US1833189A - Charge forming device - Google Patents

Description

Nov. 24, 1931. w. a. TEETER 1,833,189

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Patented Nov. 24, 1931 UNITED STATES PATENT OFFICE WILFORD H. TEETER, OF DAYTON, OHIO, ASSIGNOR, BY MESNE ASSIGNMENTS, TO DELCO PRODUCTS CORPORATION, OF DAYTON, OHIO, A CORPORATION OF DELAWARE CHARGE FORMING DEVICE Application filed September 27, 1928. Serial No. 308,847.

This invention relates to charge forming devices for internal combustion engines and more particularly to the type of charge form ing device which comprises a plurality of primary fuel mixing chambers, one for each intake port of the engine and co-operating respectively with a plurality of secondary fuel mixing chambers located adjacent the engine intake ports and receiving fuel air mixture from pipes connected with the primary carburetors, and receiving air when required through branches of an air manifold having a single air inlet for supplying air to all the secondary mixing chambers, the quantity of mixture flowing through the secondary carburetors being controlled primarily by a single main air throttle. A common fuel reservoir supplies liquid fuel to all of said primary carburetors.

An example of a charge forming device of this type is disclosed in the copending application of Fred E. Aseltine, Carl H. Kindl and W. H. Teeter, Serial No. 288,688 filed June 27, 1928.

Various means are provided in the device disclosed in the above mentioned application to control the flow of fuel and air under various operating conditions so as to secure at tioning devices are made necessary because the air flowing through the primary mixing chambers moves past the fuel jets therein at such high velocity that it creates a velocity head at said jets which is the force effective to cause fuel to flow therefrom. This velocity head builds up very rapidly on increase of engine speed and causes so rapid an increase in fuel flow as to form too rich a fuel mixture to be properly combustible unless some means are provided to compensate therefor. Since the velocity head is a variable thing, depending upon several different factors, it follows that the excess of fuel in the mixture which depends on the velocity head is also variable and it has been found to be almost impossible to correct the effect of velocity head on the fuel flow by any one compensating device, in fact difficult to secure a mixture having the desired fuel and air ratio under all operating conditions by use of any plurality of compensating, lgpl rfixture proportioning devices heretofore own.

It is the primary object of the present invention to provide a charge forming device in which the effect of the velocity head on the fuel flow is substantially eliminated under all operating conditions and to provide a simplified structure in which a fuel air mixture of desired proportions may be secured under all operating conditions without the use of various mixture proportioning devices heretofore employed.

It is a more specific object of the invention to control the flow of fuel from the jets by the impact thereon of the air entering the mixing chambers which increases as the engine speed and the velocity head increases, the increase in the effect of air impact operating to offset said increased velocity head.

These objects are accomplished accordin to the present invention by the provision of a plurality of tubes, projecting into the primary mixing chambers from the air chamber, one being associated with each of the primary mixing chambers and each being positioned in alignment with the fuel nozzle therein so that each tube serves to direct a stream of air at high velocity directly against the discharged outlet of the nozzle, the direction of flow of this air being directly opposite to that of the fuel as it issues from the nozzle.

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 invention is clearly shown.

In the drawings:

Fig. 1 is a vertical longitudinal section numeral and having t ree outlet branches 12, the middle one of which is shown herein and each of which is adapted to communi- 'cate with an intake port 14 of a multi-cylinder engine, as shown in Fig. 1. These outlet branches are each provided with an attaching flange 16 for securing the manifold to the engine block in the usual manner and adjacent its inlet the manifold is provided with a flange 18 to which thecarburetor 20 unit is adapted to be attached as shown in Fig. 1.

The carburetor unit comprises a main housing 20 having an attaching flange 22 adapted to be secured to the flange 18 by screws 24. An air inlet horn 26 is secured in position to register with an opening in the upper wall of the housing in any suitable way. A casting 28 havingcertain dash pot chambers formed therein is secured by 0 screws to the lower wall of the housing 20 and a sheet metal fuel bowl 30'is held tight against an annular shoulder 32 on a skirt 34 depending from the housing 20 by means of a screw 36. 7

Fuel is conducted from a main source of supply tothe fuel bowl through a conduit which is not shown herein and the flow of fuel to the bowl is controlled by a float 38, operating in the usual manner to maintain a substantially constant level of fuel in the bowl. Fuel flows from the bowl 30 to a pluralit of fuel nozzles 40, one of which is 10- cate in each of the primary mixing chambers 42, theconstruction of which is briefly described hereinafter. The fuel conduit between the bowl and the nozzles comprises a vertical fuel passage 44, communicating at its upper end with a horizontal fuel canal 46, which connects with each of the nozzles 40 through an orifice 48. Fuel is admitted from the fuel bowl to the passage 44 at low speeds through a fixed metering orifice 50 and at high speeds additional fuel is admitted through an orifice 52 controlled by valve 54 in the manner fully set forth in the above mentioned application. Fuel is lifted fr m the fuel bowl through the above describe d fuel passage and nozzles 38. to the mixing chambers 42, by the suction therein.

