US2303640A - Carburetor - Google Patents

Description

e- J. w. HOGG 2,303,640

CARBURETQR 'Filed June 28, 1940 s Sheets-Sheet 2 FUEL AIR THERMOSTAT John L/H099 Patented Dec; 1, 1942 I UNITED STATES PATENT OFFICE Application June 28, 343,037 .r

7 Claims.

This invention or discovery relates to carburetors; and it comprises in a carburetor for internal combustion engines and the like a body member having a fuel-air mixing chamber in communication with the intake manifold of an engine, an air conduit through the body member and a fuel conduit including a discharge jet delivering to said chamber, means for supplying fuel to said conduit under pressure, means for establishing difierential pressures in the air conduit and in the fuel conduit, a pair of flexible fluid pressure holding members linked to each other, with the facing sides of said members exposedto differential pressure in oneof said conduits and the remote sides of the members exposed to differential pressure in the other conduit, valve means in the fuel conduit in operative connection with said linkage and adapted to be opened thereby on increase in differential pressure in the air conduit and closedby differential pressure in the fuel conduit, and a throttle associated with the mixing chamber; all as more fully hereinafter set forth and as claimed.

Carburetors of the so-called floatless type, in which fuel is fed directly under pressure to a mixing chamber for mixture with air to form a charge, are attractive to the internal combustion engine art. They avoid difliculties due to selective evaporation of fuel in float chambers, they can be designed to work in any position since they do not depend on gravity for their operation, and.

they are inherently compact and simple. However, the practical difliculties in the way of supplying small quantities of fuel under pressure without a float control haveproved formidable and few floatless carburetors have met with any degree of success. In my prior Patent No. 2,004,869 there is disclosed and claimed a carburetor offloatless, direct pressure feed type in which fuel feed is controlled in a particular way by pressures developed in the air flow and in the fuel flow. The carburetor functions well in practice even under conditions where the most drastic-requirements must be met, viz, aircraft carburetion.

The present invention relates to improvements incarburetors of the type disclosed in my'prior patent, and it providesa carburetor eminently suitable for automobile use where a cheap and simplev apparatus is desired, in which proper fuel-air proportioning is maintained by a very simple arrangement of pressure responsive means. The carburetor achieves to a high degree, in a simple way, the ultimate object of all carburetion; supply to the engine of an accurately predetermined fuel-air mixture under all conditions.

The carburetor includes a body member for attachment to an engine containing a fuel-air mixing chamber with an air passage through the member and a fuelconduit delivering to the chamber, and means for establishing difierential pressures in each conduit, These may bepriflce'd members, venturis, pilot tubes, impact tubes (a variation of the pilot tube), or the equivalent. A pairof flexible diaphragms or equivalent defiectable fluid pressure holding membersare provided, linked to each other at fixed separation.

The proximate faces of the diaphragms are exposed to differential pressure in. the air conduit and the remote faces are exposed to differential pressure in the fuel conduit. The diaphragm linkage is directly connected to a fuel valvein such arrangement that increase in fuel differential pressure as a result of increased flow, tends to close the valve, and increase in air differential pressure due to increased flow tends to open it. The result achieved is correct fuel-air proportioning under a wide range of conditions, with a very simple construction, only two diaphragms being' required as described to separate the two fluids and to permit the other necessary functions. The construction is such thatfrictional engagement-of parts is or can be obviated, no rubbing of parts on each other being necessary.

This is a valuable feature in insuring accuracy :of proportioning under widely different operating conditions.

My carburetor usually includes certain additional elements, including an adjustment of the fuel differential pressure establishing means, in addition to the automatic valve, for changing the charge proportions under special circumstances; and also means for adjusting the constriction in the air conduit in accordance with atmospheric temperature and pressure changes.

-' This last means is especially useful'in carburetors for airplanes or in other cases where an engine.

is required to operate under widely variable at mospheric conditions.

In the accompanying drawings I have shown more or less diagrammatically several examples of specific embodiments of apparatus within the purview of the invention. In the drawings,

Fig. 1 is a view, partly in central vertical section-and partly in elevation, of one embodiment of the invention embodying a single pair of diato an enlarged scale an embodiment including exterior pressure-responsive flow control means; and

Fig. '7 is a similar view of a modified flow control means.

