US3409225A - Mechanical injector having needleseating spring - Google Patents

Description

Nov. 5, 1968 v R. .1. MADDALozzo ETAL 3,409,225

MECHANICAL INJECTOR HAVINGV NEEDLE-SEATING SPRING Filed June 14, 1966 IIL/l1 d 70 y- 'Raymond eldfadafalozzo f Edward @1%. SZzndee MII 10 @Mw MM5@ United States Patent() 3,409,225 MECHANICAL INJECTOR HAVING NEEDLE- SEATING SPRING v Raymond J. Maddalozzo, Chicago, and Edward A. Slindee, Elmhurst, Ill., assignors to International Harvester Company, Chicago, Ill., a corporation of Delaware Filed June 14, 1966, Ser. No. 557,460

` 17 Claims. (Cl. 239-89) ABSTRACT F THE DISCLOSURE Mechanical fuel injectorin which a l-ost motion joint is provided in the train between a mechanically reciprocated, fuel-pumping, pump-plunger needle, and pumpingpower-supplying injector drive cam, and in which an over travel spring is provided for constantly biasing the plunger needle inla direction to open up an overtravel gap in the lost motion joint Ienabling the pump-plunger needle always to seat on a seat above a sac hole provided which receivesy the tip of the pump-plunger needle. The tip of the injector is thus structurally isolated to prevent receiving direct drive cam force from the pump-plunger needle tip,'enabling the sac hole size to be reduced to an inconsequential amount.

In the drawings:

' FIGURES l, 2 and 3 are respective complete and fragmentary longitudinal sectional views of an injector embodying the present invention; and v FIGURES 4 and 5 are similar but show a modification.

In a mechanical injector equipped with a needle-seating spring 10, and as generally indicated 4at 11 in FIGURES l to 3 of the accompanying drawing, an injector body 12 carries a nozzle tip 14 and cooperates therewith to define a pump chamber 16. A plunger needle 18 having reciprocating action is slidably mounted in the body 12 to pump diesel fuel through a cylinder head 20, a minimally short sac hole 22, and plural orifice jets 24 communicating with the combustion chamber in an engine cylinder. Our invention has the practical advantage that the structure in the tip 14 is fully safeguarded from withstanding mechanical impact from the main pumping force. The importance is apparent, because without van interposed seating spring the main force would :be positively transmitted in its path and can be destructively high. In the process of redesigning a predecessor design having a long sac hole Ibelow the plunger seat, the application of the principles of this invention thereto enabled us to lower the plunger seat enough to substantially eliminate the sac hole therebelow, and at the same time to keep the seat protected from overloading.

The plunger needle 18 is part of a plunger assembly including a cup 26 having an internal recess 28 receiving the enlarged head 30 on the plunger end of the plunger needle 18. The cup 26 has a counterbore 32 receiving a heavy, suction-stroke spring 34, and also a spring seat 36 which is common to the two, coil-type springs Iand 34. The heavy spring 34 has a fixed lower end seating against a washer 38 in the body 12, and the concentric, lighter spring 10 has a lower end free to move with the needle 18 and connected thereto by a washer and a snap ring assembly collectively indicated at 40.

The injector 'body 12 is encased in a water tight sleeve 42 fixed in the head 20. At the upper end, the body 12 carries a snap ring 44, for retaining the cup 26 prior to assembly in engine. The cup 26 is reciprocated on the pumping and suction strokes as it compresses and releases the spring 34.

An injector cam 46 carried by the engine camshaft 48 applies pumping power to the plunger assembly, either diice rectly or through an intervening cam train and determines the stroke length. An illustrative cam train includes a -rollercarrying hydraulic or regular cam tappet 50 riding on the cam 46, a rocket 52, a pushrod 54 between the tappet 50 and a lash adjusting screw 53 carried lby the rocker yat one end, and a slipper 56 between the cup 26 and the other end of the rocker 52.

