Spark plug
By controlling the distribution of precipitates in the heat-affected zone in the ground electrode of the spark plug to ensure that it does not become supersaturated at high temperatures, the problem of reduced joint strength is solved and durability and corrosion resistance are improved.
Active Publication Date: 2012-12-26
NITERRA CO LTD
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- Description
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- Application Information
AI Technical Summary
Problems solved by technology
[0003] However, since the ground electrode protrudes toward the center side of the combustion chamber, it becomes extremely hot during use
Therefore, the crystallization of the metal material constituting the ground electrode becomes coarser (so-called grain growth), which may lead to internal corrosion and decrease in durability.
Method used
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Experimental program
Comparison scheme
Effect test
Embodiment Construction
[0038] One embodiment will be described below with reference to the drawings. figure 1 It is a partially cutaway front view showing the spark plug 1 . Also in figure 1 In the description, the direction of the axis line CL1 of the spark plug 1 is defined as the vertical direction in the drawing, the lower side is defined as the front end side of the spark plug 1 , and the upper side is defined as the rear end side.
[0039] The spark plug 1 is composed of an insulator 2, a cylindrical metal shell 3 holding the insulator, and the like.
[0040] It is well known that the insulator 2 is formed by firing alumina or the like, and has a cylindrical rear main body part 10 formed on the rear end side; The side is protruding outward in the radial direction; the middle body part 12 is formed to be thinner in diameter than the large diameter part 11 on the side closer to the front end than the large diameter part 11; The diameter is formed to be thinner than that of the central body port...
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Abstract
Disclosed is a spark plug wherein superior bonding strength is achieved and supersaturation of precipitate is prevented. The spark plug (1) has a primary metal part (3), and a ground electrode (27) that is bonded to the primary metal part (3) by resistance welding. The ground electrode (27) is formed from a metallic material wherein precipitates (PR), which include at least one of an oxide, an intermetallic compound, etc., form at grain boundaries. In a cross-section of a thermally affected part (27A), the diameter of the inscribed circle of the precipitates (PR) having the largest surface area is less than or equal to 50µm, and the minimum distance between the precipitates (PR) is greater than or equal to 2µm, where the thermally affected part (27A) is the part of the ground electrode (27) located within a range of 100µm from the bonding boundary between the ground electrode (27) and the primary metal part (3), and the general part (27B) is the leading end portion of the ground electrode (27). The surface area occupied by the precipitates (PR) in the cross-section of the thermally affected part (27A) (the diameter of the inscribed circle of the precipitates (PR) having the largest surface area) is greater than or equal to 65% (85%) of the surface area occupied by the precipitates (PR) in the cross-section of the general part (27B) (the diameter of the inscribed circle of the precipitates (PR) having the largest surface area).
Description
technical field [0001] The present invention relates to a spark plug for internal combustion engines and the like. Background technique [0002] The spark plug is attached to, for example, an internal combustion engine (engine), etc., and is used to ignite the air-fuel mixture in the combustion chamber. In general, a spark plug has: an insulator with a shaft hole; a center electrode inserted through the front end of the shaft hole; a body fitting provided on the outer periphery of the insulator; a ground electrode, which is joined to the front end of the body fitting by resistance welding, and connected to the center electrode. A spark discharge gap is formed between them. In addition, in order to improve corrosion resistance, electroplating treatment such as galvanizing can be applied to the main body part to which the ground electrode is welded. [0003] However, since the ground electrode protrudes toward the center side of the combustion chamber, it becomes extremely h...
Claims
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Patent Timeline
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IPC IPC(8): H01T13/39C22C19/03
CPCC22C19/03B23K35/0261H01T13/39B23K11/002B23K35/3033H01T13/32
Owner NITERRA CO LTD