JP7266109B2 - brake device - Google Patents

Description

The present disclosure relates to a braking device that applies braking force to a vehicle such as an automobile.

2. Description of the Related Art As a brake device provided in a vehicle such as an automobile, there is known a device that applies a braking force based on driving (rotation) of an electric motor when the vehicle is stopped or parked. Patent Literature 1 describes an electric brake device that limits the maximum thrust of an electric brake by calculating the thrust required to keep the vehicle stationary.

Japanese Patent Application Laid-Open No. 2007-15602

The technique of Patent Document 1 calculates the thrust required to keep the vehicle stopped using information from the vehicle weight sensor and the longitudinal G sensor. However, depending on the vehicle, there is a possibility that vehicle weight sensor information cannot be obtained.

An object of an embodiment of the present invention is to provide a braking device capable of applying a thrust force necessary to keep the vehicle stationary even if information from a vehicle weight sensor cannot be obtained.

According to one embodiment of the present invention, there is provided a brake device comprising an electric motor that drives an electric mechanism that maintains braking force of a vehicle, and a control device that controls the driving of the electric motor, wherein the control device controls the operation of the vehicle when the vehicle is running. The thrust generated by the electric mechanism for maintaining the braking force in the stopped state is changed according to the deceleration until the vehicle is shifted to the stopped state and the brake fluid pressure until the transition.

According to one embodiment of the present invention, it is possible to apply the thrust required to keep the vehicle stationary even if information from the vehicle weight sensor is not obtained.

1 is a conceptual diagram of a vehicle equipped with a brake device according to a first embodiment; FIG. FIG. 2 is an enlarged longitudinal sectional view showing a disk brake with an electric parking brake function provided on the rear wheel side in FIG. 1 ; FIG. 2 is a block diagram showing the parking brake control device in FIG. 1 together with a rear wheel side disc brake and the like; FIG. 2 is a block diagram of a thrust calculation unit according to the first embodiment; FIG. 4 is a characteristic diagram showing the relationship between brake fluid pressure (M/C fluid pressure) and vehicle deceleration; FIG. 4 is a characteristic diagram showing an example of temporal changes in the parking brake switch, vehicle speed, brake fluid pressure, longitudinal acceleration, correction coefficient (C1), and target thrust according to the first embodiment; The block diagram of the thrust calculation part by 2nd Embodiment. FIG. 4 is a characteristic diagram showing the relationship between an acceleration sensor value and a correction coefficient (C2); FIG. 11 is a characteristic diagram showing an example of temporal changes in the parking brake switch, vehicle speed, brake fluid pressure, longitudinal acceleration, correction coefficients (C1, C2), and target thrust according to the second embodiment; FIG. 11 is a characteristic diagram showing an example of temporal changes in the parking brake switch, vehicle speed, brake fluid pressure, acceleration torque, longitudinal acceleration, correction coefficient (C1), and target thrust according to the third embodiment; FIG. 11 is a characteristic diagram showing an example of temporal changes in the parking brake switch, vehicle speed, brake fluid pressure, longitudinal acceleration, correction coefficients (C1, C2), and target thrust according to the fourth embodiment; FIG. 11 is a characteristic diagram showing an example of temporal changes in the parking brake switch, vehicle speed, brake fluid pressure, longitudinal acceleration, correction coefficients (C1, C2), and target thrust according to the fifth embodiment; FIG. 11 is a characteristic diagram showing an example of temporal changes in the parking brake switch, vehicle speed, brake fluid pressure, longitudinal acceleration, correction coefficients (C1, C2), and target thrust according to the sixth embodiment;

Hereinafter, a case in which the brake device according to the embodiment is mounted on a four-wheeled vehicle will be described as an example with reference to the accompanying drawings.

1 to 6 show a first embodiment. In FIG. 1, on the lower side (road surface side) of a vehicle body 1 that constitutes the body of the vehicle, there are a total of four wheels, for example, left and right front wheels 2 (FL, FR) and left and right rear wheels 3 (RL, RR). Wheels are provided. The wheels (each front wheel 2 and each rear wheel 3) constitute a vehicle together with the vehicle body 1. As shown in FIG. A vehicle is equipped with a brake system for applying a braking force. A vehicle brake system will be described below.

The front wheels 2 and the rear wheels 3 are provided with disc rotors 4 as members to be braked (rotating members) that rotate together with the respective wheels (the front wheels 2 and the rear wheels 3). Braking force is applied to the disc rotor 4 for the front wheel 2 by a front wheel side disc brake 5 which is a hydraulic disc brake. Braking force is applied to a disc rotor 4 for the rear wheel 3 by a rear wheel side disc brake 6 which is a hydraulic disc brake with an electric parking brake function.

A pair (one set) of rear wheel side disc brakes 6 provided corresponding to the left and right rear wheels 3 apply braking force by pressing brake pads 6C (see FIG. 2) against the disc rotor 4 by hydraulic pressure. It is a hydraulic brake mechanism (hydraulic brake). As shown in FIG. 2, the rear wheel disc brake 6 includes, for example, a mounting member 6A called a carrier, a caliper 6B as a wheel cylinder, and a pair of brake pads 6C as braking members (friction members, friction pads). , and a piston 6D as a pressing member. In this case, the caliper 6B and the piston 6D constitute a cylinder mechanism, that is, a cylinder mechanism that is moved by hydraulic pressure to press the brake pad 6C against the disc rotor 4. As shown in FIG.

The mounting member 6A is fixed to a non-rotating portion of the vehicle and is formed across the outer peripheral side of the disk rotor 4. As shown in FIG. The caliper 6B is provided on the mounting member 6A so that the disc rotor 4 can move in the axial direction. The caliper 6B includes a cylinder body portion 6B1, a claw portion 6B2, and a bridge portion 6B3 connecting them. A cylinder (cylinder hole) 6B4 is provided in the cylinder body portion 6B1, and a piston 6D is fitted in the cylinder 6B4. The brake pad 6C is movably attached to the mounting member 6A and arranged to contact the disc rotor 4 . The piston 6D presses the brake pad 6C against the disc rotor 4.

Here, the caliper 6B propels the brake pad 6C with the piston 6D by supplying (applying) hydraulic pressure (brake hydraulic pressure) to the cylinder 6B4 based on the operation of the brake pedal 9 or the like. At this time, the brake pad 6C is pressed against both surfaces of the disc rotor 4 by the claw portion 6B2 of the caliper 6B and the piston 6D. Thereby, a braking force is applied to the rear wheel 3 rotating together with the disk rotor 4 .

Further, the rear-wheel disc brake 6 includes an electric actuator 7 and a rotation/linear motion converting mechanism 8 . The electric actuator 7 includes an electric motor 7A as an electric motor, a speed reducer (not shown) that reduces the rotation of the electric motor 7A, and the like. The electric motor 7A serves as a propulsion source (driving source) for propelling the piston 6D. The rotation/linear motion conversion mechanism 8 constitutes a holding mechanism (pressing member holding mechanism) that holds the pressing force of the brake pad 6C.

In this case, the rotation/linear motion conversion mechanism 8 includes a rotary/linear motion member 8A that converts the rotation of the electric motor 7A into axial displacement (linear motion displacement) of the piston 6D and propels the piston 6D. there is The rotary linear motion member 8A is composed of, for example, a threaded member 8A1 made of a rod-shaped body having a male screw formed thereon, and a linear motion member 8A2 serving as a propulsion member having a female threaded hole formed on the inner peripheral side thereof. The rotation-to-linear motion converting mechanism 8 converts the rotation of the electric motor 7A into axial displacement of the piston 6D, and holds the piston 6D propelled by the electric motor 7A. That is, the rotation/linear motion conversion mechanism 8 applies thrust to the piston 6D by the electric motor 7A, propels the brake pad 6C by the piston 6D, presses the disk rotor 4, and holds the thrust of the piston 6D.

