US3403629A

US3403629A - Fuel injection pump for internal combustion engines

Info

Publication number: US3403629A
Application number: US649280A
Authority: US
Inventors: Eheim Franz; Hofer Gerald
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1966-07-19
Filing date: 1967-06-27
Publication date: 1968-10-01
Anticipated expiration: 1985-10-01
Also published as: AT283819B; DE1275328B; FR1493671A; GB1187074A

Description

F. EHEIM ET AL Oct. 1, 19.68

FUEL INJECTION PUMP FOR INTERNAL COMBUSTION ENGINES 4 Sheets-Sheet 2 Filed June 27, 1967 hwawrops z ranz [1967M Gera/d v 5P5? F. EHEIM ET AL 3,403,629

FUEL INJECTION PUMP FOR INTERNAL COMBUSTION ENGINES Oct. 1, 1968 4 Sheets-Sheet Z5 Filed June 27, 1967 fiwsxvrog? Franz [HE/M Gera/d HOPE? F. EHEIM ET Oct. 1, 1968 4 Sheets-Sheet 4 Filed June 27, 1967 United States Patent 3,403,629 FUEL INJECTION PUMP FOR INTERNAL COMBUSTIQN ENGINES Franz Eheim and Gerald Hiifer, Stuttgart, Germany, as-

signors to Robert Bosch GmbH, Stuttgart, Germany, a company of Germany Filed June 27, 1967, Ser. No. 649,280 Claims priority, application France, July 19, 1966,

Claims. for. 10s 41 ABSTRACT OF THE DISCLOSURE determined r.p.m.

Background of the invention This invention relates to a fuel injection pump for internal combustion engines and more particularly concerns a fuel injection pump that includes a fuel pressure dependent regulating means to vary the quantity of the fuel delivered by the pump as a function of the revolution of the engine.

Fuel injection pumps including a regulating shuttle to open a discharge channel for terminating the injection of fuel before the piston pump reaches the end of its delivery stroke are known in the art. Such a pump is described, for example, in US. Patent No. 3,122,100. In these devices there is provided an auxiliary pump driven synchronously with the main fuel pump. The auxiliary pump delivers pressure to one side of a spring biased piston shuttle which reciprocates along a predetermined path in response to said pressure which drops in a controlled manner as the main pump piston performs its return stroke. As the rpm, of the engine increases, the level of said pressure also increases and as a consequence, a fluid abutment appears that shifts the path of said reciprocating shuttle. During its reciprocation along the shifted path, the shuttle clears a discharge channel through which fuel may flow from the main pump working chamber thus terminating the fuel delivery before the piston pump completes its pressure stroke. The greater the rpm, the greater the pressure buildup and the more substantial the shift of the path. Further, the greater the shift of said path, the sooner the shuttle clears the discharge channel during the deiivcry stroke of the pump piston and, as a result, the more the delivered fuel is reduced.

The displacement of the shuttle against its return spring occurs in a forced motion with the auxiliary pump transmitted by a liquid (fuel) volume enclosed between the auxiliary pump and the shuttle.

It is a disadvantage of the devices of this type that the said liquid volume, having a certain degree of compressibility, forms, together with the mass of the shuttle, a system capable of oscillation and excitable by the accelerating thrust to which the shuttle is exposed at the beginning of each displacement against its return spring. The resulting oscillations disturb the regulation of fuel delivery since they cause an undesirable change in the timing of the opening of the discharge channel and consequently cause an undesirable change in that portion of the pressure stroke during which fuel delivery takes place. As a result there is an unstable relation between the r.p.m. of the engine and the quantity of the delivered fuel under full load conditions.

Summary of the invention The aforcnoted disadvanttge of the presently known fuel injection pumps of this type is obviated according to the invention by controlling the quantity of delivered fuel under full load conditions independently of the shuttle motion.

