US2144132A - Fuel injection system for internal combustion engines - Google Patents

Description

H. WALT: 2,144,132

FUEL INJECTION SYSTEM FOR INTERNAL COMBUSTION ENGINES Jan. 17, 1939.

Filed May 31, 1935 2 Sheets-Sheet 1 H. WALT! Jan. 17, 1939.

FUEL INJECTION SYSTEM FOR INTERNAL COMBUSTIONENGINES Filed May 51', 1935 2 Sheets-Sheet 2 fly] I I I Patented Jan. 17, 1939 UNITED STATES PATENT OFFICE Heinrich Wtilti, Winterthur-Wulflingen, Switzerland, assignmto Sulzer Freres, Socit Anonyme, Wlnterthur, Switzerland Application May 31,

In Switzerland June 2, 1934 5 Claims.

This invention relates to fuel injection pumps for reversible internal combustion engines of the solid fuel injection type, and of the kind comprising a pump plunger which is reciprocated within a cylinder by a driving cam, the fuel charge being delivered under pressure.

The high pressures which obtain in fuel injection pumps of this type, and which may be some hundreds of atmospheres even in pumps supplying fuel to medium sized internal combustion engines, result in pressures of several tons on each pump plunger, this pressure having to be transmitted from the driving cam through the tappet roller to the pump plunger. In the case therefore of multi-cylinder engines wherein each engine cylinder is supplied from a pump cylinder, at least one of the pump plungers is at any given moment moving on its delivery stroke so that when the direction of operation of the engine is to be reversed it has hitherto been necessary either to cause relative adjustment of the cam and tappet roller of the pump plunger which is then moving on its delivery stroke, or to disengage the said tappet roller from its associated cam. In either case a large force, requiring a powerful transmission mechanism must be provided for the purpose of reversal. Further, in view of the high pressures occurring in the cylinders of fuel injection pumps the diameter of each pump plunger is limited whilst the quantity of fuel to be delivered is greater the smaller the speed of the engine at any given load. Owing to this limitation of the diameter of the pump plunger the plunger stroke, i. e. the lift of the driving cam, cannot be reduced belowa given value more particularly if a precise regulation of the fuel charge to be delivered is to be obtained by varying the point in the plunger stroke at which delivery from the pump commences. Again, the injection angle, that is to say the crank angle prior to the top dead centre at which injection is to commence, is smaller the lower the speed of the engine and this angle must therefore be variable not only for forward but also reverse operation of the engine.

In a fuel injection pump according to the present invention the pump plunger is driven by a cam, of which one operating face comes into action for one direction of operation of the engine and the other operating face for the same kind ofstroke of the plunger for the other direction of operation, and that controlmeans are provided whereby beginning and end of the injection .at the same load for each direction of operation of the engine are shifted to such posi- 1935, Serial No. 24,412

tions of the crank-circle that the positions for one direction are symmetrical or approximately symmetrical to the positions for. the other direction with respect to the dead centre, and that a favourable cam-life is possible also at low speeds. 5

Conveniently the control means consist of a. space (or chamber) fitted in the path of the fuel under pressure, by means of which space by making use of the compressibility of the fuel the beginning of the fuel injection in the working cylinder is' delayed in comparison with the beginning of the delivery of fuel by the pump.

In the accompanying drawings,

Figure 1 is a vertical section through the cylinder of an internal combustion engine and fuel 15 injection pump embodying one construction according to the invention,

Figure 2 is an elevation taken from the same direction as Figure 1, with parts in section, showing the governor or operating mechanism for the fuel pump control;

Figure 3 is a transverse sectional detail taken on an enlarged scale, on the line 3--3 of Figure 1, illustrating the sleeve drive;

Figure 4 illustrates the manner in which the beginning and end of each injection is altered relatively to the upper dead centre position of the engine piston,

Figure 5 is a section through the fuel delivery conduit of another arrangement also according to the invention.

Fig. 6 is an elevation of the engine showing the arrangement of the fuel lines.

Fig. 7 is a further modification of the engine with a different arrangement of fuel lines.

In the construction illustrated in Figure 1, the internal combustion engine I comprises a cylinder 2 in which a piston 3 is reciprocated from the engine crankshaft through a connecting rod 4. The fuel pump 5 is driven from the crankshaft of the internal combustion engine I, the fuel pump camshaft 6 being positively connected to the engine crankshaft by means of gearing (not shown). The camshaft 6 carries a fuel pump operating cam 'I having two operating surfaces 8 and 9, the surface 8 being operative for injection during forward operation of the engine whereas the surface 9 is operative for-injection during reverse operation of the engine. The cam 1 operates a pump plunger III which reciprocates 50 within the cylinder of thepump II, the cam engaging a tappet roller l2 at the lower end of the plunger which is furnished with a return spring-l3.

