JPH08128340A - Throttle opening control method of carburetor - Google Patents

Abstract

PURPOSE: To lower a fuel temperature, and prevent overheat of a catalyst by changing opening of a throttle valve to opening set on the basis of a catalyst temperature from opening at fuel cut time when supply of fuel is resumed by stopping a fuel cut. CONSTITUTION: When an operating condition of an engine EG satisfies conditions such as prescribed conditions that, for example, a cooling water temperature is not less than a prescribed value and a throttle valve 24 is fully closed and engine rotating speed NE is not less than prescribed rotating speed and car speed is not less than prescribed speed, a closing signal is outputted to a solenoid valve 17, and a fuel passage 16 for throw is blocked up. When rotating speed becomes fuel cut restoring rotating speed at such fuel cut time, the throttle valve 24 is opened up to throttle opening set by a three-dimensional map. This throttle opening is set in opening such as a temperature of not overheating a catalyst 42, for example, a catalyst temperature becomes about 800 deg.C, for example, at preset restoring rotating speed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a throttle opening of a carburetor when a fuel cut is restored in an automobile engine equipped with the carburetor.

[0002]

2. Description of the Related Art Conventionally, in an automobile engine, when traveling on a downhill or the like, when a throttle valve is closed and an engine brake is activated, fuel supply is stopped to suppress deterioration of emission. It is known that the control is carried out (for example, Japanese Patent Laid-Open No. 170536). Such fuel cut control is continued while the idle operation state in which the throttle valve is fully closed satisfies a predetermined condition, for example, a condition that the vehicle speed, the engine speed, etc. exceed a predetermined value, and the condition is satisfied. When it disappears,
At that point, the fuel supply is restarted. It is preferable that the engine speed at the time of returning from the fuel cut is set as low as possible in relation to the catalyst temperature.

[0003]

However, when returning from the fuel cut, the amount of fuel is small and the air-fuel ratio is lean, so that oxygen may burn in the catalyst to raise the catalyst temperature. This is remarkable when the engine speed at the time of return is high, and considering that the engine speed becomes unstable or stalls, if the engine speed for fuel cut recovery is set high, the catalyst temperature Since the fuel supply is restarted at a high value, the catalyst may overheat.

An object of the present invention is to eliminate such a problem.

[0005]

In order to achieve the above object, the present invention takes the following measures. That is, the carburetor throttle opening control method according to the present invention is an idle system including a throttle valve that controls the intake air amount according to the opening, a main system that supplies fuel, and a control valve that stops fuel supply. In an internal combustion engine in which a carburetor having a slow system that supplies fuel during operation is provided in the intake system and a catalyst is provided in the exhaust system, the control valve is operated in a predetermined operating state to throw the carburetor. The supply of fuel from the system is stopped, the rotation speed of the internal combustion engine is detected while the control valve is operating, and the operation of the control valve is stopped when at least the detected rotation speed reaches a predetermined value. In addition, the opening of the throttle valve is changed from the opening while the fuel supply is stopped to the opening set based on the temperature of the catalyst.

[0006]

