Rotor and brushless motor

Abstract

To fix a permanent magnet with appropriate pressing force while suppressing manufacturing cost while securing motor performance.SOLUTION: A rotor includes a columnar core body 20 composed of a plurality of laminated cores 29 having the same shape and having a shaft hole 21 on the rotation center side, a plurality of permanent magnets 25 that are housed and fixed in a plurality of magnet housing holes 22 that are axially penetrating around the shaft hole 21 of the core body 20 and arranged in a circular shape in the circumferential direction, and a protrusion portion 23 provided in each of the magnet housing holes 22. The protrusion portion 23 protrudes in the circumferential direction and presses against the permanent magnet 25 housed in the magnet housing hole 22 from the radially inner side. Each of the protrusion portions 23 is defined by a protrusion forming space 25 extending along the circumferential direction from a radial inner surface 22a of each of the magnet housing holes 22, and at least one of the protrusion portion 23 and the protrusion forming space 25 is located on a d-axis which is the center of the magnetic pole.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a rotor having a permanent magnet disposed inside a core body, and to a brushless motor including the rotor. [Background technology]

[0002] Conventionally, so-called IPM (Interior Permanent Magnet) rotors, in which permanent magnets are arranged inside the core body, have been known. In such rotors, centrifugal force generated by the rotation of the rotor acts on the permanent magnets, causing the permanent magnets to move, which may cause vibrations and noise, or damage to the permanent magnets. For this reason, in IPM rotors, it is necessary to securely fix the permanent magnets to the core body, and various methods have been proposed so far.

[0003] For example, Patent Document 1 discloses a rotor core (core body) that includes a press-fit protrusion that protrudes radially in a through hole in which a magnet (permanent magnet) is placed to press-fit and fix the magnet, and a cut-out portion that is formed at a position radially spaced apart from the magnet with the press-fit protrusion in between. According to Patent Document 1, the magnet is press-fitted and fixed by the press-fit protrusion, while the application of excessive pressure to the magnet is suppressed by the cut-out portion.

[0004] Patent Document 2 discloses an IPM rotor that includes a first core sheet with a spring plate portion provided in a hole where a magnet is inserted, and a second core sheet with a recessed portion provided in a position corresponding to the location of the spring plate portion of the first core sheet, and that is constructed by stacking these core sheets. With this configuration, when a magnet is inserted into the IPM rotor, the spring plate portion bent by the magnet can escape to the recessed portion of the second core sheet, and the magnet can be held in place by the restoring force of the spring plate portion. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 5918958 [Patent Document 2] Re-tabled publication No. 2018-189822 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the configuration of Patent Document 1, the press-fitting force becomes too large, and the rotor core may be scraped off and generate debris when the magnet is inserted into the rotor core. In addition, in Patent Document 2, core sheets of different shapes are stacked, which requires stacking, resulting in increased mold costs. Furthermore, depending on the positions of the protrusions and recesses, the flow of magnetic flux may be hindered, and the arrangement of these is important from the viewpoint of ensuring motor performance.

[0007] As a method of fixing magnets, it is also possible to use adhesives without forming protrusions. However, fixing with adhesives may require special equipment for application depending on the type of adhesive, and liquid adhesives take time to harden, which is not desirable in terms of improving production efficiency. Also, adhesives generally have a wear-out period, so care must be taken when managing (storing) the adhesive.

[0008] The present invention has been devised in view of such problems, and has as one object to provide a rotor and a brushless motor that can secure a permanent magnet with an appropriate press-in force while suppressing manufacturing costs and ensuring motor performance. However, the present invention is not limited to this object. Another object of the present invention is to provide an effect that cannot be obtained by conventional techniques, which is derived from each configuration shown in the below-mentioned embodiment of the invention. [Means for solving the problem]

[0009] (1) The rotor disclosed herein is made up of multiple laminated cores of the same shape. By stacking in the axial direction,The core body is configured to include a columnar core body having an axial hole on the rotation center side, a plurality of permanent magnets that are housed and fixed in a plurality of magnet accommodating holes that are axially penetrating the axial hole of the core body around the axial hole and arranged in a circular shape in the circumferential direction, and a protrusion that is provided in each of the magnet accommodating holes, protrudes in the circumferential direction, and is pressed against the permanent magnets housed in the magnet accommodating holes from the radially inner side. Each of the protrusions is formed by a protrusion forming space that extends in the circumferential direction from the radially inner side surface of each of the magnet accommodating holes, The press-contact surface is formed flush along the axial direction by the lamination, At least one of the protrusion and the protrusion forming space is located on the d-axis which is the magnetic pole center. That is, one protrusion is provided for one permanent magnet, and each protrusion is provided asymmetrically with respect to the d axis.

