JP2000131270A - Gas sensor - Google Patents

Abstract

(57) [Problem] To provide a gas sensor capable of efficiently flowing outside air into a casing while a ceramic separator has a sufficient axial cross-sectional area for inserting a lead wire. SOLUTION: The oxygen sensor is arranged such that a first portion 18a of a main body portion 75 of a ceramic separator formed with a plurality of separator side lead wire insertion holes 72 penetrating in an axial direction enters inside a filter holding portion 51. Is done. And a shape in which the axial cross section of the first portion 18a is not circular,
For example, it is formed in a polygonal shape such as a square shape. The gap 92 between the outer peripheral surface of the ceramic separator 18 and the inner surface of the filter holding portion 51 is locally expanded by making the axial cross-sectional outer shape of the main body portion 75 of the ceramic separator 18 deviate from the circle in this manner. Can be. This allows
While the ceramic separator 18 has a sufficient axial cross-sectional area for inserting lead wires, the outside air can be efficiently circulated into the casing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an oxygen sensor, an HC sensor,
The present invention relates to a gas sensor such as a sensor or a NOx sensor for detecting a component to be detected in a gas to be measured.

[0002]

2. Description of the Related Art Conventionally, a gas sensor as described above has a structure in which a rod-shaped or cylindrical detection element having a detection portion for detecting a component to be detected formed at the tip is disposed inside a metal casing. It has been known. For example, in the case of a gas sensor using the atmosphere as a reference gas, such as an oxygen sensor, it is necessary to provide an atmosphere introduction unit in a casing that houses the detection element or a filter support cylinder connected to the rear end of the casing. Such an air introduction portion can be formed by, for example, forming a gas flow hole in the casing or the rear end side wall of the filter support cylinder, and covering this with a water-repellent filter. In addition, a rubber grommet lead wire insertion hole that seals a lead wire outlet may be used as an air introduction portion. In this case, the atmosphere is introduced into the casing through a gap formed between the covering material that covers the outside of the lead wire and the lead wire insertion hole.

[0003]

By the way, in the above-mentioned gas sensor, in order to prevent the lead wires from the detection element and the heater from short-circuiting, a ceramic separator having a lead wire insertion hole is formed by a casing. (Or a filter support cylinder) in many cases. The ceramic separator is formed in a cylindrical shape corresponding to the casing (or the filter support cylinder), and is usually arranged inside the rear end of the casing (or the filter support cylinder) on the lead wire lead-out side. On the other hand, at the rear end of the casing (or the filter support tube), the above-described air introduction portion is formed, and formed between the outer peripheral surface of the ceramic separator and the inner peripheral surface of the casing (or the filter support tube). The gap often provides a path for the introduced atmosphere. However, in consideration of the recent trend of reducing the size of the sensor, it is desirable that the outer diameter of the casing (or the filter support cylinder) be as small as possible, and that there is sufficient space between the ceramic separator and the casing (or the filter support cylinder). Securing gaps is becoming increasingly difficult. In this case, it is conceivable to reduce the outer diameter of the ceramic separator in order to increase the gap. However, there is a limit in reducing the size of the ceramic separator, as long as the basic function of preventing the short circuit of the lead wire is secured.

An object of the present invention is to provide a gas sensor capable of efficiently flowing outside air into a casing while allowing a ceramic separator to have a sufficient axial sectional area for inserting a lead wire. is there.

[0005]

Means for Solving the Problems and Action / Effect In order to solve the above problems, a first configuration of a gas sensor according to the present invention comprises a shaft-shaped detection element and a cylindrical casing for housing the detection element. Arranged in the axial direction of the casing,
A plurality of lead wire insertion holes into which the respective lead wires from the detection element are respectively inserted have a columnar-shaped ceramic separator formed to penetrate in the axial direction, and the ceramic separator is orthogonal to the axis. A plane,
An inscribed circle and a circumscribed circle centered on the geometric center of gravity of an outline of an arbitrary cut surface (hereinafter, referred to as an outline forming axis cross section) in which the outline of the ceramic separator is represented by a continuous single outline. When drawing a virtual reference circle located between the inscribed circle and the circumscribed circle, a part of the outline of the contour forming axis cross section is located inside the reference circle, It is characterized in that another part is located outside the reference circle.

The point of the above configuration is that the outline of the cross section of the contour forming axis of the ceramic separator deviates at least partially from the circular shape. FIG. 8 shows an example in which the outline SH of the cross-section forming shaft section of the main body is square, and an inscribed circle IC and an circumscribed circle OC centered on the geometric center G of the outline SH. Are drawn, and the reference circle SC is drawn between them. It can be seen that a part of the outline SH is located inside the reference circle SC and the other part is located outside. This is not limited to the case where the outer shape line SH has a square shape, but is inevitably satisfied if the shape is at least partially deviated from a circular shape (polygon, ellipse, etc.).

