METHOD AND DEVICE FOR MANUFACTURING FLAT COMMUTATOR

Abstract

 Metal pieces forming segments 3 are placed in a cartridge 21, and the metal pieces are pressed by a punch 25, to perform a cartridge fitting process. Protrusions 22 which are formed radially and arranged between the metal pieces are formed on the cartridge 21, to restrict movement of the metal pieces in the circumferential direction. At a circumferential part of the cartridge 21, an outer circumferential wall 24 which end parts of the metal pieces contact is formed to restrict movement of the metal pieces in the radial directions. A punch 25 has double annular protrusions 27a and 27b formed on a surface facing the cartridge 21. The annular protrusions 27a and 27b are pressed against the metal pieces, to make the side surfaces of the metal pieces tightly contact the protrusions 22 of the cartridge 21.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a commutator for use in an electric rotating machine, and particularly to a method for manufacturing a disk-type flat commutator.

Background Art

[0002] In recent years, several of motors for use in electric power steering, an engine starter, a fuel pump, and the like have appeared with a flat commutator on demand for downsizing of devices. This flat commutator has a disk-like brush sliding surface extending radially from the rotation axis, unlike a general cylindrical commutator. A brush slides on and contacts the brush sliding surface in the axial direction, to switch an armature current.

[0003] The brush sliding surface consists of plural segments which are made of metal members called commutator metal and are arranged radially. Each segment is molded integrally with a body made of synthetic resins. These respective segments are placed in a circular cartridge. In this state, the whole segments are molded. The cartridge is provided with protrusions to hold side surfaces of the segment. The segments are placed between these protrusions.

[0004] The segments set in the cartridge are subjected to anchor press to fit the segments tightly with protrusions before a resin molding process. FIGS. 8 and 9 are illustrations showing processing states in a cartridge fitting process. As shown in these FIGS. 8 and 9, the cartridge fitting process is carried out by a punch 52 having anchor press protrusions 51 on the lower end surface thereof. The punch 52 is pressed into contact with the segments 54 from upside of the cartridge 53, and the anchor press protrusions 51 are pressed into vicinities of gaps 55 between the segments 54. In this manner, anchor traces 56 are formed in the upper surfaces of the segments 54.

[0005] In the cartridge fitting process, side surfaces of each gap 55 are deformed to swell into one of the gaps by one of the anchor press protrusions 51 located above the gap 55. In the gaps 55, protrusions 57 of the cartridge 53 are inserted. Both side surfaces of each gap 55 are pressed to one of these protrusions. In this manner, the protrusions 57 and end surfaces of the segments 54 tightly contact each other in the gap 55, so that synthetic resins can be prevented from leaking through the gaps 55 to the side of the brush sliding surface 58, in the molding process. In addition, since the parts of the protrusions 57 remain intact as concave parts between the segments 54, these concave parts directly become as slits between the segments 54.

[0006] However, in this cartridge fitting process, precise positional alignment between the anchor press protrusions 51 and the gaps 55 is necessary. Therefore, there is a problem that dimensional precision of the segments 54, cartridge 53, and punch 52 and positional alignment precision between the cartridge 53 and the punch 52 is so severe that the anchor press method is disadvantageous in view of variants of these components.

[0007] Hence, a method of using a hollow cylindrical flat punch 59 which does not necessitate positional alignment has been attempted, as shown in FIGS. 10 and 11. The bottom surface 61 of the flat punch 59 is flat and has no anchor press protrusion 51. Segments 54 are pressed not only near gaps 55 but also on the whole upper surfaces of concave parts 62 thereof by the flat punch 59.

[0008] However, in case of using the flat punch 59, the pressed area is large. Therefore, the load necessary to bring the cartridge 53 and the segments 54 into tight contact with each other is greater than that in the other case of using the anchor press protrusions 51 (e.g., 12t to 25t). Therefore, an equipment having a larger scale than that in the anchor press method is required, resulting in a problem of increased costs for the equipment. In addition, the load concentrates on a part due to dimensional variants of the segments 54 and the like. Consequently, there is a problem that the segments 54, cartridge 53, and flat punch 59 are easily damaged.

