Electric Brake Device

Abstract

To provide an electric brake device improved in safety and in brake feeling of an operator.SOLUTION: An electric brake device comprises: a brake rotor; a friction material, an electric motor, a direct-acting mechanism that converts a rotary motion of the electric motor to a rectilinear motion of the friction material; motor angle estimating means; brake force estimating means; and a control device that controls the electric motor. The control device has: a position control function of controlling a stroke position in the direct-acting mechanism on the basis of an estimated motor angle by the motor angle estimating means, in a brake released state; a function of estimating workloads by friction force generated when the friction material comes into contact with the brake rotor, in a braking state; and a function of estimating a clearance enlargement amount on the basis of the workload by the friction force and thermal contraction characteristics to elapsed time of the electric brake device in the brake-released state and diminishing the clearance enlargement amount to make the stroke position protrude so that a clearance reduces.SELECTED DRAWING: Figure 1A

Description

Technical Field

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

Background Art

[0002] Conventionally, the following techniques have been proposed in electric braking devices. (1) An electric actuator using a planetary roller screw structure (Patent Document 1). (2) An electric brake control device applying position control and load control (Patent Document 2).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the electric braking device described in Patent Document 1, by stepping on the brake pedal, the rotational motion of the motor is converted into linear motion through a linear motion mechanism using a planetary roller screw structure, and a friction material (brake pad) is pressed into contact with a brake rotor (brake disk) to generate a braking force. For example, in order not to give a sense of discomfort in brake feeling to the driver of a vehicle equipped with an electric brake or the like, 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 region of the service brake, which is frequently used during driving on public roads and has a relatively small braking force, the driver tends to feel discomfort in the brake feeling, so particularly precise braking force control may be required.

[0005] Also, for example, when controlling the braking force of an electric braking device by setting a predetermined stroke amount with respect to the operation amount of the brake pedal operation using the stroke amount of the linear motion mechanism (corresponding to the movement amount of the friction material) converted from the rotation angle of the motor (this control is also called position control), due to factors such as the friction material and brake rotor that expand due to the braking frictional heat generated when braking the vehicle and contract by cooling due to heat dissipation after releasing the brake, the gap between the friction material and the brake rotor may expand more than expected (occurrence of stroke amount error and error in the position (motor angle) of the friction material). In such a state, the braking force may not be generated in the state of the brake pedal operation amount where the braking force should originally act, and the operator may feel a sense of discomfort in the brake feeling.

[0006] Also, in Patent Document 2, for example, a braking force sensor for estimating the braking force is provided, and when braking, braking force control (or load control) is performed so that a predetermined braking force sensor output is obtained with respect to the operation amount of the brake pedal operation. When releasing the brake, a motor angle control is performed so that a predetermined pad clearance (gap between the friction material and the brake rotor) is provided from the braking force sensor output or the motor rotation angle, and a method (or position control) for controlling the electric braking device is disclosed.

[0007] However, due to factors such as the friction material and brake rotor that expand due to the brake frictional heat generated when braking the vehicle and then contract due to heat dissipation after the brake is released, the gap between the friction material and the brake rotor may expand more than expected. In such a case, when performing brake force control, the electric motor accelerates more than expected until the actual brake force is generated, resulting in a large overshoot in the brake force (braking shock phenomenon), a phenomenon where the brake force does not occur for a while and a large response delay occurs, or a combined phenomenon of these may occur. Which of these phenomena occurs depends on the magnitude of the brake command value and the parameters of the brake controller, making it difficult to adjust in advance. Also, since it is likely to occur mainly when performing relatively small brake operations, there is a possibility that the operator may feel a sense of discomfort in the brake feeling or that the safety may be reduced due to unintended brake operations.

[0008] An object of the present invention is to provide an electric brake device that improves safety and the brake feeling of the operator in order to solve the above-mentioned problems.

Means for Solving the Problems

[0009] In general, when the present invention transitions from a state where the brake is released (brake release state) to a state where a predetermined brake force is generated (brake state), if it is determined that a larger gap (pad clearance) has occurred than expected from the rotation angle of the motor (motor angle), the estimated brake force (estimated brake force), etc., after generating a predetermined brake force and then releasing the brake, the amount of gap expansion is assumed from the energy due to brake friction until the brake is released and the cooling characteristics and thermal contraction characteristics of the brake device, etc. Based on this, the linear motion mechanism is protruded in consideration of the estimated value of the amount of gap expansion.

