Rotor and motor

Abstract

A motor (10) comprises: a substantially cylindrical stator core (21); a plastic magnet (40) that includes a hollow cylindrical part (41) surrounding the stator core (21) and having an opening end (43) at one end on the 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 wall section (44) that protrudes in the first direction from the cylindrical part (41) and surrounds the substrate (50).

Description

rotor, motor

[0001] The present disclosure relates to a rotor and a motor.

[0002] Brushless DC motors with rotors made of plastic containing magnetic material are known. For example, Patent Document 1 (JP-A-2003-109526) describes a DC motor including 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.

[0003] Japanese Utility Model Application Publication No. 03-070038 Japanese Patent Application Publication No. 2019-043289

[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 injection molding plastic containing a magnetic material, with the rotating shaft and back yoke set in a mold in advance. 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 provides a motor that can be made smaller in size in the axial direction.

[0006] 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 having an open end at one end on a first axial direction side, and a plate-shaped substrate disposed on the one end side of the plastic magnet. The plastic magnet has an annular thin-walled portion protruding from the cylindrical portion in the first direction and surrounding 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.

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

[0009] FIG. 1 is a side cross-sectional view schematically showing a motor according to a first embodiment of the present disclosure. FIG. 2 is an exploded perspective view showing the motor of FIG. 1 in an exploded state. FIG. 3 is a cross-sectional view showing an enlarged portion of the cross-sectional view of FIG. 1. FIG. 4 is a cross-sectional view showing an enlarged portion of the cross-sectional view of FIG. 3. FIG. 5 is a side cross-sectional view schematically showing a motor according to a second embodiment of the present disclosure. FIG. 6 is an exploded perspective view showing the motor of FIG. 5 in an exploded state. FIG. 7 is a cross-sectional view showing a cross-section of the rotor of FIG. 5. FIG. 8 is a cross-sectional view showing a cross-section of a rotor of a comparative example.

[0010] Hereinafter, various embodiments for carrying out the present disclosure will be described with reference to the accompanying drawings. Each of the embodiments 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 each of the following embodiments are merely examples and are not intended to limit the present disclosure. Therefore, among the components in each of the following embodiments, 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 drawing, 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 1] The configuration of a motor 10 according to Example 1 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 in 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 axially in a cylindrical shape along a 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. The plastic magnet 40 has an open end portion 43 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 Example 1 is manufactured by insert molding, in which the shaft 30 is set in a mold for molding the rotor 4 in advance and molten magnetic resin (hereinafter referred to as "molten resin") is poured in. 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, Example 1 does not include a back yoke.

[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 the first embodiment, four stator cores 21, insulators 22, 23, and 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 the central hole 262 from below the stator base 26, thereby engaging with the first shaft support portion 28. The washer 34 is fitted into a circumferential groove 35 formed on the outer circumferential surface of 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 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 the motor 10 will now be described. When a drive current is supplied from the drive circuit 53 to the windings 24 based on the detection signal from the Hall element 52, a magnetic field corresponding to the drive current is generated around the stator core 21. The interaction between this magnetic field and the drive magnetic poles of the plastic magnets 40 generates a rotational torque in the rotor 4. The rotor 4 and the shaft 30 rotate around the central axis La in response to this generated rotational torque. As the shaft 30 rotates, the driven body connected to the shaft 30 rotates.

[0024] The plastic magnet 40 and the Hall element 52 will be described in detail with reference to FIGS. 3 and 4. FIG. 3 is a cross-sectional view showing an enlarged portion of FIG. 1. In FIG. 3, arrows schematically indicate the flow of magnetic flux from the plastic magnet 40. FIG. 4 is a cross-sectional view showing an enlarged portion of FIG. 3. The plastic magnet 40 of Example 1 has an annular thin-walled portion 44 that protrudes downward in the first direction from the cylindrical portion 41 and surrounds the substrate 50. In this case, the substrate 50 is located inside the hollow cylindrical plastic magnet 40. Therefore, the axial length of the motor 10 can be made thinner than when the substrate 50 is located below the plastic magnet 40. Note that, in terms of the radial thickness of the plastic magnet 40, 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 radially 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 the substrate contact surface 55 that contacts the substrate 50, it can be surface-mounted on the substrate 50. Therefore, the position of the Hall element is more stable when the Hall element is supported by contacting the substrate, compared to when the Hall element is supported floating above the substrate. Furthermore, the ability 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) made of InSb, GaAs, or the like, 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 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 is zero when the direction is parallel to the substrate contact surface 55.

