JP2001147214A - Airtight piercing part especially for measuring sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To minimize risk such that a crack is formed by internal stress. SOLUTION: A piercing part is constituted in order to fix a flat member in the through-slit 24 of a support 20 airtightly and has a receiving chamber 30 arranged so as to surround the flat member at least at one end part of the slit 24. The receiving chamber has a seal substance containing a meltable component developing sealing action by coagulation and this seal substance bonds the flat member to the support 20 airtightly. The receiving chamber 30 has inner walls 31, 32 parallel to the flat surfaces of the flat member.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[Field of the Invention] Patent application for the Federal Republic of Germany 1
From 97 07 459.6 a measuring sensor having a rotationally symmetric housing and a flat sensor element mounted therein is known, in which the gas-tight penetration of the sensor element is produced as follows. Have been. That is, the sensor element extends through a slit in the support, the slit being enlarged at one end into a cylindrical receiving chamber, which is provided with a sealing substance which can be melted and seals by solidification. The sealing substance bonds the flat part of the sensor element to the support in a gas-tight manner.

In order to create a tight connection between the support and the sensor element, a sealing pack is first inserted and pressed into the receiving chamber of this known measuring sensor,
This brings the seal pack into contact with the sensor element and the surrounding wall of the receiving chamber. The sensor element is thereby pre-fixed in the slit, and at the same time a first seal is achieved. A sealing substance containing powdered or granular glass is then placed in the receiving chamber and allowed to melt. In this case, the glass bonds with the sensor element and the wall of the receiving chamber and, in the ideal case, constitutes a completely gas-tight and gasoline-resistant penetration.

However, differences in the coefficient of thermal expansion of the glass used as support, sensor element and sealing material cause stresses in the penetrations, which may already be present during the cooling of the glass after it has been melted, or during measurement of the sensor. During subsequent use, cracks form, which inevitably leads to malfunctions of the measuring sensor.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to make it possible to simply produce a through-hole for air-tightly fixing a flat element, for example a sensor element, for example in a through-slit of a support of a measuring sensor. In such a case that the risk of crack formation due to internal stresses is small.

[0005]

This object is achieved by the following. That is, instead of the conventional circular or cylindrical receiving chamber, a receiving chamber having an inner wall parallel to the flat surface of the member is used. As a result, the residual stress between the support, the sealing material and the flat member is evenly distributed, especially frequently, due to the substantially constant thickness of the sealing material along the entire circumference of the flat member. The occurrence of stress peaks at which cracks occur is sufficiently avoided.

[0006]

In this case, furthermore, in order to limit the thermal stress, the distance between the flat surface and the respective inner wall is 1.5 times the thickness of the flat member. , Preferably less than or equal to 1.2 times the thickness. This ratio is an excellent balance between the strength of the flat part, in particular the flat sensor element, and the thermal stress exerted on it by the sealing material. In particular, in the case of a penetrating part of the measuring sensor, in terms of absolute values, the distance between the flat surface and the respectively facing inner wall is less than or equal to 1.8 mm. , Advantageously 1.5 mm
Less than or the same.

Furthermore, in order to limit the stress peaks, the curved section of the inner wall of the receiving chamber has a radius of curvature no smaller than half of the thickness of the flat member or no smaller than 0.6 mm. Has proven to be advantageous.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the structure of the present invention will be described specifically and in detail based on embodiments shown in the drawings.

FIG. 1 shows an axial sectional view of an electrochemical measuring sensor for determining the oxygen content in the exhaust gas of an internal combustion engine. The measuring sensor 10 has a metal casing 12 in which a flat sensor element 26 is mounted. The construction of such a sensor element is well known and is not critical to the invention and need not be described at length here. Casing 12
Has a thread 13 for fixing it in the hole of the exhaust gas pipe not shown. A vertical hole 15 having a ring-shaped shoulder surface 16 in the casing 12 is provided with an end surface 21 on the measurement gas side.
And a ceramic molded part 20 having an end face on the connection side and an axial through slit 24. The ceramic molded part 20 is made of, for example, aluminum oxide, and is supported on the shoulder surface 16 of the casing 12 via a seal ring 18 with a conical section formed on the outer peripheral surface. This ceramic molded part is the sensor element 26
Forming a support for

The end face 2 on the connection side of the ceramic molded part 20
2, a receiving chamber 30 surrounding the slit 24 is formed. In the receiving chamber 30 there is a seal 29, which holds the sensor element 26 in a gas-tight manner in the ceramic part 20. The sealing portion 29 is made of glass, for example, Li-Al-silicate glass or Li-Ba-Al
-Contains silicate glass. Glass seal 29
Is manufactured by placing a sealing material containing glass powder or glass particles into a receiving chamber 30 and heating to the melting temperature of the glass used. This provides an absolutely gas-tight and gasoline-resistant seal of the sensor element in the ceramic part 20. A metal sleeve 36 is fitted over the connection-side end of the casing 12;
It has a plurality of inwardly directed pawls 37 which engage within the notches in the casing. The metal sleeve 36 presses the ceramic molded part against the seal ring 18 so that the ceramic molded part 20 and the casing 12
Produces an airtight and gasoline-resistant seal between

The measuring gas side end section 27 of the sensor element 26 projects from the housing 12 and is surrounded by a double-walled protective tube 40 having a plurality of gas inlet / outlet openings 41.