Briefly stated, according to the invention the pump working chamber of the main pump is provided with a second discharge channel which, as long as the regulating shuttle returns to its initial position, is cleared by the pump piston before the regulating shuttle clears the first discharge channel, According to a preferred embodiment the novel pump is designed in such a manner that the regulating shuttle clears the first discharge channel prior to the opening of the second discharge channel only after the fluid abutment has attained a predetermined height.

In order to ensure the delivery of an additional fuel quantity during the starting of the engine, according to a further feature of the invention there is provided a slide valve in the second discharge channel clearing the latter only after a predetermined r.p.m. has been reached.

The invention will be better understood and further objects and advantages will become more apparent from the ensuing detailed specification of several exemplary embodiments taken in conjunction with the drtwings.

Brief description of the drawings FIG. 1 is a partial axial sectional view of one embodiment;

FIG. 2 shows superimposed graphs indicating the travel of the shuttle and the pump piston as a function of the rotational angle of the pump piston actuating means;

FIG. 3 shows the embodiment depicted in FIG. 1 with a modified mechanism for the delivery of an additional fuel quantity during the starting of the engine; and

FIG. 4 is a partial axial section-a1 view of a second embodiment.

Description of the embodiments Turning now to FIG. 1 there is shown a fuel injection pump comprising a piston 1 which, actuated by conventional means not shown, is adapted to perform an axial reciprocating motion for the delivery of fuel and a rotary motion for distributing the fuel into predetermined engine cylinders. Piston 1 comprises three steps or portions 1a, 1b and 1c. Step 1a which has the smallest diameter of the three steps and which operates in a terminal cylinder 2 serves as the fuel delivering piston of the injection pump proper. The cylinder 2 is disposed over and about the piston step 1a in a hat-like manner and defines with its inner face and with the end face of step In the Working chamber 3 of the fuel pump. The piston step 1b which is of the largest diameter and which operates in the cylinder 4, defines therewith an auxiliary pump for the hydraulic actuation of a regulating shuttle 5. The step 10 disposed between steps 1a and 1b has an intermediate diameter and functions as a distributor.

Step 10 is provided with a circumferential annular groove 6 into which merges a plurality of axially extending longitudinal grooves 7, the number of which equals that of the engine cylinders to be supplied with fuel. Thus, if the fuel pump is associated with a four cylinder engine, the annular groove 6 is axially extended toward step 1b by four spaced longitudinal grooves 7. The annular groove 6 communicates with the pump working chamber 3 through oblique ports 9 and an axial bore 8 all disposed in step 10. During each suction stroke of piston 1, one of the longitudinal grooves 7 communicates through a bore 10 with the suction chamber 11 to supply the pump working chamber 3 with fuel from the suction chamber 11 through bore 10, longitudinal grooves 7, annular groove 6, oblique bores 9 and axial bore 8.

From the axial bore 8 there extends further a radial bore 12 which widens into a longitudinal groove and which, during each pressure stroke of the piston 1, con meets the pump working chamber 3 with one of the pressure conduits 13 (only one shown), each connected to an engine cylinder and each containing a check valve 14. If the fuel pump serves a four cylinder engine, there are four pressure conduits 13 equidistantly spaced about the axis of piston 1.

The auxiliary pump formed by step 112 of piston 1 and cylinder 4 is supplied with fuel from the suction chamber 11 through a bore 15 and longitudinal axial grooves 16 on step 1b during each suction stroke as one of the longitudinal grooves 16 communicates with the supply bore 15. During the pressure stroke the fuel is forced from the working chamber 16a of the auxiliary pump through one of the longitudinal grooves 16 and a channel 17 into a cylinder 18 in which the regulating shuttle 5 is reciprocatingly disposed. In channel 17 there is disposed at check valve 19 closing channel 17 during suction strokes. The bore 15 and the channel 17 lie in different planes normal to the piston axis so that when One of the longitudinal grooves 16 communicates with the supply bore 15, the channel 17 is closed by the step 1b and conversely, the supply bore 15 is closed by the step 1b as long as the channel 17 communicates with one of the longitudinal grooves 16.

