JPS6325898Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a resin-molded permanent magnet rotor in which a shaft portion is formed by molding resin on the inner diameter portion of a hollow cylindrical permanent magnet. The present invention relates to a resin-molded hollow rotor that minimizes molding shrinkage of the resin by forming a section, has high dimensional accuracy, and has good motion characteristics.

It is conventionally known to form a rotor by molding resin onto the inner diameter of a hollow cylindrical permanent magnet and integrating it with a rotor shaft located at the center. However,
When a prototype is actually manufactured, it is found that it is quite difficult to accurately and completely integrate the cylindrical permanent magnet and the resin using such a resin mold. After it molds the resin,
When cooled to room temperature, the molding shrinkage of the resin is extremely large, causing sink marks (dimple-like depressions that appear on the surface of the molded product) and pores, which causes the relative position of the permanent magnet and the rotor shaft at its center to change. This means that it is difficult to maintain good dimensional accuracy as the relationship may deviate.

The main cause of resin molding shrinkage is shrinkage due to cooling, which is determined by the coefficient of thermal expansion, but various other factors also affect it. In order to reduce molding shrinkage in thermoplastic resin injection molding, it is desirable to increase the resin filling pressure, but in this case, intense internal pressure acts on the cylindrical permanent magnet, causing the permanent magnet to become ferrite. Since it is a type of ceramic, the interior is not completely uniform, and the presence of slight cracks and bubbles is inevitable, which often results in breakage due to molding pressure.

Furthermore, in conventional resin molded rotors, the space between the permanent magnets and the rotor shaft is completely filled with resin, which not only requires a large amount of resin, but also increases inertia, which may adversely affect the motion characteristics. There were also some drawbacks.

The purpose of the present invention is to solve the above-mentioned drawbacks of the conventional technology, to have high dimensional accuracy, to avoid applying excessive force to the cylindrical permanent magnet during manufacturing, so there is no risk of breakage, and to save on materials. An object of the present invention is to provide a resin-molded permanent magnet rotor that can improve motion characteristics.

In order to achieve the above object, the present invention devises the structure of the resin molded portion located between the cylindrical permanent magnet and the rotor shaft at the center thereof. That is, the resin molded part has a structure in which the inner cylindrical part that is bonded to the rotor shaft and the outer cylindrical part that is bonded to the permanent magnet are connected and integrated by a plurality of ribs that are symmetrically located in the radial direction. None, it has a structure in which a through hollow part is formed in the resin mold part.

Hereinafter, the present invention will be explained in detail based on the drawings.
FIG. 1 is a perspective view showing an embodiment of a rotor according to the present invention, and FIG. 2 is a sectional view thereof. The cylindrical permanent magnet 1 is a sintered ferrite product, and the rotor shaft 2 is located on the central axis thereof. The resin molded portion 3 interposed therebetween connects and integrates the two. The resin molded part 3 has an inner cylindrical part 3a that is bonded to the outer circumferential surface of the rotor shaft 2, and an outer cylindrical part 3b that is bonded to the inner circumferential surface of the permanent magnet 1, and is arranged at a symmetrical position with respect to the central axis between them. It has a structure in which three ribs 3c extending in the radial direction are connected and integrated. Therefore, a hollow part 4 having a structure penetrating in the axial direction is formed in the resin mold part.

In this case, the thickness of the resin is set to be as thin and uniform as possible without impairing mechanical strength. As a result, the cooling rate of the molded resin can be made uniform, and products with stable quality and less molding shrinkage, distortion, and sink marks can be produced.

The number and shape of the ribs are determined in relation to the strength, and any number of ribs may be used as long as they are arranged symmetrically about the central axis.

In this embodiment, the outer cylindrical portion 3b has a flange structure and is configured to completely cover both end surfaces of the permanent magnet 1. By covering the end face of the permanent magnet 1 with a resin flange in this way, the permanent magnet 1
The holding force is much greater than that of conventional products, preventing the occurrence of cracks and cracks, as well as the shape-retaining force that prevents the magnet from disintegrating even if cracks or cracks occur, making it a permanent magnet when molded with resin. It is possible to prevent damage to the motor and the propagation of cracks after it has been incorporated into the motor, and it is possible to increase reliability without causing the rotor to become unable to rotate during use.

FIG. 3 is a sectional view showing another embodiment of the present invention.
As shown in the figure, the structure of the resin molded portion 3 can also be a cantilever type support structure. In this way, the amount of resin can be reduced and the weight can be reduced, which is advantageous in that the motion characteristics of the rotor can be improved.

Since the present invention is a resin-molded hollow rotor constructed as described above, the molded resin is cooled uniformly, the molding shrinkage of the resin is small, and distortion and sinkage are less likely to occur, resulting in good dimensional accuracy and quality. It is possible to obtain a stable product, and since there is no need to increase the resin filling pressure, excessive force is not applied to the permanent magnet, making it less likely to be damaged.Furthermore, since the amount of resin is small, material costs can be saved. death,
It has great practical effects, such as being able to reduce weight and improve motion characteristics because the moment of inertia is reduced.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing one embodiment of the present invention;
The figure is a sectional view thereof, and FIG. 3 is a sectional view showing another embodiment. 1...Permanent magnet, 2...Rotor shaft, 3...Resin mold part, 4...Hollow part.

Claims (1)

[Scope of utility model registration request] In a resin molded permanent magnet rotor in which a rotor shaft is located at the center of a cylindrical permanent magnet and resin is molded between the two, the resin molded part is
The inner cylindrical part that adheres to the rotor shaft and the outer cylindrical part that adheres to the permanent magnet have an integral structure that is joined by a plurality of ribs located symmetrically in the radial direction, and a hollow penetrating hole is formed in the resin molded part. A resin-molded hollow rotor characterized by having a portion formed therein.