Brake device control apparatus and control method

Abstract

When releasing an electric parking brake that is activated by pressing a piston (6) of a hydraulic brake mechanism (7) with an electric actuator (9) of an electric parking mechanism (8) to press a brake pad (4) against a rotor (3), an electric booster (18) is activated to make the hydraulic pressure of the hydraulic brake mechanism (7) acting on the piston (6) negative before the pressing of the piston (6) by the electric actuator (9) is released.

Description

Brake device control device and control method

[0001] The present invention relates to a brake device control device and a control method.

[0002] The following Patent Document 1 discloses a hydraulic brake device having an electric parking mechanism, and describes that in order to increase the amount of return of the piston when the electric parking mechanism is released, when the electric parking mechanism is released, the piston is moved in a direction that presses the brake pad against the rotor, and the hydraulic pressure on the piston is made positive, thereby increasing the amount of deformation of the sealing member.

[0003] Japanese Patent Application Laid-Open No. 2012-1053

[0004] However, for example, in an electric parking state using an electric parking mechanism, the piston is pushed by a larger amount than during normal hydraulic braking, so there is a risk that the piston's return amount due to the deformation of the seal member in a positive hydraulic pressure state will not be equal to the pushed amount, and as a result, there is a risk that the required gap will not be created between the brake pads and the rotor after the electric parking state is released.An object of the present invention is to provide a brake device control device and control method that can ensure the required gap between the brake pads and the rotor after the electric parking state is released.

[0005] One aspect of the present invention is a brake device that includes a piston that is operated by hydraulic pressure, an electric parking mechanism that can press the piston in a direction that presses the brake pad against a rotor using an electric actuator, and a hydraulic pressure generating device that can make the hydraulic pressure negative, and the gist of the present invention is that the hydraulic pressure generating device is operated so that the hydraulic pressure becomes negative based on an operation to release the pressure on the piston by the electric parking mechanism.

[0006] According to one aspect of the present invention, when the electric parking is released, the piston is returned by the negative hydraulic pressure, so that the necessary clearance can be secured between the brake pad and the rotor after the electric parking is released. The objects and advantages of the present invention are realized and attained by using the elements and combinations thereof set forth in the claims. It should be understood that both the foregoing general description and the following detailed description are merely exemplary and explanatory and do not limit the invention as defined by the claims.

[0007] The present invention relates to a brake device control system for a vehicle, a brake system including a brake mechanism, a brake control system for a vehicle, a brake control device for a vehicle having an electric parking mechanism, a brake control system ...

[0008] The brake device control system of the embodiment shown in Fig. 1 controls the operating state of brake devices 2 provided on front wheels 1F and rear wheels 1R. The brake devices 2 provided on the front wheels 1F and rear wheels 1R are so-called disc brakes that apply braking by clamping brake pads 4 against disc rotors (rotors) 3 attached to the wheels (see Fig. 2). Each brake device 2 generates braking force by placing the brake pads 4 immobile on one end face of the rotor 3 within a caliper 5, and pressing the brake pad 4 on the opposite end face against the rotor 3. To this end, a piston 6 is disposed within the caliper 5 and moves back and forth between the brake pads 4 and the rotor 3 in response to hydraulic pressure (hydraulic pressure). The piston 6 moves in a direction pressing the brake pads 4 against the rotor 3 when hydraulic pressure applied to a pressure-receiving surface opposite the brake pad 4 side is positive (pressurized).

[0009] In this vehicle, the brake device 2 provided on the front wheel 1F is provided with only the hydraulic brake mechanism 7 that reciprocates the piston 6 using hydraulic pressure, as described above. Meanwhile, the brake device 2 provided on the rear wheel 1R is provided with, in addition to the hydraulic brake mechanism 7, an electric parking mechanism (hereinafter also referred to as EPB) 8 that can press the piston 6 using an electric motor (electric actuator) 9, as shown in FIG. 2 . In this embodiment, a recess 6a is provided on the side of the piston 6 opposite the brake pad 4 side, and a pressing portion 10 for pressing the piston 6 is inserted into this recess 6a. This pressing portion 10 is inserted into the recess 6a of the piston 6 so as to be movable in the contact / separation direction between the brake pad 4 and the rotor 3 (hereinafter simply referred to as the contact / separation direction), and comes into and out of contact with the end surface of the recess 6a of the piston 6 on the brake pad 4 side. A female thread is formed in the center of the pressing portion 10, the axis of which extends in the contact / separation direction, and a male thread of a shaft member 51 is threadedly engaged with this female thread. The end of the shaft member 51 opposite the male thread extends to the outside of the caliper 5 and is connected to the rotary shaft of the electric motor 9 via a two-stage reduction gear mechanism 52 .

