US1889069A - Charge forming device - Google Patents

Description

Nov. 29, 193?. .1. H. HUNT CHARGE FORMING DEVICE 2 Sheets-Shea;

Filed July 10, 1928 gm 5,5, x HM Nov. 29, 1932. J. H. HUNT 1,889,069

CHARGE FORMING DEVICE Filed July 10, 1928 2 Sheets-Sheet 2 Patented Nov. 29, 1932 UNITED STATES PATENT OFFICE JOHN H. HUNT, 013 DETROIT, MICHIGAN, ASSIGNOR, BY MESNE ASSIGNMENTS, T0 DELCO PRODUCTS CORPORATION, OF DAYTON, OHIO, A CORPORATION OF DELAWARE CHARGE FORMING DEVICE Application filed July 10,

This invention relates to charge forming devices for internal combustion engines and more particularly to that type of charge forming device comprising a plurality of primary mixing chambers, one for each intake port of the engine and cooperating respectively with a plurality of secondary mixing chambers, each located adjacent an engine intake port and receiving fuel air mixture from a pipe connected with one of the primary mixing chambers and receiving air, when required, through one branch of an air manifold which supplies air to all of the secondary mixing chambers. The primary mixing chambers receive their liquid fuel from a common fuel bowl in which the bowl'is controlled by a float valve.

Examples of charge forming devices of this type are shown in the applications of F. E. Aseltine, Serial No. 54,592, filed September 5, 1925, and Serial No. 83,979. In these devices the admission of air to the air manifold is controlled by a spring loaded valve. The throttling of the carburetor is elfectedby separate throttle valves, one in each secondary carburetor and located between the secondary mixing chamber and the engine intake port. The several throttle valves are controlled by a common operating member. The formation of a super-rich fuel mixture in each primary carburetor and the flow of this mixture to each secondary carbu-- retor is induced by the flow of air the secondary carburetor and is therefore controlled by the throttle valve therein.

The general object of this type ofcharge forming device is to secure a mixture of fuel. and air in which the fuel is evenly distributed and to deliver equal quantities of said mixture having the same mixture ratio to each cylinder of the engine under various conditions of load and speed to which the'engine may be subjected, without requiring the heating of the fuel or fuel mixture before it is delivered to the engine.

When a separate throttle is employed in each of the secondary carburetors. as in the above copending applications, difficulty may sometimes arise in securing equal distribution of the fuel mixture to the several intake ports,

1928. Serial No. 291,662.

because of the difficulty in making the several throttles of exactly the same size or securing exactly the same adjustment of said throttles under all conditions of operation, particularly if said throttles become worn or warped.

It is, therefore, the principal object of this invention to provide a charge forming devicein which all possibility of this difiiculty is eliminated, and which is operative to secure under all operating conditions, equal mixture distribution to the several engine intake ports, irrespective of wear, adjustment or warping of the ports.

In the devices disclosed'in the above mentioned applications, the velocity of air flow through the primary carburetors is so great that the flow of fuel from the jets is induced by a suction created by the air current moving at high velocity, in other words, by a velocity head rather than a static suction. This velocity head builds up very rapidly as the engine speed increases so that at higher speeds than idling the mixture becomes too rich in fuel content and means must be provided to compensate for this richness in order to provide a mixture of the desired proportions. It has been found difficult to offset the effect of the velocity head, requiring accurate synchronization of operating parts which is likely to be disturbed by ordinary use of the device, due to wear of the parts resulting therefrom and possibility of improper adjustment. Moreover the provision of means to compensate for the effect of the velocity head on the jets only adds to the complexity of the structure of the devices heretofore known.

It is therefore an additional object of the invention to provide a charge forming device in which the effect of a high velocity air current on the fuel jets has been eliminated and the flow from said jets is effected by the static suction within the air chamber.

It is a still further object of this invention to simplify the construction to facilitate manufacture and adjustment thereof.

The present invention accomplishes these general objects by a construction which avoids the use of a separate throttle valve in each of the separate secondary carburetors and which permits the use of the simplest form of secondary carburetor associated with each engine intake port. A plurality of primary carburetors are provided, one for each intake port. Fuel mixture, formed in these primary carburetors, is conveyed through small pipes to the secondary carburetors adjacent each engine intake port, where it is mixed with secondary air admitted through a. port controlled by a springheld valve. Throttling of the engine is effected by a single throttle which controls the flow of air through the main air manifold.

