Work Vehicle Engine Control Torque Converter Speed Ratio
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Solution Overview
Problem
The engine control device for wheel loaders often results in insufficient engine output torque when the accelerator pedal is eased off during excavation work or when traveling uphill, leading to potential engine stalling, especially when operating front work devices like arms and buckets.
Innovation Solution
The engine control device includes a target rotation speed correction unit that increases the target engine rotation speed based on the torque converter speed ratio when the accelerator pedal operation is reduced and the speed ratio is less than a predetermined value, ensuring sufficient torque for front work devices and preventing stalling during uphill travel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the engine rotation speed is controlled to be based on the accelerator operation amount when the accelerator pedal is eased off, then the engine rotation speed can be reduced to match the driver's input, but the engine output torque becomes insufficient to drive the front work device, causing engine stalling
Solution Approach 1:
The control device changes the engine rotation speed parameter dynamically based on the torque converter speed ratio. When the speed ratio is below the threshold and accelerator operation is small, the system sets the engine rotation speed to a predetermined value higher than the normally controlled speed, ensuring sufficient torque output to prevent stalling while still allowing speed reduction when conditions permit
Solution Approach 2:
The control device continuously monitors the torque converter speed ratio and uses this feedback to adjust the engine rotation speed control strategy. By detecting the actual operating conditions through speed ratio feedback, the system can switch between different rotation speed control modes (normal control vs. predetermined higher speed) to prevent stalling while maintaining efficiency
2Speed
If the accelerator pedal is operated in a release direction while traveling uphill, then the engine rotation speed can be reduced, but the engine output torque decreases and may become insufficient to overcome the load from gravity and vehicle weight, causing engine stalling
Solution Approach 1:
The system changes the engine rotation speed parameter based on the torque converter speed ratio detection. When traveling uphill with small accelerator operation and speed ratio below threshold, the control device maintains engine rotation speed at a predetermined higher value, ensuring sufficient power output to overcome gravitational load and prevent stalling
Solution Approach 2:
The control device takes preliminary action by detecting the torque converter speed ratio before stalling occurs. When the speed ratio indicates potential torque insufficiency (below threshold), the system proactively adjusts engine rotation speed to the predetermined higher value, preventing the stalling condition before it develops
Data Source
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AI summary
An engine control device for work vehicle includes: a target rotation speed setting unit that sets a target rotation speed of an engine corresponding to an operation amount of an accelerator pedal; a rotation speed control unit that controls a rotation speed of the engine according to the target rotation speed; a travel driving unit that transmits rotation of the engine to wheels via a torque converter; a speed ratio detection unit that detects a speed ratio between an input shaft and an output shaft of the torque converter; and a target rotation speed correction unit that corrects the target rotation speed set by the target rotation speed setting unit so as to increase the target rotation speed based on the speed ratio when the operation amount of the accelerator pedal is smaller than a predetermined value and the speed ratio detected by the speed ratio detection unit is smaller than a predetermined value within a range which is equal to or greater than 0 and less than 1.