Motor, pump provided with motor, and method for detecting displacement of rotor in motor

Abstract

The present invention detects not only a rotation angle of a rotor but also displacement in a direction orthogonal to the rotation axis of the rotor by using only one type of sensor.　Provided is a motor comprising: a rotor having a plurality of magnetic poles; a motor stator having a plurality of stator coils; a plurality of magnetic sensors provided on the motor stator and outputting voltage signals in accordance with a magnetic field from the rotor; and a control unit configured to determine a rotation angle of the rotor on the basis of the voltage signals from the plurality of magnetic sensors and configured to determine a displacement of the rotor in a plane orthogonal to the rotation axis of the rotor on the basis of the voltage signals from the plurality of magnetic sensors.

Description

Motor, pump equipped with motor, and method for detecting rotor displacement in motor

[0001] The present invention relates to a motor, a pump equipped with the motor, and a method for detecting rotor displacement in a motor.

[0002] Motors are typically used with bearings to support their rotating shafts. Magnetic bearings are a type of bearing capable of supporting the motor's rotating shaft without contact. Bearingless motors are also known as motors that combine the functions of rotating the rotating shaft and supporting it without contact (magnetic levitation). In order to control the rotation and magnetic levitation of the rotating shaft in these motors, it is important to detect the rotor's rotation angle and its displacement in a direction perpendicular to the rotation axis. Conventionally, separate sensors have been used to detect the rotor's rotation angle and its displacement in a direction perpendicular to the rotation axis (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2001-016887

[0004] Conventional bearingless motors such as those disclosed in Patent Document 1 use two types of sensors to control the rotation and levitation of the rotating shaft. Therefore, conventional control methods require space to install these two types of sensors, which limits the flexibility of the device's design layout. Therefore, it is desirable to use only one type of sensor to detect not only the rotor's rotation angle but also its displacement in a direction perpendicular to the rotor's rotation axis.

[0005] [Form 1] According to form 1, there is provided a motor comprising: a rotor having a plurality of magnetic poles; a motor stator having a plurality of stator coils; a plurality of magnetic sensors provided on the motor stator and outputting voltage signals corresponding to the magnetic field from the rotor; and a control unit configured to determine the rotation angle of the rotor based on the voltage signals from the plurality of magnetic sensors, and further configured to determine the displacement of the rotor in a plane perpendicular to the rotation axis of the rotor based on the voltage signals from the plurality of magnetic sensors.

[0006] [Form 2] According to Form 2, in the motor of Form 1, the control unit is configured to determine the displacement of the rotor in a plane perpendicular to the axis of rotation of the rotor by performing a Clarke transformation on the values ​​of the voltage signals from the plurality of magnetic sensors in a first Clarke transformation unit and then performing an inverse Park transformation on the values ​​of the voltage signals in an inverse Park transformation unit.

[0007] [Form 3] According to Form 3, in the motor of Form 2, the control unit is configured to determine the rotation angle of the rotor by Clarke transforming the values ​​of the voltage signals from the plurality of magnetic sensors in a second Clarke transform unit, and then calculating the arc tangent of the Clarke transformed value in an arc tangent calculation unit.

[0008] [Feature 4] According to feature 4, in the motor of feature 3, the control unit is configured to use the calculated arctangent value in the inverse Park transform.

[0009] [Form 5] According to form 5, in the motor of form 3, the plurality of magnetic sensors include a plurality of magnetic sensor pairs arranged opposite each other, and the control unit is configured to input the sum of the voltage signals from the magnetic sensor pairs as an input to the first Clarke conversion unit and the difference of the voltage signals from the magnetic sensor pairs as an input to the second Clarke conversion unit.

[0010] [Mode 6] According to Mode 6, there is provided a pump including the motor of any one of Modes 1 to 5 and an impeller rotated by the motor.

