Automatic Transmission Shift Control During Inertia Phase
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Solution Overview
Problem
In automatic transmissions, downshift speed changes during upshift speed changes can be difficult to progress when torque input is low, leading to challenges in raising the input shaft rotational speed to the required synchronous speed.
Innovation Solution
A control apparatus and method that prohibits shifts from upshift to downshift for a predetermined period during an inertia phase of upshift speed change, allowing torque input to rise before initiating downshift speed change, ensuring smooth progression by starting the downshift when torque becomes sufficiently high.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If downshift speed change is started immediately when torque input is low, then responsiveness is improved, but the input shaft rotational speed cannot be swiftly raised to the required synchronous speed, causing difficulty in progressing the downshift
Solution Approach 1:
The control apparatus waits for torque input to reach a predetermined level before initiating the downshift speed change. This preliminary action ensures that sufficient torque is available to swiftly raise the input shaft rotational speed to the required synchronous speed, preventing progression difficulties while maintaining responsiveness
2Reliability
If downshift speed change is delayed until torque input is high, then downshift progression is improved, but the responsiveness to downshift requests is reduced
Solution Approach 1:
The control apparatus monitors the torque input parameter and uses it as a gating condition for initiating downshift. By changing the operational parameter from immediate response to torque-threshold response, the system achieves smooth progression without excessive delay, as the threshold is set to balance responsiveness and progression reliability
3Adaptability or versatility
If multiple shifts are allowed during upshift inertia phase, then shift flexibility is improved, but engine racing occurs due to insufficient feedback control time
Solution Approach 1:
The control apparatus prohibits downshift speed change requests during the inertia phase of upshift as a preliminary protective measure. This prevents the harmful effect of engine racing before it can occur, while still allowing flexible shift transitions after the inertia phase completes by clearing the prohibition flag
Data Source
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AI summary
A control apparatus for a stepped automatic transmission (3) in which one of a plurality of shift speeds is established by selectively engaging a plurality of frictional engagement elements, the stepped automatic transmission (3) mounted on a vehicle, the control apparatus includes: an electronic control unit (5) configured to perform a control of prohibiting a plurality of shift that is transitioning from an upshift speed change to a downshift speed change, for a predetermined period, when a downshift speed change requirement is requested by an occurrence of an accelerator depression operation during an inertia phase of the upshift speed change in a driven state of a vehicle.