Engine Braking via Two-Stroke Cycle and Pressure Reservoir
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Solution Overview
Problem
Existing engine braking methods in combustion engines for heavy vehicles do not effectively generate enough braking effect during four-stroke cycle operation and result in unwanted heating of components, requiring high engine valve springs that are energy-intensive and not suitable for all engine types.
Innovation Solution
Operating the combustion engine in a two-stroke cycle with the piston displaced from the upper dead centre to the lower dead centre while keeping the inlet valve open and maintaining fluid communication with a high-pressure storage reservoir, which provides additional braking effect and reduces component heating by using the storage reservoir to control pressure and ventilation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If conventional four-stroke engine braking is used, then the braking effect is generated, but the braking effect is insufficient and components are overheated
Solution Approach 1:
The invention employs periodic opening and closing of the exhaust valve in synchronization with the piston movement during compression strokes. The exhaust valve remains closed during power strokes and opens selectively during compression strokes to create periodic backpressure, generating strong braking effect while allowing heat dissipation during exhaust strokes, thus preventing component overheating
Solution Approach 2:
The invention dynamically changes the exhaust valve state (open/closed) based on the engine cycle phase and piston position. By controlling the exhaust valve to remain closed during compression strokes and open during exhaust strokes, the system changes the pressure parameter periodically, achieving both strong braking force and heat management
2Reliability
If high spring force engine valves are used for conventional engine braking, then the valve control is maintained, but energy consumption increases and it is not suitable for engines without camshaft actuation
Solution Approach 1:
The invention utilizes the engine's own compression pressure and exhaust pressure to control the valve timing and opening, eliminating the need for additional high-energy spring forces or complex actuation systems. The valve control is achieved through the natural pressure differentials created during the engine cycle, making it suitable for engines without camshaft actuation and reducing energy consumption
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 achieves an engine braking effect exceeding that of four-stroke cycle operations while minimizing component heating and reducing the energy consumption associated with high engine valve springs, enhancing the overall efficiency of engine braking.
Implementation Method 1
a storage reservoir (11) having a third pressure P3 that is higher than said first pressure P1 and said second pressure P2
Implementation Method 2
when the piston is displaced from the upper dead centre to the lower dead centre and the inlet valves are open, the fluid communication between the storage volume and the cylinder volume is opened. I.e. air having high pressure is provided during the intake stroke
Implementation Method 3
closing the exhaust air channel/exhaust gas channel by means of a valve, whereby the combustion engine continues to operate in four-stroke cycle, and when the outlet valves of the cylinder are opened, in order to evacuate exhaust gases during normal operation, a back pressure is generated downstream the cylinder. The back pressure is used to counteract the displacement of the piston from the lower dead centre to the upper dead centre when the outlet valves are open
Data Source
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AI summary
The present invention relates to a combustion engine as well as a method for engine braking in such a combustion engine comprising at least one cylinder (2) having a cylinder volume (6) and a piston displaceable in said cylinder (6), an intake air channel (9) having a first pressure PI, a first inlet valve (7) arranged between the intake air channel (9) and the cylinder volume (6), an exhaust air channel (10) having a second pressure P2, a first outlet valve (8) arranged between the cylinder volume (6) and the exhaust air channel (10), and a storage reservoir (11) having a third pressure P3 that is higher than said first pressure PI and said second pressure P2, the storage reservoir (11) being arranged in controllable fluid communication with the cylinder volume (6). The method being characterized by taking place during two-stroke cycle and comprises the steps of, displacing the piston from the upper dead centre towards the lower dead centre, keeping the first inlet valve (7) open during at least a part of the time the piston is displaced from the upper dead centre to the lower dead centre, displace the piston from the lower dead centre towards the upper dead centre, and keeping the fluid communication between the storage reservoir (11) and the cylinder volume (6) open during at least a part of the time the piston is displaced from the lower dead centre to the upper dead centre.