Variable Valve Train Brake Cam for Engine Braking
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing internal combustion engine technologies for commercial vehicles lack an economical solution for engine braking that efficiently manages installation space and reduces load on the valve train during braking operations.
Innovation Solution
A variable valve train system with a camshaft and cam carrier that includes a first and second cam, where the second cam is designed for engine braking, allowing the first exhaust valve to be opened at the end of the compression or exhaust stroke to perform compression work and expel compressed air, potentially eliminating the need for additional braking devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a separate braking device (engine brake valve, charge air throttle valve, or retarder) is installed to achieve engine braking, then engine braking function is provided, but installation space increases and device complexity increases
Solution Approach 1:
The camshaft is designed to perform multiple functions: normal valve actuation during engine operation and engine braking control. By integrating a displaceable cam carrier with different cam profiles (first cam for normal operation, second cam for braking), the existing valve train system achieves braking functionality without requiring separate braking devices, thereby eliminating additional installation space requirements
Solution Approach 2:
The invention merges the engine braking function with the existing valve train system. The cam carrier, which normally actuates exhaust valves, is modified to also control valve timing for engine braking by displacing between two axial positions. This combines what were previously separate functions (valve actuation and braking control) into a single integrated system
2Adaptability or versatility
If a displaceable cam carrier with multiple cams is used to enable engine braking, then engine braking control is improved and valve train load is reduced, but device complexity increases
Solution Approach 1:
The cam carrier is designed to be displaceable between a first axial position (for normal operation) and a second axial position (for engine braking). This dynamic repositioning allows the same physical component to engage different cam profiles depending on operational mode, providing adaptive control without requiring completely separate mechanical systems for each function
Solution Approach 2:
The camshaft system is segmented into multiple functional components: a fixed camshaft, a displaceable cam carrier, a first cam for normal operation, and a second cam for braking operation. This segmentation allows each component to be optimized for its specific function while working together as an integrated system, managing complexity through modular functional division
3Power
If the first exhaust valve is opened during compression stroke for engine braking, then compression work is performed to brake the crankshaft, but valve train load increases
Solution Approach 1:
The system changes the timing parameters of valve operation based on operational mode. During engine braking, the second cam opens the exhaust valve at a different timing (during compression stroke or before top dead center) compared to normal operation. This parameter change optimizes the braking effect by allowing compression work to be performed while controlling valve train loads through precise timing control
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The invention relates to a variable valve train (10) for an internal combustion engine of a motor vehicle. The variable valve train has a cam carrier (14) which is arranged on a camshaft (12) so as to be rotationally fixed and axially displaceable between a first axial position and a second axial position, and which has a first cam (32) and a second cam (34). The first cam (32) is configured for normal operation of the internal combustion engine, in which the first cam (32) holds a first exhaust valve (20) open during the exhaust stroke. The second cam (34) is configured for engine braking operation of the internal combustion engine, in which the second cam (34) initially holds the first exhaust valve (20) closed during the compression stroke and/or the exhaust stroke and opens the first exhaust valve (20) before reaching top dead center of a piston movement.