JP2005271868A - Electric brake - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric brake reducing influence by reduction of a power source voltage and sufficiently maintaining responsiveness of braking. <P>SOLUTION: The electric brake has a braking member arranged on a member to be braked integrally rotated with a wheel with a clearance; an actuator for generating force for pressing after the braking member is moved until it is abutted on the member to be braked; and a control means for controlling force generated by the actuator based on braking operation. The control means has a power source voltage obtaining means for obtaining the power source voltage fed to the actuator; and a clearance adjustment means for adjusting the clearance of the braking member and the member to be braked in response to the power source voltage. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electric brake, and more particularly to an electric brake for a vehicle.

  A conventional electric brake moves a brake member disposed so as to have an interval (hereinafter referred to as a clearance) with respect to a braked member that rotates integrally with a wheel, and the brake member moves until it comes into contact with the braked member. The actuator is configured to generate a pressing force after being applied, and a control unit that controls the force generated by the actuator based on a brake operation.

For example, Patent Document 1 discloses an example of an electric brake that converts a rotational motion of a motor into a linear motion and presses a brake shoe as a braking member against a drum as a braked member by this linear motion to generate a braking force. Has been described.
JP 11-99934 A

  In a conventional electric brake, a motor as an actuator is driven by a predetermined power supply voltage, and the rotational motion of the motor is converted into a linear motion, and the brake shoe as a braking member is applied to the drum as a braked member by the linear motion. When pressed, a braking force is generated. Therefore, the brake shoe moves through the clearance at a speed corresponding to the rotational movement of the motor. The rotational motion of the motor changes according to the power supply voltage supplied to the motor.

  By the way, in a vehicle such as an automobile, the power supply voltage drops due to various factors such as lighting of a lamp and use of an air conditioner. Such a power supply voltage drop reduces the rotational motion of the motor. As a result, the power supply voltage drop decreases the speed at which the brake shoe moves through the clearance, and increases the time until the brake shoe is pressed against the drum to generate the braking force. As described above, the conventional electric brake has a problem that the responsiveness of braking is lowered due to a power supply voltage drop, and there is a risk of causing an accident.

  The present invention has been made in view of the above points, and an object of the present invention is to provide an electric brake capable of reducing the influence of a power supply voltage drop and maintaining good braking response.

  Therefore, in order to solve the above problems, the present invention provides a braking member disposed so as to have a clearance with respect to a braked member that rotates integrally with a wheel, and the brake member abuts against the braked member. An electric brake having an actuator that generates a pressing force after being moved to a position and a control unit that controls a force generated by the actuator based on a brake operation. The control unit is supplied to the actuator. Power supply voltage acquisition means for acquiring the power supply voltage, and clearance adjustment means for adjusting the clearance between the braking member and the braked member in accordance with the power supply voltage.

  In the present invention, the power supply voltage acquisition means acquires the power supply voltage supplied to the actuator, and the clearance adjustment means adjusts the clearance between the braking member and the braked member according to the power supply voltage. The clearance between the braking member and the member to be braked is adjusted so as to reduce the influence of fluctuations in the moving speed of the braking member.

  For example, when a power supply voltage drop occurs, the speed at which the braking member moves through the clearance decreases according to the power supply voltage drop. Therefore, the time from when the braking member is pressed against the braked member to generate the braking force becomes longer due to the decrease in the moving speed of the braking member. Therefore, in the present invention, when a power supply voltage drop occurs, the clearance, which is the moving distance of the braking member, is reduced by adjusting the clearance between the braking member and the braked member so that the braking member becomes the braked member. It is prevented that the time until the braking force is generated by being pressed is increased.

  The clearance adjusting means adjusts so that a clearance between the braking member and the braked member when the power supply voltage is less than a reference value is smaller than the clearance when the power supply voltage is greater than or equal to a reference value. May be.

