WO2021186818A1

WO2021186818A1 - Sensor magnet, rotor, and motor

Info

Publication number: WO2021186818A1
Application number: PCT/JP2020/046787
Authority: WO
Inventors: 藤田　淳
Original assignee: 日本電産株式会社
Priority date: 2020-03-18
Filing date: 2020-12-15
Publication date: 2021-09-23
Also published as: JPWO2021186818A1; CN115280664A

Abstract

There have been cases in which a conventional position estimation method cannot estimate the rotational position of a rotor in the range in which a rotor angle is less than one turn. Therefore, it has been difficult for the method to be applied to drive motors of applications such as, for example, robots and carrier vehicles in which a preparatory operation of rotating a rotor for a position estimation is not allowed. This sensor magnet is rotatable about the central axis. The sensor magnet has a plurality of pole pairs arranged in the circumferential direction, wherein the plurality of pole pairs have axial magnetic field intensities different from each other.　According to the present invention, provided are a sensor magnet and a rotor that eliminate the need of a preparatory rotation operation for a position estimation.

Description

Sensor magnet, rotor, motor

The present invention relates to a sensor magnet, a rotor, and a motor.

Conventionally, as a motor capable of accurately controlling the rotor position, a configuration including an absolute angle position sensor such as an optical encoder or a resolver is known. However, the absolute angle position sensor is large and expensive. Therefore, Patent Document 1 discloses a method of estimating the rotational position of the rotor of a motor without using an absolute angle position sensor.

Japanese Patent No. 6233532

In the position estimation method described in Patent Document 1, the rotation position of the rotor may not be estimated in the range where the rotor angle is less than one rotation. Therefore, it has been difficult to apply it to applications where the preliminary operation of rotating the rotor for position estimation is not allowed, for example, a drive motor such as a robot or a transport vehicle.

According to one aspect of the present invention, the sensor magnet is rotatable around the central axis and has a plurality of polar pairs arranged in the circumferential direction, and the plurality of polar pairs have different axial magnetic field strengths from each other. , Sensor magnets are provided.

According to another aspect of the present invention, there is a rotor that can rotate around a central axis, and has a rotor core and a rotor magnet fixed to the rotor core, and the rotor magnets are arranged in a plurality of circumferential directions. Provided is a rotor having a pair of pole pairs of the above, wherein the plurality of pole pairs have different axial magnetic field strengths from each other.

According to one aspect of the present invention, there is provided a sensor magnet and a rotor that can eliminate the need for preliminary rotational operation for position estimation.

FIG. 1 is a schematic cross-sectional view of the motor of the first embodiment. FIG. 2 is a perspective view of the sensor magnet of the first embodiment. FIG. 3 is a functional block diagram of the motor of the first embodiment. FIG. 4 is an explanatory diagram showing the relationship between the pole pair number, the section, and the segment. FIG. 5 is an explanatory diagram showing the relationship between the waveform of the magnetic sensor and the section. FIG. 6 is an explanatory diagram showing the feature points of the waveform of the magnetic sensor. FIG. 7 is an explanatory diagram of the position estimation method. FIG. 8 is a flowchart of the position estimation method of the first embodiment. FIG. 9 is a perspective view of the sensor magnet of the modified example. FIG. 10 is an explanatory diagram of a position estimation method using a modified example sensor magnet. FIG. 11 is a schematic cross-sectional view of the motor of the second embodiment. FIG. 12 is a perspective view of the rotor of the second embodiment. FIG. 13 is a functional block diagram of the motor of the second embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In the following description, the direction parallel to the central axis J is defined as the Z-axis direction, and is simply referred to as the "axial direction". The radial direction centered on the central axis J is simply called the "diameter direction". The circumferential direction centered on the central axis J, that is, the axial direction of the central axis J is simply referred to as the "circumferential direction". The positive side (+ Z side) in the Z-axis direction is called the "upper side", and the negative side (-Z side) in the Z-axis direction is called the "lower side". In the present embodiment, the negative side in the Z-axis direction corresponds to "one side in the axial direction", and the positive side in the Z-axis direction corresponds to "the other side in the axial direction".
The upper side and the lower side are names used only for explanation, and do not limit the actual positional relationship or direction.

(First Embodiment)
FIG. 1 is a cross-sectional view showing a motor of the first embodiment.
The motor 1 of the present embodiment includes a rotor 20 centered on a central axis J, a stator 30 arranged radially outside the rotor 20, a control board 50, a housing 11, and a plurality of

bearings

15 and 16. To be equipped. The motor 1 is an inner rotor type motor. The rotor 20 rotates about the central axis J with respect to the stator 30.

The housing 11 houses the rotor 20, the stator 30, and the control board 50. The housing 11 has a cylindrical shape extending in the axial direction. The housing 11 has a peripheral wall portion 11a, a top wall portion 11b, a bottom wall portion 11c, and a bearing holding portion 11d. The peripheral wall portion 11a has a cylindrical shape extending in the axial direction. The top wall portion 11b closes the opening on the upper side of the peripheral wall portion 11a. The bottom wall portion 11c closes the opening on the lower side of the peripheral wall portion 11a. The bottom wall portion 11c holds the bearing 16. The bearing holding portion 11d is fixed to the inner peripheral surface of the peripheral wall portion 11a. The bearing holding portion 11d holds the bearing 15.

The rotor 20 includes a shaft 21, a rotor core 22, a rotor magnet 23, and a sensor magnet 24. The shaft 21 is a columnar shape extending in the axial direction. The shaft 21 may have a cylindrical shape extending in the axial direction. The shaft 21 is rotatably supported around the central axis J by a plurality of

bearings

15 and 16. The plurality of

bearings

15 and 16 are arranged at intervals in the axial direction and are supported by the housing 11. That is, the shaft 21 is supported by the housing 11 via a plurality of

bearings

15 and 16.

The rotor core 22 has a cylindrical shape extending in the axial direction. The rotor core 22 has an outer diameter larger than that of the shaft 21. The rotor core 22 is shorter than the shaft 21 in the axial direction. The inner peripheral surface of the rotor core 22 is fixed to the outer peripheral surface of the shaft 21. The rotor core 22 is located between the pair of

bearings

15 and 16 in the axial direction. The rotor magnet 23 is fixed to the outer peripheral portion of the rotor core 22.

