Fuel Supply Control System For Automobile Engines

Abstract

A fuel supply control system for automobile engines having a fuel cutoff means provided in the carburetor to prevent a great deal of harmful exhaust gas from being discharged during the braking with the motor, and in which use is made of an auxiliary fuel supply system for correcting any delay in the recovery of fuel, in addition to the ordinary main and idle fuel supply systems provided to the carburetor, so as to ensure the automobile to shift from its coasting operation to its accelerating operation, whereby fuel may be supplied from the auxiliary fuel supply system for a predetermined time to shift the automobile from coating to fast running and thus the engine can rotate smoothly in quick response to variations in the running condition of the vehicle.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a fuel supply control system for automobile engines, and more particularly to improvements in or relating to a fuel supply control system which can prevent the unnecessary waste of a great deal of fuel and discharge of much harmful exhaust gas resulting from a high suction which develops in an intake manifold when an automobile is coasting or running while braking with the motor.

2. Description of the Prior Art

According to the prior art, the fuel supply control system of this type has a fuel cutoff valve provided in the idle or main fuel passage of the carburetor so that the fuel passage may be closed by the high suction in the intake manifold to thereby interrupt the fuel supply.

However, such a fuel supply control system resorting to fuel interruption for the control of fuel supply causes a delay in the recovery of fuel to take place due to such factors as a difference between the normal fuel level of the fuel bowl and the fuel level of the fuel passage, volume and resistance of the fuel passage, etc. when the fuel supply from the idle port needs to be recovered, or more particularly, when the automobile shifts from a slow speed to faster speed or when the clutch is released to change the speed of the vehicle from a reduced speed. In other words, the idle fuel passage is so arranged that the intermediate part thereof extends at a level higher than the normal fuel level of the fuel bowl, and this arrangement causes the fuel in the fuel bowl to be equal to or lower than the normal fuel level when the fuel passage is closed. In order that fuel may be discharged through the idle port, the fuel passage must be filled with fuel to such a degree as to cover the quantity corresponding to the aforementioned difference in level. On the other hand, the quantity of air introduced varies so quickly that a temporary scarcity of fuel mixture takes place to cause knocking which would greatly spoil the running or may sometimes stop the engine.

SUMMARY OF THE INVENTION

It is the primary object of the present invention to provide a fuel supply control system having means for cutting fuel when an automobile is coasting, and which is adapted to quickly supply fuel to the engine in response to its requirement for fuel after the speed reduction of the automobile, thereby ensuring smooth rotation of the engine in such a reduced speed condition.

According to the present invention, the carburetor is provided not only with means for closing the ordinary main and idle fuel supply systems in the reduced speed condition of an automobile, but also with an auxiliary fuel supply system which is operated for a predetermined time after the termination of the reduced speed condition of the automobile so as to compensate for any delay of fuel supply which may arise from fuel cut.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a combined longitudinal sectional view and electric circuit diagram showing an example of the fuel supply control system according to the present invention; and

FIG. 2 is a similar view and diagram showing another example of the fuel supply control system according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, there is shown a carburetor 1 which includes a fuel reservoir such as a bowl 2, an air inlet passage 3, a throttle valve 4, a main fuel system 5, and an idle fuel supply system 6. The fuel bowl 2 communicates with a fuel pump 8 through a fuel pipe 7. The main fuel system 5 is provided with a main fuel passage 9 and a main nozzle 10. The idle fuel supply system 6 includes an idle fuel passage 11 divided from the main fuel passage 9, a jet 12, an air bleed 13, an adjust screw 14 and an idle port 15. A fuel cutoff valve 16 is provided in the idle fuel passage 11 and this valve is opened and closed by a first solenoid 17 which is connected with a battery 20 through a change-over switch 18 and an ignition switch 19. There is also provided an auxiliary fuel supply system 21 which comprises an auxiliary fuel passage 23 communication the fuel bowl 2 with an intake manifold 22, and an auxiliary fuel valve 24. The open end of the auxiliary fuel passage 23 is located adjacent to the inlet port of an combustion chamber. A second solenoid 25 to open and close the auxiliary fuel valve 24 is connected with the change-over switch 18 through an auxiliary switch 26, and in parallel therewith is connected a capacitor 27. A diaphragm device 28 comprising a diaphragm 29 and a spring 30 mounted therein is connected, on the one hand, with a movable contact 31 of the change-over switch 18 through a rod shown by a dotted line, and on the other hand with the intake manifold 22 through an unnumbered pipe. The diaphragm device 28 is so arranged that the force of the spring 30 and the suction in the intake manifold 22 are both exerted on the left-hand side of the diaphragm 29 as viewed in FIG. 1. The change-over switch 18 consists of a fixed contact 32 connected with the first solenoid 17, a fixed contact 33 connected with the second solenoid 25, and the aforementioned movable contact 31. This movable contact 31 is adapted to engage the contact 32 when the suction in the intake manifold 22 does not exceed a level corresponding to the engine idling, and to engage the contact 33 when the said suction exceeds the said level. Also, the switch 26 is associated with the movable contact 31 so that it is closed when the contact 31 engages the contact 32.

