US3347216A

US3347216A - Choke control device

Info

Publication number: US3347216A
Application number: US488503A
Authority: US
Inventors: Thomas C Schultz
Original assignee: Bendix Corp
Current assignee: Bendix Corp
Priority date: 1965-09-20
Filing date: 1965-09-20
Publication date: 1967-10-17
Anticipated expiration: 1984-10-17
Also published as: DE1526630A1; GB1159668A; DE1526630B2; JPS51242B1

Description

Get. 17, 1967 Filed Sept. 20, 1965 2 Sheets-Sheet 1 3O 44 O i462 38 24 34 a G 3 o FIG. g /Q re s f l A 32 22 ml; ff/ L 1D 0 FIG. 2

+4 26 INVENTOR.

ATTORNEYS Oct. 17, 1967 CHOKE CONTROL DEVICE Filed Sept. 20, 1965 2 Sheets-Sheet 2 FIG. 4

INVENTOR. 7%0045' a SM/UATZ FIG, 5 I

ATTORNEYS T. c. SCHULTZ 3,347,216 I United States Patent 3,347,216 CHOKE CONTROL DEVICE Thomas C. Schultz, Detroit, Mich., assiguor to The Bendix Corporation, a corporation of Delaware Filed Sept. 20, 1965, Ser. No. 488,503 7 Claims. (Cl. 123-119) ABSTRACT OF THE DISCLOSURE A choke locking device for an engine carburetor having one end of a toggle linkage connected to the choke lever and the other end of the toggle linkage connected to the body of the carburetor in a manner such that the toggle linkage forms a straight line when the choke is in the closed position thereby preventing opening of the choke in combination with a temperature responsive movable member to alter the straight line relationship when the engine becomes self-operative to allow the choke to open.

The present invention relates to an automatic choke, and more particularly to a device for locking the choke valve in closed position while the engine is being started.

In conventional automotive and air-cooled engine carburetors, the choke valve is offset and spring loaded so that the air flow created upon firing of the engine will open the valve sufficiently to provide the required air to sustain operation. However, in order to provide the required air during the initial self-operation of the engine, the offset valve and spring loading relationship must be such that the choke valve will be opened with relatively little air flow until the engine is operating normally. In many engines, however, the suction created during crank ing is sufficient to cause the choke valve to open and thereby reduce the richness of the fuel-air mixture to the point where the cold engine cannot be started. This difficulty cannot be effectively corrected by adjusting the relationship of the spring force urging the valve closed and the degree of offset of the valve, since the degree of suction created during the cranking operation and during the initialsel-f-operation of the engine may be substantially the same, or the difference too small to permit effective and reliable adjustment to obtain proper choking during cranking and initial running of the engine. It is therefore one of the principal objects of the present invention to provide a mechanism for controlling the operation of an offset choke valve, which effectively retains the choke valve in closed position while the engine is being cranked to, 'give the proper enriched starting mixture, and then soon thereafter partially releases the choke valve when the engine starts to give the required air for sustaining engine operation.

Another object of the invention is to provide an automatic choke control device which positively holds the choke in closed position regardless of the cranking speed of the engine or the degree of vacuum created during starting, and which controls the choke after starting to give the required enriched mixture until the normal operating temperature of the engine has been reached.

Still another object of the invention is to provide a relatively simple, reliable choke control device of the pneumatic type which effectively provides the required enriched mixture during cranking and thereafter varies the opening of the choke valve in accordance with engine temperature and operating conditions to give the required fuel-air mixture through the warming up period of the engine.

A further object is to provide an automatic choke device which can be readily adapted to various engines and adjusted to satisfy the starting requirements from one engine to another, and which will perform satisfactorily 3,347,216 Patented Oct. 17, 1967 under various operating conditions without manual adjustment or control.

