US2919687A

US2919687A - Fuel injection pumps

Info

Publication number: US2919687A
Application number: US670105A
Authority: US
Inventors: Friedlander William
Original assignee: Mono Cam Ltd
Current assignee: Mono Cam Ltd
Priority date: 1956-07-10
Filing date: 1957-07-05
Publication date: 1960-01-05
Anticipated expiration: 1977-01-05

Description

Jan? 5, 1960 w. FRIEDLANDER 2,919,687

FUEL INJECTION PUMPS Filed July 5, 1957 \NVENTOR Wm M, M w WM ATTORNEYS,

FUEL INJECTION PUMPS William Friedlander, London, England, assignor to Mono- Cam Limited, London, England, a British company Application July 5, 1957, Serial No. 67il,1ll5

Claims priority, application Great Britain .luly 10, 1956 11 Claims. (Cl. 123-139) The invention relates to fuel injection pumps for internal combustion engines, e.g. diesel engines or other compression-ignition engines.

The invention provides, in one of its aspects, a fuel injection pump for an internal combustion engine, which pump comprises one or more pumping elements, means adapted to be driven by the engine for operating the pumping element (or each pumping element in turn) to supply fuel to an outlet for each injection period, means for causing the pumping element to supply fuel to a spill chamber at the end of each injection period so as to provide in the spill chamber a pressure which increases with increase in the engine speed, and means actuated or controlled by that pressure to advance the timing of the injection periods in relation to the operation of the engine as the said pressure increases.

Preferably the means for operating the pumping element or elements include a rotatable drive having two parts, and the said means for advancing the timing comprise a helical connection between the said two parts, means biassing the two partsaxially to assume one relative angular relationship and means for applying the said pressure in opposition to the biasing means so that the relative angular relationship between the said two parts varies with the said pressure. A

A specific construction of a fuel injection pump em bodying the invention will now be described by way of example and with reference to the accompanying drawing, which is a longitudinal sectional view of the pump. 7 In this example the pump comprises a plurality (e.g. four or six) pumping elements arranged in a circle each of which elements comprises a piston 11 working in a cylinder 12 having inlet ports 13 and an outlet 14. The

piston is urged to the limit of its suction stroke by a helical compression spring 15 which bears at one end on a washer 16 engaging a head 17 on the piston and bears at its other end on a fixed abutment 18. The head 17 bears in turn against a shoe 19 carrying a roller 21 rotatable on a pin 22 and in contact with a cam 23. The cam 23 is formed integrally with a hollow shaft 24 which fits over a shaft 25 and is mounted in

bearings

26, 27. The

shafts

24, 25 are drivingly connected by helical splines 28. The cam shaft 24 is held against axial movement but the shaft 25 is axially movable and is provided with straight splines 29 to permit it to be driven from the engine while permitting axial movement of the shaft 25. The shaft 25 is urged inwardly of the pump by a helical compression biassing spring 31 which acts between a fixed shoulder 32 and a head 33 on the shaft. That head 33 abuts, through a ball bearing 34, against the inner face of a non-rotating piston 35 working in a cylinder 36. The cylinder 36 communicates through a passage 37 with a spill chamber 38.

Each piston 11 is provided with an annular spill port 41 which is connected by a passage extending axially through the interior of the piston 11 with the working face 42 thereof. During each pressure stroke of the piston 11 the spill port 41 is covered by a controlling atent O "ice sleeve 43 until the end of the injection period, which is terminated by the spill port 41 emerging from the sleeve 43 so that the fuel is then supplied to the spill chamber instead of to the outlet 14.

The controlling sleeves 43 of all of the pumping elements are carried by a member 44 and are movable therewith all in unison. The member 44 is urged by the fuel pressure in the spill chamber against the action of a helical compression governor spring 45 which acts between a stop 46 provided on a control pin 47 and an inturned rim 48 on the member 44. The split fuel is returned to the feed circuit 49 of the pump, which is at a lower pressure, through a passage 51 and an aperture 52 formed between the interior of the member 18 and a tapered portion of the pin 47. The governed speed of the engine is determined by the position of the pin 47, which is adjustable by a lever 53, and that speed is increased by moving the pin 47 to compress the governor spring 45. This provides a spill pressure characteristic which increases with engine speed.