[0010] (2) It is preferable that the length of the projection in the width direction perpendicular to the protruding direction is not more than twice the plate thickness of one of the laminated cores. (3) It is preferable that the length of the protrusion in the width direction is equal to or greater than the plate thickness. (4) It is preferable that the length of the protrusion in the protruding direction is longer than the length of the protrusion in a width direction perpendicular to the protruding direction.

[0011] (5) The motor disclosed herein includes a rotor according to any one of (1) to (4) above, a shaft rotating integrally with the rotor, and a stator fixed to a housing, having a space on its inner diameter side in which the rotor is disposed, and having a coil. Effect of the Invention

[0012] According to the disclosed rotor and brushless motor, the protrusions are easily elastically deformed, so that the permanent magnets can be fixed to the core body with an appropriate press-fitting force. In addition, the protrusions and the spaces in which they are formed do not impede the flow of magnetic flux, so performance can be ensured. In addition, since special molds and dedicated equipment are not required, manufacturing costs can be reduced. [Brief description of the drawings]

[0013] [Figure 1] 1 is a perspective view of a brushless motor according to an embodiment; [Diagram 2] 2 is a cross-sectional view taken along the axial direction of the brushless motor of FIG. 1. [Diagram 3] 2 is an exploded perspective view showing a rotor and a stator of the brushless motor of FIG. 1. [Figure 4] 4 is a diagram for explaining a laminated core constituting the rotor of FIG. 3. FIG. [Diagram 5] 4 is a diagram for explaining the magnetic poles and magnetic flux flow of the rotor in FIG. 3. [Figure 6] 6(a) is an enlarged view of part A in FIG. 4, and FIG. 6(b) is a view showing the rotor core into which the magnet is press-fitted in FIG. 6(a). [Figure 7] 6(a) to 6(c) are diagrams for explaining a comparative example (corresponding to FIG. 6(a)). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] A rotor and a brushless motor as embodiments will be described with reference to the drawings. The embodiments described below are merely examples, and are not intended to exclude various modifications or application of techniques not explicitly described in the following embodiments. Each configuration of the present embodiment can be modified in various ways without departing from the spirit of the invention. In addition, the configurations can be selected as necessary, or can be combined as appropriate.

[0015] [1. Configuration] FIG. 1 is a perspective view of a brushless motor 1 (hereinafter referred to as "motor 1") according to this embodiment, and FIG. 2 is an axial cross-sectional view of motor 1. Motor 1 is an inner rotor type brushless DC motor, and is configured by incorporating a rotor 2 to which a shaft 10 is fixed, and a stator 3 fixed to housing 4, which forms the outer hull of motor 1. Housing 4 is cylindrical with both ends open in the axial direction, and an end bell 15 is fixed to the opening at one end (right side in FIG. 2), and a front bell 14 is fixed to the opening at the other end (output side, left side in FIG. 2). Incidentally, the exterior shape of housing 4 in this embodiment is substantially rectangular, but the shape of housing 4 is not limited to this.

[0016] FIG. 3 is a perspective view showing the rotor 2 of this embodiment disassembled from the stator 3, with the shaft 10 and the housing 4 omitted. As shown in FIGS. 2 and 3, the stator 3 is a substantially cylindrical part having a space on the inner diameter side where the rotor 2 is arranged, and includes an annular stator core 30 press-fitted and fixed in the housing 4, and a coil 32 wound around the stator core 30 via an insulator 31. As shown in FIGS. 1 and 2, the stator 3 of this embodiment includes a lead wire 6 for power input connected to the coil 32, a lead wire 7 for inputting and outputting a sensor signal, a lead wire stopper part 5 supporting the lead wire 6, and a substrate 8 having a rotation detection element for detecting a signal corresponding to the rotation position of the rotor 2. Note that the configuration of the stator 3 is not limited to this, and for example, the lead wire stopper part 5 may be omitted, or a part supporting the substrate 8 may be provided separately.

