JP3280431B2 - In-cylinder fuel injection engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an in-cylinder fuel injection type engine.

[0002]

2. Description of the Related Art In recent engines, there is a strong demand for improved fuel efficiency. For this reason, the fuel is directly injected into the combustion chamber to stratify the fuel, that is, to form a partially rich portion, and the ignition is performed by the ignition plug in the rich portion. It has been considered to perform combustion with a considerably lean mixture.

An in-cylinder fuel injection engine as described above is disclosed in Japanese Patent Application Laid-Open No. 2-305319. In this publication, in order to surely form a rich portion at a desired position, a recess is formed in the piston top surface, and an annular partition is protruded from the bottom of the recess to ignite inside the partition. A combustion chamber is configured. Then, fuel injection is performed toward the ignition combustion chamber. Of course, the ignition gap of the ignition plug is located near the ignition combustion chamber.

[0004]

According to the above-mentioned publication, although the demand for enriching the combustion chamber for ignition is considerably satisfied, the fuel in the combustion chamber for ignition is not so small by the time of ignition that the side of the outer combustion chamber is not too small. In this regard, some improvement is required in this regard. In particular, when a large amount of fuel adheres to the inner surface of the ignition combustion chamber in a liquid state, the situation in which the fuel flows out to the outer combustion chamber tends to be remarkable, and also causes a large increase in HC.

The present invention has been made in view of the above-described circumstances, and has been made so that rich fuel vaporized and atomized in an ignition combustion chamber can be more reliably retained until the time of ignition. It is an object of the present invention to provide an in-cylinder fuel injection engine.

[0006]

Means for Solving the Problems In order to achieve the above object, the present invention has the following first configuration. That is, Claim 1 in the Claims
In the in-cylinder fuel injection engine in which fuel is injected directly into the combustion chamber by the fuel injection valve and ignited by the spark plug, a recess is formed on the top surface of the piston, and By projecting an annular or substantially annular partition from the lower part, combustion for ignition having a small volume enough to form a stoichiometric air-fuel mixture with the fuel injection amount during idling or extremely light load in the partition. A swirl generating means for forming an intake swirl in the combustion chamber, wherein an annular or substantially annular outer combustion chamber having a bottom surface lower than the top of the partition is formed outside the partition; The fuel injection valve is disposed on the outer peripheral edge of the cylinder, and the direction of the direction of the fuel injected from the fuel injection valve is set at the fuel injection timing. Is set so as headed to a predetermined inner surface which is positioned farther the ignition gap of the spark plug,
At the ignition timing, it is set so as to be located in the vicinity of the predetermined inner surface of the partition wall portion, and the distance from the fuel injection valve to the predetermined inner surface is determined at the fuel injection timing by the fuel injected from the fuel injection valve. Blaze
The configuration is such that it is set to be longer than the cup length. On the premise of the first configuration, the following configuration can be adopted.

The break-up length is 35 to 4
It can be set to a range of 5 mm.

[0008] The center line of the fuel injected from the fuel injection valve may be set at an angle of 15 to 20 degrees with respect to a plane perpendicular to the cylinder axis.

[0009] The ignition gap may be set so as to be located in the combustion chamber for ignition. In this case, the ignition gap can be set so as to be located closer to the predetermined inner surface side than the center of the ignition combustion chamber.

The swirl generating means is set by setting the intake port as a helical port, and the fuel injection valve sandwiches the center of the cylinder with respect to the helical port. , And may be arranged in a portion other than the region located on the opposite side.

[0011] The height of a portion of the partition wall close to the fuel injection valve may be lower than the height of the predetermined inner surface portion.

