US3272488A

US3272488A - Carburetor

Info

Publication number: US3272488A
Application number: US332466A
Authority: US
Inventors: James T Bickhaus
Original assignee: ACF Industries Inc
Current assignee: ACF Industries Inc
Priority date: 1963-12-23
Filing date: 1963-12-23
Publication date: 1966-09-13
Anticipated expiration: 1983-09-13

Description

Sept. 13, 1966 J. T. BICKHAUS CARBURETOR 2 Sheets-Sheet 1 Filed Dec. 25 1963 INVENTOR. JAMES T. BICKHAUS AGENT Sept. 13, 1966 J. T. BICKHAUS CARBURETOR Filed Dec. 25 1963 2 Sheets-Sheet 2 FIG.2=

INVENTOR. JAMES T BICKHAUS AGENT United States Patent 0 3,272,488 CARBURETQR James T. Bickhaus, Granite City, 11]., assignor to ACE Industries, Incorporated, New York, N.Y., a corporation of New Jersey Filed Dec. 23, 1963, Ser. No. 332,466 4 Claims. (Cl 261-39) This invention relates to improvements in carburetors for internal combustion spark ignition engines, and particularly to an improvement in the application of temperature compensation to a carburetor in which an airflow responsive air valve mechanism is operative in the air flowing upstream of the fuel nozzle outlets in the mixture conduit to create a degree of depression causing fuel dis charge into the air stream of the mixture conduit passing the throttle valve.

It is well understood in the art that temperature can have a direct effect on engine starting and running. At ambient temperatures below the middle seventies Fahrenheit, a cold start requires a richer fuel mixture than a restart at normal engine operating temperatures. The degree of enrichment required to get an engine to tire and run increases with decreasing engine and ambient temperatures. Likewise, a successful cold start at temperatures below the middle seventies requires a higher maximum engine speed setting of the carburetor. After starting, an increase in the minimum engine speed setting of the carburetor is also required to maintain a stable engine idle during an engine warm-up period. operating temperature approaches the normal range for an engine, this limit on minimum engine speed setting can be gradually decreased as well as the degree of fuel mixture ratio enrichment.

These engine requirements for cold start and run operation were directly responsible for the development of the present automatic choke mechanisms for plain tube carburetors. The thermostatically controlled choke valve with modulation of valve position by engine suction provided the necessary enrichment in fuel-to-air ratio required for both cold start and warm-up. The fast idle mechanism which is a part of every choke mechanism provides proper carburetor setting for cold start and the necessary increase in carburetor engine speed control to produce a stable engine idle speed for warm-up.

Temperature compensation as applied to an air valve type of carburetor will depend to some extend upon its mode of operation as well as its particular construction. Herein described is an air valve type of carburetor having a movable air flow responsive valve means acting as a variable air flow restriction at the inlet of a mixture conduit and a variable fuel metering restriction or jet in the high speed nozzle circuit operated directly by movement of the movable air valve means. These two flow metering devices (air flow and fuel flow) are so connected that as the air valve opens, indicating an increase in air flow through the mixture conduit, the variable fuel metering restriction is operated to increase fuel flow to the mixture conduit. The discharge from the high speed nozzle circuit opens in the mixture conduit downstream of the air flow responsive valve means, but upstream of the manually operated throttle valve so that when the throttle valve opens, the air flow responsive valve means becomes a flow restriction causing a depression on its downstream side sufficient to produce a desired velocity in the fuel flow past the variable fuel metering restriction or jet. The fuel passing the metering restriction or jet is discharged into the air stream in the mixture conduit through the main or high speed fuel nozzle. This rate of fuel flow through the variable fuel metering restriction depends upon the degree of depression created in the mixture conduit by the amount of air flow restriction effected by the air valve.

As the engine 3,272,488 Patented Sept. 13, 1966 Consequently, it would be readily apparent that an air valve carburetor could be calibrated such that the degree of depression varied the rate of air flow and the mixture ratio was primarily a function of the depression created by the air valve, or, the degree of depression effected by the air valve was constant over the movable range of the air valve and the mixture ratio was primarily a function of change in size of the variable fuel metering restriction effected by movement of the air valve. This invention applies to air valve type carburetors which combine these two modes of operation.

In the air valve type carburetor herein described, there is provided a conventional low speed circuit for metering fuel at the minimum setting of the throttle valve. To avoid interference with the function of the low speed fuel metering circuit, the air valve is stopped in the minimum closed position in which it has no effect on air flow in the idle and off idle throttle positions of engine operation. This minimum closed position or datum position for the movable air valve means is twenty-thirty degrees open.

