US3791358A

US3791358A - Carburetor control mechanism for an automotive gasoline powered internal combustion engine

Info

Publication number: US3791358A
Application number: US00308561A
Authority: US
Inventors: K Masaki; H Maruoka
Original assignee: Nissan Motor Co Ltd
Current assignee: Nissan Motor Co Ltd
Priority date: 1971-12-08
Filing date: 1972-11-21
Publication date: 1974-02-12
Anticipated expiration: 1991-02-12
Also published as: AU4920172A; CA959725A; DE2259529C3; JPS5110306B2; AU446708B2; DE2259529A1; JPS4864335A; GB1386648A; FR2164368A5; DE2259529B2

Abstract

A carburetor control mechanism adapted for minimizing noxious and harmful components in exhaust gases of an automotive gasoline powered internal combustion engine. The carburetor control mechanism comprises a first vacuum responsive actuator which is responsive to vacuum prevailing in an intake manifold of the engine to automatically open a carburetor throttle valve during the warming-up period of the engine after the engine is started, a solenoid valve for providing communication between the first vacuum responsive actuator and the intake manifold during the warming-up period of the engine, an electric control device for controlling the solenoid valve and for retarding the ignition timing of the engine during the warming-up period, a second vacuum responsive actuator which is responsive to vacuum prevailing in the intake manifold to automatically open a choke valve, and a thermostat controlled device for controlling the level of vacuum acting on the second vacuum responsive actuator in accordance with the engine temperature.

Description

waited States 9ater1t Masaki et a1.

CARBURETOR CONTROL MECHANISM FOR AN AUTOMOTIVE GASOLINE POWERED INTERNAL COMBUSTION ENGINE Inventors: Kenji Masaki; Hiroyuki Maruoka,

both of Yokohama, Japan Nissan Motor Company, Limited, Yokohama City, Japan Filed: Nov. 21, 1972 Appl. No.: 308,561

Assignee:

Foreign Application Priority Data Dec. 8, 1971 Japan 46-99152 Fieiii'of search....'.....123/1 19 F, 11 R, 179 G,

References Cited UNITED STATES PATENTS 7/1973 Buck et a1 1231117 AX 3/1973 Shioya et al. 123/117 AX 1/1971 Date et a1. 123/117 12/1970 Pierlot 123/117 A 9/1970 Fort 123/119 F 4/1961 Rapplean et a1. 123/119 F Primary Examiner--Al Lawrence Smith Assistant Examiner-W. H. Rutledge, Jr.

[5 7] ABSTRACT A carburetor control mechanism adapted for minimizing noxious and harmful components in exhaust gases of an automotive gasoline powered internal combustion engine. The carburetor control mechanism comprises a first vacuum responsive actuator which is responsive to vacuum prevailing in an intake manifold of the engine to automatically open a carburetor throttle valve during the warming-up period of the engine after the engine is started, a solenoid valve for providing communication between the first vacuum responsive actuator and the intake manifold during the warmingup period of the engine an electric control device for controlling the solenoid valve and for retarding the ignition timing of the engine during the warming-up period, a second vacuum responsive actuator which is responsive to vacuum prevailing in the intake manifold to automatically open a choke valve, and a thermostat controlled device for controlling the level of vacuum acting on the second vacuum responsive actuator in accordance with the engine temperature.

4 Claims, 1 Drawing Figure PATENTEBFEB 1 21974 SE28 9:2; m 29:29

(IARBURETOR CONTROL MEfIHANlSM FOR AN AUTOMOTIVE GASOLINE POWERED INTERNAL COMBUSTION ENGINE This invention relates to an automotive internal combustion engine equipped with a carburetor and, more particularly, to a control mechanism for carburetor choke and throttle valves of such engine for minimizing the noxious and harmful components in the engineexhaust gases.

