JPH0778476B2 - Assembling structure of detection element - Google Patents

Description

Description: [Industrial application] The present invention relates to a structure for assembling a detection element to a metal shell.

[Prior Art] In recent years, various sensors have been used for the purpose of pollution prevention, energy saving, fine process control, and the like.

As one of the sensors, there is a sensor in which a detection element made of a cylindrical or plate-shaped ceramic is mounted on a cylindrical metal shell.

As this assembling method, a structure has been used in which the detecting element is inserted into the metal shell and then fixed at a predetermined position using heat resistant cement. However, this structure has the following problems.

(1) It is not easy to accurately insert and hold the detection element in a predetermined position in the metal shell and evenly inject the heat-resistant cement between the detection element and the metal shell.

(2) The relative position between the detection element and the metal shell must be temporarily fixed until the injected heat-resistant cement is cured.

(3) Since the heat-resistant cement is injected through the opening on the head side, it inevitably adheres to the head side end of the detection element and the electrode wire, and is filled with glass for the purpose of hermetic sealing in a later step. The space that should be used is narrow and limited, and a complete hermetic seal cannot be expected.

In order to solve such a problem, there is a method of supporting the position of the detection element by using a spacer made of asbestos, glass fiber or the like.

That is, first, insert a detection element with a spacer made of asbestos, glass fiber or the like into the metal shell, fill the gap between the metal shell and the detection element with talc or the like as a filling material, and then fix the filling material. This is a method of inserting or injecting a ring or glass into the metal shell.

[Problems to be Solved by the Invention] However, the above-mentioned method has the following problems.

(1) The spacer made of asbestos, ceramic fiber or the like supports the detection element in the metal shell by the frictional force between the inner wall of the metal shell and the spacer and the frictional force between the spacer and the detection element. However, since the elasticity is low, the force for pressing the detection element is weak, and the position of the detection element may shift in the process of filling the filling material.

(2) Due to lack of elasticity, many gaps may remain in the spacer and the filling powder may spill from the spacer.

(3) If the filling amount of the filling material is too large, the pressure at the time of filling becomes an unreasonable force and is applied to the detection element, which may damage the detection element. Conversely, if the filling amount of the filling material is too small, sufficient pressure may not be applied to the detection element, and the detection element may move during use.

[Means for Solving Problems] The present invention employs the following means in order to solve the above problems.

That is, the gist of the present invention is to provide a detection element that detects the state of the surrounding environment, a metal shell that stores the detection element, a spacer that supports the detection element in the metal shell, and the detection element in the metal shell. A filler that is filled so as to hold the element and that is sealed by the spacer, wherein the spacer is made of heat-resistant metal fiber or porous metal, and the detection element is supported by elastic compression of the spacer. It is in the structure for assembling the detection element.

Here, as the detection element, a solid ion conductor such as ZrO ₂ or a gas detection element using a material such as TiO ₂ whose resistivity changes depending on the ambient atmosphere, or a temperature detection element such as a thermistor can be used.

As the filler, ceramic powder such as talc or ceramic fiber such as glass fiber can be used.

The diameter of the heat-resistant metal fiber that constitutes the spacer is 0.00
A metal fiber made of stainless steel, tungsten, molybdenum or the like having a size of 1 to 0.20 mm can be used. The porous metal has a porosity of 15-
About 80% foam metal can be used. Further, the elastic deformability of the spacer is much larger than that of the conventional ceramic fiber in both the heat resistant metal fiber and the porous metal.

[Operation] Since the spacer is made of heat-resistant metal fiber or porous metal, it has high elasticity. Therefore, the detection element is strongly held by the spacer on the inner wall of the metal shell. As a result, the detection element is supported with a strong force at a predetermined position in the metal shell.

In addition, since the spacer has excellent elasticity, it can be easily compressed and deformed by being pushed in from above, and the gap almost disappears, and the elastic force bites the substrate and metal fittings, so that the filling powder spills from the spacer. There is no.

