Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
  • B60T13/00—Transmitting braking action from initiating means to ultimate brake actuator with power assistance or drive; Brake systems incorporating such transmitting means, e.g. air-pressure brake systems
  • B60T13/74—Transmitting braking action from initiating means to ultimate brake actuator with power assistance or drive; Brake systems incorporating such transmitting means, e.g. air-pressure brake systems with electrical assistance or drive
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
  • B60T8/00—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
  • B60T8/00—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force
  • B60T8/17—Using electrical or electronic regulation means to control braking
  • B60T8/171—Detecting parameters used in the regulation; Measuring values used in the regulation

Definitions

• the present invention relates to an electric brake device that applies braking force to vehicles such as automobiles.
• Patent Document 1 describes an electric disc brake that estimates the pad contact position (contact position between the brake pad and disc rotor) based on the current value (motor current) of the electric motor.
• Patent Document 1 improves the accuracy of estimating the pad contact position by subtracting (removing) noise (pulsation) with a period of one rotation of the electric motor in the clearance area from the relationship between the measured motor position and motor current (braking characteristics). However, in this case, it is not possible to remove noise (pulsation) with a period of more than one rotation of the electric motor.
• One of the objectives of the present invention is to provide an electric brake device that can improve the accuracy of estimating the contact position and the stiffness.
• An electric brake device includes an actuator that presses a braking member toward a braked member by driving an electric motor, and a contact position estimation unit that estimates the contact position between the braking member and the braked member based on the braking characteristics of the electric brake device.
• the contact position estimation unit moves the actuator position back by a predetermined value from the actuator position at that time, and estimates the contact position based on the physical quantity at the actuator position moved back by the predetermined value.
• An electric brake device includes an actuator that presses a braking member toward a braked member by driving an electric motor, and a stiffness estimation unit that estimates the stiffness of the braking member, the braked member, and the actuator based on the braking characteristics of the electric brake device, and when a physical quantity corresponding to the magnitude of the braking force of the actuator reaches a predetermined physical quantity due to contact between the braking member and the braked member, the stiffness estimation unit moves the actuator position back by a predetermined value from the actuator position at that time, and estimates the stiffness based on the physical quantity at the actuator position moved back by the predetermined value.
• FIG. 1 is a schematic diagram showing a vehicle equipped with an electric brake device according to an embodiment
• FIG. 2 is a perspective view showing the electric brake device in FIG. 1
• FIG. 2 is a cross-sectional view showing the electric brake device in FIG. 11 is a flow chart showing a process for offsetting a reference of a braking characteristic.
• 5 is a flowchart (modified version) similar to FIG. 4, but adding a process for updating the predetermined value of the return amount.
• FIG. 11 is a characteristic diagram showing an example of braking characteristics (a total of 20 types including four types of low-frequency pulsation and five types of stiffness).
• 7 is a characteristic diagram showing a portion A in FIG. 6 enlarged (enlarged by about 10 times) only in the vertical direction.
• FIG. 6 is a perspective view showing the electric brake device in FIG. 1 .
• FIG. 11 is a characteristic diagram showing braking characteristics (a total of 20 types including four types of low-frequency pulsation and five types of stiffness) according to a comparative example.
• FIG. 9 is a characteristic diagram showing braking characteristics according to the embodiment (braking characteristics obtained by offsetting the braking characteristics according to the comparative example in FIG. 8 ).
• FIG. 11 is an explanatory diagram (characteristics diagram) explaining the change (advancement) of braking characteristics accompanying pad wear.
• FIG. 5 is an explanatory diagram (characteristic diagram) showing braking characteristics (C1, C2) obtained by the processing from S3 to S6 in FIG. 4;
• FIG. 5 is an explanatory diagram (characteristic diagram) showing braking characteristics (C1, C2) obtained when the processes from S4 to S6 in FIG. 4 are performed on a memory.
• FIG. 1 shows a vehicle system.
• a vehicle 1 is equipped with a brake system 4 that applies a braking force to the wheels 2, 3 (front wheels 2L, 2R, rear wheels 3L, 3R) to brake the vehicle 1.
• the brake system 4 includes left and right front-wheel electric brake devices 5L, 5R (front brake devices) provided corresponding to the left front wheel 2L (left front wheel 2L) and the right front wheel 2R (right front wheel 2R), left and right rear-wheel electric brake devices 6L, 6R (rear brake devices) provided corresponding to the left rear wheel 3L (left rear wheel 3L) and the right rear wheel 3R (right rear wheel 3R), a brake pedal 7 (operating tool) as a brake operating member, a pedal reaction force device 8 (hereinafter referred to as a pedal simulator 8) that generates a kickback reaction force in response to the operation (pressing) of the brake pedal 7, and a pedal stroke sensor 9 as an operation detection sensor that measures the amount of operation of the brake pedal 7 by the driver.
• the left and right front wheel electric brake devices 5L, 5R and the left and right rear wheel electric brake devices 6L, 6R are configured, for example, as electric disc brakes (electric disc brakes).
• the electric brake devices 5, 6 apply braking force to the wheels 2, 3 (front wheels 2L, 2R, rear wheels 3L, 3R) by driving an electric motor 26.
• the left and right rear wheel electric brake devices 6L, 6R are equipped with a parking mechanism (not shown).
• the pedal stroke sensor 9 is provided, for example, in the pedal simulator 8.
• the pedal stroke sensor 9 may also be provided in the brake pedal 7.
