US3058727A - Automatic choke - Google Patents

Description

Oct. 16, 1962 A. s. LUCAS 3,058,727

AUTOMATIC CHOKE Filed June 26. 1959 v 3 Sheets-Sheet 1 INVENTOR. 4L w/v6T 10643 E- 5 MQML ATTDE/VE) Oct. 16, 1962 A. s. LUCAS 3,058,727

AUTOMATIC CHOKE Filed June 26, 1959 3 SheetsSheet 2 IN VEN TOR. 41 WM 5 1 00 45 ATTQENE) Uite States atent 3,958,727 AUTOMATIC CHOKE Alvin S. Lucas, Farmington, Mich, assignor to Holley Carburetor Company, Van Dyke, Mich, a corporation of Michigan Filed June 26, 1959, Ser. No. 823,213 11 Claims. (El. 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 choking mechanism provided therein.

Most carburetors of present design include a thermostatic element for controlling the amount of choke opening according to temperature. Additionally, many choke control devices employ a manifold vacuum responsive piston for initially opening the choke a predetermined degree when the cold engine starts and becomes self-sustaining.

Although this general arrangement has been accepted commercially, certain inherent characteristics thereof sometimes cause undesirable results. Some of these results are improper choke come-cit and come-on times, the come-off time being that time required to fully open the choke after the cold engine is started and the come-on time being that time required to close the choke after a substantially warmed engine is shut down.

Accordingly, this invention is directly concerned with the above problems and has as its broad purpose the objective of providing means, in a temperature responsive choke control mechanism, for controlling the choke corneoff and come-on times.

Other more specific objects and advantages will become apparent when reference is made to the following description and accompanying illustrations wherein:

FIGURE 1 is a perspective view illustrating generally a carburetor embodying the invention, with the carburetor being mounted on an engine.

FIGURE 2 is a fragmentary perspective exploded view illustrating the details of construction of the lefthand portion of FIGURE 1.

FIGURE 3 is an enlarged, fragmentary sectional view illustrating in greater detail the piston and associated elements shown by FIGURE 2.

FIGURE 4 is a cross-sectional View taken on the plane of line 44 of FIGURE 3, and looking in the direction of the arrows.

FIGURE 5 is a graph comparing the operation of a choke mechanism embodying the invention with that of presently used choke mechanisms not embodying the invention.

FIGURE 6 is a view similar to FIGURE 3, but illustrating a modification of the invention.

FIGURE 7 is a cross-sectional view taken on the plane of line 7--7 of FIGURE 6 and looking in the direction of the arrows.

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 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. The carburetor is shown mounted on the intake manifold, a portion of which is illustrated at 25.

FIGURE 2 illustrates a housing 26, suitably secured as by screws 28 to the carburetor 10 and 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 a choke lever 36, and at the other end thereof a lever 20 (FIGURE I). The choke lever 36 has an outwardly extending projecice tion 49 which is adapted to coact with the free outer end &2 of thermostatic element 44- through an arcuate opening 46 in the housing cover plate 48.

The thermostatic housing 51 has a centrally located shaft rigidly secured therein to which the inner end of the thermostatic element 44 is secured. Any suitable means such as the clamping ring 52 may be employed to hold the cover plate 43 and housing 56} in alignment with and against the housing 26. The ring 52 may be secured by means of screws 54 and the cooperating threaded portions 56.

(Ionduit 53 communicates 'between a source of heated air, such as the stove 59, and the chamber formed by the cover plate 43 and housing 56'. Its purpose is to deliver a controlled amount of air, which is at a temperature indicative of engine temperature, to the thermostatic element 44 in order that the element 44 may react to it and influence the position of the choke valve 16 accordingly. The general path of this heated air is indicated by the arrows in FIGURE 2, its ultimate exit being to the intake manifold through a porting means between the piston 32 and the walls of the cylinder 30; the latter is to be described more fully in connection with FIGURE 3.

Conduit 69 communicates generally between the cylinder 3G and a source of engine manifold vacuum in such a manner as to cause movement of the piston 32 in a direction resulting in a clockwise rotation of lever 36, and at the same time to draw the heated air referred to above through conduit 5%.

The construction described above is well known to those skilled in the art as the standard automatic choke employed on most carburetors. Other features, such as a fast idle mechanism, are normally associated therewith, but they need not be described since they form no part of the invention.

