US2958289A - Injection pump - Google Patents

Description

W. HFELE Nov. 1, 1960 INJECTION PUMP INJECTION PUMP Walter Hfele, Fellbach, Germany, assignor to Robert Bosch G.m.b.I-1., Stuttgart, Germany Filed Aug. zo, 1956, ser. No. 604,869

Claims priority, application Germany Aug. 19, 1955 1 claim. (ci. 10a- 41) The present invention relates to fuel injection equipment and more particularly to :a fuel injection pump for the selective operation of an internal combustion engine with liquid fuel alone (diesel operation) or with gas and a small quantity of liquid fuel as ignition fuel (diesel gas operation), and embodying two pump pistons one of which is adapted to supply ignition fuel and has a smaller swept volume than the other.

It has been proposed that an individual pressure valve be associated with each of the two pump pistons. If it is intended to avoid, both with disel operation and with diesel gas operation, subsequent dribbling from an associated injection nozzle and the attendant rapid carbonisation lof the nozzle apertures, both pressure valves must be constructed so as to relieve the pressure in a pressure pipe line leading from the injection pump to the injection nozzle at the end of the injection operation. This is almost essential, particularly when both pump pistons feed the same injection nozzle. In this case however the pressure valve associated with the smaller piston supplying the ignition fuel must also have the same proportions as the pressure valve associated with the larger piston supplying the main fuel in the case of diesel operation.

According to the present invention in a fuel injection pump for the selective operation of an internal combustion engine with liquid fuel alone or with gas and a relatively small quantity of liquid ignition fuel and embodying two pump pistons, one of said pistons is adapted to supply the ignition fuel and has a smaller swept volume than the other of said pistons which is adapted to supply the main fuel quantity when working Awith liquid fuel alone, both the pistons being adapted to supply a common injection nozzle of the engine through a common pressure valve and said one piston being adapted to control a supply passage through which fuel is displaced by said other piston to the pressure valve.

The invention is further described by way of example with reference to the accompanying drawings which illustrate one embodiment, and in which:

Fig. l shows a sectional View of the essential parts thereof adjusted for diesel gas operation.

Fig. 2 is a section taken on the line II--ll of Fig. l to a larger scale, and

Fig. 3 is a section taken on the line III-HI of Fig. l with adjustment for diesel operation, also to a larger scale.

In a partly shown casing 1 of an injection pump is located a pump cylinder 2 having a pump piston 3. On the upper face of the pump cylinder 2 is coaxially mounted a second pump cylinder 4. A pin 5 engaged in the two pump cylinders 2 and 4 provides relative angular location.

In the pump cylinder 4 slides a pump piston 6 which is coupled with the pump piston 3 by a T-head and slot connection so that it follows both axial and rotary displacement of the pump piston 3. A nipple 7 which is screwed into the pump casing 1 provides pressure through a packing 8 to press the cylinder 4 against the cylinder 2 which is supported in the casing 1.

tates Patint 0.,F

Patented Nov. Vl 1960 On the cylinder 4 is located a valve body 10 having a displaceable valve member 11 which, in the closed position shown, is pressed into its seat in the valve body by a compression spring 12. In this position a cylindrical attachment 14 of the valve body dips into its guide bore in the valve body 10. The spring 12 is supported against a coupling member 15 which is pressed against the valve body 10 by a collar nut 16 screwed on the nipple 7; at the same time the valve body is pressed against the pump cylinder 4. The coupling member 1S has a pump outlet aperture 17 and is used for the connection of a nonillustrated pressure pipe line leading to the corresponding injection nozzle of the internal combustion engine which is also not shown.

In the casing 1 is an annular space 18 which surrounds the cylinder 2 and communicates with a fuel inlet opening 19. The wall of the cylinder 2 has transverse passages 20 and 21 which both communicate with the annular space and deiine inlet parts. The passage 21 is also used as a return How passage. An axially directed passage 22 in the cylinder 4 connects the working chamber 23 of the piston 3, by way of a transverse bore 24, with the guide bore of the pump piston 6.

The pump piston 3 has a recess 27 which is partly limited by a helical control edge 26 and is permanently connected with the pump working chamber 23 through an Iaxial groove 28. The pump piston 6 has a recess 30 communicating through a radial bore 31 with an axial bore 33 communicating with the working chamber 32. On the side opposite the recess 30 the pump piston 6 has a second recess 35 which extends from the crown thereof to the same axial level as the lower end of the recess 30.

The transverse passage 21 enlarges into a groove at its end communicating with the annular space 18. A screw 38 located in the pump casing 1, projects by its shaft end into this groove and thus prevents the pump cylinder 2 from twisting.

The drive of the pistons 3 and 6 is effected by a nonillustrated cam against a non-illustrated return spring. The pistons 3 and 6 may be turned by a non-illustrated rack and pinion coupled to the piston 6 whose movements are followed by the piston 3.

