JP2000241379A - Gas sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a sensor structure in which a ceramic separator is held stably inside a casing, in which the structure of a sensor as a whole is made simple and compact and in which an assembling man-hour can be reduced. SOLUTION: A separator-side support part 73 which protrudes outward is formed on the outer circumferential face of a ceramic separator 18. A protrusion 60A which is coupled to the separator-side support part 73 is formed on the inner face of a cover member 16. Thereby, the ceramic separator 18 can be held stably without being rattled. A rubber ring or a wave wasger (a spring washer), between the separator-side support part 73 and the cover member 16, which is required in conventional cases can be abolished. The number of components for this sensor is reduced, and a structure can be made simple and compact so as to contribute toward reducing its cost by reducing an assembling man-hour.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oxygen sensor,
The present invention relates to a gas sensor such as a C 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 an oxygen sensor, an axial oxygen detection element made of a solid electrolyte ceramic such as zirconia is arranged in a casing with a detection section at the tip protruding, and the element is moved as the detection section comes into contact with the gas to be measured. Is output to the outside via a lead wire.

By the way, in a conventional oxygen sensor,
For example, in many cases, a ceramic separator having a flange on the outer peripheral surface is inserted into a casing, and the outside thereof is further covered with a cylindrical cover member. In this case, for example, a support portion such as a step portion is provided on the cover member,
A rubber ring or a corrugated washer (spring washer) is interposed between the flange portion of the separator and the inner surface of the stepped portion of the cover member or between the flange portion of the separator and the casing, and the cover member is attached to the casing. By pressing in the axial direction, the flange portion of the separator is pressed between the end face of the casing and the support portion of the cover member, and in this state, the cover member is fixed to the casing by caulking. At this time, the corrugated washer generates a pressure holding force between the cover member and the casing by the elastic force of the ceramic separator, thereby preventing the separator from rattling in the casing.

[0004]

In recent years, demands for oxygen sensors have increased with the rise of the automobile industry, and demands for price reduction and compactness have been increasing year by year. The oxygen sensor has a large number of components among the electrical components for automobiles, and a review of the sensor structure requires a reduction in the number of components, a reduction in the size of the sensor, and a reduction in the number of assembly steps.
However, on the other hand, another problem has arisen, such as the increase in the volume ratio due to the miniaturization, which makes it difficult to secure a ventilation path for taking in oxygen (atmosphere) required for measurement.

An object of the present invention is to provide a gas sensor structure capable of simplifying and downsizing the entire structure of the sensor and reducing the number of assembly steps while stably holding the ceramic separator in a casing. is there.

[0006]

Means for Solving the Problems and Action / Effect To solve the above problems, a gas sensor according to the present invention comprises a shaft-like detection element and a detection section formed at the tip of the detection element. A cylindrical casing accommodating the detection element and a casing coaxially provided with the casing, and directly or indirectly via another member at a casing-side support portion formed at a rear end portion of the casing. A supported ceramic separator and a cover member arranged coaxially with the casing and connected from the rear side to the casing while covering the ceramic separator from the outside, the outer peripheral surface of the ceramic separator An outwardly protruding separator-side support portion is formed, while an inner surface of the cover member is provided with the ceramic support relative to the separator-side support portion. Wherein the protrusions contact the rear side in the axial direction of Kkusepareta is formed.

According to the present invention, the protrusion formed on the inner surface of the cover member is brought into contact with the separator-side support portion from the rear side in the axial direction of the ceramic separator, and the cover member and the casing-side support portion are brought into contact with each other. The separator-side supporting portion is clamped and held between the spaces. As a result, the ceramic separator can be stably held without rattling, and the rubber ring or corrugated washer (spring washer) between the separator-side support portion and the inner surface of the cover member, which has been conventionally required, can be eliminated. As a result, the structure can be simplified and downsized due to the reduction in the number of parts of the sensor, and the cost can be reduced by reducing the number of assembly steps. From the viewpoint of reducing the number of components, it can be said that a structure in which the casing-side support portion formed at the rear end of the casing directly supports the (separator-side support portion of) the ceramic separator without any intervening members.

[0008] The above-mentioned protruding portion can be formed on the inner surface of the stepped portion of the cover member. With this configuration, the casing-side support portion can be more stably supported by the stepped portion formed on the cover member, and the above-described protruding portion can be rationally formed using the stepped portion.

