Patent Application
20130187530
The subject matter disclosed herein relates to a method of producing an electrode support for a spark plug, and more specifically to a method of producing an electrode for a spark plug using brazing.
Spark plugs include an electrode chip located at an end of a center electrode. A separate chip is also located on an end of a side or ground electrode. An air or spark gap is located between the chip positioned on the center electrode and the chip positioned on the ground electrode. In one approach, the spark plug is manufactured by welding a single chip to both the center electrode and the ground electrode. Then, the chip is then machined to create the spark gap between the center electrode and the ground electrode. The chip is generally constructed from a precious or noble metal such as, for example, a platinum based alloy. Noble and precious metals usually have a relatively high cost.
Several drawbacks in the current manufacturing approach generally exist. For example, welding may result in cracks in a weld joint, due to a mismatch in the coefficient of thermal expansion between the different materials that the chip and the center and ground electrodes are constructed from. Also, welding consumes a portion of the relatively costly material the chip is constructed from.
According to one aspect of the invention, a method of producing an electrode support for a spark plug is provided. The method includes providing the electrode support. The method includes brazing a chip to the electrode support.
According to another aspect of the invention, a spark plug is provided having an electrode support, a side chip, and a center chip. The electrode support includes a center portion and a side portion. The side chip is brazed to both the center portion of the electrode support. The center chip is brazed to the center portion of the electrode support.
These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings.
The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings.
The electrode chip 26 is constructed from an electrode material. A portion of the electrode material is eventually removed by a material removal process such as, for example, machining, to create a spark gap 50 (shown in
The electrode chip 26 is attached to either the outer surface 44 of the center portion 20 or the outer surface 46 of the corresponding side portion 22 by a brazing process. Brazing the electrode chip 26 to the electrode support involves employing a filler material to join the electrode material to the electrode support 10. Brazing may improve contact and subsequent heat transfer between the electrode chip 26 and the electrode support 10 when compared to some other types of joining processes such as, for example, welding. Brazing also reduces stress between the electrode ship 26 and the electrode support 10 by substantially reducing or eliminating the built-in stress risers that are generally associated with other types of joining approaches. Moreover, because a filler material is used, the brazed configuration between the electrode chip 26 and the electrode support 10 does not consume a portion of the relatively costly electrode material, unlike a weld joint.
The electrode support 10 may be constructed from a metal material that has a relatively low coefficient of thermal expansion such as, for example, nickel iron alloys. For example, in one embodiment, the electrode support 10 includes a coefficient of thermal expansion that ranges from between about 4×10−6 K−1 to about 12×10−6 K−1. In one exemplary embodiment, the electrode support 10 may be constructed an iron-nickel-cobalt alloy conforming to ASTM F-15 or UNS N14052. Specifically, the electrode support 10 and the electrode chip 26 may both be constructed from materials having substantially the same coefficient of thermal expansion. For example, in one embodiment, the electrode chip 26 may be constructed from a noble metal having a coefficient of thermal expansion that ranges from between about 5×10−6 K−1 to about 10×10−6 K−1. The compatible coefficients of thermal expansion results in a reduced amount of stress on the braze joint (not shown) when the electrode chip 26 and the electrode support 10 are brazed together compared to other joining approaches such as welding.
Referring generally to
While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.
