Metal Adhesive Adds E-bike Motor

2023 Author: Hannah Pearcy | [email protected]. Last modified: 2023-06-05 00:21

The wheels with Fazua drive have an integrated freewheel and thus offer a natural driving experience without mechanical resistance - even above the legal maximum speed of 25 km / h. At this speed the engine switches off imperceptibly. At the same time, the mass of the drive unit of 4 kg to be moved literally hardly matters - a big difference to most e-bikes, the drive of which weighs up to 9 kg and which therefore weigh a total of 20 kg and more.

The motor and battery visually disappear into the frame

As a further feature, the motor and battery form a closed unit. They are not only constructed in such a way that they visually disappear into the frame. They can also be removed in a few simple steps. This allows the comparatively low overall weight to be reduced by a further 3 kg, whereas the motor is always permanently installed in the frame of commercially available e-bikes. With this, the young company from Ottobrunn, just outside Munich, closes the gap between classic, muscle-powered bikes and heavy e-bikes with a lot of torque and battery capacity, which demand little of the cyclist's own performance, but can be difficult to move around when the battery is empty.

Two years after entering the market, more than 45 European bike manufacturers are already opting for this solution, especially providers of e-racing bikes and e-gravel bikes, i.e. off-road racing bikes. Ottobrunners are already market leaders in these young segments. Therefore, the drive system, which consists of bottom bracket, motor and battery, is not just about high quality. In view of a five-digit number of pieces per year, efficiency in production also plays an important role.

Correct connection technology is required

The engine concept used is crucial to making an engine compact and yet powerful. Motors that use rare earth magnets have the highest efficiency, which is why Fazua relies on them.

Traditional methods of connecting the high-quality magnets to the rotor are mechanical clamping or, in the case of surface magnets, their bandaging. Both methods are increasingly reaching their limits. The manufacturing tolerances required for clamping quickly drive up costs. Above all, however, there is a risk of destroying the magnetic coating and the magnet itself, which can lead to corrosion. The bandaging of the magnets is complex and requires valuable installation space.

Advantages when gluing magnets

When gluing, the passivation, nickel or epoxy resin coating of the magnets is protected during assembly. In addition, gluing allows the magnets to be optimally integrated into the laminated core and keeps the air gap between the magnet and the winding as narrow as possible. Adhesives are impact-resistant and their damping effect reduces vibration noises.

Brochure: Gluing for electric motors

On the other hand , gluing protects the passivation, nickel or epoxy resin coating of the magnets better than most other methods during assembly. Gluing allows the magnets to be optimally integrated into the laminated core and keeps the air gap between the magnet and the winding as narrow as possible.

Adhesive technology also offers other advantages: Adhesives are impact-resistant, which is essential in view of the high dynamic forces in electric motors. Their damping effect reduces vibration noise and thus leads to an acoustic improvement. And thanks to their large adhesive surface, tensions are distributed homogeneously, which arise, for example, from different thermal expansion coefficients due to temperature.

Adhesives for high-performance engines

Because of these advantages, Fazua also opted for adhesives for its neodymium magnets in e-bike motors. The pockets hold the passivated block magnet. The adhesive fixes the magnets here and prevents them from moving out axially.

In order for the startup to reach the market quickly and maintain agile structures, it has its motors designed and manufactured by the Swiss drive expert Smart Drives. In the selection of the adhesive, the choice fell on Delo-ML DB135 from Delo Industrie Klebstoffe after advice from the Swiss adhesive expert Credimex and own tests by Smart Drives.

Supplementary information on the topic of gluing magnets offers many advantages

When gluing, the passivation, nickel or epoxy resin coating of the magnets is protected during assembly. In addition, gluing allows the magnets to be optimally integrated into the laminated core and keeps the air gap between the magnet and the winding as narrow as possible. Adhesives are impact-resistant and their damping effect reduces vibration noises.

Hand strength reached after 2 min

This methacrylate-based metal adhesive is suitable for small gaps of up to 100 µm and is therefore often used in electric motors. The product is impact resistant and has a temperature range from -60 ° C to +180 ° C.

When manufacturing the motors, Fazua and Smart Drives use the classic, anaerobic curing option for the adhesive - i.e. at room temperature with the exclusion of oxygen. A heat hardening step, for example in an oven, is not necessary here. Instead, the product reaches its hand strength after two minutes, allowing the next process step to be carried out in production.

In the future, this time could be reduced to around 60 seconds with the additional use of an activator that is sprayed on or applied using an immersion bath. In addition, an activator also significantly increases the adhesion to coated materials and increases the maximum layer thickness to 300 µm, which could compensate for higher tolerances of the parts to be joined.

Should shorter cycle times be required in the future due to the rapidly increasing number of pieces, Fazua can use the light fixation option of the Delo-ML DB135 adhesive already in use. The adhesive hardens under high-intensity UV light at the fillet weld within less than ten seconds, which means that the components can be fixed and processed directly. The adhesive then receives its full final strength with the exclusion of air. Fazua is thus prepared for further growth in the dynamic e-bike market.

adhesive