• a pedal force sensor that measures the pedal force corresponding to the amount of operation of the brake pedal 7 may be used.
• the pedal stroke sensor 9 is connected to a first brake control ECU 10 and a second brake control ECU 11, each of which is an ECU (Electronic Control Unit) for brake control.
• the first brake control ECU 10 (also referred to as the first ECU 10) and the second brake control ECU 11 (also referred to as the second ECU 11) are provided in the vehicle 1.
• the first ECU 10 and the second ECU 11 are configured to include a microcomputer having a central processing unit (CPU), a storage device (memory), a control board, etc.
• the first ECU 10 and the second ECU 11 receive a signal from the pedal stroke sensor 9 and calculate the braking force (target braking force) for each wheel (four wheels) according to a predetermined control program.
• the first ECU 10 calculates, for example, the target braking force to be applied to the left front wheel 2L and the right rear wheel 3R. Based on the calculated target braking force, the first ECU 10 outputs (transmits) braking commands (control commands) for each of the two wheels, the left front wheel 2L and the right rear wheel 3R, to the electric brake ECUs 31, 31 via a CAN 12 (Controller area network) that serves as a vehicle data bus.
• a CAN 12 Controller area network
• the second ECU 11 calculates, for example, the target braking force to be applied to the right front wheel 2R and the left rear wheel 3L. Based on the calculated target braking force, the second ECU 11 outputs (transmits) braking commands (control commands) for each of the two wheels, the right front wheel 2R and the left rear wheel 3L, to the electric brake ECUs 31, 31 via the CAN 12.
• the first ECU 10 and the second ECU 11 are equipped with control units 10A, 11A that perform calculations based on input information (e.g., a signal from the pedal stroke sensor 9, etc.) and output the calculation results (e.g., a control command according to a target thrust).
• the first ECU 10 and the second ECU 11 receive vehicle information transmitted via CAN 12 from other ECUs mounted on the vehicle 1 (e.g., a prime mover ECU, a transmission ECU, a steering ECU, an automatic driving ECU, etc., not shown).
• the first ECU 10 and the second ECU 11 can obtain various vehicle information via the CAN 12, such as information on the AT range position or MT shift position, ignition on/off information, engine RPM information, powertrain torque information, transmission gear ratio information, steering wheel operation information, clutch operation information, accelerator operation information, vehicle-to-vehicle communication information, information on the surroundings of the vehicle from an on-board camera, and acceleration sensor information (longitudinal acceleration, lateral acceleration).
• vehicle information such as information on the AT range position or MT shift position, ignition on/off information, engine RPM information, powertrain torque information, transmission gear ratio information, steering wheel operation information, clutch operation information, accelerator operation information, vehicle-to-vehicle communication information, information on the surroundings of the vehicle from an on-board camera, and acceleration sensor information (longitudinal acceleration, lateral acceleration).
• a parking brake switch 13 is provided near the driver's seat.
• the parking brake switch 13 is connected to the first ECU 10 (and the second ECU 11 via the CAN 12).
• the parking brake switch 13 transmits a signal (operation request signal) corresponding to a request to operate the parking brake in response to an operation instruction from the driver (an apply request which is a request to hold the parking brake, and a release request which is a request to release the parking brake) to the first ECU 10 and the second ECU 11.
• the first ECU 10 and the second ECU 11 Based on the operation (operation request signal) of the parking brake switch 13, the first ECU 10 and the second ECU 11 transmit parking brake commands for each of the two rear wheels (rear wheels 3L, 3R) to the electric brake ECUs 31, 31.
• the parking brake switch 13 corresponds to a switch that operates the parking mechanism.
• FIGs 2 and 3 show the electric brake devices 5, 6.
• the electric brake devices 5, 6 include a braking mechanism 21 and an electric motor 26 that constitute an actuator, and an electric brake ECU 31.
• the electric brake devices 5, 6 apply a braking force to the vehicle 1 by controlling the position and thrust of the braking mechanism 21.
• the braking mechanism 21 includes a rotation angle sensor 32 ( Figure 3) as a position detection means that detects the motor rotation position, a thrust sensor 33 ( Figure 3) as a thrust detection means that detects the thrust generated in the piston 24 (piston thrust), and a current sensor 34 as a current detection means that detects the current of the electric motor 26 (motor current).
• the braking mechanism 21 includes, for example, a carrier 22, a caliper 23 as a cylinder (wheel cylinder), a piston 24 as a pressing member, and a brake pad 25 as a braking member (friction pad).
• the braking mechanism 21 includes an electric motor 26 to drive the braking mechanism 21, i.e., to generate a braking force by the braking mechanism 21.
• the braking mechanism 21 also includes a reduction mechanism 27, a rotary-to-linear motion conversion mechanism 28, and a return spring 29 that serves as a fail-open mechanism.
• the reduction mechanism 27 is covered by a housing 30 together with an ECU board 31B of the electric brake ECU 31.
• the housing 30, the reduction mechanism 27, the electric motor 26, the rotation angle sensor 32, and the ECU board 31B constitute a driving member that drives the braking mechanism 21.
• the carrier 22 is fixed to the body of the vehicle 1.
• the caliper 23 is supported (floatingly supported) on the carrier 22 to allow the disc rotor D to move in the axial direction.
• the electric motor 26 rotates when supplied with electricity, and propels the piston 24. In this way, the electric motor 26 applies a braking force.
