US2152078A - Automatic choke control - Google Patents

Description

March 28, 1939. E MOORE 2,152,078

AUTOMATIC CHOKE CONTROL Filed y 13, 1952 N VENTORQ Bggaf W Patented Mar. 28 1939 2,152,078 7 AUTOMATIC CHOKE CONTROL Earl El Moore, South Bend, Ind., assignor, by

mesne assignments, to

ration, South Bend, ware Bendix AviationCorpo- Ind., a. corporation of Dela Application May 13, 1932, Serial No. 611,109

1 Claim.

This invention relates to an automatic choke control and has for. its principal object the provision of simplified means for automatically controlling the choke valve of an internal combustion engine carburetor in accordance with the temperature of the engine;

A further object lies in theprovision of means which will automatically provide a rich mixture. of

fuel and air for starting purposes, but which will not so enrich the fuel mixture at such time as to cause the engine to load up or fail to explode some of the fuel charges by reason of the fuel mixture being too rich for the tion.

A still further object lies in the provision of a device of the character described which is simple and economical to manufacture, easy to install, and which will not readily get out of order in use.

Other objects and advantages of the invention will appear as the description proceeds.-

particular operating condi- The accompanying drawing shows a single air intake as indicated by the line 2-2 on Figure 1, showing the carburetor chokevalve in" open position.

Figure 3 is a sectional view on the line 3-3 of Figure 2.

Referring to the drawing in detail and particularly to Figure 1, the'numeral l generally indicates an internal combustion engine block carrying a cylinder head ll secured to the block by means of stud bolts i2 and carrying an exhaust manifold I4 and an intake manifold l5 held in place thereon by means of stud bolts Hi. The cylinder head ll carries spark plugs I! connected with a conventional ignition system, not shown, in the usual manner. A carburetor generally indicated at 20 is connected to the lower end of an intake passage 2| which extends through the exhaust manifold l4 and into the intake manifold l5. The carburetor 20 is provided with a gas intake line 23, an air intake 25, a throttle valve shaft 26 connected by a lever arm 21 with a'reciprocating link member 28 which extends to manual control devices, not illustrated. In the air intake thereof the carburetor is provided with a choke valve 30 'particularly illustrated in Figure 3, mounted upon a shaft 32 journaled in the side wallsof the air intake 25. One end of the shaft '32 extends outwardly beyond the walls of the air intake and upon this extending end there is mounted a lever arm generally indicated at 34 adapted to actuate the choke valve 30 from its open to its closed position and vice versa. A coiled thermostat 35 is mounted upon a shaft 36 journaled in a hollow casing 38 which is secured to the exhaust manifold l4 by means of an apertured lug 39 and a stud bolt 40, or by other equivalent securing means. The inner end of the thermostat is non-rotatably secured upon the shaft 36 by means .of the construction illustrated in Figure 1, in which the bent-over inner end of the thermostat is retained in a diametrical slot provided in the shaft. The outer end of the thermostat is bent outwardly as at 4| and bears against a stop 42 which may comprise a tongue stuck out of the side of the casing 38, and bent inwardly to engage the outwardly bent end 4| of the thermostat. It is to be understood, however, that various equivalent stop devices may be provided and that the stop may be made adjustable if desired. One end of the shaft 36 projects outof the casing 38 1 and upon this outwardly projecting enda lever arm 45 is non-rotatably mounted by means of a tightening screw 46 extending through ears provided upon a split end of the'lever, or by other equivalent means.

The lever arm generally indicated at 34 which is mounted upon the shaft 32 of the choke valve is formed as a bell-crank lever having a long arm 48' and a short arm 49 extending upon substantially opposite sides of the shaft 32. The lever is provided with an aperture for the shaft 32 and with a slotted portion communicating with the aperture and provided with apertured ears through which extends a tightening screw 50 for drawing the aperture through which the shaft 32 extends, closely about the shaft to non-rotatably secure the lever arm 34 upon the end of the shaft f32 The longer end 48 of the lever 34 carries at its free enda pivotally mounted block 52 through which extends a substantially diametric aperture,

and a link member 55, having its upper end pivotally secured to the free end of the lever 45, projects at its lower end through the aperture in the block 52, the block 52 being adjustably secured upon the lower end of the link by means of a set screw 51. The invention, however, is not limited to this particular form of linkage as it is apparent as a flexible member or chain, could be employed two armed lever.

with substantially the same results.

From this description, it will be observed that as the thermostat 35 tends to wind up and unwind due to changes in the temperature thereof, it will actuate the arm 45, the link 55 and the arm 34 to urge the choke valve 30 from its open toward its closedposition or vice versa.

From a further inspection of Figure 1, it will be observed that the throttle lever 21 is provided in addition to the throttle actuation part with a downwardly extending portion 60, which is preferably formed integral therewith to form a The outer end of the member 60 is provided with an aperture by means of which a block 65 is pivotally secured to the member. aperture through which extends one end of a link member 61 the other end of whichis bent over and engaged in an aperture 58 provided in the end of the short portion 49 of the bell-crank lever 34. The end of the link 61 projects beyond the block 65 and upon this projecting end there is secured a clamp H! held in position on the link by means of a screw 12 to provide an over-travel connection between the link 61' and the end of the member 60. It will be apparent in this instance also that various equivalent connecting means including a flexible member, chain, or Bowden wire may be used.

