JPH06331595A - Gas sensor - Google Patents

Abstract

PURPOSE:To improve the reliability for taking out a signal by fully securing the formation spacing of a take-out electrode and at the same time preventing the positional deviation of a sensor element. CONSTITUTION:Four corners of a rectangular section are chamfered as inclination surfaces in the outer periphery of a base edge 12 of a sensor element, each of take-out electrodes 13A-13D is formed at each chamber, and the spacing between parallel electrodes is secured. The contact pressure of the contact terminals 21A-21D which make a continuity by contact with the take-out electrodes 13A-13D is directed toward the center of a sensor element 1, thus operating to eliminating the side swing of the sensor element 1.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art An oxygen sensor used for optimal combustion control of an engine, etc. has a cylindrical housing attached to an exhaust pipe and a ceramic sensor element formed in a long plate shape is housed therein, and a sensor portion at the tip thereof is exhausted. It is exposed in the gas. As a method for extracting the signal from the sensor element, an easy and inexpensive method is to provide an extraction electrode at the base end of the sensor element and elastically contact a contact terminal provided at the tip of the lead wire extending from outside the housing. The structure is adopted.

An example of the case of an oxygen sensor is shown in FIG.
It shows in 0. Proximal end 1 of a rectangular alumina sensor element 1
2, each pair of extraction electrodes 13A and 13B of the sensor part and extraction electrodes of the heater part are formed on each of the front and rear side surfaces (only the front surface is shown), and these pair of extraction electrodes are actually formed on a small-diameter sensor element. Extend in parallel with a small distance 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, but contact from front and rear (upper and lower sides in the figure) and the contact pressure F acts only in the direction of sandwiching the sensor element 1, so the sensor element 1 can move in the left and right directions in the figure. Is. Therefore, the position of the sensor element 1 may be displaced due to vibration or the like as shown by the broken line in the figure, and the contact terminal 2
There is a problem that the conduction of 1A to 21D is impaired and, in extreme cases, the electrodes are erroneously contacted with other extraction electrodes.

The present invention solves such a problem by improving the reliability of signal extraction by ensuring a sufficient space for forming extraction electrodes on a small-diameter sensor element and preventing the sensor element from being displaced. It is an object to provide a gas sensor.

[0006]

The structure of the present invention will be described. A sensor element 1 having a tip 11 exposed in a measurement gas and extraction electrodes 13A, 13B, 13C and 13D formed on an outer periphery of a base 12 is provided as a cylinder. The leading ends of the contact terminals 21A, 21B, 21C, 21D provided in the housing 3 and connected to the base ends of the lead wires 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 so as to be conductive. In the gas sensor, the base end 1 of the sensor element 1 is
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 and 12d, one extraction electrode 13A to 13D is formed on each of at least three outer peripheral surfaces of the base end 12 including these inclined surfaces 12a to 12d, and the extraction electrode 13 is formed.
The contact terminals 21A to 21D which are in conductive contact with A to 13D
Each of the extraction electrodes 13A to 13D so that the resultant force of the contact pressures of the above-mentioned action acts to eliminate the lateral shake of the sensor element 1.
The formation position of is selected.

[0007]

In the above structure, since the outer periphery of the rectangular base end 12 of the sensor element 1 is chamfered to form the inclined surfaces 12a to 12d, the extraction electrodes 13A to 13D are formed even when the sensor element 1 has the same diameter. A sufficient space can be secured. Then, the extraction electrode 13 formed on the outer peripheral surface of the base end 12
Contact terminals 21A for contacting the positions A to 13D
Since the resultant force of the contact pressures of ˜21D is set to a 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 conductive state is maintained.

Particularly, since the sensor element 1 is positioned by utilizing 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 An example in which the present invention is applied to an oxygen sensor provided in a vehicle exhaust pipe will be described below. FIG. 1 is an overall vertical cross-sectional view of the cylindrical metal housing 3 which is screw-fixed to an exhaust pipe wall (not shown) and has a bottomed double cylindrical shape in which a large number of through holes are formed in a lower opening. The element cover 31 is attached, and the tip (lower end) of the long plate-shaped sensor element 1 is mounted in the element cover 31.
11 is located.

