JPH0244205Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to an oxygen concentration detector for detecting the oxygen concentration in exhaust gas discharged from an internal combustion engine.
In particular, the present invention relates to an improvement in an oxygen concentration detector in which a heater is placed inside a bottomed cylindrical solid electrolyte cylinder.

Conventionally, oxygen concentration batteries using oxygen ion conductive solid electrolytes such as zirconia have been used to detect the oxygen concentration in exhaust gas emitted from internal combustion engines such as automobiles and to control the air-fuel ratio of internal combustion engines. There is. This type of oxygen concentration detector has a bottomed cylindrical zirconia solid electrolyte with porous platinum electrodes attached to the inner and outer surfaces, and the electrode on the inner surface of the cylinder is connected to the atmosphere to serve as a standard oxygen partial pressure electrode. The electrode on the outside of the body is exposed to exhaust gas, which is the gas to be measured, and serves as a measurement electrode. The oxygen concentration in the gas to be measured is measured by measuring the electromotive force based on the difference in oxygen concentration between the reference electrode and the measurement electrode. however,
This electromotive force is unstable unless the solid electrolyte is heated to a certain degree, and the drawback is that the air-fuel ratio cannot be accurately controlled during idling or immediately after engine startup, when the exhaust gas from the internal combustion engine is at a low temperature.

To solve this problem, we inserted a heater with a heating wire wrapped around the insulator surface into the cylinder (Japanese Patent Application Laid-Open No. 13396/1982), and used a resistance wire coil and insulating powder with good thermal conductivity. A heater filled in a metal sleeve is inserted into the cylinder (Japanese Patent Application Laid-open No. 54-22894).
It has been proposed to forcibly heat the solid electrolyte.

However, this type of conventional oxygen concentration detector with heater has the disadvantage that it has a large number of parts and its structure is complicated.

The present invention eliminates the drawbacks of such an oxygen concentration detector with a heater, has a small number of parts, is easy to assemble, has a simple structure, and can withstand long-term use. In an oxygen concentration detector with a heater that detects the oxygen concentration in exhaust gas of an internal combustion engine by inserting a heater made of a rod-shaped ceramic heater into a cylinder of a bottom cylindrical solid electrolyte, a heat generating part and an electrode part of the heater are provided. A flange is provided on the outer periphery between the solid electrolyte and a cylindrical center electrode is arranged at the open end of the bottomed cylindrical solid electrolyte, and the heater is connected to the cylindrical center electrode with the flange of the heater on the upper end side of the cylindrical center electrode. The cylindrical center electrode is inserted into the cylinder of the cylindrical center electrode and the bottomed cylindrical solid electrolyte. An insulator having a through hole into which an electrode lead is inserted is placed, a spring is provided on the insulator, and the spring force of the spring connects the cylindrical center electrode to the flange of the heater, and the cylindrical center electrode to the flange of the heater. This is an oxygen concentration detector that is brought into pressure contact with an inner electrode of a bottomed cylindrical solid electrolyte and supports the heater, and is preferably an oxygen concentration detector with a heater that uses a ceramic heater as the heater.

The details of the present invention will be explained based on FIG. A bottomed cylindrical solid electrolyte 1 with porous platinum electrodes provided on the inner and outer surfaces is housed in a metal housing 2,
The outer electrode of the solid electrolyte 1 is electrically connected to the housing 2 through a metal packing 3. A cylindrical center electrode 4 is placed on the open end side of the solid electrolyte 1 in contact with the inner electrode of the solid electrolyte 1, and a metal flange 5 is provided on the top of the cylindrical center electrode 4. A metal flange 7 is brazed to the outer periphery of the ceramic heater 6 as a heater at a position corresponding to the flange 5. The ceramic heater 6 is inserted into the cylinder of the cylindrical center electrode 4 and the solid electrolyte 1 with its flange 7 in contact with the flange 5 of the cylindrical center electrode 4 . On the upper part of the flange 7 of the ceramic heater 6, electrode leads 9 and solid electrolyte 1 of the ceramic heater 6, which will be described later, are provided.
An insulator 8 that accommodates the electrode leads 11 and the like is arranged. The insulator 8 has a total of three through holes, one through which the electrode leads 9 and 10 of the ceramic heater 6 are inserted, and the other through which the electrode lead 11 spot-welded to the flange 7 having the same potential as the inner electrode of the solid electrolyte 1 is inserted. FIG. 1 shows a cross section of the through hole through which the electrode lead 11 is inserted.
Connecting electrodes 13 each having a flange at the bottom are inserted into the insides of the electrodes 2 . Then, the electrode leads 9, 10, 11 and the lead wires 14, 15, 16 are caulked and connected by these connecting electrodes, and the lead wires 14, 15, 16 are guided out of the case 18 through the rubber plug 17. has been done. The case 18 is fixed to the housing 2 by a caulking fixing part 21 and houses the insulator 8. A spring 19 and a rubber plug 17 are installed between the case 18 and the insulator 8.
A washer 20 is arranged to fix the case 18, and the spring 19 is compressed under pressure.
is fixed to the housing 1 by a caulking fixing part 21.

