US2711884A

US2711884A - Carburetor for internal combustion engines

Info

Publication number: US2711884A
Application number: US231685A
Authority: US
Inventors: Zarnack Werner
Original assignee: Individual
Current assignee: Individual
Priority date: 1950-06-20
Filing date: 1951-06-15
Publication date: 1955-06-28
Anticipated expiration: 1972-06-28

Description

June 28, 1955 w. ZARNACK 2,711,384

CARBURETOR FOR INTERNAL COMBUSTION ENGINES Filed June 15, 1951 fm eman' WERNER zA/M Ac/ -8 ZVM United S ttes Fatent C F CARBURETOR FOR INTERNAL COMBUSTION ENGINES Werner Zarnack, Lockstcdter Lager-Noni, near Itzehoe, Germany Application June 15, 1951, Serial No. 231,685

Claims priority, application Germany June 20, 1950 2 Claims. (Cl. 261-44) 1 This invention relates to carburettors for internal combustion engines.

Carburettors of this type are known where the mixture of air and fuel is produced at the place of its highest flow velocity and the proportion of the mixture components is automatically adjusted by a controller in accordance with a desirable scheme and independently upon the pressure at the mixture forming place.

With these carburettors the cross-section must be re duced at the throttle place to a greater extent than in the air supply in order to create a decrease in pressure which sufiices for the control and the atomization of the fuel being sucked-in by a vacuum at the throttling place. If the device is partially loaded, for instance, if the throttle slide is partially closed, the flow velocity automatically increases between the mixture forming place and the air measuring nozzle if the latter is located before the throttling place. If the throttle slide is fully opened, however, and if the carburettor is not sufliciently restricted at the throttling place it may happen that the rate of the pressure decrease does not suflice for the regulation and atomization of the fuel. On the other hand, if the carburettor is throttled excessively, this may cause a reduction of the fuel output.

If the pressure decrease at the mouth of the atomizing nozzle is not sufficient, the regulator passes into its fully open end position. In this case the amount of fuel depending on the added resistance from the float chamber to the mouth of the atomizing nozzle is too small. This particularly happens if additional air is admixed to the fuel on its way from the regulator to the nozzle to improve atomization because a small admixture of air already sufiices to considerably enlarge the resistance at the mouth of the atomizing nozzle. Since, however, the air admixture cannot be dispensed with in view of the required atomization the cross section at the mixture in accordance with a predetermined scheme, atomized air in supplied through an air slide coupled with the throttle slide of the carburettor as soon as with the partially closed throttle slide for the combustion air the pressure decrease at the atomizing nozzle has reached a value which allows the admixture of atomized air without in v fiuencing the control.

It has been found that it is preferable to stop the admission of atomized air if between three quarters and full load is reached. When the admission of atomized air is stopped the fine preparation of the fuel is only attained by the speed of the flow of the combustion air through the atomizing nozzle.

It was found that for the attainment of a minimum of fuel consumption it is highly important to have the atomization and the uniform mixture take place immeverted into pressure.

2,711,884 Patented June 28, 1955 diately at the mixing place. For this purpose a cylindrical throttle slide of the type is applied as used in connection with carburettors of motor cycles if the fuel is fed laterally at the periphery of the smallest cross section. Generally, the carburettors of motor cycles are provided in this case with a collar-like projection on the slide, said projection serving as make and break edge for the fuel escaping in the flow direction before the collar and being at this place mixed with air.

Excellent atomizing results are obtained in conformity with the invention by the formation of the throttle edge in such a manner that the possibly reduced creation of little whirls takes place at the smallest cross section of the feed pressure difference are possibly converted into flow velocity.

With this purpose in view the front face of the cylindrical slide is bevelled at the entrance edge nearly up to its center and is rounded. If this slide is partially closed a Venturi-tube-like narrowing results. The exit opening for the fuel is surrounded by a narrow ledge only at the front face of the cylindrical slide since the surface of the slide is preferably cut as an angle of 45 relative to the axis of the slide. In this manner a maximum of air flow at the mixture forming place and due to the reduction of whirls an optimal pressure decrease results. At the same time a mixture forming chamber is created having sufficient space for the entrance of the fuel and preventing final deposition at the projecting surface. As the flow velocity of the fuel mixed with the atomized air at the exit is nearly as great as that of the combustion air flowing in preferably rectangular direction thereto, the flow direction of the fuel jet will be inclined at an angle of about 45 degrees.

