Electric Brake Device

Abstract

To provide an electric brake device which has improved safety and brake feeling of an operator.SOLUTION: An electric brake device includes a brake rotor, a friction material, an electric motor, a linear motion mechanism for converting rotation motion of the electric motor into linear motion of the friction material, motor angle estimation means, brake force estimation means, and a control device for controlling the electric motor, wherein the control device has a position control part and a brake force control part, executes position control in a brake release state, executes brake force control in a brake state, and further has a control switching part for executing control of an angular velocity control part of operating the electric motor at predetermined angular velocity when a gap between the friction material and the brake rotor is determined to become larger than expected when it is shifted to the brake state from the brake release state.SELECTED DRAWING: Figure 1A

Description

[Technical field]

[0001] The present invention relates to an electric braking device. [Background technology]

[0002] Conventionally, the following techniques have been proposed for electric brake devices. (1) An electric actuator using a planetary roller screw structure (Patent Document 1). (2) An electric brake control device that applies position control and load control (Patent Document 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2006-194356 A [Patent Document 2] JP 2014-177205 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the electric brake device described in Patent Document 1, in which the rotational motion of a motor is converted into linear motion via a linear motion mechanism using a planetary roller screw structure by depressing the brake pedal, and a friction material (brake pad) is pressed into contact with a brake rotor (brake disc) to generate a braking force, for example, in order to prevent the driver of a vehicle equipped with an electric brake from feeling uncomfortable with the brakes, it is often required to finely control the pressing force between the brake rotor and the friction material as required by the driver. In particular, in the range of regular brakes with relatively small braking force that is frequently used when driving on general public roads, drivers tend to feel uncomfortable with the brakes, so there are cases in which particularly precise brake force control is required.

[0005] Furthermore, for example, when controlling the braking force of an electric brake device by using the stroke amount of a linear motion mechanism (corresponding to the amount of movement of the friction material) converted from the rotation angle of the motor to set a predetermined stroke amount relative to the amount of brake pedal operation (this type of control is also called position control), the friction material and brake rotor, etc., which expand due to brake friction heat generated when the brakes are applied to the vehicle, may be cooled and contracted due to heat released after the brakes are released, causing the gap between the friction material and the brake rotor to become larger than expected (occurrence of stroke amount error, error in the position of the friction material (motor angle)). In such a state, braking force is not generated at the brake pedal operation amount that should normally result in braking force, and there is a risk that the driver will feel an uncomfortable braking feeling.

[0006] Furthermore, Patent Document 2 discloses a method (or position control) for controlling an electric brake device by, for example, providing a brake force sensor for estimating the braking force, and performing brake force control (or load control) so that a predetermined brake force sensor output is obtained in response to the amount of brake pedal operation when the brakes are applied, and performing motor angle control so that a predetermined pad clearance (gap between the friction material and the brake rotor) is provided from the brake force sensor output and the motor rotation angle when the brakes are released.

[0007] However, if the above factors cause a state in which the pad clearance is larger than expected, a large overshoot in the braking force may occur when braking force control is executed because the electric motor accelerates more than expected before the braking force is actually generated (braking shock phenomenon), or the braking force is not generated for a while, resulting in a large response delay, or a combination of these phenomena may occur.Which of these phenomena occurs depends on the magnitude of the brake command value and the parameters of the brake controller, so it is difficult to adjust in advance, and since it is likely to occur mainly when a relatively small brake operation is performed, the driver may feel an uncomfortable braking feeling, or safety may be reduced due to unintended braking operation.

[0008] An object of the present invention is to provide an electric brake device which improves safety and braking feeling for the driver. [Means for solving the problem]

[0009] Generally speaking, the present invention is based on the following: when transitioning from a brake-released state (brake-released state) to a state in which a predetermined braking force is generated (brake state), a determination is made as to whether a pad clearance larger than expected is occurring based on the motor rotational angle (motor angle) and the estimated braking force (estimated braking force), and if said determination indicates that the pad clearance is larger than expected, motor angular velocity control is executed, and when said motor angular velocity control is executed, the magnitude of the angular velocity is changed based on a braking force command value.

[0010] In order to achieve the above object, an electric brake device according to the present invention comprises: An electric brake device comprising: a brake rotor; a friction material that generates a braking force by contacting the brake rotor; an electric motor; a linear motion mechanism that converts a rotational motion of the electric motor into a linear motion of the friction material; a motor angle estimation means that estimates a rotation angle of the electric motor; a braking force estimation means that estimates the braking force generated by the contact between the brake rotor and the friction material; and a control device that controls the electric motor, the control device includes a position control unit that controls a stroke position of the linear motion mechanism based on the motor angle estimated by the motor angle estimation means, and a braking force control unit that controls the braking force generated by contact between the brake rotor and the friction material based on the braking force estimated by the braking force estimation means, the control device controls the position control unit at least in a brake release state in which the friction material and the brake rotor are separated so as to generate a predetermined gap between them, and controls the braking force control unit at least in a brake state in which the friction material and the brake rotor are in contact with each other, Furthermore, the control device further has a control switching unit that executes control of an angular velocity control unit to operate the electric motor at a predetermined angular velocity when it is determined that the gap between the friction material and the brake rotor is larger than expected when transitioning from the brake release state to the brake state.

[0011] According to the above configuration, if the gap (pad clearance) when the brake is released is larger than expected, the motor is driven at a predetermined angular velocity until the brake is applied, thereby preventing the occurrence of a phenomenon in which braking force is not generated in response to a command to apply the brakes, or, conversely, the motor operating at too high a speed causing braking shock, thereby improving safety and braking feeling.

[0012] In the above configuration, the control switching unit When the brake release state is changed to the brake state, the stroke position of the linear motion mechanism is a position where the friction material and the brake rotor can come into contact with each other, and the estimated braking force is smaller than a predetermined value, When it is determined that the gap between the friction material and the brake rotor is larger than expected, control of an angular velocity control unit that operates the electric motor at a predetermined angular velocity may be executed.

[0013] In the above configuration, a brake command means for inputting a value corresponding to a target brake force to the control device, The angular velocity control unit may increase the target value of the angular velocity when a value corresponding to the target braking force by the brake command means increases in magnitude. This allows the angular velocity to be controlled to a relatively high speed so as to follow the target value more quickly when a relatively large target braking force is applied, and to be controlled to a relatively low speed when a relatively small target braking force is applied, thereby suppressing overshoot, thereby achieving both brake responsiveness (i.e. safety) and feeling.