The sensor magnet 24 is fixed to the upper end of the shaft 21. As shown in FIG. 2, the sensor magnet 24 has an annular magnet 25 extending in the circumferential direction around the central axis J, and a yoke 26A located on a lower surface (one side in the axial direction) of the annular magnet 25. .. The annular magnet 25 has a plurality of magnetic poles arranged in the circumferential direction on the upper surface of the annular magnet 25. In the case of the present embodiment, the north pole and the south pole are alternately arranged in the circumferential direction on the upper surface of the annular magnet 25. The annular magnet 25 has four pole pairs.

The yoke 26A is an annular magnetic plate. The yoke 26A has a structure in which a magnetic force adjusting layer 27A and a weight adjusting layer 28A are laminated in the axial direction. In the yoke 26A, the magnetic force adjusting layer 27A is located on the upper surface side (annular magnet 25 side), and the weight adjusting layer 28A is located on the lower surface side. The upper surface of the magnetic force adjusting layer 27A supports the lower surface of the annular magnet 25 from below.

The magnetic force adjusting layer 27A has a function of amplifying the magnetic force of the annular magnet 25. As a constituent material of the magnetic force adjusting layer 27A, a magnetic material that can be generally used as a yoke is used. The magnetic force adjusting layer 27A is, for example, a layer made of SUS400-based magnetic stainless steel.

The magnetic force adjusting layer 27A has a configuration in which the thickness in the axial direction continuously changes along the circumferential direction. In the case of the present embodiment, the magnetic force adjusting layer 27A is a layer whose thickness continuously changes over one circumference around the central axis J.

The weight adjusting layer 28A is made of a material or a non-magnetic material having a magnetic material weaker than the magnetic force adjusting layer 27A. The weight adjusting layer 28A is, for example, a layer made of SUS300-based non-magnetic stainless steel and having a specific gravity equivalent to that of the magnetic force adjusting layer 27A. Since the thickness of the magnetic force adjusting layer 27A changes along the circumferential direction, the weight also changes along the circumferential direction. When the yoke 26A composed of only the magnetic force adjusting layer 27A is rotated, the position of the center of gravity deviates from the central axis J, so that the vibration becomes large. Therefore, by adjusting the weight balance of the yoke 26A by the weight adjusting layer 28A, vibration during rotation can be suppressed.

The weight adjusting layer 28A has a thin shape when the magnetic force adjusting layer 27A is thick and a thick shape when the magnetic force adjusting layer 27A is thin. As a result, the yoke 26A can be made to have a uniform thickness in the circumferential direction. If the weight distribution of the yoke 26A in the circumferential direction can be made uniform, the thickness of the yoke 26A may be slightly non-uniform in the circumferential direction.

Magnetic sensors 220 (magnetic sensors 220-U, 220-V, 220-W) are arranged at positions facing the upper surface of the sensor magnet 24. The magnetic sensors 220-U, 220-V, 220-W detect the axial magnetic field of the sensor magnet 24.

Since the sensor magnet 24 includes the magnetic force adjusting layer 27A, the degree of magnetization of the magnetic force adjusting layer 27A acting on the pole pairs arranged in the circumferential direction is different for each pole pair. As a result, the plurality of pole pairs of the sensor magnet 24 are configured to have different axial magnetic field strengths from each other. In the case of the present embodiment, since the magnetic force adjusting layer 27A has a thickness that continuously changes in the circumferential direction, the axial magnetic field strength of the sensor magnet 24 has a maximum amplitude continuously along the circumferential direction. Change.

In the present embodiment, the magnetic force adjusting layer 27A is arranged on the upper surface side (the side facing the annular magnet 25) of the yoke 26A, and the weight adjusting layer 28A is arranged on the lower surface side of the yoke 26A. The axial positions of 27A and the weight adjusting layer 28A may be exchanged. That is, the yoke 26A may be used in a state where the upper and lower surfaces are turned upside down.

As shown in FIG. 1, the stator 30 faces the rotor 20 with a radial gap. The stator 30 surrounds the rotor 20 from the outside in the radial direction to the entire circumference in the circumferential direction. The stator 30 includes a stator core 31, an insulator 32, and a coil 33.

The stator core 31 is an annular shape centered on the central axis J. The stator core 31 has a cylindrical shape extending in the axial direction. The stator core 31 surrounds the rotor 20 from the outside in the radial direction. The stator core 31 is composed of, for example, a plurality of electromagnetic steel sheets laminated in the axial direction. The stator core 31 is fixed to the inner peripheral surface of the housing 11.

The stator core 31 has a core back 31a and a plurality of teeth 31b. The core back 31a has a cylindrical shape centered on the central axis J. The radial outer surface of the core back 31a is fixed to the inner peripheral surface of the peripheral wall portion 11a of the housing 11. The teeth 31b project radially inward from the inner peripheral surface of the core back 31a. The plurality of teeth 31b are arranged at intervals in the circumferential direction. The end surface of each tooth 31b facing inward in the radial direction faces the outer surface in the radial direction of the rotor 20 with a gap.

The insulator 32 is attached to the stator core 31. The insulator 32 is made of an insulating material. The insulator 32 is made of, for example, resin. The insulator 32 is an annular shape centered on the central axis J. The insulator 32 has an upper portion 32a facing the plurality of teeth 31b from at least the upper side, and a lower portion 32b facing the plurality of teeth 31b from at least the lower side. The upper portion 32a is an annular shape centered on the central axis J. Specifically, the upper portion 32a has a portion facing each tooth 31b from above and a portion facing each tooth 31b from the circumferential direction. The lower portion 32b is an annular shape centered on the central axis J. Specifically, the lower portion 32b has a portion facing each tooth 31b from the lower side and a portion facing each tooth 31b from the circumferential direction.

As shown in FIG. 1, the control board 50 is located above the bearing holding portion 11d. A control IC chip 51 or the like that drives and controls the motor 1 is mounted on the control board 50. In the case of the present embodiment, the magnetic sensor 220 is mounted in the central portion when viewed from the axial direction. That is, the control board 50 has a configuration in which the control IC chip 51 and the magnetic sensor 220 are mounted on a common circuit board 52. Therefore, the control board 50 includes a detection device 2 having a magnetic sensor 220.

