JPH06101484A - Swirl control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To improve combustibility of an engine by enlarging a region wherein a swirl is reinforced by means of a swirl control valve. CONSTITUTION:A control opening map wherein the control opening of a swirl control valve is previously stored according to an engine load and the rotation speed of an engine is set. The control opening map is divided into three regions of a full closed, an intermediate opening, and a full opening region, and a region wherein an opening is controlled to an intermediate value is positioned in the middle between the full opening region and the intermediate region. An opening is decided at S2 from the control opening map based on an actual engine load (a fundamental fuel injection amount Tp) and engine rotation speeds Ne and S1, and the opening of a swirl control valve is controlled at S3-S5 according to the decision.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a swirl control device for an internal combustion engine, and more particularly to a swirl control valve opening / closing control for generating swirl in a cylinder.

[0002]

2. Description of the Related Art Recently, a lean-burn engine has been proposed in which combustion is performed at an air-fuel ratio (for example, 20 to 25) which is much higher than the theoretical air-fuel ratio for the purpose of improving fuel economy. In such a lean burn engine, for example, when operating at low rotation speed and low load, fuel efficiency is improved by burning at the lean air-fuel ratio, and torque performance is emphasized during acceleration and high load to give a theoretical air-fuel ratio. As an air-fuel ratio (output air-fuel ratio) on the slightly rich side, both improvement of fuel efficiency and securing of output torque are achieved at the same time.

Further, a swirl control valve is provided in order to secure the ignition stability to the air-fuel mixture of the lean air-fuel ratio, and at the time of lean combustion, the swirl control valve is closed and a strong swirl is generated in the cylinder, whereby lean burn is performed. Some are pushing the limits. However,
Since the swirl control valve causes a large intake resistance, the swirl control valve is opened at the time of high load and high speed combustion at the output air-fuel ratio to obtain a desired engine output (see FIG. 5). .

[0004]

As described above, in the conventional art, the swirl control valve is closed in the lean air-fuel ratio region and the swirl control valve is opened in the output air-fuel ratio region. There was a demand to stabilize the combustion by strengthening the swirl by the action of the swirl control valve even at low load and low rotation side (intermediate load, intermediate rotation region) close to the lean air-fuel ratio region.

However, if the swirl control valve is controlled to be closed, the intake resistance becomes large, and the desired air amount (engine output) cannot be obtained. Therefore, in order to avoid the increase of the intake resistance, the open air-fuel ratio region is opened. Since the control is performed, there is a problem in that the swirl strengthening request cannot be met. Also, in the operating region where the required intake air amount is large, the swirl control valve cannot be closed to secure the air amount, and therefore a strong swirl cannot be generated, so the lean air-fuel ratio cannot be controlled. It can also be said that the lean air-fuel ratio region was limited to the region where the required air amount was small.

The present invention has been made in view of the above problems, and it is possible to improve the combustibility of an internal combustion engine by securing a necessary amount of air and expanding the region in which the swirl control valve can obtain the effect of strengthening the swirl. With the goal.

[0007]

Therefore, a swirl control system for an internal combustion engine according to the present invention is constructed as shown in FIG. In FIG. 1, a swirl control valve is provided in the engine intake system and controls swirl generation in the cylinder.

Further, the control opening storage means stores in advance a region for controlling the swirl control valve to be fully opened, a region for controlling the intermediate opening, and a region to be fully closed according to the engine load and the engine speed. is doing. In addition, the operating condition detection means detects the engine load and the engine rotation speed, respectively.

The opening / closing control means drives the opening / closing of the swirl control valve so that the control opening is obtained from the control opening storage means based on the engine load and the engine speed detected by the operating condition detecting means. .

[0010]

According to this structure, whether the swirl control valve is to be fully opened, an intermediate opening, or a fully closed state is stored in advance in accordance with the engine load and the engine rotation speed. Which opening state should be used is determined according to the load and engine speed.

Then, the swirl control valve is actually controlled to be opened / closed based on the opening determined based on the engine load and the engine rotation speed, so that the swirl control valve is fully opened, intermediately opened, or fully closed.

[0012]

EXAMPLES Examples of the present invention will be described below. In FIG. 2 showing an embodiment, air is taken into the internal combustion engine 1 through a throttle valve 2, an intake manifold 3 and an intake valve 4. At each branch portion of the intake manifold 3, a fuel injection valve 5 is provided for each cylinder. The fuel injection valve 5 is an electromagnetic fuel injection valve that is energized by a solenoid to open the valve, is deenergized and is closed, and is energized by an injection pulse signal from a control unit 16 described later to open the valve. Fuel, which is pumped from a fuel pump (not shown) and adjusted to a predetermined pressure by a pressure regulator, is injected and supplied to the engine 1.

