US3085792A - Carburetor - Google Patents

Description

April 6, 1963 A. J. HILL 3,085,792

345 I N V EN TOR;

W 4A T/fl/1? 1/9/44 ATTORNEY A ril 16, 1963 Filed March 25, 1960 A. J. HILL 3,085,792

CARBURETOR 3 Sheets-Sheet 2 4 /0 I I I 22 20 I INVENTOR.

ATTORNEY 3,085,792 CARBURETOR Arthur J. Hill, Royal Oak, Mich., assignor to Holley Carburetor Company, Van Dyke, Mich., a corporation of Michigan Filed Mar. 23, 1960, Ser. No. 17,120 Claims. (Cl. 261-39) This invention relates generally to carburetors for internal combustion engines, and more specifically to carburetors having automatic choke control mechanisms associated therewith.

It is conventional practice in present carburetors employing automatic choke control mechanisms to 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, in opposition to the thermostatic element, when the cold engine starts and becomes selfsustaining.

Although this general arrangement has been accepted commercially, certain inherent characteristics thereof often cause undesirable results. For example, the degree to which the choke is initially opened by the vacuum responsive piston is dependent on what is considered to be proper for normal cold engine driving. However, in practice, the sudden opening of the choke to the cold driving position immediately upon starting usually results in a temporarily too lean fuel-air mixture. Consequently, the engine, after running for only a brief moment after starting, usually stops. This, of course, requires subsequent restarting of the engine.

Accordingly, this invention is directly concerned with the above problem and has as its broad purpose the objective of providing means, adapted to cooperate with a temperature and pressure responsive choke control mechanism, for controlling the degree of initial choke opening upon engine starting.

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 top plan view of a carburetor embodying the invention.

FIGURE 2 is an elevational view, with a portion thereof broken away, taken on the plane of line 22 of FIGURE 1 and looking in the direction of the arrows.

FIGURE 3 is a cross-sectional view taken on the plane of line 3-3 of FIGURE 1 and looking in the direction of the arrows.

FIGURE 4 is a cross-sectional view taken along the plane of line 4-4 of FIGURE 1 and looking in the direction of the arrows.

FIGURE 5 is a cross-sectional view taken along the plane of line 5-5 of FIGURE 4 and looking in the direction of the arrows.

FIGURE 6 is a fragmentary perspective exploded view 7 generally illustrating the details of construction of the automatic choke control mechanism.

FIGURE 7 is an enlarged fragmentary view illustrating I a portion of FIGURE 6 in greater detail.

FIGURE 8 is a fragmentary view of a portion of I 3,885,792 Patented Apr. 16, 1963 secured to the intake' manifold 24 of the engine. A throttle lever 26, suitably secured to the throttle shaft 28, has an adjustable stop screw 30 at one end thereof which cooperates with the variably positioned fast idle cam member 32 in determining the degree of throttle closure during such periods as when the operator is not exercising control over the throttle by means of linkage 34. A spring 36 secured at one end to a suitable abutment causes the stop screw 30 to bear against the cam 32 by virtue of its connection with lever 26. The operation of the fast idle cam member 32 will be discussed in greater detail in subsequent portions of the specification.

FIGURE 3 illustrates the induction passage 38, with a venturi 40, formed in the body 12 of carburetor 10. The choke valve 20, secured to the pivotal shaft 22, is shown in its closed position. The throttle valve 42, mounted on shaft 28, is shown in a partiallyopen position resulting from the coaction between cam member 32 and throttle stop screw 30.

FIGURE 4 illustrates in greater detail the fast idle cam member 32 and associated linkage. The cam member 32 having a plurality of discrete steps 44, 46, 48 and 50 is pivotally mounted on the choke shaft 22 so as to have freedom of relative motion between itself and the shaft 22.

A lever 52 secured to shaft 22 in a manner so as to have no relative movement therebetween coacts with cam member 32 in a manner to be more fully discussed subsequently in the specification. A tab 54 formed on cam 32 is formed to receive an adjustable abutment screw 56 wvhich is adapted to limit the clockwise rotational movement of lever 52 with shaft 22.

