Motor Vehicle Transmission with Five Forward Gear Ratios
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Solution Overview
Problem
Current multi-ratio transmissions in motor vehicles are limited to four forward gear ratios, which restrict their adaptability to varying driving conditions, and lack efficient reverse gear ratio options.
Innovation Solution
A transmission design incorporating a planetary gear set system with specific sun gears, ring gears, planet gears, and shift elements allows for the formation of five forward gear ratios and a reverse gear ratio, utilizing frictionally and positively engaging shift elements to optimize power transmission and reduce drag losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional multi-ratio transmission with four shift elements is used, then the structure is relatively simple, but only four forward gear ratios can be formed which limits adaptability to varying driving conditions
Solution Approach 1:
The first sun gear serves multiple functions: it can be connected to the drive shaft via the third shift element, rotationally fixed by the second shift element, or connected to an electric machine (in hybrid configurations). This multi-functionality allows the same component to participate in different gear ratio formations without requiring additional dedicated components, thereby enabling five forward gear ratios while maintaining structural efficiency.
Solution Approach 2:
The transmission employs dynamically controllable shift elements (clutches and brakes) that can be selectively engaged or disengaged to change the gear ratio. The second shift element dynamically fixes the first sun gear to form certain gear ratios, while the third shift element dynamically connects the drive shaft to the second sun gear for other ratios. This dynamic control enables flexible gear selection without permanent mechanical constraints.
2Ease of operation
If frictionally engaging shift elements are used, then smooth gear transitions are achieved, but drag losses increase reducing transmission efficiency
Solution Approach 1:
The transmission utilizes periodic engagement and disengagement of shift elements to achieve smooth gear transitions. The frictionally engaging shift elements are designed to gradually engage and disengage during gear changes, creating a controlled periodic action that minimizes shock while maintaining smooth transitions. This periodic action allows the system to benefit from frictional engagement during transitions while managing energy losses through optimized engagement timing and duration.
Data Source
AI summary
A motor vehicle transmission comprising a drive shaft, an output shaft, a planetary gear set system, and four shift elements. The first planet gear meshes with the first sun gear, first ring gear, and with one of the second planet gears. The second planet gear meshes with the second sun gear and second ring gear. The first sun gear has a smaller diameter than the second sun gear. The first ring gear has a larger diameter than the second ring gear, and is connected to the output shaft. The second ring gear is rotationally fixable by closing the first shift element. The drive shaft is connectable to the second sun gear by closing the third shift element. The drive shaft is connectable to the planet carrier by closing the fourth shift element. The first sun gear is rotationally fixable by closing the second shift element.