Hydraulic System Engine Speed Control Strategy
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Solution Overview
Problem
Existing hydraulic systems for work machines face challenges in preventing engine stall and maintaining optimal engine speed under varying loads, as they rely on conventional control methods that may not effectively manage the dropping engine speed, leading to operator discomfort and potential engine stalling.
Innovation Solution
A hydraulic system that includes a prime mover, a hydraulic pump, an operation valve, and a memory with stored control characteristics, where a controller adjusts the pressure based on specific control characteristics to manage engine speed, switching between different control characteristics based on the dropping amount of actual engine speed from the target speed to prevent engine stall and maintain optimal operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional pressure control is used to prevent engine stall, then engine speed stability is improved, but operator feedback and comfort deteriorate due to insufficient response to load changes
Solution Approach 1:
The system dynamically switches between no-load control characteristics and drop control characteristics based on the actual engine speed and load conditions. This dynamic adaptation allows the pressure control valve to provide appropriate pressure adjustments that maintain engine speed stability while improving operator feedback during load changes.
Solution Approach 2:
The control device changes the control parameters by selecting different control characteristics (no-load vs. drop characteristics) based on the engine operating state. This parameter change enables the system to optimize both engine speed stability and operator feedback by adjusting pressure control behavior according to actual load conditions.
2Reliability
If rapid pressure reduction is applied to prevent engine stall, then engine speed dropping is reduced, but operator comfort deteriorates due to abrupt pressure changes
Solution Approach 1:
The system dynamically adjusts the pressure control strategy by switching between different control characteristics. During moderate load changes, it uses no-load characteristics for smooth operation. During significant load drops, it switches to drop characteristics that rapidly reduce pressure to prevent stall, thereby adapting to different operational requirements.
Solution Approach 2:
The control device continuously monitors the actual engine speed and compares it with the target speed to determine the speed drop amount. Based on this feedback, it selectively applies different control characteristics, ensuring that rapid pressure reduction is only applied when necessary to prevent stall while maintaining operator comfort during normal operations.
3Device complexity
If single control characteristic is used for all operating conditions, then device complexity is reduced, but control precision deteriorates under varying load conditions
Solution Approach 1:
The control characteristics are segmented into distinct types: no-load control characteristics for normal operations and drop control characteristics for load reduction scenarios. This segmentation allows each control characteristic to be optimized for its specific operating condition, improving overall control precision without requiring an overly complex unified control system.
Solution Approach 2:
The control device is designed with multi-functionality by incorporating multiple control characteristics within a single device. It can selectively apply different control strategies based on operating conditions, achieving high control precision across varying load conditions while maintaining relatively simple device structure through unified control logic.
Data Source
AI summary
A hydraulic system for a work machine includes a prime mover, a setup member, a hydraulic pump, an operation valve, a hydraulic device, and a memory. The memory stores first control characteristics indicating relations between the first pressure and an actual revolution speed of the prime mover, and stores a second control characteristic indicating a relation between the first pressure and the actual revolution speed of the prime mover. The hydraulic system includes a controller to set the first pressure based on the second control characteristic when a dropping amount of the actual revolution speed from the target revolution speed is less than a threshold value and to set the first pressure based on the first control characteristics determined corresponding to the target revolution speed when the dropping amount of the actual revolution speed from the target revolution speed is the threshold value or more.