US2970825A

US2970825A - Automatic choke

Info

Publication number: US2970825A
Application number: US712717A
Authority: US
Inventors: Marion L Smitley
Original assignee: Holley Carburetor Co
Current assignee: Holley Performance Products Inc
Priority date: 1958-02-03
Filing date: 1958-02-03
Publication date: 1961-02-07
Anticipated expiration: 1978-02-07

Description

Feb. 7, 1961 s TL 2,970,825

AUTOMATIC CHOKE Filed Feb. 3, 1958 '2 Sheets-Sheet 1 INVENTOR.

E 4 w mm 'M/IP/O/VL S/wnzy M. L. SMITLEY AUTOMATIC CHOKE Feb. 7, '1961 2 Sheets-Sheet 2 Filed Feb. 3, 1958 INVENTOR. 4442/04 1. 624/715) Arrow 5y AUTOMATIC CHOKE Marion L. Smitley, Huntington Woods, Mich, assignor to Holley Carburetor Company, Van Dyke, Mich., a corporation of Michigan Filed Feb. 3, 1958, Ser. No. 712,717

7 Claims. (Cl. 261-144) This invention relates generally-a carburetors for internal combustion engines and more specifically to means for automatically operating the choking mechanism within the carburetor.

Most carburetors of present design employ a coil-type thermostatic bimetal for controLing the amount of choke opening according to temperature. They also use a manifold vacuum responsive piston for initially opening the choke a predetermined degree when the cold engine starts and becomes self-sustaining. These pistons use vacuum by-pass means, such as slots or ports which are opened or closed by the position of the piston, in order to control the extent of their movement.

Such systems have proved to be unsatisfactory because even though the amount of vacuum acting on the piston has been substantially reduced by the bypass means there remains a sufiicient degree of vacuum enabling the piston to exert a continual torque against the force of the bimetal, thereby seriously affecting the proper functioning of the choke valve.

Another serious deficiency of present carburetors is that there are no means for adjusting the amount of initial choke opening, due to the piston, according to the ambient temperature. As a result, this choke opens the same amount (for all practical purposes), regardless of whether the ambient temperature is 75 F. or 30 F., for example. Because of this, the carburetors deliver a mixture which is either too lean or too rich (depending on their original calibrations and settings) during certain seasons of the year.

The invention as hereinafter disclosed is directly concerned with these problems.

Accordingly an object of the invention is to provide means for reducing the torque of the choke vacuum pis ton to an absolute zero once its function has been performed.

Another object of the invention is generally to provide means for varying the degree of initial choke opening once the engine starts; more specifically, the object is to provide means for automatically varying the degree of initial choke opening in accordance with the ambient temperature once the engine becomes self-sustaining.

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

Figure l is a perspective view illustrating generally, a carburetor embodying invention.

Figure 2 is a fragmentary perspective expoded view illustrating the details of construction of the left-hand portion of Figure 1.

Figure'3 is an enlarged fragmentary sectional view illustrating in greater detailthe piston and associated elements shown by Figure 2.

Figure 4 is an enlarged view illustrating some of the elements within the vacuum cylinder shown by Figure 3.

"invention.

Referring to the drawings in greater detail, Figure 1 illustrates a carburetor 10 having a throttle body 12, an air intake 14 with induction passages therethrough adapted to be influenced 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.

Figure 2 illustrates a housing 26, suitably secured as by screws 28 to the corburetor 10, having a cylinder 30 formed therein containing a piston 32 Which is connected through a linkage 34 to the choke lever 36. A shaft 38, extending through and rotatable in one wall of the housing 26, has secured to it at one end thereof the choke lever 36 and at its other end secured to it lever 20 (Figure 1). The choke lever 36 has an outwardly extending projection 40 which is adapted to coact with the free end 42 of thermostatic element 44 through an arcuate opening 46 in the housing cover plate 48.

The thermostatic housing 50 has a shaft located centrally Within and rigidly secured to it to anchor the other end of the thermostatic element 44. Any suitable means such as the clamping ring 52 may be employed to holdthe cover plate 48 and housing 50 in alignment with and against the housing 26. The ring 52 may be secured by means of screws 54 and cooperating threaded portions 56.

