Motor, pump with motor, and displacement detection method for rotor in motor

Abstract

To detect not only a rotation angle of a rotor but also displacement of the rotor in a direction orthogonal to a rotation axis using only one kind of sensor.SOLUTION: Provided is a motor comprising: a rotor including a plurality of magnetic poles; a motor stator including a plurality of stator coils; a plurality of magnetic sensors provided on the motor stator and configured to output 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 displacement of the rotor within a plane orthogonal to a rotation axis of the rotor based on the voltage signals from the plurality of magnetic sensors.SELECTED DRAWING: Figure 5

Description

Technical Field

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

Background Art

[0002] A motor is usually used together with a bearing for supporting its rotating shaft. As a bearing capable of supporting the rotating shaft of the motor in a non-contact manner, there is a magnetic bearing. Further, as a motor having both the function of rotating the rotating shaft and non-contact support (magnetic levitation), a bearingless motor is known. In order to control the rotation and magnetic levitation of the rotating shaft in these motors, it is important to detect the rotation angle of the rotor and the displacement in the direction orthogonal to the rotating shaft. Conventionally, separate sensors have been used for detecting the rotation angle of the rotor and the displacement in the direction orthogonal to the rotation axis of the rotor (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] A conventional bearingless motor as disclosed in Patent Document 1 uses two types of sensors for rotation control and levitation control of the rotating shaft. Therefore, the conventional control method has a drawback that a space for installing these two types of sensors is required, and the degree of freedom in the design layout of the device is limited. Therefore, it is desired to detect not only the rotation angle of the rotor but also the displacement in the direction orthogonal to the rotation axis of the rotor using only one type of sensor.

Means for Solving the Problems

[0005] [Embodiment 1] According to Embodiment 1, there is provided a motor including 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 configured to output a voltage signal corresponding to a magnetic field from the rotor, and a control unit configured to determine a rotation angle of the rotor based on voltage signals from the plurality of magnetic sensors, and further configured to determine a displacement of the rotor in a plane orthogonal to a rotation axis of the rotor based on voltage signals from the plurality of magnetic sensors.

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

[0007] [Embodiment 3] According to Embodiment 3, in the motor of Embodiment 2, the control unit is configured to determine the rotation angle of the rotor by performing a Clarke transformation on values of voltage signals from the plurality of magnetic sensors in a second Clarke transformation unit and further calculating an arctangent inverse of the value after the Clarke transformation in an inverse tangent operation unit.

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

[0009] [Embodiment 5] According to Embodiment 5, in the motor of Embodiment 3, the plurality of magnetic sensors include a plurality of pairs of magnetic sensors arranged oppositely, and the control unit is configured to use a sum of voltage signals from the pairs of magnetic sensors as an input to the first Clarke transformation unit and a difference between voltage signals from the pairs of magnetic sensors as an input to the second Clarke transformation unit.

[0010] [Embodiment 6] According to Embodiment 6, a pump is provided that includes any one of the motors of Embodiments 1 to 5 and an impeller rotated by the motor.

[0011] [Embodiment 7] According to Embodiment 7, a method for detecting the displacement of a rotor in a motor, the motor including 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 according to the magnetic field from the rotor, the method including determining the displacement of the rotor in a plane orthogonal to the rotation axis of the rotor by Clarke-transforming the values of the voltage signals from the plurality of magnetic sensors in a first Clarke transformation unit and inverse-Park-transforming the values after the Clarke transformation in the first Clarke transformation unit.

[0012] [Embodiment 8] According to Embodiment 8, in the method of Embodiment 7, the method further includes determining 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 transformation unit and calculating the inverse tangent of the values after the Clarke transformation in the second Clarke transformation unit.

[0013] [Embodiment 9] According to Embodiment 9, in the method of Embodiment 8, the plurality of magnetic sensors include a plurality of pairs of oppositely arranged magnetic sensors, and the method includes inputting the sum of the voltage signals from the pair of magnetic sensors to the first Clarke transformation unit and inputting the difference between the voltage signals from the pair of magnetic sensors to the second Clarke transformation unit. [Brief Description of the Drawings]

[0014]

Figure 1

Figure 2

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Figure 5

Figure 6

Figure 7

Figure 8

Mode for Carrying Out the Invention

[0015] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings described below, the same or corresponding components are denoted by the same reference numerals, and redundant descriptions are omitted. Also, in the following description, words indicating positions or directions such as "upper" and "lower" indicate "upper" and "lower" in the drawings to which the description using those words refers, and it should be noted that they do not necessarily indicate the positions or directions in the actual usage mode 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 along the rotation axis of the motor 10. FIG. 3 is a top view of the motor 10 as viewed from the upper direction of FIG. 1. The motor 10 includes a motor rotor 20, a motor stator 30 including 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 having both a function of rotating the motor rotor 20 and a function of magnetically supporting it.

