JP2004020377A - Catalytic combustion type gas sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a catalyst from being poisoned by a silicon compound, so as to maintain detection sensitivity for a flammable gas favorably. <P>SOLUTION: This catalytic combustion type gas sensor comprises a gas detecting element deposited with a metal oxide sintered body for carrying the catalyst on a temperature measuring resistor, a compensating element deposited with a metal oxide for carrying no catalyst on the temperature measuring resistor, an electric power source for impressing a fixed voltage to the gas detecting element and the compensating element, and a container for storing the gas detecting element and the compensating element and provided with an inlet of the flammable gas. In the gas sensor, a silicon trap filter containing a material poisoned by silicon or the silicon compound is provided in the inlet of the flammable gas. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a catalytic combustion type gas sensor for detecting a flammable gas such as hydrogen gas.
[0002]
[Prior art]
As a general contact combustion type gas sensor, for example, one having a configuration as shown in FIG. 2 is known. At each end of the cylindrical container 11, a base portion 12 and a sintered filter 13 are respectively arranged. A bridge circuit section 14 composed of an element for detecting a flammable gas or the like is fixed to the base section 12 toward the inside of the cylindrical container 11. The bridge circuit section 14 is connected to a power supply 15. ing. The bridge circuit section 14 includes a gas detection element having a structure in which a temperature measuring resistor such as a platinum coil is covered with a metal oxide sintered body carrying a catalyst active for combustible gas, and a gas detection element for combustible gas. A compensating element having the same structure as that of the gas detecting element except that it does not contain an active catalyst is used. As shown in FIG. 3, a gas detecting element 21, a compensating element 22, and two fixed resistors 23 and 24 are used. A bridge circuit is incorporated in each branch and further connected to the detection unit 25.
[0003]
Since a constant voltage is applied to this contact combustion type gas sensor by the power supply 15 and the bridge circuit is designed so that the equilibrium is maintained in the absence of combustible gas, the detection unit 25 No current is detected. When the combustible gas enters the contact combustion type gas sensor from the sintering filter 13 and comes into contact with the gas detection element 21, combustion of the combustible gas occurs, and the heat of combustion increases the electric resistance value of the temperature measuring resistor. . On the other hand, in the compensating element 22, even if the combustible gas comes into contact, combustion does not occur and no temperature change occurs. As a result, the equilibrium of the bridge circuit is lost, and an unbalanced current proportional to the concentration of the combustible gas flows to the detection unit 25, so that the concentration of the combustible gas can be detected by measuring this current.
[0004]
Such a contact combustion type gas sensor is almost unaffected by the environmental temperature and humidity, can detect almost linearly in a wide concentration range, has excellent accuracy and reproducibility of combustible gas detection, and further has a high consumption efficiency. Since the power is small and the device can be miniaturized, it is widely used in various fields.
[0005]
[Problems to be solved by the invention]
However, in the above-mentioned catalytic combustion type gas sensor, the catalyst of the sensing element is poisoned by the silicon compound in the atmosphere, particularly when used in a vehicle, the silicon compound scattered from various parts in the vehicle, and the flammable gas is burned. There is a problem that the detection sensitivity of the reactive gas is reduced. Further, there is also a problem that the poisoning by the silicon compound is selectively generated by the catalyst when the catalytic combustion type gas sensor is energized.
[0006]
Accordingly, an object of the present invention is to provide a catalytic combustion type gas sensor capable of preventing poisoning of a catalyst by a silicon compound and maintaining good detection sensitivity of combustible gas.
[0007]
[Means for Solving the Problems]
The catalytic combustion type gas sensor of the present invention comprises a gas sensing element formed by attaching a catalyst-carrying metal oxide sintered body to a resistance temperature detector, and a metal oxide not carrying a catalyst attached to a resistance temperature detector. A compensating element, a power supply for applying a constant voltage to the gas detecting element and the compensating element, a container in which the gas detecting element and the compensating element are housed and provided with a combustible gas inlet, and a combustible gas inlet And a silicon trap filter containing a material poisoned by silicon or a silicon compound.
[0008]
In the contact combustion type gas sensor of the present invention, it is preferable that a resistor is provided in the silicon trap filter, and the resistor is connected to a power supply in parallel with the gas detection element and the compensation element.
[0009]
According to the present invention, the silicon compound in the atmosphere is consumed for poisoning of the catalyst in the silicon trap filter by providing the silicon trap filter containing the material poisoned by silicon or the silicon compound at the inlet of the flammable gas. Therefore, there is an effect that the catalyst in the gas detection element is not poisoned, and the detection sensitivity of the combustible gas can be favorably maintained.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the catalytic combustion type gas sensor of the present invention will be described in more detail.
