Hybrid Work Machine Engine Speed Control for Rapid Battery Charging
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Solution Overview
Problem
Hybrid construction machines face issues with output power reduction during rapid battery charging, which can disrupt high-load torque operations like excavation, due to insufficient battery charge levels.
Innovation Solution
Implementing a hybrid system with a miniaturized engine and engine revolution speed decreasing control to reduce engine torque demand, allowing for power assistance and rapid battery charging while maintaining hydraulic pump output power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If torque reducing control is performed on the hydraulic pump to generate surplus torque for the engine during rapid charging, then the battery can be rapidly charged, but the output power of the hydraulic pump decreases
Solution Approach 1:
The invention changes the engine revolution speed parameter to a lower value (below the maximum horsepower revolution speed) to alter the engine's load characteristic curve. This parameter change enables the engine to operate in a region where torque increases as revolution speed decreases, allowing surplus torque generation for rapid battery charging while maintaining adequate hydraulic pump output power through the modified operating point
2Object-generated harmful factors
If the engine is miniaturized to improve fuel consumption and exhaust characteristics, then fuel efficiency and emissions are improved, but the engine output torque becomes insufficient for high-load operations
Solution Approach 1:
The invention introduces a generator-motor as an intermediary power source that couples the engine and hydraulic pump. The generator-motor acts as a torque amplifier by receiving electrical energy from the battery and converting it to mechanical torque at the engine output shaft, thereby compensating for the insufficient torque of the miniaturized engine during high-load operations without requiring a larger engine
Solution Approach 2:
The generator-motor serves multiple functions: it acts as a motor to amplify engine torque during high-load work, as a generator to charge the battery during surplus power conditions, and as a means to enable rapid charging by controlling engine operating points. This multi-functionality allows the miniaturized engine to meet both emission reduction goals and torque requirements
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach improves fuel consumption, exhaust characteristics, and noise reduction while enabling rapid battery charging without output power decreases, ensuring continuous operation during charging.
Implementation Method 1
the generator-motor as a generator, thereby rapidly charging the battery
Implementation Method 2
the electric power of a battery is used to operate the generator-motor as a motor, thereby compensating for the shortage of the engine output torque
Data Source
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AI summary
Provided is a hybrid work machine in which a hybrid system and a downsized engine are used. The hybrid work machine improves fuel consumption, improves exhaust characteristics, and reduces noise. The hybrid work machine also performs rapid charging of a power storage device while preventing decreases in the output power of a hydraulic pump if the charge amount of the power storage device is extremely insufficient. A vehicle body controller 46 performs engine revolution speed decreasing control in which, if the charge rate of a battery 33 becomes equal to or less than a minimum charge rate, the target revolution speed of an engine 11 is reduced. The vehicle body controller also performs torque reducing control in which the maximum absorption torque of a hydraulic pump 21 is reduced. By performing these control operations, the vehicle body controller coercively generates surplus torque for the engine and operates a generator-motor 31 as a generator with the use of the surplus torque, thereby rapidly charging the battery.