JPH0623723B2 - Oxygen sensor - Google Patents

Description

TECHNICAL FIELD The present invention relates to an oxygen sensor for measuring the oxygen concentration in the exhaust gas of an internal combustion engine of an automobile, for example.

[Prior Art] In recent years, from the viewpoint of pollution prevention, energy saving, etc., the partial pressure of oxygen gas in the exhaust gas of an internal combustion engine or the like is measured, and the air-fuel ratio is controlled based on the result. Further, the oxygen gas partial pressure in the exhaust gas is often measured using an oxygen sensor including a solid electrolyte layer having oxygen ion conductivity such as a ZrO ₂ solid solution.

The oxygen ion conductive solid electrolyte layer is formed into a tubular shape having a pair of electrodes on the inner and outer surfaces or a plate shape having a pair of electrodes on the front and back surfaces to form an oxygen sensor. These usually measure the oxygen gas partial pressure in the measurement gas by introducing the measurement gas on one surface of the electrode and the atmosphere on the other surface as a reference oxygen source.

[Problems to be Solved by the Invention] However, when formed in a tubular shape, it is not easy to form electrodes and lead wires from the electrodes because the surface is not flat. On the other hand, in the case of forming in a plate shape, it becomes easy to form electrodes and lead wires from the electrodes, but the oxygen sensor has directivity. That is, the responsiveness and durability may be different depending on whether the measurement gas hits the plate vertically or in parallel. Furthermore, in the case of plate-shaped, the fixing structure when the probe is assembled by passing through the shaft hole of the metal fixture in which the screw fixing means is formed,
There is a drawback that the strength of the sensor after assembly is also poor.

[Means for Solving Problems] The present invention adopts the following technical means as a constitution of the invention in order to solve the above problems.

That is, the oxygen sensor of the present invention is an oxygen sensor having a rod-shaped ceramic core material as a support having a groove formed on the outer peripheral surface thereof, and at least a pair of electrodes wound around the core body to form a pair on the front and back surfaces. An ion conductive solid electrolyte layer is provided, and the surface side electrode is formed so as to be distributed at substantially equal intervals in the winding direction, or the electrodes distributed at substantially equal intervals are connected to be integrated. And the back surface side electrode is arranged so as to form a reference gas introduction path between the back surface side electrode and the groove of the core body.

The core material is rod-shaped and has a groove, and this groove serves as a reference gas introduction path for introducing outside air as a reference oxygen source of an oxygen concentration battery composed of a solid electrolyte layer described later and a pair of electrodes.

This core may be solid or hollow, but in the case of a hollow, unless a partition is provided in the core, the exhaust gas leaks to the reference oxygen source side, which is not preferable.

The core material can be molded by die pressing, extrusion molding, or the like. In this case, the groove can be provided at the same time when the core material is formed. In addition, a green sheet having slits corresponding to grooves is wound around a cylindrical molded body and pressure-bonded, or a green sheet having slits corresponding to grooves is laminated and pressure-bonded on a flat green sheet, and then a jig is used. It may be used as a core and used as a core material.

The groove can be provided in a concentric shape, a linear shape in the longitudinal direction of the spiral core material, or the like, but it is preferable to provide the groove in the longitudinal direction of the outer peripheral surface of the core material for ease of manufacturing and introduction of outside air.

The solid electrolyte layer is not particularly limited as long as it is an oxygen ion conductive solid electrolyte layer, and may be, for example, Y ₂ O ₃ —Zr ₂ O _3.
Can be used _2, Ca O-Zr O ₂ or the like.

The electrode is made of a noble metal such as platinum or a mixture thereof with ceramic powder and is gas permeable.

These are, for example, a green sheet of a solid electrolyte body having a thick-film printed electrode wound around a core material such that at least a part of the electrode corresponds to the groove of the core material, and integrated by firing, thereby forming an oxygen sensor. To be done. By providing an electrode pair corresponding to each groove and electrically independent of each other, embrittlement of the outer electrode is prevented especially when a leaded fuel is used, and it is prevented from progressing to the surroundings and durable. It is also possible to guarantee deterioration of sex.

