JP2827793B2 - Signal extraction structure of gas sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a signal extracting structure of a gas sensor used for detecting the concentration of oxygen in vehicle exhaust gas.

[0002]

2. Description of the Related Art An oxygen sensor used for optimal combustion control of an engine houses a ceramic sensor element formed in a long plate shape or the like in a cylindrical housing attached to an exhaust pipe, and a tip of the sensor element is contained in exhaust gas. It is exposed. As an easy and inexpensive method of extracting signals from the sensor element, an electrode for extracting signals is provided at the base end of the sensor element, and a contact terminal connected to the inner end of a lead wire extending outside the housing is provided on the electrode. The structure which makes elastic contact is often used.

In this case, if the contact terminals are displaced due to vibration or the like, the conduction of the signal lines cannot be ensured. Therefore, various structures for positioning the contact terminals have been proposed. For example, Japanese Utility Model Application Laid-Open No. 2-1070065 discloses a method in which a contact terminal is bent in a Z-shape and pressed against the inner wall of a cylindrical insulating ceramic (first conventional example).
No. 763 discloses a contact terminal provided with a stopper piece (second conventional example).

Japanese Unexamined Patent Publication No. Sho 60-53844 discloses a contact terminal which is bent in a substantially U-shape and has stopper surfaces in contact with both sides (third conventional example).

[0005]

However, in the structures of the first and second conventional examples, the movement of the contact terminal in the direction in which the contact terminal is pulled out of the housing via the lead wire can be restricted. As a result, there is a problem that the movement in the housing may not be effectively restricted.

According to the structure of the third conventional example, the movement of the contact terminal in both directions can be restricted. However, since the structure is such that two cylindrical insulators are provided to form two stopper surfaces, the assembly is manufactured. It takes time and cost.

An object of the present invention is to solve the problems of the conventional structure, and an object of the present invention is to provide a gas sensor signal extraction structure which can restrict the movement of the contact terminal from both directions and has a simple structure and is easy to assemble.

[0008]

To explain the structure of the present invention, a sensor element 1 having a tip exposed to a measurement gas and having electrodes 11a, 11b, 11c, 11d for signal extraction formed on the outer periphery of a base is formed in a cylindrical shape. The tip 41 of the contact terminal 4, which is held inside the housing 2 and the lead wire 3 extending from the outside of the housing 2 is connected to the base end, is taken out from the extraction electrodes 11 a to 11 d of the sensor element 1.
And a part of the contact terminal 4 bulges and bends laterally, and the bent portion 42 of the cylindrical insulator 5 surrounding the contact terminal 4 is reduced in diameter to a diameter smaller than a larger diameter. The contact terminal 4 is brought into contact with the portion 51 to restrict the movement of the contact terminal 4 inserted into the large-diameter inner wall in the insertion direction, and the contact terminal 4 projects to the side and extends obliquely in the removal direction opposite to the insertion direction. Stop piece 43
And a recess 5 provided on the inner wall of the insulator 5.
2 to restrict the movement in the above-mentioned removal direction.

[0009]

In the above construction, when the contact terminal 4 is inserted into the large-diameter inner wall of the cylindrical insulator 5 when the contact terminal 4 is assembled, the bent portion 42 comes into contact with the stepped portion 51 and moves in the insertion direction. Is regulated. At the same time, the engaging piece 43 of the contact terminal 4 is engaged with the concave portion 52 of the inner wall of the insulator 5 so that the movement in the pull-out direction is restricted, and the positioning is reliably performed in both directions.

In this way, the movement of the contact terminal 4 in both directions is reliably prevented by the single cylindrical insulator 5, so that the structure is simplified and the cost is reduced.

A locking piece 43 that extends obliquely in the pull-out direction.
Does not cause any resistance when the contact terminal 4 is inserted into the insulator 5 and allows a smooth assembly.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an example in which the present invention is applied to an oxygen sensor provided in a vehicle exhaust pipe will be described. 1 is an overall longitudinal sectional view, FIG. 2 is a transverse sectional view taken along line II-II of FIG. 1, and FIG. 3 is an overall side view.

In the figure, a large number of through holes 61 are formed in a lower opening of a cylindrical metal housing 2 which is fixed to a wall of an exhaust pipe by screws.
The bottomed double cylindrical element cover 6 formed with the above is attached, and the tip (lower end) of the long plate-shaped sensor element 1 is located in the element cover 6. The sensor element 1 is mainly composed of zirconia ceramics, extends upward through an insulating member 21 provided along the inner periphery of the housing 2, and is fixed to the upper opening of the housing 2 by caulking.
And the dust cover 72 connected thereabove.
In the cylinder.

The sensor element 1 is vertically positioned by a chevron-shaped protrusion 12 provided at an intermediate position between both side surfaces, and the upper end thereof has an octagonal cross section obtained by chamfering four corners of a rectangular cross section as shown in FIG. I have. And in this chamfer,
The extraction electrodes 11a, 11b, 11c and 11d communicating with the sensing electrode and the heater electrode (not shown) are arranged in the vertical direction (FIG. 2).
(In the direction perpendicular to the plane of the drawing).

A contact terminal 4 made of a spring material is in contact with each of the extraction electrodes 11a to 11d. The outer shape of the contact terminal 4 is as shown in FIG. 4. The distal end (lower end) of the long plate-like spring plate material is formed in a substantially U-shape to form a bent portion 42 bulging to the side, and the distal end 41. A hemispherically projecting contact point is formed on the back surface. An intermediate position of the contact terminal 4 is cut and raised on both sides to form a locking piece 43 that extends obliquely downward from the rear surface. One end of the lead wire 3 is connected to a base end (upper end) of the contact terminal 4 by a caulking connector 31.

