US3326539A - Carburetor - Google Patents

Description

J. R. PHIPPS June 20, 1967 CARBURETOR 4 Sheets-Sheet l Original Filed Jan. lO, 1964 u w M June 20, 1967 1. R. PHIPPS 3,325,539

CARBURETOR Original Filed Jan. l0, 1964 4 Sheets-Sheet 2 I 7 l .E- l

INVENTOR J. R. PHlPPs June 20, 1967 CARBURETOR 4 Sheets-Sheert 5 Original Filed Jan. lO, 1964 J. R. PHIPPS CARBURETOR June 20, 1967 4 Sheets-Sheet 4 Original Filed Jan. l0, 1964 United States Patent O 3,326,539 CARBURETOR Jack R. Phipps, Berkley, Mich., assignor to The Bendix Corporation, a corporation of Delaware Continuation of application Ser. No. 337,092, Jan. 10, 1964. This application Aug. 24, 1966, Ser. No. 578,957 1 Claim. (Cl. 261-41) ABSTRACT F THE DISCLOSURE A carburetor having an induction passage with a flow nozzle therein having a discharge portion of substantially constant cross-sectional flow area and a buttery type throttle mounted downstream of said nozzle in a manner such that when fully opened said throttle creates a decrease in pressure in said nozzle without substantially decreasing the ilow area of said nozzle.

This is a continuation of application Serial No. 337,092, filed January 10, 1964, now abandoned.

This invention relates generally to carburetors for internal combustion engines and more particularly to imlprovements in air ow metering means for such carburetors.

A venturi is normally used in conventional carburetors to meter air flow. Theoretically a venturi Vprovides the lowest pressure loss of the head type uid meters and should therefore be best suited for use on internal combustion engines. However, in practice a number of didiculties are experienced with venturis. In some engines pulsations Vare created in the induction passage which render the venturi unsatisfactory as an air flow meter. The venturi also has a relatively narrow zone of lowest pressure into which the fuel discharges. The size and location of this zone make the location of the discharge rather critical in order to obtain satisfactorily uniform performance 'from mass produced carburetors. In carburetors used on present day engines, space requirements are such as to prevent the use of a classically designed venturi and modified shorter venturi forms are actually used. The theoretical advantage ofthe venturi is not .only degraded by the changein shape from the classical design, but it also degraded in practice by the effect of adding fuel to the air stream. This is true in liquid gasoline carburetors and is even more pronounced n LPG (liquified petroleum gas) carburetors which a much larger volume of fuel is introduced into the air stream.

I have found that a flow nozzle may be used in a carburetor in place of a venturi with many attendant advantages and few, if any, penalties. The How nozzle has a curved entrance to lead the -lluid to throat portion and from thence through a straight cylinder having essentially the same diameter as the throat. The flow nozzle differs :from the venturi in not having a long tapered diffuser on the outlet side. The use of the air nozzle in an inductionv passage subject to pressure pulsations has given surprisinglyV good results. On one engine, forexample, an increase in power output of more than and a decrease in specific fuel consumption of more than 3%, was obtained by changing from a venturi to an air ow nozzle of the same diameter in the same model carburetor. The use of the air nozzle has reduced criticality in design and manufacture thereby enhancing the uniform- -ity of characteristics among mass produced .carburetors Additionally, it has been noted that the air nozzle of thepresent invention provides better distribution, mixing and evaporation of the fuel than a comparable carburetor equipped with a venturi. Also, it has been found that by properly locating the-throttle with respect to the air nozzle, and by properly selecting the regions of the carburetor into which fuel is discharged, a richer fuel-air mixture ratio may be obtained at wide open throttle than at part throttle operation. Such power enrichment is, of course, required by many engines and is usually supplied by supplementary power enrich-ment apparatus in the carburetor.

It is an object of the present invention to provide, in a carburetor, an air flow meter which has improved fuel distribution and mixing characteristics and which is relatively unaflected by pressure pulsations in the induction passage. i

It is a further object of this invention to provide a carburetor construction which may Ibe readily reproduced to provide substantially uniform Iperformance at relatively low cost.

It is another object of the invention to provide a carburetor construction in which the fuel-air ratio may readily be increased during high power operation.

