US2031709A - Carburetor - Google Patents

Description

Feb. 25, 1936. s. F. HUNT 2,031,709

CARBURETOR" Filed Nov. 7, 1934 PNR 1N V EN TOR;

5Go# F HumL BY c E QATTORNEY Patented Feb. 25, 1936 y rra Scott lli'. Hunt, South Bend, lind., assignor to Bent dix Products Corporation, South Bend, Ind., a corporation of Indiana Application November '7, 1934, Serial No. 751,888

9 Claims. (Cl.'261-39) FFICE This invention relates to carburetors and more particularly to means for supplying a combustible mixture to an internal combustion engine when it is cold, as in starting. y It is known in this art to vary the fuel-to-air ratio by means of a choke valve positioned in the air inlet passage of the carburetor and operable to restrict the quantity of air entering the carburetor under various operating conditions. The choke valve is generally manually actuated' or actuated thermostatically in accordance with the temperature of the engine by a temperature responsive mechanism connected thereto.

In order to prevent a cold engine from stalling, it is necessary that it'operate at a higher speed than when it is running at normal operating temperatures, and it is also necessary that the proportion of fuel be increased to form a mixture sufficiently rich in fuel to support combustion.

This application is a continuation in part of my copending application Serial No.` 744,328, filed September 17, 1932, which discloses novel means whereby a combustible mixture may be by-passed around the throttle valve. As disclosed in that application the by-pass around the throttle valve f is controlled in accordance with the position of a thermostatlcally actuated choke valve and also by the differential of uid pressure in the carbureting passage on opposite sides of the throttle valve.

` It is an object of this invention to provide im'- proved means operable in accordance both with the position of the choke valve and the differential of fluidpressures on opposite sides of the,

throttle valve to furnish a suitable charge of c fuel mixture to the induction passage beyond the throttle valve, to support combustion when the engine is operating below normal temperatures. Another object of the invention is to provide novel auxiliary means whereby the richness of the mixture may be increased for starting the en ne when it is cold and progressivelydecre ed as the temperature of the engine isV incre sed to normal operating temperature. i

still further objectl of this invention is to pr Avide automatic means to supply an auxiliary charge of fuel forfstarting purposes, and means operable upon engine running conditionsl to interrupt the supply of auxiliary fuel.

Another object of, the invention resides in the provision of means for supplying a combustible mixture to the induction passage beyond the throttle valve when it is closed and the engine of means, operable upon a decrease in manifold vacuum while the engine is operating, to supply a combustible charge beyond the throttle valve to prevent the engine from stalling.

Other objects and advantages off this inven- V tion will be apparent from the following detailed description, together withthe illustrative embodixnents thereof in the accompanying drawing, submitted for purposes of illustration only, and not' intended to define the scope of the invention,

reference being had for that purpose to the subupper or air horn section I0, and "a lower or 25 throttle body section l2.

The air horn section Il comprises an air inlet passage I4, in which a choke valve I6, preferably of the unbalanced type and provided vwith a '-spring-pressed poppet relief valve I'I, is pivotally 30 mounted on a shaft I8 journalled in the walls of .the air inlet passage I4. A boss or housing 20 formed on one side of the air inlet passage I4, and receiving one end of the choke shaft I8, houses a portionof the choke valve actuating 35 mechanism, to be more particularly described hereinafter. The air horn section Ill-is provided with a flange 22 forming afloat chamber cover.

'he lower or throttle body section Il' com- 40 prises a main carbureting passage 24, tted with a secondary venturi 26. A primary venturi 28 is suspended in the main carbureting passage 24, and supported therein by a fin 30, in such a posinon that it discharges arme most restricted section of the secondary venturi 26. A main fuel discharge nozzle 32 projects through the n 30 and discharges at the most restricted section of the primary venturi 28.v l A conventional fuel reservoir 34 supplies fuel to the main fuel discharge .50

' nozzle 32 under a constant head.

The main carbureting passage '24 receives a' mixture of air and fuel, Vand discharges said mixture to the intake manifold 25, under the pumping y action of the pistons reciprocating within the cylinders of the engine. The flow of the combustible 'mixture through themain carbureting passage 24 is noimally controlled, in the usual manner, by a throttle valve 36 mounted on a throttle shaft 38, journalled in the walls of the throttle body section I2. Fuel for idling purposes is supplied in the known manner from the fuel reservoir 34, through a duct 40 terminating in a. port 42 immediately posterior to the throttle valve 36 when in closed position. Air for idling purposes is supplied through a port 44, immediately anterior to the throttle and communicating with the port 42. An idling adjustment screw 46 is provided to adjustably restrict the port 42 to increase or decrease the normal idling speed of the engine. the invention may be applied to carburetors of various types other than that just described and specifically illustrated in the drawing.

