JPH0119610B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to improvements in combination electrical contacts. Recently, with the development of electrical and electronic technology, various electrical
As electronic devices have become smaller, mechanical parts such as relays, breakers, and magnetic switches have also become smaller. However, when these mechanical parts are miniaturized, the contact gap becomes narrower, and the ability to block arc discharge becomes worse. In other words, the problem arises that the arc cannot be cut. Another problem is that electrical contacts tend to weld. For this reason, there is a demand for a combination electrical contact that has good arc-blocking properties and excellent welding resistance, and various combination electrical contacts have been developed, but so far none have been satisfactory. Conventionally, combination electrical contacts have been made of a silver-metal oxide in which a metal oxide is dispersed in silver, or of a silver-refractory metal system. Among these, many combination electrical contacts are used, in which contacts made of a silver-tin oxide alloy are placed facing each other. This is because the adhesion resistance of silver and tin oxide is stable and excellent, but on the other hand, tin oxide tends to aggregate, and the silver-rich layer and the tin oxide-rich layer aggregate respectively, creating a smooth surface on the contact surface. This has the drawback that unevenness is formed, which narrows the contact gap and impairs arc interrupting performance, and in extreme cases, it may not be possible to interrupt the arc. Combination electrical contacts in which contacts made of silver-nickel are placed opposite each other are also frequently used. This is because silver-nickel based electrical contacts wear out uniformly and are small, and therefore have excellent arc-blocking resistance and stable contact resistance. However, silver-nickel electrical contacts have the disadvantage that their welding resistance varies greatly due to agglomeration of nickel particles, which limits the fields in which they can be used. Conventional combination electric contacts like this use the same electrical contact material for the opposing fixed and movable contacts, so they have good welding resistance but poor arc blocking properties, and conversely, arc blocking properties are good. However, there were problems such as poor welding resistance. Therefore, the inventor of the present invention has made an earnest effort to develop a combination electrical contact that has good arc-blocking properties and excellent welding resistance even in miniaturized mechanical parts. We have found that welding resistance and arc blocking performance can be improved by using different contact materials. The present invention has been made with attention to this point, and uses silver-tin oxide contacts and silver-nickel contacts as a combination electrical contact that can reliably improve welding resistance and arc interrupting properties. The present invention provides a combination electrical contact that is oriented in the direction shown in FIG. The combined electrical contact according to the present invention includes a silver-tin oxide contact whose alloy before oxidation is composed of 2 to 15% tin and the balance silver, and at least one of nickel 10 to 60% by weight, chromium carbide, or molybdenum carbide. and a silver-nickel type contact consisting of a total of 0.5 to 5% silver and the balance silver, facing each other. The reason why the materials of the opposing contacts are limited as described above in the present invention is to take advantage of the excellent welding resistance of the silver-tin oxide system and the good arc blocking properties of the silver-nickel system, and to exploit the synergistic effect of these. This is to solve the poor welding resistance or poor arc interrupting properties of the conventional combination electrical contacts in which contacts made of the same material are placed opposite each other. In addition, the reason why the content of tin in the silver-tin oxide system was limited to 2% by weight to 15% by weight is that if it is less than 2% by weight, the welding resistance is insufficient.
This is because, if it exceeds this amount, there will be no problem with welding resistance, but the amount of tin oxide that aggregates on the contact surface will increase, leading to an increase in contact resistance. Furthermore, if the silver-nickel type nickel is 10 to 60% by weight, if it is less than 10% by weight, the nickel particles will aggregate and a silver base layer will appear when mass-produced, and the arc resistance may be extremely poor. This is because if it exceeds 60% by weight, the contact resistance becomes extremely unstable. and a total of 0.5 to 5% by weight of at least one of chromium carbide or molybdenum carbide.
The additive decomposes during the contact opening/closing operation, and the metal becomes an oxide and the carbon becomes a gas. This oxide improves the surface wettability with the mating silver-tin oxide contact, and improves welding resistance. This is because improvements will be made. Next, in order to clarify the effects of the combined electrical contact according to the present invention, specific examples and conventional examples thereof will be described. Example 1 A fixed contact with a diameter of 5 mm made of silver-tin oxide containing 7.3% by weight of tin and a movable contact with a diameter of 4 mm made of silver-nickel-chromium carbide containing 25% by weight of nickel and 2.5% by weight of chromium carbide were compared. A combination electrical contact was constructed by oriented the Example 2 Nickel 10% by weight, molybdenum carbide 1% by weight,
A fixed contact with a diameter of 5 mm made of silver-nickel-molybdenum carbide-chromium carbide containing 1% by weight of chromium carbide and a movable contact with a diameter of 4 mm made of silver-tin oxide containing 9.3% by weight of tin and the balance being silver are opposed to each other. A combination electrical contact was constructed. Example 3 Silver containing 50% by weight of nickel and 5% by weight of molybdenum carbide - Nickel - Fixed contact with a diameter of 5 mm made of molybdenum carbide and 7.3% by weight of tin and the balance being silver -
An electric contact was constructed by combining a movable contact made of tin oxide with a diameter of 4 mm and facing each other. Conventional example 1 Silver containing nickel 10% by weight - diameter 5 with nickel
A stationary contact with a diameter of mm and a movable contact with a diameter of 4 mm were made and placed facing each other to form an electric contact. Conventional Example 2 A fixed contact with a diameter of 5 mm and a movable contact with a diameter of 4 mm were made from silver-tin oxide containing 7.3% by weight of tin and were combined to form an electrical contact by facing each other. However, when each of these combinations of electrical contacts was subjected to a welding resistance test and the arc duration time at interruption was measured under the following test conditions, the following results were obtained. Welding resistance test conditions A C 100V 50Hz Closing current 40A Breaking current 10A Opening/closing frequency 20 times/min Contact force 40g Breaking force 40g Number of samples 9 pieces/combination Number of openings/closings Until welding occurs Measurement conditions for arc duration during interruption D C 24V 3A Contact gap before test 0.7mm Breaking speed 5cm/sec

[Table] As is clear from the above table, the combined electrical contact of the present invention, which has a silver-tin oxide contact and a silver-nickel contact facing each other, is said to have exceptionally good welding resistance. Conventional silver-nickel contacts, which are said to have excellent welding resistance equal to or better than electrical contacts made of silver-tin oxide contacts facing each other, and are said to have good arc-blocking properties. Shows arc interrupting properties equivalent to a combination electrical contact with two facing each other. As detailed above, the combined electrical contact of the present invention has exceptionally excellent welding resistance and arc interrupting properties, so when used in miniaturized breakers, magnetic switches, etc., it is possible to suppress the occurrence of welding. This has the advantage of being able to reliably interrupt the arc.

Claims (1)

[Claims] 1 A silver-tin oxide contact whose alloy before oxidation consists of 2 to 15% tin and the balance silver, and a nickel 10 by weight ratio.
-60%, at least one of chromium carbide or molybdenum carbide in a total of 0.5 to 5%, and the balance silver - a combination electrical contact made of facing each other.