JPS605737Y2 - Rotor of step motor for wristwatch - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a rotor for a step motor for a wristwatch.

To date, various types of step motors for wristwatches have been announced, but these step motors are most strongly required to be highly efficient and ultra-compact.

The most common solution at present is a step motor, which consists of a rotor with permanent magnets, two stators arranged to sandwich this rotor, and a coil with a magnetic core that is mechanically coupled to the stator. There is.

The rotor of this type of step motor mainly uses a strong magnetic material of the sintered alloy type, such as samarium-cobalt material.

Regarding the structure of this rotor in more detail, FIG. 1 shows a side cross section of a conventional rotor for a step motor, and in the drawing, 1 is a rotation transmission gear, and 1b is formed integrally with the rotation transmission gear. 2 is a cylindrical permanent magnet, 3 is a bushing with a collar, and 4 is an adhesive for integrally bonding the bushing and the permanent magnet.

In a conventional rotor having such a structure, the cylindrical permanent magnet 2 is loosely fitted into a bushing 3 with a flange, and an adhesive 4 is applied to both ends of the permanent magnet 2, thereby attaching the bushing 3 with a flange. The bushing and the permanent magnet were made integral, and the bushing was then driven into a shaft integrally provided with a rotation transmission gear, thus forming a rotor.

In this way, conventionally, the bush with a collar and the permanent magnet are fixed with adhesive, so other permanent magnet fixing structures,
For example, unlike tight spring fitting, even if a sintered alloy type magnet material is used, there will be no cracking or damage, and it can be securely fixed.

However, there are problems such as not only the gluing work is extremely inefficient but also difficult to assemble automatically, and the bush that is locked to the shaft is connected to the rotation transmission gear that is provided integrally with the shaft. Because the permanent magnets are supported by forming a gap at least equal to the thickness of the flange, there is a major problem in making the completed rotor smaller and thinner.

In view of the above-mentioned problems, this idea was developed by creating a rotor that has sufficient strength, enables automation of the assembly process, and reduces costs by improving the structure, as well as a rotation transmission gear installed on the shaft. This provides accurate positioning and reliable fixing of permanent magnets and a thin rotor.

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

In FIGS. 2 and 3, reference numeral 1 denotes a rotation transmission gear having teeth 1a, which is either formed directly on the shaft 1b or provided separately and integrally formed by being driven into the shaft 1b.

2 is a cylindrical permanent magnet made of a sintered alloy type material such as samarium-cobalt material or barium-ferrite material and has a plurality of magnetic poles in the horizontal direction, and has a diameter smaller than the outer diameter of the rotation transmission gear 1. A hole 2a is formed with a diameter.

A bushing 3 is made of soft metal such as brass and has a collar 3a at one end.
A is formed larger than the diameter of the hole 2a of the permanent magnet.

The outer diameter of the bushing body is smaller than the diameter iD of the hole 2a, so that it can be inserted into the hole of the permanent magnet with some margin.

Further, this bushing is generally formed in a cylindrical shape, and the shaft 1b is inserted with friction into a fitting hole 3b provided at the center.

With the above configuration, the permanent magnet 2 is inserted from below the shaft 1b, and one surface of this permanent magnet is brought into contact with one surface of the rotation transmission gear to perform axial positioning.
Insert the bushing 3 from below with the collar 3a facing down,
The outer diameter of this bushing is inserted into the hole 2a of the permanent magnet to position the permanent magnet 2 in the radial direction. The rotor is formed by pushing the shaft into a fitting hole of the bushing and friction-fitting it so that the permanent magnet is clamped and fixed between the outer shape of the bushing, the collar portion, and one surface of the rotation transmission gear. be.

As described above, this invention is a rotor configured to clamp and fix permanent magnets by the combination of one surface of the rotation transmission gear, the outer diameter of the bushing, the collar portion, and the shaft that frictionally locks the bushing. Therefore, even if a sintered alloy type permanent magnet is used, there is no risk of cracking, breakage, or other damage to the permanent magnet.In fact, it is possible to eliminate the gap between the permanent magnet and the rotation transmission gear, thereby providing a thin rotor. Since the permanent magnet is positioned by the rotation transmission gear, the position between the rotation transmission gear and the permanent magnet can be accurately determined.Furthermore, since no means such as adhesive is used, automatic assembly is easy and the cost is low. There are various effects such as being able to provide a stable rotor.

[Brief explanation of drawings]

FIG. 1 is a side sectional view showing the conventional structure of a rotor, FIG. 2 is a side sectional view showing an embodiment of the present invention along the lines 1 and 3, and FIG. 1...Rotation transmission gear, 1b...Shaft, 2
...Permanent magnet, 2a...Hole, 3...
...butshu, 3a...tsuba, 3b...
...Mating hole.

Claims (1)

[Scope of utility model registration request] A shaft integrally formed with a rotation transmission gear, a sintered metal type cylindrical permanent magnet having a hole with a diameter smaller than the outer diameter of the rotation transmission gear, and a hole inserted into the hole of the permanent magnet. Insert the shaft from one side into the hole of the permanent magnet and the bushing from the other side into the hole of the permanent magnet. A rotor for a step motor for a wristwatch, characterized in that a shaft is friction-fitted into a fitting hole of a bushing, and a permanent magnet is clamped and fixed on the shaft between one surface of the rotation transmission gear and the collar of the bushing. .