Further, when the green sheet of the fixed electrolyte body is laminated on the core material, it is preferable that the green material is positioned so that one end of the groove of the core material is closed and the other end is opened. This is to prevent the exhaust gas from leaking to the reference oxygen source side.

Further, it is preferable to provide a heating element in a portion other than the groove of the solid electrolyte layer and the core material because the measurement can always be performed at an appropriate temperature.

[Operation] The present invention forms an oxygen sensor having a reference gas introduction path by covering a groove provided in a core material with a solid electrolyte layer in which electrodes are provided in a predetermined shape and arrangement in advance. is there. Therefore, the oxygen sensor is provided with a reference gas introduction path in which it is easy to form the entire sensor and its electrodes and terminals, and in which the directionality in the plane perpendicular to the longitudinal direction in response and durability is small.

[Embodiment] FIG. 1 shows the first embodiment of the present invention.
This will be described with reference to (c), FIG. 2 and FIG. For the sake of explanation, the scale of each drawing is different.

FIG. 1A is a perspective view of this embodiment.

This example _Al 2 _{O 3} as shown in the perspective view of FIG. 1 (b)
A hollow core material 2 having four grooves 1 consisting of is covered with a solid electrolyte layer 6 provided with an inner electrode 3, an outer electrode 4 and a heating element 5. The inner electrode 3 and the outer electrode 4 are the first
They face each other with the solid electrolyte layer 6 in between as shown in the A-A end view of FIG. Also, the inner electrode 3 and the heating element 5 are respectively subjected to through-hole processing, so that the inner electrode terminal 10 and the heating element terminal 11 are formed.
Connected to. The outer electrode 4 is connected to the outer electrode terminal 12.

The core material 2 used in this embodiment is A'-A 'in FIG.
As shown in the partial cross-sectional view of FIG. 2 cut in the direction of FIG. 2, it is a hollow cylindrical shape having an outer diameter of 4.5 mm, an inner diameter of 1.5 mm, and a length of 40 mm, and a partition wall 21 is provided from one end 20 to 3 mm. is there. Also, from the other end 22 to 5 m from the end 20
Four grooves 1 having a width of 1 mm and a depth of 0.7 mm are provided up to m. This core material 2 can be easily formed by a die press.

The solid electrolyte layer 6 _is obtained by cutting and mixing a binder typically used in Y ₂ O 3 -Zr O ₂ solid solution material powder, a material obtained by a green sheet 17 mm × 37 mm. An electrode pattern as shown in FIG. 1B is provided on this green sheet by thick film printing. Electrodes 3, 4,
The heating element 5 and the terminals 10, 11 and 12 are made of Y ₂ O ₃ -Zr.
It is composed of platinum containing 15 wt% of O ₂ solid solution. An insulating layer made of alumina or the like is provided between the heating element 5 and the solid electrolyte layer 6 and / or the core material 2, although not shown.

The oxygen sensor S1 shown in FIG. 1 (a) is obtained by winding a green sheet, which will be the solid electrolyte layer 6 on which the electrode pattern is formed, around the core material 2 and press-fixing it, followed by firing in the atmosphere.

This oxygen sensor S1 has a holder 3 as shown in FIG.
1 is fixed by a glass seal 32 and a ring 33, crimp terminal fittings 34 are brazed to the terminals 10, 11 and 12, and lead wires 35 are connected by crimping. After that, the metal fitting 36, the outer cylinder 37, the sealing material 38, and the protector 39 are attached to form an oxygen detection probe 40.

Since the partition wall 21 of the oxygen sensor S1 of this embodiment is near the end portion 20 of the core material 2, the green sheet to be the solid electrolyte layer 6 is fixed by winding and pressing the green sheet to close the end portion of the groove 1. Even if a large force is applied to the side of the electrolyte layer 6 that is in contact with the end portion 20 side of the core material 2, the core material 2 is not destroyed. Further, since there are four measuring parts each consisting of the pair of electrodes 3 and 4 and the groove 1, the responsiveness and the directionality of the electrode life are small.

Further, since the core material 2 is hollow, the heat capacity is small and the heating element 5
Therefore, the temperature suitable for measurement can be easily obtained.

