Load-Sensing Hydraulic Flow Boost Using a Switched Fixed Pump
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Solution Overview
Problem
Variable displacement pumps in load-sensing hydraulic systems often undersupply hydraulic consumers during extreme situations, such as when multiple components like traction drives, steering, and lifting mechanisms simultaneously require maximum flow, leading to potential safety risks and unanticipated performance changes.
Innovation Solution
A control device that increases inlet volume flow by connecting a fixed displacement pump via a control circuit, which is activated by the operator, using a proportional valve and an electromagnetically actuated switching valve to bypass the storage tank, ensuring a boost function is only engaged when needed, thus preventing abrupt changes in performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a variable displacement pump is designed for cost reasons without maximum flow capacity, then device cost is reduced, but hydraulic consumers may be undersupplied during extreme work situations
Solution Approach 1:
The patent combines a variable displacement pump (for normal operation) with a fixed displacement pump (for extreme situations) in a hybrid pump system. The fixed displacement pump is activated only when additional flow is needed, merging the advantages of both pump types to provide sufficient flow capacity during extreme work situations while maintaining cost-effectiveness for typical operations.
Solution Approach 2:
The system dynamically switches between operating modes by activating the fixed displacement pump only when the variable displacement pump cannot meet the demanded flow rate. This dynamic activation is controlled by monitoring the load sensing pressure and operator input, allowing the system to adapt its flow capacity to actual operational needs.
2Reliability
If the fixed displacement pump is activated automatically based on flow demand, then flow supply is improved, but abrupt performance changes and safety risks occur
Solution Approach 1:
The system requires the operator to explicitly activate the fixed displacement pump through a control input (such as a button or switch) before the pump engages. This preliminary action by the operator ensures that the activation is intentional and anticipated, preventing abrupt, unexpected performance changes while still providing reliable hydraulic supply when needed.
Solution Approach 2:
The system incorporates feedback through the load sensing pressure signal that monitors the hydraulic system's flow demands. This feedback is combined with the operator's control input to determine when to activate the fixed displacement pump, ensuring that the system responds to actual operational needs while maintaining operator control and awareness.
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 control device provides a reliable and safe increase in hydraulic flow during extreme situations, preventing unexpected performance changes by requiring operator activation of the boost function, ensuring consistent and controlled operation of hydraulic consumers.
Implementation Method 1
The first control valve is a proportional valve, in particular a 2/2-way proportional valve. One control side of the first control valve is pressurized with, besides a spring pre-load, the load sensing pressure.
Implementation Method 2
an electromagnetically actuated switching valve, in particular a 2/2-way switching valve, is provided as a second control valve to be actuated by the operator
Implementation Method 3
the check valve is in the form of a spring-loaded check valve, which opens in the direction of the variable displacement pump and closes in the direction of the fixed displacement pump
Implementation Method 4
a pressure limiting valve is installed in a bypass line in parallel to the second control valve. When triggered, the volume flow of the fixed displacement pump is transmitted to the storage tank
Data Source
AI summary
A control apparatus for supplying at least one hydraulic consumer with fluid has a variable displacement pump (10) controlled by a load-sensing pressure (LS). For a case-by-case increase in the volume flow in the supply of fluid (22) to the hydraulic consumer, the load-sensing pressure (LS) is passed via a control line (28) to a control circuit (2) that ensures the increase in the supply (22) by connecting in a constant-displacement pump (16) as soon as an operator calls for the relevant function by operating the control circuit (2).