The spill pressure acting as aforesaid on the piston 35 causes it to move until a state of equilibrium is reached between the spill pressure force acting on the piston 35 and the spring 31 acting thereon. Movement of the piston 35 causes corresponding axial movement of the shaft 25, with a consequent change in the relative angular relationship between the cam shaft 24 and the shaft 25, due to the helical splines 28. The cam 23 is thus correspondingly moved angularly with respect to the drive from the engine and the timing of the injection is thus advanced with rise in engine speed and is retarded again when the engine speed falls.

The invention is not restricted to the details of the foregoing example.

T he pressure in the spill chamber varies also with the engine load in the foregoing example, so that the timing of the injection periods may become more advanced than may be considered desirable with relatively high engine speeds and relatively light loads. The travel of the piston 35 may be limited so that the automatic advance of the injection periods is effective only up to a selected speed, above which no further advance takes place.

The invention may be applied'to other kinds of fuel injection pumps for internal combustion engines eg, it may be applied to such pumps having their pumping elements arranged in-line.

I claim:

l. A fuel injection pump for an internal combustion engine, comprising in combination at least one pumping element, rotary cam means rotatable to operate said pumping element to supply fuel to an outlet for injection periods, means preventing axial movement of said cam means, coupling means for driving attachment to an internal combustion engine and to be driven thereby, a helical driving connection between said rotary cam means and said coupling means, said pumping element being reciprocable in a direction parallel to the axis of rotationof said helical driving connection, a spill chamber, means for supplying fuel to said spill chamber at the end of each injection period whereby fuel pressure in said spill chamber increases with increase in engine speed, and means responsive to said fuel pressure for advancing the timing of the ignition periods in relation to the operation of the engine as said fuel pressure increases. v

2. A fuel injection pump for an internal combustion engine, comprising in combination at least one pumping element, rotary cam means rotatable to operate said pumping element to supply fuel to an outlet for injection periods, means preventing axial movement of said cam 1 means, coupling means for driving attachment to an v.3 internal combustion engine and to be driven thereby, a helical driving connection between said rotary cam means and said coupling means, said pumping element being reciprocable in a direction parallel to the axis of rotation of the said helical driving connection, a spill chamber, means for supplying fuel to said spill chamber at the end of each injection period, and means responsive to fuel pressure in the said spill chamber for advancing the timing of the injection periods.

3. A fuel injection pump for an internal combustion engine, comprising in combination a plurality of pumping elements distributed around a pitch circle, a single annular rotary cam rotatable to operate the said pumping elements in turn to supply fuel to a plurality of outlets in turn for jection periods, means preventing axial movement of said cam, coupling means for driving attachment to internal combustion engine and to be driven thereby, a helical driving connection between said rotary cam and said coupling means, said rotary cam and said pitch circle being co-axial with said helical driving connec ion, a spill chamber, means for supplying fuel to said s ill chamber at the end of each injection period whereby fuel pressure in said spill chamber increases with increase engine speed, and means re sponsive to said fuel pressure for advancing the timing of the injection periods in relation to the operation of the engine as said fuel pressure increases.

4. A fuel injection pump for an internal combustion engine, comprising in combination at least one pumping element, relatively rotatable cam and cam follower means to operate said pumping element to supply fuel to an outlet for injection periods, means preventing axial movement of said cam, coupling means for driving attachment to an internal combustion engine and to be driven thereby, a helical driving connection between said relatively rotatable cam and cam follower means and said coupling means, said pumping element being reciprocable in a direction parallel to the axis of rotation of the said helical driving connection, a spill chamber, means for supplying fuel to said spill chamber at the end of each injection period whereby fuel pressure in said spill chamber increases with increase in engine speed, and means responsive to said fuel pressure for advancing the timing of the injection periods in relation to the operation of the engine as said fuel pressure increases.

5. A fuel injection pump for an internal combustion engine, comprising in combination a plurality of pumping elements distributed around a pitch circle, relatively rotatable cam and cam follower means to operate said pumping elements in turn to supply fuel to a plurality of outlets in turn for injection periods, coupling means for driving attachment to an internal combustion engine and to be driven thereby, means preventing axial move ment of said cam, a helical driving connection between said relatively rotatable cam and cam follower means and said coupling means, said relatively rotatable cam and cam follower means and said pitch circle being co-axial with said helical driving connection, a spill chamber, means for supplying fuel to said spill chamber at the end of each injection period, whereby fuel pressure in said spill chamber increases with increase in engine speed, and means responsive to said fuel pressure for advancing the timing of the injection periods in relation to the operation of the engine as said fuel pressure increases.

