Load-Sensing Hydraulic Coupling With Boosted Pressure Signal Control
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Solution Overview
Problem
In hydraulic systems for agricultural or construction vehicles, significant pressure losses occur in connecting elements when using load sensing systems with power-beyond connections, leading to insufficient volume flow for hydraulic consumers.
Innovation Solution
A control valve with a load signal amplification valve unit, featuring a directional control valve and a biasing stage with a preload spring, amplifies the load pressure signal from one line section to another, ensuring precise pressure increase and adjusting the variable pump's delivery volume accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a load sensing system is used with power-beyond connections, then the variable displacement pump can be controlled according to load demand, but significant pressure losses occur in connecting elements leading to insufficient volume flow for hydraulic consumers
Solution Approach 1:
A booster stage is introduced as an intermediary component in the load signal line between the remote control valve and the pressure compensator. This booster stage amplifies the load pressure signal that has lost pressure during transmission, restoring sufficient control pressure to the pressure compensator without requiring higher pump pressure, thus maintaining both energy efficiency and adequate flow delivery.
2Stress or pressure
If pressure is increased in the load signal line to compensate for losses, then sufficient control pressure reaches the pressure compensator, but the pressure difference ΔpLS between load pressure and pump pressure collapses
Solution Approach 1:
The booster stage acts as a localized pressure amplification intermediary that increases pressure only in the load signal line where needed for control, rather than increasing pressure throughout the entire hydraulic system. This maintains the necessary control signal pressure while preserving the overall pressure difference between pump discharge and load pressure for efficient energy transmission.
Solution Approach 2:
Pressure amplification is applied locally only to the load signal line at the booster stage location, rather than globally to the entire hydraulic system. This localized intervention restores control pressure where the signal has degraded due to transmission losses, without affecting the overall system pressure differential and energy efficiency.
3Reliability
If the pump delivers constant flow rate at maximum power consumption, then all hydraulic consumers are always supplied with sufficient hydraulic power, but high power loss and significant heating occur when no consumers are supplied
Solution Approach 1:
The hydraulic system transitions from a static fixed-displacement pump to a dynamic variable-displacement pump controlled by load sensing. The pump's delivery volume automatically adjusts based on actual consumer demand, maintaining reliable power supply when needed while minimizing energy consumption and heat generation during idle or low-demand conditions.
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
This solution enables delay-free operation of hydraulic consumers with desired working speed by maintaining a consistent pressure difference, reducing power consumption and heat loss, and ensuring efficient energy distribution among multiple consumers.
Implementation Method 1
A piston of the control valve which is subjected to the load pressure of the second line section acts on the valve spool
Implementation Method 2
a preload stage which acts on the front side via a preload spring on a valve spool of the directional control valve
Data Source
Figure 1
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AI summary
An attachment that has a hydraulic actuating and/or drive system can be coupled in its rear and/or front area to a hydraulic control system for working hydraulics of an agricultural or construction vehicle. A hydraulic system of the respective attachment can be connected to a hydraulic circuit of the working hydraulics by means of a hydraulic coupling system, and hydraulic consumers are functionally assigned to control units both within the hydraulic circuit and within the hydraulic system. A variable displacement pump is provided in the hydraulic circuit, the delivery volume of which can be regulated as a function of a load pressure (pLS) of the hydraulic consumers of the hydraulic circuit and of the hydraulic system assigned to the attachment. At least one hydraulic load signal line (17), which is connected to the control units, is provided as part of the regulation of the variable displacement pump, and it is between a first line section (38) of the load signal line (17), which is connected to the control units arranged within the hydraulic circuit , and a second line section (48) of the load signal line (17), which is connected to the control units of the hydraulic system, a control valve (37). A load pressure signal (pLS48) generated by one of the control units of the hydraulic system is amplified by means of this control valve (37) by means of a pressure increase from a pressure line (10). In order to design the control valve in a structurally favorable manner and to arrange it in the working hydraulics using simple means, with the hydraulic consumers of the attachment being operated without delay and at the desired working speed, the control valve (37) should have a load signal booster valve unit (39) which acts as a directional valve ( 41) is formed, this having useful connections for the pressure line (10), the first line section (38) and a return line (11) and is controlled on the one hand via the load pressure (pLS38) of the first line section (38), and the control valve ( 37) has a preload stage (40) acting on the end face via a preload spring (47) on a valve slide (45) of the directional control valve (41), which is acted upon by a load pressure (pLS48) of the second line section (48) and the load signal boosting valve unit (39 ) on the other hand controls.