JP2599232B2 - Carbon brush - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Carbon brushes used for commutator motors and the like are formed by compressing and solidifying carbon as a main component using a binder and baking at a high temperature. Has been adopted. For example, a conventional carbon brush used for an electric blower of a vacuum cleaner is formed mainly of a single type of carbon. In addition, it is necessary to increase resistance rectification in order to reduce the occurrence of sparks due to the sliding contact between the brush and the commutator. Carbon having a high resistance value of 30,000 μΩ or more per cm has been employed. Therefore, when a plurality of commutator pieces of the commutator come into contact with the tip end surface of the carbon brush, the current value for short-circuiting between the commutator pieces through the carbon brush is reduced, 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 of this brush is large (about 20 W per carbon brush). ), There is a problem that the operating efficiency of a commutator motor or the like using this carbon brush is reduced.

At the same time, since the loss is converted into heat generated by the carbon brush, for example, in a resin-bound type carbon brush using a synthetic resin as a carbon binder, thermal deterioration of the resin is easily caused, and There is a high possibility that the synthetic resin portion that insulates the commutator pieces of the commutator will deteriorate thermally. In particular, commutator motors used in electric blowers for vacuum cleaners tend to be smaller and have higher power, and the current density of carbon brushes increases accordingly.
Therefore, when the carbon brush has a high resistance, the heat generation tends to be extremely large, and the life of the carbon brush and the commutator is shortened. By the way, it is known that a conventional resin-bound type carbon brush rapidly lowers the transverse rupture strength when its temperature exceeds 200 ° C.

Accordingly, the present inventor has proposed that an electric conductor formed by solidifying powder having a lower resistivity than that of a brush main portion made of a material having the highest resistivity is extended in the main current direction of the brush main portion. I proposed the carbon brush embedded earlier. The electric conductor is made of a low-resistance copper powder, which extends in the direction of the main current and is solidified in a hole formed in the main part of the brush. 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 main portion of the brush in the direction perpendicular to the main current direction does not change, and each portion is formed in the same cross section.

[0007] Therefore, there is a problem that the workability of embedding the electric conductor in the main part of the brush is not good by filling the holes with low-resistance copper powder and squeezing them. In addition, due to the configuration of the hole, it is difficult to sufficiently spread the tamping force to the tip end of the hole, and the tamping strength of the electric conductor is weaker toward the tip end of the hole. Therefore, in combination with the configuration of the hole, after the electric conductor is exposed at the tip end surface of the carbon brush by use, the vibration of the carbon brush accompanying the sliding contact with the commutator causes There is a problem that the powder is easily broken and escapes to the outside through the gap between the commutator pieces of the commutator, and the function of the electric conductor is reduced.

[0008] It is an object of the present invention to reduce not only the resistance loss, but also to improve the life together with the commutator, and it is easy to manufacture, and the leakage of the powder material constituting the electric conductor during use is reduced. It is to obtain a carbon brush that can be used.

[0009]

According to the present invention, there is provided a carbon brush according to the present invention, wherein substantially the entire length of a portion worn in contact with a commutator extends in a main current direction and has a different resistivity.
In a carbon brush formed of more than one kind of material, a tapered tapered hole that gradually becomes thinner toward the commutator side over the substantially entire length in the main current direction is provided in the worn portion, and this hole is made of a material having the highest resistivity. Also, an electric conductor made of a material having a low resistivity is embedded, and the electric conductor is formed of a powdered material which is packed in the hole and solidified.

[0010]

In the structure of the carbon brush, an electric conductor having a lower resistivity than that of the material having the highest resistivity is buried in the direction of the main current so as to be embedded, so that the total electric resistance of the carbon brush can be reduced. In addition, since the electric conductor is smaller than the main part of the brush made of the material with the highest resistivity, the rectification resistance is significantly reduced as compared with the case where the entire carbon brush is made of a low-resistance electric conductor. In addition to the above, because the total electrical resistance of the carbon brush is small as described above, use a material with good seating properties for the commutator (the property that the carbon brush keeps contact with the commutator surface) in the main part of the brush. Therefore, the occurrence of sparks with the commutator can be reduced.

In addition, since the hole in which the electric conductor is embedded over substantially the entire length in the main current direction is formed into a tapered tapered shape that becomes gradually thinner toward the commutator, an entrance for filling the powder material forming the electric conductor into the hole is provided. It becomes wider, and the powder material can be easily put in the hole. In addition, when the powder material is stuffed into the hole and squeezed, the powder material is pushed in a gradually narrowing direction, so that the powder material can be sufficiently hardened even on the tip side of the hole. After the electric conductor is exposed on the tip end surface of the carbon brush by use, the hole has a tapered shape, so that this hole becomes a large resistance to the movement of the electric conductor to the commutator side, as described above. As described above, the powder material forming the electric conductor is sufficiently squeezed even to the tip, so that the collapse of the electric conductor in the hole can be reduced.

