JPH063319A - Sensor sealing mechanism - Google Patents

Abstract

PURPOSE:To improve the sealing property of the title mechanism by forming a locking shoulder surface which is engaged with a reduced-diameter step section from the front side on a sealing plug body arranged in a wire passing end section and provided with wire passing holes and providing a spring which forcibly presses the shoulder surface against the step section in a protective outer tube. CONSTITUTION:In an oxygen sensor 1a, a protective cap 5 is fitted to the front end side of a cylindrical housing 3 and an inner and protective outer tubes 7 and 8 are fitted to the rear end side, and then, an element 10 composed of a solid-state electric field layer is retained in the housing 3. The rear edge 7b of the inner tube 7 is formed to a receiving edge for locking the front end of a spring 31 and the rear end of the spring 31 is in contact with the front end face of an insulating tube 33 housing the connecting sections 32 of terminal 25a-25d with lead wires 30. Since the spring 31 is supported by the edge 7b of the tube 7 which is fixed to the tube 8 by caulking 9 and applies a forcing force to a sealing plug body 40 through an insulating ring 33 which is in contact with the rear end of the spring 31, the locking shoulder surface 43 of the body 40 is press-contacted with a reduced-diameter step section 8 and the peripheral surface of the body 40 is tightly brought into contact with the internal surface of a wire passing end section 8a in a sealed state. Therefore, the invasion of water or oil through the contact section between the body 40 and section 8a can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sensor sealing mechanism used for an oxygen sensor for detecting the oxygen concentration in exhaust gas from an internal combustion engine.

[0002]

2. Description of the Related Art An oxygen sensor is used as a means for detecting the oxygen concentration in exhaust gas from an internal combustion engine. In this oxygen sensor, if liquid such as water or oil enters the inside of the sensor during use, problems such as short circuit between various electrodes, corrosion of terminals, and reduction of electromotive force may occur. Various sealing mechanisms have been provided for the purpose of preventing the intrusion of liquid and liquid.

[0003]

However, the sealing property against the invasion of the liquid from the wire end of the outer cylinder is formed in the seal plug by disposing the seal plug in the mouth end. The lead wire is closely inserted through the through hole to ensure the watertightness of the peripheral surface of the lead wire, but the sealing between the seal plug and the protective outer cylinder is not always sufficient. No, further improvement is expected. An object of the present invention is to provide a sensor sealing mechanism having a configuration capable of improving sealing performance against liquid intrusion from a wire end of an outer cylinder.

[0004]

SUMMARY OF THE INVENTION According to the present invention, a diameter-reduced step portion is formed at a wire end of a protective outer cylinder, and the lead wire is disposed in the wire end of the protective outer cylinder so that the lead wire is closely contacted. A locking shoulder surface that engages with the reduced diameter step portion from the front is formed in a seal plug body having a through hole to be inserted, and further, the seal plug body is biased rearward into the protective outer cylinder to cause the engagement. It is characterized in that a spring is attached to press the shoulder surface against the reduced diameter step portion.

[0005]

[Function] Due to the urging force of the spring, the locking shoulder surface of the seal plug comes into close contact with the reduced diameter step of the protective outer cylinder from below, so that the line end of the protective outer cylinder and the peripheral surface of the seal plug are The sealing property of is improved.

[0006]

EXAMPLES Each example in which the present invention is applied to an oxygen sensor will be described. In the oxygen sensor 1a shown in FIG. 1, a protective cap 5 is attached to the front end side of a cylindrical housing 3, and an inner cylinder 7 and a protective outer cylinder 8 are attached to the rear end side thereof.
An element 10 made of a solid electrolyte is held inside. The housing 3 is provided with a hexagonal portion 13 and a mounting screw 14 on the outer peripheral portion thereof, and a tapered locking step 15 having a diameter reduced toward the tip side is formed on the inner peripheral portion.

The element 10 has a bottomed cylindrical shape with a closed front end and an open rear end, and porous platinum electrodes 17a and 17b are formed on the inner and outer surfaces thereof. Of the electrodes 17a and 17b, the outer platinum electrode 17b comes into contact with the exhaust gas from the internal combustion engine introduced into the protective cap 5, and the platinum electrode 17a comes into contact with the reference gas, so that the oxygen concentration in the gas is increased. An electromotive force is generated based on the difference between

An insulating ring 19 made of an insulating ceramic such as 92% alumina is disposed at the tip side of the annular gap 18 formed between the housing 3 and the element 10. The insulating ring 19 is made of metal. It is pressed against the locking step 15 side through the packing 20. The rear end side of the insulating ring 19 is filled with a powder sealing material 21 made of talc, and the powder sealing material 21 keeps the exhaust gas side and the reference gas side airtight. Further, a porcelain insulator 22 is arranged on the rear end side of the powder sealing material 21, and a front end edge 7a of the inner cylinder 7 is provided on the rear end face of the porcelain insulator 22 via a metal packing 23.
Is provided.

