US2988345A - Air valve carburetor - Google Patents

Description

June 13, 1961 w. H. KouBE ETAL AIR VALVE CARBURETOR 3 Sheets-Sheet 1 Filed Feb. 26, 1959 June 13, 1961 w. H. KOLBE ETAL 2,988,345

AIR VALVE CARBURETOR Filed Feb. 26, 1959 I5 Sheets-Sheet 3 INVENTORS A 7' TUR/VEP 2,988,345 AIR VALVE CARBURETOR William H. Kolbe, Birmingham, and Alexander J. Sagady,

Centerline, Mich., assignors to Generai Motors Corporation, Detroit, Mich., a corporation of Delaware Filed Feb. 26, 1959, Ser. No. 795,852 9 Claims. `(Cl. 261-50) The presen-t invention relates to a new and improved air valve carburetor in which the ilow of fuel is controlled by maintaining a substantially constant pressure drop across a fuel metering valve device to maintain a substantially constant fuelair ratio under normal operating conditions. The constant pressure drop is maintained by the provision of a unique air valve arrangement in which the quantity of air flow is varied in accordance with engine demand. Inl an air valve type carburetor the pressure drops across the air and fuel orices are maintained substantially constant `by varying the area of the orices in accordance with-engine demand.

It is one of the basic objects of the present invention to provide a carburetor of simple design utilizing fewer parts than a conventional carburetor and further in which calibration and servicing are also simplified because of the absence of air bleeds coupled with the ability to meter fuel by a single contoured needle.

It has been a basic defect with air valve `type carburetors in the past that the actual air valve mechanism has been exposed to the air stream and the fuel in such a way as to be highly susceptible to sticking of the parts thereby upsetting the desired fuel metering function. In the present invention the air valve has been uniquely constructed so that it is mounted within a chamber free of air or fuel impurities thereby insuring accurate actuation of the valve in accordance with engine demand.

The present air valve has been uniquely combined With a fuel metering valve in such a way as to insure economical use of fuel under normal operating conditions and at the same time facilitating the flow of additional fuel under conditions of high power demand.

The details as well as other objects and advantages of the present invention will be apparent from a perusal of the detailed description which follows.

in the drawings:

FIGURE l is a partially sectioned elevational view of the subject carburetor;

FIGURE 2 is a View along line 2--2 of FIGURE l;

FIGURE 2a is an enlargement of a portion of FIG- URE 2;

FIGURE 3 is a view along line 3-3 of FIGURE l;

FIGURE 4 is a view along line 4--4 of FIGURE 1;

FIGURE 5 is a view along line 5 5 of FIGURE 4; and Y FIGURE 6 is a view along line 6 6 of FIGURE 5.

Referring first to FIGURES l through 3, a carburetor is indicated generally at 10 and includes casing members l2 and :14. In order to facilitate lowering of .the height of carburetor 10, it is of the side opening type and includes an inlet passage 16 formed in casing 12. A conventional choke valve 18 is mounted in air intake 16 and may either be of the manual or automatic types as preferred. Casing l2 includes an air induction passage 20 extending generally axially thereof and which includes a throttle valve 22 rotatably mounted therein to control the quantity of combustible mixture supplied 4to any suitable engine intake manifold. i

A source of fuel or fuel reservoir is indicated generally atp24-and includes a fuel bowl 26 formed. as a part of 2,988,345 Patented .lune i3, 1961 casing 12. A cover casing 28 is adapted to enclose fuel bowl 26 and includes a fuel inlet 30 formed therein which supplies fuel through a filtering element .'52 to a passage 34 from whence the fuel will flow into bowl 26 in accordance with the position of a valve 36 controlled in the conventional manner by a tloat 38.

