US3350072A

US3350072A - Air valve carburetor

Info

Publication number: US3350072A
Application number: US553478A
Authority: US
Inventors: Michael J Thomas
Original assignee: Ford Motor Co
Current assignee: Ford Motor Co
Priority date: 1966-05-27
Filing date: 1966-05-27
Publication date: 1967-10-31
Anticipated expiration: 1984-10-31
Also published as: DE1576545A1; GB1124555A

Description

Oct. 31, 1967 M. J/THOMAS 3,350,072

AIR VALVE CARBURETOR Filed May 27, 1966 2 Sheets-Sheet 1 will F/GZ

M/CH4EL J. THOMAS 1 NVEN TOR.

I BY

A TTO/PNEVS Oct. 31, 1967 M. J. THOMAS AIR VALVE CARBURETOR 2 Sheets-Sheet 2 Filed May 27, 1966 MICHAEL J T HUM/4S INVENTOR.

BY fm A TTO/PNEVS United States Patent 3,350,072 AIR VALVE CARBURETOR Michael J. Thomas, Sun City, Calif., assignor to Ford Motor Company, Dearborn, Mich., a corporation of Delaware Filed May 27, 1966, Ser. No. 553,478 9 Claims. (Cl. 261-39) ABSTRACT OF THE DISCLOSURE An arm connected to the air valve bears on a control member fastened to a fuel valve lever that in turn is fastened to a fuel metering rod. Movement of the air valve is transmitted through the control member and the fuel valve lever to position the fuel metering rod. Passages in the carburetor body produce a fuel-air emulsion for starting and idling the engine. A thermally responsive element positions a lever pivotally mounted on the air valve shaft so that lever opens the fuel valve at low temperatures to increase fuel flow and accordingly enrich the fuel-air ratio, while opening the air valve at higher temperatures to icnrease the air flow and correspondingly decrease the fuel-air ratio. Several adjusting points are provided in the linkage so the linkage can be adapted to different carburetors.

This invention provides an air valve carburetor for an internal combustion engine that accurately produces mixtures having the fuel-air ratios required by a variety of engine operating conditions.

The fuel-air ratio required by an internal combustion engine varies with both engine power output and temperature. A high ratio is necessary when starting the engine. For idling, the ratio decreases slightly but is still higher than the ratio required for road load power. Under road load power up to about 8O percent of engine design power, the ratio is low and is substantially constant regardless of engine air consumption. Above about 80 percent of design speed and during high power requirements at lower speeds, the ratio again increases. Low temperatures increase the ratios required for both starting and idling.

Venturi carburetors are unable to provide a substantially constant ratio for the varying air consumptions occurring during road load power output without a complicated array of fuel jets since the fuel metering force provided by a Venturi is proportional to the square of air flow. The air valve carburetor was developed to overcome this difficulty.

In air valve carburetors, fuel is discharged into an induction passage between a manually positioned throttle valve and an air valve. Air valve position is determined by the air flow rate through the induction passage to provide a substantially constant vacuum in the induction passage between the air and throttle valves. This vacuum provides a fuel metering force that is independent of the air flow rate. A fuel valve controlling the fuel discharge is connected to the air valve. The air valve position, which is proportional to the air flow rate, then determines the fuel valve position and a fuel-air ratio independent of air flow is obtained.

Difliculties arise with air valve carburetors in providing enriched fuel-air ratios for starting and idling at normal and low engine temperatures and for high power output, and a transition ratio for starting and idling at transition temperatures up to normal operating temperature. Another difliculty arises in providing air valve carburetors with means opening the air valve at engine temperatures higher than normal operating temperature to provide excess air for purging the engine of flooded conditions that may have occurred.

In the carburetor of this invention, a novel linkage arrangement permits combining features from both venturi and air valve carburetors to overcome these difficulties. The linkage arrangement comprises an air valve arm operably connected to an air valve that is rotatably mounted in the induction passage anterior to a throttle valve. A fuel valve arm is contacted by the air valve arm and is connected to a fuel valve controlling the flow of fuel through a conduit. Fuel is discharged from the conduit into the induction passage between the throttle valve and the air valve.

