US2793844A - Carburetor - Google Patents

Description

May 28, 1957 OLSON 2,793,844

CARBURETOR Filed March 8, 1954 2 Sheets-Sheet l INVENTOR.

ELMEFZ OLSON A TTOBNE Y A 2,793,844 Ice Patented May 1957 CARBURETOR Elmer Olson, Rochester, N. Y., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application March 8, 1954, Serial No. 414,763

2 Claims. (Cl. 261-155) This invention relates to carburetors for internal combustion engines, particularly to carburetors for use on automotive vehiclesand, more particularly, to means for automatically and variably controlling the'fiow through the mixture passage in-response to changesinthr'ottle position as well-as in response to changes in specdiand load while the throttle remains in fixed position.

The invention is designed for use primarily in a compound carburetor in which there is a primary mixture passage which functions under all operating conditions and a secondary mixture passage which functions only after the primary throttle which controls flow through the primary mixture passage has been opened to apr'edetermined extent. However, it will be'underst'oodthat "the invention is not limited inits useto such a carburetor, butmight be employed in a carburetor of conventional design having a single mixture passage.

vide means which will be effective, :p'articularlyiin a compound carburetor, to prevent admission of suflicient air immediately following arelatively wide opening move- 'mentof the throttle, particularlywhentheengine isop'er- -ating at relatively low speed, to cause unsatisfactory operation 'of the engine.

According to the present invention, this object is attained 'by the provision of an unbalanced suction operated valve in the secondary mixture passage between the main fuel inlet which supplies fuel thereto and the throttle "which controls the amount of mixture flowing therefrom into theengine manifold. This valve is normally held closed by a spring or other suitable means which exerts a force tending to 'move the valve toward closed position and which must be overcome by the effect of suction to effect opening of the valve. The valve, therefore, does not .open as rapidly as the throttle and retards the flow through the secondary passage. 4 i

If this suction operated valve was not provided and the primary throttle Was opened wide enough, at a tim'e when the engine was operating atllow speed with the secondary throttle closed, to effect opening of the secondary throttle to any appreciable extent, the mixture would 'becorne'too lean for proper .operation' of theengine. .The reason for this is obvious. Atthe time the throttle is opened, no fuel or air is flowing through the secondary mixture and when the throttle therein is "opened, there will be a sudden in-rusho'f air with almost no flow "of fuel, due to inertia. This in-rushof 'air leans thernixture to such an extent that the engine will not function properly, but when the suction operated valve which :is the subject of this invention is provided, the opening. of the valve with respect to the secondary throttle is retarded sufliciently to substantially eliminate the ileaning of "the mixture which would otherwise occur, so that the' engine will function properly.

It might be' supposed that the conventionalaccelerator pump which is generally provided in carburetors and is :operated upon opening movements er theithrottle, to ipro r-vide a proper mixture upon acceleration, mould tak'e care of this difliculty, but if a pump was used which is-of suflicient capacity to provide a mixture of the desired fuel content when the primary throttle is opened .far enough to elfect a substantial opening of the secondary throttle, the pump capacity would be too great for lesser openings of the primary throttle and if the latter was opened to increasespeed, but not enough to open the secondary throttle, the mixture would be too rich and the engine would-function improperly upon acceleration in the lower speed ranges.

As already indicated, the valve which is the subjectof the present invention is particularly useful in a compound carburetor for correcting the difficulty previously described but is also useful in a carburetor having a single mixture passage. In such a carburetor, because of the difference in weightof the air and fuel, any opening movement of the throttle effects a quicker increase in how of air than in flow of fuel and the mixture would momentarily become leaner unless some compensating means is employed. This difiiculty is usually overcome by the provision of the conventional throttle operated accelerator pump, but if a valve such as disclosed herein is employed,a pump of smaller capacity canbe'used-successfully because the valve aids the action of the pump.

