US3529585A - Internal combustion engine fuel system - Google Patents

Description

United States Patent [72] Inventor Donald D. Stoltman Henrietta, New York [21] Appl. No. 701,482

[22] Filed Jan. 29, 1968 Continuation of Ser. No. 450,038, Apr. 22, 1965 [45] Patented Sept. 22, 1970 [73] Assignee General Motors Corporation Detroit, Michigan a corporation of Delaware [54] INTERNAL COMBUSTION ENGINE FUEL SYSTEM 2 Claims, 7 Drawing Figs.

[52] U.S.C1 123/119, 261/23, 261/39, 261/52 [51] Int. Cl. F02m l/10, F02m 11/06 [50] Field ofSearch 261/23.1,

[56] References Cited UNITED STATES PATENTS 2,702,536 2/1955 Carlson ..123/119(F)UX 2,939,445 6/1960 Sterner 261/39(.2)UX 2,943,848 7/1960 Gordon et a1... 261/39(.2)UX

....123/ll9(F)UX 129/1 19(F)UX 261/39 2,956,558 10/ l 960 Sterner et al. 2,957,465 10/1960 Wagner 3,321,193 5/1967 I-lighley Primary ExaminerRonald R. Weaver Ait0rneysA. F. Baillio, J. L. Carpenter and C. K. Veenstra period and to delay release of the secondary stage throttle from the lockout member. A throttle valve is rotatably disposed in the air inlet to control air flow therethrough. A lever arm is connected to the throttle valve for rotation therewith in a certain path. A throttle control mechanism having a member with a cam surface disposed in the path for contact with the lever arm. The cam surface variably limits closing movement of the lever arm and the throttle valve to establish a range of minimum throttle openings. A choke valve is disposed in the air-inlet and a thermostatic member responsive to engine operating temperatures is connected to the choke valve to control air flow past the. choke valve only over a first range of temperatures. The throttle control mechanism has a linkage moved by the thermostatic member for moving and controlling the position of the cam surfaced member over a range of temperatures including a second range of temperatures higher than those of the first range. The thermostatic member and the linkage provide a control for the cam surfaced member to permit a decreased minimum throttle opening upon an increase in temperature. The linkage includes a lever disposed for movement in an arcuate path. In one embodiment a baffle is located adjacent the lever and the baffle has an arcuate slot adjacent the arcuate path. The baffle has first and second apertures with an elongated spring member having one end received and substantially immobilized in the first aperture. The spring member has an intermediate portion received and supported in a second aperture. The spring member having the end opposite the one end supported by the intermediate portion in a cantilevered manner and extending through the arcuate slot into the arcuate path of movement of the lever for contact therewith. The opposite end of the spring member is disposed to contact the lever only as the mechanism is moved by the thermostatic member within the second range of temperatures. Contact of the opposite end of the spring member with the lever providing a force opposing movement of the throttle control mechanism by the thermostatic member for delaying movement of the mechanism and thereby delaying a decrease in the minimum throttle opening. 1n another embodiment the linkage includes a lever disposed for movement in an arcuate path and a shaft connected to the lever. An elongated spring member is substantially immobilized at one end and having an intermediate portion coiled about and supported by the shaft. The spring member having the end opposite one end supported by the intermediate portion in a cantilevered manner and extending into the arcuate path of movement of the lever for contact therewith. The opposite end of the spring is disposed to contact the lever only as the mechanism is moved by the thermostatic member within the second range of temperatures. Contact of the opposite end of the spring member with the lever providing a force opposing movement of the throttle control mechanism by the thermostatic member for delaying movement of the mechanism and thereby delaying a decrease in the minimum throttle opening.

Patented Sept. 22, 1970 3,529,555

Sheet 1 012 I 1\" VENTOR.

' 59022042 59. SIB/fwd ATTOK/VE) INTERNAL COMBUSTION ENGINE FUEL SYSTEM This application is a continuation of application Ser. No. 450,038, filed Apr. 22, 1965 and now abandoned.

This invention pertains to mechanism for controlling the throttle of an internal combustion engine fuel system and is particularly directed to means for extending the period of time during which throttle valve position is affected by a thermostatic control.

Most of the carburetors on automotive engines include a fast idle cam which holds the throttle valve open in varying degrees during the engine warm-up period. Such an arrangement admits sufficient air to the engine to increase the idling speed and prevent engine stalling during warm-up. The fast idle cam is generally controlled by the choke thermostat and is gradually released as the choke thermostat allows the choke valve to open. However, it is often desirable to completely open the choke valve sooner than the fast idle cam may be released to allow the throttle valve to close. Earlier proposals to achieve such a result have involved a linkage arrangement which now appears to be of unnecessary complexity. For example, see US. Pat. No. 2,957,465 issued in the name ofC. L. Wagner.