In order to achieve the above object, the present invention has the following configuration as a second configuration. That is, as described in claim 8 of the claims,
In an in-cylinder fuel injection engine in which fuel is directly injected into a combustion chamber by a fuel injection valve and ignited by a spark plug, the fuel injection valve is disposed on an outer peripheral portion of the cylinder, and the piston By forming a substantially annular partition part in which the side closer to the fuel injection valve is lower and the side farther away is higher, a combustion chamber for ignition having a small volume is formed in the partition part, and an outer combustion chamber is provided outside the partition part. A swirl generating means for generating an intake swirl in the combustion chamber is provided, and a direction of injection of fuel from the fuel injection valve is controlled by a fuel injection valve on the inner surface of the partition wall at fuel injection timing. Is set so as to face a predetermined inner surface located on the far side, and the ignition gap of the ignition plug is located near the predetermined inner surface of the partition at the ignition timing. The distance from the fuel injector to the predetermined inner surface is set to be longer than the break-up length of the fuel injected from the fuel injector at the fuel injection timing. It has such a configuration.

[0013]

According to the first aspect of the present invention, the injection speed of the injected fuel supplied into the combustion chamber for ignition is sufficiently reduced before reaching the predetermined inner surface of the partition wall, and the fuel is vaporized. Since the atomization is promoted, the ratio of slipping on the inner surface of the combustion chamber for ignition and flowing out to the outer combustion chamber is reduced, which is preferable for enhancing the ignitability, and furthermore, the inner surface of the combustion chamber for ignition is improved. This is also preferable for preventing an increase in HC since the amount of fuel adhering is also reduced. Further, the ignition gap is located in the vicinity of the predetermined inner surface where the injected fuel is directed and becomes particularly rich in the ignition combustion chamber, so that it is preferable for further improving the ignitability. Furthermore, not only the partition wall but also the intake swirl further prevents the fuel from flowing out from the combustion chamber for ignition, which is preferable for enriching the combustion chamber for ignition more reliably until ignition. Further, in order to prevent the fuel that has flowed out of the ignition combustion chamber into the outer combustion chamber that is disposed so as to surround the ignition combustion chamber, to prevent the dispersion of the fuel and improve the combustion stability after ignition, This is preferred, and the annular or substantially annular outer combustion chamber further enhances the effect of the intake swirl to trap fuel into the ignition combustion chamber.

By adopting the structure as described in claim 2, it is advantageous in practical use when taking into consideration the bore diameter of an engine, especially an automobile engine.

According to the third aspect of the present invention, it is possible to prevent the fuel colliding with the predetermined inner surface from flowing out of the ignition combustion chamber and to prevent a large amount of fuel from adhering to the ignition combustion chamber surface. This is preferable for satisfying at a high level.

By adopting the configuration as described in claim 4 or claim 5, it is more preferable to obtain more reliable ignition by the ignition gap.

According to the structure described in claim 6, the interaction between the intake swirl and the vertical vortex generated in the combustion chamber for ignition by the injected fuel causes the fuel from the combustion chamber for ignition. This is preferable in preventing a situation in which the liquid flows out.

According to the structure described in claim 7, it is possible to reliably prevent a situation in which the portion of the partition wall portion near the fuel injection valve is located on the passage of the injected fuel.
That is, it is preferable to prevent the injected fuel from interfering with the partition wall partway before reaching the ignition combustion chamber.

According to the invention described in claim 8, the injection speed of the injected fuel supplied into the combustion chamber for ignition is sufficiently reduced before reaching the predetermined inner surface of the partition wall, so that the fuel is vaporized and sprayed. Therefore, the ratio of slipping on the inner surface of the ignition combustion chamber and flowing out to the outer combustion chamber is reduced, which is preferable for enhancing ignitability. Since the amount of adhesion is also reduced, it is preferable for preventing an increase in HC. Further, the ignition gap is located in the vicinity of the predetermined inner surface where the injected fuel is directed and becomes particularly rich in the ignition combustion chamber, so that it is preferable for further improving the ignitability. Furthermore, not only the partition wall but also the intake swirl further prevents the fuel from flowing out from the combustion chamber for ignition, which is preferable for enriching the combustion chamber for ignition more reliably until ignition. Further, it is possible to dispose the fuel injection valve at a low position that is almost the same height as the top surface of the piston at the top dead center without interfering with the partition wall.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the accompanying drawings. 1 and 2, 1 is a cylinder block, 2 is a cylinder head, and 3 is a piston. An intake port 4, an exhaust port 5, and an EGR port 6 are formed in the cylinder head 2 so as to open into the cylinder. The intake / exhaust ports 4, 5 are opened and closed at well-known timings by intake valves or exhaust valves (not shown) in synchronization with the rotation of the engine. The intake port 4 is
The helical port is set to generate the intake swirl.