With the above-described arrangement of the present invention, within the normal range of engine operation, the movable contact 31 of the change-over switch 18 engages the contact 32 to excite the solenoid 17 to thereby open the fuel cutoff valve 16. At this time, the second solenoid 25 is not excited so that the auxiliary fuel valve 24 closes the auxiliary fuel passage 23.

If the automobile reduces its speed to shift into a coasting state, the suction in the intake manifold 22 rises to thereby move the diaphragm 29 against the tension of the spring 30. Thereupon, the change-over switch 18 opens its contact 31 so that the first solenoid 17 is de-energized to thereby close the fuel cutoff valve 16 and accordingly the idle fuel passage 11. This prevents an increase in amount of harmful emition of the exhaust gas which would otherwise take place due to an oversupply of fuel resulting from an increased suction in the intake manifold 22.

On the other hand, the movable contact 31 associated with the diaphragm 29 engages the contact 33 to open the auxiliary switch 26 to thereby charge the capacitor 27.

When the automobile shifts from its coasting state into an accelerated state or when the clutch is released for speed change, the suction in the intake manifold 22 falls to displace the diaphragm 29 so as to engage the movable contact 31 of the change-over switch 18 with the contact 32 and accordingly close the auxiliary switch 26. This causes the capacitor 27 to discharge through the second solenoid 25, which is thereby excited for a predetermined time and during that period the auxiliary fuel valve 24 is open so that fuel is supplied into the intake manifold 22 through the auxiliary fuel passage 23. The open end of the auxiliary fuel passage 23 is located adjacent to the inlet port of the combustion chamber as previously mentioned, and a differential fuel pressure corresponding to the difference between the fuel level in the fuel bowl 2 and the open end of the auxiliary passage 23 has already forced the fuel to reach the auxiliary fuel valve 24 by the time that the valve 24 is opened. Therefore, the opening of the auxiliary fuel valve 24 causes the fuel to be quickly admitted into the combustion chamber through the intake manifold 22. While the auxiliary fuel supply system 21 is in operation, the suction in the intake manifold 22 acts on the idle fuel passage 11 so that fuel may be admitted into the intake manifold 22 in spite of the difference between the normal fuel level of the fuel bowl and the level of the open end of the auxiliary passage and other factors. The auxiliary fuel supply system 21 remains operative until the fuel from the idle fuel supply system 6 is supplied to the combustion chamber. In this way, smooth rotation of the engine is ensured at all times when the automobile shifts from its coasting state into any other running condition.

FIG. 2 illustrates another embodiment of the present invention whereby the opening time of auxiliary fuel valve 24 can be easily set to take any value within a wider range of time. Basically, the function of this embodiment is identical with that of the embodiment of FIG. 1.

In other words, according to the embodiment of FIG. 1, when the diaphragm 29 is actuated by the intake manifold vacuum so that the movable contact 31 of the change-over switch 18 is disengaged from the fixed contact 33, the charge beforehand stored on the capacitor 27 is discharged into the coil of the second solenoid 25 to open the auxiliary fuel valve 24 for a predetermined time.

