JP2001103645A - Lead wire sealing structure and gas sensor using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lead wire sealing structure, and a gas sensor using it, in which good sealing performance can be sustained for a long term even when it is exposed to high temperature for a long time or subjected to heat cycle repeatedly. SOLUTION: The part 510 including an insertion hole fixing face 510 in a lead wire insertion hole 51a at a grommet 51 for inserting a lead wire 14 comprises a part 51b formed of a porous material and the gap between the insertion hole fixing face 510 and the outer surface of the lead wire 14 is sealed by a sealing resin layer 53. More specifically, on the adhesion face of the part 51b formed of a porous material and the sealing resin layer 53, the gap k of the porous material exposed to the surface of the insertion hole fixing face 510 at the part 51b formed of a porous material (i.e., irregularities on the insertion hole fixing face 510) is filled with the sealing resin layer 53.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead wire seal which is applied to applied electronic equipment which is provided with an electric element such as a ceramic heater, a glow plug and the like, including various gas sensors, and is used at a high temperature. Stop structure. In addition, the present invention provides, for example, an oxygen sensor, an HC sensor, a NOx
The present invention relates to a gas sensor using a lead wire sealing structure, such as a sensor, in which the electric element is a detection element for detecting a component to be detected in a gas to be measured.

[0002]

2. Description of the Related Art As an example of applied electronic equipment, an oxygen sensor for detecting the concentration of oxygen in exhaust gas discharged from an internal combustion engine of an automobile or the like has been known. In such an oxygen sensor, a detection element (electric element) composed of a solid electrolyte such as zirconia (ZrO ₂ ) or a metal oxide semiconductor is used. The detection element is arranged inside a metal outer cylinder having an opening, and its output is taken out of the outer cylinder by a lead wire connected to the detection element. A rubber grommet is fitted into the opening of the outer cylinder from which the lead wire is drawn out to prevent water or the like from entering the outer cylinder, and the lead wire passes through the grommet and extends outside the outer cylinder. Has been extended to. The space between the lead wire and the outer cylinder is sealed by the elastic force of the grommet.

Here, the oxygen sensor has an operating temperature of 30.
A structure in which the temperature is as high as 0 ° C. or higher and the detection element is forcibly heated by a heater is generally adopted. As a result, the heat generated by the engine is superimposed on the heat generated by the heater, and the temperature of the outer cylinder rises, and the grommet is exposed to a considerably high temperature due to the heat conduction from the outer cylinder. Therefore, in general, the grommet is made of a heat-resistant rubber such as a fluoro rubber to secure the sealing property between the lead wire and the outer cylinder at a high temperature. Among them, as a sealing structure that is more excellent in the above-mentioned sealing properties at high temperatures, a lead wire is inserted through a grommet made of polytetrafluoroethylene (PTFE) resin, and a cylindrical rubber seal member is arranged outside the grommet, thereby forming an outer portion. A sealing structure in which a rubber seal member is compressed by caulking a cylinder toward the rubber seal member is also employed.

[0004]

However, since the thermal expansion coefficient of the PTFE resin, which is the material of the grommet, is considerably large, the grommet expands when exposed to a high temperature for a long time in the conventional sealing structure. Excessive compressive force acts on the rubber seal member that is compressed between the grommet and the outer cylinder, and the rubber seal member may be damaged. Further, a strong caulking force is constantly applied to the rubber seal member in the compressed state, and the expansion force from the grommet is also applied to this state at a high temperature. For this reason, when a heating / cooling cycle (hereinafter, simply referred to as a heat cycle) is repeatedly added due to, for example, repetition of the operation of the internal combustion engine, the elasticity of the rubber seal member is deteriorated, and permanent deformation distortion is likely to occur in the rubber seal member. In some cases, the sealing performance may be reduced.

It is an object of the present invention to provide a semiconductor device which is exposed to a high temperature for a long time or is repeatedly subjected to a thermal cycle.
An object of the present invention is to provide a lead wire sealing structure and a gas sensor using the same, which can maintain good sealing properties for a long period of time.

[0006]

Means for Solving the Problems and Actions / Effects In order to solve the above problems, a lead wire sealing structure (hereinafter, also simply referred to as a sealing structure) according to the first invention has an electric element inside. Arranged, an outer cylinder having an opening at at least one end,
A lead wire that is electrically connected to the electrical element and extends to the outside of the outer cylinder through the opening, and has a lead wire insertion hole through which the lead wire is inserted, and is arranged inside the opening, A grommet for sealing between the lead wire and the inner wall of the opening of the outer cylinder, and a part of the grommet including at least a part of the inner surface of the lead wire insertion hole is formed of a porous body. Consisting of a porous body forming part,
In the porous body forming portion, a gap between an insertion hole sealing surface forming an inner surface of the lead wire insertion hole and an outer surface of the lead wire is sealed by a sealing resin layer.

According to the first aspect of the present invention, in the grommet into which the lead wire is inserted, the portion including the insertion hole sealing surface of the lead wire insertion hole is formed of a porous material forming portion formed of a porous material. And the space between the insertion hole sealing surface and the outer surface of the lead wire is sealed by a sealing resin layer. That is, at the contact surface between the porous body forming portion and the sealing resin layer, the void of the porous body formed by being exposed to the surface of the insertion hole sealing surface of the porous body forming portion (that is, the insertion hole sealing portion). Is filled with a sealing resin layer. Therefore, since the sealing resin layer mechanically engages with the insertion hole sealing surface of the porous body forming portion, the porous body forming portion and the sealing resin layer strongly adhere to each other. As a result, even in a severe use environment in which the device is exposed to a high temperature for a long time or a thermal cycle is repeatedly applied, the above-described sealing structure can maintain the gap between the outer surface of the lead wire and the inner wall of the opening of the outer cylinder. And good sealing properties can be maintained over a long period of time. There are cases where the entire grommet is formed of a porous body such as a porous metal, and cases where a part of the grommet (for example, only the portion including the insertion hole sealing surface) is formed of the porous body. In the latter case, when the insertion hole sealing surface of the porous body forming portion is formed over the entire circumference in the circumferential direction on the inner surface of the lead wire insertion hole, the insertion hole sealing surface surrounds the entire circumference of the lead wire. That is, the gap between the insertion hole sealing surface and the outer surface of the lead wire is sealed without any gap by the sealing resin layer. Therefore, arranging the insertion hole sealing surface of the porous body forming portion so as to surround the entire circumference of the lead wire is necessary to ensure the sealing property between the insertion hole sealing surface and the outer surface of the lead wire. desirable.