[0010] Therefore, by rotating the electric motor 9 in both forward and reverse directions, the thrust of the screw can reciprocate the pressing portion 10 in the contact and separation directions. When the pressing portion 10 is moved to the right in FIG. 2 while in contact with the piston 6 (the end surface of the recess 6 a of the piston 6), the piston 6 can press the brake pad 4 against the rotor 3. The direction in which the pressing portion 10 moves toward the piston 6 or presses the piston 6 is defined as the operating direction of the pressing portion 10. In this embodiment, as described below, when the EPB switch 11 is in the on state, the electric motor 9 moves the pressing portion 10 in the operating direction to press the piston 6, pressing the brake pad 4 against the rotor 3 and activating the electric parking brake. When the EPB switch 11 is in the off state, the electric parking brake is released. In this embodiment, the electric parking brake is also released when the accelerator pedal 17 is depressed. That is, turning off the EPB switch 11 and depressing the accelerator pedal 17 is an operation to release the pressure on the piston 6 by the EPB 8 (an operation to release the electric parking). When the electric parking is released, the pressing portion 10 is moved in a direction away from the piston 6, and this direction is defined as the return direction of the pressing portion 10, and the limit position of the pressing portion 10 in the return direction is defined as the return end. Note that a seal member 53 is interposed between the caliper 5 and the piston 6 to prevent leakage of hydraulic fluid. The operating state of the EPB 8 is controlled by an EPB controller 13.

[0011] Returning to FIG. 1 , in this embodiment, an electric booster 18 is used as a hydraulic pressure generating device that generates hydraulic pressure to the piston 6 of each brake device 2. The electric booster 18 is a hydraulic pump driven by an electric motor (electric actuator) (not shown) and can control the hydraulic pressure to the piston 6 of each brake device 2 to either positive or negative. Positive pressure generally refers to a state in which pressure is greater than atmospheric pressure, and negative pressure refers to a state in which pressure is less than atmospheric pressure. When the electric motor is not driven, the hydraulic pressure is equal to atmospheric pressure. In this embodiment, the electric booster 18 is mechanically or hydraulically connected to the brake pedal 16 and is configured to output positive hydraulic pressure corresponding to the amount of depression of the brake pedal 16 when the brake pedal 16 is depressed. The operation state of the electric booster 18 is controlled by a booster controller 19. Release of negative hydraulic pressure control by the electric booster 18, which will be described later, refers to, for example, a state in which the drive of the electric booster 18 is released and the hydraulic pressure is set to atmospheric pressure.

[0012] A hydraulic pressure regulating device (hereinafter also referred to as VDC) 20, which can individually adjust the hydraulic pressure of the brake device 2 of each wheel, is interposed between the electric booster 18 and the brake device 2 of each wheel on the hydraulic pressure output side. As described in Patent Document 1, the VDC 20 can individually maintain, reduce, or increase the hydraulic pressure of the brake device 2 of each wheel, thereby applying braking force to each wheel and increasing or decreasing that braking force. Specifically, the VDC 20 has a hydraulic pressure adjustment function equivalent to that of an anti-skid control device that reduces the tendency of wheels to lock and a vehicle behavior control device that adjusts vehicle behavior expressed by yaw rate and lateral acceleration. The VDC 20 can adjust the hydraulic pressure of the brake device 2 of each wheel regardless of the output hydraulic pressure of the electric booster 18. However, for example, a switching valve provided in the VDC 20 can connect (directly connect) the brake device 2 of each wheel to the electric booster 18 or disconnect it from the electric booster 18. That is, when the brake device 2 is directly connected to the electric booster 18, the output hydraulic pressure of the electric booster 18 is directly supplied to the brake device 2 (hydraulic brake mechanism 7), and when the brake device 2 is disconnected from the electric booster 18, the hydraulic pressure of the brake device 2 can be adjusted individually by the VDC 20. The operating state of this VDC 20 is controlled by a VDC controller 21.

