US2694560A

US2694560A - Carburetor

Info

Publication number: US2694560A
Application number: US109347A
Authority: US
Inventors: Olson Elmer
Original assignee: Motors Liquidation Co
Current assignee: Motors Liquidation Co
Priority date: 1949-08-09
Filing date: 1949-08-09
Publication date: 1954-11-16
Anticipated expiration: 1971-11-16

Description

Nov. 16, 1954 E. OLSON 2,694,560

CARBURETOR Filed Aug. 9, 1949 I 3 Sheets-Sheet l Nov. 16, 1954 E. OLSON 2,694,560

CARBURETOR Filed Alig. 9, 1949 3 Sheets-Sheet 5 INVENTOR. Elmer Olson Affomeys United States Patent CARBURETOR Elmer Olson, Rochester, N. Y., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application August 9, 1949, Serial No. 109,347

Claims. (Cl. 261-41) This invention relates to carburetors for internal combustion engines, particularly for automotive use and it is an object of the invention to provide a carburetor of improved design which is of simple and durable construction, inexpensive to manufacture and will bring about gfli cient operation of the engine under all operating con- One specific object of the invention is to minimize the heating of the fuel in the float chamber, and also to prevent the vaporization of fuel in the passages leading from the float chamber to the fuel inlets which introduce fuel into the mixture, or intake passage, particularly when the engine is stopped after operation in warm weather.

A further specific object of the invention is to provide fuel passages for supplying fuel to the mixture passage which are so arranged that there is no appreciable lag in fuel flow nor appreciable momentary reduction in engine speed at the time of transfer from operation of the engine on the idle fuel system to operation on the main fuel inlet.

An additional specific object of the invention is to provide means for permitting the escape of fuel vapor from the bottom of the accelerating pump cylinder so as to prevent any vapor which might collect below the pump piston from forcing fuel out of the pump cylinder into the intake passage.

A still further object of the invention is to provide means for preventing the formation and collection of vapor bubbles in the fuel supply passage during the idling of the engine so that the idling fuel supply is even and continuous and the engine operation during the period of transition from idling to operation under load is smooth and not irregular, as would be the case if such vapor bubbles formed and collected in the fuel passage to any appreciable extent during the idling operation.

Another purpose of the invention is to provide improved mechanism for operating the choke and throttle valves which includes means for yieldingly holding an unbalanced choke valve in closed position, means for positively moving the choke toward closed position in the event that it becomes stuck in fully open position and for increasing the opening of the throttle as the choke is closed so that I the idling speed of the engine is increased as the choke is moved toward closed position.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred embodiment of the present invention is clearly shown.

In the drawings:

Fig. 1 is a sectional view of the carburetor on line 11 of Fig. 2.

Fig. 2 is a sectional view on the line 2-2 of Fig. 1.

Fig. 3 is a sectional view on the line 33 of Fig. 1 and is drawn to a larger scale.

Fig. 4 is a sectional view on the line 44 of Fig. 1.

Fig. 5 is a fragmentary sectional view on the line 5+5 of Fig. 2.

Fig. 6 is an enlargement of a portion of Fig. 5.

Fig. 7 is a sectional view on the line 7-7 of Fig. 6.

Fig. 8 is a sectional view on the line 8-8 of Fig. 4.

Fig. 9 is a top plan view of the base casting 30.

Fig. 10 is a fragmentary sectional view on the line Iii-10 of Fig. 9.

Fig. 11 is a sectional view on the line 11-11 of Fig. 9.

Fig. 12 is an enlargement of a view on line 1212 of Fig. 11.

Fig. 13 is an enlargement of that portion of Fig. 11 within the circle 13.

Fig. 14 shows a central portion of Fig. l drawn to a larger scale.

Referring to Fig. 1, the carburetor has four castings, 30, 31, 32 and 33. Casting is a support member attachable to the engine intake and supports the float bowl 31 to which is secured the casting 32, which is a cover for the bowl, while casting 33 is secured to and depends from the cover 32 and the main fuel supply passage is formed therein. The base 30 has holes 34 to receive screws for attaching the carburetor to the manifold with a gasket between. Screws which pass through holes 36 (Fig. 9) in base 30 and into threaded holes 36a in bowl 31 (Fig. 8) secure the bowl and base together with a gasket 37 (Fig. 1) between them. As shown in Figs. 1' and 8, the bowl 31 is provided with

deep grooves

38 and 39 and with

shallower grooves

40 and 41 which reduce the area of contact of bowl 31 with the gasket 37. The grooves tend to prevent displacement of the gasket because of shrinkage and the

grooves

40 and 41 have other functions to be described later.

