PURPOSE: To circulate and feed clear oil via filters in a pump, described at the heading, which includes two exhaust valves and discharges suction air together with oil mist by guiding discharge gas of the exhaust valves to an oil deposition part at the bottom of an oil box without directly discharging the gas thereof ito discharge chamber so as to deposit water and deteriorated oil therein.

CONSTITUTION: Conduits 11 for guiding discharge gas of primary and secondary exhaust valves 1 and 2 communicate with a deposition part 10 which is disposed at the bottom of an oil box 3 and which is separated by means of a filter 9. A cover 13 is mounted to a cam rotor 8 to feed oil for the rotor through a filter 12. Discharge gas of the primary and secondary exhaust valves 1, 2 is thereby guided throughout to the deposition part 10 without being directly discharged into a discharge chamger 4. Since water, deteriorated oil and so on are deposited therein, clear oil may be circulatively supplied after passing through the filters 9, 12. And further, since oil 5 is exclusively stirred by the cam rotor 8 within the cover 13, the oil may be prevented from being deteriorated due to the stirring motion.