JPH04224247A - Control device of internal combustion engine having assist-air supply device - Google Patents

Abstract

PURPOSE:To improve assist-air effect of an assist-air supply device which supplies assist-air in the vicinty of the injection hole of a fuel injection valve approximately synchronous with fuel injection so as to promote atomization of injected fuel. CONSTITUTION:A part of intake air is led in the vicinity of the injection hole of a fuel injection valve 5 provided on the branch part of an intake manihold 4 from the upper course of a throttle valve 3 by an assist-air passage 9 through an assist-air control vector 15. Then, an intake pressure sensor 23 is arranged downstream from a throttle valve 3. An assist-air supply amount per a unit time is found out on the basis of the output of the sensor, and a correction value for expediting the injection timing of the fuel injection valve 5 is retrieved so as to correct the injection timing to be expedited by the amount of correction value.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an internal combustion engine having an assist air supply device for supplying a portion of intake air as assist air to the vicinity of the nozzle hole of a fuel injection valve provided in an intake passage.

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 to promote atomization (vaporization) (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 hole of each fuel injection valve, and the collision of the assist air with the injected fuel causes the injection. Atomizes fuel,
This improves combustion and improves exhaust performance, etc.

0004

[Problems to be Solved by the Invention] By the way, there are two methods of supplying assist air: a natural assist method in which air is jetted out based on the differential pressure between the upstream and downstream sides of the throttle valve, and a natural assist method in which air is jetted out based on the pressure difference between the upstream and downstream sides of the throttle valve. There is a supercharging assist method in which the fuel is supplied by a supercharger such as an air pump.
In the case of the natural assist method, the amount of assist air supplied changes depending on the differential pressure, and in the case of the supercharging assist method, depending on the capacity of the air pump. When the amount of assist air supplied changes, the atomization ratio of the injected fuel changes. In other words, when the amount of assist air supplied is small, atomization becomes poor. Also, in an attempt to solve this problem, it is possible to constantly inject fuel early and promote vaporization by the heat of the intake manifold and intake valve, but in order to do this,
It is necessary to calculate the fuel injection amount at an early stage, and if you calculate the fuel injection amount at an early stage, the data used for this calculation, such as intake air flow rate and engine speed, may be outdated compared to the latest data. Therefore, there was a problem in that the responsiveness deteriorated particularly during transient periods.

In view of these conventional problems, the present invention has an assist air supply device that can always obtain a good atomization state of the injected fuel without deteriorating the responsiveness during transients as much as possible. An object of the present invention is to provide a control device for an internal combustion engine.

[0006]

[Means for Solving the Problems] Therefore, as shown in FIG. 1, the present invention has a fuel injection valve in the intake passage and guides a part of intake air from upstream of the throttle valve to the injection hole of the fuel injection valve. Supply amount detection means (a) for detecting the amount of assist air supplied per unit time in an internal combustion engine having an assist air supply device nearby that supplies assist air as assist air.
and an injection timing correction means (b) for correcting the injection timing of the fuel injection valve according to the amount of assist air supplied per unit time.

[0007]

[Operation] In the above structure, the injection timing of the fuel injection valve is corrected according to the amount of assist air supplied per unit time. Specifically, when the amount of assist air supplied is small, atomization is poor, so the injection timing is corrected to inject the fuel earlier, and when the amount of assist air supplied is large, atomization is good, so the injection timing should be as early as possible. Make it. As a result, fuel can be injected at an injection timing when the injected fuel is well vaporized.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 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 an 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) is determined, and a drive pulse signal with a pulse width of this Ti is output to the fuel injection valve 5 of each cylinder independently from each other, approximately in timing with the intake stroke of each cylinder. This causes fuel injection to take place.

An assist air passage 9 is provided as an assist air supply device. The assist air passage 9 is
A portion of the intake air is guided from the assist air intake port 10 downstream of the air flow meter 2 and upstream of the throttle valve 3,
The structure is such that assist air is supplied by a pressure difference between the upstream side and the downstream side (natural assist method), and an air gallery 15 for branching is formed on the downstream side. This air gallery 15 has the same number of fuel injection valves 5 (in this example, 4 for 4 cylinders).
Assist air control valves 16 are provided, and the nozzle holes 17 of each assist air control valve 16 are connected to air inlets 21 of each fuel injection valve 5, which will be described later, through pipes 18, respectively.

As shown in FIG. 3, each fuel injection valve 5 includes a needle valve 5b inside a valve body 5a, and the nozzle hole is opened by lifting the needle valve 5b by energizing an electromagnetic coil (not shown). A cover 19 is provided surrounding the valve body 5a, and an annular passage 20 is formed between the cover 19 and the valve body 5a. Then, the pipe 18 connected to the nozzle hole 17 of the assist air control valve 16 is connected to the cover 1.
By connecting to the air inlet 21 on the side of the fuel injection valve 9, assist air is guided into the annular passage 20, and the assist air is guided by the annular passage 20 to form an annular air jet surrounding the nozzle hole 5c of the fuel injection valve 5. It is ejected from the outlet 22 and collides with the injected fuel to promote atomization of the injected fuel.

Furthermore, the assist air control valve 16 includes:
This is an electromagnetic air injection valve (injector) that has the same structure as the fuel injection valve 5, that is, it has a needle valve inside the valve body, and opens the nozzle hole and injects air by lifting the needle valve by energizing the electromagnetic coil. use. This is because it is superior in terms of responsiveness. Therefore, the assist air control valve 16 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 16 by the control unit 6, each assist air control valve 16 is controlled by outputting a drive pulse signal to each assist air control valve 16 in synchronization with the fuel injection of each fuel injection valve 5. The air control valves 16 are driven to open independently of each other. 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 16 is as shown in FIG. The control valve 16 is driven to open at a timing advanced by a predetermined period T0 from the fuel injection start timing of the fuel injection valve 5.

