Hybrid Gear Shifting via Planetary Locking and Dual Electric Machines
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Solution Overview
Problem
Existing vehicle control methods for hybrid vehicles with drive systems, particularly heavy trucks and buses, face challenges in efficient gear shifting and torque management, especially when dealing with variations in combustion engine torque and lack of energy storage means.
Innovation Solution
A method involving a power assembly configuration with two electric machines and voltage control to manage torque and energy flow, allowing one electric machine to operate as a generator and the other as a motor, with the ability to adjust fuel injection and use components like exhaust gas brakes to assist gear shifting, enabling efficient gear shifting without the need for electric energy storage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional clutch mechanism is used for gear shifting in hybrid vehicles, then the structure is simpler, but the gear shifting efficiency is lower and energy loss is higher
Solution Approach 1:
The drive system is segmented into multiple functional components: a planetary gear set with sun gear, planet gears, and ring gear; a first electric machine connected to the ring gear; a second electric machine connected to the sun gear; and a locking mechanism. This segmentation allows independent control of each component to optimize gear shifting performance while managing complexity through modular architecture.
Solution Approach 2:
The planetary gear set serves multiple functions: it provides gear multiplication during gear shifts, enables direct connection between electric machines and gear components, and allows the locking mechanism to engage/disengage for different operating modes. The first and second electric machines can alternatively function as motors or generators depending on operating conditions, providing universal functionality that improves efficiency without requiring separate specialized components.
2Adaptability or versatility
If electric energy storage means are added to the hybrid vehicle, then energy management flexibility is improved, but vehicle weight and space requirements increase
Solution Approach 1:
The system uses the kinetic energy of the vehicle itself during braking to generate electrical energy through the first electric machine acting as a generator. This self-service approach converts waste braking energy into usable electrical energy for the second electric machine, eliminating the need for external energy storage devices while maintaining energy management flexibility.
Solution Approach 2:
The system recovers energy that would otherwise be discarded during braking operations. The first electric machine captures kinetic energy during deceleration and converts it to electrical energy, which is then stored temporarily in the DC link capacitor and used by the second electric machine to assist during subsequent acceleration or gear shifting operations.
3Ease of operation
If torque balance control is implemented during gear shifting, then shifting smoothness is improved, but control complexity increases
Solution Approach 1:
The control system continuously monitors the torque output of both electric machines and the rotational speeds of the sun gear and ring gear. Based on this feedback, the controller dynamically adjusts the torque commands to each electric machine to maintain torque balance during the transition period, ensuring smooth gear shifting while managing control complexity through closed-loop control.
Solution Approach 2:
Before the actual gear shift occurs, the control system preliminarily adjusts the torque output of the first and second electric machines to achieve torque balance. This preliminary action prepares the system for smooth transitioning by pre-positioning the torque values, reducing the complexity of real-time control during the critical shift moment.
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
This approach results in energy and time-saving gear shifting, robustness against torque deviations, and a compact drive system design that reduces weight and space requirements, maintaining favorable vehicle operation across various situations.
Implementation Method 1
When braking the vehicle the electric machine generates electric energy which may be stored
Implementation Method 2
the electric energy stored may later be utilized for for example the propulsion of the vehicle
Data Source
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AI summary
A method for obtaining gear shifting of a vehicle having a planetary gearing in the drive train, a combustion engine (2) with an output shaft (35) connected to a rotor of a second electric machine (30) and to a first component (10) of the planetary gearing, a first electric machine (9) with a rotor connected to a third component (11) of the planetary gearing and an input shaft (3a) of a gearbox (3) connected to a second component (12) of the planetary gearing. The gear shifting procedure is started with the components of the planetary gearing interlocked by a locking means (15), in which they are released during the gear shifting and interlocked again after the gear shifting has been carried out.