Hydromechanical Transmission Clutch Layout for Smooth Range Shifting
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Solution Overview
Problem
Hydromechanical transmissions face issues with synchronizer degradation, increased system cost and complexity, and unwanted tradeoffs in transmission complexity, packaging efficiency, and shifting smoothness.
Innovation Solution
A transmission system with a hydrostatic assembly and mechanical branch coupled in parallel using planetary gear sets and clutches, where a controller operates the clutches to transition between drive ranges, reducing power interruptions and enhancing efficiency by additively combining and recirculating power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If synchronizing devices are used to shift between drive ranges, then shifting smoothness is improved, but system complexity and cost increase
Solution Approach 1:
The patent combines the functions of synchronizing devices and clutches into a single integrated clutch assembly. The clutch plates and synchronizing elements are merged into one component structure, eliminating separate synchronizing devices while maintaining smooth shifting capability through coordinated engagement of the clutch plates with the transmission shafts.
Solution Approach 2:
The clutch assembly performs multiple functions simultaneously: it acts as both a clutch for power transmission and a synchronizing device for smooth range transitions. The same component structure enables both power engagement/disengagement and speed synchronization during shifts between forward and reverse ranges.
2Volume of moving object
If multiple clutches are spaced away from one another, then packaging constraints are satisfied, but transmission reliability decreases due to synchronizer degradation
Solution Approach 1:
Multiple clutch assemblies are merged into a compact integrated unit where clutch plates are stacked adjacent to each other on the same shaft. This consolidation reduces the spatial separation between clutches while eliminating vulnerable synchronizing devices, thereby improving reliability through fewer degradable components.
Solution Approach 2:
The clutch plates are nested in a compact arrangement where multiple friction plates are stacked within a confined axial space. The clutch components are nested within the transmission housing, achieving dense packaging without requiring large separations between individual clutch assemblies.
3Productivity
If a compact clutch layout is used, then power interruptions during mode changes are reduced, but transmission complexity increases
Solution Approach 1:
The clutch assemblies are merged into a compact layout where multiple clutches share common shafts and housing structures. This integrated arrangement reduces the axial length and overall complexity compared to spaced-out clutches with individual mounting structures, while enabling coordinated engagement that minimizes power interruptions during range transitions.
Data Source
AI summary
Methods and systems for a hydromechanical transmission are provided herein. In one example, the transmission system includes a hydrostatic assembly and a mechanical assembly coupled in parallel to a first and second planetary gear sets. The transmission system further includes a plurality of clutches designed to shift between two drive ranges in a set of drive ranges that includes a reverse drive range and two forward drive ranges to adjust the input to output speed ratio of the transmission.