JP5268753B2 - Method for manufacturing element constituting gas detection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing the element used in a gas detector wherein a lump having a homogenous surface shape is fixed to a heater. <P>SOLUTION: The method for manufacturing the element used in the gas detector includes: the step of forming a liquid particle 3 by dripping a solution, which is prepared by mixing powder composed of a material constituting a lumpy matter with a liquid, on a platelike member 2 of which the surface has water repellency; the step of immersing the coil part 1a of the heater 1, which has the coil part 1a provided to the central part thereof, in the liquid particle 3; the step of drawing up the coil part 1a of the heater 1 from the platelike member 2 in a state that the liquid particle 3 is adhered to the coil part 1a of the heater 1; the step of volatilizing the liquid component of the liquid particle of the coil part 1a to form a powder lump to the coil part 1a; and the step of baking the lump. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a method of manufacturing each element constituting a gas detection device in combination with a sensing element sensitive to gas and a compensation element for correcting an environmental temperature.

The gas detection device is configured to measure a gas concentration by detecting a resistance change of the detection element while correcting a change in environmental temperature by combining the detection element and the compensation element by a bridge connection or the like.
As a method for producing such an element, an aqueous inorganic binder and pure water are mixed with activated alumina powder to form a paste, which is applied around a platinum coil and then heated to 500 to 800 ° C. to form a carrier as a coil. Although it is generally fixed, it is difficult to precisely control the size of the sensor element, resulting in a decrease in manufacturing yield. As a result, there is a problem that variations in characteristics such as the sensor temperature (the zero point of the bridge output of the sensor) are affected by the heat capacity, the surface area (the magnitude of heat release), and the like.

  In order to solve such a problem, as shown in Patent Document 1, the manufacture of a sensing element including a step of pre-installing a platinum coil in a container having a spherical concave surface and then injecting a paste-like material into a spherical shape A method has been proposed.

  However, because the paste-like lump is pressed against the heater and formed, the lump shape to be formed on the heater is hemispherical in cross-sectional shape with respect to the heater, and the surface of the lump has different shapes of a flat portion and a spherical portion. There exists a problem that it exists and it is easy to produce a big variation in surface temperature.

JP-A-11-132984

  The present invention has been made in view of such problems, and an object of the present invention is to propose a method for manufacturing an element for a gas detection device capable of forming a mass having a uniform surface shape on a heater.

  In order to achieve such a problem, in the present invention, a step of forming a liquid particle by dropping a solution obtained by mixing a powder made of a material constituting a lump into a liquid onto a plate-like body having a water-repellent surface. And a step of immersing the coil portion of the heater having a coil portion in the center portion in the liquid particle, a step of pulling up the plate body with the liquid particle attached to the coil portion of the heater, and the coil And a step of volatilizing the liquid part of the liquid part to form a lump of the powder in the coil part, and a step of firing the lump.

  According to the present invention, a lump having a uniform surface shape and a constant volume can be easily formed in the heater.

Drawing (a)-(c) is a figure explaining one example of the manufacturing method of the present invention, respectively. Figures (a) and (b) are diagrams for explaining another embodiment of the production method of the present invention.

An aqueous solution is prepared by dispersing a powder as a base material, for example, an activated alumina powder having electrical insulation, and an oxidation catalyst powder as a catalyst for oxidizing a combustible gas, such as platinum black powder, in water. .
On the other hand, a heater 1 is prepared in which a platinum wire is formed in a required shape, for example, a coil portion 1a at the center and linear portions 1b and 1b at both ends.

  Next, a plate-like body 2 whose surface is subjected to hydrophobic treatment is prepared, and a predetermined amount, that is, a prescribed amount of solution that is about one liquid droplet is dropped onto the surface of the plate-like body 2 to form a liquid particle 3 Let

  The coil portion 1a of the heater 1 is pressed against the liquid droplet 3 of the plate-like body so that the coil portion 1a is buried in the liquid particle, and the coil portion 1a is sufficiently adapted to the solution.

