JP2006046934A - Gas sensor and gas detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas sensor capable of certainly performing the inspection due to an inspection gas, and a gas detector. <P>SOLUTION: The gas sensor A is equipped with a cylindrical housing container 23 having a gas inflow port 8 on one end side in its axial direction and housing a gas-sensitive body 1 comprising a metal oxide semiconductor therein, a filter cap 7 having the housing container 23 fitted therein so that the gas inflow port 8 becomes the head from the opening part on one end side in the axial direction of the housing container 23 and having a vent hole 10 formed to the end surface on the other end side of the housing container 23 and the adsorbing material 12 provided to the gas flow channel between the vent hole 10 and the gas inflow port 8 to adsorb an obstruction gas and a poisoning gas. An inspection gas introducing passage 22 for introducing the inspection gas into the gas inflow port 8 from the opening part of the filter cap 7 through the gap between the outer peripheral surface of the housing container 23 and the inner peripheral surface of the filter cap 7 is provided and a notch 19 is formed to the peripheral surface on the side of the opening part of the filter cap 7 and a guide wall 20 for guiding the inspection gas to the notch 19 from the peripheral surface around the notch 19 toward the outside in the diametric direction of the notch 19 is provided in a protruded state. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a gas sensor and a gas detection device.

  As this type of gas sensor, a gas sensor using a metal oxide semiconductor whose electric resistance changes according to the gas concentration of a combustible gas such as methane to be detected has been conventionally provided (for example, a patent). Reference 1).

  FIG. 7 is a cross-sectional view schematically showing the structure of a conventional gas sensor A. A gas sensitive body 1 made of a metal oxide semiconductor has three terminals 3 inserted through a resin base 2 by insert molding. The metal cap 6 is attached to the upper surface side of the base 2 so as to cover the gas sensitive body 1. The metal cap 6 is attached with a filter cap 7 holding a filter 12 for adsorbing an interference gas such as hydrogen gas or alcohol vapor, or a poisoning gas such as silicon vapor or water vapor.

  The metal cap 6 has a gas inlet 8 in the center of the ceiling, and a stainless steel wire mesh 9 is attached to the gas inlet 8 so that gas is introduced into the gas sensitive body 1 through the wire mesh 9. It has become. The filter cap 7 is made of a cylindrical synthetic resin molded product. A vent hole 10 is formed on one end side in the axial direction so as to communicate the outside with the inside, and the metal cap 6 is formed so as to close the opening on the other end side. Is attached from the gas inlet 8 side. A stainless steel wire mesh 11 is attached to the vent hole 10 of the filter cap 7, and a filter 12 is disposed in the gas flow path between the vent hole 10 and the gas inlet 8.

  Thus, when air flows into the metal cap 6 from the outside through the vent hole 10, the filter 12, and the gas inlet 8, the electric resistance of the gas sensitive body 1 is increased according to the gas concentration of the detection target gas in the air. Since it changes, the gas concentration of the detection target gas can be detected from the change in the electrical resistance of the gas sensitive body 1. Moreover, since the interference gas and poison gas contained in the air are adsorbed by the filter 12 attached to the filter cap 7, the detection error due to the interference gas is reduced, and the influence of the poison gas on the long-term stability of the sensor characteristics. Can be reduced.

  Such a gas sensor A is used, for example, in a gas leak alarm for home use, and FIG. 8 shows a structure for attaching the gas sensor A to the alarm casing. The casing 40 of the gas leak alarm is composed of a box-shaped case 40a with a part of the front surface opened, and a cover 40b that closes the opening of the case 40a. The case 40a includes a printed wiring board. A circuit board 41 is accommodated. The circuit board 41 is formed with an alarm circuit that issues an alarm based on the sensor output of the gas sensor A, and the gas sensor A is mounted at a position facing the opening of the case 40a. The cover 40b is provided with a plurality of ventilation windows 42 in which the gas flow path is bent in a square shape. Outside air that has flowed into the housing 40 through the ventilation windows 42 passes through the ventilation holes 10 of the gas sensor A. The gas 12 reaches the gas sensitive body 1 through the gas inlet 8 and the electric resistance of the gas sensitive body 1 changes according to the gas concentration of the detection target gas contained in the outside air. In addition, the arrow D in FIG. 8 has shown the inflow route of external air.

