JPH0223702B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel injection control method for an internal combustion engine, and in particular to a method for controlling fuel injection for an internal combustion engine, and in particular for controlling the amount of fuel to be supplied to the engine during idling to a value that is more suited to the operating condition of the engine, thereby preventing engine rotational speed hunting. The present invention relates to a fuel injection control method that prevents this and improves driving performance.

The amount of fuel injected into an internal combustion engine is
In addition to the basic fuel amount depending on the engine speed and intake pipe absolute pressure, constants and/or engine operating parameters such as engine speed, intake pipe absolute pressure, engine water temperature, throttle valve opening, exhaust oxygen concentration, etc. A fuel injection control method in which the air-fuel ratio of the air-fuel mixture supplied to the engine is determined by adding and/or multiplying coefficients to an appropriate value is known, for example, from JP-A-57-137633. It is being

In addition, the volume of the engine's intake passage, especially the volume of the passage on the downstream side of the throttle valve, is designed to be large to minimize the pressure loss of intake air that occurs when the intake air flows through the intake passage, thereby increasing the filling efficiency of intake air. There are also known methods for improving engine characteristics such as increasing engine output.

However, increasing the volume of the intake passage downstream of the throttle valve reduces the degree of change in the absolute pressure in the intake pipe with respect to the degree of change in engine speed during low-load operation such as when the engine is idling. According to the basic fuel amount calculation method based on the engine speed and the absolute pressure in the intake pipe (generally referred to as the "speed density method", hereinafter simply referred to as the "SD method"), the amount of fuel to be supplied to the engine is calculated by calculating the amount of fuel to be supplied to the engine. Accurate calculations cannot be made in accordance with the driving conditions, causing engine rotational speed hunting, which adversely affects driving performance.

On the other hand, for example, the method shown in Japanese Patent Application Laid-Open No. 47-9354, that is, using a flow meter, is used to measure the amount of intake air.
According to a method (generally called the "L-dietro method") that detects Qa and determines the amount of fuel to be supplied based on the detected intake air amount Qa and engine rotation speed.
Although the aforementioned hunting phenomenon of engine speed during idling operation is less likely to occur, an expensive flow meter is required.

In order to solve the above problems, the upstream pressure of the throttle valve is reduced during low load operation such as idling operation.
The pressure ratio (P _BA /P' _A ) between P′ _A and the downstream pressure P _BA becomes less than the critical pressure ratio (0.528) that generates sonic flow, and below this critical pressure ratio, the intake air amount is lower than the throttle valve downstream pressure. Does not depend on P _BA or exhaust pressure,
A method that focuses on the dependence on the opening area of the throttle valve, detects only the valve opening of the throttle valve, detects the intake air flow rate at low load, and controls the fuel flow rate based on the detected intake air amount. The special public service was issued in 1977.
Proposed by No. 6414.

When applying this intake air amount detection method to fuel injection control that injects fuel in synchronization with the engine speed,
The fuel injection amount must be determined as a function of the engine rotational speed in addition to the intake air amount determined as described above. This is because the amount of intake air that passes through the throttle valve per unit time is constant when the opening area of the throttle valve is constant, but the amount of air taken into the engine per intake stroke changes depending on the engine speed. .

In addition, idle speed control methods that bypass the throttle valve and control the amount of auxiliary air supplied to the engine to maintain the engine speed at a constant value during idling and improve cold starting characteristics have been developed, for example. It is disclosed in Japanese Patent Application No. 57-077250 filed by the applicant. If the intake air supplied to the engine includes not only air that passes through the throttle valve but also auxiliary air that passes through a control valve installed in the auxiliary air passage that bypasses the throttle valve, only the valve opening of the throttle valve is detected. In this case, the total amount of intake air supplied to the engine cannot be detected.

The present invention has been made to solve the above-mentioned problems, and when an internal combustion engine is provided with an auxiliary air passage that opens downstream of a throttle valve and supplies auxiliary air, a specially designed flow meter is installed. An object of the present invention is to provide a fuel injection control method for an internal combustion engine that can prevent engine rotational speed hunting during low-load operation without using the engine, and thereby improve driving performance.