The rotation/linear motion conversion mechanism 8 constitutes an electric mechanism of a brake device (electric parking brake device) together with the electric motor 7A. The electric mechanism converts the rotational force of the electric motor 7A into thrust via the speed reducer and the rotation/linear motion conversion mechanism 8, and propels (displaces) the piston 6D, thereby pressing the brake pad 6C against the disc rotor 4. to maintain the braking force of the vehicle. The electric motor 7A drives the electric mechanism. Such an electric mechanism (that is, the electric motor 7A and the rotation-to-linear motion conversion mechanism 8) constitutes a braking device together with a parking brake control device 24, which will be described later.

The rear wheel side disc brake 6 propels the piston 6D by the brake fluid pressure generated based on the operation of the brake pedal 9, etc., and presses the disc rotor 4 with the brake pad 6C, thereby extending the wheel (rear wheel 3). provides braking force to the vehicle. In addition, as will be described later, the rear wheel side disc brake 6 is driven by the electric motor 7A via the rotation/linear motion conversion mechanism 8 in response to an operation request based on a signal from the parking brake switch 23 or the like. It propels the vehicle and applies the braking force (parking brake, if necessary auxiliary braking while driving) to the vehicle.

That is, the rear-wheel-side disc brake 6 drives the electric motor 7A and propels the piston 6D by the rotary motion member 8A, thereby pressing and holding the brake pad 6C against the disc rotor 4. As shown in FIG. In this case, the rear-wheel disc brake 6 propels the piston 6D with the electric motor 7A in response to a parking brake request signal (apply request signal) serving as an apply request for applying the parking brake (parking brake) to the vehicle. hold the brake. Along with this, the rear-wheel disc brake 6 brakes the vehicle by hydraulic pressure supplied from a hydraulic pressure source (a master cylinder 12 described later, and a hydraulic pressure supply device 16 if necessary) in accordance with the operation of the brake pedal 9. .

Thus, the rear-wheel disc brake 6 has the rotation/linear motion conversion mechanism 8 that presses the brake pad 6C against the disc rotor 4 by the electric motor 7A and retains the pressing force of the brake pad 6C. The brake pad 6C can be pressed against the disc rotor 4 by the hydraulic pressure applied separately from the pressing by 7A.

On the other hand, a pair (one set) of front-wheel disc brakes 5 provided corresponding to the left and right front wheels 2 are configured in substantially the same manner as the rear-wheel disc brakes 6 except for the mechanism related to the operation of the parking brake. It is That is, as shown in FIG. 1, the front wheel side disc brake 5 includes a mounting member (not shown), a caliper 5A, a brake pad (not shown), a piston 5B, and the like. The electric actuator 7 (electric motor 7A), the rotation-to-linear motion conversion mechanism 8, and the like are not provided. However, the front wheel side disc brake 5 propels the piston 5B by hydraulic pressure generated based on the operation of the brake pedal 9, etc., and applies braking force to the wheels (front wheels 2) and the vehicle. Similar to disc brake 6 . That is, the front-wheel disc brake 5 is a hydraulic brake mechanism (hydraulic brake) that presses the brake pad against the disc rotor 4 with hydraulic pressure to apply a braking force.

The front-wheel disc brake 5 may be a disc brake with an electric parking brake function, like the rear-wheel disc brake 6 . Further, in the embodiment, a hydraulic disc brake 6 equipped with an electric motor 7A is used as an electric brake mechanism (electric parking brake). However, the electric brake mechanism is not limited to this, and includes, for example, an electric drum brake in which an electric motor presses a shoe against the drum to apply a braking force, a disc brake equipped with an electric drum parking brake, and an electric motor with a cable. A cable puller type electric parking brake or the like that applies the parking brake by pulling may be used. That is, the electric brake mechanism presses (propulses) the friction member (pad, shoe) against the rotating member (rotor, drum) based on the drive of the electric motor (electric actuator), and holds and releases the pressing force. Various types of electric brake mechanisms can be used as long as they are configured to be able to operate.

A brake pedal 9 is provided on the front board side of the vehicle body 1 . The brake pedal 9 is depressed by a driver when braking the vehicle. Each of the disc brakes 5 and 6 applies and releases a braking force as a service brake (service brake) based on the operation of the brake pedal 9 . The brake pedal 9 is provided with a brake operation detection sensor (brake sensor) 10 such as a brake lamp switch, a pedal switch (brake switch), and a pedal stroke sensor.

The brake operation detection sensor 10 detects whether or not the brake pedal 9 is depressed or the amount of operation thereof, and outputs the detection signal to the ESC control device 17 . A detection signal of the brake operation detection sensor 10 is transmitted via, for example, the vehicle data bus 20 or a communication line (not shown) connecting the ESC control device 17 and the parking brake control device 24 (parking brake control output to device 24).

A stepping operation of the brake pedal 9 is transmitted via a booster 11 to a master cylinder 12 functioning as a hydraulic source (fluid pressure source). The booster 11 is configured as a negative pressure booster (air pressure booster) or an electric booster (electric booster) provided between the brake pedal 9 and the master cylinder 12 . The booster 11 increases the pedaling force and transmits it to the master cylinder 12 when the brake pedal 9 is stepped on. At this time, the master cylinder 12 generates hydraulic pressure from the brake fluid supplied (replenished) from the master reservoir 13 . The master reservoir 13 serves as a hydraulic fluid tank containing brake fluid. The mechanism for generating hydraulic pressure by the brake pedal 9 is not limited to the above configuration, and may be a mechanism for generating hydraulic pressure in accordance with the operation of the brake pedal 9, such as a brake-by-wire mechanism. .

The hydraulic pressure generated in the master cylinder 12 is sent to a hydraulic pressure supply device 16 (hereinafter referred to as ESC 16) via, for example, a pair of cylinder side hydraulic pipes 14A and 14B. The hydraulic pressure sent to the ESC 16 is supplied to the disc brakes 5, 6 via the brake side piping portions 15A, 15B, 15C, 15D. The ESC 16 is arranged between each disc brake 5 , 6 and the master cylinder 12 . Here, the ESC 16 is a hydraulic pressure control device that controls the hydraulic pressure of the hydraulic brakes (the front wheel side disc brake 5 and the rear wheel side disc brake 6). For this purpose, the ESC 16 includes a plurality of control valves, a hydraulic pump that pressurizes the brake fluid pressure, an electric motor that drives the hydraulic pump, and a fluid pressure control reservoir that temporarily stores excess brake fluid. (none of which is shown). Each control valve and electric motor of ESC 16 are connected to ESC control device 17 , and ESC 16 includes ESC control device 17 .

Opening and closing of each control valve of the ESC 16 and driving of the electric motor are controlled by an ESC control device 17 . That is, the ESC control device 17 is an ESC control unit (ESC ECU) that controls the ESC 16 . The ESC control device 17 includes a microcomputer and electrically drives and controls the ESC 16 (solenoids and electric motors of control valves thereof). In this case, the ESC control device 17 includes, for example, an arithmetic circuit that controls the hydraulic pressure supply to the ESC 16 and detects failure of the ESC 16, a drive circuit that drives the electric motor and each control valve (none of which are shown), and the like. is built-in.

The ESC control device 17 individually drives and controls each control valve (solenoid thereof) of the ESC 16 and an electric motor for a hydraulic pump. As a result, the ESC control device 17 controls to reduce, hold, increase or increase the brake fluid pressure (wheel cylinder fluid pressure) supplied to the disc brakes 5 and 6 through the brake side piping sections 15A to 15D. Each disc brake 5, 6 is performed individually. In this case, the ESC control device 17 controls the operation of the ESC 16 to perform, for example, braking force distribution control, antilock brake control (hydraulic pressure ABS control), vehicle stabilization control, slope start assist control, traction control, vehicle following control, and so on. control, lane departure avoidance control, and obstacle avoidance control (automatic brake control, collision damage mitigation brake control).

