Commutator
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a commutator, and more particularly to a flat disk commutator in which a segment is arranged on one end face in axial direction of a boss and in a circumferential direction of the boss, which is effectively employed, for instance, in an &#34;In-Tank Type Fuel Feed Pump&#34; in which a motor is integrated with a pump. 
     2. Related Art Statement 
     In general, as a fuel feed pump for feeding a fuel to a vehicle such as an automobile, an &#34;In-Tank Type Fuel Feed Pump&#34; in which a motor is integrated with a pump, which is provided in a fuel tank, has been proposed. In an &#34;In-Tank Type Fuel Feed Pump&#34;, a &#34;Flat Disk Type Commutator&#34; is employed as a motor. 
     One the other hand, an &#34;In-Tank Type Fuel Feed Pump&#34; is generally constructed so that a fuel can be fed from a pump to the outside through a motor housing. In this case, the fuel touches to the commutator of the motor. 
     By the way, in the case of use of gasohol in which alcohol is mixed with the gasoline as fuel, when copper of the commutator which is used in the motor of the fuel feed pump contacts with the gasohol, the fuel is altered, or the copper is penetrated. Hence, a commutator for gasohol is proposed in, for example, U.S. Pat. No. 5,175,463. In this patent, a protecting portion chip(s) made from carbon is(are) attached, by soldering, to at least one surface contacting a brush in a copper of a base member of a segment (commutator bar). In this commutator, carbon has almost no solderability, so that a nickeling and a coppering for a soldered face of the protecting portion chip made from carbon is proposed. 
     However, in the commutator in accordance with the prior art, a plating step is necessary, so that the manufacturing steps and the manufacturing costs increase. 
     Further, the protecting portion chip made from carbon by soldering is electrically and mechanically connected to a base material of the segment, so that there is a possibility that the soldering layer could melt and escape from a connecting surface between the carbon protecting portion chip and the base material of the segment when an armature coil is fused to the riser portion protrudely integrated with the base material. High fusing point solder is therefore used to avoid this state, operating time for the soldering become long, so that the productivity even more decreases. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a commutator in which carbon and conductive material can be connected with each other even in case of the omission of a plating step for carbon. 
     A commutator according to the present invention comprises a boss made from resin, which is unitarily formed into a disk-shape; a plurality of carbon segments arranged on an end surface of the axial direction of the boss with an equal spacing in the circumferential direction of the boss, which are insulated from each other and are fixed; and a plurality of the conductive base materials, which are electrically connected to each of the carbon segments respectively; wherein: a recess is formed at each of the carbon segments; a conductive member having conductivity and solderability is fixedly provided in the recess; and each conductive base material is touched to each of the carbon segments so as to blockade the recess by a part thereof and the blockaded portion is soldered to the conductive member. 
     Further, a commutator according to the present invention comprises a boss made from resin, which is unitarily formed into a disk-shape; a plurality of carbon segments arranged on an end surface of the axial direction of the boss with an equal spacing in the circumferential direction of the boss, which are insulated from each other and are fixed; and a plurality of the conductive base materials, which are electrically connected to each of the carbon segments respectively; wherein: a recess is formed at each of the carbon segments; a conductive binding member is filled in each of the recesses; and each conductive base material is touched to each segment so as to blockade the recess by a part thereof and the blockaded portion is bound thereby. 
     Furthermore, slits are provided between adjacent segments for insulating in a commutator. 
     According to the first commutator described hereinbefore, by a soldering of a part of the conductive base material to the conductive member filling the recess of the carbon segment, and according to the second commutator, by the conductive adhesive material; the carbon segment and the conductive base material are electrically connected with each other. Therefore, it is possible to omit the plating step for the carbon segment for connecting the conductive base material with the carbon segment. 
     Further, in the first commutator, the recess of the segment is blocked by a part of the conductive base material, so that the melting solder does not escape from the recess even in the state in which the solder layer is melted after a soldering between the conductive member and the conductive base material. Thus it is possible to avoid using a high fusing solder as solder. 
     Hence, according to the present invention, it is possible to provide a commutator in which carbon and conductive material can be connected with each other even in case of an omission of a plating step for carbon, and to realize the manufacturing easily. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1(a) is a fragmentary sectional perspective view showing a commutator in accordance with the first embodiment of the present invention, 
     FIG. 1(b) is a plan view showing a commutator in accordance with the first embodiment of the present invention, 
     FIG. 1(c) is a fragmentary sectional front view showing a commutator in accordance with the first embodiment of the present invention, 
     FIG. 2(a) is a fragmentary sectional perspective view showing a commutator in accordance with the second embodiment of the present invention, 
     FIG. 2(b) is an enlarged fragmentary sectional front view showing a commutator in accordance with the second embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In this embodiment, a commutator according to the present invention is constructed as a &#34;flat disk type&#34; and to be employed in a motor in an &#34;in tank type fuel feed pump&#34;. 
