JPS61164148A - Oxygen sensor element - Google Patents

Abstract

PURPOSE:To improve the accuracy of detecting oxygen concn. by interposing an electric insulating layer between the adhered part of a pair of electrode layer leads and lead wires by conductive paste and a solid electrolyte. CONSTITUTION:The electric insulating layer 12 is formed by printing on the right side of the solid electrolyte 11 to which lead wires 16, 17 are connected. The electrode layer 13 is then formed by printing. The film of the electrolyte 11 is directly formed on the left side of the layer 13 and the film of the lead part 13a is formed on the layer 12. A lead part 15a connected through the electrolyte 11 and the layer 12 via a conductive material to the electrode layer 15 on the other side face of the electrolyte 11 is provided on the insulating layer 12. The lead wires 16, 17 are connected by conductive pastes 18, 18 to the lead parts 13a, 15a provided atop the layer 12 in the above-mentioned manner. The leakage of the current is prevented by the layer 12 and the limiting current is distinctly obtd. even if the pastes 18, 18 connecting the lead wires 16, 18 to the electrodes approach each other on application of a voltage between the electrode layers 15 and 13. The accuracy in detecting the oxygen concn. is thus improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an oxygen sensor element. This oxygen sensor element is installed, for example, in the exhaust pipe of an internal combustion engine and detects the air in the air-fuel mixture supplied to the engine. It is used to detect the oxygen concentration in exhaust gas, which is closely related to the fuel ratio, and is used to provide feedback signals in air-fuel ratio feedback control.

(Prior Art) This type of oxygen sensor element includes, for example, those shown in FIGS. 4 and 5. This utilizes the principle that when voltage is applied between both electrode layers coated on both sides of a solid electrolyte, oxygen ions permeate from one electrode (cathode) to the other electrode (anode). By limiting the inflow, a limiting current is generated in the sensor, which
It detects the oxygen concentration in exhaust gas.

That is, as shown in the figure, on one side of a plate-shaped solid electrolyte 1 whose main component is a metal oxide such as ZrO having oxygen ion conductivity, an electrode layer 2 whose main component is platinum;
A that covers most of the electrode layer 2 except for the lead portion 2a.
A gas diffusion rate-determining diffusion layer 3 made of porous ceramic such as 1 s Os is sequentially laminated by printing.

An electrode layer 4 mainly composed of platinum is printed on the other side of the solid electrolyte 1, and the solid electrolyte 1 is connected to the lead portion of the electrode layer 4 through a conductive material penetrating the solid electrolyte 1. A lead portion 4a is provided on the side surface.

Lead wires 6.degree. 7 are bonded to these lead portions 2a and 4a, respectively, with conductive paste 5 containing platinum or the like as a component.

Then, when the electrode layer 4 is used as an anode and the electrode layer 2 is used as a cathode, and the voltage Vs applied between them is increased, the amount of oxygen permeation is limited depending on the degree of formation of the diffusion layer 3.
．． The current Is flowing between the two becomes approximately constant above a certain voltage. This current is called the limiting current. By measuring this limiting current, it is possible to measure with sufficient accuracy even in a region where the oxygen concentration in the exhaust gas is high (air-fuel ratio lean region).

<Problems to be Solved by the Invention> However, in the oxygen sensor element having such a structure, the conductive paste 5 applied to ensure continuity between each lead portion 2a, 4a and the lead wire 6. .5 approaches as devices become more compact.

At this time, current leakage occurs between the pastes 5 and 5 that are close to each other through the solid electrolyte 1, and as shown in Fig. 6, the limiting current cannot be clearly obtained and the oxygen concentration detection accuracy is reduced. There was a problem.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an oxygen sensor that can clarify the limiting current depending on the oxygen concentration and improve detection accuracy.

Means for Solving the Problems> Therefore, in this type of oxygen concentration sensor element, the present invention provides a structure in which at least a portion of each electrode layer lead portion is bonded with a conductive paste to the lead wire and a solid electrolyte. The structure includes an electrically insulating layer.

