JP2002131263A - Contact combustion type gas sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a contact combustion type gas sensor which can reduce the effects of changes in temperature on the rear side of a sensor pedestal. SOLUTION: In the contact combustion type gas sensor, where a gas detection mechanism having a detector 11a for detecting a gas to be detected, disposed in a passage of the gas and a comparator 11b for correcting ambient environment, such as temperature, is provided on the surface of the sensor pedestal, the gas detection mechanism part has pins 12a and 12b, which are connected respectively to the detector 11a and the comparator 11b, to make the detector 11a and the comparator 11b conductive from the outside, while piercing the sensor pedestal 14 so as to protrude through the rear thereof, and is provided with a heat insulating member 17 covering at least the pins 12a and 12b to protrude through the sensor pedestal 14 to block changes in outside temperature on the side of the rear from being transmitted to the pins 12a and 12b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a catalytic combustion type gas sensor, and more particularly, to a detection element for detecting a gas to be detected, which is disposed in a flow path of the gas to be detected, and correcting an ambient environment such as temperature. The present invention relates to a contact combustion type gas sensor provided with a gas detection mechanism having a comparison element.

[0002]

2. Description of the Related Art A CO concentration (CO gas concentration) in exhaust gas discharged from a combustion chamber is provided on an exhaust top (an exhaust side of a combustion chamber) of a combustion apparatus such as a water heater, a bath kettle, and a heater using gas or oil as fuel. ) Is provided, and the gas sensor detects the concentration of the test substance which is the CO concentration in the test gas which is the exhaust gas, and the detected substance detection concentration becomes a predetermined reference concentration. When it exceeds, a safety operation such as issuing an alarm or shutting off fuel supply is performed.

As this type of gas sensor, there is a catalytic combustion type gas sensor and the like, and FIG. 4 is a diagram showing a conventional catalytic combustion type gas sensor.

In FIG. 4, a contact combustion type gas sensor (hereinafter, referred to as a gas sensor) 1 used in a gas leak alarm or the like has a detection element 11a which is sensitive to a test substance in combustion exhaust gas. As shown in the explanatory diagram of the configuration of the sensing element in FIG. 5, the sensing element 11a has a coil-shaped part 11 formed in the center of a platinum wire functioning as a resistance wire. , Palladium or the like and covered with a carrier containing an appropriate combustion catalyst to form a sphere.

The gas sensor 1 further has a comparison element 11b for eliminating the influence of the ambient environment such as temperature on the measured value. This comparison element 11b is the same as the detection element 11a except that it has no combustion catalyst. Is configured. The platinum wires of these elements are connected to a pair of pins 12a, 12b penetrating the sensor base 14, and the output values from these elements are output from the pins 12a,
It is output to the outside of the sensor housing via a lead wire 16 connected to the tip of 12b.

FIG. 6 is a diagram showing a general circuit of a catalytic combustion type gas sensor. As shown in FIG. 6, the detection element 11a and the comparison element 11b are incorporated in a resistance bridge circuit. The gas sensor 1 includes a sensing element 1
An anti-interference plate 13 is provided between the wire mesh 1a and the comparison element 11b so that they do not interfere with each other.
b, a cover 15a and a sensor base 14, which are housed and protected in a sensor housing.

[0007] The wire net 15b is made of, for example, SUS100mes.
h is formed into a cylindrical shape by a double wire mesh, and has a peripheral wall and a top wall. On the peripheral wall and the top wall, minute communication holes, which are minute mesh holes of a wire mesh, are formed. When the test gas hits the wire mesh 15b, the test gas enters the wire mesh 15b so as to penetrate through the minute communication holes of the wire mesh 15b, and the flow rate of the test gas when entering the gas mesh 15b is almost nil.