  By the way, it is necessary to check whether or not the alarm operation is normally performed in the gas leak alarm device, and at the time of inspection, the inspection gas (for example, lighter gas (butane)) enters the housing 40 from the inspection hole 43 provided in the cover 40b. And alcohol gas) are injected, the inspection gas reaches the gas sensing element 1, a reaction is caused, and it is confirmed whether or not the alarm circuit operates normally.

  However, in the gas sensor configured as described above, the filter 12 is disposed in the filter cap 7 so as to face the vent hole 10, so that even if an inspection gas is injected into the filter cap 7 through the vent hole 10, the inspection gas is not filtered. Therefore, the inspection gas introduction hole 24 (for example, the hole diameter is 1.0 mm) having a smaller opening area than the vent hole 10 is passed through the circumferential surface of the filter cap 7 between the filter 12 and the gas inlet 8. The inspection gas was injected into the filter cap 7 through the inspection gas introduction hole 24 (the arrow in FIG. 7 indicates the inspection gas injection path). That is, when checking the operation of the alarm device, as shown by the arrow E in FIG. 8, if the inspection gas is injected from the inspection hole 43 provided in the cover 40 b on the front surface of the housing 40, the gas flow path 44 inside the housing 40. Since the inspection gas is introduced to the inspection gas introduction hole 24 provided on the peripheral surface of the filter cap 7 through the inspection gas, the inspection gas that has passed through the inspection gas introduction hole 24 reaches the gas sensing body 1 and the gas sensing body 1 Reacts with the inspection gas, and the operation is confirmed with the inspection gas.

  As described above, in the conventional gas sensor A, the inspection gas introduction hole 24 is formed in the peripheral surface of the filter cap 7 in order to introduce the inspection gas into the inside. There is a possibility that poison gas flows in, and the detection error increases due to the interference gas, and the sensor characteristics tend to fluctuate in the long term due to the poison gas.

Therefore, the present inventors do not form the inspection gas introduction hole 24 on the peripheral surface of the filter cap 7, but the opening between the filter cap 7 and the inner peripheral surface of the filter cap 7 and the outer peripheral surface of the metal cap 6. A gas sensor has been proposed in which a small gap is provided between the inspection gas introduction hole 24 and the inspection gas introduction path for introducing the inspection gas to the gas inlet 8 is formed by a gap that is sufficiently long compared to the entire length of the inspection gas introduction hole 24. Compared with the case where the inspection gas introduction hole 24 is formed, the airtightness of the filter cap 7 is increased, and only the inspection gas injected through the inspection gas introduction path reaches the gas sensing body 1, which is an obstacle. The adverse effects of gas and poison gas could be reduced.
JP 7-121787 A

  By the way, when performing the operation check of the alarm device using the gas sensor, the inspection gas injected from the inspection hole 43 provided in the cover 40b on the front surface of the housing 40 is allowed to pass through the gas flow path 44 inside the housing 40. The gas inlet is led to the bottom (opening) of the filter cap 7 along the surface of the circuit board 41 and through a gap (inspection gas introduction path) between the inner peripheral surface of the filter cap 7 and the outer peripheral surface of the metal cap 6. However, when the inspection gas flowing along the surface of the circuit board 41 hits the peripheral surface of the filter cap 7, a part of the inspection gas is separated from the bottom of the filter cap 7 and the circuit board 41. However, since most of the inspection gas flows outside the filter cap 7 along the peripheral surface of the filter cap 7, a small amount of inspection gas flows. The gas sensor 1 cannot reach the gas sensor 1 and the gas sensor 1 and the alarm circuit may not work even though they are operating normally. There was a problem.

