PURPOSE: To supply lubricating oil reliably into a cylinder by providing an oil reservoir in a valve plate and supplying the lubricating oil from the oil reservoir to a suction passage through a lubricating oil passage by suction vacuum pressure and dead weight so that suction resistance of the lubricating oil is reduced.

CONSTITUTION: There is provided a cylinder 5 and a piston which reciprocates on the inside face of the cylinder 5 in the horizontal direction. An oil reservoir 5a is formed on an upper face of the outside circumference of the cylinder 5, the upper face being located at a position higher than the piston. In addition, an oil reservoir hole 7a is formed in a valve plate 7 and the oil reservoir hole 7a communicates with the oil reservoir 5a through a passage 5b. A slot 14 is formed which communicates from the oil reservoir hole 7a to a suction passage 7b thereby to supply lubricating oil through the slot 14 by dead weight and vacuum pressure in the suction passage 7b.