JPH0595652A - Carbon brush - Google Patents

Abstract

PURPOSE:To decrease resistance loss, and improve the life together with an armature, and besides, facilitate the manufacture, and prevent the powder material constituting an electric conductor from coming out in use. CONSTITUTION:In a carbon brush 41, where all the section abraded by contact with an armature 15 is made of two or more kinds of materials extending in the direction of a main current and different in resistivity, the abraded section is provided, over approximately overall length in the direction of the main current, with a tapered hole 4 which becomes thinner gradually as it goes toward the armature side, and this hole 44 is plugged with an electric conductor 43 made of material lower in resistivity than the material highest in resistivity, and this electric conductor 43 is made of the powder material being stuffed and hardened in the hole 44.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carbon brush which is used in a generator, a commutator motor or the like and which makes sliding contact with a commutator.

[0002]

2. Description of the Related Art Carbon brushes used in commutator motors and the like are formed by compressing and solidifying carbon as a main component using a binder and baking it at a high temperature. The binder is usually a synthetic resin. Has been adopted. A conventional carbon brush used in, for example, an electric blower of an electric vacuum cleaner is formed of a single type of carbon as a main component. Moreover, in order to reduce the generation of sparks due to the sliding contact between the brush and the commutator, it is necessary to increase the resistance rectification. Carbon having a high resistance value of 30,000 μΩ or more per cm was adopted. Therefore, when a plurality of commutator pieces of the commutator are in contact with the tip end surface of the carbon brush, the current value for short-circuiting the commutator pieces through the carbon brush is small, and the occurrence of sparks can be reduced.

[0003]

However, as described above, in the structure of the conventional carbon brush having a large total electric resistance (about 0.2Ω), the resistance loss in this brush is large (about 20 W per carbon brush). ), There is a problem that the operation efficiency of a commutator motor or the like using this carbon brush is reduced.

At the same time, the loss is converted into heat generated by the carbon brush. Therefore, for example, in a resin-bound type carbon brush using a synthetic resin as a carbon binder, thermal deterioration of the resin is likely to occur. There is a high possibility of causing thermal deterioration of the synthetic resin portion that insulates the commutator pieces of the commutator from each other. In particular, commutator motors used in electric blowers for vacuum cleaners tend to be smaller and have higher input, and the current density of the carbon brushes increases accordingly.
Therefore, if the carbon brush has a high resistance, the heat generated by the carbon brush tends to be extremely large, and the life of the carbon brush and the commutator is shortened. By the way, it is known that the conventional resin-binding type carbon brush has a sharp decrease in transverse rupture strength when the temperature thereof exceeds 200 ° C.

Therefore, the inventor of the present invention extends an electric conductor formed by solidifying powder having a resistivity lower than that of a brush main portion made of a material having the highest resistivity to the brush main portion in the main current direction. I first proposed a carbon brush embedded with it. The electric conductor is made of a low-resistance copper powder, which extends in the main current direction and is packed in a hole formed in the brush main part and hardened. According to this carbon brush, since the total electric resistance can be reduced, resistance loss and heat generation in the carbon brush can be reduced.

However, in such a carbon brush, the size of the cross section of the hole formed in the brush main part in the direction orthogonal to the main current direction does not change, and each part is formed with the same cross section.

Therefore, there is a problem that the workability at the time of embedding the electric conductor in the brush main portion is not good by filling the hole with the low-resistance copper powder and solidifying it. Furthermore, due to the structure of the hole, it is difficult to sufficiently spread the tamping force to the tip side of the hole, and the tampering strength of the electric conductor is weaker toward the tip side of the hole. Therefore, in combination with the structure of the hole, after the electric conductor is exposed on the tip end surface of the carbon brush by use, the electric conductor is formed with the vibration of the carbon brush due to the sliding contact with the commutator. There is a problem that the powder collapses and easily escapes to the outside through the gaps between the commutator pieces of the commutator, resulting in deterioration of the function of the electric conductor.

