HYDRAULIC CONTROL DEVICE FOR DUMP TRUCK

摘要

PROBLEM TO BE SOLVED: To provide a hydraulic control device allowing the use of a main control valve easy to manufacture without requiring high precision and making a change-over means small for improving the comfortableness of a driver's seat. SOLUTION: In a dump truck with a cargo box tiltingly mounted on a body, supply side oil passages 441, 443 communicated with a discharge port of a hydraulic pump 5 are communicated with a hydraulic cylinder 3 via a main change-over valve 41 and a check valve 45 and a return side oil passage 444 communicated with the hydraulic cylinder 3 is communicated with an oil tank 6 via a change-over check valve 42 so that the main change-over valve 41 is controlled to be changed over via the air cylinder 43 with the operation of the change-over means 47 provided on the driver's seat in the vehicle and the change-over check valve 42 is controlled to be changed over with the change-over operation of the main change-over valve 41. A spool 41a of the main control valve 41 is mechanically linked to the change-over check valve 42 so that the change-over check valve 42 is controlled to be changed over with the movement of the spool 41a.