As shown in FIG. 3, the motor 1 includes a detection device 2, an amplification device 3, a position estimation device 4, a control device 5, and a drive device 6.
In this embodiment, the detection device 2, the amplification device 3, the position estimation device 4, the control device 5, and the drive device 6 are mounted on the control board 50 as software or hardware. A device other than the detection device 2 or the detection device 2 and the amplification device 3 may be provided as an external control device.
In FIG. 3, only the detection device 2 of the control board 50 is shown inside the stator 30. In FIG. 3, only the housing 11, the stator 30, and the sensor magnet 24 are shown for the mechanical components of the motor 1.

The stator 30 includes windings of a plurality of slots of U phase, V phase and W phase. The stator 30 includes a 12-slot winding consisting of a 4-slot U-phase winding, a 4-slot V-phase winding, and a 4-slot W-phase winding. A three-phase current, which is out of phase by 120 degrees, is input to the stator 30 from the drive device 6. The stator 30 generates a magnetic field acting on the rotor 20 by a three-phase current input to each of the U-phase, V-phase, and W-phase windings.

The rotor 20 rotates around the central axis by receiving the magnetic force of the stator 30. The rotor 20 has a plurality of magnetic poles arranged in the circumferential direction. The 12-slot stator 30 of the present embodiment is combined with, for example, a rotor 20 having 8 poles, 10 poles, 16 poles, and the like.

The sensor magnet 24 includes two or more pole pairs (N pole and S pole). As shown in FIGS. 2 and 3, the sensor magnet 24 includes four pole pairs as an example. The sensor magnet 24 rotates about the central axis J together with the rotor 20. In the present embodiment, the pole pair of the sensor magnet 24 is assigned a pole pair number for position estimation. Sections and segments are associated with pole pair numbers.

FIG. 4 is a diagram showing an example of the correspondence between the pole pair number, the section, and the segment. A section number group consisting of a plurality of section numbers is associated with the pole pair number. The number of section numbers is equal to the number of 12 different logics including the magnitude relation of the output signals of the three magnetic sensors 220 of the detection device 2 and the positive / negative (zero cross) of the intermediate signal. In FIG. 4, 12 section numbers from “0” to “11” are associated with the pole pair number “0”. The segment number is a unique number representing the absolute value of the mechanical angle of the rotor 20. For example, the section numbers "0" to "11" of the pole pair number "0" are associated with the segment numbers "0" to "11". For example, the section numbers "0" to "11" of the pole pair number "1" are associated with the segment numbers "12" to "23". The data table showing the correspondence shown in FIG. 4 is stored in advance in, for example, a storage device 42 described later in the position estimation device 4.

The detection device 2 is a device that detects the magnetic field strength. The detection device 2 detects magnetic field strengths at three or more locations in the vicinity of the sensor magnet 24. The detection device 2 includes three or more magnetic sensors 220. As shown in FIG. 3, the detection device 2 includes a magnetic sensor 220-U, a magnetic sensor 220-V, and a magnetic sensor 220-W. In the present specification, when the individual magnetic sensors are not distinguished, they are collectively referred to as "magnetic sensor 220". The magnetic sensor 220 is, for example, a Hall element, a linear Hall IC (integrated circuit), or a magnetoresistive sensor. In the present embodiment, the magnetic sensor will be described as a Hall element.

The magnetic sensor 220-U is a sensor that detects the magnetic field strength of the U phase. The magnetic sensor 220-U outputs a U-phase differential signal, which is a differential signal representing the U-phase magnetic field strength, to the amplification device 3. The magnetic sensor 220-V is a sensor that detects the magnetic field strength of the V phase. The magnetic sensor 220-V outputs a V-phase differential signal, which is a differential signal representing the magnetic field strength of the V-phase, to the amplification device 3. The magnetic sensor 220-W is a sensor that detects the magnetic field strength of the W phase. The magnetic sensor 220-W outputs a W-phase differential signal, which is a differential signal representing the magnetic field strength of the W-phase, to the amplification device 3.

The amplification device 3 is a device that amplifies the amplitude of the waveform of the differential signal. The amplification device 3 includes a differential amplifier 300-U, a differential amplifier 300-V, and a differential amplifier 300-W. The differential amplifier 300-U generates an analog U-phase signal Hu by executing an amplification process on the U-phase differential signal. The differential amplifier 300-V generates an analog V-phase signal Hv by executing an amplification process on the V-phase differential signal. The differential amplifier 300-W generates an analog W-phase signal Hw by executing an amplification process on the W-phase differential signal.

The position estimation device 4 is an information processing device that estimates the rotational position of the rotor of the motor. The position estimation device 4 acquires an analog U-phase signal Hu, an analog V-phase signal Hv, and an analog W-phase signal Hw from the amplification device 3. The position estimation device 4 rotates the rotor 20 by selecting the section number and the pole pair number of the sensor magnet 24 based on the detected values of the U-phase signal Hu, the V-phase signal Hv, and the W-phase signal Hw. Estimate the position. The position estimation device 4 outputs the estimation result of the rotation position to the control device 5.

The control device 5 is an information processing device that generates a control signal. The control device 5 generates a control signal based on the instruction signal. The control signal is, for example, a signal representing a register value corresponding to a designated rotation direction (CW: clockwise, CCW: counterclockwise), and a signal representing a current value of a current output from the drive device 6 to the stator 30.

The drive device 6 is a device that drives the coil 33 of the stator 30. A control signal is input to the drive device 6 from the control device 5. The drive device 6 inputs a three-phase current of the current value represented by the control signal to each coil 33 of the stator 30. The drive device 6 rotates the rotor 20 by inputting a three-phase current to each coil 33 of the stator 30. Although the details will be described later, in the motor 1, the position of the rotor 20 is estimated in a state where the three-phase current is not input from the drive device 6 to each coil 33 of the stator 30. That is, the position estimation device 4 estimates the rotational position of the rotor 20 that is stopped. The position estimation device 4 can also estimate the rotation position of the rotating rotor 20.