These and other objects and advantages of the invention will become readily apparent from the following detailed description taken in connection with the appended drawings, in which:

FIGURE 1 is a top View of a horizontal carburetor embodying the present invention,

FIGURE 2 is a sectional View taken along line 2 2 of FIGURE l,

FIGURE 3 is a sectional view taken along line 3 3 of FIGURE 1,

FIGURE 4 is a sectional view taken of FIGURE l,

FIGURES 5, 6 and 7 are fragmentary schematic views showing modifications of the fuel discharge tube,

FIGURE 8 is a schematic view showing a modification of the fuel discharge tube and also the location of the throttle with respect to the air nozzle to provide for power enrichment operation, Y

FIGURE 9 is a schematic view of a modication using a secondary air nozzle, and i -FIGURE 10 is a schematic view of a modifcationutilizing a secondary venturi.

Referring now to the drawings and more particularly to FIGURE 1, numeral 10 designates a carburetor having an air horn section 12, a' mixing section 14 and a throttle body section 16 and a fuel inlet 18V which is supplied withfuel from a suitable supply (not shown).

As shown in FIGURE 2, a choke valve 20 is mounted on a choke shaft 22 in air hornse'ction'12 and a throttle valve 24 is mounted on a throttle -shaft 26 in section 16. Section 16 is provided with a ange 28 which is adapted fo'r aconnection with an engine (not shown). An air nozzle 30 is mounted in induction passage l32 and'is provided with an inlet or entrance section 34 having curved converging walls 36 leading to a throat indicated' at 38. The exterior of entrance 34 is mounted in sealing engagement with the walls 40 of induction passage 32 whereby the .entire dow through induction pa-ssage 32 is received by the entrance section 34 of air nozzle 30. A discharge section 42 extends from the entrance section 34 of nozzle 30 and is provided with substantially cylindrical walls -or skirt 44 which define a substantially constant cross sectional ow path 46 through the discharge section. The skirt 44 is spaced substantially equidistantly over its length from the walls 40 ofthe induction passage 32 to thereby define an annulus 48 between the skirt and passage. Skirt 44 is provided with a port 50 into which a fuel discharge tube or jet 52 projects. At its discharge end, the fuel discharge tube 52 is provided with `an oblique orifice 54 vwhich opens or faces downstream and which overlaps port 50 such that a portion of the fuel discharged from the tube 52 enters the flow path 46 and another part enters the annulus 48.

As best seen in FIGURE 3, fuel discharge tube 52 extends into a fuel well 56 which is connected by means along line 4 4 of conduit 58 and main metering restriction 60, with ar fuel bowl or source of -fuel 62. Fuel is supplied to oat bowl 62 from the inlet 18 via filter 64, conduit 66 and oat needle 68 which is controlled by float mechanism 70. A combination accelerating pump and power enrichment mechanism is designated generally at 72 and provides for the discharge of fuel through tube 74 which is concentric with main lfuel discharge tube 52. In some installations the mechanism 72 may beV eliminated as not being required in view of the improvements resulting from the use of the present invention. Fuel for idling is dis charged from oat bowl 62 via metering restriction 60, conduit 58, idle tube 76, conduits 78 and 80 to ports 82 and 84. An idle air bleed is provided at 86.

As best seen in FIGURES 2 and 3, bafes 88 and 90 may be jointly or severally provided, as desired to readily control the direction and distribution of the fuel mixture discharge. A bafe such as 88 provided on the inside diameter of the ow path 46 creates an additional suction at its location and tends to draw an increased discharge in the direction of the bathe. The size, circumferential extent and location are determined empirically for each engine requirement. A bafie such as is shown at 90 between skirt 44 and the walls 40 of the induction passage closes off the discharge from the annulus and, therefore, causes a reduced ow at the location of the baffle. The size, location and circumferential extent of the baffle 90 is also empirically determined.

When air fiows through induction passage 32, a depression` is created in annulus 48 and fuel discharged from orifice 54 into annulus 48 is caused to move or fiow around the annulus such that fuel-air mixture is discharged from substantially the entire circumference of `annulus 48 into the induction passage 32. As the fuel is discharged into the annulus the pressure is increased slightly at that point and the zones of lower pressure in the annulus lying remote from the orifice then cause fuel to flow from the higher pressure discharge point around the annulus Whereby the fuel-air mixture is uniformly discharged from the entire circumference of the annulus.

In FIGURE 5, the fuel discharge tube 152 is provided with two discharge orifices 154 and 154' to discharge respectively into flow path 146 and Yannulus 148. In FIG- URE 5, tube 152 is substantially perpendicular to the walls 40 of the induction passage 32 whereby the two discharge orifices 154 and 154' lie substantially in the `sarne pressure zone.

In FIGURE 6, a modification is shown in which the fuel discharge tube 252 is at an angle to the walls 240 of induction passage 232 for manufacturing convenience and is provided with discharge orifices 254 and 254' which are subjected to substantially the same pressure.

