Torque Converter Lock-Up Clutch Control for Mobile Hydraulics
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Solution Overview
Problem
In work machines with hydraulically actuated lifting devices, such as wheel loaders and forklifts, the existing method of controlling the converter lock-up clutch based on turbine speed leads to power loss and insufficient hydraulic power during short work cycles, particularly when the clutch is closed, resulting in inadequate power for hydraulic operations and inefficient fuel usage.
Innovation Solution
The method involves actuating the converter lock-up clutch based on predetermined position limits of the lifting hydraulics, rather than turbine speed, with the clutch opening when hydraulic position exceeds a limit and closing when turbine speed exceeds a threshold, and further optimizing by considering vehicle speed and transmission torque for engine braking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the converter lock-up clutch is closed based on turbine speed threshold, then power loss in the torque converter is reduced, but insufficient power is available for the hydraulic lifting device
Solution Approach 1:
The control parameter for the lock-up clutch is changed from turbine speed to position of the lifting hydraulics. This allows the clutch state to be determined by the actual hydraulic power requirement rather than just rotational speed, resolving the contradiction between minimizing power loss and ensuring sufficient hydraulic power.
Solution Approach 2:
The system uses feedback from the lifting hydraulics position to control the lock-up clutch. By monitoring where the lifting mechanism is in its cycle, the control system can anticipate power requirements and adjust clutch state accordingly, preventing both power deficiency and unnecessary energy loss.
2Use of energy by moving object
If the converter lock-up clutch is closed to save fuel, then fuel consumption is reduced, but the engine speed becomes too low for efficient hydraulic operation
Solution Approach 1:
The control strategy changes from speed-based to position-based control. This allows the system to maintain high engine speed when hydraulic power is needed (during lifting operations) while using the lock-up clutch during position states where hydraulic power demand is low, optimizing both fuel efficiency and operational performance.
3Device complexity
If the converter lock-up clutch is controlled by turbine speed threshold, then the control system is simple, but it cannot adapt to varying hydraulic power requirements
Solution Approach 1:
The control parameter is changed from turbine speed to lifting hydraulics position. This single parameter change provides direct adaptability to hydraulic power requirements since the position directly indicates when hydraulic power will be needed, without increasing control system complexity.
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 approach ensures sufficient power is provided to the hydraulic system while minimizing power loss, enabling more efficient operation and fuel savings in work machines with short cycles at low speeds.
Implementation Method 1
a hydrodynamic torque converter (2) with a pump wheel (3), a turbine wheel (4) and a stator wheel (5) arranged between them
Implementation Method 2
When the torque converter lock-up clutch is closed, there is a lossless drive connection between the drive engine and the vehicle's transmission
Implementation Method 3
at least one hydraulically actuated lifting device (8)
Data Source
AI summary
In the proposed method for operating the torque converter lock-up clutch in a power transmission of a mobile machine comprising at least one hydraulically actuated lifting device, the lock-up clutch is actuated in the disengaged sense when a predefined limit for the position of the lifting hydraulic mechanism of the at least one lifting device is exceeded, whereas the lock-up clutch is engaged when the position of the lifting hydraulic mechanism lies below a predefined limit and the turbine speed exceeds a predefined threshold value.