Patent GB-1443378-A (GB)
Title: System for controlling the speed of a vehicle
IPC: B60T8/18
Filed: 1974-02-12
Abstract: 1443378 Automatic brake control; wear adjustment; valves; reversing gear GENERAL SIGNAL CORP 12 Feb 1974 [5 March 1973] 06341/74 Headings F2E F2F and F2D [Also in Division G3] A vehicle incorporates a control system whereby actual speed is brought into line with desired speed by actuation of actuators 35, 36 of brake units 17, 18 and actuation of speed controllers 16 of traction motors 15, the system incorporating adhesion control valves 38 to deliver fluid pressure to the units 17, 18 and/or actuators 37 of speed controllers 16 in response to phase differences between an input shaft 39 rotating at a speed proportional to desired wheel speed and a feedback shaft 42 rotating at a speed proportional to actual wheel speed. The illustrated embodiment is for a train wherein each car has two trucks having axles 13, 14 and 13a, 14a respectively. Each car has identical equipment save for the control car which also has a master signal generator 11 for supplying to a control wire 12 a signal having a frequency which represents desired train speed. Each axle of each car has its own traction motor 15 and its own disc brake units 17, 18, its own controller 19 for controlling actuators 35, 36 of units 17, 18 and actuator 37 of speed controller 16. A source 22 of hydraulic fluid under pressure is provided for the two controllers 19 of each truck and emergency brake control apparatus 23 responsive to the weight carried by the truck to control the four disc brake units 17, 18 of each truck is also provided. Master signal generator 11.-This comprises a manually adjustable potentiometer 25 for developing a variable control voltage representing desired train speed and a tachometer generator 26 driven by a sensor wheel 27 engaging a wheel 21 to provide a feedback voltage. These two voltages are delivered via lines 28, 29 to a rate control unit 31 which develops on line 32 on output voltage which varies directly with the difference between the inputs. This output and the signal on line 28 are supplied to a master frequency controller 33 which furnishes to wire 12 a master signal whose frequency changes at a rate proportional to the voltage on line 32 and which, under steady state conditions, is proportional to the desired speed signal on line 28. The signal on line 12 is delivered to a converter 34 on each car which supplies a proportional signal to the controller 19 on the car to drive a respective motor 42 for each input shaft 39 which thus rotates at a speed proportional to the frequency of the master signal. Each feedback shaft 41 is driven by a sensor wheel 27. Adhesion control valve 38.-Each valve 38 comprises an inlet port 46 connected with source 22 via a conduit 47, a pair of service ports 48, 49 connected respectively with actuators 35, 36 and with actuator 37 via conduits 51, 52 and a pair of exhaust ports 53, 54 connected with an hydraulic reservoir 55. Fluid flow is controlled by a pair of valving elements in the form of a sleeve 56 and a spool 57-the spool 57 is reciprocated through ball bearings 72, 73 by a two-piece rod 66, one end of which is coupled to the input shaft 39 through a spline connection 67 and the other end of which is coupled to feedback shaft 41 through a threaded connection 68. Rod 66 is shifted to the left or right depending upon whether input shaft 39 lags or leads feedback shaft 41. The sleeve 56 is biased to the illustrated central position by a pair of centering springs 74, 75 and is shifted in opposite directions from that position by a pair of fluid pressure actuators. One actuator includes a cylinder 78 which is in continuous communication with a sleeve passage 59 and a piston 79 which reacts against the valve body and serves to move sleeve 56 leftwardly. The other actuator includes a cylinder 81 and piston 82 which responds to the pressure in a sleeve passage 61 and acts to shift sleeve 56 to the right. The valve 38 acts to graduate the pressure at one or other of the service ports 48, 49 directly in accordance with the relative movement between the shafts 39, 41. Drive connection 43.-Fig. 4 illustrates a drive connection 43 between wheel 27 and input shaft 41. The connection 43 is enclosed in a housing 83 which is mounted for pivotal movement on an extension 84 of the valve body. The drive train includes a pair of shafts 87, 88 and two sets of bevel gears-shaft 87 is driven by axle 86 of sensor wheel 27 through gears 89, 91 and shaft 88 is connected with shaft 41 by a spline coupling 92 and is driven by shaft 87 through gear 93 and one or other of a pair of meshing gears 94, 95. Gear 93 is coupled to shaft 87 through a slip clutch 45, and each of the associated gears 94, 95 is coupled to shaft 88 through a one-way overrunning clutch 96, 97 which act in reverse senses so that the drive connection 43 always rotates shaft 41 in the same direction regardless of the direction of rotation of wheel 27. Brake apparatus.-Fig. 5 shows the source 22 of the two controllers 19 of each truck as comprising a fixed delivery pump 98 driven by an electric motor 99 and an accumulator 103 with an actuator 104, responsive to accumulator pressure, to control the power circuits 105 of motor 99. Hydraulic fluid from the source 22 may be delivered to the actuators 35, 36 via a conduit 47, valve 38 and conduit 51 or via a branch conduit 107, emergency brake apparatus 23 and a conduit 108. A double check valve 109 prevents brake operation via both paths-and the first path incorporates a valve 112 for manual release of the brakes. The apparatus 23 comprises a regulator valve 113 and a solenoid actuated emergency selector valve 115. The valve 113 includes a spool 116 with a passage 121 therethrough. The spool 116 is biased by a spring 123 having an adjustable seat 125 moved by a diaphragm 126 which responds to the pneumatic pressure in the air spring 127 of the associated track. In this embodiment the conduit 108 by-passes adhesion control valves 38 but in the modification of Fig. 6 (not shown) the adhesion control valves 38 receive the modulated output of valve 113. The brake apparatus incorporates slack adjusters 129. Each adjuster 129 comprises a differential piston 132 which divides a cylinder 131 into working spaces 133, 134. A transfer passage 135 controlled by a combined transfer and relief valve 136 extends through the piston 132-the valve 136 may be opened by a predetermined pressure differential between spaces 133, 134 or by a mechanical actuator 137. During a brake application, fluid under pressure delivered to space 133 shifts piston 132 to displace oil into actuators 35, 36. If shoe clearance is too great piston 132 will reach the end of its stroke before the brakes are applied, and actuator 137 will open valve 136 to admit oil to the actuators 35, 36 to take up clearance. If clearance is too little, the shoes will contact the disc before the piston 132 reaches the limit of its application stroke, the pressure in space 134 will rise and valve 136 will open to allow oil to be transferred to space 133. Operation.-In operation a change in the frequency of the signal on line 12, which change takes place at a rate determined by unit 31, effects a change in speed of motors 42. The shafts 39 then rotate at a speed different to that of shafts 41 which causes actuation of valves 38 to cause braking or operation of the traction motors 15 until actual vehicle speed is brought into line with desired vehicle speed. If local rail conditions cause a particular wheel 21 to spin or slip the respective valve 38 will be operated to cause reduction of traction or braking to offset the effect-the other valves 38 will be operated to make up for loss of control at the particular wheel to give overall traction or braking as required by the signal on line 12. The traction motors 15, acting as generators, will normally be utilized to provide some braking but the disclosed system automatically compensates for this. Modifications.-The master signal on line 12 may be produced at a trackside site and transmitted to receiving equipment on the train. The braking portion of the illustrated system only may be operated in response to a conventional P-wire signal, and the braking portion may serve as a slip control for a conventional brake. In this case the valves 38 are supplied with hydraulic output of the primary brake equipment which responds to P-wire current, rather than the output of a constant pressure source, and serves merely to modulate the pressure at which that fluid is delivered to the brake cylinders as needed to prevent the wheels from slipping.