The ESC 16 directly supplies the hydraulic pressure generated by the master cylinder 12 to the disc brakes 5 and 6 (the calipers 5A and 6B thereof) during normal operation by the driver's braking operation. On the other hand, for example, when executing anti-lock brake control or the like, the pressure increasing control valve is closed to maintain the hydraulic pressure of the disc brakes 5 and 6, and when the hydraulic pressure of the disc brakes 5 and 6 is reduced, The pressure reducing control valve is opened to discharge the hydraulic pressure of the disc brakes 5 and 6 so as to release it to the hydraulic pressure control reservoir. Furthermore, when increasing or increasing the hydraulic pressure supplied to the disc brakes 5 and 6 in order to perform stabilization control (anti-skid control) during vehicle travel, the electric power supply control valve is closed with the supply control valve closed. A hydraulic pump is operated by a motor, and brake fluid discharged from the hydraulic pump is supplied to the disk brakes 5 and 6 . At this time, the brake fluid in the master reservoir 13 is supplied from the master cylinder 12 side to the suction side of the hydraulic pump.

The ESC control device 17 is supplied with electric power from a battery 18 (or a generator driven by the engine) serving as a vehicle power supply through a power supply line 19 . As shown in FIG. 1, ESC controller 17 is connected to vehicle data bus 20 . It should be noted that a known ABS unit can be used instead of the ESC 16 . Furthermore, it is also possible to directly connect the master cylinder 12 and the brake-side piping sections 15A to 15D without providing the ESC 16 (that is, omitting it).

The vehicle data bus 20 constitutes a CAN (Controller Area Network) as a serial communication unit mounted on the vehicle body 1 . A large number of electronic devices mounted on the vehicle (for example, various ECUs including the ESC control device 17, the parking brake control device 24, etc.) perform multiplex communication between them in the vehicle via the vehicle data bus 20. FIG. In this case, the vehicle information sent to the vehicle data bus 20 includes, for example, the brake operation detection sensor 10, the ignition switch, the seat belt sensor, the door lock sensor, the door open sensor, the seating sensor, the vehicle speed sensor, the steering angle sensor, the accelerator sensor, and the like. (accelerator operation sensor), throttle sensor, engine rotation sensor, stereo camera, millimeter wave radar, gradient sensor (tilt sensor), shift sensor (transmission data), acceleration sensor (G sensor), wheel speed sensor, vehicle pitch direction Information (vehicle information) based on a detection signal (output signal) from a pitch sensor or the like that detects movement can be mentioned. Furthermore, the vehicle information sent to the vehicle data bus 20 includes a detection signal from a W/C pressure sensor 21 for detecting wheel cylinder pressure (W/C pressure), and an M sensor for detecting master cylinder pressure (M/C pressure). A detection signal from the /C pressure sensor 22 is also included.

Next, the parking brake switch 23 and the parking brake control device 24 will be explained.

In the vehicle body 1, a parking brake switch (PKB-SW) 23 as a switch for an electric parking brake is provided near the driver's seat (not shown). The parking brake switch 23 is an operation instruction section operated by the driver. The parking brake switch 23 outputs a signal (operation request signal) corresponding to a parking brake operation request (apply request as a hold request, release request as a release request) in response to an operation instruction from the driver. to That is, the parking brake switch 23 outputs an operation request signal (holding request signal) for applying (holding operation) or releasing (release operation) the piston 6D and thus the brake pad 6C based on the drive (rotation) of the electric motor 7A. An apply request signal serving as a signal and a release request signal serving as a release request signal) are output to the parking brake control device 24 . The parking brake control device 24 is a parking brake control unit (parking brake ECU).

When the parking brake switch 23 is operated to the braking side (apply side) by the driver, that is, when there is an apply request (brake holding request) for applying braking force to the vehicle, the parking brake switch 23 is applied. A request signal (parking brake request signal, apply command) is output. In this case, electric power is supplied to the electric motor 7A of the rear-wheel disc brake 6 via the parking brake control device 24 to rotate the electric motor 7A to the braking side. At this time, the rotation/linear motion conversion mechanism 8 propels (presses) the piston 6D toward the disk rotor 4 based on the rotation of the electric motor 7A, and holds the propelled piston 6D. As a result, the rear-wheel disc brake 6 is in a state in which braking force as a parking brake (or an auxiliary brake) is applied, that is, in an applied state (braking holding state).

On the other hand, when the driver operates the parking brake switch 23 to the brake release side (release side), that is, when there is a release request (braking release request) for releasing the braking force of the vehicle, the parking brake switch 23 outputs a release request signal (parking brake release request signal, release command). In this case, electric power is supplied to the electric motor 7A of the rear-wheel disc brake 6 via the parking brake control device 24 so as to rotate the electric motor 7A in the direction opposite to the braking side. At this time, the rotation/linear motion conversion mechanism 8 releases the holding of the piston 6D (releases the pressing force of the piston 6D) by rotating the electric motor 7A. As a result, the rear-wheel disc brake 6 is in a state in which the application of braking force as a parking brake (or an auxiliary brake) is released, that is, in a released state (braking release state).

The parking brake control device 24 as a control device constitutes a braking device together with the rear wheel side disc brake 6 (the electric motor 7A and the rotation-to-linear motion conversion mechanism 8). The parking brake control device 24 controls driving of the electric motor 7A. For this purpose, as shown in FIG. 3, the parking brake control device 24 has an arithmetic circuit (CPU) 25 and a memory 26 which are configured by a microcomputer or the like. The parking brake control device 24 is supplied with electric power from a battery 18 (or a generator driven by the engine) through a power supply line 19 .

The parking brake control device 24 controls the driving of the electric motors 7A, 7A of the rear wheel side disc brakes 6, 6, and applies braking force (parking brake, auxiliary brake ). That is, the parking brake control device 24 operates (applies and releases) the disc brakes 6, 6 as parking brakes (auxiliary brakes as necessary) by driving the left and right electric motors 7A, 7A. For this purpose, the parking brake control device 24 has an input side connected to the parking brake switch 23 and an output side connected to the electric motors 7A, 7A of the disc brakes 6, 6, respectively. The parking brake control device 24 is an arithmetic circuit for detecting a driver's operation (operation of the parking brake switch 23), determining whether or not the electric motors 7A, 7A can be driven, and determining whether the electric motors 7A, 7A should stop. 25 and motor drive circuits 28, 28 for controlling the electric motors 7A, 7A.

The parking brake control device 24 operates the left and right electric motors 7A, 7A based on an operation request (apply request, release request) by the operation of the parking brake switch 23 by the driver, an operation request by determination of auto apply/auto release, and the like. drive to apply (hold) or release (release) the left and right disc brakes 6,6. At this time, in the rear-wheel disc brake 6, the piston 6D and the brake pad 6C are held or released by the rotation/linear motion conversion mechanism 8 based on the driving of each electric motor 7A. In this way, the parking brake control device 24 controls the piston 6D (and thus the brake pad 6C) in response to the operation request signal for holding operation (apply) or release operation (release) of the piston 6D (and thus brake pad 6C). The electric motor 7A is driven and controlled to propel the pad 6C).

As shown in FIG. 3, the arithmetic circuit 25 of the parking brake control device 24 includes a parking brake switch 23, a vehicle data bus 20, a voltage sensor section 27, a motor drive circuit 28, a current A sensor unit 29 and the like are connected. From the vehicle data bus 20, it is possible to acquire various vehicle state quantities necessary for controlling (activating) the parking brake, that is, various vehicle information. The parking brake control device 24 can also output information and instructions to various ECUs including the ESC control device 17 via the vehicle data bus 20 or the communication line.