The EGR port 6 is opened and closed by an EGR valve 7 in synchronization with the rotation of the engine. EGR valve 7
Is set from the end of the exhaust stroke to the beginning of the intake stroke. That is, the EGR port 6 is communicated with the exhaust port 4 in the cylinder head 2 and serves to reduce NOx by high-temperature EGR.

As shown in FIGS. 3 and 4, a recess 11 is formed in the top surface 3a of the piston 3, and this recess 1
An annular partition 12 is formed on the bottom surface of the first partition 1. Recess 1
1 is formed as a circle centered on the center of the piston 3 (cylinder axis), and the partition 12 is also formed as an annular shape centered on the center of the piston 3. This partition 1
The outer part of 2 constitutes the outer combustion chamber 14 and the inner part of the partition part 12 constitutes the ignition combustion chamber 15. The inner surface shape of the ignition combustion chamber 15 is substantially spherical (a shape that forms part of a substantially spherical surface). Such a partition part 1
The height 2 is lower than the piston top surface 3a, and is the same over the entire circumference.

Here, the outer peripheral edge of the concave portion 11 is denoted by the symbol α, and the center line of the partition portion 12 (the line connecting the highest positions) is denoted by β. In FIG. The positional relationship between the outer combustion chamber 14 and the ignition combustion chamber 15 is shown.

1 and 2, reference numeral 21 denotes a fuel injection valve,
Reference numeral 22 denotes a spark plug. In FIG. 1, the spark plug 22 is omitted and only the mounting hole 23 is shown. The fuel injection valve 21 is located on the outer peripheral edge of the cylinder, and is located between the intake port 4 and the EGR port 6 in the cylinder circumferential direction. The spark plug 22 is located on the opposite side of the cylinder center from the fuel injection valve 21 and is located between the intake port 4 and the exhaust port 5 in the cylinder circumferential direction. However, the ignition gap 22
a is located near the ignition combustion chamber 15 as described later.

The direction of fuel injection from the fuel injection valve 21 will be described in detail with reference to FIG. First, the fuel injection valve 2
1 is attached to the cylinder head 2 and its injection hole 21
a is located above the piston 3. The center line of the injected fuel injected from the injection hole 21a into the cylinder is indicated by γ.
The inner surface of the partition wall 12 is directed toward a predetermined inner surface 15 a farther from the fuel injection valve 21.

Here, assuming that the distance between the injection hole 21a and the predetermined inner surface 15a is A, this distance A is set to be slightly larger than the break-up length of the fuel injected from the injection hole 21a. The break-up length is
As is known, it is the distance from the injection hole 21a at the time when the speed of the injected fuel starts to rapidly decrease, and the injected fuel after the break-up length has sufficiently promoted atomization. .

In the embodiment, the break-up length is
It is set so as to be approximately the same as a general cylinder bore radius in an automobile engine, more specifically, in a range of 35 to 45 mm (injection pressure is 10 to 30 MPa).
a, when the atmospheric pressure in the cylinder is 1 to 2 MPa). Therefore, the injected fuel is sufficiently atomized when it reaches the predetermined inner surface 15a. As a result, the fuel stagnation action in the ignition combustion chamber 15 is enhanced, and the amount of fuel adhering to the ignition combustion chamber 15 is also reduced. Will be done. Further, since the intake swirl is formed so as to surround the combustion chamber 15 for ignition,
The atomized fuel stays in the ignition combustion chamber 15 more favorably.