Metering jets in the carburetor of this invention establish a transition fuel-air ratio for idling at a transition temperature, which is a temperature below normal operating temperature but above the lowest expected ambient temperature. A thermostatic means responsive to engine temperature contacts the fuel valve arm to open the fuel valve for additional starting and idling fuel when engine temperature is low. At normal and higher than normal engine temperatures, the theromostatic means opens the air valve by contacting the air valve arm, whereby reducing the starting and idling ratios to desired values, as well as tending to prevent flooding and to permit purging the engine if flooding has occurred.

Refined versions of the carburetor of this invention provide a power enrichment means responsive to engine intake manifold vacuum that contacts the fuel valve arm to increase the fuel-air ratio for starting and high power demands. Means for adjusting conveniently the response of the fuel valve to the air valve also are provided. The adjusting means permit the same arms to be used on carburetors having widely varying flow characteristics including carburetorsof different designs.

Additional features appear in the following detailed description of the carburetor of this invention shown in the drawings in which:

FIGURE 1 is a side view of a carburetor of this invention with the throttle valve linkage removed for simplicity and part of the carburetor body and the theromostatic means in cross section;

FIGURE 2 is a top view of the carburetor;

FIGURE 3 is a cross-sectional side view taken along line 33 in FIGURE 2 to show the power enrichment means and the fuel valve;

FIGURE 4 is a cross-sectional side view taken along line 44 in FIGURE 2 to show the fuel-air emulsion passages;

FIGURE 5 is a cross-sectional end view line 55 in FIGURE 2 to show a transfer to transmit enriching fuel and leaning air to and to prevent undesirable fuel siphoning;

FIGURE 6 is a schematic side view of the air valve and fuel valve arms showing the position of a thermostatic lever at low engine temperatures and air flow; and

FIGURE 7 is a schematic side view of the air valve and fuel valve arms showing the position of the thermostatic lever at normal or higher than normal operating temperatures.

Referring to FIGURE 1, the carburetor has a main body 10 with an upper body 12 mounted thereon by conventional fasteners (not shown). Main body 10 has a passage portion 11 and a fuel bowl portion 13. A flange 14 at the lower end of main body 10 is adapted for mounting on the intake manifold of an internal combustion engine. Upper body 12 has an air horn 15 and a cover 17 with an embossment 21 running along air horn 15 into cover 17. An air induction passage or conduit 16 passes taken along passage used the emulsion through air horn portion and passage portion 11 and is adapted to register with induction passages in the intake manifold.

A throttle valve shaft 18 is pivotally mounted in portion 11, passing through the approximate center of passage 16. An air valve shaft 19 is pivotally mounted in air horn 15 passing asymmetrically through passage 16.

Attached to air horn 15. is a mounting shaft 20 substantially parallel to and in the same horizontal plane as shaft 19. Pivotally mounted on shaft 20 is a C-shaped fuel valve lever 22 (see FIGURE 2). On one side of shaft 20, lever 22 extends over the top of cover 17 where a block 23 is attached thereto by screw threads. Block 23 is threadably attached to a fuel metering rod 24. Above cover 17, lever 22 is engaged by the head 25 of a piston assembly that will be described subsequently. On the other side of shaft 20, lever 22 has a downwardly extending leg 26.

The inner surface of leg 26 has a pivotal projection 27 thereon, and a slot 28 is cut into leg 26 radially outward of projection 27.

A control member 29 is pivotally supported on projection 27 and is held in place by a threaded fastener 30 slidable in slot 28. Member 29 extends beneath shaft 19. When loosened, fastener 30 slides in slot 28 to adjust the position of member 29 relative to lever 22. Member 29 has a pad 32 on the upper surface of the end opposite its connection with lever 22.

An air valve arm 34 is attached to one end of shaft 19 on the same side of air horn 15 as member 29. Arm 34 extends downward toward member 29 and has a cam 36 at its lower end. Directly above shaft 19 arm 34 has an inward projection 38 (see also FIGURE 2).

A lever 40 is pivotally mounted on shaft 19 inside arm 34 and beneath projection 38. Lever 40 projects from shaft 19 in the opposite direction of arm 34. A downwardly extending rod 42 engages the projecting end of lever 40. Rod 42 is attached at its lower end to L-shaped operating lever 44 of thermostatic means 46. Lever 40 has a rounded projection 54 on its lower surface adjacent pad 32 of member 29 and a tang 56 on its upper surface adjacent projection 38 of arm 34.

