Hydraulic Pump Stand-By Pressure Control for Tractor Cold Starts
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Solution Overview
Problem
Existing hydraulic systems in mobile machines, particularly tractors, face challenges during engine start-up due to high loads from secondary drives and hydraulic pumps, which are exacerbated by increased complexity and automation, leading to inefficient engine starting, especially in cold weather, and issues with electrohydraulic load sensing systems causing erroneous pressure demands.
Innovation Solution
A control system for the hydraulic supply system that inhibits electronic load sensing functionality during engine start-up and sets a lower hydro-mechanically defined stand-by pressure differential, transitioning to full operation only after the engine reaches a stable speed, using controllers to determine engine status and adjust pump supply pressure accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the hydraulic pump operates during engine start-up to maintain stand-by pressure differential, then the hydraulic system is ready for operation, but the engine start-up becomes difficult due to high external load
Solution Approach 1:
The control system performs preliminary action by detecting engine start-up conditions before the engine reaches operating speed and proactively reducing the stand-by pressure differential. This prevents the hydraulic pump from creating excessive load during the critical start-up phase, allowing the engine to start smoothly while still maintaining sufficient hydraulic pressure for system readiness.
Solution Approach 2:
The system dynamically adjusts the stand-by pressure differential based on engine operating conditions. During start-up, the pressure is reduced to minimize load on the starter motor. Once the engine reaches operating speed and the controller detects normal operation, the pressure differential automatically increases to the required stand-by level, ensuring hydraulic system readiness without compromising start-up capability.
2Ease of operation
If the electrohydraulic load sensing system operates during engine start-up, then pressure control is available, but erroneous pressure demands occur leading to increased engine load
Solution Approach 1:
The control system extracts or isolates the load sensing functionality during engine start-up conditions. By detecting start-up through various parameters (crankcase pressure, oil pressure, temperature, RPM), the system temporarily disables the electrohydraulic load sensing operation, preventing it from generating erroneous pressure demands that would increase engine load during the vulnerable start-up phase.
Solution Approach 2:
The system applies preliminary anti-action by preemptively identifying start-up conditions and counteracting the potential harmful effects of load sensing before erroneous pressure demands can occur. The controller monitors multiple parameters and, upon detecting start-up, actively suppresses load sensing operations, thereby preventing the generation of incorrect pressure signals that would otherwise burden the engine during starting.
Data Source
AI summary
A mobile machine such as a tractor has an engine and hydraulic supply system including a pump supply with a pump (MP) driven by the engine to provide a pressurized fluid at a pump supply pressure PSP. The hydraulic supply system has an electronic load sensing system (E-LS) to regulate the pump supply pressure. The E-LS is arranged to increase a stand-by pressure differential of the pump supply once the engine is determined to be running following start-up. This enables the hydraulic supply system to be configured with a reduced hydro-mechanically defined stand-by pressure differential so that it places a reduced load on the engine when it is started. The E-LS may be arranged to inhibit LS control of the pump supply when the engine is started, with LS functionality only commenced once the engine is running. Reduced load on the engine during start-up can improve cold starting.