Closed-loop Torque Phase Control for Automatic Transmission Shifts
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Solution Overview
Problem
Conventional automatic transmission shift control methods rely on open-loop speed measurements, leading to inconsistent shift feel and undesirable shift shock due to premature or delayed release of friction elements, and are sensitive to slip conditions and friction coefficient discontinuities.
Innovation Solution
A closed-loop shift control system that measures or estimates torsional load on off-going friction elements and on-coming friction element engagement torque to optimize the timing of friction element release and engagement, ensuring consistent shift feel by maintaining torque capacity until a predetermined level is reached and then decreasing it.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If open-loop speed measurement control is used for friction element release timing, then the control system is simple, but shift feel becomes inconsistent and shift shock occurs
Solution Approach 1:
The patent implements closed-loop feedback control by continuously monitoring the actual torque transmitted through the off-going friction element and comparing it with a reference torque profile. The controller adjusts the release timing based on this feedback, ensuring consistent shift feel across different operating conditions while maintaining manageable system complexity through efficient sensor utilization and control algorithms.
2Object-affected harmful factors
If friction element release timing is advanced to prevent tie-up, then gear tie-up is avoided, but engine speed flare increases causing shift shock
Solution Approach 1:
The patent uses real-time torque feedback from the off-going friction element to dynamically adjust release timing. When torque levels indicate approaching tie-up conditions, the system delays release slightly; when torque levels suggest imminent engine flare, the system advances release. This feedback mechanism balances both harmful effects, preventing gear tie-up while minimizing engine speed flare and resulting shift shock.
3Object-affected harmful factors
If friction element release timing is delayed to prevent engine flair, then engine speed stability is maintained, but gear tie-up occurs causing shift shock
Solution Approach 1:
The closed-loop control system continuously monitors torque transmission through the off-going friction element and provides real-time feedback to the controller. This feedback enables the system to detect early signs of gear tie-up and adjust release timing accordingly, preventing tie-up while maintaining engine speed stability. The feedback mechanism ensures optimal release timing that balances both competing requirements.
4Reliability
If torque capacity is maintained throughout the shift, then torque transmission is stable, but shift smoothness decreases due to torque hole
Solution Approach 1:
The patent implements dynamic torque capacity control by continuously adjusting the torque transmission characteristics of the friction elements during the shift process. The system modulates torque capacity in real-time based on shift phase and load conditions, maintaining stability when needed while reducing torque hole effects during critical transition periods. This dynamic adjustment smooths the torque profile, reducing shift shock while preserving necessary torque transmission stability.
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 engine flair and shift shock, providing a consistent and seamless shift quality by tightly controlling torque transmission during gear ratio changes, regardless of dynamic shift conditions.
Implementation Method 1
direct measurements or estimates of torsional load exerted onto an off-going friction element are used to predict an optimal off-going friction element release timing
Implementation Method 2
these friction elements may be described as torque establishing elements although more commonly they are referred to as clutches or brakes. The friction elements function to establish power flow paths from an internal combustion engine to vehicle traction wheels
Data Source
AI summary
A closed loop shift control apparatus and method based on friction element load controls a torque transfer phase when shifting from a low gear configuration to a high gear configuration for an automatic transmission system. When pressure actuated friction elements are selectively engaged and released to establish torque flow paths in the transmission, measurements or estimates of torsional load exerted on the off-going friction element are used to predict the optimal off-going friction element release timing for achieving a consistent shift feel. The ideal timing to release the off-going friction element is uniquely defined when torque load exerted onto the off-going friction element becomes substantially zero. An on-coming clutch engagement process is controlled by a closed loop control based on measurements or estimates of on-coming clutch torque capacity for a constant shift feel under dynamically changing conditions.