stepwise manner, similar to the first filtered value SF1.

[0052] At the second timing t12 when the first raw value SR1 becomes equal to or greater than the pre-charge determination value SCth, it is determined that the driver may have started braking, and the pre-charge process is initiated. Therefore, at the second timing t12, the slave piston 492 of the electric cylinder 49 starts to move in the forward direction Za from the initial position. The slave piston 492 continues to move in the forward direction Za until it blocks the input port 495. In other words, since the slave piston 492 does not move in the forward direction Za while the input port 495 is blocked, the hydraulic pressure in the wheel cylinder 20 does not increase during the execution of the pre-charge process. Note that at the second timing t12, the first filter value SF1 and the second filter value SF2 are less than the pre-charge determination value SCth.

[0053] At the third timing t13, the first filter value SF1 becomes equal to or greater than the braking determination value SBth. However, at the third timing t13, the second filter value SF2 acquired by the upstream control unit 50 is less than the braking determination value SBth. Therefore, the braking process is not started.

[0054] At the fourth timing t14, the second filter value SF2 acquired by the upstream control unit 50 becomes equal to or greater than the braking determination value SBth. That is, at the fourth timing t14, both the first filter value SF1 and the second filter value SF2 become equal to or greater than the braking determination value SBth. Since it is determined that the driver is requesting deceleration of the vehicle, braking processing is initiated at the fourth timing t14. That is, the slave piston 492 is driven in the forward direction Za based on the target value of the hydraulic pressure in the wheel cylinder 20. As a result, as the slave piston 492 moves forward, the hydraulic pressure in the wheel cylinder 20 increases.

[0055] Here, a comparative example will be described in which the braking process is performed from the fourth timing t14 without performing the pre-charge process. In the comparative example, as shown by the dashed line in FIGS. 3(b) and 3(c), at the fourth timing t14, the slave piston 492 begins to move in the forward direction Za from the initial position. Then, at the fifth timing t15, the slave piston 492 closes the input port 495. Therefore, the hydraulic pressure in the wheel cylinder 20 begins to increase after the fifth timing t15. In other words, this embodiment can increase the hydraulic pressure in the wheel cylinder 20 more quickly than the comparative example during the period from the fourth timing t14 to the fifth timing t15.

[0056] As described above, the upstream control unit 50 of this embodiment performs a precharge process before executing the braking process, thereby shortening the time from when the driver starts operating the brake operating member 42 to when a braking force is generated on the wheel 10.

[0057] This embodiment can further provide the following effects. (1) In the braking process, the upstream control unit 50 advances the slave piston 492 until it closes the input port 495. This allows the upstream control unit 50 to quickly increase the hydraulic pressure in the wheel cylinder 20 after the conditions for starting the braking process are met. On the other hand, in the pre-charge process, the upstream control unit 50 does not allow the slave piston 492 to continue advancing after it closes the input port 495. This allows the upstream control unit 50 to suppress an increase in the hydraulic pressure in the wheel cylinder 20 before the braking process starts. In other words, the upstream control unit 50 can suppress the generation of braking force at the wheel 10 before the braking process starts.

[0058] (2) When the first filter value SF1 is used to determine whether or not to perform the pre-charge process, the timing at which the condition for executing the pre-charge process is satisfied may be delayed. In this case, the period from when the condition for executing the pre-charge process is satisfied until the condition for executing the braking process is satisfied is shortened. Therefore, when the driver operates the brake operating member 42 at a high speed, the braking process may be initiated before the input port 495 is closed due to the movement of the slave piston 492 caused by the execution of the pre-charge process. In this regard, the upstream control unit 50 of this embodiment uses the first raw value SR1, which changes more quickly than the first filter value SF1, although it contains noise, to determine whether or not to perform the pre-charge process. Therefore, the upstream control unit 50 can ensure the time required to execute the pre-charge process.

[0059] (3) The upstream control unit 50 uses the first filter value SF1 to determine whether to perform braking processing. This allows the upstream control unit 50 to accurately determine whether to perform braking processing. Furthermore, the upstream control unit 50 also uses the first filter value SF1 to calculate the target value of the hydraulic pressure of the wheel cylinder 20 during braking processing. This allows the upstream control unit 50 to accurately perform braking processing.

[0060] (4) The upstream control unit 50 acquires the first detection value S1 based on the detection signal of the first stroke sensor 43, and acquires the second detection value S2 through communication with the downstream control unit 70. The acquisition interval of the first detection value S1 is shorter than the acquisition interval of the second detection value S2. The upstream control unit 50 uses the first detection value S1, which is acquired at a shorter interval than the second detection value S2, to determine whether to perform the precharge process. This allows the upstream control unit 50 to ensure sufficient time to perform the precharge process.

[0061] (5) The upstream control unit 50 determines whether to execute the pre-charge process using the first detection value S1 of the first stroke sensor 43, which has high responsiveness to the brake operation by the driver. Therefore, the upstream control unit 50 can start the pre-charge process earlier than when the upstream control unit 50 determines whether to execute the pre-charge process using the detection value of the reaction force pressure sensor 48, which tends to change with a delay in response to changes in the amount of operation of the brake operating member 42.

