JPH0121569B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a current switch, and particularly to a radio switch suitable for switching current. In current switches that are equipped with electrical contacts that are connected to each other, for example, Ag, Ag-CdO, Ag-
Those equipped with electrical contacts such as In ₂ O ₃ and Ag-SnO ₂ (both electrodes are made of the same material) are in practical use. However, when using Ag contacts, the contact resistance is extremely low and the hardness is small, so while it has advantages such as less chattering during insertion, it has the disadvantage of poor wear resistance and welding resistance. On the other hand, Ag-CdO contacts have the advantage of being applicable to current fields that cannot be covered by Ag contacts, but they are prone to welding and wear and tear and are inferior in durability. Also, Ag−SnO ₂ and Ag−
In ₂ O ₃ contacts have excellent wear resistance, but
It has the disadvantage that it cannot sufficiently withstand harsh conditions of use such as increased frequency of use. Furthermore, attempts have been made to combine contacts for current switches used in elevators, wheels, etc., such as configuring one contact with a C-Cu type and the other with a Cu type. In this case, the phenomenon of low wettability between C element and other metals is used to reduce and suppress the welding phenomenon, but on the other hand, it is said that it is subject to heavy wear and has a poor lifespan. Defects are recognized. Therefore, the present invention aims to provide a current switch that has low contact resistance, excellent welding resistance and wear resistance, maintains and exhibits the required performance over a long period of time, and is particularly suitable for switching medium currents. It is something. To explain the present invention in detail below, the present invention provides a current switch equipped with opposing electrical contacts, in which at least one contact surface of one of the opposing electrical contacts is
Contains ~10% by weight of one or more of SnO ₂ and In ₂ O ₃ (1 to 15% by weight in the case of SnO ₂ + In ₂ O ₃ )
Ag alloy, the other opposing electrical contact is 5-15% by weight.
These current switches are each made of an Ag alloy containing ZnO. The attached figure is a cross-sectional view showing an example of the structure of the current switch according to the present invention, in which a movable base metal 1 forming a part of the current path is connected to a movable rod 2 that is movable. Further, 1 and 2 are locked by a contact spring 3, and when no external force is applied, the movable base 1 is always biased in one direction 4 by the contact spring 3. . Further, a conductive piece 5 connected to an external electric circuit
Fixed contacts 7a, 7b provided at the ends of a, 5b
Movable contacts 6a and 6b are provided at both ends of the movable base metal 1 so as to face each other. Then, the movable rod 2 operates as if a current is applied to the excitation coil 11 and the iron cores 12a and 12b are attracted, thereby bringing the movable contacts 6a and 6b into contact with the fixed contacts 7a and 7b and turning on the electric contacts. It is something to do. A contact plate spring 8 is provided on the movable contact in order to absorb the vibrations that occur when the movable contact 6a and the fixed contact 7a and the movable contact 6b and the fixed contact 7b come into contact with each other, and extinguish the arc that occurs between the two contacts. A grid 9 for this purpose is attached to the main body 10. In addition, in the attached diagram, one of the electrical contacts facing each other,
For example, the movable contacts 6a and 6b have a diameter of 5 mm and a thickness of 1 mm.
Made of SnO ₂ -Ag alloy or 2 to 10% by weight of mm
It is a disc made of 10% by weight In ₂ O ₃ -Ag alloy. Also, the other electrical contacts facing each other, for example, fixed contacts 7a, 7
b is 5-15% by weight ZnO− with a diameter of 5.5 mm and a thickness of 1 mm.
It is a disc made of Ag alloy. However, in the above
SnO ₂ −Ag-based or In ₂ O ₃ −Ag-based SnO ₂ or
The composition ratio of In ₂ O ₃ is limited to 2 to 10% by weight when each is used alone. The reason for this is that if it is less than 2% by weight, the welding resistance will be impaired, and the improvement and curing of abrasion resistance will be insufficient, and if it exceeds 10% by weight, the contact resistance will increase and the desired effect will not be obtained. . However, when SnO ₂ and In ₂ O ₃ are used in combination, the total amount can be 2 to 14% by weight, and the alloy does not need to constitute the entire contact, but at least only the contact surface. On the other hand, in the ZnO--Ag system, if the composition ratio of ZnO is less than 5%, welding failure is likely to occur, and if it exceeds 15%, cracks may occur during contact forming, and the desired effect cannot be obtained in the end. As described above, in the current switch according to the present invention, the opposing electrical contacts are made of a combination of different types of Ag alloys, and in particular contain SnO ₂ and In ₂ O ₃ .
Ag base metal contact material is installed on the polar side which shows weight loss due to current switching. Thus Ag−SnO ₂ ,
Ag−In ₂ O ₃ , Ag−SnO ₃ −In ₂ O ₃ , Ag−ZnO
By taking advantage of each of the advantages of Ag alloy, it has been able to demonstrate excellent contact performance such as welding resistance, wear resistance, and low contact resistance characteristics, allowing it to perform the required functions as a current switch for a long period of time. . Next, examples of the present invention will be described. After alloying Ag, Zn, Sn, and In with a predetermined composition ratio, it is molded and placed in an oxygen atmosphere of 4 atm.
At 700℃ for 4 days (Ag-Zn system) or 8 days (Ag
−Sn, Ag−Sn−In system) firing, internal oxidation (Cd,
(Sn and In were oxidized) to prepare electrical contacts having the composition ratios (wt%) shown in Table 1. Among the electrical contacts thus obtained, Ag-ZnO system was used as a fixed contact, and Ag-SnO ₂ , Ag-In ₂ O ₃ , Ag-
The wear amount of each electrical contact when a SnO ₂ −In ₂ O ₃ system is attached to an open electromagnetic switch as a movable contact and opened and closed 5 × ¹⁰ times at 200 V AC and 20 A power factor 0.8 ( The results of measuring mg) are also shown in Table 1.

