Multi Ratio Tractor Transmission Automatic Range Change
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Solution Overview
Problem
Multi-ratio tractor transmissions lack efficient automatic operation in both field and road working modes, particularly in ensuring the next overall available transmission ratio is maintained during range changes, requiring operator intervention and lacking seamless speed matching.
Innovation Solution
A multi-ratio transmission system combining a speed changing epicyclic gearbox and a range changing synchromesh gearbox, with a microprocessor-controlled system that automatically adjusts the speed changing gearbox ratio to maintain the next overall available ratio during range changes, allowing operator-selectable engine speed for upshifts and automatic downshifts linked to the selected upshift speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If automatic operation is implemented in both field and road working modes, then operator workload is reduced, but maintaining the next overall available ratio during range changes becomes complex without speed matching capability
Solution Approach 1:
The transmission system automatically adjusts the speed changing gearbox ratio in response to range changes in the synchromesh unit, enabling the system to self-regulate and maintain the next overall available ratio without operator intervention. This self-service capability resolves the contradiction by automating the speed matching function that would otherwise require complex manual control.
Solution Approach 2:
The control system monitors the state of both the synchromesh gearbox and epicyclic gearbox, and automatically adjusts ratios based on feedback from the range change event. This feedback mechanism ensures the transmission maintains the correct overall ratio sequence, resolving the complexity of coordinating two independent automatic transmission systems.
2Reliability
If speed matching capability is added to coordinate range changes, then the next overall available ratio is maintained, but the transmission system becomes more complex
Solution Approach 1:
The control system acts as an intermediary that coordinates between the synchromesh gearbox and epicyclic gearbox. When a range change occurs, the controller automatically selects the appropriate speed ratio in the epicyclic unit to ensure the overall transmission ratio follows the correct sequence, thereby maintaining reliability without requiring complex manual intervention.
3Device complexity
If fixed change-up speed is used, then control is simplified, but adaptability to different working conditions is reduced
Solution Approach 1:
The change-up speed is made variable rather than fixed, allowing the operator to select different engine speeds for upshifts based on working conditions. This dynamic adjustment capability enhances versatility while maintaining relatively simple control logic through operator-selectable parameters.
Solution Approach 2:
The system allows change-up speed to be changed as a variable parameter within a defined range, enabling adaptation to different field and road working conditions. This parameter change capability resolves the contradiction by providing flexibility without fundamentally complicating the control system architecture.
4Reliability
If automatic downshift is linked to change-up speed, then coordination between upshift and downshift is improved, but control flexibility is reduced
Solution Approach 1:
The downshift speed is predetermined based on the selected change-up speed, creating a coordinated control strategy. When the operator selects a change-up speed, the corresponding downshift point is automatically established (typically at 20% below the change-up speed), ensuring reliable coordination while maintaining operator flexibility in selecting the primary parameter.
Data Source
AI summary
A multi-ratio tractor transmission system including a series arrangement of a speed changing gearbox and a range changing gearbox. The system is selectively operable in a field working automatic mode and a road working automatic mode, wherein the transmission can only operate automatically within its speed change gearbox when the system is operating in the field working automatic mode.