Variable Compression Crankshaft With Intermediate Transfer Gears
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Solution Overview
Problem
Existing crankshafts for internal combustion engines with variable compression ratio face issues of overloading transfer gears due to relatively large crankpin diameters, particularly in Diesel engines, leading to potential gear damage.
Innovation Solution
The crankshaft design incorporates external first and second transfer gears that mesh with intermediate transfer gears, which are rotatably mounted to the crank webs, allowing for the distribution of forces over multiple teeth and enabling the use of larger gears, while maintaining synchronized motion of eccentric members with identical gears.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the first and second transfer gears are made relatively small to match large crankpin diameters, then the gear geometry is appropriate, but the transfer gears become overloaded
Solution Approach 1:
The patent introduces intermediate transfer gears between the transfer shaft gears and the eccentric member gears. This segments the force transmission path into multiple stages, distributing the load across multiple teeth and reducing the force concentration on any single pair of meshing teeth, thereby preventing overloading of the transfer gears.
Solution Approach 2:
The intermediate transfer gears act as mediators in the power transmission chain. These additional gears are inserted between the transfer shaft gears and the eccentric member gears to reduce the gear ratio impact and distribute forces more evenly, preventing direct overloading of the transfer gears while maintaining the required motion transmission.
2Ease of manufacture
If identical gears are used for both eccentric members, then manufacturing is simplified, but the tooth forces on transfer gears increase
Solution Approach 1:
By introducing intermediate transfer gears, the patent segments the force transmission path. This allows the use of identical, easily manufactured transfer shaft gears while the intermediate gears absorb and distribute the forces, preventing overloading. The segmentation enables standardization of critical components without compromising structural integrity.
Solution Approach 2:
The intermediate transfer gears serve as force-distributing mediators that allow identical gears to be used in the eccentric member positions. These intermediary gears handle the force transmission, enabling the use of standardized, easily manufactured transfer shaft gears while preventing direct overloading through force distribution across multiple teeth.
3Productivity
If the compression ratio is increased under part-load conditions, then efficiency improves, but the risk of gear overloading increases
Solution Approach 1:
The patent segments the force transmission path by introducing intermediate transfer gears. This segmentation distributes the increased forces from high compression ratio operation across multiple teeth and transmission stages, allowing the system to operate efficiently at high compression ratios without overloading the transfer gears, thus maintaining both productivity and reliability.
Solution Approach 2:
The intermediate transfer gears act as force-distributing mediators that enable high compression ratio operation. These intermediary gears handle the increased forces generated during high compression ratio part-load conditions, distributing them across multiple teeth to prevent overloading while maintaining the efficiency benefits of variable compression ratio operation.
Data Source
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AI summary
A crankshaft (1, 40) for an internal combustion engine including variable compression ratio comprises a main journal, a first crankpin (3a, 43a), a first and second crank web (4a, 4b, 44a, 44b) at opposite sides of the first crankpin (3a, 43a), a second crankpin (3b, 43b) and a third and fourth crank web (4c, 4d, 44c, 44d) at opposite sides of the second crankpin (3b, 43b). The crankshaft also includes a first eccentric member (6a, 45a) which is rotatably mounted on the first crankpin (3a, 43a) and a second eccentric member (6b, 45b) which is rotatably mounted on the second crankpin (3b, 43b) and a transfer shaft (19, 50) which extends through the second and third crank web (4b, 4c, 44b, 44c) and which is rotatable with respect to the second and third crank web (4b, 4c, 44b, 44c) about a transfer shaft axis. An external first transfer gear (18, 52) is fixed to the transfer shaft (19, 50) at a side of the second crank web (4b, 44b) where the first eccentric member (6a, 45a) is located and an external second transfer gear (21, 49) is fixed to the transfer shaft (19, 50) at a side of the third crank web (21, 44c) where the second eccentric member (6b, 45b) is located. The first and second eccentric members (6a, 6b, 45a, 45b) are drivably coupled to each other through the transfer shaft (19, 50). The first and second transfer gears (18, 21, 47, 48) mesh with external first and second intermediate transfer gears (17, 22, 51), respectively, which in turn mesh with the first and second eccentric member gears (10, 23, 47, 48). The first and second intermediate transfer gears (17, 22, 51) are rotatably mounted to the second and third crank webs (4b, 4c, 44b, 44c), respectively