WO2016096487A1

WO2016096487A1 - Method for producing a spark-plug electrode having a core that extends to the ignition surface

Info

Publication number: WO2016096487A1
Application number: PCT/EP2015/078710
Authority: WO
Inventors: Jorge Diaz Alfonso
Original assignee: Robert Bosch Gmbh
Priority date: 2014-12-17
Filing date: 2015-12-04
Publication date: 2016-06-23
Also published as: DE102014226226A1; CN107005031A; JP6438140B2; JP2017538269A; EP3235081A1

Abstract

The invention relates to a method for producing a spark-plug electrode (10), wherein the spark-plug electrode has a main body (15), wherein the main body (15) is produced by separation from a wire, wherein the wire has a core (17) and a sheath (18) that surrounds the core (17), and the core (17) extends over the entire length of the main body (15), wherein a plurality of main bodies (15) can be produced from the wire.

Description

description

A method of manufacturing a spark plug electrode having a core extending to the firing surface

PRIOR ART The invention relates to a method for producing a spark plug electrode.

By the increasing downsizing at the engines stand for the individual

Components in the engine compartment even less space to seduction. Also in the field of spark plug, the demand for smaller spark plugs is increasing. The trend in the automotive industry is from M14 spark plugs to M12 spark plugs and M10 spark plugs.

Spark plugs. In addition to the need to design the spark plug smaller, the combustion chamber conditions that a spark plug undergoes during operation change simultaneously in a downsizing engine. Increasing pressure in the combustion chamber is associated with rising temperatures and increasing voltages required for the ignition, thus increasing the requirements for the spark plug in terms of mechanical, chemical, thermal and electrical strength and resistance. To meet the above requirements, new design concepts for the spark plug and new manufacturing processes for the spark plug components or for the

Spark plug necessary.

Current spark plugs, as known for example from DE 10 2005 052425 AI, is based on a plug housing with welded ground electrode and an insulator which is non-positively connected to the housing. Within the insulator, a center electrode is arranged at the combustion chamber end. The ground electrode and the center electrode are thermally stressed by the resulting in the combustion chamber during the combustion of the air-fuel mixture temperatures. In order to remove as quickly as possible the heat absorbed from the combustion chamber from the spark plug electrodes via the plug housing to the cooled cylinder head, the spark plug electrodes have a core of a material with a high thermal conductivity, for example a core of copper. DISCLOSURE OF THE INVENTION However, it can be seen that heat dissipation via the previous copper core is not sufficient in the case of the known spark plug concepts, in particular in the case of increasing requirements for the spark plug in the area of the downsizing application. Due to the manufacturing process, such as a known from DE 44 24 789 AI extrusion process, the copper core does not extend over the entire length of the spark plug electrode and additionally has a reducing

Diameter in the direction of the combustion chamber-side end of the spark plug electrode, with just this end of the spark plug electrode is exposed to the highest temperatures. Due to the insufficient heat dissipation in the known spark plug electrodes, the temperature of the spark plug electrode at its combustion chamber end is too hot and the wear on the spark plug electrode increases, this in turn leads to premature failure of the spark plug. Accordingly, it is an object of the present invention to provide a method of making a spark plug electrode which produces spark plug electrodes which have improved heat dissipation and thus can meet the above requirements. This object is achieved by the method according to the invention by the characterizing part of the first claim.

A base body for a spark plug electrode is made by singulating a wire, the wire being sufficiently long to make a plurality of

Produce basic bodies. The wire has a core and a cladding surrounding the core. In the main body, the core extends over the entire length of the

Base body, ie at the end faces of the body, the core is in each case free after separation. Characterized in that according to the invention it is provided that the main body of the spark plug electrode is made by separating from a wire, wherein the wire and thus Also, the main body has a core and a jacket surrounding the core, wherein the core extends over the entire length of the body, results on the one hand, that a body with a larger core volume and thus with an improved heat dissipation than known from the prior art Spark plug electrode body is made, on the other hand simplifies the

Production method for the spark plug electrode, as can be dispensed with a complex step for introducing the core into the body by means of a flow-pressing method. By extending the core in the spark plug electrode body is the

Heat dissipation of the spark plug electrode from its combustion chamber end to its end remote from the combustion chamber, which is in contact with cooled components of the spark plug, improved. The heat generated during operation of the spark plug and received from the combustion chamber end of the spark plug can be better dissipated to the cooled cylinder head via the spark plug electrodes and the housing, thereby lowering the temperature at the combustion chamber end of the spark plug and ignition surfaces of the spark plug electrodes. This is due to excessive

Temperatures favored reduced wear on the ignition surfaces and the spark plug electrodes and extends the life of the ignition surfaces, the spark plug electrodes and the spark plug in total.

