Fuel Injection Nozzle Assembly for Internal Combustion Engines

This invention relates to a fuel injection nozzle assembly for use in externally ignited internal combustion engines of the air-fuel mixture-compressing type being provided with fuel injection into a suction tube of the engine.

The fuel injection valves built into the suction tube, which serves for the intake of air, or, the engine block are heated up strongly, especially after stopping the engine, by the heat extending from the hot engine block and the exhaust pipes. The temperature to which the fuel injection nozzle is thus brought corresponds to a vapor pressure of 4 and 5 bar depending on the kind of fuel used. Because of technical requirements in controlling the amount of fuel, the opening pressure of the fuel injection valves must not surpass a determined pressure, for example 3.5 bar; in consequence whereof fuel vaporizes into the nozzle ducts. The share of fuel thus lost must be replaced when restarting the still luke-warm or cooled-down engine. This results in considerable starting time-lags, or the engine must be restarted several times and does not idle smoothly due to failure of the nozzle to spray the fuel, or to irregular spray of fuel from the nozzle.

A main object of the invention is to provide an improved fuel injection nozzle assembly comprising a fuel injection valve which adopts the temperature of the flowing fuel during driving, notwithstanding high engine temperatures, and which delays the warm up of the fuel injection valve when the engine is shut off, until the engine has cooled off.

A further object of the invention resides in the provision of a mounting for the fuel injection nozzle such that the nozzle is readily removable from the mounting, and such that the nozzle and holder can be assembled as a unit.

These and other objects are achieved in accordance with the invention by providing a fuel injection nozzle assembly comprising heat-insulating means between the fuel injection nozzle and the wall of the suction tube by means of a substance having a low thermal conductivity, a heat-insulating sleeve of such material being advantageously arranged between a nozzle holder and a bore in the suction tube in which the nozzle is inserted.

In a preferred embodiment of the invention, the said sleeve is provided with annular beads and/or projections engaging corresponding annular grooves and/or cavities in the nozzle holder whereby a positive connection of the sleeve with the nozzle holder is effected.

The invention will be better understood and further objects and advantages will become apparent from the ensuing detailed specification of a preferred but merely exemplary embodiment taken in conjunction with the drawing.

The sole FIGURE shows a fuel injection nozzle mounting in a suction tube according to a preferred embodiment of the invention.

An injection nozzle 1 is mounted with an elongated portion in a radial bore 7 through the wall of suction tube 2 (only a portion of which is shown). A sleeve member 3 of heat-insulating material, for instance heat-resistent rubber, is interposed between the injection nozzle 1 and the wall of the suction tube 2 so as to prevent metallic contact of the injection nozzle with the suction tube.

As shown, an annular groove 4 is provided about the mantle surface of nozzle 1 which groove 4 is positively engaged by the sleeve member 3, whereby the injection nozzle can be clamped onto the suction tube 2 by means of straps 5 and a collar 6. The bore 7 has an annular bevelled face 8, on to which a frustoconical portion 9 of sleeve member 3 is pressed when the latter is fastened in bore 7; on one hand this seals off the interior of the suction tube from the outside, and on the other hand fills in the clearance resulting between sleeve member 3 and bore 7.

Thanks to the heat-insulation provided by the material of sleeve member 3, the temperature of injection nozzle 1 remains at all times below 90.degree. to 100.degree. C., whereby the flow pressure in the suction tube 2 is maintained higher than the vapor pressure of the fuel.

With the arrangement shown, it is easy to see that the injection nozzle 1 and the sleeve member 3 can be either assembled as a unit and thereafter mounted within the bore 7 and retained therein by the strap 5, or the sleeve member 3 can be mounted within the bore 7 and retained therein by the strap 5 and thereafter the injection nozzle "snapped" into the position shown. In either case, the installation is simplified and accordingly represents a cost saving in manufacture.

The sleeve member 3 is also provided with a bevelled face 10 and the injection nozzle 1 with a corresponding bevelled face which engages the face 10 in assembly. With this arrangement, the ready removability of the injection nozzle 1 from the mounting can be seen. This feature is quite desirable for the advantage derived in being able to easily and quickly replace a defective nozzle.