JP2004190532A - Cylinder direct injection spark ignition engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To ignite in the center of an air-fuel mixture mass under both a stratified high load condition and a stratified low load condition in a cylinder direct injection spark ignition engine. <P>SOLUTION: This cylinder direct injection spark ignition engine is provided with a spark plug 14a for igniting in the bottom surface vicinity of a piston cavity 4a and a spark plug 14b for igniting in the center of a combustion chamber 6. Ignition is performed by the spark plug 14a under the stratified low load condition of forming a small air-fuel mixture mass in the bottom surface vicinity of the piston cavity 4a, and the ignition is performed by the spark plug 14b under the stratified high load condition of forming a large air-fuel mixture mass in an upper part of the piston cavity 4a. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a direct injection type spark ignition engine having a fuel injection valve for directly injecting fuel into a combustion chamber, and more particularly to a technique for igniting at different positions in a combustion chamber according to operating conditions.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, an in-cylinder direct injection type spark ignition engine having a configuration including a plurality of spark plugs is disclosed in Japanese Patent Application Laid-Open Publication No. H11-157421.
[0003]
In this engine, a plurality of spark plugs are provided in a region where a combustible air-fuel mixture flows in an upper portion of a cylinder, and which spark plug is operated according to the load and rotation of the engine is determined.
[0004]
[Patent Document 1]
JP-A-2002-147242 [0005]
[Problems to be solved by the invention]
However, although Patent Literature 1 discloses a configuration in which a plurality of spark plugs are provided in a region where a combustible air-fuel mixture flows in an upper portion of a cylinder, for example, generation of a fuel-air mixture due to a change in engine load during stratified combustion Regarding the change in position, it is difficult to perform ignition at the optimum position unless the position of the spark plug in the combustion chamber and the relative position between the spark plugs are specified more specifically, and the fuel consumption and exhaust emission are sufficiently reduced. There was a problem that it could not be improved.
[0006]
The present invention has been made in view of the above problems, and has as its object to provide an in-cylinder direct injection spark ignition engine that can perform ignition at an optimum ignition position in response to a change in operating conditions. .
[0007]
[Means for Solving the Problems]
Therefore, the in-cylinder direct injection spark ignition engine according to the present invention has a configuration in which a plurality of ignition positions by the ignition plug are arranged at different heights in the combustion chamber, and the ignition is performed at different ignition positions according to the operating conditions.
[0008]
【The invention's effect】
According to the above configuration, when the optimum ignition position changes in the vertical direction in the combustion chamber depending on the operation condition, it is possible to select the optimum ignition position for each operation condition, and it is possible to improve fuel efficiency and exhaust emission. .
[0009]
In the present application, the vertical direction of the combustion chamber is the cylinder axis direction, and the side far from the piston crown is defined as the upper side of the combustion chamber, and the side closer to the piston crown is defined as the lower side of the combustion chamber.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a configuration diagram of a direct injection type spark ignition engine according to the first embodiment.
[0011]
In FIG. 1, a piston 4 is inserted into a cylinder 3 formed in a cylinder block 2 of the internal combustion engine 1 so as to be able to reciprocate.
The cylinder head 5 forms a pent roof type combustion chamber 6, and an intake port 7 and an exhaust port 8 are formed in the cylinder head 5.
[0012]
The intake port 7 is provided with an intake valve 10 driven to be opened and closed by an intake valve cam 9, and the exhaust port 8 is provided with an exhaust valve 12 driven to be opened and closed by an exhaust valve cam 11. .
[0013]
A fuel injection valve 13 is provided below the intake port 7, and the fuel injection valve 13 injects fuel directly into the combustion chamber 6.
The stratified mixture is generated in the combustion chamber 6 by receiving the fuel spray from the fuel injection valve 13 and advancing the fuel spray toward the upper part of the combustion chamber 6 on the crown surface of the piston 4. A cavity 4a is formed.
[0014]
Further, two ignition plugs 14a and 14b are provided at a radially central portion of the combustion chamber 6.
The electrode of the ignition plug 14a is elongated, and a plug gap (ignition position) at the tip is disposed below the combustion chamber 6 so that spark discharge occurs near the bottom surface of the cavity 4a.
[0015]
On the other hand, the plug gap of the ignition plug 14b is disposed above the plug gap of the ignition plug 14a, and is set so that spark discharge occurs in the radial and vertical centers of the combustion chamber 6.
[0016]
In other words, the ignition positions of the two spark plugs 14a and 14b are arranged near the center in the radial direction of the cylinder, but at different heights in the vertical direction of the combustion chamber 6 (cylinder axial direction). Will be arranged.
