JPH08185951A - Brush and its using method - Google Patents

Abstract

PURPOSE: To significantly reduce the electric loss of a brush used in an electric motor and improve the motor efficiency by forming, in the brush providing irregular parts on the sliding surface side making contact with a commutator, a low resistance thin film layer on the whole brush surface including the irregular part. CONSTITUTION: In an electric motor brush (graphite carbonaceous) having an irregular part 7 on the sliding surface side making contact with a commutator 3 having an insulating layer 2 interposed between commutator pieces 1, silver paste is applied about 50μm in thickness to the whole brush surface including the irregular part to form a low resistance thin film layer 8. The width of the groove between the protruding parts of the irregular part 7 on the brush top end is set narrower than the width of the insulating layer 2 between the commutator pieces. Thus, an electric motor is held with high efficiency and stable rectifying performance from the initial stage of the operation to improve the brush life.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric motor capable of transmitting and receiving to and from a rotor by making sliding contact between a commutator and a brush, and more particularly to an AC commutator electric motor such as an electric conducting tool and a vacuum cleaner. The present invention relates to a brush used and a method of using the brush.

[0002]

2. Description of the Related Art In response to recent energy saving, AC commutator electric motors (hereinafter referred to as electric motors) used in electric tools, electric vacuum cleaners and the like are required to have high efficiency and high output.
Motors generally have poor commutation because they do not have a commutating pole to control the commutation action. Therefore, these motors use resin brushes or graphite carbonaceous brushes that use graphite as the main raw material and resin as the binder, and have a high specific resistance of 10,000 μΩ-cm or more for resistance rectification. Most of them are resistance. Therefore, the voltage drop that occurs when the current supplied to the electric motor passes through the brush becomes large, which causes the electric loss of the brush to become large, which is one of the causes of the low motor efficiency.

As a solution to this problem, a brush for reducing the electric loss of the brush is proposed in Japanese Patent Laid-Open No. 171434/1987. The brush disclosed in this publication has a low resistance conductive layer formed by applying a paint of copper, silver or the like on five surfaces other than the sliding surface of a high resistance brush, and drying it to form a low resistance conductive layer. Is 25% or less of the voltage drop at the contact portion between the brush and the commutator. Therefore, the voltage drop of the brush is naturally small and the electric loss of the electric motor is reduced, so that the efficiency of the electric motor is improved.

However, the brush shown above is
The effect is not sufficient because the low resistance conductive layer is formed only on the top and side surfaces of the brush. Further, as to a specific method of providing a low resistance layer around the brush, JP-A-5-1 is used.
It is proposed in Japanese Patent No. 82733. The brush disclosed in this publication has five electrically conductive metal coatings applied to all five surfaces except the sliding surface of the brush by an electroless plating method to reduce the electric resistance (voltage drop) of the entire brush. 62-
Similar to the one disclosed in Japanese Patent No. 171434, the electric loss is reduced to improve the motor efficiency. Also in this case,
Similarly to the above, since the low resistance layer is not provided on the sliding surface, it is insufficient to further reduce the voltage drop.

[0005]

The electric loss of the brush is
It should be possible to further reduce the voltage drop by providing a low resistance layer on the sliding surface as well as around the brush.
However, none of the above techniques forms a low resistance layer on the brush sliding surface. The reason is that when the brush slides on the surface of the commutator, it performs a rectifying function, but at that time, the film of the low-resistance layer causes a short circuit between the commutator pieces, which causes a significant spark, resulting in poor commutation and commutation. This is because the surface of the child is blackened, damaged, etc., and eventually the life of the brush is deteriorated, and sometimes the brush disappears overnight.

The present invention makes it possible to provide a low-resistance thin film layer on the entire surface of the brush including the brush sliding surface, which has been considered impossible for the above reasons, from the beginning of operation of the electric motor. (EN) Provided are a brush for an electric motor and a method of using the brush, which has a high efficiency and is capable of improving the brush life while maintaining stable rectification performance.

[0007]

According to the present invention, there is provided a brush and a commutator having a concavo-convex portion on a sliding surface side which contacts a commutator, and a low resistance thin film layer formed on the entire surface including the concavo-convex portion. The brush, in which the low-resistance thin film layer formed on the uneven portion by sliding is peeled off, and the uneven surface is gradually worn away so that the sliding surface is only the high-resistance portion (exposed surface of the brush) and the low-resistance thin film layer on the side surface. Regarding how to use.

In the present invention, the means for forming the low resistance thin film layer is not particularly limited, and it is preferable that the low resistance thin film layer is formed, for example, by applying a low resistance substance, or by applying metallikon or plating. The thickness of the low resistance thin film layer is preferably in the range of 2 to 200 μm. As the low resistance substance, it is preferable to use a metal such as copper, silver or gold.

