Rotor and brushless motor

Abstract

The present invention provides a rotor and a brushless motor that can secure motor performance while suppressing manufacturing costs and fixing permanent magnets with an appropriate press-fitting force. The rotor comprises: a columnar core body (20) composed of a plurality of laminated cores (29) of the same shape and having an axial hole (21) on the rotation center side; a plurality of permanent magnets (25) that are respectively accommodated and fixed in a plurality of magnet receiving holes (22) that are axially penetrating and circumferentially arranged in a circular shape around the axial hole of the core body; and a protrusion (23) provided in each magnet receiving hole. The protrusion protrudes in the circumferential direction and is pressed against the permanent magnet received in the magnet receiving hole from the radial inside. In addition, each protrusion is formed by a protrusion forming space (24) extending in the circumferential direction from the radial inner side surface (22a) of each magnet receiving hole. At least one of the protrusion (23) and the protrusion forming space (24) is located on the d-axis, which is the center of the magnetic pole.

Description

Technical Field

[0001] The present invention relates to a rotor having permanent magnets arranged inside a core body and a brushless motor including the rotor. Background Art

[0002] Conventionally, so-called IPM (Interior Permanent Magnet) rotors are known, in which permanent magnets are arranged inside the core body. In such rotors, the centrifugal force generated by the rotor's rotation acts on the permanent magnets, causing them to move, potentially causing vibration, noise, or damage. Therefore, IPM rotors require that the permanent magnets be securely fixed to the core body, and various methods have been proposed.

[0003] For example, Patent Document 1 discloses a rotor core (core body) comprising: a press-fit protrusion that radially protrudes into a through-hole where a magnet (permanent magnet) is disposed, thereby press-fitting and securing the magnet; and a notch formed at a position radially separated from the magnet across the press-fit protrusion. According to Patent Document 1, the press-fit protrusion is used to press-fit and secure the magnet, while the notch prevents excessive pressure from being applied to the magnet.

[0004] Patent Document 2 discloses an IPM rotor comprising a first core sheet having spring plates provided in holes for magnet insertion, and a second core sheet having recesses provided at positions corresponding to the locations of the first core sheet with the spring plates. The IPM rotor is constructed by stacking these core sheets. This structure allows the spring plates, bent by the magnets, to enter the recesses of the second core sheet when the magnets are inserted into the IPM rotor, allowing the magnets to be retained by the restoring force of the spring plates.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent No. 5918958

[0008] Patent Document 2: Japanese Patent Application No. 2018-189822 Summary of the Invention

[0009] Problems to be solved by the invention

[0010] However, the structure of Patent Document 1 results in excessive press-fitting force, potentially causing the rotor core to be chipped when the magnets are inserted into it, resulting in the generation of debris. Furthermore, Patent Document 2 employs a structure that stacks core sheets of varying shapes, requiring rotational stacking and increasing mold costs. Furthermore, the placement of protrusions and recesses can potentially obstruct the flow of magnetic flux, making these configurations crucial for ensuring motor performance.

[0011] It should be noted that as a method of fixing the magnet, a method using an adhesive without forming a protrusion, etc. is also considered. However, the fixing method using an adhesive sometimes requires special equipment for coating, depending on the type of adhesive. In addition, in the case of liquid adhesives, since it takes time to solidify, it is not preferred in terms of achieving improved production efficiency. In addition, generally speaking, since adhesives have an expiration date, care must be taken in the management (storage) of the adhesive.

[0012] This application was developed in response to this problem, and one of its objectives is to provide a rotor and a brushless motor that can secure permanent magnets with an appropriate press-fit force while maintaining motor performance and reducing manufacturing costs. It should be noted that this application is not limited to this objective, and another objective of this application is to achieve the effects brought about by the various structures shown in the specific embodiments described below, which are not achievable with conventional technologies.