On the other hand, according to another embodiment shown in FIG. 2, when the movable contact 31 of the change-over switch 18 is disengaged from the fixed contact 33, this operation is detected by a control portion 51 to open the auxiliary fuel valve 24 for a predetermined time.

In other words, this control section 51 is so constructed as stated hereunder. The change-over switch 18 is identical with that shown in the embodiment of FIG. 1, and its fixed contact 33 is connected through a resistor 57 to a base of a transistor 52 in the control portion 51. An emitter of the transistor 52 is grounded via a lead 74 and a collector thereof is connected to the positive terminal of the battery 20 through a resistor 58 and the ignition switch 19. Thus, the transistor 52 is turned on when the movable contact 31 and the fixed contact 33 of the change-over switch 18 engage with each other, while it is turned off when these contacts are disengaged from each other. These states of the transistor 52 are transmitted to a monostable multivibrator circuit comprising transistors 53 and 54 through a differentiation circuit comprising a capacitor 60 and a resistor 65 which are connected to the collector of the transistor 52.

One end of the resistor 59 is connected to the collector of the transistor 52 and also to the base of the transistor 53 in the monostable multivibrator circuit via the capacitor 60 and a diode 64, and the other end thereof is connected to ground through the lead 74. One end of a resistor 65 is connected to the junction point between the capacitor 60 and the diode 64, and the other end is grounded through the lead 74. The emitter of the transistor 53 is grounded through the lead 74 together with the emitter of the transistor 54, and the collector of the transistor 53 is connected to one end of a resistor 61 and to one end of a capacitor 62. The other end of the capacitor 62 is connected to a base of the transistor 54 and also to one end of a resistor 63 whose other end is connected together with the other end of the resistor 61 to the positive terminal of the battery 20 through a resistor 73 and the ignition switch 19.

The base of the transistor 53 is connected to a collector of the transistor 54 through a resistor 68 and to the ground through a capacitor 67 and the lead 74. The collector of the transistor 54 is connected to the positive terminal of the battery 20 through resistors 69 and 73 and the ignition switch 19, and it is also connected to a base of a transistor 55 via a resistor 70. The transistor 55 has its emitter connected to the base of a transistor 56 and its collector connected to the collector of the transistor 56. The transistor 56 has its emitter connected to the ground through the lead 74 and its collector connected to the positive terminal of the battery 20 through the coil of the second solenoid 25 for actuating the auxiliary fuel valve 24 and the ignition switch 19.

On the other hand, a parallel connection of a Zener diode 71 and a capacitor 72 forms a kind of voltage regulator circuit. The Zener diode 71 has its cathode side connected to the junction point between the resistors 69 and 73 and its anode side connected to ground through the lead 74 to thereby maintain a source voltage supplied to the control section 51 at a constant value.

With the construction described above, the control section 51 operates in the following manner.

When the intake manifold vacuum causes the movable contact 31 of the change-over switch 18 to engage with the fixed contact 32, the fixed contact 33 is left open and thus there is no current flowing into the base of the transistor 52 so that the transistor 52 remains nonconductive.

At this time, the capacitor 60 is charged to have positive polarity on its electrode on the side of the collector of the transistor 52 and negative polarity on its electrode on the other side. There is no current flowing through the resistor 65, and there is no change in the state of the succeeding circuitry, thereby maintaining a steady state. The resistors 61, 63, 66, 68 and 69 are designed to have such values that, in the steady state of the monostable multivibrator circuit comprising the transistors 53 and 54, the transistor 53 is nonconducting and the transistor 54 is conducting. In this state the capacitor 62 is charged to have positive polarity on its electrode on the side of the collector of the transistor 53 and negative polarity on the side of the base of the transistor 54. The monostable multivibrator circuit is so designed that when a positive voltage is applied to the base of the transistor 53, the transistors 53 and 54 are caused to change their respective states to remain in the changed states until the capacitor 62 completely discharges its stored charge.

Thus, in the steady state of the monostable multivibrator circuit the transistor 54 is conducting, and the potential of the collector of the transistor 54 is substantially zero so that the transistors 55 and 56 are rendered nonconductive, because no base currents flow into their bases. In this state, there is no current flowing through the coil of the second solenoid 25 for actuating the auxiliary fuel valve 24, and hence the auxiliary fuel valve 24 remains closed.