  In addition, if the relative positional relationship between the gas flow path 44 and the opening of the filter cap 7 is shifted due to manufacturing dimensional variations of the housing 40 that houses the gas sensor A, it flows into the interior through the inspection gas introduction path. There was a possibility that the inspection gas to be used was further reduced and the inspection work with the inspection gas could not be performed reliably.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a gas sensor and a gas detection device capable of reliably performing inspection work with inspection gas.

  In order to achieve the above object, the invention of claim 1 includes a gas sensitive body for converting a gas concentration of a gas to be detected into an electrical signal, and a plurality of detection electrodes embedded and fixed in the gas sensitive body, A cylindrical storage container in which a gas inlet is formed on one end side in the axial direction and a terminal electrically connected to each detection electrode protrudes from the other end side in the axial direction, and an opening on one end side in the axial direction A cylindrical cover in which a storage container is inserted into the inside from the gas inlet side so as to close the part, and a vent hole is formed on the other end side to connect the gas inlet and the outside; A filter that is provided in a gas flow path between the gas inlet and adsorbs interference gas and poison gas, and is formed between the inner peripheral surface of the cover and the outer peripheral surface of the storage container through the cover opening. An inspection gas introduction path for introducing inspection gas to the gas inlet through the gap In the gas sensor, a notch is formed in the peripheral surface on the opening side of the cover, and a guide wall is provided protruding from the peripheral surface around the notch toward the outer side in the radial direction. .

  The invention of claim 2 is characterized in that, in the invention of claim 1, the bottom surface of the storage container is recessed inwardly of the opening edge of the cover.

  The invention of claim 3 is characterized in that, in the invention of claim 1 or 2, the distance from the opening of the cover to the bottom surface of the storage container is shorter than the depth of the notch.

  According to a fourth aspect of the invention, there is provided the gas sensor according to any one of the first to third aspects, and a detection circuit unit that detects the gas concentration of the detection target gas from the output signal of the gas sensor. .

  In the gas sensor according to the first aspect of the present invention, when the terminal protruding from one end side of the storage container is connected to the substrate, the opening of the cover faces the substrate and passes through the gap between the substrate and the opening edge of the cover. The inspection gas is introduced into the inspection gas introduction path. According to the invention of claim 1, a notch is formed in the peripheral surface on the opening side of the cover, and a radial direction is formed from the peripheral surface around the notch. Since the guide wall that guides the inspection gas to the notch protrudes outward, the inspection gas that flows along the surface of the substrate is collected in the notch by the guide wall formed on the peripheral surface around the notch. The inspection gas that has entered the inside of the cover can be allowed to flow into the inspection gas introduction path, so that unnecessary inspection gas that diffuses without flowing into the inspection gas introduction path is reduced, and even a small amount of inspection gas can be reliably inspected. There is an effect that can be performed. In addition, when this gas sensor is used in a gas leak alarm device, the position of notches formed in the gas flow path of the inspection gas formed in the housing and the peripheral surface of the cover due to manufacturing dimensional variations in the housing that houses the gas sensor Even if there is a slight deviation, the inspection gas can be collected in the notch by the guide wall, so that it is possible to increase the amount of inspection gas introduced into the notch and perform the inspection work reliably. .

  According to the invention of claim 2, since the bottom surface of the storage container is recessed inward from the opening edge of the cover, the space surrounded by the substrate on which the gas sensor is mounted, the bottom surface of the storage container, and the peripheral surface of the cover. After the inspection gas that has flowed into the cover through the notch is temporarily accumulated in this space, it passes through the inspection gas introduction path consisting of a minute gap between the inner peripheral surface of the cover and the outer peripheral surface of the storage container to the gas inlet. Since the inspection gas can be introduced, the inspection gas that has flowed in can be led to the inspection gas introduction path without escaping, and the inspection work can be reliably performed even with a small amount of inspection gas.