Conduit 58 communicates between a source of heated air and the chamber formed generally by cover plate 48 and housing 50. Its purpose is to deliver air, which is at a temperature indicative of engine temperature, to the thermostatic element 44 in order that the element may react to it and change the position of the choke valve 16 accordingly.

Conduit 6t) communicates generally between the cylinder 30 and a source of engine manifold vacuum in such a manner so as to draw air through conduit 53 and cause movement of the piston 32 in a direction so as to result in clockwise rotation of lever 36.

Figure 3 illustrates in greater detail, the details of the choke vacuum piston 32 and cylinder 30. The piston is connected to a linkage 34 by means of a pin 62; the opposite end of the link 34 is operatively connected to lever 36 by means of pin 64 which is retained within lever 36 and slideable within the lostmotion producing-slotoo of link 34. e i t V A thermostatically controlled abutment 68' is located at the substantially closed end of cylinder 30 and is thus adapted to limit the maximum movement of the vacuum piston 32. This abutment, as illustrated ingreater detail in Figure 4, is generally comprised of shaft 79 having one end thereof secured to the closed'end of cylinder 30 and other end thereof threaded with atrelatively fast acting coarsethread. A sleeve 72 having an internally threaded portion 74 coacting with a threaded portion 76 of shaft 70 has a gene-rally slotted-like indentation 78 into which one end 30 of a thermostatic element 82-is suitably secured. The other end 840i the thermostat 82 may be secured to a rod 86 in a generally loop-like manner by passing it through a slot 88 within the rod 86. The rod 86 is in turn rigidly secured at its opposite end to the closed end of cylinder 30.

Operation of invention Assuming, for the purpose of illustration, that the engine is cold and is being cranked, the thermostatic element 44 will be in its unwound condition thereby causing its end 42 to position projection 40 of lever 36 in its extreme counter-clockwise position. The lever 36 being secured to shaft 38 rotates theshaft and arm 20, which is secured to it counter-clockwise thereby causing the choke valve to assume a position which substantially closes on the-flow of air through the carburetor induction passage; 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 rises to a value sufficient to move the vacuum piston downwardly against the abutment 68 in opposition to the force of thermostat 44. This may be accomplished by means of suitable conduitry which causes the open end of piston 30 to be subjected to substantially atmospheric pressure while the closed end of the piston "is subjected to manifold vacuum. As the engine continues to run, air is drawn from a suitable stove through

conduits

58, 89 and 90, through an orifice 92 in cover plate 48, into the chamber formed by the housing 5i and cover plate 48. The air then warms the thermostat 4d and passes into the chamber formed by housing 26 and cover plate 48 through the arcuate opening 46 within the cover plate. The air is then drawn through an orifice 93, which has a restriction 94 therein communicating with conduit 96, which leads from the cylinder 30 to conduits 98 and 60 which are in turn connected to a source of manifold vacuum.

From the foregoing, it is evident that as soon as the engine starts to run the vacuum piston 32 by virtue of its movement causes the choke valve 16 to open some desired and predetermined amount. However, the amount of this opening, in order that optimum operating characteristics can be achieved, should be varied in accordance with the ambient temperature. That is, if the ambient temperature were 0 F. the choke should possibly be opened only five degrees, whereas if the ambient temperature were 65 F. the choke might have to be opened fifteen degrees. These variationsof initial choke opening are necessary in order to deliver a richer fuel-air ratio when the ambient temperature is relatively low.

The above described variations are made possible with the use of this invention. Because no air is drawn into the cylinder 30, the thermostat 82 will respond to the ambient temperature. When the thermostat 82 is cold, it will wind causing sleeve 72 to rotate on the threaded portion of shaft 70 and move away from the closed end of the cylinder. This will result'in the piston 32 having a shorter stroke and consequently result in the choke valve 16 being opened a lesser amount when the engine starts.

Once the piston has moved so as to be held against the sleeve 72 of the abutment 68, no further torque due to manifold vacuum will be experienced at the lever 36 or choke valve 16. From this point on all regulation of choke valve position is accomplished by the thermostat 44. The slot 66 in the linkage 34 is providedso that further movement of the choke valve as regulated by the thermostat, will not be prohibited because of the piston 32 being held against the abutment 68. t

From the foregoing it will be apparent that superior regulation of the choke valve will be obtained because any adverse effects of the vacuum piston are removed by having it abut against a stop which not only removes any undesirable torque but also determines the correct amount of initial choke opening in accordance with ambient temperature.

