JPH08201332A - Assembling structure of oxygen sensor - Google Patents

Abstract

(57) [Abstract] [Purpose] Both of the conductive adherent layers are electrically insulated from the metallic shell for mounting the solid electrolyte element 2 having the conductive adherent layers for electrodes formed on the inner and outer surfaces thereof. While being hermetically sealed by using the heat-resistant material powder compression body 8 for hermetic sealing, the two hermetically-insulated oxygen sensors fixed on the same axis can maintain good hermetic sealing performance. The electrical insulation performance of the heat-resistant material powder compact 8 with respect to the metal shell is improved. [Structure] The collar portion 21 of the element and the step portion 3 of the metal shell
3, a front side insulator 5 interposed between the flange 3 and the front side insulator 5, which is interposed between the flange portion and the crimp portion 34 of the metal shell, and which is close to the crimp portion. A tubular wall that includes an intermediate insulator 7 near the portion and a heat-resistant material powder compression body 8 for hermetically sealing between the insulators 6 and 7, the intermediate insulator 7 having an outer peripheral portion extending axially toward the original side. A portion 74 is provided, and an end portion of the tubular wall portion allows the axial front end portion of the original insulator to be freely fitted therein and pressurizes the heat resistant material powder compression body 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an assembly structure of an oxygen sensor for detecting the oxygen concentration in exhaust gas from an internal combustion engine, for example.

[0002]

2. Description of the Related Art In an oxygen sensor for detecting the oxygen concentration in exhaust gas from an internal combustion engine, an axial front side is closed and a front side is opened, and a conductive metallic deposition layer as an electrode is formed on the inner and outer surfaces of the front side. A tube-shaped solid electrolyte element in which is formed,
The solid electrolyte element is sealed and fixed in a coaxially inserted state, and also has a tube-shaped mounting metal shell, and when this is attached to an exhaust pipe of an internal combustion engine, an inner surface side electrode has an atmosphere as a reference oxygen concentration gas. In addition, the outer surface side electrodes are respectively brought into contact with the exhaust gas to generate an electromotive force corresponding to the oxygen concentration in the exhaust gas between both electrodes, and the electromotive force is extracted as an oxygen concentration output signal, and this is supplied to the control circuit device. There is one that inputs and controls the oxygen concentration by feedback. Among such oxygen sensors, those whose outer surface side electrode is conductively connected to the above-mentioned mounting metal shell and which is used as a ground side output terminal are those of the internal combustion engine side including the exhaust pipe attached to the exhaust pipe. Since the path is used as the ground side circuit of the control circuit device, the influence of engine system noise on the sensor output, which is originally relatively weak, for example, noise from the spark plug or fluctuation of the potential difference based on the ground current becomes a problem. Therefore, in recent years, a method in which the electrode on the outer surface of the element is electrically insulated from the mounting metal shell, and the potential of the outer electrode is directly led to a control circuit through a dedicated lead wire and grounded there has become mainstream.

