JPH0535326Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to an oxygen sensor for detecting the oxygen concentration in a gas to be measured, especially in exhaust gas discharged from an internal combustion engine, and in particular, the present invention relates to an oxygen sensor for detecting the oxygen concentration in a gas to be measured, particularly in exhaust gas discharged from an internal combustion engine. The present invention relates to an oxygen sensor having a structure in which a lead wire is inserted through a rubber stopper attached to a shaped cap, and an electrical connection is established within the sensor.

Conventionally, the oxygen concentration of exhaust gas, which is the gas to be measured emitted from internal combustion engines such as automobiles, has been detected using the oxygen ion conductive solid electrolyte such as zirconia and the principle of oxygen concentration batteries. It is known to control the air-fuel ratio. In this type of oxygen sensor, which is an oxygen concentration detector, predetermined electrodes, such as porous platinum electrodes, are attached to the inner and outer surfaces of a zirconia solid electrolyte that is cylindrical with a bottom or a flat plate with a passage provided inside. The inner electrode is brought into contact with the atmosphere to serve as the reference oxygen concentration electrode, while the outer electrode is exposed to exhaust gas, which is the gas to be measured, to serve as the measurement electrode.
Then, by detecting the electromotive force based on the difference in oxygen concentration between the reference electrode and the measurement electrode,
The oxygen concentration in such exhaust gas is measured.

In addition, the electromotive force in such a solid electrolyte is unstable unless the solid electrolyte is heated to a certain degree, so it is difficult to maintain an accurate air-fuel ratio during idling or immediately after starting when the exhaust gas of the internal combustion engine is at a low temperature. In order to solve this problem, a prescribed rod-shaped heater is inserted into the solid electrolyte cylinder, or a prescribed heater layer is combined with the solid electrolyte. Oxygen sensors equipped with heaters have been considered that have a structure in which the solid electrolyte is forcibly heated.

By the way, in the case of a conventional oxygen sensor of this type, a cylindrical cap is provided at the rear of the sensor to form an outer shell and cover various sensor parts, and an opening on the rear end side of the cap is provided. A rubber plug is attached to the cap and closes the opening of the cap, thereby forming a generally closed space at the rear of the sensor. In addition, a lead wire for extracting the electromotive force signal of the solid electrolyte and a lead wire for passing current to the heater are inserted into the sensor from the outside through a rubber stopper that closes the opening of the cap.
In other words, it is inserted into the cap, and inside the insulator inside the cap, via a predetermined connector,
The solid electrolyte and the heater are electrically connected to each other.

However, in the case of an oxygen sensor having such a structure, when the lead wire inserted from the outside is vibrated due to some phenomenon, the vibration is transmitted to the inside of the sensor, and the internal sensor parts, such as the heater. There was a problem that the leads etc. connected to the terminals were subject to fatigue failure. In particular, such oxygen sensors
Generally, since it is used to detect the oxygen concentration of exhaust gas emitted from an internal combustion engine such as an automobile, vibrations of the internal combustion engine or vibrations while the automobile is running are transmitted to the oxygen sensor. Therefore, it is easy to cause the lead wire to vibrate as described above.

The present invention was devised in view of the above circumstances, and its purpose is to effectively block vibrations transmitted to the inside of the sensor through the lead wires, so that the parts inside the sensor are not damaged by fatigue. An object of the present invention is to provide an oxygen sensor.

In order to achieve this purpose, the present invention uses a solid electrolyte provided with a predetermined electrode,
A cylindrical cap is provided at the rear of the oxygen sensor having a heater for heating the solid electrolyte to form its outer shell, and a rubber plug is attached to the opening at the rear end of the cap. through which a lead wire for extracting an electromotive force signal of the solid electrolyte and a lead wire for passing current to the heater are inserted from the outside, respectively;
The cap is electrically connected to the solid electrolyte and the heater through connectors within the insulator inside the cap, and the connector is provided with a protrusion, and the connector is connected to the insulator by the protrusion. and pressurizes the rubber stopper in its radial direction by caulking the cap from the outside;
The lead wire was fixed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to clarify the structure of the present invention more specifically, some embodiments of the present invention will be described in detail below with reference to the drawings.

