JP2012047476A - Gas sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas sensor that excels in a heat dissipation characteristic and assembly accuracy and requires low cost.SOLUTION: A pair of electrode pins 5 and a pair of electrode pins 6 are fixedly planted in a mount base 2 via pin stays 3, 4. On the electrode pins 5, for example, a detection element (gas sensing element) 7 is fixed and on the electrode pins 6, for example, a compensation element 8 is fixed. A heat shield plate 1a that is arranged between the detection element 7 and the compensation element 8 and insulates the elements from heat is disposed on a cap 1. The gas sensor is configured such that the cap 1 with the heat shield plate 1a disposed is put over and fixed on the mount base 2. The heat shield plate 1a, which is disposed on the cap 1, is in contact with the cap 1.

Description

  The present invention relates to gas sensors used in a wide range of applications such as detection of various gas leaks and toxic gases, monitoring of exhaust gas and air pollution, monitoring of various processes, etc., particularly carbon monoxide generated during incomplete combustion in a combustion apparatus. The present invention relates to a gas sensor for accurately detecting leakage of (CO) gas or hydrogen gas in a fuel cell vehicle (FCV).

  Conventionally, as a sensor for detecting a combustible gas such as hydrogen gas, methane gas, or carbon monoxide gas, there are a catalytic combustion type gas sensor, a semiconductor type gas sensor, and the like. Each of these gas sensors incorporates a heat source that is used to detect flammable gases.

  As described in Patent Document 1, for example, the catalytic combustion type gas sensor has a detection element (gas sensing element) and a compensation element (comparison element) each including a heater coil provided with a combustion catalyst as a heat source. The detection element detects the presence of the flammable gas by outputting a change in the resistance value of the heater coil due to the catalytic combustion heat of the flammable gas generated on the combustion catalyst as a voltage change.

  In addition, the semiconductor gas sensor has a gas sensitive element composed of a heater coil provided with a semiconductor layer as a heat source, and changes in the electrical conductivity of the semiconductor layer caused by the adsorption phenomenon of the combustible gas in this semiconductor layer are changed in voltage. Is output to detect the presence of combustible gas.

  These existing gas sensors have a heat source for detecting flammable gas as described above. In order to stabilize the thermal equilibrium performance of the gas sensor and to ensure the explosion-proof performance against the flammable gas, a metal mesh, a metal firing is provided. A gas permeable cap made of a kneaded body or porous ceramics is provided.

  Furthermore, in order to compensate for the influence of changes in ambient temperature, a compensation element is connected in series with the above-described sensing element, and a Wheatstone bridge circuit is configured by connecting in parallel with a series circuit in which two resistors are connected in series. Also, Patent Document 1 discloses a gas detection device that detects a voltage between a connection point of a detection element and a compensation element and a connection point of two resistors by applying a DC voltage between both ends of the parallel circuit. Are listed. As a compensation element in this case, an element in which a heater coil having the same electrical characteristics as that of the sensing element is embedded in a heat conductive layer that is not covered or supported by an oxidation catalyst is used.

On the other hand, these existing gas sensors are provided with a synthetic resin mount base having no gas permeability. The mount base supports the detection element and the compensation element in a state of passing through a pair of electrode pins electrically connected to and supported by both terminals of the detection element and the compensation element. Hold it inside.
Thus, when the sensing element and the compensating element are installed in the same housing, a metal or synthetic resin heat shielding plate is provided between the two elements in order to prevent thermal interference between the two elements. .

  However, the gas permeable cap in such a gas sensor has a function of protecting the sensing element against environmental factors. On the other hand, the gas permeable cap restricts the gas, so that the response performance of the sensor is impaired. In addition, the existing mount base does not contribute at all to the detection target gas permeating into the sensor, and therefore does not contribute to the response performance of the sensor. Furthermore, although the heat shielding plate in the contact combustion type gas sensor is provided for the purpose of heat insulation between the detection element and the compensation element, on the other hand, the atmosphere environment of both elements inside the sensor is cut off. It is not necessarily preferable for the stability of the output voltage with respect to the temperature and humidity characteristics.

  Therefore, for example, as described in Patent Document 2, in the gas sensor including the cap, the mount base, and the heat shielding plate described above, all of them are made of ceramics, preferably permeable porous ceramics. It has also been devised that the target gas can flow into the sensor from all directions, and the gas concentration inside the gas sensor matches that of the surrounding environment at high speed, thereby improving the response performance of the gas sensor output.

