| 摘要 |
A hollow poppet valve (10) is provided with a step (17) at a predetermined axial position of a diametrically small valve stem cavity (S2) formed in a valve stem (12) of the valve (10) so as to cause turbulence to occur in a coolant charged in the valve stem cavity (S2). The valve stem cavity (S2) is communicated with a valve head cavity (S1) formed in a valve head (14) which is integrally formed at one end of the valve stem (12), so that the cavities (S1 and S2) constitutes a cavity (S) that extends from inside the valve head into the stem. The cavity (S) is partially loaded with a coolant (19). The valve stem cavity has a diametrically larger first portion (S21) near the stem end and a diametrically smaller second portion (S22) near the valve head (10). The step is formed at the boundary of the first and the second portion of the valve stem cavity. The cavity (S) is loaded with the coolant (19) to a level above the step (17). In response to a reciprocal motion of the valve (10) the coolant (19) is moved in the valve stem cavity (S2) across the step (17), giving rise to turbulence in the neighborhood of the step (17), thereby stirring the coolant (19). |