Second embodiment of the present invention FIG. 4 (a) (b) (c)
Explained by. For the sake of explanation, the scale of each drawing is different.

FIG. 4A is a perspective view of the oxygen sensor S2 of this embodiment.

In this embodiment, as in the first embodiment, as shown in the perspective view of FIG. 4B, a core material 102 having four grooves 101, an inner electrode 103, an outer electrode 104 and a heating element 105 are provided. It is covered with the solid electrolyte layer 106. The inner electrode 103 and the outer electrode 104 are opposed to each other via the solid electrolyte layer 106 as shown in the BB end view of FIG. The inner electrode 103 corresponds to the groove 101. The inner electrode 103 and the heating element 105, which are provided on the inner surface of the solid electrolyte layer 106, are each subjected to through-hole processing to form the inner electrode terminal 1.
10 and the heating element 111. Also, the outer electrode 1
04 is connected to the outer electrode terminal 112.

The core material 102 used in this embodiment is made of Al ₂ O ₃ and has a diameter of 4.
It has a cylindrical shape with a content of 5 mm and a length of 40 mm, and has four grooves 101 having a width of 1.0 mm and a depth of 0.7 mm. Further, one end thereof has a substantially conical shape as shown in FIG.

The core material 102 can be easily manufactured by extrusion molding. That is, a cylinder having a groove having a predetermined width and a predetermined depth may be manufactured by extrusion molding, then the extrusion molded product may be cut into a predetermined length and one end may be molded into a substantially conical shape. In particular, if the extruded product is calcined before forming one end into a substantially conical shape, the strength of the extruded product increases and handling such as forming into a substantially conical shape becomes easy.

The solid electrolyte layer 106 is the same as that of the first embodiment except that the shape of the green sheet is different, and the material, the method of forming the electrode pattern, and the like are the same. The green sheet to be the solid electrolyte layer 106 is cut into 17 mm × 37 mm and then cut into both short side corners as shown in FIG.

Solid electrolyte layer 10 in which electrode pattern is formed on core material 102
As shown in FIG. 4 (C), the green sheet 6 becomes the groove 10
1 is wound and crimped so as to close the substantially conical side end portion. Then, by firing in the atmosphere, the oxygen sensor S2 shown in FIG. 4 (a) is obtained.

In the oxygen sensor S2 of this embodiment, the core material 102 is molded by extrusion molding, so that the core material 102 can be molded more easily than in the first embodiment.

Third embodiment of the present invention FIG. 5 (a) (b) (c)
Explained by. For the sake of explanation, the scale of each drawing is different.

FIG. 5A is a perspective view of the oxygen sensor S3 of this embodiment.

In the oxygen sensor S3 of this embodiment, as shown in FIG. 5B, unlike the first and second embodiments, the electrode pattern of the heating element 201 is formed so as to surround the inner electrode 202. Further, the number of the grooves 203 in this embodiment is three as shown in FIG. Further, as shown in FIG. 6, the position of the partition wall 205 provided in the core material 204 used in this embodiment is on the side far from the open end side of the groove 203, contrary to the first embodiment. Other parts are the same as those in the first embodiment, the outer electrode 206 faces the inner electrode 202 via the solid electrolyte layer 207, and the inner electrode 202, the outer electrode 206 and the heating element 201.
Are connected to the inner electrode terminal 208, the outer electrode terminal 209, and the heating element terminal 210, respectively. Since the oxygen sensor S3 of the present embodiment surrounds the inner electrode 202 with the heating element 201, the vicinity of the electrodes 202 and 206 can be easily brought to a predetermined temperature during measurement. Further, since the partition wall 205 of the core material 204 is near the root, the measurement gas enters the hollow portion of the core material 204, and the oxygen sensor S3 easily reaches the same temperature as the measurement gas temperature. The measurement can be performed immediately after the engine is started.

FIG. 7 (a) (b) (c) about the 4th Example of this invention.
Explained by. For the sake of explanation, the scale of each drawing is different.

FIG. 7A is a perspective view of the oxygen sensor S4 of this embodiment.

The oxygen sensor S4 of this embodiment uses a core material 304 including a core portion 301 and a groove forming body 303 forming a groove 302 as shown in FIG. 7B.

