JPS59221433A - Fuel injection controller for internal-combustion engine - Google Patents

Abstract

PURPOSE:To properly control the air-fuel ratio of an internal-combustion engine even when equipped with supercharger and also even during the acceleration period by calculating the amount of fuel to be injected on the basis of the internal pressure of the combustion chamber. CONSTITUTION:Output voltage proportional to the internal pressure of a combustion chamber is sent out by a pressure sensor 13 and put in an input port 25 after being converted into binary digits in an AD converter 28. On the basis of the internal pressure of the combustion chamber 3, obtained from output signal of the pressure sensor 13, the amount of fuel to be injected is determined. By determination of fuel injection amounts on the basis of the internal pressure of the combustion chamber, representing the amount of air actually supplied into the combustion chamber, air-fuel ratios can be properly controlled even when equipped with supercharger and also even during the supercharging period.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a fuel injection control device for an internal combustion engine.

In conventional electronically controlled internal combustion engines, the amount of fuel to be injected is usually calculated from the output signal of an air flow meter and the engine speed. However, the air flow meter cannot accurately measure the amount of intake air due to the influence of intake pulsation when the throttle is fully open, and when a supercharger is installed, the range in which the amount of intake air should be measured becomes too wide. An air flow meter cannot accurately measure the amount of intake air over the entire range, and the accuracy of measuring intake air in low flow areas and high flow areas must be reduced. As a result, when a supercharger is installed, it is difficult to accurately match the air-fuel ratio of the air-fuel mixture supplied into the engine cylinders to a predetermined air-fuel ratio in the low-flow region and high-flow region, and Even when a feeder is not attached, it is difficult to accurately match the air-fuel ratio of the air-fuel mixture supplied into the engine cylinder to a predetermined air-fuel ratio when the throttle valve is fully open.

Purpose of the Invention The present invention makes it possible to accurately measure the amount of intake air supplied to each cylinder no matter what kind of internal combustion engine there is or how the amount of intake air changes. An object of the present invention is to provide a fuel injection device for an internal combustion engine that can accurately match the air-fuel ratio of an air-fuel mixture supplied into a cylinder to a predetermined air-fuel ratio in any case.

Configuration of the Invention The configuration of the present invention includes a pressure sensor that detects the pressure within an engine combustion chamber, and an electronic control unit that calculates the amount of fuel injected from the fuel injection valve based on the output signal of the pressure sensor. be.

Referring to FIG. 1 of the embodiment, ■ is the engine body, 2 is the piston, and 3 is the engine body.
4 is an intake valve, 5 is an intake boat, 6 is a surge tank, 7 is a branch pipe connecting the intake boat 5 and the surge tank 6 of each cylinder, 8 is an intake duct, and 9 is inside the intake ducts 1 to 8. 10 indicates the air cleaner, 12 indicates the combustion chamber injection valve attached to the branch pipe 7, and fuel is supplied from the fuel injection valve 12 to the corresponding intake air. It is injected into the boat 5. Further, a pressure sensor 13 is arranged within the combustion chamber 3 to detect the pressure within the combustion chamber 3.

The electronic control units 1 to 20 consist of digital computers and are interconnected by a bidirectional bus 21.
It includes a PII (microprocessor) 22, a ROM (read only memory) 23, a RAM (random access memory) 24, an input port 25, and an output port 26. The water temperature sensor 11 generates an output voltage proportional to the engine cooling water temperature, and this output voltage is converted into a corresponding double signal by the AD converter 27 and then input to the input port 25. The pressure sensor 13 generates an output voltage proportional to the pressure inside the combustion chamber.1. 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 29 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 30 generates a reference position pulse signal when the piston is at the 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 capos 1 to 26 are connected to the fuel injection valves 12 of each cylinder via drive circuits 31, 32, 33, and 34, and fuel is simultaneously injected from each fuel injection valve 12 every 360 degrees of crank angle. be done.

According to the present invention, the pressure inside the combustion chamber 3 is detected by the pressure sensor 13 as shown in FIG.
The fuel injection amount is controlled by the output signal. When the fuel injection amount is determined based on the pressure within the combustion chamber 3 in this manner, a mixture having a predetermined air-fuel ratio can be supplied into the combustion chamber 3 at any given time regardless of the operating state of the engine. Next, the reason will be explained with reference to FIGS. 2 and 3. Figure 2 shows the pressure change in the combustion chamber 3 from the compression stroke to the expansion stroke when the intake air i (g) is constant.The solid line shows the pressure change during firing, and the broken line shows the pressure change during motoring. The pressure changes over time are shown respectively. From FIG. 2, it can be seen that until the crank angle reaches crank angle C, the pressure changes are the same whether during firing or motoring. This crank angle C is approximately 40 degrees before top dead center. On the other hand, Fig. 3 shows the relationship between the pressure P in the combustion chamber 3 and the intake air amount Gafgl at the crank angle C in Fig. 2, and from Fig. 3, the pressure P and the intake air amount Ga are expressed by a linear equation. It can be seen that it is expressed. The relationship shown in Fig. 3 is obtained when motoring, but when the intake air amount Ga is constant, as shown in Fig. 2, even when motoring at crank angle C, there is a difference during firing. However, since the pressure P is the same, the relationship shown in FIG. 3 also holds true during firing. By measuring the pressure inside the combustion chamber 3 at the determined crank angle C as described above, the amount of intake air Ga actually taken into the combustion chamber 3 can be determined, and therefore fuel injection is performed based on the pressure inside the combustion chamber 3. If the amount is determined, the intake air amount Ga
It is possible to supply fuel proportional to The present invention has been made with attention to such points, and the fuel injection control method according to the present invention will be explained below with reference to FIGS. 4 to 6.

