Brush device and motor with brush

A brush device having the longitudinal direction of a coil shaped coil spring aligned with the face of a brush holder, in which one end of a support post at the surface of a brush base is formed as a hollow cylinder and a projection at the other end is insert molded into the brush holder. There is a step on the support post. The step and the brush holder receive a cover plate which, when viewed from a direction perpendicular to the face of the brush holder, covers a winding of the coil shaped coil spring. One end of the support post is fixed to the surface of the cover plate by spreading the end of the hollow cylinder of the support post.

TECHNICAL FIELD

The present invention relates to the constitution of a brush for a motor with a brush that uses the brash made of carbon. In particular, it relates to a brush device in which the brush is pushed against a commutator by a coil spring, and a motor with a brush that is equipped with such a brush device.

BACKGROUND ART

A conventional brush device with a resilient means to impel the brush against the commutator (see Patent Document 1, for example) is shown inFIG. 16. This brush device24has a brush19formed in a substantially arc shape, which is supported by contact between part of its outer surface and the inner wall of a holder22.

The outer face of the brush19at the end facing the commutator2is made to contact the inner wall of the holder22by the force of friction with the commutator2, and the inner edge of the brush19at the end facing the torsion coil spring23is made to contact the inner wall of the holder22by impulse of the torsion coil spring23. In this way, the brush19is supported within the gap g between the inner walls of the holder22, and its ability to follow the commutator2is enhanced. Further, because the brush19is formed in an arc shape, the brush friction is maintained by rubbing and the overall diameter of the brush device is minimized.

However, there are still problems in the brush device24shown inFIG. 16, in regard to assuring reliable electrical conductivity between the commutator and the brush. InFIG. 16, the brush19is held just by providing the gap g between the inner walls of the holder22, and the commutator2comprises, as an actual product, a number of commutator blades2a. Accordingly, when the brush19straddles the space between the commutator blades2a, the support of the brush19is destabilized and vibration is liable to occur.

Further, depending on the application of the motor with a bush, the commutator will sometimes be driven in opposite directions, clockwise and counter-clockwise. With the brush device inFIG. 16, however, if the direction is reversed and the commutator is driven clockwise, the brush19is liable to drift because of its two-point support in the gap g, and the instability of support of the brush19is liable to cause vibration.

The brush device14shown inFIGS. 17 and 18was put into production in order to resolve the problems described above. In the case of this brush device14, the commutator comprises commutator blades2amounted on the outer periphery of the motor shaft1, separated by equal gaps, and the carbon brush10is fitted to and held by the support post7of the brush holder4. This brush10, as shown inFIG. 17, has a rubbing surface with electrical conductivity when in contact with the commutator blade2a. The brush10has the arched brush arm10aand the brush base10bwith the hole8through which the support post7passes for mounting the brush10on the brush holder4. By forming the brush arm10aand the brush base10bas a single unit, the brush10is formed in substantially a V shape. The coil spring5or other means of impulse is mounted on the support post7and concentric with it, so that the rubbing face of the brush10is impelled against the commutator blade2aand held in contact with the commutator2.

Because the brush device14has a means of impulse such as the coil spring5(only one of the two brushes10is shown inFIG. 18), changes to the force of contact from friction between the brush10and the commutator2are prevented, and so there is superior stability of electrical conductivity between the commutator2and the brush10. Moreover, there is the advantage that the brush arm10, which corresponds to brush19inFIG. 16, is supported by the relatively large brush base10b, and because this brush base10bis fitted to the support post7, the stability of brush support is greater than in the brush device ofFIG. 16, so that the occurrence of vibration is inhibited when the motor is driven.

Nevertheless, the structure of the brush device14is such that the brush10is mounted over the coil spring5, which is the means of impulse, and so the thickness of the brush device14increases that much more in the direction of the motor shaft1. Consequently, there is the problem that miniaturization of the brushed motor in the direction of the motor shaft is impeded.

