JPH08240552A - Moisture sensor - Google Patents

Abstract

PURPOSE: To improve measurement accuracy by thermally stabilizing a moisture sensor. CONSTITUTION: A heat-sensitive element 1 is inserted into a glass case 4 via an opening and the opening of the glass case 4 is sealed by heat while lead wires 3a and 3b are led out of the glass case 4. One and the other of a pair of glass cases 4, 4 where the heat-sensitive element 1 is enclosed are used as a moisture-sensitive equipment 5 and a temperature compensator 6, respectively, a small hole 7 is opened at the glass case 4 of the moisture-sensitive equipment 5, both equipments 5 and 6 are combined, lead wires 3a and 3b pulled out of each glass case 4 and conductors 10a and 10b of an external wiring cable 10 are connected, and the connection part is buried into a terminal plate 11. The terminal plate 11 is a forming body consisting of a material with a small thermal conductivity such as synthetic resin. The terminal plate 11 electrically insulates the connection part between the lead wire and the external wiring cable, thus preventing an external thermal influence applied to the heat-sensitive element 1 via the lead wire.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a humidity sensor for measuring temperature and humidity, gas concentration and the like using a pair of heat sensitive elements such as thermistors.

[0002]

2. Description of the Related Art A humidity sensor using a thermosensitive element such as a thermistor as a sensor element is widely used as a humidity sensor for measuring humidity in a microwave oven. This humidity sensor self-heats the thermosensitive element in the open air atmosphere and in the closed atmosphere shielded from the open air, and detects the change in the resistance value of both thermosensitive elements to detect the amount of water vapor in the air atmosphere (absolute humidity).
Is measured.

Conventionally, various types of humidity sensors using a heat sensitive element have been proposed, but in short, a heat sensitive element is incorporated in each of two cases, and a small hole is formed in one case to open the outside air. The former is combined with the other as a humidity detector and the latter as a temperature compensator.

FIG. 5 shows an example of the humidity sensor. In this example, the thermosensitive element 2 attached to the stem 21 as shown in FIG.
2 is covered with a metal cap 23, and a hole 24 is made in a part of the cap 23 to form a humidity sensor 25.
A temperature compensator 26 having no holes is prepared, and the humidity sensor 25 and the temperature compensator 26 are housed in a metal case 27. According to this example, the metal case 27 has a tubular shape covered with a metal plate having a flange 28 at one end and a hole 29 at the other end as shown in FIG. A metal cylinder 31 having a metal plate 30 fixed at one end is press-fitted, the humidity sensor 25 and the temperature compensator 26 are fixed to the metal cylinder 31, and the metal cover 32 is fixed to the flange 28 by covering the upper surface of the metal case 27. Assembled (see Jpn. Pat. Appln. KOKAI No. 4-35806).

The conventional structure of the humidity sensor is not always shown in FIG.
Although the humidity sensor and the temperature compensator are separately manufactured as described above and are not limited to the example in which the humidity sensor and the temperature compensator are assembled in a metal case, most conventional sensors include a cap, a case and other parts for covering the heat sensitive element. Metal components are used for the constituent members of the sensor including, and the structure is such that the stem and the metal cap are welded and sealed with a hermetic seal.

[0006]

However, in the case of a metal case, although an electric shielding effect can be expected, it has a drawback that it is easily affected by the surrounding thermal influence because of its excellent thermal conductivity.

However, the humidity sensor uses a soaking structure in order to prevent thermal influences from the surroundings. But,
If the ambient atmosphere changes abruptly under the condition that hot air in the microwave directly hits the humidity sensor, even if the metal surface of the humidity sensor case has a uniform heating structure, The balance is lost and accurate output cannot be obtained.

Further, even if the temperature of the case in which the heat sensitive element is mounted is abruptly changed, such as thermal influence from the wall surface of the microwave oven or heat interference from the heat source of the range itself through the lead wire of the heat sensitive element, metal is used. When the case is used, the thermal balance is inevitably lost and becomes unstable, which causes a problem in the reliability of measurement accuracy.

An object of the present invention is to provide a humidity sensor that is thermally stable and has high measurement accuracy.

[0010]

In order to achieve the above object, a humidity sensor according to the present invention is a humidity sensor having a humidity detector, a temperature compensator, and a terminal plate. The compensator is a pair of glass cases each containing a heat-sensitive element.One of the pair of glass cases is hermetically sealed, and the other has a small hole communicating with the outside air. The humidifier has a thermosensitive element housed in a glass case that communicates with the outside air, the lead wire of the thermosensitive element is drawn out of the glass case, and the temperature compensator is in a hermetically sealed glass case. The heat-sensitive element is housed in, and the lead wire of the heat-sensitive element is pulled out to the outside of the glass case, the lead wire of each heat-sensitive element is connected to the core wire of the external wiring cable outside the glass case, and the terminal board Is heat conduction Made from a less material is for embedded to isolate the wire connection portion of the lead wire and the core wire of the external wiring cable for each thermal element for each connection.