In this state, the thin-walled rear end edge 3a of the housing 3 is caulked to seal and fix the element 10 in the housing 3 through the insulating ring 19, and the front end edge 7a of the inner cylinder 7 and the porcelain tube. And 22 are held in contact with each other. Then, as will be described later, after each component is mounted on the inner cylinder 7, the protective outer cylinder 8 is caulked 9 around the inner cylinder 7 to fix the inner cylinder 7 to the protective outer cylinder 8. . Then, the protective outer cylinder 8 is joined to the housing 3 by a known connecting means such as laser welding or argon welding. This joint receives heat while receiving stress from the spring 31 when the sensor is used.
The structure is designed to relieve stress.

On the other hand, a terminal 25a connected to the electrode lead portion 20 led from the platinum electrode 17b is connected and fixed to the outer peripheral portion on the rear end side of the element 10, and a PTFE is formed on the upper surface of the terminal 25a. (Polytetrafluoroethylene)
An insulating coating 26 made of is formed.

A terminal 25b connected to the electrode lead portion 27 led from the platinum electrode 17a is arranged on the inner peripheral surface on the rear end side of the element 10. The terminal 25b is intended for heating the element 10. The heater 28 is held and fixed.
It should be noted that energizing terminals 29a and 29b are formed opposite to each other on the outer peripheral portion of the rear end of the heater 28, and terminals 25c and 25d are connected to the energizing terminals 29a and 29b by welding or the like. ing.

The terminals 25a to 25d are connected to the connecting lead wires 30 by means such as caulking. The lead wire 30 is insulated by being covered with a coating film 30a made of PTFE.

The rear end edge 7b of the inner cylinder 7 serves as a receiving edge for locking the front end of the spring 31 made of the coil spring according to the present invention, and the rear end of the spring 31 has each terminal 25a.
.About.25d and the connecting portion 32 of the lead wire 30 are in contact with the front end surface of the insulating tube 33 made of ceramics such as steatite.

Through holes 34 for isolating the lead wires 30 are provided in the insulating tube 33, and a tension is applied to the connecting portion 32 at the rear end side of the inner peripheral surface of each through hole 34. A step portion 35 is formed to disperse the force applied to the connection portion 32 and the terminal 25 when the work is performed.

Further, at the rear end side of the insulating tube 33, there is provided a through hole 41 in which each lead wire 30 is closely inserted, and a P hole is provided.
A seal plug body 40 (see FIG. 2) made of TFE is fitted inside. That is, it is formed of the same material as the coating film 30a of the lead wire 30 that penetrates the through hole 41. Also, the seal plug 4
A groove 42 is formed on the lower surface of 0, and PFA (tetrafluoroethylene-
A spacer 44 made of perfluoroalkyl vinyl ether) is fitted. This PFA has a melting temperature of about
Melting temperature lower than PTFE, which is 327 ℃ (about 315 ℃)
Therefore, the spacer 44 is welded to the seal plug 40 and the lead wire 30 by heating at around this temperature after assembling, and therefore, the spacer 44 is sealed by the through hole 41 to prevent the moisture content. The invasion can be prevented, and the airtightness can be secured.

A rubber bush 45 having a through hole 46 through which the lead wire 30 is inserted is provided at the rear of the seal plug 40.
Is internally fitted, and the seal plug 40 and the rubber bush 45 are
Thus, the wire end portion 8a of the protective outer cylinder 8 is shielded.

On the other hand, the seal plug body 40 has a rear end whose diameter is reduced to form a locking shoulder surface 43. Then, after the seal plug 40 and the rubber bush 45 are mounted in the protective outer cylinder 8, the passage end portion 8a is drawn to bring the passage end portion 8a into close contact with the locking shoulder surface 43. As a result, the diameter-reduced step portion 8b is formed in which the locking shoulder surface 43 is in close contact with the passage end portion 8a.