[0009] An object of the present invention is to provide a tool capable of making the cartridge and the segments tightly contact each other by a light load without necessitating positional alignment.

Disclosure of the Invention

[0010] According to an aspect of the present invention, a method for manufacturing a flat commutator having a holder part formed of synthetic resins in a disk-like shape, and plural segments arranged along a circumferential direction of the holder part on an end surface of the holder part in an axial direction of the holder part, comprises: a step of setting metal pieces forming the segments in a cartridge having circumferential movement restriction parts which are provided between the metal pieces, to restrict movement of the metal pieces in the circumferential direction, and a radial movement restriction part which is positioned at an end part in radial directions of the metal pieces, to restrict movement of the metal pieces in the radial directions; and a step of pressing the metal pieces with a punch having plural annular pressing parts formed on a surface facing the cartridge, to make the metal pieces tightly contact the circumferential movement restriction part of the cartridge.

[0011] In the present invention, a cartridge fitting process is carried out by use of a punch having annular protrusions. Therefore, it is possible to relax precision of positional alignment between the punch and the cartridge, compared with a conventional anchor press method. In addition, metal pieces are pressed by plural annular pressing parts formed on a punch. Therefore, the metal pieces can be deformed with a lighter load, compared with a case of pressing the metal pieces on the whole bottom surface of the punch. Further, punch-press is performed while regulating movement of the metal pieces in the circumferential direction and radial directions by the circumferential movement restriction parts and the radial movement restriction part. Therefore, deformation of the metal pieces in the circumferential direction and radial directions at the time of press can be restricted, so that the metal pieces can be let tightly contact the cartridge without pressing the metal pieces on the whole bottom surface of the punch.

[0012] In the above-described method for manufacturing a flat commutator, protrusions as the circumferential movement restriction parts may be formed radially on the cartridge. Further, as the radial movement restriction part, a wall which contacts outer circumferential parts of the metal pieces may be provided on an outer circumferential part of the cartridge. Further, as the annular pressing parts, annular protrusions may be formed on the surface of the punch facing the cartridge.

[0013] Also, in the above-described method for manufacturing a flat commutator, a first protrusion formed in an outer-diameter side of the metal pieces, and a second protrusion formed in an inner-diameter side of the metal pieces may be provided as the annular protrusions, with an interval maintained from the first protrusion, the first and second protrusions contacting gaps formed between the segments by the circumferential movement restriction parts, with an interval maintained in the radial directions between the first and second protrusions. In this case, annular punch traces may be formed in the metal pieces by the first and second protrusions, and the metal pieces and the circumferential movement restriction parts may be brought into tight contact with each other at portions of the punch traces.

[0014] According to another aspect of the present invention, a device for manufacturing a flat commutator having a holder part formed of synthetic resins in a disk-like shape, and plural segments arranged along a circumferential direction of the holder part on an end surface of the holder part in an axial direction of the holder part, comprises: a cartridge which contains metal pieces forming the segments, and has circumferential movement restriction parts which are provided between the metal pieces, to restrict movement of the metal pieces in the circumferential direction, and a radial movement restriction part which is positioned at an end part in radial directions of the metal pieces, to restrict movement of the metal pieces in the radial directions; and a punch having plural annular pressing parts formed on a surface facing the cartridge, the annular pressing parts being to be pressed against the metal pieces.

[0015] In the present invention, the plural annular pressing parts are formed on the punch which press the metal pieces. Therefore, it is possible to relax precision of positional alignment between the punch and the cartridge in a cartridge fitting process, compared with a conventional anchor press method. In addition, the metal pieces can be deformed with a lighter load, compared with a case of pressing the metal pieces on the whole bottom surface of the punch. Further, the cartridge is provided with the circumferential movement restriction parts and the radial movement restriction part. Therefore, deformation of the metal pieces are restricted in the circumferential and radial directions at the time of punch-press. Accordingly, the metal pieces can be let tightly contact the cartridge without pressing the metal pieces on the whole bottom surface of the punch.

