motor

Abstract

To provide a motor that has the improved accuracy of estimating the position of a rotor.SOLUTION: A rotor included in a motor according to an embodiment has a rotor core 31 formed of a magnetic substance, a plurality of magnets 33 arranged side by side on the rotor core 31 along the direction of rotation of the rotor, and a plurality of Hall elements arranged on a common mounting surface 41a and can detect the magnetic fields of the magnets 33. The plurality of magnets 33 each have an opposite surface 38 opposite to the mounting surface 41a, and the distance between the opposite surfaces 38 and the mounting surface 41a is constant. The rotor core 31 has an opposite surface 31b opposite to the mounting surface 41a, and has first areas R1 and second areas R2 different from each other in the distance between the opposite surface 31b and the mounting surface 41a. The first areas R1 and the second areas R2 are arranged alternately along the direction of rotation of the rotor. The number of pairs each composed of one first area R1 and one second area R2 adjacent to the first area R1 is determined according to the number of pole pairs of the magnets 33.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a motor. [Background technology]

[0002] There are known motors equipped with a position sensor for detecting the position of a rotor. The position sensor may be an optical sensor or a magnetic sensor. An example of an optical sensor is an optical encoder, and an example of a magnetic sensor is a Hall element. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6233532 Summary of the Invention [Problem to be solved by the invention]

[0004] In a motor equipped with a plurality of Hall elements as position sensors, the rotor position may be estimated by utilizing the characteristics of the voltages (Hall signals) output from the respective Hall elements.

[0005] The dimensions, shape, material properties, mounting positions, etc. of the multiple Hall elements mounted on one motor are not completely identical. In other words, there is variation among the multiple Hall elements mounted on one motor. As a result, the Hall signal output from each Hall element has its own unique characteristics due to the variations. Therefore, by having a microcomputer learn the characteristics present in the Hall signal output from each Hall element, the microcomputer can estimate the rotor position.

[0006] However, the characteristics of the Hall signals are subject to various variations and occur randomly. Therefore, it is possible that two or more Hall elements that output Hall signals with the same or nearly the same characteristics may be installed in one motor. In this case, the rotor position may be estimated incorrectly. [Means for solving the problem]

[0007] A motor according to one embodiment includes a stator and a rotor, the rotor including a rotor core made of a magnetic material, a plurality of magnets arranged on the rotor core along a rotation direction of the rotor, and a substrate, a portion of which is disposed inside the housing; and a plurality of magnetic sensors arranged on the mounting surface of the rotor and capable of detecting the magnetic field of the magnets. Each of the plurality of magnets has a facing surface facing the mounting surface, and the distance between the facing surface and the mounting surface is constant. The rotor core has a facing surface facing the mounting surface, and has first and second regions with different distances between the facing surface and the mounting surface. The first and second regions are arranged alternately in the rotation direction of the rotor. The number of pairs of one first region and one second region adjacent to the first region is determined according to the number of pole pairs of the magnets. The factor of the number of sets and the factor of the number of pole pairs of the magnet have no matching values ​​other than 1, both the number of sets and the number of pole pairs of the magnet are positive integers, and when either the number of sets or the number of pole pairs of the magnet is 1, the other is other than 1. [Effects of the Invention]

[0008] According to one aspect of the present invention, a motor is provided with improved accuracy in rotor position estimation. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is an exploded perspective view showing the structure of a motor according to an embodiment of the present invention; [Figure 2] FIG. 2 is a perspective view showing the structure of a motor. [Figure 3] FIG. 2 is a cross-sectional view showing the structure of a motor. [Figure 4] FIG. 2 is a functional block diagram of a motor. [Figure 5] FIG. [Figure 6A] FIG. 2 is a side view of the rotor core. [Figure 6B] FIG. 2 is a perspective view of a rotor core. [Figure 7] FIG. 3 is a schematic diagram showing the overlapping area between the rotor core and each magnet. [Figure 8] FIG. 10 is a diagram showing the relationship between a Hall signal and a rotation angle. [Figure 9A] FIG. 10 is a front view of another example of a rotor core. [Figure 9B] FIG. 10 is a perspective view of another example of a rotor core. [Figure 10] FIG. 10 is a diagram illustrating the relationship between the Hall signal and the rotation angle in another example. DETAILED DESCRIPTION OF THE INVENTION

[0010] <Embodiment> Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In all drawings referred to for describing the embodiment, the same reference numerals are used for the same or substantially the same components. Furthermore, as a general rule, the components that have already been described will not be described repeatedly.

