Intake Manifold Vacuum Control System

Abstract

Disclosed herein is a carburetor for reducing the amount of hydrocarbons contained in exhaust gases emitted from an automotive gasoline-powered engine during deceleration of the automobile. Such reduction is accomplished by lowering the vacuum at the intake manifold of the engine through introduction of a proper amount of air-fuel mixture into the intake manifold by way of an additional bypass passageway and in response to the drop of the vacuum at the intake manifold.

Description

The present invention relates to a carburetor adapted for reducing the amount of hydrocarbons contained in the exhaust gases that are emitted from a gasoline-powered internal combustion engine; more particularly, to a carburetor which is adapted to introduce an appropriate amount of an air-fuel mixture into the intake manifold of the engine during the deceleration of the automobile, whereby the vacuum at the intake manifold is lowered to an optimum level for reducing the hydrocarbon content of the exhaust gases to a minimum.

As is well known, the vacuum at the intake manifold of an automotive engine increases abruptly during the deceleration of the automobile, when the throttle valve of the carburetor is kept substantially fully closed. Experiments have revealed that the vacuum at the intake manifold often exceeds a level of about 650 mm. of Hg. when decelerating while it remains under 500 mm. of Hg. during idling operation. This is due to the fact that the throttle valve of the carburetor is substantially closed during deceleration, so as to shut off the flow of an air-fuel mixture to the intake manifold, although the engine continues to operate at a relatively high speed proportioned to the running speed of the automobile. The increase of the intake manifold vacuum to such a high level results in unsatisfactory combustion and misfire of the air-fuel mixture in the combustion chamber of the engine, giving rise to the high-hydrocarbon content of the engine exhaust gases emitted as unburned or partially burned compounds.

These facts indicate that the hydrocarbon content of the engine exhaust gases could be lessened if the vacuum at the intake manifold is lowered to a certain level. Attempts have been made, therefore, to control the vacuum at the intake manifold with a view to reducing the amount of the unburned compounds of the engine exhaust gases. These attempts include two major systems, one directed to maintaining the throttle valve of the carburetor in a slightly open position to allow the air-fuel mixture to flow through the throttle valve in a predetermined volume even during deceleration, and the other directed to supplying a predetermined amount of atmospheric air to the intake manifold in response to the decrease in the automobile speed.

In order to maintain the throttle valve of the carburetor in a slightly open position during the deceleration, it is required that the valve and the associated parts be designed and machined with utmost preciseness. When, moreover, the engine has been put into prolonged use, meticulous readjustment of the carburetor settings will be required from time to time to suit the alterations in the idle adjustment. The system of the former type is thus considered as lacking in practicability.

Introduction of atmospheric air into the intake manifold during the deceleration, as put into practice in the system of the latter type, on the other hand, will cause the air-fuel mixture to become too lean to assure satisfactory combustion of the mixture in the combustion chamber of the engine, sometimes resulting in further increase in the amount of unburned hydrocarbons in the exhaust gases.

In a conventional carburetor of constant venturi type, as a matter of fact, the fuel is drawn to the intake manifold through the idle and bypass ports alone, with the main fuel jet kept inoperative, with the result that the engine is not supplied with a sufficient amount of fuel during deceleration. If, then, a bypass passageway is provided to link the upstream and downstream sides of the throttle valve with each other so as to permit air to flow therethrough when the throttle valve remains closed, a problem is still encountered in that since the fuel is delivered from the idle ports alone, the air-fuel mixture to be delivered to the intake manifold is too lean to attain satisfactory combustion in the engine.

As is well known, the fuel delivered from the bypass ports is pulled over with the vacuum established by the flow of air between the edge portion of the throttle valve and the inner face of the carburetor body, said air flowing at a rate approximating that of a subsonic flow with the throttle valve held in a substantially fully closed position.

If, therefore, there is provided a bypass passageway communicating not only with the upstream and downstream sides of the throttle valve but also with the idle mixture circuit, a calibrated amount of air-fuel mixture will be supplied to the combustion chamber of the engine.