[0010] To achieve the above object, the electric brake device according to the present invention A brake rotor, a friction material that abuts against the brake rotor to generate a braking force, an electric motor, a linear motion mechanism that converts the rotational motion of the electric motor into the linear motion of the friction material, a motor angle estimation means for estimating the rotational angle of the electric motor, a braking force estimation means for estimating the braking force generated by the contact between the brake rotor and the friction material, and a control device for controlling the electric motor, in an electric brake device comprising: the control device has a position control function of controlling the stroke position in the linear motion mechanism based on the estimated motor angle by the motor angle estimation means at least in a brake release state in which at least the friction material and the brake rotor are separated so that the gap between the two becomes a predetermined amount; has a function of estimating the work amount by the frictional force generated by the contact between the friction material and the brake rotor from at least the estimated braking force by the braking force estimation means and the motion state of the brake rotor in a braking state in which the friction material and the brake rotor are in contact; has a function of storing the work amount by the frictional force from the brake release state to the braking state and until it becomes the brake release state again; has a gap adjustment function of estimating a gap expansion amount, which is an expansion amount of the gap, based on at least the stored work amount by the frictional force until the brake release state, the elapsed time in the brake release state, and the thermal contraction characteristics of the electric brake device with respect to the elapsed time, and moving the stroke position of the linear motion mechanism by a predetermined amount in a direction in which the gap is reduced by reducing the estimated gap expansion amount.

[0011] According to the above configuration of the electric brake device according to the present invention, since the control device has the above-described position control function, the function of estimating the amount of work by frictional force, and the gap adjustment function, when the gap (pad clearance) between the friction material and the brake rotor becomes larger than expected when the brake is released, based on the thermal contraction amount etc. of the brake device, the amount that is larger than expected is subtracted, and the friction material is projected by the rectilinear motion converted by the linear motion mechanism to adjust the gap amount, thereby preventing the brake force from not easily being generated in response to a brake application command, or conversely, preventing the motor from operating too fast and generating a braking shock, and improving safety and the brake feeling of the driver.

[0012] The control device has a function of estimating the rotational speed of the brake rotor. The estimated value of the estimated gap expansion amount is a value obtained by referring to at least a two-dimensional table based on the preset thermal contraction characteristics of the electric brake device with the amount of work by frictional force until the stored brake release state and the elapsed time of the brake release state as coordinates. The control device may further have a function of adjusting the elapsed time used as the reference coordinates, which are the coordinates referring to the table based on the rotational speed of the brake rotor, to be longer than the actual elapsed time.

[0013] The electric brake device is a brake device mounted on a traveling vehicle. The control device has a function of acquiring the traveling speed of the vehicle. The estimated value of the estimated gap expansion amount is a value obtained by referring to at least a two-dimensional table based on the preset thermal contraction characteristics of the electric brake device with the amount of work by frictional force until the stored brake release state and the elapsed time of the brake release state as coordinates. The control device may further have a function of adjusting the elapsed time used as the reference coordinates, which are the coordinates referring to the table based on the traveling speed of the vehicle, to be longer than the actual elapsed time.

[0014] With each of the configurations described in the above two paragraphs, for example, in a vehicle, since the rotation of the brake rotor synchronizes with the vehicle speed, the faster the brake rotor rotates, the faster the vehicle moves and the easier it is to be cooled by forced convection. Therefore, since the improvement in its heat dissipation can be replaced by the passage of time in terms of a mathematical formula (for example, if the heat dissipation amount of a predetermined object doubles, and the influence of the temperature distribution inside the object where heat moves faster compared to heat dissipation to the atmosphere can be ignored, the cooling characteristics are approximately equal to those after approximately twice the time has passed), by correcting the time referenced as coordinates, it becomes possible to more accurately estimate the amount of void expansion due to thermal contraction. Also, for example, in the brakes of an elevator or a flywheel, which are stationary brake rotors that do not move, there may be cases where the air is stirred by rotation and the heat dissipation amount increases. Therefore, although the degree of influence is less than that of a vehicle, an improvement in the estimation accuracy of the amount of void expansion can be expected.

[0015] When the control device has a function of reducing, over time, the amount of work due to frictional force to zero until the stored brake release state when the rotation of the brake rotor stops or when the brake release state is reached, when the brake state is restored again before the amount of work due to frictional force until the stored brake release state reaches zero, it may have a function of calculating the amount of work so as to further add it to the amount of work due to frictional force until the stored brake release state. Thereby, when the brake is repeatedly applied in a relatively short period of time, it is reheated before dissipating heat to a steady temperature, enabling more accurate estimation.

[0016] When the amount of work due to frictional force until the stored brake release state is greater than a predetermined value, the control device executes the void adjustment function, and when it is not greater than the predetermined value, it may not execute the void adjustment function. Thereby, it is possible to reduce the possibility of unnecessary reduction of the void and occurrence of brake dragging due to estimation errors or the like.

Advantages of the Invention

[0017] According to the electric brake device of the present invention, safety and the brake feeling of the operator can be improved.