Thermostatic means 46 is of the conventional type comprising a bimetallic element 48 having one end rigidly mounted in a housing 50 and engaging lever 44 through a connecting link 52. Further details of construction and operation of thermostatic means 46 can be found in U.S. Patent 2,862,488 which is hereby incorporated into this specification by reference.

As shown in FIGURE 2, the end of shaft 19 opposite arm 34 has an arm 58 fixed thereto and extending in the opposite direction of arm 34. Attached to the extending end of arm 58 is a tension spring 60 that has its other end anchored to body 12. An air valve 62 is attached to shaft 19 within passage 16.

Turning to FIGURE 3, a throttle valve 64 is attached to shaft 18 within passage 16. Between throttle valve 64 and air valve 62, a tube 66 projects into passage 16 from fuel bowl portion 13.

Within portion 13, a float 68 is movably mounted to admit fuel into a bowl 70 and control the level thereof by conventional means (not shown). The top of bowl 70, which serves as a fuel source, is closed by cover 17. Adjacent passage 16, a wall 72 projects downward into bowl 70 below the fuel level to form a passage 74 that communicates with tube 66. At the bottom of passage 74 is a main metering jet 76 held in place by screw threads. Jet 76, passage 74 and tube 66 form a main conduit means for flowing fuel to induction passage 16 between

valves

62 and 64. Metering rod 24 passes through cover 17 and cooperates with the metering orifice 78 in jet 76. A return spring 79 concentric with rod 24 is held between cover 17 and block 23.

On the opposite side of bowl 70, a vertical bore 80 is drilled into the top of portion 13 beneath fuel valve lever 22. A. piston 82 slidably mounted in bore 80 has a rod 84 projecting from its upper surface and passing through cover 17. Head 25 is mounted at the top of rod 84 and a spring 86 is compressed between head 25 and cover 17. A passage 88 connects the portion of bore 80 below piston 82 with passage 16 below throttle valve 64.

Means for preparing a fuel-air emulsion for starting and idling is shown in FIGURE 4. An air passage 90 is drilled in embossment 21 to communicate at the top with the atmosphere. A jet 92 is pressed into the bottom of passage 90.

Aligned in ortion 13 with passage 90 is a fuel passage 94 extending into bowl 70 below the fuel level. Threadably engaged at the bottom of passage 94 is a fuel jet 96. An emulsion passage 98 having a restriction jet 100 at its upper end is drilled in the wall between portion 13 and passage 16, and extends below throttle valve 64 where it opens into passage 16. Passage 98 communicates with

passages

90 and 94 through jet 100. The bottom of passage 98 contains a threaded idle adjustment screw 102.

As shown in FIGURE 5, a transfer passage 104 connects passage 94 below jet 100 with passage 74. Passage 104 contains an orifice 106 at its passage 74 end. FIGURE 5 also shows in more detail the assembly of fuel valve lever 22, block 23 and rod 24. Block 23 is threaded loosely into lever 22 by threaded portion 23a. Rod 24 is then threaded vertically into block 23.

Operation When the engine is being started and is idling at normal engine operating temperature, throttle valve 64 is held closed by the conventional throttle linkage (not shown) and thermostatic means 46 has moved lever 40 counterclockwise so tang 56 contacts projection 38 to open slightly air valve 62 (see FIGURE 7). At temperatures below normal operating temperature, thermostatic means 46 permits spring 60 to close valve 62 by moving lever 40 clockwise until the contact between tang 56 and projection 38 is eliminated (see FIGURE 6).

An emulsion having the transition fuel-air ratio required for idling at a transition temperature is formed by air passing through passage 90 to mix with fuel pulled up passage 94 by manifold vacuum applied through passage 98 (see FIGURE 4). Ordinarily, the transition fuel-air ratio is selected to satisfy engine idling requirements at the average ambient temperatureexpected, but it can be varied where an improvement in engine operation results. At normal temperature, the transition fuel-air ratio is reduced to the desired value by air passing air valve 62, through tube 66, orifice 106 and passage 104 to mix with the emulsion in passage 94 (see FIGURE 5). The emulsion is pulled through passage 98 into the engine induction system.

