JPH04241758A - Fuel injection amount control device for internal combustion engine provided with assist air supply device - Google Patents

Abstract

PURPOSE:To improve control accuracy of air-fuel ratio in the case of supplying assist air for atomization of injection fuel from a fuel injection valve. CONSTITUTION:After a fuel injection amount Ti is calculated(in step S1), assist air injection time Taa is calculated(in step S2), and based on this air infection time Taa, an assist air amount is detected. A correction amount is calculated (in step S3) based on the assist air amount. At this time, the assist air amount to each fuel injection valve is divided by a predetermined proportion into a self cylinder intake amount and the other cylinder intake amount to respectively calculate the assist air amount sucked to each cylinder, and based on this calculation, a cylinder correction amount Tai(x) is calculated. An individual cylinder correction amount Tai(x) is added to the fuel injection amount Ti to calculate(in step S4) the final fuel injection amount Tie. &ZS1: calculate Ti, S2: calculate air injection time Taa, S3: calculate individual cylinder correction amount Tai(x)

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection amount control device for an internal combustion engine, which includes an assist air supply device that supplies a portion of intake air as assist air to the vicinity of the nozzle of a fuel injection valve.

0002

[Prior Art] In an internal combustion engine having an electronically controlled fuel injection device, an electromagnetic fuel injection valve is provided for each cylinder in the branch part of the intake manifold or the intake port to perform fuel injection. Some are equipped with an assist air supply device for atomization (promotion of atomization) (see Japanese Patent Publication No. 64-9465, Utility Model Publication No. 63-18767, etc.).

[0003] In this system, a part of the intake air is guided from upstream of the throttle valve through an assist air passage, and is supplied as assist air near the nozzle of each fuel injection valve.The collision of the assist air with the injected fuel causes the injected fuel to This makes it possible to improve combustion and improve exhaust purification performance.

0004

By the way, in an internal combustion engine having an electronically controlled fuel injection device, an air flow meter is provided upstream of the throttle valve to measure the intake air flow rate Q, and based on this, the basic fuel injection amount Tp is determined. =K×Q/N
(K is a constant, N is the engine speed), and then various corrections are made to calculate the fuel injection amount (fuel injection time) Ti = Tp
×COEF (COEF is various correction coefficients) is determined, and a drive pulse signal with a pulse width of this Ti is output to the fuel injection valve of each cylinder independently of each other to perform fuel injection and adjust the air-fuel ratio. It's in control.

[0005] Therefore, the supply of assist air causes errors in air amount measurement as described below, which causes deterioration in air-fuel ratio control accuracy. When the assist air intake is upstream of the air flow meter, the intake air flow rate Q measured by the air flow meter does not include any assist air, and the unmeasured assist air directly causes deterioration of air-fuel ratio control accuracy.

When the assist air intake is downstream of the air flow meter, the intake air flow rate Q including the assist air is measured by the air flow meter. Although there is a time difference between the amount of air flowing through the intake passage and the amount of assist air until it is taken into the engine, it is difficult to separate them, and this causes deterioration in the accuracy of air-fuel ratio control.

In view of these conventional problems, the present invention is based on the premise that the assist air intake port is placed upstream of the air flow meter, and it is possible to prevent deterioration of air-fuel ratio control accuracy regardless of the supply of assist air. The purpose is to do so.

[0008]

[Means for Solving the Problems] Therefore, the present invention provides a fuel injection valve for each cylinder in a branch portion of an intake manifold or an intake port, and also injects a portion of intake air from upstream of a throttle valve and upstream of an air flow meter. In an internal combustion engine equipped with an assist air supply device that guides and supplies assist air to the vicinity of the nozzle of each fuel injection valve, as shown in FIG. Configure.

A. Assist air amount detection means C. for detecting the amount of assist air supplied by the assist air supply device; A fuel injection amount correction means for correcting the fuel injection amount by the fuel injection valve calculated based on the signal from the air flow meter by an assist air amount, or as shown in FIG. 2, the following means A, B, C. and constitutes a fuel injection amount control device (2).

A. Assist air amount detection means B for detecting the amount of assist air supplied to each of the fuel injection valves by the assist air supply device. C. cylinder-specific intake amount calculating means for dividing the amount of assist air into each fuel injection valve into the amount taken into the own cylinder and the amount taken into other cylinders at a predetermined ratio, and calculating the amount of assist air taken into each cylinder; Fuel injection amount correction means for correcting the amount of fuel injection by each fuel injection valve calculated based on the signal from the air flow meter by the amount of assist air taken into each cylinder; It is preferable to set the ratio with the intake air amount based on the assist air supply timing.

