JP2504021B2 - Fuel supply control method for internal combustion engine equipped with mechanical supercharger - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a fuel supply control method for an internal combustion engine including a mechanical supercharger.

(Prior Art) A fuel injection valve is provided in each intake port of an internal combustion engine,
A fuel supply control method in which the amount of fuel supplied to each cylinder is electronically controlled according to the operating state of the engine is widely adopted. This fuel supply control method uses the basic fuel injection amount based on the detection value detected by the Karman vortex type air flow sensor that detects the amount of air taken into the engine and the intake pipe internal pressure sensor that detects the intake pipe internal pressure downstream of the throttle valve. Is set, and the basic fuel injection amount is corrected according to the detected values of the engine cooling water temperature, the intake air temperature, the atmospheric pressure, the battery voltage, etc. to determine the fuel supply amount.

In the above fuel supply control method, even if the air flow sensor or the like that detects the amount of air fails, at least the engine operation parameter value that replaces the failed air flow sensor is usually provided so that at least the operation of the engine can be continued without hindrance. A backup system for detecting fuel consumption and calculating a fuel supply amount using the engine operating parameter value is incorporated. This backup system
For example, a basic fuel supply amount (backup map) according to the engine speed and the throttle valve opening is stored in advance, and a basic fuel supply amount according to the engine speed detection value and the throttle valve opening detection value when the air flow sensor fails. The fuel supply amount is read, and the fuel amount corresponding to the read value of the basic fuel supply amount is supplied to the engine.

On the other hand, it is known that a supercharger such as a supercharger mechanically driven by the engine is installed in the middle of the intake passage of the internal combustion engine and the supercharger is used to improve the output characteristics of the engine. Has been. Then, a bypass passage for bypassing the supercharger is connected to an intake passage of an internal combustion engine including the supercharger, a bypass valve is disposed in the bypass passage, and an engine for driving the supercharger is provided. An electromagnetic clutch is installed between the supercharger. Then, in the low load operation region of the engine, the electromagnetic clutch is turned off to deactivate the supercharger and the bypass valve is opened to bypass a part of the intake air supplied to the engine to bypass the supercharger. The output loss due to driving the supercharger and the pressure loss due to intake of intake air through the supercharger are reduced.

(Problems to be Solved by the Invention) When an air flow sensor of an internal combustion engine including such a supercharger fails and fuel is supplied to each cylinder by the backup system described above, in the operation operating region of the supercharger, Even if the throttle valve opening and the engine speed are constant, there is a problem that the intake air amount supplied to the engine varies due to variations in the efficiency of the supercharger, and the air-fuel ratio of the air-fuel mixture also varies accordingly. When the efficiency of the supercharger is poor, the air-fuel ratio becomes too small (overrich), so-called smoldering occurs, and when the efficiency of the supercharger is poor, the air-fuel ratio becomes excessive (over lean), knocking, etc. appear.

The present invention has been made to solve such problems, and when the air flow sensor of an internal combustion engine including a mechanical supercharger fails, there is no variation in the air-fuel ratio of the air-fuel mixture supplied to the engine by the backup system. An object of the present invention is to provide a fuel supply control method capable of continuing engine operation without causing smoldering or knocking.

(Means for Solving the Problems) According to the present invention in order to achieve the above-mentioned object, according to the present invention, in an internal combustion engine having a mechanical supercharger in an intake passage downstream of a throttle valve, an air detecting an intake air amount is provided. The fuel amount is supplied according to the detection signal of the fuel amount sensor, and when the air amount sensor is out of order, the fuel amount stored in advance according to the valve opening of the throttle valve and the engine speed is changed to the throttle valve opening. In a fuel supply control method for reading according to a detected value and an engine speed detected value and supplying a fuel amount according to the fuel amount read value, when the air amount sensor fails, the mechanical supercharger is deactivated. A fuel supply control method for an internal combustion engine including a mechanical supercharger is provided.

(Operation) By deactivating the mechanical supercharger, the amount of air taken into the engine is substantially uniquely determined according to the engine speed and the throttle valve opening, and variations in the air-fuel ratio are eliminated.

(Embodiment) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a fuel supply control device for carrying out the method of the present invention. In the figure, reference numeral 10 indicates a four-cylinder gasoline engine, for example, and an intake pipe 12 is connected to the engine 10. An air cleaner 13 is attached to the air opening end of the intake pipe 12, and a Kalman-overflow air flow sensor 14 for detecting the flow rate A of air taken into the engine 10 is arranged. It is connected to an electronic control unit (ECU) 20, which will be described later, and supplies a Kalman excess occurrence frequency detection signal corresponding to the air flow rate A to the electronic control unit 20.