[0014] In the above configuration, a brake command means for inputting a value corresponding to a target braking force and a brake release command to the control device, the angular velocity control unit includes a storage unit configured to store an amount of change in the target braking force within a predetermined time period after a state in which a brake release command is issued by the brake command means changes to a state in which a value corresponding to a target braking force is input, When the magnitude of the amount of change in the target braking force increases, the target value of the angular velocity in the angular velocity control unit may be increased. As a result, when the target braking force changes relatively rapidly, the angular velocity is controlled to a relatively high speed so as to follow the target value more quickly, and when the target braking force changes relatively slowly, the angular velocity is controlled to a relatively low speed to suppress overshoot, thereby achieving both brake responsiveness (i.e. safety) and feeling.

[0015] In the above configuration, The target value of the angular velocity in the angular velocity control unit may be increased based on a maximum value of the magnitude of the amount of change in the target braking force when the maximum value increases.

[0016] In the above configuration, A host device having a function of determining at least one of a situation in which a vehicle needs to be stopped suddenly and a situation in which a brake needs to be applied urgently, the higher-level device adds at least two levels of urgency representing a change from a normal state to an emergency state based on at least one or both of a proximity of the vehicle in which the electric brake device is mounted to a surrounding object and a vehicle behavior derived based on an acceleration of the vehicle in a predetermined direction, The control device may increase the target value of the angular velocity in the angular velocity control unit as the degree of urgency of the signal indicates a more urgent state than a normal state. As a result, when a brake command is applied due to a function related to vehicle safety, such as a collision mitigation brake or anti-skid function, the motor is driven at a relatively high motor angular velocity, thereby improving safety.

[0017] In the above configuration, The control device may, when the control switching unit has selected control of the braking force control unit, sequentially update a stroke position of the linear motion mechanism that can result in a predetermined gap amount based on the estimated braking force, the estimated motor angle in that state, and the electric brake device stiffness that is set in advance. This makes it possible to realize a stroke position determination method that provides a predetermined gap amount. Effect of the Invention

[0018] According to the electric brake device of the present invention, it is possible to improve safety and the braking feeling for the driver. [Brief description of the drawings]

[0019] [Figure 1A] 1 is a schematic block diagram showing a configuration including an electric brake device according to an embodiment of the present invention. [Figure 1B] FIG. 2 is another schematic block diagram showing a configuration including the electric brake device. [Diagram 2] FIG. 2 is a schematic block diagram showing the electric brake device according to the embodiment of the present invention, which corresponds to a plurality of brake actuators. [Diagram 3] FIG. 2 is another schematic block diagram showing the electric brake device according to the present invention, which is used to accommodate a plurality of brake actuators. [Figure 4A] FIG. 2 is a schematic block diagram showing the internal configuration of a control device. [Figure 4B] FIG. 4 is another schematic block diagram showing the internal configuration of the control device. [Figure 4C] 4 is yet another schematic block diagram showing the internal configuration of the control device. FIG. [Figure 5A] FIG. 4 is a state transition diagram showing the operation of the electric brake device. [Figure 5B] FIG. 4 is another state transition diagram showing the operation of the electric brake device. [Figure 6] FIG. 4 is a waveform diagram showing an example of the operation of the electric brake device. [Figure 7] 5 is a waveform diagram showing an example of adjustment of a target angular velocity of the electric brake device. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] FIG. 1A shows the configuration of an electric brake device 1 including at least a control device (hereinafter also referred to as an electric brake control device) 100 that controls an electric motor 210, and an electric (brake) actuator 200 using a linear motion mechanism 240 that converts the rotational motion of the electric motor 210 into the linear motion of a friction material 220. The electric brake device 1 may further include a power supply device PW, a brake instruction means 300 such as a brake pedal, and a vehicle motion control device 400 described later. The brake pedal 300 outputs a single piece of information such as a pedal stroke amount. In this embodiment, the electric brake device 1 is described as an example of a braking device for a vehicle, but the configuration of this embodiment can also be applied as a brake device for stopping other devices such as an elevator device, a power generation device, and an energy storage device such as a flywheel.

[0021] <<Configuration of the brake actuator 200>> The brake actuator 200 is composed of a brake rotor 230 that rotates together with a wheel (not shown), a friction material 220 that generates a braking force by contacting the brake rotor 230, an electric motor 210, a linear motion mechanism 240, an angle sensor 250 that detects a motor angle (specifically, a rotation angle of the motor rotor), and a load sensor 260 that detects a brake load. If necessary, a reducer or the like that reduces the rotation speed of the electric motor 210 may be provided. The electric motor 210 is, for example, a permanent magnet synchronous motor, and it is considered preferable to configure the electric motor 210 in this manner because it is space-saving, highly efficient, and has high torque. The electric motor 210 may also be, for example, a DC motor using brushes, a reluctance motor without permanent magnets, or an induction motor. The electric motor 210 may be a radial gap motor having magnetic poles in the direction of the rotation diameter, or an axial gap motor having magnetic poles in the direction of the rotation axis.

[0022] The linear motion mechanism 240 is composed of various screw mechanisms such as a planetary roller screw and a ball screw, a ball ramp mechanism, and various mechanisms capable of converting the rotational motion of the electric motor 210 into the linear motion of the friction material 220. The angle sensor 250 is, for example, a resolver or a magnetic encoder, and it is considered preferable to use these because of their high accuracy and high reliability. Note that various sensors such as an optical encoder can also be used as the angle sensor 250. Alternatively, as another configuration, it is also possible to apply angle sensorless estimation without using the angle sensor 250, for example, in which the motor angle is estimated from the relationship between voltage and current in the electric brake control device 100 described later.

[0023] The load sensor 260 is a sensor that detects distortion or deformation corresponding to the load applied by the actuator 200, for example, and is considered to be preferable because it is inexpensive and highly accurate. Note that a pressure-sensitive medium such as a piezoelectric element may also be used for the load sensor 260. Alternatively, the load sensor 260 may be a torque sensor that detects the braking torque of a brake rotor, or, in the case of an electric brake device for a vehicle, an acceleration sensor that detects the longitudinal deceleration of the vehicle.