Further, according to the present invention, the porous body forming the porous body forming portion can be a porous metal. By using a porous metal, even under the above-mentioned severe use environment, the gap does not collapse, and good sealing properties can be stably maintained over a long period of time. Further, the heat accumulated in the grommet can be effectively radiated due to the porous metal, and an excessive rise in temperature of the outer cylinder can be suppressed.

As the porous metal, stainless steel manufactured by sintering, Al (aluminum),
Al alloy, Cu (copper), Cu alloy or the like, or hard chrome plating or the like can be used. Further, in consideration of a use environment in which the porous metal is exposed to a high temperature for a long time or a thermal cycle is repeatedly applied, the porous metal desirably has a thermal expansion coefficient close to that of the sealing resin described above.

The average particle diameter of the sintered powder of the porous metal forming the porous body forming portion is 100 to 250.
It is better to adjust within the range of μm. At this time, regarding the surface roughness in the porous body forming portion, when viewed from the maximum height, 4
Can be expressed as 0～100MyumR _y, as viewed in arithmetic average roughness can be expressed as 5~15μmR _a. In addition,
Regarding the maximum height _Ry and the arithmetic average roughness _Ra , both the cutoff value and the evaluation length are JIS B0601 (19).
(Established in 1994). Here, since the maximum height is too small, voids goes below 40MyumR _y, there is a case in which the porous body forming portion and the sealing resin layer can not be strongly adhered. On the other hand, since the maximum height gap exceeds 100MyumR _y is too large, the sealing resin layer filled in gaps peeling or falling off.

Further, the sealing resin layer of the present invention is preferably sealed in a state where the sealing resin layer is joined to the insertion hole sealing surface and the outer surface of the lead wire by thermal welding. That is, as before,
When sealing by forming a caulked portion on the outer cylinder using a rubber grommet, the caulking pressure is not always uniformly applied around the lead wire insertion hole, affecting sealing performance. Sometimes occurred. However, with a configuration in which the sealing resin layer is sealed by thermal welding, high sealing properties can be reliably obtained.

The above sealing resin layer is heated to a certain degree by heating.
Fluidity (eg, 10 ³-10⁵Poise
Use a type of fluororesin that can add
However, it is convenient for enhancing the sealing effect by heat welding.
As such a fluorine-based resin, for example, tetrafluoride
Ethylene-perfluoroalkyl vinyl ether copolymer
Combined (perfluoroalkoxy alkane; hereinafter, PFA)
(Mainly abbreviated as) can be exemplified. this
Has the general structural formula shown in Chemical Formula 1. However, (-O-
Rf) is (-O-CF₃), (-OC₂F₅A)
Alkyl ether group (perfluoroalkoxy group)
You.

[0013]

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[0014] In addition, other than the above, a tetrafluoroethylene-hexafluoropropylene copolymer (FEP), a polychloro-trifluoroethylene (PCTFE), an ethylene-tetrafluoroethylene copolymer (ETF)
E) ・ Chlorotrifluoroethylene-ethylene copolymer (E
CTFE) Polyvinylidene fluoride (polyvinylidene fluoride; PVDF) Polyvinyl fluoride (polyvinyl fluoride; PV
F) etc. can be used.

[0015] In the present specification, "main component" means a component having the highest weight content, and does not necessarily mean "a component occupying 50% by weight or more".

In the case where a plurality of the lead wires of the present invention are provided in a state where the core wire is covered with a resin sheath, a plurality of lead wire insertion holes through which the respective lead wires are individually inserted are formed in the grommet. The sealing resin layer can be used to seal the space between the insertion hole sealing surface formed in each lead wire insertion hole and the outer sheath surface of the corresponding lead wire. That is, by providing a lead wire insertion hole individually for each lead wire,
By sealing the gap between each of the through-hole sealing surfaces and the corresponding outer sheath surface of the lead wire with a sealing resin layer, the sealing property between the two can be further ensured. .

Further, a counterbore portion can be formed in the lead wire insertion hole of the present invention, and the inner surface of the counterbore portion can be formed on the insertion hole sealing surface. Since the sealing resin layer is filled and formed in the spot facing portion, the positioning of the sealing resin layer with respect to the lead wire insertion hole can be performed smoothly and reliably,
Sealing properties between the insertion hole sealing surface and the outer surface of the lead wire can be reliably formed.

Further, in the porous body forming portion of the grommet of the present invention, a resin impregnated layer can be formed at least in a surface layer portion. When the grommet is formed of, for example, a porous metal, that is, a sintered metal or a sintered metal alloy, the inside of the grommet includes a large number of voids. Depending on the degree of sintering of the porous metal, the voids distributed in the porous body forming portion of the grommet are continuously formed in a series of chains from the rear end surface side to the front end surface side of the grommet or from the outer peripheral surface side to the front end surface side. In some cases, an air passage may be formed in the porous body forming portion so as to communicate between the outside and the inside of the outer cylinder. If water or the like enters through the air passage, the electric element may malfunction or become inoperable. By forming the resin-impregnated layer at least in the surface layer portion of the porous body forming portion, it is possible to close this air passage and prevent water or the like from entering. In this case, if the resin impregnated layer is formed so as to include the rear end surface of the grommet (that is, the surface exposed from the opening of the outer cylinder), or if the resin impregnated layer is formed so as to include the outer peripheral surface of the grommet. The gap on the rear end surface or the outer peripheral surface of the grommet can be reliably closed to effectively prevent water or the like from entering.