In order to achieve the above object, the present invention includes an intake passage, a throttle valve arranged in the middle of the intake passage, an auxiliary air passage that opens into the intake passage downstream of the throttle valve and communicates with the atmosphere, and an auxiliary air passage that opens into the intake passage downstream of the throttle valve and communicates with the atmosphere. placed in the aisle,
A fuel injection control method for injecting and supplying a required amount of fuel to an internal combustion engine in synchronization with the rotation of the engine, the method comprising: a control valve for controlling the amount of auxiliary air supplied to the engine through the passage; In the method of injecting and supplying fuel to the engine determined according to the pressure in the intake passage downstream of the throttle valve and the rotation speed of the engine, when the load applied to the engine is higher than the reference load, the load applied to the engine is When the load is lower than the reference load, a first coefficient value corresponding to the opening area of the throttle valve, a second coefficient value corresponding to the opening area of the control valve, and the rotation speed of the engine are respectively determined; The amount of fuel is calculated according to the sum of the first and second coefficient values and the engine speed, and the amount of fuel thus calculated is injected and supplied to the engine.

Further, a plurality of auxiliary air passages are provided that open in the intake passage downstream of the throttle valve and communicate with the atmosphere,
In the case of an internal combustion engine in which a control valve is arranged in each auxiliary air passage, the second coefficient value is set to a value corresponding to the sum of the opening areas of the control valves in the operating state among the plurality of control valves. This is how it was done.

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

FIG. 1 is a block diagram schematically showing the entirety of a fuel injection control device for an internal combustion engine including a plurality of auxiliary air amount control valves for controlling auxiliary air amount, to which the method of the present invention is applied; For example, a four-cylinder internal combustion engine is shown, and an engine 1 is connected to an intake pipe 3 and an exhaust pipe 4, both of which have an air cleaner 2 attached to their open ends. A throttle valve 5 is arranged in the middle of the intake pipe 3, and the intake pipe 3 downstream of the throttle valve 5
A first air passage 8 and a second air passage 8 open to the atmosphere and communicating with the atmosphere.
An air passage 8' is provided. First air passage 8
An air cleaner 7 is attached to the open end on the atmosphere side, and a first auxiliary air amount control valve (hereinafter simply referred to as "first control valve") 6 is disposed in the middle of the first air passage 8. The first control valve 6 is a normally closed solenoid valve, and is composed of a solenoid 6a and a valve 6b that opens the first air passage 8 when the 6a is energized.The solenoid 6a is an electronic control unit (hereinafter referred to as "ECU"). 9).

The second air passage 8' branches into a third air passage 8'' in the middle of the passage, and air cleaners 7', 7'' are provided at the open ends of the second air passage 8' and the third air passage 8'' on the atmosphere side, respectively. A control valve similar to the first control valve is installed between the branch point of the third air passage 8'' of the second air passage 8' and the atmospheric opening end side, and in the middle of the third air passage 8''. A second control valve 6' and a third control section 6'', which are normally closed solenoid valves, are respectively provided. Each control valve 6', 6'' has a solenoid 6'a,
6''a and valves 6'b, 6''b that open each passage when the solenoid is energized, and one end side of each solenoid 6'a and 6''a of each control valve 6', 6'' is grounded, and the other ends are connected to switches 18 and 19, respectively.
It is connected to the DC power supply 20 via the ECU 9 as well as to the ECU 9.

A branch passage 8b that branches downstream of the first control valve 6 is connected to the first air passage 8, and an air cleaner 11 is connected to the open end of the branch passage 8b on the atmosphere side.
is attached, and a fast idling control device 10 is disposed in the middle of the branch passage 8b. The fast idling control device 10 includes, for example, a valve body 10a that can be pressed against a valve seat 10b by a spring 10c to close the branch passageway 8b.
, a detection device 10d that expands and contracts the arm 10d' in response to the engine cooling water temperature, and a lever 10e that rotates in response to the expansion and contraction of the arm 10d' of the detection device and displaces the valve body 10a in the opening and closing direction. has been done.

