US3578881A

US3578881A - Liquid fuel pumping apparatus for supplying fuel to an internal combustion engine

Info

Publication number: US3578881A
Application number: US796315*A
Authority: US
Inventors: Dorian Farran Mowbray; Kenneth Albert Walters Kemp
Original assignee: CAV Ltd
Current assignee: CAV Ltd
Priority date: 1968-02-01
Filing date: 1969-01-31
Publication date: 1971-05-18
Anticipated expiration: 1988-05-18
Also published as: FR2001122A1; ES363416A1; DE1904779C3; DE1904779A1; GB1248039A; DE1904779B2

Abstract

A fuel injection pump having a plurality of pumping plungers mounted in separate bores and actuated by individual cams the plungers being moved inwardly by the lobes of the cams to discharge fuel from the pumping chambers through valve controlled outlets, each bore having a spill opening which at a predetermined position during the inward movement of each plunger, communicates with the pumping chamber to terminate the flow of fuel through the outlet. Each spill opening is closable by a valve for the purpose of providing an excess of fuel and the flow of fuel into each pumping chamber is controlled by a common throttle valve.

Description

United States Patent Inventors Dorian Farrar Mowbray Burnharn; Kenneth Albert Walters Kemp, Ealing, England Appl. No. 796,315

Filed Jan. 31, 1969 Patented May 18, 1971 Assignee C.A.V. Limited London, England Priority Feb. 1, 1968 Great Britain 5138/68 LIQUID FUEL PUMPING APPARATUS FOR SUPPLYING FUEL TO AN INTERNAL COMBUSTION ENGINE 6 Claims, 5 Drawing Figs.

US. Cl 417/206, 417/253, 417/495 Int. Cl. ..F04b 23/12, F04b 25/00, F04b 39/10 Field of Search 103/2, 2

(.1), 154, 41, 41.1, 41 (S), 169; 418/205, 206, 248, 253, 293, 294, 495 (inquired) [56] References Cited UNITED STATES PATENTS 3,071,074 1/1963 Bessiere 103/2(.1)UX 3,309,996 3/1967 Rosselli 103/41 3,312,209 4/1967 Chmura.... 103/2X 3,313,282 4/1967 Dreisin.... 103/41X 3,385,221 5/1968 Parks 103/41 3,396,663 8/1968 Bratten 103/4 1X 3,433,159 3/1969 Kemp 103/2 3,438,327 4/1969 Thompson 103/41 Primary ExaminerCarlton R. Croyle Assistant Examiner.lohn J. Vrablik Attorney-Holman, Glascock, Downing and Seebold ABSTRACT: A fuel injection pump having a plurality of pumping plungers mounted in separate bores and actuated by individual cams the plungers being moved inwardly by the lobes of the cams to discharge fuel from the pumping chambers through valve controlled outlets, each bore having a spill opening which at a predetermined position during the inward movement of each plunger, communicates with the pumping chamber to terminate the flow of fuel through the outlet. Each spi1l opening is closable by a valve for the purpose of providing an excess of fuel and the flow of fuel into each pumping chamber is controlled by a common throttle valve.

LIQUID FUEL PUMPING APPARATUS FOR SUPPLYING lFUlEL TO AN INTERNAL COMBUSTION ENGINE This invention relates to liquid fuel pumping apparatus for supplying fuel to an internal combustion engine and has for its object 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:

FIG. 1 is a sectional side elevation of the apparatus,

FIG. 2 is a sectional plan on the line A-A of FIG. 1,

FIG. 3 is a sectional end elevation generally on the line C'C of of FIG. 1,

FIG. 4 is a section on the line B-B of FIG. 3, and

FIG. 5 is anend view of the apparatus of FIG. 1 with parts removed for the sake of clarity.

Referring to the drawings there is provided a body part consisting of an upper portion 11 and an integral lower portion 12. The lower portion is provided with a bore which extends the full length of the body part and in which is mounted a cam shaft 14. The cam shaft is provided with three cams 15 at axially spaced intervals and each cam has three angularly spaced lobes 16 which cooperate with the wall of the bore to act as bearings for the cam shaft. At one end the bore is closed by an end closure 17 through which an extended end of the cam shaft extends. This extended end of the cam shaft is adapted for connection to the engine with which the apparatus is associated and for mounting the apparatus on the associated engine the end closure which is retained relative to the body part by bolts 18, is provided with a flange 19. In order to prevent escape of fuel along the shaft a seal 20 is provided in the housing.

