Hybrid Drive System for Tractors with High Torque Ratio
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Solution Overview
Problem
Agricultural vehicles, such as tractors, require a drive system that can achieve a torque ratio of 25:1 for maximum to minimum power transmission, which is beyond the capability of existing electric drives with a torque ratio of 5 to 7, and also needs a stepless drive over a large speed range with minimal mechanical gear shifts for efficient fuel consumption and operation.
Innovation Solution
A drive system comprising at least one electric generator and two electric machines, where the machines can be controlled to transmit mechanical torque to the drive axle, allowing for a continuously variable transmission without a continuously variable transmission, and enabling independent control of engine speed and electric machine speed for optimal power management and reduced fuel consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If only electric machines are used for drive, then stepless drive over large speed range is achieved, but torque ratio is limited to 5-7:1 instead of required 25:1
Solution Approach 1:
The patent combines electric machines with a mechanical transmission system having multiple gear shift stages. The electric machines provide stepless speed control, while the mechanical transmission provides the required torque multiplication through gear ratios, achieving both continuous variable drive and high torque ratio capabilities.
Solution Approach 2:
The drive system integrates multiple functions: electric machines serve both as motors for driving the vehicle and as generators for energy recovery, while the mechanical transmission handles both torque multiplication and speed conversion, creating a multi-functional system that addresses multiple requirements simultaneously.
2Power
If mechanical gear shifts are used to achieve high torque ratio, then power transmission capability is improved, but fuel consumption increases and drive continuity is reduced
Solution Approach 1:
The electric machines enable continuous torque delivery across the entire speed range without interruption from gear shifts. The stepless speed control maintains continuous power transmission to the drive wheels, eliminating the discontinuities and energy losses associated with mechanical gear shifting operations.
Solution Approach 2:
The patent replaces the traditional mechanical gear shifting mechanism with electrically controlled speed variation. The electric machines adjust their rotational speed electronically to achieve the required speed changes, substituting mechanical gear engagement with electrical control, thereby eliminating gear shift losses.
3Adaptability or versatility
If electric machines are oversized to handle peak loads, then load management capability is improved, but device complexity and cost increase
Solution Approach 1:
The mechanical transmission system handles the peak torque requirements through its gear multiplication capability, allowing the electric machines to be sized for continuous power delivery rather than peak loads. This partial action approach divides the torque handling between the mechanical system (peak loads) and electrical system (continuous operation).
Solution Approach 2:
The mechanical transmission system acts as an intermediary between the electric machines and the drive wheels, handling torque multiplication and peak load management. This intermediary component allows the electric machines to operate at optimal sizes while still meeting peak power requirements through the transmission's gear ratios.
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
The system allows for efficient power transmission, reduced fuel consumption, and improved usability by enabling continuous speed control and reversing without mechanical gear shifts, while avoiding oversizing of electric machines and allowing for optimal traction and reduced turning circles.
Implementation Method 1
at least one electric generator (24, 26) which can be driven with a torque generated by an engine (22) of the vehicle
Implementation Method 2
At least one of the two electrical machines (28, 30) can be driven with the electrical energy generated by the electrical generator (24, 26)
Data Source
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AI summary
The invention relates to a drive system (10) for an agricultural or industrial vehicle, preferably a tractor (12). Said drive system (19) comprises at least one electric generator (24, 26) as well as a first and a second electric machine (28, 30). The at least one electric generator (24, 26) can be driven using torque generated by a vehicle engine (22). At least one of the two electric machines (28, 30) can be driven using the electric power generated by the electric generator (24, 26). The mechanical torque generated by the first and/or the second electric machine (28, 30) can be transmitted to at least one driving axle (14, 16) of the vehicle in order to allow the vehicle to move. The invention further relates to an agricultural vehicle comprising such a drive system (10).