JP2009220807A - Motor drive for car brake - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor drive for a car brake capable of suppressing damage by temperature rise of a three-phase motor or a component of its control system. <P>SOLUTION: When an ECU determines that the temperature of a coil has reached a reference temperature (e.g. 170°C) predetermined based on the heat-resistant temperature (e.g. 180°C) and the like of a coil or a component near the coil, rotation of a rotor is advanced such that the currents (of U, V and W phases) flowing through the coils (of U, V and W phases) are shifted from a maximum peak value, and rotation of the rotor is stopped at a position where the absolute values of the V and W phase currents are equal and the U phase current becomes 0 (lowest value) [(v) position where the liquid pressure exceeds 4 MPa]. Consequently, the temperature of the coil of W phase drops and the ECU can thereby suppress temperature rise of the motor coil. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an automobile brake motor drive device used in a vehicle brake system or the like.

  As an example of what is used for a motor drive device for automobile brakes in a vehicle brake system or the like, there is an electric booster described in Patent Document 1. The electric booster includes an input member that moves forward and backward by an operation of a brake pedal, an assist member that is arranged to be movable relative to the input member, and an electric motor that is driven by a motor drive device to move the assist member forward and backward. And an urging means for urging the input member toward a neutral position of relative displacement with respect to the assist member, and the assist by the electric motor according to the movement of the input member by the brake pedal The member is moved to generate a brake fluid pressure in the master cylinder.

JP 2007-191133 A

  As the electric motor, a three-phase motor having a three-phase coil (U, V, W phase coil) that receives supply of a three-phase alternating current (for example, U, V, W phase current) corresponding to each phase is used. It is desirable.

By the way, in the above prior art, depending on the usage mode, the coil (three-phase coil) may be energized for a long time with the rotor of the electric motor (three-phase motor) being stationary (rotation of the rotor stopped). . At this time, the three-phase alternating currents (U, V, and W phase currents) are often different in phase, so that the magnitudes (absolute values) of the energization currents flowing through the respective coils are different (indicating current bias). . Then, with the rotor stationary as described above, for example, one of the three-phase coils (for example, the U-phase coil) is supplied with a peak value or a large current before and after the peak value, and the temperature greatly increases. On the other hand, the current flowing through the other phase coils (V, W phase coils) may be small and the temperature rise may be low.
For this reason, there is a risk of damage to the one-phase coil (for example, the U-phase coil) or its control system component whose temperature is greatly increased.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a motor drive device for an automobile brake that can suppress damage due to a temperature rise of components of a three-phase motor or its control system.

  The present invention is supplied to the three-phase coil when the rotation of the rotor is continued until a predetermined condition is satisfied after the rotation of the rotor is stopped while the three-phase coil of the three-phase motor is energized. The effective current applied to the three-phase coil is changed so that the absolute value of the current value of the coil of the phase having the largest current value among the respective phase currents is small, and the rotor is changed. Control is performed to move the rotational position.

  ADVANTAGE OF THE INVENTION According to this invention, the damage by the temperature rise of a three-phase motor or its control system components can be suppressed.

1 is a cross-sectional view schematically showing an electric booster according to a first embodiment of the present invention, including a master cylinder, a brake pedal, and an ECU (motor drive device). It is a circuit diagram which shows typically the three-phase coil and current sensor of the electric motor (three-phase motor) of FIG. It is a figure for demonstrating the temperature estimation of the three-phase coil of the electric motor of FIG. It is a flowchart for demonstrating the temperature estimation of the three-phase coil of the electric motor of FIG. It is a wave form diagram which shows the three-phase alternating current supplied to the electric motor of FIG. It is the wave form diagram shown corresponding to the hydraulic pressure about the three-phase alternating current supplied to the electric motor of FIG. It is a characteristic view which shows the temperature change of the three-phase coil of the electric motor of FIG. It is a flowchart which shows the effect | action of the electric booster which concerns on 1st Embodiment of this invention. It is sectional drawing which shows typically the electric disk which concerns on 2nd Embodiment of this invention including ECU (motor drive device). It is the wave form diagram shown corresponding to the electrical angle about the three-phase alternating current supplied to the electric motor which concerns on 3rd Embodiment of this invention. It is a characteristic view which shows the temperature change of the three-phase coil for demonstrating 3rd Embodiment. It is a figure which shows typically that the corresponding relationship with a hydraulic pressure has a hysteresis characteristic about the electric current supplied to the three-phase coil of the electric motor in 4th Embodiment of this invention. It is a wave form diagram which shows the electric current supplied to the three-phase coil of 4th Embodiment.

[First Embodiment]
Hereinafter, an electric booster according to a first embodiment of the present invention will be described with reference to FIGS.

In FIG. 1, an electric booster 1 includes a tandem master cylinder 10, a piston assembly 30 as a piston of the master cylinder 10, and a rotation-linear motion mechanism that linearly moves the piston assembly 30. The motor includes a ball screw mechanism 50, an electric motor 40 as a three-phase motor for operating the ball screw mechanism 50, and an ECU (electronic control unit) 70 for driving and controlling the electric motor 40.
The electric booster 1 includes a housing 2 in which a piston assembly 30 described later is shared as a primary piston of the master cylinder 10. The housing 2 includes a bottomed cylindrical housing body 3, a front cover 4, and a rear cover 6. The front cover 4 is positioned in the radial direction by fitting an annular boss portion 4a into an opening 3b formed in the bottom plate portion 3a of the housing body 3, and is fixed to the bottom plate portion 3a by a bolt (not shown). Yes. The rear cover 6 is formed in a cup shape, is fitted into the rear end opening of the housing 2, and is fixed to the end surface of the housing body 3 by bolts 5. The housing 2 is fixed to a partition wall W that partitions the engine room and the vehicle compartment by using stud bolts S planted on the rear cover 6. On the other hand, a master cylinder 10 is connected to the housing 2 by using stud bolts S ′ planted on the front cover 4.

  The front cover 4 includes a stepped cylindrical guide portion 7 extending into the housing body 3 at the center thereof. The piston assembly 30 is inserted into the cylindrical guide portion 7. On the other hand, the rear cover 6 includes a cylindrical guide portion 8 that is inserted through the partition wall W and extends into the vehicle interior at the center thereof. An input rod 9 that is interlocked with a brake pedal (not shown) is inserted into the cylindrical guide portion 8. The two cylindrical guide portions 7 and 8 are arranged coaxially.

  The tandem master cylinder 10 includes a bottomed cylinder body 11 and a reservoir 12. A cup-shaped secondary piston 13 that is paired with a piston assembly 30 (hereinafter also referred to as a piston 30 for convenience) as the primary piston is disposed on the inner side of the cylinder body 11. In this embodiment, the piston assembly 30 and the secondary piston 13 are slidably guided by two ring guides 15 and 16 disposed on both ends of a sleeve 14 fitted in the cylinder body 11. In the cylinder body 11, two pressure chambers 17 and 18 are defined by the piston assembly 30 and the secondary piston 13. Discharge ports 19 and 20 for opening the pressure chambers 17 and 18 to the outside are provided independently on the wall of the cylinder body 11.