This invention provides a much simpler arrangement for accomplishing the same result which uses means for resisting movement of the thermostat linkage beyond that portion of its movement which controls air flow. In some carburetors, it can make use of the fact that the choke valve restricts air flow through the mixture conduits only during the initial portion of its opening movement. During the final portion of the choke valve opening movement the venturi, throttle valve and throttle valve opening provides a greater restriction to air flow than that caused by the choke valve. This invention slows the choke thermostat opening movement during that portion of its movement which controls this final portion of choke valve opening movement. Thus the fast idle cam, which is controlled by the choke thermostat, does not release the throttle valve to close completely for an extended period of time.

To slow the opening movement of the choke thermostat, a spring is interposed in the path of movement of a portion of the linkage in order to resist movement of the linkage during the final opening movement. The choke operating linkage may be modified so that the thermostat assists air flow through the mixture conduit and actively pulls the choke open. As the thermostat pulls in the choke opening direction, it will meet the resistance of the spring. Thus the rate of opening movement will be reduced during the final portion of opening movement, and the fast idle cam will hold the throttle valve open for a longer period of time.

In multi-stage fuel systems wherein air inlets or mixture conduits are sequentially opened, it is often desirable to delay opening of the secondary throttle valve controlling the secondary inlet or conduit until the choke in the primary air inlet is completely open. Mechanism has been proposed which will lock out the secondary throttle valve to prevent opening during choke valve opening movement. Such mechanism occasionally is combined with or operates in conjunction with the previously discussed fast idle cam and is released to unlock the secondary throttle valve only when the choke valve is fully opened. However, it is often desirable to completely open the choke valve sooner than the secondary throttle may be unlocked. This invention, in providing means to slow the final choke thermostat opening movement when air flow is not affected, delays release of the secondary throttle valve lockout mechanism for an extended period of time.

The details as well as other objects and advantages of this invention are disclosed in the following description and in the drawings in which:

FIG. 1 is a side elevational view of a carburetor including one embodiment of this invention;

FIG. 2 is an enlarged view of a portion of FIG. 1, with parts broken away to show the embodiment in greater detail;

FIG. 3 is a perspective view of the baffle plate often used in automatic choke mechanisms and showing the spring mounted on the baffle plate;

FIG. 4 is a view along line 4-4 of FIG. 1;

FIG. 5 is a view along line 5-5 of FIG. 4;

FIG. 6 is a view of an alternative embodiment of this invention in which the choke thermostat is located remotely from the carburetor; and

FIG. 7 is a view along line 7-7 of FIG. 6.

FIG. 1 illustrates a four-barrel, multi-stage carburetor 10 having primary and secondary mixture conduits I2 and 14 respectively. A choke valve 16 is pivotally mounted in the inlet to primary mixture conduits l2 and throttle valves 18 and 20 are rotatably disposed at the outlet of mixture conduits l2 and 14 respectively.

As shown in greater detail in FIGS. 2, 4, and 5, a choke thermostat housing 22 is mounted on legs 24, 26, and 28 extending from carburetor 10. A bolt 30 secures housing 22 to carburetor 10. Housing 22 is divided into two chambers 32 and 34 by a baffle plate 36. A coiled bimetal thermostat 38 is mounted in the outer chamber 32 with its inner end secured to the cover plate 42 for housing 22. Cover plate 42 has a fitting 44 to which a conduit may be secured for conveying heated air into housing 22 from a stove on the exhaust manifold (not shown).

The outer free end of thermostat 38 is secured to a tang 46 of a lever 48 mounted in the other chamber 34. Tang 46 extends through an arcuate slot 50 provided in baffle 36.

A passage 52 is provided through leg 28 to subject chamber 34 to the manifold vacuum which exists in mixture conduit 12 below throttle 18. The vacuum will draw heated air through fitting 44 on cover plate 42, over thermostat 38 in chamber 32, and through slot 50 in baffle 36. As thermostat 38 is warmed, it will uncoil to rotate lever 48 in the clockwise direction.

Lever 48 is secured to a shaft 54 which exte.-..ls through the rear of housing 22 into carburetor 10. A lever so is secured to the other end of shaft 54 and operates link 58 which is connected to a lever 60 secured to the ChOKc valve shaft 62. Thus as the temperature of thermostat 38 Changes, its outer free end rotates lever 48, shaft 54, and lever 56 and through link 58 and lever 60 positions choke valve 16.

