Spark plug electrode precious metal pin, spark plug electrode, spark plug, and method for manufacturing a spark plug electrode

Abstract

We provide spark plug electrode precious metal pins that facilitate manufacturing, reduce costs, and enable a very good balance between spark corrosion characteristics and weldability. [Solution] The spark plug electrode precious metal pin (7) is completely alloyed within the nickel-based electrode substrate (12), and the spark plug electrode precious metal pin (7) is made of an alloy containing -30 to 60 mass% platinum, -40 to 65 mass% nickel, and -0.5 to 5 mass% iridium.

Description

Technical Field

[0001] The present invention relates to a spark plug electrode precious metal pin for use in generating sparks at a spark plug electrode of an internal combustion engine, and a spark plug electrode formed together with the spark plug electrode precious metal pin. Furthermore, the present invention also relates to a spark plug and a method for manufacturing the spark plug electrode.

Background Art

[0002] Spark plug electrodes having precious metal pins or spark plug electrodes made of precious metals are known from the prior art. For example, Patent Document 1 teaches a spark plug electrode material that is characterized by good corrosion resistance and little wear due to spark erosion. The spark plug electrode material contains a first precious metal selected from Pd, Au, Ag, Re, Os, and Ru, Ni in a proportion of 0.5 to 5% by weight based on the total weight of the spark plug electrode material, and Rh in a proportion of 0.5 to 50% by weight based on the total weight of the spark plug electrode material. The disadvantages of this spark plug electrode are still too high wear overall and the associated high cost.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

[0004] In contrast, the present invention provides a spark plug electrode precious metal pin, which is characterized by very high wear resistance and very good workability, and can be easily attached to a spark plug electrode substrate, for example, by a welding method, without losing its advantageous properties.

[0005] For this purpose, the spark plug electrode precious metal pin according to the present invention is made of an alloy containing more than 80% by mass of platinum, 1 to 10% by mass of nickel, and less than 1 to 10% by mass of iridium, based on the total mass of the spark plug electrode precious metal pin. Platinum and platinum alloys containing iridium are characterized by their low wear rate due to spark corrosion, while platinum and platinum-iridium alloys are also characterized by their high melting point. The drawback of these high melting point alloys is their difficult processability. The above amounts of elements in the spark plug electrode precious metal pin according to the present invention refer to the spark plug electrode precious metal pin in an unassembled state, i.e., before bonding with the spark plug electrode substrate.

[0006] The spark plug electrode precious metal pin is joined to the spark plug electrode base when used as specified. Long-term stable bonding between the spark plug electrode precious metal pin and the spark plug electrode base ensures high operational performance without spark failure. For this purpose, the spark plug electrode precious metal pin needs to be joined to the spark plug electrode base by welding. In this case, another advantage of the composition of the spark plug electrode precious metal pin according to the present invention becomes apparent. Specifically, a nickel content of 1-10% by mass relative to the total mass of the spark plug electrode precious metal pin reduces the melting range of the alloy, thereby improving weldability. This applies to all welding methods, but especially to back welding and when the spark plug electrode precious metal pin is completely alloyed within the spark plug electrode base. Depending on the welding method used, the composition of the spark plug electrode precious metal pin in the bonding region between the spark plug electrode base and the spark plug electrode precious metal pin may vary. For example, a weld seam can be formed having a mixed composition of the spark plug electrode precious metal pin and the spark plug electrode substrate. However, in the case of "simple" welds and back welds in which a weld seam is formed, in the standard use of the spark plug electrode precious metal pin, the surface used to generate the ignition spark (hereinafter referred to as the ignition spark surface) still has the composition disclosed above, namely, more than 80 mass% platinum, 1 to 10 mass% nickel, and less than 1 to 10 mass% iridium, respectively, relative to the total mass of the spark plug electrode precious metal pin.

[0007] Nickel is characterized by its high corrosion resistance and lower melting point than platinum and especially iridium. As a result, by mixing nickel, the melting range of the alloy can be reduced while maintaining excellent mechanical properties, which is advantageous for weldability.

