Spark plug

#1. Field of the Invention

#The present invention relates to a spark plug used for ignition of an internal combustion engine.

#2. Description of the Related Art

#FIG. 1 is a front sectional view showing a spark plug according to Embodiment 1 of the invention.

#FIG. 2 is a front sectional view showing a main part of FIG. 1.

#FIG. 3 is a front view of an inner circumferential surface 45 of a ground electrode body 4a depicted in FIG. 1.

#1: metal shell 2: insulator 3: center electrode 4: ground electrode 6: through-hole 31: second precious metal tip 41, 241: first precious metal tip 41a, 241a: leading end surface of the first precious metal tip 41, 241 100, 200: spark plug O: spark plug lengthwise axis

#The invention will now be described below with reference to the drawings. However, the present invention should not be construed as being limited thereto.

#FIGS. 1 to 3 show a resistor-including spark plug 100 according to Embodiment 1 of the invention. The resistor-including spark plug 100 has a cylindrical metal shell 1, an insulator 2, a center electrode 3, and a ground electrode 4. The insulator 2 is fitted into the metal shell 1 so that a leading end portion of the insulator 2 protrudes from the metal shell 1. The center electrode 3 is provided inside the insulator 2 while the center electrode 3 has a second precious metal tip 31 protruding from the insulator 2. The ground electrode 4 has one end (a joint surface 42 of a ground electrode body) joined to the metal shell 1. The ground electrode 4 has a first precious metal tip 41 bonded to an inner circumferential surface 45 near the other end (an end surface 44 opposite the joint surface of the ground electrode body). The ground electrode 4 is bent so that a leading end surface of the first precious metal tip 41 is disposed opposite a leading end surface of the second precious metal tip 31. A spark gap g is formed between the first precious metal tip 41 and the second precious metal tip 31.