Hybrid Powertrain Planetary Gear Layout for Engine Speed Freedom
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Solution Overview
Problem
Hybrid vehicles face challenges in optimizing fuel efficiency due to the need for combining power from motors and engines effectively across various driving conditions, particularly in parallel mode, where the engine's operation is constrained by the rotation speed of the motor, limiting its operational range and optimal operating point.
Innovation Solution
A hybrid powertrain apparatus featuring a planetary gear set with a clutch and output gear configuration that allows for flexible power transmission between an engine and motors, enabling the engine to operate at different speeds relative to the motor, thereby increasing its operational freedom and optimizing fuel efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the engine is directly connected to the motor in parallel mode, then the power transmission is simple, but the engine's operational range is limited and it cannot operate at optimal points
Solution Approach 1:
The power transmission system is segmented into multiple independent shafts (first input shaft, second input shaft, third input shaft) that can rotate at different speeds. This segmentation allows the engine to operate independently from the motor speed constraints, enabling the engine to maintain optimal operating points while the motor handles variable speed requirements.
Solution Approach 2:
The planetary gear set acts as an intermediary mechanism between the engine and motor. It provides variable speed relationships through its three rotation elements (sun gear, planet carrier, ring gear), allowing the engine to operate at different speeds relative to the motor while still transmitting power effectively. This mediator resolves the speed mismatch between engine and motor.
2Loss of energy
If the engine operates at optimal points, then fuel efficiency is improved, but the power transmission structure becomes more complex
Solution Approach 1:
The system dynamically switches between different operational modes (EV mode, series mode, parallel mode) and utilizes a clutch mechanism to engage/disconnect the planetary gear set as needed. This dynamic operation allows the engine to operate at optimal points when fuel efficiency is prioritized, while simplifying the structure when full power transmission is not required.
Solution Approach 2:
The planetary gear set serves multiple functions: it enables speed variation for engine optimization, provides direct power transmission when engaged, and can be disconnected entirely when not needed. The clutch mechanism adds universal functionality by allowing the system to adapt between complex and simple configurations based on operational requirements.
3Ease of operation
If the motor speed is constrained to match engine speed, then the power transmission is simplified, but the degree of freedom of operation is reduced
Solution Approach 1:
The system transitions from a single-dimension speed relationship (engine speed = motor speed) to a multi-dimensional speed relationship using the planetary gear set. The three rotation elements can rotate at different speeds independently, creating a speed triangle that provides two additional degrees of freedom. This allows the engine and motor to operate at different speeds while still achieving effective power transmission.
Data Source
AI summary
A hybrid powertrain apparatus for a vehicle includes an engine, a first input shaft mounted to receive power from the engine, a first motor directly connected to the first input shaft, a second input shaft disposed concentrically with the first input shaft, a second motor directly connected to the second input shaft, a planetary gear set including three rotation elements, two of which are respectively connected to the first input shaft and the second input shaft and the remaining one of which is mounted to be selectively stationary, and an output gear integrally formed with the second input shaft to draw power.