Each primary carburetor is provided with a plurality of fuel jets adapted to be successively rendered effective as the engine speed increases. Each primary carburetor is provided with a restricted air inlet and a restricted mixture outlet of constant size and between said inlet and outlet is connected to the main air passage at a point posterior to the above mentioned air valve by means of a passage much larger than either air inlet or mixture outlet. By means of this passage the suction maintained in the primary carburetor is always substantially equal to that of the main air passage.

Further objects 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 in vention is clearly shown.

In the drawings:

Fig. 1 is a plan view of the present invention attached to the engine cylinder head, a part of which is shown in section.

Fig. 2 is a. vertical section on the line 2-2 of Fig. 1.

Fig. 3 is a vertical section on the line 3-3 of Fig. 2.

The preferred embodiment of the invention disclosed herein comprises a main air manifold 10 having two outlet branches 12 and I l each of which is adapted to communicate with one of the ports 16 of a four cylinder engine. Each port serves two adjacent cylinders through valve ports 16a and 16?), as clearly indicated in Fig. 1. The cylinder head is shown in two separate fragments but it will be understood that it may be an integral structure. The branches 12 and 14: are each provided with an attaching flange 18 for securing the manifold to the engine block in the usual way. Adjacent the inlet the manifold is provided with a flange 20 to which may be secured the carburetor unit, as shown in Fig. 2.

The carburetor unit comprises a main housing in the form of a single casting 22 provided with an attaching flange 24 adapted to be secured by screws 26 to the flange 20 of the manifold. An air inlet horn 28 is secured in position over an opening in the upper wall of the housing 22 by any suitable means and admits air to said housing. The casting 30, in which is formed a dash-pot cylinder later described, is secured by screws to the bottom wall of the housing 22, and a sheet metal fuel bowl 32 is held tight against a shoulder 3st formed on a skirt 36 depending from the main housing 22, in any conventional manner.

A distributor block 38 is secured in posi tion above the fuel bowl by screws 40 passing through the top of said fuel bowl, or by any other suitable means, and two primary mixing chambers 42 and a4, hereinafter more fully described, are formed in said block 38.

Fuel is supplied to each of the primary mixing chambers by means of two fuel jets which are adapted to be successively rendered effective as the engine speed lncreases. These jets are hereinafter termed low speed andhigh speed The low speed et comprises a passage 4:6 bored through the distributor block 38 and communicating at its lower end with a tube 48 screwed into the top of the fuel bowl and projecting downwardly to a point below the normal fuel level in said bowl, the diameter of the passage it being substantially the same as the inner diameter of the tube 48. A passage 50, enlarged at its upper end as indicated at 52, forms the high speed jet and communicates at its lower end with a tube 54 of larger size than the above mentioned tube 48. This tube is supported by the top of the fluid chamber and projects downwardly into the fuel in the fuel bowl in the same way as said tube 48.

Within the enlargement 52 of the fuel passage 50, a floating fuel metering valve 58 is adapted to slide vertically, the upward movement of this valve being limited by a pin 60 projecting inwardly from wall of said en-' largenient a... llhen the engine is not running and during engine operation at low speed, this valve is seated on a seat 62 formed at the junction of the passage 50 and the enlargement 52. In this position of the valve no fuel can flow through the high speed jet to the primary mixing chamber, but on increase of engine speed the suction in the primary mixing chamber also increases and at some predetermined speed the suction bec great enough to lift the valve 58 from its seat, which permits the assage of fuel through the passage 50 and between the wall of enlargement 52 and. the valve 58, the lattcr being square in cross section to provide passages through which this fuel can flow. The engine speed at which the high speed jet becomes effective is determined by the weight of the valve and other factors controlling the suction within the mixing chamber, but by properly proportioning the parts the high speed may be rendered ef ective at substantially any predetermined speed desired.

The primary mixing chambers are identical in construction except for the fact that the said chambers are oppositely arranged, that is, the inlet of one of said chambers is on the same side of the distributor block as the outlet of the other of the said chambers. This construction was provided in order to simplify the form of conduit necessary to convey the primary fuel mixture from the primary mixing chamber in which it is formed to that branch of the manifold with which the primary mixing chamber is associated. These primary mixing chambers are parallel to each other and also parallel to the main part of the manifold 10 connecting the two outlet branches thereof, as indicated in Fig. 1.

