Excavator Hydraulic Pump Displacement Control Under Engine Torque Limits
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Solution Overview
Problem
Existing shovels with hydraulic pumps lack appropriate control over geometric displacement, leading to inefficient torque management and potential engine overload.
Innovation Solution
The implementation of electrically controlled variable displacement hydraulic pumps with regulators and a control device that calculates and adjusts the geometric displacement based on discharge pressures to prevent engine torque overload, allowing for efficient torque allocation between pumps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If hydraulic type regulators are used to control the geometric displacement of hydraulic pumps, then the control system is simple, but the geometric displacement cannot be appropriately controlled leading to inefficient torque management
Solution Approach 1:
The patent replaces hydraulic type regulators with electrically controlled variable displacement hydraulic pumps. The control device uses electrical signals to control the geometric displacement of pumps, substituting mechanical/hydraulic control with electrical control for more precise adjustment. This allows appropriate control of geometric displacement while maintaining reasonable system complexity through integrated electrical control circuits.
2Productivity
If the geometric displacement of multiple hydraulic pumps is controlled to maximize output, then the productivity increases, but the engine torque may be exceeded causing engine speed decrease
Solution Approach 1:
The control device calculates the sum of absorbed torques of multiple hydraulic pumps and compares it with the engine's rated torque. When the sum exceeds the rated torque, the control device adjusts the geometric displacement of pumps to reduce absorbed torque back within limits. This feedback mechanism ensures engine torque compliance while maximizing hydraulic output within available engine power.
Solution Approach 2:
The system dynamically adjusts the geometric displacement of hydraulic pumps based on real-time operating conditions and engine torque availability. The control device continuously monitors and modifies pump displacement to optimize the balance between productivity and engine protection, allowing flexible adaptation to varying load conditions.
3Power
If the geometric displacement of hydraulic pumps is increased to meet high demand, then the power output increases, but the torque absorption may exceed engine capacity
Solution Approach 1:
The control device changes the geometric displacement parameter of hydraulic pumps to optimize the balance between power output and torque consumption. By adjusting displacement parameters based on engine torque limits and operational demand, the system achieves maximum effective power output without exceeding engine torque capacity, preventing energy waste from overload protection.
Data Source
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AI summary
A shovel (100) includes a lower traveling structure (1), an upper swing structure (3), an engine (11), an electrically controlled left main pump (14L), an electrically controlled right main pump (14R), a left regulator (13L) that controls the geometric displacement of the left main pump (14L), a right regulator (13R) that controls the geometric displacement of the right main pump (14R), and a controller (30) that electrically controls the left regulator (13L) and the right regulator (13R). The controller (30) calculates the limit value of the respective geometric displacements of the left main pump (14L) and the right main pump (14R) based on discharge pressures with respect to the left main pump (14L) and the right main pump (14R), and controls the respective geometric displacements of the left main pump (14L) and the right main pump (14R) based on the calculated limit value.