US3248096A - Choke control for carburetor - Google Patents

Description

April26, 1966 'r. M. BALL 3,248,096

CHOKE CONTROL FOR CARBURETOR bri inal Filed Dec. 21. 19s;

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United States Patent CHOKE CQNTROL FOR CARBURETO Thomas M. Ball, Bloomfieid Hills, Mich, assignor to Chrysler Corporation, Highland Park, MiclL, a corporation of Delaware Original application Dec. 21, 1961, Set. No. 161,189. Divided and this application Oct. 8, 1963, Ser. No.

4 Claims. (Cl. 261-39) This application is a division of my copending application, Serial No. 161,189, filed December 21, 1961.

This invention relates to improvements in the automatic control of a carburetor for an internal combustion engine and has for an important object the provision of improved control means for the conventional unbalanced choke blade effective to prevent stalling of the engine immediately after it has been started.

Occasionally when an automatic engine is initially started, a rush of inlet air blows the choke blade open sufiiciently to cause the engine to stall, particularly during unfavorable weather conditions. It is accordingly another object of the invention to provide improved simple and economical means which is highly effective to enable limitedopening of the choke during starting only, so as to prevent stalling, and which allows normal choke operation after the engine has been started and the throttle has once been opened beyond the idle operating condition.

Other objects of this invention will appear in the following description and appended claims, reference being had to the accompanying drawings forming a part of this specification wherein like reference characters designate corresponding parts in the several views.

FIGURE 1 is a fragmentary and generally schematic view of a carburetor embodying the present invention, portions being broken away to illustrate details of construction, the choke blade being shown in the starting position.

FIGURE 2 is a view similar to FIGURE 1, showing the choke blade in an idle operating position.

It is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of other embodiments and of being practiced or carried out in various ways. Also it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.

Referring to the drawings, an embodiment of the present invention is illustrated by way of example comprising a carburetor for an automobile'engine, the carburetor including a body having the customary air inlet induction conduit 11. An unbalancedchoke blade or valve 12 is secured to a rotatable shaft 13 journalled at opposite ends in the body 10. The blade 12 is pivotal with shaft 13 and is located-in the upper portion of conduit 11 in accordance with conventional practice. "A throttle valve 14 secured to a rotatable shaft 15 journalled at opposite ends in the body 10 is provided at a downstream location of the conduit 11. A

Suitably located within a portion of the engine so as to be responsive to an operating temperature thereof is a spiral bi-metallic thermostat spring 16 having a fixed end secured to a fixed spindle 18. A swinging arm 19 pivotal on spindle 18 has an outer swinging end pivotally connected to the lower end of an operating link 21. A free end 22 of thermostat 16 is engaged with arm 19 to urge arm 19 counterclockwise with progressively increas- The upper end of link 21 is pivotally connected at 23 to the swinging end of a crank arm 24 keyed to the choke shaft 13.

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Keyed to the throttle shaft 15 is a throttle control lever 25 having one swinging end pivotally connected at 26 with a personally actuated throttle link 27. The other end of lever 25 is provided with a threaded boss 28 having an adjustable idle control screw or cam follower29 screwed therein. The inner end of screw 29 is adapted to engage a stepped cam surface of -a fast idle cam 31 when the latter is in a predetermined cold idle operating position as described below. The cam 31 is keyed to a rotatable axial stub 32 journalled on the body 10 and is provided with ,a counterweight portion 33 effective to urge clockwise rotation of cam 31 by gravity force toward a warm operating position.

Throttle lever 25 is normally urged clockwise toward the closed or idle position illustrated in FIGURES 1 and 2 by a customary throttle return spring 27a schematically illustrated under tension between a projection 25a of lever 25 and a fixed portion 27b of the engine. Foot pedal actuation of shaft 27 is effective to swing lever 25 counterclockwise to open the throttle 14.

Upon closing movement of choke valve 12, the fast idle cam 31 is swung counterclockwise to the cold position by means of a link 34 having an upper end pivotally connected at 35 to a crank arm 36 keyed to shaft 13. The lower end of link 34 terminates in an extension 37 which projects in a direction parallel to the pivot axis of cam 31 through a lost motion slot 38 to complete a lost motion pivotal connection between link 34 and cam 31. Slot 38 is formed arcuately within the counterweight portion 33 concentrically with the pivot axis of cam 31 to enable opening movement of choke valve 12 independently of movement of cam 31, as described below, by virtue of extension 37 riding within groove 38.