Further, the terminal plate is a synthetic resin molded body, and the connecting portion is buried including a part of the external wiring cable connected to each lead wire of the heat sensitive element, and the respective lead wires are electrically insulated from each other. To do.

Further, the terminal plate holds the humidity sensing device and the temperature compensator in a fixed upper position by holding the lead wire.

Further, it has an outer cover, and the outer cover is a hollow cylindrical body having a vent hole communicating with the outside, which is opened on one surface.
It is connected to the terminal board while covering the humidity sensor and the temperature compensator.

[0014]

The technique of encapsulating an element in a glass hollow chamber is used in the manufacturing technology of micro lamps, and the technique of encapsulating an element by processing a glass tube is used in a reed switch or the like. The present invention encloses a thermosensitive element such as a thermistor as a sensor element in a glass case by using a conventionally known glass processing technique. In the present invention, the glass includes not only glass but also ceramics such as alumina having the same effect. As the type of glass used for the glass case, there can be used those generally used for electronic parts such as lead silicate glass and borosilicate glass, and also alkali barium glass such as infrared absorbing glass. Further, in terms of crystal structure, even if it is crystallized glass,
Even non-crystalline glass causes no particular problem.

The humidity sensor is a glass case having a small hole in which a heat sensitive element is incorporated, and the temperature compensator is a hermetic glass case in which the heat sensitive element is incorporated. It is convenient to use a glass tube for the glass case. It can be easily obtained by inserting the heat sensitive element into the glass tube, pulling out the lead wire thereof to the outside of the glass tube, and sealing both ends of the glass tube.

Any of a chip type, a bead type and a disc type can be used as the heat sensitive element. If the lead wire is pulled out from both ends of the element in the opposite direction (axial type),
A pair of lead wires is drawn from both ends of the glass tube to seal each open end, and a pair of lead wires drawn from both sides of the element in the same direction (radial type) is used between both lead wires. Is pulled out from one open end of the glass tube to seal both open ends.

The lead wire of the heat-sensitive element may be usually a Dumet wire, a platinum wire or an iron / chromium wire, but is preferably made of a material which is hard to oxidize such as a copearl wire. As is the case with conventional glass-covered thermistors, the metal wires used for the lead wires can all be stably sealed by solidification of the molten glass. A small hole is optionally opened in the glass case of the humidity sensor.

Since the thermal conductivity of glass is inferior to that of metal, it is less affected by a rapid thermal change in the ambient atmosphere as compared with a metal case, but it is subject to thermal interference exceeding its thermal conductivity. It is desirable to provide a soaking body underneath for use. The soaking body is a tape or a molded body having excellent thermal conductivity, and is attached across both glass cases of the humidity sensor and the humidity compensator.

The lead wire of each heat-sensitive element used in the humidity sensor and the humidity compensator is connected to the core wire of the external wiring cable, and the terminal plate for embedding the connecting portion of both wires has a low thermal conductivity, and thus the lead wire is used. No external thermal influence is exerted on the heat-sensitive element through the line, and there is no influence of thermal interference.

In addition to synthetic resins, inorganic materials such as alumina can be used for the terminal board. Further, by forming the outer cover with the same material as the terminal board and housing the humidity sensor and the humidity compensator in the outer cover, thermal interference from the surrounding atmosphere can be prevented more effectively.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an example in which a bead type thermistor is used for the heat sensitive element 1. The heat sensitive element 1 has a pair of platinum wires as the terminal wires 2, and the platinum wires are drawn out in opposite directions from both ends of the heat sensitive element 1. Dumet wires are connected to the pair of platinum wires as lead wires 3a and 3b, respectively, one lead wire 3a is folded back, and both lead wires 3a and 3b are arranged in parallel in the same direction. The pair of heat-sensitive elements 1 are inserted into the hollow chambers of the glass case 4 each having one end opened through the openings, the openings are sealed, and the lead wires 3a and 3b drawn out of the glass case 4 are connected to the glass case 4. The thermosensitive element 1 is held in the hollow chamber of the glass case 4 by being fixed to the sealed portion.

