Powertrain Torque Coordination for Smooth Transmission Shifts
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Solution Overview
Problem
Existing vehicle powertrain control systems face challenges in efficiently managing engine torque during transmission shifts to ensure smooth power delivery and mechanical limits, particularly in coordinating clutch engagement and engine operation to prevent torque disturbances.
Innovation Solution
A controller-programmed method that adjusts engine torque by retarding the spark and shutting down engine cylinders based on threshold values to synchronize with clutch pressure changes, ensuring the engine torque is within the mechanical limits of the oncoming clutch during transmission shifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the oncoming clutch pressure is increased to engage the clutch during transmission shift, then the clutch engagement is improved, but torque disturbances and mechanical stress on the clutch are increased
Solution Approach 1:
The controller retards the engine spark timing and shuts down cylinders before the oncoming clutch is fully engaged to preemptively reduce engine torque. This preliminary torque reduction ensures that when clutch pressure increases for engagement, the torque disturbances and mechanical stress on the clutch are minimized, allowing reliable engagement without harmful torque spikes.
Solution Approach 2:
The system dynamically changes engine operating parameters (spark timing and cylinder operation) during the clutch engagement process. By retarding spark timing and selectively shutting down cylinders, the engine torque is adjusted to match the mechanical limits of the oncoming clutch, enabling smooth engagement while preventing torque disturbances that would harm the clutch.
2Object-affected harmful factors
If the engine torque is reduced during clutch engagement, then torque disturbances are minimized, but the acceleration performance is degraded
Solution Approach 1:
The controller dynamically adjusts engine torque during the clutch engagement process by selectively shutting down cylinders and retarding spark timing only for the duration of the engagement. This temporary, dynamic torque reduction minimizes disturbances, while the system quickly restores full torque after engagement, maintaining overall acceleration performance without sustained degradation.
Solution Approach 2:
The torque reduction is applied periodically only during the specific time window of clutch engagement rather than continuously. The controller temporarily reduces torque by shutting down cylinders and retarding spark, then restores full torque output after engagement is complete, achieving smooth shifting without prolonged acceleration degradation.
3Power
If all cylinders are maintained operating during clutch engagement, then the power output is maximized, but the torque control precision is reduced
Solution Approach 1:
The controller segments the engine's cylinder operation during clutch engagement by selectively shutting down specific cylinders while maintaining operation of others. This segmentation allows precise control of the total engine torque output to match clutch mechanical limits, while minimizing the impact on overall power output by keeping remaining cylinders operating at full capacity.
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 ensures continuous positive acceleration and reduces torque disturbances by optimizing engine torque and clutch pressure coordination, enhancing the efficiency and reliability of power delivery during transmission shifts.
Implementation Method 1
retard an engine spark to reduce the torque of the engine during the engagement of the oncoming clutch
Implementation Method 2
increase a pressure of an oncoming clutch to engage the oncoming clutch
Data Source
AI summary
A vehicle includes an engine, a transmission, and a controller. The engine is configured to generate power. The transmission is configured to transfer power from the engine to at least one drive wheel to propel the vehicle. The controller is programmed to, in response to a command to shift the transmission and a corresponding command to decrease a torque of the engine to less than a threshold corresponding to a spark retard limit during the shift, (i) increase the pressure of an oncoming clutch to engage the oncoming clutch, (ii) retard an engine spark at the spark retard limit to reduce the torque of the engine to the threshold during the engagement of the oncoming clutch, and (iii) shutdown at least one cylinder of the engine to further reduce the torque of the engine to less than the threshold during the engagement of the oncoming clutch.