Fuelis drawn through a suction pipe l4 and 55 suction port l5 into the working chamber l6 of the pump and is delivered from this working chamber through a delivery valve I! to a delivery pipe l8. The fuel is delivered from the pipe l8 to a fuel injection valve l9 furnished with a needle 20 which, at the commencement of each injection, is raised from its seat by the pressure of the fuel in the pipe l8. A fuel chamber 20b is associated with the lower end of the needle 20 and is in communication with the fuel pipe l8. It will be understood that instead of arranging the valve l9 adjacent to the outlet of the fuel delivery pipe, this injection valve may be arranged nearer to the fuel pump 5 at some intermediate point in the length of the delivery pipe la.

The camshaft B is coupled by gearing 20a and 200 to the governor shaft 20d with which is operatively associated a centrifugal governor 2|, the sleeve 22 of which is engaged by one arm of a bell-crank lever 23, the other arm of which is connected to a crank 24 secured to a shaft 25. A second crank 26 on the shaft 25 is connected to a rack 21 which engages a toothed rim carried by a sleeve 28 furnished with projections 29 engaging the pump plunger Ill. The plunger III is provided with an annular flange 2% having notches 29a designed to receive the projections 29 of the sleeve 28. The plunger l reciprocates within a liner sleeve 3|, said liner being positioned within a sleeve or jacket 3Ia. The lower end of the jacket 3 la is arranged to receive and partly house the spring I3. Thus, the governor 2| will turn the sleeve 28 and therefore the pump plunger I!) so as to vary the point in the delivery stroke of the plunger at which a control edge 30 on the plunger covers the fuel suction port l5. The

quantity of fuel injected at each charge is thus automatically regulated by the governor 2i.

Arranged between the pump cylinder and the fuel delivery pipe I8 is a fuel compression space or chamber 32 into which projects a displacer 33 which can be moved into or out of the fuel compression chamber 32 by means of a lever 34 having associated therewith a positioning quadrant 34a. thereby adjusting the effective volume of the chamber 32. The displacement member 33 is biased upwardly by a spring member 34?). The needle 20 of 'the fuel injection valve 19 is loaded by a spring 36 the tension of which can be adjusted by means of a hand lever 38 which cooperates with a quadrant 31.

In Figure 4 the pump driving cam I is shown in the position in which the apex A of the cam coincides with the inner dead centre of the engine piston associated with the pump, this upper dead centre position being indicated by the crank 40. Since the forward and reverse operating surfaces 8 and of the cam 1 meet at the apex A, the pump plunger Ill operated by the cam 1 will also be in its upper dead centre position, and delivery of the fuel pump under full load conditions will take place from the point B to the point C. If the cam I is to have the necessary lift, the point B must be considerably in advance of the inner dead centre of the engine piston since the end of delivery from the pump will take place at the point C when the apex A reaches the top dead centre position.

pressibility of the fuel in the space 32 has the effect of retarding the beginning of injection from the point B to the point E and the end of injection from the point C to the point F, for forward operation of the engine. Similarly, for reverse operation of the engine, the beginning of injection is retarded from the point D to the point G whilst the end of injection is retarded from the point C to the point H. As will be seen from Figure 4 the retardation of the injection is the same whether the engine is to operate in the forward direction or in the reverse direction since the points E, G and H, F lie symmetrically with respect to the inner dead centre of the engine piston. Thus, for any given load the retardation in the fuel injection will be the same whether the engine is to operate in the forward or reverse direction.

In Figure 1, the plunger I0 is in its upper dead centre position. If now the engine is operating in the forward direction rotation of the camshaft 6 and cam 1 result in the tappet roller 12 running down the operating surface 9 of the cam I, the plunger in being moved downwards by the spring l3. As soon as the control edge 30 on the plunger uncovers the suction port It fuel will be drawn into the working chamber it from the fuel supply pipe J4 until the plunger I0 reaches its bottom dead centre position, the tappet roller l2 then bearing against the concentric portion of the cam I. As the cam 1 continues to rotate the delivery stroke of the plunger Ill will commence when the eccentric portion of the operating surface 8 commences to engage the tappet roller l2. As the plunger l0 moves upwards fuel is discharged from the working chamber it through the suction port I5 until the control edge 30 closes this suction port, after which the delivery of fuel from the working chamber I6 past the valve ll commences.