[0013] The EPB controller 13 is an electronic control unit (ECU) that controls the operation state of the pressing unit 10, i.e., the operation state of the electric parking brake, by controlling the operation state of the electric motor 9 of the EPB 8. Therefore, the EPB controller 13 includes a computer system with advanced processing capabilities. Like well-known computer systems, this computer system includes a processor 14 with advanced processing capabilities and a storage device 15 that stores programs, sensor signals, and other information. The processor 14 is configured, for example, as a central processing unit (CPU) or a microprocessing unit (MPU). The storage device 15 is configured as a semiconductor storage device, a magnetic storage device, and an optical storage device. The storage device 15 may also include a register, a cache memory, and a memory used as a main storage device. The EPB controller 13 performs its processing by, for example, executing a computer program stored in the storage device 15 of the EPB controller 13. Alternatively, the EPB controller 13 may perform its processing using a functional logic circuit implemented in a general-purpose semiconductor integrated circuit. For example, the EPB controller 13 may include a programmable logic device such as a field programmable gate array. Other controllers may have similar configurations and functions. Furthermore, the controllers can share data and communicate with each other.

[0014] The vehicle is provided with an EPB switch 11 that activates the EPB 8 to activate the electric parking system. When the occupant turns the EPB switch 11 on, the EPB 8 is activated by an EPB controller 13, thereby activating the electric parking system. The vehicle is also provided with a driving characteristics selection switch 12 that allows the driver to select a driving condition of the vehicle, such as driving characteristics during cornering. The driving characteristics selection switch 12 allows the driver to select, for example, a sport driving mode that provides sharp cornering characteristics on winding roads, an eco mode that reduces fuel consumption by the engine or power consumption by the drive battery, or a snow mode that provides stable driving characteristics on slippery roads such as snowy roads. The vehicle is also provided with an accelerator sensor that detects the depression state of an accelerator pedal 17, a brake sensor that detects the depression state of a brake pedal 16, and hydraulic pressure sensors, as in a typical vehicle.

[0015] In this embodiment, the operating state of the electric motor 9 and the control of the hydraulic pressure to the brake device 2 when the electric parking function is released will be described. As described above, when the electric parking function is released, the pressing portion 10 is moved in a direction away from the piston 6 (returning direction). FIG. 3 shows the change in the motor current of the electric motor 9 over time at this time. When the electric parking function is activated, for example, the electric motor 9 is rotated in the forward direction, causing the pressing portion 10 to move the piston 6 toward the brake pad 4, and the electric motor 9 is stopped with the brake pad 4 pressed against the rotor 3. In this state, the rotor of the electric motor 9 is fixed by a brake mechanism (not shown) provided in the electric motor 9. Therefore, for example, the electric motor 9 will not rotate in the reverse direction to release the electric parking function. If an attempt is made to rotate the electric motor 9 in the reverse direction from this state to release the electric parking function, the motor current rapidly increases to resist the pressing force (frictional force) between the brake pad 4 and the rotor 3, as shown in FIG. 3. However, as the pressing force between the brake pad 4 and the rotor 3 decreases, the motor current gradually decreases, eventually reaching a substantially no-load state. By tracing the change over time in this motor current, the position of the pressing part 10 in the return direction can be detected because the electric motor 9 is rotated at a constant speed.

[0016] Next, the calculation process performed by the EPB controller 13, particularly when the electric parking function is released, will be described with reference to the flowchart in Figure 4. This calculation process is performed, for example, at a predetermined sampling period. First, in step S1, it is determined whether the EPB switch 11 is on. If the EPB switch 11 is on, the process proceeds to step S3. If not, the process proceeds to step S2. In step S3, it is determined whether the accelerator pedal 17 is depressed. If the accelerator pedal 17 is depressed, the process proceeds to step S5. If not, the process proceeds to step S13. In step S13, EPB operation control is performed in which the pressing unit 10 presses the brake pad 4 against the rotor 3 according to individual calculation processes (not shown), and then the process proceeds to step S14.

