US3174730A - Pressure carburetor - Google Patents

Description

United States Patent 3,174,739 PRESSURE CARBURETQR Edward J. Barr, Torrance, Calif, assignor to McCulloch Corporation, Los Angeles, Caiifi, a corporation of Wisconsin Filed Feb. 12, 1962, Ser. No. 172,519 4 Claims. (Cl. 261-65) This invention relates to fuel feeding systems for internal combustion engines and the like, and relates more particularly to devices or systems in which the liquid fuel is supplied thereto under super-atmospheric pressure.

While the invention has particular utility in connection with two-cycle internal combustion engines, and is disclosed in such connection, it is to be understood that its utility is not confined thereto.

Certain problems and ditliculties are involved in providing a fuel supply device which maintains a satisfactory fuel-to-air ratio over the full engine operating range, and it is an object of the present invention to provide a fuel supply or charge forming device which will solve these problems and overcome said diiiiculties.

It is another object of the invention to provide a charge forming device which maintains a satisfactory fuel-to-air ratio over the complete range of engine operation.

It is still another object of the invention to provide a charge forming device or carburetor of this character wherein the proper fuel-to-air ratio is determined by the .of this character wherein the transition from the idling range is smooth and fiat spots are eliminated.

It is still another object of the invention to provide a simplified device of this character which may be built at reasonable cost and which is capable of accurately regulating the fuel supply to maintain a proper fuel-to-air ratio through wide ranges of engine load and speed.

It is a still further object of the invention to provide a device or system of this character wherein the fuel is supplied to the nozzle at a substantially constant superatmospheric pressure and the metering of the fuel is controlled in accordance with pressures at predetermined locations in the induction passage.

The characteristics and advantages of the invention are further sufficiently referred to in connection with the following detailed description of the accompanying drawing, which represents one embodiment. After considering this example, skilled persons will understand that many variations may be made without departing from the principles disclosed, and I contemplate the employment of any structures, arrangements, or modes of operation that are properly within the scope of the appended claims.

Referring to the drawing, which is for illustrative purposes only, there is schematically shown a fuel supply system or charge forming device embodying the present invention.

Referring more particularly to the drawing, the device comprises a body having an induction passage which includes a venturi 12 therein. Anterior to the venturi is an air inlet 14 and downstream of said venturi is a throttle body section which is connected with an air fuel mixing chamber by means of a connecting chamber 20. The end of the body having the mixing chamber 18 is connected "ice to the crankcase of a two cycle internal combustion engine, not shown.

The body 10 includes a shallow recess 22 defined by a top wall 23 and an annular wall 24 normal to the top wall 23. A flexible diaphragm 25, substantially parallel to the wall 23, closes the open end of the recess 22 to thereby define a fuel chamber, said diaphragm being marginally clamped between the annular wall 24 and the upper end, as shown in the drawing, of an annular wall 26 of an intermediate plate 2% which has an upper recess 3% and a lower recess 32 separated by a partition Wall 34. Flexible diaphragm 25 serves as a movable wall separating the chamber 22 and the chamber 30.

Recess 32 has its open lower end closed by a flexible diaphragm 38 which is marginally clamped between the lower free end of the annular wall 26 and the upper free end of a wall 40 of an outer plate or cap, indicated generally at 42, cap 42 having an upwardly opening recess 44 which is closed at its upper end by the diaphragm 38 which serves as a movable wall separating the chambers 32 and 44. The intermediate plate 28 and the cap 42 are secured to the body by any suitable means such as, for example, screws, not shown.

Diaphragm 25 may be termed a wet diaphragm, since it comprises one wall of the chamber 22 which is a fuel chamber, while diaphragm 38 is a dry diaphragm.

Fuel from a pulse pump is provided by means of a conduit 48 which is connected to one end of a valve chamber or bore 50, the upper end of said bore or valve chamber having a valve seat 52. Valve chamber or bore 50 extends upwardly from the wall 23 of the fuel chamber 22 and slidably dis-posed in said bore 50 is a movable valve member 54 of polygonally shaped cross-section. The polygonally shaped cross-section of valve member 54 facilitates flow of liquid fuel along the facets of the valve body into the fuel chamber 22. There is a cone shaped tip or valve portion 56 at the inner end of the valve member 54 which cooperates with the valve seat 52 for controlling the flow of fluid from the conduit 48 into the fuel chamber 22.

