US2988344A - Automatic choke - Google Patents

Description

June 13, 1961 M. L. SMITLEY AUTOMATIC CHOKE 3 Sheets-Sheet 1 Filed May 14, 1959 HTTOP/Vf) June 13, 1961 M. L. SMITLEY AUTOMATIC CHOKE 5 Sheets-Sheet 2 Filed May 14, 1959 IN VEN TOR. MAP/0N Z. 5441 7L 5) June 13, 1961 M. 1.. SMITLEY AUTOMATIC CHOKE 3 Sheets-Sheet 3 Filed May 14, 1959 Ink l0 INVENTOR. AMP/0m 1. 5/14/74 5y BY 2,988,344 AUTOMATIC CHOKE Marion L. Smitley, Huntington Woods, Micln, assignor to Holley Carburetor Company, Warren, Mich, a corporation of Michigan Filed May 14, 1959, Ser. No. 813,213 11 Claims. (Cl. 261-39) This invention relates generally to carburetors or other fuel controls for internal combustion engines, and more particularly to means for automatically operating the chocking mechanism normally provided therein.

Most carburetors of present design include a coil-type thermostatic bimetal for controlling the amount of choke opening according to temperature. Additionally, a manifold vacuum responsive piston is employed for initially opening the choke a predetermined degree when the cold engine starts and becomes self-sustaining. The pistons so employed usually have means, such as slots or ports for example, for permitting at least a portion of the manifold vacuum to be bypassed around the piston and into the chamber containing the thermostatic element. That is, the source of heated air, the thermostatic housing, the vacuum piston and the source of manifold vacuum are arranged in series with each other.

As a result of this general arrangement, any change in restriction sizes, as between the source of heated air and the thermostatic element or between the piston and the source of manifold vacuum, always affects the responsiveness of the entire system.

The invention as hereinafter disclosed is directly concerned with this problem.

Accordingly, an object of this invention is to provide means in an automatic choke mechanism having temperature and pressure responsive elements therein for controlling the choke position, whereby the responsiveness of either the temperature responsive element or the pressure responsive element can be independently adjusted without any effect upon the other.

Other objects and advantages will become apparent when reference is made to the following description and the accompanying drawnigs in which:

FIGURE 1 is a perspective view illustrating an enginemounted carburetor embodying the invention.

FIGURE 2 is a fragmentary, perspective exploded view illustrating the details of construction of the left-hand portion of FIGURE 1.

FIGURE 3 is an enlarged fragmentary elevational view, with portions thereof cut away and in cross-section. FIGURE 3 illustrates in greater detail the piston and associated elements shown by FIGURE 2, as they would be constructed to provide one embodiment of the invention.

FIGURE 4 is a front elevational view, with portions thereof cut away and in cross-section, of a carburetor embodying a modification of the invention.

FIGURE 5 is a side elevational view taken on the plane of line 5--5 of FIGURE 4, with certain elements removed to illustrate internal constructions.

FIGURE 6 is a graph illustrating the advantages of the invention over conventional choke mechanisms.

Referring to the drawings in greater detail, FIGURE 1 illustrates a carburetor 10 having a throttle body 12 and an air intake 14 with induction passages therethrough adapted to be controlled by a choke valve 16, which is operatively connected by means of arms 18 and 20 and link 22 to the automatic choke control 24. A conduit 26 is adapted to communicate between the control 24 and the intake manifold 28 as Will be more fully explained in the specification.

FIGURE 2 illustrates a housing 30, suitably secured as niteci States Patent ice by screws 32 to the carburetor 10 and having a cylinder 34 formed therein containing a piston 36 which is connected through a linkage 38 to the choke lever 40. A shaft 42, extending through and rotatable in one wall of the housing 30, has secured to it at one end thereof the choke lever 40, and at the other end thereof a lever 20 (FIGURE 1). The choke lever 40 has an outwardly extending projection 44 which is adapted to coact with the free outer end 46 of thermostatic element 48 through an arcuate opening 50 in the housing cover plate 52.

The thermostatic housing 54 has a centrally located shaft rigidly secured therein to which the inner end of the thermostatic element 48 is secured. Any suitable means such as the clamping ring 56 may be employed to hold the cover plate 52 and housing 54 in alignment with and against the housing 30. The ring 56 may be secured by means of screws 58 and the cooperating threaded por tions 60.

Conduit 62 communicates between a source of engine heated air and the chamber formed by the cover plate 52 and housing 54, the air in most instances being heated by passing the same through a stove 64 in the exhaust manifold 65.

