Rotor

Abstract

This rotor of an electric motor comprises: a rotor core in which a permanent magnet is embedded or arranged on an outer peripheral surface; a rotor shaft that is a rotary shaft of the rotor core; an end plate that is fitted to the rotor shaft at a position in contact with one end of the rotor core in an axial direction; a first set collar that is fitted to the rotor shaft at a position in contact with the other end of the rotor core in the axial direction; a second set collar that engages with a portion of the first set collar opposite to the rotor core; and a holding member which is composed of fiber-reinforced plastic and has a cylindrical part in contact with an outer peripheral surface of the rotor core in which the permanent magnet is embedded or an outer peripheral surface of the permanent magnet arranged on the outer peripheral surface of the rotor core. A winding end portion of a fiber bundle constituting the fiber-reinforced plastic is sandwiched between the first set collar and the second set collar.

Description

rotor

[0001] The present invention relates to a rotor for an electric motor.

[0002] Known electric motors include SPM motors, in which magnets are attached to the surface of a rotor core, and IPM motors, in which magnets are embedded in the rotor core. To achieve high speeds in these electric motors, it is necessary to prevent the magnets and rotor core from breaking due to centrifugal force and the rotor core from lifting off the rotor shaft. To achieve this, a configuration is known in which a retaining member is provided to compress and hold the magnets of an SPM motor or the rotor core of an IPM motor from the outer circumferential surface toward the inside in the radial direction. JP 2017-195751 A discloses a retaining member made of fiber-reinforced plastic, which is made of fibers wound using a so-called filament winding method.

[0003] As described above, the holding member made of fiber has a problem in that the end-of-winding portion (end-processed portion) becomes loose due to environmental conditions such as friction with wind caused by high-speed rotation, vibration, and temperature cycles between high temperatures during operation and low temperatures during operation. While this problem can be solved by increasing the number of times the end-processed portion is wound, increasing the number of times the end-processed portion is wound increases the radial thickness, which may cause the holding member to rub against the stator. This rubbing may then cause the end-processed portion to become loose. In this regard, the holding member described in the above-mentioned document is configured so that the end-processed portion is located outside the axial end of the stator, and the end-processed portion is relatively thick.

[0004] However, although the configuration described in the above document can prevent friction between the end processing portion and the stator, it simply makes the end processing portion thicker, so there is room for improvement in terms of maintaining the fixation of the end processing portion even when the above environmental conditions are applied.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a rotor that can prevent the winding end portion of the fibers that make up the holding member from unwinding.

[0006] According to one aspect of the present invention, there is provided a rotor for an electric motor, comprising: a rotor core having permanent magnets embedded therein or arranged on its outer peripheral surface; a rotor shaft which is the rotation axis of the rotor core; an end plate fitted to the rotor shaft at a position where it contacts one axial end of the rotor core; a first set collar fitted to the rotor shaft at a position where it contacts the other axial end of the rotor core; a second set collar which engages with a portion of the first set collar opposite the rotor core; and a retaining member made of fiber-reinforced plastic and having a cylindrical portion which contacts the outer peripheral surface of the rotor core having permanent magnets embedded therein or the outer peripheral surface of the permanent magnets arranged on the outer peripheral surface of the rotor core, wherein the end portion of the winding of the fiber bundle which makes up the fiber-reinforced plastic is clamped between the first set collar and the second set collar.

[0007] Fig. 1 is a schematic diagram of a rotor according to a first embodiment. Fig. 2 is a diagram showing a state in which a second set collar and a holding member are removed from the rotor of Fig. 1. Fig. 3 is a diagram showing the rotor of Fig. 2 from a different angle. Fig. 4 is a diagram showing the second set collar as seen from the direction of the rotor's rotation axis. Fig. 5 is a diagram showing an example of a specific configuration of the second set collar. Fig. 6 is a side view of a rotor according to a second embodiment.

[0008] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0009] [First embodiment] The first embodiment will be described with reference to Figs. 1 to 5. Fig. 1 is a schematic diagram of a rotor 1 according to the first embodiment. Fig. 2 is a diagram showing the rotor 1 of Fig. 1 with a second set collar 6 and a retaining member 8, which will be described later, removed. Fig. 3 is a diagram showing the rotor 1 of Fig. 2 as viewed from a different angle. Fig. 4 is a diagram showing the second set collar 6 as viewed from the direction of the rotation axis of the rotor 1 (hereinafter also referred to as the axial direction). Fig. 5 is a diagram showing an example of a specific configuration of the second set collar 6.