The present applicants earlier applied, in Japanese Patent Application No. 2001-367265, for the brush device11as shown inFIGS. 19 and 20. This application provides the guide15as part of the brush base3b, as well as the recess6in the brush holder4. Within this recess6, one end of the coiled portion of the coil spring5is stopped by the stop face3cof the brush base3b, and the other end is stopped by the step4a of the brush holder4. The longitudinal direction of the coil spring5is aligned with the face of the brush holder4(the direction shown by arrow C inFIG. 20), and the winding follows the wall of at least one of the guide15and the recess6; the coil spring5and the brush3are in substantially the same plane. This is the essence of the brush device11.

By constituting the brush device11as described above, the longitudinal direction of the coil spring5is located in substantially the same plane as the face direction of the brush holder4, and so the brush device can be made thinner than earlier brush devices. Further, by applying this brush device11in a motor with a brush, it is possible to reduce the length of the motor shaft1without impairing the characteristics of the brushed motor.

DISCLOSURE OF THE INVENTION

However, the brush device11of the application described above also had shortcomings, as follows. Because the brush device11had the coil spring5mounted in substantially the same plane as the face direction of the brush holder4, the spring5is exposed when the brush holder4is viewed from a direction perpendicular to that plane. Consequently, the windings gradually push out from the recess6as the brush device11is driven; as a result, the impulse of the spring5against the brush3weakens and it gradually becomes impossible to obtain the desired impulse of the brush contact face against the commutator blades2a.

Moreover, in the manufacture of the brush device11on the basis of the content of that application, the brush3was mounted within the recess6of the brush holder4so that it could rotate around the support post7′, by inserting the support post7′ through the hole in the brush3and fitting and fixing the ring7a′. Therefore, as shown inFIG. 20, it was inevitable that the strength with which the support post was attached to the surface31bof the brush base3b(the side indicated by the arrow a in the figure) was less than the strength on the opposite side, that is, the strength with which the support post7was fixed to the recess6(the side indicated by the arrow b in the figure).

That is to say, on the arrow b side, the support post7′ was fitted and fixed to the recess6of the brush holder4, but on the arrow a side, the support post7′ was only fitted and fixed to the small ring7a′. Accordingly, when the fixing strengths on the arrow a side and the arrow b side are compared, the fixing strength on the arrow a side is markedly less, and so the support post7′ was fixed to the recess6of the brush holder4with fixing strength that was essentially a matter of one-sided support. Consequently, as the brush contact fact rubbed against the commutator blade, the support post7′ was liable to become shaky, and vibration of the support post7′ made firm support of the brush3unobtainable.

Moreover, the heat that is generated when the motor with a brush is driven could only act on the point where the support post7′ was fitted and fixed to the surface31band the point where the support post7′ was fitted and fixed to the recess6. Since the fittings were just a matter of pressure on the parts by means of stress, the action of the heat would weaken the stress and reduce the fitting strength in both places. This made the support post7′ all the more shaky, and the support of the brush3even less stable.

In this situation, there was the problem that the vibration accompanying the rotation of the commutator2was conveyed through the brush3and the support of brush3became unstable. Thus, there was a constant alternation of contact and non-contact between the commutator blades2aand the contact faces of the brushes, so that electrical and mechanical reliability was markedly reduced.

The present invention has been devised in light of these problems, and an object of the present invention is to improve the contact characteristics of the brush of the brush device with the commutator, and thus to provide the brush device capable of reliable electrical connectivity.

The present invention provides a brush device comprising a brush and a spring, the brush including a brush arm made of carbon, which is substantially arc shaped and which has a contact face that conducts electricity when in contact with a commutator, and a brush base mounted so as to rotate around a support post, the brush being mounted in a brush holder so that rotation around the support post puts a contact face in contact with the commutator, the spring impeling the brush toward the commutator, wherein one end of the support post at a face side of the brush base is formed with a hollow cylinder and the other end is formed with a projection, the projection of the support post is fixed into the brush holder by insert molding, a guide is formed on a part of the brush base, a recess is formed in the brush holder within which one end of a winding of the coil spring is stopped by the brush base and the other end is stopped by the brush holder, the coil spring and brush are placed in substantially the same plane in such a manner that a longitudinal direction of the coil spring matches a direction of a surface of the brush holder and the winding of the coil spring follows the shape of at least one of the guide and the recess, and the one end of the support post is fixed to the surface of the brush base by spreading the hollow cylindrical end of the support post.

