Vehicle braking system

Abstract

To prevent brake force from becoming excessive when a brake pedal is operated during the electric parking brake operation.SOLUTION: In a case where a brake pedal is operated quickly in a process of applying an electric parking brake, a parking brake operation is finished when a detection total pressure force Ffd which is a sum of a mechanical system pressure force M and a hydraulic system pressure force Hfd detected by a hydraulic pressure sensor reaches a first increase required pressure force FCa1 obtained by adding a first additional pressure force Fdr1 to the pressure force Fc required for parking. In a case where the brake pedal is operated gradually, the parking brake operation is finished when the detection total pressure force Ffd reaches a second increase required pressure force Fca2 smaller than the first increase required pressure force FCa1. Thereby, generation of excessive pressure force (brake force) is suppressed when the brake pedal is operated gradually.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a brake system for a vehicle, and more particularly to a brake system equipped with an electric parking brake. [Background technology]

[0002] A vehicle's brake device transmits the driver's pedal operation to brake members such as brake pads via hydraulic pressure, and presses the brake members against braked members such as disc rotors to restrict the rotation of the wheels. Recently, the number of vehicles equipped with electric parking brakes that drive the brake members using a motor and mechanically press the braked members to restrict the rotation of the wheels has been increasing. Patent Document 1 listed below discloses a brake device that performs parking brake operation using a hydraulic system (16) that drives the brake members via hydraulic pressure and an electric system (40) that includes a motor (42). The reference numerals in parentheses above are those used in Patent Document 1 listed below and are not related to the reference numerals used in the description of the embodiments of the present application. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-146751 Summary of the Invention [Problem to be solved by the invention]

[0004] In a brake device having a mechanical drive system that mechanically drives brake members using a motor and a hydraulic drive system that drives brake members via hydraulic pressure, when a parking brake is operated using the mechanical drive system and the hydraulic drive system, the braking force from both systems can be adjusted to obtain the required braking force. When the mechanical drive system supplements the braking force that is insufficient with the hydraulic drive system alone, the hydraulic pressure is detected and braking force from the mechanical drive system is generated according to the detected hydraulic pressure. The actual braking force is generated with a time delay relative to the hydraulic pressure of the hydraulic drive system. Therefore, the actual braking force from the hydraulic drive system may be smaller than the braking force corresponding to the detected hydraulic pressure, and in this case, the total braking force may be smaller than the required braking force. To avoid this, if the braking force from the mechanical drive system is constantly increased by a fixed amount, taking into account the reduction in braking force due to the delay, excessive braking force will be generated if the delay is small.

[0005] An object of the present invention is to suppress the generation of excessive braking force when the parking brake is applied. [Means for solving the problem]

[0006] A vehicle brake device according to the present invention includes a piston that pushes a brake member toward a braked member that rotates integrally with a wheel, a hydraulic drive system that drives the piston with hydraulic pressure to push the brake member and generate a pressing force against the braked member, a mechanical drive system that mechanically and directly drives the piston with a motor to push the brake member and generate a pressing force against the braked member, a hydraulic pressure sensor that detects the hydraulic pressure in the hydraulic drive system, and a control unit that, when a pressing force from the hydraulic drive system is acting during parking brake operation, controls the mechanical drive system so that a required pressing force for parking is obtained from the pressing force from the hydraulic drive system and the pressing force from the mechanical drive system. The control unit controls the mechanical drive system so that a total pressing force, which is the sum of the pressing force from the hydraulic drive system calculated based on the hydraulic pressure detected by the hydraulic pressure sensor and the pressing force from the mechanical drive system, becomes a pressing force obtained by adding an additional pressing force corresponding to the hydraulic pressure detected by the hydraulic pressure sensor to the required pressing force during parking brake operation.

[0007] Even if there is a delay in the pressure of the hydraulic drive system relative to the hydraulic pressure detected by the hydraulic pressure sensor, a pressure corresponding to the delay can be obtained, and excessive pressure can be prevented.