Further, in the above gas sensor, the casing and the cover member can be fixed in a state where the protrusion is elastically deformed via the separator-side support by the pressing of the casing-side support. Due to the elastic deformation of the protruding portion, the above-described holding force for holding against the separator-side support portion is increased, and the ceramic separator can be more stably supported.

In this case, the Vickers hardness Hvs of the protrusion is
Is preferably adjusted in the range of 150 to 300. Hvs
If the ratio is less than 150, excessive plastic deformation is likely to occur in the protruding portion, and it may not be possible to ensure a sufficient elastic clamping force. On the other hand, when Hvs exceeds 300, the rigidity of the protruding portion becomes too high, and the effect of holding pressure by elastic deformation may not be sufficiently achieved. In the cover member, when the Vickers hardness of the projecting portion is Hvs and the Vickers hardness of the main body portion is Hvh, Hvh is preferably 180 or more. If Hvh is less than 180, the strength of the cover member may be insufficient, and the durability of the sensor may not be secured. The hardness of the protrusion is preferably adjusted so that Hvh-Hvs becomes 50 or more. If Hvh-Hvs is less than 50, the amount of deformation of the protruding portion relative to the main body portion is insufficient, and the desired effect may not be sufficiently achieved.

The projecting portion can be constituted by a plurality of projections, and a gap can be formed between the projections. This gap can be used, for example, as a ventilation path for a reference gas (for example, the atmosphere). This makes it possible to secure a ventilation path for taking in the reference gas required for measurement while simplifying and reducing the size of the sensor structure and reducing the number of assembly steps.

In the gas sensor according to the present invention, the cover member is provided integrally with the rear side of the casing and has a first filter holding portion formed with a first gas introduction hole for guiding outside air into the casing; A second filter holding portion provided inside or outside the first filter holding portion and having a second gas introduction hole for guiding outside air into the casing, and between the first and second filter holding portions. The filter assembly can be configured as a filter assembly including a filter that is arranged so as to close the first and second gas introduction holes, and that prevents liquid permeation and allows gas permeation. in this case,
The first filter holding portion is connected to the casing from the rear side as a cylindrical body separate from the casing.

The gas sensor having such a structure can be manufactured by the following method. First, before being attached to the casing, the filter and the second filter holding portion are arranged outside the first filter holding portion in this order, and a crimping portion is formed in this state, whereby the second filter holding portion is formed. Then, the filter is assembled to the first filter holding portion to form a filter assembly. This filter assembly is attached to a casing as a cover member.

The gist of the above sensor configuration is that the ventilation structure including the filter is configured as a filter assembly independently of the casing, and this is connected to and integrated with the casing. Thereby, the following effects are achieved in the manufacturing method. Since the assembly of the filter assembly can be performed independently of the assembly of the oxygen sensing element or the like in the casing, for example, the lead wires of the sensing element do not interfere,
Assembly work can be performed extremely efficiently. Since the assembly of the components in the casing and the assembly of the filter assembly can be performed in parallel, the productivity is dramatically improved. Also, even if a filter assembly failure occurs, if a failure can be found at the stage of filter assembly,
The influence of the defect does not affect the finished sensor product, and waste of parts and the like hardly occurs.

In the above configuration, the flange-shaped separator-side supporting portion projecting from the outer peripheral surface at the axially intermediate position of the main body can be formed on the ceramic separator. In this case, the main body portion may be directly or at another position with respect to the rear end face of the casing at the separator-side support portion in a state where a portion located on the axial front side of the separator-side support portion is inserted inside the rear end portion of the casing. The filter holding member is disposed in such a manner that a portion on the axially rear side is protruded outside the casing while indirectly abutting via a member, and the protruding portion is formed in a cylindrical shape separate from the casing. Part can be covered. On the other hand, the outer peripheral surface of the separator-side support portion is retracted inward from the inner edge of the opening of the casing in the separator-side support portion, thereby partially eliminating the shielded state of the opening and allowing the outside air to flow into the casing. Allowable recessed portions can be formed. By forming the above-described recessed flow portion in the flange-shaped ceramic separator, in the casing, for example, through the gap between the protrusions on the cover member side and the recessed flow portion of the ceramic separator, the inside of the casing is formed. The outside air can be smoothly distributed.