As described above, an oxygen sensor of the type in which both electrodes of the solid electrolyte element are electrically insulated from the metallic shell for mounting, that is, both-insulation type oxygen sensors are conventionally disclosed, for example, in Japanese Unexamined Patent Publication (Kokai).
An oxygen sensor as described in 63-3252 was used. That is, as shown in FIG. 5, the assembly structure of the oxygen sensor substantially disclosed in the above publication is such that the front side in the axial direction is closed, the front side is opened, the flange 521 is formed in the intermediate portion, and the outer and inner surfaces are respectively formed. A tube-shaped solid electrolyte element 502 in which conductive metal deposition layers 522, 522 'extending from the front side to the front side are formed, a step portion 533 having a large diameter inner hole in the inner hole, and the diameter. A caulking portion 534 bent inward in the radial direction is formed at the end of the large inner hole on the base side, and a known residual thermal stress after thermal caulking is applied between the caulking portion and the step portion. A tube-shaped mounting metal shell 503 for clamping the collar portion 521 and fixing the solid electrolyte element 502 coaxially by the clamping force of the axial direction which is applied and used.
And an insulator made of an alumina sintered body which is coaxially arranged between the solid electrolyte element and the mounting metal shell so as to electrically insulate the solid electrolyte element and the mounting metal shell from each other. A tube-shaped front-side insulator 505 is formed such that it is interposed between the step portion of the metal shell and the collar portion of the solid electrolyte element under strong pressure.
And the former side insulator 5 which is to be interposed under high pressure between the crimped portion of the mounting metal shell and the collar portion of the solid electrolyte element.
And an insulator composed of 06. Further, between the front side insulator 505 and the source side insulator 506,
Along with the collar portion of the solid electrolyte element arranged on the front side insulator side, at least a part of the axial clamping force received from the source side insulator 506 that is strongly pressure-inserted and the collar portion of the solid electrolyte element is provided. And an airtight sealing member made of a flexible and electrically insulating ceramic powder compression body 508, wherein the mounting metal shell and the solid electrolyte element are coaxially airtight and It was integrally assembled in an electrically insulating manner. 518 and 520 are output lead wires that are electrically connected to the metallic coating layers 522 and 522 ′ on the outer and inner surfaces, respectively, and 513 is an inner housing cylinder, and 51.
Reference numeral 4 denotes an outer housing cylinder, and 516 a rod-shaped ceramic heater.

More specifically, as shown in the figure, the tubular front insulator 505 has an outer diameter substantially equal to the inner diameter of the large diameter inner hole of the metal fitting, and its front end surface 551 has a step surface of the mounting metal shell. 533 is abutted via a gasket, and a step surface 553 is formed in the inner hole of the inner side of which is a large-diameter inner hole 552 having an inner diameter substantially equal to the outer diameter of the flange portion 521. The stepped surface 553 is in contact with the collar portion in a state where the element collar portion 521 is accommodated in 552 in a depth such that the outer peripheral surface of the collar portion is just hidden. That is, the front insulator 505 has the front end surface 551 that engages with the step portion and the step surface 553 that engages with the collar portion, and mainly applies the compressive stress based on the sandwiching force exerted to the collar portion. The resulting sandwiching force transmitting portion and the annular space that extends from the outer peripheral region of the sandwiching force transmitting portion to the original side and is formed between the outer peripheral surface of the flange portion and the inner surface of the large diameter inner hole ends. The flexible electrically insulating ceramic powder compression body 508, which has a short tubular wall portion, is provided in the tubular space between the inner surface of the metal shell and the outer surface of the element in the axial direction. In the substantially tubular space limited from the end face 562 of the front side portion to the end face 555 of the short tubular wall portion of the front side insulator to the surface 525 facing the original side of the collar portion of the solid electrolyte element, and Adopting an assembled structure that is arranged as an airtight sealing member that also contacts the inner surface of the metal shell Which was.

However, the above-mentioned ceramic powder compression body is hard to be a completely airtight body, and therefore, while being used for a long period of severe use, for example, although not shown, the output lead wires 518 and 520 and the outer housing cylinder are omitted. After a harmful component such as a component generated by thermal decomposition of an airtight sealing member made of, for example, silicon rubber interposed between the electrically insulating ceramic powder compression body 508 and the like is deposited. In addition, when the ceramic powder compression body encounters a high humidity environment, a large number of parallel conduction circuits that short-circuit the metal deposition layer on the outer surface of the element and the inner surface of the metal fitting in the radial direction are formed in the ceramic powder compression body, which is temporary. There was a problem that noise was picked up in the output abnormalities.

