ROTWILD Integrated Power Unit (IPU)
Schematic drawing IPU – Integrated Power Unit by ADP Engineering, Pat. Nr. DE 10 2014 218 036.8
The ROTWILD IPU consists of a Brose drive motor and the battery unit developed by us. The aim in development was to integrate the two elements completely within the bike frame in order to retain the dynamic riding characteristics (geometry and kinematics) of classical mountain bikes. The system of the IPU has been registered as a patent with the European Patent Office under Reg. No. DE 10 2014 218 036.8.
Schematic layout Brose pedelec electric motor
BROSE motor unit forms a particularly suitable basis
The pedelec electric motor developed by the German automotive supplier BROSE forms the basis for our IPU. In electrical engineering terms, it involves a “brushless internal rotor”, which is characterized by an extremely compact design combined with high efficiency. The power from the electric motor is transmitted in two stages in a ratio of 1:27. In the first stage, a planetary gear with a transmission ratio of 1:9 is connected before the motor while transmission in the second stage takes place in a ratio of 1:3 via a belt drive. This transmission ratio is necessary so that the electric motor (driven by the rider’s relatively low pedalling frequency) always rotates within its optimum speed window in order to guarantee a high efficiency. This means that the electric motor always rotates within its optimum window of revs, guaranteeing high efficiency. Another unique design feature of the Brose motor is the use of two freewheel mechanism in the interior. This is very important in the case of pedelecs with a legally prescribed cut-off speed at 25 km/h. With the aid of the second freewheel mechanism, the electric motor disengages entirely once the 25 km/h limit has been exceeded so that the rider can continue to accelerate the bike with muscle power and without any loss in forward drive.
Schematic drawing of the IPU – housing shell
Battery designed in collaboration with a German battery producer
We designed the battery unit in collaboration with a German battery producer. Essentially, the battery consists of four basic elements: the 40 Li-ion cells, the battery management system (BMS) with cable harness and motor connector, the integrated charging socket and the housing that encloses and protects the entire battery unit.
The 40 high-grade lithium-ion cells are divided into 5 packs of 8 cells each (4P10S). One single cell delivers a potential difference of 3.6 volts (range 4.2-3.6 volts) with a capacity of 3,500 mAh. The special feature of this Li-ion cell is the chemical structure on the inside, which has been specially designed for pedelec and automotive applications.
IPU integration into various bicycle designs
Our IPU is designed in such a way that we can use it in all bike categories or ranges without any great restrictions in geometry, kínematics or compatibility, i.e. from ROTWILD MTB Cross Country via All Mountain to Enduro; yet at the same also in the multifunctional Tour or Trekking Bike sector. To this end, the motor housing becomes a permanent part of the frame, firmly bolted to the bottom tube battery and unit and the frame – the bottom tube battery unit becomes a supporting element within the frame structure. The compact design additionally enables us to achieve short chainstay lengths or appropriately position the pivot points which are important for the development of full-suspension frames.