| 摘要 |
<P>PROBLEM TO BE SOLVED: To improve reduction effect of CO and unburned HC at low-load operation, and to improve reduction effect of black smoke at high-load operation. <P>SOLUTION: In a lip part of a cavity part 22, a stepped part 30 comprising steps by being depressed downward of a cylinder with respective to an outer peripheral part 24 at a piston top face (a part 28 at which a bulb recess 26 is not formed) is formed around the entire periphery in a cylinder circumferential direction. The step at a position at which the bulb recess 26 is formed is smaller than the step at a position at which the bulb recess 26 is not formed. The inner diameter of an inner surface 30b of the stepped part 30 for connecting the outer peripheral part 24 of the piston top face (the part 28 at which the bulb recess 26 is not formed and a bottom surface 26a of the respective bulb recesses 26) with a bottom surface 30a of the stepped part 30 over the entire periphery in the cylinder circumferential direction gradually increases from the bottom surface 30a side of the stepped part 30 to the outer peripheral part 24 side of the piston top face. <P>COPYRIGHT: (C)2013,JPO&INPIT |