[0008] The dependent claims represent preferred developments of the present invention.

[0009] According to one advantageous developmental form, the alloy of the spark plug electrode precious metal pin consists substantially of more than 80 mass% platinum, especially more than 90 mass% platinum, 1 to 10 mass% nickel, especially 3 to 7 mass% nickel, and less than 1 to 10 mass% iridium, especially 1 to 3 mass% iridium. There is no need to mix in any more metals, which facilitates the manufacture of the spark plug electrode precious metal pin, reduces costs, and allows for a very good balance between spark corrosion properties and weldability.

[0010] Similarly, the present invention also discloses a first spark plug electrode comprising a spark plug electrode precious metal pin made of an alloy containing more than 80% by mass of platinum, 1 to 10% by mass of nickel, and less than 1 to 10% by mass of iridium. As already stated above, these amounts are relative to the total mass of the spark plug electrode precious metal pin. In addition, as already mentioned, different (mixed) compositions may occur in the joint region by using a welding method to form a joint between the spark plug electrode precious metal pin and the spark plug electrode substrate. However, in the standard use of the first spark plug electrode, the composition of the spark plug electrode precious metal pin in the spark surface region used to generate the ignition spark is in all cases an alloy containing more than 80% by mass of platinum, 1 to 10% by mass of nickel, and less than 1 to 10% by mass of iridium. Therefore, the present invention makes it possible to form the spark plug electrode precious metal pin as disclosed above. By using specially formulated spark plug electrode precious metal pins, the first spark plug electrode according to the present invention is characterized by less wear due to spark corrosion, especially in modern engines with high power density, and therefore high operational performance over the long term. In addition, the spark plug electrode, or more precisely the spark plug electrode base, can be joined to the spark plug electrode precious metal pins very easily and for long-term durability by welding, which prevents spark failure and even complete failure of the spark plug electrode under specified use.

[0011] In one advantageous embodiment of the first spark plug electrode, the spark plug electrode precious metal pins are joined to the nickel-based electrode substrate by a weld seam, particularly a weld seam formed by a back weld. Thus, the spark plug electrode precious metal pins, together with the nickel-based electrode substrate to which they are joined by welding, particularly a back weld, form the first spark plug electrode. The welding creates only a small weld seam between the spark plug electrode precious metal pins and the spark plug electrode substrate, thereby allowing the spark plug electrode precious metal pins to substantially, and especially, retain their composition in the area used for generating the ignition spark (ignition spark surface) in the intended use of the spark plug electrode. Thus, the advantageous effect brought to the first spark plug electrode by the spark plug electrode precious metal pins is maintained over the long term.

[0012] According to the present invention, a nickel-based electrode substrate is understood to be a spark plug electrode substrate made of nickel or a nickel alloy, where, in the case of a nickel alloy, nickel accounts for more than 50% by mass, and particularly more than 80% by mass, of the total mass of the nickel alloy. Suitable alloying metals include, for example, aluminum, silicon, yttrium, copper, iron, magnesium, manganese, titanium, zirconium, and chromium. Nickel alloys particularly suitable for use as nickel-based electrode substrates have less than 5% by mass each of the following elements, namely aluminum, silicon, copper, and yttrium, up to 25% by mass each of iron and chromium, and the remainder being nickel.

[0013] According to another preferred development, in the prescribed use of the first spark plug electrode, the alloy of the spark plug electrode precious metal pin in the area of ​​the spark plug electrode precious metal pin used for generating the ignition spark (ignition spark surface) is substantially composed of more than 80 mass% platinum, especially more than 90 mass% platinum, 1 to 10 mass% nickel, especially 3 to 7 mass% nickel, and less than 1 to 10 mass% iridium, especially less than 1 to 3 mass% iridium. This facilitates the formation of a weld seam between the spark plug electrode precious metal pin and the nickel-based electrode substrate, and allows for its long-term stable formation. The wear rate due to spark erosion of the spark plug is very low, resulting in high operational performance.

