JP2001136710A - Structure and method for removing commutator in armature for electric motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor capable of reducing voltage drop between a brush and a commutator, while restraining increase in frictional force therebetween. SOLUTION: A plurality lines of grooves 9b, extending in roughly peripheral direction are formed in a range, where a brush 8 comes into sliding contact with the outer periphery 9a of a commutator 9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor having a brush.

[0002]

2. Description of the Related Art In a motor of this type, it is known that a voltage drop occurs at a contact portion between a brush and a commutator (commutator piece). This is because as long as the motor is used in the atmosphere, the commutator surface will be covered with an oxide film or other contaminant film. Therefore, the contact area between the brush and the commutator decreases, and the contact resistance between the brushes and the commutator increases, so that the above-described voltage drop occurs.

Therefore, as one means for solving the above problem, in a motor using a metallic graphite brush, it is conceivable to increase the copper content in the composition of the brush. In this case, the number of copper particles increases, so that a so-called tunnel effect in which electrons penetrate the coating formed on the commutator surface increases, and the coating is easily broken down electrically. Therefore, the electrical contact area between the brush and the commutator increases, and the voltage drop can be reduced.

As another means, it is conceivable to increase the pressing force of the brush against the commutator. This makes it easier for the brush to mechanically break the film formed on the commutator surface. Therefore, similarly to the above, the electrical contact area between the brush and the commutator increases, and the voltage drop can be reduced.

[0005]

However, when a brush having a high copper content is used, the friction coefficient of the brush increases, and the frictional force between the brush and the commutator increases.
Also, even if the pressing force of the brush against the commutator is increased, the frictional force between the brush and the commutator also increases. Therefore, the increase in the frictional force causes a large loss in the rotational force, which causes new problems such as a decrease in the output of the motor and an increase in the heat generation temperature between the motors.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to reduce the voltage drop between brushes and commutators while suppressing an increase in frictional force. Is to provide.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, an invention according to claim 1 is a motor including a commutator having a plurality of commutator pieces and a brush sliding on an outer peripheral surface of the commutator. In at least the range of the outer peripheral surface of the commutator in which the brush slides,
A plurality of grooves or protrusions extending substantially in the circumferential direction were formed.

According to a second aspect of the present invention, in the motor according to the first aspect, the plurality of grooves or protrusions are formed to meander. According to a third aspect of the present invention, in the motor according to the first aspect, the plurality of grooves or protrusions are formed linearly.

According to a fourth aspect of the present invention, in the motor according to the first aspect, the plurality of grooves or projections are linearly connected to a first groove or first projection formed in a meandering manner. And a second groove or a second protrusion formed in the second groove.

[0010] The invention described in claim 5 is the invention according to claim 2 or 4.
In the motor described in the above, the meandering groove or protrusion,
It was formed in a sine wave shape that changes periodically. Therefore, according to the first aspect of the present invention, the brush partially contacts the outer peripheral surface of the commutator due to the plurality of grooves or protrusions formed on the outer peripheral surface of the commutator. Will be higher. For this reason, a film such as an oxide film at the contact portion becomes thin and the tunnel effect becomes large, that is, so-called electrical breakdown increases, and the film is easily broken mechanically. Therefore, the electrical contact area between the brush and the commutator increases, and the voltage drop between them decreases. In addition, since the copper content of the brush is not increased and the pressing force of the brush against the commutator is not increased as in the related art, the frictional force between the brush and the commutator can be reduced.

According to the second aspect of the present invention, in the process of abrasion of the brush, the protrusion is formed on the brush contact surface by the groove or the protrusion, but the groove or the protrusion of the commutator is meandering. Thus, the protruding side surface of the brush contact surface receives a pressing force from the groove of the commutator or the side surface of the protruding portion. Therefore, the contact pressure at the contact portion is increased, and the coating is easily destroyed electrically and mechanically.