Under these conditions, if the engine is decelerated, the intake manifold vacuum goes higher to retract the diaphragm 29 so that the movable contact 31 is disengaged from the fixed contact 32 and engages with the fixed contact 33, thereby supplying a base current to the transistor 52 to turn it conductive. When this happens, the charge beforehand stored in the capacitor 60 will be discharged through the transistor 52 and the resistor 65. In this case, however, a negative voltage is applied to the anode of diode 64 so that no change takes place in the monostable multivibrator circuit and thereafter, thereby maintaining the same state.

Then, upon changing of the operating state of the engine from deceleration to acceleration, the intake manifold vacuum is lowered to switch the movable contact 31 of the change-over switch 18 from the side of the fixed contact 33 to the side of the fixed contact 32.

This causes the conducting transistor 52 to become nonconductive and the potential of the collector of the transistor 52 rises to thereby supply a charging current to the capacitor 60 and to apply a positive voltage to the base of the transistor 53. Consequently, the transistor 53 becomes conductive and the charge beforehand charged in the capacitor 62 is discharged to apply a reverse bias between the base and emitter of the transistor 54 so that the transistor 54 is maintained nonconductive until the capacitor 62 finishes discharging. This in turn results in a rise in the potential of the collector of the transistor 54 so that the transistors 55 and 56 are rendered conductive and a current flows into the coil of the second solendoid 25 from the positive terminal of the battery 20 through the transistor 56, thereby opening the auxiliary fuel valve 24 to directly supply fuel into the intake manifold. In this way, a delay in fuel supply which tends to occur during a great acceleration can be eliminated to improve engine performance.

If an arrangement is made so that the fuel of the auxiliary fuel supply system is introduced directly from the fuel pump 8, instead of through the fuel bowl 2, then the higher pressure provided by the pump 8 will enable the fuel to be admitted into the intake pipe 22 more rapidly and more finely when the auxiliary fuel valve 24 is opened, and this will substantially eliminate any delayed supply of fuel to the intake manifold 22.

Also, the means for operating the auxiliary fuel valve 24 may be any other suitable means than that shown and described with respect to the foregoing embodiments.

Claims

We claim:

1. In an automobile engine comprising a carburetor having an air inlet passage, a throttle valve disposed in said air inlet passage, a fuel bowl and a fuel passage through which said fuel bowl communicates with said air inlet passage; and an intake manifold coupled to said carburetor; a fuel supply control system for the automobile engine comprising: an auxiliary fuel passage interconnecting said fuel bowl and said intake manifold, a first electromagnetic valve disposed in said fuel passage, a second electromagnetic valve disposed in said auxiliary fuel passage, a first solenoid of said first electromagnetic valve being connected to a power source through a change-over switch coupled to means for detecting a decelerating state of said engine so that said first solenoid is denergized upon deceleration of said engine to cause said first electromagnetic valve to close said fuel passage, a second solenoid of said second electromagnetic valve being connected to said power source through said change-over switch coupled to said means for detecting a decelerating state of said engine, switching means and timer means which is associated with said change-over switch and said switching means so that said second solenoid of said second electromagnetic valve is energized upon termination of said decelerating state of said engine for a period of time determined by said timer means to cause said second solenoid valve to open said auxiliary fuel passage, wherein said timer means comprises a monostable multivibrator connected in parallel with said power source through said change-over switch with respect to said second solenoid.