[0017] The motor rotor (hereinafter referred to as the rotor) 20 is composed of permanent magnets having a plurality of magnetic poles. In the example of the figure, the rotor 20 is composed of a ring-shaped magnet. The number of magnetic poles of the rotor 20 may be arbitrary. For example, the rotor 20 may have magnetic poles such as 4 poles, 6 poles, 8 poles, etc. The rotor 20 may be the permanent magnet itself, or may be configured such that the permanent magnet is embedded in a member made of a non-magnetic material. The shape of the rotor 20 is not limited to the ring shape, and may be other shapes such as a disc shape, for example.

[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 rotation axis of the rotor 20, and a plurality of core rods 322 erected from the core base 321 toward the rotor 20 along the rotation axis of the rotor 20. The plurality of core rods 322 are arranged at equal intervals along the circumferential direction of the ring of the core base 321. In the example of the figure, the stator core 32 includes six core rods 322, but the number of core rods 322 may be arbitrary. Each core rod 322 has a main portion 322a extending parallel to the rotation axis of the rotor 20, and an end portion 322b bent in the direction toward the rotation axis at the tip of the main portion 322a. The tip of the end portion 322b of the core rod 322 is located near the rotor 20. The stator coils 34 are wound around the main portions 322a of the core rods 322, respectively.

[0019] A magnetic sensor 40 is arranged near the tip of the end portion 322b of the core rod 322. In the example of the figure, a magnetic sensor 40 is arranged in each gap between the end portions 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 sensor 40 is for detecting a change in the magnetic field generated by the rotation of the rotor 20. The magnetic sensor 40 may be, for example, a Hall sensor, but this is not a limitation, 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. In FIG. 1, for simplicity of the drawing, only a part of the connections between the magnetic sensors 40 and the stator coils 34 and the control unit 50 are shown by solid lines, and the others 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 orthogonal to the rotation axis of the rotor 20 based on the signals from the respective magnetic sensors 40. The calculation algorithms for the rotation angle and the displacement (hereinafter also referred to as in-plane displacement) will be described later.

[0021] The control unit 50 further determines the value of the current flowing through each stator coil 34 based on the calculated rotation angle and displacement of the rotor 20, and is configured to supply a drive current (for example, drive currents of the U-phase, V-phase, and W-phase) based thereon to the stator coil 34. For example, the control unit 50 determines the value of the drive current for applying a rotational torque to the rotor 20 based on the calculated rotation angle of the rotor 20, and also determines the value of the position control current for applying a translational force to the rotor 20 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 coil 34 as the drive currents of the U-phase, V-phase, and W-phase. Thereby, a combined magnetic force that can simultaneously perform rotation and magnetic support on the rotor 20 from the stator 30 acts.

[0022] FIG. 4 is a cross-sectional view showing a schematic configuration of a pump 100 according to an 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 has a casing body 105, a suction port 106 having a suction opening, and a discharge port 107 having a discharge opening. The casing body 105 is configured in a generally cylindrical shape, the suction port 106 extends upward from the central portion of its upper surface, and the discharge port 107 extends radially outward from a part of the cylindrical side surface of the casing body 105. Further, the bottom surface of the casing body 105 has its central portion partially protruding downward to form a rotor housing portion 108 for housing the motor rotor 20. The pump casing 104 is disposed above the motor 10 such that the rotor housing portion 108 enters a space surrounded by the plurality of core rod ends 322b of the motor 10. Also, the motor rotor 20 is disposed inside the casing body 105 and inside the rotor housing portion 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 main body of the impeller 102 and a cylindrical convex portion protruding downward from the main body of the impeller 102 may be formed of an integral member, and the rotor 20 made of a permanent magnet may be embedded inside this cylindrical convex portion. The impeller 102 is positioned entirely or mostly above the rotor housing portion 108 and rotates integrally with the motor rotor 20. By the rotation of the impeller 102, fluid (liquid or gas) is sucked from the suction opening of the suction port 106 and introduced into the inside of the casing body 105, and further discharged from the discharge opening of the discharge port 107 to the outside of the pump 100.