Brief Description of the Drawings

[0018]

Figure 1A

Figure 1B

Figure 2A

Figure 2B

Figure 3A

Figure 3B

Figure 4

Embodiments for Carrying Out the Invention

[0019] In FIG. 1A, there is shown a configuration of an electric brake device 1 including at least a control device 100 that controls an electric motor 210 (hereinafter also referred to as an electric brake control device) and an electric actuator 200 that uses a linear motion mechanism 240 to convert the rotational motion of the electric motor 210 into the linear motion of a friction material 220. Note that 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, for example. In the present embodiment, the electric brake device 1 will be described as an example of a braking device mounted on a traveling vehicle. However, the configuration of the present embodiment can also be applied to a braking device for stopping other energy storage devices such as lifting devices, power generation devices, and flywheels.

[0020] <<Configuration of Brake Actuator 200>> The brake actuator 200 includes a brake rotor 230 that rotates integrally with a wheel (not shown), a friction material 220 that contacts the brake rotor 230 to generate a braking force, an electric motor 210, a linear motion mechanism 240, an angle sensor 250 that detects a motor angle (specifically, the rotation angle of the motor rotor), a load sensor 260 that detects a brake load, and a brake rotor rotation sensor 270 that detects a rotation speed that may correspond to the rotation angle of the brake rotor 230 or the rotation speed of the above wheel. In addition, a speed reducer or the like for reducing the rotation speed of the electric motor 210 may be provided as necessary. The electric motor 210 is, for example, a permanent magnet synchronous motor, and with this configuration, it is considered suitable because it saves space, is highly efficient, and has high torque. In addition, other types of electric motors 210 can also be applied, such as a DC motor using brushes, a reluctance motor without using permanent magnets, or an induction motor. Further, the electric motor 210 may be a radial gap motor having magnetic poles in the rotational radial direction, or an axial gap motor having magnetic poles in the rotational axis direction.

[0021] 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 that can convert 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 suitable to use these because they are highly accurate and reliable. In addition, various sensors such as an optical encoder can also be applied to the angle sensor 250. Or as another configuration, angle sensorless estimation can be applied, such as estimating the motor angle from the relationship between voltage and current in the electric brake control device 100 described later without using the angle sensor 250.

[0022] The load sensor 260 is a sensor that detects, for example, strain, deformation, etc. according to the load applied by the actuator 200, and it is considered suitable because it can achieve low cost and high precision when used. Note that the load sensor 260 can also use a pressure-sensitive medium such as a piezoelectric element. Alternatively, for the load sensor 260, a torque sensor that detects the braking torque of the brake rotor, or in the case of a vehicle electric brake device, an acceleration sensor that detects the longitudinal and lateral accelerations of the vehicle may be used.

[0023] For the brake actuator 200, as other elements not shown in other figures, various sensors such as a temperature sensor like a thermistor may be separately provided according to requirements. Also, a mechanism for locking the operating part (power transmission part) of the actuator with a solenoid or a DC motor can be provided to make it an actuator with a parking brake.

[0024] <<Configuration of the Electric Brake Control Device 100>> The electric brake control device 100 includes, for example, a brake controller BC that performs calculations and controls for brake operations, a motion state estimator ME that calculates and estimates the operating state of the motor, a brake force estimator 170 that estimates the brake force from the output of the load sensor 260, etc. and outputs the estimated brake 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. Further, the electric brake control device 100 may include, for example, a brake rotor angular velocity estimator (a kind of brake rotor speed estimation means for estimating the rotational speed of the brake rotor) 180 that estimates the angular velocity of the brake rotor 230, and a gap adjuster GA that adjusts the gap (pad clearance) between the friction material 220 and the brake rotor 230.

[0025] The motion state estimator ME includes an angle estimator (motor angle estimation means) 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 the estimated motor angle), and an angular velocity estimator 160 that estimates the rotational angular velocity of the rotor (calculates the estimated angular velocity). Alternatively, the motion state estimator ME may be provided with functions such as estimating a predetermined differential value such as the angular acceleration of the electric motor 210, and further functions such as estimating disturbances. Further, the motion state estimator ME has a function of appropriately obtaining necessary physical quantities based on a control configuration such as the electrical angular phase used for current control and the total rotation angle obtained by correcting the overlap and underlap of the angle sensors 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, for example, the angle of a predetermined part of the speed reducer obtained based on the reduction ratio when the speed reducer is provided, or the position and speed obtained based on the equivalent lead of the screw mechanism or the like. The estimation of the physical quantity may be performed using, for example, a configuration such as a state estimation observer, or may be a direct calculation such as inverse calculation based on a differential or an inertial equation.

