Patent GB-690732-A (GB)
Title: Speed governors for internal combustion engines
IPC: F02D1/00
Filed: 1949-01-26
Abstract: 690,732. Fluid-pressure servomotor-control systems; hydraulic machines; accumulators. DUNLOP, S. (Fiat Soc. per Azioni). Jan. 26, 1949, No. 2151/49. Classes 69(ii) and 135 The delivery and the injection timing of the fuel injection pump of an internal-combustion engine are correlated with the rotational speed of the engine under the control of separate servomotors fed with motive fluid from a single pump and each provided with feed-back from output to input to give correspondence control, and in the case of the system controlling the fuel delivery, the feed-back connection from output to control valve is a rigid one. In an embodiment, changes of speed of a diesel engine. as detected by a centrifugal governor 8, Fig. 1, are applied to a piston valve 10, to control the flow and exhaust of pressure liquid to a servopiston 16 which actuates a rod 18 controlling the delivery of the fuel-injection pump. Hunting is prevented by applying the movements of the servo-piston through a lever 24 to a sleeve valve 9 constituting a movable seat for the valve 10. The pressure liquid for actuating the servomotor is obtained from a gear pump 5 which is driven from the injection pump shaft 2 and which, through gearing 7, drives the governor 8 and also continuously rotates sleeve valve 9. The rod 18 can be actuated manually for stopping and starting by pushing and pulling on an extension 17 thereof and to enable this to be done, the piston 16 has a resilient connection with rod 18 by means of a spring 19 whose ends abut loose washers 20, 21 carried on a reduced portion of rod 18 inside the stem of the piston. Modified forms of the connection between rod 18 and extension 17 are described. To enable the speeder spring 11 of the governor to return to its normal length after a speed correcting movement, the movement of servo-piston 16 is applied through a lever 29 to an end stop 28<SP>1</SP> for the spring. The lever carries a fork at its upper end engaging a pin on a sleeve 32 which has a resilient connection with the piston stem similar to the device connecting the piston stem with rod 18. To prevent instability arising during a speed correcting movement, the correction applied by lever 29 is slowed up by connecting its lower end to a dash-pot consisting of a piston 36 moving in a cylinder of which the outlet is controlled by a needle valve 37. An intermediate point of lever 29 is pivoted on an internally screwed sleeve which engages over a screwed extension of stop 281, and this extension can be rotated to advance the stop to set the datum speed by moving an adjusting rod 44 which carries a rack to rotate a pinion 45 carried by a sleeve 46, the latter having a sliding but non-rotating connection with the extension to stop 28<SP>1</SP>. The degree of " irregularity " of this isodromic stabilizing device can be varied by adjustment of the position of the " fixed " pivot point 31 of lever 29. This is effected by placing the. pivot 31 on a lever 40, pivoted at 43 and adjustable in position by rotating an eccentrically mounted pin 41 which engages in a slot in the lever. The piston and cylinder servomotor may be replaced by a radial vane working in a cylinder, and in a further modification, the control valve is rotatable and is housed in the pivot-stem of the vane which thus provides the moving seat followup for the valve. In another modification, lever 24 connects the servo-piston to the valve 10 and a further lever acted on by the piston is connected to valve 9 by a resilient device which is also connected to a dashpot similar to 36, 37. Movement of rod 44 also advances a piston valve 50, Fig. 10, which controls the flow and exhaust of pressure liquid to a servo-piston 53 which adjusts the injection timing through a slotted quadrant 59 and lever 56. A lever 54 connected between'the servopiston and a sleeve valve 52 which forms a moving seat for valve 50 constitutes an anti-hunting device. Modified forms of the transmission between rod 44 and valve 50 and between servo-piston 53 and the means to adjust the injection timing are described. The motive fluid for the servomotors is delivered by the pump 5, Fig. 12, and normally flows through conduit 61, past a check valve 65, to conduit 13 leading to the control valves. When pressure in conduits 13, 66 is low, a spring-pressed valve 63 cuts off conduit 61 from a sump connection 61<SP>11</SP>. As the pressure in conduit 13 rises, a valve 67 is pushed back to the position, shown and the fluid can flow into an accumulator 69. On further rise of pressure, valve 63 is lowered to allow the-excess quantity delivered by pump 5 to flow to sump. Valve 63 snaps from one limiting position to another due to a spring clip 73 which engages in one or other of two grooves in the stem of the valve. The accumulator 69 includes a spring-loaded piston, oil proof rubber bag, or metallic bellows to keep the air from contact with the liquid.