JPH0127532B2 - - Google Patents

Description

Detailed Description of the Invention (a) Technical Field of the Invention The present invention relates to a reed switch in which reed pieces of magnetic material are enclosed from both ends in a glass tube, and contacts are opened and closed at mutually overlapping portions of the reed pieces; In particular, it relates to reed switches for large currents.

(b) Background of the technology As shown in Figure 1A, a normal reed switch is sealed in an inert gas atmosphere with a pair of lead pieces 2 and 3 inserted from both ends of a glass tube 1. Manufactured by When the excitation coil 4 disposed outside the glass tube 1 is energized, the magnetic flux passing through both the reed pieces 2 and 3 closes the gap 5 at the overlapping contact 6 of the reed pieces, turning on the switch. Next, when the excitation coil 4 is de-energized, the magnetic attraction force of the contact gap 5 disappears, the contact gap 5 opens, and the switch is turned off.

For the contact portion at the inner end of the lead piece, a contact point 6 made of a noble metal material or a high melting point material is provided at the tip of the lead pieces 3, 2 as shown in (b), so that the contact resistance is small and the life is long. The magnetic material of the reed piece is usually permalloy, especially 52% alloy called 52 alloy.
An alloy of nickel and 48% iron is widely used. Gold, silver, copper, gold-based alloys (Au--Co, Au--Ni), etc. are used as the contact material.

(c) Conventional technology and its problems By the way, ordinary reed switches are not suitable for large currents.
It used to be possible to turn on and off only about 1A, but as the uses of reed switches have recently expanded, there is a demand for devices that can turn on and off currents of 1A or more. In order to be able to handle large contact currents, the following issues arise.

(a) First, the electrical resistivity of the lead piece must be low. If the electrical resistivity of the lead piece is high, the voltage drop across the lead piece will be large, and the contact portion will also reach a high temperature due to heat generation, deteriorating the characteristics of the contact point. It is also important that the contact resistance of the contact portion be small. Contact resistance is the sum of lumped resistance Rc and film resistance Rf. If the contact resistance is large, the voltage drop at the contact point will also increase as the contact energizing current increases, so in the case of a reed switch for large currents, it is required to reduce the contact resistance as much as possible.

(b) An arc occurs when the contacts open while current is flowing. That is, the discharge when the contacts open becomes an arc discharge with a high current density and a high temperature of several thousand degrees. Therefore, if the arc continues for a long time, the contact wears out rapidly, shortening the life of the contact. It is therefore necessary to keep the arc duration as short as possible.

(c) When the contact current increases, contact chattering phenomenon occurs when the contact opens, that is, EMB.
(Electro Magnetic Bounce) is likely to occur. That is, when the contacts of the reed pieces open when the contacts are opened, it becomes difficult for current to flow, the magnetic flux between the contacts of the reed pieces increases, the attractive force increases, and a force to close the contacts is generated. As a result, when the contact closes, the contact current starts flowing again, and the contact force of the contact decreases due to the magnetic field of the contact current, causing the contact to open. Repeating this operation causes the contacts to chattering. This EMB is a troublesome problem for large current reed switches because it depends on the contact current.

These new problems arise in reed switches that handle large currents, and it is necessary to solve them.

(d) Purpose of the Invention The present invention solves these problems in reed switches for large currents, has low electrical resistivity of the reed pieces, shortens the life of the contacts, shortens the duration of the arc, and reduces EMB. The purpose is to realize a large current reed switch.

(e) Structure of the Invention The technical means of the present invention taken to achieve this object is that in a reed switch that turns on and off a direct current of 2A or more, the reed piece is equipped with Fe (10
~18%) - Co (remainder) alloy is used, and the internally sealed gas is He, N ₂ or a mixture of both.

(f) Embodiments of the Invention Next, examples will explain how the reed switch according to the present invention is actually implemented. In the present invention, improvements have been made in terms of the material of the lead piece and the gas enclosed. That is, it has conventionally been the mainstream as a lead piece. Instead of 52 alloy, an alloy material of Co and Fe is used. That is, Fe is 10-18%, Co
The remaining 82 to 90 magnetic materials are used. As described in Japanese Patent Application No. 57-91377 previously filed by the applicant of the present invention, magnetic materials with such a composition have extremely low electrical resistivity and are suitable for lead pieces of large current lead strings. It is most suitable as Figure 2 is
This is a diagram showing the electrical resistivity of Fe—Co alloys, where the horizontal axis is the content of iron (Fe) in cobalt (Co), and the vertical axis is the electrical resistivity. Same coefficient of thermal expansion as glass
In the region of 8.5-20% Fe, the electrical resistivity is 12-14 μΩ
cm, which is far superior to the 35μΩcm electrical resistivity of 52 alloy, the most commonly used lead material.