The purpose of conduit 62 is to deliver a controlled amount of air, which is at a temperature indicative of engine temperature, to the thermostatic element 48 in order that the element 48 may react to it and influence the position of the choke valve 16 accordingly. The path of this heated air is indicated by the arrows in FIGURE 2, its ultimate exit being to the intake manifold '28 through a port 66 communicating with the chamber 68 formed generally by the cover plate 52 and the housing 30.

Conduit 70, having a restriction 72 therein, serves to communicate a source of vacuum which causes the heated air to be drawn past the thermostatic element 4-8, through the slot 50 and into chamber 68, through port 66 and conduit 74 and subsequently into the intake manifold 28. Conduit 26, which has a restriction 78 therein, communicates between the cylinder 34 and conduit 70 on the vacuum side of restriction 72.

FIGURE 3 illustrates the piston 36 as having a cavity portion 80 which is adapted to receive linkage 38. The linkage 38 may be secured to the piston in any suitable manner such as by a pin 82. The other end of linkage 38 is secured to the choke lever 40, as by a pin 84 slidably retained within slot 76.

A pressure responsive flexible diaphragm 86, which is connected to the piston 36, has its outer diameter secured by any suitable means to the wall of cylinder 34. A stop member 88 located at the closed end of cylinder 34 may I be provided in order to limit the travel of the piston 36.

It is of course apparent that the stop 88 could be made adjustable by the use of a screw-like member properly sealed against vacuum loss. In any event, the stop would provide a particular degree of initial choke opening without having to rely on the particular dimensions of the diaphragm 86.

Operation of invention Assuming for the purpose of illustration that the engine is cold and is being cranked, the thermostatic element 48 will be in its unwound condition, thereby causing its end 46 to position projection 44 of lever 40 in its extreme counter-clockwise position. The lever 40, being secured to shaft 42 rotates the shaft and arm 20, which is secured to it, counter-clockwise to cause the choke valve 16 to assume a position which substantially closes off the flow of air through the carburetor induction passage 14. All of these elements will continue to occupy these respective positions while the engine is being cranked.

As soon as the engine fires and becomes self-sustaining,

manifold vacuum in conduits 70 and 26 rises to a value sufiicient to move the diaphragm 86 and vacuum piston 36 downwardly in opposition to the force of thermostat 43. The extent of movement of the piston is determined by the stop 88 within the cylinder 34.

As the engine continues to run, air is drawn from the stove 64 through conduits 62, 90 and 92, through an orifice 94 in the cover plate 52, and into the chamber formed by the housing 54 and cover plate 52. This air warms the thermostat 48 and passes through the arcuate opening 50 within the cover plate and into the chamber 68 formed by the housing 3% and cover plate 52. The air in chamber 68 then passes through port 66 and into conduits 74 and 70 and subsequently into the intake manifold 28.

The time required for the choke valve 16 to fully open after the engine is started is referred to as come-off time and is a function of the heated air flow past the thermostatic element 48. From this it is evident that the restriction 72 in conduit 70 determines the air flow and consequently determines the come-off time. On the other hand, restriction 73 in conduit 26 acts as a pneumatic dashpo-t in that it prevents the piston and diaphragm from both responding to fluctuations of manifold vacuum during periods such as cranking and opening the choke valve too quickly immediately after the engine is started. In other words, the restrictions 72 and 78 individually control the responsiveness of the thermostatic element 4.8 and the piston 36, respectively.

FIGURES 4 and illustrate modifications wherein the thermostatic element 46 and the piston 36 are divorced; that is, the elements are not contained in the same general mechanism, but rather are located in some spaced relationship to each other and in their own particular housings. The elements of FIGURES 4 and 5 which are like or similar to those of FIGURES 1-3 are identified with like primed reference numerals.

FIGURE 4, a front elevational view of a carburetor embodying a modification of the invention, has a thermostatic element 48 whose free end 46 acts as a movable abutment for lever 40 The lever 40 is of course rigidly coupled as by shaft 42 to lever 20 One end of the choke shaft 17 is rigidly secured to the lever 18 which in turn operates the linkage 22 the other end of the shaft 17 is secured to a linkage 96 which is operatively connected to the piston 36 through a linkage 98. The linkage 98 may be secured to the vacuum piston 36 by any suitable means such as a pin 100; additionally, a slotted portion 102 may be provided within the linkage 98 so as to permit continued movement of the choke 16 after the movement of the Vacuum piston has been arrested, if such be the case, by a stop member 104.