[0017] In step S5, "Electric parking will be cancelled" is output by voice and / or displayed on the monitor, and then the process proceeds to step S6. Meanwhile, in step S2, it is determined whether the hydraulic pressure is pressurized and the vehicle is stopped. If the hydraulic pressure is pressurized and the vehicle is stopped, the process proceeds to step S4. If not, the process proceeds to step S6. In step S4, a command is output to the VDC controller 21 to maintain the hydraulic pressure of the brake device 2 not equipped with EPB (front wheel 1F) and to connect the hydraulic pressure of the brake device 2 equipped with EPB (rear wheel 1R) to the electric booster 18, and then the process proceeds to step S6. In step S6, a command is output to the booster controller 19 to make the hydraulic pressure negative by the electric booster 18, and then the process proceeds to step S7.

[0018] In step S7, the pressing unit 10 is moved in the return direction (away from the piston 6), and then the process proceeds to step S8. In step S8, it is determined whether the pressing unit 10 has reached a predetermined return position. If the pressing unit 10 has reached the predetermined return position, the process proceeds to step S9. If not, the process returns to step S7. This predetermined return position is set to a value equivalent to the return position of the piston 6 when hydraulic pressure is released (at atmospheric pressure) in a hydraulic brake (hydraulic brake mechanism 7) without an EPB 8. That is, if the negative hydraulic pressure created by the electric booster 18 is released at this point, the piston 6 will stop at the return position of a normal hydraulic brake. In step S9, it is determined whether the sports driving mode has been selected by the driving characteristics selection switch 12. If the sports driving mode has been selected, the process proceeds to step S10. If not, the process proceeds to step S11.

[0019] In step S10, the command to the booster controller 19, i.e., the negative pressure control of the hydraulic pressure by the electric booster 18, is released, and then the process proceeds to step S12. In step S12, the pressing unit 10 is returned to a specified return position, and then the process proceeds to step S14. This specified return position may be the return end position of the pressing unit 10, or may be a predefined position between the return end and the predetermined return position. On the other hand, in step S11, the pressing unit 10 is returned to the return end, and at that timing the command to the booster controller 19, i.e., the command to control the negative pressure of the hydraulic pressure by the electric booster 18, is released, and then the process proceeds to step S14. In step S14, the command to the VDC controller 21, i.e., the command to maintain the hydraulic pressure of the brake device 2 for the front wheel 1F and to connect the hydraulic pressure of the brake device 2 for the rear wheel 1R to the electric booster 18, is released, and then the process returns.

[0020] According to this calculation process, when the EPB switch 11 is in the ON state, the EPB 8 is activated and the electric parking function is activated. On the other hand, when the EPB switch 11 is in the OFF state or the accelerator pedal 17 is depressed, the EPB 8 is deactivated and the electric parking function is released. When the electric parking function is released, the output hydraulic pressure of the electric booster 18 becomes negative, so the piston 6 is pulled in the return direction. At this time, for example, if the EPB switch 11 is in the OFF state but the brake pedal 16 is depressed (hydraulic pressure is increased) and the vehicle is stopped, for example, the traffic light ahead may be green, but the vehicle ahead will not start moving, and as a result, the vehicle itself may not be able to start moving. Since the hydraulic pressure is in a positive state when the brake pedal 16 is depressed, the vehicle is kept stopped by maintaining the hydraulic pressure of the brake device 2 of the front wheel 1F which does not have an EPB 8, and in that state the hydraulic pressure of the brake device 2 of the rear wheel 1R which has an EPB 8 is connected to the electric booster 18, and then the output hydraulic pressure of the electric booster 18 is made negative, which also makes it possible to pull the piston 6 in the return direction.

[0021] In this way, if the hydraulic pressure is made negative and the pressing portion 10 is moved in the return direction while pulling the piston 6 in the return direction, the piston 6 will move in the return direction together with the pressing portion 10. Although the pressing portion 10 does not have the function of moving the piston 6 in the return direction, by making the hydraulic pressure negative and then moving the pressing portion 10 in the return direction, the pressing portion 10 will not separate from the piston 6. If the hydraulic pressure were made negative after moving the pressing portion 10 in the return direction first, the pressing portion 10 would separate from the piston 6, and the piston 6, which is then pulled in the return direction by the hydraulic pressure, would come into contact with the pressing portion 10, causing noise and vibration. However, by not allowing the pressing portion 10 to separate from the piston 6, this noise and vibration can be avoided. Then, when the piston 6 reaches the return position of a normal hydraulic brake, it is determined whether the sports driving mode is selected. If the sports driving mode is not selected, moving the pressing portion 10 to the return end will also move the piston 6 to the return end (unless there is a mechanical restriction), and at that point the negative hydraulic pressure of the electric booster 18 is released.

