US1819527A - Charge forming device - Google Patents

Description

Aug, 18, 1933, w. H. TEETER CHARGE FORMING DEVICE Filed Sept. 22, 1928 Patented Aug. 18, 1931 PATENT OFFICE NITED. ST

WILFORD H. TEETER, F DAYTON, OHIO, ASSIGNOR, BY MESNE ASSIGNMENTS, T0 DELCO PRODUCTS CORPORATION, OF DAYTON, OHIO, A CORPORATION OF DELAWARE CHARGE FORMING DEVICE Applicafion' filed September 22, 1928. Serial No. 307,747.

This invention relates to charge forming devices for internal combustion engines and more particularly to devices having a plurality of primary carburetors adapted to supply a primary mixture of air and fuel to a plurality of secondarycarburetors, in which additional air may be mixed with the primary mixture under certain operating conditions.

An example of a charge forming device of 1 this character is disclosed in the copending application of Wilford H.'Teeter et al, Serial No. 288,683, filed June 10,1928. 7 I

In the device disclosed in the above mentioned application and other earlier devices of the same general type means have been provided to enrich the mixture during the acceleration period, generally in the form of a fuel pump to temporarily supply additional fuel to the mixing chamber subsequent to an opening movement of the throttle. These pumps have been ineffective under certain operating conditions to enrich the mixture immediately onopening of the throttle and have also been operable to supply variable amounts of fuel under the same operating conditions and with the same throttle movement.

It is therefore the object of the present invention to provide a novel and improved device, more particularly a fuel pump, for

enriching the mixture. during the acceleration period, and which will always enrich the mixture substantially simultaneously with the opening of the throttle, and to the same degree for any given opening movement of the 85 throttle under substantially the same operating conditions.

Further obj acts and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings, wherein a preferred form of embodiment of the present invention is clearly shown.

In the drawings:

Fig. 1 is a vertical section through the carburetor unit and one outlet branch of the manifold.

Figsr2 and 3 are fragmentary sections on the lines 22 and 3-3 respectively of Fig. 1.

The device disclosed herein comprises a 5 main air manifold indicated in its entirety by middle branch 12 being shown herein. Each of these branches is adapted to be connected with one of the intake ports 14 of a multicylinder engine. Each of these ports serves two adjacent cylinders in the manner well known and fully illustrated in the copending application previously referred to.

The manifold is provided with an attaching flange 16 to which the. main carburetor unit is secured. The carburetor comprises a main housing in the form of a single casting 18 which is provided with an attaching flange 20, adapted to be'secured by machine screws 22 to the flange 16 of the manifold. An air inlet horn 24, through which the flow of air is regulated in a manner later described, is secured in position over an air inlet opening inthe top wall of said housing 18 and a casting 26, provided with certain dashpot chambers and fuel passages later described, is secured to the bottom wall of the main housing by any suitable means, for example, as disclosed-in the copending case above referred to. A sheet metal fuel bowl 28 is held tight against a shoulder 30 formed on the housing 18, by means of a screw 32, screwed into a post 34 depending from the casting 26, a gasket 36 being provided to prevent leakage around said screw. The fuel is supplied to said fuel chamber from a main fuel supply by means of a fuel line and connection of the same form as shown in the copending application referred to, and the level of fuel within the bowl 28 is maintained substantially constant by means of a float 38 whichoperates in the usual manner.

Fuel is conducted from the fuel bowl to a plurality of primary fuel nozzles 40 located in the primary mixing chambers 42 formed in the central part of the main housing 18. That portion of the said housing 18 in which the primary mixing chambers are located, for convenience may be termed the distributor block. The construction of said distributor block and cooperating elements will be more fully described later. To enable the fuel to flow from the fuel bowl 28 to the primary nozzles 40 the casting 26 is provided with a vertical fuel channel 44 which'communicates at its upper end. with a horizontal fuel canal 46, connecting Witheach of the than said predetermined speed fuel is also the fuel bowl and the nozzle.

admitted to the fuel channel 44 through an orifice 52, controlled by a fuel valve 54 which is operated by means fully disclosed in the copending application above referred to and which need not be illustrated herein. The fuel admitted through the orifice 52 flows through a horizontal channel 56 which connects with the lower end of the channel 44.