The contact terminal 3 is accommodated in a cylindrical ceramic insulator 5 disposed in a dust cover 72 (FIG. 1), and the contact point of the tip 41 is connected to the extraction electrodes 11a to 11a of the sensor element 1. 11d (FIG. 2). The insulator 5 is a cylindrical body of a different diameter having a small diameter in the upper half and a large diameter in the lower half, and the inner wall of the lower half thereof faces the extraction electrodes 11a to 11d of the sensor element 1 as shown in FIG. The contact portion 4 recedes into a rectangular shape to have a large diameter, where the bent portion 42 of the contact terminal 4 is located, and the inner wall stepped portion 51 above the bent portion 42.
(FIG. 1).

The upper half of the contact terminal 4 is located in each of small-diameter through holes provided in four places in the upper half of the insulator 5.
The inner wall of each through hole has a stepped portion 51 from the upper open end to the lower end.
A concave groove 52 is formed up to the vicinity, and the contact terminal 4 is formed.
Of the locking piece 43 is in contact with and engaged with the lower end surface of the concave groove 52.

With this structure, the upward movement of the contact terminal 4 is restricted by the bent portion 42 abutting on the stepped portion 51 of the insulator 5, and the downward movement is caused by the engagement between the locking piece 43 and the end face of the concave groove 52. Regulated by engagement.

The through hole 721 of the dust cover 72 and the center through hole 53 of the insulator 5 are formed through the air introduction hole 731 of the filter cover 73 which covers the upper outer periphery of the dust cover 72.
Through the air inlet 12 at the center of the sensor element 1 (FIG. 2)
Is guided to the outside air.

When assembling the oxygen sensor, as shown in FIG. 5, the lead wire 3 is inserted into the through hole of the insulator 5 and pulled up. 5 enters the lower half, and the bent portion 42 is positioned in contact with the stepped portion 51. At this time, the locking piece 43 enters the through hole in a folded state, and when it reaches the concave groove 52, it is elastically restored in the opening direction and engages with the end face thereof.

The dust cover 72 and the filter cover 73 are swaged and fixed to the outer periphery of the insulator 5 to which the four contact terminals 4 are assembled (FIG. 6), and the sensor element 1 held in the housing 2 is fixed. When the upper end is inserted into the insulator 5, the extraction electrodes 11a to 11
The leading end of each contact terminal 4 makes contact conduction with d. The sensor cover 71 is connected to the dust cover 72 by caulking.

According to the above take-out structure, one insulator 5
Since the contact terminal 4 can be positioned in any of the upper and lower directions with a simple structure by the stepped portion 51 and the concave groove 52 formed in
Even if vibration or the like is input, the position of the contact terminal 4 does not shift up and down, and no conduction failure occurs.

Further, since the contact terminals 4 can be smoothly inserted into the insulator 5, assembly is simple.

The engaging piece 43 of the contact terminal 4 is formed, for example, as shown in FIG.
2, a structure formed diagonally below the rear surface of the base, or a structure formed diagonally below the front surface at the intermediate position as shown in FIG.

[0025]

As described above, according to the signal take-out structure of the present invention, the contact terminals can be securely fixed with a simple and inexpensive structure, and the occurrence of poor conduction can be effectively prevented.

[Brief description of the drawings]

FIG. 1 is an overall vertical sectional view of an oxygen sensor having a signal extracting structure according to the present invention.

FIG. 2 is a transverse sectional view taken along the line II-II in FIG.

FIG. 3 is an overall side view of the oxygen sensor.

FIG. 4 is a side view and a front view of the contact terminal.

FIG. 5 is a cross-sectional view of an insulator.

FIG. 6 is an exploded sectional view of the oxygen sensor.

FIG. 7 is a side view and a front view showing another example of the contact terminal.

FIG. 8 is a side view and a front view showing still another example of the contact terminal.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sensor element 11a, 11b, 11c, 11d Extraction electrode 2 Housing 3 Lead wire 4 Contact terminal 41 Tip 42 Bent part 43 Locking piece 5 Insulator 51 Stepped part 52 Groove (concave)

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Masahisa Suzuki 1-1-1 Showa-cho, Kariya-shi, Aichi Japan Inside Denso Co., Ltd. (56) References JP-A-4-310856 (JP, A) JP-A-2 JP-A-1990757 (JP, A) JP-A-61-108953 (JP, A) JP-A-2-144762 (JP, U) JP-A-60-137366 (JP, U) JP-A-4-110972 (JP, U) ) Hikaru Hei 2-146365 (JP, U) Hikaru Hei 2-144761 (JP, U) Hikaru Sho 60-150449 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01N 27/409

Claims (1)

(57) [Claims] 1. A sensor element having a tip exposed in a measurement gas and having a signal extraction electrode formed on the outer periphery of a base end thereof is held in a cylindrical housing, and a lead wire extending from outside the housing is connected to the base end. The tip of the terminal is brought into contact conduction with the extraction electrode of the sensor element, a part of the contact terminal is expanded and bent to the side, and the bent portion is made smaller in diameter than the large diameter of the cylindrical insulator surrounding the contact terminal. The contact terminal, which has been inserted into the large-diameter inner wall, is prevented from moving in the insertion direction by abutting the stepped portion of the inner wall whose diameter is reduced, and the contact terminal protrudes sideways and is inclined in the removal direction opposite to the insertion direction. A signal extraction structure for a gas sensor, wherein a locking piece extending to the inner surface of the insulator is formed, and this is engaged with a recess provided on the inner wall of the insulator to restrict the movement in the removal direction.