JP2006057604A - Cylinder direct injection internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To secure igniting stability while preventing deposition on ignition plugs. <P>SOLUTION: A spray axial line which is formed by the mutual collision of fuel sprays from two nozzle holes of a fuel injection valve 12 is changed with a change in the flow rate of fuel from each nozzle hole in response to a needle (valve element) lift amount. In the maximum needle lift (a main injection period), the deposition on the plug is prevented by avoiding the fuel sprays from being directed to a plug gap between the adjacent ignition plugs 10. In a reduction of needle lift (an injection finishing period), igniting stability is secured by allowing the fuel sprays to be directed to the plug gap. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an in-cylinder direct injection internal combustion engine in which an injection hole of a fuel injection valve and a plug gap of an ignition plug are arranged close to each other, and more particularly to a technique capable of maintaining good ignition performance.

In spark ignition combustion, an internal combustion engine that performs highly diluted combustion by directly injecting fuel into the cylinder from the fuel injection valve and forming a stratified mixture in the cylinder is especially at low and medium loads It is known that fuel consumption can be greatly reduced.
In such an in-cylinder direct injection type spark ignition engine, in Patent Document 1, a plug gap of an ignition plug is disposed in the vicinity of the injection hole of the fuel injection valve, and direct spark ignition is performed on the fuel spray injected from the fuel injection valve. It is burning.
JP-A-6-42352

However, in the method in which the fuel spray injected from the fuel injection valve is directly ignited and burned, if the fuel spray and the plug gap of the spark plug are arranged close to each other, the stability of ignition is improved, but the fuel spray is improved. The problem is fogging of the spark plug due to the direct hit of the plug gap.
On the other hand, if the plug gap of the spark plug is moved away from the fuel spray in order to avoid the cover of the spark plug, the combustion stability is deteriorated. In other words, both are in a trade-off relationship. In the prior art related to this combustion technique, there is no one showing a measure for the above problem.

  The present invention has been made in view of such a problem, and in a technique of directly igniting and burning a fuel spray injected from a fuel injection valve, it is possible to achieve both prevention of fogging of the spark plug and combustion stability. It aims at providing the means to do.

For this reason, the present invention sets the fuel injection direction so that the fuel injected from the injection hole of the fuel injection valve passes through the vicinity of the plug gap of the spark plug,
A configuration in which the fuel passage position at the end of the injection period in which the valve body lift amount of the fuel injection valve is lowered and seated is closer to the plug gap position than the fuel passage position in the main injection period in which the valve body lift amount is maximum. It was.

  According to this configuration, during the main injection period in which the valve body lift amount is maximum, the fuel spray is not directed to the vicinity of the plug gap position, and at the end of the fuel injection, the fuel spray is changed to the plug gap position according to the decrease in the needle lift amount. By directing in the vicinity, the fuel spray injected during the main injection period avoids the plug gap to avoid fogging of the spark plug, and at the timing of spark ignition at the end of the fuel injection, the fuel spray passes through the plug gap. It becomes possible to ignite surely to be oriented.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In FIG. 1, the internal combustion engine has a combustion chamber 4 composed of a cylinder head 1, a cylinder block 2 and a piston 3, introduces fresh air from an intake port 6 via an intake valve 5, and passes through an exhaust valve 7. The exhaust is discharged from the exhaust port 8. A fuel injection valve 9 and a spark plug 10 are mounted at the center of the cylinder head 1, and a nozzle hole 91 provided at the tip of the fuel injection valve 9 and a plug gap 10 a provided at the tip of the spark plug 10 are provided. It arrange | positions so that it may adjoin and may face in the combustion chamber 4. FIG. The plug gap 10a can be directly ignited by the injected fuel spray, but is offset from the spray center axis in order to avoid problems such as plug fog caused by direct fuel spray hit.

A fuel pump 11 is disposed at the end of the cam shaft that drives the intake valve 5. The fuel pressurized by the fuel pump 11 is injected into the combustion chamber 4 from the fuel injection valve 9 through the fuel pipe 12.
The internal combustion engine is integrally controlled by an engine control unit (ECU) 13. Therefore, the ECU 13 receives a crank angle sensor signal, a coolant temperature, and an accelerator opening signal, and performs fuel injection and ignition control based on these signals. In the internal combustion engine, the combustion mode mainly includes a stratified combustion mode in which a lean operation is realized by performing fuel injection during the compression stroke (particularly in the latter half of the compression stroke) to improve fuel consumption, and during the intake stroke (particularly the intake stroke). A homogeneous combustion mode in which fuel injection is performed in the first half of the stroke and a stoichiometric operation (theoretical air-fuel ratio operation) is realized, and is selected according to the operating state.