[0008] A space layer is formed between the cover 15a erected on the surface of the sensor base 14 and the peripheral wall of the wire net 15b. A flange is formed at the upper end of the cover 15a, and the front end of the flange extends inward (to the side of the wire mesh 15b) and is in contact with the upper end of the peripheral wall of the wire mesh 15b. As a result, the space layer becomes a closed space, and exhibits a heat blocking effect. Then, when the gas sensor 1 is installed in the flow path of the test gas in a horizontal state, the cover 15a is orthogonal to the flow of the test gas.

The gas detecting mechanism of the gas sensor 1 includes a detecting element 11a, a comparing element 11b, pins 12a and 12b, an interference preventing plate 13, a cover 15a, a wire net 15b, and the like.

Next, FIG. 7 is a view for explaining the outline of the gas water heater. For example, the above-described gas sensor 1 is installed in an exhaust gas flow rate reduction chamber 27 formed at a corner of the exhaust passage 8 of the combustion device 22 in the gas water heater.

The gas water heater of this type is further provided with a combustion control device 21.
By the control of 1, the fuel gas is supplied from the gas pipe 25 to the nozzle holder 24 in the combustion chamber 29, while the combustion fan 2
By the rotation of 3, the air enters the apparatus from the intake unit 30 as shown by the arrow B in the drawing, and is sent to the burner side (not shown), and the burner is burned by the air and the fuel gas. The water supplied from the water supply pipe 26 to the heat exchanger 22 is heated by the burner combustion through the heat exchanger 22 to become hot water and supplied from the hot water supply pipe 28 to a desired place such as a kitchen. Has become.

The detection element 11a and the comparison element 11
b is heated to a predetermined temperature (for example, about 200 ° C.) by energization through the lead wire 16 and the pins 12a and 12b, and the test gas, which is the exhaust gas generated by the combustion operation, is Flows through the exhaust passage 8 as shown in FIG.
When the contact element 1a comes into contact with the reference element 11b, a catalytic combustion reaction occurs due to a catalyst, and the reaction increases the temperature of the detecting element 11a, thereby increasing the electrical resistance.
A change in the voltage taken out of the resistance bridge circuit of the gas sensor 1 occurs in accordance with the loss of the resistance balance, and the concentration of the test substance is detected based on the change.

In the conventional gas sensor 1 described above,
By using the cover 15a and the wire net 15b, the detecting element 1
Since the protection device 1a and the comparison element 11b are protected, the error in the output value of the gas sensor 1 has been reduced by reducing the temperature distribution due to the wind speed of the test gas.

[0014]

However, as shown in FIG. 7, on the back side of the sensor base 14 of the gas sensor 1, a gas having a structure for taking in air from the intake section 30 into the apparatus as shown by an arrow B is shown. When the gas sensor 1 is installed in the water heater, a temperature change occurs on the back surface side of the sensor base 14 due to the influence of wind or the like, and the change is caused by the pin 1 which is a heat conducting member
2a, 12b, the detecting element 11a and the comparing element 11b
When the delicate thermal balance between the detection element 11a and the comparison element 11b is lost, the base fluctuates, and an error occurs in the output value of the gas sensor 1. .

Accordingly, the present invention has been made in view of the above-described problems,
An object of the present invention is to provide a contact combustion type gas sensor that reduces the influence of a temperature change on the back side of a sensor base.

[0016]

According to a first aspect of the present invention, there is provided a contact combustion type gas sensor provided in a flow path of a gas to be detected and detecting the gas to be detected. In a contact combustion type gas sensor in which a gas detection mechanism unit having an element and a comparison element for correcting an ambient environment such as temperature is provided on a surface of a sensor base, the gas detection mechanism unit is configured to externally detect the detection element and the comparison element. In order to energize each of the elements, the sensor element has a pin connected to each of the detection element and the comparison element and protruding from the sensor base to the rear surface, and at least the rear surface of the sensor base. A heat insulating member provided so as to cover the pin protruding from the rear surface and preventing the external temperature change on the back side from being transmitted to the pin.

