GB530945A - Improvements in and connected with fuel-injection pumps for internal combustion engines - Google Patents

Abstract

530,945. Fuel injection pumps. DAIMLERBENZ AKT.-GES. July 7, 1939, No. 19806. Convention date, July 12, 1938. [Class 102 (i)] A fuel injection pump for an internal combustion engine particularly for motor vehicles has an adjustable pressure operated piston valve 15 located in the passage leading to the injection nozzle and serving to adjust the timing and quantity of the injection independently of pump piston adjustment. In one form the main pump piston 2, operated by a, cam 4 has an inclined control edge 5 leading from a longitudinal groove 6 to an annular groove 7 in the piston. A fuel supply passage 11 above the piston and an overflow passage 12 leading into a discharge pipe 14, which may be common to several side by side pump cylinders, both open into a space 10 above the pump. The piston valve 15 located above the space 10 has a screwed stem 16 which is adjustable by nuts 17, 18, the lower nut being urged by a spring 19 to engage a slotted flange on the nut with a seating 20 on the guide 21. A control bore 26 in this valve leads to a radial passage 25 communicating with an annular groove 22 which coacts with a shoulder 23 on the guide. A two-part abutment 28 limits upward movement of the valve by engaging the stem 16 and the bore 29 leads to the injection nozzle. In operation, on descent of piston 2 fuel is drawn into the space 10 and on upward movement the fuel is discharged through passage 12 until the upper edge 21 cuts off passage 12. Further upward movement compresses the fluid in space 10 until the valve 15 is lifted. As soon as the groove 22 clears the shoulder 23 fluid flows into space 24 and thence to the injection nozzle, the flow continuing until the curved edge 5 rises above outlet 12 thus allowing liquid to escape from chamber 10 along pipe 12. This point may be adjusted by rotating the piston 2 from gearing 8. The relief of pressure from space 10 causes the valve 15 to be returned by its spring and stops flow to the nozzle. The timing of the' start of the injection period, which is terminated by the edge 5, may be controlled by adjustment of the valve 15 by its screw. The adjustment also varies the capacity of the space 10. In a modification the flange of the nut 17 forms a continuous surface so that backward surge of liquid fuel is prevented. In a further modification, Fig. 3, the passage 26 may have a number of radial ports 30 ... 32 of different levels which come into action successively as the pump is adjusted for progressively larger deliveries, resulting in increasing travel of the valve 15. In another modification, the piston 2 may have an inclined upper edge 2<SP>11</SP>, Fig. 5, to control the start of the injection period instead of the edge 5 controlling the termination thereof. In other modifications, the piston valve 15 may be of greater or less diameter than the pump piston.