In a carburetor, such as above described, there is but one main metering point (neglecting air bleeds) in the high speed fuel circuit which is the variable fuel metering restriction, or in this case, a metering rod. The same applies to the conventional low speed circuit. Once these circuits are properly calibrated to deliver the right mixture ratio to run an engine at normal operating temperature for that engine, the metering should not be changed. A car buretor when so calibrated will not start an engine at lower than normal engine operating temperatures satisfactorily, nor would it keep the engine running until normal engine operating temperatures are reached even if it were once started. Accordingly, it is one of the objects of this invention to provide a temperature compensator for the starting fuel mixture ratio in a carburetor of the air valve type described.

It is still a further object of this invention to provide a novel carburetor which will produce a good cold start, smooth engine operation during the subsequent warm-up period.

It is still another object of this invention to incorporate into an air valve type of carburetor a novel temperature compensator to provide the proper enrichment of the mixture ratio for cold start and warm-up of an engine.

In accordance with these objects of the invention, the carburetor is provided with means indicating the temperature of the engine and means responsive to this engine temperature indicating means for changing the air valve datum position and the air valve response so as to tend to decrease the rate of air flow past the throttle during engine cranking and subsequent start and run. Means are also provided for increasing the rate of fuel supply to the fuel circuits in accordance with the movement of the air valve from the datum position setting at normal operating temperatures for the engine. The last said means may be, in .part at least, a mechanical linkage connected with a fuel valve to change the carburetor setting for engine cranking and warm-up after a cold start.

Other objects and advantages of this invention will appear from the following description which is in such clear, concise and exact terms as will enable any person skilled in the art to make and use the same when taken in conjunction with the accompanying drawings, forming a part thereof, and in which: FIGURE 1 is a schematic illustration partly in section illustrating a carburetor equipped with a temperature compensator mechanism in accordance with the invention and in which the parts of the carburetor are illustrated in the position for minimum idle speed and for normal engine operating temperature; and

FIGURE 2 is an enlarged schematic illustration of the J carburetor of FIGURE 1 with parts in section illustrating the temperature compensator mechanism with the parts of the carburetor in a position for cold engine start.

Turning now to the exemplary mechanisms shown in the drawings, FIGURE 1 schematically illustrates a carburetor having a body 1 provided with a through passage 2 forming a mixture conduit extending from an air horn section 3 to the discharge outlet of the mixture conduit which is surrounded by flange 4 fixed to engine E. The discharge outlet of the mixture conduit 2 is connected with the inlet of an engine intake manifold M, provided with a mounting pad on which the flange 4 is seated and to which the flange 4 is secured by studs, or the like, all in a well-known manner.

The body 1 of the carburetor is formed with an integral fuel bowl 6 having a fuel supply inlet 7. A fuel line 9 has a threaded connection with the fuel supply inlet 7 and with a fuel pump P and fuel .tank T. inlet 7 is thereby connected to a source of fuel under pressure in line 9. A needle valve mechanism 11 of conventional construction, controls the flow of fuel through inlet 7 into fuel bowl 6. Actuation of the needle valve 11 is by a float 13 mounted on a float lever 14 which is in turn pivoted in the fuel bowl at 16 and has an end bearing against the movable valve part of the needle valve mechanism 1 1. The setting of the needle and float is such as to limit the maximum depth of fuel in the fuel bowl 6 and maintain the fuel metering restrictions or jets 19 and 20 in the bottom of the fuel bowl completely submerged in fuel at all times.

Fuel passage 22 is supplied with fuel from the fuel bowl 6 by way of jet 19, all of the time, and, by way of jet 20 under certain engine temperature conditions as will later appear. A fuel well 24 is supplied with fuel through the passage 22. In the fuel well 24 is a vent tube 25 (FIGURE 2) forming a part of the main, or high speed, fuel circuit. In this particular case, the vent tube 25 has perforated walls and an expanded lower end press fitting inside the fuel well 24. The upper open end of the vent tube 25 connects with a passage 27 in the main fuel nozzle 28. Pairs of outlets 29 and 30 provide for discharge of fuel from the passage '27 into the mixture conduit 2 from the main, or high speed, nozzle 28. As pointed out heretofore, the vent tube 25 has perforated walls forming air bleeds for. the main nozzle which are supplied by a vent passage 32 communicating with atmosphereic pressure in fuel bowl 6.