A spark plug 6 is provided in each combustion chamber of the engine 1 to spark-ignite and ignite and burn the air-fuel mixture. Exhaust gas is discharged from the engine 1 through the exhaust valve 7, the exhaust manifold 8a, the exhaust duct 8b, and the catalyst 9. The control unit 16 includes a CPU, ROM, R
A microcomputer including an AM, A / D converter, an input / output interface, etc. is provided, receives input signals from various sensors, and calculates a fuel injection amount Ti by the fuel injection valve 5 as described later. The operation of the fuel injection valve 5 is controlled based on the fuel injection amount Ti.

As the various sensors, an air flow meter 10 for detecting the intake air flow rate Q of the engine, a crank angle sensor 11 for extracting a rotation signal from a crank shaft or a cam shaft,
Further, an oxygen sensor 12 for detecting the air-fuel ratio of the engine intake air-fuel mixture based on the oxygen concentration in the exhaust gas is provided. still,
By measuring the cycle of the detection signal output from the crank angle sensor 11 at every predetermined crank angle or the number of detection signals generated within a predetermined time, the engine rotation speed Ne is measured.
Can be calculated.

Here, the CPU of the microcomputer incorporated in the control unit 16 has the engine load and the engine speed N represented by the basic fuel injection amount Tp in advance.
Equipped with an air-fuel ratio map in which a target air-fuel ratio is set according to e, and the intake air flow rate Q and the engine speed Ne to form a mixture of the target air-fuel ratio stored in this air-fuel ratio map.
The basic fuel injection amount Tp (= K × Q /
Ne; K is a constant) while the basic fuel injection amount T is calculated.
Various corrections (including air-fuel ratio feedback control using the oxygen sensor 12) depending on engine operating conditions are applied to p to calculate the final fuel injection amount Ti. Then, an injection pulse signal having a pulse width corresponding to the fuel injection amount Ti is output to each fuel injection valve 5 in synchronization with the intake stroke of each cylinder.

In the air-fuel ratio map, a lean air-fuel ratio (for example, 20 to 25) which is much higher than the theoretical air-fuel ratio (14.7) is set as the target air-fuel ratio in the low load / low rotation operation region, and the lean combustion is set. The high load / high rotation operating region other than the operating region is the output combustion operating region in which the theoretical air-fuel ratio or an air-fuel ratio slightly smaller than the theoretical air-fuel ratio (for example, an output mixture ratio of about 13) is set as the target air-fuel ratio. .

Further, in the engine 1 of this embodiment, a swirl control valve (hereinafter abbreviated as SCV) 13 is provided at each intake port portion of the intake manifold 3. The SCV13 is a butterfly-type throttle valve having a notch. When the SCV13 is closed to adjust the flow rate, a swift flow creates a swirl in the cylinder. In addition, it is possible to improve the ignition stability during lean combustion.

A diaphragm 14 is provided as an actuator for driving the SCV 13 to open and close, and the introduction of engine negative pressure into the pressure chamber of the diaphragm 14 is controlled by an electromagnetic three-way switching valve 15 to control the SC.
V13 can be driven to open and close, and the SCV13 can also be controlled to an intermediate opening by controlling the duty of the three-way switching valve 15.

A motor may be used as an actuator for driving the SCV 13 to open and close. The three-way switching valve 15 is controlled by a control unit 16,
16 determines the opening of the SCV 13 as shown in the flowchart of FIG. 3 described later, and outputs a control signal corresponding to the opening to 3
By outputting to the direction switching valve 15, the opening degree of the SCV 13 is controlled.

In the flowchart of FIG. 3, first, in step 1 (denoted as S1 in the figure, the same applies hereinafter),
The basic fuel injection amount Tp representing the engine load and the engine rotation speed Ne are read. At the next step 2, the opening degree of the SCV 13 is determined by referring to the opening / closing control map of the SCV 13 stored in the control unit 12 in advance.

As shown in FIG. 4, the opening / closing control map shows the engine load (basic fuel injection amount Tp) and the engine speed N.
The three operating regions divided based on e are a fully closed region, an intermediate opening region, and a fully closed region, respectively. The fully closed region corresponds to the lean burn operation region in the air-fuel ratio map, and the SCV 13 is closed during lean burn to generate a strong swirl, thereby improving ignition stability with respect to the lean air-fuel mixture.

On the other hand, the output mixture ratio region in the air-fuel ratio map is divided into an intermediate opening region and a fully closed region, and the high load /
On the high rotation side, the SCV 13 is fully opened to avoid an increase in intake resistance and a required output can be secured, but an intermediate opening area is provided between the fully open area and the fully closed area. That is, even in the output mixture ratio region, in the region of relatively low load and low rotation, the SCV 13 is not controlled to be fully opened, but is controlled to an intermediate opening degree.
It is possible to improve the combustibility by strengthening the swirl while avoiding a decrease in output due to an increase in intake resistance.

