Power Split Transmission with Two EVT Modes and Four Fixed Gears
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Solution Overview
Problem
Existing Power Split Transmissions (PSTs) for hybrid electric vehicles lack low power split ratios, four well-distributed gears, and efficient front E-motor designs, leading to high development costs and limited efficiency in engine operation.
Innovation Solution
A Power Split Transmission with two Electric Variable Transmission (EVT) modes and four fixed gears, utilizing three planetary gear sets and four selectively engageable clutches, where power is transmitted only mechanically for highest efficiency, and E-motors can be located in a front or center design for modularity and lower component speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high-power E-motors and power electronics are used to cover full load engine operation, then the engine can operate at full load, but the component speeds become very high increasing complexity and cost
Solution Approach 1:
The transmission is divided into two distinct operational modes: EVT modes for low-load operation and fixed gear modes for high-load operation. This segmentation allows the E-motor to operate at lower speeds during EVT modes while a fixed gear handles high-speed power transmission during fixed gear modes, resolving the contradiction between power coverage and component speed
Solution Approach 2:
The system dynamically switches between EVT modes and fixed gear modes based on operating conditions. The clutch mechanism enables dynamic reconfiguration of the power transmission path, allowing the system to adapt component speeds to match the operational requirements, thereby managing both power coverage and speed constraints
2Device complexity
If conventional geared transmissions with fixed ratios are used, then the structure is simple, but the engine cannot operate near the best efficient load point across varying speeds
Solution Approach 1:
The transmission is segmented into EVT modes for efficient low-load operation and fixed gear modes for high-load operation. This segmentation allows the system to use the simple fixed gear structure when appropriate while utilizing the variable ratio capability of EVT modes when fuel efficiency is the priority, thus balancing structural simplicity with energy efficiency
Solution Approach 2:
The system changes the transmission ratio parameter dynamically by switching between EVT modes with variable ratios and fixed gear modes. This parameter change enables the engine to operate near its best efficient load point during EVT modes while maintaining structural simplicity through the use of conventional fixed gears during other operations
3Adaptability or versatility
If PST allows no carry over of parts from conventional transmissions, then the transmission can be optimized for hybrid operation, but development costs become very large
Solution Approach 1:
The patent merges the EVT mechanism with conventional fixed gear transmission components. The fixed gear sets and clutch mechanisms are integrated into the existing PST architecture, allowing parts to be carried over from conventional transmissions while maintaining optimization for hybrid operation, thereby reducing development costs without sacrificing adaptability
Solution Approach 2:
The transmission system is designed with multi-functionality, where the same component structure serves both EVT modes and fixed gear modes. This universality allows conventional transmission parts to be utilized in the hybrid optimized system, reducing development costs while maintaining versatility for different operational requirements
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables optimal fuel efficiency and performance with lower component speeds, covering full load engine operation and providing both efficient EVT modes for low load city driving and fixed gears for high load operations, reducing development costs and improving transmission efficiency.
Implementation Method 1
The first planetary gear set includes a first sun gear, a first ring gear, and a first planetary pinion rotatably mounted on a first planetary carrier, wherein the first planetary pinion is disposed in a meshing relationship with the first sun and first ring gears
Implementation Method 2
a first electric motor connected to second planetary gear set, a second electric motor connected to the first planetary gear set
Data Source
AI summary
The present disclosure provides a power split transmission with two Electric Variable Transmission (EVT) modes and four fixed gears for use in hybrid electrical vehicles (HEV). The present disclosure utilizes two electric motors (“E-motors”), an engine, three planetary gear sets, and four selectively engageable clutches. The clutches are engaged in different combinations to engage the different gears and EVT modes. In the four fixed gears, power is transmitted only on the mechanical path for the highest transmission efficiency. In the two EVT modes, a part of the power is transmitted electrically. Alternatively, the E-motors can be located in the middle integrated with the transmission design. Advantageously, the present invention works with lower component speeds than existing two-mode hybrid transmissions. This can be achieved with a front E-motor design enabling modularity and also with a center E-motor design.