[0024] Brake actuator 200 may be provided with various sensors, such as a temperature sensor such as a thermistor, as other elements not shown in the drawings, depending on requirements. Also, a mechanism for locking the operating part (power transmission part) of the actuator using a solenoid, DC motor, or the like may be provided to make the actuator have a parking brake.

[0025] <<Configuration of the electric brake control device 100>> The electric brake control device 100 is composed of, for example, a brake controller BC that calculates and controls the brake operation, a motion state estimator ME that calculates and estimates the operating state of the motor, a braking force estimator 170 that estimates the braking force from the output of a load sensor 260 etc. and outputs the estimated braking force, a motor controller MC that controls the motor current to obtain a predetermined motor output, a motor driver MD that supplies power to the motor, and a current sensor CS that detects the motor current.

[0026] The motion state estimator ME includes an angle estimator (motor angle estimator) 150 that receives the output of the angle sensor 250 and estimates at least the rotation angle of the rotor of the electric motor 210 (calculates an estimated motor angle), and an angular velocity estimator 160 that estimates the rotation angular velocity of the rotor (calculates an estimated angular velocity). Alternatively, the motion state estimator ME may be provided with a function for estimating a predetermined differential integral value such as the angular acceleration of the electric motor 210, and a function for estimating disturbances. The motion state estimator ME also has a function for appropriately determining a required physical quantity based on a control configuration such as an electrical angle phase used for current control and a total rotation angle corrected for overlap and underlap of an angle sensor used for angle control. In addition, the angle (rotation angle) and angular velocity (rotation angular velocity) of the electric motor 210 may be, instead of the rotor of the electric motor 210, an angle of a predetermined part of the reducer determined based on a reduction ratio when the electric motor 210 has a reducer, or a position and velocity determined based on an equivalent lead of a screw mechanism. The estimation of the physical quantity may be performed using a configuration such as a state estimation observer, or may be performed by direct calculation such as inverse calculation based on differentiation or an inertia equation.

[0027] The current sensor CS may be, for example, a sensor including an amplifier that detects and amplifies the voltage across a shunt resistor provided in the current path, or a non-contact sensor that detects magnetic flux around the current path. Alternatively, the current sensor CS may be configured to detect the voltage between terminals of elements that configure the motor driver MD. The current sensor CS may be provided between phases of the electric motor 210, or one or more current sensors may be provided on the low potential side or high potential side. Alternatively, feedforward control may be performed based on motor characteristics such as inductance and resistance without providing a current sensor.

[0028] The brake controller BC has a function of receiving inputs such as an estimated braking force and an estimated motor angle, calculating an operation amount for the brake actuator 200 to perform a desired follow-up operation in response to a predetermined command input (command signal) from the brake pedal 300, the vehicle motion control device 400, etc., and converting it into a motor drive signal. The brake controller BC mainly includes a position control unit 110 that controls the moving position (stroke position or stroke amount) of a so-called rod, which is a component that performs linear motion of the linear motion mechanism 240, a braking force control unit 120 for controlling the braking force generated by the contact between the friction material 220 and the brake rotor 230, an angular velocity control unit 130 for controlling the movement of the friction material 220 according to a predetermined motor angular velocity, and a control switching unit 140 for switching between them.

[0029] The position control unit 110 has a function of determining the motor drive amount so as to control the stroke amount of the linear motion mechanism 240 converted from the motor rotation amount or the motor angle based on various specifications of the brake actuator 200, such as the equivalent lead when a screw mechanism is used, the reduction ratio when a reducer is provided, etc. Note that the function may be a function of providing a stroke sensor or the like (not shown) separately and feedback-controlling the signal from the sensor to a predetermined target value. The position control unit 110 exerts its function when the stroke amount is set to a value that allows a predetermined gap to exist between the friction material 220 and the brake rotor 230 so that they do not come into contact with each other as much as possible when the brake is released (brake release state). The stroke amount that allows the predetermined gap to exist can be set, for example, as a position where the motor is rotated by a predetermined amount from the motor angle that results in a predetermined estimated braking force, or a position where the motor is rotated by a predetermined amount after the estimated braking force stops changing with respect to the transition of the motor angle (or after the change amount becomes small). In addition, the position control unit 110 may function to set the gap between the friction material 220 and the brake rotor 230 to a stroke state close to zero or a negative value less than zero (in terms of calculation and control) in order to control extremely slight braking forces that may be difficult to detect using a load sensor 260 or a torque sensor that detects braking forces.

[0030] The braking force control unit 120 has a function of determining a motor drive amount (an amount for driving the motor, such as a motor angle) in order to control the braking force in a braking state in which the friction material 220 and the brake rotor 230 are in contact with each other so as to follow a desired target value. In the figure, the pressing force between the friction material 220 and the brake rotor 230 is detected by a load sensor 260, and an example is shown in which the braking force control unit 120 functions based on a fixed braking force estimated by a braking force estimator 170 from the output of the load sensor 260, but the braking force can also be controlled using a torque sensor or the like that detects the braking torque of the brake rotor 230.

[0031] The angular velocity control unit 130 has a function of determining the motor drive amount so that the electric motor 210 operates according to a predetermined motor angular velocity to cause the linear motion mechanism 240 to perform a stroke operation (so that the stroke position shifts). When, for example, a desired braking force is generated from a brake release state to a brake state, and the gap between the friction material 220 and the brake rotor 230 is wider than expected, the angular velocity control unit 130 strokes the linear motion mechanism 240 at a predetermined motor angular velocity until the friction material 220 and the brake rotor 230 come into contact with each other. Note that, for example, when the stroke position of the linear motion mechanism 240 is a position where the friction material 220 and the brake rotor 230 come into contact with each other and the estimated braking force is smaller than a predetermined value, it is determined that the gap between the friction material 220 and the brake rotor 230 is wider than expected. At this time, a trade-off occurs in that the faster the motor 210 is operated, the faster the brake response becomes, but an overshoot is more likely to occur because it takes time to decelerate the motor 210 after detecting the contact between the friction material 220 and the brake rotor 230. For this reason, it is desirable that the angular velocity control unit 130 be provided with a function for appropriately changing the target angular velocity depending on any of the conditions such as the brake operation and the state of the vehicle, taking the above trade-off into consideration.

