Brake device for vehicle

Abstract

To suppress dragging torque from being generated excessively.SOLUTION: A vehicular brake device is provided with: a disc rotor; a pair of brake pads; a brake caliper supporting the pair of brake pads; a caliper piston arranged in a caliper cylinder of the brake caliper; a piston ring seal arranged between the caliper cylinder and the caliper piston; a liquid-pressure sensor that detects brake liquid pressure that is supplied to the caliper cylinder; an electric actuator that enables the caliper piston to move back and forth with respect to the disc rotor; and a control device that controls operation of the electric actuator, on the basis of a detected value by the liquid-pressure sensor. When the detected value by the liquid-pressure sensor exceeds a predetermined threshold during brake operation, the control device makes the electric actuator operate in a direction in which the caliper piston retreats from the disc rotor, at the time of releasing a brake.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The technology disclosed in this specification relates to a brake device for a vehicle. [Background technology]

[0002] Patent Document 1 describes a brake device for a vehicle. This brake device includes a disc rotor that rotates together with the vehicle wheel, a pair of brake pads that face each other across the disc rotor, a brake caliper that supports the pair of brake pads, a caliper piston that is disposed in a caliper cylinder of the brake caliper and presses one of the pair of brake pads against the disc rotor in response to brake fluid pressure supplied to the brake caliper, and a piston ring seal that is disposed between the caliper cylinder and the caliper piston. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-241389 Summary of the Invention [Problem to be solved by the invention]

[0004] It is known that in the above-mentioned brake devices, drag torque occurs when the brakes are released and the supply of brake fluid pressure is stopped. This drag torque varies depending on the magnitude of the brake fluid pressure during braking, and the greater the brake fluid pressure, the greater the drag torque. The generation of excessive drag torque results in unnecessary energy loss, which can be a factor in reducing the vehicle's energy efficiency (energy consumption per distance traveled).

[0005] In view of the above, the present specification provides a technique that can avoid or suppress the generation of excessive drag torque even after braking due to high brake fluid pressure. [Means for solving the problem]

[0006] The technology disclosed in this specification is embodied in a brake device for a vehicle. The brake device includes a disc rotor that rotates with a wheel of the vehicle, a pair of brake pads that face each other across the disc rotor, a brake caliper that supports the pair of brake pads and has a caliper cylinder, a caliper piston disposed in the caliper cylinder and that presses one of the pair of brake pads against the disc rotor in response to brake fluid pressure supplied to the caliper cylinder, a hydraulic pressure sensor that detects the brake fluid pressure supplied to the caliper cylinder, an electric actuator that moves the caliper piston forward and backward relative to the disc rotor, and a control device that controls operation of the electric actuator based on a value detected by the hydraulic pressure sensor. When the value detected by the hydraulic pressure sensor exceeds a predetermined threshold during braking operation in which the brake fluid pressure is supplied to the brake caliper, the control device operates the electric actuator in a direction in which the caliper piston retracts from the disc rotor when the supply of brake fluid pressure is subsequently stopped and the brake is released.

[0007] As mentioned above, the greater the brake fluid pressure during braking, the greater the drag torque that occurs afterward. This is because the greater the brake fluid pressure, the greater the strain that occurs in the brake caliper and brake pads, causing the caliper piston to move more. This increased caliper piston movement also increases the amount of movement required when the caliper piston returns to its initial position after the supply of brake fluid pressure is stopped. As a result, reverse strain occurs in the piston ring seal, and this restoring force presses the brake pads against the disc rotor, generating a relatively large drag torque.

