JPS6315824B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnet holding structure for a small permanent magnet excited starter used in a motorcycle or the like, and is applicable to rotating electric machines other than starters.

Conventionally, this type of device has a yoke 1 as shown in Figure 1.
However, since the ferrite magnet 3 is hard and brittle, it has disadvantages such as corners etc. cracking during the adhesion, assembly and transportation processes. Note that 4 in the figure is a rotor. Furthermore, as magnets have become smaller and more powerful in recent years, they have become more energetic, and as a result, their impact resistance has deteriorated (they have become more brittle), and the operating conditions for generators and motors have become more severe, making them difficult to operate in locations with large temperature changes. It has the disadvantage that it cracks when used, as if the magnet were to peel off. This cracking or peeling of the magnet deteriorates the output characteristics, and also has the drawback that it is stuck by the magnetic force on the magnet surface and gets caught between the magnet and the rotor, causing a lock.

The present applicant had previously proposed a method for eliminating the drawbacks of the conventional method in Japanese Patent Applications No. 54-60375 and No. 54-138758, but the present invention further improves these improved methods. It is something that

In general, starters for motorcycles are mounted exposed on the front of the engine, so they are exposed to high and low temperatures, as well as severe vibrations and impacts from stone chips, and are used under extremely harsh conditions.
In principle, the present invention provides a structure that can cope with these severe conditions without using adhesives as in the above-mentioned improved proposal.

An example of implementing the present invention will be described with reference to FIG. 2 and subsequent figures. In the figure, 1 is a yoke, 3 is a magnet, and 5 is an aluminum magnet cover.

The magnet cover 5 has a cylindrical shape and has a bottom and a skirt, and is made of a thin aluminum plate. Since it has a bottom and a skirt, it is rigid and has the function of firmly fixing the magnet 3 inside the yoke 1. Furthermore, since the magnetic cover 5 is made of a non-magnetic material, there is no magnetic loss.

The magnet 3 is a ferrite magnet, and as shown in FIG. 3, the outer circumferential edge 3a of the inner circumferential surface of the magnet facing the rotor is chamfered, and the magnet is fitted with a positioning projection protruding from the inner surface of the yoke 1. Part 3b
Four arcuate segmented magnets are used in this example. The cross-sectional shape of the chamfer 3a of the magnet 3 can have various shapes as shown in FIGS. 3B and C.
This has the effect of facilitating the formation of an overhang in the direction of the yoke. In this embodiment, two fitting parts 3b of the magnets 3 are provided, and positioning protrusions on the inner surface of the yoke 1 are provided correspondingly to each part, but the fitting parts 3b of adjacent magnets 3 are made to be common. There may be half as many protrusions, or the fitting portion 3b itself may be one in the center of each magnet 3, with a corresponding positioning protrusion provided thereon.

The completed shape of the present invention is as shown in Figures 2A and B. During the manufacturing process, an elastic body such as urethane rubber was attached to the tip of the upper punch of the manufacturing device, and as a result of pressing through this, a magnet was formed. The cover 5 is formed to extend toward the yoke 1, and at the same time, the fitting portion 3b of the magnet 3 reliably engages with the inner surface protrusion 1a of the yoke 1. As a result of the overhang formation, the magnet cover 5 has a joining part 5a with the inner surface of the magnet 3, a joining part 5b with the end face of the magnet 3, a joining part 5c with the yoke 1, and a joining part 5c with the bottom part of the magnet 3 and the edge. A U-shaped overhanging portion 5d extending in the yoke direction between the magnets 3 and an overhanging portion 5e extending in the yoke direction between the magnets 3 are formed, respectively, to firmly and reliably fix the magnet 3 to the yoke 1 without using adhesive. . In this case, since the height of the inner surface protrusion 1a is greater than the depth of the fitting portion 3b, the protrusion 1a comes into contact with the magnetic cover 5 as shown in FIG. 2A.

Furthermore, if necessary, it is also possible to drip adhesive from above FIG. 2A, thereby making the fixation even more complete. In this case, since the skirt portion of the magnetic cover 5 is press-fitted to form the joint portion 5c with the yoke 1, there is no risk of adhesive leakage.

The permanent magnet excited starter of the present invention has the following effects.

(1) The magnet cover fits tightly to the chamfered part of the magnet, firmly fixing the magnet to the yoke.

(2) The magnet cover is pushed out into the space between the magnets to form an overhang, and firmly fixes the magnets to the yoke.

(3) Since the magnetic cover has a bottom, the urethane rubber swells the bottom without escaping in the inner circumferential direction during press-fitting, and the cross section becomes almost U-shaped, increasing the strength of the magnet's fixation.

(4) When the bottom is inflated, the magnet is pushed in the direction of the positioning protrusion of the yoke by the force of the inflation, so it can be fixed correctly at the set position without bending or other problems.

(5) In a drop test, the magnet peeled off and chipped when the product without a magnetic cover was dropped from a height of 0.5 to 1 m, but the product of the present invention was dropped from a height of 3 m.
It was able to withstand some falls.

According to the present invention, it is possible to completely fix the ferrite magnet in the yoke without using adhesives, and to fully demonstrate the function of the starter under severe conditions. It can be manufactured by attaching an elastic body such as urethane rubber to the upper punch of the device, and its practical effects are extremely remarkable.

[Brief explanation of the drawing]

FIG. 1 is an explanatory cross-sectional view showing an example of a conventional method.
FIGS. 2A and 2B are a partially cutaway front view and a partially cutaway plan view taken along line A-A, showing an example of the implementation of the present invention, and FIGS. FIG. The symbols in the drawings indicate the following members, respectively. 1: Yoke, 1a: Inner protrusion, 2: Adhesive, 3: Magnet, 3a: Chamfered portion, 3b: Fitting portion, 4: Rotor, 5: Magnetic cover, 5a, 5b, 5c:
Joining part, 5d: U-shaped overhanging part, 5e: Overhanging part.

Claims (1)

[Claims] 1. When a magnet is disposed inside the yoke by engaging with a positioning protrusion on the inner surface of the yoke and is held by a magnet cover made of a thin plate of non-ferrous metal such as aluminum, The magnet cover is made of a cylindrical material and has a U-shaped protrusion that bulges out in the radial direction along the chamfer of the magnet, and a groove that is in close contact with the circumferential inner surface of the magnet and the inner surface of the yoke. The first and second joint parts are connected to form a third joint part that engages with the positioning protrusion of the yoke, and the magnetic cover is further provided with the magnet. A magnet holding structure for a permanent magnet-excited starter, etc., characterized in that a protruding portion in the yoke direction is formed between adjacent magnets along the left and right chamfered portions of the magnet.