Patent GB-819473-A (GB)
Title: Improvements in and relating to speed governors for prime movers
Inventor: EMERSON REGINALD STANLEY
IPC: G05D13/00
Filed: 1955-04-04
Abstract: 819,473. Fluid-pressure servomotor control systems. BERGER Ltd., B. April 30, 1956 [April 4, 1955], No. 9776/55. Class 135. In an engine speed governor comprising positive hydraulic displacement means discharging pressure liquid through a jet nozzle to impinge on and displace a baffle member in opposition to a biasing force to produce a mass flow that varies in accordance with engine speed, the baffle member is coupled directly or by way of an hydraulic servomotor to an engine controlling member. As shown, to control the fuel supply to an I.C. engine, an engine-driven pump 1, Fig. 1, delivers operating oil to a jet nozzle 3 to impinge on a baffle member 4 carried by a bellcrank lever 15 to which is connected one end of a helical control spring 5 biasing the baffle towards the nozzle. The spring at its other end is connected through a pinion 55 and gear quadrant 56 to a speed selector lever 6 whilst the lever 15 is connected through a link 17 to a floating lever 7 connected to a control valve piston 9 and a double-acting servomotor piston 8. The piston in turn is connected to a bellcrank lever 11 mounted on a shaft 23 and operably connected to the fuel injection pump. The shaft 23 also mounts a cocking lever 63 and a hub member 67 loaded by a flat coil spring 24. The jet nozzle 3 comprises a fixed spear rod 37 and a slidable sleeve 35 urged upwardly by a spring 36 to reduce the nozzle outlet so that the velocity of nozzle discharge remains substantially constant irrespective of engine speed. The product of the mass flow and jet velocity through the nozzle constitutes speed sensing mechanism. After passing the baffle, the pressure liquid can pass through a duct 26 to the control valve and a duct 27 having ports 32 controlled by a spring-loaded sleeve 33 to the inlet side of the pump 1. To start the engine and run it at idling speed, the lever 6 is first set at the desired speed, the spring 5 moving the valve piston 9 leftwardly so that liquid passes to the left of the piston 8. As speed increases and pressure is built up the piston 8 moves rightwardly to overcome the spring 24, adjust the fuel injection pump and re-centre the valve piston, any further increase in pressure raising the spring-loaded sleeve 33, and, if sufficient, spilling liquid through the ports 32. As the engine approaches idling speed the increased flow will have produced a thrust sufficient to move the baffle 4 against the control spring 5 and so move the valve piston 9 rightwardly. The piston 8 then moves to move the lever 11 to decrease the fuel supply to the engine until a steady speed is attained and the valve 9 returns to its central position. To compensate for temperature changes in the operating liquid the material of the nozzle loading spring 36 may be chosen to modify its force in accordance with temperature. Alternatively a flap valve 41 susceptible to temperature changes may be fitted controlling a duct 39 which may be fitted with a manuallyadjustable restriction 42. In another arrangement, the sleeve 35, or rod 37 or both may be displaced axially by means of a Bourdon tube coupled to a container filled with mercury and sensitive to temperature changes. Stopping mechanism may be provided comprising a spring-loaded plunger 45, Fig. 2, including a disc valve 49 urged if necessary by a spring to close plunger holes 48. In steady running condition the spring 50 holds the plunger clear of a pivoted link 7a associated with the valve piston 9. If the plunger is manually depressed against the spring 50 pressurized liquid below the plunger passes through the now open disc valve 49 to the other side of the piston to permit the valve piston 9 to be displaced rightwardly against the baffle mechanism, whence the piston 8 moves leftwardly to cut off fuel supply to stop the engine. To preset the fuel injection pump to a suitable position prior to starting, provision is made to overcome the effect of the spring 24. On moving the cocking lever 63 against a stop 64 the shaft 23 is free to rotate within the cocking lever boss limited only by the stroke of the piston 8. On moving the lever anticlockwise a pad 65 thereon engages a pad 66 on the bellcrank lever 11 to rotate the latter lever which through pins 70, rotates the hub member 67 until a pin 68 engaged by the spring-loaded sleeve 33 engages a notch 69 in the hub member just as the piston 8 reaches its full travel position. The hub 67 now being locked, the cocking lever can be rotated clockwise and the lever 11 set in any desired position. On the engine gaining sufficient speed after starting the sleeve 33 is raised to release the pin 68 so that the spring 24 turns the hub 67 until it contacts the pins 70. To adjust the speed droop characteristic of the governor, the spindle 16 on which the lever 15 is mounted may be provided with an arm 71, Fig. 3, engageable with an elastic beam 73 whose position is adjustable by a thimble 74. Rotation of the spindle 16 by the baffle 4 will be resisted by the beam 73, the resistance increasing with increased distance between the spindle axis and the end of the beam. The greater the resistance the greater must be the speed change necessary to cause unit deflection of the baffle and therefore the speed droop of the engine relative to a given increase in load. To decrease the droop characteristic immmediately below the speed at which the load on the engine may be suddenly increased, e.g. in marine applications having a clutch between the engine and the load, a, further lever loaded by an adjustable spring is mounted on the spindle 16, pins on the lever boss co-operate with elongated recesses in a freely rotating hub connected to the control spring 5 so that at high speeds the adjustable spring supplements the spring 5. To overcome increasing torque reaction of the spring 5 at higher speeds, a rod 57 connected to the gear quadrant 56 is surrounded by a spring 58 and slidable in a fixed but pivoted spring abutment 59 so that the spring 58 produces a balancing torque. In a modified construction, the baffle 4 is mounted on a rod 94, Fig. 6, loaded by a compression spring in lieu of the helical spring 5, the other end of the rod being connected directly to the floating lever 7. In this embodiment the rod 18 of the piston 8 is hollowed out to receive a dash-pot piston 99 loaded by a spring 101. On, e.g., a slowing down of the engine consequent upon an increase in load, the baffle will move towards the nozzle whence the pistons 8, 99 will move together leftwards against the spring 101 until the valve 9 is re-centred by the floating lever 7. The spring 101 will then move the piston 99 in stages to the right to re-adjust the valve 9 rightwards and the piston 8 leftwards until the engine regains its set speed. In a further modification, whereby output engine torque is controlled as a function of the speed by the torque demanded by e.g. an engine-driven generator or torque converter, the servomotor control valve comprises a valve piston 123, Fig. 8, positioned by a cam 125 by a speed setting lever 6 and a ported sleeve 117 connected to the governor output shaft 23. On, e.g., decrease in engine speed, the shaft 23 moves the sleeve 117 rightwards to exhaust liquid from the right-hand side of the piston 129 which through a rack and gear quadrant adjusts an electrical control 130 to reduce the load absorbed by the generator until engine speed is regained and the sleeve returned to its original position. To prevent aeration of the operating oil should a shortage thereof occur, a tank 89, Fig. 5, housing a float-actuated valve 91 is connected in circuit with a header tank 82, the pump 1 and the governor 87. On a lowering of oil level in the header tank the valve 91 opens to exhaust oil from beneath the spring-loaded stop plunger 45 and so stop the engine.