  In the present invention, when the power supply voltage is less than the reference value, it is determined that a power supply voltage drop has occurred, and the clearance between the braking member and the braked member when the power supply voltage is less than the reference value is It can be adjusted to be smaller than the clearance when the voltage is equal to or higher than the reference value.

  The clearance adjusting means may adjust the clearance according to a predetermined power supply voltage-clearance characteristic.

  In the present invention, when the power supply voltage is less than the reference value, the clearance can be adjusted according to a predetermined power supply voltage-clearance characteristic.

  The clearance adjusting means is configured to perform the brake operation from when the power supply voltage is lower than a reference value and when the power supply voltage is higher than a reference value until the braking member contacts the braked member. You may adjust the said clearance so that time may be made comparable.

  In the present invention, the clearance can be adjusted so that the time until braking occurs is the same when the power supply voltage is less than the reference value and when the power supply voltage is greater than or equal to the reference value.

  ADVANTAGE OF THE INVENTION According to this invention, the electric brake which can reduce the influence by a power supply voltage drop and can maintain the responsiveness of a brake favorable can be provided.

  Next, the best mode for carrying out the present invention will be described based on the following embodiments with reference to the drawings. In this embodiment, an electric drum brake is described as an example of the electric brake. However, the electric brake is any electric brake that generates a braking force by pressing the braking member against the member to be braked by driving the actuator. May be.

  FIG. 1 is a configuration diagram of an example of an electric brake system including an electric drum brake according to the present invention. The electric brake system includes an electric disc brake 10, an electric drum brake 20, an electric control device 30, a drive circuit 40, a battery 50, and a brake pedal 60.

  The electric disc brake 10 is provided on the left front wheel (FL) and the right front wheel (FR). The electric disc brake 10 is non-rotatably held by a disc rotor (not shown) that is a braked member that rotates integrally with a wheel and a mounting bracket that is a vehicle body side member, and is fixed to the disc rotor. Brake pad (not shown) as a braking member disposed so as to have a clearance, a motor 11 as an actuator that generates a force corresponding to a supplied power supply voltage, and a position sensor that detects a position X of the brake pad 12 and a pressure sensor 13 are included.

  The electric disc brake 10 moves the brake pads toward the disc rotor by the force generated by the motor 11 and further presses the brake pads against the disc rotor, thereby rotating the left and right front wheels (FL, FR). Generates braking force to suppress. The position sensor 12 detects the position X of the brake pad driven by the motor 11. The pressure sensor 13 is a strain sensor, and is attached to a member that is pressed with the same force as that when the brake pad is pressed against the disc rotor. The pressure sensor 13 detects the pressure P from the amount of strain detected by the strain sensor.

  The electric drum brake 20 is provided on the left rear wheel (RL) and the right rear wheel (RR). The electric drum brake 20 is non-rotatably held by a drum 21 that is a braked member that rotates integrally with a wheel and a backing plate that is a vehicle body side member, and has a predetermined clearance with respect to the drum 21. A brake shoe 22 as a braking member, a motor 23 as an actuator that generates a force corresponding to the supplied power supply voltage, a position sensor 24 for detecting the position X of the brake shoe, and a pressure sensor 25. Including.

  The electric drum brake 20 is moved by the force generated by the motor 23 until the brake shoe 22 comes into contact with the inner peripheral surface of the drum 21 and further presses the brake shoe 22 against the inner peripheral surface of the drum 21. A braking force that suppresses rotation of the left and right rear wheels (RL, RR) is generated.

  FIG. 2 is a cross-sectional view of an example of an electric drum brake. FIG. 2 shows an example of a duo servo type electric drum brake. The electric drum brake includes a backing plate 200, a pair of brake shoes 202 a and 202 b, a drum 206, and an actuator 207.

