Planetary Gear Train for 9-Speed Automatic Transmission
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Solution Overview
Problem
Automatic transmissions with increased shift stages face challenges in installability, production cost, weight, and power flow efficiency due to the need for more planetary gear sets and control elements, which complicates achieving better fuel consumption and drivability.
Innovation Solution
A planetary gear train design that utilizes four planetary gear sets and six control elements to achieve at least nine forward speeds and one reverse speed, optimizing power delivery and fuel consumption by minimizing the number of parts and improving engine rotation speed compatibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the number of speed stages is increased to enhance fuel consumption and drivability, then fuel efficiency and drivability are improved, but the number of internal components (planetary gear sets) increases, deteriorating installability, production cost, weight and power flow efficiency
Solution Approach 1:
The patent merges multiple planetary gear sets into a single integrated structure where three planetary gear sets share a common carrier. This consolidation reduces the total number of independent planetary gear sets from what would traditionally be required for 9-speed transmission, thereby improving fuel efficiency while avoiding the complexity penalty of multiple separate gear sets
Solution Approach 2:
The common carrier structure serves multiple functions simultaneously: it supports planet gears for three different planetary gear sets, provides a mounting structure for control elements, and acts as a structural element for torque transmission. This multi-functionality allows the transmission to achieve 9 forward speeds and reverse speeds without proportionally increasing component count
2Adaptability or versatility
If three to four planetary gear sets and five to six control elements are used to achieve eight or more shift stages, then more speed stages are obtained, but the transmission becomes lengthy, deteriorating installability
Solution Approach 1:
The patent employs a nested arrangement where three planetary gear sets are integrated within a shared carrier structure. The planet gears of different planetary gear sets are arranged concentrically and share the same carrier space, creating a compact nested configuration that achieves 9-speed capability without increasing transmission length proportionally
Solution Approach 2:
Instead of arranging planetary gear sets in a linear sequence along the transmission axis, the patent utilizes radial and axial spacing within a compact volume. The gear sets are distributed in three-dimensional space around the common carrier, transforming a one-dimensional linear arrangement into a multi-dimensional compact layout that reduces overall transmission length
3Device complexity
If dog clutches are used instead of wet-type control elements to reduce part count, then number of parts is reduced, but shift-feel deteriorates
Solution Approach 1:
The patent employs control elements that are designed for controlled wear and replacement. The wet-type clutches and brakes are engineered with friction materials that can be replaced independently, allowing the transmission to maintain smooth shift-feel over extended periods while using a minimal number of control elements (only 6 total)
Solution Approach 2:
The patent optimizes the friction characteristics and engagement parameters of the wet-type control elements to achieve smooth shift-feel with fewer components. By carefully controlling engagement pressure, friction coefficients, and timing, the transmission delivers superior shift quality using only 6 control elements rather than the 5-6 typically required for 8-speed transmissions
Data Source
AI summary
A planetary gear train of claim of an automatic transmission for a vehicle may include an input shaft for receiving an engine torque, an output shaft, a first planetary gear set, a second planetary gear set, a third planetary gear set, a fourth planetary gear set, a first shaft, a second shaft directly connected with the input shaft, a third shaft, a fourth shaft, a fifth shaft selectively connectable with each of the third shaft and the fourth shaft, a sixth shaft selectively connectable with the second shaft, a seventh shaft, and an eighth shaft directly connected with the output shaft.