[0017]
Detection signals from a load sensor 16 for detecting an engine load, a rotation sensor 17 for detecting an engine rotation speed, and the like are input to a control unit 15 containing a microcomputer, and based on these detection signals, the fuel injection valve is used. 13 and the ignition by the spark plugs 14a and 14b.
[0018]
Each of the two spark plugs 14a and 14b has an ignition coil and a power transistor, so that ignition can be controlled independently.
Here, the engine 1 stratifies the mixture in the combustion chamber 6 by fuel injection in the compression stroke to perform combustion, and homogenizes the mixture in the combustion chamber 6 by fuel injection in the intake stroke. The operation is switched to homogeneous operation in which combustion is performed.
[0019]
Under the low load condition during the stratified operation, as shown in FIG. 2 (A), an air-fuel mixture having a small combustible air-fuel ratio is formed near the bottom surface of the cavity 4a, that is, at a position below the combustion chamber 6.
[0020]
Therefore, under low load conditions during stratified operation, no flammable mixture exists near the plug gap of the ignition plug 14b, but exists only around the plug gap (ignition position) of the ignition plug 14a. become.
[0021]
Therefore, the control unit 15 energizes only the ignition coil on the ignition plug 14a side so that the air-fuel mixture is ignited by the ignition plug 14a provided with a plug gap near the bottom surface of the cavity 4a.
[0022]
On the other hand, under a high load condition during the stratification operation, a mixed air mass is formed using substantially the entire cavity 4a, and as a result, as shown in FIG. The air mass spreads and the formed air mass is larger than at the time of low load, and its center is displaced above the combustion chamber 6 than at the time of low load.
[0023]
In addition, during the homogeneous operation, a uniform air-fuel mixture is formed in the combustion chamber.
Therefore, under the high load condition during the homogeneous operation and the stratified operation, the control unit 15 ignites the air-fuel mixture by the spark plug 14b having a plug gap disposed in the center of the combustion chamber 6 in the radial and vertical directions. In order to cause this, only the ignition coil on the ignition plug 14b side is energized.
[0024]
As described above, by providing the two spark plugs 14a and 14b having different ignition positions at different heights, even if the size of the air-fuel mixture formed in the combustion chamber 6 and the center position thereof change. The ignition can take place approximately at the center of the mixture.
[0025]
As a result, stable combustion without misfire can be realized, fuel economy is good, and stratified combustion with little exhaust emission can be performed.
In the above embodiment, the plug gap is provided with two ignition plugs 14a and 14b arranged above and below the combustion chamber 6, and the stratification operation is divided into a high load and a low load, and the two ignition plugs 14a , 14b are selectively used, but three or more spark plugs whose plug gaps are arranged at different positions in the vertical direction of the combustion chamber 6 are provided, and the load conditions are determined in three or more stages to selectively use the spark plugs. You may do it.
[0026]
Further, even when the fuel injection valve 13 is arranged at the center of the combustion chamber, the same operation and effect are exhibited, and the arrangement of the fuel injection valve 13 and the shape of the cavity 4a are not limited.
[0027]
FIG. 3 shows a second embodiment.
The second embodiment shown in FIG. 3 is different from the first embodiment shown in FIG. 1 in that ignition positions are arranged at two upper and lower positions in the combustion chamber 6 by one ignition plug 14c. Are different.
[0028]
Therefore, elements other than the ignition plug 14c are denoted by the same reference numerals, and detailed description thereof will be omitted.
In the second embodiment shown in FIG. 3, the ignition plug 14c is provided with two plug gaps 14c1 and 14c2, and one of the plug gaps 14c1 is disposed below the combustion chamber 6 and near the bottom surface of the cavity 4a. The other plug gap 14c2 is arranged above the one plug gap 14c1, and is set to ignite at the center of the combustion chamber 6 in the radial direction and the vertical direction. I have.
[0029]
The gap of the plug gap 14c1 located below is set larger than the plug gap 14c2 located above.
The two plug gaps 4c1 and 14c2 of the ignition plug 14c are supplied with a secondary voltage from a common ignition coil.
[0030]
According to the above configuration, in the high load condition during the homogeneous operation or during the stratified operation in which a mixed air mass is formed using substantially the entire cavity 4a as in the case of FIG. Although the air-fuel mixture exists in both of the gaps 14c1 and 14c2, sparks fly to the upper plug gap 14c2 where the size of the gap is relatively small. Therefore, ignition occurs at the plug gap 14c2 located at the center of the air-fuel mixture. Is performed.