The present invention further provides a brush device comprising a brush and a spring, the brush including a brush arm made of carbon, which is substantially arc shaped and which has a contact face that conducts electricity when in contact with a commutator, and a brush base mounted so as to rotate around a support post, the brush being mounted in a brush holder so that rotation around the support post puts a contact face in contact with the commutator, the spring impeling the brush toward the commutator, wherein one end of the support post is formed with a hollow cylinder and the other end is formed with a projection, the projection of the support post is fixed into the brush holder by insert molding, a recess is formed in the brush holder, the brush base made of a sheet material includes an insertion tube for insertion of the support post and a guide for accommodating the coil spring, which are integrated with the brush member as a single unit, the brush is accommodated within the recess of the brush holder by insertion of the support post into the insertion tube, one end of a winding of the coil spring is stopped by the brush base and the other end is stopped by the brush holder, the coil spring and brush are placed in substantially the same plane in such a manner that a longitudinal direction of the coil spring matches a direction of a surface of the brush holder and the winding of the coil spring follows the shape of at least one of the guide and the recess, and the one end of the support post is fixed to one end of the insertion tube by spreading the hollow cylindrical end of the support post.

The present invention also provides a brush device comprising a brush and a spring, the brush including a brush arm made of carbon, which is substantially arc shaped and which has a contact face that conducts electricity when in contact with a commutator, and a brush base mounted so as to rotate around a support post, the brush being mounted in a brush holder so that rotation around the support post puts a contact face in contact with the commutator, the spring impeling the brush toward the commutator, wherein one end of the support post is formed with a hollow cylinder and the other end is formed with a projection, the projection of the support post is fixed into the brush holder by insert molding, the spring is constituted so as to be a torsion coil spring, a recess is formed in the brush holder, the brush base is made of a sheet material and includes an insertion tube for insertion of the support post that is integrated with the brush member as a single unit, the brush is accommodated within the recess of the brush holder by insertion of the support post into the insertion tube, the torsion coil spring is fitted over an outer periphery of the insertion tube in such a manner that a longitudinal direction of the torsion coil spring is placed perpendicular to a direction of the face of the brush holder, an end of a spring wire that extends from one side of a winding of the torsion coil spring is stopped by the brush holder and another end of the spring wire that extends from the other side is stopped by the brush, and the one end of the support post is fixed to one end of the insertion tube by spreading the hollow cylindrical end of the support post.

The present invention also provides a brush device comprising a brush and a spring, the brush including a brush arm made of carbon, which is substantially arc shaped and which has a contact face that conducts electricity when in contact with a commutator, and a brush base mounted so as to rotate around a support post, the brush being mounted in a brush holder so that rotation around the support post puts a contact face in contact with the commutator, the spring impeling the brush toward the commutator, wherein a guide is formed on a part of the brush base, a recess is formed in the brush holder within which one end of a winding of the coil spring is stopped by the brush base and the other end is stopped by the brush holder, the coil spring and brush are placed in substantially the same plane in such a manner that a longitudinal direction of the coil spring matches a direction of a surface of the brush holder and the winding of the coil spring follows the shape of at least one of the guide and the recess, and there is provided a cover plate attached so as to cover a winding of the coil spring when viewed from a direction perpendicular to the face of the brush holder.

The present invention further provides a brush device comprising a brush and a spring, the brush including a brush arm made of carbon, which is substantially arc shaped and which has a contact face that conducts electricity when in contact with a commutator, and a brush base mounted so as to rotate around a support post, the brush being mounted in a brush holder so that rotation around the support post puts a contact face in contact with the commutator, the spring impeling the brush toward the commutator, wherein a recess is formed in the brush holder, the brush base made of a sheet material includes an insertion tube for insertion of the support post and a guide for accommodating the coil spring, which are integrated with the brush member as a single unit, the brush is accommodated within the recess of the brush holder by insertion of the support post into the insertion tube, one end of a winding of the coil spring is stopped by the brush base and the other end is stopped by the brush holder, the coil spring and brush are placed in substantially the same plane in such a manner that a longitudinal direction of the coil spring matches a direction of a surface of the brush holder and the winding of the coil spring follows the shape of at least one of the guide and the recess, and there is provided a cover plate attached so as to cover a winding of the coil spring when viewed from a direction perpendicular to the face of the brush holder.