  According to the invention of claim 3, a part of the storage container can face the notch, and the inspection gas flowing into the cover through the notch hits the part of the storage container facing the notch, whereby the flow direction of the inspection gas is changed. Instead, inspection gas can easily enter the inspection gas introduction path consisting of a minute gap between the inner peripheral surface of the cover and the outer peripheral surface of the storage container, so that it is possible to perform inspection work reliably even with a small amount of inspection gas. .

  According to the invention of claim 4, by using any one of the gas sensors of claims 1 to 3, a gas detection device capable of surely checking the operation of the gas sensor and the detection circuit can be realized.

  Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1)
As shown in FIGS. 2 and 3, the gas sensor A of the present embodiment includes a resin base 2, three terminals 3 embedded and fixed to the base 2 by insert molding, a heater 3 electrode 4 and a center electrode 5. A sensor body B comprising a gas sensitive body 1 electrically connected via a base and a metal cap 6 crowned to the base 2, and a filter cap as a cover attached to the metal cap 6 of the sensor body B 7.

The gas sensitive body 1 converts the gas concentration of the detection target gas into an electrical signal. For example, an elliptical sphere is formed by a metal oxide semiconductor such as SnO ₂ whose electric resistance is changed by the action of the detection target gas. The heater-sensitive electrode 4 made of coiled platinum is embedded in the gas-sensitive body 1 and the center made of platinum is penetrated through the center of the coil portion of the heater-functional electrode 4. An electrode 5 is embedded. Here, by alternately applying two levels of electric power to the heater electrode 4, the temperature of the gas sensitive body 1 can be intermittently heated in two levels, the voltage between the electrodes 4 and 5 at that time. The electrical resistance of the gas sensitive body 1 is obtained from the value, and from this resistance value, a combustible gas such as methane gas or propane gas is detected when the gas sensitive body 1 is at a high temperature, and carbon monoxide is detected when the temperature is low.

  The base 2 is formed in a disc shape from a synthetic resin such as PBT, and three terminals 3 are embedded and fixed in a row so as to penetrate the base 2 in the thickness direction. One end of the center electrode 5 is electrically connected to the upper portion of the central terminal 3, and both ends of the coiled heater combined electrode 4 are electrically connected to the upper portions of the terminals 3 on both sides.

  The metal cap 6 has a bottomed cylindrical shape that is open at one end in the axial direction, and a gas inlet 8 that communicates the inside and the outside is formed at the center of the bottom that forms the ceiling. It is attached to the gas sensitive body 1 side of the base 2 so as to cover it. In order to ensure explosion-proof performance, for example, a stainless steel 100 mesh wire mesh 9 is double-fixed to the gas inlet 8 provided in the ceiling portion of the metal cap 6, and the outside (filter cap 7 The gas is introduced into the gas sensitive body 1 from the inner space of the gas sensor. The peripheral surface of the base 2 and the inner peripheral surface of the metal cap 6 are joined in a highly airtight manner, so that gas is introduced only through the gas inlet 8. The base 2 and the metal cap 6 constitute a storage container 23 that stores the gas sensitive body 1.

  The filter cap 7 is formed in a cylindrical shape from a synthetic resin, and the sensor main body B is fitted from the opening on one end side in the axial direction to the gas inlet 8 side as the head. The opening is closed. The filter cap 7 has an end face (ceiling) on the other end side, and a vent hole 10 is provided through the gas inlet 8 and the outside. Further, a notch 19 is formed in the opening edge on one end side of the filter cap 7 by recessing a part of the opening edge toward the ceiling, and the filter cap 7 has filter portions on both sides in the circumferential direction. Guide walls 20, 20 protrude from the peripheral surface of the cap 7 toward the outside in the radial direction.