In operation, the pumping stroke of the plunger assembly has three phases. Before and during initial downward travel, the head 30 and the floor of the recess 28 define a maximum gap (GM FIGURE 2) because t-he seating spring 10 is expanded to the full extended length. Partway through the pumping stroke, the resistance of fuel trapped in the pumping chamber 16 increases so as to overcome the force of the spring 10, forcing the head 30 against the bottom of the recess 28. The gap reduces to zero gap as indicated at G0 in FIGURE 3.

Tow-ard completion of the pumping str-oke by the cam 46, the cup 26 is stopped at the point of maximum cam lift by contact with a cup stop 57 which is provided, but the plunger needle 18 overtravels due to re-expansion of the spring 10 until the needle rests solidlyon a seat 'by the sac hole 22 and over the jets 24. At that point a partial gap G (FIGURE l) develops between the head 30 and the confronting floor of the recess 28. The relation of cup stop 57 and maximum cam lift is 'adjusted by screw 53.

Without any stop 57 being provided, the lash adjusting `screw S3 in the cam train is preferably adjusted with the ideal goal being to keep the gap at zero gap value G0. Upon eventual wear 'of the needle tip, cam, or other parts of the train singly or collectively in service, or in the eventuality of slack in the train caused `by initial underadjustment of the screw 53 so that it does not project sufficiently far in the direction of the companion pushrod 54, the spring 10 is present and insures automatic take-up in the train. The spring 10, by expanding at the end of the injection stroke, thus always causes full seating of the plunger needle when the wear or the referred to underadjustment or the like occurs somewhere in the cam train.

During pumping, the slight amount of leakage fuel which escapes along the length of the plunger needle 18 enters a diagonal collection passage 58 in the body 12 and is returned to the fuel tank in a path as indicated by a chain line of arrows and leading through a nozzle drairr fitting 60.

During the suction stroke of the injector, the spring 34 by expanding holds the tappet 50 against the receding surface of the rotating cam 46. The gap G is restored to the maximum gap GM ('FIGU-RE 2) by the spring 10 and the plunger assembly is forced by the spring 34 into the starting position.

The cycle is completed by replenishing the chamber 16 with the amount of fuel sprayed through the jets 24. Thus following the suction-stroke, a metered amount of fuel is introduced under pressure into the nozzle body 12 in a path as indicated by a solid line of arrows and leading through a nozzle inlet fitting 62, a first passage 64, a spring loaded check valve 66, and a second passage 68 interconnecting the check valve and the pump chamber 16 which, at that point, is opened at the side by the retracted needle end of the plunger needle.

The plunger needle 18 is in one piece and constitutes a solid plunger having its head 30 and its adjacent upper end controlled by the cup 26 and by the seating spring 10.

If a two-piece plunger needle is employed, a double seat is achieved, although the practical advantages inherent in a one-piece needle body cannot be realized.

In the embodiment of the invention as shown in FIG- UIRES 4 and 5, such a two-piece, two seat structure shown, wherein the seating is accomplished in two stages.V A first, 0or lower point 73 stops fuel 'flow and a second point 74 acts as a stop to remove mechanical cam load from the tip.

The injector body 12 carries a slightly modified nozzle 14a, but otherwise the parts are the same as in FIGURES 1 to 3, preceding, the fuel supply and drain paths and the pump suction stroke are the same, and the same reference numerals are employed.

' More specifically, the needle part, indicated at 18a, of the plunger needle is slidably joined to the main plunger part 18b in a receiving bore, and the two parts mutually define a chamber 28a.

A bevel 70 on the needle seats at a first point 73 adjacent the sac hole 22 and a bevel 72 on the main plunger 18b seats at a spaced apart second point 74 in the nozzle tip 14a. The bevels 70 and 72 are limited in their normal distance apart by means of a connection between a pin 76 carried by the plunger and a slot wall 78 defined by a slot which is formed in the needle 18a and which receives the pin 76. In the normal condition, there is contact between the pin and wall 78 and therefore there is a zero gap, as indicated at G0 in FIGURE 5.

