US2797905A - Carburetor - Google Patents

Description

July 2, 1957 OLSON CARBURETOR Filed Sept. 21,

INVENTOR. 5mm 0150 H/s ATTOHNIY CARBURETOR Elmer Olson, Rochester, N. Y., assignor to General Motors Corporation, Detroit, Mich, a corporation of Delaware Application September 21, 1954, Serial No. 457,344

4 Qlaims. (Cl. 261-41) This invention relates to a carburetor for supplying a combustible mixture of fuel and air to an internal combustion engine, particularly an engine for automotive use and is concerned primarily with the specific construction of the fuel supply means in the carburetor.

It is generally the practice in carburetors at the present time to introduce fuel, when the engine is idling, through an inlet or inlets positioned adjacent the throttle and fuel is supplied thereto through a conduit which is, at least in part, separate from the main fuel supply system. The main fuel inlet, to which fuel is supplied by another conduit, is not operative during idling, but when the engine is operating under load and the throttle is moved toward open position at some point in the throttle movement, the main fuel inlet becomes effective. Also, at some point in the throttle movement the idling fuel inlet becomes ineffective, the amount of fuel supplied by the idling fuel inlet decreasing as the throttle is moved toward open position, while the fuel supplied by the main inlet increases as the throttle opens.

During a part of the opening movement of the throttle, both main and idle fuel inlets are effective, but ultimately, the throttle reaches a position where the supply of fuel from the idling system ceases entirely and thereafter, as the throttle moves from this position until it is wide open, all of the fuel supplied to the carburetor comes from the main fuel inlet.

It has been found that during some engine operation with the throttle partly open before the idling system ceases to function and when the transfer from the idling fuel system to the main supply system is effected, the flow of fuel, particularly from the main fuel inlet, is somewhat irregular and it is the primary object of the present invention to overcome this difficulty and provide means for improving the function of the main fuel supply system under the specific conditions referred to.

Further objects and advantages of the present invention will be aparent 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:

Figure l is vertical section through the entire carburetor taken on the line 1-1 of Figure 2;

Figure 2 is a plan view of the fuel chamber casting as seen from the line 22 of Figure 1;

Figure 3 is a fragmentary section on the line 3-3 of Figure 2; and

Figure 4 is a detail section on line 4-4 of Figure 3.

The carburetor shown in the drawings is a dual carburetor intended primarily for use on an eight-cylinder engine and in many respects its construction is the same as carburetors which have been previously designed. Therefore, much of the construction of the carburetor is not described in any degree of detail.

As illustrated, the carburetor includes three separate castings 2, 4 and 6 positioned above each other and separated by suitable gaskets. An air passage 8 is formed 2,797,905 Fatented July 2, 1957 ice in casting 2 and this passage supplies air to two mixing chambers 10 and 12 formed in the casting 4 and separated by a partition wall 14 which is a part of casting 4. In these chambers a combustible mixture is formed which is conveyed to the intake manifold through two outlet passages 16 and 18, which are formed in the casting 6 and connect with passages formed in the manifold. The casting 6 is supported directly on the manifold in the conventional manner.

The quantity of mixture which passes through passages 16 and 18 is controlled by throttles 20 and 22, respectively, both of which are secured to a single manually operated throttle shaft 24 suitably journalled for rotation in the wall of casting 6 and operated by an arm 26 secured in any desirable way to the right end of shaft 24 as seen in Figure l. The arm 26 is adapted to be connected by a suitable operating connection (not shown) to the conventional foot operated accelerator pedal. The operating mechanism for the throttle shaft is neither shown nor described in detail herein as the construction of this mechanism is a matter entirely immaterial so far as the present invention is concerned.

Air enters the passage 8 through an opening 28 and the admission of air to such passage is controlled by a choke valve 30 which is secured to a shaft 32 suitably journalled for rotation in the wall of casting 2. The particular arrangement of the opening 28 and control valve 39 therefor is not shown in detail as such construction is not material with respect to the invention claimed.