An intake pipe absolute pressure sensor is connected to the intake pipe 3 through a fuel injection valve 12 and a pipe 15 between the engine 1 and the first air passage opening 8a and the second air passage opening 8'a. 16 are attached respectively. The fuel injection valve 12 is connected to a fuel pump (not shown) and electrically connected to the ECU 9, and the absolute pressure sensor 16 is also connected to the ECU 9.
Electrically connected to ECU9. Furthermore, the throttle valve 5 is provided with a throttle valve opening sensor 17.
However, the engine 1 body has an engine water temperature sensor 13.
The sensor 13 is made of a thermistor or the like, and is inserted into the circumferential wall of the engine cylinder filled with cooling water, and supplies the detected water temperature signal to the ECU 9.

An engine rotation speed sensor (hereinafter referred to as "Ne sensor") 14 is attached around the camshaft or crankshaft (not shown) of the engine, and the Ne sensor 14 receives a TDC signal, that is, a predetermined value every 180° rotation of the engine crankshaft. It outputs one pulse at the crank angle position of ECU9.
sent to.

Reference numeral 21 indicates an electrical device such as a headlight, a brake light, a radiator cooling fan, etc., and the electrical device 21 is connected to the ECU via a switch 22.
It is electrically connected to 9. Reference numeral 23 indicates an atmospheric pressure sensor, and an atmospheric pressure signal detected by the atmospheric pressure sensor 23 is supplied to the ECU 9.

Next, the operation of the fuel injection control device configured as described above will be explained.

First, the switch 18 operates in conjunction with, for example, an air conditioner switch (not shown) that operates an air conditioner (not shown), and when the switch 18 is closed, it supplies an air conditioner signal indicating the operation of the air conditioner to the ECU 9 and also controls the second control valve 6'. The solenoid 6'a is energized to open the valve 6'b, and a predetermined amount of auxiliary air is supplied to the engine 1 in response to the increase in engine load due to the operation of the air conditioner during idling. For example, in the case of an internal combustion engine equipped with an automatic transmission, the switch 19 is attached to a shift lever (not shown), and when the shift lever is operated to the engagement position of the automatic transmission, the switch 19 closes and engages the automatic transmission. An on signal (hereinafter referred to as the "D range signal") indicating the automatic transmission is supplied to the ECU 9, and the solenoid 6"a of the third control valve 6" is energized to open the valve 6"b, thereby controlling the automatic transmission during idling. A predetermined amount of auxiliary air is supplied to the engine 1 in response to an increase in engine load due to operation.

As mentioned above, the second and third control valves are used individually for loads on auxiliary machines such as air conditioners and automatic transmissions that are directly driven by the engine, that is, mechanical loads that are relatively large loads on the engine. is provided to keep the idle speed constant according to each load.

The fast idling control device 10 operates when the engine cooling water temperature is lower than a predetermined value (for example, 50° C.), such as during a cold start. More specifically, the detection device 1 of the fast idling control device 10
0d expands and contracts the arm 10d' in response to the engine cooling water temperature. Various devices can be used as the detection device 10d, for example, it may be filled with wax and utilize its thermal expansion characteristics. When the engine cooling water temperature is lower than a predetermined value, the arm 10d' of the detection device 10d is in a contracted state, and the lever 10e is rotated by the spring 10f, and the valve body 10a is moved to the right against the spring 10c. The branch passage 8b is opened by displacement. When this branch passage 8b is open, sufficient auxiliary air is supplied to the engine 1 via the filter 11 and the passages 8b and 8, so the engine rotation speed can be maintained at a rotation speed higher than the normal idle rotation speed, so it is cold. Normal operation is ensured without fear of engine stall during idling operation.