[0031]
Further, under a low load condition during stratification operation in which a small mixture is formed near the bottom surface of the cavity 4a, a mixture is formed around the plug gap 14c1, and the mixture is formed near the plug gap 14c2. Is not formed.
[0032]
For this reason, the spark becomes easier to fly in the lower plug gap 14c1, and as a result, ignition is performed by the plug gap 14c1.
Therefore, even if the formation position of the air-fuel mixture changes, ignition can be performed at the approximate center of the air-fuel mixture, thereby achieving stable combustion without misfiring, improving fuel efficiency, and of course, improving exhaust emissions. The stratified combustion with less heat can be performed.
[0033]
Furthermore, since the gap of the plug gap 14c1 is made larger than that of the plug gap 14c2, when there is an air-fuel mixture between the two (at the time of homogeneous operation and stratified high load conditions), ignition occurs at the upper plug gap 14c2. Can be performed, and the selection of the ignition position can be easily performed while using only one ignition plug.
[0034]
As described above, in the configuration using one ignition plug, three or more plug gaps may be provided in one ignition plug, and the gap may be wider as the lower plug gap is formed.
[0035]
FIG. 4 shows a third embodiment, and the spark plug 14d shown in FIG. 4 is used in place of the spark plug 14c shown in FIG.
The ignition plug 14d shown in FIG. 4 includes one center electrode (plus side electrode) 141 and two side electrodes (minus side electrodes) 142a and 142b, and the two side electrodes 142a and 142b are one center electrode 141. Are formed to form two plug gaps 14d1 and 14d2 which are located above and below in the combustion chamber 6.
[0036]
The plug gap 14d1 is provided so as to be ignited near the bottom surface of the cavity 4a, and the plug gap 14d2 is provided so as to be ignited at the center in the radial and vertical directions of the combustion chamber 6.
[0037]
Only one of the two side electrodes 142a and 142b is connected to the ground via a changeover switch 143 controlled by the control unit 15.
[0038]
The control unit 15 controls the changeover switch 143 to connect the side electrode 142a to the ground under the stratified low-load operation condition, and is located below the combustion chamber 6 so that the cavity 4a is positioned under the stratified low-load operation condition. The ignition is performed at the plug gap 14d1, which is located at the center of the small air-fuel mixture formed near the bottom surface.
[0039]
Further, under the stratified high load operation condition and the homogeneous operation condition, the switch 143 is controlled so as to connect the side electrode 142b to the ground, and the ignition is performed by the plug gap 14d2 located at the center of the combustion chamber 6.
[0040]
Therefore, even if the formation position of the air-fuel mixture changes, ignition can be performed at the approximate center of the air-fuel mixture, thereby achieving stable combustion without misfiring, improving fuel efficiency, and of course, improving exhaust emissions. The stratified combustion with less heat can be performed.
[0041]
Further, by selectively connecting the side electrodes 142a and 142b of the plug gaps 14d1 and 14d2 to the ground, it is possible to reliably select the ignition position while using only one ignition plug.
[0042]
In the above embodiment, a plurality of plug gaps are formed by a plurality of side electrodes sharing one center electrode, but a plurality of center electrodes (positive side electrodes) sharing one side electrode (minus side electrode). Electrodes) to form a plurality of plug gaps, and the plurality of center electrodes (plus-side electrodes) may be selectively connected to the secondary side of the ignition coil by a changeover switch.
[0043]
FIG. 5 shows a fourth embodiment.
In the present embodiment, the fuel injection valve 13 is disposed approximately at the center of the combustion chamber 6, and the fuel injection valve 13 has a small change in the spray shape even when the in-cylinder pressure increases in the latter half of the compression stroke, and has high directivity. A hole nozzle injection valve is used.
[0044]
In the center of the crown surface of the piston 4, a circumferential cavity 4a is formed around an axis parallel to the cylinder axis.
Further, two ignition plugs 14a and 14b are provided, and the ignition plug 14a is configured to ignite near the bottom surface of the cavity 4a and near the periphery of the cavity 4a. 6 is configured to perform ignition at the center in the radial and vertical directions.
[0045]
Here, the relationship between the mixture and the ignition position under the stratified low load operation condition and the stratified high load operation condition in the fourth embodiment is shown in FIG.
Under the stratified low-load operation condition, the fuel spray injected from the fuel injection valve 13 collides with the cavity 4a and proceeds along the shape of the cavity. To form
[0046]
Here, since the ignition plug 14a is disposed so as to ignite near the side wall of the cavity below the combustion chamber, the ignition plug 14a is controlled so as to ignite under the stratified low load operation condition (FIG. 6 (A)).