According to the first aspect of the present invention, since the pins protruding from the back surface of the sensor base are covered by the heat insulating member, the pins protruding from the back surface of the sensor base are connected to the outside. Even if the temperature changes, the temperature change is prevented from being transmitted to the sensing element and the comparison element via the pin. Therefore, the contact combustion type gas sensor is less affected by the temperature distribution on the back surface side of the sensor base, so that a delicate thermal balance between the detection element and the comparison element is prevented from being lost, and the contact combustion type gas sensor outputs. An error included in the output value can be reduced. Therefore, since it is hard to be affected by the temperature change generated on the back surface side of the sensor base, it is possible to provide a contact combustion type gas sensor which can be easily attached to a place or a device where the temperature change is sharp.

According to a second aspect of the present invention, there is provided a contact combustion type gas sensor which is provided in a flow path of a test gas, and a detecting element for detecting the test gas and a surrounding element such as a temperature. In a contact combustion type gas sensor in which a gas detection mechanism section having a comparison element for correcting an environment is provided on a surface of a sensor base, the gas detection mechanism section supplies power to each of the detection element and the comparison element from outside. In order to connect to each of the sensing element and the comparison element, and to have a pin that penetrates the sensor base and protrudes to the back side, the back side of the sensor base flows on the back side. A windproof wall is provided so that gas does not directly hit the pins.

According to the contact combustion type gas sensor of the present invention described in claim 2, the windbreak wall provided on the back surface of the sensor base has a pin through which gas flowing on the back surface side of the sensor base projects from the back surface. To prevent direct hits. Therefore, the gas protruding from the back surface of the sensor base is not directly hit by the gas flowing on the back surface side, and the temperature change caused by the influence of the gas flow is transmitted to the detection element and the comparison element via the pin. Therefore, it is possible to prevent a delicate thermal balance between the detection element and the comparison element from being lost, so that an error included in an output value output from the contact combustion type gas sensor can be reduced. Therefore, since it is hard to be affected by the temperature change generated on the back surface side of the sensor base, it is possible to provide a contact combustion type gas sensor which can be easily attached to a place or a device where the temperature change is sharp.

According to a third aspect of the present invention, there is provided a gas sensor according to the second aspect, wherein the windproof wall is a peripheral wall surrounding the pin protruding from the back surface. And

According to the gas sensor of the present invention described in claim 3, an air layer is formed between the windproof wall and the pin by surrounding the pin projecting from the back surface of the sensor base with the windproof wall. This air layer prevents the influence of a temperature change occurring on the back side of the sensor base from being transmitted to the sensing element and the comparison element via the pin. Therefore, an air layer is formed on the back surface of the sensor base surrounded by the windbreak wall, and this air layer becomes a closed space and has a heat insulating effect. Since it is less affected by the temperature distribution, it is possible to prevent a delicate thermal balance between the detection element and the comparison element from being lost, and to reduce an error included in an output value output from the contact combustion gas sensor. Therefore, with a simple configuration in which a windbreak wall is provided on the back surface of the sensor base, it is possible to reduce the influence of a temperature change occurring on the back surface side.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a gas sensor according to the present invention will be described below with reference to FIGS.

An embodiment of the catalytic combustion type gas sensor according to the present invention will be described below with reference to the drawings. The same or corresponding portions as those described in the description of the related art are denoted by the same reference numerals, and detailed description thereof will be omitted.

First, a first embodiment according to the present invention will be described with reference to FIGS. 1 and 2. FIG. FIG. 1 is a cross-sectional view for explaining a first embodiment of a contact combustion type gas sensor according to the present invention, and FIG. 2 is a diagram showing wind speed characteristics of the contact combustion type gas sensor.

The basic configuration of a contact combustion type gas sensor (hereinafter referred to as a gas sensor) 1 is the same as the configuration described in the related art, and includes a gas detection mechanism. This gas detection mechanism section includes a detection element 11a and a comparison element 1 shown in FIG.
1b, pins 12a, 12b, anti-interference plate 13, cover 1
5a, a wire net 15b, and the like, and are provided on the front side of the sensor base 14.