A primary object of the present invention is thus to provide a carburetor which is adapted for effectively reducing the amount of hydrocarbons in the engine exhaust gases emitted during deceleration of an automobile.

Another primary object of the invention is to provide a carburetor which is adapted to lower the vacuum at the intake manifold of the engine for reducing the hydrocarbon content of the exhaust gases during deceleration.

A further primary object of the invention is to provide a carburetor for introducing an air-fuel mixture, which is appropriate in volume and mixture ratio, into the intake manifold of the engine in close response to the rise in the vacuum at the intake manifold, thereby lowering the said vacuum to a level which is appropriate for suppressing the emission of unconsumed fuel from the combustion chamber of the engine.

A still further object of the invention is to provide a carburetor having a bypass passageway communicating not only with the upstream and downstream sides of the throttle valve, but, also with the the idle mixture circuit, whereby an appropriate amount of air-fuel mixture is supplied to the engine through the bypass passageway even during deceleration, and which the throttle valve is substantially fully closed, thus contributing to the reduction of the amount of hydrocarbons to be emitted during deceleration.

These and other object and features of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a graphical representation of a typical example of the relationship between the intake manifold vacuum and the amount of unburned hydrocarbons;

FIGS. 2 and 3 are views showing, in vertical section, a carburetor of constant venturi type incorporating the improvement according to the invention, the control valve being shown in position for throttle part and closed-throttle operations, respectively;

FIGS. 4 and 5 are views showing, in vertical section, a modification of the carburetor of FIGS. 2 and 3, the control valve being shown in position for part and closed throttle operations, respectively;

FIGS. 6 and 7 are views showing, in vertical section, a carburetor of variable venturi type incorporating the improvement according to the invention, the control valve being shown in position for part and closed throttle operations, respectively; and

FIGS. 8 and 9 are views showing, in vertical section, a modification of the control valve shown in FIGS. 2 to 7.

FIG. 1 is presented to explain how sharply the quantity of hydrocarbons contained in the exhaust gases increases if the intake manifold vacuum rises in excess of 600mm. of Hg. or more, while such quantity remains substantially negligible as long as the intake manifold vacuum is kept lower than about 550mm. of Hg. Therefore, to reduce the unburned hydrocarbon content of the engine exhaust gases to a minimum, from a theoretical point of view, it would be best to maintain intake manifold vacuum below 550mm. of Hg. It is, however, empirically known that reduction in the intake manifold vacuum to such a low level is detrimental to the driveability of the automobile, especially to the braking performance of the engine. Thus, the reasonable level to which the intake manifold vacuum should be lowered with satisfactory results is considered to lie in the neighborhood of 600mm. of Hg. for all practical reasons.

In FIGS. 2 and 3, there is shown an embodiment of the carburetor according to the invention, the carburetor being shown to be of constant venturi type by way of example. As shown, the carburetor includes, similarly to an existing counterpart, a carburetor body 10, a constant or fixed area venturi 11, a throttle valve 12, a main jet 13 for delivering liquid fuel during the full and part throttle operations, and an idle mixture circuit 14 for delivering liquid fuel during the idle and decelerating operations. The idle mixture circuit 14 comprises an air bleed opening 15 communicating with the atmosphere, a bypass passageway 17, an idle port 18 opening into the intake manifold of the engine (not shown), an idle adjustment screw 19 and a bypass port 20 opening into the carburetor body.

During the full or part throttle operation, as shown in FIG. 2, air introduced from the atmosphere by way of the air cleaner (not shown) is mixed with the liquid fuel delivered from the main jet 13 and forced to gush into the intake manifold. When, however, the throttle valve 12 is held in a substantially fully closed position, as is the case during deceleration, the flow of air and fuel through the venturi 11 ceases so that the air-fuel mixture is substantially prohibited from passing beyond the throttle valve 13. This causes the vacuum at the intake manifold in increase abruptly and, as a consequence, the air-fuel mixture fed to the idle mixture circuit 14 is pulled over to the intake manifold through the idle and bypass ports 18 and 20. Since, in this instance, the amount of the air-fuel mixture to be supplied to the engine through the circuit 14 is so determined as to provide for normal combustion of the mixture during the idle operation, it is inadequate in volume and mixture ratio to provide for satisfactory combustion during deceleration.

