US3729274A

US3729274A - Injection pump with regulation of injection timing

Info

Publication number: US3729274A
Application number: US00156315A
Authority: US
Inventors: E Hatz; E Samitz
Original assignee: Motorenfabrik Hatz GmbH and Co KG
Current assignee: Motorenfabrik Hatz GmbH and Co KG
Priority date: 1970-07-02
Filing date: 1971-06-24
Publication date: 1973-04-24
Anticipated expiration: 1990-04-24
Also published as: DE2032704A1

Abstract

In a fuel injection pump for internal combustion engines, a reciprocable piston injects fuel on each compression stroke. The cylinder in which the piston reciprocates has an overflow port which is controlled by at least one control edge of the piston so as to effect injection during the portion of the compression stroke when the overflow port is closed. The beginning and/or end of injection are variably regulated relative to the compression stroke by a setting member which varies the stroke of the piston relative to the overflow port, and hence the elapsed time between the beginning of the compression stroke and the beginning and/or end of the injection.

Description

United States Patent [191 Hatz et al.

11] 3,729,274 5] Apr. 24, 19 73 INJECTION PUMP WITH REGULATION OF INJECTION TIMING [73] Assignee: Motorenfabrik Hatz KG, Ruhstort,

Germany [22] Filed: June 24,1971

[21] Appl. No.: 156,315

[30] Foreign Application Priority Data [56] References Cited UNITED STATES PATENTS Koster ..417/387 Bessiere ..417/387 3,029,737 4/ 1962 Bessiere ..417/387 3,492,947 2/1970 Paine ..417/490 FOREIGN PATENTS OR APPLICATIONS 736,380 6/1943 Germany ..417/493 Primary ExuminerWilliam L. Freeh AAZYISIHHI Examiner-John T. Winburn Atmrney-Larson, Taylor and Hinds [5 7] ABSTRACT In a fuel injection pump for internal combustion engines, a reciprocable piston injects fuel on each compression stroke. The cylinder in which the piston reciprocates has an overflow port which is controlled by at least one control edge of the piston so as to effect injection during the portion of the compression stroke when the overflow port is closed. The beginning and/or end of injection are variably regulated relative to the compression stroke by a setting member which varies the stroke of the piston relative to the overflow port, and hence the elapsed time between the beginning of the compression stroke and the beginning and/or end ofthe injection.

7 Claims, 5 Drawing Figures INJECTION PUMP WITH REGULATION OF INJECTION TIMING FIELD OF THE INVENTION The present invention relates to an injection pump, and in particular a fuel injection pump for internal combustion engines, in which the beginning and/or end of the injection is adjustable by means of a regulating device.

BACKGROUND AND SUMMARY OF THE INVENTION In the case of injection pumps with pistons arranged in a series and a driving shaft, use is generally made of an injection regulator or distributor which is used to produce a degree of preliminary turning of thecamshaft for the purpose of varying the moment of injection. In the case of injection pumps in an annular arrangement this control is brought about by relative movement of the driving ring. The reactant forces which in this case are imposed on the driving element are very powerful, particularly during the injection phase, so that the injection regulator or distributor which also is operative during this phase, has to overcome these reactionary forces to effectively perform the adjusting movement. For this reason it has been found necessary to operate the injection regulator or distributor with the assistance of a powerful centrifugal regulator or hydraulic adjusting means. Operating means of this kind, because of their robust construction, demand a large amount of space for their installation and involve a complicated and expensive structure. The resulting drawback is that such arrangements are not generally used.

It is an object of the present invention to avoid the drawbacks of these known constructions and to procure an injection regulating arrangement which can be operated to a large extent independently of these reactionary forces and consequently with small demands on adjusting effort, whereby such an arrangement can be used in injection pumps where space is limited, as for example in the case of pumps which are driven by the engine crankshaft and thus through nonadjustable driving cams.

This object is met in the present invention by the fact that the regulating device includes a feed member which is disposed in advance of the compression valve ofthe pump and is propelled to perform the feed movement and a setting member which varies the effective stroke of the feed member and thus determines the beginning and/or the end ofthe delivery.