From an inspection of Figures 2 and 3, it will be observed that the choke valve shaft 32 is disposed materially below the center of the discshaped choke valve 30 when the valve is in closed position, and that the carburetor air intake is provided with opposite straight portions and I6 and offset horizontal shoulders 11 and 18 which permit the disc-shaped valve member 38 to assume a horizontal position illustrated in Figure 3 when fully open, even though the shaft 32 is offset from the center of the disc-shaped valve member. This construction provides an unbalanced valve which atmospheric pressure outside of the carburetor will tend to open to admit air to the carburetor through the air intake 25 when the vacuum in the carburetor reaches a-predetermined limit. I

The operation of the device is as follows: Assuming that the engine is cold and that it is desired to start the same, under the condition of a cold engine the thermostat 35 will tend to unwind and move the arm 45, the link 55 and the arm 34 to close the choke valve 30. The connection 61, however, between the lever arm 34 andthe throttle lever 2'! will maintain the choke valve 30 in a slightly open position as long as the carburetor throttle is closed. Therefore, in order to obtain easy starting the manual control of the carburetor throttle must be actuated to open the throttle a slight amount and relieve the tension on the link 61 to permit the choke valve 30 to close. The engine can now be started with the throttle valve slightly open and the choke valve in its fully closed position. If, after the engine has been started, the manual control is actuated to close the carburetor throttle to cause the engine to idle and draw its fuel supply from the idling jet of the carburetor, the connection 61 and related parts will slightly open the choke valve 30 to permit passage of suflicient air through the air intake 25 to prevent vacuum in the carburetor from being built up to a point at which the engine will draw fuel from the main carburetor jet as well as from the idling jet, and there- 'I'his block is provided with a transverseby prevent the fuel mixture from becoming sufflciently rich to cause the engine to load up and stop. If the manual control of the throttle valve is now actuated to move the valve from its-closed or idling position toward its open position, tension,

on the link 61 will first be relieved thereby placing the choke valve 30 completely under the control of the thermostat 35. After the tension on the member 51 has been relieved, the block 65 will slide along the member so that the throttle lever 21 no longer has any effect upon the choke valve 30. As the throttle is new advanced toward open position, the thermostat 35 tends to hold the choke valve 30 toward its closed position, but as the choke valve 30 is unbalanced by being mount-' ed elf-center on the shaft 32, the atmospheric pressure upon the outer side of the valve, caused by increasing vacuum within the carburetor chamber, will tend to open the valve against the resilient action of the thermostat to admit suflicient air for proper fuel combustion at any engine speed within the operative range of the engine. As the thermostat 35 is mounted upon the exhaust manifold of the engine in heat transferring relation therewith, as the engine approaches its normal operating temperature heat will be transferred to the thermostat causing it to wind up and move the arm 45, link 55 and arm 34 in a direction to move the choke valve toward its fully open position as illustrated in Figure 3.

The opening of the choke valve 30 caused by the link 61 is not a matter of extreme accuracy,

as it is simply necessary to admit a suflicient amount of air to the carburetor to prevent a high vacuum being formed therein when the engine is idling. The degree of throttle opening which permits the choke valve 30 to close is, however, chosen with considerable care as the lowest engine speed which will insure continued operation of the engine taking into consideration the strength of the thermostat and the amount of unbalance of the choke valve. The thermostat is so positioned in relation to the choke valve that the angle be tween the arm 45 and the link 55 when the choke valve is fully closed is sufllciently acute to afford a comparatively high initial resistance to opening of the choke valve 30. Also the strength of the thermostat and the amount that the shaft 32 is offset from the center of the valve 30 must be carefully balanced in order that just suflicient air will be admitted to the carburetor to insure an explosive fuel mixture at the instant engine temperature, and the air will be accurately metered for the entire operative range of engine speeds and temperatures.- If the amount the shaft is off center is too great or if the-thermostat is too weak, the fuel mixture will tend to be too lean for proper starting results, and if, on the other hand, the thermostat is too strong orthe amount of offset of the shaft 30 is too small, there will be a tendency for-the thermostat to hold the valve 3!! closed and unduly limit the amount of air flowing into the carburetor thereby causing too rich a mixture to permit the engine to run smoothly after it has been started. It has been found, however, that if the strength of the thermostat and the unbalance of the valve 30 are in proper relation to each other, immediate starting and smooth subsequent operation of the engine are assured, and it has also been found that a. connection as illustrated between the throttle lever and the choke valve to cause a slight opening of the choke valve when the throttle is closed will prevent the choke from stopping the engine when it is idling at a comparatively low operating temperature.

Having now described my invention so that others skilled in the art may clearly understand the same, what I desire to secure by Letters Patent is as follows:

The combination with an internal combustion engine having an intake and an exhaust manifold, and a carburetor connected to said intake manifold having an air intake and a throttle valve, of an automatic control for said carburetor air intake comprising, a choke valve in said air intake eccentrically mounted on a shaft journaled in said air intake, 2. double armed choke valve lever having a long and a short arm, on said shaft,

thermostat is below a predetermined limit, a twoarmed throttle valve lever and an over-travel connection between one arm of said throttle valve lever and the short end of said choke valve lever to restrain said thermostat from completely clos-' ing said choke valve when said throttle valve is 10 closed.

( EARL E. MOORE.

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