  The cylinder body 11, the sleeve 14, and the ring guides 15, 16 are formed with relief ports 21, 22 that connect the reservoirs 12 to the pressure chambers 17, 18. A pair of seal members 23 and 24 for sealing between the piston assembly 30 and the secondary piston 13 are disposed in front and rear of the ring guides 15 and 16 so as to sandwich the relief ports 21 and 22. . Each of the pressure chambers 17, 18 is brought into sliding contact with the outer peripheral surface of the corresponding piston 30, 13 by the pair of seal members 23, 24 in accordance with the advancement of the pistons 30, 13. Will be closed against. In each of the pressure chambers 17 and 18, return springs 25 and 26 for urging the piston assembly 30 as the primary piston and the secondary piston 13 in the backward direction are disposed.

  The configuration of the master cylinder 10 described above is the same as that of a conventional general-purpose tandem master cylinder except for the piston assembly 30 as a primary piston. In the master cylinder 10, the brake fluid sealed in the pressure chambers 17 and 18 is discharged from the discharge ports 19 and 20 to the outside as the pistons 30 and 13 advance. In the present embodiment, brake pipes 28 and 28 'extending from a hydraulic circuit (not shown) are connected to the discharge ports 19 and 20, respectively. The brake fluid in each of the pressure chambers 17 and 18 is adjusted in pressure by the hydraulic circuit and supplied to a wheel cylinder (not shown) such as a corresponding disc brake caliper.

  The piston assembly 30 includes a cylindrical booster piston 31 and an input piston (input member) 32 disposed in the booster piston 31 so as to be relatively movable therewith. The booster piston 31 is slidably fitted into the cylindrical guide portion 7 of the front cover 4 and the ring guide 15 in the master cylinder 10. The front end portion of the booster piston 31 extends into the pressure chamber (primary chamber) 17 of the master cylinder 10. On the other hand, the input piston 32 is slidably fitted into an annular wall 31 a formed on the inner periphery of the booster piston 31. The front end portion of the input piston 32 extends into the pressure chamber 27 in the same manner as the front end portion of the booster piston 31. Note that through holes (not shown) that can communicate with the relief ports 21 and 22 in the master cylinder 6 are formed in the front end portion of the booster piston 31 and the front end portion of the secondary piston 13, respectively. When the brake is not operated, the pressure chambers 17 and 18 and the reservoir tank 12 are in communication with each other through these through holes.

  Here, the booster piston 31 and the input piston 32 constituting the piston assembly 30 are sealed by a seal member (reference numeral omitted) disposed on the front side of the annular wall 31 a of the booster piston 31. This seal member and the seal members 23 on both ends of the ring guide 15 prevent leakage of brake fluid from the pressure chamber 17 to the outside of the master cylinder 10. The seal member disposed on the front side of the annular wall 31 a of the booster piston 31 is fixed in position by a cylindrical member 36 that is housed in the booster piston 31 and receives one end of the return spring 25 in the pressure chamber 17. A seal member 37 is interposed between the inner peripheral surface of the cylindrical guide portion 7 of the front cover 4 of the housing 2 and the booster piston 31 to prevent foreign matter from entering between the two.

  On the other hand, the rear end portion of the input piston 32 is connected to the front end portion of the input rod 9 interlocking with the brake pedal so as to be swingable. The input piston 32 moves forward and backward in the booster piston 31 by operating the brake pedal. A flange portion 38 is integrally formed in the middle of the input rod 9. Since the flange portion 38 is in contact with an inward projection 39 formed integrally with the rear end of the cylindrical guide portion 8 of the rear cover 6, movement of the input rod 9 to the rear side (vehicle compartment side) is restricted. . The input rod 9 is connected in a state in which the spherical portion 9a at the tip thereof is fitted in a spherical concave portion 32a formed at the rear end of the input piston 32. Thereby, the swing of the input rod 9 is allowed.

  In the housing 2 of the electric booster 1, an electric motor 40 as a three-phase motor that operates by receiving supply of a three-phase alternating current, and the piston assembly is converted by converting the rotation of the electric motor 40 into a linear motion. A ball screw mechanism 50 serving as a rotation-linear motion converting mechanism that is transmitted to a booster piston 31 that constitutes the three-dimensional body 30 is provided. The electric motor 40 generates power for assisting the depressing force from the brake pedal, thereby moving the booster piston 31 and generating hydraulic pressure in each of the pressure chambers 17 and 18 to generate a braking force of the vehicle. It has become. As the electric motor 40, a three-phase concentrated winding DC brushless motor is used. The electric motor 40 includes a stator 41 housed in the housing 2, a hollow rotor 42, and a rotation sensor 66 such as a resolver as a rotational position detector. The stator 41 is disposed between the housing body 3 and the rear cover 6 in a fixed manner. In this embodiment, the stator 41 is composed of 16 poles and 18 slots. The rotor 42 is rotatably supported by the housing body 3 and the rear cover 6 via bearings 43 and 44. In the present embodiment, the rotor 42 has a permanent magnet for 16 poles attached to the outer periphery thereof.

  The ball screw mechanism 50 includes a nut member 52 that is non-rotatably fitted to the rotor 43 of the electric motor 40 via a key (not shown), and a hollow screw shaft that is engaged with the nut member 52 via a ball 53. (Linear motion member) 54. A slit 55 extending in the axial direction is formed at the rear end of the screw shaft 54. An inward projection 39 at the rear end of the rear cover 6 is inserted into the slit 55. That is, the screw shaft 54 is disposed in the housing 2 so as not to rotate but to be movable in the axial direction. Accordingly, when the nut member 52 rotates integrally with the rotor 42, the screw shaft 54 moves linearly. On the other hand, the screw shaft 54 includes an inner flange 56 at the start end portion of the slit 55. An outer flange portion 57 a formed at the rear end of the extension cylinder portion 57 of the booster piston 31 is in contact with the inner flange portion 56.

  A potentiometer 65 (not shown in FIG. 1) for detecting the absolute displacement of the input piston 32 (input rod 9) with respect to the vehicle body through the movement of the brake pedal is disposed in the fixed portion in the vehicle compartment. On the other hand, a rotation sensor 66 (resolver) that detects the absolute displacement of the booster piston 31 relative to the vehicle body from the rotational displacement of the electric motor 40 is disposed in the housing 2. A pressure sensor 69 for detecting the brake fluid pressure in the pressure chamber 17 of the master cylinder 10 is provided on one of the brake pipes 28 connecting the master cylinder 10 and the hydraulic circuit. As shown in FIG. 2, detection signals from the potentiometer 65, the rotation sensor 66, the pressure sensor 69, and a temperature sensor 80 (thermistor) described later are sent to an ECU (electronic control unit) 70 serving as a motor driving device. It is like that.

