US2777390A

US2777390A - Fuel injection pump

Info

Publication number: US2777390A
Application number: US192672A
Authority: US
Inventors: Heinrich K Links
Original assignee: Daimler Benz AG
Current assignee: Daimler Benz AG
Priority date: 1949-10-31
Filing date: 1950-10-28
Publication date: 1957-01-15
Anticipated expiration: 1974-01-15

Description

Jan. 15, 1957 H. K. LINKS FUEL INJECTION PUMP Filed Oct. 28, 1950 15 Claims. (Cl. 10S-38) The invention refers to a fuel injection pump, particularly a pump, the quantity of injection of whlch 1s regulated by stroke regulating and the piston stroke'end of which coincides with the end of the injection period, and is furthermore particularly designed for small injection quantities.

Subject of the invention is above all a pump, the quantity of injection of which can be regulated very exactly; furthermore such a pump, by which a slow injection at the end of the pressure stroke is avoided. Furthermore such problems are to be solved with the simplest constructive mediums possible.

The manufacturing of exactly working injection pumps for combustion engines is particularly diicult, if the engines and in 'accordance with these the injection pumps are small. This is for example particularly the case, if two stroke motor cycle engines are to be equipped with injection pumps, in which engines the injected quantities are under circumstances almost one decimal smaller than in normal passenger Vehicle engines, for example, the injected quantities amount to 6 mm.3 per stroke. At these small injection quantities the losses in venting quality of the pumps play an important role both immediately after the closing of the suction boring and immediately before the opening of a boring for letting escape spilled or expanded quantities of fuel which amount to a considerable fraction of the injected quantity. The loss of venting quality is hereby particularly large, because at this moment of the piston stroke the full pump pressure exists in the pump space.

These losses of venting quality can be avoided before the opening of a spill boring by providing a fuel injection pump without spill regulating means, that is a pump piston, the str-oke end of which coincides with the end of the injection period, particularly an injection pump with a stroke regulation of the pump piston. On the other hand such pumps have the disadvantage that they are, liable due to lack of a sudden decrease in pressure, to delay the end of the injection period so that the same extends over too large a crank angle.

In ycontradistinction thereto according to the invention the return path of the piston pump after the completion of the injection period is carried out by restricted positive guiding means. The return path of the fuel mixture is established by Ia suction cam separate from the pressure cam, which are subject to corresponding guiding'curves. Furthermore the end ofthe pressure stroke regulates preferably the injection quantity, whereby the cams are formed in such a manner and are arranged relatively to each other, that each time lafter the adjustable end of the pressure stroke the suction cam starts immediately the return path of the pump piston. Furthermore the pressure :cam is formed as an axially adjustable regulating cam, while the suction cam for example is shaped as non-adjustable internal cam. The pump may be designed without a restoring spring and the suction stroke of the pump piston may, upon completion of the return nited States Patent lll rice

path of the suction cam be limited by a stop, so that the pressure cam is separated from the pump piston or from a pump plunger as soon as the pump piston has reached the final position determined by the stop.

Further objects and advantages of the invention will be apparent from the following detailed description of an embodiment thereof.

In the drawing Figure l shows an axial section through an injection pump, in accordance with the invention,

Figure 2 is a diagram for explaining the operation of the pump shown in Fig. l, and

Figure 3 is a section on an enlarged scale of certain parts of Figure 1.

' In the casing 1 of the fuel pump, which is for example hanged to the gear case 2 of the combustion engine, a pump piston 4 is arranged in a cylinder 3, so that it can be moved upv and down. On one hand the suction opening 6, which iscontrolled by the4 pump piston, and on Ithe other hand the pressure or injection piping 8, which is controlled by the check valve 7, are connected to the pump space 5. The check valve 7 is actuated by a spring 7a.

The pump is driven by the driving shaft 9, which (for example in two-stroke engines) may be directly the crankshaft or yalso the camshaft for the valves (not shown) of the combustion engine. The suction cam disk 11, which bears an internal guiding curve or cam 12, is rigidly connected with the shaft 9 or the toothed wheel 10 carried by same. The conical cam disk 14 with the pressure cam 15 is furthermore coupled with the cam disk 11 so as to be axially sliding, but not revolving. The cam disk 14 is supported by a ball bearing lo on an axle 17, which can be moved in axial direction from the outside, for example by a lever (not shown), which acts at 18.