In order to permit the engine to receive an optimum amount of air-fuel mixture, there are further provided in the carburetor according to the invention, an air passageway 21 communicating with the atmosphere, a mixture passageway 22 communicating with the intake manifold, a branch passageway 23 branched from the bypass passageway 17 and communicating with both of the passageways 21 and 22, and a control valve assembly 24.

The passageway 21 has its inlet at a suitable location upstream of the venturi 11 and communicates with the passageways 22 and 23. The passageway 22 opens into the carburetor body at a suitable location downstream of the throttle valve 12. The outlet and inlet of the passageways 21 and 22 serve as valve seats for the valve assembly 24.

The control valve assembly 24 is divided by a diaphragm member 25 into two separate chambers defining a suction chamber 26 and an atmospheric chamber 27. The suction chamber 26 has accommodated therein a coil spring 28 depressing the diaphragm member 25. The atmospheric chamber 27 has accommodated therein a valve member 29 which is secured at one end to the diaphragm member 25 through a rod 31 and is normally held at the other in a position to abut against the valve seats 32, 33 and 34 to isolate the passageway 21 from the passageway 22, as shown in FIG. 2.

The suction chamber 26 communicates with the intake manifold of the engine by way of the suction conduit 35.

In operation, when the throttle valve 12 is kept fully or partly opened, the vacuum at the intake manifold is maintained at a relatively low level with the air-fuel mixture drawn from the venturi, so that the valve member 25 is held in an abutting engagement with the valve seats 32, 33 and 34 by the action of the coil spring 28, thereby prohibiting the air from the passageway 21 and mixture from the passageway 23 to flow into the passageway 22, as shown in FIG. 2.

When, as illustrated in FIG. 3, the throttle valve 12 is substantially fully closed during deceleration, causing a rapid increase in the intake manifold, the gas in the suction chamber 26 is pulled over to the intake manifold through the conduit 35, so that the valve member 29 is moved away from the valve seats 32, 33 and 34 against the action of the coil spring 28, permitting the passageways 21 and 23 to communicate with the passageway 22. Then, the air fed to the passageway 21, and the air-fuel mixture fed to the passageway 23, are allowed into the intake manifold by way of the passageway 22, thereby enabling the engine to operate with an air-fuel mixture of optimum volume and mixture ratio. The amount of air and air-fuel mixture to be contained in the final air-fuel mixture may be metered by means of orifices 36 and 37, respectively.

It is important, in this instance, that the tension of the coil spring 28 and the total area of the diaphragm member 25 be so determined as to overcome the force of the vacuum exercised on the diaphragm member 25 during the full and part throttle operations, as well as during the idle operation, but, to yield to the same during deceleration. Where a carburetor having a low-speed mixture circuit is used, the bypass mixture circuit 14 of the above described embodiment may be made to communicate with the low speed mixture circuit.

As illustrated in FIGS. 4 and 5, the low speed mixture circuit comprises, as is well known, a liquid fuel supply passageway 38 communicating with the fuel source (not shown), a first air bleed opening 39 vented from the atmosphere, a jet 40 at which the air delivered from the air bleed opening 39 and liquid fuel delivered from the passageway 38 are mixed with each other and metered to a predetermined mixture ratio, and a second air bleed opening 41 vented from the atmosphere and communicating with the jet 40 for supplying additional air to the air-fuel mixture from the jet 40.

Under full or part throttle operation, as best illustrated in FIG. 4, the vacuum at the intake manifold of the engine is kept at a relatively low level so that the diaphragm member 25 is urged toward the atmospheric chamber 27, by the action of the coil spring 28, to cause the valve member 25 to abut closely against the valve seats 32 to 34 so as to shut off the air and air-fuel mixture into the passageway 35.