[0026] The current sensor CS can use, for example, a sensor including an amplifier that detects and amplifies the voltage across a shunt resistor provided in the energization path, or a non-contact sensor that detects the magnetic flux around the energization path. Alternatively, the current sensor CS may be configured to detect, for example, the voltage between terminals of an element constituting the motor driver MD. Further, the current sensor CS may be provided between the phases of the electric motor 210, and one or more may be provided on the low potential side or the high potential side. Alternatively, feedforward control can also be performed based on motor characteristics such as inductance and resistance value without providing a current sensor.

[0027] The brake controller BC receives inputs such as the estimated braking force and the estimated motor angle, and obtains an operation amount for the brake actuator 200 to preferably follow the operation in response to a predetermined command input (command signal) from the brake pedal 300, the vehicle motion control device 400, etc., and converts it into a motor drive signal. The brake controller BC mainly has a function of controlling the moving position (stroke position or stroke amount) of a so-called rod, which is a component that performs the linear motion of the linear motion mechanism 240 (this function is executed by the internal position control unit 110), a function for controlling the braking force generated by the contact between the friction material 220 and the brake rotor 230 (braking force control function), and a function for switching between these (switching function). By providing these, it is desirable to achieve highly accurate brake control.

[0028] The position control unit 110 has a function of determining the driving amount of the motor so as to control the stroke amount (or stroke position) of the linear motion mechanism 240 converted from the motor rotation amount or the motor angle based on various introductions of the brake actuator 200, such as the equivalent lead in the case of using a screw mechanism or the reduction ratio in the case of providing a speed reducer. In addition, a stroke sensor (not shown) or the like may be separately provided, and it may be a function of performing feedback control of the signal from the sensor to a predetermined target value. The position control unit 110 functions, for example, when the friction material 220 and the brake rotor 230 are separated so as not to contact each other as much as possible when the brake is released, and a stroke amount in which a predetermined amount of gap can exist between them (in the brake release state). The stroke amount that can become the predetermined gap is, for example, a position where the motor is rotated by a predetermined amount from the motor angle (estimated motor angle by the angle estimation unit (motor angle estimation means) 150) that becomes a predetermined estimated brake force, or after the estimated brake force no longer changes (or the change amount becomes small) with respect to the transition of the motor angle (estimated motor angle), and the motor is rotated by a predetermined amount. The position control unit 110 can also function, for example, to make the gap between the friction material 220 and the brake rotor 230 in a stroke state where the gap is near zero or a negative value smaller than zero (in terms of calculation and control) in order to control an extremely slight brake force that may be difficult to detect with a load sensor 260 or a torque sensor that detects the brake force.

[0029] The above brake force control function has a function of determining the motor driving amount (which is the amount for driving the motor such as the motor angle) so as to control the brake force in the brake state where the friction material 220 and the brake rotor 230 are in contact to follow a desired target value. For example, the pressing force between the friction material 220 and the brake rotor 230 is detected by the load sensor 260, and the brake force control function functions based on the estimated brake force estimated by the brake force estimator 170 from the output of the load sensor 260. In addition, brake force control can also be performed using a torque sensor or the like that detects the braking torque of the brake rotor 230.

[0030] The switching function mainly has a function of switching the control content of the brake controller BC between the function of the aforementioned position control unit 110 and the brake force control function according to the situation of the vehicle equipped as described above. For example, when shifting from the brake release state to the brake state, the switching function causes the position control unit 110 to function until the position state where the friction material 220 and the brake rotor 230 can come into contact, and when it is determined from the estimated brake force that the friction material 220 has come into contact with the brake rotor 230, the control can be switched so that the brake force control function functions. Further, when switching from the brake state to the brake release state, the switching function causes the brake force control function to function in a state where it is determined from the estimated brake force that the friction material 220 is in contact with the brake rotor 230, and after it is determined that the friction material 220 has separated from the brake rotor 230 from the estimated brake force, the control can be switched so that the position control unit 110 functions to provide a desired gap between the friction material 220 and the brake rotor 230.

[0031] 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 a desired amount. The motor controller MC stores in advance in a LUT (Look Up Table) or the like the optimum current conditions for obtaining a desired torque in a state of a predetermined motor angular velocity, and determines the target current value from the current motor angular velocity so that the motor current becomes a desired current value. It is considered suitable because high-precision control can be performed at low cost. Note that the motor controller MC can also have a function of calculating relational expressions of current and voltage for deriving the output of the motor and obtaining drive conditions in real time.

[0032] The motor driver MD is configured with a bridge circuit or the like using a switching element such as a FET (Field Effect Transistor), and performs PWM (Pulse Width Modulation) control to determine the motor applied voltage based on a predetermined duty ratio. This is considered to be inexpensive, high-performance, and suitable. Alternatively, the motor driver MD can be configured with a transformer circuit or the like and perform PAM (Pulse Amplitude Modulation) control.

