NSK Ltd. (TYO: 6471) has developed a wheel hub motor with an integrated transmission that it claims can provide a power output of up to 120 kilowatts (kW). The company recently demonstrated the technology at the annual Tokyo Motor Show.

The new wheel hub motor is based on NSK's "WTS" (Winding Torque Sensor) technology, which it has been working on since 2005. The WTS is a sensor that can detect the winding torque of an electric motor with high precision. The company has used this technology to develop a wheel hub motor that does not require a gearbox, as the WTS can control the output torque of the motor with high accuracy.

In addition, the new motor is compact and lightweight, thanks to the use of NSK's "Super Precision Plus" (SPP) technology. SPP is a manufacturing technology that enables the production of miniature bearings with extremely high precision. NSK has used this technology to develop a wheel hub motor that is 30% smaller and lighter than a conventional motor with a gearbox.

The new motor has a diameter of just over 300 millimeters (mm) and a width of 190 mm. It weighs 14 kilograms (kg). In contrast, a conventional motor with a gearbox has a diameter of 450 mm and a width of 250 mm, and weighs 23 kg. NSK says that the new motor can be installed in a vehicle without the need for significantchanges to the suspension or brakes.

The company has also developed a "split-type" transmission that can be integrated with the wheel hub motor. The split-type transmission has two features that NSK says are ideal for electric vehicles (EVs). Firstly, it has a "direct-drive" function that allows the motor to be directly connected to the wheels. This reduces energy loss and improves efficiency. Secondly, the transmission is "coaxial", which means that it can be installed in a vehicle without the need for a driveshaft. This reduces the risk of the driveshaft breaking, and also reduces weight and space requirements.

NSK says that the new wheel hub motor with integrated transmission can provide a power output of up to 120 kW. This is significantly higher than the maximum power output of 80 kW that is possible with a conventional motor and gearbox. The new motor will be available for use in EVs from 2020.