JPH02198352A - Sensor element of oxygen sensor - Google Patents

Abstract

PURPOSE:To obtain an element characterized with high accuracy and easy realization of machinability, thin-film formation and mass productivity by forming many pin holes whose number per unit area, diameters and arrangement are regulated in a cap. CONSTITUTION:This element is composed of the following parts: a pellet comprising solid-state electrolyte; electrodes formed on both surfaces of the pellet; and a porous body having many pin holes whose number per unit area, diameters and arrangement are regulated and which are formed on one electrode. A sensor having the pin holes is inputted into a measuring gas atmosphere. A voltage is applied across both electrodes. Then, oxygen is uniformly diffused to the electrodes and the pellet by way of each pin hole. The voltage- current characteristic is stabilized by the uniform oxygen pin hole action. The limit current value without dispersion can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a sensor element of an oxygen sensor used for measuring acid A f1 degree in various atmospheres.

[Conventional technology]

First, the basic configuration and operation of the Pa yarn sensor will be briefly explained.

As shown in FIGS. 3(A) and 3(B), the oxygen sensor Δ is composed of solid electrolyte pellets la (for example, zirconium oxide (
ZrO: zirconia) with gold aM compound (for example, YO%C
made of stabilized zirconia with a solid solution of aO, etc.) and an electrode 1b formed on both sides of the pellet 1a (for example,
(platinum, etc.); and a cap 1C that is bonded to the pellet 1a on the one electrode 1b side of the electrode 1b, has a diffusion-controlled small hole 1C1 in the upper part, and is equipped with a heating heater C2; It is composed of a stem 2 having a terminal 2a that supports the element 1, and a mesh cover 3 fitted to the stem 2.

Then, when the above-mentioned oxygen sensor A is placed in #i elemental atmosphere and a voltage E1 is applied between the electrodes 1b and a voltage E2 is applied to the heating heater C, the oxygen that enters the cap 1C from the small hole 1C1 is heated. Oxygen bombing effect of pellet 1a (
Due to the oxygen ion conductivity of the stabilized zirconia pellet 1a, a phenomenon in which oxygen moves through the pellet 1a via the oxygen ion vacancies), a current using oxygen ions as carriers flows, and the oxygen molecules in the pellet 1C flow. The loss is made through the pellet 1a.

Voltage at this time -′? As shown in FIG. 4, the current characteristics are such that a flat region of current appears in the region of voltage.

This flat region occurs because the inflow of air is restricted by the small hole 1C1 (diffusion rate limiting), and the current at this time is called a limiting current.

Figure 5 shows the limiting current characteristics at various oxygen concentrations,
In addition, Figure 6 shows the relationship between the oxygen concentration and the limiting current value.As can be seen from these figures, there is a one-to-one relationship between the oxygen level and the limiting current value (linear when taken logarithmically). relationship), it is possible to apply a constant voltage vw across the electrodes 1b and detect the oxygen concentration from the limiting current value at that time.

As described above, the oxygen sensor A has, for example, a small hole 1C1 of expansion Rttl+speed in the cap 1G, but conventionally, a single-hole type having one small hole 1C1 has been usual.

[Problem to be solved by the invention]

In the case of the single-hole type, if the molded thickness of the cap is 11 degrees, there will be little variation in the limiting current value, and a highly accurate sensor element can be obtained.

However, differences in hole position during drilling (for example, hydrostatic drilling) cause a time lag in oxygen diffusion to the electrode and pellet, which impedes oxygen ion conduction and causes variations in the limiting current value. Because of this, a high level of machining accuracy is required, and there are problems with machinability, especially when considering 1llllization and mass production, and if the hole becomes clogged, it will lose its function as a sensor element. There was a problem.

In view of the above-mentioned problems of the prior art, the present invention provides an advantageous processability and refinement by forming a large number of pinholes in a cap with a regulated number of pinholes per unit area, hole diameter, and arrangement. One of our objectives is to eliminate S and provide a sensor element suitable for mass production.

[Means to solve the problem]

In order to achieve the above object, the sensor element of the M-sensor sensor of the present invention includes a pellet made of solid-state VN material, electrodes formed on both sides of the pellet, and a sensor element formed on one electrode side of the pellet. The special feature is that it is composed of a multi-hole body and a large number of pinholes whose number, hole diameter, and arrangement are regulated.
11.

