US2969783A - Choke actuating mechanism - Google Patents

Description

Jan. 3l, 1961 A. F. BRAUN v CHoxE ACTUATING MECHANISM 2 Sheets-Sheet 1 Filed Aug. 13, 1958 ATTORNEY Jan. 3l, 1961 A. F. BRAUN 2,959,783

CHOKE ACTUATING MECHANISM Filed Aug. l5, 1958 2 Sheets-Sheet 2 "`\\\\\\\\\\k I l INVENTOR.

United States Patent O `CHOKE ACTUATING MECHANISM Adolph F. Braun, Pittsford, N.Y., assgnor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed Aug. 13, 1958, Ser. N0. 754,841

'12 Claims. (Cl. 12S-119) The present invention relates to an actuating mecha-` nism in which the choke valve is moved toward a closed' position during accelerating or high load operating conditions when the engine is only partially warm. In addition to providing means for moving the choke valve in a closed or enriching direction, the present device includes a throttle controlled latching mechanism for preventing the choke from being fully closed and thereby preventing overenrichment.

In order to improve the economy of carburetor operation, it has been found that'except for certain limited operating conditions it is possible to take oif or open a choke valve more rapidly than has been done in the past. The result of rapid choke valve come-off is a leaner and more economical fuel-air mixture. However, it is not enough to simply set an automatic choke operating mechanism for leaner operation since there are certain operating conditions under which a partially warmed engine will not function properly on a lean mixture when overloaded. In other words, shortly after an engine has been started and during steady-state operation, eg. `one in which the engine is only lightly or gradually loaded, it is possible to open the choke valve and operate on a relatively lean mixture. However, with the engine only partially warmed and the choke essentially fully open, a sudden loading of the engine as occurs during accelerating conditions will cause the engine to falter due to a too lean fuel-air mixture.

In the present invention a choke controlling mechanism is provided in which the choke is adapted to open and rapidly lean out the fuel-air mixture shortly after starting to increase fuel economy under conditions which have in the past used excessive fuel to cover a few operating contingencies. However, in addition the present choke actuating mechanism includes a device which is adapted to automatically return the choke to a partially closed position when a partially warmed engine is suddenly heavily loaded. In this way the fuel-air mixture is momentarily enriched to accommodate the increased engine load and the engine will continue to function smoothly.' After a predetermined time interval the choke valve will again resume its open position returning the carburetor to its most economical type of operation.

An important feature of the present choke actuating mechanism is the provision of the throttle control means .for insuring that the choke valve is prevented from closing to too great an extent whereby overenrichment and equally objectionable rough engine operation is avoided.

More specifically, the present invention includes a vacuum actuated servo device which is adapted after the engine becomes operative to crack open the choke valve to thereby partially lean out the fuel-air mixture beyond that-required for initial starting. The present choke actuating mechanism includes a temperature responsive coil adapted to maintain the choke valve in a closed position with a force inversely proportional to engine temperature and further which choke valve is unbalanced so as ICC to be opened in accordance with the quantity of air ow through the induction passage.

In addition, the choke actuating mechanism includes a pressure responsive device operable in conjunction with the vacuum actuated servo device to momentarily close the choke valve when the load on the engine increasesy beyond a predetermined value causing a corresponding drop in manifold vacuum. This choke closing mechanism.4 also includes means for rendering itself inoperative after` the choke valve has opened beyond a predetermined ex.

tent. The desirability of this feature is apparent when it is realized that after the engine has warmed sufficiently it is unnecessary to cover the engine operation by partial closing o-f the choke valve and as a matter of fact such choking operation with a fully warmed engine would be detrimental in terms of loss of power and economy.

Finally the present choke actuating mechanism also includes a throttle controlled mechanism operating in` conjunction with the vacuum servo and pressure responsive devices for preventing the temperature responsive element from moving the choke valve to a fully closed position.

The details as well as other objects and advantages of the present invention will be apparent from a persusal of the description which follows.

In the drawings:

Figure l is a diagrammatic representation of the subject choke actuating mechanism; and i Figure 2 is a partial view of Figure 1 showing the parts in position when engine becomes operative.

