IVT Power Management via Dynamic Torque Limiting
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Solution Overview
Problem
Off-highway vehicles, such as wheel loaders, face inefficiencies due to fixed power splits between drivetrains and hydraulic systems, leading to wasted fuel and excessive crowd force at low speeds, which reduces material handling efficiency.
Innovation Solution
A power management system that includes a vehicle control unit communicating with the engine, transmission, and power management actuator to dynamically set a maximum torque limit based on ground speed, engine speed, and implement velocity, allowing for efficient power distribution between the drivetrain and hydraulic system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a torque converter is used to govern power split between drivetrain and hydraulic system, then the power split relationship is fixed for the life of the vehicle, but this results in wasted fuel and excessive crowd force at low speeds
Solution Approach 1:
The patent applies dynamics by transitioning from a fixed torque converter-based power split to a dynamic, electronically controlled hydrostatic transmission system. The vehicle control unit continuously monitors operating conditions (ground speed, engine speed, implement velocity) and dynamically adjusts the maximum torque limit delivered to the drivetrain, allowing the power split ratio to change in real-time based on actual operational needs, thereby eliminating fuel waste associated with fixed ratios
Solution Approach 2:
The patent implements parameter changes by modifying the torque limit parameter delivered to the drivetrain based on multiple operating parameters. The system changes the maximum torque parameter dynamically according to ground speed, engine speed, and implement velocity, allowing optimization of power distribution across different operating conditions rather than maintaining a constant power split ratio
2Loss of energy
If an Infinitely Variable Transmission (IVT) or hydrostatic transmission is used, then efficiency at stall condition is improved, but relatively too much power and very high crowd force are generated at low ground speeds
Solution Approach 1:
The patent applies feedback by implementing a control system that continuously monitors ground speed, engine speed, and implement velocity, then uses this feedback information to dynamically adjust the maximum torque limit. This closed-loop feedback mechanism allows the system to respond to actual operating conditions and prevent excessive crowd force generation at low speeds while maintaining the efficiency benefits of hydrostatic transmission at stall conditions
3Power
If maximum torque is delivered to the drivetrain without limitation, then power availability is maximized, but the wheel loader's ability to move material efficiently is reduced due to incorrect balance between hydraulic power and drivetrain power
Solution Approach 1:
The patent implements parameter changes by dynamically adjusting the maximum torque parameter delivered to the drivetrain based on real-time operating conditions. The vehicle control unit modifies the torque limit parameter to achieve the correct balance between hydraulic system power and drivetrain power, thereby simultaneously maximizing power availability and maintaining material handling efficiency
Solution Approach 2:
The patent applies dynamics by replacing static torque delivery with a dynamic control system that continuously adapts the drivetrain torque limit. This dynamic adjustment ensures optimal power balance between hydraulic and drivetrain systems across varying operating conditions, preventing both power waste and productivity loss
Data Source
AI summary
The invention relates to power management of a off-highway vehicle. A power management apparatus is described as a vehicle control unit coupled to a vehicle and the vehicle control unit is in communication with an engine and a transmission controller. In response to power management input, the vehicle control unit sends a message to the transmission controller commanding a maximum torque limit based on the maximum drivetrain torque. The maximum torque limit is configured to optimize power to the vehicle implement.