FIG. 4 shows the control timing, and in FIG. 4, CB is a reference position pulse signal emitted by the crank reference position sensor 30, C is an output pulse signal emitted by the crank angle sensor 29 every 5 degrees of crank angle, and CL is the contents of a crank angle count which will be described later, P is the combustion chamber pressure which is the basis for calculating the fuel injection amount, T is the fuel injection period, and CA is the crank angle.

Next, the fuel injection control method will be explained with reference to FIG. 5 while referring to FIG. 4. Referring to FIG. 5, first, in step 40, it is determined whether or not the crank angle reference position sensor 30 is emitting a reference position pulse signal, that is, for example, whether or not the piston 2 of the No. 1 cylinder is at the compression bottom dead center. do.

If the piston 2 is at the compression bottom dead center, the crank angle counter CL is reset in step 41, and then the process proceeds to step 42. In step 42, the pressure in the combustion chamber 3 is calculated from the output signal of the pressure sensor 13, and the pressure when the piston 2 is at the compression bottom dead center is stored in the RAM 24 as Pm1n. This pressure Pm1n serves as a reference when calculating the pressure P in the combustion chamber 3.

Meanwhile, in step 60, the crank reference position sensor 3
0 is not generating the reference position pulse signal, the process proceeds to step 43, where the crank angle counter CL is counted up by 1, and then, in step 44, the crank angle at which the current pressure in the combustion chamber 3 is to be measured (upper row front 40 degree) or not, that is, the crank angle counter CL is 14015
It is determined whether or not. When the current pressure in the combustion chamber 3 is at the crank angle at which it should be measured, in step 45, the current pressure Po in the combustion chamber 3 is read from the output signal of the pressure sensor 3, and from this pressure Po, the pressure at the compression bottom dead center Pm1n The production is reduced and the result of the production reduction is defined as pressure P.

Next, in step 46, the injection amount calculation request flag is set. When this flag is set, the fuel injection time is calculated as will be described later.

When the determination in step 44 is NO, the process proceeds to step 45, where it is determined whether or not it is fuel injection timing, and if it is the fourth fuel injection period, fuel is injected from all fuel injection valves 12 at the same time. That is, in step 45, the crank angle counter CL is 30015 (the crank angle is 3 from the compression bottom dead center).
00 degrees), or in step 46
When it is determined that the crank angle counter CL is 66015 (the crank angle is 660 degrees from the compression bottom dead center), the process proceeds to step 47, and data representing the fuel injection time TAU calculated as described later is stored in the RAM.
24 to the CPU 22 and converts it into a fuel injection time t. Next, in step 48, fuel injection is performed based on this fuel injection time t.

Next, calculation of the fuel injection time will be explained with reference to FIG. If it is determined in step 50 that the injection amount calculation flag (see step 46 in FIG. 5) is set, the process proceeds to step 51 and Ga
2) Calculate the intake air lGafgl from the relationship: /k+. Here, P is the pressure determined in step 45 of FIG. Further, (P-2)/2 represents the relationship shown in FIG. 3, and k, , and 2 are constants determined by experiment. Next, in step 52, the basic fuel injection time τ is calculated from the intake air amount Ga and the required airflow relationship. Here, γj is the specific weight of the fuel, and kinj is the flow coefficient of the fuel injection 12. Next, in step 54, one fuel injection time TAU is determined from the relationship TAU=τ×f/2. Here, f is a correction coefficient for increasing the fuel injection amount according to the engine cooling water temperature, and τ
The reason why xf is divided by 2 is that injection is performed twice every 360 degrees within a crank angle range of 720 degrees. This way...
The obtained TAll is stored in the RAM 24 as data representing the fuel injection time. Next, in step 55, the injection amount calculation request flag is reset, and then step 5
In step 6, other necessary processing is performed.

Effects of the Invention By determining the fuel injection time based on the pressure inside the combustion chamber representing the amount of intake air actually supplied into the combustion chamber, the air-fuel ratio of the air-fuel mixture supplied to the combustion chamber can be maintained at a constant predetermined air-fuel ratio. can be exactly matched. Therefore, even when a supercharger is installed, the desired air-fuel ratio can be set.In addition, the desired air-fuel ratio can be set even during transient operation such as during acceleration operation.

[Brief explanation of the drawing]

Figure 1 is a side sectional view of the internal combustion engine, Figure 2 is a diagram showing pressure changes in the combustion chamber, Figure 3 is a diagram showing the relationship between the pressure in the combustion chamber and the amount of intake air, and Figure 4 is a diagram showing the control timing. 5 is a flowchart, and FIG. 6 is a flowchart. 3... Combustion chamber, 1.2... Fuel injection valve, 13...
Pressure Kasen No. 20...Electronic control unit. Patent Applicant: Toyota Motor Corporation Patent Application Agent Akira Aoki Patent Attorney Kazuyuki Nishidate Patent Attorney Kyosuke Donakayama Patent Attorney Akira Yamaguchi Figure 2 Figure 3 Ga (g) Figure 4 BDCTDC Figure 5

Claims (1)

[Claims] An internal combustion engine equipped with a fuel injection valve, which is equipped with a pressure sensor that detects the pressure within the combustion chamber of the engine, and an electronic control unit that calculates the amount of fuel injected from the fuel injection valve based on the output signal of the pressure sensor. Fuel injection control device for internal combustion engines.