The other end of the cam shaft mounts the rotary part of a vane type' feed pump indicated at 22. The inlet of the feed pump is in communication with an inlet chamber 23 and provided in this chamber, is a spring 24 which acts to urge the port block of the pump into contact with the rotor. Fuel flows to the inlet chamber by way of a fuel inlet 25. The fuel inlet 25 is connected by way of a filter element 28 and a pair of

nonreturn valves

26 and 27 to an inlet 29. Also provided is a priming pump 30 which incorporates a spring loaded pumping element 31 which is manually operable and which when depressed forces fuel from its pumping chamber past the nonretum valve 26. When the pumping element moves under the influence of its spring the nonreturn valve 27 opens to permit fuel to flow into the pumping chamber of the priming pump ready for the next pumping stroke thereof.

Formed in the upper portion 11 of the body part are three bores which are aligned with the earns 15 respectively. Each bore accommodates a pumping plunger 41 the lower ends of which bear against roller shoes 42 respectively the latter supporting rollers 43 respectively for cooperation with the cam lobes 16. The roller shoes 42 are guided by the opposed surfaces 44 respectively of a slot which is formed in the body part and means is provided to prevent axial movement of the rollers. Considering firstly the roller which cooperates with the center cam there is provided at opposite ends respectively of the roller a locating member 45. Each locating member is of generally rectangular form having a curved surface at its lower end which cooperates with a cylindrical surface 46 fonned on the cam shaft intermediate adjacent cams. The upper portion of the locating member is provided with a slot 47 to receive an ear 48 formed on the adjacent end of the roller shoe and in this manner the locating members are retained from angular movement about the axis of rotation of the cam shaft and they prevent axial movement of the roller. A similar locating member 45 is provided at the left-hand end of the cam shaft this locating member being slidable upon a cylindrical portion of the cam shaft which is positioned between the adjacent cam 15 and a pulley 50 the purpose of which will be described. At the opposite end of the cam shaft the locating member 51 is of annular form but having a projecting tongue in which the slot 47 is defined. The bases of the slots 47 constitute stops for the ears 48 and the arrangement is such that at the lowermost position of the plungers the rollers leave the surface of the cam to permit relubrication of the cooperating surfaces. The gap is very small and is too small to show on the drawings.

The open ends of the bores 40 are closed by delivery valves respectively indicated at 52 in FIG. 3 each delivery valve comprises a body portion 53 which at one end is screw threaded for mounting in the upper portion 11 of the body part and which at its other end defines a pipe connection whereby a pipe may be secured thereto. In use the pipe is connected at its other end to a fuel injection nozzle unit incorporating a spring loaded control valve. The body portion 53 is provided with a stepped bore 54 and slidable within the bore 40 is a plug 57 also incorporating an axial passage. The plug is provided with a peripheral flange which engages with the step in the bore 54 to limit the extent of movement of the plug. The end of the passage in the plug adjacent the body portion 53 defines a seating with which cooperates a valve element 56 which is loaded by a coiled compression spring 55. In use, as fuel is expelled from the bore 40 the plug 57 together with the valve element 56 move against the action of the compression spring until further movement of the plug is prevented. During this time fuel flows to the pipe but continued flow of fuel from the bore 40 lifts the valve element 56 from its seating. When the flow of fuel from the bore 40 ceases the valve element 56 closes onto its seating and the plug together with the valve element return to the position in which they are shown in the drawing under the action of the coiled compression spring 55. During this movement a predetermined quantity of fuel flows from the pipe.

Each bore 40 is provided with a circumferential groove 58 and the grooves 58 are in communication with each other and also with a passage 59. The passage 59 is controlled by a manually operable valve 60 so that flow of fuel through the passage 59 can be controlled as desired. Furthermore, each bore 40 is provided with a second annular groove 61 and again the grooves 61 are in communication with each other and with a passage 62 FIG. 2 which terminates in a port 63 formed in the wall of a bore 64. The axis of the bore 64 is disposed parallel to the axis of rotation of the cam shaft and mounted within the bore is a throttle valve 65 having a groove 66 formed on its periphery and disposed intermediate its ends. The groove 66 is in communication with a passage 67 which communicates with the outlet of the feed pump 22. Moreover, for controlling the outlet pressure of the feed pump a spring loaded relief valve 68 is provided this being illustrated in FIG. 4. The throttle valve is urged in one direction by the action of a governor spring 69 and movement in this direction increases the effective opening of the port 63. Movement of the throttle valve in the opposite direction is accomplished by a centrifugally operable mechanism 70 which is driven by means of a belt 71 from the pulley 50.