That is, in the configuration of the conventional gas sensor,
The ceramic separator has, without exception, a circular shape with a contoured shaft, and as described above, there is a limit to expanding the gap between the ceramic separator and the inner surface of the filter support cylinder. However, in the present invention, by breaking the common sense and deviating the outline of the contour forming axis cross section of the ceramic separator from a circle, the gap between the outer peripheral surface of the ceramic separator and the inner surface of the casing or the filter support cylinder is locally localized. It can be expanded dynamically. Accordingly, the outside air can be efficiently circulated into the casing while the ceramic separator has a sufficient axial sectional area for inserting the lead wire.

When the ceramic separator has, for example, a column-shaped main body and a flange-shaped separator-side support protruding from the outer peripheral surface of the main body,
The outline of the cross section of the outline forming axis may be at least one of the outline of the main body and the outline of the separator-side support.

A second configuration of the gas sensor according to the present invention comprises a detection element having an axial shape, a cylindrical casing accommodating the detection element, and a rear end outside the casing. A filter support cylinder provided substantially coaxially, and a plurality of lead wire insertion holes which are arranged in the axial direction of the filter support cylinder and through which respective lead wires from the detection element are respectively inserted are formed penetrating in the axial direction. And a columnar-shaped ceramic separator, a flange-shaped separator-side support portion is formed on the outer peripheral surface of the ceramic separator, and on the rear end side of the filter support cylinder behind the separator-side support portion, A filter that blocks liquid permeation and allows gas permeation is disposed, and a gas communication portion is formed in the separator-side support portion in the axial direction.

[0010] In this specification, the side of the detection element that faces the front end in the axial direction is the “front side (front end side)”, and the side that faces the opposite direction is the “rear side (rear end side)”. And

As described above, the flange-like separator-side support portion is formed on the outer peripheral surface of the ceramic separator, and the rear side of the separator-side support portion and the rear end side of the filter support cylinder prevent liquid from permeating. By arranging a filter that allows gas permeation and forming a gas communication part in the separator-side support part in the axial direction, the outside air introduced from the filter is separated from the gas communication part formed in the separator-side support part in the axial direction. And smoothly and speedily led into the casing. In addition, since a filter that blocks the permeation of liquid and allows the permeation of gas is arranged, for example, when mounted on an exhaust pipe close to the undercarriage of the vehicle, it can be used when running in rain or when washing the car. External air can be introduced even when water droplets are injected. Therefore, the outer diameter of the gas sensor can be reduced without impairing the performance of the sensor.

The gas communication portion can form a part of a flow path of the outside air from the filter to the inner front end of the casing along the outer peripheral surface of the ceramic separator. In this way, when the outside air introduced from the filter can be guided to the inner front end side of the casing through the shortest circulation path, circulation of the outside air serving as the reference gas is promoted,
The ventilation performance is improved, and the gas concentration can be accurately detected.

Further, according to the present invention, the outline of the contour forming shaft section in the separator-side support portion has a polygonal shape, and the gas communication portion has an inner surface of the filter support cylinder and a separator-side support portion including the outline. It can be formed between the outer peripheral surface. In this case, the gap between the outer peripheral surface of the separator-side support portion and the inner surface of the filter support cylinder can be locally expanded, and the amount of outside air flowing into the casing can be secured. In addition, since the outline of the cross section of the contour forming axis is polygonal, it is possible to form a uniform outside air flow state in the circumferential direction.

Further, the gas communication portion of the present invention can be formed in a flat surface or a groove shape on the outer peripheral surface of the separator side support portion, or can be formed in a hole shape penetrating the separator side support portion. In any case, since the gas communication portion can be integrally formed at the time of molding the ceramic separator, the production is easy and inexpensive.

Regarding the first or second configuration of the gas sensor of the present invention, the following embodiment is also conceivable. That is, on the rear end side of the casing, a cylindrical filter holding portion having one or more gas inlet holes formed in a wall portion, and a gas inlet hole of the filter holding portion are arranged so as to close the gas inlet hole. The filter has a filter that blocks the permeation of gas and allows gas to pass therethrough, and a gas introduction structure for introducing outside air into the casing through the gas introduction hole and the filter is formed.The main body of the ceramic separator is arranged in the axial direction of the detection element. The rear side is disposed so as to enter the inside of the filter holding portion, and a gap formed between the outer peripheral surface of the main body portion and the inner peripheral surface of the filter holding portion forms an outside air passage toward the inner front end side of the casing via the filter. It can also form part of a distribution channel.