  The ECU 70 is defined and arranged on the outer peripheral side of the electric motor 40 in the housing 2 and controls the rotation of the electric motor 40 (rotor 43) based on the signals of the respective sensors. The ECU 70 includes an inverter circuit 71 that supplies current to the electric motor 40, a driver circuit 72 that operates a switching element of the inverter circuit, and a control circuit 73 that controls the driver circuit. The above-described potentiometer 65, rotation sensor 66, pressure sensor 69, and temperature sensor 80 are connected to the control circuit 73. The control circuit 73 recognizes the rotation angle that is the rotation position of the rotor 42 of the electric motor 40 from the signal of the rotation sensor 66. Then, the control circuit 73 drives the driver circuit so that a current having a phase corresponding to the rotation angle flows through the three-phase coils (U, V, W-phase coils 81U, 81V, 81W) of the stator 41, and the inverter circuit 71. Thus, the rotation of the electric motor 40 (rotor 42) is controlled by causing a current to flow through the three-phase coils (U, V, W-phase coils 81U, 81V, 81W).

  The temperature sensor 80 is arranged in the vicinity of the joint surface with the housing 2 in the ECU 70, and measures both the temperature of the housing 2 and the temperature of the ECU 70.

In the electric booster 1 of the present embodiment, the depression of the brake pedal, that is, the forward movement of the input piston 32 is detected by the potentiometer 65, and the electric motor 40 is rotated according to the detected value. The rotation of the electric motor 40 is converted into a linear motion by the ball screw mechanism 50, and the booster piston 31 moves forward. As a result, brake fluid pressure corresponding to the input thrust applied from the brake pedal to the input piston 32 and the booster thrust applied from the electric motor 40 to the booster piston 31 is generated in the pressure chambers 17 and 18 in the master cylinder 10. .
In the electric booster 1, when the brake pedal is held down and a constant hydraulic pressure is generated, a current flows through the electric motor 40 and torque is generated. 42 is not rotating and remains stationary. Since a three-phase DC brushless motor is used as the electric motor 40, the phase current flowing in each phase of the electric motor 40 is shifted in phase by 120 ° in terms of electrical angle. Assuming that the electric motor 40 is stationary while generating a constant torque, the absolute values of the current values of the phase currents flowing through the U, V, and W phase coils 81U, 81V, and 81W are different for each phase, and the coils for each phase A difference will be produced in the temperature of 81U, 81V, and 81W. Therefore, among the coils 81U, 81V, 81W of each phase, the coil of the phase having the largest absolute value of the current value of the phase current is the coil having the highest temperature.

Here, in this embodiment, one temperature sensor 80 such as a thermistor is provided, and the temperature sensors 80 are not provided in the coils 81U, 81V, 81W of the respective phases, and the detection value of the temperature sensor 80 is used. Thus, the temperatures of the coils 81U, 81V, 81W of the respective phases are estimated, and this estimated value is used for the rotor rotational position movement control described later.
Prior to the description of the operation of the present embodiment, the method for calculating the estimated temperatures of the coils 81U, 81V, 81W of each phase and the hydraulic pressure (the hydraulic pressure generated by the electric booster in the pressure chamber 17 of the master cylinder 10). And the corresponding relationship between each phase coil current (U, V, W phase current) will be described.

  The electric motor 40 has three coils 81U, 81V, 81W corresponding to three phases (U, V, W phase). The coils 81U, 81V, 81W for each phase are connected to the inverter circuit 71 via wiring extending to the ECU 70. Current sensors 83U, 83V, and 83W are provided for wiring in the ECU 70, respectively. Current sensors 83U, 83V, and 83W measure currents flowing through U, V, and W phase coils 81U, 81V, and 81W, and output detection signals to control circuit 73. Note that three current sensors are not necessarily required, and it is also possible to measure the current of two phase coils and obtain the remaining one phase coil current by calculation.

  First, the heat generation of the coils 81U, 81V, 81W of each phase is 2 of the resistance of the coils 81U, 81V, 81W of each phase and the current value (U, V, W phase current) of the coils 81U, 81V, 81W of each phase. It is a product of powers. From this, the temperature rise of each coil 81U, 81V, 81W can be estimated from the current value of each coil 81U, 81V, 81W. That is, the temperature rise ΔTu1, ΔTv1, ΔTw1 due to the currents of the coils 81U, 81V, 81W of each phase is the product of the proportionality constant k1, the square of each coil current Iu, Iv, Iw and the energization time (unit time) Δt. Determined. The temperature rises ΔTu1, ΔTv1, ΔTw1 can be expressed as (1), (1) ′, (1) ″, respectively.

ΔTu1 = k1 · Iu2 × Δt (1)
ΔTv1 = k1 · Iv2 × Δt (1) ′
ΔTw1 = k1 · Iw2 × Δt (1) "

Using this equation, the temperature rise in the heat insulation condition of the heating element (coil) can be found. In the present embodiment, in order to improve accuracy, the characteristics of heat transfer from the coils 81U, 81V, 81W of the respective phases to the housing 2 and the like are grasped as follows.
The heat generated in the coils 81U, 81V, 81W of each phase flows to the housing 2 side through the iron core of the stator 41 and also flows to other adjacent coils through the iron core of the stator 41. In the present embodiment, the characteristics of these two heat transfer paths are grasped, the material and shape of the housing 2 are set so as to obtain good heat transfer characteristics, and the temperature distribution is set to be small. The heat transfer is modeled as shown in FIG.

  And the temperature change of the coil by the heat transfer from the coils 81U, 81V, 81W of each phase to the housing 2 includes the difference between the coil temperature Tu, Tv, Tw and the housing temperature Th by the temperature sensor 80, and the coil 81U of each phase. , 81V, 81W and the characteristics of heat transfer between the housing 2 and the housing 2. Assuming that k2 is a constant for heat transfer between the coil and the housing, the temperature changes ΔTu2, ΔTv2, ΔTw2 of the coil in unit time Δt are respectively expressed by equations (2), (2) ′, and (2) ″. be able to.

ΔTu2 = (Tu−Th) × (1−EXP (k2 × Δt)) (2)
ΔTv2 = (Tv−Th) × (1-EXP (k2 × Δt)) (2) ′
ΔTw2 = (Tw−Th) × (1-EXP (k2 × Δt)) (2) ”

  Further, the one-phase coil (U-phase coil) by heat transfer from the one-phase coil (for example, U-phase coil 81U) of the stator 41 to the other-phase coils (V, W-phase coils 81V, 81W). 81U) temperature change (ΔTu3) can be obtained from the difference in coil temperature of each phase and the characteristics of heat transfer between the coils. That is, if k3 is a constant for heat transfer between the coils, the temperature change ΔTu3 of the U-phase coil 81U per unit time Δt is affected by the temperature difference from the V phase and the temperature difference from the W phase. It becomes like the formula. Further, the temperature changes ΔTv3 and ΔTw3 of the V and W phase coils 81V and 81W are expressed by equations (3) ′ and (3) ”, respectively.

