JP2011113978A - Spark plug ground electrode having multilayer structure, and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a spark plug ground electrode having significantly extended usable life and operating period, a method of manufacturing the same, and a spark plug including the spark plug ground electrode. <P>SOLUTION: The spark plug ground electrode (1) having a multilayer structure includes: a base (2) formed of a ground electrode material; an alloy layer (3) comprising a first noble metal melted in one region of the base (2) and part of the ground electrode material; and a reinforcing layer (4) formed of a second noble metal pressed and welded in/to the alloy layer (3). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a spark plug ground electrode having a multilayer structure, a method of manufacturing the spark plug ground electrode, and a spark plug having at least one spark plug ground electrode.

  Background art is known of ground electrodes with noble metal reinforcement to reduce wear. The noble metal is in this case placed on the ground electrode and is fixed by resistance welding or laser welding, or melts together with the ground electrode material to form an alloy. This known spark plug ground electrode or known spark plug is suitable for traveling up to 100.000 km in the vehicle technology.

  An object of the present invention is to provide a spark plug ground electrode having a significantly extended service life or operation period, a method for manufacturing the spark plug ground electrode, and a spark plug including the spark plug ground electrode.

  In order to solve this problem, according to the configuration of the present invention, a spark plug ground electrode having a multilayer structure, which is composed of a base made of a ground electrode material, a first noble metal melted in a region of the base, and a ground An alloy layer made of a part of the electrode material and a reinforcing layer made of the second noble metal, pressed and welded into the alloy layer.

  The spark plug ground electrode according to the invention according to claim 1 or the method according to the invention according to claim 7 provides a spark plug, especially for use in stationary engines, whose wear strength is a special gas, for example Even operation with landfill gas enables a service life of 2000 hours or more. According to the present invention, a region provided with a noble metal that is wear resistant is enlarged. Furthermore, since the welded reinforcement is not directly connected to the ground electrode material, the thermal stress of this reinforcement is reduced. According to the present invention, since the alloy layer exists between the reinforcing layer and the base made of the ground electrode material, the thermal expansion coefficient of each contact layer of the spark plug ground electrode is thereby approximated. After a predetermined wear of the spark plug ground electrode according to the invention, an edge is formed in the wear area due to different wear caused by different noble metal content in different layers. This edge increases the electric field strength, thereby reducing the flashover voltage, which additionally reduces spark erosion. All these advantages are in accordance with the present invention, a base comprising a ground electrode material, an alloy layer comprising a first noble metal and a portion of the ground electrode material melted within a region of the base, Obtained by means of a multi-layer spark plug ground electrode having a reinforcing layer made of a second noble metal, pressed and welded.

  The dependent claims contain advantageous configurations of the invention.

  In an advantageous configuration, the reinforcing layer is exclusively in contact with the alloy layer. Accordingly, the second noble metal of the reinforcing layer is embedded in an alloy composed of the first noble metal and the ground electrode material. The reinforcing layer is incorporated in the base by the alloy layer and is therefore incorporated in the spark plug ground electrode. Thus, the thermal expansion coefficients of the different materials at the layer transition are approximately equal to each other, which ultimately reduces the thermal stress in the welded reinforcement layer.

  More advantageously, the alloy layer is surrounded by a base, and the surface on one side of the spark plug ground electrode is formed by the base, the alloy layer and the reinforcing layer. This one side of the spark plug ground electrode is advantageously located on the inside of the spark plug and facing the center electrode and is therefore described as the working surface. Since the work surface has all three layers of different materials, the thickness of the wear is different, so that at the transition from the reinforcement layer to the alloy layer and at the transition from the alloy layer to the base Edges are generated. At this edge, the electric field strength is increased, which reduces the flashover voltage and consequently reduces the additional spark erosion.

  Advantageously, the reinforcing layer is arranged in the middle of the surface, and the alloy layer surrounds the reinforcing layer in an annular shape. The alloy layer and the reinforcing layer are preferably formed in a circular or elliptical shape when viewed in plan view of the working surface of the spark plug ground electrode. In this case, the alloy layer is preferably somewhat longer and / or wider than the reinforcing layer. Thereby, the reinforcing layer is completely surrounded by the alloy layer.

  More preferably, the first noble metal is not the same as or the same as the second noble metal, and the first and / or second noble metal is platinum and / or iridium and / or rhodium and / or ruthenium and / or It contains rhenium and / or palladium. That is, the first noble metal and / or the second noble metal may itself consist of an alloy, and platinum or iridium is preferably used as the base for the alloy. A preferred ground electrode material is a nickel alloy.

  The present invention further provides a spark plug having at least one of the above spark plug ground electrodes, the spark plug being specifically configured for use in a gas operated stationary engine. In a particularly advantageous use, the spark plug is used in stationary engines operated with special gases, in particular landfill gas. Advantageously, the spark plug according to the invention is used in an Otto engine, in particular for motor vehicles.