The present invention includes a brush device comprising a brush and a spring, the brush including a brush arm made of carbon, which is substantially arc shaped and which has a contact face that conducts electricity when in contact with a commutator, and a brush base mounted so as to rotate around a support post, the brush being mounted in a brush holder so that rotation around the support post puts a contact face in contact with the commutator, the spring impeling the brush toward the commutator, wherein one end of the support post at a face side of the brush base is formed with a hollow cylinder and the other end is formed with a projection, the projection of the support post is fixed into the brush holder by insert molding, a guide is formed on a part of the brush base, a recess is formed in the brush holder within which one end of a winding of the coil spring is stopped by the brush base and the other end is stopped by the brush holder, the coil spring and brush are placed in substantially the same plane in such a manner that a longitudinal direction of the coil spring matches a direction of a surface of the brush holder and the winding of the coil spring follows the shape of at least one of the guide and the recess, a step is formed on the support post, there is provided a cover plate attached so as to cover the winding of the coil spring when viewed from a direction perpendicular to the face of the brush holder, which is received by the step of the support post and a portion of the brush holder, and the one end of the support post is fixed to the surface of the cover plate by spreading the hollow cylindrical end of the support post.

The present invention includes a brush device comprising a brush and a spring, the brush including a brush arm made of carbon, which is substantially arc shaped and which has a contact face that conducts electricity when in contact with a commutator, and a brush base mounted so as to rotate around a support post, the brush being mounted in a brush holder so that rotation around the support post puts a contact face in contact with the commutator, the spring impeling the brush toward the commutator, wherein one end of the support post is formed with a hollow cylinder and the other end is formed with a projection, the projection of the support post is fixed into the brush holder by insert molding, a recess is formed in the brush holder, the brush base made of a sheet material includes an insertion tube for insertion of the support post and a guide for accommodating the coil spring, which are integrated with the brush member as a single unit, the brush is accommodated within the recess of the brush holder by insertion of the support post into the insertion tube, one end of a winding of the coil spring is stopped by the brush base and the other end is stopped by the brush holder, the coil spring and brush are placed in substantially the same plane in such a manner that a longitudinal direction of the coil spring matches a direction of a surface of the brush holder and the winding of the coil spring follows the shape of at least one of the guide and the recess, a step is formed on the support post, there is provided a cover plate attached so as to cover the winding of the coil spring when viewed from a direction perpendicular to the face of the brush holder, which is received by the step of the support post and a portion of the brush holder, and the one end of the support post is fixed to the surface of the cover plate by spreading the hollow cylindrical end of the support post.

The present invention provides a motor with a brush equipped with any one of the brush devices described above.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the first embodiment of the brush device of the present invention will be described referring toFIGS. 1 through 9. Now, for parts that are the same as those of the prior art, the same reference numerals are used.FIGS. 1 and 2are plan views of a brush device11of the first embodiment.FIG. 3is a plan view showing the exterior of a cover plate30installed on a brush device11.FIG. 4is a partial cross sectional view of a brush holder4of the brush device11, taken along the dash-dotted line A—A inFIG. 2.FIGS. 5 through 7show a support post7that fixes a brush3in place.FIG. 8is a perspective view of the brush3. AndFIG. 9is a perspective view of a coil spring5used in the brush device11.

As shown inFIGS. 1 and 2, there is in the flat surface of a brush holder4a recess6that accommodates the brushes3and the coiled springs5shown by broken lines inFIG. 2. The recess6has 180 degree rotational symmetry centered on the axis B—B that runs through the center of the brush holder4. In a brush base3bof each brush3there is a hole8for insertion of the support post7as shown inFIG. 8. The brush3is formed in part in an arc shape, and has a guide15that holds at least a portion of the winding of the coil spring5. Reference numeral1denotes a motor shaft, placed so that it can rotate, of the motor with a brush that is not shown. A commutator2comprises a number of commutator blades2amounted equidistant around the outer periphery of the motor shaft1.

