Hybrid Powertrain Layout With Single Planetary Gear for EV Efficiency
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Solution Overview
Problem
Existing hybrid vehicle drive systems suffer from inefficiencies due to a large number of tooth engagements in purely electric operation, leading to reduced efficiency.
Innovation Solution
A compact drive train design utilizing a single planetary gear with a stepped transmission, where the first electric machine is connected to a second transmission element of the planetary gear, and the internal combustion engine is directly connected to the transmission output shaft via a shifting element, with a brake element locking the first transmission element in electric driving modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple planetary gear sets are used to provide multiple gear ratios, then the versatility of the transmission system is improved, but the device complexity increases
Solution Approach 1:
The transmission system is segmented into a single planetary gear set for ratio variation and a stepped transmission for additional gear stages. This segmentation allows the planetary gear set to focus on providing smooth ratio changes while the stepped transmission provides discrete gear ratios, reducing overall complexity compared to using multiple complete planetary gear sets.
Solution Approach 2:
The patent merges a single planetary gear set with a stepped transmission into one integrated system. The planetary gear set's sun gear, ring gear, and planet carrier are combined with the stepped transmission's intermediate shafts and gears to provide multiple gear ratios through a unified structure, reducing the number of separate components needed.
2Force
If a large number of tooth engagements are used in purely electric operation, then the torque transmission capability is improved, but the energy efficiency deteriorates
Solution Approach 1:
The system dynamically switches between different operating modes using switching elements. In purely electric operation, the switching elements configure the transmission to minimize tooth engagements and reduce mechanical losses. The planetary gear set can be disengaged or placed in a low-friction configuration during electric-only modes, allowing the electric machines to operate more efficiently while maintaining torque transmission capability when needed.
Data Source
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AI summary
The invention relates to a powertrain for a motor vehicle, comprising an internal combustion engine (ICE), a first electric machine (E1), a second electric machine (E2), a transmission unit (10) with a transmission input shaft (12), only one planetary transmission (PG) with three transmission elements (1G, 2G, 3G), and a stepped transmission (17) with a first intermediate shaft (Z1), a second intermediate shaft (Z2), and a transmission output shaft (13). The stepped transmission has at least two gears (1, 2, 3, R) with different rotational speed transmission ratios. The transmission input shaft (12) is rotationally connected to a first transmission element (1G) of the planetary transmission (PG), and a third transmission element (3G) is rotationally connected to the first intermediate shaft (Z1). The first electric machine (E1) is rotationally connected to a second transmission element (2G) of the planetary transmission (PG), and the second transmission element (2G) of the planetary transmission (PG) can be secured to the housing (11) via a first brake element (19). The second electric machine (E2) can be rotationally connected to the first transmission output shaft (13), and the internal combustion engine (ICE) can be rotationally connected directly to the transmission output shaft (13) via a first shift element (18).