[0028] On the other hand, the plastic magnet 40 supplies magnetic flux radially inward from the inner circumferential surface 49 of the cylindrical portion 41. The Hall element 52 has a board contact surface 55 that is parallel to a plane perpendicular to the axial direction, and therefore has a problem in that it is less sensitive to the magnetic flux from the cylindrical portion 41 if it does not have the thin-walled portion 44.

[0029] The thin-walled portion 44 is a magnetic body that guides the magnetic flux from the cylindrical portion 41 in the axial direction. The Hall element 52 is located 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 the magnetic flux that penetrates the board contact surface 55 in the axial direction. Therefore, when the thin-walled portion 44 is provided, 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 order to increase the detection signal of the Hall element 52, in the first embodiment, the Hall element 52 is disposed near the thin-walled portion 44. In this case, by positioning the Hall element 52 as close as possible to the plastic magnet 40, more magnetic flux can be detected. Here, as shown in FIG. 4 , the vicinity of the thin-walled portion 44 may be a range in which the radial distance from the inner circumferential surface 48 of the thin-walled portion 44 is equal to or less than the radial width L52 of the Hall element 52. In other words, the shortest distance D from the inner circumferential surface 48 of the thin-walled portion 44 to the Hall element 52 may be shorter than the radial width L52 of the Hall element 52. As an 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 the first embodiment, the board contact surface 55 contacts the surface of the board 50 opposite 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 board 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 10 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.

[0035] [Item 1] A motor (10) comprising: a substantially cylindrical stator core (21); a plastic magnet (40) that is a cylindrical portion surrounding the stator core (21), the plastic magnet (40) including a hollow cylindrical portion (41) having an open end (43) at one end on a first direction side in the axial direction; and a plate-shaped substrate (50) arranged on one end side of the plastic magnet (40), wherein 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).

[0036] [Item 2] The motor (10) according to item 1, having a board contact surface (55) that contacts the board (50), and including a Hall element (52) that detects magnetic flux from the plastic magnet (40).

[0037] [Item 3] The motor (10) according to Item 2, wherein the thin-walled portion (44) is a magnetic body that guides magnetic flux from the cylindrical portion (41) in the axial direction, and the Hall element (52) is disposed 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 magnetic flux that penetrates the board contact surface (55) in the axial direction.

[0038] [Item 4] The motor (10) according to item 2, wherein the Hall element (52) is disposed near the thin-walled portion (44).

[0039] [Item 5] The motor (10) according to Item 3, wherein the substrate abutment surface (55) abuts against a surface of the substrate (50) opposite to the stator core (21).

[0040] The present disclosure has been described above based on Example 1. Example 1 is merely an example, 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.

[0041] In the description of the first embodiment, an example was shown in which the outermost portion 56 of the Hall element 52 is located radially outward from the inner circumferential surface 49 of the cylindrical portion 41, 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 of the cylindrical portion 41.

[0042] In the first embodiment, the rotor 4 does not have a back yoke, but the rotor 4 is not limited to this. For example, the rotor may include a member that surrounds the outer circumferential surface of the cylindrical portion of the plastic magnet.

[0043] In the description of the first embodiment, the Hall element 52 is made of a compound semiconductor such as InSb or GaAs, but is not limited thereto. For example, the Hall element may be made of a semiconductor made of a single element such as silicon (Si).