Since the opening / closing control map is stored in the control unit 16 as described above, the control unit 16 has a function as a control opening storage means,
Further, since the engine load is represented by the basic fuel injection amount Tp, the operating condition detecting means in this embodiment corresponds to the air flow meter 10 and the crank angle sensor 11. In step 2, the opening degree of the SCV 13 is determined by referring to the opening / closing control map based on the current engine load and the engine rotation speed Ne, depending on the determination results of the fully closed region, the intermediate opening region, and the fully opened region. , Step 3, 4 or 5, and outputs a control signal corresponding to the opening degree of the opening / closing control map to the three-way switching valve 15
13 is controlled to the opening degree of the opening / closing control map.

The above steps 2 to 5 show the function of the control unit 16 as opening / closing control means. As described above, according to the present embodiment, in the low load / low rotation region where the lean burn is executed, the SCV 13 is fully closed to generate a strong swirl, so that the ignition stability for the lean air-fuel mixture is enhanced and the lean burn limit is reached. Can be increased. On the other hand, in the output mixture ratio region, the SCV13 is fully opened to avoid a decrease in output due to an increase in intake resistance. However, even in the output mixture ratio region, the SCV13 is set to an intermediate value in a relatively low load / low rotation region. Opening degree is controlled, S
While avoiding an increase in intake resistance due to CV13, the effect of swirl strengthening due to SCV13 can be obtained to some extent to improve combustibility.

In other words, in the region where the SCV 13 is controlled to the intermediate opening in this embodiment, there is a possibility that the required air amount cannot be secured if the SCV 13 is controlled to be fully closed, but it is the region where the swirl is to be strengthened by the action of the SCV 13. Yes, by controlling the SCV13 to an intermediate opening, the required air volume is secured and
Although the effect is less than when fully closed, the effect of SCV13 swirl strengthening was obtained, and it was possible to satisfy the contradictory requirements of securing air volume and swirl strength to some extent at the same time.

In this embodiment, the air-fuel ratio of the intake air-fuel mixture is controlled to be near the stoichiometric air-fuel ratio in the operating region where the SCV13 is controlled to the intermediate opening, but it is also possible to control it to the intermediate opening. Since the effect of improving combustibility by strengthening the swirl is obtained, lean combustion is performed in both the fully closed control region and the intermediate opening control region of SCV13, or the fully closed control is performed in the intermediate opening control region. Lean combustion may be performed with an air-fuel ratio smaller than the region.

Further, the area for controlling the intermediate opening may be divided into a plurality of areas depending on the level of the required air amount, and the opening of the SCV 13 may be gradually increased as the closed area approaches the fully open area.

[0028]

As described above, according to the present invention, in the intermediate region between the region where the swirl control valve is fully closed and the region where the swirl control valve is fully opened, the intermediate opening is controlled to secure the air amount. At the same time, since the effect of strengthening the swirl is obtained to some extent, there is an effect that the combustibility in the intermediate region can be improved.

[Brief description of drawings]

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

FIG. 2 is a system schematic diagram showing an embodiment of the present invention.

FIG. 3 is a flowchart showing SCV opening control in the embodiment.

FIG. 4 is a diagram showing an SCV control opening map in the embodiment.

FIG. 5 is a diagram showing a conventional SCV control opening map.

[Explanation of symbols]

 1 engine 2 throttle valve 5 fuel injection valve 10 air flow meter 11 crank angle sensor 13 swirl control valve (SCV) 14 diaphragm 15 3 direction switching valve 16 control unit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masao Nakamura 1671, Kasukawa-cho, Isesaki-shi, Gunma 1 NIPPON ELECTRIC EQUIPMENT CO., LTD. Equipment Co., Ltd. (72) Inventor Yoshito Ino, 1671 Kasukawa-cho, Isesaki-shi, Gunma Nippon Electric Equipment Co., Ltd. (72) Hideo Kato 1671 1 Kasukawa-cho, Isesaki-shi, Gunma Nippon Electric Equipment Co., Ltd. Within

Claims (1)

[Claims] 1. A swirl control valve provided in an engine intake system for controlling swirl generation in a cylinder; a region for controlling the swirl control valve to fully open, a region for controlling an intermediate opening and a region for fully closing. Is stored in advance according to the engine load and the engine rotation speed, the operating condition detection means for detecting the engine load and the engine rotation speed respectively, and the engine load and the engine load detected by the operation condition detection means. A swirl control device for an internal combustion engine, comprising: an opening / closing control unit that drives the swirl control valve to open and close so as to achieve a control opening determined from the control opening storage unit based on an engine rotation speed.