[0011]

[Operation] In the device configuration of (1) above, by detecting the amount of assist air by the assist air supply device and correcting the amount of fuel injection of the fuel injection valve based on this,
Improves air-fuel ratio control accuracy. In the device configuration (2) above, the assist air supply device detects the amount of assist air supplied to each fuel injection valve, but the amount of assist air supplied to each fuel injection valve is not necessarily the amount of assist air sucked into its own cylinder. Since the assist air amount to each fuel injection valve is divided into the own cylinder intake and the other cylinder intake at a predetermined ratio, the assist air intake to each cylinder is Calculate each amount of air. Therefore, by correcting the fuel injection amount of each fuel injection valve based on the calculated amount of assist air taken into each cylinder, the accuracy of air-fuel ratio control can be further improved.

[0012] The reason why the ratio between the intake amount of the own cylinder and the intake amount of other cylinders is set by the assist air supply timing is because as this timing becomes earlier than the intake valve opening timing, the amount of air taken into other cylinders increases. be.

[0013]

Embodiment An embodiment of the present invention will be described below with reference to FIGS. 3 to 7. FIG. 3 shows a system diagram of an intake system of an internal combustion engine. After passing through an air flow meter 2, air from the air cleaner 1 is sucked in under the control of a throttle valve 3 that is linked to an accelerator pedal, and reaches an intake manifold 4. Then, at the branch portion or intake port, the mixed fuel is mixed with the fuel injected from the fuel injection valve 5 provided for each cylinder, and is sucked into the cylinder of the engine.

The fuel injection valve 5 is an electromagnetic fuel injection valve (injector) that opens when an electromagnetic coil is energized and closes when the energization is stopped, and opens when energized by a drive pulse signal from the control unit 6. The fuel in the fuel gallery 8 is injected by a fuel pump (not shown) and regulated to a predetermined pressure by the pressure regulator 7.

Here, the control unit 6 uses a built-in microcomputer to determine the basic fuel injection amount Tp=K×Q/N (K is a constant, N is the engine The rotational speed) is calculated, various corrections are made to this, and the fuel injection amount Ti=T
p×COEF (COEF is various correction coefficients), and further calculate the correction amount Ta for each cylinder based on the amount of assist air, which will be described later.
i(x) is added to determine the final fuel injection amount Tie, and the timing is adjusted to the intake stroke of each cylinder independently for the fuel injection valve 5 of each cylinder. By outputting a drive pulse signal having a pulse width of this Tie so as to be near the intake TDC, fuel injection is performed in a so-called sequential injection method. The reason why the fuel injection end timing is set near the intake TDC is to prevent the injected fuel from being directly sucked into the cylinder and promote atomization of the fuel.

An assist air passage 9 is provided as an assist air supply device. The assist air passage 9 is
It is configured to supply assist air by the pressure difference between the upstream side and the downstream side (natural assist method), and a part of the intake air is guided from the assist air intake port 10 upstream of the throttle valve 3 and upstream of the air flow meter 2. This leads to an air gallery 11 for branching. This air gallery 11 is provided with the same number of assist air control valves 12 as the fuel injection valves 5 (four for four cylinders in this example), and the nozzle 13 of each assist air control valve 12 is
are connected by pipes 14 to air inlet ports 17 of each fuel injection valve 5, which will be described later.

As shown in FIG. 4, each fuel injection valve 5 includes a needle valve 5b in a valve body 5a, and a nozzle 5c is opened by lifting the needle valve 5b by energizing an electromagnetic coil (not shown). A cover 15 is provided surrounding the valve body 5a, and an annular passage 16 is formed between the cover 15 and the valve body 5a. Then, the pipe 14 connected to the nozzle 13 of the assist air control valve 12 is connected to the cover 1.
By connecting to the air inlet 17 on the side of the fuel injection valve 5, assist air is introduced into the annular passage 16, and the annular air outlet is connected to the annular passage 16 to guide the assist air and surround the injection port 5c of the fuel injection valve 5. 18 and collides with the injected fuel to promote atomization of the injected fuel.

Furthermore, the assist air control valve 12 includes:
Uses an electromagnetic air injection valve (injector) that has the same structure as the fuel injection valve 5, that is, has a needle valve inside the valve body, and opens the nozzle and injects air by lifting the needle valve by energizing the electromagnetic coil. do. This is because it is superior in terms of responsiveness. Therefore, the assist air control valve 12 is also energized and opened by the drive pulse signal output from the control unit 6.