• the electric motor 26 is controlled by the electric brake ECU 31 based on a braking command (control command) from the first ECU 10 or the second ECU 11.
• the reduction mechanism 27 is composed of, for example, a gear reduction mechanism, and reduces the rotation of the electric motor 26 before transmitting it to the rotary-linear conversion mechanism 28.
• the rotary-linear conversion mechanism 28 converts the rotation of the electric motor 26, transmitted via the reduction mechanism 27, into axial displacement (linear displacement) of the piston 24.
• the piston 24 is driven by the electric motor 26 to move the brake pad 25.
• the brake pad 25 is pressed against the disc rotor D by the piston 24.
• the pair of brake pads 25, 25 are located on both axial sides of the disc rotor D and are each supported by the carrier 22.
• the disc rotor D which serves as the braked member (rotor), rotates together with the wheels 2L, 2R, 3L, 3R.
• the return spring 29 applies a rotational force in the direction of releasing the brake to the rotating member of the rotary-to-linear motion conversion mechanism 28.
• the piston 24 is driven by the electric motor 26 to press the brake pad 25 against the disc rotor D. That is, based on a braking request (braking command), the braking mechanism 21 transmits the thrust generated by the driving of the electric motor 26 to the piston 24, which moves the brake pad 25. In this way, the braking mechanism 21 presses the brake pad 25 against the disc rotor D.
• an electric brake ECU 31 is provided for each braking mechanism 21.
• the electric brake ECU 31 is configured to include, for example, a microcomputer having a central processing unit (CPU), a storage device (memory), a control board, etc., and a drive circuit (e.g., an inverter) for supplying power to the electric motor 26.
• the electric brake ECU 31 includes an ECU board 31B in which a calculation circuit, etc. is built in.
• the electric brake ECU 31 controls the electric motor 26 that operates the braking mechanism 21 based on commands from the first ECU 10 or the second ECU 11.
• the electric brake ECU 31 is equipped with a control unit 31A (in other words, an ECU board 31B) that performs calculations based on input information (e.g., signals corresponding to control commands, etc.) and outputs the calculation results (e.g., electric motor drive commands according to the control commands).
• the electric brake ECU 31 controls the drive of the electric motor 26 based on a braking command (control command) input to the electric brake ECU 31.
• the rear wheel electric brake ECU 31 controls the drive (apply, release) of the parking mechanism based on a parking operation command input to the electric brake ECU 31.
• a signal corresponding to a braking command and a signal corresponding to a parking operation command are input to the electric brake ECU 31 from the first ECU 10 or the second ECU 11.
• the rotation angle sensor 32 detects the rotation angle (motor rotation angle) of the rotating shaft 26A of the electric motor 26.
• the rotation angle sensor 32 is provided corresponding to each electric motor 26 of each braking mechanism 21, and constitutes a position detection means for detecting the rotation position (motor rotation position) of the electric motor 26, and by extension the position of the piston 24 (piston position).
• the rotation angle sensor 32 is composed of, for example, a magnet 32A, which is a magnetic member attached to the rotating shaft 26A of the electric motor 26, and a magnetic detection IC chip 32B, which is a magnetic signal receiver provided in the electric brake ECU 31 (ECU board 31B).
• the electric brake ECU 31 (ECU board 31B) can calculate and detect the rotation angle of the rotating shaft 26A of the electric motor 26 by detecting the change in the magnetic flux of the rotating magnet 32A with the magnetic detection IC chip 32B.
• the thrust sensor 33 detects the reaction force against the thrust (pressing force) from the piston 24 to the brake pad 25.
• the thrust sensor 33 is provided in each braking mechanism 21, and constitutes thrust detection means that detects the thrust (piston thrust) generated in the piston 24.
• the thrust sensor 33 is provided in the rotary-linear conversion mechanism 28.
• the current sensor 34 detects the current (motor current) supplied to the electric motor 26.
• the current sensor 34 is provided corresponding to each electric motor 26 of each braking mechanism 21, and constitutes current detection means that detects the current (motor current, motor torque current) supplied to the electric motor 26.
• the rotation angle sensor 32, thrust sensor 33, and current sensor 34 are connected to the electric brake ECU 31.
• the electric brake ECU 31 (and the first ECU 10 and second ECU 11 connected to this electric brake ECU 31 via CAN 12) can obtain the rotation angle of the electric motor 26 based on a signal from the rotation angle sensor 32.
• the electric brake ECU 31 (and the first ECU 10 and second ECU 11) can obtain the thrust generated in the piston 24 based on a signal from the thrust sensor 33.
• the electric brake ECU 31 (and the first ECU 10 and second ECU 11) can obtain the motor current supplied to the electric motor 26 based on a signal from the current sensor 34.
• the first ECU 10 and the second ECU 11 output a command corresponding to the depression of the brake pedal 7 (a control command corresponding to the target thrust command value) to the electric brake ECU 31 based on the detection signal input from the pedal stroke sensor 9.
• the electric brake ECU 31 drives (rotates) the electric motor 26 in the forward direction, i.e., in the direction of applying braking, based on the command from the first ECU 10 and the second ECU 11.
• the rotation of the electric motor 26 is transmitted to the rotary-to-linear motion conversion mechanism 28 via the reduction mechanism 27, and the piston 24 moves forward toward the brake pad 25.
• the brake pads 25 are pressed against the disc rotor D, applying a braking force.
