US 3343820 A
Description (OCR text may contain errors)
Sept. 26, 1967 w. B. ELLIOTT CARBURETOR Filed Dec. 1, 1965 PART rmarns A/R FOW CJ-T/l I. H6: 4 M41475? 5.
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United States Patent 3,343,829 CARBURETOR Walter B. Elliott, Royal Oak, Mich., assignor to Holley Carburetor Company, Warren, Mich, a corporation of Michigan Filed Dec. 1, 1965, Ser. No. 510,789 9 Claims. (Cl. 261-23) This invention relates generally to internal combustion engine carburetors, and more particularly to a novel fuel metering system therefor.
In many current internal combustion engine applications, it is necessary or desirable to maintain the fuel-air ratio of the mixture supplied to the engine during part throttle operation within much closer limits than was heretofore required. This is particularly desirable for engines on automobiles to be sold in States, such as California, having rigid smog emission control laws and regulations. Since most driving is done under part throttle conditions, maintaining the main fuel-air ratio vs. air flow curve at part throttle within predetermined closer limits will assure a leaner fuel-air mixture and reduce the objectionable emission of unburned hydrocarbons. At the same time, however, the mixture cannot be too lean for proper operation of the engine.
The invention provides means by which the part throttle fuel-air mixture may be more closely controlled by the use of an adjustable screw means for varying an auxiliary fuel opening, which, in the carburetor shown, co-operates with the usual power fuel system. With such a structure, a predetermined amount of fuel is permitted to flow through the opening into the main well, regardless of whether the power valve is open or closed. The adjustable screw means would be set during final calibration of each carburetor and then locked in place so that the resulting fuel-air mixture supplied during part throttle conditions will be within the limits required to meet the state laws involved.
Accordingly, a main object of the invention is to provide novel means of more precisely setting the maximum fuel that can be supplied during part throttle engine operation.
Another object of the invention is to provide a novel and relatively simple adjustment mechanism for controlling the fuel-air ratio of the mixture supplied during part throtle, without effecting wide open throttle operation.
Another object of the invention is to provide structure which permits relatively quick and simple final calibration.
A more specific object of the invention is to provide a structure which includes an auxiliary fuel system associated with the main and power fuel systems.
A further object of the invention is to provide an auxiliary fuel system having screw adjustment means which, once installed and set at final calibration, can be permanently fixed and made inaccessible, so as to be tamper and vibration proof.
A still further object of the invention is to provide an adjustable auxiliary or supplemental fuel system which may be used in conjunction with'any type of power enrichment system, such as the well-known vacuum actuated diaphragm, vacuum actuated piston and mechanical linkage types.
Other objects and advantages of the invention will become more apparent when reference is made to the following specification and the accompanying drawings wherein:
FIGURE 1 is a fragmentary cross-sectional view of a carburetor embodying the invention;
FIGURE 2 is a fragmentary cross-sectional view of a modification of a portion of the FIGURE 1 structure;
3,343,828 Patented Sept. 26, 1967 FIGURE 3 is a fragmentary cross-sectional view of a modification of a portion of the FIGURE 2 structure;
FIGURE 4 is a graphical representation of a characteristic of the invention, and
FIGURE 5 is ,a schematic illustration of a dual carburetor application of the invention.
Referring to the drawings in greater detail, FIGURE 1 illustrates a carburetor 10 mounted on an engine intake manifold 12 by any suitable means such as bolts 14. The carburetor 10 is formed to provide an induction passage 16 having the usual choke plate 18 mounted on a shaft 20, venturi 22, main fuel nozzle 24, throttle plate 26 mounted on a shaft 28 and fuel reservoir 30. The fuel reservoir 30 includes the usual fioat assembly 32.
As further illustrated in FIGURE 1, the fuel reservoir 30 also includes the usual main metering jet 34 forming a part of a conduit 36 communicating between the reservoir 30 and the main well 38 of the main metering system 40. If desired, a main well tube 42 may be mounted by any convenient means so as to be suspended into the main well 38. The main well tube 42 contains a plurality of bleed passages 44 through its wall so as to communicate air supplied via an inlet 46 formed at the top of the tube 42 to the main well chamber 38. In the structure shown, the top of the main well chamber 38 intersects a conduit 48 which communicates with the induction passage 16 via the outlet nozzle 24.
Typical power enrichment systems are illustrated in FIGURES 1-3, FIGURES l and 2 comprising vacuum responsive types, while FIGURE 3 comprises a mechanically actuated type. The FIGURE 1 system 50 includes a diaphragm 52 forming a movable wall between a fuel chamber 54 and an air chamber 56. A passage 58 communicates between the fuel reservoir 30 and the chamber 54, while a passage 60 including a calibrated restriction 62 leads from the chamber 54 to the main well chamber 38. A passage 64 communicates between the air chamber 56 and a location in the induction passage 16 below the throttle valve when closed.
The tapered end 66 of the passage 58 serves as a valve seat for a valve 68 having a stem 70 extending through the passage 58 and secured in any suitable manner to the center of the diaphragm 52. A spring 72 mounted between the reservoir wall and a shoulder 74 formed on the end of the valve 68 urges the valve 68 away from the seat 66.
