US3320892A - Fuel injection system - Google Patents

Description

May 3, 6 5. 0. WOLFF FUEL INJECTION SYSTEM 2 Sheets-Sheet 1 Filed Dec. 20, 1965 May 23, 1967 G. D. WOLFF FUEL INJECTION SYSTEM 2 Sheets-Sheet 2 Filed Dec. 20, 1965 United States Patent 3,3203% FUEL FNJECTEUN SYSTEM George D. Wolff, Hazel Crest, lill., assignor to Allis- Chalrners Manufacturing Company, Miiwaukee, Wis. Filed Dec. 20, 1965, Ser. No. 522,007 8 Claims. (Cl, 1il3-2) This is a continuationin-part of application Ser. No. 405,1-89, iiled Oct. 1964, now abandoned.

This invention relates to a fuel injection system for diesel engines and particularly to precharging the fuel injection lines prior to injection.

In the usual fuel injection pump the delivery passage is connected to the supply pressure chamber for a brief interval following injection to terminate injection. It is also known that pressure relief after injection is necessary in order to absorb the reflected pressure waves from the nozzle. If such relief is not afforded, pressure surges occurring after cutoff of fuel delivery to the injector may cause secondary injection which in turn causes a decrease in combustion efliciency. Relieving the pressure by use of a retraction delivery valve or by connecting the fuel delivery lines briefly to the supply chamber or to a low pressure portion of the system is usually effective in preventing secondary injection; however, voids often develop from this relief in the injection lines which cause erratic pump performance. Voids in the injection lines make it particularly difiicult to control the injection in the low speed range of the engine and at low fuel delivery.

In fuel injection pumps using retraction delivery valves, the retraction of the delivery valve serves to relieve pressure in the delivery line at termination of injection. More specifically the retraction delivery valve reduces the reflection of the pressure wave returning from the injector after the end of the pumping stroke. To do this a small volume of fuel, the retraction volume, is displaced by the delivery valve, upon its closing, from the high pressure system back into the pumping chamber. Thus, a void is created into which the fuel carried in the returning pressure wave from the injector is dumped. Ideally, the volume of fuel carried in the returning wave is equal to the void created (the retraction volume) and in such a case the returning pressure wave is completely absorbed so that a reflection pressure wave will not be created at the pump end of the delivery line.

The amplitude of the returning pressure wave and consequently the volume of fuel carried by this wave, however, is not only a function of dimensional parameters, such as delivery line ID and injector orifice area, but is also a function of the amplitude of the primary wave initiated at the pump during the pumping stroke. It is known that the amplitude of the primary wave varies with speed and load. When the engine rpm. is increased the plunger moves faster and a pressure wave with a higher amplitude is created. When the fuel delivery of the pump is increased, the pressure buildup in the pump will be greater than with a smaller delivery. Thus, the amplitude of the primary pressure wave initiated at the pump during the pumping stroke varies with engine speed and load and so also does the amplitude of the returning pressure wave. Ideally, therefore, a delivery valve retraction volume should also vary with speed and load. As this is not practical, a retraction volume is conventionally selected which is ideal only for one speed load combination. For all other conditions it will be a compromise i.e. either too large, resulting in a negative reflection of the returning wave and thus voids in the high pressure system, or too small, resulting in a positive reflection and thus possibly leading to secondary injections.

Thus, the development engineer is confronted with the problem of tailoring his injection equipment to achieve ice satisfactory injection with low injection quantities and low speeds (low idle) without having secondary injections with high injection quantities and high speeds (full load). The speed and load range of the modern diesel engine is progressively expanding and the task of achieving satisfactory injection throughout this increasing range is becoming more and more diflicult. The beforementioned limitation of the conventional injection system is an important restrictive factor in the further development of high speed, high BMEP diesel engines leading to such expensive solution as unit injectors or separate pumps for each cylinder.

Another serious problem has arisen as higher performance and greater economy of operation are sought in diesel engines. As the brake mean effective pressure (BMEP) of diesel engines has increased, inwardly opening fuel injectors, with high opening pressure, have become the generally accepted type of fuel injector. Inwardly opening injectors characteristically employ a differential area valve with high opening pressure and somewhat lower closing pressure. The spring loading of the valve is chosen to provide a sufficiently high closing pressure to prevent combustion gases from entering the pressure chamber of the injector.