Likewise, in any carburetor, whether a single outlet device or compound carburetor, the provision of a valve such as that which is the subject of this invention, aids in stabilizin'g'the mixture proportions upon changes in speed and load with fixed throttle position. Forexaniple, if :a'vehidle on which a carburetor having the valve disclosed herein is employed, starts downhill, there will be an increase iii-engine speed due to reductioninload. This will cause an increase in flow through the mixtureipassag'es and because of the inertia of the fuel, the amount of "air drawn into themanifold will increase faster than the fuel. If a valve such as that disclosed herein 'is provided, the flow 'of'air will be retarded sufliciently'to cause the flow of air an'd'fueltoincreasesubstantially at the same rate and the mixture formed is a more stable one than if the valve -was.'not employed. 7

An'unbalan'ced flat valve of the butterfly type has atendency to hang as it approaches its wide open position so that the valve does not open fully. "This is due to the fact that as the valve approaches its wide open position, the pressures effective onopposite sides of the valve shaft become so nearly equal that there is 'insuflicie'nt "force effective to move the valve further toward its open position. Accordingly, it is one of the more specific objects of the present invention to provide a suction opened valve in the intake passage between the fuel inlet and throttle whichnormally held in closed position but is opened by suction and which will be opened to its fullest extent when the throttle reaches fully open position.

Further objects and advantages of the present invention will be apparent from the following description, reference being'had to the accompanying drawings where- 'in a preferred embodiment of the present invention is clearly shown.

In the drawings:

Figure l is a side elevation of a compound carburetor embodying the present invention and cut away to 'show some parts in section on the line 11 of Figure 2; v

Figure 2 is a bottom plan view of the device of Figure 1;

Figure 3 is a fragmentary section onthe line 3+3 of Figure 1; and

Figure 4 isa view similar to Fig. 3 showing am'odified form of'the invention. I l p In the drawings, the invention is shownas incorporated in a compound carburetor of the type shown in applicants :co pending application S. N. 264,136, filedfDecember' z 9, 1 9 52, :in which there are four 'entirely separat'e mixture passages each of which has a separate outlet which connects with a separate passage in the intake manifold. The detailed construction of this carburetor is not in any way material so far as the present invention is concerned and for this reason, only the outline of the carburetor and the general arrangement of two of the mixture passages are shown in the drawings.

As shown, the carburetor comprises three separate castings, 2, 4 and 6 which are secured together in any suitable way and when assembled, four mixture passages, in each of which a combustible mixture of air and fuel is formed, extend through the castings and when the carburetor is positioned on the manifold, are in registry with four passages that are formed in such manifold and convey the mixture formed in the carburetor to the engine intake ports.

The casting 2 is an air inlet casting and air enters inlet ports at the top and flows into mixing chambers which are formed in the casting 4. There are four of these mixing chambers, two of which are primary mixing chambers which function at all engine speeds and all throttle positions and the other two are secondary mixing chambers which are brought into action to supply additional mixture only in the upper part of the speed range, for example, speeds above 40 or 50 miles per hour. In Fig. 1 the two secondary mixing chambers 8 and 10 are shown. The casting 6 is the outlet casting and this casting is adapted to be secured in the usual way to the engine intake manifold, being provided with an attaching flange 12, as best shown in Fig. 2 for this purpose. This flange has holes 14 through which attaching bolts extend when the carburetor is assembled in operative position.

Secured to a primary throttle shaft 16 suitably journalled in the casting 6 are two primary throttles 18 and 20, while secured to a secondary throttle shaft 22, also rotatably journalled in casting 6 are two secondary throttles 24 and 26. The primary throttles control the quantity of mixture supplied to the manifold through outlets 28 and 30 which are supplied with a mixture of fuel and air by primary mixing chambers associated therewith, while the secondary throttles control similar outlet passages 32 and 34 which are supplied with combustible mixture by secondary mixing chambers 8 and 10 which are of the construction shown in Fig. 2. The primary throttle shaft 16 is operated by a manually actuated operating connection which is connected thereto and there is an operating connection between shafts 16 and 22 which is so constructed that the shaft 22 is not moved until shaft 16 has made a predetermined movement toward open throttle position. This mechanism is not shown herein because its specific construction is of no moment so far as the present invention is concerned, but such mechanism may be of the same construction as shown in application S. N. 264,136.

