Clutch Torque Trajectory Correction for Ratio Upshifts
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Solution Overview
Problem
Conventional automatic transmissions experience torque transients, known as 'torque holes,' during upshifts, which cause unpleasant shift shocks and reduced powertrain performance due to the sudden drop in output shaft torque as the off-going clutch torque capacity is reduced.
Innovation Solution
A control strategy utilizing torque sensors and algorithms to accurately measure and manage the friction element torques of oncoming and off-going clutches, ensuring seamless torque transitions by adjusting actuator pressures and maintaining the off-going clutch locked, thereby minimizing torque disturbances and eliminating torque holes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the off-going clutch torque capacity is reduced during the torque phase to prepare for release, then the upshift can be initiated, but this causes a sudden drop in output shaft torque creating a torque hole
Solution Approach 1:
The controller increases the oncoming clutch torque capacity in advance during the preparatory phase before the off-going clutch is released. This preliminary action ensures that the oncoming clutch is ready to immediately assume the torque load, preventing the torque hole that would otherwise occur when the off-going clutch torque capacity is reduced.
Solution Approach 2:
The system uses torque sensors to provide real-time feedback on the actual torque being transmitted through the clutches. This feedback allows the controller to dynamically adjust the oncoming and off-going clutch torque capacities to maintain constant output shaft torque, eliminating the torque hole by continuously monitoring and correcting torque transmission during the upshift.
2Force
If the off-going clutch is allowed to slip at a controlled rate during the torque phase, then torque transmission can be managed, but this creates torque transients and shift shocks
Solution Approach 1:
Torque sensors provide real-time feedback on the actual torque being transmitted, allowing the controller to precisely control the torque capacity of both clutches. This feedback control eliminates uncontrolled slipping and the associated torque transients by continuously adjusting clutch torque to match the desired torque profile, thereby eliminating shift shocks.
Solution Approach 2:
The system dynamically changes the torque capacity parameter of the clutches during the upshift event. By precisely controlling the torque capacity of the oncoming clutch to increase and the off-going clutch to decrease in a coordinated manner, the system maintains constant output torque and eliminates harmful torque transients and shift shocks.
3Measurement precision
If torque sensors are used to provide real-time feedback for correcting clutch torque estimates, then torque hole filling can be achieved, but this increases system complexity
Solution Approach 1:
Torque sensors provide real-time feedback on actual torque transmission, enabling the controller to correct estimates of friction element torque in a closed-loop fashion. This feedback mechanism achieves precise torque hole filling by continuously monitoring and adjusting clutch torque based on measured values, directly resolving the technical problem despite the added measurement capability.
Solution Approach 2:
The control system uses the torque sensor feedback to self-correct torque transmission issues without external intervention. The controller automatically adjusts clutch torque capacities based on real-time measurements, enabling the system to eliminate torque holes and shift shocks through self-regulating feedback control, thereby managing the complexity through automation.
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
The solution effectively reduces or eliminates torque transients during upshifts, ensuring a smooth and predictable power delivery by accurately controlling clutch torques, thus enhancing the shift quality and reducing perceived shift shocks.
Implementation Method 1
Torque sensors may be used, together with physical properties and functions of the transmission and driveline components, algorithms governing those functions and appropriate transfer functions, to provide accurate torque values for the oncoming and off-going clutches.
Implementation Method 2
The friction torque establishing devices include friction elements, such as multiple plate clutches and band brakes, which may be actuated hydraulically or mechanically.
Implementation Method 3
The friction torque establishing devices include friction elements, such as multiple plate clutches and band brakes, which may be actuated hydraulically or mechanically.
Data Source
AI summary
A multiple ratio transmission having an input shaft, an output shaft and oncoming clutch and off-going clutch for effecting ratio upshifts is provided. The transmission also includes a transmission controller configured for controlling shifts. During the torque phase of a ratio upshift, the controller increases input torque. Next, the controller estimates an oncoming clutch target torque. The controller controls a torque input to ensure the off-going clutch remains locked. The controller measures an actual transmission value for a torque transmitting element of the transmission and corrects the oncoming clutch target torque using the actual transmission value whereby an increasing torque for the oncoming friction element is achieved with minimal torque transients along the output shaft during the upshift.