Variable Valve Mechanism Cam Carrier Design
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Solution Overview
Problem
Existing engine variable valve mechanisms face challenges in achieving high camshaft supporting rigidity and ease of assembly, particularly in multi-cylinder engines, due to limited space and complexity in forming hydraulic actuators and oil passages, and they are not suitable for high-speed engines as they cannot set different lift degrees for valves.
Innovation Solution
The engine incorporates a cam carrier with a cam bearing portion and rocker shaft support at the bore center, a switching device with a connecting pin, hydraulic cylinder, and piston, and a lost-motion spring system, allowing for high-speed and low-speed rocker arms to be disconnected and connected, respectively, while maintaining high camshaft rigidity and enabling compact assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the hydraulic actuator is provided between the valve springs in a small size engine, then the variable valve mechanism can be implemented, but the spacing between valve springs is small and there is little free space, making it difficult to form cylinder holes with high precision and assemble the piston and rocker arm
Solution Approach 1:
The invention moves the hydraulic actuator from the vertical space between valve springs to the horizontal plane at the camshaft support position. This dimensional relocation provides sufficient space for the cylinder hole and piston assembly while maintaining the variable valve mechanism functionality, resolving the contradiction between adaptability and ease of manufacture.
Solution Approach 2:
The camshaft support structure is designed to serve multiple functions: supporting the camshaft, housing the hydraulic actuator, and providing mounting points for rocker arms. This multi-functionality eliminates the need for separate components and simplifies assembly, addressing the manufacturing precision and assembly ease issues.
2Ease of operation
If the cylinder hole is formed at the cylinder head for the hydraulic actuator, then the actuator can be assembled, but it is difficult to form the cylinder holes with high precision in a multi-cylinder engine and the oil passage is complicated
Solution Approach 1:
The invention combines the hydraulic actuator housing with the camshaft support structure into a single integrated component. This merging eliminates the need for separate cylinder holes in the cylinder head and simplifies the oil passage routing, reducing both manufacturing complexity and precision requirements while maintaining assembly ease.
3Device complexity
If the low speed rocker arm pushes two valves together in the same cylinder, then the mechanism is simplified, but different lift degrees cannot be set for these valves and the camshaft cannot be supported at the bore center, reducing supporting rigidity
Solution Approach 1:
The invention segments the valve control mechanism by providing separate rocker arms for each valve, with each rocker arm independently controllable through the variable valve mechanism. This segmentation enables different lift degrees for different valves while maintaining reasonable mechanism complexity through the shared camshaft and hydraulic actuator system.
4Volume of moving object
If the low speed rocker arm is provided at the bore center, then the structure is compact, but the camshaft cannot be supported at the bore center, resulting in low supporting rigidity for high speed engines
Solution Approach 1:
The invention relocates the camshaft support from the vertical bore center position to the horizontal plane at the cylinder head periphery, where sufficient space exists for rigid support. This dimensional relocation maintains mechanism compactness through integrated design while providing the camshaft supporting rigidity required for high-speed engine operation.
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 configuration enhances camshaft supporting rigidity, allows for easy engine assembly, and enables the setting of different lift degrees for valves, improving the engine's suitability for high-speed operations and reducing size while simplifying the formation of oil passages.
Implementation Method 1
a hydraulic piston moving the connecting pin, thereby connecting or disconnecting the low speed rocker arm and the high speed rocker arm
Implementation Method 2
A lost-motion spring shaft is provided in the rocker shaft support and a lost-motion spring is wound around the lost-motion spring shaft. The lost-motion spring urges the high speed rocker arm so that the high speed rocker arm and the connecting pin are engaged with each other
Data Source
AI summary
An engine having a variable valve mechanism arranged to switch a lift degree of a valve between a low speed state and a high speed state includes a cam carrier defined by a cam bearing portion, a rocker shaft support, and a hydraulic cylinder support. The cam bearing portion is provided on a line passing through the bore center of a cylinder in a plane perpendicular or substantially perpendicular to the camshaft. The low speed rocker arm swings in response to the low speed cam of the camshaft. The high speed rocker arm swings in response to the high speed cam of the camshaft. The low speed rocker arm includes a through hole. A connecting pin is slidably inserted into the through hole and urged toward the hydraulic cylinder support. A hydraulic cylinder is provided in the hydraulic cylinder support.