JPH11183426A - Oxygen sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oxygen sensor capable of reducing dispersion in the performance of the sensor by fixing the locational relationship of the ventilating openings of a casing and a filter fixing member. SOLUTION: The fitting part 62 of the second outer tube 15 and the fitting part 66 of a filter fixing member 54 are shaped like the same octagon (radial cross-sectional shape) so that the fitting parts 62 and 66 are fitted with each other hardly with any gap in the case that the filter fixing member 54 is fitted over the second outer tube 15. Therefore, the inner ventilating opening 52 of the second outer tube 15 and the outer ventilating opening 67 of the filter fixing member 54 are matched at the same location in the case that in the case that the filter fixing member 54 is fitted over the second outer tube 15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oxygen sensor for detecting oxygen concentration in exhaust gas of an internal combustion engine or an oxygen sensor for detecting oxygen in a predetermined gas.

[0002]

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

Furthermore, recently, an oxygen sensor having a structure in which the inside of the oxygen sensor and the atmosphere side are communicated via a ventilation filter has been developed. The oxygen sensor with this structure is capable of quickly discharging such gases to the outside when any gas is generated inside the oxygen sensor or when exhaust gas enters the inside of the oxygen sensor. Is to ensure.

[0005]

However, when manufacturing an oxygen sensor having the above-described ventilation filter, as shown in FIG. 4, the outer periphery of a cylindrical casing P2 having an inner ventilation hole P1 is provided. Then, the cylindrical ventilation filter P3 is fitted, and then the cylindrical filter fixing member P5 provided with the outer ventilation hole P4 is externally fitted to the casing P2 so as to cover the outer periphery of the ventilation filter P3, and caulked. Therefore, the position of the inner ventilation hole P1 of the casing P2 and the position of the outer ventilation hole P4 of the filter fixing member P5 may be shifted.

In other words, when the ventilation filter P3 is fitted around the outer periphery of the casing P2, the position of the inner ventilation hole P1 of the casing P2 cannot be seen. Therefore, when the filter fixing member P5 is attached to the casing P2, the inner and outer ventilation holes P1 are removed. , P4 sometimes did not match.

In particular, since both the casing P2 and the filter fixing member P5 are cylindrical members, the filter fixing member P5 is easy to rotate.
There is a problem that the positions of P1 and P4 are easily shifted. Then, if the positions of the ventilation holes P1 and P4 are shifted, a variation occurs in the gas discharging ability, and as a result, the performance of the oxygen sensor varies.

The present invention has been made in view of the above problems, and has as its object to provide an oxygen sensor which can determine the positional relationship between the casing and the ventilation hole of the filter fixing member to reduce variations in sensor performance. And

[0009]

According to a first aspect of the present invention, there is provided a cylindrical casing accommodating an oxygen sensing element, and a rear end side of the casing (for example, a vent hole formed in a second outer cylinder). Part), an inner ventilation hole provided in the radial direction, a ventilation filter covering the inner ventilation hole and disposed on the outer peripheral side of the casing, and an outer ventilation hole corresponding to the inner ventilation hole. And a cylindrical filter fixing member that fits and is fixed to the casing while covering the outer peripheral side of the casing, wherein a fitting portion (for example, a fitting portion) between the casing and the filter fixing member includes: A rotation preventing mechanism for preventing rotation of the filter fixing member when fitted is provided, and the positions of the inner ventilation hole of the casing and the outer ventilation hole of the filter fixing member are set so that the casing and the filter fixing member are fitted. If you decide in advance And gist oxygen sensor, characterized in that set so that relationship.

In the present invention, since the rotation preventing mechanism is provided at the fitting portion between the casing and the filter fixing member, the filter fixing member does not rotate when the filter fixing member is fitted to the casing. Further, the positions of the inner ventilation hole of the casing and the outer ventilation hole of the filter fixing member are set so as to have a predetermined relationship when the filter fixing member is fitted to the casing. In such a case, the positions of the inner and outer ventilation holes are naturally determined.

That is, when the casing and the filter fixing member are fitted together, the positional relationship between the inner and outer ventilation holes is automatically determined, and the filter fixing member does not rotate. The position is always constant and does not shift. Therefore, even when a large number of oxygen sensors are manufactured, the ability to discharge gas through the ventilation holes can always be kept constant, so that the performance variation of the oxygen sensors is reduced.