The object of the present invention is not only to reduce the resistance loss, but also to improve the life of the commutator together with the commutator, and it is easy to manufacture, and the powder material forming the electric conductor is prevented from coming out to the outside during use. To get a carbon brush that can.

[0009]

In order to achieve the above-mentioned object, the carbon brush of the present invention has a different resistance because the substantially entire length of the portion which is worn by contacting the commutator extends in the main current direction.
In a carbon brush formed of more than one kind of material, a tapered taper hole is formed in the wear portion over substantially the entire length of the main current direction in the direction of the commutator side, and the hole has a higher resistivity than the material having the highest resistivity. In addition, an electric conductor made of a material having a low resistivity is embedded, and the electric conductor is packed in the hole and formed by a powdered material.

[0010]

In the structure of the carbon brush, since the electric conductor having the lower resistivity than the material having the highest resistivity is extended and embedded in the main current direction, the total electrical resistance of the carbon brush can be reduced. In addition, since the electric conductor is smaller than the brush main part made of the material having the highest resistivity, the rectification resistance is significantly reduced compared to the case where the entire carbon brush is made of the low resistance electric conductor. In addition, because the carbon brush has a low total electrical resistance as described above, use a material with good sitability for the commutator (characteristic that the carbon brush keeps contact with the commutator surface) in the brush main part. Therefore, it is possible to reduce the occurrence of sparks between the commutator.

Moreover, since the hole in which the electric conductor is buried over substantially the entire length in the main current direction is tapered so that it becomes thinner toward the commutator side, the inlet when the powder material forming the electric conductor is packed in the hole is It becomes wider and the powder material can be easily put into the hole. In addition, when the powder material is packed in the hole and solidified, the powder material is pushed toward the gradually narrowing side, so that the powder material can be sufficiently solidified even at the tip side of the hole. After the electric conductor is exposed on the tip end surface of the carbon brush due to use, the hole has a tapered taper shape, and thus this hole becomes a great resistance against the movement of the electric conductor toward the commutator side. As described above, since the powder material forming the electric conductor is sufficiently compacted up to the tip portion thereof, it is possible to reduce the collapse of the electric conductor in the hole.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. In FIG. 3, reference numeral 1 is a metal electric motor case, which is composed of a case body 2 and a case end plate 3.

The case body 2 is formed by opening a cylindrical portion 4 having a bottom 4a on the side opposite to the bottom 4a, and integrally mounting a mounting portion 5 on the peripheral portion of the opening. The mounting part 5 is
It is formed by the annular flat surface portion 6, the tubular portion 7, and the projecting edge 8. The annular flat surface portion 6 is formed by integrally protruding from the opening edge of the case body 2 toward the outside of the body 2, and the tubular portion 7 is formed.
Is bent from the outer periphery of the annular flat surface portion 6 toward the bottom 4a side and is formed parallel to the case body 2, and the projecting edge 8 is formed by bending at a right angle from the tip of the tubular portion 7 toward the outside. .. An exhaust hole 9 is provided on the bottom plate 4a side of the cylindrical portion 4, and an exhaust hole (not shown) is also provided on the bottom plate 4a. A bearing mounting portion 11 accommodating the bearing 10 is formed in the center of the bottom plate 4a.

The case end plate 3 has, for example, a substantially band plate shape whose plane shape extends in the radial direction so as to traverse the one end opening of the case main body 2 in the radial direction, and a bearing in which the bearing 12 is housed in the central portion thereof. The mounting portion 13 is integrally formed. Both ends of the case end plate 3 are screwed to the annular flat surface portion 6. Therefore, the one end opening of the case body 2 is partially opened without being completely closed.

A stator 14 and a rotor 16 with a commutator 15 disposed inside the stator 14 are housed in the case body 2. The stator core of the stator 14 has a substantially quadrangular outer diameter when viewed from the axial direction, and the four chamfered corners thereof are fixed to the case body 2 while being in close contact with the inner surface of the cylindrical portion 4. Due to this fixing, air passages 19 are formed between the inner surface of the cylindrical portion 4 and the outer surface of the stator core. Rotor 16
The rotor shaft 17 is supported rotatably by the bearings 10 and 12, and the rotor shaft 17 penetrates the bearing 12 and the bearing mounting portion 13.

