PISTON, PISTON RING, PISTON PIN [SKYACTIV-D 2.2]

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Purpose, Function

Piston

•  The piston in the cylinder of the cylinder block moves reciprocally by the pressure received when the air-fuel mixture combusts.

Piston ring

•  The piston ring consists of the compression ring (top ring, second ring) and the oil ring, and has the following function.

―  The compression ring prevents leakage of pressure in the cylinder from the piston circumference.

―  The oil ring clears off extra engine oil adhered to the cylinder wall.

•  The piston ring transmits piston heat to the cylinder wall to cool the piston.

Piston pin

•  The reciprocating movement of the piston is transmitted to the connecting rod by the connection of the piston pin to connecting rod.

Construction

Piston

•  An offset piston has been adopted in which the center of the piston has been offset from the piston center. As a result, piston slap is suppressed.

•  Striation processing is employed on the piston skirt. As a result, engine oil is retained in the striation grooves so that an oil film is maintained between the piston skirt and the cylinder.

•  A graphite coating is applied to the piston skirt. As a result, sliding resistance is reduced.

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•  The sliding resistance and part mass have been reduced by decreasing the surface area of the piston and the thickness, and reducing the piston pin diameter.

•  With the adoption of a wide diameter combustion chamber for the piston, high engine output, low emission, and low fuel consumption have been realized.

•  A cooled ring carrier has been adopted to the cooling grooves of the piston corresponding to the wide diameter combustion chamber. As a result, the temperature around the combustion chamber decreases efficiently.

•  An offset crank has been adopted in which the center of the cylinder bore and the center of the crankshaft axle have been offset. As a result, the sliding resistance has been reduced by decreasing the piston-side force at the expansion stroke.

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Piston ring

•  A barrel-face ring for the top ring and a taper-face ring for the second ring have been adopted.

•  A two-piece oil ring for the oil ring have been adopted.

•  Tracking capability to the cylinder wall has been improved by thinning down the piston ring. As a result, a low-tension piston ring has been implemented without increasing the engine oil consumption, and the sliding resistance has been reduced during reciprocating movement.

•  The sliding surfaces of the top ring and oil ring are subjected to PVD treatment to reduce the sliding resistance and improve engine oil consumption.

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Piston pin

•  The piston is a full-floating type.