Applicants novel choke valve actuating mechanism comprises a bell crank having arms 48 and 58, fixed to the choke shaft I8 and enclosed in the housing 28. The housing 20 is closed by a plate 52, which carries a choke shaft bearing 54, to support one end of the choke shaft I8. The

. arm 48 is provided with a pin 56 projecting through a slot 58 in the plate 52, and positioned to be actuated by one end of a bimetallic thermostat 68. The other end of the thermostat ,60 is fixed to a stud 63, enclosed in a casing 62, adjustably clamped to the housing 20. For purposes of illustration the thermostat is shown as heated by an electric coil 66 positioned within the cas-l ing 62. It is understood, however, that the thermostat may be heated by other means, such as those disclosed in my copending applications Serial No. 718,633, filed April 2, 1934, and Serial No. 744,329, filed September 17, 1934; or if desired the choke valve may be of the manually aetuated type such as that disclosed in my copending application Serial No. 701,740, filed December 11, 1933,

A4 cylindrical bore 68 formed in a longitudinal boss 10 carried by the throttle body section I2 communicates with the interior of thehousing 20 by means of a sleeve 1I. A passageway 12 communicating with the main carbureting passage 24 posterior to the throttle valve 36 serves to interconnect that portion of the carbureting passage with the interior of the bore 68. It Will be understood that passageway I2 may lead directly to the interior of the intake manifold, rather than to thepassage 24 of the carburetor, if desired.

A second passageway 18 communicating with the main carbureting passage 24 anterior to the throttle valve 36 serves to interconnect that portion of the carbureting passage with the bore 68.

A hollow spool-shaped valve member 80, having a small vent 8| n the lower part of the section of reduced outer diameter, is slidably mounted within the bore 68 and'is yieldingly urged toward the upper end of the cylinder by a light coiled spring 82. The spring .82 engages a section of the valve of reduced internal diameter 84.

is provided with a small vent 90 designed to'be .obstructed by the section of reduced internal diameter 84 of the valve member 80. Means are provided whereby liquid fuel may se discharged into the bore 68 to mix with air It should be noted, however, that v mixture is discharged through passage 12.

drawn through the passageway 18-so that a combustible mixture is discharged through the pasageway 12 to the carbureting passage 24 posterior to the throttle valve 36. A fuel supply duct 92'communicating with the idling fuel duct 48 terminates in an auxiliary fuel supply passage 84 discharging into the interior of the bore 68. The fuel supply passage 94 is so positioned as to be swept by the flow of air passing through the bore 68 and to be closed by the enlarged upper i section of the spool-shaped valve when said valve is in or near its lowermost position, as shown in Figure 3.

The operation of this device is as follows: When the engine is cold, the thermostat 60 will have rotated to close the choke valve I6, and to lift the plunger 86. This position of the parts is shown in Figure l, in which it will be noted that the spool-shaped valve 80 is urged to the upper end of the cylinder 68 by the spring 82.

When the engine is cranked, the choke valve f16 being held in the closed position by the thermostat 60,l arelatively high suction is exerted on the fuel discharge nozzle 32 and the fuel supply passage 94 to draw a quantity of fuel therefrom. 'Ille fuel mixes with air admitted through the relief valve '11, positioned in the choke valve I6, to produce a. combustible mixture in the main carbureting passage 24. Since thespool-shaped valve 88 is in the upper end of the bore 68, free communication is established between the passages 18 and 12. The combustible mixture formed When the engine begins running under its own power .an increased suction is exerted on the 'passageway 12, so that air is withdrawn from the interior of the spool valve member 88 and the lower portion of the bore 68 through the vent BI. vThe spool valve 88 is thereupon urged downwardly in the cylinder so that its upper section partially closes the passageway 18 and the fuel duct 94, so that a decreased quantity of combustible During this period of operation a combustible mixture. is supplied through 'the idling passages 44 and 42, so that the additional combustible charge l supplied through the passageway 12 will produce a fast idle,'to prevent. the engine from stalling while it is cold.

When the spool-shaped valve member 80 moves downwardly in the bore 88 the vent 9U in the plunger 88 becomes exposed above the top of the valve member 8i). Since the vents 8| an'd 30 are of substantially the same size and the vent 80 communicates with atmosphere through the aperture 81 in the boss 10 and a vent 89 in the sleeve 1I, the partial vacuum existing within the lower portion of the bore 68 is destroyed. The valve member 80 will then be held temporarily in equilibrium.

