Four-Planetary Gear Transmission for Vehicle
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Solution Overview
Problem
Automatic transmissions with increased shift ranges face challenges in manufacturing cost, weight, and power transmission efficiency due to the increased number of parts, necessitating a gear train structure that achieves maximum efficiency with fewer components to improve fuel efficiency and driving comfort.
Innovation Solution
A transmission system utilizing four planetary gear sets with three rotary elements each, connected by clutches and brakes, allowing for selective engagement and disengagement to achieve multiple gear ratios, including ten or more forward shifting steps and one reverse shifting step, while maintaining a reduced part count.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the shift ranges increase in automatic transmission, then fuel efficiency improves through multiple steps of shifting, but the number of parts increases making the transmission difficult to mount and increasing manufacturing cost and weight
Solution Approach 1:
The patent combines multiple planetary gear sets (first, second, third, and fourth planetary gear sets) into a single integrated transmission system where gear sets share common components such as carriers and sun gears. This merging approach enables multiple shift ranges to be achieved without proportionally increasing the number of parts, as shared components reduce overall complexity while maintaining the capability for multiple gear ratio changes.
Solution Approach 2:
The planetary gear sets are designed with multi-functional rotary elements that can serve multiple purposes. For example, the first rotary element of the first planetary gear set is selectively connected with the third rotary element of the fourth planetary gear set, allowing a single component to participate in multiple gear ratio configurations. This universality enables the system to achieve multiple shift ranges without requiring dedicated components for each function.
2Use of energy by moving object
If the shift ranges increase in automatic transmission, then fuel efficiency improves through multiple steps of shifting, but the weight increases
Solution Approach 1:
The patent merges multiple planetary gear sets into a compact integrated structure where components are shared across different gear sets. By combining gear sets and eliminating redundant parts, the overall weight of the transmission system is reduced while maintaining the capability for multiple shift ranges that improve fuel efficiency.
Solution Approach 2:
The planetary gear sets are arranged in a nested configuration where inner gear sets are positioned within or alongside outer gear sets. This nesting approach allows multiple planetary gear sets to occupy reduced spatial volume and minimizes overall transmission weight while enabling multiple gear ratio changes for improved fuel efficiency.
3Use of energy by moving object
If the shift ranges increase in automatic transmission, then fuel efficiency improves through multiple steps of shifting, but power transmission efficiency deteriorates
Solution Approach 1:
The integrated planetary gear set design reduces the number of discrete components and connection points in the power transmission path. By merging gear sets and using shared components, the patent minimizes energy losses at interfaces and maintains high power transmission efficiency across multiple shift ranges.
Solution Approach 2:
The transmission system employs dynamic engagement and disengagement of friction members (clutches and brakes) to selectively connect different planetary gear sets based on operating conditions. This dynamic configuration allows the system to optimize power transmission efficiency for each gear ratio while maintaining the capability for multiple shift ranges that improve overall fuel efficiency.
Data Source
AI summary
A transmission may include input shaft connected to second rotary element of the third planetary gear set and first clutch; first shaft connecting first rotary element of the second planetary gear set, and second clutch; second shaft connecting first rotary element of the third planetary gear set and first brake; third shaft connecting first rotary element of the first planetary gear set and third clutch; fourth shaft connecting third rotary element of the fourth planetary gear set, the third clutch, and second brake; fifth shaft connecting second rotary element of the first planetary gear set, second rotary element of the second planetary gear set, and third rotary element of the third planetary gear set; and sixth shaft connecting third rotary element of the first planetary gear set, third rotary element of the second planetary gear set, first rotary element of the fourth planetary gear set, and fourth clutch.