Variable Displacement Hydraulic Pump Load Control for Engine Stall Prevention
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Solution Overview
Problem
Wheel loaders experience engine stall due to rapid application of high hydraulic loads during low idling, which is exacerbated by slow torque increase at low engine speeds, leading to inefficiencies in fuel consumption and vehicle performance.
Innovation Solution
A load control device with variable displacement hydraulic pumps and a control system that detects engine speed and reduces absorption torque when it drops below a threshold, shifting hydraulic load to a lower line to maintain engine torque and prevent stalling, while minimizing the need for increased engine size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the low idling speed of the engine is set to a relatively high level to quicken the increase of torque, then the engine torque can be increased as rapidly as the rapid increase of the high hydraulic load, but the fuel efficiency while idling is deteriorated and stronger creep occurs in the torque converter
Solution Approach 1:
The patent applies dynamics by making the pump displacement variable rather than fixed. The controller dynamically adjusts the pump displacement based on detected engine speed, increasing displacement when engine speed drops to prevent stall, and reducing displacement when engine speed recovers or is high, thereby optimizing fuel efficiency across different operating conditions
Solution Approach 2:
The patent changes the parameter of pump displacement based on engine speed conditions. When engine speed is at or below a predetermined threshold, the pump displacement is increased to provide more torque and prevent stall. When engine speed exceeds the threshold, displacement is reduced to improve fuel efficiency, creating an adaptive system that responds to real-time operating conditions
2Power
If the displacement of the fixed displacement hydraulic pump is set low to reduce the torque absorbed by the hydraulic pump, then the torque itself absorbed by the hydraulic pump is reduced, but the steering cannot be turned sufficiently during low idling and the speed of raising or lowering the loader is reduced
Solution Approach 1:
The patent transforms the fixed displacement pump into a variable displacement system where the pump displacement is dynamically adjusted based on engine speed and hydraulic load conditions, allowing the system to provide high torque when needed for steering and loader operations while reducing torque absorption during normal idling to prevent engine stall
Solution Approach 2:
The patent changes the pump displacement parameter in response to detected engine speed and operational demands. When the engine operates at low idling speed, displacement is increased to ensure sufficient steering capability and loader performance. When engine speed is adequate, displacement is reduced to minimize torque absorption and prevent stall, thereby optimizing both performance and reliability
3Power
If the displacement of the fixed displacement hydraulic pump is set small to reduce torque absorption, then the amount of flow is decreased, but the speed of raising or lowering the loader is reduced and the working efficiency is impaired
Solution Approach 1:
The patent implements a dynamic displacement control system that adjusts pump output based on real-time engine speed detection and hydraulic load requirements, ensuring high flow rates are available when needed for loader operations while reducing flow and torque absorption during idle conditions to maintain engine stability
Solution Approach 2:
The patent dynamically changes the pump displacement parameter based on operating conditions. When engine speed indicates sufficient power availability, displacement is increased to maximize flow rate and loader raising/lowering speed for high productivity. When engine speed drops below thresholds, displacement is reduced to prevent torque absorption from causing engine stall, thereby optimizing the balance between productivity and engine stability
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
Prevents engine stall during high hydraulic load applications without deteriorating fuel efficiency or vehicle performance, ensuring reliable operation and improved working efficiency.
Implementation Method 1
a steering hydraulic pump is driven by the engine, and pressure oil discharged from the steering hydraulic pump is supplied to a steering hydraulic cylinder
Data Source
AI summary
A device for use in a work vehicle such as a wheel loader, capable of reliably preventing engine stall due to rapid application of high hydraulic load, without causing problems such as deterioration in fuel efficiency or vehicle performance and waste of energy. When determining that an engine speed detected by the engine speed detecting sensor has been decreased to the threshold value or lower, the controller implements a control to reduce the absorption torque of the variable displacement hydraulic pump. The hydraulic load is thus shifted to a low hydraulic load line. The change of the hydraulic load from the high hydraulic load to the low hydraulic load gives a margin to the current torque of the engine with respect to the low hydraulic load. Consequently, the actual speed of the engine is increased to return onto the regulation line, exceeding the threshold value.