JP2952289B2 - DC contact for engine starter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Industrial application field The present invention relates to a long-life DC contact for an engine starter having excellent environmental resistance.

(2) Prior Art The structure of a DC contact for an engine starter is as shown in FIG. 1 and comprises one disk-shaped movable contact 2 and a pair of fixed contacts 1a and 1b.

In conventional DC contacts for engine starters, the movable contact side and the fixed contact side are both made of the same tough pitch copper, and the movable contact side is made of tough pitch copper and the fixed contact side is made of a copper-tungsten alloy. Are known.

When the ignition key of the car is turned, the movable contact 2 is strongly pressed against the fixed contacts 1a and 1b by the action of the electromagnet formed by the retracting coil 5, and the pressure is
A is 1 mm ² per 25g (2.5Kg / 100mm ²⁾ or more, it becomes more than 100 times the contact pressure of the contact in the normal electrical circuits. In addition, an excessive current, which reaches 1200 A instantaneously when the current is cut off, flows through the battery-side contact (1a) of the fixed contacts, thereby increasing the consumption thereof.

As one of the materials for the contact for the starter, conventionally, tough pitch copper has been adopted as a material for both the fixed contact and the movable contact. The contact of this combination withstands about 50,000 uses under a normal atmosphere and a normal load current, and sufficiently satisfies the requirements for use under normal operating conditions.

Further, a combination using tough pitch copper for the movable contact and copper-tungsten for the fixed contact was later developed as a contact that can withstand long-term use. This combination of contacts can withstand 3 to 4 times the use of tough pitch copper under normal use atmosphere and load current, but is repeatedly exposed to strong oxidizing atmosphere, high and low temperature. In a cold region environment or a humid atmosphere containing salt water near the coast, oxidation or corrosion may occur, resulting in poor conduction.

Japanese Patent Application Laid-Open No. 50-2165 discloses that one of Cu and Ag is used as a material for a medium-load contact that requires a large number of switching times and a long life, such as a contact for an elevator or an escalator.
One contact made of an alloy containing 15% by weight or more of C as a seed, and 0.1 to 1.5% by weight of Cr, 0.1 to 1.0% by weight of Zr and 0.0% by weight of Si
A combination with the other contact made of a copper alloy containing any two of 05 to 1.0% by weight is described. However, this contact is completely different from the contact of the present invention in the conditions of use and therefore the alloy composition.

Further, according to Japanese Patent Publication No. 56-9257, Sn 3-9% by weight, In 1-3% by weight, Cd 0.2-
A material obtained by internally oxidizing an alloy consisting of 1% by weight, Ni of 0.01 to 1% by weight and the balance of Ag is known. This is a contact for a switch for medium load AC, which is used under a low contact pressure. However, the present invention is not intended to be used under severe conditions of receiving a high contact pressure for direct current as in the invention of the present application. By the way, it is clear from the specification of this prior art that no evaluation test is made in the examples when the materials described therein are used as DC contacts.

It is also used as a lead material for semiconductor devices.
No. materials are known. This material is composed of Cr 0.05-1% by weight, Zr 0.005-0.3% by weight, C 5-60ppm, Ni, S
0.005 to 2% by weight of at least one element selected from the group consisting of n, Fe, Co and Be, with the balance being Cu, and excellent press punching properties, heat resistance, It is intended to simultaneously have various properties such as heat dissipation, strength, and conductivity, but is not intended to be used as an electrical contact at all.

(3) Problems to be Solved by the Invention In view of the above-mentioned prior art, the contact life is longer than that of a contact made of a combination of tough pitch copper and copper-tungsten, and is repeatedly exposed to a strong oxidizing atmosphere, high and low temperatures. There has been a strong demand for the development of a contact material that can operate safely even in a humid atmosphere containing salt water or an environment.

(4) Means for Solving the Problems Accordingly, as described above, the inventors of the present invention have conducted intensive studies on combinations of materials that satisfy the rigorous use conditions required for a DC contact for an engine starter. The following combinations of contact materials have been developed.
That is, at least one of the fixed contacts is composed of 2 to 10% by weight of tin, 1 to 5% by weight of indium, 0.2 to 6% by weight of cadmium, 0.01 to 1% by weight of at least one kind of iron group element, and the balance of silver and unavoidable impurities. A DC contact for an engine starter consisting of a pair of fixed contacts and a movable contact made of a copper-based material, which are materials obtained by internal oxidation of

The movable contact is 0.05-1% by weight of chromium, and zirconium is 0.1%.
005-0.5% by weight, carbon 5-60ppm, magnesium 0.001-
The direct current contact for an engine starter according to the above (1), comprising 0.2% by weight, 0.001 to 0.2% by weight of silicon, the balance being copper and inevitable impurities.

It is.