  Further, for example, a stainless steel mesh 100 made of stainless steel is inserted into the filter cap 7 from the opening and fixed to the bottom (ceiling) of the filter cap 7 by a method such as adhesion, and then the granular shape is formed from the opening. An adsorbent (filter) 12 made of activated carbon was filled, and a pressing member 14 made of an annular synthetic resin molded product was inserted from the opening, and formed on the circumferential surface of the pressing member 14 along the circumferential direction. The pressing member 14 is fixed in the tube of the filter cap 7 by engaging the concave groove 15 and the protrusion 16 formed along the circumferential direction with the inner peripheral surface of the filter cap 7. For example, a stainless steel mesh 100 made of stainless steel is fixed to the upper surface of the pressing member 14 (the surface on the ceiling portion side of the filter cap 7) in advance, and when the pressing member 14 is inserted into the cylinder of the filter cap 7, The adsorbent 12 is held between the two metal meshes 11 and 13. Here, a filter for adsorbing an interfering gas such as hydrogen gas or alcohol vapor or a poisoning gas such as silicon vapor or water vapor from the layer of the adsorbent 12 is configured. The two metal meshes 11 and 13 are formed in a disk shape having a slightly smaller outer diameter than the diameter of the inner peripheral surface of the filter cap 7, and each mesh has a hole diameter smaller than the particle diameter of the adsorbent 12. It has become.

  A communication hole 17 is formed in the center of the pressing member 14 so as to pass through the pressing member 14 in the thickness direction and communicate between the gas inlet 8 and the vent hole 10 as shown in FIGS. 4 (a) and 4 (b). The gas flowing in from the vent hole 10 of the filter cap 7 is introduced into the gas inlet 8 of the metal cap 6 through the metal mesh 11 → the adsorbent 12 → the metal mesh 13 → the communication hole 17 of the pressing member 14. Yes. A plurality of concave grooves 18 having a depth of about 0.1 mm are radially formed on the lower surface of the pressing member 14 (the surface facing the metal cap 6). Each concave groove 18 extends from the outer peripheral surface side of the metal cap 6 toward the gas inlet 8 side, and a conductive path is formed between these concave grooves 18 to conduct gas between the opposing surface of the metal cap 6. The

  A method for manufacturing the gas sensor having the above configuration will be described below. First, after the three terminals 3 are formed simultaneously with the base 2 by insert molding, the coil-shaped heater combined electrode 4 and the center electrode 5 are attached to the tip of each terminal 3 by welding or brazing. Next, a tin oxide powder to which a catalyst such as Pd and Pt has been added is added to a paste by adding a solvent to electrodes 4 and 5, and both electrodes 4 and 5 are embedded in the ellipsoidal gas-sensitive gas. After the body 1 is formed and sintered at about 600 ° C., a silica-based binder is applied in order to increase the mechanical strength of the gas-sensitive body 1 and fired again at about 600 ° C. Then, the metal cap 6 is fitted on the upper surface side of the base 2 so as to cover the gas sensitive body 1, and is fixed to the base 2 by caulking the metal cap 6, and the assembly of the sensor body B is completed.

  Next, with the ceiling portion of the filter cap 7 facing downward, the wire mesh 11 is inserted into the filter cap 7, and the wire mesh 11 is adhered and fixed to the peripheral portion of the vent hole 10 provided in the ceiling portion of the filter cap 7. By doing so, the particulate adsorbent 12 is packed from the opening of the filter cap 7 after closing the vent hole 10. Next, the pressing member 14 having the metal mesh 13 fixed to one surface is press-fitted into the filter cap 7 with the metal mesh 13 facing downward, and the concave groove 15 of the pressing member 14 is formed on the inner peripheral surface of the filter cap 7. The pressing member 14 is fixed to the inside of the filter cap 7 by engaging the formed protrusion 16 with the concave and convex portions, and the wire mesh 11 fixed to the ceiling portion of the filter cap 7 and the wire mesh 13 fixed to the pressing member 14. The granular adsorbent 12 is held between the two. In this state, the sensor main body B is inserted from the opening of the filter cap 7 with the gas inlet 8 side as the head, and the sensor main body B is fixed to the filter cap 7 by a method such as press fitting or adhesion. Here, when the sensor main body B is inserted into the filter cap 7 until the ceiling surface of the metal cap 6 comes into contact with the pressing member 14, a space is formed between the bottom surface of the base 2 and the end of the filter cap 7 on the opening side. 21 is formed.

