Compact Variator-Assisted CVT Packaging
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Solution Overview
Problem
Variator-assisted continuously variable transmissions (CVTs) are large and heavy, making them difficult to package and expensive, limiting their use in on-highway applications such as trucks and buses, where a wide range of gear ratios are needed without the bulk of conventional CVTs.
Innovation Solution
A compact variator-assisted CVT design that includes a variator with adjustable transmission ratios, differential and range transmissions, and connecting components strategically located to reduce size and weight, allowing for direct connection between the variator and output shaft, enabling efficient packaging and operation in smaller vehicles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional CVT is used to provide a wide spread of gear ratios, then the gear ratio range is sufficient, but the transmission becomes large and heavy
Solution Approach 1:
The transmission is divided into two separate pathways: a direct path through the summing transmission and a variable path through the variator. This segmentation allows the system to achieve wide gear ratio ranges without requiring a single large conventional CVT, thereby reducing overall transmission weight while maintaining adaptability.
Solution Approach 2:
The patent combines a conventional transmission (summing transmission) with a variator in a hybrid configuration. By merging these two different transmission types, the system achieves the gear ratio versatility of a conventional CVT while using the simpler summing transmission for certain pathways, reducing the need for a fully oversized conventional CVT.
2Adaptability or versatility
If the transmission components are arranged to provide all necessary connections, then the transmission functionality is complete, but the transmission size increases
Solution Approach 1:
The patent positions connecting components in three-dimensional space to optimize packaging. Specifically, the first and second connecting components are located in a connecting space defined between the differential and range transmissions, while the third connecting component is positioned on the opposite side of the range transmission. This spatial arrangement allows all necessary connections to be made without increasing the overall transmission volume.
3Adaptability or versatility
If a variator-assisted CVT is designed for wide gear ratios, then the gear ratio spread is adequate, but the transmission becomes more expensive and complicated
Solution Approach 1:
The transmission functionality is segmented into discrete pathways with dedicated connecting components. This segmentation allows each component to perform a specific function, simplifying the overall design and control logic compared to a fully integrated conventional CVT, while still achieving the desired gear ratio spread.
Solution Approach 2:
The summing transmission serves multiple functions: it can operate in direct connection mode for certain gear ratios and can also work in conjunction with the variator for other ratios. This multi-functionality reduces the need for separate dedicated components, thereby reducing overall transmission complexity while maintaining adequate gear ratio spread.
Data Source
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AI summary
A continuously variable transmission (CVT) is provided, where the CVT has an input shaft (2) drivable by an engine, and an output shaft (4) connectable to a load. A variator (12) has an input side connected to the input shaft (2), and an output side. The variator (12) is adjustable so as to vary a transmission ratio between the input and output sides. A differential transmission (34) has a first differential input element connected to the input shaft (2), a second differential input element connected to the output side of the variator (12), and first and second differential output elements. A range transmission (60) has a first range input element (58), and at least one range output element (75) connected to the output shaft (4). A first connecting component (52) selectively connects the first differential output element to the first range input element (58). A second connecting component (56) selectively connects the second differential output element to the first range input element (58). The first and second connecting components (52,56) are located in a connecting space defined between the differential and range transmissions (34,60). The transmission further comprises a third connecting component (84) which selectively connects the first range input element (58) to the output shaft (4). The third connecting component (84) is located on the opposite side of the range transmission (60) from the connecting space. A vehicle incorporating this CVT, and a method of operating the CVT are also provided.