JPH0531276B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a spark plug for an internal combustion engine, which is provided with an insulator made of ceramic and which penetrates into a combustion chamber, the insulator being fixed on the outside. surrounded immovably and gas-tightly by a metal casing comprising a member and having a ground electrode on the ignition side, said insulator having a connecting pin on the connecting side in its axially extending longitudinal hole; On the ignition side, an oxygen sensor is provided on the insulator leg that has a center electrode electrically connected to the connecting pin and is exposed to the combustion chamber, and the output of the oxygen sensor is An electrical connection is provided on the outer surface of the insulator at a position protruding from the metal casing via two conductor tracks arranged side by side and spaced apart from each other in the axial direction on the outer surface of the insulator. It relates to a type of connection member that has been derived as a standard connection member.

BACKGROUND OF THE INVENTION According to DE 30 28 359 A1, a spark plug is already known in which an oxygen sensor is arranged in the insulator foot. In this known spark plug, the oxygen sensor is arranged in a blind hole on the outside of the insulator foot in such a way that the parts (electrodes, solid electrolyte, etc.) are located one above the other in this blind hole. The conductive material forming the electrical connection to the electrodes of the oxygen sensor is applied as a platinum suspension guided through long through holes produced in a rubber pressing process; Placing the sensor in the insulator foot of the spark plug is expensive and involves high manufacturing risks.

Oxygen sensors for use in spark plugs are particularly suitable for use with potentiometer-operated sensors, which have a multilayer solid electrolyte that conducts oxygen ions, and whose electrical resistance changes depending on the gas composition. Oxygen sensors are also particularly suitable. Oxygen sensors of this type are described, for example, in German Patent Application No. 2855012;
2909201, 2617031, 2826515, Federal Republic of Germany Patent Application Publication No. 2651160, Federal Republic of Germany Patent No. 1954663 and United States Patent No. 3719564,
It is known from the specification No. 4007435. Also,
Oxygen sensors with solid electrolytes conducting oxygen ions electrically connected in series are also already known (US Pat. No. 3,216,911).

[Problem of the Invention] An object of the present invention is to improve the spark plug of the type mentioned at the beginning so that it is easy to manufacture and has low manufacturing costs.
Moreover, the aim is to provide something that operates reliably.

[Means for Solving the Problem] According to the present invention, which solves this problem, the oxygen sensor is directly provided over the entire circumference of the outer peripheral surface of the insulator foot, which is not provided with a recess. It consists of a pair of electrodes arranged side by side on the outer circumferential surface at a distance from each other, and a porous solid electrolyte layer that covers the pair of electrodes and conducts oxygen ions and allows gas to pass through. , the outer surface area of the insulator, on which the conductor track is arranged, is covered with a band-shaped insulating layer, excluding the electrical connection element.

[Effects] The spark plug according to the present invention has the advantages of being easy to manufacture, having a low manufacturing cost, and operating reliably.

Advantageous embodiments and improvements of the spark plug according to the invention are possible with the aid of the dependent claims. An oxygen sensor is used with a solid electrolyte that conducts oxygen ions and allows gas to pass through. It is particularly advantageous if it is covered.

[Example] Next, the configuration of the present invention will be specifically described with respect to an example shown in the drawings.

The spark plug 10 shown in FIGS. 1 to 3 has a metal casing 11. The spark plug 10 shown in FIGS. This metal casing 11 has a mounting screw as a fastening element 12 on the outside and is used together with a hexagonal part 13 for mounting on a cylinder head (not shown) of an internal combustion engine. The metal casing 11 has an inner hole 14 which surrounds most of the generally annular insulator 15. This metal casing 11 has a hook-shaped ground electrode 17 on its end face 16 on the ignition side. A sealing ring for mounting a spark plug in a cylinder head (not shown) of an internal combustion engine is not shown.

The insulator 15, which consists essentially of aluminum oxide in a known manner, has shoulders 18, 19 on the outside, on which sealing rings 20 are fitted.
a and 20b are mounted. This seal ring 20
The insulator 15 is embedded in the metal casing 11 with the insulators a and 20b interposed therebetween by a well-known heat caulking process. This heating caulking process is for the purpose of making the seal between the insulator 15 and the metal casing 11 more reliable, as can be seen from the formation of a spherical contraction area 21 in the metal casing 11. be.

