HYDRAULIC CIRCUIT FOR TRACTOR

PURPOSE:To utilize a hydraulic pump with a small displacement and efficiently operate is by providing a main hydraulic circuit and an auxiliary hydraulic circuit, and providing a load sensing valve device feeding the operating oil of a main pump to an auxiliary hydraulic device when the main hydraulic circuit is nonoperational. CONSTITUTION:A main hydraulic circuit 1 feeding the operating oil to a main hydraulic device 7 for lifting a three-point link mechanism 6 from a main pump 4 via a main pipe 5 and an auxiliary hydraulic circuit 2 feeding the operating oil to an auxiliary hydraulic device 10 from an auxiliary pump 8 via an auxilia ry pipe 9 are provided. A load sensing valve device 3 with a spring offset pilot type three-port two-point selector valve 19 is provided, the pressure of a pilot circuit 20 is reduced when the main hydraulic device 7 is nonoperational, thus the selector valve 19 is switched to the right position, and the operating oil of both pumps 4 and 8 is merged at this switching position and fed to the auxil iary hydraulic device 10. The auxiliary pump 8 with a small displacement can be employed.