A known gasoline powered internal combustion engine used in a motor vehicle usually includes a carburetor which is adapted to provide an air-fuel mixture having a richer air-fuel ratio during the Warming-up or cold period of the engine by closing a carburetor choke valve to effect a satisfactory operation of the engine, since the extent of the fuel vaporization is small when the engine is cold. Consequently, a large amount of noxious and harmful components such as carbon monoxide and hydrocarbon gases are inevitably contained in the engine exhaust gases when the engine is running cold. The carburetor is also adapted to open the choke valve as the engine temperature (as represented by the engine cooling liquid or exhaust gas temperature) increases during the warming-up period of the engine, whereby an air-fuel mixture having a proper air-fuel ratio is supplied to the engine thereby providing a satisfactory combustion of the air-fuel mixture in the'engine which remarkably reduces the noxious and harmful components such as carbon monoxide and hydrocarbon in the exhaust gases. In such carburetor, it is desirable and effective to control the choke valve according to the engine temperature (typically represented by the engine cooling liquid temperature), since the vaporization of fuel mainly depends upon the engine temperature.

It will be understood from the foregoing facts that the more rapidly the engine temperature is increased during the warming-up period of the engine, the earlier the choke valve is opened. This results in further reduction of the noxious and harmful components in the engine exhaust gases.

in order to expedite the warming-up of the engine, it is considered to be most effectively achieved by retarding the ignition timing of the engine; Retarding the ignition timing of the engine causes a delay of the combustion of air-fuel mixture in a combustion chamber of the engine with the consequent result that the heat transfer rate to the engine coolant is increased thereby rapidly raising the temperatures of the engine, the cooling liquid and the exhaust gases owing to the after-buming effect. However, retarding the ignition timing of the engine along tends to cause the engine to stall. To eliminate such engine stall, it is expedient to open the throttle valve after the engine has been started thereby to increase the engine speed, simultaneously retarding the ignition timing of the engine. in this manner, the warming-up of the engine can be carriedout more rapidly to reduce the warming-up period to H3 to 1/5 of the time otherwise needed thereby shortening the choking period.

Accordingly, in a gasoline powered engine equipped with a carburetor in which the throttle valve is opened after the engine is started while the ignition timing of the engine is simultaneously retarded, the noxious and harmful gases in the engine exhaust gases can be remarkably reduced by rapidly opening the choke valve as the warming-up of the engine progresses thereby reducing the fuel concentration in the air-fuel mixture supplied to the engine. I

This invention-contemplates to provide a novel and improved control mechanism for the choke and throttle valves in an automotive gasoline powered internal combustion engine on the basis of the abovementioned facts.

It is, therefore, an object of the present invention to provide an automatic control mechanism for minimizing the noxious and harmful components in the exhaust gases of an engine during the warming-up period.

It is another object of the present invention to provide an automatic choke and throttle control mechanism adapted for promoting the rate of increase in temperature of an engine during the Warming-up period.

It is still another object of the present invention to provide an automatic choke and throttle control mechanism for an engine which mechanism is highly reliable in operation.

It is a further object of the present invention to provide an automatic choke and throttle control mechanism which is low in manufacturing cost and which can readyly be installed in customary types of engines, and particularly to thetypes usually employed on motor vehicles without requiring any. significant changes or modifications.

Briefly, the foregoing and other objects of the present invention are attained by a control mechanism having the following features.