Further, another embodiment as follows is also conceivable.
That is, the ceramic separator is formed with a flange-shaped separator-side support portion protruding from the outer peripheral surface at an axially intermediate position of the main body portion, and the main body portion has a casing located at a position axially forward of the separator-side support portion. In the state of being inserted inside the rear end portion, the separator-side support portion directly or indirectly abuts the rear end surface of the casing via another member, while the rear portion in the axial direction projects outside the casing. And the projecting portion is covered by a filter holding portion formed in a cylindrical shape separate from the casing, and further, on the separator-side support portion, from the inside of the filter holding portion to the inside of the casing. May be formed in the axial direction to allow the gas to flow.

[0017]

Embodiments of the present invention will be described below with reference to embodiments shown in the drawings. FIG. 1 shows the internal structure of an oxygen sensor as an embodiment of the gas sensor of the present invention. The oxygen sensor 1 includes an oxygen detection element (detection element) 2 which is a hollow shaft-shaped solid electrolyte member having a closed end, and a heating element 3. The oxygen detecting element 2 is formed hollow by an oxygen ion conductive solid electrolyte mainly composed of zirconia or the like. A metal casing 10 is provided outside the oxygen detecting element 2.

The casing 10 includes a metal shell 9 having a screw portion 9b for mounting the oxygen sensor 1 to a mounting portion such as an exhaust pipe, and a main body 9 connected to one opening of the metal shell 9 so that the inside communicates with the opening. A cylinder 14 is provided with a protector 11 attached to the metallic shell 9 from the side opposite to the main cylinder 14 and the like. As shown in FIG. 2, a pair of electrode layers 2 b, which are made of, for example, Pt or a Pt alloy, are formed on the inner and outer surfaces of the oxygen detection element 2 so as to cover almost the entire surface.
2c is provided.

Returning to FIG. 1, the above-mentioned main cylinder 14 is crimped to the opening on the rear side of the metal shell 9 via a ring 15 between the main cylinder 14 and the insulator 6. The assembly 16 is fitted and fixed from the outside.
The rear end opening of the filter assembly 16 is sealed with a grommet 17 made of rubber or the like, and a ceramic separator 18 is further provided further inward. Then, lead wires 20 and 21 for the oxygen detecting element 2 and a lead wire (not shown) for the heating element 3 are arranged so as to penetrate the ceramic separator 18 and the grommet 17.

Next, as shown in FIG. 3, a plurality of separator-side lead wire insertion holes 72 (lead wire insertion holes) through which the respective lead wires 20 and 21 are inserted are passed through the ceramic separator 18 in the axial direction. A flange-like separator-side support portion 73 is formed at an intermediate position in the axial direction so as to protrude from the outer peripheral surface. The ceramic separator 18 is provided with a separator-side support portion 73.
In a state in which the portion located on the front side is inserted inside the rear end of the main cylinder 14, the separator abuts against the rear end face of the main cylinder 14 at the separator-side support portion 73 and is rearward of the separator-side support portion 73. It is arranged in a state where a portion located on the side protrudes outside the main cylinder 14.

Returning to FIG. 1, one lead wire 20 for the oxygen detecting element 2 is electrically connected to the above-mentioned electrode layer 2c (FIG. 2) inside the oxygen detecting element 2 via a fixing bracket 23. I have. On the other hand, the other lead wire 21 is connected to another fixing bracket 33.
Through the electrode layer 2b (FIG. 2) outside the oxygen detection element 2. The oxygen detecting element 2 is activated by being heated by the heating element 3 arranged inside.
The heating element 3 is a rod-shaped ceramic heater. When a heating section 42 having a resistance heating wire section (not shown) is energized through a lead wire (not shown), the tip of the oxygen detection element 2 (detection section) is detected. Part).

Next, as shown in FIG. 3, the filter assembly 16 has a cylindrical shape which is substantially coaxially connected to the main cylinder 14 (casing 10) from the rear outside, and the inside of the main cylinder 14 is formed. A filter holding section 51 (filter support cylinder) is provided which communicates with the outside and has a plurality of gas introduction holes 52 formed in a wall portion. Then, the filter holding unit 5
A cylindrical filter 53 that closes the gas introduction hole 52 is disposed outside the filter 1, and one or more auxiliary gas introduction holes 55 are formed in the wall outside the filter 53. An auxiliary filter holding unit 54 for holding the filter 53 sandwiched between the filter holding unit 51 and the filter 53 is provided. Specifically, the gas introduction hole 52 and the auxiliary gas introduction hole 55 are spaced from each other at predetermined intervals along the circumferential direction with respect to the filter holding portion 51 and the auxiliary filter holding portion 54 at a positional relationship corresponding to each other at the axial intermediate portions. Is formed of
The filter 53 is arranged so as to surround the filter holder 51 in the circumferential direction. The filter 53 prevents permeation of a liquid mainly composed of water such as water droplets by, for example, a porous fiber structure of polytetrafluoroethylene (trade name: for example, Gore-Tex (Japan Gore-Tex Co., Ltd.)). In addition, the filter is configured as a water-repellent filter that allows the transmission of gas such as air and / or water vapor. Each of the main cylinder 14 and the filter holding part 51 has a cylindrical shape.

