JPS6394151A - Oxygen sensor - Google Patents

Abstract

PURPOSE:To normally measure the concn. of oxygen even if defective contact of the base end of a zirconia tube coated with a platinum electrode arises by constituting a titled sensor in such a manner that electromotive force is taken out of the base end of said tube and is taken out of the top end side as well. CONSTITUTION:Electrodes 5A, 5B are provided to the inside and outside of the zirconia tube 2. A conductive plate part 21A is brought into pressurized contact with the base end face of the inside electrode 5A and is connected via a conductive pipe part 21B and a conductive plate 24 to a lead wire 11. A conductive electrode bar 23 is mounted to the top end of the inside electrode 5A and is connected via a conductive compression spring 26 and the conductive plate 24 to the lead wire 11. The electromotive force based on the concns. of the oxygen in the outdoor air to contact the electrode 5A and the exhaust gas to contact the electrode 5B is taken out of the base end of the electrode 5A through the plate part 21A and is taken out of the top end through the electrode bar 23. Since the electromotive force is taken out by the electrode bar, the exact detection is permitted even if the defective contact on the base end side arises.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an oxygen sensor used for detecting the oxygen concentration in exhaust gas in, for example, an internal combustion engine.

<Prior Art> Conventionally, as an example of this type of oxygen sensor, there is one shown in FIG. 2 (see Japanese Utility Model Application Publication No. 59-37558, etc.).

To explain this, the proximal end of the zirconia tube 2 is locked to the distal end of the holder 1 attached to the exhaust pipe wall via the seal washer 3, and the closed distal end of the zirconia tube 2 has a slit 4a. It is covered by protector 4.

Further, on a part of the inner and outer surfaces of the zirconia tube 2, an inner electrode 5A and an outer electrode 5B are formed by platinum paste or the like, extending from the base end to the distal end along the axial direction of the zirconia tube 2. . Zirconia tube 2
A contact plate 6 is brought into contact with the base end of the cylindrical isolation bushing 7, and the contact plate 6 is pressed by the distal end surface of a cylindrical isolation bushing 7. The isolation bush 7 is fixed to the holder 1 by caulking, and is fixed with a cover 8 via a counter spring 9. Then, the lead wire 11 is crimped and fixed to the terminal rod 10 connected to the contact plate 6 and extending inside the isolation bushing 7, and the lead wire 11 is installed in the hole at the proximal end of the isolation bushing 7. It is drawn through the Lahar tube 12 and led out to the outside.

In this oxygen sensor, the exhaust gas introduced through the slit 4a of the protector 4 is brought into contact with the outside of the zirconia tube 2, and the atmosphere is brought into contact with the inside of the zirconia tube 2, thereby creating a gap between the inner electrode 5A and the outer electrode 5B. An electromotive force is generated according to the ratio of each oxygen concentration in the atmosphere and in the exhaust gas, and the oxygen concentration in the exhaust gas is detected based on this electromotive force value.

<Problems to be Solved by the Invention> However, the contact plate 6 and the inner electrode 5A are brought into contact by exposing the inner electrode 5A to the base end of the zirconia tube 2 and pressing the contact plate 6 into contact with it from above. Moreover, since the contact plate 6 is flat, there is a step between the contact surfaces of the two. Also,
Zirconia tube 2. Because there are differences in the flatness of the contact plate 6 and the isolation bushing 7, and variations in the exposed length of the inner electrode 5A, the contact plate 6 is partially attached to the base end of the zirconia tube 2. The contact plate 6 may shift due to vibrations of the internal combustion engine, etc.
As shown in FIG.
It is easy to lift up from A and cause poor contact. In addition, the inner electrode 5A may deteriorate and become disconnected, resulting in poor characteristics of the oxygen sensor.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide an oxygen sensor that can normally detect oxygen concentration even if a contact failure or disconnection occurs in the inner electrode.

<Means for Solving the Problems> For this reason, the present invention provides a conductor that is brought into contact with the base end of the inner electrode at the base end of the zirconia tube, and a distal end of the inner electrode that extends to the distal end of the zirconia tube. The structure is such that the parts are electrically connected to each other by a conductive member.