• the drive of the electric motor 26 is controlled by detection signals from the pedal stroke sensor 9, the rotation angle sensor 32, the thrust sensor 33, etc., and a braking state is established.
• a force in the brake release direction is applied to the rotating member 28A of the rotary-linear motion conversion mechanism 28, and ultimately to the rotating shaft 26A of the electric motor 26, by the return spring 29 provided in the braking mechanism 21.
• the first ECU 10 and the second ECU 11 output a command corresponding to this operation (a control command corresponding to the target thrust command value) to the electric brake ECU 31.
• the electric brake ECU 31 drives (rotates) the electric motor 26 in the reverse direction, i.e., in the direction of releasing the brake, based on the command from the first ECU 10 and the second ECU 11.
• the rotation of the electric motor 26 is transmitted to the rotary-linear conversion mechanism 28 via the reduction mechanism 27, and the piston 24 retreats in a direction away from the brake pad 25.
• the brake pedal 7 is completely released, the brake pad 25 moves away from the disc rotor D, and the braking force is released.
• the return spring 29 provided in the braking mechanism 21 returns to its initial state.
• the first ECU 10 and the second ECU 11 determine the braking force to be generated by the electric brake devices 5, 6, i.e., the target thrust to be generated by the piston 24, based on detection data from various sensors (e.g., pedal stroke sensor 9), automatic brake commands, etc.
• the first ECU 10 and the second ECU 11 output braking commands (control commands) according to the target thrust to the electric brake ECU 31.
• the electric brake ECU 31 performs thrust control on the electric motor 26 by feeding back the piston thrust detected by the thrust sensor 33, and position control by feeding back the motor rotation position detected by the rotation angle sensor 32, so that the piston 24 generates the target thrust.
• the braking mechanism 21 adjusts the thrust of the piston 24 based on the braking command (target thrust) from the first ECU 10 and the second ECU 11 and a feedback signal from a thrust sensor 33 that measures the thrust of the piston 24.
• torque control of the electric motor 26 is performed via the rotary-linear conversion mechanism 28 and the reduction mechanism 27, i.e., current control is performed based on a feedback signal from a current sensor 34 that measures the amount of current flowing to the electric motor 26.
• a current sensor 34 that measures the amount of current flowing to the electric motor 26.
• the braking force (braking force) by the electric brake devices 5, 6 is generated by pressing the brake pads 25 against the disc rotor D.
• the driver's braking request is detected by the pedal stroke sensor 9.
• the driver's braking request detected by the pedal stroke sensor 9 is input to the electric brake ECU 31 (ECU board 31B) as a braking command from the first ECU 10 and the second ECU 11.
• the electric brake ECU 31 (ECU board 31B) controls the electric motor 26 based on the braking command corresponding to the driver's request and a signal from the thrust sensor 33 (a signal corresponding to thrust).
• the torque generated by the electric motor 26 is amplified by the reduction mechanism 27 and converted into thrust by the rotary-linear conversion mechanism 28, i.e., thrust in the axial direction of the piston 24, and the brake pads 25 are pressed against the disc rotor D by the piston 24.
• the electric motor 26 is controlled by detecting the rotation angle of the rotating shaft 26A, which is the rotation angle of the electric motor 26, with a rotation angle sensor 32. That is, the electric motor 26 is controlled by detecting the change in the magnetic flux of the magnet 32A, which rotates together with the rotating shaft 26A, with a magnetic detection IC chip 32B, which serves as a magnet signal receiver. At this time, the amount of clearance between the brake pads 25 and the disc rotor D can be adjusted by controlling the position of the piston 24 using the rotation angle of the electric motor 26 detected by the rotation angle sensor 32.
• the stiffness of the braking member, the member being braked, and the actuator also needs to be accurately estimated depending on the specifications of the thrust sensor, or for control without using a thrust sensor (thrust sensorless control). That is, the contact position is necessary to accurately control the pad clearance, and the stiffness is necessary to accurately control the braking force (thrust) (more specifically, to accurately control the thrust without using a thrust sensor). For this reason, in order to control an electric brake device with high precision, it is necessary to accurately estimate the contact position and/or stiffness. However, if noise (pulsation) is introduced into the sensor value of the controlled object, the accuracy of estimating the contact position and the accuracy of estimating the stiffness decrease.
• the reference position is a position that is set back a predetermined value from the position where a predetermined motor current is reached so that a clearance is always present.
• the contact position and stiffness are estimated based on the braking characteristics (the relationship between the piston position or motor position and the piston thrust or motor current) in which the motor current at this reference position is offset to the zero point (0). This reduces the effects of low-frequency pulsation, and improves the accuracy of estimating the contact position and the stiffness. This reduces the variation in contact position and stiffness, and prevents the gap (clearance) between the braking member and the braked member from becoming too small or too large. As a result, the drag torque between the braking member and the braked member can be reduced, and responsiveness when applying braking force can be improved.
• Figure 6 shows the braking characteristics of the electric brake devices 5, 6, specifically, the braking characteristics represented by the "motor position” which is the rotational position of the electric motor 26 and the “motor current” which is the current value of the electric motor 26.
• the braking characteristics represented by the "motor position” which is the rotational position of the electric motor 26 and the “motor current” which is the current value of the electric motor 26.
• a total of 20 types of characteristics are shown, including four types of low-frequency pulsation and five types of stiffness.
• the position where the motor current suddenly increases corresponds to the position (contact position) where the braking member (brake pad 25) and the member to be braked (disc rotor D) come into contact. In the clearance area before the contact position, four types of low-frequency pulsation appear, and after the contact position, five types of stiffness appear overlapping.
