JPS61167850A - Apparatus for producing gas sensor - Google Patents

Abstract

PURPOSE:To stick a carrier or carrier with a catalyst only to the limited part of a hot filament by discharging a slurry from a syringe-shaped aperture provided to an electrophoretic vessel, inserting the hot filament into the outflow slurry and effecting electrophoresis. CONSTITUTION:The slurry 7 dispersed therein with the carrier or the carrier with the catalyst is poured into the electrophoretic vessel 1 until an electrode 5 is immersed into the slurry. A liquid drop 8 of the slurry is formed to the aperture 2 at the bottom end of the vessel 1 or the slurry is continuously run down by the aperture 2. The outflow rate of the slurry from the aperture 2 is adjusted by a needle valve 4. The part to be coated of the coiled hot filament 10 fixed onto a U-shaped jig 9 made of a metal is inserted into the formed liquid drop 8 or the continuously flowing-out slurry and the jig 9 is connected to a DC power source 6 to transfer the dispersion particles in the slurry 7 toward the filament 10 by which the carrier or the carrier with the catalyst is stuck to the required point of the hot filament.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an apparatus for manufacturing a gas detection element and a temperature compensation element used in a catalytic combustion type gas sensor.

(Prior Art) As shown in FIG. 3, a gas detection element used in a catalytic combustion type gas sensor is made of a hot wire 10 made of a coiled wire made of a material with a high temperature coefficient of resistance such as platinum, and a carrier such as activated alumina. 12, and a catalyst with excellent oxidation performance against combustible gases is adhered to the carrier 12, and the temperature compensating element is inert to combustible gases. It has the same shape as the sensing element. As shown in FIG. 4, the actual sensor is constructed by forming a bridge with resistors 15 and 16 so that the gas detection element 13 and the temperature compensation element 14 are located in adjacent branches.
7, the connection point of pixel element 13.14 and resistor 15.1
It is constructed by connecting the output detection section 18 between the connection point No. 6 and the connection point No. 6.

The gas detection element and the temperature compensation element are usually manufactured by a method in which a carrier is attached to a hot wire and then a suitable heat treatment is performed to fix the carrier to the hot wire. Furthermore, for gas detection elements, a method is usually used in which a carrier is fixed and then an appropriate catalyst is supported on it. A method of attaching it to the strips may also be used.

As one of the methods of coating hot filaments with a carrier, Japanese Patent Application Laid-Open No. 1973-
There is a method using electrophoresis as described in Japanese Patent No. 83890. Figure 5 shows a general method for forming a coating layer on a hot wire using this electrophoresis method, in which an electrode 5 made of platinum or the like is placed on one side in a slurry 7 in which carrier powder such as activated alumina is dispersed. , the hot filament 10 on which the carrier is to be attached is immersed, the electrode 5 and the hot filament 10 are connected to the 6 poles of the DC power source 6, and a potential with the opposite sign to the charge on the carrier powder in the dispersion medium is applied. By applying heat to the hot streak 10
A carrier is attached to the surface of the carrier. This method has the advantage of being able to control the amount of carrier deposited by the voltage value, voltage application time, etc., making it easy to align the size of the elements, reducing the variation in sensor performance S, and being excellent in mass production. There is. However, although this method of forming elements by electrophoresis has the advantages listed in item L, it also has problems with manufacturing technology as described below.

That is, when the apparatus shown in FIG. 5 is used as it is, the carrier will adhere to all parts of the hot wire that are immersed in the dispersion medium. However, in actual centimeters, both ends of the hot wire need to be connected to conductive terminal rods, so
This part must not be covered with an electrically insulating carrier.

Furthermore, the commonly used hot wire has a coiled shape as shown in FIG. 3, and it is desirable to attach the carrier only to this coiled portion. For this reason, the fifth
When attaching the carrier to the hot wire using the device shown in the figure,
Either remove the carrier attached to unnecessary parts of the hot filament by some method, or cover the part of the hot filament where you do not want the carrier to be attached with an electrically insulating resin film, and then attach the carrier by electrophoresis. Then, operations such as burning and removing the insulating film by heating at a high temperature are required. Therefore, these methods are unfavorable in terms of mass production because they increase the number of work steps such as removing the carrier once attached and coating the insulating film.