The air which flows through the opening 28 and passage 8 enters a chamber 33 in the upper part of the casting 4 which is not divided, as is the lower part of such casting. Positioned in the chamber 33 are two primary venturi tubes '34 and 36 which discharge approximately at the throat of larger venturi tubes 38 and 40, respectively, formed by the wall of casting 4 and in which are the mixing chambers 10 and 12. The main fuel inlets, which will be later described, supply fuel to these primary venturi tubes, in which a relatively rich mixture of fuel and air is formed and such mixture is discharged into the mixing chambers 10 and 12 where it is mixed with additional air from the chamber 33, forming a mixture of combustible proportions which is supplied to the engine through the outlet passages 16 and 18.

The position of the choke valve is controlleld automatically in response to variations in engine suction and temperature by mechanism of the same general construction as that shown in copending application, Serial No. 264,136 filed December 29, 1951, of Olson et al. In View of this disclosure and because the choke control mechanism forms no part of the present invention, the structure of such mechanism is not shown in detail and is only briefly described.

The shaft 32 has secured thereto at the left end, as seen in Fig. 1, an arm 42 having a laterally extending portion 44 which is engaged by the free end of a coiled bimetallic thermostat 46, the other end of which is connected to a stud 48 which is fixed in position so that upon changes,

reached, there is substantially closing pressure on the choke valve.

The lower end of arm 42 is pivotally connected to a rod extending from a piston 59 slidable in a cylinder 52 to which the manifold suction or partial vacuum is communicated. Upon increase in manifold vacuum, the piston 50 is moved in a direction to open the valve 30 against the 1 pressure exerted by the thermostat. l

assapos ,Ihe,. end ofishaft .32 extends into a. supplemental housing 54 which is secured in any suitable way to the casting 2, and the choke operating mechanism is all positioned within this housing. .A cover plate '56 which may be either metal qrplastic and islgenerally the latter, as indicated in Fig. l, is secured to the'housing 54 in any suitableway; as;by screws 58. This plate is adjustable on the housing ,to-vary theinitialpressure exerted by the thermostatiQr any, given temperature. Thisis effected byrotationof therstud tfi which is fixed in the cover plate and towhichone end, of the thermostat is connected. Heated air is drawn through the passage 61) in the cover plate ,to heatther'thermostatiin the conventionalway.

mechanism so far described forms no part of the inyention claimjedin this application, which relates entirely tormeans forintroducing fuel into the venturi tubes 341and3fi and thisrnechanism will now be described.

In this deyice, the float chamber instead of being more or'less concentric with reference to the intake passages, as is trueof most present day carburetors. is positioned entirely atone sideof the intake passages, as shown in Fig. 311. jfiqat. ham i designated y e mera 79 and isa part of ,thecasting A, The valve which controls admission of fuel to the chamber 79 is of standard conventional constructionand is not shown, but the action of such valyeis controlled by a float 72 in the usual way to maintain a constant fuel level in the chamber 78. The float is pivqtedon a pin 76 mounted in brackets 77 dependingfromi-the casting 2 and the valve which controls fuel flow into chamber 7%) rests on plate 78 which is secured to the float and is pivoted on pin 76, so that upward movement of the float closes the valve when fuel chamber reaches the proper level. The means for conveying fuel from chamber 70 to the two venturi tubes is the sainein construction and Fig. 3 shows the means for supplying fuel to tube 36.

means includes a bore 78 in the wall of casting 4 which connects the" chamber '78 with a vertical well 80 also ronaed'n thecastin g The well, at its upper end, connects 'with'a chamber 82 formed in a small casting 8 4 which is secured screws'87 to a horizontal surface of the c'asangaaad. the venturi tubes 34 and 36 are formed ir'fthis Easting Also formed in the casting 84 is a passage '85; one end of which connects with the venturi "Edafid'the other eiidfop en s into chamber 33 to repeiye aif therefrom. A suitable gasket 88 is positioned between 't'hefcas'ting84' and the surface of casting 4 to which it is seciired. 'i i The chamber' 82 and the passage 86 are connected by a. bore in which is tightly fitted a fuel supply tube 99 which csauue srui from the well 80 to the passage 86. This tube isfofithef shape shownin Fig. 3, is closed at its lower end and the end ofzthe tube is bevelled, as indicated at QZQfoIa' purpose which will be set forth later. The tube new. 1 admittedt the topof the well through a vent passage: 96 indicated diagrammatically by dotted lines in Fig. 3. As the throttle is' progressively opened, the suction in the venturi tube 36 will increase, the level of fuel in the well will fall and the openings 94 will be progressively uncovered, permitting air to flow through such openings into tube to form an emulsion of fuel and air therein.