Each of said mixing chambers is provided with an air inlet bushing 64 having a flange 66 and adapted to be fixedly mounted in the inlet end of the mixing chamber with the flange engaging the end of distributor bloclr, as shown in Fig. 8. Each air inlet bushing is provided with a restricted passage 68 therethrough adapted to admit just enough air to form a mixture of proper proportions prior to the. opening of the throttle valve hereinafter more specifically described. At its in ner end, the bushing 64 has a projecting portion 70 of reduced diameter so asto form between itself and the wall of the primary mixing chamber a dead air space 72. In the construction illustrated herein the low speed fuel jet 46 discharges fuel into the space 72 so that the flow of fuel from the low speed jet is not induced by the aspiratingr effect of the air flowing through the air inlet bushing at high velocity. but by the static suction of the primary mixin chamber. While the high speed jet is not illustrated herein discharging into the dead air space. the projecting portion of.the air inlet bushing might iust as well be made suificientlv long to over lie the high speed jet also. Such a construction is not novel. having been discl sed in the above mentioned application of F. E. Aseltine. Serial No. 54.592, and if desired may be substituted for the construction shown herein without departing from the present invention.

Outlet conduits an d 82 communicate with the mixing chambers 42 and 44 respectively, and operate to convey the primary mixture to the branches 12 and 14 respective ly, of the main air manifold. The mixing chambers 42 and 44 are enlarged at their out let ends to form recesses 86 in which the inlet ends of delivery conduits 80 and 82 may be secured in any desirable manner. Each of the delivery conduits is connected at its delivery end to an elbow 88 which is secured by means of screws to a boss 90 nroiecting from and integral with the manifold 10, as shown in Fig. 1. The elbows 88 communi-- cate with tubes 92 and 94 in the outlet branches 12 and 14 respectively. Th e tubes may be secured in position in the ma I: fold in any desirable way and as shown provided with a flange 96 which is held in position by the elbow 88 when the device is assembled, as shown in Fig. 3. These tubes and the delivery conduits 80 and 82 convey the primary mixture from the mixing chambers 42 and 44 to the secondary mixing chambers hereinafter described.

Each of the delivery conduits 80 and 82 is provided with a fixed restriction 98 which may be formed in any desirable manner as by suitably squeezing the tube which is formed of relatively thin metal and easily distorted, v The restriction is of such a sufficient size as to supply a proper quantity of mixture to the secondary mixing chambers prior to the opening of the throttle valve to idle the engine the desired speed.

With the exception of the small quantity of air admittedthrough the restricted passages 68 in the air inlet bushings previously described, all of the air entering; the carburetor flows through the air horn 28, the flow therethroiui h being controlled by a main air valve 100, normally held against a seat 102 by a spring 104. Air flows past the valve into a main air chamber 106 formed in the housing 22 and from said chamber to the inlet 108 of the air manifold through an air 110 controlled by a throttle valve 112 secured to a shaft 114 rotatably mounted in the walls of the passage 110 and provided with an operating lever 116 secured on the end of said shaft, and to which is adapted to be connected a suitable operating means extending from said lever to a point convon wt to the operator of the vehicle on which the charge forming device is used.

The air valve 100 may be adjustably secured on a stem by means of a coupling member 119 screwed thereon, or in any other conventional manner. The stem 120 is mounted in a guide sleeve 122 screwed into the bottom wall of the main air chamber 106. Surrounding the guide sleeve is another sleeve 124, the lower end of which is provided with a flange 126 projecting therefrom which provides a seat for the spring;' 104, the latter being received between. the flange and the lower face of the air valve. The construction of the air valve forms no part of the present invention and any conventional form of valve may be employed.

On opening movement of the throttle the suction below the air valve is increased and the valve is opened against the tension of its spring; permitting an inrush of air to the secondary mixing chambers hereinafter described, which would be sufiicient to lean the mixture unless means are provided to retard the opening movement of said valve. By retarding the opening of the valve fluttering of said valve may also be prevented. To re- 1 opening of the valve as described a taro the dash-pot provided, comprising a piston 130 secured in any desirable manner to the lower end of the valve stem 120, as by a nut 182,

a-nd a cylinder 1.34 formed in the casting 30, and in which the piston 130 is adapted to slide. The cylinder is provided at its lower end with a closure member 186 having an opening 138 therein to permit fuel to enter the cylinder 13% from the fuel bowl. The flow of fuel through this opening is controller by a valve 140 mounted in a valve cage 1 12 and operating to close orifice 138 on downward movement of the piston 136, but lifting to permit a flow of fuel through said orifice on upward movement of the pi ton, which accompanies the closing movement of the air valve. This is an ordinary construction of liquid dash-pot.