A conventional vent tube 48 extends from the top of fuel bowl 26 and opens into air inlet passage 16 anteriorly of choke valve 18 to permit fuel vapors to be vented from the fuel reservoir. An additional vent valve 42 is mounted on fuel bowl 26 and is adapted to be opened by a lever 44 operatively connected with throttle valve 22 when the throttle is in its fully closed position. Thus when the engine is operative and air is being drawn `in through air intake passage 16, float bowl 26 will be internally vented through tube 4b whereas when the engine is inoperative the bowl will be externally vented through vent valve 42.

Referring more particularly to FIGURE 2, it will be seen that the intake end of casing l2 is enlarged at 46 to provide a housing for an air valve m-ember indicated generally at 48. Air valve 48 includes a contoured diffuser or valve element 5t) centrally apertured at 52 to support a hollow sleeve or stem member 54 slidably disposed within a corresponding cylinder 56 formed integrally on cover casing 14. A flexible diaphragm S8 is clamped at its internal periphery to a radially extending flange 68 on valve element 50. Diaphragm 58 is supported against ange 60 by a dish-shaped supporting member 62 secured thereto through a plurality of rivets 64. The outer periphery of diaphragm S8 is clamped between casings `l2 and 14 so as to respectively define therewith chambers 66 and 68.

Air valve element 50 includes an annular shoulder portion 78 adapted to coaot with an annular seat 72 on casing l2 to provide an annular air orifice or passage 74, the cross sectional area of which is variable in accordance with the axial position of valve element 50. As best seen in the sectioned portion of FIGURE l, air inlet passage 16 openly communicates with chamber 66 dened by enlarged portion 46 of casing 12 and diaphragm 58.

Chamber 68 dened by diaphragm 58 and cover casing 14 communicates through a conduit 76 with induction passage 20 intermediate throttle valve 22 and seat 72. A spring element 78 is seated against casing 14 and is adapted to normally bias air valve element 50 in a direction so as to restrict the quantity of ilow through annular air passage 74.

An adjustable stop 88 is mounted in casing 12 and includes a plunger element 82 slidably mounted within threaded stud 84. Plunger 82 is adapted to engage diffuser or valve clement 50 to limit the latters closing movement to insure adequate air flow under engine idling conditions. Plunger 82 includes a` collar 85 to limit the plungers outward movement by a spring 86. The idle air adjustment is set by threading stud 84 within casing 12 and locking the same in position through nut 88. The plunger may be depressed to` open the air valve to check whether the idle mixture is satisfactory. To illustrate, if plunger 82 is depressed to open valve element 50 and an increase in engine speed follows, the idle mixture is too rich which can be corrected by reducing idle fuel iiow, infra.

The actuation of air valve 48 is as follows: as already noted a constant pressure drop is maintained across annular air passage 74 by varying the cross sectional area of the passage through movement of the air valve, The

depression in induction passage caused by the engine pumping air is imposed on portion 90 of valve element 50 designated at area A1. This creates a force acting in the direction of throttle 22 tending to reduce the cross section of passage 74. This same depression is transmitted through conduit 76 to chamber 68 and acts over an area A14-A2 to create a larger force tending to open valve element 50. Area A1 thus contains the same pressure on both sides and is balanced. However, area A2 has induction passage depression on one side and intake air pressure on the other acting to open element 50. This then is the pressure drop controlled by spring 78. Since spring 78 wants to lclose the air valve and the depression over A2 endeavors to open the valve, a balanced situation prevails. At each new position of throttle 22 a new balance obtains with a corresponding change in the cross sectional area of air passage 74.

As best seen in FIGURES 2 and 4 through 6, a fuel metering mechanism is shown generally at 92. Mechanism 92 includes a casing portion 94 disposed coaxially within induction passage 20 and supported upon a web section 96 extending from casing 12. Air valve element 50 includes a recess 98 formed in portion 90 which recess is radially and longitudinally spaced from the upper end of valve casing 94. Casing 94 and recess 98 define a downwardly opening chamber 100. An orifice sleeve 102 is threadably mounted within the upper end of casing 94 and is adapted to slidably receive a tapered fuel metering needle 104. Needle 104 is secured to air valve element 50 through a wire 106 the other end of which is adjustably secured within stem 54 through an adaptor 108.