ΔTu3 = (Tu−Tv) × (1−EXP (k3 × Δt)) + (Tu−Tw) × (1−EXP (k3 × Δt)) (3)
ΔTv3 = (Tv−Tw) × (1−EXP (k3 × Δt)) + (Tv−Tu) × (1−EXP (k3 × Δt)) (3) ′
ΔTw3 = (Tw−Tu) × (1−EXP (k3 × Δt)) + (Tw−Tv) × (1−EXP (k3 × Δt)) (3) ”

  From the temperature rises ΔTu1, ΔTv1, ΔTw1 of the coils 81U, 81V, 81W of the respective phases obtained from the coil energization currents of the expressions (1), (1) ′, (1) ”, (2), (2) ′, (2) The temperature decrease ΔTu2, ΔTv2, ΔTw2 due to the characteristics of heat transfer between the coils 81U, 81V, 81W and the housing 2 of each phase of the equation (3), (3) ′, (3) ” By subtracting the temperature decrease ΔTu3, ΔTv3, ΔTw3 due to heat transfer between the coils 81U, 81V, 81W of each phase, the temperature change of the coils 81U, 81V, 81W of each phase per unit time Δt is estimated. The coil temperature of each previous phase estimated based on the actually measured temperature (initial value) of the temperature sensor 80 attached to the housing for the estimated temperature change of the coils 81U, 81V, 81W of each phase. Estimated value of By adding, it is possible to estimate the current coil temperatures Tu (n), Tv (n), and Tw (n) of each phase, and the calculation formulas at this time are the following (4), (4) ′, ( 4) "

Tu (n) = (k1 × Iu2) × Δt− (Tu (n−1) −Th) × (1-EXP (k2 × Δt))
− (Tu (n−1) −Tv (n−1)) × (1-EXP (k3 × Δt))
− (Tu (n−1) −Tw (n−1)) × (1-EXP (k3 × Δt))
+ Tu (n-1) (4)
Tv (n) = (k1 × Iv2) × Δt− (Tv (n−1) −Th) × (1-EXP (k2 × Δt))
− (Tv (n−1) −Tw (n−1)) × (1-EXP (k3 × Δt))
− (Tv (n−1) −Tu (n−1)) × (1-EXP (k3 × Δt))
+ Tv (n-1) (4) '
Tw (n) = (k1 × Iw2) × Δt− (Tw (n−1) −Th) × (1-EXP (k2 × Δt))
− (Tw (n−1) −Tu (n−1)) × (1-EXP (k3 × Δt))
− (Tw (n−1) −Tv (n−1)) × (1-EXP (k3 × Δ) t))
+ Tw (n-1) (4) "

  The estimation of the coil temperature Tu, Tv, Tw of each phase is performed for each unit time Δt while the brake system is in operation, and the above equations (4), (4) ′, (4) ″ Tu (n−1), Tv (n−1), and Tw (n−1) of the above are stored the previous estimated values of the coil temperature of each phase, and the initial value Tu (1) of the coil temperature. ), Tv (1), Tw (1)) are stored with housing temperature Th (actually measured temperature as the initial value) when the brake system is activated.

  FIG. 4 shows the temperature estimation of each coil in the flowchart. The temperature estimation process for each coil is continuously performed by the control circuit 73 while the brake system is activated.

  In step S1, for example, when the ignition key is turned on and the brake system is activated, the current I does not flow through the coils 81U, 81V, 81W of the phases, so the coils 81U, 81V, 81W of the phases and the housing 2 Are estimated to be equal to each other, and the estimated temperatures of the coils 81U, 81V, 81W of the respective phases are set to the same value as the housing temperature (the housing temperature Th is measured when the system is started) as an initial value.

  In step S2, the housing temperature Th is measured, and in step S3, the temperature change of the coils 81U, 81V, 81W of each phase during the unit time Δt and the previous estimated coil temperature values Tu (n−1), Tv. By adding (n-1) and Tw (n-1), the current estimated coil temperature values Tu (n), Tv (n), and Tw (n)) can be obtained. Then, it is determined in step S4 whether or not the brake system has stopped, and steps S2 and S3 are repeated while the brake system is operating. When the ignition key is turned off and the brake system is stopped in step S4, the temperature estimation of each coil is finished.

Next, an outline of the control of the electric motor in the present embodiment will be described.
In braking operation while the vehicle is running, if the generated hydraulic pressure is low, the amount of heat generated by the coils of each phase is small, and if the generated hydraulic pressure is high, the vehicle decelerates or stops in a short time. The temperature rise of the booster motor is generally not large. Rather, the temperature rise for the electric motor of the electric booster is severe when the brake pedal is continuously depressed while the vehicle is stopped.
In particular, when the rotation of the electric motor 40 is stopped and the hydraulic pressure generated in the master cylinder 10 is maintained at a constant hydraulic pressure, the phase having a large absolute value of the current value of the three-phase coils 81U, 81V, 81W. The coil heat generation increases. And if the temperature rise of a coil progresses and the temperature will exceed the heat-resistant temperature also in the coil of one phase, there exists a possibility of causing the burning of a coil.

  The ECU 70 (control circuit 73) determines the electrical angle of the motor so that the current flows efficiently according to the rotational position of the rotor 42 detected by the rotation sensor 66, and based on this, the three-phase coil of the electric motor 40 The current flowing through 81U, 81V, and 81W is determined by the electric angle of the motor as shown in FIG. When the motor is rotating, the temperature rises in the same manner in each phase because there is a similar amplitude of current in each phase. However, when torque is generated in a state where rotation is stopped, heat generation differs depending on the motor position, and the heat generation of the coil is maximized at a position where an alternating peak current (current indicating a peak value) flows. In the position (i) in FIG. 5, the heat generation of the U-phase coil, the W-phase coil at the position (ii), and the V-phase coil at the position (iii) are maximized.

As described above, in the present embodiment, the brake fluid pressure is generated in the pressure chambers 17 and 18 in the master cylinder 10. The generated hydraulic pressure of the master cylinder 10 and the coil currents (U, V, W phase currents) of the U, V, W phases of the motor have a correspondence relationship as shown in FIG. 6, for example.
The electric motor 40 generates torque in proportion to the three-phase effective current, and the torque required for the electric motor 40 increases as the hydraulic pressure increases, so the current amplitude (effective current) increases.
Since the heat generation of the electric motor 40 is proportional to the square of the current, the higher the generated hydraulic pressure, the larger the effective current and the greater the heat generation.
Usually, the hydraulic pressure generated by the electric booster 1 is generated according to the depression force of the brake pedal. However, when the brake pedal is stepped for a long time with a strong force, the coil 81U, 81V, 81W of each phase of the electric motor 40 is prevented from being burned out and the hydraulic pressure generation time by the master cylinder 10 is prevented. Need to be long.