The external device 7 is an information processing device that generates instruction signals such as the rotation direction, rotational force (torque), rotation angle, and rotation speed of the rotor. The external device 7 outputs an instruction signal to the control device 5.

Next, the details of the configuration example of the position estimation device 4 will be described.
As shown in FIG. 3, the position estimation device 4 includes a conversion device 40, an arithmetic unit 41, and a storage device 42. The conversion device 40 is a device that converts an analog signal into a digital signal. The conversion device 40 includes a conversion unit 400-U, a conversion unit 400-V, and a conversion unit 400-W.

The three conversion units 400-U, 400-V, and 400-W are devices that convert analog signals into digital signals. The conversion unit 400-U converts the analog U-phase signal acquired from the differential amplifier 300-U into a digital U-phase signal. The conversion unit 400-V converts the analog U-phase signal acquired from the differential amplifier 300-V into a digital V-phase signal. The conversion unit 400-W converts the analog W-phase signal acquired from the differential amplifier 300-W into a digital V-phase signal.

The arithmetic unit 41 is an apparatus that executes arithmetic processing. A part or all of the arithmetic unit 41 is realized by a processor such as a CPU (Central Processing Unit) executing a program expanded in a memory. A part or all of the arithmetic unit 41 may be realized by using hardware such as LSI (Large Scale Integration) or ASIC (Application Specific Integrated Circuit).

The arithmetic unit 41 includes a section selection unit 412 and an estimation unit 413.
The section selection unit 412 is connected to the conversion device 40. The estimation unit 413 is connected to the section selection unit 412. The estimation unit 413 is connected to the control device 5.

The section selection unit 412 acquires the detected values of the magnetic field strengths of the rotor 20 at three or more locations. The section selection unit 412 acquires the digitally converted U-phase signal Hu, V-phase signal Hv, and W-phase signal Hw from the conversion device 40.

The estimation unit 413 acquires the detected value of the magnetic field strength and the section number corresponding to the current position of the sensor magnet 24 from the section selection unit 412. The estimation unit 413 calculates the length of the composite vector obtained by three-phase and two-phase conversion of the detected value of the magnetic field strength as the pole-to-feature amount, and calculates the calculated pole-to-feature amount of the rotor 20 that has been learned in advance. Check the relationship between the pole pair number and the pole pair feature quantity. The estimation unit 413 outputs the estimation result of the rotation position of the rotor 20 to the control device 5.

The storage device 42 is preferably a non-volatile recording medium (non-temporary recording medium) such as a flash memory or an HDD (Hard Disk Drive). The storage device 42 may include a volatile recording medium such as a RAM (Random Access Memory). The storage device 42 stores data tables such as programs and learning values.

Next, the learning operation will be described.
FIG. 5 is a diagram showing an example of a waveform of magnetic field strength. In the case of this embodiment, the length of the composite vector obtained by three-phase and two-phase conversion of the detected value of the magnetic field strength for each segment is calculated as the pole pair feature amount. In the case of the first embodiment, the calculated pole pair feature amount is used as a learning value in association with each segment of the sensor magnet 24.

The learning value of the pole pair feature amount is generated in advance. The pre-generation processing of the learning value of the pole pair feature amount is performed, for example, before the shipment of the motor 1. In the pre-generation processing of the learning value of the pole pair feature amount, for example, the rotor 20 is rotated at a constant speed with the external position sensor connected to the rotor 20, and the waveform output from the detection device 2 is amplified by the amplification device 3. After that, it is performed by calculating the pole pair feature amount in the position estimation device 4.

The waveform shown in FIG. 5 is a waveform of the magnetic field strength according to the rotor angle of the rotor 20 when the rotor 20 is rotating in the pre-generation processing of the learning value of the pole pair feature amount. In FIG. 5, the correspondence between the learning value of the waveform of the U-phase signal Hu, the learning value of the waveform of the V-phase signal Hv, the learning value of the waveform of the W-phase signal Hw, and the section is the waveform of each magnetic field strength. It is shown as an example of the correspondence between the learning value of and the section. The digital value of the amplitude, which is a positive value, represents, for example, the digital value of the magnetic field strength of the N pole. The digital value of the amplitude, which is a negative value, represents, for example, the digital value of the magnetic field strength of the S pole.

As shown in FIG. 5, a section between two points arranged adjacent to each other among a plurality of zero cross points of three waveforms and a plurality of intersections of waveforms is set as a section. In the example shown in FIG. 5, the section from the zero crossing point of the U-phase signal Hu to the intersection of the U-phase signal Hu and the W-phase signal Hw is section “0”, and from the intersection of the U-phase signal Hu and the W-phase signal Hw. The section up to the zero crossing point of the W phase signal Hw is set in section "1". Hereinafter, a section is set for each section until the intersection of the waveforms or the zero crossing point is passed.

Here, the three-phase two-phase conversion of the detected value of the magnetic field strength will be described.
The waveform of the magnetic field strength of the sensor magnet 24 is shown in the upper part of FIG. As shown in FIG. 2, the sensor magnet 24 includes the magnetic field adjusting layer 27A whose thickness continuously changes along the circumferential direction, so that the maximum amplitude continuously changes along the circumferential direction. Has axial magnetic field strength. Therefore, the axial magnetic field strength of the sensor magnet 24 detected by the magnetic sensor 220 has a waveform in which the maximum amplitude continuously changes in the rotation direction, as shown in FIG.

The position estimation device 4 converts the U-phase signal Hu, the V-phase signal Hv, and the W-phase signal Hw input from the amplification device 3 into digital values by the conversion device 40, and then uses the matrix formula shown in the middle of FIG. Perform a phase-two-phase conversion. By the three-phase two-phase conversion, the U-phase signal Hu, the V-phase signal Hv, and the W-phase signal Hw are converted into α-axis and β-axis signals of the two-phase coordinate system. The converted signals Hα and Hβ can be expressed as composite vectors (Hα and Hβ) of the Cartesian coordinate system as shown in the lower part of FIG.