it will be understood from the foregoing that the throttle 112 constitutes the only throttling means for controlling the engine speed. The restrictions 98 in delivery conduit through which the primary mixture flows to the secondary mixing chan'lber 0pcrate to determine the speed of the engine at idling, and being of fixed size the idling speed is fixed. For all other operating conditions the engine speed is controlled by the position of the throttle 112, which regulates the quan tity of air flowing through the passage 110 to ail the secondary mixing chambers and thus regulates the quantity of mixture flowing through all of said secondary mixing chambers to the engine intake ports.

As has been previously stated, considerable difficulty has been presented in charge forming devices of this type heretofore known because of the presence of a velocity suction at the fuel jet-s. It is one of the primary purposes of this invention to provide means to prevent the formation of a velocity head at the high and low speed fuel jets in device disclosed and instead to maintain at said jets, during engine operation at all speeds and under all operating conditions, a suction which is substantially the same as the suction within the air chamber 106. To this end each of the primary mixing chambers 42 and i l communicates with the air passage 110 at point anterior of the throttle 112 by means of a passage 150. Each of these passages 150 is of relatively large size and is bored through the top wall of the mixing chamber and the bottom wall of the main air passage, as shown in Fig. 8. The cross sectional area of the passage 150 at all points therein is considerably larger than the combined area of the restricted air inlet 68 and the restricted pri mary mixture outlet 98. In view of the relative sizes of said passages 150, 68 and 98, the velocity of flow through the primary mixing chambers can never be great, regardless of engine speed.

The suction in the primary mixture delivery conduits at points between the restriction 98 and the secondary mixing chamber is relatively high at all times, but owing to the excess in size of the passage 150 over that of the restriction 98, the suction at points anterior to the restriction 98 must be low in fact, under all conditions must be substantially equal to the suction in the passage 110 at the point where the passage 150 communicates therewith, and therefore is substantial- 1y equal to the suction in the air chamber 106, the suction in passage 110 being obviously substantially the same as that in chamber 106. There will, of course, be a flow of air from the passage 110 through the passages 150 to the primary mixing chambers, under certain operating conditions, thence through the restriction 98 and conduits 80 and 82 to the secondary mixing chambers. However, in view of the comparative sizes of passage 150 and the restriction 98, this flow of air will be very slow irrespective of the engine speed. In fact, as the throttle opens and the suction in the space 110 increases there may be a flow of primary mixture from the primary chamber 42 and 44, through passages 150 and 110 to the secondary mixing chambers, brought about largely by the frictional resistance offered by the restriction 98 to direct flow through the delivery conduits 80 and 82. However, the suction in the primary mixing chambers will be always approximately the same as that of the air chamber, regardless of direction of flow from the primary mixing chambers.

Each secondary chamber comprises a Venturi tube 160. There are two of these tubes which are identical in construction and are positioned in the branches 12 and 14 of the manifold 10, in such relation to the primary mixture delivery tubes 92 and 94: that the point of greatest depression in eachVenturi tube is immediately adjacent the outlet end of the primary mixture delivery conduit as sociated therewith. Each venturi is provided, with a projecting rib 162 which fits when the manifold is attached to the engine block, both in the engine intake port and in a recess 164 formed in the end of the associated manifold branch, the rib being clamped between shoul ders 166 and 168 on the manifold and the engine block, respectively. These Venturi tubes cause the air flowing through the secondary mixing chambers to assume high velocity at the end of the delivery conduits 92 and 94- creating in each of these conduits a high suction under all operating conditions.

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.

lVhat is claimed is as follows:

1. A charge forming device for internal combustion engines having in combination a primary mixture passage, of fixed cross sectional area, means for supplying fuel thereto, a restricted air inlet of fixed area admitting air thereto, a secondary mixing chamber into which the primary mixture passage delivers, an air passage supplying air to said secondary mixing chamber, and a manually adjustable throttle for controlling the passage of air therethrough.