As the cylinder pressures are increased, as by turbocharging, the injectors have been designed with higher opening pressure so that the closing pressure would be above the cylinder pressure. A high closing pressure results in high seating forces being imposed on the valve seat. These forces tend to pound out the seat, thus resulting in short injector life. Although engine output can be increased by increasing engine speed, there are well known practical limitations in this route to increased performance. Increases in power, other than by increasing speed, results in higher combustion pressures and higher injector valve seating forces and hence reduced valve seat life.

it is an object of this invention to provide a fuel injection system which obviates the problems hereinbefore outlined.

It is a further object of this invention to provide an improved fuel injection system for high BMEP diesel engines utilizing a distributor type fuel pump.

It is a further object of this invention to provide a new and improved fuel injection system using a distributor type pump wherein the injection lines are connected to a low pressure supply during a major part of the time that they are not used for injection and the injectors have a relatively low opening pressure without the problem of combustion gases entering the pressure chamber of the injectors after injection.

It is a further object of this invention to provide a fuel pump which achieves proper performance of the engine within a very wide speed and load range.

It is a further object of this invention to provide a fuel pump wherein voids in the high pressure system are elimi nated prior to the beginning of the delivery stroke.

It is a further object of this invention to provide a fuel pump wherein the fuel injection lines are connected to the fuel pump supply chamber to provide equalization of pressure in the injection lines and precharging thereof during the time they are not being employed to inject fuel.

It is a further object of this invention to provide a fuel pump which permits a short period of fuel injection without the problems of secondary injection or voids in the fuel line.

It is a further object of this invention to provide a single plunger distributor type fuel pump with a passageway in the plunger connecting the delivery lines with the supply chamber during most of the period between injections.

It is a further object of this invention to provide a fuel injection system of the type having a low pressure zone, a high pressure zone and an intermediate pressure zone and to provide means for connecting the fuel delivery passageways to the intermediate pressure zone for the major portion of time they are disconnected from delivery pressure.

These and other objects will be apparent to those familiar with the art when the following description is read in conjunction with the drawings in which:

FIG. 1 is a view of a fuel injection system, including a fuel injection pump in section, in which the present invention is incorporated;

FIG. 2 is a section view taken along the lines II-II in FIG. 1;

FIG. 3 is a section view taken along the line IIIIII in FIG. 2;

FIG. 4 is a partial view of the pump plunger; and

FIG. 5 is a section view taken along the line VV in FIG. 1.

Referring to FIG. 1, my precharged fuel injection system includes a pump 8 having a plunger 11 reciprocated in a plunger bore 112 of the head portion of pump housing 9 by a cam 13 formed on the pump drive shaft 14. The plunger 11 is rotated by a gear train including gears 16, 17 of supply pump 15 and gears 1-8, 19. The plunger 11 is connected to rotate with the gear 19 and reciprocate relative thereto. Gears 16 and 18 are integrally formed to provide a gear cluster and gear 17 is nonrotatably secured to the drive shaft 14.

The pump housing 9 includes a governor compartment 21, which is at fuel tank pressure by virtue of its being connected thereto by a return line indicated schematically by dot-dash lines 22. The housing 9 also includes a supply chamber 26 which is supplied fuel by the gear pump 15 by way of conduit 27 in which a fuel filter 23 is interposed. The supply pump 15 draws fuel from the fuel tank 29 by way of conduit 31. The fuel tank 20 and governor compartment 21 may be maintained at near atmospheric pressure and the supply chamber 26 is maintained at an intermediate pressure, such as 50 pounds per square inch, by a pressure maintaining valve 32 disposed between the supply chamber 26 and the governor chamber 21. A plurality of fuel delivery passages 36 are adapted at their outer ends, by threaded openings 37, for connection to fuel injection conduits or lines leading to the injectors. The inner ends of the passages 36 terminate, as illustrated in FIG. 2, at openings 38 which are equally circumferentially spaced.

Although my precharged pump will operate satisfactorily with inwardly opening (differential area) injectors,

I have found that outwardly opening injectors may be advantageously employed. In FIG. 1, I show an out- .wardly opening injector 61 connected in fluid communication to one of the passages 36 by line 62, indicated schematically.