[0010] The rotor 1 is one of the components that make up an electric motor. In this embodiment, the electric motor is a so-called SPM motor, that is, a rotating field synchronous motor in which permanent magnets 4 are attached to the surface of the rotor core 2, but this is not limiting. For example, the electric motor may be a so-called IPM motor in which permanent magnets are embedded inside the rotor core.

[0011] As shown in FIG. 1 , the rotor 1 includes a rotor shaft 3 , a rotor core 2 , permanent magnets 4 , end plates 7 , a first set collar 5 , a second set collar 6 , and a retaining member 8 .

[0012] The rotor core 2 is fixedly supported by a rotor shaft 3, which is a rotating shaft. The rotor core 2 is made by laminating thin electromagnetic steel sheets, for example, and has a coil (not shown) wound around it.

[0013] The permanent magnets 4 are generally fan-shaped and are arranged in a line in the circumferential direction on the outer circumferential surface of the rotor core 2 .

[0014] The end plates 7 are fitted to the rotor shaft 3 at a position where they contact one axial end of the rotor core 2. The first set collars 5 are fitted to the rotor shaft 3 at a position where they contact the other axial end of the rotor core 2. In other words, the rotor core 2 is sandwiched in the axial direction between the end plates 7 and the first set collars 5. The permanent magnets 4 attached to the outer peripheral surface of the rotor core 2 are also sandwiched in the same manner. The shape of the first set collars 5 will be described later.

[0015] The second set collar 6 engages with a portion of the first set collar 5 on the opposite side from the rotor core 2. The shape of the second set collar 6 will be described later.

[0016] The holding member 8 is cylindrical and made of fiber-reinforced plastic wound around the outer periphery of the permanent magnet 4. Specifically, a fiber bundle impregnated with a thermosetting resin is wound around the permanent magnet 4 using a filament winding method, and after winding is completed, the fiber bundle is placed in an oven (not shown) to harden. The winding path for the fiber bundle will be described later. The fiber is preferably carbon fiber, and the thermosetting resin is preferably epoxy resin. While FIG. 1 shows an axial gap in the holding member 8 through which the permanent magnet 4 can be seen, this is for simplification purposes. In reality, the axial gap disappears after multiple reciprocating movements between the end plate 7 and the first set collar 5.

[0017] At the start of winding of the holding member 8, the fiber bundle is temporarily fixed to the surface of the permanent magnet 4. By moving back and forth multiple times as described above, the fiber bundle is layered on top of the temporarily fixed portion, and the start of winding is fixed.

[0018] The end of the winding of the holding member 8 is clamped between the first set collar 5 and the second set collar 6. The clamping method will be described later.

[0019] 2 and 3 , the first set collar 5 includes a large diameter portion 5A that contacts the rotor core 2, a small diameter portion 5B that is coaxially disposed on the surface of the large diameter portion 5A opposite the surface that contacts the rotor core 2, and a guide portion 5D that connects the outer circumferential surface of the large diameter portion 5A with the outer circumferential surface of the small diameter portion 5B. The first set collar 5 also includes a stepped portion 5C that protrudes toward the rotor shaft tip from a surface S1 of the large diameter portion 5A that is on the rotor shaft tip side. The stepped portion 5C includes an inclined portion 5E that connects the rotor shaft tip side surface S1 of the large diameter portion 5A with a rotor shaft tip side surface S2 of the stepped portion 5C on an extension line of the small diameter portion side end of the guide portion 5D along the circumferential direction.

[0020] The first set collar 5 also has a lightening portion 5F at the stepped portion 5C. The lightening portion 5F is provided to align the rotational center of gravity of the first set collar 5 with the rotational center of gravity of the rotor shaft 3. The specific shape and depth of the lightening portion 5F are individually set depending on the shape of the stepped portion 5C, etc. However, in order to offset the increase in weight due to the stepped portion 5C, the depth needs to be at least longer than the axial distance between the surface S2 and the surface S1.

