| 摘要 |
<p>PROBLEM TO BE SOLVED: To effectively prevent occurrence of fine particles by the friction of a seal member and the like, by arranging a minute clearance between the inner surface of a cylinder and the peripheral surface of a piston, arranging liquid feeding and exhausting passages communicated with the minute clearance, and making forcible flow and passing extrapure water into/through the liquid feeding and exhausting passages so as to form a liquid film in the minute clearance. SOLUTION: In a constant amount of liquid feeding pump, check valves 5a, 6b are actuated to be opened and closed by being interlocked with the reciprocating motion of a piston 4 by a driving mechanism 10, liquid sucked from a liquid suction passage 5 to the inside of a cylinder 1 is compressed at the time of retreating motion, and fed from a liquid feeding passage 6 at the time of advancing motion. At this time, in the suction stroke of the piston 4, suction liquid pressure P2 in a pressure regulating chamber 2 is equalized to leakage water pressure P3 in a liquid exhausting passage 8 by nitrogen pressureΔP applied to a liquid tank 9, therefore extrapure water and the like forming a liquid film in a minute clearance between the cylinder 1 and the piston 4, is prevented from being entrapped into the pressure regulating chamber 2. While, at the time of a discharge stroke, P1 becomes larger than P3 , thereby liquid in the pressure regulating chamber 2 is leaked to the liquid discharging passage 8 through the minute clearance, and the minute clearance is cleaned.</p> |