Since the pressure in the space 32 at the end of the previous injection period corresponds to the closing pressure of the needle 20 it is necessary, in order for injection to commence, first to raise the pressure in the pipe M3 to the opening pressure of the needle 20. That is to say, injection will not commence until the pressure at the outlet end of the delivery pipe I8 reaches the opening pressure of the needle 20. The presence of the space 32, however, results in the degree to which the fuel on the delivery side of the pump can be compressed being increased, this increase being in accordance with the effective volume of the space 32. Thus, the greater the volume of the space 32 the later in the delivery stroke of the plunger ID will the necessary pressure be reached in the delivery pipe Hi to raise the needle 20 of the injection valve IS. The commencement of injection is thus retarded as above described with reference to Figure 4.

When the apex A of the cam I engages the tappet roller 12 the plunger reaches the end of its delivery stroke and delivery from the pump 5 is thus terminated, the valve I1 closing. The end of injection will, however, take place somewhat later, that is tohsay when the pressure in the space 32 and pipe l8 have fallen to a value which permits the spring 36 to move the needle 2|] into its closed position. The end of injection is thus also retarded as described with reference to Figure 4.

Though the chamber 32 and displacer member 33 are both of constant cross-section, the form of the space 32 and/or of the displacer member 33 may be such as to avoid any sudden change in the cross-section available for the flow of fuel from the pump to the delivery pipe 18. .If such sudden change in cross-section is avoided the tendency to weaken or damp out the pressure wave in the fuel delivery system will be reduced. Further, instead of providing an enlarged compression space, such as the space 32, the retardation space may be provided by a pipe or conduit of substantially constant cross-section so that each pressure impulse will be propagated through, the column of fuel without the interference which would be introduced by a sudden variation in the cross-section of the passage through which the fuel flows to the fuel injection valve. A retardation space provided by a pipe or conduit of constant cross-section is, therefore, advantageous in that the desired retardation of the commencement of each injection relatively to the inner or top dead center of the engine piston is determined actually in accordance with the velocity of propagation of each pressure wave which is in turn dependent on the length of the pipe or conduit, i. e., the length and compressibility of the said fuel column. The practically undamped propagation of the pressure wave through the fuel column results in the velocity conditions provided by the operating surface of the cam being substantially fully utilized so that reliable opening of the fuel injection valve is ensured even at minimum load. In the case of fuel .pumps supplying multi-cylinder engines, each delivery pipe of the fuel pump may be made of the same length, as shown in Figure 8, even when some cylinders are farther from their associated injection pump cylinders than others. Alternatively, the pipes or conduits leading to cylinders which are nearer to their associated pump cylinders may have a greater internal diameter than the pipes or conduits which are farther from their associated pump cylinders, as shown in Figure 9, so that, for example, each delivery pipe has the same capacity.

The displacer member 33 may, if desired, be automatically operated, as shown in Figure 2, in accordance with a working value, such for example as the speed of or load on the engine and, with a view to ensuring eflective injection at small loads, the tension of the loading spring 36 of the fuel injection valve I9 may be automatically controlled by a governor driven by the engine, for example, in the same manner as that shown for controlling the position of the plunger "33-in'Figure 2. *Instead of varying the effective volume available for the fuel between the pump andthe injection valve as described with reference to Figure 1, means may be provided whereby the effective length of the delivery conduit throughwhich the fuel is delivered from the pump to the injection valve can be varied. One such arrangement is illustrated in Figure 5 in which a member 60 is arranged in the delivery system between the pump and the fuel injection valve, this member being furnished with a fuel delivery bore 6| with which a conduit from the fuel pump communicate's as at 6la. The opposite end of the bore 6| communicates as at Blb with a conduit in communication with the fuel valve. The member 60 has two pairs of conduits 62, 63 and 64, 65, the outer ends of the conduits 62, 63 being connected by a pipe 66, whilst the conduits 64, 65 are similarly connected by a pipe 6611. A rotary valve 61 is provided whereby communication between the conduit 6| and the conduits 64, 65 can either be cut off by moving the valve 61 to the position III as shown in the drawings or, by setting the valve 61 in the position IV, the fuel can be caused to be deviated from the conduit 6| through the conduit 64 and conduit 65 to the fuel injection valve. The conduits 62, 63 can similarly be connected to the conduit 6| by means of a rotary valve 68. Thus, by moving either or both the valves 61, 68 into the position IV the effective length of the delivery conduit is increased and the time required to compress the fuel lying between the pump and the injection valve is increased, thereby increasing the retardation of the commencement and end of each injection as described with reference to Figure 4.