• the "motor position” is detected, for example, by the rotation angle sensor 32, and the "motor current” is detected by the current sensor 34.
• the "motor position” is correlated with the "piston position", which is the axial position of the piston 24. Therefore, the “piston position” may be used as the braking characteristic instead of the "motor position”. In this case, the "piston position” may be detected or calculated from the “motor position”.
• a displacement sensor that detects the displacement of the piston 24 may be provided in the braking mechanism 21.
• the "motor current” is correlated with the "motor torque”, which is the torque of the electric motor 26, or the "piston thrust", which is the thrust of the piston 24. Therefore, the "motor torque” or “piston thrust” may be used as the braking characteristic instead of the "motor current”.
• the "motor torque” or “piston thrust” may be detected or calculated from the “motor current”.
• a torque sensor that detects the torque of the electric motor 26 (rotating shaft 26A) may be provided.
• the thrust sensor 33 When detecting the "piston thrust”, it can be detected by the thrust sensor 33.
• the motor current (motor torque, piston thrust) rises sharply as the brake pad 25 (braking member) comes into contact with the disc rotor D (braked member).
• the braking characteristics at this time i.e., the relationship between the "motor position (piston position)" and the “motor current (motor torque, piston thrust)", correspond to the rigidity of the brake pad 25, disc rotor D, and braking mechanism 21.
• the rigidity when the change (increase) in the motor current (motor torque, piston thrust) relative to the displacement (advance) of the motor position (piston position) is large, the rigidity is high, and when the change (increase) in the motor current (motor torque, piston thrust) relative to the displacement (advance) of the motor position (piston position) is small, the rigidity is low.
• Figure 7 shows part A in Figure 6 enlarged (e.g., enlarged by about 10 times) only in the vertical axis direction (up and down direction).
• the contact position where the motor current (motor torque, piston thrust) begins to rise sharply gradually advances due to wear of the brake pad 25 and disc rotor D, etc.
• contact positions P1, P2, P3 gradually move to the right in the order P1 ⁇ P2 ⁇ P3 as wear of the brake pad 25 and disc rotor D progresses.
• the rigidity of the brake pad 25, disc rotor D, and braking mechanism 21 varies not only due to wear and uneven wear of the brake pad 25 and disc rotor D, but also due to the temperature and efficiency of the actuator (braking mechanism 21, electric motor 26), etc.
• the motor current (thrust) varies by four times the amplitude of the pulsation even with the same stiffness, as shown in the "+low-frequency single-sided swing upper limit” characteristic and the "+low-frequency single-sided swing lower limit” characteristic in Figures 6 and 7. Therefore, if the contact position and/or stiffness is estimated based on this characteristic, the estimation results will also vary.
• FIG. 8 shows the braking characteristics before the process of FIG. 4 is performed as a comparative example.
• FIG. 9 shows the braking characteristics after the variation is improved by performing the process of FIG. 4 as an embodiment.
• the process shown in FIG. 4 is a process for offsetting (correcting) the braking characteristics from FIG. 8 to FIG. 9. As shown in FIG.
• the process shown in FIG. 4 offsets (corrects) the braking characteristics so that the motor current (motor torque, piston thrust) at point B becomes a reference (for example, zero). This makes it possible to obtain the offset (corrected) braking characteristic (corrected braking characteristic) shown in Figure 9 from the braking characteristic shown in Figure 8.
• the process shown in FIG. 4 is performed, for example, by the electric brake ECU 31 (control unit 31A).
• the electric brake ECU 31 can start the process in FIG. 4 based on, for example, a command (offset command) from the first ECU 10 or the second ECU 11. The specific timing for starting the process will be described later.
• a predetermined value S of the return amount (piston return amount S, motor return amount S) is determined (calculated) in advance.
• This determined predetermined value S is stored, for example, in the memory of the electric brake ECU 31.
• the predetermined value S is the return amount of the electric motor 26 (piston 24) used in the processing of S4 described below.
• the predetermined value S can be stored in memory in advance (before the electric brake devices 5, 6 are started to be used), such as when the vehicle 1 is manufactured, and it is not necessary to perform the processing of S1 every time.
• the magnitude of the predetermined value S will be described later.
• a contact position estimation and stiffness estimation mode is started. In other words, a process of offsetting the braking characteristics is started.
• the process proceeds to S3, and the electric motor 26 is driven in the forward direction, i.e., in the direction in which the brake pad 25 abuts against the disc rotor D (the direction in which a braking force is applied).
• the piston 24 advances, the brake pad 25 comes into contact with the disc rotor D, and the motor current begins to increase as the brake pad 25 presses (clamps) the disc rotor D.
• Figure 11 shows two characteristics C1 and C2, that is, the characteristic C1 of "+ low-frequency single-sided swing upper limit side" and the characteristic C2 of "+ low-frequency single-sided swing lower limit side".
• the electric motor 26 is driven in the forward direction until the physical quantity (motor current, piston thrust, motor torque) corresponding to the magnitude of the braking force reaches a predetermined physical quantity T (predetermined current T, predetermined thrust T, predetermined torque T).
• a predetermined physical quantity T predetermined current T, predetermined thrust T, predetermined torque T.
• Point A in Figures 8 and 11 corresponds to the point where the predetermined current T, which becomes the predetermined physical quantity, is reached.
