US3412682A

US3412682A - Liquid fuel pumps

Info

Publication number: US3412682A
Application number: US443027A
Authority: US
Inventors: Kemp Kenneth Albert Walters
Original assignee: CAV Ltd
Current assignee: CAV Ltd
Priority date: 1964-03-31
Filing date: 1965-03-26
Publication date: 1968-11-26
Anticipated expiration: 1985-11-26
Also published as: DK109622C; DE1451969B1; CH423358A; GB1057731A; BE661812A; ES311560A1; NL6504026A

Description

Nov. 26, 1968 K. A. w. KEMP 3,412,682

LIQUID FUEL PUMPS Filed March 26, 1965 3 Sheets-Sheet l Nov. 26, 1968 K. A. W. KEMP LIQUID FUEL PUMPS 3 Sheets-Sheet 2 Filed March 26, 1965 Nov. 26, 1968 K. A. w. KEMP LIQUID FUEL PUMPS Z5 Sheets-Sheet 5 Filed March 26, 1965 NN M United States Patent 3,412,682 LIQUID FUEL PUMPS Kenneth Albert Walters Kemp, London, England, assignor to CAN. Limited, London, England Filed Mar. 26, 1965, Ser. No. 443,027 Claims priority, application Great Britain, Mar. 31, 1964, 13,099/ 64 3 Claims. (Cl. 103-2) ABSTRACT OF THE DISCLOSURE The invention relates to liquid fuel pumps for supplying fuel to an internal combustion engine and of the kind comprising a body part, an injection pump mounted within the body part and operable in timed relationship to an engine with which the pump is associated, and a passage within the body part through which fuel can be supplied to the injection pump during each filling stroke thereof, said passage being in communication with a source of fuel the pressure of which is dependent upon the speed of rotation :of the engine.

The object of this invention is to provide such a pump in a simple and convenient form.

According to the invention a pump of the kind specified includes a cylinder formed in the body part, one end of said cylinder being in communication with said source, a plunger slidably mounted in said cylinder, the position of said plunger serving to control the flow of fuel through said passage, resilient means urging said plunger towards said one end of the cylinder, a restriction through which the outer end of the cylinder is in communication with said source, and valve means operable to allow fuel to escape from the other end of the cylinder, the arrangement being such that when said valve means is operated the pressure of fuel in said other end of the cylinder will be reduced and the position of the plunger, and

hence the quantity of fuel flowing through the passage, will be determined by the pressure of fuel acting on the end of the plunger in opposition to the force exerted by the resilient means, and when said valve means is not operated the pressure of fuel at the opposite ends of the cylinder will be substantially the same and the position of the plunger will be such as to allow a maximum quantity of fuel to flow through said passage.

In the accompany drawings:

FIGURE 1 is a sectional side view of one example of a liquid fuel pump incorporating one example of the invention,

FIGURE 2 is a plan view of part of the pump shown in FIGURE 1,

FIGURE 3 is a sectional view taken on the line 33 of FIGURE 1,

FIGURE 4 is a sectional view taken on the line 4-4 of FIGURE 1,

FIGURE 5 is an enlarged scrap view of part of the pump shown in FIGURE 1,

FIGURE 6 is a scrap view of part of the pump shown in FIGURE 1,

FIGURE 7 is a diagrammatic view of a tractor transmission mechanism Iand engine, and

FIGURE 8 is an enlarged view of the gear selector gate of the transmission mechanism shown in FIGURE 7.

Referring to the drawings there is provided a body part 10 in which is mounted a rotary cylindrical distributor member 11 which is coupled to an input shaft 12 arranged to be driven in timed relationship to an engine 13 with which the pump is associated. Within the distributor is formed a transverse bore 14 in which are mounted a pair of reciprocable plungers 15 and which are arranged to be moved inwardly, as the distributor rotates, through the intermediary of a pair of rollers 16 respectively, by cam lobes (not shown) formed on an annular cam ring 17 mounted for angular movement within the body. Also formed in the distributor is a longitudinally extending passage 18 which at one end is in communication with the transverse bore and at its other end is in communication with a radially disposed delivery passage 19 The delivery passage 19 is arranged to register, in turn, with a plurality of equi-angularly spaced delivery ports. constituted by passages 20, formed in the body part 10 and which :are adapted to be connected by pipe lines to injection nozzles 21 mounted on the engine. The aforesaid registration with one of the ports takes place during the whole time the plungers 15 are being moved inwardly so that liquid fuel contained within the transverse bore 14 will be displaced to a combustion space of the engine.

At another point the longitudinal passage is in communication with a plurality of equi-angularly spaced and radially disposed inlet passages 22 which are arranged to register, in turn with an inlet port 23 formed in the body part. The inlet port 23 is in communication with a control port 25, by way of a passage 24, and the control port is in communication with the outlet 26 of a feed pump 27.