That is, the air injection start time is calculated by advancing the fuel injection start time by a predetermined period T0, and control is performed based on this. Note that the predetermined period T0 takes into consideration the response delay of air supply (due to piping volume), and the air injection end time may be the same as the fuel injection end time. Furthermore, as a configuration according to the present invention, an intake pressure sensor 23 is installed in the intake manifold 4, and the throttle valve 3
Negative pressure PB on the downstream side is detected. Since the upstream side of the throttle valve 3 is at atmospheric pressure, the differential pressure between the upstream side and the downstream side of the throttle valve 3 can be detected by detecting the negative pressure PB.

This is because the amount of assist air supplied is determined by the differential pressure. Next, the effect will be explained. The control unit 6 outputs a drive pulse signal to the fuel injection valves 5 of each cylinder, independently from each other, approximately in time with the intake stroke of each cylinder, and with a pulse width commensurate with the amount of intake air. Inject fuel according to the method. Note that this injection timing is subject to a correction that will be described later.

[0017] Furthermore, in advance of this, the control unit 6 outputs a drive pulse signal to the corresponding assist air control valve 16 at a time advanced by a predetermined period T0 from the fuel injection start time of each fuel injection valve 5. Then, the assist air control valve 16 is driven to open. As a result, part of the intake air can be supplied as assist air only to the fuel injection valve 5 during fuel injection near its nozzle hole 5c, and assist air can be supplied to the fuel injection valve 5 during fuel injection stop. By stopping the supply, high idle can be prevented.

Furthermore, with reference to the flowchart of FIG.
A method of correcting the injection timing according to the present invention will be explained. In step 1 (denoted as S1 in the figure; the same applies hereinafter), the cylinder to which injection is to be performed next is determined, and in step 2, it is determined whether the assist air control valve 16 corresponding to that cylinder is normal. This is done by detecting whether or not current flows through the assist air control valve 16 when the drive pulse signal is output from the control unit 6, and checking for the presence or absence of a disconnection.

If the result of the determination is normal, proceed to step 3 and calculate the assist air supply amount Qai per unit time based on the negative pressure PB detected by the intake pressure sensor 23 with reference to the map, and if it is not normal. Then, the process proceeds to step 4 and the assist air supply amount Qai per unit time is set to zero. Here, steps 3 and 4 correspond to the supply amount detection means.

[0020] Then, in step 5, a correction value C for advancing the preset injection timing is searched by referring to a map according to the assist air supply amount Qai per unit time. The correction value C is a value that becomes smaller as the assist air supply amount Qai per unit time increases. This is because when the amount of assist air Qai is large, atomization is good, so there is no need to advance the injection timing too much.

Thereafter, in step 6, the fuel injection amount Ti is calculated based on data such as the engine speed N and the intake air flow rate Q at that time, and in step 7, the injection end time is determined to be at a predetermined time in the intake stroke ( The start timing is calculated so as to be synchronized with the intake TDC. Then, in step 8, this start time is corrected to be earlier by the correction value C obtained in step 5.

Here, step 8 corresponds to injection timing correction means. This routine ends, but after this, as described above, the supply of assist air is started at a time T0 earlier than the corrected injection time. In the above embodiment, the assist air supply method is limited to the natural assist air method, but an air pump may be provided in the middle of the assist air passage 9 to actively supply assist air (supercharging assist method). In addition, the assist air passage 9 is branched in the middle, and an air pump for supercharging is provided on one side, and an electromagnetic on-off valve for switching is provided on the other, so that the natural assist method and the supercharging assist method can be used together. You can do it like this. When such a supercharging assist method is adopted, it is preferable to provide a discharge pressure sensor on the downstream side of the air pump so that the amount of assist air supplied per unit time can be detected based on the discharge pressure.

Note that the assist air supply amount Qai may be estimated from parameters representing the operating state, such as the engine speed N and the intake air flow rate Q, without providing the intake pressure sensor 23.

[0024]

As explained above, according to the present invention, the injection timing of the fuel injector is corrected according to the amount of assist air supplied per unit time, so that the atomization rate of the injected fuel is anticipated. By correcting the injection timing, it is possible to inject the fuel at a time when the injected fuel is well vaporized, instead of always injecting it early.

[0025] As a result, the assist air effect can be enhanced and the exhaust performance can be improved.

[Brief explanation of the drawing]

FIG. 1 is a functional block diagram showing the configuration of the present invention.

FIG. 2 is a system diagram of an intake system of an internal combustion engine showing an embodiment of the present invention.

FIG. 3 is a sectional view of a main part of a fuel injection valve having an air jet port.

FIG. 4 is a diagram showing the relationship between fuel injection and air injection.

FIG. 5 is a flowchart for correcting injection timing.

[Explanation of symbols]

2 Air flow meter 3 Throttle valve 4 Intake manifold
5 Fuel injection valve 5c injection hole
6 Control unit

Claims (1)

[Claims] [Claim 1] An internal combustion engine having a fuel injection valve in an intake passage and an assist air supply device that guides a part of intake air from upstream of a throttle valve and supplies it as assist air near the nozzle hole of the fuel injection valve. The present invention is characterized by providing a supply amount detection means for detecting the amount of assist air supplied per unit time, and an injection timing correction means for correcting the injection timing of the fuel injection valve according to the amount of assist air supplied per unit time. A control device for an internal combustion engine having an assist air supply device.