JPH034738B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention provides a method for applying so-called L-jetronic
According to the system, when the engine load is greater than a predetermined value, the so-called D-Jetronic
The present invention relates to an improvement of a control device for an electronic fuel injection engine that controls the amount of fuel injection based on a method.

Prior art As a control device for an electronic fuel injection engine,
Currently, two types of systems are generally known: the so-called L-dietronic system (hereinafter referred to as the L-J system) and the D-dietronic system (hereinafter referred to as the DJ system).

The L-J method determines the fuel injection amount that provides the optimum air-fuel ratio according to the engine operating condition based on the detection output signal of an air flow sensor installed in the intake pipe upstream of the throttle valve and the detection output signal of an engine rotation speed detector. This method determines the fuel injection amount and controls the opening time of the fuel injection valve so that fuel is injected with this fuel injection amount. Although this method has good detection accuracy, there is a problem in that the area with good detection accuracy is limited. for example,
The air flow meter commonly used with this method is equipped with a dynamic pressure measurement plate rotatably mounted in the intake pipe and a spring that biases this plate against the airflow. The amount of intake air is detected by the displacement angle of the corresponding plate. For example, since the intake air amount of an engine generally fluctuates greatly, the displacement angle of a single dynamic pressure measurement plate is used to detect the intake air amount. Therefore, there was a problem in that it was difficult to detect the amount of intake air with high accuracy.

On the other hand, the D-J method detects the intake pipe pressure and engine speed, calculates the amount of intake air per engine revolution based on these detection signals, and performs fuel injection that provides the optimal air-fuel ratio depending on the engine operating condition. This method calculates the fuel injection amount and controls the opening time of the fuel injection valve so that fuel is injected with this fuel injection amount. This method focuses on the fact that when the engine speed is constant, the amount of intake air is almost proportional to the pressure inside the intake pipe, and the fuel control circuit stores in advance the basic fuel injection for the amount of intake air according to the pressure inside the intake pipe. The fuel injection amount is determined by storing the basic fuel injection amount and further correcting the basic fuel injection amount based on the engine rotation speed. However, when making corrections based on engine speed, the correction coefficients in the low rotation and low load range vary widely, so
There was a problem that the desired fuel injection amount could not be calculated with high accuracy. In other words, even if the intake pipe pressure and engine speed are fixed, the calculated intake air amount tends to deviate from the desired value depending on the engine operating state, outside air conditions, etc., and the deviation tends to be particularly large in the low speed region. However, the DJ system has the problem of poor air-fuel ratio control accuracy in the low-speed, low-load range.

In order to compensate for the shortcomings of the L-J method and the DJ method and take advantage of their strengths, the L-J method is used when the amount of intake air is below a predetermined amount, and the D-J method is used when the amount of intake air is above the predetermined amount. Therefore, a control device for an electronic fuel injection type engine that controls the amount of fuel injection has been proposed in Japanese Patent Publication No. 7017/1983. This method has the advantage that it is possible to accurately calculate and control the fuel injection amount that provides the optimum air-fuel ratio over a wide range of intake air amount fluctuations.

By the way, in electronic fuel injection engines,
Engines are equipped with so-called air-fuel ratio feedback control means that detects the air-fuel ratio of the air-fuel mixture actually supplied to the engine using an air-fuel ratio sensor and controls the fuel injection amount so that the air-fuel ratio reaches a desired value. It is being

In an engine equipped with such an air-fuel ratio feedback control means, an air-fuel ratio feedback control correction value is calculated according to the difference between the actual air-fuel ratio and the target air-fuel ratio, and the final fuel injection amount is determined based on this correction value. It is becoming more and more determined.

Problems to be solved However, depending on the operating condition as disclosed in Japanese Patent Publication No. 59-7017, the L-J method and the D-J method
When performing air-fuel ratio feedback control as described above in a control device for an electronic fuel injection engine that switches between the L-J method and the L-J method, the intake air amount detection method that is the basis for calculating the air-fuel ratio is and the DJ system, switching between the two causes a stepwise change in the supply amount and changes the actual air-fuel ratio value, which may deteriorate the responsiveness of the feedback control.