[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 denotes a metal motor case, which is formed of a case main body 2 and a case end plate 3.

The case main body 2 is formed by opening a cylindrical portion 4 having a bottom 4a on the side opposite to the bottom 4a, and integrally providing a mounting portion 5 at a peripheral portion of the opening. The mounting part 5
It is formed by an annular flat portion 6, a cylindrical portion 7, and a protruding edge 8. The annular flat portion 6 is formed integrally from the opening edge of the case main body 2 so as to protrude outward from the main body 2, and is formed into a cylindrical portion 7.
Is bent from the outer periphery of the annular flat portion 6 toward the bottom 4a to be formed parallel to the case body 2, and the protruding edge 8 is formed to be bent at a right angle outward from the tip of the cylindrical portion 7. . 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. At the center of the bottom plate 4a, a bearing mounting portion 11 that houses the bearing 10 is formed.

The case end plate 3 has, for example, a substantially strip shape extending in the radial direction so as to cross the one end opening of the case body 2 in the radial direction, and has a bearing 12 in the center thereof. The attachment portion 13 is formed integrally. Both ends of the case end plate 3 are screwed to the annular flat portion 6. For this reason, one end opening of the case main body 2 is partially opened without being completely closed.

In the case body 2, a stator 14 and a rotor 16 with a commutator 15 disposed inside the stator 14 are housed. The outer diameter of the stator core of the stator 14 when viewed from the axial direction is substantially square, and the four chamfered corners are fixed to the case body 2 so as to be in close contact with the inner surface of the cylindrical portion 4. Due to this fixation, air passages 19 are respectively 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 rotatably provided with the rotor shaft 17 supported by the bearings 10 and 12, and the rotor shaft 17 passes through 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 15 a 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 15a at intervals in the circumferential direction. The ends of the rotor windings are electrically connected to these commutator pieces 15b.

A brush device 18 on the positive electrode side and a brush device 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 the brush devices 18 will be described below with reference to FIGS. .

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

A metal brush guide 27 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 opposite to the commutator 15, a retaining piece 28 that is hooked on the opening edge of the insertion hole 23 is bent, and the main body 2 of the brush guide 27 is bent.
A cut-and-raised piece 25 that hooks on the end face of the main body 22 is formed at the base protruding from the base 2. The cut-and-raised piece 25 fixes the brush guide 27 to the brush holder 21 with the main body 22 interposed between the piece 25 and the retaining piece 28.

The main body 22 of the brush holder 21 has a terminal mounting hole 29. The mounting hole 29 is provided in the insertion hole 2
3, and a terminal metal fitting 30 for current supply is mounted inside thereof.

The terminal fitting 30 is made of sheet metal, and
3 and a terminal attachment hole 29
And the stopper piece 32 to be inserted into the body. The retaining piece 32 has a convex portion 33 curved in an arc-shaped cross section.
An elastically deformable bent portion 34 is formed continuous with the convex portion 33 and bent into a mountain shape. The convex portion 33 and the top of the bent portion 34 are pressed against the inner surface of the terminal mounting hole 29. Have been.

The distal end of the bent portion 34 is
From the main body case 2 and projecting portions 34
A locking piece 35 that hooks on the end face of the main body 22 is integrally cut and raised in a. The locking piece 35 is a cap piece 3
The terminal fitting 30 is prevented from coming out of the terminal mounting hole 29 with the main body 22 interposed therebetween. Projection 34a
Is the terminal block 3 attached to the stator core of the stator 14.
6 is connected to a stator winding via this terminal (not shown).

Inside the brush guide 27, a rod-shaped carbon brush 41 whose cross section in the direction perpendicular to the axis is substantially square in its entirety is housed so as to be movable in the axial direction. At least a portion of the brush 41 that is worn in contact with the commutator 15 (a portion of the effective use length A shown in FIG. 1) is the brush main portion 4.
2 and an electric conductor 43 buried in the main portion 42 so as to extend substantially parallel to the direction in which the main current flows. The brush main part 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.

At the center of the brush main portion 42, for example, a hole 44 is provided substantially over the entire length in the axial direction (that is, extending substantially over the entire length in the main current direction of the brush main portion 42). The hole 44 has a tapered shape gradually tapering toward the commutator 15. 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,
4 has a tip diameter D of about 1.5 mm.

