JP3115414B2 - Reed switch - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reed switch,
In particular, the present invention relates to a reed switch having excellent corrosion resistance in a corrosive environment.

[0002]

2. Description of the Related Art As shown in FIG. 2, for example, a reed switch is connected to one end of a pair of elongated lead pieces 11a and 11b made of a metal magnetic material such as Fe or Ni.
A and 12b have a structure in which they are sealed in a container such as the glass tube 2 together with a vacuum state or an inert gas. The contact portions 12a and 12b are kept at a predetermined overlap and interval from each other. On the surfaces of the lead terminals 13a and 13b, Fe
In order to prevent the generation of corrosion products such as Ni and Ni, so-called rust, plating is performed.

In the reed switch having the above structure, for example, by applying a magnetic field from a coil from the outside, the contact portions 12a and 12b have different polarities and come into contact with each other by a magnetic attraction force. The effective conduction state is obtained. When the external magnetic field is removed, the contact portions 12a and 12b are restored and opened at a predetermined interval, so that the lead terminals 13a and 13b are electrically insulated. This reed switch has a contact portion 12
Since a and 12b are sealed in the glass tube 2, they are less susceptible to external harmful gases and dust. Usually, it is further used in a resin 3 package.

[0004]

The above-described reed switch has the following problems when a voltage is applied for a long time in a high-temperature, high-humidity corrosive environment in a state where the contacts are separated. That is, the insulation resistance of the resin 3 decreases due to the moisture absorption of the resin 3 due to the high temperature and high humidity and the intrusion of moisture from the gap between the resin 3 and the lead terminals 13a and 13b. Further, since a voltage is applied to both ends of the lead terminals 13a and 13b, the lead terminals 13a and 13b are connected via the resin 3 having a reduced insulation resistance.
A leak current flows between a and 13b. Since the leak current has the lowest insulation resistance and flows through the shortest path, for example, if the lead terminal 13a is an anode and the lead terminal 13b is a cathode, as shown by the arrow in the figure, the leak current is sealed on the anode side. It is released from the lead terminal 13a in contact with the portion 2a and easily flows to the lead terminal 13b in contact with the sealing portion 2b on the cathode side through the resin 3 whose insulation resistance is reduced or the gap between the resin 3 and the glass tube 2.

At this time, at the place where the current of the lead terminal 13a on the anode side begins to flow, that is, at the place where the lead terminal 13a is in contact with the sealing portion 2a, so-called electrolytic corrosion occurs in which plating coated on the surface is eluted. Eventually, the underlying Fe and Ni are exposed, and rust is generated on the surface. The sealing portion 2a of the glass tube 2 is broken by the volume expansion due to the formation of rust, and moisture and gas enter the inside of the glass tube 2. The invading moisture or gas causes contact failure of the reed switch. An object of the present invention is to solve the above problems.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, according to the present invention, one end of a pair of lead pieces is sealed in a container as a contact, and the other end of each lead piece is exposed as a terminal. In a reed switch in which a part of each of the lead pieces exposed from the container and the container is packaged with a resin in a state where the container is in a state where the insulation between the terminals is secured, at least the anode of the pair of lead pieces is used. The present invention is characterized in that a conductive coating film is provided between the lead piece used and the resin from the terminal side of the lead piece to the surface of the container.

[0007]

