Separation Clutch Creep Control for Fuel-Efficient Drivetrains
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Solution Overview
Problem
Automated transmissions with soft torque converters experience inefficient fuel consumption due to slow acceleration and high creeping velocities when using long gearing, while hard torque converters result in unacceptably high creeping speeds, and there is a need to reduce energy consumption during idle engine conditions.
Innovation Solution
A method and drive train configuration that decouples the internal combustion engine and torque converter using a separation clutch, allowing for controlled slippage to adjust creeping velocity, utilizing a hard torque converter with long gearing to achieve a predetermined creeping speed of 5 to 10 km/h, and adjustable slipping rates to manage torque augmentation and maintain constant engine speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a long gearing (overdrive) is used in the startup gear to save fuel, then fuel consumption is reduced, but the creeping velocity becomes unacceptably high when using a hard torque converter
Solution Approach 1:
A separation clutch is introduced as an intermediary element between the internal combustion engine and the torque converter. This clutch can be operated in a slipping manner to reduce the pump shell speed, thereby controlling the creeping velocity while maintaining the long gearing configuration for fuel efficiency.
Solution Approach 2:
The operating parameters of the separation clutch are adjusted to achieve the desired creeping velocity. By controlling the slip rate of the separation clutch, the pump shell speed is reduced from the engine idle speed, enabling precise control of the creeping velocity while maintaining fuel-efficient long gearing.
2Loss of energy
If a hard torque converter is used to improve efficiency, then torque converter efficiency is improved, but the creeping velocity becomes unacceptably high with long gearing
Solution Approach 1:
The separation clutch serves as a mediator that decouples the engine speed from the pump shell speed. This allows the use of a hard torque converter for improved efficiency while the separation clutch compensates by reducing the pump shell speed to achieve the desired creeping velocity.
Solution Approach 2:
The separation clutch is operated dynamically in a slipping manner during the creeping process. This dynamic operation allows continuous adjustment of the pump shell speed to maintain the desired creeping velocity while preserving the benefits of the hard torque converter.
3Speed
If the separation clutch is operated with slippage to reduce creeping velocity, then creeping velocity is controlled, but thermal loading of the separation clutch increases
Solution Approach 1:
The control system monitors the operating conditions and adjusts the separation clutch slip rate accordingly. Feedback control ensures that the clutch operates within safe thermal limits while achieving the desired creeping velocity, preventing excessive thermal loading.
Solution Approach 2:
The separation clutch is operated with partial slippage rather than full engagement or complete disengagement. This partial action allows sufficient torque transmission to control creeping velocity while minimizing the thermal loading through reduced friction and heat generation.
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
The solution reduces fuel burn and allows for adjustable creeping velocities, maintaining efficient engine speed and torque transfer while minimizing energy consumption during idling, with robust control over creeping torque and thermal loading protection.
Implementation Method 1
the separation clutch is operated at least partially slipping during the creeping process
Data Source
AI summary
A drive train of a motor vehicle with an internal combustion engine, a torque converter and a transmission, wherein a separation clutch is provided between the internal combustion engine and the torque converter. In order to be able to perform a creeping process at a certain creeping velocity, the separation clutch is operated slipping. This way, the gearing of the startup process can be configured long, even when using a so-called hard torque converter, without having to tolerate a creeping velocity, which is too high.