Torque Control for SCR Urea Depletion in Work Vehicles
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Solution Overview
Problem
Existing exhaust gas purification systems for work vehicles, such as wheel loaders, face challenges in managing engine output when the reducing agent solution, like urea water, is depleted, leading to potential engine stall due to varying load conditions and operational states, as they are not adequately designed to handle the distinct relationships between engine and hydraulic pump outputs.
Innovation Solution
A work vehicle system incorporating a hydraulic pump, rotational speed detection, an exhaust gas purification device, a remaining amount detection device, and a torque control unit that adjusts engine output torque and rotational speed based on the reducing agent solution's level, ensuring the engine's output torque is maintained above a threshold at low rotational speeds to prevent stall, even when the reducing agent is scarce.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the engine output is reduced when the reducing agent solution is depleted (as in automobile technology), then the exhaust gas purification is maintained, but the engine load becomes excessively large and engine stall occurs in work vehicles
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the engine output torque based on the detected engine rotational speed and the remaining amount of reducing agent solution. When the reducing agent is depleted and engine speed is high, torque is reduced to maintain exhaust purification. When engine speed is low, torque is maintained to prevent stall. This dynamic parameter adjustment resolves the contradiction between maintaining purification and preventing power loss.
Solution Approach 2:
The patent implements dynamics by making the engine output torque characteristic changeable according to operating conditions. The control device adjusts the torque reduction strategy based on real-time engine rotational speed and reducing agent remaining amount, transitioning from a static torque reduction approach to a dynamic one that adapts to varying work and travel states, thereby preventing both purification failure and engine stall.
2Reliability
If the engine output is reduced to maintain exhaust gas purification when reducing agent is depleted, then nitrogen oxide reduction is maintained, but the hydraulic pump output becomes insufficient and work performance deteriorates
Solution Approach 1:
The patent changes the parameter of engine output torque based on the relationship between engine rotational speed and reducing agent remaining amount. At high engine speeds where exhaust purification is critical, torque is reduced. At low engine speeds where work performance is more sensitive, torque is maintained. This selective parameter adjustment maintains nitrogen oxide reduction while minimizing impact on hydraulic pump output and work performance.
Solution Approach 2:
The patent applies local quality by implementing different torque control strategies for different engine operating regions. High-speed regions prioritize exhaust purification with torque reduction, while low-speed regions prioritize work performance with torque maintenance. This localized control approach ensures that nitrogen oxide reduction is achieved when most effective while preserving work performance when most needed.
3Reliability
If a fixed torque reduction strategy is applied when reducing agent is depleted, then exhaust gas purification is ensured, but the system cannot adapt to varying load conditions and operational states
Solution Approach 1:
The patent transforms a static torque reduction strategy into a dynamic one by continuously monitoring engine rotational speed and reducing agent remaining amount. The control device adjusts the torque characteristic in real-time based on the detected parameters, enabling the system to adapt to varying load conditions and operational states while ensuring exhaust gas purification is maintained when reducing agent is depleted.
Solution Approach 2:
The patent implements feedback control by using the remaining amount detection device and rotational speed detection device to continuously monitor system state, and the control device adjusts engine output torque based on this feedback. This closed-loop control enables the system to adapt to varying conditions while maintaining exhaust purification, resolving the contradiction between fixed purification strategy and adaptability to load changes.
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 effectively prevents engine stall by maintaining adequate engine output torque at low rotational speeds, allowing for continued operation and prompting the operator to replenish the reducing agent, thus ensuring reliable performance during varying work and travel states.
Implementation Method 1
an exhaust gas purification device that purifies nitrogen oxide in exhaust gas discharged from the engine using a reducing agent solution stored in a reducing agent tank
Implementation Method 2
purifies nitrogen oxide in exhaust gas discharged from the engine using a reducing agent solution
Data Source
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AI summary
A work vehicle includes: a hydraulic pump (11) driven by an engine (190); a rotational speed detection unit (13) that detects an actual rotational speed of the engine; an exhaust gas purification device (161) that purifies nitrogen oxide in exhaust gas discharged from the engine (190) using a reducing agent solution (urea) stored in a reducing agent tank (162); a remaining amount detection device (163) that detects a remaining amount of the reducing agent solution in the reducing agent tank (162); a torque control unit that decreases output torque of the engine (190) according to decrease of the detected remaining amount of the reducing agent solution; wherein when the actual rotational speed of the engine (190) is not more than a threshold value, the torque control unit does not decrease the output torque of the engine regardless of the detected remaining amount of the reducing agent solution.