[0016] In the above-described device for manufacturing a flat commutator, protrusions as the circumferential movement restriction parts may be formed radially on the cartridge. Further, as the radial movement restriction part, a wall which contacts outer circumferential parts of the metal pieces may be provided on an outer circumferential part of the cartridge. Further, as the annular pressing parts, annular protrusions may be formed on the surface of the punch facing the cartridge.

[0017] Also, in the above-described device for manufacturing a flat commutator, a first protrusion formed in an outer-diameter side of the metal pieces, and a second protrusion formed in an inner-diameter side of the metal pieces may be provided as the annular protrusions, with an interval maintained from the first protrusion, the first and second protrusions contacting gaps formed between the segments by the circumferential movement restriction parts, with an interval maintained in the radial directions between the first and second protrusions. In this case, annular punch traces may be formed by the first and second protrusions, and the metal pieces and the circumferential movement restriction parts may be brought into tight contact with each other at portions of the punch traces.

Brief Description of the Drawings

[0018] 

FIG. 1 is a partially cut-away perspective view showing an example of a flat commutator manufactured in a manufacturing method (or by a manufacturing device) according to the present invention;

FIG. 2 is a perspective view showing the structure of one of individual metal pieces forming segments;

FIG. 3 is an explanatory view showing the structure of a cartridge;

FIG. 4(a) is a cross-sectional view of a punch according to an embodiment of the present invention and FIG. 4(b) is a bottom view thereof;

FIGS. 5 are explanatory views showing a processing state in a cartridge fitting process, (a) is a plan view of the cartridge in a state in which segments are placed, and (b) is a cross-sectional view cut along the line A-A in FIG. 5(a) and shows a state in which the punch is put close to the cartridge kept in the state shown in FIG. 5(a) from upside;

FIG. 6 is a cross-sectional view showing a state where the punch is pressed against the segments;

FIG. 7 is an explanatory view showing a state of the segments after the cartridge fitting process;

FIG. 8 is an explanatory view showing a conventional processing state in the cartridge fitting process;

FIG. 9 is an explanatory view showing a conventional processing state in the cartridge fitting process;

FIG. 10 is an explanatory view showing another conventional processing state in the cartridge fitting process; and

FIG. 11 is an explanatory view showing another conventional processing state in the cartridge fitting process.

Best Mode for Carrying Out the Invention

[0019] Hereinafter, an embodiment of the present invention will be described in details by referring to the accompanying drawings. FIG. 1 is a partially cut-away perspective view showing an example of a flat commutator manufactured according to a manufacturing method of the present invention.

[0020] A commutator 1 is constructed in a flat structure as shown in FIG. 1, and is used in a starter motor, ink-tank-type fuel feed pump, and the like. The commutator 1 has a holder part 2 made of synthetic resins, and plural segments 3 made of metal. The segments 3 are molded integrally with the holder part 2. Surfaces of the segments 3 (upper surfaces in FIG. 1) constitute a brush sliding surface 4 which a brush (not shown) contacts from an axial direction.

[0021] In this commutator 1, the respective segments 3 are placed in a circular cartridge. Kept in this state, the whole segments are subjected to synthetic-resin molding to form the commutator 1. The commutator 1 thus molded is assembled together with a rotation shaft (not shown), armature core, a coil wire, and the like. Thereafter, a coating of synthetic resins is provided thereon to complete an armature assembly.

[0022] The holder part 2 is formed in a thick and substantially disk-like shape. A shaft hole 5 to fix a motor rotation shaft is formed in the center part of the holder part 2. On one end surface in the axial direction of the holder part 2, plural segments 3 are provided at equal intervals. The segments 3 each are formed in a substantially sector shape, and are arranged radially on the surface of the holder part 2. Slits 6 are formed between the segments 3, to insulate electrically adjacent segments 3 from each other.

