US3788546A

US3788546A - Fuel injection system

Info

Publication number: US3788546A
Application number: US00266137A
Authority: US
Inventors: J Bailey; S Kranc; Keyser R De
Original assignee: Caterpillar Tractor Co
Current assignee: Caterpillar Inc
Priority date: 1972-06-26
Filing date: 1972-06-26
Publication date: 1974-01-29
Anticipated expiration: 1991-01-29
Also published as: CA976821A; DE2332666A1; BE801363A; JPS4950321A; GB1397700A

Abstract

There is disclosed a fuel injection nozzle and valve assembly having a closed leakage collection chamber surrounding the valve assembly. The collection chamber comprises an annular chamber defined by the valve housing and a bore formed in the cylinder head of an engine.

Description

United States Patent [191 Bailey et al.

[451 Jan. 29, 1974 FUEL INJECTION SYSTEM 3,628,736 12/1971 Mowbray 239/533 3 434 667. 3/1969 Chmura 239/533 [75] Bailey Dunlap; my 2 886 014 5 1959 K d t al 239 533 x Kranc, Morton; Richard A. De mm c Keyser ll an of Primary Examiner--M. Henson Wood, Jr. [73] Assignee: Caterpillar Tractor Co., Peoria, Ill. AS81310"! Examiner-John Love I [22] Filed: June 26, 1972 V fitglrney, Agent, or Fzrm-Fryer, TJBIISVOld, PhllllpS &

. p 7 [21] Appl. No.: 266,137

[57] ABSTRACT [52] US. Cl. 239/120, 239/533 There is disclosed a fuel injection nozzle and valve as- [51] Int. Cl 1305b 1/30 m ly h ving a closed leakage collection hamber [58] Field of Search 239/533, 120 ounding the valve assembly. The collection chamber comprises an annular chamber defined by the [56] References Cited valve housing and a bore formed in the cylinder head UNITED STATES PATENTS of an engme- 3,510,062 5/1970 Waldman 239/533 X 8 Claims, 1 Drawing Figure /7 L 1 8 r/O 1 -21 3 5S 9 2..) bi 7 1 y /3 b3 22 I 2 8 53- l FUEL INJECTION SYSTEM BACKGROUND OF THE INVENTION The present invention relates to fuel injection systems, and pertains more particularly to an injection valve assembly for an internal combustion engine.

Compression ignition engines commonly employ fuel injection nozzles for delivering a timed injection of fuel into the engine combustion chamber. Such nozzles are normally controlled by a pressure responsive check valve to prevent dribbling of fuel into the combustion chamber between injection strokes. Numerous types of different check valve arrangements have been used in such nozzles; however, each arrangement has been found to have its own peculiar problem.

The simple inlet check valve is exemplified by U.S. Pat. No. 2,410,946, issued Nov. 12, 1946 to Lloyd E. Johnson. Other types of valve arrangements have been proposed to overcome problems of the simple check valve.

major problem with thatarrangement is that the accumulator chamber for leakage fuel is not adequate on some occasions, such as during the cranking mode of the engine for starting purposes. During the engine cranking period prior to normal injection cycles, fuel in the valve chamber tends to remain pressurized, thereby allowing significantly more fuel to leak into the accumulator chamber. This leakage of fuel, in combination with insufficient volume of the accumulator chamber, will reSult in a cumulative build-up of pressure, thus causing a hydraulic block.

The just described arrangement above also prevents use of the normal procedure for checking the valve opening pressure. The common procedure to check the fuel nozzle to insure the proper pressure for valve opening is accomplished by connecting a hydraulic pressure supply to the nozzle and slowly increasing the pressure until the valve opens. The opening pressure is The accumulator type of fuel nozzle assembly is exemplified by U.S. Pat. No. 2,985,378, issued May 23, 1961 to R.F. Falberg, and U.S. Pat. No. 2,556,369, issued June 12, 1951 to H. Hogeman. These types of fuel nozzle arrangements have the disadvantage of being complex, in that they require the use of at least two check valves to control the inlet and outlet from the accumulator chamber.