[Embodiment] An embodiment of the present invention will be described with reference to the drawings.
Note that the scale of each drawing is different for the sake of explanation.

In this embodiment, an oxygen sensor S using a plate-shaped oxygen detecting element 10 is used.
FIG. 1 is a partially cutaway perspective view of the oxygen sensor S to which the present invention is applied. Incidentally, for the sake of explanation, the oxygen detection element 10
Is drawn without breaking.

A metallic shell 12 made of stainless steel (SUS430) is formed in a cylindrical shape for fixing an oxygen detecting element 10 described later and for mounting the sensor on an internal combustion engine. On the outer periphery of the metal shell 12, a screw portion 12a for mounting an internal combustion engine is engraved.

The protector 14 is attached to the tip of the metallic shell 12 on the internal combustion engine side, and protects the oxygen detection element 10. The inner cylinder 16 and the outer cylinder 18 are attached to the metal shell 12 to protect the oxygen detection element 10, its pin terminals 10a, 10b, 10c and the lead wires 20a, 20b, 20c connected to the pin terminals. The oxygen detecting element 10 is held by the metal shell 12 and the inner cylinder 16 via the spacer 22, the filling powder 24, and the glass seal 26. The seal material 28, which is held by the outer cylinder 18 and is made of silicon rubber, is the lead wire 20.
This is for insulating and protecting a, 20b, 20c and the terminals 10a, 10b, 10c from the oxygen detection element 10 protruding from the glass seal 26. The details of the space 22 will be described later.

Here, the filling powder 24 is alumina, zirconia, mullite,
It consists of porous ceramic powder such as silica and talc. The glass seal 26 is made of glass and prevents leakage of the detection gas and protects the terminals 10a, 10b and 10c of the oxygen detection element 10.

The connection between the lead wires 20a, 20b, 20c and the terminals 10a, 10b, 10c is performed as follows.

First, the sealing material 28 and the lead wires 20a, 20
Hold b and 20c, connect caulking metal fittings to the ends of the lead wires 20a, 20b, and 20c, and then attach the caulking metal fittings to the terminal 10.
Connect with a, 10b, 10c by caulking or welding.

An example of the oxygen detection element 10 described above will be described with reference to the partially cutaway perspective view of FIG.

The oxygen detecting element 10 uses, as a gas sensitive layer, titania whose conductivity changes according to the partial pressure of oxygen gas in the ambient atmosphere.

The oxygen detection element 10 is formed on the ceramic substrate 42 and the ceramic substrate 42, and the terminals 43a, 43b, 43e.
Detection electrode 4 connected to platinum lead wires 44a, 44b, 44e at
6a, 46b and the electrode pattern 46 such as the thermal resistance electrode 46e, is laminated on the ceramic substrate 42 and the electrode pattern 46 and integrated with the ceramic substrate 42, and a ceramic laminated plate 48 having a window portion 48a, The window portion 48a of the ceramic laminated plate 48 is filled so as to cover the detection electrode patterns 46a and 46b, and the gas sensitive layer 50 made of titania, and from Al ₂ O ₃ laminated on the gas sensitive layer 50. And a coat layer 52. In addition, the platinum lead wires 44a, 44b,
44e are respectively connected to the above-mentioned pin terminals 10a, 10b, 10c.

Assembly of the oxygen detection element 10 to the metal shell 12 will be described with reference to the sectional view of FIG.

First, a washer having a hole in the center for loosely fitting the detecting element 10 and having an outer diameter slightly smaller than the inner diameter of the metal shell 12.
60 is inserted from the terminal side of the detection element 10. Subsequently, a spacer 22 made of cotton-like stainless fiber having a hole having an inner diameter slightly smaller than the outer circumference of the detection element 10 and having an outer diameter slightly larger than the inner diameter of the metal shell 12 is provided from the terminal side of the detection element 10. , Is fitted on the outer periphery of the detection element 10. Since the spacer 22 has elasticity, it firmly grips the detection element 10.

