Electric CVT Layout With External Machines for Lower Losses
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Solution Overview
Problem
Hydraulic continuously variable transmissions (CVT) suffer from efficiency losses due to fluid friction and pumping losses, are heavy and bulky, while electric CVT systems lack optimal configurations for varying applications and often require custom designs, increasing costs in lower production markets like agriculture.
Innovation Solution
An electric continuously variable transmission (CVT) with a planetary gear set coupled to off-the-shelf electric machines and an internal combustion engine, allowing for flexible selection and configuration, including a PTO system and hybrid capabilities, to optimize gear ratios and power delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If hydraulic CVT systems are used, then power output is increased and engine efficiency is improved, but efficiency losses occur due to fluid friction and pumping losses, and the system becomes heavy and bulky
Solution Approach 1:
The patent replaces the hydraulic system with an electric system. Specifically, hydraulic components (pumps, fluid circuits) are substituted with electric machines (motors/generators) and electronic control systems. This substitution eliminates fluid friction and pumping losses inherent in hydraulic systems while maintaining the ability to vary gear ratios continuously and decouple input/output speeds, thereby resolving the contradiction between power output and energy efficiency.
2Power
If hydraulic CVT systems are used, then power output is increased, but the transmission becomes heavy and bulky due to hydraulic fluid and components
Solution Approach 1:
The patent substitutes heavy hydraulic components (pumps, reservoirs, fluid circuits) with lighter electric machines and electronic control systems. The electric machines can be mounted externally on the housing, eliminating the need for integrated hydraulic fluid systems. This substitution significantly reduces the overall weight of the transmission system while maintaining the capability to deliver increased power output through electric torque multiplication.
3Ease of operation
If electric CVT systems are designed with integrated electric machines, then control over speed and torque is improved, but the system requires custom designs for different applications, increasing costs in lower production markets
Solution Approach 1:
The patent divides the electric CVT system into modular components: a standardized transmission housing containing the planetary gear set and control systems, with electric machines as separate, interchangeable modules. This segmentation allows the core transmission architecture to be mass-produced as a standardized platform, while different electric machine configurations can be attached to suit various applications. This resolves the contradiction by maintaining ease of operation through standardized control interfaces while reducing manufacturing costs through volume production of the housing and core components.
Solution Approach 2:
The patent designs the transmission housing and planetary gear set as universal components that can accommodate different electric machine types and configurations. The standardized interface and mounting system allow a single housing design to support multiple applications (agricultural, industrial, automotive) by simply changing the electric machine modules. This universality enables mass production of the core transmission system while maintaining adaptability to various applications, thereby reducing costs in lower production markets without sacrificing control capabilities.
Data Source
AI summary
In one example, an assembly is provided comprising a transmission at least partially enclosed in a housing. The transmission includes a planetary gear set coupled to a multispeed sub-transmission. The planetary gear set is configured to be coupled to a first electric machine and an internal combustion engine on a first side, and configured to be coupled to a second electric machine on a second side, where the first side and the second are defined by a vertical plane that is perpendicular to a central axis of rotation of the planetary gear set. The first electric machine, the second electric machine, and the internal combustion engine are arranged outside of the housing.