As shown inFIGS. 1,2and8, the brush3is formed in substantially a V shape, with a brush arm3i a, which has a contact face that rubs against the commutator2, and the brush base3bconnected as a single unit. The brush3can be made with only the brush arm3abeing carbon, but this embodiment is explained as an example of having the brush3as a whole made of carbon. Now, the brush arm3ais formed in substantially the shape of a gentle arc.

A brush3is installed in the recess6as shown inFIG. 4and inFIGS. 5 and 6. After a projection7bthat is formed on the other end of the support post7is insert molded into the brush holder4, the hole8in the brush3is fitted over the support post7shown inFIGS. 5 and 6. The support post7is molded of a metallic material such as brass. As shown inFIG. 4andFIGS. 5 and 6, the support post that is fixed into the brush holder4by insert molding is formed with a hollow cylinder as the end7dthat is positioned by a flat surface31bof the brush base3b. That is, it is formed as a substantially cylindrical post with a bore7athat extends part way along the length (the direction of arrow D inFIGS. 5 and 6) of the support post7.

One end5aof the winding of the coil spring5shown inFIG. 9is stopped by a stop face3cformed in advance on the brush3, and the other end5bis stopped by a step4aestablished in the shape that makes up the recess6. The longitudinal direction of the coil spring5(the direction of arrow E inFIG. 9) is aligned with the direction of the flat surface of the brush holder4(the direction of arrow C inFIG. 4), and the coil spring5is accommodated within the recess6with a part of the winding following at least one of the guide15and the recess6.

Because the coil springs5stretch out along the guide15and the wall of the recess6, the two brushes3rotate around the support posts7in the direction of the commutator2, and the contact faces at the tips of the brush arms3aare impelled toward and have contact with the commutator blades2a.

After the hole8is fitted over the support post7, a cover plate30like that shown inFIGS. 1 through 4is fastened to the support post7. The cover plate30has in it a hole30athat fits over the support post7, and by fitting this hole30aover the support post7it is possible to mount the cover late30on the brush holder4. At that time, the flat surface of the cover plate30adjacent to the hole30ais received by a step7con the outer periphery of the support post7(seeFIGS. 4 through 6). Meanwhile, the flat surface of edges30band30cof the cover plate30are received by a step4bthat is a part of the brush holder4shown inFIGS. 2 and 4. The step7cand the step4bare constituted so as to have the same height in the direction perpendicular to the flat surface of the brush holder4(the direction of the arrow C inFIG. 4). The height of the step7cand the step4bis preferably 0.1 to 0.2 mm higher than the separation between the flat surface31band the bottom of the recess when the brush3is fitted on the support post7(dimension G inFIG. 4) and the height of the winding of the spring5(dimension H inFIG. 4).

The size of the cover plate30is determined so that when installed on the brush holder4as shown inFIGS. 1 and 2, it will cover and conceal the winding of the spring5when viewed from the direction perpendicular to the direction of the surface of the brush holder4(the direction of the arrow C inFIG. 4). More preferably, it is determined so that it will cover and conceal the winding even when the winding extends as the brush arm3awears away.

After the cover plate30is in place, one end of the support post7is fixed to the flat surface of the cover plate30, as shown inFIGS. 4 and 7, by spreading the end7dwith a caulking iron. During the fixing with the caulking iron, the cover plate30is received by the step7cand the step4b, and so the cover plate30is prevented from applying excessive pressure to the brush3. Accordingly, it is possible for the brush3to rotate freely as impelled by the spring5.

When the motor with a brush in which the brush device11is mounted is started up, the motor shaft1that is a rotor begins to revolve, and electrical conductivity is established by the rubbing together of the commutator2and the brushes3, so that the motor can be driven. When the motor has operated for a long period, the contact faces of the brushes3are worn away by friction with the commutator2and the brush arms3agradually grow shorter, but because the coil springs5constantly impel the brushes3toward the commutator2, as described above, the electrical conductivity between the commutator2and the brushes3is maintained without interruption.