Flow of fuel from the chamber 70 into the well 80 is controlled by a fuel metering plug 98 screwed into the wall of casting 4 and having a calibrated fuel passage 100 therein.

Positionedwithin the fuel tube 99 is a partition plate 101 which terminates at the upper end of the tube, as indicated in Fig. 3 and as shown, extends toward the bottom of the tube for approximately two-thirds of the length. of .the tube, but the length of the plate may. be somewhat varied. This plate divides the upper portion of .thertube into two' fuel delivery passages of substantially equal cross-sectional area and performs a function more fully described later. a

dedwith a series of openings 94 and air is F As already. indicated,. the construction. of the fuel well and associated pants cooperating with each of the venturi tubes is identical, there being two wells 80, two fuel tubes 90 and associated parts of exactly the same construction. In addition to the bore 7 8 for supplying fuel to each well 80, each well has an auxiliary fuel passage 102 leading to a bore 104 formed in the casting 4 below chamber 70 at a point about midway between the two ends of chamber 7Q, as seen in Fig. 2. Flow of fuel into this bore from the chamber 70 is controlled by a single valve which is operable in response to variations in manifold vacuum. A valve housing 106 is positioned in the bore 104 and has a passage 108 connecting the interior of the housing with the chamber 70. This passage is controlled by a valve 110 positioned in the housing and normally urged toward closing position by a spring 112, also positioned in the housing between a shoulder on the valve and a closure member 1 14 at the bottomof the :housing to permit fuel toflow from the housinginto passage 70 when the valve t lt) ;is open.

The .valve is operated by .a rod 118 which is lifted by manifold suction during most operation with the throttle only partly. open :so. that spring 112 will hold the valve 110v closed. However, as. the throttles move toward open position, the manifold suction falls and the rod moves-downwardly, opening the valve 110 and permitting fuel to flow from the chamber .70. into housing 106 and through passage 102,'to augment the fuel supplied to the well 80 by the main metering passage 100. This auxiliary fuel. supply means and control mechanism is of substan tially ,the. same construction as shown in the copending application previously referred to.

It will be apparent upon consideration of Fig. 3 that the partition plate 101 divides the upper end of the fuel delivery tube 90- into two separate fuel outlets 120 and 122 which areat different levels, the outlet 122 being above the outlet 1120. Fuel is caused to flow from these outlets by the pressure differential between the atmospheric pressure which is maintained above the fuel in chamber 70 and the subatmospheric pressure which is maintainedlin the passage 86, and it is obvious that a slightly greater pressure differential is required to cause flow of fuel from the, outlet 120 than is necessary to effect flow from the outlet 122.

The. idling fuel supply system is not shown herein because its construction is not material with reference toend qteashu e 0 incr ase an b mes sufiicientto cease a flow of-fuel from both outlets, but flow from ut et .1 2 ill art before f fr m Outlet 20 w l be initiated. Therefore, as the flow of fuel from the idling fuel system decreases during opening of the throttles, flow fromv each main supply tube 90 will begin and will increase as the throttles open, but it will increase more gradually than if the partition plate 101- was not provided, because the outlets 122 and 120 are successively rendered efiective. Therefore, during opening of the throttles, in this particular part of the operating range, there is a gradual and smooth increase in fuel flow from each main supply tube, whichwould not be effected without the partition plate. This will result in smoother and more satisfactory engine operation under the conditions dect d By beyelling the delivery end of tube 90 as indicated in the drawings, the. aspiratingeifect of the air which fiowsthrough passage..86 at relatively high velocity is increased. and .the elevation ofoutlet 120 with reference tooutlet 122- isinere asedv by comparison with what itwould be if the entire end of the tube was flush with the wall of passage 86.

Attention is also called to the fact that the partition 101 would aid in eliminating any difficulties which would be encountered if any large vapor bubbles were formed in the lower part of tube 90. If such bubbles were formed, and the partition plate not present, these large bubbles would pass out of tube 90 into passage 86, resulting in appreciable irregularity of fuel flow. If the partition plate is provided, any large bubbles which might be formed are broken up by the plate into much smaller bubbles which, although carried on into the passage 86, will create much less irregularity in fuel flow than would be effected by the larger bubbles which might be introduced into passage 86 without the plate 101. Also, the plurality of smaller bubbles would probably not reach passage 86 at exactly the same time, which would also decrease irregularity of flow.