The governor spring comprises a first relatively strong spring 72 and a second relatively weak spring 73. The two springs are separated by an abutment member 74 which is a cup-shaped form and is slidable on the internal periphery of a cup shaped part 75 which is mounted for sliding movement in a wider portion of the bore 64. The position of the cup-shaped part 75 is controlled by an operator adjustable member 76 which is operable from the exterior of the apparatus.

Each plunger 41 is provided with a blind stepped bore 80 the wider end of which extends from the end of the plunger remote from the cam shaft. The narrower end of the bore is in communication with a circumferential groove 81 which is formed on the periphery of the plunger. Furthermore, the step defined between the wider and narrower portions of the bore 80 defines a valve seating for a ball valve 82, and the extent of movement of the ball valve away from its seating is controlled by a pin 83. The wider portion of the bore 80 is also in communication with a circumferential groove 84 formed on the periphery of the plunger.

The operation of the apparatus will now be described considering plunger movement from the position shown in FIG. 3. As the cam shaft rotates inward movement of the plunger 41 will occur as the roller 43 rides up onto the cam lobe 16. During the initial movement of the plunger fuel will be expelled from the pumping chamber which is defined intermediate the plunger and the plug, through the passage 59 this is of course assuming that the valve 60 is open. When the end of the plunger covers the groove 58, fuel will flow through the axial passage in the plug 57 as described and injection of fuel will take place to the engine. This injection of fuel continues until the groove 84 registers with the groove 58 and at this point providing the manually operable valve 60 is open the remaining fuel in the pumping chamber escapes therefrom by way of the passage 59. During the inward or upward movement of the plunger the ball valve 82 is in sealing engagement with the seating. At all times during the movement of the plunger the grooves 61 and 81 are in register with each other and at the end of the inward movement of the plunger and when the roller 43 has cleared a cam lobe 16 fuel under pressure will flow into the bore 80 past the ball valve 82 by way of the grooves 81 and 61, the passage 62, the port 63 and the groove 66 from the outlet of the feed pump. The quantity of fuel which flows depends upon the effective opening of the port 63. The flow of fuel as described causes the plunger to move towards the position in which it is shown in FIG. 3 and if the port 63 is fully open the plunger will actually assume the position in which it is shown in FIG. 3. if the opening of the port 63 is reduced, the plunger will not have time to reach the position in which it is shown. In HO. 3, the plunger is shown in the position in which the normal maximum quantity of fuel is delivered to the engine but ifthe manually operable valve 60 is closed fuel will be unable to escape through the passage 59 both at the beginning and at the end of the stroke of the plunger. The result of this is that an excess of fuel will be supplied to the engine for starting purposes only. The manually operable valve 60 although it can be moved to a closed position by the operator will automatically be moved to an open position by means not shown, once the engine has started.

The opening of the port 63 is controlled in part by the mechanism 70 and in part by the operator adjustable member 76. The mechanism 70 in conjunction with the governor springs 72 and 73 acts as a speed sensitive governor of a wellknown type. As the speed at which the engine operates increases then with a given setting of the member 76 the springs 72 and 73 will be compressed thereby reducing the opening of the port 63. Conversely if the speed decreases the opening of the port 63 will be increased thereby increasing the quantity of fuel which is supplied to the engine.

It will be noted that the relief valve 68 allows fuel to discharge from the passage 67 into the various chambers defined in the apparatus. in particular it allows fuel to discharge into the bore in which the cam shaft is accommodated. This fuel acts as the lubricant and coolant for the various working surfaces and additionally acts to cool the driving belt 71. Surplus fuel is returned to the fuel inlet by way of a spring relief valve 90 which is located in the housing 21 which accommodates the various fuel supply passages and which also carries the priming pump and the filter. in addition the cavity within the housing 21 is provided with a bleed 91 through which a restricted flow of fuel takes place to a drain which is conveniently, the fuel tank. This drain allows for the escape of any air or vapor which may collect in the upper portion of the chamber.

