JPH0323539Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a positive temperature coefficient thermistor device suitable as a sensor for, for example, a liquid level gauge, a flow meter, or a thermometer.

As is well known, a positive temperature coefficient thermistor is constructed by attaching electrodes to barium titanate semiconductor porcelain, which has _a positive temperature coefficient of resistance. It exhibits a unique positive resistance-temperature characteristic in which the electrical resistance value increases rapidly when the temperature exceeds . FIG. 2 is a diagram showing the basic structure of this PTC thermistor, in which electrodes 2 and 3 are formed on both sides of the PTC thermistor body 1. When an alternating current or direct current voltage is applied between the electrodes 2 and 3, at the beginning of the voltage application, since the resistance value is low as shown in FIG. 1, a relatively large inrush current flows and the positive temperature coefficient thermistor self-heats. When the heat generation temperature exceeds the Curie temperature TC ₁ , the resistance value increases rapidly and the current is throttled, and the heat generation temperature and current of the positive temperature coefficient thermistor become stable at the point where the input energy and the amount of heat dissipation are balanced.

The applied voltage applied between electrodes 2 and 3 is V ₁ ,
(V), current I ₁ (A), heat generation temperature T (℃),
The temperature of the surrounding medium in which a positive temperature coefficient thermistor is placed
Assuming Ta (°C), the following equation approximately holds true at thermal equilibrium.

V ₁・ I ₁ = D (T - Ta) ... (1) where D is the heat dissipation coefficient The left side of the above equation (1) indicates the input energy of the positive temperature coefficient thermistor, and the right side indicates the amount of heat dissipation. . In other words, the positive temperature coefficient thermistor has a heat dissipation amount D
When (T-Ta) increases or decreases, the input energy V ₁ ·I ₁ also increases or decreases, and thermal equilibrium is achieved at the point where both become equal. Therefore, when the applied voltage V ₁ is constant, if the heat dissipation amount D (T - Ta) increases or decreases, the current _{I 1} increases or decreases accordingly, so the heat dissipation amount D It is possible to detect a change in (T-Ta), that is, a change in the cooling effect that the surrounding medium has on the positive temperature coefficient thermistor. The cooling effect of the surrounding medium on a positive temperature coefficient thermistor is
Since it depends on the physical properties of the thermally conductive rod of the surrounding medium, temperature, flow velocity, etc., changes in the type of surrounding medium, temperature, flow velocity, etc. can be detected from changes in the current _I1 . Focusing on these characteristics,
A positive temperature coefficient thermistor device using a positive temperature coefficient thermistor has been proposed as a sensor part of a liquid level gauge, a flow meter, or a thermometer.

FIG. 3 shows a front sectional view of a conventional positive temperature coefficient thermistor device embodied as a liquid level sensor for a liquid level gauge, and a flat positive temperature coefficient thermistor 5 is built inside the glass tube 4 near one end. Finally, elastic electrode terminals 6 are connected to the electrodes provided on both sides of the positive temperature coefficient thermistor 5.
and the electrode terminals 7 are brought into contact with each other, and the lead wires 8 and 9 are brought into contact with the electrode terminals 6 and 7 from the axial direction, and the lead wires 8 and 9 are led out to both ends of the glass tube 4 in the axial direction. It has a similar structure.

However, this conventional positive temperature coefficient thermistor device
The positive temperature coefficient thermistor 5 and electrode terminals 6 and 7 are stacked in the axial direction of the glass tube 4, and lead wires 8 and 9 are connected from both sides.
Because the structure is supported by the PTC thermistor 5 and the electrode terminals 6 and 7, it is not easy to assemble, and the stability after assembly is poor. There were some drawbacks. In addition, a positive characteristic thermistor 5, an electrode terminal 6,
Since the assembly structure of No. 7 has a structure that extends long in the axial direction of the glass tube 4, the volume of the internal space in which the positive temperature coefficient thermistor 5 is inserted becomes large, resulting in poor thermal response and low sensitivity.

Furthermore, since the lead wires 8 and 9 have to be led out to both ends of the glass tube 4 in the axial direction, when used for a liquid level sensor, etc., one lead wire 9 must pass through the liquid. However, it has the disadvantage that it tends to impair electrical insulation against liquids. In addition, since the lead wire 9 passes through the end surface of the glass tube 4, both 9-
If a gap is created at the interface between the tubes 4 and 4, the liquid will enter the inside of the glass tube 4 through the gap, causing malfunction, and in the worst case, short circuit between the electrodes, leading to inoperability or destruction. There were cases.

The present invention eliminates the above-mentioned conventional drawbacks, and has high stability against mechanical shock and vibration, high detection sensitivity, and highly reliable positive characteristics with excellent electrical insulation and sealing properties against the surrounding medium. The purpose is to provide a thermistor device.

