This application is based upon and claims benefit of priority of Japanese Patent Application No. 2003-305891 filed on Aug. 29, 2003, the content of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a method of manufacturing an armature of a rotary electric machine such as a direct current motor and to the armature manufactured by that method.
2. Description of Related Art
Recently, it has been becoming more important to develop automotive parts that are light in weight and small in size to reduce fuel consumption in an automobile vehicle and thereby to cope with the problem of global warming. One example of a light and small motor, which was invented by one of inventors of the present invention, is disclosed in JP-B2-2924605. In the armature of this motor, a conventional commutator is eliminated, and a commutator formed by part of the conductors disposed in an armature core is utilized. A pair of conductors consisting of an inner conductor and an outer conductor, each formed in a U-shape, is inserted in each slot formed in an armature core. Ends of the conductors are electrically and mechanically connected to thereby form an armature winding.
In the armature disclosed in JP-B2-2924605, however, the conductors are formed in a U-shape before they are inserted into the slots, and conductor portions disposed along the axial end surfaces of the armature core have to be skewed relative to the radial direction. The conductor has to be formed one by one using a complex transfer press, and therefore it has been difficult to further enhance the manufacturing speed. Further, it has not been easy to insert conductors, each having a U-shape and skewed ends, into the slots of the armature core. Therefore, there has been a certain limit in enhancing manufacturing speed in an automated assembling line.
The present invention has been made in view of the above-mentioned problem, and an object of the present invention is to provide an improved method of manufacturing an armature of a rotary electric machine and to provide an armature manufactured by the improved method. It is an object of the present invention, in particular, to speed up the process of manufacturing the armature that is small in size and light in weight.
The armature is composed of an armature core made by laminating plural steel plates, an armature winding disposed in slots formed in the armature core and an armature shaft connected to the armature core by forcibly inserting into a center hole of the armature core. The armature winding is composed of plural conductors electrically connected one another. In each slot of the armature core, an inner conductor is disposed at an inner portion of the slot and an outer conductor at an outer portion of the slot. Each of the inner and outer conductors is composed of an in-slot portion and a pair of side portions extending from both ends of the in-slot portion.
The armature is manufactured in the following manner. A conductor bar including plural conductors connected in a straight line is formed. Then, individual conductors are cut out from the conductor bar. The in-slot portion of the inner conductor is first inserted into each slot, and side portions are bent toward the axial end surfaces of the armature core, so that the side portions are positioned substantially in parallel to the axial end surfaces. The side portions are skewed by a predetermined angle α relative to the radial direction. The process of skewing may be performed simultaneously with the process of bending.
Then, the in-slot portion of the outer conductor is inserted into each slot and is firmly held in the slot by bending claws formed at the open edge of the slot. The side portions of the outer conductor are bent and skewed in the same manner as the inner conductor. However, the side portions of the outer conductor are skewed by another predetermined angle β in the opposite direction to the angle α. Then, ends of the side portions of both the inner and outer conductors are electrically and mechanically connected by welding to form the armature winding. Finally, an armature shaft is forcibly inserted into the center hole of the armature core.
The conductors are not bent in a U-shape before they are inserted into the slots. Therefore, the conductor bar including plural conductors connected in a straight line can be easily and speedily manufactured. It is easy to insert the conductors into the slots because they are straight. After the conductors are inserted into the slots, they are bent toward the axial end surfaces of the armature core and skewed. Therefore, the process of assembling the conductors to the armature core is simplified. If the bending process and the skewing process are performed at the same time, the manufacturing process is further speeded up.
The outer surface of the side portions circularly arranged on the axial end surface of the armature core is used as a commutator surface which brushes slidably contact. A cross-sectional area of each side portion is made so that its electrical resistance is uniform throughout its entire length. Since the outer surface of the side portions is utilized as the commutator surface without using a conventional commutator, the axial length of the armature is considerably shortened.
Other objects and features of the present invention will become more readily apparent from a better understanding of the preferred embodiment described below with reference to the following drawings.
A preferred embodiment of the present invention will be described with reference to accompanying drawings. In this embodiment, the present invention is applied to an armature of a starter motor for cranking an internal combustion engine. As shown in
The armature shaft 2 is rotatably supported by a pair of bearings 4, 5 that is fixedly held in a motor housing (not shown). At an left end (in
An inner conductor 7 and an outer conductor 8 are inserted into each slot 3b, and the inner conductor 7 is positioned at the bottom of the slot 3b and the outer conductor 8 on the inner conductor, as shown in
The width of the in-slot portion 7a shown in
The width of the side portion 7b is gradually decreased as it proceeds to the tip (tapered) as shown in
The outer conductor 8 is formed in a similar manner as the inner conductor 7. As shown in
The width of the in-slot portion 8a shown in
The width of the side portion 8b is gradually decreased (tapered) as it proceeds to the tip as shown in
Now, referring to
Advantages obtained in the embodiment described above will be summarized. It is not required to form the inner and outer conductors 7, 8 in a U-shape (which has been conventionally done) before they are inserted into the slots 3b of the armature core 3. Therefore, a straight conductor bar including plural inner or outer conductors connected in line can be easily manufactured by a rolling process, for example. In other words, the inner and the outer conductors can be continuously and economically manufactured without using an expensive transfer press. Since the inner and outer conductors 7, 8 are in a straight form (not in the U-shape as in the conventional case), the conductors 7, 8 are easily and correctly positioned in the process of inserting into the slots 3b. Accordingly, the inserting process can be speeded up.
Since both projections 7d and 8d are positioned to face each other and welded together, as shown in
Since the side portions 7b, 8b of the inner and outer conductors 7, 8 are bent toward the axial surfaces of the armature core 3 after the in-slot portions 7a, 7b are inserted into the slots 3b, the projections 7d, 8d do not hinder smooth insertion of the conductors 7, 8 into the armature core 3. Since the outer conductors 8 inserted into the slots 3b are firmly held by bending the claws 3c and then the side portions 8b are bent toward the axial surface of the armature core 3, it is not necessary to hold the outer conductors 8 with jigs or tools in the process of bending the side portions 8b. Accordingly, the bending process is simplified and speeded up.
Since the bending portions 7c, 8c of the inner and outer conductors 7, 8 are made thinner than the thickness of the in-slot portions 7a, 8a, the side portions 7b, 8b can be easily and precisely bent. Therefore, the bending process can be preformed with a smaller bending force, and positioning of the projected portions 7d, 8d can be easily done to exactly face each other.
Since the axial surface of the side portions 8b is utilized as a commutator surface, a conventional cylindrical commutator to be connected to the armature shaft 2 is eliminated. Therefore, the armature 1 can be made smaller and lighter. Since the width of the side portion 8b of the outer conductor 8 is made to be gradually widened from the inside toward the outside, as shown in
A modified form of the present invention will be described with reference to
While the present invention has been shown and described with reference to the foregoing preferred embodiment, it will be apparent to those skilled in the art that changes in form and detail may be made therein without departing from the scope of the invention as defined in the appended claims.
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