As will be noted in FIGS. 1 and 3, the upper end of the bore 12 is closed to form a high pressure chamber 41. The high pressure chamber 41 is at injection pressures only during the upward movement (pumping stroke) of the plunger 11. The plunger 11 includes a pumping portion 42, a distributing portion 43 and an effective stroke control portion 44. Referring also to FIGS. 2 and 3, the distributing portion 43 of the plunger, which serves as rotating valve means to cyclically and individually connect in a sequential manner the high pressure chamber 41 with the delivery passages 36, includes a radially opening port 46 which is placed in free flow fluid communication with the injection pressure chamber 41 by an axial passage 47 in the plunger 11. The passage 47 is open at its upper end and connects to radial passages 48 in the effective stroke control portion 44- of the plunger 11, which cyclically register with grooves 49 in control collar 51. FIG. 5 illustrates the registrability of passages 48 with grooves 49.

As shown in FIGS. 1, 2, 3 and 4, a recess 55 is formed in the distributing portion of the plunger 11 in circumferentially spaced relation to port 46. The recess 55 has a circumferential width several times the circumferential width of port 46 and is placed in free flow fluid communication with the supply chamber 26 by an axial groove 56. As is illustrated in FIG. 2, the recess 55 places the fuel delivery passages 36 in free flow fluid communication with the supply chamber 26 during a substantial portion of the time that they are out of registry with the port 46.

Operation of the fuel injection system As the plunger 11 commences its upward stroke it simultaneously rotates so that its supply and spill passages 48 move out of registery with the axial grooves 49. When this occurs further upward movement of the rotating plunger 11 effects high pressure in the injection chamber 41 and simultaneously brings the delivery port 46 into registry with one of the delivery passages 36. A majority of the other delivery passages 36 are connected to the supply chamber 26 by way of recess 55 and groove 56. As the plunger continues to rotate and move upwardly in its pumping stroke, the top series of passages 48 in the control portion of the plunger will move above the collar 51, thereby spilling the pressure fluid from the pressurized delivery passage 36 by way of the delivery port 46 which still is in registration therewith. Further rotative movement of the plunger will move the port 4.6 out of registry with the pressure relieved passage 36 and connect the latter in free flow fluid communication with the passageway formed by recess 55 and groove 56.

When the upper row of supply passages 48 moves above the collar and relieves the pressure in the delivery passage 36 with which the delivery port 46 registers at the time, the injector valve at the engine cylinder will close and the returning pressure wave in the passage 36 is channeled to the supply chamber 26 by way of delivery port 46, passages 47, 48 and grooves 49. Thus the returning pressure wave from the injector travels to the supply chamber, where it is absorbed, by way of port 46, passages 47, 48. The time interval for this communication between passage 36 and chamber 26 is not SllfilClfiIlt to permit equalization of pressure in the delivery passage and in fact a low pressure condition in the delivery passage may result which in turn may induce formation of cavities. The cavities of which I speak are those formed of vapor, entrained in air and dissolved air which is liberated from the liquid fuel at low pressure. The use of passage means 55, 56, which serve as a rotating valve to cyclically connect the delivery passages 36 to the supply chamber 26, is effective to equalize the pressure in, and precharge the delivery passages 36, since the latter are connected to the supply chamber 26 for a relatively long time interval.

As is apparent from my construction, during pump operation the individual delivery passages 36 are connected to the supply chamber 26 for a major portion of the time, that is, over one-half the time. In a pump having three or more delivery passages, it may be practical to use as short a time interval for precharging as the time interval required for two injection cycles. Equalization of the pressure in the delivery passages and precharging them to supply chamber pressure, insures equal delivery of pressure fluid to the cylinder injectors during injection.

Although a fuel pump using my precharging concept could be provided with a delivery valve between the injection chamber 41 and the port 46, I have found the delivery valve to be unnecesary and its elimination results in further improvement in engine performance. The delivery valve is a source of reflection for the returning pressure wave in the delivery lines and hence its elimination is beneficial. Also, elimination of the delivery valve decreases the volume of the high pressure system of the pump with resulting improvement in delivery performance. My fuel pump also makes it possible for a given fuel system to have a shorter duration of injection and this provides fast burning of the fuel and more efficient combustion.

Having essentially elimiated the reflected pressure wave by means of the precharging concept, I have found that diesel injectors with outwardly opening valves may be used to great advantage over inwardly opening injectors. As herein before discussed the closing pressure for inwardly opening injectors has necessarily been increased as engine BMEP has increased, thus reducing valve seat life. Since the combustion gases tend to force the outwardly opening valve 63 closed rather than open (as occurs in an inwardly opening injector), a lower closing pressure can be used for valve 63 without permitting entrance of combustion gases into injector pressure chamber 64. Reducing closing pressure of the injector valve results in longer life of the valve seat 66. Also, as is well known, the cost of outwardly opening injectors is substantially less than inwardly opening nozzles.

