JPS61137056A - Oxygen sensor - Google Patents

Abstract

PURPOSE:To prevent the corrosion of a connector part, by forming the connector part performing the electrical connection of an oxygen sensor element and an external circuit in an air-tight state. CONSTITUTION:An oxygen sensor element 1 is inserted in a protective tube body 20. The tube body 20 is constituted of a protective cover part 20a and a protective cylinder part 20b surrounding the oxygen detection part 4 of the sensor element 1 and gas to be measured is flowed in from a gas introducing port 7 to be contacted with the oxygen detection part 4 of the gas to be mea sured. A connector insulator 5 is engaged with and inserted in the tube body 20 from above and a rubber gasket 8 having lead wires 11-13 inserted therethrough are engaged with and inserted in the upper end surface of said tube body 20 to perfectly close said tube body 20.

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 the 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. There are known products that purify water and reduce fuel consumption.

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, atmospheric air is usually used as the reference substance, and therefore, conventional oxygen sensors take in this atmospheric air and bring it into contact with the reference electrode. An atmospheric air intake hole is provided on the outer surface of the oxygen sensor case.

(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 installed in a vehicle such as the one described above, There could be water intrusion, or even salt water intrusion along the coastline.

If such foreign matter enters the oxygen sensor, it may corrode the metal parts that are in contact with the oxygen sensor element surface. Contacts (metal lead members that elastically contact the terminals arranged on the surface of the oxygen sensor element) that make up the connector section may become corroded due to accumulation of moisture or salt water, resulting in poor contact or It is conceivable that the insulation may be poor between the cases or between the cases.

(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 making the connector part airtight, even if foreign substances such as moisture or salt water enter the oxygen sensor through the air intake hole, the connector part will not be corroded, resulting in poor detection or malfunction. can be prevented from occurring.

(Example) A first embodiment of the 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 gap 30 formed in the longitudinal direction of the sensor element 1 is provided.

This gap 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 is an oxygen detection section 4, and although not shown, a measurement electrode is provided on the surface of the oxygen detection section 4, and a measurement electrode on the inner wall of the cavity 30 is provided on the surface of the oxygen detection section 4. Reference electrodes are provided at back-to-back positions. Similarly, an oxygen pump electrode (as shown) is provided on the surface of the oxygen detection section 4 and the inner surface of the cavity 30 (some devices are equipped with a heater).

Since the measurement electrode, reference electrode, etc. mentioned above need to be electrically connected to external circuits (signal processing circuit, power supply circuit, etc.), a lead terminal is attached to the end of the oxygen sensor element 1 on the opposite side from the oxygen detection section 4. (as shown), and these lead terminals and the measurement electrodes are connected by a conductor. Furthermore, by fitting the connector insulator (connector part) 5 provided with the lead wires 11 to 13 connected to an external circuit to the end where the lead terminals are provided, the lead wires 11 to 13 are fitted.
is configured to be electrically connected to the lead terminal.

As shown in FIG. 1, the protective tube body 20 has a distal end that covers a portion of the protective cover 2 that surrounds the oxygen detection section 4 of the oxygen sensor element 1.
0a, and a protective cylindrical portion 20b that accommodates parts other than the oxygen sensing portion 4.

The oxygen sensor element 1 is mounted on the side surface of the protective cover part 20a.
A total of eight measurement gas introduction holes 7, four of which are lined up in the longitudinal direction, are provided at positions on both sides of the width direction, and the measurement gas flowing from these measurement gas introduction holes 7 is detected as oxygen. It is adapted to come into contact with part 4. Further, the oxygen sensor element 1 is placed at the tip of the protective cover part 20a in the protective tube body 20.
An opening 20c is formed into which a jig for insertion and positioning is inserted.

An oxygen sensor 10 is provided on the outer periphery of the upper end of the protective cylinder portion 20b.
A housing 15 for fixing the 0 to a partition wall 25 that separates the gas to be measured from other parts, such as the exhaust pipe wall of a vehicle, is fitted and fixed, and the housing 15 and the protective cylinder part 20b are fixed to each other. The boundary between the housing 15 and the protective cylindrical portion 20b is sealed by a stainless steel airtight ring 16 so that the gas to be measured does not leak from the boundary.

Further, the central portion of the oxygen sensor element 1 is located within the protective cylinder portion 2Ob between the first to third insulators 17°3.2 and the first to third insulators 17°3.2. It is fixed by a second gas-tight member 6.14. The first airtight member 6 has a function of fixing the oxygen sensor element l, and also has a function of preventing the gas to be measured from entering the inside of the protective cylinder part 20b from the side of the protective cover part 20a. It is made by compacting inorganic fillers such as cement and talc.

A presser plate 18 disposed on the upper surface of the second insulator 3
b and the caulking portion 22, the above-mentioned first. Second insulator 17
．． 3 and the first airtight member 6 are prevented from shifting upward.

The connector insulator 5 is fitted into the protective tube body 20 from above, and the rubber stopper 8 through which the lead wires 11 to 13 are inserted is fitted into the upper end surface of the protective tube body 20, thereby completely closing the connector insulator 5. Further, the rubber plug 8 is caulked from the outer periphery of the protective tube body 20, and the caulked portion 21 prevents the rubber plug 8 from being removed and improves airtightness.

Further, on the lower end surface of the connector insulator 5, a third insulator 2,
A second airtight member 14 is disposed, and the second airtight member 14
The presser plate 18a and the caulking portion 23 arranged on the lower surface prevent 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 l. 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 by the rubber plug 8 or the second airtight member 14, and the side surface is covered by the protective tube body 2.
0, the connector insulator 5 is kept completely airtight.

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

With the above configuration, the connector part, that is, the connector insulator 5 is completely sealed, so that the oxygen sensor of this embodiment prevents foreign substances such as moisture and salt water from entering the inside of the connector insulator 5 from the outside. can be definitely prevented. 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 element 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 present invention.

This embodiment differs from the first embodiment shown in FIG.
The third insulator 17, 3.2 and the first insulator 17, 3.2. Second airtight member 6.1
4 are gathered downward and fixed by one presser plate 18c and a caulking part 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 the material, it is preferable to use ceramics with a high degree of sintering.

Therefore, even if foreign substances such as moisture try to enter from the air intake hole 43, the probability that it will reach the oxygen sensor element 1 through 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 TA aqueous 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 half-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. FIG. 4 is a half-sectional view showing the configuration of a third embodiment of the present invention. FIG. 5 is a perspective view showing the shape of the second insulator in FIG. 4. 100.20Q, 300...Oxygen sensor...Oxygen sensor element

Claims (1)

[Claims] 1. An oxygen sensor comprising an oxygen sensor element having a predetermined electrode formed mainly using an oxygen ion conductive solid electrolyte and housed in a predetermined case, comprising: An oxygen sensor characterized in that a connector part for electrically connecting a sensor element and an external circuit is accommodated therein, and the connector part is formed airtight.