As shown in the lower part of FIG. 6, the tip positions of the composite vectors (Hα, Hβ) move in a spiral shape centered on the origin as the rotor 20 rotates. That is, the magnitude of the composite vector (Hα, Hβ) changes continuously with the rotation of the rotor 20. The magnitude of the composite vector (Hα, Hβ) corresponds to the axial magnetic field strength of the sensor magnet 24. The position estimation device 4 calculates the magnitude of the composite vector (Hα, Hβ) as the pole pair feature quantity.

In the learning operation, a data table showing the correspondence between the pole pair feature amount, which is the magnitude of the composite vector (Hα, Hβ), and the segment number of the sensor magnet 24 is created. As a result, for example, a data table in which the pole pair features are associated with each of the 48 segments shown in FIG. 4 is created. The created data table is stored in advance in, for example, the storage device 42.

Next, an operation example of the position estimation device 4 will be described with reference to FIGS. 7 and 8.
FIG. 7 is a diagram showing an example of detecting a waveform of magnetic field strength. At the time of detection shown in FIG. 7, the rotation of the rotor 20 is stopped, and the detection device 2 is energized. The reference numeral “kT” shown in FIG. 7 represents the rotor angle (rotational position) of the rotor 20 at the time when the detected value in the waveform of the magnetic field strength is sampled by the section selection unit 412.

The position estimation device 4 estimates the current position of the rotor 20 by executing steps S101 to S106 shown in FIG. 8, and outputs the current position to the control device 5.
In step S101, the section selection unit 412 receives the detection value of the sample point 100 of the correction waveform of the V-phase signal Hv, the detection value of the sample point 110 of the correction waveform of the W-phase signal Hw, and the correction waveform of the U-phase signal Hu. The detected value of the sample point 120 of the above is input.

In step S102, the section selection unit 412 sets the magnetic field strengths of the U-phase signal Hu, the V-phase signal Hv, and the W-phase signal Hw from among the plurality of sections predetermined with the pole pair numbers shown in FIG. Select a section based on the detection value.

Specifically, the section selection unit 412 determines the mutual magnitude relationship between the detected values of the three

sample points

100, 110, and 120 shown in FIG. 7, and the positive and negative values of the sample points 110, which are the detected values having an intermediate size. Select a section based on. As shown in FIG. 5, there is a certain relationship between the section and the waveform of the magnetic intensity. Can be selected. In the case of the waveform shown in FIG. 7, the section selection unit 412 selects the section number “8”. The section selection unit 412 outputs the selected section number to the estimation unit 413 together with the detected value of the magnetic field strength.

In step S103, the estimation unit 413 executes a three-phase two-phase conversion with respect to the detected value of the magnetic field strength input from the section selection unit 412 by the determinant shown in the middle of FIG. The estimation unit 413 calculates the length of the composite vector (Hα, Hβ) obtained by the three-phase two-phase transformation as the pole pair feature quantity.

In step S104, the estimation unit 413 reads out the learning value of the pole pair feature amount from the storage device 42. The estimation unit 413 acquires the pole pair feature amount corresponding to the section number input from the section selection unit 412. In the case of the present embodiment, the estimation unit 413 acquires four learning values as the pole pair features of the section number "8" belonging to each of the four pole pair numbers "0", "1", "2", and "3". do.

In step S105, the estimation unit 413 compares the calculated value of the pole pair feature amount calculated in step S103 with the four learning values of the pole pair feature amount acquired in step S104.
In step S106, the estimation unit 413 specifies the learning value of the value closest to the calculated value among the four learning values of the pole pair feature amount. The estimation unit 413 selects the pole pair number corresponding to the specified learning value. In the case of the present embodiment, the estimation unit 413 selects any of the four pole pair numbers "0", "1", "2", and "3" as the pole pair numbers of the rotation positions.

By the above operation, the position estimation device 4 can select the section number and the pole pair number of the sensor magnet 24 at the current rotation position of the rotor 20. As a result, the position estimation device 4 can specify the segment number shown in FIG. The position estimation device 4 outputs the specified segment number to the control device 5 as the rotation position of the rotor 20.

The information output from the position estimation device 4 to the control device 5 is not limited to the segment number. For example, the position estimation device 4 may output the section number and the pole pair number to the control device 5. Further, when the position estimation device 4 can execute the position estimation process described in the republished WO2016 / 104378 (Japanese Patent Application No. 2016-566319), the selected segment number and the detected value of the magnetic field strength are used. Based on this, the mechanical angle of the rotor 20 can be calculated with even higher resolution. The position estimation device 4 may output the calculated high-resolution mechanical angle to the control device 5.

As described above, the position estimation device 4 of the first embodiment includes a section selection unit 412 and an estimation unit 413. The section selection unit 412 acquires the detected values of the magnetic field strengths at three or more points of the rotor 20 regardless of the rotational state of the rotor 20. The section selection unit 412 selects a section from a plurality of sections predetermined by the pole pair number of the rotor 20 based on the detected value of the magnetic field strength. The estimation unit 413 calculates the pole pair feature amount by three-phase and two-phase conversion of the detected value of the magnetic field strength, and associates with the selected section whether or not it matches the pole pair feature amount learned in advance. Judgment is made for each pair of poles. The estimation unit 413 selects the pole pair number corresponding to the pole pair feature amount having the value closest to the calculated value, and estimates it as the rotation position of the rotor 20.

Thereby, the position estimation device 4 of the first embodiment can estimate the rotation position of the rotor 20 without rotating the rotor 20. The motor 1 provided with the position estimation device 4 does not have to adjust the origin of the rotation position of the rotor 20 when the power is turned on. Since the motor 1 does not require a preliminary operation for adjusting the origin, it can be suitably used for a drive motor application such as a robot or a transport vehicle in which the preliminary operation is not allowed. Since the motor 1 does not require a preliminary operation for adjusting the origin, the drive time and power consumption required for the preliminary operation can be reduced.

(Modification example)
FIG. 9 is a diagram showing a modified example of the sensor magnet 24. The sensor magnet 24 shown in FIG. 9 includes a yoke 26B having a structure different from that of the first embodiment.
The yoke 26B is an annular magnetic plate. The yoke 26B has a structure in which the magnetic force adjusting layer 27B and the weight adjusting layer 28B are laminated in the axial direction. In the yoke 26B, the magnetic force adjusting layer 27B is located on the upper surface side (annular magnet 25 side), and the weight adjusting layer 28B is located on the lower surface side. The upper surface of the magnetic force adjusting layer 27B supports the lower surface of the annular magnet 25 from below.