As the impregnated resin forming the resin impregnated layer, for example, a resin mainly composed of a thermoplastic polyimide (hereinafter abbreviated as TPI) resin can be used. T
The PI resin is a heat-resistant resin having a melting point exceeding 300 ° C. and has excellent moldability.

Further, according to the present invention, the grommet is arranged inside the opening of the outer cylinder, and the entire circumferential joint for joining the inner wall of the opening and the outer peripheral surface of the grommet is formed along the circumferential direction of the grommet. it can. Along the circumferential direction of the grommet (that is, the circumferential direction of the opening of the outer cylinder), the entire circumferential joint is formed by, for example, laser welding, resistance welding, brazing, or the like, so that the inner wall of the outer cylinder opening and the outer circumference of the grommet are formed. The gap between the surface and the surface is closed, so that intrusion of water or the like from the gap can be effectively prevented.

On the other hand, in order to solve the above-mentioned problems, in a gas sensor according to a second aspect of the present invention, the electric element is a detecting element for detecting a component to be detected in a gas to be measured. It is characterized in that the lead wire sealing structure according to the first invention is used. Specifically, the gas sensor is provided with a detection element for detecting a component to be detected in a gas to be measured inside, an outer cylinder having an opening at at least one end, and electrically connected to the detection element, A lead wire extending through the opening to the outside of the outer cylinder, a lead wire insertion hole through which the lead wire is inserted, and the lead wire and the outer cylinder are disposed inside the opening; A grommet for sealing between the opening inner wall and a portion including at least a part of the inner surface of the lead wire insertion hole, the grommet comprising a porous body forming portion formed of a porous body. Wherein, between the insertion hole sealing surface forming the inner surface of the lead wire insertion hole and the outer surface of the lead wire in the porous body forming portion is sealed by a sealing resin layer. .

According to the second aspect of the invention, for example, when a gas sensor is installed in an exhaust pipe or the like, the gas sensor is exposed to a high temperature for a long time or subjected to severe thermal cycles. Even in the use environment, the gas sensor can maintain good sealing performance between the outer surface of the lead wire and the inner wall of the opening of the outer cylinder for a long period of time. If the above-mentioned sealing property is maintained, intrusion of water or the like into the gas sensor is prevented, so that the detection element functions without malfunction or inoperability. Therefore, the electric output from the detection element can be obtained in a stable state.

[0023]

Embodiments of the present invention will be described below with reference to embodiments shown in the drawings. FIG. 1 shows an oxygen sensor 1 for detecting the concentration of oxygen in exhaust gas discharged from an internal combustion engine of an automobile or the like as an embodiment of applied electronic equipment configured using the lead wire sealing structure of the present invention. Is shown. The oxygen sensor 1 is a typical gas sensor commonly called a λ-type oxygen sensor, and includes a detection element 2 (electric element).
Has a structure fixed in an axial insertion hole 31 provided inside the cylindrical metal shell 3. Then, the detecting portion D on the tip end side of the detecting element 2 is mounted so as to be located in the exhaust pipe by the mounting screw portion 3a formed on the outer peripheral surface of the metal shell 3, and is exposed to high-temperature exhaust gas flowing in the exhaust pipe. . The metal shell 3 is provided with a flange 3d having a hexagonal cross section and having a predetermined width and protruding from the outer peripheral surface at an intermediate portion of the metal shell 3 in the axial direction of the insertion hole 31. Therefore, when a tool such as a wrench is fitted and rotated in the flange 3d, the oxygen sensor 1 is mounted at a predetermined position in the exhaust pipe by the mounting screw 3a via the gasket 3b.

The detecting element 2 is an elongated element having a rectangular cross section. As shown in FIG. 2A, an oxygen concentration cell element 20 and a oxygen concentration cell element 20 each formed in a horizontally long plate shape are formed. Ceramic heater 2 for heating to a predetermined activation temperature
2 are stacked. The oxygen concentration cell element 20 has an element main body layer 21 made of a solid electrolyte having oxygen ion conductivity. A typical example of such a solid electrolyte is ZrO _{2 in} which Y ₂ O ₃ or CaO is dissolved, but a solid solution of another alkaline earth metal or rare earth metal oxide and ZrO ₂ is used. May be used. Further, HfO ₂ may be contained in ZrO _{2 serving as} a base.

On the other hand, the ceramic heater (hereinafter, also simply referred to as a heater) 22 has a configuration in which a resistance heating element pattern 23 made of a high melting point metal or conductive ceramic is embedded in a ceramic base. Specifically, the heater 2
2 is a first insulating layer 24, a resistance heating element pattern 23,
It has a multilayer structure including a first heater main body layer 28 and a second heater main body layer 29. Among them, the first insulating layer 24
Is formed at an intermediate position in the thickness direction of the heater 22 by an alumina-based ceramic mainly composed of alumina as an insulating ceramic. The resistance heating element pattern 23
Are formed along the plate surface direction of the heater 22 so as to be embedded in the first insulating layer 24. The first heater main body layer 28 and the second heater main body layer 29 are
Are sandwiched from both sides in the thickness direction, and each is made of an oxygen ion conductive solid electrolyte containing zirconia as a main component.

The oxygen concentration cell element 20 has porous electrodes 25 and 26 having oxygen molecule dissociation ability on both sides near one end (a part protruding from the tip of the metal shell 3) in the longitudinal direction. Is formed. Then, the electrodes 25 and 26 and the solid electrolyte portion sandwiched between them form the detection portion D. In the following description, the side protruding from the metal shell 3 in the axial direction (longitudinal direction) of the detection element 2 is referred to as “front side (or front end side)”, and the opposite side is referred to as “rear side (or rear end side)”. "
The description is made as follows.

