US2657631A

US2657631A - Liquid fuel pump

Info

Publication number: US2657631A
Application number: US238631A
Authority: US
Inventors: Evans Fraser Mackie
Original assignee: CAV Ltd
Current assignee: CAV Ltd
Priority date: 1950-08-16
Filing date: 1951-07-26
Publication date: 1953-11-03
Anticipated expiration: 1970-11-03

Description

Nov. 3, 1953 F. M. EVANS LIQUID FUEL PUMP 2 Sheets-Sheet 1 Filed July 26, 1951 Nov. 3, 1953 F. M. EVAN S LIQUID FUEL PUMP 2 Sheets-Sheet 2 Filed July 26, 1951 Fig.3

I NS 1.14 7 h. IN

Patented Nov. 3, 1953 LIQUID FUEL PUMP Fraser Mackie Evans, Acton, London, England, assignor to C. A. V. Limited, Acton, London,

England Application July 26, 1951, Serial No. 238,631

Claims priority, application Great Britain August 16, 1950 6 Claims.

This invention relates to variable-delivery liquid fuel injection pumps for internal combustion engines, of the kind in which a reciprocatory plunger (or each of a plurality of such plungers) has mounted on it a slidably adjustable sleeve for controlling a spill passage in the plunger. The object of the invention is to enable the rate of output of such a pump to be automatically controlled in a simple manner.

According to the invention there is provided in a pump of the kind above specified, a control means comprising the combination of a spill chamber, a sleeve adapted to control communication between the spill passage in the plunger and the spill chamber, a throttle adapted to control a discharge passage from the spill chamber, a stop which determines the normal position of the sleeve, and a spring adapted to move the sleeve towards the stop, the liquid pressure in the spill chamber being utilised for moving the sleeve away from the said position.

In the accompanying drawings:

Figures 1, 2, 3 and 4 are sectional views illustrating diagrammatically four typical embodiments of the invention.

Referring to Figure 1, there is formed in the body a of the pump, a bore b in which is slidable the plunger c. The discharge stroke of the plunger is effected by a rotary cam d acting on a slipper e which supports one end of the plunger, the suction stroke being effected by a spring I.

The working chamber of the pump is supplied from the fuel inlet it through an annular chamber 12 and ports At the discharge end of the chamber g is arranged a delivery valve 70 loaded .by a spring m. Fuel discharged past the valve f .is delivered through the outlet 11..

In the body part a is formed a spill chamber 0, and adjacent to this chamber is formed a subchamber p, the two chambers being separated by an annular land q through which extends the sleeve 1- which is slidable on the plunger. The sleeve has formed on it a collar s which abuts against one end of the sub-chamber under the action of a spring t contained in the sub-chamber. The end of the sub-chamber against which the collar s abuts serves as a stop for determining the normal position of the sleeve r.

In the plunger 0 is formed the spill passage u leading from the working chamber of the pump 2 by way of radial ports '0 to an annular'groove w on the plunger, which groove is controlled by the sleeve. If desired a non-return valve :1: may be provided in the plunger, as shown, or elsewhere between the working chamber 9 and the subchamber p.

The drawing shows the plunger at the commencement of its delivery stroke. The first effect of the plunger during this stroke is to out oi the ports 7'. Later the fluid is discharged through the valve It. When the plunger approaches the end of this stroke, the groove w on the plunger passes out of the sleeve, and so allows fuel to escape to the spill chamber, so preventing further discharge through the valve k.

To enable the pump output to be automatically controlled, the spill chamber is provided with an outlet passage y leading to a passage .2 which communicates with the inlet chamber 2', and for controlling the rate of fiow through the passage y there is provided a throttle 2. In the example shown the throttle is adjustable by a lever which is operable manually or automatically. 0r alternatively provision may be made for adjusting the spring t. The sub-chamber p may also be arranged in communication with the passage 2.

The arrangement is such that so long as the output of the pump does not exceed a predetermined rate, then for a given setting of the throttle, the fuel entering the spill chamber will pass out to the passage 2 at a rate which will allow the spring t to hold the sleeve r in its normal position as shown in the drawing. But if the rate of pump output exceeds the predetermined amount, liquid fuel pressure will build up in the spill chamber sufficient to move the sleeve against the action of the spring t and so allow the liquid fuel to escape into the spill chamber at a correspondingly earlier period in the discharge stroke of the plunger, the extent of movement of the sleeve being dependent (for a given setting of the throttle) on the rate of output of the pump. Consequently, so long as the rate of actuation of the pump remains normal, the sleeve will remain in its normal position but when the said rate of actuation is exceeded, the sleeve will move and reduce the rate of fuel output from the pump.

' The normal setting can be varied by appropriate is essentially the same as that shown in Figure 1, but differs in the following details.

At one side of the spill chamber there is formed in the body part a of the pump, a cylindrical chamber 3 which contains a piston 4 loaded by a spring 5. The piston 4 is connected to the sleeve 1 by a bell-crank lever 6. The extent of movement of the piston 4 under the action of the spring 5 is limited by a projection 1 on the piston which can abut against the adjacent wall of the spill chamber, which wall serves as a stop. The spill chamber is provided with an outlet passage :1 which is controlled by the throttle 2. This throttle may be adjustable as shown, or alternatively the spring 5 may be adjustable. As in the arrangement shown Figure l, the pas-- sage y opens into a passage z'Iea-ding to the inlet chamber 2'. Also the chamber 3 is in communication with the passage 2.

The normal position of the. sleeve 1 is that shown in the drawing, and the sleeve remains in this position so long as a normal pressure exists in the spill chamber. But in the event of the rate of output of the pump exceeding a predetermined-amount, the pressure in the spill chamber increases'and-byits action on the piston 4, causes the latter to-move the sleeve r in the direction for allowing. fuel to escape from the working chamber of the pump at an earlier instant. during the delivery stroke of the plunger 0.

