Tractor Hydraulic Steering Pressure Feedback for Stable Load Sensing
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Solution Overview
Problem
The existing load-controlled hydraulic systems in agricultural tractors experience undesired changes in steering behavior due to the shift state of the shuttle valve arrangement, leading to inconsistent hydraulic supply and potential functional impairments in critical systems like hydrostatic vehicle steering and hydraulic braking.
Innovation Solution
An arrangement that adjusts the displacement volume of the hydraulic pump based on load-indicating pressures, using a pressure-regulating valve and a shuttle valve arrangement with indirect feedback through a pressure-copying valve to maintain consistent steering behavior and prioritize hydraulic supply to critical systems, while limiting hydraulic pressure to prevent overpressure and ensure stable operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the shuttle valve arrangement directly compares load-indicating pressures from multiple hydraulic consumers, then the hydraulic pump can be adjusted to meet the highest demand, but the steering behavior becomes inconsistent due to pressure variations caused by valve shifting
Solution Approach 1:
A pressure-copying valve is introduced as an intermediary between the steering system's load-indicating pressure line and the shuttle valve arrangement. This mediator copies the pressure signal to feed the shuttle valves, preventing direct hydraulic connections that would cause steering inconsistencies while still enabling the pump to respond to the highest pressure demand from any consumer
Solution Approach 2:
The hydraulic feedback system is segmented into separate pressure signaling paths. Each hydraulic consumer maintains its own load-indicating pressure line, and the pressure-copying valve creates independent copies of these pressure signals for the shuttle valve arrangement, preventing interference between different hydraulic circuits while preserving individual system performance
2Quantity of substance
If the hydraulic pump increases displacement volume to meet high pressure demands from secondary hydraulic consumers, then adequate hydraulic supply is provided, but the steering system experiences pressure drops and functional impairments
Solution Approach 1:
The shuttle valve arrangement continuously compares load-indicating pressures from all hydraulic consumers and provides feedback to the hydraulic pump's actuating device. This feedback mechanism ensures the pump automatically adjusts its displacement volume to meet the highest pressure demand, while the pressure-copying valve ensures steering pressure signals are accurately transmitted without being affected by shifts in other consumers' pressure lines
Solution Approach 2:
The pressure-copying valve acts as a mediator that separates the steering system's pressure signaling from the direct hydraulic feedback path. This allows the pump to respond to high pressure demands from secondary consumers without causing pressure drops in the steering system, as the steering pressure is copied rather than directly contested in the feedback loop
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 ensures consistent and dynamic adaptation of hydraulic pressure for hydrostatic vehicle steering, prevents jamming at low temperatures, and maintains functional integrity of superordinate hydraulic functions by prioritizing hydraulic supply and limiting pressure to prevent damage.
Implementation Method 1
a pressure-regulating valve, which is connected upstream of the steering orbitrol and is actuated in accordance with a pressure difference that decreases across a throttle element
Implementation Method 2
The displacement volume of the hydraulic pump is adjusted in accordance with a load-indicating pressure transmitted to an actuating device of the hydraulic pump
Implementation Method 3
the shuttle valve arrangement compares the second load-indicating pressure with the first load-indicating pressure and transmits the respectively higher pressure to the actuating device of the hydraulic pump
Data Source
AI summary
An arrangement for operating a load-controlled hydraulic system of an agricultural tractor, includes a hydraulic pump generating a system pressure and having an actuating device to adjust a displacement volume, a hydrostatic vehicle steering system connected to the hydraulic pump and having a steering orbitrol and a first load-indicating pressure, a pressure-regulating valve connected upstream of the steering orbitrol and actuated via a pressure difference decreasing across a throttle element counter to a predetermined restoring force in accordance with the first load-indicating pressure, a second hydraulic consumer connected to the hydraulic pump and feeding a second load-indicating pressure back to a shuttle valve arrangement, which compares and transmits the respectively higher of the first and second load-indicating pressures to the actuating device to adjust the displacement volume, and a pressure-copying valve indirectly feeding back the first load-indicating pressure to the shuttle valve arrangement.