When the arm 10d' of the detection device 10d expands due to thermal expansion as the engine cooling water temperature increases due to warm-up operation, the arm 10d' pushes the lever 10e upward and rotates it clockwise. At this time, the valve body 10a gradually moves to the left due to the pressing force of the spring 10c, and when the engine cooling water temperature reaches a predetermined value or higher, the valve body 10a finally comes into contact with the valve seat 10b and closes the branch passage 8b. The supply of auxiliary air via the fast idling control device 10 is stopped.

On the other hand, the engine 1 of electrical equipment 21 such as headlights, brake lights, and radiator cooling fans
The first control valve 6 is used to control the supply amount of auxiliary air to respond to the electrical load, which is a relatively small load, and to accurately increase or decrease the amount of auxiliary air so that the engine speed reaches the target idle speed. It will be done. That is, the ECU 9 detects the throttle valve opening sensor 17 for each top dead center (TDC) signal of the engine.
The first control valve 6 is controlled based on the values of engine operating parameter signals supplied from the absolute pressure sensor 16 , cooling water temperature sensor 13 , engine speed sensor 14 , and atmospheric pressure sensor 23 and the electrical load status signal from the electrical device 21 . In addition to determining the operating condition in which auxiliary air should be supplied by Calculate the auxiliary air amount and therefore the valve opening duty ratio Dou _T of the first control valve 6 to eliminate the difference, and send a drive signal to the first control valve 6 to operate the first control valve 6 according to the calculated value. supply

The solenoid 6a of the first control valve 6 is energized for a valve opening time corresponding to the valve opening duty ratio Dou _T , opens the valve 6, opens the first air passage 8, and opens the first air passage 8. A fixed amount of air is supplied to the first air passage 8 and
It is supplied to the engine 1 via the intake pipe 3.

On the other hand, the ECU 9 calculates the fuel injection time Tou _T of the fuel injection valve 12 based on the above-mentioned various engine operating parameter signal values and in synchronization with the TDC signal using the formula shown below.

Tou _T = Ti × K ₁ + K ₂ ... (1) Here, Ti indicates the basic injection time, and the basic injection time Ti is in a region where the engine meets a predetermined idle operating condition, as will be described in detail later. The setting is made according to either the above-mentioned SD method or the method according to the present invention.

The correction coefficients or correction values K ₁ and K ₂ are determined by the various sensors mentioned above, that is, engine operating parameter sensors such as the intake pipe absolute pressure sensor 16, the cooling water temperature sensor 13, the Ne sensor 14, the throttle valve opening sensor 17, and the atmospheric pressure sensor 23. A correction coefficient or correction value that is calculated according to the engine operating parameter signal from the engine, and is predetermined so that various characteristics such as starting characteristics, exhaust gas characteristics, fuel efficiency characteristics, engine acceleration characteristics, etc. are optimized according to the engine operating state. It is calculated based on the calculation formula.

The ECU 9 supplies the fuel injection valve 12 with a drive signal to open the fuel injection valve 12 based on the fuel injection time Tou _T determined as described above.

Figure 2 is a diagram showing the circuit configuration inside the ECU 9 in Figure 1, and shows the engine rotation speed Ne sensor 14 in Figure 1.
The output signal is waveform-shaped by a waveform shaping circuit 901 and then supplied to a central processing unit (hereinafter referred to as "CPU") 903 as a TDC signal.
It is also supplied to the Me counter 902. The Me counter 902 counts the time interval from the input of the previous TDC signal from the engine rotation speed Ne sensor 14 to the input of the current TDC signal.
Me is proportional to the reciprocal of the engine speed Ne. Me
Counter 902 supplies this count value Me to CPU 903 via data bus 910.

After the respective output signals from the throttle valve opening sensor 17, intake pipe absolute pressure P _BA sensor 16, cooling water temperature sensor 13, and atmospheric pressure sensor 23 shown in FIG. The signals are sequentially supplied to an A/D converter 906 by a multiplexer 905. A/D converter 9
06 sequentially converts the output signals from each of the sensors described above into digital signals and supplies the digital signals to the CPU 903 via the data bus 910.