[0008] In the above-mentioned vehicle brake device, the control unit can set the additional pressure to a first additional pressure when the hydraulic pressure detected by the hydraulic pressure sensor increases at a rate exceeding a predetermined value, and can set the additional pressure to a second additional pressure that is smaller than the first additional pressure when the hydraulic pressure detected by the hydraulic pressure sensor increases at a rate below the predetermined value.

[0009] The calculation load for control is reduced compared to when the additional pressure is continuously changed in accordance with the hydraulic pressure.

[0010] In the above-described vehicle brake device, the hydraulic drive system may include a manual operation mechanism that transmits the movement of a brake operator operated by a driver to a piston via fluid to drive the piston.

[0011] In the above-described vehicle brake device, the hydraulic drive system may include a master cylinder that converts movement of a brake operator into hydraulic pressure, and the hydraulic pressure sensor may detect the hydraulic pressure in the master cylinder. [Effects of the Invention]

[0012] Even if there is a delay in the pressure of the hydraulic drive system relative to the hydraulic pressure detected by the hydraulic pressure sensor, the pressure can be prevented from becoming excessive, which is advantageous in terms of the strength and durability of the device. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a diagram schematically illustrating a configuration of a brake device of a vehicle. [Figure 2] FIG. 2 is a diagram for explaining the operation of a brake device of a vehicle. [Figure 3]10 is a diagram showing the relationship between the delay in hydraulic system pressure and the additional pressure to be added to the required pressure, relative to the rate of increase in hydraulic pressure in the hydraulic drive system. FIG. [Figure 4] FIG. 2 is a diagram for explaining the actual operation of a brake device of a vehicle. DETAILED DESCRIPTION OF THE INVENTION

[0014] An embodiment of the present invention will now be described with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of a vehicle brake device 10 according to this embodiment. The brake device 10 includes a disk-shaped disc rotor 12 that rotates integrally with the vehicle wheel, and brake pads 14 that come into sliding contact with the rotating disc rotor 12 and apply braking force to the disc rotor 12 by friction. The disc rotor 12 is an example of a braked member that rotates integrally with the wheel, and another example of a braked member is a brake drum. The brake pads 14 are an example of a braking member that comes into sliding contact with the braked member. A brake shoe is an example of a braking member that corresponds to the brake drum.

[0015] The brake device 10 further includes a brake caliper 16 (hereinafter referred to as the caliper 16) in which the brake pads 14 are incorporated, and the caliper 16 further includes a brake piston 18 (hereinafter referred to as the piston 18) for pushing the brake pads 14 toward the disc rotor 12, which is slidably incorporated in a cylinder chamber 20 defined within the caliper 16. The piston 18 includes a hollow cylindrical portion 18a and an end surface portion 18b provided to close the end of the cylindrical portion 18a on the brake pad 14 side. The brake device 10 includes a hydraulic drive system 22 that drives the piston 18 via hydraulic pressure, and a mechanical drive system 24 that directly mechanically drives the piston 18 without using fluid pressure such as hydraulic pressure.

[0016] The hydraulic drive system 22 includes a master cylinder 28 that generates hydraulic pressure according to the amount of depression of the brake pedal 26, and a hydraulic circuit 30 that can increase or decrease the hydraulic pressure generated by the master cylinder 28. The hydraulic circuit 30 includes a hydraulic pump (not shown) that increases the hydraulic pressure supplied to the cylinder chamber 20 when the pressure in the master cylinder 28 is insufficient. The hydraulic circuit 30 may be a hydraulic circuit of a device called a vehicle behavior control device, an anti-skid device, or the like. A vehicle behavior control device individually controls the braking force generated at each wheel, and uses the braking force to generate a yaw moment of the vehicle and stabilize the vehicle's behavior. Hydraulic pressure from the master cylinder 28 is supplied to the cylinder chamber 20 via the hydraulic circuit 30. This pressure drives the piston 18, which pushes the brake pad 14 toward the disc rotor 12. As a result, the disc rotor 12 is clamped by the brake pads 14 facing each other across the disc rotor 12, generating braking force.