On the other hand, in order to further improve the airtightness (compression density) of the above-mentioned ceramic powder compression, it is caused to act between the caulking portion and the stepped portion of the metal fitting and left after the hot plastic deformation caulking process. When an attempt is made to increase the axial clamping force (and therefore the compression pressure for the compressed ceramic powder) based on the thermal stress, that is, when the pressure load during the processing is increased, the compressed ceramic powder moves the original side of the collar portion 521. The cracking force or the like in the tip side insulator facing outward in the radial direction becomes large due to the cracking force exerted on the vicinity of the end surface 555 of the tip side insulator due to the flow along the facing inclined surface 525, and thus cracks easily occur. There is a dimensional limit even if it is attempted to increase the thickness of the insulator around the collar portion in order to cope with the above, and on the other hand, increasing the thickness of the insulator around the collar portion is a surface facing the element side of the collar portion. 525 This leads to a decrease in the projected area in the axial direction, which in turn reduces the axial contact force between the element flange portion and the front insulator, making it difficult to maintain airtightness at that portion. As a result, it is difficult to effectively implement the measures against the above-mentioned problems.

[0007]

The problems to be solved by the present invention are as follows.
Therefore, in the assembling structure of the metal shell for mounting the double-insulation oxygen sensor and the solid electrolyte element as described above, a heat-resistant material as a member for hermetic sealing while maintaining a good hermetic sealing property as an oxygen sensor. The object is to eliminate the above-mentioned problems caused by the above-described phenomenon of deterioration of the electric insulation of the powder compact.

[0008]

The invention relating to the assembling structure of an oxygen sensor for solving the above-mentioned problems is an axial front side closed and a base side opened, a collar portion is formed at an intermediate portion, and inner and outer surfaces are respectively formed with a front portion. A solid electrolyte element in the form of a tube in which a conductive coating layer extending from the side to the original side is formed, a step portion having the original side as a large-diameter inner hole in the inner hole, and the original side end portion of the large-diameter inner hole. A crimping portion bent inward in the radial direction is formed, and the collar portion is clamped by utilizing the axial clamping force exerted between the stepped portion and the crimping portion. -Shaped mounting metal fitting for coaxially fixing the metal shell, and a tubular shape arranged coaxially between the solid electrolyte element and the mounting metal shell to electrically insulate between the solid electrolyte element and the mounting metal shell. Is an insulator of, and is strongly interposed between the step portion and the collar portion, and the clamping force is At least one of the sandwiching force, which is at least part of the stepped portion exerted on the collar portion, and the insulator, which is the insulator and is strongly pressure interposed between the crimp portion and the collar portion. A portion for applying a portion from the crimped portion to the collar portion, and the former side insulator between the crimped portion and the collar portion, but close to the collar portion side, and a high pressure In a mounting structure of an oxygen sensor having a heat-resistant material powder compression body for hermetically sealing, which exerts at least a part of the sandwiching force received through the original side insulator on the collar portion, Another insulator, which is strongly pressure-inserted between the heat-resistant material powder compression body and the collar portion, and receives the axial clamping force received by the heat-resistant material powder compression body on the collar portion. An intermediate insulator is provided, and the intermediate insulator is positioned between the compressed powder of the heat-resistant material and the collar in the axial direction. Occupy a pinching force transmitting portion that mainly generates a compressive stress based on the axial pinching force, and extends from the outer peripheral area of the transmitting portion to the axial direction base side so as to accommodate the heat-resistant material powder compact. A tubular wall portion, wherein the extended end portion of the tubular wall portion allows the front end portion of the original insulation to freely fit therein, and the end surface of the front end portion has the heat resistant material in the tubular wall portion. It is characterized in that the powder compact is pressurized.

