GB2062093A

GB2062093A - Combined Fuel Injection Pump and Injector

Info

Publication number: GB2062093A
Application number: GB8023487A
Authority: GB
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1979-10-11
Filing date: 1980-07-17
Publication date: 1981-05-20
Also published as: GB2062093B

Abstract

A bore 11 which houses a pump plunger 12 is contained in a body 10 which defines a chamber 15 housing closing spring 20 of an injector valve member 19. Fuel under pressure from the bore 11 passes along a passage 27 which extends in an axial direction between the wall of the spring chamber 15 and the exterior surface of the elongated body. The inlet and outlet passages (30, 31), Fig. 2 (not shown), of the pumping chamber may extend obliquely to the bore axis. <IMAGE>

Description

SPECIFICATION Fuel Pumping Apparatus This invention relates to fuel pumping apparatus of the kind comprising a fuel injection pump housed in a body and a fuel injection nozzle secured to the body, such apparatus hereinafter being referred to as a pump/injector.

In a known form of such apparatus the pump comprises a cylindrical part which defines a bore in which a plunger is mounted. The injection nozzle is of conventional form including an inwardly opening valve member which is biassed to the closed position by the action of a spring.

The spring is housed within a chamber which is connected with a fuel drain to allow the fuel leaking into the chamber from the nozzle to escape. The spring chamber is formed in a tubular member which is positioned between the aforesaid cylindrical part and the nozzle and the tubular part has an end closure which serves to close the end of the bore in the cylindrical part. A passage is formed in the wall of the cylindrical part and connects the bore with the fuel supply passage of the nozzle. The various parts are held in assembled relationship by means of a cap nut which engages a flange on the nozzle, the nut being in screw thread engagement with a body part of the pump/injector and in which the aforesaid cylindrical part is mounted.

The screw thread connection must be sufficiently strong to establish a fuel tight seal between the end closure and the cylindrical part in spite of the force developed by the fuel pressure in the bore acting on the end closure. In addition it is necessary to ensure a fuel tight seal around the aforesaid passages. The practice with modern engines is for the pressure attained during delivery of fuel to increase with the result that the force developed and which must be resisted by the screw thread connection, is increased. In addition engine manufacturers are calling for the diameters of the parts to be reduced or kept as small as possible. As a result it is considered that the screw thread connection between the cap nut and the body part of the pump is no longer adequate.

The object of the present invention is to provide a pump/injector in a simple and convenient form.

According to the invention a pump/injector comprises an elongated body, a blind bore extending into the body from one end face thereof, a plunger slidably mounted in said bore, a chamber extending into the body from the other end face of the body, an outlet passage communicating with the blind end of said bore, said outlet passage passing between the wall of said chamber and the exterior wall of the body and opening onto said other end face of the body, an injection nozzle body secured relative to the aforesaid body, said injection nozzle body having a fuel passage in communication with said outlet passage and the nozzle body mounting a fuel pressure operable valve member, and resilient means located in said chamber, said resilient means being operatively connected to said valve member to urge the valve member to a closed position.

An example of a pump/injector in accordance with the invention will now be described with reference to the accompanying drawings in which: Figure 1 is a part sectional side elevation of a portion of the injector, and Figure 2 shows a modification to the pump/injector of Figure 1.

Referring to the drawings and the pump/injector comprises an elongated generally cylindrical body 10 and extending into the body from one end face thereof is a cylindrical bore 11.

Mounted within the bore 11 is a pumping plunger 12 which can be reciprocated under the action of a cam and a return spring. Opening into the bore 11 at a position to be covered by the plunger 1 2 is a filling port 13 which opens onto the periphery of the body 10.

Extending into the body from the other end face 14 thereof is a chamber 1 5. The chamber 1 5 communicates with the exterior of the body 10 by way of a passage shown in dotted outline at 1 6.

Also provided is a fuel injection nozzle which is generally indicated at 17. The nozzle is of conventional construction and is of the inwardly opening type. The nozzle body 18 is of stepped construction and slidable within the body is a valve member 19. The valve member is urged into contact with a seating defined in the nozzle body by means of a coiled compression spring 20 which is located within the chamber 1 5 and which at its end closer to the nozzle body engages a spring abutment 21 which is carried on a reduced portion 22 of the valve member 19.

The reduced portion of the valve member extends through an aperture formed in a stop plate 23 the latter being held between the body 1 8 of the nozzle and the aforesaid end face 14.