[0023] FIG. 2 is a perspective view showing one of individual metal pieces forming the segments 3. As shown in FIG. 2, each segment 3 has a body part 7 where a brush sliding surface 4 is formed, and an outer circumferential part 8 formed outside the body part 7, stepped therefrom. A U-shaped coil mount groove 9 is provided in the outer circumferential part 8. To the coil mount groove 9, an armature coil (not shown) is fixed by fusing or the like.

[0024] A boss part 11 is provided in the inner circumferential side of the body part 7. A tapered part 12a is formed on the inner surface side. The boundary between the body part 7 and the outer circumferential part 8 forms a step part 13. The inner surface side of the step part 13 also forms a tapered part 12b. The tapered parts 12a and 12b widen toward the body part 7, forming an anchor part 14 which serves as a fall stopper to prevent the segment 3 from axially slipping off from the holder part 2.

[0025] The segments 3 as described above are placed in the cartridge 21 and subjected to synthetic-resin molding, and are subjected to a cartridge fitting process to make the segments 3 and the cartridge 21 tightly fit each other, before a molding process. FIG. 3 is an explanatory view showing the structure of the cartridge 21. As shown in FIG. 3, the cartridge 21 is provided with protrusions (circumferential movement restriction parts) 22 to hold the respective segments 3. The protrusions 22 each are formed in a wedge-like shape. The body parts 7 of the segments 3 are held between the protrusions 22. A step part 23 to support the step parts 13 of the segments 3 and an outer circumferential wall (radial movement restriction part) 24 which contacts the outer circumferential surface of the outer circumferential part 8 are provided at the outer circumferential part of the cartridge 21. The segments 3 are held between the protrusions 22, and are placed in the cartridge 21, held by the step part 23 and the outer circumferential wall 24.

[0026] In the present embodiment, the cartridge fitting process is carried out by use of a punch 25 as shown in FIGS. 4. FIG. 4(a) is a cross-sectional view of the punch 25 according to an embodiment of the present invention. FIG. 4(b) is a bottom view thereof. The punch 25 is formed in a hollow cylindrical shape as shown in FIG. 4. On the bottom surface 26 of the punch 25, two annular protrusions (annular pressing parts) 27a and 27b are formed. The annular protrusion 27a (first protrusion) is formed along the outer circumference (in the outer diameter side) of the punch 25. The other annular protrusion 27b (second protrusion) is formed along the inner circumference (in the inner diameter side) of the punch 25 with an interval maintained from the annular protrusion 27a. The top surfaces of the annular protrusions 27a and 27b are flat. Both of the annular protrusions 27a and 27b are formed to have an equal height. A concave part 28 is formed between the annular protrusions 27a and 27b.

[0027] FIGS. 5 are explanatory views showing a processing state in the cartridge fitting process. FIG. 5(a) is a plan view of the cartridge 21 where the segments 3 are placed. FIG. 5(b) shows a state in which the punch 25 is put close, from upside, to the cartridge 21 kept in the state of FIG. 5(a). The part of the cartridge 21 corresponds to the cross-section cut along the line A-A in FIG. 5(a). FIG. 6 is a cross-sectional view showing a state in which the punch 25 is pressed against the segments 3. FIG. 7 is an explanatory view showing a state of the segments 3 after the cartridge fitting process.

[0028] As shown in FIGS. 5 and 6, the annular protrusions 27a and 27b of the punch 25 enter from upside into the anchor parts 14 of the segments 3. In the anchor parts 14, the annular protrusions 27a and 27b contact and press the bottom surfaces 14a of the anchor parts. At this time, between the annular protrusions 27a and 27b and the segments 3, only dimensions in the radial directions need to be managed such that the annular protrusions 27a and 27b fit in the anchor parts 14. That is, precision of positional alignment between the punch 25 and the cartridge 21 is greatly relaxed, compared with a conventional anchor press method. Therefore, dimensional precision of the segments 3 can be relaxed, the yield can be improved, and the number of processing steps is reduced. As a result, manufacturing cost can be reduced.

