The electrification of Japan's JR railways has progressed to the point that one half of the roughly 20,000 km of lines in operation have been converted to electricity, and there is less call for diesel cars. At this seminar, we will cover the situation facing diesel locomotives today, and will also discuss maintenance and other diesel engine-related aspects in a question and answer format.
1 Diesel Locomotives in Japan Today
Numbering more than 3000 cars at their peak, diesel locomotives have decreased with the passing of time. Currently, the JR Group owns 637 diesel locomotive cars, 293 or nearly one half of which belong to JR Freight. (See Table 1.1.)
Most of the cars are DD51 and DE10 cars; the DE15 is a DE10 equipped with a snowplow used in mid-winter. The cars were all developed in the 1960s to complement each other; the DD51 as a main line passenger/goods traction car and the DE10 as a main line lightweight traction car. Table 1.2 gives the main specifications of the locomotives. All the locomotives have one or two DML61 engines, and the liquid transmission varies between DW2A and DW6.
1.1 DD51 Diesel Locomotives
The axle positioning follows the B-2-B format, and the central 2-axle bogie is an idler which does not transfer any motive power. There is a pneumatic spring between this bogie and the car body, and when air enters, the axle load of both side bogies decreases, much the same as when three people carry a heavy load and the person in the center bears the brunt of the weight. When the amount of air is decreased, the axle load of both side bogies increases. With this "variable axle load system" between 14 t and 15 t, the axle load is kept at 15 t at low speeds when starting, even where the track load is light, to achieve maximum adhesion.
1.2 DE10 Diesel Locomotives
Track conditions in Japan today are much improved. The DE10 is a 5-driving wheel diesel locomotive developed in the 1960s when track conditions were worse, to keep axle load down to 13 t. It consists of 2-axle bogies and 3-axle bogies, with the 3-axle bogies characterized by their 3-axle coupling devices and car body load-bearing mechanism.
