US2754813A

US2754813A - Fuel injection systems for internal combustion engines

Info

Publication number: US2754813A
Application number: US273502A
Authority: US
Inventors: Purdie William Hamilton; Jackson Percy
Original assignee: William Doxford and Sons Ltd
Current assignee: William Doxford and Sons Ltd
Priority date: 1951-02-26
Filing date: 1952-02-26
Publication date: 1956-07-17
Anticipated expiration: 1973-07-17

Description

July 17, 19-56 W.'H. PURDIE ETAL 2,754,813

FUEL INJECTION SYSTEMS FOR INTERNAL COMBUSTION ENGINES Filed Feb. 26, 1952 4 Sheets-Sheet 1 17) well far-J Wi I l i 0/" l/anu'lz'an Purdzl 5 Percy Jackson y 1956 yv. H. P URDIE ETAL 2,754,813

FUEL INJECTION SYSTEMS FOR INTERNAL COMBUSTION ENGINES Filed Feb. 26, 1952 4 Sheets-Sheet 2 aye/lions- William #:7011110 Pan/[e a Ferry Jacfirah I July 17, 1956 w. H. PURDIE ETAL 2,754,813 FUEL INJECTION SYSTEMS FOR INTERNAL. COMBUSTION ENGINES Filed Feb. 26, 1952 4 Sheets-Sheet 3 lore/1 era Will 1' din dmi/fob Kurd/ed Perry Jlaf'ooa 957w fi wo x July 17, 1956 w, PURDIE r 2,754,813

FUEL INJECTION SYSTEMS FOR INTERNAL COMBUSTION ENGINES Filed Feb. 26, 1952 4 Sheets-Sheet 4 Perg Mac-firm:

William Hamilton Purdie and United States Patent Qfiice 2,7 54,813 Patented July 17, 1956 FUEL INJECTION SYSTEMS FOR INTERNAL COMBUSTION ENGINES Percy Jackson, Sunderland, England, assignors to William Doxford and Sons Limited, Sunderland, England, a British company Application February 26, 1952, Serial No. 273,502

Claims priority, application Great Britain February 26, 1951 10 Claims. (Cl. 123-139) The invention relates to fuel systems for internal combustion engines and particularly for internal combustion engines operating on the diesel or semi-diesel cycles.

The invention relates to air-less injection internal combustion engines of the kind having a fuel injection system 0 comprising a variable delivery fuel pump with a delivery connection to a cylinder injection nozzle, a hydraulic accumulator embodying a movable plunger or the like and connected in the pump delivery connection for re- 9 taining under pressure the quantity of fuel delivered by the pump at each operating stroke, discharge valve means controlling the connection at a position between the accumulator and the nozzle and means for operating the valve means in timed relation with the engine to open the connection from the accumulator to the nozzle and thereby to permit the accumulator pressure to inject into the engine cylinder at the appropriate time in the cycle the measured quantity of fuel delivered by the pump.

in engines of the above kind as at present proposed, spring means operating on the plunger or the like are employed to maintain the pressure on the fuel in the accumulator and to effect the injection of the fuel into the engine cylinder. The fuel pressures required in practice are however very high, commonly of the order of six to eight thousand pounds per square inch, and in pumps for largeengines the springs required are not only of very heavy construction but are diificuit to manipulate. One object of the present invention is to provide an arrangement whereby the use of springs may be avoided or springs of much lighter construction employed.

In the present invention fluid pressure in a pressure chamber is employed for maintaining the pressure on the fuel in the accumulator and to effect the injection of the fuel into the engine cylinder.