[0032] The control switching unit 140 has a function of switching the control contents of the brake controller BC between the position control unit 110, the braking force control unit 120, and the angular velocity control unit 130, mainly depending on the above-mentioned conditions of the vehicle. For example, when transitioning from the brake release state to the brake state, the control switching unit 140 can perform control switching so that the position control unit 110 functions until the friction material 220 and the brake rotor 230 are in a position state where they can come into contact with each other, and if the estimated braking force is a value smaller than a predetermined value, such as zero or a minute value equivalent to zero, even if the friction material 220 is in a position state where it can come into contact with the brake rotor 230, the angular velocity control unit 130 functions because it is determined that the gap is wider than expected, and the braking force control unit 120 functions when it is determined that the friction material 220 has come into contact with the brake rotor 230 from the estimated braking force. In addition, when switching from a brake state to a brake release state, the control switching unit 140 can perform control switching so as to cause the braking force control unit 120 to function when it is determined from the estimated braking force that the friction material 220 is in contact with the brake rotor 230, and to cause the position control unit 110 to function so as to provide a desired gap between the friction material 220 and the brake rotor 230 after it is determined from the estimated braking force that the friction material 220 has separated from the brake rotor 230.

[0033] The motor controller MC has a function of controlling the motor current so that the motor drive amount included in the motor drive signal obtained by the brake controller BC becomes the desired amount. The motor controller MC stores the optimum current conditions in advance in a look-up table (LUT) or the like to obtain a desired torque at a predetermined motor angular velocity, and determines a target current value from the current motor angular velocity to control the motor current to the desired current value, which is considered to be preferable because it can perform high-precision control at low cost. The motor controller MC can also have a function of calculating relational expressions of current and voltage that derive the motor output and determining the drive conditions in real time.

[0034] The motor driver MD is configured with a bridge circuit or the like using switching elements such as FETs (Field Effect Transistors) and is configured to perform PWM (Pulse Width Modulation) control that determines the motor application voltage by a predetermined duty ratio, which is considered to be preferable because it is inexpensive and has high performance. Alternatively, the motor driver MD can be provided with a transformer circuit or the like and configured to perform PAM (Pulse Amplitude Modulation) control.

[0035] <<Other>> For example, in an electric brake device for an automobile, the power supply device PW may be a low-voltage battery, a high-voltage battery and a step-down converter for stepping down the high-voltage battery, or a high-capacity capacitor, or may be used in parallel for redundancy. In addition, it is preferable that the power supply device PW directly supplies power to the motor driver and the solenoid driver described above as elements not shown in the figure, and a small step-down converter is applied to the computing unit in each control device. Alternatively, the power supply device PW may be configured to supply power via a step-up converter to either or both of the motor driver and the solenoid driver, and to supply power directly to the computing unit. As the brake command means, various operation means that can be operated by the driver, such as a volume, a joystick, or a switch, may be used instead of the brake pedal 300.

[0036] The vehicle motion control device 400 includes an automatic brake function unit 410 for preventing a vehicle collision or reducing the impact of a collision, a skid prevention function unit 420 for preventing at least a vehicle spin caused by braking when the vehicle is in a skid state, and an anti-skid control unit 430 for preventing the wheels from locking due to braking and making the vehicle behavior unstable. The vehicle motion control device 400 may be an integrated control device that integrates information from various on-board sensors such as a gravity sensor, an objective sensor, and a GPS (Global Positioning System) (not shown) and performs calculations required for each of the above functions. The brake operation amount determined by the vehicle motion control device 400 is also transmitted to the electric brake control device as a target brake force via the command signal.

[0037] The various calculation functions of the controller and the like in the electric brake control device 100 described above are preferably configured by a calculation unit or hardware, such as a microcomputer having a processor operated by a program, an ASIC (Application Specific Integrated Circuit), or an FPGA (Field Programmable Gate Array), because they are inexpensive and have high performance. In addition, the functional blocks shown in the figure are provided merely for convenience of description, and do not restrict the type of configuration by hardware or software, or the partition of functions, etc. In addition, the specific configuration of the software and hardware can be arbitrarily configured as long as it does not interfere with the functions shown in the figure, and the functions of each block shown in the figure may be integrated or divided as necessary. Alternatively, elements not shown in the figure can be added as long as it does not interfere with the functions shown in the figure, and it is preferable to appropriately add safety mechanisms in case of failure of various functions or sensors based on system requirements, for example.

[0038] Fig. 1B shows a configuration example in which a command signal from the brake pedal 300 is taken into the vehicle motion control device 400, and is sent to the electric brake control device 100 as an integrated target brake force together with the brake operation amount determined by the vehicle motion control device 400 in Fig. 1A, unlike Fig. 1A. While there is an advantage in that more integrated brake control can be executed compared to Fig. 1A, there is a disadvantage in that a safety mechanism is required in case a malfunction occurs in the vehicle motion control device 400. Note that a configuration in which the configurations in Fig. 1A and Fig. 1B are combined may also be used.

[0039] FIG. 2 shows a system configuration example including a plurality of electric brake devices 1 having the configuration of FIG. 1A, and the target brake force by the vehicle motion control device 400 is transmitted independently and individually to each of the four electric brake control devices 100A to 100D. In this configuration, the brake pedal outputs a single command information such as a pedal stroke amount, but the command information is transmitted independently and individually to each of the four electric brake control devices 100A to 100D. Note that, as is done for the front and rear brakes of current four-wheeled automobiles, the brake forces actually generated for the same brake stroke amount can be different for the front and rear electric brake control devices, or the front, rear, left and right electric brake control devices. Here, each of the electric brake control devices 100A to 100D corresponds one-to-one to each of the brake actuators 200A to 200D. The number of electric brake devices configured as a brake system is appropriately determined according to the requirements of the brake system. FIG. 3 shows an example of an electric brake control device configured in FIG. 2, in which a single electric brake control device controls a plurality of brake actuators. In the figure, a configuration example is shown in which two brake actuators 200A, 200B (200C, 200D) are controlled by one electric brake control device 100A (100B), but the number of brake actuators connected to one electric brake control device can be appropriately determined according to system requirements. Note that the configurations in Figures 2 and 3 may be used together.

