JPH11190715A - Gas sensor and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oxygen sensor having an excellent heat resistance by improving an operability and a sensor performance and a method for manufacturing it. SOLUTION: Body metal fittings locking part 44 annularly protruding in a radially inward side is provided at a front end side of a body metal fitting 9. A rear end face 44a of the locking part 44 is formed in a tapered state. A protector side locking part 46 annually protruding in a radially outside is provided at a rear end side of a protector 11. The locking part 46 is formed in an obliquely tapered state similar to the end face 44a of the locking part 44. The locking part 46 us disposed between a ceramic holder 7 and the locking part 44, and hence performs a function as a buffer material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an oxygen sensor for detecting an oxygen concentration in exhaust gas of an internal combustion engine, an oxygen sensor for detecting oxygen in a predetermined gas, a NOx sensor for detecting a NOx concentration in a gas, and the like. The present invention relates to various gas sensors and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, various oxygen sensors have been developed as gas sensors for use in, for example, air-fuel ratio control of internal combustion engines such as automobile engines. In recent years, in particular, in order to cope with environmental protection problems such as air pollution caused by exhaust gas, demand for a high-performance and long-life oxygen sensor for detecting the oxygen concentration in the exhaust gas is increasing.

[0003] For example, as a typical example of such an oxygen sensor, an oxygen detecting element (formed in a hollow shaft with a closed end) made of an oxygen ion conductive solid electrolyte such as ZrO ₂ is used. Oxygen sensors are known. In this oxygen sensor, the oxygen sensing element is housed in a cylindrical metal casing, the outer periphery of the tip of the oxygen sensing element is brought into contact with the atmosphere to be detected (exhaust gas), and the atmosphere as a reference gas is introduced into the inner space. Then, the oxygen concentration in the exhaust gas is measured by the electromotive force of the oxygen concentration cell generated in the oxygen sensing element.

[0004] In the above-described oxygen sensor, a cap-shaped protector is attached to the distal end side of the casing to protect the oxygen detecting element. Therefore, the exhaust gas does not directly reach the oxygen detection element, but is indirectly guided to the oxygen detection element via a gas transmission port provided in the protector.

The following method is known as a method for fixing this protector to the distal end of a casing. As shown in FIG. 5 (a), a talc P4 and a ceramic holder P5 are arranged between a metal shell P2 constituting a casing P1 and an oxygen detecting element P3, and a cushion material is provided on both upper and lower sides of the ceramic holder P5. Metal plate packings P6 and P7 are arranged. Further, an annular fixing portion P8 is provided by extending the distal end side of the metal shell P2. A rear end P of the cap-shaped protector P9 is attached to the fixing portion P8.
10, the rear end portion P10 is welded to the fixing portion P8, and the protector P9 is joined to the metal shell P2.

[0006] As shown in FIG.
Between the metal shell Q2 and the oxygen sensing element Q3
The talc Q4 and the ceramic holder Q5 are arranged, and the plate packings Q6 and Q7 are arranged as cushioning materials. Further, the distal end side of the metal shell Q2 is extended to form an annular fixing portion Q.
8 is provided. A rear end portion Q (extending outward) of the cap-shaped protector Q9 is provided inside the fixed portion Q8.
After disposing 10, the fixing portion Q8 is bent inward and the rear end portion Q10 is crimped to fix the protector Q9 to the metal shell Q2.

[0007]

However, the above method is not always sufficient. For example, in the above-described method, a welding process is required, and accordingly, operations such as replacement of electrodes for welding are required. Also,
If the height (length in the axial direction) of the fixing portion P8 of the metal shell P2 is large, the flow of the exhaust gas is hindered by that much, which has a problem that the performance of the oxygen sensor is affected.

Further, in the above-mentioned method, it is necessary to work the front end of the metal shell Q2 into a shape suitable for caulking and caulking work. However, the front end of the oxygen sensor is exposed to high-temperature exhaust gas. During use, the crimped portion may be loosened or deteriorated due to oxidation. That is, the method has a problem in heat resistance.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an oxygen sensor which can improve workability and sensor performance and has excellent heat resistance, and a method for manufacturing the same.

