| 摘要 |
PURPOSE:To achieve the equalization of deterioration state in a gas seal performance by positioning the grooves, which are provided on the upper surface and the like of a cylinder block so as to surround the outer circumference of cylinder bores, farther toward the outside in the diametral direction to the combustion chamber than the other parts. CONSTITUTION:In an engine structure where inner and outer tow concentric ring-shaped grooves 7, 8 are formed so that they are arranged on the upper surface 1a of a cylinder block 1 so as to surround the outer circumferences of cylinder bores 3 respectively and to function as a labyrinth seal, the center O2 of curvature of respective grooves 7, 8 is set so as to be eccentric by an appropriate dimension l toward the knocking zoner side 9 (on the side opposite to the direction in which an ignition plug 6 is eccentrically placed, and in the position in the vicinity of an exhaust valve 5) from the center O1 of each cylinder bore 3. Thus, with regard to the spacing between the inner circumferential periphery of the groove 7 and the bore wall side, by making the spacing S1 on the knocking zone 9 side larger than that S2 on the counter-knocking zone 9 side, the expected object can be achieved. |