In FIGURE 7, a discharge tube 352 is provided with a single discharge orifice 354 located to discharge into the outlet of the flow path 346 of air nozzle 330.

In FIGURE 8, a fuel discharge tube 452 is shown discharging entirely at a single orifice 454 into annulus 448 between skirt 444 of air nozzle 430 and walls 440 of induction passage 432. A throttle valve 424 is mounted on a shaft 426 disposed a predetermined distance from the end of skirt 444 such that when the throttle valve is in -substantially the wide open position as shown by the dotted lines, the end 424 of the throttle is disposed in the outlet lfrom the fiow path 446 which creates an effect similar to a decrease in the size of the ow path which results in higher uid velocities at the outlet which in turn results in a lower pressure in the fiow path and consequently an increase in fuel ow. This results in a power enrichment similar to that obtained by means of the mechanism shown at 72 in FIGURE 3 and will obviate the need for such mechanisms in some installations.

FIGURES 9 and l0-respectively show modifications in which a secondary air nozzle and secondary venturi are combined with a main air nozzle. Referring to FIGURE 9, a secondary air nozzle 594 is disposed in induction passage 532 to discharge into the substantially constant cross sectional flow path 546 of main flow nozzle 530. Fuel is discharged from main fuel discharge tube 552 via orifices 554 and 554. The use of the secondary air nozzle 594 provides for greater suction than the single air nozzle version shown in the prior embodiments.

The embodiment shown in FIGURE 10 is similar to that of FIGURE 9 except that a secondary venturi 696 is provided in the induction passage 632 to discharge into the ow path 646 of main air nozzle 630. Main discharge tube 652 is provided with an annular discharge port 654 at the throat of the throat of the secondary venturi.

In carburetors embodying the present invention, the carburetor designed is given a rather large leeway in determining where to have the main fuel discharged. In the prior art venturi carburetors, the designer was limited to the throat of the venturi. The present invention gives the carburetor designer a great deal of latitude in positioning the main discharge orifice either in the flow path 46 or in the annulus 48 or a combination of the two so as to provide the proper mixture anddistribution for a given engine. Also the location of the main fuel discharge jet is not as critical from a manufacturing standpoint in carburetors embodying the present invention as it is in prior art carburetors utilizing venturis. Carburetors embodying the present invention tolerate minor manufacturing differences without affecting the characteristics of the carburetor there-by enhancing the manufacturing of the carburetors by mass production methods with a minimum number of rejects. The carburetors embodying the present invention have also shown substantial improvements when used with engines such as four cylinder engines wherein pressure pulsations are normally experienced in the induction pipe. VThe air flow nozzle of the present invention operates relatively unaffected by such pulsations in situations Where a comparable carburetor equipped with the venturi would be wholly ineffective to operate the engine. Although the invention has been shown and described with reference to specific embodiments, it will be readily apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit of the invention.

I claim: i

A carburetor for supplying fuel to an internal combustion engine having a source of fuel comprising: an induction passage, a -buttery type throttle in said passage, a flow nozzle mounted in said passage and forming a part of said passage, said fiow nozzle having a converging upstream end and a downstream end disposed upstream of said throttle, a throat section is said fiow nozzle having a predetermined cross-sectional fiow area, a discharge section in said flow nozzle having a substantially constant cross-sectional flow area equal to said predetermined crosssectional fiow area extending from said throat to said downstream end of said fiow nozzle, fuel discharge means communicating with said induction passage and being responsive to the pressure in said passage between a crosssectional plane through said throat section and a crosssectional plane adjacent said discharge end for discharging fuel into said passage, said fiow nozzle being constructed such that said planes define a volume of substantially equal pressure in Vsaid passage, means adapted to connect said source to said fuel discharge means, said throttle being rotatably mounted in said induction passage a predetermined distance downstream of said downstream end of said nozzle such as to provide a predetermined small clearance between the downstream end of said nozzle and an edge of said throttle when said throttle is in the wide open position, said throttle creating a decrease in pressure in said volume of substantially equal pressure without decreasing the fiow area of said nozzle to thereby influence the quantityY of fuel discharged `by said fuel discharge means.

(References on following page) 5 6 References Cited FOREIGN PATENTS UNITED STATES PATENTS 1,132,254 l; 1957 lrancel.3

, 29 7 1914 reat rtan.

3/1939 Kjllmeyer et al. 261-78 2/ 1956 Dorlaud 261-65 X HARRY B. THORNTON, Primary Examiner.

4/1962 Phillips- T. R. MILES Assistant Examiner.

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