US2118578A - Fuel injection pump - Google Patents

Description

May 24, 1938. G. J. TRAPF; A 2,118,578-

FUEL INJECTION PUMP Filed 'Aug. 15; 1935 3 Sheets-Sheet 1 INVENTOI? GLJ. Trap o.

May 24, 1938. G. J. TRAPP FUEL INJECTION PUMP Filed Aug. 15', 1935 3 Sheets-Sheet 2 .May 24, 1938. s. J. TRAPP FUEL INJECTION PUMP Filed Aug. 15, 1935 a Sheets-Sheet 5 [Inf/V701? 'earye J Trap 0. .5 7

I M Jifys Patented May 24, 1938 UNITED STATES PATENT OFFICE FUEL INJECTION PUIWP ited, London, England Application August 15, 1935, Serial No. 36,413 In Great Britain August 16, 1934 2 Claims.

This invention relates to fuel injection pumps for internal combustion engines, and more particularly to fuel injection pumps having a working plunger or piston of constant stroke reciprocating in a sleeve or cylinder which communicates through anon-return valve with the injection nozzle; the beginning and end of the injection period are determined by control grooves or the like, formed upon the plunger and cooperatingwith the fuel-admission and return or release ports in the cylinder wall, one of the grooves being provided with a helical or inclined edge for varying the point of opening of the respective port by relative rotation of the pump plunger and cylinder.

It is one object of the present invention to provide an improved construction of fuel injection pump which is simple to manufacture, and which provides two independent controls, for

varying on the one hand the quantity of fuel injected per stroke, and on the other hand the timing of the injection.

It is a further object of the invention to provide an improved construction in which the timing of the injection is adjusted by moving a cylinder sleeve axially, the arrangement being such that axial movement of the sleeve does not change the volume of the compression space, so that movement of the sleeve can be rendered extremely light, thus simplifying the governing arrangements which are usually associated with fuel injection pumps. The invention further provides an improved arrangement in which the usual cylinder and reciprocating plunger, to-

gether with those parts associated therewith, can be withdrawn readily as a single unit, thus facilitating examination and assembly, both before and after the pump is put into service.

It is a still further object of the invention to provide an improved port construction in the reciprocatory plunger and cylinder, said ports being. formed with comparatively long controlling edges which serve to produce rapid opening and closing, and which avoid the constricting tendency which is experienced when the ports in the plunger and/ or the cylinder are circular in shape.

Another object of the invention is to provide an improved inlet and spill passage arrangement in which the fuel rejected by the reciprocatory plunger after the point of cut-off is reached,

is delivered into a channel or passageway separate from the inlet passage serving the pump, the rejected fuel thus having an opportunity of becoming de-aerated before it is returned to the inlet passage.

The invention is illustrated by way of example in the accompanying drawings in which Figure 1 is a cross-sectional elevation through a fuel injection pump unit in which the cylinder sleeve is arranged for both axial and rotational 5 movement;

Figure 2 is a fragmentary view to an enlarged scale showing the arrangement of the port groove on the recip-rocatory plunger;

Figure 3 is a development diagram showing 10 the manner in which the ports coact, the cylinder sleeve being adjusted to produce a large injection;

Figure 4 is a diagram corresponding to Figure 3, the cylinder sleeve being adjusted to pro- 15 duce a small injection;

Figure 5 is a perspective view of the end of the plunger illustrated in Figures 1 and 2;

Figure 6 is a view corresponding to Figure 5 showing a modified construction; 20

Figure '7 is a fragmentary sectional elevation showing a modified cylinder and plunger assemblyin which the reciprocatory plunger is adapted for angular adjustment to vary the quantity of fuel injected; 7 25 Figure 8 is an enlarged fragmentary side View of the cylinder sleeve and plunger shown in Figure '7, looking from the left hand side;

Figure 9 is a similar view looking from the right hand side; 30

Figure 10 is a development diagram illustrating the action of the ports shown in Figure '7;

Figure 11 is a fragmentary perspective view of a modified form of plunger having a pair of diametrically opposite control grooves. 35