In the oxygen concentration cell element 20, the porous electrodes 25 and 26 have electrode lead portions 25a extending toward the mounting base end side (rear end side) of the oxygen sensor 1 along the longitudinal direction of the element main body layer 21. , 26a are integrally formed. Of these, the electrode 25 not facing the heater 22
The end of the electrode lead portion 25a is
Used as On the other hand, the electrode lead portion 26a of the electrode 26 on the side facing the heater 22 is formed on the opposite element surface by a via 26b crossing the element body layer 21 in the thickness direction, as shown in FIG. It is connected to the electrode terminal 7. That is, the oxygen concentration cell element 20 has a shape in which the electrode terminal portions 7 of the porous electrodes 25 and 26 are formed side by side at the end of the plate surface on the electrode 25 side. Each of the electrodes 25,
26, the electrode terminal portion 7 and the via 26b are obtained by forming a pattern by screen printing or the like using a paste of a metal powder having a catalytic activity of an oxygen molecule dissociation reaction such as Pt or a Pt alloy, and baking this. Things.

On the other hand, the resistance heating element pattern 2 of the heater 22
The lead portions 23a, 23a for supplying current to
As shown in (d), the oxygen concentration cell element 2 of the heater 22
Electrode terminal portions 7, 7 formed at the end of the plate surface on the side not facing 0 are connected via vias 23b, respectively.

As shown in FIG. 2B, the heater 22
On the first heater main body layer 28 side, it is joined to the porous electrode 26 side of the oxygen concentration cell element 20 via a second insulating layer 27 made of alumina-based ceramic. Then, the porous electrode (reference electrode) 26 on the joining side includes
One end of the electrode lead portion 26a (which is also porous) is connected, and a porous electrode (measurement electrode) 2 on the opposite side is connected.
5, a very small pumping current is applied in the direction in which oxygen is pumped into the porous electrode 26 side. Here, the electrode lead portion 26a is located inside the ceramic element 2 so as to be sandwiched between the joined oxygen concentration cell element 20 and the heater 22, and the terminal face thereof is located on the mounting base end side of the ceramic element 2. It is exposed at the end face to form a gas discharge port. The pumped oxygen is supplied to the electrode lead 26a.
Through the gas outlet to the atmosphere. As a result, the oxygen concentration in the porous electrode 26 is maintained at a value slightly higher than that in the atmosphere, and functions as an oxygen reference electrode. On the other hand, the porous electrode 25 on the opposite side becomes a measurement electrode that comes into contact with the exhaust gas.

As shown in FIG. 1, such a detecting element 2 is inserted through an insertion hole 31 formed in the metal shell 3, and the space between the inner surface of the insertion hole 31 and the outer surface of the detecting element 2 is Glass (for example, crystallized zinc silica borate glass)
Is sealed by a sealing material layer 32 mainly composed of The detecting element 2 includes a metallic shell 3 whose distal end detecting portion D is fixed to the exhaust pipe by the sealing material layer 32 or the like.
Is fixed in the metallic shell 3 in a state protruding from the tip of the metal shell. On the outer periphery of the distal end portion 3h of the metal shell 3, double protective covers 6a and 6 made of metal cover the protruding portion of the detection element 2.
b is fixed by laser welding or resistance welding (for example, spot welding). These covers 6a, 6b
Has a cap-like shape, and has openings 6c and 6d formed at its tip and surroundings for guiding high-temperature exhaust gas flowing through the exhaust pipe into the covers 6a and 6b. On the other hand, the rear end portion of the metal shell 3 is inserted inside the front end portion of the outer cylinder 18, and at the overlapped portion, a welded portion (for example, a laser welded portion) 35 is formed in the circumferential direction as an annularly connected portion so as to be airtight. It is joined by.

Each of the electrode terminals 7 (collectively referred to as four poles) of the detecting element 2 is connected to a lead wire 1 via a first connector A, a conducting wire 8 (a long metal thin plate) and a second connector 13.
4 are electrically connected. The four lead wires 14 are connected to an opening 18 formed on the rear end side of the outer cylinder 18.
A connector plug (not shown) is connected to a tip end of the grommet 51 which extends through the grommet 51 fitted inside the c. Further, the grommet 51 of each lead wire 14
A portion extending further outward is covered with a protective tube 17 that converges and protects them.

FIG. 3 shows an example of the lead wire sealing structure 50. In the embodiment of FIG. 3, the sealing structure 50 is a grommet 5
1. It is composed of an entire circumference welded portion 52, a sealing resin layer 53, and the like. The grommet 51 is formed such that a lead wire insertion hole 51a through which the lead wire 14 is inserted is formed to penetrate in the axial direction, and is fitted inside the opening 18c of the outer cylinder 18 so that the lead wire 14 and the outer cylinder 18 are The space between the opening 18c and the inner wall is sealed. The grommet 51 is entirely composed of a porous body forming portion 51b formed of a porous metal. Specifically, the porous body forming portion 51b (the grommet 5)
1) is made of stainless steel (for example, SUS304) manufactured by sintering. Accordingly, even when the oxygen sensor 1 is exposed to high temperature for a long time or a thermal cycle is repeatedly applied, the gap k formed in the porous body forming portion 51b does not collapse, and the sealing structure 50 is not damaged. Can maintain good sealing performance between the outer surface of the lead wire 14 and the inner wall of the opening 18c of the outer cylinder 18.

As shown in FIG. 3B, there are four lead wires 14 for convenience, and each lead wire 14 has a core wire 14a.
Is covered with a jacket 14b made of a polytetrafluoroethylene (PTFE) resin tube. In the grommet 51, four lead wire insertion holes 51a into which the respective lead wires 14 are individually inserted penetrate in the axial direction, respectively, and the center of each lead wire 14 is perpendicular to the axis of the lead wire insertion hole 51a. They are arranged at equal intervals on a single pitch circle P. And, between the inner surface of each lead wire insertion hole 51a and the outer surface of the outer jacket 14b of the corresponding lead wire 14,
It is sealed by a sealing resin layer 53 mainly composed of PFA resin. Here, the sealing resin layer 53 is formed by heat welding so that the inner surface of each lead wire insertion hole 51a and the outer
It is sealed while being joined to the outer surface. A counterbore portion 51a 'is formed in each lead wire insertion hole 51a of the grommet 51, and a sealing resin layer 53 is filled in the counterbore portion 51a'.

