GB2111410A

GB2111410A - Yoke assembly manufacturing method

Info

Publication number: GB2111410A
Application number: GB08235286A
Authority: GB
Inventors: Isao Hamano
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 1981-12-10
Filing date: 1982-12-10
Publication date: 1983-07-06
Also published as: FR2518327B1; GB2111410B; JPS58103863A; FR2518327A1

Abstract

A method of manufacturing a yoke assembly is disclosed in which a yoke 2 is formed by drawing a soft steel plate and permanent magnet poles 3 are bonded to the yoke. The resulting assembly is then coated with a film 6 of coating material to protect the yoke from corrosion and prevent moisture from reaching the bonding adhesive 4. Machining is then carried out to form bearing fitting and fitting surfaces B,A. <IMAGE>

Description

SPECIFICATION Yoke assembly manufacturing method Background of the Invention This invention relates to an improved method of manufacturing a yoke assembly for use in a permanent magnet type DC motor or the like.

A conventional method of manufacturing a yoke assembly of this type will be described with reference to Fig. 1. In Fig. 1, reference numeral 1 designates a yoke assembly; and 2, the cylindrical yoke of the yoke assembly 1. The yoke 2 is formed as follows: After the surface of a soft steel plate which has been subjected to deep drawing is treated by color zinc plating, a fitting part A and a bearing member fitting part B, which are necessary for the field system, are formed by machining. Further in Fig. 1, reference numeral 3 designates magnetic poles made up of ferrite permanent magnets. The magnetic poles 3 are fixedly secured to predetermined portions of the inner wall of the yoke 2 with an adhesive 4, the yoke having been plated and machined as described above.

The conventional yoke assembly of the permanent magnetic type DC motor, manufactured as described above, and especially those in which the magnetic poles 3 made up of ferrite permanent magnets are bonded to the zincplated surface of the yoke 2 with epoxy resin adhesive, suffer from the following drawback: Water permeates into the porous interior of the ferrite permanent magnet, to reach the adhesive surface, and there causes a chemical reaction, whereby the adhesive strength between the yoke 2 and the magnetic poles 3 is extremely diminished.

Summary of the Invention Accordingly, an object of this invention is to provide a yoke assembly manufacturing method in which, after a film coating is formed over the entire surface of a primary product fabricated by bonding magnetic poles to a yoke, a fitting part and a bearing member fitting which are necessary for the yoke assembly are formed by machining, whereby the above-described drawback is eliminated. The manufactured yoke assembly has an excellent anticorrosion characteristic even though the yoke is not plated.

Brief Description of the Drawings Fig. 1 is a sectional side view of a yoke assembly fabricated according to a conventional manufacturing method; Figs. 2 and 3 are sectional side views showing steps of a method of manufacturing a yoke assembly according to one embodiment of this invention; and Fig. 4 is a sectional side view showing a yoke assembly fabricated according to the manufacturing method of the invention.

Detailed Description of the Preferred Embodiments One embodiment of this invention will now be described with reference to Figs. 2, 3 and 4. A cylindrical yoke 2 having the required configuration is fabricated by subjecting a soft steel plate to deep drawing. Magnetic poles 3 made up of ferrite permanent magnets are fixedly secured to predetermined portions of the inner wall of the yoke 2 with epoxy resin adhesive 4, to provide a partially completed yoke assembly 1 a (hereinafter referred to as "the primary product").

Next, a coated film 6 (cf. Fig. 4) is formed over the entire surface, including the inner and outer walls, of the primary products 1 a of Fig. 2 by spraying a coating solution 5 thereonto or by immersing the primary product 1 a in coating solution, as shown in Fig. 3. Thereafter, a fitting part A and a bearing member fitting B, which are necessary for the field system, are formed as shown in Fig. 4, whereby a complete yoke assembly 1 is obtained.

In the yoke assembly manufactured according to the method of this invention, the film 6 prevents water from reaching the adhesive between the yoke 2 and the magnetic poles 3, and accordingly prevents the difficulty of a decayed adhesive allowing the magnetic poles 3 to come off of the yoke 2. As substantially the entire yoke assembly is coated with the film 6, the yoke assembly is thus protected from corrosion.

In the above-described embodiment, magnetic poles made up of ferrite permanent magnets are bonded to a yoke formed of a soft steel plate.

However, according to the invention, the yoke and the magnetic poles may be made of other materials. Furthermore, in the above-described embodiment, the coated film 6 is formed by use of a coating solution; however, the coated film may be formed using painting materials such as coating powders, other than liquid-phase painting material.

As is clear from the above description, the yoke assembly according to the invention is formed according to a method in which a coating film is formed over the entire surface of a primary product produced by bonding magnetic poles of a yoke, and then a fitting part and a bearing member fitting are formed by machining. Therefore, it is unnecessary to plate the yoke, and the yoke assembly according to the invention has an excellent anticorrosion characteristic and can be manufactured at a relatively low cost.