My prechar-ged fuel injection system provides improved fuel injection through precise and equal delivery of fuel to the engine cylinders, permits higher cylinder operating pressures without attendant problems of combustion gases entering the injectors or excessive injector valve closing pressures and affords a marked reduction in cost of injection equipment through reduced pump and injector costs.

The embodiments of the invention for which an exelusive property or privilege is claimed are defined as follows:

1. In a distributor type fuel injection pump the combination comprising:

a pump housing including a bore, a plurality of valveless delivery passages adapted to connection to fuel delivery lines, respectively, an injection pressure chamber, and a supply chamber, means supplying fuel to said supply chamber and maintaining the latter at a pressure substantially above atmospheric pressure, means for cyclically transferring fuel from said supply chamber to said injection pressure chamber and for pressurizing it to an injection pressure including a reciprocable pump plunger in said bore, and

rotating valve means in said housing between said in jection pressure chamber and said delivery passages cyclically and individually connecting said delivery passages to said injection pressure chamber during the pumping stroke of said plunger and passage means in said valve means independent of said second named means cyclically connecting said delivery passages in continuous free flow fluid communication with said supply chamber during a major portion of the time they are disconnected from said injection pressure chamber.

2. The fuel pump set forth in claim 1 wherein said delivery passages number at least three and during an injection cycle and delivery passages are in free flow fluid communication with said supply chamber for a greater interval of time than the interval of time required to effect injection through two of said delivery passages.

3. In a distributor type fuel injection pump the combination comprising:

a pumping housing including a high pressure chamber, a supply chamber, a bore between said chambers, and a plurality of delivery passages terminating at their inner ends at said bore in circumferentially spaced openings and adapted at their outer ends for connection to fuel delivery lines, means suplying fuel to said supply chamber and maintaining the latter at a pressure substantially above atmospheric pressure, and

a pump plunger reciprocably and rotatably mounted in said bore having cyclically open and closed passage means extending between said high pressure chamber and said supply chamber, and

a valve portion defining a passage means operable upon rotation of said plunger to cyclically and individually connect said delivery passages to said high pressure chamber during injection and another passage means independent of said cyclically open and closed pasage means operable upon rotation of said plunger to cyclically connect said delivery passages in free flow fluid communication with said supply chamber during a substantial portion of the time the delivery passages are disconnected from said high pressure chamber.

4. The structure set forth in claim 3 wherein said another passage means is a recess registrable with said openings during rotation of said plunger and an axially extending groove in the periphery of said plunger extending between said recess and a portion of said plunger disposed in said supply chamber.

5. A fuel injection pump comprising:

a housing including a supply chamber,

a plunger bore opening at one end into said supply chamber and closed at its other end to provide a high pressure chamber,

fuel delivery openings intermediate said high pressure chamber and said supply chamber, equally spaced circumferentially about and opening into said bore,

fuel delivery passages connected to said openings,

respectively,

a plunger reciprocably and rotatively disposed in said bore including a distributing portion,

a radially opening port in said distributing portion,

passage means in said plunger between said high pressure chamber and said port,

a circumferentially extending recess in said distributing portion spaced circumferentially from said port and in constant free flow communication with said supply chamber, said recess extending circumferentially a distance greater than the circumferential distance between said fuel delivery openings,

drive means for reciprocating said plunger in said bore to pump fuel and for rotating said plunger to distribute fuel being pumped thereby to said openings by cyclically registering said port with said openings one at a time.

6. A fuel injection pump comprising:

a housing including a supply chamber a plunger bore opening at one end into said supply chamber and closed at its other end to provide a high pressure chamber, and

a plurality of valveless fuel delivery passages having inner ends terminating in equally and circumferentially spaced openings respectively at said bore intermediate said high pressure chamber and said supply chamber and having outer ends adapted for connection with fuel injection conduits respectively.