First, in FIG. 1, 2 is a bottomed cylindrical solid electrolyte made of zirconia or the like, and predetermined electrodes, for example, porous platinum electrodes (not shown) are provided on the inner and outer surfaces of the solid electrolyte, respectively. These electrodes allow the electromotive force of the solid electrolyte 2 to be detected, as is well known.

A cylindrical metal housing 4 is attached to the outer circumference of the solid electrolyte 2 on the open side via a contact packing 8, and is exposed to the outer surface of the closed end of the solid electrolyte 2, such as an automobile, etc. The solid electrolyte 2 is arranged so that the inside of the cylinder of the solid electrolyte 2 is airtightly isolated from the exhaust gas (gas to be measured).
is stored and maintained. Specifically, in a state where the solid electrolyte 2 is inserted into the flow of exhaust gas with respect to a passage member (not shown) such as an exhaust gas pipe through which the exhaust gas passes, the housing 4 is inserted into the flange portion 6 of the solid electrolyte 2. By installing the solid electrolyte 2 in the cylinder, the inside of the cylinder of the solid electrolyte 2 is isolated from the exhaust gas as the gas to be measured.

Note that the solid electrolyte 2 for this housing 4
By housing the solid electrolyte 2, the outer electrode (measuring electrode) of the solid electrolyte 2 is connected to the housing 4 via the contact packing 8 interposed in the abutting portion between them, and the outer electrode (measuring electrode) of the solid electrolyte 2 is The potential of the outer electrode is taken out to the outside. Further, the housing 4 is provided with a protective cover 10 for protecting the outer surface of the solid electrolyte 2 from exhaust gas, and a gasket 1 for sealing between the passage member and the flange portion 6.
2 is provided.

Further, the housing 4 has a cylindrical protrusion 14 that forms an opening on the atmosphere communication side at the end of the solid electrolyte 2 on the opening side, and the housing 4 has a cylindrical protrusion 14 that forms an opening on the atmosphere communication side. Various sensor parts (members) are connected or arranged to protrude further outward from the protrusion 14 to constitute a sensor.

That is, a round rod-shaped heater 16 of a predetermined length is housed in the cylinder of the solid electrolyte 2, and the rear part of the heater 16 is arranged so as to protrude rearward from the cylindrical protrusion 14. There is.
Furthermore, two cylindrical insulators 18 and 20 that surround the rearward protruding portion of the heater 16 and form an insulating space are assembled via a spacer member 22, and the end of one of the insulators 18 The insulator 18 is fitted into the cylindrical protrusion 14 of the housing 4 so that the heater 16 is inserted through the cylindrical projection 14 of the housing 4. Further, a center electrode lead 24 having an annular shape is inserted outside the heater 16, and is held under narrow pressure between the rear end surface of the solid electrolyte 2 and the front end surface of the insulator 18 at its flange portion. As a result, it is brought into contact with a conductive portion extending from the inner electrode (reference electrode) of the solid electrolyte 2, and is connected to the inner electrode.

Then, such sensor members (16, 18,
A cylindrical metal cap 26 is inserted and arranged so as to surround the outside of the caps (20, 22, 24, etc.) and cover them with a predetermined space between them. It is fitted onto the outer circumferential surface of the cylindrical protrusion 14 of the housing 4, and further fixed by caulking at a plurality of locations in the circumferential direction. Further, on the other end side of the cap 26, a small diameter part 30 is provided following the step part 28, into which a rubber plug 32 is fitted and attached. The rear end opening is closed. The three lead wires 34a, 34b, 34c are
Each of them passes through the rubber stopper 32 and is guided into the insulator 20 from the outside.

Moreover, as is clear from the enlarged view of FIG. 2, after the rubber plug 32 is fitted into the small diameter portion 30 of the cap 26 as described above,
Also, the lead wires 34a to 34 are connected to the rubber stopper 32.
After C is inserted, it is caulked from the outside over the entire circumference, thereby forming a continuous caulked portion (concave groove) 36 extending in the circumferential direction. By this caulking, compressive force in the radial direction is applied to the rubber plug 32, and the lead wires 34a to 34c inserted through the rubber plug 32 are effectively fixed. That's what happens.

A disc spring 38 is disposed on the step 28 on the side of the small diameter part 30 at the rear end of the cap 26, and the disc spring 38 presses the insulators 20, 18 against the housing 4. It is beginning to receive a biasing force.

