Usually, when we think of V8 lorries and SUVs, the first thing that comes to mind is their size — and high fuel consumption. However, models are also available that use little fuel relative to their weight and horsepower — and thus also have lower carbon dioxide emissions. A Controlled Piston (CP) from FTE automotive plays a critical role in helping these vehicles save fuel.
Wherever automation of hydraulic clutch operations is required, the electrohydraulic actuator unit provides high efficiency over a wide pressure and volume range. The prerequisite for this is a highly accurate drive — such as the ECI motor from St. Georgen. We might say that it puts the “Controlled” in “Controlled Piston.” The ECI provides an ideal starting point for this application, as it is highly dynamic and thus can move to the necessary positions with great accuracy.
High-precision switching in lorries
The lorry’s gear shift mechanism uses a ECI 76.45. The fully automated clutch switches gears much more quickly, accurately and smoothly than previous models. This is not only more pleasant for the driver, it also saves fuel. For example, the gear shift mechanism allows downshifting at an early stage when driving uphill, making it possible to maintain speed without using more petrol. Basically, the engine actuates the piston of the CP only if the driver is actually switching gears. In the old pneumatic system, a constant supply of pressure had to be provided. This would not be possible without the fast and accurate activation by the ECI motor.
However, the motor also has to withstand some tough conditions: vibration, heat and cold over endless kilometres. “Over its service life, the lorry goes through millions of gear shifts,” says Peter Metzger, Automotive Sales Manager at ebm-papst St. Georgen, illustrating the challenge. “During this entire time, the motor has to withstand extreme mechanical and thermal loads.”
The brushless ECI motor is ideally suited to this task. The highly complex control system also has to withstand these loads. The integrated electronics are a joint development of ebm-papst and FTE. The centrepiece is called “flex technology”: in a certain area, the printed circuit board can be bent by up to 180 degrees and folded together. This enabled FTE automotive to integrate the electronics into the CP module in a space-saving manner.
Smooth transitions in the hybrid
The intelligent control system for operating the CP in large sportscars also presented a great challenge. The result of the co-operation of FTE and the developers in St. Georgen: “Fully integrated, four-wheel drive compatible control of the entire powertrain, which comes together in our control system — and is one-of-a-kind on the European market.” In this car, the CP system actuates the cutout clutch and switches the different operating modes.
The parallel full hybrid provides the cars with petrol-sipping power, but thanks to the intelligent electronics, this does not mean any less performance or driving dynamics. For this purpose, the control system uses either the combustion engine or the electric motor or a combination of the two. The electric drive keeps the car moving with zero emissions at speeds up to 50 kilometres per hour in city traffic, but also maintains the car’s speed while cruising on the motorway. If the driver spontaneously needs to use the full engine output, the combustion engine and electric motor provide a simultaneous boost. The individual operating states have to be closely matched to each other. This is carried out by the CP, an intelligent control system that shifts gears so smoothly that the car’s occupants do not even notice it.
At the heart of the hybrid CP, an ECI 56.45 actuates the piston. The “little brother” of the lorry motor, it is located in the wheel well along with the module, remaining quiet and inconspicuous. “During development, we tried out different lubricants to decrease the already low noise even more,” reports Metzger. Thus the small, smart drive not only helps the vehicles attain lower emissions, it also makes driving more fun!
Controlled Piston (CP)
The CP electrohydraulic actuator from FTE automotive is an actuator unit for use in clutches and hybrid applications. It enables highly dynamic hydraulic applications to be implemented in the area of mobile drives. The central element of the CP is the ECI brushless DC motor from St. Georgen. It drives a recirculating ball screw spindle that moves a hydraulic piston for pressure generation and volume displacement.
Therefore, the CP provides the following advantages:
• High overall efficiency
• High dynamics
• Innovative integrated electronics
• Low pulsation
• Low noise level