FIG. 5 illustrates a linkage arrangement for controlling the primary and secondary throttles in accordance with temperature changes. As discussed above, it is often necessary to limit closing of primary throttles 18 to maintain a higher idling speed when the engine is cold. in addition, secondary throttles 20 should be prevented from opening when the engine is cold.

As shown in FIG. 5, a lever 64 is secured to the primary throttle shaft 66 and carries an adjusting screw 68. A second lever 70 is rotatably mounted on primary throttle shaft 66 and is gravitationally biased counterclockwise to remain in contact with adjusting screw 68. As primary throttles l8 rotate in the clockwise direction to close, adjusting screw 68 pushes lever 70 in the clockwise direction until it contacts a fast idle cam member 72 and prevents further closure of throttles 18. Fast idle cam member 72 is rotatably mounted upon shaft 54.

A pin 76 is carried by shaft 54 and extends through a slot 78 in member 72. A large mass 80 on the end of member 72 gravitationally biases member 72 so that the end 82 of slot 78 rests against pin 76. As thermostat 38 is warmed, shaft 54 and pin 76 will be rotated clockwise to allow member 72 to also rotate clockwise.

When primary throttles 18 are opened and levers 64 and 70 rotate counterclockwise, member 72 will be free to follow shaft 54 and pin 76 so that the cam will be appropriately positioned whenever throttles 18 are closed. If, on the other hand, primary throttles 18 are closed while the thermostat 38 is warmed, the force of the throttle return spring (not shown) transmitted through primary throttle shaft 66 and lever 64 will hold lever 70 against cam 72 with sufficient force to prevent rotation of member 72. As the thermostat is warmed, shaft 54 and pin 76 will rotate away from the end 82 of slot 78. When primary throttles 18 are later opened, member 72 will rotate due to its gravitational bias and catch up with pin 76.

A tang 84 on lever 64 is adapted to engage an arm 86 on lever 70 to rotate lever 70 clockwise as primary throttles 18 approach wide open. Arm 86 will engage a protrusion 88 on member 72 to rotate member 72 clockwise. The clockwise motion of member 72 will be transmitted through pin 76, shaft 54, lever 56, link 58 and lever 60 (see FIG. 4) to open or unload the choke valve 16.

A lever 90 is rotatably mounted upon leg 24 and is gravitationally biased clockwise to engage a pin 92 carried by the secondary throttle shaft 94. Lever 90 prevents rotation of pin 92 and thus prevents opening of the secondary throttles 20. As thermostat 38 warms and members 72 rotates clockwise, a protrusion 96 on member 72 engages an arm 98 of lever 90 to rotate lever 90 out of engagement with pin 92, thereby unlocking the secondary throttles.

[n the illustrated carburetor construction, the choke blade 16 ceases to restrict air fiow before it reaches a wide open position. This has been attributed to the fact that the air-flow area offered by the venturis 100 in the primary mixture conduits 12 or the air-flow area about wide open primary throttles I 18 is less than the total area opened by the choke blade 16. Therefore, during its final opening movement, the choke valve 16 offers no restriction to air flow.

Since this final opening movement offers no restriction to air flow, such final opening movement may be retarded without adversely affecting the operating characteristics of the automatic choke. This invention retards the final opening movement of the choke to extend the period in which the primary throttles 18 are held open by the fast idle cam member 72 and the secondary throttles 20 are locked in a closed position by the lockout lever 90.

Referring to FIGS. 2 and 3, a wire spring 102 is secured through a pair of holes 104 and 106 in baffle 36. A tang 108 on the end of spring 102 extends through the slot 50 and is disposed in the path of tang 46 and the free end of thermostat 38. The notch 109 in baffle 36 fits over a protrusion 110 within housing 22 to properly align baffle plate 36 and spring 102 with respect to the movement of thermostat 38. As thermostat 38 is warmed and its free end, together with tang 46 on lever 48, moves in a clockwise direction, it will encounter the resistance of spring 102. The movement of thermostat 38 and lever 48 will be retarded by spring 102 until the force of thermostat 38 is sufficient to overcome the force of spring 102. The free end of thermostat 38 will then move in an opening direction at a reduced rate.

The reduced rate of movement of thermostat 38 results in a slowing of the final opening movement of choke thermostat 38 and choke valve 16 and will extend the period of operation before primary throttles 18 are released from the fast idle cam member 72 and will also delay the release of secondary throttles 20 from the lockout lever 90.