[0013] Solutions to Problems

[0014] (1) The rotor disclosed herein comprises: a columnar core body composed of a plurality of laminated cores of the same shape and having an axial hole on the rotation center side; a plurality of permanent magnets respectively housed and fixed in a plurality of magnet housing holes, the plurality of magnet housing holes being axially through-holes around the axial hole of the core body and arranged circumferentially in a circular shape; and a protrusion, one of which is provided in each magnet housing hole and protrudes circumferentially, the protrusion being pressed against the permanent magnet housed in the magnet housing hole from the radial inside. Each of the protrusions is formed by a protrusion-forming space extending circumferentially from the radial inside surface of each magnet housing hole, and at least one of the protrusion and the protrusion-forming space is located on the d-axis, which is the center of the magnetic pole.

[0015] That is, one protrusion is provided for each permanent magnet, and the protrusions are provided asymmetrically with respect to the d-axis.

[0016] (2) Preferably, the length of the protrusion in the width direction perpendicular to the protruding direction is not more than twice the thickness of one sheet of the laminated core.

[0017] (3) Preferably, the length of the protrusion in the width direction is equal to or greater than the plate thickness.

[0018] (4) It is preferable that the length of the protrusion in the protruding direction is longer than the length of the protrusion in the width direction perpendicular to the protruding direction.

[0019] (5) In addition, the motor disclosed herein includes: a rotor according to any one of claims 1 to 4; a shaft portion that rotates integrally with the rotor; and a stator that is fixed to a housing and has a space on the inner diameter side for arranging the rotor and has a coil.

[0020] Effects of the Invention

[0021] According to the disclosed rotor and brushless motor, the protrusions easily elastically deform, allowing the permanent magnets to be fixed to the core body with appropriate press-fit force. Furthermore, the protrusions and the spaces formed by the protrusions do not obstruct the flow of magnetic flux, thereby ensuring performance. Furthermore, since special molds and dedicated equipment are not required, manufacturing costs can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a perspective view of a brushless motor according to an embodiment.

[0023] Figure 2 It is along Figure 1 Axial cross-sectional view of a brushless motor.

[0024] Figure 3 It shows Figure 1 Exploded perspective view of the rotor and stator of a brushless motor.

[0025] Figure 4 Is used to illustrate the composition Figure 3 Diagram of the laminated core of the rotor.

[0026] Figure 5 Is used to illustrate Figure 3 Diagram of the rotor's magnetic poles and the flow of magnetic flux.

[0027] Figure 6 (a) is Figure 4 A magnified view of part A, Figure 6 (b) is shown in Figure 6 (a) shows a rotor core with magnets pressed into it.

[0028] Figure 7 (a) to (c) are figures for explaining comparative examples. Figure 6 (a) corresponds to the figure].

[0029] Description of Reference Numerals

[0030] 1 motor (brushless motor)

[0031] 2 rotors

[0032] 3 Stator

[0033] 4. Housing

[0034] 10 Shaft

[0035] 20 rotor core (core body)

[0036] 21 shaft hole

[0037] 22 magnet receiving holes

[0038] 22a Inner surface (radially inner surface)

[0039] 23 protrusion

[0040] 24 Protrusions create space

[0041] 25 Magnet (permanent magnet)

[0042] 25a Radially inner side

[0043] 29 Laminated Core

[0044] C Center of rotation

[0045] L: Protrusion length (length in the protruding direction)

[0046] T Laminated core thickness

[0047] W is the width dimension of the protrusion (length in the width direction). DETAILED DESCRIPTION

[0048] The rotor and brushless motor according to the embodiments will be described with reference to the accompanying drawings. The embodiments described below are merely illustrative and are not intended to exclude various modifications or technical applications not explicitly described in the embodiments. The various structures of the present embodiments can be implemented with various modifications without departing from their main purpose. Furthermore, these structures can be selected or discarded as needed, or appropriately combined.

