JPH097445A - Sliding contact of electric equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sliding contact by which a gall is hardly caused and friction is reduced and contact resistance at current-conduction is reduced. SOLUTION: A coating film of a composite material by dispersing graphite particles in a silver matrix is formed on a sliding contact surface 15 with mating conductors 10 and 11 of a movable conductor 5 by electroplating. C has excellent lubricating ability, and has electric conductivity at the same time, and since it does not melt in Ag at all, when a coating film by finely dispersing C in a matrix of Ag is applied to a sliding surface, a gall is hardly caused, and contact resistance in a sliding process is kept low, and even if a contact part is melted by heating at large electric current flow, they are hardly welded to each other, and the sliding contact surface is kept smooth, and stable current- conduction is maintained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive contact member (referred to as a sliding contactor) for making electrical connection by sliding contact with a mating conductor in various electric devices such as a circuit breaker. And particularly to its surface treatment.

[0002]

2. Description of the Related Art In electrical equipment having a mechanically moving conductive portion such as a circuit breaker, a disconnecting contactor, a load switch or a connector, the sliding contact is used between a movable portion and a fixed portion. . Since the contact point of the sliding contactor, which is energized, changes momentarily during the sliding process, the contact resistance during the sliding process is more unstable and tends to be higher than in the stationary state. When the contact resistance becomes high, the contact portion is heated by Joule heat, and when the conductor is copper or a copper alloy, the contact resistance becomes higher due to oxidation, which further promotes the oxidation. In order to prevent such a vicious circle, conventionally, in a sliding contact element through which a large current is applied, the sliding contact surface is plated with silver (Ag).

[0003]

However, Ag plating is soft and easily galls, and is easily abraded to expose the conductor base even when opening and closing without load. In addition, during energization, Joule heat softens Ag, and galling is more likely to occur, and sliding causes peeling of the plating layer. Further, when the electric current increases, the contact portion melts due to heat generation, and finally arc melting. This heat generation can be suppressed to some extent by increasing the contact force of the sliding contact, but the movement of the sliding contact becomes worse with it, so a drive mechanism for moving it and a spring mechanism for increasing the contact force. Becomes large. Also, as the contact force increases, the frictional force increases, so
The wear of the plating layer increases even when no current is applied or when a minute current is applied.

As a means for coping with the above phenomenon, conductive grease is applied to the Ag plating film. This method is effective in preventing galling, and the contact resistance in the stationary state is low and stable, but in the experiments of the inventors, the contact resistance in the sliding process was high, and a large current was applied. In some cases it was easier to melt than the one without grease. Further, grease tends to solidify when used at high temperatures for a long time, which limits its use at high temperatures. Therefore, an object of the present invention is to provide a sliding contactor having a large abrasion resistance and capable of obtaining stable energization with a low contact resistance even in a sliding process.

[0005]

In order to solve the above-mentioned problems, the present invention disperses graphite (C) particles in a silver (Ag) matrix on the sliding contact surface of a sliding contact with a mating conductor. The composite film thus formed is formed by electroplating. The composition of the plating solution used at that time is as follows: metallic silver concentration 2 to 100 g / liter, potassium cyanide 2 to 250 g / liter, potassium hydroxide 0.5 to 15 g / liter, graphite powder 1 to 550 g / liter, plating solution It is recommended to use 10 to 2000 ppm of a graphite powder dispersion aid.

[0006] C has excellent lubricity and at the same time conductivity, and it does not melt at all with Ag. The present invention
Paying attention to such characteristics of C, C in the matrix of Ag
When a coating with finely dispersed is applied to the sliding surface, galling is unlikely to occur, the contact resistance during the sliding process is kept low, and even if the contact part melts due to heat generation when a large current flows, welding This is because it was found that the sliding contact surface is kept smooth without mutual contact, and excellent properties such that stable energization can be maintained for a long period of time can be obtained.