2. A charge forming device for internal combustion engines having in combination a primary mixture passage, means for supplying fuel and air thereto, a restriction of fixed area in said passage for controlling the flow therethrough, a secondary mixing chamber into which said primary mixture passage delivers, and an adjustable throttle for controlling the flow through said secondary mixing chamber.

3. A charge forming device for an internal combustion engine having in combination, a plurality of primary mixing chambers, means supplying fuel thereto, a plurality of secondary carburetors into which said primary carburetors are adapted to deliver fuel mixture, an air chamber for supplying air to all of said primary carburetors, a single throttle for controlling the flow through said secondary carburetors and means for making the static suction of the air chamber the dominant factor controlling the flow of fuel to the primary carburetors under all operating conditions.

4. A charge forming device for an internal combustion engine having in combination, a plurality of primary mixing chambers, means for supplying fuel and air thereto, a plurality of secondary carburetors into which said primary carburetors are adapted to deliver fuel mixture, an air chamber for supplying air to all of said secondary carburetors, a single throttle for controlling the flow through said secondary carburetors, and means for making the static suction of the air chamber the dominant factor controlling the flow of fuel to the primary carburetors under all operating conditions.

5. A charge forming device for internal combustion engines comprising a mixing chamber, a fuel inlet for supplying fuel to said mixing chamber, an air chamber adapted to supply air to said mixing chamber, a restricted air inlet connecting the mixing chamber with the atmosphere, means for restricting the outlet from the mixing chamber under all operating conditions, and means for mak ing the static suction of the air chamber the dominant factor controlling the flow of fuel comprising a passage connecting the mixing chamber and the air chamber which is of greater area than either the restricted air inlet or said outlet.

6. In a charge forming device for internal combustion en ines having a plurality of intake ports, a main air manifold having outlet branches leading to said intake ports and comprising secondary mixing chambers, separate primary carburetors, each of which is adapted to supply a mixture of fuel and air "take ports,

to one of said secondary mixing chambers,

means for supplying fuel and air to said primary carburetors, primary mixture conduits for conveying the primary mixture of fuel and air'from said primary carburetors to said secondary mixing chambers, and a single throttle for controlling the flow through all of said secondary mixing chambers.

7. In a charge forming device for internal combustion engines having a plurality of ina main air manifold having outlet branches leading to said intake ports and comprising secondary mixing chambers,separate primary carburetors, each ofwhich is adapted to supply a mixture of fuel and air to one of said secondary mixing chambers,

means for supplying fuel and air to said primary carburetors, primary mixture conduits for conveying the primary mixture of fuel and air from said primary carburetors to said secondary mixing chambers, a' suction operated air valve for controlling admission of air to saidair manifold and a single throttle for controlling the flow through all of said secondary mixing chambers.

8. In a charge forming device for internal combustion engines having a plurality of intake ports, a main air manifold having outlet branches leading to said intake ports and comprising secondary mixing chambers, separate primary carburetors, each of which is adapted to supply a mixture offuel and air to one of said secondary mixing chambers, means for supplying fuel and air to said priadapted to supply a mixture of fuel and air I to one of said secondary mixing chambers, means for supplying fuel and air to said primary carburetors, primary mixture conduits connected With said primary carburetors and projecting into the branches of the main air manifold for conveying the primary mixture to the secondary mixing chambers, and a throttle in the air manifold anterior to the ends of the primary mixture conduits for controlling the flow through said manifold branches.

10. In a charge forming device for internal combustion engines having a plurality of intake ports, a main air manifold having mary carburetors, primary mixture conoutlet branches leading to said intake ports and comprising secondary mixing chambers,

separate primary carburetors, each of Which I is adapted to supply a mixture offuel and air to one of said secondary mixing chambers, means for supplying fuel and air to said primary carburetors, constantly open primary mixture conduits for conveying the primary mixture of fuel and air to said secondary mixing chambers, and a single throttle for controlling the flovv through all of said secondary mixing chambers.

11. In a charge forming device for internal combustion engines having a plurality of intake ports, a main air manifold having outlet branches leading to said intake ports and comprising secondary mixing chambers, separate primary carburetors, each of Which is adapted to supply a mixture of fuel and air to one of said secondary mixing chambers,

means for supplying fuel and air to said primary carburetors, primary mixture conduits of fixed area for conveying the primary mixture of fuel and air to said secondary mixing chambers, and a single throttle for control ling the fioW through all of said secondary mixing chambers.

In testimony whereof I hereto aflix my signature.

JOHN H. HUNT.

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