In accordance with further features of the invention the setting member can either be adjustable by hand or by means of an operating device dependent on the rate of rotation ofthe engine.

In a preferred embodiment of the invention the feed member is in the form of a piston biassed by a return spring and movable in a feed chamber disposed in advance of the compression valve, this piston having at least one control edge which governs a return flow or overflow of the feed liquid.

The arrangement of the control edges on the feed member can be implemented in a multiplicity of ways within the scope of the present invention. Use may be made of control edges which are at right angles to the direction of travel of the feed member, in conjunction with a setting member with an inclined setting edge which limits the return movement of the feed member. As an alternative inclined control edges may be employed and the setting member may be in the form ofa toothed rod or rack which is used to angularly adjust the feed member.

In the case ofinjection pumps with cam driven pump pistons movable in an operating chamber, in accordance with a further feature of the invention the arrangement is such that the lower end of the feed member closes off the operating chamber so that the pump piston propels the feed member through a liquid cushion in the operating chamber.

A further embodiment of the invention is found in pumpshaving a reciprocating plunger, the arrangement here being that the feed member cooperates directly with the plunger and is operated thereby to perform a delivery stroke.

DESCRIPTION OF THE DRAWINGS Embodiments of the described with reference drawings, in which:

FIG. 1 is a longitudinal section through an injection FIG. 2 is a plan of a detail,

invention are hereafter to the accompanying FIG. 3 shows the pump in another operative position,

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 illustrates an injection pump the casing 10 of which is incorporated, in a manner known per se, in the motor housing (not shown) so that the piston 12 of the pump is driven at its lower end by a cam on the camshaft of the engine (directly or through the intermediary of rollers). As a general rule the pump casing 10 is flanged on the motor housing. The piston 12 of the pump operates in a chamber '14 which communicates through a suction duct 16 with an annular suction chamber 18. This suction chamber in turn is connected through a conduit (not shown) with a power source (fuel tank). The pump piston 12 is provided with a control groove 12a which communicates through

ducts

12b and 12c with the operating chamber 14 on the compression side of the pump piston 12.

The compression valve 20 of the pump is disposed in a valve body 22 and a screwed sleeve 26 holds it, and the return spring 24 thereof, in casing 10. The compression conduit 28 is mounted on the screwed sleeve 26 by means of a cap nut 30. The form and arrangement of the pump hitherto described is that ofa known form ofinjection pump. In accordance with the present invention, however, there is associated with this known form. of pump a feed member in the form ofa piston 32 which closes the cylindrical operating chamber 14 above piston 12 and defines a cylindrical feed chamber 34. in advance of the compression valve 20. A return spring 36 for the feed member 32 is arranged in this cylindrical chamber 34. A setting member 38 of rod form is displaceable in the pump casing 10 transversely to the common axis of the

cylindrical chambers

14 and 34. This member 38 has a forked end 38a' (FIG. 2) the upper surface of which, facing the compression valve 26, is slightly inclined to the axis. The fork 38a engages around a thin neck 32a provided in the feedpiston 32, suchwise that the upper edge 32b of ,the recess machined in the feed member 32 to form neck 32a seats on the inclined surface 38b of the setting member 38 and thereby holds this feed member at a predetermined level dependent on the positioning of the seating member. FIG. 1 illustrates the upper limit position, and FIG. 3 the lower limit position, of this member 32.

The feed chamber 34 is connected through a bore 32c, parallel with the axis of the pump and through a transverse duct 32d, with a control groove 32s at the periphery of feed member 32. A control duct 40 from the suction chamber 18 opens into this groove.