[0017] The mechanical drive system 24 includes an electric motor 32 (hereinafter referred to as the motor 32) and a mechanical transmission mechanism 34 that transmits the rotation of the motor 32, converts it into linear motion, and drives the piston 18. Therefore, the mechanical drive system 24 is an electric actuator that electrically drives the piston 18. The mechanical transmission mechanism 34 includes a gear train 36 that reduces the rotation of the motor 32 before transmitting it, a feed screw shaft 38 that is rotationally driven by the gear train 36, and a thrust nut 40 that is threadedly coupled to the feed screw shaft 38. The feed screw shaft 38 and the thrust nut 40 are disposed coaxially with the piston 18 inside the cylindrical portion 18a of the piston 18. The thrust nut 40 is restricted from rotating relative to the piston 18 and the caliper 16, and moves along the axial direction of the feed screw shaft 38 when the feed screw shaft 38 rotates. The feed screw shaft 38 and the thrust nut 40 constitute a motion conversion mechanism that converts the rotational motion of the motor 32 into linear motion. When the thrust nut 40 is driven toward the end face portion 18b of the piston 18, the piston 18 pushes the brake pads 14 toward the disc rotor 12. As a result, the disc rotor 12 is sandwiched between the brake pads 14 that face each other across the disc rotor 12, generating a braking force.

[0018] The disc rotor 12, caliper 16, hydraulic drive system 22, and mechanical drive system 24 are provided for each of a plurality of wheels, and Fig. 1 shows the configuration for one wheel. The mechanical drive system 24 may be provided for only some of the wheels, for example, for only the two rear wheels in a four-wheel vehicle such as a typical passenger car.

[0019] The brake device 10 includes a control unit 42 that controls the operation of the hydraulic drive system 22 and the mechanical drive system 24 of each wheel. The control unit 42 controls the hydraulic circuit 30 to control the hydraulic pressure supplied to the cylinder chamber 20 by the hydraulic drive system 22. At this time, feedback control may be performed based on the hydraulic pressure detected by a hydraulic pressure sensor 44 that detects the hydraulic pressure of the hydraulic drive system 22. The hydraulic pressure sensor 44 may be disposed in or near the master cylinder 28 to detect the hydraulic pressure of the master cylinder 28. The control unit 42 also controls the current supplied to the motor 32 to control the driving force of the piston 18 by the mechanical drive system 24. The force driving the piston 18 can be detected based on the value of the current supplied to the motor 32. Furthermore, the control unit 42 drives and controls the motor 32 based on the operation of an electric parking brake switch 46 (hereinafter referred to as the EPB switch 46) by the occupant, thereby advancing and retracting the thrust nut 40. When the EPB switch 46 is turned on, the thrust nut 40 is driven to advance toward the end surface 18b of the piston 18, and when the EPB switch 46 is turned off, the thrust nut 40 is driven to retreat in the opposite direction.

[0020] The parameters used in the following description are defined as follows: The force with which the brake pads 14 press against the disc rotor 12 is referred to as the "total pressing force F." The braking force acting on the vehicle is proportional to the pressing force. The pressing force by the hydraulic drive system 22 is referred to as the "hydraulic system pressing force H," and the pressing force by the mechanical drive system 24 is referred to as the "mechanical system pressing force M." The sum of the hydraulic system pressing force H and the mechanical system pressing force M is the total pressing force F. When parking on a slope with a specified inclination angle, the pressing force required to keep the vehicle stopped is referred to as the "required pressing force Fc."

[0021] The brake device 10 normally applies the parking brake by operating only the mechanical drive system 24. When the EPB switch 46 is turned on, the control unit 42 supplies power to the motor 32, causing the feed screw shaft 38 to rotate and the piston 18 to advance toward the brake pad 14. The control unit 42 monitors the current I supplied to the motor 32, and when the mechanical system pressing force M corresponding to this current reaches a value corresponding to the required pressing force Fc, the control unit 42 stops the supply of the current I to stop the motor 32 and stop the parking brake operation.

