INTRO: Since Japanese National Railways was divided into separate companies in 1987, JR-Central has put into service around 600 new vehicles for its 1067mm gauge network that carries over half a million passengers a day. Tilting trains have helped cut journey times on key routes
BYLINE: Kazuhiro Yoshikawa
Manager, Rolling Stock Department
Conventional Lines Operations Division
Central Japan Railway Co
IN THE 10 YEARS since Japanese National Railways was broken up, JR-Central has worked hard to develop rolling stock for its 1067mm gauge lines that will lift comfort standards, reduce operating costs and permit faster journey times. Running on 12 routes serving central Japan to cities such as Nagoya and Shizuoka, the JR-Central narrow gauge fleet comprises around 1500 vehicles. Of these, 1130 are EMU cars and 240 are DMU vehicles used on the 490route-km of non-electrified track. Every day around 520000 people ride JR-Central’s narrow gauge trains.
The first type of train developed independently by JR-Central was the Series 85 Kiha DMU. This was launched on express services in 1989.
Powered by two British 350hp engines giving balancing speeds in excess of 100 km/h on gradients of up to 2%, Series 85 had a major impact on Japanese DMU design. The choice of engine was central to the Series 85 development process; power plants from many different countries were assessed against the criteria of high performance and good fuel economy. To combine a maximum speed of 120 km/h with adequate acceleration and deceleration on medium-speed sections in mountainous territory, a torque converter was used to increase the number of gear stages. Power control and gear changing is managed by computer.
Right from the start of development work, careful attention was paid to the bodyshell and interior design rather than adopting the latest fashionable shapes and colour schemes. A stainless steel body combining attractive lines with easy maintenance was eventually chosen.
Introduction of the Series 85 DMU brought Hida Limited Express journey times down by 41min to 2h 9min, and cut Nanki Limited Express timings by 51min to 3h 22min. Thanks to the shorter timings, traffic on these routes has been steadily increasing.
Lower maintenance costs
The Series 373 Limited Express EMU was introduced in 1995, following development work that focused on reducing maintenance costs. The Series 373 is a three-car EMU, to which extra cars can be added if required. A total fleet of 42 Series 373 cars replaced 57 older vehicles, with drive maintenance costs reduced by the adoption of a format of one motor car and two trailers.
Class 373 has a monitoring system for equipment that was specified with low maintenance costs in mind. This ensures that the performance of equipment on board the train is checked whenever the train is in use; it monitors the VVVF inverter control and brushless traction motors, the inverter-based auxiliary power supply, contactless master controllers, scroll air compressors, vacuum toilets and electric water pumps.
The bogies have been designed so that they are compatible with automated robots.
These design features have reduced maintenance costs by 50% compared with earlier types of train. Future rolling stock development is likely to pay even closer attention to lower vehicle life cycle costs.
Second generation tilting trains
Developed to replace the Series 381, Japan’s first train incorporating passive tilt technology introduced in 1973, the Series 383 EMU first entered service in December 1996. This 1·5 kV DC tilting train was developed to provide faster, more comfortable services, and to be easier to operate.
Higher speeds through curves remains an important goal for the railways in Japan, which is a mountainous country. The Class 381 was able to operate at maximum speed on only 16% of the 175 km Nagoya - Shiojiri section of the Chuo line, as 58% of the route is subject to curve-related speed restrictions.
Work began in 1989 on improving speeds through curves, concentrating on rail load forces, ride quality and stability in side winds. The fruits of the development programme applied to the Class 383 included a lightweight body with a low centre of gravity, new self-steering bogies and active body tilting.
Self-steering bogie
JR-Central developed and introduced a self-steering bogie based on the theories of Yoshihiro Suda, an associate professor at Tokyo University. The support stiffness of the leading axle has been made softer than that of the trailing axle, reducing the angle of attack between wheel and rail in curves and cutting load forces applied to the rail. The average reduction in lateral force, which tends to be high on curves with a radius of less than 500m, is around 30%.
The support stiffness of the axles in each Series 383 car was initially configured in a soft-hard-soft-hard arrangement, with the first soft axle leading and the configuration reversed when the train changed direction. During test runs with the prototype in 1994, we found that there was no need to make the third axle soft when bolsterless air sprung bogies were used. The axle stiffness configuration was accordingly modified to soft-hard-hard-soft, removing the need to switch the configuration when the train reverses.
Designed with a low centre of gravity, the Series 381’s passive body tilting works by centrifugal force. Ride comfort was impaired by the delay in tilting when the train entered a curve and the ’overtilt’ experienced on leaving it.
Active tilt
Series 383 has active tilt, with the body smoothly angled by air cylinders following the instructions of an on-board computer programmed with track data (above). The roller guides supporting the body on the Series 381 were replaced on the Series 383 by bearing guides.
Series 383 has a maximum speed of 130 km/h and the fastest curving speed of any Japanese narrow gauge train. It can negotiate a 600m radius at 125 km/h, 35 km/h above the usual speed for such a curve. It was put into service on the Shinano Limited Express in December 1996 and has cut 10min from the Nagoya - Nagano run. Tilting services operated with Series 383 EMUs are expected to play an important part in transporting people to and from the 1998 Winter Olympics in Nagano. o
CAPTION: Kiha 85 DMU in use on Limited Express services is powered by Cummins engines
CAPTION: Series 373 three-car EMUs have made an important contribution to cutting JR-Central’s maintenance costs