Moreover, the support post7that supports the brush3has one end fixed in place by spreading with the caulking iron and the other end is fixed by insert molding into the brush holder4. In other words, the means used for fixing both ends of the support post7are means in which the fixing strength does not change even in the presence of the heat that accompanies operation of the motor, and so both ends remain firmly fixed even when the motor has been driven for a long period. Accordingly, the brushes3and the commutator blades2aare always in contact, and so it is possible to increase the electrical and mechanical reliability of contact between the commutator2and the brushes3when the motor is driven for a long period.

Further, by using the caulking iron to fix the support post7at the flat surface31bof the brush base3b, it is possible to assure adequate fixing strength relative to the fixing of the other end by insert molding. Accordingly, it is possible to firmly fix both ends of the support post7, and so the support of the brush3is firm. It is possible, as a result, to keep the brush3and the commutator blades2ain contact at all times, and so the electrical and mechanical reliability of contact between the brushes3and the commutator2in motors driven over long periods can be increased.

In addition, since the cover plate30is fixed to the support post7so as to cover the winding of the spring5, it is possible to control the pushing up of the spring5. Accordingly, it is possible to keep the contact face of the brush rubbing against the commutator blades2awith the desired impulse.

Herein, this embodiment can be varied in numerous ways on the basis of technical considerations. For example, the cover plate30could be omitted and the end7dcould be spread with the caulking iron and fixed to the flat surface31b. Or the support post7could be a solid post without the hole30aand the cover plate30could be attached to the brush device11by inserting that post into the hole30a. Needless to say, however, this embodiment is optimum from the perspective of obtaining both the results of improving electrical and mechanical reliability and keeping the spring5from pushing up.

Next, the second embodiment of the brush device of the present invention will be described referring toFIGS. 10 through 12.FIGS. 10 and 11are plan views of a brush device13of the second embodiment, andFIG. 12is a perspective view of a brush3′ in the brush device13ofFIGS. 11 and 12. Now, the description of the second embodiment is limited to those points that differ from the first embodiment; structural parts which are the same as those in the first embodiment are given the same reference numerals, and duplicate descriptions are omitted or simplified.

As shown inFIGS. 11 and 12, a brush base3′bof the brush3′ is made of a metallic sheet material. It has a hole8for insertion of the support post7in the designated location, and an insertion tube9for the insertion of the support post7is formed as a single unit with the brush base3′b, extending from the hole8. The brush arm3′athat has a contact face that rubs against the commutator2is a separate piece. By clamping the brush arm3′awith a contact face and an opposite end in a damper3′con the brush base3′b, the brush3′ that is substantially V-shaped as a whole is formed. In this embodiment, the brush arm3′ais made of carbon and is formed in the shape of a gentle arc. The hole8, the insertion tube9, and the damper3′cof the brush base3′bare formed as a unit by press processing of sheet metal.

As in the first embodiment, the support post7is fixed to the brush holder4by insert molding, and then the support post7is inserted into the hole8and inside the insertion tube9, by which means the brush3′ is accommodated in the recess6and is free to rotate around the support post7. When the brush3′ is accommodated in the recess6, the step7cof the support post7is higher than the end9aof the insertion tube9(seeFIG. 12). One end5a(seeFIG. 9) of the winding of the coil spring5is stopped by the end face of the brush arm3′anear the clamper, and the other end5bis stopped by the step4athat is part of the shape of the recess6.

Next, the longitudinal direction of the coil spring5(the direction of the arrow E inFIG. 9) is aligned with the direction of the surface of the brush holder4(the direction of the arrow C inFIGS. 10 and 11), and the coil spring5is accommodated within the recess6with a part of the winding of the coil spring5following at least one of the wall of the recess6and a guide16that is a single unit with the brush base3′b.

Because this coil spring5stretches out along the guide16and the wall of the recess6, when the two brushes3′ rotate around the support posts7in the direction of the commutator2, the contact faces at the tip of the brush arms3′aare impelled toward and have contact with the commutator blades2a.

