JP4389562B2 - Electrical contacts made of internal silver oxide-oxide material for miniaturized electromagnetic relays with high conductivity - Google Patents

Description

  The present invention has high electrical conductivity and excellent electrical contact characteristics over a long period of time in a reduced diameter state, that is, excellent welding resistance and wear resistance, and is used particularly for a miniaturized electromagnetic relay. The present invention relates to an electrical contact made of an internal silver oxide-oxide material suitable for the above.

Generally, various electromagnetic relays are used as structural parts such as automobiles and office machines.
In the electromagnetic relay, for example, as shown in a schematic longitudinal sectional view in FIGS. 3A and 3B, an electromagnet including an iron core magnetic pole and a coil, an armature, and an electrical contact are respectively arranged to be opposed to one end portion. When the current is passed through the coil of the electromagnet, the state shown in FIG. 1B, that is, one end of the armature is magnetically attracted to the iron core magnetic pole. Thus, the other end of the armature displaces one end of the movable contact spring upward, and the electrical contact fixed to the tip of the movable contact spring is fixed to the tip of the fixed contact spring. When contact is made and current flows and the relay functions, on the other hand, when energization of the coil of the electromagnet is stopped, the state shown in FIG. 1 (a) is reached and the electrical contact is opened and the relay function is stopped. Work to become It is also known to have a function.
In the case of an electromagnetic relay having the above structure, for example, for an automobile, it is used under a load condition of power supply voltage: DC 14V, rated current: 20 to 30A. In this case, the dimensions of the electrical contact are those of a normal ribbed shape. Those having a warp of 3 to 5 mm are common.
In addition, various materials have been put to practical use and proposed for the electrical contacts of the electromagnetic relay having the above structure. Among them, materials shown below, that is, in mass% (hereinafter,% indicates mass%),
Sn: 4.5-10%,
In: 0.1 to 5%,
Bi: 0.01-5%,
And the rest of the Ag alloy having a composition composed of Ag and inevitable impurities is subjected to an internal oxidation treatment, that is, in an oxidizing atmosphere at a temperature of 650 to 750 ° C. for 15 to 30 hours. An internal silver oxide-oxide-based material that has a structure in which a Sn-based oxide and an In-based oxide are precipitated has attracted attention.
US Pat. No. 4,680,162

  In recent years, the functions and performance of automobiles and office machines have been remarkably improved, and the progress of miniaturization and weight reduction has been remarkable. As a result, the structural electromagnetic relays have also been reduced in size. The built-in electrical contacts are also tending to have a small diameter, and a ribbed shape with a head diameter of 1.5 to 2.5 mm is required. On the other hand, even if the size of the electromagnetic relay is reduced, for example, for automobiles, it is used under load conditions that are not different from the conventional load conditions, that is, power supply voltage: DC 14V, rated current: 20-30A. The smaller the electrical contact diameter, the higher the current density per unit area becomes. However, the electrical contact made of the internal silver oxide-oxide material for electromagnetic relay (hereinafter simply referred to as electrical contact). ), Since the conductivity is relatively low, the heat generation between the contacts is increased by reducing the diameter, and the contact itself softens, so that the resistance to welding suddenly decreases, As a result, the wear resistance is remarkably lowered and the service life is reached in a relatively short time.

Therefore, the present inventors have focused on the above-described conventional electrical contact from the above viewpoint, and as a result of conducting research to improve the conductivity thereof,
The contents of Sn, In, and Bi, which are alloy components of the Ag alloy before the internal oxidation treatment constituting the conventional electrical contact,
Sn: 5.1-9%
In: 1.5-5%
Bi: 0.005 to 0.06%,
After being subjected to internal oxidation treatment under the above normal conditions, and then subjected to heat treatment at 900 to 960 ° C. for 10 to 20 hours in the air atmosphere, it is contained as an alloy component. Due to the action of the Bi component, the ultrafine Sn-based oxide and In-based oxide precipitated by the internal oxidation treatment are diffused and aggregated by the heat treatment, and are coarsened to become complex oxide coarse particles, which are formed on the Ag base. As a result, the Ag base material is free of ultra-fine Sn-based oxides and In-based oxides deposited by internal oxidation treatment. As a result, the conductivity of the contact itself is remarkably improved. However, since the heat generation is remarkably suppressed even in practical use at a high current density due to the small diameter, there has been a research result that the welding phenomenon between the contacts is eliminated and excellent contact characteristics are exhibited over a long period of time. Than is.

