Off-Going Clutch Torque Control for Transmission Shifts
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Solution Overview
Problem
Conventional automatic transmission shifting strategies often result in incomplete torque transfer during gear shifts due to the off-going clutch losing torque capacity during the inertia phase, leading to inefficient power transmission and increased shift times.
Innovation Solution
A control strategy that maintains non-zero torque capacity for the off-going clutch throughout the inertia phase by commanding a series of sequential torque capacities based on measured or inferred torque, slip, and inertia torque, allowing for smoother and quicker shifts by coordinating the torque profiles of both the oncoming and off-going clutches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the off-going clutch torque capacity is reduced to zero during the inertia phase, then the shift element can be fully disengaged, but incomplete torque transfer occurs leading to increased shift times and reduced transmission efficiency
Solution Approach 1:
The control strategy applies preliminary action by maintaining off-going clutch torque capacity into the inertia phase rather than reducing it to zero. This preliminary maintenance of torque capacity ensures that torque transfer is completed before the clutch is fully disengaged, thereby reducing shift time while preventing energy loss through incomplete torque transfer.
Solution Approach 2:
The invention implements dynamics by dynamically adjusting the off-going clutch torque capacity throughout the shift process. Instead of a static zero-torque approach, the system continuously modulates torque capacity to maintain optimal levels during different phases of the shift, ensuring efficient torque transfer while enabling timely engagement of the oncoming clutch.
2Ease of operation
If the off-going clutch torque capacity is maintained at non-zero levels during the inertia phase, then smoother and quicker shifts are achieved, but the complexity of the control system increases
Solution Approach 1:
The control system employs feedback mechanisms to monitor shift phase and clutch slip conditions, using this information to dynamically adjust off-going clutch torque capacity. This feedback-driven approach enables smooth and quick shifts while managing control complexity through adaptive rather than purely predetermined control strategies.
Solution Approach 2:
The invention utilizes parameter changes by modifying the torque capacity parameter of the off-going clutch based on the shift phase and measured slip conditions. This dynamic parameter adjustment allows for optimized shift quality while keeping the control system manageable through rule-based or model-based parameter modulation rather than complex multi-variable control.
3Loss of energy
If sequential torque capacities are commanded to the off-going clutch based on measured torque, slip, and inertia torque, then thermal efficiency is improved, but the measurement and control requirements become more stringent
Solution Approach 1:
The control strategy implements self-service by using the transmission system's own operational parameters (measured torque, slip, and inertia torque) to determine the appropriate off-going clutch torque capacity. This self-service approach improves thermal efficiency through adaptive torque management while relying on existing sensors and control capabilities rather than requiring external or additional measurement systems.
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 enhances transmission performance by reducing shift times while ensuring smooth transitions between gears, improving shift quality and thermal efficiency by maintaining clutch engagement during the inertia phase.
Implementation Method 1
the off-going clutch continues to have torque capacity during the inertia phase... the off-going clutch brakes the output shaft throughout an entire duration of the inertia phase
Data Source
AI summary
A powertrain includes a transmission having an input shaft, an output shaft, and a plurality of clutches engageable in various combinations to establish varying power flow paths between the input and output shafts. A controller is programmed to, responsive to a shift of the transmission: reduce torque capacity of an off-going one of the clutches and increase torque capacity of an oncoming one of the clutches during a torque transfer phase of the shift, and, in response to an inertia phase of the shift, continue to command non-zero torque capacity to the off-going clutch such that the off-going clutch brakes the output shaft throughout an entire duration of the inertia phase.