Hybrid Power Train With Nested Planetary Gears
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Solution Overview
Problem
Hybrid vehicles require a power train that can efficiently provide driving force and improve fuel efficiency by allowing operation in various modes, including a fixed gear ratio mode using only the engine, while minimizing exhaust emissions and optimizing power transmission.
Innovation Solution
A power train design for hybrid vehicles incorporating a first and second planetary gear set, clutches, and brakes, allowing connection and disconnection of power sources and output elements to achieve fixed gear ratio, electric vehicle, and hybrid modes, with overlapping rotary shafts and adjustable gear teeth configurations for enhanced flexibility and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a hybrid vehicle uses only engine and motor generator with conventional transmission, then the structure is simpler, but the fuel efficiency and driving flexibility are limited
Solution Approach 1:
The power train is divided into two independent planetary gear sets (first and second PGS) that can operate separately or together. The first PGS handles engine power transmission while the second PGS handles motor generator power, allowing independent optimization of each subsystem for fuel efficiency without requiring a completely complex integrated structure.
Solution Approach 2:
The planetary gear sets are designed to serve multiple functions: the first PGS can operate independently for engine-only driving, the second PGS can operate independently for motor generator driving, and both can work together for hybrid driving. This multi-functionality achieves high fuel efficiency across different driving conditions without requiring entirely different transmission systems.
2Productivity
If a hybrid vehicle operates in fixed gear ratio mode using only engine, then fuel efficiency improves, but the adaptability to different driving conditions decreases
Solution Approach 1:
The power train employs dynamic switching mechanisms (clutches and brakes) that allow the system to transition between different operating modes: fixed gear ratio mode for fuel efficiency, electric vehicle mode for low-speed operation, and hybrid mode for high-load conditions. This dynamic adaptability maintains high fuel efficiency while responding to varying driving requirements.
Solution Approach 2:
The system changes operational parameters by engaging different clutches (first and second clutches) and brakes (first and second brakes) to alter the gear ratio and power source configuration. This allows the vehicle to switch between engine-only fixed gear operation for efficiency and other modes for adaptability, resolving the contradiction through parameter variation.
3Adaptability or versatility
If the planetary gear sets are designed with independent sun gears and long pinion, then the gear ratio flexibility increases, but the manufacturing complexity increases
Solution Approach 1:
The first planetary gear set incorporates a long pinion that engages with two different sun gears (first and third sun gears) with different numbers of teeth. This nested configuration allows the same pinion to provide different gear ratios when engaged with different sun gears, achieving gear ratio flexibility without requiring multiple separate pinions, thereby simplifying manufacturing.
Data Source
AI summary
A power train for a hybrid vehicle may include: a first planetary gear set that includes at least four rotary elements; a second planetary gear set that includes at least three rotary elements one of which is connected with at least one of the rotary elements of the first planetary gear set; a first clutch that is configured to connect/disconnect a rotary element of the first planetary gear set with/from a rotary element of the second planetary gear set; and a first brake that is provided to restrain rotation of a rotary element of the second planetary gear set, wherein at least two or more independent power sources and an output element are connected to the rotary elements of the first planetary gear set and the second planetary gear set.