Motor

Abstract

To provide a motor which can be downsized in an axial direction.SOLUTION: A motor 10 comprises: a substantially cylindrical stator core 21; a plastic magnet 40 including a hollow cylindrical part 41, the cylindrical part encircling the stator core 21 and having an opening end portion 43 at one end on a first-direction side in the axial direction; and a plate-like substrate 50 disposed on one end side of the plastic magnet 40. The plastic magnet 40 has an annular thin portion 44 protruding from the cylindrical part 41 in the first direction and encircling the substrate 50.SELECTED DRAWING: Figure 3

Description

[Technical Field]

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

[0002] Brushless DC motors with rotors made of plastic containing magnetic material are known. For example, Patent Document 1 describes a DC motor that includes an iron-core stator with windings around an iron core, a rotor made of plastic containing magnetic material, a drive magnet, and a back yoke, and a rotating shaft. In this motor, the cylindrical portion of the rotor body is magnetized to serve as a drive magnet. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Utility Model Application Publication No. 03-070038 Summary of the Invention [Problem to be solved by the invention]

[0004] In the electric motor described in Patent Document 1, the cylindrical portion of the rotor body is magnetized to serve as a drive magnet. The rotor body is manufactured by pre-setting the rotating shaft and back yoke in a mold and then injection-molding plastic containing a magnetic material. However, in this electric motor, the circuit board is located axially outward of the rotor body, leaving room for improvement in terms of axial miniaturization.

[0005] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a motor that can be made smaller in size in the axial direction. [Means for solving the problem]

[0006] To solve the above problems, a motor according to one aspect of the present disclosure includes a substantially cylindrical stator core, a plastic magnet having a cylindrical portion surrounding the stator core and including a hollow cylindrical portion with an open end at one end on a first axial direction side, and a plate-shaped substrate disposed on one end of the plastic magnet. The plastic magnet has an annular thin-walled portion that protrudes from the cylindrical portion in the first direction and surrounds the substrate.

[0007] Any combination of the above components, and conversion of the present disclosure into a method, device, system, recording medium, computer program, etc., are also valid aspects of the present disclosure. [Effects of the Invention]

[0008] According to the present disclosure, it is possible to provide a motor that can be made smaller in size in the axial direction. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view schematically illustrating a motor according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is an exploded perspective view showing the motor of FIG. 1; [Figure 3] FIG. 2 is an enlarged cross-sectional view showing a part of the cross-sectional view of FIG. [Figure 4] FIG. 4 is an enlarged cross-sectional view of a portion of the cross-sectional view of FIG. 3.

[0010] Hereinafter, embodiments for carrying out the present disclosure will be described with reference to the accompanying drawings. Each of the examples described below represents a preferred specific example of the present disclosure. Therefore, the numerical values, shapes, materials, components, the arrangement and connection of the components, steps (processes), and the order of steps shown in the following examples are merely examples and are not intended to limit the present disclosure. Therefore, among the components in the following examples, components that are not recited in the independent claims that represent the highest concept of the present disclosure will be described as optional components. Furthermore, in each figure, substantially identical components are assigned the same reference numerals, and redundant explanations will be omitted or simplified.

[0011] Furthermore, terms including ordinal numbers such as first and second are used to describe various components, but these terms are used only to distinguish one component from another and do not limit the components.

[0012] [Example] The configuration of a motor 10 according to an embodiment of the present disclosure will be described with reference to Figures 1 and 2. Figure 1 is a side cross-sectional view that schematically illustrates the motor 10. This figure shows a cross section of the motor 10 cut along a plane that passes through the central axis La of the shaft 30. Figure 2 is an exploded perspective view that illustrates the motor 10. The motor 10 is a brushless DC motor that is suitable for use in, for example, rotating the blades of a ventilation fan.

[0013] Hereinafter, for convenience, the direction along the central axis La of the shaft 30 will be referred to as the "axial direction," and the circumferential direction and radial direction of a circle centered on the central axis La on a plane perpendicular to the central axis La will be referred to as the "circumferential direction" and the "radial direction," respectively. Also, a plane perpendicular to the axial direction will be referred to as the "axially perpendicular plane."

[0014] The motor 10 mainly includes a stator 2, a rotor 4, a shaft 30, a first bearing 31, a second bearing 32, and a substrate 50. The stator 2 and the substrate 50 form a stationary body, and the rotor 4 and the shaft 30 form a rotating body.