[0016]

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 which is an embodiment of the gas sensor of the present invention.
Is an enlarged view of a main part. The oxygen sensor 1 includes an oxygen detection element 2 which is a hollow shaft-shaped solid electrolyte member having a closed end, and a heating element 3 inserted into a hollow portion 2a of the oxygen detection element 2. The oxygen detecting element 2 is formed hollow by an oxygen ion conductive solid electrolyte mainly composed of zirconia or the like. Further, a metal casing 10 is provided outside the intermediate portion of the oxygen detection element 2 via insulators 6 and 7 formed of insulating ceramic and ceramic powder 8 formed of talc. In the following description, the side (closed side) toward the axial end of the oxygen detection element 2 is referred to as “front side”, and the side toward the opposite direction is referred to as “rear side”.

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 an opening on the rear side of the metal shell 9 so as to communicate with the inside. It includes a cylinder 14, a protector 11 attached to cover a front opening of the metal shell 9, and the like. The oxygen sensor 1 of the present invention is located forward of the screw 9b (FIG. 1).
Is located in an engine such as an exhaust pipe, and the rear (upper in FIG. 1) is located in the outside atmosphere and used. As shown in FIG. 2, the outer surface of the oxygen detecting element 2 and the inner surface of the hollow portion 2a are formed on the outer electrode layer 2b and the inner electrode layer made of porous material such as Pt or Pt alloy so as to cover almost the entire surface. 2c is provided.

In the opening on the rear side of the metal shell 9, the main cylinder 14 (casing) is provided with a ring 15 between the main cylinder 9 and the insulator 6.
A cylindrical filter assembly 16 (cover member) is fitted and fixed to the main cylinder 14 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. And these ceramic separators 1
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 pass through the grommet 8 and the grommet 17.

A cylindrical protector mounting portion 9a is formed at the front opening of the metallic shell 9, and the oxygen detector 2
A cap-shaped protector 11 is attached so as to cover the front end side (detection unit) of the first case with a predetermined space therebetween. The protector 11 has a plurality of gas transmission ports 1 through which exhaust gas is transmitted.
2 are formed in a penetrating form.

The filter assembly 16 has a cylindrical shape that is substantially coaxially connected to the main cylinder 14 (casing 10) from the rear outside and has a plurality of gas introduction holes 52 formed in a wall. A holding section 51 is provided. Outside the first filter holding portion 51, a cylindrical filter 53 for closing the gas introduction hole 52 is arranged, and outside the filter 53, one or more gas introduction holes 55 are formed in a wall portion. Are formed, and the filter 53 is formed.
Is held between the first filter holding portion 51 and the second filter holding portion 54.

The grommet 17 is provided in the first filter holding section 5.
1 has a seal-side lead wire insertion hole 91 through which the respective lead wires 20, 21 and the like are inserted elastically inside the rear side opening, and the outer surfaces of the lead wires 20, 21 and the like. The space between the first filter holding portion 51 and the inner surface is sealed.

A plurality of separator-side lead wire insertion holes 72 for inserting the respective lead wires 20, 21 and the like are formed in the ceramic separator 18 so as to penetrate in the axial direction.
At an intermediate position in the axial direction, a flange-shaped separator-side support portion 73 is formed so as to protrude from the outer peripheral surface.
Then, as shown in FIG.
Allows the portion located on the front side of the separator-side support portion 73 to enter the main cylinder hole 90a inside the rear end of the main cylinder 14, and the front end face 73a of the separator-side support portion 73
By contacting the rear end surface (casing-side support portion 90), a portion located on the rear side of the separator-side support portion 73 is arranged so as to protrude outside the main cylinder 14.

One lead wire 20 for the oxygen detecting element 2
The internal electrode of the oxygen detecting element 2 described above passes through an internal electrode connecting metal member 23 (first connecting metal member) including a connector 23a, a lead wire portion 23b, a metal body main portion 23a, and a heating element grip portion 23d formed integrally with each other. It is electrically connected to the layer 2c (FIG. 2). On the other hand, the other lead wire 21 has a connector 33a and a lead wire portion 33b formed integrally with each other.
Electrode connection metal fitting 33 having a metal body 33c and a metal body 33c
Through the (second connection fitting), it is electrically connected to the external electrode layer 2b (FIG. 2) of 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, and includes a heating section 3a having a resistance heating wire section (not shown).
By being energized via lead wires (not shown) connected to the positive electrode side and the negative electrode side heating element terminal portions 3b, 3b,
The tip (detection section) of the oxygen detection element 2 is heated.