The vehicle information acquired from the vehicle data bus 20 may be acquired by directly connecting a sensor that detects the information to (the arithmetic circuit 25 of) the parking brake control device 24 . Further, the arithmetic circuit 25 of the parking brake control device 24 is configured to receive an operation request based on determination of auto apply/auto release from another control device (for example, the ESC control device 17) connected to the vehicle data bus 20. You may In this case, the auto-apply/auto-release determination may be controlled by another control device such as the ESC control device 17 instead of the parking brake control device 24 . That is, it is possible to integrate the control contents of the parking brake control device 24 into the ESC control device 17 .

The parking brake control device 24 is provided with a memory 26 as a storage unit, such as flash memory, ROM, RAM, EEPROM, and the like. The memory 26 stores a processing program used for controlling the parking brake. In the embodiment, the parking brake control device 24 is separated from the ESC control device 17, but the parking brake control device 24 and the ESC control device 17 are integrated (that is, integrated by one braking control device) ) may be configured. Further, the parking brake control device 24 controls the two rear wheel disc brakes 6, 6 on the left and right, but it may be provided for each of the left and right rear wheel disc brakes 6, 6. In some cases, each parking brake control device 24 can be provided integrally with the rear wheel side disc brake 6 .

As shown in FIG. 3, the parking brake control device 24 includes a voltage sensor unit 27 that detects the voltage from the power supply line 19, left and right motor drive circuits 28 that respectively drive the left and right electric motors 7A, 7A, left and right Left and right current sensor units 29, 29 for detecting respective motor currents of the electric motors 7A, 7A are incorporated. The voltage sensor section 27, the motor drive circuit 28, and the current sensor section 29 are connected to the arithmetic circuit 25, respectively. As a result, the arithmetic circuit 25 of the parking brake control device 24 detects the current value of the electric motor 7A (change in value) detected by the current sensor unit 29 when the parking brake is applied or released. It is possible to determine whether to stop driving (determination of application completion, determination of release completion), and the like. In the illustrated example, the voltage sensor unit 27 is configured to detect (measure) the power supply voltage. It is good also as a structure which measures by

By the way, the electric parking brake uses the voltage and current applied to the electric motor to control the thrust required to keep the vehicle stationary. Here, the thrust to be generated by the electric parking brake is, for example, the minimum value assumed for the vehicle in the maximum loading state, the pad μ (coefficient of friction), and the slope of the road surface on which the vehicle is parked (stopped). It is conceivable to set a value that allows the vehicle to be stopped even when is the maximum value assumed. However, in an actual vehicle, there are few cases where the vehicle is fully loaded, the pad μ is at the assumed minimum value, and the slope of the road surface on which the vehicle is parked (stopped) is at the assumed maximum value. For this reason, constantly applying the thrust as described above may result in excessive specifications and an increase in cost.

On the other hand, the technique of Patent Document 1 described above calculates the thrust required to keep the vehicle stationary using information from the vehicle weight sensor and the longitudinal G sensor. According to this technology, the target thrust can be adjusted according to the vehicle weight. However, the information of the vehicle weight sensor is not an interface signal defined by, for example, the VDA standard (German Automobile Manufacturers Association Standard). Therefore, there is a possibility that information from the vehicle weight sensor cannot be obtained depending on the vehicle.

Therefore, in the embodiment, the target thrust of the parking brake is variably controlled according to the state of the vehicle, specifically, the vehicle weight and the vehicle deceleration and brake fluid pressure, which are alternative characteristics of the pad μ. That is, in the first embodiment, the target thrust of the parking brake is controlled to be reduced from the maximum value according to the deceleration and the brake fluid pressure when the vehicle decelerates. Further, in a second embodiment, which will be described later, the target thrust of the parking brake is controlled to be reduced from the maximum value according to the vehicle deceleration, the brake fluid pressure, and the inclination angle. As a result, in the embodiment, even if information from the vehicle weight sensor is not obtained, it is possible to apply the thrust required to keep the vehicle stopped. That is, it is possible to suppress the thrust from becoming larger than necessary, and to improve the durability. The control for calculating the target thrust of the parking brake will be described below.

The parking brake control device 24 is an electric mechanism (electric motor) for maintaining the braking force when the vehicle is stopped in accordance with the deceleration of the vehicle until it transitions from the running state to the stopped state and the brake fluid pressure until the transition. The thrust generated by 7A and the rotation/linear motion conversion mechanism 8) is changed. In this case, as shown in FIG. 5, which will be described later, the parking brake control device 24 changes the thrust based on the characteristics of deceleration (vehicle deceleration) and brake fluid pressure (M/C pressure). More specifically, the parking brake control device 24 uses a characteristic calculated from deceleration and brake fluid pressure (eg, characteristic line 52 in FIG. 5) and a reference characteristic of deceleration and brake fluid pressure (eg, in FIG. 5). 5, a correction coefficient (C1) for correcting the thrust is calculated, and the thrust is changed by the correction coefficient (C1). Note that the reference characteristic (characteristic line 51) is the deceleration and brake fluid when the vehicle is in a fully loaded state, the pad μ is the assumed minimum value, and the road surface inclination is the assumed maximum value. Corresponds to pressure characteristics. Also, the hydraulic pressure (M/C pressure or W/C pressure) detected by a hydraulic pressure sensor (M/C pressure sensor 22 or W/C pressure sensor 21) can be used as the brake hydraulic pressure. For deceleration, longitudinal acceleration (longitudinal G) detected by an acceleration sensor (not shown) mounted on the vehicle can be used. Also, the deceleration can use the wheel speed detected by a wheel speed sensor (not shown). Brake hydraulic pressure and longitudinal acceleration can be obtained from the vehicle data bus 20 .

As described above, in the first embodiment, the thrust required to keep the vehicle stationary is calculated according to the vehicle deceleration and the brake fluid pressure, and the thrust can be reduced from the reference value corresponding to the assumed maximum thrust. If there is, the target value is changed using the correction coefficient C1. In order to change the thrust in this way, the parking brake control device 24 has a thrust calculation section 31 shown in FIG. The thrust calculation unit 31 calculates the wheel speed V, which is the value of the wheel speed sensor (not shown) (wheel speed sensor value), the longitudinal acceleration g, which is the value of the acceleration sensor (not shown) (G sensor value), Using the hydraulic pressure (M/C pressure or W/C pressure) p, which is the value (hydraulic pressure sensor value) of the hydraulic pressure sensor (M/C pressure sensor 22 or W/C pressure sensor 21), the parking brake target Calculate thrust. The wheel speed V, the longitudinal acceleration g and the hydraulic pressure p can be obtained via the vehicle data bus 20, for example.

As shown in FIG. 4, the thrust calculation unit 31 includes a hydraulic pressure detection unit 32, a braking determination unit 33, a speed determination unit 34, a vehicle deceleration calculation unit 35, and a hydraulic pressure-deceleration characteristic plot unit 36. , a correction coefficient calculator 37 serving as a characteristic comparator, and a target thrust calculator 38 . A sensor value (sensor signal) of a hydraulic pressure sensor is input to the hydraulic pressure detection unit 32 via the vehicle data bus 20 . The hydraulic pressure detection unit 32 detects the hydraulic pressure from the sensor value, and outputs the detected hydraulic pressure p to the braking determination unit 33 and the hydraulic pressure-deceleration characteristic plot unit 36 . The braking determination unit 33 receives the hydraulic pressure p from the hydraulic pressure detection unit 32 . The braking determination unit determines whether or not braking is being performed from the hydraulic pressure p, and outputs the determination result to the vehicle deceleration calculation unit 35 . A wheel speed V, which is a detected value of the wheel speed sensor, is input to the speed determination unit 34 via the vehicle data bus 20 . The speed determination unit 34 determines whether or not the vehicle is running from the wheel speed V, and outputs the determination result to the vehicle deceleration calculation unit 35 .

