Clutch Torque Gradient Control for Rail-Free Vehicle Engine Start
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Solution Overview
Problem
Conventional vehicles with only an internal combustion engine as the drive unit face excessive load on the dual mass flywheel during tow-starting at higher speeds, leading to mechanical stress and discomfort, and existing methods are not suitable for vehicles without an electric machine support.
Innovation Solution
A method involving three controlled steps to engage and disengage the clutch, with varying torque gradients to manage the load on the two-mass flywheel, including a pilot-controlled partial engagement, passing through resonance speed range, and smooth speed matching, to reduce vibration and torque jumps, and optionally using an electric starter if conditions are not favorable.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the internal combustion engine is towed at higher speeds using conventional methods, then the engine can be started from sailing operation, but extreme stress is applied to the dual-mass flywheel causing mechanical stress and discomfort
Solution Approach 1:
The clutch engagement process is divided into three distinct process steps with different torque gradients. The first step uses a first torque gradient to initially engage the clutch, the second step uses a second torque gradient (less steep than the first) to pass through the resonance speed range, and the third step completes the engagement. This segmentation allows the system to reach higher engine speeds while controlling the stress on the dual-mass flywheel during critical phases.
Solution Approach 2:
The clutch torque gradient is dynamically adjusted during the towing process. The control system varies the torque gradient based on the current engine speed and the identified process step. By making the torque gradient less steep during the second process step when passing through resonance speed, the system adapts to the changing mechanical conditions and reduces harmful vibrations and stress on the dual-mass flywheel.
2Reliability
If a robust electric starter is used to cope with intensive sailing mode cycles, then the starter can handle the load, but space, weight, and cost increase
Solution Approach 1:
The vehicle uses itself to start the engine by towing the internal combustion engine using kinetic energy from the moving vehicle. The clutch engagement process harnesses the vehicle's motion to rotate the engine crankshaft, eliminating the need for an oversized electric starter. The system serves its own starting function through the controlled towing process described in the three process steps.
Solution Approach 2:
The mechanical towing process replaces the electrical starting system. Instead of using an electric starter motor to crank the engine, the system uses the vehicle's kinetic energy transmitted through the clutch and transmission to mechanically rotate the engine crankshaft. This substitution allows for a smaller, lighter electric starter since it no longer needs to cope with intensive sailing mode cycles.
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 the load on the two-mass flywheel, minimizing vibrations and torque jumps, allowing for comfortable and efficient tow-starting of the internal combustion engine without the need for a robust and costly electric starter, specifically designed for conventional vehicles.
Implementation Method 1
the clutch is closed from its open state with a first torque gradient at least until its clutch torque exceeds the drag torque of the internal combustion engine
Implementation Method 2
the clutch is further controlled with a second torque gradient, which is less steep than the first torque gradient, at least until the speed of the internal combustion engine exceeds a resonance speed
Implementation Method 3
until the speed of the internal combustion engine exceeds a resonance speed of a two-mass flywheel arranged between the clutch and the output shaft of the internal combustion engine
Implementation Method 4
the internal combustion engine is towed by closing the clutch
Data Source
Figure 1~2
Figure 3
AI summary
The method involves closing a coupling from an opened condition till coupling torque of the coupling exceeds drag torque of an internal combustion engine. The coupling is controlled with a torque gradient till rotational speed of the engine exceeds a resonance rotational speed of a two-mass-flywheel that is arranged between the coupling and an output shaft of the engine. The coupling is closed completely in such a manner that the rotational speed of the engine is matched with an input-sided rotational speed of a transmission in a skip-free manner.