【table】

[Table] As is clear from Table 1, in the case of the current switch according to the present invention, the amount of wear of the contacts is small, and the amount of wear of the movable contacts and the fixed contacts is about the same, which is advantageous in terms of reliability. On the other hand, for the current switch with the above configuration, the opening force
Table 2 shows the results of the welding resistance test after the ASTM contact test under the conditions of 100 g, contact force of 100 g, AC 200 V x 70 A.

[Table] As can be seen from Table 2, Reference Example 4 with a relatively small amount of ZnO and the combination of ZnO-based comrades (Reference Example -
In case 6), welding occurred 18 to 35 times during 5×10 ⁴ openings and closings, but when a contact containing a predetermined amount of ZnO was present on one side, the likelihood of welding occurring was low. The fluctuation range of contact resistance after opening and closing 5×10 ^-4 times was also large in Reference Examples 4 and 6, and there was surface roughness. In addition, in the above embodiment, the fixed side contact is Ag-
Although ZnO type was set, the opposite may be used. In other words, on the side where the electrical contacts wear out more during operation, which is affected by the structure of the switch, the heat capacity of the conductive parts, etc.
Ag-SnO ₂ system, Ag-In ₂ O ₃ system, or Ag-
It is sufficient to set the SnO ₂ −In ₂ O ₃ system. Regarding the ZnO-based specimens used in Example 9, Example 13, and Reference Example 5, in order to increase the efficiency of internal oxidation treatment,
A material containing approximately 0.01% to 0.1% of Bi, Ni, In, Sn, etc. was used.

[Brief explanation of drawings]

The drawing is a sectional view showing a configuration example of a current switch according to the present invention. DESCRIPTION OF SYMBOLS 1... Movable base metal, 2... Movable rod, 3... Contact spring, 5a, 5b... Conductive piece, 6a, 6b...
...Movable contact, 7a, 7b...Fixed contact, 8...Contact plate spring, 9...Decentering grit, Ou...Magnetic coil, 12a, 12b...Iron core.

Claims (1)

[Claims] 1 At least the contact surface of one of the electrical contacts facing each other is made of 2 to 10 wt% (wt%) of one or more of SnO ₂ and In ₂ O ₃ (however, SnO ₂ + In ₂ O ₃ is 2 to 14 wt%)
A current switch characterized in that the other electrical contact contacting this contact is each made of an Ag alloy containing 5 to 15 wt% ZnO.