  The backing plate 200 has a disk shape, and is attached to a vehicle body side member (not shown) so as not to rotate. The brake shoes 202a and 202b are provided on the packing plate 200 and are generally arcuate. The drum 206 has a friction surface on the inner peripheral surface 204 and rotates together with the wheels. The actuator 207 expands one end portions of the pair of brake shoes 202a and 202b.

  The pair of brake shoes 202a and 202b are engaged with an anchor pin 208 fixed to the backing plate 200 at one end facing each other, so that the pair of brake shoes 202a and 202b can rotate while being prevented from rotating together with the drum 206. Is retained. Further, the other ends of the pair of brake shoes 202a and 202b are connected to each other by a strut 210, and the force acting on one brake shoe by the strut 210 is transmitted to the other brake shoe. The pair of brake shoes 202a and 202b can be moved along the surface of the backing plate 200 by shoe hold-down devices 212a and 212b.

  The other ends of the pair of brake shoes 202a and 202b are urged toward each other by a spring 214 as shown in FIG. Further, one end portions of the pair of brake shoes 202a and 202b are urged toward the anchor pin 208 by the shoe return springs 215a and 215b. A return spring 218 is also provided at one end.

  Brake linings 219a and 219b are held on the outer peripheral surfaces of the brake shoes 202a and 202b, respectively. The pair of brake linings 219a and 219b are frictionally engaged with the inner peripheral surface 204 of the drum 206, thereby A frictional force is generated between the linings 219 a and 219 b and the drum 206. In the electric drum brake of FIG. 2, the strut 210 is provided with an adjusting mechanism, and the clearance between the brake linings 219 a and 219 b and the inner peripheral surface 204 of the drum 206 is adjusted according to wear of the brake linings 219 a and 219 b. .

  Each brake shoe 202a, 202b includes rims 224a, 224b and webs 222a, 222b, respectively, and one ends of the levers 230a, 230b are rotatably provided via pins 232a, 232b. Cutouts are provided in portions of the levers 230a and 230b and the webs 222a and 222b facing each other. Struts 216 engage these notches.

  An actuator 207 including the motor 23 is connected to the other end of the lever 230a. When the brake pedal 60 is operated, the lever 230a is rotated by driving the motor 23 (actuator 207). The pair of brake shoes 202 a and 202 b are expanded by the strut 216, and the brake linings 219 a and 219 b are pressed against the inner peripheral surface 204 of the drum 206. That is, the frictional force is generated between the brake linings 219 a and 219 b and the drum 206 by the frictional engagement of the brake linings 219 a and 219 b with the inner peripheral surface 204 of the drum 206. Therefore, the rotation of the wheel is suppressed, and the braking torque T is applied to the wheel.

  In the electric drum brake of FIG. 2, the driving force based on the frictional force generated in one brake shoe 202b and the brake operating force D by the actuator 207 are applied to the other brake via the strut 210 from the other end. It is transmitted to the other end of the shoe 202a. The brake operating force D can be considered as an expanding force that expands the pair of brake shoes 202a and 202b.

  As a result, the other brake shoe 202a is pressed against the inner peripheral surface 204 of the drum 206 by the sum of the accompanying force and the spreading force, and a larger frictional force is generated than the one brake shoe 202b. Thus, since the output of one brake shoe 202b becomes the input of the other brake shoe 202a, the duo-servo type electric drum brake can obtain a large braking torque T.

  A strain sensor 312 that detects a load applied to the anchor pin 208 as the pressure sensor 25 is attached to the anchor pin 208. The force transmitted to the other brake shoe 202a via the strut 210 is further increased by the servo effect of the other brake shoe 202a and acts on the anchor pin 208. As a result, if the braking torque is obtained based on the load applied to the anchor pin 208, the braking torque T generated in the duo-servo type electric drum brake can be detected. This braking torque T is equivalent to the force (pressing force P) that the brake shoes 202a and 202b, which are braking members, are actually pressed against the drum 206, which is a member to be braked, as long as the wheel rotates.

