US3227428A

US3227428A - Automatic choke mechanism

Info

Publication number: US3227428A
Application number: US214234A
Authority: US
Inventors: William W Charron
Original assignee: Ford Motor Co
Current assignee: Ford Motor Co
Priority date: 1962-08-02
Filing date: 1962-08-02
Publication date: 1966-01-04
Anticipated expiration: 1983-01-04
Also published as: GB965526A; DE1937127U

Description

Jan. 4, 1966 w. w. CHARRON AUTOMATIC CHOKE MECHANISM Filed Aug. 2, 1962 W/L L /AM l4. CHARRON INVENTOR A/KM 2 m 4M ATTORNEYS United States Patent f 3,227,428 AUTOMATIC CHOKE MECHANISM. William W. Charron, Livonia, Mich., assignor to Ford Motor Company, Dearboru, Mich., a corporation of.

Delaware Filed Aug. 2, 1962, Ser. No. 214,234 2 Claims. (Cl. 261-39) becomes toolean forsustained operation during warm up, the choke valve should close momentarily to enrich the mixture andpreventengine stalling. Although the aforementioned functions are well understood, the numerous attempts to provide a choke mechanism that satis factorily performs these functions have not been completely successful.

Hunt Patent No. 1,996,245 is illustrative of the types of choke mechanisms that have been employed with varying degrees of success. In each of the embodiments of the Hunt patent, a choke valve that tends to be opened by engine suction is positioned in the induction passage of the carburetor. Latching means are provided to maintain the choke valve in a closed position during low tem-. perature engine cranking. When the engine starts the.

latching means yields and allows the choke valve to open for sustained operation.

In one of the embodiments of the Hunt patent a perma-v nent magnet is utilized as the latching means for holding the choke valve in a closed position during engine crank-.

ing. The magnet exerts a small force which tends to close the choke valve if an overlean mixture causes the engine to stall during warm up. The strength and location of the magnets conventionally employed for this purpose are not sufiicient, however, to close the choke valve once it has opened any appreciable extent.

It is, therefore, the principle object of this invention to provide an improved choke mechanism that utilizes magnetic means for latching the choke valve in a closed position during cranking.

It is a further object of this invention to provide a choke mechanism that automatically closes the choke valve during warm up to prevent engine stalling by enriching an otherwise overlean mixture.

A carburetor embodying this invention incorporates an unbalanced. choke valve that tends to be opened by engine suction. Magnetic means are juxtaposed to a portion of the choke mechanism, when the choke valve is in its closed position, for resisting engine suction induced opening of the choke valve. Spring means are additionally provided for resisting engine suction induced open ing of the choke valve.

Further objects and advantages of this invention will become more apparent as this description proceeds, particularly when considered in conjunction with the accompanying drawings, wherein:

FIGURE 1 is a partially exploded perspective view of a portion of a carburetor embodying this invention;

FIGURE 2 is a cross sectional view taken along line 22 of FIGURE 1;

FIGURE 3 is a view in part similar to FIGURE 2 showing the choke valve in another position;

FIGURE 4 is a view in part similar to FIGURES 2 and 3 showing the choke valve in still another position; and,

FIGURE 5 is a perspective view of a portion of the choke mechanism.

Referring now in detail to the drawings, and in particular to FIGURE 1, there is shown generally at 11 a portion of the carburetor of an internal combustion engine. The carburetor 11 is of the two stage, four barrel type. That is, two primary induction passages (not shown) and two secondary induction passages 12 and 13 are formed in a main body 14 of the carburetor. Throttle valves are positioned in the primary and secondary induction passages to control the flow of mixture therethrough in a known manner.

An air horn 15 is secured to the main body 14 of the carburetor by threaded fasteners (not shown). The air horn 15 defines induction openings above the secondary passages 12 and 13 and has a raised portion 16 that forms a common induction passage for the primary passages. A choke valve 17 is pivotally supported within the raised air horn portion 16 by a choke shaft 18. The

choke valve 17 is of the unbalanced type. That is, it is on the upper unequal surface area of the choke valve 17 to rotate the choke valve 17 into an open position.

