Crankshaft Torque Control During Transmission Shifts
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Solution Overview
Problem
Automatic transmissions face challenges in achieving shorter shift times and a greater range of torque reduction authority during upshifts, as existing systems relying on spark retard can negatively impact fuel economy and may not provide sufficient control.
Innovation Solution
A control system that utilizes a combination of slow and fast torque actuators, including airflow, spark, and fuel actuators, to manage crankshaft torque during transmission shifts, with algorithms determining the appropriate actuation range based on target gear, shift duration, and vehicle operating conditions, allowing for independent requests of these actuators to achieve precise torque control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If spark retard is used for torque reduction during a shift, then fast torque control is achieved, but fuel economy deteriorates
Solution Approach 1:
The torque reduction task is segmented between two different actuators: spark retardation handles the fast initial torque reduction, while airflow reduction handles the sustained torque reduction. This segmentation allows each actuator to operate in its optimal performance range, achieving fast control response without excessive fuel waste.
Solution Approach 2:
The airflow actuator is commanded in advance before the spark actuator during the shift event. This preliminary action allows the airflow system to begin its torque reduction process early, so that when the spark actuator engages, the total torque reduction is already partially achieved, reducing the burden on the spark system and minimizing fuel economy impact.
2Device complexity
If spark retard alone is used for torque reduction, then simple control is maintained, but torque reduction range and shift time are insufficient
Solution Approach 1:
The system merges two torque actuators (spark and airflow) into a coordinated control system. The spark actuator provides fast initial torque reduction, while the airflow actuator provides sustained torque reduction capability. This combination extends the effective torque reduction range and enables shorter shift times while maintaining manageable control complexity through coordinated actuation.
3Device complexity
If airflow actuator is commanded after spark actuator, then simple sequencing is used, but torque control precision deteriorates
Solution Approach 1:
The conventional sequencing is inverted: instead of commanding the spark actuator first and then the airflow actuator, the system commands the airflow actuator in advance before the spark actuator. This inversion compensates for the slower response time of the airflow system, ensuring that airflow torque reduction is already underway when the spark actuator engages, thereby improving overall torque control precision.
Data Source
AI summary
A control system for use with an engine and a transmission in a vehicle is provided that includes at least one controller having a processor with at least one stored algorithm that determines different crankshaft torque capacities associated with different respective torque actuators including a relatively slow torque actuator, such as an airflow actuator, and at least one relatively fast torque actuator, such as a spark actuator or a fuel actuator. The algorithm determines a torque actuation range over which to modify engine torque during an oncoming shift of the transmission. The torque actuation range may be based at least partially on a target gear of the upshift, desired shift duration, and a vehicle operating condition indicative of an operator intent regarding shift duration. Requests for torque modification by use of the torque actuators are then made to provide the torque actuation range.