Therefore, due to the spring force of the spring 19, the cylindrical center electrode 4 and the inner electrode of the solid electrolyte 1 are brought into contact with each other such that the reliability of electrical contact is high. Further, the flange 7 of the ceramic heater 6 is held between the insulator 8 and the cylindrical center electrode 4 by spring force, so that the ceramic heater 6 is firmly supported.

An embodiment of the ceramic heater used in the present invention will be explained with reference to FIG. 2. A heat generating part 22 and an electrode lead-out part 23 are formed in a ceramic rod-like body, in which a resistance pattern is formed from a resistance material such as tungsten or molybdenum. . Electrode lead-out section 23
is led to the outside of the heater at the upper part of the ceramic heater, and electrode leads 24 and 25 are brazed thereto. Further, the ceramic heater may be one in which a heating wire 26 is embedded in a rod-shaped sintered ceramic 27, as shown in FIG.

In addition to metallizing the outer periphery and brazing the flange, methods for attaching a flange to the outer periphery of such a ceramic heater include providing a taper on the outer periphery of the ceramic heater and supporting it with a flange, or attaching a flange to the outer periphery of the ceramic heater. It is also possible to use a material with a lower coefficient of thermal expansion than the ceramic material.

Note that the heater is not limited to the ceramic heater shown in FIGS. 2 and 3, and as shown in FIG. A sheath heater may be used in which the space between the wires 26 is filled with powder 29 having good thermal conductivity such as magnesia. In this case, the flange is attached by brazing, welding, or the like. As shown in FIGS. 2 to 4, the heating section of the heater is preferably provided only at the tip of the heater, since the solid electrolyte 1 can be heated efficiently.

In addition, it is preferable to provide a notch 30 at the contact portion of the cylindrical center electrode 4 with the solid electrolyte 1 as shown in FIG. This can be prevented. The shape of the contact portion of the cylindrical center electrode 4 with the inner electrode of the solid electrolyte 1 is not limited to that shown in FIG. 1 or FIG. 5. For example, as shown in FIG. It may be provided with a flange that comes into contact with the flange, or a notch may be provided in this flange. In this case, the inner electrode of the solid electrolyte 1 extends to the upper end surface of the solid electrolyte 1.

As shown in FIG. 7, the cylindrical center electrode 4 is provided with a support part at its lower end that supports the side surface of the heater, so that the heater is not shaken when external vibrations, shocks, etc. are applied to the oxygen concentration detector. It is preferable to reduce the movement.
In this case, the shape of the support part may be such that the lower end 31 of the cylindrical center electrode as shown in FIG. Although a slight gap may be provided between the side surfaces of the heater, it is preferable to form a cylindrical support along the outer surface of the heater as shown in FIG. And the cylindrical support part has an eighth
It is preferable to provide a notch 30 as shown in the figure. The cylindrical center electrode 4 and the flange 7 may be integrally formed from a metal member by machining such as drawing or cutting. This case is advantageous in assembling the oxygen concentration detector.

