Toyota Jidosha Kabushiki Kaisha

Ngk Spark Plug Company, Limited

Toyota Jidosha Kogyo Kabushiki Kaisha

Kazuhisa Mayumi

Katsumi Suzuki

Yorishige Maeda

Norio Sasaki

Fujio Tsuboi

A piston and piston-ring assembly includes a piston and piston-rings located in piston-ring grooves formed in the piston. Such a kind of surface hardening treatment as is accompanied by an increase in surface roughness, such as alumite treatment, is applied to at least a lower groove surface of a top piston-ring groove. On the other hand, a resin with an excellent adhesive property is coated on a portion of a surface of the piston-ring opposing the hardened surface of the piston-ring groove. The heat resistive property of the assembly is improved by the surface hardening treatment without being accompanied by an increase in blowby gas amount and oil consumption because resin removed from the piston ring fills the valleys of the rugged hardened surface of the piston-ring groove.

Aluminum alloy piston and piston-ring assembly treated to suppress

A spark plug is disclosed, in which the insulator is formed with a stepped portion near its tip portion and the housing which surrounds the insulator is formed with an inner constriction which opposes the smaller portion of the insulator, near the stepped portion, with a small annular gap being left therebetween, thereby hindering the entry of air/fuel mixture and carbon particles into the inner space between the housing and the insulator, and thus reducing the buildup of carbon on the insulator.

Spark plug with a stepped insulator and an inner constriction in the

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Aichi, Japan

Kazuhisa Mayumi