Enrichment of the idling ratios for starting is provided by the action of head 25 which is urged against lever 22 by spring 86, thereby raising rod 24. Enriching fuel is drawn through jet 76 into passage 74 and through orifice 106 and passage 100 into passage 94 where it mixes the emulsion. When the engine starts, the high manifold vacuum is applied to piston 82 via passage 88 to pull head 25 out of contact with lever 22. This lowers rod 24 to close orifice 78, thereby stopping the fuel flow through jet 76 into passage 74.

Opening throttle valve 64 to increase engine speed transmits manifold vacuum into passage 16 between valves 62 and 64 (see FIGURE 3). The pressure differential then existing across valve 62 opens the latter against the restraining force of spring 60. Spring 60 is calibrated so a partial vacuum exists in passage 16 between

valves

62 and 64 that is independent of the position of valve 64 and, consequently, of the air flow through passage 16. The partial vacuum provides a constant fuel metering force acting through tube 66 on fuel passage 74.

Referring primarily to FIGURE 1, counterclockwise movement of valve 62 is manifested by a similar move- 75 ment of arm 34. Arm 34 transmits this movement via cam 36 to member 29 which pivots lever 22 clockwise about shaft 20, thereby raising metering rod 24. Rod 24 is calibrated using conventional techniques to admit the amount of fuel into passage 74 that will result in the desired fuelair ratio for normal road load power.

One means of adjusting the fuel flow rate into passage 74 relative to the various positions of valve 62 is by selecting the proper taper of the metering tip of rod 24. An external means of accomplishing this adjustment is provided in this invention by loosening fastener 30 and pivoting member 29 about projection 27 untilthe desired relationship is attained. The surface of member 29 contacted by cam 36 can be contoured to provide additional adjustment if desired. Rotating rod 24 in block 23 provides independent adjustment of the flow stopping position of rod 24 in jet 76.

An increase in the fuel-air ratio for high power demand is provided in the carburetor of this invention by piston 82 acting on lever 22. Under normal power conditions, the high engine intake manifold vacuum is transmitted via passage 88 to the lower side of bore 80 where it urges piston 82 downward. Under these conditions, lever 22 operates substantially unalfected by piston 82. Movement of piston 82 resulting from a gradual decrease in manifold vacuum is calibrated to correspond with movement of lever 22 producing gradual increases in vehicle speed so nonactuating contact is maintained between head 25 and lever 22 for gradual increases in power demand up to about 80 percent of engine design power.

Decreased vacuum accompanying sudden power demands permits spring 86 to move head 25 into actuating engagement with lever 22, thereby raising rod 24 to increase the fuel-air ratio. The decreased vacuum that exists when the engine is operating above about 80 percent of design power acts in the same manner to increase the fuelair ratio to the required values.

Operation of the carburetor of this invention to increase the fuel-air ratio for engine starting and idling at low temperatures will now be described. At low temperatures, thermostatic means 46 acts through rod 42 to pull lever 40 downward to its low temperature position shown in FIGURE 6. In this position projection 54 contacts pad 32, thereby pivoting member 29 and lever 22 about shaft 20 to raise rod 24, overriding the elfect of head 25 during starting as desired. Additional fuel metered by rod 24 into passage 74, through orifice 106 and passage 104 to passage 94 increase the fuel-air ratio of the emulsion supplied through passage 98 to provide an enriched starting and idling mixture. Bending pad 32 relative to the main portion of member 29 provides adjustment of the low temperature fuel-air ratio.

If desired, a fast'idle cam associated with shaft 18 to open valve 64 at low temperatures can be provided to permit air for fast idling to enter the engine manifold. Spring 60 is then calibrated to permit slight opening of valve 62. Air passing valve 62 reaches the emulsion in passage 98 through tube 66 as described above (see FIG- URE and also passes by valve 64. A typical fast idle cam is shown in US. patent application S.N. 367,098, now US. Patent 3,284,062, issued November 8, 1966, which is hereby incorporated into this specification.

