JPS6013943A - Fuel injection controlling method for internal- combustion engine - Google Patents

Abstract

PURPOSE:To obtain a maximum output torque irrespective of inconsistency of the constituent parts of an internal combustion engine having a fuel injection valve, by controlling the injection quantity of fuel on the basis of the mean effective pressure in a combustion chamber of the engine. CONSTITUTION:An internal combustion engine 1 has a fuel injection valve 12, and a pressure sensor 13 for detecting the pressure in a combustion chamber 3 is disposed in the combustion chamber 3. An electronic control unit 20 furnishes fuel injection control signals to the fuel control valve 12. The injection quantity of fuel is controlled on the basis of the mean effective pressure calculated by the electronic control unit 20. By employing such a method, it is enabled to obtain a maximum output torque of an engine irrespective of inconsistency of the constituent parts of the engine.

Description

TECHNICAL FIELD The present invention relates to a method of controlling fuel injection for an internal combustion engine, and more particularly to a method of controlling the amount of fuel injection based on combustion pressure within a combustion chamber.

In the conventional electronically controlled fuel injection device, the air-fuel ratio can be controlled in a closed loop using, for example, an oxygen concentration sensor or the like so that the air-fuel ratio becomes a set air-fuel ratio. However, when the throttle valve is fully opened, it is common to add an appropriate increase to the basic fuel amount to set the output air-fuel ratio, and this is performed by open loop control.

When performing open-loop control like this, if there are manufacturing variations in components such as air flow sensors and fuel injection valves,
The air-fuel ratio, which has been constantly increased, begins to show slight variations in each engine, and the air-fuel ratio deviates from the optimum air-fuel ratio for obtaining maximum torque.

OBJECTS OF THE INVENTION An object of the present invention is to provide a fuel injection control method for an internal combustion engine that can correct variations in the output air-fuel ratio due to variations in each component as described above.

DESCRIPTION OF THE INVENTION In the present invention, the average effective pressure is used to correct the output air-fuel ratio. The average effective pressure corresponds to the output torque, and when the output air-fuel ratio deviates from the optimum air-fuel ratio, the average effective pressure decreases. Therefore, the fluctuations in the output air-fuel ratio are known from the fluctuations in the average effective pressure, and the air-fuel ratio can be controlled by the average effective pressure.

Example Embodiments of the present invention will be described below with reference to the drawings.

Referring to Figure 1, ■ is the engine body, 2 is the piston, and 3 is the engine body.
is the combustion chamber, 4 is the intake valve, -5 is the intake port 7, 6 is the surge tank, 7 is the intake port 5 and surge tank 6 of each cylinder
8 is an intake duct, 9 is an intake duct s
10 is an air cleaner;
1 is a water temperature sensor that detects the engine cooling water temperature, 12 is a branch pipe 7
The fuel injection valves 12 are shown respectively attached to the fuel injection valves 12, and fuel is injected into the corresponding intake ports 5. Further, a pressure sensor 13 is arranged within the combustion chamber 3 to detect the pressure within the combustion chamber 3. Water temperature sensor 11. Pressure sensor 13 and crank reference position sensor 1 (not shown)
4. Output signals from the crank angle sensor 15 and throttle sensor 16 are input to an electronic control unit 20, and a fuel injection control signal is sent from the electronic control unit 20 to the fuel control valve 12. Other signals such as an output signal of an air flow meter (not shown), an engine rotation speed signal, etc. can be input to the electronic control unit 20.