As is well known in the art, when the throttle valve is closed or nearly closed and manifold vacuum is high, the pressure differential across the diaphragm 52 is such that the valve 68 is urged downwardly against the seat 66, overcoming the spring 72. When the throttle is opened in response to a power demand and manifold vacuum is low, say less than 8 Hg, the pressure differential across the diaphragm 52 is decreased to the point where the spring 72 urges the valve 68 off the seat 66, thus providing communication between the fuel reservoir 30 and the main well chamber 38 so that additional fuel to meet the demand for increased power is supplied to the main well through the orifice or metering restriction 62.
The piston type power enrichment system 76, illustrated in FIGURE 2, includes a passage 78 which, like passage 64 of FIGURE 1, communicates between the induction passage 16 and a chamber 80 in which the piston 82 is slidably mounted. A stem 84 having a spring retainer 86 formed at the end thereof extends downwardly from the piston 82 through an opening 88 into the. fuel reservoir 30. A spring 90 is mounted between the wall of the reservoir around the opening 88 and the retainer 86.
A valve 92 is mounted in a chamber 94, which is comparable to the chamber 54 of FIGURE 1. A spring 96 mounted in the chamber 94 urges the valve 92 toward the seat 98 at the end of the passage 100 which is comparable to the passage 58 of FIGURE 1. A stem 102 extends upwardly from the valve 92 through the passage 100 into the reservoir 30 adjacent the retainer 86. As in FIGURE 1, when the vacuum in the chamber 80 above the piston 82 is sufliciently reduced, the pressure differential across the piston will be such that the spring 90 will urge the piston 82, and thus the stem 84 and retainer 86, downwardly into contact with the valve stem 102, thereby opening the valve 92 and supplying the required additional power fuel.
The FIGURE 3 power enrichment system 104, which is similar to the FIGURE 2 structure, except as illustrated, is actuated by linkage means 106 which moves the stem 108 vertically in response to rotational movement of the throttle shaft 28 (FIGURE 1) to which the linkage 106 is suitably connected.
According to current practice, the normal production dimensional tolerances for the components of the above described FIGURES 1-3 structures are such that the part throttle curve for a given production carburetor will normally lie somewhere in a comparatively wide range between the limits defined generally by the dash-dot curves A and B of FIGURE 4. In other words, allowable variation in the dimensions of the drilled passages 34, 62, 44, 46, 24 and 22, in production will cause the resultant part throttle curve to fall somewhere between relatively wide limits, such as A and B.
However, under the aforementioned Emission Control regulations, the range A-B is not acceptable, and the invention contemplates the addition of an auxiliary fuel system 110 (see FIGURE 1) by which the limits within which the part throttle curve will fall may be more closely controlled, the range being illustrated by the dash line curves C and D of FIGURE 4. Consequently, the fuel-air ratio of the mixture supplied at part throttle, by any given production carburetor, will never be so rich as to exceed permissible hydrocarbon emission, nor so lean as to compromise engine operation.
The construction and operation of the auxiliary fuel system 110 will now be explained. First, it may be noted that an additional means of communication between the fuel chamber 54 (or the chamber 94 of FIGURE 2) and the fuel reservoir 30 has been provided. This consists of a passage 112, a restriction 114 and an intermediate passage or chamber 116, the outer portion of which is threaded. An adjustable screw 118 is threadedly mounted in the chamber 116 in a manner such that the tapered end 120 formed thereon may vary the size of the restriction 114. Once set, the screw 118 is secured in place by any suitable means, such as by staking or filling that portion of the passage 116 adjacent the slotted head of the screw 118 with any suitable material, such as lead or sealing wax, etc.
In accordance with the invention, an undersized main metering restriction or jet 34 size is selected to assure that the resultant fuel-air mixture ratio will produce a part throttle curve below the lower dash line D of FIG- URE 4. At the time of final calibration, the adjustable screw 118 would first be turned all the Way in to close restriction 114 and then turned outwardly, away from the restriction 114, until enough additional fuel is being supplied through the passage 112, past the tapered end 120 into the chamber 54 (chamber 94 in FIGURE 2) and then through the fixed restriction 62 and into the main well 38 so that the part throttle fuel-air ratio vs. air flow curve will fall between the dash line limits C and D, which represent the acceptable range under present Emission Control regulations.
In order that the total fuel flow at wide open throttle operation, when the power valve 68 is open, may be the same as that in a carburetor without the auxiliary fuel system 110, the power valve channel restriction 62 is made slightly larger than usual, it being remembered that the main metering restriction 34 was made slightly smaller than usual, as explained above. Thus, the total amount of fuel supplied at wide open throttle conditions, through the main metering jet 34 and through the parallel path including the common restriction 62 and either one or both of the two parallel passages 58 and 112/114 will be substantially the same as in the prior art system.
Obviously, the auxiliary fuel system would be equally applicable to carburetors having the power enrichment systems 76 and 104 illustrated in FIGURES 2 and 3.