The general construction of one form of fuel injection pump according to the invention is illustrated in Figures 1 and 2, said pump comprising a body III, the lower part of which is arranged to form a casing H for a cam shaft 40 I2. As is usual with this form of pump, the cam shaft l2 can carry a plurality of cams for operating a series of pumps arranged side by side, one for each cylinder of the engine, but for simplicity one pump only is illustrated in Fig- 45 ures 1 and 2. A cam 13 formed upon the shaft I2 is adapted to co-operate with a roller 54 carried by a tappet 15, the latter being adapted to slide vertically in a tappet guide it, the tappet guides for the whole set of pumps preferably 50 being formed as a single detachable unit secured by screws, one of which is indicated at ll. The upper part of the body It! is bored for the reception of a tubular cylinder casing l8, which latter is normally held upon its seating I9 by 55 downward pressure exerted upon the flange 29 of a delivery valve guide 21 through the medium of a screw-threaded plug member 22. The dclivery valve is indicated at 23 and is held upon its seating by a spring 24 in the usual manner; but the lower part of the housing 2| is extended downwardly to form a stationary plunger 25 bored co-axially at 26 to take the delivery fuel. Disposed between the stationary plunger 25 and the cylinder casing l8 is a sleeve 21 which serves as a cylinder and is arranged for limited vertical sliding movement as well as rotational movement for controlling the injection of fuel, as will be hereinafter explained. The means used for imparting these movements to the cylinder sleeve 21 comprise a pair of rack bars 28, 29, which engage with rotating members in the form of pinions 39 and 3| respectively.

The pinion 30 is screw-threaded internally for engagement with a screw-thread 32 formed upon the exterior of the cylinder sleeve 21, so that, assuming this sleeve to be held against rotation, endwise movement of the rack bar 28 will turn the pinion 30, thus moving the sleeve 21 either in an upward or a downward direction, since the pinion 30 is anchored against endwise displacement by suitably forming the body with a shoulder, indicated at 33. The pinion 3| serves to locate the cylinder sleeve 21 in any desired angular position and for this purpose splines 34 are formed down the exterior of the cylinder sleeve 21 and engage the pinion 3|, so that an gular movement imparted to the latter by means of the rack bar 29 is correspondingly transferred to the cylinder sleeve 21.

Operating within the lower end of the cylinder sleeve 21 is a reciprocatory plunger 35 the lower end of which is provided with a head 36 engaged by a readily removable washer 31, the latter serving as an abutment for a helical compression spring 38 for returning the plunger 35 during the suction stroke. The washer 31 is slotted radially at 39 so that it can be readily removed by temporarily relieving the pressure of the spring 38, thus freeing the lower end of the plunger 35 and enabling the latter to form part of a readily removable assembly unit comprising in addition to the plunger, the cylinder sleeve 21, the pinion 30, the cylinder casing I8, and the upper plunger 25, together with the associated delivery valve guide 2|. It will be observed from Figure 1 that by removing the plug member 22 and slacking off a check screw 40, the whole of this unit can be withdrawn in an upward direction for cleaning, replacement, inspection or any other purpose.

The body I is formed with a common longitudinally extending inlet passage 4| communieating through a hole 42 in the cylinder casing l8 with a control port 43 formed in the cylinder sleeve 21, while for the purpose of enabling fuel to flow into and out of the annular space 44 around the top of the cylinder sleeve 21 as the latter is adjusted axially, and also for relieving any pressure which might occur in said space 44 due to leakage of fuel past the fixed plunger 25, a passage 45 is arranged to communicate with the inlet passage 4|.

As will be seen from Figure 5, the upper end of the plunger 35 is formed with a helical port groove 46 which opens into the end surface of the plunger 35 for communicating with the working space in the cylinder sleeve 21, said groove 46 being adapted to co-operate with a port opening formed in the cylinder sleeve 21, as indicated at 41 (Figs. 3 and 4). This port is substantially triangular in shape and is arranged so that its lower edge 43 lies substantially parallel with the con trolling edge 49 of the groove 46, while its upper edge 50 is similarly parallel with the upper controlling edge of the plunger 35. This controlling edge is arranged obliquely by cutting away the corner of the plunger, the purpose of this being to compensate for the slight axial movement of the cylinder sleeve 21 which is caused when the pinion 30 is rotated, with a View to adjusting the amount of fuel. The edge 5| therefore defines a helix having a pitch and direction of progress similar to that of the screwthread 32. It will be understod that the plunger and sleeve may be provided with a pair of oppositely disposed helical grooves, as shown in Figure 11 for the purpose of providing a large port opening and also equalizing the pressure on the plunger, the position of such a second groove being indicated at 46a, while the corresponding controlling edge on the end of the piston is similarly indicated at 5la. In this case a second inlet passage similar to the passage 4| can be incorporated in the body In.

