JPH0666754A - Gas sensor - Google Patents

Abstract

PURPOSE:To improve the durability of a gas sensor against impacts and vibrations and manufacturing workability of the sensor by fitting the projecting section of a heating means (exothermic body) in a fitting section between electric connecting means (lead pins) fitted to a pedestal. CONSTITUTION:A pair of lead pins 2 and 2' for a heater and another pair of lead pins 3 and 3' for the electrode of a sensor element 8 are erected on a pedestal 1. A film-like gas sensible substance 5 is provided on an insulating substrate 4. On the rear side of the element 8, an exothermic body 7 provided with heater electrodes on both front and rear surfaces is fixed in such a state that at least part of the body 7 protrudes from the element 8. Since the projecting section of the body 7 is fitted in a fitting section formed between the pins 2 and 2' facing each other, the body 7 is electrically connected to and held by the pins 2 and 2'. Since the interval between the pins 2 and 2' is set so that the interval can be widened when the projecting section is fitted, the projecting section can be held sufficiently strongly by the action of stresses which forcibly return the pins 2 and 2' to their original states.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas sensor used for a gas detector or the like, and more particularly to a gas sensor devised to improve durability against shock and vibration and workability in manufacturing.

[0002]

_2. Description of the Related Art Conventionally, SnO ₂ , ZnO, In
Gas sensors (semiconductor gas sensors) using a metal oxide semiconductor such as ₂ O ₃ or WO ₃ as a gas-sensitive substance are well known. These gas sensors use the reducing gas (reducing gas The gas is detected by utilizing the change in the electric resistance value of the gas-sensitive body caused by the adsorption and desorption of the test gas).

Generally, in order for these gas sensors to show a sufficient response in practical use and to perform stable gas detection,
It is necessary to maintain a constant heating condition for the gas sensitive body. In addition, the structure must have sufficient durability against shock and vibration caused by dropping or the like.

An example of the semiconductor gas sensor as described above is shown in FIG. In FIG. 4, first, reference numeral 101
Is a base made of a heat-resistant insulating resin such as polyphenylene sulfide resin (PPS resin). The base 101 has lead pins 102a, 102b, 102c, 102.
d, 102e, and 102f are planted, and a tubular sensor element 104 is connected to and held by these lead pins via a lead wire 103, respectively. The sensor element 104 has a heating heater coil 105 built therein, a pair of electrodes facing each other on the outer peripheral surface thereof, and a gas sensitive body made of a metal oxide semiconductor provided on both electrodes. . Both ends of the heating heater coil 105 are electrically connected to the lead pins 102b and 102e, one of the pair of electrodes is connected to the lead pins 102a and 102c, and the other is electrically connected to the lead pins 102d and 102f.
The base 101 is covered with a stainless wire mesh 106 to protect the sensor element.

In the gas sensor having the above structure, the electric resistance value of the gas sensitive material between the electrodes changes in accordance with the concentration of gas in the atmosphere when the heating heater coil 105 heats the sensor element 104. The gas is detected by taking it out as an output.

In the above gas sensor, the sensor element 104 is held by the lead wire 103, but a platinum (Pt) thin wire of about 0.1φ is adopted as the lead wire 103, and the lead wire is also used. 10
Since the lead wire 103 is sunk into the gas-sensitive body at the connecting portion between the sensor element 104 and the sensor element 104, the lead wire 103 may be broken or the gas-sensitive body may be exposed to shock or vibration caused by a drop or the like. There are problems such as damage.

On the other hand, in recent years, a flat plate type gas sensor different from the tube type gas sensor has been developed and reported. An example thereof is shown in FIG.

In FIG. 5, reference numeral 204 is an insulating substrate inside which a heater is provided.
Includes a pair of electrodes 205, 205 ', a gas-sensitive body 206 mainly composed of a metal oxide semiconductor formed between the electrodes, and an electrode bonding pad 20 electrically connected to the pair of electrodes.
7, 207 ', and heater bonding pads 208, 208' that are electrically connected to the heater. Code 2
Reference numeral 01 is a base made of a heat resistant insulating resin such as PPS resin. The base 201 has lead pins 202a, 202
b, 202c, 202d are planted, and lead frames 203a, 203b,
One ends of 203c and 203d are connected by welding. The other ends of the lead frames 203a and 203c are connected to the heater bonding pads 208 and 208 ',
The other ends of the lead frames 203b and 203d are connected to the electrode bonding pads 207 and 207 'by welding. That is, the insulating substrate 204 is held by the lead pins and the lead frame. The base 2
The wire mesh 209 made of stainless steel is covered on 04.

In the gas sensor thus constructed, the heater incorporated in the insulating substrate 204 generates heat by applying a predetermined voltage to the lead pins 202a and 202c, and the gas sensitive body 206 is heated through the insulating substrate 204. It At this time, the electrical resistance value between the electrodes changes due to the adsorption and desorption of the test gas to and from the gas sensitive body 206, and the electrical resistance value between the electrodes changes via the lead frames 203b and 203d.
The gas is detected by taking out as a sensor output from 2d.