All of the mixing chambers, both primary and secondary, are of similar construction and in each there is a primary venturi tube, such tubes being designated 40, and each of these tubes discharges into a large venturi tube 42. The tubes 40 are each supported by a tubular arm, as shown in the above application, which has a bore that conveys a rich mixture of fuel and air which is introduced into the tube 40 through orifice 41, while the larger tubes 42 are integral with the casting 4 and form the wall of each mixing chamber. Primary and secondary fuel chambers are formed in the casting 4, the secondary chamber being indicated at 44 and supplying fuel to the two secondary mixing chambers 8 and 10 while the primary fuel chamber, which is not shown, supplies fuel to the two primary mixing chambers in the same way as fuel is supplied to the secondary mixing chambers 8 and 10.

All of the mechanism so far described is disclosed in the earlier application above referred to and now, the mechanism which has been added to such device according to the present invention, will be described. In each of the secondary mixing chambers 8 and 10 a suction operated valve has been provided between the discharge end of the venturi tube 40 and the bottom of the casting 4 so that such valves are positioned between the venturi tubes 40 and the secondary throttles 24 and 26. There are two forms of the invention disclosed and in each the function is substantially the same and the suction operated valve is supported for rotation in a cylindrical insert which is press-fitted or otherwise supported in a recess formed in the wall of the secondary mixing chamber at the lower end thereof, adjacent the bottom of casting 4.

As disclosed in Fig. 3, the outlet end of the mixing chamber shown therein is enlarged as indicated at 50 and fitted in this enlargement is a cylindrical insert 52 of such width that when seated against the shoulder 54, the lower edge of such insert terminates flush with the bottom of casting 4 and engages the gasket 56 which separates the castings 4 and 6. A short shaft 58 is rotatably mounted in this insert 52 and secured to this shaft by screws 60 is a valve 62 which is normally held in a position where one edge of the valve engages a pin 64 which is press fitted in an opening 66 in the wall of the insert and the inner end of which extends for a very short distance into the mixing chamber, as shown in Fig. 3.

To move the valve to this position, an arm 68 has an offset extension 70 through which a screw extends, so that extension 70 is clamped between the screw and the valve 62. Secured in the other end of arm 68, in any suitable way, is a pin 72. This pin is engaged by a loop formed in one end 74 of a spring which has a coiled portion 76 and another end portion 78 which is looped around a pin 80 mounted in the insert 52 and extending across a slot 82 formed therein and into which the spring end 78 extends. The spring ends 78 and the center coil 76 of the spring are both received in a slot 84 formed in the large venturi tube 42 and the spring end 74 extends through a slot 86 formed in the wall of the small venturi tube 40. These slots prevent any lateral movement of the spring and maintain it in proper position when the device is assembled. This spring normally holds the valve closed and the valve is progressively opened against the force of such spring as the throttle is opened, the shaft 58 being mounted off-center so that the valve is unbalanced and moves in response to variation in the suction effective thereon.

The valve 62 is not a flat plate, as butterfly valves usually are, but different parts of the valve lie in different planes, which are at angles to each other. This form of valve is provided because, if the valve is a flat plate it has a tendency to hang as it approaches open position and sometimes will fail to reach the fully open position. This is due to the fact that as the valve moves counter-clockwise, upon an increase in the suction effective thereon, it reaches a position so much in line with the path of the entering air that the forces effective on opposite sides of the valve shaft are almost balanced and sometimes the effective force tending to rotate the valve will be insufficient to overcome the forces opposing movement thereof. To overcome this difiiculty, the valve 62 has four parts designated A, B, C and D, all of which lie in different planes. During the first part of the opening movement of the valve the efiect of suction on the part D opposes opening of the valve, but due to the angularity of such part D, as the valve approaches open position, the top of such part passes the center line of the shaft 58 so that the effect of suction on such part also tends to open the valve, aiding the efiect of suction on the part A, so that the valve will be carried to full open position. The position of the part D as the valve approaches open position is indicated in dotted lines in Fig. 3 and the effect of suction on such part will be clearly apparent.

