JP2021035206A - Motor drive device - Google Patents

Abstract

To provide a motor drive device capable of performing a high rotational output at emergency without increasing a physical construction of a motor.SOLUTION: In a motor drive device 10 which is adopted to a brake system of a vehicle to generate a brake fluid pressure by an output of a motor 80, a drive control part 200 controls an electric conduction to a coil to drive the motor 80. The drive control part 200 contains: a booster circuit 30 increasing a DC voltage Vb of a battery (an electric power supply) 15; a driving circuit 40 that outputs an AC voltage by converting an input voltage Vinv to be increased by the booster circuit 30; and a control circuit 20 that controls an operation of the booster circuit 30 and the driving circuit 40. The control circuit 20 includes an emergency determination part 25 that determines an emergency when a request for braking the vehicle at emergency is generated, and increases a step-up ratio of the booster circuit 30 at the emergency as compared with a normal time other than the emergency.SELECTED DRAWING: Figure 5

Description

The present invention relates to a motor drive device.

Conventionally, a motor is known to have a tubular stator in which a coil is wound and a rotor having a plurality of magnetic poles and provided inside the stator in the radial direction, and the rotor is rotated by an electromagnetic force generated by energizing the coil. Has been done. Further, a motor drive device is known in which the energization of a coil is controlled by a control unit to drive a motor.

For example, the electric motor disclosed in Patent Document 1 constitutes an electric actuator that presses a brake disc via an interlocking conversion mechanism in a brake system.

JP-A-2017-104010

Here, the background of the motor technology in the vehicle braking system will be described. In recent years, the adoption of automatic braking systems has been increasing in order to improve the safety functions and the needs for automobile auxiliary equipment systems accompanying automatic driving. In addition, with the increase in hybrid vehicles and electric vehicles, the adoption of hydraulic electric brake systems that replace the pressurizing source, which was previously covered by negative engine pressure, with an electric motor is increasing.

The hydraulic brake system includes a type that generates brake hydraulic pressure by operating the piston in the cylinder by converting the motor rotation into a linear motion with a ball screw, and the type that transmits the motor rotation to the gear mechanism as it is and the gear teeth. There is a type of gear pump that transports fluid at the meshing part and generates brake fluid pressure.

Further, the hydraulic brake is required to have a hydraulic pressure holding force for maintaining the braking force when the vehicle is stopped and a high followability to the braking operation. Therefore, the motor used in the hydraulic electric brake system is required to have both a high restraint torque in a low rotation region and a high rotation in a no-load (or low load) region.

Further, in the present specification, when a request for urgent braking of the vehicle occurs, such as when the driver suddenly depresses the brake pedal or when the front camera recognizes an obstacle in the automatic driving system, "emergency" is defined. Is defined as. There is a problem that the physique of the motor becomes large when trying to make a configuration capable of outputting up to the high rotation range required for emergency braking in an emergency.

The present invention has been created in view of the above points, and an object of the present invention is to provide a motor drive device capable of high rotation output in an emergency without increasing the physique of the motor.

The motor drive device of the present invention includes a motor (80) and a drive control unit (200), is applied to a vehicle brake system, and generates a brake hydraulic pressure by the output of the motor. The motor has a tubular stator (60) around which a coil (68) is wound, and a rotor (50) provided with a plurality of magnetic poles (57) in the circumferential direction and rotatable inside the stator. The drive control unit controls the energization of the coil to drive the motor.

The drive control unit includes a booster circuit (30) that boosts the DC voltage of the power supply (15), a drive circuit (40) that converts the input voltage boosted by the booster circuit and outputs an AC voltage, and a booster circuit and drive. A control circuit (20) for controlling the operation of the circuit is included. The control circuit has an emergency determination unit (25) that determines that it is an emergency when a request to brake the vehicle is urgently generated, and the boost ratio of the booster circuit is increased in an emergency as compared with a normal time other than an emergency. Enlarge.

Since the motor drive device of the present invention secures an increase in output required for emergency braking by boosting drive, the motor may satisfy the required output in the normal torque-rotation speed region. Therefore, high rotation output is possible in an emergency without increasing the physique of the motor.

When the supplied power is constant, the motor rotation speed increases due to the boosting, but the amount of current required for torque decreases. However, since the characteristic required for emergency braking is high rotation and low torque, the effect of a decrease in the amount of supplied current is small.