As shown in FIG.
The outer surface of the heating element 3 is gripped by the inner surface of the heating element grip portion 23d formed on the distal end side, and the inner electrode connection fitting 23 and the heating element are formed by contact between the outer surface of the fitting body 23c and the inner surface of the oxygen detection element 2. It serves to fix the position of the body 3 in the axial direction. One end of the lead wire portion 23b is
The connector 23a is integrated so as to be connected to one circumferential position of c, and the connector 23a is integrated at the other end.

The heating element grip 23d has a C-shaped cross-sectional shape surrounding the heating element 3. When the heating element 3 is not inserted, the heating element 3 has an inner diameter slightly smaller than the outer diameter of the heating element 3 and elastically expands with the insertion of the heating element 3 to grip the heating element 3 by its frictional force. I do.

The metal fitting body 23c surrounds the heating element 3 by bending a plate-like portion having a plurality of saw blade-like contact portions 23e formed on both left and right edges thereof into a cylindrical shape. (That is, the heating element 3 is inserted). Then, the internal electrode connection fitting 23 and the heating element 3 are hollowed by the frictional force between the outer peripheral surface and the contact portion 23e of the metal fitting main body 23c and the inner wall surface (the inner surface of the internal electrode layer 2c) of the hollow portion 2a of the oxygen detection element 2. In addition to the role of positioning in the axial direction with respect to the portion 2a, the plurality of contact portions 23
At each of the tips e, contact and conduction with the inner surface of the internal electrode layer 2c are made.

On the other hand, the external electrode connection fitting 33 has a cylindrical fitting body 33c and a lead wire 33b.
Is integrated with one end of the metal fitting body 33c in a circumferential direction, and a connector 33a is integrated with the other end. On the other hand, on the side opposite to the connection point of the lead wire portion 33b across the center axis, a slit 3 in the axial direction is provided.
3e is formed. The rear end of the oxygen detecting element 2 is inserted into the inside of the metal fitting body 33c from the inside in such a manner as to elastically push the oxygen detecting element 2 apart. Specifically, a conductive layer 2f as an external output extraction portion is formed in a strip shape along the circumferential direction at the rear end portion of the outer peripheral surface of the oxygen detection element 2. The external electrode layer 2b is formed by, for example, electroless plating.
The entire surface of the main part on the front end side of the engagement flange 2s of the oxygen detection element 2 is covered. On the other hand, the conductive layer 2f
For example, it is formed by pattern formation and baking using a metal paste, and is electrically connected to the external electrode layer 2b via the similarly formed connection pattern layer 2d in the axial direction.

The oxygen detecting element 2 of the bracket main body 33c
For example, if an insertion guide portion 33f that opens outward along the circumferential direction is formed in the opening on the insertion side, it is difficult for the insertion to be caught at the time of insertion and the assembly can be performed more smoothly. Further, for the same purpose, a chamfered portion 2g can be formed at the outer edge of the opening of the oxygen detection element 2.

FIG. 4 shows an assembled state of the filter assembly 16. Gas introduction hole 52 and gas introduction hole 55
Are formed at predetermined intervals along the circumferential direction with respect to the first filter holding portion 51 (cover member) and the second filter holding portion 54 at a position corresponding to each other at the intermediate portions in the axial direction. Is the first filter holding unit 51
Are arranged in a 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 first filter holder 51 and the second filter holder 54 has a cylindrical shape. Further, a filter 53 and a second filter holding portion 54 are arranged on the inner surface side of the first filter
May be pinched and held between the inner surface of the first filter holding portion 51 and the outer surface of the second filter holding portion 54.

The second filter holding portion 54 has a filter 5 on both sides in the axial direction with a row of gas introduction holes 55 interposed therebetween.
An annular filter caulking portion 56 that couples the second filter holding portion 54 to the first filter holding portion 51 through
A gap 58 is formed between the outer surface of the first filter holding portion 51 and the filter 53.
On the other hand, the first filter holding portion 51 has a stepped portion 60 formed at an intermediate portion in the axial direction of the first filter holding portion 51. As 62, the second portion 62 is configured to be smaller in diameter than the first portion 61, and the gas introduction hole 52 is formed in the wall of the second portion 62. Further, the outer diameter of the second filter holder 54 is formed smaller than the outer diameter of the first portion 61 of the first filter holder 51. A plurality of grooves 69 serving as a gas introduction part into the protective cover 64 are formed at predetermined intervals along the circumferential direction on the outer peripheral surface of the first portion 61 of the first filter holding part 51.