The electronic control unit 20 consists of a digital computer, with CPUs interconnected by a bidirectional bus 21.
(Microprocessor) 22. l? OM (Read Only Memory) 23. RAM (random access non-memory) 2
4. It has an input port 25 and an output port 26. The water temperature sensor 1 generates an output voltage proportional to the engine cooling water temperature, and this output voltage is A
After being converted into a corresponding binary signal in the D converter 27, it is input to the input port 25. The pressure sensor 3 generates an output voltage proportional to the pressure within the combustion chamber 3, and after this output voltage is converted into a binary number by the AD converter 28, it is input to the input port 25. The crank angle sensor 5 generates an output pulse signal every 5 degrees of crank angle, and this output signal is input to the input port 25. The crank reference position sensor 4 generates a reference position pulse signal when the piston 2 is at the compression bottom dead center, and therefore this reference position pulse signal is generated every 720 degrees of crank angle. This reference position signal is input to the input port 25. on the other hand,
The output boat 26 has drive circuits 31 , 32 , 33 , 3
4 to the fuel injection valves 12 of each cylinder, and fuel is simultaneously injected from each fuel injection valve 12 at every 360 degrees of crank angle.

Next, to explain the basic principle of the present invention, there is a relationship between the average effective pressure and the air-fuel ratio as shown by curve P in Figure 2, and the air-fuel ratio is optimal for obtaining the maximum value of the average effective pressure. value
Regardless of whether the pressure changes from rich to lean, the average effective pressure decreases, and the output torque decreases in response to the average effective pressure. In the present invention, the actual air-fuel ratio at that time is estimated by detecting the average effective pressure, and the air-fuel ratio is controlled so as to approach the optimum value X, thereby actually obtaining the highest output. .

There are two states in which the estimated actual air-fuel ratio is in the left region where it is thinner than the optimum value X. In other words, even if the amount was increased last time, it is still weak! 3A and state B, which has been diluted due to previous weight loss correction. In either state A or B, there is an increase in the current amount as shown by the broken line. Similarly, in the right region darker than the optimum value X, there are two states C and D, and weight loss is expected this time.

The average effective pressure Pf is generally calculated using the following formula.

Pi=S P-dV/Vh (]) When formula (1) is rewritten using the crank angle θ, it becomes. However, P: pressure, v: volume, vh: stroke volume. In the example shown below, the average effective pressure Pi is calculated as an integrated value every 685 degrees.

FIG. 3 shows a subroutine for calculating the average effective pressure among the calculations performed by the electronic control unit 20, and is performed by an interrupt every 5 degrees of the crank angle. First, in step 31, it is determined whether the crank reference position signal is ON. It is assumed that the crank reference position signal turns ON at the compression bottom dead center of the cylinder whose combustion pressure is to be measured. If it is determined that the position is the reference position, the crank angle counter (crank CL) is reset (step 32); if not, the counter CL is set to "1".
are added (step 33). That is, the counter CL is zero at the reference position, and is counted up by "1" every 5 degrees of the crank angle. Next, the combustion pressure A at that time
/D conversion value is fetched from the dedicated register and stored in RAM 24.
(step 34). Subsequently, the next A/D conversion is started (step 35).

Referring also to FIG. 4, in step 36, it is determined whether the crank CL is within 360° CA. YE
If S, the process proceeds to step 37 and executes a process to calculate the average effective pressure Pi, but if NO, the process proceeds to step 4.
Proceed to step 4. In step 37, find the differential value ΔV of the stroke volume for every 5 degrees of crank angle stored in the ROM 23,
The steering knob 38 calculates ΔPi=PXΔV and stores it in the RAM 24. By integrating this ΔPi, the average effective pressure Pi can be determined, but the processing differs depending on whether the piston is in the compression stroke or the expansion stroke.

If it is in the compression stroke, it means that it is doing negative work, and the integrated value of ΔPi during this stroke is stored as PiO, and if it is in the expansion stroke, it is doing positive work.
It is integrated as PiO. The process during this time is step 39.
The process starts from step 41.

Next, in step 42, it is determined whether the crank angle has passed 360 degrees or not, and a flag Pi is set to request Pi calculation in the base routine only when YES, that is, when the crank angle is at the 360 degree position. (Step 43).

Although the subsequent steps are not directly related to the features of the present invention, the injection start timing (7.7 because all cylinders are simultaneously injected) is determined by the counter CL.
2 times in 20 degrees m), and if it is the injection time, execute the injection process.Steps 44, 45,
46) , 5th interrupt processing ends.