The present choke actuating mechanism is adapted for use with any carburetor employing what may be termed an automatic type choke. For the purposes of the present invention, an automatic choke mechanism may be considered to include a choke valve whose operation is automatically controlled in accordance with certain engine operating conditions such as temperature and air flow. As suggested, any type of carburetor, such as that shown in Patent 2,771,282 Olson et al., may be used in conjunction with the present type choke actuating mechanism and the carburetor does no-t, per se, constitute a part of the present invention except insofar as elements thereofare combined with such mechanism. For illustrative purposes a carburetor is schematically shown at 10 and includes an air induction passage 12 which is adapted to supply air to the intake manifold of an internal combustion engine. A choke valve 14 is pivotally supported on a shaft 16 within induction passage 12 and is adapted to be actuated in order to vary the fuel-air ratio in ac- A throttle valve 20 is also pivotally mounted withinl induction passage 12 upon a shaft 22 and is adapted to be suitably connected to an accelerator pedal to control the quantity of fuel-air mixture supplied to the engine.

Choke valve 14 includes a lever 24 fixed to shaft 16 and to which lever one end of a rod 26 is articulated. Similarly, a lever 28 is fixed to throttle shaft 22 and also has one end of a rod 30 articulated thereto. The other ends o-f rods 26 and 30 are respectively articulated to parts of a choke actuating mechanism indicated generally at 32 and the details of which will now be consideredQ Choke actuating mechanism 32 includes a first bifur-y cated lever 34 which is pivotally mounted upon pivot shaft 36 supported upon carburetor 10. Also fixed to" Patented Jan. 31, 1961 'j lever 34, or integrally formed therewith, is a lever 38 articulated at its free end to choke controlling rod 26. Arm 40 o-f bifurcated lever 34 includes an oiset tang 42 formed at one end: thereof and. which is adapted to be engaged by the free end 44 of thermostaticcoil 18. The otherend 46 of coil 18'is anchored toV pivot'shaft'36; Coil 18; is so constructed as to urge levers 34 and 38. ina counterclockwise, or choke valve closing.. direction as: temperature decreases..

Choke actuating mechanism 32 includes a servo device indicated generally at 50 and having a pair of casing members S2 and 54l peripherally clamping a flexible da phragm` 56 therebetween. Diaphragm 56 coacts with casing members 52 and 54 to provide chambers 5S and 60". Chamber 58y communicates through passages 62 and 63y with a conduitf64 which in turn connects with a source of engine: manifold vacuum. Passage 62y has an orifice 65disposed therein to limit-thev rate of opening of. choke valve 14 as will subsequently be considered in greater detail. A apper or reed type valveY 67 is disposed in chamber 58 and is normally closed by manifold vacuum in conduit 64 preventing air from being evacuated from chamber 58 through passagey 63.

Chamber 60 includesan atmospheric passage 66 con.- trolled by a reed type valve 68 adapted to admit air under atmospheric pressure to the chamber as diaphragm S6 moves to the right. A- filter 70 is provided at the inlet of passage 66.

In addition, chamber 60 communicates with a second passage 72 formed in casing 52 which is. adapted to deliver air under slightly superatmospheric pressure to a second servo device indicated generally atV 74. The details of servo device. 74 will be considered subsequently.

A control rod 76 is slidably supported within an axial passage 78 formed in servo casing S4. End 80 of rod 76 is disposed within chamber 58 and includes a washer member 82 fixed thereto to provide a seat for a spring member 84. The other end of spring 84 biases against. casing S4 to urge. rod 76 in a leftwardly direction as shown in Figure 1. The other end 86 of rod 76 is axially aligned with a tang 88 formed at the end of. arm 90 of bifurcated lever 34.

Diaphragm 56 includes a dish-shaped washer member' 92y mounted centrally thereon and which provides a seat for one end of a spring 94. The other end of. spring 94 seats within a counterbored portion 96' of casing 54. Spring 94 normally biases the diaphragm. in a leftwardly direction whereby the diaphragm abuts againstcasing'52. AV reinforcing washer 98 is similarly centrally mounted upon diaphragm 56 and includes a plurality'of circumferentially spaced. projections 100 which slightly space the diaphragm away from the casing to maintain communication between chamber 60 and passage 72 when the diaphragm is in the position shown in Figure l.

Referring specifically to Figure l, the parts are lin the position which they assume when the engine is inoperative and cold. Under these conditions it will be apparent that thermostatic coil 18 will maintain choke valve 14 in a closed position insuring a rich starting mixture.