The suction chamber 11 is supplied with fuel through a pressure channel 21 by means of a supply pump (such as a gear pump) 20 driven by the engine with which the presently described fuel injection pump is associated. In order to obtain a rpm. dependent pressure in suction chamber 11, the pressure channel 21 is connected with the suction channel 23 through a bypass channel 22 in which there is disposed a throttle 24 controlled by a piston valve 25. The piston valve 25 is on one side exposed to the fuel pressure prevailing in the pressure channel 21 and is displaced against the force of a return spring 26 to an increasing extent with increasing r.p.m. As a result, the effective area of throttle 24 is accordingly varied to control the bypass flow from pressure channel 21 through bypass channel 22.

The regulating shuttle 5 is displaced in the cylinder 18 against the return spring 27 by the fuel forced into cylinder 18 by the auxiliary pump assembly 112, 4 and 16a during the delivery stroke of the piston 1. Between two delivery strokes of the piston 1 the regulating shuttle 5 returns into its position of rest which is determined by a fixed abutment 28. During this return motion the regulating shuttle 5, driven by the return spring 27, displaces one part of the fuel from the cylinder 18 through channel 62 and controlled throttle 61 back into working chamber 16a for the purpose of dampening the return motion of the regulating shuttle 5. The working area of the throttle 61 is adjustable by means of setting screw 63.

Above a predetermined number of revolutions per minute, depending upon the setting of throttle 61, the fluid pressure in cylinder 18 becomes effective, that is, the regulating shuttle 5 does no longer return into its initial position against abutment 28. Stated in different terms, the increase in pressure in cylinder 18 forms a fluid abutment and, the initial and terminal point of the reciprocating motion of regulating shuttle 5 shifts in the direction of the spring 27 as the fuel pressure increases in cylinder 18 beyond said predetermined r.p.m. As a result, the quantity of fuel forced by step 1a by each delivery stroke to one of the injection nozzles (not shown) will decrease as it will be described hereinafter.

Under full load conditions the engine-rpm. is suflici- 4t ently low so that the initial position of the regulating shuttle 5 is defined by the stationary abutment 28. Only with decreasing load and consequently increasing r.p.m. does the fluid abutment become etfective and shifts the initial and terminal point of the reciprocating motion of regulating shuttle 5 in the direction of spring 27.

The regulating shuttle 5 is provided with a circumferential annular groove 29 which is in constant communication with portion 30a of a first discharge channel and interconnects the portion 30a with a second portion 38b of this discharge channel when the regulating shuttle 5, in its motion against the force of compression spring 27, has traveled a determined path. The other end of channel portion 30a merges into the cylinder in which the piston step 1c reciprocates and is in continuous communication with the pump working chamber 3 through the annular groove 6, oblique ports 9 and axial bore 8. It is to be noted that the bore 10 and the discharge channel portion 30a lie in defterent planes normal to the axis of piston 1. The discharge channel portion 30b communicates with the suction chamber 11 through a channel 31. At the moment when the annular groove 29 of regulating shuttle 5 establishes communication between the

discharge channel portions

38a and 30b during the delivery stroke, the fuel injection is interrupted since the fuel which continues to be displaced from the pump working chamber 3 by piston step 1a is directed into the suction chamber 11 through axial bore 8, oblique ports 9, the

first discharge channel

30a, 30b and the channel 31.

According to the invention, with the pump working chamber 3 there is associated a second discharge channel 32 controlled by the piston 1.

The second discharge channel 32 extends from a circumferential annular groove 33 provided in the cylinder face associated with the piston step 10 and is, during normal operation, in communication with the suction chamber 11 through a channel 32a. Communication is established between the discharge channel 32 and the pump working chamber 3 toward the end of the pressure or delivery stroke of piston 1 when the annular groove 6 registers with the annular groove 33. At this moment the fuel injection is interrupted since the fuel flows from the pump working chamber 3 into the suction chamber 11 through the axial bOre 8, the oblique ports 9, the annular grooves 6, 33 and the channels 32, 32a (during normal operation the slide valve 34, the function of which will be described hereinafter, does not obstruct communication between channels 32 and 32a).

