US2212258A - Carburetor - Google Patents

Description

Patented Aug. 20, 1940 UNITED STATES PATENT OFFICE Ludwig Beck, 221 2333011, Germany Application January 13, 1938, Serial No. 184,762 In Germany January 15, 1936 4 Claims. (Cl. 261-42) This invention relates to a carburetor intended for use in connection with internal combustion engines, particularly for motor vehicles.-

This improved carburetor is distinguished from those of the prior art, particularly by its economic consumption of fuel, as well as by its capacity to make the motor start with particularly greater power. The invention'utilizes, for the purposes in view, a peculiar phenomenon appearing especially with two-cycle motors and rendering it possible to control the pressure of the air con- The invention is illustrated diagrammatically and by way of example in the accompanying drawing in which Figure 1 shows an arrangement intended to demonstrate the effect utilized in thepresent invention. Figure 2 isv a diagrammatic representation of thepressurecurve aris-' ing in the suction channel of a carburetor. Figure 3 is a representation of the pressure curve obtained by giving the pressure shocks shown in Fig. 2 a uniform direction. Figure 4 shows a device for ascertaining a pressure curve for the correction of the fuel supply of an injection nozzle. tended for the same purpose; and Figure 6 shows a carburetor in which the fuel supply is regulated by controlling the air pressure existing in the float chamber.

Referring to Fig. 1, there is shown a normal carburetor for two-cycle'motors and in the suct'ion channel I thereof, in front of the mixing throttle valve 2, an outwardly opening nozzle 3.

If a funnel 4 is arranged in front of said nozzle 3, a manometer 5 connected tosaid nozzle will indicate a pressure above the atmospheric pressure within a certain distinct range of the suction speeds, which is a surprise in that in the suction channel I itself a pressure below the atmospheric pressure exists. Thorough investigations have shown that this phenomenon is due to temporary damming pressures of very short duration which arise at the moment of the shutting-off of the valve within the suction channel I and are transmitted to the manometer 5 by means of the nozzles 3 and 4.

Fig. 2 shows in the manner of an oscillogram the progress of a curve as arising in the suction channel I when the motor is running. The exterior atmospheric pressure is indicated by the dotted line pa. The suction stroke commences Figure 5 shows a modified device inat the point of time it and terminates in the point of time h when the piston closes the valve slots of the cylinder. At this momentthe air has within said channel a very high speed of flow so that it is dammed'up by reason of its kinetic energy, whereby a steep rise of the pressure during a short period of time, t1ta is obtained. At the point of time t 'o the next suction stroke commences.

The combined nozzles 3; 4 act now, so to say, as a rectifier. In the period of time tan-i1 the nozzle 3 sucks air in the direction indicated by the arrow 6 and exerts, therefore, only aslight sucking action on the funnel 4 and on the} column of the liquid of the manometer 5; However, in the period of time t1tz a jet of compressed air escapes from the nozzle 3 in the direction indicated by the arrow 1. This very direct jet of compressed air is intercepted by the funnel 4 and produces in the manometer tube 5 a short and practically sudden rise of the pressure. This rise fades away, it is true, in the then following period of time tzt1, especially under the action of the slight suction existing during said period of time, but as trials prove it is, under certain circumstances, sufficient to produce a medium pressure pa above the atmospheric pressure at the manometer 5.

The height of the pressure value 172,111) to which the damming-up pressure rises, depends on the height of the pressure Pl-WhiCh is produced during the suction stroke in the suction channel. and represents at the same *time a measure for the suction speed. With small suction' speeds the kinetic force of the streaming air is only slight and there arise only so slight pressure'shocks interrupted, besides, by long pauses that the pressure in the manometer 5 does not surpass the pressure Pa of the outer atmosphere. But with the increasing suction speed the intensity and the frequency of the damming-up pressure rise so that the pressure 113 in the manometer 5 likewise rises. With very high suction speeds, 'on the other hand, the pressure p1 decreases very strongly, and as, furthermore, the density of the streaming column of air and, therefore, also the kinetic force thereof likewise decreases, the damming-up pressure shocks lose their intensity with the increase of the suction speed; they are then no more able to compensate for the suction taking place in the intermediate periods of time (to-t1) so that the manometer 5 indicates a pressure below the atmospheric pressure. Tracing the pressure 113 which the manometer indicates in at a suitable place is the nozzle l5.

dependency of the number of revolutions R. of the motor, there will then be obtained, in the case of the throttling flap being open, a diagram p3=j (R), as in Fig. 3.