[0011] [Form 7] According to Form 7, there is provided a method for detecting rotor displacement in a motor, the motor comprising a rotor having a plurality of magnetic poles, a motor stator having a plurality of stator coils, and a plurality of magnetic sensors provided on the motor stator and outputting voltage signals corresponding to a magnetic field from the rotor, the method including the steps of: performing a Clarke transform on values ​​of the voltage signals from the plurality of magnetic sensors in a first Clarke transform unit; and performing an inverse Park transform on the values ​​after the Clarke transform in the first Clarke transform unit, thereby determining the displacement of the rotor in a plane perpendicular to the axis of rotation of the rotor.

[0012] [Form 8] According to form 8, the method of form 7 further includes the steps of: performing a Clarke transformation on the values ​​of the voltage signals from the plurality of magnetic sensors in a second Clarke transformation unit; and calculating the arc tangent of the values ​​after the Clarke transformation in the second Clarke transformation unit, thereby determining the rotation angle of the rotor.

[0013] [Form 9] According to form 9, in the method of form 8, the plurality of magnetic sensors include a plurality of magnetic sensor pairs arranged opposite each other, and includes a step of inputting a sum of voltage signals from the magnetic sensor pairs to the first Clarke conversion unit, and a step of inputting a difference of voltage signals from the magnetic sensor pairs to the second Clarke conversion unit.

[0014] FIG. 1 is a perspective view showing a schematic configuration of a motor according to one embodiment of the present invention. FIG. 2 is a cross-sectional view taken along the rotation axis of a motor according to one embodiment of the present invention. FIG. 3 is a top view of a motor according to one embodiment of the present invention. FIG. 4 is a cross-sectional view showing a schematic configuration of a pump according to one embodiment of the present invention. FIG. 5 is a functional block diagram of a control unit for detecting the rotation angle and in-plane displacement of a rotor in a motor according to one embodiment of the present invention. FIG. 6 is a diagram showing a schematic configuration of a motor according to another embodiment of the present invention. FIG. 7 is a perspective view showing a schematic configuration of a motor also provided with a magnetic bearing according to another embodiment of the present invention. FIG. 8 is a cross-sectional view taken along the rotation axis of a motor also provided with a magnetic bearing according to another embodiment of the present invention.

[0015] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings described below, identical or corresponding components will be designated by the same reference numerals, and redundant description will be omitted. Furthermore, in the following description, it should be noted that terms indicating a position or direction, such as "upper" or "lower," refer to the "upper" or "lower" in the drawings to which the description in which the term is used refers, and do not necessarily refer to the position or direction in the actual use of the object.

[0016] Fig. 1 is a perspective view showing a schematic configuration of a motor 10 according to an embodiment of the present invention. Fig. 2 is a cross-sectional view taken along the rotation axis of the motor 10. Fig. 3 is a top view of the motor 10 as seen from above in Fig. 1. The motor 10 includes a motor rotor 20, a motor stator 30 consisting of a stator core 32 and a stator coil 34, a plurality of magnetic sensors 40, and a control unit 50. The motor 10 is a bearingless motor that combines the function of rotating the motor rotor 20 with the function of magnetically supporting it.

[0017] The motor rotor (hereinafter referred to as rotor) 20 is composed of a permanent magnet with multiple magnetic poles. In the illustrated example, the rotor 20 is composed of a ring-shaped magnet. The number of magnetic poles of the rotor 20 may be any number. For example, the rotor 20 may have four, six, eight, or other magnetic poles. The rotor 20 may be a permanent magnet itself, or may be configured with a permanent magnet embedded in a non-magnetic material. The shape of the rotor 20 is not limited to a ring shape and may be other shapes, such as a disk shape.