[0021] After the fiber bundle, which is the material of the holding member 8, has traveled back and forth between the end plate 7 and the large diameter portion 5A a predetermined number of times, it is wound around the outer peripheral surface of the large diameter portion 5A and then further wound from the outer peripheral surface of the large diameter portion 5A to the small diameter portion 5B along the guide portion 5D and the inclined portion 5E. Then, the fiber bundle wound around the small diameter portion 5B, i.e., the winding end portion of the holding member 8, is pressed radially by the second set collar 6. In other words, the second set collar 6 is attached to the first set collar 5 after the winding of the fiber bundle to form the holding member 8 has been completed. As a result, the winding end portion of the holding member 8 is sandwiched between the first set collar 5 and the second set collar 6.

[0022] In the configuration in which the fiber bundle wound around the small diameter portion 5B is clamped by the second set collar 6 from the radially outer side to hold down the holding member 8 as described above, it is desirable to hold down as much of the fiber bundle as possible with the second set collar 6 to prevent the holding member 8 from unraveling from the end of the fiber bundle. Therefore, the axial dimension of the second set collar 6 is set to be at least twice the width of the fiber bundle constituting the holding member 8. This allows the fiber bundle to be wound at least two times around the area where the second set collar 6 and the small diameter portion 5B face each other, preventing the holding member 8 from unraveling from the end of the fiber bundle. In other words, the reliability of the fastening of the end portion of the holding member 8 can be improved.

[0023] 4, the second set collar 6 has an annular shape with an opening 6A provided in the center that engages with the small diameter portion 5B of the first set collar 5. The second set collar 6 also has a slit 10 that extends tangentially from the opening 6A to the outer circumferential surface of the second set collar 6. The reason for providing the slit 10 is as follows.

[0024] After winding the fiber bundle under tension using the filament winding method, the second set collar 6 must be attached while maintaining that tension. To achieve this, the fiber bundle must not be cut at the end of the winding and must remain connected to the fiber bundle roll on the winding machine (not shown) until the second set collar 6 is attached. However, if this state is maintained, the fiber bundle extending tangentially from the end of the winding will interfere with the second set collar when attaching the second set collar 6. Therefore, a slit 10 is provided to allow the fiber bundle extending tangentially from the end of the winding to pass through. That is, the slit 10 is provided to allow the excess fiber bundle near the end of the fiber bundle to pass through. By aligning the position of the slit 10 with the fiber bundle extending tangentially when attaching the second set collar 6, the fiber bundle can be prevented from interfering with the attachment of the second set collar 6.

[0025] The second set collar 6 only needs to have the above-mentioned slit 10, and may be divided into two in the circumferential direction, for example.

[0026] 5 shows an example of a two-piece second set collar 6. In this example, the collar is divided into an upper member 61 and a lower member 62 by a dividing line located at positions 180 degrees apart in the circumferential direction when viewed in the axial direction. Each dividing line extends in a tangential direction of the opening 6A. The upper member 61 and the lower member 62 each have a bolt through-hole and a bolt hole (neither of which are shown) and are fastened together by a bolt 11 as shown in the figure.

[0027] In the second set collar 6 having the above-described structure, the upper member 61 is attached to the small diameter portion 5B from the axially upper side, and the lower member 62 is attached to the small diameter portion 5B from the axially lower side. At this time, one of the dividing lines is aligned with the fiber bundle extending from the small diameter portion 5B toward the winding machine. In other words, one of the dividing lines functions as the slit 10 described above.

[0028] As described above, the second set collar 6 has a two-piece structure, which facilitates the attachment work to the first set collar 5. Furthermore, by fastening with the bolt 11, even if there is dimensional variation in each part, the fiber bundle can be reliably fixed by adjusting the tightening of the bolt 11.

[0029] As described above, this embodiment provides a rotor 1 for an electric motor, the rotor 1 including: a rotor core 2 having permanent magnets 4 embedded therein or disposed on its outer circumferential surface; a rotor shaft 3 serving as the rotational axis of the rotor core 2; an end plate 7 fitted to the rotor shaft 3 at a position contacting one axial end of the rotor core 2; a first set collar 5 fitted to the rotor shaft 3 at a position contacting the other axial end of the rotor core 2; a second set collar 6 engaging with a portion of the first set collar 5 opposite the rotor core 2; and a retaining member 8 made of fiber-reinforced plastic and having a cylindrical portion contacting the outer circumferential surface of the rotor core 2 having the permanent magnets embedded therein or the outer circumferential surface of the permanent magnets 4 disposed on the outer circumferential surface of the rotor core 2. In this rotor 1, the winding end portion of the fiber bundle constituting the fiber-reinforced plastic is clamped between the first set collar 5 and the second set collar 6. This simple configuration of clamping the winding end portion between the first set collar 5 and the second set collar 6 can prevent the winding end portion from unwinding and loosening the tension of the retaining member 8.