[0022] On the other hand, when the sports driving mode is selected, the negative hydraulic pressure of the electric booster 18 is released when the piston 6 is in the return position corresponding to a normal hydraulic brake, preventing the piston 6 from moving further in the return direction. In this state, the pressing portion 10 is returned to the specified return position, thereby separating the pressing portion 10 from the piston 6. For example, on road surfaces requiring quick steering and acceleration / deceleration, such as winding roads, it is desirable to ensure that there is no discrepancy between the depression of the brake pedal 16 and the deceleration feel of the vehicle. Therefore, when the sports driving mode is selected, the piston 6 is returned to the return position corresponding to a normal hydraulic brake, rather than to the return end (equivalent to the pressing portion 10), thereby enabling the depression of the brake pedal 16 and the deceleration feel of the vehicle to match. On the other hand, when a driving mode other than the sports driving mode is selected, the piston 6 is returned to the return end (equivalent to the pressing portion 10), reliably separating the brake pads 4 from the rotor 3, thereby preventing a deterioration in fuel economy (electricity efficiency) due to so-called brake drag.

[0023] In this way, in the brake device control system of this embodiment, the electric booster 18 is operated so that the hydraulic pressure becomes negative for a predetermined time based on the operation of releasing the pressure on the piston 6 by the EPB 8, and when the electric parking is released, the piston 6 is moved in the return direction by the negative hydraulic pressure, so that the necessary gap can be secured between the brake pad 4 and the rotor 3 after the electric parking is released.

[0024] Furthermore, when canceling the electric parking function, the pressing portion 10 is moved in the return direction and the electric booster 18 is activated so that the hydraulic pressure becomes negative before the pressing portion 10 separates from the piston 6, thereby avoiding noise and vibration caused by a collision between the pressing portion 10 and the piston 6. Here, for example, the start of the predetermined time period is when the electric booster 18 is activated so that the hydraulic pressure becomes negative. Furthermore, when canceling the electric parking function, the pressing portion 10 is moved in the return direction and the electric booster 18 is activated so that the hydraulic pressure becomes negative before the pressing portion 10 reaches the return end of the return direction. This allows the piston 6 to return to the return position of a normal hydraulic brake, thereby reducing the discrepancy between the depression of the brake pedal 16 and the feeling of deceleration of the vehicle. Furthermore, when canceling the electric parking function, the pressing portion 10 is moved in the return direction and the electric booster 18 is activated so that the hydraulic pressure remains negative until the pressing portion 10 reaches the return end of the return direction. This reliably separates the brake pads 4 from the rotor 3, thereby preventing a deterioration in fuel economy (electricity efficiency). Here, for example, the end of the predetermined time period is when the operation of the electric booster 18 that causes the hydraulic pressure to become negative is deactivated.

[0025] Furthermore, when depression of the accelerator pedal 17 is detected, the electric parking mode is released and the electric booster 18 is operated so that the hydraulic pressure becomes negative, thereby enabling the electric parking mode to be released reliably before the vehicle starts moving. Furthermore, positive hydraulic pressure is generated in the brake device 2 in accordance with the depression state of the brake pedal 16, and when the electric parking mode is released, the hydraulic pressure of the brake device 2 without the EPB 8 is maintained by the VDC 20 and the hydraulic pressure of the brake device 2 with the EPB 8 is supplied from the electric booster 18, thereby maintaining the vehicle in a stopped state until depression of the brake pedal 16 is released and enabling the electric parking mode to be released before depression of the brake pedal 16 is released.

[0026] Although the brake device control method and control device according to the embodiment have been described above, the present invention is not limited to the configurations described in the above embodiment and various modifications are possible within the scope of the present invention. For example, in the above embodiment, a hydraulic brake device without an EPB 8 is provided for the front wheel 1F, but it is also possible to provide brake devices 2 with EPBs 8 for all front and rear wheels 1R. In such a vehicle, when the EPB switch 11 is in the OFF state and the brake pedal 16 is depressed to stop the vehicle, for example, the hydraulic pressure of the brake device 2 for the rear wheel 1R may be maintained and the EPB 8 for the front wheel 1F may be released first, and then the hydraulic pressure of the brake device 2 for the front wheel 1F may be increased to maintain the vehicle in a stopped state, and the EPB 8 for the rear wheel 1R may be released in that state.