The commutator 15 is located on the bearing 10 side and is fixed to the rotor shaft 17. The commutator 15 includes a boss portion 15a made of synthetic resin that rotates integrally with the rotor shaft 17,
A large number of commutator pieces 15b are provided on the outer periphery of the boss portion 15a and are spaced apart in the circumferential direction. The terminals of the rotor winding are electrically connected to these commutator pieces 15b.

Brush devices 18 on the positive electrode side and the brush devices 18 on the negative electrode side are attached to the cylindrical portion 4 of the case body 2 with a commutator 15 interposed therebetween. The details of these brush devices 18 will be described below with reference to FIGS. 1 and 2. ..

A brush holder 21 provided in the brush device 18.
Is made of an electrically insulating material such as synthetic resin, and the main body 22 has an insertion hole 23 and has a substantially rectangular tube shape.
The main body 22 includes a support piece 24 that overlaps the outer surface of the case main body 2.
Are projected integrally. As shown in FIG. 3, the brush boulder 21 has a mounting opening 4 b for opening the main body 22 into the cylindrical portion 4.
It is fixed to the case body 2 by inserting the support piece 24 into the cylindrical portion 4 with the screw 26 and tightening the support piece 24 with the screw 26.

A brush guide 27 made of metal is fitted in the insertion hole 23 of the brush holder 21. The brush guide 27 projects from the main body 22 toward the commutator 15. At the end of the guide 27 on the side opposite to the commutator 15, a retaining piece 28 that is hooked at the opening edge of the insertion hole 23 is bent, and the main body portion 2 of the brush guide 27 is provided.
A cut-and-raised piece 25 that hooks on the end surface of the main body portion 22 is formed at the root portion protruding from 2. The cut-and-raised piece 25 fixes the brush guide 27 to the brush holder 21 by sandwiching the main body portion 22 with the retaining piece 28.

The main body 22 of the brush holder 21 has a terminal mounting hole 29. The mounting hole 29 is used as the insertion hole 2
3 is provided substantially in parallel with 3, and a terminal fitting 30 for supplying a current is attached inside thereof.

The terminal fitting 30 is made of sheet metal and has an insertion hole 2
3, a cap piece 31 for covering the open end of 3, and a terminal mounting hole 29.
It integrally has a retaining piece 32 that is inserted into the. The retaining piece 32 includes a convex portion 33 curved in an arc shape in section.
And an elastically deformable bent portion 34 that is bent into a mountain shape continuously from the protruding portion 33, and the tops of the protruding portion 33 and the bent portion 34 are pressed against the inner surface of the terminal mounting hole 29. Has been.

The tip of the bent portion 34 has a terminal mounting hole 29.
From the inside to the inside of the body case 2, and the protruding portion 34
A locking piece 35 hooked to the end surface of the main body 22 is integrally cut and raised at a. This locking piece 35 is a cap piece 3.
The main body 22 is sandwiched between the terminal fitting 1 and the terminal 1 to prevent the terminal fitting 30 from coming off from the terminal mounting hole 29. Protruding portion 34a
Is a terminal block 3 attached to the stator core of the stator 14.
It is adapted to be inserted into a connecting terminal (not shown) of No. 6 and to be connected to the stator winding through this terminal.

Inside the brush guide 27, a rod-shaped carbon brush 41 whose cross section in the direction perpendicular to the axis is generally quadrangular is accommodated so as to be movable in the axial direction. At least a portion of the brush 41 that is in contact with the commutator 15 and is worn (a portion of the effective use length A shown in FIG. 1) is the brush main portion 4
2 and an electric conductor 43 embedded in the main portion 42 so as to extend substantially parallel to the direction in which the main current flows. The brush main portion 42 is formed by sintering a material obtained by compression-molding a conductive material containing carbon as a main component together with a binder made of synthetic resin.

