Variable Displacement Feed Pump for Hydraulic Oil Supply
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Solution Overview
Problem
Self-propelled road pavers with closed hydraulic circuits face high fuel consumption and drag power issues, especially during cold starting, due to excessive hydraulic oil supply and inefficient scavenging processes.
Innovation Solution
Implementing a method that controls the supply of hydraulic oil to a closed hydraulic circuit based on operating parameters, using a variable displacement feed pump and a separate constant scavenging pump for cooling and lubrication, to optimize oil supply and reduce power losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a constant pump with constant volumetric displacement is used to supply hydraulic oil to the closed hydraulic circuit, then the oil supply is sufficient to compensate for the hydraulic oil volume taken from the circuit per unit of time under loading conditions, but the pump output is always designed for oversupply of the circuit with hydraulic oil, resulting in excess amounts lost as power losses and unnecessary fuel consumption
Solution Approach 1:
The patent applies a variable displacement pump instead of a constant displacement pump, allowing the pump to dynamically adjust its delivery rate according to actual circuit requirements. The pump's volumetric displacement is made variable through a control mechanism that responds to system conditions, enabling the pump to deliver exactly the amount of hydraulic oil needed without excessive oversupply, thereby reducing power losses while maintaining reliable oil supply compensation
Solution Approach 2:
The patent changes the key parameter of pump delivery rate from constant to variable. By controlling the volumetric displacement parameter of the pump based on operating conditions (such as circuit pressure, flow demand, or temperature), the system optimizes the balance between sufficient oil supply and energy efficiency, eliminating the fixed oversupply characteristic of constant displacement pumps
2Reliability
If a constant pump with constant volumetric displacement is used to supply hydraulic oil to the closed hydraulic circuit, then the oil supply is sufficient under loading conditions, but the excessive delivery rate causes unnecessary consumption of fuel
Solution Approach 1:
The variable displacement pump dynamically adjusts its delivery rate to match actual circuit needs, preventing the fixed excessive delivery that causes unnecessary fuel consumption. The pump's displacement is modulated based on system conditions, ensuring adequate oil supply while minimizing energy waste
Solution Approach 2:
The system incorporates feedback control mechanisms that monitor circuit conditions (such as pressure, flow, or temperature) and use this information to adjust the pump's volumetric displacement in real-time, optimizing fuel consumption while maintaining sufficient oil supply
3Reliability
If a constant pump with constant volumetric displacement is used, then the pump output is designed for oversupply of the circuit with hydraulic oil, but problems frequently occur during starting, especially during cold starting of the internal combustion engine, because the produced drag loads are very high
Solution Approach 1:
The variable displacement pump can be controlled to provide reduced delivery during starting conditions, particularly cold starting, thereby reducing drag loads on the internal combustion engine. The pump's displacement is dynamically adjusted based on operating conditions, allowing easy starting while still ensuring adequate oil supply when needed
Solution Approach 2:
The system can pre-adjust the pump's volumetric displacement based on anticipated operating conditions or current system state, reducing initial drag loads during cold starting before the engine is fully warmed up, while maintaining sufficient oil supply capability as conditions change
Data Source
AI summary
The present invention relates to a method for operating a hydraulic system of a self-propelled road paver, in particular, for the supply of hydraulic oil as needed to a closed hydraulic circuit of the road paver, a hydraulic system of a road paver for performing the method and a road paver having such a hydraulic system. The extraction and/or return of the quantity of hydraulic oil occur depending on at least one operating parameter of the road paver.