Referring to the drawings, and more particularly to Figs. 1 and 2, the carburetor includes a tubular housing or barrel I the upper part of which forms an air conduit and the lower part of which defines a mixing chamber II. A throttle I2 is provided in the mixing chamber. A pair of diaphragms I3 and I4 is provided, linked together by a rod I5 with stifiening discs I6 and I1 next the diaphragms as shown. The diaphragms are supported from a partition I8 in tube I0, by cylinders I9 perforated at 20. Air flows through the assemblage as indicated by arrows. An orifice 25 in the partition I8 creates a differential pressure in the air flow so that -'the downwardly exposed face of diaphragm I3 is exposed to higher pressure than the upwardly exposed face of diaphragm I4.

view taken along line 4-4- form of manually from the drivers seatby a suitable con-'- nection, or, if desired, it can be controlled automatically under the influence of engine speed or other variable, to enrich the mixture at-idling speed or when heavy loads are encountered or to make it leaner at some cruising speed range. In Fig. 1 the valve is shown as regulated in accordance with engine speed, through the agency of a governor I00 driven by the engine (not shown) and adapted to move a cam IOI bearing against the pin I02 of valve I33. In Fig. 3 the pin I02 is shown as moved under control of a bimetallic thermostat element I04 responsive to engine temat 59, for balancing purposes.

A cap 26 surrounds the upper face of diaphragm I3 defining a chamber 21 put under pressure through a conduit 28 from the fuel line 29, which receives gasoline, etc. under pressure from a fuel pump 30. Conduit 20 delivers at 3| to a corresponding chamber 32 below diaphragm I4; a restricted orifice 33 in housing I09 being interposed in the fuel. line as shown, to establish differential pressure therein.

The lower end of rod I5 carries a balanced fuel valve including two valve points 34 and 35 cooperating with a valve body member 36 to control the fuel flow from chamber 32. Fuel leaves the chamber at a jet nipple 3'! having a small jet orifice 38. Advantageously, a check valve is provided for this orifice, to prevent leakage when the engine is not running. This valve includes a stem 39 urged upwardly by a spring 40 and having a flaring head 4| to distribute the fuel as a spray.

Adjustment for idling is conveniently made by screw I08, forming a stop for part 35 (Fig. 3).

In operation, assuming the engine to be running, air is drawn in by engine suction flowing the course of the arrows in Fig. 1. The air flow has a tendency to open the fuel valve. Fuel is supplied under pump pressure and the fuel flow tends to close 'the fuel valve. The netresult is a quite constant proportioning of fuel and air despite wide variations in air flow and in pump pressure. The throttle works in the usual way.

The relative proportion of fuel and air is determined by the setting of a needle valve I33 operating in orifice 33. This valve can be contr l ed 1 isnot iliustrated. A

perature. The valve I33 is advantageously constructed with a very narrow taper, say a reduction in diameter of 0.01 inch per inch of length.

A balanced fuel valve as shown in Fig. 1 is sometimes unnecessary; a simple valve suflices for small units (of. Fig. 7).

In the modification shown in Figs. 3 and 4, diaphragms of different size are employed in the fuel pressure responsive means and in the air pressure responsive means. By making the fuel pressure diaphragm smaller, less differential pressure need be established in the air flow. As shown, two small fuel pressure diaphragms and 5| and two larger air pressure diaphragms 52 and 53 are provided, all linked together by rod 5!.

Housings 55 and 56, supported from the chamber 51 by rods 58, enclose the space between each pair of diaphragms, this space being vented to the air The space above the upper fuel diaphragm is capped by a cover and is connected to lower fuel diaphragm communicating through conduit 63 with the enriching valve I09 in the fuel line. Rod '54 operates a fuel valve 34, 35 as in Fig. 1. A conduit 04 leads from the valve to fuel jet I31; shown as placed downstream (on the engine side) of the throttle I2, a construction which has advantages, in certain relations, over the conventional arrangement wherein the fuel jet is upstream with respect to the throttle. 1

Figs. 3 and 4 also serve to illustrate the feature of the invention of varying the constriction in the air flow in accordance with the density of the air being metered. The flow 'of air across a sharp-edged orifice or other constriction is given by the expression'F=CK1\/D /H, wherein C is the pipe coefficient of discharge, K1 is a dimensional constant, -D H is the differential head. The density of air varies with altitude and temperature. In order to keep the flow constant I arrange for varying the discharge coeflicient in a reciprocal relation to the density, such that CX\ D,-- Kz (a constant),

thereby making the flow proportional simply to This end is achieved by varying the area of a sharp-edged orifice in the air flow. An iris diaphragm is provided including a stationary annulus 10, a set of leaves 1| and amovable annulus 12 which determines the diaphragm opening by its angularposition. The diaphragm is of .a type known per se and its interior construction bellows l3, partlyfilled with air or other gas or with a liquid (not shown) having appreciable vapor tension, is mounted in a'chamber 14 opening into the tube 51 and exposed to the incoming a The moving end ofthe bellows carries a post I5, supported at I0, bearing a cam I6 operating a pin 11 on the diathe fuel line at -6I. The is covered by a cap 5 is the density of the air and aeoacco phragm annulus. The pin is'urged against the cam by a spring 19 operating on the diaphragm annulus I2 as shown. The bellows expands and contracts as the air density decreases and increases respectively, and in so doing it tends respectively to increase and to decrease the orifice area of the diaphragm opening. Cam .16 is of such shape that the discharge coeflicient varies vided formanually enriching the mixture when desired. An automatically controlled valve asin in an inverse manner to the square root of the density, whereby the relation C /D is maintained constant.