[0040] <<Example of brake controller configuration>> Fig. 4A shows a further configuration example within the brake controller BC of Fig. 1A (Fig. 1B). The stroke command calculation function unit 111, the position controller 113, and the stroke reference compensation function unit 115 correspond to the position control unit 110. The angular velocity command calculation function unit 131 and the angular velocity controller 133 correspond to the angular velocity control unit 130. The braking force command calculation function unit 121 and the braking force controller 123 correspond to the braking force control unit 120. The control switching function unit 141 and the controller reset function unit 143 correspond to the control switching unit 140.

[0041] The brake force command calculation function unit 121 has a function of converting a brake command value, which is a command related to the brake force such as the brake operation amount (command signal in FIG. 1A and FIG. 1B), into a brake force or a value equivalent to the brake force, which is a physical quantity to be actually controlled, to generate a brake force control target value. The brake command value is, for example, a stroke amount of a brake pedal, a brake torque, a vehicle deceleration, a master cylinder hydraulic pressure assumed value, which is a conversion value in a conventional hydraulic brake, a brake load, etc., and the brake force control target value is, for example, a brake load, a brake torque, a vehicle deceleration, etc. A designer appropriately determines which parameters are used for the brake command value and the brake force control target value. In addition, the brake force command calculation function unit 121 may be provided with a function of performing, for example, a filtering process for suppressing the influence of noise, etc., and a limit process for removing a command value that causes an actuator to be in a state where it cannot operate. The brake force controller 123 has a function of feedback-controlling a predetermined estimated physical quantity corresponding to the brake force control target value with respect to the target value.

[0042] The angular velocity command calculation function unit 131 has a function of converting a response speed command value, which is a command related to the operating speed of the electric brake device 1, into a motor angular velocity or a value equivalent to the motor angular velocity, which is a physical quantity to be actually controlled, to generate an angular velocity control target value. The response speed command value may be the same value as the change speed of the stroke of the linear actuator or the brake command value, or may be configured to directly command the motor angular velocity or the like. Alternatively, the response speed command value may be a signal indicating the degree of urgency based on a predetermined protocol from a higher-level device HD (such as an ECU [Electronic Control Unit] or a VCU [Vehicle Control Unit]) that has a function of determining, for example, a situation in which the vehicle needs to be stopped suddenly or a situation in which the brake needs to be operated urgently. The angular velocity control target value is, for example, the motor angular velocity, the linear actuator stroke speed derived from an equivalent lead, or the like.

[0043] When the same value as the brake command value is applied to the response speed command value, a process may be performed to increase the angular velocity control target value when the brake command value (value corresponding to the target brake force) becomes large. For example, when a relatively large brake command value is input, such as when a vehicle driver strongly depresses the brake pedal 300, it is considered that a relatively high-speed brake operation is often required to improve safety, and if the brake command value is relatively large, it is easy to decelerate the motor from when the friction material 220 and the brake rotor 230 (FIG. 1A) come into contact with each other until the target brake force is generated, making it difficult for overshoot to occur. Therefore, it is considered reasonable to increase the angular velocity control target value when the brake command value becomes large, as described above.

[0044] In addition, when the same value as the brake command value is applied to this response speed command value, the change amount (or the maximum value of this change amount) of the brake command value within a predetermined time after the brake command value changes from a state in which the brake command value is a command value instructing brake release to a state in which the brake command value is a command value for exerting a predetermined brake force (a value corresponding to a target brake force) may be stored in a predetermined storage unit ST (FIG. 1A), and a process of increasing the target value in the angular velocity control may be performed when the change amount increases. Note that, based on the maximum value of the magnitude of the change amount of the brake command value (target brake force), the target angular velocity during the angular velocity control may be increased when the maximum value increases. For example, in general, when the brake command value changes relatively abruptly, such as when a vehicle driver suddenly depresses the brake pedal, it is considered that a relatively high-speed brake operation is often required to improve safety, and further, when the brake command value changes abruptly, it is considered that a sense of incongruity is unlikely to be felt even if an overshoot occurs in the response of the brake force. Therefore, it is considered reasonable to increase the angular velocity control target value when the brake command value changes abruptly as described above. For example, when a vehicle driver suddenly depresses brake pedal 300 (FIG. 1A), the pedal stroke amount changes abruptly at the beginning of brake pedal operation and then changes more slowly. Therefore, it is considered preferable to store the maximum value of the magnitude of the change in the brake command value within a predetermined time after the brake command value changes from a brake command value for releasing the brakes to a brake command value for exerting a braking force.

[0045] When a signal representing the urgency of the brake operation is applied to the response speed command value, the angular velocity control target value may be increased as the urgency of the signal represents a more urgent state. For example, in a vehicle equipped with this electric brake device, when the object distance (proximity) from the vehicle is rapidly reduced, when the vehicle exhibits unintended vehicle behavior such as skidding, or when these occur in combination, it is possible to determine multiple levels of urgency for operating the brake based on these factors, and since safety takes top priority in these high urgency states, it is considered reasonable to increase the angular velocity control target value as the urgency becomes more urgent, as described above. The angular velocity controller 133 has a function of feedback-controlling a predetermined estimated physical quantity corresponding to the angular velocity control target value with respect to the target value.

[0046] The stroke command calculation function unit 111 has a function of converting an air gap command value, which is a command related to the air gap between the friction material 220 and the brake rotor 230 (FIG. 1A) when the brake is released, into a motor angle or a value equivalent to the motor angle, which is a physical quantity to be actually controlled, to generate a position control target value. The air gap command value can be a desired air gap amount between the friction material 220 and the brake rotor 230 when the brake is released. The position control target value can be a motor angle that can be the air gap amount calculated from the correlation between the rotation amount and the linear amount depending on, for example, the equivalent lead of the linear actuator or the reduction ratio of the reducer, and may be a value based on the air gap command value when the brake is released and zero when the brake force is generated. Alternatively, the position control target value may be the air gap amount itself, in which case the linear position is calculated from the motor angle as a feedback parameter in the position control controller 113 described later. 4A does not refer to an angle (e.g., electrical angle 0 to 360 degrees) that periodically overlaps / underlaps depending on the mechanical angle or electrical angle of the motor rotor, but refers to a total amount of rotation that is an accumulation of how much the motor has rotated in total. The position controller has a function of feedback-controlling a predetermined estimated physical quantity corresponding to the position control target value against the target value.