In the gas sensor having the above structure, a flat plate type lead frame having a strength higher than that of the lead wire in the conventional example shown in FIG. 4 is adopted, and the lead frame and the bonding pad are welded to each other, so that the conventional tube type gas sensor can be manufactured. As described above, the lead wire is prevented from being broken and the gas sensitive body is prevented from being damaged.

[0011]

However, even such a gas sensor has the following problems.
That is, since the connection between the lead pin and the lead frame and the connection between the lead frame and the bonding pad is performed by a relatively difficult welding work, there is a problem that the work efficiency at the time of manufacturing is very poor. Further, due to its structure, the welded portion is likely to be loaded, and when excessive impact or vibration such as dropping is applied, there is a risk that the welded portion will come off and lose its function as a gas sensor.

The present invention has been made on the basis of the above points, and an object of the present invention is to exhibit sufficient strength against excessive shock and vibration such as dropping, and at the same time, in manufacturing workability. It is also to provide an excellent gas sensor.

[0013]

In order to achieve the above object, a gas sensor according to the present invention comprises a sensor element composed of a pair of electrodes and a film-shaped gas sensitive material provided on an insulating substrate, and polymerized and fixed to the sensor element. A heating means, an electrical connection means for electrically connecting to the sensor element and the heating means, and a base, at least a part of the heating means is projected from the sensor element, and the protruding portion is formed. Is held by being fitted to the fitting portion of the electrical connecting means for electrically connecting the heating means attached to the base.

It is also conceivable that, when the protruding portion of the heating means is fitted into the fitting portion, the fitting portion is formed by arranging the pair of lead pins so as to face each other with an interval such that the lead pins can be spread. . Furthermore, in the gas sensor,
It is also conceivable to add a means to support the sensor element and at the same time to obtain an electrical connection of the element by means of a pair of lead pins which are erected parallel to the sensor element.

[0015]

According to the present invention, the projecting portion of the heating means is held together with the sensor element by fitting the protruding portion of the heating means into the fitting portion of the electrical connecting means for electrically connecting the heating means. Therefore, it is possible to provide an excellent gas sensor having a high work efficiency and exhibiting sufficient strength against excessive shock or vibration such as dropping.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 and 2, reference numeral 1 is a base made of polyphenylene sulfide resin (PPS resin). The base 1 has a pair of lead pins 2 and 2'for heaters made of Ni and a pair of sensors. The element electrode lead pins 3, 3'are erected. Reference numeral 4 is an insulating substrate whose main component is alumina.
A pair of electrodes 6, 6'is provided, and a film-shaped gas sensitive body 5 containing a metal oxide semiconductor as a main component is provided between the electrodes. In this embodiment, the film-like gas sensitive body 5 is made of In
₂ O ₃ is used as the electrodes 6 and 6 ′, and Pt is formed by the sputtering method.

Here, on the back side of the sensor element 8 composed of the insulating substrate 4, the pair of electrodes 6, 6'formed on the insulating substrate 4, and the film-shaped gas sensitive body 5, heater electrodes are provided on both front and back sides. As shown in FIG. 2, the heating element 7 having the above is polymerized and fixed by a ceramic adhesive (not shown) in a state in which at least a part thereof protrudes from the sensor element 8.

The heating element 7 is a ceramic PTC.
A heater or the like is used. Since many kinds of these having different heat generation temperatures, shapes, etc. are commercially available, these may be used. Further, in this polymerization fixing, the heating element 7
However, if the shape and polymerization fixing position are sufficiently considered so as to heat the entire membranous gas-sensitive body 5 to a predetermined temperature,
Fixing is possible by methods other than those shown in.

As described above, the protruding portion of the heating element 7 superposed and fixed on the insulating substrate 4 is fitted into the fitting portion formed by the pair of opposed heater lead pins 2 and 2 '. It is electrically connected and retained. However, in the fitting portion, when the protruding portion of the heating element 7 is fitted,
The pair of heater lead pins 2 and 2'are formed so as to be opposed to each other at an interval such that they can be spread apart. As a result,
The protruding portion is sufficiently held by the action of the stress that tends to push back the fitting portion. In addition, in order to further strengthen the holding, the fitting portion is reinforced with an adhesive or the like,
Further, it is possible to increase the contact area by cutting the side of the heater lead pins 2, 2'that contacts the heating element 7 to form a flat surface.

The sensor element electrode lead pins 3,
3'is set up on the base 1 in parallel with the sensor element 8, and in order to take out the sensor output and hold the sensor element 8 more firmly, for example, a conductive adhesive is applied to the sensor element electrodes 6, 6 '. Are electrically connected by. Reference numeral 9 is a stainless steel wire net provided on the base 1.