The fuel is lifted from the fuel bowl through the nozzles 40 to the primary mixing chambers by the suction maintained therein. When the'throttle is moved toward closed position to reduce the engine speed there is a sudden reduction in suction effective on the vertical column of fuel between This reduction in suction might permit this column of fuel to drop sufiiciently to cause a emporary .fuel starving of the engine unless some means were provided to prevent such action; To

, this end a check valve 58is seated in an enlarged chamber 60 at the junction of the channel 44 and fuel canal 46, and on reduction of suction in the primary mixing chambers,.said valve seats on the bottomof the chamber 60, preventing downward flow through the channel 44.

The metering orifice is drilled in the casting 26 and the drill hole on the opposite side of the fuel channel 44 is closed by a screw 62.- I r Each primary fuel nozzle is provided with a main fuel outlet 64 in the top of the nozzle and a secondary fuel outlet comprising two holes 66 and 68 formed in the vertical wall of the nozzle near the bottom of theprimary mixing chamber as disclosed in Fig. 1. At higher engine speeds sufiicient suction is maintained in the primary mixing chambers to draw fuel through the main fuel outlet 64 as well as from the holes 66 and 68; During idling or other operation at very' low spee however, there is insuflicient suction to lift the fuel to the top of the nozzle, the fuel at such time standing in the nozzle at a point somewhere between the to of said nozzle and the orifices66 and 68, owing from said orifices by the action of gravity. Each fuel nozzle is provided with a restricted fuel metering orifice 7 0.

There are three rimary mixturepassages 42 formed in the distributor block, such passages being close together and parallel to each other as indicated in Fig. 2. Each of these mixture passages communicates with a conduit which conveys the primary mixture to secondary mixing chambers formed in each branch of the manifold where such manifold branches connect with the engine intake ports, such structure being fully described in the copending application above referred to. Only one of the said primary mixture conduits is disclosed herein. This conduit is indicated by the reference character 72 and is connected to the middle one of the primary mixture passages 42 and conveys the primary mixture to the secondary mixing chamber formed in the middle outlet branch 12 of the air manifold. The inlet ends of the primary mixture passages 42 where the nozzles 40 projectinto such passages which are of greater diameter than the outlet ends thereof and between the nozzle and outlet end of each passageits cross sectional area is reduced as indicated at 74, for the purposeof reducing the velocity of flow through the said mixture passage adjacent the primary nozzle.

Flow of primary mixture through the passages 42 is controlled by a single throttle valve 76 which extends across all of said passages 42 and has grooves-7 8 formed therein which register with the passages 42. This throttle valve is operated by means fully disclosed in the copendingapplication referred toand a groove 80 is provided in the external surface of said throttle which cooperates with the inner end of a screw 82 adjustable in the casting to prevent longitudinal movement of said throttle.

All of the air entering the carburetor with the exception of a small quantity of air which is supplied to carry the fuel when the choke mechanism is operated flows throu h the air horn 24, the flow being controlled y a main air valve 84 normally held against a seat 86 by a spring 88. The air flows past said valve into a ma1n air chamber 90 formed in the housing 18. A main air conduit 92 controlled by a valve mechanism hereinafter described connects'said air chamber with the main air manifold '10 while a hole 94 in the floor of said air chamber permits the air to flow therefrom into an auxiliary air chamber 96 which communicates directly with the inlet end of each primary mixture passage 42. When the carburetor is choked to facilitate starting of the engine the air valve 84 is held closed and to rovide suflicient air to carry the starting uel from nozzles 40 to the engine when said 'valve isclosed, an air inlet 98 is provided in the form of an elongated slot cut through a plate 100 detachably secured to the housing 18 as shown in Fig. 1. The air valve 84 is adjustably secured on a stem 102 slidably mounted in a guide sleeve 104 fixed in the main housin 18. Surrounding the guide sleeve is a slldable sleeve 106 provided with a flange 108 at its lower end which is adapted to be engaged by a lever, not shown herein, to lift the sleeve into engagement with the air valve for the purpose of holding said valve against its seat to choke the carburetor- This sleeve may also be lifted partially by the choke mechanism as fully described in. the above copending application, to vary the compression of the spring88 which normally holds the valve closed.