[0047] The stroke reference compensation function unit 115 has a function of compensating for an error in the reference position when deriving a position where a predetermined gap amount can be obtained. The reference position may have an error from a previously recognized (or assumed) actuator reference position during operation, for example, when the friction material 220 or the brake rotor 230 is heated due to frictional heat, when the friction material 220 or the like is worn, when a power transmission structure with a predetermined slip such as a pulley belt or a traction drive structure is provided for power transmission of the linear actuator, or when an induction motor is applied to the electric motor 210 (FIG. 1A). Therefore, the stroke reference compensation function unit 115 calculates a predetermined compensation value that compensates for the error in the reference position by comparing an estimated brake force with a motor angle when the electric brake device is generating a brake force.

[0048] The compensation value may be, for example, a reference motor angle set based on a preset stiffness of the electric brake device and a brake force and a motor angle under a predetermined sampling condition. Alternatively, the compensation value may be a reference motor angle set based on the stiffness and a change in the brake force and a change in the motor angle in a predetermined sampling section. The reference motor angle may be set as a position where the friction material 220 and the brake rotor 230 start to come into contact with each other, where the brake force becomes exactly zero. Alternatively, the reference motor angle may be set as a position where a non-zero brake force can be exerted as the motor angle. The stiffness of the electric brake device may be updated sequentially using information on the brake force and the motor angle when the electric brake device 1 is operated, with respect to a preset initial stiffness.

[0049] The control switching function unit 141 has a function of determining and outputting the driving force (electric motor driving force) of the electric motor 210 from the operation amounts derived by the braking force controller 123, the angular velocity controller 133, and the position controller 113 (or a function of selecting at least one of the controls or outputs of these three controllers). The electric motor driving force output from the control switching function unit 141 may be, for example, a motor torque command value as shown in the figure, or may be a motor current, a motor voltage, or the like. Which of these is used for the electric motor driving force depends on the control design and is appropriately determined by the designer. In addition, the electric motor driving force may adopt the derived result (operation amount) of any one of the above controllers, or may be an integration (weighted average) of multiple operation amounts of each controller at a predetermined integration ratio. Furthermore, the control switching function unit 141 performs control switching based on the above-mentioned various command values ​​and feedback values, etc., so as to mainly use the operation amount of the position controller 113 when releasing the brake, mainly use the operation amount of the braking force controller 123 when generating braking force, and mainly use the operation amount of the angular velocity controller 133 in at least a part of the case where the linear motion mechanism is stroked from the brake release state until the braking force is generated.

[0050] The controller reset function unit 143 has a function of appropriately resetting the internal calculation parameters of each controller for the purpose of improving the stability of the control operation when switching between the controllers and preventing overflow of the calculation parameters. For example, when the controller switching operation is performed, an appropriate calculation initial value can be set for the controller executed immediately after the switching, so that unnecessary motor driving is not performed at the time of switching. Specifically, for example, in switching from one controller to another controller, or in a predetermined calculation cycle (cycle k) in which the change in the integration ratio of the manipulated variable is determined, an initial value may be set for the state quantity of the controller so that u'(k)≒u(k) for the manipulated variable u(k) by the controller before switching from the manipulated variable u(k) by the controller after switching. Note that this is merely an example, and the type of reset operation to be performed is determined appropriately according to the requirements at the time of design, etc.

[0051] As for the controller reset function unit 143, for example, when a comparatively large compensation value is determined by the stroke reference compensation function unit 115 and an overflow or underflow of a variable may occur in the subsequent calculation process, it is preferable to reset the compensation value of the stroke reference compensation function unit 115 once and also reset the calculation values ​​of other related controllers so that the motor is not driven unintentionally due to the resetting of the compensation value. Specifically, for example, in a certain calculation cycle k, the position control target value θr(k) and the stroke compensation value θz(k) are set as target values, and based on the current motor angle θ(k), the operation amount up(k) is calculated according to the control calculation formula fcp as follows: up(k) = fcp(θr(k) + θz(k), θ(k) ) In the situation obtained by the above, the operation amount up'(k) when resetting θz(k) = 0 is expressed by the following formula: up'(k) = fcp(θr(k), θ'(k) ) ≒ up(k) However, this is merely an example, and the type of reset operation is to be determined as appropriate according to the requirements at the time of design.

[0052] FIG. 4B shows an example in which the same function as that in FIG. 4A is realized by a different configuration. The contents described with reference to FIG. 4A may be omitted below. The angular velocity command calculation function unit 131 and the target position addition function unit 135 not shown in FIG. 4A correspond to the angular velocity control unit 130 in FIG. 1A. The stroke command calculation function unit 111 and the stroke reference compensation function unit 115 correspond to the position control unit 110 in FIG. 1A. The braking force command calculation function unit 121 and the braking force compensation function unit 125 not shown in FIG. 4A correspond to the braking force control unit 120 in FIG. 1A. The position controller 113A is a controller having functions shared by all of the position control unit 110, the angular velocity control unit 130, and the braking force control unit 120. The control switching function unit 141 and the controller reset function unit 143 correspond to the control switching unit 140 in FIG. 1A.

[0053] The braking force command calculation function unit 121 has a function of calculating a motor angle at which a braking force corresponding to a braking command value can be generated as a position control target value (braking generation position). The motor angle is found based on the stiffness of the electric brake device. The braking force compensation function unit 125 has a function of calculating a position control compensation value that results in a desired braking force from the estimated braking force, motor angle, and electric brake device stiffness, while also taking into account, for example, the correlation between the stroke position and the braking force. In other words, this function can be said to compensate for the error between the actual electric brake device stiffness and an internal estimated value thereof, which occurs due to the temperature of the electric brake device, the wear state of the friction material and the brake rotor, and the like.

[0054] Target position addition function unit 135 judges whether or not to execute angular velocity control by referring to the angular velocity control execution signal from control switching function unit 141, and if it is to be executed, calculates an increase in the position control target value per predetermined unit time according to the angular velocity control target value from angular velocity command calculation function unit 131. This angular velocity control is equivalently realized by changing the target position in a ramp shape. In other words, the angular velocity is constant, and the amount of change in the target position is constant.

