V-Type Engine Gear Drive for Compact Timing
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Solution Overview
Problem
Existing V-type internal combustion engines with overhead camshafts face issues of stress on the crankshaft and timing mechanism due to expansion and wear in endless timing drive belts, leading to reliability and durability problems, and struggle with compact construction due to the size of the driven wheel and transverse width.
Innovation Solution
The implementation of a gear drive system with idler shafts and timing drive chains that decelerate the camshafts to half crankshaft speed, using idler gears with a 1:2, 2:3, 3:4, or 4:5 gear ratio to reduce the diameter of camshaft sprockets and timing chain winding radii, allowing for a more compact engine design without direct crankshaft drive, and positioning tensioners on the outer sides to maintain tension.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the endless timing drive belt is directly wound around the crankshaft to drive the valve operating camshaft, then the camshaft can be driven, but expansion and wear occur in the timing drive belt due to variations in crank angle speed, causing deterioration in reliability and durability
Solution Approach 1:
The patent introduces a gear shaft as an intermediary component between the crankshaft and the camshaft. The gear shaft rotates at half the crankshaft speed and drives the camshaft through a timing drive belt, preventing the belt from being directly wound around the crankshaft. This intermediary mechanism eliminates the expansion and wear problems caused by direct crankshaft rotation while maintaining reliable power transmission.
2Measurement precision
If a speed reduction is required between the drive and driven ends to provide correct valve timing, then the correct valve timing can be achieved, but the diameter of the driven wheel is limited, making it difficult to achieve compact construction of the cylinder head
Solution Approach 1:
The gear shaft serves as a mediator that provides the necessary speed reduction (half crankshaft speed) without requiring a large-diameter driven wheel. By positioning the gear shaft appropriately and using it to drive the camshaft through a timing belt, the system achieves precise valve timing while maintaining a compact cylinder head design.
3Ease of operation
If the axis of one of the camshaft driven wheels is offset relative to the crankshaft axis to drive the camshaft, then the camshaft can be driven, but the overall engine width increases in the direction perpendicular to the crankshaft axis
Solution Approach 1:
The patent employs an asymmetric layout where the gear shaft is positioned offset from the crankshaft axis, and the camshaft is driven from this offset position. This asymmetric arrangement allows the camshaft to be driven effectively while minimizing the increase in engine width perpendicular to the crankshaft axis, achieving a compact overall engine design.
Data Source
AI summary
A number of embodiments of double overhead cam shaft V type engines wherein the drive arrangement for the camshafts permits not only a compact design but also one in which the timing loadings are decreased to improve engine life, performance and reduced servicing.