[0018] The stator core 32 of the motor stator (hereinafter referred to as the stator) 30 includes a ring-shaped core base 321 concentric with the rotational axis of the rotor 20, and multiple core rods 322 extending from the core base 321 toward the rotor 20 along the rotational axis of the rotor 20. The multiple core rods 322 are arranged at equal intervals around the circumferential direction of the ring of the core base 321. In the illustrated example, the stator core 32 includes six core rods 322, but the number of core rods 322 may be any number. Each core rod 322 has a main portion 322a extending parallel to the rotational axis of the rotor 20 and an end portion 322b bent at the tip of the main portion 322a toward the rotational axis. The tip of the end portion 322b of the core rod 322 is located near the rotor 20. A stator coil 34 is wound around each of the main portions 322a of the core rods 322.

[0019] A magnetic sensor 40 is disposed near the tip of the end 322b of each core rod 322. In the example shown in the figure, a magnetic sensor 40 is disposed in each gap between the ends 322b of the six core rods 322. The number of magnetic sensors 40 may be less than the number of gaps between the core rods 322. The magnetic sensors 40 are for detecting changes in the magnetic field caused by the rotation of the rotor 20. The magnetic sensors 40 may be, for example, Hall sensors, but are not limited to these, and any other type of magnetic sensor capable of detecting a magnetic field may be used.

[0020] The control unit 50 is electrically connected to each magnetic sensor 40 and each stator coil 34. Note that in FIG. 1 , for simplicity, only some of the connections between the magnetic sensors 40 and the stator coils 34 and the control unit 50 are shown with solid lines, and the rest are omitted. Each magnetic sensor 40 outputs a voltage signal proportional to the magnitude of the detected magnetic field to the control unit 50. The control unit 50 is configured to calculate the rotation angle of the rotor 20 and the displacement of the rotor 20 in a plane perpendicular to the rotation axis of the rotor 20 based on the signal from each magnetic sensor 40. The calculation algorithm for the rotation angle and displacement (hereinafter also referred to as in-plane displacement) will be described later.

[0021] The control unit 50 is further configured to determine the value of a current to be passed through each stator coil 34 based on the calculated rotation angle and displacement of the rotor 20, and to supply drive currents (e.g., U-phase, V-phase, and W-phase drive currents) based on the determined current values ​​to the stator coils 34. For example, the control unit 50 determines the value of a drive current for applying a rotational torque to the rotor 20 based on the calculated rotation angle of the rotor 20, and determines the value of a position control current for applying a translational force to the rotor 20 so as to compensate for the in-plane displacement of the rotor 20 based on the calculated in-plane displacement of the rotor 20, and supplies a current obtained by summing these two current values ​​to the stator coils 34 as the U-phase, V-phase, and W-phase drive currents. As a result, a combined magnetic force acts from the stator 30 on the rotor 20, which can rotate and magnetically support the rotor 20 simultaneously.

[0022] 4 is a cross-sectional view showing a schematic configuration of a pump 100 according to one embodiment of the present invention. The pump 100 is configured using the motor 10 described with reference to FIGS. 1 to 3, and additionally includes an impeller 102 and a pump casing 104 as components other than the motor 10.

[0023] The pump casing 104 includes a casing body 105, a suction port 106 having a suction port, and a discharge port 107 having a discharge port. The casing body 105 is generally cylindrical, with the suction port 106 extending upward from the center of its top surface and the discharge port 107 extending radially outward from a portion of the cylindrical side surface of the casing body 105. The bottom surface of the casing body 105 partially protrudes downward at its center to form a rotor accommodating section 108 for accommodating the motor rotor 20. The pump casing 104 is disposed above the motor 10 such that the rotor accommodating section 108 extends into a space surrounded by the multiple core rod ends 322b of the motor 10. The motor rotor 20 is disposed within the casing body 105, inside the rotor accommodating section 108.

