Semi-Power Split Hybrid Transmission with Fixed Gears
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Solution Overview
Problem
Conventional Power Split Transmissions (PSTs) for Hybrid Electric Vehicles (HEVs) require high-powered electric motors and complex power electronics, leading to high development costs and inefficiencies, as they struggle to cover all engine loads and speeds, lack reverse torque, and have limited fixed gears.
Innovation Solution
A semi-power split transmission system with multiple Electric Variable Transmission (EVT) modes and fixed gears, utilizing two electric motors and various planetary gear sets, including dual-sun and dual-ring Ravigneaux-type gear sets, to reduce E-motor power requirements and enhance efficiency by employing fixed gears at high loads and EVT modes at light loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional Power Split Transmission uses high-powered electric motors to cover full load engine operation, then the transmission can operate in EVT modes across all engine loads, but the E-motor size and power electronics requirements increase significantly
Solution Approach 1:
The transmission system is segmented into two distinct operational paths: EVT modes for light-to-medium loads and fixed gears for high loads. This segmentation allows the E-motor to be sized appropriately for EVT operations without needing excessive power capacity for high-load fixed gear operations, thereby reducing E-motor size while maintaining versatility
Solution Approach 2:
The system dynamically switches between EVT modes and fixed gears based on load conditions. The control system selects the appropriate operational mode (EVT or fixed gear) depending on the current engine load, allowing the transmission to adapt its characteristics to match operational requirements rather than maintaining constant high-power capability
2Use of energy by moving object
If Power Split Transmission uses variable transmission ratios in EVT modes, then the engine can operate near the best efficient load point, but the E-motor power requirements increase to cover all engine loads and speeds
Solution Approach 1:
The operational range is segmented into light-to-medium loads where EVT modes with variable ratios optimize engine efficiency, and high loads where fixed gears are used. This allows the system to capture efficiency benefits of variable ratios where applicable while avoiding the penalty of requiring oversized E-motors to handle all load conditions
Solution Approach 2:
The system changes operational parameters by switching between EVT mode (with variable transmission ratios for efficiency) and fixed gear mode (for high load capability). This parameter change allows the E-motor to be sized for efficiency optimization rather than maximum power coverage
3Adaptability or versatility
If existing HEV PSTs use high power E-motors to cover full load operation, then the transmission can provide full hybrid capabilities, but the development costs and device complexity increase
Solution Approach 1:
The hybrid transmission system is segmented into EVT modes for light-to-medium loads and fixed gears for high loads. This segmentation reduces the required E-motor power rating, which in turn reduces power electronics complexity and development costs while maintaining full hybrid capabilities through the combination of both operational modes
Solution Approach 2:
The transmission system achieves multi-functionality by combining EVT modes and fixed gears in a single system. This universal approach allows the transmission to handle all hybrid operations (series, parallel, regenerative braking) without requiring a dedicated high-power E-motor, thereby reducing overall system complexity
4Ease of operation
If Power Split Transmission lacks fixed gears and relies solely on EVT modes, then the E-motor can provide variable ratios, but the system cannot efficiently handle high load operations
Solution Approach 1:
The transmission system segments operational responsibilities: EVT modes handle light-to-medium loads with variable ratios for ease of operation, while fixed gears handle high load operations. This segmentation allows each subsystem to be optimized for its specific operational range without compromising overall system capability
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
The semi-power split transmission achieves reduced E-motor power consumption, increased engine efficiency, and full hybrid capabilities, with well-distributed fixed gears for high loads and EVT modes for light loads, eliminating the need for a torque converter and minimizing E-motor size while maintaining efficient energy regeneration.
Implementation Method 1
Power split transmissions utilize epicyclic differential gearing (i.e., planetary gear sets) in a way that a part of the power of an internal combustion engine is transmitted through a mechanical path to the output
Implementation Method 2
The electrical path includes two E-motors, one of them operating as a motor and the other as a generator. Variable transmission ratios can be obtained by varying the speeds of the E-motors
Implementation Method 3
The electrical path includes two E-motors, one of them operating as a motor and the other as a generator
Data Source
AI summary
The present disclosure provides a semi-power split transmission with multiple Electric Variable Transmission (EVT) modes and fixed gears for use in hybrid electrical vehicles (HEV). The present disclosure utilizes two electric motors (“E-motors”), an engine, and two planetary gear sets. The planetary gear sets can include a dual-sun Ravigneaux-type gear set (DS-RGS), a dual-ring Ravigneaux-type gear set (DR-RGS), a three-sun Ravigneaux-type gear set (TS-RGS), and a normal planetary gear set (PGS). The E-motors can be placed at the front end of the transmission, with one E-motor at the front and one in the middle between the gear sets, and with both E-motors in the middle between the gear sets.