One preferred type of fuel nozzle, because of its operational simplicity, is the differential area type check valve as exemplified by U.S. Pat. No. 2,379,399, issued June 26,- 1945 to I-I.F. I-laines, U.S. Pat. No. 2,865,675,

issued Dec. 23, 1958 to-V.D. Roosa, and U.S. Pat. No. 3,224,684, issued Dec. 21, 1965 to V.D. Roosa. The major problem with these types of fuel nozzle and valve arrangements is that they must employ a low pressure chamber into which the valve stem must extend in order to provide a low pressure in opposition to the actuating pressure to provide the necessary pressure dif ference for actuation of the valve. Suchvalve arrangements result in leakage around the valve stem to the low pressure chamber, and a resultant blocking of the valve if the fluid from the low pressure chamber is not drained back to the reservoir or to some other place.

The aforementioned differential area valves employ the common practice of a fuel'leak-off fitting attached to the nozzle assembly toreturn the leaked fuel back to the. reservoir. The major problem with this arrangement is that it complicatesthe installation and removal procedures by adding an additional conduit to each nozzle assembly, which must be removed and attached when a nozzle assembly is replaced. This not only increases the likelihood of fuel leakage, but adds considerably to the bulk and complexity of. the'nozzle itself. One approach to this problem has been to provide a drain passage for the leakage fuel directly to the intake manifold of the engine. This arrangement is disclosed, for example, in-U.S. Pat. No. 3,382,851, issued May 14, 1968 to F. De Luca. One problem with this arrangement isthat this leakage fuel can result in an increased emission of smoke and hydrocarbons from the engine and can cause carbon deposits on the inlet valve.

Another proposed solution to the aforementioned problem is disclosed in U.S. Pat. No. 3,598,314, issued Aug. 10, 1971 to the present inventor and others, and assigned to the assignee of the present invention. One

tem. However the slow build-up of fuel pressure within the valve chamber permits a greater amount of fuel to leak into the relatively small accumulator chamber of this system, so that the fuel trapped in the accumulator chamber creates a hydraulic block, preventing the valve from opening;

SUMMARY OF THE INVENTION It is the primary object of the present invention to provide a fuel nozzle assembly of the differential area type that overcomes the above mentioned problems of the prior art.

Another object is to provide a siinple and inexpensive fuel nozzle assembly that eliminates the leakage problems of the prior art.

A further object of the present invention is to provide a fuel nozzle assembly of the differential area type that eliminates the fluid blocking problems of the prior art devices.

In accordance with the present invention, there is provided a fuel nozzle assembly having a leakage collection chamber surrounding the fuel nozzle assembly with the chamber having sufficient capacity for extended cranking of the engine. The leakage collection chamber comprises an annular chamber defined by the fuel nozzle assembly housing and a bore formed in the cylinder head of the engine, and is operative to eliminate complex drainage conduits and eliminate fluid blocking common in the prior art.

BRIEF DESCRIPTION OF THE DRAWINGS The above mentioned and other objects and advantages of the present invention will become apparent from the following specification when read in conjunction with the accompanying drawing, wherein the FIG- URE is a view in section of a preferred embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Referring particularly to the drawing, there is illustrated a fuel injection system embodying the principles of the present invention, generally designated by the reference numeral 10. The fuel injection system comprises the combination of a cylinder head 11 having an elongated cylindrical bore 12 formed therein. The bore 12 is formed to have a conical extension 13 communicating by way of an opening 14 with a combustion chamber (not shown). The opposite end of the bore 12 is provided with a counterbore 15 for receiving a seal element 16, and a threaded portion 17 disposed inwardly adjacent to the counterbore. A threaded retainer nut member 18 is operative to connect and retain a fuel supply line 19, and a nozzle assembly in position.

