JP2024068424A - motor - Google Patents

Abstract

[Problem] To improve the accuracy of magnet position detection by a magnetic sensor without adding any additional motor components. [Solution] A motor includes a rotor 3 having magnets 31 arranged in the circumferential direction and a rotor core 33 that houses the magnets 31, a shaft 2 fixed to the rotor 3, a magnetic sensor 81 that detects the number of rotations of the rotor 3, and a magnetic body 7 that covers one surface of the magnet 31 in the axial direction, the magnetic body 7 having a protruding portion 71 that protrudes in the axial direction, and the magnetic sensor 81 facing the protruding portion 71 in the axial direction. [Selected Figure] Figure 1

Description

The present invention relates to a motor.

Motors are used as the driving source for various devices. There are many different types of motors, and each type is selected depending on the purpose and situation of use. Among them, the Interior Permanent Magnet Synchronous Motor, which has a magnet embedded inside the rotor core, is well known. Since IPMSMs have a high degree of freedom in designing performance and shape, they are used in a wide range of applications, such as home appliances, automotive, and industrial fields.

The rotor section of the IPMSM comprises a rotor core stacked in the axial direction and magnets housed in housing holes formed along the axial direction from the end face of the rotor core. A technique is known for holding the magnets in the IPMSM by providing end plates at the axial ends to cover the openings of the housing holes (see, for example, Patent Document 1).

In order to control the current supply to the stator windings according to the rotational position of the rotor, IPMSMs are often provided with a magnetic sensor that detects the rotational position of the rotor based on the magnetic field generated by the rotor magnet. There is known technology for enabling a magnetic sensor to accurately detect the magnetic field generated by the rotor magnet in a motor (see, for example, Patent Documents 2 and 3).

Japanese Patent Application Laid-Open No. 9-233750 JP 2002-101583 A JP 2004-129456 A

However, the above technology requires the installation of additional components in the motor to improve the accuracy with which the magnetic sensor detects the magnet's position. For this reason, further improvements are required in this respect in conventional technology.

The present invention has been made in consideration of the above background, and aims to provide a technology that improves the accuracy of magnet position detection by a magnetic sensor without adding additional motor components.

To achieve the above object, the motor according to the present invention comprises a rotor having magnets arranged in the circumferential direction and a rotor core that houses the magnets, a shaft fixed to the rotor, a magnetic sensor that detects the rotation speed of the rotor, and a magnetic body that covers one side of the magnet in the axial direction, the magnetic body having a protruding portion that protrudes in the axial direction, and the magnetic sensor facing the protruding portion in the axial direction.

1 is a cross-sectional view of a motor according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of the motor according to the present embodiment, and is a partially enlarged cross-sectional view mainly showing a rotor, a plate, and a magnetic sensor in FIG. FIG. 2 is a perspective view of a plate included in the motor according to the present embodiment. 11 is a diagram showing the characteristics of the distance from the end face in the axial direction of the rotor and the magnetic flux density in the axial direction in the motor according to the present embodiment and a motor of a comparative example. FIG.

An exemplary embodiment of the present invention will be described below with reference to the drawings.

Figure 1 is a vertical cross-sectional view of the motor 1 according to this embodiment, and Figure 2 is a partially enlarged cross-sectional view showing mainly the rotor 3, plate 7, and magnetic sensor 81 of the motor 1 shown in Figure 1.

In the description of this embodiment, the terms "upper" and "lower" refer to the upper and lower positions in FIG. 1 and do not necessarily coincide with the upper and lower positions in the direction of gravity.
Furthermore, in the direction of the axis X (hereinafter also referred to as the "axial direction"), the direction of the arrow a is the upper side a, and the direction of the arrow b is the lower side b. In addition, in the direction perpendicular to the axis X (hereinafter also referred to as the "radial direction"), the direction away from the axis X (the direction of the arrow c) is the outer circumferential side c, and the direction toward the axis X (the direction of the arrow d) is the inner circumferential side d. The circumferential direction (as viewed from the upper side a) about the rotation axis X is the circumferential direction.
These definitions and symbols regarding directions will also apply in the following explanation.

The motor 1 in this embodiment is a type of inner rotor type brushless motor, a spoke type interior permanent magnet synchronous motor (IPMSM). An IPMSM is a motor with a magnet embedded in the rotor, and is also called an interior permanent magnet type motor. There are various types of IPMSM, but a spoke type IPMSM is known in which the longitudinal direction of magnets with a rectangular cross section is arranged radially inside the rotor core. In this spoke type IPMSM, the surfaces on the long sides become magnetic poles, and the opposing magnetic pole faces of adjacent magnets in the circumferential direction are of the same polarity.