[0033] The brake rotor angular velocity estimator 180 has a function of estimating the rotational angular velocity of the brake rotor from the output of the brake rotor rotation sensor 270 that detects the rotation of the brake rotor 230. As the brake rotor rotation sensor 270, for example, a sensor that provides a plurality of magnetic poles on a component that rotates synchronously with the brake rotor, such as an ABS (Anti-lock Brake System) sensor, and outputs a plurality of pulses (rotation pulses) per unit rotation can be used. The angular velocity of the brake rotor 230 can be estimated from the pulse width of the rotation pulses or the number of pulses per unit time, and which one to use can be appropriately determined based on requirements and circumstances.

[0034] The gap adjuster GA includes a brake work amount estimator 120 that estimates the amount of work generated by the frictional force generated by the contact between the friction material 220 and the brake rotor 230, a brake release time measurement unit 130 that measures the elapsed time since the brake was released (since the brake release state), and a gap expansion amount calculation unit 140 that estimates the amount by which the gap between the friction material 220 and the brake rotor 230 has expanded during brake release (specifically, the amount of the gap that has expanded more than expected). In the present embodiment, when the gap is different from the assumption, based on the thermal shrinkage amount of the brake device or the like, the difference from the assumption is added or subtracted, and the friction material 220 is protruded by the linear motion converted by the linear motion mechanism 240 to adjust the gap amount. Specifically, as will be described later, when the gap has expanded more than expected, the target stroke amount or the current stroke amount is changed to adjust the gap amount so that the amount of expansion more than expected can be offset.

[0035] The brake work amount estimation unit 120 has a function of estimating the work amount of the frictional force generated by the contact between the friction material 220 and the brake rotor 230 from the estimated braking force and the motion state of the brake rotor 230 in a braking state where the friction material 220 and the brake rotor 230 are in contact (more specifically, the friction material 220 and the brake rotor 230 are in contact with a predetermined pressing force). The motion state of the brake rotor 230 refers to the rotational speed of the brake rotor, or a change in the rotational angle or rotational angular acceleration that can be converted into the rotational speed, or the vehicle body speed of the vehicle having the brake rotor that can be synchronized with the rotation of the brake rotor.

[0036] The work amount may be derived, for example, from the braking torque τbl acting on the brake rotor 230 and the rotational angular velocity ωbr of the brake rotor by an arithmetic expression (W = ∫{τbl × ωbr}dt). However, the arithmetic expression is not limited to this, and any arithmetic expression that can be equivalent to the above may be appropriately determined according to the convenience of the designer. Also, considering heat dissipation from the brake rotor 230 and the brake actuator 200 even during the braking state, it is also possible to calculate by subtracting a predetermined amount of heat dissipation for each unit time in addition to the above formula. Note that the brake work amount estimation unit 120 may have a function (described later) of storing the work amount by the frictional force from the brake release state to the transition to the braking state and until it becomes the brake release state again.

[0037] The brake release time measurement unit 130 has a function of measuring the elapsed time since the friction material 220 and the brake rotor 230 are separated with a predetermined gap (brake release state).

[0038] The gap expansion amount calculation unit 140, in the brake release state, estimates the amount by which the gap between the friction material 220 and the brake rotor 230 expands due to heat dissipation of the brake device (hereinafter also referred to as the gap expansion amount) based on at least the elapsed time in the brake release state (specifically, the elapsed time since the brake release state) and the amount of work stored by the frictional force until the brake release state (hereinafter also referred to as the brake work amount). Note that the gap expansion amount may be further estimated based on the thermal contraction characteristics of the electric brake device 1 with respect to the elapsed time.

[0039] The thermal contraction characteristics include characteristics in which the temperature of each component of the electric brake device 1 is estimated using an arithmetic expression from the heat capacity, heat transfer characteristics of each component, the heat dissipation coefficient into the air, and the thermal contraction amount is derived from the temperature. However, since the arithmetic expression for this estimation is complex and contains many error factors, for example, after generating a predetermined amount of work in a brake operation in advance, the transition of the gap over time is obtained by analysis or actual measurement, and based on the result, it is configured to obtain from a LUT (Look Up Table) or the like using the brake work amount and the elapsed time as reference coordinates, which is considered suitable because simple calculations can be performed. As a result, the estimated value of the estimated gap expansion amount is a value obtained by referring to at least a two-dimensional table based on the preset thermal contraction characteristics of the electric brake device with the amount of work by the frictional force until the stored brake release state and the elapsed time in the brake release state as coordinates. Further, based on the brake rotor rotation speed, the elapsed time used as the reference coordinates in the table can be adjusted to be longer than the actual elapsed time. Note that the table can also be configured as a three-dimensional or higher-dimensional table in which other parameters affecting brake heat dissipation, such as the outside air temperature, are added as coordinates.

