Hybrid Power Transmission for Forest Machines
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Solution Overview
Problem
Hydrostatic power transmission in forest machines suffers from poor efficiency, especially at high driving speeds and varying load conditions, and replacing it with electrical power transmission does not significantly improve overall efficiency or offer advantages in the forest machine environment, requiring high-capacity power transmission systems and uneven loading of the primary power source.
Innovation Solution
Converting part of the primary power source's effect into electric energy, which is stored and reused to generate hydraulic power via a hydraulic pump, allowing for optimized power distribution and reduced primary power source size, enabling better loading and fuel economy, and decentralizing components for reduced noise and vibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If hydrostatic power transmission is used in forest machines, then flexible mounting and manoeuvrability are improved, but efficiency deteriorates particularly at high driving speeds
Solution Approach 1:
The power transmission system is segmented into multiple independent hydraulic circuits, each serving specific functions (driving, steering, work equipment). This allows optimization of each circuit for its specific purpose rather than using a single hydrostatic system for all functions, thereby improving overall efficiency while maintaining flexibility.
Solution Approach 2:
The system employs dynamically adjustable hydraulic components with variable displacement pumps and motors that can adapt their operating characteristics in real-time based on load conditions and speed requirements, optimizing efficiency across different operating ranges while maintaining manoeuvrability.
2Loss of energy
If electrical power transmission is used to replace hydrostatic power transmission, then efficiency is improved, but device complexity increases due to requiring high-capacity power transmission systems
Solution Approach 1:
The patent introduces an intermediary energy storage system (battery or capacitor) between the prime mover and the hydraulic components. This intermediary allows the prime mover to operate at optimal efficiency points while the stored energy handles peak power demands, simplifying the overall system architecture compared to direct electrical transmission while maintaining high efficiency.
Solution Approach 2:
The system uses periodic charging of the energy storage device during low-power phases and discharging during high-power phases, creating a rhythmic operation pattern that allows the prime mover to operate efficiently while meeting variable power demands without requiring a constantly oversized power transmission system.
3Power
If the primary power source is dimensioned for maximum power requirements, then power availability is improved, but loading becomes uneven and fuel economy deteriorates
Solution Approach 1:
The system performs preliminary action by charging the energy storage device during periods when power demand is low, preparing energy in advance for subsequent high-power operations. This allows the prime mover to operate continuously at or near its optimal loading point, improving fuel economy while ensuring power availability when needed.
Solution Approach 2:
The system changes the operating parameters of the power transmission by introducing variable displacement hydraulic components and energy storage, allowing the prime mover to operate at constant optimal parameters while the hydraulic system and energy storage handle the variability in power demand, thus improving fuel economy without sacrificing power availability.
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 solution enhances the total efficiency of forest machines, allows for smaller and more optimally dimensioned power sources, reduces fuel consumption, and improves structural and operational efficiency by enabling better power distribution and placement of components, while minimizing noise and vibration.
Implementation Method 1
hydrostatic power transmission, typically composed of a hydraulic pump and a hydraulic engine
Implementation Method 2
converting part of the primary power source's effect into electric energy
Implementation Method 3
hydrostatic power transmission, typically composed of a hydraulic pump and a hydraulic engine
Data Source
Figure 1~2
Figure 3
AI summary
A method and an arrangement in power transmission of a forest machine (1), the forest machine comprising a primary power source (5) for generating power required for moving and controlling the forest machine and/or actuators (6, 7) therein. In the present method and arrangement, at least part of the power generated by the primary power source (5) is converted into electric energy by means of a generator arrangement (8). This electric energy can be stored at least partly in an electricity storage means (9), from which part thereof can be used, when required, for generating pressure medium- transmitted power for implementing a pressure medium-transmitted function of the forest machine (1) or at least one actuator (6, 7) therein.