Advantageous developments of the invention are the subject of the dependent claims.

Typically, the base body after singulation, and in particular prior to forming, has a length of not less than 0.5 cm, and more particularly a length of not greater than 6.0 cm, in particular not less than 1.0 cm. This results in advantageous that the main body already has the desired length for the spark plug electrode and the body does not necessarily have an additional

Process step must be shortened or extended to the desired length for the spark plug electrode.

The main body has a cylindrical shape, wherein the end faces, on which the core is exposed, correspond to the base surfaces of the cylinder. The shell of the body forms the lateral surface of the cylinder. The longitudinal axis of the body corresponds to the

Cylinder axis. The base surfaces of the cylinder or the cross-sectional areas or the End surfaces of the basic body may be round, oval or polygonal, in particular quadrangular. The diameter refers to the perimeter of the respective area.

Advantageously, the core of the base body has a constant diameter over the entire length of the base body, in particular after separation and before possible deformations of the base body.

Advantageously, it is provided that the core of the wire and the core of the

Body consists of a material that has a higher thermal conductivity than a material of the shell. The core consists for example of copper, silver or an alloy containing copper and / or silver, or a nickel alloy with yttrium. The jacket is in particular made of a material with a higher

Wear resistance as the material of the jacket. The jacket is made, for example, of a nickel-containing alloy containing further additives such as chromium, yttrium and / or silicon.

Alternatively or additionally, it can be provided that the jacket has a plurality of layers, in particular composed of two layers. The layers are arranged concentrically around the core of the base body. For example, a core of copper or a copper alloy may be surrounded by a cladding having a NiY layer and a NiCr layer. The NiY layer is disposed between the core and the NiCr layer. When comparing the three materials, the NiCr layer has the highest wear resistance. The thermal conductivity of the NiY layer is between the thermal conductivity of the copper and the NiCr alloy.

The wire and thus also the base body after singulation, and in particular before a subsequent forming step, have a diameter of not less than 1 mm, and in particular not greater than 4 mm, in particular not less than 1.5 mm and / or not greater than 3.5 mm.

The method may have, in particular after singulation, a step in which the base body is at least partially reshaped, so that a region of the base body with a larger diameter than before forming (DIN 8582) is formed, in particular the diameter is at least 5% increased. By means of pressure forming (DIN 8583-1 to -6), such as upsetting (DIN 8583-3) of the body along its longitudinal axis, the area of the body is formed with the larger diameter. For example, by this process step, an electrode head for a center electrode may be formed.

Alternatively or additionally, the method, in particular after singulation, have a step in which the base body is at least partially reshaped, so that a region of the base body with a smaller diameter than before forming (DIN 8582) is formed, in particular the diameter around at least 5% smaller. By means of pressure forming (DIN 8583-1 to -6), such as rolling (DIN 8583-2) of the body perpendicular to its longitudinal axis, the area with the smaller diameter is formed on the body. For example, through this

Process step, an electrode foot are formed for a center electrode.

Alternatively or additionally, the method, in particular after the singulation and / or after the forming, have a step in which at a

combustion chamber side end face of the main body of the main body with a

Closing body is materially connected. The cohesive connection can by means of resistance welding or laser welding, for example with a

Fiber laser or a disk laser, which is preferably operated in CW mode done. Other methods for a cohesive connection are also possible.

The closing body may for example consist of a nickel-containing alloy. Then it can additionally be provided that a noble metal-containing ignition surface is arranged on the end body or on the base body. Alternatively, it can also be provided that the closing body itself is the noble metal-containing ignition surface.

Advantageously, the base body is at least partially reshaped during forming such that the base body has at least a first and a second region Bl and B2 with different diameters Dl and D2, wherein in particular within the first and the second region Bl and B2, the respective diameters Dl and D2 are constant. The first and second regions Bl and B2 have, in particular, a length which corresponds at least to the respective diameter D1, D2 of the respective region B1, B2.

