Mechanical Reverse Assembly for Hybrid Transmission Operability
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Solution Overview
Problem
Existing hybrid vehicle transmissions that rely solely on electric reverse functionality become inoperable when the traction battery has a low state of charge, and the mechanical reverse arrangements in these systems provide limited reverse drive options and are space inefficient, leading to potential powertrain component degradation.
Innovation Solution
A mechanical reverse assembly with a reverse gearset and coupling device is integrated into the transmission, allowing for mechanical reverse operation in hybrid, full electric, and full internal combustion engine modes, enabling efficient reverse drive functionality without relying solely on electric power and maintaining compactness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If electric reverse functionality is used in hybrid vehicle transmissions, then the transmission arrangement can be compact and complexity is reduced, but the reverse drive becomes inoperable when the traction battery has a low state of charge
Solution Approach 1:
The reverse drive system is segmented into two independent subsystems: an electric reverse subsystem (motor-driven) and a mechanical reverse subsystem (gearset-driven). This segmentation allows the system to switch between electric power and mechanical power sources, ensuring that reverse drive functionality remains available even when battery state of charge is low. The mechanical reverse gearset operates independently from the electric motor, providing a backup reverse drive path.
Solution Approach 2:
A coupling device acts as an intermediary mechanism that selectively connects either the electric motor or the mechanical reverse gearset to the transmission output shaft. This coupling device mediates between the two power sources and the output, enabling smooth transitions between electric reverse and mechanical reverse modes without requiring complex control systems or additional components.
2Reliability
If a mechanical reverse arrangement is coupled to a countershaft attached to an engine, then reverse drive functionality is provided, but the transmission becomes space inefficient and complexity increases
Solution Approach 1:
The mechanical reverse gearset is merged with the existing transmission structure by integrating it into the space between the electric motor and the output shaft. Rather than adding a separate countershaft assembly attached to the engine, the reverse gearset is combined with the transmission's existing shafts and gears, utilizing unused spatial volume within the transmission housing. This merging approach provides mechanical reverse functionality while maintaining compact transmission dimensions.
Solution Approach 2:
The reverse gearset is nested within the existing transmission structure, with reverse gears positioned concentrically or adjacently to the forward drive gears. The reverse idle gear is nested between the reverse driving gear and the transmission case, efficiently utilizing the available space without increasing the overall transmission envelope. This nesting arrangement allows multiple gear functions to coexist in a compact configuration.
3Adaptability or versatility
If a planetary gearset is used for power split functionality, then both negative and positive power split modes are enabled, but the arrangement is space inefficient and component degradation likelihood increases
Solution Approach 1:
The complex planetary gearset required for power split functionality is extracted and replaced with a simpler dual-clutch gear selection mechanism. Instead of using a planetary gearset that enables both negative and positive power split modes, the invention uses two separate clutch mechanisms that selectively engage different gear sets on the primary shaft. This extraction of the planetary gearset reduces transmission space requirements and decreases the number of moving parts, thereby reducing the likelihood of component degradation while maintaining the ability to operate in both forward and reverse directions.
Data Source
AI summary
A transmission system is provided that includes a mechanical reverse assembly designed to selectively mechanically couple a reverse gearset to an output shaft of an electric machine and a first primary shaft. In the mechanical reverse assembly, a coupling device may be automatically shifted to attach the reverse gearset to the first primary shaft in a reverse drive configuration in any of a hybrid mode, a full electric vehicle (EV) mode, and a full internal combustion engine (ICE) mode.