The present invention uses such Fe (10~18%)-Co (remainder)
An alloy is used as the lead piece, and He, N ₂ or a mixture of both is used as the filler gas. The inventors of the present invention previously proposed in Japanese Patent Application No. 178900/1987 that adhesion problems could _be improved by filling in argon. Mixed gases have been found to be extremely effective.

Figure 3 is a diagram comparing the arc duration of a Fe (10-18%)-Co (remainder) alloy lead piece and a 52 alloy lead piece for each filled gas. Using _N2 , the contact current is 100 VDC (resistive load) with a triangular wave.
The measurement was performed by driving the device twice. The horizontal axis is the contact current, and the vertical axis is the average arc duration time. As is clear from this characteristic diagram, when Ar is used as the filler gas, the arc duration is shorter for Co-Fe alloy than for 52 alloy, but the arc duration is shorter than for those filled with He or _N2 . The time is extremely long. Furthermore, when He is sealed, the arc duration time of Co-Fe alloy is extremely short compared to 52 eye. Although N ₂ encapsulated is inferior to He encapsulated Co-Fe alloy, Co-Fe alloy is still far superior to He encapsulated 52 alloy and N ₂ encapsulated 52 alloy. . In this way, the Co--Fe alloy is superior to 52 aloin in terms of arc duration. Furthermore, when using He or N ₂ as the filler gas in a Co--Fe alloy lead piece, further improvement can be achieved.

The reason why Co-Fe alloy has a shorter arc duration than 52 alloy is because Co-Fe alloy has a shorter arc duration than 52 alloy.
This is due to the fact that it generates less heat due to its lower electrical resistivity than 52 alloy. In other words, the contact points of any 52 alloy lead piece easily reach the boiling point due to overheating, and arc discharge is also likely to occur. In contrast to this
Co--Fe alloy lead pieces have a low temperature rise at the contact points, making it difficult for arc discharge to occur.

However, such excellent characteristics are observed only when the contact current is 2A or more, and only when the contact current is 1A.
Below, the difference is hardly noticeable. Therefore, for reed switches for large currents of 2A or more,
Co-Fe alloy is used as the lead piece, and He or
Enclosing _N2 is extremely effective.

FIG. 4 is a diagram showing the EMB characteristics when the contacts open and open, and the average number of bounces per drive was measured under the same conditions as in FIG. 3. The horizontal axis is the contact current, and the vertical axis is the average number of bounces. In this case, too, there is no noticeable difference when the current is 1A, but when the voltage exceeds 2A, the filled gas becomes Ar,
In both He and _N2 cases, Co- is used as the lead piece.
The one using Fe alloy is much better. However, when using Ar as the filler gas, He or
Somewhat worse than a 52 alloy reed piece filled with _N2 .
Therefore, using Co--Fe alloy as the lead piece, He or
EMB is also better if it contains _N2 .

The reason why the Co--Fe alloy has better EMB properties is due to the difference in the Curie point between the two. In other words, the Curie point of 52 alloy is 540℃
On the other hand, that of Co--Fe alloy is as high as about 1000°C, so in the case of 52 alloy, the heat generated by the lead piece reduces the magnetism at the tip of the lead piece, making the contact easily open. Co-Fe alloys do not lose their magnetism up to around 1000℃, so their magnetism does not deteriorate even under high-temperature conditions, and Co-Fe alloys are also better for EMB, which depends on the magnetic attraction force at the tip of the lead piece. Are better.

As for the filler gas, He is better in terms of arc duration and chattering overall, but since He is expensive, it is practical to use a mixed gas of He and N ₂ and the characteristics are satisfactory.

(g) Effects of the invention As described above, according to the present invention, the lead piece has
A magnetic material made of Fe (10 to 18%) - Co (remainder) alloy is used, and He, N ₂ or a mixture of both is used as the internally sealed gas. Therefore, even in a reed switch that handles a very large contact current of 2A or more, the electrical resistivity of the reed piece is low, and the arc duration and EMB of the contact are improved. As a result, it is possible to realize a highly practical reed switch with a long contact life.

[Brief explanation of drawings]

Figure 1 is a sectional view showing the structure of the reed switch.
Figure 2 is a diagram showing the electrical resistance characteristics of Co-Fe alloy.
FIG. 3 is a diagram showing the arc duration time of the reed switch according to the present invention and the conventional reed switch.
The figure is a diagram showing the EMB characteristics of the reed switch according to the present invention and the conventional reed switch. In the figure, 1 is a glass tube, 2 and 3 are lead pieces, 4 is an excitation coil, 5 is a gap, and 6 is a contact.

Claims (1)

[Claims] 1. In reed switches that turn on and off direct current of 2A or more, the lead piece is made of Fe (10 to 18%) - Co.
A reed switch that uses a magnetic material made of (remaining) alloy and uses He, _N2, or a mixture of both as the internal gas.