7 Additional objects and advantages of the invention will become apparent from the following description and accompanying drawings, wherein:

FIGURE 1 is a front elevational view of a carburetor with the present automatic choke control device mounted thereon in operative position;

FIGURE 2 is a side elevational view of the carburetor and choke control device shown in FIGURE 1;

FIGURE 3 is an enlarged fragmentary cross sectional view of the choke control device, the section being taken on line 3-3 of FIGURE 1;

FIGURE 4 is a fragmentary cross sectional view of a portion of the carburetor and choke control linkage, illustrating the manner in which the device operates, the section being taken on line 44 of FIGURE 2; and

FIGURE 5 is an elevational view of the choke control linkage shown in the preceding figures.

Referring more specifically to the drawings, numeral 10 designates generally a carburetor and 12 the pneumatic automatic choke device embodying the present invention. For the purposes of the present description, carburetor 10 may be considered a conventional float type carburetor from an air-cooled engine, consisting of body 14 having an induction passage with an air inlet 16, a fuel-air mix ture outlet 18, and a float chamber 20 disposed beneath and supported by carburetor body 14. A throttle (not shown) is disposed in the induction passage on throttle shaft 22 controlled manually by a suitable linkage connected to lever 24. The fuel is supplied to the float chamber through valve 26 and is discharged in the induction passage through a main discharge nozzle (not shown) and through an idle system controlled by valve 28.

A choke valve 30 is mounted on shaft 32, offset with the larger portion of the valve above shaft 32, and is secured to the shaft for rotation therewith by screws 34 and 36 extending through the valve and threaded into shaft 32. The shaft is journalled in

bosses

38 and 40 and extends laterally to the left, as viewed in FIGURES 1 and 4 for receiving the operating mechanism of the automatic choke. The choke valve, being offset with respect to the induction passage, is urged in the open direction by vacuum in the induction passage downstream from the choke valve and the opening thereof is opposed, under certain conditions hereinafter described, by a spring forming a part of the choke control device. Valve 30 contains a poppet valve 42 consisting of a leaf spring secured to the inner side of valve 30 and seating over opening 44 in the choke valve. The poppet valve spring calibration is such that the poppet valve will remain closed during cranking and will open under the high intake vacuum created promptly when the engine has started running.

The choke control device 12 includes a pneumatic unit 60 consisting of a housing 62 having sections 64 and 66 secured together by a plurality of screws 67 extending through holes in the margins of section 66 and threadedly seating in holes in the margins of section 64, unit being supported on the side of the carburetor body by a bracket 68 secured thereto by screws 69. A fluid-impervious diaphragm 70 is secured at its marginal edge between housing sections 64 and 66 in fluid-tight relation, thu forming two

separate chambers

72 and 74 on the left and right-hand sides thereof, as viewed in FIGURE 3. The diaphragm is reinforced by stiffening plates 76 and 78 on the right and left sides of the diaphragm, and is urged toward chamber 72 by a coil spring 80 reacting between stiffening plate 76 and the inner end wall of section 66, chamber 74 being vented to ambient air by one or more ports 82 in the wall of section 66. A stem 86 extends through the center of diaphragm 70 and is 72 is connected by a tube 94 and conduit 96 in stem 98 I to a bulb 99 located in the mufiier, exhaust passage or manifold. The bulb, tube 94, conduit 96 and chamber 72 form, in effect, a closed chamber, filled with a gas which expands as the manifold temperature rises and urges diaphragm 70 to the right, as viewed in FIGURES 2 and 3, moving stem 86 axially to the right from the position shown in full lines to the position shown in broken lines.

