One-Piece Planet Carrier With Offset Pockets
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing two-piece planet carrier design for planetary gearboxes in automatic transmissions is costly and reduces load capacity due to the need for additional assembly and complex manufacturing processes, such as casting with melt-out cores or machining, which are expensive and difficult to execute.
Innovation Solution
A one-piece planet carrier design with angled offset pockets for accommodating planetary gears of each stage, allowing for conventional casting and reduced production costs, where the pockets are formed using radial slides, and optionally featuring webs for increased stiffness and individual adaptation of planetary stages based on torque requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the planet carrier is manufactured as one piece using conventional casting processes, then production costs are reduced and manufacturing is simplified, but the pockets for accommodating planetary gears cannot be formed due to undercut geometry
Solution Approach 1:
The patent applies asymmetry by offsetting the pockets for accommodating planetary gears of the first stage relative to the pockets for the second stage in the circumferential direction. This asymmetric arrangement eliminates the undercut geometry that prevents conventional casting, allowing the planet carrier to be manufactured as a one-piece component using standard casting processes without requiring expensive melt-out cores or post-casting machining.
2Ease of manufacture
If the planet carrier is designed as two separate pieces to accommodate planetary gears of different stages, then the pockets can be formed during casting, but additional assembly steps are required which increase production cost and reduce load capacity
Solution Approach 1:
The patent merges the two separate planet carrier pieces into a single integrated component. By offsetting the pockets circumferentially, the design allows all pockets to be formed during a single casting process, eliminating the need for joining two separate pieces. This results in a one-piece planet carrier with improved load capacity and structural integrity while maintaining manufacturing simplicity.
3Device complexity
If expensive casting procedures with melt-out cores or post-casting machining are used to manufacture a one-piece planet carrier, then the undercut pockets can be formed, but production costs significantly increase
Solution Approach 1:
The asymmetric circumferential offset of pockets eliminates the undercut geometry that necessitates expensive melt-out cores or post-casting machining. This allows the use of conventional, cost-effective casting processes to manufacture the one-piece planet carrier, achieving both structural integration and cost efficiency.
Data Source
AI summary
A planetary gearbox, for an automatic transmission of a motor vehicle, comprising two stages, each provided with a sun gear, a ring gear and interposed planetary gears. The ring gear of the first planetary stage also forms the sun gear of the second stage, and the planetary gears of both stages are guided by a common planet carrier, produced from a casting material, which accommodates the planetary gears of the first stage at an axial offset position to the planetary gears of the second stage. The planet carrier is designed as one-piece such that pockets are respectively disposed in the planet carrier for receiving the planetary gears of the first stage at an offset angle, in the circumferential direction, to the pockets for receiving the planetary gears of the second stage, so that it is possible to form the pockets during casting using slides.