| 摘要 |
1,187,517. Electric control systems for brakes. MASCHINENFABRIK OERLIKON. 24 May, 1968 [1 June, 1967], No. 24968/68. Heading F2F. [Also in Division G3] Apparatus for controlling the pneumatic brakes of a train (which may have electric traction and braking) includes an Integral or Proportional Plus Integral control circuit. For a short train integral control is adequate, and the brake error signal (i.e. difference between actual and desired deceleration) is fed to an integrator circuit having a time constant such that the rate-of-change of air pressure in the train pipe is equal to or less than the rate-of-change of air pressure in any brake cylinder. In longer trains, the length of the brake pipe causes delayed rise in brake cylinder pressure and proportional + integral control is desirable, for stability, as shown diagrammatically in Fig. 4, where the braking error signal a be is applied through a limiting amplifier to an integrator 15 and through a parallel ohmic channel 16. A more detailed arrangement of this circuit is illustrated in Fig. 7 with additional features. The error signal a k is amplified at 21 to provide the proportional signal f a and also fed to limiting amplifier 23, with limit diodes 25, 26, and thence to integrator 32, and the combined signals are amplified at 38, basically as in Fig. 4. Additional features: (i) a measuring trigger circuit 40 at the output, operates at a certain minimum output to correct for small pressure drops in the train pipe; (ii) for Downhill travel at Constant Speed a switching signal c from the train controller (not shown) biases diodes 29, 36, 37 to depress the limiting level of amplifier 23 and suppress the proportional signal f a -the proportional signal is replaced at the start of braking by a signal from trigger 48 (to " memory " 47 and capacitor 44) which decays in a few seconds. This signal is negligible in normal braking. Further, the switching signal c biases diodes 54, 55 to reduce the air brake signal ak by a fraction of the desired retardation a c , so that the electric brake operates on slight slopes. |