In the catalytic combustion type gas sensor of the present invention, a gas detection element in which a metal oxide sintered body supporting a catalyst is attached to a resistance temperature detector, and a metal oxide not supporting a catalyst is connected to the resistance temperature detector. A compensating element attached is used. Examples of the metal oxide used for these devices include at least one selected from alumina and zeolite, but they need not be the same metal oxide. Further, it is preferable that the catalyst used in the gas detecting element is appropriately selected from the group consisting of platinum, ruthenium, and rhodium depending on the type of the combustible gas to be detected.
[0011]
As a method for manufacturing the above gas detection element and the compensation element, for example, first, a platinum wire having a diameter of 60 μm is wound 10 times around an outer diameter of 0.6 mm to manufacture a coil having a length of 1.5 mm. Next, an alumina paste is adhered to the platinum coil, baked at 800 ° C., and an alumina carrier is fixed to the platinum coil, whereby a compensating element is manufactured. Next, this alumina sintered carrier is immersed in an aqueous chloroplatinic acid solution, pulled up, and then thermally decomposed at 600 ° C. to carry a platinum catalyst on the alumina sintered carrier, thereby producing a gas detection element.
[0012]
As described above, the gas sensing element and the compensating element obtained as described above, together with the two fixed resistors, constitute a balanced bridge circuit in a state where a constant voltage is applied by the power supply, and An inventive catalytic combustion gas sensor is formed. In this contact combustion type gas sensor, a combustible gas enters the inside of the sensor from the sintered filter, and when it comes into contact with the gas detection element, it is burned by the presence of a catalyst, and the heat of combustion increases the electric resistance value of the temperature measuring resistor. . On the other hand, since the compensating element does not include a catalyst, combustion does not occur even if the combustible gas comes into contact. As a result, the equilibrium in the bridge circuit is disrupted, and the concentration of the combustible gas is detected by an unbalanced current generated in proportion to the concentration of the combustible gas.
[0013]
Here, in the catalytic combustion type gas sensor of the present invention, as shown in FIG. 1, a bridge circuit 14 including a gas detecting element and a compensating element is housed, and a sintered filter 13 is provided at an inlet of a combustible gas. It consists of a cylindrical container 11, and a silicon trap filter 16 is provided on this sintered filter. The silicon trap filter 16 is formed to contain a material poisoned by silicon or a silicon compound, and is configured in a porous shape. Since all the gas entering the catalytic combustion type gas sensor of the present invention passes through the trap filter 16, the silicon compound which can poison the catalyst in the gas detection element is not affected by the poisoning of the catalyst in the silicon trap filter 16. Consumed. Therefore, the silicon compound 17 can be prevented from entering the catalytic combustion type gas sensor of the present invention, the catalyst in the gas detection element is not poisoned, and the detection sensitivity of the combustible gas can be maintained well. Can be.
[0014]
In addition, it is preferable that the silicon trap filter 16 in the contact combustion type gas sensor of the present invention has a function of energizing the conductive wire 18 and the like. In this way, by energizing the silicon trap filter 16 and raising the temperature, the catalyst in the silicon trap filter 16 is made to have almost the same environmental conditions as the catalyst in the energized gas detection element, and the catalyst in the trap filter 16 is poisoned. Can be further promoted, and a silicon compound that can poison the catalyst in the gas detection element can be reliably captured.
[0015]
The contact combustion type gas sensor of the present invention is not limited to the configuration shown in FIG. 1 as long as it has such features, and can be applied to the configuration of a generally known contact combustion type gas sensor. is there.
[0016]
【The invention's effect】
As described above, according to the catalytic combustion type gas sensor of the present invention, the silicon compound in the atmosphere is provided by providing the silicon trap filter containing the material poisoned by silicon or the silicon compound at the inlet of the flammable gas. Since the catalyst is consumed by the poisoning of the catalyst in the silicon trap filter, the catalyst in the gas detecting element is not poisoned, and the detection sensitivity of the flammable gas can be favorably maintained.
[Brief description of the drawings]
FIG. 1 is a diagram schematically showing a configuration of an example of a contact combustion type gas sensor of the present invention.
FIG. 2 is a diagram schematically showing an example of a conventional catalytic combustion type gas sensor.
FIG. 3 is a diagram showing a bridge circuit of the catalytic combustion type gas sensor.
[Explanation of symbols]
11 ... cylindrical container, 12 ... base, 13 ... sintered filter, 14 ... bridge circuit part, 15 ... power supply, 16 ... silicon trap filter,
17: trapped silicon compound, 18: conductive wire, 21: gas detection element,
22: compensating element, 23, 24: fixed resistance, 25: detecting section.

Claims (2)

A gas detection element formed by attaching a metal oxide sintered body carrying a catalyst to a resistance temperature detector,
A compensating element formed by attaching a metal oxide that does not carry a catalyst to the resistance temperature detector,
A power supply for applying a constant voltage to the gas detection element and the compensation element;
A container in which the gas detection element and the compensation element are housed, and in which a combustible gas inlet is provided;
A contact combustion type gas sensor, comprising: a silicon trap filter provided at an inlet of the combustible gas and containing a material poisoned by silicon or a silicon compound. 2. The silicon trap filter according to claim 1, wherein a resistor is provided in the silicon trap filter, and the resistor is connected to a power supply in parallel with the gas detection element and the compensation element. Contact combustion type gas sensor.

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