Referring now to FIGURE 3, piston 32 has a cavity 66 formed therein which is adapted to receive the linkage 34. The other end of the piston is closed and is subjected to manifold pressures as previously described. One end of the linkage 34 may be secured to the piston 32 by any suitable means such as pin 62; the other end of linkage 34 has a slot 35 therein which is adapted to slidably receive a pin 64 which is secured to the lever 36. The slots 68, which constitute the porting means already referred to above, may be formed in the wall of cylinder 30.

A thermostatic assembly '70, as illustrated in FIGURE 4, serves to control a vent 72 adapted to communicate with the atmosphere. The assembly 76' is comprised generally of a thermostatic element 74- secured at one end to a mounting member 76 as by a rivet 78. The mounting member may of course be secured to the housing 26 in any suitable manner, or alternatively be formed as an integral portion of the housing 26. The free end of the thermostatic element 74 has a valve member 89 operatively connected thereto and positioned in such a manner so as to be capable of controlling the flow of air through vent 72. The relative positions of vent 72 and valve '80 may be of course, adjusted by inserting any suitable tool into the slot 73 and turning the body portion of vent 72 so as to raise or lower it.

Operation of Invention Assuming for the purpose of illustration that the engine is cold and is being cranked, the thermostatic element 44 may 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 the shaft and arm 20 which is secured to it counter-clockwise to cause the choke valve 116 to assume a position which substantially closes on the flow of air through the carburetor induction passage 14. All

I 3 of these elements will continue to occupy these respective positions while the engine is being cranked.

As soon as the engine tires and becomes self-sustaining, manifold vacuum rises to a value sufiicient to move the vacuum piston 32 downwardly in opposition to the force of thermostat 44. The extent of movement of this piston is determined by the position of the porting means, that is, slots 68 within the cylinder 30.

As soon as the piston 32 uncovers the ends of the slots 68, the eifect of the manifold vacuum on the piston is reduced to such a degree that the piston is unable to further overcome the opposing force of the thermostat 44. As the engine continues to run, air is drawn from any suitable stove '59 through conduits 58, 82, and 84, throughorifice 86 in cover plate 48, and into the chamber formed by the housing '50 and cover plate 48. This air warms the thermostat 44 and passes through the arcuate opening 46 Within the cover plate. The air is then drawn through the slots 68 in cylinder 30. Ultimately, the air is drawn through orifice 88 into conduit 90 leading from the cylinder to conduits 92 and 60, which are in turn connected to a source of manifold vacuum.

After the piston has performed its function of opening the choke '16 a predetermined degree, the thermostatic element 44 is then required to control the choke position until it has been fully opened. One of the most serious defects of this arrangement, which till this point of the discussion is common to those choke mechanisms currently used, is that the come-off time is excessive. At-

' temps to correct this defect by the substitution of a higher rate thermostatic element failed because the combustible mixture supplied by the carburetor during the period that the choke was progressively opening was made overly lean.

The invention, in order to correct these problems of improper come-off and come-on times, provides means such as illustrated by the thermostatic assembly 70 for varying the responsiveness of the thermostat 44.

The graph of FIGURE 5 illustrates three separate curves A, B, and C of choke valve position in relation to time. Of course, the choke valve position corresponds to the position assumed by the free end 42 of the thermostat 44 until it is fully opened, after which the end 42 continues to move some amount away from the projection of arm .36. The points Y and Z illustrate such overtravel by the free end 42.

Referring again to FIGURE 4, let it be assumed, for purposes of illustration, that the engine on which the carburetor is to be used has the characteristic which requires that the choke valve 16 be at a point P at some time X after the engine is started. In order to accomplish this, a thermostat 44 is provided whichwill have a particular rate whereby the performance slope passes through points M and P. When this is done, however, the come-off time, as determined at point N, is excessive; this causes overly rich combustible mixtures and poor economy.

Realizing that the desired come-off time is at some point R, a thermostatic element of higher rate could be used so as to have a slope passing through points M and R. With this change, however, it is to be noted that for the same time X the choke 16 will have assumed a more nearly open position S, than it had previously at point P. In other words, with such a change the come-off time would be proper but the combustible mixture supplied as a consequence of choke position would be too lean for proper engine operation during the warm-up period.