[0017] 2 and 3, the rotor 2 is an IPM (Interior Permanent Magnet) rotor including a rotor core 20 (core body) that rotates integrally with the shaft 10 around a rotation center C, and a plurality of magnets 25 (permanent magnets) 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 that extracts the output (mechanical energy) of the motor 1 to the outside. The shaft 10 is provided with bearings 11 and 12 at two positions on either side of the rotor 2. In this embodiment, the bearing 11 is fixed to the front bell 14 and rotatably supports the middle part of the shaft 10, and the bearing 12 is fixed to the end bell 15 and rotatably supports the end part (the right end part in the figure) of the shaft 10.

[0018] The rotor core 20 is formed by stacking a plurality of laminated cores 29 in the axial direction. FIG. 4 shows a plan view and a side view of the laminated core 29 of this embodiment side by side. The laminated cores 29 are thin electromagnetic steel sheets having an axial hole 21 to which the shaft 10 is fixed on the side of the rotation center C, and are all formed to the same shape. A plurality of magnet accommodating holes 22 are provided axially around the axial hole 21 of the laminated core 29. The magnet accommodating holes 22 are through holes in which the magnets 25 are accommodated and fixed, and the same number of magnet accommodating holes 22 are provided as the number of magnets 25. In the rotor 2 of this embodiment, there are 14 magnets 25 and magnet accommodating holes 22, although the number is not limited to this.

[0019] The multiple magnet accommodating holes 22 are arranged side by side in a circular shape in the circumferential direction as viewed from the axial direction, along the outer periphery of the laminated core 29. The multiple magnets 25 are accommodated one by one in each magnet accommodating hole 22, and are arranged such that the magnetic poles (N pole, S pole) of adjacent magnets 25 in the circumferential direction are opposite to each other, as shown in Fig. 5. This causes a flow of magnetic flux between adjacent magnets 25 as indicated by the dashed arrows in the figure.

[0020] As shown in Fig. 4 and Fig. 6(a), the magnet accommodating hole 22 in this embodiment is long in a direction perpendicular to the radial direction when viewed from the axial direction, has an isosceles trapezoid shape with R at the corners, and the radially outer surface (the part corresponding to the "upper base" or "lower base" of the trapezoid) is wider than the radially inner surface (the part corresponding to the "upper base" or "lower base" of the trapezoid). Two magnet accommodating holes 22 adjacent in the circumferential direction are provided with adjacent end faces (surfaces extending in the radial direction and parts corresponding to the "legs" of the trapezoid) parallel to each other and with a gap between these two end faces. This gap overlaps with the q-axis (see Fig. 5), which is the magnetic pole boundary.

[0021] As shown in Fig. 2 and Fig. 3, the magnet 25 has a rectangular parallelepiped shape with an axial length equivalent to that of the rotor core 20. More specifically, as shown in Fig. 6(b), when viewed from the axial direction, the height (radial dimension) of the rectangle of the axial end face of the magnet 25 is equivalent to the radial length equivalent to the "height" of the trapezoid of the magnet accommodating hole 22, and the width (dimension in a direction perpendicular to the radial direction) of the rectangle is such that a small gap is formed between the surface equivalent to the "leg" of the magnet accommodating hole 22. The magnet 25 is fixed to the rotor core 20 by press-fitting without using adhesive. The rotor 2 is provided with a protrusion 23 for press-fitting and fixing the magnet 25, and a protrusion forming space 24 for forming the protrusion 23.

[0022] As shown in Fig. 4 and Fig. 6(a), one protrusion 23 is provided for each magnet accommodating hole 22, and the number of protrusions 23 is the same as the number of magnet accommodating holes 22 and magnets 25. The protrusions 23 are provided to protrude along the circumferential direction on the radial inner side surface 22a (hereinafter referred to as "inner side surface 22a") of the magnet accommodating hole 22. In other words, the protrusion direction of the protrusions 23 is mainly the circumferential component, and extends along the inner side surface 22a of the magnet accommodating hole 22 when viewed from the axial direction, and is formed in an asymmetric shape with respect to the d-axis which is the center of the magnetic pole. The protrusions 23 in this embodiment are provided to protrude toward the d-axis when viewed from the axial direction, and a part of the protrusions 23 is provided to enter the inside of the magnet accommodating hole 22.

[0023] 6(b), when the magnet 25 is accommodated in the magnet accommodating hole 22, the protrusion 23 elastically deforms toward the rotation center C and presses against the magnet 25 accommodated in the magnet accommodating hole 22 from the radially inner side. As a result, the protrusion 23 presses the magnet 25 radially outward as shown by the white arrow in the figure, fixing the magnet 25 in the magnet accommodating hole 22.