[0010]

According to a first aspect of the present invention, there is provided a cylindrical casing for accommodating a gas detecting element (for example, an oxygen detecting element); And a cap-shaped protector that is disposed on the tip side) and covers the tip side of the gas detection element.
A casing-side engaging portion protruding radially inward, and a protector-side engaging portion formed at a rear end side of the protector and projecting radially outward, wherein the protector protrudes forward from the casing. The gas sensor is characterized in that the gas sensor is arranged so as to be locked at the protector side locking portion and the casing side locking portion.

In the present invention, since the casing-side engaging portion protruding inside the casing and the protector-side engaging portion protruding outside the protector are provided, the protector is inserted into the casing and mounted on the casing. In this case, the position of the protector can be determined by locking the protector-side locking portion to the casing-side locking portion.

With such a configuration, the conventional welding process is not required, and the work such as replacement of the welding electrode is not required. Therefore, the working process can be simplified. Further, since it is not necessary to extend the fixing portion from the front end side of the metal shell as in the related art, it is possible to ensure a sufficient flow of exhaust gas and to ensure high performance of the oxygen sensor. Furthermore, unlike the related art, it is not necessary to caulk the distal end side of the metal shell, so that the caulked portion does not loosen or deteriorate due to oxidation, and is excellent in heat resistance. In addition, in the present invention, since positioning can be performed only by inserting the protector into the casing, mounting work of the protector is extremely easy.

According to a second aspect of the present invention, the gas sensor according to the first aspect is characterized in that the protector is fixed in a state in which the protector is stressed inward from the casing by being pressed into the casing. And In the present invention,
The protector is pressed into the casing. And
By this press-fitting, the protector is fixed by receiving the stress from the casing. That is, since the protector can be firmly fixed simply by press-fitting the protector, the mounting work of the protector can be greatly simplified.

According to a third aspect of the present invention, the protector-side locking portion has a ring shape having a taper that is inclined toward a rear end side toward the outer peripheral side.
The gist is the gas sensor described in (1). The present invention exemplifies the shape of the protector, and the shape of the tapered protector-side locking portion allows the protector to be smoothly pressed into the casing.

According to a fourth aspect of the present invention, in the gas sensor according to any one of the first to third aspects, the protector-side locking portion is disposed between the casing-side locking portion and the ceramic ring. Make a summary. The present invention, as before,
A metal plate packing as a cushioning material is not disposed between the casing and the ceramic holder, but a protector-side locking portion is disposed between the casing-side locking portion and the ceramic ring. Packing can be omitted.
That is, in the present invention, since the protector side locking portion functions as a cushioning material, the plate packing and the mounting operation thereof can be omitted, and the configuration of the gas sensor and the manufacturing method thereof can be simplified.

According to a fifth aspect of the present invention, there is provided the gas sensor manufacturing method according to any one of the first to fourth aspects, wherein the protector is press-fitted from the rear end side of the casing with the tip end side of the protector first. The gist of the present invention is a method of manufacturing a gas sensor, wherein a tip side of a protector is projected from a tip side of a casing, and a position of the protector is determined by locking a protector-side locking portion and a casing-side locking portion.

According to the present invention, when manufacturing the gas sensor, the protector is press-fitted from the rear end side of the casing with the front end side of the cap-shaped protector first, and the front end side of the protector projects from the front end side of the casing. Let it. Then, the position of the protector is determined by locking the protector side locking portion and the casing side locking portion.

That is, simply by press-fitting the protector into the casing, the position of the protector can be determined and fixed, and the operation is extremely easy. Here, various sensors such as an oxygen sensor and a NOx sensor can be adopted as the gas sensor.

For example, the material of the oxygen sensing element of the oxygen sensor is ZrO ₂ in which Y ₂ O ₃ or CaO is dissolved.
Is a typical one, but a solid solution of ZrO ₂ and an oxide of another alkaline earth metal or rare earth metal may be used. Further, ZfO _{2 serving as} a base may contain HfO ₂ .