The top of the fuel chamber 22 is provided with an elongated recess 60 in which is disposed a pin 61 providing a pivotal support for a lever member 62. Lever member 62 has an inverted U-shaped portion 63 receiving the pin 61. From one arm of the U-shaped portion 63 there is a horizontal portion 64, as viewed in the drawing, and an inclined portion 65 which is provided with an arcuately shaped end 66 engaging a plate '67 disposed centrally on the upper side of the diaphragm and secured thereto by any suitable well known means. The opposite side of the diaphragm 25 is provided with a plate 68 similarly secured to said diaphragm. The upper end of a pin 69 engages the plate 68 and said pin is slidably received in a bore '70 provided therefor in the partition 34 of plate 28. The lower end of pin 69 is engaged by a plate 71 secured to the upper surface of the dry diaphragm 38, there being a plate 72 secured to the opposite side of said diaphragm.

Lever 62 has a second horizontal portion '74 which extends beneath the valve member 54, said valve member having a rounded lower end portion 75 operably engaged by the lever portion 74. Body 10 also is provided with a bore 76 which extends upwardly from the top of the fuel chamber 22 and in which is disposed a spring 77 which reacts between the upper end of the bore 76 and the horizontal portion 64 of the lever 62 to urge the lever in the clockwise direction on pivot pin 61 and thereby urge the valve member 54 in the closing direction.

Fuel is supplied to the induction passage of the carburetor from a fuel jet or nozzle 80 which is connected with the fuel chamber 22 by means of a conduit 81. The fuel supplied to the jet 80 through the conduit 81 is controlled by a needle valve 82 having an externally V threaded body 83 threadably received in a tapped bore 84 in a boss 85 of the body 10. The inner end of the body 83 of the needle valve isprovided with a cone shaped tip 86 which extends into a portion ofthe conduit 81. The outer or free end of the body 83 is provided with a slotted head 87 whereby the valve 82 may be turned to move the tip 86 in the conduit 81 and vary' the effective size thereof and thereby determine the quantity of fuel delivered to the jet or nozzle 80. There is an air-bleed passage 88 in the boss 85 whereby atmospheric air is supplied to the fuel passage 81 downstream of the tip 86 of the needle valve 82.

Chambers 30 and 44 are vented to atmosphere by means of passages 90 and 91, respectively. The dry chamber 32 above the dry diaphragm is connected with the induction passage by an air passage 92 and a branch passage 93 connected to the induction passage at the I throat 94 of the venturi 12.

There is means for modifying the value of the. suction transmitted from the venturi throat 94 to the dry diaphragm chamber 32 and said means comprises a pair of ports 98 and 99 positioned respectively upstream and downstream of the trailing edge of a butterfly valve member 100 when said valve member is in the closed position. Valve member 100 is operably mounted on a valve shaft 101 which is connected to any suitable control mechanism, not shown. Parts 98 and 99 are connected to a chamber 102 which has a connection 103 with the conduit 92.

There is means for regulating the modifying action on the suction to the chamber 32, said means comprising a needle valve 105 having an externally threaded body or stem 106 threadably disposed in a tapped opening 107 provided therefor in the body 10. The inner end of the body 106 is provided with a cone-shaped tip 108 which extends into the passage 103 at its point of connection with the chamber 102, said cone cooperating with a valve seat 109 provided therefor at the junction of said conduit or passage 103 and the chamber 102. The outer or free end of the valve 105 is provided with a slotted head 110 whereby said valve may be rotated to vary the position of the tip 108 relative to the valve seat 109 which thereby provides a variable orifice.

The usual reed valve 115 is operably positioned at the outlet of the fuel-air mixing chamber 18.

In operation the pin 70 provides a. connection between the wet and dry diaphragm 25 and 38, respectively, so that suction signals from theinduction passage of the carburetor are transmitted from the dry to the wet diaphragm.

More particularly, whenthe throttle or butterfly valve 100 is at the idling position, as shown in the drawing, there is relatively low pressure at the discharge side of said throttle valve and substantially atmospheric pressure at the upstream or anterior side of said valve. Thus, the suction on port 99 is relatively high with air bleeding into the air metering system through connections or ports 99 and 93, which reduces the effective force of the signal transmitted to the chamber 32.