A throttle valve 15 is arranged in the intake pipe 12, and a supercharger 16 is arranged in the intake pipe 12 between the throttle valve 15 and the engine 10. This supercharger 16
Is a roots-type supercharger mechanically driven by the engine 10, and the electromagnetic clutch 17 controls the connection with the engine 10. That is, the electromagnetic clutch 17 is connected to the output side of the electronic control unit 20, is energized by the drive signal from the electronic control unit 20 and is turned on (engaged), and the supercharger 16 is operated.

A bypass passage 22 that bypasses the supercharger 16 is connected to the intake pipe 12, one end of the bypass passage 22 is located downstream of the throttle valve 15 and upstream of the supercharger 16, and the other end is located downstream of the supercharger 16. Intake pipe
12 are in communication with each other.

A bypass valve 23 that opens and closes the bypass passage 22 is arranged in the middle of the bypass passage 22, and the bypass valve 23 is driven by an actuator 24 that responds to negative pressure via its valve shaft 23a. Actuator 24 is housing 24a
And an air chamber 24d that communicates the inside of the housing 24a with the atmosphere.
And a negative pressure chamber 24c, the diaphragm 24b to which the valve shaft 23a of the bypass valve 23 is connected, and the diaphragm 24b housed in the negative pressure chamber 24e and closing the bypass valve 23.
And a spring 24c that presses 24b.

Reference numeral 26 in FIG. 1 denotes an electromagnetic switching valve.
The valve body 2 has three ports 26a to 26c, and selectively switches and closes one of the ports 26b and 26c.
6d and a solenoid 26e for switching the valve 26d. The solenoid 26e is an electronic control unit 20.
Is connected to the output side of and is energized by an energizing signal from the electronic control unit 20. When the solenoid 26e is energized, the valve body 26d moves to the port 26b side to close the port 26b, and when the solenoid 26e is deenergized, it moves to a position where the port 26c is closed by a spring (not shown).

One end of a conduit 27 is connected to the negative pressure chamber 24e of the actuator 24, and the other end of the conduit 27 is connected to the port 26a of the electromagnetic switching valve 26.
It is connected to the. The line 2 is connected to the port 26b of the electromagnetic switching valve 26.
One end of 8 is connected, and the other end of the conduit 28 is connected to a port 12b provided in the intake pipe 12 downstream of the throttle valve 15 and upstream of the supercharger 16. Port 2 of electromagnetic switching valve 26
One end of the conduit 29 is connected to the 6c, and the other end of the conduit 29 is a port 12a provided in the intake pipe 12 downstream of the supercharger 16.
It is connected to the.

An electromagnetic fuel injection valve 29 is provided in each intake port of the engine 10, and each injection valve 29 is connected to the output side of the electronic control unit 20 and is opened and opened by an energizing signal from the electronic control unit 20. Fuel is injected into the engine 10 for the duration of the valve. The amount of fuel supplied to each cylinder of the engine 10 is proportional to the valve opening time of the fuel injection valve 29, and the valve opening time is calculated and set by the electronic control unit 20 according to the operating state of the engine 10 as described later.

Various sensors on the input side of the electronic control unit 20, for example, a throttle opening sensor 30 for detecting the valve opening of the throttle valve 15, an engine rotation attached to a camshaft (not shown), and detecting the rotation speed of the engine 10. A number sensor 31, an engine water temperature sensor 32 for detecting the cooling water temperature of the engine 10 and the like are connected, and these sensors supply detection signals to the electronic control unit 20.

Next, the operation of the fuel supply control device configured as described above will be described with reference to FIGS.

First, in the negative pressure chamber 24e of the actuator 24, the pressure generated in the intake pipe 12 downstream of the throttle valve 15 and upstream of the supercharger 16 and the intake pipe 12 downstream of the supercharger 16
The pressure generated inside is selectively supplied by the valve switching of the electromagnetic switching valve 26. Then, the valve opening degree (stroke) of the bypass valve 23 changes according to the magnitude of the negative pressure supplied to the negative pressure chamber 24e, as shown in FIG. That is, the negative pressure chamber 24
When the negative pressure supplied to e is small, the spring force of the spring 24c prevails and the bypass valve 23 remains closed.However, when the negative pressure exceeds the predetermined value P1, the bypass valve 23 resists the spring force of the spring 24c. 23 starts to open, reaches the predetermined value P2, and the bypass valve 23 is fully opened.