With the above structure, the heating element 7 generates heat by applying a predetermined voltage between the pair of opposing heater lead pins 2 and 2 ', and the film-shaped gas sensing element 5 is heated via the insulating substrate 4. To be done. At this time, when the test gas is adsorbed and desorbed on the film-shaped gas sensitive body 5, the electric conductivity of the film-shaped gas sensitive body 5 is changed, and the resistance value between the electrodes 6 and 6 ′ is changed. Sensor element electrode lead pins 3, 3'connected to
Can be taken out as a sensor output.

Here, in order to compare the durability and the manufacturing workability of the gas sensor according to the present embodiment with the conventional gas sensor, ten gas sensors were prepared and used as samples, and the following test and I conducted a survey. The results are shown in Table 1, Table 2 and Table 3. Here, Comparative Example 1 is shown in FIG. 4 of the conventional example, and Comparative Example 2 is shown in FIG.
It is shown in.

1) Drop test Drop on a concrete floor from a height of 3 m. 2) Vibration test The vibration frequency is 600 times per minute, and vibration with a total amplitude of 5 mm is applied in three directions of up, down, left and right, and front and back for 20 minutes. 3) Workability The work time required for manufacturing the gas sensor is investigated.

[0024]

[Table 1]

[0025]

[Table 2]

[0026]

[Table 3]

As is clear from the results of Table 1, Table 2 and Table 3, the gas sensor according to the present embodiment has excellent durability against shock and vibration as compared with the conventional gas sensor, and has a good manufacturing workability. You can see that is also excellent.

The present invention is not limited to the above-described embodiment, and for example, as shown in FIG. 3, a fitting portion formed by the protruding portion of the heating element 7 and the heater lead pins 2, 2'is provided. A structure provided in the base 1 can be considered.
That is, by shortening the portion of the heater lead pins 2, 2 ′ that is erected from the base 1, the force received by the heater lead pins 2, 2 ′ against shock and vibration is mitigated, and durability is further improved. In addition, since the position of the sensor element 8 is lowered on the base 1, the gas sensor itself can be downsized.

[0029]

As described in detail above, according to the present invention, since the fitting portion is formed by using the lead pin and the sensor element is firmly held by the fitting portion, it is possible to prevent excessive shock or vibration such as dropping. In addition, the work of fitting the protruding part from the sensor element of the heating element to the fitting part requires less work steps and is easier than the conventional welding connection using a lead frame. Therefore, it is possible to improve work efficiency. Therefore, it is possible to provide a gas sensor having excellent durability, reliability, and manufacturing workability. Further, when a ceramic PTC heater is used as the heating element, its self-temperature control characteristic keeps the heating state of the gas-sensitive body constant against changes in the ambient temperature and performs better gas detection. In addition, the constant current circuit is unnecessary and the detection circuit can be inexpensive.

[Brief description of drawings]

FIG. 1 is a view showing an embodiment of the present invention and is a perspective view of a gas sensor.

2A and 2B are views showing an embodiment of the present invention, FIG. 2A is a front view of a main part of a gas sensor, and FIG. 2B is a sectional view taken along line AA ′ of FIG.

3A and 3B are views showing an embodiment of the present invention, FIG. 3A is a front view of a main part of a gas sensor, and FIG. 3B is a sectional view taken along line BB ′ of FIG.

FIG. 4 is a view showing a conventional example and is a perspective view of a gas sensor.

FIG. 5 is a view showing a conventional example and is a perspective view of a gas sensor.

[Explanation of symbols]

 1 Base 2 Heater lead pin 2'Heater lead pin 3 Sensor element electrode lead pin 3'Sensor element electrode lead pin 4 Insulating substrate 5 Membrane gas sensor 6 Electrode 6'electrode 7 Heating element 8 Sensor element 9 Stainless steel wire mesh

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[Procedure amendment]

[Submission date] October 15, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0024

[Correction method] Change

[Correction content]

[0024]

[Table 1]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0025

[Correction method] Change

[Correction content]

[0025]

[Table 2]

Claims (3)

[Claims] 1. A sensor element comprising a pair of electrodes and a film-shaped gas-sensitive material provided on an insulating substrate, heating means superposed on and fixed to the sensor element, and electrically connected to the sensor element and the heating means. In a gas sensor consisting of an electrical connection means for connecting to the base and a base, at least a part of the heating means is projected from the sensor element, and the projection is electrically connected to the heating means mounted on the base. A gas sensor characterized in that the gas sensor is held by being fitted into the fitting portion of the mechanical connection means. 2. The gas sensor according to claim 1, wherein when the protruding portion of the heating means is fitted into the fitting portion, the fitting portion is arranged so as to face each other at an interval such that the pair of lead pins can be spread. , A gas sensor characterized by being formed. 3. The gas sensor according to claim 1 or 2, further comprising means for supporting the sensor element by a pair of lead pins erected in parallel with the sensor element and at the same time obtaining electrical connection of the element. A gas sensor characterized in that