In order to achieve the above object, the present invention provides a positive temperature coefficient thermistor device in which a positive temperature coefficient thermistor that is elastically supported between a pair of electrode terminals is enclosed inside a glass container, wherein the glass container has a tip end. The hollow tube body is closed like a bag by a continuous glass wall, and the opening on the rear end side is sealed with a glass sealing plug. An electrode terminal having a concave portion formed by recessing the side thereof, and another electrode terminal having a curved portion formed by curving a flat tip portion into a hook shape, and the electrode terminal includes the concave portion and the curved portion. The positive temperature coefficient thermistor is placed in the concave portion formed in the electrode terminal, with one end side firmly attached to the sealing plug so that the two portions face each other in the hollow portion of the glass container. In addition to positioning and fixing,
The curved portion of the other electrode terminal is brought into pressure contact with the electrode on the upper surface side of the positive temperature coefficient thermistor, and the curved portion of the another electrode terminal is held elastically between the electrode terminals. Connect a pair of independent lead wires with conductivity,
The present invention is characterized in that the vitreous coatings of these lead wires are integrally fixed and connected to the sealing plug.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The content of the present invention will be specifically described below with reference to the accompanying drawings, which are examples. FIG. 4 is a front sectional view of a positive temperature coefficient thermistor device according to the present invention. In the figures, the same reference numerals as in FIG. 3 indicate functionally identical structural parts.

In this embodiment, the vitreous container 4 made of glass or glass ceramic has a tip 4a.
is a bag-like hollow tube sealed by a continuous wall,
A pair of electrode terminals 6-7 are arranged in parallel in the hollow part of the container 4 by sealing the opening at the rear end with a glass sealing plug 10 of the same quality, and embedding one end in the sealing plug 10.
It has a structure in which a positive temperature coefficient thermistor 5 is supported in between.

As mentioned above, the vitreous container 4 has a tip end 4a.
is a hollow tube closed like a bag by a vitreous continuous wall, and the opening on the rear end side is a vitreous sealing plug 1.
0, the tip part 4a, which becomes the detection end in the liquid, has a completely sealed structure with a continuous glass wall, and there is no room for liquid etc. to enter into the glass container 4, and the liquid malfunction due to intrusion,
Short circuits between electrodes, etc. can be almost completely prevented.

Also, one end of the pair of electrode terminals 6 and 7 is sealed with the plug 1.
If the structure is such that the positive temperature coefficient thermistor 5 is embedded within the electrode terminals 6 and 7, the support structure for the electrode terminals 6 and 7 becomes strong, and the electrode terminals 6 and
7 is eliminated, even if mechanical shock or vibration is applied, the positive temperature coefficient thermistor 5 can be connected to the electrode terminal 6.
-7 can be reliably pressed and accidents such as falling off can be prevented. Moreover, a pair of electrode terminals 6,
Since only one end of 7 is embedded in the sealing plug 10 and the other end is open in the hollow part, the vitreous container 4
The location where thermal stress occurs due to the difference in thermal expansion coefficient between the sealing plug 10 and the electrode terminals 6, 7 is limited to only the embedded portions of the electrode terminals 6, 7, and the length of the electrode terminals 6, 7 is No tensile thermal stress is generated from both ends in the longitudinal direction. Therefore, the spring properties of the electrode terminals 6 and 7 do not deteriorate thermally, and the positive temperature coefficient thermistor 5 can be stably supported over a long period of time.

Further, there is a structure in which the electrode terminals 6 and 7 are arranged in parallel and the PTC thermistor 5 is supported between them, that is, the electrode terminals 6 and 7 and the PTC thermistor 5 are arranged in parallel inside the container 4. Therefore, compared to the case of the axial arrangement shown in FIG. 3, the volume of the internal space of the container 4 can be significantly reduced, the thermal response of the PTC thermistor 5 can be improved, and the detection sensitivity can be improved.

Furthermore, since the position where the positive temperature coefficient thermistor 5 is supported by the electrode terminals 6 and 7 is inside the hollow part of the glass container 4, the positive temperature coefficient thermistor 5 is not affected by the thermal expansion, heat capacity, etc. of the glass container 4. disappears. Therefore, thermal stress on the PTC thermistor 5 is alleviated, thermal deterioration of the PTC thermistor is prevented, and even minute temperature changes can be reliably sensed.

The coupling structure between the positive temperature coefficient thermistor 5 and the electrode terminals 6 and 7 is as shown in an enlarged view in FIG.
A concave portion 7 is formed on one side of the plate by means such as press processing.
a, and a positive temperature coefficient thermistor 5 is inserted and positioned in the recessed part 7a, and a spring piece 6a of an electrode terminal 6 is pressed against the upper electrode of the positive coefficient thermistor 5. . With such a structure, positioning of the positive temperature coefficient thermistor 5 with respect to the electrode terminals 6 and 7 becomes easy, and at the same time,
Misalignment is prevented, and falling off of the PTC thermistor 5 is more completely prevented.

