Transmission Pressure and Torque Control for Shift Element Disengagement
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Solution Overview
Problem
Existing drivetrain transmission systems cannot disengage positively locking shift elements in a force-locking-free state without establishing a force locking action, which is necessary for smooth gear ratio changes, especially during sailing mode.
Innovation Solution
The method involves increasing system pressure on the shift elements, then increasing and subsequently reducing torque output by the drive assembly to disengage positively locking shift elements without creating a force locking action, using control mechanisms that adjust pressure and torque based on rotational speed differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a positively locking shift element is disengaged in a force-locking-free state, then the transmission can change gear ratios smoothly, but a force locking action must be established which complicates the disengagement process
Solution Approach 1:
The system increases system pressure before the actual disengagement of the positively locking shift element. This preliminary pressure increase prepares the friction clutch to slip and absorb shocks, creating favorable conditions for smooth disengagement without requiring force locking actions.
Solution Approach 2:
The system dynamically changes the torque output by the drive assembly during the disengagement process. By increasing torque temporarily and then reducing it, the system optimizes the disengagement conditions, allowing the shift element to open smoothly without establishing force locking action.
2Ease of operation
If system pressure is increased to facilitate shift element disengagement, then disengagement becomes easier, but energy consumption increases
Solution Approach 1:
The system applies pressure increases and torque interventions in a periodic, controlled manner rather than continuously. The pressure is increased only when needed for disengagement, and the torque is temporarily increased and then reduced, minimizing overall energy consumption while achieving the disengagement goal.
Solution Approach 2:
The friction clutch is designed to slip and absorb shocks during disengagement, utilizing its own friction characteristics to facilitate the process. This self-service mechanism reduces the need for continuous high pressure input, thereby reducing energy consumption.
3Reliability
If torque output by the drive assembly is increased to assist disengagement, then the shift element can be opened more reliably, but the drive assembly experiences higher stress
Solution Approach 1:
The system increases torque output by the drive assembly as a preliminary action before the actual disengagement occurs. This temporary torque increase prepares the system for reliable disengagement, and the torque is subsequently reduced to minimize stress on the drive assembly.
Solution Approach 2:
The system dynamically adjusts the torque output by the drive assembly during the disengagement process. By temporarily increasing torque and then reducing it, the system achieves reliable disengagement while minimizing the duration and magnitude of stress on the drive assembly.
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 allows for reliable and force-locking-free disengagement of positively locking shift elements, enhancing the transmission's operational efficiency during gear changes, particularly in sailing mode, without inducing a force locking action.
Implementation Method 1
a system pressure acting on the shift elements is firstly increased
Implementation Method 2
The frictionally locking shift elements are in particular friction clutches or brakes
Data Source
AI summary
A method for operating a drivetrain of a motor vehicle includes elevating a system pressure acting on a plurality of shift elements (A, B, C, D, E, F) when one of at least one positively locking shift element (A, F) is closed in a force-locking-free state, increasing a torque output by a drive assembly (15) and then subsequently reducing the torque output by the drive assembly (15) while the system pressure is elevated by an intervention with the drive assembly (15), and reducing the system pressure after reducing the torque output by the drive assembly (15). The one of the at least one positively locking shift element (A, F) closed in the force-locking-free state or another one of the at least one positively locking shift element (A, F) is opened while the system pressure is elevated and the torque output by the drive assembly (15) changes.