FIGURE 5 illustrates the spring 58 which operatively connects lever 52 with cam 32. A post 60, rigidly secured to cam 32 has its projecting end adapted to retain one end of spring 58 while the other end of the spring is retained by the tab portion 62 of lever 52. When the cam 32 is in the position illustrated by FIGURE 4, the spring 58 is effective for keeping the tab 62 against the abutment 64 formed on cam 32.

FIGURE 6 illustrates a housing 66 suitably secured to the carburetor body 12 and having a cylinder 68 formed therein containing a piston 70 which is connected through a linkage 72 to the choke lever 74. The choke shaft 22, extending through and rotatable in one wall of the housing 66, has secured to it at one end thereof the choke lever 74, and at its other end generally, the choke valve 20. The choke lever 74 has an outwardly extending projection 76 which is adapted to coact with the free outer end 78 of thermostatic element 80 through an arcuate opening 82 in the housing cover plate 84.

The thermostatic housing has a centrally located shaft rigidly secured therein to which the inner end of the thermostatic element 80 is secured. Any suitable means i such as the clamps '86 (FIGURE 2) may be employed to hold the cover plate 84 and housing 88 in alignment with and against the housing 66. The clamps 86 may, of course, be secured as by means of screws 90.

Conduit 92 communicates between a source of heated air, such as the stove 94, and the chamber formed by the cover plate 84 and housing 88. The purpose of conduit 92 is to deliver a controlled amount of air, which is at a temperature indicative of engine temperature, to the thermostatic element 80 in order that the element 80 may react to engine temperature and influence the position of the choke valve 20 accordingly. The general path of this heated air is indicated by the arrows, its ultimate exit being to the intake manifold, or any suitable source of engine related suction, through suitable conduit means 96 which may be in direct communi cation with the chamber formed by the cover plate 84 and housing 66.

FIGURE 7 illustrates in greater detail the choke vacuum piston 70 and cylinder 68. The piston is connected to the linkage 72 by means of a pin 98; the opposite end of the linkage 72 is operatively connected to lever 74 by means of a pin 100 which is retained within lever 74 and slideable within the lost motion-producing slot 102 of linkage 72.

A conduit 104, having a restriction 106 therein, communicates between the chamber formed generally by piston 70 and cylinder 68 and conduit 96, which also contains a restriction 108. Of course, conduit 104 would be connected to conduit 96 on the vacuum side of restriction 108.

FIGURE 8 illustrates a difierent type of vacuum responsive piston which can be employed in practicing the invention. All elements which are like or similar to those of FIGURE 7 are identified with like primed reference numbers. The primary distinction between the two vacuum pistons is that piston 70 has a projection 110 formed thereon which is adapted to abut against surface 112 of cylinder 68. In other words, projection 119 forms a stop which limits the normal ultimate travel of piston 70' and consequently positively limits the effect which the vacuum piston has in determining the degree to which the choke is opened initially for cold drive away.

Operation Before proceeding to the general operation of the invention, the following is presented as a brief summary of the relationships existing between the various elements:

(1) Throttle valve 42, throttle shaft 28, lever 26 and abutment screw 30 are all rigidly secured together so as to require the movement of all whenever any one of them is moved.

(2) Choke valve 20, choke shaft 22, lever 52, and lever 74 are connected to each other so that all move whenever any one of them moves.

(3) Spring 58 normally keeps the freely pivoted cam member 32 against the tab 62 of lever 52.

(4) The degree of throttle closure is dependent on which step of cam 32 that abutment screw 30 is bearing.

(5) The vacuum piston 70 is effective for moving the choke valve towards the open position against the force of thermostatic element 80.

Assuming, for the purpose of illustration, that the engine is cold and is being cranked, the thermostatic element 80 will be in its unwound condition, thereby causing its end 78 to position projection 76 of lever 74 in its extreme counter-clockwise position. The lever 74,

being secured to choke shaft 22, rotates the shaft counterclockwise, thereby causing the choke valve 20 to assume a position which substantially closes off 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 suliicient to move the vacuum piston 70 to the right against the tension of the thermostatic element 80. At this time, however, cam member 32 is retained in the position illustrated by FIGURES 2, 3 and 4 by the action of abutment screw 30 and the throttle return spring 36. Accordingly, the movement of the piston 7 0 is then limited by the position of the cam member 32. That is, as piston 70 rotates shaft 22, lever 52 is caused to rotate also. However, the degree to which lever 52 is permitted to rotate is determined by the setting of screw 56, since screw 56 is in the path of travel of tab 62. Consequenlty, it becomes apparent that the initial movement of piston 70 and choke valve 20, upon engine starting, is determined by the position of fast idle cam member 32.