[0027] 1F...front wheel, 1R...rear wheel, 2...brake device, 3...rotor, 4...brake pad, 6...piston, 7...hydraulic brake mechanism, 8...electric parking mechanism (EPB), 9...electric motor (electric actuator), 10...pressure unit, 11...EPB switch, 13...EPB controller, 14...processor, 15...storage device, 16...brake pedal, 17...accelerator pedal, 18...electric booster (hydraulic pressure generating device), 20...VDC (hydraulic pressure adjusting means)

Claims

1. A brake device control device comprising: a piston that is moved in a direction pressing a brake pad against a rotor when hydraulic pressure is positive and that moves the brake pad in a direction away from the rotor when the hydraulic pressure is negative; an electric parking mechanism capable of pressing the piston in the direction pressing the brake pad against the rotor by an electric actuator; a hydraulic pressure generating device that can make the hydraulic pressure negative; and a controller that controls the hydraulic pressure generating device so that the hydraulic pressure becomes negative for a predetermined period of time based on the operation of releasing the pressure on the piston by the electric parking mechanism.

2. The brake device control device according to claim 1, characterized in that the electric parking mechanism has a pressing part that moves back and forth in the contact and separation direction of the brake pad and the rotor to be brought into contact with and separated from the piston, and the hydraulic pressure generating device is operated so that the pressing part moves in a direction away from the piston based on an operation of the electric parking mechanism to release the pressure on the piston, and the hydraulic pressure becomes negative before the pressing part separates from the piston.

3. A brake device control device as described in claim 1 or 2, characterized in that the electric parking mechanism has a pressing part that moves back and forth in the direction in which the brake pads and the rotor come into contact with and separate from the piston, and operates the hydraulic pressure generating device so that the pressing part moves in a direction away from the piston based on an operation of the electric parking mechanism to release the pressure on the piston, and the negative hydraulic pressure is released before the pressing part reaches the return end in the direction away from the piston.

4. A brake device control device as described in claim 1 or 2, characterized in that the electric parking mechanism has a pressing part that moves back and forth in the direction in which the brake pads and the rotor come into contact with and separate from the piston, and operates the hydraulic pressure generating device so that the pressing part moves in a direction away from the piston based on an operation of the electric parking mechanism to release the pressure on the piston, and the hydraulic pressure remains negative until the pressing part reaches the return end in the direction away from the piston.

5. A brake device control device as described in claim 1, characterized in that, when depression of the accelerator pedal is detected, the pressure applied to the piston by the electric parking mechanism is released and the hydraulic pressure generating device is operated so that the hydraulic pressure becomes negative.

6. The brake device control device according to claim 1, characterized in that the hydraulic pressure generating device is configured to be able to generate the hydraulic pressure as a positive pressure or a negative pressure depending on the depression state of the brake pedal, and is provided with a hydraulic pressure adjusting means capable of individually adjusting the hydraulic pressure of the brake device of each wheel, and the hydraulic pressure is generated depending on the depression state of the brake pedal, and the hydraulic pressure of the brake device not having the electric parking mechanism is held by the hydraulic pressure adjusting means based on the operation of releasing the pressure on the piston by the electric parking mechanism, and the hydraulic pressure of the brake device having the electric parking mechanism is supplied from the hydraulic pressure generating device.

7. A brake device comprising a piston that is moved in a direction pressing the brake pad against a rotor when hydraulic pressure is positive and that is moved in a direction moving the brake pad away from the rotor when the hydraulic pressure is negative, an electric parking mechanism capable of pressing the piston in the direction pressing the brake pad against the rotor by an electric actuator, and a hydraulic pressure generating device capable of making the hydraulic pressure negative, characterized in that a brake device control method is performed by operating the hydraulic pressure generating device so that the hydraulic pressure becomes negative for a predetermined time based on an operation of releasing the pressure on the piston by the electric parking mechanism.

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