In contrast to the curves A and C, the invention pro-' vides means whereby the performance curve of a particular thermostat having a definite rate can be controlled so as to deliver the proper richness of the combustible mixture and yet attain the desired come-off time. Such a curve is illustrated at B in FIGURE 5.

The method by which the invention accomplishes this is by the use of the thermostatic assembly 70. That is,

as the engine is started cold, the valve 8t) is held away from the port 72 by means of thermostatic element 74.

As a result of this, the vacuum which exists generally Within the chamber 26 as described previously causes 5 some unheated atmospheric air to be drawn in instead of all heated air through the conduit 58. By such means the heating effect upon the thermostat 44- is minimized generally during the time X.

As the thermostatic element 74 becomes heated, the port 72 is progressively closed causing less unheated atmospheric air to be drawn in and conversely more heated air to be supplied to the thermostat 44. In this manner, the performance curve can be shaped so as to pass through the desired points M, P, and R.

Additionally, an added feature of this invention is that the come-on time can be prolonged. That is, the present choke mechanisms are too quick in the responsiveness after the engine is shutdown. This usually occurs as a result of the use of low rate thermostats which when exposed to the full heat of the warmed engine have only a slight movement away from the lever 40, as illustrated by the position of point Z on the ordinate scale.

By the use of .a high rate thermostat 44 in the invention, a point Y can be attained which is substantially increased ordinate-Wise over the point Z. As a result of this, the engine has to cool to a greater degree, which in turn requires a longer period of time, before the choke 16 will again begin to close. This feature again improves the economy.

A modification of this invention, as illustrated in FIG- URE 6, employs mechanical means for controlling the amount of unheated bleed air instead of the thermostatic means disclosed in FIGURES 2, 3 and 4. All of the elements in FIGURE 6 which are identical or similar to those of the prior figures are identified with primed numerals. 1

In this embodiment, a spring 94 having a valving member 96 secured to one end of it is mounted on the housing 26' by any suitable means such as a block 93. The spring 94 may be secured to the block 98 in any suitable manner such as by a rivet 100. The arm portion 37 of lever 36' has a projecting member 102 which is adapted to be in continuous contact with the spring 94.

FIGURE 7 illustrates a typical coaction of the various elements of the modification. Referring more specifically to FIGURE 7, it can be seen that the spring 94 is formed so as to present a generally inclined cam surface 104 to member 1102-, so that as the member 102 traverses along the length of the spring the valving member 96 is progressively and continuously brought closer to the bleed jet 72.

The movement of the lever 36' is again a function of the choke plate 16 position. Since the choke plate posi- .tion is an indication of the temperature of thermostat 44, it might be stated broadly that this mechanical embodiment is again indicative of'engine temperature. As 7 I the valving member 96 approaches the bleed jet 72, the

' amount of cold air drawn into housing 26' by virtue of the manifoldflvacuum existing therein is reduced. As the quantity of cold air is reduced, the quantity of heated air is consequently increased so as to cause a more rapid heating of the thermostat 44. The end result of this modification is the same as that illustrated in the previous figures in that the come-off and come-on times plus the fuel-air ratio during theinterim periods can be controlled by the shape and position of the mechanical spring 94.

Although only two embodiments of the invention have been disclosed and described, it is apparent that other 7|) modifications of the invention are possible Within the scope of the appended claims.

What I claim as my invention is: 1 In a carburetor for van'internal combustion engine having an induction passage and a choke valve controlling the flow of air therethrough, a housing, a thermostatic element in said housing operatively connected to said choke valve for regulating the opening and closing of said choke valve in accordance with engine temperature, means including an inlet in said housing for directing a flow of heated fluid to said thermostatic element, and means for reducing the temperature of said fluid flow passing through said inlet until a predetermined temperature is attained.

2. In a carburetor for an internal combustion engine having an induction passage and a choke valve controlling the fiow of air therethrough, a first thermostatic element operatively connected to said choke valve for regulating the opening and closing of said choke valve in accordance with engine temperature, and additional thermostatic means for delaying the full application of engine heat to said first thermostatic element until a predetermined engine temperature is attained.

3. In a carburetor for an internal combustion engine having an induction passage and a choke valve controlling the flow of air therethrough, a housing, a thermostatic element in said housing operatively connected to said choke valve for regulating the opening and closing of said choke valve in accordance with engine temperature, and means for admitting cold ambient air into said housing in decreasing quantities as the temperature of said engine increases.