Cover 32 is secured to the bowl 31 by screws received in tapped holes 43. A gasket 44 (Fig. l) is located between cover 32 and bowl 31. The area of the surfaces of the bowl and cover in contact with the gasket 44 being relatively narrow, the transfer of heat between them is relatively low. The member 33 is secured to cover 32 by a screw 45 (Fig. 5) with a small gasket 46 between them and member 33 has a lug 47 which enters a notch 48 in cover 32 when the parts are assembled to prevent relative movement. Since the area contacted between cover 32 and member 33 is restricted, the transfer of heat to the member 33 is relatively low. Thus, the transfer of heat from the engine to the bowl and other parts of the carburetor is kept as low as possible. A substantial amount of heat is dissipated from the bowl 31 to the surrounding atmosphere under the hood of the automobile from the relatively large outer wall of the bowl and the interior wall thereof is cooled by vaporization of the fuel as it is introduced into the intake passage.

The main fuel inlet for supplying fuel to the intake passage discharges fuel within a primary venturi tube 50 supported by ribs 52 at the center of the intake passage and the primary venturi extends into a secondary venturi 51, which is the wall of the intake passage and is also the interior wall of the float bowl.

Referring to Fig. 1, the fuel is supplied to the float bowl through coupling to the passage 61 and flows from this passage into the bowl through a bushing 62 providing a valve seat 63 for a float valve 64 having the conventional flat sides 65 and operable by a finger 66 integral with a lever 67 pivoted on rod 68, supported by two lugs 69, extending downwardly from the cover 32. As shown in Fig. 2, lever 67 is attached to floats 70. The mechanism described maintains a substantially constant level of fuel in the bowl, and a finger 71 integral with lever 67 engages the bushing 62, if for any reason the float chamber is emptied so as to prevent the floats striking the bottom of the float chamber and also to prevent the floats moving downwardly enough to permit the valve 64 to fall out of the bushing into the float chamber.

As shown in Figs. 1 and 5, the main fuel supply passage 75 through which fuel flows from the bowl to the intake passage, is formed in the member 33. Admission of fuel to the passage 75 is controlled by the main metering plug 76.

Under certain operating conditions, fuel is also admitted to the passage 75 through two notches 77 formed in a horizontal projecting portion of the member 33, as shown in Fig. 7. These notches communicate with a passage 77a (Fig. 6), which admits fuel to a space connected by a passage 79 with the passage 75, the flow through passage 79 being controlled by a metering plug 78. Flow through passage 77a is controlled by a ball check valve 83 which, under operating conditions where the intake suction is low, as when operating at wide open throttle and relatively low speed, for example, is positioned to open the passage 77a, so that the amount of fuel flowing into passage 75 is somewhat increased and the mixture enriched, as is desirable under such conditions. Under those operating conditions wherethe intake suction is high, as for example when operating with partially open throttle and light load, a leaner mixture is desirable and the additional supply of fuel through the passage 79 is not necessary. Under such conditions, the check valve 83 is moved to position to close the passage 79.

. When the suction is low, a spring 81 moves rod 82 downwardly and holds the ball 83 in the position shown in Fig. 8, with the passage 77a open against the action of spring 84 which is positioned below the ball in a bushing 85. Rod 82 is connected to the hollow piston 87 operable by spring 81 and slidable in-a cylinder 86 formed in a part of the cover 32 and to which the manifold suction is communicated through a passage 88, which connects with passage 89 in the bowl casting 31 (Fig. 2), communicating with groove 40 also in the bowl casting, as shown in Fig. 8. The groove 40 connects with the passage 90 in the casting 30, as shown in Fig. and when the carburetor is installed, the manifold suction is communicated to passage 90 through the passage 91.