The stroke portion necessary to obtain registry between annular grooves 6 and 33 is selected to be of such a magnitude that under full load conditions, that is, as long as there is no fluid abutment for shuttle 5 in cylinder 18, the said registry takes place before the portions 30a 30b of the first discharge channel are interconnected by annular groove 29 of the regulating shuttle 5. This means therefore that under full load conditions the termination of the fuel injection will be determined by the second discharge channel 32 controlled by the pump piston 1 and will not be terminated by the regulating shuttle 5. The aforenoted oscillations of the regulating shuttle 5 (referred to in the introduction), caused by the compressibility of the fuel, the mass of the regulating shuttle 5 and the acceleration during the start of the stroke of piston step 112 have thus no eifect on the fuel regulation under full load conditions. In order to securely exclude such an effect, the axial spacing of

portions

30a, 30b and the axial dimension of annular groove 29 are designed in such a manner that under full load conditions the regulating shuttle 5 after the annular groove 6 has registered with annular groove 33 has to travel a safe distance before it establishes communication between the

portions

30a and 30b of the first discharge channel. Thus, the fluid abutment, as the load decreases (partial load) and the revolution of the engine increases, first has to reach a predetermined height in cylinder 18 before both discharge channels are opened at the same time. Beyond such an rpm, the fuel control is taken over by regulating shuttle 5 since now it establishes communication between

discharge channel portions

30a and 30b before the pump piston 1 establishes communication between discharge channel 32 and the pump working chamber 3. If the rpm. further increases, the level of the fluid abutment further raises in cylinder 18 and consequently, during each delivery stroke of piston 1, the length of time during which communication exists between channel portions 30a, 301; will increase. As a result, the fuel delivered through pressure conduit 13 will gradually decrease.

Turning now to FIG. 2, there are shown two superimposed diagrams to facilitate the understanding of the operation of the aforedescribed structure. In the upper diagram the ordinate C indicates the traveled path of the regulating shuttle 5 while along the abscissa there is measured the angle of rotation a of an actuating means (usually a rotary cam) causing a reciprocating motion of piston 1. In the lower diagram the ordinate indicates the piston stroke C of the piston 1 and the fuel quantity Q delivered by the pump whereas the abscissa is the same as in the upper diagram.

In the upper diagram there are shown three curves: a solid line I, a dash-dot line II, and a dashed line III. The solid line I describes the path of the shuttle 5 as long as it is permitted to return to the abutment 28.

The dash-dot line II shows the path of the shuttle 5 after the fluid abutment has increased to such an extent that the shuttle 5 opens the first discharge channel 30a, 3912 at the same time that the pump piston 1 opens the second discharge channel 32.

The dashed line III shows the motion of the regulating shuttle 5 and the height of the liquid abutment where the injected quantity is determined exclusively by the regulating shuttle 5.

The regulating shuttle 5 opens the first discharge channel 30a, 3012 each time when, in its upward motion against the force of spring 27, it reaches a position which, in the upper diagram of FIG. 2, corresponds to the horizontal line d.

In the lower diagram the sinusoidal line IV shows the motion of piston 1. The horizontal line d indicates the position of the piston 1 in which it establishes communication between the annular groove 6 and the second discharge channel 32 during its pressure stroke.

It is seen from the two diagrams, that the piston 1 at the moment communication is established between an nular groove 6 and the second discharge channel 32, has delivered a fuel quantity Q shown by the point of intersection f of the line IV with the horizontal line d If now the regulating shuttle 5 moves according to line I, the piston 1 establishes communication between annular groove 6 and discharge channel 32 at the moment (shown at f on line IV) when the regulating shuttle 5 has reached the point g Thus, it is seen that the regulating shuttle 5 has not yet reached the horizontal line d wherefrom it would establish communication between the

portions

30a and 30b of the first discharge channel. Thus, during full load conditions it is the piston 1 which determines the injected quantity by establishing communication between the second discharge channel 32 and the working chamber 3.