The lead wires 34a to 34c are inserted through the rubber plug 32 and guided into the sensor, in other words, into the cap 26, and are then guided into the insulator 20 through the holes 40 at the rear end of the insulator 20. The lead wires 34a to 34c are connected at their ends to the center electrodes 22 through connectors 42.
The signal lead 44 extending from the center electrode 24 is connected to the leads 44 and 46 extending rearward from the heater 16 by crimping, thereby establishing electrical connection.
The central electrode 4 is provided integrally with the end of the rear pressing piece, and the rear end is crimped together with the lead wire 34a by a connector 42, thereby electrically connecting the lead wire 34a, and an electromotive force signal derived from the electrode of the solid electrolyte 2 is taken out through the lead wire (signal wire) 34a. The heater lead 46 extending from the rear of the heater 16 is connected to the heater conductive part at the rear of the heater 16 by soldering, and is further connected together with the lead wires 34b and 34c as heater wires by crimping the connector 42, thereby electrically connecting the lead wire 34a to the heater 16.
A predetermined current can be passed through 4b and 34c.

Moreover, in this embodiment, the connector 42 has protrusions 48, 48 integrally formed on both sides of the connector 42, as shown enlarged in FIGS. 3 and 4. And those protrusions 4
8, 48 act so as to come into contact with and be locked to the inner wall surface of the connector housing hole 50 of the insulator 20, furthermore, the vibration of the connector 42 portion can be effectively prevented. Therefore, by fixing the periphery of the connecting portion between the leads 44, 46 and the connector 42, which are prone to fatigue fracture, an even more excellent fatigue fracture prevention effect can be achieved.

Note that the connector 42 has three caulked parts 42.
a, 42b, and 42c, and mainly, in the 42a portion, the outer covering portion of the lead 34 wire a is fixed by caulking, and in the central portion 42b, the conductive core wire portion is caulked and fixed, and the end portion is fixed by caulking. 42
At portion c, the lead 44 is fixed by caulking. When the protruding pieces 48, 48 are provided between these caulked portions and are forcibly accommodated in the connector accommodation hole 50 of the insulator 20, the protruding pieces 48, as shown in FIG. , deformed from the solid line state to the two-dot chain line state, thereby being housed in the connector accommodation hole 50 in a fixed position,
They will be forced to place it.

Therefore, in the oxygen sensor configured as described above, the lead wires 34a to 34c, which are inserted into the sensor through the rubber plug 32 attached to the cap 26 constituting the rear outer shell, are connected to the cap. These lead wires 34a are firmly fixed by the compression and pressure action of the rubber stopper 32 by the caulking 36 at the small diameter portion 30 of the lead wire 34a.
Even if ~34c is caused to vibrate for some reason, the vibration is blocked by the rubber stopper 32, and the vibration is thereby transmitted to the inside of the sensor.
Lead 4 connected to internal components, e.g. heater
6 etc. could be effectively prevented from suffering fatigue failure.

Moreover, in the sensor structure of the above example, the connector 42 for connecting the lead wires 34a to 34c, the signal lead 44, and the heater lead 46 is connected to the connector receiving hole of the insulator 20 by the protrusion 48 provided thereon. Since the connector 42 is held in a fixed position within the connector 50, the vibration of the connector 42 is more effectively prevented, thereby further enhancing its effectiveness.

It should be noted that the present invention is by no means to be construed as being limited to these specific examples, and each configuration has various aspects that can achieve similar objectives and effects.

For example, a protrusion for vibration prevention, which is advantageously employed in the present invention, is provided on a connector 42 that connects each lead wire 34a to 34c with an internal component, in other words, a lead member (44, 46, 46). 5 and 6, or 7.
Structures such as those shown in FIG. 8 and FIG. 8 can be adopted.

Incidentally, in the examples shown in FIGS. 5 and 6, the connector 52 is connected to the lead wire 3.
4a, 34b, 34c, a portion 52a for fixing the outer sheath by caulking, a portion 52b for fixing the core wire portion by caulking, and a portion 52c for fixing the leads 44, 46 by caulking, and two engaging protrusions at the ends thereof. 54, 54 are provided, and the engaging protrusion 54 is bent as shown by the two-dot chain line in FIG. 6 to engage with the inner surface of the insulator 20, thereby preventing its vibration. (See Figure 4).

