JPH0479574B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an oxygen sensor for detecting the oxygen concentration in a gas to be measured, and particularly relates to an oxygen sensor that has been improved to prevent deterioration of a connector part. Regarding sensors.

(Prior Art) Conventionally, so-called oxygen sensors have been used to detect the oxygen concentration contained in the exhaust gas of an internal combustion engine, and to control the combustion state of the internal combustion engine optimally based on the detection signal. purification,
Devices that reduce fuel consumption are known.

Such an oxygen sensor generally consists of a measurement electrode exposed to a gas to be measured such as exhaust gas, and a reference electrode exposed to a reference material with a constant oxygen concentration, sandwiched between an oxygen ion conductive solid electrolyte. The output from the oxygen ion conduction effect between the two electrodes is used as the detection signal.

By the way, the above-mentioned reference substance is usually the atmosphere, and for this reason, conventional oxygen sensors are provided with an atmosphere intake hole on the outer surface of the case of the oxygen sensor to take in this atmosphere and bring it into contact with the reference electrode. .

(Problem to be Solved by the Invention) However, in the case of an oxygen sensor provided with an atmospheric intake hole as described above, especially when mounted on a vehicle as described above, There could be water intrusion, or even salt water intrusion along the coastline.

If such foreign matter enters the oxygen sensor,
If the metal parts in contact with the surface of the oxygen sensor element corrode, or if the metal parts that are in contact with the surface of the oxygen sensor element corrode, especially if the connector part is provided for electrical connection with an external circuit, the contact elements that make up this connector part (the surface of the oxygen sensor element) Corrosion caused by accumulation of moisture or salt water on the metal lead member (a metal lead member that elastically contacts the terminal section arranged on the terminal) may cause poor contact, or poor insulation between contacts or between cases. It is possible that

(Means for Solving the Problems) In order to solve the above problems, the present invention includes a connector part for electrically connecting the oxygen sensor element and an external circuit in a case housing the oxygen sensor element. and the connector portion is formed airtight.

(Function) By forming the above connector part airtight,
Even if foreign matter such as moisture or salt water enters the inside of the oxygen sensor through the air intake hole, the connector part will not be corroded, and detection failures and malfunctions can be prevented.

(Example) A first example of the present invention is shown in FIGS. 1 and 2.

The oxygen sensor 100 of this embodiment has an oxygen sensor element 1 formed in the shape of a longitudinal plate housed in a cylindrical metal protective tube body 20.

The oxygen sensor element 1 has a base plate made of an oxygen ion-conducting solid electrolyte (hereinafter referred to as "solid electrolyte plate"), and as shown in FIG. A cavity 30 is provided extending in the longitudinal direction of the sensor element 1 .

This cavity 30 communicates with the outside only through a through hole 32 formed in the center of the oxygen sensor element 1, and the other portions are completely closed.

One end of the oxygen sensor element 1 serves as an oxygen detection section 4, and although not shown, a measurement electrode is provided on the surface of the oxygen detection section 4.
A reference electrode is provided on the inner wall of the space 30 at a position facing back to back to the measurement electrode. Similarly, oxygen pump electrodes (not shown) are provided on the surface of the oxygen detection section 4 and on the inner surface of the space 30 (some devices are equipped with heaters).

Since the measurement electrode, reference electrode, etc. need to be electrically connected to external circuits (signal processing circuit, power supply circuit, etc.), a lead terminal ( (not shown) are provided, and these lead terminals and the measurement electrodes are connected by a conductor. Furthermore, a connector insulator (connector part) includes lead wires 11 to 13 connected to an external circuit at the end where the lead terminal is provided.
5 are fitted, the lead wires 11 to 1
3 is configured to be electrically connected to the lead terminal.

As shown in FIG. 1, the protective tube body 20 includes a protective cover portion 20a that surrounds the oxygen detecting section 4 of the oxygen sensor element 1, and a protective tube section that accommodates parts other than the oxygen detecting section 4 at its distal end. 20b.

On the side surface of the protective cover part 20a, a total of eight measurement gas introduction holes 7, four in a row in the longitudinal direction, are provided at positions on both sides of the oxygen sensor element 1 in the width direction. The gas to be measured that has flowed in through the measurement gas introduction hole 7 comes into contact with the oxygen detection section 4 . Furthermore, an opening 20c is formed at the tip of the protective cover portion 20a for inserting a jig for inserting and positioning the oxygen sensor element 1 into the protective tube body 20.

The oxygen sensor 100 is attached to the outer periphery of the lower end of the protective cylinder part 20b, for example, on the exhaust pipe wall of a vehicle.
A housing 15 is fitted and fixed to a partition wall 25 that separates the gas to be measured from other parts, and a stainless steel housing 15 is fitted to prevent the gas to be measured from leaking from the boundary between the housing 15 and the protective cylinder portion 20b. The boundary between the housing 15 and the protective cylinder portion 20b is sealed by the airtight ring 16.

Furthermore, the central portion of the oxygen sensor element 1 is
Inside the protective cylinder part 20b, the first to third insulators 17, 3, 2 and the first and second airtight members 6, 14
It is fixed by. The first airtight member 6
In addition to fixing the oxygen sensor element 1, the gas to be measured flows from the protective cover part 20a side to the protective cylinder part 2.
It has the function of preventing intrusion into the inside of the 0b, and is made by compacting an inorganic filler such as cement or talc.

The presser plate 18b and the caulking portion 22 arranged on the upper surface of the second insulator 3 prevent the first and second insulators 17, 3 and the first airtight member 6 from shifting upward. There is.