The porous body forming portion 51 shown in FIG.
b at the contact surface between the sealing resin layer 53 and the sealing resin layer 53.
The void k of the porous metal formed on the inner surface of the a ′ (lead wire insertion hole 51a) (that is, the porous metal formed by being exposed on the surface of the insertion hole sealing surface 510 of the porous body forming portion 51b). The gap k) is filled with the sealing resin layer 53. That is, since the sealing resin layer 53 mechanically engages with the insertion hole sealing surface 510 of the porous body forming portion 51b, the porous body forming portion 51b and the sealing resin layer 53 are strongly adhered. Then, the counterbore portion 51a '(lead wire insertion hole 5)
The sealing resin layer 53 is joined by heat welding so as to seal between the inner surface of 1a) and the outer surface of the jacket 14b of the lead wire 14, thereby realizing a sealing structure having good sealing properties. .

Here, the counterbore portion 51a 'is shown in FIG.
As shown in the figure, the grommet 51 is provided up to approximately half the axial length starting from the rear end surface. Counterbore 51
The front end of a ′ has a reduced diameter on the front side, and the sealing resin layer 53 is formed.
Also, corresponding to the reduced diameter portion, the thickness decreases toward the front side. As a result, the length of the sealing resin layer 53 in the axial direction is shorter than that of the grommet 51. Thus, a part of the inner surface of the lead wire insertion hole 51a,
That is, an inner surface portion corresponding to the axial length of the counterbore portion 51a 'forms the insertion hole sealing surface 510. However, the insertion hole sealing surface 510 of the porous body forming portion 51b is formed over the entire inner surface of the lead wire insertion hole 51a (counterbore portion 51a ') in the circumferential direction, and the insertion hole sealing surface 510 is formed. Are arranged so as to surround the entire circumference of the lead wire 14. Then, the space between the insertion hole sealing surface 510 and the outer surface of the jacket 14b of the lead wire 14 is sealed by the sealing resin layer 53 without any gap. Therefore, the porous body forming part 5
If the insertion hole sealing surface 510 of 1b is arranged so as to surround the entire circumference of the lead wire 14, the sealing performance between the insertion hole sealing surface 510 and the outer surface of the outer cover 14b of the lead wire 14 is further ensured. Of course, the insertion hole sealing surface 510 may occupy the entire inner surface of the lead wire insertion hole 51a (see, for example, FIG. 7B). The above-described shape of the spot facing portion 51a 'may be formed when the grommet 51 is molded and sintered into a desired shape by a die press.

The stainless steel (for example, SUS304) forming the porous body forming portion 51b has a porosity of 25 to 45% (preferably 30 to 45%).
40%), and the average particle size of the sintered powder is 100 to 250 μm.
m (preferably 150 to 200 μm).

Depending on the degree of sintering of the porous metal, the gap k distributed in the porous body forming portion 51b of the grommet 51 extends in a series from the rear end surface to the front end surface of the grommet 51 or from the outer peripheral surface to the front end surface. Lined continuously in a chain,
An air passage K may be formed in the porous body forming portion 51b so as to communicate the outside and the inside of the outer cylinder 18 (FIG. 3).
(C)). In such a case, if the resin impregnated layer 51b 'is formed (impregnated) on the respective surface layer portions on the rear end surface, outer peripheral surface, and front end surface of the porous body forming portion 51b of the grommet 51, the resin impregnated layer 51b 'Closes the air passage K and prevents water or the like from entering.

The grommet 51 is connected to the opening 18c of the outer cylinder 18.
It is inserted inside and forms a full circumference weld 52 (full circumference joint) by, for example, laser welding or resistance welding along the circumferential direction of the grommet 51 (or the opening 18c of the outer cylinder 18). The inner wall and the outer peripheral surface of the grommet 51 are joined. As a result, the gap S between the inner wall of the opening 18c of the outer cylinder 18 and the outer peripheral surface of the grommet 51 is closed, and intrusion of water or the like from the gap S is prevented.

Such a sealing structure 50 can be formed, for example, as follows. First, as shown in FIG. 4A, a lower punch LP is inserted into a pressurizing chamber formed at the center of a mold M, and a sintered metal powder of stainless steel is used as a porous metal material for forming the grommet 51. T is filled in the pressurizing chamber of the mold M. After the filling is completed, the upper punch UP is inserted into the pressurizing chamber of the mold M from above. At this time, four pins FP fixed to the pedestal B are buried in the filling layer of the sintered powder T, and the fixed pins FP also pass through the upper punch UP via the lower punch LP and the pressure chamber. Each fixing pin FP has a lead wire insertion hole 51a for inserting the lead wire 14 and a counterbore 5 for forming the sealing resin layer 53.
1a '. When the upper punch UP is pressurized, the porous grommet molded body 51A is pressed.
Is obtained, the lower punch LP is raised, and the grommet molded body 51A is extracted. In addition, in order to make the grommet molded body 51A after pressure molding a porous body, the following adjustment is performed so that the density of the grommet molded body 51A becomes 4.5 to 6.5 g / cm ³ . That is, the lower punch LP is moved up and down when filling the sintered powder T to adjust the powder filling amount, and the stroke amount of the upper punch UP during pressure molding (corresponding to the axial dimension of the grommet molded body 51A).
To adjust. The density of the grommet molding 51A is 4.5 g.
If it is less than / cm ³ , the grommet molded body 51A may not be sufficiently hardened and may remain in a powder state. on the other hand,
If the density exceeds 6.5 g / cm ³ , the porous body may not be formed because the void k does not sufficiently remain.