In order to render the position of choke valve 12 responsive to the pressure in conduit 11 downstream of throttle valve 14, a vacuum cylinder 40 formed integrally with body 10 contains a reciprocable piston 41 therein. A link 54 is provided with an upper end pivotally connected at 55 to the outer end of a projection 45 secured to valve 12-so as to swing the latter in a clockwise opening movement upon rightward movement of link 54. The opposite end of link 54 is pivotally connected at 56 to one end of a short connecting link 57, the other end of the latter link being pivotally connected at 58 to piston 41 to complete a toggle connection. A notch 59 is provided in the inner sidewall of cylinder 40 adjacent the latters left end to receive a depending projection 60 of link 54, FIGURE 1. The notch 59 is dimensioned so that immediately after starting the engine with the throttle 14 open, opening of choke valve 12 will be limited by engagement between projection 60 and the right edge of notch 59 to prevent stalling of the engine as described above. right end of cylinder 40 is connected by means of duct 46 with induction conduit 11 at a location downstream of throttle valve 1,4,FIGURE 2, thereby to urge opening of choke 12 against the force of thermostat spring 16 when the pressure downstream of throttle valve 14 is low, i.e during engine idling.

In the operation of the structure illustrated, throttle 14 is preferably open during starting. When the cold engine is initially started and while the throttle 14 is still open, limited opening of choke 12, as for example approximately 10 to a starting position, is enabled by the lost motion of projection 60 in notch 59. When the throttle 14 is subsequently returned to the idle position in FIG- URE 1, the low pressure induced downstream of throttle 14 and conducted to the right side of piston 41 will exert sufficient force on the latter piston to pull projection'60 upwardly from notch 59 and enable operation of choke valve 12 in the customary manner. When the engine is -operated under load, the downward flow of air through The to maintain choke 12 open sufiiciently to prevent extension 60 from re-entering'notch 59, regardless of the temperature condition of thermostat 16. By this time, the danger of engine stalling will have passed, because the stalling tendency described occurs only in' the first two or three seconds of engine operation.

When screw 29 is in contact with the stepped cam surface, the frictional contact between screw 29 and cam 31 resulting from the tension of spring 27a is suflicient to prevent pivotal movement of cam 31 in consequence of the normal forces acting thereon, such as the forces resulting from counterweight 33, thermostat coil 16, piston 41, or the downwardly flowing air in conduit'll acting on the unbalanced blade 12. In consequence, when the carburetor parts are in the cold position illustrated in FIGURE 1 and the engine is idling, the throttle 14 will be maintained in a fast idle position by reason of screw 29 engaging the fast idlestep of the cam surface of cam 31. At the fast idle position, throttle 14 is cracked slightly open as illustrated in FIGURE 1, so that the engine will idle .etfectively in the cold condition. Thereafter, when throttle valve 14 is opened from the fast idle position to accelerate the engine, the frictional engagement between screw 29 and cam 31 will be released to enable opening of choke valve 12 to the usual operating condition.

If the throttle 14 is then returned to a cold idle position so as to engage one of the lesser steps of the cam surface of cam 31, the latter will be locked against swinging movement as aforesaid by virtue of its frictional contactwith screw 29. However, the cam 31 will receive extension 37 within slot 38. Thus if the engine is allowed to run at idle for sufiicient time to relax the closing force of thermostat spring 16 as a result of warming of the engine, throttle valve 12 will be free to open by virtue of movement of extension 37 along slot 38, FIGURE 2.

If the engine is operated in the warm condition under load and is then turned olf and allowed to cool, choke valve 12 will be locked against return movement to the closed position by contact between fast idle cam 31 and screw 29. Accordingly, in order to return the carburetor mechanism to the position illustrated in FIGURE 1, throttle 14 must first be opened to release the engagement between cam 31 and screw 29 thereby to enable thermostat spring 16 to return choke valve 12 and cam 31 to the position of FIGURE 1. Thereafter upon closing of throttle 14, screw 29 will engage the cold starting step of cam 31 as illustrated in FIGURE -1.

I claim:

1. In a fuel charging device for an internal combustion engine, air inlet conduit means, a choke valve in said conduit means having an unbalanced pivotal blade adapted to be urged to an open position by the air flow in said conduit means impinging on said blade, thermostatic means responsive to decreasing temperature for yielding- 1y closing said choke valve, a throttle valve in said conduit means movable between open and idle position, means to enable limited air flow induced opening of said choke blade to a starting position and to block further opening thereof to prevent a sudden flow of inlet air in said conduit means suflicient to stall said engine immediately after the latter has begun to operate under its own power with said throttle valve at its open position comprising pressure actuated means responsive to the pressure in said conduit means downstream of said throttle valve and operatively coupled with said choke valve to open the latter in opposition to said thermostatic means when said throttle valve is at said idle position and to release said choke valve for closing when said throttle valve is at its openposition, operable movement limiting means cooperable with said pressure actuated means and choke valve to block air flow induced opening of the latter beyond said starting position when said throttle valve is at its open position and to release said choke valve for opening when said throttle valve is .at said idle position.