The tip structure of the fuel injection valve 9 is shown in FIG. 2, and the fuel spray characteristics in the main injection period and the injection end timing are shown in FIG.
The fuel injection valve 9 injects fuel by a needle (valve element) 15 reciprocating in the axial direction in the nozzle body 14, and the needle 15 is seated with respect to the axial direction of the fuel injection valve 9. Two injection holes 91a and 91b are provided on the spark plug 10 side in the circumferential direction. Note that by using an electromagnetic coil as a means for lifting the needle 15, a fuel injection valve can be created at a relatively low cost.

  The nozzle holes 91a and 91b are the curtain area of the inlet side opening (the area of the side surface formed when the nozzle hole cross-sectional shape is extended until it collides with the valve body in the nozzle hole axis direction) 91A and 91B. However, the curtain area 91B is formed larger than the curtain area 91A. Note that one injection hole 91 c is provided in the axial direction of the fuel injection valve 9 on the side other than the spark plug 10 side.

  The axis (spray axis) 20 of the nozzle hole 9b having the larger curtain area is oriented near the position of the plug gap 10a of the spark plug 10, and the axis (spray axis) 22 of the nozzle hole 9a having the smaller curtain area is directed. Is not directed near the plug gap position 12a. Further, the nozzle hole axes 20 and 22 have intersections in the space, and the fuel sprays injected from the respective nozzle holes collide and proceed in the direction of the collision spray axis 21.

Here, as shown in FIG. 3A, the spray axis 21 is set so as not to be directed near the position of the plug gap 10a when the needle 15 is fully lifted. As a result, during the main injection period when the needle 15 is at the maximum lift, the fuel spray does not directly hit the plug gap 10a, and fogging of the spark plug 10 can be prevented.
On the other hand, as shown in FIG. 3B, when the lift amount of the needle 15 decreases, the difference between the curtain areas 91A and 91B increases, and the flow rate of fuel injected from the nozzle hole 9a where the curtain area 91A decreases greatly is shown. Since the ratio with respect to the fuel flow rate injected from the nozzle hole 9b in which the curtain area 91B is kept relatively large is relatively lowered, the spray axis 21 approaches the spray axis 20.

As a result, the fuel spray is directed near the plug gap position at the end of fuel injection, and it is possible to ensure the stability of ignition.
As shown in FIG. 2A, when the fuel injection valve 9 has a sac part (volume part) 23 at the lower end, the upper injection hole 9a is formed on the wall of the nozzle body 14 above the sack part 23. By providing the lower injection hole 9b in the sack portion 23, the difference between the two curtain areas 91A and 91B can be further increased, and the fuel spray characteristics can be easily changed. Further, the provision of the sack portion 23 increases the fuel injection amount at the injection end timing, and improves the stability of ignition.

On the other hand, as shown in FIG. 2B, even in a sacless type fuel injection valve 9 that does not include a sack portion, the curtain areas 91A and 91B of the two injection holes 9a and 9b provided on the wall of the nozzle body 14 are provided. The curtain areas 91 </ b> A and 91 </ b> B are different from each other as long as the curtain areas 91 </ b> A and 91 </ b> B are different.
In addition, when the needle is seated, if the cross-sectional area of the nozzle hole 9b with the larger curtain area is made smaller than the cross-sectional area of the nozzle hole 9a with the smaller curtain area, the fogging suppression function of the spark plug will be strengthened. In addition, if the cross-sectional area of the nozzle hole 9b having the larger curtain area is made larger than the cross-sectional area of the nozzle hole 9a having the smaller curtain area, the ignition stability function is enhanced. What is necessary is just to set so that both functions can be obtained with the best balance according to performance etc.

As described above, according to the present embodiment, during the main injection period, the fuel sprays injected from at least two different nozzle holes are caused to collide, so that the traveling direction of the fuel sprays depends on the valve lift amount. Can be controlled automatically.
In particular, when the needle is seated, at least two injection holes 9a and 9b have different entrance side opening curtain areas 91A and 91B, so that the fuel injected from the injection holes having a small curtain area near the injection end timing. Since the flow rate is relatively smaller than the fuel flow rate injected from the nozzle hole having a large curtain area, the traveling direction of the collided fuel spray can be easily changed.

However, the present invention is not limited to this method as long as the fuel spray is not directed to the vicinity of the plug gap position when the needle is at the maximum lift, but is directed to the vicinity of the plug gap position as the needle lift amount decreases.
FIG. 4 shows various examples of electrode shapes in the spark plug 10. Since the distance from the injection hole 9a of the fuel injection valve 9 to the plug gap 10a of the spark plug 10 is short and the mixture formation of fuel spray is not sufficient, the region of the combustible mixture is not sufficiently large. The semi-creeping electrode type shown in Fig. 5 is more preferable because a wide ignition region can be secured. However, it may be a parallel electrode type as shown in FIG. 5B or a hybrid type having both parallel electrodes and creeping electrodes as shown in FIG. However, it is not limited to these.