The grommet molded body 51A thus obtained is fired in a nitrogen atmosphere at a temperature of about 1120 ° C. for about 1 hour. As a result, as shown in FIG. 4B, a grommet sintered body 51B having four lead wire insertion holes 51a and its counterbore portion 51a 'and entirely formed of a porous body forming portion 51b is provided. Is obtained.

Next, as shown in FIG. 5A, a thermoplastic polyimide (hereinafter abbreviated as TPI) resin in an emulsion state is stored in an immersion tank T, and if necessary, diluted with a solvent to reduce the resin content to 20%. About 40% by weight (for example, 30% by weight) of the impregnating agent E is prepared. The grommet sintered body 51B prepared in FIG. 4 (b) is soaked in the impregnating agent E of the immersion tank T, and distributed on the respective surface layer portions on the rear end surface, the outer peripheral surface, and the front end surface of the porous body forming portion 51b. The void k is filled with an impregnating agent (TPI resin emulsion) E.

Further, as shown in FIG. 5 (b), the surface layer of the porous body forming portion 51b is impregnated with the impregnating agent E by vacuum evacuation at room temperature and dried at 200 to 400 ° C. (for example, 380 ° C.). The resin impregnated layer 51b 'is formed on the surface of the porous body forming portion 51b. As a result, the air gaps k are continuously arranged in a series of chains, and the air passage K formed between both end faces of the grommet sintered body 51B or between any one of the end faces and the outer peripheral face is changed to the air gap k. It is closed by filling with the impregnating agent E (see FIG. 3C).

Next, as shown in FIG. 6A, a PFA resin tube 53 'corresponding to the sealing resin layer 53 (FIG. 3) to be formed is prepared. Then, these PFA resin tubes 53 'are attached to the respective lead wires 14 outside the jacket 14b. In this embodiment, the PFA resin tube 5
The inner diameter of the hole 3 ′ is set slightly larger than the outer diameter of the lead wire 14 from the viewpoint of facilitating insertion of the lead wire 14 and improving work efficiency. On the other hand, the inner diameter of the hole of the PFA resin tube 53 ′ may be set slightly smaller than the outer diameter of the lead wire 14. In this case, there is an advantage that the PFA resin tube 53 'can be easily positioned at a predetermined position on the lead wire 14 by friction.

Now, the four cores N buried in the grommet sintered body 51B in FIG.
When the grommet is pulled out from the side where 1a 'is formed, four lead wire insertion holes 51a and counterbore portions 51a' penetrating in the axial direction appear in the grommet sintered body 51B. Therefore, FIG.
As shown in (b), each lead wire 14 to which the PFA resin tube 53 'is attached is connected to a grommet sintered body 51, respectively.
B is inserted into the lead wire insertion hole 51a. At this time, each P
The FA resin tube 53 'enters the counterbore portion 51a' of the lead wire insertion hole 51a together with the lead wire 14 and is stopped by hitting a reduced diameter portion formed at the tip of the counterbore portion 51a '. Thus, the lead wire 14 is positioned and mounted on the grommet sintered body 51B. In addition,
When positioning the PFA resin tube 53 ′, it is advantageous to set the inner diameter of the lead wire insertion hole 51 a to be slightly smaller than the outer diameter of the lead wire 14. The inner diameter of the lead wire insertion hole 51a is set to be slightly larger than the outer diameter of the lead wire 14 in order to ensure the efficiency of insertion.

In the state of FIG. 6B, the whole is heated above the softening point of the PFA resin (for example, at 360 ° C. for 20 minutes).
As a result, as shown in FIG. 6C, the PFA resin tube 53 'is fused to the inner surface of the counterbore portion 51a', that is, the insertion hole sealing surface 510, and the outer surface of the sheath 14b of the lead wire 14, respectively. The sealing resin layer 53 becomes the grommet 51. In addition, as a method of forming the sealing resin layer 53, there is the following method other than the method of forming using the PFA resin tube 53 '. That is, the lead wire insertion hole 51a (the counterbore 51)
a ′) may be filled with a powder, solution, emulsion or the like of the PFA resin and heated to a temperature higher than the softening point of the PFA resin in the same manner as described above.

Then, as shown in FIG. 6C, the grommet 51 is inserted inside the rear end side opening 18c of the outer cylinder 18, and the rear end face of the grommet 51 and the opening 18c of the outer cylinder 18 are inserted.
Align with the trailing edge. Then, in this state, the entire circumference welded portion 52 is formed along the circumferential direction of the grommet 51 (or the opening 18c of the outer cylinder 18), and the inner wall of the opening 18c and the outer peripheral surface of the grommet 51 are joined. Specifically, a YAG (yttrium, aluminum, garnet) laser beam LB emitted from the laser light source L is applied to the outer cylinder 18.
Irradiation is performed in a substantially horizontal direction on the outer peripheral surface of the opening 18c. At this irradiation position, the outer peripheral surface of the grommet 51 and the inner wall of the opening 18c of the outer cylinder 18 are welded to each other by metal, so that the outer peripheral surface of the grommet 51 and the opening 18c of the outer cylinder 18 are fused.
The gap S formed between the inner wall and the inner wall is closed. The sealing structure 50 is completed as described above.

Next, returning to FIG. 1, in the axial direction of the detection element 2, in a form adjacent to at least one side of the sealing material layer 32 (in this embodiment, A buffer layer 38 made of a porous inorganic material is formed (adjacent to the near end face side). The buffer layer 38 is formed as a green compact or a porous calcined body of an inorganic material powder such as talc (talc), and the ceramic element 2 projecting from the sealing material layer 32 in the axial direction is externally formed. It supports so as to wrap, and plays a role of suppressing excessive bending stress and thermal stress from being applied to the detection element 2.