The fuel injection system further comprises a fuel injection nozzle assembly 20, disposed within the bore 12 of the cylinder head 11. All components of the fuel injection nozzle assembly 20 are encapsulated in a hollow cylindrical case or housing 21, which is formed with a conical section 22 at its lower end, which section is in sealing engagement with the conical section 13 of the bore. The case is formed with an inwardly directed lip 23 disposed at its upper end for retaining the working components therein. A leakage collection chamber 55 is formed by annular clearances between the case 21, the outer surface of the flanged portion of fuel inlet line 19, retainer nut 18 and the wall of the bore 12. This chamber is further defined by the sealing of conical surface 22 against the conical surface 13, and by the sealing of seal 16.

The nozzle assembly includes a nozzle tip 24, a sleeve 25, a stop member 26, and a nut 27, disposed within the case in a stacked end-to-end relation with the nozzle tip being positioned within the conical section 22. The nozzle tip is formed with a cylindrical bore 28 and a conical valve seat 29 concentric with a passage 30 communicating with a plurality of discharge orifices 30a disposed at the terminal end thereof. The tip or terminal end of the nozzle projects into a combustion chamber of an engine to deliver a metered quantity of fuel thereto.

A valve chamber 31 is formed by an axial bore 32 in the sleeve 25, and by a conical cavity 33 formed in the nozzle tip 24. A conical cavity or low pressure chamber 35 is defined by a conical abutment surface 34 of the stop member 26.

A low pressure chamber 35, formed by the conical abutment surface 34, communicates by way of an axial passage 34a and a radially extending passage 36, with an annular groove 37 formed on the periphery of the stop member. The stop member 26 is arranged such that the annular groove 37 communicates with an outlet port 38 of the case or housing, which opens into chamber 55. A recess 39 is formed on the upper end of the stop member 29 and communicates with the valve chamber 31 through one or more longitudinally disposed passages 40.

The nut 27 is provided with an axially disposed threaded bore 41 to receive threaded fitting 42 of supply line 19. A counterbore 43, which is adjacent to the recess 39 of the stop member 26, receives a filter assembly 44 to filter incoming fuel.

A needle valve 45 is mounted within the valve chamber 31 and includes a guide portion 46 and a stop surface 47 formed on the upper end and extending into chamber 35. The needle valve further includes an enlarged lower section 48, and a needle end extending downward therefrom with a conical seating surface 49 formed on the lower end thereof. This arrangement is termed an inwardly opening valve. The seating surface 49 of the needle valve seats against valve seat 29 of the nozzle tip 24 in the normal valve-closed condition. The lift stop surface 47 contacts the conical abutment surface 34 in stop member 26 when the needle valve is in the full open position.

A guide collar 50 is provided with an axial bore 51 which is closely and slidably fitted to the guide portion 46 of needle valve 45. A spherical bearing face 52 is formed on the upper end of the guide collar and bears against the conical abutment surface 34 of the stop member 26, to provide self-aligning mounting means for valve 45. A shim 53 is mounted on the needle valve stem 45 abutting the enlarged section 48, and a spring 54 is disposed between the guide collar and the shim to hold the spherical face 52 in sealing contact with the abutment surface 34 and to resiliently urge the seating surface 49 of the needle valve 45 into seating engagement with the valve seat 29.

The retainer nut 18, by means of threads engaging with the threaded portion 17 of the cylinder head 11, serves to secure the fuel injection nozzle 20 in the cylinder head and to insure sealing at conical section 22 of the nozzle 20, and at the upper and lower faces of the flange portion of the fuel supply line 19. The seal 16 is disposed within a counterbore 15 of the cylinder head, and seals against this counterbore and against the outer diameter of the retainer nut 18.

OPERATION While the operation of the present invention is believed apparent from the foregoing description, further amplification will be made in the following brief summary.