[0024] As shown in Figs. 6(a) and (b), the protrusion 23 is formed by a protrusion forming space 24 extending from the inner surface 22a of the magnet accommodating hole 22 along the circumferential direction. The protrusion forming space 24 is a notch (hole) that penetrates in the axial direction and communicates with the magnet accommodating hole 22, and is provided on the radial inside 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 provided overlapping the d axis, and the protrusion 23 is provided close to the d axis. In this way, both the protrusion 23 and the protrusion forming space 24 are provided near the center of the width direction (direction perpendicular to the radial direction) of the magnet 25, so that the flow of magnetic flux (broken arrow in the figure) is not obstructed. The positioning hole 26 is formed near the d axis with a gap between it and the protrusion forming space 24.

[0025] As shown in FIG. 6(a), in the rotor 2 of this embodiment, the length L of the protruding portion 23 in the protruding direction (hereinafter referred to as the "protruding length L") is longer than the length W of the protruding portion 23 in the width direction perpendicular to the protruding direction (hereinafter referred to as the "width dimension W"). This makes the protruding portion 23 more elastically deformable, and prevents the press-fitting force from becoming excessive. In addition, the protruding portion 23 of this embodiment is formed so that its width dimension W is twice or less than the plate thickness T (see FIG. 4) of one laminated core 29. Since the longer the width dimension W of the protruding portion 23 is, the greater the press-fitting force becomes, so setting it to twice or less than the plate thickness T suppresses the excessive press-fitting force. Furthermore, in this embodiment, the width dimension W of the protruding portion 23 is set to be greater than or equal to the plate thickness T, which enables normal press working.

[0026] [2. Actions and Effects] (1) In the rotor 2 described above, the protrusions 23 are provided protruding in the circumferential direction rather than the radial direction (the protruding direction of the protrusions 23 includes a circumferential component), which makes it easier for the protrusions 23 to deform elastically, thereby optimizing the press-in force when the magnet 25 is pressed in. This solves the problem of "generating debris" that occurs when the press-in force is excessive.

[0027] 7(a) shown as a comparative example, when a magnet (not shown) is press-fitted into a rotor core 50X without protrusions, the shape of the magnet accommodating hole 52 is made slightly smaller than the outer shape of the magnet (not shown) to provide a press-fit allowance, but in this case, the press-fit force becomes excessive and debris is generated. In contrast, with the rotor 2 (rotor core 20) described above, the shape of the protrusions 23 can be devised to optimize the press-fit force as described above, so no debris is generated.

[0028] In addition, in the rotor 2 described above, the protrusions 23 and the protrusion forming spaces 24 are both disposed near the center near the d-axis, so they do not impede the flow of magnetic flux. This makes it possible to prevent a decrease in magnetic flux and ensure the performance of the motor 1.

[0029] As comparative examples, a rotor core 50Y having two protrusions 53Y is shown in Fig. 7(b), and a rotor core 50Z having two protrusions 53Z is shown in Fig. 7(c). These rotor cores 50Y, 50Z are similar to the protrusions 23 of the rotor core 20 described above in that the two protrusions 53Y, 53Z each protrude in the circumferential direction from the inner surface 52a, but differ in that there are two of them, and that their arrangement is plane-symmetrical with respect to the d axis.

[0030] More specifically, in a rotor core 50Y shown in Fig. 7(b), two protrusions 53Y are spaced apart from each other and protrude toward the d axis, and a protrusion forming space 54Y extends from the inner surface 52a radially inward toward the q axis (not shown). In addition, in a rotor core 50Z shown in Fig. 7(c), two protrusions 53Z are spaced apart from each other and protrude toward the q axis, and a protrusion forming space 54Z extends from the inner surface 52a radially inward toward the d axis. The positioning hole 56 is formed on the d axis.

[0031] A simulation of the magnetic flux reduction rate for each rotor having rotor cores 50Y and 50Z showed that the magnetic flux reduction rate for the rotor having rotor core 50Y in Fig. 7(b) was 3.7%, while the magnetic flux reduction rate for the rotor having rotor core 50Z in Fig. 7(c) was 2.1%. Note that the magnetic flux reduction rate refers to the percentage reduction in magnetic flux relative to the magnetic flux of a rotor having a rotor core with no protrusions (for example, a rotor core like that in Fig. 7(a)).