2. In a fuel charging device for an internal combusr tion engine, air inlet conduit means, a choke valve in said conduit means having an unbalanced blade adapted to be urged to an open position by the air'flow in said inlet conduit means impinging on said blade, a throttle valve in said conduit means movable between idle and open I positions, means to enable limited air flow induced OP'fiIl'. ing of said blade to astarting position and to block further opening thereof to prevent a sudden flow of inlet air in said conduit means sufficient to stall said engine .im-. mediately after the latter has begun to operate under its own power with said throttle valve at an open position comprising a fixed stop, toggle means including a pair of links having inner ends pivotally connected and having outer ends relatively movable toward and from each other to fold and unfold said toggle means respectively, said starting position and being movable out of engagement with said stop to free said choke valve for opening upon unfolding of said toggle means, piston meansconnected with said other end and responsive to the pressure in said conduit means downstream of said throttle valve when the latter is in an [idle operating condition to move said other end in said direction away from said one end, thereby to unfold said toggle means and open said choke valve.

3. In a fuel charging device for an internal combustion engine, air inlet conduit means, a choke valve in said conduit means having an unbalanced blade adapted.

to be urged to an open position by the air flow in said inlet conduit means impinging .on said blade, thermostatic means responsive to decreasing temperaturetfor yieldingly closing said valve, a throttle valve in said ,conduit means movable between idle and open positions, a fixed abutment, means to enable limited opening of said blade to a starting position and to block further opening thereof to prevent a sudden flow of inlet air in said conduit means sufficient to stall said engine immediately after the latter has begun to operate under its own power with said throttle valve at an open position comprising an operating member connected with said choke valve for actuation conjointly therewith and having a movement limiting portion engageable with said fixed abutment'upon said limited opening of said choke valve blade to said starting position, piston means operably connected with I said operating member and responsive to the pressure in said conduit means downstream of said throttle valve when the latter is in an idle operating condition to move said movement limiting portion out of engagement with said abutment and urge said choke valve blade toward an sition, means operatively connecting said valve and cam.

means to pivot the latter to said cold position upon closing of said valve, a throttle valve in said conduit means movable between idle and open positions, idle control means movable with said throttle valve and engageable with said cam means at the cold position to limit closing movement of said throttle valve to a fast idle position, 'said idle control means engaging said cam means to prevent pivoting of said cam means until said throttle valve is opened from said fast idle position, means to enable limited air flow induced opening of said blade to a starting position and to block further opening thereof to prevent a sudden flow of inlet air in said conduit means sufiicient to stall said engine immediately after the latter has begun to operate under its own power with said throttlevalve at an open position comprising a fixed stop, toggle means having one of opposite ends connected to said choke valve to move toward the other of said ends and fold said toggle means upon air flow induced opening of said choke valve from its closed position and adapted to unfold and pull said one end to open said choke valve upon movement of said other end in the direction awayfrom one end, movement limiting means movable with said toggle means into engagement with said stop on folding of said toggle means to limit said folding and said air flow induced opening of said choke valve blade to said star-ting position and being movable out of engagement with said stop to free said choke valve for opening upon unfolding of said toggle means, piston means connected with said other end and responsive to the pressure in said conduit means downstream of said throttle valve when the latter is in an idle operating condition to move said other end in said direction away from said one end, thereby to unfold said toggle means and open said choke valve.

References Cited by the Examiner UNITED STATES PATENTS 2,408,104 9/ 1946 Stanton.

2,420,917 5/ 1947 Sutton et a1.

2,540,607 2/1951 Boyce 261-52 X 2,746,439 5/ 1956 Hunt.

2,762,354 9/ 1956 'Winkler.

HARRY B. THORNTON, Primary Examiner.

RONALD R. WEAVER, Assistant Examiner.

Claims (1)

1. 3. IN A FUEL CHARGING DEVICE FOR AN INTERNAL COMBUSTION ENGINE, AIR INLET CONDUIT MEANS, A CHOKE VALVE IN SAID CONDUIT MEANS HAVING AN UNBALANCED BLADE ADAPTED TO BE URGED TO AN OPEN POSITION BY THE AIR FLOW IN SAID INLET CONDUIT MEANS IMPINGING ON SAID BLADE, THERMOSTATIC MEANS RESPONSIVE TO DECREASING TEMPERATURE FOR YIELDINGLY CLOSING SAID VALVE, A THROTTLE VALVE IN SAID CONDUIT MEANS MOVABLE BETWEEN IDLE AND OPEN POSITIONS, A FIXED ABUTMENT, MEANS TO ENABLE LIMITED OPENING OF SAID BLADE TO A STARTING POSITION AND TO BLOCK FURTHER OPENING THEREOF TO PREVENT A SUDDEN FLOW OF INLET AIR IN SAID CONDUIT MEANS SUFFICIENT TO STALL SAID ENGINE IMMEDIATELY AFTER THE LATTER HAS BEGUN TO OPERATE UNDER ITS OWN POWER WITH SAID THROTTLE VALVE AT AN OPEN POSITION COMPRISING AN OPERATING MEMBER CONNECTED WITH SAID CHOKE VALVE FOR ACTUATION CONJOINTLY THEREWITH AND HAVING A MOVEMENT LIMITING PORTION ENGAGEABLE WITH SAID FIXED ABUTMENT UPON SAID LIMITED OPENING OF SAID CHOKE VALVE BLADE TO SAID STARTING POSITION, PISTON MEANS OPERABLY CONNECTED WITH

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