JPS5856106B2 - How to check for leaks in reed switches - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a leak check method for detecting leakage of a glass tube sealing portion of a reed switch.

Generally, reed switches have contact parts that are flattened.
It has a structure in which two lead terminals are enclosed within a glass tube.

In order to prevent deterioration of the lead piece metal and contacts and to stabilize switch characteristics, an inert gas such as N2 is usually filled in the glass tube.

If the seal between the glass tube and the lead piece terminal is poorly sealed, the sealed gas will leak and the switch characteristics will change.

Therefore, the characteristics of reed switches mass-produced in factories vary, reducing the reliability of the product.

In order to eliminate such problems, a leak check is performed at the final stage of manufacturing the reed switch to detect leakage of the gas filled in the reed switch.

Conventional leak checking methods include He gas or K
A method using a He leak detector or a radio flow meter that non-destructively measures a small amount of leak using r gas,
Alternatively, a red check method has been implemented in which a reed switch is immersed in a red pressurized liquid and a leak is detected by the intrusion of the red liquid into the inside of the reed switch.

However, such conventional leak checking methods have drawbacks such as high equipment costs and a large amount of effort and time required for detection.

A leak check method that does not have these drawbacks is a leak check method that measures the withstand voltage between the contacts of a reed switch under reduced pressure and detects a leak when this measured value is lower than a predetermined value for a normal reed switch. Proposed by the applicant.

Such a leak check method is effective for a pressurized switch in which the internal gas of the reed switch is sealed in a pressurized state.

However, in a non-pressure switch where the internal gas of the reed switch is sealed under atmospheric pressure, even if the withstand voltage between the contacts of a leaky IJ-de switch is measured in a vacuum condition, the measured value will be the same as that of a normal reed switch. The difference with the withstand voltage value is small, making it difficult to determine the leak check.

SUMMARY OF THE INVENTION An object of the present invention is to provide a leak check method that eliminates these drawbacks and can easily detect leaks in a short time, especially in non-pressure reed switches.

For this reason, in the present invention, a reed switch to be inspected is arranged inside a vacuum container, and while the pressure inside the vacuum container is maintained at a predetermined degree of vacuum, a gas that reduces the withstand voltage between the contacts of the reed switch at this vacuum pressure is introduced. is filled into the vacuum container, and in this state, the withstand voltage between the contacts of the reed switch is measured, and this measured value is compared with a predetermined breakdown voltage value corresponding to the reed switch to detect a leak in the reed switch. To provide a leak check method for a reed switch.

The present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a schematic diagram of an embodiment of the invention. Base plate 10
The bell jar 3 placed on top constitutes a vacuum container.

Each terminal 5, 5 of the reed switch 4 to be inspected is placed on a conductive reed switch holding stand 9, 9 installed in the bell jar 3.
is placed.

Each terminal 5, 5 of the reed switch 4 is connected to a contact-to-contact dielectric strength meter 6 via a reed switch holding stand 9, 9.

The inside of the bell gear 3 is communicated with an Ar gas cylinder 13 through a pipe 14.

8 is a vacuum pump, 7.12 is a cock, and 11 is a pressure gauge.

Figure 2 shows the product P of the distance d between the switch contacts and the pressure P.
It is a Paschen curve showing the breakdown voltage Vs against d, and a
,b.

C is each N2. Characteristics in Ar and He atmospheres are shown.

The method of the present invention is carried out as follows.

First, the N2 gas-filled reed switch 4 to be inspected is placed on the reed switch holding stands 9, 9 inside the bell jar 3.

Next, the bell jar 3 is placed over the bell jar 3, and the inside is brought to a degree of vacuum near the minimum breakdown voltage presentation pressure (corresponding to point P1 in FIG. 2) at which the minimum breakdown voltage occurs between the contacts of the reed switch 4 using the vacuum pump 8.

While keeping the inside of the bell gear 3 in this vacuum state, open the cock 12.
Open the bell gear 3 and fill the inside of the bell gear 3 with Ar gas.

In this state, the breakdown voltage Vs of the reed switch 4 is measured using the inter-contact withstand voltage meter 6.

Ar gas reduces the withstand voltage between the contacts of the reed switch at the above vacuum pressure.

The glass tube of reed switch 4 is completely sealed.
If there is no gas leakage, even if the bell gear 3 is filled with Ar gas, the contacts of the reed switch 4 will still be in the initial N2 gas atmosphere, so the measured value of the breakdown voltage Vs will be a predetermined value corresponding to this reed switch 4 ( For example, Figure 2 shows PO point).

On the other hand, if the sealing of the glass tube of the reed switch 4 is incomplete and N2 gas is leaking, if the pressure inside the bell jar 3 is reduced and Ar gas is filled, the reed switch 4 will also be filled with Ar gas.
Gas enters and the contact becomes in an Ar gas atmosphere.

Therefore, the measured value of the breakdown voltage Vs is a value corresponding to point 217 in FIG.

This 217 point is P corresponding to the breakdown voltage value of a normal reed switch.

Since the value is sufficiently low compared to the point, it is easy to identify a leak.

The gas to be filled in the bell jar 3 is not limited to Ar, but any gas that exhibits a low breakdown voltage in the Paschen curve characteristic depending on the characteristics of the reed switch to be inspected and the degree of vacuum to be decompressed can be used. <He gas or other gases can also be used.

If the above-described leak check method is used, leaks can be detected easily and reliably in a short time even in a reed switch having a non-pressurized sealed gas.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an embodiment of the present invention, and FIG. 2 is a schematic diagram of an embodiment of the present invention.
Each Paschen curve of Ar + He is shown. 3... Bell jar, 4... Reed switch, 6... Contact voltage proof meter, 8... Vacuum pump, 13... Ar gas cylinder.

Claims (1)

[Claims] 1. A reed switch filled with unpressurized gas to be tested is placed in a vacuum container, and while the pressure inside the vacuum container is maintained at a predetermined degree of vacuum, the withstand voltage between the contacts of the reed switch is reduced at this vacuum pressure. Fill the vacuum container with a suitable gas, measure the withstand voltage between the contacts of the reed switch in this state, and compare this measured value with a predetermined breakdown voltage value corresponding to the reed switch to detect leaks in the reed switch. How to check for reed switch leaks.