In addition to the above, the following configuration is preferable. First, a plane H1 orthogonal to the cylinder axis
(This plane is considered to be a plane drawn as the inner surface of the cylinder head 2 in FIG. 4).
The angle θ formed by the center line γ with respect to 1 is 15 degrees to 20 degrees.
It is preferable to set the temperature in the range of degrees (the direction of the fuel injected from the fuel injection valve 21 is substantially along the plane H1).

By setting the angle θ in the range of 15 to 20 degrees as described above, it is possible to prevent the injection fuel from flowing out of the ignition combustion chamber 15 and to prevent the injection fuel from flowing out.
This is preferable in reducing the amount of fuel attached to the inner surface. That is, if the angle θ is less than 10 degrees, the rate at which the fuel colliding with the predetermined inner surface 15a flows out of the ignition combustion chamber 15 increases. Conversely, if the angle θ is larger than 20 degrees, the amount of fuel adhering to the inner surface of the ignition combustion chamber 15 increases, which is not preferable in terms of reducing HC. Of course, when the engine is operating, the fuel is injected during the displacement of the piston 3, but the angle θ of 15 to 20 degrees takes this point into consideration. .

The ignition gap 2 of the ignition plug 22 (
2a) may be at a position above the ignition combustion chamber 15 as long as it is near the predetermined inner surface 14a at the ignition timing (for example, see FIG. 8 described later).
At the ignition timing, the ignition gap 22a is located in the ignition combustion chamber 15. In this case, the ignition combustion chamber 1
Even in the area 5, the vicinity of the predetermined inner surface 15a is most likely to be rich. Therefore, by positioning the ignition gap 22a in this richest part, it is preferable to obtain more reliable ignition.

More specifically, as shown in FIG.
In order to clearly show the dimensions B, C1, and C2, hatching to the piston 3 is omitted).
The height position of a (discharge gap position) is larger than C1 because it is located in the ignition combustion chamber 15 (the partition wall portion 12).
Below the top surface of Inserting too deeply into the combustion chamber for ignition 15 increases the rate at which the injected fuel collides with the ignition gap 22a,
In consideration of the fact that most of the vaporized and atomized fuel is located above the lower part of the ignition combustion chamber 15, it is preferable to set the position higher than half the value of C2 shown in FIG.

The ignition gap 22a is located farther from the center of the ignition combustion chamber 15 than the fuel injection valve 21 because it is located closer to the predetermined inner surface 15a (set within a range indicated by B in FIG. 5). ). More specifically, the ignition combustion chamber 15
(1/3 to 1)
It is good to be located in the size range of B (ignition combustion chamber 15
From the position closer to the predetermined inner surface 15a by 1/3 of the distance from the position closer to the predetermined inner surface 15a).

Further, (the injection hole 21a of the fuel injection valve 21)
Is preferably provided in the region S1 or S2 shown in FIG. 6, and it is better to avoid providing it in the region S3 which is opposed to the intake port 4 with the cylinder center interposed therebetween. To explain this point, the ignition combustion chamber 15
Inside, the injected fuel becomes vertical vortex due to inertia, and the interaction between the vertical vortex of this fuel and the intake swirl is considered. When the fuel injection valve 21 is disposed in the regions S1 and S2, due to the above interaction, as shown by the solid line arrow in FIG.
In contrast, when the fuel injection valve 21 is disposed in the region S3, the flow as indicated by the broken line arrow in FIG. Thus, the fuel in the ignition combustion chamber 15 tends to flow out from the left side of FIG. 4 to the outside. The fuel injection valve 2 is provided in a portion other than the regions S1, S2 and S3.
When 1 is provided, the above interaction becomes practically irrelevant.