The electronic control unit 20 has an engine speed N,
Based on the detected values of the throttle valve opening α and the like, it is detected whether the engine 10 is in the operating region where supercharging should be performed, and the engine 10
When it detects that it is in the operation region where supercharging is required, the electromagnetic clutch 17 is turned on to operate the supercharger 16, and at the same time, an urging signal is supplied to the electromagnetic switching valve 26 to turn it on. The electronic control unit 20 is the solenoid switching valve 26
When the energizing signal is output to the pipe 27 and the pipe
29 is communicated, and the pressure generated in the air supply pipe downstream of the supercharger 16 is supplied to the negative pressure chamber 24e.
At this time, the supercharger 16 is in operation, and the pressure in the intake pipe 12 downstream of the supercharger 16 is higher than the pressure in the intake pipe 12 downstream of the throttle valve 15 and upstream of the supercharger 16 (negative pressure is low). , When this pressure is supplied to the negative pressure chamber 24e, the diaphragm 24b
15 Downstream and supercharger 16 Upstream of the intake pipe 12 will be pressed by a larger pressure than is pressed,
Bypassing of the bypass valve 23 at the time of high supercharging can be prevented, and moreover, the bypass valve 23 can be closed more reliably at the switching timing of the electromagnetic switching valve 26.

On the other hand, when the electronic control unit 20 detects a region other than the operating region where the engine 10 should be supercharged, the electromagnetic clutch 17 is turned off to deactivate the supercharger 16 and an urging signal is output to the electromagnetic switching valve 26. Turn this off without. The electronic control unit 20 is the solenoid switching valve 26
When the energizing signal is not output to the pipe line 27 and the pipe line 28 are communicated with each other, the negative pressure chamber 24e is supplied with the pressure generated in the intake pipe downstream of the throttle valve 15 and upstream of the supercharger 16. Become. At this time, the bypass valve 23 is the intake pipe downstream of the throttle valve 15 and upstream of the supercharger 16.
The valve is opened / closed according to the negative pressure generated in the valve 12, and is closed when the negative pressure falls below the predetermined negative pressure P1 shown in FIG. 2 (when it rises in absolute pressure).

FIG. 3 is a flow chart showing a fuel control procedure by the electronic control unit 20, and the electronic control unit 20 first executes step 41 of FIG. 3 to determine whether or not the air flow sensor 14 is out of order. This failure determination is performed by, for example, a Kalman overflow air flow sensor.
When the frequency signal is not input for a predetermined time (for example, 200 msec) from 14, the airflow sensor 14 is determined to be defective, and the determination result is negative (N
In the case of o), that is, when there is no abnormality in the air flow sensor 14, the routine proceeds to step 42, where normal fuel control is executed.

The valve opening time T of the fuel injection valve 29 by this normal fuel control
Is, for example, a parameter value A / N calculated by the air flow rate A detected by the air flow sensor 14 and the engine speed N detected by the engine speed sensor 31.
It is calculated from the following equation based on (basic fuel injection amount).

T = K1 × (A / N) × K2 + T _B Here, K1 is a constant for converting the calculated fuel supply amount into the opening time of the fuel injection valve 29, and K2 is the throttle valve opening from the throttle opening sensor 30. Degree α, engine water temperature sensor 32
Is a correction coefficient that is set according to the engine water temperature Tw from, the oxygen concentration in the exhaust gas detected by an O ₂ sensor (not shown), and T _B is a correction value that is set according to the voltage of the battery (not shown) Is.

The electronic control unit 20 supplies a valve opening energizing signal corresponding to the calculated valve opening time T to the fuel injection valve 29 to supply a required fuel amount to the engine 10.

When the determination result of the step 41 is affirmative (Yes), that is, when it is determined that the Kalman excess occurrence frequency signal corresponding to the intake air amount A is not input and the air flow sensor 14 is abnormal, the electronic control unit 20 determines that the Disable charger 16. That is, the electronic control unit 20 turns off the electromagnetic clutch 17, and
An ON signal is output to 26 to switch the electromagnetic switching valve 26 so that the pressure generated in the intake pipe 12 downstream of the supercharger 16 is supplied to the negative pressure chamber 24e of the actuator 24 (step 43). In this case, since the supercharger 16 is deactivated, the supercharger 16 will
Acts as a fluid resistance in the supercharger 16
The pressure in the downstream intake pipe 12 is smaller than the pressure in the intake pipe 12 downstream of the throttle valve 15 and upstream of the supercharger 16 in absolute pressure (large negative pressure). Therefore, when the pressure in the intake pipe 12 downstream of the supercharger 16 is introduced into the negative pressure chamber 24e, the negative pressure chamber 24e
Becomes a negative pressure, and the bypass valve 23 is forcibly opened. Thus, when the air flow sensor 14 fails, the supercharger 16 is forcibly deactivated, and therefore, the intake air supplied to the engine 10 is not supercharged by the supercharger 16, so the intake amount is equal to the throttle valve opening. It is almost uniquely determined by the engine speed.

Next, the electronic control unit 20 reads the A / N value corresponding to the throttle valve opening detection value α and the engine speed detection value N from the α-N map stored in the storage means (ROM) not shown.