4. In a carburetor for an internal combustion engine having an induction passage and a choke valve controlling the flow of air therethrough, a source of engine heat, a thermostatic element operatively connected to said choke valve for regulating the opening and closing of said choke valve, means for continually directing said engine heat to said thermostatic element so as to cause said thermostatic element to react generally in accordance with engine temperature, and separate mechanical means for reducing the degree of said engine heat supplied to said thermostatic element until said engine attains a predetermined temperature.

5. In a carburetor for an internal combustion engine having an induction passage and a choke valve controlling the flow of air therethrough, a housing, a source of engine heat, a thermostatic element contained within said housing and operatively connected to said choke valve for regulating the opening and closing of said choke valve, means for directing said engine heat to said thermostatic element so as to cause said thermostatic element to react generally in accordance with engine temperature, and separate mechanical valve means for reducing the supply of said engine heat to said thermostatic element by admitting cold ambient air into said housing until said choke valve attains a predetermined degree of opening.

6. The method of controlling the richness of the combustible mixture delivered to an internal combustion engine having a carburetor with an induction passage and a choke valve in said induction passage adapted to be controlled by a thermostatic element responsive to the heat generated by said engine, the steps comprising the method being first, minimizing the degree of said heat applied to said thermostatic element by the addition of cold ambient air until a first predetermined engine temperature is attained; second, increasing the degree of said heat applied to said thermostatic element by reducing the quantity of cold ambient air after said first predetermined temperature is attained and until a second predetermined engine temperature is reached; and last, eliminating all cold ambient air and applying all of said heat to said thermostatic element after said second predetermined engine temperature is attained.

7. 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, 9. 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 communicating with 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 between said second arm and said piston enabling said piston to oppose the movement of said thermostat whenever said engine is running, cam operated valve means adapted to at times communicate between the atmosphere and the interior of said housing, and means secured to said second arm for actuating said cam operated valve means in accordance with the position of said second arm member.

8. In a carburetor for an internal combustion engine having an induction passage with 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 communicating with a source of heated air at substantially atmospheric pressure, first thermostatic means Within said housing adapted to bias said projection in a direction so as to close said choke valve, connecting means between said second arm and said piston enabling said piston to oppose the movement of said thermostat whenever said engine is running, valve means adapted to at times communicate between the atmosphere and the interior of said housing, and second thermostatic means for actuating said valve means in accordance with the temperature of said engine.

9. The method of controlling the richness of the combustible mixture delivered to an internal combustion engine having a carburetor with an induction passage and a choke valve in said induction passage adapted to be controlled by a thermostatic element responsive to the heat generated by said engine, the steps comprising the method being first, minimizing the degree of said heat applied to said thermostatic element by the addition of cold ambient air at low engine temperatures; second, progressively increasing the degree of said heat applied to said thermostatic element by progressively reducing the quantity of said cold ambient air as engine temperature increases and until a predetermined higher engine temperature is reached; and last, eliminating all of said cold ambient air and applying all of said heat to said thermostatic element after said predetermined higher engine temperature is attained.

10. In a carburetor for an internal combustion engine having an induction passage and a choke valve controlling the flow of air therethrough, a housing, a thermostatic element in said housing operably connected to said choke valve for resisting the opening of said choke valve with decreasing force as engine temperature increases, means including an inlet to said housing for directing a flow of heated fluid indicative of engine temperature to said thermostatic element, and means responsive to the temperature of said fiuidfor introducing decreasing amounts of cold ambient air as the temperature of said fluid increases.

11. In a carburetor for an internal combustion engine having an induction passage and a choke valve controlling the flow of air therethrough, a housing, a thermostatic element in said housing operably connected to said choke valve for resisting the opening of said choke valve with decreasing force when engine temperature increases, means including an inlet to said housing for directing a flow of heated fluid indicative of engine temperature to said thermostatic element, and means responsive to the position of said choke valve for introducing decreasing amounts of cold ambient air as said choke valve moves to a more fu'lly opened position.

1 References Cited in the file of this patent UNITED STATES PATENTS 2,698,168 Olson Dec. 28, 1954 2,719,706 Winkler Oct. 4, 1955 2,803,442 Hausburg Aug. 20, 1957 2,848,201 Bennett Aug. 19, 1958 2,937,635 Carlson et a1 May 24, 1960 2,942,596 Carlson June 28, 1960

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