JPH0416218Y2 - - Google Patents

Description

[Detailed description of the invention] This invention uses a bottomed cylindrical oxygen detection element made of a solid electrolyte as an oxygen sensor for detecting the oxygen concentration in exhaust gas in various combustion equipment including internal combustion engines. The present invention also relates to an oxygen sensor equipped with means for heating the oxygen detection element to maintain its activity in a low temperature range.

An oxygen sensor using a bottomed cylindrical oxygen detection element made of a solid electrolyte such as partially stabilized zirconia has an internal electrode layer and a porous hole extending from the bottom of the element to the inner and outer peripheral surfaces toward the opening above. forming an external electrode layer made of a thin film of a refractory metal such as platinum, disposing the oxygen detection element so as to be exposed to the exhaust gas, while supplying outside air into a bottomed cylinder;
An electromotive force corresponding to the difference in oxygen concentration between the exhaust gas and the outside air is generated between the inner and outer electrode layers, and is taken out from an output terminal connected to the internal electrode layer. In addition to mechanical connection and mechanical fixation, a means for supplying outside air into the bottomed hole provided with the internal electrode layer is required, as well as a means for heating to maintain activity at low temperatures. In this case, electrical conductivity and fixation to the heating means are also required, so it has been difficult to satisfy these functions and mass productivity at the same time.

The present invention has succeeded in satisfying both the required functionality and mass productivity of an oxygen sensor equipped with the heating means, and the embodiments shown in the drawings will be described below.

In the figure, 1 is made of an oxygen ion solid electrolyte such as partially stabilized zirconia, has a bottomed hole 11, and has a rectangular cross section or a rectangular shape with an arcuate surface to facilitate molding, in this case a rectangular annular shape. An open end 13 above the closed end 12 shows an oxygen detection element.
The internal electrode layer 2a extending laterally and the porous external electrode layer 2b are formed of a thin film of a refractory metal such as platinum. Reference numeral 3 denotes a heater housed in the bottomed hole 11 of the oxygen detection element, in which a meandering heating section 32a and a pair of conductive paths 32 extending upward from both ends of the heating element 32a are provided in the ceramic 31, such as high alumina porcelain.
b, 32b' are formed of a thin layer of heat-resistant metal such as tungsten or molybdenum, and the conductive paths 32b,
In the notch located at the end of 32b', there is a lead wire l made of the same heat-resistant metal and connected to an external power source.
A ceramic heater is shown in which terminal portions 32c and 32c' are provided for connecting the ceramic heater 3
For example, on one main surface of the first ceramic green sheet, there is a meandering pattern 32a that is made of a heat-resistant metal paste such as tungsten or molybdenum and serves as a heat generating part, and a conductive path extending upward from both ends of the pattern 32a. A pair of belt-shaped parts 32b, 3
It can be easily manufactured using basic manufacturing techniques for ceramic heaters, such as printing a thin layer of 2b', covering the printed surface with a second ceramic green sheet of the same quality, pressing, and firing. Next, 4a and 4a' are recessed portions 41 that come into contact with the opposite side of the heater 3.
a, 41a' and a pair of elastic metal plates made of phosphor bronze, brass, etc., which fix the heater 3 to the shaft hole 11 by means of protrusions 41b, 41b' that press against the shaft hole 11 of the oxygen detection element 1; On the other hand, here, the end _4a1 on the 4a side is projected outward as an output terminal.
The small protrusions 41c and 41c' that form a gap with the bottomed hole 11 of the oxygen detection element are connected to the heater 3.
Although the heater is fitted with the small protrusion of the heater to ensure secure holding, it may be omitted together with the small protrusion of the heater. Reference numeral 5 denotes a mounting fitting that fixes the closed end 12 side of the oxygen detection element in exhaust gas such as an exhaust pipe and also serves as a grounding terminal that is electrically connected to the external electrode layer 2b of the oxygen detection element. The mounting means for connecting the terminal end _4a1 of the elastic metal plate 4a, which also serves as an output terminal corresponding to the grounding terminal, with a lead wire (not shown), and the introduction of outside air into the bottomed hole 11 of the oxygen detection element are known. Further, the heater 3 is not limited to the illustrated ceramic heater, but can be freely selected such as an insulated metal heating wire, but the cross-sectional shape of the heater 3 is not limited to the ceramic heater shown in the figure. A rectangular shape, particularly a rectangle, is preferable if an arcuate surface corresponding to the bottom hole is allowed.

As described above, the oxygen sensor of the present invention consists of a heater housed in a bottomed hole of an oxygen detection element made of a bottomed cylindrical solid electrolyte having a rectangular cross-sectional shape with an internal electrode layer and an external electrode layer formed on the inner and outer surfaces. A pair of voids formed between opposing side walls of the oxygen sensing element and a side wall of the bottomed hole of the oxygen detection element that are electrically connected to the internal electrode layer of the sidewall of the bottomed hole, and Similarly, since the bottomed hole of the oxygen detection element is loaded with a pair of elastic metal plates with unevenness for fixing the heater, there is no fear of blocking the introduction of outside air into the bottomed hole of the oxygen detection element. The heater, which activates the oxygen detection element in a low temperature range, can be fixed by the above-mentioned elastic metal plate, which is either integrated or divided into a pair, and the output of the oxygen detection element can be taken out, which significantly reduces the size of the device and structure. , which has a great effect of simplification.

[Brief explanation of the drawing]

Figure 1 is a vertical cross-sectional view of the oxygen sensor of the present invention, Figure 2 is a longitudinal sectional view of the oxygen sensor of the present invention.
The figure is a side view with a cutaway section of the main part, and Figure 3 is a side view of the main part.
FIG. 1...Oxygen detection element, 11...Bottomed hole, 2a...
...Internal electrode layer, 2b...External electrode layer, 3...Heater, 4a, 4a'...Elastic metal plate.

Claims (1)

[Scope of utility model registration request] Internal electrode layer 2a and external electrode layer 2b on the inner and outer surfaces
The opposing side wall of the heater 3 housed in the bottomed hole 11 of the oxygen detection element 1, which is made of a bottomed cylindrical solid electrolyte and has a rectangular cross-sectional shape, and the bottomed side wall of the oxygen detection element facing the side wall. electrically connected to the internal electrode layer 2a on the side wall of the bottomed hole 11 in a pair of gaps formed between the side wall of the hole 11;
Similarly, the heating element 3 is placed in the bottomed hole 11 of the oxygen detection element.
A pair of elastic metal plates 4a provided with unevenness for fixing the
Oxygen sensor loaded with 4a'.