Fig. 5 shows a simplified embodiment of the I invention in which thediaphragm-coupling member itself forms part of the fuel conduit,

with a reduction in the number of parts. of flexible diaphragms 88 and 8I closed in a housing comprising into which fuel is admitted under to the space above the upper diaphragm and air is admitted at 85 to the space between the proximate sides of the diaphragms. Air leaves thebody at 86 and is shown delivered to an engine supercharger 81. The fuel discharge conduit is shown at 88. The body member is constricted at 89 so as to establish a difierential pressure in the air fiow. The shape of the body member resembles a Venturi passage but purposely departs from true Venturi construction so that the pressure loss at the constriction 89 will not all be regained by the time the fiowing air comes in contact with diaphragm 8|.

The diaphragms. are coupled by a tube 92 terminating at a restricted fuel orifice 93 above diaphragm 80 and extending below diaphragm 8|. The lower end 94 of" the tube forms a variable A pair is provided, en-

an hour-glass pressure at 28 throttling valve at. I44 to establish difierential' opening valve in conjunction with an adjustable taper-headed pin 95, as shown.

In operation, air fiow diflerential pressure across constriction 89 tends to urge the fuel valve toward open position and fuel fiowdifierential pressure across orifice 93 has an opposite efi'ect. Constant proportioning is provided.

It is sometimes desirable to minimize obstruction to the air flow for the engine by disposing the pressure-responsive devices and valves outside the air conduit proper. Figs. 6 and 7 show such modifications. In Fig. 6 anair conduit or chamber IIU is provided, defining a mixing chamber III near one end and having mounted exteriorly thereof a housing H2 separated into three chambers H3, H4 and H5 by two 'diaphragms I I6 and II! coupled together by a rod .8. Chamber closely surrounding the rod but leaving a small annular orifice I2Il. Chambers H3 and H5 are connected through conduits I2I and I22 terminating in the air passage at. upwardly turned ends I23 and I24 respectively. The pressure 'in chamber H5 is maintained higher than that in chamber II3 by virtue of the disposition of these ends,. I23 and I24. This diflerentia'l is advantageouslyenhanoed by provision of an orifice I25 in the airkconduit, which however need not be much smaller in diameter than the air conduit. Y

Fuel is supplied through a conduit'2 3 with a branch 126 leading to the lower part of chamber 4' and a branch leading to the upper part of the chamber, as shown, in communication with the lower face .of diaphragm 8. Fuel is discharged through a conduit I21, which communicates with a valve housing I28 cooperating with valve members I29 and acting on the diaphragms differential pressure. provided for the .diaphragms, terminating in,

Figs. 1 and 3 can be substituted for valve I 3| if desired.

The apparatus of Fig. 6 functions similarly to the embodiments shown in Figs. 1 to 5 and no special description'of its operation is necessary.

In Fig. 7, the pressureresponsive means and valves are simplified. Housing I40 contains a pair of diaphragms H6 and Ill as in Fig. 6, the proximate faces of which are put under air differential pressure through ducts I2I and I22 and the remote faces of which are under fuel A connecting rod I is a tapered valve member I42 controlling fuel flow. Fuel is supplied to chamber II5 and thence to chamber II3 through branch I43, with a pressure in the fuel flow. Orifice I20 around the rod is made as small as possible without rubbing contact.

tions to meet particular requirement. The carburetors are or can be embodied in the usual materials: brass, steel etc. for the metal parts and synthetic rubber or thin corrugated metal for the diaphragms. The embodiments shown are primarily intended for use with gasoline or other liquid fuels. but canlbe use with gaseous fuels,

What I claim is:

1. In a carburetor readily adapted for of the type described, a

' body member for attachment to an engine in- H4 is divided by a partition H9 take, a fuel-air mixing chamber in communication with said member and an air conduit delivering to said chamber a fuel conduit including a discharge orifice delivering to said chamber, means for supplying fuel tosaid fuel conduit under pressure, orifice means adjustable as to discharge coefiicient for establishing differential pressure in the air conduit and means for establishing difierential pressure in the fuel conduit,

'a pair of pressure-responsive members coupled to each other and each adapted to deflect under influence of fluid pressure, the proximate sides of said members being exposed to differential pressure in one of said conduits and the remote sides of said members being exposed to diflerential pressure in the other conduit, valve means in the fuel conduit in operative driven connection with said coupled members and arranged to be urgedthereby toward open position on increase in differential-pressure in the air conduit and urged toward closed position. by increase in pressure in the fuel conduit, and pressureeresponsive means communicating with the air bei ng metered. and constructed and arranged to reduce the. discharge coefiicient of said orifice. -means on increase in air density and* vice versa.

