Variable Valve Train Engine Braking Cam Switching
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Solution Overview
Problem
Existing variable valve trains for internal combustion engines lack a simple and reliable mechanism to switch exhaust valves into an engine braking mode, limiting their efficiency and flexibility.
Innovation Solution
A variable valve train system with dual idle-stroke devices, controlled by a hydraulic actuation system, allows selective activation of either a normal operating cam or an engine braking cam, incorporating non-return valves for hydraulic lash compensation and fluidic control of rocker arms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a dual cam system with separate rocker arms is used for normal and braking modes, then engine braking capability is improved, but device complexity increases
Solution Approach 1:
The patent combines the first and second rocker arms into a single integrated rocker arm structure that can selectively engage with either the first cam (normal mode) or the second cam (braking mode). This merging reduces the number of separate components while maintaining the dual-mode functionality, thereby improving adaptability without proportionally increasing device complexity.
Solution Approach 2:
The single rocker arm is designed with universal functionality to perform both normal valve actuation and engine braking valve actuation by selectively engaging with different cams. This multi-functionality allows one component to replace what would traditionally require separate dedicated components, reducing overall system complexity while maintaining versatility.
2Reliability
If hydraulic actuation with dual idle-stroke devices is implemented, then switching reliability is improved, but device complexity increases
Solution Approach 1:
The patent introduces a hydraulic intermediary system that mediates between the control signal and the rocker arm engagement. The hydraulic fluid acts as an intermediary to transmit force and enable smooth, reliable switching between the first and second idle-stroke devices, improving switching reliability while keeping the control mechanism manageable through fluid-based actuation.
3Manufacturing precision
If non-return valves are added for hydraulic lash compensation, then valve control precision is improved, but device complexity increases
Solution Approach 1:
The non-return valves are integrated into the hydraulic system to provide automatic, self-regulating lash compensation. The valves allow hydraulic fluid to flow in one direction to adjust valve clearance while preventing backflow, enabling the system to self-compensate for thermal expansion and wear without requiring external adjustment mechanisms, thereby improving precision with minimal additional complexity.
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
Enables efficient engine braking by selectively activating cam profiles, enhancing engine performance and reducing mechanical complexity while allowing for easy integration of additional features like hydraulic lash adjustment.
Implementation Method 1
a valve assembly configured to selectively connect (e.g., only) the first free-stroke device or (e.g., only) the second free-stroke device to the fluid supply line
Implementation Method 2
incorporating non-return valves for hydraulic lash compensation
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The invention relates to a variable valve train (10) for switching an outlet valve (22) of an internal combustion engine to an engine braking mode. The variable valve train (10) has a camshaft (12) with a first cam (34), which is designed as a normal operation cam, and a second cam (36), which is designed as an engine braking cam. A first rocking lever (14) has a first stroke device (38) which is designed for selectively making or breaking a first operative connection between the first cam (34) and the outlet valve (22) by means of the first rocking lever (14). A second rocking lever (16) has a second stroke device (40) which is designed for selectively making or breaking a second operative connection between the second cam (36) and the outlet valve (22) by means of the second rocking lever (16). A valve device (60) selectively connects the first stroke device (38) or the second stroke device (40) to a fluid feed line (66).