FIG. 1 shows the elements in the lower dead center position. If, from this position, the pump piston 12 performs a stroke in which the leading end thereof closes the reflux duct 16, this traps a cushion of liquid in the operating chamber 14 and this, during the further stroke of the piston 12, acts on the feed member 32 to cause it to perform a stroke against the action of its return spring 36. At the beginning of this stroke of the feed member 32 a certain amount of liquid first flows from the feed chamber 34 to the suction chamber 18,

- because the control groove 32: is still open through duct 40 to the suction chamber 1 8. As soonfhowever, as the lower edge of the control groove 32s slides past the duct 40 to close the latter, and thereby interrupt the return flow of liquid to the suction chamber, the actual feed of liquid or fuel then starts from the feed chamber 34 through compression valve 20 into compression conduit 28. This feed only stops when the lower trailing edge 32k comes into register with the overflow duct 40 and then permits an overflow from the operating chamber 14. At the end of this feed stroke the feed member 32 remains stationary at its uppermost position, whilst the pump piston 12 continues to carry out a residual part of its stroke, the control edge 12a coming into register with the overflow duct 16 during this residual part of the stroke to allow a return flow from the operating chamber 14 through this duct 16 as well. Thereafter the return movement of the feed member 32 commences under the action of spring 36.

During the return movement of piston 12 from the upper to the lower dead center position the operating chamber 14 fills again from suction chamber 18, the feed piston 32 returns to a position in which it engages the

setting member

38, 38a, and the feed chamber 34 also then fills from the suction chamber 18.

At this point it should be mentioned that the control edge 12a of the pump piston 12 has no direct influence in the present instance on the feed which is performed through member 32. Pump piston 12 is only used to produce a compressed cushion in the operating chamber 14 to provoke a stroke on the part of the feed member 32, i.e. to cause the feed of liquid. Care must requires a small operating effort. For this purpose, for

be exercised to see that the control edge 12a-of the piston is so related to thelower edge ofduct l6 that'a" pressure cushionremains in theoperating chamberduring a stroke of the pump pis ton 12 which is equ'al to" or more than the maximum stroke of feed member 32'.

This can beachieved by suitable dimensioning of'the angular setting of they pump piston 12 (full load setting).

Asregards the'considerations which now follow it is assumed that the adjustments in level by the setting member 38 of the feed member 32 produces an overall setting stroke V 2 mm between the two limit positions illustrated in FIGS. 1 and 3. In the regulated position seen in'FIG. l the overflow should be possible through a route U,-= 2 mm, whilst the actual effective length of the feed member 32 is G 8 mm. Moreover, for reasons of simplicity, the surface of the feed member 32 which is effective as far as performing the feed is concerned is assumed to be F mm From this it is found as shown by the diagramof FIG. 4 that the quantity returning or overflowing from the feed chamber 34 before the commencement of the feed by the feed member 32 is 200 mm and the beginning of the feed is initiated at Al corresponding to time t1. The

maximum quantity then forwarded until the end of the feed at A3 (time t3) is then M,=F-h,

where h =G (U +V,)

M,= 100 4=400 mm The injection which begins at A1 and terminates at A3 will thus, with the setting of FIG. 1 give a maximum injection quantity of 400 mm I In the setting of FIG. 3, however, because of the lower setting of the feed member 32, the setting stroke V 0, whilst U =4 mm. Thus in the second case the maximum quantity from A2 to A4 is The maximum quantity delivered is thus the same in both settings, but in that of FIG. 3 the commencement of the injection.(A2 at :2) and the end of the injection (A4 at t4) are much later than in the case of FIG. 1. Thus, for the same maximum injection quantities, in FIG. 1 there is an earlier injection time and in FIG. 3 a later injection time. Thus a required regulation or displacement of the injection time can be achieved by raising or lowering the starting position of the feed member 32 within the range of adjustment V by means of setting member 38. The pressures in the chamber 14 and the chamber 34 are both equal or approximately equal during the suction period and also during the compression period. The feed member 32 can therefore readily be adjusted at any time with the assistance of setting member 38 because the movement will only have to be performed against the pressure of return spring 36 at the most. Consequently the setting member can be adjusted either by hand or by a device which is dependent on the speed of the engine and only example, a small simple and inexpensive revolution governor can be used such as is already at present on theengine or can be added.