Preferably, the ratios between the cross-sectional area of the core and the cross-sectional area of the main body in the at least first and second areas Bl and B2 do not differ by more than 10%, in particular not more than 5%. For the production of a ground electrode can be provided that the method includes a step in which the base body is bent, so that a

Roof electrode, a stirrup electrode or a side electrode is formed.

Furthermore, the invention relates to a spark plug electrode, which after the

A method according to the invention for producing a spark plug electrode has been produced, and thus has a base body with a core and a jacket surrounding the core, wherein the core extends over the entire length of the base body. This means that the core extends from end to end of the main body.

For a sufficiently good heat dissipation in the spark plug electrode, it has been found to be advantageous that a ratio of a cross-sectional area of the core to a cross-sectional area of the base body over the length of the base body is virtually constant over the length of the base body, which is meant to be quasi-constant, that the ratio Cross sections within the body changes by no more than 10%. It is advantageously provided that the cross-sectional area of the core does not correspond to less than 20% and / or not more than 80% of the cross-sectional area of the main body. The cross-sectional area of the main body corresponds to the sum of the cross-sectional area of the shell and the cross-sectional area of the core. In each case, the cross-sectional area within the same plane are compared or set in relation to each other.

The shell of the main body has a layer thickness b which is not smaller than 0.1 mm and / or not larger than 0.8 mm, in particular not smaller than 0.2 mm and / or not larger than 0.6 mm, more particularly not less than 0.3 mm and / or not greater than 0.5 mm. The minimum layer thickness b of the sheath ensures that the core, which is made of less wear resistant material than the sheath, is sufficiently protected from the chemical stresses generated during operation of the spark plug. The layer thickness of the shell is limited so that the proportion of the

Core volume is not too small on the total volume of the body and thus the heat dissipation in the body is sufficiently large.

The main body has on its combustion chamber side end face on a closure body which is in contact with the core, in particular is in direct contact with the core. This ensures that the closing body in thermal contact with the Core stands. The closing body is welded, for example, to the base body. As a welding method, for example, resistance welding,

Electrode beam welding or laser welding with, for example, a fiber laser or a disk laser, wherein the laser welding can be performed with a CW laser or a pulsed laser. The closing body can at the

For example, weld completely melted.

As the material for the closing body, for example, an identical or similar nickel-containing alloy can be used as for the shell of the body.

The welding takes place along the circumference of the body, wherein at the

Welded seam along, in particular entire, circumference of the base body is formed, so that the closing body, the combustion chamber side end of the

Body as gas-tight as possible, ie the leakage rate is less than 10 ^"7 mbar l / s, concludes and thus the core of the body is protected.

Advantageously, the closure body is formed flush with the end face of the body, i. in that the closing body has the same diameter as the end face of the main body to which the closing body is arranged. Alternatively or additionally, it can be provided that the closing body has a diameter which is greater than the diameter of the core on the end face of the base body, on which the

Closing body is arranged.

It has proven to be advantageous if the end body has a thickness d which is at least as large as the smallest layer thickness b of the shell, wherein the thickness d of the end body is measured perpendicular to the end face of the body on which the end body is arranged. For example, the

End body have a thickness d, which is equal to or greater than the layer thickness d of the shell on the front side of the body on which the closing body is arranged.

In addition, it can be provided that the spark plug electrode has a noble metal-containing ignition surface. The ignition surface may, depending on the intended use of the spark plug electrode on the end body or at the combustion chamber end of the

Be arranged lateral surfaces. The ignition surface has a higher wear resistance than the material of the shell. Alternatively it can be provided that the closing body itself is the noble metal-containing ignition surface.

The spark plug electrode according to the invention may be a ground electrode and / or a center electrode.

Furthermore, the invention relates to a spark plug, the at least one

has spark plug electrode according to the invention as the center electrode and / or ground electrode.