[0040] The gap enlargement amount calculation unit 140 further has a function (hereinafter also referred to as the gap adjustment function) of protruding the stroke position of the linear motion mechanism by a predetermined amount so as to reduce the estimated gap enlargement amount and cause the gap to shrink. Thereby, the gap adjuster GA can transmit to the brake controller BC an adjustment command value for stroking the linear motion mechanism so as to suppress the enlargement of the gap from the gap enlargement amount in the brake release state.

[0041] <<Others>> The power supply device PW can use, for example, 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, etc. in an automotive electric brake device, or these may be used in parallel for redundancy. Also, as an element not shown in the figure, it is preferable to supply power directly from this power supply device PW to the motor driver and the solenoid driver described above, and apply a small step-down converter in the control device to the arithmetic unit etc. in each control device. Alternatively, power may be supplied to either or both of the motor driver and the solenoid driver via a step-up converter, and power may be supplied directly from this power supply device PW to the arithmetic unit etc. As the brake command means, various operation means operable by the operator such as a volume, a joystick, a switch, etc. may be used instead of the brake pedal 300.

[0042] The vehicle motion control device 400 includes an automatic brake function unit 410 for preventing a collision of the vehicle or reducing the impact at the time of collision, a skid prevention function unit 420 for preventing at least vehicle spin etc. by the brake when the vehicle is in a skidding state, an anti-skid control unit 430 for preventing the wheels from locking due to the brake and the vehicle behavior from becoming unstable, etc. The vehicle motion control device 400 may be an integrated control device that integrates information from various in-vehicle sensors such as a gravity sensor, an object sensor, and a GPS (Global Positioning System) not shown in the figure and performs calculations necessary for the above functions. The brake operation amount determined by these vehicle motion control devices 400 is also transmitted as a target brake force to the electric brake control device via the command signal.

[0043] In the above electric brake control device 100, various arithmetic functions such as those of the controller are preferably configured by, for example, a microcomputer having a processor that operates according to a program, an arithmetic unit such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array), or hardware, as this results in low cost and high performance. In addition, the functional blocks shown in the figure are provided solely for convenience of description and do not restrict the type of configuration by hardware or software or the partitioning of functions. Also, the specific configuration of the software and hardware can be arbitrarily set as long as it does not interfere with the functions shown in the figure, and the functions of the respective blocks shown in the figure may be integrated or divided as necessary. Alternatively, it is possible to add elements not shown in the figure as long as it does not interfere with the functions in the figure. For example, it is preferable to appropriately add a safety mechanism in the event of failure of various functions and sensors based on system requirements.

[0044] Figure 1B, unlike Figure 1A, shows an example in which the electric brake device 1 is provided with vehicle motion estimation means 400' similar to the vehicle motion control device 400, and the vehicle speed and the brake work amount are transmitted from the vehicle motion estimation means 400' to the electric brake control device 100. The vehicle motion estimation means 400' includes the above-described automatic brake function unit 410, skid prevention function unit 420, anti-skid control unit 430, etc., and further includes the brake work amount estimation unit 120 of the gap adjuster GA shown in the example of Figure 1A. Thereby, for example, it becomes possible to have the function of a brake work amount estimation unit that estimates the brake work amount from the change in kinetic energy when a vehicle of a predetermined vehicle weight decelerates. Note that the output signal of the brake rotor rotation sensor 270 is input to the vehicle motion estimation means 400', and the electric brake control device 100 does not have the brake rotor angular velocity estimator 180 shown in the example of Figure 1A. The function of the brake rotor angular velocity estimator is included in the vehicle motion estimation means 400'.

[0045] Figure 2A shows an example of the correlation between the brake release time and the amount of clearance increase in each situation of the brake work amounts W1, W2, and W3 (W1 < W2 < W3). As the brake work amount increases, the heat generation amount of the brake device increases, so the amount of clearance increase becomes larger, and the amount of thermal contraction that occurs with the passage of time after brake release also tends to increase. On the other hand, Figure 2B shows an example of the correlation between the brake release time and the amount of clearance increase in each situation where the vehicle is run with the brake rotor at angular velocities ω1, ω2, and ω3 after performing a brake operation with a predetermined brake work amount (constant value) (ω1 < ω2 < ω3). The brake rotor speed is approximately equivalent to the vehicle speed when the vehicle is running stably. Since the brake device is cooled more rapidly as the brake rotor speed increases, the amount of thermal contraction with respect to the elapsed time after brake release tends to increase rapidly (the overall rise becomes steeper). Note that the case where the brake work amount is a constant value indicates that the temperature rise degree due to braking by the friction material 220 is the same, and the amount of clearance increase is the same when finally sufficiently cooled.