[0049] [1.Structure]

[0050] Figure 1 1 is a perspective view of a brushless motor 1 (hereinafter referred to as “motor 1”) according to the present embodiment. Figure 2 : is an axial cross-sectional view of the motor 1. The motor 1 is an inner rotor type brushless DC motor, and the motor 1 is composed of a rotor 2 with a shaft 10 fixed thereto and a stator 3 fixed to the housing 4, which forms the outer contour of the motor 1. The housing 4 is a cylindrical shape with both ends open in the axial direction, and one end side ( Figure 2 The end cap 15 is fixed to the opening of the right side of the middle part, and the end cap 15 is fixed to the opening of the right side of the middle part. Figure 2 The front cover 14 is fixed to the opening of the housing 4 (on the left side). It should be noted that the outer shape of the housing 4 in this embodiment is a substantially rectangular parallelepiped, but the shape of the housing 4 is not limited thereto.

[0051] Figure 3 This is a perspective view showing the rotor 2 of this embodiment decomposed from the stator 3, and omitting the shaft 10 and the housing 4. Figure 2 as well as Figure 3 As shown, the stator 3 is a substantially cylindrical member having a space for arranging the rotor 2 on the inner diameter side, and the stator 3 includes: an annular stator core 30, which is press-fitted and fixed to the housing 4; and a coil 32, which is wound around the stator core 30 via an insulating member 31. Figure 1 as well as Figure 2 As shown, the stator 3 of this embodiment includes: a power supply input lead 6 connected to the coil 32; a sensor signal input / output lead 7; a lead fixing member 5 supporting the lead 6; and a substrate 8 having a rotation detection element for detecting a signal corresponding to the rotational position of the rotor 2. It should be noted that the structure of the stator 3 is not limited to this; for example, the lead fixing member 5 may be omitted, or a separate member supporting the substrate 8 may be provided.

[0052] like Figure 2 as well as Figure 3 As shown, the rotor 2 is an IPM (Interior Permanent Magnet) rotor and includes: a rotor core 20 (core body) that rotates integrally with the shaft 10 around the center of rotation C; and a plurality of magnets 25 (permanent magnets) that are fixed inside the rotor core 20. The shaft 10 is a rotating shaft that supports the rotor 2 and also functions as an output shaft for extracting the output (mechanical energy) of the motor 1 to the outside. Bearings 11 and 12 are provided at two positions of the shaft 10 across the rotor 2. In this embodiment, the bearing 11 is fixed to the front cover 14 and supports the middle portion of the shaft 10 so that it can rotate freely, and the bearing 12 is fixed to the end cover 15 and supports the end portion (the right end portion in the figure) of the shaft 10 so that it can rotate freely.

[0053] The rotor core 20 is formed by stacking a plurality of laminated cores 29 in the axial direction. Figure 42 shows a plan view and a side view of the laminated core 29 of the present embodiment. The laminated core 29 is a thin electromagnetic steel plate having an axial hole 21 for fixing the shaft portion 10 on the side of the rotation center C, and all the laminated cores 29 are formed into the same shape. A plurality of magnet receiving holes 22 are provided axially around the axial hole 21 of the laminated core 29. The magnet receiving holes 22 are through-holes for receiving and fixing the magnets 25, and the same number of magnet receiving holes 22 is provided as the number of magnets 25. In the rotor 2 of the present embodiment, there are 14 magnets 25 and 14 magnet receiving holes 22, but the number is not limited to this.

[0054] The plurality of magnet receiving holes 22 are arranged in parallel in a circular shape in the circumferential direction when viewed from the axial direction along the outer periphery of the laminated core 29. Figure 5 As shown in FIG1 , the magnetic poles (N pole, S pole) of the magnets 25 adjacent to each other in the circumferential direction are arranged opposite to each other. As a result, a flow of magnetic flux as indicated by the dotted arrows in the figure is generated between the adjacent magnets 25 .

