US3451626A

US3451626A - Nonleak-off fuel injection nozzle

Info

Publication number: US3451626A
Application number: US609174A
Authority: US
Inventors: Vernon D Roosa
Original assignee: HARTFORD MACHINE SCREW CO
Current assignee: HARTFORD MACHINE SCREW CO
Priority date: 1967-01-13
Filing date: 1967-01-13
Publication date: 1969-06-24
Anticipated expiration: 1986-06-24
Also published as: DE1601413A1; ES349031A1; GB1220261A; DE1601413B2; SE343924B; FR1550869A; DE1601413C3

Description

`Fume 24, 1969 v. D. RoosA NONLEAK-OFF FUEL INJECTION NOZZLE Filed Jan. 13, 1967 mm Nq NN www f ATTORNEYS IUnited States Patent O "ice 3 451 626 NoNLEAK-oFF FEL INJECTION NozzLE Vernon D. Roosa, West Hartford, Conn. The Hartford Machine Screw Company, P.0. Box 1440, Hartford,`

Filed Jan. 13, 1967, ser. No. 609,174 Int. cl. Bosh 1/30 U.S. Cl. 239-533 Conn.

6 Claims ABSTRACT OF THE DISCLOSURE This invention relates to 'fuel injection nozzles for internal combustion engines and more particularly to an improvement on the nozzle described in my prior Patent 3,224,684 issued Dec. 21, 1965 and entitled Fuel Injection Nozzle.

In the operation of inward opening pressure actuated fuel injection nozzles of the type contemplated by thisk invention, the plunger or valve is lifted from its seat by the pressure of fuel delivered to the nozzle from an associated high pressure charge pump which provides timed high pressure pulses of fuel to the nozzle. The discharge of fuel from the nozzle is effected by the pressure of the fuel acting on the valve to lift it from the valve seat in opposition to the force exerted by a biasing spring. The biasing spring is disposed in a spring chamber in the nozzle at the opposite end of the valve from the valve seat with the guide which mounts the valve for reciprocating movement separating the spring chamber from the high pressure fuel. inherently, in such an arrangement leakage of the fuel between the guide and the valve takes place, and in the past it has been the practice to provide a leak-off system to return the leakage fuel from the spring chamber to the Lfuel tank. Such a leak-off system is disclosed in my prior Patent 2,829,004 issued Apr. 1, 1958, and entitled, Leak-off Fuel Collecting System for Fuel Injection Engines.

A principal object of this invention is the provision of a fuel injection nozzle of the type described which does not require a leak-olf collection system.

Another object of this invention is to provide a nozzle of the type described which is self-sufficient to accommodate leakage of fuel into the spring chamber.

A still further object of the invention is to provide a fuel injection nozzle which accommodates leakage of fuel into the spring chamber which is rugged and durable yet simpliiied in construction and low in cost.

It is another object to provide a fuel injection nozzle having a sealed spring chamber.

A still further object of the invention is to provide a fuel injection nozzle of the type described which facilitates yfuel injection during the initial starting of an associated engine. Included in this object is the provision of an arrangement whereby the force biasing the valve against the valve seat is reduced during the initial starting of the engine.

'Other objects will be in part obvious and in part pointed out more in detail hereinafter.

rllhe invention accordingly consists in the features of construction, combination of elements and arrangement of parts which is exemplified in the construction here- 3,451,626 Patented June 24, 1969 after set forth, and the scope of the invention is indicated in the appended claims.

In the drawing:

FIG. 1 is a fragmentary cross-sectional view of a portion o-f a fuel injection nozzle embodying the present invention; and

FIG. 2 is a fragmentary cross-sectional view exempli- `fying a modified form of the present invention.

The exemplary nozzles shown in the drawing and embodying the present invention are generally similar to that illustrated in my `Patent No. 3,224,684 and includes a generally elongated tubular body 10 having a discharge tip 12 at one end thereof and a central longitudinal bore 14 extending throughout its length. Located in the central bore 14 is a rod-like valve 116 having a conical tip 17 which cooperates with a conical valve seat 18 formed in the tip 12 to control the discharge of fuel from the nozzle body 10. A valve guide 20 positioned in the bore 14 of the nozzle body at a position remote from the valve seat slidably mounts and aligns the valve 16 for rapid reciprocating movement of the valve under the i11- fluence of fuel pressure within the bore 14 acting against the bias of a spring 22. The valve is provided with a lfuel inlet 24 communicating `with the bore 14 for the delivery of pulses of high pressure 'fuel to the bore 14 adjacent the guide 20 from an associated high pressure charge pump, not shown.