The plunger roll 19 of the plunger 2) of the pump piston 4 is in contact with the cam disk 14, while the axle journal 21 of the roll 19 is engaged with the cam guidance 12 of the suction cam. A stop 22a limits the downward stroke of the plunger 2li and therewith of the piston 4. The stop 22a is connected with a screw 22 engaging the plunger 26.

In Figure 2 the diagram -for the regulation of the stroke is shown, whereby the stroke of the roll 19 is shown in action over the lower edge a of the suction opening 6. The roll is hereby lifted during a pressure stroke by the pressure cam 15, and returned by the suction cam 12, which guides the axle journal Z1. The straight line a represents the lowest position of the face of the pump piston 4, which is determined by the stop 22. ln the position b the suction opening is closed, whilethe straight line c corresponds to the highest position of the piston face, or the'roll 19. The total stroke x is accordingly composed of the idle stroke xn until closing of the suction opening and the adjustable effective pressure stroke xi. j

If the cam disk is in the left final position as shown in Figure l, the roll 19 and therewith the pump piston It carries out its largest stroke. in the diagram in accordance with Figure 2 the cam line, which is guiding in this case, is shown by the curve 15 with maximal cam lifting. The movement of the cam can be taken as going in direction p. As soon as the roll 19 has reached its highest point at the end of the elfective pressure stroke or the injection period, it is pressed downward again by the suction cam l2, in that the axle journal 21 is guided along the guidance curve of the suction cam 12. The stroke x ofthe suction cam can hereby correspond to the stroke x of the roll and is suitably a little smaller than the maximal cam lifting of the pressure cam 15, so

3 that the latter can be lifted from the roll in the lowest position of the latter and a jamming is rendered impossible. Simultaneously hereby a faster movement of the piston in the pressurel stroke or the suction strokel is rendered possible. i

By an axial adjusting of the cam disk 14 along the rods i3 to the right cam curves of smaller diameter are made effective, for example in accordance with the curves 1 5" and 15 (Fig. 3). The latter are for example by appropriate shaping of the cam l5 staggered relatively to each other in such a manner, that they have a common downward course of the curves. The roll 19 can consequently be restored to its original position by the same unchangeable suction cam curve 12. However, at the lowermost position (a), the pressure strokes start in different turning positions 19,', 19", 19', so that simultaneously the time of injection point changes. The pressing 0f the roll. 1.9 against the pressure cam 15 is in this case effected by the oppositely acting liquid pressure in the pump Space- Hereby it is possible to, lay on one hand the moments of the injection period at random and on the other hand to effect a continuously controlled guidance of the pump piston, which is for the main part free from play, both in the suction stroke and in the pressure stroke.

Upon displacing of the pressure cam 14 into its right final position the roll 1,9 or the pump piston 4 carry out only one stroke xu in accordance with the curve 15, so that the quantity of injection is no longer delivered.

The invention is not restricted to, the illustrated embodiment, but can be varied at discretion within the individual ideas of the` invention.

What I claim is: 1. Fuel injection pump comprising a reciprocatin pump piston, a driving shaft normalV to said pump piston, means for positively driving the pump, pistonl in the one stroke direction, means f0.1' `positively driving the pump the pressure stroke, au injection piping, valve means. con,V

trolled by the pressure in the pump space and controlling the injection piping in dependence upon the pump-piston in Such 'rl 11131111.6 1 that the` end of the injection coincides.

with the end of the pressure stroke, second means for positively driving the pump piston on the reverse stroke after the end of the pressure stroke, wherein one of saidk two means for positively driving the pump piston are driven by the driving shaft While the other of said means for positively driving the pump piston are driven by but separate from the first means and from the driving shaft and a non-rotatable means operatively associated with said second means for aaiallyv adjusting said second means with respect to said driving shaft and thereby with respect to said pump piston.

3. Fuel injection pump comprising a reciprocating pump piston, a driving shaft perpendicular to said pump piston, means for positively driving the piston on the pressure stroke, means for positively driving the pump piston on the reverse, stroke after completion of the pressure stroke, and means for adjustingV at least one of said driving means, wherein the first means for positively driving the pump piston are driven by the driving shaft while the second means for positively drivingthe pump piston are driven by but Separate fromt the first, means and from the driving shaft and non-rotatable means operatively associated with said second means for axially adjusting said second means with respect to said driving shaft and thereby with respect to said pump piston.