As shown in FIG. 2, the first filter holder 5
1 allows the rear projecting portion of the ceramic separator 18 to enter and cover the inside of the second portion 62,
The plurality of projections 60A (projections) provided on the inner surface of the stepped portion 60 are formed from the side opposite to the main cylinder 14 (that is, from the rear side of the separator-side support portion 73).
It is arranged so that it may contact. On the other hand, at the tip side of the first filter holding portion 51, that is, at the first portion 61, the main cylinder 1
4 (casing 10) is arranged from the outside so as to overlap therewith, and at the overlapping portion, a casing crimping portion 76 for connecting the first filter holding portion 51 to the main cylinder 14 in an airtight state. Are formed.

Outside the second 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 retention space 65 between the protective cover 64 and the second filter holding portion 54, and has an external communication port 68 on the front edge thereof over the entire circumference.
The outside air introduced from the external communication port 68 passes through the gap between the groove 69 formed on the outer peripheral surface of the first portion 61 of the first filter holding portion 51 and the protective cover 64 and enters the gas retaining space 65. Reach. The protective cover 64 is attached to the first filter holding portion 51 by two caulking portions 66 and 67 at the front and rear.
It is joined by. The front side caulking portion 66 overlaps the groove portion 69, but the groove portion 69 remains after caulking due to adjustment of the caulking force or the like.

The rear end face of the ceramic separator 18 is located rearward of the gas introduction hole 52 in the axial direction, and a predetermined gap 98 is formed between the grommet 17 and the ceramic separator 18. A gap 92 is also formed between the inner peripheral surface of the first filter holding portion 51 and the outer peripheral surface of the ceramic separator 18. Then, the gas from the gas introduction hole 52 is supplied into the gap 92, and is further guided into the casing 10 through the gap K formed between the separator-side lead wire insertion hole 72 and the lead wire.

In the oxygen sensor 1, the atmosphere as the reference gas is supplied from the external communication port 68 → the groove 69 → the gas retaining space 65.
→ gas introduction hole 55 → filter 53 → gas introduction hole 52 → gap 92 → gap 98 → gap K → hollow portion 2a (first ventilation path)
Through the oxygen detection element 2 (internal electrode layer 2c). On the other hand, the outer surface of the oxygen detecting element 2 has a protector 1
The exhaust gas introduced through the first gas permeation port 12 comes into contact with the oxygen gas, 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 electromotive force of the oxygen concentration cell is used as a detection signal of the oxygen concentration in the exhaust gas from the inner and outer electrode layers 2 c and 2 b (FIG. 2) to connect the fittings 23 and 3.
The oxygen concentration in the exhaust gas can be detected by extracting the gas through the lead wire 3 and the lead wires 20 and 21.

As shown in FIG. 5, the first filter holder 5
A plurality of (four in the figure) projections 60A (projections) are formed at predetermined intervals in the circumferential direction to protrude from the inner surface of the stepped portion 60 of one (cover member). Abuts (engages) on rear end face 73b of side engaging portion 73
In this state, the main cylinder 14 (casing) and the first filter holding portion 51 (cover member) are joined by the caulking portion 76 (see FIGS. 2, 4, and 8). The first filter holder 51 is made of, for example, stainless steel (for example, SUS3
04), and each projection 60A is formed in a hemispherical shape by, for example, press molding.

The Vickers hardness Hvs of the projection 60A is adjusted to, for example, 150 to 300. The protrusion 60A
The protrusions 60A can be configured to have a lower hardness than the cover member main body (in this case, the stepped portion 60) by local heating or the like. In this case, the protrusion 60A is relatively easily compressed and deformed, and the elasticity retaining effect by the spring action can be more effectively brought out. In this case, if the Vickers hardness Hvh of the main body is set to 180 or more, the hardness difference Hv
It is desirable that h-Hvs be 50 or more. * Since it is technically difficult, I tried to express it with the nuance "I can do it."

The projections 60A are provided at appropriate intervals (90 ° intervals in the figure), and when assembled, form a ventilation path between the projections 60A and the rear end face 73b of the separator-side engaging portion 73. Further, on the outer peripheral surface of the separator-side engaging portion 73, for example, the same number of cutouts 73c (recessed flow portions) as the protrusions 60A having a semicircular cross section are formed at an appropriate angle (45 in FIG.
Degree), a series of air passages are formed in communication with the gap between the projections 60A because they are provided shifted. That is, the first ventilation path (gas introduction hole 52 → gap 92) described above with reference to FIG.
The air branched off from the gap is formed by the gap formed by the protrusion 60A → notch 73
c (gap K ′) → main cylinder hole 90 a → separator-side lead wire insertion hole 72 → a second air passage of the hollow portion 2a is formed to complement the first air passage which has been narrowed due to downsizing of the sensor and the like.