To explain the control of the assist air control valves 12 by the control unit 6, each assist air control valve 12 is controlled by outputting a drive pulse signal to each assist air control valve 12 in synchronization with the fuel injection of each fuel injection valve 5. The air control valves 12 are driven to open independently of each other. As a result, part of the intake air can be injected and supplied as assist air only to the fuel injection valve 5 that is injecting fuel into the vicinity of its nozzle 5c, and assist air can be supplied to the fuel injection valve 5 that is not injecting fuel. By stopping the supply, high idle can be prevented.

However, the relationship between the drive pulse signal (fuel injection) to the fuel injection valve 5 of a certain cylinder and the drive pulse signal (air injection) to the corresponding assist air control valve 12 is shown in FIG.
As shown in the figure, the assist air control valve 12 is driven to open at a predetermined time T0 advance from the fuel injection start time of the fuel injection valve 5. This predetermined time T0 takes into consideration the response delay (by piping volume) of air injection. Note that the air injection end time may be the same as the fuel injection end time.

Next, correction of the fuel injection amount based on the assist air amount will be explained. FIG. 6 is a flowchart of the fuel injection amount calculation routine. In step 1 (marked as S1 in the figure, the same applies hereafter), the fuel injection amount Ti (Tp=K
×Q/N, Ti=Tp×COEF). In step 2, assist air injection time Taa=Ti+T0
Calculate.

In step 3, a cylinder-specific correction amount calculation routine shown in FIG. 7, which will be described later, is executed to calculate the cylinder-specific correction amount Tai(x
) is calculated. In step 4, the cylinder-specific correction amount Tai(x) is added to the fuel injection amount Ti to calculate the final fuel injection amount Tie=Ti+Tai(x). Next, the cylinder-by-cylinder correction amount calculation routine shown in FIG. 7 will be explained.

In step 11, the injection cylinder is determined, and
Branches to steps 12 to 15, and in the case of the first cylinder, x=1
, for the second cylinder, x=2, for the third cylinder, x=3,
In the case of the fourth cylinder, x=4 is set. After these steps, proceed to step 16. In step 16, the assist air injection time Taa calculated in step 2 is calculated as shown in the following equation.
Based on this, a correction amount Tai0 corresponding to the amount of assist air to the fuel injection valve is calculated by multiplying this by various coefficients.

Tai0=Taa×KTai×KTA×KPB where,
KTai is the reference coefficient, KTA is the intake air temperature sensor 19 (Fig. 3
), a correction coefficient based on the intake air temperature detected by
is a correction coefficient based on the intake manifold negative pressure (differential pressure across the throttle valve) detected by the intake pressure sensor (FIG. 3). In other words, the amount of assist air to the fuel injection valve is calculated from the assist air injection time, the assist air temperature (intake temperature), and the assist air pressure (differential pressure before and after the throttle valve), and the corresponding correction amount for the fuel injection amount is calculated. It is calculating.

In step 17, based on the assist air injection timing, the own cylinder intake rate DT is determined with reference to the map.
Set ai by searching. This own cylinder intake rate DTai
In this case, the amount of assist air to the fuel injection valve does not necessarily match the amount of assist air sucked into the injection cylinder, and since it is also sucked into other cylinders, the amount of assist air to the fuel injection valve is equal to the amount sucked into the own cylinder. This is the ratio of the amount of air taken into the own cylinder to the amount of assist air when divided into the amount of air taken into other cylinders. Here, assuming that the earlier the assist air injection timing is, the more time it takes for the intake valve to open, the amount of air inhaled into other cylinders will increase. The smaller the rate DTai is and the later the assist air injection timing is, the larger the own cylinder intake rate DTai is set.

In step 18, as shown in the following equation, the correction amount Tai0 corresponding to the amount of assist air to the fuel injection valve is multiplied by the own cylinder suction rate DTai, and then the other cylinder assist air amount Ta accumulated as described later is calculated. (x) is added to obtain the correction amount (correction amount for each cylinder) Tai(x) corresponding to the amount of assist air sucked into the injection cylinder (intake amount for each cylinder)
Calculate.

Tai(x)=Tai0×DTai+Ta(x)
In step 19, the amount of used assist air from other cylinders T
Clear a(x). In step 20, the value of x is determined and the process branches to steps 21-24. For example x=
1 (first cylinder), proceed to step 21, and
Regarding the 4th cylinder, other cylinder assist air portion Ta(2),
In order to integrate Ta(3) and Ta(4), y=2
, 3, 4.