Here, the well-known thermal crimping method is used for the axial clamping force exerted on the collar portion between the crimping portion and the step portion of the mounting metal shell via the both insulators. Then, while applying a compressive load in the axial direction from the crimped portion of the metal fitting, the metal is energized to generate heat particularly in a part of the metal part in the axial direction of the metal fitting, and is heated to a temperature sufficiently higher than the operating temperature to cause plastic deformation and continue. After the residual stress in the metal fitting is removed while hot, it is preferable that the residual thermal stress in the axial direction that is generated when the heating by the energization is stopped and the temperature is lowered is used. Further, in the above-mentioned thermal caulking process, a flexible member including a springy member made of a metal (for example, spring steel), which deforms while resisting pressure in response to an axial plastic deformation caused by a compressive load, is used as the attachment main body. It is preferable to interpose between the caulking portion and the stepped portion of the metal fitting, but it also serves as the heat-resistant material powder compression body as the airtight sealing member and is flexible, that is, against compression force. It is preferable to employ, for example, a flaky powder of a heat-resistant material such as a metal, a semiconductor metal oxide, or a ceramic having a property of deforming while exhibiting resistance.

It is preferable that the insulator is a ceramics sintered body having heat resistance and electrical insulation and high strength, for example, 90% or more high purity alumina sintered body. The portion where the front insulator abuts the step of the mounting metal shell and receives the sandwiching force may directly abut, but for airtight sealing of a metal (for example, stainless steel) gasket or the like. A member or a cushion member may be additionally interposed.

A portion where the front insulator abuts on the collar portion of the solid electrolyte element and transmits the sandwiching force may also directly abut, but a hermetically sealed metal (eg, stainless steel) gasket or the like. A stopping member or a cushioning member may be additionally interposed. A portion where the intermediate insulator contacts the flange portion of the solid electrolyte element and transmits the sandwiching force may be directly contacted, but an airtight sealing member such as a gasket made of metal (for example, stainless steel) or A cushioning member may be additionally interposed. Even if the pressing member is intervened by abutting on the surface of the pinching force transmitting portion where the axial pinching force is directly transmitted from the heat resistant material powder compact to the intermediate insulator. Good. Here, the pressing member is a tubular member made of a heat-resistant material such as relatively hard and high-strength metal (for example, stainless steel) or ceramics and having an appropriate cross-sectional shape, and is in the axial direction received from the original insulator. To prevent the intermediate insulator from receiving a reaction force outward in the radial direction from the heat resistant material powder compression body as much as possible when the clamping force is transmitted to the element flange portion through the heat resistant material powder compression body. It is an auxiliary member and can be interposed if necessary.

[0012]

In the assembly structure of the oxygen sensor of the present invention, the tube-shaped solid electrolyte element and the tube-shaped mounting metal shell are arranged coaxially between the two in order to electrically insulate them. An insulator similar to the above-mentioned insulator, which is a high-pressure insulator interposed between the step portion and the collar portion and exerts at least a part of the clamping force from the step portion to the collar portion. In addition, a source side insulator that is interposed between the caulking portion and the collar portion by a strong pressure and exerts at least a part of the sandwiching force from the caulking portion to the collar portion, and the caulking portion, At least a part of the pinching force received through the original insulator together with the original insulator between the flange and the original insulator, but with strong pressure interposed between the original insulator and the original insulator. In the assembly structure of the oxygen sensor having a heat-resistant material powder compression body for airtight sealing, An intermediate insulator, which is an edge member, is strongly interposed between the heat-resistant material powder compact and the flange portion, and exerts the axial clamping force received by the heat-resistant material powder compact on the collar portion. The intermediate insulator is located between the heat-resistant material powder compression body in the axial direction and the flange portion, and a clamping force transmitting portion mainly generates a compressive stress based on the axial clamping force, and And a tubular wall portion that extends inward in the axial direction so as to accommodate the heat-resistant material powder compact inside from the outer peripheral region of the transmission portion, wherein the extended end portion of the tubular wall portion is the source-side insulating material. Since the front end is freely fitted and the end face of the front end presses the heat-resistant material powder compact in the tubular wall portion, the heat-resistant material powder compact is attached to the metal shell as described above. It is electrically insulated by the tubular wall and runs along the surface of the insulator. Creepage electrical insulating path the tubular wall portion is electrically insulating supposed to long be include partial axial path allowed to fitting the tip portion of the source-side insulator is improved. Therefore, an electrically conductive powder can be used as the heat-resistant material powder compact, and even when an electrically insulating powder is used, it is contaminated as described above, and then encounters a humid environment to temporarily establish a conductive state. Even if it occurs, the metallic coating layer (outer surface electrode) on the outer surface of the element and the inner surface of the metal fitting are not short-circuited, and still good electrical insulation is maintained, and the above-mentioned malfunction of output abnormality is solved. .

