Interpretation of Electric Propulsion System Architecture for Hybrid Electric Vehicles

“P” means that the product has entered the preparatory stage: P0 to P4 in the figure are the electric propulsion system architecture that BorgWarner is currently developing.

Few people predicted five years ago that the pattern of global automotive powertrain, transmission systems and fuels will be so diverse in 2017. Today, however, almost everyone believes that it is important to develop all types of hybrid vehicles, whether they are to meet the latest emission reduction standards in Europe, North America and Asia, or to achieve longer-term electrification goals.

According to John Barlage, director of product strategy at BorgWarner Power Drive Systems, "From the flame-start system to the pure electric car, we see this journey as the history of electric car evolution." Other planners of the first-tier manufacturers of power systems see the same, he also believes that in the next cycle (2019-2021), more vehicles will be equipped with 48V hybrid system, and "the number will be quite large."

From the 48V system that has already landed in Europe, these systems from Audi and other German OEMs can provide powerful on-board power, and achieve the effect of energy saving and emission reduction through electric boosting, etc. The Driver Assistance System (ADAS) sensing kit provides up to 3 kilowatts of electrical energy.

Barlage said with confidence, "Because the economic benefits of the 48V system are very attractive, it will soon become popular in North American models." When it comes to this technology, the industry generally believes that only ordinary (power split) hybrid systems are needed. At 30% of the cost, you get the equivalent of 70% of its performance. BorgWarner engineers also believe that as system architecture and packaging technology continue to upgrade, 48V or higher voltage hybrid modules will be developed to achieve P2 architecture applications.

In the P2 layout, the motor will be placed between the internal combustion engine and the gearbox (see illustration). Other industry-recognized hybrid architecture layouts (from front to back) include: P0 (mainly track-AC motor-starting mechanism, referred to as "BAS"); P1 (for example, Honda IMA at the flywheel position); P3 (motor placed On the gearbox output shaft in front of the main reducer; and P4 (also known as the four-wheel drive hybrid architecture, using the rear axle electric drive). In addition to P2, several other methods have torque vector control.

Barlage notes, “For the drivetrain, the P2 architecture has brought many opportunities, including working with dual clutch transmissions (DCT) and even automatic clutches (see http://articles.sae.org for details). /15576/), it is also very suitable for plug-in hybrid vehicles. The plug-in hybrid electric vehicle (PHEV) in P2 configuration, the overall energy efficiency in pure electric mode is even higher than the hybrid mode. If you want To build an electric car suitable for highway driving, or to realize the electrification of the truck, the P2 architecture must be the first choice.

Joel Maguire, a technical researcher at BorgWarner's Advanced Engineering Division, said the company's strategic plan is to "play a variety of hybrid architectures." (Source: BorgWarner)

“In the development of other 48V application architectures, we chose to start with P0 first,” said Joel Maguire, technical researcher at BorgWarner's Advanced Engineering Department. “This allows the same motor to be used in different locations to produce scale effects.”

Maguire told AutoEngineering International that his product development team designed the "electromagnetic material for the P2, P3 or P4 hybrid system" based on the OEM's needs. The series of compact, powerful motors that meet OEM automotive packaging requirements, and some (competitor) power split products, and even some P2 architectures, must make some compromises in design because of the flexibility of the car structure. And the existing automotive packaging technology, but also does not work well with 48V hardware devices."

A major feature of the BorgWarner P2 architecture is its 167 mm (6.57 in.) axial length. According to company internal data, the rated maximum torque at this length can exceed 330 Nm (243 lb-ft) and the maximum power can exceed 80 kW (107 hp). This model applies regardless of whether the coaxial (the input shaft of the transmission, the crankshaft of the engine and the torque damper are on the same shaft) or the different axes. For the different axes, because it is installed above the transaxle box, this is also a drive chain drive solution that can meet the packaging requirements of smaller transverse engine/front wheel drive vehicles.

“The space savings are mainly between the wheels, and because the shaft length is constant, mechanical damage can be avoided,” explains Maguire. “This model deprecates the AC motor and can integrate the air conditioner compressor. On a chain drive, the 48V system can still keep the air conditioner running when the engine is off."

Both of these P2 modules include a split clutch that fits into the integrated structure of the motor and dual mass flywheel and can be used with the most popular drive technology available today, including planetary gear stepped automatic transmissions, dual clutch transmissions. (DCT), continuously variable transmission (CVT), and automatic shifting systems. BorgWarner's engineers pointed out that another major advantage of the P2 architecture is that it can continue to use existing engines and transmissions.

“With the P2 architecture, a module can be added between the engine and the gearbox. Of course, this solution is not absolutely ideal,” says Barlage. “But it is still more economical than a transmission specifically designed for hybrids. The choices involved will be much less, and the size can be changed.” With the DCT configuration, the P2 architecture can be used as a three-clutch arrangement, which is what BorgWarner calls “K-Zero”. The system includes a disconnect clutch that is connected to the motor and K1 and K2 clutches that are responsible for switching between the two sets of gears.

Maguire specifically pointed out that "Our strategic planning is to play with various drive architectures, from P0 to P4 can be applied freely. By observing the OEM's exploration of various hybrid drive architectures, and continuous learning and research, we have Created a system that can be used in a variety of design layouts."