Assuming now that the rpm. of the engine increases, the regulating shuttle 5 no longer returns to abutment 28 due to the appearance of the fluid abutment in cylinder 18. When this fluid abutment has reached the height 12,, the line II, now representing the new stroke of the shuttle 5, intersects the horizontal line d at point g at the same moment when the line IV of the pump piston 1 intersects the horizontal line :1 in point f Thus, both discharge channels are opened simultaneously. Up to and including the height b of the fluid abutment, the injected fuel quantity remains unchanged at value Q.

If the revolution of the engine increases to such an extent that the fluid abutment attains the height b then the new stroke of the regulating shuttle 5 will be described by the line III. When the shuttle 5 operates from this height, it first opens

discharge channel

30a, 30b at point g which corresponds to point f of line IV which, as seen, lies before the point f (the point where the piston 1 opens the second discharge channel 32). Due to the effect of the fluid abutment, the injected fuel quantity will thus be limited by the regulating shuttle 5 to Q It is apparent from the diagrams of FIG. 2 that the fluid abutment has to attain a certain height (larger than b in order that the regulating shuttle 5 has an effect on the quantity control of the delivered fuel.

According to a further feature of the invention, there is delivered, during the starting of the engine, an additional quantity of fuel which is automatically discontinued when the engine has reached a predetermined revolution per minute.

Turning once again to FIG. 1, there is disposed for the aforenoted purpose, between the second discharge channel 32 and the channel 32a, a slide valve 34 adapted to reciprocate in a cylinder 35. Cylinder 35 is connected by means of channel 33 with the suction chamber 11 in which a r.p.rn.-dependent pressure prevails. A compression spring 37 urges the slide valve 34 into its initial position against the abutment 38. Slide valve 34 is provided wth a circumferential annular groove 39 which is in constant communication with the discharge channel 32. The channel 32a, on the other hand is by means of the valve portion disposed above the annular groove 39, closed as long as the slide valve 34 is in its initial position as shown in FIG. 1. When the pressure in the suction chamber 11 reaches a predetermined value subsequent to the starting of the engine and after a predetermined r.p.m. has been reached, the slide valve 34 is displaced against the force of spring 37 towards a fixed abutment 38a whereby communication is established between channels 32 and 32a through the annular groove 39. It is only at this moment that the second discharge channel 32 may become operative in decreasing the fuel quantity to be delivered. The timing when the slide valve 34 interconnects channels 32 and 32a may be adjusted by varying the force of the spring 37 or by varying the pressure-rpm. relation in the suction chamber 11.

In order to render the control of the slide valve 34 generally independent of the possible pressure fluctuations in the suction chamber 11, the channel 36 interconnecting cylinder 35 with suction chamber 11 is provided with a throttle 4% Cylinder 35 in which the slide valve 34 operates is, laterally of the spring 37, connected by means of a channel 41 with a chamber 42 in which there prevails a constant low pressure and which houses the driving means (not shown) for the piston 1. In the channel 41 there is preferably disposed a throttle 43.

The effect of the slide valve 34 is also shown in the diagrams of FIG. 2. As long as the slide valve 34 blocks the second discharge channel 32 from channel 32a, the entire quantity delivered by the piston 1 is injected until the time the regulating shuttle 5 establishes communication between the

