JPH0760626B2 - Thermal protector - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal protector suitable for preventing burnout of compressor-related motors for refrigerators and the like.

2. Description of the Related Art In the conventional thermal protector of this type, a movable electrode and a fixed electrode are provided so as to face each other, both electrode leads are welded with bead glass to form a mount body, and the mount body is housed in a glass container. Then, the indoor air in this is about 300 Tor
After sealing under a gas pressure of r, the glass container is sealed at 10 ^-9 cm ³ He / sec (0 to 1
It is hermetically sealed at 60 ℃.

Problems to be solved by the invention When the contacts of the thermal protector are opened / closed under an inductive load energization condition, arc discharge is generated between the contacts, and this arc discharge becomes large as the voltage becomes high and the current becomes large. Become. The heat generated from the contacts due to this arc discharge causes the contact materials to be consumed more heavily, and due to the scattering of these contact spatters, the snap action heat-responsive metal elements are burned and deteriorated, resulting in large changes in characteristics such as operating temperature and operating time.
Further, there is a problem that contact welding occurs and the contact opening / closing force is lost.

The present invention has been made to solve these problems, and provides a thermal protector capable of stabilizing characteristics such as an operating temperature and an operating time in a contact opening / closing operation process and improving endurance reliability of a contact opening / closing life. It is provided.

Means for Solving the Problems In order to solve such problems, the present invention provides a container with a movable electrode body and a fixed electrode body facing each other, with nitrogen of 50 to 80% by weight and the balance of oxygen. Enclose the mixed gas of
Further, the invention is characterized by a thermal protector in which the gas pressure of the mixed gas is 400 Torr or more.

By adopting nitrogen-oxygen gas with such composition ratio,
Arc discharge is less likely to occur between the contact points of the fixed electrode and the movable electrode, and the contact pressure material is prevented from evaporating due to the increase in the filling pressure of the filling gas.

Embodiments Embodiments of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, in the thermal protector of the embodiment of the present invention, a silver-based contact 2 is welded to the tip of the snap action thermoresponsive metal element 1 and the lower end of the snap action thermoresponsive metal element 1 is welded. For example, a metal auxiliary plate 3 made of a stainless plate or the like is welded (see FIG. 2). Further, the metal auxiliary plate 3 is welded to the lead wire 4 made of, for example, noborate dimet to form a movable electrode body. On the other hand, the silver-based contact 5 is welded and fixed to the tip of the lead wire 6 made of, for example, noborate dimet to form a fixed electrode body. These electrode bodies are positioned so that the silver-based contacts 2 and 5 face each other, and integrated with low-melting-point glass, for example, lead glass-based sintered bead glass 7, to form a mount body.

The mount body is housed in a glass container 8 made of soda glass, lead glass or the like, the lower end thereof is heat-sealed, and further exhausted, and then a mixed gas of a fixed ratio composition with purified oxygen is added therein. The inside of the glass container 8 is highly airtight at 10 ⁻⁹ cm ³ He / sec (0 to 160 ° C.) by enclosing the glass container 8 under increased pressure and heating the tip of the glass container 8 to chip off. It is what

Next, the enclosed gas and the enclosed gas pressure will be described with reference to FIGS. 3 and 4.

The samples used to obtain the experimental results shown in FIGS. 3 and 4 have the same shape (5 mm × 10 m) instead of the snap action thermo-responsive metal element in order to keep the measurement conditions constant.
m) is a thermal protector of the above-mentioned structure, which uses a stainless steel plate having the same thickness (0.105 mm) and does not respond to heat, and has a fixed interval of 0.2 mm between the contacts, which corresponds to the interval just before the closing of the contacts. The experimental results shown in FIGS. 3 and 4 are
Both are based on the average value of the sample number n = 10. In addition, all measured values are relative percentages of each, assuming that the arc discharge switching voltage when general room air is enclosed is 100.
Is displayed in.

As shown in Fig. 3, the arc discharge inception voltage in the case of nitrogen-containing gas composition of 50 to 80% by weight and the balance of oxygen is more than double that of general room air filling, especially 65% by weight of nitrogen and the balance of oxygen filling. In case of gas composition, the arc discharge starting voltage becomes the highest. That is, arc discharge is difficult to occur with a composition of 50 to 80% by weight of nitrogen and the balance gas of oxygen.

In general indoor air, in addition to 75.5% by weight of nitrogen and 23% by weight of oxygen, noble gases such as argon, carbon dioxide, hydrocarbons, oxygen sulfide, moisture, etc. are contained, so the presence of these impurities causes arc discharge. It is considered that this was the cause of lowering the starting voltage.

As for the charged gas pressure, as shown in Fig. 4, when a mixed gas of 65 wt% nitrogen and the balance oxygen was adopted as the optimum mixed gas composition of the charged gas, when the arc discharge starting voltage was 400 Torr Since it is 2.5 times that of air and increases slightly linearly up to around 600 Torr, increasing the pressure of the enclosed gas not only prevents the occurrence of arc discharge but also suppresses the evaporation of contact material. Yes, it has a long life. As described above, by using a mixed gas of nitrogen 50 to 80% by weight as the filling gas in the glass container and the balance oxygen, and setting the filling gas pressure to 400 Torr or more, arc discharge is difficult, and the operating temperature of contact opening and closing and Stabilization of operating time characteristics, improvement of durability reliability such as contact opening / closing life, and improvement of rated voltage and rated current are possible.

These mixed gases are easily available, and the pressure of the enclosed gas is increased by heating and sealing the mount body and the glass container, and after evacuation, give a certain cooling time to turn off the heating tip of the tip part. This can be easily performed by heating or chipping off after cooling by blowing air into the glass container.

When a large number of the thermal protectors shown in the above-mentioned examples were manufactured and a contact test life of the finished product was compared with the conventional product, the results shown in the following table were obtained.

The contact open / close life test was conducted by connecting a thermal protector to an AC power supply of 250 V via an inductive load (power factor 0.5) and setting the circuit current to 8 A. The open / close circuit in that case was defined as the contact open / close life.

As is clear from the above table, the thermal protector of the present invention has a contact opening / closing life that is three times longer than that of the conventional thermal protector, and there is little change in operating temperature and operating time after 10,000 opening / closing operations, and durability reliability is high. It can be seen that it is significantly improved.

Advantageous Effects of Invention As described above, the present invention provides a thermal protector having excellent effects such as improvement of contact opening / closing life, less change of operating temperature and operating time in the life process, and improvement of durability reliability. Is something that can be done.

[Brief description of drawings]

FIG. 1 is a partially cutaway side view of a thermal protector according to an embodiment of the present invention, FIG. 2 is a perspective view of a movable electrode, and FIG. 3 is a characteristic diagram showing a relationship between a mixed composition of enclosed gas and an arc discharge starting voltage.
FIG. 4 is a characteristic diagram of the relationship between the enclosed gas pressure and the arc discharge starting voltage. 1 ... Snap action thermo-responsive metal element, 2,5 ...
Contact points, 3 ... Auxiliary metal plate, 4 ... Lead wire for movable electrode, 6 ... Lead wire for fixed electrode, 7 ... Bead glass, 8 ... Glass container.

Claims (1)

[Claims] 1. A movable electrode body and a fixed electrode body are provided to face each other in a container, a mixed gas of 50 to 80% by weight of nitrogen and the balance of oxygen is sealed, and the pressure of the sealed gas of the mixed gas is adjusted.
A thermal protector characterized by having 400 Torr or more.