Hybrid Powertrain Range Gearbox Seamless Shifting
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Solution Overview
Problem
Conventional hybrid powertrains face challenges in achieving gear shifts without torque interruption and optimal brake regeneration, while also requiring a large torque and a large number of gear steps, which is not efficiently addressed by existing technologies.
Innovation Solution
A hybrid powertrain design that includes a range gearbox with a third planetary gear and a coupling device to connect and disconnect the sun wheel with the planetary wheel carrier, allowing for gear shifts without torque interruption and enabling a high range position without the use of an energy storage device, utilizing a method that controls the electrical machines to synchronize rotational speeds and disconnect components for seamless gear transitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a conventional clutch is used to disconnect the gearbox input shaft from the internal combustion engine during shifting processes, then gear shifts can be achieved, but torque interruption occurs, causing heating of clutch discs, wear, increased fuel consumption, and reduced reliability
Solution Approach 1:
The patent introduces an intermediary mechanism (the third planetary gear and fourth coupling device) between the internal combustion engine and the gearbox that enables gear shifts without requiring clutch disconnection. The third planetary gear acts as a mediator that can be selectively connected or disconnected from the input shaft, allowing smooth transitions between different gear ranges without interrupting torque transmission from the engine.
Solution Approach 2:
The transmission system is segmented into multiple independent planetary gear sets (first, second, and third planetary gears) with separate connection paths to the input shaft. This segmentation allows one planetary gear to be disengaged while another remains engaged, enabling continuous torque transmission during gear shifts without requiring the entire transmission to be disconnected from the engine.
2Force
If the electrical machine's highest torque is lower than the internal combustion engine's highest torque (adjusted by gear ratio), then the electrical machine cannot generate sufficient reaction torque, but using a larger electrical machine increases weight and cost
Solution Approach 1:
The patent employs dynamic control of the third planetary gear's connection to the input shaft, allowing the system to adaptively switch between different torque paths. During regenerative braking, the third planetary gear can be connected to enable the electrical machine to provide full reaction torque. During acceleration, the system can disconnect the third planetary gear and rely on the combined torque from the internal combustion engine and electrical machine through the first and second planetary gears, avoiding the need for an oversized electrical machine.
3Reliability
If multiple planetary gears and coupling devices are added to enable seamless gear shifts, then gear shift reliability improves, but device complexity increases
Solution Approach 1:
The third planetary gear and fourth coupling device serve multiple functions: they enable seamless gear shifts between ranges, provide an additional torque path during regenerative braking, and allow the electrical machine to operate as a generator without interrupting vehicle propulsion. This multi-functionality justifies the added complexity by eliminating the need for separate components for each function.
4Adaptability or versatility
If a large number of gear steps are achieved through additional planetary gears, then the transmission ratio range increases, but the device becomes more bulky and heavier
Solution Approach 1:
The patent nests the third planetary gear within the existing transmission structure, sharing common components such as the input shaft and housing with the first and second planetary gears. This nested arrangement allows the addition of a third planetary gear set without proportionally increasing the overall transmission volume, as the new gear set utilizes the space and structural framework already provided by the existing planetary gears.
Data Source
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Figure 2b
AI summary
The present invention relates to a hybrid powertrain, comprising an internal combustion engine (4); a gearbox (2) with an input shaft (8) and an output shaft (20); a range gearbox (11), connected to the output shaft (20); a first planetary gear (10), connected to the input shaft (8); a second planetary gear (12), connected to the first planetary gear (10); a first electrical machine (14), connected to the first planetary gear (10); a second electrical machine (16), connected to the second planetary gear (12); at least one gear pair (60, 72), connected with the first planetary gear (10) and the output shaft (20); and at least one gear pair (66, 78), connected with the second planetary gear (12) and the output shaft (20), wherein the internal combustion engine (4) is connected with the first planetary gear (10) via the input shaft (8). The range gearbox (11) comprises a third planetary gear (110) with a third sun wheel (112) and a third planetary wheel carrier (114), and a fourth clutch device (130) is arranged to connect and disconnect the third sun wheel (112) with/from the third planetary wheel carrier (114). The invention also relates to a method to control such a hybrid powertrain (3) in order to achieve a shift to a high range position without torque interruption.