JP2016042771A - Rotor and electric motor including the rotor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rotor structure which provides high motor characteristics and long-term reliability by fixing permanent magnets in a magnet embed-hole on a rotor iron core in a high-reliable manner.SOLUTION: The rotor iron core is formed of laminated steel plates and permanent magnets are disposed in the magnet embed-holes formed in the rotor iron core. In the magnet embedding holes, the permanent magnets are fixed to the wall surface at the outer side in a radial direction of the rotor iron core via an adhesive 5. The rotor iron core has an air space 8.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an electric motor and a rotor having a configuration in which a permanent magnet is embedded in a magnet embedding hole of a rotor.

  In motors in the home appliance field, industrial equipment field, electrical field, etc., a magnet-embedded motor (hereinafter referred to as an IPM motor) is used because of its high operational efficiency and robustness. In this IPM motor, the rotor has a permanent magnet embedded in the rotor core, and a permanent magnet is generally fixed by injecting resin into the magnet embedding hole or by a caulking method.

  An example of a typical rotor structure of an IPM motor for industrial equipment will be described with reference to FIGS. FIG. 1 shows a structure in which a magnet embedding hole 3 is formed in a rotor core 2 on which steel plates 1 are laminated, and a permanent magnet 4 is inserted and embedded in the magnet embedding hole 3. 2 is a cross-sectional view of a plane orthogonal to the axial direction of the rotor of FIG. The shape of the permanent magnet and the embedded hole of the permanent magnet has various shapes such as a flat plate shape, a kamaboko shape, and a semicircular cross-sectional shape.

  When permanent magnets are inserted and fixed in the magnet embedding holes formed in the rotor core of the IPM motor, variations in the fixing positions of the permanent magnets occur in the respective magnet embedding holes. With this displacement of the permanent magnet fixing position, it is known that rotor imbalance and torque ripple increase and motor characteristics deteriorate. In order to solve this problem, the following studies have been made conventionally.

  For example, in Patent Document 1 and the like, a groove is provided in an inner corner of a magnet embedding hole of a rotor core, and an elastic body such as a spring is press-fitted and attached to the groove to fix the permanent magnet. A motor having a rotor that is biased radially outward of a magnet embedding hole and fixed with a permanent magnet is described.

  For example, in Patent Document 2, a permanent magnet is inserted into a magnet embedding hole by inserting a string-like rubber elastic body in a state of extending in the axial direction of the rotor in a gap between the magnet embedding hole of the rotor core and the permanent magnet. The structure of an embedded permanent magnet rotor that is held in a pressed state on the radially outer peripheral side wall surface is described.

  For example, in Patent Document 3 and the like, a hole for resin injection that communicates with the magnet embedding hole is provided inside the magnet embedding hole of the rotor core, and the resin is injected by using a mold from the hole. The structure of a permanent magnet embedded rotor in which a magnet is pressed against the radially outer peripheral side wall surface of the magnet embedded hole is described.

  For example, Patent Document 4 describes a rotor structure in which a permanent magnet is bonded and fixed to a magnet embedding hole by interposing an adhesive sheet between the permanent magnet and the magnet embedding hole of the rotor core.

JP 2000-341920 A Japanese Patent Application Laid-Open No. 2012-244677 JP 2002-34187 A JP-A-9-163649

  However, the conventional method of press-fitting an elastic body such as a spring or rubber between the inner wall surface in the radial direction of the magnet embedding hole and the permanent magnet has long-term reliability in terms of impact resistance and environmental resistance. Ensuring sex is difficult. Moreover, in order to effectively use the magnetic flux of the permanent magnet, the rotor with a thin bridge portion of the rotor core is deformed when the elastic body is press-fitted in the above-described technology, and the motor characteristics are deteriorated. Is also considered.

  Further, in the prior art, a method for injecting resin using a molding die from a hole provided for injecting a resin in a radial inner side of a rotor core and communicating with a magnet embedding hole is a method of resin molding. It is also considered that the molding resin flows into the gap between the steel plates on which the rotor cores are laminated due to the molding pressure of the rotor core, causing the rotor cores to be deformed, resulting in a decrease in motor characteristics. Also, when the hole of the rotor core is completely filled with resin, the thermal resistance with the peripheral part of the permanent magnet tends to be high, and when the motor drive is overloaded, the permanent magnet It is also considered that heat generation becomes excessive and demagnetization occurs.

  Furthermore, in the prior art, when the permanent magnet is bonded and fixed in the magnet embedding hole of the rotor core with an adhesive sheet, the permanent magnet moves closer to the inner side in the radial direction of the rotor due to the thickness of the adhesive sheet. It is also considered that the gap between the magnet and the stator iron core becomes large, and the magnetic flux of the rotor cannot be utilized effectively, leading to a reduction in motor performance. Moreover, the manufacturing process of the rotor becomes complicated, and the mass productivity tends to be poor.