[0025] FIG. 5 is a functional block diagram of the control unit 50 for detecting the rotation angle and in-plane displacement (i.e., displacement in a plane orthogonal to the rotation axis) of the rotor 20 in the motor 10. Hereinafter, the motor 10 having a configuration in which a total of six magnetic sensors 40#1 to 40#6 are arranged one by one between adjacent core rod ends 322b will be described.

[0026] As described above, each of the magnetic sensors 40#1 to 40#6 outputs a voltage signal corresponding to a magnetic field change due to the rotation of the rotor 20. Let the output signals from the magnetic sensors 40#1, 40#2, 40#3, 40#4, 40#5, and 40#6 be v1, v2, v3, v4, v5, and v6, respectively. The output signals from each of the magnetic sensors 40#1 to 40#6 are input to the addition unit 502 and the subtraction unit 503. The addition unit 502 adds the signals from the magnetic sensors arranged at opposite 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 obtain sum signals v a+ (=v1 + v4), v b+ (=v2 + v5), and v c+ (=v3 + v6) and outputs them. The output signals v a+ , v b+ , v c+ from the addition unit 502 are input to the first Clarke conversion unit 504. The subtraction unit 503 subtracts the signal of one magnetic sensor from the signal of the other magnetic sensor arranged at the opposite position to obtain difference signals v a- (=v1 - v4), v b- (=v2 - v5), and v c- (=v3 - v6) and outputs them. The output signals v a- , v b- , v c- from the subtraction unit 503 are input to the second Clarke conversion unit 505.

[0027] The second Clarke conversion unit 505 performs Clarke conversion (three-phase to two-phase conversion) on the signals v a- , v b- , v c- which are three-phase signals from the subtraction unit 503 to calculate two-phase signals v α- , v β- . The two-phase signals v α- , v β- are input to the arctangent operation unit 506, and the arctangent operation unit 506 determines the rotation angle θ of the rotor 20 by calculating the arctangent of the ratio v β- / v α- of the two-phase signals.

[0028] The first Clarke conversion unit 504 performs Clarke conversion on the signals v which are three-phase signals from the addition unit 502a+ , v b+ , v c+ is Clarke-transformed to calculate two-phase signals v α+ , v β+ . The two-phase signals v α+ , v β+ are input to the inverse Park transformation unit 508. The value of the rotor 20's rotation angle θ calculated by the inverse tangent operation unit 506 is also input to the inverse Park transformation unit 508. The inverse Park transformation unit 508 uses a rotation matrix based on the rotation angle θ to perform an inverse Park transformation (orthogonal coordinate transformation) on the two-phase signals v α+ , v β+ to calculate the displacement of the rotor 20 in the plane (xy plane) orthogonal 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).

[0029] Thus, according to an embodiment of the present invention, by using the output signal from one type of magnetic sensor (e.g., only a Hall sensor), in addition to the rotation angle θ of the rotor 20, the in-plane displacements Δx and Δy of the rotor 20 can also be calculated. Therefore, the configuration of the sensor for detecting the magnetic field is simplified, and the cost reduction of the device and the improvement of the degree of freedom of the design layout can be achieved.

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

[0031] FIG. 6 is a diagram showing a 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' including a stator core 32' and a stator coil 34, a plurality of magnetic sensors 40, and a control unit 50. The motor 11 is a radial gap type bearingless motor that has both a function of rotating the motor rotor 20 and a function of magnetically supporting it. The motor 11 is different from the motor 10 described with reference to FIGS. 1 to 3 only in the shape of the stator core 32', and the configurations and functions of the other parts are the same as those of the motor 10. Since the shape of the stator core 32' itself is known, a detailed description thereof is omitted.

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

[0033] The motor 12 includes a motor rotor 20, a motor stator 30' including 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 in the same manner as the plurality of magnetic sensors 40 in the motor 11 of FIG. 6. The motor rotor 20, the stator core 32', the stator coil 34, the motor stator 30', and the plurality of magnetic sensors 40 of the motor 12 are the same as the corresponding (same reference numeral) elements in the motors 10 and 11 described with reference to FIGS. 1 to 3 and 6, and redundant descriptions are omitted. The motor rotor 20 of the motor 12 is fixed to the rotation axis 13, and the motor rotor 20 and the rotation axis 13 rotate integrally by driving the motor 12.