Again the pressure produced at the cooling fan of the engine, (dependent on the speed of revolution of the engine) or the reduced pressure in the exhaust pipe of theen'ginetalso dependent on the engine speed), could be exploited to act on the setting member 38 through a pressure regulator (piston or diaphragm). The choice of means for operating the setting member 38 will thus be suited to the prevailing operating conditions and requirements. in the embodiment of the invention illustrated in FIGS. 1 and 4 the setting of the starting and finishing of the injection is performed by permitting the overflow of a predetermined quantity of liquid before and after the injection. This has the advantage that the maximum quantity of injected liquid (full load quantity) remains the same. In the partial load range the overflow after the injection procedure will be eliminated, depending on the particular angular position of the pump piston in each individual case, and the injection period will terminate at the end of the actual pump piston stroke. The angular adjustment of the pump piston in the partial load range is mostly performed in any internal combustion engine by means ofa regulator which turns the pump piston so that the return flow duct 16 comes into communication with the control edge 12a of the piston 12 earlier than does the edge 32k with the return flow duct 40. Thus in the partial load range there is no overflow at 40 after the delivery movement of the feed member 32.

It is to be pointed out that, instead of using the principal of raising and lowering the feed member 32 by means of the setting member 38 in the case of control edges which are at right angles to the axis of travel of this member, as in the case illustrated and described above, use could be made ofa form of feed member as illustrated in FIG. 5, this being denoted 132 and having inclined control edges 132k and 132s. An angular rotation of feed member 132 and its

control edges

132s, 132k in relation to the return flow opening 40 can in this case be performed by means of a toothed rod 138 which engages in teeth 13211 at the periphery of the feed member 132. The delivery-effecting stroke of the feed member 132 is in this case regulated by angular rotation of this member to achieve the same effect as in the case of the first embodiment illustrated in FIGS. 1 to 4. Finally it is to be noted that instead of moving the feed member through a compressed cushion above the pump piston, this member could be given a mechanical drive, for example through a cam driven plunger the stroke of which is adjustable, for example by the speed regulator.

We claim:

1. In an injection pump for internal combustion engines, means defining a feed chamber having a fluid inlet and a fluid injection outlet, an injection valve controlling said outlet, a feed member reciprocably disposed in said feed chamber for effecting injection of fluid from said chamber through said outlet during a portion of its reciprocatory cycle, means for effecting reciprocation of said feed member, and setting means for selectively varying the timing of the injection portion of each cycle relative to the cycle, wherein said feed member includes a control edge extending at right angles relative to the axis of travel of said feed member, and wherein said setting means comprises a setting member having an inclined edge for variably limiting the extent of return movement of said feed member.

2. Apparatus as claimed in claim 1 wherein said setting means selectively varies the timing of the beginning ofinjection relativeto the cycle.

Apparatus as claimed in claim 1 wherein said setting means selectively varies the timing of the end of injection relative to the cycle. I

4. Apparatus as claimed in claim 1 wherein said setting means selectively varies the timing of both the beginning and end of injection relative to the cycle and without varying the quantity of fluid injected.

5. Apparatus as claimed in claim 1 wherein said feed chamber includes an overflow port, and wherein said feed member comprises a piston having at least one control edge controlling flow through said port and thus controlling the timing of the injection, and wherein said setting means comprises means for varying the relationship between said control edge and said overflow port.

6. Apparatus as claimed in claim 5 wherein said setting means varies the position of said control edge relative to said overflow port at the end of a return stroke of said piston following injection.

7. In an injection pump for internal combustion engines, means defining a feed chamber having a fluid inlet and a fluid injection outlet, an injection valve controlling said outlet, a feed member reciprocably disposed in said feed chamber for effecting injection of fluid from said chamber through said outlet during a portion of its reciprocatory cycle, means for effecting reciprocation of said feed member, and setting means for selectively varying the timing of the injection portion of each cycle relative to the cycle, wherein said feed member includes a control edge inclined relative to the axis of travel of said feed member, and wherein said setting means comprises a setting member for varying the angular setting of said feed member and its control edge relative to said fluid inlet.

Claims

2. Apparatus as claimed in claim 1 wherein said setting means selectively varies the timing of the beginning of injection relative to the cycle.

3. Apparatus as claimed in claim 1 wherein said setting means selectively varies the timing of the end of injection relative to the cycle.