[0011] FIG. 1 is an exploded perspective view showing the structure of a motor 1A according to one embodiment. FIG. 2 is a perspective view showing the structure of the motor 1A. FIG. 3 is a cross-sectional view showing the structure of the motor 1A. The cross-section shown in FIG. 3 is a cross-section of the motor 1A taken along line XX in FIG. 2.

[0012] <Motor Overview> The motor 1A includes a housing 10, a stator 20, a rotor 30, and a substrate 40. The rotor 30, housed in the housing 10, is disposed radially inside the stator 20, which is also housed in the housing 10, and is rotatable relative to the stator 20. In other words, the motor 1A is an inner rotor type motor.

[0013] <Housing> The housing 10 is composed of two members that are fitted together. More specifically, the housing 10 is composed of a base member 11a and a cover member 11b. Note that the cover member 11b is not shown in Figures 2 and 3. The base member 11a has a bottom wall portion 12, a pair of fixing pieces 13a, 13b, and a pair of ribs 14a, 14b.

[0014] The bottom wall 12 of the base member 11a is circular or approximately circular, and has a through hole 15 at its center. Furthermore, a cylindrical shaft holder 16 that communicates with the through hole 15 is provided on the bottom wall 12 of the base member 11a.

[0015] The fixing pieces 13a and 13b protrude parallel to the bottom wall 12 from the edge of the bottom wall 12. Meanwhile, the ribs 14a and 14b rise perpendicularly to the bottom wall 12 from the edge of the bottom wall 12. Each of the fixing pieces 13a and 13b has a screw hole through which a screw for fixing the motor 1A in a predetermined position is inserted. The ribs 14a and 14b are curved along the edge of the bottom wall 12.

[0016] The cover member 11b has a cylindrical peripheral wall portion 17 and a top wall portion 18 that closes one end of the peripheral wall portion 17. When the base member 11a and the cover member 11b are combined, the peripheral wall portion 17 of the cover member 11b is disposed outside the ribs 14a, 14b of the base member 11a, and the top wall portion 18 of the cover member 11b faces the bottom wall portion 12 of the base member 11a. As a result, an accommodation space surrounded by the peripheral wall portion 17 is formed between the bottom wall portion 12 and the top wall portion 18. Note that a portion of the accommodation space is doubly surrounded by the ribs 14a, 14b and the peripheral wall portion 17.

[0017] <Stator> The stator 20 is formed in an annular shape surrounding the rotor 30, and is fixed to the inside of the housing 10. Between the stator 20 and the rotor 30, a predetermined gap (air gap) is provided.

[0018] The stator 20 has a stator core 21 fixed to the inner circumferential surface of the housing 10. The stator core 21 is formed from a single sheet of electromagnetic steel or multiple laminated sheets. The stator core 21 has a plurality of teeth 22 that protrude radially inward (toward the rotor 30). More specifically, the stator core 21 has 12 teeth 22 arranged at 30-degree intervals. From another perspective, the stator 20 has 12 slots.

[0019] In addition to a stator core 21 , the stator 20 has insulators 23 provided around the respective teeth 22 , and coils 24 provided around the respective insulators 23 .

[0020] The insulator 23 is made of an insulating material (for example, a resin material). The coil 24 is made of a conductive wire (for example, a copper alloy wire) wound around the insulator 23.

[0021] Of the twelve coils 24, four are U-phase coils, four are V-phase coils, and four are W-phase coils. From another perspective, three-phase currents, each shifted in phase by 120 degrees, are input to the stator 20. When a current (coil current) is supplied to each of the U-, V-, and W-phase coils 24, the coils are excited and generate a magnetic field that acts on the rotor 30.

