GB1428824A - Fuel injection pumps - Google Patents

Abstract

1428824 Fuel injection pumps SIGMA DIESEL 3 May 1973 [8 May 1972] 21145/73 Heading F1A A fuel injection pump has a rotary delivery valve 2 which is displaced axially to alter the pumps delivery and angularly to alter the timing of the injection and a governer which indirectly moves the valve 2. A drive-shaft 4 driven by the associated engine (not shown) has a part 4a to which is keyed a cam surface 7, the lobes of which operate main pump pistons 5 through rollers 9 and push-rods 10 against return springs 11. From an inlet 16 fuel is fed via a pressing pump 15 to orifices 22, the number of which equal the number of cylinders of the engine, which terminate in a bore 3 of the main body 1 of the pump. The valve 2 is rotatable and axially moveable in this bore 3 and has on its surface a helical suction groove 23 and delivery groove 25 which communicate with an annular groove 24 in continuous connection with the bores 6 of the pump. Delivery from the main pump is via passages 8. The governer comprises two centrifugal weights 28 pivotable about respective pivots 29 and their radial outward movement due to rotation of the shaft 4, results in a push piece 31, moving a ring 32 which rotates with but slides inside the shaft 4. A spring 27 is located between the ring 32 and a face 2c on the valve 2. The ring 32 is slidably secured to the valve 2 by a pin 33 engaging in diametrically opposed grooves 34 in the wall of a hollow end of the valve 2 and a rod 42 is connected to the pin 33, passes through the valve 2 and carries at its other end a ferrule 45 having a frusto-conical surface 46. A similarly shaped cap 47 surrounds this surface 46 and is mounted within a sleeve 48. Balls 51 Fig. 2 are located between the cap 47, ferrule 45 and an endface 2d of the valve 2. One end of a rocker lever 40 abuts against the cap 47 and the other end abuts a cap 35a which is slidably mounted on a bush 35 itself slidable upon a guide rod 37 parallel to the slide valve 2 and spaced from a similar bush 36. A spring s extends between the bush 36 and cap 35a and has a stiffness less than the spring 27. Springs R extend between the bushes 35, 36 and have a stiffness greater than the spring 27. The compression of the springs R is adjusted by a cam 38 connected to a throttle of the engine (not shown). Operation. On starting the engine, the cam 38 pushes the bush 36 towards the bush 35 and the spring s urges the cap 35a towards the right (as viewed in Fig.). The valve 2 is therefore displaced leftwards to a maximum by the lever 40 and grooves 23, 25 are arranged so that pump delivery will then be at a maximum. As the rotational speed of the shaft 4 increases the centrifugal weights cause the ring 32, valve 2 and rod 42 all to move to the right without any relative linear movement therebetween since the spring 27 has greater stiffness than the spring s which is compressed by the lever 40 until the cap 35a abuts the bush 35. Movement of the valve 2 to the right causes a reduction in pump delivery per revolution. Further increase in the speed of the shaft 4 causes the ring 32 to move right, relative to the valve 2 since the spring 27 has smaller stiffness than the springs R which therefore hold the cap 47 stationary via bush 35, cap 35a and the lever 40. The rod 42 attached to the ring 32 by pin 33 consequently moves relative to the cap 47 causing ascent of the balls 51 on the frusto-conical surfaces which in turn act on the end-face 2d of the valve 2 and so cause it to move leftwards and thereby increase the pump's delivery. Simultaneously the relative movement between the rod 42 and valve 2 causes rotation of the valve 2 due to the pin 31 in the grooves 34 and thereby the injection timing is also altered. The rightward movement of the ring 32 relative to the valve 2 continues until the end f of the valve abuts the push piece 31 after which any increase in pump speed and therefore displacement force due to the weights 28 causes the springs R to be compressed so that ring 32, valve 2, and rod 42 once again jointly move to the right causing a decrease in the fuel delivery. Complete fuel cutoff occurs when the valve 2 is fully displaced to the right. Several shapes of the ferrule 45 are disclosed which give different fuel delivery to shaft 4 speed characteristics and one of which causes the valve 2 to be displaced in the same sense as the rod 42. Specification 1080819 is referred to. Reference has been directed by the Comptroller to Specification 947158.