The switch 18 that opens the second control valve 6' when the air conditioner is activated, the switch 19 that opens the third control valve 6'' when the automatic transmission is engaged, and the switch 22 of the electric device 21 shown in FIG. - Each off signal is corrected to a predetermined voltage level by a level correction circuit 912, and then converted into a predetermined signal by a data input circuit 913 and sent to the CPU 900 via a data bus 910.
supplied to

The CPU 903 further uses a read-only memory (hereinafter referred to as "ROM") via a data bus 910.
907, random access memory (hereinafter referred to as "RAM") 908 and drive circuit 909, 9
11, RAM908 is connected to CPU90
3. Temporarily stores the calculation results etc. in ROM90.
7 stores control programs and the like executed by the CPU 903.

The CPU 903 determines the engine operating state according to the aforementioned various engine parameter signals and the on/off states of the switches 18, 19, and 21 according to the control program stored in the ROM 907, and opens the aforementioned first control valve 6. In addition to calculating the valve duty ratio Dou _T , the valve opening time Tou _T of the fuel injection valve 12 is calculated as will be described in detail later, and a control signal corresponding to these calculated values is sent to the drive circuit 911 and the control signal via the data bus 910. 909 respectively. The drive circuits 911 and 909 send a drive signal to open the first control valve 6 and the fuel injection valve 12 while the above-mentioned control signal is supplied to the control valve 6 and the fuel injection valve 12.
supply each.

Figure 3 is executed by the CPU 903 in Figure 2.
This is a flowchart showing a method of calculating the valve opening time Tou _T of the fuel injection valve 12. Steps 1 to 3 in FIG. 3 are for determining whether or not the engine has met a predetermined idle operating condition.
In step 1, the engine speed Ne is the predetermined speed.
It is determined whether or not the engine speed is below N _IDL (for example, 1000 rpm), and if the determination result is negative (No), the idle operation condition is not satisfied and the process immediately proceeds to step 4, which will be described later. The determination result of step 1 is positive (Yes)
If so, proceed to step 2 and calculate the intake pipe absolute pressure P _BA
It is determined whether or not the engine load is lower than the reference pressure P _BA c, that is, below the reference pressure P _BA c. This reference pressure P _BA c is the ratio (P _BA /P _A ') of the absolute pressure P _BA in the intake pipe on the downstream side of the throttle valve 5 to the absolute pressure P _A ' in the intake pipe on the upstream side of the throttle valve 5. The reference pressure P _BA c, which is set to determine whether or not the intake flow velocity becomes equal to or lower than the critical pressure ratio (0.528) at which the air flow becomes sonic, is given by the following equation.

P _BA c=P _A ′×(critical pressure ratio) =P _A ′×(2/χ+1)〓 ^/ 〓 ^-1 =0.528×P _A ……(2) Here, χ is the specific heat ratio of air (χ=1.4 ) and
Since the absolute pressure P _A ' in the intake pipe upstream of the throttle valve 5 is approximately equal to the atmospheric pressure P _A detected by the atmospheric pressure sensor 23 in FIG. The relationship between pressure P _BA c and atmospheric pressure P _A is the fourth
As shown in the figure.

If the determination result in step 2 is negative (No),
It is determined that the predetermined operating condition is not met and the process proceeds to step 4, and if affirmative (Yes), the process proceeds to step 3. In step 3, it is determined whether the valve opening _θTH of the throttle valve 5 is less than or equal to a predetermined opening _θIDLH . The reason for this determination is that when the throttle valve 5 shifts from an idling operating state in which the throttle valve 5 is in a substantially fully closed position to an accelerating operating state in which the throttle valve is rapidly opened, the engine speed and intake pipe absolute If the acceleration operation state is determined only by pressure changes, the detection of the acceleration operation state will be delayed due to the response delay of the absolute pressure sensor, etc. Therefore, the acceleration operation state is detected by the throttle valve degree, and when the acceleration operation state is detected, This is because it is necessary to calculate an appropriate amount of acceleration fuel using the SD method, which will be described later, and supply this amount of fuel to the engine. If the determination result in step 3 is negative (No), it is assumed that the predetermined idling operation condition is not satisfied, and the process proceeds to step 4; if affirmative (Yes), the process proceeds to step 6.