With such a structure, in a predetermined operating state, the control valve provided in the slow system of the carburetor is operated to stop the fuel supply, and at least the rotational speed reaches a predetermined value. At this time, the operation of the control valve is stopped and the supply of fuel is restarted, and the opening of the throttle valve is changed from the opening in the predetermined operating state to the opening set based on the temperature of the catalyst. In other words, in the operating state where the fuel supply is stopped, the throttle valve is almost fully closed, so by changing the opening, the throttle valve is opened and the intake air amount corresponding to the opening is increased. It Therefore, the amount of fuel restarted to be supplied increases, the air-fuel ratio does not become lean, and the set catalyst temperature is maintained. As a result, the catalyst temperature can be prevented from overheating and the rotation speed at the time of restarting the fuel supply can be set high, so that the operating state of the internal combustion engine does not become unstable and the occurrence of stall is prevented.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, an engine EG for automobiles is used.
Is equipped with the carburetor 1 in its intake system 3 and its exhaust system 4
A catalyst 42 is attached to the exhaust manifold 41. The carburetor 1 is formed by integrally forming a carburetor main body 1a and a body portion 1b forming a part of the intake system 3. The carburetor main body 1a includes a float chamber 11 for temporarily storing fuel, and a main well 1 communicating with the float chamber 11.
2 and the main well 1 disposed in the main well 12
The fuel stored in the main well 12 communicating via the main jet 14 with the emulsion tube 13 having a plurality of through holes for mixing air bubbles in the fuel stored in 2 below the liquid surface of the fuel. A main nozzle 15 leading to a small venturi 22 formed in the body portion 1b, a slow fuel passage 16 forming a slow system, a solenoid valve 17 provided as a control valve in the slow fuel passage 16, and an idle port 18 The idle adjust screw 19 for adjusting the amount of fuel during idle operation by changing the opening area of the idle throttle, and the throttle valve 24 that is provided upstream of the idle port 18 and is fully closed during idle operation are closed. And a port 20. In the vaporizer 1 having such a configuration, the main system is composed of the main well 12, the emulsion tube 13, the main jet 14, and the main nozzle 15, and the slow system is the slow fuel passage 16
It includes a solenoid valve 17, an idle port 18, an idle adjust screw 19, and a slow port 20.

The body portion 1b has an air chamber 21 to which air from an air filter (not shown) reaches, a small venturi 22 provided in the air chamber 21, a large venturi 23 provided downstream thereof, and a downstream of the large venturi 23. A throttle valve 24 that is rotatably provided and a mixing chamber 25 that is formed downstream of the throttle valve 24 are provided. The throttle valve 24 rotates in conjunction with an accelerator pedal (not shown),
An actuator (not shown) rotates a predetermined opening when the fuel cut is restored, and the opening, that is, the throttle opening is detected by the throttle opening sensor 7. The opening signal Sta output from the throttle opening sensor 7 is input to the control unit 6 that incorporates a microcomputer system.

The control unit 6 includes a central processing unit 6a that constitutes a microcomputer system, a storage unit 6b that stores programs and data, an input interface 6c that outputs each externally input signal to the central processing unit 6a, and It is configured to have an output interface 6d that outputs a signal output from the central processing unit 6a to each control element. The input interface 6c of the control unit 6 has a rotation speed signal Sne output from the rotation speed sensor 14 for detecting the engine speed NE and a vehicle speed signal output from the vehicle speed sensor 15 for detecting the vehicle speed. Ssp, the water temperature signal Stw output from the water temperature sensor 30 for detecting the cooling water temperature of the engine EG, etc. are input. On the other hand, the output interface 6d outputs a closing signal Scl to the solenoid valve 19 of the slow system to close the slow fuel passage 16 when the fuel is cut.

Further, the storage device 6b of the control unit 6 stores a control program for the solenoid valve 19, a throttle opening control program for controlling the throttle valve 24 after fuel cut and data for the throttle opening control. There is. The control program for the throttle valve 24 is
The operating condition of the engine EG is a predetermined condition, for example, the cooling water temperature is a predetermined value or more, the throttle valve 24 is fully closed, the engine speed NE is a predetermined speed or more, the vehicle speed is a predetermined speed or more. It is determined whether or not, and if it is determined that the predetermined conditions are satisfied as a result of the determination, the closing signal Scl is output to the solenoid valve 17. This allows the solenoid valve 1
7, the slow fuel passage 16 is closed, and the fuel sucked into the intake system 3 from the idle port 18 disappears.

On the other hand, the throttle opening control program is
It is as follows. When performing this throttle bar opening control, the fuel cut return rotational speed is stored as data, and the engine rotational speed NE and the throttle opening during deceleration when the accelerator pedal is not depressed as shown in FIG. And the catalyst temperature are set as a three-dimensional map. In this three-dimensional map, the higher the engine speed NE and the larger the throttle opening, the higher the catalyst temperature is set.