[0022] When hydraulic pressure in the hydraulic drive system 22 is maintained by the hydraulic circuit 30, or when hydraulic pressure is generated by the driver pressing the brake pedal 26, if the mechanical drive system 24 is operated until the mechanical system pressing force M reaches the required pressing force Fc, as in the case when there is no hydraulic pressure, the total pressing force F is the sum of the required pressing force Fc and the hydraulic system pressing force H. This pressure is excessive relative to the required pressing force Fc. Furthermore, even if the hydraulic system pressing force H is reduced from a state in which the hydraulic system pressing force H and the mechanical system pressing force M are acting, the total pressing force F does not change because the position of the piston 18 is fixed by the mechanical drive system 24. Therefore, even if the hydraulic pressure decreases when the driver releases his / her foot from the brake pedal 26, the excessive pressing force is maintained. In this brake device 10, when the hydraulic system pressing force H is acting when the parking brake is applied, the required pressing force Fc is obtained not only by the mechanical system pressing force M but also by the hydraulic system pressing force H and the mechanical system pressing force M. Furthermore, as described above, even if the hydraulic pressure H decreases while the mechanical pressure M is acting, the necessary pressure Fc is ensured.

[0023] 2 is a diagram for explaining the operation when applying the parking brake of the brake device 10. More specifically, it is a diagram showing the pressing force and the motor current I when the brake pedal 26 is depressed and the hydraulic pressure of the hydraulic drive system 22 acts in the process of applying the parking brake.

[0024] When the EPB switch 46 is turned on at time t1, a motor current I is supplied to the motor 32. The motor current I is large when the motor 32 is started but quickly decreases. The thrust nut 40 advances toward the piston 18 and, at time t2, contacts the piston 18 and begins to push against it, generating a mechanical system pressing force M. As the mechanical system pressing force M increases, the motor current I also increases. Furthermore, at time t3, the brake pedal 26 is depressed, increasing the hydraulic pressure of the hydraulic drive system 22. The pressing force based on the hydraulic pressure detected by the hydraulic pressure sensor 44 is indicated by the symbol Hd. This pressing force Hd is referred to as the detected hydraulic system pressing force Hd. If the rate of increase in hydraulic pressure is high, the pressing force Hr actually acting on the disc rotor 12 increases with a delay relative to the increase in hydraulic pressure. This pressing force Hr is referred to as the actual hydraulic system pressing force Hr. The actual hydraulic system pressing force Hr begins to increase at time t4, a time delay from time t3. The sum of the detected hydraulic pressure Hd and the mechanical pressure M is indicated by the symbol Fd (= M + Hd), and this pressure Fd will be referred to as the detected total pressure Fd. Furthermore, the sum of the actual hydraulic pressure Hr and the mechanical pressure M is indicated by the symbol Fr (= M + Hr), and this pressure Fr will be referred to as the actual total pressure Fr. Furthermore, the rate at which hydraulic pressure increases will be referred to as the "increase rate."

[0025] At time t5 when the detected total pressing force Fd reaches the required pressing force Fc, the detected total pressing force Fd, the mechanical pressing force M, the detected hydraulic pressure system pressing force Hd, and the actual hydraulic pressure system pressing force Hr are denoted as Fd5, M5, Hd5, and Hr5, respectively. Fd5=M5+Hd5=Fc is.

[0026] At time t5, the actual total pressing force Fr5 is smaller than the detected total pressing force Fd5 and also smaller than the required pressing force Fc because the actual hydraulic system pressing force Hr is smaller than the detected hydraulic system pressing force Hd. Fr5=M5+Hr5 <Fc

[0027] When the motor 32 is stopped at time t5, the mechanical pressure M is maintained at M5, as indicated by the symbol MA. Meanwhile, the actual total pressure Fr increases after time t5 as the actual hydraulic pressure Hr increases, as indicated by the symbol FrA. When the driver releases his / her foot from the brake pedal 26, the actual hydraulic pressure Hr becomes zero. However, the movement of the piston 18 is restricted by the thrust nut 40, so the piston 18 does not retract and its position remains unchanged. The pressure of the brake pad 14 against the disc rotor 12 is determined by the position of the piston 18. Therefore, unless the piston 18 retracts, the pressure does not change even if the actual hydraulic pressure Hr becomes zero. Therefore, the actual total pressure Fr becomes Fr5, a value determined by the amount of advancement of the piston 18 at time t5. In other words, the mechanical pressure M increases to compensate for the lost actual hydraulic pressure Hr, and the actual total pressure Fr becomes Fr5 due to the mechanical pressure M alone. This actual total pressing force Fr5 does not reach the required pressing force Fc. This is due to the difference Hdr between the detected hydraulic pressure system pressing force Hd and the actual hydraulic pressure system pressing force Hr. Therefore, by taking this difference into consideration in advance and stopping the motor 32 after the detected total pressing force Fd exceeds the pressing force obtained by adding a predetermined value to the required pressing force Fc, the final actual total pressing force Fr can be made equal to or greater than the required pressing force Fc.

