| 摘要 |
The piston lower portion (1) with gudgeon pin (18) bore secured by screws to an upper portion (2) with piston crown (3) and skirt (4) with piston ring (6) grooves. The underside (12) of the upper portion is centred on the upper face (13) of a collar (14), forming the outer boundary (44) of an annular recess (43) around a central boss (28) on the lower portion. Together with a dome-shaped space in the upper portion, it forms a cooling oil chamber (33), connected via inclined bores (34) in the upper portion to an outer chamber (35) in both protions. The upper portion (2) is an iron or steel casting, whilst the lower portion consists of pressure die-cast or hot-pressed aluminium or aluminium alloy. Oil for shaker cooling is supplied via the connecting rod (25- 38) and a central bore (29) in the boss, of which the upper end (32) defines the oil level in the cooling oil chamber, to pass via the inclined bores to the outer chamber and downward discharge ducts (39).
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