US1948012A - Charge forming device - Google Patents

Description

Feb. 20, 1934. w H. TEETER 1,948,012

CHARGE FORMING DEVICE Filed Oct. 2, 1929 gmx/whew Wilford f Jeeze YgMWJMhW M511;

Patented Feb. 20, 1934 imam CHARGE FORIVIING DEVICE Wilford HVTeeter, Dayton, Ohio, assignor Vto Delco Products Corporation, Dayton, Ohioya corporation of Delaware Application October 2, 1929. Serial No. 396,701

Claims.

This invention relates to charge forming devices for internal combustion engines and more particularly to devices of this character which comprise a plurality of primary carburetors,

il which deliver a primary mixture of fuel and air to a plurality of secondary mixing chambers located adjacent rthe engine intake ports and in which the primary mixture is mixed with additional air under certain operating conditions.

Devices of this character are described in the copending applications of Fred E. Aseltine, Wilford H. Teeter and Carl H. Kindl, Serial No. 288,- 683, led June 27, 1928 and Wilford H. Teeter, Serial No. 221,372, filed September 22, 1927.

Vllt is the principal object of -this invention to provide means in a device of the general character above referred to, for improving the operation of the engine with which the device is associated during the acceleration period following opening of the throttle, and which will prevent loading of the engine, or the supplying of too much fuel thereto temporarily, on deceleration under any operating conditions.

A further object of the invention is to provide a device of this character which is so designed that the mixture flowing throughthe primary tubes is of more nearly correct proportions when additional air is being admitted to the secondary mixing chambers, and which will enable the engine to be run on the mixture supplied by the primary carburetors alone until a'much higher engine speed has been reached than has been heretofore possible.

A still further object of the invention is to provide a charge forming device of this type which is so designed that substantially novelocity head is created at the fuel nozzles. n l

All of these objects have been accomplished according to the present inventionby making the primary mixture passages of `as large size as is possible, while such passages are still effective to maintain suicient Velocity of flow therethrough to prevent precipitation and puddling of liquid fuel in said passages under rsuch operating conditions as will produce the lowest possible pressure differential between the opposite ends of said primary mixture passages.

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

In the drawing:

Fig. lis a vertical section through a charge forming device in which the present invention is embodied and an engine intake port with which it is associated.

Fig. 2 is a fragmentary, vertical section on'the line 2 2 of Fig. 1.

The device disclosed comprises a main air manifold 10, having three outlet branches, the middle branch 12 being shown herein. Each of these branches communicates with one of the intake ports r14 of a multicylinder engine. The 65. outlet branches are each provided with an attaching fiange 16 for securing the manifold to the engine block inV the usual manner, and a flange 18 to which the carburetor unit is secured.

'I'he carburetor unit comprises a main housing 70v 20, having an attaching flange 22, adapted to be secured to the flange 18 by screws 24. An air inlet coupling 28 is secured in position toregister with an opening in the upper wall of the housing 20, in any suitable way and may be connected with an air cleaner if desired. A casting 30, in which the passages supplying fuel to the nozzles are formed, is secured by screws to the lower wall of housing 20, and a sheet metal fuel bowl 32 is held tight against'an annular shoulder 34 90 on the housing 20 by any suitable means. Fuel is conducted from a main source of supply to the fuel bowl through a conduit (not shown) and the flow to the bowl is controlled by a float 36, operating in the usual manner to maintain a substantially constant. level of fuel therein.

Fuel iiows from the bowl 32 to a plurality of primary fuel nozzles 38, one of which is located in each of the primary mixing chambers 40, the construction of which is briefly described hereinafter. The fuel conduit between the fuel bowl and the nozzles comprises the vertical fuel passage 42 communicating at its upper end with the horizontal fuel canal 44, which connects with each of the nozzles 38 through an orifice 46. 95 Fuel is admitted from the fuel bowl to the passage 42 at all engine speeds, through a fixed metering orifice 48 and at high speeds additional fuel is admitted through an orifice 50 controlled by a valve 52, operated in the manner set forth in the above mentioned applications. This operating means forms no part of the present invention and need not be described further herein except to say that the valve 52 begins to open at substantially the same time as the air throttle hereinafter described.

Fuel is lifted from the fuel bowl through the above described fuel passages and nozzles 38 to the primary mixing chambers by the suction therein. Opening movements of the throttle llo als cause a reduction in mixing chamber suction which might permit the fuel column to drop sulciently to cause a temporary fuel starving of the engine unless means are provided to prevent this action. For this purpose a check Valve 54 is provided in an enlarged chamber 56 at the junction of the channels 42 and 44, and on reduction of mixing chamber suction, seats on the bottom of the chamber, preventing downward ow of fuel.

