Hybrid Vehicle Transmission Two-Mode EVT Design
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
One-mode Electrically Variable Transmissions (EVTs) in hybrid vehicles increase vehicle costs due to the need for high-capacity motor/generators for high power transmission, especially during initial starting and high-speed sections, which affects space utilization and hydraulic supply.
Innovation Solution
A two-mode EVT structure using two motor/generators with a specific configuration of planetary gear trains and external gear pairs, allowing for improved space utilization and hydraulic supply passage, including a one-way clutch and reduction gears to optimize motor/generator placement and gear ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a one-mode EVT structure is used, then high power transmission capability is achieved, but vehicle cost increases and space utilization deteriorates
Solution Approach 1:
The patent divides the single motor/generator into two separate motor/generators (first and second motor/generators), each handling different power ranges. The first motor/generator handles high-power operations during initial starting and high-speed sections, while the second motor/generator handles lower-power operations, thereby reducing the cost and size of individual components while maintaining overall high power transmission capability
Solution Approach 2:
The patent utilizes the radial space around the input shaft by positioning the first planetary gear train and first motor/generator in a radial arrangement, rather than only axial arrangement. This allows for more compact packaging and improved space utilization within the transmission housing
2Power
If a one-mode EVT structure is used, then high power transmission capability is achieved, but transmission size and weight increase
Solution Approach 1:
By segmenting the power transmission function into two separate motor/generators with different capacity levels, the patent avoids the need for a single oversized high-capacity motor/generator. This results in reduced overall transmission weight while maintaining the ability to handle high power transmission requirements when needed
Solution Approach 2:
The patent employs nested planetary gear trains where the first and second planetary gear trains are arranged concentrically around the input shaft, with components nested within each other's spatial envelope. This compact nested arrangement reduces the overall transmission size and weight compared to separate gear trains
3Device complexity
If a two-mode EVT structure is used, then space utilization is improved, but hydraulic supply passage becomes difficult to secure
Solution Approach 1:
The patent incorporates hydraulic supply passages directly into the transmission case design from the outset, with passages pre-routed to deliver hydraulic fluid to the friction elements (clutches and brakes) located within the compact two-mode EVT structure. This preliminary planning of hydraulic pathways during the design phase ensures ease of manufacture despite the compact arrangement
Data Source
AI summary
A hybrid vehicle transmission includes input and output shafts, first and second motor/generators, a first planetary gear train in which one rotary element of three rotary elements is connected to the input shaft and another thereof is connected to the first motor/generator, a second planetary gear train in which one of three rotary elements is connected to the output shaft and another thereof is connected to the second motor/generator, a first external gear pair consisting of a first gear, connected to a remaining rotary element of the first planetary gear train, and a second gear, connected to a remaining rotary element of the second planetary gear train, and a second external gear pair consisting of a third gear, connected to the input shaft, and a fourth gear directly connected to one rotary element of the second planetary gear train.