JP3568060B2 - Gas sensor - Google Patents

Description

[0001]
Field of application of the invention
The present invention relates to a gas sensor for detecting gases such as CO, methane, hydrogen, and water vapor, and more particularly to a filter for removing interfering gases such as alcohol. In this specification, gas is treated as containing water vapor.
[0002]
[Prior art]
In the field of a metal oxide semiconductor gas sensor, a solid electrolyte gas sensor such as a Na ion conductor, a proton conductor, or ZrO2, or a contact combustion type gas sensor in which a coil such as Pt is embedded in a contact combustion catalyst, a filter is provided on the cap of the gas sensor. It is known to remove unnecessary gases. As the filter, for example, activated carbon (JP-A-6-160323), zeolite (JP-A-6-186198), silica gel, activated clay and the like are used. The function of the filter is to select the type of filter according to the gas to be detected by absorbing or absorbing unnecessary gases such as ethanol, NOx, and ammonia.
[0003]
Almost no study has been made on the setting of a filter on a cap. For example, in the above-mentioned JP-A-6-160323 and JP-A-6-186198, a filter is arranged at the tip of a cap, and the filter is sandwiched between two wire meshes to form a cap. It only suggests fixing. However, attaching the wire mesh to the cap is cumbersome. The wire mesh on the distal end side may be fixed to the cap by welding or an adhesive, but the wire mesh on the base end side (gas sensor main body side) is inside the cap, and it is difficult to weld it to the cap. Similarly, it is difficult to fix the wire mesh to the cap with an adhesive. Unless the base wire mesh is fixed to the cap, the filter cannot be held by the cap.
[0004]
[Problems of the Invention]
An object of the present invention is to provide a structure that can easily hold a wire mesh on the base end side of a filter to a cap (claims 1 to 3).
[0005]
Configuration of the Invention
The gas sensor according to the present invention has a gas sensor main body whose electric output changes by contact with a gas mounted on a cap having a filter at the tip and an opening at the other end, and a pair of wire nets 20, which sandwich the filter 18. 22 is provided, a ring 24 is provided below the wire mesh 22 on the base end side, and the ring 24 is disposed at a depth of an inward projection 26 provided on the cap 16, and the ring 24 is held by the projection 26. And
[0006]
The ring may be a simple ring, but preferably the ring 24 is provided with a notch 28. By doing so, when the ring 24 is pushed into the depth of the projection 26, the notch 28 deforms the ring 24 and facilitates pushing the ring 24. Moreover, after being pushed in, the ring 24 tends to return to its original shape due to its spring property, and the projection 26 can securely hold the ring 24.
[0007]
The cap 26 may be made of metal or synthetic resin, but if made of metal, the projection 26 can be easily provided. The protrusions 26 may be provided on the entire circumference of the cap in the circumferential direction. However, if a plurality of protrusions 26 are arranged at the same height along the circumferential direction, resistance when pushing the ring 24 is small, It becomes easy to push.
[0008]
The filter used is one that absorbs or absorbs unnecessary gas such as activated carbon, silica gel, zeolite, activated clay, polyethylene glycol, etc., and removes it. Solid or liquid, but in the case of liquid, carrier such as activated clay or silica gel To be used. The shape of the filter may be granular, sheet-like (for example, when using activated carbon fiber), disk-like, or the like.
[0009]
Effect of the Invention
In the present invention, the filter 18 is set on the cap 16, and the wire mesh 22 and the ring 24 on the proximal end side are pushed into the projection 26. Then, the ring 24 is inserted into and held by the projection 26, and the ring 24 presses the wire mesh 22 on the proximal end side, and the filter 18 is pressed by the wire mesh 22, so that the filter 18 can be easily set.
[0010]
【Example】
1 to 4 show an embodiment. In these figures, reference numeral 2 denotes a gas sensor, which may be a sensor for detecting so-called gas such as CO, methane or hydrogen, or a sensor for detecting water vapor. 4 is a base made of, for example, a synthetic resin, 6 is, for example, four stems embedded in the base 4, and 8 is a gas sensor main body. In the gas sensor main body 8 of the embodiment, a metal oxide semiconductor 10 and a film-shaped heater 12 are provided on a heat-resistant insulating substrate, and an electrode connected to the heater 12 is provided on a surface on the metal oxide semiconductor film 10 side through an end surface of the substrate. It is assumed that four pads are drawn out and provided on the upper surface of the substrate, and a lead wire 14 is connected to each pad and connected to the stem 6. ZrO2, a proton conductor, a Na ion conductor, or the like may be used in place of the metal oxide semiconductor, and the structure of the main body 8 is arbitrary. For example, a Pt coil is embedded in a catalytic combustion catalyst, and the combustible catalyst is used. A contact combustion type gas sensor that detects the combustion heat of the reactive gas from the coil resistance temperature count may be used.
[0011]