Further, since the above-mentioned assembly structure is adopted, in order to improve the airtight sealing between the element flange portion and the original side insulator, the compressive force (that is, the caulking of the metallic shell) against the heat resistant material powder compact is improved. Even when increasing the axial clamping force between the step portion and the stepped portion), the heat resistant material powder compact is provided in contact with the outer peripheral surface of the element body portion at a position farther from the element collar portion and closer to the original side than the collar portion. Therefore, for example, as in the case of being provided in contact with the element flange portion, the front end of the heat-resistant material powder compact is extruded radially outward along the surface facing the original side of the flange portion, and There is no such thing as a reaction force that goes outward in the direction, and the radial cracking outward stress does not become excessive. Therefore, the compression pressure that is larger than that in the past is applied to compress it. It is possible to increase the density and improve the hermetic sealing property. Further, the wall thickness dimension of the tubular wall portion 74 of the intermediate insulator can be determined independently of the outer diameter dimension of the element flange portion, and it is also free to increase it to increase the strength against the splitting force.

Therefore, since the compression density of the heat-resistant material powder compact is improved, the heat-resistant material powder compact is less likely to be contaminated with harmful gas components, and the cause itself of the above-described malfunction of the output abnormality is less likely to occur. Become.

The increased compressive force applied to the heat-resistant material powder compact acts as a sandwiching force for the collar portion of the solid electrolyte element via the intermediate insulator and the front insulator, respectively. The airtight sealing property of the contact portion is advantageously improved as compared with the conventional case.

Further, since the airtight sealing property between the original insulator and the caulked portion of the metal shell can be maintained relatively high easily, the step portion of the front insulator and the metal shell can be maintained. For leak inflow of the exhaust gas toward the inside of the solid electrolyte element through the sealing contact between the front side insulator and the flange portion of the solid electrolyte element. It becomes safe because it will be doubly sealed, while on the other hand, for leak inflow of exhaust gas along the outer surface of the solid electrolyte element, good heat-tight sealing property can be obtained by the heat-resistant material powder compression body of increased compression density. Since it is maintained, the airtight sealing property as the oxygen sensor against the leak inflow of the exhaust gas toward the inside of the solid electrolyte element is improved as compared with the conventional case.

Further, as the compressive force for the heat-resistant material powder compact, the axial clamping force acting between the caulking portion and the stepped portion of the metal shell is used as it is, so that the axial clamping is performed. The force can be made smaller than in the conventional case, and the load burden on the front insulator is reduced accordingly.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on the embodiments shown in the drawings. 1 to 3 showing a first embodiment, 1 is an oxygen sensor, 2 is a tubular solid electrolyte element, preferably made of a stabilized or partially stabilized zirconia ceramic sintered body, and its axis The front side of the direction is closed and the front side is opened, and at the axially intermediate portion, there is a flange portion 21 that projects outward, and the outer and inner surfaces respectively extend from the front side to the front side and the electrodes 22 (22 ') and Conductive metallic coating layers 24, 2 which are used as the leads 23, 23 '.
With 4 '. Reference numeral 3 denotes a tubular metal fitting for attachment, preferably made of stainless steel, which has a difference-diameter step portion 33 having a large-diameter inner hole 32 on the original side in the inner hole 31, and the large-diameter inner hole 3 described above.
1 has a caulking portion 34 at the end portion on the original side, and the collar portion acts by thermal caulking between the step portion and the caulking portion in a state where the solid electrolyte element is coaxially inserted. Fix it by pinching it with the axial pinching force. Incidentally, reference numeral 35 denotes a portion which is plastically deformed by the heat crimping process.