  FIG. 4 is a cross-sectional view of a conventional gas sensor disclosed in Patent Document 2, and shows a state before the cap is joined. FIG. 5 is a perspective sectional view of a gas sensor according to the prior art and shows the internal structure of the gas sensor. Reference numeral 12 denotes a mount base. A pair of electrode pins 15 and a pair of electrode pins 16 are planted and fixed to the mount base 12 via pin stays 13 and 14. For example, the detection element 18 is fixed to the electrode pin 15, and the compensation element 19 is fixed to the electrode pin 16, for example. Between the electrode pin 15 to which the detection element 18 is connected and fixed and the electrode pin 16 to which the compensation element 19 is connected and fixed, a heat shielding plate 17 is fixed so as to block each other. The heat shield plate 17 is embedded and fixed in the mount base 12. And from above, it arrange | positions so that the circular cap 11 may be covered, and it joins, and comprises the gas sensor.

  In both cases of the above-mentioned Patent Document 1 and Patent Document 2, the heat shielding plate provided for the purpose of heat insulation between the detection element and the compensation element of the catalytic combustion type gas sensor is fixed to the mount base.

JP 2001-349862 A JP 2006-121610 A

  However, in the conventional gas sensor, as described above, the electrode pin of the sensing element or each electrode pin of the compensation element is supported through the mount base, and is provided for the purpose of heat insulation between the sensing element and the compensation element. The heat shielding plate is also embedded and held in the mount base. The conventional gas sensor disclosed in Patent Document 1 has a problem that the heat generated in the heater coil is conducted and the sensor output decreases. This is also considered to be caused by poor heat dissipation from the mount base and the heat shielding plate or the sensor cap.

  Moreover, in the conventional gas sensor disclosed in Patent Document 2, a heat shielding plate is inserted into a fixing groove provided in the mount base, and is bonded through a glass adhesive. There is a gap for insertion between the fixing groove of the mount base and the heat shielding plate, and there is a problem that it is difficult to fix at a right angle with high accuracy.

  In addition, in the conventional gas sensor disclosed in Patent Document 2, the mount base and the heat shielding plate are manufactured in separate processes, and a process of bonding with a glass adhesive is required, so the number of parts is large, There is a problem that the process becomes long and the cost becomes high.

  Furthermore, in the gas sensor having the conventional configuration disclosed in Patent Document 2, the mount base and the heat shielding plate are manufactured in separate processes, and a process of bonding with a glass adhesive is required. However, there is a problem that the yield reduction in manufacturing affects the yield reduction of the finished product and increases the cost.

  Further, since the heat shielding plate is fixed to the mount base, the heat conduction efficiency of the heat generated by the gas sensitive element from the heat shielding plate is poor, and the heat dissipation performance is lowered.

  The present invention seeks to provide a gas sensor with improved assembly accuracy and reduced cost, and further a gas sensor with excellent heat dissipation.

  In order to solve the above problems, a gas sensor of the present invention includes an electrode pin that supports a gas sensitive element and a compensation element, a mount base that supports and fixes the electrode pin, and heat insulation of the gas sensitive element and the compensation element. In the gas sensor having a heat shield plate and a cap that covers the gas sensitive element and the compensation element and is fixed to the mount base, the heat shield plate is fixed to the cap.

  Further, any one of the side portions of the heat shielding plate may be in contact with the inner wall surface of the cap.

  The heat shield plate may be configured not to contact the mount base.

  The heat shield plate can be formed integrally with the cap.

  The cap may be formed of a porous material that allows gas to pass therethrough.

  The heat shield plate may be formed of a porous material that allows gas to pass therethrough.

  According to the gas sensor of the present invention, since the heat shielding plate is fixed to the cap and is not in contact with the mount base, the heat generated in the heater coil and the gas sensitive element is transferred from the heat shielding plate to the cap side. Therefore, the heat dissipation characteristics are excellent, and the decrease in sensor output can be suppressed. In addition, since the heat shielding plate can be integrally formed, it can be formed at right angles with high accuracy, the number of components is small, and there are few factors that decrease the yield, so that the manufacturing cost can be suppressed, An inexpensive gas sensor can be provided.

Front sectional view of a gas sensor according to this embodiment Side sectional view of the gas sensor according to this embodiment Side sectional view of a gas sensor according to another embodiment Front sectional view showing a conventional gas sensor Perspective sectional view of a gas sensor according to the prior art

Hereinafter, embodiments for carrying out the present invention will be specifically described with reference to the drawings.
First, a preferred embodiment of a gas sensor according to the present invention will be described with reference to FIGS.

