US2021554A - Carburetor - Google Patents

Description

Nov. 19, 1935. HANs-EBERHARD JAcoBY Er Al. 2,021,554

.CARBURETOR Filed Nov. 28, 1934 Inventors:

Zia. M

M i, @Mt/ Patented Nov. 19, '1935 miss @PATENT OFFICE CARBURETOR Hans-Eberhard Jacoby, Wetzikon, and Hans Nssli, Hinwil, Switzerland Application November 28, 1934, Serial No. 755,168 In Switzerland March 17, 1934 5 Claims.

In carburetors for internal combustion engines the proportion of the volume of air to the engine speed is referred to as the air curve, and the proportion of the quantity of liquid fuel to the engine speed is referred to as the fuel curve. It is considered that the ideal condition is reached when the proportion of fuel to air over the whole range of the revolutions of the engine remains constant, so that the fuel curve and the air curve are in substantially the same relationship through the range of engine speeds. This condition could hitherto not be attained in practice and variations in the proportions of fuel and air in the mixture occurred. In practice this means that the best performance is not obtainable from the engine throughout its range of speeds.

It has been proposed temporarily to overcome this disadvantage by providing a fuel accelerating pump, or automatic air valves. However, these arrangements had the disadvantage that they adversely influenced the fuel consumption'.

The present invention is concerned with carburetors having a spring loaded mushroom valve arranged in the choke tube and carried by a hollow stem slidable on a tubular member through which fuel is admitted to the choke the area of which is variable in accordance with the airflow and in which the vacuum necessary for the delivery of the fuel is taken from the choke, and it has for its object to provide an arrangement which will satisfy the condition set forth above.

With this object in View the invention comprises the provision at the upper end of the tubular member of an ante-chamber into which a damped pipe line from the float chamber enters above the fuel level and from which a further damped pipe line opens into the atmosphere.

In order that the invention may be more clearly understood two particular embodiments thereof will now be described by way of example, with reference to the accompanying drawing wherein:-

Figure 1 is a sectional View of one embodiment of the invention and Figure 2 is a similar View of a further embodiment.

Referring to; Figure 1 of the drawing the fresh air is drawn in the usual manner through a pipe 2, chamber 1, choke tube 5, chamber 3 and throttle into the inlet pipe 5 of the engine. The choke tube 6 is closed by a mushroom valve 8 which is subject to the action of a spring 9 which tends to hold said valve in closed position. The valve 8 has a hollow stem I9 the upper end of which isprovided With an abutlflilelll3 I4 for the spring 9 and slides on a tubular guide member I I secured to the carburetor casing. The abutment I4 may itself be formed as a valve to produce a damping effect. Secured to the valve member 8 is a needle valve I6 located in the tubular member II and 5 rio-operating at its upper end with a jet I 'I to vary the area of the opening of said jet.

The jet I'I divides the hollow space I2 from the hollow space I9 which serv-es as an antechamber into which opensthe air pipe a, and the 10 fuel pipe b from the float chamber I9. A further pipe c may also open into the ante-chamber I8, the other end of said pipe opening into the casing 55 between the throttle 4 and the engine. In the p-ipes c, b, and c restrictions or dampers at, y, and z 15 are provided.

In operation, owing to the aspirating action of the engine the mushroom valve S is automatically adjusted in the choke tube 9 in such a manner that the annular space between said choke tube 6 20 and the valve 8 hereinafter referred toas choke tube area, takes up a position under the combined action of the air speed and the spring 9 which affords passage to the air drawn in, such Y air having a certain minimum speed. Due to the Z5 air speed at any given time and the corresponding vacuum in the choke tube area an aspirating action becomes effective in the space I through the channel I3, the hollow space I 2 and the jet I'I, whereby the fuel is drawn into the chamber I8 30 from the oat chamber I9 through the pipe b and the restricting jet c'. These normal processes are insufficient tov secure that the fuel and air curves maintained in the same relationship throughout the'range of engine speeds, this being achieved 35 the following manner:-

During the movement of the needle valve I 6 the area of the opening in the jet I I is varied according to the position of the mushroom valve 53 in ther choke tube S and the corresponding posi- 40 tion of the needle point I6 in the jet Il, owingv to the fact that the needle has a conical end. The result is that the aspirating action which causes the fuel to be drawn in is varied according to the area of the opening. The air curve is lfierefore determined by the form of the choke tube and the spring 9 and the fuel curve is determined by the form of the point of the needle I, that is by the various areas of the opening in the jet I1 which correspond to the 50 positions of the valve 8 and are determined by 'the needle point. In order to compensate for the effects of the resulting friction of the parts atmospheric air is admitted into the antechamber I8 through the pipe a and a restriction 55 or damper whereby the vacuum in the chamber I8 falls to a certain extent. As a result the Vacuum in the chamber I8 never reaches the same value as in the annular choke area between 6 and 8 whereby undue enrichment of the fuel curve owing to the Variable area of the opening between the jet I1 and needle I6 is prevented. This action may also be explained as followsz In the idle running position of the throttle the choke tube area and the area of the opening between the jet I'I and needle I6 are at their smallest. When the throttle 4 is opened the vacuum in the chamber 3 is increased. The Valve 8 momentarily remains in the original position, whereby the vacuum in the choke area between 6 and 8 becomes effective through the channel I3 in the hollow space I2. Owing to the considerably smaller cross sectional area of the opening between the jet I'I and the needle I6 and to the secondary air entering through pipe a similar increase of the Vacuum in the ante-chamber I8 is prevented, so that the supply of fuel to the space through pipe b is not accelerated to the extent corresponding to the increase of Vacuum in the choke area between 6 and 8 and no waste of fuel occurs. If now the valve 8 succumbs to the aspirating action of the vaccum, that is if it descends the annular opening between the members 6 and 8 that is the choke tube area, is increased, the needle point I6 descends and the area of the opening in the jet I1 is correspondingly enlarged, so that the vacuum may have a correspondingly stronger action through channel i3 and hollow space I2 in the chamber I8, whereby the amount of fuel is increased in accordance with the volume of air passing through the annular choke tube area 6, 8.

