| 摘要 |
A spark plug having sufficient durability for an internal combustion engine is provided by means of restraining a sharp increase in resistance of a resistor while the diameter (size) of the spark plug is reduced. A spark plug 1 includes an insulator 2 having an axial hole 4, a metallic shell 3 provided on the outer circumference of the insulator 2, a center electrode 5 inserted into a front end portion of the axial hole 4, a terminal electrode 6 inserted into a rear end portion of the axial hole 4, and a ground electrode 35. A circular columnar resistor 7 is disposed within the axial hole 4 between the center electrode 5 and the terminal electrode 6, thereby electrically connecting the center electrode 5 and the terminal electrode 6. The resistor 7 is formed from a resistor composition mainly composed of a carbon black 53 serving as a conductive material, a glass powder 51, and ceramic particles 54. The ceramic particles 54 have a maximum particle size of 0.5 µm or less. |
