Schaeffler has introduced a new P2 high-voltage hybrid module that is arranged between the internal combustion engine and transmission, and is capable of transmitting internal-combustion torques of up to 800 Nm to the transmission.
This has been made possible by distributing the flow of forces in an innovative way, with torques transmitted to the crankshaft via a 300 Nm disconnect clutch, while traction torques from the internal combustion engine are transmitted to the transmission via a one-way clutch. Schaeffler's new drive train electrification solution, which can be matched to a large number of drive concepts on a modular basis, can be seen at the International Motor Show (IAA).
This new P2 module from Schaeffler consists of an automated disconnect clutch and the electric machine. The disconnect clutch is operated by an electromechanical central clutch release system that directly engages the clutch mechanically via a ball screw drive without a hydraulic transfer path; this means that no extra installation space for actuators is needed outside the module.
In order to transmit torques of 800 Nm efficiently without having to incorporate a commensurately expensive clutch, torque conveyance depends on its direction: A one-way clutch is used for transmitting traction torque, while torsional torque in the direction of the internal combustion engine is conveyed via the clutch. The clutch can therefore have a compact design, even at high torques, with the corresponding advantages in terms of space utilization and cost.
There are other benefits from using the one-way clutch. Regulating the connection to the engine when accelerating is normally a complicated matter that involves the internal combustion engine, the disconnect clutch, the electric machine, and the transmission. The one-way clutch provides an immediate mechanical connection to the engine as soon as the engine and electric motor speeds synchronize.
This allows regulation to take place much more quickly. As the driver operates the gas pedal, he is more obviously aware of the dynamic connection with the engine, yet in a way that is very comfortable - due to the fact that the clutch is operated in slippage mode on the transmission side during the initial phase. When the electric machine is running as a generator to capture electrical energy, moments are no longer being transmitted by the one-way clutch and the clutch is open which means that the engine does not have to be "dragged along with it."
The hybrid module is also extremely efficient in another respect: Active vibration damping of rotational irregularities in the drivetrain. By optimizing the damper in conjunction with active vibration damping at lower speeds and with clutch micro-slip starting at approx. 1,500 rpm, it is possible to achieve perfect comfort and reduce the installation space at the same time.
This new hybrid module will go into volume production for the first time in China in 2017 in a version without a one-way clutch for internal-combustion torques of up to 250 Nm. This hybrid module has a considerably higher electrical power of 80 kW, and this can be used as a plug-in hybrid, thereby providing up to 75 percent reductions in fuel consumption compared to similar vehicles with internal combustion engines.
This is important, as statutory regulations on consumption and emissions in China now include minimum distances for purely electric travel. Plug-in hybrid vehicles can only meet these requirements if the electric motor provides the necessary power. This therefore avoids having to engage the engine in the medium power range, such as when accelerating away from traffic signals or on long-distance trips.
The electric motor used in the hybrid module for volume production in China has an efficiency of more up to 96 percent. This provides dual benefits to the system, both in terms of capturing energy during braking and electric driving. This means a smaller battery can be used for the same range, saving space, mass, and cost.
The new generation P2 hybrid module from Schaeffler, with its high versatility and very wide torque range, can be used in both medium and very high performance transmission concepts and can make a considerable contribution to further reductions in consumption and emissions in plug-in hybrid vehicles.
