JPH0334585B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing a solid electrolyte sensor such as a lean sensor used in an internal combustion engine.

[Conventional technology]

A lean sensor corresponds to a type of oxygen sensor, and is used when the oxygen concentration of the mixed gas (hereinafter referred to as detection gas) whose air-fuel ratio is to be measured is high.
In other words, it is called this because it is a sensor that detects the oxygen concentration on the fuel lean side, where the fuel concentration is low. Unlike concentration cell type sensors, which are the mainstream of conventional sensors for detecting oxygen concentration, they do not require standard gas and can accurately measure the air-fuel ratio of the detected gas on the fuel lean side, so they have been attracting attention recently. is bathed in

By the way, this lean sensor mainly uses a solid electrolyte element (for example, zirconia) having an electrode.
and an insulator (for example, alumina, in the case of a lean sensor, a gas diffusion control layer made of a porous ceramic layer) to protect the element, and the oxygen in the sensing gas is ionized. By passing through the element in this state, a current (limiting current) flows between the electrodes to which a voltage is applied, and by measuring the value of this current, the air-fuel ratio is detected. For example, it is manufactured as follows.

To explain with reference to FIG. 1, (1) a solid electrolyte element 1 (one piece) comprising electrodes 1a, 1a on both the front and back sides; (2) a solid electrolyte element 1 (one piece) that is larger than the element 1 and has electrodes 1a, 1a on both sides;
A metal lead wire 2b having a hole 2a at a position corresponding to a and abutting the electrode on one side,
(2) first insulators 2 (two sheets) each having a metal heater wire 2c on the other surface; and (3) a first insulator 2 having approximately the same size as the first insulator 2 and having holes 3a in the same position as described above. Two insulators 3 (2
1), and each member 1, 2, and 3 is fired in advance to impart strength. After that, first insulators 2, 2 are placed on both sides of the solid electrolyte element 1,
Metal lead wires 2b, 2b of the first insulators 2, 2
The second insulators 3, 3 are stacked on both sides of the three-layer body obtained by stacking the layers in such a way that the surface thereof is located on the element 1 side.
A five-layer body is obtained by stacking the first and second insulators 2 and 3 with their holes 2a and 3a aligned. After that, in order to make it easier to generate a limiting current, a porous protective layer 4 (for example, made of alumina, which becomes a gas diffusion rate controlling layer in the case of a lean sensor) is formed on the detection section and its surrounding area. Thus, a lean sensor as shown in FIG. 2 is manufactured. In this figure, 5 is an adhesive layer (for example, glass), and the adhesive layer 5 integrates the solid electrolyte element 1 and the first insulators 2, 2.

[Problem to be solved by the invention]

However, these manufacturing methods have the following problems.

That is, the electrode 1 provided on the insulators 2, 2
The problem is that the electrodes 1a and 1a are heated when the insulators 2 and 2 are fired, and also when the layers of the laminate are bonded together using the adhesive 5, causing thermal deterioration of the electrodes 1a and 1a. When the electrodes deteriorate due to heat, changes in current in the solid electrolyte cannot be accurately detected, leading to a decrease in sensor performance.

Therefore, an object of the present invention is to eliminate thermal deterioration of the electrodes due to the influence of heating during bonding of the laminates by forming the electrodes in a solid electrolyte after the laminates are bonded.

[Means to solve the problem]

The present invention achieves the above object of the present invention by the following configuration.

The present invention manufactures a solid electrolyte sensor in which electrodes with lead wires are provided on both sides of a solid electrolyte element, an insulator is brought into contact with parts other than the electrode part, and the electrode part is covered with a porous material. It's a method.

First, an insulator provided with holes is laminated on both sides of a solid electrolyte element on which lead wires for connection to electrodes are formed, respectively, such that a portion of the lead wires faces into the holes.

Thereafter, the element and the insulator are integrated by heating or pressure bonding.

Next, electrodes are formed on both sides of this integrated structure by bringing them into contact with metal lead wires.

Furthermore, a solid electrolyte sensor is manufactured by covering the solid electrolyte sensor with a porous material.

[Effect]

According to the solid electrolyte sensor manufacturing method of the present invention, since the electrodes are not provided on the solid electrolyte element in advance, the electrodes are not affected by heating during lamination and integration of the solid electrolyte element and the insulator.

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 3 and 4.

