GB1183156A - Improvements in or relating to Fuel Injection Valves - Google Patents

Abstract

1,183,156. Fuel injectors. ROBERT BOSCH G. m. b. H. Oct. 17, 1968 [Oct. 18, 1967], No. 49309/68. Heading F1B . The invention relates to a fuel injection valve for pre- and main fuel injection, the valve shown in Fig. 1 comprising a nozzle body 1 secured to the nozzle holder 3 by means of a clamping nut 2, a spacing plate 4 being located between the parts 1 and 3. A hollow needle valve 5 is mounted for axial movement in the body 1 and a needle valve 7 is mounted for axial movement within the valve 5, both the valves 5 and 7 being of stepped form to provide pressure faces 5f and 7c. A valve seating 1c is provided between the body 1 and the hollow valve 5 and a valve seating 5c is provided between the hollow valve 5 and the needle valve 7, the valve assembly being loaded by a spring 18 acting through a spring seat 19 on the needle valve 7 so that both valves 1c and 5c are normally closed. The assembly also comprises a pre-injection piston 11 which is disposed in a bore 10 in the nozzle body 1, the piston being formedwithathroughbore 16 with which is associated a spring-loaded non-return valve 17. The piston is loaded by a spring 12. An extension on the piston serves to limit axial movement of the piston in conjunction with abutment 21. Fuel under pressure is supplied through bore 9 to the annular recess 15 and through bore 14 to the pressure space 6. Fuel pressure acting on the piston 11 moves the piston to the left whereby fuel below the piston is discharged through passage 13 to the pressure space 8, such pressure acting on the surfaces 7c whereby the needle valve 7 is moved to the right against the loading of spring 18. The pre-injection charge of fuel thus discharges through the open valve 5c and injection orifices 1d into the engine cylinder, the needle valve 7 then closing. With the reduction of fuel pressure in the space 8, the fuel pressure in the space 6 acting on the annular surface 5e acts to move the hollow valve 5 to the right so opening the valve 1 c whereby the main injection charge of fuel discharges through the orifices 1d into the cylinder; the hollow valve carries the needle valve 7 with it as it moves to the right. In Fig. 5 a spring 22 acts against the needle valve 7 and a spring 25 acts against the hollow needle 5, the spring 22 acting against a member 24 secured to the hollow needle; the member 23 between the needle valve 7 and the spring 22 has an extension 23a which serves to limit opening movement of the needle valve. In Fig. 6 the abutment for the spring 22 (similar to Fig. 5) is provided by a rod 27 which extends from the far end of the spring cavity 20. In Fig. 7 (not shown), the needle valve opens by forward movement in the same direction as the flow of fuel. In Fig. 8 the fuel discharged by the pre-injection piston 11 passes to pressure space 6 and acts to open the hollow needle 5, the main injection being produced by opening of the needle valve 7 in response to fuel pressure in chamber 8. The needle valve spring 22 is separate from the spring 25 of the hollow needle 5 (as in Fig. 6). In Fig. 9 flow of fuel to the passage 14 and pressure chamber 6 is delayed until the pre-injection piston 11 has moved a predetermined distance along the bore 11; this serves to prevent opening of the main injection valve 5 as a result of pressure surges. In Figs. 10 and 11 (not shown), the pre-injection piston 11 is of stepped formation which permits pressure increase in the chamber 8. In Fig. 12 the pre-injection piston 11f is located within the hollow needle 5, the bore of the needle being sealed by a plug 36 which is engaged at one end by the spring plate 26 and at the other end by the piston 11f. Fuel under pressure passes from passage 14 to pressure chamber 6 and from there through bores 37 to the face of the preinjection piston 11f which causes fuel in chamber 8 to open the needle valve 7 and discharge into the engine cylinder, the needle valve opening in the same direction as the flow of fuel. Fuel pressure in chamber 6 then causes the hollow needle 5 to open against loading of spring 25 and main injection occurs. Movement of the piston 11f causes the stem 39 to shut-off the valve opening 42, the stem and piston being returned to their initial positions by the force of spring 12. Clearance is provided between the piston 11f and its cylinder.