Each primary fuel nozzle is provided witha main fuel outlet 58 in the top of the nozzle and a secondary fuel outlet comprising two orifices 60 and 62 in the vertical wall of the nozzle near the bottom of the mixing chamber. At relatively *high speeds, the mixing chamber suction is sufcieni to lift fuel from the main outlet as well as from orifices 60 and 62. At idling, or low speed operation under load, however, the suction is enough to lift fuel only to some point between the top of the nozzle and the orifices 60 and 62, fuel flowing from these orifices by the action of gravity under such operating conditions. Each nozzle is provided with a restricted fuel metering orifice 63. The primary mixing chambers comprise the slightly enlarged anterior ends of the primary mixture passages 64, which are parallel to each other and close together, as indicated in Fig. 2. When the carburetoris attached to the manifold, these passages register with conduits which convey the primary mixture to` the secondary mixing chambers, as fully disclosed in the applications above referred to.

A single throttle Valve 68, which extends across all the primary mixture passages', controls the ow therethrough and is provided with grooves 70, which register with said mixture passages. This throttle is operated in a manner hereinafter more fully described. The middlev4 primary mixture passage communicates with a tube 72 fixed in the manifold branch l2. This tube constitutes oneu of the primary mixture conduits above referred to'and conveys the primary mixture to the secondary mixing chamber located inthe middle branch of the manifold.

VNearly all of the air entering the carburetor o'ws through theinlet coupling 28 and is controlled by the marin air va1ve74, 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 84, fixed in the housing 20, and serving also as a guide for the stem 86 to which the air valve is secured. When it is desired to choke the carburetor to facilitate starting of the engine, the flange is adapted to be lifted by means not shown herein, but fully described inv the above applications, until the upper end' of the sleeve 82 engages the air valve to lhold it closed. Sufficient air to carry the starting fuel from the nozzles to the intake ports is admitted through an elongated slot 87, formed in a plate 88, secured to the housing 20, as shown in Fig. 1.

The valve '74 admits air to the air chamber 90, from which air flows from the primary passage through an orifice 92 in the bottom of the air chamber and to the secondary mixing chambers through a passage 94, which connects' with an inlet of the manifold 10. The flow of air through this passage is controlled by a manually operable throttle 96, secured to a shaft 98, rotatably mounted in the main housing4 and by a suction operatedA valve 100, secured toa shaft 102, also rotatably mounted in the main housing. n

The operating connections for the two throttle valves constitute no part of the present invention and are not described herein, it being sufficient for the purposes of this disclosure to describe briefly the mode of operation of these valves. The primary throttle is connected to the main air throttle 96 by a lost motion connection, which permits a predetermined movement of the primary throttle independent of the throttle 96, and is capable of adjustment. It is generally adjusted so that the primary throttle is movable without accompanying movement of the air throttle until the former reaches a position corresponding to a Vehicular speed of approximately 15 to 20 miles per hour on the level. On further opening of the primary throttle, the air throttle is moved simultaneously therewith.

On opening o-f one or both of the throttle valves, the suction in the air chamber 90 is increased and the valve 74 is opened to admit additional air and increase the quantity of mixture supplied tothe engine. The opening of this valve is retarded-to prevent fluttering of the valve and to restrict the admission of air so-as to enrich the mixture to some extent whenever the throttles are opened'. For this purpose a dashpot is provided comprising a cylinder 104 which receives fuel from the reservoir 32, and a' piston 106, secured to the lower end of the valve stem 86 by any suitable means. A check valve is provided in the bottom of the dashpot cylinder, as shown in the above applications, to admit fuel thereto on closing movements of the valve and to prevent escape of fuel therefrom as the valve is opened. The specific construction of this dashpot is not material so far as this invention isv concerned, and may be any conventional form of liquid dashpot which will properly retard the opening of the air valve.

As hereinb'efore stated, the valve 100 is opened by engine suction when the air throttle 96 is opened. In earlier devices of this type, such as that disclosed in the above mentioned'copending applications, a dashpot has been provided for the purpose of retarding the opening of the valve 100 vwhenever the air throttle 96 is opened. The purpose of this dashpot and its construction are fully disclosed in the applications referred to, but its function is briefly set forth here in order to facilitate a clearer understanding of the present invention. If the valve 100 were allowed to open freely, the air admitted through the passage 94 wo-uld reach the secondary mixing chambers before the increased quantity of primary mixture resulting from the opening of the throttle and the mixture formed in the secondary mixing chambers would, therefore, be too lean to properly operate the engine immediately following any opening of the throttle. By retarding the opening of the valve 100, the time required for the air supplied through passage 94 to reach the secondary mixing chambers is substantially that required for the increased supply of primary mixture to reach said mixing chambers.

