JP2003043001A - Gas sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the sealability between an outer jacket and a protective outer jacket by suppressing the deformation of a separator in a gas sensor. SOLUTION: The gas sensor 1 is provided with the separator 16 which protects the connection between a lead frame 25 connected to the electrode section 11b of a detecting element 11 and lead wires 18, and prevents the infiltration of water, oil, etc., into the sensor 1 from the space between the outer jacket 13 and the protective outer jacket 14 by means of a rubber packing 15 provided around the separator 16. The deformation of the separator 16 can be prevented by providing a metallic protective cover 24 between the separator 16 and packing 15. Consequently, the sealability between the jackets 13 and 14 is improved, because spaces do not occur between the jackets 13 and 14 and the packing 15 due to the deformation of the separator 16.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas sensor attached to an exhaust pipe of an internal combustion engine of an automobile or the like and used for detecting a component to be detected in exhaust gas flowing through the exhaust pipe.

[0002]

2. Description of the Related Art As a conventional gas sensor, for example, an oxygen sensor 2 as shown in FIG. 4 is known. That is, the oxygen sensor 2 is provided with a detection portion 11a at the tip (hereinafter, the direction from the center to the detection portion 11a in the oxygen sensor 2 is referred to as the lower side) and an electrode portion 11b at the rear end (hereinafter, the oxygen sensor 2 is referred to as the center) (The direction of the electrode part 11b is referred to as the upper side from the above part) is installed, and the long plate-shaped detection element 11 and the detection element 11a are held in a protruding state, and the detection part 11a is exposed to the measurement gas atmosphere. Tubular metal shell 12 attached to the exhaust pipe as shown in FIG.
2 and a hollow cylindrical outer cylinder 13 connected coaxially.

The outer cylinder 13 is provided with an insulating holder 23 for holding the detecting element 11 via an insulating porcelain tube 20. The insulating holder 23 is attached to the metal shell 12 via the talc powder 21 and the fixing member 22. Further, the lower end of the metal shell 12 is covered with a double-walled cylindrical protector 19a having a bottom so as to surround the detection part.
Also, the protector 19b is coaxially attached.

On the other hand, the oxygen sensor 2 is electrically connected to the electrode portion 11b of the detecting element 11 inside the outer cylinder 13,
A lead frame 25 that is pulled out upward from the upper opening of the
The lead wire 18 is further drawn to the outside.

The lead frame 25 and the lead wire 18
The connection portion with is protected by the separator 16. The separator 16 is made of a resin material and has a shape in which two types of cylinders having different diameters are stacked with their central axes aligned. The separator 16 is provided with a plurality of axially penetrating holes for inserting the electrode terminals of the lead frame 25 and the lead wires 18, and protects the connecting portion between the lead frame 25 and the lead wires 18 inside the holes. In addition, the short circuit between the lead wires is prevented. The separator 16 has a small diameter side inserted into the outer cylinder 13,
The insertion joint portion and the periphery of the separator 16 are surrounded by the protective outer cylinder 14. Further, in order to maintain the airtightness between the outer cylinder 13 and the protective outer cylinder 14, a ring-shaped rubber packing 15 is attached to the outer periphery of the columnar cylinder of the separator 16 having a small diameter.

Further, the opening of the protective outer cylinder 14 on the side opposite to the outer cylinder 13 side is arranged so as to be hermetically sealed by a rubber cap 17. The rubber cap 17 has the lead wire 18 hermetically inserted therein.

[0007]

By the way, since the oxygen sensor is exposed to a high temperature during use, the rubber packing 1
In No. 5, thermal expansion and thermal contraction due to temperature change occur. For this reason, the rubber packing 15 may deform the separator 16 that is under compressive stress. Note that the rubber packing 15 is deformed when the separator 16 is deformed at this time.
Since a compressive stress is applied to 6 in the radial direction, the diameter is reduced. The rubber packing 15 is sandwiched between the separator 16 from the upper side and the outer cylinder 13 from the lower side in the axial direction. Therefore, due to the thermal expansion and thermal contraction of the rubber packing 15, the separator 16 is deformed in the axial direction to some extent.

As a result, the rubber packing 15 is also reduced in diameter as the separator 16 is reduced in diameter, so that a space is created between the protective outer cylinder 14 and the rubber packing 15. Further, since the rubber packing 15 moves while sticking to the end surface of the separator 16 which is deformed in the axial direction, a space is also created between the outer cylinder 13 and the rubber packing 15. Therefore, the sealing property between the outer cylinder 13 and the protective outer cylinder 14 deteriorates. Therefore, conventionally, it has been necessary to use a heat-resistant resin (for example, PEEK material) that is not affected by the thermal expansion and thermal contraction of the rubber packing for the separator, resulting in high cost. Although the problem can be solved by forming the separator from a material such as ceramic, there is a problem that the ceramic is cracked by an external impact and a problem that it is heavy.

Therefore, in the present invention, it is possible to surely maintain the sealing property without using the expensive heat-resistant resin separator used in the conventional gas sensor.
It is an object of the present invention to provide a gas sensor that is cheaper than a conventional gas sensor.