The motor 1 includes a shaft 2 that serves as a rotating shaft, a rotor 3, a stator 4, a housing 5, bearings 61 and 62, a plate 7, a circuit board 8, and a magnetic sensor 81.

The shaft 2 has two ends 2a and 2b. One end 2b of the shaft 2 on the housing body 51 side is rotatably supported by one bearing 61 relative to the housing body 51. The other end 2a of the shaft 2 on the cover 52 side is rotatably supported by the other bearing 62. In other words, the shaft 2 is rotatably fixed to the housing body 51 via the bearing 61 and to the cover 52 via the bearing 62. One end 2a of the shaft 2 protrudes from the cover 52. The shaft 2 is designed to be able to output a rotational force from the one end 2a to the outside. The shaft 2 is fixed to the rotor 3, and rotates together with the rotor 3 when the rotor 3 rotates due to the electromagnetic action between the stator 4 and the rotor 3.

The rotor 3 is made of a magnetic material and has magnets 31 arranged inside a rotor core 33, and is fixed to the shaft 2 so that it rotates together with the shaft 2. The rotor 3 is arranged so that there is a predetermined gap between it and the stator 4.

The magnet 31 is attached to the outer periphery of the rotor 3, i.e., the side facing the inner periphery of the stator 4. The magnet 31 is held by the rotor core 33. The magnet 31 is arranged along the outer periphery of the rotor 3. The magnet 31 may be a plurality of magnets arranged along the outer periphery of the rotor 3, or a magnet formed in a ring or approximately ring shape may be arranged along the outer periphery of the rotor 3.

The rotor core 33 is formed by laminating multiple magnetic bodies. The multiple magnetic bodies that make up the rotor core 33 are, for example, electromagnetic steel plates. The rotor core 33 is provided with a space capable of accommodating the magnets 31 so that the magnets 31 can be arranged along the outer peripheral surface.

The stator 4 has a stator core 41 including teeth 43, and a coil 42. The coil 42 is wound around the stator core 41. The stator 4 is arranged to surround the rotor 3.

The stator core 41 is a laminate of magnetic material such as electromagnetic steel sheets. The stator core 41 has an annular portion (hereinafter referred to as the "annular portion") 44 arranged coaxially with the shaft 2, and a plurality of magnetic pole portions (hereinafter referred to as the "teeth portion") 43 formed to extend from the annular portion 44 toward the shaft 2.

The coils 42 are wound around each of the multiple teeth 43 of the stator core 41. The stator core 41 and the coils 42 are insulated by an insulator 45 made of an insulating material.

The housing 5 has a housing body 51 and a cover 52. The housing body 51 houses some or all of the components of the motor 1, such as the rotor 3 and the stator 4, and the stator 4 is fixed thereto.

The housing body 51 has a bottom portion 51a with a protrusion 51aa, a cylindrical portion 51b, and an outer peripheral portion 51c.

The cover 52 covers an opening provided at the top of the housing body 51. The cover 52 has an annular flat plate portion 52a having a protrusion 52aa, and an outer periphery 52c. The protrusion 52aa of the cover 52 is provided on the flat plate portion 52a and protrudes in the direction toward the rotor 3 (lower side b) in the longitudinal direction (axis X direction) of the shaft 2. In the motor 1, the outer periphery 51c of the housing body 51 and the outer periphery 52c of the cover 52 are fixed (fastened) to each other, shielding the inside of the housing 5 from the outside.

The motor 1 is provided with a plurality of bearings 61, 62 (two in this embodiment) that rotatably support the shaft 2 relative to the housing 5. One of the bearings 61, 62, is provided on the bottom 51a of the housing body 51. The bottom 51a of the housing body 51 that supports the bearing 61 is provided with a protruding portion (hereinafter referred to as the "bearing housing") 51aa that protrudes toward the rotor 3 (upper side a) in the longitudinal direction (axis X direction) of the shaft 2 and a hole portion 51ab, and the bearing 61 is fixed to the bearing housing 51aa by press-fitting or the like. The other bearing 62 is fixed to the protruding portion (hereinafter referred to as the "bearing housing") 52aa of the cover 52 by press-fitting or the like. In the radial direction, the outer diameter and inner diameter of one bearing 61 and the outer diameter and inner diameter of the other bearing 62 are approximately the same.