Whenever the engine speed increases the suction below the air valve 84 is increased and said valve is opened against the closing force of the spring 88, and would admit enough air to lean the fuel mixture unless means were provided to retard the opening movement of said valve. By retarding the opening of the valve, fluttering of said valve as well as leaning of the mixture will be prevented. To retard the opening movement of said valve the lower end of the valve stem 102 has secured thereto a piston 110 which slides in a cylinder 112 formed in the casting 26.

Fuel is admitted to the cylinder through the bottom thereof by means fully disclosed in the above mentioned prior application and the construction of said cylinder and piston form no part of the present invention. The cylinder and piston constitute a dashpot which will retard any downward motion of the valve 84.

The flow of air from the air chamber 90 through the passage 92 to the secondary mixing chamber is controlled. by two valves, a manually operated throttle 114 and a'suction operated valve 116. The throttle is fixed on a shaft 118, journalled in the walls of the housing 18 and is operated concurrently with the throttle 76 in a manner hereinafter described. The valve 116 is fixed to a shaft 120 which is positioned off center with respect to the valve, a greater portion of the valve being below the shaft than above. The shaft 120 is jourxialled in the housing 18 and the valve 116 is operated primarily by engine suction, its opening movement being retarded for reasons later set forth.

The mode of operation and the functions of the two throttle valves are substantially as follows: At engine speeds up to approximately that speed which corresponds to a vehicular speed of 20-25 miles per hour on a level only the throttle is open and the primary mixture is of properly combustible proportions, and sufficient in quantity to meet the requirements of the engine. At speeds above the specific speed mentioned the capacity of the primary mixture passages is insufiicient to supply a suflicient quantity of charge to the engine and the air throttle begins to open to supply additional air which is mixed with the primary mixture in the secondary mixing chambers, later described. The mechanism for operating the throttles as described is fully disclosed in the above mentioned copending application.

The purpose of the supplementary air valve 116 and the mechanism retarding the opening movement thereof will now be explained. Whenever the throttle valve is opened to accelerate the speed itis necessary to enrich the fuel mixture to some extent immediately in order to secure proper operation of the engine. In order to enrich the mixture according to the present invention, a pump, hereinafter described in detail, is provided to force additional fuel into the primary mixing chambers and at the same time the opening movement of the valve 116 is retarded to assist the action of the pump.

The opening movement of the air valve is retarded for the purpose of producing at all times, when the throttle 114 is opened, a suflicient pressure difierential between the inlet and outlet ends of the primary mixing tubes to create a velocity of flow through said tubes great enough to transport the primary mixture from the primary mixing chambers to the secondary mixing chambers almost immediately. In the device' disclosed herein the aforementioned pump forces fuel for acceleration purposes into the primary mixing tubes in order to form a super rich mixture therein. If the air valves were allowed to open freely, the pressure differential between the two ends of the primary tubes would be too low to create a high air velocity therein and a perceptible interval of time would be required to carry this super rich mixture to the secondary mixing chambers. The secondary air entering through the passage 92 would reach the secondary mixing chambers before the, super rich mixture and would weaken the mixture therein instead of enriching it, thus defeating the purpose of the fuel pump. By retarding the opening movement of the valve 116 this difiiculty is avoided. The suction at the outlet ends of the primary mixing tubes is maintained suflicient to produce so high a velocity of air flow through the primary tubes that the super rich primary mixture reaches the secondary mixing chambers substantially simultaneously with the opening of the throttle. The retarding of the opening movement of the valve 116 also increases the time interval necessary for the air. admitted on opening of the throttle 114 to reach said secondary mixing chambers so that this interval is substantially the same as that required for the rich primary mixture to reach said secondary mixing chambers, and the secondary air and rich primary mixture reach the secondary mixing chambers substantially simultaneously.

