Two-Stage Planetary Gear Transfer Case Axial Design
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Solution Overview
Problem
Two-stage transfer cases in countershaft construction require significant installation space, making them unsuitable for applications with limited space, while planetary designs face high switching forces due to the mass of the planetary carrier and gears, leading to delayed shifting operations.
Innovation Solution
A compact axial design for the transfer case with a two-stage planetary drive where only the lightweight ring gear is axially displaced, eliminating the need to shift the heavy planetary carrier and gears, using a shift sleeve to change gear positions and employing clutches for torque transfer, allowing for smaller shifting forces and faster switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a two-stage transfer case is designed in countershaft construction, then it represents a relatively inexpensive and technically simple solution, but it requires a comparatively large amount of installation space axially
Solution Approach 1:
The patent inverts the conventional approach by making the ring gear movable instead of the planetary carrier. In traditional designs, the planetary carrier must be shifted axially, but this invention displaces the ring gear along the axial direction while the planetary carrier remains stationary. This inversion resolves the contradiction by achieving gear stage switching without moving the heavy planetary carrier, thus reducing axial installation space requirements while maintaining manufacturing simplicity
2Length of moving object
If a two-stage transfer case is designed with planetary construction, then it achieves a space-saving axial design, but a comparatively large mass has to be shifted during shifting operations requiring high switching forces
Solution Approach 1:
The patent extracts the movable function from the planetary carrier and assigns it to the ring gear instead. By making the ring gear the movable component while keeping the planetary carrier stationary, the design eliminates the need to shift the large mass of the planetary carrier and planetary gears. This extraction principle resolves the contradiction by achieving compact axial design while significantly reducing the mass that must be moved during shifting operations
Solution Approach 2:
The patent inverts the conventional planetary gear switching mechanism by making the ring gear movable instead of the planetary carrier. This inversion allows the lighter ring gear to be displaced axially while the heavy planetary carrier remains fixed, thus reducing both axial installation space and the shifting forces required during gear changes
3Adaptability or versatility
If the planetary carrier with planetary gears is shifted during gear changing, then gear stages are switched, but the large mass requires high switching forces and leads to delays in switching processes
Solution Approach 1:
The patent extracts the shifting function from the planetary carrier and assigns it to the ring gear. By making the ring gear the movable component, the design eliminates the need to shift the heavy planetary carrier mass during gear changes. This extraction enables rapid gear stage switching with reduced mass movement, thus reducing shifting time and delays while maintaining full gear stage switching capability
Solution Approach 2:
The patent inverts the conventional approach by making the ring gear movable instead of the planetary carrier. This inversion enables the lighter ring gear to be displaced axially for gear stage switching, significantly reducing the mass that must be moved and thereby decreasing shifting time and delays while preserving complete gear stage adaptability
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables a compact, space-efficient transfer case with reduced shifting forces and faster gear changes, suitable for applications with limited space, and enhances the robustness and reliability of the gear shifting process.
Implementation Method 1
the ring gear (6) can be brought into a first and a second axial position by means of a shift sleeve (10), which is mounted in an axially displaceable manner
Implementation Method 2
In the first axial position, the ring gear (6) can be coupled in a torque-proof manner to a transmission housing (9) via a first clutch (11)
Data Source
Figure 1
AI summary
The invention relates to a two-stage planetary drive (2) for a transfer case (1) of a motor vehicle, comprising a planet carrier (5), a ring gear (6), a sun gear (7), and planet gears (8, 8'), wherein the planetary drive (2) is arranged concentrically within a drive gear (5'). The planetary drive (2) according to the invention is characterized in that the ring gear (6) is arranged to be axially displaceable within the planetary drive (2). The invention further relates to a corresponding transfer case.