6. A fuel injection pump for an internal combustion engine, comprising in combination at least one pumping element, relatively rotatable cam and cam follower means to operate said pumping element to supply fuel to an outlet for injection periods, the operative face of said cam being transverse to the axis of rotation of the cam, means preventing axial movement of said cam, coupling means for driving attachment to an internal combustion engine and to be driven thereby, a helical driving connection between said relatively rotatable cam and cam follower means and said coupling means, said pumping element being reciprocable in a direction parallel to the axis of rotation of the said helical driving connection, a spill chamber, means for supplying fuel to said spill chamber at the end of each injection period whereby fuel pressure in said spill chamber increases with increase in en ine speed, and means responsive to said fuel pressure for advancing the timing of the injection periods.

7. A fuel injection pump for an internal combustion engine, comprising in combination at least one pumping element, a single annular rotatable cam having a cylindrical bore, means preventing axial movement of said cam, helical threads formed on the surface of the said cylindrical bore, a cylindrical driving shaft rotatable within the said bore, corresponding helical threads formed on the surface of the said shaft and meshing with the said helical threads on the surface of the cylindrical bore, longitudinal splines formed on the surface of the said shaft for engagement with corresponding parts in an internal combustion engine, and at least one cam follower means to operate the said pumping element, a spill chamber, means for supplying fuel to said spill chamber at the end of each injection period, whereby fuel pressure in said spill chamber increases with increase in engine speed, and means, responsive to said fuel pressure, whereby said driving shaft is moved axially relatively to said cam to advance the timing of the injection periods in relation to the operation of the engine as said fuel press are increases.

8. A fuel injection pump for an internal combustion engine, comprising in combination at least one pumping element, a single annular rotary cam rotatable to operate said pumping element to supply fuel to an outlet for injection periods, means preventing axial movement of said cam, coupling means for attachment to an internal combustion engine and to be driven thereby, a helical driving connection between said rotary cam and said coupling means, said rotary cam being coaxial with said helical driving connection, a spill chamber, means for supplying fuel to said spill chamber at the end of each injection period, whereby fuel pressure in said spill chamber increases with increase in engine speed, and means responsive to said fuel pressure for advancing the timing of the injection periods in relation to the operation of the engine as said fuel pressure increases.

9. A fuel injection pump for an internal combustion engine, comprising in combination at least one pumping element, a spill chamber, means for supplying fuel to said spill chamber at the end of each injection period whereby fuel pressure in said spill chamber increases with increase in engine speed, a rotary cam having an axis of rotation parallel to the direction of reciprocation of the pumping element to operate the said pumping element to supply fuel to an outlet during an injection period and having an operative face transverse to the axis of rotation of the cam and provided with an axial cylindrical bore formed with helical threads on the surface of the bore, means preventing axial movement of said cam, a cylindrical driving shaft rotatable within said bore, helical threads formed on the shaft and meshing with said helical threads on the surface of the bore of the cam, longitudinal splines formed on the shaft for engagement with corresponding parts in an internal combustion engine, at least one cam follower means to operate the said pumping element, a cylinder communicating with said spill. chamber, a cylindrical piston in said cylinder and eyond one end of the said shaft, whereby as the said fuel pressure increases said piston moves in response thereto and is constrained by the cylinder to bear against the one end of the driving shaft and push it relatively to said cam to advance the timing of the beginning and the end of each injection period in relation to the operation of the engine.

ii). A fuel injection pump as claimed in claim 9, in which a plurality of pumping elements are arranged around a pitch circle co-axial with the said axis of rotation of the cam.

11. A fuel injection pump as claimed in claim 9, in which the said means for supplying fuel to said spill chamber at the end of each injection period comprise a member reciprocable in said spill chamber and co-operating with each pumping element, the position of said member in said spill chamber being determined by said fuel pressure in said spill chamber, whereby the said 6 timing of the end of each injection period is detrrriineci by the combination of the angular position of said cam with respect to the said driving shaft and the position of said member in said spill chamber, and the timing of the beginning of each injection period is independent of the position of said member in said spill chamber.

References Cited in the file of this patent UNITED STATES PATENTS FOdOl Mar. 5, 1946