  Next, when the heater 1 has the straight portions 1b and 1b and is lifted away from the plate-like body, it is released from the plate-like body 2 with the liquid particles 3 attached to the coil portion 1a. When minute vibration is applied to the heater 1 at the time of pulling up, the liquid particles 3 smoothly move toward the coil portion 1a and securely enclose the coil portion 1a.

  Naturally, the hydrophilicity of the coil part 1a is higher than that of the plate-like body 2, so that the liquid becomes spherical due to surface tension and becomes liquid droplets 3 'so as to wrap around the coil part 1a.

  When the moisture in the liquid droplet 3 'is volatilized in this state, the mixture of activated alumina and platinum black in the liquid particle becomes a mass having a circular cross section so as to wrap around the coil portion 1a.

  Preferably, when the straight portion 1b at both ends of the heater 1 is kept horizontal and is rotated around a center line of the coil portion 1a at a speed at which excessive centrifugal force does not act on the liquid particles, The powder composing the catalyst is uniformly hardened so as to center on the coil portion.

  Finally, when this lump is fired together with the heater 1 at a temperature suitable for firing, a lump having a circular cross section containing the oxidation catalyst in the coil part 1a, that is, the sensitive part is completed.

  In the above-described embodiment, liquid droplets are formed on the surface of the plate-like body. However, as shown in FIG. 2, a predetermined volume, that is, a volume that can cover the coil portion 1a of the heater 1 is provided. The recess 2a is formed in the plate-like body 2, and at least the surface of the recess 2a is water-repellent processed.

  When a prescribed amount of the above-described solution is dropped into the recess 2a, the coil portion 1a of the heater 1 is immersed in the recess 2a, and the coil is pulled up in a sufficiently familiar state, the solution adhering to the coil portion 1a To adhere to the coil portion 1a in a spherical shape.

Further, in the above-described embodiment, the gas detection element that detects the resistance change accompanying the temperature rise of the heater 1 by oxidizing the combustible gas by the oxidation catalyst by the oxidation catalyst contained in the powder has been described, but the combustible gas has been described. Needless to say, the present invention can also be applied to the manufacture of a compensation element for detecting the ambient temperature as the resistance of the heater regardless of the presence or absence of the above.
That is, it is only necessary to prepare an aqueous solution by dispersing powder that does not have an oxidation catalytic action for the flammable gas in water and firing this aqueous solution on the coil portion 1a of the heater 1 by the above-described steps.

  Thereby, the compensation element having the same shape as the element that reacts with the combustible gas can be easily manufactured.

1 Heater 1a Coil part 2 Plate body 3 Liquid particle

Claims (5)

A step of dropping a solution obtained by mixing a powder made of a material constituting a lump into a liquid onto a plate-like body having a water-repellent surface to form a liquid particle, and the coil portion of the heater having a coil portion at the center portion A step of immersing the liquid particles in the liquid particles, a step of pulling up the liquid particles from the plate in a state in which the liquid particles are attached to the coil portions of the heater, and volatilizing the liquid particles in the coil portions. Forming a lump of the powder, and baking the lump,
A manufacturing method of an element constituting a gas detection device comprising: 2. The method of manufacturing an element constituting the gas detection device according to claim 1, wherein the powder is composed of a mixture of a powder of a material having electrical insulation and a powder of an oxidation catalyst for combustible gas. 2. The method for manufacturing an element constituting the gas detection device according to claim 1, wherein the powder is made of powder of a material having electrical insulation. 2. The step of volatilizing a liquid component of the coil part to form a lump made of powder as a base material in the coil part, wherein the coil part is rotated around the coil part. 4. A method of manufacturing an element constituting the gas detection device according to claim 3. 4. The method for manufacturing an element constituting the gas detection device according to claim 1, wherein a recess having a predetermined volume whose surface is water repellent is formed in the plate-like body.

Images