Electrical generator or motor structure – Dynamoelectric – Rotary
Patent
1988-10-11
1990-06-12
Skudy, R.
Electrical generator or motor structure
Dynamoelectric
Rotary
310 45, 310 71, 310234, H02K 1304
Patent
active
049335871
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a dc motor and a method for manufacturing a d/c, motor and, more particularly, to a dc motor for an engine starter including an improved commutator.
BACKGROUND ART
A conventional d.c. motor for use in an engine starter is constructed as illustrated in FIG. 1, from which it is seen that the conventional d.c. motor comprises a rotary shaft 3 on which an armature core 2 is firmly secured by means of splines 1 formed on the circumferential surface of the rotary shaft 3. A commutator 4 is mounted on one end portion of the rotary shaft 3.
The commutator 4 comprises a plurality of commutator segments 5 made of copper mounted at equal circumferential intervals on a resin portion 6 made of an electrically insulating material which is secured on the rotary shaft 3 through a bushing 8. The commutator 4 comprises a cylindrical sliding contact portion 4a on which brushes (not shown) of the motor are brought into a sliding contact relationship and a large-diameter connecting portion 4b provided at a first end of the sliding contact portion 4a. Each of the commutator segments 5 extends in a substantially axial direction over both the sliding contact portion 4a and the connection portion 4b. Radially outer ends of the connection portions 4b of the segments 5 are electrically connected to an end of an armature coil 7 wound on the armature core 2.
The armature coils of many of such d.c. motors are made of an aluminum conductor due to its lightweight, and the mechanical and electrical connection between thee aluminum coil conductor and the copper connection portion 4b of the commutator segment 5 has been achieved by the ultrasonic welding of these two different materials.
However, it is difficult to obtain sufficient mechanical strength between the aluminum conductor and the copper segment through ultrasonic welding. Also, the weld is inferior in terms of corrosion resistance.
While it has been proposed to interpose a layer such as of nickel or tin between the aluminum. conductor and the copper segment, the mechanical strength obtained has not been satisfactory.
DISCLOSURE OF INVENTION
Accordingly, the present invention has been made in order to solve the above discussed problems of the conventional starter d.c. motor, and has as its object the provision of a d.c. motor in which an armature coil made of aluminum wound on an armature core is mechanically joined firmly to a commutator segment made of copper.
Another object of the present invention is to provide a method for manufacturing a d.c. motor in which an armature coil made of an aluminum conductor wound on an armature core can be mechanically joined firmly to a commutator segment made of copper.
The armature of an engine starter d.c. motor of the present invention comprises a rotary shaft, an aluminum armature coil and a commutator disposed on the rotary shaft, with a plurality of copper commutator segments each including a sliding contact surface and an aluminum connecting surface. The aluminum armature coil is electrically and mechanically connected to the aluminum connecting surface of the commutator segments to form an electrical and mechanical connection therebetween.
The electrical and mechanical connection between the segment sliding contact surface and the armature coil may be coated with an electrically insulating resin.
The method for manufacturing a d.c. motor armature of the present invention comprises the steps of inserting a copper tube into an aluminum tube and firmly putting them together to form a composite tube; forging the composite tube to form a plurality of axially extending grooves in the inner surface of the composite tube; forming an electrically insulating segment carrier member on the grooved inner surface of the composite tube; partly removing material from the aluminum tube, the copper tube and the insulating carrier member to form an essentially cylindrical commutator assembly, on the outer surfaces of which copper sliding contact surfaces of the commutator segments and aluminum connecting s
REFERENCES:
patent: 732235 (1903-06-01), Swan
patent: 3664012 (1972-05-01), Wilke
patent: 4584498 (1986-04-01), Strobl
patent: 4656380 (1987-04-01), Strobl
patent: 4764700 (1988-08-01), Strobl
patent: 4769627 (1988-09-01), Baines
patent: 4833769 (1989-05-01), Tomite
Tanaka Toshinori
Yoshino Souichi
Mitsubishi Denki & Kabushiki Kaisha
Skudy R.
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