In addition, in the above-mentioned Japanese Patent Application Laid-Open No. 48-83890, a coating layer is formed on the surface of the hot filament by electrophoresis, but there is no specific method for coating only the four essential parts of the hot filament. is not listed.

[Problem that the invention seeks to solve]

The problem to be solved by the present invention is that when manufacturing the gas detection element and temperature compensation element of a catalytic combustion type gas sensor by electrophoresis, the carrier or the carrier with catalyst is attached only to a limited part of the hot wire. The goal is to obtain equipment that can.

[Failure to solve the problem]

According to the present invention, the above-mentioned problems can be solved by (1) in a device for manufacturing a catalytic combustion gas sensor comprising a gas sensing element and a temperature compensating element in which the surface of a hot wire is coated with a carrier or a carrier with a catalyst by electrophoresis; Means for flowing out the slurry in which coated particles are dispersed through a dropper-shaped opening provided in the electrophoresis tank (2) Means for inserting the portion of the hot filament to be coated into the flowing slurry (3) The hot filament and the inside of the electrophoresis bath This problem is solved by having means for applying a DC voltage between the electrodes.

As a means for draining the slurry when installing the present invention, it is preferable to let the slurry fall naturally from a dropper-shaped opening. In this case, the falling speed is adjusted by the amount of outside air introduced at the end of the electrophoresis tank. The slurry can be controlled by the degree of opening of the needle pulp, but in addition to this natural falling method, it is also possible to adopt a method in which the slurry is forced to flow out using a pump or the like.

Further, the shape of the slurry flowing out depends on the flow rate and the cross-sectional shape of the dropper-like opening, but shapes such as a droplet shape, a cylindrical shape, and a band shape can be used.

[Effect]

In the present invention, by forming a dropper-like narrow opening in a part of the electrophoresis tank charged with slurry, the amount of slurry flowing out from the opening is restricted, and the slurry is applied only to a limited part of the hot wire. By applying a voltage while the two are in contact with each other, the carrier or the carrier with catalyst can be attached only to the necessary portions of the hot wire.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

In FIG. 1, reference numeral 1 denotes an electrophoresis tank, which is equipped with a thin dropper-like opening 2 at the lower end, and a slurry inlet 3 and needle pulp 4 at the upper end. An electrode 5 is disposed within the electrophoresis tank 1, and the electrode 5 is connected to one pole of a DC power source 6.

In preparation, first, a slurry 7 in which a carrier or a carrier powder with a catalyst is dispersed is injected into the electrophoresis tank l through the slurry inlet 3 until the electrode 5 is submerged in the slurry. Next, droplets 8 of the slurry are formed in the opening 2 at the lower end of the electrophoresis tank 1, or the slurry is allowed to flow down continuously from the opening 2.

In this case, the flow rate of the slurry from the opening 2 can be adjusted by the opening degree of the needle pulp 4.

Next, the part to be coated of the coiled hot wire lO fixed on a metal U-shaped jig 9 is inserted into the formed droplets 8 or the continuously flowing slurry fluid, and Ingredients 9
By connecting to the DC power supply 6, the dispersed particles in the slurry 7 are moved toward the hot wires 10, and the carrier or the carrier with a catalyst is attached to the desired location of the hot wires.

Note that during the adhesion operation by electrophoresis, it is possible to stop the outflow of the droplet and keep it stationary; however, by placing a hot wire inside the droplet that has not yet separated from the opening, All four songs are possible with droplets falling intermittently.

Example 1 Using the apparatus shown in FIG. 1, a slurry consisting of activated alumina fine powder, alumina sol, and water is injected from the slurry inlet 3, the inlet 3 is closed, and the needle pulp 4 is operated to fill the lower end of the opening 2. formed droplets. On the other hand, the wire diameter is 30s
Both ends of a hot wire made of platinum wire with a coil outer diameter of 0.8 fins and a number of turns of 10 are welded to a U-shaped nickel jig 1.
The coil part of the hot wire was set in a position inside the droplet.

