Motor rotor

Abstract

This invention provides an electric motor rotor that allows for the optimization of the magnetic flux shape even when permanent magnets are bonded and fixed using a molded resin containing soft magnetic powder. [Solution] The rotor for electric motors of the present invention comprises a rotor core formed by laminating multiple electromagnetic steel sheets, The rotor core is provided with a permanent magnet located in a through-hole that penetrates the rotor core in the axial direction. Furthermore, the permanent magnet has a flattened shape in which the length in the longitudinal direction and the length in the short direction are different when viewed axially, and has flux barriers at both ends in the longitudinal direction, and both surfaces on the long side of the permanent magnet are bonded and fixed to the rotor core with molded resin, and the molded resin contains soft magnetic powder, so that a rotor for an electric motor can be provided in which the shape of the magnetic flux can be optimized.

Description

Technical Field

[0001] The present invention relates to a rotor for an electric motor, and more particularly to an interior permanent magnet type rotor.

Background Art

[0002] An interior permanent magnet (IPM) motor in which permanent magnets are embedded in a rotor core can actively utilize the rotational force (reluctance torque) generated by the change in the position of magnetic energy, is highly efficient, and can operate in a wide speed range, so it is used in electric vehicles.

[0003] The above permanent magnet is adhesively fixed to the rotor core. However, in the case of fixing with an adhesive, it is difficult to apply the adhesive without excess or deficiency and to apply the adhesive to the entire adhesive surface, so the adhesive strength is likely to vary.

[0004] Patent Document 1 discloses that the permanent magnet is fixed by press-fitting a mold resin between the rotor core and the permanent magnet. According to this fixing method, the mold resin spreads over the entire adhesive surface, and the permanent magnet can be firmly fixed.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, in the rotor described in Patent Document 1, since the entire flux barrier is filled with molded resin, if soft magnetic powder is added to the molded resin to facilitate the passage of magnetic flux, the magnetic flux will also pass through the flux barrier portion. Therefore, it is not possible to optimize the design by generating magnetic saliency so that the magnetic flux links with the stator, making it difficult to improve the reluctance torque.

[0007] This invention has been made in view of the problems of the prior art, and its objective is to provide a motor rotor that can optimize the shape of the magnetic flux even when a permanent magnet is bonded and fixed with a molded resin containing soft magnetic powder. [Means for solving the problem]

[0008] The inventors of this invention conducted extensive research to achieve the above objective and discovered that this objective can be achieved by bonding and fixing the entire surface of both sides of the long edge of a permanent magnet with a mold resin containing soft magnetic powder, thus completing the present invention.

[0009] In other words, the motor rotor of the present invention comprises a rotor core formed by laminating multiple electromagnetic steel sheets, The rotor core is provided with a permanent magnet located in a through-hole that penetrates the rotor core in the axial direction. Furthermore, the shape of the permanent magnet described above is a flattened shape in which the length in the longitudinal direction and the length in the short direction are different when viewed in the axial direction, and it has flux barriers at both ends in the longitudinal direction. The entire surface of both sides of the long edge of the permanent magnet is bonded and fixed to the rotor core with molded resin. The above-mentioned mold resin is characterized by containing soft magnetic powder. [Effects of the Invention]

[0010] According to the present invention, since the entire surface of both sides of the long side of a flattened permanent magnet is bonded and fixed with a molded resin containing soft magnetic powder, it is possible to provide a motor rotor that can improve magnet torque. [Brief explanation of the drawing]

[0011] [Figure 1] This is a quarter-scale plan view of a rotor for an electric motor. [Figure 2] This diagram illustrates the procedure for manufacturing a rotor for an electric motor. [Figure 3] This diagram illustrates the location of the gate marks on an electric motor rotor. [Figure 4] This is a diagram illustrating the thickness of the molding resin. [Figure 5] This diagram illustrates the state of the mold resin that leaked into the flux barrier. [Modes for carrying out the invention]

[0012] The rotor for electric motors of the present invention will be described in detail. The rotor for an electric motor of the present invention comprises a rotor core and permanent magnets. The rotor core described above is formed by laminating multiple electromagnetic steel sheets, each having an insulating coating on both its front and back surfaces, and has through-holes that penetrate in the axial direction. The permanent magnet has a flattened shape when viewed in the axial direction and is installed within the through-holes of the rotor core. The flattened shape can be approximately rectangular or arc-shaped, as long as the lengths of the longitudinal and transverse directions differ when viewed in the axial direction.