Within the vent tube 25 and concentric therewith is an idle tube 33 projecting below the fuel =level in the well 24. The upper end of the idle tube 33 has a press fit connecting it with fuel passage 35 which in turn delivers fuel to vertical passage 37 extending through the wall of the carburetor body from the air horn section 3 to a fuel port 39 located above the edge of throttle 40 when the throttle is closed to the idle setting. Below the throttle is a fuel port 41 controlled by a needle valve 43 and also supplied from the vertical passage 37. Vertical passage 37 has an inside vent opening in the mixture conduit 2 at 44 and passage 35 has a similar atmospheric vent extending from an opening 45 in the mixtrue conduit through passage 46 and metering restriction 47 to connect with passage 35 supplying fuel in the low speed circuit. Economizer metering restriction 48 in the passage 35 is fed an emulsion of fuel and air supplied respectively by the idle tube 33 and the vent 4 5. This emulsion is further agitated by air through vent 44 and restriction 50 before it is discharged from ports 39 and 41. These elements, just described, comprise the low speed, or idle fuel circuit, for the carburetor.

The rate of discharge of fuel and air to the engine is under control of the throttle 40 pivotally mounted by a throttle shaft 52. A compound lever 53 fixed on the end of the throttle shaft 52 has one arm apertured at 54 to connect with a throttle actuating linkage 51. Another arm 55 carries an adjustable idle screw 56 hearing against the lower step of a fast idle cam 58. A stud 63 fixed to the carburetor body rot-atably carries the fast idle cam 58 and also rotatably mounts a compound lever 61 carrying a lug 60. The eccentricity of the fast idle cam 58 biases the fast idle cam 58 counterclockwise as seen in FIGURE-S 1 and 2 and places cam 58 into engagement with the lug 60 extending from lever 61 into the path of rotation of cam 58.

On the throttle lever 53 is a shoulder 65 which travels in an arcuate path on actuation of the throttle valve 40 to contact the lower end of a rod 67 guided for reciprocating movement on the body of the carburetor 1 by fixed bearings 69. The upper end of rod 67 is positioned to engage with a crank arm 71 fixed to air valve shaft 73 which is rotatable in bearings in opposite sides of the mixture conduit 2. Air valve 75 is eccentrically mounted on the rotatable shaft 73 so as to rotate therewith and, because of its eccentricity, is aerodynamically unbalanced to open in response to air flow through the mixture conduit 2 from the air horn 3 to its discharge outlet.

Fixed to a free end of the shaft 73 is a compound lever 78. One arm of the compound lever 78 connects with rod 79 of an air motor 80. Within the air motor casing is a flexible diaphragm 81. Backing plates 82 on opposite sides of the diaphragm 81 are secured to the rod 79 between a shoulder and a headed over end of the rod 79 which clamps the plates against the opposite sides of the diaphragm 81. A low rate coil spring 84 is compressed between backing plates 82 and the end of the motor casing to bias the rod 79 in a direction to close the air valve 75. Rod 79 projects through a suitable aperture 86 in the casing wall of the motor which provides for atmospheric pressure to enter the casing of the motor 80 on the right hand side of the diaphragm 81, as shown. The opposite end of the casing is connected to a suction line 88 with a pair of

branched passages

89 and 90 which lead anterior to and posterior of the throttle 40. In each

branch passage

89 and 90 is a suitable metering restriction 89a and 90a respectively to prevent an unrestricted air flow to and from the mixture conduit 2 around the throttle 40. The metering restriction in each

branch

89 and 90 creates a pressure gradient therebetween, which pressure gradient in turn is communicated to the diaphragm 81 to operate the air motor 80 and adjust the position of the air valve 75. The pressure difference sensed on opposite sides of the diaphragm 81 is balanced against the spring force 84 to determine the air valve position. If this pressure difference is greater than spring resistance, air valve 75 will be displaced from its datum position, as shown in FIGURE 1, towards an open position. As will be apparent from inspection of FIGURE 1 branch passage 89 has an outlet connection which will sense the depression created by the air valve 75 in the mixture conduit 2 and branch passage 90 has an outlet in the mixture conduit 2 which will sense the depression created by both air valve 75 and throttle valve 40.

Movement of the compound lever 78 in response to the change in position of air valve 75 is communicated directly to metering rod 95, to move the metering rod with respect to the jet 19. As the air valve 75 opens, the cylindrical step 96 will move into the jet 19 reducing the flow capacity of this jet until the air valve 75 opens far enough so that the stepped cylindrical portion 97 moves into the jet to increase the capacity of the jet 19. This is a two step metering rod which in operation cuts down the flow of fuel as the air valve opens to a position corresponding to part throttle road load operation of the engine and then increases the fuel flow above these throttle positions for full power, or full speed engine operation.

The structure of the carburetor, so far described, is entirely suitable for operating a spark ignition internal combustion engine at normal engine operating temperatures or, at ambient temperatures above the middle seventy range Fahrenheit.