The suction transmitted to the chamber 32 through the air metering system causes a reduction of pressure in said chamber 32 so that atmospheric pressure in the chamber 44 at the opposite side of diaphragm 38 causes said diaphragm to move upwardly and said upward movement is transmitted through the pin 70 to the dry diaphragm 25. Such upward movement of the diaphragm 25 forces an additional amount of fuel to the fuel nozzle 80 and simultaneously actuates the lever'62 in a counterclockwise direction to effect proper opening of the fuel valve 54.

Upon opening movement of the throttle valve 100 from the idling position, the lower edge of said valve reaches a point adjacent port 98 which reduces bleeding of air into the signal system through said port, since said port is now at least partially subjected to the lower pressure or higher suction donwstream of the valve 100. When the lower edge of the valve 1% reaches the above described open position there is a reduction of pressure at the downstream side of said valve and hence on said port 99. Upon opening of the valve the speed of the engine will increase causing an increase in air flow through the venturi 12 and effect a lowering of the pressure or increase of the suction on the conduit or passage 93. The net result is an increase in the strength of the signal to the chamber 32 and an increase in the amount of fuel discharged by the fuel nozzle in accordance with the amount of air drawn through the induction passage, including the mixing chamber 18.

At Wide open throttle there is suction at the ports 98 and 99 and at the entrance to the passage 93. The suc-' tion at the throat 94 of the venturi 12 constitutes the major source of signal strength because of the increase in air flow, and hence drop in pressure at the throat of the venturi, and the reduction of manifold vacuum at the ports 98 and 99. With the throttle in the full open position a signal system is responsive to the air flow through the induction passage and primarily through the throat of the venturi 12.

As the throttle valve moves toward the closed position the pressures transmitted to the chamber 32 through the ports 98, 99 and the passage 93, will occur in the reverse sequence from that hereinabove described.

It has been found that with the foregoing arrangement a suitable fuel-to-air ratio is provided throughout the range of engine operation and the fuel-to-air ratio is pre cisely tailored to the demands of the engine under such conditions.

The invention and many of its attendant advantages will be understood from the foregoing description and it Will be apparent that various changes may be made in the form, construction and arrangement of parts of the invention without departing from the spirit and scope thereof or sacrificing its material advantages, the arrange ment hereinbefore described being merely for purposes of illustration.

I claim: I

1. A pressure carburetor comprising: a body having an induction passage therethrough, said induction passage including an air inlet portion, a venturi receiving air from said air-inlet portion and having a throat of restricted diameter, a throttle valve portion, an enlarged air-and fuel mixing chamber at the outlet end of said induction passage said mixing chamber being enlarged relative to the portion of said induction passage containing said throttle valve, and a recess; a butterflly throttle valve in said throttle valve portion; a wet diaphragm closing one side of said recess to define a fuel chamber, said dia phragm having top and bottom discs secured centrally thereto; a plate having top and bottom recesses, said plate being attached to said body and marginally securing the wet diaphragm so that said diaphragm forms a movable wall between the fuel chamber in the body and an atmospheric chamber defined by one of the recesses in said plate and said diaphragm, a partition in said plate dividing said chambers therein; a dry diaphragm closing the opposite recess of said plate and defining there- With a variable air pressure chamber; said dry diaphragm having discs secured thereto at the center thereof; a cover having a recess therein secured to the plate and marginally securing the dry diaphragm to said plate, the recess in said cover being at the opposite side of said variable pressure chamber and defining an atmospheric chamber; means operably interconnecting said diaphragms so that movement of either diaphragm toward the other will effect corresponding movement of said other diaphragm; said body having a fuel inlet for fuel under super atmospheric pressure; said inlet including a valve 7 chamber; a multi-sided fuel valve in said valve chamber, said fuel valve controlling the inflow of fuel to the fuel chamber; a fuel valve control lever pivotally mounted in the fuel chamber and having one end engaging the upper disc of the wet diaphragm and the opposite end operably engaging the fuel valve; spring means urging the lever in a direction to effect closing movement of the fuel valve and constituting the sole spring means acting on said fuel valve; means defining a main fuel nozzle for discharging fuel into the enlarged air-and-fuel mixing chamber, said main nozzle being connected with the fuel chamber; variable orifice means including a manually adjustable needle valve having a tip controlling the fuel flow to the main fuel nozzle; air-bleed passageway means connecting the main nozzle with atmosphere; air signal pressure means comprising passageway means having one end connected with said air pressure chamber, chamber means, orifice means providing the sole communication between said chamber means and said passageway means, needle valve means in said orifice means for selectively varying said communication between said air pressure chamber and said passageway means, connection means providing communication between said passageway means and said induction passage at the throat of said venturi, and additional connection means providing communication between said chamber means and said induction passage at opposite sides of the trailing edge of said throttle valve and adjacent thereto when said throttle valve is in the closed position; and an outwardly opening reed valve at the outflow end of the induction passage.