In one form of the invention the fuel pump comprises r apump plunger operating in a pump chamber and making one operating stroke for each injection of fuel and there is also in the pump chamber (e. g. in opposition to the pump plunger) a freeplunger urged into the pump chamber by fluid pressure on the outer end of the plunger, the arrangement being such that on the operating stroke of the pump plunger the fuel pumped thereby forces the free plunger outwardly and is accumulated in the pump chamber under the pressure applied to the free plunger and on the opening of the discharge valve the free plunger moves inwardly of the chamber to discharge the accumulated fuel to the injection nozzle. In one embodiment of this arrangement the outer end of the free plunger is contained within a pressure chamber maintained under fluid (e. g. fuel :or 'air') pressure 'to urge the plunger into the pump chamber as aforesaid. 'When liquid pressure is employed the pressure chamber and any connections thereto are preferably made of substantial volume and the resilience of the pressure chamber and connections together with the compressibility of the liquid may be relied upon to accommodate the changes in volume as the free plunger moves. The pressure chamber may be maintained under liquid (e. g. fuel) pressure by a pump which may be engine driven, for example a reciprocatory pump driven by the shaft employed to drive the fuel pump or by other means. Means may be included for varying the pressure maintained in the pressure chamber by the pump. In an alternative arrangement the pressure chamber is maintained under gas (e. g. air) pressure supplied by a separate compressor (e. g. engine driven) or from a supply of air under pressure maintained in air bottles for engine starting purposes or it may be bled off from the engine cylinder. The gas pressure in the pressure chamber may be made variable by means of an adjustable reducing valve.

If necessary or convenient the outer end of the free plunger may have an area greater than that of the end within the pump chamber to effect a multiplication of the pressure.

The plunger or a piston associated therewith may be provided with sealing means to prevent leakage between the pressure chamber and the pump chamber, this feature being of especial importance when multiplication of the pressure as just described is employed.

in the form of the invention in which a reciprocatory fuel pump is employed the quantity of fuel delivered by the pump at each stroke may be controlled by returning to the fuel supply a variable proportion of the pump output. The return of the fuel may be controlled by a valve operated in timed relation with the operating strokes of the pump plunger to shut off the fuel return at a position in the pump stroke where the volume of the re mainder of the stroke equals the volume of fuel required for injection, the position being adjustable to vary the volume as required to suit the running conditions of the engine or the pump may be of the port control type in which the plunger is axially rotatable for adjustment and a port in the plunger or cylinder co-operates with a groove or surface in the other of these members to determine, according to the position of rotational adjustment of the plunger, the position in the stroke of the plunger at which the port is covered, the groove .or surface extendingat a uniforrnangle (i. e., helically) or at a changing angle to the operating movements of the plunger. Preferably the port is in the cylinder. The fuel may be returned to the supply either through the inlet to the pump or through a separate by-pass. In the former case the return of the fuel may be controlled by the inlet valve of the pump and in the latter case there may .be an .independent valve in the bypass.

A reciprocatory pump as just described may also be used to charge the pressure chamber with fuel or other liquid.

Some specific constructions .of engine according .to the invention will now be described by way of example .and

with reference to the drawings, in which:

Figure 1 shows a section through a combined fuel pump and accumulator,

Figure 2 is a rear view of the pump shown in Figure -1,

Figure 3 shows acharging pump for maintaining pressure in the accumulator pressure chamber,

Figure 4 shows a section through a second form of fuel pump and accumulator.

The engine forming the subject of the first example is shown in Figures 1 to 4. The engine is athree-cylindrical opposed piston reversing marine engine operating on the full diesel cycle, with air-less injection. Each of the cylinders 1, 2, 3 has a combined pump and accumulator shown at 4, 5 and 6. The three pumps are driven from a common cam-shaft driven by a chain 8 from the engine crankshaft. All the accumulator chambers ,of the pumps are interconnected by a pipe (not shown) and they are all connected to a single charging pump also driven from the shaft 7. If desired a second charging pump may be provided and the two pumps may be used, simultaneously or alternatively.

