Vehicle Drive Train Coasting Mode Actuation via Shifting Elements
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current vehicle drive train systems lack spontaneity in activating and deactivating coasting modes, leading to inefficiencies in fuel consumption and operational complexity, particularly in transitioning between gear ratios during coasting operations.
Innovation Solution
A method for operating a vehicle drive train with a transmission featuring a positive-locking shifting element and multiple frictional-locking shifting elements, allowing for seamless activation and deactivation of coasting modes by controlling gear ratios through 'gear tracking' and adjusting shifting element states to optimize power flow and reduce actuation effort.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a positive-locking shifting element is used to switch gear ratios, then the transmission can achieve precise gear ratio changes, but the actuation lacks spontaneity and responsiveness during coasting mode transitions
Solution Approach 1:
The transmission system is segmented into two types of shifting elements: positive-locking shifting elements for precise gear ratio changes and frictional-locking shifting elements for spontaneous actuation during coasting mode. This segmentation allows each type to specialize in its strength, resolving the contradiction between precision and spontaneity.
Solution Approach 2:
The system dynamically switches between positive-locking and frictional-locking shifting elements based on the operating mode. During coasting mode transitions, frictional-locking elements provide spontaneous actuation, while during normal operation, positive-locking elements ensure precise gear ratio changes. This dynamic adaptation resolves the contradiction.
2Loss of energy
If the drive unit is switched off during coasting mode, then fuel consumption is reduced, but the transition back to powered mode lacks spontaneity and increases engine coastdown time
Solution Approach 1:
The frictional-locking shifting elements are preliminarily positioned and ready to actuate immediately when the driver requests power during coasting mode. This preliminary preparation eliminates delays in transitioning from coasting to powered mode, reducing engine coastdown time while maintaining fuel efficiency during coasting.
Solution Approach 2:
The system changes the operational parameters of the shifting elements based on the mode: during coasting, frictional-locking elements are disengaged to minimize drag and maximize fuel savings; when power is requested, they rapidly re-engage to minimize coastdown time. This parameter switching resolves the contradiction.
3Ease of operation
If multiple frictional-locking shifting elements are used for coasting mode actuation, then spontaneity and responsiveness are improved, but the device complexity increases
Solution Approach 1:
Both positive-locking and frictional-locking shifting elements are designed with a unified structural framework and control system. This multi-functionality allows the system to achieve spontaneous coasting mode actuation while minimizing the increase in overall device complexity through design standardization.
4Stability of the object's composition
If the positive-locking shifting element remains closed during coasting mode, then gear ratio stability is maintained, but power flow separation and coasting activation become less efficient
Solution Approach 1:
The shifting elements are segmented into positive-locking and frictional-locking types, allowing the positive-locking element to remain closed for gear ratio stability while frictional-locking elements open to enable power flow separation during coasting mode activation.
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 fuel consumption by enabling rapid and spontaneous transitions between gear ratios, improving driving comfort and efficiency by minimizing engine coastdown time and avoiding undesirable rotational speed increases, thus enhancing the overall performance of the vehicle drive train.
Implementation Method 1
a transmission with nine forward gears and one reverse gear is known from DE 10 2008 000 429 A1. The multi-speed transmission includes four planetary gear sets, eight rotatable shafts and six shifting elements.
Implementation Method 2
At least two of the shifting elements of the multi-speed transmission are formed as positive-locking shifting elements, which are switched off only during upshifts.
Data Source
AI summary
A method for operating a vehicle drive train includes operating the vehicle drive train with a drive unit switched on, with the drive unit connected to an output by a transmission, and with a positive-locking shifting element open. In response to a coasting operating state request for the vehicle drive train and a rotational speed of a transmission output being greater than a threshold, the drive unit is switched off and power flow between the drive unit and the output is interrupted by opening at least one of a plurality of frictional-locking shifting elements. The method also includes closing the positive-locking shifting element during the coasting operating state and no later than a leave coasting operating state request.