Friction Clutch Slipping State for ATF Heating
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Solution Overview
Problem
Automatic transmission fluid (ATF) in vehicles often does not reach operating temperature during driving scenarios like the FTP emissions test cycle, leading to reduced transmission efficiency and fuel economy, and existing supplemental heating systems are complex and costly.
Innovation Solution
A system and method that utilizes a friction clutch to generate heat by selectively engaging it in a slippingly engaged state when not generating gear ratios, heating the ATF and improving transmission efficiency, specifically by moving the clutch to a partial engagement position between disengaged and engaged states to produce heat without additional components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a friction clutch is used to generate heat by friction, then the ATF can be rapidly heated to operating temperature, but the clutch wear increases due to continuous friction engagement
Solution Approach 1:
The controller selectively engages the friction clutch in a slippingly engaged state only during specific gears (2nd through 6th gears) and only when ATF temperature is below a threshold, creating periodic rather than continuous friction engagement. This allows heat generation when needed while limiting total friction exposure to preserve clutch life.
Solution Approach 2:
The clutch is engaged in a partial slippingly engaged state rather than fully engaged, generating sufficient heat for ATF warming while limiting the friction force and wear. The partial engagement provides just enough thermal energy without the excessive friction that would cause rapid degradation.
2Temperature
If additional heating systems (engine coolant waste heat or electric heaters) are used to heat ATF, then ATF can reach operating temperature, but the system complexity and cost increase
Solution Approach 1:
The friction clutch serves dual functions: (1) its primary function of generating gear ratios through engagement, and (2) a secondary function of generating heat for ATF warming during slippingly engaged states. This eliminates the need for dedicated heating components, reducing system complexity and cost.
Solution Approach 2:
The transmission system uses its own existing clutch mechanism to generate the heat needed for ATF warming, rather than requiring external or additional heating systems. The clutch's friction engagement naturally produces thermal energy that is utilized to heat the ATF.
3Productivity
If the friction clutch is continuously engaged to generate heat, then ATF heating efficiency is maximized, but the transmission shifts between gears are delayed or prevented
Solution Approach 1:
The clutch engagement state is dynamically adjusted based on real-time operating conditions. The controller selectively transitions the clutch between disengaged, slippingly engaged, and fully engaged states depending on whether gear shifting is needed or ATF heating is the priority, optimizing both heating efficiency and shifting capability.
Solution Approach 2:
The clutch is engaged in slippingly engaged state only during specific gears (2nd through 6th gears) and disengaged during other gears, creating periodic heating cycles that avoid interfering with gear shifts while still achieving effective ATF warming over time.
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 rapidly heats the ATF, reducing viscosity and improving fuel economy by quickly reaching operating temperature, thus enhancing transmission efficiency and reducing the need for additional heating systems, which are costly and complex.
Implementation Method 1
the friction clutch generates heat from friction to thereby rapidly heat the ATF in the housing
Data Source
AI summary
An automatic transmission system includes a housing containing automatic transmission fluid (ATF), a plurality of clutches configured to be engaged to generate gear ratios corresponding to forward speeds of the automatic transmission, wherein one clutch of the plurality of clutches is a friction clutch movable between a disengaged state, an engaged state utilized to create one or more gear ratios of the automatic transmission, and a slippingly engaged state between the disengaged state and the engaged state where the friction clutch is not engaged to create a gear ratio of the automatic transmission, and a controller configured to selectively move the friction clutch to the slippingly engaged state when the friction clutch is not being utilized to generate the one or more gear ratios, such that the friction clutch generates heat from friction to thereby rapidly heat the ATF in the housing and improve operating efficiency of the transmission.