All the connections to the member 60, that is to say for example as the connection between each end of the pipe 66 and the conduits 62 and 63, are such that sealing of the joint is effected at the inner end of the connection so that the bores of the conduits which are connected together are directly in registration and sudden increases in the internal diameter of the conduits through which the fuel flows is avoided so that the pressure wave of the fuelflow is not weakened by any sudden enlargement.

The rotary valves 61 and 68 may be automatically controlled in accordance with a working value of the internal combustion, say, the speed of or load on the engine. Thus, for example, the valves '61 and 68 may be automatically operated by a. governor driven by the engine, their handle levers 69 being connected to a governor in a manner similar to that of lever 34, as shown in Figure 2.

The invention is advantageous in that when the direction of operation of the engine is reversed each tappet roller of the pump can remain in engagement with its associated operating cam so that difiiculties in reversal, due to the large forces which are applied to the plunger, do not arise. Further, the quantity of fuel injected at each charge can be adjusted relatively to the end of injection by varying the point in the plunger stroke at which delivery from the pump commences. At small loads therefore the commencement of injection is shifted relatively to the inner dead centre position of the engine piston. Even at low loads injection will take place at a high pressure and a high temperature within the working chamber of the engine cylinder so that ignition of the fuel charge is ensured.

Since the cam for driving each pump plunger has operating surfaces for the two directions of operation of the engine respectively, when the crank angle between the beginning of the injection and the inner dead center of the engine piston is to besmall, say, for a low speed engine, the lift of the cam must be short. With a view to reducing the tendency forshocks to be imparted from the cam to its associated tappet roller, each operating surface of the cam may be tangential to the concentric part of the cam. The invention is also advantageous in that it makes it possible to avoid undesirable low-lift cams which would not only involve excessive pressures on the pump plunger but would also tend to prevent fine regulation of the quantity of fuel injected by adjusting the point in the delivery stroke of the plunger at which the pumpcommences to deliver fuel.

The control of the member 33 by the lever 34 may be manual, as shown in Figure 1, or may be automatic, as shown in the modification of Figure 2. As described in connection with Figure 1 the shaft is moved in response to the movement of the governor 2|. This movement of the shaft 25 is effective, as above described, to move the rack 21. The governor 2| may be connected so as to operate the lever 34 directly, if it is desired to provide an automatic control and movement for the member 33. Thus as shown in Figure 2, a link I4 issecured at one end to the outer end of the bell crank lever 23, which is itself in contact with the sleeve 22 of the governor 2|. The other end of the link 14 is secured to the lever 34 and thus movement of the governor is effective through the bell crank lever 23, the link 14 and the lever 34 automatically to move the member 33. It is to be understood that this automatic connection, whereby the governor moves and controls the position of the member 33 may or may not be used, and the control of this member may thus be either manual or automatic.

As illustrated in Figure 6, l is the engine, II is the multicylinder pump. A conduit 10 runs to each cylinder from the pump. These conduits are of constant and identical cross section and are shaped so that irrespective of the actual distance from the pump to each cylinder, the length of the conduit and the space within the conduit is, therefore, identical for each cylinder.

The engine shown in Figure 6 appears again in Figure 7, but instead of providing conduits from the pump to each cylinder of constant diameter and length, the conduits are of different diameters and different lengths. Thus the conduit I0 is the shortest, but is of the greatest diameter. The conduit 12 is somewhat longer and of somewhat less diameter than the conduit H and the conduit 13 is the longest and is of the least diameter. Thus the space enclosed within each conduit between the pump and the cylinder to which that conduit leads is the same for all of the conduits and in the form of the device shown in Figures 6 and 7, all delivery pipes to the various cylinders have the same capacity.

As above pointed out, the retardation space might include a special space such as the space 32 of Figure 1, or it might include a fuel conduit between the pump and fuel valve of variable length, as shown in Figure 5, or it might include a combination of the two. In general, therefore, the retardation space is positioned somewhere in the path which the fuel travels in moving from the pump to the fuel valve or injection valve past which fuel is discharged toward or into the cylinder.

I claim: I

l. combination a fuel injecting pump for reversible internal combustion engines with airless injection of fuel, a pressure actuated injection valve and a fuel line connecting said valve with said pump, a cam having adjoining symmetrical operating faces for driving said pump,

control means for retarding the period of injection with reference to the period: of the delivery of fuel by said pump, said control means comprising conduits in controlled communication with the fuel line and of uniform cross-sectional area substantially equal to the cross-sectional area of said fuel line whereby pressure waves of fuel flow are not weakened by sudden enlargements of the conduit.