[0008] Based on the above findings, the brake device according to the present technology is provided with an electric actuator. This electric actuator can move a caliper piston toward and away from a disc rotor. The brake fluid pressure is monitored during braking, and when the brake fluid pressure exceeds a predetermined threshold, the electric actuator moves the caliper piston away from the disc rotor when the brake is subsequently released. This makes it possible to avoid or suppress the generation of excessive drag torque even after braking due to high brake fluid pressure. [Brief explanation of the drawings]

[0009] [Figure 1] 1 shows a schematic diagram of a brake device 10 according to an embodiment of the present invention. [Figure 2] A braking device 10 that operates with normal brake fluid pressure is shown schematically. [Figure 3] 4 shows a schematic view of the brake device 10 in a deactivated state from the state shown in FIG. [Figure 4] 1 shows a schematic representation of a braking device 10 that operates with brake fluid pressure above a threshold value. [Figure 5] 5 is a schematic diagram showing the brake device 10 in a deactivated state from the state shown in Fig. 4. The piston ring seal 22 is elastically deformed in the opposite direction compared to Fig. 4. [Figure 6] 4 is a flowchart showing a series of processes executed by a control device 28. DETAILED DESCRIPTION OF THE INVENTION

[0010] In one embodiment of the present technology, the control device may increase the amount of operation of the electric actuator as the detected value by the hydraulic pressure sensor increases. With this configuration, the electric actuator can be operated just enough according to the magnitude of the brake hydraulic pressure generated during braking.

[0011] In one embodiment of the present technology, the electric actuator may be an actuator for a parking brake. In recent years, electric parking brakes have become widespread, and a parking brake actuator is often mounted on a brake caliper. In this case, by using the parking brake actuator, the brake device according to the present technology can be manufactured at low cost.

[0012] In one embodiment of the present technology, the brake fluid pressure supplied to the brake caliper may be adjusted in response to a user operation. In this case, as an example, the user operation may be a user operation of a brake pedal. Furthermore, the user operation of the brake pedal may be converted into brake fluid pressure by a brake master cylinder.

[0013] Additionally or alternatively, the brake fluid pressure supplied to the brake caliper may be adjusted by a brake actuator, which refers to a device that includes an electric pump, an electric valve, or the like, and that can adjust the brake fluid pressure without requiring user operation. [Example]

[0014] A brake device 10 according to an embodiment will be described with reference to the drawings. The brake device 10 according to the embodiment is a brake device for a vehicle, and is provided on each wheel of the vehicle. Although not particularly limited, the brake device 10 according to the embodiment can be used in an electric vehicle that travels on a road surface. The electric vehicle referred to here includes a battery-powered electric vehicle, a hybrid vehicle, a plug-in hybrid vehicle, a fuel cell vehicle, and the like.

[0015] 1, the brake device 10 includes a disc rotor 12 that rotates together with a vehicle wheel (not shown), a pair of brake pads 14a, 14b that face each other across the disc rotor 12, and a brake caliper 16 that supports the pair of brake pads 14a, 14b. The brake caliper 16 applies a braking force to the wheel that rotates together with the disc rotor 12 by pressing the pair of brake pads 14a, 14b against the disc rotor 12.

[0016] The brake caliper 16 is provided with a caliper cylinder 18 and a caliper piston 20. The caliper cylinder 18 has a cylindrical shape extending in the left-right direction in the drawing and houses the caliper piston 20 therein. The caliper cylinder 18 is filled with brake fluid. A brake actuator 46 and a brake master cylinder 44 are connected to the caliper cylinder 18 via brake piping 40.

[0017] The brake master cylinder 44 supplies brake fluid pressure to the caliper cylinder 18 in response to the operation of the brake pedal 42 by the user. The brake fluid pressure supplied to the caliper cylinder 18 varies in response to the operating force (i.e., the depression force) applied to the brake pedal 42, and the stronger the user operates the brake pedal 42, the higher the brake fluid pressure supplied to the caliper cylinder 18. Note that the specific configuration of the brake master cylinder 44 is not particularly limited.

[0018] The brake actuator 46 is provided between the brake master cylinder 44 and the caliper cylinder 18. The brake actuator 46 has an electric pump, an electric valve, etc., and can adjust the brake fluid pressure without the need for the user to operate the brake pedal 42. The brake actuator 46 functions as an actuator that operates the brake device 10 in an anti-lock brake system, a collision avoidance assistance system, or an autonomous driving system. However, the brake actuator 46 is not necessarily required.