That is, first, for the fixed contact, in the conventional tough pitch copper and copper-tungsten combined contact,
In order to further extend the service life by a factor of two, several types of materials that can be substituted for the copper-tungsten of the fixed contact were examined, and the tests were repeated, and finally, the above-mentioned silver-oxide-based material was found to be the most suitable. found. In a copper-tungsten-based material, in an oxidizing atmosphere, a humid atmosphere containing seawater, or an environment repeatedly exposed to high and low temperatures, tungsten may be selectively oxidized or oxidized to cause conduction failure.

On the other hand, a silver-oxide-based material is a skeletal material.
Since SnO ₂ -In ₂ O ₃ is an oxide from the beginning, it is extremely stable in any use atmosphere, while silver is oxidized or sulfide or chloride layer is formed. It has been found that since the contact pressure during use is extremely high, these insulating films are easily broken, and there is no possibility of causing poor conduction. Therefore, it is most suitable as a material that can withstand opening and closing that can be several times the number of times of normal use under severe use conditions. It is for this reason that this material is the only one selected from a number of candidate materials for the fixed contact in the present invention.

Next, the reason why the Cu-Cr-Zr-based material was selected for the movable contact is as follows. First, the adoption of a harder silver-oxide material as the fixed contact of the mating material required higher welding resistance and higher resistance to deflection than tough pitch copper, but Cu-Cr- Zr-based materials satisfy this requirement well. In addition, Cu-
The Cr-Zr-based material is rich in thermal conductivity and excellent in high-temperature characteristics, and therefore has an advantage that thermal deformation can be avoided when used as a contact. In the present invention, this material is selected for the movable contact for such a reason.

In the actual combination of contact materials, only the fixed contact on the battery side, whose use condition is extremely severe compared with the motor side with respect to the arc resistance, of the pair of fixed contacts is made of a silver-oxide-based material. It has been found that a sufficiently long life can be obtained.

(5) Function The reason why the content of each component is selected within the range defined in the claims for each material of the above-mentioned fixed contact and movable contact is as follows.

(Hereinafter,% represents weight%.) About movable contact material (a) Cr Cr forms a solid solution in copper to about 0.4% and raises the softening temperature (about 200 ° C.) of copper to about 500 ° C. For this reason, Cr
It has the effect of improving rigidity (deflection resistance) and heat deformation resistance. However, if the content is less than 0.05%, the desired effect cannot be obtained. On the other hand, if the content is 1% or more, the conductivity is reduced. Therefore, the content was determined to be 0.05 to 1%.

(B) Zr Zr precipitates at the grain boundaries of an alloy of copper and Cr, and has an effect of preventing welding when coming into contact with a dissimilar metal. Its content
If the content is less than 0.005%, the desired effect cannot be obtained. On the other hand, if the content is 0.5% or more, segregation occurs during dissolution and workability is extremely deteriorated. Therefore, the content is set in the range of 0.005 to 0.5%.

(C) C This component forms carbides and contributes to the refinement of crystal grains and the size of inclusions in the matrix, and has the effect of improving rigidity. However, the content is desired if the content is 5 ppm or less. Stiffness cannot be obtained. On the other hand, if it exceeds 60 ppm, the workability will be deteriorated.
6060 ppm.

(D) Mg and Si Each of these components has a deoxidizing effect and an effect of improving conductivity, but the content is 0.001%.
If less than the desired effect is not obtained, while the content is 0.2
%, The effect tends to deteriorate.
The range of the content of these elements is 0.001 to 0.2, respectively.
%.

Regarding Fixed Contacts (a) The content of Sn in molten Sn is preferably 2 to 10%, and if it is less than 2%, the current interrupting characteristics are not sufficient. Oxidation treatment becomes difficult.

(B) In The content of In at the time of melting is preferably 1 to 5%,
If it is less than 1, the effect of promoting the oxidation of Sn is small, and 1% or more is preferable in order to enhance the welding resistance and arc wear resistance for medium to heavy loads. If it exceeds 5%, the arc wear resistance is reduced, so the upper limit is made 5%.

(C) Cd Cd improves the castability of the smelted alloy. The content of Cd at the time of smelting is preferably 0.2 to 6%, and if it is less than 0.2%, it is insufficient to maintain castability comparable to that of an Ag-Cd alloy, and the Cd content exceeds 6%. , The arc wear resistance deteriorates, so the upper limit is set to less than 6%.

(D) Iron group element The iron group element at the time of smelting disperses other oxides finely.
It is known as an additive for refining the Ag matrix. In the present invention, the content of 0.01 to 1% is appropriate. If the content is less than 0.01%, the effect of addition does not appear,
On the other hand, if it exceeds 1%, the oxides cannot be uniformly dispersed in Ag.

(6) Examples Hereinafter, the present invention will be specifically described with reference to examples.

Each material having the composition shown in Table 1 below is processed into the shape shown in the drawings to form a combined contact, and a durability test (Example 1) and an environmental test (Example 2) are performed on these contacts.
Was carried out.