Since under hood temperatures in the modern automobile are often excessive, in the sense that they exceed the boiling point of the fuel, it is often desirable to provide a hot idle compensator. Such a device is shown schematically in FIGURE 1 in operative condition, The hot idle compensator comprises a passage 101 which forms an atmospheric bleed extending around both the air valve 75 and the throttle 40. The inlet of this bypass 101 is controlled by a valve 102 mounted on a thermostatic strip 104 positioned to be responsive to under hood temperatures, such as those in the mixture conduit 2 anterior of the air valve 75. The thermostatic strip 104 is anchored at one end to a structure 105 stationary with re spect to the inlet of the bypass 101. At high temperatures, thermostat strip 104 responds opening the valve 102 a predetermined degree so as to bleed air into mixture conduit 2 and thereby lean out the idle mixture being delivered through the low speed system of fuel metering.

The invention here is primarily concerned, however, with the application of low temperature compensating means as applied to an air valve carburetor of the class described. The particular construction of the temperature compensating means and its application is described as follows. Connected to the body 1 of the carburetor is a closed cylindrical housing 110 containing an inlet connection 111 and an outlet connection 112 opening in the mixture conduit 2 and posterior of the throttle plate 40. Inlet connection 111 is supplied through a conduit 113 with heated air from a stove S located on, or adjacent, the exhaust manifold EM of the engine or a heated water jacket thereof. Hot air is drawn by manifold vacuum from this stove through the inlet 111, through the cylindrical casing 1111 and into the mixture conduit 2 through the passage 112.

The casing 111 has a cover, and this cover has a central inwardly protruding boss 114 slotted to receive one end of a thermostat spring 115. The opposite end of thermostat spring 115 has a bent end received in a slot within an arm 116, which arm is fixed on a shaft 117 rotatable in the opposite end of the cylindrical casing 110. Actually, the boss 114 and the shaft 117 are axially aligned, but are shown here displaced to facilitate the illustration. Thermostat strip, or spring, 115 is so constructed that as temperature is increased it tends to wind up thus rotating the shaft 117 in a counterclockwise direction, as viewed in FIGURE 1. As the spring 115 senses lower temperatures, it unwinds producing clockwise rotation of the shaft 117. Circulation from the stove through the casing 111) depends upon engine operation, consequently, when the engine is not running, the thermostat 115 senses ambient temperatures. When these ambient temperatures are in the range of the middle seventies, or higher, the position of the parts in the temperature compensating mechanism is represented by FIGURE 1. On the other hand, when the engine is not running, no heat will be delivered from the stove to the casing 110 and the temperature sensed by the thermostat 115 will eventually stabilize close to ambient temperatures. Especially is this so if the engine has been stopped an appreciable length of time of several hours. Should these ambient temperatures sensed be below the middle range of the seventies Fahrenheit, the position of the parts affected by the thermostat 115 will be in some degree such as that shown in FIGURE 2.

As shown in FIGURE 2, shaft 117 extends into a second closed housing 124. The thermostat spring 115 is unwound from the position shown in FIGURE 1 and shaft 117 has been rotated clockwise. This movement of the shaft 117 opens a valve 120 in a metering restriction 121. Air in casing 124 is at atmospheric pressure through an inlet 123 into the casing 124. The casing 124 communicates with the motor 80 through restriction 121, the bypass passage 126, which connects with passage 88 as shown in the figures. The degree of metered opening between the metering valve 120 and its restriction 121 is sufficient to effect a change in displacement of the air valve for a given rate of air flow through the mixture conduit 2 as compared with the displacement of the air valve 75 in response to the same rate of air flow at normal operating temperatures of the engine.

The ambient temperatures sensed by the thermostat spring when the engine is stopped also changes the minimum closed or datum position of the air valve 75 due to the rotation of the shaft 117 in a clockwise direc-.

tion. This change in datum position is effected by an arm, or lever, 128 rotated with the shaft 117 in a clockwise direction which in turn through intermediate link 13%) causes rotation of control arm 132 in a clockwise direction. The aforementioned lug 71 on the air valve shaft 73 extends over the upper surface of control arm 132 as well as being aligned with the end of the .rod 67. Control arm 132 therefore sets the datum position of the air valve 75 by limiting its closing movement and, as shown in FIGURE 2, when rotated to the position of the parts corresponding with the low temperature sensed by the thermostat 115, it will permit closing of the air valve 75 from its position, shown in FIGURE 1, where it is twentythirty degrees open. Rotation of the arm, or lever, 128 clockwise simultaneously operates through link 129 connected to lever 61 to rotate the compound lever 61 in a like direction so that the lug 60 raises the fast idle cam 58 so that the outer steps of the fast idle cam 58 prevent throttle closing by engagement with the idle set screw 56.