[0015] The rotor 4 is rotatably supported relative to the stator 2 via a first bearing 31 and a second bearing 32. The rotor 4 mainly includes a shaft 30 and a cup-shaped plastic magnet 40. The shaft 30 extends cylindrically in the axial direction along the central axis La. The plastic magnet 40 has a hollow cylindrical portion 41 that surrounds the stator core 21 and a fixed end portion 42 that extends from one end of the cylindrical portion 41 to the outer circumferential surface of the shaft 30, and an open end portion 43 is provided at the end of the cylindrical portion 41 opposite the fixed end portion 42.

[0016] The plastic magnet 40 is formed by resin molding such as injection molding using a plastic such as polyamide resin mixed with magnetic powder (hereinafter referred to as "magnetic resin"). The rotor 4 of this embodiment is manufactured by insert molding, in which molten magnetic resin (hereinafter referred to as "molten resin") is poured into a molding die containing the shaft 30. The shaft 30 and the plastic magnet 40 are integrated by insert molding.

[0017] The plastic magnet 40 is a polar anisotropic plastic magnet with a high residual magnetic flux density. The plastic magnet 40 is insert molded while a polar anisotropic magnetic field is applied. A predetermined number of driving magnetic poles are provided on the inner circumferential surface of the cylindrical portion 41 of the plastic magnet 40 by a magnetization process. Due to the characteristics of polar anisotropic magnets, no magnetic poles are formed on the outer circumferential surface of the cylindrical portion 41. For this reason, a back yoke is not provided in this embodiment.

[0018] In the axial direction, the side where the open end 43 is provided relative to the fixed end 42 is referred to as the first direction. In each drawing, the first direction is indicated by the direction of arrow Z1. The first direction side may also be referred to as the lower side, and the opposite side as the upper side. These directional notations do not limit the orientation of the motor 10, and the motor 10 may be used in any orientation.

[0019] The stator 2 mainly includes a stator core 21, a pair of insulators 22, 23 that sandwich the stator core 21 from both sides in the axial direction, a winding 24 wound around the stator core 21 via the insulators 22, 23, a stator base 26, and shaft supports 28, 29. The insulators 22, 23 are resin members formed by molding. The insulators 22, 23 include a first insulator 22 arranged above the stator core 21 and a second insulator 23 arranged below the stator core 21. The stator core 21, the insulators 22, 23, the winding 24, and the substrate 50 are integrated to form a stator unit 25. In this embodiment, four windings 24 are provided at 90° intervals in the circumferential direction.

[0020] The stator base 26 is a disk-shaped member that supports the stator unit 25. The shaft supports 28, 29 are members that rotatably support the base end side of the shaft 30, and include a first shaft support 28 provided on the upper side of the stator base 26 and a second shaft support 29 provided on the lower side of the stator base 26 and engaged with the first shaft support 28.

[0021] The first shaft support portion 28 is formed integrally with the stator base 26. The second shaft support portion 29 is inserted into a central hole 262 of the stator base 26 from below, thereby engaging with the first shaft support portion 28. The washer 34 is fitted into a circumferential groove 35 formed in the shaft 30. The washer 34 functions as a retainer that regulates the axial position of the shaft 30 between the second bearing 32 and the first shaft support portion 28.

[0022] The substrate 50 is a substantially semicircular printed circuit board extending along a plane perpendicular to the axial direction. A Hall element 52 and a drive circuit 53 are mounted on the substrate 50. When magnetic flux from the drive magnetic pole of the cylindrical portion 41 passes through the Hall element 52, the Hall element 52 outputs a detection signal that is substantially proportional to the magnetic flux density of the magnetic flux. The drive circuit 53 supplies a drive current to the winding 24 based on the detection signal from the Hall element 52. The lower part of the second insulator 23 is fixed to the substrate 50.

[0023] The operation of motor 10 will now be described. When a drive current is supplied from drive circuit 53 to windings 24 based on the detection signal from Hall element 52, a magnetic field corresponding to the drive current is generated around stator core 21. Interaction between this magnetic field and the drive magnetic poles of plastic magnet 40 generates a rotational torque in rotor 4, and in response to this torque, rotor 4 and shaft 30 rotate around central axis La. As shaft 30 rotates, the driven body connected to shaft 30 rotates.

[0024] The plastic magnet 40 and the Hall element 52 will be described in detail with reference to Figures 3 and 4. Figure 3 is a cross-sectional view showing an enlarged portion of Figure 1. In Figure 3, arrows schematically indicate the flow of magnetic flux from the plastic magnet 40. Figure 4 is a cross-sectional view showing an enlarged portion of Figure 3. The plastic magnet 40 of the embodiment has an annular thin-walled portion 44 that protrudes downward in a first direction from the cylindrical portion 41 and surrounds the substrate 50. In this case, since the substrate 50 is located inside the hollow cylindrical plastic magnet 40, the motor can be made thinner in the axial direction than when the substrate 50 is located below the plastic magnet 40. Note that, in terms of radial thickness, the cylindrical portion 41 has a thick-walled portion 45 that is thicker than the thin-walled portion 44.