Schematic diagram of the vehicle braking system. FIG. 3 is an axial sectional view of a motor used in the motor driving device of one embodiment. FIG. 2 is a sectional view taken along the line III-III in the radial direction of FIG. FIG. 3 is an enlarged view of part IV. The block diagram of the motor drive device of one Embodiment. Torque-rotation speed characteristic diagram showing the output characteristics of the motor. A radial enlarged cross-sectional view showing a tooth shape of another embodiment.

As used herein, the term "embodiment" means an embodiment of the present invention. Hereinafter, an embodiment of the motor drive device will be described with reference to the drawings. The motor drive device of the present embodiment includes a motor and a drive control unit, is applied to a vehicle brake system, and generates brake fluid pressure by the output of the motor.

FIG. 1 schematically shows a vehicle braking system 90. The motor drive device 10 includes a motor 80 and a drive control unit 200 that drives the motor 80. The hydraulic pressure generated by the hydraulic pressure device 91 due to the output of the motor 80 is supplied to the brake caliper 93 via the pipe 92. The brake caliper 93 presses the pad against the brake disc 94 to brake the wheels.

Next, the configuration of the motor 80 will be described with reference to FIGS. 2 to 4. The motor 80 of the present embodiment is a three-phase brushless motor, and the housing 70, the stator 60, the rotor 50, and the like are provided coaxially with the rotation shaft O.

As shown in FIG. 2, the housing 70 has a bottomed tubular shape including a tubular portion 72 and a bottom portion 73. A collar portion 71 is formed around the open end of the cylinder portion 72. A bearing accommodating portion 74 for accommodating the bearing 77 on the bottom side is formed in the center of the bottom portion 73. A bearing accommodating portion 76 for accommodating the bearing 78 on the opening side is formed in the center of the housing cover 75 mounted on the opening side of the housing 70.

The tubular stator 60 is housed inside the tubular portion 72 of the housing 70, and a three-phase coil 68 is wound around the slot. The rotor 50 is provided inside the stator 60, and the shaft 59 is fixed to the center. Both ends of the shaft 59 are rotatably supported by bearings 77 and 78. The rotor 50 shown in FIG. 2 is configured by laminating a plurality of thin plate-shaped rotor cores in the axial direction, but may be configured by an integral rotor core.

As shown in FIGS. 3 and 4, the rotor 50 is provided with a plurality of (for example, 10 poles) permanent magnet magnetic poles 57 in the circumferential direction, and is rotatable inside the stator 60. A plurality of meat stealing portions 52 are formed in the radial intermediate portion of the rotor core 51. The rotor 50 of the present embodiment is configured by an IPM structure in which a plurality of magnetic poles 57 are embedded in the rotor core 51. Specifically, the plurality of magnetic poles 57 are embedded in the annular portion on the radial outer side of the meat stealing portion 52. The outer side of the magnetic pole 57 in the radial direction is covered with the front yoke portion 55, and the salient pole portion 53 is formed between the magnetic poles 57 adjacent to each other in the circumferential direction.

The stator 60 has a plurality of (for example, 12) teeth 62 protruding inward from the core back 61. A three-phase coil 68 is wound in a slot between adjacent teeth 62. The stator 60 illustrated in FIGS. 3 and 4 is composed of divided cores divided in the circumferential direction, but may be formed of an integral core.

Further, the teeth 62 of the present embodiment are formed in a straight shape having the same circumferential width between the tip portion 63 and the root side. This configuration is disclosed in Japanese Patent No. 5862145 (corresponding US publication: US9531222B2).

The brushless motor 80 having such a configuration rotates by the interaction between the rotating magnetic field formed in the stator 60 by energizing the coil 68 and the magnetic field by the magnetic pole 57 of the rotor 50, and outputs torque. Here, the motor used in the hydraulic electric brake system is required to have both a high restraint torque in a low rotation region and a high rotation in a no-load (or low load) region. In this embodiment, an IPM motor is selected in order to achieve both.