As shown in FIG. 4, the auxiliary filter holder 5
In FIG. 4, annular filter caulking portions 56 and 57 (hereinafter, also simply referred to as caulking portions 56 and 57) are formed on both sides in the axial direction of the row of the auxiliary gas introduction holes 55. The auxiliary filter holding unit 54 is connected to the filter holding unit 51 by the caulking units 56 and 57 with the filter 53 interposed therebetween. Further, a gap 58 is formed between the outer surface of the filter holding portion 51 and the filter 53. On the other hand, the filter holding portion 51 has a stepped portion 60 formed at an intermediate portion in the axial direction of the filter holding portion 51. The second portion 62 is configured to be smaller in diameter than the first portion 61. The gas introduction hole 52 is provided in the second part 6.
2 is formed on the wall. Further, the auxiliary filter holder 54 has an inner diameter smaller than the outer diameter of the first portion 61 of the filter holder 51.

Returning to FIG. 3, the filter holding portion 51 allows the protruding portion of the ceramic separator 18 to enter and cover the inside of the second portion 62, and at the stepped portion 60 to the separator-side support portion 73 with respect to the main portion. It is arranged to be in contact with the cylinder 14 via the metal elastic member 74 from the opposite side. On the other hand, the filter holding portion 51 is disposed so as to overlap with the main cylinder 14 (casing 10) from the outside at the distal end side, that is, the first portion 61, and the filter holding portion 51 is provided at the overlapping portion. A casing caulking portion 76 that is connected to the casing 14 in an airtight state is formed.

Outside the auxiliary filter holding portion 54, a cylindrical protective cover 64 is provided so as to cover it.
The protective cover 64 is arranged so as to form a gas retaining space 65 as shown in FIG. 3, and is joined to the filter holding portion 51 by crimping portions 66 and 67. In addition,
As shown in FIG. 4, the first portion 61 of the filter holding portion 51
A plurality of grooves 69 serving as a gas introduction portion into the protective cover 64 are formed at predetermined intervals along the circumferential direction on the outer peripheral surface of the protective cover 64.

Returning to FIG. 3, the ceramic separator 18
In the axial direction of the oxygen detection element 2, the rear side enters the inside of the filter holding portion 51, and the front side also
It is arranged so as to enter the inside of the (casing 10),
Each of the lead wires 20, 21 and the like is inserted in the separator side lead wire insertion hole 72 in the axial direction. On the other hand, grommet 1
7 is resiliently fitted inside the rear opening 51a of the filter holding portion 51, and the lead wires 20, 21
And the like, and a seal-side lead wire insertion hole 91 for inserting the same, and seals between the outer surfaces of the lead wires 20 and 21 and the inner surface of the filter holding portion 51.

The rear end face of the ceramic separator 18 is located rearward of the gas introduction hole 52 in the axial direction, and the gap defining projection 9 formed at the center of the rear end face.
The top surface of 6 is in close contact with the front end surface of the grommet 17.
A predetermined amount of gap 98 is formed between the grommet 17 and the ceramic separator 18 by the gap defining protrusion 96. The gap defining protrusion 96 may be formed not on the ceramic separator 18 but on the front end surface of the grommet 17. Also, a gap 9 is provided between the inner peripheral surface of the filter holding portion 51 and the outer peripheral surface of the ceramic separator 18.
2 are formed. Then, the gas from the gas introduction hole 52 is supplied into the gap 92, and is further guided into the casing 10 through a gas introduction portion 93 formed in the ceramic separator 18. Specifically, the ceramic separator 18 is formed with an axial ventilation through-hole 95 separately from the separator-side lead wire insertion hole 72, and one end thereof communicates with the through-hole 95 on the rear end surface thereof. The ventilation groove 9 whose other end is open to the outer peripheral surface of the ceramic separator 18
4 are formed. That is, these ventilation through holes 9
5 and the ventilation groove portion 94 form a gas introduction portion 93.