[0044] BACKGROUND ART Rotors for use in brushless DC motors, which have a motor shaft supporting a magnet, are known. For example, Patent Document 2 describes a rotor including a cylindrical motor shaft that forms the rotation axis of the motor and a plastic magnet fixed to the shaft.

[0045] In the rotor described in Patent Document 2, the motor shaft is set in a mold for a plastic magnet beforehand, and the molten plastic magnet is poured into the mold and solidified to form an integrated unit. The motor shaft has a through-hole that penetrates between two opposing side surfaces, and the molten plastic magnet is poured into the through-hole to form an integrated unit, increasing the friction and resistance between the plastic magnet and the motor shaft.

[0046] However, conventional rotors have room for improvement in terms of making it easier for the molten plastic magnet to flow.

[0047] The present disclosure provides a rotor that can facilitate the flow of molten plastic magnets.

[0048] A rotor according to one aspect of the present disclosure includes a cylindrical shaft extending in the axial direction and a plastic magnet that annularly covers the outer circumferential surface of the shaft and rotates integrally with the shaft. The shaft has a cylindrical through-hole that penetrates from a predetermined position on the outer circumferential surface to an opposing position opposite the predetermined position and into which the plastic magnet is poured. The through-hole has inclined portions for guiding the plastic magnet from openings at both ends of the through-hole into the inside of the shaft.

[0049] 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.

[0050] Effect of the Invention According to the present disclosure, a rotor that can facilitate the flow of plastic magnets can be provided.

[0051] 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, component placement and connection configurations, steps (processes), and step order 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.

[0052] 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.

[0053] [Example 2] The configuration of a motor 1010 including a rotor 1004 according to Example 2 of the present disclosure will be described with reference to Figures 5 and 6. Figure 5 is a side cross-sectional view schematically illustrating the motor 1010. This figure shows a cross section of the motor 1010 cut along a plane passing through the central axis Lb of the shaft 1030. Figure 6 is an exploded perspective view illustrating the motor 1010. The motor 1010 is a brushless DC motor that is suitable for use in, for example, rotating the blades of a ventilation fan.

[0054] Hereinafter, for convenience, the direction along the central axis Lb of the shaft 1030 will be referred to as the "axial direction," and the circumferential direction and radial direction of a circle centered on the central axis Lb on a plane perpendicular to the central axis Lb 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."

[0055] The motor 1010 mainly includes a stator 1002, a rotor 1004, a shaft 1030, a first bearing 1031, a second bearing 1032, and a substrate 1050. The stator 1002 and the substrate 1050 form a stationary body, and the rotor 1004 and the shaft 1030 form a rotating body.

[0056] The rotor 1004 is rotatably supported relative to the stator 1002 via a first bearing 1031 and a second bearing 1032. The rotor 1004 mainly includes a shaft 1030 and a cup-shaped plastic magnet 1040. The shaft 1030 extends axially and cylindrically along a central axis Lb. The plastic magnet 1040 has a hollow cylindrical portion 1041 that surrounds the stator core 1021 and a fixed end portion 1042 that extends from one end of the cylindrical portion 1041 to the outer circumferential surface of the shaft 1030. The plastic magnet 1040 has an open end portion 1043 at the end of the cylindrical portion 1041 opposite the fixed end portion 1042.

[0057] The plastic magnet 1040 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 1004 of Example 2 is manufactured by insert molding, in which the shaft 1030 is set in advance in a mold for the rotor 1004, and molten magnetic resin (hereinafter referred to as "molten resin") is poured in. The shaft 1030 and the plastic magnet 1040 are integrated by insert molding.

[0058] The plastic magnet 1040 is a polar anisotropic plastic magnet with a high residual magnetic flux density. The plastic magnet 1040 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 1041 of the plastic magnet 1040 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 1041. For this reason, Example 2 does not include a back yoke.