In addition, when used as a liquid level gauge, liquid volume meter, or temperature sensor, the positive temperature coefficient thermistor 5 is normally a minute component with a size of about 1 mm square, so while ensuring a high degree of support stability, the heat capacity of the support structure is It is necessary to adopt a structure that reduces the detection sensitivity and increases the detection sensitivity. In the present invention, as described above, the electrode terminal holding the PTC thermistor 5 has the electrode terminal 7 having the recessed part 7a formed by recessing one side of the flat plate, and the electrode terminal 7 having the flat tip thereof hooked. The positive temperature coefficient thermistor 5 is placed in the recessed part 7a formed in the electrode terminal 7, and is positioned and fixed. Since the structure is such that the curved portion 6a of the electrode terminal 6 is brought into pressure contact with the electrode on the upper surface side of the PTC thermistor 5 and the PTC thermistor 5 is elastically held, even if the PTC thermistor 5 is minute, it can be reliably Can be stably supported. Moreover, since the electrode terminals 6 and 7 are made of flat plate members and have a small and thin shape with only the concave portion 7a and the curved portion 6a, the heat capacity can be reduced and the detection sensitivity can be increased.

One ends of lead wires 8, 9 coated with a glassy coating 11 are connected and fixed to one ends of the electrode terminals 6, 7 by, for example, spot welding or the like. The lead wires 8 and 9 are integrally fixed to the base of the vitreous coating 11 to the sealing plug 10 and led out in the same direction. With such a structure, the electrical insulation and sealing properties for the lead wires 8, 9, electrode terminals 6, 7, and positive temperature coefficient thermistor 5 are extremely high, and reliability is improved.

In addition, in this embodiment, the connection parts between the electrode terminals 6, 7 and the lead wires 8, 9 are sealed inside the glass sealing plug 10 to reinforce the connection parts with weak mechanical connection strength, and the lead wires 8, 9 are sealed. , 9 are prevented from peeling off from the electrode terminals 6, 7 due to tensile force or the like. Note that the lead wires 8 and 9 are connected to the vitreous coating 11 and the sealing plug 10.
It is preferable to use a conductive wire, such as a composite wire, having a coefficient of linear expansion as close as possible to that of .

Figure 6 shows a voltage-current characteristic diagram when the positive temperature coefficient thermistor according to the present invention is used as a liquid level sensor for a liquid level gauge, and the horizontal axis represents the applied voltage (DCV).
The vertical axis shows the current (mA). Curve A ₁ shows the characteristics when the glass container 4 containing the positive temperature coefficient thermistor 5 is placed in water, and curve A ₂ shows the characteristics when the container 4 is lifted out of water and placed in air.

As the positive characteristic thermistor 5, the Curie temperature
TC ₁ = 90℃, room temperature (20℃) resistance R ₂₀ = 170Ω,
Use a 1x1x0.5 ^t mm shape and convert it to 3.3φmm
It was sealed in a glass container 4.

As shown in the figure, the difference between the case where the glass container 4 is placed in water and the case where it is placed in the air is 2 to 4 m.
Since a current change of about A can be obtained, a liquid level sensor with high detection sensitivity can be realized. In addition, even if the applied voltage changes, it will be 2 to 4 m at the same voltage.
Since a current change of approximately A can be obtained, a sensor that operates stably against voltage fluctuations can be obtained.

As described above, according to the present invention, the following effects can be obtained.

(a) In a positive temperature coefficient thermistor in which a positive temperature coefficient thermistor elastically supported between a pair of electrode terminals is enclosed inside a glass container, the tip of the glass container is formed into a bag shape by a continuous glass wall. Since it is a closed hollow tube and the opening on the rear end side is sealed with a vitreous sealing plug, the tip of the vitreous container, which becomes the detection end in the liquid, is completely sealed by the vitreous continuous wall. It has a sealed structure, and there is no room for liquid etc. to enter into the glass container.
Therefore, malfunctions caused by liquid intrusion, short circuits between electrodes, etc. can be almost completely prevented.

(b) A pair of electrode terminals were arranged side by side with one end fixed to a glass sealing plug so as to face each other inside the hollow part of the glass container, and a positive temperature coefficient thermistor was elastically sandwiched between the electrode terminals. , the following effects can be obtained.

(b1) The support structure of the electrode terminal becomes stronger,
Since there is no wobble, even if mechanical shock or vibration is applied, the positive temperature coefficient thermistor can be reliably pressed between the electrode terminals, and accidents such as falling off can be prevented.