As soon as the engine starts, manifold vacuum will be supplied through conduit 64 to chamber 58 moving diaphragm S6 to the right at a rate determined by orice 65, as shown in FigureA 2, in which circumstancey abutment 102 on diaphragm 56 will engage end 80 of rod 76 to move the rod to. the right against the force of spring`A 84. In so moving, end 86 of the rod will. engage tang88 of arm 90 rotating levers 34 and 38 in a clockwise direc- :tion to partially open choke 14. This actuation of diaphragm 56 opens the choke valve approximately. 20 from its closed position and insures a leaning out of the fuel-.air mixture. commensurate1 with the cold. running requirements of the engine. ing out of the fuel-air mixture is necessary since, under anyconditions, it requires less enrichment to run. theengine than is required for starting purposes. OrificeA 65 It is apparent that this leanin passage 62. will bev of a size determined by the. operating characteristics of the particular engine involved, but at any rate will limit the choke opening rate to a value which will preclude stalling the engine due to a too lean fuel-air ratio.

As previously mentioned, choke actuating mechanism 32 is designed for the purpose'ofproviding more economical carburetor operation during, the.l warmup period. Accordingly, thermostatic coil 18 is adapted to wind ina clockwise direction rather rapidlyV as, the engine begins to warm causing the free end' 44 thereof to move away Y from arm tang 42 and permitting air flow through the induction passage. 12 tov open choke valve 14. While this fast opening choke operation is. desirable for steadyrate operation, itis foundY that while the engine is still not fully warmed the rapid come-oftc of the choke valve may cause operating difficulties when the engine is subjected to severev loads as may occur during acceleration conditions' or.v when climbing a. hill.- Inorder to vinsure that the engine will notY stumble under such highv load operating conditions,- a choke-.closing or kicker device-74 drawn into chamber S0-past valve 68. With. the: enginel only partially. warm. and choke valve:V 14 only partially' opened, .asudden increase in load onthe engine, as.-Would. occur during accelerating conditions,.causes thefmanifold vacuum in. chamber 58. to drop` below a predetermined. value, e.g. 6 inches. of mercury, permitting spring 94- to@ move. theldiaphragm to the-left.. In. so moving valve-68 is closed. thereby increasing the pressure-of. the air trap.-l

ped in chamber 60 to a slightly superatmospheric value; Theair under pressurefis conveyed. through passage 72 to piston cylinder lcausing piston 104to be movedto the right. This piston movement rotates levers 34 and. 38 in a counterclockwisedirection. and moves choke valve. 14 in a closing-direction.y Inthisy way the fuelair mixture is temporarily enrichedrto4 provide the requisite power under the increased engine load conditions.

During accelerating conditions.` as just noted, the pres-I sure in conduit 64 is substantially atmospheric, accord-1 ingly, thev leftward movementof diaphragm S6 by spring. 94 will open flapper valve` 67 so as not tolimitV the.

closing action of ch0ke'14 aswould otherwise occur be cause of orifice 65 in passage 62.

In order that kicker or choke closing device 74 be rendered inoperative. afterthe choke has opened beyond a predetermined amountindicating av fully warmed enf gine, a relieved portion 112 is provided in piston cylinder casing 106. After they choke valve has been opened.E sufliciently to move piston 104 into adiacentrelationship; to relieved portion 112, any pressure in passage 72 will bel communicated with both sides of the piston thereby rendering the same ineffective; to move the choke valve in a closing direction..

While itis desired to move vthe choke valve in a-closing. directionunder the highV load conditions with a partially' warmed engine as-just described, it is undesirable that` the choke valvebemovedY toa fully closed position. Ac-

cordingly, a throttle controlled latch mechanism is pro-1 vided and. indicated generally. at 114. Mechanism 114.

comprisesv a bell crank. typedever 116 pivotally mounted on a shaft 118.. Arm 120 of. lever. 116.is adapted to bei engaged by one endofa spring` element 122, the. otherendl ofwhicllis supported upon. a seat 124. Spring 122; normally-urgesthe lever. 116.,in a counterclockwise direc-- tion.4 Arm.126rof 1ever1'116: includes'. an end. portion adaptedA pt o coact with a oircumferentially relieved portion 130 formed on rod 76 when the rod is moved by diaphragm 56 to its choke valve opening position as shown in Figure 2. y

A lever 132 is pivotally mounted on a shaft 134 and includes an arm 136 having a tang 138 adapted to coact with arm 120 of lever 116. The other end of lever 132 is articulated to throttle control rod 30. When the throttle is in a closed position, as shown in Figure l, lever 132 is adapted to rotate bifurcated lever 114 in a clockwise direction moving end 128 of arm 126 out of engagement with notch 130 in control rod 76.

