Diesel Power Unit (DPU) | We support the world’s industrial base by supplying products, such as rolling stock parts, universal joints and heat exchangers, to railway operators and iron manufacturers

All functions in one unit
All-in-One Compact Power Unit

Since its establishment in 1929, Najico has been selling diesel rolling stock parts, as well as designing and manufacturing drive shafts and cooling systems.
Today, Najico has grown with its customers to handle a wide range of parts, not only for diesel cars but also for many other types of cars, including bullet trains.
Today the market faces various challenges, such as securing underfloor rigging space to cater to the shift to electric and hybrid diesel vehicles and the need to save labor due to the declining birthrate and aging population. We sat down and considered how we could use our extensive experience with diesel railway cars to provide new value to the market, and we have now commercialized DPU (diesel power unit) products for next-generation railway cars.

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Concept
All in one
Compact
Maintenance
mounting/dismounting steps
main specifications
Najico’s vision of future diesel rolling stock

DPU

[Concept]

Bring innovation to train cars through power unit modularization

ALL IN ONE

Standardization and commonization
Reduce design workload
Understand performance as a unit
COMPACT

Optimized component layout
Secure rigging space
Less weight and easy component upgrading
MAINTENANCE

Electric type and fewer parts
Anti-clogging radiator
Monitor equipment

[All-in-One] Unit configuration

[Compact design] Component layout comparison

Estimated mass of entire system: approx. 3750 kg
(including suspension fittings, receiving fittings, piping, etc.)
Estimated mass of entire system: approx. 3788 kg
(without the entanglement prevention board)

[Maintenance]　Main advantages

～With Najico handling everything, from procuring after-market parts to carrying out actual maintenance work, you don’t need to retain maintenance personnel or worry about skill succession. ～

Electric type and fewer parts

With electric main/auxiliary machine drives, the DPU uses fewer parts, reducing maintenance work.
Anti-clogging radiator

The radiator employs square wavy fins developed by Najico for cooling, which prevent a decrease in heat dissipation performance due to clogged fins as well as help save labor for air blow cleaning and other maintenance work.
Monitor equipment

Information from the engine and radiator controllers can be utilized for CBM and failure prediction.

[DPU mounting/dismounting steps]

With fewer mounting/dismounting interfaces, the DPU enables quick unit replacement.
Traditionally, train cars had to be kept in the servicing area for inspection for a few weeks to a month. With the DPU, however, they can be put back into service quickly by replacing it with a spare one, which enables more efficient use of rolling stock.

[DPU main specifications]

Item		Unit	Specifications
Name		ー	Diesel Power Unit
Intended purpose		ー	Diesel power generator for railway cars (underfloor mounting)
Engine	Number of cylinders	ー	6
	Bore diameter × stroke	mm	140×165
	Rated output	kW	331
	Rated rotation speed	min⁻¹	2000
	Total displacement	L	15.24
	Fuel injection system	ー	Common rail type
	Emissions reduction	ー	Equivalent to UIC2
	Mass	㎏	1920
Main generator	Method	ー	Three-phase cage-type induction generator
	Output	kW	270 （at 1670min⁻¹）
	Mass	㎏	860
Cooling system	Cooling performance	ー	Engine output 316 kW, inlet air temperature designed to be 45℃
	Core model	ー	SW5-6, square wavy fins
	Core size, number of fins	ー	550ｗ × 580H × 107D, 3 fins
	Cooling fan	ー	Φ515mm×3
	Fan motor	ー	Flat-type synchronous induction motor, 3.7 kW × 3 units
	Mass	㎏	328（110 × 2 units, 108 × 1 unit）
Other mounted equipment	ー	ー	Air cleaner, top tank, reserve tank, fuel pre-filter, main generator cooling blower
Unit outer dimensions	L×W×H	mm	3189 L × 2440 W × 838 H (without entanglement prevention board)
Unit mass	Dry mass	㎏	3788 (Frame: 336 kg)
Unit mass	Mass in working order	㎏	3958 (without entanglement prevention board)
Accessories	ー	ー	Engine control panel Fan control unit for cooling system (inverter) Radiator-exhaust-air entanglement prevention board (optional)

【Najico’s vision of future diesel rolling stock】

NEXT NAJICO

Japan aims to realize a carbon neutral,
decarbonized society by 2050.
The railway industry needs to evolve to keep up.

Normally, the underfloor components for diesel trains are installed in separate locations.
The DPU integrates the main components into one unit, saving more space around the underfloor area.
This enables a smooth shift to a different power source in the future.

We have now set out on our journey towards a carbon neutral society.

Around 1980

Diesel car underfloor area

Japan aims to realize a carbon neutral,
decarbonized society by 2050.
The railway industry needs to evolve to keep up.
2024

DPU-mounted underfloor area

Normally, the underfloor components for diesel trains are installed in separate locations.The DPU integrates the main components into one unit, saving more space around the underfloor area.
This enables a smooth shift to a different power source in the future.
2029

The DPU five years from now

Najico’s 100th anniversary

Pursue a reduction in engine output with improved storage battery performance.
Reduce the total mass by reducing the number of radiators mounted.
Through these efforts, Najico aims to further reduce CO2 emissions and costs.
2050

Underfloor area in the future

We have now set out on our journey towards a carbon neutral society.
In the future, we expect a yet unseen engine to fit into the empty space.