Powertrain Upshifting via Two-Stroke Engine Braking
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Solution Overview
Problem
Existing powertrain systems for heavy-duty vehicles face inefficiencies during gear upshifting, particularly in maintaining turbocharger speed and achieving rapid rotational speed adaptation, which affects vehicle acceleration and emission control.
Innovation Solution
A method that switches the internal combustion engine from a four-stroke operation to a two-stroke braking mode during gear upshifting, allowing for rotational speed synchronization between the engine and transmission while maintaining exhaust gas flow, thereby maintaining turbocharger speed and enabling more precise engine braking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional four-stroke engine operation is used during upshifting, then engine stability is maintained, but rotational speed adaptation is slow and turbocharger speed drops
Solution Approach 1:
The engine operation mode is dynamically changed from four-stroke to two-stroke braking mode during upshifting events. This dynamic adaptation allows the engine to rapidly reduce rotational speed while maintaining control stability, resolving the contradiction between fast speed adaptation and operational stability.
Solution Approach 2:
The stroke cycle parameter is changed from four-stroke to two-stroke during upshifting. This parameter change enables the engine to achieve faster rotational speed reduction while the exhaust gas flow is maintained to keep turbocharger speed stable, thus improving speed adaptation without sacrificing reliability.
2Speed
If engine braking is applied during upshifting, then rotational speed reduction is achieved, but turbocharger speed drops affecting acceleration
Solution Approach 1:
The engine switches to two-stroke braking operation where exhaust valves are opened at specific crank angle positions to maintain continuous exhaust gas flow to the turbocharger. This parameter change in valve timing and stroke cycle allows engine braking while preserving turbocharger rotational speed.
Solution Approach 2:
The exhaust gas flow to the turbocharger is maintained continuously during the braking operation. By carefully timing the exhaust valve openings in the two-stroke cycle, the system ensures uninterrupted exhaust flow, keeping the turbocharger spinning at the required speed for rapid acceleration after upshifting.
3Productivity
If rapid upshifting is implemented, then productivity is improved, but shifting smoothness and emission control deteriorate
Solution Approach 1:
The engine dynamically switches to two-stroke braking mode with precisely controlled exhaust valve timing during upshifting. This dynamic control allows rapid gear changes while maintaining proper exhaust flow characteristics that prevent soot formation, achieving both high productivity and low emissions.
Solution Approach 2:
The control system monitors engine operating conditions and triggers the two-stroke braking mode at the optimal moment during upshifting. This feedback-based control ensures that the rapid speed reduction does not create conditions favorable for soot generation, maintaining emission control during high-speed shifting.
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 enhances powertrain performance by facilitating rapid gear upshifting, improving vehicle acceleration, reducing engine soot emissions, and ensuring smoother shifting through precise engine braking and synchronization, while maintaining turbocharger efficiency.
Implementation Method 1
reducing the rotational speed of the engine output shaft by adjusting the operation of the engine from the four-stroke operation to a two-stroke braking operation
Data Source
AI summary
The invention relates to a method (100) for controlling a powertrain system (10) of a vehicle (1) during gear upshifting, said powertrain system comprising: an internal combustion engine system (11) comprising an internal combustion engine (12) configured to output a rotational speed (W1) via an engine output shaft (8); a transmission arrangement (14) having a number of gear stages to obtain a set of gears, the transmission arrangement being operatively connected to the internal combustion engine via a transmission input shaft (64) and further having a transmission output shaft (24) for providing a rotational speed to one or more drive wheels (26) of the vehicle; the method comprising the steps of: operating (110) the engine in a four-stroke operation to provide engine rotational speed output via the engine output shaft; receiving (120) an indication of an intended upshifting from a gear of the set of gears to a higher gear of the sets of gears; reducing (130) the rotational speed of the engine output shaft by adjusting the operation of the engine from the four-stroke operation to a two-stroke braking operation; and, when said engine is in the two-stroke braking operation, performing (140) the intended upshifting from said gear of the set of gears to said higher gear of the sets of gears.