In step 4, which is executed when the idle operating conditions are not satisfied, the basic fuel injection time Ti is determined by the SD method. In other words, the _ECU
The basic fuel injection time Ti stored in the ROM 907 in ROM 907 is read out. Based on the basic injection time Ti thus determined, the fuel injection time Tou _T is calculated based on the equation (1) (step 5).

In step 6, which is executed when the idle operating condition is satisfied, the basic injection time Ti is determined by the method according to the present invention (hereinafter referred to as the "KMe method"), and the fuel injection time Tou _T is determined by this basic injection time Ti. is calculated (step 5).

In addition, in the determination of steps 1 to 3 above,
The discrimination value in each step is set to a different value when the engine enters and leaves the operating range where the predetermined idle operating conditions are satisfied, and
The selection of the KMe method and the SD method may have hysteresis characteristics to stabilize engine operation control.

FIG. 5 is a flowchart showing the procedure for determining the basic injection time Ti value using the KMe method executed in step 6 of FIG. First, the formula for calculating the basic injection time Ti according to the KMe method according to the present invention shown in the flowchart of FIG. 5 is derived as follows.

When the pressure downstream of a constriction such as a throttle valve provided in the intake passage is below the critical pressure shown in step 2 of FIG. 3, the flow of intake air passing through the constriction is sonic flow or blockage. As long as the opening area A of the diaphragm does not change, the air flow rate Ga(A) per unit time passing through the diaphragm remains constant. On the other hand, the fuel flow rate Gf per unit time to obtain a predetermined air-fuel ratio (A/F) ₀ during idle operation is given by Gf=Ga(A)/(A/F) ₀ (3).

The above-mentioned fuel flow rate Gf is also given by the following equation.

Gf = 2Ne/60・γf・(ΔQ/ΔTi)・Ti/1000 = γf/Me・(ΔQ/ΔTi)・Ti...(4) Here, 2Ne/60 is per unit time (sec) of a 4-cylinder engine The number of injections, γf is the specific weight of the fuel,
(ΔQ/ΔTi) is the fuel volumetric flow rate per unit valve opening time of the fuel injection valve 12, Ti is the basic injection time (msec),
Me is TDC signal pulse generation time interval (msec)
are shown respectively, and Me is determined by the engine speed Ne.
=60/2Ne. From the above equations (3) and (4), Ti=Ga(A)/(A/F) ₀・(ΔQ/ΔTi)・γf・Me is obtained, and K(A)=Ga(A)/(A /F) ₀・(ΔQ/ΔTi)・γf, Ti is expressed as Ti=K(A)・Me...(5). Since the opening area coefficient K(A) is given as a value proportional to the opening area A of the throttle section, the opening area coefficients of each of the throttle valve 5, the first to third control valves, and the fast idling control device 10 are expressed as Kθ. , K _AI c, K _A c, K _AT , K _FI, equation (5) becomes Ti=K(A)・Me=(Kθ+K _AI c+K _A c +K _AT +K _FI )Me ……(5)′ It can be rewritten.

Step 1 in Fig. 5 is to obtain the opening area coefficient value Kθ for the throttle valve 5. The Kθ value is obtained from the graph showing the relationship between the throttle valve opening _θTH and the opening area coefficient Kθ shown in Fig. 6. It will be done. More specifically, for example, predetermined values Kθ 1 to Kθ 5 are stored in advance in the ROM 907 in the ECU 9 as Kθ values corresponding to the throttle valve openings θc ₁ to θc ₅ , and the predetermined values Kθ ₁ to Kθ ₅ are stored adjacent to the actual throttle valve opening value θ _TH . ROM the two Kθ values
The opening area coefficient value Kθ corresponding to the actual throttle valve opening value _θTH is determined by reading out from 907 and performing interpolation calculation.

Next, in step 2, the opening area coefficient value Kθ of the first control valve 6 is determined.

