US2407535A - Carburetor - Google Patents

Description

Patented Sept. 10, 1946 CARBURETOR Harold A. Carlson, University City, and Olin J.

Eickmann, Normandy, Mo., assignors to Carter Carburetor Corporation, St. Louis, Mo., a corporation of Delaware Application June 24, 1943, Serial No. 492,144

2 Claims.

This invention relates to carburetors for internal combustion engines and consists particularly in novel means for influencing the character of the fuel supplied by the carburetor in accordance with suction.

Where a function of the carburetor, such as a fuel metering valve or fuel pump, is controlled by a suction responsive device, it has proved diflicult or impossible to provide for proper progressive operation of the device as the carburetor suction varies. Where the device is made sufficiently sensitive to provide for such operation, fluttering or hunting is likely to occur. Thus, such suction responsive elements usually have been constructed to have only two positions of operation, namely, the contracted or charged position attained during idling and part throttle or economy range operation, and the fully expanded or discharged position which is reached at some lower point in the carburetor suction range or when the throttle is more fully open. However, it is desirable to provide for progressive movement of the suction responsive element, particularly, wher this element actuates a metering valve. The use of a diaphragm accentuates the erratic operation of the suction responsive device because of the change in shape of the exposed dia- .phragm in intermediate positions.

It is the main object of the present invention to provide a suction responsive control for a carburetor function in which the suction responsive element is caused to move progressively and stably from its high to its low suction positions.

A more detailed object is to provide means for moderating the effective suction applied to the suction responsive element at periods of highest carburetor suction and reducing the moderating.

effect as the suction drops so that the change in suction applied to the suction responsive element willbe substantially less than exists in the carburetor. V I

These objects and other more detailed objects hereafter appearing are attained substantially by the devices illustrated in the accompanying drawing, in which:

Fig. 1 is a top view of a carburetor embodying the invention. a V

Fig. '2 is a side View, partly in section of the carburetor and illustrating one form of th novel suction moderating device.

Fig. 3 is a detail section illustrating another form of the device.

The carburetor illustrated is of the downdraft typ v including an air inlet horn In at the upper end of the mixture conduit controlled by a butterfly choker valve H. Located below the choke in the mixing chamber portion of the conduit, are a series of venturis l3 and a butterfly throttle valve I4 controlling the supply of mixture through the outlet portion of the carburetor. At the bottom of the carburetor there is provided a flange I 5 for attachment to an engine intake manifold (not shown). The throttle valve is controlled by a lever lfi, perforated at IT for attachment of a link which extends to the usual-accelerator pedal in the drivers compartment. Adjacent the carburetor barrel there is provided a fuel bowl 1-8 from the lower portion of which there projects a casing I9 between which and the bodyof' the fuel bowl there is secured'a diaphragm 253; A metering pin 2! is secured to and projects'inwardly from the diaphragm through a main metering orifice element 22, the pin being tapered so as to vary the effective size of the orifice element according to the position of the diaphragm.

Fuel for high speed operation is supplied through the metering orifice element to an upwardly extending passage 25 and main nozzle 26 discharging into the smallest or primary venturi l3. An interconnected idling system is shown including a metering tube 27 and communicating passages 28 and 29 extending to idling port 30 abreast the edge of throttle valve #4 when closed. A screw 3| carried bythrottle lever l6 abuts a fixed stop 32 on the carburetor barrel for adjusting the portion of idle port 38 exposed belowthe throttle valve during idling and, consequently, the idling speed. An idling economizer restriction is shown at 33 and idling air bleed restrictions 34 and 35 are provided, the lattenopening into the air horn through a passaged rib- 35 and a tube 31.

The suction chamber 40 on the right hand side of diaphragm 20 is provided with'a coiledspring 4| which constantly urges the diaphragm toward the left. A passage 42 connects-this chamber to a port 43 communicating with the carburetor mixture conduit posterior to the throttle. A second passage 44 connects the diaphragm suction chamber to the carburetor air horn. During operation, substantially atmospheric pressure exists in the carburetor air horn and passage 44 is extended into' the air horn rather than outside the carburetor so that air passing therethrough will be strained by the usual air filter mounted on the air horn. Passage 44 communicates with the diaphragm suction chamber through a restriction 45 and this restriction is controlled by a graduated valve 46 which extends outwardly from diaphragm 20 and moves therewith. The diaphragm tion changes in the carburetor.

is secured between cup washers 41 and 41*, the former serving as a stop.