Example 1 (Durability test) A contact test in which various materials listed in Table 1 were combined was subjected to a durability test under the following test conditions.

Power when energized: DC 24 volts, 50 amps Contact force: 500 g Separation force: 1000 g Switching frequency: 1200 times / hour Environment: Indoor air atmosphere Test switching frequency: 10,000 times Shape of contact test piece: shown in Fig. 2 As described above, both the fixed contact and the movable contact have the same rivet shape.

Table 2 shows the total consumption and contact resistance of the test pieces of the movable contact and the fixed contact after opening and closing 10,000 times using a large relay.

Among the conventional contacts, in a contact obtained by combining tough pitch copper and tough pitch copper, the cause of finally becoming unusable is poor conduction due to wear of the contact portion.

The tough pitch copper and copper-tungsten alloy contacts may eventually become unusable due to poor electrical conduction due to wear, but they have a variable life cycle and are subject to high-temperature, high-humidity environments and corrosive gases. Corrosion may occur in an atmosphere containing.

On the other hand, in the combined contact of the silver-oxide based alloy fixed contact and the tough pitch copper movable contact according to the present invention starting from the Ag-Sn-In based alloy, the chromium matrix added as described above is used. Of the tough pitch copper and the tough pitch copper combined contact of the conventional product, shows about four times the number of lifetimes due to the strengthening action of the alloy and the action of preventing the hard intermetallic compound generated by chromium and zirconium respectively. In the combined contact of a fixed contact of a silver-oxide-based alloy and a movable contact of a copper-chromium-zirconium-based alloy starting from an Ag-Sn-In-based alloy,
The lifetime count is further improved based on the absence of image sticking.

Example 2 (Environmental test of contact for starter) An environmental resistance test was performed on the contacts in which various materials listed in Table 1 were combined under the following test conditions.

Among various combinations of fixed contacts and movable contacts, Ag-Sn-In alloy (indicated by the composition before internal oxidation treatment) is used as the fixed contact, and tough pitch copper or copper-chromium-zirconium is used as the movable contact. The contact using the alloy is the contact of the present invention.

 Table 3 shows the results of the environmental test.

Each contact was exposed to an ozone atmosphere, an air atmosphere in which a high-temperature (120 ° C) and low-temperature (-30 ° C) cycle was repeated, and an atmosphere of sprayed salt water for 500 hours. Was measured.

A contact using tough pitch copper for both the fixed contact and the movable contact has a high contact resistance value in any of the above three atmospheres, indicating that a deteriorated layer (mainly an oxide film) is likely to be formed on the contact surface.

Next, the contact using copper-tungsten for the fixed contact and tough pitch copper for the movable contact shows good environmental resistance under the environment subjected to the cooling and heating cycle and the atmosphere of the sprayed salt water, and keeps the contact resistance at a low value. It can be seen that copper-tungsten corrosion is slightly greater in an atmosphere containing ozone.

On the other hand, the contact of the present invention, that is, the fixed contact of silver-oxide alloy and the tough pitch copper or copper-chromium-
A contact formed by a combination with a movable contact made of a zirconium-based alloy shows a stable low contact resistance value in all three types of atmospheres.

(7) Advantageous Effects of the Invention As described in detail above, the contact of the present invention is used as a DC contact for an engine starter that frequently opens and closes, in a highly oxidizing atmosphere, in a cold environment, and in the vicinity of a coast. It shows sufficient corrosion resistance in a salty environment and is optimal as a starter contact.

[Brief description of the drawings]

FIG. 1 is a view showing the structure of a DC contact for an engine starter. FIG. 2 is a view showing a shape of a contact test piece used for a durability test. 1a, 1b ... fixed contact, 2 ... movable contact, 3 ... operation switch,
4 ... Battery, 5 ... Retraction coil, 6 ... Support coil, 7 ... Motor, 8 ... Operation shaft.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takuo Iwamura 1-297 Kitabukurocho, Omiya-shi, Saitama Mitsubishi Metals Central Research Laboratory (72) Inventor Toyozo Kusaka 2--22 Higashisakura, Naka-ku, Nagoya-shi, Aichi Prefecture No. 18, Nikko Building, 4th floor, Mitsubishi Metal Corporation Name: Furuya Branch (56) References JP-A-50-5867 (JP, A) JP-A-58-87713 (JP, A) JP-A-3-201324 (JP, A) A) JP-A-50-2165 (JP, A) JP-A-53-106625 (JP, A) JP-A-62-70542 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) ) H01H 1/00-1/04

Claims (1)

(57) [Claims] 1. A DC contact for an engine starter comprising a movable contact and a fixed contact, wherein the movable contact has a chrome of 0.05-.
1% by weight, 0.005-0.5% by weight of zirconium, carbon 5-60
ppm, magnesium 0.001-0.2% by weight, silicon 0.001--0.
A direct current contact characterized by an alloy consisting of 2% by weight, the balance being copper and unavoidable impurities.