US3127454A - Return flow carburetor - Google Patents

Description

March 31, 1964 T. M. BALL RETURN FLOW CARBURETOR original Filed'June 5, 1959V /a Uf JNVENTOR.

United States Patent O 3,127,454 RETURN FLGW CARBURETOR Thomas M. Ball, Bloomfield Hills, Mich., assigner to Chrysler Corporation, Highland Park, Mich., a corporation of Delaware Original application .lune 5, 1959, Ser. No. 318,349, now Patent No. 3,098,885, dated July 23, 1963. Divided and this application Mar. 23, 1961, Ser. No. 97,775 Claims. (Cl. 261-36) This invention relates to improvements in a carburetor particularly adapted for use with -an automobile internal combustion engine `and is a division of my copending application Serial No. 818,349, tiled June 5, 1959, new Patent No. 3,098,885.

In conventional carburet-ors, .a float controlled fuel inlet needle valve is employed to regulate the fuel level in the carburetor fuel bowl. Small dirt particles sometimes interfere with effective operation of the valve, as for example by becoming lodged between mating valve seats which otherwise cooperate to regulate the fuel ilow into the fuel bowl. Also the floats require considerabie size in order to be `effective because o-f the companatively lo-w specific gravity of the fuel. In consequence the size of the fuel bowl must be appreciably larger than is otherwise desired.

An important object of the present invention is to provide an improved carburetor which avoids the foregoing objections and `in particular to provide a fioatless carburetor which does not require a fuel inlet needle valve.

Another object is to provide such a construction including ,an overllow standpipe in the fuel bowl having an upper opening Iwhich determines the maximum fuel level in the bowl. A fuel inlet pump is provided to pump fuel into the bowl at a rate in `excess of demand. The excess fuel overllows into the standpipe and is returned to the fuel tank. ln order to overcome `adverse grade conditions which prevent the excess fuel from returning to the tank by gravity flow, a scavenging pump is provided in the fuel return line between the overflow standpipe and the tank.

Among other advantages of the above structure, elimination of the necessarily large fioat enables utilization of a comparatively small fuel bowl closely adjacent the inlet air induction conduits of a multiple barrel carburetor, for example, The small fuel bowl thus located is less sensitive to grade and inertial effects and enables uniform fuel distribution to each of the several induction conduits. Also recirculation of the fuel drives off its more volatile fuel fractions and thereby minimizes some of the problems of the conventional fioat controlled carburetor, as for example those concerned with vapor formation.

ln order to provide adequate fuel during maximum engine speed at wide open throttle, a fuel inlet pump is provided Iwhich delivers an excess supply of fuel to the fuel bowl during all operating conditions of the engine. When the throttle is suddenly closed while the engine is still operating at high speed, unless some provision is made to the contrary, `approximately 98% of the fuel supplied to the fuel bowl will be recirculated, whereas approximately only 2% of the fuel will be used by the engine. ln general the life of a fuel pump and in particular the life of an engine driven diaphragm type pump, which is preferred for supplying fuel in the quantity required and at a substantially uniform pressure regardless of changes in engine speed, depends upon the quantity of fuel pumped.

For the above reasons, as well as the desirability of conserving power in an automobile engine and of minimizing fuel heating by excessive recirculation, another object of the present invention is to provide improved simple and highly effective means for supplying fuel to the fuel bowl in reasonable and safe amounts related to engine requirements.

Another object is to provide a bypass conduit which extends from the discharge side of the fuel supply pump to the inlet side of the pump and which contains a suitable valve adjustable -in response to variations in engine load for controlling the fuel flow in the bypass conduit.

Other and more specific objects are to adjust the bypass control valve by a `direct linkage with the throttle actuating mechanism.

Other objects of this invention will appear in the following description and `appended claims, reference being had to the accompanying drawing forming a part of this specioation wherein like reference characters designate corresponding parts in the single view.

The figure is a schematic mid-sectional view of a return flow carburetor and pump embodying the present invention.