[0013] As shown in Figure 1, the permanent magnet is not provided to occupy the entire through-hole, but rather to the center of the through-hole, and flux barriers are formed at both ends in the longitudinal direction of the permanent magnet, i.e., on the short side. This makes it possible to generate magnetic salient polarity so that the magnetic flux links with the stator.

[0014] The through-holes and permanent magnets described above can be arranged according to the magnetic circuit. Figure 1 shows the through-holes and permanent magnets arranged with their longitudinal direction facing the circumferential direction, but their longitudinal direction may also be facing the radial direction, or a direction intermediate between the circumferential and radial directions.

[0015] In the rotor for an electric motor of the present invention, among the gaps formed between the permanent magnet and the rotor core, mold resin is press-fitted into the gaps on the long-side of the permanent magnet excluding the flux barrier portion, that is, the gaps at both ends in the short-side direction, and the permanent magnet and the rotor core are adhesively fixed by this mold resin.

[0016] Thus, by press-fitting the mold resin into the gap, it is possible to control the flow of the mold resin in the gap, and the mold resin can be filled in the entire gap on the long-side of the permanent magnet, and the entire surfaces on both sides of the long-side of the permanent magnet can be adhered to the rotor core, so that the adhesive strength can be improved.

[0017] In the present invention, "the entire surfaces on both sides of the long-side of the permanent magnet are adhered and fixed to the rotor core with the mold resin" means that the entire gap formed between the rotor core formed on the long-side of the permanent magnet is filled with the mold resin, and it does not mean that there are no voids in the mold resin.

[0018] Also, since the mold resin of the present invention contains soft magnetic powder, the magnetic flux of the permanent magnet easily passes through the mold resin. Since the mold resin through which the magnetic flux easily passes is applied to the entire surface on the long-side of the permanent magnet as described above, the magnetic flux easily extends in the short-side direction through the mold resin from the long-side of the permanent magnet, generating magnetic salient poles and allowing the magnetic flux to interlink with the stator, so that the torque of the electric motor can be improved.

[0019] Here, a method for manufacturing the rotor for an electric motor of the present invention will be described. As shown in FIG. 2, the rotor for an electric motor can be manufactured by inserting a permanent magnet into the through-hole of the rotor core, inserting pins of a mold into the portion forming the flux barrier to block the gaps at both circumferential ends of the permanent magnet, and press-fitting mold resin into the two gaps on the long-side of the permanent magnet from the axial ends.

[0020] By replacing the pins in the above-mentioned mold with a resin that does not contain soft magnetic powder, which has been pre-formed into the shape of a flux barrier, or by filling the through-hole flux barrier portion with the above-mentioned resin that does not contain soft magnetic powder and then press-fitting mold resin, a labyrinth structure can be created in which the flux barrier portion is filled with the resin that does not contain soft magnetic powder, thereby firmly bonding the permanent magnet to the rotor core.

[0021] The molding resin used can be a thermoplastic resin or a thermosetting resin that melts into a liquid state up to a predetermined temperature and hardens through a chemical reaction above that temperature. Examples of thermosetting resins include epoxy resins.

[0022] Examples of curing agents for the epoxy resin mentioned above include polyaddition curing agents having two or more active hydrogen atoms, catalytic curing agents containing cations or anions, two-component curing agents that are mixed with the epoxy resin immediately before curing, and capsule-type curing agents.

[0023] In particular, the above-mentioned capsule-type curing agent is a curing agent in which the curing agent component is encapsulated in microcapsules. When the capsule is broken by pressure or heat, the curing agent component seeps out and hardens the epoxy resin, allowing for adjustment of the curing start timing, and is therefore preferable to use.

[0024] The above-mentioned thermosetting resins generally have low viscosity and high fluidity before undergoing the above-mentioned chemical reaction, which helps to suppress the occurrence of filling defects.

[0025] In the electric motor rotor of the present invention, it is preferable that the thickness of the molded resin is thinner on the inner diameter side than on the outer diameter side. By positioning the permanent magnets within the through-holes towards the outer diameter side, the permanent magnets are brought closer to the stator, achieving an effect similar to reducing the air gap, and thus improving the torque of the electric motor.

