Hydraulic Excavator Engine Torque Control for Transient Load Management
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Solution Overview
Problem
Hydraulic excavators face challenges in managing sharp changes in hydraulic pump load, leading to inefficient fuel consumption and increased emissions of particulate matter (PM) and nitrogen oxides (NOx) due to rapid changes in engine speed and torque, which existing hybrid configurations struggle to optimize effectively.
Innovation Solution
A hybrid-driven hydraulic work machine with an electric assist motor and engine, featuring an engine speed and torque setter that adjusts the target rotational speed and torque to follow a predetermined route, ensuring favorable combustion states during transient operations, while limiting rate changes to maintain fuel efficiency and reduce pollutant emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the engine speed and torque are allowed to change rapidly to respond to hydraulic pump load changes, then the productivity and responsiveness of the hydraulic work machine is improved, but the fuel efficiency deteriorates and emissions of PM and NOx increase
Solution Approach 1:
The engine speed and torque setter pre-calculates target values that follow a predetermined route before transient changes occur, allowing the engine to transition smoothly through favorable combustion states. This preliminary planning of the operating route prevents the engine from entering fuel-inefficient regions while maintaining productivity.
Solution Approach 2:
The system dynamically adjusts engine speed and torque targets along a predetermined route that changes with operating conditions. The engine operating point is kept moving along an optimal trajectory rather than making abrupt jumps, maintaining fuel efficiency while responding to load changes.
2Productivity
If the engine speed and torque are allowed to change rapidly to respond to hydraulic pump load changes, then the productivity and responsiveness of the hydraulic work machine is improved, but the emissions of PM and NOx increase
Solution Approach 1:
The engine speed and torque setter pre-calculates target values that follow a predetermined route before transient changes occur, allowing the engine to transition smoothly through favorable combustion states. This preliminary planning of the operating route prevents the engine from entering high-emission regions while maintaining productivity.
Solution Approach 2:
The system dynamically adjusts engine speed and torque targets along a predetermined route that changes with operating conditions. The engine operating point is kept moving along an optimal trajectory rather than making abrupt jumps, maintaining low emissions while responding to load changes.
3Object-generated harmful factors
If gas emissions aftertreatment devices such as DPF and urea SCR system are added to meet emissions regulations, then the emissions of PM and NOx are reduced, but the device complexity and cost increase
Solution Approach 1:
The invention converts the potential harm of rapid engine transients (which cause high emissions) into a benefit by using the hybrid powertrain to enable smooth, controlled transitions. The electric assist motor allows the engine to operate in favorable combustion states during transients, turning a emission-problematic situation into a low-emission operation without needing complex aftertreatment devices.
Solution Approach 2:
The invention replaces the need for complex mechanical aftertreatment devices (DPF, urea SCR system) with a control-based solution using the hybrid powertrain. Instead of mechanically filtering or chemically treating exhaust gases, the system prevents harmful emissions from forming in the first place by controlling engine operating conditions through coordinated engine-motor operation.
4Use of energy by moving object
If a compact engine generating rated output power equivalent to average horsepower needed is used, then the fuel economy is improved, but the ability to handle abrupt hydraulic load increases deteriorates
Solution Approach 1:
The invention merges the compact engine with an electric assist motor to create a hybrid powertrain. The compact engine provides base power for fuel economy, while the electric assist motor supplements power during abrupt load increases, combining the advantages of both power sources to handle both fuel efficiency and peak power demands.
Solution Approach 2:
The hybrid powertrain dynamically balances power contribution between the compact engine and electric assist motor based on instantaneous load requirements. During steady-state operation, the compact engine operates efficiently; during abrupt load increases, the electric motor dynamically supplements power, allowing the use of a smaller, more fuel-efficient engine without sacrificing peak power capability.
Data Source
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AI summary
This invention is a hydraulic work machine having an electric assist motor coupled to an engine and a hydraulic pump, in the hydraulic work machine of which, a rotational speed and torque of the engine are controlled so that an operating point of the engine moves along a predetermined route for yielding a combustion state of the engine under a transient state that the engine changes in speed and torque. A target speed and torque of the engine 7 are set so that the rotational speed and torque of the engine 7 will change along a predetermined route F in a running region of the engine, respective rates of change of the target rotational speed and torque of the engine 7 are limited, and the engine 7 is controlled to yield the target engine speed. In addition, torque of the assist motor 10 is controlled to yield the target torque of the engine.