US2895425A - Fuel injection pumps for internal combustion engines - Google Patents

Description

July 21, 1959 E. E. CHATTERTON- Filed .Jan. 18, '19s? INQENTOQ ERNEAT E. Guava-321m United States Patent '0 F signor to D. Napier & Son Limited, London, England, a company of Great Britain Application January 18, 1957, Serial No. 634,882

Claims priority, application Great Britain February 29, 1956 3 Claims. (Cl. 103-154) This invention relates to fuel injection pumps for internal combustion engines, of the kind comprising a barrel in which slides a plunger, the fuel being forced by the plunger out of the barrel at high pressure through a delivery valve and into a fuel delivery pipe or pipes leading to one or more injectors which spray the fuel into a pumping pressure which tends to force the delivery valve chamber away from the plunger, the reaction of this force being transmitted back from the delivery valve chamber to the cam box of the pump. The resulting stresses produce corresponding strains in the stressed parts tending to reduce the said clamping force and increasing the risk of leakage between the delivery valve chamber and the pump barrel.

Where the initial clamping force is aplied through the pump body, for instance in a case where the pump barrel has an external shoulder which engages an internal shoulder formed in a recess in the pump body and the delivery valve chamber has an external shoulder engaged by a ring nut which screws into the said recess in the pump body, the strains due to the pumping reaction which would reduce the clamping force are those of the delivery valve chamber and of the pump body as far as the said shoulder in the recess therein. In a case where the pumping reaction is transmitted from the delivery valve chamber directly to the cam box, for instance by bolts passing freely through the pump body, the strains in question will be those of the delivery valve chamber and of these bolts.

According to the present invention, in a fuel injection pump of the kind specified the delivery valve chamber includes an internal sleeve through which an initial clamping force pressing this chamber or an interposed sealing member on to the barrel is transmitted as an axial compressive force, the longitudinal compression of the sleeve produced by the initial clamping force being substantially greater than the extension produced by the reaction to the pumping pressure in the parts which transmit this reaction Thus the extension of the sleeve permitted by the extension of the parts stressed by the reaction to the pumping pressure will represent only a fractional change in the compressive load on the sleeve, and the initial clamping force will be reduced by only this fractional amount.

By making the sleeve of a material having a low modulus of elasticity compared with that of the parts of the pump that transmit the reaction to the pumping pressure,

R 2,895,425 Patented July 21, 1959 2 for instance an alloy steel, the initial clamping force required to produce the necessary initial compression of the sleeve can be low in relation to clamping forces hitherto employed. l

Moreover by making the sleeve of a material having an appropriate coeificient of thermal expansion, the clamping force can be maintained. more closely at the desired value despite the thermal expansion of the pump body, orother parts. i

.The invention may be performed in various ways and one particular form of pump embodying the invention will now be described by way of example with reference to the. accompanying drawing, which is a sectional elevation of the pump.

The pump shown in the drawing comprises a cast body 10 made of aluminium or aluminium alloy accommodating a pump barrel 11 and a delivery valve chamber 12. The delivery valve chamber 12 contains an inserted seating 13 on which seats a delivery valve 14 which is pressed on to its seating by a compression spring 15. Screwed on to the upper end of the delivery valve chamber 12 is a connector 16 to which can be attached a fuel delivery pipe (not shown) leading to the injector.

The barrel 11 is provided with an external shoulder 17 which seats upon a corresponding internal shoulder 18 formed in the pump body 10.

The delivery valve chamber 12 is provided with an external shoulder 19 upon which presses the lower end of a ring nut 20 which surrounds the delivery valve chamber and which screws into the pump body 10.

The upper end of the barrel 11 is provided with a flat mating surface 21 against which seats a corresponding fiat mating surface 22 on the inserted valve seat 13. The inserted valve seat thus constitutes a sealing member between the barrel 11 and the delivery valve chamber 12.

The lower end of the insert 13 is provided with a flange 23 while the interior of the delivery valve chamber 12 is provided with a transverse shoulder 24. Between the flange 23 and the shoulder 24 there is provided a compression sleeve 25 made of a material having a modulus of elasticity which is low compared with that of the materials of the other parts of the pump, for

instance an alloy steel having the following analysis:

Percent Carbon Approximately 0.7 Sicilcn Approximately 0.5 Manganese 3.5 to 5.5 Nickel 11 to 14- Chromium At least 3 Molybdenum 0 to 0.5 Vanadium 0 to 0.25 Tungsten 0 to 1 The length and the material of the sleeve 25 are such that the compressive strain which it undergoes when the ring nut 20 is screwed tightly down into the pump body 10 substantially exceeds the total tensile strains of the other stressed parts of the pump. Consequently, when the pump pressure is applied by a pump plunger 27 being driven up further into the barrel 11, and the pump is stressed in the sense tending to separate the delivery valve chamber 12 from the barrel 11, the additional tensile strain or extension of these parts resulting from these additional stresses is less than the overall initial compression of the sleeve 25. Thus although the sleeve 25 will then expand through a distance equal to the additional extension of the other parts it will still retain the remainder of its initial compressive strain and so will continue to press the inserted valve seat 13 firmly against the barrel 11, thereby continuing to exert a clamping force between the surfaces 21 and 22 and obviatingleakage between these surfaces.

What I claim as my invention and desire to secure by LettersPatent is: u

1. A fuelinjection. pump, for an internal combustion enginecomprisingv arbody, a barrelfseateddnzsaid body.

and having an upper end surface, a plunger slidable in.

said barrel, a, delivery, valve, a delivery valvehousing enclosing saiddelivery valve, an internahsleevein said delivery valvehousingshaving an upper. end andvailower.

end, a shoulder. in said delivery valve;h0using engaging the upper end'of said sleeve, ab'utmentmeanssupporting said lower endof said sleeve uponsaidbarreLandclamping means securing; said delivery valve. housing-1o.v said v body and urging said shoulder towardssaidjupper. end surface of said barrel to maintain substantially. the whole of said sleeve under longitudinal compressions substan:

tially greater than the extension of said clampingmeans.

which said abutment meansv comprises an interposed? memberrb'etweenl, said lower end of saidsleeveand said upper end surface of said barrel.

References Cited in-thefile of-thispatent UNITED STATES: PATENTS;

Bremser' Aug. 13, 1940 Fleck ..s .v,Dec. 26, 1950 www-

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