Returning to FIG. 1, a cylindrical protector mounting portion 9a is formed in the front opening of the metal shell 9, and the distal end side (detection portion) of the oxygen detection element 2 is separated by a predetermined space. A cap-shaped protector 11 is mounted to cover. The protector 11 is formed with a plurality of gas transmission ports 12 through which the exhaust gas passes.

In the oxygen sensor 1, the atmosphere as the reference gas is introduced through the filter 53 of the auxiliary filter holding section 54 as described above, while the gas detection port 12 of the protector 11 is provided on the outer surface of the oxygen detection element 2. The exhaust gas introduced through the oxygen sensor comes into contact with the oxygen detection element 2, and an oxygen concentration cell electromotive force is generated in the oxygen detection element 2 according to the difference in oxygen concentration between the inner and outer surfaces. Then, the oxygen concentration in the exhaust gas is detected by extracting the electromotive force of the oxygen concentration cell from the electrode layers 2b and 2c (FIG. 2) through the leads 21 and 20 as a detection signal of the oxygen concentration in the exhaust gas. it can.

The main cylinder 14 of the filter assembly 16
Is assembled as follows, for example. That is, as shown in FIG. 14A, the metal elastic member 74 is extrapolated into the ceramic separator 18, and the front end side of the ceramic separator 18 is inserted into the main cylinder 14. On the other hand, the filter assembly 16 is pre-assembled as shown in FIG. 4, and this is assembled in the filter holding portion 51 of the ceramic separator 18 as shown in FIG.
And cover from outside the main cylinder 14. Note that the oxygen detection element 2
The heating element 3 and the like (FIG. 1) are assembled in the main cylinder 14 in advance, and the lead wires 20 and 21 therefrom are passed through the separator-side lead wire insertion hole 72 of the ceramic separator 18 (FIG. 3). The filter holding portion 51 is extended outward from the rear end opening.

Subsequently, as shown in FIG. 14B, an axial compressive force is applied to the main cylinder 14 and the filter assembly 16. Thereby, the metal elastic member 74 is compressed and deformed between the filter holding portion 51 and the separator-side support portion 73 of the ceramic separator 18, and the ceramic separator 18 is pressed.
Is generated between the main cylinder 14 and the filter holding portion 51. Then, while maintaining this state, a casing caulking portion 76 is formed between the filter holding portion 51 and the main cylinder 14 as shown in FIG. Next, as shown in FIG. 14D, the rubber grommet 17 is fitted into the rear end side opening of the filter holding portion 51, and further, the protective cover 64 is covered, and as shown in FIG. And 67 are formed, and the assembly of the oxygen sensor 1 is completed.

Next, as shown in FIG. 5A, the main body 75 of the ceramic separator 18 has a shape deviating at least partially from a circular shape, specifically, a square cross-sectional outer shape. I have. In the present embodiment, the main body 75 (hereinafter also referred to as FIG. 3) is a portion (hereinafter, referred to as a first portion) 18 that enters the second portion 62 of the filter holding portion 51.
a and a portion (hereinafter, referred to as a second portion) 18b that enters the inside of the main cylinder 14, and at least the first portion 18a has a quadrangular prism shape, as shown in FIG. 7A. A gap 92 between the filter holding portion 51 and the inner surface thereof.
Can be secured relatively large, and smooth circulation of outside air can be secured. The main body 75
May be formed in a columnar shape. In addition, in FIG. 5A, the gap defining protrusion 96 is also in the shape of a quadrangular prism, but it may be in the shape of a cylinder or other shapes.

Here, in the oxygen sensor 1 of the present embodiment, as shown in FIG. 3, a cylindrical filter holding portion 51 having a gas introduction hole 52 formed in a wall portion is provided outside the rear end of the casing 10. A (filter support cylinder) is coaxially covered on the casing 10 from the rear side. In the filter assembly 16, a filter 53 that blocks liquid permeation and allows gas permeation is disposed so as to cover the gas introduction hole 52 of the filter holding unit 51.
To form a gas introduction structure for introducing outside air into the casing 10. Also, the ceramic separator 18
Is arranged such that the first portion 18a on the rear side enters the inside of the filter holding portion 51,
A gap 92 formed between the outer peripheral surface of the first portion 18a (main body portion 75) and the inner peripheral surface of the filter holding portion 51
It is configured to form a part of a flow path of the outside air guided into the casing 10 through the filter 53. In this configuration, the air flows first from the filter 53 into the gap 92 that is sufficiently wide, so that the flow of the outside air in the casing 10 can be further smoothed.