The pistons 3 and 6 of the injection pump are shown at bottom dead-centre and -in the angular position to which they :are adjusted when the engine is being operated with gas and with va small quantity of liquid as ignition fuel, that is to say during `diesel lgas operation. The two pump working chambers 23 `and 32 have become fille-d with fuel from the annular space 18 through the passages 20, 21, and 22 during the preceding suction stroke. In the angular position of the pistons shown in Fig. l and to which they have been adjusted by the aforementioned rack, the groove 28 of the pump piston 3 communicates permanently with the return flow passage 21. Upon the pressure stroke all the fuel displaced by the pump piston 3 is therefore returned to the annular space 18 through the [groove 28 land the return ow passage 21. The fuel displaced by the pump piston 6 is also urged into the annular chamber 18, by way of the pump working chamber 23, until the opening of the passage 24 into the bore of the cylinder 4 has been covered by the piston 3 when the pressure in the working chamber 32 rises. This fdisplaces the valve member 11 to rise from its seat and, after the emergence of its attachment 14 from its guide bore, opens the passage to the pump outlet opening 17 an-d therefor to the injection nozzle. The pump piston- 6 then supplies fuel to the injection nozzle until its recess 30 uncovers the transverse bore 24 and thereby establishes a connection between the working chamber 32 and the working chamber 23 and the annular space 18 through the bores 33 and 31 and the passage 22. At this moment the injection operation, caused by the piston 6 alo-ne, terminates and the valve member 11 sinks, under the iniluence of the spring 12, back onto its seat. At the same time the pressure valve, las a result of the entry of its cylindrical attachment 14 into its `guide bore,` increases the effective volume of the pressure pipe line disposedl between the pressure valve and the injection nozzle thereby reducing the pressure in this pipe line to lavoid dribbling from the injection nozzle. The fuel thus injected into a highly compressed gas/air mixture in the combustion chamber of the engine spontaneously ignites and ignites the mixture.

When the engine is operated entirely with liquid fuel, that is with pure diesel operation, the pump pistons 3 and 6 yare adjusted into the angular position shown in Figs. 2 and 3. In this position only the part of the recess 27 in the piston 3 which is limited by the inclined control edge 26 communicates with the return flow opening 21, whilst the groove 28 no longer communicates with the transverse passage 21 as in the angular piston position illustrate-d in Fig. l. The recess 35 of the pump piston 6 is now opposite the transverse bore 24. During the pressure stroke the pump piston 3 is therefore able, after the closing of the inlet passages 20 and 21, to supply fuel through the passage 22 into the pump chamber 32 and through the opened pressure Valve 11 to the injection nozzle until the inclined control edge 26 opens the return flow passage 21. The pump piston 6 supplies the injection nozzle when the pistons are in this angular position, with the entire quantity of fuel displaced by it after the operation of the piston 3 has commenced.

What is claimed as new and `desired to be secured by Letters Patent is:

In a fuel injection pump for operating an engine either with liquid fuel alone or with gas and a relatively small amount of liquid fuel, in combination, :a main cylinder having a working chamber at one end portion thereof, said main cylinder being formed with a rst passage leading from said working chamber to the exterior of said main cylinder; a housing carrying said main cylinder and formed with -a fuel supply and return chamber communicating with said first passage so that fuel ilo-ws to or from said `working chamber of said main cylinder through said first passage thereof; an auxiliary cylinder co-axial with said main cylinder, having a smaller diameter than the same, and located ahead of said working chamber thereof, said auxiliary cylinder having -a working chamber at an end portion 4distant from said main cylinder; a passage means formed at least in part in said auxiliary cylinder and leading vfrom said working chamber of said main cylinder to said working chamber of said auxiliary cylinder; a main piston in said main cylinder having an `axial groove communicating with said rst pass-age in one angular position of said main piston so that no fuel will be pumped by reciprocation of said main piston when it is in said one angular position there of, said axial groove extending from the head end of said main piston `at said working chamber, and said main piston bein-g formed with `an annular groove having a helical edge intersecting said axial groove so that said main piston will pump Ia predetermined amount of fuel depending upon the angle through which it is turned from said one angular position; an auxiliary piston in said `auxiliary cylinder connected to said main piston for axial and angular movement therewith, said auxiliary piston pumping liquid from said working chamber of said auxiliary cylinder and said auxiliary piston yhaving an outer surface portion spaced from the inner surface of said auxiliary cylinder and angularly displaced from said passage means When said main piston is in said one angular position thereof so that said auxiliary piston will during its reciprocation close said passage means when said main piston is in said one angular position thereof, said outer surface portion of said auxiliary piston overlapping said passage means when said main piston is angularly displaced fromV said one angular position thereof, so that fuel pumped by said main piston will pass through said pass-age means to said working chamber of said auxiliary cylinder during reciprocation of said auxiliary piston; and a single `discharge valve communicating with said Working chamber of said auxiliary cylinder for discharging from the pump all fuel pumped by said pistons.

References Cited in the file of this patent UNITED STATES PATENTS 833,457 Hammond Oct. 16, 1906 1,760,237 Iversen May 27, 1930 2,163,313 Voit June 20, 1939 2,612,842 Steven et al. Oct.7, 1952 2,623,468 Steven et al. Dec. 30, 1952 2,670,877 Logue Mar. 2, 1954 2,676,544 Schauer Apr. 27, 1954 2,804,825 Mansfield et al. Sept. 3, 1957 FOREIGN PATENTS 577,288 Germany May 29, 1933

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