Closing movement of the throttle causes a check valve 56 is provided in an enlarged chamber 58 at the junction of the channel 44 and canal 46, and on reduction of mixing chamber suction seats on an u Wardly projecting annular rib 59, surroun ing the outlet of passage 44 in the chamber 58, preventing downward flow of fuel.

Each primary fuel nozzle 40 is provided with a main fuel outlet 60 in the top of the nozzle and a secondary fuel outlet comprising two orifices 62 and 64 in the vertical wall of the nozzle immediately above the bottom of the associated mixing chamber 42. At relatively high speeds the mixing chamber suction is enough to lift fuel from the main outlet as well as from the orifices 62 and 64. At idle or low speed operation under load, however, the suction is suflicient to lift fuel only to some. point between the top of the nozzles and orifices 62 and 64, the fuel flowing from these orifices by action of gravity. Each nozzle is provided with a.re-'

stricted fuel metering orifice 66. The primary mixture passages 42 are parallel to each other and close together as indicated in Fig. 2, and-when the carburetor is attached to the manifoldthese passages register with conduits which convey the primary 7 mixture to the secondary mixing chambers as fully disclosed in the cope-riding application referred to. v

A single throttle valve 68 which extends across all the primary mixture passages. controls the flow therethrough and is provided with grooves 7 0 which register withsaid mixture passages. This throttle is operated by means fully disclosed in the above mentioned application and which forms no part of the present invention. The middle primary mixture passage connects with a tube 72 fixed in the middle branch 12 of manifold, which conveys the primary mixture to the secondary mixing chamber in that particular manifold branch.

Substantially all of the air entering the carburetor flows through the air horn 26 controlled by a main air valve 74, normally held against a seat 76 by a' spring 78 received between the valve and a flange 80 projecting from a sleeve 82 slidably mounted on a stationary guide sleeve for the stem 86 to which the air valve is secured.

Suflicient air to carry the starting fuel from the nozzles to the intake ports of the engine is admitted through an elongated slot 88 formed in a plate 90 secured to thehousing 20 as shown in Fig. 1.

The valve 7 4 admits air to a main air chamber 92 from which air flows to the primary mixture passages, through an orifice 94 in the floor of the air chamber, and to the secondary mixing chambers through a passage 96 which connects with the inlet of the manifold 10. A manually operable throttle 98 and a suctio-n operated valve 100 control the flow of air through the passage 96, the operating connections for said valves being fully shown and described in the above mentioned copending application.

011 opening of either or both of the throttles 68 and 98 the suction in the air chamber 92 is increased and the/air valve is opened against the tension of its spring toadmit additional air and to increase the quantity of mixture supply to the engine. The opening of the valve is retarded to some extent, however, to prevent admission of sufficient air to lean the mixture, a dash pot being provided to accomplishthis result and to prevent fluttering of the valve, comprising a cylinder 102 forming a part of the casting 28 and a piston 104 secured to the valve stem in any desirable manner, as by means of a nut 106 threaded on the valve stem. This dash pot may be of any desired form and the particular construction thereof constitutes no part of the present invention.

lVhile the operating connections for the two throttle valves 68 and 98 constitute no part in the present invention the mode of operation of these valves'will now be briefly described in order to enable a better understanding of the function of the whole device. At engine speeds up to approximately that speed which corresponds to a vehicular speed of 20-25 miles on a level, only the primary throttle (38 is opened and the primary mixture is of proper combustible proportions and sufficient in quantity to meet the volumetric requirements of the engine. At speeds alrove the specific speed referred to the capacity of the primary mixture passage is such that the velocity of flow therethrough would increase very rapidly. To enable the device. to be successfully calibrated and for other reasons set forth in the copending application referred to hereinafter, it is necessary that the increase in velocity of flow through the primary tubes be prevented. To admit additional airto the secondary mixing chambers and effect the above described result operating means are provided for the throttle valves which effect opening of the throttle (58 independently of the throttle 98 at low speeds and begin to open the throttle 08 at substantially the speed above referred to while at speeds higher than that the two throttles are opened simultaneously until said throttles reach full open position.