[0028] The difference between the detected hydraulic pressure system pressing force Hd and the actual hydraulic pressure system pressing force Hr due to the delay, that is, the pressing force decrease Hdr due to the delay, is almost the same value at any time while the two are changing, so it can be represented by the value at time t5, Hdr=Hd5-Hr5 A value Fdr equal to this pressure force decrease Hdr is added to the required pressure force Fc, and when the detected total pressure force Fd reaches this pressure force (Fc + Fdr), the motor 32 is stopped. The pressure force Fdr added to the required pressure force Fc is referred to as the additional pressure force Fdr, and the pressure obtained by adding the additional pressure force Fdr to the required pressure force Fc is referred to as the increased required pressure force Fca.

[0029] The control unit 42 supplies the motor current I until time t6 when the detected total pressing force Fd reaches the required increased pressing force Fca, and stops supplying the motor current I at time t6. The detected total pressing force Fd, the mechanical pressing force M, the detected hydraulic pressure system pressing force Hd, the actual hydraulic pressure system pressing force Hr, and the actual total pressing force Fr at time t6 are denoted as Fd6, M6, Hd6, Hr6, and Fr6, respectively. At time t6, Fd6=M6+Hd6=Fca Fr6=M6+Hr6=Fc is.

[0030] After time t6, the mechanical pressure M is maintained at M6, as indicated by the symbol MB, while the actual total pressure Fr increases after time t6 as indicated by the symbol FrB in accordance with the increase in the actual hydraulic pressure Hr. When the driver releases his / her foot from the brake pedal 26, the actual hydraulic pressure Hr disappears, and the mechanical pressure M increases to compensate for the lost pressure Hr, reaching a value determined by the amount of advancement of the piston 18 at time t6, i.e., Fr6. Therefore, the actual total pressure Fr becomes Fr6 (= Fc).

[0031] FIG. 3 shows the relationship between the rate of increase in hydraulic pressure and the additional pressure Fdr. As the rate of increase in hydraulic pressure increases, the pressure reduction amount Hdr due to the delay also increases. When the hydraulic pressure H increases during the process of applying the parking brake, the additional pressure Fdr, which is equal to the pressure reduction amount Hdr at that time, is added to the required pressure Fc each time to calculate the increased required pressure Fca. By controlling the mechanical pressure M based on this increased required pressure Fca, the required pressure Fc can always be obtained after the hydraulic pressure H decreases (i.e., finally). In this way, by continuously changing the additional pressure Fdr in accordance with the increase or decrease in the rate of increase in hydraulic pressure, the parking brake can always be maintained at the required pressure Fc.

[0032] In this brake device 10, control is performed simply by using two values ​​of additional pressure Fdr. When the hydraulic pressure increase rate exceeds a predetermined threshold value Th, a first additional pressure Fdr1 is used, and when the rate is equal to or less than the threshold value Th, a second additional pressure Fdr2 having a value smaller than the first additional pressure Fdr1 is used. When the brake pedal 26 is suddenly operated and there is a large delay in the hydraulic drive system 22, the brake device 10 obtains the required pressure Fc by using a large first additional pressure Fdr1, and when the brake pedal 26 is slowly operated or not operated at all, the brake device 10 uses a small second additional pressure Fdr2 to prevent the pressure during parking braking from becoming excessive.