FIG. 4 shows an α-N map stored in advance in the storage means, corresponding to each value of the throttle valve opening α _{1 to} α _{i in} the i stage and the engine speeds N _{1 to} N _{j in} the j stage. Each (A / N) _ij
The value is stored. And the throttle valve opening sensor
From the throttle valve opening α detected by 30 and the engine speed N detected by the engine speed sensor 31, four points (A corresponding to the throttle valve opening α _i and the engine speed N _j adjacent to these values are shown. / N) value is read from the α-N map, and an A / N value corresponding to the throttle valve opening α and the engine speed N is calculated by a known interpolation method. The calculated A / N value is applied to the above-described calculation formula to calculate the fuel injection time T.

The electronic control unit 20 supplies a valve opening energizing signal corresponding to the calculated valve opening time T to the fuel injection valve 29, so that the operation of the engine 10 can be reliably and stably continued even if the air flow sensor 14 is out of order. Engine 10 the amount of fuel needed to
Supply to.

The air amount sensor for detecting the intake air amount of the method of the present invention is not limited to the Karman vortex type air flow sensor 14,
A negative pressure sensor or the like for detecting the pressure generated in the intake pipe 12 downstream of the throttle valve 15 may be used.

Further, in the above-described embodiment, the actuator 24 that responds to the negative pressure generated in the intake pipe is used as the actuator that opens and closes the bypass valve 23, but the present invention is not limited to this, and the bypass valve 23 is a solenoid valve or the like. It may be.

(Effect) As described above in detail, according to the fuel supply control method for the internal combustion engine including the mechanical supercharger of the present invention, the mechanical supercharger is deactivated when the air amount sensor fails, and the throttle valve is operated. The fuel amount stored in advance according to the valve opening and the engine speed is read according to the throttle valve opening detection value and the engine speed detection value, and the fuel amount according to the fuel quantity read value is read. Since the air-fuel ratio is supplied to the engine, the problem that the air-fuel ratio of the air-fuel mixture supplied to the engine fluctuates due to the variation in the operating efficiency of the supercharger is eliminated, and so-called smoldering is possible even when the air amount sensor fails. It has an excellent effect that the engine operation can be continued reliably and stably by avoiding knocking and knocking.

[Brief description of drawings]

The drawings show one embodiment of the present invention, and FIG. 1 is a block diagram showing the overall configuration of a fuel supply control device for carrying out a fuel supply control method for an internal combustion engine equipped with a mechanical supercharger according to the present invention. 1 is a graph showing the relationship between the opening degree (stroke) of the bypass valve 23 shown in FIG. 1 and the magnitude of the negative pressure supplied to the negative pressure chamber 24e of the actuator 24, and FIG. 3 is the electronic control of FIG. FIG. 4 is a flow chart showing the control procedure of the bypass valve executed by the unit 20, and FIG. 4 shows an α-N map stored in the storage means incorporated in the electronic control unit 20 of FIG. And A / N stored according to the engine speed N
It is a map figure which shows the relationship of a value. 10 ... Internal combustion engine, 12 ... Intake pipe (intake passage), 14 ... Air flow sensor (air amount sensor), 15 ... Throttle valve, 16
… Supercharger, 17… Electromagnetic clutch,
20 ... Electronic control unit, 22 ... Bypass passage, 23
... Bypass valve, 24 ... Actuator, 24e ... Negative pressure chamber, 26 ... Electromagnetic switching valve, 30 ... Throttle opening sensor, 31 ...
Engine speed sensor.

Continuation of the front page (56) Reference JP-A-61-89956 (JP, A) JP-A-61-268847 (JP, A) JP-A-59-165841 (JP, A) Actual development 61-167445 (JP , U) Actually open 61-17428 (JP, U) Actually open 62-6431 (JP, U)

Claims (3)

(57) [Claims] 1. An internal combustion engine equipped with a mechanical supercharger in an intake passage downstream of a throttle valve supplies a fuel amount according to a detection signal of an air amount sensor for detecting an intake air amount, while At the time of failure, the fuel amount stored in advance according to the valve opening of the throttle valve and the engine speed is read according to the throttle valve opening detection value and the engine speed detection value, and the fuel amount read value is read. In a fuel supply control method for supplying a fuel amount according to the above, the fuel supply control of an internal combustion engine having a mechanical supercharger is characterized in that the mechanical supercharger is deactivated when the air amount sensor fails. Method. 2. The mechanical supercharger is driven by the internal combustion engine via a clutch, and when the air amount sensor fails, the clutch is deactivated. A fuel supply control method for an internal combustion engine including a mechanical supercharger. 3. A bypass passage for bypassing the mechanical supercharger is connected to the intake passage, a bypass valve is disposed in the middle of the bypass passage, and the bypass valve is opened when the air amount sensor fails. A fuel supply control method for an internal combustion engine comprising the mechanical supercharger according to claim 1 or 2.