The course of the pressure in the funnelv 4 is now used, according to the present invention, for the correction of the amount of fuel which the injection nozzle of the carburetor delivers. can be attained, for instance, by connecting the funnel 4 with that opening by which the nozzle is air-vented in the usual manner.

The carburetor shown in Fig. 4 consists of the suction space 8 which is provided with the Venturi valve 9 into which the injection nozzle HI extends in the usual manner. This nozzle is composed of a small plain tube II and a doublecap I2 placed thereon and extending downwardly to below the level c-b of the float. The usual air opening of said nozzle is connected with the air-pipe I3 from which the regulating air enters into the nozzle in the direction indicated by the arrow l4. The air entering into the nozzle is controlled, according to this invention, by the following device: Mounted to the suction channel In correspondence with the actions which have been described in the preceding lines in connection with the Figs. 1-3, the air forced out of the nozzle during the back-shock phase leaves the nozzle in the form of a very direct jet and streams in this state to the damming-up funnel Hi. This latter is connected with a small air-vessel I'I, ahead of which a stream-line body I 8 may be inserted into the connecting pipe [9. As the body l8 counteractspthe air current in the direction of the arrow by means of resistance-forming eddies which are exceedingly small in the direction of said arrow, but extraordinarily large in the other direction, it acts like a return-valve. There obtain such values the rise of pressure mentioned is, according to this invention,- subjected to a correction by means of a control member coupled positively with the throttling valve of the carburetor. This control member may, for instance, consist of valve which is located either directly in the regulating air pipe l3 or which connects this pipe with the outer atmosphere. The'best means for the purpose in view is, however, a diaphragm which intercepts the directed air current more or less strongly; this arrangement warrants a very great security of service.

An arrangement of this kind is illustrated in Fig. 5. The back-push" above mentioned is obtained in this instance from carburetor air channel 2! at a placelocated between the throttle flap 22 and the Venturi valve 23, where there is an angular nozzle 24." Between the orifice'of said nozzle and the damming-up funnel 25 is arranged a diaphragm drum 26 which is connected with the axle of the throttle flap 22 and intercepts,-

according to its adjustment; more or less the airjet produced by theback-shock; When the dimensions of the nozzle and the funnel are suitably chosen, then, in order to accommodate the carburetor to different motors, or to diflerent This service conditions respectively, as occur in summer-time and in winter-time, on running up-hill, etc., nothing else is necessary than merely to exchange the diaphragm drum. I

Another way for the control of the fuel supply with the aid of the pressure curve as shown and as obtained bythe rectification of back-shocks consists in acting on the air-pressure existing in the float chamber above-the level, of the fuel. The lower that air-pressure is, the lower will be the fuel supply of the injection nozzle, as is A carburetor of this kind is illustrated in Fig. 6. The injection nozzle 28 which extends into the carburetor channel 29 is connected with the floatchamber 33 in the. usual manner; the cover 3| of this chamber is air-tight attached to it. Into the Venturi valve extends the pipe 33 which is connected with the nozzle or jet 34. Opposite this nozzle is a funnel 35 which is connected with the cover 3| of the float chamber 30 by the pipe 36. It is suited to the purpose in view to surround the place of interruption between the members 34 and with a tube 31 of wire-gauze which, on the one hand, prevents the admission of foreign bodies, and on the other hand, serves as a resistance to flow in the case of high suction speeds, the resistance increasing the strength of the suction transmitted to the float chamber 30.

