Engine Starting Method Reduces Dual-Mass Flywheel Stress
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Solution Overview
Problem
Internal combustion engines experience mechanical stress on dual-mass flywheels during startup due to resonance vibrations, which can lead to reduced service life and potential engine stall, especially in start/stop vehicles, as the resonance range of the vibration damping element is passed through during engine start, causing oscillations and increased mechanical loads.
Innovation Solution
A starting method that reduces the combustion air charge in the engine cylinders before starting, rotating the engine with a reduced air charge to minimize energy input into the vibration damping element, thereby reducing oscillations and mechanical stress, and then increases the air charge once the engine speed reaches a threshold to complete the starting process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the engine is started with normal combustion air charge, then the starting process is fast and efficient, but the dual-mass flywheel experiences high mechanical loads and resonance vibrations
Solution Approach 1:
The patent applies preliminary action by reducing the combustion air charge before the engine starts rotating. The control device reduces the air charge to a first value before engine startup, which softens the torque curve during the initial rotation phase and prevents resonance excitation of the dual-mass flywheel. After the engine passes through the resonance range, the air charge is increased to a second value to complete the starting process efficiently.
Solution Approach 2:
The patent changes the parameter of combustion air charge during the starting process. By dynamically adjusting the air charge from a first reduced value to a second higher value based on engine speed and resonance detection, the system optimizes both the protection of the dual-mass flywheel and the overall starting performance.
2Reliability
If the combustion air charge is reduced before starting, then mechanical loads on the vibration damping element are reduced, but the starting process may be delayed
Solution Approach 1:
The patent uses periodic action by implementing a two-stage air charge strategy. The air charge is first reduced to protect the dual-mass flywheel during the critical resonance passage, then increased to complete the starting process. This time-dependent switching of air charge levels minimizes both resonance exposure time and overall starting delay.
Solution Approach 2:
The patent applies the skipping principle by rapidly transitioning through the resonance speed range with reduced air charge, minimizing the time spent in the harmful resonance zone. The control device quickly adjusts the air charge and engine speed to pass through the critical resonance frequencies before restoring normal air charge for completion of startup.
3Reliability
If mechanical solutions are used to protect the dual-mass flywheel, then the flywheel is protected during resonance, but additional devices and design changes are required
Solution Approach 1:
The patent replaces mechanical protection solutions with a control-based approach. Instead of adding mechanical devices to the dual-mass flywheel or its mounting, the system uses a control device that adjusts the combustion air charge and ignition timing to prevent resonance excitation. This software/control solution avoids additional mechanical complexity while achieving the same protective effect.
4Loss of time
If the resonance speed is run through quickly, then the exposure time to resonance is minimized, but the mechanical stresses during resonance passage are increased
Solution Approach 1:
The patent applies preliminary action by reducing the combustion air charge before the engine reaches resonance speeds. This pre-adjustment softens the torque characteristics during the approach to and passage through resonance, reducing mechanical stresses while maintaining a relatively quick transition. The control device monitors engine speed and adjusts air charge in advance of the resonance zone.
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 reduces the mechanical load on the vibration damping element and suspension, enhances comfort, and extends the service life of the dual-mass flywheel by minimizing resonance excitations during engine startup, allowing for a smoother and more efficient starting process.
Implementation Method 1
The primary and secondary flywheel masses are connected to each other with spring-damper units and dampen any vibrations that occur in the drive train
Implementation Method 2
The flywheel is typically designed as a dual-mass flywheel (also referred to below as 'DMF')... in order to absorb torsional vibrations generated by the ICE
Implementation Method 3
When the engine is started, the resonance speed of the drive train is run through, which can lead to high loads in the dual-mass flywheel... The use of a dual-mass flywheel can reduce the resonant frequency of the drive train to speeds below the idle speed of the ICE
Data Source
Figure 1~2
Figure 3~4
AI summary
The present invention relates to a starting method for an internal combustion engine (3) of a drive train (2) of a motor vehicle (1), wherein the internal combustion engine (3) has at least one cylinder (3a-c) and wherein the drive train (2) comprises the internal combustion engine (3), a transmission (6) and a vibration damping element (4) coupled between the internal combustion engine (3) and the transmission (6), wherein the method comprises: detecting (31) a start request to the internal combustion engine (3); reducing (32) a combustion air charge of the at least one cylinder (3a-c) of the internal combustion engine (3); rotating (33) the internal combustion engine (3) for a predetermined number of revolutions; and increasing (34) the combustion air charge of the at least one cylinder (3a-c) of the internal combustion engine (3).