Electronic torque and pressure control for load sensing pumps

Abstract

An electric torque and pressure control for load sensing pumps includes a variable open circuit pump with a swash plate angle sensor. The pump is connected in line with a pressure compensated load sensing control having an electrically variable pressure relief valve and orifice. Connected to the circuit is an engine speed sensor, a user input device, and a micro-controller. The micro-controller has software that controls a pressure relief setting of the electrically variable pressure relief valve in the pressure sensing control based upon signals from the swash plate sensor and the engine speed sensor and inputs from the user input device.

What is claimed is: 
     
         1 . A control system for a load sensing circuit, comprising:
 a variable open circuit pump with a swash plate angle sensor;   a pressure compensated load sensing control having an electrically variable pressure relief valve and orifice;   an engine having a maximum torque output capability delivered to the variable open circuit pump;   an engine speed sensor;   a user input device;   a micro-controller having software that controls a pressure relief setting of the electrically variable pressure relief valve in the pressure compensated load sensing control; and   wherein the software continuously calculates a maximum pressure that would result in a torque level delivered by the engine to the variable open circuit pump at a sensed displacement of a swashplate and sends a current to the electrically variable pressure relief valve to produce the calculated maximum pressure.   
     
     
         2 . The system of  claim 1  wherein the software calculates the maximum pressure required that would result in an operative torque level produced at variable swash plate displacements. 
     
     
         3 . The system of  claim 1  further comprising a pressured transducer that monitors a pressure required for a lift function. 
     
     
         4 . The system of  claim 1  further comprising a dump valve to reduce a set point of a pump engine cranking. 
     
     
         5 . The system of  claim 1  wherein the software adjusts a first function output by a first command when a second command is received to output a second function and a torque set point of the pump does not allow a load to be lifted until pump displacement is decreased to a point that will have a high enough pressure to lift the load on the second function. 
     
     
         6 . The system of  claim 2  wherein the operative torque level is where and when an input torque to the pump does not exceed a torque output capability of the engine and does not result in a stalled engine. 
     
     
         7 . The system of  claim 1  wherein a control for the load sensing pump changes a maximum pressure point automatically without manual intervention. 
     
     
         8 . A control system for a load sensing circuit, comprising:
 a variable open circuit pump with a swash plate angle sensor;   a pressure compensated load sensing control having an electrically variable pressure relief valve and orifice;   an engine having a maximum torque capability delivered to the variable open circuit pump;   an engine speed sensor;   a user input device;   a micro-controller having software that controls a pressure relief setting of the electrically variable pressure relief valve in the pressure compensated load sensing control; and   the software is configured to calculate a maximum pressure based on signals received from the swash plate angle sensor, wherein the maximum pressure is equal to a maximum torque level the engine can produce without stalling at a pressure;   the software is configured to send a current to the electrically variable pressure relief valve to produce the maximum pressure while maintaining a torque level required by an operator's command that is no higher than the maximum torque level.   
     
     
         9 . The system of  claim 8  wherein the software is configured to send the current to the electrically variable pressure relief valve while the operator's command is maintained. 
     
     
         10 . The system of  claim 8  wherein the software is configured to send a current to the electrically variable pressure relief valve to achieve the calculated maximum pressure.