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 functions.

―  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 pin 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 skirt 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 worsening 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.

Natural Sound Smoother (with Natural Sound Smoother)

•  A natural sound smoother part has been integrated with the piston pin.

•  Vibrational energy of the piston and the connecting rod is absorbed and decreased by vibration of the weight on both sides of the natural sound smoother to suppress diesel knocking noise.

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