Reference numeral 4 denotes a tubular shape in which the solid electrolyte element and the mounting metal shell are arranged coaxially and in a spaced relationship with each other so as to electrically insulate them from each other. In this case, it is an insulator of a ceramic sintered body made of an alumina ceramic sintered body. This insulator 4
Here, the front insulator 5 is interposed between the step portion of the mounting metal shell and the collar portion of the solid electrolyte element under strong pressure.
And a source-side insulator 6 that is interposed between the crimped portion of the mounting metal shell and the brim portion of the solid electrolyte element and closer to the crimped portion, and is strongly pressure-inserted. An intermediate insulator 7 which is located between the crimped portion of the metal shell and the collar portion of the solid electrolyte element, and which is located nearer to the collar portion and is interposed under high pressure.
It consists of Reference numeral 8 denotes a flexible and electrically insulating ceramic powder, here a compressed body of talc powder, which is interposed between the source side insulator 6 and the intermediate insulator 7 under a strong pressure, and the source side insulator The axial clamping force received from 6 is transmitted to the collar portion of the solid electrolyte element via the intermediate insulator 7.

By the way, the front insulator 5 is formed with an end surface 51 facing the axial front side and abuts on the stepped portion 33 of the mounting metal shell, and the inner side thereof has a diameter in the axial front side. A step surface 53 serving as a large inner hole 52 is formed, and the step surface 53 is in contact with the flange portion 21 in a state where the flange portion 21 is shallowly accommodated in the large diameter inner hole 52. On the other hand, in the original insulator 6, the end face 62 of the original portion 61 has the crimped portion 34 of the metallic shell 3.
, And the end face 64 of the front portion 63 presses the flexible ceramic powder compact. On the other hand, the intermediate insulator 7 is provided with an end surface 71 that comes into contact with the flange portion and an annular step surface 72 that comes into contact with the flexible ceramic powder compression body, and is sandwiched mainly by compressive stress due to the axial clamping force. An attachment force transmission portion 73 (a portion that receives the axial clamping force from the flexible ceramic powder compression body and transmits it to the collar portion),
From the outer peripheral area of the transmission portion 73, the large-diameter inner hole 32 of the metallic shell 3 and the flexible ceramic powder compression body or the original side insulator 6 are formed.
A tubular wall portion 74 extending axially toward the base side so as to occupy a tubular space formed between the front side portion 61 and the front side portion 61, and the extended end portion freely fits the front side portion of the source side insulator. Equipped with.

Reference numeral 9 is an annular metal plate having a sufficiently large inner diameter and interposed between the end face 64 of the base side portion 63 of the base side insulator 6 and the caulking portion 34 under strong pressure. Reference numeral 10 denotes a metal gasket that is auxiliary interposed between the end surface 51 of the front insulator 5 and the step portion 33 of the metal shell. Reference numeral 11 denotes a metal gasket that is auxiliary interposed between the step surface 53 of the front insulator 5 and the collar portion 21 of the solid electrolyte lion. Reference numeral 12 is a metal gasket that is auxiliary interposed between the end surface 71 of the intermediate insulator 7 and the collar portion 21 of the solid electrolyte element. Reference numeral 13 denotes a metal inner housing cylinder, and a tip end portion thereof that is bent outward in the radial direction is a second
Between the end face of the original side insulator and the caulking portion 34, which is interposed in contact with the metal plate 9 and is fixed coaxially to the metal shell, and 14 is an outer housing cylinder made of the same metal. And 15 which are coaxially joined to the inner housing cylinder by welding or the like, and 15 is made of a heat-resistant metal for exposing the front side detection portion of the element to the exhaust gas through the exhaust gas but protecting it from the attack. A perforated protective cylinder, 16 is a round rod-shaped ceramic heater, 17 is a terminal fitting for taking out the output for the outer electrode, and the end portion extending to the original side thereof is a crimp terminal, and 18 is the crimp terminal section. A grounded output lead wire is connected, 19 is an output takeout terminal metal fitting for the inner electrode which also serves as a ceramic heater gripping metal fitting, and the end portion extending to the original side thereof is a crimp terminal, and 20 is the above Non-contact connected by crimp terminal Side output lead, 121,12
1 is a lead wire for power supply for the ceramic heater, 1
Reference numeral 22 denotes a ventilation spacer made of fluororesin or the like which is water repellent but breathable and electrically insulating, 123 is an intermediate spacer made of an electrically insulating material, and 124 is an airtight sealing spacer such as elastic and electrically insulating silicon rubber. . It should be noted that the atmosphere flows into the inner hole of the solid electrolyte element through a minute communication hole in the air permeable spacer 21 from a slight gap in the overlapping portion of the inner housing cylinder 13 and the outer housing cylinder 14 to generate the reference oxygen. Form a concentration source.