By the way, as a method for manufacturing the above-mentioned composite material, a method of mixing silver powder and graphite powder and sintering the mixture can be considered. However, the preferable coating thickness in the present invention is on the order of several μm to several tens of μm, and the shape of the sliding surface is not limited to a flat plate, so that such a thin material should be formed along a complicated sliding surface shape. It is practically impossible to manufacture it by the sintering method. Also, since the silver-graphite sintered material cannot be directly joined to the mating metal, it is necessary to separately form a layer of silver on the joining surface and braze it to the mating metal via this silver layer. so,
It is extremely difficult to apply such a joining method to the above-mentioned thin materials. According to the present invention, since the above coating is formed by electroplating, it is possible to freely form a coating having a required thickness on a sliding surface having an arbitrary shape.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below for a sliding contact of a circuit breaker (wiring breaker) as shown in FIG. Here, FIG. 1A is a plan view of a closed state of the movable contactor portion of the circuit breaker, and FIG. 1B is a side view thereof. In FIG. 1, reference numeral 1 denotes a fixed contactor made up of a fixed conductor 2 made of a copper material fixed to a case of a circuit breaker (not shown) with a screw, and a contact 3 attached to the tip of the fixed conductor 4, and 4 is driven by an opening / closing mechanism not shown. A movable contactor composed of a movable conductor 5 made of a copper material that is opened and closed and a contact 6 attached to the tip of the movable conductor 5, 7 is an insulator holder for holding the movable contact 4, and 8 is an overcurrent trip device (not shown). It is a fixed conductor that communicates with the heating element of the device.

The fixed conductor 8 is an L-shaped conductor 9 which is upright and screwed to a case, and is also horizontally joined to the L-shaped conductor 9.
It is composed of a character-shaped conductor 10 and an S-shaped conductor 11 joined in parallel to the character-shaped conductor 10, and the conductors 10 and 11 form a bifurcated arm which is in sliding contact with the conductor 5 sandwiched as shown in the drawing. A support shaft 12 for rotating the movable conductor 5 is inserted through the movable conductor 5 and the conductors 10 and 11, and both ends of the support shaft 12 have holders 7.
Is held in. The compression springs 13 are inserted between the conductors 10 and 11 and the holder 7, respectively, and
Is pressed against the movable conductor 5. Reference numeral 14 denotes a contact spring inserted between the rear end of the movable conductor 5 and the case, which urges the movable conductor 5 counterclockwise in the drawing to generate a contact pressure between the fixed contact 3 and the movable contact 6. I am letting you.

In such a state, the current flowing from the fixed contact 1 to the movable contact 4 flows to the fixed conductor 8 through the sliding contact portion 15 between the movable conductor 5 and the conductors 10 and 11, and further overcurrent (not shown). It reaches the load side terminal plate through the trip device. When the operation handle (not shown) is opened or the overcurrent trip device trips in the closed state of the figure, the opening / closing mechanism (not shown) is actuated to rapidly pull up the movable contact 4, and the support shaft 12 is used as a fulcrum. Rotate in the clockwise direction of 1 (B). At that time, the movable conductor 5 and the conductors 10 and 11 slide on each other at the sliding contact portion 15.

In the movable contactor portion of such a circuit breaker, in the embodiment, the movable conductor 5 and the fixed conductor 8 are each made of a composite material (Ag- A 6% C) coating was formed by electroplating to a thickness of 7 μm (Example 1). FIG. 2 is an electron micrograph (magnification: 900 times) showing the dispersed state of C in the plating film thus obtained, in which the black dots are C. [Composition of plating solution] Metallic silver concentration: 35 g / liter Potassium cyanide: 110 g / liter Potassium hydroxide: 8 g / liter Graphite powder: 20 g / liter (C grain size is
0.5-2 μm in major axis, 0.2-0.5 μm in minor axis) Dispersion aid of graphite powder in plating solution: 200 ppm [Working conditions] Anode: Silver plate Bath temperature: 20 ° C Current density: 1 A / dm ² Agitation: Yes

Similarly, a coating of Ag-3% C (volume%) was formed on each of the movable conductor 5 and the fixed conductor 8 by electroplating to a thickness of 7 μm (Example 2). The plating conditions at that time are as follows: bath temperature 35 ° C., major axis of C grains 0.8 to 5 μm, minor axis 0.3.
.About.1 .mu.m, otherwise the same as in Example 1. Also,
As comparative examples, the same movable conductor 5 and fixed conductor 8 (Comparative Example 1) plated with Ag of 7 μm, and the one coated with grease (Comparative Example 2) were prepared.

[0013]

[Table 1]

The movable conductor 5 and the fixed conductor 8 were assembled in a circuit breaker, and a no-load switching test and a large current breaking test were carried out. In the no-load switching test, the sliding contact part 15
Repeats reciprocating sliding in the non-energized state, and in the large current interruption test, the contact portion 15 slides in the energized state. Table 1 shows the test results. According to this, it can be seen that the copper base material is less likely to be exposed in the plated Ag-C composite material than in the ordinary Ag-plated material or the grease-coated material.

FIG. 3 shows the results of measuring the contact resistance of the sliding contact portion 15 by sliding the sliding contacts of Example 1, Comparative Example 1 and Comparative Example 2 in the state of flowing DC 10A.
Although the contact resistances in the static state differ little among the three parties, the contact resistance of Ag-6% C is the lowest in the sliding process, and there is little fluctuation. Generally, the temperature of the electrical contact portion of the contact is said to be proportional to the voltage (= current × contact resistance) of the contact portion, and therefore the temperature during sliding energization can be said to be the smallest at Ag-6% C.