[0033] Fig. 4 is a diagram showing the operation of the brake device 10 during parking braking. Fig. 4 shows the pressures when the brake pedal 26 is suddenly operated during the process of applying the parking brake, and when the brake pedal 26 is operated and maintained in that state before applying the parking brake. The detected hydraulic pressure when the brake pedal 26 is suddenly operated is indicated by symbol Hfd, the actual hydraulic pressure Hfr, the detected total pressure by symbol Ffd, and the actual total pressure by symbol Ffr. Furthermore, when the brake pedal 26 is not operated, i.e., does not move, the detected hydraulic pressure is indicated by symbol Hsd, the actual hydraulic pressure by symbol Hsr, the detected total pressure by symbol Fsd, and the actual total pressure by symbol Fsr.

[0034] First, we will explain what happens when the driver suddenly depresses the brake pedal 26 while the parking brake is operating. When the EPB switch 46 is turned on at time t1, the parking brake operation begins and a motor current I is supplied to the motor 32. The motor current I is large when the motor 32 starts but quickly decreases. Driven by the motor 32, the thrust nut 40 advances toward the piston 18, and at time t2 it comes into contact with the piston 18 and begins to push the piston 18, generating a mechanical pressing force M. As the mechanical pressing force M increases, the motor current I also increases.

[0035] At time t3, the brake pedal 26 is depressed, increasing the hydraulic pressure of the hydraulic drive system 22. If the rate of increase in the detected hydraulic pressure Hfd detected by the hydraulic pressure sensor 44 exceeds the threshold value Th (see FIG. 3), the control unit 42 sets a first increased required pressure Fca1, which is the sum of the required pressure Fc and the first additional pressure Fdr1. The control unit 42 monitors the mechanical pressure M and the detected hydraulic pressure Hfd, and when the sum Ffd (= M + Hfd) reaches the first increased required pressure Fca1 (time t6), the control unit 42 stops the supply of motor current I, thereby terminating the parking brake operation. After the supply of motor current I stops and the motor 32 stops, the mechanical pressure M is maintained at pressure M6, as indicated by the symbol Mf. Meanwhile, the actual total pressure Ffr increases as the actual hydraulic pressure Hfr increases. When the driver releases the brake pedal 26, the actual hydraulic pressure Hfr decreases to zero, and the mechanical pressure Mf increases to a value Ffr6 at time t6 to compensate for the lost pressure Hfr, and the actual total pressure Ffr becomes Ffr6. If the pressure reduction Hdr due to the delay is equal to or less than the first additional pressure Fdr1, the final actual total pressure Ffr will be equal to or greater than the required pressure Fc (Ffr≧Fc). Therefore, the braking force required for parking is ensured.

[0036] Next, we will explain the operation when the EPB switch 46 is turned on while the driver is depressing the brake pedal 26, and the brake pedal 26 is not moved after the EPB switch 46 is turned on. In this case, the hydraulic pressure H is constant, and there is no delay between the actual hydraulic pressure Hsr and the detected hydraulic pressure Hsd, so they are the same value. When the EPB switch 46 is turned on at time t1, parking brake operation is initiated, and a motor current I is supplied to the motor 32. Driven by the motor 32, the thrust nut 40 advances toward the piston 18, and at time t2, it contacts the piston 18 and begins to push it, generating a mechanical pressure M. As the mechanical pressure M increases, the motor current I also increases.

[0037] If the hydraulic pressure does not increase or if the rate of increase is equal to or less than the threshold value Th, the control unit 42 sets a second required additional pressure Fca2, which is the required pressure Fc plus a second additional pressure Fdr2, which is smaller than the first additional pressure Fdr1. The second required additional pressure Fca2 may be set as an initial value, and when the rate of increase in the hydraulic pressure exceeds the threshold value Th, the setting may be changed to the first required additional pressure Fca1. The control unit 42 monitors the mechanical pressure M and the detected hydraulic pressure Hsd, and when their sum Fsd (= M + Hsd) reaches the second required additional pressure Fca2 (at time t7), the control unit 42 stops the supply of motor current I and terminates the parking brake operation. After the supply of motor current I stops and the motor 32 stops, the mechanical pressure M is maintained at pressure M7, as indicated by the symbol Ms. Since the actual hydraulic pressure Hsr is also constant, the actual total pressure Fsr is also maintained at the pressure Fsr7 (=Fca2=M7+Hsr7) at time t7. When the driver releases his / her foot from the brake pedal 26, the actual hydraulic pressure Hsr decreases to zero, and the mechanical pressure Ms increases to the value Fsr7 at time t7 to compensate for the lost pressure Hsr (the actual total pressure Fsr is maintained at Fsr7). If the rate of increase in the hydraulic pressure is equal to or less than the threshold value Th, the final actual total pressure Fsr will be equal to or greater than the required pressure Fc (Fsr≧Fc).