As the lever 61 rotates clockwise, and in accordance with the invention, it moves rocker arm 134 through connecting link 135 connected to lever arm 61b. Metering rod 136 pivoted on the rocker 134 has a tapered end 138 which is withdrawn from the jet 20 opening the jet 20 to the passage of fuel in an amount depending upon the displacement of the shaft 117 by the temperature sensing thermostat spring 115. This withdrawal of the metering rod 136 from the jet 20 has the same, or similar, effect as if the size of metering jet 19 had been increased while the metering rod 95 remains constant in size. The metering rod 136 is further provided with a tapered end portion 133 and a conical shoulder 141). Jet 20 is provided with a central passage 142 which cooperates with tapered portion 138 to regulate flow of fuel in accordance with temperature.- A conical surface 144 above the central passage 142 is adapted to mate with conical shoulder to shut off fuel flow whenever the temperature of thermostat 115 is above a predetermined temperature.

Norm-ally if the engine is stopped and allowed to cool, the carburetor parts under the control of thermostatic coil 115 are prevented from moving from their relative positions of FIGURE 1 to their relative positions of FIG- URE 2 since the idle screw 56 is held against the innermost step of cam 58 by the throttle closing spring R (FIGURE 2). This prevents through the lug 60 the movement of

levers

61, 128 and 134 under the bias of the cooling thermostatic spring 115. However, upon the subsequent manual opening of the throttle 4t) preparatory to the starting of the engine, screw 56 releases cam 58 which permits the rotation of

levers

61, 128 and 134 clockwise toward their respective positions shown in FIG- URE 2. Then, when released, the idle screw 56 will rest on the outer starting step of cam 58 and the carburetor parts are in condition for a cold start, indicated in FIG- URE 2.

In order to facilitate an understanding of the carburetor above described, this description will deal first with the operation of the carburetor when the ambient temperatures are above the middle seventy range, or the engine is at normal operating temperature. Thereafter, the tem pe-rature compensating mechanism will be described by explaining its effect on the relationship of the various parts and the modification in result produced.

As shown in FIGURE 1, the carburetor parts are in a 75 at and above these normal operating temperatures.

relative position which would be typical during engine idling condition at normal engine operating temperature. Throttle 40 is cracked open slightly to the dead idle setting position determined by the low step of the fast idle cam 58. This setting of the throttle is such as to produce a desirable idle engine speed, which may be in the range between three hundred and fifty and six hundred and fifty r.p.m. Air valve 75 is held open by the control arm 132 to about twenty to thirty degrees from its closed position by engagement of lug 71 on control arm 132. This can be considered the datum position for the air valve In the datum position, the air valve 75 will produce no detectable difference in pressure on opposite sides (upstream and downstream sides) of the valve at normal engine idle speed in the range above specified. At normal idle speed a depression will be produced below the throttle of approximately seventeen to nineteen inches mercury pressure suction. During engine braking operation, when the engine is being driven by the car, the depression can be in the range of twenty-four to twenty-six inches of mercury pressure suction.

One branch 90 of line 88 will therefore sense a high depression below the throttle 40 during engine operation at the idle setting for the throttle 40. The other branch 89 will sense substantially atmospheric pressure since there is no depression below the air valve 75. Since the metering restrictions 89a and 90a respectively in the

branches

89 and 90 are substantially equal in flow capacity, a pressure gradient will exist between them. The pressure gradient creates a subatmospheric pressure in conduit 88, which is communicated to the motor 80 and the diaphragm 81, but this depression is not of a degree sufficient to compress the spring 84 to open the valve 75 from its datum position even though bleed 121 is closed.

At idle speed setting of the carburetor for normal idle operation, the low speed fuel circuit will be operative to deliver an air and fuel emulsion through port 41. Because the valve 75 is open, however, and because the air flow is low at idle speed, the air valve 75 is not an air restriction creating depression in the mixture conduit 2, consequently, the low speed circuit functions uneffected by the air valve 75 under this setting condition of the carburetor parts.

As the throttle is moved to the off idle positions, the edge of valve 40 uncovers the slot 39, first partially, and then fully. More air passes the throttle and more fuel flow takes place in the low speed fuel circuit because both ports 41 and 39 are exposed to suction below the throttle. The engine responds so as to develop more power in the idle speed range or, increases in speed above the idle speed range an amount depending on the load on the engine. Other conditions described for the air valve 75 will remain about the same. Although air flow increases around the valve 75, no detectable depression occurs downstream between the valve 75 and the throttle 40. Consequently, motor 80 remains inactive.