The vehicle deceleration calculator 35 receives the longitudinal acceleration g detected by the acceleration sensor (G sensor) and the wheel speed V detected by the wheel speed sensor via the vehicle data bus 20 . Further, the vehicle deceleration calculation unit 35 receives the result of determination as to whether the vehicle is being braked from the braking determination unit 33 and the result of determination as to whether the vehicle is running from the speed determination unit 34 . The vehicle deceleration calculator 35 calculates the deceleration α when the vehicle transitions from the running state to the stopped state. In this case, the vehicle deceleration calculator 35 calculates the deceleration α from the following Equation 1, and outputs the calculated deceleration α to the hydraulic pressure-deceleration characteristic plotter 36 .

In the equation (1), g is the longitudinal acceleration detected by the acceleration sensor, gn is the natural deceleration, and g.theta.0 is the longitudinal acceleration immediately before the start of deceleration of the vehicle. The natural deceleration gn corresponds to the longitudinal acceleration when no braking force is applied by the disk brakes 5 and 6 during running. That is, gn corresponds to deceleration based on vehicle rolling resistance, air resistance, and engine braking, for example. The longitudinal acceleration gθ0 immediately before the vehicle starts decelerating corresponds to the longitudinal acceleration immediately before the vehicle starts to decelerate due to the application of the braking force of the disc brakes 5 and 6 . That is, gθ0 corresponds to deceleration based on the inclination angle of the vehicle (road surface) immediately before deceleration is started, for example. 4 (and FIG. 7, which will be described later), the vehicle deceleration calculator 35 receives the wheel speed V, which is the detected value of the wheel speed sensor. Then, it is possible to calculate the longitudinal acceleration from the detected value of the wheel speed sensor. Therefore, the vehicle deceleration calculator 35 may be configured to receive only one of the detection value of the acceleration sensor and the detection value of the wheel speed sensor.

The hydraulic pressure-deceleration characteristic plotting unit 36 receives the hydraulic pressure p from the hydraulic pressure detecting unit 32 and the deceleration α from the vehicle deceleration calculating unit 35 . The hydraulic pressure-deceleration characteristic plotting unit 36 obtains, for example, the characteristics of the deceleration and the brake hydraulic pressure until the vehicle transitions from the running state to the stopped state from the hydraulic pressure p and the deceleration α. For example, the characteristic line 52 shown in FIG. 5 is plotted. Then, the hydraulic pressure-deceleration characteristic plotting unit 36 outputs the deceleration α1 when the hydraulic pressure is p based on the characteristic line 52 to the correction coefficient calculating unit 37 as the deceleration α1 during the current deceleration.

The correction coefficient calculation unit 37 receives the deceleration α1 during the current deceleration from the hydraulic pressure-deceleration characteristic plot unit 36 . Further, the correction coefficient calculator 37 receives the deceleration α0 based on the basic characteristic information. The deceleration α0 based on the basic characteristic information is the reference deceleration α0. That is, the reference deceleration α0 is the deceleration and braking when the vehicle is fully loaded, the pad μ is the assumed minimum value, and the slope of the road on which the vehicle is parked is the assumed maximum value. This is the deceleration at the hydraulic pressure p obtained from the characteristic with the hydraulic pressure (characteristic line 51 in FIG. 5). The reference deceleration α0 can be obtained in advance by experiments, calculations, simulations, or the like. The correction coefficient calculator 37 corresponds to a comparator that compares the deceleration α1 during the current deceleration with the deceleration α0 of the reference value. The correction coefficient calculator 37 calculates a correction coefficient C1 by dividing the deceleration α1 during the current deceleration by the deceleration α0 of the reference value, and outputs the correction coefficient C1 to the target thrust force calculator 38 . The correction coefficient C1 is the thrust (reference thrust F0) when the vehicle is in a fully loaded state, the pad μ is the assumed minimum value, and the slope of the road on which the vehicle is parked is the assumed maximum value. This is the ratio of the thrust (target thrust) to be applied after the current deceleration.

The target thrust calculation unit 38 receives the correction coefficient C<b>1 from the correction coefficient calculation unit 37 . The target thrust calculation unit 38 calculates the target thrust Ftarget by multiplying the reference thrust F0 by the correction coefficient C1. The reference thrust force F0 is the thrust force when the vehicle is fully loaded, the pad μ is at the assumed minimum value, and the slope of the road on which the vehicle is parked is at the assumed maximum value. The target thrust force calculator 38 corrects the reference thrust force F0 with the correction coefficient C1, and outputs the corrected target thrust force Ftarget. The parking brake control device 24 drives the electric motor 7A so as to achieve the target thrust Ftarget to apply the parking brake.

The brake system for a four-wheeled vehicle according to the embodiment has the configuration described above, and the operation thereof will now be described.

When the driver of the vehicle depresses the brake pedal 9, the depressing force is transmitted to the master cylinder 12 via the booster 11, and the master cylinder 12 generates brake fluid pressure. The brake hydraulic pressure generated in the master cylinder 12 is supplied to the disc brakes 5 and 6 via the cylinder side hydraulic pipes 14A, 14B, ESC 16 and the brake side pipe portions 15A, 15B, 15C, 15D, and is applied to the left and right front wheels. 2 and the left and right rear wheels 3 are each given a braking force.

In this case, in each of the disc brakes 5 and 6, the pistons 5B and 6D are slidably displaced toward the brake pad 6C as the brake fluid pressure in the calipers 5A and 6B increases, and the brake pad 6C moves toward the disc rotors 4 and 4. pressed against. Thereby, a braking force based on the brake fluid pressure is applied. On the other hand, when the brake operation is released, the supply of brake fluid pressure to the calipers 5A, 6B is stopped, so that the pistons 5B, 6D are displaced away from the disc rotors 4, 4 (retracted). As a result, the brake pad 6C is separated from the disc rotors 4, 4 and the vehicle is returned to the non-braking state.

Next, when the driver of the vehicle operates the parking brake switch 23 to the braking side (apply side), power is supplied from the parking brake control device 24 to the electric motors 7A of the left and right rear wheel side disc brakes 6, The motor 7A is rotationally driven. In the rear-wheel disc brake 6, the rotary motion of the electric motor 7A is converted into linear motion by the rotary motion converting mechanism 8, and the piston 6D is propelled by the rotary motion member 8A. As a result, the disc rotor 4 is pressed by the brake pad 6C. At this time, the rotation/linear motion conversion mechanism 8 (linear motion member 8A2) is kept in a braking state by, for example, a frictional force (holding force) due to screwing. Thereby, the rear-wheel disc brake 6 is operated (applied) as a parking brake. That is, the piston 6D is held at the braking position by the rotation-to-linear motion conversion mechanism 8 even after power supply to the electric motor 7A is stopped.

On the other hand, when the driver operates the parking brake switch 23 to the brake release side (release side), power is supplied from the parking brake control device 24 to the electric motor 7A so as to rotate the motor in reverse. This power feed causes the electric motor 7A to rotate in a direction opposite to that when the parking brake is actuated (applied). At this time, the holding of the braking force by the rotation-to-linear motion conversion mechanism 8 is released, and the piston 6D can be displaced away from the disk rotor 4 . As a result, the operation of the rear-wheel disc brake 6 as a parking brake is canceled (released).

Here, FIG. 6 shows the parking brake switch (PKB_SW), vehicle speed V (Vehicle Speed), brake fluid pressure P (Pressure), longitudinal acceleration α (Longitudinal Acceleration), and correction coefficient C1 (Correction Coefficient) according to the first embodiment. and target thrust Ftarget (PKB Target Force). In FIG. 6, "t0" on the time axis is the time when the driving force by the vehicle is released, and "t1" on the time axis is the time when the braking force by the service brake (hydraulic pressure brake) starts to be generated. The longitudinal acceleration G(gn) due to the running resistance of the vehicle is obtained when no driving force (for example, driving force of the engine) is generated and no braking force is generated by the service brake. Here, it is better to refer to the value of the longitudinal acceleration G(gn) by the acceleration sensor closer to t1 between time t0 and time t1. In the first embodiment, for example, the value immediately before time t1 when the braking force is applied by the service brake is used.