[0024] The impeller 102 is attached to the upper surface (the side closer to the suction port 106) of the motor rotor 20 so as to be concentric with the motor rotor 20. The impeller 102 may be integrally formed with the motor rotor 20. For example, the body of the impeller 102 and a cylindrical protrusion protruding downward from the body of the impeller 102 may be formed as a single member, with the rotor 20 made of a permanent magnet embedded inside the cylindrical protrusion. The entire or most part of the impeller 102 is located above the rotor housing 108 and rotates integrally with the motor rotor 20. As the impeller 102 rotates, fluid (liquid or gas) is sucked in through the suction port 106, introduced into the casing body 105, and then discharged from the discharge port 107 to the outside of the pump 100.

[0025] 5 is a functional block diagram of a control unit 50 for detecting the rotation angle and in-plane displacement (i.e., displacement in a plane perpendicular to the rotation axis) of the rotor 20 in the motor 10. The following describes a motor 10 configured with six magnetic sensors 40#1 to 40#6, one between each of the adjacent core rod ends 322b.

[0026] As described above, each of the magnetic sensors 40#1 to 40#6 outputs a voltage signal corresponding to a change in the magnetic field caused by the rotation of the rotor 20. The output signals from the magnetic sensors 40#1, 40#2, 40#3, 40#4, 40#5, and 40#6 are respectively represented by v １ , v ２ , v ３ , v ４ , v ５ , v ６ The output signals from the magnetic sensors 40#1 to 40#6 are input to an adder 502 and a subtracter 503. The adder 502 adds the signals from the magnetic sensors arranged at opposing positions (i.e., magnetic sensors 40#1 and 40#4, magnetic sensors 40#2 and 40#5, magnetic sensors 40#3 and 40#6) to generate a sum signal v ａ＋ (=v １ +v ４ ), v ｂ＋ (=v ２ +v ５ ), and v ｃ＋ (=v３ +v ６ The output signal v from the adder 502 is ａ＋ , v ｂ＋ , v ｃ＋ is input to the first Clarke transform unit 504. The subtraction unit 503 subtracts the signal of one magnetic sensor from the signal of the other magnetic sensor arranged at an opposing position to obtain a difference signal v ａ－ (=v １ -v ４ ), v ｂ－ (=v ２ -v ５ ), and v ｃ－ (=v ３ -v ６ The output signal v from the subtractor 503 ａ－ , v ｂ－ , v ｃ－ is input to the second Clarke transform unit 505.

[0027] The second Clarke transform unit 505 converts the signal v from the subtraction unit 503, which is a three-phase signal, into ａ－ , v ｂ－ , v ｃ－ is transformed by Clarke transformation (three-phase to two-phase transformation) to obtain the two-phase signal v α－ , v β－ Calculate the two-phase signal v α－ , v β－ is input to the arctangent calculation unit 506, which calculates the ratio v of the two-phase signals. β－ / v α－ The rotation angle θ of the rotor 20 is determined by calculating the arc tangent of

[0028] The first Clarke transform unit 504 converts the signal v from the adder unit 502, which is a three-phase signal, into ａ＋ , v ｂ＋ , v ｃ＋ is transformed by Clarke transformation, and the two-phase signal v α＋ , v β＋ Calculate the two-phase signal v α＋ , v β＋ is input to the inverse Park transform unit 508. The value of the rotation angle θ of the rotor 20 calculated by the arctangent calculation unit 506 is also input to the inverse Park transform unit 508. The inverse Park transform unit 508 converts the two-phase signal v α＋ , vβ＋ By performing an inverse Park transform (orthogonal coordinate transformation) on the above, the displacement of the rotor 20 in a plane (xy plane) perpendicular to the rotation axis (z axis) of the rotor 20 (i.e., the displacement Δx in the x-axis direction and the displacement Δy in the y-axis direction) is calculated.

[0029] As described above, according to one embodiment of the present invention, by using output signals from one type of magnetic sensor (for example, only a Hall sensor), it is possible to calculate the in-plane displacements Δx and Δy of the rotor 20 in addition to the rotation angle θ of the rotor 20. This simplifies the configuration of the sensor for detecting the magnetic field, thereby reducing the cost of the device and improving the degree of freedom in design layout.