The number and size of the protrusions 60A and the notches 73a can be appropriately increased and decreased.
Both may be made to match in the circumferential direction. As for the shape of the projection 60A, a fan-shaped projection 60B as shown in FIG.
Etc. can be appropriately changed. The same applies to (b) of the notch 73c.
It can be appropriately changed to a cylindrical hole 73d or the like.

Hereinafter, a method for manufacturing the oxygen sensor 1 will be described. First, as shown in FIG. 8A, the heating element 3 is inserted into the hollow portion 2a of the oxygen detection element 2 which has been assembled in the main cylinder 14 in advance, and the filter assembly 16 is inserted.
The first filter holding portion 51 is placed on the main cylinder 14, and the ceramic separator 18 is made to approach in the axial direction toward the rear end of the oxygen detection element 2. Thereby, the external electrode connection fitting 3
3 and the metal body 23c of the internal electrode connection metal 23 are positioned in the opening of the oxygen detection element 2. Then, in this state, the ceramic separator 18 is further moved in the axial direction toward the oxygen detecting element 2 while the rear end edges of the two metal fitting main bodies 33c and 23c are brought into contact with the front end surface of the ceramic separator 18.

As a result, as shown in FIG. 2, the rear end of the oxygen detecting element 2 is relatively pushed into the inside of the fitting main body 33c, and the fitting main body 23c is pushed into the inside of the oxygen detecting element 2. . At this time, both metal fitting main body parts 33
Since the rear end edges of c and 23c are in contact with the front end surface of the ceramic separator 18, smooth assembly can be achieved without causing drawbacks such as buckling of the lead wire portions 33b and 23b due to the axial pushing force. ing.

In FIG. 10B, the first filter holder 51 and the main cylinder 14 are pressed in the axial direction to compress and deform the projection 60A. Then, a casing caulking portion 76 is formed and the two are combined to complete the assembly. This projection 7
The elastic restoring force of 0 A acts as a clamping support force of the separator-side support portion 73, and contributes to preventing the ceramic separator 18 from rattling.

Instead of the intermittent protrusions 60A or 60B in the circumferential direction as shown in FIG. 5 or FIG. 6, a circumferential protrusion 60C can be formed as shown in FIG. In this case, the notch 7 is formed in the rear end face 73b of the separator-side support portion 73.
A groove 73e communicating with 3a may be provided, and air may be secured in the groove 73e.

The protrusion 60A can be formed by a method other than press working, for example, by welding or brazing a formed body. Further, the protrusion 60A may be subjected to a local softening heat treatment by electric heating or the like for adjusting the hardness. Further, instead of the notch 73a, for example, the first filter holding portion 51 and the separator-side support portion 73 have different cross-sectional shapes (for example, the former is circular, and the latter is rectangular), and a gap formed between the two is used for the ventilation path. You can also.

Hereinafter, reference inventions other than the invention described in the claims (hereinafter referred to as the claimed invention: described above with reference to FIGS. 1 to 8) will be described with reference to FIGS. It is described below.

The detection element 2 having an axial shape, a cylindrical casing 14 for accommodating the detection element 2 in a state in which a detection portion formed at the tip of the detection element 2 is projected, and a coaxial And a ceramic separator 18 supported directly or indirectly via another member at a casing-side support portion 90 formed at the rear end of the casing 14, and disposed coaxially with the casing 14. A cover member 51 connected to the casing 14 from the rear side while covering the ceramic separator 18 from outside, and a separator-side support portion 73 protruding outward is provided on the outer peripheral surface of the ceramic separator 18. A projection 73A is formed on the rear end surface 73b of the separator-side support portion 73 to engage with the inner surface of the cover member 51. There.

According to this configuration, a protrusion engaging with the inner surface of the cover member is formed at the rear end surface of the separator-side support portion, and the separator-side support portion is pressed between the cover member and the casing-side support portion. It was kept. As a result, the ceramic separator can be stably held without rattling, and the rubber ring or corrugated washer (spring washer) between the separator-side support portion and the inner surface of the cover member, which has been conventionally required, can be eliminated. As a result, the structure can be simplified and downsized due to the reduction in the number of parts of the sensor, and the cost can be reduced by reducing the number of assembly steps. From the viewpoint of reducing the number of parts, it can be said that a structure in which the casing-side support portion formed at the rear end of the casing directly supports the (separator-side support portion of) the ceramic separator without any intervening members.