The magnetic force adjusting layer 27B has a function of amplifying the magnetic force of the annular magnet 25. As the constituent material of the magnetic force adjusting layer 27B, the same material as the magnetic force adjusting layer 27A of the first embodiment can be used. The magnetic force adjusting layer 27B has a configuration in which the thickness in the axial direction changes stepwise along the circumferential direction. In the case of the present embodiment, the magnetic force adjusting layer 27A has a different thickness for each of the two magnetic poles of the annular magnet 25.

The weight adjusting layer 28B is a layer made of a material or a non-magnetic material having a magnetic material weaker than the magnetic force adjusting layer 27B and having a specific gravity equivalent to that of the magnetic force adjusting layer 27B. The constituent material of the weight adjusting layer 28B is the same as that of the weight adjusting layer 28A of the first embodiment.
The weight adjusting layer 28B is thin at a position where the magnetic force adjusting layer 27B is thick, and is thick at a position where the magnetic force adjusting layer 27B is thin. As a result, the thickness of the yoke 26B can be made uniform in the circumferential direction. By adjusting the weight balance of the yoke 26B by the weight adjusting layer 28B, vibration during rotation can be suppressed. If the weight distribution of the yoke 26B in the circumferential direction can be made uniform, the thickness of the yoke 26B may be slightly non-uniform in the circumferential direction.

Since the sensor magnet 24 of the modified example includes the magnetic force adjusting layer 27B, the degree of magnetization of the magnetic force adjusting layer 27B acting on the pole pairs arranged in the circumferential direction is different for each pole pair. As a result, the plurality of pole pairs of the sensor magnet 24 are configured to have different axial magnetic field strengths from each other. In the case of the present embodiment, since the magnetic field adjusting layer 27B has a thickness that changes stepwise along the circumferential direction, the axial magnetic field strength of the sensor magnet 24 changes stepwise along the circumferential direction. do.

In the above modification, the magnetic force adjusting layer 27B is arranged on the upper surface side (the side facing the annular magnet 25) of the yoke 26B, and the weight adjusting layer 28B is arranged on the lower surface side of the yoke 26B. The axial positions of 27B and the weight adjusting layer 28B may be exchanged. That is, the yoke 26B may be used in a state where the upper and lower surfaces are turned upside down.

The calculation of the pole pair feature amount in the motor 1 provided with the sensor magnet 24 of the modified example will be described with reference to FIG.
The upper part of FIG. 10 shows the waveform of the magnetic field strength of the sensor magnet 24 of the modified example. As shown in FIG. 9, the sensor magnet 24 of the modified example has an axial magnetic field strength in which the maximum amplitude changes stepwise along the circumferential direction. Therefore, as shown in FIG. 10, the axial magnetic field strength of the sensor magnet 24 detected by the magnetic sensor 220 has a waveform in which the maximum amplitude changes stepwise in the rotation direction.

The position estimation device 4 converts the U-phase signal Hu, the V-phase signal Hv, and the W-phase signal Hw input from the amplification device 3 into digital values by the conversion device 40, and then uses the matrix formula shown in the middle of FIG. Perform a phase-two-phase conversion. By the three-phase two-phase conversion, the U-phase signal Hu, the V-phase signal Hv, and the W-phase signal Hw are converted into the signals Hα and Hβ of the two-phase coordinate system. The signals Hα and Hβ can be expressed as composite vectors (Hα and Hβ) in the Cartesian coordinate system as shown in the lower part of FIG.

Since the magnitude of the composite vector (Hα, Hβ) corresponds to the axial magnetic field strength of the sensor magnet 24, the magnitude of the composite vector (Hα, Hβ) changes stepwise as the rotor 20 rotates. As shown in the lower part of FIG. 10, the tip positions of the composite vectors (Hα, Hβ) move concentrically around the origin as the rotor 20 rotates. In FIG. 10, the locus of the tip position of the composite vector (Hα, Hβ) is represented by three concentric circles, but in the case of the sensor magnet 24 having four pole pairs, the locus of the tip position of the composite vector (Hα, Hβ) The locus is represented by four concentric circles.

In the modified example sensor magnet 24, since the thickness of the magnetic force adjusting layer 27B is different for each pole pair, the size of the composite vector (Hα, Hβ) also changes according to the position of the pole pair. The magnitude of the composite vector (Hα, Hβ) is a substantially constant value except at the position where the thickness of the magnetic force adjusting layer 27B changes. When the sensor magnet 24 having four pole pairs is used, the magnitude of the composite vector (Hα, Hβ) is any of the four values at most rotation positions.

The position estimation device 4 calculates the magnitude of the composite vector (Hα, Hβ) as the pole pair feature quantity. In the learning operation, a data table showing the correspondence between the pole pair feature amount, which is the magnitude of the composite vector (Hα, Hβ), and the pole pair number of the sensor magnet 24 is created. As a result, for example, a data table in which the pole pair features are associated with each of the four pole pairs shown in FIG. 4 is created. The created data table is stored in advance in, for example, the storage device 42.

In the position estimation operation by the position estimation device 4, a data table in which the above-mentioned pole pair features and pole pair numbers are associated with each other is used.
In the flowchart shown in FIG. 8, steps S101 to S103 are common to the first embodiment.

In step S104, the estimation unit 413 reads out four learning values of the pole pair features corresponding to the pole pair numbers “0”, “1”, “2”, and “3” from the storage device 42.
In step S105, the estimation unit 413 compares the calculated value of the pole pair feature amount with the four learned values read out.
In step S106, the estimation unit 413 selects the pole pair number corresponding to the learning value of the value closest to the calculated value.

As described above, even in the motor 1 provided with the sensor magnet 24 of the modified example, the section number and the pole pair number of the sensor magnet 24 can be selected without rotating the rotor 20. As a result, the segment number of the sensor magnet 24 can be selected, so that the rotation position of the rotor 20 can be estimated without rotating the rotor 20.
According to the configuration of the modified example, since it is only necessary to hold the learning value corresponding to the pole pair number in the data table, there is an advantage that the data table can be made smaller.