In the glass case 4 in which the thermosensitive element 1 is enclosed, one is a humidity sensor 5 and the other is a temperature compensator 6. A small hole 7 is opened in a part of the glass case 4 of the humidity sensor 5 to communicate with the outside air. The absolute humidity sensor 8 is a humidity sensor 5.
And the temperature compensator 6. A heat equalizer 9 is attached around both of the glass cases 4 and 4 so as to extend over both the humidity sensor 5 and the temperature compensator 6.

As the soaking body 9, a tape or a molded body having excellent thermal conductivity can be used. When the soaking body 9 is a tape, it suffices to wind the tape around the glass cases 4 and 4. When a molded body is used as the heat equalizing body 9, although not shown, a molded body having a certain shape may be provided with a housing groove for the glass case, and the humidity sensor and the temperature compensator may be housed in the groove. However, the small hole 7 opened in the glass case 4 of the humidity sensor 5 must be open to the atmosphere.

The embodiment of FIG. 1 shows an example in which the thermosensitive element 1 having terminal lines 2 and 2 extending in opposite directions to each other is used, but it is the same as the double-sided electrode of the element like a radial type thermistor. Even when using a heat-sensitive element having a pair of terminal lines extending in the same direction, the sealing procedure is exactly the same.

The lead wires 3 a and 3 b drawn out of the glass case 4 are the core wires 10 of the external wiring cable 10.
a, 10b are connected to each of the heat sensitive elements 1, 1 by welding, soldering, terminal crimping or the like, and the core wires 10a, 1
0b and the lead wires 3a and 3b are connected to each other by the terminal board 1
It is buried in 1. The terminal board 11 is a standard molded body obtained by processing a resin having a low thermal conductivity, for example, a resin such as PBT or PPS, and at the time of molding the terminal board 11, the connection portion of the both wires and the outer wiring cable 10 are covered. A part of the lead wires 3a, 3b is embedded in the molded body so as to be exposed on the upper surface of the molded body, and the respective lead wires 3a, 3b are held on the molded body of the terminal board 11 for moisture sensing. The vessel 5 and the temperature compensator 6 are held in a fixed position above the terminal board 11. The exposed portion of each lead wire should be as short as possible. By shortening the exposed portion of the lead wire, it is possible to prevent the heat effect applied to the heat sensitive element through the lead wire.

As a result, the lead wires 3a and 3b and the core wire 1 are
The connection parts with 0a and 10b are isolated from each other in the molded body and electrically insulated. Further, an external cover 12 may be attached to cover the humidity sensor 5 and the temperature compensator 6 if necessary. The outer cover 12 is a hollow cylindrical body made of a synthetic resin body having the same small thermal conductivity as the terminal board 11 and having a vent hole 13 on the upper surface and an open lower edge. The moisture cover 5 and the temperature compensator are provided. The humidity sensor 5 and the temperature compensator 6 are isolated from the ambient atmosphere by covering the upper portion 6 and connecting the lower edge to the terminal plate 11, but the inside of the outer cover 12 is communicated with the outside air only by the vent hole 13. Therefore, the thermal stability with respect to a sudden change in the ambient atmosphere is improved. However, since the outer cover 12 is not in direct contact with the humidity sensor 5 and the temperature compensator 6, it has little direct thermal effect on both devices, and therefore its material is a heat conductive material such as metal. It doesn't matter.

FIG. 2 shows an example in which a glass tube 14 having both ends open is used in a glass case. The thermosensitive element 1 having terminal wires extending in opposite directions at both ends is inserted into the glass tube 14, and the terminal wire or the lead wire 3 connected to the terminal wire.
The a and 3b are pulled out from both ends of the glass tube 14, the both ends of the glass tube 14 are sealed, and the heat-sensitive element 1 is held in the hollow chamber of the glass tube 14 by supporting the terminal wire or the lead wire with the sealed portion of the glass. Glass tube 1 with both ends sealed in FIG.
Reference numeral 4 denotes a glass case. The glass tube 14 having the small holes 15 formed therein serves as the moisture sensitive device 5, and the one having both ends sealed is the temperature compensator 6. The absolute humidity sensor 8 is completed by wrapping a tape around the glass tubes 14, 14 of both devices as a heat equalizing body 9 if necessary. In this example, a small hole 15 is opened in one glass case 4 through the heat equalizer 9.

In the present embodiment, the lead wires 3a and 3b drawn out from the glass cases of the humidity sensor 5 and the temperature compensator 6 are bent at a right angle, and the ends thereof are connected to the terminal board 1.
In the molded body of 1, core wires 10a, 1 of the external wiring cable 10
0b, the terminal board 11 embeds a part of the external wiring cable 10 as in the previous embodiment, and each lead wire 3a,
3b is held in shape, and the humidity sensor 5 and the temperature compensator 6 are supported in a fixed position above.