The nozzle body is held is sealing engagement with the stop plate 23 and the latter in sealing engagement with the surface 14 by means of a cap nut 25 which has a central aperture in its base wall through which extends the narrower portion of the nozzle body. The internal surface of the cap nut is screw threaded for engagement with a complementary screw thread formed on the body 10. The cap nut however is provided with an extension 26 which is spaced from the body 10 to define an annular space into which extends the passage 1 6.

The blind end of the bore 11 communicates with an outlet passage 27 which extends axially within the body 10 between the exterior surface thereof and the wall of the chamber 1 5. The passage 27 breaks out onto the end surface 14 and communicates with a drilling formed in the stop plate 23. This in turn communicates with a fuel passage 28 which is formed in the nozzle body.

In use, when the plunger 12 is moved downwardly as shown in the drawing, fuel will flow through the port 13 from the portion of the bore defined beneath the plunger, until the port 1 3 is covered by the plunger. Thereafter the fuel displaced by the plunger will flow through the passages 27 and 28 and the pressure of the fuel will act upon the valve member 19 to move it against the action of the spring. When the valve member is lifted from its seating the fuel will flow through outlet orifices indicated at 29 at the narrower end of the nozzle body.

The amount of fuel which flows through the orifices 29 can be controlled in a well known manner such for example as by a helical groove formed on the plunger and which during the inward movement of the plunger is brought into communication with the port 13 or a similar port.

The angular setting of the plunger adjusts the amount of fuel which flows through the orifices 29.

It is intended that the pump/injector should be mounted in a bore in the cylinder head of an engine, with the bore defining a fuel supply gallery. For this purpose the extension 26 of the cap nut may mount a resilient sealing member as also may the body 10, the sealing member in the case of the body 10 being disposed on the remote side of the port 13 from the nozzle.

Turning now to Figure 2, the body 10 defines the bore 11 and chamber 1 5 as in the example of Figure 1, moreover, the outlet passage 27 extends as in the example of Figure 1, between the wall of the chamber 1 5 and the outer wall of the body 10. The passage 27 is connected to the blind end of the bore by means of an inclined drilling 31 and conveniently this is formed at the same time as the port 30. In Figure 2 it will be noted that the port 30 is also inclined and this enables the drilling 31 to be formed.

The apparatus described is capable of supplying fuel at a pressure of at least 12,000 Ibs/sq. ins. The only surfaces between which seals must be established are those between the body 10 and the stop plate 23 and between the stop plate and the nozzle body around the passages.

Since the area around these passages is small only a moderate clamping pressure is required.

Claims

1. A pump/injector comprising an elongated body, a blind bore extending into the body from one end face thereof, a plunger slidably mounted in said bore, a chamber extending into the body from the other end face of the body, an outlet passage communicating with the blind end of said bore, said outlet passage passing between the wall of said chamber and the exterior wall of the body and opening onto said other end face of the body, an injection nozzle body secured relative to the aforesaid body, said injection nozzle body having a fuel passage in communication with said outlet passage and the nozzle body mounting a fuel pressure operable valve member, and resilient means located in said chamber, said resilient means being operatively connected to said valve member to urge the valve member to a closed position.

2. A pump/injector substantially as hereinbefore described with reference to the accompanying drawings.

2. A pump/injector according to claim 1 including a stop plate located between said nozzle body and said other end face of the elongated body, and a drilling in said stop plate and through which said outlet passage and said fuel passage communicate with each other.

3. A pump/injector according to claim 1 or claim 2 including a port formed in the wall of said bore, said port being covered by the plunger during its movement towards the blind end of said bore, said port being obliquely disposed relative to the axis of the bore and aligned with the initial portion of said passage extending from said bore.

4. A pump/injector substantially as hereinbefore described with reference to the accompanying drawings.

New Claims or Amendments to Claims filed on 2nd March1981 Superseded Claims 1 to 4.

New or Amended Claims:

1. A pump/injector comprising an elongated body, a blind bore extending into the body from one end face thereof, a plunger slidably mounted in said bore, a chamber extending into the body from the other end face of the body, an outlet passage communicating with the blind end of said bore, said outlet passage passing between the wall of said chamber and the exterior wall of the body and opening onto said other end face of the body, an injection nozzle body secured relative to the aforesaid body, said injection nozzle body having a fuel passage in communication with said outlet passage and the nozzle body mounting a fuel pressure operable valve member, resilient means located in said chamber, said resilient means being operatively connected to said valve member to urge the valve member to a closed position, and a port formed in the wall of said bore, said port being covered by the plunger during its movement towards the blind end of said bore, said port being obliquely disposed relative to the axis of the bore and being aligned with the initial portion of the outlet passage extending from said bore.