| 2. Long-Life, Low-Cost Anti-Lock Brake System for Freight Cars | |||
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High-speed freight container cars require brake performance comparable to that of EMU's. There are, however, many problems to be solved, such as wheel maintenance necessary as a result of wheel flat and vibration/noise. In contrast to the anti-lock brake system (ABS/WSP) of EMU's, development of ABS for freight container cars faces the challenges of securing the power supply and reducing costs, thus hindering its implementation. A system was therefore developed to include the electric power storage and energy-saving anti-skid valve essential to the construction of ABS for freight cars. To address the problem of a lack of power supply, an electric power storage system was developed in which a generator also serving as a speed sensor is set up at the axle end, and the power generated is stored in an electric double layer capacitor (Fig.1). The capacitor uses an aqueous electrolyte solution and ceramic containers, and a life acceleration test suggested possible stable maintenance-free performance for at least 10 years in an outdoor temperature environment. An energy-saving anti-skid valve was also developed to reduce the capacity of the electric power storage for reasons of cost reduction (Fig.2). The valve combines the two functions of lockout and exhaust in one electromagnetic coil, and also boasts such features as enhanced insulation and a reduction in friction parts. These features enable valve price reductions of 50% or more over conventional EMU valves, while at the same time securing energy savings (10% or less than that of conventional EMU valves) and weathering resistance.
A running test performed after adding these components to ABS and mounting the system on a freight container car verified satisfaction of ABS requirements for freight cars. With this ABS, even using an automatic air brake system, braking deceleration equivalent to that of commuter electric trains can now be achieved, along with the prevention of wheel flat.
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