The normal distance between bevels 70 and 72 exceeds, by a slight amount of difference, the fixed distance between the first and second seating points 73, 74. The needle part 18a rst stops at the point 73 whereupon, in continuing to move so as to be stopped in the desired way at the second point 74, the plunger 18b slightly overtravels relative to the stopped needle 18a, creating a finite gap GF (FIGURE 4) between the pin and slot wall parts 76, 78.

An equalizing hole 80 through the wall of the main plunger 1817 in alignment with the bore, intercommunicates the chamber 28a and a pumping chamber 16 thereby normally placing the needle part 18a in hydraulic balance at its opposite end surfaces.

The main plunger 1811 carries ahead 30 as in the prior embodiment, but the head 30 is made rigid with a cup 26 of the plunger assembly by means of a snap ring 82. Therefore the slipper 56 of the cam train, not shown, and a heavy suction-stroke spring 34 control the full travel (and overtravel) of the main plunger 18b.

In operation during the pumping stroke, the plunger and needle have the operative relation illustrated in FIG- URE 5, practically to the point of completion of that stroke. T-here is zero gap G0, as described, followed by the two-stage seating at the first and second points 73 and 74 so as to open the gap GF to a finite value. The bevel 72 at that point blocks the intercommunication leading from the hole 80, thus sealing the chamber 28a and hydraulically locking the needle 18a on its seat. Hence firing pressures in the engine cylinder, not shown, are ineffective for reversal of fiuid flow through the jets 24 so as to unseat the needle part 18a.

In common in the foregoing injector pumps, we provide a seating-spring-biased, gap-joint-forming means connecting the plunger needle part and a second part of the plunger assembly, which is always effective as a safeguard to create an overtravel gap during completion of the pumping stroke. The seating force on the plunger needle part is thus limited to the force of the seating spring 10 or 10a, and therein resides one of the primary features of the invention. Due to its position as the unsupported thin walled part of the nozzle, the tip 14 or 14a is comparatively weak structure, but mechanical injection therethrough with our invention never subjects it to the direct force of the cam train. Thus if slight over-adjusting of the lash adjusting screw 53 occurs in the field, creating excess length in the cam train, the tip retains the safety factor of the gap in the joint to isolate it from the full force.

The resulting gap GF (FIGURE 4) is held to a minimum, for example 0.002-0.004 inch, so as to obviate an excessive hydraulic lock problem from occurring after the pumping chamber 16 is blocked by the bevel 70, but prior to seating of the bevel 72. Similarly, the gap G (FIGUR-E l) is kept to a minimum to obviate any appreciable un- 4 seating effect on the needle dueto fripg pressure in the engine cylinder.

What is claimed is:

1. A mechanical injection pump having:

seating means;

a plunger assembly seating thereon and including a fuelpumping plunger needle;

an injector drive cam; y

means including recessed -means (28) receiving the plunger needle and directlydrivingly interconnecting it and the dri-ve cam to pumpufuel; and y a seating spring (10) acting between th recessedmeans and the plunger needle, the seating spring adjusting in length, and a part of said plunger needle and the confronting part of the recessed means being similarly adjusted, to open an overtravel. gap (G). created in the joint therebetween, during completion of each pumping stroke. A

2. A mechanically-pumped injector having:

a pump plunger needle part seating thereon;

an injector drive cam (46) having meansof direct driving connection to said part;

a cup part (26) included in said means of connection which, for a major portion of the pumping stroke, moves with the needle part but which has more limited duration so as to stop prior to the stopping of the needle stroke, said needle part being capable of limited pumping movement relative to the cup part; and

energy-storing spring-force means (10) between the parts which, as the cup part stops, responds with the release of spring energy forcing the pump-plunger needle part to complete its stroke.