[0055] like Figure 4 as well as Figure 6 As shown in (a), the magnet receiving hole 22 of this embodiment is an isosceles trapezoidal shape that is longer in a direction perpendicular to the radial direction when viewed from the axial direction and has rounded corners, and the radially outer surface (equivalent to the "upper base" or "lower base" of the trapezoid) is wider than the radially inner surface (equivalent to the "lower base" or "upper base" of the trapezoid). The adjacent end surfaces (surfaces extending in the radial direction and equivalent to the "waist" of the trapezoid) of two magnet receiving holes 22 adjacent in the circumferential direction are parallel to each other, and the two magnet receiving holes 22 are arranged with a gap between the two end surfaces. The gap portion is parallel to the q-axis (refer to the q-axis) serving as the magnetic pole boundary. Figure 5 )overlapping.

[0056] like Figure 2 as well as Figure 3 As shown in FIG. 1 , the magnet 25 is in the shape of a rectangular parallelepiped having an axial length equal to that of the rotor core 20. More specifically, as shown in FIG. Figure 6 As shown in (b), when viewed axially, the height (radial dimension) of the rectangle on the axial end surface of magnet 25 is equal to the radial length of the trapezoidal "height" of magnet housing hole 22, and the width (dimension in a direction perpendicular to the radial direction) is sufficient to create a slight gap with the surface corresponding to the "waist" of magnet housing hole 22. Magnet 25 is secured to rotor core 20 by press-fitting, without the use of adhesive. The rotor 2 is provided with a protrusion 23 for press-fitting magnet 25 and a protrusion-forming space 24 for forming protrusion 23.

[0057] like Figure 4 as well as Figure 6 As shown in (a), one protrusion 23 is provided in each magnet receiving hole 22, and the number of magnet receiving holes 22 and the number of magnets 25 are set to the same. The protrusion 23 is provided in a circumferentially protruding manner on the radial inner side surface 22a (hereinafter referred to as the "inner side surface 22a") of the magnet receiving hole 22. That is, the protruding direction of the protrusion 23 is mainly the circumferential component, and it extends in a manner along the inner side surface 22a of the magnet receiving hole 22 when viewed from the axial direction, and is formed into an asymmetric shape with respect to the d-axis which is the center of the magnetic pole. The protrusion 23 of this embodiment is provided in a protruding manner toward the d-axis when viewed from the axial direction, and a part of the protrusion 23 is provided so as to enter the inner side of the magnet receiving hole 22.

[0058] like Figure 6 As shown in (b) of FIG. 2 , when the magnet 25 is received in the magnet receiving hole 22, the protrusion 23 elastically deforms toward the rotation center C and presses against the magnet 25 received in the magnet receiving hole 22 from the radially inner side. Thus, the protrusion 23 presses the magnet 25 radially outward as indicated by the hollow arrow in the figure, thereby securing the magnet 25 in the magnet receiving hole 22.

[0059] like Figure 6 As shown in (a) and (b), the protrusion 23 is formed by a protrusion-forming space 24 extending circumferentially from the inner side surface 22a of the magnet receiving hole 22. The protrusion-forming space 24 is a cutout (hole portion) that penetrates axially and communicates with the magnet receiving hole 22, and is arranged on the radial inner side of the protrusion 23. At least one of the protrusion 23 and the protrusion-forming space 24 is located on the d-axis. In this embodiment, the protrusion-forming space 24 is arranged to overlap with the d-axis, and the protrusion 23 is arranged close to the d-axis. In this way, the protrusion 23 and the protrusion-forming space 24 are both arranged near the center of the width direction (direction orthogonal to the radial direction) of the magnet 25, so as not to hinder the flow of magnetic flux (dashed arrow in the figure). It should be noted that the positioning hole 26 is separated from the protrusion-forming space 24 by a gap and is formed near the d-axis.