In the examples illustrated by Figures 1 and 2, only the'plu-nger c is shown. But it will be understood that two or more plungers may be provided, each having associated with it-a controlling sleeve 1', spillchambero, and-throttle 2 as above described.

Figure 3 illustrates an application of the .in-

- vention-to a pump'of the kind in which the reciprocatory motion of a single plunger serves to effiectthe pumping action, and which rotary motion of the plunger" about its longitudinal axis serves "to distribute successive discharges to each in turn of aplurality'of engineeylinders. the

example shown, reciprocation of the plunger is. eflected .by'the alternate ,actions of a rotary cam 9 on a lever t0, and 1a spring. Rotary motion isimparted to theplunger through helical gear wheels 12. Liquid .fuel is supplied: at-. the inlet 11., from which it passes through the chamber 2' tothe ports aqleading to-the working chamber g of the pump. During the deliveryp-strokepf the plunger 0 thealiquidpasses. down the axial boreu to a radial port ,t3zand thence, by way-:of alongitudinal groove [4 in-theplun-ger to each in turn of thev'outlet passages-15 (of which two are shown in the drawing).

The application ofthe {present invention $015136 pump shown in Figure 3 iszessentially'similar to that shown in Figure 1, corresponding Parts being identified by the same reference :letters.

Figure 4 illustrates the application of the ,inventionin a modified formtoa pumpo-f the kind shown in Figure 3. In this modification, .the plunger 0 has formed on it. a coaxial. extension 16, and the working chamber -g of. thepump is of annular form.. Liquid fuel is admitted to the working chamber from .an inleth through-acyli-ndrical-chamber t1, passages 18 and ports t9, and liquid can passfrom the-working chamber to the-bore u throughayradial port 26, vthebo-re it being closed at its upper end. On the plunger ;a ;.pist,on ;;2.. In. this. .exarnplerthe-spillchamber o is formed by the upper portion of the chamber 4 l1, and the sleeve 1' is held in its normal position against an adjustable stop 2| by the spring t. The spill chamber is provided with an outlet 1/ which is controlled by a throttle 2 and which opens into a passage 2 leading to the inlet chamber IT. The action of the sleeve r is essentially similar to that already described. When the plunger 0 approaches the end of its discharge stroke, the annular groove w on the plunger extension IG (which communicates with the axial bore w through ports Incomes opposite the passage 22 in the sleeve and allows liquid to escape trom the working chamber 9 to the spill chamber 0, So long as the rate of output of the pump remains below the amount determined by the throttle the sleeve-remains in its normal position, but when the rate is exceeded, the liquid pressure in the spill chamber moves the sleeve inoppositionto the spring t for effecting earlier discharge from the working chamber to the spill chamber.

As already mentioned, the sleeve in the example shown in Figure 4 is closed at one end, thus forming a chamber 24 between one end of the plunger extension and the closed end of the sleeve. This chamberis in permanentcommunication with the inlet chamber 1.! by way of a passage .25.

By this invention, automatic restrictionof the r f utput of pum c h ind des be to anvdesired am untecan-b f ct d a e y simpleand convenient manner.

Having thus described my invention what I ciaim as new and desireto securev by- Letters: Patout is:

1. In a variable-delivery liquid fuel injection pump-for an internal combustion engine, of the kind having a reciproeatory plunger means slidable in a bore, the combination comprising a spill chamber surrounding the plunger means, passage meansada-pted to afford communication between the eliecti-ve end of the plunger means and-the spill chamber, a sleeve surrounding the plunger means for controlling communication between the saidpassage-means and-the-spill chamber, a discharge-passage 'com-rminicating with the spill chamber,throttle-means insaid discharge passage for restricting -fiow therein, stop means for determining the position of the sleeve'to afford normal-pump output by permitting spill to occur'towards the end of the. plunger stroke, spring means for urging the sleeve towards the said step means, and piston means operatively associated with the sleeve and exposed ,to the liquid pressure afforded in the spill chamber .by

thea-ioresa-i'd throttle means whereby the sleeve will be moved away from "thestopv means and thereby reduce-the effective stroke-10f: the plunger when said-pressure overcomes the force otthe spring means.

2. A fuel pump accordingfto claim. 1, comprising a sub-chamber associated with :thespill chamber, the sleeve bei ng slidably' mounted. .on the plunger at apositidrrbetweerr thespillchamher and the sub-chamber, 'one'end of the sleeve being exposed' to pressure liquid in the spill chamber and the other end having a formation adapted to co-operate with a part of the subchamber wall which constitutes the stop means.

'3. A fuel pum paccording to claim I, in which the sleeve is slid'able on apart of the plunger extending. through the spill chamber and comprising a. spri'ng loade'd piston arranged to be subject to the liquid" pressure in" the spill chamher, an operative connection between said piston and the sleeve, and stop means engageable by the piston for determining the normal position of the sleeve.

4. A fuel pump according to claim 1, in which the plunger receives both reciprocatory and rotary movements, the rotary movement serving to distribute successive charges to a plurality of engine cylinders.

5. A fuel pump according to claim 1, in which the plunger receives both reciprocatory and rotary movements, the rotary movement serving to distribute successive charges to a plurality of engine cylinders, and in which the sleeve is associated with an extension of the plunger.

6. A fuel pump according to claim 1, in which the throttle means is adjustable.

FRASER MACKIE EVANS.

References Cited in the file of this patent UNITED STATES PATENTS 10 Number Name Date 2,187,151 Gillen Jan. 16, 1940 2,393,544 Lum Jan. 22, 1946 2,517,483 Haut et al Aug. 1, 1950