Another feature of the invention relates to a method of preparing the fuel mixture where the fuel is fed along the axis of the air flow and stop of the atomized air flow, even if fully loaded, is presented the known action of the multiplicator nozzle being utilized at the mixture forming place. A small Venturi-tube is used for the formation and control of the mixture in such a manner that the mouth of this small tube having the spraying tube located in its smallest cross section opens into the smallest cross section of an outer air hopper feeding the main flow of the combustion air. In this manner the pressure decrease at the mouth of the spraying tube is increased in proportion of the exit cross section of the I small Venturi-tube to its smallest cross section relative to the use of only one sole air hopper, provided that the enlarging cone of the small Venturi-tube is so flat that the flowing velocity in the enlargement is fully con- The enlargement of the pressure decrease is limited in the customary carburettors because in accordance with a large pressure decrease the main nozzle is proportionally reduced to the multiplicator effect; in this manner dimensions result which are so small that they interfere with the working safety of the carburettor. Since in these carburettors the multiplicator tube is arranged in the flow direction before the throttle chamber also the produced mixture, when partially loaded, is deposited at the surface of the throttle device arranged across the flow direction and must be formed again at the edge of thte throttle fiap in the manner of the carburettors not provided with multiplicator nozzles.

In conformity with a further feature of the invention the multiplicator tube of a carburettor having automatic fuel control is located in the very throttle cross section and is so dimensioned that a greatest possible multiplicator effect is obtained at the narrowest place of the small Venturi-tube. The vacuum produced at the narrowest place of the multiplicator tube may be five to six times as great as the flow vacuum at the narrowest place a of the carburettor; in this manner the rate of pressure decrease sufiices for the regulation and it is possible to add atomized air from the running without load until the running with full load without the regulator moving into its end position or the cross section of the carburettor being inadmissibly restricted if running with full load.

If the above described throttle slide is used the multiplicator atomizing nozzle may be arranged in parallel to the main air flow of the carburettor in such a manner that the conical enlargement preferably opens rectangularly to the main fiow direction of the suction air of the carburettor. This enlargement may also be arranged at the periphery of the throttle cross section and coaxially with the latter.

1 In conformity with a further feature of the invention the axis of the multiplicatornozzle is arranged coincidentally with the middle axis of the air flow so that a more uniform mixture is formed over the entire cross section. Due to the multiplicator effect the mixture of fuel and atomized air escapes into the main air flow of the multiplicator tube practically with sound velocity from running empty up to running with full load.

It is apparent from the above that the invention solves the problem of providing controlling means for a carburettor which automatically regulates the fuel mixture according to a desired order said controlling means enabling the production of a sufficient rate of pressure decrease towards vacuum over the entire load range, but. not narrowing the cross section of the suction tube to such an extent that this narrowing leads to pressure losses. For this purpose the feeding of atomized air is stopped according to the invention within the range of about three quarters and full load and a. multiplicator atomizing nozzle is arranged within the throttle cross section. The fact that it is already known per se to regulate the additional air in dependency upon the adjustment of the throttle flap, to use a Venturi-tube atomizer and to provide a symmetrically adjustable throttle having a changeable Venturi cross section does not interfere with the novelty and usefulness of the combination of means in accordance with the invention.

Several preferred embodiments of the invention are illustrated in the attached drawings.

In these drawings,

Fig. l is a vertical sectional View of a carburettor constructed in conformity with the invention,

Fig. 2 is a vertical sectional view of the throttle slide,

Fig. 3 is a front view of the slide shown in Figure 2,

Figs. 4 and 5 are vertical sectional views of a further embodiment of the invention. Figure 5 being a scctiona1 view on line 5 to 5 of Figure 4.

