ARMATURE

Abstract: In an armature (10) of DC motor, plural first slots (12A) and at least one second slot (12B) of larger width (L) than the first slots (12A) are formed in a core-­ sheet lamination assembly (11), and both wrapping end parts (4a, 4b) of an insulation paper (4) always overlapped each other in the second slot (12B).

Description: FIELD OF THE INVENTION AND RELATED ART STATEMENT 1. FIELD OF THE INVENTION The present invention relates to an armature of a DC motor. 2. DESCRIPTION OF THE RELATED ART FIG.13 is a perspective view showing a part of a conventional armature of a DC motor. In the figure, an armature comprises a core-sheet lamination assembly 3 which is composed of a lamination of plural core-sheets 2. FIG.12 is a plane view of the core-sheet 2. As shown in the figure, the core-sheet 2 has plural oblong apertures 2a which are arranged at regular intervals in a circumference thereof. Each of the oblong apertures 2a is formed long in a radial direction of the core-sheet 2, and opens to the circumference of the core-sheet 2 with a pair of projections 2c retained. In FIG.13, plural core-sheets 2 are laminated so that the oblong apertures 2a are aligned in an axial direction of the armature, thereby to form the slot 2A in the axial direction of the armature. Several coils 5 are mounted in this slot 2A whereon an insulation paper 4 is fitted. As shown in FIGs. 12 and 13, the projections 2c semienclose the slot 2A (the aperture 2a) in order to prevent the coils 5 from going out of the slot 2A by centrifugal force and shorten apparent air-gap formed between an outer circumference of the core-sheet lamination assembly 3 and an internal circumference of a stator (not shown). Next, working steps of the above-mentioned conventional armature are described. In a preliminary state before making such state shown in FIG.12, the core-sheet 2 is formed in a configuration shown in FIG.11. In the figure, a pair of the projections 2c are faced and projected outward in radial direction with inclinations toward center line of each aperture 2a, so that the aperture 2a is open outward. FIG.14 is a cross-sectional view of the armature taken on the core-sheet 2. After laminating of plural core-sheets 2, not only an outer surface of the core-sheet lamination assembly 3 but also indented surfaces of the slots 2A are wrapped up in the insulation paper 4. Next, plural coils 5 are mounted in the slots 2A, and the projections 2c are bent inward to semienclose the slots 2A, as shown in FIG.12. At that time, an extended V-shaped concave 2d serves as a relief to smoothly bend the projections 2c. Thereafter, the outer surface of the core-sheet lamination assembly 3 is slightly cut, and thereby exposed portions 4d of the insulation paper 4 are removed. Thus, the core-sheet lamination assembly 3 as shown in FIG.13 is completed. Next, construction of an end part of the conventional armature is described. FIG.16 is a cross-sectional view of the conventional armature taken on the insulation sheet 7 attached to an end sheet of the core-sheet 2. In the figure, the insulation sheet 7 has U-shaped apertures 7a which precisely correspond to the apertures 2a. Each aperture 7a has the same width as the aperture 2a of the core-sheet 2, and that width is uniform from the aperture's top to bottom. This insulation sheet 7 is of circle-shape as a whole. After lamination of the plural core-sheets 2, two insulation sheets 7 are attached to respective end sheets of the core-sheets 2 in an axial direction thereof. The aperture 7a is also wrapped up in the insulation paper 4. After that, as aforementioned, the projections 2c are bent inward to semienclose the slots 2A, and the outer surface of the core-sheet lamination assembly 3 is slightly cut, thereby to remove the exposed portions 4d of the insulation paper 4. FIG.17 is a plane view of a part of the armature. The insulation sheet 7 is provided so that a bent part 5c of the coil 5, which is led out of the slot 2A to the axial direction of the core-sheet lamination assembly 3, does not directly touch the core-sheet 2 of metal. Therefore, as shown in FIG.16, it has been enough for the insulation sheet 7 to have a smaller diameter than that of the core-sheet 2. In the above-mentioned conventional armature, there has been some problems as described hereafter. FIG.15(a) and FIG.15(b) are cross-sectional views of the armature taken on the core-sheet 2. It is a desirable state that an end part 4a of the insulation paper 4 and the other end part 4b thereof touch with each other. However, such a state may occur that both end parts 4a and 4b of the insulation paper 4 overlap each other as shown in FIG.15(a) or that the both end parts 4a and 4b do not reach with each other as shown in FIG.15(b), for instance, owing to a working error. Hereupon, each apperture 2a has a uniform configuration, and when the insulation paper 4 is fitted over the indented surface of the slot 2A, there