Stem 86 is connected to shaft 32 by a linkage consisting of lever 100 pivoted at its lower end on pin 101 rigidly supported by two bosses 102 and 103 mounted on section 66 of housing 62. Lever 100 is operatively connected to stem 86 by a reduced diameter portion 106 on stem 86 which seats in a slot 108 of lever 100, the larger diameter portion of stem 86 on opposite sides of portion 106 forming abutments for engaging the lever on either side of slot 108 and for pivoting the lever angularly, as illustrated in FIGURE 2 in broken lines. An enlarged opening 110 at the upper end of slot 108 is provided to permit the reduced diameter portion 106 to be inserted in the slot. The upper end of lever 100 is connected to shaft 32 by a lever 112 extending radially from the end of shaft 32 and a crank-like lever 114 pivotally connected at one end to lever 112 and at the other end to the upper end of lever 100, the upper end of lever 114 extending through a hole in lever 112 and the lower end thereof extending through an eye 116 in lever 100. Lever 112 is rigidly secured to shaft 32 and rotates therewith as the choke valve is moved between opened and closed positions by lever 100, as will be more fully explained hereinafter.

In order to retain the choke valve in closed position during cranking, a toggle-like relationship is provided between

levers

112, 114 and 100 as determined by the position of pivot point 118 between

levers

112 and 114, pivot point 120 between the lower end of lever 114 and lever 100, and the pivot point 122 provided by pin 101 at the bottom of the latter lever. The three pivot points 118,

120 and 122 are on substantially a straight line when the choke valve is fully closed; preferably, however, pivot point 120 is slightly offset to the left, as viewed in FIG- URE 3, so that the slight downward rotation of lever 112 will not break. the toggle relationship between the several pivot points. It is thus seen that while the choke valve is closed, as illustrated in FIGURE 3, the relationship of

pivot points

118, 120 and 122 forms a positive stop means to prevent lever 112 and shaft 32 from rotating, and thereby positively holds the choke valve in closed position. Lever 100 remains in the position shown in FIGURE 3 until the engine starts, and as soon as the engine fires and the gas in bulb 99 expands, the pressure in chamber 72 increases, and thevlever is moved by the diaphragm 70 and stem 86 to the right, as viewed in FIGURE 3, initially breaking the toggle relationship between

pivot points

118, 120 and 122, and thereafter rotating lever 112 of shaft 32 in the counter-clockwise direction to open the choke valve.

In the operation of the present choke control device, starting with a cold engine, the pressure in the temperature sensitive bulb '99, tube 94, and chamber 72 is of such volume that spring 80 holds the diaphragm and, consequently, stem 86, in the position shown in FIGURE 3 and in full lines in FIGURE 2. With stem 86 and lever 100 in this position, the

pivot points

118, 120 and 122 are in substantial alignment, thus forming the toggle relationship which positively holds lever 112 in its raised position and the choke valve in its closed position. While the engine is being cranked, the toggle relationship of the three pivot points is maintained and the choke valve is held in closed position. The small amount of air required for the enriched starting mixture is provided by leafspring 42, which opens in response to the vacuum created during cranking. As soon as the engine fires, the required amount of air initially is likewise provided by valve 42 in the choke valve. Thereafter, as the heat in the exhaust pipe or manifold heats bulb 99, the gas therein expands, moving diaphragm 70 and stem 86 to the right, as viewed in FIGURE 3, thus moving lever in the clockwise direction and breaking the toggle relationship between

pivot points

118, and 122. Inasmuch as the choke valve 30 is on an offset shaft, the air flow through the carburetor intakepassage urges the choke valve in the opening direction to provide sufficient air throughout the warming up period of the engine. While the engine is passing through the warming up period, the full opening of the choke valve is resisted by spring 80, the force of which is transmitted to the choke valve by stem 86 and lever-s 100, 114 and 112, and choke shaft 32. Spring 80 permits the choke valve to vary its position in response to variations in the pressure differential across the choke valve while the engine is operating during the warming up period. When the engine has become fully warm, the expansion of the gas in bulb 99 urges the diaphragm 70 fully to the right, as viewed in FIGURE 3,-thus moving stem 86 and levers 100, 114 and 112 to the position shown in FIGURE 5, and moving the choke valve to the fully opened position.

