US2759716A - Idling system for two-cycle engines - Google Patents

Description

Aug. 21, 1956 Filed Jan. 21, 1954 M. E. JONES IDLING SYSTEM FOR TWO-CYCLE ENGINES 2 Sheets-Sheet l H B /7 ,5 so 7 I8 l I 1 8/ k l l l F l G. 2

INVENTOR.

MALDWYN E. JONES ay z/ w ATTORNEY Aug. 21, 1956 M. E. JONES 2,7 7

IDLING SYSTEM FOR TWO-CYCLE; ENGINES Filed Jan. 21, 1954 2 Sheets-Sheet 2 INVENTOR. MALDWYN E. JONES gm w ama ATTORNEY States atent Free IDLING SYSTEM FOR TWO-CYCLE ENGINES Maldwyn E. Jones, Ferguson, M0., assignor to ACF Industries, Incorporated, New York, N. Y., a corporation of New Jersey Application January 21, 1954, Serial No. 405,336

2 Claims. (Cl. 261-41) This invention relates to fuel feeding and fuel mixture distribution systems for internal combustion engines. More specifically, the invention resides in a charge-forming device comprising a novel combination of a carburetor with a plurality of intake manifolds for proper fuel distribution in different ranges of engine speed. The novelty resides in the manner of interconnection of the elements of the combination, one with the other, wherein part or all of the fuel mixture can be supplied by the carburetor to the engine intake ports through one manifold in one range of throttle openings and engine speeds, or part or all of the fuel mixture can be supplied by the carburetor to the engine intake ports through another manifold in other ranges of throttle openings and engine speeds.

One of the disadvantages of the usual carburetor manifold combinations is unequal distribution between the cylinders of a multi-cylinder engine. This disadvantage may arise .at different engine speeds for different engine manifold combinations, and has been found, as a matter of practical design, to be unavoidable in at least some degree in any design. By way of example, if it is possible to obtain gooddistribution at idle and in the full throttle range of the carburetor, then it often occurs that the distribution in the part-throttle ranges of the carburetor is wholly unsatisfactory. The engine operation may be eX- ceedingly rough at speeds above idling, due to the fact that only some of the cylinders will receive an ignitab'le mixture.

On the other hand, by way of example, if it is possible to obtain good distribution Within the part-throttle and full-thrott1e ranges of the carburetor, then distribution at idle is wholly unsatisfactory. Where either of these conditions prevails, it often occurs that the cause may be traced to the collection of fuel somewhere in the manifold in a puddle.

Under conditions such as those above explained, the present invention may be utilized to obtain satisfactory distribution throughout the entire range, including all throttle openings and all engine speeds. In this invention, the carburetor is mounted on a primary fuel mixture distributing manifold connected to the engine intake ports. The usual idle fuelnozzle adjacent the edge of the carburetor throttle valve is eliminated. Instead, a plurality of nozzles are located adjacent a valve intake port to the engine within the primary manifold, and are suitably connected by a secondary fuel mixture manifold with the idling system of ports and passages in the carburetor.

During engine idling, the proper amount of fuel is metered by the carburetor idling nozzle system, and is delivered to the individual cylinders adjacent each cylinder intake by the secondary manifold. This eliminates the effect on distribution during idling caused by pulsations Within the manifold, and the effect of unbalance of flow therein created by the pulsations or by unevenly timed intake cycles, if such be the case.

The carburetor used in this invention contains within the main mixture conduit a suitable high-speed fuel nozthrottle range to supply the primary manifold with a mixture sufficient to supplement that supplied by the idle system of the carburetor through the secondary manifold. This supplies the demand at increased engine power outputs for additional air and gasoline.