It is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of other embodiments and of being practiced or carried out in various ways. Also it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.

Referring to the figure, `the carburetor shown comprises a cast housing forme-d to provide an air inlet induction conduit including a venturi portion 10 having a restricted venturi 111 at its upper portion and a throttle blade 12 pivotally mounted on a shaft 13 at a lower portion usually referred to as the throttle body. An upper portion of the casting is formed to provide an air horn 14 adapted to be connected with the usual air lter and opening at its downstream end into the venturi 11 to supply air thereto. The casting portions 10 and 1'4 are suitably secured together, as for example by screws not shown, and comprise an upper portion of the air inlet and fuel mixing induction -system which extends downstream of the throttle valve i12; and discharges into the usual engine cylinders in a conventional manner.

Integral with the casting 10 in the present instance is a fuel bowl casting 115 containing an annular chamber or fuel bowl `lo enclosing a cylindrical standpipe or weir 17 which also serves as an `acceleration pump cylinder containing a plunger 1S reciprocable in its lower portion and secured to a plunger Ishaft 1'9 for actuation thereby. Where desired the shaft 19 is connected by suitable linktage with a pedal operated accelerator mechanism which controls the opening and closing of valve 12 to operate conjointly therewith. 'Upon upward movement of plunger 13, fuel is drawn into the lower portion of chamber 17 via conduit 20 in communication with the bowl 16. A suitable check valve illustrated schematically as a ball check element Z1 nonmally seats at the mouth of the duct 20 opening into the lower portion of chamber 17 to pre-vent loss cf fuel therefrom but is raised from its seat by tbe fuel flow into chamber 17 on the upstroke of plunger 18. Upon downward movement of plunger 118 the fuel is forced from chamber 17 into the induction conduit via yacceleration fuel conduit I2.2, ball check valve 23, land nozzle 4 which latter discharges into the induction conduit at a location immediately above the throat of venturi 11. The check valve 23 is schematically illustrated as a ball normally urged by a spring to a seated position closing nozzle 24 from the interior of chamber 17, the ball being readily movable upward against the tension of its seating spring by the acceleration fuel pressure upon downward movement of plunger 18. The main fuel to the engine is supplied via duct 25 which opens a-t its lower end through metering port 26 into the fuel bowl 16 and communicates at its upper end with a fuel nozzle 27 hav-ing its dit-charge orifice located Within the thro-at of venturi 1-1.

In accordance with the structure described thus far, fuel entering the bowl 16 in excess of engine requirements overflows the upper edge of standpipe 17 which thereby maintains the fuel in the bowl 16 at a predetermined maximum level determined by the effective height of the standpipe y17 without recourse to a float operated mechanism. Fuel is supplied to the bowl16 from a suitable fuel tank -28b via conduit 28.

A multiple piece fuel pump housing 37 comprising an upper dome 38 and a lower basin 39 cooperate with diaphragms 40 and 41 respectively to provide an inlet fuel pumping or working chamber 42 and an exhaust fuel pumping or scavenging chamber 43. Springs 44 and 45 under compression between portions of housing 37 and diaphragms 40 and 41 respectively urge the former diaphragm upwardly and the latter diaphragm downwardly to effect the pumping strokes for the respective chambers 42 and 43.

The upper working chamber 42 comprises a portion of supply duct 2S which communicates upstream of chamber 42 with the fuel tank. Fuel enters and leaves chamber 42 via an inlet port 46 and a discharge port 47 associated with check valves 48 yand 429 respectively. Upon downward movement of diaphragm 41B as explained below, fuel is drawn in the direction of the arrow 28a from the tank and through inlet port 46 into working cham-ber 42. During this operation ball valve 48 is forced from its seat at port 46 by the fuel flow, and ball valve 49 seats at the discharge port `47 to close the latter from the fuel bowl 16. Upon upward movement of diaphragm 40, ball valve 48 is caused to` seat at port 46 to close the Working chamber 42 from the fuel tank. During this operation, the pressure exerted in chamber 42 unseats ball valve 49 from port l47 and supplies fuel via conduit 28 to the fuel bowl 16. The spaces at the sides ofthe diaphragms 40 and 41 opposite chambers 42 and 43 respectively are vented to the atmosphere by ducts 50' and 51 to facilitate the pump operation.