remains the same width as a diameter of the coil 5 in the slot 2A. Therefore, as shown in FIG.15(a), when both end parts 4a and 4b overlap each other, the overlapped part obstructs some coils 5 to surely mount in the slot 2A. The highest one of the coil 5, namely the most outside one in a radial direction of the core-sheet 2, stays between the projections 2c and 2c. As a result, at the time when the both projections 2c are bent to semienclose the slot 2A, the highest one of the coil 5 are squeezed into the slot 2A by the both projections 2c, 2c. Thereby, an insulation film which is coated on a surface of the coil 5 may be broken, thereby resulting in short-circuit. Further, in FIG.15(b), since a part of the slot 2A (the aperture 2a) is exposed between the both end parts 4a and 4b, the coil 5, which is bent at both ends of the core-sheet lamination assembly 3 as shown in FIG.17, may directly touch the exposed part of the slot 2A. As a result, the insulation film of the coil 5 is broken, thereby resulting in the short-circuit. If the insulation paper 4 are always fitted on the slot 2A in such a manner that the both end parts 4a and 4b just touches with each other, the above-mentioned problems do not occur. However, it is very difficult to fit the insulation paper 4 as aforementioned manner. Next, in FIG.16, when the coil 5 mounted in the slot 2A is bent at an axial end part of the core-sheet lamination assembly 3, such a state may occur that the most outside one of the coil 5 rises higher than a predetermined position owing to the extended V-shaped concave 2d. In this state, when the projections 2c are bent to semienclose the slot 2A, the risen coil 5 is pressurized by the projections 2C under an abnormal contacting state with each other. As a result, the insulation film of the coil 5 is broken, thereby resulting in grounding to the core-sheet 2 of metal. Next, FIG.18 is a plane partial view of the core-sheet lamination assembly 3 and the coil 5 at the end part of the armature. As shown in the figure, the projections 2c have a tendency to warp outward of the core-sheet lamination assembly 3. Furthermore, each coil 5 is bent at the end part of the core-sheet lamination assembly 3. Therefore, the coil 5 may be touched with an edge or the projections 2c of the core-sheet 2, thereby resulting in grounding. Other known armatures are disclosed in GB-A-15826 and CH-A-551099. OBJECT AND SUMMARY OF THE INVENTION The object of the present invention is to offer an armature which prevents short-circuit or grounding of a coil. In order to achieve the above-mentioned object, an armature in accordance with the present invention comprises: a core-sheet lamination assembly wherein a plurality of first slots and at least one second slot of larger width than the first slots are formed in an axial direction thereof by laminating a plurality of disk-shaped core-sheets, each of the core-sheets having a plurality of first radial apertures and at least one second radial aperture of larger width than said first aperture at regular intervals in a circumference thereof; an insulation paper which is fitted on the first slots and the second slot, both wrapping end parts of the insulation paper being overlapped each other in the second slot; and a plurality of coils which are mounted in the first slots and the second slot. Other aspects of the invention are disclosed in the claims. BRIEF DESCRIPTION OF THE DRAWINGS FIG.1 is a plane view showing a core-sheet before assembly to an armature of an embodiment of the present invention. FIG.2 is a plane view showing a core-sheet after assembly to an armature of an embodiment of the present invention. FIG.3(a) is a perspective partial view showing an armature of an embodiment of the present invention. FIG.3(b) is a cross-sectional partial view showing an armature of an embodiment of the present invention before cutting an insulation paper 4. FIG.4 is a perspective partial view showing an armature of an embodiment of the present invention. FIG.5(a) is a cross-sectional partial view of FIG.4 taken on a core-sheet 12. FIG.5(b) is a cross-sectional partial view of FIG.4 taken on an insulation sheet 15. FIG.6 is a cross-sectional partial view showing an armature of an embodiment of the present invention before cutting an insulation paper 4. FIG.7 is a front view showing an armature of another embodiment of the present invention. FIG.8 is a plane partial view showing an end part of an armature of another embodiment of the present invention. FIG.9 is a plane partial view showing a core-sheet having U-shaped slots in accordance with another embodiment of the present invention. FIG.10(a) is a cross-sectional view showing punching of a core-sheet by a press machine. FIG.10(b) is a cross-sectional view showing a part of a core-sheet which is punched out in FIG.10(a). FIG.11 is the plane view showing the core-sheet before assembly to the conventional armature. FIG.12 is the plane view showing