At the part-throttle range, distribution is aided by the supplementary fuel and air delivered by the secondary manifold because throttle deflections cannot affect distribution by the secondary manifold fuel nozzle. Furthermore, since, within the part-throttle range at least, a smaller amount of liquid fuel is delivered to the engine by the primary manifold, puddling of the fuel within the primary manifold is eliminated. This can be readily understood when it is realized that the mixture carried in the primary manifold is much more lean in fuel content than would ordinarily be the case. Where, in a manifold, the mixture contains a smaller weight of fuel, the weight of air supplied becomes larger in proportion to the weight of fuel and more effective as a fuel carrier because the saturation effect is reduced, causing less accumulation of fuel along the walls of the primary manifold.

In the full thi-ottle range of operation of the engine, operation of the secondary manifold is not required, because engine speeds create an air velocity in the manifold ordinarily sufficient to give good distribution. However, if desired, the fuel system in the carburetor can be so adjusted that the secondary manifold will be supplied with fuel mixture throughout the entire range of throttle openings and engine speeds.

In order to illustrate the invention, reference is made to the accompanying drawings, in which:

Fig. 1 is a top plan view of a carburetor and manifolds according to the present invention.

Fig. 2 is a side elevational view in section of the carburetor and manifolds shown in Fig. 1.

Fig. 3 is a front elevational view on a reduced scale illustrating the mixture passages within the manifold shown in Figs. 1 and 2.

:Fig. 4 is a modification of the invention illustrated in Figs. 1 and 2 showing a different form for the secondary manifold.

Referring now to the drawings in detail, the chargeforming device illustrated is specifically designed for a tandem, two-cylinder, two-cycle engine such as commonly used on outboard marine engines, chain saws, mowers, and gasoline power driven, portable implements. Bu!t it should be understood that the invention is equally applicable to engines of a larger size wherein the manifold on the engine may be of entirely different configuration, and to four-cycle engines as well.

In Fig. l the carburetor body casting 2 is formed with a mixture conduit 3 containing a venturi 4. Posterior of the venturi 4 is a throttle valve 5 suitably mounted on a throttle shaft 6 rotatable in bearings 7 and 8 within the main carburetor body casting 2. The throttle valve 5 is designed to be closed in sealing relation to the mixture conduit 3 and, when closed, suitable air adjustment for engine idling conditions is supplied through a pair of apertures 10 and 11, which can be suitably calibrated for the urpose. Fixed to the throttle shaft 6 is a throttle arm 13 which mounts a pin 14 for cooperation with the usual cam actuated by the manual operated speed controller for the outboard engine. Torsion spring 15 surrounds the throttle shaft 6 and has one end hooked at 17 for abutting engagement with throttle arm 13. The opposite end of the sprin E5 is engaged by the fixed abutment 18 in the carburetor body casting 2. Spring 15 tends to maintain the throttle 5 closed in the mixture conduit 3.

Anterior of the venturi 4 and mounted within the mixture conduit is a choke valve 20 suitably mounted upon a rotatable choke shaft 21. An arm 22 is fixed to the choke shaft 21 to provide a manual control.

The carburetorbody casting 2 is formed with a dependent, intcgralboss located opposite the throat of the venturi 4. Threads 26 within the boss 25 receive threaded nipple 27 with an integral flange which abuts the periphery of an aperture within the fuelbowl 28 and secures the bowl to the carburetor body casting 2,- as illustrated in Fig. 2. Suitable gaskets are provided between the aperture of the bowl and the end of the boss 25, as well as the upper rim of the bowl 28 and the body casting 2,to prevent the leakage of fuel from within the fuel'bowl 28. Surrounding the boss 25 and within the fuel'bowl28 is a float 36 for operating a needle valve (not shown) in the fuel supply inlet to the fuel bowl 28.

A fuel passage 32 communicates between the fuel bowl 28 and the interior of the hollow boss 25. This inlet is located'above the end of the nipple 27, which is suitably threaded interiorly to receive a needle valve 35. A suitable packing gland 36 is provided for the needle valve which extends upwardly within the boss 25 into an orifice 37' of a main fuel nozzle 40, which is exposed to the flow of'air in the throat of the venturi 4. The fuel nozzle 40 is suitably secured by its threaded end 41 within the boss25.