portions

30a and 30b of the first discharge channel. This occurs at point g where the line I intersects the horizontal line d. At this moment the piston 1 (curve IV) has reached the point f It is thus seen that during starting the quantity injected equals Q wherefrom the additional quantity is Q Q The fuel quantity which is supplied by the piston 1 under full load conditions, that is, before the opening of the first or the second discharge channels, may be additionally set by axially shifting the cylinder 2 in which the step 1a of piston 1 operates. The cylinder 2 is urged against an adjustable setting screw 45 by means of a compression spring 44 which at its other end engages the pump housing. The cylinder 2 has a plurality of radial bores 46 whereas the step 1a is provided with a plurality of radial bores 47 which merge into the axial bore 8. Preferably, the radial bores 46 and 47 lead into a respective annular groove which partially overlap one another in the position of rest of the pump piston 1 as shown in FIG. 1. The cylinder 2 is disposed in a chamber 48 which communicates through a channel 49 with the pressure conduit 21 of the gear pump it Or, instead, the chamber 48 may be connected with the cam chamber &2 directly by means of a channel (not shown). It is seen that the delivery of the fuel may start only when no communication exists between the radial bores 46 and 47. In the example shown in FIG. 1, the necessary path for the piston 1 to travel for such a separation is h. This stroke portion which depends upon the axial position of the cylinder 2 results in a displaced quantity Q shown in the lower diagram of FIG. 2. This stroke portion thus causes the quantities Q Q and Q to be decreased by the quantity Q In the preceding description the stroke portion 11 was assumed to be zero (this may be obtained by an appropriate setting of the screw 45).

In FIG. 3 there is shown a further feature of the fuel injection pump for providing an additional fuel quantity for the starting of the engine. In addition to the embodiment shown in FIG. 1, the regulating shuttle 5 is delayed in its operation during the delivery of the additional fuel quantity for starting the engine. For this purpose, from the working chamber 16a of the auxiliary pump comprising step 112 and cylinder 4 there extends a port 51 which is controlled by the slide valve 34 and which merges into channel 32a. When the slide valve 34 is in its initial position resting against abutment 38, the port 51 is open through a second circumferential annular groove 52 provided in the slide valve 34.

Due to the aforedescribed arrangement the regulating shuttle 5 remains in its position of rest against abutment 28 as long as the slide valve 34 remains in engagement against the abutment 38 whereby the second discharge channel 32 is also closed. Thus, in this embodiment where the regulating shuttle 5 remains in its position of rest during the starting of the engine, the additional fuel quantity is larger than that delivered by the previous embodiment because now the pump piston 1 delivers fuel quantities for injection to the point where it reaches its upper dead center.

It is preferred to provide a throttle 53 at the location where the port 51 merges into cylinder 35. If for some unforeseen reason the slide valve 34 sticks in its position of rest, throttle 53 could still cause a sufiicient pressure buildup in cylinder 18 to enable the regulating shuttle 5 to start its quantity control after a predetermined r.p.m. before the motor races out of control.

Turning now to the embodiment shown in FIG. 4, here the second discharge channel is controlled by the step In and not by the step 1c of piston 1 as it was the case in the embodiments shown in FIGS. 1 and 3. For this purpose the step 1a is provided with a plurality of radial openings 54 which merge into a circumferential annular groove 54a which, during the pressure stroke of piston 1, registers with the radial bores 55 in cylinder 2a for terminating the fuel delivery during the pressure stroke. During normal operation the radial bores 55 which in this embodiment have the role of the second discharge channel, communicate (but for sleeve 58, the function of which will become more apparent hereinafter) with a chamber 56 which surrounds the cylinder 2a. Chamber 56 communicates with the suction chamber 11 through a channel 57.

Similarly to the embodiments of FIGS. 1 and 3, under full load conditions the delivered fuel quantity is determined by the opening of the second discharge channel, in this case by the registry of discharge bores 55 with radial bores 54.

The start of the fuel delivery is, in the embodiment shown in FIG. 4, determined by the step 1c of the piston 1 when during the axial and rotary motion of the piston the axial bore 8 is separated from the supply bore 10.

Similarly to the embodiment shown in FIGS. 1 and 2 the fuel quantities delivered by each stroke during full load conditions may be additionally varied by axially adjusting the cylinder 2a, whereas in the embodiment according to FIG. 4, the termination of the delivery is varied by the step In,

In order to deliver an additional fuel quantity for starting, in chamber 56 there is disposed about cylinder 2a a sleeve 58 which is urged against an abutment 60 "by means of a spring 59. In the position of rest shown in FIG. 4 the discharge bores 55 are closed by the sleeve 58. If subsequent to the starting operation the pressure in suction chamber 11 and consequently that in chamber 56 increases due to the increase in the r.p.m. of the engine, the sleeve 58 is displaced against the spring 59 thus uncovering the discharge bores 55 so that no additional fuel quantijes are delivered thereafter.

