Nippon Piston Ring Co., Ltd.

Nittan Valve Co., Ltd.

Kiyoshi Suwa

Kenichi Sato

Hiroshi Oshige

Katsuaki Ogawa

Satoshi Ikemi

Ayato Oikawa

Kouji Kunitake

Ryouichi Yoshino

Provided is a valve seat insert for an internal combustion engine, which has both an excellent heat dissipation property and excellent wear resistance. The valve seat insert for an internal combustion engine is used while being press-fitted into an aluminum alloy cylinder head, is made of an iron-based sintered alloy, is formed by integrating two layers of a functional member side layer and a supporting member side layer, and has a plating film on at least an outer peripheral side. The plating film is preferably a copper plating film. The plating film is a plating film having a thickness of 1 to 100 &#x3bc;m and a hardness of 50 to 300 HV, and the hardness of the plating film is adjusted so as to satisfy a range of 1.05 to 4.5 times hardness of the cylinder head in Vickers hardness HV. Pores contained in the valve seat insert are preferably sealed with a curable resin before plating treatment. Consequently, a valve seat insert for an internal combustion engine which does not go through complicated processes, is not accompanied by a significant decrease in wear resistance compared with the prior art, and has an excellent heat dissipation property is provided. If a roughened surface region is further formed at at least one portion on the outer peripheral surface of the valve seat insert in addition to the plating film, a falling out resistance property is improved. The same effect can be obtained even if the valve seat insert is a single layer of only the functional member side layer.

Iron-based sintered alloy valve seat for internal combustion engine

In an assembly of a hollow poppet valve and a valve seat insert, the hollow poppet valve's head is integrally formed with a stem end, a hollow part is formed from the head to a stem, and coolant is filled into the hollow part along with an inert gas. The valve seat insert is formed of iron base sintered alloy and obtained by integrating two layers of a supporting material side layer and a valve contact face side layer. The hollow poppet valve is formed of a material having thermal conductivity of 5-45 (W/m&#xb7;K) at 20-1000&#xb0; C. The valve seat insert includes the supporting material side layer having thermal conductivity of 23-50 (W/m&#xb7;K) at 20-300&#xb0; C. and a valve contact face side layer having thermal conductivity of 10-22 (W/m&#xb7;K) at 20-300&#xb0; C. This enables a valve temperature decrease throughout an engine's entire RPM range compared with the prior art.

Assembly of internal combustion engine valve and valve seat

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Tochigi, Japan

Kiyoshi Suwa