Transmission Control Method for Spontaneous Torque Increase
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Solution Overview
Problem
Current transmission systems fail to provide a spontaneous increase in traction force or thrust torque at the drive output when a downshift command is issued, as they do not adequately consider the current operating conditions, often resulting in unintended multiple downshifts or insufficient torque changes.
Innovation Solution
A method where each gear ratio is associated with a threshold value based on transmission output speed, allowing the target gear to be selected as a function of the current transmission output speed, ensuring a gear ratio with a threshold value greater than or equal to the current speed is chosen, thereby adapting to the vehicle's operating conditions for a more spontaneous torque increase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a simple downshift to the next-lower gear ratio is authorized by the tip-minus function, then the gear ratio change is straightforward and predictable, but the torque increase at the drive output is insufficient when starting from low engine running speeds
Solution Approach 1:
The system changes the parameter of target gear selection based on the current operating state (engine running speed, current gear ratio). When engine speed is low and overdrive gear is engaged, the control system selects a target gear that differs by two gear ratio steps instead of one, thereby achieving sufficient torque increase while maintaining simple tip-minus operation.
2Power
If multiple consecutive downshifts are commanded to achieve significant torque increase, then the desired torque change can be achieved, but the response time is too long for spontaneous driving situations such as overtaking
Solution Approach 1:
The control system performs preliminary assessment of the current operating state (engine speed, current gear) before executing a downshift command. This allows the system to pre-determine the appropriate target gear (one or two steps down) in advance, so that when the driver commands a downshift, the system can immediately execute the correct multi-step downshift without sequential delays, achieving rapid torque increase for spontaneous situations.
3Device complexity
If the same target gear is selected regardless of current gear ratio, then the control logic is simple, but the torque change does not adapt to the current operating conditions of the vehicle
Solution Approach 1:
The control system adjusts the target gear selection parameter based on two key operating parameters: current gear ratio and engine running speed. When the vehicle is in overdrive gear with low engine speed, the system selects a target gear two steps down; otherwise, it selects one step down. This adaptive parameter change ensures optimal torque increase for each operating condition while maintaining relatively simple control logic.
Data Source
AI summary
A method of operating a transmission having a plurality of gears which can operate in an automatic shifting mode, during which a gear is selected automatically depending on the current driving situation, and also in a manual shifting mode during which a gear is selected depending on a driver's command. When the driver commands a shift, a change takes place from the automatic shifting mode to the manual shifting mode. A specific threshold value of the transmission output speed or an equivalent rotational speed value is associated with each gear and, when the driver commands a downshift, a target gear is determined as a function of the current transmission output speed or the equivalent rotational speed value. The gear selected as the target gear is the gear whose specific threshold value is higher than or equal to the current transmission output speed or the equivalent rotational speed value.