The remote from the combustion chamber end face of the spark plug electrode or the

Basic body is arranged in the formation of the spark plug electrode according to the invention as a ground electrode on the housing of the spark plug, wherein preferably the connection of the spark plug electrode is formed with the housing so that the core of the body is protected from the influence of the combustion chamber gases. In the

Formation of the spark plug electrode according to the invention as a center electrode is arranged in the insulator so that the combustion chamber facing away from the end face of the spark plug electrode or the base body arranged by a likewise in the insulator

Resistive element is covered gas-tight.

drawing

FIG. 1 shows an example of the method according to the invention for producing a spark plug electrode

Figure 2 shows an example of a finished spark plug electrode, which after the

FIG. 3 shows an example of a spark plug, which is at least one after the

According to the method of the invention has prepared spark plug electrode

Description of the embodiment FIG. 1 schematically shows various steps of the method according to the invention for producing a spark plug electrode 10. In a first step, a wire is singulated, whereby a spark plug electrode main body 15 is formed. A supply of the wire is for example on a wire reel. The wire is so long that a plurality of spark plug electrode main body 15 can be manufactured by singulating the wire. The wire has a core 17 and a sheath 18 which surrounds the core 17. The core 17 extends substantially the entire length of the wire. The core 17, the sheath 18 and thus also the wire itself have constant dimensions, diameter, thickness and width over their entire length. By constant in this context is meant that the dimensions do not change by more than 10% over the length. The wire has a diameter in the range 1 mm to 4 mm. The sheath of the wire has a layer thickness d in the range of 0.1 mm to 0.8 mm. In this embodiment, the wire has a diameter of 2.7 mm and the jacket has a layer thickness b of 0.5 mm.

The main body 15 has a length of at least 5 mm after the separation of the wire. For the production of a center electrode of the main body has a length of up to 60 mm. For the production of a ground electrode, the main body has a length of up to 20 mm. At the end faces 14, 13 of the main body of the core 17 is free. The core 17 and the jacket 18 have after separation constant dimensions, such as diameter, thickness or width, or constant cross-sectional areas over the length of the main body 15th

In a subsequent step, the base body 15 is converted according to a planned use as a center electrode or ground electrode. The main body is clamped in a tool 30. As in Figure 1 b), by the tool 30th

For example, a first area Bl can be produced which has a small cross-sectional area or smaller dimensions, such as diameter or width, as an unconverted area B2 of the main body 15. The first area Bl with the smaller diameter is formed, for example, by means of rollers. In this

Embodiment, the area Bl has a diameter Dl of 2.4 mm and a layer thickness b for the shell of about 0.45 mm.

Alternatively or additionally, a third region B3 can also be produced, which has a larger cross-sectional area or larger dimensions than the one not deformed region B2 of the main body 15. The third region B3 with the larger diameter is formed, for example, by upsetting.

In principle, it is possible for the main body and the later spark plug electrode to have a plurality of first, second and / or third regions.

In Figure 1 c), an example of the spark plug electrode 10 is shown after the forming. The spark plug electrode 10 or the main body 15 has at least three regions: a first region Bl of the main body 15 with a reduced by forming cross-sectional area or a reduced diameter Dl, a second

Region B2 of the base body 15 with an unchanged diameter D2 or unchanged cross-sectional area, and a third region B3 with an enlarged by reshaping cross-sectional area or an enlarged diameter D3. Typically, the first region Bl of the main body 15 is formed at the combustion chamber end of the main body and the third region B3 is remote from the combustion chamber end of the body

Basic body 15 is formed. In a center electrode, the third area B3 of the main body 15 corresponds to the electrode head 19 which rests in the spark plug 1 on a seat formed on an inner side of the insulator 3. FIG. 2 shows a finished spark plug electrode 10, which is designed as a center electrode 12. The center electrode 12 has at its combustion-chamber-side end 14 a closing body 16, which has been materially connected by welding to the end face 14 of the main body 15. The end body 16 has a thickness d, the

at least the layer thickness b of the shell 18 of the base body 15 at its combustion chamber side end face 14 corresponds. The end body 16 has a

Diameter, which is greater than the diameter of the core 17 at the combustion chamber-side end face 14 of the base body 15. The closing body is flush with the

arranged combustion chamber side end face 14 of the body. FIG. 3 shows a schematic representation of a spark plug 1 with at least one spark plug electrode 10 according to the invention. The spark plug 1 has a metallic housing 2 with a thread for mounting the spark plug 1 in a cylinder head. Furthermore, the housing has a hexagonal section 9, on which a tool for the assembly of the spark plug 1 is set in the cylinder head. Within the housing 2, an insulator 3 is arranged. A center electrode 12 and a Connection bolts 4 are arranged inside the insulator 3 and are electrically connected via a resistance element 5.

