The introductions of lightweight cars and increased speed have resulted in conspicuous vertical elastic vibration of carbodies (primary bending vibration in particular) and rigid body mode vibration at natural frequency, thereby often lowering ride comfort against vertical vibration. A method to control the damping force of axle damper and air spring is therefore developed in order to suppress these vibrations and significantly improve ride comfort against carbody vertical vibration.

To reduce vibration by controlling the axle-damper damping force, a variable damping-force axle damper is developed, which features superior damping force characteristics against minor amplitudes and has a damping force controllable up to about 10 Hz. To reduce vibration by controlling air spring damping force, a throttle-controllable valve is also developed, which can be incorporated into an air spring and enables the supply of a large volume of air by a small differential pressure at the maximum opening. By using these two components, a method is devised to effectively reduce the vertical vibration of carbody.

With the components mounted on a model equivalent to Shinkansen car, an excitation test is implemented to simulate actual running conditions at a rolling stock test plant. The results confirmed that both vibrations of the carbody primary bending mode and the rigid body mode substantially decreased, improving the ride comfort level (LT) by up to about 5 dB. The test at the rolling stock test plant also proved that such damping force control had little effect on the critical speed of hunting motion.

Running tests with Shinkansen cars are planed to confirm the performance of these components.