If the manifold vacuum is relatively high, as on part throttle operation, it is effective to lift the piston and rod 82 against the force of spring 81 so that check valve 8; will be moved by spring 84 to close the passage As shown in Figs. 1 and 14, extending across the air intake 95 and integral therewith is a conduit 96 in which a fuel passage is provided having

parts

97, 98 and 99 of different diameters, the part 97 connecting with the main fuel passage 75. A tube 100 is positioned in the part 98 of the conduit 96 and this tube has a restriction 101 at its right end. A relatively large air bleed 102, formed in a bushing 103 and

smaller bleeds

104 and 105 admit air to the fuel conduit 96, as shown best in Fig. 14. The part 99 of the fuel conduit connects with a passage 106, extending downwardly in the casting 31, which at its lower end connects with the groove 41, as shown in Fig. 8, and this groove connects with the bore 107 in the base 30, as shown in Fig. 11. The bore 107 is connected by passage 108 with the intake passage posterior to the throttle 110, which is supported on a rotatable shaft 111. Flow through passage 108 is controlled by the manually adjustable valve 112, held in any set position by the friction spring 113. Connecting the intake passage with the bore 107 slightly anterior to the throttle, when in closed position, are three

small orifices

115, 116 and 117, for a purpose to be later set forth.

During idling of the engine when the throttle is substantially or nearly closed, the high suction which is maintained posterior thereto is communicated to the fuel in passage 75 through the above described arrangement of passages. This will cause fuel to flow from passage 75 through passage 97, tube 100,

passages

99, 106, 107 and 108 into the intake. A solid stream of fuel flows through the

passages

75 and 97 during idling, but this fuel is mixed with air which enters the

bleed holes

102, 104, 105 and 120 to form a rich mixture for idling and this mixture is carried from that point on through the previously mentioned passages into the intake, the quantity of idling mixture being regulated by adjustment of the valve 112. Some additional air will flow into the mixture as it is drawn through bore 107 through the

holes

115, 116 and 117 if the throttle is closed to such an extent thatsuch holes are anterior to the throttle.

During idling there is practically no flow of air through the primary venturi tube and no introduction of fuel into such tube. However, as the throttle is moved toward its open position from the idling position, shown in Fig. 11, the flow of air through .the primary venturi will be increased and the suction will ultimately become great enough to effect a flow of fuel from the main fuel inlet 122 which connects with the part 98 of the fuel conduit immediately adjacent the end of the passage 97 directly below the air bleeds 102, 104 and 105, and has a bushing 121 therein, provided with a restriction 120 which aids in breaking up the fuel which is discharged into the primary venturi.

"The flow of fuel from the main inlet 122 begins before the flow of idling mixture ceases, but as the 3 throttle is progressively opened, the suction in the primary venturi will become so great by comparison with the suction at the end of passage 108 that flow from passage 108 will cease and instead, there will be a flow from the intake into passage 108 and a reverse flow from that point back through the idling mixture passages to the main fuel inlet.

In carburetors of the prior art there has been some difficulty encountered at the time of transfer of operation from the idling system to the main fuel supply due to a momentary leaning of the mixture at this time. This was due to the fact that while the idling system functioned, the fuel for the main fuel inlet was maintained at an appreciable distance from such inlet, so

that before the main fuel inlet began to function, the fuel had to move through this distance. Due to its inertia, this movement of the fuel to the main inlet required an appreciable interval of time so that there was a slight lag in the fiow of fuel from the main inlet with respect to the flow of air through the intake passage. In the device disclosed herein, the above described difficulty is substantially eliminated because a solid column of fuel is maintained in the passages and '97 to a point immediately adjacent the main fuel inlet. Therefore, when the main inlet begins to function, the fuel does not have to be moved through any appreciable distance. It is already maintained at a point immediately adjacent the fuel inlet 122 before the latter starts to function.

The bleed holes 102, 104 and not only admit air to form the idling mixture, but also prevent the formation of bubbles, of sufiicient size to cause any appreciable irregularity in flow through the idling passage which otherwise might tend to occur under some operating conditions, if the several orifices were not provided to supply air to the space posterior to the end of passage 97. The admission of air at relatively high velocity through the

several orifices

102, 104, 105 and aids in effecting a thorough atomization of the fuel which is discharged from the passage 97 to form a homogeneous idling mixture.

As the throttle begins its opening movement from the position shown in Fig. 11, the

holes

115, 116 and 117 are successively brought on the high suction side of the throttle. This action will progressively increase the suction effective on the idling fuel supply passages and slightly increase the idling mixture.

As already set forth, the device disclosed is formed of three separate castings separated by gaskets and has other means to minimize the heating effect of the engine on the fuel in chamber 31 and the various fuel passages. In addition, the main fuel supply passage is so arranged that there will be substantially no vaporization of fuel in the passage after the engine has stopped, even at the highest temperatures encountered in summer operation.