• the magnitude of the predetermined physical quantity T predetermined current T, predetermined thrust T, predetermined torque T
• the motor current is returned in the X-axis direction by a predetermined value S from the position where the motor current (piston thrust, motor torque) reaches the predetermined current T (predetermined thrust T, predetermined torque T).
• the electric motor 26 is stopped at a position corresponding to point A, and from this position, the electric motor 26 is driven in the reverse direction, that is, in the direction in which the brake pad 25 moves away from the disc rotor D (the direction in which the application of the braking force is released), thereby returning to a position corresponding to point B.
• the motor current priston thrust, motor torque
• predetermined current T predetermined thrust T, predetermined torque T
• the motor current (piston thrust, motor torque) at point B is offset to a reference value (e.g., zero). That is, as shown by the arrows in Figures 8 and 11, the motor current (piston thrust, motor torque) at point B is offset to zero. In other words, if the value in the Y-axis direction (motor current, piston thrust, motor torque) at point B is yb, then yb is set to 0.
• the electric motor 26 is driven in the forward direction again, and the contact position and rigidity are estimated based on the characteristics at that time (i.e., the braking characteristics in Figure 9, and the characteristics C1, C2 after offset in Figure 11).
• the predetermined value S is set to be equal to or greater than the maximum displacement amount until the predetermined physical quantity T is reached, which is assumed to include wear of the brake pad 25, uneven wear, inclination of the disc rotor D, temperature, efficiency of the braking mechanism 21, pulsation, etc. That is, the predetermined value S can be calculated based on the largest displacement amount (motor displacement amount, piston displacement amount) until the physical quantity (motor current, piston thrust, motor torque) corresponding to the magnitude of the braking force reaches the predetermined physical quantity T (predetermined current T, predetermined thrust T, predetermined torque T).
• the predetermined physical quantity T is set to a value greater than the maximum amplitude of the pulsation of the detected value of the physical quantity caused by the actuator (braking mechanism 21, electric motor 26), including pulsation, or a value greater than twice the maximum amplitude if the pulsation is one-way. That is, the predetermined physical quantity T (predetermined current T, predetermined thrust T, predetermined torque T) can be set to a value greater than the maximum amplitude of the pulsation of the detected value of the physical quantity (motor current, piston thrust, motor torque) caused by the actuator (braking mechanism 21, electric motor 26).
• the predetermined physical quantity T may also be changed depending on the temperatures of the actuator (brake mechanism 21, electric motor 26), brake pad 25, disc rotor D, etc.
• the clearance between the brake pad 25 and disc rotor D can be made equal to or greater than 0, and the variation in the physical quantities (motor current, piston thrust, motor torque) corresponding to the magnitude of the braking force at the contact position can be minimized.
• the processing from S4 onward in FIG. 4 may be performed in the memory of the electric brake ECU 31.
• the electric motor 26 continues to drive even after the predetermined current T, which is the predetermined physical quantity, is reached.
• the characteristics stored in the memory at this time that is, the relationship between the motor current (piston thrust, motor torque) and the motor position (piston position) are offset in the memory.
• the thick solid line characteristic C1 is obtained by driving the electric motor 26, the motor current (piston thrust, motor torque) at point B, which is a predetermined amount S back from point A, is offset to 0.
• the offset (corrected) thin solid line characteristic C1 can be obtained in the memory.
• the thick dashed line characteristic C2 is obtained by driving the electric motor 26, the motor current (piston thrust, motor torque) at point B, which is a predetermined amount S back from point A, is offset to 0.
• the offset (corrected) thin dashed line characteristic C2 can be obtained in the memory.
• the electric brake device 5, 6 includes an actuator and a contact position estimation unit.
• the actuator presses the brake pad 25, which is a braking member, toward the disc rotor D, which is a braked member, by driving the electric motor 26.
• the actuator corresponds to, for example, the braking mechanism 21 and the electric motor 26.
• the contact position estimation unit estimates the contact position between the brake pad 25 and the disc rotor D based on the braking characteristics.
• the contact position estimation unit corresponds to, for example, the electric brake ECU 31 (control unit 31A).
• the contact position estimation unit (control unit 31A) returns a predetermined value S from the actuator position (e.g., motor position, piston position) when a physical quantity (e.g., motor current, piston thrust, motor torque) corresponding to the magnitude of the braking force of the actuator (braking mechanism 21, electric motor 26) reaches a predetermined physical quantity T (e.g., predetermined current T, predetermined thrust T, predetermined torque T) due to contact between the brake pad 25 and the disc rotor D. Then, the contact position estimation unit (control unit 31A) estimates the contact position using the physical quantities (motor current, piston thrust, motor torque) at the position returned by the predetermined value S as a reference (e.g., zero).
• a reference e.g., zero
• the electric brake device 5, 6 is also provided with a stiffness estimation unit.
• the stiffness estimation unit estimates the stiffness of the brake pad 25, the disc rotor D, and the actuator (the brake mechanism 21, the electric motor 26) based on the braking characteristics.
• the stiffness estimation unit corresponds to, for example, the electric brake ECU 31 (control unit 31A).