During hot soaking periods flooding can occur if the idle emulsion is siphoned into the engine. This is prevented by contact of tang 56 which projection 38 as shown in FIGURE 7 at normal and higher than normal temperatures. Tang 56 holds air valve 62 open during the soaking period to admit air to passage 16. Passing through tube 66, this air reaches passage 104 where it prevents siphoning of fuel through passage 98. Excess fuel vapors escape past valve 62. .During cranking after a hot soak, air passing valve 62 enters passage 94 as described above where it mixes with fuel from orifice 96 to reduce the fuel-air ratio of the emulsion passing through passage 98.

The carburetor of this invention thereby provides linkage operatively connecting the air valve with the fuel valve that permits accurate fuel-air ratios for road load operation. In addition, the linkage permits the use of jets to provide accurate starting and idling ratios at normal operating temperatures and provides means for enriching the ratios required for starting and idling at temperatures below normal operating temperature. The linkage also contains numerous adjustment features permitting the use of the same linkage elements on carburetors of widely varying designs as well as providing simple adjustments to absorb production variations.

7 It is emphasized that the invention is not limited to the exact constructions shown or described but that changes and modifications can be made Without departing from the spirit and scope of the invention as defined in the claims.

I claim:

1. A carburetor for an internal combustion engine comprising a carburetor body having an induction passage,

a throttle valve rotatably mounted in said induction passage,

an air valve attached to a shaft rotatably mounted in the carburetor body, said air valve being rotatably mounted in said induction passage anterior to said throttle valve, an air valve arm fastened to said shaft,

means positioning said air valve to maintain a substanstantially constant vacuum between said air valve and said throttle valve during road load operation of the engine,

conduit means for flowing fuel to the induction passage between the throttle valve and the air valve,

a fuel valve controlling the flow of fuel through said conduit means and operably connected to a fuel valve arm, said fuel valve arm being operably engaged by said air valve arm to position the fuel valve responsive to the position of the air valve, and

thermostatic means responsive to engine temperature comprising a lever pivotally mounted on said shaft adjacent a portion of the fuel valve arm, said lever operably contacting the fuel valve arm at low engine temperatures to open the fuel valve and contacting the air valve arm at higher engine temperatures to open the air valve.

2. The carburetor of claim 1 comprising means responsive to engine manifold vacuum contacting the fuel valve arm to increase fuel flow when manifold vacuum is low.

3.. The carburetor of claim 2 comprising means for adjusting the response of the fuel valve to the air valve.

4. The carburetor of claim 3 in which the adjusting means comprises a control member operably contacted by the air valve arm, said control member being adjustably mounted to said fuel valve arm.

5. The carburetor of claim 4 comprising means for preparing a fuel-air emulsion and passage means transmitting said emulsion to the induction passage posterior to the throttle valve.

6. The carburetor of claim 1 comprising means responsive to engine manifold vacuum contacting the fuel valve arm to increase fuel flow when manifold vacuum is low.

7. The carburetor of claim 1 comprising means for adjusting the response of the fuel valve to the air valve.

8. The carburetor of claim 1 in which the fuel valve arm is attached to said fuel valve and a control member is operably contacted by the air valve arm, said control member being adjustably mounted to said fuel valve arm to provide means for adjusting the response of the fuel valve to the air valve.

9. In an air valve carburetor for an internal combustion engine having a fuel source, a throttle valve and an air valve mounted in an air induction conduit, and a fuel metering valve mounted in a main fuel conduit connecting said fuel source with said induction conduit between said air valve and said fuel valve, means supplying fuel and air for engine idling that comprises a fuel emulsion passage opening into the induction passage below the throttle valve,

an air passage connecting the atmosphere with said fuel emulsion passage,

a fuel passage connecting said fuel source with said fuel. emulsion passage,

a transfer passage connecting said main fuel conduit downstream of said metering valve with said fuel passage,

metering means establishing a fuel-air mixture passing through said fuel emulsion passage, said fuel-air mixture having a fuel-air ratio suitable for engine idling at a transition temperature, and

thermostatic means opening said fuel metering valve at temperatures below the transition temperature to increase the fuel-air ratio of said mixture, and opening said air valve at temperatures above the transition temperature to decrease the; fuel-air ratio of said mixture.

References Cited UNITED STATES PATENTS Wolfard 261-50 Winter.

Linga.

Phillips 261-41 Rapplean 26141 Mick.

Mick 261-50 Mick.

