AUXILIARY PUMP

摘要

PROBLEM TO BE SOLVED: To suppress power loss to a small degree by putting an auxiliary pump in pumping action only when the delivery pressure of a main pump is small. SOLUTION: A by-pass passage 46 is provided between an intake passage and a discharge passage. A spool chamber 55 having an intake port 56 and a discharge port 57 is provided at an intermediate part of the by-pass passage 46. A spool 59 for opening/closing the discharge port 57 on the outer peripheral surface is slidably accommodated in the spool chamber 55. An intake pressure lead-in chamber 70 normally communicated with the intake port 56 is formed on one end face side of the spool 59 in the spool chamber 55. An atmospheric pressure lead-in chamber 71 is formed on the other end face side of the spool 59 in the spool chamber 55. The atmospheric pressure lead-in chamber 71 is provided with a spring 72 energizing the spool 59 in the direction of closing the discharge port 57 against the pressure of the intake pressure lead-in chamber 70. When the pressure of the intake passage 44 becomes the set pressure or more, the spool 59 opens the discharge port 57 against the force of the spring 72.