[0022] <Rotor> The rotor 30 has a rotor core 31, a rotor hub 32, a magnet 33, and a shaft 34, and is rotatable about a central axis C as a rotation axis. Here, the direction of the central axis C is defined as the up-down direction. According to this definition, the base member 11a and the cover member 11b constituting the housing 10 face each other in the up-down direction. More specifically, the bottom wall portion 12 of the base member 11a and the top wall portion 18 of the cover member 11b face each other in the up-down direction. In the following description, for convenience, the side of the bottom wall portion 12 may be referred to as the "lower side" or "below" and the side of the top wall portion 18 may be referred to as the "upper side" or "upper." Furthermore, the direction of rotation of the rotor 30 about the central axis C as a rotation axis may be referred to as the "circumferential direction."

[0023] The rotor core 31 is made of a magnetic material and has a cylindrical shape that extends in the vertical direction. A rotor hub 32 is provided inside the rotor core 31, and a plurality of magnets 33 are provided outside the rotor core 31.

[0024] The rotor hub 32 has a cylindrical side surface portion 32a whose outer diameter is smaller than the inner diameter of the rotor core 31, and a disk-shaped upper surface portion 32b that closes one end of the side surface portion 32a. The side surface portion 32a and the upper surface portion 32b are integrally molded from a non-magnetic material.

[0025] The rotor hub 32 is fitted inside the rotor core 31, and the two are fixed so as not to rotate relative to each other. More specifically, the inner peripheral surface of the rotor core 31 and the outer peripheral surface of the rotor hub 32 are fixed to each other. In other words, the rotor core 31 and the rotor hub 32 are integrated.

[0026] The multiple magnets 33 are arranged on the rotor core 31 along the rotation direction (circumferential direction) of the rotor 30. More specifically, ten magnets 33 are arranged on the rotor core 31 at equal intervals along the circumferential direction. The ten magnets 33 are arranged so that their north and south poles alternate along the circumferential direction. Each magnet 33 is fixed (adhered) to the outer circumferential surface of the rotor core 31.

[0027] The shaft 34 is fixed to the rotor hub 32. More specifically, the base end of the shaft 34 passes through the shaft holder 16 and protrudes from the shaft holder 16. Furthermore, the base end of the shaft 34 protruding from the shaft holder 16 is press-fit into the center of the rotor hub 32.

[0028] The shaft 34 is rotatably supported by bearings 35a and 35b provided inside the shaft holder 16. The bearings 35a and 35b are stacked one on top of the other, and a spring washer 36 is interposed between the bearings 35a and 35b.

[0029] On the other hand, the tip of the shaft 34 penetrates the bottom wall portion 12 of the base member 11a and protrudes from the housing 10. Furthermore, a pinion gear 37 is attached to the tip of the shaft 34 protruding from the housing 10.

[0030] <Substrate> The substrate 40 is a flexible substrate. A portion of the substrate 40 is disposed inside the housing 10, and another portion of the substrate 40 is drawn out to the outside of the housing 10. In the following description, the portion of the substrate 40 disposed inside the housing 10 may be referred to as the "main body portion 41," and the other portion of the substrate 40 drawn out to the outside of the housing 10 may be referred to as the "drawout portion 42," to distinguish between the two. However, this distinction is made merely for the sake of convenience.

[0031] The main body 41 of the substrate 40 is disk-shaped and covers almost the entire bottom wall 12 of the base member 11a, avoiding the shaft holder 16. On the other hand, the drawer 42 is strip-shaped and extends outside the housing 10, passing between the fixed piece 13a and the rib 14b of the base member 11a.

[0032] <Magnetic sensor> A plurality of magnetic sensors capable of detecting the magnetic field of the magnet 33 provided on the rotor 30 are mounted on the substrate 40. More specifically, three Hall elements 50u, 50v, and 50w are mounted on the substrate 40. The Hall elements 50u, 50v, and 50w are mounted at equal intervals along the circumferential direction on the surface 41a of the main body 41. In other words, the surface 41a of the main body 41 is a common mounting surface for the three Hall elements 50u, 50v, and 50w. Therefore, in the following description, the surface 41a of the main body 41 may be referred to as the "mounting surface 41a." Furthermore, the Hall elements 50u, 50v, and 50w may be collectively referred to as the "Hall elements 50."