If, at this time, the throttle is manually opened some amount so as to move the abutment screw 30 away from step 44 of cam 32, the piston 70 would then move some additional amount, thereby further opening the choke valve 20. In the case of the construction illustrated by FIGURE 8, the addtional amount would be determined by the coaction of stop with surface112. In view of the above, it becomes apparent that the invention provides an intermediate choke position which results in a slightly richer fuel-air mixture upon engine starting.

The operation of the thermostatic element 30 is, of course, conventional. That is, as the engine continues to run, air is drawn from the stove 94 through conduit 92 into the chamber formed by the housing 83 and cover plate 84. The air then warms the thermostat 30 and passes into the chamber formed by housing 66 and cover plate 84 through the arcuate opening 82 within the cover plate. The air is then drawn through con duit 96 and into the induction manifold 24.

Although only the preferred embodiment of the invention has been disclosed and described, other modifications are possible within the scope of the appended claims.

What I claim as my invention is:

1. An internal combustion engine carburetor, comprising a body having an induction passage, a choke valve pivoted in said passage, said choke valve being opened on starting of said engine by engine vacuum responsive means acting against engine temperature responsive means urging said choke valve closed with decreasing force as engine temperature increases, cam means connected so as to be positioned by said choke valve, a throttle valve pivoted in said passage on the engine side of said choke valve, said throttle valve being spring-loaded to close and having abutment means disposed in the plane of and engageable with said cam so as to variably limit the closing of said throttle valve depending upon the position of said cam, and at least two stop means for limiting the opening of said choke valve by said vacuum responsive means, one of said stop means including an abutment formed on said cam and providing a variable initial choke position dependent upon the position of said cam, the other of said stop means including a fixed abutment.

2. A carburetor for an internal combustion engine, comprising a body, an induction passage formed through said body, a pivotally mounted choke valve in said induction passage, a throttle shaft, a throttle valve pivotally mounted on said throttle shaft downstream of said choke valve for controlling the flow of combustible mixtures, an automatic choke control device, said device comprising a first lever operatively connected to said choke valve and adapted to rotate therewith, thermostatic means urging said first lever in the choke closing direction when cold, vacuum responsive means operative upon engine starting for initially moving said choke valve in the opening direction against the action of said thermostatic means, a pivotally supported second lever operatively connected to said choke valve and adapted to rotate in accordance therewith, a third lever operatively connected to said throttle shaft and adapted to rotate therewith, a pivotally mounted cam member adaped to cooperate with said third lever for variably limiting the closing movement of said throttle valve, and abutment means formed on said cam member and cooperating with said second lever for limiting the degree of said initial choke valve opening movement by said pressure responsive means.

3. An internal combustion engine carburetor, comprising a body having an induction passage extending therethrough, said passage being formed to provide a venturi, a choke valve pivotally mounted in said venturi on a choke shaft having one end thereof extending through the outside wall of said body, a throttle valve pivotally mounted in said passage at the engine side of said choke valve on a throttle shaft also having one end thereof extending through the outside wall of said body, said throttle being urged in the closing direction by a first spring, engine temperature responsive means connected with said chok'e shaft, said means .urging said choke valve closed when said engine is cold and decreasingly resisting the opening of said choke valve as engine temperature increases, engine vacuum responsive means connected to said choke shaft and urging said choke valve open upon starting of said engine, said connections of said temperature and vacuum responsive means being such as to allow further opening of said choke valve against the resistance of said temperature responsive means regardless of the position of said vacuum responsive means, an eccentric carn mounted on and for rotation with respect to said choke shaft, 21 first lever mounted on said throttle shaft for manually opening said throttle valve against said first spring, an adjustable abutment on said lever for engaging said cam so as to control the closing movement of said throttle in accordance with the position of said cam, said first spring having .suflicient force to prevent the further rotation of said cam until said throttle is moved in the open direction so as to disengage said abutment from said cam, a first stop member on said cam, a second lever mounted for rotation with said choke shaft and connected to said cam by a second spring, said second lever having a portion adapted to engage said first stop member so as to variably limit the initial opening of said choke valve against the force of said second spring by said vacuum responsive means on starting of the engine to a position dependent upon the position of said cam, and second stop means limiting the further opening of said choke valve by said vacuum responsive means on opening of said throttle to disengage said abutment means from said cam.