Means for Solving the Problem The present invention was constructed in view of the above circumstances, and is capable of providing an appropriate amount of fuel injection by appropriately switching between the L-J method and the D-J method depending on the operating condition. It is an object of the present invention to provide an electronic fuel injection engine capable of performing air-fuel ratio feedback control with good responsiveness while suppressing the adverse effects caused by the switching.

The electronic fuel injection engine of the present invention includes an air flow meter installed in the intake system to detect the amount of intake air, and a load detection means that outputs a signal corresponding to the intake negative pressure downstream of the throttle valve or the opening degree of the throttle valve. An engine rotation speed detection means for detecting the engine rotation speed, a first fuel control means for controlling the fuel injection valve based on the output of the air flow meter, that is, a fuel control means using an L-J method, the load detection means and the engine. A second fuel control means for controlling the fuel injector based on the output from the rotational speed detection means, that is, a fuel control means based on the DJ system; switching means for switching from fuel injection amount control based on the fuel injection amount control to fuel injection amount control based on the second fuel control means.

Furthermore, the electronic fuel injection engine of the present invention includes:
An air-fuel ratio sensor detects the air-fuel ratio of the air-fuel mixture, and the fuel injection amount is adjusted to a target air-fuel ratio based on the output of the air-fuel ratio sensor only when injection amount control is performed based on the first fuel control means. The present invention is characterized by comprising an air-fuel ratio control means for performing correction control.

According to the present invention, in a low-medium load operating region where the intake air amount is relatively small, the fuel injection amount is controlled by the first fuel control means, that is, the fuel control means using the L-J method, and the intake air amount is kept at a predetermined value. When the operating state shifts to the high load side, the fuel injection amount is controlled by the second fuel control means.

In the present invention, feedback control of the air-fuel ratio is also performed in addition to this LD switching control. In this case, when the fuel injection amount control is performed by the first fuel control means, that is, the L-
Air-fuel ratio feedback control is performed only in an operating state where fuel injection amount control based on the J method is being performed.

Effects of the Invention According to the present invention, when the operating condition changes and the intake air amount exceeds a predetermined amount, the fuel injection amount control means is switched from the L-J method to the DJ method. Thereby, accurate fuel injection amount control can be performed over the entire operating range. In this case, immediately after switching between the L-J method and the DJ method, the value of the intake air amount may deviate because the intake air amount detection methods are different.

In view of these circumstances, the present invention provides the above-mentioned L-
When switching from J method to D-J method,
Air-fuel ratio feedback control is stopped. As a result, stable and responsive air-fuel ratio feedback control can be performed without being affected by the switching of the detected value of the intake air amount, which is the basis for calculating the air-fuel ratio.

Note that in the present invention, air-fuel ratio feedback control is not performed when fuel injection amount control is performed using the D-J method, but originally this control is not effective in the normal operating range where the operating conditions are relatively stable. This has a significant meaning, and there is little demand for air-fuel ratio feedback control under the DJ system fuel injection amount control, which is frequently used in high-load areas and on an unsteady basis. There is no practical problem even if this is not done.

Embodiments Hereinafter, embodiments of the present invention will be described in detail based on the accompanying drawings.

FIG. 1 is an overall schematic diagram of an engine according to an embodiment of the present invention. The engine 1 includes a piston 3 that reciprocates within a cylinder bore 2, and a space above the piston 3 in the cylinder bore 2 is a combustion chamber 4.
It consists of A spark plug 4a is provided in the combustion chamber 4.
is faced, and an intake port 5 and an exhaust port 6 are open, respectively, and an intake valve 7 and an exhaust valve 8 are combined with the intake port 5 and the exhaust port 6, respectively. Furthermore, an intake passage 9 and an exhaust passage 10 communicate with the intake port 5 and the exhaust port 6, respectively. An air cleaner 11 is installed at the upstream end of the intake passage 9, an air flow meter 12 is installed in the intake passage 9 downstream of the air cleaner 11, a throttle valve 13 is installed downstream of the air flow meter 12, and a throttle valve 13 is installed downstream of the air flow meter 12. Fuel injection valves 14 are provided downstream of the fuel injection valves 13, respectively.

In the exhaust passage 10, there is an air-fuel ratio sensor 15 for detecting the oxygen concentration in the exhaust gas and controlling the air-fuel ratio.
is installed.