In conventional down-draft carburetors of the prior art where the fuel passages leading to the main and idling fuel inlets are formed in the wall of the float chamber, vaporization of fuel in these passages, or what is known as percolation has caused very considerable trouble with the highly volatile fuels now in use. The formation of fuel vapor in the fuel will create sufficient pressure to cause discharge of fuel in the fuel passages between the vapor and the fuel inlets which supply fuel to the intake passage. This process may be repeated many times if the temperature is high and may result in emptymg the float chamber completely. By providing the fuel passage 75 which extends downwardly into the fuel chamber from above the fuel and the passage 97, that supplies fuel to the main and idling fuel inlets, lying entirely above the float chamber 31, the formation of vapor in the fuel passages is substantially prevented. If the fuel in chamber 31 gets hot enough to form fuel vapor bubbles, they will not enter the passage 75, and since passage 75 extends upwardly to the passage 97, there will be substantially no vaporization of fuel in the passage 75, itself. The only vaporization of fuel in the bowl 31 will be adacent the bottom wall thereof and passage 75 is sufficiently above the bottom of the bowl to be out of the area where the heat may be enough to cause some vaporizatlon.

Also

fuel passages

75 and 97 are formed in the upper casting 32 which forms the air intake and cover for the float chamber. This casting is separated from the float chamber by a gasket so that there is no metallic conductrvity between the manifolds and the passages 75 and 97'. This, of course, reduces the heating of such passages, but since the

passages

75 and 97 are entirely above or extend upwardly from the fuel level, if under any circumstances such passages get hot enough to form vapor, such vapor forms above the level of fuel and merely passes into the intake without forcing any liquid fuel in said intake, so that there is no percolation.

At the left of Fig. 1 there is shown mechanism for operating the shaft 130 which supports a choke valve 131 and also means through the medium of which the position of the choke valve controls the idling position of the throttle under certain circumstances.

Also there is disclosed a cylinder 132 which with its associated mechanism constitutes an accelerator pump for supplying additional fuel when the throttle is opened to increase the speed. Neither the choke operating mechanism nor the accelerator pump constitute any part of the invention which is claimed in this application and for this reason such devices are not described specifically herein.

It may be said, however, that the cylinder 132 of the accelerator pump is in communication with the space above the fuel in the float chamber 31 and in order to provide a vent for this space so as to maintain therein a pressure which approaches that of the atmosphere, a tube 134 connects the top of cylinder 132 with the intake passage adjacent the air inlet end thereof anterior to the choke valve. Because of the slight restriction to the admission of air imposed by the air cleaner, this tube 134 is effective to maintain in the float chamber a pressure just barely less than that of the atmosphere. This vent forms no part of the present invention and is of the type now conventionally used in the art.

While the embodiment of the present invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted.

What is claimed is as follows:

1. A carburetor for an internal combustion engine having, in combination, a constant level fuel supply chamber, an intake passage provided with a throttle valve for controlling the how of combustible mixture therethrough, main and idling fuel inlets for supplying fuel to the mixture passage, an inverted U-shaped passage for supplying fuel to said inlets, said passage having a leg extending downwardly into the fuel chamber and through which only fuel flows, said passage having means below the level of fuel in said chamber for admitting fuel thereto so that liquid fuel stands in said leg when the engine is inoperative and flows therethrough when the engine is running, the other leg of such passage extending downwardly to supply idling fuel to the idling fuel inlet, a horizontal connecting passage located above the level of fuel in the fuel chamber for connecting the upper ends of the legs of the U-shaped passage and connecting with the main fuel inlet to supply fuel thereto and a plurality of orifices admitting air to said connecting passage adjacent the point of connection of the main fuel inlet therewith so as to atomize the fuel flowing therethrough and to effect a substantially even flow of fuel for idling when the idling fuel system is in operation, said orifices being of different size and the larger of said orifices being substantially coaxial with the main fuel inlet.

2. A carburetor for an internal combustion engine having, in combination, a constant level fuel supply chamber, an intake passage provided with a throttle valve for controlling the flow of combustible mixture therethrough, main and idling fuel inlets for supplying fuel to the mixture passage, an inverted U-shaped passage for supplying fuel to said inlets, said passage having one leg extending downwardly into the fuel in said fuel chamber so as to be entirely surrounded with fuel and having no metallic contact with said fuel chamber, through which only fuel flows, another leg extending downwardly to supply idling fuel to the idling fuel inlet and a horizontal passage located above the fuel level in the fuel chamber for connecting the upper ends of the downwardly extending legs of said fuel passage and communicating with the main fuel inlet, a plurality of fuel inlets in said first named U leg of the passage positioned below the level of fuel in the fuel chamber for admitting fuel thereto, said fuel inlets being open when the engine is inoperative and during engine operation when the engine suction is low and means also having no metallic contact with the fuel 6 chamber for automatically closing one of said fuel inlets when the engine suction is relatively high.