(Second Embodiment)
FIG. 11 is a cross-sectional view showing the motor of the second embodiment.
The basic configuration of the motor 1A of the second embodiment is the same as that of the motor 1 of the first embodiment. The motor 1A of the second embodiment is different from the first embodiment in the configuration of the rotor 20, the detection device 2A, and the control board 50A. FIG. 12 is a perspective view showing the rotor 20 of the second embodiment. FIG. 13 is a functional block diagram of the motor 1A of the second embodiment.

As shown in FIG. 11, the rotor 20 includes a shaft 21, a rotor core 22, and a rotor magnet 23. In the case of this embodiment, the sensor magnet is not installed on the shaft 21. The rotor magnet 23 is fixed to the outer peripheral portion of the rotor core 22.

As shown in FIG. 12, the rotor magnet 23 is composed of four

magnet pieces

23a, 23b, 23c, and 23d arranged in the circumferential direction. In FIG. 12, the rotor core 22 is not shown. Each of the magnet pieces 23a to 23d has a fan shape with a central angle of approximately 90 °. Each of the magnet pieces 23a to 23d is magnetized in the circumferential direction. Therefore, on the upper surface of the rotor magnet 23, the north pole and the south pole are alternately arranged in the circumferential direction. The rotor magnet 23 has four pole pairs.

As shown in FIG. 12, the magnet pieces 23a to 23d are arranged at different axial positions from each other. When viewed from above, the

magnet pieces

23a, 23b, 23c, and 23d are arranged clockwise. Of the magnet pieces 23a to 23d, the magnet piece 23a is located on the uppermost side. The axial position is gradually positioned downward in the order of the

magnet pieces

23b, 23c, and 23d. Therefore, the upper surface of the rotor magnet 23 has stepped steps at a plurality of points in the circumferential direction.

Magnetic sensors 220 (magnetic sensors 220-U, 220-V, 220-W) are arranged at positions facing the upper surface of the rotor magnet 23. The magnetic sensors 220-U, 220-V, 220-W detect the axial magnetic field of the rotor magnet 23.

In the rotor 20 having the above configuration, the positions of the magnet pieces 23a to 23d in the axial direction are different from each other, so that the distance between the magnet pieces 23a to 23d and the magnetic sensor 220 is different for each magnet piece. As a result, the plurality of pole pairs of the rotor magnet 23 have different axial magnetic field strengths with respect to the magnetic sensor 220. In the case of the present embodiment, since the upper surface position of the rotor magnet 23 changes stepwise in the circumferential direction, the maximum amplitude of the axial magnetic field strength detected by the magnetic sensor 220 changes stepwise along the circumferential direction. ..

In the motor 1A of the second embodiment, the magnetic sensor 220 detects the axial magnetic field of the rotor magnet 23. Therefore, as shown in FIG. 11, the detection device 2A including the magnetic sensor 220 includes the rotor 20 and the bearing holding portion 11d. Located between and. In the case of this embodiment, the detection device 2A is located inside the stator 30 in the radial direction.

The control board 50A is located above the bearing holding portion 11d. The control board 50A and the detection device 2A are connected via a cable (not shown). A control IC chip 51 or the like that drives and controls the motor 1A is mounted on the control board 50A. For example, the amplification device 3, the position estimation device 4, the control device 5, and the drive device 6 shown in FIG. 13 are mounted on the control board 50A. The amplification device 3 may be mounted on a common substrate with the detection device 2A. A part or all of the control board 50A may be configured as an external control device.

As shown in FIG. 13, the magnetic sensors 220-U, 220-V, 220-W of the detection device 2A detect the magnetic flux of the rotor magnet 23. The configurations of the amplification device 3, the position estimation device 4, the control device 5, and the drive device 6 are the same as those in the first embodiment.

The position estimation operation in the motor 1A of the second embodiment is the same as that of the motor 1 provided with the sensor magnet 24 of the modified example shown in FIG. In the motor 1A of the second embodiment, the waveform of the magnetic field strength detected by the magnetic sensor 220 is a waveform in which the maximum amplitude changes stepwise along the circumferential direction, as shown in the upper part of FIG. In the position estimation operation, the pole pair number, the section number, and the segment number shown in FIG. 4 are set for the rotor magnet 23.

In the learning operation, as in the modified example, a data table showing the correspondence between the pole pair feature amount, which is the magnitude of the composite vector (Hα, Hβ), and the pole pair number of the rotor magnet 23 is created. As a result, for example, a data table in which the pole pair features are associated with each of the four pole pairs shown in FIG. 4 is created. The created data table is stored in advance in, for example, the storage device 42.

As described above, also in the motor 1A of the second embodiment, the section number and the pole pair number of the rotor magnet 23 can be selected without rotating the rotor 20. As a result, the segment number of the rotor magnet 23 can be specified, so that the rotation position of the rotor 20 can be estimated without rotating the rotor 20.

According to the motor 1A of the second embodiment, the rotation position of the rotor 20 can be estimated without providing the rotor 20 with a sensor magnet. According to the motor 1A of the second embodiment, the same effects as those of the motor 1 of the first embodiment and the modified example can be obtained, and further, the number of parts can be reduced and the size and weight can be reduced.

In the second embodiment, the axial magnetic field strength of the rotor 20 is adjusted by making the axial positions of the magnet pieces 23a to 23d different from each other. However, by installing the magnetic field adjusting member in the rotor 20, the rotor is rotated. The axial magnetic field strength of 20 may be adjusted. For example, the magnetic force adjusting layer 27A of the first embodiment or the magnetic force adjusting member having the same configuration as the magnetic force adjusting layer 27B of the modified example may be installed on the upper surface or the lower surface of the rotor magnet 23. The magnetic force adjusting member may be a member that partially shields the axial magnetic field of the rotor magnet 23.

Although the embodiments of the present invention have been described in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and includes designs and the like within a range that does not deviate from the gist of the present invention. Further, the configurations of the respective embodiments can be combined within a range that does not contradict each other.

