Fluid sprinkling – spraying – and diffusing – Fluid pressure responsive discharge modifier* or flow... – Fuel injector or burner
Patent
1995-09-13
1997-09-02
Morris, Lesley D.
Fluid sprinkling, spraying, and diffusing
Fluid pressure responsive discharge modifier* or flow...
Fuel injector or burner
2395337, 2395339, F02M 6108
Patent
active
056622759
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a fuel injection nozzle for supplying fuel to an internal combustion engine and of the kind comprising an elongated nozzle body, a bore extending axially between the ends of the body, a seating surface defined on the body at one end of the bore, a valve member movable in the bore, the valve member having a head for engagement with the seating surface, an elastic member coupled to the valve member, the elastic member extending within the bore and acting to bias the head of the valve member into engagement with the seating surface and means for admitting fuel under pressure into said bore, the arrangement being such that in use, when the fuel pressure in the bore attains a predetermined value the head of the valve member will be lifted from the seating surface to allow fuel flow from the one end of the bore to the associated engine, the end of the elastic member remote from the head being engaged with a collar between which and an adjacent portion of the nozzle body is located a shim.
Such nozzles are known in the art as outwardly opening nozzles and have important advantages over the more common inwardly opening nozzle. One advantage is that when the valve head is in contact with the seating surface no fuel can dribble from the nozzle. In the case of an inwardly opening nozzle there remains a volume of fuel downstream of the seating surface when the valve member is in contact with the seating surface and this volume of fuel can dribble from the nozzle and cause an increase in the hydrocarbon content of the engine exhaust.
An example of such a nozzle is seen in DE-A-3139170. In this case the thickness of the shim has to be selected so as to provide the desired nozzle opening pressure.
Another example of a nozzle is seen in FR-A-921787. The elastic member is in the form of a rod which at its end remote from the valve member is secured within a screw threaded bush. Engaged with the screw threads of the bush is a nut which also engages the adjacent end of the nozzle body and relative rotation of the bush and nut will vary the tension in the elastic member and thereby the pressure of fuel required to lift the valve member from the seating surface. GB-A-586213 shows another form of nozzle in which the end of the elastic member remote from the valve head is provided with a screw thread and is engaged by a nut whereby the tension in the elastic member can be varied. The use of screw threaded members to adjust the nozzle opening pressure has been found to be unsatisfactory for a number of reasons. Firstly the method of adjustment has to allow for coarse adjustment to take account of manufacturing tolerances but also fine adjustment to alter the tension in the elastic member. In order to provide the fine adjustment the screw threads have to have a low pitch and it has been proposed to achieve this by means of a differential nut. However, the space available is small and it is difficult to form the threads to the high degree of accuracy required. In addition the threads provide regions of high stress concentration.
The object of the present invention is to provide a fuel injection nozzle of the kind specified in a simple and convenient form.
According to the invention in a nozzle of the kind specified the head of the valve member is located beyond the one end of the bore and the thickness of the said shim being such as to generate a tension force in the elastic member in excess of that required to provide the desired nozzle opening pressure and means is provided for applying a compressive force to a part of said nozzle body to reduce the tension force in the elastic member.
An example of a fuel injection nozzle in accordance with the invention will now be described with reference to the accompanying drawing which shows the nozzle and parts associated therewith in sectional side elevation.
With reference to the drawing the nozzle comprises a nozzle body 10 of stepped cylindrical form. The body has a narrower portion 11 which extends in use through a bore 12 formed in the cylinder head of the a
REFERENCES:
patent: 4730785 (1988-03-01), Seifert
Lucas Industries Public Limited Company
Morris Lesley D.
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