US3496876A - Fuel injection pump for internal combustion engines - Google Patents

Description

Fb. 24,1970 BSSIR'E 3,496,876?

FUEL INJEoTiQNIMP'FR INTERNAL comusiou ENGINES,

` mea Nov. 17.1967 SShetS-She 1 TMs/L0? I 'l Feb. 24, 1970 .P. E. BESSIERE 3496,76

FUEL INJECTION PUMP FOR INTERNAL COMBUSTION ENGINES Filed Nov. 17, 1967 5 Sheets-Sheet 2 Pierre E. essvrze Feh 24, 1970 P. E. BESSIERE 3,496,876

FUEL INJECTION PUMP FOR INTERNAL coMBUsTIoN ENGINES Filed Nov. 17, 1967 v .'5 Sheets-Sheet 5 Phew@ E. Bess- Re- United States Patent O 3,496,876 FUEL INJECTION PUMP FOR INTERNAL COMBUSTION ENGINES Pierre E. Bessire, Paris, France, assignor to Robert Bosch G.m.b.H., Stuttgart, Germany, a corporation of Germany Filed Nov. 17, 1967, Ser. No. 683,977

Int. Ci. F04b 49/00, 19/02; F22b 7/00 U.S. Cl. 103-37 3 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION The invention relates to a fuel injection pump for internal combustion engines, said pump being of the type including a rotary distributor having a head through which there extends a transversal bore receiving at least one -pump piston driven by a stationary cam ring surrounding said head. The injection pump further includes at least one control piston which, for the purpose of changing the timing of the injection, is exposed to a fuel pressure which, in turn, is responsive to the r.p.m. of the engine.

Fuel injection 'pumps of the aforenoted type are known wherein the control piston displaces the cam ring for the purpose of changing the instant when the fuel injection begins. Such a pump is described in U.S. Patent No.

2,660,992, entitled Automatic Timing Means for Fuel Pumps. A disadvantage of an adjustable cam ring resides in the fact that the pump pistons act back upon the stationary cam ring and tend to angularly displace it by impact. Such an angular displacement of the cam ring is highly undesirable since it would result in an accidental shift in the timing of the injection. In order to counteract the forces tending to accidentally displace the cam ring, a check valve has been installed in the supply conduit for pressurizing the fuel that acts upon the control piston and further, a throttle-controlled discharge conduit has been provided for the relief of the pressure chamber over the control piston.

In another known fuel injection pump of the abovenoted type, the control piston includes a control valve responsive to the pressure of the control fluid. Such a pump is described in U.S. Patent No. 3,116,728, entitled Liquid Fuel Pumps.

In addition to the accidental angular displacement of the cam ring, the afore-described pumps are disadvantageous in that they are relatively expensive, and due to the tangential arrangement of the control piston externally of, and with respect to, the cam ring, they take up substantial structural space.

It is still a further important disadvantage of the aforenoted distributor-type injection pumps that the rotary distributor must have a relatively large control orice since, when the cam ring is angularly displaced, the position of said orifice also changes with respect to the mouth of the pressure conduits.

Fuel injection pumps are further known wherein the pum-p drive shaft carries cam means to drive the pump pistons radially arranged in the pump housing and wherein the timing of the fuel injection is varied by changing the angular position of the distributor head with respect to the pump drive shaft Iwhich is operatively connected 3,496,876 Patented Feb. 24, 1970 ICC thereto. Such a pump is described in British Patent No. 1,003,180 entitled Improvements in Fuel Injection Pumps.

SUMMARY AND ADVANTAGES OF THE INVENTION The principal object of the invention is to provide an improved fuel injection pump of the ty-p'e including a rotary distributor head containing -radially operating pump piston means driven by a stationary cam ring wherein the disadvantages set forth hereinbefore are avoided.

Briefly stated, the invention resides in a novel cornbination of a fuel pump distributor containing radially operating pump piston means driven by a stationary, angularly non-displaceable cam ring with control means for varying the angular position of the distributor head with respect to the pump drive shaft to change the timing of the fuel injection. The control means comprises at least one control piston slidably disposed in the distributor head parallel to the axis thereof. According to a preferred embodiment, the control piston, acted upon by an r.p.m.-dependent fuel pressure, displaces a coupling element threadedly connected to the drive shaft and to the distributor head. The coupling element, by virtue of its threaded connection with the drive shaft and the distributor head, will also cause, during its displacement, an angular shift between the shaft and the distributor head. The novel combination eliminates the bulky features of both types of fuel injection pumps (those according to U.S. Patent No. 2,660,992 on the one hand, and those described in British Patent No. 1,003,180, on the other hand) and also obviates all other drawbacks referred to hereinbefore.