As explained above, the oxygen concentration detector with heater of the present invention has a structure in which the flange 7 brazed to the ceramic heater 6 is held between the cylindrical center electrode 4 and the insulator 8 by the spring force of the spring 19. Therefore, supporting the ceramic heater 6 is extremely simple, and assembly is also easy. Furthermore, since the outer diameter of the flange 7 can be made sufficiently larger than the outer diameter of the ceramic heater 6, the perpendicularity of the flange 7 to the ceramic heater 6 can be easily achieved, and the tip of the ceramic heater 6 can come into contact with the inner surface of the solid electrolyte 1. There is little chance of damage to the electrode surface.

Also, to explain the temperature increase in the spring 19 due to the insertion of the ceramic heater 6, heat conduction of the ceramic heater to the spring 19 is caused by the thin flange 7 and the flange 7, which have a large thermal resistance.
Since the ceramic heater 6 passes through the contact surface of the insulator 8, the temperature of the spring 19 does not increase much even if the ceramic heater 6 is inserted, and therefore the thermal durability of the spring 19 is lower than when the ceramic heater 6 is not inserted. Almost no decline.

As described in detail above, the oxygen concentration detector with a heater of the present invention has a flange on the heater, and the flange of the heater is placed on the cylindrical center electrode that contacts the solid electrolyte. A simple structure in which the center electrode and the solid electrolyte are inserted into a cylinder, and an insulator and a spring are placed in sequence on the top of the heater flange to ensure sufficient conduction between the electrodes by the spring force of the spring and support the heater. Moreover, it is easy to assemble and has excellent electrical conductivity and thermal durability of the spring part.It can be used to detect the oxygen concentration in the exhaust gas of various internal combustion engines, and is extremely useful from an industrial and pollution prevention perspective. Useful.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a specific example of the oxygen concentration detector of the present invention, and FIGS. 2, 3, and 4 are sectional views showing specific examples of the heater used in the oxygen concentration detector of the present invention. , FIG. 5, FIG. 6, FIG. 7, and FIG. 8 are perspective views of cylindrical electrodes according to embodiments of the present invention, respectively. 1...Solid electrolyte, 2...Housing, 3...
Metal packing, 4... cylindrical center electrode, 5... flange of cylindrical center electrode, 6... ceramic heater, 7... flange of ceramic heater, 8...
Insulator, 9, 10, 11...electrode lead, 12
...Through hole, 13... Connection electrode, 14, 15, 1
6...Lead wire, 17...Rubber plug, 18...Cap, 19...Spring, 20...Washer, 21...Clinching fixing part, 22...Heating part, 23
... Electrode lead-out part, 24 ... Electrode lead, 25 ...
Electrode lead, 26... Heat generating wire, 27... Sintered ceramic, 28... Metal sheath, 29... Good thermal conductive powder, 30... Notch, 31... Lower end of cylindrical center electrode.

Claims (1)

[Claims for Utility Model Registration] 1. A heater that detects the oxygen concentration in exhaust gas from an internal combustion engine by inserting a heater made of a rod-shaped ceramic heater into a bottomed cylindrical solid electrolyte cylinder having electrodes on its inner and outer surfaces. In the oxygen concentration detector, a flange is provided on the outer periphery between the heat generating part and the electrode part of the heater, and a cylindrical center electrode is arranged at the open end of the bottomed cylindrical solid electrolyte. The heater is inserted into the cylindrical body of the cylindrical center electrode and the bottomed cylindrical solid electrolyte with the flange on the upper end side of the cylindrical center electrode, and the heating is performed on the upper surface of the flange of the heater. An insulator having a through hole through which the electrode lead of the heater and the electrode lead from the flange are inserted is placed on the top of the container, and a spring is provided on the insulator, and the spring force of the spring causes the cylindrical shape to be Pressing the center electrode and the flange of the heater and the cylindrical center electrode and the inner electrode of the bottomed cylindrical solid electrolyte into contact with each other,
An oxygen concentration detector with a heater, characterized in that the heater is supported. 2. The oxygen concentration detector with a heater according to claim 1, wherein the flange of the heater and the cylindrical center electrode are integrally formed. 3. The oxygen concentration detector with a heater according to any one of claims 1 to 2 of the utility model registration claim, wherein the cylindrical center electrode is provided with a notch in the portion that contacts the bottomed cylindrical solid electrolyte. 4. The oxygen concentration detector with a heater according to any one of claims 1 to 3, wherein the cylindrical center electrode is in contact with the side surface of the heater.