In the base routine shown in FIG. 5, the amount of fuel is increased only at full load positions, and the air-fuel ratio is controlled by a separately determined method at times other than full load. The injection fuel amount control is performed by controlling the injection time of the fuel injection valve 12, and the injection time T is performed by T-TX (1+0.15+FBPsoR)+3). Here, the second term 0.15 is a fixed increase in output, and the third term FBPWR is a closed loop correction increase. That is, the air-fuel ratio is corrected by increasing or decreasing FBPWR.

In FIG. 5, the flag Pi is first checked, and if the crank CL is 360 degrees, Pi calculation is executed, and if not, the process proceeds to (2). The average effective pressure is the previously stored PiO,
Using Pi□, it is determined by Pi-'(PiO-PiO)/vh. Next, in step 53, it is determined whether the throttle is fully open, and if NO, the process proceeds to step 61. If the throttle is fully open, it is determined whether flag F=1. Here, the flag F=1 indicates that the correction was made to the increase side last time, and referring to FIG. 2, the control to the right was performed last time and there are states A and C. Flag F
=O means that it was controlled in the direction of decreasing weight last time,
There are states B and D since leftward control was performed last time.

If flag F=1, a=Pi, b=Piold
(previous Pi) (step 55), flag F=0
If so, set a=)'1old and b=Pi (step 56).

In step 57, a and b are compared, and if a≧b, C
= +0.005 cents and set flag F=1 (step 58). If a<b, c=--0,005 is set and the flag F=0 (step 59).

Next, the process proceeds from step 60 to step 65, and the opening time of the fuel injection valve 12 is calculated. To explain this clearly, if flag F = 1 and a≧b, it means that the average effective pressure approaches the maximum value from the left side in Figure 2, and in this case, further increase correction will reduce the output empty. As the fuel ratio approaches the optimum air-fuel ratio, the average effective pressure approaches its maximum value. This situation is shown in FIG. Then, when the average effective pressure Pi finally becomes smaller than Piold (Y in FIG. 6), the flag F=1 and a<b, and in this case, according to step 59, I! This corresponds to approaching the maximum value from the right side in FIG. As a result, the peak on the right side of Y becomes larger again as shown in FIG. In the next cycle, flag F=0. An example of control near the maximum value is shown in FIG. 7, and it can be seen that the average effective pressure Pi is controlled so as to always approach the maximum value.

In the above embodiment, closed loop control is performed only when the throttle is fully open, but when the throttle is not fully open,
For example, closed loop control can be performed when the throttle angle is ≧50 degrees.

Effects As is clear from the above explanation, according to the present invention, maximum output torque can be obtained regardless of variations in component parts.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of an internal combustion engine to which the present invention is applied, Fig. 2 is a graph showing the difference between the average effective pressure and the output air-fuel ratio to explain the invention in detail, and Fig. 3 is the average effective pressure calculation. A flowchart showing the process, FIG. 4 is a diagram for explaining the operation of the flowchart in FIG. 3, FIG. 5 is a flowchart for controlling the air-fuel ratio by determining the average effective pressure, and FIGS. 6 and 7 are 6A and 6B are diagrams each explaining the operation of the flowchart in FIG. 5. FIG. ■... Engine body, 3... Combustion chamber, 5... Intake boat, 12... Fuel injection valve, 13... Pressure sensor, 2
0...Electronic control unit. Patent applicant Toyota Motor Corporation Patent application agent Akira Aoki Patent attorney Kazuyuki Nishidate Patent attorney Kyosuke Tsuchinakayama Patent attorney Akira Yamaguchi

Claims (1)

[Claims] A fuel for an internal combustion engine equipped with a fuel injection valve, which detects the pressure in the combustion chamber of the engine, calculates an average effective pressure, and controls the fuel injection amount based on the calculated average effective pressure. Injection control method.