The invention according to claim 2 is characterized in that the positions of the inner ventilation hole of the casing and the outer ventilation hole of the filter fixing member are set to coincide with each other when the casing and the filter fixing member are fitted. The gist is the oxygen sensor according to claim 1. The present invention exemplifies the formation position of the ventilation hole, by setting the position of the ventilation hole inside and outside the casing and the filter fixing member so as to match when the filter fixing member is fitted to the casing,
A suitable ventilation state can be realized. In other words, the ventilation holes become clogged, and, for example, generated gas and invading exhaust gas can be quickly discharged. Further, since the positions of the ventilation holes coincide, the diameter of the ventilation holes can be reduced, which contributes to downsizing of the ventilation filter and the like.

According to a third aspect of the present invention, the rotation preventing mechanism is formed in a polygonal shape in accordance with the shape of the fitting portion of the casing having a polygonal cross section in the radial direction and the shape of the fitting portion of the casing. 3. An oxygen sensor according to claim 1, wherein the oxygen sensor comprises a fitting portion of the filter fixing member.

The present invention exemplifies a rotation preventing mechanism, and the shape of the fitting portion between the casing and the filter fixing member is the same polygon. For example, when the shape of the fitting portion of the casing is an octagon, the shape of the fitting portion of the filter fixing member is the same as that of the octagon.
Make it square.

Therefore, once the filter fixing member is fitted into the casing, the filter fixing member does not rotate. However, at the stage before fitting, which side of the casing is to be matched with which side of the filter fixing member,
Since the filter fixing member is not fixed (unless some kind of matching mark or the like is used in particular), the positional relationship between the inner and outer ventilation holes is determined even when the filter fixing member is fitted in any rotational direction (for example, the matching is performed). It is desirable to provide inner and outer ventilation holes as shown in FIG.

For example, if one or a plurality of ventilation holes are provided for each side or each vertex, the positional relationship between the inside and outside ventilation holes is always kept constant regardless of how the filter fixing member is fitted. Because of the drop, the workability of the oxygen sensor assembling process is greatly improved. According to a fourth aspect of the present invention, the rotation preventing mechanism includes a concave portion or a convex portion formed at the fitting portion of the casing, and a convex portion or a convex portion formed at the fitting portion of the filter fixing member in accordance with the concave portion or the convex portion. And a concave portion. The gist of the oxygen sensor according to claim 1 or 2, wherein the oxygen sensor is constituted by:

The present invention exemplifies a rotation preventing mechanism. When a projection is provided at a fitting portion of a casing, the projection is locked at a fitting portion of a filter fixing member. A recess is provided. Conversely, when a concave portion is provided in the fitting portion of the casing, a convex portion locked in the concave portion is provided in the fitting portion of the filter fixing member.

This also prevents the rotation of the filter fixing member. In particular, in this case, there is no need to process the entire fitting portion of the casing and the filter fixing member into a polygon as in the third aspect, and thus there is an advantage that the processing is easy.

Here, as a material of the oxygen sensing element, ZrO _{2 in} which Y ₂ O ₃ or CaO is dissolved is a typical one, but other oxides of alkaline earth metals or rare earth metals are used. And a solid solution of ZrO ₂ may be used. Further, ZfO _{2 serving as} a base may contain HfO ₂ .

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an example (embodiment) of an oxygen sensor 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 ceramic casing 8 formed of talc, a metal casing 10 is provided, and the oxygen sensing element 2 penetrates the casing 10 while being electrically insulated from the casing 10.

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

Although not shown, the inner surface and the outer surface of the oxygen sensing element 2 are, for example, Pt
Are provided. A protector 11 is attached to one opening of the metal shell 9 so as to cover the distal end side of the oxygen sensing element 2 with a predetermined space therebetween. The protector 11 has a plurality of gas permeation ports 12 through which exhaust gas passes. Have been.

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
Are the connector part 34 of another terminal fitting 33 and the insulating tube 35
a and the external electrode connection portion 35
Through b, it is electrically connected to the electrode layer outside the oxygen sensing element 2.

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 filter assembly 16 will be described in detail.