In conformity with Fig. l the fuel is sucked in through spray nozzle 1 by the vacuum prevailing in the part of the carburettor having the smallest cross section. The output of the motor is limited by the slide 2. The quantity of air sucked in is controlled at the constriction 3 of the air suction joint, said constriction being shaped in accordance with the known rules to measure the rate and quantity of the air flow. The sucked-in air controlled pressure volume is by the difference at the inlet openings of the pipes 4 and 5.

The fuel enters into the float chamber 7 through pipe 6 and flows through pipe 8 to the main orifice 9. Posterior to this orifice 9 a channel 10 leads to the chamber 11 of the fuel regulator. In this fuel-filled chamber the same vacuum prevails as posterior to the main orifice 9. The chamber 12 of the fuel regulator is connected by pipe 5 with the narrowest portion of the nozzle 3. Chambers 11 and 12 are separated from each other by the membrane 13. The fuel supply is controlled by a valve of which the needle 14 coacts with a flat seat provided at the exit of nozzle 15 and is adapted to fully close it.

If the sucked-in air volume increases by opening the throttle slide 2, the vacuum in the nozzle 3, the pipe 5 and the chamber 12 also increases. The membrane 13 is moved to the left and clears the passage through the nozzle 15; thereby also the vacuum posterior to the fuel nozzle 9 increases. This vacuum tends to move the membrane again to the right, until the pressure within the chambers 11 and 12 is equalized.

In the embodiment of the invention shown in Fig. 1 the atomized air is sucked-in through nozzle 19, which is controlled by a slide 16. This slide 16 is connected by rod 17 with the one arm of a double armed lever 18; the other lever arm is connected with slide 2 by rod 171:. Lever 18 is rotatably supported upon pivot 18a. If the throttle 2 has opened the cross section of the carburettor, e. g. for three quarters, the slide 16 stops the entrance of the atomized air through nozzle 19. The change-over time may be altered in accordance with the Working conditions of the carburettor by an adjusting device provided in connection with rod 17, but not shown in the drawmgs.

The shape of the slide 2 is more clearly shown in Figs. 2 and 3.

As apparent from these figures numeral 20 denotes the throttling edge of the slide. The shape of the en trance edge 21 of the slide is apparent from Fig. 3, this edge 21 contrary to the customary shapes is bevelled and rounded in order to possibly eliminate loss of pressure of the air passing the throttling edge or the mouth of the nozzle. The edge 21 forms a straight intersecting line with the front face of the slide 2. The intersecting line is so far displaced beyond the middle of the slide 2 that the discharge edge may embrace the nozzle mouth with an optuse angle a, as apparent from Fig. 3. Since the air is admixed to the fuel exiting from spraying nozzle 1 it is discharged from this nozzle with essentially the same speed as the combustion air flowing perpendicularly thereto. In order to prevent the fuel to meet baffle faces the slide 2 is bevelled posterior to the edge forming the optuse angle at an angle of preferably 45. This bevelled face of the slide 2 is designated in Figs. 2 and 3 with the refer ence numeral 22.

In the embodiment of the invention shown in Figs. 4 and 5 the pipes 22' and 23 correspond to the pipes 5 and 4 of Fig. 1 respectively. Also this constriction 24 of the air suction pipe is constructed in accordance with accepted rules.

The air nozzle 19 of Fig. 1 corresponds to the nozzle 25 of Fig. 5.

According to this embodiment of the invention the supply of atomized air is not controlled in dependency upon the throttle adjustment; in this case a vacuum increasing tube-shaped device is provided having its on trance opening located along the center axis of the constriction 24 and its exit in the center axis of the narrowest throttle cross section. As a result of the action and of the spraying nozzle 26 of this tube the rate of pressure decrease at the mixing place 27 of the tube always suffices to allow the admixture of atomized air by the nozzle 25 within the entire loading range of the motor. The spraying nozzle 26 even causes that the vacuum at the two exit places reaches the critical rate of pressure decrease if the slide is partially closed whereby the air flows in this case through the nozzle 26 with the velocity of the sound.