[0046] Figure 3A shows an example of the operation flow of the gap adjuster GA in Figure 1A. At S.1 after startup, it is determined whether the electric brake device 1 is in the braking state (braking condition). If it is in the braking state, at S.2, the braking work amount W(k) at time k is calculated (calculation of the cumulative work amount) using the braking work amount W(k - 1) at time (k - 1) and the current braking work amount P, and the work amount W(k) calculated at S.3 is saved. The braking work amount W(k) can be calculated as the work amount equivalent to the amount by which the kinetic energy of the vehicle has decreased. For example, it can be calculated as "braking pressing force × sliding distance between the friction material and the brake rotor per unit time". Note that the sliding distance can be obtained from a preset brake effective diameter, brake rotor speed, and braking time. Alternatively, when configured to be able to grasp the states of a plurality of brake devices mounted on the vehicle and the motion state of the vehicle, the work amount of each brake device may be obtained from the vehicle deceleration, vehicle weight, and braking force distribution ratio of each brake device. Additionally, for example, the air resistance of the vehicle may be derived in advance and a function may be provided to correct so as not to include the work amount due to air resistance, or an inclination angle sensor may be provided and a function may be provided to correct so as not to include the change in the potential energy of the vehicle.

[0047] Also, when it is determined at S.1 that it is not in the braking state (in the case of determining the brake release state), it is determined at S.4 whether it is immediately after the brake release. If it is determined to be immediately after the brake release, after saving the work amount W(k) generated during braking in the variable Wst (S.5), the work amount W(k) is cleared (S.6). Next, referring to the actual elapsed time Δt at time k, the brake release time TREL(k) at time k is measured (S.7), and from the work amount Wst until the brake is released and the elapsed time TREL(k) after the brake is released, the gap expansion amount Δx is calculated by a given predetermined correlation function h(w, t) (S.8). The operation amount Δx' of the linear motion mechanism is determined to reduce the gap according to the gap expansion amount Δx (S.9).

[0048] In this embodiment, Δx’ = α·Δx. At this time, regarding the correction coefficient α, α = 1 may be set so that Δx = Δx’. However, when the linear motion mechanism is operated larger than the original void expansion amount due to the estimation error, the void amount between the friction material 220 and the brake rotor 230 becomes insufficient, and there may be a problem that the fuel consumption and power consumption deteriorate due to the dragging torque. Therefore, it is considered desirable to apply a coefficient (α < 1) such that the linear motion mechanism does not operate too much in consideration of the error in advance. Further, the correction coefficient α may be set to α = 0 when Δx is smaller than a predetermined value, for example, so as not to reduce the void. Also, when the work amount due to the frictional force until the stored brake release state is not larger than a predetermined value, α = 0 may be set so as not to execute the void adjustment function. In that case, the risk of the void becoming insufficient due to the estimation error can be more reliably avoided.

[0049] Figure 3B shows an example in which, for a part of the operation flow in Figure 3A, the work amount W(k) generated during braking is not cleared (Figure 3A, S.6) immediately after brake release (Figure 3A, S.4), but is decreased over time until it becomes zero, and also the process in which the thermal contraction amount Δx increases rapidly according to the brake rotor speed is added. In the following, the explanation will focus on the flow added to Figure 3A, and the explanation of the same flow as in Figure 3A will be omitted. If it is determined in S.4 that it is not immediately after brake release, the work amount W(k) generated during braking is stored in the variable Wst (S.5), but the clearing of the work amount W(k) as in S.6 of Figure 3A is not performed. Therefore, next, the brake rotor speed ωbr is obtained (S.15), and the work amount W(k) is decreased by a value obtained by a preset function f(ω) that becomes a value according to the brake rotor speed (S.16). Note that the work amount W(k) has zero as the lower limit value and does not take negative values. Instead of clearing the work amount W(k) as in S.6 of Figure 3A, by decreasing the work amount W(k) over time in S.16, for example, when the brake operates again within a relatively short time, in a situation where work is generated by the brake before the brake device is sufficiently cooled, the amount of void expansion due to thermal contraction can be estimated more accurately. Note that when it becomes the braking state again before the work amount becomes zero, it has a function of calculating the work amount so as to add further to the work amount (S.1 ⇒ S.2 ⇒ S.3). After the subtraction of the work amount W(k) as described above, the brake release time TERL is measured (S.17). At this time, different from S.7 of Figure 3A, when calculating the brake release time TERL, by applying a correction coefficient obtained by a preset correction function g(ω) according to the brake rotor angular velocity to the actual elapsed time Δt at time k, equivalently, the higher the brake rotor speed, in other words, the higher the vehicle speed, the faster the brake device is cooled can be reflected in the estimation of the amount of void expansion. That is, the correction function g(ω) is a correlation function set such that the correction coefficient obtained increases as ωbr increases, and can be set in advance by analyzing or actually measuring the vehicle speed and the cooling rate of the brake device. Note that instead of the brake rotor speed ωbr shown in this figure, the estimated vehicle speed may be applied.

