WO2013141681A1

WO2013141681A1 - Ignition spark plug

Info

Publication number: WO2013141681A1
Application number: PCT/LT2013/000007
Authority: WO
Inventors: Mikhael CHVARTSMAN
Original assignee: KLIMAITIENĖ, Otilija
Priority date: 2012-03-22
Filing date: 2013-03-22
Publication date: 2013-09-26
Also published as: LT5904B; LT2012023A

Abstract

The invention relates to ignition spark plugs used in car engines, more particularly to spark plugs of improved construction for use in internal combustion engines, where the discharge spark between the central electrode and the surrounding annular ground electrode (2) is formed essentially horizontally. Positive technical effect is attained by improved lower part of a spark plug wherein the improvement comprises forming the ground electrode (2) as an element encircling and enclosing the central electrode, where the ground electrode (2) is having end rims (4) inwardly extending to the central electrode and formed parallel to the side surface of said central electrode and forming at least one bore (5) and/or slit in the side of the ground electrode (2) at an angle to the back surface of said ground electrode (2).

Description

Ignition spark plug

Field of the invention

The invention relates to ignition spark plugs used in car engines, more particularly to spark plugs of improved construction for use in internal combustion engines, were the discharge spark between the central electrode and the surrounding annular ground electrode forms essentially horizontally.

Description of the Related Art

Spark plug of today's petrol internal combustion engines generally comprises a metal shell, an insulator, a central electrode and a ground electrode. Metal shell generally has a threaded part with an external thread for screwing the spark plug into the engine. The insulator has a longitudinal bore along its central axis and is immovably fixed in the metal shell in such a manner, that its distal end is extruding from the threaded part of the metal shell. The central electrode is fixed in the hollow part of the insulator so, that its end extrudes from the insulator's shell.

At certain values of the voltage between the central electrode and ground electrode a spark is generated which ignites the mixture of petrol and gas in a combustion cylinders of an internal combustion engine. Commonly a ground electrode is formed as a hook of a conductive metal facing the central electrode.

Each spark erodes the ground electrode at a place of interaction. Subsequently the electrical resistivity of an eroded zone increases compared to the zone that didn't have contact with a spark, thus a new spark will be directed to the zone of lowest electrical resistivity. After a certain period of time the electrode erodes to the extent that the spark plug becomes unusable. The central electrode also wears and becomes shorter with time also rendering the spark plug less efficient.

At the instance of burning of mixture of fuel and gas the part of the spark plug which is inside the engine's combustion cylinder is subjected to high temperatures. This increases the wear rate of the ground electrode weakening its mechanical properties which can lead to burning off of the electrode and falling into the combustion cylinder, causing possible damage to the engine.

In the petrol internal combustion engine the mixture of fuel and gas has to be ignited to initiate an explosion to move the pistons which subsequently move a crankshaft. The spark for ignition of said mixture is generated by a spark plug. When the engine is running a high voltage pulses are sent to the lover part of a spark plug, thus generating a spark between tips of two electrodes. Each combustion cylinder of an engine receives the pulses subsequently, ensuring a smooth work and maximum power of an engine.

As the compression rate of a fuel and gas mixture in an internal combustion engines increases in order to produce more power and consume less fuel, the required voltage for the spark to be generated in the spark plug increases. It becomes more difficult for an effective vertical spark to form between conventional hook-like shape ground electrode and central electrode of a spark plug due to increase in the ignition voltage which can result in a side spark. Said side spark creeps between the outer surface of an insulating layer of the central electrode and the inside surface of a threaded part of the metal shell of a spark plug. This results in weaker spark unable to properly ignite a mixture of fuel and gas. Prolonged usage of a spark plug also results in forming of a layer of deposits on functional surface areas of electrodes, weakening the generated spark. As the rims of the ground electrode and central electrode wears off, distance between tips of said electrodes increases, increasing the required voltage to compensate for the increased gap, decreasing the performance of a spark plug.

For the reasons stated above the generated spark is too week to effectively ignite the mixture of fuel and gas, resulting in weak and non-sequential explosions in combustion cylinders and decrease of engine power.