2. In a pressure carburetor for an internal combustion engine: a body having an induction passage therethrough, said induction passage including a venturi having a throat; a butterfly throttle valve in said induction passage posterior to said venturi; a flexible wet diaphragm; means defining a fuel chamber at one side of said diaphragm and an atmospheric chamber at the other side of said wet diaphragm, said diaphragm forming a movable wall between the fuel chamber and said atmospheric chamber; a dry diaphragm axially aligned with said wet diaphragm; means defining a signal pressure chamber at one side of said dry diaphragm and an atmospheric chamber at the other side of said dry diaphragm, said dry diaphragm forming a movable wall between said signal pressure chamber and the last mentioned atmospheric chamber; an operable connection between said diaphragm; means defining a fuel inlet passage for said fuel chamher, said inlet passage including a valve chamber; a multisided fuel valve in said valve chamber, said fuel valve controlling the inflow of fuel to the fuel chamber; a fuel valve control lever pivotally mounted in the fuel chamber and having one end engaging the wet diaphragm and the opposite end operably engaging the fuel valve; spring means urging the lever in a direction to effect closing movement of the fuel valve, said spring means automatically effecting closing of said fuel valve when said engine is not in operation; means defining a main fuel nozzle for discharging fuel into the induction passage downstream of the throttle valve, said main nozzle being connected with the fuel chamber and having an air-bleed from atmosphere; air signal pressure means comprising passageway means having one end connected with said signal pressure chamber, chamber means, orifice means providing the sole communication between said chamber means and said passageway means, needle valve means in said orifice means for selectively varying said communication between said chamber and said passageway means, connection means providing communication between said passageway means and said induction passage at the throat of said venturi, and additional connection means providing communication between said chamber means and said induction passage at opposite sides of the trailing edge of said throttle valve and adjacent thereto when said throttle valve is in the closed position; and an air-and-fuel mixing chamber at the outlet end of said induction passage, said mixing chamber being enlarged relative to the portion of said induction passage containing said throttle valve, with said main fuel nozzle being disposed to discharge fuel into said enlarged mixing chamber.

3. In a pressure carburetor: a body having an induction passage therethrough with an enlarged air-fuel mixing chamber at the outlet end, said induction passage including a venturi having a throat; a butterfly throttle valve in said induction passage posterior to said venturi; said mixing chamber being enlarged relative to the portion of said induction passage containing said throttle valve; a flexible wet diaphragm; means defining a fuel chamber at one side of said diaphragm and an atmospheric chamber at the other side of said wet diaphragm, said diaphragm forming a movable wall between the fuel chamber and said atmospheric chamber; a dry diaphragm axially aligned with said wet diaphragm; means defining a signal pressure chamber at one side of said dry diaphragm and an atmospheric chamber at the other side of said dry diaphragm, said dry diaphragm forming a movable wall between said signal pressure chamber and the last mentioned atmospheric chamber; an operable connection between said diaphragm; means defining a fuel inlet passage for said fuel chamber, said inlet passage including a valve chamber; a fuel valve in said valve chamber, said fuel valve controlling the inflow of fuel to the fuel chamber; a fuel valve control lever pivotally mounted in the fuel chamber and having one end engaging the wet diaphragm and the opposite end operably engaging the fuel valve; spring means urging the lever in a direction to effect closing movement of the fuel valve; means defining a main fuel nozzle for discharging fuel into the enlarged air-fuel mixing chamber of the induction passage, downstream of the throttle valve, said main nozzle being connected with the fuel chamber and having an air-bleed from atmosphere; and air signal pressure means comprising passageway means having one end connected with said signal pressure chamber, chamber means, orifice means providing the sole communication between said chamber means and said passageway means, needle valve means in said orifice means for selectively varying said communication between said chamber and said passageway means, connection means providing communication between said passageway means and said induction passage at the throat of said venturi, and additional connection means providing communication between said chamber means and said induction passage at opposite sides of the trailing edge of said throttle valve and adjacent thereto when said throttle valve is in the closed position.

