JP2003035694A - Gas sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas sensor for preventing a lead wire from being cracked due to bending or the like. SOLUTION: A grommet 60 has four cylindrical projections 60b that project upward from the end face at the upper side of a body section 60a that is formed cylindrically. The projections 60b form an insertion hole 60c that is provided through the body section 60a and is inserted through each lead wire 10. In an oxygen sensor having the grommet 60 that is composed in this manner, the projections 60b are also bent accordingly even if the lead wire 10 is bent, so that a load being centered at the base point section of the lead wire 10 is dispersed since bending has been made with the opening end in the insertion hole of a sealing member that does not have any projections 60b as a base point conventionally. Therefore, the use of the oxygen sensor reliably prevents the crack in the lead wire 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas sensor having a structure in which a lead wire connected to a signal extraction portion of a detection element is drawn out from the inside of an internal space formed on the signal extraction portion side of the detection element to the outside. The present invention relates to a structure of a seal member that forms an internal space together with a case and has an insertion hole for drawing out a lead wire.

[0002]

2. Description of the Related Art Conventionally, a detection element for outputting an electric signal corresponding to a physical quantity to be measured, and a detection element for exposing the detection part of the detection element to a measurement gas,
There is a gas sensor that has a case that forms an internal space on the signal output side of the detection element, and that draws the lead wire connected to the signal output of the detection element from the inside of the case to the outside.

[0003] In the case of a gas sensor having such a structure, a rubber seal member called a grommet is usually attached, which has a through hole through which a lead wire connected to a signal extraction portion of a detection element can be inserted. The seal member forms an internal space together with the case.

The lead wire is inserted into the insertion hole of the seal member and is drawn out from the inside of the internal space to the outside.

[0005]

However, as shown in FIG. 5, the conventional insertion hole 110 is simply formed by perforating the seal member 100, and the seal member 10 is also provided.
Since 0 is made of a material having a relatively high hardness among rubber materials, when the lead wire 120 is pulled at the time of wiring work or the like, the lead wire 120 is bent with the opening edge of the insertion hole 110 as a base point. However, there is a problem that the load is concentrated on one point of the base point portion A of the lead wire 120, and the coating of the lead wire 120 is peeled off or scraped off.

Therefore, it is an object of the present invention to provide a gas sensor capable of preventing breakage of a lead wire due to bending of the lead wire or the like.

[0007]

Means for Solving the Problems and Effects of the Invention The invention according to claim 1 for achieving the above object comprises a detector and
A detection element having a signal extraction part for extracting an electric signal from the detection part, and holding the detection element so that the detection part is exposed to a measurement gas, and an internal space on the signal extraction part side of the detection element. And a lead wire connected to the signal take-out portion for taking out the electric signal to the outside of the internal space, and an insertion hole through which the internal space is formed together with the case and through which the lead wire can be inserted. And a seal member formed, through the insertion hole of the seal member, a gas sensor in which the lead wire is pulled out from the inside of the internal space to the outside, the outer surface of the seal member, A tubular portion forming the insertion hole is formed.

When the cylindrical portion having the insertion hole is provided on the outer surface of the sealing member as described above, even if the lead wire is bent by pulling the lead wire or the like, the cylindrical portion also follows. Since the lead wire bends and is supported by the inner wall surface of the tubular portion, the load concentrated at one point when the seal member having no tubular portion is used is dispersed over the entire inner wall surface of the tubular portion.

Therefore, when the gas sensor according to the first aspect is used, damage to the lead wire can be reliably prevented even if the lead wire is bent. R is provided at the corner where the outer surface of the cylinder and the outer surface of the seal member intersect to prevent damage such as cracking at the corner when the cylinder bends. It is preferable.

Further, in the gas sensor according to the second aspect, it is preferable that the cylindrical portion is formed so as to project from the outer surface of the seal member. Next, as in the gas sensor according to the third aspect, the seal member is preferably made of rubber having a rubber hardness of JIS-A 70 ° to 90 °. If the hardness of the rubber is too soft, when the lead wire bends, a gap may be created between the rubber and the lead wire, and water may enter the internal space. On the other hand, if the hardness of the rubber is too hard, This is because there is a risk that the lead wire may be bent from the tip of the tubular portion as a base point and the lead wire may be destroyed.