2. In a carburetor of the type described, a

I30 on rod I I 8 as shown. -ho1lo'w barrel for attachment to an engine ing A slight bleed of air takes place through this orifice but insufficient to affect. the operation'of the carburetordeleteriously. Fuel leaves the housing at 64.

take and having an air passage extending therethrough to said intake, a fuel-air mixing chamher in the barrel, said barrel being provided with a restricted orifice upstream with respect to said mixing chamber and adapted to establishdifierential pressure in the air passage, a fuel conduit including a discharge orifice terminating in the mixing chamber, means for supplying fuel to the fuel conduit under pressure, means for establishing differential pressure in the fuel conduit, flexible pressure-responsive means fixed in the barrel upstream with respect to said orifice, flexible pressure-responsive means fixed in the barrel downstream with respect to said orifice, whereby the proximate sides of said flexible pressure-responsive means are exposed respectively to high and low air pressure, means coupling said pressure-responsive means together in mutual driving relation, closure means surrounding the remote sides of said pressure-responsive means, conduit means for supplying fuel from a point in the fuel conduit, upstream with respect to the differential pressure-establishing means therein,

to the space between the high pressure flexible means and the closure means therefor, conduit means for supplying fuel, from a point downstream with respect to the fuel differential pressure establishing means, to the space between the low pressure flexible means and the closure means therefor, and valve means in the fuel conduit in operative driven connection with the coupling means and arranged to be urged toward open position on increase in differential pressure across said constriction means andurged toward closed position by increase in differential pressure'in the fuel conduit.

3. In a carburetor of the type described, a body member including a fuel-air mixing chamber in communication with an engine intake, a tubular housing having an upstream portion open to the air and a downstream portion opento the intake of an engine and a fuel-air mixing chamber in said downstream portion, means in the 'housing for establishing differential pressure between the upstream portion and the downstream portion, a pair of spaced diaphragms, one small and one large, disposed in the upstream portion of v the housing and a pair of spaced diaphragms, one

small and one large, disposed in the downstream portion thereofv with the large diaphragms of the 150 two pairs facing each other, the proximate faces of the near diaphragms of the two pairs being exposed to air pressure in the conduit upstream and downstream of the differential pressure establishing means, means coupling said two pairs of diaphragms together, means enclosing the space between each pair of diaphragms and the outer face of the'outer diaphragms, vents leading from said spaces between each pair of diaphragms to the open air, a fuel conduit with branches leading to the spaces surrounding the outer faces of the diaphragms, differential pressure establishing means in the fuel conduit between said branches, a valve in the fuel conduit operatively coupled to the diaphragm coupling means, and a fuel jet in said mixing chamber delivering fuel from the valve thereto.

4. In an engine carburetor of the typedescribed comprising a hollow body member including a fuel-air mixing chamber delivering to the intake of an engine, an air conduit and a fuel conduit delivering to the mixing chamber, a valve in the fuel conduit and means responsive to air pressure operatively connected to the valve; the improvement comprising orifice means in the air conduit adjustable as to discharge coefiicient means responsive to differential pressure across said orifice means and operatively connected to the fuel valve, and a pressure responsive means exposed to the atmosphere and operatively connected to said orifice means whereby to vary the discharge coefficient of the orifice. in inverse quadratic relation to the density of. the air.

5. In a carbureter, a tubular body member opening, at one end to the intake of an engine and at the other end to a supply of air, means within said member for establishing differential pressure in air flowing through the member, a pair of coupled diaphragms supported within the body member with their proximate sides exposed to air upstream and downstream with respect to said means, a fuel conduit terminating at a discharge jet within the body member, valve means in the fuel conduit in operative connection with the coupled diaphragms and adapted to be urged toward open position on'increase in air, differential pressure, means for establishing differential pressure in the fuel-conduit and means for applying the higher fuel differential pressure to the remote face of the diaphragm exposed to the higher air pressure, and the lower fueldifferential pressure to the remote face of the other diaphragm, whereby a substantially constant fuelair mixture ratio is provided, additional differential pressure establishing means in the fuel conduit and means for controlling said means wherea by a temporarily'richer or leaner mixture can be provided.

6. The carburetor of claim 2 wherein the pressure-responsive means are single flexible diaphragms.

7..Ihe carburetor of claim 2 wherein the pressure-responsive means are double spaced diaphragms and the spaces intermediate the diaphragms are vented to the atmosphere.

:, JOHN WEBB HOGG.

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