The volume of the combustion chamber 15 for ignition should be a minimum volume necessary for ignition, that is, the mixture of the stoichiometric air-fuel ratio should be determined by the amount of fuel injected at the time of idling or extremely light load where the ignitability is most important. Is preferably a volume that can be formed in the combustion chamber 15 for ignition. In order to increase the air utilization rate utilizing the air in the outer combustion chamber 14 and its surrounding space sufficiently from this point of view, the volume of the ignition combustion chamber 15 is the sum of the outer combustion chamber 14 and the ignition combustion chamber 15. Preferably, the volume is around 10% of the volume. In addition, from the viewpoint of increasing the air utilization rate, the shape and arrangement of the outer combustion chamber 14 are determined in consideration of the intake swirl as described above.
Is preferably formed as a substantially circular shape having the center as the center.

The ignition combustion chamber 15 is sufficient if it is necessary to keep the minimum necessary air-fuel mixture necessary to reliably perform ignition, particularly at the time of idling or extremely light load. The height and diameter of the partition 12 may be determined. Further, the supplied fuel is minimized to the ignition combustion chamber 15.
While preventing the formation of a state in which fuel is unlikely to remain partially in the ignition combustion chamber 15 and preventing the fuel from adhering, while allowing the air-fuel mixture to move toward the inner surface of the cylinder head. In order to have a large amount, it is preferable that the inner surface has a substantially spherical shape (a shape that forms a part of a spherical surface) as in the embodiment.

FIGS. 7 and 8 show another embodiment of the present invention. The same components as those of the above embodiment are denoted by the same reference numerals and the description thereof will be omitted. In this embodiment, the partition 12 in the above embodiment is offset to the side away from the fuel injection valve 21 so that the height of the predetermined inner surface 15a of the partition 12 is substantially increased to the height of the recess 11. It was made. 7 and 8, the fuel injection can be changed to be performed from the left side in the figures. In this case, it is preferable to avoid interference of the injected fuel with the partition wall 12 on the side closer to the fuel injection valve 21. It will be. Of course, in this case,
The ignition gap 22a is changed to the right position in the figure.

FIGS. 9 and 10 show still another embodiment of the present invention. In this embodiment, the piston top surface 3a
The partition wall 41 (corresponding to 12) is formed without forming the concave portion 11 on the inside, and the inside thereof is used as an ignition combustion chamber 42 (corresponding to 15). In this case, the partition wall portion 41 has the highest height on the side of the predetermined inner surface 15a corresponding to the fuel injection valve 21 and gradually lowers as the distance from the predetermined inner surface 15a in the circumferential direction of the cylinder increases.
In the vicinity of 1, the height of the partition 32 is practically zero. In addition, 43 is an intake valve and 44 is an exhaust valve.

9 and 10, even if the fuel injection valve 21 is set at a low position which is almost the same height as the top surface 3a of the piston 3 at the top dead center position, the fuel injection valve 21 does not interfere with the partition 41. The predetermined inner surface 1 located far from the fuel injection valve 21
The injected fuel can be made to reach 5a. The height of the partition 41 may be reduced only in the vicinity of the fuel injection valve 21 as shown by the dashed line in FIG. 10, and the other portions may be the same as the height at the predetermined inner surface 15a.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing an embodiment of the present invention.

FIG. 2 is a view of the cylinder head in FIG. 1 as viewed from an inner surface side thereof.

FIG. 3 is a plan view showing the shape of the top surface of the piston.

FIG. 4 is a view for explaining a break-up length of a fuel injection valve and a preferable spray angle.

FIG. 5 is a view for explaining a preferred arrangement position of an ignition gap.

FIG. 6 is a view showing a preferred arrangement position of a fuel injection valve.