Incidentally, JIS-A is based on "JIS K6301" using an A type hardness tester, and a load of 9.80 (N).
Is the rubber hardness when measured by adding. Further, as in the gas sensor according to claim 4, as the seal member,
Vents for passing air between the inner space and the outside through the seal member are formed, and the vents may be closed by a waterproof breathable filter. Of course.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION A first embodiment of a gas sensor to which the present invention is applied will be described below. In this embodiment, an oxygen sensor which is a kind of gas sensor will be described. Among the drawings used in the following description, FIG.
Sectional drawing which shows the whole structure of the oxygen sensor 1 of this embodiment, FIG. 2 is explanatory drawing of a grommet, (a) is a perspective view of a grommet, (b) is an AA 'sectional view of (a). 1) Overall Structure of Oxygen Sensor As shown in FIG. 1, the oxygen sensor 1 according to the present embodiment is provided with a detection unit 2a at the front end and an electrode (not shown) (corresponding to a signal extraction unit of the present invention) on the outer wall surface at the rear end. A long plate-shaped detection element 2 on which is installed, and a hollow cylindrical metal shell 4 that surrounds and holds the rear end side of the detection element 2 so that the detection portion 2a is exposed to the measurement gas atmosphere. , A hollow cylindrical shape coaxially connected to the metal shell 4 on the side opposite to the side (hereinafter referred to as the lower side) where the detection unit 2a is exposed to the measurement gas atmosphere (hereinafter referred to as the lower side). An outer cylinder 6 is provided.

Further, the oxygen sensor 1 of the present embodiment is electrically connected to the electrode of the detection element 2 in the cylinder of the metal shell 4 and is drawn out upward from the upper opening of the metal shell 4. 8 and an outer cylinder 6 on the lead frame 8.
It is provided with a lead wire 10 that is electrically connected inside and is drawn out of the outer cylinder 6.

The metal shell 4 includes a ceramic holder 40, a talc powder 42, and a ceramic sleeve 44, which are sequentially stacked in the cylinder from the lower side to the upper side. Among these, the ceramic holder 40 and the ceramic sleeve 44 are formed in a cylindrical shape that can be inserted into the cylinder of the metal shell 4, and insertion holes 40a and 44a through which the detection element 2 is inserted are formed in the axial center portions thereof, respectively. ing.
Further, the ceramic sleeve 44 is provided with a columnar protruding portion 44b that protrudes to the upper side of the upper opening of the metal shell 4 when fitted into the metal shell 4. The protruding portion 44b is formed in a cylindrical shape having a smaller diameter than the main body portion 44c of the ceramic sleeve 44, and is formed coaxially with the main body portion 44c.

Further, the metallic shell 4 is provided with a bottomed cylindrical double protector 9a, 9b at the lower end thereof so as to surround the detection portion 2a. This protector 9a,
9b is attached coaxially to the metal shell 4. Further, the metal shell 4 is provided with a fixing groove 4a on the outer peripheral surface for screwing and fixing the detecting portion 2a in the exhaust pipe so that the detecting portion 2a is arranged in the exhaust pipe.