[0030] It should be noted that the specific configurations of the motor 10 and pump 100 described with reference to Figures 1 to 4 are merely examples and do not limit the present invention. For example, the motor 10 shown in Figures 1 to 3 has a configuration called a temple motor, but the present invention is not limited to temple motors and can also be applied to, for example, a general radial gap motor.

[0031] FIG. 6 is a diagram showing the schematic configuration of a motor (radial gap motor) 11 according to another embodiment of the present invention. The motor 11 includes a motor rotor 20, a motor stator 30' consisting of a stator core 32' and a stator coil 34, multiple magnetic sensors 40, and a control unit 50. The motor 11 is a radial gap type bearingless motor that combines the function of rotating the motor rotor 20 with the function of magnetically supporting it. The motor 11 differs from the motor 10 described with reference to FIGS. 1 to 3 only in the shape of the stator core 32'; the configuration and function of the other parts are the same as those of the motor 10. Note that the shape of the stator core 32' itself is well known, so a detailed description thereof will be omitted.

[0032] Furthermore, the present invention is not limited to the bearingless motors described so far, but can also be applied to motor systems that combine a motor and magnetic bearings. Fig. 7 is a perspective view showing the schematic configuration of such a motor system, and Fig. 8 is a cross-sectional view taken along the rotation axis. The motor system includes a motor 12, a magnetic bearing 700, and a control unit 50. The motor 12 is disposed between two magnetic bearings 700, and the two magnetic bearings 700 support the rotating shaft 13 of the motor 12 from both sides of the motor 12 in a non-contact manner.

[0033] The motor 12 includes a motor rotor 20, a motor stator 30' consisting of a stator core 32' and a stator coil 34, and a plurality of magnetic sensors 40. Although the magnetic sensors are not shown in FIG. 7, the motor 12 has a plurality of magnetic sensors arranged similarly to the plurality of magnetic sensors 40 in the motor 11 of FIG. 6. The motor rotor 20, stator core 32', stator coil 34, motor stator 30', and a plurality of magnetic sensors 40 of the motor 12 are the same as the corresponding elements (with the same reference numerals) in the motors 10 and 11 described with reference to FIGS. 1 to 3 and 6, and therefore a redundant description will be omitted. The motor rotor 20 of the motor 12 is fixed to a rotating shaft 13, and when the motor 12 is driven, the motor rotor 20 and the rotating shaft 13 rotate integrally.

[0034] The magnetic bearing 700 includes a rotor 720 and a stator 730 consisting of a stator core 732 and a stator coil 734. The rotor 720, stator core 732, stator coil 734, and stator 730 of the magnetic bearing 700 have the same configurations as the motor rotor 20, stator core 32′, stator coil 34, and motor stator 30′ of the motor 12, respectively. The rotor 720 of the magnetic bearing 700 is fixed to the rotating shaft 13 of the motor 12 and rotates together with the rotating shaft 13.

[0035] 5 , based on signals from the multiple magnetic sensors 40 provided in the motor 12. The control unit 50 then determines the value of a drive current for applying a rotational torque to the motor rotor 20, based on the calculated rotation angle of the motor rotor 20, and supplies the determined drive current to the stator coil 34 of the motor 12. This causes the rotation shaft 13 of the motor 12 to rotate. The control unit 50 also determines the value of a position control current for applying a translational force to the motor rotor 20 so as to compensate for the in-plane displacement of the motor rotor 20, based on the calculated in-plane displacement of the motor rotor 20, and supplies the determined position control current to the stator coil 734 of the magnetic bearing 700. As a result, in the magnetic bearing 700, a force that magnetically supports the rotating shaft 13 of the motor 12 acts on the rotor 720 from the stator 730, and the rotating shaft 13 is supported in a non-contact manner.