[0026] Such a rotor for an electric motor can be manufactured by providing protrusions that project outward in the radial direction within the through-holes of an electromagnetic steel sheet, and then press-fitting the above-mentioned molded resin while pressing the permanent magnets in the radial direction.

[0027] The gates for press-fitting the above-mentioned mold resin are provided in the gaps at both ends of the permanent magnet in the short direction (both of the two long sides), and two or more gates are provided at separate locations.

[0028] Specifically, as shown in Figure 3, when the mold resin is divided into three sections, the gates are provided not in the central section of the three sections, but at both ends in the longitudinal direction. By positioning the gates in this way, the mold resin flows evenly in the longitudinal direction, preventing the occurrence of filling defects. The gate marks mentioned above are formed on the axial end face.

[0029] Furthermore, as shown in Figure 4, the above-mentioned molded resin preferably has portions at both ends in the longitudinal direction that are thicker than the central portion; in other words, it is preferable that the gap between the permanent magnet and the rotor core is wider at both ends in the longitudinal direction.

[0030] The longitudinal ends of a permanent magnet have relatively less influence on the flux line compared to the central part, resulting in less impact on performance. By widening the gap in these areas, it becomes easier to fill the mold resin axially, preventing the occurrence of filling defects.

[0031] The gaps formed at both ends of the permanent magnet in the longitudinal direction can be created by cutting either the permanent magnet or the electromagnetic steel sheet, but since the electromagnetic steel sheet can be die-cut, it is easier to create the gaps by cutting the electromagnetic steel sheet.

[0032] It is preferable that the above-mentioned mold resin does not leak to the longitudinal end face of the permanent magnet, i.e., the flux barrier portion, but leakage to the longitudinal end face of the permanent magnet may occur due to mold tolerances.

[0033] Even if the molded resin leaks to the short-side end face of the permanent magnet, as shown in Figure 5, the molded resin is interrupted at the short-side end face of the permanent magnet and does not connect from one long side to the other. This makes it difficult for a self-short circuit path of magnetic flux to form, thus suppressing the reduction of the motor's torque improvement effect.

[0034] Examples of how the mold resin leaks into the flux barrier include leakage from the long side of the permanent magnet, and leakage through the end face of the rotor core and accumulation in the short-side center of the flux barrier.

[0035] As described above, in the motor rotor of the present invention, the entire surface of both sides of the long side of the permanent magnet is bonded and fixed with a molded resin containing soft magnetic powder. Therefore, the magnetic flux does not leak to the short side, and it has salient polarity that extends in the short direction through the molded resin on the long side, and can be linked with the stator, thereby improving the magnet torque. [Explanation of Symbols]

[0036] 1 permanent magnet 2. Mold resin 21 Gate ruins 3 rotor cores 4. Flux barrier 5 gaps 6. Pins of the mold S stata

Claims

1. The rotor for electric motors of the present invention comprises a rotor core formed by laminating multiple electromagnetic steel sheets, The rotor core is provided with a permanent magnet located in a through-hole that penetrates the rotor core in the axial direction. Furthermore, the permanent magnet described above has a flattened shape in which the length in the longitudinal direction and the length in the short direction are different when viewed in the axial direction, and has flux barriers at both ends in the longitudinal direction. The entire surface of both sides of the long edge of the permanent magnet is bonded and fixed to the rotor core with molded resin. A rotor for an electric motor, characterized in that the above-mentioned molded resin contains soft magnetic powder.

2. The motor rotor according to claim 1, characterized in that the thickness of the molded resin is thinner on the inner diameter side than on the outer diameter side.

3. The above molded resin has a mold gate mark on its axial end face. The motor rotor according to claim 1, characterized in that the gate marks described above are formed on both the outer diameter side and the inner diameter side of at least both ends in the circumferential direction when the molded resin is divided into three parts in the circumferential direction.

4. The above-mentioned molded resin is characterized in that both the outer diameter side and the inner diameter side have portions at both ends in the circumferential direction that are thicker than the central portion, as described in claim 3.

5. The rotor for an electric motor according to claim 3, characterized in that the molded resin that has leaked onto the longitudinal end face of the permanent magnet is interrupted between one long side and the other long side of the permanent magnet.

6. The rotor for an electric motor according to claim 5, characterized in that the molded resin that leaked in the short direction of the permanent magnet is present in the center of the permanent magnet in the short direction.

7. The motor rotor according to claim 1, characterized in that the flux barrier is filled with a resin that does not contain soft magnetic powder.

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