Load-Sensing Hydraulic Supply With Pressure Limiting for Tractors
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Solution Overview
Problem
Existing load-controlled hydraulic supplies for agricultural implements fail to account for the limited hydraulic resources of the high-pressure hydraulic source, leading to potential undersupply or oversupply of hydraulic fluid, which can cause malfunctions in safety-relevant systems like hydraulic steering or braking.
Innovation Solution
A load-controlled hydraulic supply system with a pressure-compensated control valve, pressure limiting device, and valve arrangements to adjust flow rates and pressures based on load sensing, using a combination of 2/2-way proportional and pressure regulating valves, and pilot-operated 2/2-way valves to maintain consistent flow and prevent inefficiencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a load-sensing hydraulic supply system is used to provide demand-based hydraulic fluid to implements, then the hydraulic supply efficiency is improved, but the limited hydraulic resources of the high-pressure source may be insufficient to supply both the implement and safety-relevant tractor functions simultaneously
Solution Approach 1:
The hydraulic supply system is segmented into two independent circuits: a load-sensing circuit for implement functions and a separate circuit for safety-relevant tractor functions (steering, braking). This segmentation allows each circuit to be controlled independently, ensuring that safety functions always receive sufficient hydraulic fluid while the implement receives demand-based supply, resolving the contradiction between supply efficiency and resource availability.
2Reliability
If attachments transmit excessive load signal pressure to the hydraulic supply, then the supply pressure exceeds actual demand, but this causes efficiency losses in the hydraulic supply operation
Solution Approach 1:
A pressure limiting valve is introduced as an intermediary component in the load-sensing line. This valve limits the maximum pressure signal transmitted from the attachment to the hydraulic supply, preventing excessive pressure signals that would cause the supply pressure to exceed actual demand. The valve acts as a mediator that ensures accurate pressure signaling while preventing energy losses, resolving the contradiction between pressure signal reliability and hydraulic supply efficiency.
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 ensures appropriate hydraulic fluid supply to actuators, preventing malfunctions by maintaining consistent flow rates and pressures, even with load fluctuations, thus optimizing the use of limited hydraulic resources.
Implementation Method 1
a pressure-compensated control valve with an actuating device for adjusting the flow rate is provided in the supply line
Implementation Method 2
the pressure-regulating valve compares an outlet-side hydraulic pressure with an inlet-side hydraulic pressure at the 2/2-way proportional valve and adjusts to a fixed differential pressure
Implementation Method 3
the 2/2-way proportional valve can be moved into its open position by means of the actuating device, which can be electrically or mechanically controlled, against a restoring force generated by a spring element
Implementation Method 4
the load sensing line can be connected to a pressure limiting device. The pressure limit is adjusted to the expected hydraulic supply requirements of the hydraulic actuators
Data Source
Figure 1
Figure 2
AI summary
Load-controlled hydraulic supply (10) for an implement (14) attached to an agricultural tractor (12), comprising a supply line (24) fed by a high-pressure hydraulic source (22), a return line (30) leading into a hydraulic reservoir (28), and a load-sensing line (26), wherein the hydraulic supply (10) provides a flow rate through the supply line (24) according to a pressure feedback signal at the load-sensing line (26). A pressure-compensated control valve (44) with an actuating device (46) for adjusting the flow rate is provided in the supply line (24).