[0033] The Hall element 50u is a magnetic sensor for detecting the magnetic field strength of the U phase and outputs a voltage (Hall signal / differential signal) corresponding to the magnetic field strength of the U phase. The Hall element 50v is a magnetic sensor for detecting the magnetic field strength of the V phase and outputs a voltage (Hall signal / differential signal) corresponding to the magnetic field strength of the V phase. The Hall element 50w is a magnetic sensor for detecting the magnetic field strength of the W phase and outputs a voltage (Hall signal / differential signal) corresponding to the magnetic field strength of the W phase.

[0034] Each of the Hall elements 50u, 50v, and 50w is electrically connected to a wiring formed on the substrate 40. Hall signals output from the Hall elements 50u, 50v, and 50w are input to a predetermined device, processing unit, control unit, etc. via the wiring formed on the substrate 40.

[0035] 4 is a functional block diagram of the motor 1A. The motor 1A has an amplifier 60, a position estimation unit 61, a control unit 62, a drive unit 63, etc. Hall signals output from the Hall elements 50u, 50v, and 50w are input to the amplifier 60 via the substrate 40. The amplifier 60 amplifies the input Hall signals and outputs them to the position estimation unit 61.

[0036] The position estimation unit 61 is an information processing device for estimating the position of the rotor 30, and includes a calculation unit, a storage unit, etc. The position estimation unit 61 estimates the position of the rotor 30 based on values ​​calculated based on the input Hall signals, information stored in advance in the storage unit, etc., and outputs the estimation result to the control unit 62. The position estimation unit 61 can estimate the position of the rotor 30 when it is stopped, the position of the rotor 30 while it is rotating, etc.

[0037] The control unit 62 generates a control signal based on the position of the rotor 30 estimated by the position estimation unit 61 and an instruction signal input from an external device, and outputs the generated control signal to the drive unit 63. The instruction signal is, for example, a signal representing the rotation direction, rotational force, rotation angle, rotation speed, etc. of the rotor 30. The control signal is, for example, a signal representing a register value corresponding to the rotation direction represented by the instruction signal, or a signal representing the current value of the current output from the drive unit 63 to the stator 20.

[0038] The driver 63 drives the stator 20 based on the input control signal. The driver 63 rotates the rotor 30 in a specified direction at a specified speed, for example, by supplying a three-phase current of a current value indicated by the control signal to each coil 24 of the stator 20.

[0039] <Rotor core shape> Fig. 5 is a front view of rotor 30. Fig. 6A is a side view of rotor core 31, and Fig. 6B is a perspective view of rotor core 31. Fig. 7 is a schematic diagram showing the overlapping area between outer peripheral surface 31a of rotor core 31 and each magnet 33. From another perspective, Fig. 7 is a development view of rotor core 31.

[0040] As described above, ten magnets 33 are attached to the outer peripheral surface 31a of the rotor core 31, with the north poles and south poles arranged alternately in the circumferential direction. In other words, the rotor core 31 is provided behind (inside) the ten magnets 33 arranged in an annular pattern, and functions as a back yoke. In the following description, one north-pole magnet 33 and one south-pole magnet 33 adjacent to each other may be referred to as a pole pair. In other words, five magnets 33 are attached to the rotor core 31.

[0041] The ten magnets 33 are arranged at constant intervals in the circumferential direction (arrangement direction), and the height of the ten magnets 33 relative to the mounting surface 41a is also constant. Here, the height of the magnets 33 relative to the mounting surface 41a means the shortest linear distance from the mounting surface 41a to the opposing surface 38 of the magnet 33 that faces the mounting surface 41a.

[0042] In the following description, for convenience, the ten magnets 33 may be distinguished by being called "magnet 33a," "magnet 33b," "magnet 33c," etc.

[0043] While the height of the ten magnets 33 relative to the mounting surface 41a is constant, the height of the rotor core 31 relative to the mounting surface 41a is not constant. More specifically, the height of the rotor core 31 relative to the mounting surface 41a varies along the circumferential direction. Note that the height of the rotor core 31 relative to the mounting surface 41a refers to the shortest linear distance from the mounting surface 41a to the opposing surface 31b of the rotor core 31 that faces the mounting surface 41a.

