Excavator Hydraulic Pump Control for Engine Torque Limiting
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Solution Overview
Problem
Existing shovels with hydraulic pumps face challenges in appropriately controlling the geometric displacements of multiple variable displacement hydraulic pumps, leading to inefficiencies and potential overload on the engine.
Innovation Solution
The implementation of electrically controlled variable displacement hydraulic pumps, controlled by a processing circuitry that calculates and adjusts the geometric displacements based on discharge pressures to prevent exceeding the engine's rated torque, using a controller to manage the hydraulic system efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If hydraulic type regulators are used to control geometric displacement of hydraulic pumps, then the control system is simple, but the geometric displacement cannot be appropriately controlled leading to potential engine overload
Solution Approach 1:
The patent replaces the mechanical hydraulic regulator system with an electrically controlled system. The controller receives signals from operation amount detection means and torque detection means, then electrically controls the variable displacement hydraulic pumps to adjust their geometric displacement. This substitution of mechanical control with electrical control enables more precise and reliable control of pump displacement while preventing engine overload.
2Productivity
If multiple variable displacement hydraulic pumps are used to increase productivity, then the shovel can handle multiple operations simultaneously, but the engine may be overloaded if geometric displacements are not properly controlled
Solution Approach 1:
The patent implements a feedback control system where torque detection means continuously monitors the engine's actual torque output. The controller receives this torque information along with operation amount signals from multiple operating levers. Based on the feedback from torque detection, the controller adjusts the geometric displacement of each variable displacement hydraulic pump to ensure the total torque demand does not exceed engine capacity, enabling multiple operations without overload.
Solution Approach 2:
The patent employs dynamically adjustable geometric displacement for each hydraulic pump based on real-time operating conditions. The controller continuously modifies the displacement of each pump according to the current operation demands and engine torque availability, allowing the system to adaptively balance the torque load across multiple pumps while maintaining high productivity.
3Ease of operation
If geometric displacement is controlled based on operating lever amount only, then the control is simple, but the engine torque limit is not considered leading to potential overload
Solution Approach 1:
The patent merges multiple control inputs into a unified control system. The controller integrates signals from operation amount detection means (operating lever positions) with torque detection means (engine torque output). By combining these two inputs, the system maintains ease of operation through lever-based control while simultaneously managing engine torque limits to prevent overload, achieving both simplicity and power management.
Data Source
AI summary
A shovel includes a lower traveling structure, an upper swing structure swingably mounted on the lower traveling structure, an engine mounted on the upper swing structure, a first hydraulic pump and a second hydraulic pump each configured to be driven by the engine, a first regulator configured to control the first geometric displacement of the first hydraulic pump, a second regulator configured to control the second geometric displacement of the second hydraulic pump, and processing circuitry configured to electrically control the first and second regulators. Each of the first and second hydraulic pumps is an electrically controlled variable displacement hydraulic pump. The processing circuitry is configured to calculate the limit value of the first and second geometric displacements based on the respective discharge pressures of the first and second hydraulic pumps, and to control each of the first and second geometric displacements based on the calculated limit value.