The control mechanism comprises a first vacuum responsive actuatoror sensor sensing intake manifold depression for controlling the degree of opening of a carburetor throttle valve. The first vacuum responsive actuator has a diaphragm member operatively connected to the carburetor throttle valve of the engine, a diaphragm chamber communicating selectively with an intake manifold of the engine and the atmosphere, and a compression spring disposed in the diaphragm chamber for urging the diaphragm member in one direction. The diaphragm member responds to vacuum prevailing in the intake manifold moving in another direction against the force of the compression spring to open the throttle valve. The control mechanism also comprises a solenoid valve for selectively introducing the vacuum prevailing in the intake manifold or atmospheric pressure into the diaphragm chamber. The control'mechanism further comprises an electric control device for controlling the solenoid valve and adjusting the ignition timing of the engine thereby to introduce the vacuum prevailing in the intake manifold into the diaphragm chamber simultaneously retarding the ignition timing of the engine when the engine is running cold and idling, and to introduce atmospheric pressure to the diaphragm chamber simultaneously releasing the ignition timing retard when the engine has warmed up. The control mechanism also includes a first set of two rotatableengaging members mounted on a throttle shaft. The first set of two rotatable engaging members each has projections which engage each other to open the throttle valve when vacuum prevailing in the intake manifold is introduced into the diaphragm chamber 'in the first vacuum responsive actuator. One of the engaging members is operatively connected at its one end to the diaphragm member in the first vacuum responsive actuator and is rotatably mounted on the throttle shaft at its other end and is independent of the throttle shaft rotation. The other of the engaging members is at its one end mounted fixedly on the throttle shaft and is adapted to turn the shaft, and is further connected at the other end to the accelerator pedal through a linkage. The control mechanism also includes a second vacuum actuator or sensor sensing intake manifold depression for controlling the degree of opening of a carburetor choke valve. The second vacuum responsive actuator includes a diaphragm member operatively connected to the choke valve, a diaphragm chamber communicating with the intake manifold, and a compression spring disposed in the diaphragm chamber for urging the diaphragm member in a direction to close the choke valve. The diaphragm member responds to the vacuum in the intake manifold moving in another direction against the force of the compression spring to open the choke valve. The control mechanism further comprises a thermostat or a temperature sensor controlled device associated with the second vacuum responsive actuator, for controlling the level of the vacuum acting on the diaphragm member on dependence on the temperature of the engine thereby to control the degree of opening of the choke valve, an actuating lever connected to the choke valve, and a link connected to the actuating lever. The control mechanism also comprises a second set of two rotatable engaging members having projections which engage each other when the throttle valve is fully opened, one of the engaging members being connected to the linkage, and the other being connected to one of the first set of two engaging members connected to the accelerator pedal. When the throttle valve is fully opened, the projections of the second set of two engaging members engage each other for thereby causing the link and the actuating lever to hold the choke valve in its open position.

These features of the present invention will become more apparent from the following description when taken in conjunction with the single FIGURE of the accompanying drawings.

The FIGURE is a schematic view of a preferred embodiment of a control mechanism according to the present invention.

Referring now to the drawing, there is schematically shown a preferred embodiment of an air-fuel mixer and ratio control mechanism according to the present invention, which mechanism is specifically suited for use in a known internal combustion engine. The internal combustion engine, partly shown, which is generally represented by reference numeral 10, has, as customary, an air-fuel supply system comprising a carburetor 11 leading from an air cleaner 12, a choke valve 14 fixedly mounted on a rotatable choke shaft 15, and a throttle valve 16 fixedly mounted on a rotatable throttle shaft 17. The internal combustion engine also includes an intake manifold 13 and an engine body 18 in which a water jacket 19 is formed. An accelerator pedal 20 is provided for opening the throttle valve 16 via a linkage 21.

The control mechanism includes a first vacuum responsive actuator or sensing means 22 mounted on the carburetor 11. The first vacuum responsive actuator or sensing means 22 is arranged to be actuated by or to sense vacuum or depression prevailing in the intake manifold 13 in a manner as will be hereinafter discussed in detail. This first vacuum actuator or sensor 22 includes a housing 23 having formed therein a diaphragm chamber 24, which communicates with the intake manifold 13 through a conduit 25. A diaphragm member such as a flexible diaphragm 26 is mounted in the housing 23 and carries a connecting rod 27. A compression spring 28 is disposed in the diaphragm chamber 24 for urging the diaphragm member 26 in one direction.

The control mechanism also includes a first set of two engaging

multi-arm levers

29 and 30 mounted on the throttle shaft 17. The engaging multi-arm levers 29 and 30 have projections 29a and 30a, respectively, which selectively engage each other to open the throttle valve 16. The engaging member 29 is rotatably mounted on the throttle shaft 17 and is independent of the throttle shaft rotation, and is further connected at its one end to the connecting rod'27 of the first vacuum responsive actuator 22. The engaging member 30 is fixedly mounted on the throttle shaft 17 and is arranged to turn the shaft 17, and is also connected at its one end to the accelerator pedal 20 via the linkage 21.