Casing 94 is communicated with fuel reservoir 24 through passages 110 and 112 whereby fuel is supplied through ports 114 in orifice sleeve 102 to the space between the latter sleeve and needle 104. Sleeve 102 includes primary and secondary fuel orifices 116 and 118 with which metering needle 104 coacts to regulate fuel flow. Thus as air fiows through induction passage 20 a depression occurs creating a pressure drop across primary fuel orifice 116 causing fuel to ow into the air stream. It is apparent that due to the tapered nature of needle 104, as air valve element 50 moves axially with respect to casing 12 the quantity of fuel supplied to the induction passage will be varied. Thus as the air valve moves away from throttle 22 due to increased air ow, the opening between primary orifice 116 and needle 104 will be increased to increase the quantity of fuel supplied to the air stream.

As best seen in FIGURES 2 and 5, a piston 120 is slidably disposed in the end of casing 94 closed by a disc 122. Piston 120 includes a hollow portion adapted to receive the lower end of metering needle 104. The lower end of fuel valve mechanism 92 closed by a disc 122 and slidable piston 120 defines a chamber 124 which communicates through a passage 126 within casing 12 with the induction passage 20 posteriorly of throttle valve 22. A spring member 128 is disposed within chamber 124 and endeavors to bias piston 120 into abutting relation with-a secondary fuel orifice member 118.

The purpose of piston is to provide additional fuel under conditions of high power demand. Piston 120 includes a plurality of radially disposed ports 130 which are adapted, under certain conditions, to communicate with radial ports 132 formed in casing 94. Under normal operating conditions, c g., manifold depression above 5 inches Hg, the manifold vacuum in chamber 124 will overcome spring 120 and shift piston' 120 to its lowermost position wherein ports 130 and 132 are out of registry. However, under conditions of high power demand manifold vacuum will decrease sufficiently to permit spring 123 to move piston 120 to its uppermost position in which ports 130 and 132 are in registry and which will permit fuel to be drawn through secondary fuel orifice 118 into the air stream. In this Way the fuel from ports 132 supplement the regularly supplied fuel from the main metering orifice 116.

In order to prevent manifold vacuum from sucking fuel around piston 120 under normal operating conditions and thus upsetting the normal fuel-air ratio, a suction breaking device is provided and comprises an annular groove 134 formed in piston 120 which is adapted to register with a plurality of radially disposed ports 136 formed in casing 94 when the piston is in its retracted or nonpower position. In this way any manifold vacuum tending to draw such fuel past piston 120 is bled out by ports 136.

As best seen in FIGURE 2, air valve element S0 terminates at its lower end in a tapered portion or shroud 90 which, as already noted, provides a recess 98 or shroud for the upper end of fuel metering valve mechanism 92. This shroud arrangement protects the main fuel metering orifice 116 from the impact pressure of air entering induction passage 20 which might otherwise upset the quantity of fuel to be supplied in accordance with the volume or mass of air entering induction passage 20.

The upper end of fuel metering needle 104 is formed with a baffle portion 138 which assists in deecting the fuel being drawn through main metering orifice 116 downwardly into the air stream. Baffie 138 also assists in the atomization of the fuel by causing the same to be broken into smaller particles.

Wire 106 connecting fuel metering needle 104 with adaptor 108 serves two purposes, the first of which is to relieve critical alignment problems and, secondly, as a spring when bent or given a bias, holds needle 104 against the orifice openings relieving chatter and the resulting irregular ow caused thereby.

By removal of a casing plug 142, idle fuel adjustment is achieved by threading adaptor 108 within stem 54 to vary the opening between metering needle 104 and primary fuel orifice 116.

Idle mixture adjustment past throttle 22 is regulated by an idle stop screw 144 disposed on the throttle linkage and which stop is adapted to abut against casing 12 to vary the amount of throttle opening at idle.