At the right of Fig. 1 is shown a link 130 the upper end of which is pivotally connected to an arm secured to the choke valve shaft 32. At its lower end, this link is connected to an idle control mechanism which is not shown but which, when the temperature is low, causes the throttle to be a little further open at its idling position so that the idle speed is increased at low temperatures. This mechanism forms no part of the invention claimed and need not be fully illustrated or described herein.

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. In a carburetor having a mixture passage adapted to supply a combustible mixture of fuel and air to an internal combustion engine, a throttle valve for controlling the quantity of mixture supplied to the engine and an air inlet for admitting air to said mixture passage; means for supplying fuel to said mixture passage comprising a fuel supply chamber, a substantially vertical fuel well in communication with and receiving fuel from said fuel chamber, a fuel delivery tube extending downwardly into said well and supplying fuel to said mixture passage, said fuel delivery tube being positioned at an angle to the vertical adjacent its discharge end, a partition plate in said fuel delivery tube dividing said tube into two seperate fuel delivery passages positioned at different levels, a passage with which the discharge end of said fuel delivery tube communicates, the axis of which is substantially normal to the axis of said tube and having at one end an air inlet, said fuel delivery tube having its discharge end terminating at an acute angle to the axis of the tube adjacent such discharge end, whereby the tube at one side projects appreciably into said last named passage and at the opposite side terminates substantially flush with the wall of said passage.

2. In a carburetor having a mixture passage adapted to supply a combustible mixture of fuel and air to an internal combustion engine, a throttle valve for controlling the quantity of mixture supplied to the engine and an air inlet for admitting air to said mixture passage, means for supplying fuel to said mixture passage comprising a fuel supply chamber, a fuel well in communication therewith and receiving fuel therefrom, a fuel supply passage connecting with the mixture passage so that air is drawn through said supply passage at a. speed proportional to the flow of air through the mixture passage, a fuel delivery tube positioned in said well and delivering fuel to said fuel supply passage, and a partition plate in the outlet end of said tube and extending longitudinally with respect thereto, said tube having a beveled edge projecting within said supply passage, said partition plate terminating at one end in the beveled end of said tube so as to divide said tube into two separate fuel delivery passages, one of which is upstream of the other relative to the air flowing through the fuel supply passage, said beveled edge increasing in length in the upstream direction so that air flowing through the fuel supply passage will cause fuel to flow first through the upstream fuel delivery passage.

3. In a carburetor as set forth in claim 2 in which said tube is closed at its lower end and has fuel inlet ports in the side wall thereof, and further in which said partition plate extends downwardly in said tube through the major part of its length but terminates an appreciable distance from the closed lower end of the tube.

4. In a carburetor having a mixture passage adapted to supply a combustible mixture of fuel and air to an internal combustion engine, a throttle valve for controlling the quantity of mixture supplied to the engine and an air inlet for admitting air to said mixture passage, means for supplying fuel to said mixture passage comprising a fuel supply chamber, a fuel well in communication therewith and receiving fuel therefrom, the axis of said fuel well being substantially parallel to the axis of the mixture passage, a fuel supply passage connecting at an oblique angle with the mixture passage so that air is drawn through said supply passage at a speed proportional to the flow of air through the mixture passage, a fuel delivery tube positioned in said well and delivering fuel to said fuel supply and partition plate in the outlet end of said tube and extending longitudinally with respect thereto, said tube having a beveled edge projecting within said supply passage, said partition plate terminating at one end in the beveled end of said tube so as to divide said tube into two separate fuel delivery passages, one of which is upstream of the other relative to the air flowing through the fuel supply passage, said beveled edge increasing in length in the upstream direction so that air flowing through the fuel supply passage will cause fuel to flow first through the upstream fuel delivery passage.

References Cited in the file of this patent UNITED STATES PATENTS 1,935,350 Chandler Nov. 14, 1933 2,114,970 Rullison et al Apr. 19, 1938 2,215,683 Wirth Sept. 24, 1940 2,635,861 Olson Apr. 21, 1953

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