  The present invention solves the above problems, and by fixing a permanent magnet to a magnet embedding hole of a rotor core in a highly reliable manner, a rotor having high motor characteristics and long-term reliability is achieved. The purpose is to provide a structure.

  The present invention relates to a permanent magnet and a magnet embedding hole in an embedded magnet type rotor having a plurality of magnet embedding holes that are embedded by embedding permanent magnets in an iron core of an electric motor rotor formed by laminating steel plates. The rotor has a structure in contact with the outer wall surface in the radial direction of the rotor, and has a space layer between the permanent magnet and the rotor inner wall surface of the magnet embedding hole.

  According to the present invention, the structure of the rotor has a structure in which the permanent magnet is in contact with the wall surface outside the rotor of the magnet embedding hole, and the induced voltage is reduced by reducing the rotor imbalance and torque ripple. And a rotor that realizes high motor characteristics. In addition, since a pressing member for fixing the permanent magnet is not used, stress applied to the permanent magnet can be reduced, and the permanent magnet can be prevented from cracking or coming off, thereby providing a highly reliable rotor. Is possible.

  As described above, the rotor structure of the present invention is a rotor that can achieve high motor characteristics and reliability, and is less restricted by the use environment as compared with conventional rotors. Useful for high output.

A perspective view showing a conventional general permanent magnet embedded rotor Sectional view of a conventional general permanent magnet embedded rotor Sectional drawing of the permanent magnet embedded type rotor in Example 1 of this invention The figure which shows the outline | summary of the rotor manufacturing process in Example 1 of this invention.

  The present invention will be described below with reference to the drawings and tables. In addition, this invention is not limited by the following this Example or Example.

  FIG. 3 is a cross-sectional view of a permanent magnet embedded rotor using the present invention. The rotor core is composed of laminated steel plates, and a permanent magnet is arranged in a magnet embedding hole provided in the rotor core. In FIG. 3, the sectional shape of the permanent magnet and the magnet embedding hole is a flat plate, but each shape is not limited thereto. In the magnet embedding hole, the permanent magnet is fixed via a wall surface and an adhesive 5 arranged on the outer side in the radial direction of the rotor core.

  As the adhesive used in the present embodiment, it is preferable to use an epoxy adhesive excellent in adhesive strength and chemical resistance.

  Table 1 shows the types and properties of adhesives. When an anaerobic adhesive is used, the rotor core is formed by laminating steel plates, and therefore exists in the air layer 8 in the gap between each steel plate and the steel plate or in the rotor core axial end surface portion of the magnet embedding hole. The adhesive causes poor curing. Similarly, when a moisture-curing adhesive is used, poor curing of the adhesive occurs at a location that does not come into contact with air, such as a gap between a steel plate and a permanent magnet. In addition, when an ultraviolet curable adhesive is used, there is a portion that is not exposed to the ultraviolet light inside the magnet embedding hole even when the ultraviolet light is irradiated, so that the adhesive is hardened.

以上のように硬化不良が発生した場合、モータを起動させ回転子を回転させた際に未硬化状態の接着剤が遠心力により、回転子から飛散し、モータをロックする等の不具合を起こす可能性があり、モータの信頼性を低下させる原因となる。また、２液性接着剤は作業性が悪く生産性を悪化させるため本実施例には適していない。

When curing failure occurs as described above, when the motor is started and the rotor is rotated, the uncured adhesive may scatter from the rotor due to centrifugal force and cause problems such as locking the motor. This causes a reduction in the reliability of the motor. Also, the two-component adhesive is not suitable for this embodiment because it has poor workability and deteriorates productivity.

  In addition, when a rare earth magnet such as a neodymium magnet or a samarium iron nitrogen magnet is used as the permanent magnet, it is easy to rust in a humid atmosphere, and therefore surface treatment for the purpose of rust prevention is essential. Table 2 shows the surface treatment method of the rare earth permanent magnet, the strength measurement result of the epoxy adhesive, and the corrosion resistance of the surface treatment. From the results of these adhesive strengths, it is desirable to use nickel as the surface treatment method of the rare earth magnet when considering the reliability of the rotor.

次に、上記のように構成される本実施例における回転子の製造方法について説明する。
本実施例では、永久磁石を磁石埋設孔内に挿入する前に、予め未着磁状態の永久磁石の回転子鉄心の半径方向外側に配する壁面に接着剤を適量塗布し、その後、磁石埋設孔内に挿入する。

Next, a method for manufacturing a rotor in the present embodiment configured as described above will be described.
In this embodiment, before inserting the permanent magnet into the magnet embedding hole, an appropriate amount of adhesive is applied to the wall surface arranged on the radially outer side of the rotor core of the unmagnetized permanent magnet in advance, and then the magnet embedding is performed. Insert into the hole.

