JPS5827056A - Oxygen gas sensor - Google Patents

Abstract

PURPOSE:To attain sensors with thermal shock resistance and good durability by a construction wherein electrodes are formed on a raw sheet containing stabilized ZrO2 powder, a resin bonding agent and a plasticizer, and thus formed two sheets are bonded under high-temperature and high-pressure through a hollow raw sheet containing ZrO2 and then are sintered. CONSTITUTION:A raw sheet which contains ZrO2 powder stabilized with Y2O3, a bonding agent such as polyvinylbutyral, and a plasticizer such as polyethyleneglycol or octylphthalate, is punched into a disc 23 formed with a fine hole 53 at its center. Dick- like platinum electrode 43 and lead portions 61 are formed on both sides of the disc 23 through screen printing. Thus obtained two discs 23 are superimposed on both sides of an annular disc raw sheet 12 (made of the same material as the disc 23) having a larger outer diameter than the disc 23, and then are sintered under high-temperature after heating and pressure-bonding them. With one disc electrode 42 of thus obtained sensor being as a sensing electrode, voltage is applied to the other disc electrode 41 through a feedback amplifier, thereby to measure O2 density. This sensor has good thermal shock resistance, will never undergo separation at the bonded portions and has a prolonged service life. In addition, the measured results with good linearity can be attained with respect to O2 density.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an oxygen sensor that does not require a reference atmospheric pressure. Oxygen gas sensors are necessary for industrial measurement control or automobile exhaust gas control, and various types of sensors have been put into practical use. Among these, in recent years, R11 elemental concentration cell type sensors using zirconia solid electrolytes have been developed as sensors that are reliable in dirty exhaust gas and can be inserted directly into high-temperature flues, and as sensors for automobile pollution prevention. It is widely used in practical applications. The disadvantages of this oxygen concentration battery type oxygen sensor are that it requires a reference oxygen concentration gas buried in the sensor, and because it uses normal atmospheric pressure, the opening must be exposed outside the flue. . Recently, in order to improve this point, a new type of zirconia oxygen gas sensor that does not require a reference oxygen concentration gas has been proposed. The structure of this known sensor consists of one cylindrical spacer 6 as shown in FIG.
Two zirconia disks are bonded on both sides of υ with adhesive glasses (31) and (32).

Platinum electrodes (41m) are placed on both sides of this zirconia.
41b), (42m), (42b) are deposited,
Moreover, there are pores (51) and (52) in the center of this disk.
is the provision. Now, this pair of electrodes (41m), (
4th) when a voltage V is applied across the terminal.

Oxygen gas is introduced through zirconia aυ as a solid electrolyte. When oxygen gas is introduced into the cylinder, platinum 1
At the same time, an electromotive force is generated at both ends of the poles (42m) and (42b), and at the same time, the oxygen gas introduced inside the pores (sl)
, (52).

At this time, as shown in FIG. 2, a circuit using a feedback amplifier is configured to keep the electromotive force constant.

When the oxygen concentration is measured at a constant temperature, the flowing current xp is proportional to the oxygen concentration, so it can be used as a sensor. This sensor shows very linear characteristics regarding the oxygen concentration in N2 gas or CO2 gas, but
As the sensor is constructed by bonding glass to both ends of two cylindrical spacers, when used for long periods of time at high temperatures, the bonding glass diffuses into the cylindrical spacers and the grain boundaries of the zirconia, causing heat cycles between high and room temperatures. If this process is repeated, microcracks will occur at the grain boundaries.

There was a problem with durability. In addition, even if glasses with similar coefficients of thermal expansion are selected and used for rapid heating or cooling, cracks are likely to occur due to differences in heat conduction and temperature distribution during heating and cooling, making it unreliable. There were also problems in terms of gender. In order to improve this drawback, the present invention uses zirconia for the spacer part, and the joint part with the zirconia disk is not bonded to glass, but the half that is integrated at 1II and 11 in the sintering process is used at high temperatures for a long time. The purpose of the present invention is to provide a sensor that is resistant to thermal shock as well as thermal shock. That is, while the conventional sensor used a spacer and a zirconia disk as a furnace solid and was constructed by glass bonding, the present invention uses zirconia powder, a thermoplastic organic binder, and a zirconia disk as a spacer and a zirconia disk. A raw sheet containing an organic plasticizer is made by punching and forming, an electrode pattern is formed by screen printing as the desired electrode of a zirconia disk, the spacer and the disk are bonded by heat and pressure, and then the binder is removed. The present invention relates to a sensor characterized by a f′1fc-shaped structure manufactured by high-temperature sintering in a sintering process including:

The above raw sheet is made using thermoplastic! I1. As the M mixture, polyvinyl butyral, polyvinyl acetal resin, etc. are used, and as the organic plasticizer, polyethylene glycol, phthalic acid ester, etc. are used, and these are kneaded or made into a slurry through a solvent, and then processed by the roll method, extrusion method, or A green sheet is created using a doctor blade method or the like.