[0062] <Example of change> This embodiment can be modified as follows: This embodiment and the following modifications can be combined and implemented within the scope of technical compatibility.

[0063] The vehicle may be a vehicle capable of cooperatively controlling the regenerative braking force generated by the motor generator and the hydraulic braking force corresponding to the hydraulic pressure in the wheel cylinder 20. In this vehicle, the required hydraulic braking force increases from "0" when the regenerative braking force that the motor generator can generate falls below the required braking force of the vehicle or when the regenerative braking force is replaced by hydraulic braking force. In this way, when the required hydraulic braking force becomes greater than "0," the pre-charge process of the above embodiment may be performed so that hydraulic braking force can be generated at the wheel 10 without delay. In this case, the pre-charge process is performed earlier than the required hydraulic braking force becomes greater than "0."

[0064] Although not described in the above embodiment, the vehicle includes a rotating body that rotates integrally with the wheel 10 and a friction material that does not rotate integrally with the wheel 10. The friction material is configured to move toward the rotating body as the hydraulic pressure in the wheel cylinder 20 increases. When braking force does not need to be generated at the wheel 10, such as when the brake operating member 42 is not operated, a gap is provided between the friction material and the rotating body to prevent the friction material from contacting the rotating body. Therefore, even if brake fluid is supplied to the wheel cylinder 20, no braking force is generated at the wheel 10 until the friction material contacts the rotating body. Therefore, for a short period after the slave piston 492, moving in the forward direction Za, closes the input port 495, no braking force is generated at the wheel 10, even if the hydraulic pressure in the wheel cylinder 20 increases as the slave piston 492 moves. Therefore, during the pre-charge process, the upstream control unit 50 may continue to move the slave piston 492 in the forward direction Za even after the input port 495 is closed, as long as the movement is within a range in which braking force is not generated at the wheel 10.

[0065] The upstream control unit 50 may use only the first filter value SF1 to determine whether to perform braking. That is, if the first filter value SF1 exceeds the braking determination value SBth, braking may be performed regardless of the magnitude of the second filter value SF2. This configuration also provides the same advantages as the advantages (2) and (3) of the above embodiment.

[0066] The upstream control unit 50 may use the first filter value SF1 to determine whether to perform the precharge process and the second filter value SF2 to determine whether to perform the braking process. In this case, the precharge process is started when the first filter value SF1 exceeds the precharge determination value SCth, and the braking process is then executed when the second filter value SF2 becomes greater than the braking determination value SBth. This configuration also provides an effect equivalent to effect (4) of the above embodiment.

[0067] The upstream control unit 50 may use the first raw value SR1 to determine whether to perform the pre-charge process and the first filtered value SF1 to determine whether to perform the braking process. In this case, the pre-charge determination value SCth and the braking determination value SBth may be the same value. The first raw value SR1 is a value that includes noise and is therefore larger than the first filtered value SF1. Therefore, even if the pre-charge determination value SCth and the braking determination value SBth are set to the same value, if the first raw value SR1 is larger than the pre-charge determination value SCth and the first filtered value SF1 is smaller than the braking determination value SBth, the pre-charge control is performed before the braking process.

[0068] The detection value used by the upstream control unit 50 for the braking process and the pre-charge process may be a detection value of a sensor that detects a parameter that changes in response to the driver's brake operation. For example, the detection value may be a detection value of the reaction pressure sensor 48. The detection value may also be a detection value of a pedal force sensor (not shown) that detects the force with which the driver operates the brake operating member 42, or a detection value of a master pressure sensor (not shown) that detects the master pressure, which is the hydraulic pressure in the master chamber Rm. In this case, the upstream pressurizing device 40 may be provided with a master pressure sensor instead of the reaction pressure sensor 48.

[0069] In the braking control device 30, the configuration related to the downstream pressure device 60 can be omitted. The braking control device 30 may have a configuration different from that shown in Fig. 1 as long as it includes an electric cylinder 49 and can supply brake fluid to the wheel cylinders 20 by operating the electric cylinder 49. For example, the braking control device 30 may be configured so that one electric cylinder 49 can supply brake fluid to all of the wheel cylinders 20 without going through the master cylinder 45. The braking control device 30 may also have multiple electric cylinders 49.

[0070] During pre-charge control, the slave piston 492 does not have to completely close the input port 495. For example, the slave piston 492 may be advanced to a position where it partially covers the input port 495, and then the pre-charge control may be terminated. In other words, the input port 495 may be partially opened after the pre-charge control is executed. In this case, the amount of movement of the slave piston 492 from the initial position in the forward direction Za is less than the predetermined amount described above. Even in this case, the time from when the braking process is executed until the hydraulic pressure in the wheel cylinder 20 is increased can be shortened compared to when the pre-charge control is not executed.

[0071] The slave piston 492 does not have to have the through-hole 497. In this case, the slave piston 492 only needs to be disposed in the slave cylinder 491 so as not to block the input port 495 when it is in the initial position.