In the conduit 25 between the intake manifold 13 and the diaphragm chamber 24 of the first vacuum responsive actuator 22 there is provided a solenoid valve 31 for selectively introducing vacuum prevailing in the intake manifold 13 or atmospheric pressure into the diaphragm chamber 24. An electric control device 32 is provided for controlling the solenoid valve 31 and for adjusting the ignition timing of the engine 10. The electric control device 32 includes a switch 33 which is close when the engine is idling while cold, a thermoswitch of first temperature sensor 34 which is closed when the engine is cold, an ignition switch 35, and an ignition timing control device 36 for adjusting the ignition timing.

An actuating lever 37 is connected to the choke shaft 15 to actuate the choke valve 14.

The control mechanism also includes a second vacuum responsive actuator or sensing means 38 mounted on the carburetor body, which has a construction similar to the first vacuum responsive actuator 22. The second vacuum responsive actuator or sensing means 38 is arranged to be actuated by or to sense the vacuum or depression prevailing in the intake manifold 13 in a manner as will be hereinafter discussed in detail. This second vacuum responsive actuator 38 includes a housing 39 having formed therein a diaphragm chamber 40, which communicates with the intake manifold 13 through a conduit 41. A diaphragm member such as a flexible diaphragm 42 is mounted in the housing 39 and carries a connecting rod 43 to which the actuating lever 37 is operatively connected so that the choke valve 14 is opened and closed by the movement of the diaphragm member 42. A compression spring 44 is disposed in the diaphragm chamber 40 for urging the diaphragm member 42 in a direction to close the choke valve 1 6.

As mentioned above, the diaphragm chamber 40 communicates with the intake manifold 13 of the engine through the conduit 14 so that the diaphragm member 42 disposed in the diaphragm chamber 40 is responsive to the vacuum prevailing in the intake manifold 13 to move in another direction to open the choke valve 14 against the force of the spring 44. In order to control the level of the vacuum acting on the diaphragm member 42, the control mechanism also includes a thermostat or temperature sensor controlled device 45. In the illustrated embodiment of the FIG- URE, the thermostat controlled device 45 is shown as interposed between the diaphragm chamber 40 of the second vacuum responsive actuator 33 and the intake manifold 13 but may be disposed in any suitable part of the engine.

As seen in the FIGURE, the thermostat controlled device 45 includes a housing 46 having formed therein a vacuum level control chamber 47 communicating with the intake manifold 13 via a conduit 48 and with the diaphragm chamber 40 via conduit 41. A partition wall member 49 is mounted in the housing 46 for defining the vacuum level control chamber 47. As shown, the partition wall member 49 is formed with a control aperture 50. The housing 46 also has an air supply port 51 which opens to the atmosphere and which communicates with the vacuum control chamber 47 through the control aperture 50. A valve member 52 is positioned opposite to the control aperture 50 for controlling the degree of communication between the air supply port 51 and the vacuum level control chamber 47 so that the level of the vacuum acting on the diaphragm member 42 is varied. The thermostat controlled device 45 also includes a thermostat 53 which is fixed to the valve member 52, and associated therewith for controlling the movement thereof toward and away from the control aperture 50 in accordance with the engine temperature. When the engine temperature exceeds a predetermined level, the thermostat 53 causes the valve member 52 to move towards the control aperture 50 to decrease the communication between the air supply port 51 and the vacuum level control chamber 47 for thereby increasing the level of vacuum acting on the diaphragm member 42 of the second vacuum responsive actuator 38. For detecting the engine temperature, the thermostat 53 is mounted in the water jacket 49 formed in the engine body 18. It is to be noted that the thermostat 53 is shown as disposed in the water jacket 19 in the embodiment ,of the FIGURE, but may be mounted in any suitable part of the engine.