[0019] The caliper piston 20 is supported so as to be slidable along the axial direction within the caliper piston 20 (i.e., along the left-right direction in the drawing). One of the brake pads 14a is attached to the caliper piston 20. The caliper piston 20 slides within the caliper piston 20, thereby moving the one of the brake pads 14a forward and backward relative to the disc rotor 12.

[0020] A piston ring seal 22 is provided between the caliper cylinder 18 and the caliper piston 20. The piston ring seal 22 is an annular member that seals the gap between the caliper cylinder 18 and the caliper piston 20. The piston ring seal 22 is made of a polymer material such as rubber, and is capable of elastic deformation.

[0021] As shown in FIG. 2, when brake fluid pressure is supplied to the caliper cylinder 18 by, for example, operating the brake pedal 42, the caliper piston 20 moves toward the disc rotor 12. This presses one brake pad 14a against the disc rotor 12. At the same time, the body of the brake caliper 16 moves in the opposite direction (to the right in the figure). As the body of the brake caliper 16 moves, the other brake pad 14b attached to the body is pressed against the disc rotor 12 from the opposite side. As a result, the brake device 10 is activated, and a braking force is applied to the wheel via the disc rotor 12.

[0022] During operation of the brake device 10, elastic deformation occurs in the piston ring seal 22. Therefore, as shown in Fig. 3, for example, when the brake pedal 42 is released and the supply of brake fluid pressure is stopped, the caliper piston 20 returns to its initial position due to the restoring force of the piston ring seal 22. As a result, the pair of brake pads 14a, 14b are separated from (or slightly in contact with) the disc rotor 12, and the operation of the brake device 10 is released.

[0023] Returning to FIG. 1 , the brake device 10 further includes an electric actuator 24, a hydraulic pressure sensor 26, and a control device 28. The electric actuator 24 is provided in the brake caliper 16, and is capable of moving the caliper piston 20 forward and backward relative to the disc rotor 12. The electric actuator 24 is originally an actuator for a parking brake. The operation of the electric actuator 24 is controlled by the control device 28. By controlling the electric actuator 24, the control device 28 can continuously operate the brake device 10 while the vehicle is stopped. The electric actuator 24 may be, for example, an electric motor, but is not limited to an electric motor.

[0024] As an example, in this embodiment, the electric actuator 24 is connected to the caliper piston 20 via a feed screw 25. When the electric actuator 24 rotates the feed screw 25 in one direction, the caliper piston 20 moves toward the disc rotor 12 together with one of the brake pads 14a. At this time, the other brake pad 14b also moves toward the disc rotor 12 from the opposite side together with the main body of the brake caliper 16. When the electric actuator 24 rotates the feed screw 25 in the other direction, the caliper piston 20 moves away from the disc rotor 12 together with one of the brake pads 14a. At this time, the other brake pad 14b also moves away from the disc rotor 12 together with the main body of the brake caliper 16.

[0025] The hydraulic pressure sensor 26 is provided in the brake piping 40 and detects the brake hydraulic pressure supplied to the caliper cylinder 18. The location of the hydraulic pressure sensor 26 is not limited to the brake piping 40. The hydraulic pressure sensor 26 is electrically connected to the control device 28, and the detected value by the control device 28 is input to the control device 28.

[0026] In the brake device 10 of this embodiment, drag torque occurs when the brake is released and the supply of brake fluid pressure is stopped. This drag torque varies depending on the magnitude of the brake fluid pressure during braking, and the greater the brake fluid pressure, the greater the drag torque. This point will be explained with reference to FIGS. 4 and 5. As shown in FIG. 4, the greater the brake fluid pressure, the greater the strain generated in the brake caliper 16 and the brake pads 14a, 14b, which increases the amount of movement of the caliper piston 20. As the amount of movement of the caliper piston 20 increases, the amount of movement of the caliper piston 20 when it returns to its initial position after the supply of brake fluid pressure is stopped also increases. As a result, as shown in FIG. 5, reverse strain occurs in the piston ring seal 22, and the restoring force of this strain presses the pair of brake pads 14a, 14b against the disc rotor 12, generating a relatively large drag torque.

