Automatic Transmission Upshift Pressure Ramping for Low-Torque Shifts
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Solution Overview
Problem
Existing automatic transmission systems face challenges in efficiently managing upshifts when driver-demanded torque is low, particularly during mid-shift changes in driver input, such as accelerator pedal tip-in or brake application, leading to prolonged shift times and poor driveline synchronization.
Innovation Solution
A controller-programmed strategy that dynamically adjusts pressure to the oncoming shift element, initiating a series of sequentially ramping pressures to increase torque capacity and lock the element, allowing for quicker and more responsive upshifts by detecting torque capacity and adapting to changing conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a traditional pressure control strategy is used for oncoming shift elements during low torque upshifts, then the shift element engages smoothly, but the shift duration is prolonged and driveline synchronization is poor
Solution Approach 1:
The patent applies dynamics by transitioning from a static pressure control approach to a dynamic one. The controller continuously monitors torque capacity of the oncoming shift element and adjusts pressure in real-time based on detected torque capacity levels. This dynamic adaptation allows the system to optimize both shift speed and synchronization quality by varying pressure according to actual component engagement state rather than using a fixed pressure schedule.
Solution Approach 2:
The patent implements feedback control by using the detected torque capacity of the oncoming shift element as a feedback signal to adjust the pressure command. The controller detects torque capacity through torque sensor signals and uses this information to modulate the pressure applied to the shift element. This closed-loop feedback mechanism ensures that pressure application is precisely coordinated with the actual engagement state, improving both shift duration and driveline synchronization.
2Productivity
If pressure is increased early to build torque capacity quickly, then shift duration is reduced, but driveline shock and synchronization quality deteriorate
Solution Approach 1:
The system dynamically adjusts pressure based on the detected torque capacity of the oncoming shift element. Rather than applying maximum pressure immediately, the controller modulates pressure in response to real-time torque capacity measurements, enabling rapid torque buildup while maintaining driveline synchronization quality and avoiding shock.
Solution Approach 2:
The feedback mechanism monitors torque capacity continuously and uses this information to regulate pressure application. This ensures that pressure is increased at the optimal rate to build torque capacity quickly without causing driveline shock, as the controller can detect and respond to the actual engagement state of the shift element.
3Loss of time
If pressure is increased to lock the oncoming shift element quickly, then shift duration is reduced, but torque capacity overshoot and instability increase
Solution Approach 1:
The controller dynamically adjusts pressure based on real-time detection of torque capacity. As the oncoming shift element approaches full engagement, the controller modulates pressure to prevent overshoot, maintaining stable torque capacity throughout the shift process while minimizing shift duration.
Solution Approach 2:
The feedback control system detects torque capacity levels and uses this information to regulate pressure application. When torque capacity approaches the desired level, the controller reduces pressure increase rate or holds pressure constant, preventing torque capacity overshoot and ensuring stable engagement of the oncoming shift element.
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 reduces shift duration, improves driveline synchronization, and enhances vehicle performance by ensuring timely torque capacity buildup during upshifts, even under variable driver inputs.
Implementation Method 1
command a first pressure, that is greater than zero, to an oncoming shift element associated with the upshift
Implementation Method 2
The oncoming clutch pack includes a plurality of friction plates alternately interleaved with a plurality of steel plates
Data Source
AI summary
According to one embodiment, a vehicle includes a transmission, a brake pedal, and a controller. The controller is programmed to, in response to an upshift of the transmission, a driver-demanded torque being zero, and the brake pedal being released, command a first pressure, that is greater than zero, to an oncoming shift element associated with the upshift such that the oncoming shift element has a torque capacity of zero, in response to the brake pedal being applied during the upshift of the transmission, command a second, larger pressure to the oncoming shift element to increase the torque capacity to a non-zero value, and, in response to expiration of a threshold time from the brake pedal being applied, command a series of sequentially ramping pressures to the oncoming shift element to further increase the torque capacity and lock the oncoming shift element.