<Function> As a result, even if the conductive pastes are brought close to each other, current leakage can be prevented by the electrical insulating layer, thereby clarifying the limiting current and improving oxygen concentration detection accuracy.

<Example> An example of the present invention will be described below with reference to FIGS. 1 and 2.

In the figure, on one side of the solid electrolyte 11, on the right side of the figure where the lead wires are connected, an electrical insulating layer 12 mainly composed of A 1 t 03 or the like is printed, and then an electrical insulating layer 12 mainly composed of platinum or the like is printed. The electrode layer 13 is printed and coated. Therefore, most of the left side of the electrode layer 13 in the figure is directly coated on the solid electrolyte 11 as in FIGS. 4 and 5, but the lead portion 1
Most of 3a is coated on top of the electrically insulating layer 12.

Also, as in FIGS. 4 and 5, most of the left side of the electrolyte layer 13 is coated with a diffusion layer 14, and the other side of the solid electrolyte 11 is coated with an electrode layer 15. A solid electrolyte 11 and an electrical insulating layer 12 are provided on the electrode layer 15 on the side surface.
The lead portion 15a is connected via a conductive material that penetrates through the lead portion 15a.
is provided on the electrically insulating layer 12.

In this way, lead wires 16.17 made of platinum or the like are connected to the leads 13a, 15a provided on the upper surface of the electrically insulating layer 12 using a conductive paste 18.18 mainly composed of platinum.

Note that a paste 19 having the same quality as the electrical insulating layer 12 is applied to the edge of the electrically insulating layer 12 on the lead wire 16, 17 side to stably fix the lead wires 16, 17.

With such a configuration, the electrode layer 15 (anode), the electrode layer 13
(cathode) When a voltage Vs is applied between the pair of lead wires 16. Conductive paste connecting IT to electrodes 18.1
8 come close to each other, the electrical insulating layer 12 prevents current leakage.

As a result, as shown in FIG. 3, the limiting current is clarified and the accuracy of oxygen concentration detection is improved.

<Effects of the Invention> As explained above, according to the present invention, an electrically insulating layer is interposed between at least the portion of the lead portion of a pair of electrode layers that is bonded to the lead wire by conductive paste and the solid electrolyte. Because of this configuration, current leakage between the pair of conductive paste bonded parts is prevented, the limiting current is stabilized, and the oxygen concentration detection accuracy is improved. .

Furthermore, by preventing current leakage, it is possible to further reduce the size of the device.

[Brief explanation of drawings]

FIG. 1 is a plan view showing an oxygen sensor element according to an embodiment of the present invention, FIG. 2 is a sectional view taken along the line X-X in FIG. FIG. 4 is a plan view showing an example of a conventional oxygen sensor element, and FIG. 5 is a diagram showing the applied voltage-output current characteristics.
A sectional view taken along the Y arrow and FIG. 6 are diagrams showing the characteristics of the oxygen sensor element mentioned above. 11... Solid electrolyte 12... Electrical insulating layer 1
3... Electrode layer (cathode) 14... Diffusion layer 15...
・Electrode layer (anode) 16.17...Lead wire
18... Conductive Base Patent Applicant Japan Electronics Co., Ltd. Agent Patent Attorney Fujio Sasashima Figure 1 Figure 2 Figure 3 Applied Electricity Vs

Claims (1)

[Claims] Electrode layers are coated on both sides of a plate-shaped solid electrolyte having oxygen ion conductivity, and most of the electrode layer on one side except for the lead portion is coated with a diffusion layer for gas diffusion rate control, and the lead portion is coated with a diffusion layer for controlling gas diffusion rate. and a lead portion provided on one side so as to be connected to the electrode layer on the other side via a conductive material penetrating the solid electrolyte, and a lead wire is bonded with a conductive paste to each of the oxygen sensor elements, An oxygen sensor element characterized in that an electrical insulating layer is interposed between at least the lead wire bonding portion of the lead portion of each electrode layer and one side surface of the solid electrolyte.