[0050] FIG. 4 shows a schematic diagram of an operation example when the brake is operated again after a certain period of time has elapsed after performing a brake operation with a relatively large workload. FIG. 4(a) shows an operation example when the configuration of the present embodiment is applied. After the brake is released (time t1), according to the result of estimating the amount of void expansion due to thermal contraction using the flows of FIGS. 4A, 4B, etc., the electric motor 210 is rotated in the shrinking direction (section T in the figure) to correct the amount of voids. When the brake is operated again (time t2), a large braking load can be applied without a large response delay (time t3).

[0051] On the other hand, FIG. 4(b) shows an operation example when the configuration of the present embodiment such as the prior art is not applied. In the case of FIG. 4(b), although the gap between the friction material 220 and the brake rotor 230 has expanded more than expected due to thermal contraction after the brake is released (time t1), since the rotation of the electric motor 210 for correcting the amount of voids is not performed, when the brake is operated again (time t2), a response delay of the braking load occurs (time t5). That is, in the figure, t3 < t5.

[0052] The embodiments disclosed this time should be considered as illustrative in all respects and not restrictive. The scope of the present invention is shown not by the above description but by the claims, and it is intended that all modifications within the meaning and scope equivalent to the claims are included.

Explanation of Reference Numerals

[0053] 1 Electric brake device 100 Electric brake control device (control device) 110 Position control unit 120 Braking force workload estimation unit 130 Brake release time measurement unit 140 Void expansion amount calculation unit 150 Angle estimation unit (motor angle estimation means) 170 Braking force estimator (braking force estimation means) 180 Brake rotor angular velocity estimator 210 Electric motor 220 Friction material 230 Brake rotor 240 Linear motion mechanism 270 Brake rotor rotation sensor 300 Brake pedal (brake command means) HD ECU (upper device) ST storage unit

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, a position control function of controlling a stroke position of the linear motion mechanism based on the motor angle estimated by the motor angle estimation means in a brake release state in which at least the friction material and the brake rotor are separated from each other so that a gap between the two is a predetermined amount; and a function of estimating, in a braking state in which the friction material and the brake rotor are in contact with each other, at least from the braking force estimated by the braking force estimation means and the motion state of the brake rotor, an amount of work caused by a friction force generated when the friction material and the brake rotor are in contact with each other; A function of storing the amount of work caused by the frictional force from the brake release state to the brake state and back to the brake release state; and a gap adjustment function of estimating an amount of expansion of the gap based on at least the work amount due to frictional force until the stored brake release state is reached, the elapsed time of the brake release state, and the thermal contraction characteristic of the electric brake device with respect to the elapsed time, in the brake release state, and moving a stroke position of the linear motion mechanism by a predetermined amount in a protruding direction so as to reduce the gap by canceling out the estimated amount of expansion of the gap. Electric brake device.

2. 2. The electric brake device according to claim 1, The control device has a function of estimating a rotational speed of the brake rotor, the estimated value of the gap expansion amount is a value acquired by referring to at least a two-dimensional table based on preset thermal contraction characteristics of the electric brake device, the table having coordinates of the stored work amount due to frictional force until the brake is released and the elapsed time of the brake released state, The control device further includes a function of adjusting an elapsed time used as a reference coordinate, which is the coordinate referred to in the table, based on a rotational speed of the brake rotor so that the elapsed time is longer than an actual elapsed time. Electric brake device.

3. 2. The electric brake device according to claim 1, The electric brake device is a brake device mounted on a traveling vehicle, The control device has a function of acquiring a traveling speed of the vehicle, the estimated value of the gap expansion amount is a value acquired by referring to at least a two-dimensional table based on preset thermal contraction characteristics of the electric brake device, the table having coordinates of the stored work amount due to frictional force until the brake is released and the elapsed time of the brake released state, The control device further includes a function of adjusting an elapsed time used as a reference coordinate, which is the coordinate referred to in the table, based on a traveling speed of the vehicle so that the elapsed time is longer than an actual elapsed time. Electric brake device.

4. In the electric brake device according to any one of claims 1 to 3, The control device, When the rotation of the brake rotor stops or the brake is released, the stored work amount due to the frictional force until the brake is released is reduced over time until it becomes zero, When the brake state is again established before the stored amount of work caused by the frictional force until the brake is released becomes zero, the amount of work is calculated so as to be further added to the stored amount of work caused by the frictional force until the brake is released. Electric brake device.

5. The electric brake device according to any one of claims 1 to 4, The control device executes the gap adjustment function when the work amount due to the frictional force until the stored brake release state is reached is greater than a predetermined value, and does not execute the gap adjustment function when the work amount is not greater than the predetermined value. Electric brake device.

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