Torque Converter Bypass Clutching for High-Speed EV Powertrains
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Solution Overview
Problem
In powertrains, especially in electric vehicles, torque converters are inefficient at higher speeds and increase rotational inertia, limiting motor-generator unit (MGU) performance and energy efficiency due to centrifugal forces and hydraulic pressure requirements.
Innovation Solution
A system that includes a torque converter bypass shaft and clutches to selectively bypass the torque converter, allowing torque transmission through the bypass shaft at higher speeds, controlled by a computerized transmission mode controller to manage clutch engagement and hydraulic pressure, reducing rotational inertia and energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the torque converter is connected to the MGU output shaft, then torque transmission and vibration filtering are improved, but rotational inertia increases and energy efficiency deteriorates at higher speeds
Solution Approach 1:
The system dynamically switches between two torque transmission paths: through the torque converter (for low-speed operation requiring vibration filtering and torque multiplication) and through the bypass shaft (for high-speed operation requiring energy efficiency). The disconnect clutch and torque converter clutch enable this dynamic reconfiguration based on operating conditions, allowing the MGU to operate beyond torque converter speed limits while maintaining optimal performance characteristics for each regime.
2Stability of the object's composition
If the torque converter is connected to the MGU output shaft, then vibration filtering is improved, but centrifugal forces and hydraulic pressure requirements increase at higher speeds
Solution Approach 1:
The torque transmission system is segmented into two independent paths: one through the torque converter (providing vibration filtering and torque multiplication) and one through the bypass shaft (providing direct, efficient torque transmission). The segmentation allows the system to select the appropriate path based on operating conditions, avoiding the hydraulic pressure and centrifugal force issues of the torque converter at high speeds while retaining its vibration filtering benefits at low speeds.
3Power
If the torque converter is connected to the MGU output shaft, then torque multiplication is improved, but device complexity increases with additional clutches and control systems
Solution Approach 1:
The torque converter assembly serves multiple functions: it provides torque multiplication during low-speed operation, acts as a vibration filter during transient conditions, and can be selectively disconnected during high-speed operation to reduce rotational inertia. The bypass shaft and dual-clutch system enable this multi-functionality, allowing the same physical assembly to adapt its behavior based on operating conditions rather than requiring separate systems for each function.
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
This solution enhances energy efficiency by avoiding centrifugal forces and reducing hydraulic pressure load, allowing the MGU to operate beyond torque converter speed limits and conserving energy by disconnecting the torque converter at high speeds.
Implementation Method 1
A fluid coupling of the torque converter may smooth or filter out vibrations and oscillating torques that are applied to either the torque converter input shaft or the torque converter output shaft.
Implementation Method 2
inefficient at higher speeds and increase rotational inertia, limiting motor-generator unit (MGU) performance and energy efficiency due to centrifugal forces and hydraulic pressure requirements
Data Source
AI summary
A system for bypassing a torque converter in a powertrain is provided. The system includes a torque generating device including an output shaft and a transmission assembly. The transmission assembly includes a transmission output shaft and a torque converter, a torque converter bypass shaft. The transmission assembly further includes a disconnect clutch selectively coupling the torque converter with the torque generating device and a torque converter clutch selectively coupling the torque converter bypass shaft with the torque generating device. Engaging the disconnect clutch and disengaging the torque converter clutch enables the torque generating device to transmit torque to the transmission output shaft through the torque converter. Engaging the torque converter clutch and disengaging the disconnect clutch enables the torque generating device to transmit torque to the transmission output shaft through the torque converter bypass shaft.