Hydraulic Pump Torque-Rate Control to Prevent Engine Lugging
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Solution Overview
Problem
Existing construction machines with hydraulic drive systems experience engine lugging down due to rapid increases in demanded torque from high-speed operation of the control lever, leading to engine speed fluctuations, especially in hydraulic closed circuits without restrictor elements.
Innovation Solution
A construction machine equipped with a variable displacement hydraulic pump, pressure sensors, and a controller that estimates demanded torque based on actuator velocity and pressure, limits velocity to manage torque change rates, and adjusts delivery flow rates to prevent engine lugging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the control lever is operated at high speed to increase actuator velocity, then productivity is improved, but engine lugging down occurs due to rapid torque increase
Solution Approach 1:
The controller predicts future demanded torque based on current operation state and actuator characteristics before the actual torque demand occurs. This preliminary prediction allows the system to prepare and adjust engine output in advance, preventing engine lugging down when the operator rapidly moves the control lever.
Solution Approach 2:
The system dynamically adjusts the commanded torque to the engine based on real-time operation conditions, including control lever speed, predicted torque demand, and engine response characteristics. This dynamic control optimizes the balance between maintaining high actuator velocity for productivity and preventing engine instability.
2Loss of energy
If restrictor elements are removed from the hydraulic circuit to reduce fuel consumption, then energy efficiency is improved, but engine lugging down becomes more noticeable due to direct load transmission
Solution Approach 1:
The controller continuously monitors actuator velocity, demanded torque, and engine response, using this feedback to predict future torque demands and adjust engine commanded torque accordingly. This closed-loop control compensates for the direct load transmission in the restrictor-less hydraulic circuit, preventing engine lugging down while maintaining energy efficiency.
Solution Approach 2:
By predicting torque demand based on current operation state and hydraulic circuit characteristics, the system prepares the engine output in advance, allowing smooth torque transitions without the buffering effect of restrictor elements, thereby maintaining engine stability in the energy-efficient restrictor-less configuration.
3Productivity
If the hydraulic pump delivers high flow rate to meet rapid actuator velocity demand, then productivity is improved, but demanded torque increases sharply causing engine lugging
Solution Approach 1:
The controller predicts future torque demand based on current actuator velocity, control lever operation speed, and hydraulic circuit characteristics. This prediction allows the system to gradually increase the commanded torque to the engine before the peak demand occurs, matching the engine's torque response characteristics and preventing lugging while still achieving high actuator velocity.
Solution Approach 2:
The system dynamically optimizes the commanded torque profile based on real-time operation conditions, adjusting the rate of torque increase to match both the productivity requirements (high actuator velocity) and the engine's torque response capabilities, thereby preventing engine lugging during high-demand operations.
Data Source
AI summary
An object of the present invention is to provide a construction machine capable of suppressing lugging down of an engine irrespective of contents of operation of an operator and the load state of a hydraulic actuator. A controller 50 includes: a demanded torque estimating section 50c configured to estimate demanded torque as torque demanded from an engine 9 by the first hydraulic pump on the basis of a demanded velocity of a first hydraulic actuator 1 and a load pressure on the first hydraulic actuator; a demanded velocity limiting section 50d configured to, in a case in which a demanded torque change rate as a change rate of the demanded torque exceeds a predetermined change rate, limit the demanded velocity such that the demanded torque change rate becomes equal to or lower than the predetermined change rate; and a command calculating section 50e configured to calculate a delivery flow rate of the first hydraulic pump on the basis of the demanded velocity of the first hydraulic actuator, the demanded velocity being limited by the demanded velocity limiting section.