As shown in FIG. 2, the filter assembly 16
Are a second outer cylinder (filter holding portion) 15 that is externally fitted to the first outer cylinder 14 and fixed by crimping, and a filter fixing member that is externally fitted to the second outer cylinder 15 and fixed by crimping ( (A protective cover) 54 and a ventilation filter 53 disposed between the second outer cylinder 15 and the filter fixing member 54.

Of these, the second outer cylinder 15 is
2 has a cylindrical shape that is connected substantially coaxially from the rear (upper side in FIG. 2) to the outside, the inside communicates with the inside of the first outer cylinder 14, and the wall (vent hole forming portion) 63 thereof. Has a plurality of ventilation holes (inner ventilation holes) 52.

The diameter of the second outer cylinder 15 is reduced stepwise from the distal end side (the lower part in FIG. 2), and the second outer cylinder 15 has the largest diameter from the distal end side and is fixed to the first outer cylinder 14 by caulking. A cylindrical large-diameter portion 61, an octagonal fitting portion 62 (in a radial cross section) to which the filter fixing member 54 is fitted, and an inner ventilation hole 52, and a ventilation filter 53 is fitted externally. It comprises a cylindrical ventilation hole forming portion 63 and a small-diameter portion 64 which is externally fitted to the elastic seal member 17 and fixed by caulking.

On the other hand, the filter fixing member 54 is
It has substantially the same shape as the upper structure so as to cover the upper structure of the outer tube 15, that is, to cover the fitting portion 62, the vent hole forming portion 63, and the small diameter portion 64 of the second outer tube 15. . Specifically, the diameter of the filter fixing member 54 is reduced stepwise from the distal end side, and is an octagon having the largest diameter from the distal end side and the same shape as the fitting portion 62 of the second outer cylinder 15. A fitting portion 66 having a diameter that can be fitted to the outside, a cylindrical ventilation hole forming portion 68 having a ventilation hole (outside ventilation hole) 67 and covering the outer periphery of the ventilation filter 53, And a small-diameter portion 69 which is externally fitted to the small-diameter portion 64 of the cylinder 15 and fixed by caulking.

The ventilation filter 53 is a cylindrical member which is externally fitted to the ventilation hole forming portion 63 of the second outer cylinder 15 and whose vertical position is determined by the stepped portion 55. 15 is disposed in the space between the vent hole forming portion 63 and the vent hole forming portion 68 of the filter fixing member 54,
It is fixed by caulking.

The ventilation filter 53 is formed by molding an unfired molded article of, for example, polytetrafluoroethylene (PTFE),
A porous fiber structure obtained by stretching in one or more directions at a heating temperature lower than the melting point of TFE (trade name:
For example, Gore-Tex (Japan Gore-Tex Co., Ltd.)
By this, permeation of liquid mainly composed of water such as water droplets is prevented,
In addition, the filter is configured as a water-repellent filter that allows transmission of gas such as air and / or water vapor.

In particular, in this embodiment, as shown in FIG. 3 (before assembly), the shape of the fitting portion 62 of the second outer cylinder 15 and the fitting portion 66 of the filter fixing member 54 are different from each other. The same octagonal shape (radial cross-sectional shape) is adopted so that when the fixing member 54 is externally fitted to the second outer cylinder 15, the respective fitting portions 62 and 66 are fitted with almost no gap. So
The inner ventilation hole 52 of the second outer cylinder 15 and the outer ventilation hole 67 of the filter fixing member 54 are used to connect the filter fixing member 54 to the second outer cylinder 1.
When they are fitted to the outside, their positions match.

More specifically, both the ventilation hole forming portion 63 of the second outer cylinder 15 and the ventilation hole forming portion 68 of the filter fixing member 54 correspond to the apexes of the polygons of the fitting portions 62 and 66, respectively. 4 vent holes 5 each, one at every other vertex
2, 67 are provided. Thus, when the filter fixing member 54 is externally fitted to the second outer cylinder 51, the positions of the inner and outer vent holes 52 and 67 match.

In the case of assembling, if the fittings are shifted by one vertex, the positions of the ventilation holes 52 and 67 do not coincide with each other. c) Next, among the methods for manufacturing the oxygen sensor 1, a method for forming the filter assembly 16, which is a main part of the present embodiment, will be described.