  Here, in the present embodiment, the inspection gas introduction path 22 is configured from a minute gap formed between the outer peripheral surface of the metal cap 6 and the inner peripheral surface of the filter cap 7. The size of the inspection gas introduction path 22 is as follows. Since it is determined by the dimensional tolerance of the outer peripheral surface of the metal cap 6 and the dimensional tolerance of the inner peripheral surface of the filter cap 7, the inspection gas introduction hole having a small hole diameter is provided in the peripheral surface of the filter cap 7 like a conventional gas sensor. Compared to the above, the gas introduction path can be easily formed. Moreover, the total length of the inspection gas introduction path 22 is substantially the same as the height dimension of the sensor body B (the distance from the bottom surface of the base 2 to the ceiling surface of the metal cap 6), and is sufficiently long. It is possible to increase the performance compared to the conventional one. Therefore, compared with the gas sensor having the structure shown in FIG. 7, the interference gas and poison gas flowing from the gas introduction path by natural diffusion are reduced, the detection error due to the interference gas is increased, and the long-term stability of the sensor characteristics due to the poison gas is deteriorated. Can be suppressed.

  By the way, the gas sensor A of this embodiment is used for a gas leak alarm for home use, for example, and as shown in FIG. 1, the gas sensor A is mounted on the circuit board 41 accommodated in the casing 40 of the alarm. The housing 40 of the alarm device is composed of a box-shaped case 40a with a part of the front surface opened, and a cover 40b that closes the opening of the case 40a. Inside the case 40a is a circuit board made of a printed wiring board. 41 is stored. The circuit board 41 is formed with an alarm circuit that issues an alarm based on the sensor output of the gas sensor A, and the gas sensor A is mounted at a position facing the opening of the case 40a. The cover 40b is provided with a plurality of ventilation windows 42 in which the gas flow path is bent in a square shape. Outside air that has flowed into the housing 40 through the ventilation windows 42 passes through the ventilation holes 10 of the gas sensor A. The gas 12 reaches the gas sensitive body 1 through the gas inlet 8 and the electric resistance of the gas sensitive body 1 changes according to the gas concentration of the detection target gas contained in the outside air.

  The cover 40b on the front surface of the housing 40 is provided with an inspection hole 43 for injecting and injecting inspection gas, and the inspection gas injected and injected from the inspection hole 43 passes through the gas passage 45 inside the housing 40 and is filtered. It is guided to the bottom side of the cap 7, that is, to the opening side of the filter cap 7. The gas sensor A is arranged such that a notch 19 formed on the peripheral surface on the opening side of the filter cap 7 faces the outlet of the gas flow path 45, and the inspection gas that has passed through the gas flow path 45 enters the notch 19. be introduced. At this time, the inspection gas guided to the notch 19 through the gas passage 45 flows from the front into the notch 19 (the flow of the inspection gas is indicated by arrows in FIGS. 2C and 5). Then, it flows into a space 21 surrounded by the filter cap 7, the base 2 bottom surface, and the substrate 41, and is temporarily stored in the space 21. Further, guide walls 20, 20 project from the circumferential surface of the filter cap 7 toward the outer side in the radial direction from both sides in the circumferential direction with respect to the notch 19. A part of the inspection gas flowing out to the right in FIG. 2C hits the guide walls 20, 20, is deflected and collected in the notch 19, and flows into the space 21 through the notch 19. The inspection gas once accumulated in the space 21 passes through a gap (inspection gas introduction path 22) formed between the outer peripheral surface of the metal cap 6 and the inner peripheral surface of the filter cap 7, and the upper side in FIG. (The path through which the inspection gas flows is indicated by an arrow in FIG. 1. Actually, the gap 22 is a minute interval having an annular cross section, but this is emphasized and shown in the figure). Since it hits the lower surface of the member 14 (the surface facing the metal cap 6) and is guided to the gas inlet 8 of the metal cap 6 through the recessed groove 18 formed in the lower surface of the pressing member 14, It flows into the metal cap 6 through the attached wire mesh 9. Therefore, since the inspection gas is introduced to the gas sensitive body 1 by passing through the inspection gas introduction path 22 without passing through the adsorbent 12, the inspection gas is not adsorbed by the adsorbent, The operation check with the inspection gas can be surely performed.

