Chain Casing Rigidity via Cylindrical Bosses
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Solution Overview
Problem
The internal combustion engine's chain casing experiences vibration and deformation due to insufficient rigidity, particularly in the bulging portion covering the variable valve timing mechanism, which has a large internal space and limited support from the cylinder head.
Innovation Solution
The chain casing is reinforced by incorporating cylindrical intake and exhaust side cylinder portions, fastening boss portions, and a reinforcement rib, along with a specific arrangement and connection structure to enhance rigidity and strength, particularly around the bulging portion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a bulging portion with large internal space is formed in the chain casing to cover the variable valve timing mechanism, then the variable valve timing mechanism can be adequately covered and positioned, but the rigidity of the bulging portion becomes insufficient causing vibration and deformation
Solution Approach 1:
The chain casing is divided into multiple cylindrical portions (intake side cylinder portion and exhaust side cylinder portion) that are connected to each other. This segmentation allows each portion to be optimized for its specific function while collectively providing the needed rigidity and space coverage for the variable valve timing mechanism.
Solution Approach 2:
Fastening boss portions are added in the vertical dimension below the bulging portion to attach the chain casing to the cylinder head. This dimensional addition provides direct support points that enhance rigidity without reducing the internal space of the bulging portion.
2Area of stationary object
If the bulging portion is made larger to cover more of the variable valve timing mechanism, then better coverage is achieved, but the number of support positions from the cylinder head remains limited causing insufficient rigidity
Solution Approach 1:
The chain casing is segmented into multiple cylindrical portions that can be independently optimized. The intake side and exhaust side cylinder portions are arranged to provide distributed support, effectively increasing the number of support positions without compromising the surface area of the bulging portion.
Solution Approach 2:
Fastening boss portions extend in the vertical dimension below the bulging portion, creating additional support positions that do not reduce the horizontal surface area of the bulging portion. This allows the bulging portion to maintain its large area while gaining rigidity through vertical support structures.
3Strength
If cylindrical portions are added to reinforce the chain casing, then rigidity and strength are improved, but the structural complexity increases
Solution Approach 1:
The cylindrical portions serve multiple functions: they provide structural rigidity, define mounting positions for hydraulic control valves, and facilitate attachment to the cylinder head through fastening boss portions. This multi-functionality reduces the need for separate reinforcement elements, simplifying the overall structure.
Solution Approach 2:
The reinforcement structure is merged with the functional components of the chain casing. The cylindrical portions are integrated with the fastening boss portions and the bulging portion, creating a unified structure that provides both strength and functionality without adding separate complex reinforcement elements.
Data Source
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AI summary
[Object] To provide an internal combustion engine capable of suppressing vibration and deformation of a chain casing. [Solution] A chain casing 20 includes a cylindrical intake side cylinder portion 23 bulging in a crank shaft direction and allowing an intake hydraulic control valve 15 to be inserted thereinto, a cylindrical exhaust side cylinder portion 24 bulging in the crank shaft direction and allowing an exhaust hydraulic control valve 16 to be inserted thereinto, and an intake side fastening boss portion 25 and an exhaust side fastening boss portion 26 arranged below a bulging portion 21 and attaching the chain casing to a cylinder head 3. A lower portion of the bulging portion 21 is connected to upper portions of the intake side cylinder portion 23 and the exhaust side cylinder portion 24. An upper portion of the intake side fastening boss portion 25 is connected to a lower portion of the intake side cylinder portion 23. An upper portion of the exhaust side fastening boss portion 26 is connected to a lower portion of the exhaust side cylinder portion 24.