According to the present invention means are provided to prevent the velocity head which is created in the primary mixture passages by the high velocity of flow therethrough acting to cause the flow of fuel fro-m the nozzles 40, in other words, means are provided to eliminate the effect of this velocity head on the fuel flow. As has been pointed out previously various difficulties must be overcome when the velocity head is the principal factor in effecting the fuel flow.

It is notdeemed necessary to di cuss these difficulties in detail herein since s eh difli'culties are fully described in the'applicants copending application Serial No. 288,685, filed June 27, 1928.

In the device disclosed herein means are provided by which the impact of the air enterin g the primary mixture passages is made use of to offset the action of the velocity head. To this end a plurality of small tubes 110 are screwed into orifices in the bottom wall of the air chamber 92 until flanges 112 thereon engage said wall. These tubes are positioned directly in alignment with the nozzles 40 and immediately above said nozzles so as to direct a stream of air flowing in a direction opposite to the direction of fuel flow from the nozzles against the main nozzle outlets It will be clear that as the speed of the engine increases the velocity of flow through these tubes also increases so that the retarding effect of the current of air flowing through such tubes on the flow of fuel on the nozzles also increases to counterbalance the increase in velocity head which is ordinarily effective on the nozzles as the engine speed increases.

The tubes 110 are each provided with a restriction 114 near the upper end thereof which is operative to properly control the velocity of air through the tubes. It has been found by experiment if said tubes are of the same diameter throughout, even if that diameter were the same as'the diameter at the restriction. the velocity of flow through the tubes would be suflicient to retard the flow from the nozzles to such an extent that the effect of the velocity head would be more than balanced and the fuel flow would not be sufficient to form a mixture of proper proportions. By forming a restriction throughout only a part of the length of the tubes at their inlet ends and providing a bore of larger diameter throughout the remainder of the length of said tubes, the velocity of the air as it leaves each tube 110 is somewhat less than it would be if the diameter of the tube were the same throughout its length. By making the parts of proper size the retarding effect of the air flowing through the tubes 110 can be made to properly balance the action of the velocity head so that the flow of fuel from the nozzles is substantially that which would be produced if the nozzles were subject only to the static suction as determined by the spring held air valve 74.

A pump is provided to inject additional fuel into the primary mixture passages on opening of the throttles to enrich the mixture slightly for acceleration. The dash pot previously described, comprises the above mentioned pump and is provided with a fuel delivery passage 120 extending to a horizontal passage 122 which is connected by vertical passages 124 with each of the primary mixture passages. The construction of this pump is just the same as that disclosed in the copending application above-referred to and need not be further described herein.

7 Means are provided to retard the opemng of the suction operated air valve 100 positioned in the air passage 96 on opening of the throttle 98 to secure proper enrichment of the fuel mixture for acceleration. This means constitutes no part of the present invention and is therefore not described herein but is illustrated and fully described in the copending application referred to in the preceding paragraph.

Each primary mixture passage delivers primary mixture to a secondary mixing chamber. There are three of these chambers which are identical in construction and each of which comprises a Venturi tube 130 positioned so that the point of greatest suction therein is immediately adjacent the outlet end of the primary mixture tube which is associated therewith. Each Venturi is provided with an annular rib 132 which fits, when the manifold is attached to the engine block in a recess 134 in the end of the associated branch of the manifold and a corresponding recess in the block, being clamped between shoulders-136 and 138 on the manifold and the block respectively. A channel 140 is formed in the outer wall of the venturi at the bottom of said element when the device is assembled to prevent any fuel which proceeds out of the. mixture and collects on the wall of the manifold branch to flow into the engine intake bore. The Venturi tubes increase the velocity of the air flowing past the ends of the primary mixture conduits and insure at all times a high suction in said conduits.

While the form of embodiment of the present invention as herein disclosed, constitut es 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 having in combination a mixing chamber, a fuel inlet orifice, for supplying fuel thereto, an air chamber for supplying air thereto, and means for preventing the formation of a velocity head at the fuel inlet comprising means for directing a stream of air from the air chamber against the fuel inlet orifice with increasing velocity as the engine speed increases.

2. A charge forming device for internal combustion engines having in combination a mixing chamber, a fuel nozzle projecting into the mixing chamber and having an outlet in the end, anair chamber supplying airth'ereto and means for progressively retarding the flow from said nozzle as the engine speed in creases, comprising a tube communicating with the air chamber and arranged coaxially with said nozzle, whereby it is adapted to direct a stream of air against its open end.