[0010]

In order to achieve the above object, the invention according to claim 1 has a detection portion formed at one end in the axial direction and the detection portion at the other end. A detection element to which an electrode terminal for extracting a signal to the outside is connected, a tubular metal shell that holds the axial center portion of the detection element in a housing hole, and the metal shell of the detection element with respect to the metal shell. An outer cylinder joined to the electrode terminal side and surrounding an end portion of the detection element on the electrode terminal side, and an outer side of the outer cylinder opposite to the metal shell is closed from the outside,
In order to protect the connection between the electrode terminal and the lead wire protruding from the opening, a resin separator having a hole for inserting the electrode terminal and the lead wire, and derived from the resin separator With the lead wire inserted, a protective outer cylinder arranged to protect the periphery of the resin separator, and the lead wire is airtightly inserted with respect to the resin separator in the protective outer cylinder. A rubber cap, which is airtightly sealed from the opening opposite to the outer cylinder side, is arranged between the resin separator and the outer cylinder, and hermetically seals between the protective outer cylinder and the outer cylinder. The rubber packing is characterized in that a protective cover made of metal is disposed between the rubber packing and the resin separator.

That is, in the gas sensor of the present invention (claim 1), since the metal cover is provided between the separator and the rubber packing, even if the rubber packing is thermally deformed, the compressive stress is not applied to the separator. . Therefore, the separator does not deform and the rubber packing is not affected by the deformation of the separator. As a result, no space is created between the outer cylinder and the rubber packing and between the protective outer cylinder and the rubber packing, and the effect of maintaining the sealability between the outer cylinder and the protective outer cylinder is obtained.

Here, the material of the rubber packing is not particularly limited as long as it has elasticity and can secure the sealing property between the two members, but fluororubber is particularly adherent to metal. Therefore, it is preferable to use fluororubber for the rubber packing as in the second aspect of the invention. That is, if fluororubber is used for the rubber packing as in the invention described in claim 2, the space between the rubber packing and the metal protective cover, the space between the rubber packing and the outer cylinder, and the space between the rubber packing and the protective outer cylinder are increased. Each can be sufficiently adhered. As a result, it is possible to more reliably seal the space between the outer cylinder and the protective outer cylinder.

On the other hand, the metallic protective cover may be any metallic cover arranged between the rubber packing and the separator, and for example, even if it is a simple tubular shape, it is not possible to prevent the separator from being deformed. it can. However, a simple tubular shape can prevent radial force due to thermal expansion and thermal contraction of the rubber packing, but cannot prevent axial force. Therefore, the problem that the separator is deformed in the axial direction remains. However, as in the third aspect of the invention, a metal protective cover having a tubular portion and a flange portion projecting to the periphery at one axial end of the tubular portion is provided. If the flange portion is attached to the end surface of the separator, the metal protective cover can effectively prevent the radial and axial forces on the separator due to the deformation of the rubber packing. Therefore, the separator is prevented from being deformed in the axial direction, and the space between the rubber packing and the protective outer cylinder and between the rubber packing and the outer cylinder does not occur, and the sealing performance between the outer cylinder and the protective outer cylinder is further improved. Is obtained.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying the present invention will be described below with reference to the drawings. In this embodiment, the present invention is applied to an oxygen sensor which is a kind of gas sensor. FIG. 1 is a cross-sectional view showing the overall configuration of the oxygen sensor 1 of this embodiment, and FIG. 2 is an enlarged view showing the separator 16 and its surroundings in FIG. 1 in an enlarged manner.

As is apparent from FIGS. 1 and 2, the oxygen sensor 1 of this embodiment is basically constructed in the same manner as the conventional oxygen sensor 2 shown in FIG.
The difference is that the protective cover 24 is provided between the separator 16 and the rubber packing 15. Therefore,
In the following description, only the protective cover 24 and its peripheral members (separator 16, rubber packing 15, etc.) in the oxygen sensor 1 according to the present embodiment will be described with reference to FIG. 3, and other portions will be described with reference to FIGS. The same reference numeral as that of the conventional oxygen sensor 2 is given to 2, and the description thereof is omitted.

First, as shown in FIG. 3A, the separator 16 has a shape in which two types of cylinders made of a resin material and having different diameters are stacked with their central axes aligned. Further, a plurality of recesses 16a are provided on the side surface of the cylinder having the larger diameter. A plurality of holes 16b for passing the lead frame 25 and the lead wires 18 are provided in the axial direction.

Next, as shown in FIG. 3B, the protective cover 24 is made of a metallic material, and has a cylindrical portion 24b having a diameter capable of containing the smaller diameter side of the separator 16 and one axial end thereof. It has a collar portion 24a that projects from the side to the periphery by the difference in diameter between the two cylinders that form the separator 16. Then, in the protective cover 24, the tubular portion 24b encloses the side of the separator 16 having the smaller diameter, and the collar portion 24a is in contact with the end surface of the column having the larger diameter of the separator 16,
It is attached to the separator 16 (see FIGS. 1 and 2).