In order to prevent too great an excess of fuel from being pumped to bowl 116 when the engine 4is operating at comparatively light load, a bypass conduit 42a is provided which communicates at opposite ends with the discharge and inlet sides of chamber 42 respectively at locations downstream of port 47 and upstream of port 46. A valving port or orifice 29 in conduit 42a is controlled by a tapered needle valve 76 registering with port 29 at the latters high pressure side. Upon downward movement of valve 76, orifice 29 is progressively restricted to reduce the fuel flow therethrough as described below.

Fuel is returned in the direction of arrow 52a from standpipe 17 to the fuel tank 23b via fuel return conduit 52 which includes chamber 43 as a portion thereof. Inasmuc-h as fuel return conduit 52 in cooperation with fuel tank 21811 and a portion of inlet conduit 28 return the overflow fuel from standpipe 17 to the inlet side of pumping chamber 42, the three elements co-mprising conduit 52, fuel tank 28h, and the portion of conduit 2S upstream of pumping chamber 42 may be considered part of the fuel return system or means. Upstream, the conduit 52 communicates with standpipe 17 at a location above the uppermost limit rof movement of plunger 18. The return fuel enters chamber 43 via port 53 and discharges from chamber 43 via port 54. Ball check valves 55 and 56 are associated with ports 53 and 54 respectively, so that upon upward movement of diaphragm 41 as described below, ball 56 seats against port 54 to close chamber 43 from the fuel tank. During this operation, ball 55 is unse-ated from port 53 to open communication between chamber 43 and standpipe '17 and to draw fuel from the latter. Upon downward movement of diaphragm 41, ball 55 is seated against port 53 to close chamber 43 from standpipe 17. Simultaneously ball 56 is unseated from port 54 by the pressure in chamber 43 to discharge fuel from the latter in the direction of arrow 52a to the tank. Movement limiting pins in the conduits 23 and 52 associated with the ball valves 48, 49, 55 and 56 prevent undue movement of the balls from their associated ports. inasmuch as the check 'valves are well known, these are merely shown schematically and are not discussed in further detail.

Actuation of the diaphragms 40 and 41 is accomplished by driving shafts 57 and 58 connected to these diaphr-agms and terminating yin enlarged heads 59 and 60 respectively. Pivotal levers 61 and 62 are pivoted on housing 37 at locations '63 and 64 respectively between their ends. Each lever has one end engaged with a rotating eccentric cam' 65 mounted on -a shaft 66 driven by the automobile en gine. The opposite ends of the levers 61 and 62 are pro-y vided with oversized openings 67 and 68 through which the rods 57 and 58 extend freely to enable their relative sliding movement with respect to the levers 61 and 62 until the levers engage the enlarged heads 59 and 60.

Upon operation of the automobile engine, shaft 66 is rotated to turn eccentric cam 65 and thereby cause pivot,- ing of levers 61 and `62. Upon clockwise pivoting of lever 61, or counterclockw'ise pivoting of lever 62, the head 59 or 60 is engaged to pull the associated rod 57 and 58 in the direction to compress the spring 44 and 45 as the case might be. Upon counterclockwise pivoting of lever 61 and clockwise pivoting of lever 62, the oversized openings 67 and 68 enable the levers to swing independently of the shafts 57 and '58, whereupon springs 44 and 45 are released to force diaphragms 40 and -41 in pumping actions toward the associated dome 38 or basin 39. The pivotal action of levers 61 and 62 merely compresses the springs 44 and 45 alternately, which latter then exert resilient force to effect the pumping action of the associated diaphragms 40 and 41. In consequence, fuel is discharged from chamber 42 at a uniform optimum pressure determined by the force of spring 44. Upon the upward spring urged pumping stroke of diaphragm 40, fuel is discharged via port 47 to fuel bowl 16. All fuel in excess of engine requirements overflows the standpipe 17 and returns by conduit 52 tochamber 43 via port 53, whereupon the fuel is pumped to the fuel tank by downward spring urged pumping movement of diaphragm 41.