Moreover, the effective size of the control port 25 can be varied by varying the angular setting of a valve member 28 which has a groove formed therein and the arrangement is such that when an inlet passage 22 registers with the inlet port 23 fuel will flow from the outlet of the feed pump to the transverse bore 14 to move the plungers 15 outwardly. The aforesaid registration takes place only during the time when the delivery passage 19 is out of register with the passages 20 and during the time when the rollers 16 are clear of the cam lobes. By adjusting the setting of the valve member 28 the rate at which fuel can flow to the bore 14 can be controlled and hence also the amount of fuel delivered to the engine is controlled.

The feed pump 27 is provided with an inlet 29 in the body part and this is in communication with an inlet port 30 formed in a hollow part 31 secured to the body part. The part 31 has mounted therein a tubular filter element 32 and a relief valve which includes a spring loaded element 33. One end of the element 33 is exposed to the pressure of fuel delivered by the feed pump and controls the size of a spill port 34 and and arrangement is such that the feed pump always pumps more fuel than is delivered to the engine with the result that the output pressure of the feed pump is controlled in a manner which is dependent upon the speed of the engine and which increases with the speed thereof.

As previously mentioned the cam ring 17 is angularly adjustable to vary the time of delivery of fuel to the engine. This adjust-ment is achieved by a spring loaded piston 35, mounted in a chamber 36, and which is connected to the cam ring by a radial peg 37. Fuel is supplied to one end of the cylinder 36 to move the piston in opposition to its spring, from the outlet 26 of the feed pump, and since the pressure of fuel is dependent upon the speed of rotation of the engine, the angular setting of the cam ring and hence the timing of injection of fuel to the engine is also dependent upon the speed of the engine. The fit of the piston 35 within the cylinder 36 is slack so that leakage occurs therebetween. Moreover, a check valve 38 inincorporated in the supply passage to the cylinder 36 and this closes to prevent fuel passing from the cylinder to the supply passage due to the interaction of the rollers with the cam lobe.

The angular setting of the valve member 28 is conveniently controlled by a mechanical governor which includes weights 39 which are mounted to be rotated by the drive shaft 12, and which act on an axially movable flanged collar 40. The axial movement of the collar is resisted by a governor spring 41 which is mounted between one end of a pivotal lever 42. and an operator adjustable member 43, the other end of the lever 42 bearing upon the collar. Furthermore, said one end of the lever is connected by tie rod 44 to the member 28 and the arrangement is such that as the speed of rotation of the engine rises the collar 40 will be moved axially by the weights against the action of the governor spring and during this movement the member 28 will be moved angularly to reduce the quantity of fuel delivered to the engine. At some speed an equilibrium position will be reached and if the speed of the engine falls, as for instance when an increased load is applied to the engine, the force applied to the collar by the weights will be reduced and the member 28 will be moved to increase the fuel supplied to the engine to cater for the extra load. The setting of the operator adjustable member 43 can be varied to vary the force imposed by the spring 41 on the lever and by this means the governed speed of the engine may be varied.

The engine 13 to which the pump is fitted is as shown in FIGURE 7, intended to be used for driving the road wheels 45 of a road vehicle through a conventional axle unit and a multispeed gearbox 46. Furthermore, as shown in FIGURE 8, the gearbox is provided with a selector lever 47 which moves within a selector gate 48. When a vehicle is in use it is often desirable to be able to limit the speed of the vehicle when the selector lever is set in the high gear position, i.e., when the speed of the engine is lowest for a given speed of the road wheels, but it is also desirable that the speed of the engine should not be limited when the selector lever is in one of its alternative positions so that full power may be obtained from the engine and transmitted to the road wheels as when negotiating a steep incline. In order to cater for this requirement means, which is described below, is embodied in the pump and said means is brought into operation by a switch 49 mounted in the gearbox 46 and arranged to be operated when the selector lever 47 is moved to the high gear position.

Referring now to FIGURES 3, and 6, said means comprises a cylindrical bore 50 longitudinally disposed within the body part and which intermediate its ends intersects the portion of the supply passage lying intermediate the control and inlet ports. Moreover, within the bore is slidably mounted a plunger 51 having a reduced portion 52 intermediate its ends, and this lies when the plunger is in the inoperative position as shown, in a position so that the iiow of fuel to the inlet port 23 is not restricted. Furthermore, the plunger is loaded towards one end of the cylinder by a coiled compression spring 53 which is interposed between the plunger and an axially movable abutment 54 mounted in the bore. The axial setting of the abutment can be pre-set from the exterior of the pump by an adjuster 55 having a tapered end which co-acts with the adjacent tapered end of the abutment.