FIGS. 2-4 show plan views of the connecting end surface 22 of the ceramic molded part according to various embodiments of the present invention.
In the embodiment of FIG. 2, the receiving chamber 30 comprises four inner wall sections 3 parallel to the straight wide and narrow outer surfaces of the sensor element or the side walls of the corresponding slit 24, respectively.
1, 32, and each of these inner wall sections is 1
Are connected by a / 4 circle section 33. Inner wall section 3
The width of the receiving chamber 30 between each of the slits 1 and 32 and the side wall of the slit 24 is 1.25 mm. The radius of curvature of the quarter circle section 33 is approximately 0.8 mm.

The embodiment of FIG. 3 also has an inner wall section 31 which is parallel to the long sides of the slit 24. Instead of the inner wall section 32 and the quarter circle section 33, two semicircular arc sections 34 are provided. In the embodiment of FIG. 4, a straight section 35 is provided instead of the quarter circle section 33. Since these straight sections intersect the adjacent inner wall sections 31 and 32 at an obtuse angle of 135 °, the risk of cracks from the corners is again reduced in this case.

[Brief description of the drawings]

FIG. 1 is an axial sectional view of a measurement sensor having a penetration according to the present invention.

FIG. 2 is an axial plan view of a first embodiment of the insulating bush of the measurement sensor of FIG. 1;

FIG. 3 is an axial plan view of a second embodiment of the insulating bush of the measuring sensor of FIG. 1;

FIG. 4 is an axial plan view of a third embodiment of the insulating bush of the measurement sensor of FIG. 1;

[Explanation of symbols]

Reference Signs List 10 measurement sensor, 12 casing, 13 screw thread, 15 vertical hole, 16 shoulder surface, 18 seal ring, 20 ceramic molded part, 21 measurement gas side end surface, 22 connection side end surface, 24 slit,
26 sensor element, 27 end section, 29 seal part, 30 receiving chamber, 31 inner wall section, 32
Inner wall section, 33 1/4 circle section, 34 semi-arc section, 35 straight section, 36 metal sleeve, 37
Claws, 40 protection tube, 41 gas inlet / outlet opening

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Helmut Weil, Germany Schwieberdingen Peter Fau Koblenz 34 (72) Inventor Bernhard Wild, Germany Marc Greiningen-Uhlandstrasse 7 (72) Inventor Karl-Hellman Frize Germany Leonberg-Obe les Burgharde 54

Claims (6)

[Claims] 1. A through-hole for hermetically fixing a flat member (26) in a through-slit (24) of a support (20), wherein at least one end of the slit (24) is flat. It has a receiving chamber (30) arranged to surround the member (26), the receiving chamber comprising a sealing substance (29) containing a meltable and solidifying component which seals. The sealing material is of the type which connects the flat member (26) to the support (20) in a gas-tight manner, wherein the receiving chamber (30) has inner walls (31, 32) parallel to the flat surface of the member. A through portion for hermetically fixing a flat member in a through slit of the support. 2. The distance between the flat surface and the respective inner wall (31, 32) facing each other is 1.5 times the thickness of the flat member (26), preferably 1. Characterized by being less than or equal to twice the thickness,
The penetration according to claim 1. 3. The distance between the flat surface and the respectively facing inner wall (31, 32) is less than or equal to 1.8 mm, preferably 1.5 m
3. The penetration according to claim 1, wherein the penetration is smaller than or equal to m. 4. A curved section (3) of the inner wall of the receiving chamber (30).
4. The penetration according to claim 1, wherein the flat part has a radius of curvature not less than half of the thickness of the flat part. 5. A curved section of the inner wall of the receiving chamber.
Has a radius of curvature not less than 0.6 mm. 5. The penetration according to claim 1, wherein 6. A fuel measuring sensor having a rotationally symmetric casing (12) and a flat sensor element (26) mounted therein, wherein the casing is one of claims 1 to 5. Fuel measuring sensor, characterized in that it has a support (20) for the penetration according to claim 1 and the flat element is a sensor element (26).