Next, while the vehicle is decelerating (between time t1 and time t2), by referring to the value of the hydraulic pressure P from the hydraulic pressure sensor and the value of the longitudinal acceleration G from the acceleration sensor, the hydraulic pressure information generated by the braking operation is obtained. and vehicle deceleration. Here, the timing for referring to the hydraulic pressure sensor and the acceleration sensor may be at one point during deceleration of the vehicle, or may be made multiple times at continuous time intervals. Note that wheel speed sensors for four wheels may be used to calculate the deceleration of the vehicle. At time t2, a correction coefficient C1 is calculated. In the first embodiment, the correction coefficient C1 is calculated at time t2 when the vehicle deceleration ends. good too. Here, a method for calculating the correction coefficient C1 will be described.

Assuming that the braking force generated in the vehicle is "F", the vehicle weight is "M", and the vehicle deceleration is "α", these relational expressions are given by Equation 2 below.

In Equation 2, “α” is the braking torque component of vehicle deceleration, “αn” is the vehicle running resistance component of vehicle deceleration, and “α1” is the vehicle deceleration. These are actual measurements. Note that the vehicle running resistance component includes the following.・Wheel rolling resistance ・Vehicle air resistance ・Vehicle engine braking ・Tilt angle

Also, since the braking force is generated in each of the four wheels when the vehicle is braked, the left side of the above equation (2) can be expressed as the following equation (3).

In Equation 3, "P" is the hydraulic pressure generated in each wheel, "S" is the piston area of the caliper attached to each wheel, and "μ" is the pressure applied to each wheel. "Rrot" is the coefficient of friction of the pad, "Rrot" is the rotor diameter of the front and rear wheels, and "Rtire" is the effective tire diameter of the front and rear wheels. As for subscripts, "FL" corresponds to the front left wheel, "FR" corresponds to the front right wheel, "RL" corresponds to the rear left wheel, and "RR" corresponds to the rear right wheel. , "F" corresponds to the front wheels and "R" corresponds to the rear wheels.

Here, assuming that the hydraulic pressure generated at the left and right wheels, the piston area, and the pad μ are ideally equal, Equation 3 can be expressed as Equation 4 below.

Furthermore, when the front-rear distribution is an ideal distribution, since the generated hydraulic pressure is equal between the front and rear wheels, it can be expressed as the following equation (5).

From Equation 5, it can be seen that the braking force F can be described by the hydraulic pressure P and the pad friction coefficient μ. Then, the reference value that is the assumed minimum value (the assumed worst value) of the pad μ is set to “μ0”, and the true value is set to “μ1”. Also, let "M0" be the reference value that is the assumed maximum value (the assumed worst value) of the vehicle weight M, and "M1" be the true value. When the hydraulic pressure p is measured, the assumed minimum value (reference value) of deceleration from FIG. It can be expressed as Equation 6.

Further, the correction coefficient C1 can be expressed as the following Equation 7 from Equations 2, 5, and 6. In Expression 7, the reference value (assumed worst value) is assigned "0" and the true value is assigned "1".

The correction coefficient C1 obtained by Equation 7 is affected by the vehicle weight and the front and rear wheel pads μ. Since the parking brake generates a braking force only on the rear wheels, the influence of the front wheel pad μ will be considered. The pad μ becomes smaller when the temperature is high, but in the case of braking operation in the normal use area, the temperature rise of the pad due to the braking operation is limited, so the front wheel side pad μF and the rear wheel side pad μR are μF ≈ μR. From this, it is considered that the effect of the pad μ on the estimation of the required thrust of the parking brake by the correction coefficient C1 is small. When estimating the required thrust in a state where the braking frequency is high, calculation may be performed by multiplying the previous value of the correction coefficient C1 by a constant factor, taking into consideration the braking interval. In FIG. 6, at time t4, a command to apply the electric parking brake is input. At time t4, the target thrust force Ftarget is calculated by the following equation (8). Note that F0 corresponds to the braking force that should be generated when the vehicle is fully loaded, the pad μ is the assumed minimum value, and the slope of the road on which the vehicle is parked is the assumed maximum value. It is the thrust that

Thus, according to the first embodiment, the parking brake control device 24 generates a thrust force generated by the electric mechanism (the electric motor 7A and the rotation/linear motion conversion mechanism 8) according to the deceleration of the vehicle and the brake fluid pressure. to change Therefore, even if information from the vehicle weight sensor cannot be obtained, it is possible to apply the thrust required to keep the vehicle stopped. As a result, it is possible to prevent the thrust from becoming larger than necessary, compared to a configuration in which the target thrust is applied based on the assumption of the maximum load, the minimum pad μ, and the maximum tilt angle. That is, it is possible to reduce the frequency with which the maximum thrust is applied assuming the maximum load, the minimum pad μ, and the maximum tilt angle, and improve the durability.

More specifically, the target thrust force F of the electric parking brake can be expressed by the following equation (9).

In Equation 9, “rt” is the tire effective diameter (constant), “Mv” is the vehicle weight, “θ” is the inclination angle of the road surface on which the vehicle is stopped, and “μ” is the pad μ (friction coefficient of the pad) and "rc" is the caliper effective diameter (constant). From Equation 9, the target thrust force F can be reduced by estimating the actual vehicle weight (load weight) compared to the case where the maximum weight is assumed and applied. Also, the target thrust force F can be reduced by estimating the actual pad μ, compared to the case where the minimum value is assumed. Furthermore, the target thrust force F can be reduced more than when the maximum value is assumed and applied by considering the actual inclination angle when the vehicle is stopped. In addition, in the first embodiment, the tilt angle can be the assumed maximum value, but as in the second embodiment, it is also possible to consider the actual tilt angle when the vehicle is stopped. In any case, in the first embodiment, the target thrust can be reduced according to the vehicle weight and the vehicle deceleration and brake fluid pressure, which are substitute characteristics for the pad μ, and the durability can be improved.

According to the first embodiment, the parking brake control device 24 changes the thrust based on the characteristics of deceleration and brake fluid pressure. Therefore, based on the characteristics of deceleration and brake fluid pressure, it is possible to apply a thrust corresponding to the vehicle weight and pad μ at that time (when the vehicle decelerates).

According to the first embodiment, the parking brake control device 24 compares the characteristics calculated from the deceleration and the brake fluid pressure with the reference characteristics of the deceleration and the brake fluid pressure, and corrects the thrust. A correction coefficient C1 is calculated, and the thrust is changed by the correction coefficient C1. For this reason, for example, by changing the thrust (reference thrust) required at the time of the maximum load, minimum pad μ and maximum tilt angle with the correction coefficient C1, the vehicle weight at that time (when the vehicle decelerates) and the pad μ can be reduced to a thrust corresponding to

7 to 9 show a second embodiment. The feature of the second embodiment resides in that the thrust is changed (reduced) in consideration of not only the deceleration and the brake fluid pressure but also the tilting state (tilt angle) of the vehicle when the vehicle is stopped. In addition, in 2nd Embodiment, the same code|symbol is attached|subjected to the same component as 1st Embodiment, and the description is abbreviate|omitted.

In the second embodiment, the parking brake control device 24 changes the thrust according to the tilt state (tilt angle) of the vehicle when the vehicle is stopped. That is, the parking brake control device 24 controls the electric mechanism (electric motor The thrust generated by 7A and the rotation/linear motion conversion mechanism 8) is changed.