It is preferable that the uneven portion provided on the sliding surface of the brush that comes into contact with the commutator has a triangular shape with a sharp tip. If the width m of the groove between the convex portion of the concave and convex portion and the adjacent convex portion is made narrower than the dimension t of the insulating groove between the commutator pieces, the low resistance thin film formed on the concave and convex portion by sliding with the commutator. The layers are peeled off, whereby the high resistance portion of the brush can be brought into contact with the commutator pieces, so that a short-circuit current flowing between the commutator pieces can be reduced and commutation sparks can be suppressed, which is preferable.

It is preferable that the uneven portion provided on the sliding surface side of the brush is provided in the same direction as the commutator piece, because a short circuit between the commutator pieces can be suppressed. Further, in the present invention, since the low resistance thin film layer is provided on the entire surface of the brush, a part of the brush current may flow through the metal fitting of the brush holder, and the side surface of the brush may be melted and welded or fixed. If the side is in contact with the brush retainer, the low resistance thin film layer formed on the surface easily peels off due to sliding friction with the commutator, and the high resistance part of the brush is exposed, so that it flows to the brush retainer. It is preferable because the current can be suppressed.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a cross-sectional side view showing a usage example of a brush according to an embodiment of the present invention. 1 is a commutator piece, 2 is an insulating layer, 3 is a commutator, 4 is a lead wire, 5 is a lead wire 4. The filling powder 6 using copper powder to be fixed is a graphite carbonaceous brush, and the present invention provides an uneven portion 7 on the lower surface of the brush 6, that is, the sliding surface side in contact with the commutator 3, and 50 silver paste (manufactured by Hitachi Chemical Co., Ltd., not for sale) on the entire surface of the brush 6 including the part 7
The low-resistance thin film layer 8 is formed by applying it to a thickness of μm.

2 (a) to 2 (d) are partially omitted cross-sectional side views showing the course of changes in the uneven portions of the brush according to the embodiment of the present invention, and (e) to (h) are bottom views thereof. It is a figure. In addition, (a) and (e) of FIG. 2 are unused brushes, (b) and (f) are brushes at the initial stage of operation (after 30 seconds), and (c) and (g) are after 20 hours of operation. The brushes, (d), and (h) show the state of the brush after the uneven portion 7 is completely worn away after 50 hours of operation.

When the brush 6 according to the embodiment of the present invention is inserted into a brush holder (not shown) and an electric current is passed through an electric motor (not shown) to rotate the electric motor, the tip of the sliding surface of the brush 6 is Within a short time, the high resistance portion 9 is immediately exposed by abrasion as shown in FIGS. 2 (b) and 2 (f). The high resistance portion 9 can reduce the short-circuit current that tends to flow between the commutator pieces and suppress the generation of sparks. Further, even if the brush 6 is worn away and changes as shown in FIGS. 2 (c) and 2 (g), sparks are rarely generated, and the uneven portion 7 is completely worn away.
In the case of (d) and (h), the sliding surface has a high resistance portion 9
Also, since only the low resistance thin film layer is formed on the side surface, a stable sliding state can be maintained up to the wear limit.

Although FIGS. 1 and 2 have described the examples in the general state where the rectification of the electric motor is relatively good, FIG. 3 shows the present invention when applied to the electric motor in the state where the rectification is relatively poor. An effective way of taking the dimension of the uneven portion 7 of the brush 6 according to the embodiment will be described. In FIG. 3, t represents the thickness of the insulating layer 2 between the commutator pieces, T represents the width of the commutator piece, M of the brush 6 is the groove depth of the uneven portion 7, and m is adjacent to the convex portion. The width of the groove between the convex portion and the convex portion. The short-circuit current flowing on the brush surface flows between the commutator segments a and b through the sliding surface portion of the low resistance thin film layer 8 of the brush, but due to the sliding contact, the low resistance thin film layer 8 is formed as shown in FIG. Also, as shown in (f), the high resistance portion 9 of the brush is exposed by abrasion and the short circuit current can be reduced. In this case, in order to maintain a rectified state and a stable voltage drop state from the initial stage of operation, it is necessary to make the depth of the tip of the brush 6 and the groove of the uneven portion 7 appropriate. In order to reduce the short-circuit current between the commutator pieces, the high resistance part 9 that suppresses the short-circuit current must be located between the commutator pieces. That is, if the width m of the groove between the convex portion of the uneven portion at the tip of the brush and the adjacent convex portion is narrower than the width t of the insulating layer 2 between the commutator pieces, the high resistance portion 9 is always positioned between the commutator pieces. Therefore, the short-circuit current that tends to flow on the brush surface can be reduced. The depth M of the unevenness is not particularly limited, but it is sufficient if it is about the height M ′ of the central portion between the commutator arc and the brush width.