After that, proceed to step 25 and set y=2,
Regarding 3 and 4, the other cylinder assist air portion Ta(y) is integrated as shown in the following equation. Ta(y) = Ta(y) +Tai0×(1-DTa
i)/3, that is, the correction amount Tai0 corresponding to the amount of assist air to the fuel injection valve and the intake rate of other cylinders (1-DTai)
Multiply this value by 1/3 and then integrate the value.

As described above, on the premise that the assist air intake port 10 is disposed upstream of the air flow meter 2, the accuracy of air-fuel ratio control can be improved regardless of the supply of assist air. Here, steps 2 and 16 correspond to the assist air amount detection means, and steps 17 and 1
8 (and 19 to 25) corresponds to cylinder-specific intake amount calculation means, and step 4 corresponds to fuel injection amount correction means.

In the above embodiment, the assist air is supplied by the pressure difference between the upstream side and the downstream side of the assist air passage 9 (natural assist system). A configuration may be adopted in which a supercharger such as an air pump is provided to actively supply assist air (supercharging assist method). In the supercharging assist method, when calculating the amount of assist air, when correcting the amount of assist air using the assist air pressure, the discharge pressure of the air pump, etc. is directly or indirectly detected, and this discharge pressure is It may be corrected using the pressure (or the differential pressure between this and the intake manifold negative pressure).

[0031] Furthermore, an assist air passage for a natural assist type and an assist air passage for a supercharged assist type are arranged side by side,
It may be possible to selectively switch to use the natural assist type assist air passage when the load is low and to use the supercharged assist type assist air passage when the load is high.

[0032]

[Effects of the Invention] As explained above, according to the present invention, by correcting the fuel injection amount according to the amount of assist air, it is possible to reduce the error due to the amount of assist air, and the accuracy of air-fuel ratio control is improved. do. In addition, the amount of assist air to each fuel injection valve is divided into the amount taken into its own cylinder and the amount taken into other cylinders at a predetermined ratio, and the amount of assist air taken into each cylinder is calculated respectively. By correcting the fuel injection amount of each fuel injection valve according to the intake amount of assist air, the accuracy of air-fuel ratio control is further improved.

Furthermore, by setting this ratio based on the assist air supply timing, the calculation becomes accurate and the air-fuel ratio control accuracy is further improved.

[Brief explanation of the drawing]

[Fig. 1] Functional block diagram showing the first configuration of the present invention

[Fig. 2] Functional block diagram showing the second configuration of the present invention

[Fig. 3] System diagram of an intake system of an internal combustion engine showing an embodiment of the present invention

[Figure 4] Cross-sectional view of essential parts of a fuel injection valve with an air jet port

[Figure 5] Diagram showing the relationship between fuel injection and air injection

[
Figure 6: Flowchart of fuel injection amount calculation routine

[
Figure 7: Flowchart of cylinder-specific correction amount calculation routine

[Explanation of symbols]

2 Air flow meter 3 Throttle valve 4 Intake manifold 5 Fuel injection valve 5c spout 6 Control unit 9 Assist air passage 10 Assist air intake 12 Assist air control valve 18 Air outlet

Claims (3)

[Claims] Claim 1: A fuel injection valve is provided for each cylinder in a branch part of an intake manifold or an intake port, and a portion of intake air is guided from upstream of a throttle valve and upstream of an air flow meter to assist near the nozzle of each fuel injection valve. In an internal combustion engine equipped with an assist air supply device that supplies air, the assist air amount detection means detects the amount of assist air supplied by the assist air supply device, and the fuel injection valve is operated based on a signal from the air flow meter. A fuel injection amount control device for an internal combustion engine equipped with an assist air supply device, characterized in that the fuel injection amount correction means corrects the fuel injection amount based on the amount of assist air. [Claim 2] A fuel injection valve is provided for each cylinder in a branch part of an intake manifold or an intake port, and a part of the intake air is guided from upstream of the throttle valve and upstream of the air flow meter to assist near the nozzle of each fuel injection valve. In an internal combustion engine equipped with an assist air supply device that supplies air as air, an assist air amount detection unit that detects the amount of assist air supplied to each of the fuel injection valves by the assist air supply device; Divide the amount into the intake of the own cylinder and the intake of other cylinders at a predetermined ratio,
cylinder-specific intake amount calculation means for calculating the amount of assist air taken into each cylinder, and the amount of fuel injected by each fuel injection valve calculated based on the signal from the air flow meter, and the amount of assist air taken into each cylinder. What is claimed is: 1. A fuel injection amount control device for an internal combustion engine, comprising: fuel injection amount correction means for correcting each amount based on the amount of air. 3. A fuel injection amount control device for an internal combustion engine equipped with an assist air supply device according to claim 2, wherein the ratio is set based on assist air supply timing.