Hybrid Powertrain Torque Converter Clutch Control Logic
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Solution Overview
Problem
In hybrid electric powertrains with a P2 configuration, the interposition of a hydrokinetic torque converter complicates torque blending operations during mode transitions, leading to undesirable driveline torque disturbances due to suboptimal methods for connecting or disconnecting the engine from the transmission input member.
Innovation Solution
A controller is configured to control shift progression and engine ON/OFF transitions by selectively overriding the torque converter clutch to ensure it remains open until the engine disconnect clutch is fully disengaged, using speed differentials across the torque converter to determine the engine state and execute smooth electric vehicle mode shifts using machine torque from the rotary electric machine.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the torque converter clutch is allowed to close before the engine disconnect clutch is fully disengaged during mode transitions, then the transition process is simpler and faster, but driveline torque disturbances occur and torque blending becomes suboptimal
Solution Approach 1:
The controller executes preliminary sequencing of clutch operations where the engine disconnect clutch is commanded to disengage before the torque converter clutch is allowed to close. This preliminary action ensures that the engine is fully disconnected from the transmission input shaft before torque multiplication begins, preventing torque disturbances during the mode transition.
Solution Approach 2:
The control system dynamically adjusts the timing and sequencing of clutch operations based on real-time operating conditions. The controller monitors the states of both clutches and dynamically coordinates their transition to ensure smooth torque blending while minimizing disturbances, adapting the transition profile to current powertrain demands.
2Device complexity
If suboptimal methods are used for connecting or disconnecting the engine from the transmission input member, then the control logic is simpler, but torque blending operations are complicated by the torque converter interposition
Solution Approach 1:
The controller implements feedback-based control by continuously monitoring the states of the engine disconnect clutch and torque converter clutch, as well as operating parameters such as turbine speed and pump speed. This feedback enables the controller to make real-time adjustments to clutch actuation commands, ensuring optimal torque blending while accounting for the complex interactions introduced by the torque converter.
Solution Approach 2:
The controller acts as an intermediary that coordinates the operations of two separate clutches (engine disconnect clutch and torque converter clutch) to achieve smooth torque blending. By mediating between these components and sequencing their operations appropriately, the controller simplifies the overall control strategy while eliminating torque blending complications.
3Device complexity
If the engine disconnect clutch is an integral component of the torque converter without active control, then the device structure is more compact, but execution of disclosed logic is required to compensate for the absence of active control
Solution Approach 1:
The passive one-way engine disconnect clutch operates on a self-service basis, automatically engaging or disengaging based on torque flow direction and magnitude without requiring active actuation signals. This self-service mechanism simplifies the mechanical structure while the controller compensates by implementing sophisticated logic to predict and respond to clutch state changes based on operating conditions.
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 approach optimizes mode transitions and EV shifts by ensuring seamless torque blending, reducing driveline disturbances and improving fuel efficiency by allowing precise control over engine and electric machine torque contributions.
Implementation Method 1
a hydrokinetic torque converter between the engine and the transmission. As will be appreciated by those of ordinary skill in the art, a torque converter includes a stator disposed between an engine-connected impeller or pump and a turbine connected to the transmission's input shaft
Implementation Method 2
The TCC is selectively applied under certain conditions to securely lock the pump to the turbine, thereby eliminating slip across the torque converter
Implementation Method 3
a passive one-way clutch is used as the engine disconnect clutch on the turbine side of the torque converter. When the engine disconnect clutch is open, the engine is completely disconnected from the transmission's input shaft regardless of the state of the TCC
Data Source
AI summary
A hybrid electric powertrain for a vehicle includes an engine, electric machine, torque converter having a pump, turbine, and torque converter clutch (“TCC”) configured, when applied, to lock the pump to the turbine, a one-way engine disconnect clutch connected to the turbine, a transmission, and a controller. A transmission input shaft directly couples to the electric machine, and is selectively coupled to the engine via the disconnect clutch. An output shaft is connectable to road wheels of the vehicle. The controller, in response to an engine-off request, determines turbine and pump speeds of the turbine and pump, respectively, registers that the engine is in an engine-off state when the pump speed is less than the turbine speed, and executes an electric vehicle (“EV”) mode shift using machine torque from the electric machine when the pump speed is zero during the engine-off state.