3. A cam driven injector pump having:

multiple seating means having first and second seat points;

an injector drive cam;

a main plunger part connected between the seating means and the drive cam and movable by the latter on pumping strokes toward the second point in the seating means;

a needle part which is carried by lost motion connection by the plunger part and which, for a major portion of the pumping stroke, moves with the plunger part but which engages the first point in the seating means thereby stopping prior to the stopping ofthe plunger stroke, said parts being capable of limited relative movement in the direction of the pumping axis; and

energy-storing biasing means (10a) between the parts which, as the needle part stops, accommodates relative movement between the parts in a manner to hold a needle part seated and to store spring energy while the plunger part completes its pumping stroke.

4. A mechanical injector comprising:

a body;

a plunger assembly slidable therein;

a pump plunger needle part in the assembly and a nozzle part on the body coacting during plunger pumping strokes whereby one of the parts seats in the other; and

seating-spring-biased, gapped-joint-forming means connecting the plunger needle part and a second part of the plunger assembly effective always to make an overtravel gap open up in the joint during completion of the pumping stroke, whereby the seating force on the plunger needle part is limited to the force of the seating spring.

5. The invention of claim 4, characterized by a suction-stroke spring (34) acting against the assembly to effect the pump suction-stroke.

6. The invention of claim 5, characterized by the suction-stroke spring being coaxial to the seating spring and acting between the body and the second part of the assembly.

7. The invention of claim 6, characterized by: an injector drive cam; and means comprising a plunger cup (26) included in the assembly and interconnecting it and the drive cam. 8. The invention of claim 7, the suction-stroke spring characterized by being within the plunger cup.

9. The invention of claim 8, said cup characterized by constituting the second part of the plunger assembly.

10. The invention of claim 7 said seating and suctionstroke springs characterized by comprising coil springs (10, 34), disposed concentrically Within one another and together within said cup.

11. The invention of claim 9, characterized in that the plunger needle part is of a one piece construction forming the plunger proper as well.

12. The invention of laim 8, characterized by said second part of the plunger assembly comprising a main plunger (18b).

13. The invention of claim 12, the joint formed by said means connecting the needle and second parts characterized by the main plunger slidably receiving the needle part and together defining a chamber behind the needle part, said seating spring being located in the chamber and pressing outwardly against the two parts.

14. The invention of claim 3, characterized by said first point comprising a first assumed seat taken by the needle part effective to stop injection;

said plunger part slidably receiving the needle part and together defining a chamber (28a) behind the needle part; and

an equalizer hole interconnecting the plunger part and the fluid inside said chamber;

said second point comprising a second assumed seat taken by the plunger part, said seating spring pressing the needle part on the rst seat and the seating of said plunger part stopping the movement thereof and hydraulically locking the needle part in its seated position.

15. The invention of claim 14, the described part reception characterized by a pin and slot wall connection between the main plunger and plunger needle parts, the distance apart between the first and second points (73, 74) in the seating means being less, by a small amount of difference, than the normal distance apart of the cornpanion seated portions (72, of the main plunger and plunger needle parts;

the needle part seating first and the plunger part overtraveling by said amount of difference before it seats and.stops, said connection accommodating whereby a gap results between the pin and slot wall equal t0 the amount of overtravel.

16. The invention of claim 15, the injector pump characterized by a nozzle tip having jet means;

there being at least one seat (73) of said multiple seating means located in the nozzle tip operatively adjacent at least one jet means (24) therein.

17. The invention of claim 1, the means which includes the recessed means (28) characterized by a cam train which, together with the plunger needle part, has parts subject to wear;

said cam train having a lash adjusting screw part (53) which is also subject to underadjustment causing eX- cess lash;

said seating spring (10) automatically adjusting in length to open an overtravel gap (G) during completion of each pumping stroke following wear in, and/or underadjustment in the effective length of, the cam train.

References Cited UNITED STATES PATENTS 1,060,151 4/1913 Bader 239-95 X 1,834,224 12/1931 Salisbury 239-91 X 1,852,191 4/1932 Salisbury 239-88 2,144,861 l/1939 TruXell 239-88 X 3,072,114 l/1963 Colgate 239-87 X M. HENSON WOODS, Prz'maly Examiner.

HOWARD NATTER, Assistant Examiner.

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