The construction shown in Fig. 4 is substantially the same as that of Fig. 3 except for the fact that the spring means which holds the valve closed and opposes opening movement of the valve is somewhat different. A spring 96 has one end connected to a tang 98 punched out of the valve and the other end connected in a hole 100 formed in a lug 102 which is secured in position on the inner wall of the insert 52 by a screw 104, or in any other suitable way.

The spring arrangement is such that the force exerted thereby in opposition to opening movement of the valve does not increase as much per unit of movement of the valve when the valve approaches open position as when the valve starts to move. This is to compensate for the reduction in eflective suction as the valve moves toward open position and to bring about movement of the valve at a reasonably uniform rate during its whole range of movement.

The operation of the valve is apparent. When the throttle is opened to increase the speed of the engine the suction elfective on the valve 62 is, of course, increased and the valve will open in response thereto. However, the opening of the valve, being opposed by the spring which is effective thereon, is somewhat retarded and a sudden increase in air flow as compared to fuel flow such as would take place if the valve was not provided, is substantially prevented and a rich enough mixture is maintained for proper acceleration. Also, if there is an increase in suction at points anterior to the throttle, due to a change in speed While the throttle is in fixed position, as would take place upon reduction in load due to descent of an incline, the provision of the valve 60 tends to stabilize the mixture proportions and prevent such fluctuations therein as would bring about unsatisfactory operation.

It will be understood that there are similar suction operated valves in each of the secondary mixture passages but such valves are not provided in either of the primary mixture passages as they are not necessary therein. Also, While the invention is shown as embodied in a four-outlet carburetor having two primary mixture passages and two secondary mixture passages, the invention is applicable to a dual carburetor in which there is only one primary and one secondary mixture passage, and also to a single outlet carburetor, as it is also desirable to retard the admission of air to the mixture passages of such carburetors upon acceleration. By temporarily restricting the air flow the effect of the conventional accelerator pump is augmented so that a pump of less capacity can be employed and a mixture of proper proportions more easily obtained.

While the embodiments of the present invention as herein disclosed constitute preferred forms, it is to be understood that other forms might be adopted.

What is claimed is as follows:

1. In a carburetor, a mixture passage having a mixture chamber formed therein, means for introducing fuel and air into said mixing chamber to form a combustible mixture thereof, a throttle valve posterior to the mixing chamber and controlling the flow of mixture therefrom, an annular recess formed in the wall of the mixture passage adjacent the outlet end of the mixing chamber, a sleeve positioned in said recess and having the same internal diameter as that of the mixture passage adjacent thereto, a shaft rotatably supported in said sleeve and terminating within said recess a suction operated valve fixed to said shaft for controlling flow through the mixing chamber rotatably supported in said sleeve, a spring means also supported on said sleeve and connected to said last-named valve so as to normally hold the valve in closed position, said spring being disposed in said mixing chamber.

2. A carburetor as defined in claim 1 in which said valve includes an anteriorly projecting arm and further in which said spring means comprises a single spring element disposed anteriorly of said valve and fixed at one end to said sleeve and at the other end to said arm.

References Cited in the file of this patent UNITED STATES PATENTS 1,904,634 Teeter Apr. 18, 1933 2,026,947 Leibing Jan. 7, 1936 2,093,961 Ericson Sept. 21, 1937 2,209,329 Ericson July 30, 1940 2,346,016 Ericson et a1. Apr. 4, 1944 2,420,925 Wirth May 20, 1947 2,434,192 Braun Jan. 6, 1948

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