The low speed nozzle system is supplied with fuel by idle tube 45 press-fitted in the wall of the body casting 2. A plug 46 is threaded in a boss in the carburetor main body casting 2 forming a chamber in communication with idle tube 45. The idle tube 45 projects downwardly within the main fuel nozzle 40 to a point adjacent the main orifice 37 below the fuel level.

Within the main carburetor body casting 2 is a passage 50 shown in Fig. 2 extending from an orifice 51, anterior of throttle valve 5, to the chamber above the idle tube 45. A passage threaded as at 56 receives an idle adjustment screw 57. Passage 55 is in communication with the idle tube 45, and the idle screw 57 cooperates with a metering orifice 59 for controlling the flow of the mixture of fuel and air from idle tube 45 and orifice 51 to outlets 60, one of which is shown in Fig. 2.

Turning now to Figs. 1 and 3, the carburetor main body casting 2 is flanged at 62 and secured to a manifold 65 by a pair of cap screws 66 and 67. The mixture conduit 3 communicates with a U-shaped passage 69 within the manifold '65, and is located in one of the legs of the U-shaped passage as illustrated in Fig. 3. Adjacent the ends 70 and 71 of the U-shaped passage are engine intake valves 73 and 74, respectively. As shown in Fig. 2, these are triple valves, in this instance, provided with individual operating flexible reeds 75 and 76. The primary manifold is suitably apertured about its periphery to receive bolts for securing the manifold to the engine. it also has apair of openings illustrated as 79 and 80 in Fig. 3, through which project fuel nozzles 81 and 82 connected with branches of a secondary manifold 84 and 85, which, in turn, are connected to the outlets 60 of the low speed or idling system of the carburetor.

An outboard engine of the type under consideration here is provided with an engine speed controller as mentioned above,-which is, in turn, connected with both the spark advance mechanism of the magneto and with a cam which cooperates with the follower pin 14 of the carburetor. Operation of the controller in one direction advances the spark from a retarded position, and the cam co-operating with the follower 14 is so designed that during this movement to advance the spark, the throttle valve 5 remains stationary in a closed position. After the controllerhas advanced the spark to speed the engine from a' slow idle to a fast idle speed, the cam operated by 'the controller progressively opens the throttle by coaction with the follower 14.

With the spark fully retarded by the controller, throttle 5 will be closed, and main fuel nozzle 40 inoperative. The ports 10 and 11 in the throttle allow the passage of some air through the mixture conduit 3 into the primary manifold passage 69, and from thence to the intake valves of the engine. While the throttle is closed, however,.and the fuel nozzle 40 is inoperative, most of the primary manifold will be dry, since no fuel will be supplied thereto.

The fuel supplied to the engine in the idle range of speeds with the throttle valve 5 closed is delivered exclusively by the secondary manifold. The fuel in the secondary manifold is in the form of a mixture of air and fuel, however, due to the fact that suction on the fuel nozzles 81 and 82 will not only siphon fuel through the idle tube 45, but also air from the port 51 which, with the throttle closed, forms an atmospheric bleed. The port 51 has been shown adjacent the throttle valve 5 so as to be swept by air passing around the throttle valve 5 during its opening movement, but this is not absolutely necessary, and the location of the port 51'at this point is purely optional. Air from the port 51 will mix with fuel from the idle tube 45 and pass through the metering orifice 59 under control of the needle valve 57. This mixture will then enter the secondary manifold through the ports 60 and flow directly to a point adjacent the intake valve of the engine through the tubes 84 and 85 and the fuel nozzles 81 and 82.

The location of the fuel nozzles 81 and 82 provides for even distribution of the air and fuel mixture passing through the secondary manifold, while the air passing through the metered ports 10 and 11 furnishes the additional air necessary to maintain a proper combustible mixture and at the same time prevent the accumulation of fuel within the primary manifold passages 69.

