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Hitachi Nico Transmission Co.,Ltd.

Image : Hydraulic Coupling

The coupling can start empty, with all the oil expelled from the impeller, so the motor starts unladen. After the motor begins running at full speed, the impeller is filled with oil to start the driven side and begin accelerating it. Torsional vibration generated by the engine is absorbed, so uniform torque is transmitted, while load overtorque is handled by slipping.
Charging and draining the oil inside the impeller makes it act as a clutch, so even intense repetitions of on-off running will never cause damage, in contrast to a mechanical clutch. This clutch action can be used to easily achieve trial running of the motor in isolation. In multiple drive systems, motors can be stopped as required, and only the motors that are required can be left running at maximum efficiency.


  • Smooth, shockless startup.
  • Absorption of torsional vibration and shocks prevent mechanical damage and extend the service life of machinery.
  • Can be used as a clutch.
  • The structure is simple and includes no frictional parts, so it is highly durable and easy to handle and service.
  • Clutch operation can be controlled simply by opening and closing the oil supply valve, which is easy to control from the machine-side or remote, allowing simple operation.