The invention will be better understood and further objects and advantages will become more apparent from the ensuing detailed specification of a preferred embodiment taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an enlarged axial sectional View of a fuel injection pump according to the invention;

FIG. 2 is a view of one part of the pump taken along line II-II of FIG. 1; and

FIG. 3 is a view taken along line III-III of FIG. 2.

DESCRIPTION OF A PREFERRED EMBODIMENT Turning now to FIG. 1, there is shown in its entirety a fuel injection pump comprising a rotary distributor 2 including a distributor head 1 and an axle portion 2a integral therewith. The distributor head 1 is provided with a transversal bore 3 in which there are slidably disposed, in spaced, axial alignment, two oppositely operating pump pistons 4. As best seen in FIG. 3, the pump pistons 4 are driven by a stationary cam ring 5 when the distributor 2 is rotated by a pump drive shaft 6 disposed in axial alignment therewith. The distributor head 1 is connected to the shaft 6 by means of a coupling mechanism generally indicated at 7, the structure, function and operation of which will be described in detail as the specication progresses.

The drive shaft 6, which journals in a pump housing 8, drives, *by means of a key 9, a gear pump 10. The pressure delivered by gear pump 10 Varies as a function of the r.p.m. of the engine. This pressure may be adjusted by means of a valve (not shown) disposed in a bore 11 of the housing 8. The gear pump 10 communicates with a suction chamber 14 of the fuel injection pump through a pressure conduit 12 in housing 8 and an external conduit schematically shown at 13. The suction chamber 14 is formed by the internal wall poriton of the housing 8 and a large annualr groove provided in a block 15 par- 3 tially extending into the housing 8 and iixedly held with respect thereto.

Through block there extends an axial bore 16 which reveives the axle portion 2a of distributor 2. The distributor head 1 is disposed externally of block 15 within pump housing 8. The pump pistons 4 working in bore 3 of the distributor head 1 are in engagement through pusher members 17 and rollers 18 with the inner cam face of the stationary cam ring 5 which is prevented from relative rotation with respect to housing 8 by means of a locking pin 19 extending through the wall of the housing 8 and protruding into the wall of the cam ring 5. From the pump work chamber 20 defined by the transversal bore 3 and the two adjacent end faces of pump pistons 4, the fuel is delivered by known means, not shown here, into pressure conduits and to injection nozzles associated with the engine.

As best seen in FIG. 2, through the distributor head 1 there extends, spaced from bore 3, a further bore 21 which receives reciprocating pistons 22. The bore 21 and the opposed end faces of the two pistons 22 define a pump work chamber 23. The pump pistons 22, similar to the pump pistons 4, are in enagement with the inner face of cam ring 5 through the pusher members 17 and rollers 18. The common axis of the pump pistons 22 lies in a plane defined by the axes of the distributor 2 and the injection pump pistons 4. The bore 21, pistons 22 and work chamber 23 define an auxiliary pump which forms part of a system for varying the quantity of the injected fuel. This system, other elements (not shown) of which are disposed in block 1S, operates on the principle of fluid abutment Iand is described, e.g. in U.S. Patent No. 3,122,100, entitled Self-Regulating Pumps in Particular for the Injection of Fuel Into Internal Combustion Engines.

The coupling mechanism 7, effecting a change in the timing of the injection, is actuated by control pistons 24 slidably disposed in bores 25 which extend into the distributor head 1 parallel to the axis thereof. T he bores 25 are separated from one another by bores 3 and 21. The bores 25 extend approximately up to the plane which intersects longitudinally the transversal bore 21 and is normal to the distributor axis. The plane containing the axes of bores 25 and distributor 2 is normal to the plane containing the axes of the pump pistons 4 and distributor 2.

The suction chamber 14 communicates with bores 25 through a channel 26 extending through the block 15, a circumferential annual groove 27 -machined in the distributor axle 2a and channels 28 disposed within said axle.