The upper end of the valve 16 engages a spring seat 26 located in a spring chamber 28 which is isolated from the bore 14 by the guide 20, and the other end of the spring 22 is similarly provided with a second spring seat 30 which engages an adjustable stop 32 shown as being threadably received in the bore 34 of the spring chamber 28 to set the bias pressure of the spring holding the valve 16 against the valve seat 18. A second stop 36 also is shown as being threadably received in bore 34 o'f spring chamber 28 to adjustably x the lift olf 'the valve 16 from the valve seat by the engagement between iiange 38 thereof and shoulder 40 of the valve When the nozzle has been assembled and placed in operation, timed pulses of yfuel under high pressure are introduced into the nozzle through inlet 24 and act on the valve 16 to overcome the bias of spring 22 to lift the valve from the valve seat 18 and the discharge of fuel through the oriiices in tip 12 takes place. When fuel pressure in the bore 14 is reduced after the pulse of fuel is discharged 'from the nozzle tip, the spring 22 exceeds the hydraulic pressure acting on the valve 16 and returns it to closed position.

As hereinbefore described, the high pressure of the fuel within the bore 14 relative to that in spring chamber 28 during the injection of fuel from the nozzle inherently results in a small amount of leakage into the spring chamber 28 between the valve 16 and the guide 20. The valve, in moving away from the valve seat causes its guide portion 16a to enter the spring chamber 28 to lill a portion thereof corresponding to the volume of the area of the guide portion 16a times the amount of lift of the valve from the valve seat. Since liquid fuel is relatively inelastic, it will be readily apparent that as the quantity of fuel leakage into the spring chamber 28 increases, the pressure in spring chamber 22 acting to aid the spring in holding the valve 16 against the valve seat increases. In addition, where the liquid fuel leakage into spring chamber 28 becomes suliicient to substantially iill the spring chamber, the pressure of the fuel in the spring chamber tends to increase drastically and ultimately, in conjunction with spring 22, will prevent the proper lifting of the valve 16 unless the pressure in chamber 28 is relieved.

This invention provides an arrangement for accommodating the displacement of the valve 16 into the spring chamber 28 during opening without the use of a leak-off return network connecting the spring chamber 28 with the fuel tank and without an undue increase in pressure in spring chamber 28.

As shown in FIG. 1, an externally threaded closed cap 42 is positioned over the end of the nozzle body 10 and is sealed thereto by means of an apertured coupling nut 44 which threadably engages the threads 46 of the cap 42 to clamp a ferrule 48, formed of a yieldable material such as a metal or plastic, which is shown as being deformed to enter the external recesses 50 provided on the outside of the nozzle body under the clamping pressure of tightening .the coupling nut 44 to the cap 42.

While sealing the spring chamber 28 against the leakage of fuel, the cap 42 is so constructed as to accommodate the displacement of the fuel in the spring chamber 28 by the end of the valve guide 16a as the valve 16 lifts from the valve seat 18 without an undue increase of pressure in chamber 28. A passage 39 is provided in the adjustable stop 32 to provide communication between the spring chamber 28 and the interior of the cap 42. In practice, I have found that by making the peripheral wall 42a with a thickness of about -20 mils the wall 42a Will bow outwardly to provide the additional capacity required by the displacement of the valve guide 16a entering the spring chamber so as to limit the pressure in the spring chamber 28 to a level which allows the desired movement of the valve 16 away from the valve seat 18 to allow the proper discharge of fuel through the nozzle tip 12. For example, with a pressure in the bore 14 at the time of injection of, say, about 2800 psi., this construction will limit the maximum pressure in the spring chamber to any desired value, say, 500 p.s.i.

Not only does this invention eliminate the need for a leak-off collection system from each nozzle and thereby simplify ythe layout of the fuel injection system by providing self-sufiicient nozzles, but it also permits the use of a lower biasing pressure setting for spring 22 since the pressure in spring chamber 28 reaches a predictable level under steady state conditions. Such pressure assists the spring 22 in biasing the valve 16 toward the valve seat 18. Because of this, the injection of fuel by the nozzle is facilitated during initial starting conditions when the engine is being cranked at low speeds. At such times, leakage past the guide 20 has not built up the pressure in the spring chamber 28 to its steady state value so that the combined biasing force of spring 22 and the pressure of the fuel in the spring chamber 28 is lower than under steady state conditions whereby a lower pressure in bore 14 will lift the valve 16 from the valve seat.

It will be understood that any pressure differential of the pressure in spring chamber 28 from that in bore 14 will tend to equalize between the intervals of high pressure pulses of fuel delivered by the associated charge pump. The discharge of fuel by the nozzle occurs over, say, a maximum of about 20 of crankshaft rotation of the associated engine and in a 4-cycle engine each nozzle discharges fuel once in every two revolutions of the engine, i.e., or 720 of crankshaft rotation. Accordingly, the pressure level of the fuel in spring chamber 28 may leak past the guide 20 back into bore 14 for about 97% of the time so as to stabilize the pressure in chamber 28 during operation to a pressure correlated with the inlet residual pressure in the bore 14.