According to the above configuration, even if a contact failure occurs on the base end side of the inner electrode or a disconnection occurs in the middle part of the inner electrode, the electromotive force can be detected through the tip of the inner electrode. This allows normal oxygen concentration detection.

<Example> An example of the present invention will be described below based on FIG. 1. Incidentally, the same parts as in the prior art are given the same reference numerals, and the description thereof will be omitted.

In FIG. 1, the contact plate 21 of this embodiment, which is electrically connected to the inner electrode 5A, is sandwiched between the base end of the zirconia tube 2 and the front end surface of the isolation bushing 7, and is connected to the inner electrode 5A. It consists of a substantially flat plate portion 21A that is pressed against the base end side of the tube 5A, and a cylindrical pipe portion 21B that is inserted into the cylindrical isolation bushing 7 from the plate portion 21A. An electrode rod 23 is attached as a conductive member that passes through the hole 22 in the center of the plate portion 21A from the pipe portion 21B side and has its tip pressed against the tip of the inner electrode 5A. Furthermore, a disk-shaped four-electric plate 24 to which the lead wire 11 is connected is provided in the pipe portion 21B so as to be in contact with the inner wall of the pipe portion 21B, and a cylindrical isolation cover 25 is fitted above it. The end of the pipe portion 21B is bent and locked. Furthermore, a compression spring 26 made of a conductive material is interposed between the conductive plate 24 and the flange 23a of the electrode rod 23.
As a result, the tip of the electrode rod 23 is pressed against the tip of the inner mold 4M5A, and the conductive plate 24 is pressed against and fixed to the isolation cover 25 side.

According to this configuration, the atmosphere that contacts the inner electrode 5A,
The electromotive force generated between the electrodes 5A and 5B based on the ratio of the oxygen concentrations of the exhaust gas that contacts the outer electrode 5B is generated from the base end of the inner electrode 5A to the plate portion 21B of the contact plate 21, the pipe portion 21B, The electrode rod 23, compression spring 26. Conductive plate 2
4 and the lead wire 11 as well.

Therefore, even if a contact failure occurs between the plate portion 21A of the contact plate 21 and the inner electrode 5A, or a disconnection occurs at the intermediate portion of the inner electrode 5A due to deterioration of the inner electrode 5A, the above-mentioned Scratching stick 23. Compression spring 26. The path leading to the conductive plate 24 and the lead wire 11 allows the electromotive force generated between the inner electrode 5A and the outer electrode 5B to be taken out to the outside, thereby preventing the poor characteristics of the oxygen sensor due to the aforementioned poor contact or disconnection. can be prevented.

Note that the mounting structure of the electrode rod as a conductive member is not limited to this embodiment, and any structure may be used as long as it can reliably detect the electromotive force from the tip of the inner electrode.

(Effects of the Invention) As described above, according to the present invention, the electromotive force, which was conventionally taken out only from the base end side of the inner electrode, is now taken out from the tip side of the inner electrode in parallel. Therefore, even if there is a disconnection in the inner electrode or a poor contact at the proximal end, which is the conventional electromotive force extraction part, the electromotive force can be accurately detected without causing characteristic defects, and the durability of the oxygen sensor can be improved. Lifespan can be improved.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a main part of an embodiment of the present invention, FIG. 2 is a sectional view of an example of a conventional oxygen sensor, and FIG. 3 is a diagram illustrating problems of the conventional oxygen sensor. 2... Zirconia tube 5A... Inner electrode 5
B...Outside if Pole 7...Isolation bushing 9...Set spring 11...Lead wire 21.
...Contact plate 2LA...Plate part 2
1B... Pipe part 23... Electrode rod 24...
・4 electric temporary 25...Isolation cover 26・
...Compression spring patent applicant Fujio Sasashima, agent of Japan Electronics Co., Ltd., patent attorney Figure 2

Claims (1)

[Claims] The oxygen sensor is configured such that a conductor is pressed by the distal end surface of an isolation bush to the proximal end of a zirconia tube whose distal end is closed and whose inner and outer surfaces are coated with platinum electrodes so as to come into contact with the platinum electrodes on the inner surface side. An oxygen sensor comprising a conductive member that electrically connects the conductor to the tip of the platinum electrode on the inner surface side that extends to the closed tip of the zirconia tube.