  As described above, in this embodiment, the notch 19 is formed in the peripheral surface on the opening side of the filter cap 7, and the guide wall that guides the inspection gas to the notch 19 from the peripheral surface around the notch 19 toward the outside in the radial direction. 20, the inspection gas flowing along the surface of the substrate 41 is collected in the notch 19 by the guide wall 20 formed around the notch 19, and enters the inside of the filter cap 7 through the notch 19. Since the inspection gas can be caused to flow into the inspection gas introduction path 22, useless inspection gas that does not flow into the inspection gas introduction path 22 but diffuses can be reduced, and the inspection work can be reliably performed even with a small amount of inspection gas. Further, since the bottom surface of the storage container 23 (that is, the bottom surface of the base 2) is recessed inward from the opening edge of the filter cap 7, the substrate 41 on which the gas sensor A is mounted, the bottom surface of the base 2, and the peripheral surface of the filter cap 7 are provided. A check gas introduction path 22 between the inner peripheral surface of the filter cap 7 and the outer peripheral surface of the metal cap 6 is temporarily stored after the check gas flowing into the space 21 through the notch 19 is temporarily stored. Since the flow rate that can pass through the inspection gas introduction path 22 is small, the inspection gas that escapes outside before flowing into the inspection gas introduction path 22 can be reduced, and the inlet of the inspection gas introduction path 22 can be reduced. The inspection gas that has arrived can be reliably introduced into the inspection gas introduction path 22 without escaping. Furthermore, the distance from the opening edge of the filter cap 7 to the bottom surface of the storage container 23 (that is, the bottom surface of the base 2) is shorter than the depth of the notch 19 (length dimension along the axial direction). A part of the storage container 23 can face the notch 19, and the gas flowing into the filter cap 7 from the notch 19 hits the outer peripheral surface of the storage container 23, thereby changing the gas flow. It becomes easy to flow into the inspection gas introduction path 22 between the inner peripheral surface of the filter cap 7 and the filter cap 7. Further, even if the position of the gas flow path 45 formed in the housing 40 and the notch 19 formed in the peripheral surface of the filter cap 7 are slightly shifted due to dimensional variations in manufacturing the housing 40, the guide walls 20 and 20 Thus, the inspection gas deviated from the notch 19 can be collected in the notch 19, so that the amount of inspection gas introduced into the notch 19 can be increased and the inspection work can be performed reliably.

In this embodiment, a gas sensor that detects flammable gas such as methane or carbon monoxide is described as an example. However, the detection target gas is not limited to the above gas, but H ₂ or the like. Needless to say, the gas sensor may be a detection target.

  In the present embodiment, the gas sensitive body made of a metal oxide semiconductor has been described as an example, but the gas sensitive body is not intended to limit the gas sensitive body to a metal oxide semiconductor. Needless to say, an electrochemical sensor may be used.

