| 摘要 |
PROBLEM TO BE SOLVED: To provide a combustion chamber structure for a spark ignition engine capable of practically and effectively enhancing a compression ratio by improving knocking resistance performance. SOLUTION: The combustion chamber structure for a spark ignition engine includes two intake ports 21 and at least one exhaust port 22 which are opened sandwiching a cylinder bore axial line, and a first ignition plug 15 provided to the midsection in the cylinder bore radial direction. A second ignition plug 15a is provided between respective intake ports and to a cylinder bore peripheral edge part. A combustion chamber 14 is formed of a first combustion space 14a continuing from the periphery of the first ignition plug to the periphery of the second ignition plug and of a second combustion space 14b of the cylinder bore peripheral edge part. A small clearance part 5 which communicates with the first combustion space 14a and second combustion space 14b and keeps the clearance between a ceiling wall 11 and piston top face 4 narrower than the surrounding, is formed in a midway position from the periphery of the first ignition plug to the cylinder bore peripheral edge on the exhaust side. COPYRIGHT: (C)2007,JPO&INPIT
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