[0014] Furthermore, the present invention also discloses a second spark plug electrode comprising a spark plug electrode precious metal pin, wherein the spark plug electrode precious metal pin is completely alloyed within a nickel-based electrode substrate, and the spark plug electrode precious metal pin consists of an alloy containing 30-60 mass% platinum, 40-65 mass% nickel, and 0.5-5 mass% iridium.

[0015] The spark plug electrode precious metal pins disclosed above can also be used for the second spark plug electrode. However, by completely alloying the spark plug electrode precious metal pins within the nickel-based electrode substrate, the composition of the spark plug electrode precious metal pins changes in all areas of the pre-placed spark plug electrode precious metal pins. This is due to the composition of the nickel-based electrode substrate containing more than 50% by mass, particularly more than 80% by mass, of nickel (relative to the total mass of the nickel-based electrode substrate).

[0016] In other words, the second spark plug electrode can be obtained by using a spark plug electrode precious metal pin made of an alloy containing more than 80 mass% platinum, 1 to 10 mass% nickel, and less than 1 to 10 mass% iridium, and by completely alloying the spark plug electrode precious metal pin with a nickel-based electrode substrate. By using a spark plug electrode precious metal pin, alloying with a nickel-based electrode substrate is facilitated, the bond formed between the spark plug electrode precious metal pin and the nickel-based electrode substrate is stable over the long term, and high long-term operating performance without spark generation failure of the second spark plug electrode. Therefore, the second spark plug electrode is also very well protected from wear due to spark corrosion.

[0017] The particularly good bonding between the spark plug electrode noble metal pin and the nickel-based electrode substrate in the second spark plug electrode is obtained when the alloy of the spark plug electrode noble metal pin consists substantially of 30-60 mass% platinum, particularly 40-50 mass% platinum, 40-65 mass% nickel, particularly 50-60 mass% nickel, and 0.5-5 mass% iridium, particularly 0.8-2 mass% iridium.

[0018] Furthermore, the present invention also indicates a spark plug comprising a first spark plug electrode and / or a second spark plug electrode. The spark plug according to the present invention is characterized by very good spark erosion behavior and, consequently, a low rate of wear due to spark erosion. In addition, spark generation failure due to improperly processed and unbonded precious metal pins of the spark plug electrode is prevented, thereby the spark plug has high operating performance over the long term, especially in the latest high-power density engines.

[0019] Furthermore, the present invention also discloses a first method for manufacturing a spark plug electrode, comprising the step of welding, particularly back-welding, a spark plug electrode precious metal pin to a nickel-based electrode substrate. The spark plug electrode precious metal pin used in the welding method consists of an alloy containing more than 80% by mass of platinum, 1 to 10% by mass of nickel, and less than 1 to 10% by mass of iridium. Due to the composition of the spark plug electrode precious metal pin, a homogeneous and therefore long-term stable weld seam is formed between the spark plug electrode precious metal pin and the nickel-based electrode substrate by welding, particularly by back-welding, thereby preventing displacement or detachment of the spark plug electrode precious metal pin over the long term. The first method yields a spark plug electrode characterized by less wear due to spark corrosion and high operating performance, i.e., the first spark plug electrode according to the present invention. When a spark plug manufactured by the first method is used as specified, the surface of the precious metal pin of the spark plug electrode used to generate the ignition spark (ignition spark surface) is made of an alloy containing 80% by mass of platinum, 1 to 10% by mass of nickel, and less than 1 to 10% by mass of iridium.