  The actuator 207 includes a speed reducer and a ball screw mechanism in addition to the motor 23. The rotation of the output shaft of the motor 23 is decelerated by the speed reducer, and the rotational motion of the output shaft is converted into linear motion by the ball screw mechanism, and this linear motion is transmitted to the lever 230a connected to the output member of the ball screw mechanism. .

  The position sensor 24 is provided in the motor 23, and detects the position X of the brake shoes 202a and 202b by detecting the rotation of the output shaft of the motor 23. The position X of the brake shoes 202a and 202b may be directly detected by a gap sensor or the like fixed to the backing plate 200 or the like. The motors 11 and 23 can use DC motors, ultrasonic motors, or the like.

  Returning to FIG. 1, the electric control device 30 includes a microcomputer 31 having a memory and a CPU (not shown). The electric control device 30 executes a program stored in the memory. The electric control device 30 includes position sensors 12, 24, pressure sensors 13, 25, a vehicle speed sensor 51 for detecting a vehicle speed (hereinafter referred to as a vehicle speed) SPD, a parking brake operation switch 52, a pedal force sensor 53, The stroke sensor 54, the motor current sensor 55, the wheel speed sensor 56, and the battery 50 are connected, and various signals are input.

  The vehicle speed sensor 51 detects the vehicle speed SPD by detecting the rotation of the output shaft of the transmission (not shown). The parking brake operation switch 52 is operated by the driver to generate a parking brake instruction signal PKB, and controls the operation of the parking brake. The pedal effort sensor 53 detects the pedal effort F of the brake pedal 60 by the driver. The stroke sensor 54 detects the operation stroke ST of the brake pedal 60. The wheel speed sensor 56 is provided on each of the four wheels (FL, FR, RL, RR), and detects the wheel speed Vw of each wheel.

  The motor current sensor 55 is connected to the coils of the motor 11 of the electric disc brake 10 and the motor 23 of the electric drum brake 20, and is supplied from the battery 50 as a power source to the motors 11 and 23 via the drive circuit 40. The supplied current value I is detected, and a signal defining the supplied current value I is output to the electric control device 30. The output signal represents the supply current value I as the voltage height.

  A drive circuit 40 is connected to the output side of the electric control device 30. When the brake pedal 60 is operated, a command is supplied from the electric control device 30 to the drive circuit 40, and in response to the command, the drive circuit 40 supplies a current from the battery 50 to the motor 11 of the electric disc brake 10 and the electric drum brake 20. The motor 23 is supplied.

  The electric control device 30 monitors the power supply voltage of the battery 50. A power supply voltage sensor that monitors the power supply voltage of the battery 50 may be provided separately. In this case, the electric control device 30 acquires the monitoring result of the power supply voltage from the power supply voltage sensor. The electric control device 30 performs a process for adjusting the clearance between the drum 21 as the braked member and the brake shoe 22 as the braking member, as will be described later, according to the monitoring result of the power supply voltage of the battery 50.

  The memory of the microcomputer 31 stores a program for performing processing for adjusting the clearance. The microcomputer 31 reads a program for performing a process for adjusting the clearance from the memory, and executes the process represented by the flowchart of FIG.

  FIG. 3 is a flowchart of an example of a process for adjusting the clearance. In step S <b> 1, the microcomputer 31 acquires the power supply voltage of the battery 50. The power supply voltage of the battery 50 usually fluctuates due to various factors such as lamp lighting and use of an air conditioner. Therefore, the microcomputer 31 may use the average value of the acquired power supply voltages, or may select and use the power supply voltage in a time zone with little fluctuation. The time zone in which the fluctuation of the power supply voltage is small means, for example, a time zone in which the power supply voltage is not used so much that there is no lighting of a lamp or use of an air conditioner. Since the electric control device 30 can detect lighting of a lamp, use of an air conditioner, and the like, it is possible to select a time zone in which the power supply voltage is not used much.

