CVT Manual Mode Entry Gear Selection During Transient Driving
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Solution Overview
Problem
Current continuously variable transmission (CVT) systems experience excessive shifting during transient driving conditions when transitioning to manual mode, as they rely on steady-state driving ratio maps, leading to inconsistent and slow gear changes.
Innovation Solution
The system splits the range of CVT ratios into multiple bins, freezing a predicted gear ratio close to the real ratio at manual mode entry, with an offset based on the real ratio's rate of change, retrieved from a calibratable lookup table, to improve shift consistency and speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If steady-state driving ratio maps are used to determine the frozen variator ratio during manual mode entry, then the transmission control system is simple to implement, but excessive shifting occurs during transient driving conditions
Solution Approach 1:
The patent transitions from using static steady-state driving ratio maps to a dynamic approach that incorporates the rate of change of the real variator ratio. The system now adapts the frozen variator ratio selection based on transient conditions by evaluating how quickly the ratio is changing, allowing the control system to respond dynamically to accelerating or decelerating conditions while preventing excessive shifting during manual mode entry
Solution Approach 2:
The patent changes the parameters used for determining the frozen variator ratio from solely steady-state map data to include the rate of change of the real variator ratio. By introducing this additional parameter that captures transient behavior, the system can distinguish between steady-state and transient conditions, selecting appropriate frozen ratios that prevent excessive shifting during manual mode transitions
2Device complexity
If the frozen variator ratio is determined using steady-state driving ratio map data, then the algorithm is simple to implement, but shift time is excessive during transient conditions
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing optimal frozen variator ratios in lookup tables that are indexed by the rate of change of the real variator ratio. During manual mode entry, the system quickly retrieves the appropriate frozen ratio based on the current rate of change condition, avoiding the need for complex real-time calculations and significantly reducing shift time during transient conditions
3Ease of manufacture
If steady-state driving ratio map data is used for frozen variator ratio selection, then the system is easy to calibrate, but shift consistency is poor during transient driving conditions
Solution Approach 1:
The patent segments the transient driving conditions by dividing the range of rate of change values into multiple discrete bins. Each bin corresponds to a specific range of rate of change conditions and has an associated optimal frozen variator ratio stored in lookup tables. This segmentation allows the system to handle diverse transient conditions with discrete, pre-calibrated solutions, improving shift consistency while maintaining calibration simplicity through the structured binning approach
Data Source
AI summary
A system of selecting a transmission manual mode entry gear during transient driving conditions of an automobile vehicle includes a transmission in an automobile vehicle. An engine is connected to the transmission. A torque converter is connected to the transmission, and a differential provides drive output. A controller is in communication with the engine and the transmission. A shift device is in communication with the controller allowing manual selection by an operator of the automobile vehicle between a Park, a Reverse, a Neutral, a Drive and a Low or Manual (PRNDL) operating modes. A predicted gear is frozen close to a real gear at a time of entrance into the Manual mode.