The fuel pipe 28 shown in Fig. 5 corresponds to the fuel pipe 5 shown in Fig. 1 leading from the controller to the spraying nozzle 1. The spraying nozzle 26 may be arranged at one side within the air suction pipe, but it is recommendable in view of a satisfactory air flow and obtainment of the vacuum if this mixing nozzle for the fuel and the combustion air is provided in the middle axis of the air suction pipe. With this purpose in view, two slides 29, Figure 4, moving in opposite directions are used for throttling the air of combustion, said slides being actuated in the manner indicated in Figs. 4 and 5. In the casing of the air suction joint the axis 35 of a double-armed lever 30 is pivotally supported. T he main operating lever 31 of the carburettor is attached to the same axis 35. The two ends of the double-arm lever 30 are pivotally connected by means of connecting rods 33 with the one end of two other double-

arm levers

32 and 32a respectively, the other ends of which are connected with the slides 29 by pushing rods 34. If the double-arm lever 30 is rotated about its axis in the clockwise direction the throttle slides are outwardly moved. If, however, the double-arm lever turns in an anti-clockwise direction the throttle slides move inwardly and stop the air supply. Instead of the throttle slides flap-like controlling organs may be provided.

The entrance edges of the throttle slides or valves 29 are rounded in a similar way as the entrance edge of throttle valve 2 shown in Fig. 3; however, the slides are each provided with a semi-cylindrical recess 35 adapted to enclose the opening of the spray nozzle 26, if the slides 29 are in their idle position. The discharge edges of the throttle slides are enlarged into flat portions so that in the fully opened position shown in Fig. 4 they will reduce without causing throttling losses the flow velocity of the air from the narrowest place up to the place at which the slides 29 have the largest distance from each other. In this manner the fiow resistance of the carburettor has in the fully opened position of the slides 29 the smallest possible output so that the motor will have its maximum efficiency, if the slides 29 are fully opened. By narrowing the cross section at the slides 29 to their fully opened position a vacuum is produced at the mouth of the spraying nozzle 26, which vacuum suffices for the continuous .5

supply of atomized air through the nozzle 25.

Having thus particularly described the nature of my said invention and the manner in what the same is to be performed, What I wish to have covered by Letters Patent is:

1. Carburettor for internal combustion engines cornprising, in combination, an air pipe having a venturi adapted to form the mixture and to produce a vacuum for sucking-in the fuel, a spraying nozzle provided at the venturi of said air pipe, a regulator adapted to automatically adjust the proportion of mixture according to a desired rule, a fuel supplying pipe connecting said regulator with said spraying nozzle, an atomizing air nozzle provided in said supplying pipe between the regulator and the spraying nozzle, a throttle device comprising at least one throttle slide provided at said air pipe and adapted to adjust the output of the engine, an auxiliary venturi tube arranged coaxially to the main air flow and adapted to produce the rate of decrease of air pressure required for the regulation of atomizing air supply, the exit mouth of said auxiliary venturi tube being coincident with the narrowest place of the throttle device.

2. Carburettor for internal combustion engines comprising, in combination, an air pipe having a venturi adapted to form the mixture and to produce a vacuum for sucking-in the fuel, and a nozzle adapted to meter the rate of flow, a spraying nozzle provided at the throttle place of said air pipe, a regulator adapted to automatical- 1y adjust the proportion of mixture according to a desired rule, a fuel supplying pipe connecting said regulator with said spraying nozzle, an atomizing air nozzle provided in said supplying pipe between the regulator and the spraying nozzle, two throttle slides provided in the air pipe and adapted to adjust the output of the engine, means adapted to adjust said slides, an auxiliary venturi tube the entrance opening of which is arranged on the axis of the said air pipe and the exit opening of which is arranged on the middle axis of the throttle cross section formed by said throttle slides, the front faces of said slides being provided with semi-cylindrical recesses adapted to enclose the exit mouth of the auxiliary venturi tube, when the slides are adjusted to the idle running position, and having Venturi-tube-like rounded and bevelled entrance and exit edges.

References Cited in the file of this patent UNITED STATES PATENTS