[0020] The present invention also discloses a second method for manufacturing a spark plug electrode, comprising the step of completely alloying the spark plug electrode precious metal pin into a nickel-based electrode substrate. In the second method as well, the spark plug electrode precious metal pin used consists of an alloy containing more than 80% by mass of platinum, 1 to 10% by mass of nickel, and less than 1 to 10% by mass of iridium. By completely alloying the spark plug electrode precious metal pin into a nickel-based electrode substrate, the composition of the spark plug electrode precious metal pin is changed, thereby the composition of the spark plug electrode precious metal pin after completion of the spark plug electrode existing in the form of the second spark plug electrode is substantially -30 to 60 mass% platinum, especially 40 to 50 mass% platinum, -40 to 65 mass% nickel, especially 50 to 60 mass% nickel, -0.5 to 5 mass% iridium, especially 0.8 to 2 mass% iridium This is the result. Also by the second method, a spark plug electrode characterized by little wear due to electrical discharge machining and very high operating performance can be obtained, that is, the second spark plug electrode according to the present invention.

[0021] In order to further simplify the above method by reducing the melting range of the noble metal pin of the spark plug electrode used in the method, the alloy of the noble metal pin of the spark plug electrode used for welding consists essentially of more than 80% by mass of platinum, particularly more than 90% by mass of platinum, 1 to 10% by mass of nickel, particularly 3 to 7% by mass of nickel, and less than 1 to 10% by mass of iridium, particularly 1 to 3% by mass of iridium.

Brief Description of the Drawings

[0022] [Figure 1] It is a view of a part of a spark plug cut according to the first embodiment. [Figure 2] It is a schematic partial cross-sectional view of a spark plug according to the second embodiment. [Figure 3] It is a schematic partial cross-sectional view of a spark plug according to the third embodiment. [Figure 4] It is a schematic partial cross-sectional view of a spark plug according to the fourth embodiment.

Mode for Carrying Out the Invention

[0023] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0024] In the figure, only important components of the present invention are shown, and all other components are omitted for clarity. Further, the same parts / components are given the same reference numerals.

[0025] As can be seen from FIG. 1, the spark plug 1 according to the present invention includes a ground electrode 2, a center electrode 3, and an insulator 4. A housing 5 surrounds the insulator 4 at least partially. The housing 5 is provided with a thread 6 designed to attach the spark plug 1 to the cylinder head 10.

[0026] As disclosed above, the ground electrode 2, and alternatively or additionally the center electrode 3, can be formed as the first spark plug electrode 8 or the second spark plug electrode 9.

[0027] Figure 2 schematically shows a portion of the first spark plug electrode 8, which is shown here as an illustrative central electrode. The first spark plug electrode comprises a nickel-based electrode substrate 12, the nickel-based electrode substrate containing more than 50% by mass of nickel relative to the total mass of the nickel-based electrode substrate 12. The nickel-based electrode substrate 12 is joined to the spark plug electrode precious metal pin 7 by a weld seam 11.

[0028] In the prescribed use of the first spark plug electrode 8, the spark plug electrode precious metal pin 7 has an ignition spark surface 13 used for generating an ignition spark and is made of an alloy containing more than 80 mass% platinum, 1 to 10 mass% nickel, and less than 1 to 10 mass% iridium. In particular, the alloy is substantially made of more than 80 mass% platinum, especially more than 90 mass% platinum, 1 to 10 mass% nickel, especially 3 to 7 mass% nickel, and less than 1 to 10 mass% iridium, especially 1 to 3 mass% iridium.

[0029] The welding of the spark plug electrode precious metal pin 7 to the nickel-based electrode substrate 12 can be performed using conventional welding methods, thereby allowing the spark plug electrode precious metal pin 7 to substantially maintain its composition, particularly at the ignition spark surface 13. The weld seam 11 is characterized by very good stability and homogeneity, which is due to the above composition of the spark plug electrode precious metal pin 7 containing 1 to 10 mass% nickel, thereby reducing the melting range of the spark plug electrode precious metal pin 7 and facilitating weldability. In addition, the spark plug electrode precious metal pin 7 is characterized by high wear due to spark erosion due to its high precious metal content, thereby giving the first spark plug electrode 8 high operational performance.