The air valve dash pot previously described constitutes the pump which supplies the additional fuel for acceleration to the primary mixing chambers. To this end a conduit 130 is connected through the cylinder wall 112 near the bottom thereof and at its upper end said conduit connects with a chamber 132 formed in a block 134 secured by screws or in any other desirable manner to the bottom of the distributor block. Formed in said block and communicating with the chamber 132 are fuel passages 136 and 138 which communicate in turn with two vertical passages 140 and 142 formed in the floor of the distributor block and communicating with the two outer primary mixture passages 42 as clearly shown in Fig. 3. The chamber 132 communicates directly with a vertical passage 144 which connects with the middle primary mixture passage. Received within the chamber 132 is a check valve 146 which rests on an annular seat 148 when the engine is not running. This Valve is lifted on the downward movement of the dash pot piston 110.to permit fuel to be forced by said piston through the conduit 130 and connecting passages to the primary mixture, but at all other times rest-s on its seat to keep the column of fuel in the conduit 130 from flowing downward to the cylinder 112. Air is admitted to chamber 132 through a small orifice 149. This air mixes with the fuel forced through conduit 130 by the pump, forming an emulsion therewith which flows into the mixture passages 42 through the passages 140, 142, and 144. The reason for this admission of air to chamber 132 is to prevent the high suction in the primary carburetors acting to draw fuel from the pump cylinder independent of the pumping action of the piston 110. It will be understood that under all conditions of operation a high suction is maintained in the primary mixture passages and unless the fuel delivery conduit between these passages and the dash pot cylinder be vented to atmosphere at some point therein, this suction would lift fuel from the pump cylinder at all times, whereas it is desirable to deliver fuel to the mixture passages only on downward movement of the pump piston. By admitting air to the chamber 132 the suction effective to lift the fuel through conduit 130 is never great enough to lift fuel to said chamber, but is sufficient to lift the fuel only to some point intermediate the chamber and pump cylinder, preferaby to a point immediately below chamber 13 The function of the check valve and the purpose served thereby will be best understood by consideration of the pump disclosed in the above mentioned copending application in which the valveis not provided. \Vhcn the valve is not provided, the downward movement of the piston operatesto force fuel into the primary mixture passages through the delivery conduit and connecting passages, but as soon as the piston comes to rest the fuel drops in the conduit, for as stated above, the suction in chamber 132 is insufiicient to lift fuel to that point. The level of the fuel in conduit 130 will depend on the suction maintained in the mixture passages and also varies with the engine speed and load. For instance, if the dash pot piston comes to rest with the throttle 1n position to give a vehicular speed of 30 miles per hour on a level the level of fuel in the conduit 130 is not the same as when the piston comes to rest with the throttle in position to a speed of '45 miles per hour on a level. Also if the piston comes to rest with the throttle in position toigive a 30 mile per hour speed on a level and the vehicle is going up a hill,