In the above embodiment, two examples of the sliding contactor of the circuit breaker are shown. However, since the effect of the present invention depends on the property of C, the C% and the size of the C grain depend on them. It's not limited. The ease of galling and melting of the sliding contact part is also affected by the size and surface pressure of the contact part.
The C% and the size of the C grains should be decided comprehensively. However, although C has conductivity, its electric resistance is several hundred to several thousand times that of Ag. Therefore, it is not preferable to unnecessarily increase the C% or to use large C grains that penetrate the plating thickness, because this will increase the heat generation of the sliding contact portion.

Since the presence of C on the sliding contact surface contributes to the prevention of galling or the prevention of welding, it is effective to form the Ag-C coating on only one of the movable conductor and the fixed conductor. . In this case, it is desirable that the other part is Ag-plated, but since C has an antioxidant effect, a certain level of current-carrying characteristics can be obtained even with copper. The coating need not be applied to the entire surface of the conductor and may be formed only on the sliding contact surface.

The fine particles of Ag-C as the third particles are fine hard particles such as SiC, WC, ZrB, Al ₂ O ₃ , ZrO ₂ ,
Cr ₂ O ₃ , TiO ₂ , R ₂ O ₃ , ThO ₂ , Y ₂ O ₃ , Mo
By dispersing particles of O ₃ , W ₂ C, TiC, B ₄ C, CrB ₂ or the like, the hardness of the entire coating can be increased and a long-life contact portion that is less likely to wear can be formed.

As for the plating conditions, the plating solution composition is a basic bath having a metal silver concentration of 2 to 100 g / liter, potassium cyanide of 5 to 250 g / liter, and potassium hydroxide of 0.5 to 15 g / liter. 1-550
It can be used in the range of g / liter. Graphite diameter is
0.05 to 25 μm can be used, but 0.2 to 10 μm is preferable.
m.

[0020]

According to the present invention, by forming a coating film of a composite material in which C is dispersed in an Ag matrix on the sliding contact surface, the contact resistance in the sliding process is kept low and the heat generated by the applied current is generated. Is suppressed and mechanical sliding wear is reduced, so that a sliding contactor having a large current carrying capacity and a long life can be configured. Further, since the heat generation is small, the contact force can be reduced, and as a result, the spring mechanism for applying the contact force or the drive mechanism for moving the contactor can be made to have a small capacity, and the overall size of the device can be reduced. Further, by forming the coating by plating, it is possible to freely form a coating having an arbitrary thickness on the sliding surface having a complicated shape.

[Brief description of drawings]

1A and 1B show a movable contactor portion of a circuit breaker to which the present invention is applied, FIG. 1A being a plan view and FIG. 1B being a side view thereof.

FIG. 2 is an electron micrograph showing a metal structure of a sliding contact portion in FIG.

FIG. 3 is a diagram showing a measurement result of contact resistance of a sliding contact.

[Explanation of symbols]

 1 Fixed contactor 2 Movable contactor 5 Movable conductor 8 Fixed conductor 15 Sliding contact part

Continued Front Page (72) Inventor Kenyuki Kanda 1-1 Tanabe Shinden, Kawasaki-ku, Kawasaki-shi, Kanagawa Fuji Electric Co., Ltd. (72) Inventor Munejun Matsumura 1-5-1, Exit Hirakata, Osaka Prefecture Uemura Kogyo Co., Ltd. Central Research Institute (72) Inventor Satoshi Chiba 1-5-1, Exit, Hirakata-shi, Osaka Uemura Kogyo Co., Ltd. Central Research Laboratory (72) Inventor Shigeharu Miyazaki 1-1, Torigoe, Taito-ku, Tokyo No. 2 Uemura Industrial Co., Ltd. Tokyo branch office

Claims (2)

[Claims] 1. A slide for an electric device, characterized in that a coating film of a composite material in which graphite (C) particles are dispersed in a silver (Ag) matrix is formed on a sliding contact surface with a mating conductor by electroplating. Dynamic contactor. 2. A sliding contact for electric equipment according to claim 1, wherein the coating film is formed by using a plating solution having the following composition. [Composition of plating solution] Metallic silver concentration 2 to 100 g / liter, potassium cyanide 2 to 250 g / liter, potassium hydroxide
0.5 to 15 g / liter, graphite powder 1 to 550 g / liter, auxiliary material for dispersing graphite powder in plating solution 10 to 20
00ppm.