As the enginel continues to run, the thermostat 60 will become heated, and tend to coil more tightly upon itself, thereby decreasing the force urging theV choke valve I6 toward the closed position. As theair entering the air-inlet vpas- .sage I4 strikes against the unequal areas of the the position of the valve 80 controlling the by-` choke valve I6 on either side of the chokel shaft I8, it will tendto rotate the valve I6 to open it more or less, depending upon the speed of the engine. As thel choke valve I6 is gradually opened, the crank arm 50 is rotated so that the plunger 86 `is moved downwardly in the valve member 80. The vent 90 is then closed by the section of reduced internal diameter 84 of the valve member 88, and air is withdrawnl from the interior of the valve member 88, whereupon it will be moved downwardly in the bore 68, to reduce the quantity of combustible mixture sup. plied to the engine through the passageway 12. This process is repeated until the engine is running at normal operating temperature, at which time the choke valve I6 will be completely open. The vent 90 in the plunger 86 is then closed by the section of reduced internal diameter 84 of the valve member 80, and the valve member 80 is drawn downwardly to the bottom of the bore 68 by the suction exerted through the passageway 12 and the vent 8|'. It will be noted that in this position the enlarged upper portion of the valve member 88 closes off the passageway 18 so that no communication is established between the passageways 12 and 18. g

When the engine has been running at normal operating temperature and has been stopped, the choke valve I6 will remain in the fully open position; the spool valve k8l) will be urged to the upper end of the bore 68 by the spring 82, and the plunger 86 will be extended into the valve member 80. established between the passageways 12 and 18,

so that air will be drawn from the carburetingl passage 24 anterior to thevthrottle valve 36, through the passageway 18,l past the end of the fuel supply passage 94. Liquid fuel will then be drawn from the passage 94 to form a combustibleV mixture to be passed to the carbureting passage 24, posterior to the throttle valve 36, through the passageway 12. engine has started running under its own power, the interior of the valve member 88 and the lower portion of the bore 68 will be evacuated, and the spool-shaped valve member 80' will be urged downwardly against the force of the spring 82. As the valve m'ember 80 moves downwardly,

the upper surface obstructs the fuel supply passage 94 and closes the passageway 18 leading to the carbureting passage 24 anterior to the throttle valve 36. The engine will then operate at idling speed on the `mixture supplied through the idling ports 42 and 44. The device thus operates not only to provide a rich mixture to prevent the 'engine from` stalling when it is cold, but also to provide an increased volume of fuel mixture for starting the engine under all operating conditions. rThe engine will therefore start quicker and require less manual control onthe part of the operator. A

Attention is directed to the fact that as the plunger 86 moves downwardly Vlto such a pointv tending to move the choke valve I 6 toward the open position. A fluid pressure actuated motor is thus provided which operates to modify the position of the choke valve. As previously indicated the position of the choke valve inuences In this position communication isl As soon as the' pass around the throttle valve 36. l

It will be observed that this device also operates as an anti-stall device, If the engine slows down below normal idling speed, when lthe throttle valve 36 is in the closed position, the suction exerted in thepassageway 12 and transmitted to the interior of the valve member 80, through the vent 8l, is partially destroyed, whereupon the spring 82 will force the valve memberl 80 upestablished between the passageway 12 and 13, whereupon an additional quantity of combustible mixture is supplied to the carbureting passage 24 posterior to the throttlevalve 36whichwillY prevent the engine from stalling. As soon as the -engine begins running again at normal idling speed, air will be withdrawn` from .the interior of the valve member 80, and it will again move to the bottom of bore 68, to cut off the excess charge of combustible mixture discharged Vthrough the passage 12 to the carbureting passage posterior to the throttle valve 36.

While the invention ha's been described with,

reference to apreferred embodiment, it is not intended that the invention shall be limited to vthat embodiment as various changes in the specific structure may be employed. as, for instance, any suitable valve structure may b'e substituted for the one specifically shown, without departing.