(Embodiment 2)
An embodiment of a gas detection apparatus using the gas sensor described in Embodiment 1 will be described with reference to FIG. This gas detection device detects the gas concentration of a detection target gas (for example, flammable gas such as methane gas or propane gas, or carbon monoxide) using the gas sensor A, and issues a notification when the detected concentration exceeds a predetermined threshold value. The gas alarm device detects the gas concentration of the gas to be detected from the voltage value between the gas sensor A and the electrodes 4 and 5 of the gas sensor A, that is, the electric resistance of the gas sensor 1, and the detected concentration is predetermined. A detection circuit 50 that outputs a notification signal when the threshold value is exceeded, and an output circuit 51 that issues a warning by sound or light when the notification signal is input from the detection circuit 50 and outputs a notification signal to an external device. I have.

  This gas detection device B stores a circuit board (not shown) on which circuit components constituting the gas sensor A and the detection circuit 50 and the output circuit 51 are mounted in a container (not shown). The operation of the gas sensor A, the detection circuit 50, and the output circuit 51 is inspected by injecting inspection gas into the body from the inspection hole provided in the body. The gas sensor A is the same as that described in the first embodiment. Therefore, even with a small amount of inspection gas, it is possible to reliably check the operation with the inspection gas.

  In addition, although this embodiment demonstrated the form which applied the gas sensor A demonstrated in Embodiment 1 to the gas alarm device, it is not the thing of the meaning which limits a gas detection apparatus to a gas alarm device, The detection result of gas sensor A Needless to say, the gas sensor A of the first embodiment may be applied to an air purifier or the like that controls the air purifying ability based on the above.

It is sectional drawing which showed typically the state which mounted the gas sensor of this embodiment in the housing | casing of the gas leak alarm device. The same as above, (a) is a partially broken front view, (b) is a side view seen from the left side, and (c) is a bottom view. It is a top view which can be partially broken same as the above. The spacer used for the above is shown, (a) is a front view, (b) is a side view partially broken. It is explanatory drawing explaining the flow of inspection gas same as the above. It is a block diagram of the gas detection apparatus using the same as the above. It is sectional drawing which showed the structure of the conventional gas sensor typically. It is sectional drawing which showed typically the state accommodated in the housing | casing of the gas leak alarm device same as the above.

Explanation of symbols

A Gas sensor 1 Gas sensitive body 7 Filter cap 8 Gas inlet 10 Vent 12 Adsorbent 19 Notch 20 Guide wall 22 Gap 23 Storage container

Claims (4)

A gas sensitive body for converting the gas concentration of the detection target gas into an electrical signal;
A plurality of detection electrodes embedded and fixed in the gas sensitive body;
The gas sensitive body is housed therein, a gas inlet is formed on one end side in the axial direction, and a terminal electrically connected to each detection electrode projects from the other end side in the axial direction A storage container;
The storage container is fitted into the inside from the gas inlet side so as to close the opening on one end side in the axial direction, and a vent hole is formed on the other end side to communicate the gas inlet with the outside. A cylindrical cover,
A filter that is provided in a gas flow path between the vent and the gas inflow port and that adsorbs interference gas and poison gas,
In the gas sensor provided with the inspection gas introduction path for introducing the inspection gas to the gas inlet through a minute gap formed between the inner peripheral surface of the cover and the outer peripheral surface of the storage container from the opening of the cover,
A gas sensor, wherein a notch is formed in a peripheral surface on the opening side of the cover, and a guide wall that guides inspection gas to the notch from a peripheral surface around the notch toward a radially outer side is provided.   The gas sensor according to claim 1, wherein a bottom surface of the storage container is recessed inward from an opening edge of the cover.   The gas sensor according to claim 1 or 2, wherein a distance from an opening edge of the cover to a bottom surface of the storage container is a distance shorter than a depth of the notch.   A gas detection apparatus comprising: the gas sensor according to claim 1; and a detection circuit unit that detects a gas concentration of a detection target gas from an output signal of the gas sensor.

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