A hole 44 is provided in, for example, the central portion of the brush main portion 42 over substantially the entire length in the axial direction (that is, extends over the entire length in the main current direction of the brush main portion 42). The hole 44 has a tapered shape that gradually becomes thinner toward the commutator 15 side. For example, the total length B of the hole 44 is 23 m
m, the inlet diameter C of the hole 44 is about 2.5 mm, the hole 4
4 has a tip diameter D of about 1.5 mm.

The electric conductor 43 is formed by filling a powder material having a resistivity lower than that of the conductive material forming the brush main portion 42, for example, copper powder, into the hole 44 and compacting the same. .. Therefore, the electric conductor 43 is in direct contact with the brush main portion 42. In this embodiment, in order to further reduce the resistivity of the electric conductor 43, the copper powder used is silver-plated.

The diameter of this electric conductor 43 is equal to that of the brush main portion 42.
It is smaller than the vertical and horizontal dimensions of the cross section. The end surface of the electric conductor 43 disposed inside the brush main portion 42 on the side of the commutator 15 is covered by the tip end portion 42a of the brush main portion 42 in the initial use of the carbon brush 41 as shown in FIG.

One end of a pigtail 45 is connected to the carbon brush 41. That is, one end of the pigtail 45 is inserted into the inlet-side end of the hole 44, and is fixed by the copper powder packed around it. In order to ensure this fixing, the powder portion surrounding one end of the pigtail 45 is soaked with a liquid adhesive and cured. Therefore, the pigtail 45
The connection is made by first tamping the copper powder packed in the hole 44 leaving the inlet side end, and then inserting the one end of the pigtail 45 into the inlet side end and filling the copper powder. Then tamper with this powder, and finally in the hole 44
It is done by soaking the liquid adhesive from the outside into the entrance of the. The other end of the pigtail 45 is the insertion port 2
It is spot-welded to the cap piece 31 that closes the open end of No. 3.

A compression coil spring 46 is interposed between the other end surface of the carbon brush 41 and the cap piece 31 closing the opening end of the insertion hole 23. Compression coil spring 46
Always presses the carbon brush 41 toward the commutator 15. By this pressing, the commutator 1 of the carbon brush 41
The end on the fifth side projects from the brush guide 27, and the commutator 15
Is slidably pressed against the outer peripheral surface of the. The motor case 1, the bearings 10, 12, the stator 14, which have been described above,
A commutator motor is formed by the rotor 16 and the brush device 18.

As shown in FIG. 1, a centrifugal fan 52 that rotates integrally with the rotor shaft 17 is attached to the end of the rotor shaft 17 that protrudes from the motor case 1 via a nut 51. The fan 52 has a suction port 53 in the central portion and a discharge port 54 in the peripheral portion. The centrifugal fan 52 is covered with a fan cover 55. The cover 55 is fitted and mounted on the mounting portion 5 of the main body case 2, and the fan cover 55 has an opening 56 for sucking air. Opening 56
Has entered the suction port 53.

Therefore, when the centrifugal fan 52 is rotated, air is sucked through the opening 56, and the sucked air is discharged from the discharge port 54 of the centrifugal fan 52. Between the centrifugal fan 52 and the mounting portion 5, a centrifugal fan 52
Straightening plate 5 that guides the air discharged from the inside of the motor case 1
7 is provided. The rectifying plate 57 rectifies the air discharged from the centrifugal fan 52 and at the same time rectifies the pressure of the air from dynamic pressure to static pressure, and is screwed to the frame end plate 3. The air rectified by the rectifying plate 57 flows into the motor case 1 and flows through the air passage 19 and then from the exhaust port 9 to the motor case 1.
Is discharged to the outside.

In the electric blower having the above-described structure, the electric current flowing between the commutator piece 15b of the commutator 15 and the pigtail 45 during its operation is the electric conductor 4 of the carbon brush 41.
3 mainly flows. In this way, the carbon brush 41
However, since the electric conductor 43 having an electric resistance smaller than that of the brush main portion 42 containing carbon as a main component is embedded in the brush main portion 42 over substantially the entire length thereof, the total electric resistance of the carbon brush 41 can be reduced. By the way, the total electric resistance of the carbon brush 41 in this embodiment is about 0.0.
It was 5Ω, which was about 1/4 of the conventional value. Therefore, the resistance loss of the current in the carbon brush 41 can be reduced, and the operating efficiency of the commutator motor for the electric blower can be improved accordingly.

