JP3304510B2 - 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 oxygen concentration 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 exhausts a sensor part at the tip thereof. Exposure to gas. As an easy and inexpensive method of extracting signals from the sensor element, an extraction electrode is provided at the base end of the sensor element, and a contact terminal provided at the tip of a lead wire extending from the outside of the housing is brought into elastic contact with this. Structure is adopted.

FIG. 1 shows an example of an oxygen sensor.
0 is shown. Base end 1 of rectangular alumina sensor element 1
2, a pair of extraction electrodes 13A and 13B of the sensor unit and a pair of extraction electrodes of the heater unit are formed on each of the front and rear side surfaces (only the front surface is shown), and the pair of extraction electrodes is actually formed on a small-diameter sensor element. Extend in parallel at a small interval d of 1 mm or less.

[0004]

FIG. 1 shows each extraction electrode.
As shown in FIG. 1, known contact terminals 21A, 21B, 21
C and 21D make elastic contact with each other, but contact from the front and rear (upper and lower sides in the figure), and the contact pressure F acts only in the direction of clamping the sensor element 1, so that the sensor element 1 can move in the left and right direction in the figure. It is. For this reason, the position of the sensor element 1 may be shifted as shown by a broken line in the drawing due to vibration or the like.
There is a problem that the conduction of 1A to 21D is impaired, and in severe cases, it makes erroneous contact with another extraction electrode.

The present invention has been made to solve the above-mentioned problem, and it is necessary to secure a sufficient interval between the extraction electrodes on a small-diameter sensor element, to prevent a displacement of the sensor element, and to improve the reliability of signal extraction. It is an object of the present invention to provide a gas sensor.

[0006]

To explain the structure of the present invention, the sensor element 1 having the tip 11 exposed in the measurement gas and the extraction electrodes 13A, 13B, 13C, 13D formed on the outer periphery of the base 12 is formed as a cylinder. The distal ends of the contact terminals 21A, 21B, 21C, 21D, which are provided inside the housing 3 and connected to the base end of a lead wire 22 extending from the outside of the housing 3, are brought into contact with the respective extraction electrodes 13A to 13D of the sensor element 1 to conduct. In the gas sensor, the base 1 of the sensor element 1 is provided.
2 The outer periphery is formed into a rectangular cross section, and at least two corners thereof are chamfered to form inclined surfaces 12a, 12b, 12
c, 12d, and each of the extraction electrodes 13A to 13D is formed on at least three surfaces of the outer peripheral surface of the base end 12 including these inclined surfaces 12a to 12d, respectively.
The contact terminals 21A to 21D which are in contact with and conduct to A to 13D.
The extraction electrodes 13A to 13D are arranged so that the resultant force of the contact pressures acts to eliminate the lateral vibration of the sensor element 1.
Are selected.

[0007]

In the above configuration, since the outer surfaces of the rectangular base end 12 of the sensor element 1 are chamfered to form the inclined surfaces 12a to 12d, even when the sensor element 1 has the same diameter, the extraction electrodes 13A to 13D are formed. A sufficient interval can be ensured. Then, the extraction electrode 13 formed on the outer peripheral surface of the base end 12
The positions of A to 13D are changed by contact terminals 21A that come into contact with them.
Since the resultant force of the contact pressures of .about.21D is set to the position where the lateral vibration of the sensor element 1 is eliminated, the sensor element 1 is not displaced by vibration or the like, and a reliable conduction state is maintained.

In particular, since the sensor element 1 is positioned using the contact pressure of the contact terminals 21A to 21D without providing any special positioning means, the structure is simple and the cost is low.

[0009]

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. FIG. 1 is an overall vertical sectional view of the cylindrical metal housing 3. The cylindrical metal housing 3 is screw-fixed to an exhaust pipe wall (not shown). The element cover 31 is attached, and the tip (lower end) of the long plate-shaped sensor element 1 is provided in the element cover 31.
11 is located.

The sensor element 1 extends upward through an insulating member 32 provided along the inner periphery of the housing 3, and passes through a main body cover 33 fixed to the upper opening of the housing 3 by caulking. It reaches inside the cylinder of the upper dust cover 34.

The details of the sensor element 1 are shown in FIGS.
The main body of the sensor element 1 is a long plate made of alumina having a rectangular cross section, and a mountain-shaped projection 16 is formed on both side surfaces at an intermediate position for vertical positioning. A long thin plate made of zirconia is joined to the front surface of the sensor element 1 to form a sensor section 14. An air introduction hole 15 provided at the center of the sensor element 1 is provided at the tip of the element behind the sensor section 14. It is open. Thus, according to a known principle, an output corresponding to the difference in oxygen concentration between the introduced air and the exhaust gas is obtained in the sensor unit 14, which is formed by the lead electrodes 17 on the extraction electrodes 13A, 13A, 13
It is led to B.

A heater made of a ceramic thin plate is joined to the back surface of the sensor element 1 (not shown), and a lead electrode extending therefrom is also connected to an extraction electrode of a sensor base end 12, which will be described in detail later.

FIG. 5 shows the details of the base end of the sensor element 1. The base end 12 is an octagonal cross section having four inclined surfaces 12a, 12b, 12c, 12d and four general surfaces 12e, 12f, 12g, 12h with four corners of a rectangular cross section chamfered, as shown in FIG. As described above, the extraction electrodes 13A and 13B of the sensor unit 14 and the inclined surfaces 12a and 12b are provided on the inclined surfaces 12a and 12b.
Extraction electrodes 13C and 13D of the heater section are formed on c and 12d, respectively.

