The Birth of DC Servo motor

The development of “Minertia motor” changed the industry’s common standard.

Minertia motor

If Yaskawa Electric Corporation had not created the “Minertia motor” in 1958, high-speed chip mounters might not have been developed yet. The Minertia motor was an innovative product simply because of its unique structure of placing a conductor directly on the motor rotor, high response characteristics which was 100 times better than conventional motors and high rectification capability.

It is said that this innovative idea of Minertia motor design occurred to an engineer in 1958 when he saw a picture of a plum tree which his little child drew with fingers on the mortar wall in the bathroom. The Minertia motor techniques which feature high response and high precision that were not attained by hydraulic servos were then applied widely for various uses.
The development of Minertia motor turned out to significantly change the industrial trend to the present, high precision and high speed trend, and give the permanent recognition of “Yaskawa as a manufacturer of DC servomotors” in the industry.


Print motor (above)
Cup motor (below)

Transition from “Print motor” to “Cup motor”

At that time, a “print motor” which was planned to be manufactured had problems in terms of mass productivity and durability. The engineers solved these problems by establishing a rotor manufacturing method that used notching instead of etching by using the motor core punching techniques/know-how which they had cultivated since the establishment of the company. Furthermore, the engineers improved the motor performance dramatically by ensuring the rotor manufacturing method. Thus, Yaskawa succeeded in commercializing the print motor and putting it into practical use.

This then leads to the development of “cup motor” in 1966 which was to respond to the need for larger capacity print motor.

The “Minertia motor”, “print motor” and “cup motor” that were developed using Yaskawa’s unique techniques were put out into the market as Yaskawa’s unique servomotors that competitors could not copy at that time. Those motors made great contributions, as leaders, to the automation of the industry in the high economic growth period.