The center electrode 12 typically protrudes from the insulator 3 at the combustion chamber end of the spark plug 1. With its electrode head 19, the center electrode 12 rests on a seat formed on the inside of the insulator 3. The center electrode 12 has a main body 15 and a closing body 16 arranged at the combustion chamber end of the main body 15. The main body has a core, not shown here, which is surrounded by a jacket.

At the combustion chamber end of the housing 2, a ground electrode 11 is arranged. Which forms a spark gap together with the center electrode 12. The ground electrode 11 may be formed as a roof electrode, side electrode or stirrup electrode. The ground electrode 11 has a main body 15 and a closing body 16 arranged at the combustion chamber end of the main body 15. The main body has a core, not shown here, which is surrounded by a jacket.

Claims

claims

A method for producing a spark plug electrode (10), wherein the spark plug electrode has a base body (15), characterized in that the

Main body (15) is produced by singulation from a wire (20), wherein the wire (20) has a core (17) and a jacket (18) surrounding the core (17), and that the core (17) extends over the extends the entire length of the base body (15), wherein from the wire (20) a plurality of basic bodies (15) can be produced.

2. The method according to claim 1, characterized in that the base body (15) after the separation, and in particular before a subsequent forming step, a length of not smaller than 0.5 cm and / or a length of not greater than 6.0 cm

3. The method according to any one of the preceding method claims, characterized in that the base body (15) is at least partially reshaped so that a region (B3) on the base body (15) with a larger diameter (D3) than before forming, in particular the Diameter increased by at least 5%.

4. The method according to any one of the preceding method claims, characterized in that the base body (15) is at least partially reshaped so that an area (Bl) on the base body (15) with a smaller diameter (Dl) than before forming, in particular the Diameter reduced by at least 5%.

5. The method according to any one of the preceding Verfahrensansprüche, characterized in that the base body (15) on a combustion chamber-side end face (14) of the base body (15) is integrally connected to a closing body (16).

6. The method according to any one of the preceding Verfahrensansprüche, characterized in that in the base body (15) arranged core (17) has a constant diameter over the entire length of the base body (15), in particular before forming.

7. The method according to any one of the preceding method claims, characterized in that the base body (15) is at least partially reshaped so that the base body (15) at least a first and a second region (Bl, B2) with different diameters (Dl, D2) wherein, in particular within the first and the second region (Bl, B2), the respective diameters (D1, D2) are constant.

8. The method according to the method claim 7, characterized in that the ratios between the cross-sectional area of the core (17) and the cross-sectional area of the base body (15) in the at least first and second areas (Bl, B2) differ by not more than 10% , in particular not more than 5%.

9. spark plug electrode (10), manufactured according to one of the preceding

A method claim, comprising a main body (15) having a core (17) and a jacket (18), characterized in that the core (17) extends over the entire length of the base body (15).

10. spark plug electrode (10) according to claim 9, characterized in that a ratio of a cross-sectional area of the core (17) to a cross-sectional area of the base body (15) changes by not more than 10% over the length of the body.

11. spark plug electrode (10) according to one of the preceding device claims, characterized in that a closing body (16) on the end face (14) of the base body (15) is fixed, wherein the closing body (16) in, in particular direct, contact with the core (17) stands.

12. spark plug electrode (10) according to the device claim 9, characterized

characterized in that the closing body (16) is arranged flush with the end face (14) of the base body (15).

13. spark plug electrode (10) according to any one of the preceding device claims, characterized in that a thickness (d) of the end body (16) is at least as large as a layer thickness (b) of the jacket (18), wherein the thickness (d) the dimension of the end body (16) in the longitudinal direction of the base body (15).

14. spark plug electrode (10) according to one of the preceding device claims, characterized in that the layer thickness (b) of the jacket (18) is not smaller than 0.1 mm, and in particular not greater than 0.8 mm.

15. Spark plug electrode (10) according to one of the preceding device claims, characterized in that the spark plug electrode (10) is a ground electrode (12) and / or center electrode (11).

16. Spark plug (1), characterized in that the spark plug (1) has at least one spark plug electrode (10) according to one of the preceding device claims and / or at least one of the preceding one

Method claims manufactured spark plug electrode (12).