  The present invention further provides a method for manufacturing a spark plug ground electrode having a multi-layer structure, comprising the steps of: preparing a base made of a ground electrode material; A wire segment is pushed into the base and the first wire segment is melted, thereby forming an alloy layer composed of the first noble metal and a portion of the ground electrode material, and a second layer composed of the second noble metal. This is solved by a method of manufacturing a spark plug ground electrode, comprising the step of pressing a wire section into the alloy layer and welding a second wire section to the alloy layer to form a reinforcing layer. Accordingly, the first wire section is inserted into the base made of the ground electrode material. In this case, the first wire section is pushed into the ground electrode and is completely melted. An alloy zone is formed consisting of the first noble metal and a portion of the ground electrode material. A second wire section is then pushed into the alloy area or the alloy layer and welded.

  In an advantageous configuration of the method according to the invention, the first wire section is melted by a laser and / or the second wire section is welded by a laser.

  In an advantageous configuration, the first wire section is completely melted and / or the second wire section is melted for welding only at the contact surface with the alloy layer. The complete melting of the first wire section results in an alloy layer that is as large as possible, into which the second wire section can be pushed. The second wire section is advantageously melted only at the contact surface with the alloy layer and is therefore welded to this alloy layer. This leaves most of the second precious metal in the reinforcement layer, thus forming a wear resistant layer of the spark plug ground electrode.

  More advantageously, the second wire section is welded on the back side, and the energy required for welding is applied to the side of the spark plug ground electrode opposite the second wire section. Thus, the second wire section is pushed into the alloy layer on the working side of the spark plug ground electrode, where energy for welding is applied to the side of the spark plug ground electrode opposite to the working side. For this purpose, a controlled laser welding process is preferably used.

1 is a cross-sectional view illustrating a first embodiment of a spark plug ground electrode according to the present invention. It is the top view which showed 1st Example of the spark plug ground electrode by this invention. It is the figure which showed the welding of the back side of the reinforcement layer of the spark plug ground electrode of 1st Example by this invention. It is the figure which showed the state after abrasion of the spark plug ground electrode of 1st Example by this invention. It is the top view which showed 2nd Example of the spark plug ground electrode by this invention. It is the top view which showed 3rd Example of the spark plug ground electrode by this invention.

  The spark plug ground electrode 1 according to the first embodiment of the present invention will be described below with reference to FIGS.

  FIG. 1 shows an overall cross-sectional view of a spark plug ground electrode 1 having a base 2, an alloy layer 3, and a reinforcing layer 4. In a state where the spark plug ground electrode 1 is incorporated in the spark plug, the working side 5 of the spark plug ground electrode 1 is located facing the center electrode. The side opposite to the working side 5 of the spark plug ground electrode 1 is referred to as the back surface 6 or the opposite side.

  FIG. 1 shows a state in which the alloy layer 3 is embedded in the base 2. The reinforcing layer 4 is embedded in the alloy layer 3. Accordingly, the reinforcing layer 4 is in contact only with the alloy layer 3. Furthermore, the surface of the working side 5 is flat in the unworn state of FIG. 1, from the pure ground electrode material of the base 2, the first noble metal in the alloy layer 3 and a part of the ground electrode material. And a second noble metal in the reinforcing layer 4.

  FIG. 2 shows a plan view of the working side 5 of the spark plug ground electrode 1. According to this figure, it can be seen that the reinforcing layer 4 is formed as a circle having the first diameter D1 and is located at the center of the spark plug ground electrode 1. The reinforcing layer 4 is surrounded by a ring-shaped alloy layer 3 having a second diameter D2. The first diameter D1 of the reinforcing layer 4 is smaller than the second diameter D2 of the alloy layer 3. Further, the reinforcing layer 4 is located in the middle of the alloy layer 3 and is completely surrounded by the alloy layer 3. In this case, the alloy layer 3 and the reinforcing layer 4 are concentric with each other and have a common center point M arranged in the middle of the spark plug ground electrode 1.

  FIG. 3 shows manufacturing steps of the spark plug ground electrode 1. Prior to the manufacturing step shown in FIG. 3, the first wire section is pressed into the base 2 and completely melted, resulting in the alloy layer 3. Further, a second wire made of a second noble metal is pressed into the alloy layer 3. FIG. 3 shows the welding of the back side of the reinforcing layer 4 by the laser 8. The energy of the laser 8 is applied to the back surface 6 of the spark plug ground electrode 1, thereby producing a heat and energy input 7. By this heat / energy input 7, the reinforcing layer 4 is welded to the alloy layer 3 on the back side.

