JP2005300374A - Combustible gas detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a combustible gas detector capable of performing switching required when a combustible gas is detected without using an electronic circuit such as a comparator, a relay or the like. <P>SOLUTION: The combustible gas detector is equipped with a gas responsive element 12 constituted of a metal oxide semiconductor of which the resistance value is lowered by the contact with the combustible gas and a heat responsive element 13 responding to heat. If the resistance value of the gas responsive element 12 is reduced by the contact of the combustible gas with the gas responsive element 12 by feeding a current to the gas responsive element 12, a current flows to the gas responsive element 12 in large quantities and the temperature of the gas responsive element 12 is suddenly raised by self-generation of heat. Therefore, the heat responsive element 13 is operated to perform switching. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a combustible gas detector using a metal oxide semiconductor as a gas sensitive element.

Conventionally, as a combustible gas detection device using a metal oxide semiconductor as a gas sensitive element, there is one disclosed in Japanese Patent Application Laid-Open No. 2001-124716. In this product, a gas-sensitive element is formed by applying and sintering a metal oxide semiconductor (for example, tin oxide) to a metal wire filament, and the metal oxide semiconductor is combustible when it is energized and heated. When the gas comes into contact, the combustible gas burns and the resistance of the metal oxide semiconductor increases and the resistance value decreases. It is used for switching such as alarm and control.
JP 2001-124716 A

  However, in the case of the above-described one, it is necessary to use an electronic circuit such as a comparator or a relay to perform the switching necessary when the combustible gas is detected, which is expensive and non-compact.

  The present invention has been made in view of the above-described circumstances, and therefore, the purpose thereof can be performed when a combustible gas is detected without using an electronic circuit such as a comparator and a relay. An object of the present invention is to provide an inexpensive and compact combustible gas detection device.

  In order to achieve the above object, the combustible gas detection device of the present invention comprises a gas sensitive element composed of a metal oxide semiconductor whose resistance value is reduced by contact with a combustible gas, and the heat of the gas sensitive element. And a thermally responsive element, wherein the gas sensitive element is energized.

  According to the above means, when the resistance value of the gas sensitive element decreases due to contact of the combustible gas with the gas sensitive element, a large amount of current flows through the gas sensitive element, and the temperature of the gas sensitive element rises rapidly due to self-heating. Due to this temperature rise, the thermally responsive element operates and switches. Thus, it is possible to perform a necessary switching when a combustible gas is detected without using an electronic circuit such as a comparator or a relay, and it is possible to provide an inexpensive and compact combustible gas detection device. It is.

Hereinafter, an example (one embodiment) of the present invention will be described with reference to the drawings.
First, FIG. 2 shows the entire combustible gas detection device in an exploded state, and a case 1 thereof includes a case main body 1a and a case base 1b. The case main body 1a is a cylindrical container with a lid, and has a mouth 2 at the lid, and has a plurality of locking portions 3 and a plurality of through holes 4 around the mouth 2. On the other hand, the case base 1b has a plurality of mounting holes 5 on the outer periphery.

  On the other hand, the heater 6 is composed of a heater body 6a and electrodes 6b and 6c located on both upper and lower sides thereof. In this case, the heater body 6a is a disc chip as shown in FIG. It consists of a PTC thermistor sintered in a shape.

  Of the electrodes 6b, 6c, one electrode 6b has a circular portion 7 at one end, and this circular portion 7 is slightly larger in diameter than the heater body 6a, and the upper surface of the circular portion 7 It has many grooves 8 extending from the outer periphery to the opposing outer periphery. Further, the one electrode 6b has a stopper portion 9 on the other end side, and the one electrode 6b is bent at a substantially right angle at an intermediate point between the stopper portion 9 and the circular portion 7. doing.

  The other electrode 6c is substantially straight at one end and has a stopper 10 at the other end, and is bent at a substantially right angle at an intermediate point therebetween. A heater presser 11 is attached to the upper surface of one end of the other electrode 6c. The heater presser 11 has a trifurcated shape, and has elasticity by bending each tip portion in a U-shape toward the center, and the center portion is one end portion of the other electrode 6c. It is attached by welding to the upper surface of the.