Next, the cover plate30is attached. As in the first embodiment, the size of the cover plate30is determined so that when installed on the brush holder4as shown inFIGS. 1 and 2, it will cover and conceal the winding of the spring5when viewed from the direction perpendicular to the direction of the surface of the brush holder4. More preferably, it is determined so that it will cover and conceal the winding even when the winding extends as the brush arm3awears away. When the plate is placed in the recess6, the flat surface of the cover plate30adjacent to the hole30ais received by a step7con the outer periphery of the support post7(seeFIGS. 5 through 7). In addition, the flat surface of the edges30band30cof the cover plate30are received by the step4bthat is a part of the brush holder4. As in the first embodiment, the step7cand the step4bare constituted so as to have the same height in the direction perpendicular to the flat surface of the brush holder4(the direction of the arrow C inFIGS. 10 and 11). The height of the step7cand the step4bwhen the insertion tube9is fitted to the support post7is preferably 0.1 to 0.2 mm higher than the end face9aof the insertion tube9and the height of the winding of the spring5(dimension H inFIG. 4).

After the cover plate30is in place, one end of the support post7is fixed to the flat surface of the cover plate30by spreading the end7dwith the caulking iron as shown inFIG. 7. During the fixing with the caulking iron, the cover plate30is received by the step7cand the step4b, and so the cover plate30is prevented from applying excessive pressure to the brush3′. Accordingly, it is possible for the brush3′ to rotate freely as impelled by the spring5.

As in the first embodiment, both ends of the support post7are fixed by means in which the fixing strength does not change even in the presence of the heat that accompanies operation of the motor, and so both ends remain firmly fixed even when the motor has been driven for a long period, and the brushes3and the commutator blades2aare always in contact. Thus, it is possible to increase the electrical and mechanical reliability of contact between the commutator2and the brushes3when the motor is driven for a long period.

Further, by using the caulking iron to fix one end of the support post7, it is possible to assure adequate fixing strength, and both ends of the support post7can be firmly fixed, and so the support of the brush3is firm. It is possible, as a result, to keep the brush3and the commutator blades2ain contact at all times, and so the electrical and mechanical reliability of contact between the brushes3and the commutator2in motors driven over long periods can be increased.

In addition, since the cover plate30is fixed to the support post7so as to cover the winding of the spring5, it is possible to control the pushing up of the spring5. Accordingly, it is possible to keep the contact face of the brush rubbing against the commutator blades2awith the desired impulse.

In addition to the effects described above, in this embodiment it is possible to reduce thickness by forming the brush base3′bof a sheet material and, taking advantage of that reduced thickness, to have the longitudinal direction of the coil spring5in almost the same plane as the surface of the brush holder4, so that the windings of the coil spring5do not protrude beyond the thickness of the brush3′.

Further, because the brush arm3′aand the brush base3′bare separate pieces in this embodiment, it is possible to replace just the brush arm when it becomes worn, and there is no need to replace the entire brush3′ and maintenance characteristics of the brush device are superior to that extent.

Herein, this embodiment can be varied in numerous ways on the basis of technical considerations. For example, the cover plate30could be omitted and the end7dcould be spread with a caulking iron and fixed to the end face9aof the insertion tube9. Or the support post7could be a solid post without the hole30aand the cover plate30could be attached to the brush device. Needless to say, however, this embodiment is optimum from the perspective of obtaining both the results of improving electrical and mechanical reliability and keeping the spring5from pushing up.

Next, the third embodiment of the brush device of the present invention will be described referring toFIGS. 13 and 14.FIG. 13is a plan view of a brush device12of the third embodiment.FIG. 14is a partial cross sectional view of the brush holder4of the brush device12ofFIG. 13, taken along the dash-dotted line D—D. Herein, the description of the third embodiment is limited to those points that differ from the first and second embodiments. Parts which are the same as those in these embodiments are denoted by the same reference numerals, and duplicate descriptions are omitted or simplified.

As shown inFIG. 13, the brush base3′bof the brush3′ is made of a metallic sheet material, and it has a hole (not illustrated) for insertion of the support post7in the designated location, and an insertion tube (not illustrated) for the insertion of the support post7is formed as a single unit with the brush base3′b, extending from the hole8. The brush arm3′ais a separate piece; by clamping it with the damper3′c, the brush3′ that is substantially V-shaped as a whole is formed. In this embodiment, the brush arm3′ais made of carbon and is formed in the shape of a gentle arc.