[0044] From another perspective, the rotor core 31 has a region (first region) R1 whose width continuously narrows toward the upper side along the circumferential direction of the rotor core 31 and then continuously widens toward the opposing surface 31b along the circumferential direction of the rotor core 31, and a region (second region) R2 whose width remains constant. The first regions R1 and the second regions R2 are alternately arranged along the circumferential direction of the rotor core 31. A first region R1 and a second region R2 adjacent to the first region R1 are referred to as one set. When multiple first regions R1 and multiple second regions R2 are formed in the rotor core 31, multiple sets are arranged along the circumferential direction of the rotor core 31. FIGS. 6A and 6B show a case where four first regions R1 and four second regions R2 are formed, resulting in a total of four sets. The number of sets can be referred to as the number of repetitions (periods) of the first regions R1 and the second regions R2. That is, the height of the opposing surface 31b of the rotor core 31 relative to the mounting surface 41a varies periodically.

[0045] The number of the above-mentioned sets (i.e., periodicity) is determined according to the number of pole pairs of the magnet 33. In this case, the number of sets and the number of pole pairs of the magnet 33 satisfy the following conditions (1) to (3).

[0046] (1) There is no value other than 1 where the factor of the number of sets and the factor of the number of pole pairs of the magnet 33 match. (2) The number of sets and the number of pole pairs of the magnet 33 are both positive integers. (3) When either the number of sets or the number of pole pairs of the magnet 33 is 1, the other is other than 1. Figure 7 shows the overlapping area between the outer peripheral surface 31a of the rotor core 31 and each magnet 33 when the number of sets is set to 4 to satisfy the above conditions (1) to (3) and the number of pole pairs of the magnet 33 is set to 5 (the number of poles of the magnet 33 is 10).

[0047] While the height of the magnets 33 is constant, the height of the rotor core 31 varies as described above, resulting in different overlapping areas between the rotor core 31 and each magnet 33. Specifically, magnets 33a, 33b, 33c, 33d, 33e, 33f, 33g, 33h, 33i, and 33j are arranged in this order along the circumferential direction. Furthermore, magnet 33a, located at one end of the arrangement direction, is arranged in a second region R2 of the rotor core 31 where the width is wider, while magnet 33j, located at the other end of the arrangement direction, is arranged in a first region R1 where the width of the rotor core 31 is narrower than that of the second region R2. Therefore, the overlapping area between magnet 33j and the rotor core 31 is smaller than the overlapping area between magnet 33a and the rotor core 31. Furthermore, as described above, the width of first region R1 continuously narrows toward the upper side along the circumferential direction of the rotor core 31, and then continuously widens toward the opposing surface 31b along the circumferential direction of the rotor core 31. Therefore, the overlapping areas of the other magnets 33b to 33i and the rotor core 31 are different from one another.

[0048] As described above, in this embodiment, the overlapping areas of the rotor core 31, which functions as the back yoke, and each magnet 33 are different. Therefore, the magnetic resistance of the magnetic circuit including the magnetic flux of one magnet 33 and the Hall element 50 does not match the magnetic resistance of the magnetic circuit including the magnetic flux of another magnet 33 and the Hall element 50.

[0049] Therefore, the Hall elements 50 output Hall signals of different magnitudes (voltages) for each magnet 33. More specifically, even if the characteristics of the three Hall elements 50u, 50v, and 50w mounted on the motor 1A coincidentally match, the maximum values, minimum values, and waveforms of the Hall signals output from these Hall elements 50u, 50v, and 50w differ for each magnet 33.

[0050] FIG. 8 shows the relationship between the Hall signal and the rotation angle when the number of pairs is four and the number of pole pairs of the magnet 33 is five. In FIG. 8, the horizontal axis represents the rotation angle and the vertical axis represents the Hall signal output. In FIG. 8, the Hall signal output from the Hall element 50u is represented by waveform s1, the Hall signal output from the Hall element 50v is represented by waveform s2, and the Hall signal output from the Hall element 50w is represented by waveform s3. As shown in FIG. 8, during one rotation of the rotor 30, the shapes of the waveforms s1, s2, and s3 at a certain angle do not match the shapes of the waveforms s1, s2, and s3 at other angles. In other words, no two or more Hall elements 50 output Hall signals with the same or nearly the same characteristics. As a result, the accuracy of the position estimation of the rotor 30 is improved.