• the stiffness estimation unit (control unit 31A) returns a predetermined value S from the actuator position (for example, the motor position, the piston position) when the physical quantity (for example, the motor current, the piston thrust, the motor torque) corresponding to the magnitude of the braking force of the actuator (the brake mechanism 21, the electric motor 26) reaches a predetermined physical quantity T (for example, a predetermined current T, a predetermined thrust T, a predetermined torque T) due to contact between the brake pad 25 and the disc rotor D. Then, the stiffness estimation unit (control unit 31A) estimates stiffness by using the physical quantity (the motor current, the piston thrust, the motor torque) at the position returned by the predetermined value S as a reference (for example, zero).
• a reference for example, zero
• the specified physical quantity T (e.g., specified current T, specified thrust T, specified torque T) is set to a value greater than the maximum amplitude of the pulsation of the detected value of the physical quantity (e.g., motor current, piston thrust, motor torque) caused by the actuator (brake mechanism 21, electric motor 26).
• the specified physical quantity T (specified current T, specified thrust T, specified torque T) is set to a value greater than the maximum amplitude of the "+ low frequency single swing upper limit side".
• the specified value S is calculated, for example, based on the largest displacement amount (motor displacement amount, piston displacement amount) before the physical quantity (motor current, piston thrust, motor torque) corresponding to the magnitude of the braking force reaches the specified physical quantity T (specified current T, specified thrust T, specified torque T).
• the predetermined value S can be the displacement amount (motor displacement amount, piston displacement amount) that allows the physical quantity (motor current, piston thrust, motor torque) to return to the clearance area from the position where the physical quantity (motor current, piston thrust, motor torque) reaches the predetermined physical quantity T (predetermined current T, predetermined thrust T, predetermined torque T) even when the low-frequency single-sided swing is at the "+low-frequency single-sided swing lower limit side.”
• the electric brake ECU 31 estimates the contact position and/or stiffness using as a reference (zero) the motor current at a position that is a predetermined value S back from the motor position when the motor current reaches the predetermined current T, as shown in Figures 8, 11, and 12.
• the electric brake ECU 31 (control unit 31A) may also estimate the contact position and/or stiffness using as a reference (zero) the piston thrust at a position that is a predetermined value S back from the piston position when the piston thrust reaches the predetermined thrust T.
• the electric brake ECU 31 may also estimate the contact position and/or stiffness using as a reference (zero) the motor torque at a position that is a predetermined value S back from the motor position when the motor torque reaches the predetermined torque T.
• the contact position and/or stiffness can be estimated based on the braking characteristics in which the motor current, piston thrust, or motor torque at the position returned by a predetermined value S is set to a reference (zero), i.e., based on braking characteristics in which the variation in the braking characteristics associated with low-frequency pulsation as shown in FIG. 9 is suppressed.
• a reference zero
• the gap (clearance) between the brake pad 25 and the disc rotor D can be prevented from becoming too small or too large.
• the drag torque between the brake pad 25 and the disc rotor D can be reduced, and the responsiveness when applying the braking force can be improved. Furthermore, since the variation in stiffness can be reduced, the braking force can be controlled with high precision, and fine vehicle control can be achieved.
• the specified current T is set to a value greater than the maximum amplitude of pulsation of the detected value of the motor current caused by the braking mechanism 21 (e.g., the maximum amplitude of the "+low frequency one-way swing upper limit side”).
• the specified thrust T is also set to a value greater than the maximum amplitude of pulsation of the detected value of the piston thrust caused by the braking mechanism 21 (e.g., the maximum amplitude of the "+low frequency one-way swing upper limit side").
• the specified torque T is also set to a value greater than the maximum amplitude of pulsation of the detected value of the motor torque caused by the braking mechanism 21 (e.g., the maximum amplitude of the "+low frequency one-way swing upper limit side"). This makes it possible to remove pulsation of the detected values of physical quantities (motor current, piston thrust, motor torque) caused by the braking mechanism 21.
• the predetermined value S is calculated based on the largest displacement (motor displacement, piston displacement) until the physical quantity (motor current, piston thrust, motor torque) corresponding to the magnitude of the braking force reaches the predetermined physical quantity T (predetermined current T, predetermined thrust T, predetermined torque T). Therefore, the position where the predetermined value S is returned can be set as the position (clearance area) where there is a clearance before the brake pad 25 and the disc rotor D come into contact.
• the thrust sensor 33 may be omitted. That is, the electric brake devices 5, 6 may be configured without the thrust sensor 33.
• the contact position, stiffness, and therefore the thrust can be estimated based on the braking characteristics between the motor position and the motor current. As shown in FIG. 9, the variation in the braking characteristics between the motor position and the motor current can be suppressed, so that the estimation accuracy of the contact position, stiffness, and therefore the thrust can be improved.
• the ideal timing for performing the process in FIG. 4 is, for example, when the vehicle 1 is stopped and not braking.
• the process in FIG. 4 can be performed when the vehicle 1 is started (when the start switch is turned on, when the engine is started).
• the process from S4 onward in FIG. 4 is performed on memory, it can be performed regardless of whether the vehicle 1 is stopped or not, and during normal braking.
• the process in FIG. 4 (the process of offsetting the braking characteristic standard) can be performed simultaneously on the electric brake devices 5 and 6 of the four wheels when the vehicle 1 is definitely stopped and braking force is not required, such as in pad replacement mode when replacing the brake pads 25.
• wheels that do not have a parking mechanism are parked when the parking brake is applied
• wheels that have a parking mechanism are parked when the vehicle can be stopped without the braking force of one of the wheels that has a parking mechanism.
• the predetermined value S always uses a preset value.
• the predetermined value S may be updated.
