| 摘要 |
PURPOSE:To prevent a vortex flow from damping near TDC at the end of a compression stroke by providing guide grooves for the vortex flow on the roof of a piston crown surface so as to intersect a roof ridgeline. CONSTITUTION:On the roof 4 of a piston crown surface 3. plural guide grooves 7 for a vortex flow are provided over inclined surfaces 3f, 3a, 3b, 3e or 3e, 3c, 3d, 3f which form upgrade slopes A, C and downgrade slopes B, D on both the right and the left side of a roof ridgeline 5 so as to intersect it. Each of the said guide grooves 7 is curved along a concentric circle with a different radius centering a cavity 6 (or a piston 1), and its bottom is formed flatly. Therefore, the vortex flow S swirling on the piston crown surface 3 during a compression stroke can flow smoothly. over the roof 4 from the said of the upgrade slopes A, C to the side of the downgrade slopes B, D. Specially, even when the piston 1 rises near TDC. the vortex flow s can pass through the said guide grooves 7.
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