Next, in step 2, the opening area coefficient value K _AI c of the first control valve 6 is determined. The opening area of the first control valve 6, and therefore the K _AI c value, can be determined as a function of the valve opening duty ratio Dou _T , and FIG. 7 shows the opening duty ratio Dou _T of the first control valve 6 and the opening area coefficient. K _AI
This is a graph showing a table of the relationship between c and c, and the opening area coefficient value K _AI c corresponding to the valve opening duty ratio of the first control valve 6, that is, the opening area, is calculated using the same method as the opening area coefficient Kθ of the throttle valve. is required.

In step 3, the aperture area coefficient value K _FI of the fast idling control device 10 is determined. 1st
The passage opening area of the fast idling control device 10 shown in the figure, and therefore the K _FI value, can be determined as a function of the cooling water temperature T _W , and FIG. 8 shows the relationship between the engine cooling water temperature T _W and the opening area coefficient K _FI . The opening area coefficient value K _FI of the fast idling control device 10 is determined by the same method as the opening area coefficient Kθ of the throttle valve described above.

In step 4, the opening area coefficient value K _A c of the second control valve 6' is determined. The second control valve 6' is fully open or fully closed depending on the on/off state of the switch 18 communicating with the air conditioner switch.
8 is in the on state, a predetermined value K _A c corresponding to the aperture area when fully opened is read from the ROM 907 .

Step 5 is executed when the method of the present invention is applied to an internal combustion engine equipped with an automatic transmission, in which the switch 19 indicating engagement of the automatic transmission is turned on.
The third control valve 6'' is fully opened by the ON signal of
The predetermined value K _AT corresponding to the opening area when fully opened is
Read from ROM907. The CPU 903 calculates each opening area coefficient obtained as described above using the above formula.
(5)' is added, and this sum is multiplied by the Me value supplied from the Me counter 902 to calculate the basic injection time Ti (step 6).

As described in detail above, according to the fuel injection control method for an internal combustion engine of the present invention, the amount of fuel injection is controlled in accordance with the pressure in the intake passage downstream of the throttle valve and the engine speed in medium to high load conditions of the engine. On the other hand, in a predetermined low load state where the intake flow rate passing through the throttle valve is a sonic flow, the amount of intake air passing through the throttle valve is accurately determined by a first coefficient value corresponding to the opening area of the throttle valve. Since the amount of auxiliary air passing through the control valve is detected by the second coefficient value depending on the opening area of the control valve, the total intake into the engine at this time is determined by the sum of both coefficient values. In addition to being able to accurately detect the amount of air, by using the engine speed Ne as an operating parameter, the total amount of intake air per intake stroke can be detected. Therefore, by calculating the fuel injection amount according to the detected total intake air amount per intake stroke, it is possible to inject and supply the optimum amount of fuel to the engine according to the engine load, and at the same time, it is possible to avoid expensive flow. Hunting of the engine speed during low-load operation such as idling operation can be prevented without adopting the L-dietro system that requires a meter, and driving performance can be improved.

Moreover, the detection of the opening area of the throttle valve and the opening area of the control valve is performed using existing control systems (throttle valve opening sensor, engine rotation speed sensor,
ECU, etc.) can be used as is, and together with not using the flow meter mentioned above, costs can be reduced.