  FIG. 1 is a front sectional view of a gas sensor according to this embodiment (a sectional view when a gas sensitive element and a compensation element of the gas sensor are viewed in parallel), and FIG. 2 is a side sectional view of the gas sensor according to the present embodiment (gas sensitive element). FIG. 6 is a cross-sectional view when viewed from either element side of the compensation element.

  Reference numeral 2 denotes a mount base. A pair of electrode pins 5 and a pair of electrode pins 6 are planted and fixed to the mount base 2 via pin stays 3 and 4. For example, a detection element (gas sensitive element) 7 is fixed to the electrode pin 5, and a compensation element 8 is fixed to the electrode pin 6, for example.

  Reference numeral 1 denotes a cap having gas permeability, which is formed of ceramics, preferably porous ceramics. The cap 1 is provided with a heat shielding plate 1a disposed between the detection element 7 and the compensation element 8 for heat insulation. And the gas sensor of a present Example is comprised by covering the cap 1 provided with this heat shielding board 1a from the upper direction of the mount base 2, and fixing.

  As described above, since the heat shielding plate 1 a according to the gas sensor of the present embodiment is provided on the cap 1, the heat shielding plate 1 a is in contact with the cap 1. And as shown in FIG. 2, it is set as the structure which the side part 3 side of the heat shielding board 1a contact | connected the inner side wall part of the inner side upper part of the cap 1, and an inner side part. According to such a structure, since the heat of the heat shielding plate 1a can be released to the outside through the cap, the heat dissipation performance can be improved.

  The heat shielding plate 1a is configured with a gap d so as not to come into contact with the mount base 2 when the cap 1 is joined to the mount base 2. For this reason, it is possible to conduct heat to the cap side without accumulating the heat of the heat shielding plate on the mount base side, thereby improving the heat radiation performance.

  The heat shield plate 1a can be formed integrally with the cap 1 by press molding or the like. According to such a configuration, since the heat shielding plate can be accurately formed at a right angle, the number of parts is reduced. In addition, since there are few factors that decrease the yield, the manufacturing cost can be reduced, and an inexpensive gas sensor can be provided.

  The cap 1 can be formed of a porous material that allows gas to pass therethrough. Furthermore, the heat shielding plate can also be formed of a porous material that allows gas to pass therethrough. According to such a configuration, the concentration of the target detection gas on the detection element side and the compensation element side can be made uniform.

  FIG. 3 is a cross-sectional side view of a gas sensor according to another embodiment (a cross-sectional view when viewed from either the gas-sensitive element or the compensation element). In this embodiment, the heat shielding plate 1 b provided on the cap 1 is in contact with only the inner upper surface of the cap 1. According to such a configuration, the concentration of the target detection gas on the detection element side and the compensation element side can be made more uniform.

  Further, the heat shielding plate 1 b is configured with a gap so as not to come into contact with the mount base 2 when the cap 1 is joined to the mount base 2. For this reason, it is possible to conduct heat to the cap side without accumulating the heat of the heat shielding plate on the mount base side, thereby improving the heat radiation performance.

  Further, the heat shielding plate is formed integrally with the cap, and the cap and the heat shielding plate can be formed of a porous material that allows gas to pass through, as in the previous embodiment.

DESCRIPTION OF SYMBOLS 1 Cap 1a Heat shielding board 1b Heat shielding board 2 Mount base 3 Pin stay 4 Pin stay 5 Electrode pin 6 Electrode pin 7 Detection element 8 Compensation element 11 Cap 12 Mount base 13 Pin stay 14 Pin stay 15 Electrode pin 15
16 Electrode pin 15
17 Heat shielding plate 18 Sensing element 19 Compensating element

Claims (6)

An electrode pin for supporting the gas sensitive element and the compensation element, a mount base for supporting and fixing the electrode pin, a heat shielding plate for insulating the gas sensitive element and the compensation element, and the gas sensitive element and the compensation element are covered. A gas sensor having a cap fixed to the mount base.
The gas sensor according to claim 1, wherein the heat shielding plate is fixed to a cap.   2. The gas sensor according to claim 1, wherein any one of the side portions of the heat shielding plate is in contact with the inner wall surface of the cap.   The gas sensor according to claim 1, wherein the heat shielding plate is not in contact with the mount base.   The gas sensor according to claim 1, wherein the heat shielding plate is formed integrally with a cap.   The gas sensor according to claim 1, wherein the cap is a porous body that allows gas to pass therethrough. The gas sensor according to claim 1, wherein the heat shielding plate is a porous body that allows gas to pass therethrough.

Images