The electric conductor 43 is formed by packing 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 squeezing it. . Therefore, the electric conductor 43 is in direct contact with the brush main part 42. In this embodiment, in order to further reduce the resistivity of the electric conductor 43, the copper powder used is plated with silver.

The diameter of this electric conductor 43 is
Are smaller than the vertical and horizontal dimensions of the cross section. The end face of the electric conductor 43 on the commutator 15 side arranged inside the brush main part 42 is covered with the tip part 42a of the brush main part 42 at the initial stage of using 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 end of the hole 44 on the entrance side, and is fixed by the copper powder packed around the end. To ensure this fixation, the powder portion surrounding one end of the pigtail 45 is hardened by impregnating a liquid adhesive. Therefore, pigtail 45
First, after squeezing the filled copper powder into the hole 44 while leaving the inlet end thereof, insert one end of the pigtail 45 into the inlet end and fill the copper powder with the copper powder. And squeeze this powder, and finally,
It is performed by injecting a liquid adhesive from the outside into the entrance. The other end of the pigtail 45 is the insertion port 2
3 is spot-welded to the cap piece 31 which closes the open end.

A compression coil spring 46 is interposed between the other end surface of the carbon brush 41 and the cap piece 31 that covers the opening end of the insertion opening 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 protrudes from the brush guide 27, and the commutator 15
Is slidably pressed against the outer peripheral surface of the first member. The motor case 1, the bearings 10, 12, the stator 14,
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 via a nut 51 is attached to an end of the rotor shaft 17 that protrudes outside the motor case 1. The fan 52 has a suction port 53 at the center and a discharge port 54 at the periphery. 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. A centrifugal fan 52 is provided between the centrifugal fan 52 and the mounting portion 5.
Rectifier plate 5 that guides the air discharged from the motor into motor case 1
7 are provided. The rectifying plate 57 rectifies the air discharged from the centrifugal fan 52 and changes the pressure of the air from the dynamic pressure to the static pressure in the rectifying process, and is screwed to the frame end plate 3. The air rectified by the rectifying plate 57 flows into the motor case 1, flows through the air passage 19, and then flows from the exhaust port 9 to the motor case 1.
Is discharged to the outside.

In the electric blower constructed as described above, the current flowing between the commutator piece 15b of the commutator 15 and the pigtail 45 during operation thereof is controlled by the electric conductor 4 of the carbon brush 41.
3 flows mainly. Thus, the carbon brush 41
However, since the electric conductor 43 having a smaller electric resistance than the brush main portion 42 mainly containing carbon 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. Incidentally, the total electric resistance of the carbon brush 41 in this embodiment is approximately 0.0
5Ω, which is about 1/4 of the conventional value. For this reason, 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.

As described above, since the total electrical resistance of the carbon brush 41 can be reduced, the heat generated by 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 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 part 42. The number of the electric conductors 43 on the contact surface with the commutator 15 is smaller than that of the main portion 42.
Is smaller than the cross-sectional area of the brush main part 42. Therefore, the rectification resistance does not significantly decrease as compared with the case where the entire carbon brush 41 is made of a low-resistance electric conductor, so that the short-circuit current during rectification can be reduced. Second, since the electric resistance of the entire carbon brush 41 is small as described above, the brush main portion 42 can be made of a material having good seating properties, for example, a resin-bound type conductive material. Thus, the elastic coefficient of the entire carbon brush 41 can be reduced.

That is, as described above, the carbon brush 4
Since the heat generation of 1 itself is small and the heating by spark is also small, the temperatures of the carbon brush 41 and the commutator 15 can be suppressed low.

Therefore, since the carbon brush 41 and the commutator 15 can be prevented from being thermally degraded, their life can be improved and the commutator motor is suitable for high input and small size. In addition, since the temperature rise of the carbon brush 41 and the commutator 15 is small as described above, the size of the carbon brush 41 can be reduced accordingly.
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 is used.
Since the damage of the brush main part 42 due to the heat generation 1 is prevented for the following reasons, the life of the commutator motor generally defined by the life of the carbon brush 41 can be improved.