Next, as shown in FIG. 4, a conventional brush in which a low resistance thin film layer is not formed at all on the surface (a) is provided with a low resistance thin film layer 8 on five surfaces except the sliding surface side in contact with the commutator. An example of the present invention in which the formed conventional brush is provided with uneven portions on the sliding surface side that contacts (b) and the commutator, and the low-resistance thin film layer 8 is formed on all surfaces (6 surfaces) including the uneven portions. The voltage drop was measured for these three types of brushes, with the brush that becomes as (c). In FIG. 4, the arrow indicates the sliding direction of the brush 6. For the measurement, the above brushes (a), (b) and (c) (both having a specific resistance of 50,000 μΩ-cm and a brush for an electric vacuum cleaner motor) 6 were rotated at a rotational speed of 30,000 min ^−1.
The brush 6 was slid on the rotating commutator surface, and a current of 10 A was applied to the brush 6, and the voltage drop of two brushes (only one is shown in FIG. 5) was measured by the test circuit shown in FIG. Figure 5
In V., the voltage drop depending on the resistance value of the lead wire 4 and the brush 6 is Vh, the contact voltage drop between the lower end of the brush 6 and the commutator 3 is Vc, and the total of Vh and Vc is represented by the total voltage drop V. . The measurement result of the total voltage drop V is shown in FIG. Figure 6
In (b1), the total voltage drop of the brush in (b) was measured at the initial stage of operation, and in (b2), 10
The measured total voltage drop after running for 0 hours is shown.
Further, (c1) shows the total voltage drop measured in the initial stage of operation of the brush of (c), and (c2) shows the total voltage drop measured after operating the brush of (c) for 100 hours.

As shown in FIG. 6, the total voltage drop of the brush is (a), (b1), (b2), (c2) and (c).
It was confirmed that the size became smaller in the order of 1). More specifically, the brush (b) having a low resistance thin film layer formed on the five surfaces has a high total voltage drop at the beginning of operation, and its value is slightly decreased after 100 hours of operation. It is considered that this is because the contact of the brush with the commutator is insufficient at the initial stage of operation, and the low resistance thin film layer on the side surface of the brush does not contact with the commutator, resulting in a slightly high value.

On the other hand, in the brush of (c) according to the embodiment of the present invention, since the low-resistance thin film layer is formed on the entire sliding surface in the initial stage of operation, the total voltage drop is small, and the contact is sufficient for 100 hours. On the contrary, the total voltage drop after operation is slightly larger. It is considered that this is because the high resistance portion of the brush was exposed after 100 hours of operation.

Further, compared with Vh of the brush of (a), V of the brushes of (c1) and (c2) according to the embodiment of the present invention.
It is shown that h is about 44% smaller and Vh of the brushes of (c1) and (c2) according to the embodiment of the present invention is about 66% smaller than Vh of the brushes of (b1) and (b2). Be done. The contact voltage drop Vc of the brush is 1.8 regardless of whether the low resistance thin film layer is formed on the brush surface or not.
It is within the range of to 2.2V, and it is shown that the sliding state is stable without much difference.

[0019]

The brush according to the present invention can reduce the short-circuit current that tends to flow between the commutator pieces, thereby suppressing sparks and further reducing the voltage drop due to the brush current. Not only the electric loss is significantly reduced and the motor efficiency can be improved by 1 to 3%, but also the brush temperature is low, the damage to the commutator is small, and the life of the brush can be improved.

[Brief description of drawings]

FIG. 1 is a sectional side view showing a usage example of a brush according to an embodiment of the present invention.

2 (a) to (d) are partially omitted cross-sectional side views showing changes in the uneven portions of the brush according to the embodiment of the present invention, and (e) to (h) are bottom views thereof.

FIG. 3 is a partially omitted cross-sectional side view for explaining how to effectively use the dimension of the uneven portion of the brush according to the embodiment of the present invention.

FIG. 4 is a perspective view showing a configuration of each brush for measuring a voltage drop.

FIG. 5 is a partially omitted schematic diagram showing a circuit for measuring a voltage drop of a brush.

FIG. 6 is a graph showing measurement results of voltage drop.

[Explanation of symbols]

 1 Commutator piece 2 Insulating layer 3 Commutator 4 Lead wire 5 Packing powder 6 Brush 7 Uneven portion 8 Low resistance thin film layer 9 High resistance portion

Claims (5)

[Claims] 1. A brush comprising a concavo-convex portion provided on the sliding surface side in contact with a commutator, and a low-resistance thin film layer formed on the entire surface including the concavo-convex portion. 2. The low resistance thin film layer is formed by applying a low resistance material, or by applying metallikon or plating.
The listed brush. 3. The brush according to claim 1, wherein the uneven portion is a triangular uneven portion having a sharp tip. 4. The brush according to claim 1, 2 or 3, wherein the width m of the groove between the convex portion of the concave-convex portion and the adjacent convex portion is smaller than the dimension t of the insulating groove between the commutator pieces. 5. The low resistance thin film layer formed on the uneven portion by sliding with the commutator is peeled off, and the sliding surface is separated from the high resistance portion (exposed surface of the brush) and the side surface while gradually abrading the uneven portion. 3. A low-resistance thin film layer only,
The method of using the brush according to 3 or 4.