The action of the ports is shown clearly in Figures 3 and 4 in which the top of the plunger 35, as shown in full lines at 52, is in the position corresponding to the lowest part of its active stroke for the particular position of the cylinder port 41. Assuming that the plunger 35 is travelling upwardly, it will be seen that the controlling edge 5| is just about to complete the closing of the cylinder port 41, and thereafter until the plunger assumes the position indicated in dotted lines at 53, said port 41 is closed by the uncut substantially triangular portion 54 of the plunger 35. At the position 53, however, the controlling edge 49 of the groove 46 passes across the edge 48 of the port 41, thus opening the working space of the pump to the inlet pipe, by way of the groove 46 and so causing the injection of fuel to cease. It will be readily seen that by shaping the port 41 so that its edges 48 and 50 are parallel respectively with the controlling edges 49 and 5|, a comparatively large area of passage for the release of rejected fuel and a comparatively quick cut-01f are provided, thus avoiding the constricting effect which is produced when a circular port is arranged to slide over a straight or oppositely curved controlling edge, as in fuel injection pumps which have hitherto been proposed.

Figure 4 corresponds to Figure 3 but the cylinder port 41 has been moved to the right by rotation of the pinion 3| (see Figure l), a slight rising movement being also imparted to the cylinder sleeve 21 due to the screw-thread 32, so that the port 41 in fact follows the slope of the controlling edge 5|. In this case it will be seen that injection ceases when the piston reaches the position indicated in broken lines at 55, i. e., when the controlling edge 49 begins to overlap the controlling edge 48 of the port 41, the amount of fuel injected being proportional to the distance a travelled by the plunger 35 as compared with the distance 72 shown in Figure 3.

Axial displacement of the cylinder sleeve 21 by rotation of the pinion 30 brings about movement of the port 41 in the direction of the arrows c in Figure 3, and it will be seen that this causes the beginning and the end of injection to be advanced or retarded simultaneously and to the same extent, thus providing a timing control which does not alter the quantity of fuel injected.

As before mentioned, the controlling edge 5| iii on the plunger 35 must be of the same hand as the screw-thread 32. The direction of rotation of the pinion 30, to produce, say, upward movement of the cylinder sleeve 21 may require to be reversed, and in this case a thread of opposite hand would be necessary, the top of the plunger being shaped as shown in Figure 6, due compensation being made in the helix angle of the port groove 46.

In the arrangement shown diagrammatically in Figure '7, the cylinder sleeve 21 instead of being rotated about its axis in order to produce variations in the quantity of fuel injected, is held against rotation by the engagement of the check screw 40 with a longitudinal slot 56 formed in the end portion at least of said cylinder sleeve 21, thus enabling a limited endwise movement to be imparted to said sleeve by actuation of the rack 28 and the pinion 30. The quantity of fuel injected per stroke, however, is regulated by rotational adjustment of the plunger 35, and in the construction illustrated, said plunger is formed with a diametral pin ladapted to engage in slots 58 formed in a sleeve 59, which latter is attached to or produced in one with the pinion 3|.

A modified port arrangement, which is incorporated in Figure 7 will be seen more clearly by reference to Figures 8 and 9 and to the development diagram (Figure which latter represents the whole circumference of the reciprocatory plunger 35 and the internal surface of the cylinder sleeve 21, the ports in the sleeve being shown in full lines and those in the plunger by dotted lines. The end part of the plunger 35 is drilled axially at 60 and diametrically at 6|, the extremities of the hole 8| being extended to form an inlet groove 62 arranged circumferentially, and a spill-port 63 extending obliquely as shown. At one side the cylinder sleeve is formed with an inlet port 54 communicating with an inlet passage 65 in the body ID (see Figure 7), while at the opposite side of the cylinder, a spill port 66 is formed obliquely and similarly communicates with a spill-passage 61. This construction again provides extensive controlling edges which produce substantial passages almost immediately after overlapping, but otherwise works in accordance with known principles.