As the throttle moves beyond the off idle range, after the edge of the throttle 40 has fully uncovered port 39, the carburetor can be considered as then operating in the part throttle range. Air valve 75 begins to have a distinct throttling effect and creates a definite depression in the mixture conduit posterior of the valve 75 and anterior of the throttle 40. This depression has two distinctly different operational effects. The depression below the valve 75 and above the throttle causes a difference in air pressure to exist between the fuel bowl and the high speed nozzle outlets 29 and 30 causing fuel to discharge into the mixture conduit 2. A depression is also sensed on both sides of the throttle valve 40 by

branch passages

89 and 90 to further drop the pressure in conduit 88 and motor 80. Also a difference in pressure exists on opposite sides of the unbalanced valve 75. These forces overcome the resistance of spring 84 in the motor 80 bringing the motor into operation, and

moving the air valve open to a position in which the force exerted by the spring 84, when compressed, balance out the forces tending to compress the spring 84 which include the forces on the valve and the force exerted by atmospheric pressure on the diaphragm 81. The change in position of the air valve 75 moves the step 96 fully into the jet 19. The variable metering restriction formed by the step 96 in the jet 19 then maintains a low capacity flow through the jet and, consequently, through the main or high speed circuit to provide a lean economy mixture for engine operation in the part throttle range.

Beyond the range of throttle positions in the economy or part throttle range, air valve 75 opens still further due to the unbalanced air pressure sensed on the valve 75 itself and due to the fact that depression sensed at the outlet of branch 89 approaches and becomes equal to the depression sensed at the outlet of branch passage 90. Of course, when the former equals the latter, then the branch passage 90 cease-s its function as a modulator of the depression sensed below the throttle. In a sense, it can be stated that the air valve opening then becomes almost directly proportional to air flow so that if the throttle is held open wide at any engine speed, the valve responds to maintain a substantially constant pressure drop or constant degree of depression due to its throttling effect. It is the degree of depression created by the valve 75 which directly effects the rate of fuel flow through the variable metering restriction formed by jet 19 and rod in both the part throttle and the full throttle range. However, in the part throttle range the depression created by the air valve may be less than at full throttle operation of the carburetor, and this is due to the pressure gradient between the

branches

89 and 90. The fact that the depression created by the air valve is less than at full throttle during the part throttle range is beneficial in obtaining a leaner economy mixture.

As set forth above, the engine requires different air to fuel ratios at different engine and ambient temperatures for both starting and running. A carburetor is normally calibrated, as above explained, to deliver air/ fuel ratios according to engine requirements at normal engine operating temperatures. These requirements are usually represented by calibration curves of desired fuel ratios over the entire engine speed range. The calibration of these curves are derived by operating a particular make and size of engine in the various speed ranges possible at part throttle and at full throttle to obtain best performances at every engine speed and load. Cold start and run operation is obtained by adding temperature compensating means to modify the calibration of a carburetor calibrated to deliver according to these predetermined fuel ratio curves for normal operating temperature. Most engines will start when cold it primed with a very rich mixture. Most engines will run when cold if the ratio curves are raised, in other words, if the fuel to air ratios are increased uniformly over the range of engine operating speeds. This is the function of the temperature compensating means, the structure of which has been heretofore described in detail. The operation of such a mechanism, however, can be explained only generally.

Assuming the engine temperature is below the middle range of the seventies Fahrenheit and the engine has not been running so that it has reached a stabilized temperature, then thermostat spring will have reacted to these lower temperatures and produced a bias rotating shaft 117 clockwise from the position shown in FIGURE 1. The degree of biasing force will be proportional to the difference between temperature sensed by the thermostat in the range below the middle seventies. If as described above, the throttle is operated to release the fast idle cam 58, the various parts will move toward their position shown in FIGURE 2. Arms and 132 are moved by spring 115 to release air valve 75 and allow the air valve to move toward closed position from its datum position. Economy step 96 on the metering rod 95 is lifted in the jet 19. Metering valve 136 is raised to open jet 20 to some degree and, air bleed 121 is cracked to modulate the depression gradient sensed between the outlets of

branch passages

89 and 90. Each of these actions produces its own effect upon fuel mixture.

The starting step on the fast idle cam holds the throttle sufficiently open to pass enough air and fuel to produce a starting mixture so that the engine will fire and run.

As the air valve moves from its datum toward closed position, it will definitely increase its throttling effect even at low engine speed and also increase the degree of depression created between the air valve and the throttle both when the engine is cranked and after it fires and runs. This effect of the air valve will depend, as to degree, on the opening of bleed 121, because, if this bleed is opened far enough, the force produced in the motor 80 would be negligible in its effect to open the air valve 75. Whereas at normal operating temperatures the motor would furnish the predominant control force for the valve 75; at low temperature, the predominant opening force for the valve 75 would be its aerodynamic unbalance creating a differential in air pressures on opposite sides of the valve acting directly on the unbalance to rotate the valve open. Since the rate of flow of fuel in the fuel circuits, especially in the high speed circuit, increases proportional to depression created by valve 75, then fuel mixture would be enriched on cranking because the valve 75 is closed, and enriched during engine warm-up because the degree of opening of valve 75 will be less for a given rate of air flow at any engine speed setting of the throttle.