That is, for example, as shown in FIG. 6, when energized continuously at a position [(iv)] where the generated hydraulic pressure is 4 MPa, the current flowing through the W-phase coil 81 </ b> W (W-phase current) has a peak value. For this reason, the temperature rise of the W-phase coil 81W increases.
For example, when energization is started at a position where the generated hydraulic pressure is 4 MPa as shown in FIG. 6 when the temperature in the engine room is 100 ° C. and the electric booster is also 100 ° C., each phase coil 7, for example, changes as shown in FIG. 7, and the temperature rise of the W-phase coil 81W in which the current is at a peak value proceeds rapidly, and reaches 170 ° C. in about 1200 seconds after the start of energization.

  When the peak current continues to flow through the W-phase coil 81W, the temperature of the W-phase coil 81W is about 180 seconds, which is the heat resistance temperature of each coil 81U, 81V, 81W, or a component in the vicinity of these coils. It will reach ℃. In this embodiment, the reference temperature T0 for limiting the temperature rise of the coil so as not to reach the heat resistant temperature is set to 170 ° C., and when the reference temperature T0 is reached, the current is deviated from the peak value. Control to move the. That is, in order to make the absolute values of the V and W phase currents equal to each other and the U phase current to 0 (minimum value) by energizing between the two phases (between W and V), for example, (ii) The electrical amplitude is increased by 30 ° from the state of the electrical angle of 150 °) so that the electrical angle is increased by 180 °. As the current amplitude increases, the rotor 42 rotates by an angle corresponding to an electrical angle of 30 °, and the electrical angle shifts from a state of 150 ° to 180 °. Thereby, the temperature of W-phase coil 81W can be lowered to 160 ° C., and an increase in coil temperature of electric motor 40 can be suppressed. Further, as described above, the time to reach the heat resistant temperature of 180 ° C. is extended to about 7000 seconds by one control. As a result, the hydraulic pressure generation time by the master cylinder 10 can be extended. Note that the above time varies depending on the coil material, wire diameter, heat resistance temperature of components in the vicinity of the coil or components in the ECU 70, etc. For example, if a coil with a smaller wire diameter is used, the heat resistance of the coil The above time becomes a shorter time because the characteristics are reduced.

  In the present embodiment, an increase in the coil temperature of each phase of the electric motor 40 can be suppressed as described above. In addition, in order to suppress an increase in the coil temperature of each phase of the electric motor 40, it may be possible to perform control to shift the phase to an inefficient electric angle without moving the rotor position. The efficiency of the motor is reduced, and the generated motor torque is reduced. In the present embodiment, this can be avoided.

Next, details of the control of the electric motor in the present embodiment will be described.
In order to prevent burning of the coils 81U, 81V, 81W of the respective phases of the electric motor 40 described above, the energizing current control shown in the flowchart of FIG. 8 is performed by the ECU 70 (control circuit 73).
First, this control is performed in parallel with the control to the electric motor 40 for propelling the booster piston 31 after the potentiometer 65 detects that the brake pedal has been depressed.

  In step S11, whether or not the brake pedal is being depressed with a constant force is determined based on the detection signal of the rotation angle sensor 66 based on whether or not the rotation of the rotor 42 continues for a predetermined time. If it is determined in step S11 that the rotor 42 has stopped rotating for a predetermined time, the process proceeds to step 12. Here, the predetermined time is set to be shorter than the time required to reach the heat resistant temperature when the maximum peak current value at the maximum hydraulic pressure of the master cylinder 10 is passed through the coils 81U, 81V, 81W of the respective phases. ing. Further, in the present invention, “rotation stop of the rotor 42 is continued” means that the change in the electrical angle of the three-phase coils 81U, 81V, 81W is not limited to the case where the rotor 42 has completely stopped rotating. It is used to include a case where the rotor 42 rotates very slightly within a range in which any one of the phases does not deviate from the peak value or a large current value before and after the peak value.

  In step S12, the temperature estimation result of each coil shown in the flowchart of FIG. In step 13, among the coils 81U, 81V, 81W of each phase, any one of the coil temperatures Tu, Tv, Tw is determined based on the reference temperature T0 (predetermined based on the above-described heat resistant temperature (for example, 180 ° C.)) For example, it is determined whether or not the temperature has reached 170.degree. This determination is performed until the coil temperature Tu, Tv, Tw of any phase reaches the reference temperature T0, and the detection signal of the rotation angle sensor 66 indicates that the rotor 42 has started to rotate again by operating the brake pedal. If it is determined in step S14 based on this, the control of this flowchart is terminated.

  If the coil temperature Tu, Tv, Tw of any phase reaches the reference temperature T0 in step S13, the current values (U, V, W) flowing through the coils 81U, 81V, 81W of the respective phases in step S15. In the direction in which the hydraulic pressure generated in the master cylinder 10 increases (the direction in which the booster piston 31 moves forward), that is, in the direction in which the rotor 42 advances by 60 ° in terms of electrical angle, so that the phase current is shifted from the peak value. Control to rotate forward. In this control, for example, the coil temperature Tw of the W-phase coil 81W is set to the reference temperature T0 when the electrical angle of the rotor 42 is at the position (ii) in FIG. 5, that is, the position (iv) in FIG. When it reaches, the rotor 42 is rotated in a direction that increases the electrical angle by 60 °.

  In this case, the W-phase coil 81W has a U-phase coil 81U whose absolute value of the current value of the W-phase coil 81W becomes equal to the current value when the coil current decreases from the peak value and becomes smaller. It becomes the same value as the temperature. At this time, by rotating the rotor 42 in the direction in which the booster piston 31 moves forward, the hydraulic pressure in the pressure chamber 17 of the master cylinder 10 increases, and the reaction force corresponding to the hydraulic pressure is transmitted via the input rod 17. In this embodiment, since the electrical angle of 60 ° is 7.5 ° of the rotation angle of the rotor 42, the hydraulic pressure rises slightly, and the brake pedal is transmitted to the brake pedal. Because it is stepped on with a strong force, it does not give the driver a sense of incongruity.

  Next, in step S16, the temperature estimation result of each coil is acquired again as in step 12, and the process proceeds to step 17. In Step 17, as in Step 13, it is determined whether any one of the coil temperatures Tu, Tv, Tw among the coils 81U, 81V, 81W of each phase has reached the reference temperature T0. This determination is performed until the coil temperature Tu, Tv, Tw of any phase reaches the reference temperature T0, and the detection signal of the rotation angle sensor 66 indicates that the rotor 42 has started to rotate again by operating the brake pedal. If it is determined in step S18 based on this, the control of this flowchart is terminated.