After the projection7bthat forms one end of the support post7is fixed to the brush holder4by insert molding as shown inFIG. 14, then the support post7is inserted into the hole and inside the insertion tube, by which means the brush3′ is accommodated in the recess6and is free to rotate around the support post7. A torsion coil spring5′ is fitted over the outer periphery of the insertion tube. The end5′cof spring wire that extends from one side of the winding of the torsion coil spring5′ is stopped by the brush holder4, and the end5′dof spring wire that extends from the other side is stopped by the end face of the brush arm3′athat is part of the brush3′, near the clamper.

By means of the elastic force of this torsion coil spring5′, the two brushes3′ rotate around the support posts7in the direction of the commutator2, and the contact faces at the tips of the brush arms3′aare impelled toward and have contact with the commutator blades2a.

Next, the end7d(seeFIGS. 5 through 7) of the hollow cylinder of the support post7is spread with the caulking tool, and the end of the support post7is fixed to the end face9a(seeFIG. 12) of the insertion tube. Accordingly, as in the embodiments described above, both ends of the support post7are fixed by means in which the fixing strength does not change even in the presence of the heat that accompanies operation of the motor, and so both ends remain firmly fixed even when the motor has been driven for a long period, and the brushes3′ and the commutator blades2aare always in contact. Thus, it is possible to increase the electrical and mechanical reliability of contact between the commutator2and the brushes3when the motor is driven for a long period.

Further, using the caulking iron to fix one end of the support post7, it is possible to assure adequate fixing strength, and both ends of the support post7can be firmly fixed, and so the support of the brush3′ is firm. It is possible, as a result, to keep the brush3′ and the commutator blades2ain contact at all times, and so the electrical and mechanical reliability of contact between the brushes3′ and the commutator2in motors driven over long periods can be increased.

In addition to the effects described above, in this embodiment the thickness is reduced by forming the brush base3′bof the brush3′, of a sheet material. In this way, even though the longitudinal direction of the torsion coil spring5′ is perpendicular to the direction of the face of the brush holder4(arrow C), the winding of the torsion coil spring5′ does not extend above the thickness of the brush arm3′a. Accordingly, it is possible to form a brush device that is thinner than the conventional brush device.

Further, because the brush arm3′ais a separate piece in this embodiment, it is possible to replace just the brush arm when it becomes worn, and there is no need to replace the entire brush3′ and maintenance characteristics of the brush device are superior to that extent.

Three representative embodiments of the present invention are described above, but the present invention is not limited to those three. It is possible, for example, to have the brush arm3aand the brush base3bof the first embodiment be separate pieces, as shown inFIG. 15, with only the brush arm3abeing made of carbon.

INDUSTRIAL APPLICABILITY

As stated above, the present invention uses the means of insert molding the support posts that support the brushes into the brush holder and the means of fixing the other end of each support post by spreading with the caulking iron, and so makes it possible to prevent reduction of fixing strength as an action of heat generated as the motor to which the brush device is fitted and fixed is driven. Accordingly, the fixing of both ends of the support posts can be kept firm even as the motor is driven over a long period, and stability of support of the brushes can be maintained. Therefore, the brushes are always in contact with the commutator, and so the reliability of electrical and mechanical contact between the brushes and commutator can be improved in motors driven for long periods.

Further, by using the caulking iron to fix the ends of the support posts as described above, it is possible to assure adequate fixing strength relative to the other ends, which are fixed by insert molding. Accordingly, it is possible to fix both ends firmly, and so it is possible to have firm support of the brushes. As a result, it is possible to keep the brushes and commutator always in contact, and so the reliability of electrical and mechanical contact between the brushes and commutator can be improved in motors driven for long periods.

Moreover, by having the cover plate to cover the windings of the springs, in brush devices that use coil springs, it is possible to control the pushing out of the springs that occurs when the brush holder is driven. Accordingly, it is possible to keep the contact faces of the brushes rubbing the commutator blades2awith the desired impulse.

When the cover plate is used, there will be a step on the support post and the cover plate is received by that step and a part of the brush holder. This prevents the cover plate from applying excessive pressure to the brush during fixing with the caulking iron, and so the brush is able to rotate freely under the impulse of the spring.