Since during idling the secondary air entering the chamber I8 through pipe a and restriction or damper'n: may, in certain circumstances cause the vacuum to sink below the value necessary for the fuel supply during idling, a pipe c having a restriction or damper y is provided, connecting the air intake of the engine with the chamber I 8, so that by means of the pipe line suction at the intake of the engine increases the vacuum in said chamber I8, so that the amount of fuel entering the chamber I8 through the pipe b is increased.

In practical constructions it may be desirable to dispense with the needle valve I6, so that the variable annular space between the members I6 and I'I is non-existent. In this case the action of this space is repla-ced by a jet having an opening of a constant area and the Vacuum necessary for the supply of the fuel to chamber I8 is taken from a constant area choke tube disposed in front of the choke tube with a variable annular space between members 8 and 6.

In this embodiment, illustrated in Figure 2 an annular space is formed between the choke tube 6 and the valve 8 that is the choke tube area, when said valve 8 descends. The choke area at S above the Valve 8, is variable, by means of a suitably formed enlargement or thickening 22 formed at the lower end of the sleeve I II the area of the opening at s varying according tothe position of the valve 8. 'Ihe Vacuum at s which determines the fuel curve is thereby corrected, so that the fuel curve is determined in accordance with the air curve of the carburetor which in turn depends upon the dimensions of the choke area 6 and the strength of the spring 9.

The jet 2| has a constant area. From the pipe c a pipe g having a damper t leads to the narrowest part of the choke tube 28.

In operation, owing to the aspirating action of the engine the valve 8 is automatically adjusted in the choke tube area 8 and assumes a position 5 in accordance With the counter action of spring 9 which affords passage for the air drawn in, such air having a certain minimum speed. Due to the air speed at any given time and the corresponding vacuum in the choke area between 6 10 and 8 the fuel in the chamber I8 is drawn in through the channel I3 and the hollow space I2 past the jet 2|. The jet 2l also has the effect that the suction can only influence the delivery of fuel in the chamber I8 to a slight extent. 15

The Vacuum necessary for the supply of the fuel and determining the amount of fuel is admitted to the choke tube 6 through damper c, pipe g, pipe c and pipe a of chamber I8, reduced by the secondary air admitted through the 20 damper x and pipe The vacuum so created in chamber I8 draws fuel from the float chamber I9. The damper v has for its object to prevent in the idling position of the carburetor when the vacuum in the choke tube 6 is no longer sufficient 25 for the delivery o-f the fuel, the admissionof too much secondary air to the chamber I8 through pipe g and pipes c-a, so that the Vacuum in the choke tube area 6, 8 may reach the chamber I8 through channel I3, hollow space I2, jet 2I. 30 Should this vacuum in the chamber I8 prove insufficient for the supply of fuel while idling it is increased to the vacuum between the throttle 4 and the engine through the damper y and pipes c and a. 35

We claim:-

1. A carburetor for internal combustion engines, comprising a choke tube, a vertically disposed tubular member adapted to supply fuel, a spring loaded mushroom valve in said choke tube 40 and adapted to control the flow of air through said choke tube, said valve being slidable on said tubular member, means effecting communication between the choke tube and the tubular member whereby the vacuum necessary for the delivery 45 of the fuel is taken from the choke tube and fuel is discharged into said choke tube, means for varying the effective cross-sectional area of said tubular member in accordance with the air flow in said choke tube, said tubular member having 50 an ante-chamber formed in the upper end thereof, a float chamber adapted to contain fuel, a damped pipe line effecting communication between said fioat chamber and said antechamber whereby fuel is supplied to said tubular member, 55 and a damped pipe line open to the atmosphere and leading into said antechamber.

2. A carburetor as specified in claim 1 in which the said means for varying the effective crosssectional area of said tubular member comprise 60 a needle valve located in the tubular member, said needle valve being operatively connected to the mushroom valve whereby the effective crosssectional area of the opening between the said needle valve and the said tubular member varies 65 proportionately with the effective area between the said choke tube and said mushroom valve.

3. A carburetor as specified in claim 1, in which the mushroom valve has a hollow stem provided on its external diameter with a swelling located 70 where the stem enters the choke tube and the tubular member is provided with a constant area jet and a damped pipe line leading from the throat of the choke tube to the said antechamber. A

4. A carburetor as specified in claim 1 having 75 the arrangement wherein the vacuum in the antechamber is increased when the carburetor is in the idle running position through a. pipe which opens the antechamber to the dep-ression between the throttie and the engine through a restriction or damper.

5. A carburetor as specied in claim 1 in which the hollow stem of the mushroom valve is provided With an abutment for the spring, said abutment also forming a damping device.

HANS-EBERHARD JACOBY.

HANS NssLI.

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