  If the coil temperature Tu, Tv, Tw of any phase reaches the reference temperature T0 in step S17, the current (U, V, W phase) flowing through the coils 81U, 81V, 81W of the respective phases is determined in step S19. Control is performed so that the booster piston 31 moves backward, that is, the rotor 42 rotates reversely in a direction where the electrical angle is reduced by 60 ° so that the current is shifted from the peak value. In this control, since the electrical angle of the rotor 42 is in the position (iii) of FIG. 5 by the process of step S15, the coil temperature Tv of the V-phase coil 81V at which the current is at the peak value. When the temperature reaches the reference temperature T0, the rotor 42 is rotated in a direction to reduce the electrical angle by 60 °, and the rotor 42 is returned to the original rotational angle position. In this case, the V-phase coil 81V has a U-phase coil 81U whose absolute value of the current value of the V-phase coil 81V becomes equal to the current value when the coil current decreases from the peak value and becomes smaller. It becomes the same value as the temperature. In this case, the braking force is slightly weakened. However, since the braking force is slightly strengthened in the previous step S15, only the original braking force is returned, and no trouble is caused.

  When the process of step S19 is completed, the process returns to step S12 again, and in step S14 or step 18, any one of the coils 81U, 81V, 81W of each phase is operated until the brake pedal is operated and the rotor 42 starts to rotate again. Each time the coil temperature of the current reaches the reference temperature T0, the forward and reverse rotation of the rotor 42 is repeated between the positions (ii) and (iii) of the electrical angle in FIG. An increase in coil temperature of the coils 81U, 81V, 81W of each phase can be suppressed. The generated hydraulic pressure of the master cylinder 10 that increases in the process of step 15 is generated by rotating the rotor 42 in the direction in which the booster piston 31 moves backward by the process of step S19. Will decrease and return to the original hydraulic pressure. At this time, in step S11, the generated hydraulic pressure of the master cylinder 10 at the time when it is determined that the rotor 42 has stopped rotating for a predetermined time is made not to fall below. By alternately moving the rotational position of the rotor 42 in this manner, the hydraulic pressure generated in the master cylinder 10 does not continue to increase by continuing to step on the brake pedal, so that the driver does not feel uncomfortable. In addition, when the rotational position of the rotor 42 is moved alternately, if the rotor 42 is determined not to drop below the generated hydraulic pressure of the master cylinder 10 when it is determined that the rotor 42 has stopped rotating for a predetermined time, As described above, it is not necessary to move between two points, and various movement patterns can be taken. Further, when the generated hydraulic pressure of the master cylinder 10 is sufficiently large in a stopping situation such as stopping on a horizontal road surface, the rotor 42 has stopped rotating for a predetermined time within a range where there is no problem in stopping. It is also possible to make it lower than the generated hydraulic pressure of the master cylinder 10 at the determined time. Furthermore, in the flowchart of FIG. 8 described above, this may be omitted if the predetermined time in step S11 is short.

  In the first embodiment, the case where the temperature of the coils 81U, 81V, 81W of each phase is estimated from the energization current and the detected value of the temperature sensor 80 is taken as an example, but the inverter circuit 71 is provided with an FET. In this case, the junction temperature of the FET can be estimated from the energization current and the detected value of the temperature sensor 80. In this case, in addition to the one temperature sensor 80 protecting the motor from overheating as executed in the first embodiment, the one temperature sensor 80 also provides the overheating protection of the ECU 70. It becomes possible to plan. In this case, the temperature sensor 80 can be used more efficiently. Of course, a temperature sensor may be provided for each phase coil 81U, 81V, 81W so as not to estimate the temperature of each phase coil 81U, 81V, 81W.

  In the above-described embodiment, the control of the electric motor 40 is such that the position of the rotor 42 is held after the electric motor 40 is driven, and the current flowing in the three-phase coils 81U, 81V, 81W at the time of the holding is a one-phase peak value. An example is given of the case where the coil (in the above example, the W-phase coil 81W) is performed at a predetermined temperature. Instead, the control of the electric motor 40 is set to a predetermined time in anticipation of the temperature rise of the coil temperature regardless of the detected value or estimated value of the coil temperature, and the rotational position of the rotor 42 is stopped after the electric motor 40 is driven. May be performed when the predetermined time has elapsed.

Further, in the above embodiment, it is detected based on the detection signal of the rotation angle sensor 66 that the rotation stop of the rotor 42 is continued after the rotation of the rotor 42 is stopped while the three-phase coils 81U, 81V, 81W are energized. The electric motor 40 is controlled when the one-phase coil (W-phase coil 81W) having the largest current value among the three-phase coils 81U, 81V, 81W reaches a predetermined temperature. As an example. Instead of this, it may be configured to detect that the rotation stop of the rotor 42 is continued based on the detection signal of the pressure sensor 69 that the generated hydraulic pressure of the master cylinder 10 is kept constant. Good. Further, it may be configured to detect that the rotation stop of the rotor 42 is continued by keeping the movement of the input piston (input member) 32 detected by the potentiometer 65 constant.
Further, the electric booster to which the present invention is applied is not limited to the electric booster shown in the present embodiment, and applies a force in the linear motion direction to the master cylinder using a three-phase motor. For example, the present invention can be applied to a motor driving device of an electric booster as shown in WO2004-5095.

[Second Embodiment]
In the first embodiment, the case where the ECU 70 as the motor driving device for the automobile brake and the electric motor 40 as the three-phase motor are used in the electric booster is taken as an example. You may make it use. One example (second embodiment) will be described with reference to FIGS. Of course, even when the present invention is used for an electric disc brake, the present invention is not limited to the second embodiment, and can be applied to other electric disc brakes using other three-phase motors. is there.
In FIG. 9, the electric disc brake 1A according to the second embodiment includes an ECU 70A and an electric motor 40A in place of the ECU 70 and the electric motor 40 of the first embodiment.
Further, in place of the temperature sensor 80, a rotor temperature sensor 80A (not shown) for detecting the temperature of the rotor 25A of the electric motor 40A is provided.

  The electric disc brake 1A supplies a control current from the inverter circuit 71A by the ECU 70A based on the operation of a brake pedal (not shown) by the driver to rotate the rotor 25A of the electric motor 40A. The rotation of the rotor 25A is decelerated at a predetermined reduction ratio by the differential reduction mechanism 100, converted into a linear motion by the ball ramp mechanism 101, and advances the piston 102. As the piston 102 advances, one of the brake pads 103 and 104 is pressed against the disc rotor 106. The caliper body 107 is moved by the reaction force of the piston 102 pressing, and the claw portion 108 presses the other brake pad 104 against the disc rotor 106 to generate a braking force. Further, after the braking operation, when the driver releases the brake pedal, the brake pads 103 and 104 return to the initial positions.

  With respect to wear of the brake pads 103 and 104, the adjustment screw 110 of the pad wear compensation mechanism 109 moves forward by the amount of wear to advance the ball ramp mechanism 101. The pad wear compensation mechanism 109 keeps the pad clearance between the disc rotor 106 and the brake pads 103 and 104 constant during non-braking.