All three accumulator pumps are alike in construction and operation and only one will be described in detail. The pump is shown in Figures 2 and 3 and has a plunger 12 operated by an eccentric 13 on the cam-shaft 7 of the engine and the measured quantity of fuel to be injected is trapped in the space 14 during upward movement of the plunger and when the suction valve 15 has been permitted to seat by the cam 16 and thus to prevent escape of fuel from the space. Above the space 14 there is a free plunger 17 of which the lower end is subjected to the pressure of the fuel in the space 14 and the upper end is subjected to the pressure of oil in an accumulator chamber 19. -This chamber is, as stated already, connected to the charging pump 10, the inlet to the chamber being at 20. The charging pump 10 is driven by a cam 22 (see Figure 3) on the shaft 7. The quantity of fuel oil delivered by the pump into the chamber 19 and hence the pressure in the chamber can be regulated by axial rotation of the plunger by means of the control rack 23 operated by lever 24 in the manner later described with reference to the pump shown in Figure 4, the present pump having a plunger and inlet ports similar to those shown in Figure 5. Alternatively the lever 24 may control a pressure relief valve. The

lever 24 is coupled through link mechanism 25 to the control gear 26 of the engine so that the pressure in the accumulator chambers 19 may be varied according to the speed and load of the engine. The pump 16 can be actuated by hand to raise the pressure in the accumulator chambers 19 before the engine is started by actuating the handle 28 which lifts the lever 29 by rotation of the cam 30 to operate the pump. (In the drawing the lever 29 is shown raised by the cam 22.)

The lift of the free plunger 17 will vary according to the amount of fuel injected (i. e. according to the load on the engine) and a tell-tale plunger 32 is provided, in this example, at the upper end of the plunger 17 to indicate the travel of the plunger 17 and thereby to show that this is correct according to the load and to indicate that all the plungers are rising by equal amounts.

A spring 53 is provided in the accumulator chamber 19 engaging with the plunger 17 to augment the action of the pressure in the chamber and to ensure that there is a minimum injection pressure should there be a failure in the delivery of the pump 10.

In the operation of the engine the plunger 12 traps in the space 14 a quantity of fuel determined by the position of the plunger at which valve 15 seats. The pressure of the fuel in the space 14 is equal to that of the oil in the chamber 19 plus the pressure due to the spring 32. When the delivery valve 34 of the pump is opened by cam 35 on shaft 7, the plunger 17 falls rapidly under the action of the pressure in the chamber 19 and the spring and the fuel in the space 14 is injected into the engine cylinder.

The position in the upward stroke of the plunger 12 at which the suction valve 15 is allowed to seat and, consequently, the amount of fuel delivered by each stroke, is variable by rotation of an eccentric 36 on a shaft 37 rotatable from the engine control gear 26 by linkwork 38. The timing of the opening of the discharge valve 34 is simultaneously movable, in like manner, by means of an eccentric 39 on the shaft 37.

Figure 4 shows another construction of fuel pump which may be used in place of that shown in Figures 1 and 2 and which, in view of the simplicity, is to be preferred for many applications. The pump is, as in the previous example, driven from the shaft 7 by an eccentric 40 which reciprocates the pump plunger 41. This plunger is also rotatable by means of a rack 42 engaging with pinion teeth 43 on the plunger, the rack being reciprocable by suitable link means from the engine control gear 26. The plunger 41 is formed, at its upper end, with a recess 42 bounded on one side by a helical step 43. This step cooperates with a port 44 in the cylinder wall leading back to the fuel supply, to close the port at a position in the stroke of the plunger 41 depending upon the rotational position of the plunger. Hence the amount of fuel trapped in the space 46 and pumped may be varied. The plunger also has a central passageway 45 leading to a circumferential groove 47 which registers with a discharge port 48 at the upper limit of movement of the plunger.

Opposed to the plunger 41 there is a free plunger 50 which is urged downwardly, as in the previous example, by hydraulic pressure in a chamber 51 and by a spring 52.

In the operation of the pump, fuel is drawn into the pump cylinder during the downward stroke of plunger 41 and during the first part of the upward movement a portion of this fuel (the amount depending upon the rotational position of the plunger) is returned to the supply through port 44. The remainder of the fuel is trapped in space 46 and further movement of the plunger 41 causes plunger 50 to be raised. When groove 47 registers with port 48 the plunger 50 rapidly descends and forces the trapped fuel through the discharge port 48 to the injection nozzle.