Hereinafter, the present invention will be explained according to examples.

Example 577% trichlorethylene TO (by weight), 30% by weight ethyl alcohol (40gr mixed solvent, 3.5gr B1J vinyl butyral as a binder, 3.7gr polyethylene glycol (octyl phthalate) as a plasticizer) 3.
After adding and dissolving 2gr and adding triolein as a dispersant, 1'20gr of ZrO2 powder stabilized with Y2O (10% by weight) was added and mixed in a ball mill for 10 hours to create a slurry. . After degassing this slurry,
After pouring onto a polyester film and making a sheet with a doctor blade having a gap of 0.8 m, and drying the sheet.

I! As shown in Figure 3, there is a 0.1m hole (53) in the center.
Two disks (c) with a diameter of 15 cm were made by punching. Next, a screen is formed on the platinum using platinum paste so that a platinum electrode (43) with a diameter of 10 mm and a take-out lead part (61) are placed in the center of the front and back surfaces of this disk, as shown in FIG. Printed.

Further, an annular disk a2 having an inner diameter of 13-1 and an outer diameter of 155 m as shown in FIG. 5 was punched out as a spacer.

The above-mentioned disks were stacked on top and bottom and were heat-pressed at 160C. This was inserted into an electric furnace and cast at 1600C for 5 hours. The sensor created in this way is used as the sensing electrode in the t-pole pair on one disk, and a voltage is applied to the %-pole pair on the other disk through a feedback amplifier in the same manner as shown in Fig. 2. As a result of examining the relationship with the oxygen concentration in nitrogen at 800C, a characteristic with good linearity was obtained as shown in FIG. Next, this sensor was heated and cooled repeatedly between room temperature and 1200 tl' for 100 cycles, but no microcracks were observed. Also, 5o
Equivalent abnormality F can also be caused by rapid cooling by heating to OC and then cooling to room temperature.
I didn't recognize it.

Note that these test conditions were conditions that conventional sensors constructed using glass adhesive could not withstand.

In the second embodiment, the shape is a combination of a disk and a bank-like plate, but other shapes may be used.

As explained above, according to the present invention, it is possible to make a closed hollow shape sensor that does not use glass adhesive at the joint, has pores for diffusion, and has electrodes on the inner and outer surfaces, and has excellent durability and Its reliability against thermal shock is extremely high, and its industrial utility value is significant.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view showing the configuration of a known oxygen sensor, Fig. 2 is a principle diagram of a measurement circuit using a feedback amplifier, Fig. 3 is a plan view of the raw sheet for electrode parts of the present invention, and Fig. 4 is FIG. 5 is a plan view showing a state in which printed electrodes and extraction leads are formed, FIG. 5 is a plan view of a raw sheet for a spacer, and FIG. 6 is a view showing an example of the characteristics of the sensor of the present invention. In the figure, a is a hollow forming spacer, r2υ. (2) Hasilconia, (31) and (32) are adhesive glasses. (41), (42) are platinum electrodes, (51),
(52), (53) Fi diffusion pore, (2) is zircochia raw sea), (43) is printed-pole, (61)
is a printed drawer lead. Agent Shin Kuzuno - Engraving of the drawings (no changes to the contents) Figure 1 Figure 2 Figure 3r! J [Figure 4 Figure 5 Figure 6 Acid nose two domain degree (〃] Procedural amendment (method) February 19, 1932 Director-General of the Patent Office 1, Indication of case Patent application No. 126329/1989 2, Name of the invention: Oxygen gas sensor 3, relationship with the amended case Patent applicant address: 2-3 Marunoshiratama-chome, Chiyoda-ku, Tokyo Name (601): Mitsubishi Electric Corporation Representative Jinhachibe Katayama 4, Agent Address: 2-3-6, Shiratama-chome, Maruno, Chiyoda-ku, Tokyo, Specifications and drawings to be amended.

Claims (1)

[Claims] A step of preparing a raw sheet containing a stabilized zirconia solid electrolyte powder, a thermoplastic organic binder, and an organic plasticizer to a desired thickness; The process of forming. A step of heating and kakuta-bonding the two raw sheets on which the electrodes were formed and a spacer made from the raw sheet having closed sides for forming a hollow part to create a hollow closed shape;
1. An oxygen gas sensor having diffusion pores, which comprises a step of subsequently heating at a high temperature and sintering.