Smith 261-50 Braun et a1. 261-60 Braun et a1. 26-150 Smith 2.6150 Braun et al 26150 HARRY B. THORNTON, Primary Examiner.

TIM R. MILES, Examiner.

Claims

1. A CARBURETOR FOR AN INTERNAL COMBUSTION ENGINE COMPRISING A CARBURETOR BODY HAVING AN INDUCTION PASSAGE, A THROTTLE VALVE ROTATABLY MOUNTED IN SAID INDUCTION PASSAGE, AN AIR VALVE ATTACHED TO A SHAFT ROTATABLY MOUNTED IN THE CARBURETOR BODY, SAID AIR VALVE BEING ROTATABLY MOUNTED IN SAID INDUCTION PASSAGE ANTERIOR TO SAID THROTTLE VALVE, AN AIR VALVE ARM FASTENED TO SAID SHAFT, MEANS POSITIONING SAID AIR VALVE TO MAINTAIN A SUSBTANSTANTIALLY CONSTANT VACUUM BETWEEN SAID AIR VALVE AND SAID THROTTLE VALVE DURING ROAD LOAD OPERATION OF THE ENGINE, CONDUIT MEANS FOR FLOWING FUEL TO THE INDUCTION PASSAGE BETWEEN THE THROTTLE VALVE AND THE AIR VALVE, A FUEL VALVE CONTROLLING THE FLOW OF FUEL THROUGH SAID CONDUIT MEANS AND OPERABLY CONNECTED TO A FUEL VALVE ARM, SAID FUEL VALVE ARM BEING OPERABLY ENGAGED BY SAID AIR VALVE ARM TO POSITION THE FUEL VALVE RESPONSIVE TO THE POSITION OF THE AIR VALVE, AND THERMOSTATIC MEANS RESPONSIVE TO ENGINE TEMPERATURE COMPRISING A LEVER PIVOTALLY MOUNTED ON SAID SHAFT ADJACENT A PORTION OF THE FUEL VALVE ARM, SAID LEVER OPERABLY CONTACTING THE FUEL VALVE ARM AT LOW ENGINE TEMPERATURES TO OPEN THE FUEL VALVE AND CONTACTING THE AIR VALVE ARM AT HIGHER ENGINE TEMPERATURES TO OPEN THE AIR VALVE.

9. IN AN AIR VALVE CARBURETOR FOR AN INTERNAL COMBUSTION ENGINE HAVING A FUEL SOURCE, A THROTTLE VALVE AND AN AIR VALVE MOUNTED IN AN AIR INDUCTION CONDUIT, AND A FUEL METERING VALVE MOUNTED IN A MAIN FUEL CONDUIT CONNECTING SAID FUEL SOURCE WITH SAID INDUCTION CONDUIT BETWEEN SAID AIR VALVE AND SAID FUEL VALVE, MEANS SUPPLYING FUEL AND AIR FOR ENGINE IDLING THAT COMPRISES A FUEL EMULSION PASSAGE OPENING INTO THE INDUCTION PASSAGE BELOW THE THROTTLE VALVE, AN AIR PASSAGE CONNECTING THE ATMOSPHERE WITH SAID FUEL EMULSION PASSAGE, A FUEL PASSAGE CONNECTING SAID FUEL SOURCE WITH SAID FUEL EMULSION PASSAGE, A TRANSFER PASSAGE CONNECTING SAID MAIN FUEL CONDUIT DOWNSTREAM OF SAID METERING VALVE WITH SAID FUEL PASSAGE, METERING MEANS ESTABLISHING A FUEL-AIR MIXTURE PASSING THROUGH SAID FUEL EMULSION PASSAGE, SAID FUEL-AIR MIXTURE HAVING A FUEL-AIR RATIO SUITABLE FOR ENGINE IDLING AT A TRANSITION TEMPERATURE, AND THERMOSTATIC MEANS OPENING SAID FUEL METERING VALVE AT TEMPERATURES BELOW THE TRANSITION TEMPERATURE TO INCREASE THE FUEL-AIR RATIO OF SAID MIXTURE, AND OPENING SAID AIR VALVE AT TEMPERATURES ABOVE THE TRANSITION TEMPERATURE TO DECREASE THE FUEL-AIR RATIO OF SAID MIXTURE.