[0051] In the above description, the rotor core 31 has four sets and five pole pairs of the magnet 33. However, this is not limiting. For example, the number of sets may be one and the number of pole pairs of the magnet 33 may be two, which satisfies the above-described conditions (1) to (3). FIG. 9A is a side view of the rotor core 31 when the number of sets is one and the number of pole pairs of the magnet 33 is two, and FIG. 9B is a perspective view of the rotor core 31. FIG. 10 shows the relationship between the Hall signals and the rotation angle in this case. In this case, too, during one rotation of the rotor 30, the shapes of the waveforms s1, s2, and s3 at a certain angle do not match the shapes of the waveforms s1, s2, and s3 at other angles. In other words, two or more Hall elements 50 do not output Hall signals with the same or substantially the same characteristics. Therefore, even when the number of sets is one and the number of pole pairs of the magnet 33 is two, two or more Hall elements 50 do not output Hall signals with the same or substantially the same characteristics, improving the accuracy of the position estimation of the rotor 30. That is, the shape of the opposing surface 31b of the rotor core 31 may be determined based on the number of sets that satisfy the above-mentioned conditions (1) to (3) and the number of pole pairs of the magnet 33.

[0052] In the above description, rotor core 31 is assumed to have a shape that satisfies the above conditions (1) to (3) so that there is no angle at which the shapes of waveforms s1, s2, and s3 coincide as shown in Figures 8 and 10. However, there is also a method of attaching magnets 33 to rotor core 31 at different heights from mounting surface 41a to obtain waveforms s1, s2, and s3 as shown in Figures 8 and 10.

[0053] The present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the spirit of the present invention. For example, the numbers of teeth 22, magnets 33, and Hall elements 50 can be changed as appropriate. Figure 4 shows only one example of a functional block, and the input destination of the Hall signal is not limited to the amplifier unit 60. [Explanation of symbols]

[0054] 1A motor 10. Housing 11a Base member 11b Cover member 12 Bottom wall 13a,13b Fixed piece 14a,14b Ribs 15 through holes 16 Shaft holder 17 Peripheral wall section 18 Ceiling wall 20 Stator 21 Stator core 22 Teeth 23 Insulator 24 coils 30 rotors 31 rotor core 31a Outer surface 31b Opposite surface 32 rotor hub 32a Side part 32b Top part 33 Magnet 34 Shaft 35a, 35b bearings 36 Spring washer 37 Pinion gear 38 Opposite Surface 40 boards 41 Main body 41a Surface (mounting surface) 42 Drawer section 50, 50u, 50v, 50w Hall element 60 Amplification section 61 Position estimation part 62 Control Unit 63 Drive unit

Claims

1. A motor comprising a stator and a rotor, The rotor is a rotor core formed of a magnetic material; a plurality of magnets arranged on the rotor core along the rotation direction of the rotor; a substrate having a portion disposed within the housing; a plurality of magnetic sensors arranged on the mounting surface of the board and capable of detecting the magnetic field of the magnet; and each of the plurality of magnets has a facing surface facing the mounting surface, and the distance between the facing surface and the mounting surface is constant; the rotor core has an opposing surface facing the mounting surface, and a first region and a second region having mutually different distances between the opposing surface and the mounting surface; the first regions and the second regions are arranged alternately along the rotation direction of the rotor, the number of pairs of one first region and one second region adjacent to the first region is determined according to the number of pole pairs of the magnet, A motor in which the factor of the number of sets and the factor of the number of pole pairs of the magnet have no matching value other than 1, the number of sets and the number of pole pairs of the magnet are both positive integers, and when one of the number of sets and the number of pole pairs of the magnet is 1, the other is other than 1.

2. 2. The motor according to claim 1, the rotor further includes a rotor hub formed of a non-magnetic material; an inner circumferential surface of the rotor core is fixed to an outer circumferential surface of the rotor hub; The motor, wherein the plurality of magnets are fixed to the outer peripheral surface of the rotor core.

3. 3. The motor according to claim 1, a position estimator that estimates a position of the rotor based on a signal output from the magnetic sensor;

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