[0060] like Figure 6 As shown in (a), in the rotor 2 of this embodiment, the length L of the protrusion 23 in the protruding direction (hereinafter referred to as "protruding length L") is longer than the length W of the protrusion 23 in the width direction perpendicular to the protruding direction (hereinafter referred to as "width dimension W"). As a result, the protrusion 23 is easily elastically deformed, and the pressing force does not become excessive. In addition, the width dimension W of the protrusion 23 of this embodiment is formed to be the thickness T of a single laminated core 29 (refer to Figure 4). The longer the width W of the protrusion 23, the greater the press-in force. Therefore, by setting it to be no greater than twice the plate thickness T, excessive press-in force can be suppressed. Furthermore, in this embodiment, the width W of the protrusion 23 is set to be greater than the plate thickness T, enabling normal stamping.

[0061] [2. Action, effect]

[0062] (1) In the rotor 2 described above, since the protrusions 23 are not radially protruding but circumferentially protruding (the protrusions 23 protrude in the circumferential direction), the protrusions 23 are easily elastically deformed, and the pressing force when the magnets 25 are pressed in can be optimized. This solves the problem of "chip generation" that occurs when the pressing force is too large.

[0063] In addition, as shown as a comparative example Figure 7 As in (a), when a magnet (not shown) is press-fitted and fixed to a rotor core 50X without a protrusion, the shape of the magnet receiving hole 52 is made slightly smaller than the outer shape of the magnet (not shown) to provide a press-fitting amount. However, in this case, the press-fitting force is excessive, resulting in the generation of debris. In contrast, in the rotor 2 (rotor core 20) described above, the shape of the protrusion 23 is refined, thereby achieving a reasonable press-fitting force as described above, thereby preventing the generation of debris.

[0064] In the rotor 2 , the protrusion 23 and the protrusion-forming space 24 are both located near the center of the d-axis, so that the flow of magnetic flux is not blocked. This prevents a reduction in magnetic flux and ensures the performance of the motor 1 .

[0065] Here, as a comparative example, Figure 7 (b) shows a rotor core 50Y having two protrusions 53Y. Figure 7 (c) shows a rotor core 50Z having two protrusions 53Z. In these rotor cores 50Y and 50Z, the two protrusions 53Y and 53Z protrude circumferentially from the inner side surface 52a, similar to the protrusions 23 of the rotor core 20 described above. However, they differ in that there are only two protrusions and that their arrangement is symmetrical about the d-axis plane.

[0066] More specifically, in Figure 7 In the rotor core 50Y shown in (b), the two protrusions 53Y are separated from each other and protrude toward the d-axis, and the protrusion forming space 54Y extends from the inner side surface 52a toward the radial inside and toward the q-axis (not shown). Figure 7In the rotor core 50Z shown in (c), two protrusions 53Z are separated from each other and protrude toward the q-axis, and a protrusion forming space 54Z extends radially inward from the inner side surface 52a and toward the d-axis. It should be noted that the positioning hole 56 is formed on the d-axis.

[0067] The results of simulation of the magnetic flux reduction rate for each rotor having these rotor cores 50Y and 50Z are as follows: Figure 7 In the rotor core 50Y of (b), the magnetic flux reduction rate is 3.7%. Figure 7 In the rotor of the rotor core 50Z of (c), the magnetic flux reduction rate is 2.1%. It should be noted that the magnetic flux reduction rate refers to the rotor core having no protrusions (for example Figure 7 The ratio (%) of the reduction in magnetic flux relative to the magnetic flux of the rotor core as shown in (a) is taken as the reference.

[0068] That is, Figure 7 As shown in (b), when two protrusions 53Y are provided for each magnet receiving hole 52, the two protrusions 53Y are arranged separately from each other, so that each protrusion 53Y overlaps with the flow of magnetic flux (the channel of magnetic flux) as shown by the double-dotted line in the figure. Therefore, the protrusion 53Y and the protrusion forming space 54Y hinder the flow of magnetic flux, the magnetic flux reduction rate becomes higher, and the performance of the motor is reduced. It should be noted that in Figure 7 In the rotor core 50Z of (c), the magnetic flux reduction rate is also high for the same reason.