Slots 106 may be formed in the walls of cylinder 34 so as to efiectively diminish the force of the vacuum on the piston 36 after the end 108 of the piston is drawn down past the edge of the slots. This, in effect, establishes the degre of initial choke opening due to engine vacuum. The slots are not absolutely necessary and are illustrated only as one possible construction of the vacuum piston assembly. Various combinations are possible; that is, one construction could be completely devoid of slots, another could have no slots but provide a positive stopsuch as illustrated at 104-,while a third could use both the slots and a positive stop member. The precise construction in any event would be a matter of design based on the particular characteristics of both the carburetor and the engine on which it was to be used.

Conduit 110, having a restriction 112 therein, communicates between a source of engine vacuum and the lower end of the cylinder 34 The restriction 112, although illustrated as being an adjustable one, may alternatively be a fixed one inserted into the conduit 116. It should also be noted that it is not necessary to vent the other end of cylinder 34- to the inside of the air cleaner 114; it may insteadbe vented, if desired, to the atmosphere. This consideration again becomes a matter of design.

The graph of FIGURE 6 illustrates a second major advantage of the invention. Reference to FIGURE 6 will disclose the comparative functioning of a conventional pressure responsive choke mechanism and one constructed in accordance with the invention.

In the conventional mechanism, as soon as the engine fires, the choke is opened to some point P It has been found in many cases that the time to reach this point is too short and causes too sudden of a change in the fuelair ratio, consequently, stalling the engine. In contrast to this, the invention, by providing a separate restriction for the pressure responsive member of the choke mechanism, is capable of adjusting the reaction time of the pressure responsive member. By this method, the same degree of choke opening can be attained; that is, point P represents the same amount of choke opening, but represents a different point in time. Accordingly, the engine has sufficient time to adapt itself to the changing fuel-air ratio.

In summarizing, it can be said that broadly the invention provides means for controling the choke come-01f time and rapidity with which the choke is initially opened. This is accomplished by providing individual conduits, arranged in parallel, communicating between the thermostatic housing and the pressure responsive member, and a source of engine vacuum. Additionally individual restrictions are located within the conduits which determine the rate of flow therethrough.

Although but two embodiments of the invention have been disclosed and described, it is evident that others are possible within the scope of the appended claims.

What I claim as my invention is:

1. A carburetor for an internal combustion engine, comprising a choke valve, a source of suction related to engine operation, a housing containing temperature responsive means influencing the position of said choke valve, pressure responsive means including a diaphragm member operatively connected to said choke valve, a source of heated air, first conduit means communicating only between said source of heated air and said housing for supplying all of the required heated air to said housing, second conduit means including a first restriction therein communicating only between said source of suction and said housing and a third conduit means including a second restriction therein communicating only between said pressure responsive means and said second conduit on the suction side of said first restriction.

2. A carburetor for an internal combustion engine, including a choke valve mounted therein and an automatic choke control device, said device comprising a thermostatic control for said choke valve, first conduit means adapted to draw all the required warm air past said thermostatic control in response to an engine created vacuum, vacuum responsive means operative when the engine starts to move said choke valve in the opening direction, and additional means for controlling the responsiveness of said vacuum responsive means, said additional means comprising second separate and distinct conduit means including a restriction therein communicating only between said vacuum responsive means and a source of said engine created vacuum.

3. A carburetor for an internal combustion engine, including a choke valve mounted therein and an automatic choke control device, said device comprising a thermostatic control for said choke valve, first conduit means adapted to draw warm air past said thermostatic control in response to an engine created vacuum, vacuum responsive means dissociated from said choke control device operative when the engine starts to move said choke valve in the opening direction, and additionalmeans for controlling the responsiveness of said vacuum responsive means, said additional means comprising second separate and distinct conduit means including an adjustable restriction therein communicating between said vacuum responsive means and a source of said engine created vacuum.

4. A carburetor for an internal combustion engine, including a choke valve and an automatic choke control device, said device comprising a choke shaft secured to said valve, a member secured to said shaft and adapted to be rotated therewith, a housing, a second shaft mounted through one side of said housing and adapted to be rotated therein, an arm secured to one end of said second shaft externally of said housing so as to be rotatable therewith, means connecting said member with said arm, a cylinder open at one end and substantially closed at its other end, a piston in said cylinder, a second arm having a projection thereon secured to the other end of said second shaft within said housing and being adapted to rotate said second shaft, a sealing member between said piston and said cylinder, first conduit means including a first restriction therein leading from the space between said piston and the closed end of said cylinder and communicating with a source of engine suction, thermostatic means within said housing adapted to bias said projection in a direction so as to close said choke valve, second conduit means leading from the said housing and communicating with a source of heated air at substantially atmospheric pressure, and third conduit means including second restrictive means therein communicating between said housing and said source of engine suction.