In order to hold the detection element 2 by using the metal shell 4, the ceramic holder 40 is inserted into the cylinder while passing the detection element 2 through the insertion hole 40a, and talc powder 42 is filled from above. And further, the lead frame 8
The detection element 2 is placed on the outer wall surface of the detection element 2 such that the lower end of the detection element 2 comes into contact with the electrode, and the detection element 2 is inserted into the insertion hole 44 together with the lead frame 8.
The ceramic sleeve 44 is inserted into the cylinder while passing through a. Then, the main body portion 44c of the ceramic sleeve 44
The metal packing 7 is placed on the upper end surface of the metal shell 7 so as to surround the protrusion 44b, and the upper end of the metal shell 4 is swaged inward so as to cover the metal packing 7 from above, and the ceramic sleeve 44 is pressed downward. Then, the talc powder 42 is sandwiched between the ceramic holder 40 and the ceramic sleeve 44 and pressed, the talc powder 42 is tightened, and the detection element 2 is held.
Further, when the detection element 2 is held by the metal shell 4 in this way, the upper end portion of the lead frame 8 is inserted into the insertion hole 4 of the ceramic sleeve 44 which is opened at the upper end surface of the protruding portion 44b.
The lead frame 8 is held by the metal shell 4 in a state in which the lead frame 8 is extended upward from the opening of 4a.

Next, the outer cylinder 6 has a grommet 60 (corresponding to a seal member of the present invention) fitted into the cylinder so as to close the opening on the upper side, and a ceramic fitted below the grommet 60. And a separator 62. Of these, the ceramic separator 62 supports the lead wire 10 in the outer cylinder 6. The lead frame 8 is connected to the lead wire 10 by resistance welding.

Further, the grommet 60 is formed in a cylindrical shape, and the lead wire 1 supported by the ceramic separator 62.
In order to pull out 0 to the outside of the outer cylinder 6, a plurality of insertion holes, which will be described later, are bored in the axial direction. The grommet 60 is formed of rubber having a hardness of JIS-A 70 ° to 90 °, and after it is fitted into the outer cylinder 6, the wall surface of the outer cylinder 6 in which the grommet 60 is fitted is caulked inward. Fixed. At that time, the lead wire 10 inserted into the insertion hole is fixed in a state of being fitted into the insertion hole.

The outer cylinder 6 is closed by thus inserting the grommet 60 into the upper opening,
Further, the opening on the lower side is closed by being connected to the metal shell 4 to form an internal space 64 that is watertightly isolated from the atmosphere. 2) Structure of Grommet Next, the grommet which is a characteristic part of the present embodiment will be described in detail.

The grommet 60 of this embodiment is shown in FIG.
As shown in (a), the body portion 60 formed in a cylindrical shape.
a and 4 provided on the upper end surface of the main body 60a.
It is provided with one tubular portion 60b. As shown in FIG. 2B, the tubular portion 60b forms an insertion hole 60c that penetrates the main body portion 60a and that inserts each lead wire 10 therein.

Further, the tubular portion 60b is formed so that H / t ≧ 1 where H is the height from the upper end surface of the main body portion 60a and t is the wall thickness so that the tubular portion 60b is bent together with the lead wire 10. It is preferable that the wall thickness t is equal to the cylindrical portion 60b.
Is more preferably 0.5 mm or more so as not to be broken.

Further, it is preferable to provide R at the corner where the outer surface of the insertion hole 60c and the upper end surface of the grommet 60 intersect. When the lead wire 10 is pulled in a direction parallel to the upper end surface of the grommet 60 and the tubular portion 60b is bent accordingly, it is possible to prevent the grommet 60 from being damaged due to cracks or the like at the corners. Because. 3) Action / Effect In the oxygen sensor 1 including the grommet 60 configured as described above, even if the lead wire 10 is bent by pulling the lead wire 10 in the left-right direction in FIG. Since 60b is also bent and the lead wire 10 is supported on the inner wall surface of the tubular portion 60b, the load concentrated at one point when the grommet 60 having no tubular portion 60b is used is
It is dispersed over the entire inner wall surface of the tubular portion 60b.