[0069] To address this problem, in the rotor 2, as described above, the protrusions 23 and the protrusion-forming spaces 24 are arranged so as not to obstruct the flow of magnetic flux. Figure 7 As a result of the same simulation as (b) and (c), it was found that the magnetic flux reduction rate became 0.0% in the rotor 2. Therefore, according to the motor 1 including the rotor 2, the performance of the motor 1 can be ensured.

[0070] Furthermore, the plurality of laminated cores 29 constituting the rotor core 20 described above all have the same shape, eliminating the need for rotational lamination as described in Patent Document 2. Consequently, there is no increase in mold costs, and manufacturing costs can be suppressed. Furthermore, no adhesive is used to secure the magnets 25 to the rotor core 20, eliminating the drawbacks associated with adhesives, such as the need for drying time, specialized equipment, and the need to manage the adhesive's expiration date. This is another advantage of the rotor 2 and motor 1 described above.

[0071] (2) In the rotor 2 and motor 1 described above, the width W of the protrusion 23 is less than or equal to twice the thickness T of one laminated core 29 . This prevents the press-fitting force from becoming excessive, and prevents the generation of chips when the magnet 25 is pressed in.

[0072] (3) Furthermore, since the width dimension W of the protrusion 23 is greater than or equal to the plate thickness T (ie, "T≤W≤2×T"), the laminated core 29 can be formed by ordinary press working without using a special die or the like. This can reduce manufacturing costs.

[0073] (4) In the above-described rotor 2 and motor 1 , the protruding length L of the protrusion 23 is longer than the width W, thereby preventing the press-fitting force from becoming excessive and ensuring the elastic force accompanying the elastic deformation of the protrusion 23 .

[0074] [3. Others]

[0075] The configurations of the rotor 2 and motor 1 described in the above embodiment are merely examples and are not limited thereto. For example, the protrusion 23 may be positioned so as to overlap the d-axis, or the protrusion length L and width W of the protrusion 23 may be set to dimensions different from those described above.

[0076] In addition, the shapes and structures of the stator 3 and the housing 4 are not limited to those described above.

Claims

1. A rotor, characterized in that: have: A columnar core body formed by stacking a plurality of laminated cores of the same shape in the axial direction and having an axial hole on the rotation center side; a plurality of permanent magnets, each of which is received and fixed in a plurality of magnet receiving holes, wherein the plurality of magnet receiving holes are axially penetrated around the axial hole of the core body and are circumferentially arranged in parallel in a circular shape; as well as A protrusion is provided in each magnet receiving hole and protrudes in the circumferential direction, wherein the protrusion is pressed against the permanent magnet received in the magnet receiving hole from the radial inner side. Each of the protrusions is formed by a protrusion-forming space extending circumferentially from the radially inner side surface of each of the magnet receiving holes. The protrusion and the protrusion forming space are provided only near the center in the width direction of the permanent magnet. At least one of the protrusion and the protrusion forming space is located on the d-axis which is the center of the magnetic pole.

2. The rotor according to claim 1, characterized in that The length of the protrusion in the width direction perpendicular to the protruding direction is not more than twice the thickness of one sheet of the laminated core.

3. The rotor according to claim 2, characterized in that The length of the protrusion in the width direction is equal to or greater than the plate thickness.

4. The rotor according to any one of claims 1 to 3, characterized in that The length of the protrusion in the protruding direction is longer than the length of the protrusion in the width direction perpendicular to the protruding direction.

5. A brushless motor, characterized in that: have: The rotor according to any one of claims 1 to 4; a shaft portion that rotates integrally with the rotor; and The stator is fixed to the housing, has a space on the inner diameter side for arranging the rotor, and has a coil.

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