[0059] In the axial direction, the side where the open end 1043 is provided relative to the fixed end 1042 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 may also be referred to as the upper side. Such directional notations do not limit the orientation of the motor 1010, and the motor 1010 may be used in any orientation.

[0060] The stator 1002 mainly includes a stator core 1021, a pair of insulators 1022 and 1023 that sandwich the stator core 1021 from both sides in the axial direction, a winding 1024 wound around the stator core 1021 via the insulators 1022 and 1023, a stator base 1026, and shaft support portions 1028 and 1029. The insulators 1022 and 1023 are resin members formed by molding. The insulators 1022 and 1023 include a first insulator 1022 arranged above the stator core 1021 and a second insulator 1023 arranged below the stator core 1021. The stator core 1021, the insulators 1022 and 1023, the winding 1024, and the substrate 1050 are integrated to form a stator unit 1025. In the second embodiment, four stator cores 1021, insulators 1022 and 1023, and windings 1024 are provided at 90° intervals in the circumferential direction.

[0061] Stator base 1026 is a disk-shaped member that supports stator unit 1025. Shaft supports 1028, 1029 are members that rotatably support the base end side of shaft 1030, and include a first shaft support 1028 provided on the upper side of stator base 1026 and a second shaft support 1029 provided on the lower side of stator base 1026 and engaged with first shaft support 1028.

[0062] The first shaft support portion 1028 is formed integrally with the stator base 1026. The second shaft support portion 1029 is inserted into the central hole 10262 from below the stator base 1026, thereby engaging with the first shaft support portion 1028. The washer 1034 is fitted into a circumferential groove 1035 formed on the outer circumferential surface of the shaft 1030. The washer 1034 functions as a retainer that regulates the axial position of the shaft 1030 between the second bearing 1032 and the first shaft support portion 1028.

[0063] The substrate 1050 is a substantially semicircular printed circuit board extending along a plane perpendicular to the axial direction. A Hall element 1052 and a drive circuit 1053 are mounted on the substrate 1050. The Hall element 1052 outputs a detection signal substantially proportional to the magnetic flux density of the magnetic flux from the drive magnetic pole of the cylindrical portion 1041 when the magnetic flux passes through the Hall element 1052. The drive circuit 1053 supplies a drive current to the winding 1024 based on the detection signal from the Hall element 1052. The lower part of the second insulator 1023 is fixed to the substrate 1050.

[0064] The operation of the motor 1010 will now be described. When a drive current is supplied from the drive circuit 1053 to the windings 1024 based on the detection signal from the Hall element 1052, a magnetic field corresponding to the drive current is generated around the stator core 1021. The interaction between this magnetic field and the drive magnetic poles of the plastic magnet 1040 generates a rotational torque in the rotor 1004. In response to this generated rotational torque, the rotor 1004 and the shaft 1030 rotate around the central axis Lb. As the shaft 1030 rotates, the driven body connected to the shaft 1030 rotates.

[0065] The shaft 1030 and the plastic magnet 1040 will be further described with reference to Figures 7 and 8. Figure 7 is a cross-sectional view showing a cross section of the rotor 1004 of Example 2. Figure 8 is a cross-sectional view showing a cross section of the rotor 1004B of the comparative example. Figure 7(A) shows a cross section of the rotor 1004, Figure 7(B) shows an enlarged cross section of a portion of the rotor 1004, Figure 7(C) shows a cross section of the shaft 1030, and Figure 7(D) shows an enlarged cross section of a portion of the shaft 1030. Figure 8(A) shows a cross section of the rotor 1004B, Figure 8(B) shows an enlarged cross section of a portion of the rotor 1004B, Figure 8(C) shows a cross section of the shaft 1030B, and Figure 8(D) shows an enlarged cross section of a portion of the shaft 1030B.

[0066] 7 and 8, a downward-pointing triangle marked with the symbol G indicates the position of the gate G during resin molding. The rotor 1004B of the comparative example was prototyped for comparison purposes during the development of the rotor 1004 of Example 2. To distinguish between the elements of the rotor 1004B of the comparative example, the letter "B" is added to the symbol of each element.