(b2) Since only one end of the pair of electrode terminals is embedded in the sealing cap, and the other end is open in the hollow space, the difference in thermal expansion coefficient between the glass container and the sealing cap and the electrode terminal The location where the resulting thermal stress occurs is limited to only the embedded portion of the electrode terminal, and no tensile thermal stress is generated from both longitudinal ends of the electrode terminal. Therefore, the spring properties of the electrode terminals are not thermally degraded, and the positive temperature coefficient thermistor can be stably supported over a long period of time.

(b3) Since the structure is such that the electrode terminals are arranged in parallel and the positive temperature coefficient thermistor is supported between them, the third
Compared to the case of the axial arrangement shown in the figure, the volume of the internal space of the container can be significantly reduced, the thermal response of the PTC thermistor can be improved, and the detection sensitivity can be improved.

(b4) Since the position where the PTC thermistor is supported by the electrode terminal is within the hollow part of the glass container, the PTC thermistor is not affected by thermal expansion, heat capacity, etc. of the glass container. Therefore, thermal stress on the PTC thermistor is alleviated, thermal deterioration of the PTC thermistor is prevented, and even minute temperature changes can be reliably sensed.

(c) A pair of electrode terminals includes an electrode terminal having a recessed part formed by recessing one side of a flat plate, and another electrode having a curved part formed by curving the tip of the flat plate into a hook shape. The positive temperature coefficient thermistor is positioned and fixed by being placed in a recess formed in the electrode terminal, and the positive temperature coefficient thermistor has an electrode on the upper surface side of the positive temperature coefficient thermistor.
Since the structure is such that the curved portion of another electrode terminal is pressed into contact with the other electrode terminals and elastically sandwiched between the electrode terminals, the following effects can be obtained.

(a1) Even if the positive temperature coefficient thermistor is minute,
The positive temperature coefficient thermistor can be easily positioned with respect to the electrode terminal, and at the same time, positional deviation is prevented, and the positive temperature coefficient thermistor can be more completely prevented from falling off, and can be supported reliably and stably.

(c2) Since the electrode terminal is made of a flat plate member and has a small and thin shape with only a recessed part and a curved part, the heat capacity can be reduced and the detection sensitivity can be increased.

(d) Furthermore, a pair of independent glass-coated lead wires are electrically connected to the electrode terminals through the sealing plugs, and the glassy coatings of these lead wires are integrally fixed to the sealing plugs so as to connect them continuously. As a result, electrical insulation and sealing properties for lead wires, electrode terminals, and positive temperature coefficient thermistors are extremely high, and reliability is improved.

[Brief explanation of the drawing]

Figure 1 is a resistance temperature characteristic diagram of a positive temperature coefficient thermistor.
Figure 2 is a sectional view showing its basic structure.
FIG. 3 is a front sectional view of a conventional positive temperature coefficient thermistor device for a liquid level gauge, FIG. 4 is a front sectional view of a positive temperature coefficient thermistor device according to the present invention, and FIG. 5 is an enlarged exploded perspective view of the main parts. FIG. 6 is a voltage-current characteristic diagram when used as a liquid level sensor. 4... Glass container, 5... Positive temperature coefficient thermistor, 6, 7... Electrode terminal, 8, 9... Lead wire,
10...Sealing, 11...Glass coating.

Claims (1)

[Claims for Utility Model Registration] (1) A PTC thermistor device in which a PTC thermistor elastically supported between a pair of electrode terminals is enclosed inside a glass container, wherein the glass container has a tip end. The hollow tube body is closed like a bag by a continuous glass wall, and the opening on the rear end side is sealed with a glass sealing plug. Consisting of an electrode terminal having a concave portion formed by recessing the side, and another electrode terminal having a curved portion formed by curving a flat tip portion into a hook shape,
The concave portion and the curved portion are arranged side by side with one end fixed to the sealing plug so as to face each other in the hollow portion of the glass container, and the positive temperature coefficient thermistor is formed on the electrode terminal. The PTC thermistor is inserted into the concave portion, positioned and fixed, and the curved portion of the other electrode terminal is brought into pressure contact with the electrode on the upper surface side of the PTC thermistor to be elastically sandwiched between the electrode terminals. On the other hand, a pair of independent lead wires coated with glass are electrically connected through the sealing plug, and the glassy coatings of these lead wires are integrally fixed to the sealing plug and continuous. Characteristic positive characteristic thermistor device. (2) The connection portion between the electrode terminal and the lead wire is
The positive temperature coefficient thermistor device according to claim 1, wherein the PTC thermistor device is located within the sealing plug. (3) The positive temperature coefficient thermistor device according to claim 1 or 2, wherein the lead wire is made of a composite wire.