Nested Gear Shift Control for Automatic Transmissions
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Solution Overview
Problem
Existing methods for operating automatic transmissions with five or more switching elements are inadequate for managing multiple gear shifts efficiently, particularly in transmissions with eight forward gears and one reverse gear, as they fail to effectively prepare and execute successive upshifts and downshifts.
Innovation Solution
A method that controls two successive upshifts or downshifts by performing a first upshift or downshift as a multiple shift, where a switching element is opened and another is closed, and prepares a third and fourth switching element for subsequent changes, ensuring at least one element remains closed during both shifts, and optionally adjusts torque to support nested gear changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the known method from DE 100 35 479 A1 is used for automatic transmissions with five or more switching elements, then the switching speed can be improved through nested upshifts and downshifts, but the method becomes unsuitable for transmissions with eight forward gears and one reverse gear requiring at least five switching elements with at least three closed
Solution Approach 1:
The patent applies dynamics by making the shift execution strategy adaptive rather than fixed. The control system dynamically determines whether to execute shifts as simple or multiple shifts based on real-time transmission state, driver requests, and gear position. This dynamic adaptation allows the same control method to work across different transmission configurations (5-speed, 8-speed, etc.) while maintaining high switching speed through nested shifts when appropriate.
Solution Approach 2:
The patent changes the parameter of shift execution mode from a fixed approach to a variable one. By introducing the concept of multiple shifts where switching elements are prepared in advance and executed in sequence rather than simultaneously, the system can adapt to different transmission configurations. The method dynamically adjusts the number and timing of shift operations based on the specific transmission setup, enabling versatility across various gear configurations.
2Speed
If multiple shifts are executed simultaneously in automatic transmissions, then the gear change speed is improved, but the control complexity increases significantly for transmissions with five or more switching elements
Solution Approach 1:
The patent applies segmentation by dividing a complex multiple shift operation into separate, sequential simple shift operations. Instead of attempting to execute all switching element changes simultaneously, the control system breaks down the shift into individual steps, each involving a manageable number of switching element transitions. This segmentation reduces control complexity while still achieving rapid overall gear changes through the nested structure of prepared and executed shifts.
Solution Approach 2:
The patent applies preliminary action by preparing switching elements in advance before they are actually needed for the shift. The control system anticipates future shift requirements and pre-positions switching elements (changing their state from open to closed or vice versa) during the current shift operation. This preliminary preparation eliminates waiting time and allows seamless execution of multiple successive shifts, maintaining high speed while simplifying control through staged preparation.
3Speed
If switching elements are prepared in advance during ongoing shifts, then the switching speed for successive gear changes is improved, but the coordination difficulty among multiple switching elements increases
Solution Approach 1:
The patent applies preliminary action by preparing switching elements during ongoing shifts rather than waiting until the shift is complete. The control system identifies which switching elements will be needed for subsequent shifts and begins changing their state in advance, during the execution of the current shift. This preliminary preparation ensures that when the current shift completes, the next shift can begin immediately without additional preparation delay, maintaining high switching speed while distributing the coordination task across time rather than requiring simultaneous coordination of all elements.
Solution Approach 2:
The patent applies continuity of useful action by ensuring that the preparation of switching elements is an ongoing process that occurs continuously during shift execution rather than as a separate discrete step. The control system maintains continuous monitoring and adjustment of switching element states, preparing elements for future shifts while current shifts are being executed. This continuous preparation process eliminates idle time and ensures seamless transitions between shifts, improving overall switching speed while simplifying coordination through continuous rather than batch processing.
Data Source
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AI summary
The invention relates to a method for operating a drive train of a motor vehicle comprising at least one automatic transmission and one drive unit. According to the invention, in an automatic transmission with at least five switching elements, of which at least three switching elements are closed and the remaining switching elements are open for torque or power transmission in a forward gear or a reverse gear, two successive upshifts or two successive downshifts can be carried out by controlling at least five switching elements such that: a) a first upshift or downshift is carried out as a multiple shift, wherein a single shift or a multiple shift is prepared as the subsequent second upshift or downshift during the ongoing first upshift or downshift; b) during the execution of the first upshift or downshift,a) During downshifting as a multiple shift, a first shift element of the automatic transmission is opened and thus deactivated, and a second shift element of the automatic transmission is closed and thus engaged; c) during the execution of the first upshift or downshift as a multiple shift, a third shift element of the automatic transmission is prepared to open and thus deactivate, and a fourth shift element of the automatic transmission is prepared to close and thus engage for the subsequent second upshift or downshift; d) during the execution of the first upshift or downshift and during the execution of the second upshift or downshift, at least a fifth shift element is closed or kept nearly closed.