First, as shown in FIG. 1, the inner structure of the metal shell 9 and the first outer cylinder 14 and the lead wires 2 extending therefrom.
After the main parts of the oxygen sensor 1 such as 0 and 21 are formed, the second outer cylinder 15 is externally fitted from the rear end side of the first outer cylinder 14. Next, as shown in FIG. 3, the ventilation filter 53 is externally fitted from the rear end side of the second outer cylinder 15, and the ventilation filter 53 is arranged on the step 55.

Next, the filter fixing member 54 is covered from the rear end side of the second outer cylinder 15, and the outer peripheral side of the ventilation filter 53 is covered with the ventilation hole forming portion 68 of the filter fixing member 54. The filter fixing member 54 is
Of the fitting portion 66 is fitted outside. Thereby, the ventilation filter 5
3 is sandwiched between the ventilation hole forming portion 63 of the second outer cylinder 15 and the ventilation hole forming portion 68 of the filter fixing member 54. Further, since both fitting portions 62 and 66 are formed in a similar octagon, when the filter fixing member 54 is fitted to the second outer cylinder 15, the circumferential position of the filter fixing member 54 is determined. The rotation of the lever is prevented and
2 and the position of the outer ventilation hole 67 coincide. Next, fixing work by caulking is performed sequentially.

Specifically, as shown in FIG. 2, first, the large-diameter portion 61 of the second outer cylinder 15 is crimped from eight directions from the front end side, and the second outer cylinder 15 is attached to the first outer cylinder 14. Fixed to. Next, the fitting portion 66 of the filter fixing member 54 is swaged from eight directions corresponding to each side thereof, and the filter fixing member 54 is fixed at the fitting portion 62 of the second outer cylinder 15. Next, the upper and lower positions of the ventilation hole forming portion 68 of the filter fixing member 54 with the outer ventilation hole 67 interposed therebetween are annularly caulked (round caulking) to fix the ventilation filter 53. Thereby, the ventilation filter 5
3 is sandwiched between the ventilation hole forming portions 63 and 68 without any gap between the ventilation holes 52 and 67 in the vertical direction. Further, the small-diameter portion 69 of the filter fixing member 54 is swaged from eight directions, and the filter fixing member 54 and the second outer cylinder 1 are tightened.
5 is fixed to the elastic seal member 17.

In the oxygen sensor 1 of this embodiment manufactured in this manner, the fitting portion 62 of the second outer cylinder 15 and the fitting portion 66 of the filter fixing member 54 are similarly octagonal.
In addition, inner and outer ventilation holes 52 and 67 are provided corresponding to the vertices of the polygon (for each one). Therefore, the second outer cylinder 1
Only by fitting the filter fixing member 54 to the position 5, the positions of the inner ventilation hole 52 and the outer ventilation hole 67 can be easily matched.

That is, when the filter fixing member 54 is fitted to the second outer cylinder 15, the positional relationship between the ventilation holes 52 and 67 is automatically determined.
4 does not rotate, so that the positions of the inside and outside vent holes 52 and 57 are always constant and do not shift. Therefore, even when a large number of oxygen sensors 1 are manufactured, the ability to discharge gas through the ventilation holes 52 and 67 can always be kept constant, so that there is a remarkable effect that variations in performance of the oxygen sensors 1 are reduced. To play.

Further, in this embodiment, since the positions of the inner ventilation hole 52 and the outer ventilation hole 67 are easily matched, the ventilation state can be suitably maintained. 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.

(1) In the above-mentioned embodiment, the filter fixing member and the fitting portion of the second outer cylinder are formed in a polygonal shape to prevent the rotation of the filter fixing member.
On the filter fixing member side, for example, a concave portion or a convex portion extending linearly in the axial direction is provided so as to be easily fitted, and the second outer cylinder side is similarly linearly formed in the axial direction so as to fit therewith. An extending convex portion or concave portion may be provided. In addition, you may provide a convex part in a dot shape instead of a linear shape.

(2) In the above embodiment, the position of the vent hole is
Although one is set for every two vertices of the polygon, one (or plural) may be set for each vertex, or one (or plural) may be set for each side. In this case, there is an advantage that the position of the ventilation hole does not shift even if the fitting is shifted by one vertex during the assembling operation.