In FIG. 2, first, in step S1, it is determined whether or not the fuel cut is returning. When not returning to fuel cut, that is, during fuel cut, when this throttle bar opening control is finished and returning to fuel cut,
That is, at least when the engine speed NE reaches the fuel cut return speed during the fuel cut, the process proceeds to step S2. In step S2, since it is at the time of returning, the solenoid valve 19 is opened and the throttle valve 2 is opened.
4 is opened up to the throttle opening set in the three-dimensional map. The throttle opening may be set to a temperature at which the catalyst 42 does not overheat, for example, at a preset return speed, for example, an opening at which the catalyst temperature becomes about 800 ° C.
In step S3, the throttle valve 24 is held (fixed) at the opened throttle opening. Next, step S4
Then, it is determined whether or not the engine speed NE after the fuel cut is returned to be equal to or lower than a predetermined rotation speed. If it is not lower than the predetermined rotation speed, the process returns to step S3, and if it is lower than the predetermined rotation speed. Go to step S5. This step S
By repeatedly executing Step 3 and Step S4, the throttle valve 24 causes the engine speed NE after fuel cut
Is maintained at a predetermined opening degree until the rotation speed reaches a sufficient speed at which the catalyst does not overheat. Then, when the engine speed NE becomes sufficiently low, that is, when the engine speed NE becomes equal to or lower than the predetermined speed, the throttle valve 24 is closed in step S5 to maintain the throttle opening in the normal idle operation state.

As described above, when the fuel is restored from the fuel cut, the control proceeds from step S1 to step S2 to step S3, the fuel supply is restarted at the set relatively high return rotational speed, and the return rotation is performed. The throttle valve 24 is opened to a predetermined opening all at once. When the throttle opening becomes a predetermined opening at the same time when the fuel cut is resumed, more air flows into the intake system 3 during the fuel cut by the opening of the throttle valve 24, and more fuel than in the normal idle operation state. That is, fuel is supplied to the intake system 3 from the idle port 18 and the slow port 20.
In this state, the engine speed NE does not increase,
It is substantially idle. As a result, the combustion temperature decreases, and the catalyst temperature becomes lower than the catalyst temperature at the return rotation speed. From that state, the control proceeds from step S4 to step S5, and the engine speed NE changes from the return rotation speed. When the rotation speed is further reduced, the throttle valve 24 in the normal idle operation state, that is, the fully closed state is controlled. Therefore, it is possible to set the return rotational speed at the time of returning to the fuel cut relatively high, and it is possible to maintain the catalyst 42 at an appropriate catalyst temperature without overheating.

The present invention is not limited to the embodiment described above.

Besides, the configuration of each part is not limited to the illustrated example, and various modifications can be made without departing from the spirit of the present invention.

[0017]

As described above in detail, according to the present invention, when the fuel cut is stopped and the fuel supply is restarted, the opening degree of the throttle valve is based on the opening degree during the fuel cut and the temperature of the catalyst. The amount of intake air flowing into the intake system increases with the change of the opening, and the amount of fuel increases and the combustion temperature can be reduced. As a result, it is possible to prevent overheating of the catalyst, set a high rotation speed when restarting the fuel supply, and prevent the internal combustion engine from stalling.

[Brief description of drawings]

FIG. 1 is a schematic configuration explanatory view showing an embodiment of the present invention.

FIG. 2 is a flowchart showing a control procedure of the embodiment.

FIG. 3 is an explanatory view of the operation of the same embodiment.

[Explanation of symbols]

 1 ... Vaporizer 3 ... Intake system 5 ... Control valve 6 ... Control part 7 ... Throttle opening sensor 14 ... Main jet 15 ... Main nozzle 16 ... Slow fuel passage 17 ... Solenoid valve 18 ... Idle port 20 ... Slow port 42 ... Catalyst

Claims (1)

[Claims] 1. A throttle system for controlling an intake air amount according to an opening degree, a main system for supplying fuel, and a slow system system for supplying fuel during idle operation, which has a control valve for stopping the supply of fuel. A carburetor provided with is provided in the intake system, and in the internal combustion engine having a catalyst provided in the exhaust system, the control valve is operated in a predetermined operating state to stop the supply of fuel from the slow system, The rotation speed of the internal combustion engine is detected while the control valve is operating, and the operation of the control valve is stopped at least when the detected rotation speed reaches a predetermined value, and the opening of the throttle valve is supplied with fuel. A throttle opening control method for a carburetor, characterized in that the opening during stop is changed to an opening set based on the temperature of the catalyst.