[0030] In this embodiment, the first set collar 5 includes a large diameter portion 5A that contacts the rotor core 2, a small diameter portion 5B that is provided coaxially with the large diameter portion 5A on the surface of the large diameter portion 5A opposite the surface that contacts the rotor core 2, and a guide portion 5D that connects the outer circumferential surface of the large diameter portion 5A to the outer circumferential surface of the small diameter portion 5B. This allows the fiber bundle to be wound from the large diameter portion 5A to the small diameter portion 5B via the guide portion 5D, so that the fiber bundle does not come into contact with an edge portion of the large diameter portion 5A. If the fiber bundle comes into contact with an edge portion, the contacting portion is prone to wear due to vibration, and if the wear progresses and breaks, the tension of the retaining member 8 will be loosened. However, this embodiment can prevent this.

[0031] In this embodiment, the second set collar 6 has an annular shape with an opening 6A at the center that engages with the small diameter portion 5B of the first set collar 5, and is provided with a slit 10 that extends tangentially from the opening 6A to the outer circumferential surface and through which the fiber bundle passes. This prevents the fiber bundle from getting in the way when the second set collar 6 is attached to the first set collar 5.

[0032] In this embodiment, the first set collar 5 includes a stepped portion 5C that protrudes from the rotor shaft tip-side surface of the large diameter portion 5A toward the rotor shaft tip and includes a guide portion 5D. The stepped portion 5C includes an inclined portion 5E that connects the rotor shaft tip-side surface of the large diameter portion 5A to the rotor shaft tip-side surface of the stepped portion 5C on a circumferential extension of the small diameter portion-side end of the guide portion 5D. The fiber bundle is wound from the outer peripheral surface of the large diameter portion 5A to the small diameter portion 5B along the guide portion 5D and the inclined portion 5E, and the fiber bundle wound around the small diameter portion 5B is pressed radially by the second set collar 6. By providing the inclined portion 5E as described above, the fiber bundle does not come into contact with the edge of the stepped portion 5C, thereby suppressing wear due to vibration.

[0033] In this embodiment, the second set collar 6 has a structure in which it is divided into two in the circumferential direction by two dividing lines provided at positions 180 degrees apart in the circumferential direction when viewed in the axial direction, and both of the two dividing lines extend in the tangential direction of the circular opening 6A, with one of the dividing lines functioning as the slit 10. The two-divided structure makes it easy to avoid interference with the fiber bundle when attaching the second set collar 6.

[0034] In this embodiment, the first set collar 5 is provided in the stepped portion 5C at the lightening portion 5F, so that the rotational center of gravity coincides with the rotational center of gravity of the rotor shaft 3. This makes it possible to suppress deterioration of balance during rotation due to the provision of the stepped portion 5C.

[0035] In this embodiment, the axial dimension of the second set collar 6 is at least twice the width of the fiber bundle, which allows the fiber bundle to be wound at least two times around the area of ​​the small diameter portion 5B facing the second set collar 6, thereby improving the reliability of fastening the end portion of the holding member 8.

[0036] Second Embodiment A second embodiment will be described with reference to Fig. 6. Fig. 6 is a side view of a rotor 1 according to the second embodiment.

[0037] The differences from the first embodiment are the structure of the first set collar 5 and the second set collar 6, and the structure for clamping the end of the winding of the holding member 8. The following description will focus on these points.

[0038] The first set collar 5 comprises a large diameter portion 5A and a small diameter portion 5B, and does not have the stepped portion 5C described above. The second set collar 6 has an integral structure and does not have the slit 10 as in the first embodiment. The second set collar 6 is press-fitted into the small diameter portion 5B from the axial tip side.

[0039] The fiber bundle is wound around the small diameter portion 5B at least once, and the end of the winding 8A is clamped between the surface of the large diameter portion 5A on the rotor shaft tip side and the surface of the second set collar 6 on the large diameter portion 5A side, which is press-fitted into the small diameter portion 5B.

[0040] According to this configuration, once the winding of the fiber bundle is completed, the winding end portion of the fiber bundle is fixed simply by press-fitting the second set collar 6 into the small diameter portion 5B while the winding end portion of the fiber bundle is connected to the winding machine side (i.e., while tension is applied to the fiber bundle), which simplifies assembly. After press-fitting the second set collar 6, the fiber bundle protruding from the gap between the second set collar 6 and the first set collar 5 is cut off.