For this reason, the spring 31 has a rear end edge 7 of the inner cylinder 7 whose front end is fixed to the protective outer cylinder 8 by caulking 9.
Since the urging force is applied to the seal plug 40 through the insulating ring 33 which is supported by b and the rear end of which is in contact with the seal plug 40, the locking shoulder surface 43 presses against the reduced diameter step portion 8b, and Four
The peripheral surface of 0 and the inner surface of the wire end portion 8a are sealed, and water and oil are prevented from entering from this gap.

In the above structure, the seal plug 40 may be made of an elastic material such as fluororubber. In this case, the seal plug 40 causes permanent compression strain due to fatigue over time, but the strain amount is corrected by the rib 31 and the sealing action can always be maintained.

A second embodiment of the present invention will be described with reference to FIG. In each embodiment described later, the same components as those in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted. The oxygen sensor 1b of the present embodiment has substantially the same tip end side as that of the first embodiment, but is different in the rear end side of the housing 3. The inner cylinder is not connected to the upper end portion 3a of the housing 3, and the protective outer cylinder 58 has laser welding, argon welding,
The entire circumference is joined in a hermetically sealed manner by a known connecting means such as brazing. An annular seat portion 58c is formed near the center of the protective outer cylinder 58 by caulking.
The lower end of the spring 31 is supported by 8c.

A seal plug 50 made of PTFE is formed on the upper portion of the rib 31. This seal plug 5
No. 0 has a through hole 51 as shown in FIG. Then, the lead wire 30 whose surface is covered with the covering portion 30a made of PTFE is inserted into the through hole 51. Further, a seal piece 54 made of PFA is further fitted inside the rear portion of the seal plug 50, and the lead wire 30 is inserted through the through hole 55. And the seal plug 50 and the seal piece 5
4 shields the wire end portion 58a of the protective outer cylinder 58,
The sealing piece 54 is welded to the lead wire 30 by heating in the vicinity of the melting temperature of A.

The seal plug 50 has a rear end whose diameter is reduced to form a locking shoulder surface 53. Then, after the seal plug 50 and the seal piece 54 are mounted in the protective outer cylinder 58, the passage end portion 58a is drawn to bring the passage end portion 58a into close contact with the locking shoulder surface 53. As a result, the diameter-reduced step portion 58b with which the locking shoulder surface 53 comes into close contact is formed at the passage end portion 58a.

Thus, in the spring 31 whose lower end is supported by the annular seat portion 58c, the locking shoulder surface 53 of the seal plug body 50 with which the rear end contacts is elastically contacted with the reduced diameter step portion 58b, whereby the seal is formed. The peripheral surface of the stopper 50 and the inner surface of the protective outer cylinder 58 are sealed to prevent water and oil from entering.

Next, a third embodiment will be described with reference to FIG. As shown in FIG. 5, the oxygen sensor 1c of the present embodiment is
The front end side is almost the same as that of the first embodiment, but the rear end side is different.

A seal piece 64 made of PFA and a seal plug body 60 made of PTFE are disposed on the insulating ring 33, as shown in FIG. Further, a tapered convex portion 64a protruding upward is formed on the upper portion of the seal piece 64, and correspondingly, a tapered concave portion 62 opening downward is formed on the lower surface of the seal plug body 60 in each through hole. It is provided for each 61. Then, the tapered convex portion 64 a becomes the tapered concave portion 6.
By being press-fitted in 2, the lead wire 30 can be vertically communicated. Further, a tapered engagement shoulder surface 63 is formed on the upper peripheral surface of the seal plug body 60, and the diameter-reducing step portion 6 formed of a diameter-reducing collar edge formed on the wire end 68a of the protective outer cylinder 68.
The locking shoulder surface 63 is brought into contact with 8b, and the biasing force of the spring 31 mounted in the protective outer cylinder 53 is applied to the seal plug body 60 via the insulating ring 33 and the seal piece 64, and the locking shoulder surface 63 is elastically contacted with the reduced diameter stepped portion 68b. Thus, the watertightness around the seal plug 60 is ensured. In this embodiment,
There are advantages that the number of constituent parts is reduced and the caulking process of the seal portion can be omitted.

