| 摘要 |
PURPOSE:To improve the fuel consumption rate by machining a petal type cavity into a twisted petal type and making a part of the side wall face a reentrant shape and the other pert an open shape. CONSTITUTION:Concentric circles having a center O and radiuses r2, r3 are drawn at the center of the top face of a piston 5, and a straight line is drawn passing a point D1 uniformly dividing the small circle with the radius r3 into four at an angle theta in the opposite direction to the swirl S. The axis of a milling cutter with a diameter of 2r1 is made parallel with the axis of a cavity 6, and the bottom center of the cutter is moved for cutting along a cubic curve D1, E'1 connecting the point D1 and the foot E'1 of a vertical line from the intersection E1 with a large circle with the radius r2 to the bottom of the cavity 6 to form the petal-shaped wall of the cavity 6. In addition, similar operations are performed for other equipartition points of the large circle, and the twisted petal type cavity 6 is formed as a whole. The inclination of the depth wall face is made a reentrant shape at the point P1 and a vertical wall face at points R1, R2, the upper section side wall face is made an open type, thus the fuel consumption rate can be improved.
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