The connector insulator 5 is fitted from above the protective tube body 20, and the lead wire 1 is attached to the upper end surface of the connector insulator 5.
The rubber stopper 8 into which numbers 1 to 13 have been inserted is inserted to completely close the hole. Furthermore, this rubber plug 8 is caulked from the outer periphery of the protective tube body 20, and this caulked portion 21 allows the rubber plug 8 to be crimped.
It has been improved to prevent it from falling out and to improve its airtightness.

Further, a third insulator 2 and a second airtight member 14 are arranged on the lower end surface of the connector insulator 5, and a presser plate 18a is further arranged on the lower surface of the second airtight member 14.
The caulking portion 23 prevents the second insulator 2 and the second airtight member 14 from shifting downward.

The connector insulator 5 is provided with a contact 5a (one is shown in the figure, but it has three other contacts) having a spring property that presses into contact with the lead terminal of the oxygen sensor element 1. A ground lead 10 or lead wires 11 to 13 are connected to these contacts 5a.

In this way, the top and bottom of the connector insulator 5 are covered with the rubber plug 8 or the second airtight member 14, and the side surface is covered with the protective tube body 20, so that the connector insulator 5 is maintained in a completely airtight state. has been done.

An airtight space 9 is formed between the two presser plates 18a and 18b. This airtight space 9 only communicates with the air 30 through a through hole 32 formed in the center of the oxygen sensor element 1 .

With the above configuration, the connector part, that is, the connector insulator 5 is completely sealed, so that
The oxygen sensor of this embodiment can reliably prevent foreign substances such as moisture and salt water from entering the inside of the connector insulator 5 from the outside. Thereby, there is no risk of corrosion of the contactor 5a, the life of the contactor 5a can be extended, and detection failures and malfunctions can also be prevented.

Furthermore, in this embodiment, the air intake hole that the conventional oxygen sensor had was eliminated, and the inside of the protective cylinder part 20b was also made airtight, so that the airtightness of the connector insulator 5 was further improved and the oxygen sensor 1 is protected from corrosion caused by foreign substances from the outside.

In this embodiment, the reference substance necessary for measurement, that is, the atmosphere, is stored in an airtight space 9 having a relatively large capacity, so that there is no problem in measurement. Further, the oxygen concentration in the airtight space 9 is maintained at a constant value by appropriately driving the oxygen pump electrode to pump oxygen from the measurement gas.

Next, FIG. 3 is a diagram showing a second embodiment of the present invention.

This embodiment has a structure having an air intake hole as in the conventional structure. However, in order to ensure the airtightness of the connector part, as shown in FIG. 3, an air intake hole 41 is formed in the protective cylinder part 20b surrounding the airtight space 9 of the oxygen sensor 100 of the first embodiment. It is characterized by The other configurations are the same as the first embodiment.

With such a configuration, air can be taken in freely, and the airtightness of the connector insulator 5 is guaranteed.

Note that by providing the air intake hole 41, the oxygen pump electrode provided in the first embodiment can be omitted, and the number of parts can be reduced.

FIG. 4 shows a third embodiment of the invention.

This embodiment differs from the first embodiment shown in FIG. 1 in that the first to third insulators 17, 3, 2 are vertically separated by two holding plates 18a, 18b,
The second airtight members 6 and 14 are gathered downward and fixed by one presser plate 18c and a caulking portion 24.

Therefore, also in this embodiment, the connector insulator 5
is kept airtight. Further, an airtight space 46 is formed between the connector insulator 5 and the holding plate 18c.

In this embodiment, a second insulator 44 is disposed in a portion where the through hole 32 of the oxygen sensor element 1 is located, and an air intake hole 43 is formed in the protective cylinder portion 20a surrounding the second insulator 44. There is.

Furthermore, as shown in FIG. 5, the second insulator 44 has pores 45 formed in the radial direction to communicate the inner and outer surfaces. As for the material, it is preferable to use ceramics with a high degree of sintering.

Therefore, even if foreign matter such as moisture attempts to enter through the air intake hole 43, the probability that it will reach the oxygen sensor element 1 via the pores 45 of the second insulator 44 is low.

Note that if the second insulator 44 is formed using a material that can selectively transmit only the reference substance, there is no need to provide the pores 45, and processing becomes easier. Examples of such materials include glass fibers hardened with a water-repellent substance such as Teflon.

(Effects of the Invention) As explained in detail above, the present invention has an airtight connector part for electrically connecting an oxygen sensor element and an external circuit, so that foreign substances such as moisture and salt water can be Even if it gets into the sensor case, there is no risk of it reaching the connector part.

Therefore, it is possible to prevent corrosion of the connector portion, and it is possible to effectively eliminate detection failures and malfunctions due to poor contact of the connector portion.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing the configuration of the first embodiment of the present invention, FIG. 2 is a perspective view showing the shape of the oxygen sensor element in FIG. 1, and FIG. 3 is a diagram showing the configuration of the second embodiment of the present invention. Fig. 4 is a judgment view showing the structure of the third embodiment of the present invention, and Fig. 5 is a judgment view showing the structure of the third embodiment of the present invention.
FIG. 2 is a perspective view showing the shape of an insulator. 100, 200, 300...Oxygen sensor, 1...
...Oxygen sensor element, 5...Connector insulator (connector part), 6, 14...Airtight member, 8...Rubber plug,
20...Protective pipe body (case), 30...Empty, 3
2...Through hole, 41, 43...Air intake hole, 44...
...Insulator, 45...Pore.

Claims (1)

[Scope of Claims] 1. An oxygen sensor in which an oxygen sensor element including a predetermined electrode formed mainly using an oxygen ion conductive solid electrolyte is housed in a predetermined case, wherein the oxygen sensor is housed in the case. An oxygen sensor characterized in that a connector section for electrically connecting an element and an external circuit is accommodated therein, and the connector section is formed in an airtight manner.