| 摘要 |
1528208 Braking systems KNORR-BREMSE GmbH 2 Dec 1975 [31 Dec 1974] 49540/75 Heading F2F [Also in Division B7] A (rail) vehicle wheel anti-lock device B is associated with a device which applies sand (or like particulate friction providing material) to the wheel if the wheel does not start to accelerate within a waiting time #T interval commencing with the operation of the antilock device. Fig. 1 shows a flow diagram of apparatus for . carrying out the invention for a rail vehicle. If during braking, wheel slip exceeds a predetermined value, which may be velocity-dependent, the device B generates a speed-comparison signal D which controls solenoid valves for bringing about brake release. On receipt of the signal D a comparator device #V determines whether the vehicle velocity is above a predetermined value and if so the waiting time #T commences. Immediately prior to or during waiting time #T, wheel deceleration is tested to see whether it has exceeded a predetermined value and if this condition is satisfied then the device W tests whether the wheel deceleration becomes negative within the waiting time #T, i.e. whether the wheel is again accelerated. If however the wheel is not re-accelerated and wheel deceleration continues indicating poor adhesion, then sanding is effected by a device S for an adjustable period of time-if the vehicle velocity falls below the predetermined value, sanding is immediately terminated. It is envisaged that instead of the speed comparison signal other signals derived from the anti-locking device may be used as an input variable for the sanding device, e.g. acceleration signals, or the brake release signal. Fig. 2 illustrates a block diagram of an apparatus of the invention, including an input divider 1 to calibrate a signal G proportional to wheel velocity which is then supplied to a comparator 6 and to a "steep discharge" 2 which provides a wheel speed proportional voltage which is then differentiated in a circuit 3. A comparator 4 tests whether the sign of the acceleration signal, and comparator 6 tests whether the wheel (vehicle) velocity is above the predetermined value-if so a signal is supplied to monostable flip-flops 7, 8 the switch on duration of flip-flop 7 representing the waiting time. A logic circuit 5 can thereby generate a sanding signal to control a flip-flop 9 which determines the sanding duration, the sanding signal being amplified in a driver 10 to control sand-strewing elements, e.g. solenoid valves. Figs. 3a, 3b (not shown) illustrate the detailed electronic make-up of the blocks of Fig. 2. The Specification envisages the invention as also covering the possibility of a sanding device being associated with an anti-spin device which reduces drive power in the event of wheel spin, sanding being initiated subsequently if necessary during a waiting time. |