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, examples (embodiments) of a gas sensor and a method of manufacturing the same according to the present invention will be described. (Example) a) First, the overall configuration of the oxygen sensor of the present example will be described.

As shown in FIG. 1, the oxygen sensor 1 of this embodiment
Is a hollow shaft-shaped, for example, Zr having a closed end (the lower part in FIG. 1).
It comprises an oxygen sensing element 2 which is a solid electrolyte member mainly composed of O ₂ and a heating element 3 which is a shaft-shaped ceramic heater, and is constituted as an assembly of various members constituting their outer shells.

Outside the intermediate portion of the oxygen sensing element 2, ceramic holders 6, 7 made of insulating ceramic are provided.
And a metal casing 10 provided via the ceramic powder 8 formed of talc and the oxygen sensing element 2
Penetrates while being electrically insulated from the casing 10.

The casing 10 has a screw 9a (for example, made of stainless steel JIS SUS304) for mounting the oxygen sensor 1 to a mounting portion such as an exhaust pipe, and one opening of the metal shell 9. A first outer cylinder (main cylinder) 14 connected so that the inside communicates with the first cylinder;
The outer cylinder 14 is formed of a cylindrical second outer cylinder 15 which is fitted to the rear end side.

Although not shown, the inner surface and the outer surface of the oxygen sensing element 2 are, for example, Pt
Are provided. One opening of the metal shell 9 covers the distal end of the oxygen sensing element 2 with a predetermined space (for example, JIS S).
Protector 1 (comprising US310, SUS310S, etc.)
1, a protector 11 is formed with a plurality of gas permeation ports 12 for transmitting exhaust gas.

In the other opening of the metal shell 9, a first outer cylinder 14 is caulked with the ceramic holder 6 via a ring 30, and the first outer cylinder 14 is formed into a hollow cylindrical shape as a whole. Filter assembly (gas introduction structure) 1 formed
6 are fitted and fixed from the outside.

The opening on the upper end side of the filter assembly 16 is sealed with an elastic seal member 17 made of rubber or the like.
8 are provided. And the ceramic separator 1
The lead wires 20 and 21 for the oxygen sensing element 2 and the lead wire (not shown) for the heating element 3 are arranged so as to penetrate through the elastic member 8 and the elastic seal member 17.

One lead wire 20 for the oxygen sensing element 2
Is electrically connected to the electrode layer inside the oxygen sensing element 2 through the connector part 24 of the terminal fitting 23, the lead wire part 25 covered with the insulating tube 25 a, and the internal electrode connecting part 26 of the terminal fitting 23. ing. The other lead wire 21 is electrically connected to an outer electrode layer of the oxygen sensing element 2 through a connector portion 34 of another terminal fitting 33, a lead wire portion 35 covered with an insulating tube 35a, and an external electrode connection portion 35b. It is connected.

A pair of heater terminals 40 for supplying electricity to the heating element 3 are fixed to the rear end side of the heating element 3 (upper side in FIG. 1). Is supplied to a heating resistor circuit (not shown) embedded in the heater. b) Next, the configuration of the protector 11 as a main part of the present embodiment and the vicinity thereof will be described in detail.

As shown in FIG. 1 and FIG. 2 in which a main part thereof is enlarged, the ceramic holder 7 is provided with a step part 41 protruding inward from a central part thereof, and a rear end face of the step part 41 (FIG. Between the upper surface of the oxygen sensing element 2 and the flange portion 42 at the intermediate portion of the oxygen sensing element 2 as a cushioning material (for example, JIS SU
An annular plate packing 43 made of metal (comprising S310, SUS310S, etc.) is arranged.

The front end face (the lower face in FIG. 2) 7a of the ceramic holder 7 is formed in a tapered shape inclined at, for example, about 120 ° toward the rear end side toward the outer peripheral side. Also,
A metal shell side locking portion 44 having an inner diameter of 9.6 mm and projecting radially inward in a ring shape is provided on the distal end side of the metal shell 9. The rear end surface 44a of the metal shell side locking portion 44 is formed in a tapered shape with the same inclination as the front end surface 7a of the ceramic holder 7.