The extraction electrodes 13A to 13D have contact terminals 21A, 21A made of a spring material, respectively.
B, 21C, and 21D are in contact conduction. Contact terminal 21
A to 21D are formed by bending the distal end (lower end) of a long plate-shaped spring plate material into a substantially U-shape (FIG. 1), and housed in a cylindrical ceramic insulator 35 disposed in a dust cover 34. Positioned, the contact point 23 (FIG. 2) at the tip is in elastic contact with each of the extraction electrodes 13A to 13D. One end of a lead wire 22 (FIG. 1) extending from the outside is connected to a base end (upper end) of each of the contact terminals 21A to 21D by a caulking connector.

In such a structure, as shown in FIG.
Inclined surfaces 12a to 12d and general surfaces 12e, 1 between them
The front and rear surfaces (upper and lower surfaces in the figure) of the sensor element base end 12 composed of 2f have a sufficiently large area, and each of the inclined surfaces 12a to 12d
A sufficiently large interval between the extraction electrodes formed on the substrate can be ensured. At this time, the contact terminals 2
The contact pressure F acting from 1A-21D is
The sensor elements 1 are directed perpendicular to 12d toward the center of the sensor element 1, and the resultant force acts to return the sensor element 1 to its original position when the sensor element 1 oscillates.

Thus, the sensor element 1 is reliably positioned by the contact pressure of the contact terminals 21A to 21D without providing any special positioning means, and the distance between the parallel take-out electrodes 13A, 13B and 13C, 13D is sufficiently wide. Secured. Therefore, the contact continuity between the contact terminal and the corresponding extraction electrode can be reliably guaranteed with a simple and inexpensive structure without causing erroneous contact.

[0017]

[Other Embodiments] As shown in FIG.
2 is a square cross section of only the inclined surfaces 12a, 12b, 12c and 12d, and the extraction electrodes 1 are provided on the inclined surfaces 12a to 12d.
The same effect as in the above embodiment can be obtained by the structure in which 3A, 13B, 13C, and 13D are formed.

As shown in FIG. 8, the inclined surfaces 12a,
12d are two radially symmetric positions, and these inclined surfaces 12d
a, 12d and the extraction electrodes 1 on the remaining general surfaces 12e, 12f.
Similar effects can be obtained by forming 3A, 13B, 13C, and 13D.

In the case where one of the sensor signals is provided with three extraction electrodes 13A, 13C and 13D by body earthing or the like, as shown in FIG. 9, the corners on the same side are chamfered to form inclined surfaces 12a and 12b. None, extraction electrode 13
A similar effect is obtained by a structure in which C and 13D are formed and the extraction electrode 13A remaining on the opposite general surface 12f is formed.

[0020]

As described above, according to the gas sensor of the present invention, the inclined surfaces are formed on the outer peripheral surface at the base end of the sensor element, and the interval between the extraction electrodes formed on the outer peripheral surface including these inclined surfaces is sufficiently ensured. In addition, since the contact pressure of the contact terminal in contact with the extraction electrode acts so as to eliminate the lateral vibration of the sensor element, reliable signal extraction can be performed easily and at low cost.

[Brief description of the drawings]

FIG. 1 is an overall vertical sectional view of a gas sensor showing one embodiment of the present invention.

FIG. 2 is a cross-sectional view of the gas sensor taken along the line II-II of FIG.

FIG. 3 is a plan view of a sensor element.

FIG. 4 is an overall side view of the sensor element.

FIG. 5 is a perspective view of a base end of a sensor element.

FIG. 6 is a schematic plan view of a sensor element base end.

FIG. 7 is a schematic plan view of a sensor element proximal end showing another embodiment of the present invention.

FIG. 8 is a schematic plan view of a sensor element proximal end showing another embodiment of the present invention.

FIG. 9 is a schematic plan view of a sensor element proximal end showing another embodiment of the present invention.

FIG. 10 is a perspective view of a conventional sensor element base end.

FIG. 11 is a schematic plan view of a sensor element base end.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sensor element 11 Front end 12 Base end 12a, 12b, 12c, 12d Inclined surface 13A, 13B, 13C, 13D Extraction electrode 21A, 21B, 21C, 21D Contact terminal 22 Lead wire 3 Housing

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Masahisa Suzuki 1-1-1, Showa-cho, Kariya-shi, Aichi Japan Inside Denso Co., Ltd. (56) References JP-A-60-53844 (JP, A) JP-A-60 −42649 (JP, A) Japanese Utility Model Application No. 2-146365 (JP, U) Japanese Utility Model Application No. Sho 61-70763 (JP, U) Japanese Utility Model Application Model No. 2-144762 (JP, U) (58) Fields surveyed (Int. . ^7, DB name) G01N 27/409 G01N 27/12 G01N 27/41

Claims (1)

(57) [Claims] 1. A sensor element having a distal end exposed in a measurement gas and an extraction electrode formed on the outer periphery of a base end is provided in a cylindrical housing, and a lead wire extending from the outside of the housing is connected to a contact terminal connected to the base end. In a gas sensor having a distal end in contact with each electrode of the sensor element, the outer periphery of the base end of the sensor element is formed into a rectangular cross section, and at least two corners thereof are chamfered to form inclined surfaces. One of the extraction electrodes is formed on at least three of the outer peripheral surfaces of the base end including the surface, and the resultant force of the contact pressure of the contact terminals that makes contact with the extraction electrode acts to eliminate lateral deflection of the sensor element. As described above, a gas sensor characterized in that the formation position of each of the extraction electrodes is selected.