US3465677A - Liquid fuel pumping apparatus - Google Patents

Description

p 1969 I G. A. F. CLARKE I 3,465,677

LIQUID FUEL PUMPING APPARATUS Filed Oct. 4, 1967 United States Patent 3,465,677 LIQUID FUEL PUMPING APPARATUS Graham Albert Flemming Clarke, Ruislip, England, as-

signor to C.A.V. Limited, London, England, a British US. Cl. 103-2 8 Claims ABSTRACT OF THE DISCLOSURE A liquid fuel pumping apparatus for supplying fuel to an internal combustion engine and including an injection pump which supplies fuel through a delivery passage formed in a rotary distributor member, the delivery passage being arranged to register in turn with delivery ports, there being provided a groove positioned to register with the delivery port as soon as the delivery passage has moved out of register therewith, the groove communicating with a restricted leakage path and means being provided to prevent the fiow of fuel from the outlet port to the injection pump at the end of the delivery of fuel through said port.

This invention relates to liquid fuel pumping apparatus for supplying fuel to internal combustion engines and of the kind comprising an injection pump :for supplying liquid fuel to an outlet.

The object of the invention is to provide such an apparatus in a simple and convenient form.

One example of a liquid fuel pumping apparatus in accordance with the invention will now be described with reference to the accompanying drawings in which:

FIGURE 1 is a sectional diagrammatic view of the apparatus, and

FIGURE 2 is a section on the line 22 of FIGURE 1.

As shown in the drawings the apparatus comprises a body part 10 including a sleeve 11 in which is mounted a rotary cylindrical distributor 12 which is arranged to be driven in timed relationship with an engine with which the apparatus is associated. At one end of the distributor there is provided a transverse bore 13 in which are mounted a pair of reciprocable plungers 14 Which are arranged to be moved inwardly through rollers 14a respectively by a plurality of equi-angularly spaced pairs of inwardly exending cam lobes formed on the internal periphery of a cam ring 15 which is mounted within the body part and which surrounds the distributor at this point. The pumping chamber which is defined intermediate the pair of plungers is in communication with a longitudinal passage 16 extending within the distributor.

At its end remote from the pumping chamber the longitudinal pasage 16 is enlarged and the step thus defined in the passage constitutes the seating of a spring loaded plate valve 17. The enlarged end of the passage is closed by a suitable plug 18 which also constitutes the abutment for the spring of the plate valve. Moreover, the abutment supports a stop 19 whereby to limit the movement of the plate valve. The enlarged portion of the longitudinal passage which is downstream of the plate valve communicates with a radially disposed delivery passage 20 and this is arranged to register in turn as the distributor rotates, with a plurality of equi-angularly disposed outlet ports 21 formed in the body part. In use, the outlet ports are in communication with a plurality of injection nozzles respectively which are mounted to direct fuel into the combustion spaces of the associated engine. Furthermore, the communication of the delivery passage 20 with an outlet port 21 is arranged to occur whilst the plungers 14 are being moved inwardly by the cam lobes.

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Upstream of the plate valve 17 the longitudinal passage 16 is in communication with a plurality of radially extending inlet passages 22 which are arranged to communicate as the distributor rotates, with a plurality of inlet ports 23 formed in the body part. The inlet ports each communicate with an annular passage 24 defined in the body.

Also provided is a vane type feed pump 25 which has an inlet 26 and an outlet 27. In a practical construction the feed pump 25 would be mounted within the body part and its rotary part would be driven by the distributor 12. The inlet and outlet of the feed pump would also be formed in the body part.

The inlet and outlet of the feed pump are interconnected by way of a valve 28 which is so arranged that the output pressure of the feed pump varies in a manner dependent upon the speed of rotation of the engine. The inlet of the feed pump in use, is connected to a source of liquid fuel and the outlet of the feed pump is in communication with a supply conduit 29 formed in the body part.

The communication of the inlet ports 23 and the inlet passages 22 is arranged to occur when the plungers 14 are permitted to move outwardly by the cam lobes and during this time fuel from the feed pump enters the pumping chamber. In order to control the quantity of fuel which flows to the pumping chamber a throttle 30 is provided the setting of which is determined by a speed sensitive governor. The governor incorporates manually adjustable means whereby the quantity of fuel which is supplied to the engine can be increased or decreased as and when desired.

The operation of the apparatus so far described is as follows. Consider that the delivery passage 20 has just registered with a delivery port 21 and that the plungers 14 have just started their inward movement under the action of a pair of cam lobes. As the distributor rotates the plungers will be moved inwardly and fuel contained within the pumping chamber will flow by way of the longitudinal passage 16 to the delivery port and during this time the plate valve 17 will be lifted from its seating. When the plungers have moved inwardly to their maximum extent, the flow of fuel as described above will cease and the plate valve under the action of its spring, will close. As the distributor further rotates the inlet passages are brought into register with the inlet ports and a quantity of fuel flows to the pumping chamber to move the plungers outwardly. As mentioned above the quantity of fuel which flows to the pumping chamber during this period is determined by the throttle 30. During further rotation of the distributor the cycle described above is repeated and fuel is supplied to the engine cylinders in turn.