Further, as shown in FIG. 3, on the rear end side of the protector 11, an outer diameter φ11.
A 5 mm protector-side locking portion 46 is provided. The protector side locking portion 46 is provided with the metal shell side locking portion 4.
4 is formed in a tapered shape with the same inclination as the rear end surface 44a.

The protector side locking portion 46 is
As shown in FIG. 2, since the ceramic holder 7 is disposed between the front end face 7 a of the ceramic holder 7 and the rear end face 44 a of the metal shell side locking portion 44, it functions as a cushioning material.
At the same time, the protector-side locking portion 46 is locked by the metal shell-side locking portion 44, thereby exhibiting a function as a positioning material on the distal end side in the axial direction.

The cylindrical portion 1 of the protector 11
The outer diameter of 1a is slightly larger (for example, by 0.1 mm) than the inner diameter of the metal shell side locking portion 44. Therefore, when the protector 11 is pressed into the casing 10 (specifically, the metal shell 9), the inner peripheral surface 44 of the metal shell side locking portion 44 is formed.
At b, the outer peripheral surface 11b of the protector 11 is pressed inward in the radial direction, and is fixed under a stress.

C) Next, of the methods of manufacturing the oxygen sensor 1, a method of mounting the protector 11, which is a main part of the present embodiment, will be described. First, as shown in FIG. 4, a cap-shaped protector 11 is provided from the rear end side (upper side of the figure) of the metal shell 9.
Press-fit.

In this case, the metal shell 9 is fixed by a jig (not shown), and the cap-shaped protector 11 is disposed such that the tip side (the lower side in the figure) comes first. Then, a rod-shaped press-fitting member 51 is inserted from the rear end side of the protector 11, and the press-fitting member 51 is moved downward in FIG.
Is pressed downward in the figure.

Accordingly, the protector 11 is press-fitted to a position where the protector-side locking portion 46 is locked to the metal shell-side locking portion 44, and the inner peripheral surface 4 of the metal shell-side locking portion 44 is pressed.
4b, the outer peripheral surface 11b of the protector 11 is fixed in a state of being pressed inward in the radial direction.

Thereafter, the press-fitting member 51 is removed, and the components of the oxygen sensor 1, ie, the ceramic holder 7 and the plate packing 4, are successively arranged in a normal procedure as shown in FIG.
3. Oxygen sensing element 2, including heating element 3, ceramic powder 8, ceramic holder 6, ring 30, first outer cylinder 14.
And so on.

Thereafter, the rear end portion of the metal shell 9 is caulked by heat caulking to fix the above-described components, and then the filter assembly 16 and the like on the rear end side of the oxygen sensor 1 are formed. Thus, the oxygen sensor 1 is completed. In the oxygen sensor 1 of the present embodiment manufactured in this manner, the protector 11 is press-fitted from the rear end side of the metal shell 9 and fixed, so that the conventional welding process is unnecessary. Therefore, it is not necessary to replace the electrode to be welded, so that the working efficiency is improved and the cost is reduced.

Further, since there is no need to extend a fixing portion on the tip end side of the metal shell 9 as in the related art, there is an advantage that the flow of exhaust gas is hardly hindered and the performance of the oxygen sensor 1 is improved. This configuration is effective in improving the performance of the oxygen sensor, particularly when used in an oxygen sensor of a type in which the oxygen detection element 2 does not protrude much toward the exhaust gas.

Furthermore, unlike the conventional method, the front end of the metal shell 6 is not swaged at the extended portion, and there is no swaged portion directly exposed to the exhaust gas.
Of the protector 11 even if the tip side of the
The heat-resistant part is not damaged and the part to which it is attached is excellent.

Further, since the protector side locking portion 46 has a taper which is inclined toward the rear end side as it goes to the outer periphery, there is an advantage that the press-fitting operation is easy. Further, at the time of press-fitting, the protector side locking portion 46 is connected to the metal shell side locking portion 4.
At this point, the press-fitting operation may be completed at the time of locking to the position 4, and the position of the protector 11 can be automatically determined.