The assembly structure of the oxygen sensor of the above embodiment is such that a flexible and electrically insulating ceramic powder compression body for airtight sealing is insulated from the original side insulation at the end of the tubular wall portion 74 of the intermediate insulation body. Insulation is performed by a creeping electric insulation path that is lengthened by the depth of fitting of the front side portion of the body (which is at least larger than the amount by which the metal shell 3 is compositionally deformed in the axial direction and contracted by the heat crimping process). Even if a phenomenon in which the electric insulation of the insulating ceramic powder compact itself is deteriorated occurs, good electric insulation performance is still maintained and it is safe.
Moreover, since the ceramic powder compression body for airtight sealing is made to be flexible and also serves as a flexible member, the structure when heat crimping is adopted becomes simple.

The second embodiment is different from the first embodiment in that the intermediate insulator 7 is provided between the compressed powder of heat-resistant material for hermetic sealing and the annular step surface 72 of the intermediate insulator 7. 1B, except that a tubular pressurizing member 25 is interposed so as to prevent a reaction force directed outward in the radial direction from being generated. FIG. Is shown in FIG. Incidentally, FIG.
In FIGS. 1 to 3, members or parts given the same reference numerals as those in FIGS. 1 to 3 are members or portions having the same function, and therefore the description thereof will be omitted. Here, the pressing member 25 is made of a relatively hard and high-strength metal (for example, stainless steel) or ceramics, and has a cross-sectional shape, for example, as shown in FIG. The ridge portion where the contacting end face and the side face that limits the outer diameter intersect is chamfered. In the assembly structure of the oxygen sensor of the second embodiment, when the compression density of the heat-resistant material powder compression body for hermetic sealing is increased, a reaction force outward in the axial direction is generated and reaches the intermediate insulator. Can be prevented more easily and surely.

[0024]

EFFECTS OF THE INVENTION The present invention provides an assembly structure in which a solid electrolyte element and a metallic shell for mounting of the above-mentioned two-insulation oxygen sensor are assembled by using a compressed powder of a heat resistant material as an airtight sealing member, and the element and the While maintaining good airtight sealing between the metal fittings, the problem of poor oxygen concentration detection accuracy due to the occurrence of the phenomenon of deterioration of electrical insulation due to contamination of the heat-resistant material powder compact was solved. Withstands the use of and can always maintain good electrical insulation performance. Therefore, it is necessary to improve the air-fuel ratio measurement accuracy in the oxygen sensor technology, which is one of the core technologies for exhaust gas purification technology for passenger cars powered by an internal combustion engine, and to endure and maintain the accuracy for long-term use under severe conditions. It has a great effect that it can meet the challenges.

[Brief description of drawings]

FIG. 1 is a sectional view showing an assembly structure of an oxygen sensor of a first embodiment of the present invention, FIG. 1 (a) is a sectional view showing the whole assembly structure of an oxygen sensor, and FIG. It is a principal part expanded sectional view for showing the detail of a principal part.