Referring now to FIG. 2, in which like numerals refer to like parts, a modied form of the invention is illustrated.

In this modified form of the invention, the peripheral wall 34 of the spring chamber 28 is provided with an unthreaded end extension 34a, and the stop nut 32 is provided with a mating longitudinal extension 32a concentrically disposed within the peripheral extension 34a to provide an annular recess or clearance 54 therebetween. A resilient O-ring 52, formed of any suitable material such as a solid synthetic rubber, is positioned in the annular clearance 54 in engagement with the longitudinal extension 32a and the peripheral end extension 34a to provide a seal therebetween. The O-ring 52 is slidably movable in the annular clearance 54 and is biased in the direction of the spring chamber 28 by an axially movable ring 55 backed by a plurality of Belleville washers 56. The stack of Belleville washers 56 are secured against longitudinal movement by a spring retaining ring 58 mounted in groove 60 of the longitudinal extension 32a.

In the form of the invention exemplified by FIG. 2, the displacement of fluid within the spring chamber 28 caused by the lifting of the valve 16 from the seat 18 is accompanied by an enlargement of the volume of the spring chamber 28 due to the longitudinal movement of the sealing O-ring 52 which is subjected to the pressure in chamber 28 through passage 39a as well as the opposing bias of the Belleville washers 56. It will be readily apparent that this arrangement likewise automatically establishes a maximum pressure in the valve chamber 28 under conditions of equilibrium reached during operation in a manner similar to that of the emobdiment of FIG. 1.

Thus, it may be seen that the self-sufficient no leak-off nozzle design of this invention automatically accommodates for fuel leakage into the spring chamber without the use of a leak-off connection system for returning leakage fuel from each of the nozzles of an engine to the fuel tank in an organization which aords the additional advantages. heretofore described.

As will be apparent to persons skilled in the art, various modifications and adaptations of the structure abovedescribed will become readily apparent without departure from the spirit and scope of the invention, the scope of which is defined in the appended claims.

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

1. In a fuel injection nozzle for internal combustion engines having an inwardly opening pressure operated valve disposed in the bore of the nozzle body, an apertured guide spaced from the discharge end of `the nozzle for mounting the valve for reciprocating movement toward and away from a valve seat and forming a Wall of a first chamber for receiving fuel under pressure to open the valve, a second chamber in the nozzle body separated from said lirst chamber by said guide, and a spring in said second chamber for biasing the valve toward the valve seat, the improvement wherein a cap forms a closure for said second chamber, said cap having a peripheral wall dimensioned to bow outwardly to increase the volume of said second chamber when the valve is lifted from the valve seat.

2. A device as recited in claim 1 wherein the open end of Said cap is threaded and surrounds the end of the nozzle body remote from the discharge end thereof, and an apertured mating coupling nut surrounding the nozzle body coacts with said cap to compress a yieldable ferrule disposed between the coupling nut and the cap into compressive engagement with said nozzle body to secure and seal the cap to the nozzle body.

3. In a fuel injection nozzle for internal combustion engines having an inwardly opening pressure operated valve disposed in the bore of `the nozzle body, an apertured guide spaced from the discharge end of the nozzle for mounting the valve for reciprocating movement toward and away from a valve seat and forming a wall of a first chamber for receiving fuel under pressure to open the valve, a second chamber in the nozzle body separated from said first chamber by said guide, and a spring in said second chamber for biasing the valve toward the valve seat, the improvement wherein means are provided for sealing said second chamber to prevent leakage therefrom and for increasing the volume of said second chamber when the valve is lifted from the valve seat, said sealing means comprising a member having an outwardly extending shank disposed concentrically within a bore of the second chamber to define an annular recess therewith, an

5 axially movable seal positioned in said annular recess and engaging said shank and the wall of said bore, and resilient means biasing said seal in a direction to reduce the volume of said second chamber.

4. A device as recited in clairn 3 wherein said seal comprises a resilient O-ring and said resilient means comprises a stack of Belleville washers.

5. A device as recited in claim 4 wherein said shank is provided with a shoulder for securing a seat for said Belleville Washers.

6. In a fuel injection nozzle for internal combustion engines having an inwardly opening pressure operated valve disposed in the bore of the nozzle body, an apertured guide spaced from the discharge end of the nozzle for mounting the valve for reciprocating movement toward and away from a valve seat and forming a wall of a first chamber for receiving fuel under pressure to open the valve, a second chamber in the nozzle body separated from said rst chamber by said guide, and a spring in said second chamber for biasing the valve toward the valve seat, the improvement wherein a cap telescopically engages the end of the nozzle body providing said second 6 chamber to form a closure therefor, said cap having a peripheral wall dimensioned lto bow outwardly to increase the volume of said second chamber when the valve is lifted from the valve seat.

References Cited UNITED STATES PATENTS M. HENSON WOOD, JR., Primary Examiner.

B. BELKIN, Assistant Examiner.