  Then, in the case 1, one electrode 6b is inserted into the case main body 1a from the lower side of FIG. It is fixed by being engaged with the through hole 4. Next, the heater body 6a is inserted into the case body 1a from the lower side of FIG. Then, the other electrode 6c is inserted into the case main body 1a from the lower side in FIG. 2 and the heater main body 6a is pressed by the heater press 11 while the one electrode 6b protrudes from the other one through hole 4. The stopper 10 is fixed by being locked in the through hole 4 (see FIG. 5).

On the other hand, the gas sensitive element 12 is formed by sintering a metal oxide semiconductor whose resistance value is lowered by contact with a combustible gas, in this case, tin oxide (SnO ₂ ) into a disk chip shape. This is inserted into the case main body 1a from above in FIG. 2 and placed on the upper surface of the circular portion 7 of the one electrode 6b.

  As a result, the heater 6 is in close contact with the lower surface, which is one surface of the gas sensitive element 12, and more specifically, one electrode 6b of the heater 6 is in close contact with the gas sensitive element 12 at the circular portion 7. Thus, one of the electrodes 6b functions as a common electrode with the gas sensitive element 12. Further, the groove 8 is formed on the upper surface of the circular portion 7 of the one electrode 6b, and the groove 8 allows the combustible gas to contact the gas sensitive element 12 without any trouble.

  In this case, the heat responsive element 13 is basically a bimetal switch. Specifically, as shown in FIG. 4, the heat responsive element 13 has a metal sealed container 14 as an outer shell, and a fixed contact 15 and a fixed contact 15 therein. A movable contact 16 that is always in contact is disposed, a bimetal presser 17 that is attached to the lower surface of the movable contact 16, and a bimetal 18 that is fixed to the bottom of the hermetic container 14 by the bimetal presser 17 are disposed. Each electrode 19 and 20 of the movable contact 16 protrudes upward from the container 14. In addition, a plurality of attachment claws 21 are attached to the outer surface of the airtight container 14 of the thermally responsive element 13 by, for example, welding.

Accordingly, the case 1 is inserted into the case main body 1a from above in FIG. 2 and the attachment claw 21 is engaged with the engagement portion 3, so that the thermal activation element 13 is provided. The gas sensitive element 12 is fixed in a state where it is placed in contact with the upper surface (see FIG. 5).
As a result, the heat-responsive element 13 is in close contact with the surface on the other side opposite to the surface on the one side of the gas-sensitive element 12 (the surface on which the heater 6 is in close contact). The metal sealed container 14 of the responsive element 13 is in close contact with the gas sensitive element 12, so that the metal sealed container 14 functions as one electrode of the gas sensitive element.

  In addition, the case base 1b is coupled to the case body 1a, and in this state, the entire combustible gas detection device is attached to an optimum place where the combustible gas should be detected by a screw or the like passing through the mounting hole 5. It is to be installed.

  FIG. 1 schematically shows the configuration of the above-described combustible gas detection device, that is, the heater 6, the gas sensitive element 12, and the thermal sensitive element 13 are laminated in order from the bottom, and the heaters of these are stacked. 6 and the gas sensitive element 12 are connected in parallel to a power source (commercial power source) E. Further, the thermally responsive element 13 is inserted and connected to an alarm circuit or a control circuit.

Next, the operation of the above configuration will be described.
In a state in which the heater 6 and the gas sensitive element 12 are connected to the power source E, the gas sensitive element 12 is heated to a predetermined temperature as the heater 6 generates heat. The temperature is a temperature at which the sensitivity of the gas sensitive element 12 is stably improved.