In the engine fuel supply system of this embodiment, fuel is introduced from a fuel tank 16 into a fuel pump 17, passes through a fuel filter 18, is regulated to a predetermined pressure by a fuel pressure regulator 19, and is sent to a fuel injection valve 14. In this embodiment, in order to control the fuel injection amount so as to obtain the optimum air-fuel ratio,
A fuel injection amount control device 20 preferably including a microcomputer is provided. The fuel injection amount control device 20 detects a signal indicating the opening degree of the throttle valve 13, an intake pipe pressure detection signal from an intake pipe pressure sensor 21 provided in the intake pipe downstream of the throttle valve 13, and the engine rotation speed. The fuel injection amount control device 20 receives a signal from the rotation sensor 22, an oxygen concentration signal from the air-fuel ratio sensor 15, and a signal representing the cooling water temperature.
Based on these input signals, predetermined calculations are performed to calculate the fuel injection amount, and the opening time of the fuel injection valve 14 is controlled.

FIG. 2 shows a fuel injection amount control device 2 according to the present invention.
FIG. 2 is a block diagram showing the configuration of one embodiment of the invention.

In FIG. 2, the fuel injection amount control device 20 is
Based on the detection signals of the air flow meter 12, rotation sensor 22, and intake pipe pressure sensor 21, L-
L-J that calculates the basic fuel injection amount τ _l using the J method
A system basic fuel injection amount calculation means 23 and a DJ system basic fuel injection amount calculation means 24 for calculating the basic fuel injection amount τ _d according to the DJ system are provided.

Further, the fuel injection amount control device 20 of this example uses the intake pipe internal pressure value output from the intake pipe internal pressure detection sensor 21 and a predetermined L-J method determined experimentally in advance.
An intake pipe pressure determination means 25 that compares and determines the magnitude with the D-J method switching pressure value, and a basic fuel injection amount value calculated according to the L-J method or the D-J method based on this determination signal. Select one L
-J system/DJ system switching means 26.

The fuel injection amount control device 20 of this example includes outputs from an intake pipe pressure detection sensor 21, a rotation sensor 22, an air-fuel ratio sensor 15, an L-J type basic fuel injection amount calculation means 23, and an intake pipe pressure determination means 25. If the operating state is in the L-J method control region, the target air-fuel ratio is set according to the operating state, and the actual air-fuel ratio is calculated from the output of the air-fuel ratio sensor 15, so that the air-fuel ratio becomes the target air-fuel ratio. Feedback control means 27 is provided for performing feedback control of the air-fuel ratio so that the air-fuel ratio is maintained.

The fuel injection amount control device 20 also includes a fuel injection amount correction means 28 that makes various corrections to the basic fuel injection amount value outputted from the L-J method/DJ method switching means, and The fuel injection control means 29 receives the signal and controls the opening time of the fuel injection valve 14.

In this case, the signal from the feedback control means 27 is input to the fuel injection amount correction means 28, and the fuel injection amount is corrected based on this signal value.

An example of fuel injection amount control in this example will be described below.

FIG. 3 is a flowchart showing a control method in the fuel injection amount control device 20 shown in FIG. In FIG. 3, first, intake air flow rate data Qa detected by the air flow meter 12,
Engine speed data Ne detected by the crank angle sensor 22 and intake pipe pressure data Pm detected by the intake pipe pressure sensor 21 are input, respectively. Next, based on these input data, the basic fuel injection amount τ _l is calculated based on the L-J method by the L-J method calculating means as τ _l =K×Qa/
Ne×C _AIR (K: coefficient, C _AIR : intake air temperature correction coefficient)
is calculated in the form of injection time, and the basic fuel injection amount τ _d is calculated based on the D-J method by the D-J method calculation means by adding correction by the intake air temperature correction coefficient C _AIR to the value read from the map. Calculated in the form of injection time.

Next, the intake pipe pressure data detected by the intake pipe pressure detection means such as the intake pipe pressure sensor 21
Pm is compared with a predetermined intake pipe internal pressure _P0 by the intake pipe internal pressure determining means 25, and the determination result is L-J.
The signal is output to the system/DJ system switching means 26. L
-J method/D-J method switching means 26 converts the output value τ _l of the L-J method calculating means into the basic fuel injection value when the input signal from the intake pipe pressure determining means 25 is Pm<P ₀ . When Pm≧P ₀ , the output value τ _d of the DJ method calculation means is selected as the basic fuel injection amount value.