It is, however, evident that the abutment 68 could be replaced by a solid abutment, as compared to 68 whose length is regulated by a thermostatic element 82. If such a modification were employed in a choke mechanism, the undesirable torque created by the vacuum piston would be removed. Even though there would be no correction of initial choke opening determined by ambient temperature, the resulting choke valve action would still be more accurately correlated to engine requirements than those chokes of present construction.

Other modifications may be made without'exceeding the scope of the invention, as defined by the attached claims.

What I claim as my invention is:

1. In a carburetor, a choke valve, a. source of suction, temperature responsive means influencing the position of the choke valve, pressure'responsive means communicating with the source of suction operatively connected to said choke valve, and positive abutment means for limiting theamount of choke movement due to said pressure responsive means, and second temperature responsive means for adjustably positioning said abutment means.

2. In a carburetor for an internal combustion engine having a choke valve mounted therein, an automatic choke device, comprising a thermostatic control for said choke valve, pressure responsive means operative when the engine starts to move said choke valve in the opening direction, and additional temperature responsive means for limiting the amount of movement of said pressure responsive means.

3. In a carburetor for internal combustion engines, a choke valve, means including a heat responsive device to close said choke valve at low temperatures, a device responsive to engine suction for causing at least a partial opening of said chokevalve against the tension of said heat responsive devide upon starting of the engine, and abutment means associated with said suction responsive device adapted to limit the amount of choke opening due to said suction responsive device.

4. A mixture control for internal combustion engines comprising, a carburetor, a choke valve, thermostatic means for closing said choke valve at low temperatures, pressure responsive means coacting with said temperature responsive means adapted to initially open said choke valve upon starting of the engine, abutment means cooperating with said pressure responsive means and adapted to positively limit said initial choke movement, and lost motion connecting means connected to said pressure responsive means for providing for the exclusive control of the choke valve by said thermostatic means for all choke valve movements beyond said initial choke movement.

5. A control mechanism for an internal combustion engine carburetor having a pressure responsive choke valve comprising, a thermostat tensioned for variably opposing the opening of the choke valve as a function of temperature, said thermostat being so constructed and arranged as to initially oppose the choke movement with maximum tension and being rendered ineffective to op pose further choke movement after normal operating tem perature is attained, pressure responsive means opposing said thermostat when said engine is started, limit means for rendering said pressure responsive means ineffective before normal engine operating temperatures are reached, and a one-way connecting linkage cooperating with said thermostat and said pressure responsive means for providing choke control by said thermostat.

6. In a carburetor having a choke valve therein, an automatic choke control 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 adapted to rotate said second shaft, conduit means leading from the space between the said piston and the closed end of said cylinder and communicating with a source of engine suction, second conduit means leading from the said housing and communicatingwith a source of heated air at substantially atmospheric pressure, thermostatic means within said housing adapted to bias said projection in a direction so as to close said choke valve, connecting means including a lost motion coupling therein between said second arm and said piston enabling said piston to oppose the movement of said thermostat whenever said engine is running, and a thermostatically controlled stop member between said piston and said closed end of said cylinder for limiting the degree of opposition by said piston.

7. In a carburetor for internal combustion engines, a choke valve, means including a heat responsive device to close said choke valve at low temperatures, a device responsive to engine suction for causing at least a partial opening of said choke valve against the tension of said heat responsive device upon starting of the engine, and abutment means associated with and adapted to limit the movement of said suction responsive device in order to limit the amount of choke opening due to said suction responsive device, said abutment means comprising a first externally threaded member rigidly secured to said carburetor, a second internally threaded member adapted to cooperate with said first member in a manner 15 2,818,239

so as to provide for relative axial movement between said first and second members, a thermostatic element coiled about said second member and having one of its ends secured to said second member, and an anchor member rigidly mounted to said carburetor and adapted to retain the other end of said thermostatic element thereby allowing said thermostatic element to cause axial adjustment of said first member relative to said second member in accordance with temperature.

References Cited in the file of this patent UNITED STATES PATENTS Olson Dec. 31, 1957 Eickmeier et al Dec. 31, 1957