[0067] The rotor 1004B of the comparative example is different from the rotor 1004 of the second embodiment in that it includes a shaft 1030B that has a different shape from the shaft 1030. The shaft 1030B is a cylindrical member that extends in the axial direction and has the same external shape as the shaft 1030.

[0068] As described above, the rotor 1004 of Example 2 and the rotor 1004B of the comparative example each include a cylindrical shaft 1030, 1030B extending in the axial direction and a plastic magnet 1040 that annularly covers the outer circumferential surface of the shaft 1030, 1030B and rotates integrally with the shaft 1030, 1030B. The shaft 1030, 1030B has a cylindrical through-hole 1036, 1036B that penetrates from a predetermined position on the outer circumferential surface to a position opposite the predetermined position. Molten plastic magnet 1040 is poured into the cylindrical through-hole 1036, 1036B to form an integral part of the rotor 1004, 1004B. The portion of the plastic magnet 1040 that is poured into the through-hole 1036, 1036B is referred to as the hole interior 1046. As an example, the through-holes 1036, 1036B have a circular cross-section.

[0069] By providing through holes 1036, 1036B in shafts 1030, 1030B, hole interiors 1046 are formed. The action of through holes 1036, 1036B and hole interiors 1046 can increase the pull-out strength between plastic magnet 1040 and shafts 1030, 1030B, and can increase the rotational strength between plastic magnet 1040 and shafts 1030, 1030B.

[0070] First, the rotor 1004B of the comparative example will be described. The through-hole 1036B of the shaft 1030B penetrates in a direction perpendicular to the axial direction from one opening 1037 at a predetermined position on the outer circumferential surface to the other opening 1037 at an opposing position. Each opening 1037 of the through-hole 1036B has an edge portion 1039.

[0071] The arrows indicate the flow direction of the molten resin injected from gate G. The flow of the molten resin injected from gate G is hindered at edge portion 1039. Here, when the molten resin thermally contracts, distortion that can become the starting point of cracks may occur around edge portion 1039 due to the difference in linear expansion coefficient between the metal shaft and the plastic magnet made of resin. When an external twisting force acts between shaft 1030B and plastic magnet 1040, stress concentrates on edge portion 1039, which may cause cracks in plastic magnet 1040 around edge portion 1039.

[0072] Based on the description of the comparative example, a rotor 1004 of Example 2 will be described. As shown in Fig. 7 , through holes 1036 of a shaft 1030 of Example 2 each have inclined portions 1038 for guiding plastic magnets 1040 from openings 1037 at both ends of the through hole 1036 to the inside of the shaft 1030. By providing the inclined portions 1038, sharp edges 1039 are eliminated, and molten resin is guided into the through hole 1036 along the inclined portions 1038.

[0073] Furthermore, in rotor 1004 of Example 2, inclined portions 1038 are provided around the entire circumference of opening 1037 at both ends of through hole 1036. In this case, by providing inclined portions 1038 around the entire circumference of opening 1037, the molten resin can flow more easily into through hole 1036 compared to when inclined portions 1038 are provided only on part of opening 1037, and damage to the resin during cooling during molding can be reduced.

[0074] The shape of the inclined portion 1038 is not particularly limited as long as it can improve the fluidity of the molten resin. However, in the rotor 1004 of Example 2, the through hole 1036 passes through the central axis Lb of the shaft 1030, and the inclined portion 1038 has a conical shape whose diameter increases as it approaches the openings 1037 at both ends. In other words, the inclined portion 1038 has a tapered portion whose diameter increases as it approaches the openings 1037 at both ends. The shape of the inclined portion 1038 can be set by experiment or simulation from the viewpoint of ensuring a desired level of fluidity of the molten resin around the openings 1037. The inclination angle of the inclined portion 1038 may be set, for example, in the range of 20° to 70° with respect to the extension direction of the through hole 1036, and the depth of the inclined portion 1038 from the openings 1037 may be set in the range of 0.5 mm to 3.0 mm. In Example 2, the shape of the inclined portion 1038 is a chamfer of C1 (45°, depth 1 mm). In other words, the inclination angle of the inclined portion 1038 is set to 45°, and the depth dimension of the inclined portion 1038 from the opening 1037 is set to 1 mm.

