JPS6093342A - Method for regulating output of element for detecting oxygen concentration - Google Patents

Abstract

PURPOSE:To regulate easily the output from a limit current type element for detecting oxygen concn. after assembly by providing plural output regulating holes in addition to a diffusion hole and closing the regulating holes after assembly of the element thereby specifying the output. CONSTITUTION:A limit current type element for detecting oxygen concentration is constituted of a solid electrolyte case 1 provided with a negative electrode 4, a positive electrode 5, etc., a sealing material 10, a ceramic cover body 4 provided with a diffusion hole 7 and plural output regulating holes 7', etc. The output of the limit current type element for detecting oxygen concn. is easily regulated after assembly by measuring the output of said element in the atm. air at a prescribed temp. by an ammeter after assembly, determining the difference thereof from a prescribed output, closing the holes 7' to decrease the output and packing a paste, etc. consisting of ceramics, glass, etc. into the holes 7' to be closed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for adjusting the output of a limiting current type oxygen concentration detection element for detecting oxygen concentration in a gas atmosphere.

[Prior art]

Oxygen concentration detectors are used to control the air-fuel ratio and purify exhaust gas in internal combustion engines such as automobiles, and to control the combustion state of boilers. Various types of oxygen concentration detectors are known, and a limiting current type oxygen concentration detector has been developed as one of them. This limiting current type oxygen concentration detector has electrodes on both sides of an oxygen ion-permeable solid electrolyte to form the element body, and when a constant voltage is applied between both electrodes of the element body, one electrode (cathode) side Oxygen ions permeate to the other electrode (anode) side, so if you limit the amount of oxygen ions entering (or exiting) from at least one electrode, there will be a limit between the two electrodes depending on the oxygen concentration in the gas being measured. It takes advantage of the fact that current flows. In this limiting current type oxygen concentration detector, as a method for controlling the diffusion rate of oxygen to one electrode surface of the element body, for example, a ceramic This method involves arranging a diffusion plate with pores at predetermined positions on the plate.

However, in the above method, due to variations occurring in the process of forming diffusion holes at predetermined positions and in each subsequent process, considerable variations in output occurred when the detection element was finally incorporated into the shape. Therefore, methods of manufacturing elements with no difference in output compared to conventional methods have been sought.

[Purpose of the invention]

The present invention is intended to meet the above-mentioned conventional demands, and provides a method for adjusting the output of a limiting current type oxygen concentration detection element, which allows a desired output to be easily obtained after the element is assembled in a form that provides an output. That is.

[Structure of the invention]

Limiting current formula rf1 of the present invention. The method for adjusting the output of the elementary concentration detection element is to assemble the element having a diffusion hole and one or more output adjustment holes in a form that can obtain an output, and then adjust the output by one of the above output ii'ltl holes in order to obtain the required output. It is characterized by occluding the above.

As mentioned above, the limiting current type oxygen concentration detector is made up of an element body by providing breathable thin film electrodes made of platinum or the like in correspondence with each other on both the front and back sides of a solid electrolyte cell such as zirconia. When a voltage is applied between the electrodes, oxygen ions permeate from the negative electrode side to the positive electrode side, and a current flows between the two electrodes. However, if the amount of oxygen ions that permeate is limited,
The current increases in proportion to the increase in voltage up to a value of N, Mf.

The oxygen concentration is detected by detecting the phenomenon in which the current does not increase and measuring the current value (limit current value) at this time.

When a main diffusion hole and one or more output adjustment holes are provided as diffusion holes, the size of the output adjustment holes and the decrease in output of the detection element due to their blockage are as follows: The approximately 11th order formula I: 8 = 1/+8- (1) [In the formula, △I represents the magnitude of the current reduced by blocking the output adjustment hole (mA), and S represents the opening of the output adjustment hole. It represents the area (nffl), and l represents the depth u) of the output adjustment hole. It was found that there is a relationship expressed by

The output I is proportional to the amount of oxygen that passes through the diffusion holes and reaches the cathode surface. That is, the more acid Ri there is, the greater the output will be. Therefore, when considering the diffusion hole as a thin tube, the amount of gas passing through the diffusion hole Q is proportional to its area S but inversely proportional to its depth l, and is expressed as Q cyC-S/1. Based on the experimental results, the proportionality constant is determined, and the relationship expressed by the above formula I is obtained.