Further, in the vehicle braking system 90, there may be a request to urgently brake the vehicle, such as when the driver suddenly depresses the brake pedal or when the front camera recognizes an obstacle in the automatic driving system. .. There is a problem that the physique of the motor 80 becomes large when trying to make a configuration capable of outputting to a high rotation range required for an emergency brake in such an emergency. Therefore, the motor drive device 10 of the present embodiment is configured to be capable of high rotation output in an emergency without increasing the physique of the motor 80.

[Composition of motor drive device]
Next, the motor driving device 10 will be described with reference to FIGS. 5 and 6. The drive control unit 200 of the motor drive device 10 controls energization of the coil 68 to drive the motor 80. As shown in FIG. 5, the current sensor 85 detects two or more phase currents Iu, Iv, and Iw energized by the drive control unit 200 to the motor 80. Further, in the example of FIG. 5, a position sensor for detecting the rotor rotation angle of the motor 80 is not provided, and the motor 80 is driven without a sensor. The sensorless drive system is effective for reducing parts and space.

The drive control unit 200 includes a booster circuit 30, a drive circuit 40, and a control circuit 20. The booster circuit 30 boosts the DC voltage (hereinafter, “battery voltage”) Vb of the battery 15 as a “power source”. The drive circuit 40 converts the input voltage Vinv boosted by the booster circuit 30 and outputs an AC voltage. The control circuit 20 controls the operation of the booster circuit 30 and the drive circuit 40.

In the example of FIG. 5, the booster circuit 30 is composed of a chopper type boost converter including a filter capacitor 31, an inductor 32, a high potential side switching element 33, and a low potential side switching element 34. The filter capacitor 31 is provided at the input portion of the booster circuit 30 and removes power supply noise from the battery 15. One end of the inductor 32 is connected to the battery 15, and the other end is connected to the connection point between the high potential side switching element 33 and the low potential side switching element 34. An induced voltage is generated in the inductor 32 with a change in the current IL flowing in the booster circuit 30, and electrical energy is stored.

The high-potential side switching element 33 and the low-potential side switching element 34 are connected in series between the power supply line Lp and the ground line Lg of the drive circuit 40. The high-potential side switching element 33 and the low-potential side switching element 34 are complementarily turned on and off according to a gate signal commanded by the booster circuit control unit 23 of the control circuit 20.

When the high potential side switching element 33 is off and the low potential side switching element 34 is on, energy is stored in the inductor 32. When the high-potential side switching element 33 is on and the low-potential side switching element 34 is off, the energy stored in the inductor 32 is released, so that the input voltage Vinv in which the battery voltage Vb is boosted charges the smoothing capacitor 39. Will be done. Hereinafter, the ratio of the input voltage Viv to the battery voltage Vb is expressed as a step-up ratio K (= Vinv / Vb).

In the example of FIG. 5, the drive circuit 40 is composed of a three-phase inverter including six bridge-connected switching elements 41 to 46. The switching elements 41, 42, and 43 are U-phase, V-phase, and W-phase upper arm switching elements, respectively, and the switching elements 44, 45, and 46 are U-phase, V-phase, and W-phase lower arm switching elements, respectively. It is an element. The switching elements 41 to 46 of each phase are turned on and off according to a gate signal commanded by the drive circuit control unit 24 of the control circuit 20.

In this way, the drive circuit 40 converts the DC power of the input voltage Vinv into three-phase AC power, and applies the three-phase voltages Vu, Vv, and Vw to the motor 80. The smoothing capacitor 39 provided in the input portion of the drive circuit 40 smoothes the input voltage Vinv.

The control circuit 20 includes a booster circuit control unit 23 and a drive circuit control unit 24. The booster circuit control unit 23 and the drive circuit control unit 24 operate the booster circuit 30 and the drive circuit 40 based on well-known techniques such as duty ratio calculation and PWM control based ^{on the torque command Trq * or the like acquired from the upper vehicle control circuit.} Calculate the gate signal to be made.

Here, the booster circuit control unit 23 and the drive circuit control unit 24 may appropriately acquire information such as the battery voltage Vb, the booster circuit current IL, and the input voltage Vinv of the drive circuit 40 directly from the voltage sensor, the current sensor, or the like. Often, it may be calculated based on other parameters.