The rear end face of the main body 75 of the ceramic separator 18 is located on the rear side of the gas introduction hole 52 provided in the filter holding portion 51. It is formed penetrating in the axial direction. In this case, the outside air introduced from the gas introduction hole 52 is
It is guided to the tip of the detection element 2 through the gap 92, and the circulation route is as follows. In other words, the introduced outside air flows from the gap 92 to the rear side of the ceramic separator 18, and further flows to the inside front end side of the detection element 2 through the ventilation hole 95. Since the main body portion 75 (the first portion 18a thereof) of the ceramic separator 18 has a polygonal shape, a smooth gas flow through the gap 92 is realized.

Here, as shown in FIGS. 5 (a) and 3, the ceramic separator 18 has four lead wires on the separator side for inserting lead wires from the oxygen detecting element 2 and the heating element 3. The holes 72 are formed such that their centers are arranged on a virtual circumferential path (separator-side pitch circle) C1. In addition, the through hole 95 for ventilation is formed at the center of the ceramic separator 18.
It is formed in a region surrounded by these four separator-side lead wire insertion holes 72. Further, the ventilation groove 94
Are formed in a cross shape on the rear end face of the ceramic separator 18 at positions not interfering with the four separator side lead wire insertion holes 72. The front end face of the grommet 17 is in contact with the ceramic separator 18 at the opening position of the ventilation hole 95, but since the ventilation groove 94 is formed, the flow of gas from the gap 92 to the ventilation hole 95 is prevented. Nothing.

In FIG. 3, the grommet 17 is formed with the seal-side lead wire insertion holes 91 arranged so as to be positioned on the seal-side pitch circle, and the separator-side pitch circle (diameter D1) described above. And the seal-side pitch circle (diameter D2) are set such that one of them has a larger diameter than the other. For example, in FIG. 3, D1> D2, and as shown in FIG. 5A, the gap defining protrusion 96 is positioned inside the separator-side lead wire insertion holes 72 arranged on the separator-side pitch circle. It is formed in the region to be. In this case, each lead wire has a grommet 17
Bend occurs between the grommet 17 and the ceramic separator 18, but since the gap 98 is formed between the grommet 17 and the ceramic separator 18 based on the gap defining protrusion 96, the lead wire is used when the sensor 1 is assembled. Is hardly bent, so that troubles such as pain and disconnection hardly occur. In addition, even if a pressing force in the axial direction acts on the grommet 17, the movement of the grommet 17 is stopped by the gap defining protrusion 96, so that the gap amount is hardly changed, and strong bending or the like on the lead wire is prevented. .

Next, FIG. 7 shows the ceramic separator 18.
The example in which the axial cross-sectional shape of the body part 75 of FIG. FIG. 7 (a) is a rectangular prism-shaped one already shown,
(B) is an example of a triangular prism shape, and (c) is an example of a hexagonal prism shape. As can be seen from this, when the axial cross-sectional outer shape of the main body 75 is a polygon, the shape becomes closer to a circle as the number of sides increases, so the gap 92 between the filter holding portion 51 (and the second portion 62 thereof) is formed. The effect of enlargement is not noticeable. On the other hand, as for the separator-side pitch circle, when there are four lead wires, for example, the pitch circle may be too small in the triangular prism shape shown in FIG. Therefore, it can be said that a quadrangular prism shape that can ensure a sufficiently large pitch circle while securing a sufficient gap 92 is more preferable as the shape of the main body 75 of the ceramic separator 18.

In this case, if the gas introduction holes 52 are provided corresponding to each side of the axial cross section of the main body portion 75, gas can be efficiently introduced into the gap 92 between the ceramic separator 18 and the filter holding portion 51. Can be. In addition, by chamfering or rounding each ridge portion, problems such as damage to the casing during assembly are reduced.

FIG. 9 shows an example in which the axial section of the main body 75 has a shape other than a polygon. (A) is an example in which a pair of flat portions 75a, 75a that are substantially parallel to each other are formed by notching both sides of an axis of a circular axis cross section. On the other hand, (b) is an example in which the axial cross section is made elliptical.

Next, the ceramic separator 18 shown in FIG. 5 (b) does not have the gas introduction portion 93 including the ventilation groove 94 or the ventilation through hole 95 as shown in FIG. 5 (a). Further, a gap defining protrusion 96 is formed at the center of the rear end surface of the ceramic separator 18. In this case, as shown in FIG.
An air gap 99 (see FIG. 6) is formed along the circumferential direction between the lead wire 2 and each of the lead wires 20, 21, and the like. It is configured to be guided to the detection element 2 through the passing gap 99. In this case, the labor for forming the gas introduction portion 93 is omitted, and the groove 94 and the like that straddle the gap defining protrusion 96 are not formed as shown in FIG. 5A, so that the shape is simple and the manufacturing is easy. is there.