  In step S2, the microcomputer 31 determines whether the power supply voltage is lower than a predetermined reference voltage (for example, 12V). If it is determined that the power supply voltage is lower than the reference voltage (YES in S2), the microcomputer 31 proceeds to step S3 and performs a clearance adjustment process described later. On the other hand, if it is determined that the power supply voltage has not dropped below the reference voltage (NO in S2), microcomputer 31 returns to step S1.

  In the clearance adjustment process in step S3, for example, the process represented by the flowchart of FIG. 4 is executed. FIG. 4 is a flowchart of an example of the clearance adjustment process. In step S 11, the microcomputer 31 instructs the drive circuit 40 to move the brake shoe 22 toward the inner peripheral surface of the drum 21 by the force generated by the motor 23, thereby reducing the clearance by a predetermined value.

  In step S12, the microcomputer 31 determines the left and right rear wheels (RL, RR) based on various signals input from the position sensor 24, the pressure sensor 25, the vehicle speed sensor 51, a vehicle body deceleration sensor (G sensor) (not shown), and the like. It is determined whether or not a braking force that suppresses rotation is generated.

  If the braking force is not generated (NO in S12), the microcomputer 31 returns to step S11 and further reduces the clearance by a predetermined value. On the other hand, if a braking force is generated (YES in S12), the microcomputer 31 controls the clearance by moving the brake shoe 22 toward the opposite side of the inner peripheral surface of the drum 21 by the force generated by the motor 23. The process is terminated after increasing the power so that no power is generated.

  The clearance adjustment process of FIG. 4 addresses the problem that the moving speed of the brake shoe 22 decreases when the power supply voltage is in a power supply voltage drop state where the power supply voltage drops below a predetermined reference voltage. The time from when the brake shoe 22 is pressed against the inner peripheral surface of the drum 21 until the braking force is generated becomes longer due to the decrease in the moving speed of the brake shoe 22. In other words, the responsiveness of braking is deteriorated, which may lead to an accident.

  Therefore, in the clearance adjustment process of FIG. 4, the clearance between the brake shoe 22 and the drum 21 is reduced to such an extent that no braking force is generated when the power supply voltage drops. Thus, if the clearance between the brake shoe 22 and the drum 21 is reduced, the moving distance of the brake shoe 22 is reduced. As a result, the time until the braking force is generated does not increase even in the power supply voltage drop state, and the braking response can be maintained well.

  In the clearance adjustment process of step S3, the process represented by the flowchart of FIG. 5 may be executed. FIG. 5 is a flowchart of another example of the clearance adjustment process. In step S21, the microcomputer 31 determines a clearance according to the power supply voltage acquired in step S1 and the power supply voltage-clearance characteristics as shown in FIG. 6 stored in the memory.

  FIG. 6 is a diagram illustrating an example of power supply voltage-clearance characteristics. The power supply voltage-clearance characteristic in FIG. 6 defines the relationship between the power supply voltage and the clearance. The power supply voltage-clearance characteristics in FIG. 6 are adjusted based on, for example, the power supply voltage-output characteristics of the motor 23 so that the time until the braking force is generated is approximately the same.

  Further, the microcomputer 31 may determine the clearance step by step according to the power supply voltage acquired in step S1 and the power supply voltage-clearance characteristics as shown in FIG. 7 stored in the memory.

  FIG. 7 is a diagram illustrating another example of the power supply voltage-clearance characteristics. The power supply voltage-clearance characteristic in FIG. 7 defines the relationship between the power supply voltage and the clearance. The power supply voltage-clearance characteristics in FIG. 7 are adjusted stepwise so that the time until the braking force is generated is approximately the same based on the power supply voltage-output characteristics of the motor 23, for example.

  Returning to FIG. 5, in step S <b> 22, the microcomputer 31 instructs the drive circuit 40 to move the brake shoe 22 by the force generated by the motor 23, thereby adjusting the clearance determined in step S <b> 21 and processing. finish.