The outer diameter and inner diameter of one bearing 61 and the outer diameter and inner diameter of the other bearing 62 are approximately the same, but the outer diameter, inner diameter, or both of the other bearing 62 may be larger than the outer diameter, inner diameter, or both of the one bearing 61. Also, the hole 51ab does not have to be provided in the bottom 51a.

The plate 7 is an example of a magnetic body, and is provided so as to face one surface of the rotor 3 in the axial direction, that is, the upper surface of the rotor 3 in the axial direction (hereinafter referred to as the rotor upper surface 34) as shown in FIG. 2. The plate 7 covers the rotor upper surface 34. As described above, the magnets 31 are arranged in a ring shape in the circumferential direction of the rotor 3 along the outer peripheral surface of the rotor 3. The plate 7 covers the upper surface of the magnet 31 in the axial direction (hereinafter referred to as the magnet upper surface 35). The plate 7 covers the rotor upper surface 34 and the magnet upper surface 35 to prevent the magnet 31 from moving in the axial direction. In other words, the plate 7 is an end plate provided at the end of the rotor 3 in the axial direction, and holds the magnet 31 by covering the opening of the space in the rotor core 33 in which the magnet 31 is accommodated.

Figure 3 is a perspective view of the plate 7 provided in the motor 1. The plate 7 is formed of a magnetic material such as S45C or an electromagnetic steel plate. The plate 7 has a protrusion 71, an outer peripheral end 72, an upper end 73, a disk portion 74, and a hole portion 75.

The protruding portion 71 is a portion that protrudes upward in Figs. 1 and 2 from the disk portion 74 in the up-down direction (the direction in which the surface of the disk portion 74 expands, the axial direction) in a direction away from the rotor 3. The protruding portion 71 is provided at the outer peripheral end portion 72, which is the end portion on the outer peripheral side of the disk portion 74 in the radial direction. The outer peripheral end portion 72 of the protruding portion 71, which is the outer peripheral side surface in the radial direction, may form a surface that is continuous with the end portion, which is the outer peripheral side surface in the radial direction of the rotor core 33. As shown in Figs. 1 and 2, the protruding portion 71 is formed by bending the outer peripheral end portion 72 of the disk portion 74 in a cross-sectional shape into an L-shape or a substantially L-shape.

The disk portion 74 is formed so that the surface opposite to the direction in which the protrusion 71 protrudes, i.e., the lower surface 74b, is in contact with or faces the rotor upper surface 34 of the rotor 3, thereby being able to bear the magnetic force generated by the magnet 31 of the rotor 3. A hole 75 for inserting the shaft 2 is provided in the center of the disk portion 74. Note that the disk portion 74 is not limited to the example shown in Figures 1 to 3, which is formed in a disk-like or approximately disk-like shape having a flat or approximately flat surface. The disk portion 74 may have a shape that corresponds to the shape of the rotor upper surface 34, or a shape that is suitable for bearing the magnetic force from the magnet 31, for example.

In the plate 7 configured as described above, the protruding portion 71 can guide the magnetic flux from the magnet 31 attached to the rotor core 33 in one direction in the up-down direction from the disk portion 74, for example, in the direction of the magnetic sensor 81 provided on the upper side of the plate 7. Specifically, in the plate 7, the disk portion 74 faces the rotor upper surface 34 and the magnet upper surface 35 of the rotor 3, and thus is affixed with the magnetic flux from the magnet 31. And, because the protruding portion 71 protrudes from the disk portion 74 so as to approach the magnetic sensor 81, the magnetic flux from the magnet 31 is guided to the magnetic sensor 81 as indicated by the arrow M shown in FIG. 2.

The protrusion 71 is not limited to being provided at the outer peripheral end 72 of the disk portion 74, but may be provided at any suitable position in the radial direction of the disk portion 74.

The circuit board 8 is provided above the plate 7, facing the plate 7 in the axial direction. In addition to the magnetic sensor 81, the circuit board 8 is provided with various electronic components for operating the motor 1, and circuits for making these electronic components function. The magnetic sensor 81 is provided on the mounting surface 82 of the circuit board 8 so that the part that detects the magnetic field faces the protrusion 71, that is, faces downward, so that the magnetic force generated from the magnet 31 can be detected via the protrusion 71. The magnetic sensor 81 is provided at a position facing the protrusion 71 in the axial direction. It is desirable that the magnetic sensor 81 is provided so that a part of it overlaps with the protrusion 71 when viewed from the axial direction.

[Motor Action]
Next, the operation of the motor 1 having the above-described configuration will be described.

