12-Speed Planetary Gear Train with Nested Shaft Configuration
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Solution Overview
Problem
Automatic transmissions face challenges in achieving high fuel efficiency and reducing drag torque due to increased complexity and weight with more transmission steps, which complicates mountability, cost, and efficiency.
Innovation Solution
A planetary gear train with a minimum configuration that implements forward 12-speed and reverse 1-speed transmission using five planetary gear sets and six friction elements, minimizing non-operating friction elements to reduce drag torque and enhance power transmission performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the number of transmission steps is increased to improve fuel efficiency, then fuel efficiency is improved, but the number of internal components increases causing deterioration in mountability, cost, weight, and transmission efficiency
Solution Approach 1:
The patent merges multiple planetary gear sets into a integrated structure where five planetary gear sets share common rotational shafts and friction elements. The first and second planetary carriers are connected to the same rotational shaft, as are the first and second ring gears, allowing multiple gear sets to operate cooperatively with shared components rather than as separate units
Solution Approach 2:
Each friction element is designed to perform multiple functions across different transmission steps. The six friction elements selectively connect various rotational shafts and the transmission housing to achieve 12 forward speeds and 1 reverse speed, allowing each element to engage different gear sets at different times rather than requiring dedicated friction elements for each transmission step
Solution Approach 3:
The planetary gear sets are arranged in a nested configuration along the input shaft, with gear sets positioned sequentially from the engine side. The rotational shafts are interconnected such that multiple planetary carriers and ring gears share common shafts, creating a compact nested structure that reduces overall system complexity
2Adaptability or versatility
If more friction elements are used to achieve more transmission steps, then transmission steps increase, but drag torque increases due to more non-operated friction elements
Solution Approach 1:
The system uses exactly six friction elements to achieve 12 forward transmission steps and 1 reverse step, which is a minimal configuration. Each friction element is strategically positioned to enable multiple transmission ratios through selective engagement, avoiding the need for additional friction elements that would increase drag torque during non-operational states
Solution Approach 2:
Friction elements are selectively engaged and disengaged based on the required transmission step. When a friction element is not needed for the current transmission ratio, it is disengaged to minimize drag torque, and recovered for use in subsequent transmission steps where it may be required
Data Source
AI summary
A planetary gear train of an automatic transmission may include an input shaft, a first planetary gear set including a first sun gear, a first planetary carrier, and a first ring gear, a second planetary gear set including a second sun gear, a second planetary carrier, and a second ring gear, a third planetary gear set including a third sun gear, a third planetary carrier, and a third ring gear, a fourth planetary gear set including a fourth sun gear, a fourth planetary carrier, and a fourth ring gear, a fifth planetary gear set including a fifth sun gear, a fifth planetary carrier, and a fifth ring gear, first to ninth rotational shafts, and six friction elements selectively connecting the rotational shafts and the rotational shaft and the transmission housing.