A connecting pin (not shown) and a central electrode 22 projecting from the termination section of the insulator 15 on the ignition side are provided in a vertical hole (not shown) in the insulator 15 . The connecting pin and the center electrode 22 are electrically connected to each other within the vertical hole of the insulator 15 by a conductive packing material (not shown). The end section of the center electrode 22 on the ignition side is kept at a distance (for example 0.8 mm) from the ground electrode 17.
The section of the connecting pin (not shown), which projects from the insulator 15 on the connection side, is provided with a connecting nut 23 . The section of the insulator 15 that protrudes from the metal casing 11 to the connection side is
It has a plurality of coaxially arranged annular grooves 24 as current leakage barriers between the connecting nut 23 and the connecting nut 23.

An oxygen sensor 2 is located in the area of the insulator 15 exposed to the combustion chamber of the internal combustion engine, that is, insulator foot 15'.
5 is attached, this oxygen sensor 24 consists of several layers and advantageously includes an insulator 15
and the metal casing 11 in the region of the insulator foot 15', which is located close to the sealing region between the metal casing 11 and the metal casing 11. The oxygen sensor 25 is connected to the insulator foot 15' on the opposite side of the insulator 15 from the vertical hole (not shown).
attached in a ring shape to the surface of the Instead of using an annular oxygen sensor 25, the insulator foot 1
It is also possible to use an oxygen sensor provided over only a portion of the outer circumference of 5'. The connection between the oxygen sensor 25 and the section projecting from the metal casing 11 toward the connection side takes place via conductor tracks 26, 27. The connecting ends of these conductor tracks 26, 27 are designed as connecting media 28, 29 in the form of metal layers. In order to provide electrical insulation between the conductor tracks 26, 27 and the metal casing 11, the conductor tracks 26, 27 are provided with an insulating layer 30. Electrical connection to the connecting nut 23 and electrical connection members 28, 29 for the oxygen sensor 25
A fixing groove 31 is formed on the outside of the metal casing 11 in order to insert in the correct position a connection plug (not shown) used to make an electrical connection to the metal casing 11. A corresponding protrusion (not shown) of a connection plug (not shown) is fitted therein.

In particular, as seen in FIGS. 2 and 3, the oxygen sensor 25 has a solid electrolyte layer 32 that conducts oxygen ions.
It operates according to the well-known principle of an oxygen concentration cell with a Such a solid electrolyte, for example consisting of a shape-stable zircon dioxide, is applied as a 100 μm thick layer to the insulator foot 15' in a known manner, for example by a printing process, and kept spaced apart from each other. It covers electrodes 33 and 34 arranged in the same manner. The electrodes 33 and 34 are also attached to the insulator foot 15' in a known manner, preferably by a printing process. In a preferred embodiment, the electrodes 33, 34 have interlocking comb teeth 3.
3' and 34'. two electrodes 33, 34
is connected to the gas to be measured via a gas-permeable solid electrolyte layer 32, so that one of the electrodes 33 or 34 is made of a material that does not or only slightly generates a catalytic reaction, while the other electrode Made of lively material. Platinum, for example, is suitable as a material that is active in catalytic reactions, and gold, for example, is suitable as a material that does not cause catalytic reactions. The platinum or gold electrodes 33, 34 have ceramic bearing frames (not shown). The bearing frame is made of aluminum oxide, for example. Electrodes 33, 34 with a thickness of about 10 μm
The width of the electrode chamber 35 is advantageously in the range between 100 μm and 500 μm, with the electrode intermediate chamber 35 having a width of at least 100 μm and 1.5 mm.
in the range between. For reasons of manufacturing technology, the conductive elements 26, 27 connected to the electrodes 33, 34 are preferably made of the same material as the electrodes 33, 34, but of other materials that can withstand the operating loads. You can leave it there. The metal layer, preferably made of platinum, which is used as the electrical connection element 28, 29 in the terminal section on the connection side of the conductor tracks 26, 27 has a thickness of 0.1 mm and a width of 1.5 mm, and has a thickness of 0.1 mm and a width of 1.5 mm. not covered by Solid electrolyte layer 3
The insulating layer 30, slightly covered by 2, is made of aluminum oxide and has a maximum thickness of 200 μm. The thickness of the insulating layer 30 is advantageously
Between 30 μm and 100 μm, two conductor tracks 2
6 and 27, and is manufactured by a known method such as a printing process. Instead of forming the insulating layer 30 in the form of a strip, it may also be formed as a layer covering the entire circumference of this area in a known manner (for example by a winding or spraying process). Such an insulating layer 30 surrounding the insulator is particularly suitable if a number of oxygen sensors 25 with conductor tracks 26, 27 are mounted on the spark plug 10.