3. A carburetor for an internal combustion engine having, in combination, a constant level fuel supply chamber, an intake passage provided with a throttle valve for controlling the flow of combustible mixture therethrough, main and idling fuel inlets for supplying fuel to the mixture passage, an inverted U-shaped passage for supplying fuel to said inlets, said passage having one leg extending downwardly into the fuel in said fuel chamber so as to be entirely surrounded with fuel and having no metallic contact with said fuel chamber, through which only fuel flows, another leg extending downwardly to supply idling fuel to the idling fuel inlet and a horizontal passage located above the fuel level in the fuel chamber for connecting the upper ends of the downwardly extending legs of said fuel passage and communicating with the main fuel inlet, a plurality of fuel inlets in said first named leg of the passage positioned below the level of fuel in the fuel chamber for admitting fuel thereto, means for maintaining both of said inlets open when the engine is inoperative and during engine operation when the engine suction is low and suction operated means also having no metallic contact with the fuel chamber for rendering said last named means ineffective and causing the closing of lone}:1 of said fuel inlets when the engine suction is relatively 4. A carburetor for an internal combustion engine having, in combination, a constant level fuel supply chamber, an intake passage provided with a throttle valve for controlling the flow of combustible mixture therethrough, main and idling fuel inlets for supplying fuel to the mixture passage, an inverted U-shaped passage for supplying fuel to said inlets, said passage having a leg extending downwardly into the fuel chamber and through which only fuel flows, said passage having means below the level of fuel in said chamber for admitting fuel thereto so that liquid fuel stands in said leg when the engine is inoperative and flows therethrough when the engine is running, the other leg of such passage extending downwardly to supply idling fuel to the idling fuel inlet, a horizontal connecting passage located above the level of fuel in the fuel chamber for connecting the upper ends of the legs of the U-shaped passage and connecting with the main fuel inlet to supply fuel thereto, a restriction in the horizontal passage posterior to the main fuel inlet, said horizontal passage posterior to the restriction being larger than the restriction, and a plurality of orifices admitting air to said horizontal passage adjacent said restriction to atomize the fuel in said passage and including a relatively large orifice anterior to said restriction and substantially coaxialwith the main fuel inlet.

5. A carburetor for an internal combustion engine having, in combination, a constant level fuel supply chamber, an intake passage provided with a throttle valve for controlling the How of combustible mixture therethrough, main and idling fuel inlets for supplying fuel to the mixture passage, an inverted U-shaped passage for supplying fuel to said inlets, said passage having a leg extending downwardly into the fuel chamber and through which only fuel flows, said passage having means below the level of fuel in said chamber for admitting fuel thereto so that liquid fuel stands in said leg when the engine is inoperative and flows therethrough when the engine is running, the other leg of such passage extending downwardly to supply idling fuel to the idling fuel inlet, a horizontal connecting passage located above the level of fuel in the fuel chamber for connecting the upper ends of the legs of the U-shaped passage and connecting with the main fuel inlet to supply fuel thereto, a restriction in the horizontal passage posterior to the main fuel inlet, said horizontal passage posterior to the restriction being larger than the restriction, and a plurality of orifices admitting air to said horizontal passage adjacent said restriction to atomize the fuel in said passage and including a relatively large orifice anterior to said restriction and substantially coaxial with the main fuel inlet and two smaller orifices on opposite sides of the larger orifice.

(References on following page) 7 References Cited in the file of this patent N mber UNITED STATES PATENTS Number Name Date 2,307,486 1,909,389 Ball et a1 May 16, 1933 5 2,327,300 2,017,890 Bracke Oct. 22, 1935 2,393,125 2,035,636 Chandler Mar. 31, 1936 2,397,392 2,065,167 Wirth et a]. Dec. 22, 1936 2,407,535 Carlson et al Sept. 10, 1946 2,087,293 Olson July 20, 1937 2,415,491 Hieger Feb. 11, 1947 2,162,056 Bracke June 13, 1939 10 2,426,272 Hennemann Aug. 26, 1947 2,215,683 Wirth Sept. 24, 1940