In this state, a direct current voltage was applied using the hot wire as a cathode and the electrode as an anode, thereby causing carrier particles to adhere to the coil portion of the hot wire. Next, this hot wire was removed from the jig and heated to 800°C in an electric furnace.
was heated to fix the attached carrier particles to the hot wire. The thus obtained element had a cylindrical shape in which only a predetermined position of the coil portion 11 of the hot wire was covered with a carrier 12, as shown in FIG.

Example 2 Using the installation shown in FIG. 1 and using the same slurry as in Example 1, the opening degree of the needle pulp 4 was fully adjusted to form the opening 2.
The falling speed of the droplets was set to about 1 droplet every 5 seconds. Next, prepare the same jig and hot wire as in Example 1, install the coil part of the hot wire inside the droplet at a position that has not yet separated from the opening, and attach the coil in the same manner as in Example 1. As a result of attaching a carrier to the portion and performing the same heat treatment as in Example 1, an element having a shape similar to that shown in FIG. 2 was obtained.

Example 3 Using the apparatus shown in FIG. 1 and using the same slurry as in Example 1, the degree of opening of the needle pulp 4 was adjusted so that the slurry continuously flowed down from the opening 2. Next, prepare the same jig and hot wire as in Example 1, set the hot wire so that the coil portion of the hot wire is located inside the cylindrical slurry formed near the opening, and prepare the coil in the same manner as in Example 1. A carrier was attached to the part. Note that during this operation, electrophoresis tank 1
The amount of slurry charged and the rate of slurry flow were adjusted so that the electrode 5 inside was located inside the slurry during one deposition operation. The shape of the element to which the carrier was attached by continuously flowing the slurry in two C streams was also the same as that shown in FIG. 2.

The area covered by the hot filament is determined by the size of the droplet or the continuously flowing fluid, but for example, when the inner diameter of the opening is 0.5 mm, The length of the section is approximately 1.51 m.

〔Effect of the invention〕

The apparatus of the present invention, when manufacturing gas detection elements and temperature compensation elements used in catalytic combustion type gas centimeters, collects slurry in the form of droplets through a dropper-shaped opening provided in an electrophoresis tank.
The device has a means for flowing out the slurry in a columnar or band shape, and a hot wire is inserted into the inside of the slurry to perform electrophoresis. Alternatively, by adjusting the size of the band-shaped slurry, the area of the hot filaments covered with the carrier can be limited to a predetermined range.

Furthermore, according to the apparatus of the present invention, the inherent features of the electrophoresis method, such as less variation in element shape and excellent mass productivity, can be effectively utilized, and the performance and mass productivity of catalytic combustion gas centimeters can be improved. This is something that can be greatly contributed to improvement.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of the device of the present invention, Fig. 2 is a partially cutaway perspective view of an element manufactured by the device of the present invention, and Fig. 3 is a part of a gas detection element generally used in a catalytic combustion type gas sensor. FIG. 4 is a cutaway perspective view, FIG. 4 is a circuit connection diagram used in a catalytic combustion type gas centimeter, and FIG. 5 is a configuration diagram of an apparatus for carrying out a conventional method. 1...Electrophoresis tank, 2...Opening, 3...Suf 9-inlet, 4-21 dollar palme, 5...Electrode, 6...DC power supply, 7...Slurry , 8...
Droplet of slurry, 9...U-shaped jima, io −
... Hot filament, 11 ... Coil part of hot filament, 12
...Carrier.

Claims (1)

[Claims] 1) In a manufacturing device for a catalytic combustion gas sensor consisting of an element in which a coating layer is formed on the surface of a hot wire by electrophoresis, a slurry in which particles to be coated are dispersed flows out from a dropper-shaped opening provided in an electrophoresis tank. and means for inserting the portion of the hot filament to be coated into the flowing slurry;
1. An apparatus for manufacturing a gas sensor, comprising means for applying a DC voltage between an electrode in an electrophoresis tank and the hot wire.