The control mechanism also includes a second set of engaging

multi-arm levers

54 and 55 which are rotatably mounted on a shaft 56 fastened to a suitable part of the engine body. The engaging

multi-arm levers

54 and 55 have formed thereon projections 54a and 55a, respectively, which selectively engage each other. The engaging member 54 is connected at its one end to a link 57 connected to the actuating lever 37 while the engaging member 55 is connected at its one end to one end of a connecting member 58. The connecting member 58 is operatively connected at the other end to the engaging member 30. l

The FIGURE shows the control mechanism of the present invention when engine has not been started. In this state, the choke valve 14 is substantially closed by the force of the compression spring 44. The throttle valve 16 is also substantially closed since the accelerator pedal 20 is not depressed.

When the engine is started, the

switches

33, 34, 35 are all closed thereby to energize the coil of the solenoid valve 31. When the coil is energized, the solenoid valve 31 introduces the vacuum prevailing in the intake manifold 13 into the diaphragm chamber 24 of the first vacuum responsive actuator or sensor 22. The diaphragm member 26 is responsive to this vacuum to move in a direction to lower the connecting rod 27 against the force of the spring 28. As the connecting rod 27 is lowered, the engaging member 29 is rotated counterclockwise so that the projection 29a of the engaging member 29 is brought into engagement with the projection 30a of the engaging member 30 thereby to rotate" the engaging member 30 counterclockwise. Consequently, the throttle valve 16 connected to the engaging member 30 is opened to reach a proper position. Simultaneously, the ignition timing is retarded by the ignition timing control device 36. In this condition, the valve member 52 is away from the control aperture 50 to permit air to flow into the vacuum control chamber 47 since the engine is cold. Therefore, no significant vacuum develops-in the vacuum control chamber 47. Consequently, the choke valve 14 is kept closed.

When the engine has warmed up and the motor vehicle is started to move, the

switches

33 and 34 open to deenergize the coil of the solenoid valve 31. When the coil is deenergized, the solenoid valve 31 introduces atmospheric pressure into the diaphragm chamber 24 of the first vacuum resonsive actuator 22. The diaphragm member 26 responds to the atmospheric pressure moving in a direction to allow lifting of the connecting rod 27 by the force of the spring 28. As the connecting rod 27 is lifted, theengaging member 29 is rotated clockwise so that the projection 29a disengages the projection 3tla. Simultaneously, the ignition timing retard is released. Depression of the accelerator 20 causes the motor vehicle to start to move and travel in a normal manner.

As the temperatureof cooling water increases the valve member 52 moves towards the control aperture 50 to restrict the atmospheric'flow therethrough. Consequently, the vacuum in the vacuum control chamber 47 is increased. Then, this vacuum is introduced into the diaphragm chamber 40, and the diaphragm member 42 moves-in a direction to open the choke valve. During the cruising of the motor vehicle, the choke valve is kept in a fully open position.

When the throttle valve 16 is fully opened as when the motor vehicle is accelerated by depressing the accelerator 2b, the vacuum prevailing in the intake manifold 13 is reduced with the consequent'result that the choke valve 14 tends to close owing to the rightward movement of the connecting rod 43 by the force of the spring 44. In order to prevent this, the control mechanism of the present invention provides the second set of two

engaging members

54 and 55. As the throttle valve 16 is moved to its fully open position by depressing the accelerator 20, the engaging member 30 is caused to rotate counterclockwise thereby moving the connecting member 58 upwardly. Thus, the engaging member 55 is rotated counterclockwise so that the projection 55a of the engaging member 55 is brought into engagement with the projection 54a of the engaging member 54 thereby rotating theengaging member 54 counterclockwise. Consequently, the link 57 is moved leftwardly to rotate the actuating lever 37 clockwise and, thus, the actuating lever 37 holds the choke valve 14 in its open position, against the force of the spring 44.

As the throttle valve 16 is closed by releasing the accelerator pedal 20, the engaging member 34) is held in a position to cause the projections 54a and 55a to-disengage so that the choke valve 14 is controlled by the second vacuum actuator 38.

The lengths of the projections 54a and 55d are selected so that the accelerator pedal can be operated smoothly.