[0029] On the cartridge 21, the segments 3 are held between the protrusions 22 each formed like a wedge, so that movement/deformation is restricted in the inner circumferential side. In addition, in the outer circumferential side; movement/deformation is restricted by the step part 23 and the outer circumferential wall 24. Hence, when pressing is performed by the punch 25, the side surfaces exposed to the gaps 29 between the segments 3 are deformed so as to swell into the gaps 29 as the upper surfaces of the segments 3 are pressed against the annular protrusions 27a and 27b. At this time, a punch trace 31 as shown in FIG. 7 is formed on the segments 3, so that the protrusions 22 and the segments 3 contact tightly each other at and near the part of the punch trace 31. Although parts opposed to the concave parts 28 are not directly applied with pressing force, deformation at both side surfaces of the segments 3 facing each gap 29 due to the annular protrusions 27a and 27b reaches the parts opposed to the concave parts owing to extension of materials.

[0030] The protrusions 22 of the cartridge 21 are inserted in the gaps 29. Both side surfaces of the segments 3 facing each gap 29 are pressed against the protrusions 22. That is, the protrusions 22 and the end surfaces of the segments 3 tightly contact each other in the gaps 29, due to press/contact by the punch 25 and extension of materials. In addition, extension of the material of the segments 3 causes the segments 3 to contact tightly the step part 23 and the outer circumferential wall 24, so that the segments 3 contact tightly the cartridge 21.

[0031] Thus, in the present invention, the punch 25 presses the segments 3 via the annular protrusions 27a and 27b, so that the load can be concentrated on the concave parts. Therefore, deformation of the segments 3 can be started even with a light load. In addition, movement and deformation of the segments 3 are restricted by the wedge-like protrusions 22, step part 23, outer circumferential wall 24, and the like. Therefore, the segments 3 are buckled in directions toward the gaps 29 due to pressure of the punch 25. Thus, it is possible to make the segments 3 and the cartridge 21 contact tightly each other, effectively even with a light load. Accordingly, a large-scale equipment is not needed, and the pressure load is light. Hence, even if load is concentrated due to dimensional variants, the punch 25, the cartridge 21, and the like are hardly damaged, contributing to reduction in manufacturing costs. According to experiments conducted by the present inventors, the segments 3 and the cartridge 21 contacted each other with sufficient tightness with a load of 12t. In the molding process, there was no leakage of synthetic resins.

[0032] It goes without saying that the present invention is not limited to the above embodiment, and various changes may be made without departing from the scope of the invention.

[0033] For example, in the punch 25 used, the annular protrusions are formed double. However, triple or more annular protrusions may be formed, to form a multiple-ring shape. The positions where the annular protrusions 27a and 27b are formed are not limited to the outer and inner circumferential parts but may be apart from the outer and inner circumferential edges. Note that, in the embodiment described above, the step part 23 together with the outer circumferential wall 24 functions as a radial movement restriction part. However, at least one of the step part and the wall is sufficient for the radial movement restriction part, i.e., both of the step part and the wall are not always necessary for the radial movement restriction part.

[0034] In the method and device for manufacturing a flat commutator, according to the present invention, the cartridge fitting process is carried out by use of a punch having annular protrusions. Therefore, it is possible to relax precision of positional alignment between the punch and the cartridge, compared with a conventional anchor press method. Accordingly, the dimensional precision of segments and the like can be relaxed, the yield can be improved, and the number of processing steps can be reduced. As a result, manufacturing cost can be reduced.