2. In combination a fuel injecting pump for reversible internal combustion engines with airless injection of fuel, a pressure actuated injection valve and a fuel line connecting said valve with said pump, a cam having adjoining symmetrical operating faces for driving said pump, control means for retarding the period of injection with reference to the period of the delivery of fuel by said pump, said control means comprising conduits of uniform cross-sectional area substantially equal to the cross-sectional area of the fuel line and adjustably jointed thereto, each joint for the conduits being such that the two conduits connected together are in direct registration, thereby avoiding an enlargement in the cross section at the joint whereby pressure waves of fuel flow are not weakened by said sudden enlargement.

3. In combination, with a reversible two-stroke cycle internal combustion engine a cylinder, a piston, a crank shaft, a connection between the piston and crank shaft, a fuel pump comprising a cylinder and a pump plunger, an injection valve, a fuel conduit between the pump cylinder and injection valve, a drive for the pump plunger actuated by movement of the engine crank shaft, the drive being so arranged and proportioned that the pump plunger is at inner dead center at approximately the time that the engine piston is at innerdead center, and a cam adapted to actuate said pump plunger, said cam being provided with a pair of symmetrical faces, the upper ends of said faces adjoining each other, the capacity of the conduit between the pump cylinder and injector being such that the injection period is delayed with respect to the movement of the pump plunger and delivery of fuel from the injection valve to the engine cylinder continues a predetermined time after the pump plunger has reached its inner dead center and after discharge of fuel from the pump cylinder to the conduit has terminated, and means for varying the capacity of said conduit.

4.-In combination, with a reversible two-stroke cycle internal combustion engine a cylinder, a piston, a crank shaft, a connection between the piston and crank shaft, a fuel pump comprising a cylinder and a pump plunger, an injection valve, a fuel conduit between the pump cylinder and injection valve, means controlling the passage of fluid from the pump cylinder to the conduit, said means comprising a valve, adapted to open upon pressure from the pump cylinder to permit passage of fuel into the conduit, and

adapted to close automatically to prevent return flow of fuel into the cylinder, a drive for the pump plunger actuated by movement of the engine crank shaft, the drive being so arranged and proportioned that the pump plunger is at .inner dead center at approximately the time that the engine piston is at inner dead center, and a cam adapted to actuate said pump plunger, said cam being provided with a pair of symmetrical faces, the upper ends of said faces adjoining each other, the cam faces being related to the crank shaft or the engine in such manner that when the engine piston and the pump plunger are at approximately their respective inner dead centers, the peak of the cam at which the upper ends of said cam faces join, is in contact with the driving means for actuating the said plunger, the capacity of the conduit between the pump cylinder and injector being such that the injection period is delayed with respect to the movement of the pump plunger and delivery of fuel from the injection valve to the engine cylinder continues a predetermined time after discharge of fuel from the pump cylinder to the conduit has terminated, and means for varying the capacity of said conduit.

5. In combination, with a reversible two-stroke cycle internal combustion engine a cylinder, a piston, a crank shaft, a connection between the piston and crank shaft, a fuel pump comprising a cylinder and a pump plunger, an injection valve, a fuel conduit between the pump cylinder and injection valve, means controlling the passage of fluid from the pump cylinder to the conduit, said means comprising a valve, adapted to open upon pressure from the pump cylinder to permit passage of fuel into the conduit, and adapted to close automatically to prevent return flow of fuel into the cylinder, a drive for the pump plunger actuated by movement of the engine crank shaft, the drive being so arranged and proportioned that the pump plunger is at inner dead center at approximately the time that the engine piston is at inner dead center, and a cam adapted to actuate said pump plunger, said cam being provided with a pair of symmetrical faces, the upper ends of said faces adjoining each other, the cam faces being related to the crank shaft of the engine in suchmanner that when the engine piston and the pump plunger are at approximately their respective inner dead centers, the

peak of the cam at which the upper ends of said" 'cam facesjoin, is in contact with the drivingmeans for actuating the said plunger, the capacity of the conduit between the pump cylinder and injector being such that the injection period is delayed with respect to the movement of the pump plunger and delivery of fuel from the injection valve to the engine cylinder continues a predetermined time after the pump plunger has reached its inner dead center and after discharge of fuel from the pump cylinder to the conduit has terminated, and means for varying the capacity of said conduit, and additional means actuated at varying speeds in conformity with variationin the engine speed for controlling the movement of said capacity varying member to control the capacity of said conduit automatically in conformity with variations in the engine speed. HEINRICH wiiL'r

Images