In the reed switch having such a structure, when the insulation resistance of the resin is reduced due to moisture absorption or the like, the leakage current flowing from the anode side lead piece to the cathode side lead piece through the resin is the lowest of the insulation resistance. It is released from a lower path, that is, from the tip of the conductive coating covering the surface of the container. Therefore, the leakage current is not directly emitted from the lead piece on the anode side, and electrolytic corrosion of the lead piece is prevented.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of a reed switch according to the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of a reed switch showing one embodiment of the present invention. As shown in the figure, the reed switch of the present invention uses a pair of elongated lead pieces 11a and 11b made of a metal magnetic material such as Fe and Ni as one end of each of the contact pieces 12a and 12b, and together with a vacuum state or an inert gas. It has a structure sealed in a glass tube 2. The contact portions 12a and 12b are kept at a predetermined overlap and interval from each other. Also, the lead terminals 13a, 1 at the other end
The surface of 3b is plated to prevent the generation of corrosion products such as Fe and Ni, so-called rust. The surface of the lead terminal 13a to the surface of the glass tube 2 is continuously covered with the conductive coating 4a, and the surface of the lead terminal 13b to the surface of the glass tube 2 is continuously coated with the conductive coating. It is covered with the film 4b. However, a predetermined interval is provided between the conductive coating 4a and the conductive coating 4b, and the insulating state between the lead terminals 13a and 13b is maintained. As the conductive coating films 4a and 4b, for example, conductive silicon rubber is used. In addition, this reed switch
It is packaged with resin 3.

The reed switch configured as described above is
For example, when a magnetic field is applied from the outside of the coil, the contact portions 12a and 12b have different polarities and come into contact with each other by magnetic attraction, so that an electrically conductive state is obtained between the lead terminals 13a and 13b. When the external magnetic field is removed, the contact portions 12a and 12b are restored and opened at a predetermined interval, so that the lead terminals 13a and 13b are electrically insulated.

Next, a case where a voltage is applied for a long time in a corrosive environment of high temperature and high humidity in a state where the contact portions are separated will be described. Under the above environment, the package resin 3
And the infiltration of moisture from the gap between the resin 3 and the lead terminals 13a and 13b, the insulation resistance of the resin 3 decreases. Since a voltage is applied to both ends of the lead terminals 13a and 13b for a long time, a leak current starts to flow from the anode side to the cathode side via the resin 3 whose insulation resistance has been reduced. Since the leakage current flows through a path having a low electric resistance, the lead terminal 13a is
If b is a cathode, the leakage current is released from the conductive coating 4a on the anode side and passes through the gap between the resin 3 or the resin 3 and the glass tube 2 whose insulation resistance is reduced, as indicated by the arrow in the figure. And flows into the conductive coating film 4b on the cathode side which is close in distance. Therefore, no leakage current is emitted from the lead terminal 13a on the anode side, and no electrolytic corrosion is observed in the plating layer on the surface. For this reason, the metal magnetic body such as Fe or Ni forming the lead piece is protected by the plating layer, and the generation of rust is suppressed.

In the above embodiment, the conductive coatings 4a and 4b are provided on both sides of the anode and the cathode. However, in consideration of the occurrence of electrolytic corrosion due to leakage current on the anode side, the conductive coatings 4a and 4b are used. The coating may be applied to only one terminal. However, in this case, some indication is required on the package resin or the lead terminal so that the coated terminal side can be used as an anode.

[0012]

As described above in detail, according to the reed switch of the present invention, a conductive coating film is provided between the reed switch and the resin from the terminal side of the reed to the surface of the container in which the reed is sealed. As a result, it is possible to prevent the leakage current from the lead piece directly to the resin having reduced insulation. Therefore, the electrolytic corrosion of the lead pieces can be suppressed, and good connection can be maintained even in a corrosive environment of high temperature and high humidity.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a reed switch showing one embodiment of the present invention.

FIG. 2 is a configuration diagram of a conventional reed switch.

[Explanation of symbols]

 2 Glass tube (container) 4a, 4b Conductive coating film 11a, 11b Lead piece 12a, 12b Contact part

Claims (1)

(57) [Claims] 1. One end of each of a pair of lead pieces is sealed in a container as a contact, and the other end of each of the lead pieces is exposed as a terminal, and the lead and the respective lead pieces exposed from the container are exposed. In a reed switch in which a part of the lead is packaged with a resin, in a state where insulation between the terminals is secured, at least the terminal side of the lead piece used as an anode of the pair of lead pieces has the surface of the container. Wherein a conductive coating is provided between the reed switch and the resin.