4. Fuel injection pump comprising a reciprocating pump piston, a driving shaft perpendicular to said pump piston, an injection piping, valve means controlled by the pressure in the pump space and controlling the injection piping in dependence upon the stroke of the pump piston in such a manner that the end of the injection coincides with the end of the pressure stroke, means for positively driving the pump piston on the. pressure stroke and means for positively driving the piston on the reverse stroke upon termination of the pressure stroke, wherein the first means for positively driving the pump piston are driven by and secured to the driving shaft while the second means for positively driving the pump piston arc driven by but separate from the first means and from the driving shaft and non-rotatable means operatively associated with said second means for axially adjusting said second. means withv respect to said driving shaft and thereby with, respect to said pump piston.

5. Fuel injection pump comprising a reciprocating pump piston, a drive cam with outside.` Cam face for driving the pump piston in one stroke direction, a drive cam with inside cam face, and means connecting said first drive Cam for driving the pump piston` with the other drive cam.

6. Fuel injection Pump in accordance` with claim 5, wherein the first mentioned. cam is provided with a conical outside cam face, and further comprising means for axially adjusting the said cam for regulating the stroke of the pump piston. i

7. Fuelv injection pump comprising a reciprocating piston pump, a driving shaft, a first driving cam with conical cam face, saidl first driving cam being adjustably coupled withy the shaft in the direction of rotation and engageable with` said pump. piston to drive the pump piston in one stroke direction, means operatively connected to said cam for adjusting the cam in an axial direction ofthe driving shaft for regulatingthe stroke of thc pump piston, and a second driving cam coupled with the driving shaft in the direction of rotation to drive the pump pis-ton in the opposite stroke direction.

8. Fuel; injection pumpcomprising a reciprocating pump piston, a roller, a journal for supporting the roller against the pump piston, wherein the journal has a onesided prolongation, a first driving cam in engagement with theroller to drive the pump piston in one stroke direction and a second driving cam in engagement with the prolongation of the journal to drive the pump piston in the other stroke direction.

9; Fuel injection pump comprising a reciprocating pump piston, a cam, with outside conical cam face for driving the pump piston in the one stroke direction, a cam disk with inside cam face and engageable with said pump piston for driving the pump piston in the other stroke direction, and means operatively connected to said cam for axially adjusting the cam relatively to the cam disk, said adjusting means axially adjusting the two cams toward each other.

10. Fuel injectionv pump in accordance with claim 9, wherein said,v means comprise a journalheld against rotation, and means interposed between said adjusting means and Said'rst cam for axially displacing the first cam with the journal.

11. Fuel injection pump in accordance with claim l, further comprising a stop engageable by said pump piston for limiting the stroke of the pump piston in the second mentioned stroke direction.

l2. Euelinjection pump in accordance with claim 4, further comprising an adjustable stop engageable by said pump piston for limiting the stroke of the pump piston on the reverse stroke.

1 3. Fuel injection` pump in accordance with claim 2, comprising a suction piping and wherein the means for controlling the injection pipingi comprise a check valve positioned in said injecting piping, and wherein the suction piping is controlled by the pump piston.

14. Fuel injection pump in accordance with claim 4, wherein the means -for regulating the injection quantity comprise means operatively associated with said pump piston for changing the pump stroke in such a manner that the end of the injection period remains substantially constant.

15. Fuel injection pumps comprising a reciprocating pump, a first drive cam having a central axis substantially perpendicular to the axis of said injection pump, a cam face formed by an outer peripheral surface of said drive cam, means cooperating with said cam face for driving the pump piston in one stroke direction, a second drive cam coaxial to said rst drive cam and having an inside cam face, means cooperating with said inside cam face for driving the pump piston in the other direction, one of drive cams having in axial direction different cam faces, and means operatively associated with one of said drive cams for axially adjusting said one of said drive cams with respect to the other drive cam.

References Cited in the tile of this patent UNITED STATES PATENTS Shedlock July 20, Lyford et al. Aug. 25, Woerner Apr. 26, Woerner Nov. 18, ODonnell Mar. 2, Spreen Dec. 8, Woerner Oct. 12, Hueber May 31, Dllstrom Dec. 3, Retel Dec. 17, Rumpp Nov. 25, Bovard Dec. 2, Rose Dec. 9, Ashton July 30,

FOREIGN PATENTS Germany Dec. 6,