[0027] The generation of excessive drag torque leads to unnecessary energy loss and can be a factor in reducing the energy efficiency of the vehicle (energy consumption per travel distance). Therefore, in the brake device 10 of this embodiment, the control device 28 is configured to execute a series of processes shown in Fig. 6, thereby avoiding or suppressing the generation of excessive drag torque. Hereinafter, the series of processes executed by the control device 28 will be described with reference to Fig. 6.

[0028] As shown in Fig. 6, the control device 28 determines whether the braking device 10 is in operation based on the operation of the brake pedal 42 by the user or the operation of the brake actuator 46 (S12). If the braking device 10 is in operation (YES in S12), the control device 28 acquires the brake fluid pressure detected by the fluid pressure sensor 26. If the detected brake fluid pressure exceeds a predetermined threshold (YES in S16), the control device 28 stores a predetermined flag (S18). That is, this flag is a parameter indicating that the brake fluid pressure has exceeded the predetermined threshold while the braking device 10 is in operation. The above process is repeatedly executed until the operation of the braking device 10 is released (S20).

[0029] When the operation of the brake device 10 is released (YES in S20), the control device 28 determines whether or not the above-mentioned flag is stored (S22). If the flag is stored (YES in S22), the control device 28 operates the electric actuator 24 in a direction in which the caliper piston 20 moves away from the disc rotor 12. This makes it possible to avoid or suppress the generation of excessive drag torque even after the brakes are applied by a large brake fluid pressure that exceeds a threshold value.

[0030] In the above-described embodiment, the amount of operation of the electric actuator 24 by the control device 28 may be constant regardless of the value detected by the hydraulic pressure sensor 26. Alternatively, the control device 28 may increase the amount of operation of the electric actuator 24 as the value detected by the hydraulic pressure sensor 26 increases. With this configuration, the electric actuator 24 can be operated just enough according to the magnitude of the brake hydraulic pressure generated while the brake device 10 is in operation.

[0031] Although the embodiments of the present technology have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and alterations of the specific examples exemplified above. The technical elements described in this specification or drawings exhibit technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technology exemplified in this specification or drawings simultaneously achieves multiple objectives, and achieving one of these objectives itself has technical utility. [Explanation of symbols]

[0032] 10: Brake device 12: Disc rotor 14a: Brake pads 14b: Brake pads 16: Brake caliper 18: Caliper cylinder 20: Caliper piston 22: Piston ring seal 24: Electric actuator 25: Feed screw 26: Hydraulic pressure sensor 28: Control device 40: Brake piping 42: Brake pedal 44: Brake master cylinder 46: Brake actuator

Claims

1. A braking device for a vehicle, a disc rotor that rotates together with the wheel of the vehicle; a pair of brake pads facing each other with the disc rotor in between; a brake caliper that supports the pair of brake pads and has a caliper cylinder; a caliper piston disposed in the caliper cylinder and configured to press one of the pair of brake pads against the disc rotor in response to brake fluid pressure supplied to the caliper cylinder; a piston ring seal provided between the caliper cylinder and the caliper piston; an electric actuator that moves the caliper piston back and forth relative to the disc rotor; a hydraulic pressure sensor that detects the brake hydraulic pressure supplied to the caliper cylinder; a control device that controls the operation of the electric actuator based on the detection value of the hydraulic pressure sensor; Equipped with When the detection value by the hydraulic pressure sensor exceeds a predetermined threshold during braking operation in which the brake hydraulic pressure is supplied to the brake caliper, the control device operates the electric actuator in a direction in which the caliper piston retracts from the disc rotor when the brake is released and the supply of the brake hydraulic pressure is subsequently stopped. Brake device.

2. 2. The brake device according to claim 1, wherein the control device increases the amount of movement of the electric actuator as the detected value by the hydraulic pressure sensor increases.

3. 3. The brake device according to claim 1, wherein the electric actuator is an actuator for a parking brake.

4. The brake device according to claim 1 , wherein the brake fluid pressure supplied to the caliper cylinder is adjusted in response to an operation by a user.

5. 5. The brake device according to claim 1, wherein the brake fluid pressure supplied to the caliper cylinder is adjusted by a brake actuator.

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