A gap 33 surrounding the periphery of the sealing material layer 32 is provided between the inner surface of the insertion hole 31 and the inner surface of the outer cylinder 18.
However, it is formed in a form in which a part of the metal shell 3 is cut out. The gap 33 has an annular shape formed in the circumferential direction of the insertion hole 31 of the metal shell 3, and is a groove extending in the forming direction of the insertion hole 31 at a middle portion in the thickness direction of the metal shell 3 ( Hereinafter, the groove portion 33). In the present embodiment, the bottom surface 33 a of the groove 33 is located on the tip side of the corresponding end surface of the sealing material layer 32 in the axial direction of the detection element 2.

The grooves (voids) 33 serve as a heat insulating layer when a sudden change in temperature or the like is applied to the sensor 1, and the influence of the thermal shock is less likely to reach the sealing material layer 32. Further, since the metal shell portion 3g forming the outer wall of the groove 33 can act as a buffer for absorbing an impact due to its own deformation, the influence on the sealing material layer 32 can be reduced. The bottom surface 33a of the groove 33 is formed so as to extend to the front end side from the rear end edge 3e of the flange 3d of the metal shell 3 in the axial direction of the detection element 2. Thereby, the groove 33
Is formed over the entire length of the thin portion 3f to which the outer cylinder 18 on the rear end side of the metal shell 3 is joined. In this case, the bottom surface 33a of the groove 33 is located closer to the distal end than the welded portion 35 in the axial direction of the detection element 2.

Hereinafter, the operation of the oxygen sensor 1 and the sealing structure 50 will be described.
The operation of will be described. That is, the oxygen sensor 1
As described above, the screw 3a of the metal shell 3 is fixed to the exhaust pipe of the vehicle or the like, and each lead wire 14 is connected to the controller via a connector plug (not shown) for use. Then, when the detection unit D is exposed to the exhaust gas, the porous electrode 25 (FIG. 2) of the oxygen concentration cell element 20 comes into contact with the exhaust gas, and the oxygen concentration cell element 20 detects the oxygen concentration in the exhaust gas. The corresponding oxygen concentration cell electromotive force is generated.
This electromotive force is taken out as a sensor output via the electrode terminal portions 7, 7 via the electrode lead portions 25a and 26a, and further via the lead wires 14, 14. This type of λ-type oxygen sensor is widely used for air-fuel ratio detection because it exhibits a characteristic that the concentration cell electromotive force changes abruptly in the vicinity where the exhaust gas composition reaches the stoichiometric air-fuel ratio.

Here, the mounting position of the oxygen sensor 1 in, for example, an automobile is an exhaust manifold, an exhaust pipe close to a portion around a foot of the vehicle, or the like, and the temperature is considerably high. However, in the sealing structure 50, the sealing resin layer 53 is filled in the void k of the porous metal formed in the portion including the insertion hole sealing surface 510 of the grommet 51, and the sealing resin layer 53 is sealed with the porous body forming portion 51b. It is strongly adhered to the resin layer 53.
As a result, even in a usage environment that is exposed to high temperatures for a long time,
The sealing structure 50 can maintain good sealing performance between the outer surface of the lead wire and the inner wall of the opening of the outer cylinder for a long time.

Further, the attachment position is liable to be splashed. However, in the sealing structure 50,
A resin-impregnated layer 51b 'is formed on the surface of the porous body forming portion 51b of the grommet 51, and blocks the air passage K. Further, the grommet 51 (or the opening 18c of the outer cylinder 18)
A circumferential welded portion 52 is formed along the circumferential direction of the outer cylinder 18 to close the gap S between the outer peripheral surface of the grommet 51 and the inner wall of the opening 18 c of the outer cylinder 18. As a result, the sealing structure 50 can maintain good waterproof performance for a long period of time even under a use environment in which water is easily splashed.

FIG. 7 shows a modification of the lead wire sealing structure. In the sealing structure 60 of FIG. 7A, the entire circumference brazing portion along the circumferential direction of the grommet 51 (or the opening 18c of the outer cylinder 18) is used instead of the full circumference welding portion 52 of FIG. 54 (all circumferential joints) are formed. Specifically, a brazing portion 54 is formed over the entire length of the grommet 51 in the axial direction along the circumferential direction, and a gap S between the outer peripheral surface of the grommet 51 and the inner wall of the opening 18 c of the outer cylinder 18 is formed. Is blocking.
Parts common to the embodiment of FIG. 3A are denoted by the same reference numerals, and description thereof is omitted.

In the sealing structure 70 of FIG. 7B, the non-porous grommet 51 is provided on the grommet 51 through the entire circumference brazing layer 51c formed along the circumferential direction of the outer peripheral surface of the porous body forming portion 51b. The metal ring 51d is integrally joined and inserted inside the opening 18c of the outer cylinder 18. Further, an all-around welded portion 52 (all-around joint) is formed along the circumferential direction of the grommet 51 (or the opening 18c of the outer cylinder 18). Specifically, the entire circumference welded portion 52 is formed by laser welding or the like, and the gap S between the outer peripheral surface of the grommet 51 (non-porous metal ring 51d) and the inner wall of the opening 18c of the outer cylinder 18 is closed. . The gap S ′ between the outer peripheral surface of the porous body forming portion 51b and the inner peripheral surface of the non-porous metal ring 51d is
The grommet 51 (porous body forming portion 51b) is closed over the entire length in the axial direction by a circumferential brazing layer 51c formed along the circumferential direction.

In the sealing structure 70 shown in FIG.
A slightly larger diameter lead wire insertion hole 51 is provided at the center of the grommet 51.
a is formed, a plurality of lead wires 14 are collectively inserted therein, and the outer surfaces of the respective lead wires 14 and the inner surface of the lead wire insertion hole 51a (constituting the insertion hole sealing surface 510). Are sealed by an integral sealing resin layer 53. Parts common to the embodiment of FIG. 3A are denoted by the same reference numerals, and description thereof is omitted.

