Actuator Mounting Rigidity in Variable Compression Ratio Engines
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Solution Overview
Problem
The actuator mounting portion on the side wall of the engine main body requires high rigidity to withstand greater combustion and inertia loads, but existing methods, such as fixing the actuator between two components, are difficult to manufacture accurately and increase costs.
Innovation Solution
Incorporating rigidity improvement sections within the inter-bolt distance between fixing bolts, including an upper oil pan lower surface flange and bolt boss portions, to enhance the mounting rigidity of the actuator on the engine main body.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the actuator is fixed on both the side walls of two components (cylinder block and upper oil pan), then the sealing characteristic can be ensured, but the side walls need to be accurately formed to be flush with each other, making processing difficult and increasing cost
Solution Approach 1:
The mounting structure is segmented into two parts: the actuator mounting portion provided on the upper oil pan, and the rigidity improvement sections (flange portion and bolt boss portions) that connect to the cylinder block. This segmentation allows each component to be manufactured and processed independently with standard tolerances, avoiding the need for highly accurate flush processing of two side walls while maintaining sealing through the gasket between upper oil pan and cylinder block.
2Strength
If the actuator is fixed on both the side walls of two components, then the mounting rigidity can be improved, but the processing work becomes difficult and cost increases
Solution Approach 1:
Instead of requiring the entire side wall interface to have high precision for rigidity, the invention applies local quality enhancement through rigidity improvement sections. The flange portion and bolt boss portions are locally reinforced with increased thickness and stiffness only in the regions where mounting rigidity is needed, while the rest of the components can be manufactured with standard tolerances, reducing overall processing difficulty.
3Manufacturing precision
If rigidity improvement sections are provided within the inter-bolt distance, then the mounting rigidity and positioning accuracy are improved, but the structural complexity increases
Solution Approach 1:
The rigidity improvement sections are merged with existing structural elements of the upper oil pan. The flange portion is integrated with the upper oil pan's lower surface, and the bolt boss portions are formed as integral features of the upper oil pan. This merging approach provides the necessary rigidity and positioning accuracy without adding separate, complex structural components, thereby minimizing device complexity.
Data Source
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AI summary
A variable compression ratio internal combustion engine includes a variable compression ratio mechanism arranged to vary an engine compression ratio in accordance with a rotational position of a control shaft, and an actuator arranged to drivingly rotate the control shaft. The actuator is fixed to an actuator mounting portion (40) provided to a side wall of an upper oil pan (12) which is a main body of the engine, with a plurality of fixing bolts. A first rigidity improvement section (41) and a second rigidity improvement section (42) arranged to improve the rigidity of the actuator mounting portion (40) are provided within an intern-bolt distance (46) between the two fixing bolts positioned at both sides in a direction of a crank shaft, of the plurality of the fixing bolts.