For example, the drive circuit control unit 24 acquires the phase currents Iu, Iv, and Iw detected by the current sensor 85, and calculates a gate signal to the drive circuit 40 by current feedback control. Here, in the sensorless control, the estimated angle θ is used as the angle information in the coordinate conversion calculation or the like. Further, the estimated angular velocity ω, which is a differential value of the estimated angle θ, is also used in the booster circuit control unit 23. The estimated angle θ is calculated by, for example, the technique disclosed in Japanese Patent Application Laid-Open No. 2009-148017.

Further, the control circuit 20 has an emergency determination unit 25 as a configuration peculiar to the present embodiment. The emergency determination unit 25 determines that it is an emergency when a request for urgently braking the vehicle occurs. For example, the emergency determination unit 25 determines that it is an emergency based on the depression speed and pedaling force of the brake pedal by the driver, the image of the front camera in the automatic driving system, and the like. In addition, the time other than the emergency is called the normal time.

When the emergency determination unit 25 determines that the control circuit 20 is in an emergency, the control circuit 20 increases the boost ratio K of the booster circuit 30 as compared with the normal time. FIG. 6 shows the torque-rotation speed characteristics of the motor 80. Normally, a normal range from low torque to high torque is used at low rotation speed. In an emergency, a high speed, low torque emergency braking area is used.

For the sake of simplicity, the boost ratio K in the normal state is set to 1, and the boost ratio K in the emergency is set to a value larger than 1, for example, 2. That is, it is assumed that the normal time is substantially "non-boosting" and the emergency is "boosting". As in this example, it is preferable that the boost ratio in an emergency is set to a value that is twice or more the boost ratio in a normal state.

In FIG. 6, the motor characteristic at the time of non-boosting to cover the normal area at the minimum passes through the point Pn of the maximum rotation speed at the maximum torque Tmax_n at the time of non-boost, and is along the boundary between the normal area and the emergency braking area. It is indicated by the characteristic line Cn. Further, the motor characteristics at the time of boosting to cover the emergency braking area at the minimum pass through the point Pb of the maximum rotation speed at the maximum torque Tmax_b at the time of boosting, and the characteristic line Cb substantially parallel to the characteristic line Cn at the time of non-boosting. Shown.

The control circuit 20 determines the boost ratio K at the time of boosting so as to realize these characteristic lines Cn and Cb. When the battery voltage Vb is low, for example, the boost ratio K in the normal state may be 1.5 and the boost ratio K in the emergency may be 3. In that case, "at the time of non-boost" may be read as "at the time of low boost" and "at the time of boost" may be read as "at the time of high boost" in the above description.

As described above, in the motor drive device 10 of the present embodiment, the output increase required for the emergency brake is secured by the boost drive. Therefore, if the motor 80 satisfies the output required in the normal torque-rotation speed region. Good. Therefore, high rotation output is possible in an emergency without increasing the physique of the motor 80.

When the supplied power is constant, the motor rotation speed increases due to the boosting, but the amount of current required for torque decreases. However, since the characteristic required for emergency braking is high rotation and low torque, the effect of a decrease in the amount of supplied current is small.

Further, in the motor 80 of the present embodiment, the rotor 50 is configured by an IPM structure. As a result, as described above, in the hydraulic electric brake system 90, both high torque in the low rotation region and high rotation in the no-load (or low load) region are realized.

Further, in the sensorless drive, the difference between the q-axis inductance and the d-axis inductance is large, and the salient pole ratio, that is, the ratio of the q-axis inductance to the d-axis inductance (Lq / Ld) should be separated from 1. In the present embodiment, the rotor 50 has a salient pole portion 53 formed between the magnetic poles 57 adjacent to each other in the circumferential direction. Therefore, when the salient pole ratio is larger than 1, the effect of increasing the salient pole ratio can be obtained. Be done.

However, when the motor 80 having the salient pole 53 is driven without a sensor, the salient pole 53 is activated when the salient pole 53 and the teeth 62 of the stator 60 are energized and started at a rotation position near an advance angle of 0 degrees. Magnetic saturation is likely to occur, making it difficult to maintain the salient pole ratio required for position estimation.

On the other hand, in the motor 80 of the present embodiment, since the tip 63 of the teeth 62 is formed in a straight shape, the tip of the teeth has a shape that extends to both sides in the circumferential direction as shown in FIG. It is possible to suppress the leakage flux from both ends in the circumferential direction to the front yoke portion 55. Therefore, the salient pole portion 53 is less susceptible to the influence of the stator excitation, and is less likely to be magnetically saturated.