The apparatus shown in F I65. 6 and 7 illustrates an alternative embodiment of the apparatus contained in housing 22. In some situations it is desirable to mount thermostat 38 remotely from carburetor 10, in a stove within the exhaust manifold or in the water manifold as schematically illustrated at l l 1.

In this alternative embodiment, the thermostat 38 drives a link 112 to operate a lever 114 secured to the shaft 54. Shaft 54 is in all other respects identical with that earlier described with reference to FIGS. 4 and 5. Shaft 54 extends from carburetor through a bracket 116 spaced from carburetor 10 upon legs 24, 26, and 28. Bracket 116 is secured to carburetor 10 by bolt 30.

A wire spring 118 is coiled about shaft 54 and is retained under tension by tangs 120 and 122 bent outwardly from bracket 116.

As the thermostat 38' is warmed, it will force link 112 upwardly to rotate lever 114 and shaft 54 in a clockwise direction. Near the end of the choke opening movement, a tang 124 on lever 114 engages spring 118. Spring 118 stops the choke thermostat and choke valve opening movement until the force of thermostat 38' is sufficient to overcome the force of spring 118. Thermostat 38 will then open choke valve 16 at a reduced rate. This alternative embodiment will thus slow the final choke thermostat and choke valve opening movement to delay the release of primary throttles 18 from fast idle cam member 72 and delay the unlocking of secondary throttles 20 from lever 90.

l claim:

1. An internal combustion engine fuel system comprising an inlet for air flow to the engine, a throttle valve rotatably disposed in said inlet to control air flow therethrough, a lever arm connected to said throttle valve for rotation therewith, said lever arm rotating in a certain path, a throttle control mechanism, said mechanism having a member with a cam surface disposed in said path for contact with said lever arm, said cam surface providing means for variably limiting closing movement of said lever arm and said throttle valve to establish a range of minimum throttle openings, a choke valve disposed in said inlet to control air flow therethrough, a thermostatic member responsive to engine operating temperatures, means for connecting said choke valve to said thermostatic member to control air flow past said choke valve only over a first range of temperatures, said throttle control mechanism also having linkage means moved by said thermostatic member for moving and controlling the position of said cam surfaced member over a range of temperatures including a second range of temperatures higher than those of said first range whereby said thermostatic member and said throttle control mechanism provide means to control the minimum throttle opening over a range of temperatures including said second range, said thermostatic member and said linkage means providing means for controlling said cam surfaced member to permit a decreased minimum throttle opening upon an increase in temperature, said linkage means including a lever disposed for movement in an arcuate path, a baflle located adjacent said lever, said baffle having an arcuate slot adjacent said arcuate path, said baffie further having first and second apertures, an elongated spring member having one end received and substantially immobilized in said first aperture, said spring member having an intermediate portion received and supported in said second aperture, said spring member having the end opposite said one end supported by said intermediate portion in a cantilevered manner and extending through said arcuate slot into the arcuate path of movement of said lever means for contact therewith, said opposite end being disposed to contact said lever means only as said mechanism is moved by said thermostatic member within said second range of temperatures, contact of said opposite end of said spring member with said lever means providing a force opposing movement of said throttle control mechanism by said thermostatic member for delaying movement of said mechanism and thereby delaying a decrease in the minimum throttle opening.

2. An internal combustion engine fuel system comprising an inlet for air flow to the engine, a throttle valve rotatably disposed in said inlet to control air flow therethrough, a lever arm connected to said throttle valve for rotation therewith, said lever arm rotating in a certain path, a throttle control mechanism, said mechanism having a member with a cam surface disposed in said path for contact with said lever arm, said cam surface providing means for variably limiting closing movement of said lever arm and said throttle valve to establish a range of minimum throttle openings, a choke valve disposed in said inlet to control air flow therethrough, a thermostatic member responsive to engine operating temperatures, means for connecting said choke valve to said thermostatic member to control air flow past said choke valve only over a first range of temperatures, said throttle control mechanism also having linkage means moved by said thermostatic member for moving and controlling the position of said cam surfaced member over a range of temperatures including a second range of temperatures higher than those of said first range whereby said thermostatic member and said throttle control mechanism provide means to control the minimum throttle opening over a range of temperatures including said second range, said thermostatic member and said linkage means providing means for controlling said cam surfaced member to permit a decreased minimum throttle opening upon an increase in temperature, said linkage means including a lever means disposed for movemechanism is moved by said thermostatic member within said second range of temperatures, Contact of said opposite end of said spring member with said lever means providing a force opposing movement of said throttle control mechanism by said thermostatic member for delaying movement of said mechanism and thereby delaying a decrease in the minimum throttle opening.

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