Momentary enrichment of the fuel-air ratio is achieved for purposes of acceleration. As throttle 22 is rapidly opened, as occurs during acceleration, the engines effort to draw more air into induction passage 20 results in increased depression in the passage. The full force of this increased depression is momentarily not transmitted to air valve chamber 68 due to a restriction 146 in conduit 76. Thus the demand for more air is momentarily not reected in an increased vacuum force on air valve area A2 which would otherwise open annular air passage 74. For this momentary period the full force of the increased depression in passage 20 acts only on fuel metering mechanism 92 increasing fuel fiow through orifice 116 to provide temporary enrichment of the fuel-air ratio.

While not shown, it is contemplated that restriction or orifice 146 may be made adjustable to vary the time interval over which enrichment would occur.

We claim:

l. A charge forming device for an internal combustion engine comprising an air intake casing, an induction passage in said casing having inlet and outlet portions, a seat formed in said passage intermediate the inlet and outlet portions, a member slidably mounted within said casing and adapted to coact with the seat to maintain a substantially constant pressure drop across said seat, a cover casing, a diaphragm peripherally clamped between said casings, said diaphragm and intake casing defining a first chamber communicating with the inlet portion of said passage, the diaphragm and cover casing defining a second chamber, 4a conduit communicating the intake passage posteriorly of said seat with the second chamber causing said slidable member to move away from said seat in proportion to the mass of air fiow through said induction passage, spring means biasing said slidable member toward said seat, adjustable means for limiting the closing movement of said slidable member, a fuel valve mechanism disposed within said induction passage posteriorly of said slidable member, said valve mechanism including )an element operatively connected to and movable with said slidable member for controlling the fuel flow through said mechanism in accordance with air flow.

2. A charge forming device of the type including an induction passage, a throttle valve for controlling the flow of combustible mixture through said passage, air valve means actuated by the flow of air through said induction passage `and across which a const-ant pressure drop is maintained, and a fuel metering mechanism operatively connected to said air valve adapted to supply fuel in proportion to the quantity of air liow through said air valve, in which said air valve means includes first :and second casing members radially enlarged with respect to the induction passage, a valve element adapted to coact with one of said casing members to define an lannular air passage the pressure drop across which is substantially constant, a fiexible diaphragm fixed at its inner periphery to said valve element and the outer periphery of which is clamped between said casing members, said diaphragm and said first casing member defining a first chamber in communication with said induction passage, said diaphragm and said second casing member defining a second chamber, conduit means communicating said induction passage intermediate said throttle and said air valve with said second chamber, said valve element including a first portion exposed to the pressure in said induction passage posteriorly of said annular air passage, and a second portion extending radially outwardly of said first portion and fixed to the inner end of said diaphragm, said valve element adapted to be moved in an opening direction with a force proportional to the effective area differential between said first portion and the second portion plus said diaphragm, said second casing member including a hollow cylinder, a stem fixed to said valve element and slidably disposed within said casing cylinder, and spring means seated upon said second casing member and n0rmally biasing said valve element in a direction tending to restrict Ifiow to said annular air passage.