[0055] When releasing the brake, the control switching function unit 141 adopts a position control target value which is the gap position derived by the stroke command calculation function unit 111. When generating braking force, the control switching function unit 141 adopts a position control target value which generates braking force derived by the braking force command calculation function unit 121, and outputs a braking force control execution signal to the braking force compensation function unit 125 to execute braking force control. When executing the angular velocity control, the control switching function unit 141 outputs the angular velocity control execution signal to the target position addition function unit 135 to execute angular velocity control.

[0056] In addition, the action of the controller reset function on the braking force compensation function and the target position addition function is the same as the action on the stroke reference compensation function unit 115.

[0057] FIG. 4C shows an example in which compensation values ​​by the stroke reference compensation function unit 115, the braking force compensation function unit 125, and the additive stroke compensation function unit 137 (not shown in FIG. 4B) are applied to the motor angle fed back instead of the position control target value. The additive stroke compensation function unit 137 has a function similar to that of the target position addition function 135, and while the target position addition function 135 changes the target position in a ramp-like manner to perform angular velocity control equivalently, the additive stroke compensation function unit 137 adds a ramp-like compensation value to the motor angle fed back to perform angular velocity control equivalently. The configurations of FIG. 4B and FIG. 4C can be used together as necessary. For example, a part of the compensation values ​​by the stroke reference compensation function unit 115, the braking force compensation function unit 125, and the target position addition function unit 135 can be applied to the position control target value, and the other compensation values ​​excluding the part can be applied to the above-mentioned fed back motor angle. In this case, if the target position addition function 135 is not applied to the position control target value, the addition stroke calculation function 137 is applied to the fed back motor angle.

[0058] 5A is a state machine showing an example of state transition of the control state in the operation of the control switching unit 140 shown in FIG. 1A and the like, and FIG. 5B is a state machine different from FIG. 5A, which performs approximately the same control and transition operation. In state ST.0, the control state is a state in which the position control unit 110 in FIG. 1 is mainly executed (i.e., a state in which the control switching unit 140 selects the control of the control unit) (position control state), in state ST.1, the control state is a state in which the angular velocity control unit 130 in FIG. 1 is mainly executed (angular velocity control state), and in state ST.2, the control state is a state in which the braking force control unit 120 in FIG. 1 is executed (braking force control state). Note that each of the above states represents a case in which the control of each control unit is selectively executed, and also includes a case in which the operation amount resulting from executing a plurality of those controls is integrated at a predetermined integration ratio (weighted average). In the latter case, each state of the state machine indicates that the control ratio of that control unit is dominant in the weighted average calculation, i.e., the control ratio of position control unit 110 is dominant in state ST.0, the control ratio of angular velocity control unit 130 is dominant in state ST.1, and the control ratio of braking force control unit 120 is dominant in state ST.2. Note that an algorithm for further changing the above ratio may be provided in each state.

[0059] In FIG. 5A, at the first branch after power is turned on by an ignition switch or the like, if no braking force is generated, the state transitions to state ST.0, and if braking force is generated, the state transitions to state ST.2. In the position control state of state ST.0, when braking is requested, the gap is reduced and control is executed based on a position control target value at which the friction material 220 and the brake rotor 230 (FIG. 1A) come into contact with each other. The position control target value at this time can be a target value for making the gap zero, or a position control target value based on a negative gap (in terms of calculation and control) so that the linear motion mechanism 240 moves in a direction in which the friction material 220 comes into contact with the brake rotor 230. Here, if braking force is requested to be generated and the estimated gap is equal to or less than zero, but braking force is not generated, the state transitions to state ST.1 (angular velocity control state) in FIG. 5A, and if braking force is generated, the state transitions to state ST.2 (brake force control state). Note that even if braking force is requested to be generated and braking force is generated, the state transitions to state ST.2 (brake force control state).

[0060] In the angular velocity control state of state ST.1, the electric brake control device 100 is operated at a predetermined motor angular velocity in the direction in which the friction material 220 and the brake rotor 230 (FIG. 1A) come into contact with each other. If a braking force is generated in the angular velocity control state of state ST.1 of FIG. 5A, a transition is made to state ST.2 (brake force control state). In the braking force control state of state ST.2, when a request is made to release the brake, control is executed based on a braking force control target value that reduces the braking force and separates the friction material 220 and the brake rotor 230 (FIG. 1A). In this case, the braking force control target value may be a braking force target value that sets the braking force to zero, or a braking force control target value based on a negative braking force so that the linear motion mechanism 240 operates in a direction in which the friction material 220 separates from the brake rotor 230. Here, when a request is made to release the brake and no braking force is generated (i.e., the estimated value of the air gap is equal to or greater than zero), a transition is made to the position control state of state ST.0. The state in which braking force is generated / not generated includes not only a state in which the braking force is non-zero / zero, but also a state in which the estimated braking force is substantially non-zero / zero determined from, for example, the estimated braking force exceeding / falling below a predetermined threshold. Also, the estimated gap is the amount of gap estimated from the predetermined reference position and the current motor angle described in the explanation of Fig. 3A, and the estimated gap being zero or less includes a state in which the estimated gap is greater than zero but is so small that it may be considered that the gap has disappeared.

[0061] Regarding FIG. 5B, differences from FIG. 5A will be mainly described. In FIG. 5B, in the position control state of state ST.0, when a brake request occurs, the state transitions to state ST.2 (brake force control state). In the brake force control state of state ST.2, when no brake force is generated and the estimated gap is zero or less, the state transitions to state ST.1 (angular velocity control state). Note that, in the brake force control state of state ST.2, when a brake release is requested, the state transitions to state ST.0 (position control state). Note that the state machines of FIG. 5A and FIG. 5B can be combined within a range that does not contradict. For example, the condition for transitioning from state ST.2 to state ST.0 in FIG. 5B may be appropriately combined, such as a state in which a brake release request is made and no brake force is generated (i.e., the estimated gap value is zero or more) as in FIG. 5A.