FIG. 2 is a perspective view of a solid electrolyte element in the assembly structure of the oxygen sensor of the first embodiment.

3A and 3B are perspective views of a tubular insulator in the assembly structure of the oxygen sensor of the first embodiment. FIG. 3A is a perspective view of a front insulator, and FIG. 3B is a perspective view of an intermediate insulator. , (C)
[Fig. 4] is a perspective view of a base-side insulator.

FIG. 4 is an enlarged sectional view of an essential part showing only a portion different from that of the first embodiment of the assembly structure of the oxygen sensor of the second embodiment of the present invention.

FIG. 5 is a cross-sectional view showing an assembly structure of a conventional representative oxygen sensor.

[Explanation of symbols]

 1: Oxygen sensor 2: Solid electrolyte element 21: Collar of solid electrolyte element 3: Metal shell for mounting 31: Inner hole of metal shell for mounting 32: Large diameter inner hole of metal shell for mounting 33: Metal shell for mounting Step part 34: Crimped part of the metallic shell for mounting 5: Front side insulator 6: Source side insulator 61: Front side portion of the source side insulator 62: End face of the front side portion of the source side insulator 7: Intermediate insulation Body 73: Clamping force transmitting portion of intermediate insulator 74: Tubular wall portion of intermediate insulator 8: Heat-resistant material powder compact

[Procedure amendment]

[Submission date] January 31, 1996

[Procedure Amendment 2]

[Document name to be corrected] Drawing

[Correction target item name] All drawings

[Correction method] Change

[Correction content]

FIG.

[Fig. 2]

[Figure 3]

[Figure 4]

[Figure 5]

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuhiro Yamada 14-18 Takatsuji-cho, Mizuho-ku, Aichi Prefecture Nagoya City Japan Special Ceramics Co., Ltd.

Claims (1)

[Claims] 1. A tube-shaped solid body in which an axial front side is closed, a base side is opened, a collar portion is formed in an intermediate portion, and conductive coating layers extending from the front side to the front side are formed on inner and outer surfaces, respectively. An electrolyte element, a step portion having a large diameter inner hole in the inner hole, and a caulking portion bent inward in the radial direction at the original side end portion of the large diameter inner hole. A tubular metal shell for fixing the solid electrolyte element coaxially by sandwiching the flange portion by utilizing an axial sandwiching force exerted between the solid member and the crimp portion; A tubular insulator disposed coaxially between the electrolytic element and the metallic shell for attachment so as to electrically insulate them, and a strong pressure is interposed between the step portion and the collar portion. A front side insulator mounted to exert at least a part of the sandwiching force from the step portion to the collar portion,
A source side insulator, which is the above-mentioned insulator, is strongly interposed between the caulking portion and the collar portion and exerts at least a part of the sandwiching force from the caulking portion to the collar portion, At least the sandwiching force, which is disposed between the caulking portion and the collar portion together with the former side insulator, but closer to the collar portion side, is strongly pressed and received through the former side insulator. In an oxygen sensor assembling structure having a heat-resistant material powder compression body for hermetically sealing a part of the heat-resistant material powder compression body, the other insulator is the heat-resistant material powder compression body and the collar section. And an intermediate insulator that is interposed between the and and exerts the axial clamping force received through the heat-resistant material powder compression body on the collar portion,
The intermediate insulator occupies a position between the heat-resistant material powder compact in the axial direction and the collar portion, and a sandwiching force transmitting portion that mainly generates a compressive stress based on the axial sandwiching force, and the intermediate portion of the transmitting portion. And a tubular wall portion extending inward in the axial direction so as to accommodate the compressed powder of the heat-resistant material from the outer peripheral region to the inside, wherein the extended end portion of the tubular wall portion is the front end of the original side insulation. An assembly structure for an oxygen sensor, characterized in that a portion is freely inserted and an end face of the front end portion presses the heat-resistant material powder compact inside the tubular wall portion.