According to the third aspect of the present invention, since the groove or the protrusion is formed in a straight line, the formation of the groove or the protrusion becomes easy. According to the invention as set forth in claim 4, in the process of abrasion of the brush, the first and second grooves or the first and second projections form projections on the brush contact surface, respectively. Because the groove or the first protrusion meanders, the side surface of each protrusion of the brush contact surface receives a pressing force from the side surface of each groove or protrusion of the commutator. Further, since the second groove or the second protrusion is linear, depending on the rotation angle of the commutator,
Mutual grooves or protrusions formed in the commutator approach and separate in the axial direction. Therefore, the pressing force from each groove or protrusion of the commutator that acts on the side surface of the protrusion of the brush contact surface increases, and the contact pressure at the contact portion increases.

According to the fifth aspect of the present invention, since the meandering groove or protrusion is formed in a simple sinusoidal shape that changes periodically, the formation of the groove or protrusion is facilitated.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. As shown in FIG. 1, a housing 2 of the DC motor 1 has a magnet 3 having a plurality of poles fixed on an inner peripheral surface thereof, and accommodates a rotor 4 inside the magnet 3. The rotor 4 has a rotating shaft 5, which is rotatably supported by bearings 6, 7 provided on the housing 2. Further, a cylindrical commutator 9 with which a plurality of (in this case, two) brushes 8 are in sliding contact is fixed to the rotating shaft 5.

The brush 8 is held by a brush holder 10 supported by the housing 2 and pressed against the outer peripheral surface 9a of the commutator 9 by a pressing means 11 such as a spring. A driving power is supplied to the brush 8 from an external power supply (not shown), and the power is rectified by the brush 8 and the commutator 9 and supplied to the rotor 4, so that the rotor 4 rotates. It has become.

As shown in FIG. 2, the commutator 9
Comprises a cylindrical base 12 made of an insulating material for fixing to the rotating shaft 5, and a plurality of commutator pieces 13 fixed to the outer peripheral surface of the base 12.

An outer peripheral surface 9a of the commutator 9 (commutator piece 13) is provided in a range in which the brush 8 slides.
A plurality of annular grooves 9b extending in the circumferential direction are formed at equal intervals in the axial direction. This annular groove 9b has the same shape,
In the present embodiment, the width of 14 to 70 [μm] and the width of 10 to 5
20 to 30 [lines / cm] in the axial direction at a depth of 0 [μm]
At a pitch of Each annular groove 9b is slightly meandered in the axial direction toward the circumferential direction. More specifically, the meandering shape of each annular groove 9b is a one-period sine wave shape, and the meandering width is preferably 14 to 70 [μm] corresponding to the groove width. Incidentally, in FIG. 2, in order to make the annular groove 9b easy to see, the number of the grooves 9b is smaller than the actual number,
The serpentine shape is exaggerated. Such an annular groove 9b
Is formed simply by applying a cutting tool (not shown) to the outer peripheral surface 9a of the commutator 9 and rotating the commutator 9 (rotor 4).

Since the DC motor 1 constructed as described above is used in the atmosphere, the outer peripheral surface 9a of the commutator 9 is covered with an oxide film or another contaminant film. In the present embodiment, the brush 8 does not entirely contact the outer peripheral surface 9a of the commutator 9 due to the annular groove 9b formed on the outer peripheral surface 9a of the commutator 9, and a predetermined portion such as between the annular grooves 9b is formed. There will be partial contact. Therefore, the contact pressure increases due to concentration of the contact pressure of the brush 8 acting on the contact portion.

Accordingly, the thickness of the coating at the contact portion is reduced, so that the tunnel effect is increased, and the coating at the contact portion is easily damaged electrically. As a result, the electrical contact area between the brush 8 and the commutator 9 increases, and the voltage drop between them decreases.

Further, when the contact pressure of the brush 8 is partially increased, the coating on the contact portion is easily broken not only electrically but also mechanically. Therefore, brush 8
The electrical contact area between the commutators 9 increases, and the voltage drop between them decreases as described above.

Further, in the process of abrasion of the brush 8, a protrusion (not shown) is formed on the contact surface 8a of the brush 8 so as to protrude into the annular groove 9b. Since it is meandering in the direction, the pressing force by the side surface (slope) of the annular groove 9b acts on the side surface (slope) of the projection. Therefore, not only the coating at that portion becomes thinner and the tunnel effect becomes larger, but also it is easily broken mechanically, which is the same as above.