(Other embodiments)
(A) In the motor of the above embodiment, the teeth 62 of the stator 60 are formed in a straight shape. On the other hand, as shown in FIG. 7, the tip portion 639 of the teeth 62 may have a shape extending on both sides in the circumferential direction.

(B) The three-phase brushless motor shown in FIGS. 3 and 4 has a configuration of 10 poles and 12 slots, but the number of magnetic poles and slots (or teeth) is not limited to this. Further, the number of phases of the motor is not limited to three, and a multi-phase motor having four or more phases may be used.

(C) The rotor of the motor is not limited to the IPM structure in which a plurality of magnetic poles are embedded in the rotor core 51, and may be configured by an SPM structure in which a plurality of magnetic poles are installed on the surface of the rotor core. For example, FIG. 39, paragraph [0156] of Japanese Patent Application Laid-Open No. 2014-121189 discloses an inset type SPM structure in which magnetic poles are attached to recesses formed on the outer peripheral surface of a rotor core. In this structure, the q-axis inductance and the d-axis inductance are different and have a salient polarity, so that sensorless drive can be performed by position estimation using the salient pole ratio.

(D) The method for estimating the angle of rotation by sensorless drive is not limited to the method disclosed in Japanese Patent Application Laid-Open No. 2009-148017, and a well-known method using an extended induced voltage or the like may be adopted. Further, the drive of the motor is not limited to the sensorless drive method, and may be driven by a method of feeding back the rotation angle by a position sensor.

As described above, the present invention is not limited to such embodiments, and can be implemented in various embodiments without departing from the spirit of the present invention.

The drive control unit and its method described in the present disclosure are provided by a dedicated computer provided by configuring a processor and memory programmed to perform one or more functions embodied by a computer program. It may be realized. Alternatively, the drive control unit and its method described in the present disclosure may be realized by a dedicated computer provided by configuring the processor with one or more dedicated hardware logic circuits. Alternatively, the drive control unit and its method described in the present disclosure are a combination of a processor and memory programmed to perform one or more functions and a processor composed of one or more hardware logic circuits. It may be realized by one or more dedicated computers configured by. Further, the computer program may be stored in a computer-readable non-transitional tangible recording medium as an instruction executed by the computer.

10 ・ ・ ・ Motor drive device,
15 ・ ・ ・ Battery (power supply),
200 ... Drive control unit,
20 ・ ・ ・ Control circuit, 25 ・ ・ ・ Emergency judgment unit,
30 ・ ・ ・ Boost circuit, 40 ・ ・ ・ Drive circuit,
50 ・ ・ ・ Rotor, 57 ・ ・ ・ Magnetic pole,
60 ・ ・ ・ Stator, 68 ・ ・ ・ Coil,
80 ... Motor.

Claims (4)

A tubular stator (60) around which a coil (68) is wound, and a motor (80) having a rotor (50) that is provided with a plurality of magnetic poles (57) in the circumferential direction and can rotate inside the stator. ,
A drive control unit (200) that controls energization of the coil and drives the motor,
It is a motor drive device that is applied to the brake system of a vehicle and generates a brake fluid pressure by the output of the motor.
The drive control unit includes a booster circuit (30) that boosts the DC voltage of the power supply (15), a drive circuit (40) that converts the input voltage boosted by the booster circuit and outputs an AC voltage, and the booster. Includes a control circuit (20) that controls the operation of the circuit and the drive circuit.
The control circuit has an emergency determination unit (25) that determines that it is an emergency when a request for urgently braking the vehicle occurs, and the booster circuit is used in the emergency as compared with a normal time other than the emergency. Motor drive device that increases the boost ratio of. The motor drive device according to claim 1, wherein the rotor is composed of an IPM structure in which a plurality of the magnetic poles are embedded in a rotor core (51). The motor driving device according to claim 1 or 2, wherein the rotor has a salient pole portion (53) formed between the magnetic poles adjacent to each other in the circumferential direction. The stator has a plurality of teeth (62) protruding inward from the core back (61).
The motor drive device according to any one of claims 1 to 3, wherein the teeth are formed in a straight shape having the same circumferential width between the tip portion (63) and the root side.

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