In the above, if the area of the diffusion hole is made smaller while keeping the depth l constant, the output can be changed because the number of gases passing through the diffusion hole once decreases. The present invention has been completed based on this knowledge.

The size, shape, number, position, etc. of the diffusion holes depend on the accuracy of output adjustment,
Optimal selection should be made taking into consideration workability during occlusion, mechanical strength and performance of the detection element, etc.

Normally, it is best to provide at least one main diffusion hole and one or more diffusion holes smaller than the main diffusion hole as output adjustment holes around the main diffusion hole or at an appropriate location, but it is recommended to provide multiple diffusion holes of the same size. It's okay.

As a method of closing the output adjustment hole, for example, a paste of a corrosion-resistant material such as various ceramics or glass of the same or different type as the element is injected using a injection tool such as a dropper, dried, and then fired. Another method is to insert a rod or fiber of a predetermined length made of a corrosion-resistant material such as ceramic or glass into the output adjustment hole and fix it by heating. You may.

In this case, inject a small amount of paste such as ceramic or glass into the output adjustment hole as an adhesive in advance, or apply a small amount to the top of the insertion end after inserting the rod or fiber described above to close the gap. It is even better if you bake it after cooking.

Further, when there are two or more blocked locations, it is preferable to close them symmetrically with respect to the main diffusion hole.

〔Example〕

The present invention will be explained below using examples. Note that the present invention is not limited to the following examples.

FIG. 1 is a partially cutaway exploded perspective view of a detection element showing an embodiment of the present invention. In the figure, 1 is a solid electrolyte container, 2 is a metallized layer, 3 is a lead part, 4 is a negative electrode, 5 is a positive electrode, 6
7 is a ceramic lid body, 7 is a gas diffusion hole, 7' is an output adjustment hole, 8 is a metallized layer, 9 is a lead portion, and 10 is a sealing material.

After assembling the detector element, the output (limit current value) in the atmosphere at a predetermined temperature is measured using an ammeter, and the difference from the predetermined output is calculated. From the relationship of the above formula (■), by closing the output adjustment hole, for example, depth l: = 1 mm, diameter φ = (L
For a 1 mm hole, approximately 1.3 rnA, depth l:
= 1.5 m, for a hole with diameter φ = 0.2 m, approximately!
h, a decrease in output of 5 mA occurs, so the number of holes to be plugged is determined according to the difference from the predetermined output, and the holes are plugged with ceramic, glass, etc. paste, rods, or fibers.

2 and 3 are cross-sectional views of a detection element representing other embodiments of the present invention, and the output adjustment holes/
The output of the detection element can be adjusted to a predetermined value by closing 0 in the same manner as described above. In the figure, 1' represents a solid electrolyte disk, and the others have the same meanings as in FIG.

〔Effect of the invention〕

As described above, in the present invention, the output can be adjusted after manufacturing a complete element, and the adjustment method is also simple, and a detection element having the desired output can be easily obtained. Therefore, it has the advantage of eliminating the need to strictly control the ceramic material, particle size, etc., or to unnecessarily strictly control the element assembly process, as in the past. In addition, in the conventional method, if a %-rated element does not have a predetermined output, it is considered defective and cannot be used, but the method of the present invention can eliminate such waste. .

[Brief explanation of drawings]

FIG. 1 is a partially cutaway exploded perspective view of a detection element 1B showing a first embodiment of the present invention, and FIGS. 2 and 6 are cross-sectional views of detection elements showing other embodiments. In the figure, 11. , solid electrolyte container 1'... solid electrolyte disk 2...
...Metallized layer 5...Lead part 4...Cathode
5...Positive electrode 6...Ceramic lid body 7...Gas diffusion hole 7,7...Output adjustment hole 8...Metallized layer 9...Lead part 10...Sealing material (other 1 name) -yf1 figure

Claims (1)

[Claims] Limiting current type oxygen, characterized in that after assembling an element having a diffusion hole and one or more output adjustment holes in a form that produces an output, one or more of the output adjustment holes are closed in order to obtain the required output. How to adjust the output of the concentration detection element.