Further, a plurality of auxiliary air passages are provided that open in the intake passage downstream of the throttle valve and communicate with the atmosphere,
In the case of an internal combustion engine in which a control valve is arranged in each auxiliary air passage, the second coefficient value is set to a value corresponding to the total opening area of the control valves in the operating state among the plurality of control valves. As a result, driving performance can be improved in the same way as described above.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram of a fuel injection control device for an internal combustion engine equipped with a plurality of auxiliary air amount control valves for controlling auxiliary air amount, to which the method of the present invention is applied;
The diagram shows the electronic control unit (ECU) in Figure 1.
Figure 3 is a flowchart showing the method for calculating the opening time Tou _T of the fuel injection valve. Figure 4 shows the absolute pressure in the intake passage and the sonic velocity of the intake air passing through the throttle valve. FIG. 5 is a graph showing the relationship between the standard pressure _PBAc set to determine whether the pressure is a flow or not and the atmospheric pressure _PA . Flowchart showing the procedure for determining the basic fuel injection time Ti by
Fig. 6 is a graph showing a table of the relationship between the throttle valve opening area coefficient Kθ and the throttle valve opening θ _TH , and Fig. 7 shows the same control as the opening area coefficient K _AI c of the first control valve 6 in Fig. 1. A graph showing a table of the relationship between the valve opening duty ratio Dou _T and FIG.
2 is a graph showing a table of the relationship between the opening area coefficient K _FI and the engine coolant temperature T _W of the fast idling control device shown in the figure. 1...Internal combustion engine, 3...Intake passage, 5...
Throttle valve, 6...first control valve,
6'...Second control valve, 6''...Third control valve, 8,
8', 8''...first, second and third air passages, 9...
...Electronic control unit (ECU), 10...
Fast idling control device, 12...Fuel injection valve, 14...Engine speed sensor, 16...
...Intake pipe absolute pressure sensor, 17...Throttle valve opening sensor, 23...Atmospheric pressure sensor, 903...
CPU, 907...ROM.

Claims (1)

[Scope of Claims] 1. An intake passage, a throttle valve disposed in the middle of the intake passage, an auxiliary air passage that opens into the intake passage downstream of the throttle valve and communicates with the atmosphere, and an auxiliary air passage arranged in the auxiliary air passage. A fuel injection control method for injecting and supplying a required amount of fuel to an internal combustion engine in synchronization with the rotation of the engine, the control valve comprising: , in a method for injecting and supplying to the engine an amount of fuel determined according to the pressure in the intake passage downstream of the throttle valve and the rotation speed of the engine, when the load applied to the engine is higher than a reference load; When the applied load is lower than the reference load,
a first coefficient value according to the opening area of the throttle valve;
a second coefficient value according to the opening area of the control valve;
the number of revolutions of the engine is determined, the amount of fuel is calculated according to the sum of the first and second coefficient values and the number of revolutions of the engine, and the thus calculated amount of fuel is injected and supplied to the engine. A fuel injection control method for an internal combustion engine. 2. Fuel injection control for an internal combustion engine according to claim 1, wherein the fuel amount is calculated according to a value obtained by dividing the sum of the first and second coefficient values by the engine rotation speed. Method. 3. An intake passage, a throttle valve disposed in the middle of the intake passage, a plurality of auxiliary air passages that open into the intake passage downstream of the throttle valve and communicate with the atmosphere, and a plurality of auxiliary air passages arranged in each of the auxiliary air passages. , and a plurality of control valves for controlling the amount of auxiliary air supplied to the engine through the passage, the required amount of fuel is injected and supplied to an internal combustion engine each time a pulse of a predetermined control signal representing a predetermined crank angle position occurs. A fuel injection control method, wherein when the load applied to the engine is higher than a reference load, a fuel amount determined according to the pressure in the intake passage downstream of the throttle valve and the rotation speed of the engine is injected to the engine. In the method of supplying,
When the load applied to the engine is lower than the reference load, a first coefficient value corresponding to the opening area of the throttle valve, and a first coefficient value corresponding to the total opening area of the control valves in the operating state among the plurality of control valves. 2 and the generation time interval between the previous pulse and the current pulse of the control signal, and calculate the fuel consumption according to the sum of the first and second coefficient values and the pulse generation time interval of the control signal. 1. A fuel injection control method for an internal combustion engine, comprising: calculating a fuel amount, and injecting and supplying the calculated fuel amount to the engine. 4. The internal combustion system according to claim 3, wherein the fuel amount is calculated according to a product obtained by multiplying the sum of the first and second coefficient values by the pulse generation time interval of the control signal. Engine fuel injection control method. 5. Claim 3, wherein the second coefficient value is obtained as an additive sum of coefficient values set according to the opening area of each of the control valves.
5. The fuel injection control method for an internal combustion engine according to item 4.