For this reason, the parking brake control device 24 includes a hydraulic pressure detection unit 32, a braking determination unit 33, a speed determination unit 34, a vehicle deceleration calculation unit 35, a hydraulic pressure-deceleration characteristic plot unit 36, and a characteristic In addition to a correction coefficient calculation section 37 and a target thrust calculation section 38 serving as a comparison section, a stop determination section 41 , a tilt angle component calculation section 42 , and a tilt correction coefficient calculation section 43 are provided. The vehicle stop determination unit 41 receives the wheel speed V detected by the wheel speed sensor via the vehicle data bus 20 . The stop determination unit 41 determines whether or not the vehicle is stopped from the wheel speed V, and outputs the determination result to the tilt angle component calculation unit 42 . The tilt angle component calculator 42 receives, via the vehicle data bus 20, the longitudinal acceleration g, which is the detected value of the acceleration sensor (G sensor), and the determination result of whether the vehicle is stopped from the vehicle stop determination unit 41. . The vehicle deceleration calculator 35 outputs the longitudinal acceleration g when the vehicle is stopped to the tilt correction coefficient calculator 43 as the longitudinal acceleration gθ (=g) based on the tilt of the vehicle when the vehicle is stopped.

The tilt correction coefficient calculator 43 receives the longitudinal acceleration gθ based on the tilt of the vehicle when the vehicle is stopped from the vehicle deceleration calculator 35 . Further, the acceleration g0 based on the basic tilt angle component information is input to the correction coefficient calculator 37 . The acceleration g0 based on the basic tilt angle component information is the reference tilt acceleration g0. That is, the reference tilt acceleration g0 corresponds to the maximum value of the assumed road surface tilt. The tilt correction coefficient calculation unit 43 divides the longitudinal acceleration gθ when the vehicle is stopped by the reference tilt acceleration g0 to calculate a correction coefficient C1 corresponding to the tilt state of the vehicle, and outputs the correction coefficient C1 to the target thrust calculation unit 38 .

A characteristic line 53 in FIG. 8 indicates the relationship between the longitudinal acceleration (G sensor value) when the vehicle is stopped and the correction coefficient C2. When the absolute value of the longitudinal acceleration when the vehicle is stopped is less than or equal to a predetermined value (gmin), the correction coefficient C2 is a constant value (minimum value), and the absolute value of the longitudinal acceleration when the vehicle is stopped is greater than the predetermined value (gmin). When it is large, the correction coefficient C2 also increases as the longitudinal acceleration increases. The correction coefficient C2 becomes 1 when the longitudinal acceleration gθ when the vehicle is stopped is g0. The relationship between the longitudinal acceleration (G sensor value) when the vehicle is stopped and the correction coefficient C2 can be obtained in advance by experiments, calculations, simulations, or the like.

The target thrust calculation unit 38 receives the correction coefficient C<b>1 from the correction coefficient calculation unit 37 and the correction coefficient C<b>2 from the inclination correction coefficient calculation unit 43 . The target thrust calculation unit 38 calculates the target thrust Ftarget by multiplying the reference thrust F0 by the correction coefficient C1 and the correction coefficient C2. The parking brake control device 24 drives the electric motor 7A so as to achieve the target thrust Ftarget to apply the parking brake.

FIG. 9 shows an example of temporal changes in the parking brake switch, vehicle speed V, brake fluid pressure P, longitudinal acceleration α, correction coefficient C1, correction coefficient C2, and target thrust Ftarget according to the second embodiment. At time t3 in FIG. 9, it is determined that the vehicle is stopped, and while the vehicle is stopped (between time t3 and time t4), the value of longitudinal acceleration G (gn) obtained by the acceleration sensor is referred to. , the longitudinal acceleration based on the inclination angle of the road surface on which the vehicle is stopped is obtained. Here, the acceleration sensor may be referenced at one point while the vehicle is stopped, or may be referenced multiple times at continuous time intervals. In FIG. 9, at time t4, a command to apply the electric parking brake is input. At time t4, the correction coefficient C2 and the target thrust force Ftarget are calculated. The correction coefficient C2 may be calculated, for example, at time t3 when the vehicle stops, or may be calculated at any timing between time t3 and time t4.

The correction coefficient C2 is calculated by the following equation (10). In Equation 10, "g0" is the longitudinal acceleration at the assumed maximum tilt angle, and "gθ" is the longitudinal acceleration detected by the acceleration sensor.

The target thrust force Ftarget is calculated by the following equation (11).

In the second embodiment, the correction coefficient C2 as described above is also used to calculate the target thrust, and the basic action thereof is not significantly different from that in the first embodiment. In particular, in the second embodiment, the parking brake control device 24 changes the thrust according to the tilt state of the vehicle when the vehicle is stopped. Therefore, when the vehicle is decelerated, it is possible to apply a thrust corresponding to the vehicle weight, the pad μ, and the inclination state (inclination angle) of the vehicle at the stop position.

Next, FIG. 10 shows a third embodiment. The feature of the third embodiment resides in that a correction coefficient for changing thrust is calculated by generating hydraulic pressure while driving and applying driving force to keep the speed constant. . In addition, in 3rd Embodiment, the same code|symbol is attached|subjected to the component same as 1st Embodiment and 2nd Embodiment, and the description is abbreviate|omitted.

In the third embodiment, hydraulic braking is performed only on the front wheels 2 or only on the rear wheels 3 while the vehicle is running. Thereby, the correction coefficient C1 is calculated only for the front wheels or only for the rear wheels. In this case, for example, control is performed such that hydraulic pressure is generated only in the rear wheel side disc brake 6 while the vehicle is running, and driving force is applied to keep the vehicle speed constant. As a result, the influence of the pad μ on the rear wheel 3 side can be derived, and the necessary thrust force of the electric parking brake can be obtained with higher accuracy.

Next, FIG. 11 shows a fourth embodiment. The feature of the fourth embodiment resides in the configuration in which the correction coefficient is calculated by the regenerative cooperation compatible vehicle. In the fourth embodiment, the same components as those in the first to third embodiments are denoted by the same reference numerals, and descriptions thereof are omitted.

In the fourth embodiment, the vehicle performs regenerative cooperative control when applying braking force. Regenerative cooperative control recovers (regenerates) kinetic energy as electric power by rotating the electric motor for traction based on the inertial force of the vehicle during braking. By subtracting the braking force (regenerative braking force) from the hydraulic brake and adjusting the braking force (friction braking force) from the hydraulic pressure brake, these two braking forces are used to obtain the desired braking force for the entire vehicle. . In the case of a vehicle that performs such control, both the regenerative braking force and the hydraulic braking force are applied during deceleration.

Therefore, in the fourth embodiment, the characteristics of the hydraulic pressure and the deceleration are set so that when the braking force due to regeneration becomes sufficiently small when you do). That is, the parking brake control device 24 acquires information on the brake fluid pressure and acceleration for obtaining the characteristics of the fluid pressure and deceleration when the braking force due to regeneration is zero. As a result, it is possible to prevent the thrust of the electric parking brake from becoming larger than necessary even for the regenerative cooperation compatible vehicle, and the durability can be improved. In FIG. 11, the braking force due to regeneration becomes 0 at time t1'. In the fourth embodiment, the correction coefficient C1 is calculated based on the brake fluid pressure and acceleration at time t1', but the correction coefficient C1 may be calculated at time t2, or The correction coefficient C1 may be calculated at any timing between and.

Next, FIG. 12 shows a fifth embodiment. The feature of the fifth embodiment is that it is configured to add a thrust corresponding to the creep torque when the vehicle stops on a downward slope. In addition, in the fifth embodiment, the same components as those in the first to fourth embodiments are denoted by the same reference numerals, and the description thereof is omitted.

The fifth embodiment (FIG. 12) differs from the fourth embodiment (FIG. 11) after time t4. In the fifth embodiment, the vehicle is an AT vehicle, and creep torque is applied as driving force when the vehicle is stopped. When such an AT vehicle stops on a downhill (downhill where the front side of the vehicle goes down), if the driver releases the brake pedal while the shift lever is in drive, the vehicle will move forward in addition to the downhill. A creep torque is applied. In order to keep the vehicle stopped even in such a case, in the fifth embodiment, when the vehicle stops on a downward slope, the target thrust of the electric parking brake is added by the creep torque. As a result, it is possible to prevent the vehicle from slipping forward on a downhill.

