DCT with Nested Planetary Gears for 8-Speed Transmission
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Solution Overview
Problem
Current power transmission systems for vehicles, such as double clutch transmissions (DCTs), face limitations in achieving a high number of forward and reverse speed stages while maintaining fuel economy and minimizing component count and weight.
Innovation Solution
The integration of two planetary gear sets and two synchronizers into a DCT configuration, allowing for the achievement of eight forward speed stages and one reverse speed stage, simplifies the interior layout and reduces the number of components, thereby improving fuel economy and enabling smooth shifting between even and odd-numbered speed stages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If more forward and reverse speed stages are achieved using conventional transmission systems, then the number of speed stages increases, but the device complexity and number of components increase
Solution Approach 1:
The patent combines two planetary gear sets (first and second planetary gear sets) with a double clutch transmission system, integrating multiple gear multiplication functions into a unified structure. This merging allows achieving eight forward speed stages and two reverse speed stages without proportionally increasing component count, as the planetary gear sets share common elements and are integrated with the existing DCT architecture.
Solution Approach 2:
The planetary gear sets are designed to serve multiple functions: they provide both forward speed multiplication (through different gear combinations) and reverse speed multiplication (through the third synchronizer and reverse gear mechanism). The same planetary gear sets are used across multiple speed stages, making them universal components that perform multiple gear ratio functions rather than requiring separate mechanisms for each speed stage.
2Adaptability or versatility
If more speed stages are achieved by adding components, then the number of speed stages increases, but the weight of the transmission system increases
Solution Approach 1:
The patent merges the planetary gear sets with the DCT structure, where the planetary gears share mounting spaces and structural elements with the existing transmission housing and shafts. This combined design avoids the need for completely separate gear multiplication mechanisms, thereby reducing the additional weight that would result from fully independent component sets.
Solution Approach 2:
The first and second planetary gear sets are arranged in a nested or closely integrated configuration within the transmission housing, with the first planetary gear set positioned to utilize space around the second planetary gear set. This nesting approach minimizes the overall volume and weight of the gear multiplication system while maintaining all necessary gear stages.
3Adaptability or versatility
If more speed stages are achieved by adding components, then the number of speed stages increases, but the length of the transmission system increases
Solution Approach 1:
The planetary gear sets are nested within the existing DCT structure, with the first planetary gear set arranged concentrically or adjacently to the second planetary gear set. This nesting allows multiple gear multiplication functions to be packed into a compact radial and axial space, preventing proportional increases in transmission length as speed stages are added.
Solution Approach 2:
Instead of arranging gear stages in a linear sequence that would increase length, the patent utilizes radial and axial dimensions by positioning the two planetary gear sets in different spatial arrangements (one potentially surrounding or adjacent to the other). This dimensional reorganization maintains a compact overall length while achieving the required number of speed stages through three-dimensional space utilization.
4Use of energy by moving object
If conventional DCT is used, then the structure is simple, but fuel economy is not optimized
Solution Approach 1:
The patent combines planetary gear sets with the DCT to create an integrated system that achieves superior fuel economy through enhanced gear ratio options. The merger allows for more precise gear ratio selection across a wider range, optimizing engine operating points for better fuel efficiency without requiring a completely different transmission architecture.
Solution Approach 2:
The planetary gear sets enable continuous variation of gear ratios across eight forward speed stages and two reverse speed stages, providing finer control over transmission parameters. This parameter flexibility allows the system to maintain optimal engine operating conditions across diverse driving scenarios, thereby improving fuel economy while adapting to different load and speed requirements.
Data Source
AI summary
A power transmission apparatus for a vehicle may include a first input shaft, a second input shaft, a third input shaft, an intermediate shaft disposed parallel to the first, second, and third input shafts, a transfer gear fixedly disposed on the intermediate shaft and outputting torque thereof, an first shifting member changing torque of an engine into first and second preliminarily shifted torques, and outputting the first and second preliminarily shifted torques, an second shifting member changing the torque of the engine into third and fourth preliminarily shifted torques, and outputting the third and fourth preliminarily shifted torques, and a third shifting member changing the torque of the engine transmitted from the first input shaft and the first preliminarily shifted torque to the fourth preliminarily shifted torque selectively transmitted from the first shifting member or the second shifting member into eight forward speed stages and one reverse speed stage.