Automatic Transmission Radial Size Reduction via Axial Coupling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing automatic transmissions with four planetary gear sets and five frictional engagement elements face challenges in reducing size perpendicular to the axial direction without downsizing gears, due to the need for coupling members that increase radial size.
Innovation Solution
The configuration includes a double pinion first planetary gear set, single pinion second to fourth planetary gear sets, and specific clutch and brake arrangements to minimize coupling members passing through the circumferential sides of the gear sets, allowing the output to be directly coupled to the fourth ring gear without additional coupling members, thus reducing radial size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If coupling members pass through the outer or inner circumferential sides of the planetary gear sets to connect input and output, then the transmission can achieve multiple gear ratios, but the radial size of the automatic transmission increases
Solution Approach 1:
The patent reconfigures the transmission system by arranging four planetary gear sets coaxially along the axial direction rather than radially, and by having coupling members connect components along the axial direction. This dimensional reorganization allows multiple gear ratios to be achieved without increasing radial size, as the complexity is resolved in the axial dimension instead.
Solution Approach 2:
The patent employs a nested arrangement where four planetary gear sets are arranged coaxially, with each gear set containing sun gears, carriers, and ring gears that are interconnected through coupling members. The coupling members connect components of different planetary gear sets along the axial direction, creating a compact nested structure that achieves multiple gear ratios without radial expansion.
2Ease of manufacture
If three coupling members pass through the inner circumferential side of the fourth planetary gear set, then the gear set can be integrated into the transmission, but the size of the part around the fourth planetary gear set in the radial direction largely increases
Solution Approach 1:
The patent extracts the problematic configuration of having coupling members pass through the fourth planetary gear set's circumferential side. Instead, the coupling members are reconfigured to connect the fourth planetary gear set to other components along the axial direction, removing the radial space occupation while maintaining the integration capability.
Solution Approach 2:
The coupling members that previously occupied radial space by passing through the fourth planetary gear set are repositioned to operate in the axial dimension. This allows the fourth planetary gear set to be integrated into the transmission without increasing radial size, as the coupling connections are established along the axial direction instead.
3Power
If the output is coupled to the ring gear of the fourth planetary gear set to apply great force to the gears, then the transmission can deliver high power, but it is difficult to downsize the gears
Solution Approach 1:
The patent creates a multi-functional transmission system where four planetary gear sets work cooperatively to achieve multiple gear ratios and power delivery functions. By distributing the power transmission path across multiple gear sets connected through coupling members, the system can deliver high power without requiring any single gear set to be oversized, as the load is shared across the coordinated gear sets.
Data Source
AI summary
An automatic transmission (1) includes a first planetary gear set (PL1) of a double pinion type, second to fourth planetary gear sets (PL2-PL4) of a single pinion type, first to third clutches (CL1-CL3), and first and second brakes (B1 and B2). A third carrier (C3) and a fourth sun gear (S4) are always coupled to an input (i.e., an input shaft (3)). An output (i.e., an output gear (7)) is always coupled to a fourth ring gear (R4). A first carrier (C1) is always coupled to a third sun gear (S3). A second sun gear (S2) is always coupled to a third ring gear (R3). A first ring gear (R1) is always coupled to a second ring gear (R2).