In the ceramic separator 18 shown in FIG. 5 (b), as shown in FIG. 5 (c), a ventilation groove 94 is formed from the outer peripheral edge of the rear end face toward each separator side lead wire insertion hole 72. It may be formed. This allows
The flow of the outside air to the detection element 2 (FIG. 1) inside the casing is performed more effectively.

FIGS. 10 to 13 and FIG. 15 show modified examples of the separator-side support portion 73 of the ceramic separator 18. The ceramic separator 18 shown in FIG.
By retracting the inner side of the opening inner edge 14a of the (casing 10), the shielding state of the opening by the separator-side support portion 73 is partially eliminated, thereby allowing the outside air to flow into the main cylinder 14. 80 (gas communication part)
Are formed in the axial direction. Each withdrawal distribution section 80
Are formed in a flat surface shape. Thereby, the main cylinder 14
A relatively large gap 81 is formed between the inner edge 14a of the opening and the outer edge of the separator-side support portion 73, so that smoother gas flow can be ensured. Here, the separator-side support portion 73 is formed in a shape of a plurality of flat surface-like recessed flow portions 80 formed on the outer peripheral surface thereof so as to be continuous in the circumferential direction, thereby forming a polygonal shape (square shape in the present embodiment). It has an outer shape. Thereby, the separator-side support portion 7
In the circumferential direction 3, a more uniform gas flow state can be formed.

As shown in FIG. 11, a groove-like recessed flow portion 83 (gas communication portion) may be formed on the outer peripheral surface of the separator-side support portion 73. FIG.
Is a separator-side support portion 73 instead of the recessed flow portion.
This is an example in which an air hole 84 (gas communication portion) penetrating through in the axial direction is formed. Further, as shown in FIG.
(A) The main body 75 may be formed in a columnar shape.

Next, the ceramic separator 18 shown in FIG. 15 has a flange-like separator-side support portion 73 formed on the outer peripheral surface on the rear end side in the axial direction so as to integrally and outwardly project over the entire circumference. ing. In the rear end face of the ceramic separator 18, a ventilation groove 100 (gas communication portion)
Are formed in a direction not orthogonal to the axis in a cross shape at positions not interfering with the four separator-side lead wire insertion holes 72, and the respective ventilation grooves 100 reaching the outer periphery of the rear end face are turned at right angles from there, It extends axially forward along the outer peripheral surface of the support portion 73.

FIG. 16 shows an example of an oxygen sensor incorporating the ceramic separator of FIG. The cylindrical outer cylinder member 101 (filter support cylinder) has a large diameter at the front side in the axial direction, and is fitted to the metal shell 9 (casing 10) from the outside. On the other hand, the rear side in the axial direction of the outer cylinder member 101 is formed to have a small diameter, the ceramic separator 18 is accommodated therein, and the grommet 17 is fitted into the rear end opening. The outer cylinder side support portion 102 of the outer cylinder member 101 receives and supports the separator side support portion 73 of the ceramic separator 18. A central through hole 17b is provided at the radial center of the grommet 17, and this central through hole 1b is provided.
A filter 53 is fitted in 7b. The ventilation surface of the filter 53 is provided on the end surface at the rear end, and a cylindrical filter support member 53a is fitted into the cylindrical peripheral surface from the inside.

In the oxygen sensor 1 shown in FIG. 16, the air as the reference gas is supplied to the ventilation end face of the filter 53 → the ventilation groove 73 of the ceramic separator 18 → the radial gap S1, between the outer cylinder member 101 and the ceramic separator 18. S2 → the inner surface of the oxygen detecting element 2 via the hollow portion 2a (the inner electrode layer 2
c) (see arrow R in FIG. 16). Note that FIG.
In FIG. 6, the same reference numerals are given to the same parts as those in FIG. 3 or 6, and the description is omitted.

In each of FIGS. 10 to 13 and FIG. 15, the gas communication portion (retracted flow portion 83, air hole 84, or ventilation groove 100) is provided at a predetermined interval along the circumferential direction of the separator side support portion 73. , And are formed in the axial direction. Therefore, this gas communication part is provided with the filter 53.
And a part of a flow path of the outside air flowing toward the front end side of the inside of the casing 10 along the outer peripheral surface of the ceramic separator 18. In the case where the gas communication portion is formed in the separator-side support portion 73 as described above, the gas flow portion (for example, the gas passage groove 94 or the gas passage hole in FIG. 3) penetrating the main body 75 of the ceramic separator 18 in the axial direction. The hole 95 or the ventilation gap 99 in FIG. 6 may not be particularly formed (for example, see FIGS. 15 and 16).