The solid electrolyte element 6 made of zirconia or the like stabilized with yttrium oxide or the like and the insulators 7, 7 are plate-shaped bodies having substantially the same shape and size except that the latter has holes 7a, 7a. Then, by applying a metal paste such as platinum paste to both sides of the element 6 in a predetermined pattern, the metal lead wires 6a,
6a and the metal heater wires 6b, 6b are formed at locations apart from the lead wires 6a, 6a. Element 6 and insulators 7, 7 having such a configuration
The integration is performed as follows. That is, the insulators 7, 7 are placed on both sides of the element 6, and the metal lead wires 6a, 6a are positioned so that only their tips are visible through the holes 7a, 7a of the insulators 7, 7 to form a three-layer structure. This is done by heating and compressing the entire member at a temperature below that of the constituent material of each member 6, 7. Then, metal lead wires 6a are placed as described above in the single layer part of the integrated three-layer body, that is, on both sides of the element 6 that can be seen from the outside through the holes 7a, 7a of the insulators 7, 7. Electrodes 6c, 6c are formed in contact with 6a. In this case, the electrodes 6c, 6c are applied as a metal paste and then solidified by heating to be formed on the surface of the element 6. Thereafter, a porous protective layer 8 made of alumina, spirene, etc. is formed in the holes 7a, 7a of the three-layer structure in which the electrodes 6c, 6c are formed, and their surrounding areas by means such as dipping or coating. is completed.

The lean sensor manufactured in this way also operates normally. That is, a voltage is applied to the electrodes 6c, 6c through the lead wires 6a, 6a, and a current flows therethrough. This current value changes depending on the oxygen concentration in the detection gas around the electrodes 6c, 6c, and detects the air-fuel ratio of the detection gas. In addition, heater wires 6b, 6b
A voltage is also applied to generate heat, heating the electrodes 6c, 6c and the element 6.

The following effects are specific to this embodiment.

) The ceramic materials that make up the element and insulator are fired at the same time, which simplifies the firing process.In addition, when firing each component (element and insulator) individually, each component is less likely to warp after firing. This solves the problem of not being able to obtain a good laminate due to differences in the laminates.

) The element and the insulator, which have the same shape and size, are integrated by heat and pressure bonding at the firing temperature of their constituent materials, so no adhesive is required for integration. For this reason, there are problems caused by the use of conventional adhesives, such as the adhesive interfering with the contact area between the electrode and the metal lead wire and inhibiting the conduction of electricity. Therefore, considerable care must be taken to ensure conduction of electricity. This eliminates the problem of having to pay a large amount of adhesive and using a considerable amount of adhesive, which reduces the strength of the adhesive and reduces the strength of the five-layer lean sensor.

) Since the solid electrolyte element and the insulator that make up a conventional lean sensor differ in size and shape, it was difficult to position the element with respect to the insulator, but according to this example, the solid electrolyte element Since the insulator and the insulator have the same shape and size, they can be easily positioned by aligning their end surfaces.

) Also, since not only electrodes but also metal lead wires and metal heater wires are provided directly on the element,
The insulator may be laminated one layer on each side of the element, and a lean sensor can be obtained as a thinner laminate than in the past.

Furthermore, in the past, the metal heater wire was positioned quickly relative to the element for structural reasons, resulting in poor thermal efficiency and the element could not be heated that much even if the voltage applied to the heater was increased. It is also sufficient to heat the element etc. with a metal heater wire.

〔Effect of the invention〕

According to the method for manufacturing a solid electrolyte sensor of the present invention, since the electrodes are formed on the solid electrolyte after the laminates are bonded, it is possible to eliminate thermal deterioration of the electrodes due to the influence of heating during the bonding of the laminates. .

[Brief explanation of drawings]

Fig. 1 is an exploded view of a lean sensor to explain an example of the conventional method, Fig. 2 is a sectional view of a lean sensor obtained by the above example, and Fig. 3 is an illustration of an embodiment of the method of the present invention. An exploded view of the lean sensor for
FIG. 4 shows a sectional view of the rinsing sensor obtained in this example. In the figure: (1), 6... solid electrolyte element, (2),
(3), 7...Insulator, (2b), 6a...Metal lead wire, (2c), 6b...Metal heater wire, (1a), 6c
...Electrodes, where the symbols in parentheses indicate conventional ones.

Claims (1)

[Scope of Claims] 1. A solid electrolyte sensor in which electrodes with lead wires are provided on both sides of a solid electrolyte element, an insulator is brought into contact with parts other than the electrode parts, and the electrode parts are covered with a porous material. A manufacturing method, which comprises laminating an insulator with holes on both sides of a solid electrolyte element each having lead wires for connection to electrodes so that a part of the lead wires faces into the holes. After that, the element and the insulator are integrated by heating or compression heating, and then electrodes are formed on both sides by contacting the lead wire, and then the solid electrolyte is covered with a porous material. How to manufacture the sensor.