In an application of a patent EP 2 139 082 a modification of a common spark plug is disclosed. The modification allows increasing the functional surface area of the ground electrode so the life time of a spark plug would be increased. This is achieved by providing a ring-shaped ground electrode. The ring-shaped ground electrode is fixed to the metal shell by one or two legs.

In patent WO 93/21674 a solution is disclosed to minimize the wear of a ground and central electrodes by increasing the functional surface area of a central electrode and forming the ground electrode as a cylindrical extension of the metal shell. Increasing functional surface for the spark to be generated at, increases the performance of a spark plug, decreases the delay of an ignition, increases the burning efficiency of a mixture of fuel and gas in a combustion chamber, increases the engine power, decreases fuel consumption and makes it possible for the engine to run at lower temperatures. In patent US 3 958 144 structural adjustments of a spark plug are disclosed which are close to the ones disclosed in our invention. The ground electrode is disclosed in several configurations being a cylindrical extension of a metal shell and provided with slits and/or side-holes. Herein problems of charring of electrodes, prolonging functional time of a spark plug, increasing power output of an engine are addressed.

In patent US 5 623 179 a disclosed improvement increases functional life time of a spark plug, decreases the heating of a plug, increases the output power of an engine, decreases fuel consumption and emission of exhaust gas. The inventive part of said spark plug is an external electrode of special, prolonged shape.

In patent US 5 892 319 a disclosed improvement is the encircling of the central electrode by a ground electrode. This increases the functional surface area for the spark to be generated at. Several instances of a configuration of electrodes are provided.

In patent US 6 583 539 a disclosed improvement is the encircling of the central electrode by a ground electrode and providing said ground electrode with side-holes. This increases the functional life time of a spark plug and by decreasing the wear of electrodes increases functional area of electrodes for the spark to appear at, increases output power of an engine and so on.

The closest prototype is application of a patent US 2009/0140623. A disclosed spark plug comprises common elements like central electrode, ceramic insulator, metal shell and ground electrode. The spark plug has a cylindrical ground electrode for minimizing the creeping discharge, a discharge that forms between a ground electrode and an insulation layer of a central electrode. Further, the upper rim of a ground electrode is extended horizontally inwards to the central electrode, resulting in a better defined spark gap and generating of more effective spark. Bores provided in the side of a cylindrical encircling ground electrode increases burning efficiency of mixture of fuel and gas.

Said improvements allow avoiding most of earlier mentioned problems because the hook-like shaped ground electrode is replaced by a cylindrical ground electrode and a central electrode is encircled by the ground electrode to provide maximum functional surface area between two electrodes for a strong horizontal ignition spark to be formed here between. Nevertheless some problems are left unaddressed. Short description of the invention

This invention is intended for improving the functional properties and efficient functional time of a spark plug for a petrol internal combustion engine. Disclosed invention solves earlier described problems. A spark plug having an improved construction consist of cylindrical insulating element with a bore along its central axis, a central electrode disposed in said bore, were the far end of a central electrode is projecting from the insulating element at the spark generation end, a metal shell having a threaded part and a bore along its central axis, wherein the said insulating element is disposed, and a ground electrode at one end connected to the said metal shell. The ground electrode having at least one side bore is shaped to encircle and enclose the central electrode. The upper part of the spark plug protruding at the outside of an engine and the middle part of a spark plug, which is screwed into an engine frame, have essentially a common spark plug construction. The novelty in the invention is its lower part, right after the middle part: the common hook-like shaped ground electrode is replaced by a cylindrical ground electrode, extending from the middle part and enclosing the central electrode. The surface of the upper rim of the inwards extending ground electrode is parallel to the side surface of the central electrode and at least one side bore of the ground electrode and/or slit is formed at an angle directed to the back surface of said electrode.

Further, bores and/or slits are made at an angle to the side part of an electrode, where the angle to the back surface of the ground electrode is between 20 and 30 degrees, preferably 24 degrees. The best effect is reached when three such bores and/or slits are provided therein.

Inner and outer surfaces of the spark plug are convex, giving the plug a sleek shape: the ground electrode has a cylindrical sleek shell shape, where the end rim of the shell extends inwards to the central axis of the plug in such a way, that it is parallel to the side surface of the central electrode were the said surface has two non-rounded edges.