A pair of pins 12a to which a detection element 11a sensitive to a test substance in the combustion exhaust gas is connected and a comparison element 11b for eliminating the influence of ambient environment such as temperature on the measured value are connected. One end of each of the pair of pins 12 b protrudes from the back surface of the sensor base 14. A lead wire 16 is connected to the end.

In the present invention, a change in the outside air temperature on the back surface of the sensor
The heat insulating member 17 for preventing transmission to the
It is provided so as to cover 2a, 12b and a part of the lead wire 16. As the heat insulating member 17, for example, a material having a heat insulating effect such as glass, epoxy resin, phenol resin, and cement can be used.

In the first embodiment, the heat insulating member 17 is provided so as to cover the entire back surface of the sensor base 14. However, the present invention is not limited to this, and the present invention is not limited thereto. Various embodiments can be adopted, such as providing a heat insulating member 17 so as to cover only the pins 12a and 12b.

Next, the results of the wind speed test of the gas sensor 1 according to the first embodiment configured as described above will be described.

FIG. 2A is a diagram showing the wind speed characteristics of the conventional gas sensor 1, and FIG. 2B is a diagram showing the wind speed characteristics of the gas sensor 1 according to the present invention. In FIG. 2, the vertical axis represents the concentration converted into the serial output of the gas sensor 1 [ppm: part
s per million], and the horizontal axis indicates the wind speed [m / s] from the detection element 11a side to the comparison element 11b side with respect to the back side of the gas sensor 1.

First, in a wind speed test on the conventional gas sensor 1, when a wind speed of 0.5 [m / s] is received on the back side,
It can be seen that the air base fluctuates greatly as the output conversion concentration is about -250 [ppm]. And
When the wind speed is 2.0 [m / s] or later, the detected conversion concentration is about -15.
A saturated state occurs at 0 [ppm].

However, when the heat insulating member 17 is provided on the back surface of the sensor base 14 of the gas sensor 1 as in the present invention, when the wind speed of 0.5 [m / s] is received on the back surface side, the output is reduced. The conventional gas sensor has a converted concentration of about -75 [ppm], and thereafter the output converted concentration is -50 and -25 [ppm] each time the wind speed increases to 1.0 and 2.0 [m / s]. It is reduced from 1. And the wind speed is 3.0
[M / s], the output converted density is about 0 [pp
m], it is not affected by the wind speed.

As can be seen from the above test results, the pins 12 a projecting from the sensor base 14 by the heat insulating member 17,
12b, for example, on the back side of the gas sensor 1 mounted on the gas water heater shown in FIG.
As shown in the figure, even if air flows from the intake unit 30, the influence of the temperature change generated on the back side of the sensor base 14 is caused by the pins 12a,
Transmission to the sensor element via 12b can be prevented by the heat insulating member 17.

Therefore, the gas sensor 1 is hardly affected by the temperature distribution on the back side of the sensor base 14,
The delicate thermal balance between the detection element 11a and the comparison element 11b is prevented from being lost, and errors included in the output value output by the gas sensor 1 can be reduced. Therefore,
Since the gas sensor 1 is less susceptible to a temperature change occurring on the back surface side of the sensor base 14, the gas sensor 1 can be provided which can be easily attached to a place or a device where the temperature change is sharp.

Next, a second embodiment of the present invention will be described with reference to FIG. Here, FIG. 3 is a sectional view for explaining a second embodiment of the catalytic combustion type gas sensor according to the present invention.

In the first embodiment described above, the pins 12a projecting from the back surface of the sensor base 14 of the gas sensor 1,
Although the case where 12b is covered with the heat insulating member 17 has been described, the present invention is not limited to this. For example, a configuration like the second embodiment shown in FIG. 3 can be adopted.