With the engine running, rod 76 will be in its rightWard position as shown in Figure 2. lf then the throttle is opened to increase engine speed, lever 132 will be rotated in a counterclockwise direction moving tang 138 away from arm 120 of lever 114 permitting spring 122 to rotate the lever in a counterclockwise direction and thereby moving arm portion 128 into engagement with rod notch 130. This operation then locks control rod 76 in its choke cracking position. Thus, even though the manifold vacuum in chamber 58 drops below said predetermined value causing spring 94 to move diaphragm 56 to the left and thereby to move the piston -4 causing the choke valve to be moved in a closing direction, tang 88 of lever 34 will engage end 86 of rod 76 preventing the choke valve from being fully closed. In this way overenrichment due to complete closing of the choke is avoided.

When the throttle is returned to its closed position lever 114 will again be moved out of locking relationship with rod 76 and movement of the rod will again be under the control of diaphragm S6 and spring 84.

In summary, it will be seen that a choke controlling mechanism is provided which will insure a rapid comeoff or opening of the choke valve for providing for maximum economy of operation and which mechanism further provides means for temporarily moving the choke valve toward a closed position when the engine is only partially warmed and subjected to high load conditions. Finally, such mechanism provides throttle controlled means for preventing the choke from being closed to too great an extent during the aforesaid high load operating conditions insuring against overenrichment.

It is apparent that various structural modifications may be made within the scope of the invention as set forth in the hereinafter appended claims.

I claim:

1. A charge forming device for an internal combustion engine comprising an induction passage, a throttle valve rotatably disposed in said passage, a choke valve rotatably mounted in said passage, a temperature responsive element operatively connected to said choke valve and adapted to urge the same in a closing direction with a force inversely proportional to engine temperature, a first servo mechanism adapted to move said choke valve to a partially opened position when said engine becomes operative, a second servo device operatively connected to said choke valve and adapted to move said choke valve in a closing direction when the load on said engine exceeds a predetermined value, and a throttle controlled device adapted to coact with said choke valve to prevent said second servo device from moving said choke valve to a fully closed position.

2. A charge forming device for an internal combustion engine comprising an induction passage, a throttle valve rotatably mounted within said induction passage, an air ow responsive choke valve disposed in said induction passage anteriorly of said throttle valve, a temperature responsive element operatively connected to said choke valve and adapted to urge the same in a closing direction with a force inversely proportional to engine temperature, an engine manifold vacuum responsive servo mechanism adapted to coact with said choke valve to move the latter to a partially open position when said manifold vacuum exceeds a predetermined value, a throttle controlled lever mechanism adapted to coact withsaid servo:Y mechanism to prevent said choke valve from being moved` to a fully closed position, and a second servo device co? acting with said rst servo device to move the choke valve in a closing direction when manifold vacuum falls below a predetermined value.

3. A charge forming device for an internal combustionv engine comprising an induction passage, a throttle valve rotatably mounted within said induction passage, an air flow responsive choke valve disposed in said induction passage anteriorly of said throttle valve, a temperature mechanism including a diaphragm, a control rod andk spring means adapted to maintain said rod out of operative engagement with the choke valve, said diaphragmv being adapted to engage said rod to move the choke valve to a partially vopen position when manifold vacuum exceeds a predetermined value, a throttle controlled lever mechanism adapted to coact with said servo mechanism to prevent said choke valve from being moved to a fully closed position, and a second servo device operable by said rst servo device to move the choke valve in a closing direction when manifold Vacuum falls below a predetermined Value. y

4. A charge forming device as set forth in claim 3 in which the throttle controlled mechanism includes a pivotally mounted lever having one end adapted to lock- -ingly engage the control rod to limit the closing movement of the choke valve by the second servo device.