[0025] The outer peripheral surface of the thin-walled portion 44 has the same outer diameter as the outer peripheral surface of the cylindrical portion 41, and the thin-walled portion 44 and the cylindrical portion 41 are continuous with each other vertically. The inner peripheral surface 48 of the thin-walled portion 44 has a larger outer diameter than the inner peripheral surface 49 of the cylindrical portion 41 and is recessed outward from the inner peripheral surface 49 of the cylindrical portion 41 to form a step. The substrate 50 is disposed below the cylindrical portion 41 in the space inside the thin-walled portion 44. In the radial direction, the outer edge of the substrate 50 is located outside the inner peripheral surface 49 and inside the inner peripheral surface 48.

[0026] The Hall element 52 has a substrate contact surface 55 that contacts the substrate 50, and detects the magnetic flux from the plastic magnet 40. In this case, since the Hall element 52 has a substrate contact surface 55 that contacts the substrate 50, it can be surface-mounted on the substrate 50, and the position of the Hall element is more stable than when the Hall element is supported floating above the substrate. Being able to surface-mount the Hall element 52 is advantageous in terms of improving productivity. The Hall element 52 outputs a detection signal whose magnitude corresponds to the magnetic flux density of the magnetic flux from the plastic magnet 40.

[0027] The Hall element 52 includes a semiconductor thin film (not shown) such as InSb or GaAs that is parallel to the substrate contact surface 55. The Hall element 52 outputs a detection signal whose magnitude is proportional to the product of the current flowing through the semiconductor thin film and the magnetic flux density of the magnetic flux passing through the semiconductor thin film in its thickness direction. In the example of FIG. 3, the magnitude of the detection signal of the Hall element 52 is approximately proportional to the magnetic flux density of the magnetic flux passing through the substrate contact surface 55 that is parallel to the semiconductor thin film. The magnitude of the detection signal of the Hall element 52 is maximum when the direction of the passing magnetic flux is perpendicular to the substrate contact surface 55, decreases as the direction is inclined from the perpendicular direction, and becomes zero when the direction is parallel to the substrate contact surface 55.

[0028] On the other hand, the plastic magnet 40 supplies magnetic flux in the radial direction from the inner circumferential surface 49 of the cylindrical portion 41. Therefore, the Hall element 52 has a board contact surface 55 parallel to the plane perpendicular to the axial direction, and therefore, if the thin-walled portion 44 is not provided, there is a problem that the sensitivity to the magnetic flux from the cylindrical portion 41 is low.

[0029] The thin-walled portion 44 is a magnetic body that guides the magnetic flux from the cylindrical portion 41 in the axial direction, and the Hall element 52 is located axially between the end 46 of the cylindrical portion 41 in the first direction and the end 47 of the thin-walled portion 44 in the first direction, and detects the magnetic flux that penetrates the board contact surface 55 in the axial direction. In this case, as shown in Fig. 3, the magnetic flux from the cylindrical portion 41 is more likely to detour in the axial direction and pass through the board contact surface 55 approximately perpendicularly, resulting in an increased detection signal from the Hall element 52.

[0030] In this embodiment, the Hall element 52 is disposed near the thin-walled portion 44 to increase the detection signal of the Hall element 52. In this case, by placing the Hall element 52 as close as possible to the plastic magnet 40, more magnetic flux can be detected. The vicinity of the thin-walled portion 44 may be a radial distance from the thin-walled portion 44 that is equal to or less than the radial width L52 of the Hall element 52. In other words, the shortest distance D from the thin-walled portion 44 to the Hall element 52 may be shorter than the radial width L52 of the Hall element 52. For example, when the cylindrical portion 41 and the Hall element 52 are projected in the axial direction, the outer contour of the Hall element 52 may overlap the outer contour of the cylindrical portion 41. In other words, the outermost portion 56 of the Hall element 52 is located radially outward of the inner circumferential surface 49 of the cylindrical portion 41.

[0031] In this embodiment, the substrate contact surface 55 contacts the surface of the substrate 50 opposite to the stator core 21. In this case, the Hall element 52 is less susceptible to the magnetic flux from the stator core 21. Furthermore, by mounting the drive circuit 53 on the same surface as the Hall element 52, the substrate 50 can be an inexpensive single-sided printed circuit board. Furthermore, the Hall element 52 can be disposed at a desired distance from the cylindrical portion 41.