Next, the washer 60 loosely fitted to the detection element 10 is the metal shell.
Detecting element so as to engage with stepped portion 62 provided on the inner surface of 12
Insert 10 from the side opposite to the threaded portion 12a of the metal shell 12 (see FIG. 1).

After that, compressive force is applied from above the metal shell 12 to the spacer 22.
Is firmly filled between the detection element 10 and the inner surface of the metal shell 12. Then, the spacer 22 is permanently deformed, fills the internal gap, and the elasticity of the spacer 22 causes the detection element 10 to move.
Is held in the metal shell 12.

Further, an appropriate amount of the filler 24 made of ceramic powder is inserted from the same direction to fix the detection element 10 in the metal shell 12.

As described above, when the detection element 10 is assembled to the metal shell 12,
Due to the large elastic force of the spacer 22 made of cotton-like stainless fiber, the detection element 10 is strongly held in the metal shell 12.
Therefore, the position of the detection element 10 does not shift during the filling process of the filling material 24.

Further, the filling pressure of the filling material 24 almost eliminates the gap in the spacer 22, and the filling material 24 does not spill out from the spacer 22.

Further, due to the elasticity of the spacer 22, the force applied to the detection element 10 is appropriate even if the filling amount of the filling material 24 changes to some extent.

Another embodiment of the present invention is shown in the sectional view of FIG.

In the present embodiment, instead of the washer 60 and the step portion 62 on the inner surface of the metal shell 12 of the above-described embodiment, a protrusion 65 is provided on the inner surface of the metal shell 12, and the spacer 22 is supported by the protrusion 65. By doing so, in addition to the effects of the above-described embodiment, there are effects of resource saving and reduction of the number of processes due to the reduction of the number of parts used.

Also, if the tip of the protrusion 65 is a tapered surface as shown in the figure,
When the detection element 10 is inserted into the metallic shell 12, the spacer 22 bites between the tip of the tapered surface and the detection element 10 and receives a strong compressive force. As a result, the spacer 22 is preferable because it holds the detection element 10 more firmly.

[Advantages of the Invention] The present invention has the following advantages by adopting the above-mentioned configuration.

(1) Since the spacer has a large elasticity, both the inner wall of the metal shell and the detection element are pressed by the large elasticity of the spacer. Therefore, the force for supporting the detection element is strong, and the position of the detection element does not shift during the filling process of the filling material.

(2) Due to the filling pressure of the filling powder, the gap between the spacers is almost eliminated, and the filling powder does not spill out of the spacer.

(3) Due to the elasticity of the spacer, the force applied to the detection element is appropriate even if the filling amount of the filling material changes to some extent.

[Brief description of drawings]

FIG. 1 is a partially cutaway perspective view of an embodiment of the present invention, FIG. 2 is a partially cutaway perspective view showing an example of an oxygen detection element used therein, and FIG. 3 is a view of an oxygen detection element in one embodiment of the present invention. FIG. 4 is a sectional view for explaining the assembling, and FIG. 4 is a sectional view for explaining the assembling of the oxygen detecting element in another embodiment of the present invention. 10 …… Oxygen detecting element, 12 …… Metal fitting, 14 …… Protector 16 …… Inner cylinder, 18 …… Outer cylinder 20a, 20b, 20c …… Lead wire 22 …… Spacer, 24 …… Filling powder 26 …… Glass seal 28 …… Seal material, 60 …… Washer 62 …… Step, 65 …… Projection

Claims (1)

[Claims] 1. A detection element for detecting the state of the surrounding environment, a metal shell for housing the detection element, a spacer for supporting the detection element in the metal shell, and a holding element for the detection element in the metal shell. And a filler filled with the spacer and sealed by the spacer, wherein the spacer is made of heat-resistant metal fiber or porous metal, and the detection element is supported by elastic compression of the spacer. Characteristic detection element assembly structure.