  In this situation, if the combustible gas comes into contact with the gas sensitive element 12, the combustible gas is combusted. As a result, the number of electrons of the metal oxide semiconductor constituting the gas sensitive element 12 increases and the resistance value is, for example, several hundred kΩ ] To a few [kΩ]. If the resistance value of the gas sensitive element 12 decreases, a large amount of current flows from the power source E, and the gas sensitive element 12 self-heats. For this reason, the temperature of the gas sensitive element 12 rises rapidly, and the heat is conducted from the sealed container 14 of the heat responsive element 13 to the bimetal 18, whereby the bimetal 18 is heated and reversed, and the movable contact 16 is moved from the fixed contact 15. Switching is performed so as to be separated and opened. This switching is used for applications such as alarming and control.

  As described above, in this configuration, it is possible to perform the necessary switching when the combustible gas is detected by the detection device alone without using an electronic circuit such as a comparator and a relay, and thus it is inexpensive. In addition, a compact combustible gas detection device can be provided.

In addition, in the case of this configuration, the heater 6 is provided so that the gas sensitive element 12 is heated to a predetermined temperature. Thereby, the sensitivity of the gas sensitive element 12 can be improved stably.
In particular, in this case, the heater 6 is composed of a positive temperature coefficient thermistor, and as its characteristics, the heat generation of the heater 6 and the heating temperature of the gas sensitive element 12 are constant in relation to the ambient temperature. The sensitivity of the element 12 can be further stabilized and improved.

  The heater 6 is in intimate contact with one surface of the gas sensitive element 12, and the heat sensitive element 13 is in intimate contact with the other surface of the gas sensitive element 12 on the opposite side. Compared to the fact that the surface on one side of 12 is in close contact with the heater 6 and the temperature is high, the surface on the other side of the gas sensitive element 12 (the surface on which the thermal sensitive element 13 is in close contact) has a lower temperature. Since the temperature becomes high as described above based on the contact of the combustible gas, the temperature change is large, and the thermal actuator 13 can be more accurately actuated.

Further, the heater 6 has electrodes 6 b and 6 c on both sides, and one of the electrodes 6 b is brought into close contact with the gas sensitive element 12, thereby making the one electrode 6 b common to the gas sensitive element 12. Thereby, a structure can be rationalized and it can be made cheaper.
Further, the heat-responsive element 13 has a metal sealed container 14 as an outer shell, and the metal sealed container 14 is brought into close contact with the gas sensitive element 12 to be one electrode of the gas sensitive element 12. Also by this, the configuration can be rationalized and can be made cheaper.

In addition, the thermally responsive element 13 has the metal sealed container 14 as an outer shell as described above, and the fixed contact 15 and the movable contact 16 are disposed therein. Thereby, the oxidation of the contact portions of the fixed contact 15 and the movable contact 16 can be prevented by the metal hermetic container 14, and the mechanical protection thereof can also be performed.
In addition, this invention is not limited only to the Example shown above and shown in drawing, In the range which does not deviate from a summary, it can change suitably and can implement.

The figure which shows one Example of this invention with the whole schematic structure and electrical connection Whole exploded vertical section Exploded perspective view of heater Enlarged longitudinal sectional view of thermal actuator Overall assembly vertical section

Explanation of symbols

  In the drawings, 6 is a heater, 6b is one electrode, 6c is the other electrode, 12 is a gas sensitive element, 13 is a thermally responsive element, 14 is a metal sealed container, and E is a power source.

Claims (5)

A gas sensitive element composed of a metal oxide semiconductor whose resistance value is reduced by contact with combustible gas, and
A heat sensitive element that responds to the heat of the gas sensitive element,
A combustible gas detection device, wherein the gas sensitive element is energized.   The combustible gas detection device according to claim 1, further comprising a heater for heating the gas sensitive element to a predetermined temperature.   3. The combustible gas detection device according to claim 2, wherein the heater is in close contact with one surface of the gas sensitive element, and the thermally sensitive element is in close contact with the other surface of the gas sensitive element on the opposite side.   4. The combustible gas according to claim 3, wherein the heater has electrodes on both sides, and one of the electrodes is brought into close contact with the gas sensitive element, thereby making the one electrode common to the gas sensitive element. Detection device. The heat-responsive element has a metal sealed container as an outer shell, and the metal sealed container is used as one electrode of the gas-sensitive element by being brought into close contact with the gas-sensitive element. Combustible gas detector.

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