DEVICE AND METHOD FOR CHANGING MARGIN PRESSURE AS FUNCTION OF PUSH AMOUNT OF PUMP IN OPEN CIRCUIT PUMP EQUIPPED WITH LOAD DETECTION CONTROLLER

摘要

PROBLEM TO BE SOLVED: To improve control operation of an operator to operation of an apparatus such as a backhoe by fluidwise connecting a variable orifice to a load detector via a servo pressure conduit so as to change proportionally in correspondence with the fluid push amount of a pump. ;SOLUTION: A pump device 10 is provided with a variable displacement type open circuit pump 12 sucking and pressurizing hydraulic fluid from a fluid sump 14, and in the pump 12 a discharge guide pipe 20 is fluidwise connected to a fluid pressure load apparatus 22, while a load control valve 24 is provided at the discharge guide pipe 20 upstream of the apparatus 22. To the valve 24, a pressure compensation pilot valve 28 and a load detection controller 30 are connected via a load signal guide pipe 26. Downstream of the pump 12 and the controller 30, a variable orifice 87 is disposed which is proportionally changed corresponding to the level of fluid push amount of the pump 12 while being fluidwise connected to the controller 30 via a servo pressure guide pipe 70.;COPYRIGHT: (C)1999,JPO