According to the present invention, the primary mixing chambers and the primary mixture passages 64 lea-ding from said mixing chambers to the secondary mixing chambers are larger than in earlier devices of this type, such as' those disclosed in the applications above referred to, the mixture passages being very much larger than formerly. By making these passages of such size, a number of most desirable results are obtained, and before discussing the size which apparently gives the most desirable results, the difficulties which are overcome and the advantages obtained by the provision of the enlarged passages Will be briefly discussed, to enable a clearer understanding of Vtheir function.

When a vehicle equipped with a charge forming device of the type shown in the earlier applications is being operated at a speed of 45 miles per hour for VVexample, the primary throttle and the air throttle are both open and the velocity of flow in the primary mixture passages is less than it would be if such passages were larger. This is due to the fact that a lesser proportion of the total amount of air entering the carburetor flows through such passagesand the resistance to flow through such passages is much greater than through the larger secondary air passage. This condition results in a relatively large quantity of fuel being present in the primary mixture passages and moving relatively slowly therethrough. On deceleration, when the throttles are moved toward closed position, sufficiently to substantially close the air throttle, the velocity of flow through the Yprimary mixture passages is very greatly increased, resulting in the sweeping into the engine, almost immediately, of the fuel which was in transit during the former running condition. This is too much fuel for proper combustion, resulting in loading and irregular engine operation. By providing larger primary mixture passages, the resistance to flow through such passages is less, with correspondingly greater velocity vwhen the air throttle is open. If the throttle is closed, as previously set forth, with large primary passages the increase in velocity of flow in lthe said primary passages is much less than with smaller passages and is insulcient to sweep the fuel therein into the engine immediately as in the previously described example. Consequently, the difficulties due to loading of the engine are substantially eliminated and the engine operates smoothly and satisfactorily under decelerating conditions. Y

Y The previously described air valve 100 is provided, as set forth hereinbefore, for the purpose of retarding the ow of secondary air following any opening movement of the air throttle so as to enable the increased quantity of primary mixture resulting from an opening of the throttle to reach the secondary mixing chamberssubstantially simultaneously with the air. Because of the small size of the primary mixture passages in the earlier devices, with the accompanying resistance to, and slow velocity of flow therethrough, the resistance of the dashpot controlling the valve 100 had to be relatively great and the ports had to be acy trolling the air valve is obviously much reduced.

With such a construction, a much less accurately fitting dashpot will control the air valve in an entirely satisfactory manner, thus simplifying the manufacturing problems and lowering the cost of the device. Moreover, since the retarding effect of the air valve is much less with the larger primary passages, any failure of the valve to operate properly will interfere less with the proper operation of the engine than in the earlier forms of the device where the valve must be retarded accurately to produce satisfactory engine operation during acceleration.

Although the velocity of flow through the enlarged primary passages is greater than in smaller passages, when the air throttle is open, owing to the more nearly equalized resistance to flow throughr the primary mixture passages and secondary air passages, the velocity through such passages is obviously less when the air throttle is closed. Therefore, by use of larger primary mixture passages, the velocity at the nozzles can be Vreduced so that there is substantially no velocity head created at said nozzles, which permits more accurate control of the mixture proportions Without the use of the various compensating devices described in application Serial No. 288,683, which are made necessary by the formation o a velocity head at said fuel nozzles.

Also by providing larger primary mixture passages, a larger quantity of air is admitted therethrough than when smaller passages are employed, which makes it unnecessary to open the secondary air passage, until higher engine speeds are reached, resulting in a more nearly correct mixture being maintained in the primary tubes subsequent to the opening of the air throttle and less necessary dilution of the primary mixture in the secondary mixing chambers. Such a condition brings about several advantages. There is generally better distribution of the mixture, because there is but little difficulty with distribution observed in a device of this character as long as the engine is operating on the primary mixture passages alone and the provision ofthe larger primary mixture passages has greatly increased this range of engine operation. Further, in View of the fact that with the large primary mixture passages, a much greater proportion' of the total mixture passes therethrough when the air throttle isopen than with relatively small primary passages, the synchronism of the primary throttle, air throttle and high speed fuel valve 52 does not need to be so accurate to produce satisfactory results. If the synchronism of these parts is disturbed, the percentage of error rreated thereby in the mixture proportions is much less, With the large primary passages where the air throttle does not open until the engine is operating at a speed corresponding to a vehicular speed of 45 miles per hour, than with small primary passages when the air throttle opens at an engine speed corresponding to a vehicular speed of 15 to 20 miles per hour.