[0032] That is, as shown in Fig. 7(b), when two protrusions 53Y are provided for each magnet accommodating hole 52, the two protrusions 53Y are arranged apart from each other, so that each protrusion 53Y overlaps with the flow of magnetic flux (path of magnetic flux) as shown by the two-dot chain line in the figure. Therefore, the protrusions 53Y and the protrusion forming space 54Y obstruct the flow of magnetic flux, increasing the flux drop rate and ultimately causing a decrease in motor performance. The flux drop rate is also high in the rotor core 50Z of Fig. 7(c) for the same reason.

[0033] To address this issue, in the rotor 2 described above, the protrusions 23 and protrusion-forming spaces 24 are arranged so as not to impede the flow of magnetic flux, as described above. A simulation similar to that shown in Figs. 7(b) and (c) was performed on the rotor 2 having the rotor core 20 described above, and it was found that the magnetic flux drop rate of the rotor 2 is 0.0%. Therefore, by using a motor 1 equipped with the rotor 2, the performance of the motor 1 can be ensured.

[0034] In addition, since the multiple laminated cores 29 constituting the rotor core 20 described above all have the same shape, there is no need for stacking as in Patent Document 2. This prevents an increase in mold costs and reduces manufacturing costs. Furthermore, since no adhesive is used to fix the magnets 25 to the rotor core 20, there are no disadvantages associated with using an adhesive, such as the need for drying time, the need for dedicated equipment, and the absence of management of the expiration date of the adhesive, which are also advantages of the rotor 2 and motor 1 described above.

[0035] (2) In the rotor 2 and motor 1 described above, the width dimension W of the protrusion 23 is less than twice the plate thickness T of one laminated core 29, so that the pressing force can be prevented from becoming excessive, and the generation of debris when the magnet 25 is pressed in can be prevented. (3) Furthermore, since the width dimension W of the protrusion 23 is equal to or greater than the plate thickness T (i.e., "T≦W≦2×T"), the laminated core 29 can be formed by normal press processing without using a special die, etc. This makes it possible to reduce manufacturing costs.

[0036] (4) Furthermore, in the rotor 2 and motor 1 described above, the protruding length L of the protrusion 23 is longer than the width dimension W, so that the spring force associated with the elastic deformation of the protrusion 23 can be secured while preventing the press-fit force from becoming excessive.

[0037] [3.Other] The configurations of the rotor 2 and the motor 1 described in the above embodiment are merely examples and are not limited to those described above. For example, the protrusion 23 may be provided at a position overlapping the d-axis, and the protruding length L and width dimension W of the protrusion 23 may be set to dimensions different from those described above. Furthermore, the shapes and configurations of the stator 3, the housing 4, etc. are not limited to those described above. [Explanation of symbols]

[0038] 1 Motor (brushless motor) 2 Rotors 3 Stator 4. Housing 10 Shaft 20 Rotor core (core body) 21 Shaft hole 22 Magnet receiving hole 22a Inner surface (radial inner surface) 23 Protrusion 24 Protrusion formation space 25 Magnets (permanent magnets) 25a Radial inner side 29 Laminated Core C Rotation center L: Projection length of the protrusion (length in the projecting direction) T: thickness of laminated core W Width of protrusion (length in width direction)

Claims

1. The core body is a columnar core having an axial hole on the rotation center side and is constructed by stacking multiple laminated cores of the same shape in the axial direction. A plurality of permanent magnets are accommodated and fixed in a plurality of magnet accommodating holes that are axially penetrating the periphery of the axial hole of the core body and are arranged side by side in a circular shape in the circumferential direction; a protrusion provided in each of the magnet accommodating holes, protruding along a circumferential direction, and pressing against the permanent magnet accommodated in the magnet accommodating hole from a radially inner side; Each of the protrusions is formed by a protrusion forming space extending from a radially inner side surface of each of the magnet accommodating holes along a circumferential direction, and has the pressure-contact surface formed to be flush along the axial direction by the lamination, 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. A rotor comprising:

2. The length of the protruding portion in the width direction perpendicular to the protruding direction is equal to or less than twice the plate thickness of one of the laminated cores. A rotor according to claim 1 , characterized in that it comprises:

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

4. The length of the protruding portion in a protruding direction is longer than the length of the protruding portion in a width direction perpendicular to the protruding direction. A rotor according to any one of claims 1 to 3.

5. A rotor according to any one of claims 1 to 4, A shaft that rotates integrally with the rotor; a stator fixed to a housing, having a space on an inner diameter side in which the rotor is disposed, and having a coil; A brushless motor characterized by:

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