  FIG. 4 shows the spark plug ground electrode 1 after being worn to some extent. Due to the different materials of the base 2, the alloy layer 3 and the reinforcing layer 4, these layers have different thicknesses of wear. As a result, a first edge 9 is generated around the entire circumference of the alloy layer 3 at the transition from the alloy layer 3 to the base 2. The wear of the reinforcing layer 4 is somewhat insignificant, resulting in a second edge 10 around the reinforcing layer 4 at the transition from the reinforcing layer 4 to the alloy layer 3. In this embodiment, each circular edge 9, 10 is advantageously produced with the same edge height.

  FIG. 5 shows a second embodiment of the present invention. The same or functionally identical components are given the same reference numbers in all embodiments.

  FIG. 5 shows a plan view of the working side 5 of the spark plug ground electrode 1. According to this figure, it can be seen well that the reinforcing layer 4 is formed in a rectangular shape and is located in the center of the spark plug ground electrode 1. The reinforcing layer 4 is surrounded by an alloy layer 3 which is also formed in a rectangular shape. The reinforcing layer 4 is mounted in the middle of the alloy layer 3 and is therefore completely surrounded by the alloy layer 3.

  FIG. 6 shows a third embodiment of the present invention. The same or functionally identical components are given the same reference numbers in all embodiments.

  FIG. 6 shows a plan view of the working side 5 of the spark plug ground electrode 1. According to this figure, it can be seen well that the reinforcing layer 4 is formed in a rectangular shape and is located in the center of the spark plug ground electrode 1. The reinforcing layer 4 is surrounded by the alloy layer 3 on three sides. In this case, the short side surface of the reinforcing layer 4 is in direct contact with the base 2.

  According to this embodiment, it can be seen that the thermal stress in the reinforcing layer 4 can be reduced by changing the coefficient of thermal expansion only slightly at different layer boundaries. The configuration of the first edge 9 and the second edge 10 increases the electric field strength, thereby reducing the flashover voltage and consequently reducing the wear due to spark erosion. Therefore, the structure of the spark plug ground electrode 1 according to the present invention makes it possible to manufacture a spark plug having a significantly extended service life or operation period. The spark plug ground electrode 1 is particularly advantageously used in stationary engines, in particular gas engines for use for special gases.

  DESCRIPTION OF SYMBOLS 1 Spark plug ground electrode, 2 Base, 3 Alloy layer, 4 Reinforcement layer, 5 Working side, 6 Back surface, 7 Heat / energy input, 8 Laser, 9 First edge, 10 Second edge

Claims (10)

A spark plug ground electrode (1) having a multilayer structure,
A base (2) made of a ground electrode material;
An alloy layer (3) composed of a first noble metal and a portion of the ground electrode material melted in a region of the base (2);
A spark plug ground electrode comprising a reinforcing layer (4) made of a second noble metal, pressed into the alloy layer (3) and welded.   The spark plug ground electrode according to claim 1, wherein the reinforcing layer (4) is in contact only with the alloy layer (3).   The spark plug according to claim 1 or 2, wherein the surface of one side (5) of the spark plug ground electrode (1) is formed of a base (2), an alloy layer (3) and a reinforcing layer (4). Ground electrode.   The spark plug ground electrode according to claim 3, wherein a reinforcing layer (4) is arranged in the middle of the surface and the alloy layer (3) surrounds the reinforcing layer (4) in a ring shape.   The first noble metal is not the same as or the same as the second noble metal, and the first noble metal and / or the second noble metal is platinum and / or iridium and / or rhodium and / or ruthenium and / or rhenium and / or The spark plug ground electrode according to any one of claims 1 to 4, comprising palladium.   A spark plug comprising a spark plug ground electrode (1) according to any one of claims 1 to 5, wherein the spark plug is formed especially for use in a gas operated stationary engine. A spark plug characterized by A method for producing a spark plug ground electrode (1) having a multilayer structure, comprising the following steps:
Preparing a base (2) made of a ground electrode material;
Pushing a first wire section made of a first noble metal into the base (2);
Melting the first wire section, thereby forming an alloy layer (3) consisting of the first noble metal and part of the ground electrode material;
Pushing a second wire section made of a second noble metal into the alloy layer (3);
A method for producing a spark plug ground electrode (1), comprising the step of welding a second wire section to an alloy layer (3) to form a reinforcing layer (4).   8. The method according to claim 7, wherein the first wire section is melted by a laser (8) and / or the second wire section is welded by a laser (8).   The method according to claim 7 or 8, wherein the first wire section is completely melted and / or the second wire section is melted for welding only at the contact surface with the alloy layer (3).   The second wire section is welded on the back side, with the energy required for welding being applied to the surface (6) of the spark plug ground electrode (1) located on the opposite side of the second wire section. The method according to any one of claims 7 to 9, which is added.

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