2. A fuel supply control system for an internal combustion engine comprising:

a carburetor having

an air inlet passage,

a throttle valve disposed in said air inlet passage,

a fuel reservoir,

a first fuel passage providing fuel communication between said reservoir and said air inlet passage, and

an intake manifold coupled to said carburetor, said fuel supply control system comprising:

a second fuel passage, in addition to said first fuel passage, for providing fuel communication between said reservoir and said intake manifold;

first valve means, disposed in said first passage, for controlling the quantity of fuel flowing from said reservoir to said air inlet passage;

second valve means, disposed in said second fuel passage for controlling the quantity of fuel flowing from said reservoir into said intake manifold; and

means for effecting the closure of said first fuel passage by said first valve means in response to the commencement of deceleration of said engine and for effecting the opening of said second valve means for a predetermined period of time in response to the termination of deceleration of said engine,

said effecting means comprises means, switchably connectable with each of said first and second valve means, for supplying first and second control signals thereto for effecting the opening and closing thereof and means, responsive to the pressure in said intake manifold, for effecting the supplying of said control signals to said first and second valve means by said first switch means, in accordance with the deceleration condition of said engine, and

said control signal supplying means comprises a source of electric power, a first switch means, having an input terminal and first and second output terminals, coupled to said source of electric power at the input terminals thereof, for supplying said first control signal to said first valve means at the first output terminal thereof and said second control signal to said second valve means at the second output terminal thereof, the application of said control signals to said first and second valve means from said output terminals being effected by said pressure-responsive means and means, coupled to said second output terminal of said first switch means and said second valve means, for maintaining the application of said second control signal to said second valve means for said predetermined period of time,

said maintaining means comprises a storage circuit coupled to said second output terminal and switchably coupled to said second valve means, for generating said second control signal upon the termination of deceleration of said engine, said storage means comprising a capacitor connected between said second output terminal and a source of reference potential,

whereby the delay in the supplying of fuel from said fuel supply subsequent to the deceleration of the engine is compensated so as to maintain the air-fuel mixture ratio at a suitable level.

3. A fuel supply control system for an internal combustion engine comprising:

a carburetor having

an air inlet passage,

a throttle valve disposed in said air inlet passage,

a fuel reservoir,

a first fuel passage providing fuel communication between said reservoir and said air inlet passage, and

an intake manifold coupled to said carburetor, said fuel supply control system comprising:

a second fuel passage, in addition to said first fuel passage, for providing fuel communication between said reservoir and said intake manifold;

first valve means, disposed in said first fuel passage, for controlling the quantity of fuel flowing from said reservoir to said air inlet passage;

second valve means, disposed in said second fuel passage for controlling the quantity of fuel flowing from said reservoir into said intake manifold; and

means for effecting the closure of said first fuel passage by said first valve means in response to the commencement of deceleration of said engine and for effecting the opening of said second valve means for a predetermined period of time in response to the termination of deceleration of said engine,

said effecting means comprises means, switchably connectable with each of said first and second valve means, for supplying first and second control signals thereto for effecting the opening and closing thereof and means, responsive to the pressure in said intake manifold, for effecting the supplying of said control signals to said first and second valve means by said first switch means, in accordance with the deceleration condition of said engine, and

said control signal supplying means comprises a source of electric power, a first switch means, having an input terminal and first and second output terminals, coupled to said source of electric power at the input terminals thereof, for supplying said first control signal to said first valve means at the first output terminal thereof and said second control signal to said second valve means at the second output terminal thereof, the application of said control signals to said first and second valve means from said output terminals being effected by said pressure-responsive means and means coupled to said second output terminal of said first switch means and said second valve means, for maintaining the application of said second control signal to said second valve means for said predetermined period of time,

said maintaining means comprises a storage circuit coupled to said second output terminal and switchably coupled to said second valve means, for generating said second control signal upon the termination of deceleration of said engine, said storage means including a timing circuit connected between said second output terminal and said second valve means and including a capacitor connected between said second output terminal and a source of reference potential,

whereby the delay in the supplying of fuel from said fuel supply subsequent to the deceleration of the engine is compensated so as to maintain the air-fuel mixture ratio at a suitable level.