In FIG. 3, the basic configuration of a contact combustion type gas sensor (hereinafter, referred to as a gas sensor) 1 is the same as the configuration described in the prior art, similarly to the first embodiment. It has. The gas detection mechanism section includes the detection element 11a, the comparison element 11b, the pins 12a and 12b, the interference prevention plate 13, the cover 15a, and the wire net 15b shown in FIG.
Is provided on the front side.

In the gas sensor 1 according to the second embodiment, the pins 12a, 1
A tubular windbreak wall 18 is provided upright on the back surface of the sensor base 14 so that the wind does not directly hit the sensor base 2b. This windbreak wall 18
For example, a material such as metal, glass, or epoxy resin can be used. As a result, an air layer is formed on the back surface of the sensor base 14 surrounded by the windbreak wall 18, and this air layer becomes a closed space and exhibits an insulating effect. Therefore, the pins 12a protruding from the sensor base 14,
Temperature changes occurring on the back side of the sensor base 14 are less likely to be transmitted to the sensor base 12b.

The gas sensor 1 of the second embodiment configured as described above was also subjected to a wind speed test in the same manner as the first embodiment. Similar test results could be obtained.

As can be seen from the above description, the windbreak wall 1
8, the pins 12 projecting from the back surface of the sensor base 14
a, 12b to cover the pins 12a, 12b.
b, for example, even if air flows from the intake section 30 as shown by the arrow B on the back side of the gas sensor 1 mounted on the gas water heater shown in FIG. The effect of the temperature change that occurs on pins 12a, 1
Transmitted to the sensor element through the windshield 18b.
Can be blocked by

Therefore, even when the windbreak wall 18 is formed as in the second embodiment, the gas sensor 1 is hardly affected by the temperature distribution on the back surface side of the sensor base 14, so that the detection element 11a and the comparison element It is possible to prevent a delicate thermal balance with 11b from being lost, and to reduce an error included in an output value output by the gas sensor 1. Therefore, by providing the windproof wall 18 on the back surface of the gas sensor 1, the gas sensor 1 is less likely to be affected by a temperature change occurring on the back surface side, so that the gas sensor 1 can be easily attached to a place or a device where the temperature change is sharp. be able to.

In the above-described second embodiment, the cover 15a and the windbreak wall 18 are formed as separate bodies. However, the present invention is not limited to this. Can be extended to realize the windbreak wall 18. Further, the windproof wall 18 is not limited to a structure that completely blocks the ventilation, and may have a fine mesh shape as long as it can prevent direct contact with the wind.

Further, in the above-described second embodiment,
Although the case where the windproof wall 18 is a peripheral wall surrounding the pins 12a and 12b has been described, the present invention is not limited to this. For example, the rear surface side of the gas sensor 1 mounted on the gas water heater shown in FIG. , As indicated by arrow B,
For example, a plate-shaped windbreak wall such that air flowing from zero does not directly hit the pins 12a and 12b is provided near the pin 12a or the pin 12b located on the upstream side of the air flow.
Various embodiments are possible.

As described above, the conventional gas sensor 1
Can be dealt with by simply providing a heat insulating member 17 shown in the first embodiment, a windbreak wall 18 shown in the second embodiment, and the like on the back surface of the gas sensor 1 without changing the configuration of FIG. Therefore, it can be easily handled.

[0045]

As described above, according to the contact combustion type gas sensor of the first aspect of the present invention, the contact combustion type gas sensor is hardly affected by the temperature distribution on the back side of the sensor base. It is possible to prevent a delicate thermal balance between the element and the comparison element from being lost, and to reduce an error included in an output value output from the catalytic combustion gas sensor. Therefore, since it is less susceptible to the temperature change occurring on the back side of the sensor base, it is possible to provide a contact combustion type gas sensor which can be easily attached to a place or an apparatus where the temperature change is sharp. .