When the vehicle stops on an uphill (uphill where the front side of the vehicle rises), creep torque is applied in the direction opposite to the direction in which the vehicle slides down. However, for example, there is a possibility that the idling stop control of the engine stops the engine and the creep torque is no longer applied. Therefore, when the vehicle stops on an uphill slope, the thrust for the creep torque is not subtracted so that the vehicle can be kept stationary even if creep torque is no longer applied due to idling stop. That is, when the vehicle stops on an uphill slope, the creep torque is not converted into the target thrust in consideration of the loss of the creep torque due to the idling stop. As a result, it is possible to prevent the vehicle from rolling down regardless of whether the vehicle is going uphill or downhill. Incidentally, when the vehicle is stopped on a horizontal road surface, the creep torque may be added to the target thrust.

Next, FIG. 13 shows a sixth embodiment. A feature of the sixth embodiment resides in that the target thrust is changed to a specified value when the vehicle starts moving. In addition, in the sixth embodiment, the same components as those in the first to fifth embodiments are denoted by the same reference numerals, and descriptions thereof are omitted.

In the sixth embodiment, it is determined that the vehicle has stopped at time t3, and the correction coefficient C2 is calculated. After that, the vehicle starts at time t4. The parking brake control device 24 changes the target thrust force Ftarget to the prescribed value F0 when the vehicle starts moving. That is, the parking brake control device 24 changes the target thrust force Ftarget from the value multiplied by the correction coefficients C1 and C2 to the specified value F0 when the vehicle starts moving. The specified value F0 is the reference thrust F0 required to keep the vehicle stationary when the vehicle is fully loaded, the pad μ is the assumed minimum value, and the road surface inclination is the assumed maximum value. (assumed maximum thrust). Note that the target thrust force Ftarget can be changed to the specified value F0, for example, when the parking brake operation is completed. According to the sixth embodiment as described above, even if the vehicle weight, pad μ and inclination angle when the vehicle is stopped this time are different from the vehicle weight, pad μ and inclination angle when the vehicle is stopped next time, the vehicle is stopped next time. A thrust corresponding to the vehicle weight, the pad μ, and the inclination angle can be applied.

In each embodiment, the rear wheel disc brake 6 is a hydraulic disc brake with an electric parking brake function, and the front wheel disc brake 5 is a hydraulic disc brake without an electric parking brake function. explained with an example. However, the invention is not limited to this. For example, the rear wheel disc brake 6 may be a hydraulic disc brake without an electric parking brake function, and the front wheel disc brake 5 may be a hydraulic disc brake with an electric parking brake function. good. Further, both the front wheel disc brake 5 and the rear wheel disc brake 6 may be hydraulic disc brakes with an electric parking brake function. In short, at least a pair of left and right wheels among the wheels of the vehicle can be braked by an electric parking brake.

In each embodiment, the hydraulic disc brake 6 with an electric parking brake was described as an example of the electric brake mechanism. However, the brake mechanism is not limited to the disc brake type, and may be configured as a drum brake type brake mechanism. In addition, various configurations of the electric parking brake can be adopted, such as a drum-in-disc brake in which a drum-type electric parking brake is attached to the disc brake, or a configuration in which the parking brake is held by pulling a cable with an electric motor. can. Furthermore, each embodiment is an example, and it goes without saying that partial substitutions or combinations of configurations shown in different embodiments are possible.

As a brake device based on the embodiment described above, for example, the following modes are conceivable.

According to a first aspect, a brake device includes an electric motor that drives an electric mechanism that maintains the braking force of a vehicle, and a control device that controls the driving of the electric motor, wherein the control device controls the movement of the vehicle from a running state to a stop. The thrust generated by the electric mechanism for maintaining the braking force in the stopped state is changed according to the deceleration until the transition to the state and the brake fluid pressure until the transition.

According to this first aspect, the thrust generated by the electric mechanism is changed according to the deceleration of the vehicle and the brake fluid pressure. Thrust can be applied. As a result, it is possible to prevent the thrust from becoming larger than necessary, compared to a configuration in which the target thrust is applied based on the assumption of the maximum load, the minimum pad μ, and the maximum tilt angle. That is, it is possible to reduce the frequency with which the maximum thrust is applied assuming the maximum load, the minimum pad μ, and the maximum tilt angle, and improve the durability.

As a second aspect, in the first aspect, the control device changes the thrust based on the characteristics of the deceleration and the brake fluid pressure. According to the second aspect, it is possible to apply thrust corresponding to the vehicle weight and pad μ at that time (when the vehicle decelerates) based on the characteristics of deceleration and brake fluid pressure.

As a third aspect, in the first aspect or the second aspect, the control device includes a characteristic calculated from the deceleration and the brake fluid pressure, and a reference characteristic of the deceleration and the brake fluid pressure. and are compared to calculate a correction coefficient for correcting the thrust force, and the thrust force is changed by the correction coefficient. According to this third aspect, for example, by changing the required thrust force at the time of maximum load, minimum pad μ and maximum tilt angle with a correction coefficient, the vehicle weight at that time (when the vehicle decelerates) and the pad can be reduced to a thrust corresponding to μ.

As a fourth aspect, in any one of the first to third aspects, the control device changes the thrust according to the tilting state of the vehicle in the stopped state. According to the fourth aspect, it is possible to apply a thrust corresponding to the vehicle weight, the pad μ, and the tilted state of the vehicle at the stop position when the vehicle is decelerated.

As a fifth aspect, in any one of the first to fourth aspects, the control device changes the target thrust to a specified value when the parking brake operation is completed or when the vehicle starts moving. . According to the fifth aspect, even if the vehicle weight or pad μ when the vehicle is stopped this time and the vehicle weight or pad μ when the vehicle is stopped next time are different, the vehicle weight and pad μ when the vehicle is stopped next time are different. It is possible to give a thrust corresponding to

In addition, the present invention is not limited to the above-described embodiment, and includes various modifications. For example, the above-described embodiments have been described in detail in order to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the configurations described. Also, part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Moreover, it is possible to add, delete, or replace part of the configuration of each embodiment with another configuration.

This application claims priority based on Japanese Patent Application No. 2019-176376 filed on September 27, 2019. The entire disclosure, including the specification, claims, drawings, and abstract of Japanese Patent Application No. 2019-176376 filed on September 27, 2019, is incorporated herein by reference in its entirety.

6 rear wheel side disc brake 7A electric motor (electric motor, electric mechanism) 8 rotation/linear motion conversion mechanism (electric mechanism) 24 parking brake control device (control device) 31 thrust calculation unit

Claims (5)

A braking device, the braking device comprising:
an electric motor that drives an electric mechanism that maintains the braking force of the vehicle;
a control device that controls driving of the electric motor,
The control device generates braking force by the electric mechanism for maintaining the braking force in the stopped state according to the deceleration of the vehicle until the vehicle shifts from the running state to the stopped state and the brake fluid pressure until the transition. A braking device characterized by changing the thrust that causes the In the braking device according to claim 1,
The brake device, wherein the control device changes the thrust based on characteristics of the deceleration and the brake fluid pressure. In the braking device according to claim 1 or 2,
The control device compares a characteristic calculated from the deceleration and the brake fluid pressure with a reference characteristic of the deceleration and the brake fluid pressure to calculate a correction coefficient for correcting the thrust, A braking device, wherein the thrust is changed by the correction coefficient. In the braking device according to any one of claims 1 to 3,
The brake device, wherein the control device changes the thrust according to the tilting state of the vehicle when the vehicle is stopped. In the braking device according to any one of claims 1 to 4,
The braking device, wherein the control device changes the thrust force to a specified value when the parking brake operation is completed or when the vehicle starts moving.

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