In an intermittent manner, fuel pressure is developed by a fuel injection pump (not shown) and is delivered through supply line 19, filter assembly 44, recess 39, passage 40, and into valve chamber 31. Prior to the beginning of an injection cycle, needle valve 45 is seated on valve seat 29 and as the fuel pressure develops, it acts on an area equal to the cross-sectional area of the guide portion 46 of valve 45, less the effective seating area of the needle valve. This hydraulic force exerts a net upward force on the needle valve 45, because of the differential areas, urging it to unseat or open in an inward direction. This force is resisted by the bias of the spring 54. When the fuel pressure reaches the level required to exert a force equal to the predetermined spring force, the needle valve 45 unseats, moving the seating surface 49 from valve seat 29, allowing fuel to flow into the passage 30 and thence through the orifices 30a of nozzle tip 24. The fuel pressure then exerts an upward force on the entire cross-sectional area of the guide portion of check valve 45, to produce a more rapid, upward movement of the check valve 45, with a resulting pop action. The needle valve continues its upward movement until the lift stop surface 47 abuts the surface 34 in stop member 26.

During periods when fuel pressure exists in chamber 31, leakage of fuel occurs between the slidably fitted guide portion 46 of needle valve 45 and bore 51 of guide collar 50. The leakage passes into low pressure chamber 35 through passages 34a and 36 and annular groove 37, and is expelled through outlet port 38 into an annular leakage collection chamber 55. This collection chamber is confined to substantially the same longitudinal dimensions as the essential valve elements of the nozzle assembly. This results in a more compact arrangement of valve assembly and resultant leakage reservoir. Moreover, this construction permits the low pressure chamber to be only large enough to readily accommodate movement of the valve member, whereas the annular collection chamber exceeds the volume of the low pressure chamber by an amount sufficient to accommodate leakage fuel. Also, the annular collection chamber can be readily enlarged simply by enlarging the cylindrical bore thereof with any alteration whatsoever in the fuel nozzle assembly.

Over an extended period of time, the annular chamber becomes filled with fuel and the pressure in chambers 35 and 55 and connecting passages increases during each cycle of pressure development in chamber 31 to an extent determined directly by the amount of leakage, the upward displacement of needle valve 45, the bulk modulus of the fuel, and inversely by the combined volumes of the aforementioned chambers and passages. Because the total volume of the chambers and passages is relatively large, the increase in pressure therein, during each cycle of pressure development in chamber 31, is relatively small. Because of the relatively small pressure build-up in chamber 35, chamber 55, and connecting passages, normal operation of the fuel nozzle is assured before hydraulic blocking can occur.

During normal operation of the fuel nozzle, when the development of fuel pressure from the fuel pump is terminated, the pressure in the valve chamber 31 decreases as a result of the flow of fuel through the discharge orifices 31 and the reverse flow of fuel through the supply line 19, and back to the pump in a conventional manner. When the fuel pressure has sufficiently decreased, the spring 54 urges the needle valve 45 downwardly, causing the seating surface 49 to be seated against the valve seat 29. Since the pressure of the fuel in chambers 35 and 55, and connecting passages is then greater than'the pressure within the valve chamber 31, reverse leakage into the valve chamber occurs, reducing the pressure in the aforementioned chambers and passages. After some number of injections, the average pressure existing in the annular passage will reach anequilibrium wherein leakage into and out of the annular chamber will be the same, and, because of this equilibrium flow, no hydraulic blocking of the valve will occur.

While the present invention has been illustrated by means of a single embodiment, it is apparent that many chamges and modifications may be made in the illustrated structure without departing from the spirit and scope of the invention as defined by the appended claims.

What is claimed is:

1. A fuel injection system, said system comprising in combination: 4

a cylinder head having a bore formed therein in communication with a combustion chamber;

a fuel nozzle assembly comprising a housing defining a central valve chamber, and defining with said bore an enclosed annular leakage collection chamber surrounding said housing;

an inwardly opening valve member mounted in said valve chamber and operative to control dispensing of fluid from said valve chamber by way of a nozzle orifice;

a low pressure chamber in said housing;

said valve element having a first area acted on by pressurized fluid in said valve chamber and an opposing area acted on by fluid in said low pressure chamber; and,

means providing fluid communication between said low pressure chamber and said leakage collection chamber.