We claim:

1. A variable delivery fuel pump for an airless injection internal combustion engine, which pump comprises a pump chamber, a pump plunger reciprocably operable in said chamber, engine-driven means for operating said pump plunger, a fuel inlet connection to said chamber, a delivery connection from said chamber, discharge valve means for controlling the flow through said delivery connection, engine-driven means for operating said discharge valve means whereby fuel is accumulated in said chamber until released by said valve means, a free plunger of which one end extends into said chamber, a pressure chamber surrounding the other end of said free plunger, fluid pressure means including a separate engine-driven pump providing a controlled variable fluid pressure on the free plunger independently of the pressure of the fuel supply in said chamber to urge said free plunger into said first mentioned chamber, and spring means also urging said free plunger into said first mentioned chamber.

2. A variable delivery fuel pump for an airless injection internal combustion engine, which pump comprises a pump chamber, a pump plunger reciprocably operable in said chamber, engine-driven means for operating said pump plunger, a fuel inlet connection to said chamber, a delivery connection from said chamber, discharge valve means for controlling the flow through said delivery connection, engine-driven means for operating said discharge valve means whereby fuel is accumulated in said chamber until released by said valve means, a free plunger of which one end extends into said pump chamber, a pressure chamber surrounding the other end of said free plunger, a separate engine-driven pump providing a controlled variable liquid pressure in said pressure chamber urging said free plunger into said pump chamber independently of the pressure of the fuel supply, and spring means also urging said free plunger into said pump chamber.

3. A variable delivery fuel pump for an airless injection internal combustion engine, which pump comprises a pump chamber, a pump plunger reciprocably operable in said chamber, engine-driven means for operating said pump plunger, a fuel inlet connection to said chamber, a delivery connection from said chamber, discharge valve means for controlling the flow through said delivery connection, engine-driven means for operating said discharge valve means whereby fuel is accumulated in said chamber until released by said valve means, a free plunger of which one end extends into said chamber, a pressure chamber surrounding the other end of said free plunger, which other end has an area greater than that of said one end Within the pump chamber, a separate pump providing a controlled variable liquid pressure in said pressure chamber independently of the pressure of the fuel supply, and spring means also urging said free plunger into said pump chamber.

4. A variable delivery fuel pump for an airless injection internal combustion engine, which pump comprises a pump chamber, a pump plunger reciprocably operable in said chamber, engine-driven means for operating said pump plunger, a fuel inlet connection to said chamber, a delivery connection from said chamber, adjustable discharge valve means for controlling the flow through said delivery connection, means for returning to the fuel supply an adjustable proportion of the pump output, enginedriven means for operating said discharge valve means whereby fuel is accumulated in said chamber until released by said valve means, a free plunger in said chamber, fluid pressure means including a separate engine driven pump providing a controlled variable fluid pressure on the free plunger opposite the pump chamber independent of the pressure of the fuel supply said free plunger into said chamber, and spring means also urging said free plunger into said chamber.

5. A variable delivery fuel pump for an airless injection internal combustion engine, which pump comprises a pump chamber, a pump plunger reciprocably operable in said chamber, engine-driven means for operating said pump plunger, a fuel inlet connection to said chamber, a delivery connection from said chamber, adjustable discharge valve means for controlling the flow through said delivery connection, means for returning to the fuel supply an adjustable proportion of the pump output, engine-driven means for operating said discharge valve means whereby fuel is accumulated in said chamber until released by said valve means, a free plunger of which one end extends into said pump chamber, a pressure chamber surrounding the other end of said free plunger, a separate engine-driven pump providing a controlled variable liquid pressure in said pressure chamber independent of the pressure of the fuel supply to urge said free plunger into said pump chamber, and spring means also urging said free plunger into said pump chamber.

6. A variable delivery fuel pump for an airless injection internal combustion engine, which pump comprises a pump chamber and a co-operating pump plunger reciprocably operable and axially rotatable in said chamber, one member of said chamber and plunger having a helical groove leading into the pump chamber beyond the end of the plunger and the other member of said chamber and plunger having a port co-operating with said helical groove and leading to the fuel supply whereby an adjustable proportion of the pump output is returned to the fuel supply dependent on the angular position of said plunger relative to said chamber, a delivery connection from said chamber, discharge valve means operated by said plunger for controlling the flow through said delivery connection whereby fuel is accumulated in said chamber until released by said valve means, a free plunger in said chamber, fluid pressure means including a separate engine driven pump providing a controlled variable fluid pressure on the free plunger opposite the pump chamber independent of the pressure of the fuel supply said free plunger into said chamber, and spring means also urging said free plunger into said chamber.