4. A fuel supply control system for an internal combustion engine comprising:

a carburetor having

an air inlet passage,

a throttle valve disposed in said air inlet passage,

a fuel reservoir,

a first fuel reservoir,

a first fuel passage providing fuel communication between said reservoir and said air inlet passage, and

an intake manifold coupled to said carburetor, said fuel supply control system comprising:

a second fuel passage, in addition to said first fuel passage, for providing fuel communication between said reservoir and said intake manifold;

first valve means, disposed in said first fuel passage, for controlling the quantity of fuel flowing from said reservoir to said air inlet passage;

second valve means, disposed in said second fuel passage, for controlling the quantity of fuel flowing from said reservoir into said intake manifold; and

means for effecting the closure of said first fuel passage by said first valve means in response to the commencement of deceleration of said engine and for effecting the opening of said second valve means for a predetermined period of time in response to the termination of deceleration of said engine,

said effecting means comprises means, switchably connectable with each of said first and second valve means, for supplying first and second control signals thereto for effecting the opening and closing thereof and means, responsive to the pressure in said intake manifold, for effecting the supplying of said control signals to said first and second valve means by said first switch means, in accordance with the deceleration condition of said engine, and

said control signal supplying means comprises a source of electric power, a first switch means, having an input terminal and first and second output terminals, coupled to said source of electric power at the input terminals thereof, for supplying said first control signal to said first valve means at the first output terminal thereof and said second control signal to said second valve means at the second output terminal thereof, the application of said control signals to said first and second valve means from said output terminals being effected by said pressure responsive means and means, coupled to said second output terminal of said first switch means and said second valve means, for maintaining the application of said second control signal to said second valve means for said predetermined period of time,

said maintaining means comprises a storage circuit coupled to said second output terminal and switchably coupled to said second valve means, for generating said second control signal upon the termination of deceleration of said engine, said storage means including a timing circuit comprising a monostable multivibrator switchably coupled between the second output terminal of said first switch means and second valve means,

whereby the delay supplying of fuel from said fuel supply subsequent to the deceleration of the engine is compensated so as to maintain the air-fuel mixture ratio at a suitable level.

5. In a automobile engine comprising a carburetor having an air inlet passage, a throttle valve disposed in said air inlet passage, a fuel bowl and a fuel passage through which said fuel bowl communicates with said air inlet passage; and an intake manifold coupled to said carburetor; a fuel supply control system for the automobile engine comprising: an auxiliary fuel passage interconnecting said fuel bowl and said intake manifold, a first electromagnetic valve disposed in said fuel passage, a second electromagnetic valve disposed in said auxiliary fuel passage, a first solenoid of said first electromagnetic valve being connected to a power source through a change-over switch coupled to means for detecting a decelerating state of said engine so that said first solenoid is deenergized upon deceleration of said engine to cause said first electromagnetic valve to close said fuel passage, a second solenoid of said second electromagnetic valve being connected to said power source through said change-over switch coupled to said means for detecting a decelerating state of said engine, switching means and timer means which is associated with said change-over switch and said switching means so that said second solenoid of said second electromagnetic valve is energized upon termination of said decelerating state of said engine for a period of time determined by said timer means to cause said second solenoid valve to open said auxiliary fuel passage, wherein said timer means comprises a capacitor connected in parallel with said power source through said change-over switch with respect to said second solenoid.

6. A system according to claim 2, wherein each of said first and second valve means comprises means, responsive to the application of electrical signals thereto, for opening and closing said fuel passages.

7. A system according to claim 6, wherein said valve means comprises electro-magnetic valve means, the solenoid of said first valve means being connected to said first output terminal of said first switch means and the solenoid of said second valve means being connected to said maintaining means.

8. A system according to claim 4, wherein said timing circuit further includes a first transistor switching circuit connected between said monostable multivibrator and said second output terminal and an output driving circuit for supplying the output of said monostable multivibrator to said second valve means.

9. A system according to claim 8, wherein said timing circuit further includes a capacitor connecting said first transistor switching circuit to said monostable multivibrator.

10. A system according to claim 9, wherein said valve means comprise electro-magnetic valve means, the solenoid of said first valve means being connected to the first output terminal of said first switch means and the solenoid of said second valve means being connected to said output driving circuit.

11. A system according to claim 10, wherein said timing circuit further includes a voltage regulator circuit connected between said source of electric power and said reference potential.

12. A system according to claim 11, further including a switch connected between said source of electric power and the input terminal of said first switch means.

13. A system according to claim 3, wherein said timing circuit further includes a switch connected between said second terminal of said switch means and said second valve means, said switch being responsive to said pressure responsive means.