[0030] Figure 3 shows a schematic partial cross-sectional view of another first spark plug electrode 8, shown here illustratively as a ground electrode. In this case, the first spark plug electrode 8 is also a nickel-based electrode substrate 12, and comprises a spark plug electrode substrate containing more than 50% by mass of nickel relative to the total mass of the nickel-based electrode substrate 12. Unlike the first spark plug electrode 8 shown in Figure 2, the first spark plug electrode 8 shown in Figure 3 is fabricated by back welding. As a result, the composition of the spark plug electrode noble metal pins 7 at least on the surface used to form a joint with the nickel-based electrode substrate 12 in the welded area (see welding seam 11) is changed, and it consists of a mixed alloy of the nickel-based electrode substrate 12 alloy and the spark plug electrode noble metal pins 7 alloy. However, the composition of the spark plug electrode precious metal pin 7 in the region of the ignition spark surface 13 is still the same as the composition of the spark plug electrode precious metal pin 7 before back welding, that is, this composition consists of an alloy containing more than 80 mass% platinum, 1 to 10 mass% nickel, and less than 1 to 10 mass% iridium. In particular, this alloy consists substantially of more than 80 mass% platinum, especially more than 90 mass% platinum, 1 to 10 mass% nickel, especially 3 to 7 mass% nickel, and less than 1 to 10 mass% iridium, especially 1 to 3 mass% iridium.

[0031] Figure 4 shows a schematic partial cross-sectional view of the second spark plug electrode 9, which is also shown as an example ground electrode in this case. The second spark plug electrode 9 is a nickel-based electrode substrate 12, and comprises a spark plug electrode substrate containing more than 50% by mass of nickel relative to the total mass of the nickel-based electrode substrate 12.

[0032] The spark plug electrode noble metal pin 7 is completely alloyed within the nickel-based electrode substrate 12. Therefore, no weld seams exist.

[0033] The spark plug electrode precious metal pin 7 similarly has an ignition spark surface 13 and is made of an alloy containing 30-60% by mass of platinum, 40-65% by mass of nickel, and 0.5-5% by mass of iridium.

[0034] In particular, the alloy forming the spark plug electrode precious metal pin 7 consists substantially of 30-60 mass% platinum, especially 40-50 mass% platinum, 40-65 mass% nickel, especially 50-60 mass% nickel, and 0.5-5 mass% iridium, especially 0.8-2 mass% iridium.

[0035] By completely alloying the spark plug electrode precious metal pin 7 within the nickel-based electrode substrate 12, a particularly stable bond is formed between the spark plug electrode precious metal pin 7 and the nickel-based electrode substrate 12. This effectively prevents displacement or detachment of the spark plug electrode precious metal pin 7 even during long-term use of the second spark plug electrode 9 as specified, while still significantly reducing wear due to spark corrosion, thereby improving the long-term performance of the second spark plug electrode 9. [Explanation of symbols]

[0036] 1 Spark plug 2 Ground electrode 3 Center electrode 4. Insulator 5 Housing 6 threads 7 Spark plug electrode precious metal pin 8. First spark plug electrode 9. Second spark plug electrode 10 Cylinder head 11 Weld seam 12 Nickel-based electrode substrate 13 Ignition spark surface

Claims

1. A spark plug electrode comprising a spark plug electrode precious metal pin (7), wherein the spark plug electrode precious metal pin (7) is completely alloyed within a nickel-based electrode substrate (12), and the spark plug electrode precious metal pin (7) is -30 to 60 mass% platinum, -40 to 65 mass% nickel and -0.5 to 5 mass% iridium and A spark plug electrode made of an alloy containing [a specific substance].

2. The aforementioned alloy is substantially, -30 to 60 mass% platinum, especially 40 to 50 mass% platinum, -40 to 65 mass% nickel, especially 50 to 60 mass% nickel, -0.5 to 5 mass% iridium, especially 0.8 to 2 mass% iridium A spark plug electrode according to claim 1, comprising the above.

3. A spark plug comprising the spark plug electrodes (8, 9) described in claim 1 or 2.

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