Transfer Case Gear Ratio Adaptation for Power-Split Transmission
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Solution Overview
Problem
Existing drive-trains for agricultural machines with power-split transmissions face challenges in handling higher engine power, leading to increased pressure in hydrostats beyond permissible limits, necessitating costly modifications to accommodate varying engine power categories.
Innovation Solution
Incorporating a transfer case with a step-down ratio between the drive motor and power-split transmission, allowing for the use of existing power-split transmissions in vehicles with higher engine power by adjusting the gear ratio, and optionally featuring auxiliary power take-offs and a spur gear system for flexibility and independent housing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If existing power-split transmissions are used in vehicles with higher engine power, then the engine power handling capability is improved, but the pressure in hydrostats increases beyond permissible limits
Solution Approach 1:
A transfer case is introduced as an intermediary component between the engine and the power-split transmission. This transfer case includes a transfer case input shaft connected to the engine and a transfer case output shaft connected to the power-split transmission input shaft, along with a transfer case gear set that provides gear reduction. This intermediary mechanism reduces the rotational speed and increases the torque before it reaches the hydrostats, thereby keeping the hydrostat pressure within permissible limits while enabling the system to handle higher engine power.
Solution Approach 2:
The transfer case gear set changes the rotational speed and torque parameters of the drive train. By providing a gear reduction ratio, it transforms the high-speed, low-torque output from the engine into lower-speed, high-torque input for the power-split transmission, which in turn keeps the pressure parameters within the hydrostats within their permissible operating range.
2Power
If modifications are made to accommodate higher engine power in existing power-split transmissions, then the power handling capability is improved, but the manufacturing cost increases
Solution Approach 1:
The drive train is segmented into distinct functional modules: the engine, the transfer case, and the power-split transmission. The transfer case is designed as a separate, standalone component with its own housing, input shaft, output shaft, and gear set. This segmentation allows the existing power-split transmission to be used without modification while the transfer case handles the adaptation to higher engine power, thereby avoiding costly modifications to the power-split transmission itself.
Solution Approach 2:
The transfer case serves multiple functions: it provides gear reduction to match the engine output to the power-split transmission input requirements, it adapts the drive train for higher engine power applications, and it maintains compatibility with existing power-split transmissions. This multi-functionality makes the transfer case a versatile solution that can be applied across different power categories without requiring modifications to the core power-split transmission design.
3Adaptability or versatility
If the transfer case is designed with a completely independent housing, then the adaptability to different power categories is improved, but the device complexity increases
Solution Approach 1:
The transfer case is designed as a completely independent housing that encapsulates all its internal components (input shaft, output shaft, gear set). This segmentation creates a self-contained module that can be easily adapted to different power categories by simply changing the gear ratio within the transfer case, without affecting the external structure or requiring integration modifications with the power-split transmission.
Solution Approach 2:
The independent transfer case housing acts as an intermediary structure that isolates the complexity of gear ratio variations from the rest of the drive train. By containing all adaptation mechanisms within its own housing, it provides a clean interface with the engine and power-split transmission, thereby managing complexity locally while maintaining simplicity and adaptability at the system level.
Data Source
AI summary
A drive-train of an agricultural machine, such as a tractor, has a power-split transmission (1) and a separate transfer case (2). The transfer case (2) can be connected to a drive motor and the gear ratio of the transfer case (2) can be adapted in such manner that the power-split transmission (1) can be used for various drive powers.