MAKEUP CHECK VALVE DEVICE AND HYDRAULIC CIRCUIT

摘要

PROBLEM TO BE SOLVED: To reduce generation of an excessive energy loss and heating by preventing generation of a vacuum by an insufficient replenishing flow rate. SOLUTION: A hydraulic fluid supply circuit 26 is arranged for supplying a hydraulic fluid supplied by a pump 22 from a tank 21 to a hydraulic motor 24 for turning and the other hydraulic actuator 25 by controlling the direction by a control valve 23. A makeup circuit 37 is arranged for replenishing oil to a part 24a having the possibility of generating the vacuum when switching to a neutral position of the control valve 23 from between the control valve 23 and a makeup check valve device 27 of one return circuit 28 for returning return oil discharged from the hydraulic motor 24 for turning to the tank 21. The makeup check valve device 27 has a back pressure check valve 41, and a backflow check valve 24 for communicating only in the upstream side direction of the back pressure check valve 41 from the downstream side of the back pressure check valve 41. A return passage 33 of the one return circuit 28 is communicated with a return passage 34 of the other return circuit 29.