5. An automatic choke device for an internal combustion engine carburetor, comprising a choke valve, a housing, a thermostatic element contained within said housing, a cylinder formed within a portion of said housing and having one end substantially open, a piston slidably received within said cylinder, connecting means operatively connecting said piston, thermostatic element and choke valve each to the other, a source of heated air, first conduit means communicating between said source of heated air and said housing, a source of vacuum related to engine operation, second conduit means including first restrictive means therein communicating between said housing and said source of vacuum, third conduit means including second restrictive means therein communicating between said source of vacuum and the space defined by the closed end of said cylinder and said piston, and sealing means cooperating with said piston and said cylinder in a manner so as to cause said piston to be responsive to a pressure differential created by the pressure existing within said chamber and said space within said cylinder.

6. A carburetor for an internal combustion engine having an induction passage, said carburetor including a choke valve controlling the admission of air to said induction passage, an air cleaner operatively connected to said carburetor, a first housing, a thermostatic element contained within said first housing, a second housing, a cylinder formed within said second housing and having one end exposed to the pressure existing within said air cleaner, a piston slidably received within said cylinder, a choke shaft, means operatively connecting said choke shaft with said thermostatic element and said piston, a source of heated air, a source of vacuum related to engine operation, first conduit means communicating between said source of heated air and said first housing, second conduit means including first restrictive means therein communicating between said source of vacuum and said first housing, and third conduit means including second restrictive means therein communicating between said source of vacuum and said cylinder in a manner so as to render said piston responsive to the pressure differential created by the said vacuum and the pressure existing within said air cleaner.

7. A carburetor for an internal combustion engine, comprising, a choke valve, a source of suction related to engine operation, a housing containing temperature responsive means influencing the position of said choke valve, a pressure responsive diaphragm means operatively connected to said choke valve, said diaphragm means being received within said housing in a manner so as to form a substantially sealed chamber, a source of heated air, first conduit means communicating between said source of heated air and said housing, second conduit means including a restriction therein communicating between said source of suction and said housing and third conduit means of a restrictive character communicating between said chamber formed by said pressure responsive diaphragm means and said second conduit on the suction side of said restriction.

8. A carburetor for an internal combustion engine, comprising a choke valve, a source of suction related to engine operation, a housing containing temperature responsive means influencing the position of said choke valve, a source of heated air, first conduit means communicating between said source of heated air and said housing for supplying all of the heated air required to said housing, second conduit means including a restriction therein communicating between said source of suction and said housing for drawing all of? the heated air supplied by said first conduit means past said temperature responsive means and through said housing, pressure responsive means operatively connected to said choke valve and operative upon the starting of said engine to urge said choke valve in the opening direction in opposition to said temperature responsive means and an additional third conduit means of a restrictive character communicating only between said pressure responsive means and said source of suction.

9. A carburetor for an internal combustion engine, comprising a choke valve, a source of suction related to engine operation, a housing containing temperature responsive means influencing the position of said choke valve, a source of heated air, first conduit means communicating between said source of heated air and said housing for supplying all of the heated air required to said housing, second conduit means including a restriction therein communicating between said source of suction and said housing for drawing all of the heated air supplied by said first conduit means past said temperature responsive means and through said housing, pressure responsive means including a piston therein operatively connected to said choke valve and operative upon the starting of said engine to urge said choke valve in the opening direction in opposition to said temperature responsive means and an additional third conduit means of a restrictive character communicating only between said pressure responsive means and said source of suction.

10. A carburetor for an internal combustion engine developing a source of suction related to engine operation, comprising a choke valve, a housing containing temperature responsive means influencing the position of said choke valve, pressure responsive means operatively connected to said choke valve, a source of heated air, first conduit means communicating between said source of heated air and said housing, second conduit means communicating between a source of said suction and said housing, and third conduit means communicating between said pressure responsive means and a source of said suction, said housing and said pressure responsive means being contructed to provide a seal therebetween so as to prevent said heated air from entering said third conduit means.

11. A carburetor for an internal combustion engine developing a source of suction related to engine operation, comprising a choke valve, a housing containing temperature responsive means influencing the position of said choke valve, pressure responsive means operatively connected to said choke valve, a source of heated air, first conduit means communicating between said source of heated air and said housing, second conduit means communicating between a source of said suction and said housing, and third conduit means communicating between said pressure responsive means and a source of said suction, and housing and said pressure responsive means be-' 8 References Cited in the file of this patent UNITED STATES PATENTS 2,705,484 Jorgensen et a1. Apr. 5, 1955 2,798,704 Winter July 9, 1957 2,808,244 Dermond Oct. 1,,1957

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