Since the total electrical resistance of the carbon brush 41 can be reduced as described above, the heat generation of the brush 41 can be reduced. In addition, the occurrence of sparks between the carbon brush 41 and the commutator 15 can be reduced for the following reasons.

First, since the electric conductor 43 is embedded in the brush main body 42, the diameter of the conductor 43 is naturally smaller than the vertical and horizontal dimensions of the cross section of the brush main portion 42. The number of electric conductors 43 is smaller than that of the main portion 42, and the electric conductor 43 on the contact surface with the commutator 15
Is smaller than the cross-sectional area of the brush main part 42. Therefore, compared with the case where the entire carbon brush 41 is made of an electric conductor having a low resistance, the rectification resistance is not significantly reduced, so that the short-circuit current during rectification can be reduced. Secondly, since the carbon brush 41 as a whole has a low electric resistance as described above, the brush main portion 42 can be made of a material having a good sitting property, for example, a resin binding type conductive material. Thereby, the elastic coefficient of the entire carbon brush 41 can be lowered.

That is, as described above, the carbon brush 4
Since the amount of heat generated by 1 itself is small and the amount of heat generated by sparks is small, the temperatures of the carbon brush 41 and the commutator 15 can be suppressed low.

Therefore, the thermal deterioration of the carbon brush 41 and the commutator 15 can be prevented, so that the life of the carbon brush 41 and the commutator 15 can be extended, and the commutator motor is suitable for high input and downsizing. Moreover, since the temperature rises of the carbon brush 41 and the commutator 15 are small as described above, the carbon brush 41 can be made smaller accordingly, and
The axial length of the commutator 15 can be reduced. Therefore, the length of the rotor shaft 17 can be shortened, and accordingly, the entire electric blower can be downsized in the axial direction.

Moreover, the carbon brush 4 at the time of use
Since damage to the brush main portion 42 due to heat generation of No. 1 is prevented for the following reason, the life of the commutator motor, which is generally defined by the life of the carbon brush 41, can be improved.

In the initial use of the carbon brush 41, the tip 42a of the brush main portion 42 covers the end of the electric conductor 43 on the commutator side, so that the contact of the carbon brush 41 with the commutator 15 is prevented. The brush main portion 42 and the electric conductor 43, which have different physical properties in the unfamiliar state, have the commutator 1
No sliding contact with 5. Therefore, the initial performance is stable, and the carbon brush 41 to the commutator 15 is
The brush main portion 42 and the electric conductor 43 can be brought into sliding contact with the commutator 15 in a state in which the contact is familiar.

In addition, since the hole 44 at the tip portion 42a of the brush main portion 42 forms the bottom, it is easy to fill the hole 44 with the copper powder which becomes the electric conductor 43. In addition, since the hole 44 has a tapered shape that gradually becomes thinner toward the commutator 15, the electrical conductor 4
The inlet for filling the hole 44 with the copper powder forming No. 3 is wide, and the hole 44 can be easily filled with the copper powder. further,
When the copper powder is packed in the hole 44 and tamped, the copper powder is pushed toward the gradually narrowing of the hole 44.
The copper powder can be hardened sufficiently on the tip side of
Therefore, the tamping strength of the electric conductor 43 can be increased even at the tip portion thereof. In this way, the workability of embedding the electric conductor 43 in the brush main portion 42 can be improved.

After the electric conductor 43 is exposed on the tip surface of the carbon brush 41 by use, the hole 44 is formed.
Is tapered, the taper of the hole 44 becomes a large resistance when the electric conductor 43 tries to move to the tip side (commutator 15 side) thereof. In addition, as described above, since the copper powder forming the electric conductor 43 is sufficiently hardened to the tip portion thereof, the electric conductor 43 is less likely to collapse.