In addition, since the protector-side locking portion 46 is disposed between the metal shell-side locking portion 44 and the ceramic ring 7, it can function as a cushioning material. There is no need to arrange plate packing as a material. It should be noted that the present invention is not limited to the above-described embodiment at all, and it goes without saying that the present invention can be implemented in various modes without departing from the gist of the present invention.

For example, in the above embodiment, the protector was press-fitted into the metal shell. However, by adjusting the dimensions of the protector and the metal shell, the protector was simply inserted into the metal shell instead of press-fitting. The rear end may be fixed by caulking or the like.

[0044]

As described in detail above, according to the first aspect of the present invention, when the protector is inserted into the casing and mounted on the casing, the protector-side locking portion is locked to the casing-side locking portion. , The position of the protector can be determined. For this reason, the conventional welding process is not required, and the working process can be simplified. Further, since it is not necessary to extend the distal end side of the metal shell as in the related art, it is possible to ensure a sufficient flow of exhaust gas, and to ensure high performance of the oxygen sensor. Furthermore, since it is not necessary to caulk the tip side of the metal shell as in the past,
Excellent heat resistance. In addition, since the positioning can be performed only by inserting the protector into the casing, the mounting work of the protector is extremely easy.

According to the second aspect of the present invention, since the protector can be firmly fixed to the casing only by press-fitting the protector, the mounting work of the protector can be greatly simplified. According to the third aspect of the present invention, the shape of the tapered protector side locking portion allows the protector to be smoothly pressed into the casing.

According to the fourth aspect of the present invention, when the ceramic holder is used, the protector side locking portion functions as a cushioning material, so that the conventional plate packing and its mounting work can be omitted, and the configuration of the gas sensor and its gas sensor. The manufacturing method can be simplified. According to the fifth aspect of the invention, the position of the protector can be determined and fixed simply by press-fitting the protector into the casing, and the operation is extremely easy.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating an overall configuration of an oxygen sensor according to an embodiment.

FIG. 2 is an explanatory diagram showing an enlarged configuration of a protector and a mounting portion of the protector according to the embodiment.

FIG. 3 is a perspective view showing a protector of the embodiment.

FIG. 4 is an explanatory diagram showing a method of mounting the protector of the embodiment.

FIG. 5 is an explanatory diagram showing a conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Oxygen sensor 2 ... Oxygen detecting element 6, 7 ... Ceramic holder 9 ... Metal shell 10 ... Casing 11 ... Protector 44 ... Metal shell side locking part 46 ... Protector side locking part

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Koji Matsuo 14-18 Takatsuji-cho, Mizuho-ku, Nagoya-shi, Aichi Japan

Claims (5)

[Claims] 1. An oxygen sensor, comprising: a cylindrical casing for accommodating a gas detection element; and a cap-shaped protector disposed on a tip side of the casing and covering a tip side of the gas detection element. A casing-side locking portion formed on the distal end side of the protector and protruding radially inward, and a protector-side locking portion formed on the rear end side of the protector and protruding radially outward, the protector includes: A gas sensor, wherein the gas sensor is arranged so as to protrude from the inside of the casing toward the distal end, and is locked by the protector-side locking portion and the casing-side locking portion. 2. The gas sensor according to claim 1, wherein the protector is fixed in a state in which the protector is stressed inward from the casing by being pressed into the casing. 3. The gas sensor according to claim 1, wherein the protector-side locking portion has a ring shape having a taper that is inclined toward a rear end side toward the outer peripheral side. 4. The gas sensor according to claim 1, wherein the protector-side locking portion is disposed between the casing-side locking portion and a ceramic ring. 5. The method for manufacturing a gas sensor according to claim 1, wherein the protector is press-fitted from a rear end side of the casing with a front end side of the protector first. A method of manufacturing a gas sensor, comprising: projecting a distal end side of the protector from a distal end side of a casing, and locking the protector side locking portion and the casing side locking portion to determine a position of the protector.