7. A variable delivery fuel pump for an airless injection internal combustion engine, which pump comprises a pump chamber and a co-operating pump plunger reciprocably operable and axially rotatable in said chamber, one member of said chamber and plunger having a helical groove leading into the pump chamber beyond the end of the plunger and the other member of said chamber and plunger having a port co-operating with said helical groove and leading to the fuel supply whereby an adjustable proportion of the pump output is returned to the fuel supply dependent on the angular position of said plunger relative to said chamber, a delivery connection from said chamber, discharge valve means operated by said plunger for controlling the flow through said deliv ery connection whereby fuel is accumulated in said chamber until released by said valve means, a free plunger of which one end extends into said pump chamber, a pressure chamber surrounding the other end of said free plunger, a separate engine-driven pump providing a controlled variable liquid pressure in said pressure chamber independent of the pressure of the fuel supply, to urge said free plunger into said pump chamber, and spring means also urging said free plunger into said pump chamber.

8. A variable delivery fuel pump for an airless injection internal combustion engine, which pump comprises a pump chamber, a pump plunger reciprocably operable in said chamber, engine-driven means for operating said pump plunger, a fuel inlet connection to said chamber, a delivery connection from said chamber, discharge valve means for controlling the fiow through said delivery connection, engine-driven means for operating said discharge valve means whereby fuel is accumulated in said chamber until released by said valve means, a free plunger of which one end extends into said pump chamber, a pressure chamber surrounding the other end of said free plunger, a separate engine-driven variable delivery pump of the port control type providing a controlled variable liquid pressure in said pressure chamber independent of the pressure of the fuel supply to urge said free plunger into said pump chamber, and spring means also urging said free plunger into said pump chamber.

9. A variable delivery fuel pump for an airless injection internal combustion engine, which pump comprises a pump chamber, a pump plunger reciprocably operable in said chamber, engine-driven means for operating said pump plunger, a fuel inlet connection to said chamber, a delivery connection from said chamber, discharge valve means for controlling the flow through said delivery connection, engine-driven means for operating said discharge valve means whereby fuel is accumulated in said chamber until released by said valve means, a free plunger of which one end extends into said pump chamber, a pressure chamber surrounding the other end of said free plunger, a separate engine-driven reciprocating pump for maintaining liquid pressure in said pressure chamber to urge said free plunger into said pump chamber, spring means also urging said free plunger into said pump chamber, and a manually-operable drive for operating said separate reciprocating pump whenthe engine is not running.

10. A variable delivery fuel pump for an airless injection internal combustion engine comprising a pump chamber, a pump plunger reciprocably operable in said chamber, engine driven means for operating said pump plunger, a fuel inlet connection to said chamber, a delivery connection from said chamber, discharge valve means for controlling the flow through said delivery connection, engine driven means for operating said discharge valve means whereby fuel is accumulated in said chamber until released by said valve means, a free plunger in said chamber, fiuid pressure means delivering a controlled variable fluid pressure on the free plunger independently of the pressure of the fuel supply and urging the free plunger into said chamber, and spring means continuously acting on the free plunger in cooperation with the fluid pressure means whereby to provide continuous pressure on the plunger.

References Cited in the file of this patent UNITED STATES PATENTS (Other references on following page) UNITED STATES PATENTS Sprado Feb. 5, 1935 Sass et a1 Oct. 29, 1935 Retel Dec. 17, 1940 FOREIGN PATENTS Great Britain June 20, 1929 8 Great Britain Aug. 23, 1949 Switzerland Jan. 2, 1933 Switzerland Sept. 16, 1933 France Apr. 27, 1934 France Jan. 11, 1943