The other parts are almost the same as in the third embodiment, and the core member 304
Is an inner electrode 305, a heating element 306, an outer electrode 307,
It is covered with a solid electrolyte layer 311 provided with an inner electrode terminal 308, a heating element terminal 309, and an outer electrode terminal 310.

This example is made of Al ₂ O ₃ and has a diameter of 3.0 mm and a length of 40 m.
m core part 301 is formed by extrusion molding, and 9.5 m
Alumina green sheet having a size of mx 37 mm and a thickness of 0.7 mm was used as the groove forming body 303, and the groove 3 having a size of 1.0 mm x 30 mm was used.
Two pieces of 02 are provided and wound around the core portion 301 to form the core material 304, and thereafter, a green sheet to be the solid electrolyte layer 311 having the electrode pattern provided on the core material 304 is wound and fixed by compression in the same manner as in the other examples. Although it may be manufactured by sintering, it is easier to place and press-bond the groove forming body 303 on the green sheet to be the solid electrolyte layer 311 in advance, and then wind the groove forming body 303 around the core portion 301 and press-fix.

In this embodiment, the groove 302 in the core material 304 is the groove molding 3
Since it is formed by 03, a plurality of changes can be easily made. Further, since the core portion 301 has a simple cylindrical shape, it can be easily molded.

[Advantages of the Invention] In the oxygen sensor of the present invention, the electrodes are provided at substantially equal intervals around the rod-shaped core material or are integrally provided by connecting them, so that the responsiveness and durability are improved. The feature is that there is little directionality in.

Further, since the solid electrolyte layer having the electrodes formed in advance is wound around the core material as the support having the grooves formed in advance,
The bar sensor is extremely easy to manufacture.

In particular, there are advantages that the formation of the reference gas introduction path and the formation of the electrodes and terminals are extremely easy, and the degree of freedom in the shape of the electrodes is large.

Moreover, since the core functions as a support, the solid electrolyte layer can be made to have a minimum thickness, and thus the expensive solid electrolyte can be saved.

Further, when a plurality of grooves are formed in the longitudinal direction and are formed at equal intervals on the outer periphery of the core body, and a plurality of pairs of front and back electrodes are provided in the solid electrolyte layer so as to correspond to the above grooves, the electrode material is saved. Also, in terms of maintaining the durability of the electrode, an oxygen sensor having no directionality can be obtained.

[Brief description of drawings]

1 (a) is a perspective view of the first embodiment of the present invention, FIG. 1 (b) is a perspective view for explaining it, and FIG. 1 (c) is an AA end view for explaining it. FIG. 2 is a partially cutaway view of a core material used therein, FIG. 3 is a partially cutaway view of an oxygen detection element using the same, FIG. 4 (a) is a perspective view of a second embodiment of the present invention, and FIG. (B) is a perspective view for explaining it, FIG. 4 (c) is a BB end view for explaining it, FIG. 5 (a) is a perspective view of a third embodiment of the present invention, and FIG. ) Is a perspective view for explaining it, FIG. 5 (C) is a C-C end view for explaining it, FIG. 6 is a partially cutaway view of a core material used for it, and FIG. 7 (A) is for explaining the present invention. 4 is a perspective view of the fourth embodiment, FIG. 7 (b) is a perspective view for explaining it, and FIG. 7 (c) is a D-D end view for explaining it. 1, 101, 203, 302 ... Groove 2, 102, 204, 304 ... Core material 3, 4, 103, 104, 202, 206, 305, 3
07 ... Electrodes 6, 106, 207, 311 ... Solid electrolyte layer

Claims (1)

[Claims] 1. A rod-shaped ceramic core material as a support having grooves formed on its outer peripheral surface, and an oxygen ion conductive material having at least a pair of electrodes which are wound and wrapped around the core body to form a pair on the front and back surfaces. And a solid electrolyte layer, and the surface-side electrode is formed so as to be distributed at substantially equal intervals in the winding direction, or is formed so as to connect electrodes that are distributed at substantially equal intervals to be integrated. Further, the oxygen sensor is characterized in that the back surface side electrode is arranged so as to form a reference gas introduction path with the groove of the core body.