As explained, therefore, the degree of depression created by the valve 75 at cold temperatures affects fuel ratio, but, in addition, the fuel ratio will be likewise affected by the .increase in fuel supplied to the fuel circuits. In accordance with this invention, the capacity for fuel flow in the fuel circuits is increased by the opening of the valve 138. The opening of the valve 133 would be equivalent to increasing the size of the metering jet 19 and its effect upon the fuel metering curves for normal engine oper ating temperatures would be the same as increasing the size of the jet 19 and the fuel mixtures are enriched at idle and part throttle settings by a relatively large percentage. Also, in the full throttle range, the percent of enrichment is proportional to the percent of increased opening provided by the valve 138.

If, during engine cranking, the mixture is too rich to start, it is possible to stop the delivery of fuel by the carburetor during cranking or, unload. This operation is performed automatically if the throttle 40 is opened manally to wide open. Shoulder 65 on throttle arm 53 contacts the lower end rod 67 which in turn engageg lug 7.1 rotating the air valve 75 toward wide open position. When the throttle is wide open, the idle jets 39 and 41 are out of operation, which means that no fuel will be delivered through the low speed circuit. When the air valve 75 is opened, no depression will exist below the valve during cranking to cause the difference in pressure necessary to create a flow of fuel in the high speed circuit. Cranking of the engine under these conditions draws air through the carburetor to sweep excessive fuel out of the manifold.

As the engine starts and runs, engine temperature will increase and the temperature of air delivered to the inlet 111 of housing 110 will increase with engine temperature warming thermostat 115. The thermostat then responds tending to wind up and rotate the shaft 117 counterclockwise. Eventually the temperature within the housing 110 reaches the point corresponding to normal operating temperatures and thermostat 115 has returned the shaft 117 to the position shown in FIGURE 1.

Changes in and modifications of the construction described may be made without departing from the spirit of my invention or sacrificing its advantages.

I claim:

1. A carburetor comprising a body structure having an air and fuel mixture conduit therethrough, a throttle valve mounted across said mixture, conduit for movement from an open to a position closing said mixture conduit, a throttle lever connected to said throttle valve and movable therewith for operating said throttle valve, an air valve mounted within said mixture conduit anteriorly of said throttle valve for movement in response to air flow through said mixture conduit from a position closing said mixture conduit to an open position, a spring connected between said air valve and said carburetor body and biasing said air valve toward a closed position, said carburetor body including a fuel reservoir and first and second fuel passages connected between said fuel reservoir and said mixture conduit, a first metering rod movably mounted on said carburetor and having portions varying sequentially from a first small thcikness to a larger thickness to a second small thickness positioned for movement into said first fuel passage for varying the flow of fuel therethrough, linkage means connecting said metering rod operatively to said air valve to be moved therewith upon the opening and closing movement of said air valve, a second metering rod movably mounted on said carburetor body and having a portion of varying size including a conical shoulder extending into said second fuel passage, a conical surface in said second fuel passage, a temperature sensitive spring connected to said second rod for biasing said second metering rod portion into said second fuel passage at temperatures above a predetermined value to reduce fuel flow to said -mixture conduit, said temperature sensitive coil being responsive to temperature below said predetermined value to move said second metering rod portion progressively out of said second fuel passage to increase fuel fiow in response to drops in temperature.

2. The invention of claim 1 including a stop mounted on said carburetor body and movable to varying amounts into the path of said throttle lever to hold said throttle lever open at corresponding different amounts, said stop being operatively connected to said temperature sensitive spring to be moved at progressively greater amounts into the path of said throttle lever as said temperature drops a predetermined amount.

3. A carburetor comprising a body structure having an air and fuel mixture conduit therethrough, a throttle valve mounted across said mixture conduit for movement from an open to a position closing said mixture conduit, means for operating said throttle valve, an air valve mounted within said mixture conduit anteriorly of said throttle valve for movement in response to air flow through said mixture conduit from a position closing said mix ture conduit to an open position, a spring connected between said air valve and said carburetor body and biasing said air valve toward a closed position, said carburetor body including a fuel reservoir and a fuel passage extending from said fuel reservoir to said mixture conduit be tween said air valve and said throttle valve, a first means movably positioned in said fuel passage for varying fuel flow therethrough, said first means having sequentially arranged portions of a first small diameter, a larger diameter and a second small diameter, said first means being operatively connected to said air valve for simultaneous movement therewith, a second means including a metering rod movably mounted within said carburetor body and having a portion extending into said fuel passage for control-ling fuel flow from said reservoir to said mixture conduit, a temperature sensitive spring, means including a lever connecting said metering rod to said temperature sensitive spring for biasing said metering rod portion into said fuel passage at temperatures above a predetermined value to reduce fuel flow to said rnixture conduit, said temperature sensitive spring being responsive to temperatures below said predetermined value to move said metering rod portion progressively out of said fuel passage to increase fuel flow to said mixture conduit in response to successive drops in temperature below said predetermined value, said connecting lever rotatably mounted on said carburetor body and having a stop portion movable into the path of movement of said throttle lever to hold said throttle lever open below said predetermined temperature value.