• the processes S1 to S6 in FIG. 5 are the same as the processes S1 to S6 in FIG. 4.
• the contact position is learned in advance. That is, in the process in FIG. 5, the contact position has already been learned (for example, the contact position has been estimated or detected at least once at the time of shipment). Then, when the contact position/rigidity estimation mode is started in S2, the electric motor 26 is driven in the forward direction (the direction in which the piston 24 advances) in S3.
• S12 following S3 it is determined whether or not a predetermined physical quantity T is reached while advancing by the predetermined value S from the contact position.
• the displacement until the predetermined physical amount T is reached is updated to a new predetermined value S in S13.
• the initial predetermined value S can be made smaller than the predetermined value S used in FIG. 4. This can further reduce the effects of low-frequency pulsation.
• the predetermined physical quantity T predetermined current T, predetermined thrust T, predetermined torque T
• the amount of displacement until the physical quantity reaches the predetermined physical quantity is set as the new predetermined value.
• This new predetermined value is stored in the memory of the electric brake ECU 31 as the updated predetermined value S.
• the initial value of the predetermined value S i.e., the predetermined value S of S1
• the predetermined value S can be updated to an appropriate value. This makes it possible to further reduce the effects of low-frequency pulsation.
• control unit 10A of the first ECU 10 controls the left front wheel electric brake device 5L and the right rear wheel electric brake device 6R
• control unit 11A of the second ECU 11 controls the right front wheel electric brake device 5R and the left rear wheel electric brake device 6L
• the control unit 10A of the first ECU 10 may control the right front wheel electric brake device 5R and the left rear wheel electric brake device 6L
• the control unit 11A of the second ECU 11 may control the left front wheel electric brake device 5L and the right rear wheel electric brake device 6R.
• the braking mechanism 21 has been described as a so-called floating caliper type disc brake in which the piston 24 is provided on the inner side of the caliper 23.
• the braking mechanism may be, for example, a so-called opposed piston type disc brake in which a piston is provided on each of the inner and outer sides of the caliper.
• the braking mechanism 21 is a disc brake.
• the braking mechanism may be, for example, a drum brake that presses a shoe (friction pad) against a drum rotor that rotates together with the wheel.
• the front wheels may have hydraulic brakes and the rear wheels may have electric brakes, or the front wheels may have electric brakes and the rear wheels may have hydraulic brakes.
• the vehicle braking control device has a first ECU 10, a second ECU 11, and an electric brake ECU 31.
• the first ECU 10 and the second ECU 11 may be configured as a single ECU, or the first ECU 10, the second ECU 11, and the electric brake ECU 31 may be configured as a single ECU.
• the contact position estimation unit and/or the stiffness estimation unit may be provided in the first ECU 10, the second ECU 11, the electric brake ECU 31, or another ECU. In other words, the contact position estimation unit and/or the stiffness estimation unit may be provided in any of the ECUs (control devices, control units) mounted on the vehicle.
• the contact position estimation unit estimates the contact position by returning a predetermined value from the actuator position when the physical amount corresponding to the magnitude of the braking force of the actuator reaches a predetermined physical amount due to contact between the braking member and the braked member, and using the physical amount at the position returned by the predetermined value as a reference. Therefore, the contact position can be estimated based on the braking characteristics that are adjusted to the physical amount at the position returned by the predetermined value as a reference, that is, braking characteristics in which the variation in the braking characteristics due to low-frequency pulsation is suppressed. This reduces the influence of low-frequency pulsation and improves the estimation accuracy of the contact position.
• the variation in the contact position can be reduced, and the gap (clearance) between the braking member and the braked member can be prevented from becoming too small or too large. Therefore, the drag torque between the braking member and the braked member can be reduced, and responsiveness when applying braking force can be improved.
• the stiffness estimation unit moves the actuator position back by a predetermined value from the position when the physical quantity corresponding to the magnitude of the braking force of the actuator reaches a predetermined physical quantity due to contact between the braking member and the braked member, and estimates stiffness using the physical quantity at the position moved back by the predetermined value as a reference. Therefore, stiffness can be estimated based on braking characteristics that are set to the physical quantity at the position moved back by the predetermined value as a reference, that is, braking characteristics in which the variation in braking characteristics due to low-frequency pulsation is suppressed. This reduces the effects of low-frequency pulsation and improves the accuracy of stiffness estimation. As a result, the variation in stiffness can be reduced and the braking force can be controlled with high precision, allowing fine vehicle control.
• the predetermined physical quantity is set to a value greater than the maximum amplitude of the pulsation of the detected value of the physical quantity caused by the actuator. Therefore, the pulsation of the detected value of the physical quantity caused by the actuator can be removed.
• the predetermined value is calculated based on the largest amount of displacement before the physical quantity reaches the predetermined physical quantity. Therefore, the position where the predetermined value is returned can be the position (clearance area) where there is a clearance before the braking member and the braked member come into contact.
• the amount of displacement until the physical quantity reaches the predetermined physical quantity is set as the new predetermined value. For this reason, the initial value of the predetermined value can be set small. Then, the predetermined value can be updated to an appropriate value. This makes it possible to further reduce the effects of low-frequency pulsation.
• the present invention is not limited to the above-described embodiments, but includes various modified examples.
• the above-described embodiments have been described in detail to clearly explain the present invention, and are not necessarily limited to those having all of the configurations described. It is also possible to replace part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. It is also possible to add, delete, or replace part of the configuration of each embodiment with other configurations.

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