Dual Hydraulic Machines With Pressure-Based Return Flow Control
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Solution Overview
Problem
Hybrid hydraulic systems in working machines, such as wheel loaders, face inefficiencies due to the direct coupling of driveline and work hydraulics systems, leading to problematic interactions and a need for improved fuel efficiency and component capacity.
Innovation Solution
A hydraulic system with two electric machines connected to hydraulic machines and a valve arrangement that directs return flow based on requested pressure, allowing the second hydraulic machine to support the first when needed, providing redundancy and flexibility, and enabling smaller component usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single hydraulic machine is used to power all hydraulic consumers, then the system structure is simple, but the component capacity must be oversized to meet maximum torque and pressure requirements
Solution Approach 1:
The hydraulic system is segmented into two independent hydraulic machines (first and second hydraulic machines), each capable of powering hydraulic consumers independently. This segmentation allows each component to be sized for partial capacity rather than requiring a single oversized component, resolving the contradiction between system simplicity and component capacity requirements.
2Loss of energy
If the driveline and work hydraulics systems are directly coupled to the engine shaft, then the power transmission is efficient, but the interaction between systems becomes problematic
Solution Approach 1:
The patent introduces a valve arrangement as an intermediary component between the driveline and work hydraulics systems. This valve arrangement mediates the interaction by controlling fluid flow distribution, allowing efficient power transmission while preventing problematic system interactions through regulated fluid distribution.
3Reliability
If one hydraulic machine fails, then the system reliability is compromised, but using redundant components increases system complexity
Solution Approach 1:
The patent merges the functions of two hydraulic machines into a single integrated hydraulic system where both machines operate together to power shared hydraulic consumers. This combining approach provides redundancy (if one machine fails, the other can continue operation) while avoiding the complexity of completely separate independent systems, as the machines share common control and distribution infrastructure.
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
The system achieves maximum torque and pressure requirements, offers redundancy, and ensures efficient operation even if one component malfunctions, allowing safe completion of tasks without additional assistance.
Implementation Method 1
the valve arrangement is configured to control a return flow of hydraulic fluid from the hydraulic consumer to either the input side of the first hydraulic machine or an input side of the second hydraulic machine based on a requested output pressure from the first hydraulic machine
Data Source
AI summary
A hydraulic system for a working machine includes a first electric machine connected to a first hydraulic machine; a second electric machine connected to a second hydraulic machine, an output side of the second hydraulic machine being connected to an input side of the first hydraulic machine; at least one hydraulic consumer hydraulically coupled to an output side of the first hydraulic machine via a supply line and configured to be powered by the first hydraulic machine; and a valve arrangement arranged between the hydraulic consumer and the first and second hydraulic machines, wherein the valve arrangement is configured to control a return flow of hydraulic fluid from the hydraulic consumer to either the input side of the first hydraulic machine or an input side of the second hydraulic machine based on a requested output pressure from the first hydraulic machine.