  When the position of the rotor 25A is held while the electric motor 40A (three-phase motor) is energized, the ECU 70A has one of the coil temperatures (the temperatures of the coils 81U, 81V, 81W of each phase) [see FIG. When it is determined that the temperature has reached a predetermined temperature or higher based on the heat-resistant temperature (for example, 180 ° C.) of the coil or a component in the vicinity of the coil, as in the case of the first embodiment, the three-phase coil 81U , 81V, and 81W, the three-phase coils 81U, 81V, and 81W are energized so that the absolute value of the current value of the coil of the phase that has the largest current value among the phase currents that are supplied to The electric motor 40A is controlled so as to move the rotational position of the rotor 25A in the direction in which the pressing force of the brake pad 103 increases by changing the effective current.

  In the second embodiment, the ECU 70A and the electric motor 40A are used for the electric disc brake 1A. However, in the second embodiment as well, the ECU 70A controls the electric motor 40A as described above, and thus the first embodiment and the first embodiment. Similarly, the temperature rise of the coils 81U, 81V, 81W of each phase, and consequently the electric motor 40A can be suppressed. Of course, even when the present invention is used for an electric disc brake, the present invention is not limited to the second embodiment, but can be applied to other types of electric disc brakes using a three-phase motor. is there.

[Third Embodiment]
Next, 3rd Embodiment of this invention is described based on FIG. The third embodiment relates to control in the electric booster 1 shown in the first embodiment, and will be described with reference to FIGS. In the first embodiment described above, when the rotation of the rotor 42 is continuously stopped, it is assumed that the current of the coil of any one of the three-phase coils is at the peak value, and the electric angle is simply set. In the above description, the angle is advanced by 30 ° or 60 °. However, the phase coil with the highest temperature is not necessarily at the peak value. Even if it is not at the peak value in this way, it can be sufficiently applied by advancing the appropriate electrical angle of about 60 ° or more, but in the third embodiment, the rotation of the rotor 42 is stopped. Will be described in a more reliable manner even when the coil of the phase with the highest temperature is not at the peak value when it is continued for a predetermined time.
FIG. 10 is a waveform diagram showing the three-phase alternating current supplied to the electric motor 40 according to the third embodiment of the present invention corresponding to an electrical angle in which one cycle is 360 °. FIG. 11 is a characteristic diagram showing temperature changes of three-phase coils (U, V, W-phase coils 81U, 81V, 81W) for explaining the third embodiment of the present invention.

As in FIG. 6, the three-phase coils (U, V, W-phase coils 81U, 81V, 81W) shown in FIG. 2 have three-phase currents (U, V, W-phase currents) as shown in FIG. ) Is energized.
In the present embodiment, when the rotation stop of the rotor 42 shown in FIG. 1 is continued for a predetermined time while the electric motor 40 is energized, three-phase coils (U, V, W-phase coils 81U, 81V, 81W) are used. ) To determine which phase of the coil has the highest temperature. At this time, the absolute value of the current value of the phase current of the coil having the highest temperature is larger than the absolute value of the current value of the other two-phase currents, and each coil has a predetermined value. The electrical angle is In this case, the current of the phase current of the coil having the highest temperature is obtained by rotating the rotor 42 so that one of the other two-phase coils has an electrical angle at which the maximum peak current value is obtained. The absolute value is small. The relationship between the electrical angle having a predetermined width that varies depending on each coil and the electrical angle at which the rotor 42 should be rotated is as follows for each coil.

  When the temperature of the U-phase coil 81U is the highest and reaches the reference temperature T0 of 170 ° C, the electrical angle is between 30 ° and less than 150 °, or between 210 ° and less than 330 ° This is the case. When the electrical angle is between 30 ° and less than 150 °, the rotor 42 is moved to a rotational position where the electrical angle is 150 °. When the electrical angle is between 210 ° and less than 330 °, the rotor 42 is moved to a rotational position where the electrical angle is 330 °.

  In addition, when the temperature of the W-phase coil 81W reaches 170 ° C. which is the highest temperature and the reference temperature T0, the electrical angle is between 90 ° and less than 210 °, or 0 ° to less than 30 °. And between 270 ° and 360 °. When the electrical angle is between 0 ° and less than 30 °, the rotor 42 is moved to a rotational position where the electrical angle is 30 °. When the electrical angle is between 270 ° and 360 °, the rotor 42 is moved to a rotational position where the electrical angle of the next cycle is 30 °. When the electrical angle is between 90 ° and less than 210 °, the rotor 42 is moved to a rotational position where the electrical angle is 210 °.

  Furthermore, when the temperature of the V-phase coil 81V is the highest and reaches the reference temperature T0 of 170 ° C, is the electrical angle between 0 ° and less than 90 ° and between 330 ° and 360 ° or less? Or a case where the angle is between 150 ° and less than 270 °. When the electrical angle is between 0 ° and less than 90 °, the rotor 42 is moved to a rotational position where the electrical angle is 90 °. When the electrical angle is between 270 ° and 360 °, the rotor 42 is moved to a rotational position where the electrical angle of the next cycle is 90 °. When the electrical angle is between 150 ° and less than 270 °, the rotor 42 is moved to a rotational position where the electrical angle is 270 °.

  For example, when the rotation of the rotor 42 shown in FIG. 1 is stopped when the electric motor 40 is energized and is energized at a position where the electrical angle is 80 °, the current value to the U-phase coil 81U is the highest. The absolute value is a large current value, and the temperature of the U-phase coil 81U is high. When the temperature of the U-phase coil 81U reaches 170 ° C., which is the reference temperature T0, the current electrical angle is 80 °, so the master angle is set to 150 ° from the current electrical angle. The rotor 42 is moved to the rotational position on the side where the hydraulic pressure of the cylinder 10 is increased. Thereby, the absolute value of the current value of the phase current of the U-phase coil 81U can be reduced.

  Furthermore, the relationship between the elapsed time and the coil temperature at this time is as shown in FIG. That is, energization is started at an electrical angle of 80 °, and after about 1400 seconds have elapsed, the temperature of the U-phase coil 81U reaches 170 ° C., which is the reference temperature T0. Here, as described above, when the rotor 42 is moved to the rotational position on the side where the hydraulic pressure of the master cylinder 10 is increased so that the electrical angle becomes 150 °, the temperature of the U-phase coil 81U decreases.

However, since the current of the W-phase coil 81W becomes the maximum peak current value, the W-phase temperature increases this time and reaches 170 ° C. in about 1750 seconds.
Therefore, this time, since the temperature of the W-phase coil 81W becomes the highest temperature, the rotor 42 is moved to the rotational position on the side where the hydraulic pressure of the master cylinder 10 is increased so that the electrical angle becomes 210 °, and the U-phase is moved. The temperature of the coil 81U is lowered. Next, when the temperature of the V-phase coil 81V reaches 170 ° C. in about 2000 seconds, the temperature of the V-phase coil 81V becomes the highest temperature, so that the master cylinder 10 has an electrical angle of 90 ° in the next cycle. The rotor 42 is moved to the rotational position on the side where the hydraulic pressure is increased to lower the temperature of the V-phase coil 81V.
Thereafter, the processing described above is repeated (150 ° → 210 ° → 90 ° of the next cycle). By performing such repeated processing, an increase in the motor coil temperature can be suppressed.

