HYDRAULIC PUMP DRIVING SYSTEM CONTROLLER

PURPOSE:To change it to an input torque limited value commensurate to working details or working surroundings, by installing a desired displacement setting device, which sets the desired displacement being approximate to a constant torque characteristic of a discharge controlling device according to a signal out of a designating device, in a controlling part. CONSTITUTION:A functional relationship being approximate to plural constant torque characteristics between signal values P1 and P2 of pressue signals 11a and 12a being varied according to size of a signal 7a (a signal value S) designating a maximum value of the input torque of a variable displacement pump and regulator desired displacements XL1 and XL2 is set up at 24 and 25. Deviations DELTAX1 and DELTAX2 between these regulator displacements and tilting values X1 and X2 are amplified at both amplifiers 27 and 28, outputting operating signals 13b and 13c. A regulator is controlled so as to cause these deviations DELTAX1 and DELTAX2 to be adjusted to zero, thus the discharge capacity of a hydraulic pump is controlled.