3. A charge formmg device for internal combustion engines having in combination a primary mixture passage, a secondary mixmg chamber with which said primary mixture passage communicates, an air chamber adapted to supply air to said mixture passage and said secondary mixing chamber, a fuel inlet orifice supplying fuel to said mixture passage and means controlling the flow of fuel from said orifice comprising a tube communicating with said air chamber and directing a stream of air therefrom against the fuel inlet orifice.

4. A charge forming device for internal combustion engines having in combination a mixing chamber, a fuelnozzle supplying fuel thereto, an air inlet therefor, a plurality of fuel feeding orifices in said nozzle, means for controlling the flow of fuel from one of said orifices by the velocity of the air passing through the mixing chamber and means for controlling the flow of fuel from the other of said orifices by the impact of the air entering the mixing chamber on said orifice.

5. A charge forming device for internal combustion engines having in combination a plurality of primary mixture passages adapted to deliver a primary mixture to a plurality of secondar mixing chambers a common air supply c amber adapted to supply air to all of said rimary mixture passages, a fuel feedin ori ce in each of said mixture passages, an means for directing a stream of'air against each of said orifices to control the flow of fuel therefrom comprising a plurality of tubes each of which projects from the air supply chamber into one of the mixture assages to a point in proximity to the fuel ceding orifice therein.

6. A charge forming device for internal combustion engines having in'combination a pluralityof prlmary mixture passages adapted to deliver a primary mixture to a plurallty of secondary mixing chambers, a common air supply chamber, positioned above all of said primary mixture passages, fuel nozzles extending upwardly into each of said mixture passages and provided with a fuel outlet in the upper ends and a plurality of tubes adapted to direct a stream of air against each of said fuel outlets, said tubes bein positioned in alignment with the fuel nozz es and extending downwardly from the air supply chamber into the mixture passages.

7. A charge forming device for internal combustion engines having, in combination, a mixing chamber, a fuel inlet orifice sup plying fuel thereto, an air chamber supplying air thereto, means for maintaining a Varying degree of pressure within the air chamber as the engine speed varies, and means for directing a stream of air from said air chamber against the fuel inlet orifice whereby the flow of fuel is controlled by the impact of said air.

8. A charge forming device for internal combustion engines having, in combination, a mixing chamber, a fuel inlet orifice supplying fuel thereto, an air chamber supplying air thereto, means for maintaining a sub-atmospheric pressure in said air chamber, and means for directing a stream of air from said air chamber against the fuel inlet orifice whereby the fiow of fuel is controlled by the impact of said air.

9. A charge forming device for internal combustion engines having, in combination, a mixing chamber, a fuel inlet orifice supplying fuel thereto, an air chamber supplying air thereto, a suction operated, spring controlled valve for maintaining the admission of air to said air chamber, and means for directing a stream of air from said air chamber against the fuel inlet orifice whereby the flow of fuel is controlled by the impact of said air.

10. A charge forming device for internal combustion engines having, in combination, a mixing chamber, a fuel inlet orifice supplying fuel thereto, an air chamber for supplying air thereto, and means for preventing the formation of a velocity head at the fuel inlet which is effective to cause a flow of fuel therefrom, said means comprising means for directing a flow of air from said air chamber against the fuel inlet orifice, whereby the flow 0 fuel is retarded by the impact of the air.

11. A charge forming device for internal combustion engines having, in combination, a mixing chamber, a fuel inlet orifice supplying fuel thereto, an air chamber for supplying air thereto, and means for preventin the formation of a velocity head at the fue inlet which is effective to cause a flow of fuel therefrom, said means comprising a tube extending from the air chamber into said mixing chamber for directing a stream of air against the fuel inlet orifice, whereby the flow 0 fuel is retarded by the impact of the air.

12. A charge forming device for internal combustion engines having, in combination, a mixing chamber, a fuel inlet orifice supplying fuel thereto, an air chamber for supplying air thereto, and means for preventing the formation of a velocity head at the fuel inlet which is effective to cause a flow of fuel therefrom, said means com rising a tube extending from the air cham er into said mixin chamber and arranged normal to and coaxially with the fuel feeding orifice, whereby the air flowin through said tube is effective ifzio retard the ow from said fuel feeding ori- 13. A charge forming device for internal combustion engines having, in combination, a mixture passage, an air chamber positioned above said passage and adapted to supply air thereto, a fuel nozzle extending upwardly nature.

WILFORD H. TEETER.

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