4. In a charge forming device for internal combustion engines: means defining an induction passage including a venturi having a throat; a throttle valve in said induction passage posterior to said venturi; a flexible wet diaphragm; means defining a fuel chamber at one side of said diaphragm and an atmospheric chamber at the other side of said wet diaphragm, said diaphragm forming a movable wall between the fuel chamber and said atmospheric chamber; a dry diaphragm axially aligned with said wet diaphragm; means defining a signal pressure chamber at one side of said dry diaphragm and an atmospheric chamber at the other side of said dry diaphragm, said dry diaphragm forming a movable wall between said signal pressure chamber and the last mentioned atmospheric chamber; an operable connection between said diaphragms; means defining a fuel inlet for said fuel chamber; a fuel valve controlling the fiow of fuel into the fuel chamber; connecting means between the wet diaphragm and said fuel valve; yielding means urging the fuel valve in the closing direction and effecting closing of said valve when the engine is not running; means defining an air-bled main fuel nozzle connected with the fuel chamber and discharging fuel into the induction passage downstream of the throttle valve; and air signal pressure means comprising passageway means having one varying said communication between said chamber and said passageway means, connection means providing communication between said passageway means and said 1nduction passage at the throat of said venturi, and additional connection means providing communication between said chamber means and said induction passage at opposite sides of the trailing edge of said throttle valve and adjacent thereto when said throttle valve is in the closed position; and an air-and-fuel mixing chamber at the outlet end of said induction passage, said mixing chamber being enlarged relative to the portion of said induction passage containing said throttle valve, with said main fuel nozzle being disposed to discharge fuel into said enlarged mining chamber.

References Cited in the file of this patent UNITED STATES PATENTS 2,447,791 Barford Aug. 24, 1948 2,722,208 Conroy et a1 Nov. 1, 1955 2,774,582 Bracke Dec. 18, 1956 2,779,576 Morgenroth Jan. 29, 1957 2,841,372 Phillips July 1, 1958 FOREIGN PATENTS 577,770 Great Britain May 30, 1946

Claims (1)

1. 4. IN A CHARGE FORMING DEVICE FOR INTERNAL COMBUSTION ENGINES: MEANS DEFINING AN INDUCTION PASSAGE INCLUDING A VENTURI HAVING A THROAT; A TROTTLE VALVE IN SAID INDUCTION PASSAGE POSTERIOR TO SAID VENTURI; A FLEXIBLE WET DIAPHRAGM; MEANS DEFINING A FUEL CHAMBER AT ONE SIDE OF SAID DIAPHRAGM AND AN ATMOSPHERIC CHAMBER AT THE OTHER SIDE OF SAID WET DIAPHRAGM, SAID DIAPHRAGM FORMING A MOVABLE WALL BETWEEN THE FUEL CHAMBER AND SAID ATMOSPHERIC CHAMBER; A DRY DIAPHRAGM AXIALLY ALIGNED WITH SAID SET DIAPHRAGM; MEANS DEFINING A SIGNAL PRESSURE CHAMBER AT ONE SIDE OF SAID DRY DIAPHRAGM AND AN ATMOSPHERIC CHAMBER AT THE OTHER SIDE OF SAID DRY DIAPHRAGM, SAID DRY DIAPHRAGM FORMING A MOVABLE WALL BETWEEN SAID SIGNAL PRESSURE CHAMBER AND THE LAST MENTIONED ATMOSPHERIC CHAMBER; AN OPERABLE CONNECTION BETWEEN SAID DIAPHRAGMS; MEANS DEFINING A FUEL INLET FOR SAID FUEL CHAMBER; A FUEL VALVE CONTROLLING THE FLOW OF FUEL INTO THE FUEL CHAMBER; CONNECTING MEANS BETWEEN THE WET DIAPHRAGM AND SAID FUEL VALVE; YIELDING MEANS URGING THE FUEL VALVE IN THE CLOSING DIRECTION AND EFFECTING CLOSING OF SAID VALVE WHEN THE ENGINE IS NOT RUNNING; MEANS DEFINING AN AIR-BLED MAIN FUEL NOZZLE CONNECTED WITH THE

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