Automatic Transmission Shifting Control for Torque Shock Reduction
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Solution Overview
Problem
Automatic transmissions with hydraulic friction-locking shifting elements face delays and discomfort due to the need for preparatory measures that disrupt continuous speed changes, especially during rapid gear shifts and downshifts, and the challenge of safely integrating positive-locking shifting elements without extending shifting time or causing torque surges.
Innovation Solution
A method that ensures safe and convenient insertion of positive-locking shifting elements by determining and reducing the differential speed of clutch halves before closing, using a nested shifting process where all frictional-locking elements are closed before engaging the positive-locking element, and employing engine interventions to manage speed differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If preparatory measures are taken for friction-locking shifting elements (filling process), then the shifting element is properly prepared for torque transfer, but delay times occur and continuous speed change is disrupted
Solution Approach 1:
The patent applies preliminary action by preparing the friction-locking shifting element in advance through a two-phase filling process (quick filling phase followed by filling equalization phase) before the actual gear shift is needed. This ensures the shifting element is ready for immediate torque transfer when the shift command is executed, reducing the impact of preparation time on the overall shifting duration.
Solution Approach 2:
The patent segments the preparatory filling process into two distinct phases: a quick filling phase for rapid oil delivery and a filling equalization phase for eliminating play in the multi-plate clutch. This segmentation allows each phase to be optimized independently, with the quick filling phase minimizing delay time and the equalization phase ensuring proper mechanical engagement.
2Productivity
If multiple shifting elements are closed in sequence (nested shifting), then gear ratio changes are achieved efficiently, but the differential speed of positive-locking element must be controlled to prevent torque shocks
Solution Approach 1:
The patent implements feedback control by continuously monitoring the differential speed between the two halves of the positive-locking shifting element during the nested shifting process. When the differential speed exceeds a predetermined threshold, the system responds by adjusting the engagement timing or speed control to reduce the differential speed before closing the positive-locking element, thereby preventing torque shocks while maintaining efficient gear ratio changes.
3Loss of time
If positive-locking shifting element is engaged directly without speed control, then shifting time is reduced, but differential speed may exceed safe limits causing damage or torque surges
Solution Approach 1:
The patent applies preliminary action by determining and controlling the differential speed of the positive-locking shifting element before engagement occurs. The system calculates the speed difference between the two halves and, if necessary, adjusts it to within a safe range prior to closing the shifting element. This preliminary speed control ensures safe engagement without significantly extending the overall shifting time, as the control actions are performed in parallel with other shifting operations.
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 shifting time, enhances shifting comfort, and prevents torque shocks by ensuring the differential speed is within a safe range for the positive-locking element engagement, maintaining continuous traction and wear-free operation.
Implementation Method 1
The switching elements are closed by applying a hydraulic pressure or another force to them
Implementation Method 2
In the case of a frictionally engaged hydraulic shifting element to be engaged, the transmission capacity of the shifting element is correspondingly increased
Data Source
Figure 1a~1b
Figure 2a
Figure 2b~2c
AI summary
The invention relates to a method for operating an automatic transmission (1), comprising a plurality of frictional switching elements (B, C, D, E) and at least one positively engaged switching element (A, F), wherein for the representation of a transmission gear and thus of a flux of force through the automatic transmission (1) at least three switching elements are closed, wherein during a switching operation between two specific transmission gears ("7" and "3") at least two switching elements (D, E) are opened and at least two more switching elements (B, F), including at least one positively engaged switching element (F) and at least one frictional switching element (B), are closed, in the chronological sequence of the switching operation the closing of the positively engaged switching element (F) takes place only after all frictional switching elements (B) are closed.