The end of the plunger 51 remote from the spring, when in the inoperative position, bears against a stop defined by a plug 56, and this end of the plunger is arranged to be exposed to the outlet prsesure of the feed pump by way of a clearance defined between the plunger and the bore. Moreover, the space intermediate the plunger 51 and the abutment 54 is in communication with the feed pump outlet by way of a passage 57 in the plunger and this passage incorporates a restriction 57a. Furthermore, in the abutment 54 is formed an unrestricted passage 58 which places the aforesaid space in communication with the space at the end of the bore adjacent the tapered end of the abutment.

The end of the bore 50 adjacent the adjuster 55 is in communication with one end of a passage 59 in the body part 10, and the other end of this passage communicates with the space in which the weights 39 are accommodated, and this space communicates with a drain outlet 62. The passage 59 incorporates a valve intermediate its ends, and this includes a seating 60 and a closure member 61. The closure member as shown in FIGURE 3 is operable by an armature 63 movable by a solenoid 64. The solenoid is connected in circuit with the switch 49 and the latter is of the normally closed type. When the solenoid is deenergised the pressure of fuel acting on the closure member 61 moves it to allow fuel to flow through the passage 59.

In use, when the solenoid is energised the valve will be closed with the result that the pressure in the chamber defined intermediate the plunger 51 and the abutment 54 will be the same as the outlet pressure of the feed pump. As a result the fuel pressure acting on the plunger will be balanced and the plunger will be maintained in the position shown in FIGURE 5 by the spring 53. As previously stated, the flow of fuel to the injection pump when the plunger is in this position is not restricted. If now the solenoid is de-energised the valve will be opened and, as a result of this, fuel will flow from the chamber defined intermediate the plunger 51 and the abutment 54, and the restriction 57a will cause a pressure drop. As the output pressure of the feed pump increases the pressure drop will also increase and at a predetermined value the plunger will be moved against the action of the spring 53 with the result that the flow of fuel to the inlet port 23 will be restricted and the quantity of fuel which can be supplied to the engine and hence the speed of the engine will be limited. The degree of restriction depends upon the speed of the engine and consequently a governing action is created which is additional to the action of the main governor. The speed at which the restriction is imposed depends on the force exerted by the spring and this may be adjusted by means of the adjuster 55 and the setting of this will depend on the ratio of the gearing of the vehicle.

Although solenoid operation is preferred the valve member may be moved by mechanical or hydraulic means associated with the selector lever 47 of the gearbox.

Owing to the fact that the fuel pressure which acts on the end of the plunger remote from the spring has to pass through a restriction defined between the plunger and the wall of the bore the rate at which the plunger can move in either direction is restricted. This is particularly useful because oscillation of the plunger is minimised when the output pressure of the fuel pump varies rapidly.

In some vehicles a multi-ratio rear axle is provided in which case a further switch or switches may be provided to cause de-energisation of the solenoid when a high gear is selected.

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 a body part, and injection pump mounted within the body part and operable to supply fuel in timed relationship to the engine, a fuel supply pump located within the body part, valve means for control-ling the output pressure of the fuel supply pump in accordance with the rate at which the apparatus is driven, passage means through which fuel flows from the supply pump to the injection pump, a throttle for controlling the rate of fuel flow through said passage means, operator adjustable speed responsive governor means for determining the setting of said throttle thereby to control the quantity of fuel delivered by the injection, a plunger slidable within the body part and operable to limit the rate of fuel flow through said passage means irrespective of the setting of said throttle, resilient means biasing said plunger to a position in which no limitation of the rate at which fuel is supplied occurs and means operable from the exterior of the apparatus to permit the pressure of fuel developed by the supply pump to be applied to the plunger to move it in opposition to its resilient loading thereby to limit the rate of fuel flow when the speed at which the apparatus is driven exceeds a predetermined value.

2. An apparatus as set forth in claim 1 in which said plunger is mounted within a cylinder defined in the body part, a conduit through which one end of said cylinder communicates with the supply pump, a restriction through which the opposite ends of the cylinder are in communi cation with each other, and the valve means operable from the exterior of the apparatus to permit fuel to escape from said other end of the cylinder.

3. An apparatus as set forth in claim 2 including an adjustable abutment whereby the force exerted by said resilient means on the plunger can be varied.

References Cited UNITED STATES PATENTS 1,336,462 4/1920 Church "74-472 2,641,238 6/1953 Roosa -123-140 2,719,437 10/1955 Nallinger 74-472 3,209,613 10/1965 Potter 74- 472 10 3,286,543 11/1966 Porter 74-472 FRED C. MATTERN, JR., Primary Examiner.

W. I. KRAUSS, Assistant Examiner.