Variable Displacement Hydraulic Pump for Stable Cycle Time Control
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Solution Overview
Problem
Conventional hydraulic systems in power machines rely on constant displacement pumps, leading to sub-optimal performance and increased wear due to varying hydraulic flow rates with engine speed, affecting cycle times and stability.
Innovation Solution
Implementing a cycle time control system that adjusts hydraulic flow rates for a hydraulic pump based on engine speed and various operational parameters, using a continuously variable displacement pump to maintain target flow rates and cycle times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a constant displacement pump is used in a hydraulic system, then the system structure is simple, but the hydraulic flow rate varies with engine speed causing sub-optimal performance and increased wear
Solution Approach 1:
The patent applies a variable displacement pump instead of a constant displacement pump, allowing the pump displacement to be dynamically adjusted based on engine speed and hydraulic system demands. This dynamic adjustment maintains consistent hydraulic flow rate and pressure across varying operating conditions, resolving the contradiction between structural simplicity and performance consistency.
Solution Approach 2:
The system changes the displacement parameter of the pump based on engine speed and hydraulic demands. By varying the pump displacement parameter dynamically, the system maintains optimal hydraulic flow rates regardless of engine speed fluctuations, thereby improving reliability while managing complexity through controlled parameter variation.
2Quantity of substance
If engine speed is increased to provide increased hydraulic flow rate, then the hydraulic flow rate increases, but the cycle time control precision decreases
Solution Approach 1:
Instead of changing engine speed to control hydraulic flow rate, the system changes the pump displacement parameter while maintaining engine speed within a narrow range. This approach provides precise cycle time control because the pump displacement can be adjusted independently and continuously, allowing exact flow rate control without the variability introduced by engine speed changes.
Solution Approach 2:
The system replaces the mechanical approach of controlling flow rate through engine speed variation with a controlled displacement mechanism. This substitution allows for more precise control of hydraulic flow rate independent of engine speed, thereby improving cycle time control precision while maintaining the required hydraulic flow quantity.
3Manufacturing precision
If a variable displacement pump is used to maintain target flow rate, then cycle time control precision is improved, but the device complexity increases
Solution Approach 1:
The system employs feedback control where the actual hydraulic flow rate or pressure is monitored and compared with the target value. The pump displacement is then adjusted based on this feedback to maintain the target flow rate. This feedback mechanism achieves precise cycle time control while managing the increased complexity through automated closed-loop control.
Solution Approach 2:
The variable displacement pump serves multiple functions: it maintains target flow rate for precise cycle time control, adapts to varying engine speeds, and responds to different hydraulic system demands. This multi-functionality justifies the increased device complexity by providing comprehensive control capabilities that improve overall system performance and precision.
4Productivity
If hydraulic flow rate is increased to reduce cycle time, then productivity is improved, but energy consumption and wear increase
Solution Approach 1:
The system optimizes the pump displacement parameter to provide the minimum necessary hydraulic flow rate to achieve the target cycle time. By precisely controlling the displacement parameter rather than using high flow rates, the system reduces energy consumption and wear while maintaining improved productivity through consistent cycle time control.
Data Source
AI summary
A hydraulic work system can include a continuously variable displacement hydraulic pump that is powered by an engine and is in communication with a hydraulic actuator. A run-time displacement of the hydraulic pump for movement of the hydraulic actuator can be controlled based on a speed of the engine.