4. An internal combustion engine carburetor, comprising a body having an induction passage extending therethrough, said passage being formed to provide a venturi, a choke valve pivotally mounted in said venturi on a choke shaft having one end thereof extending through the outside wall of said body, a throttle valve pivotally mounted in said passage at the engine side of said choke valve on a throttle shaft also having one end thereof extending through the outside wall of said body, said throttle being urged in the closing direction by a first spring, engine temperature responsive means connected with said choke shaft, said means urging said choke valve closed when said engine is cold and decreasingly resisting the opening of said choke valve as engine temperature increases, engine vacuum responsive means connected to said choke shaft and urging said choke valve open upon starting of said engine, said connections of said temperature and vacuum responsive means being such as to allow further opening of said choke valve against the resistance of said temperature responsive means regardless of the position of said vacuum responsive means, an eccentric cam mounted (for rotation with respect to said choke shaft, a first lever mounted on said throttle shaft for manually opening said throttle valve against said first spring, an adjustable abutment on said lever for engaging said cam so as to control the closing movement of said throttle in accordance with the position of said cam, said first spring having sufiicient force to prevent the further rotation of said cam .until said throttle is moved in the open direction so as to disengage said abutment from said cam, a first stop member on said cam, and a second lever mounted for rotation with said choke shaft and connected to said cam by a second spring, said second lever having a portion adapted to engage said first stop member so as to variably limit the initial opening of said choke valve against the force of said second spring by said vacuum responsive means on starting of the engine to a position dependent upon the position of said cam.

5. An internal combustion engine carburetor, comprising a body having an induction passage therethrough with a choke valve and throttle valve pivotally mounted therein, manually positioned linkage means for opening and closing said throttle valve, engine vacuum responsive means adapted to open said choke valve to an initial degree when said engine is started, and manually variable abutment means adapted to at times be in engagement with said manually positioned linkage means so as to at those times determine said initial degree to which said choke valve is opened by said engine vacuum responsive means.

References (Cited in the file of this patent UNITED STATES PATENTS 2,719,706 Winkler Oct. 4, :1955 2,808,244 Dermond Oct. 1, 1957 2,943,848 Gordon et al July 5, 1960 2,970,825 Smitley Feb. 7, 19'61

Claims (1)

1. AN INTERNAL COMBUSTION ENGINE CARBURETOR, COMPRISING A BODY HAVING AN INDUCTION PASSAGE, A CHOKE VALVE PIVOTED IN SAID PASSAGE, SAID CHOKE VALVE BEING OPENED ON STARTING OF SAID ENGINE BY ENGINE VACUUM RESPONSIVE MEANS ACTING AGAINST ENGINE TEMPERATURE RESPONSIVE MEANS URGING SAID CHOKE VALVE CLOSED WITH DECREASING FORCE AS ENGINE TEMPERATURE INCREASES, CAM MEANS CONNECTED SO AS TO BE POSITIONED BY SAID CHOKE VALVE, A THROTTLE VALVE PIVOTED IN SAID PASSAGE ON THE ENGINE SIDE OF SAID CHOKE VALVE, SAID THROTTLE VALVE BEING SPRING-LOADED TO CLOSE AND HAVING ABUTMENT MEANS DISPOSED IN THE PLANE OF AND ENGAGEABLE WITH SAID CAM SO AS TO VARIABLY LIMIT THE CLOSING OF SAID THROTTLE VALVE DEPENDING UPON THE POSITION OF SAID CAM, AND AT LEAST TWO STOP MEANS FOR LIMITING THE OPENING OF SAID CHOKE VALVE BY SAID VACUUM RESPONSIVE MEANS, ONE OF SAID STOP MEANS INCLUDING AN ABUTMENT FORMED ON SAID CAM AND PROVIDING A VARIABLE INITIAL CHOKE POSITION DEPENDENT UPON THE POSITION OF SAID CAM, THE OTHER OF SAID STOP MEANS INCLUDING A FIXED ABUTMENT.

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