[0047]
On the other hand, under the stratified high-load operation condition, the fuel spray injected from the fuel injection valve 13 collides with the cavity 4a and then flows upward through the cavity side wall due to a large injection amount and a large momentum of the spray. The advancing and injected spray flow causes the mixture to have a swirling flow velocity.
[0048]
As a result, an air-fuel mixture is positively formed around the ignition plug 14b above the cavity 4a, and by performing control to cause ignition by the ignition plug 14b under stratified high load operation conditions (FIG. 6 ( B)), stable combustion without misfiring can be realized, fuel economy is good, and stratified combustion with little exhaust emission can be performed.
[0049]
Note that, as shown in FIG. 5, in a configuration in which the fuel injection valve 13 is disposed at the center of the combustion chamber 6, a configuration in which one ignition plug has a plurality of plug gaps as shown in FIGS. Can be applied.
[Brief description of the drawings]
FIG. 1 is a system configuration diagram of an engine according to a first embodiment.
FIG. 2 is a view showing a relationship between an air-fuel mixture and an ignition position under a stratified low load condition and a stratified high load condition in the first embodiment.
FIG. 3 is a system configuration diagram of an engine according to a second embodiment.
FIG. 4 is a diagram showing a configuration of a spark plug according to a third embodiment.
FIG. 5 is a system configuration diagram of an engine according to a fourth embodiment.
FIG. 6 is a diagram showing a relationship between an air-fuel mixture and an ignition position under a stratified low load condition and a stratified high load condition in the fourth embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 4 ... Piston 4a ... Cavity 6 ... Combustion chamber 13 ... Fuel injection valve 14a, 14b, 14c, 14d ... Spark plug 15 ... Control unit

Claims (10)

In a direct injection type spark ignition engine equipped with a fuel injection valve that injects fuel directly into the combustion chamber,
An in-cylinder direct injection spark ignition engine, wherein a plurality of ignition positions by a spark plug are provided at different heights in the combustion chamber, and ignition is performed at different ignition positions according to operating conditions. The in-cylinder direct injection type spark ignition engine has stratified operation conditions in which the air-fuel mixture is stratified and combusted in the combustion chamber,
2. The direct injection type spark ignition engine according to claim 1, wherein, during the stratified operation, the higher the engine load, the higher the ignition position at which the ignition is performed. The in-cylinder direct injection type spark ignition engine has a homogeneous operation condition in which the air-fuel mixture is homogenized and burned in the combustion chamber,
3. The direct injection spark ignition engine according to claim 1, wherein the ignition is performed at an upper ignition position among the plurality of ignition positions during the homogeneous operation. The cylinder according to any one of claims 1 to 3, wherein one spark plug is provided with a plurality of plug gaps, and a plurality of ignition positions are arranged at different heights in the combustion chamber. Direct injection spark ignition engine. The said one spark plug is comprised including the some side electrode which shares one center electrode, or the some center electrode which shares one side electrode. In-cylinder direct injection spark ignition engine. 6. The direct injection type spark ignition engine according to claim 4, wherein a plurality of plug gaps provided in the one spark plug are formed to be wider as they are located lower in the combustion chamber. . The in-cylinder direct injection spark according to claim 4 or 5, wherein a plug gap to be connected to an ignition circuit is selected by switching a switch from among a plurality of plug gaps provided in the one spark plug. Ignition engine. A fuel injection valve is arranged in the center of the combustion chamber, and a cavity is formed in the center of the piston crown surface,
Among the plurality of ignition positions, the one located above the combustion chamber is arranged at the center in the radial direction of the cavity, and the one located lower inside the combustion chamber is arranged closer to the periphery of the cavity. The in-cylinder direct injection spark ignition engine according to claim 1 or 2. A configuration formed by a cavity formed in a piston crown surface to receive a fuel spray injected from the fuel injection valve and generate a stratified mixture,
Under low-load operation conditions during stratified operation, a mixed air mass is formed on the bottom surface of the cavity, and under high-load operation conditions during stratified operation, an air-fuel mixture is formed inside the cavity and above the cavity. The direct injection type spark ignition engine according to any one of claims 1 to 7. Under high load operation conditions during the stratified operation, a mixed air mass formed in the cavity and above the cavity has a swirling flow due to the flow of the fuel spray injected from the fuel injection valve. Item 14. An in-cylinder direct injection spark ignition engine according to item 9.

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