During deceleration of the automobile, when the vacuum at the intake manifold increases to an extremely high level, as shown in FIG. 5, the valve member 29 is released from the valve seats as previously described to permit the passageways 21 and 23 to communicate with the passageway 22 to allow the air-fuel mixture into the intake manifold of the engine by way of the conduit 35.

Referring now to FIGS. 6 and 7, there is shown a carburetor of variable venturi type incorporating the improvement according to the invention. As shown, the carburetor largely comprises a carburetor body 42, a throttle valve 12', a flow control assembly 44 having a suction piston 45 of known construction, a venturi 46 defined by the bottom wall of the suction piston 45 and a bridge 47, a fuel jet 48 opening at the bridge 47 into the carburetor body, and a tapered needle 49 secured to the bottom wall of the suction piston 45 and movably inserted into the fuel jet 48. The sectional area of the venturi 46 is varied with the mechanical displacement of the piston 45, which moves up and down in FIGS. 6 and 7 with the fluctuation in the gas pressure in the carburetor upstream of the throttle valve 12', so as to regulate the flow of air and fuel into the engine combustion chamber (not shown).

The carburetor according to the invention further comprises a slow-speed mixture passageway 17' corresponding to the bypass passageway 17 in FIGS. 1 to 2 which communicates at one end with the fuel source (not shown) through a passage 53 by way of a slow jet 54 and at the other end with a slow pilot outlet 20' and a slow bypass 18' in which the amount of the mixture passing therethrough is regulated by a slow pilot screw 19', and which is vented from a slow air bleed 41', a fuel passageway 50 branched from the slow-speed mixture passageway 17', an air passageway 51 opening into the carburetor body downstream of the venturi 46, and a mixture passageway 52 opening into the carburetor body downstream of the throttle valve 12'. The establishment of a communication between the fuel and air passageways 50 and 51 and the mixture passageway 52 is regulated by the control valve assembly 24.

Under full or part throttle operation, as illustrated in FIG. 6, the vacuum at the intake manifold of the engine is kept at a relatively low level so that the diaphragm member 25 is urged toward the atmospheric chamber 27 by the action of the coil spring 28, as previously described, thereby causing the valve member 29 to isolate the mixture passageway 52 from the fuel and air passageways 50 and 51.

During deceleration of the automobile, when the vacuum at the intake manifold increases to an extremely high level, the diaphragm member 25 is pulled over toward the suction chamber 26 so that the valve member 29 is moved against the action of the spring 28 in a direction to permit the passageway 52 to communicate with the fuel and air passageway 50 and 51, thereby supplying the air-fuel mixture to the intake manifold, as seen from FIG. 7.

As an alternative to the aforementioned diaphragm valve assembly 24, there may be provided, intermediate the passageways 21 and 22, a needle valve member 55 which is operatively connected with a solenoid device 56 and releasably inserted into the fuel passageway 23, as shown in FIGS. 8 and 9. The solenoid valve device 56 may be of known construction and is arranged to function in such a manner as to keep the passageways 21 and 22 insolated while the device 56 remains deenergized, and to allow such passageways to communicate with each other while the device 56 remains energized.

The solenoid device 51 is grounded at one terminal thereof through an electrical power source 57, and connected at the other with a diaphragm switch assembly 58 through a wire connection 59. The diaphragm switch assembly 58 is divided by a diaphragm member 60 into two separate chambers defining a suction chamber 61 and atmospheric chamber 62. The suction chamber 61 communicates with the intake manifold 63 of the engine (not show) through a suction conduit 64. The atmospheric chamber 62 communicates with the atmosphere through an air vent (not shown), and has accommodated therein a moving contact 65 connected with the conductor wire connection 59, a stationary contact 66 which is grounded, a rod 67 mechanically connecting the moving contact 54 with the diaphragm member 60, and a coil spring 68 acting to normally keep the moving contact 65 released from the stationary contact 66.

