Skip to main content

Hitachi

Hitachi Nico Transmission Co.,Ltd.

Gear design and fabrication

The large marine gears we manufacture include some that weigh 100 tons and can transmit 25,000kW of power, and we design gears for optimum load transmission. This large gear is machined on the latest high-precision gear grinder, and we check the required tooth forms while the gear is still on the grinder, as it is machined.
For spiral bevel gears, we use Klingelnberg-type equal-height gears with super-hard finishing, cut with a CBN cutter developed by Klingelnberg of Germany. These gears are used in our final reduction gears and reduction gears for vertical shaft propulsion systems.
The gears have characteristics that ensure the ideal tooth contact during meshing, and they are machined with high precision, to achieve low levels of noise and vibration. We can design and produce gears of this kind for direct meshing at peripheral speeds of 60m/sec.
The gears are the key component of the gearbox, and we are researching them for further improvements.

Hybrid active shift transmission (referred to below as HAST *)

This is a result of our joint development project with Hokkaido Railway Company on application of automobile-type hybrid systems for railcars. HAST drive combines a high-efficiency active shift transmission with a motor.
When used on trains, it makes use of the predictability of operation patterns for efficient energy management that allows even better use of the advantages of hybrid systems than is possible in road vehicles. Also, because only the motor is used around stations, the system also cuts noise in stations. Both drive performance and environmental performance are achieved together, at levels impossible with conventional technology.
The development of “Diesel-electric parallel hybrid rolling stock” using HAST Drive has been awarded the best paper prize at the 2008 World Congress on Railway Research and the award for excellence of the 36th Environment Award in 2009.

*
HAST Drive is our registered trademark for Hybrid Active Shift Transmission.

Slipping clutch

We use a combination of the Omega Clutch, which is a slipping wet multiplate hydraulic clutch that controls the level of engagement (slippage rate) between the clutch friction plates and delivers the required speed (stepless shift control, constant speed control, dead slow control, braking control, etc.), a CSU (constant speed unit for generator drive) and the right selection of clutch friction plates for the situation, in order to manage the coefficient of friction. In the event of a load in excess of the set value, there is a reduction gear with integral torque limiter that allows the clutch to slip.

Helical involute gear (conical gear)

If conical involute gears (conical gears) are used as shaft gears on nonparallel, nonintersecting shafts, the contact between pairs of gears is theoretically a point contact, leading to a problem that tooth strength is lower than for flat and bevel gears, which mesh with a linear contact.
We worked jointly with Yamagata University on a solution to this problem, establishing a technology for making the tooth contact closer to a linear contact, and we have used that technology in many conical drive marine gears (MGNV type) that are inclined relative to the output shaft.
This conical involute gear is applicable to many uses beyond marine gearboxes, and is in use in devices such as escalator reduction gears.

Load distribution mechanism for planetary gears

A planetary gear system is constructed to transmit power with multiple gears (planetary gears) meshed simultaneously around a gear (sun gear). Dividing the power for transmission across multiple gears enables size and weight reductions.
Therefore, the load distribution mechanism, which divides power uniformly among multiple gears, is an important element of the planetary gears.
With the exception of a few applications, we reduce size and weight by using our unique flexible pin system, with cantilevered support shafts for the planetary gears, as the load distribution mechanism.