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NSK demonstrates transmission-equipped wheel hub motor

NSK Ltd. has successfully demonstrated the first transmission-equipped wheel hub motor, designed to improve the environmental performance, safety, and comfort of automobiles. Building on the knowledge it has gained from the prototype wheel hub motor it developed, NSK is aiming to commercialize wheel hub components such as the hub unit bearing with built-in speed reducer, the one-way clutch unit, the miniature cage and roller bearing, and the anti-corrosion bearing.

In-wheel motors that can work with various drive systems independent of the body structure of automobiles are attracting interest as next-generation electric drive devices. An in-wheel motor located near the wheel can reduce the weight of the vehicle, control the drive force of each wheel for improved torque vectoring, and enable the expansion of the size of the cabin space, thereby improving environmental performance, safety, and comfort.


However, enlarging the size of a wheel-hub motor in order to achieve both the large drive torque necessary for acceleration and hill climbing and a sufficient maximum speed is challenging.

To make in-wheel motors more compact, NSK developed a transmission-equipped wheel hub motor that uses two motors and a special transmission.

This wheel hub motor is equipped with two motors and a transmission composed of two planetary gears, which can achieve both high drive torque and a sufficient maximum speed with a small motor. In addition, this transmission has a feature that enables smooth gear changing even during acceleration by controlling the speed and torque of the two motors.


NSK demonstrated the superior performance of this technology using an experimental vehicle equipped with a prototype wheel hub motor.




The automobile is on a headlong path to becoming an appliance. This innovation a great example, its similar to the transmission in a washing machine. if you think about it appliances are long lasting, upgradeable, something you never think about or worry about. But the OEM industry is fighting back because their marketing methods of selling machismo and power don't work selling appliances. They want to sell complex fuel cell systems, hybrids, etc. But all that becomes irrelevant once the battery range reaches 250 miles.


This is a solution for class 8 trucks if it can be increased to 200hp/250/lbft. Put 4 of them between the drive wheels of the tractor. Design a genset that will produce enough power to push a fully loaded 52 ft trailer @ 70mph. It can be run in binary mode in very limited rev range. Any fuel or combustion combo ..hcci rcci etc. 4 gallons/hr @ 60mph = 20mpg. I think Walmart will buy them.


4 gallons/hr @ 60mph = 15mpg


Till the sprung weight can be reduced current best levels these will be only applicable to low speed or off highway apps. There are many uses for such.
It really depends how fast you want to go and the vehicles ride or handling expectation.

Heavy vehicle classes where currently the weight relation, another example of steam era designs and the if it aint broke dont fix it approach, (heavy wheels tyres brakes etc) are more favorable vs. scaling De Dion style solutions should still offer more possibilities.

Current CV shafts are not very heavy and the sprung component is a fraction of the total.
They could easily be reduced in weight by ~60% via hollow alloy or carbon shafts and aluminium (carbon composite?) axle housings as per many proven custom engineered.

Disc bakes and e-motors mounted inboard will be hard to better.
Active suspension would overcome wheel motor sprung mass problems but that is a whole extra and immature solution.
Every journey starts with the first step.


Wheel motors have been and will continue to be of interest. I agree that the inboard motors with CV shafts is a good method.


Too heavy! Either gear reduction to a shaft to an inboard motor, or a high power density hub motor.


Wheel motors are to heavy, too. The dynamics of ride quality suffer with increase wheel weight. Auto Engineers have a formula variable inwhich wheel weight is a big factor for ride quality. Small motors are cheaper to manufacture. My guess the industry will migrate to independent smaller motors mounted on subframe assembled with small transmission. Probably an satelite gearing. Motor and trans would share one casting assembly. Typical driveshaft to wheel. Electornic control for improved, traction, steering, and stopping. You couldn't spin the wheels if you tried, nor lock up brakes. Yes, the electric drive becomes a standardized component from supplier shared by automotive companies. Electric drive has lots of advantages. Batteries, no.

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