     A flat disk type commutator 1 according to the embodiment comprises: a boss 16 which is formed into an approximately thick disk-shape; a plurality of segments 21, each of which is formed into an approximately sector, which are radially arranged on the surface of the boss 16 with an approximately equal spacing; a riser bar 4 which is electrically connected to each segment 21, as a conductive base material; and a slit 20 for insulating adjacent segments 21 from each other. A shaft hole 17 is opened at the boss 16 for fixing a motor shaft by passing it therethrough. 
     Each segment 21 is formed by baking a work made from carbon powder with an appropriate binder, a recess 11 is respectively provided in a sinking manner on each segment 21 facing the boss 16. The riser bar 4 consisting of copper or alloyed copper is unitarily connected in a state in which the riser bar 4 gets between the segment 21 and the boss 16. A projecting portion (connected portion) 6 is projectingly formed at the inside end portion of the riser bar 4 by a press-plastic working, the projecting portion 6 is positioned by being inserted in the recess 11 of the segment 21, an opening portion of the recess 11 is blockaded by the inside end portion. A copper powder layer 12 as a conductive member is formed in the recess 11 of the copper powder layer 12, by a caulking of copper powder. An inside end portion including the projecting portion 6 of the riser bar 4 is electrically connected to the copper powder layer 12, by a soldering. Thus, the riser bar 4 is in a state to be electrically connected to the segment 21 through the solder layer 14 and the copper powder layer 12. 
     Further, at both sides of the projecting portion 6 on the inside end of an enlarging portion 5 continuously provided to the riser bar 4, a pair of engaging claws 7 constructing an anchor for fixing the riser bar 4 to the boss 16, is formed so as to project to the opposite end side of a projecting side of the projecting portion 6, and is buried in the boss 16. 
     On an inside circumferential surface and an outside circumferential surface of an end surface of the segment 21, an inside step 9 and an outside step 10 are formed with a constant width and height. The inside step 9 and the outside step 10, after the boss 16 is formed by resin, is in a state to be engaged to a part of the boss 16, and is constructed so that the boss 16 and each carbon segment can be unitarily connected to each other by connecting in the axial direction and the diameter direction thereof. 
     In the flat disk type commutator 1 constructed as above, after the shaft hole 17 is fixed in a fitting manner to the motor shaft, an armature coil (not shown) is contacted (e.g. hitched, entwined) to each riser bar 4, which is electrically contacted thereto by a fusing. When fusing, the riser bar 4 is heated. Then, the solder layer 14 is formed in the recess 11, moreover, it is blockaded by the projecting portion 6 of a part of the riser bar 4, so that solder material does not escape from the inside of the recess 11 even in a state in which the solder layer 14 being a liquid state due to fusing. Hence, it is unnecessary to use a high fusing solder as the solder layer 14. 
     Hereinafter are the advantages which are attained through the above embodiment. 
     (1) Since a plating step for the carbon plate is omitted, it is possible to decrease the number of manufacturing steps and the cost. 
     (2) Since it is unnecessary to use a high fusing solder as the solder layer 14, it is possible to shorten the operating time for the soldering. Further, since the solder layer 14 is formed in the recess 11, it is possible to avoid that the total length of the commutator will be long. 
     FIG. 2(a) and FIG. 2(b) show a commutator in accordance with the second embodiment, FIG. 2(a) is a fragmentary sectional perspective view, FIG. 2(b) is an enlarged fragmentary sectional front view. 
     A point in which the second embodiment differs from the first embodiment, is that the projecting portion 6 of a part of the riser bar 4 is bound on a conductive binding member 12A filled in the recess 11 of the segment 21. The conductive binding member 12A is constructed from material in which powder and/or granular material, short fiber-like material and the like consisting of conductive material are mixed in the binder, which has an adhesive property for each surface of carbon and copper, and is constructed so as to be able to electrically connect carbon and copper with each other in a binding state thereto. 
     In the second embodiment, since each riser bar 4, and each segment 21 are electrically connected with each other by the conductive binding member 12A, it is unnecessary to plate the carbon plate 8. Further, since the conductive binding member 12A is not melted by a fusing for the riser bar 4, it is also possible to obtain the same advantages as the first embodiment in the second embodiment. 
     The present invention is not limited to these embodiments; in so far as the essence of the invention is not deviated from, it goes without saying that the present invention can be modified, prevention of the escape of the solder layer 14 is not limited by the behave of the projecting portion 6 of the riser bar 4, for example, it is possible to behave in accordance with a part of the riser bar 4.