the core-sheet after assembly to the conventional armature. FIG.13 is the perspective partial view showing the conventional armature. FIG.14 is the cross-sectional view showing the conventional armature before cutting the insulation paper 4. FIGs. 15(a) and 15(b) are cross-sectional partial views showing the conventional armature taken on the core-sheet 2. FIG.16 is the cross-sectional partial view showing the conventional armature taken on the insulation sheet 7. FIG.17 is the plane partial view showing the end part of the conventional armature. FIG.18 is the plane partial view showing the core-sheet lamination assembly 3 and the coil 5 at the end part of the conventional armature. DESCRIPTION OF THE PREFERRED EMBODIMENT Hereafter, preferred embodiments of the present invention are described with reference to the accompanying drawings. FIG.3(a) is a perspective partial view of an armature, for instance, of a DC motor. In the figure, an armature 10 comprises a core-sheet lamination assembly 11 which is composed of a lamination of plural core-sheets 12. FIG.2 is a plane view of the core-sheet 2. As shown in the figure, the core-sheet 12 has twenty-one oblong apertures 12a and 12b which are arranged at regular intervals in a circumference thereof. Each of the oblong apertures 12a and 12b is formed long in a radial direction of the core-sheet 12, and opens to the circumference of the core-sheet 12 with a pair of projections 12c retained. In FIG.3(a), plural core-sheets 12 are laminated so that the oblong apertures 12a and 12b are aligned in an axial direction of the armature, thereby to form a first slot 12A and a second slot 12B in the axial direction of the armature, respectively. An insulation paper 4 is fitted on these slot 12A and 12B, and thereon four coils 5 are mounted. As shown in FIGs. 2 and 3(a), the projections 12c semienclose the first slot 12A and the second slot 12B (the apertures 12a and 12b) in order to prevent the coils 5 from going out of these slots 12A and 12B by centrifugal force and shorten apparent air-gap formed between an outer circumference of the core-sheet lamination assembly 11 and an inner circumference of a stator (not shown). Next, working steps of the above-mentioned armature are described. In a preliminary state before making such a state shown in FIG.2, the core-sheet 12 is formed in a configuration shown in FIG.1. In the figure, a pair of the projections 12c are faced and projected outward in radial direction with inclinations toward center line of each aperture 12a, so that the apertures 12a and 12b are open outward. FIG.3(b) is a cross-sectional view of the armature under assembly taken on the core-sheets 12 in an axial direction thereof. In the figure, after laminating of plural core-sheets 12, not only an outer surface of the core-sheet lamination assembly 11 but also indented surfaces of the slots 12A and 12B are wrapped up in the insulation paper 4. Next, four coils 5 are mounted in the slots 12A and 12B, and the projections 12c are bent inward to semienclose the slots 12A and 12B, as shown in FIG.2. At that time, an extended V-shaped concave 12d serves as a relief to smoothly bend the projections 12c. Thereafter, the outer surface of the core-sheet lamination assembly 11 is slightly cut, and thereby exposed portions 4d of the insulation paper 4 are removed. Thus, the core-sheet lamination assembly 11 as shown in FIG.3(a) is completed. In FIG.3(a), a width ℓ of the first slot 12A holds the following relation: ℓ ≒ 2m + d, wherein: m; thickness of the insulation paper 4, d; diameter of the coil 5. And, a width L of the second slot 12B is larger than the width ℓ, that is: L ≒ 3m + d. As shown in FIG.3(a), when both end parts 4a and 4b of the insulation paper 4 are overlapped each other, there remains the same width as a diameter of the coil 5 in the second slot 12B. Therefore, all of the coils 5 are smoothly and orderly mounted into predetermined positions thereof in the second slot 12B without any staying, and grounding short-circuit does not occur. Hereupon, as shown in FIG.3(b), the core-sheet lamination assembly 11 is wrapped up in the insulation paper 4 in such a manner that the both end parts 4a and 4b are always overlapped each other in the second slot 12B. Working errors about wrapping of the insulation paper 4 are compensated by change of overlapping lengths so as not to expose a surface of the second slot 12B. Since the second slot 12B must be positioned at a start point of the insulation paper 4 and an end point of that, a position of the second slot 12B should catch a person's attention to prevent a mistake of assembly. In this embodiment, as shown in FIG.2, the second slot 12B is disposed just above a key groove 18 formed in a circumference of a centre through-hole 17. Basically, it is sufficient to form only one second slots 12B in one core-sheet 12. But, when the core-sheet lamination assembly 11 is rotated, only one second slot 12B