This invention was made based on the above research results,
Sn: 5.1-9%
In: 1.5-5%
Bi: 0.005 to 0.06%,
An ultra-fine Sn precipitate deposited on an Ag substrate of the internal oxidation treatment material by subjecting the internal oxidation treatment material of the Ag alloy having the composition of Ag and inevitable impurities to the inner oxidation treatment material to a precipitation oxide diffusion collective growth heat treatment. Composite oxide coarse particles obtained by diffusing and growing oxide-based oxides and In-based oxides and coarsening are dispersed and distributed on the Ag base, and the ultrafine Sn-based oxides and In-based oxides are not present. It is characterized by a highly conductive electrical contact suitable for use in a miniaturized electromagnetic relay composed of an internal silver oxide-oxide material having a texture .

Next, the reason why the composition of the Ag alloy constituting the electrical contact of the present invention is limited as described above will be described.
(A) Sn
The Sn component has the effect of forming a thermally stable Sn-based oxide by internal oxidation treatment and improving the contact detachability and welding resistance. However, when the content ratio is less than 5.1%, Since the ratio of the Sn-based oxide to be precipitated is not sufficient, a desired improvement effect cannot be obtained in the above-described action. On the other hand, when the content ratio exceeds 9%, the hardness rapidly increases, the wire drawing workability and Since the header processability is impaired, the content ratio is set to 5.1 to 9%.

(B) In
The In component promotes the precipitation of Sn-based oxides in the internal oxidation treatment, and also forms a thermally stable In-based oxide itself. In the coexistence with the Sn-based oxides, Although there is an effect of improving the welding resistance, if the content ratio is less than 1.5%, the precipitation of the Sn-based oxide becomes insufficient, and as a result, the Sn component is contained as a solid solution in the substrate as an alloy component. As a result, it is difficult to ensure high conductivity. On the other hand, if the content exceeds 5%, the hardness tends to increase, and the wire drawing workability and header workability will decrease. The content ratio was set to 1.5 to 5%.

(C) Bi
In the Bi component, the precipitation oxide diffusion aggregate growth heat treatment significantly promotes the diffusion aggregation growth of ultrafine Sn-based oxides and In-based oxides precipitated by internal oxidation treatment, and these are coarsened to form composite oxides. Although there is an effect of forming coarse grains, if the content ratio is less than 0.005%, the diffusion aggregate growth of the ultrafine Sn-based oxide and In-based oxide is not performed satisfactorily, and the ultrafine particles are not formed on the substrate. Sn-based oxide and In-based oxide remain, and a sufficient conductivity improvement effect cannot be obtained. On the other hand, if the content ratio exceeds 0.06%, the complex oxide coarse particles become too large, Since the area ratio which occupies becomes too large, and this causes a decrease in welding resistance, the content ratio is determined to be 0.005 to 0.06%.

  Since the electrical contact of the present invention has excellent conductivity, heat generation between the contacts is remarkably suppressed even under the use conditions where the current density is high due to the reduction in the diameter of the electromagnetic relay, resulting in the temperature of the contact itself. Since softening due to the rise is eliminated and excellent welding resistance is maintained between the contacts, excellent electrical contact characteristics over a very long period, that is, excellent welding resistance and wear resistance are exhibited.

  Next, the electrical contact of the present invention will be specifically described with reference to examples.

  An Ag alloy having the component composition shown in Table 1 is melted using a high-frequency melting furnace, cast into a cylindrical ingot, and subjected to hot extrusion in a state where the ingot is heated to 700 ° C. 30 mm × thickness: a plate with a dimension of 10 mm, this plate is subjected to hot rolling at a heating temperature of 700 ° C. to obtain a plate with a width of 30 mm × thickness: 3 mm, and intermediate annealing is added to this plate While cold rolling, a thin plate material having a width of 30 mm × thickness: 0.6 mm was cut along the length direction at an interval of width: 2 mm, and length: 30 mm × width: 2 mm × thickness. : A strip having a size of 0.6 mm, and this strip is subjected to internal oxidation treatment in an oxygen atmosphere and at a temperature of 700 ° C. for 24 hours to obtain an internal oxidation treatment material for a conventional internal oxidation electrical contact. A-1 to A-13 and comparative internal oxidation electricity Each of the internal oxidation treatment materials B-1 to B-9 for air contact is formed, and then each of the strip-shaped internal oxidation treatment materials is placed in a mold and compression-molded to have a diameter: 70 mm × length: A cylindrical molded body having a dimension of 70 mm is formed, and this cylindrical molded body is hot-extruded at a heating temperature of 800 ° C. to form a wire with a diameter of 7 mm, and further hot drawn at a heating temperature of 800 ° C. To obtain a wire rod having a diameter of 2 mm, and using this header, a rivet shape and a head diameter: 2.3 mm × head thickness: 0.3 mm × foot diameter: 1.5 mm × foot length: 1.5 mm Conventional internal oxidized electrical contacts 1-13 having dimensions and comparative internal oxidized electrical contacts 1-9 were produced respectively.