,fuel in conduit 130 is not the same as if the piston comes to rest with the throttle in the same position whefi the vehicle is going down hill. This is due to the difference in engine sucfiion brought about by the variation in loa 7 If the throttle be opened to increase the vehicular speed 10 miles per hour after the dash pot piston has come to rest under the various conditions above referred to, it should be clear that the piston must move the accelerating fuel different distances under these various operating conditions to force it into the mixing chambers, which will result in varying time intervals being required for the fuel to reach the mixing chambers, and varying amounts of fuel being delivered to said mixing chamber as a result of the same throttle movement. It is desirable to supply a quantity of fuel for acceleration every time the throttle is opened from one given pos1t1on to another given position at any giyen engine speed and to supply such fuel without delay. The provision of the check valve 146 accomplishes these results. In this device when the piston 110 comes to rest with the throttle in any position, the check valve operates to maintain the level of fuel in conduit 130 immediately below the valve irrespective of the position of the throttle, or'

engine speed or load. Hence, if the throttle be opened from any position after the piston has come to rest, the fuel will be forced into the mixture passages practically simultaneously with the movement of the piston and identical movements of the throttle will always force the same amount of fuel into said mixture passages, when the engine is operating at any given speed under the same operating conditions.

Each primary mixture conduit 72 conveys the primary mixture to a secondary mixing chamber, which comprises a Venturi tube 150. There are three of these Venturi tubes which are identical in construction and are positioned in each outlet branch of the manifold 10, in such relation to the primary mixing conduits that the point of greatest suction in each Venturi tube is immediately adjacent the outlet of the primary conduit associated therewith. Each Venturi is provided with an annular projecting rib 152 which fits, when the manifold is attached to the engine block, both in. the engine intake port and in a recess 154 in the end'of the associated branch of the manifold, the rib being clamped between the shoulder 156 on the manifold and a corresponding shoulder 158 on the intake port; A channel 160 isformed in the outer wall of the Venturi tube positioned at the bottom of the element when the device is assembled, to permit any fuel which precipitates out of the mixture and collects, on the wall of the manifold branch to flow into the engine intake port. The Venturi tubes cause the air entering the manifold through the passage 92 to assume high velocity at the ends of the primary mixture conduits creating a high suction in each conduit.

It will be understood that the charge formingdevice disclosed herein is old in the copending application above referred to with exception of the fuel pump. While this pump is particularly adapted to cooperate with a, charge forming device such as dis closed herein, it is adapted to be embodied in any form of charge forming device to supply an enriched mixture for acceleration.

While the form of embodiment of the present invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. A charge forming device for internal combustion engines comprising a secondary mixing chamber, a primary mixture passage for supplying a rich mixture to said 'secondary mixing chamber, means for supplying fuel and air to said primary mixture passage, means for supplying air to said secondary mixing chamber, a throttle in said primary mixture passage, and means for supplyingadditional fuel to said primary mixture passage substantially simultaneously with open ing movements of the throttle.

2. A charge forming device for internal combustion engines comprising a secondary mixing chamber, a primary mixture passage for supplying a rich mixture to said secondary mixing chamber, means for supplying fuel and air to said primary mixture passage, means for supplying air to said secondary mixing chamber, a throttle in said primary mixture passage, a fuel pump operative on opening movements of the throttle to supply additional fuel to said primary mixture passage, a conduit connecting the pump and said mixture passage and means for keeping said conduit substantially filled with fuel when the pump is inoperative.

3. A .charge forming device for internal combustion engines comprising a secondary mixing chamber, a primary mixture passage for supplying arich mixture to said secondary mixing chamber, means for supplya plurality of intake ports, comprising a plurality of mixture passages one associated with each intake port, means for supplying fuel and air to said passages, a throttle controlling all of said mixture passages, means for supplying additional fuel to all of said passages on opening movements of the throttle and means for rendering saidfuel supplying means effective to supply fuel to all of said mixture passages substantially simultaneously with the opening of said throttle.

5. A charge forming device for multicylinder internal combustion engines having a plurality of intake ports, comprising a plurality of mixture passages one associated with each intake port, means for supplying fuel and air to said passages, a throttle controlling all of said passages, a fuel pump for supplying additional fuel to said passages, a fuel delivery conduit communicating with the pump and having a branched delivery end connecting with all of said mixture passages and a check valve in said conduit immediately adjacent the branched end thereof.

In testimony whereof I hereto aflix my signature.

WILFORD H. TEETER.

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