At the end of the injection period and owing to the action of the plate valve 17 a considerable pressure is locked off in the outlet port 21 and in the line which connects the outlet port to the associated nozzle. In previous pumps of this type this pressure has been partially relieved by providing for a predetermined quantity of fuel to fioW back into the pumping chamber by way of the longitudinal passage and the delivery passage at the end of the injection stroke. In the present example a longitudinal groove 31 is formed in the periphery of the distributor 12 and this is positioned behind the delivery passage 20 so that the longitudinal groove will be brought into communication with the outlet port after the delivery passage has moved out of communication therewith. The longitudinal groove is in communication with a circumferential groove 32 formed in the periphery of the distributor and this is in constant communication with a passage formed in the body part which breaks into at a point intermediate its ends, a cylinder 33 formed in the body part. One end of the cylinder is in communication with the inlet of the feed pump and mounted within the cylinder is a valve member 34 which is urged towards the other end of the cylinder by a coiled compression spring 35 located between valve member and an adjustable abutment located at or adjacent said one end of the cylinder. The abutment comprises a cylindrical member 36 slidable within the cylinder and having an aperture formed therein so that the adjacent end of the valve member 34 is exposed to the inlet pressure of the feed pump. The cylindrical member 36 is shaped for co-operation with an adjuster 37 operable from the exterior of the body part and by which means the force exerted by the spring on the valve member can be adjusted.

The valve member is provided with a neck 38 intermediate its ends and the annular space defined by the neck and the Wall of the bore 33 is in communication with the inlet of the feed pump by way of an axial passage 39 formed in the valve member. When the apparatus is at rest and with the valve member moved to its fullest extent by the spring it is arranged that the passage which communicates with the circumferential groove 32 is disposed substantially mid-way between the necked portion of the valve member and the end thereof against which the spring bears. Moreover, the portion of the valve member which extends from said passage towards the necked portion thereof is of slightly reduced diameter so as to define with the wall of the bore an annular leakage path.

In use, when the longitudinal groove 31 on the periphery of the distributor is brought into communication with the outlet port fuel will flow from the latter by way of the leakage path. The length of the leakage path and the time during which the groove is in communication with the outlet port together with the pressure in the output port determine the amount of fuel which flows from the outlet port and therefore the amount of pressure relief which occurs. The other end of the bore 33 is in communication with the feed conduit 29 through an annular restricted passage and so the axial setting of the valve member will be determined by the output pressure of the feed pump and as the latter increases the valve member will move against the action of its spring and the length of the leakage path will be decreased. By adjustment of the adjuster 37 the apparatus may be adjusted for use with a particular engine and by suitable choice of the area and length of the leakage path any required characteristic may be obtained. Thus, by varying the amount of pressure relief which occurs it is possible to obtain a control of the shape of the maximum fuel curve over the speed range of the apparatus.

In an alternative arrangement not illustrated, the plate valve is omitted however, the cam lobes are so shaped that the plungers 14 are held at their innermost position until after the groove 31 has moved out of register with the outlet port, i.e. after the pressure in the pipe line and outlet port have been relieved.

In addition, by preventing any relief at cranking speeds the apparatus can be arranged to supply fuel for starting purposes. This can be achieved by arranging for the valve member to be moved under the action of its spring, to a position to cover the point of entry into the bore 33 of the passage which is in communication with the longitudinal groove 31.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

1. A liquid fuel pumping apparatus for supplying fuel to an internal combustion engine and comprising in combination, a body part, a distributor member rotatably mounted in the body part, the distributor member in use, being driven in timed relationship with the engine with which the apparatus is associated, an injection pump arranged to deliver fuel to a delivery passage formed in the distributor member, an outlet port with which the delivery passage registers during the delivery of fuel by the injection pump, means for preventing the return flow of fuel from the outlet to the injection pump, a restricted leakage path, said restricted leakage path including a groove formed on the distributor member for registration with said outlet port after the delivery passage has moved out of register therewith, passage means interconnecting said groove with a port formed in the wall of said bore, an elongated valve member slidable axially within the bore and a clearance defined between a portion of said valve member and the wall of said bore, said clearance forming part of the restricted leakage path and defining the restrictor of the leakage path, the axial position of the valve member determining the degree of restriction offered by said restrictor.

2. An apparatus as claimed in claim 1 in which the setting of said valve member is varied in accordance with the speed at which the apparatus is driven.

3. An apparatus as claimed in claim 1 including a feed pump for supplying fuel under pressure to said injection pump, valve means for controlling the output pressure of the feed pump so that the pressure varies in accordance with the speed at which the apparatus is driven, the output pressure of the feed pump acting on an end of said valve member, a spring acting on the valve member in opposition to the force exerted by the fuel pressure, so that the setting of the valve member is dependent upon the speed at which the apparatus is driven.

4. An apparatus as claimed in claim 3 including a restriction through which the output pressure of the feed pump is applied to said end of the valve member.

5. An apparatus as claimed in claim 4 in which said means comprises a one way valve disposed intermediate the injection pump and said delivery passage.

6. An apparatus as claimed in claim 4 in which the injection pump includes a plunger and an actuating cam, said means being constituted by an extension of said cam so that the plunger is held in a fixed position when the delivery of fuel to the outlet has ceased.

7. An apparatus as claimed in claim 5 in which the valve member under the action of its spring and when the apparatus is at rest moves to close said leakage path so that when starting the associated engine an excess of fuel will be supplied to the engine until the output pressure of the feed pump has increased sufiiciently to move the valve member.

8. An apparatus as claimed in claim 6 in which the valve member under the action of its spring and when the apparatus is at rest moves to close said leakage path so that when starting the associated engine an excess of fuel will be supplied to the engine until the output pressure of the feed pump has increased sufficiently to move the valve member.

References Cited UNITED STATES PATENTS 2,997,093 8/1961 Harris 10341 X 3,100,449 8/ 1963 Dahl 1032 3,107,661 10/1963 Kemp. 3,115,304 12/ 1963 Humphries. 3,331,327 7/1967 Roosa. 3,352,245 11/1967 Wolff 103-2 3,364,863 1/ 1968 Olszewski et al.

DONLEY J. STOCKING, Primary Examiner W. J. KRAUSS, Assistant Examiner US. Cl. X.R. 10341

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