PISTON, PISTON RING, PISTON PIN [SKYACTIV-G 1.3, SKYACTIV-G 1.5]SM2759793
PISTON, PISTON RING, PISTON PIN [SKYACTIV-G 1.3, SKYACTIV-G 1.5]

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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

• The high-temperature strength piston is made of aluminum alloy with excellent thermal conductivity.
• By flattening the top surface of the piston, the airflow in the cylinder before combustion is increased and high compression is achieved. (with EGR cooler)
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• The piston has a cavity on its top surface to achieve the following (without coolant control valve and with or without EGR cooler):
― Air-fuel mixture is formed near spark plug to facilitate engine warm-up
― Cooling loss is reduced by preventing flame from contacting top of piston in early stage of combustion
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• The sliding resistance and the part mass have been reduced by reducing the surface area of the piston skirt and thinning the thickness.
• 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.
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Piston ring

• A barrel-face ring for the top ring and a taper under cut ring for the second ring have been adopted.
• A three-piece oil ring consisting of a side rail and spacer have been adopted for the oil ring.
• 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.


Piston pin

• The piston is a full-floating type.