The present choke control device can be effectively used in conjunction with other types of automatic chokes, including the bi-metallic and vacuum types, While only one embodiment of the present device has been described in detail herein, various changes and modifications may be made without departing from the scope of the inven- I claim:

1. A choke control device for a carburetor having a axially by said movable wall, a lever movable angularly by said stem and extending at one end toward said shaft and having a pivot means at the other end thereof, a lever extending radially from and being fixedly secured to said shaft for angular movement, and a member pivotally connected at one end to said first mentioned lever and at the other end to said second mentioned lever, said levers and member being in such relation to one another that the pivotal connections of said memher and the pivot means of said first mentioned lever are on a straight line when said choke is in closed position and said unit is in cold engine position, thereby locking said choke'in closed position regardless of manifold vacuum until said straight line relationship is altered by movement of said stem.

2. A choke control device for a carburetor having a body, an induction passage, a shaft and an offset choke valve in said passage mounted on said shaft, and for an engine having an exhaust passage: comprising a unit responsive to engine temperatures for controlling the choke valve, including a housing with a chamber, a movable wall for said chamber, a bulb in the engine exhaust passage, a conduit connecting said bulb with said chamher, a stem movable axially by said movable wall, a lever movable angularly by said stem and extending at one end toward said shaft and having a pivot means at the other end thereof, a lever extending radially from and being fixedly secured to said shaft for angular movement, and a member pivotally connected at one end to said first mentioned lever and at the other end to said second mentioned lever, said levers and member being in such relation to one another that the pivotal connections of said member and the pivot means of said first mentioned lever are on a straight line when said choke is in closed position and said unit is in cold engine position, thereby locking said choke in closed position regardless of engine manifold vacuum until said straight line relations-hip is altered by movement of said stem.

3. A choke control device for a carburetor having a body, an induction passage, a shaft and an offset choke valve in said passage mounted on said shaft: comprising a unit responsive to engine temperature for controlling the choke valve, a lever movable angularly by said unit and extending at one end toward said shaft and having a pivot means at the other end thereof, a lever extending radially from and being fixedly secured to said shaft for angular movement, and a member pivotally connected at one end to said first mentioned lever and at the other end to said second mentioned lever, said levers and member being in such relation to one another that the pivotal connections of said member and the pivot means of said first mentioned lever are on a straight line when said choke is in closed position and said unit is in cold engine position, thereby locking said choke in closed position regardless of engine manifold vacuum until said straight line relationship is altered by movement of said stem.

4. A choke control device for a carburetor having a body, an induction passage, a shaft and a choke valve mounted on said shaft in said passage, and for an engine having an exhaust passage: comprising a unit responsive to engine temperature for controlling the choke valve, including a housing with a chamber, a movable wall for said chamber, a bulb in the engine exhaust passage, a conduit connecting said bulb with said chamber, a stem movable axially by said movable wall, a lever extending radially from and being fixedly secured to said shaft for angular movement, and a pivoted lever movable by said stern on a plane parallel with the plane of rotation of said first mentioned lever and from a point tangent with the end of said first mentioned lever when the choke valve is in closed position and said unit is in cold engine position to a point substantially parallel with said first mentioned lever when the choke valve is in open position and said unit is in Warm engine position, and a member pivotally connected at one end to said first mentioned lever and at the other end to said second mentioned lever, said levers and member being in such relation to one another that the pivotal connections of said member and the pivot means of said second mentioned lever are on a straight line when said choke is in closed position and said unit is in cold engine position, thereby locking said choke in closed position regardless of engine manifold vacuum until said straight line relationship is altered by movement of said stem.