As the controller for the engine is operated to advance the spark, engine speed will increase from 400 or so R. P. M. to approximately 1,000 R. P. M. At this higher speed throttle valve 5 still remains closed, and the mixture for combustion is supplied exclusively by the idle system of the carburetor through the secondary manifold in a manner the same as that above described.

Further operation of the engine controller will progressively open the throttle valve 5. The increased flow of air through the mixture conduit 3 and the venturi 4 will bring into operation the main fuel nozzle 40. At the same time, if the atmospheric bleed port 51 is located adjacent the edge of the throttle valve 5, the flow of air will produce a drop in pressure adjacent this port 51 to enrich the mixture in the idle system of the carburetor. This will cover the transition point between the operation of the idle system and the main nozzle system and, furthermore, it will eliminate the effects produced by deflection of the air stream in the primary manifold due to the inclined position of the throttle valve 5. Oftentimes it has been found that throttle valve deflection is a serious cause of poor distribution. In this invention, however, since the primary source of fuel is from the secondary manifold during early stages of throttle valve opening, the effectof deflection from the throttle valve will be negligible.

At some point in the operation of the engine controller to open the throttle valve 5, the engine speed and intake air velocity will become sufiicient to bring the nozzle 40 into full operation, but, before this has happened, the mixture supplied through the secondary manifold has decreased so as to have little effect upon the mixture ratio entering the engine, and, although it may happen that the secondary manifold continues to operate throughout the entire range of throttle positions and engine speeds, its delivery will be so reduced in the range of wide open throttle positions that it can be readily compensated for by adjustments of the main nozzle needle valve 35. Consequently, it makes little difference in this range of throttle positions whether the secondary manifold continues to operate or not, since its effect can be compensated for in the calibration of the carburetor.

Turning now to Fig. 4, the top view of the carburetor manifold combination is similar to that shown in Fig. l, and the same parts havebeen indicated by the same reference characters. In this modification, the connection of the idle system with the secondary manifold has been modified slightly to provide a single connection 60 with the secondary manifold 84 and 85. This modified form of secondary manifold is U-shaped and provided with a mixture conduit connection in one leg of the U. In design it is, therefore, substantially identical with the primary manifold, which has a U-shaped passage 69 and a mixture conduit connection 3 in one leg of the U. It has been found that this design for the secondary manifold provides improved distribution, and that the combination of a primary and a secondary manifold of substantially identical shape is beneficial to engine performance for this reason.

The modification shown in Fig. 4 is the same in other respects as the one above described in Figs. 1 and 3.

A structure has been described above which will carry out all the objects of the present invention, but it should be understood that this description is by way of illustration only, since obvious modifications will occur to anyone skilled in the art.

I claim:

1. A charge-forming device for internal combustion engines comprising, in combination, a carburetor, including a mixture conduit, a fuel bowl, a high-speed fuel nozzle system supplied with fuel from said bowl and opening in said mixture conduit, a throttle in said mixture conduit posterior of said high-speed fuel nozzle, a low-speed fuel nozzle system, an idle tube for said lowspeed fuel nozzle system supplied with fuel from said high-speed nozzle system, independent means to meter the fuel supply to said low-speed fuel nozzle system, and an atmospheric air bleed for said low-speed fuel nozzle system adjacent said independent means to meter said fuel and controlled by throttle position, means for distributing the mixture supplied by said carburetor, including a first manifold connected with said mixture conduit under control of said throttle, a second manifold con nected with said low-speed fuel nozzle system regulated by said independent fuel metering means and said throttle, and means for supplying a metered amount of air to said first manifold when said throttle is closed to the idle position.

2. The combination defined in the preceding claim including outlet nozzles for said second manifold projecting into said first manifold.

References Cited in the file of this patent UNITED STATES PATENTS 1,069,502 Wadsworth Aug. 5, 1913 2,621,030 Henning Dec. 9, 1952 2,639,699 Kiekhaefer May 26, 1953 2,656,166 Foster Oct. 20, 1953

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