(3) The connection between the second outer cylinder and the filter fixing member is not limited to caulking, and various methods such as welding can be adopted. (4) Further, as a caulking procedure, the caulking of the second outer cylinder and the filter fixing member and the caulking of the ventilation filter portion may be performed simultaneously.

[0047]

As described above in detail, in the first aspect of the present invention, since the rotation preventing mechanism is provided at the fitting portion between the casing and the filter fixing member, the casing and the filter fixing member are fitted. In such a case, the relationship between the positions of the inner and outer vents is automatically determined, and the filter fixing member does not rotate, so that the positions of the inner and outer vents are always constant and do not shift. Therefore, even when a large number of oxygen sensors are manufactured, the ability to discharge gas through the ventilation holes can always be kept constant, so that the performance variation of the oxygen sensors is reduced. In addition, there is an advantage that the work of matching the ventilation holes is facilitated.

According to the second aspect of the present invention, a suitable ventilation state is realized by setting the positions of the ventilation holes inside and outside the casing and the filter fixing member so as to coincide with the case where the filter fixing member is fitted to the casing. it can. Also,
The diameter of the ventilation hole can be reduced, which contributes to downsizing of the device.

According to the third aspect of the present invention, the shape of the fitting portion between the casing and the filter fixing member is the same polygon. Therefore, the fitting operation is easy, and once the filter fixing member is fitted to the casing, the filter fixing member does not rotate.

According to the fourth aspect of the present invention, when a convex portion is provided at the fitting portion of the casing, a concave portion is provided at the fitting portion of the filter fixing member to lock the convex portion. When a concave portion is provided in the fitting portion, a convex portion locked in the concave portion is provided in the fitting portion of the filter fixing member. This also has the advantage that the rotation of the filter fixing member can be prevented and the processing is 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 around a filter assembly according to the embodiment.

FIG. 3 is an explanatory view showing a state before assembling a second outer cylinder and a filter fixing member of the embodiment.

FIG. 4 is an explanatory view showing a filter assembly before improvement.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Oxygen sensor 2 ... Oxygen detecting element 10 ... Casing 14 ... 1st outer cylinder (main cylinder) 15 ... 2nd outer cylinder (filter fixing part) 16 ... Filter assembly 52 ... Inner ventilation hole (venting hole) 53 ... Ventilation filter 54: Filter fixing member (protective cover) 62, 67 ... Fitting part 63, 68 ... Vent formation part 67: External vent (vent)

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shoji Akatsuka 14-18 Takatsuji-cho, Mizuho-ku, Nagoya-shi, Aichi Japan Special Ceramics Co., Ltd.

Claims (4)

[Claims] 1. A cylindrical casing for accommodating an oxygen sensing element, an inner vent provided radially at a rear end of the casing, and an outer peripheral side of the casing covering the inner vent. And a tubular filter fixing member having an outer vent hole corresponding to the inner vent hole, covering an outer peripheral side of the vent filter, and being fitted and fixed to the casing. An oxygen sensor comprising: a rotation prevention mechanism for preventing rotation of the filter fixing member when fitted in a fitting portion between the casing and the filter fixing member; An oxygen sensor, wherein the positions of the pores and the outer ventilation holes of the filter fixing member are set so as to have a predetermined relationship when the casing and the filter fixing member are fitted. Sa. 2. The method according to claim 1, wherein the position of the inner ventilation hole of the casing and the position of the outer ventilation hole of the filter fixing member are set to coincide with each other when the casing and the filter fixing member are fitted. The oxygen sensor according to claim 1, wherein 3. The rotation preventing mechanism, wherein the fitting portion of the casing having a polygonal cross section in a radial direction is formed in a polygonal shape in accordance with the shape of the fitting portion of the casing. The oxygen sensor according to claim 1, further comprising: a fitting portion of the filter fixing member. 4. The rotation preventing mechanism comprises: a concave portion or a convex portion formed at a fitting portion of the casing; and a convex portion formed at a fitting portion of the filter fixing member in accordance with the concave portion or the convex portion. The oxygen sensor according to claim 1, wherein the oxygen sensor comprises: a portion or a concave portion.