The restriction of orifice 29 is controlled by a mechanid cal linkage with the throttle valve mechanism. A valve actuating stem 77 secured to valve 76 extends upwardly therefrom and through a housing 75 and is yieldingly urged downwardly by a coil spring 78 under compression around stem 77 between a portion of housing 75 and a spring retaining seat 79 suitably secured to stem 77. The latter extends upwardly and is freely slidable through an oversized hole 80 in a dog-leg bracket 81 and terminates in an enlarged head 82 which is unable to pass through opening 80. Bracket 81 is secured to the upper horizontal portion of a dog-leg lever 83 having a vertical depending portion. A connecting link S4 is pivotally connected at 85 to the lower depending portion of lever 83 and is also pivotally connected at 86 to the outer swinging end of a crankarm 87 which in turn is keyed to an extension of valve shaft 13 exteriorly of the induction conduit 10.

Upon pivoting of crankarm 87 as for example by linkage S8 suitably connected with crankarm 87 and the customary pedal operated throttle mechanism, valve 12 is opened or closed. Upon clockwise pivoting of crankarm 87, throttle valve 12 is progressively opened and lever 83y is moved downwardly, causing bracket 81 to slide down wardly freely along valve stem 77 and enabling spring 78` to force stem '77 and valve 76 downwardly to increase the restriction at orifice 29. In consequence upon opening of the throttle valve 12 during increased engine load, bypass fuel flow through orifice 29 is decreased and fuel flow to bowl 16 is increased. Upon counterclockwise orl closing movement of valve 12 with decreasing engine load, lever 83 is moved upwardly. Bracket 81 then engages the enlarged head 82 and raises stem 77 against the force of spring 78 Valve 76 then progressively opens orifice 29, increasing the bypass fuel fiow in conduit 42a and reducing the fuel flow to bowl 16. In this regard the resistance to fuel flow in conduit 28 downstream of bypass conduit 42a is preferably greater than the corresponding resistance in bypass conduit 42a and is predetermined, as for example by a restricted orifice 30, in order to assure adequate fluid flow in bypass conduit 42a when Valve 76 opens.

Having thus described my invention, I claim:

l. In a carburetor for an internal combustion engine having a fuel and air induction system, a floatless fuel bowl, duct means connecting said bowl and system for supplying fuel to the latter, a fuel pump having an inlet adapted to be connected with a source of fuel and also having an outlet, inlet conduit means connecting said outlet and fuel bowl for supplying fuel to the latter upon operation of said pump, means for maintaining the fuel in said bowl at a predetermined level comprising an overflow Weir in said bowl defining at least in part a chamber adapted to receive excess fuel overflowing said weir from said bowl when the fuel in said bowl attains said predetermined level, fuel return means in communication with said chamber to drain fuel therefrom upon overfiow of excess fuel from said bowl into said chamber, a bypass duct connecting said inlet with said inlet conduit means at a location downstream of said outlet, means for prorating the fuel flow from said outlet to said fuel bowl and bypass duct including valve means in said bypass duct for controlling the fuel flow therein and thereby to control the fuel flow to said bowl, control means including a throttle valve in said system for controlling the air flow therein, and means operably connecting said control means and valve means for adjusting the latter in accordance with operation of said throttle valve to increase the fuel flow in said inlet conduit means to said fuel bowl with opening of said throttle valve.

