Engine Brake Valve Actuation for Compression-Release Braking
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing engine braking systems face challenges in increasing braking power while managing the increased exhaust back pressure, which requires higher force to open the exhaust valve and can reduce the loading on the valve opening mechanism, and also generate more noise and require additional components.
Innovation Solution
The method involves actuating an engine valve for brake gas recirculation and compression-release events with a cam profile that includes a main exhaust lobe, a brake gas recirculation lobe, and a compression-release lobe, with specific lift adjustments to maintain the valve open between events and increase lift during critical phases, and using an exhaust restriction means to increase back pressure in the exhaust manifold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If exhaust back pressure is increased to increase braking power, then gas pressure in the cylinder increases, but the force required to open the exhaust valve increases
Solution Approach 1:
The valve is opened in advance during the intake stroke (before compression begins) to allow exhaust gases to enter the cylinder. This preliminary opening occurs when cylinder pressure is low, avoiding the high force requirement that would exist if the valve were opened during compression when cylinder pressure is high. The valve remains open through part of the compression stroke, maintaining low force requirements while still achieving the desired gas pressure increase for braking power.
2Ease of operation
If the exhaust valve is opened rapidly between BGR and compression-release events, then braking control is achieved, but noise increases and component wear increases
Solution Approach 1:
The exhaust valve undergoes periodic opening and closing actions at specific intervals in the engine cycle. The valve opens during the intake stroke for BGR, closes before compression, opens again near TDC for compression-release braking, and closes afterward. This periodic action pattern allows controlled braking while managing noise through timing rather than continuous operation.
Solution Approach 2:
The valve transition between BGR and compression-release events is accomplished by allowing the valve to close and then re-open rather than maintaining continuous rapid oscillation. This skipping approach avoids sustained high-frequency valve movement that would generate excessive noise, while still achieving the necessary braking control through the compression-release event.
3Adaptability or versatility
If multiple cam lobes are used for BGR and compression-release events, then valve actuation control is improved, but cam complexity increases
Solution Approach 1:
The camshaft is divided into multiple distinct lobes, each responsible for a specific valve event: a first lobe for BGR during the intake stroke, and a second lobe for compression-release braking near TDC. This segmentation allows independent control of each function while keeping the overall cam design relatively simple, as each lobe can be optimized for its specific purpose without interfering with the other.
Solution Approach 2:
A single exhaust valve serves multiple functions by being actuated by different cam lobes at different times in the engine cycle. The same valve is used for both BGR during intake and for compression-release braking during compression, eliminating the need for separate valves for each function and reducing overall system complexity despite the multi-functional requirement.
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 enhances braking power by increasing gas pressure in the cylinder, reduces the force required to actuate the exhaust valve, and minimizes noise and component complexity, offering improved control and reduced wear on service brakes.
Implementation Method 1
The introduction of exhaust gases from the exhaust manifold into the cylinder may pressurize the cylinder with a charge faster than it would otherwise occur during the compression stroke. The increased gas pressure in the engine cylinder may increase the braking power produced by the compression-release event.
Implementation Method 2
The method involves actuating an engine valve for brake gas recirculation and compression-release events with a cam profile that includes a main exhaust lobe, a brake gas recirculation lobe, and a compression-release lobe, with specific lift adjustments to maintain the valve open between events and increase lift during critical phases.
Data Source
AI summary
Methods and apparatus for actuating an engine valve provided between an engine cylinder and an exhaust manifold to provide compression-release engine braking in combination with exhaust gas restriction and brake gas recirculation are disclosed. In a first embodiment of the present invention, the engine valve used to provide brake gas recirculation and compression-release braking may be maintained slightly open between the brake gas recirculation and compression-release events. In another embodiment of the present invention, the cam closing ramp for a main exhaust event may be extended to terminate near the beginning of a brake gas recirculation event to facilitate refilling a hydraulic valve actuation system used to in association with the exhaust valve.