Torque Converter Slip Control for Hybrid Driveline Damping
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Solution Overview
Problem
Conventional hybrid vehicle engine start strategies fail to smoothly transition power from electric drive mode to hybrid drive mode, leading to driveline torque disturbances that result in noise, vibration, and harshness (NVH), while also reducing efficiency due to the disengagement of the torque converter bypass clutch.
Innovation Solution
A control system for a hybrid vehicle with a torque converter that manages slip speed between the impeller and turbine to maintain constant turbine torque during engine start, using a disconnect clutch and torque converter clutch to control slip speed and torque ratio, allowing for a controlled slip mode that dampens driveline disturbances and improves efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the torque converter bypass clutch is disengaged during engine start to mitigate driveline torque disturbances, then NVH is reduced, but energy efficiency is reduced due to increased slip losses
Solution Approach 1:
The bypass clutch is transitioned from a static disengaged/engaged state to a dynamic controlled slip mode during engine start. The clutch is partially engaged to provide just enough coupling to dampen driveline torque disturbances while minimizing slip losses, optimizing the balance between NVH reduction and energy efficiency.
Solution Approach 2:
The clutch apply pressure is dynamically adjusted during engine start to achieve an optimal pressure level that provides sufficient torque disturbance mitigation while minimizing energy losses. The pressure parameter is changed from fully disengaged (0 pressure) to fully engaged (maximum pressure) through a controlled intermediate state.
2Loss of energy
If the torque converter bypass clutch is locked during electrical drive mode to improve efficiency, then energy efficiency is improved, but driveline torque disturbances are increased
Solution Approach 1:
The bypass clutch control system dynamically transitions from a locked state during electrical drive mode to a controlled slip mode during engine start. This dynamic adjustment allows the system to maintain efficiency during normal operation while providing disturbance mitigation during transition events.
Solution Approach 2:
The control system prepares for potential driveline torque disturbances by having the bypass clutch ready to transition to controlled slip mode before engine start occurs. This preliminary preparation allows for smoother transition and reduced disturbances when the engine starts during rolling operation.
3Device complexity
If traditional control approaches are used during rolling engine start, then system simplicity is maintained, but driveability and power transition smoothness are degraded
Solution Approach 1:
The control system uses feedback from engine speed sensors and torque converter slip calculations to dynamically adjust bypass clutch apply pressure during rolling engine start. This feedback mechanism enables smooth power transition and improved driveability while maintaining reasonable control complexity through algorithmic management.
Solution Approach 2:
The patent replaces complex mechanical linkage systems with electronic control of the bypass clutch. The control module electronically manages the clutch apply pressure based on operating conditions, substituting mechanical complexity with electronic control logic that achieves smoother power transitions and better driveability.
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 reduces NVH and improves driveability and energy efficiency by maintaining constant turbine torque during engine start, effectively addressing the challenges of power transition and driveline disturbances, while enhancing fuel economy by optimizing torque converter operation.
Implementation Method 1
The hydrodynamic coupling allows the engine to continue running while connected to the transmission when the vehicle is stationary. In addition, the torque converter provides torque multiplication to assist vehicle launch and provides damping of driveline torque disturbances.
Implementation Method 2
A torque converter clutch or bypass clutch may be provided to mechanically or frictionally couple the impeller and the turbine to eliminate the slip and associated losses to improve efficiency.
Data Source
AI summary
A system and method for controlling a hybrid vehicle including a transmission having a torque converter with a bypass clutch include controlling the slip between the impeller and the turbine of the torque converter in slip mode operation to regulate the converter torque ratio and maintain substantially constant torque at the turbine. Controlled slip uses the hydrodynamic coupling of the torque converter to balance the desired and delivered torque while damping torque disturbances transmitted through the driveline to manage noise, vibration and harshness (NVH).