Therefore, by using the oxygen sensor 1 of the present embodiment, even if the lead wire 10 is bent, it is possible to reliably prevent the lead wire 10 from being damaged. Further, in the oxygen sensor 1 of the present embodiment, the grommet 60 is made of rubber having the above-described hardness, so that, for example, when the lead wire 10 is bent because the hardness of the rubber is too soft, the grommet 60 is inserted. A gap is formed between the hole 60c and the lead wire 10 to allow moisture to enter the inner space, or the hardness of the rubber is too hard, so that the tip of the tubular portion 60b is not covered by the tubular portion 60b.
A phenomenon similar to that before the provision of the
Can be prevented from being damaged.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments.
Various aspects can be adopted. For example, in the case of an oxygen sensor of the type in which a reference gas is introduced into the outer cylinder and the oxygen concentration of the measurement gas atmosphere to which the tip of the detection element is exposed is detected based on this reference gas, as shown in FIG. A grommet 160a having an introduction hole for introducing the reference gas into the outer cylinder is provided at the center of the cylinder. This grommet 1
A gas-permeable filter 160d for separating the outside air from the reference gas space in the outer cylinder is installed in the introduction hole of 60a, and a cylindrical fitting member for fixing the filter 160d in the introduction hole is inserted. To be done. And this filter 1
As shown in FIG. 3, 60d covers the atmosphere side opening of the fitting member 160e inserted in the introduction hole, and the fitting member 1
A filter 16 is provided between the outer peripheral surface of 60e and the inner peripheral surface of the introduction hole.
It is fixed in the introduction hole by sandwiching the end of 0d.
The plurality of cylinder portions 160b provided in such a grommet 160a are provided at equal intervals at positions surrounding the opening portion of the introduction hole opened at the upper end surface of the grommet 160a.

Further, the cylindrical portion 260b has a sectional shape
As shown in FIG. 4A, it may be formed in a truncated cone shape. Further, as shown in FIG. 4B, the tubular portion 360b may be provided with a hole portion 360x on the surface of the grommet on the atmosphere side, and may be provided inside the hole portion 360x.

In the present embodiment, the metal shell 4 and the outer cylinder 6 correspond to the case of the present invention.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the overall configuration of an oxygen sensor of this embodiment.

FIG. 2 is an explanatory view of a grommet, (a) is a perspective view of the grommet, and (b) is a sectional view taken along the line AA ′ of (a).

FIG. 3 is a cross-sectional view of a grommet, which is a modified example of the present embodiment.

FIG. 4 is a cross-sectional view of a grommet, which is a modified example of the present embodiment.

FIG. 5 is a cross-sectional view of a conventional seal member.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Oxygen sensor, 2 ... Detection element, 2a ... Detection part, 4 ... Metal shell, 4a ... Fixing groove, 6 ... Outer cylinder, 7 ... O-ring, 8 ...
Lead frame, 10 ... Lead wire, 40 ... Ceramic holder, 40a ... Insertion hole, 42 ... Talc powder, 44 ... Ceramic sleeve, 44a ... Insertion hole, 44b ... Projection part, 4
4c ... Main body, 60 ... Grommet, 60a ... Main body, 6
0b ... protrusion, 60c ... insertion hole, 62 ... ceramic separator, 64 ... internal space, 160a ... grommet, 16
0b ... protrusion, 160d ... introduction hole

Claims (4)

[Claims] 1. A detection element having a detection part and a signal extraction part for extracting an electric signal from the detection part, and holding the detection element so as to expose the detection part to a measurement gas, and the detection element. A case forming an internal space on the side of the signal extraction part, a lead wire connected to the signal extraction part for extracting the electric signal to the outside of the internal space, and forming the internal space together with the case, A gas sensor having a seal member having an insertion hole through which the lead wire can be inserted, wherein the lead wire is pulled out from the inside of the internal space to the outside via the insertion hole of the seal member, A gas sensor, wherein a cylindrical portion that forms the insertion hole is formed on an outer surface of the seal member. 2. The gas sensor according to claim 1, wherein the tubular portion is formed so as to project from an outer surface of the seal member. 3. The rubber hardness of the seal member is JIS-A.
The gas sensor according to claim 1, wherein the gas sensor is made of 70 ° to 90 ° rubber. 4. The seal member is formed with a vent hole that penetrates the seal member and allows air to flow between the inner space and the outside, and the vent hole is a waterproof breathable filter. It is closed by the following.
3. The gas sensor according to any one of 3 above.