The coupling mechanism 7, for varying the timing of the injection, comprises a threaded I,bushing 29 having a multiple external coarse-pitch thread 30 which is in engagement with a complementa] internal thread 31 of a coupling member 32 keyed to drive shaft 6. The bushing 29 is further provided with a multiple internal coarsepitch thread 33 which is in engagement with a complemental external thread 34 of a stub shaft 35 integral with, or rigidly affixed to, the distributor head 1. The threads 30, 31 on the one hand, and 33, 34 on the other hand, are of opposed pitch.

For transmitting forces from the control pistons 24 to the threaded bushing 29, there is provided a plate 36 which is secured to the bushing 29 by means of a snap ring 37. To plate 36 there are riveted stems 38 each of which extends into a hollow control piston 24 and engages the internal terminal face thereof through supports 39. A coil spring 40, compressed between the plate 36 and an annular shoulder of coupling member 32, urges the threaded bushing 29 and plate 36 into their initial position against the distributor head 1.

Between the drive shaft 6 and the stub shaft 35 there is compr$$1 ,a Coil spring 41 which urges stub shaft 35 and drive shaft 6 axially away from one another. One radial end face of the coupling member 32 is in engagement with a cover plate 42 by means of a roller bearing 43, while one radial end face of the distributor head 1 is in engagement with the block 15 by means of a roller bearing 44.

As long as the engine operates at low rpm., the threaded bushing 29 remains in engagement with the distributor head 1 by virtue of spring 40 since the pressure in suction chamber 14 is relatively low and consequently, the force of the fluid pressure exerted on control pistons 24 does not yet effectively counteract the force of spring 40. If now the pressure increases in the suction chamber 14 due to the increasing operational speed of the gear pump 10 caused by an increased r.p.m. of the engine, control pistons 24, plate 36 and threaded bushing 29 are displaced against the force of spring 40 in the direction of the drive shaft 6. An axial displacement of the threaded bushing 29 causes relative rotation of the distributor 2 with respect to the drive shaft 6. The result of the new angular position between the drive shaft 6 and the distributor 2 is that the instant has been advanced when the injection begins. The extent of the shift in timing is determined by the extent the pressure delivered by the gear pump increases in response to the r.p.rn. of the engine.

The afore-described structure of the coupling mecha-v nism 7 is particularly advantageous since, due to the very large pitch of the threads for causing only slight angular displacements, the rotary driving forces and the pushing forces of the pump pistons exert only small axial pressures on the threaded bushing 29 and thus on the control pistons 24.

What is claimed is:

1. In a fuel injection pump associated with an internal combustion engine, said pump being of the known type having (A) a rotary distributor Pump (B) a pump drive shaft,

(C) a multi-part coupling mechanism operatively connecting said drive shaft with said distributor head, said mechanism adapted to transmit a torque from said shaft to said distributor head and, upon actuation, adapted to change the angular position of said distributor head with respect to said drive shaft to thereby vary the timing of the fuel injection, and

(D) pump piston means disposed in said distributor head and reciprocating radially with respect to the axis of said pump,

the improvement comprising:

(a) control piston means disposed in said distributor head and movable along a path parallel to the axis of said distributor head and spaced from the path of reciprocation of said pump piston means,

(b) channel means in said distributor head communicating with said control piston means for admitting an engine r.p.m.dependent pressure thereto to cause displacement of said control piston means, and

(c) an axially movable member forming part of said coupling mechanism and drivingly connecting said shaft with said distributor head, said member being axially movable by said control piston means and, when axially displaced, effecting a change in said angular position.

2. A fuel injection pump as defined in claim 1, wherein said pump piston means include two oppositely reciprocating pistons disposed in a single radial bore in said distributor head, said control piston means include two control pistons disposed in said distributor head in two spaced bores parallel to the axis of said distributor head, the plane defined by the axes of said control pistons and said distributor is normal to the plane defined by the axes of said pump pistons and said distributor.

3. A fuel injection pump as defined in claim 1, includhead axially disposed in said 5 6 ing an auxiliary pump having auxiliary piston means 2,806,431 9/ 1957 Woyot 103-227 radially reciprocating in said distributor head, the axis 3,013,547 12/ 1961 Miracki et al. 123-139 of said auxiliary piston means being contained in a plane 3,074,345 1/ 1963 Scheow 103-173 dened by the axes of said pump piston means and said distributor head. 5 OTHER REFERENCES References Clfed 860,654 4/1959 Great Britain. UNITED STATES PATENTS WILLIAM L. FREEH, Primary Examinar 1,825,691 10/1931 Hall 103--38 X 2,227,631 1/1941 Carter. U'S' C1' X'R'

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