5. A choke control device for a carburetor having a body, an induction passage, a shaft and a choke valve mounted on said shaft in said passage: comprising a unit responsive to engine temperature for controlling the choke valve, a lever extending radially from and being fixedly secured to said shaft for angular movement, a pivoted lever movable by said unit on a plane parallel with the plane of rotation of said first mentioned lever and from a point tangent with the end of said first mentioned lever when the choke valve is in closed position and said unit is in cold engine position to a point substantially parallel with said first mentioned lever when the choke valve is in opened position and said unit is in warm engine position, and a member pivotally connected at one end to said first mentioned lever and at the other end to said second mentioned lever, said levers and member being in such relation to one another that the pivotal connections of said member and the pivot means of said second mentioned lever are on a straight line when said choke is in closed position and said unit is in cold engine position, thereby locking said choke in closed position regardless of engine manifold vacuum until said straight line relationship is altered by movement of said stem.

6. A choke control device for a carburetor having a body, an induction passage, a shaft and a choke valve mounted on said shaft in said passage: comprising a unit responsive to engine temperature for controlling the choke valve, a lever movable angularly by said unit and extending at one end toward said shaft and having a pivot means at the other end thereof, a lever extending radially from and being fixedly secured to said shaft for angular movement, and a member pivotally connected at one end to said first mentioned lever and at the other end to said second mentioned lever, said levers and member being in such relation to one another that the pivotal connections of said member and the pivot means of said first mentioned lever are on a straight line when said choke is in closed position and said unit is in cold engine position, thereby locking said choke in closed position regardless of engine manifold vacuum until said straight line relationship is altered by movement of said unit.

7. In a choke control device for a carburetor having an induction passage, a shaft and a choke valve mounted on said shaft in said passage: a unit responsive to engine temperature for controlling the choke valve, a lever extending radially from and being fixedly secured to said shaft for angular movement, and a pivoted lever movable by said unit on a plane parallel with the plane of rotation of said first mentioned lever and from a point tangent with the end of said first mentioned lever when the choke valve is in closed position and said unit is in cold engine position to a point substantially parallel with said first mentioned lever when the choke valve is in opened position and said unit is in warm engine position, and a linkage pivotally connecting the end of said first mentioned lever with the adjacent end of said second mentioned lever, said levers and member being in such relation to one another that the pivotal connections of said member and the pivot means of said second men tioned lever are on a straight line when said choke is in closed position and said unit is in cold engine position, thereby locking said choke in the closed position regardless of engine manifold vacuum until said straight line relationship is altered by movement of said unit.

AL LAWRENCE SMITH, Primary Examiner.

Claims

3. A CHOKE CONTROL DEVICE FOR A CARBURETOR HAVING A BODY, AN INDUCTION PASSAGE, A SHAFT AND AN OFFSET CHOKE VALVE IN SAID PASSAGE MOUNTED ON SAID SHAFT: COMPRISING A UNIT RESPONSIVE TO ENGINE TEMPERATURE FOR CONTROLLING THE CHOKE VALVE, A LEVER MOVABLE ANGULARLY BY SAID UNIT AND EXTENDING AT ONE END TOWARD SAID SHAFT AND HAVING A PIVOT MEANS AT THE OTHER END THEREOF, A LEVER EXTENDING RADIALLY FROM AND BEING FIXEDLY SECURED TO SAID SHAFT FOR ANGULAR MOVEMENT, AND A MEMBER PIVOTALLY CONNECTED AT ONE END TO SAID FIRST MENTIONED LEVER AND AT THE OTHER END OF SAID SECOND MENTIONED LEVER, SAID LEVERS AND MEMBER BEING IN SUCH RELATION TO ONE ANOTHER THAT THE PIVOTAL CONNECTIONS OF SAID MEMBER AND THE PIVOT MEANS OF SAID FIRST MENTIONED LEVER ARE ON A STRAIGHT LINE WHEN SAID CHOKE IS IN CLOSED POSITION AND SAID UNIT IS IN COLD ENGINE POSITION, THEREBY LOCKING SAID CHOKE IN CLOSED POSITION REGARDLESS OF ENGINE MANIFOLD VACUUM UNTIL SAID STRAIGHT LINE RELATIONSHIP IS ALTERED BY MOVEMENT OF SAID STEM.