2. The fuel injection system of claim 1 wherein said collection chamber has substantially the same longitudinal dimensions as said nozzle and valve assembly.

3. The fuel injection system of claim 1 wherein:

said valve chamber and said low pressure chamber are separated by mounting means for said valve element;

said mounting means comprising a sleeve having a spherical bearing surface formed on one end '.thereof;

said valve element being reciprocably mounted in said sleeve;

a conical bearing surface formed in said housing for receiving said spherical bearing surface; and,

spring means resiliently coupled between said valve element and said sleeve and urging said bearing surfaces into engagement.

4. The fuel injection system of claim 1 wherein the volume of said collection chamber exceeds the volume of said low pressure chamber.

5. A fuel injection system including a fuel nozzle assembly, comprising in combination:

a cylindrical bore communicating with the combustion chamber of an internal combustion engine;

a housing defining a central valve chamber disposed in said bore and with said cylindrical bore defining an enclosed annular leakage collection chamber surrounding said valve chamber;

an inwardly opening pressure responsive valve member mounted in said valve chamber and operative to control dispensing of fluid from said valve chamber by way of a nozzle orifice;

said valve element having a first area acted on by pressurized fluid insaid valve chamber and an opposing area acted on by fluid in a low pressure chamber; and

means communicating said low pressure chamber and said leakage collection chamber.

1 6. The fuel injection system of claim 5 wherein the volumetric capacity of said collection chamber exceeds that of said low pressure chamber.

7. The fuel injection system of claim 6 wherein the length of said collection chamber is substantially the same as the housing of said valve assembly.

8. The fuel injection system of claim 5 comprising sealing means sealing said housing at each end thereof within said bore to define said collection chamber.

Claims

1. A fuel injection system, said system comprising in combination: a cylinder head having a bore formed therein in communication with a combustion chamber; a fuel nozzle assembly comprising a housing defining a central valve chamber, and defining with said bore an enclosed annular leakage collection chamber surrounding said housing; an inwardly opening valve member mounted in said valve chamber and operative to control dispensing of fluid from said valve chamber by way of a nozzle orifice; a low pressure chamber in said housing; an inwardly opening valve member mounted in said valve chamber and operative to control dispensing of fluid from said valve chamber by way of a nozzle orifice; a low pressure chamber in said housing; said valve element having a first area acted on by pressurized fluid in said valve chamber and an opposing area acted on by fluid in said low pressure chamber; and, means providing fluid communication between said low pressure chamber and said leakage collection chamber.

3. The fuel injection system of claim 1 wherein: said valve chamber and said low pressure chamber are separated by mounting means for said valve element; said mounting means comprising a sleeve having a spherical bearing surface formed on one end thereof; said valve element being reciprocably mounted in said sleeve; a conical bearing surface formed in said housing for receiving said spherical bearing surface; and, spring means resiliently coupled between said valve element and said sleeve and urging said bearing surfaces into engagement.

5. A fuel injection system including a fuel nozzle assembly, comprising in combination: a cylindrical bore communicating with the combustion chamber of an internal combustion engine; a housing defining a central valve chamber disposed in said bore and with said cylindrical bore defining an enclosed annular leakage collection chamber surrounding said valve chamber; an inwardly opening pressure responsive valve member mounted in said valve chamber and operative to control dispensing of fluid from said valve chamber by way of a nozzle orifice; said valve element having a first area acted on by pressurized fluid in said valve chamber and an opposing area acted on by fluid in a low pressure chamber; and means communicating said low pressure chamber and said leakage collection chamber.

6. The fuel injection system of claim 5 wherein the volumetric capacity of said collection chamber exceeds that of said low pressure chamber.