brings unbalance of centrifugal force owing to a wide width thereof. Thereby, such a state may occur that the armature 10 cannot rotate normally, for instance, accompanying with noise or vibration. Therefore, it is desirable to keep balance that from 2 to 4 of the second slot 16 are arranged in a circumference of the core-sheet 12 at regular intervals. Especially, in the core-sheet 2 having 21 slots, namely a multiple of three, three second slots 12B which are arranged with three equal intervals present an excellent balance to the core-sheet lamination assembly 11. Next, construction of an end part of the armature 10 is described. FIG.4 is a perspective partial view of the armature 10 from a side of an insulation sheet 15 which is attached to an end sheet of the core-sheet 12. The insulation sheet 15 is made of such an insulation material as a fiber-sheet, and has a disk-shaped configuration as a whole and U-shaped apertures 15a which precisely correspond to the slot 12A of the core-sheet 12. A diameter of the insulation sheet 15 is nearly equal to or slightly smaller than a diameter of the core-sheet 12. Each aperture 15a has the same width as the aperture 12a (FIG.3(a)) of the core-sheet 12, and that width is uniform from aperture's top to bottom. FIG.5(a) is a cross-sectional view of FIG.4 taken on the core-sheet 12, and FIG.5(b) is a cross-sectional view of FIG.4 taken on the insulation sheet 15. In the core-sheet lamination assembly 11 as shown in FIG.5(a), both end parts 4e of the insulation paper 4 touches each other as if they are folding their palms, and thereby the whole inner circumference of the slot 12A is covered by the insulation paper 4. On the other hand, in FIG.5(b), the both end parts 4e are open, and a circumference of these end parts 4e is filled with a varnish, thereby to make the end parts 4e hard and close the aperture 15a of the insulation sheet 15. FIG.6 is a cross-sectional partial view of the armature under assembly taken on the insulation sheet 15. In the figure, since the diameter of the insulation sheet 15 is nearly equal to or slightly smaller than that of the core-sheet 12, the extended V-shaped concave 12d is hid behind the insulation sheet 15. Therefore, the slot 12A is ended by the aperture 15a of the insulation sheet 15 at both ends of the assembled core. And, the aperture 15a tightly catch the coils 5 in the predetermined position, so that the coils 5, especially the most outside coil 5, does not rise upward (radially outward) even at the time when the coil 5 is bent to reform after leading out of the aperture 15a. Thereafter, the projections 12c are bent inward to semienclose the slot 12A. At that time, since the most outside coil 5 is kept in the predetermined position, it does not suffer damage by pushing of the projections 12c. Further, as aforementioned, since the aperture 15a is closed by the varnish together with the insulation paper 4, wrinkling of the insulation paper 4 is prevented at the time of cutting thereof. Next, another embodiment of the present invention is described. FIG.7 is a front view of the armature 10, and FIG.8 is a plane partial view of an armature core 10A. This armature core 10A comprises the core-sheet lamination assembly 11 at a center part thereof, a pair of second cores 20 at both ends thereof and thereon a pair of insulation sheets 22. The second core 20 has plural U-shaped open apertures 20a as shown in FIG.9, and is thicker than the core-sheet 12. The insulation sheet 22 has also plural U-shaped open apertures similar to that of the first embodiment. By providing with the second core 20, thickness of the insulation sheet 22 can be made thinner than that of the first embodiment. The armature core 10A is mounted on an armature rotation shaft 21. The coil 5 passes through the armature core 10A with coil end parts 5a and 5b exposed, and is connected to a commutator 23. In FIG.8, round edges 12e of the core-sheet 12 are arrayed to direct outward of the core-sheet lamination assembly 11 (rightward of the figure). This round edge 12e is made by punching. As shown in FIG.10(a), the projection 12c of the core-sheet 12 is punched out of a steel plate 26 by a punch 25 of press. FIG.10(b) is an enlarged view of "A" in FIG.10(a). On an end of the projection 12c, the round edge 12e, a sheared surface 12h, a break surface 12g and a burr 12f are formed. In FIG.8, since a root part 5c of the coil 5 which is led out of the core-sheet lamination assembly 11 touches the round edge 12e, grounding short-circuit between the coil 5 and the core-sheet 12 is prevented. Though the grounding short-circuit generally liable to occur at the end part of the core-sheet lamination assembly 11, a risk of the grounding short-circuit is avoidable owing to the construction that the second cores 20 having the U-shaped open apertures 20a are provided at both ends of the core-sheet lamination assembly 11. Thereby, a productivity of the armature is improved.