Further, the other examples shown in FIGS. 7 and 8 differ from the previous example in that the protrusion is separate from the connector. That is, there, the protrusion is formed by the protrusion forming member 5.
The cylindrical portion 60 is formed with a notched skirt portion 60 that is integrally provided with the cylindrical portion 58 of No. At 60, the connector 62 is locked to the inner surface of the connector receiving hole 50 of the insulator 20, thereby preventing vibration of the connector 62.

Furthermore, in the present invention, each lead wire 34a
If 34c to 34c is applied to a structure that is directly connected to internal parts of the sensor in the form of a connector, the contact reliability will be extremely favorable. Such a fitting connection structure using a connector type can be suitably employed in an oxygen sensor that generally uses a flat solid electrolyte.
At the rear end of such a flat solid electrolyte, an electrode provided on the solid electrolyte, or a printed or laminated heater provided on the solid electrolyte is directly connected to each lead wire. It will be done.

In addition, various changes, modifications, improvements, etc. may be made to the present invention based on the knowledge of those skilled in the art, although they will not be listed one by one, as long as they do not depart from the spirit of the present invention. It goes without saying that the invention also includes such embodiments.

As described in detail above, the present invention allows the lead wire to be inserted into the sensor by passing through the rubber plug attached to the cylindrical cap constituting the rear outer shell of the oxygen sensor, by caulking the cap. It is firmly fixed with a rubber stopper, and the connector is fixed inside the insulator with a protrusion, so that even if the lead wire is vibrated for some reason, the vibration will not be transmitted to the inside of the sensor. It has achieved excellent effects such as blocking vibrations to prevent vibrations from occurring, effectively preventing fatigue failure of parts inside the sensor, and thereby increasing the reliability of the sensor. This invention has extremely significant industrial significance.

[Brief explanation of drawings]

FIG. 1 is a partial cross-sectional view showing an embodiment of an oxygen sensor according to the present invention, FIG. 2 is an enlarged cross-sectional view of a main part of the rear part of such an oxygen sensor where a rubber plug is disposed, and FIG. 4 are a front view and a rear view of the connected state of the lead wire and the lead, respectively, for explaining the structure of the connector in the embodiment of FIG. 1, and FIGS. FIGS. 7 and 8 are perspective views showing other structures of connectors used in the present invention and explanatory diagrams showing connection forms between lead wires and leads, and FIGS. 7 and 8 respectively show other structures of connectors that can be used in the present invention. Fig. 7 is a perspective view of the protrusion forming member, and Fig. 8 shows a state in which such a protrusion forming member is attached to a connector and placed in an insulator. FIG. 2...Solid electrolyte, 4...Housing, 16...
... Heater, 18, 20 ... Insulator, 24 ... Center electrode, 26 ... Cap, 30 ... Small diameter part, 3
2... Rubber plug, 34a, 34b, 34c... Lead wire, 36... Caulking part, 42... Connector, 44
...Signal lead, 46...Heater lead, 48...
... Projection piece, 50 ... Connector accommodation hole.

Claims (1)

[Claims for Utility Model Registration] (1) A cylindrical cap that forms the outer shell of an oxygen sensor that has a solid electrolyte provided with a predetermined electrode and a heater for heating the fixed electrolyte. A rubber plug is attached to the rear end opening of the cap, and a lead wire for extracting an electromotive force signal of the solid electrolyte and a lead wire for passing current to the heater are inserted through the rubber plug. Each is inserted from the outside, and electrically connected to the solid electrolyte and the heater side through a connector inside the insulator inside the cap, and a protrusion is provided on the connector, and the protrusion connects the An oxygen sensor characterized in that the connector is fixed within the insulator and the cap is caulked from the outside to pressurize the rubber stopper in its radial direction, thereby fixing the lead wire. (2) The oxygen sensor according to claim 1, wherein the connector is directly connected to an electrode provided on the solid electrolyte or to the heater. (3) Utility model registration claim 1 or 2, characterized in that the connector is connected to the electrode of the solid electrolyte or the heater via a predetermined lead member. Oxygen sensor as described.