In addition, in the present embodiment, the brush 8 with respect to the commutator 9 is not increased without increasing the copper content of the brush 8.
Since the pressing force is not increased, the frictional force between the brush 8 and the commutator 9 is kept low, and the loss of rotational force is kept small.

As described above, according to the present embodiment,
It has the following effects. (1) The brush 8 partially contacts the outer peripheral surface 9a of the commutator 9 due to the plurality of annular grooves 9b formed on the outer peripheral surface 9a of the commutator 9, so that the contact pressure at the contact portion increases. Therefore, the film at the contact portion becomes thin and the tunnel effect increases, so-called electrical destruction increases, and the film is easily broken mechanically.
Therefore, the electrical contact area between the brush 8 and the commutator 9 can be increased, and the voltage drop between them can be reduced.

(2) In this embodiment, since the copper content of the brush 8 is not increased or the pressing force of the brush 8 against the commutator 9 is not increased, the frictional force between the brush 8 and the commutator 9 can be reduced. As a result, loss of rotational force can be reduced.

(3) In the process of abrasion of the brush 8, projections are respectively formed on the contact surfaces 8a of the brush 8 by the annular grooves 9b. Since the annular grooves 9b are formed in a meandering manner, the side surfaces of the projections are formed. A pressing force is received from the side surface of the annular groove 9b. Therefore, the contact pressure at the contact portion can be increased, and the coating can be easily broken electrically and mechanically. As a result, the voltage drop between the brush 8 and the commutator 9 can be further reduced.

(4) Since the protrusion formed on the contact surface 8a of the brush 8 and the annular groove 9b are engaged in the axial direction, the position of the brush 8 is regulated in the same direction, and the brush 8 is moved in the same direction. Vibration is reduced. Therefore, the noise of the motor 1 can be reduced.

(5) Since the meandering shape of the annular groove 9b is a simple one-cycle sinusoidal shape, the groove 9b can be easily formed. (6) Since all the annular grooves 9b have the same shape and are formed at equal intervals in the axial direction, the grooves 9b can be easily formed.

The embodiment of the present invention may be modified as follows. In the above embodiment, the entire annular groove 9b is meandered, but it is not necessary to meander the entirety, and a part of the annular groove 9b may be meandered. A specific example is shown in FIGS.

As shown in FIG. 3, a plurality of annular grooves 14b are formed on the outer peripheral surface 14a of the commutator 14, and grooves located at both ends in the axial direction, that is, first annular grooves 14c are formed in a meandering manner. The other groove, that is, the second annular groove 14d is formed linearly. The first annular groove 14c is formed in a one-period sine wave shape as in the above embodiment.

In this way, as shown in FIG. 4, during the process of wear of the brush 8, the first and second annular grooves 14c, 1c are formed.
The protrusions 8b and 8c are respectively formed on the contact surface 8a of the brush 8 by 4d. However, since the first annular groove 14c is meandering, the side surface of each of the protrusions 8b and 8c becomes the respective annular groove 14c.
A pressing force is received from the side surface of 14d. At this time, since the second annular groove 14d is linear, the two annular grooves 14c and 14d are mutually moved depending on the rotation angle of the commutator 14 as shown in FIG.
As shown in FIG. 4A, they are close to each other in the axial direction, or are separated as shown in FIG. Therefore, the pressing force received by the side surfaces of the protrusions 8b and 8c from the side surfaces of the annular grooves 14c and 14d becomes larger, so that the contact pressure at the contact portion can be further increased. Incidentally, FIG. 4A is a cross-sectional view of a position where the grooves 14c and 14d are closest to each other, and FIG. 4B is a cross-sectional view of a position where the grooves 14c and 14d are farthest from each other.

Further, as in the commutator 15 shown in FIG. 5, one of the plurality of annular grooves 15b formed on the outer peripheral surface 15a has a meandering first annular groove 15c, and all the others are straight linear grooves. The two annular grooves 15d may be used. FIG.
As shown in (1), the first annular groove 15c may be formed in a sine wave shape having one or more cycles. Even if you do this,
There is an effect similar to that of the embodiment of FIG.