In the initial stage of 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. When the brush main part 42 and the electric conductor 43 having different physical properties are not combined with each other,
No sliding contact with 5. Therefore, the initial performance is stable, and the carbon brush 41
The brush main part 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 forms the bottom of the tip portion 42a of the brush main portion 42, it is easy to fill the hole 44 with copper powder to be the electric conductor 43. In addition, since the hole 44 has a tapered shape that gradually narrows toward the commutator 15, the electric conductor 4
The entrance when the copper powder forming the third material is packed in the hole 44 is widened, so that the copper powder can be easily filled into the hole 44. further,
When the copper powder is packed in the hole 44 and squeezed, the copper powder is pushed into the hole 44 gradually narrowing.
The copper powder can be hardened sufficiently even on the tip side of
Therefore, the compacting strength of the electric conductor 43 can be increased even at the tip end. Thus, the workability of embedding the electric conductor 43 in the brush main part 42 can be improved.

After the electric conductor 43 is exposed on the tip end surface of the carbon brush 41 by use, a 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). In addition, as described above, since the copper powder forming the electric conductor 43 is sufficiently squeezed even to the tip, the electric conductor 43 is less likely to collapse.

Therefore, depending on the use, the carbon brush 4
After the electric conductor 43 is exposed on the end face of the commutator 15, 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 removed by the commutator 15.
Of the electric conductor 43 can be reduced, and the desired function of the electric conductor 43 can be maintained.

Of course, the electric conductor 43 is embedded in the brush main part 42 and is surrounded by the brush main part 42, so that the reliability of holding the electric conductor 43 is improved and the commutator 1
The electric conductor 43 can be prevented from peeling off from the brush main part 42 regardless of an external force or the like acting on the sliding contact with the brush 5.

Further, since the electric conductor 43 is directly in close contact with the brush main portion 42, the brush main portion 42 and the electric conductor 43 both come into sliding contact with the commutator 15 due to the wear of the carbon brush 41. The abrasion powder generated at this time does not include a substance that impedes the flow of current between the carbon brush 41 and the commutator piece 5b. Incidentally, in a configuration in which the electric conductor 43 is bonded to the brush main portion 42 using an adhesive, electrical resistance is generated due to abrasion powder of the adhesive, but such a problem does not occur in the carbon brush 41 having the above configuration.

The present invention is not limited to the above embodiment. For example, the electric conductor 43 is not limited to copper powder,
Depending on the difference of the components, the density, and the manufacturing method, a carbon powder having a smaller electric resistance than the carbon constituting the brush main portion 42 may be used, and a powder of silver or gold may be used. Good. In the present invention, two or more materials having different resistivity may be formed, and the cross-sectional shape of the low-resistance electric conductor for lowering the electric resistance of the whole brush is circular, square, triangular. In this case, the vertical and horizontal dimensions of the cross section indicate the maximum vertical and horizontal dimensions of the cross section of the entire brush. Further, in the above-described embodiment, the pigtail is connected, but the pigtail has no brush tail and a conductive plate spring serving as a current path is used to press the carbon brush against the commutator. Can also be applied.

[0044]

In the structure of the carbon brush of the present invention described in detail above, since the electric resistance is reduced by embedding the electric conductor over substantially the entire length in the main current direction, the operating efficiency of a commutator motor or the like using this carbon brush is reduced. In addition, heat generation due to current can be reduced and spark generation between the commutator can be reduced, so that the temperature rise of the carbon brush is suppressed, and the carbon brush itself and a commutator motor using the same are used. Life can be improved. And, since the hole in which the electric conductor is embedded is formed into a tapered taper shape that gradually becomes narrower toward the commutator side, the workability of filling the powder material forming the electric conductor into the hole can be improved, and the productivity can be improved. After the electric conductor is exposed on the tip surface of the carbon brush by use, the powder material is less likely to be drawn out to the commutator side, so that the desired function of the electric conductor can be maintained.

[Brief description of the drawings]

FIG. 1 is a vertical sectional side view of a brush device provided with a carbon brush according to one embodiment of the present invention.

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

FIG. 3 is a side view showing a partially sectioned electric blower provided with the brush device shown in FIG. 1;

[Explanation of symbols]

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

 ──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-54-154009 (JP, A) JP-A-57-201068 (JP, U) JP-A-4-88363 (JP, U)

Claims (1)

(57) [Claims] In a carbon brush formed of two or more materials having different resistivity from each other, a substantially entire length of a portion to be worn in contact with a commutator extends in a main current direction, and the worn portion has a main current direction. A tapered tapered hole that gradually becomes thinner toward the commutator side over substantially the entire length is provided, and an electric conductor made of a material having a lower resistivity than the material having the highest resistivity is embedded in the hole, and the electric conductor is inserted into the hole. A carbon brush characterized by being formed from a stuffed and hardened powder material.