\ a fuel passage adapted to discharge fuel into the cylinder and to be closed by the piston under cerwardly Ain the bore 68.v Communication is then tain operating conditions, and connecting means the position of the piston, said motor acting also to interconnect thev main carbureting passage on 'either side of the throttle valve when said choke valve is actuated by said temperature responsive means. v

\ 2. In a carburetor, a main induction passage, a

choke valve, a throttle valve, thermostatic means to actuate the chokevalve', a fluid actuated motor including a cylinder communicating with the induction passage on either side of the throttle valve, a piston in said cylinder, a fuel passage positioned to discharge fuel into the cylinder under ycertain f operating conditions, and connecting means between a portion of said motor and the thennostatic means whereby said motor modifies the action of said thermostatic means.

3. In a carburetor, a main induction passage, a

choke Valve, a throttle valve, thermostatic means to actuate the choke valve, a fluid actuated motor ^including a cylinder communicating with the induction passage on either side of the throttle n thermostatic means whereby said motor modiesthe action of said thermostatic means.

4; In a carburetor having a main carbureting passage, a throttle valve, an unbalanced choke Cil , conditions, yielding means urging the piston to bureting passage posterior to the throttle valve, a l

one extreme position, a vent in a portion of the piston operable to subject the interior of the piston and a portion of the cylinder to suction eX- isting in the `main carbureting passage posterior tothe throttle valve, and connecting means between the piston and the choke Valve.

5. In a carburetor having a main carbureting passage, a throttle valve, an unbalanced choke valve, temperature responsive means urging the choke valve closed when cold, a fluid motor including a cylinder communicating with the main carbureting passage on either side of the throttle valve, a hollow spool-shaped piston slidably mounted within the cylinder, a fuel passage positioned to discharge fuel into the cylinder and to Abe closed by the piston under certain operating conditions, yielding means urging the piston to one extreme position, a Vent in aportion of the piston operable to subject the interior of the piston and a portion of the cylinder to suction existing in the main carbureting passage posterior to the throttle valve, a hollow plunger slidable -within said piston, a vent in a portion of said plunger operable to destroy the vacuum Within said piston and a portion of the cylinder under certain operating conditions, and connecting means between the plunger and the choke valve 6. In a carburetor having a main carbureting passage, a throttle valve, a choke valve, thermostatic -means operably connected to the choke valve, a cylinder formed integral with the main carbureting passage, connecting means between the cylinder and the carbureting passage on either side of the throttle valve, a hollow spoolshaped piston slidably mounted within the cylinder, a fuel passage positioned to discharge into the cylinder and to be closed by the piston under certain operating conditions, yielding means urging the piston to one extreme position, a vent in a portion of the piston operable to subject the interior of the piston and a portion of the cylin der to the pressure existing in the main carportion of said piston being of reduced internal diameter, a hollow plunger slidable within said piston, a vent in a portion of the plunger designed to be closed under certain operating conditions by the portion of said piston of reduced internal diameter, and connecting means between said plunger and said 'choke valve.

'7. In a carburetor having a main carburetingr passage, a throttle valve, a choke valve having a spring pressed poppet relief valve, thermostatic means operably connected to the choke valve, a motor including a cylinder formed integral with the main carbureting passage, connecting means between the cylinder and the carbureting passage on either side of the throttle valve, a hollow spool-shaped piston slidably mounted within the cylinder, a fuel passage positioned to discharge into the cylinder and to be closed by the piston under certain operating l conditions, yielding means urging the piston to one extreme position, a vent in a portion of the piston operable to subject the interior of the piston and a portion of the cylinder to the pressure existing in the main carbureting passage posterior to the throttle valve, a portion of said piston being of reduced internal diameter, a hollow plunger slidable within said piston, a vent in a portion of the plunger designed to be closed under certain operating conditions by thegportion of said piston of reduced internal diameter, and connecting means between said plunger and said choke valve whereby the motor influences the position of the choke valve and the thermostatic means influences the position of the piston whereby a charge of combustible mixture is by-passed beyond the throttle valve until the choke valve approaches substantially full open position.

8. In a carburetor, a fuel reservoir, a thermo-l statically actuated choke valve, a throttle valve, a mixture bypass around the thottle valve, a valve controlled jointly by fluid pressure beyond the throttle valve and by the position of the choke valve controlling the bypass, and a fuel passage communicating with the fuel reservoir adapted to supply fuel to the bypass under certain operating conditions.

9. A carburetor having a fuel reservoir, a thermostatically actuated choke valve. a throttle valve. a mixture bypass around the throttle valve. a valve controlled jointly by fluid pressure beyond the throttle valve and by the position of the choke valve controlling the bypass, and a fuel passage in the walls of the bypass and communicating with the fuel reservoir adapted to supply fuel to the bypass under certain operating conditions.

' SCO'I'I F. HUNT.

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