1. A yoke assembly manufacturing method, comprising; bonding magnetic poles to the yoke, forming a coated film over the surface of the yoke, including said bonded magnetic poles, and machining a fitting part and a bearing member fitting necessary for said yoke assembly.

2. A method as claimed in claim 1 , wherein said

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Yoke assembly manufacturing method Background of the Invention This invention relates to an improved method of manufacturing a yoke assembly for use in a permanent magnet type DC motor or the like. A conventional method of manufacturing a yoke assembly of this type will be described with reference to Fig. 1. In Fig. 1, reference numeral 1 designates a yoke assembly; and 2, the cylindrical yoke of the yoke assembly 1. The yoke 2 is formed as follows: After the surface of a soft steel plate which has been subjected to deep drawing is treated by color zinc plating, a fitting part A and a bearing member fitting part B, which are necessary for the field system, are formed by machining. Further in Fig. 1, reference numeral 3 designates magnetic poles made up of ferrite permanent magnets. The magnetic poles 3 are fixedly secured to predetermined portions of the inner wall of the yoke 2 with an adhesive 4, the yoke having been plated and machined as described above. The conventional yoke assembly of the permanent magnetic type DC motor, manufactured as described above, and especially those in which the magnetic poles 3 made up of ferrite permanent magnets are bonded to the zincplated surface of the yoke 2 with epoxy resin adhesive, suffer from the following drawback: Water permeates into the porous interior of the ferrite permanent magnet, to reach the adhesive surface, and there causes a chemical reaction, whereby the adhesive strength between the yoke 2 and the magnetic poles 3 is extremely diminished. Summary of the Invention Accordingly, an object of this invention is to provide a yoke assembly manufacturing method in which, after a film coating is formed over the entire surface of a primary product fabricated by bonding magnetic poles to a yoke, a fitting part and a bearing member fitting which are necessary for the yoke assembly are formed by machining, whereby the above-described drawback is eliminated. The manufactured yoke assembly has an excellent anticorrosion characteristic even though the yoke is not plated. Brief Description of the Drawings Fig. 1 is a sectional side view of a yoke assembly fabricated according to a conventional manufacturing method; Figs. 2 and 3 are sectional side views showing steps of a method of manufacturing a yoke assembly according to one embodiment of this invention; and Fig. 4 is a sectional side view showing a yoke assembly fabricated according to the manufacturing method of the invention. Detailed Description of the Preferred Embodiments One embodiment of this invention will now be described with reference to Figs. 2, 3 and 4. A cylindrical yoke 2 having the required configuration is fabricated by subjecting a soft steel plate to deep drawing. Magnetic poles 3 made up of ferrite permanent magnets are fixedly secured to predetermined portions of the inner wall of the yoke 2 with epoxy resin adhesive 4, to provide a partially completed yoke assembly 1 a (hereinafter referred to as "the primary product"). Next, a coated film 6 (cf. Fig. 4) is formed over the entire surface, including the inner and outer walls, of the primary products 1 a of Fig. 2 by spraying a coating solution 5 thereonto or by immersing the primary product 1 a in coating solution, as shown in Fig. 3. Thereafter, a fitting part A and a bearing member fitting B, which are necessary for the field system, are formed as shown in Fig. 4, whereby a complete yoke assembly 1 is obtained. In the yoke assembly manufactured according to the method of this invention, the film 6 prevents water from reaching the adhesive between the yoke 2 and the magnetic poles 3, and accordingly prevents the difficulty of a decayed adhesive allowing the magnetic poles 3 to come off of the yoke 2. As substantially the entire yoke assembly is coated with the film 6, the yoke assembly is thus protected from corrosion. In the above-described embodiment, magnetic poles made up of ferrite permanent magnets are bonded to a yoke formed of a soft steel plate. However, according to the invention, the yoke and the magnetic poles may be made of other materials. Furthermore, in the above-described embodiment, the coated film 6 is formed by use of a coating solution; however, the coated film may be formed using painting materials such as coating powders, other than liquid-phase painting material. As is clear from the above description, the yoke assembly according to the invention is formed according to a method in which a coating film is formed over the entire surface of a primary product produced by bonding magnetic poles of a yoke, and then a fitting part and a bearing member fitting are formed by machining. Therefore, it is unnecessary to plate the yoke, and the yoke assembly according to the invention has an excellent anticorrosion characteristic and can be manufactured at a relatively low cost. CLAIMS

2. A method as claimed in claim 1 , wherein said magnetic poles are adhesively bonded to said yoke, and said coated film prevents moisture from reachina the adhesive.

3. A method as claimed in claim 1 , wherein said coated film is formed over the entire surface of said yoke by spraying.

4. A method as claimed in claim 1, wherien said coated film is formed over the entire surface of said yoke by dipping.

5. A method as claimed in claim 1, wherein said yoke is formed by deep drawing a soft steel plate, and said coated film is applied directly to said yoke, said coated film forming an anti-corrosive layer over said yoke.

6. Amethod as claimed in claim 1, wherein said machining operation removes said coated film only from surfaces substantially spaced from said magnetic poles.