Nittan Valve Co., Ltd.

Nittan Corporation

Jin Hasegawa

Hiroki Onuma

Koichi Homma

Yuki Sasagawa

Koji Kunitake

In a hollow exhaust poppet valve including a fillet increasing in diameter toward a leading end, a stem, and a head and having a coolant within a hollow part formed from the head to the stem, the stem includes a first stem part on a base end side, and a second stem part integrated with the first stem part via a step part and integrated with the fillet, and the hollow part includes a first hollow part formed inside the first stem part, and a second hollow part formed inside the second stem part, the fillet, and the head in such fashion as to have a constant inner diameter greater than the first hollow part and formed so as to be continuous with the first hollow part via a tapered part or a curved part.

Hollow exhaust poppet valve

A hollow poppet valve () is provided with an additional flange shape cavity (S), in addition to an ordinary valve head cavity (S) formed in the valve head () of the valve () in communication with a valve stem cavity (S) formed in a valve stem (). A coolant () is loaded in the cavities to facilitate dissipation of heat out of the valve. This flange shape cavity (S) extends radially outwardly round a bottom portion of the valve head cavity (S), extending close to a valve seat, thereby significantly facilitating heat transfer between the coolant () and the valve seat of the valve, yet, since the flange shape cavity (S) does not influences the thickness of other regions of the valve, it does not degrade durability of the valve.

Hollow poppet valve

To provide a hollow poppet valve having an improved heat reduction effect. In a hollow poppet valve () having a valve head () and a stem () integral with the valve head (), the hollow poppet valve () is formed with an internal cavity S that extends in the valve head () and the stem (). The internal cavity S is charged with a coolant () and an inert gas. The internal cavity S has a generally disk-shape internal cavity Sand an internal stem cavity Sformed in the stem () and connected to the internal valve head cavity Sat a right angle. During a reciprocal motion of the valve (), a vertical convective flow of coolant () along the axis L of the valve () is established at least in the internal valve head cavity S, thereby enhancing its heat reduction effect.

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Hadano, Japan

Jin Hasegawa