During full and part throttle operations of the automobile, when the vacuum at the intake manifold 63 is maintained at a relatively low level, as shown in FIG. 8, the tension of the coil spring 68 overcomes the force of the vacuum exercised on the diaphragm member 60, so that the moving contact 65 connected with the diaphragm member through the rod 67 remains released from the stationary contact 66, thus keeping the solenoid device 51 deenergized. The result is that the needle valve member 55 intrudes into the passageways 23 and between the passageways 21 and 22, so that air from the passageway 21 and the mixture from the passageway 23 is prohibited from flowing into the passageway 22 while in full or part throttle operation.

During deceleration, when the intake manifold vacuum increases abruptly to an extremely high level as shown in FIG. 9, the tension of the coil spring 67 yields to the force of the vacuum exercised on the diaphragm member 60 so that the moving contact 65 is brought into abutting engagement with the stationary contact 66, thereby causing the solenoid device 56 to become energized. With the solenoid device 56 thus energized the valve member 55 is actuated to withdraw from the passages 21, 22 and 23, so as to permit the air-fuel mixture to flow into the passageway 22 and down into the intake manifold of the engine.

From the foregoing description, it will be understood that according to the present invention, the engine can operate invariably under sound conditions and with the least emission of hydrocarbons since the vacuum at the intake manifold is maintained under a predetermined level throughout the varying driving conditions of the engine, and since the engine is supplied with an air-fuel mixture which is suitable in both volume and mixture ratio for satisfactory combustion in the combustion chamber of the engine, even during deceleration of the automobile.

While a few embodiments of the invention have been shown and described in detail, it will be apparent to those skilled in the art that such embodiments are disclosed by way of illustration only, and that numerous changes may be made thereto without departing the spirit and scope of the present invention which is defined by the appended claims.

Claims

I claim:

1. In a carburetor for a gasoline-powered engine for a motor vehicle, in which the engine has an intake manifold, and in which the carburetor has a throttle chamber communicating with the intake manifold, a throttle valve within such throttle chamber, and an idle bypass passageway connected at one end to a source of fuel and at its other end to the throttle chamber downstream of the throttle valve, the improvement comprising:

a control chamber having first, second and third ports,

a fuel passageway interconnecting the idle bypass passageway with said first port,

an air passageway interconnecting the throttle chamber upstream of the throttle valve with said second port,

a mixture passageway interconnecting the throttle chamber downstream of the throttle valve with said third port,

control valve means held within said control chamber for movement between a sealing position wherein said first, second and third ports are sealed against intercommunication, and a deceleration position wherein said ports are in mutual communication,

means urging said control valve means into its sealing position, and,

means connected to said control valve means and responsive to the vacuum in the intake manifold of the engine for moving said control valve means into said deceleration position when said intake manifold vacuum increases beyond a predetermined level representing deceleration of the motor vehicle.

2. The invention as set forth in claim 1, in which said means responsive to the vacuum in the intake manifold comprises a vacuum chamber having a movable diaphragm, a passageway interconnecting said intake manifold with said vacuum chamber, said diaphragm is fixed to said control valve means for movement therewith in response to changes in pressure within said vacuum chamber; and in which said means urging said control valve means into its sealing position comprises a compression spring mounted within said vacuum chamber and in contact with said said diaphragm for urging said control valve into its sealing position and for compressing under force of said movable diaphragm when said intake manifold vacuum increases past said predetermined level.

3. The invention as set forth in claim 1, in which said means responsive to the vacuum in the intake manifold comprises a solenoid fixed to said control valve means, electrical switching means electrically connected to said solenoid, a vacuum chamber having a movable diaphragm, said vacuum chamber connected in pressure communication with the intake manifold, said electrical switching means is fixed to said movable diaphragm for movement from a solenoid energizing position to a solenoid deenergizing position, and a compression spring mounted within said vacuum chamber and in contact with said diaphragm for urging said switch into position for causing the energization state of said solenoid to urge said control valve means into said sealing position, and for compressing under force of said movable diaphragm when intake manifold vacuum increases past said predetermined level.

4. The invention as set forth in claim 1, in which said predetermined level is about -600 mm. of Hg.