[0036] Although the embodiments of the present invention have been described above based on several examples, the above-described embodiments of the invention are intended to facilitate understanding of the present invention and are not intended to limit the present invention. The present invention may be modified or improved without departing from the spirit thereof, and the present invention naturally includes equivalents thereof. Furthermore, any combination or omission of the components described in the claims and specification is possible within the scope of solving at least part of the above-described problems or achieving at least part of the effects.

[0037] REFERENCE SIGNS LIST 10 Motor 11 Motor 12 Motor 20 Motor rotor 30 Motor stator 32 Stator core 321 Core base 322 Core rod 322a Core rod main part 322b Core rod end 34 Stator coil 40 Magnetic sensor 50 Control unit 100 Pump 102 Impeller 104 Pump casing 105 Casing body 106 Suction port 107 Discharge port 108 Rotor accommodating section 502 Addition section 503 Subtraction section 504 First Clarke transformation section 505 Second Clarke transformation section 506 Arc tangent calculation section 508 Inverse Park transformation section 700 Magnetic bearing

Claims

1. A motor comprising: a rotor having a plurality of magnetic poles; a motor stator having a plurality of stator coils; a plurality of magnetic sensors provided on the motor stator and outputting voltage signals corresponding to a magnetic field from the rotor; and a control unit configured to determine a rotation angle of the rotor based on the voltage signals from the plurality of magnetic sensors, and further configured to determine a displacement of the rotor in a plane perpendicular to a rotation axis of the rotor based on the voltage signals from the plurality of magnetic sensors.

2. The motor of claim 1, wherein the control unit is configured to determine the displacement of the rotor in a plane perpendicular to the axis of rotation of the rotor by Clarke transforming values ​​of voltage signals from the plurality of magnetic sensors in a first Clarke transform section and further inverse Park transforming them in an inverse Park transform section.

3. The motor described in claim 2, wherein the control unit is configured to determine the rotation angle of the rotor by subjecting the values ​​of the voltage signals from the multiple magnetic sensors to Clarke transformation in a second Clarke transformation section, and further calculating the arc tangent of the Clarke transformed value in an arc tangent calculation section.

4. The motor of claim 3, wherein the control unit is configured to use the calculated arctangent value in the inverse Park transform.

5. The motor according to claim 3, wherein the plurality of magnetic sensors include a plurality of magnetic sensor pairs arranged opposite each other, and the control unit is configured to input a sum of voltage signals from the magnetic sensor pairs as an input to the first Clarke conversion section, and to input a difference of voltage signals from the magnetic sensor pairs as an input to the second Clarke conversion section.

6. A pump comprising a motor according to any one of claims 1 to 5 and an impeller rotated by said motor.

7. A method for detecting a displacement of a rotor in a motor, the motor comprising: a rotor having a plurality of magnetic poles; a motor stator having a plurality of stator coils; and a plurality of magnetic sensors provided on the motor stator for outputting voltage signals corresponding to a magnetic field from the rotor, the method comprising: performing a Clarke transformation on values ​​of the voltage signals from the plurality of magnetic sensors in a first Clarke transformation unit; and performing an inverse Park transformation on the values ​​after the Clarke transformation in the first Clarke transformation unit, thereby determining the displacement of the rotor in a plane perpendicular to the axis of rotation of the rotor.

8. The method of claim 7, further comprising: determining a rotation angle of the rotor by: performing a Clarke transform on values ​​of voltage signals from the plurality of magnetic sensors in a second Clarke transform unit; and calculating the arc tangent of the values ​​after Clarke transformation in the second Clarke transform unit.

9. The method according to claim 8, wherein the plurality of magnetic sensors comprises a plurality of magnetic sensor pairs arranged opposite each other, and the method includes the steps of: inputting a sum of voltage signals from the magnetic sensor pairs to the first Clarke conversion unit; and inputting a difference of voltage signals from the magnetic sensor pairs to the second Clarke conversion unit.

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