Apart from the structural differences described hereinabove, the embodiment shown in FIG. 4 operates similarly to those illustrated in FIGS. 1 and 3.

Although only several embodiments of the invention have been depicted and described, it will be apparent that these embodiments are illustrative in nature and that a number of modifications in the apparatus and variations in its end use may be effected without departing from the spirit or scope of the invention as defined in the appended claims.

What is claimed is:

1. In a fuel injection pump for internal combustion engines of the type including a main pump piston reciprocating in cylinder means for delivering fuel for injection from a pump working chamber during the pressure stroke of said piston, an auxiliary pump operating synchronously with said piston, a first discharge channel connected to said working chamber, a shuttle urged against a fixed abutment by resilient means, during the pressure stroke of said piston said auxiliary pump supplying fluid pressure to said shuttle causing it to be displaced against said resilient means to open said first discharge channel thereby interrupting the fuel delivery for injection during said pressure stroke, said shuttle adapted to return to said fixed abutment during the suction stroke of said piston as long as the rpm. of the internal combustion engine is below a predetermined value, said fluid pressure supplied by said auxiliary pump forming a fluid abutment for said shuttle when the r.p.m. of said engine is above said predetermined value, said fluid abutment preventing said shuttle from returning to said fixed abutment into its initial position, the improvement comprising, a second discharge channel connected to said working chamber, said second discharge channel as long as said shuttle returns to said fixed abutment adapted to be opened by said piston before said shuttle opens said first discharge channel.

2. A fuel injection pump as defined in claim 1, wherein said shuttle is adapted to open said first discharge channel before said piston opens said second discharge channel when said fluid abutment has reached a predetermined distance from said fixed abutment.

3. A fuel injection pump as defined in claim 1, wherein said second discharge channel merges into said cylinder means and is directly controlled by said pump piston.

4. A fuel injection pump as defined in claim 1, wherein said piston comprises a plurality of steps or portions, one of said portions is adapted to force said fuel from said pump working chamber, another of said portions functions as fuel distributor, said second discharge channel is controlled by said last named portion of said piston.

5. A fuel injection pump as defined in claim 1, including valve means to control said second discharge channel for supplying an additional quantity of fuel during the starting of said engine.

6. A fuel injection pump as defined in claim 5, wherein said valve means is r.p.m.-responsive and is adapted to open said second discharge channel only after a predetermined r.p.m. has been attained subsequent to the starting of said engine.

7. A fuel injection pump as defined in claim 6, Wherein said valve means is urged into its closed position by valve spring means and is urged into its open position by an rpm-dependent fiuid pressure.

8. A fuel injection pump as defined in claim 5, wherein said second discharge channel is' formed by radial bores extending through said cylinder means, said valve means is formed 'by a sleeve axially slidably surrounding said cylinder means, said sleeve adapted to clear said radial bores in one of its end positions and obturate said radial bores in the other of its end positions.

9. A fuel injection pump as defined in claim 1, wherein 1 0 10. A fuel injection pump as defined in claim 9, Wherein said terminal cylinder is axially adjustable by a setting screw.

References Cited UNITED STATES PATENTS 3,079,862 3/ 1963 Raibaud. 3,091,180 5/1963 Bessiere. 3,320,893 5/1967 Koster et a1. 3,333,542 8/1967 Eheim. 3,339,534 9/1967 Eheim et al. 3,358,662 12/1967 Kulke 10341 X 3,363,574 1/1968 Aldinger 103-41 said cylinder means includes a terminal cylinder adapted 15 FRED MATTERN Prima'y Examiner to be axially adjusted.

W. J. KRAUSS, Assistant Examiner.