  FIG. 4 is a cross-sectional view when the rotor is manufactured in the present embodiment of the present invention. A state is shown in which a rotor core is inserted into a jig 6 in which permanent magnets 7 having the same number of stations as the rotor are embedded, and the permanent magnets in the magnet embedding holes are arranged radially outward of the rotor core. The permanent magnets inserted into the magnet embedding holes of the rotor core are magnetically attracted by the permanent magnets 7 embedded in the jig 6 and arranged outside the magnet embedding holes in the radial direction. By applying heat to the rotor core while maintaining this state, the rotor core and the permanent magnet are fixed by the thermosetting adhesive applied to the permanent magnet, and the permanent magnet is fixed in the magnet embedding hole.

  By using the above method, it becomes possible to fix the permanent magnet in a state where the permanent magnet is disposed radially outside the rotor core in the magnet embedding hole, and it is possible to design the magnetic flux of the permanent magnet effectively. A motor with high induced voltage can be provided. Furthermore, by using the jig 6 as described above, it is possible to define the circumferential position of the permanent magnet in the magnet embedding hole. As a result, the positions of the permanent magnet in the radial direction and the circumferential direction in the magnet embedding hole are uniformly determined, thereby suppressing the unbalance of the rotor and the increase of the torque ripple, thereby improving the motor characteristics and reducing the variation. .

  Moreover, in the process of the present embodiment, a thermosetting adhesive is applied to the wall surface arranged radially outward of the rotor core of the permanent magnet, and the viscosity of the adhesive is reduced by applying heat, and the rotor core After the adhesive flows radially outward, it hardens. Thereby, the effect which improves the intensity | strength of the bridge | bridging part of a rotor core, and the throwing-in effect of an adhesive agent can also be anticipated, and a reliable rotor can be provided.

  In recent years, due to demands for miniaturization and high output of motors, the rotor core bridge portion has been made thinner in order to effectively use the magnetic flux of the permanent magnet, and there is a concern that the strength of the rotor core may be reduced. The present invention can improve the strength of the bridge portion of the rotor core, and is a particularly useful invention for miniaturization and high output of the motor. Furthermore, by fixing the permanent magnet to the wall surface on the radially outer side of the magnet embedding hole, there is no stress in the direction to peel off the adhesive surface even when the rotor rotates. Can be provided.

  As in the present embodiment, by fixing the permanent magnet in a state where the permanent magnet is disposed radially outside the rotor core in the magnet embedding hole, a space layer can be provided on the radially inner side of the rotor of the magnet embedding hole. . This makes it possible to relieve stress on the permanent magnet that occurs when the shaft is press-fitted and fixed in the shaft insertion hole of the rotor.

  If the design is such that, as in the prior art, an additional member is provided on the radially inner side of the rotor in the magnet embedding hole to press the permanent magnet, the stress on the rotor core that occurs when the shaft is pressed into the permanent magnet May cause problems such as cracking or dropping off of the permanent magnet. When the rotor is small, the above problem is likely to occur. Therefore, it can be seen that the present invention is a particularly useful technique for a small rotor.

Further, in this embodiment, since the space layer is provided between the permanent magnet and the magnet embedding hole on the inner side in the radial direction and the circumferential direction of the rotor, the space layer heated by the heat generated by the permanent magnet when the rotor rotates. The air is replaced with the surrounding air, and the heat of the permanent magnet can be effectively radiated. For this reason, it is possible to prevent the permanent magnet from generating heat and demagnetizing during motor operation.
By the above method, the permanent magnet can be fixed uniformly, and a highly reliable rotor can be provided.

  The field of use of the present invention is used for the structure of a rotor in which a permanent magnet is fixed to a rotor core, and is particularly useful for improving the reliability of a device having a rotor such as a motor that is desired to be reduced in size and output. It is.

DESCRIPTION OF SYMBOLS 1 Steel plate 2 Rotor core 3 Magnet embedding hole 4 Permanent magnet 7 Permanent magnet 8 Air layer

Claims (7)

An embedded magnet type rotor having a plurality of magnet embedding holes, in which permanent magnets are inserted and embedded in an iron core of an electric motor rotor formed by laminating steel plates, the rotor radius of the permanent magnet and the magnet embedding hole A rotor having a structure in contact with a wall surface on the outer side in the direction and having a space layer between the permanent magnet and a rotor inner wall surface of the magnet embedding hole. The rotor according to claim 1, wherein a space layer is provided between the permanent magnet and at least one wall surface in the circumferential direction of the rotor of the magnet embedding hole. The rotor according to claim 1, wherein a resin layer is provided between the permanent magnet and a wall surface on the outer peripheral side of the rotor radial direction of the magnet embedding hole. 2. The rotor according to claim 1, wherein the thickness dimension of the resin layer between the permanent magnet and the wall surface on the outer peripheral side in the rotor radial direction of the magnet embedding hole has a value substantially equal to each other in each of the magnet embedding holes. Child. The rotor according to claim 1, wherein a material of the resin layer is a thermosetting resin adhesive. The rotor according to claim 1, further comprising a surface layer body covering a surface of the permanent magnet, wherein the surface layer body includes nickel. An electric motor comprising the rotor according to claim 1.

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