Reference numeral 16 denotes a cap, which may be made of synthetic resin, but is made of metal here, preferably cylindrical, and has a shape with a bottom at the tip. In the embodiment, the main body 8 side with respect to the cap 16 is the base end side, and the opposite side is the distal end side. Reference numeral 18 denotes a filter, for example, activated carbon, silica gel, zeolite, activated clay, or a material carrying a gas-absorbing solvent such as polyethylene glycol, and has a granular, disk-like, or sheet-like shape. In the case of a disk shape, the particles of the filter are formed into a disk shape with an adhesive or the like. For example, a rectangular opening 17 is provided at the tip of the cap 16, and wire meshes 20 and 22 of 100 mesh or 200 mesh are provided so as to sandwich the filter 18, and a ring 24 is provided below the wire mesh 22 on the base end side. The wire mesh 20 on the tip side is fixed to the inner surface of the tip of the cap 16 by, for example, welding or an adhesive. The wire net 20 may be simply placed between the filter 18 and the opening 17 without being fixed to the back surface of the tip of the cap 16. When welding, for example, the wire mesh 20 may be set on the back surface of the tip of the cap 16 and the tip of the welding electrode may be set on the wire mesh 20 for welding.
[0012]
Reference numeral 26 denotes a plurality of inward protrusions provided on the cap 16, as shown in FIG. 4, a plurality of protrusions at the same height along the circumferential direction of the cap 16, four in the embodiment, and preferably three to six. , Provided separately. After forming the general shape of the cap 16 by, for example, drawing a metal plate, the side surface of the cap 16 is pushed inward using a jig to form the projection 26. The projection 26 may be an annular projection continuous in the circumferential direction as shown by a chain line in FIG. 4, but such a projection requires a more complicated jig than the projection 26 of the embodiment, and a ring. The resistance when pushing in 24 is large, and the protrusion 26 of the embodiment is more preferable. Since the projections 26 can be easily made of metal, the cap 16 is preferably made of metal. On the other hand, in the case of a synthetic resin, the processing for forming the projection 26 is complicated. For example, in the case of a cap made of a synthetic resin, a jig composed of four pins is heated to abut against the cap 16 to form a projection 26. On the other hand, in the case of the metal cap 16, it is sufficient to simply push in four pins.
[0013]
The ring 24 may be made of metal or synthetic resin such as rubber, and is preferably an elastic ring so that it can be easily pushed into the projection 26 and does not come off easily after being pushed. In the case of metal, an elastic material such as phosphor bronze is preferable. In the embodiment, a notch 28 is provided in the ring 24 as shown in FIG. 3 to form a washer. Therefore, when the ring 24 is pushed, the ring 24 is deformed and passes through the projection 26. Once the ring 24 is pushed, the ring 24 does not come off from the projection 26 in an attempt to return to its original shape due to elasticity.
[0014]
Explaining the assembly of the gas sensor 2 according to the embodiment, the main body 8 is welded to the stem 6 fixed to the base 4 in advance. The cap 16 is formed by drawing or the like, and a jig is pushed in from the side to form the projection 26. Next, the wire net 20 on the tip side is set and fixed to the back surface of the tip of the cap 16 by, for example, welding. The wire net 20 may not be fixed to the cap 16 but may be simply arranged on the back surface of the tip of the cap 16. Next, the filter 18 is set, the wire net 22 on the base end side is set, and the ring 24 is pushed in. Then, the ring 24 is slightly deformed, passes through the protrusion 26, and goes into the back, and is held by the protrusion 26 in an attempt to return to the original shape by elasticity. As a result, the wire mesh 22 on the proximal end side is fixed by the ring 24, so that the filter 18 can be prevented from falling off. The wire net 22 and the ring 24 may be set in advance on the cap 16 after being integrated by welding or the like in advance.
[0015]
【The invention's effect】
According to the first aspect of the present invention, after the filter 18 is set, the filter 18 can be mounted on the cap 16 simply by pushing the wire mesh 22 and the ring 24 on the base end side into the projection 26. In addition, in the invention of claim 2, in addition to this, the ring 24 is deformed at the notch portion 28 to facilitate the mounting of the ring 24, and after the mounting, the ring 24 does not come off from the projection 26 due to the spring property of the ring 24. According to the third aspect of the present invention, since the cap is a metal cylindrical cap, the projections 26 can be easily provided, and since the plurality of projections 26 are independently provided, the ring 24 can be easily pushed in.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a gas sensor according to an embodiment. FIG. 2 is a plan view of a cap according to the embodiment. FIG. 3 is a plan view of a ring according to the embodiment. FIG. 4 is a perspective view of the cap according to the embodiment.
2 Gas Sensor 16 Cap 4 Base 17 Opening 6 Stem 18 Filter 8 Gas Sensor Body 20, 22 Wire Mesh 10 Metal Oxide Semiconductor Film 24 Ring 12 Heater 26 Projection 14 Lead Wire 28 Notch

Claims (3)

In a gas sensor attached to a gas sensor body whose electrical output changes by contact with gas, a cap provided with a filter at the tip and an opening at the other end,
A pair of wire meshes (20) and (22) sandwiching the filter (18) is provided, a ring (24) is provided below the wire mesh (22) on the proximal end side, and an inward projection ( 26. A gas sensor, wherein a ring (24) is arranged at the back of (26), and the ring (24) is held by a projection (26). 2. The gas sensor according to claim 1, wherein a notch is provided in the ring. The gas sensor according to claim 1, wherein the cap (16) is a metal cap having a cylindrical cross section, and a plurality of protrusions (26) are provided at the same height along the circumferential direction of the cap (16). .

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