It will be appreciated that the control mechanism of the present invention has the advantages of not only automatically controlling the choke and throttle valves of the engine carburetor but also effecting faster warming-up of the engine thereby to minimize the total amount of noxious and harmful components emitted with the engine exhaust gases, but also has the advantages of being highly reliable in operation, low in manufacturing cost and can readily be installed in known types of engines without requiring any significant change or modification.

What is claimed is 1. In an internal combustion engine of a vehicle having an intake manifold and a carburetor having a choke valve with a choke shaft and a throttle valve with a throttle shaft, the combination comprising a first vacuum responsive actuator for controlling the degree of opening of said throttle valve, said vacuum responsive actuator including a diaphragm member operatively connected to said throttle valve, a diaphragm chamber communicating selectively with said intake manifold and the atmosphere, and a spring disposed in said diaphragm chamber for urging said diaphragm member in one direction, said diaphragm member being responsive to vacuum prevailing in said intake manifold to move in another direction against the force of said spring to open said throttle valve, a solenoid valve for selectively introducing vacuum prevailing in said intake manifold and atmospheric air into said diaphragm chamber, and an electric control device for controlling said solenoid valve and adjusting the ignition timing of the engine thereby to introduce the vacuum prevailing in said intake manifold into said diaphragm chamber simultaneously retarding the ignition timing when the engine is running cold and idling, and to introduce atmospheric air into said diaphragm chamber simultaneously releasing the ignition timing retard when the engine has warmed up, a first set of two rotatable engaging members having projections which engage each other to open said throttle valve when the vacuum prevailing in said intake manifold is introduced into said diaphragm chamber in said first vacuum responsive actuator, one of said engaging members being operatively connected at its one end to said diaphragm member in said first vacuum responsive actuator and being rotatably mounted on the throttle shaft at its other end inde pendently of the throttle valve rotation, the other of said engaging members being mounted fixedly on the throttle shaft and being connected via links at another end to an accelerator pedal, a second vacuum responsive actuator for controlling the degree of opening of said choke valve, said second vacuum responsive actuator including a diaphragm member operatively connected to said choke valve, a diaphragm chamber communicating with said intake manifold, and a spring disposed in said diaphragm chamber for urging said diaphragm member in a direction to close said choke valve, said diaphragm member being responsive to the vacuum prevailing in said intake manifold to move in another direction against the force of said spring to open said choke valve, and a thermostat controlled device associated with said second vacuum responsive actuator for controlling the level of said vacuum acting on said diaphragm member of said second vacuum responsive actuator in accordance with the temperature of 7 said engine thereby to control the degree of opening of nected to one member of said first set of two engaging members connected to the accelerator pedal, whereby when said throttle valve is fully opened, said projections of said second set of two engaging members engage each other for thereby causing said actuating lever to hold said choke valve in its open position.

2. The combination as claimed in claim 1, wherein said electric control device includes an idling switch adapted to close when the engine is idling while cold, a thermoswitch adapted to close when the engine temperature is below a certain value, and an ignition timing control device for adjusting the ingition timing of the engine.

3. The combination as claimed in claim 1, wherein said thermostat controlled device includes 'a vacuum level control chamber located between said diaphragm chamber of said second vacuum responsive actuator and said intake manifold and having an inlet communicating with said intake manifold and an outlet communicating with said diaphragm chamber of said second vacuum responsive actuator, a partition wall member for defining said vacuum level control chamber and having formed therein a control aperture which opens to said vacuum level control chamber, an air supply passageway communicating with said control aperture, a valve member provided for controlling the degree of communication between said air supply port and said vacuum level control chamber in dependence on engine temperature thereby to control the level of said vacuum acting on said diaphragm member of said second vacuum responsive actuator, and a thermostat fixed to said valve member for controlling the movement thereof toward and away from said control aperture formed in said partition wall member, said thermostat being responsive to the temperature of said engine, whereby when said engine temperature exceeds a predetermined level, said thermostat causes said valve member to move toward said control aperture to decrease the communication between said air supply passageway and said vacuum level control chamber for thereby increasing the level of said vacuum acting on said diaphragm member of said second vacuum responsive actuator.