2. In a carburetor for an internal combustion engine having a fuel and air induction system, a throttle valve in said system, a floatless fuel bowl, duct means connecting said bowl and system, a fuel pump, having an inlet and an outlet, first conduit means connecting said outlet with said fuel bowl for supplying fuel to the latter upon operation of said pump, means for maintaining the fuel in said bowl at a predetermined level comprising an overflow weir in said bowl defining at least in part a chamber adapted to receive excess fuel overflowing said weir from said bowl when the fuel in said bowl attains said predetermined level, fuel return means for returning excess fuel from said chamber to said inlet including a fuel return conduit in communication with said chamber to drain fuel therefrom upon overflow of excess fuel thereinto from said bowl, means for diverting a portion of the fuel in said first conduit means from said fuel bowl and system including bypass conduit means connecting said first conduit means with said fuel return means, means for proportioning the fuel flow from said fuel pump to said bowl and bypass conduit means including a predetermined restriction in said rst conduit means at a location between said bowl and the connection of said bypass conduit means with said first conduit means, said means for proportioning also including valve means in said bypass conduit means for controlling fuel fiow in the latter, and means responsive to engine load for adjusting said valve means comprising an operable linkage connecting said throttle valve and valve means.

3. In a carburetor for an internal combustion engine having a fuel and air induction system, a throttle valve in said system, a fioatless fuel bowl, duct means connecting said bowl and system, a fuel pump having an inlet and an outlet, first conduit means connecting said outlet with said fuel bowl for supplying fuel to the latter upon operation of said pump, means for maintaining the fuel in said bowl at a predetermined level comprising an overflow Weir in said bowl defining at least in part a chamber adapted to receive excess fuel overflowing said Weir from said bowl when the fuel in said bowl attains said predetermined level, fuel return means for returning excess fuel from said chamber to said inlet including a fuel return conduit in communication with said chamber to drain fuel therefrom upon overiiow of excess fuel thereinto from said bowl, means for diverting a portion of the fuel in said first conduit means from said fuel bowl and system including bypass conduit means connecting said first conduit means with said fuel return means, means for proportioning the fuel flow from said fuel pump to said bowl and bypass conduit means including a predetermined restriction in said first conduit means at a location between said bowl and the connection of said bypass conduit means with said first conduit means, said means for proportioning also including valve means in said bypass conduit means for controlling fuel flow in the latter, and means responsive to engine load for adjusting said valve means comprising an operable linkage connecting said throttle valve and valve means to decrease the fuel flow in said bypass conduit means progressively upon progressive opening of said throttle Valve.

4. In a carburetor for an internal combustion engine having a fuel and air induction system, a throttle valve in said system, a fioatless fuel bowl, duct means connecting said bowl and system, a fuel pump having an inlet and an outlet, first conduit means connecting said outlet with said fuel bowl for supplying fuel to the latter upon operation of said pump, means for maintaining the fuel in said bowl at a predetermined level comprising an overflow Weir in said bowl defining at least in part a chamber adapted to receive excess fuel overflowing said Weir from said bowl when the fuel in said bowl attains said predetermined level, fuel return means for returning excess fuel from said chamber to said inlet including a fuel return conduit in communication with said chamber to drain fuel therefrom upon overflow of excess fuel thereinto from said bowl, means for diverting a portion of the fuel in said first conduit means from said fuel bowl and system including bypass conduit means connecting Said first conduit means with said fuel return means, means for proportioning the fuel flow from said fuel pump to said bowl and bypass conduit means including a predetermined restriction in said first conduit means at a location between said bowl and the connection of said bypass conduit means with said first conduit means, said means for proportioning also including valve means in said bypass conduit means for controlling fuel fiow in the latter, means responsive to engine load for adjusting said valve means comprising an operable linkage connecting said throttle valve and valve means, said linkage including actuating means movable in one direction for actuating said valve means to decrease the fuel flow in said bypass conduit means progressively with progressive opening of said throttle valve, and resilient means assisting movement of said actuating means in said one direction.