In the motor 1 described above, the plate 7 covering the rotor upper surface 34, which is one surface of the rotor 3 in the axial direction, is made of a magnetic material, and covers the magnet upper surface 35, which is one surface of the magnet 31 in the axial direction. The plate 7 has a protruding portion 71 that protrudes in the axial direction away from the rotor 3. In addition, the motor 1 has a magnetic sensor 81 that detects the rotation speed of the rotor 3, which is provided facing the protruding portion 71 in the axial direction, and detects the magnetic force generated by the protruding portion 71.

The motor 1 also includes a circuit board 8 that faces the plate 7 in the axial direction, and a magnetic sensor 81 is positioned so that it partially overlaps with the protrusion 71 when viewed from the axial direction.

The motor 1 configured as described above allows the magnetic flux generated from the rotor 3 to be concentrated at the magnetic sensor 81 by the protruding portion 71 of the plate 7, improving the accuracy of magnetic detection of the rotor 3 by the magnetic sensor 81. Here, the plate 7 is a part that holds the magnet 31.

In other words, the motor 1 can improve the accuracy of the position detection of the magnet 31 by the magnetic sensor 81 without adding any components to the motor 1.

Figure 4 is a diagram showing the relationship between the distance from the end face in the axial direction of the rotor 3 and the magnetic flux density in the axial direction for motor 1 and a motor of a comparative example. In Figure 4, the motor of the comparative example corresponds to a motor that does not have a protrusion 71 on the outer peripheral end 72 of the plate 7 provided in the motor. Figure 4 also shows data calculated by magnetic field analysis. In Figure 4, the working example is shown by a solid line, and the comparative example is shown by a dashed line.

As shown in FIG. 4, the motor 1 having the protrusion 71 on the plate 7 has a larger magnetic flux density in the axial direction than the comparative motor. In other words, the motor 1 can increase the amount of magnetic flux required for the magnetic sensor 81 to detect the rotational position of the rotor.

In addition, the motor 1 has a protrusion 71 provided at the outer peripheral end 72, which is the radial end of the plate 7.

With the motor 1 configured as described above, the protrusion 71 can be used as a hook for an assembly jig when assembling the motor 1, improving the workability of mounting the plate 7. In addition, with the motor 1, the protrusion 71 can be formed simply by bending the outer peripheral end 72 of the plate 7, improving the accuracy of magnetic detection of the rotor 3 through a simple assembly process.

In addition, the outer peripheral end 72 of the motor 1, which is the radial end of the protrusion 71, is flush with the radial end of the rotor 3.

The motor 1 configured as described above can improve the magnetic detection accuracy of the rotor 3 without increasing the size of the device configuration in the radial direction of the motor 1.

In addition, those skilled in the art may modify the motor of the present invention as appropriate in accordance with previously known knowledge. As long as such modifications still provide the configuration of the present invention, they are of course included in the scope of the present invention.

Reference Signs List 1...motor, 2...shaft, 2a, 2b...end, 3...rotor, 31...magnet, 33...rotor core, 34...upper surface of rotor, 35...upper surface of magnet, 4...stator, 41...stator core, 42...coil, 43...teeth portion, 44...ring portion, 45...insulator, 5...housing, 51...housing body, 51a...bottom, 51aa...bearing housing (protruding portion), 51ab...hole portion, 51b...tubular portion, 51c...outer periphery, 52...cover, 52a...flat plate portion, 52aa...bearing housing (protruding portion), 52c...outer periphery, 61...bearing, 62...bearing, 7...plate (magnetic material), 71...protruding portion, 72...outer periphery end, 73...upper end, 74...disk portion, 74b...lower surface, 75...hole portion, 8...circuit board, 81...magnetic sensor, 82...mounting surface

Claims (4)

a rotor having magnets arranged in a circumferential direction and a rotor core that houses the magnets;
A shaft fixed to the rotor;
A magnetic sensor for detecting the rotation speed of the rotor;
a magnetic body covering one surface of the magnet in the axial direction;
Equipped with
The magnetic body has a protruding portion protruding in an axial direction,
The magnetic sensor faces the protrusion in the axial direction.
motor. a circuit board facing the magnetic body in the axial direction;
A portion of the magnetic sensor faces the protrusion in the axial direction.
The motor according to claim 1 . The protrusion is provided at an end portion on an outer circumferential side of the magnetic body in a radial direction.
2. The motor according to claim 1. In the radial direction, an outer peripheral side surface of the protrusion and an outer peripheral side surface of the rotor core form a continuous surface.
The motor according to claim 3.

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