Further, as in the commutator 16 shown in FIG. 6, the plurality of annular grooves 16b formed on the outer peripheral surface 16a may be all formed in a straight line. With this configuration, the shape of the annular groove 16b is simplified, so that the annular groove 16b can be easily formed.

Although the annular grooves 9b, 14d, 15d, and 16b are formed at equal intervals as shown in FIGS. 2, 3, 5, and 6, they need not be at equal intervals. Further, as shown in FIGS. 2, 3 and 5, the annular grooves 9b, 14c and 15c are formed in a sine wave shape, but may be formed in other meandering shapes.

As shown in FIGS. 2, 3, 5, and 6, the annular grooves 9b, 14b, 15b, and 16b are fitted to the outer peripheral surfaces 9a, 14a, and 15 of the commutators 9, 14, 15, and 16.
Although the brushes 8a and 16a are formed in a range where the brush 8 is in sliding contact with the outer surfaces 9a and 1b, the grooves 9b, 14b, 15b and 16b may be formed at least in that range.
4a, 15a and 16a may be formed over the entirety.

Further, the grooves 9b, 14b, 15b, 16b do not have to be formed in a ring shape, but only need to extend substantially in the circumferential direction. In the above embodiment, the annular groove 9b is set to 10 to 50 [μ
m] at a pitch of 20 to 30 lines / cm in the axial direction, but is not limited to this value.

In the above-described embodiment, the annular groove 9b is formed by rotating the commutator 9 (rotor 4) by applying a cutting tool to the outer peripheral surface 9a of the commutator 9, but using other methods. An annular groove may be formed.

In the above embodiment, the groove 9b is used.
The same applies to the protrusions protruding from the outer peripheral surface 9a. Of course, similar to the above-described annular grooves 9b, 14b, 15b, and 16b, the same operation and effect can be obtained even if all or a part of the annular protrusion is formed in a meandering shape or all are formed in a straight line.

In the above embodiment, the present invention is applied to the DC motor 1, but may be applied to a motor having another brush.

[0039]

As described in detail above, according to the present invention,
It is possible to provide a motor that can reduce a voltage drop between brushes and commutators while suppressing an increase in frictional force between the brushes and the commutator.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a motor according to an embodiment.

FIG. 2 is an enlarged view of a commutator of one embodiment.

FIG. 3 is an enlarged view of another example of a commutator.

FIG. 4 is an enlarged sectional view of another example of a brush and a commutator.

FIG. 5 is an enlarged view of another example of a commutator.

FIG. 6 is an enlarged view of another example of a commutator.

[Description of Signs] 8: Brush, 9, 14, 15, 16 ... Commutator, 9
a, 14a, 15a, 16a: outer peripheral surface, 13: commutator piece, 9b, 14b, 15b, 16b: annular groove, 14c,
15c: a first annular groove as a first groove, 14d, 15d
... A second annular groove serving as a second groove.

Continued on the front page (72) Inventor Yasuhide Ito 390 Umeda, Kosai-shi, Shizuoka Prefecture Asmo Co., Ltd. F-term (reference) 5H613 AA01 AA03 BB04 BB14 BB15 GA04 GB01 KK01

Claims (5)

[Claims] 1. A motor comprising: a commutator having a plurality of commutator pieces; and a brush that slides on an outer peripheral surface of the commutator, wherein at least an area of the outer peripheral surface of the commutator is in sliding contact with the brush. A motor, wherein a plurality of extending grooves or protrusions are formed. 2. The motor according to claim 1, wherein the plurality of grooves or protrusions are formed in a meandering manner. 3. The motor according to claim 1, wherein said plurality of grooves or projections are formed in a straight line. 4. The motor according to claim 1, wherein the plurality of grooves or protrusions include a first groove or first protrusion formed to meander, and a second groove formed linearly. Or a motor provided with a second projection. 5. The motor according to claim 2, wherein the meandering groove or protrusion is formed in a sine wave shape that changes periodically.