The structure of the sensor of the present invention described above, the gas sensor other than oxygen sensor, for example, HC sensor and NO _X
The same can be applied to sensors and the like.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an oxygen sensor as one embodiment of a gas sensor of the present invention.

FIG. 2 is an enlarged cross-sectional view showing the oxygen detection element portion.

FIG. 3 is an enlarged sectional view showing a main part of FIG. 1;

FIG. 4 is a front partial cross-sectional view of the filter assembly.

FIG. 5 is a perspective view showing a ceramic separator together with a modified example thereof.

FIG. 6 is an enlarged sectional view of an oxygen sensor using the ceramic separator of FIG. 5 (b).

FIG. 7 is a cross-sectional view showing a contour forming axis cross-sectional shape of a main body of a ceramic separator together with a modified example thereof.

FIG. 8 is a view for explaining the characteristics of the outline of the contour forming shaft cross-sectional shape of the main body.

FIG. 9 is a cross-sectional view showing some further modified examples of the contour forming shaft cross-sectional shape of the main body.

FIG. 10 is a perspective view showing a first modified example of the separator-side support portion of the ceramic separator, and a diagram for explaining the characteristics of the outline of the contour forming shaft cross-sectional shape of the separator-side support portion.

FIG. 11 is a perspective view showing a second modified example.

FIG. 12 is a perspective view showing a third modification.

FIG. 13 is a perspective view showing a fourth modified example.

FIG. 14 is an explanatory view of a process of assembling the filter assembly.

FIG. 15 is a perspective view showing a fifth modification of the separator-side support portion of the ceramic separator.

FIG. 16 is an enlarged sectional view of an oxygen sensor using the ceramic separator of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Oxygen sensor (gas sensor) 2 Oxygen detection element (detection element) 10 Casing 16 Filter assembly (gas introduction structure part) 18 Ceramic separator 51 Filter holding part (filter support cylinder) 52 Gas introduction hole 53 Filter 72 Separator side lead wire insertion hole (Lead wire insertion hole) 73 Separator-side support part 75 Main body part 80, 83 Retraction flow part (gas communication part) 84 Air hole (gas communication part) 92 Gap 95 Gas through hole 100 Vent groove (gas communication part) 101 Outer tube member (filter support tube)

Claims (7)

[Claims] 1. A detection element having an axial shape, a cylindrical casing accommodating the detection element, and a plurality of leads arranged in the axial direction of the casing and through which respective lead wires from the detection element are respectively inserted. A column-shaped ceramic separator in which a line insertion hole is formed penetrating in the axial direction, the ceramic separator being a plane orthogonal to the axis and having a single external shape continuous with the ceramic separator; Draw an inscribed circle and a circumscribed circle centered on the geometric center of gravity for an outline of an arbitrary cut plane (hereinafter, referred to as a contour forming axis cross section) represented by an outline, and further draw the inscribed circle and the circumscribed circle When a virtual reference circle located in the middle of the circle is drawn, a part of the outline of the cross section of the contour forming axis is located inside the reference circle, and another part is located outside the reference circle. Specially Gas sensor. 2. The gas sensor according to claim 1, wherein the ceramic separator has a polygonal outer shape line in the cross section of the contour forming axis. 3. A detection element having an axial shape, a cylindrical casing accommodating the detection element, a filter support cylinder provided substantially coaxially with respect to the casing outside a rear end of the casing. A plurality of lead wire insertion holes, each of which is arranged in the axial direction of the filter support cylinder and through which each lead wire from the detection element is inserted, has a columnar ceramic separator formed so as to penetrate in the axial direction. A flange-shaped separator-side support portion is formed on an outer peripheral surface of the ceramic separator, and a liquid permeation is prevented and a gas permeates behind the separator-side support portion toward the rear end of the filter support cylinder. A gas sensor, wherein an allowable filter is disposed, and a gas communication portion is formed in the separator side support portion in the axial direction. 4. The gas sensor according to claim 3, wherein the gas communication portion forms a part of a flow path of outside air from the filter to a front end side inside the casing along an outer peripheral surface of the ceramic separator. 5. The separator-side support section, wherein the contour-forming shaft section of the separator-side support section has a polygonal outer shape, and the gas communication section includes an inner surface of the filter support cylinder and the outer shape line. The gas sensor according to claim 3, wherein the gas sensor is formed between an outer peripheral surface of the portion. 6. The gas sensor according to claim 3, wherein the gas communication portion is formed in a flat surface or a groove shape on an outer peripheral surface of the separator-side support portion. 7. The gas sensor according to claim 3, wherein the gas communication portion is formed in a hole shape penetrating the separator-side support portion.