On the other hand, as shown in FIG. 3C, the rubber packing 15 is formed in a ring shape like the conventional one, and in this embodiment, the material thereof is fluororubber. Then, the rubber packing 15 has a protective cover 24.
The cylindrical portion 24 of the protective cover 24 while being in contact with the collar portion 24a of the
It is attached to the outer circumference of b (see FIGS. 1 and 2).

The separator 16, the protective cover 24, and the rubber packing which are assembled and integrated as described above have the outer cylinder 13 on the side on which the rubber packing 15 is mounted.
The metal shell is joined to the opening on the side opposite to the metal shell. Then, the lead frame 25 and the lead wire 18
Are inserted into the holes 16b of the separator, and they are electrically joined inside.

A tubular protective outer cylinder 14 is mounted so as to surround the separator 16 and the joint between the separator 16 and the outer cylinder 13. In addition, the protective outer cylinder 14
The opening opposite to the outer cylinder 13 is hermetically sealed by the rubber cap 17 with the lead wire 18 inserted therein.

As described above, in the oxygen sensor 1 of this embodiment, the protective cover 24 is sandwiched between the separator 16 and the rubber packing 15. Therefore, the rubber packing 15
The protective cover can absorb the radial and axial forces on the separator 16 due to the thermal expansion and thermal contraction. As a result, deformation of the separator 16 due to thermal expansion and contraction of the rubber packing 15 is suppressed, and the space between the outer cylinder 13 and the rubber packing 15 due to the deformation of the separator and the protective outer cylinder 14 are suppressed.
There is no space between the rubber packing 15 and the rubber packing 15. Therefore, the oxygen sensor of the present embodiment can improve the sealing property between the outer cylinder 13 and the protective outer cylinder 14 as compared with the conventional oxygen sensor.

Further, in this embodiment, since the material of the rubber packing 15 is fluororubber, the rubber packing 15 has a characteristic of adhesion to metal, and therefore the protective cover 24, the outer cylinder 13 and the protection of the rubber packing 15 are provided. Outer cylinder 1
The adhesion to 4 can be improved. Therefore, in the oxygen sensor of the present embodiment, the sealability between the outer cylinder 13 and the protective outer cylinder 14 can be improved by the characteristics of the rubber packing 15 itself.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modes can be adopted. For example, instead of separately preparing the protective cover 24, the separator-side end portion of the outer cylinder 13 may be formed into the shape of the protective cover 24 to obtain the same operation and effect as already described in the present embodiment.

Further, by using a simple protective cover in which the collar portion 24b of the protective cover 24 is omitted, the effect close to the above-mentioned embodiment can be obtained although the effect is slightly inferior to the above-mentioned embodiment. Becomes In addition, although the example in which the plate-shaped element is used as the detection element is described in the embodiment, a cup-shaped element may be used as the element shape.

[Brief description of drawings]

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

FIG. 2 is an enlarged view centering on a portion of a separator 16 in FIG.

FIG. 3 is a perspective view showing a separator 16, a protective cover 24, and a rubber packing 15.

FIG. 4 is a cross-sectional view showing the overall configuration of a conventional oxygen sensor.

[Explanation of symbols]

1 ... Oxygen sensor, 11 ... Detection element, 12 ... Metal shell, 1
3 ... Outer cylinder, 14 ... Protective outer cylinder, 15 ... Rubber packing, 16
... Separator, 17 ... Rubber cap, 18 ... Lead wire,
Reference numeral 19 ... Protector, 20 ... Insulator porcelain tube, 21 ... Talc powder, 22 ... Fixing member, 23 ... Insulation holder, 24 ... Protective cover, 25 ... Lead frame.

Claims (3)

[Claims] 1. A detection element having a detection portion formed at one end in the axial direction, and an electrode terminal for extracting a signal of the detection portion to the outside at the other end, and an axial center portion of the detection element. A tubular metal shell held in the accommodation hole; an outer cylinder joined to the metal shell with respect to the electrode terminal side of the detection element, and surrounding the electrode terminal side end of the detection element; In order to close the opening of the outer cylinder on the side opposite to the metal shell from the outside and to protect the connecting portion between the electrode terminal and the lead wire protruding from the opening, the electrode terminal and the lead wire are provided. A resin separator having a hole for insertion, the lead wire derived from the resin separator is inserted, and a protective outer cylinder arranged to protect the periphery of the resin separator, and the lead Lines are hermetically interpolated A rubber cap that hermetically seals the resin separator from the opening on the side opposite to the outer cylinder side in the protective outer cylinder; and a rubber cap disposed between the resin separator and the outer cylinder. A rubber packing that hermetically seals between an outer cylinder and the outer cylinder, wherein a metal protective cover is arranged between the rubber packing and the resin separator. . 2. The gas sensor according to claim 1, wherein the rubber packing is fluororubber. 3. The metal protective cover comprises a tubular portion and a flange portion that projects outwardly at one axial end of the tubular portion, and the tubular portion is inserted into the opening portion of the outer cylinder. The gas sensor according to claim 1, wherein the collar portion is in contact with an end surface of the separator.