  In the third embodiment, the current value of the coil of the phase in which the current (U, V, W phase current) flowing through the coils of each phase (U, V, W phase coils 81U, 81V, 81W) is the largest current value. Control is performed to move the rotational position of the rotor 42 of the electric motor 40 so that the absolute value of the electric angle becomes small. For this reason, similarly to the first embodiment, an increase in the motor coil temperature can be suppressed. In addition, it is possible to avoid unnecessarily reducing the generated motor torque as compared with the prior art in which the motor effective current is lowered in order to prevent the motor coil temperature from rising. It is possible to avoid an extremely long time. In this embodiment, every time the temperature of each phase coil (U, V, W phase coils 81U, 81V, 81W) reaches the reference temperature T0, the rotation position on the side where the hydraulic pressure of the master cylinder 10 is increased is set. The rotor 42 is moved, but when the temperature drop for each phase coil (U, V, W phase coils 81U, 81V, 81W) is completed, the rotational position on the side where the hydraulic pressure of the master cylinder 10 is lowered. Alternatively, the rotor 42 may be moved. By repeating this every round, it is possible to prevent an enormous increase in the hydraulic pressure of the master cylinder over time.

[Fourth Embodiment]
Next, an electric booster according to a fourth embodiment of the present invention will be described with reference to FIGS. The fourth embodiment relates to control in the structure of the electric booster 1 shown in the first embodiment, and will be described with reference to FIGS. The electric booster according to the fourth embodiment utilizes the fact that the current-generated hydraulic pressure characteristic of the electric motor (three-phase motor) included therein has a hysteresis characteristic when the hydraulic pressure is raised or lowered.
FIG. 12 shows the current supplied to the three-phase coils (U, V, W-phase coils 81U, 81V, 81W; see FIG. 2) of the electric motor 40 (see FIG. 1) in the fourth embodiment of the present invention. It is a figure which shows typically that correspondence with a hydraulic pressure has a hysteresis characteristic.

FIG. 13 is a waveform diagram showing currents supplied to the three-phase coils 81U, 81V, 81W of the fourth embodiment.
In the fourth embodiment, as shown in FIG. 12, when the effective current of the electric motor 40 is increased, the hydraulic pressure generated in the master cylinder 10 increases. Further, when the generated hydraulic pressure of the master cylinder 10 is increased and when it is decreased, the required current is different, and as described above, the current-generated hydraulic pressure characteristic of the electric motor 40 has a hysteresis characteristic.
On the other hand, the currents (U, V, W phase currents) flowing through the three-phase coils 81U, 81V, 81W corresponding to the hydraulic pressure are as shown in FIG. Become.

  In the fourth embodiment, a current is flowed so as to generate 4 MPa as the generated hydraulic pressure of the master cylinder 10 at the position (vi) in FIG. 13, for example, and then the pressure is lowered to the position (vii). Hold the hydraulic pressure.

  According to the fourth embodiment, hysteresis characteristics can be used, and the effect of reducing current (heat generation) is increased. When the electric booster according to the fourth embodiment is used for an automatic brake, in the automatic brake, a pressure larger than the target hydraulic pressure is once generated and held at a slightly returned position to efficiently generate heat. Well, it can be suppressed.

  DESCRIPTION OF SYMBOLS 1 ... Electric booster, 10 ... Master cylinder, 32 ... Input piston (input member), 40 ... Electric motor (three-phase motor), 42 ... Rotor, 50 ... Ball screw mechanism (rotation-linear motion conversion mechanism), 70 ... ECU (motor drive device), 81U, 81V, 81W ... U, V, W phase coils (three phase coils).

Claims (10)

In an automobile brake motor driving device for generating a braking force by energizing alternating phase currents having different phases to three-phase coils of a three-phase motor to rotate a rotor of the three-phase motor,
Each phase supplied to the three-phase coil when the rotation of the rotor is continued until a predetermined condition is satisfied after the rotation of the rotor is stopped while the three-phase coil of the three-phase motor is energized. The rotational position of the rotor is changed by changing the effective current applied to the three-phase coil so that the electrical angle position where the absolute value of the current value of the coil of the phase having the largest current value among the currents becomes small is obtained. A motor drive device for an automobile brake, characterized by performing control for moving the vehicle.   2. The motor driving device for an automobile brake according to claim 1, wherein the motor driving device drives a three-phase motor in conjunction with a brake pedal, and a rotational-linear motion in which a rotational force of a rotor of the three-phase motor is transmitted. It is characterized by driving a three-phase motor of an electric booster that generates a hydraulic pressure in the master cylinder by moving a force in a linear motion direction on the piston of the master cylinder by a conversion mechanism. Motor drive device for automobile brakes.   2. The motor drive device for an automobile brake according to claim 1, wherein the motor drive device is a three-phase electric disc brake that generates a braking force by pressing a friction pad against the disc rotor by the operation of the three-phase motor. A motor driving device for an automobile brake, which drives a motor.   4. The motor driving device for motor vehicle brake according to claim 1, wherein the predetermined condition is when a predetermined time has elapsed after the rotor has stopped rotating. .   4. The motor drive device for an automobile brake according to claim 1, wherein the predetermined condition is when a temperature of a coil of any one of the three-phase coils is equal to or higher than a predetermined temperature. A motor drive device for an automobile brake characterized by   The motor driving device for an automobile brake according to claim 2, wherein the rotational position movement control of the rotor is performed so as to move the rotor rotational position in a direction in which a generated hydraulic pressure of the master cylinder increases. Motor brake motor drive device.   4. The motor drive device for an automobile brake according to claim 3, wherein the rotational position movement control of the rotor is performed so as to move the rotor rotational position in a direction in which the pressing force of the friction pad increases. Motor drive device for automobile brakes.   The motor drive device for an automobile brake according to any one of claims 1, 2, 3, 6, and 7, wherein the rotational position movement control of the rotor is performed in a state where the rotation of the rotor is stopped, A motor driving device for an automobile brake, which is performed every time a coil of any phase of the coils reaches a predetermined temperature or higher.   7. The motor drive device for an automobile brake according to claim 1, wherein the rotational position movement control of the rotor is performed when the rotational position of the rotor is moved a plurality of times, and the generated liquid of the master cylinder A motor driving device for an automobile brake, wherein the rotor rotational position is moved alternately in a direction in which the pressure increases and a direction in which the pressure decreases.   8. The motor driving device for an automobile brake according to claim 1, wherein the rotational position movement control of the rotor is performed by pressing the friction pad when the rotational position of the rotor is moved a plurality of times. A motor drive device for an automobile brake, wherein the rotor rotation position is moved alternately in a direction in which the rotor increases and a direction in which the rotor decreases.