The accurate course of the pressure curve shown in Fig. 3 depends, first of all, on the construction of the combined nozzles 34 and 35 and of the wire-gauze tube 31.

That course can he regulated between very wide limits by varying the distance between or jet 34 and the funnel 35, for which purpose said jet 34 may be arranged for lengthwise adjustment with respect to funnel 35 as by means of screw threads 34a. It is, however, of decisive importancethat the pressure in the float chamber 30 at first rises in correspondence with the augmentation of the suction speed, in such a manner, that a maximum pressure is attained at medium suction speeds, whereaiter, when the suction speed further increases, the pressure decreases more or less steeply. This particular course of the pressure can be obtained obviously only with the employment of a flow-rectifier, as represented by the combined members 34 and 35.

The particular course of the curve, as taking place at the members It, 25 and 35 is of decisive importance for the manner of operation of the present improved carburetor. As this pressure attains a maximum at medium suction speeds, the Venturi valve (9, 23, 32) can have a considerably larger diameter without entailing the risk of an inadmissible diminishment of the amount of fuel in themixture, as has been possible hitherto. Owingthereto a better admission is obtained 'for all numbers of revolution, and at the same time the sinking-of the pressure curve provides at high suction speeds for an accommodation of the fuel delivery to the reduction of the admission. Trials'have shown that by a suitable accommodation of all individual parts with respect to one another a maintenance of the most suitable ratio of mixture over nearly the 'entire range of the numbers of revolution can be attained while likewise maintaining the full performance of the motor, if notevendncreasing ereby, of course, the greatest eflithe same ciency is ob ained and, besides, also great saving or the motor is warranted.

The phenomenon mentioned in the first part moment of the highest suction speed, so that par- 2,212,258 of this specification becomes especially distinct with two-stroke cycle motors, because the valve slots of a motor of this type are shut-off at the ticularly ,diigh dam'ming-up pressures arise. With the four-stroke cycle motor, however, the valves are closed only when the piston approaches the dead-center position, that is to say,

moves already with a decreasing speed. In spite thereof, a curve of the shape shown in Fig. 3 may be obtained also with a four-stroke cycle motor, although it is not actually easy-to increase the pressure p; beyond the level pa. With four- ,/stroke cycle motors the entire, curve pa==f (R) I extends, therefore below the level line pa and A it is therefore, necessary to give the injectionnozzle a somewhat larger transverse section nozzle being arranged for supplying fuel to said channel, fluid flow rectifying means, including an outwardly opening air jet projecting from said channel, a tube having a funnel shaped opening aligned in spaced relation to said jet, and conduit means connecting said tube with said fuel supply means, said air jet being adapted to transmit damming pressure occurring in said air nozzle to said air channel.

channel to said tubeto control the flow of fuel through said fuel supply means to said air channel..

2. A carburetor comprising a nozzle, an air channel, said nozzle being afianged for supplyin; fuel to said channel, an air inlet chamber connected to said nozzle, an air jet outwardly projecting from said channel, a funnel disposed opposite said air jet, and a conduit connecting said funnel with said chamber for controlling the fuel supply to said channel in accordance with damming pressures occurring in said channel.

3. A carburetor comprising in combination arr air suction channel, a"fuel. nozzle provided with an air inlet, said fuel nozzle and said air inlet being arranged for delivering a mixture of fuel and air to said channel, an air jet projecting outwards-from said channeljaiunnel arranged opf posite said air jet, and a tube connecting said funnel with said air inlet of said fuel nozzle. 4. A carburetor comprising in combination an air suction channel, a nozzle adapted to supply fuel to said channel, a flow chamber connected.

with said fuel nozzle, an air jet arrangement communicating with and projecting outwards from said channel, said jetarrangement including a funnel regulatable with respect thereto, and. a conduit connecting said funnel with said float chamber, said air jet arrangement being adapted to. transmit damming pressure from said air channel through said funnel to control flow of fuel from said float chamber through said fuel LUDWIG BECK.

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