In the sealing structure 70 shown in FIG. 7B, the outer circumferential surface of the grommet 51 (non-porous metal ring 51d) and the opening of the outer cylinder 18 are formed by forming the entire circumference welded portion 52 by laser welding or the like. When the gap S ′ between the outer peripheral surface of the porous body forming portion 51b and the inner peripheral surface of the non-porous metal ring 51d as well as the clearance S between the inner wall of the porous body forming portion 51b is closed, In some cases, it is not necessary to provide the brazing layer 51c. Also, in the sealing structure 70 of FIG. 7B, instead of the full circumference welded portion 52, a full circumference brazing portion 54 described in the example of FIG. 7A is replaced with a grommet 51 (non-porous metal ring). 51d) may be formed between the outer peripheral surface and the inner wall of the opening 18c of the outer cylinder 18.

[0057] Incidentally, the second invention, HC sensor in addition to the oxygen sensor, NOx sensor, CO sensor, can also be applied to CO ₂ sensor or the like other gas sensors. Further, as applied electronic equipment to which the first invention is applied, in addition to these gas sensors, a ceramic heater, a glow plug, and the like can be given.

As the porous body, a porous ceramic or the like can be used in addition to the porous metal described above. Further, a porous body can be formed by spraying a metal, a ceramic or the like on the surface thereof.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an example of an oxygen sensor which is an embodiment of applied electronic equipment to which a lead wire sealing structure according to the present invention is applied.

FIG. 2 is an explanatory diagram showing a structure of a detection element in FIG.

FIG. 3 is a vertical cross-sectional view, a horizontal cross-sectional view, and a main part enlarged cross-sectional schematic view illustrating an example of a lead wire sealing structure.

FIG. 4 is an explanatory view of an assembling process of the lead wire sealing structure of FIG. 3;

FIG. 5 is an explanatory view following FIG. 4;

FIG. 6 is an explanatory view following FIG. 5;

FIG. 7 is a longitudinal sectional view showing a modified example of the lead wire sealing structure.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Oxygen sensor (gas sensor; applied electronic equipment) 2 Detecting element (electric element) 20 Oxygen concentration cell element 22 Ceramic heater (heater) 14 Lead wire 14a Core wire 14b Jacket 18 Outer cylinder 18c Opening 50, 60, 70 Lead wire sealing Stopping structure 51 Grommet 51a Lead wire insertion hole 51a 'Counterbore part 51b Porous body forming part 51b' Resin impregnated layer 510 Insertion hole sealing surface 52 Fully welded part (entirely joined part) 53 Sealing resin layer 54 All around Brazing part (All-around joint)

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Takashi Nakao 14-18 Takatsuji-cho, Mizuho-ku, Nagoya-shi, Aichi F-term in Japan Special Ceramics Co., Ltd. 2G004 BB01 BB04 BC07 BF13 BF18 BF27 BG05 BH02 BH09 BJ02 2G060 AA01 AB05 AB08 AB09 AB10 AB16 AB19 AE19 AF09 AG11 BB09 HA01 HB06 JA01 KA01 5G375 AA02 BA09 BB48 BB55 BB60 CA02 CA19 CB03 CB05 CB06 CC10 DA04 DA05 DB16 DB32 DB44

Claims (10)

[Claims] 1. An outer cylinder having an electric element disposed therein and having an opening at at least one end; a lead wire being electrically connected to the electric element and extending to the outside of the outer cylinder through the opening; A grommet having a lead wire insertion hole through which the lead wire is inserted, and being disposed inside the opening to seal between the lead wire and an inner wall of the opening of the outer cylinder; Inside, a portion including at least a part of the inner surface of the lead wire insertion hole is formed of a porous material forming portion formed of a porous material, and the inner surface of the lead wire insertion hole is formed in the porous material forming portion. Wherein the gap between the insertion hole sealing surface to be inserted and the outer surface of the lead wire is sealed by a sealing resin layer. 2. The lead wire sealing structure according to claim 1, wherein said porous body is a porous metal. 3. The lead wire encapsulation according to claim 1, wherein the sealing resin layer is sealed to the insertion hole sealing surface and an outer surface of the lead wire in a state of being joined by heat welding. Construction. 4. The lead wire sealing structure according to claim 1, wherein the sealing resin layer is mainly made of a tetrafluoroethylene-perfluoroalkyl vinyl ether resin. 5. A plurality of said lead wires are provided in a state where a core wire is covered with a resin sheath, and said grommet is formed with a plurality of said lead wire insertion holes through which respective lead wires are individually inserted. 5. The sealing resin layer is used to seal a gap between the insertion hole sealing surface formed in each lead wire insertion hole and the outer surface of a corresponding sheath of the lead wire. The lead wire sealing structure according to any one of the above. 6. The lead wire according to claim 1, wherein a counterbore portion is formed in the lead wire insertion hole, and an inner surface of the counterbore portion forms the insertion hole sealing surface. Sealing structure. 7. The lead wire sealing structure according to claim 1, wherein a resin-impregnated layer is formed at least in a surface layer portion of the grommet at the porous body forming portion. 8. The lead wire sealing structure according to claim 7, wherein said resin-impregnated layer is mainly composed of a thermoplastic polyimide resin. 9. The grommet is arranged inside the opening of the outer cylinder, and a full-circumferential joint that joins the inner wall of the opening and the outer peripheral surface of the grommet is formed along the circumferential direction of the grommet. The lead wire sealing structure according to any one of claims 1 to 8, wherein: 10. A detection element for detecting a component to be detected in a gas to be measured is disposed inside, an outer cylinder having an opening at at least one end, and an opening connected to the detection element. A lead wire passing through and extending to the outside of the outer cylinder; and a lead wire insertion hole through which the lead wire is inserted, and disposed inside the opening, and the inner wall of the opening of the lead wire and the outer cylinder. A grommet for sealing between the grommet and a portion including at least a part of the inner surface of the lead wire insertion hole is formed of a porous body forming portion formed of a porous body; A gas sensor, wherein a gap between an insertion hole sealing surface forming an inner surface of the lead wire insertion hole and an outer surface of the lead wire in the body forming portion is sealed by a sealing resin layer.