Short description of the drawings

Fig. 1 View of the structure of the ground electrode

Fig. 2 More detailed view of the lower part of the ground electrode

Main elements of the spark plug are enumerated in the figures. Isolating element of a spark plug of general structure has a bore extending along its central axis (1). A central electrode is disposed therein. A ground electrode (2) having' the shape of a solid shell enclosing central electrode, at one end is joined to the metal shell (3) of the spark plug. Upper rims (4) of the ground electrode (2) are extending inwardly and being parallel to the side surface of the central electrode and the bores (5) at the sides of the ground electrode (2) are formed at an angle a with respect to the back surface of the said ground electrode (2).

Detailed description of the preferred embodiment

From the point of view of function our invention resembles a general spark plug, but with a different structure of the lower part.

The improved lower part of the spark plug enables it to overcome problems characteristic to the spark plugs having lower part of general structure. New type of the lower part of a spark plug allows reaching more efficient operation. The annular ground electrode (2) enclosing the distal protruding end of the central electrode has stronger construction compared to the hook-like shaped protruding ground electrode and has bores and/or slits (5) for cooling the plug. The bores and/or the slits (5) are formed at an angle to the side portion of an electrode (2) and the inclination angle of the holes to the back surface of an electrode (2) is from 20 to 30 degrees, preferably 24 degrees. Ground electrode preferably has 3 bores and/or slits (5) for the best performance.

The spark plug of described embodiment retains high performance for longer period of time compared to spark plug of a general construction and is 90% safer to use in an engine due to removed ground electrode having a hook-like shape.

Additionally, spark of a spark plug having general construction forms only at one spot. After certain period of operational time operational parts of two electrodes chars, is covered by sub products of combustion process which leads to decrease of the performance of a spark plug, in particular weakening of the generated spark. This may lead to difficult engine start or failure to start it. The improved construction of the lower part of a spark plug ensures that igniting spark will be generated at several zones between a central electrode and end rims (4) of the ground electrode (2), were the end rims are parallel to the side surface of the central electrode, protruding from the insulating element. This increases the efficiency of ignition of fuel and gas mixture. Said spark generation method increases voltage between two contacts, leading to self-cleaning of the spark plug electrodes. It also increases the power output of an engine consuming less fuel and extends functional lifetime of a spark plug by 70-80%. During tests two types of spark plugs were compared. One of the plugs was manufactured by BOSH and the second one was our improved spark plug. Both plugs were examined after engine run for 37 000 km at 3000 rpm. After the test run the voltage of a general spark plug was 21 ,7 kV and the voltage of improved spark plug was 25,3 kV at pressure of 8,4 g/kg.

Claims

1. A spark plug consisting of an insulating cylindrical element having a bore extending along the central axis of the insulator, a central electrode disposed in said bore having a distal end protruding from the insulating cylindrical element at the spark generation zone, a metal shell having a threaded part and a bore extending along its central axis wherein said insulating element is disposed and a ground electrode at one end joined to the metal shell and enclosing the central electrode with enclosure having at least one side hole, characterized in, that ground electrode (2) is formed as an element, encircling and enclosing the central electrode, where the upper rims (4) of the ground electrode (2) are extending inwardly and are parallel to the side surface of the central electrode and at least one bore and/or slit (5) at the sides of the ground electrode (2) is formed at an angle a with respect to the back surface of the said ground electrode (2).

2. A spark plug according to claim 1 , characterized in, that inner and outer surfaces of the ground electrode (2) are convex with respect to its central axis (1).

3. A spark plugs according to claim 1 or 2, characterized in, that the angle of the bore and/or slit (5) is from 20 to 30 degrees.

4. A spark plug according to claim 3, characterized in, that the angle of the bore and/or slit (5) is preferably 24 degrees.

5. A spark plug according to any preceding claim, characterized in, that the ground electrode (2) has at least two evenly formed bores and/or slits (5).

6. A spark plug according to any preceding claim, characterized in, that the ground electrode (2) has three evenly formed bores and/or slits (5).