At least one of the following requirements can be added to the above-mentioned reference invention. The projecting portion 73 </ b> A is a stepped portion 6 of the cover member 51.
0 is engaged with the inner surface. The casing 14 and the cover member 5 are pressed in a state where the protrusion 73A is elastically deformed via the separator-side support 73 by the pressing of the casing-side support 90.
1 is fixed. The protrusion 73A is composed of a plurality of protrusions, and a gap is formed between the protrusions. The operation and effect of each requirement addition are substantially the same as the case where the cover member-side protrusion 60A shown in FIG. 5 and the like is provided instead of the protrusion 73A.

In FIGS. 9 and 10, the same number of notches 73c (recess flow portions) as the protrusions 73A are formed on the outer peripheral surface of the separator side engaging portion 73, and the cutouts 73c are formed at an appropriate angle in the circumferential direction with respect to the protrusion 73A. Since it is provided shifted by 45 degrees in the figure, a series of ventilation paths is formed in communication with the gap formed by the projection 73A. The protruding portions are a hemispherical projection 73A, a fan-shaped projection 73
B, the wave-shaped continuous projection 73C and the like can be changed. Notch 7
3c can be modified in the same manner as the claimed invention.
In addition, parts common to the claimed invention are denoted by the same reference numerals, and detailed description is omitted.

The structure of the sensor of the present invention (or reference invention) described above can be similarly applied to a gas sensor other than the oxygen sensor, for example, an HC sensor or a NOx sensor.

[Brief description of the drawings]

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

FIG. 2 is a longitudinal sectional view showing a main part of the oxygen sensor of FIG. 1;

FIG. 3 is an exploded perspective view showing a state of being assembled to a ceramic separator.

FIG. 4 is a partial longitudinal sectional view of the filter assembly in an assembled state.

FIG. 5 is an exploded perspective view of the first filter holding portion 51 and the ceramic filter 18.

FIG. 6A is a bottom view showing another embodiment of the protruding portion, and FIG. 6B is a perspective view showing another embodiment of the ventilation path.

FIG. 7 is a perspective view showing still another embodiment of the protrusion and the ventilation path.

FIG. 8 is a process explanatory view showing one example of an assembling method of the oxygen sensor of FIG. 1;

FIG. 9 is a longitudinal sectional view showing a main part of the oxygen sensor according to the reference invention.

FIG. 10 is a perspective view of the ceramic separator of FIG. 9;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Oxygen sensor (gas sensor) 2 Oxygen detection element (detection element) 10 Casing 14 Main cylinder 16 Filter assembly (Cover member) 18 Ceramic separator 51 First filter holding part (Cover member) 60 Stepped part 60A, 60B, 60C Projection ( Projecting portion) 73 Separator-side support portion 73c, 73d, 73e Ventilation path 90 Casing-side support portion

Claims (5)

[Claims] An axial detection element, a cylindrical casing for housing the detection element in a state where a detection section formed at the tip of the detection element is projected, and provided coaxially with the casing. A ceramic separator that is directly or indirectly supported via another member at a casing-side support portion formed at a rear end portion of the casing, and is disposed coaxially with the casing, and the ceramic separator is disposed from outside. A cover member connected from the rear side to the casing in a covered state, and a separator-side support portion projecting outward is formed on an outer peripheral surface of the ceramic separator, while an inner surface of the cover member is formed on an inner surface of the cover member. A projection is formed to contact the separator-side support from the rear side in the axial direction of the ceramic separator. Gas sensor and wherein the door. 2. The gas sensor according to claim 1, wherein the projecting portion is formed on an inner surface of a step portion of the cover member. 3. The gas sensor according to claim 1, wherein the casing and the cover member are fixed in a state where the protrusion is elastically deformed via the separator-side support portion by the pressing of the casing-side support portion. 4. The Vickers hardness Hvs of the protrusion is set to 1
The gas sensor according to claim 3, wherein the gas sensor has a diameter of 50 to 300. 5. The gas sensor according to claim 1, wherein the projecting portion is constituted by a plurality of projections, and a gap is formed between the projections.