a plunger reciprocably and rotatively disposed in said bore including a distributing portion,

a radially opening port in said distributing portion in communication with said high pressure chamber,

drive means for reciprocating said plunger in said bore to pump fuel and for rotating said plunger to sequentially distribute fuel to said delivery passages by cyclically registering said port with said fuel delivery passages, and a passageway formed in said distributing portion placing said delivery passages in continuous free flow fluid communication with said supply chamber during a portion of thetime they are out of registry with said port, said portion of time being at least as great as the time interval for injections through two adjacent delivery passages. 7. A fuel injection system comprising: an injection pump having a housing including a high pressure chamber,

a supply chamber,

a bore extending between said chambers, and

at least three valveless delivery passages defining openings in said bore between said chambers and at equally spaced circumferential intervals,

a rotatable and reciprocable pump plunger in said bore having a radially opening port cyclically registrable with said passages one at a time during rotating of said plunger,

passage means connecting said port in fluid receiving relation to said high pressure chamber, cyclically open and closed passage means extending between said high pressure chamber and said supply chamber, eans maintaining said supply chamber at an intermediate pressure, and

passage means independent of said cyclically open and closed passage means continuously connecting said delivery passages to said supply chamher during a substantial portion of the time they are out of registry with said port, said portion of time being at least twice the time required for said port to rotate through two of said circumferential intervals.

8. A fuel injection pump comprising: wall means defining a high pressure chamber,

8 a supply chamber,

a bore, and a plurality of valveless delivery passages adapted at their outer ends for connection to fuel injection conduits respectively and terminating at their inner ends in said bore at equally and circumferentially spaced openings, means maintaining said supply chamber at an intermediate pressure means for cyclically transferring fuel from said supply chamber to said high pressure chamber and for cyclically pressurizing the transferred fuel to an injection pressure including a reciprocable pump plunger, rotating valve means in said bore cyclically and individually connecting said delivery passages to said high pressure chamber to effect delivery of fuel therethrough at injection pressure, and passage means independent of said second named means connecting said delivery passages in continuous free flow fluid communication with said supply chamber during at least one quarter of the time the delivery passages are disconnected from said high pressure chamber.

References Cited by the Examiner UNITED STATES PATENTS 2,544,561 3/1951 Meyer 103-2 2,804,825 9/1957 Mansfield et al 103-41 2,813,523 11/1957 Bischofl' 103-2 2,965,087 12/1960 Bischolf et al 103-2 2,969,784 1/1961 High 103-2 3,023,705 3/1962 Heiser 103-2 3,099,217 7/1963 Bessiere 103-2 3,146,716 9/1964 Dreisin 103-2 FOREIGN PATENTS 359,603 10/1931 Great Britain.

804,026 11/1958 Great Britain.

971,536 9/1964 Great Britain.

349,124 11/1960 Switzerland.

DONLEY I. STOCKING, Primary Examiner.

W. J. KRAUSS, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,320,892 May 23, 1967 George D. Wolff It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column 5 line 35, "to" should read for line 58 "and" should read said line 72, "suplying" should read supplying Signed and sealed this 19th day of August 1969.

(SEAL) Attest:

Edward M. Fletcher, Jr. E.

Attesting Officer Commissioner of Patents

Claims (1)

1. IN A DISTRIBUTOR TYPE FUEL INJECTION PUMP THE COMBINATION COMPRISING: A PUMP HOUSING INCLUDING A BORE, A PLURALITY OF VALVELESS DELIVERY PASSAGES ADAPTED TO CONNECTION TO FUEL DELIVERY LINES, RESPECTIVELY, AN INJECTION PRESSURE CHAMBER, AND A SUPPLY CHAMBER, MEANS SUPPLYING FUEL TO SAID SUPPLY CHAMBER AND MAINTAINING THE LATTER AT A PRESSURE SUBSTANTIALLY ABOVE ATMOSPHERIC PRESSURE, MEANS FOR CYCLICALLY TRANSFERRING FUEL FROM SAID SUPPLY CHAMBER TO SAID INJECTION PRESSURE CHAMBER AND FOR PRESSURIZING IT TO AN INJECTION PRESSURE INCLUDING A RECIPROCABLE PUMP PLUNGER IN SAID BORE, AND ROTATING VALVE MEANS IN SAID HOUSING BETWEEN SAID INJECTION PRESSURE CHAMBER AND SAID DELIVERY PASSAGES CYCLICALLY AND INDIVIDUALLY CONNECTING SAID DELIVERY PASSAGES TO SAID INJECTION PRESSURE CHAMBER DURING THE PUMPING STROKE OF SAID PLUNGER AND PASSAGE MEANS IN SAID VALVE MEANS INDEPENDENT OF SAID SECOND NAMED MEANS CYCLICALLY CONNECTING SAID DELIVERY PASSAGES IN CONTINUOUS FREE FLOW FLUID COMMUNICATION WITH SAID SUPPLY CHAMBER DURING A MAJOR PORTION OF THE TIME THEY ARE DISCONNECTED FROM SAID INJECTION PRESSURE CHAMBER.

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