| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a charging pump circuit capable of constantly and appropriately maintaining an hydraulic oil amount in a closed circuit. <P>SOLUTION: The charging pump circuit of the closed circuit is equipped with the closed circuit 21 capable of driving a hydraulic motor 4 by hydraulic oil from a first hydraulic pump P1, a second hydraulic pump P2 for replenishing the hydraulic oil to the closed circuit 21 according to leakage of the hydraulic oil from the closed circuit 21, and a third hydraulic pump P3 for replenishing an insufficient amount of hydraulic oil replenishment by the second hydraulic pump P2, and is constituted so that when at least the second hydraulic pump P2 does not follow to replenish the hydraulic oil to the closed circuit 21, the third hydraulic pump P3 supplies the hydraulic oil to the closed circuit 21. According to this structure, even when the leakage amount of the hydraulic oil from the hydraulic motor 4 exceeds the discharge flow rate of the second hydraulic pump P2 and the leakage amount cannot be fully replenished by the discharge flow rate from the hydraulic pump P2, the leakage amount can be positively replenished by supply of the hydraulic oil from the third hydraulic pump P3 to the closed circuit 21 and an appropriate output characteristic of the hydraulic motor 4 can be secured. <P>COPYRIGHT: (C)2009,JPO&INPIT |