4. The combination as claimed in claim 3, wherein said thermostat is mounted in a water jacket formed in a body of said internal combustion engine, said thermostat being subject to an engine cooling liquid in said water jacket, whereby the movement of said valve member is controlled by said thermostat in response to the temperature of said cooling liquid.

Claims

1. In an internal combustion engine of a vehicle having an intake manifold and a carburetor having a choke valve with a choke shaft and a throttle valve with a throttle shaft, the combination comprising a first vacuum responsive actuator for controlling the degree of opening of said throttle valve, said vacuum responsive actuator including a diaphragm member operatively connected to said throttle valve, a diaphragm chamber communicating selectively with said intake manifold and the atmosphere, and a spring disposed in said diaphragm chamber for urging said diaphragm member in one direction, said diaphragm member being responsive to vacuum prevailing in said intake manifold to move in another direction against the force of said spring to open said throttle valve, a solenoid valve for selectively introducing vacuum prevailing in said intake manifold and atmospheric air into said diaphragm chamber, and an electric control device for controlling said solenoid valve and adjusting the ignition timing of the engine thereby to introduce the vacuum prevailing in said intake manifold into said diaphragm chamber simultaneously retarding the ignition timing when the engine is running cold and idling, and to introduce atmospheric air into said diaphragm chamber simultaneously releasing the ignition timing retard when the engine has warmed up, a first set of two rotatable engaging members having projections which engage each other to open said throttle valve when the vacuum prevailing in said intake manifold is introduced into said diaphragm chamber in said first vacuum responsive actuator, one of said engaging members being operatively connected at its one end to said diaphragm member in said first vacuum responsive actuator and being rotatably mounted on the throttle shaft at its other end independently of the throttle valve rotation, the other of said engaging members being mounted fixedly on the throttle shaft and being connected via links at another end to an accelerator pedal, a second vacuum responsive actuator for controlling the degree of opening of said choke valve, said second vacuum responsive actuator including a diaphragm member operatively connected to said choke valve, a diaphragm chamber communicating with said intake manifold, and a spring disposed in said diaphragm chamber for urging said diaphragm member in a direction to close said choke valve, said diaphragm member being responsive to the vacuum prevailing in said intake manifold to move in another direction against the force of said spring to open said choke valve, and a thermostat controlled device associated with said second vacuum responsive actuator for controlling the level of said vacuum acting on said diaphragm member of said second vacuum responsive actuator in accordance with the temperature of said engine thereby to control the degree of opening of said choke valve, an actuating lever connected to said choke valve, a link connected to said actuating lever, a second set of two rotatable engaging members having projections which engage each other when said throttle valve is fully opened, one of said engaging members being connected to said link, and the other being connected to one member of said first set of two engaging members connected to the accelerator pedal, whereby when said throttle valve is fully opened, said projections of said second set of two engaging members engage each other for thereby causing said actuating lever to hold said choke valve in its open position.

3. The combination as claimed in claim 1, wherein said thermostat controlled device includes a vacuum level control chamber located between said diaphragm chamber of said second vacuum responsive actuator and said intake manifold and having an inlet communicating with said intake manifold and an outlet communicating with said diaphragm chamber of said second vacuum responsive actuator, a partition wall member for defining said vacuum level control chamber and having formed therein a control aperture which opens to said vacuum level control chamber, an air supply passageway communicating with said control aperture, a valve member provided for controlling the degree of communication between said air supply port and said vacuum level control chamber in dependence on engine temperature thereby to control the level of said vacuum acting on said diaphragm member of said second vacuum responsive actuator, and a thermostat fixed to said valve member for controlling the movement thereof toward and away from said control aperture formed in said partition wall member, said thermostat being responsive to the temperature of said engine, whereby when said engine temperature exceeds a predetermined level, said thermostat causes said valve member to move toward said control aperture to decrease the communication between said air supply passageway and said vacuum level control chamber for thereby increasing the level of said vacuum acting on said diaphragm member Of said second vacuum responsive actuator.