  The clearance adjustment process of FIG. 5 addresses the problem that the moving speed of the brake shoe 22 decreases when the power supply voltage is in a power supply voltage drop state where the power supply voltage drops below a predetermined reference voltage. The time from when the brake shoe 22 is pressed against the inner peripheral surface of the drum 21 until the braking force is generated becomes longer due to the decrease in the moving speed of the brake shoe 22. In other words, the responsiveness of braking is deteriorated, which may lead to an accident.

  Therefore, in the clearance adjustment process of FIG. 5, the clearance between the brake shoe 22 and the drum 21 is set so that the time until the braking force is generated is approximately the same as that when the power supply voltage is not reduced when the power supply voltage is reduced. It is adjusted. In this way, if the clearance can be adjusted so that the time until the braking force is generated is the same when the power supply voltage is dropped and when the power supply voltage is not dropped, the time until the braking force is generated is It does not become long, and the response of braking can be maintained well.

  The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above-described embodiments, and various modifications and substitutions can be made to the above-described embodiments without departing from the scope of the present invention. Can be added.

  For example, in the above embodiment, the power supply voltage-clearance characteristics of FIGS. 6 and 7 are based on the power supply voltage-output characteristics of the motor 23, but may not be based on the power supply voltage-output characteristics of the motor 23. For example, the power supply voltage-clearance characteristic may be such that when the power supply voltage is in a drop state, the predetermined clearance is shorter than the clearance when the power supply voltage is not drop. Further, the clearance may be adjusted according to the ratio between the reference voltage and the power supply voltage when the power supply voltage is in a drop state.

  The power supply voltage acquisition means described in the claims corresponds to the process of step S1 realized by the microcomputer 31 executing the program, and the clearance adjustment means is realized by the microcomputer 31 executing the program. This corresponds to the processing of steps S2 and S3.

It is a lineblock diagram of an example of an electric brake system containing an electric drum brake by the present invention. It is sectional drawing of an example of an electric drum brake. It is a flowchart of an example of the process for adjusting a clearance. It is a flowchart of an example of a clearance adjustment process. It is a flowchart of another example of clearance adjustment processing. It is a figure of an example showing a power supply voltage-clearance characteristic. It is a figure of another example showing a power supply voltage-clearance characteristic.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Electric disc brake 11, 23 Motor 12, 24 Position sensor 13, 25 Pressure sensor 20 Electric drum brake 21 Drum 22 Brake shoe 30 Electric control device 31 Microcomputer 40 Drive circuit 50 Battery 51 Vehicle speed sensor 52 Parking brake operation switch 53 pedal force sensor 54 stroke sensor 55 motor current sensor 56 wheel speed sensor 60 brake pedal

Claims (4)

A braking member disposed so as to have a clearance with respect to the braked member that rotates integrally with the wheel;
An actuator for generating a pressing force after moving the braking member until it comes into contact with the braked member;
An electric brake having control means for controlling a force generated by the actuator based on a brake operation,
The control means is a power supply voltage acquisition means for acquiring a power supply voltage supplied to the actuator;
An electric brake having a clearance adjusting means for adjusting a clearance between the braking member and the braked member in accordance with the power supply voltage.   The clearance adjusting means adjusts so that a clearance between the braking member and the braked member when the power supply voltage is less than a reference value is smaller than the clearance when the power supply voltage is greater than or equal to a reference value. The electric brake according to claim 1.   3. The electric brake according to claim 2, wherein the clearance adjusting means adjusts the clearance according to a predetermined power supply voltage-clearance characteristic.   The clearance adjusting means is configured to perform the brake operation from when the power supply voltage is lower than a reference value and when the power supply voltage is higher than a reference value until the braking member contacts the braked member. 2. The electric brake according to claim 1, wherein the clearance is adjusted so that the time is substantially the same.

Images