The pellet is made of stabilized zirconia, and the electrodes are formed by sputtering platinum.

Further, the porous body is formed by forming pinholes in a polyimide film or a zirconia plate formed by a green sheet method.

[For production]

When an oxygen sensor having a sensor element with the above configuration is placed in a measurement gas atmosphere and a voltage is applied between both electrodes, oxygen is uniformly diffused into the electrode and pellet through each pinhole of the porous body, resulting in uniform deposit bombing. As a result, the response of the voltage-current characteristic becomes sharp, and a limit current value with no variation among each sensor element can be obtained.

(Example) Embodiments of the present invention will be described with reference to the drawings.

Figure 1 shows the first example.10 is a solid electrolyte pellet, for example, a stable electrolyte made of zirconium oxide (ZrO: zirconia) with a metal oxide (e.g., Y O, CaO, etc.) dissolved in solid solution. The pellets 10 are made of oxidized zirconia.
Electrodes 11 (for example, platinum, etc.) are formed on both sides of the substrate 0 by sputtering.

12 is a porous body made of a polymer compound, for example, a polyimide film (about 100 μm thick), in which pinholes 13 with a diameter of 5 μ7 rL are formed at 1# intervals at a predetermined number per unit area using a needle press machine. has been done.

Due to its flexibility, the porous body 12 allows the electrode 1 to
The 'a1' right surface of one of the 1's is attached to the surface.

FIG. 2 shows a second embodiment, in which 10 is a solid electrolyte pellet, 11 is an electrode, and these are the same as in the #1 distribution first embodiment.

Reference numeral 14 is a porous body, in which pinholes 13 with a diameter of 5 μm are formed at 1 m intervals using a needle press machine in a zirconia plate (approximately 0.5 am thick) made by the green sheet method.
are machined with pinholes at a predetermined number per unit area.

In addition, since the zirconia plate is not flexible, Bellet 10
It is glued to the support leg 15 which is glued to.

Therefore, the number of pinholes per unit area determines the limit at current value associated with equalization of the oxygen bombing effect, so
F, which is advantageous in processability and suitable for thinning and mass production;
A sensor element of a viscous oxygen sensor is obtained.

(Effects of the Invention) The present invention is provided with a multi-hole body as a cap having a large number of bottles/holes with a defined number and arrangement of holes per unit area. The time lag seen in the case of a single-hole type is eliminated, and the distribution of the current becomes uniform, and the equalization of the oxygen bombing effect stabilizes the voltage-current characteristics, resulting in a highly accurate sensor element with no variation in limit current value.

In addition, since it is a multi-hole body, it can be machined without requiring the same precision as in the case of a single-hole type.
It is easy to process, and can be made into a thin film and produced in M size.

Furthermore, even if some of the pinholes become clogged, the sensor element will not immediately lose its functionality.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of the first embodiment of the present invention, FIG. 2 is a sectional view of the second embodiment of the present invention, and FIG. 3 is a conventional example. Figure, same figure (B
) is a cross-sectional view of the oxygen sensor, FIG. 4 is a voltage-current characteristic diagram, FIG. 5 is each oxygen concentration-eye field current characteristic diagram, and FIG. 6 is an M-element turbidity-limiting current characteristic diagram. V (VOlrl Name 4 Figure V (volt) Certain 5 Cause 10...Bellet, 11...Electrode, 12.14...
・Multi-hole body, 13...pinhole.

Claims (6)

[Claims] 1. A solid electrolyte pellet, electrodes formed on both sides of the pellet, and a porous body having a large number of pinholes with a regulated number per unit area, hole diameter, and arrangement formed on one electrode side of the electrode. The sensor element of the oxygen sensor. 2. The sensor element for an oxygen sensor according to claim 1, wherein the pellets are made of stabilized zirconia. 3. The sensor element for an oxygen sensor according to claim 1, wherein the electrode is made of platinum. 4. 2. The sensor element for an oxygen sensor according to claim 1, wherein the electrodes on both surfaces of the pellet are formed by sputtering. 5. 2. The sensor element for an oxygen sensor according to claim 1, wherein the porous body is formed by machining pinholes in a polyimide film. 6. 2. The sensor element for an oxygen sensor according to claim 1, wherein the multi-hole holes are formed by machining pinholes in a zirconia plate formed by a green sheet method.