It should be apparent that the use of the fuel flow control or auxiliary system 110 provides, by means of a quick and easy adjustment at the time of the final calibration of each carburetor 10, a method for maintaining the part throttle curve within relatively narrow limits without the necessity of tightening production tolerances. With a lower upper limit C for the part throttle curve, rather than \the prior higher upper limit A, the rigid Smog Emission Control laws and regulations can easily be fully complied with. While the desired result is efiiciently accomplished, wide open throttle operation of the carburetor is not effected.
FIGURE 5 is a schematic illustration of a dual carburetor application of the invention wherein like parts are identified with the same reference numerals as those employed in FIGURES 1-4. It will be apparent that the dual carburetor application includes two main wells 38, two main jets 34 and two fixed restrictions 62 through which the power fuel system, including the single power valve 68, and the auxiliary fuel system, including the single manually adjustable screw 118, supply fuel to the main wells. The auxiliary fuel, when the power valve is closed, and the power fuel is, of course, divided equally through the fixed restrictions 62 so that only a single screw 118 is required. As in the case of a single barrel carburetor installation, the part throttle range of the main fuel systems can be more accurately controlled without effecting wide open throttle operation.
The invention has been shown and described in such clear and concise terms so as to enable anyone skilled in the art to practice the same. While but one embodiment of the invention has been shown and described, in conjunction with each of the three typical power enrichment systems, it is apparent that modifications of the invention are possible, and no limitations are intended except as recited in the following claims.
What I claim as my invention is:
1. An internal combustion engine carburetor, comprising an induction passage, a throttle valve in said induction passage, a fuel reservoir and a plurality of co-operating fuel systems for supplying fuel from said reservoir to said induction passage during part and wide open throttle operation of said carburetor, said systems including a main fuel system, an auxiliary fuel system and a power fuel system, each of said systems having its own means communicating with said reservoir through which fuel is supplied thereto, said means for said main and auxiliary systems comprising separate fixed constantly-open metering restrictions and said means for said power fuel system comprising an orifice controlled by a valve for closing said orifice except when power fuel is required, a common fixed metering restriction connecting said auxiliary and power fuel systems to said main system and of sufficient capacity to flow fuel simultaneously from both of said auxiliary and power fuel systems.
2. A carburetor such as that recited in claim 1, wherein said common metering restriction communicates with said main fuel system at a point downstream of said main system metering restriction.
3. A carburetor such as that recited in claim 1, wherein said auxiliary system metering restriction is manually adjustable.
4. A carburetor such as that recited in claim 3, wherein said manually adjustable restriction in said auxiliary system includes means to prevent subsequent changes in the adjustment thereof by tampering or vibration.
5. A carburetor such as that recited in claim 1, wherein said power system includes means to control the valve in accordance with engine manifold vacuum.
6. A carburetor such as that recited in claim 1, wherein said power system includes means to control the valve in accordance with throttle valve position.
7. A carburetor such as that recited in claim 1, wherein said main fuel system comprises a fuel passage extending from said reservoir to said induction passage, said main fuel passage including a main well and said fixed metering restriction comprising the reservoir end of said main fuel passage, said power valve system comprises a fuel passage communicating with said fuel reservoir, said common metering restriction communicating said fuel reservoir with said main well, said main fuel system and said power fuel system constituting parallel fuel paths to said main well, said power fuel system including means permitting fuel flow therethrough only when power fuel is required by the engine, and said auxiliary fuel system comprises a fuel passage between said reservoir and said fuel chamber of said power fuel system, said latter passage including a seat and a set screw threadable through an opening into said passage from the outside of said carburetor to vary the restriction at said seat, said set screw being shorter than said opening through which it is threaded so that once it is properly set the outer end thereof may be sealed to prevent subsequent turning thereof.
8. A carburetor such as that recited in claim 1, wherein that portion of said main fuel system up to and including said fixed metering restriction and that portion of said power fuel system up to and including said common metering restriction constitute parallel sources of fuel feeding into that portion of :said main fuel system downstream of said restrictions and wherein said auxiliary fuel system and said power system constitute parallel sources of fuel, said auxiliary system feeding into said power system at a point upstream of said common metering restriction and including an initially manually adjustable orifice with means for fixing the same against further adjustment once said initial adjustment is made, said auxiliary fuel system supplementing said main fuel system at all times during part and wide open throttle operation and said power fuel system including means responsive to an engine operating condition and supplementing said main and auxiliary fuel systems only during wide open throttle operation.
9. A carburetor such as that recited in claim 1, wherein there are a plurality of main fuel systems, each main system being supplied with additional fuel through a common metering restriction supplied by said auxiliary and power fuel systems.
References Cited UNITED STATES PATENTS 1,958,690 5/1934 Ball et al. 3,078,078 2/1963 Carlson 26151 X 3,166,292 1/1965 Forman 26-1--66 X 3,172,923 3/1965 Romeo et a1 261-69 HARRY B. THORNTON, Primary Examiner. RONALD R. WEAVER, Examiner.