The position of choke valve 17 is controlled by an automatic choke actuating mechanism indicated generally at 19 and shown in exploded view in FIGURE 1. The automatic choke actuating mechanism 19 includes a thermostatic spring 21- secured at one end to a plastic thermostatic spring cover 22. The other end of .the thermostatic spring 21 is coiled as at 23 to receive the projecting end 24 of a thermostatic spring lever 25. The thermostatic spring lever 25 is rigidly secured to a bushing 26 having an enlarged end 27. A coiled torsional spring 28 encirclesthe bushing 26 and is contained between the enlarged end 27 and the thermostatic spring lever 25. A choke housing shaft 29 is rotatably supported within the bushing 26. Secured to the end of the choke housing shaft 29 is a lever 31 having a plurality of contacts a tang 36 formed upon the thermostatic spring lever 25 and the other end 37 of the torsional spring 28 contacts one of the tangs 33 formed upon the lever 31.

The thermostatic spring lever 25 and the choke housing shaft 29 therefore normally tend to rotate as a unit. .The preload on the torsional spring 28*may bevaried by altering which of the tang-s 33 the end 37 contacts.

The plastic thermostatic spring cover 22 is secured to a choke housing 38 by a clamp 39 and a plurality of threaded fasteners 41. The choke housing 38 is secured upon the carburetor 11 by a plurality of fasteners 42 (only one of which is shown) which are threaded into bosses 43 formed integrally with the main body 14. Mean-s are provided for supplying a source of air heated by the engine to the choke housing 38 and thermostatic spring 21 in a known manner.

When the automatic choke actuating mechanism 19 is secured to the carburetor 11 as an assembly, a portion of the choke housing shaft 29 extends from within the choke housing 38. Nonrotatably secured to this portion of the choke housing shaft 29 is a lever 44. The lever 44 is fixed axially upon the choke housing shaft 29 Patented Jan. 4, 19661 3 by a nut 45 threaded upon the externally threaded end 46 of the choke housing shaft 29. A lever 47 is nonrotatably secured to the exposed end of the choke shaft 18. A choke valve rod 48 is pivotally connected to the levers 47 and 44 and transmits motion from the choke housing shaft 29 to the choke shaft 18.

A permanent magnet 49 is secured in a sheet metal housing 51 that is, in turn, secured to the raised air horn portion 16 by threaded fasteners 52. The permanent magnet 49 is positioned in the periphery of the induction passage contiguous to the edge of the long end of the choke valve 17 when the latter is in its closed position (FIG- URE 2). The choke valve 17 is formed of a magnetic material and hence is attracted by the permanent magnet 49. The permanent magnet 49, therefore, tends to hold the choke valve 17 in a closed position.

Operation Under low ambient temperatures, the thermostatic spring 21 rotates the thermostatic spring lever 25 in a counterclockwise direction. The motion of the thermostatic spring lever 25 is transmitted to the lever 31 and choke housing shaft 29 through the torsional spring 28. This results in counterclockwise rotation of the lever 44 drawing the choke valve rod 48 downwardly. Downward movement of the choke valve rod 48 causes counterclockwise rotation of the choke shaft lever 47 and choke shaft 18. This moves the choke valve 17 to a closed position wherein it is attracted by the magnet 49 (FIGURES 1 and 2).

During engine cranking there is insufficient engine suction to cause the choke valve 17 to open. Once the engine fires and commences running, however, a decrease in pressure occurs below the choke valve 17. When the difference between the pressure below the choke valve 17 and the atmospheric pressure acting upon the choke valve 17 exceeds the force exerted by the permanent magnet 49 and the preload of the torsion spring 28, the choke plate will partially open (FIGURE 3) and permit the engine to run. The lost motion connection provided by the aperture 34 in the thermostatic spring lever 25 and the tang 32 of the lever 31 permits this opening of the choke valve 17. An additional load is thereby put upon the torsion spring 28.

If during warm up an overlean mixture tends to cause engine stalling, the pressure on the downstream side of the choke valve 17 will increase (engine suction decreases). The preload of the torsion spring 28 then overcomes the unbalanced pressure upon the choke valve 17 and moves the choke valve 17 toward a fully closed position. The attraction of the magnet 49 may cause complete closing of the choke valve 17 if necessary until the engine again runs evenly.