4. A carburetor comprsing a body structure having an air and fuel mixture conduit therethrough, a throttle valve mounted across said mixture conduit for movement from an open to a position closing said mixture conduit, means for operating said throttle valve, an air valve mounted Within said mixture conduit anteriorly of said throttle valve for movement in response to air flow through said mixture conduit from a position closing said mixture conduit to an open position, said carburetor body including a fuel reservoir and a fuel passage extending from said fuel reservoir to said mixture conduit between said air valve and said throttle valve, said fuel passage including a restricted portion of predetermined size, a first metering rod having portions varying in thickness sequentially from a first small thickness to a larger thick ness to a second small thickness, means connecting said first metering rod to said air valve for simultaneous movement therewith, a second metering rod movably mounted in said carburetor body and having a portion of varying size including a conical shoulder extending into said fuel passage to control fuel flow to said mixture conduit, means movably responsive to temperature, a lever pivotably mounted on said carburetor body and having a stop portion movable into the path of movement of said throttle lever, means joining said lever to said second metering rod and to said temperature responsive means for moving said stop and said second metering rod simultaneously in response to changes of temperature.

References Cited by the Examiner UNITED STATES PATENTS 2,098,202 11/1937 Weber 26150 X 2,341,694 2/1944 Cofley 261-39 2,969,965 1/1961 Braun 261-39 2,996,051 8/1961 Mick 26150 3,001,774 9/1961 Sarto 261-39 3,044,751 7/1962 Sarto 261-39 X 3,190,622 6/1965 Sarto 26139 X HARRY B. THORNTON, Primary Examiner.

T. R. MILES, Assistant Examiner.

Claims

1. A CARBURETOR COMPRISING A BODY STRUCTURE HAVING AN AIR AND FUEL MIXTURE CONDUIT THERETHOUGH, A THROTTLE VALVE MOUNTED ACROSS SAID MIXTURE, CONDUIT FOR MOVEMENT FROM AN OPEN TO A POSITION CLOSING SAID MIXTURE CONDUIT, A THROTTLE LEVER CONNECTED TO SAID THROTTLE VALVE AND MOVABLE THEREWITH FOR OPERATING SAID THROTTLE VALVE, AN AIR VALVE MOUNTED WITHIN SAID MIXTURE CONDUIT ANTERIORLY OF SAID THROTTLE VALVE FOR MOVEMENT IN RESPONSE TO AIR FLOW THROUGH SAID MIXTURE CONDUIT FROM A POSITION CLOSING SAID MIXTURE CONDUIT TO AN OPEN POSITION, A SPRING CONNECTED BETWEEN SAID AIR VALVE TOWARD A CLOSED POSITION, SAID AND BIASING SAID AIR VALVE TOWARD A CLOSED POSITION, SAID CARBURETOR BODY INCLUDING A FUEL RESERVOIR AND FIRST AND SECOND FUEL PASSAGES CONNECTED BETWEEN SAID FUEL RESERVOIR AND SAID MIXTURE CONDUIT, A FIRST METERING ROD MOVABLY MOUNTED ON SAID CORBURETOR AND HAVING PORTIONS VARYING SEQUENTIALLY FROM A FIRST SMALL THICKNESS TO A LARGER THICKNESS TO A SECOND SMALL THICKNESS POSITIONED FOR MOVEMENT INTO SAID FIRST FUEL PASSAGE FOR VARYING THE FLOW OF FUEL THERETHROUGH, LINKAGE MEANS CONNECTING SAID METERIAL ROD OPERATIVELY TO SAID AIR VALVE TO BE MOVED THEREWITH UPON THE OPENING AND CLOSING MOVEMENT OF SAID AIR VALVE, A SECOND METERING ROD MOVABLY MOUNTED ON SAID CARBURETOR BODY AND HAVING A PORTION OF VARYING SIZE INCLUDING A CONICAL SHOULDER EXTENDING INTO SAID SECOND FUEL PASSAGE, A CONICAL SURFACE IN SAID SECOND