Next, a fourth embodiment will be described with reference to FIG.
In the oxygen sensor 1d of this embodiment, the seal stopper 70 is made of PTF.
It is formed of E, the lower part thereof projects in the circumferential direction, and the upper surface thereof serves as a locking shoulder surface 73. Further, a groove 72 is formed on the lower surface thereof, a spacer 74 made of fluororubber is fitted in the groove 72, and the lead wire 30 is inserted into the through hole 71.
Further, a packing 75 made of fluororubber is disposed on the locking shoulder surface 73 so as to be in close contact with a reduced diameter stepped portion 78b formed of a reduced diameter brim edge formed on the wire end portion 78a of the protective outer cylinder 78. ing. Even with such a configuration, the protective outer cylinder 78
The locking shoulder surface 73 of the seal plug body 70 is pressed against the reduced diameter step portion 78b of the line end portion 78a via the packing 75 by the spring 31 attached inside. At this time, the packing 75 generates compressive strain due to aged fatigue, but
It will be corrected by the urging force of.

Further, a fifth embodiment will be described with reference to FIG. In the oxygen sensor 1e of this embodiment, the seal plug 80 is made of fluororubber, and the insulating ring 33 and the insulating sheet 84 made of PTFE are arranged between the seal plug 80. Then, the lead wire 30 is inserted through the through hole 81, and the locking shoulder surface 83 of the lead wire 30 has a reduced diameter flange formed on the through wire end portion 88a of the protective outer cylinder 88 by the adhesiveness of rubber and the biasing force of the spring 31. The reduced-diameter step portion 88b composed of the edge is brought into pressure contact. Even with this configuration, the compressive strain due to the aged fatigue of the seal plug 80 is corrected by the biasing force of the rib 31.

In each of the above-mentioned constitutions, the spring 31 is constituted by the coil spring, but a plurality of disc springs may be laminated,
Alternatively, a leaf spring may be used as the spring.

[0029]

As described above, according to the present invention, a sealing plug body is provided in which a diameter-reduced step portion is formed at a wire end of a protective outer cylinder, and which is disposed in the wire end of the protective outer cylinder. A locking shoulder surface that engages with the reduced diameter step portion from below is formed, and the seal plug body is biased upward by a spring attached in the outer cylinder to press the locking shoulder surface against the reduced diameter step portion. Therefore, the sealing property between the inner surface of the wire end portion of the protective outer cylinder and the peripheral surface of the seal plug body is improved, and the watertightness inside the sensor can be ensured. Therefore, it is optimal as a sealing means for the oxygen sensor and the like And so on.

[Brief description of drawings]

FIG. 1 is a side view showing a right half of a first embodiment in a vertical section.

FIG. 2 is a perspective view of a seal plug body 40 and a rubber bush 45.

FIG. 3 is a side view showing a right half of the second embodiment in a vertical section.

FIG. 4 is an exploded perspective view of a seal plug body 50 and a seal piece 54.

FIG. 5 is a side view of a main part of the third embodiment, which is vertically sectioned in the right half.

FIG. 6 is an exploded perspective view of a seal plug body 60 and a seal piece 64.

FIG. 7 is a side view of the main part of the right half of the fourth embodiment, which is vertically sectioned.

FIG. 8 is a side view of the main part of the fifth embodiment, showing the right half in a vertical section.

[Explanation of symbols]

 1a, 1b, 1c, 1d Oxygen sensor 7 Inner cylinder 7b Rear end edge 8, 58, 68, 78 Protective outer cylinder 8a, 58a, 68a, 78a Passage end 8b, 58b, 68b, 78b Reduced diameter step 58c Annular Seat portion 30 Lead wire 31 Spring 32 32 33 34 25 36 36 27 38 39 40, 50, 60, 70 Seal plug 41, 51, 61, 71 Through hole 43, 53, 63, 73 Locking shoulder surface

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takao Kojima 14-18 Takatsuji-cho, Mizuho-ku, Nagoya City Nippon Special Ceramics Co., Ltd.

Claims (3)

[Claims] 1. A reduced diameter step portion is formed at a wire end portion of a protective outer cylinder,
A locking shoulder surface that engages with the reduced diameter step portion from the front is formed in a seal plug body provided in a wire end of the protective outer cylinder and having a wire hole for closely inserting a lead wire. A sealing mechanism for a sensor, further comprising a spring provided in the protective outer cylinder for biasing a seal plug backward so as to press the locking shoulder surface against the reduced diameter step portion. 2. An inner cylinder is inserted into a protective outer cylinder at a front position of a ridge that biases the seal plug backward, and a front end of the ridge is locked by a rear end edge of the inner cylinder. The sealing mechanism for a sensor according to claim 1, wherein: 3. The inner cylinder is fixed to the protective outer cylinder by caulking from the outside, and the front end of the rib is locked at the rear end edge of the inner cylinder. Sensor sealing mechanism.