During continued warm up the thermostatic element 21 causes additional opening of the choke valve 17 (FIG- URE 4). During this stage of operation there is less tendency for the engine to stall because of a lean mixture. The,trsi0n spring 28 and permanent magnet 49 will, therefore, have less effect upon the position of the choke valve 17.

It should be readily apparent that the combined action of the torsion spring 28 and permanent magnet 49 provided the desired choke action. That is, the choke valve 17 is held closed during engine cranking; however, the choke plate may open to permit sufficient air flow to allow sustained engine operation during warm up. The torsion spring will tend to close the choke valve if an overlean mixture tends to cause engine stalling. The permanent magnet will assist in this operation if required.

It is to be understood that this invention is not limited to the exact construction shown and described, but that various changes and modifications may be made without departing from the spirit and scope of the invention.

I claim:

1. A carburetor for an internal combustion engine comprising an induction passage, a throttle valve positioned in said induction passage, a choke valve positioned in said induction passage anterior to said throttle valve, said choke valve being unbalanced so that engine suction tends to open said choke valve, means operably connected to said choke valve for moving said choke valve between an opened and a closed position, spring means operably connected to said choke valve for resisting engine suction induced opening of said choke valve, and magnetic means supported by said carburetor in said induction passage for engaging said choke valve when said choke valve is in its fully closed position, said choke valve being formed at least in part of a magnetic material whereby said magnetic means resists engine suction induced opening of said choke valve.

2. A carburetor for an an internal combustion engine comprising an induction passage, a throttle valve positioned in said induction passage, a choke valve positioned in said induction passage anterior to said throttle valve, said choke valve being unbalanced so that engine suction tends to open said choke valve, thermally responsive means operatively connected to said choke valve for moving said choke valve between an opened and a closed position in response to temperature changes, spring means operatively connected to said choke valve for resisting engine suction induced opening of said choke valve, and magnetic means supported by said carburetor in said induction passage for engaging said choke valve when said choke valve is in its fully closed position, said choke valve being formed at least in part of a magnetic material whereby said magnetic means resists engine suction induced opening of said choke valve.

References Cited by the Examiner UNITED STATES PATENTS 1,996,245 4/1935 Hunt 26139 2,158,424 5/ 1939 Hunt. 2,325,918 8/1943 Perrine 26139 2,818,238 12/1957 Olson 261-39 2,998,233 8/1961 Marsee 26139 HARRY B. THORNTON, Primary Examiner.

HERBERT L. MARTIN, Examiner.

Claims

1. A CARBURETOR FOR AN INTERNAL COMBUSTION ENGINE COMPRISING AN INDUCTION PASSAGE, A THROTTLE VALVE POSITIONED IN SAID INDUCTION PASSAGE, A CHOKE VALVE POSITIONED IN SAID INDUCTION PASSAGE ANTERIOR TO SAID THROTTLE VALVE, SAID CHOKE VALVE BEING UNBALANCED SO THAT ENGINE SUCTION TENDS TO OPEN SAID CHOKE VALVE, MANS OPERABLY CONNECTED TO SAID CHOKE VALVE FOR MOVING SAID CHOKE VALVE BETWEEN AN OPENED AND A CLOSED POSITION, SPRING MEANS OPERABLY CONNECTED TO SAID CHOKE VALVE FOR RESISTING ENGINE SUCTION INDUCED OPENING OF SAID CHOKE VALVE, AND MAGNETIC MEANS SUPPORTED BY SAID CARBURETOR IN SAID INDUCTION PASSAGE FOR ENGAGING SAID CHOKE VALVE WHEN SAID CHOKE VALVE IS IN ITS FULLY CLOSED POSITION, SAID CHOKE VALVE BEING FORMED AT LEAST IN PART OF A MAGNETIC MATERIAL WHEREBY SAID MAGNETIC MEANS RESISTS ENGINE SUCTION INDUCED OPENING OF SAID CHOKE VALVE.