Planetary Multi-Speed Transmission With Reduced Step Ratio Variation
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Solution Overview
Problem
Existing multi-speed transmissions exhibit significant variation in step ratios, leading to rough shifting and inefficiencies.
Innovation Solution
A multi-speed transmission design utilizing not more than four planetary gear sets and six control elements, including specific configurations of single- and double-pinion type planetary gear mechanisms, to achieve at least ten forward and two reverse gear ratios with reduced step ratio variation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional multi-speed transmission designs are used, then the number of gear ratios can be achieved, but significant variation in step ratios occurs leading to rough shifting
Solution Approach 1:
The patent applies parameter changes by carefully selecting and optimizing the tooth ratios of each planetary gear set (first through fourth) to achieve a specific sequence of step ratios. The tooth ratios are designed to follow a geometric progression pattern, which systematically controls the variation in step ratios across all gear stages, thereby smoothing the shifting characteristics without adding mechanical complexity
2Adaptability or versatility
If more planetary gear sets and control elements are added, then more gear ratios can be produced, but the device complexity increases
Solution Approach 1:
The patent implements universality by designing a compact transmission system where four planetary gear sets and six control elements serve multiple functions simultaneously. The control elements are strategically configured to engage different planetary gear sets in various combinations, enabling the system to achieve ten forward gear ratios and two reverse gear ratios without requiring additional components. This multi-functional design maximizes gear ratio versatility while minimizing device complexity
3Ease of operation
If step ratio variation is reduced for smooth shifting, then gear transition quality improves, but the design complexity of the planetary gear sets increases
Solution Approach 1:
The patent applies segmentation by dividing the transmission system into four distinct planetary gear sets, each with optimized tooth ratios. This segmentation allows independent optimization of each gear set's parameters to achieve the desired geometric progression of step ratios. By breaking down the complex requirement of smooth shifting across ten forward stages into manageable segments, the design achieves smooth transitions while maintaining manufacturability of individual gear sets
Data Source
AI summary
A multi-speed transmission includes: an input member; an output member; first to fourth planetary gear sets arranged in order in an axial direction from the input member toward the output member and each including a sun gear, a planetary carrier and a ring gear; first to third clutches; and first to third brakes. Each of the first to third clutches and the first to third brakes is operatively coupled to at least one planetary gear set of the planetary gear sets, and selectively engageable to produce a set of different gear ratios including at least ten forward gear ratios and at least two reverse gear ratios between the input member and the output member. The first clutch selectively couples the third sun gear of the third planetary gear set to the fourth planetary carrier of the fourth planetary gear set.