[0035] In addition, metal pieces are pressed by plural annular pressing parts formed on a punch. Therefore, the metal pieces can be deformed with a lighter load, compared with a case of pressing the metal pieces on the whole bottom surface of the punch. Further, punch-press is performed while regulating movement of the metal pieces by the circumferential movement restriction parts and the radial movement restriction part. Therefore, deformation of the metal pieces at the time of press can be restricted, so that the metal pieces can be let tightly contact the cartridge without pressing the metal pieces on the whole bottom surface of the punch. Accordingly, a large-scale equipment in the case using a flat punch is not needed, and the pressure load is light. Hence, even if the load is concentrated due to dimensional variants, the punch, cartridge, and the like are hardly damaged, contributing to reduction in manufacturing costs.

Claims

1. A method for manufacturing a flat commutator having a holder part formed of synthetic resins in a disk-like shape, and plural segments arranged along a circumferential direction of the holder part on an end surface of the holder part in an axial direction of the holder part, the method characterized by comprising:

a step of setting metal pieces forming the segments in a cartridge having circumferential movement restriction parts which are provided between the metal pieces, to restrict movement of the metal pieces in the circumferential direction, and a radial movement restriction part which is positioned at an end part in radial directions of the metal pieces, to restrict movement of the metal pieces in the radial directions; and

a step of pressing the metal pieces with a punch having plural annular pressing parts formed on a surface facing the cartridge, to make the metal pieces tightly contact the circumferential movement restriction part of the cartridge.

2. The method according to claim 1, characterized in that the circumferential movement restriction parts are protrusions formed radially on the cartridge.

3. The method according to claim 1 or 2, characterized in that the radial movement restriction part is a wall which is provided on an outer circumferential part of the cartridge and contacts outer circumferential parts of the metal pieces.

4. The method according to any one of claims 1 to 3, characterized in that the annular pressing parts are annular protrusions formed on the surface of the punch facing the cartridge.

5. The method according to claim 4, characterized in that the annular protrusions include a first protrusion formed in an outer-diameter side of the metal pieces, and a second protrusion formed in an inner-diameter side of the metal pieces, with an interval maintained from the first protrusion, the first and second protrusions contacting gaps formed between the segments by the circumferential movement restriction parts, with an interval maintained in the radial directions between the first and second protrusions.

6. The method according to claim 5, characterized in that annular punch traces are formed in the metal pieces by the first and second protrusions, and the metal pieces and the circumferential movement restriction parts are brought into tight contact with each other at portions of the punch traces.

7. A device for manufacturing a flat commutator having a holder part formed of synthetic resins in a disk-like shape, and plural segments arranged along a circumferential direction of the holder part on an end surface of the holder part in an axial direction of the holder part, the device characterized by comprising:

a cartridge which contains metal pieces forming the segments, and has circumferential movement restriction parts which are provided between the metal pieces, to restrict movement of the metal pieces in the circumferential direction, and a radial movement restriction part which is positioned at an end part in radial directions of the metal pieces, to restrict movement of the metal pieces in the radial directions; and

a punch having plural annular pressing parts formed on a surface facing the cartridge, the annular pressing parts being to be pressed against the metal pieces.

8. The device according to claim 7, characterized in that the circumferential movement restriction parts are protrusions formed radially on the cartridge.

9. The device according to claim 7 or 8, characterized in that the radial movement restriction part is a wall which is provided on an outer circumferential part of the cartridge and contacts outer circumferential parts of the metal pieces.

10. The device according to any one of claims 8 to 9, characterized in that the annular pressing parts are annular protrusions formed on the surface of the punch facing the cartridge.

11. The device according to claim 10, characterized in that the annular protrusions include a first protrusion formed in an outer-diameter side of the metal pieces, and a second protrusion formed in an inner-diameter side of the metal pieces, with an interval maintained from the first protrusion, the first and second protrusions contacting gaps formed between the segments by the circumferential movement restriction parts, with an interval maintained in the radial directions between the first and second protrusions.

12. The device according to claim 11, characterized in that annular punch traces are formed in the metal pieces by the first and second protrusions, and the metal pieces and the circumferential movement restriction parts are brought into tight contact with each other at portions of the punch traces.

Drawing