[0034] The magnetic bearing 700 includes a rotor 720 and a stator 730 including a stator core 732 and a stator coil 734. The rotor 720, the stator core 732, the stator coil 734, and the stator 730 of the magnetic bearing 700 are respectively of the same configuration as the motor rotor 20, the stator core 32’, the stator coil 34, and the motor stator 30’ of the motor 12. 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] The control unit 50 calculates, according to the same algorithm described with reference to FIG. 5, the rotation angle of the motor rotor 20 and the displacement of the motor rotor 20 in the plane orthogonal to the rotating shaft 13 of the motor 12 based on the signals from the plurality of magnetic sensors 40 provided in the motor 12. Then, the control unit 50 determines the value of the 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. Thereby, the rotating shaft 13 of the motor 12 rotates. Further, the control unit 50 determines the value of the 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. Thereby, in the magnetic bearing 700, a force for magnetically supporting the rotating shaft 13 of the motor 12 acts from the stator 730 on the rotor 720, and the rotating shaft 13 is supported in a non-contact manner.

[0036] As described above, the embodiments of the present invention have been described based on several examples. However, the above-described embodiments of the invention are for facilitating the understanding of the present invention and do not limit the present invention. The present invention can be changed and improved without departing from its gist, and it goes without saying that equivalents of the present invention are included. Also, within the scope of solving at least a part of the above-described problems or achieving at least a part of the effects, any combination or omission of each component described in the claims and the specification is possible.

Description of Symbols

[0037] 10 Motor 11 Motor 12 Motor 20 Motor Rotor 30 Motor Stator 32 Stator Core 321 Core Base 322 Core Rod 322a Main Part of Core Rod 322b End Part of Core Rod 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 Accommodation Part 502 Addition Part 503 Subtraction Part 504 First Clarke Transformation Part 505 Second Clarke Transformation Part 506 Arctangent Inverse Calculation Part 508 Inverse Park Transformation Part 700 Magnetic Bearing

Claims

1. 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, 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 orthogonal to the rotation axis of the rotor based on the voltage signals from the plurality of magnetic sensors, A motor comprising the above.

2. The motor according to claim 1, wherein the control unit is configured to perform Clarke transformation on the values of the voltage signals from the plurality of magnetic sensors in a first Clarke transformation unit, and further perform inverse Park transformation in an inverse Park transformation unit, thereby determining the displacement of the rotor in a plane orthogonal to the rotation axis of the rotor.

3. The motor according to claim 2, wherein the control unit is configured to perform Clarke transformation on the values of the voltage signals from the plurality of magnetic sensors in a second Clarke transformation unit, and further calculate the arctangent of the values after the Clarke transformation in an inverse tangent operation unit, thereby determining the rotation angle of the rotor.

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

5. The plurality of magnetic sensors include a plurality of pairs of oppositely arranged magnetic sensors, The control unit is configured to use the sum of the voltage signals from the magnetic sensor pairs as an input to the first Clarke transformation unit, and the difference between the voltage signals from the magnetic sensor pairs as an input to the second Clarke transformation unit, The motor according to claim 3.

6. A motor according to any one of claims 1 to 5, An impeller rotated by the motor, A pump comprising the above.

7. A method for detecting the displacement of a rotor in a motor, wherein The motor includes 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 includes A step of performing Clarke transformation on the values of the voltage signals from the plurality of magnetic sensors in a first Clarke transformation unit, A step of performing inverse Park transformation on the values after the Clarke transformation in the first Clarke transformation unit, A method including determining displacement of the rotor in a plane orthogonal to the rotation axis of the rotor. **Claim 8** The step of performing Clarke transformation on the values of the voltage signals from the plurality of magnetic sensors in a second Clarke transformation unit; The step of calculating the arctangent of the value after Clarke transformation in the second Clarke transformation unit; The method according to claim 7, further comprising determining the rotation angle of the rotor by the above. **Claim 9** The plurality of magnetic sensors include a plurality of pairs of magnetic sensors arranged opposite to each other, The step of inputting the sum of the voltage signals from the pair of magnetic sensors to the first Clarke transformation unit; The step of inputting the difference between the voltage signals from the pair of magnetic sensors to the second Clarke transformation unit; The method according to claim 8, including the above.

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