[0072] The brake control device 30 is only required to include at least an "electric pressure device" that can electrically increase the hydraulic pressure in the wheel cylinder 20. The upstream control unit 50 may be configured as a circuit including one or more processors operating according to a computer program, one or more dedicated hardware circuits such as dedicated hardware for performing at least some of the various processes, or a combination thereof. Examples of dedicated hardware include an application-specific integrated circuit (ASIC). The processor includes a CPU and memory such as RAM and ROM, which store program code or instructions configured to cause the CPU to perform the processes. The memory, i.e., storage medium, includes any available medium accessible by a general-purpose or dedicated computer. The same applies to the downstream control unit 70. [Explanation of symbols]

[0073] 10(11~12)…Wheel 20 (21-24)... Wheel cylinder 30...Brake control device 40...Upstream pressure device 41...Reserve tank 42...Brake operating member 43...First stroke sensor (first sensor) 48...Reaction force pressure sensor 49...Electric cylinder 491...Slave cylinder 492...Slave Piston 493...Electric motor 494...Linear motion conversion mechanism 495...input port 496...Output port 497...Through hole 50...Upstream control section 60...Downstream pressure device 61...Front wheel pressure unit (pressure unit) 62...Rear wheel pressure unit (pressure unit) 63...Second stroke sensor (second sensor) 70...Downstream control section Re…liquid chamber S1 (SR1, SF1)...First detection value S2 (SF2)...Second detection value SBth: Braking judgment value SCth: Precharge threshold Za…Forward direction Zb…Backward direction

Claims

1. A braking control device that generates braking force on a vehicle wheel by adjusting hydraulic pressure in a wheel cylinder, A reserve tank for storing brake fluid; an electric cylinder having a slave cylinder with a fluid chamber defined therein, a slave piston slidable within the slave cylinder, and an electric motor for driving the slave piston, and supplying brake fluid from the fluid chamber to the wheel cylinder by moving the slave piston in a forward direction; a sensor for detecting a parameter that changes in response to a driver's braking operation; a control unit that controls the electric cylinder, The slave cylinder is formed with an input port that connects the fluid chamber with the reserve tank, the slave piston opens the input port when located at an initial position, and closes the input port by moving in the forward direction from the initial position; The control unit a braking process in which, when the detection value of the sensor is equal to or greater than a braking determination value, the slave piston is moved in the forward direction to supply brake fluid from the fluid chamber to the wheel cylinder; a precharge process for moving the slave piston in the forward direction from the initial position until the slave piston closes the input port before the braking process is performed; Braking control device.

2. A braking control device that generates braking force on a vehicle wheel by adjusting hydraulic pressure in a wheel cylinder, A reserve tank for storing brake fluid; an electric cylinder having a slave cylinder with a fluid chamber defined therein, a slave piston slidable within the slave cylinder, and an electric motor for driving the slave piston, and supplying brake fluid from the fluid chamber to the wheel cylinder by moving the slave piston in a forward direction; a sensor for detecting a parameter that changes in response to a driver's braking operation; a control unit that controls the electric cylinder, The slave cylinder is formed with an input port that connects the fluid chamber with the reserve tank, the slave piston opens the input port when located at an initial position, and closes the input port by moving in the forward direction from the initial position; The control unit a braking process in which, when the detection value of the sensor is equal to or greater than a braking determination value, the slave piston is moved in the forward direction to supply brake fluid from the fluid chamber to the wheel cylinder; a pre-charge process for moving the slave piston in the forward direction from the initial position before executing the braking process, the detected value includes a raw value before low-pass filtering is performed on the detected signal of the sensor; The control unit executes the precharge process when the raw value is equal to or greater than a precharge determination value. Braking control device.

3. A braking control device that generates braking force on a vehicle wheel by adjusting hydraulic pressure in a wheel cylinder, A reserve tank for storing brake fluid; an electric cylinder having a slave cylinder with a fluid chamber defined therein, a slave piston slidable within the slave cylinder, and an electric motor for driving the slave piston, and supplying brake fluid from the fluid chamber to the wheel cylinder by moving the slave piston in a forward direction; a first control unit that controls the electric cylinder; a first sensor that detects a parameter that changes in response to a brake operation by a driver and outputs a detection signal to the first control unit; a pressure unit that is provided separately from the electric cylinder and supplies brake fluid to the wheel cylinder; a second control unit capable of communicating with the first control unit and controlling the pressurizing unit; a second sensor that detects the parameter that changes in response to a brake operation by the driver and outputs a detection signal to the second control unit; The slave cylinder is formed with an input port that connects the fluid chamber with the reserve tank, the slave piston opens the input port when located at an initial position, and closes the input port by moving in the forward direction from the initial position; the second control unit transmits the second detection value of the second sensor to the first control unit at predetermined intervals; The first control unit a braking process in which, when both the first detection value and the second detection value of the first sensor are equal to or greater than a braking determination value, the slave piston is moved in the forward direction to supply brake fluid from the fluid chamber to the wheel cylinder; a precharge process for moving the slave piston from the initial position in the forward direction before the braking process is performed; Braking control device.

4. the detection value includes a filtered value obtained by performing low-pass filtering on the detection signal of the sensor, The control unit executes the braking process when the filter value is equal to or greater than the braking determination value. The braking control device according to claim 2.

Images