[0075] As described above, the plastic magnet 1040 has a hollow cylindrical portion 1041 that surrounds the stator core 1021 and a fixed end portion 1042 that extends from one end of the cylindrical portion 1041 to the outer circumferential surface of the shaft 1030. The through hole 1036 in Example 2 overlaps with the fixed end portion 1042 in the radial direction. That is, the axial range of the through hole 1036 overlaps with the axial range of the fixed end portion 1042. In Example 2, molten resin is injected from a gate G provided on the upper surface of the fixed end portion 1042, and the molten resin flows radially through the fixed end portion 1042. When the axial ranges of the through hole 1036 and the fixed end portion 1042 overlap, the molten resin flowing radially from the fixed end portion 1042 tends to flow smoothly into the through hole 1036.

[0076] The axial thickness of the fixed end 1042 is larger than the diameter of the openings 1037 at both ends. In this case, the large thickness of the fixed end 1042 allows the molten resin to flow smoothly inside the fixed end 1042 and more easily into the through-hole 1036. In Example 2, the portion of the fixed end 1042 that contacts the shaft 1030 covers the entire opening 1037 in the axial direction.

[0077] The features of rotor 1004 configured as described above will be described. Rotor 1004 is a rotor having a cylindrical shaft 1030 extending in the axial direction and a plastic magnet 1040 that annularly covers the outer peripheral surface of shaft 1030 and rotates integrally with shaft 1030. Shaft 1030 has a cylindrical through-hole 1036 that penetrates from a predetermined position on the outer peripheral surface to a position opposite said predetermined position. Molten plastic magnet 1040 is poured into through-hole 1036 and is integrally formed as rotor 1004. Through-hole 1036 has inclined portions 1038 for guiding plastic magnet 1040 from openings 1037 at both ends of through-hole 1036 into the inside of shaft 1030.

[0078] According to this configuration, the presence of the inclined portion 1038 eliminates sharp edges 1039, and the molten resin is guided along the inclined portion 1038 into the through-hole 1036. This makes it easier for the molten resin to flow into the through-hole 1036, making distortion less likely to occur. In addition, stress concentration when a twisting external force acts between the shaft 1030 and the plastic magnet 1040 is also alleviated. As a result, cracks are less likely to occur, and the pull-out strength and rotation strength between the plastic magnet 1040 and the shaft 1030 can be easily ensured.

[0079] An outline of one aspect of the present disclosure is as follows.

[0080] [Item 6] A rotor (1004) having a cylindrical shaft (1030) extending in the axial direction and a plastic magnet (1040) that annularly covers the outer peripheral surface of the shaft (1030) and rotates integrally with the shaft (1030), wherein the shaft (1030) has a cylindrical through-hole (1036) that penetrates from a predetermined position on the outer peripheral surface to an opposing position opposite the predetermined position and into which the plastic magnet (1040) is poured, and the through-hole (1036) has inclined portions (1038) for guiding the plastic magnet (1040) from openings (1037) at both ends of the through-hole (1036) into the inside of the shaft (1030).

[0081] [Item 7] The rotor (1004) according to Item 6, wherein the inclined portion (1038) is provided around the entire circumference of the opening (1037) at both ends of the through hole (1036).

[0082] [Item 8] The rotor (1004) according to Item 7, wherein the through hole (1036) passes through the central axis (Lb) of the shaft (1030), and the inclined portion (1038) has a conical shape whose diameter increases as it approaches the openings (1037) at both ends.