In order to stop the engine with which the apparatus is associated a shut off valve 86 provided this being operable from the exterior of the pump and sewing to control communication between the outlet of the feed pump and the port 63. It is to be noted however that the shut off valve is disposed downstream of the relief valve so that when it is closed and before the engine has stopped, excessive pressures will not be developed at the outletpf the feed pump.

The apparatus described has the particular advantage that no springs are required to effect the return motion of the pumping plungers. The absence of the springs removes the problem of corrosion which occurs on the springs and seriously reduces their life.

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

We claim:

1. A liquid fuel pumping apparatus for supplying fuel to an internal combustion engine and comprising a body part, a plurality of bores defined in the body part, outlets from pumping chambers at one end of the bores, plungers slidable within the bores, cam means for effecting inward movement of the plungers towards said one end of the bores thereby to discharge fuel through said outlets, each cam means including a cam having a plurality of lobes, a drive shaft rotatable within the body part, each cam being mounted on the drive shaft, the cam lobes cooperating with the wall of a bore within the body part to define bearings for the shaft, inlet conduits formed in the body part and plungers, said conduits communicating with a source of fuel under pressure and with the pumping chambers, nonretum valves in said conduits respectively, said nonreturn valves serving to prevent flow of fuel through said conduits during the discharge of fuel from the respective pumping chambers, a throttle valve for controlling the rate of flow of fuel from said source to the pumping chambers during movement of the plungers away from said ends of the bores, spill openings in the walls of said bores, grooves on the plungers respectively for cooperation with said openings, said grooves communicating with the pumping chamber and serving at predetermined positions during movement of the plungers towards said ends of the bore to terminate the delivery of fuel through said outlets, and valve means operable to prevent flow of fuel through said spill openings to enable the apparatus to deliver an excess of fuel for starting purposes.

2. A pumping apparatus as claimed in claim 1 including rollers for cooperation with the cams respectively, means being provided to separate the rollers from the cams during rotation of the shaft thereby to facilitate lubrication of the working surfaces.

3. A pumping apparatus as claimed in claim 2 including shoes carrying the rollers respectively, each shoe defining ears which project beyond the ends of the respective roller and which engage in slots respectively formed in a pair of locating pieces accommodated in the body part, the locating pieces acting to locate the roller at the bases of the slots serving as stops to limit the movement of the roller.

4. A pumping apparatus as claimed in claim 3 including a centrifugally operable mechanism for varying the setting of said throttle valve said mechanism being driven from said shaft by means ofa belt.

5. A pumping apparatus as claimed in claim 4 including a governor spring acting on said throttle valve so as to increase the flow of fuel through the conduits in opposition to the force exerted by the centrifugally operable mechanism, manually operable means being provided to enable the force exerted by the governor spring to be adjusted.

6. A pumping apparatus as claimed in claim 5 in which the shaft carries the rotary part of a fuel feed pump, the fixed part of the feed pump being carried by the body.

Claims

2. A pumping apparatus as claimed in claim 1 including rollers for cooperation with the cams respectively, means being provided to separate the rollers from the cams during rotation of the shaft thereby to facilitate lubrication of the working surfaces.
3. A pumping apparatus as claimed in claim 2 including shoes carrying the rollers respectively, each shoe defining ears which project beyond the ends of the respective roller and which engage in slots respectively formed in a pair of locating pieces accommodated in the body part, the locating pieces acting to locate the roller at the bases of the slots serving as stops to limit the movement of the roller.
4. A pumping apparatus as claimed in claim 3 including a centrifugally operable mechanism for varying the setting of said throttle valve said mechanism being driven from said shaft by means of a belt.
5. A pumping apparatus as claimed in claim 4 including a governor spring acting on said throttle valve so as to increase the flow of fuel through the conduits in opposition to the force exerted by the centrifugally operable mechanism, manually operable means being provided to enable the force exerted by the governor spring to be adjusted.
6. A pumping apparatus as claimed in claim 5 in which the shaft carries the rotary part of a fuel feed pump, the fixed part of the feed pump being carried by the body.