Hybrid Powertrain with Mechanical Reverse Gear
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Solution Overview
Problem
Conventional power split hybrid electric vehicle powertrains face inefficiencies in negative power split mode due to power circulation, reduced torque capacity in reverse drive, and reliance on large generator sizing for heavy applications.
Innovation Solution
A hybrid powertrain design incorporating a dual-clutch multiple-ratio transmission with a mechanical reverse gear and ring gear locking capability, allowing for series operation and reducing reliance on motor torque for reverse driving, thereby enhancing efficiency and torque capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If negative power split mode is used to regulate engine speed at high vehicle speeds, then engine speed control is improved, but powertrain efficiency deteriorates due to power circulation losses
Solution Approach 1:
The transmission is segmented into two distinct modes: power split mode for low-speed operation and power shift mode for high-speed operation. This segmentation allows the system to avoid power circulation losses at high speeds by disengaging the planetary gearset and using direct mechanical gear transmission instead.
Solution Approach 2:
The system dynamically switches between power split and power shift modes based on vehicle speed and operating conditions. The automated clutches enable real-time transition between the planetary gearset-based power split configuration and the direct mechanical power shift configuration, optimizing efficiency across different speed ranges.
2Adaptability or versatility
If the planetary gearset is used for power delivery, then e-CVT characteristics are achieved, but reverse drive torque capacity deteriorates due to inability to provide negative torque output
Solution Approach 1:
The transmission system is divided into two functional segments: the planetary gearset for forward drive with e-CVT characteristics, and a separate mechanical reverse gear for reverse drive. This segmentation allows each component to be optimized for its specific function without compromise.
Solution Approach 2:
The transmission system achieves multi-functionality by combining the planetary gearset (for forward propulsion and e-CVT operation) with a mechanical reverse gear (for reverse propulsion). This unified system handles both forward and reverse driving requirements through different mechanical paths.
3Force
If the generator is sized large enough to hold engine torque for heavy vehicle applications, then torque capacity is improved, but device complexity and cost deteriorate
Solution Approach 1:
The torque delivery system is segmented into two paths: an electrical path through the generator for low-speed/high-torque situations, and a mechanical path through the power shift transmission for high-speed torque delivery. This reduces the generator's torque burden.
Solution Approach 2:
The power shift transmission acts as an intermediary between the engine and the wheels, providing a mechanical torque path that bypasses the generator. This mediator reduces the generator's workload and allows for smaller, less expensive generator sizing.
4Ease of operation
If the motor is used to balance ring gear torque for reverse drive, then reverse drive capability is achieved, but reverse drive torque capacity deteriorates due to motor limitations
Solution Approach 1:
The reverse drive function is segregated from the motor and assigned to a dedicated mechanical reverse gear. This eliminates the need for the motor to balance ring gear torque and provides sufficient torque capacity through direct mechanical engagement.
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 design improves powertrain efficiency by minimizing power circulation losses, increasing reverse drive torque capacity, and enabling efficient engine starting without motor assistance, thus optimizing power distribution and reducing generator size requirements.
Implementation Method 1
a planetary gearset, a countershaft and a motor, establish a mechanical torque flow path
Implementation Method 2
The combination of a generator, a motor and a planetary gearset thus can be considered to have electrical continuously variable (e-CVT) transmission characteristics
Implementation Method 3
the generator, which implies that the engine speed can be decoupled from the vehicle speed within the allowed speed range of the generator
Implementation Method 4
the electric motor draws power from the battery and drives the vehicle independently of the engine
Data Source
AI summary
A hybrid electric vehicle powertrain having a mechanical power source and an electro-mechanical power source, including a generator, a motor and a battery. Driving torque developed by the mechanical power source is delivered through one clutch of a geared transmission to a power output shaft. The electric motor of the electro-mechanical power source delivers driving torque through a second clutch of the geared transmission. A mechanical reverse drive torque is used to improve reverse drive performance. A reduction in duration of operation in a negative power split during a driving event is achieved to improve vehicle powertrain efficiency. A series drive is available as the mechanical power source drives the generator to charge the battery, which drives the motor. The generator may act as an engine starter motor.