[0038] When the brake pedal 26 is not operated or is operated slowly, the generation of excessive pressure can be suppressed by using a second increased required pressure Fca2 that is smaller than the first increased required pressure Fca1 when the brake pedal 26 is suddenly operated.

[0039] In the above embodiment, the first and second required increased pressures Fca1 and Fca2 are used as the required increased pressure Fca depending on the rate of increase of the hydraulic pressure, but three or more values ​​may be used. Also, the required increased pressure Fca may be continuously changed depending on the rate of increase of the hydraulic pressure. [Explanation of symbols]

[0040] 10 Brake device, 12 Disc rotor (Brake member), 14 Brake pad (Brake member), 16 Caliper, 18 Piston, 20 Cylinder chamber, 22 Hydraulic drive system, 24 Mechanical drive system, 26 Brake pedal (Brake operator), 28 Master cylinder, 30 Hydraulic circuit, 32 Motor, 34 Mechanical transmission mechanism, 36 Gear train, 38 Feed screw shaft, 40 Thrust nut, 42 Control unit, 44 Hydraulic pressure sensor, 46 Electric parking brake (EPB) switch, F Total pressing force, Fc Required pressing force, Fd Detected total pressing force, Fr Actual total pressing force, Fdr Added pressing force, Fca Increased required pressing force, H Hydraulic system pressing force, Hd Detected hydraulic system pressing force, Hr Actual hydraulic system pressing force, Hdr Pressing force reduction due to delay, M Mechanical system pressing force, Ff, Hf, Mf Brake pedal pressing force when suddenly operated, Fs, Hs, Ms Brake pedal pressing force when gently operated.

Claims

1. a piston that pushes the braking member toward a member to be braked that rotates integrally with the wheel; a hydraulic drive system that drives the piston by hydraulic pressure to push out the braking member and generate a pressing force against the member to be braked; a mechanical drive system that mechanically drives the piston directly using a motor to push out the braking member and generate a pressing force against the member to be braked; a hydraulic pressure sensor for detecting the hydraulic pressure of the hydraulic drive system; a control unit that controls the mechanical drive system when a pressing force from the hydraulic drive system is acting during parking brake operation so that a necessary pressing force for parking can be obtained by the pressing force from the hydraulic drive system and the pressing force from the mechanical drive system; Equipped with the control unit controls the mechanical drive system so that, during parking brake operation, a total pressing force, which is the sum of a pressing force by the hydraulic drive system calculated based on the hydraulic pressure detected by the hydraulic pressure sensor and a pressing force by the mechanical drive system, becomes a pressing force obtained by adding an additional pressing force corresponding to the hydraulic pressure detected by the hydraulic pressure sensor to the required pressing force; Furthermore, the control unit sets the additional pressure to a first additional pressure when the hydraulic pressure detected by the hydraulic pressure sensor increases at a rate exceeding a predetermined value, and sets the additional pressure to a second additional pressure that is smaller than the first additional pressure when the hydraulic pressure detected by the hydraulic pressure sensor increases at a rate equal to or less than the predetermined value. Vehicle braking system.

2. 2. The vehicle brake device according to claim 1, wherein the hydraulic drive system includes a manual operation mechanism that transmits movement of a brake operator operated by a driver to the piston via a fluid to drive the piston.

3. 3. The vehicle brake device according to claim 2, wherein the hydraulic drive system includes a master cylinder that converts movement of the brake operator into hydraulic pressure, and the hydraulic pressure sensor detects the hydraulic pressure in the master cylinder.

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