[0062] Fig. 6 is a schematic diagram showing an example of the operation of the electric brake device when the actual friction material 220 and the brake rotor 230 (Fig. 1A) are farther apart than the assumed gap amount. Fig. 6(a) shows an example of the use of the electric brake device 1 of this embodiment. According to this figure, when a control target value (dashed line) for generating a braking force is applied and the brake actuator 200 operates, angular velocity control is executed after it is determined that the gap amount is larger than assumed, and the electric brake device is operated at a predetermined angular velocity, so that the braking force (estimated value) is controlled to follow the braking force target value at time t1 without a large response delay or overshoot (solid line).

[0063] FIG. 6(b) shows an example where the electric brake control device is adjusted so that no overshoot occurs in the braking force without using the electric brake device 1 of this embodiment. In this case, the amount of air gap is larger than expected, and the motor angular velocity is prevented from increasing sharply, so that a large response delay occurs in the braking operation at the above-mentioned time t1 (time t2: solid line), which may cause concerns about the feeling and safety. FIG. 6(c) shows an example where the electric brake control device is adjusted so that sufficient responsiveness can be exhibited without using the electric brake device 1 of this embodiment. In the case where the air gap is larger than expected and sufficient responsiveness is exhibited, the motor angular velocity increases more than expected, causing a large overshoot in the braking force (estimated value) generated at time t1 (solid line), which may cause concerns about the feeling and safety.

[0064] FIG. 7 shows an example of adjusting the target angular velocity in the angular velocity control unit 130 shown in FIG. 1A and the like. FIG. 7(a) shows an example of setting the target angular velocity to be large as the target braking force becomes large. The process of reaching the upper limit value at a target braking force F1 equal to or larger than a predetermined value shown in this figure may not be performed, and the upper limit value may be appropriately determined according to the motor characteristics and design requirements. Furthermore, this figure shows an example in which the target angular velocity changes linearly with respect to the target braking force, but it may change in stages. FIG. 7(b) shows an example in which the target angular velocity is set to be large as the change amount of the target braking force becomes large. FIG. 7(c) shows an example in which a plurality of levels of urgency of the braking operation are provided, and the target angular velocity is set for each level. The urgency of the braking operation can be determined, for example, from the object approach speed, object distance, degree of skid, etc. in a vehicle equipped with an electric brake device. In the figure, the target angular velocity is a discrete value, but as shown in Figures 7(a) and 7(b), the urgency level may be a linearly changing level (i.e., a continuous value) and the target angular velocity may be made to change linearly.

[0065] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0066] 1 Electric brake device 100 Electric brake control device (control device) 110 Position control section 120 Brake force control unit 130 Angular velocity control section 140 Control switching unit 150 Angle estimator (motor angle estimator) 170 Brake force estimator (Brake force estimation means) 210 Electric Motor 220 Friction material 230 Brake rotor 240 Linear motion mechanism 300 Brake pedal (brake command means) HD ECU (upper device) ST memory

Claims

1. An electric brake device comprising: a brake rotor; a friction material that generates a braking force by contacting the brake rotor; an electric motor; a linear motion mechanism that converts a rotational motion of the electric motor into a linear motion of the friction material; a motor angle estimation means that estimates a rotation angle of the electric motor; a braking force estimation means that estimates the braking force generated by the contact between the brake rotor and the friction material; and a control device that controls the electric motor, the control device includes a position control unit that controls a stroke position of the linear motion mechanism based on the motor angle estimated by the motor angle estimation means, and a braking force control unit that controls the braking force generated by contact between the brake rotor and the friction material based on the braking force estimated by the braking force estimation means, the control device controls the position control unit at least in a brake release state in which the friction material and the brake rotor are separated so as to generate a predetermined gap between them, and controls the braking force control unit at least in a brake state in which the friction material and the brake rotor are in contact with each other, Furthermore, the control device further includes a control switching unit that executes control of an angular velocity control unit that operates the electric motor at a predetermined angular velocity when it is determined that the gap between the friction material and the brake rotor is larger than expected when transitioning from the brake release state to the brake state. Electric brake device.

2. 2. The electric brake device according to claim 1, The control switching unit is When the brake release state is changed to the brake state, the stroke position of the linear motion mechanism is a position where the friction material and the brake rotor can contact each other, and the estimated braking force is smaller than a predetermined value, When it is determined that the gap between the friction material and the brake rotor is larger than expected, the electric motor is operated at a predetermined angular velocity by controlling an angular velocity control unit. Electric brake device.

3. 3. The electric brake device according to claim 1, a brake command means for inputting a value corresponding to a target brake force to the control device, the angular velocity control unit increases the target value of the angular velocity when a magnitude of a value corresponding to the target braking force by the brake command means increases. Electric brake device.

4. 3. The electric brake device according to claim 1, a brake command means for inputting a value corresponding to a target braking force and a brake release command to the control device, the angular velocity control unit includes a storage unit configured to store an amount of change in the target braking force within a predetermined time period after a state in which a brake release command is issued by the brake command means changes to a state in which a value corresponding to a target braking force is input, When the magnitude of the change amount of the target braking force increases, the target value of the angular velocity in the angular velocity control unit is increased. Electric brake device.

5. 5. The electric brake device according to claim 4, a target value of the angular velocity in the angular velocity control unit is increased when the maximum value of the magnitude of the change amount of the target braking force is increased based on the maximum value of the magnitude of the change amount of the target braking force. Electric brake device.

6. 3. The electric brake device according to claim 1, A host device having a function of determining at least one of a situation in which a vehicle needs to be stopped suddenly and a situation in which a brake needs to be applied urgently, the higher-level device adds, as information, at least two or more levels of urgency representing a change from a normal state to an emergency state, based on at least one or both of a proximity of the vehicle on which the electric brake device is mounted to a surrounding object and a vehicle behavior derived based on an acceleration of the vehicle in a predetermined direction; the control device increases the target value of the angular velocity in the angular velocity control unit as the degree of urgency becomes more urgent than a normal state; Electric brake device.

7. The electric brake device according to any one of claims 1 to 6, the control device, in a state in which the control switching unit selects control of the braking force control unit, sequentially updates a stroke position of the linear motion mechanism that can achieve a predetermined gap amount based on the estimated braking force, the estimated motor angle in the state, and a preset stiffness of the electric brake device. Electric brake device.

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