[0083] [Item 9] The rotor (1004) according to Item 6, wherein the plastic magnet (1040) has a hollow cylindrical portion (1041) for surrounding the stator core (1021) and a fixed end portion (1042) extending from one end of the cylindrical portion (1041) to the outer circumferential surface of the shaft (1030), and the through hole (1036) overlaps with the fixed end portion (1042) when viewed in the radial direction.

[0084] [Item 10] The rotor (1004) according to item 9, wherein the axial thickness of the fixed end (1042) is greater than the diameter of the openings (1037) at both ends.

[0085] [Item 11] A motor (1010) including the rotor (1004) according to any one of items 6 to 10.

[0086] The present disclosure has been described above based on Example 2. Example 2 is merely an example, 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.

[0087] In the description of the second embodiment, an example in which the rotor 1004 does not have a back yoke is shown, but the present invention is not limited to this. For example, the rotor may include a member that surrounds the outer circumferential surface of the cylindrical portion of the plastic magnet.

[0088] In the description of the second embodiment, the inclined portion 1038 has a conical surface, but is not limited to this. For example, the inclined portion may include a curved surface.

[0089] In the description of the second embodiment, an example in which the injection gate G is provided on the upper surface of the fixed end portion 1042 has been shown, but the present invention is not limited to this. For example, the injection gate may be provided on the cylindrical portion, the open end portion, or the like.

[0090] 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 portion in first direction 48 Inner peripheral surface 49 Inner peripheral surface 50 Substrate 52 Hall element 53 Drive circuit 55 Substrate contact surface 56 Outermost portion 262 Central hole La Central axis Z1 Arrow L52 Radial width D Shortest distance 1002 Stator 1004, 1004B Rotor 1010 Motor 1021 Stator core 1022 First insulator 1023 Second insulator 1024 Winding 1025 Stator unit 1026 Stator base 1028 First shaft support portion 1029 Second shaft support portion 1030, 1030B Shaft 1031 First bearing 1032 Second bearing 1034 Washer 1035 Circumferential groove 1036, 1036B Through hole 1037 Opening 1039 Edge portion 1038 Inclined portion 1040 Plastic magnet 1041 Cylindrical portion 1042 Fixed end portion 1043 Open end portion 1050 Circuit board 1051 Board body 1052 Hall element 1053 Drive circuit 10262 Central hole Lb Central axis Z2 Arrow G Gate

Claims

1. A motor comprising: a substantially cylindrical stator core; a plastic magnet that is a cylindrical portion surrounding the stator core and includes a hollow cylindrical portion having an open end at one end on a first direction side in the axial direction; and a plate-shaped substrate that is placed on the one end side of the plastic magnet, wherein the plastic magnet has an annular thin-walled portion that protrudes from the cylindrical portion in the first direction and surrounds the substrate.

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

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

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

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

6. A rotor having a cylindrical shaft extending in the axial direction and a plastic magnet that annularly covers the outer circumferential surface of the shaft and rotates integrally with the shaft, wherein the shaft has a cylindrical through-hole that penetrates from a predetermined position on the outer circumferential surface to an opposing position opposite the predetermined position and into which the plastic magnet is poured, and the through-hole has inclined portions for guiding the plastic magnet from openings at both ends of the through-hole into the inside of the shaft.

7. A rotor according to claim 6, wherein the inclined portion is provided over the entire circumference of the opening at both ends of the through hole.

8. A rotor according to claim 7, wherein the through hole passes through the central axis of the shaft, and the inclined portion has a conical shape whose diameter increases as it approaches the openings at both ends.

9. The rotor according to claim 6, wherein the plastic magnet has a hollow cylindrical portion for surrounding the stator core and a fixed end portion extending from one end of the cylindrical portion to the outer circumferential surface of the shaft, and the through hole overlaps with the fixed end portion when viewed in the radial direction.

10. A rotor according to claim 9, wherein the axial thickness of said fixed end is greater than the diameter of said openings at both ends.

11. A motor equipped with a rotor according to any one of claims 6 to 10.

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