When Pm<P ₀ , feedback control means 2
Step 7 reads the value of the L-J method basic fuel injection amount τ _l and determines whether or not it is in the air-fuel ratio feedback control region. In this case, the air-fuel ratio feedback control region is set within the L-J system control region in relation to the engine speed and engine load, as shown in FIG. Furthermore, if it is in the feedback control region, the feedback control means 27 determines whether other feedback control conditions are satisfied, and if the conditions are satisfied, executes air-fuel ratio feedback control. That is, a feedback correction control value _CFB for the fuel injection amount is calculated based on the difference between the target air-fuel ratio and the actual air-fuel ratio so that the air-fuel ratio becomes the target air-fuel ratio.

Next, the fuel injection amount control device 20 calculates a warm-up correction coefficient Cw and a battery voltage correction coefficient C _BAT .

Finally, the fuel injection amount control device 20 adjusts the final fuel by taking into consideration the various correction coefficients obtained in the above procedure, such as the valve 17 feedback correction control value C _FB , the warm air correction coefficient Cw, and the battery voltage correction coefficient C _BAT . Calculate the injection time T that gives the injection amount.

In this example, when the operating region is within the DJ method control region, feedback control is not performed, so in this case, the feedback correction control value _CFB is not taken into account.

The fuel injection amount control device 20 outputs a command signal to the fuel injection valve 14 to open the valve for a fuel injection time T corresponding to a predetermined fuel injection timing.

According to the control of this example described above, since the fuel injection amount control by the L-J method and the DJ method is appropriately switched depending on the operating condition, accurate fuel injection is performed over the entire operating range. Injection amount control can be performed. The electronic fuel injection engine of this example also performs air-fuel ratio feedback control, but this feedback control is performed only within the frequently used L-J control region. - It is possible to perform stable and responsive air-fuel ratio feedback control without being adversely affected by switching between the J method and the DJ method.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram of an electronic fuel injection type engine according to an embodiment of the present invention, FIG. 2 is a block diagram of a fuel injection amount control device, and FIG. 3 is a diagram of an electronic fuel injection type engine according to an embodiment of the present invention.
Flowchart of fuel injection amount control according to an embodiment,
FIG. 4 is a graph showing the feedback control region, L-J control region, and DJ control region in the relationship between engine load and engine speed. 1...Engine, 2...Cylinder bore, 3...
Piston, 4... Combustion chamber, 5... Intake port, 6
...Exhaust port, 7...Intake valve, 8...Exhaust valve,
9...Intake passage, 10...Exhaust passage, 11...Air cleaner, 12...Air flow meter, 13
...Throttle valve, 14...Fuel injection valve, 15...
...Air-fuel ratio sensor, 16...Fuel tank, 17...
fuel pump, 18... filter, 19... fuel pressure regulator, 20... fuel injection amount control device,
21... Intake pipe pressure sensor, 22... Rotation sensor, 23... L-J method basic fuel injection amount calculation means, 24... D-J method basic fuel injection amount calculation means, 25... Intake pipe pressure determination means , 26... Switching control means, 27... Air-fuel ratio feedback control means, 28... Correction means, 29... Injection amount control means.

Claims (1)

[Claims] 1. An air flow meter installed in the intake system to detect the amount of intake air, a load detection device that outputs a signal corresponding to the intake negative pressure downstream of the throttle valve or the opening degree of the throttle valve, and an engine rotation speed meter that detects the engine rotation speed. a detection means, a first fuel control means for controlling the fuel injection valve based on the output of the air flow meter, and a second fuel control means for controlling the fuel injection valve based on the output of the load detection means and the engine rotation speed detection means. means, in an operating region where the intake air amount or load exceeds a predetermined value, the fuel injection amount is controlled based on the second fuel control means, and in an operating region where the intake air amount or load is below the predetermined value, the fuel injection amount is controlled based on the first fuel control means. an air-fuel ratio sensor that detects the air-fuel ratio of the air-fuel mixture; and a target air-fuel ratio sensor that detects the target air-fuel ratio based on the output of the air-fuel ratio sensor only when injection amount control is performed based on the first fuel control means. 1. A fuel control device for an electronic fuel injection engine, comprising an air-fuel ratio control means for correcting and controlling a fuel injection amount so as to achieve a fuel ratio.