Claims: An armature (10 comprising: a core-sheet lamination assembly (11) wherein a plurality of first slots (12A) and at least one second slot (12B) of larger width than said first slots (12A) are formed in an axial direction thereof by laminating a plurality of disk-shaped core-sheets (12), each of said core-sheets having a plurality of first radial apertures (12a), and at least one second radial aperture (12b) of larger width than said first aperture at regular intervals in a circumference thereof; an insulation paper (4) which is fitted on said first slots (12A) and said second slot (12B) both wrapping end parts (4a, 4b) of said insulation paper (4) being overlapped each other in said second slot (12B); and a plurality of coils (5) which are mounted in said first slots (12A) and said second slot (12B). An armature (10) in accordance with claim 1, wherein from 2 to 4 second radial apertures are formed in each of said core-sheets (12) at regular intervals in a circumference thereof. An armature (10) in accordance with claim 1, wherein said second radial aperture is larger than said first radial aperture by a thickness of said insulation paper (4). An armature (10) comprising: a core-sheet lamination assembly (11) wherein a plurality of slots (12A, 12B) are formed in an axial direction thereof by laminating a plurality of disk-shaped core-sheets (12), each of said core-sheets (12) having a plurality of radial apertures (12a, 12b) which are formed at regular intervals and being open in a circumference thereof with plural pairs of projections (12c) faced for semienclosing said apertures (12a, 12b); a pair of disk-shaped insulation sheets (15) which are attached to both axial ends of said core-sheet lamination assembly (11), each of said insulation sheets (15) having a plurality of substantially U-shaped uni-width apertures (15a) corresponding to said slots (12A, 12B) by substantially the same width as said slots and substantially the same diameter as said core-sheets (12); and a plurality of coils (5) which are mounted in said slots (12A, 12B) and said uni-width apertures (15a). An armature (10) comprising: a core-sheet lamination assembly (11) wherein a plurality of slots (12A, 12B) are formed in an axial direction thereof by laminating a plurality of disk-shaped core-sheets (12), each of said core-sheets having a plurality of radial apertures (12a, 12b) which are formed at regular intervals and being open in a circumference thereof with plural pairs of projections (12c) faced for semienclosing said apertures (12a, 12b); a pair of disk-shaped cores (20) which are attached to both axial end of said core-sheet lamination assembly (11), each of said cores (20) having a plurality of substantially U-shaped open apertures (20a) corresponding to said slots; and a plurality of coils (5) which are mounted in said slots and said open apertures (20a). An armature (10) in accordance with claim 5, wherein a thickness of said disk-shaped core (20) is larger than that of said core-sheet (12). An armature (10) in accordance with claim 5, wherein a round edge (12e) of said core-sheet (12) is directed outward in an axial direction of said core-sheet lamination assembly (11).

Inventors: MIYAZAKI, SHIGEKAZU C/O HIMEJI SEISAKUSHO, MORISHITA, AKIRA C/O HIMEJI SEISAKUSHO, TANAKA, TOSHINORI C/O HIMEJI SEISAKUSHO
Applicants: MITSUBISHI DENKI KABUSHIKI KAISHA
Application year: 1988
Main classification: H02K3
IPC codes: H02K3, H02K1