[0032] The features of the motor 10 configured as described above will be described below. The motor 10 includes a substantially cylindrical stator core 21, a plastic magnet 40 that is a cylindrical portion that surrounds the stator core 21 and includes a hollow cylindrical portion 41 that has an open end 43 at one end on the first direction side in the axial direction, and a plate-shaped substrate 50 that is disposed on one end side of the plastic magnet 40. The plastic magnet 40 has an annular thin-walled portion 44 that protrudes from the cylindrical portion 41 in the first direction and surrounds the substrate 50.

[0033] With this configuration, the substrate 50 is located inside the hollow cylindrical plastic magnet 40, so the motor can be made smaller in the axial direction than if the substrate 50 were located below the plastic magnet 40. In addition, the substrate 50 is surrounded by the thin-walled portion 44, so the substrate 50 can be protected.

[0034] An outline of one aspect of the present disclosure is as follows. [Item 1] a substantially cylindrical stator core (21); a plastic magnet (40) including a hollow cylindrical portion (41) surrounding the stator core (21), the hollow cylindrical portion having an open end (43) at one end on a first direction side in the axial direction; a plate-shaped substrate (50) disposed on one end side of the plastic magnet (40); Equipped with The motor (10) includes a plastic magnet (40) having an annular thin-walled portion (44) that protrudes in a first direction from a cylindrical portion (41) and surrounds a substrate (50).

[0035] [Item 2] Item 1. The motor (10) according to item 1, having a substrate contact surface (55) that contacts the substrate (50), and including a Hall element (52) that detects magnetic flux from the plastic magnet (40).

[0036] [Item 3] The thin-walled portion (44) is a magnetic body that guides magnetic flux from the cylindrical portion (41) in the axial direction. The motor (10) described in item 2, wherein the Hall element (52) is arranged axially between the first-direction end (46) of the cylindrical portion (41) and the first-direction end (47) of the thin-walled portion (44), and detects magnetic flux passing through the board contact surface (55) in the axial direction.

[0037] [Item 4] 3. The motor (10) according to item 2, wherein the Hall element (52) is disposed in the vicinity of the thin portion (44).

[0038] [Item 5] 4. The motor (10) according to item 3, wherein the board contact surface (55) contacts the surface of the board (50) opposite to the stator core (21).

[0039] The present disclosure has been described above based on examples. These examples are merely illustrative, and it will be understood by those skilled in the art that various modifications are possible in the combination of each component or each treatment process, and that such modifications are also within the scope of the present disclosure.

[0040] In the description of the embodiment, an example has been shown in which the outermost portion 56 of the Hall element 52 is located radially outward from the inner circumferential surface 49, but the present invention is not limited to this. The outermost portion of the Hall element may be configured to be located radially inward from the inner circumferential surface 49.

[0041] In the description of the embodiment, an example was shown in which the rotor 4 does not have a back yoke, but this is not limiting. For example, the rotor may be provided with a member that surrounds the outer circumferential surface of the cylindrical portion of the plastic magnet.

[0042] In the description of the embodiment, the Hall element 52 is made of a compound semiconductor such as InSb or GaAs, but is not limited to this. For example, the Hall element may be made of a semiconductor made of a single element such as silicon. [Explanation of symbols]

[0043] 2 Stator, 4 Rotor, 10 Motor, 21 Stator core, 22 First insulator, 23 Second insulator, 24 Winding, 25 Stator unit, 26 Stator base, 28 First shaft support portion, 29 Second shaft support portion, 30 Shaft, 31 First bearing, 32 Second bearing, 34 Washer, 35 Circumferential groove, 40 Plastic magnet, 41 Cylindrical portion, 42 Fixed end portion, 43 Open end portion, 44 Thin portion, 45 Thick portion, 46, 47 End portions in first direction, 50 Substrate, 52 Hall element, 53 Drive circuit, 55 Substrate abutment surface, 262 Central hole.

Claims

1. a substantially cylindrical stator core; a plastic magnet including a hollow cylindrical portion that surrounds the stator core and has an open end at one end on a first direction side in the axial direction; a plate-shaped substrate disposed on the one end side of the plastic magnet; Equipped with The plastic magnet has an annular thin-walled portion that protrudes from the cylindrical portion in the first direction and surrounds the substrate.

2. 2. The motor according to claim 1, further comprising a Hall element having a board contact surface that contacts the board and detects magnetic flux from the plastic magnet.

3. the thin-walled portion is a magnetic body that guides magnetic flux from the cylindrical portion in the axial direction, 3. The motor according to claim 2, wherein the Hall element is disposed axially between the first end and the first end of the thin-walled portion, and detects magnetic flux passing through the board contact surface in the axial direction.

4. The motor according to claim 2 , wherein the Hall element is disposed near the thin portion.

5. The motor according to claim 3 , wherein the substrate contact surface contacts a surface of the substrate opposite to the stator core.

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