3. A charge forming device of the type including an induction passage, a throttle valve for controlling the liow of combustible mixture through said passage, air valve means actuated by the liow of air through said induction passage and across which a constant pressure drop is maintained, and a fuel metering mechanism operatively connected to said air valve adapted to supply fuel in proportion to the quantity of air flow through said air valve, in which said Jair valve means includes first and second casing members, a valve element adapted to coact with one of said casing members to define an annular air passage the pressure drop across which is substantial-ly constant, `a fiexible diaphragm fixed at its inner periphery to said valve element and the outer periphery of which is clamped between said casing members, said diaphragm and said first casing member defining ya first chamber in communication with said induction passage, said diaphragm and said second casing member defining a second chamber, conduit means communicating said induction passage intermediate said throttle and said air valve with said second chamber, an orice disposed in said conduit means, sudden opening of said throttle momentarily increasing the pressure drop across the annular passage, said orifice momentarily delaying the transmission of the increased vacuum through the conduit means permitting said vacuum to increase fuel flow through the metering mechanism for acceleration purposes, said second casing member including a hollow cylinder, a stern fixed to said valve element and slidably disposed within said casing cylinder, and spring means seated upon said second casing member and normally biasing said valve element in a direction tending to restrict flow t0 said annular Passage 4. A charge forming device of the type including an induction passage, va throttle valve for controlling the fiow of combustible mixture through said passage, air valve means actuated by the flow of air through said induction passage and across which a constant pressure drop is maintained, and a fuel metering mechanism operatively connected to said air valve adapted to supply fuel in proportion to the quantity of air fiow through said air valve, in which said air valve means includes first and second casing members, a valve element adapted to coact with one of said casing members to define an annular air passage the pressure drop across which is substantially constant, a fiexible diaphragm fixed yat its inner periphery to said valve element and the outer periphery of which is clamped between said casing members, said diaphragm and said first casing member defining a first chamber in communication with said induction passage, said diaphragm and said second casing member defining a second chamber, conduit means communicating said induction passage intermediate said throttle and said air valve with said second chamber, said second casing member including a hollow cylinder, a stem fixed to said valve element and slidably disposed within said easing cylinder, and spring means seated upon said second casing member and normally-biasing said valve element in a direction tending to restrict iiow to said annular air passage, said fuel metering mechanism comprising a cylindrical casing disposed in said induction passage intermediate the throttle and air valves, a fuel source, conduit means communicating the fuel source with the interior of the cylindrical casing, primary and secondary fuel metering orifices in said casing, a tapered metering needle extending through said orifices, means connecting one end of the metering needle to said air valve to increase fuel flow through the primary fuel orifice as air fiow increases, and means normally blocking fuel fiow from the secondary fuel orifice to the induction passage, said latter means permitting secondary orifice fuel flow when induction passage pressure exceeds a predetermined value.

5. A charge forming device as set forth in claim 4 in which the means for blocking secondary orifice fuel fiow comprises a hollow piston slidably disposed in the cylindrical casing, said piston being closed at one end and open at the other end, said open end being disposed adjacent the secondary fuel orifice, radial ports in said piston and cylindrical casing, spring means biasing the piston to a position in which the piston and casing ports are in registry permitting fuel to fiow from the secondary fuel orifice to the induction passage, conduit means communicating the space between the closed end of the piston and the cylindrical casing with the induction passage posteriorly of the throttle valve, the pressure differential across said piston being sufficient under normal operating conditions to shift the piston to a position moving the piston ports out of registry with the casing ports.

6. A charge forming device as set forth in claim 4 in which said primary fuel metering orifice opens upstream and is enshrouded by a portion of said air valve element the latter portion opening downstream whereby fuel flow between the primary fuel orifice and the metering needle is infiuenced solely by the pressure drop across the primary orifice.

7. A charge forming device as set forth in claim 4 in which said primary fuel metering orifice opens upstream and the metering needle includes a baffle element proximate said primary orifice for deiiecting fuel flow downstream.

8. A charge forming device as set forth in claim 4 in which the means connecting the metering needle and the air valve comprises an axially adjustable plug disposed in said stem and a wire element connected intermediate the needle and the plug for moving the metering needle relative to the fuel orifices with movements of the air valve.

9. A charge forming device as set forth in claim 5 in which a second Vset of radial ports-are formed in sa'id cylindrical casing, an annularV groove formed in the outer surface of said piston, said groove registering with said ports when the piston is in the position in which the piston ports are out of registry with the rst set of casing ports.

Reference! cited in the me of this paren:

UNITED STATES PATENTS Mock lune 1, Waters et al. Mar. 14, Hammond Dec. 19, Bracke Ian. 2, Dawes Aug. 3,

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