The sensor element 1 extends upward through an insulating member 32 provided along the inner circumference of the housing 3, passes through a body cover 33 which is caulked and fixed to an upper opening of the housing 3, and further has its base end 12 further. It reaches the inside of the cylinder of the dust cover 34 above.

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 mountain-shaped protrusions 16 are 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 portion 14, and an air introduction hole 15 provided at the center of the sensor element 1 is located at the tip of the element behind the sensor portion 14. It is open. Therefore, according to the 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 the lead electrode 17 and the extraction electrode 13A formed in the sensor base end 12 which will be described in detail later. Thirteen
Guided by B.

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

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

The extraction electrodes 13A to 13D have contact terminals 21A, 21 made of a spring material, respectively.
B, 21C, and 21D are in contact conduction. Contact terminal 21
A to 21D are long plate-shaped spring plate members formed by bending the tip (lower end) into a substantially U-shape (FIG. 1) and housed in a cylindrical ceramic insulator 35 arranged in a dust cover 34. After being 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 the 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-12d and general surfaces 12e, 1 between them
The front and rear surfaces (upper and lower surfaces of 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.
It is possible to secure a sufficiently wide interval between the extraction electrodes formed on the substrate. At this time, contact terminals 2 contacting each extraction electrode
The contact pressure F acting from 1A to 21D is the inclined surface 12a to
12d goes toward the center of the sensor element 1 perpendicularly to each other, and the resultant force acts to restore the sensor element 1 to its original position when the sensor element 1 shakes laterally.

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 interval between the parallel extraction electrodes 13A, 13B and 13C, 13D is sufficiently wide. Reserved. Therefore, the contact conduction between the contact terminal and the extraction electrode corresponding to the contact terminal can be reliably ensured by a simple and inexpensive structure without causing erroneous contact.

[0017]

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

Further, as shown in FIG. 8, the inclined surfaces 12a,
12d are two radially symmetrical positions, and these inclined surfaces 12
a and 12d and the general electrodes 12e and 12f which remain and the extraction electrode 1
The same effect can be obtained by forming 3A, 13B, 13C and 13D.

If only three extraction electrodes 13A, 13C and 13D are required by body-earthing one of the sensor signals, as shown in FIG. 9, the corners on the same side are chamfered to form inclined surfaces 12a and 12b. None, take out electrode 13 to these
The same effect can be obtained by the structure in which C and 13D are formed and the extraction electrode 13A that remains on the opposite general surface 12f is formed.

[0020]

As described above, according to the gas sensor of the present invention, the inclined surface is formed on the outer peripheral surface of the base end of the sensor element, and the space between the extraction electrodes formed on the outer peripheral surface including these inclined surfaces is sufficiently secured. In addition, since the contact pressure of the contact terminals in contact with these extraction electrodes acts to eliminate the lateral shake of the sensor element, reliable and simple signal extraction can be performed.

[Brief description of drawings]

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

2 is a cross-sectional view of the gas sensor, which is a cross-sectional view 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 a sensor element.

FIG. 5 is a perspective view of a base end portion of the 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 base end according to another embodiment of the present invention.

FIG. 8 is a schematic plan view of a sensor element base end according to another embodiment of the present invention.

FIG. 9 is a schematic plan view of a sensor element base end according to 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 base end of a sensor element.

[Explanation of symbols]

 1 Sensor element 11 Tip 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

Front Page Continuation (72) Inventor Masatoshi 1-1 1-1 Showa-cho, Kariya City, Aichi Prefecture Nihondenso Co., Ltd.

Claims (1)

[Claims] 1. A sensor element having a leading 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 outside the housing is connected to a base end of a contact terminal. In a gas sensor in which the tip is brought into contact with each electrode of the above-mentioned 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 an inclined surface. Each one of the extraction electrodes is formed on at least three surfaces of the base end outer peripheral surface including the surface, and the resultant force of the contact pressures of the contact terminals in contact with the extraction electrodes acts to eliminate the lateral shake of the sensor element. As described above, the gas sensor is characterized in that the formation positions of the respective extraction electrodes are selected.