Side rail

#This disclosure relates to a side rail that is combined with an annular space expander and constitutes, together with the space expander, a multi-piece oil ring used in an internal combustion engine.

#In addition to a compression ring configured to seal combustion gas, an oil ring configured to control oil on a cylinder inner surface is installed in a piston of a reciprocating engine (a reciprocated internal combustion engine). As such an oil ring, a multi-piece oil ring formed by combining one side rail or a pair of side rails with an annular space expander has been popularly used.

#The side rail used for a multi-piece oil ring is formed in a split ring shape with an opening. When the side rail is pressed by the space expander such that the diameter of the side rail extends, the outer peripheral surface thereof comes in contact with the cylinder inner surface with a predetermined contact pressure (a surface pressure). When the engine operates and the piston reciprocates, the outer peripheral surface of the side rail slides on the cylinder inner surface, forming an oil film with an appropriate thickness on the cylinder inner surface and scraping off excess oil adhered to the cylinder inner surface toward a crankcase to prevent the oil from climbing up.

#In the accompanying drawings:

#FIG. 1 is a plan view of a multi-piece oil ring including a side rail according to an embodiment of this disclosure;

#FIG. 2 is a longitudinal cross-sectional view of the multi-piece oil ring illustrated in FIG. 1 in use;

#This disclosure will be illustrated in more detail below with reference to drawings.

#As illustrated in FIG. 1, a side rail 1 according to an embodiment of this disclosure forms a multi-piece oil ring (an oil control ring) 3 along with a space expander 2. As illustrated, the multi-piece oil ring 3 is a 3-piece type including a pair of side rails 1 provided on both sides of the space expander 2 in the axial direction. When used, the multi-piece oil ring 3 is mounted in a ring groove 4a formed in an outer peripheral surface of a piston 4 of a reciprocating internal combustion engine such as a gasoline engine, as illustrated in FIG. 2.

#The multi-piece oil ring 3 may be a two-piece type, which is a combination of only one side rail 1 and the space expander 2.