5. A charge forming device for an internal combustion engine comprising an induction passage, a throttle valve,

rotatably mounted within said induction passage, an air ow responsive choke valve disposed in said induction passage anteriorly of said throttle valve and adapted to be moved in .an opening direction by air ow through said induction passage, and a choke valve actuating mechanism comprising rst lever means articulated to said choke valve, a temperature responsive element connected to said first lever means and adapted to rotate the same to urge said choke valve in a `closing direction with a force inversely proportional to engine temperature, a manifold vacuum responsive servo device adapted to coact with said rst lever means to move said choke valve to a partially open position when manifold vacuum exceeds a predetermined value, a second lever means articulated to said throttle valve, said second lever means adapted to coact with said servo device to prevent the choke valve from being fully closed when said throttle valve is moved to a partially open position, and a second servo device operatively connected to said first lever means and coacting with said first servo means to move said choke valve in a closing direction when manifold vacuum decreases beyond a predetermined value.

6. A charge forming device for an internal combustion engine comprising an induction passage, a throttle valve rotatably mounted within said induction passage, a choke valve disposed in said induction passage anteriorly of said throttle valve, and a choke valve actuating mechanism comprising first lever means articulated to said choke valve, a temperature responsive element connected to said first lever means and adapted to rotate the same to urge said choke valve in a closing direction with a force inversely proportional to engine temperature, a manifold vacuum responsive servo device adapted to coact with said first lever means to move said choke valve to a partially open position when manifold vacuum exceeds a predetermined value, a second lever means articulated to said throttle valve, said second lever means adapted to coact with said servo device to prevent the choke valve from being fully closed when said throttle valve is moved to a partially open position, and a second servo device operatively connected to said first lever means and coact- A 7 i'ngrvvithr said' iirst servo means to move said choke valve inv la closingV directionA when" manifold vacuum decreases beyond a predetermined value.

7.v A charge forming device for an internal combustion engine comprising an induction passage, a throttle valve rotatably mounted within said induction passage, an air How responsive choke valve disposed in' said induction passage anteriorly of said throttlevalve and adapted to lie4 movedinl an opening direction by air flow through saidy induction passage, anda choke valve actuating mechanism comprising iirst lever means articulated to said-choke valve, a temperature responsive element concted to said rst lever means and adapted to rotate the same to'urge saidchoke valve in a closing direction with a force `inversely proportionalA to engine temperature, a manifold vacuum responsive servo device including a diaphragm, a control' rod, and spring means adapted to maintainl said rod'- out ofV operative engagement with the choke valve, said diaphragm beingadapted to engage said rod to" move into engagement with the lirst lever means to partially open the choke' valve when manifold vacuum exc'eeds a predetermined value, a second lever means articulatedV tov saidV throttleV valve, said second lever means adapted to coact with said control rod to prevent the choke valve from being fullyi'closed when said throttle valve is moved toa partially open position, and a secondv servo device operatively connected to said first lever means and operable by said first servo means to move said choke valve in a closing direction when manifold vacuum decreases beyond -a predetermined value.

8f. A charge forming device as set forth in claim 3 in which said second servo device comprises a cylinder, a piston slidably disposed in said cylinder, link means operativ'ely connecting said piston to said choke valve, a conduit connecting. said tirst servo device and said cylinder spaanse whereby' said springmeanswill move the diaphragm-in a5' direction causing' supjeratmospheric pressure air'to be transmitted' through said conduit to move saidpiston'gin a choke closing direction.

opened beyond a predetermined amount.

l0. A chargel forming device as set forth in claim 9vv in which said means for rendering the second servov device inoperative comprises a passage formed in said cylinder, said passage communicatingfwith said conduit tov admit the superatmospheric pressure air to both sides of said pist0n afterl the latter has moved beyond a predetermined position within said cylinder.-

ll.- A; chargev forming device as seti forth' in claim 2I in which the engine manifold vacuum responsiveI servo mechanismv includes a exible diaphragm, conduit means adapted to communicate manifold vacuum with". said dia. phraggmv andf passagevv means intermediate the conduit means andl the-diaphragm to provide relatively slow movement of the diaphragm in the choke. opening direction and fast movement in the'opposite direction. Y I

I2'. A charge formingfdevice as set forth'y in'A claim lll' in which the passage meansincludes a. first passag'cfhaving: an' orifice therein, ai second unrestricted passagel and a" valve member associated with the second passage,` mani`- fold vacuum normally closingsaid valve to prevent ow. through the second passage.

References Cited in the le of thisV patent UNITED STATES PATENTS Sutton Mar. 26,- 1957

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