Therefore, by using the carbon brush 4
After the electric conductor 43 is exposed on the tip end surface of the No. 1, regardless of the vibration of the carbon brush 41 caused by the sliding contact with the commutator 15, the copper powder forming the electric conductor 43 is
It is possible to reduce the possibility that the commutator pieces 15a will not come out through the gap between the commutator pieces 15a, and the intended function of the electric conductor 43 can be maintained.

Of course, since the electric conductor 43 is embedded in the brush main portion 42 and surrounded by the brush main portion 42, the reliability of holding the electric conductor 43 is improved and the commutator 1 is provided.
It is possible to prevent the electric conductor 43 from being peeled off from the brush main portion 42 regardless of an external force or the like that is caused by sliding contact with the brush 5.

Moreover, since the electric conductor 43 is in direct contact with the brush main portion 42, the abrasion of the carbon brush 41 causes the brush main portion 42 and the electric conductor 43 to come into sliding contact with the commutator 15. The abrasion powder generated at this time does not include a substance that obstructs the flow of current between the carbon brush 41 and the commutator piece 5b. By the way, in the structure in which the electric conductor 43 is adhered to the brush main portion 42 using the adhesive, electric resistance is generated due to the abrasion powder of the adhesive, but such a problem does not occur in the carbon brush 41 having the above structure.

The present invention is not limited to the above embodiment. For example, the electric conductor 43 is not limited to copper powder,
Due to the difference in contained components, the density, and the manufacturing method, a carbon powder having an electric resistance smaller than that of the carbon forming the brush main portion 42 may be adopted, and a powder such as silver or gold may be used. Good. Further, in the present invention, two or more kinds of materials having different resistivities may be formed, and the cross-sectional shape of the low-resistance electric conductor for reducing the electric resistance of the entire brush therein is round, square or triangular. Etc., any shape may be used, and in that case, the vertical and horizontal dimensions of the cross section refer to the maximum vertical and horizontal dimensions of the entire cross section of the brush. Further, in the above-mentioned one embodiment, although the pigtail is connected, a carbon brush such as a commutator motor having a brush device for pressing the carbon brush against the commutator with a conductive leaf spring which does not have a pigtail and serves as a current path is provided. Can also be applied.

[0044]

In the structure of the carbon brush of the present invention described in detail above, since the electric conductor is embedded over substantially the entire length in the main current direction to reduce the total electric resistance, the operating efficiency of a commutator motor or the like using this carbon brush is reduced. The temperature rise of the carbon brush is suppressed, and the carbon brush itself and the commutator motor that uses the carbon brush are suppressed because the heat generation by the current and the generation of sparks with the commutator can be reduced. The life of can be improved. Since the hole in which the electric conductor is embedded has a tapered shape that becomes gradually thinner toward the commutator side, the workability of filling the hole with the powder material forming the electric conductor is improved and the manufacturability can be improved. After the electric conductor is exposed on the tip end surface of the carbon brush by use, the powder material is rarely extracted to the commutator side, so that the desired function of the electric conductor can be maintained.

[Brief description of drawings]

FIG. 1 is a vertical sectional side view of a brush device including a carbon brush according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line ZZ of FIG. 1 according to the embodiment.

3 is a side view showing an electric blower provided with the brush device shown in FIG. 1 in a partial cross section.

[Explanation of symbols]

15 ... commutator, 41 ... carbon brush, 42 ... brush main part, 43 ... electric conductor, 44 ... hole.

Claims (1)

[Claims] 1. A carbon brush made of two or more kinds of materials having different resistivities, which extend in the main current direction so that substantially the entire length of the wear portion in contact with the commutator is in the main current direction in the wear portion. A tapered taper hole that tapers off toward the commutator side is provided over substantially the entire length, and an electric conductor made of a material having a lower resistivity than the material having the highest resistivity is embedded in this hole, and the electric conductor is placed in the hole. A carbon brush characterized by being formed of a powder material packed and hardened.