In the position of the ports shown in Figure 10, the fuel injection is just about to commence, as the port 62 with its controlling edge 68 is just passing off the port 64 with its controlling edge 69. Injection will thereafter take place until the controlling edge 10 of the port 63 reaches the controlling edge H of the port 66, when the pressure in the working space of the pump will be released by the passage of rejected fuel downwardly through the bore 60, 6|, through the spill port 66 into the passageway 61. This passageway can communicate with the inlet passage 65 for conducting the rejected fuel back to the cylinder, or alternatively said rejected fuel may be returned to the usual supply tank. It is found in practice that this construction gives the advantage of allowing the rejected fuel to become de-aerated before passing once again into the pump cylinder. Rotational adjustment of the reciprocatory plunger 35 to the right (as seen in Figure 10) has no effect on the commencement of injection, as the port 62 is merely moved to a position indicated at 62a. On the other hand, the port 63 assumes a position 63a in which it requires less vertical movement of the reciprocatory plunger 35 before the controlling edge 1E) overlaps the controlling'edge H, thus terminating injection. Axial movement of the cylinder sleeve, say in an upward direction, moves both of the ports 64 and 66 also in an upward direction, thus retarding the beginning and the end of injection to an equal extent without altering the quantity of fuel delivered.

It will be understood that the invention is not limited to the constructions illustrated and the axially adjustable cylinder sleeve and stationary plunger may be used in fuel injection pumps of different design. Moreover it is evident that in the embodiments illustrated, the port arrangement shown in Figures 1 to 6 may be used in conjunction with a plunger which is arranged for rotational adjustment, and in this case the controlling edge 5| will normally extend circumferentially. Also where the ports shown in Figures 7 and 10 are employed with a cylinder sleeve controlled as in Figure 1, the ports 62 and 64 would be arranged obliquely to compensate for the action of the screw thread 32.

What I claim is:--

1. A fuel injection pump comprising a body formed with a bore, a cylinder casing fixedly mounted within but removable from the bore, a tubular cylinder mounted within the casing and capable of sliding axially therein, a one-piecereciprocating plunger closing the lower end of the cylinder, means for reciprocating the plunger, an axially bored fixed plunger extending into the upper end of the cylinder to close the latter, a one-way delivery valve closing the bore in the fixed plunger, a fuel inlet passage in the body, a port in the cylinder wall communicating with said inlet passage, a controlling edge on the plunger determining the beginning of fuel injection and another edge thereon determining the end of injection, means for moving the cylinder axially to alter the time of the beginning and the ending of injection simultaneously and to the same extent, means for bringing about relative rotation between the reciprocating plunger and the cylinder to vary the quantity of fuel delivered at each stroke, and a passage connecting with the inlet passage, an annular space embracing the fixed plunger and bounded by the slidably adjustable cylinder, the arrangement being such that the cylinder casing when removed from the body carries with it as a unit the cylinder, the fixed plunger and the reciprocating plunger.

2. A fuel injection pump comprising a body formed with a bore, a cylinder casing fixedly mounted within but readily removable from said bore, a tubular cylinder mounted within said casing and slidable axially therein, a reciprocating plunger closing the lower end of said cylinder, means for reciprocating said plunger, an axially bored fixed plunger extending into the upper end of the cylinder, the fixed and reciprocating plungers being of equal diameter, and the bore of the cylinder being constant in diameter throughout its length, an outward radial flange formed in one with the fixed plunger and arranged to bear upon the upper end of the cylinder casing to keep the latter in position, a plug member screw threaded into the body and bear ing upon said outward radial flange, a fuel inlet passage formed in the body, a controlling edge on the reciprocating plunger arranged to coact with a port in the cylinder to determine the commencement of injection, another edge on the reciprocating plunger coacting with an edge on the cylinder to determine the end of injection, means for bringing about relative rotation between the cylinder and the reciprocating plunger to regulate the quantity of fuel injected at each stroke, means for axially moving the cylinder within the cylinder casing to change the timing of the injection without altering the quantity, and a passage connecting with the inlet passage the space between the upper end of the cylinder and the outward flange formed upon the fixed plunger.

GEORGE JOSEPH TRAPP.

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