The illustrated embodiment of the spark plug 10 with the oxygen sensor 25 is a preferred embodiment, but variations of this are of course possible. Electrode 33,3
4 does not necessarily have to include the comb tooth-like protrusions 33', 34'. It is also possible to arrange a number of potentiometrically operated oxygen sensors 25 in series on the insulator foot 15' in order to obtain a strong measuring signal (see US Pat. No. 3,216,911). Instead of making the insulating layer 30 from aluminum oxide, it can also be made from enamel (lead borosilicate glass). The electrical connections 28, 29, which are designed as metal layers, can likewise be adapted to the intended use. That is, it can also be configured as a soldered flat plug. The oxygen sensor 25 does not necessarily have to operate on a potentiometric measuring principle, but may also operate on a polarographic measuring principle. In this polarographic measuring principle, the electrodes are connected to the same voltage and are fitted with a dispersion barrier for oxygen molecules in a known manner. In this oxygen sensor embodiment, a gas-permeable solid electrolyte layer 32 can be provided as a dispersion barrier. The layers of the oxygen sensor 25, the conductor tracks 26, 27 and the insulation layer 30 are fixed to the insulation 15 of the spark plug 10 by sintering.

Since the oxygen sensor 25 attached to the spark plug 10 according to the present invention has a simple shape, it can be manufactured economically using manufacturing equipment suitable for mass production, and can be installed in the combustion chamber of an internal combustion engine. It can be used both to measure combustion conditions and to control the combustion process.

[Brief explanation of the drawing]

1 is an enlarged and partially sectional view of a spark plug with an oxygen sensor according to the invention; FIG. 2 is a further enlarged and developed plan view of a part of the oxygen sensor according to FIG. 1; The figure is a sectional view along the - line of the oxygen sensor according to FIG. 2. 10...Spark plug, 11...Metal casing, 12...Fixing member, 13...Hex corner, 14...
...Inner hole, 15...Insulator, 15'...Insulator foot,
16... End face, 17... Ground electrode, 18, 19...
...Shoulder, 20a, 20b...Seal ring,
21... Contraction area range, 22... Center electrode, 23...
... Connection nut, 24 ... Annular groove, 25 ... Oxygen sensor, 26, 27 ... Conductor path, 28, 29 ... Connection member, 30 ... Insulating layer, 31 ... Fixing groove, 3
2... Solid electrolyte layer, 33, 34... Electrode, 3
3', 34'... comb tooth-shaped protrusions, 35... electrode intermediate chamber.

Claims (1)

[Scope of Claims] 1. A spark plug for an internal combustion engine, which is provided with an insulator 15 made of ceramic and protrudes into a combustion chamber, the insulator 15 having a fixing member on the outside and a ground electrode on the ignition side. 17, said insulator 15 has a connecting pin in its axially extending longitudinal bore on the connecting side, and on the ignition side,
Center electrode 22 electrically connected to this connection pin
and an oxygen sensor 25 is provided on the insulator foot 15' exposed to the combustion chamber, the output of the oxygen sensor being spaced axially from one another on the outer surface of the insulator 15. Electrical connection members 28 and 29 provided on the outer surface of the insulator 15 at positions protruding from the metal casing 11 are connected via two conductor paths 26 and 27 arranged side by side with each other. In the derived type, the oxygen sensor 25 is connected to the insulator foot 1
A pair of electrodes 33 and 34 are provided directly over the entire circumference of the outer circumferential surface without a recess on the outer surface of the electrode 5', and are arranged side by side on the outer circumferential surface at a distance from each other; The outer surface area of the insulator 15, in which the conductor paths 26 and 27 are arranged, is composed of a porous solid electrolyte layer 32 that covers the pair of electrodes and conducts oxygen ions and allows gas to pass through.
A spark plug equipped with an oxygen sensor, characterized in that the electrical connection members 28 and 29 are covered with a band-shaped insulating layer 30. 2 The oxygen sensor 25 is connected to the ignition side seal ring 20 between the insulator 15 and the metal casing 11.
2. The spark plug as claimed in claim 1, wherein the spark plug is arranged in the region of the insulator foot 15' located near the insulator foot 15'.