[0041] As described above, in this embodiment, the first set collar 5 includes a large diameter portion 5A that contacts the rotor core 2 and a small diameter portion 5B that is provided coaxially with the large diameter portion 5A on the surface of the large diameter portion 5A opposite the surface that contacts the rotor core 2, and the second set collar 6 has an integral structure and an annular shape with an opening 6A at its center that engages with the small diameter portion 5B of the first set collar 5, and the winding end portion of the fiber bundle wound around the small diameter portion 5B is clamped between the surface of the large diameter portion 5A on the rotor shaft tip side and the surface of the second set collar 6 that is press-fitted into the small diameter portion 5B on the large diameter side. This eliminates the need for alignment with the fiber bundle and, in the case of a split structure, alignment between the upper member 61 and the lower member 62, thereby simplifying installation of the second set collar 6.

[0042] Although the embodiments of the present invention have been described above, the above embodiments merely illustrate some of the application examples of the present invention, and it is not intended that the technical scope of the present invention be limited to the specific configurations of the above embodiments.

Claims

1. A rotor for an electric motor, comprising: a rotor core having permanent magnets embedded therein or arranged on its outer peripheral surface; a rotor shaft which is the rotation axis of the rotor core; an end plate fitted with the rotor shaft at a position where it contacts one axial end of the rotor core; a first set collar fitted with the rotor shaft at a position where it contacts the other axial end of the rotor core; a second set collar which engages with a portion of the first set collar on the opposite side from the rotor core; and a retaining member made of fiber-reinforced plastic, having a cylindrical portion which contacts the outer peripheral surface of the rotor core having the permanent magnets embedded therein, or the outer peripheral surface of the permanent magnets arranged on the outer peripheral surface of the rotor core, wherein the end portion of the winding of the fiber bundle which makes up the fiber-reinforced plastic is clamped between the first set collar and the second set collar.

2. A rotor according to claim 1, wherein the first set collar comprises a large diameter portion that contacts the rotor core, a small diameter portion that is provided coaxially with the large diameter portion on the surface of the large diameter portion opposite the contact surface with the rotor core, and a guide portion that connects the outer circumferential surface of the large diameter portion with the outer circumferential surface of the small diameter portion.

3. A rotor according to claim 2, wherein the second set collar has an annular shape with an opening at the center that engages with the small diameter portion of the first set collar, and is provided with a slit that extends tangentially from the opening to the outer circumferential surface and through which the fiber bundle passes.

4. A rotor as claimed in claim 3, wherein the first set collar comprises a stepped portion which protrudes from the surface of the large diameter portion on the rotor shaft tip side towards the rotor shaft tip and which comprises the guide portion, the stepped portion comprising an inclined portion which connects the surface of the large diameter portion on the rotor shaft tip side with the surface of the stepped portion on the rotor shaft tip side, on an extension line along the circumferential direction of the end of the small diameter portion side of the guide portion, the fiber bundle is wound from the outer peripheral surface of the large diameter portion to the small diameter portion along the guide portion and the inclined portion, and the fiber bundle wound around the small diameter portion is pressed radially by the second set collar.

5. A rotor as claimed in claim 4, wherein the second set collar has a structure in which it is divided into two circumferentially by two dividing lines provided at positions 180 degrees apart in the circumferential direction when viewed in the axial direction, both of which extend in the tangential direction of the circular opening, and one of the dividing lines functions as the slit.

6. A rotor according to claim 4, wherein the first set collar is provided in a hollowed-out portion in the stepped portion, so that the center of rotation of the first set collar coincides with the center of rotation of the rotor shaft.

7. A rotor according to claim 4, wherein the axial dimension of said second set collar is at least twice the width of said fiber bundle.

8. A rotor as claimed in claim 1, wherein the first set collar comprises a large diameter portion in contact with the rotor core and a small diameter portion provided coaxially with the large diameter portion on the surface of the large diameter portion opposite the contact surface with the rotor core, the second set collar is of an integral structure and has a circular ring shape with an opening at the center that engages with the small diameter portion of the first set collar, and the end of the fiber bundle wound around the small diameter portion is clamped between the surface of the large diameter portion on the rotor shaft tip side and the surface of the second set collar on the large diameter portion side that is press-fitted into the small diameter portion.

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