According to the contact combustion type gas sensor of the present invention described in claim 2, the gas protruding from the back surface of the sensor base is not directly hit by the gas flowing on the back surface side.
To prevent the temperature change caused by the gas flow from being transmitted to the sensing element and comparison element via the pin, and to prevent the subtle thermal balance between the sensing element and the comparison element from being broken. Therefore, it is possible to reduce an error included in an output value output by the catalytic combustion type gas sensor. Therefore, since it is less susceptible to the temperature change occurring on the back side of the sensor base, it is possible to provide a contact combustion type gas sensor which can be easily attached to a place or an apparatus where the temperature change is sharp. .

According to the invention described in claim 3, according to claim 2
In addition to the effects of the invention described in the above, an air layer is formed on the back surface of the sensor base surrounded by the windbreak wall, this air layer becomes a closed space, and has a heat insulating effect, so the contact combustion type gas sensor is Because it is less affected by the temperature distribution on the back side of the sensor base, the delicate thermal balance between the detection element and the comparison element is prevented from being lost, and the error included in the output value output by the contact combustion gas sensor is reduced. Can be reduced. Therefore, with a simple configuration in which a windbreak wall is provided on the back surface of the sensor base, the effect of a temperature change occurring on the back surface side can be reduced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a first embodiment of a catalytic combustion type gas sensor according to the present invention.

FIG. 2 is a diagram showing wind speed characteristics of a contact combustion type gas sensor.

FIG. 3 is a sectional view for explaining a second embodiment of the catalytic combustion type gas sensor according to the present invention.

FIG. 4 is a view showing a conventional catalytic combustion type gas sensor.

FIG. 5 is a diagram illustrating the configuration of a sensing element in FIG. 4;

FIG. 6 is a diagram showing a general circuit of a catalytic combustion type gas sensor.

FIG. 7 is a diagram for explaining the outline of a gas water heater.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Contact-combustion gas sensor 11a Detection element 11b Comparison element 12a, 12b Pin 14 Sensor base 17 Heat insulation member 18 Windproof wall

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Izumi Katsube 23 Minamikashima, Futamata-machi, Tenryu-shi, Shizuoka Prefecture Inside Yazaki Keiki Co., Ltd. 72) Inventor Keiichi Miura 93 Edocho, Chuo-ku, Kobe City, Hyogo Prefecture Inside Noritz Co., Ltd. AB08 AE19 AF09 BA03 BB02 BB07 BD02 HA01 HB06 HC02 HC07 HE01

Claims (3)

[Claims] A gas detection mechanism disposed in a flow path of the test gas and having a detection element for detecting the test gas and a comparison element for correcting an ambient environment such as temperature; In the catalytic combustion type gas sensor provided in the above, the gas detection mechanism is connected to each of the detection element and the comparison element in order to externally energize each of the detection element and the comparison element, and the sensor It has a pin that penetrates the base and protrudes from the back surface, and is provided so as to cover at least the pin protruding from the back surface of the sensor base, and an external temperature change on the back surface is transmitted to the pin. A contact-combustion gas sensor, comprising a heat insulating member that prevents the gas sensor from burning. 2. A gas detection mechanism disposed in a flow path of a test gas and having a detection element for detecting the test gas and a comparison element for correcting an ambient environment such as temperature is provided on a surface of the sensor base. In the catalytic combustion type gas sensor provided in the above, the gas detection mechanism is connected to each of the detection element and the comparison element in order to externally energize each of the detection element and the comparison element, and the sensor A contact that has a pin that penetrates the base and protrudes to the rear surface, and a windbreak wall is provided on the rear surface of the sensor base so that gas flowing on the rear surface side does not directly hit the pin. Combustion gas sensor. 3. The windproof wall according to claim 2, wherein the windproof wall is a peripheral wall surrounding the pin protruding from the back surface.
4. The contact combustion gas sensor according to claim 1.