  In any of the electrodes (a) to (c), the ignition direction in the plug gap at the time of ignition is perpendicular to the spark plug axis, so that the ignition of the combustible mixture is spatially wide. This makes it possible to improve the stability of ignition.

Configuration diagram of an internal combustion engine in an embodiment Sectional drawing which shows the front-end | tip part structure of the fuel injection valve used for embodiment same as the above Fuel spray characteristics of the fuel injection valve in the main injection period and injection end timing The figure which shows the various shapes of the electrode of the spark plug used for embodiment same as the above

Explanation of symbols

DESCRIPTION OF SYMBOLS 3 Piston 3a Bowl part 4 Combustion chamber 9 Fuel injection valve 10 Spark plug 10a Plug gap 13 Engine control unit (ECU)
14 Nozzle body 15 Needle 20 Aperture axis (spray axis)
21 Collision spray axis 22 Injection hole axis (spray axis)
91a nozzle hole 91b nozzle hole 91A nozzle hole curtain area 91B nozzle hole curtain area

Claims (15)

In the cylinder direct injection internal combustion engine in which the nozzle hole provided at the tip of the fuel injection valve and the plug gap provided at the tip of the spark plug are arranged close to each other,
While setting the fuel injection direction so that the fuel injected from the injection hole of the fuel injection valve passes through the vicinity of the plug gap of the spark plug,
The fuel passage position at the end of the injection period in which the valve body lift amount of the fuel injection valve decreases and becomes seated is made closer to the plug gap position than the fuel passage position in the main injection period where the valve body lift amount is maximum. An in-cylinder direct injection internal combustion engine.   The in-cylinder direct injection internal combustion engine according to claim 1, wherein the fuel passage position is brought closer to the position of the plug gap as the valve body lift amount decreases.   3. The direct injection type internal combustion engine according to claim 1, wherein the fuel injected at the end of the injection period is ignited by the spark ignition plug when passing through the vicinity of the plug gap. 4. .   The fuel injection valve injection hole and the spark plug plug gap are arranged close to each other in the center of the combustion chamber surrounded by two intake valves and two exhaust valves. Item 5. The direct injection type internal combustion engine according to any one of items 3 to 4.   5. The fuel injection valve according to claim 1, wherein at least two injection holes are formed at a front end portion of the fuel injection valve, and fuel injected from the two injection holes is caused to collide. In-cylinder direct injection internal combustion engine. The inlet side opening formation position of the two injection holes is set so that the flow rate ratio of the fuel injected from the two injection holes changes according to the valve lift amount. In-cylinder direct injection internal combustion engine.   At the time of seating of the valve body, at least two injection hole entrance side opening curtain areas (area of the side surface formed when the injection hole cross-sectional shape is extended until it collides with the valve element in the injection hole axial direction) The in-cylinder direct injection internal combustion engine according to claim 5 or 6, characterized in that are different from each other.   The fuel injection valve according to claim 7 and a direct injection type internal combustion engine using the same according to claim 7, wherein the curtain area is smaller than the sectional area of the nozzle hole in the nozzle hole having the smaller curtain area.   The inlet-side openings of the two nozzle holes are provided in the nozzle body on the side of the conical surface of the valve body tip when seated on the valve body, and on the side wall of the volume provided near the valve body tip. The direct injection type internal combustion engine according to any one of claims 5 to 8.   The in-cylinder direct injection internal combustion engine according to any one of claims 5 to 9, wherein an axis of the injection hole having the larger curtain area is directed near a plug gap position.   The direct injection type internal combustion engine according to any one of claims 5 to 10, wherein the axis of the injection hole having the smaller curtain area does not point near the plug gap position.   The in-cylinder according to any one of claims 5 to 11, wherein a cross-sectional area of the nozzle hole having the larger curtain area is smaller than a cross-sectional area of the nozzle hole having the smaller curtain area. Direct injection internal combustion engine.   The in-cylinder according to any one of claims 5 to 12, wherein a cross-sectional area of the nozzle hole having the larger curtain area is larger than a cross-sectional area of the nozzle hole having the smaller curtain area. Direct injection internal combustion engine.   The direct injection type internal combustion engine according to any one of claims 5 to 13, wherein an electromagnetic coil is used as means for lifting the valve body.   The in-cylinder direct injection internal combustion engine according to any one of claims 5 to 14, wherein a spark direction at the time of ignition in the plug gap of the spark plug is a direction perpendicular to the spark plug axis. .

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