By recording a program for realizing the function of the position estimation device in the present invention on a computer-readable recording medium (not shown), and causing the computer system to read and execute the program recorded on the recording medium. The procedure of each process may be performed. The term "computer system" as used herein includes hardware such as an OS and peripheral devices. Further, the "computer system" shall also include a WWW system provided with a homepage providing environment (or display environment). Further, the "computer-readable recording medium" refers to a portable medium such as a flexible disk, a magneto-optical disk, a ROM, or a CD-ROM, or a storage device such as a hard disk built in a computer system.
Furthermore, a "computer-readable recording medium" is a volatile memory (RAM) inside a computer system that serves as a server or client when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. In addition, it shall include those that hold the program for a certain period of time.

Further, the above program may be transmitted from a computer system in which this program is stored in a storage device or the like to another computer system via a transmission medium or by a transmission wave in the transmission medium. Here, the "transmission medium" for transmitting a program refers to a medium having a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line. Further, the above program may be for realizing a part of the above-mentioned functions. Further, it may be a so-called difference file (difference program) that can realize the above-mentioned function in combination with a program already recorded in the computer system.

1,1A ...

Motor

2,2A ... Detection device 3 ... Amplification device 4 ... Position estimation device 5 ... Control device 6 ... Drive device 7 ... External device 11 ...

Housing

15, 16 ... Bearing 20 ... Rotor 21 ... Shaft 22 ... Rotor core 23 ...

Rotor magnet

23a, 23b, 23c, 23d ... Magnet piece 24 ... Sensor magnet 25 ...

Circular magnet

26A, 26B ...

Yoke

27A, 27B ... Magnetic

force adjustment layer

28A, 28B ... Weight adjustment layer 30 ... Stator 31 ... Stator core 31a ... Core Back 31b ... Teeth 32 ... Insulator 33 ... Coil 40 ... Conversion device 41 ... Computing device 42 ...

Storage device

50, 50A ... Control board 51 ... Control IC chip 52 ... Circuit board 220, 220-U, 220-V, 220-W ... Magnetic sensor 300-U, 300-V, 300-W ... Differential amplifier 400-U, 400-V, 400-W ... Conversion unit 412 ... Section selection unit 413 ... Estimating unit Hu ... U phase signal Hv ... V phase Signal Hw ... W phase signal Hα, Hβ ... Signal J ... Central axis

Claims

A sensor magnet that can rotate around the central axis
It has multiple pole pairs arranged in the circumferential direction,
The plurality of pole pairs have different axial magnetic field intensities from each other.
Sensor magnet.
It has an axial magnetic field strength that changes continuously in the circumferential direction.
The sensor magnet according to claim 1.
It has an axial magnetic field strength that changes stepwise in the circumferential direction.
The sensor magnet according to claim 1.
An annular magnet extending in the circumferential direction and
It has a yoke located on one side of the annular magnet in the axial direction, and has a yoke.
The yoke has a magnetic force adjusting layer whose thickness changes according to the circumferential position.
The sensor magnet according to any one of claims 1 to 3.
The yoke has the magnetic force adjusting layer and a weight adjusting layer made of a magnetic material or a non-magnetic material weaker than the magnetic force adjusting layer.
The magnetic force adjusting layer is laminated on the surface of the weight adjusting layer on the annular magnet side.
The sensor magnet according to claim 4.
The yoke has the magnetic force adjusting layer and a weight adjusting layer made of a magnetic material or a non-magnetic material weaker than the magnetic force adjusting layer.
The weight adjusting layer is laminated on the surface of the magnetic force adjusting layer on the annular magnet side.
The sensor magnet according to claim 4.
The yoke has a uniform thickness in the circumferential direction.
The sensor magnet according to claim 5 or 6.
A rotor that can rotate around the central axis
It has a rotor core and a rotor magnet fixed to the rotor core.
The rotor magnet has a plurality of pole pairs arranged in the circumferential direction.
The plurality of pole pairs have different axial magnetic field intensities from each other.
Rotor.
The rotor magnet has a plurality of magnet pieces arranged in the circumferential direction, and has a plurality of magnet pieces.
The plurality of magnet pieces are arranged at different axial positions from each other.
The rotor according to claim 8.
A magnetic force adjusting member that partially amplifies or shields the axial magnetic field of the rotor magnet.
The rotor according to claim 8.
A rotor that can rotate around the central axis and
A stator facing the rotor in the radial direction and
The sensor magnet according to any one of claims 1 to 7, which is mounted on the shaft of the rotor.
Three or more magnetic sensors that detect the magnetic field of the sensor magnet,
Equipped with a motor.
A position estimation device for estimating the rotation position of the rotor is provided.
The position estimation device is
The detected values of the magnetic field strengths of three or more places of the sensor magnet are acquired through the magnetic sensor, and the detected values of the magnetic field strengths are obtained from a plurality of sections predetermined for the pole pair numbers of the sensor magnets. And the section selection section that selects the section
The length of the composite vector obtained by three-phase and two-phase conversion of the detected value of the magnetic field strength is calculated as the pole pair feature amount, and the calculated pole pair feature amount is the pole pair of the sensor magnet learned in advance. An estimation unit that estimates the pole pair number of the rotation position of the rotor by collating the relationship between the number and the pole pair feature amount, and
Have,
The motor according to claim 11.
The rotor according to any one of claims 8 to 10, and the rotor.
A stator facing the rotor in the radial direction and
Three or more magnetic sensors that detect the magnetic field of the rotor magnet,
Equipped with a motor.
A position estimation device for estimating the rotation position of the rotor is provided.
The position estimation device is
The detected values of the magnetic field strengths at three or more places of the rotor magnet are acquired through the magnetic sensor, and the detected values of the magnetic field strengths are obtained from a plurality of sections predetermined for the pole pair numbers of the rotor magnets. And the section selection section that selects the section
The length of the composite vector obtained by three-phase and two-phase conversion of the detected value of the magnetic field strength is calculated as the pole pair feature amount, and the calculated pole pair feature amount is the pole pair of the rotor magnet learned in advance. An estimation unit that estimates the pole pair number of the rotation position of the rotor by collating with the relationship between the number and the pole pair feature amount.
Have,
The motor according to claim 13.