  Subsequently, the above-mentioned strip-shaped conventional internal oxidation treatment materials A-1 to A-13 for internal oxidation electrical contacts and internal oxidation treatment materials B-1 to B-9 for comparative internal oxidation electrical contacts are respectively charged into the molds. Then, it is compression molded to form a cylindrical molded body having a diameter of 70 mm × length of 70 mm, and the diffusion of precipitated oxides in an air atmosphere at a predetermined temperature within a range of 900 to 950 ° C. for 12 hours. As shown in Table 2, electrical contacts 1 to 13 of the present invention and comparative electrical contacts 1 to 9 containing no Bi as an alloy component were produced under the same conditions except that the aggregate growth heat treatment was performed.

  Next, regarding the various electrical contacts obtained as a result, when the structure was observed using a scanning electron microscope (magnification: 20,000 times), all of the electrical contacts 1 to 13 of the present invention were precipitated by internal oxidation treatment. There is no ultra-fine Sn-based oxide and In-based oxide as they are, and these ultra-fine oxides are diffusion-growth-growth by precipitation oxide diffusion-aggregation heat treatment and coarsened to become composite oxide coarse-grains, In contrast to the composite oxide coarse particles dispersed and distributed in the Ag substrate, the conventional internal oxidation electrical contacts 1 to 13 have ultrafine Sn-based oxides and In-based oxides in the Ag substrate. The structure | tissue which exists in the state as deposited by oxidation treatment was shown, and the same structure | tissue was seen also in the comparative electrical contacts 1-9 which do not contain Bi as an alloy component. Of these structural observation results, the structure of the electrical contact 3 of the present invention is shown in FIG. 1, and the structure of the conventional internal oxidation electrical contact 3 is shown in FIG.

Furthermore, for the various electrical contacts described above, an ASTM electrical contact testing machine was used.
Motor lock load system,
Power supply voltage: DC 14V,
Rated current: 23A
Contact contact force: 15 gf,
Contact opening force: 15 gf
The open / close test was conducted under the conditions described above, and the number of open / close operations (endurance open / close count) until opening / closing was impossible was measured. These results are shown in Tables 1 and 2. Tables 1 and 2 show the measurement results of electrical conductivity (IACS%) and the micro Vickers hardness (Hv) for the purpose of evaluating the electrical conductivity of the electrical contacts.

From the results shown in Tables 1 and 2, there is no presence of ultrafine Sn-based oxides and In-based oxides that have been deposited on the Ag substrate by the internal oxidation treatment, and these ultrafine oxides grow by diffusion aggregation. In addition, the electrical contacts 1 to 13 of the present invention forming the complex oxide coarse grains have a rivet-shaped head diameter of 2.3 mm, which results in a high current density operating condition. Because of its high conductivity, heat generation between the contacts is remarkably suppressed, softening due to temperature rise of the contact itself is eliminated, and excellent welding resistance is maintained between the contacts. In addition, conventional internal oxidation electrical contacts 1 to 13 in which Sn-based oxide and In-based oxide are dispersed and distributed in an Ag base in a state of ultrafine particles that have been deposited by internal oxidation treatment, and comparative electrical contacts 1 to 9 that do not contain Bi. Are both Sex is low, the heat generation between the contacts becomes high at high operating conditions of current density, since it becomes difficult to maintain a good welding resistance, it is apparent that lead to a relatively short time service life.
As described above, the electrical contact of the present invention exhibits excellent electrical contact characteristics over a long period of time, that is, excellent welding resistance and wear resistance even when the diameter is reduced and the current density per unit area is increased. Therefore, it can sufficiently satisfy the miniaturization of electromagnetic relays.

It is a copy figure which shows the structure | tissue (magnification: 20,000 times) of this invention electrical contact 3. FIG.

It is a copying figure which shows the structure | tissue (magnification: 20,000 times) of the conventional internal oxidation electrical contact 3.

The schematic longitudinal cross-sectional view of an electromagnetic relay is shown, (a) shows the time of relay stop, (b) shows the time of relay operation.

Claims (1)

% By mass
Sn: 5.1-9%
In: 1.5-5%
Bi: 0.005 to 0.06%,
An ultra-fine Sn precipitate deposited on an Ag substrate of the internal oxidation treatment material by subjecting the internal oxidation treatment material of the Ag alloy having the composition of Ag and inevitable impurities to the inner oxidation treatment material to a precipitation oxide diffusion collective growth heat treatment. Composite oxide coarse particles obtained by diffusing and growing oxide-based oxides and In-based oxides and coarsening are dispersed and distributed on the Ag base, and the ultrafine Sn-based oxides and In-based oxides are not present. A highly conductive electrical contact suitable for use in a miniaturized electromagnetic relay, characterized by comprising an internal silver oxide-oxide-based material having a texture .

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