Vehicle Clutch Transition for Smooth Overrun Cut-Off
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Solution Overview
Problem
Drivers experience discomfort and irritation due to unexpected transitions from coasting or free-rolling mode to fuel cutoff mode, particularly in situations like following another vehicle or driving downhill, where the sudden increase in drag torque from the internal combustion engine causes unexpected braking effects.
Innovation Solution
The vehicle electronics gradually and gently increase the drag torque of the internal combustion engine during the transition from coasting or free-rolling mode to fuel cutoff mode by slowly closing the clutch and reducing fuel supply, ensuring the change in vehicle deceleration does not exceed a preset value, allowing for a smooth transition that is imperceptible to the driver.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the clutch is closed quickly to switch from coasting mode to fuel cutoff mode, then the switching speed is improved, but the driver comfort deteriorates due to sudden additional braking effect
Solution Approach 1:
The clutch engagement process is made dynamic and adaptive rather than fixed. The control unit adjusts the clutch engagement speed based on detected driving situations - using faster engagement when no braking is detected, and slower engagement when braking is detected, thereby optimizing both switching speed and driver comfort for different operational contexts
Solution Approach 2:
The system changes the parameter of clutch engagement time based on detected driving conditions. When braking is detected, the system extends the clutch engagement time to allow gradual torque transfer, preventing sudden braking effects while still achieving mode transition
2Loss of energy
If the drag torque is increased quickly to achieve fuel cutoff mode, then the fuel saving efficiency is improved, but the vehicle stability deteriorates due to unexpected braking effects
Solution Approach 1:
The system performs preliminary detection of braking status before executing the fuel cutoff mode transition. By detecting braking requests in advance, the system can prepare an appropriate engagement strategy that prevents sudden deceleration changes, thereby maintaining vehicle stability while still achieving fuel savings
Solution Approach 2:
The control unit continuously monitors braking status and uses this feedback to adjust the clutch engagement process. The feedback loop ensures that if braking is detected during the transition, the system adapts the engagement speed to maintain stable vehicle deceleration while still achieving the fuel cutoff objective
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 method allows for a seamless transition from coasting or free-rolling mode to fuel cutoff mode, eliminating driver discomfort by minimizing noticeable changes in vehicle deceleration, thereby enhancing the driving experience.
Implementation Method 1
the motor vehicle experiences a deceleration due to the drag torque of the internal combustion engine
Implementation Method 2
the clutch engaged... the combustion engine acting as a brake
Data Source
Figure 1~2
AI summary
The invention relates to a method and a device for switching from a sail or freewheel mode of a motor vehicle, comprising an internal combustion engine and an automatic clutch which is opened during the sail or freewheel mode, to an overrun cut-off mode in which the clutch is closed, wherein, prior to the clutch being closed, the internal combustion engine is set to a speed at which closing of the clutch induces no or minor changes in torque in the drive train, and, after closing the clutch, fuel supply to the internal combustion engine is reduced. According to the invention, under one or a plurality of pre-determined conditions, the drag torque of the internal combustion engine that affects the motor vehicle increases so slowly during the switch from sail or freewheel mode to overrun cut-off mode that the switch is not usually noticed by the driver.