5. In a carburetor for an internal combustion engine having a fuel and air induction system, a throttle valve in said system, a oatless fuel bowl, duct means connecting said bowl and system, a fuel pump having an inlet and an outlet, first conduit means connecting said outlet with said fuel bowl for supplying fuel to the latter upon operation of said pump, means for maintaining the fuel in said bowl at a predetermined level comprising an overfiow weir in said bowl defining at least in part a chamber adapted to receive excess fuel overflowing said Weir from said bowl when the fuel in said bowl attains said predetermined level, fuel return means for returning excess fuel from said chamber to said inlet including a fuel return conduit in communication with said chamber to drain fuel therefrom upon overflow of excess fuel thereinto from said bowl and also including return fuel pumping means operable in synchronism with said fuel pump, means for diverting 'a portion of the fuel in said first conduit means from said fuel bowl and system including by- `pass conduit means connecting said rst conduit means with said fuel return means, means for proportioning the fuel ow from said fuel pump to said bowl and bypass conduit means including a predetermined restriction in said rst conduit means at a location between said bowl and the connection of said bypass conduit means with said rst conduit means, said means for proportioning also including metering valve means in said bypass conduit means for controlling fuel ow in the latter, means responsive to engine load for adjusting said valve means comprising an operable linkage connecting said throttle valve and valve means, said linkage including actuating lmeans movable in one direction for actuating said valve meansY to decrease the fuel liow in said bypass conduit means progressively with progressive opening of said throttle valve, and resilient means assisting movement of said actuating means in said one direction.

References Cited in the file of this patent UNITED STATES PATENTS f

Claims (1)

1. IN A CARBURETOR FOR AN INTERNAL COMBUSTION ENGINE HAVING A FUEL AND AIR INDUCTION SYSTEM, A FLOATLESS FUEL BOWL, DUCT MEANS CONNECTING SAID BOWL AND SYSTEM FOR SUPPLYING FUEL TO THE LATTER, A FUEL PUMP HAVING AN INLET ADAPTED TO BE CONNECTED WITH A SOURCE OF FUEL AND ALSO HAVING AN OUTLET, INLET CONDUIT MEANS CONNECTING SAID OUTLET AND FUEL BOWL FOR SUPPLYING FUEL TO THE LATTER UPON OPERATION OF SAID PUMP, MEANS FOR MAINTAINING THE FUEL IN SAID BOWL AT A PREDETERMINED LEVEL COMPRISING AN OVERFLOW WEIR IN SAID BOWL DEFINING AT LEAST IN PART A CHAMBER ADAPTED TO RECEIVE EXCESS FUEL OVERFLOWING SAID WEIR FROM SAID BOWL WHEN THE FUEL IN SAID BOWL ATTAINS AID PREDETERMINED LEVEL, FUEL RETURN MEANS IN COMMUNICATION WITH SAID CHAMBER TO DRAIN FUEL THEREFROM UPON OVERFLOW OF EXCESS FUEL FROM SAID BOWL INTO SAID CHAMBER, A BYPASS DUCT CONNECTING SAID INLET WITH SAID INLET CONDUIT MEANS AT A LOCATION DOWNSTREAM OF SAID OUTLET, MEANS FOR PRORATING THE FUEL FLOW FROM SAID OUTLET OT SAID FUEL BOWL AND BYPASS DUCT INCLUDING VALVE MEANS IN SAID BYPASS DUCT FOR CONTROLLING THE FUEL FLOW THEREIN AND THEREBY TO CONTROL THE FUEL FLOW TO SAID BOWL, CONTROL MEANS INCLUDING A THROTTLE VALVE IN SAID SYSTEM FOR CONTROLLING THE AIR FLOW THEREIN, AND MEANS OPERABLY CONNECTING SAID CONTROL MEANS AND VALVE MEANS FOR ADJUSTING THE LATTER IN ACCORDANCE WITH OPERATION OF SAID THROTTLE VALVE TO INCREASE THE FUEL FLOW IN SAID INLET CONDUIT MAEANS TO SAID FUEL BOWL WITH OPENING OF SAID THROTTLE VALVE.

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