During operation, diaphragm 20 responds to the differences in pressure between the outlet and inlet portions of the carburetor mixture conduit so asto cause the diaphragm to fluctuate back and forth against spring 4| and cause diiferent portions of metering pin 2| to extend into the orifice element 22 so as to vary the quantity of fuel drawn through the metering orifice and, consequently, the richness of the fue1 supplied by the carburetor. When the highest suctions exist posterior to the throttle, that is, during idling and early part throttle operation, diaphragm 20 will be drawn fully to the right with stop 41 engaging the inner wall of casing l9 so that a relatively large portion of pin 2| will be positioned in orifice element 22. At the same time, a relatively small portion of bleed controlling valve 46 will be located in restriction 45 so that air bleed 44 will a exert its maximum moderating effect upon the suction transmitted through suction passage 42. Spring 4|, of course, will be calibrated to provide for a properly lean mixture in the economy or part throttle range, and a considerably weaker spring 4| will be required than would be the case where air bleed 44 were omitted.

As the accelerator pedal and throttle lever l5 are moved to open the throttle, the suction in the carburetor outlet will be decreased so that diaphragm will move to the left by spring 4| to bring a smaller portion of metering pin 2| into the metering orifice and enrich the mixture.

Coincidentally, a larger portion of bleed controlling valve 45 will be moved into restriction 45 so that the moderating effect of the bleed air entering through passage 44 will be reduced as the diaphragm moves to the left. The effect of this variation of the effective air bleed is to substantially reduce the suction changes applied to the diaphragm which results in properly modulated or progressive action of the diaphragm as the carburetor suction drops. Consequently, it is possible to use a metering pin 2| having a plurality of graduated steps or a tapered portion instead of a pin having merely lean and rich positions. The effective sizes of passages 44 and 42 can be adjusted to provide for the desired movement of the diaphragm responsive to suc- In Fig. 3, diaphragm suction chamber 50 is connected to the carburetor mixture conduit by means of a passage 5| opening into the conduit through a pair of ports 52 and 53.' Port 52 is preferably in the form of an elongated slot and is positioned so as to be wholly or mostly anterior to the edge of throttle l4 when fully closed to its idling position. Idling port 36 is shown slightly spaced from port 52.

In this form, upper port 52 acts as an air bleed, when the throttle is closed, for moderating the suction effect transmitted to the diaphragm through port 53. As the accelerator pedal and throttle lever are moved to open the throttle, plate l4 moves upwardly along port 50 and progressively exposes less of the area of this port to the relatively high pressure above the throttle so that the bleeding or moderating effect thereof will be reduced until the edge of the throttle is 4 above the port. In other words, throttle plate |4 itself performs the function of the air bleed moderating valve 45 in Fig. 2 and, in the modification, the differences of suction in chamber 58 will be substantially less than would be the case if bleed port 52 were omitted. The shape and exact position of port 52 may be varied, if desired, to extend,v or increase the moderating effect thereof upon the effective suction applied to the diaphragm.

In both forms, the suction responsive element is shown as controlling a metering pin, but the invention may be advantageously applied to a similar element which controls another carburetor function, such as an accelerating pump. Obviously, a suction piston may be substituted for the diaphragm and various features of the carburetor such as the type of main nozzle and idling system, the Venturi construction, etc., are not essential. The invention may be modified in these and other respects as will occur to those skilled in the art and the exclusive use of all modifications as come Within the scope of the appended claims is contemplated.

We claim:

1. In a carburetor, a mixture conduit having a throttle therein, an idling fuel passage and a second fuel passage discharging into said conduit, a valve controlling the flow through said second passage, and a device for operating said valve including a suction chamber having a movable wall, spring means normally urging said Wall in the direction to open said valve, and a suction passage connecting said chamber to said mixture conduit, said passage opening into said conduit through port means located partly posterior and partly anterior to said throttle when closed, the posterior part of said port means being at least as large, effectively, as said anterior part, whereby the suction in said chamber decreases with the suction posterior to said throttle as said throttle is opened, said anterior port means being close to the edge of said throttle so as to be increasingly exposed to engine suction as said throttle opens whereby the suction moderating effect thereof is reduced.

2. In a carburetor, a mixture conduit having a throttle therein, an idling fuel passage and a second fuel passage discharging into said conduit, and a device for controlling the flow through said second passage including a suction chamber having a movable wall, spring means normally urging said wall in the direction to enrich the fuel supply, and a suction passage connecting said chamher to said mixture conduit, said suction passage opening into said conduit through suction port means located wholly posterior to said throttle when closed and air bleed port means located slightly anterior to said throttle when closed, said suction port means being of greater effective area than said air bleed port means whereby, during operation, the suction in said chamber decreases with the suction posterior to said throttle, as said throttle is opened, and the suction moderating effect of said air bleed port means is coincidentally reduced.

' HAROLD A. CARLSON.

OLIN J. EICKMANN.

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