As described above, in the embodiment of FIG. 3, an example in which both terminal wires or lead wires of the element are drawn out from both ends in the longitudinal direction of the glass tube has been described. However, two lead wires are provided from one sealing portion of the glass tube. May be one that draws out.

In the above embodiment, an example in which two glass cases are combined has been described, but the point is that the heat sensitive element of the humidity sensor and the heat sensitive element of the temperature compensator are isolated between the cases. Therefore, as shown in FIG. 4, one case 4 may be divided into two chambers by the partition plate 16 and the heat-sensitive elements 1 and 1 may be installed in the respective chambers, respectively. The use of one case further simplifies the steps of processing and assembling. As described above, also in the embodiments shown in FIGS. 3 and 4, the moisture sensor and the temperature compensator may be covered with an external cover if necessary.

[0031]

As described above, according to the present invention, the glass case is used for enclosing the heat-sensitive element constituting the humidity sensor and the temperature compensator, and the lead wire of the heat-sensitive element pulled out from the glass case, Since the connection part with the core wire of the external wiring cable is embedded in the terminal plate made of a molded body of a material with low thermal conductivity, a rapid thermal change in the ambient atmosphere and the thermal interference applied to the thermosensitive element through the lead wire Can be effectively prevented to stabilize the measurement accuracy. In particular, since the glass used for the case has a low thermal conductivity, there is little thermal interference between the humidity sensor and the temperature compensator, the balance with respect to the ambient temperature change is maintained, and the same conditions can be maintained thermally. Also,
By embedding the connecting portion of the lead wire and the core wire in the terminal board, the connection portion can be reliably insulated, and the lead wire can be held to support the humidity sensor and the temperature compensator in place.
Increased mechanical strength and tensile strength, twisting of lead wires,
It is possible to prevent disconnection accidents due to turning, etc., and also prevent microwave intrusion. Further, according to the present invention, by combining the terminal plate with the outer cover to cover the humidity sensor and the temperature compensator, each heat-sensitive element is doubly isolated from the ambient atmosphere to effectively prevent external heat interference. it can.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a diagram showing an assembling procedure of another embodiment of the present invention.

FIG. 3 is a diagram showing another embodiment of the present invention.

FIG. 4 is a diagram showing still another embodiment of the present invention.

FIG. 5 is a diagram showing a conventional example of an absolute humidity sensor.

FIG. 6 is a diagram showing a humidity sensor used in a conventional absolute humidity sensor.

[Explanation of symbols]

 1 Heat Sensitive Element 2 Terminal Wires 3a, 3b Lead Wire 4 Glass Case 5 Humidifier 6 Temperature Compensator 7 Small Hole 8 Absolute Humidity Sensor 9 Heat Sink 10 External Wiring Cable 10a, 10b Core Wire 11 Terminal Board 12 External Cover 13 Vent Hole 14 Glass tube 15 Small hole 16 Partition plate

Claims (4)

[Claims] 1. A humidity sensor having a humidity sensor, a temperature compensator, and a terminal board, wherein the humidity sensor and the temperature compensator each house a thermosensitive element in a pair of glass cases. One of the pair of glass cases is hermetically sealed, and the other has a small hole that communicates with the outside air.The humidity sensor has a thermosensitive element housed in a glass case that communicates with the outside air. , The lead wire of the heat-sensitive element is pulled out to the outside of the glass case, the temperature compensator accommodates the heat-sensitive element in a hermetically sealed glass case, and the lead wire of the heat-sensitive element is
It is drawn out of the glass case, the lead wire of each heat sensitive element is connected to the core wire of the external wiring cable outside the glass case, and the terminal board is made of a material with low thermal conductivity, and is connected to the lead wire of each heat sensitive element. A humidity sensor, characterized in that a connection portion with a core wire of an external wiring cable is isolated and embedded for each connection. 2. The terminal plate is a synthetic resin molded body, and the connecting portion is embedded including a part of the external wiring cable connected to each lead wire of the heat-sensitive element, and the lead wires are electrically connected to each other. The humidity sensor according to claim 1, wherein the humidity sensor is insulated. 3. The humidity sensor according to claim 1, wherein the terminal plate holds the humidity sensor and the temperature compensator in a fixed upper position by holding the lead wire. 4. An outer cover, which is a hollow cylindrical body having a vent hole communicating with the outside open on one side, and which is connected to the terminal board while covering the humidity sensor and the temperature compensator. The humidity sensor according to claim 1, wherein the humidity sensor is provided.