FurtherVit is obvious that the larger the primary mixture passages, the more correct the proportions of the primaryv mixture are under all operating conditions. This mixture, therefore, will require less dilutionY in the secondary mixing chambers after the valve 100 is opened and the mixture formed therein will be a more homogeneous mixture than where small primary mixture passages are employed.

The most desirable or ideal size of the primary mixture passages by comparison to the secondary air passage varies to some extent with different engines. It has been found that to secure best results, the diameter of the primary mixture passages should vary from a minimum of one third the diameter of the secondary air passage to a maximum of two thirds the diameter of said secondary air passage. However, whatever the relative sizes of the primary and secondary passages may be to suit the requirements of some particular engine, the primary passages should be as large as possible, While still maintaining sufcient air velocity therein to carry the fuel from the nozzles to the engine intake ports, without permitting precipitation and puddling of the fuel in such passages. In other words, the passages should be large enough to prevent the primary mixture from sweeping into the engine substantially instantaneously on closing of the air throttle, but not large enough to permit the puddling of the fuel as above referred to.

In the drawing a passage 110 is shown for admitting air from the main air chamber to the primary mixture passages in advance of lthe fuel nozzles. The purpose of such passage is to reduce the velocity of flow at the nozzles, and it may be omitted if desired.

The secondary mixing chambers are of identical construction and each comprises a Venturi tube 112, positioned adjacent the outlet end of the primary mixture conduit. Each venturi is provided with an external rib 114, adapted to be clamped between the shoulders 116 and 118 on the manifold and engine block respectively, when the device is assembled. The Venturi tubes serve to accelerate the flow through the primary mixture conduits in the manner fully disclosed in the earlier applications.

While not shown herein and forming no part of this invention, a fuel pump of any desired form, such for example as shown in either one of the earlier applications referred to, may lee embodied in the device if desired.

While the form of embodiment of the present invention as herein disclosed, constitutes a preferred form, itis 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 primary mixture passage, means for supplying fuel and air thereto, a secondary mixing chamber into which the primary mixture passage delivers a primary mixture of air and fuel and located relatively remote from the point at which fuel is supplied to the primary mixture passage, a secondary air passage adapted to supply auxiliary air to said secondary mixing chamber, the primary mixture passage being cf as large diameter as possible to maintain a velocity of iiow therethrough under those operating conditions which produce the lowest pressure differential between opposite ends of the mixture passage that will be great enough to cause a continuous flow of fuel within the mixture passage, and without puddling of the fuel on the walls of the mixture passage.

2. A charge forming Vdevice for internal combustion engines comprising a primary mixture passage, means for supplying fuel and air thereto, a secondary mixing chamber into which the primary mixture passage delivers a primary mixture of air and fuel, a secondary air passage adapted to supply auxiliary air to said secondary mixing chamber, a throttle, a valve in said secondary air passage adapted to be closed as said throttle is moved toward closed position, said primary mixture passage being of suicient diameter to prevent enough increase in velocity therethrough on closing of said valve to carry the primary mixture in said mixture passage into the engine intake port substantially simultaneously with the closing of the valve, and small enough to maintain sufficient air velocity therein under those operating conditions which produce the lowest possible pressure differential between opposite ends of said mixture passage, that will be great enough to cause a continuous flow of the fuel within the passage, and without puddling of the fuel on the walls of the mixture passage.

3. A charge forming device for internal combustion engines comprising a primary mixture passage, means for supplying fuel and air thereto, a secondary mixing chamber into which the primary mixture passage delivers a primary mixture of air and fuel, and a secondary air passage adapted to supply air to the secondary mixing chamber, said primary mixture passage being at least one-third and not more than two-thirds the diameter of the secondary air passage.

4. A charge forming device for internal combustion engines comprising a primary mixture passage, means for supplying fuel and air thereto, a secondary mixing chamber which is located relatively close to the engine intake port and remote from the primary mixing chamber and into which the primary passage delivers a primary mixture of air and fuel, and a secondary air passage adapted to supply air to the secondary mixing chamber, said primary mixture passage being at least one-third and not more than twothirds the diameter of the secondary air pas- Sage.

5. A charge forming device for multi-cylinder internal combustion engines comprising a plurality of vprimary mixture passages, one for each intake port, means for supplying fuel and air to said primary passages, a plurality of secondary mixing chambers into each of which one of said primary mixture passages delivers a mixture of fuel and air, and a secondary air passage for supplying air to all of said secondary mixing chambers, said primary mixture passages each being at least one-third and not more than twothirds the diameter of the secondary air passage.

WILFORD H. TEETER.

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