FIG. 7 is a view showing another embodiment of the present invention and corresponding to FIG. 3;

8 is a side sectional view of an engine using the piston shown in FIG. 7, and is a sectional view corresponding to line X8-X8 in FIG. 7;

FIG. 9 is a view showing still another embodiment of the present invention and corresponding to FIG. 3;

10 is a side sectional view of an engine using the piston shown in FIG. 9, and is a sectional view corresponding to line X10-X10 in FIG. 9;

[Explanation of symbols]

 2: Cylinder head 3: Piston 3a: Piston top surface 4: Intake port 11: Recess 12: Partition wall 14: Outer combustion chamber 15: Ignition combustion chamber 15a: Predetermined inner surface 21: Fuel injection valve 21a: Injection hole 22 : Ignition plug 22a: ignition gap 41: partition wall 42: combustion chamber for ignition

Claims (8)

(57) [Claims] An in-cylinder fuel injection engine in which fuel is directly injected into a combustion chamber by a fuel injection valve and ignited by a spark plug, a recess is formed in a top surface of a piston, and a low level of the recess is formed. Department
By projecting an annular or substantially annular partition wall from
Fuel injection during idle or very light load inside the partition
Volume small enough to form a stoichiometric air-fuel mixture
Combustion chamber for ignition is formed, and on the outside of the partition wall
An annular or substantially annular bottom surface of which is lower than the top of the partition wall.
An outer combustion chamber is formed , a swirl generating means for generating an intake swirl is provided in the combustion chamber, and the fuel injection valve is disposed at an outer peripheral portion of the cylinder, so that fuel injected from the fuel injection valve is provided. The directional direction is set so as to be directed to a predetermined inner surface located on a side farther from the fuel injection valve on the inner surface of the partition at the fuel injection timing, and the ignition gap of the ignition plug is set at the ignition timing. The distance from the fuel injection valve to the predetermined inner surface is longer than the break-up length of the fuel injected from the fuel injection valve at the fuel injection timing. An in-cylinder fuel injection engine, which is set to be: 2. The in-cylinder fuel injection engine according to claim 1, wherein the break-up length is 35 to 45 mm. 3. The method of claim 1, wherein the center line of the fuel injected from the fuel injection valve is set at an angle of 15-20 degrees relative to a plane perpendicular to the cylinder axis, that In-cylinder fuel injection type
Engine . 4. The in-cylinder fuel injection system according to claim 1, wherein the ignition gap is set to be located in the ignition combustion chamber.
Engine . 5. The in-cylinder fuel injection according to claim 4, wherein the ignition gap is set to be located closer to the predetermined inner surface than the center of the ignition combustion chamber. Expression engine . 6. The intake port according to claim 1, wherein said swirl generation means is set by setting an intake port to a helical port, and said fuel injection valve is set to said helical port. An in-cylinder fuel injection engine , which is provided in a portion other than a region located on the opposite side of the cylinder center with respect to the cylinder center. 7. The fuel cell system according to claim 1, wherein a height of a portion of the partition wall near the fuel injection valve is:
Being lower than the height of the predetermined inner surface portion ,
In-cylinder fuel injection engine . 8. A fuel injection valve for directly injecting fuel into a combustion chamber.
And ignite with a spark plug.
In the in-cylinder fuel injection type engine, the fuel injection valve is disposed on the outer peripheral edge of the cylinder , and the side near the fuel injection valve is lower and farther on the piston top surface.
By forming a substantially annular partition wall portion where
When a small-volume ignition combustion chamber is formed in the wall,
In addition, an outer combustion chamber is formed outside the partition, and swirl generating means for generating an intake swirl in the combustion chamber is provided.
Provided, orientation of the fuel injected from the fuel injection valve, the fuel injection
At the timing, the fuel injection on the inner surface of the partition wall
Set so that it faces a predetermined inner surface located on the far side from the valve.
Is, ignition gap of the spark plug, your ignition timing
And located near the predetermined inner surface of the partition.
Is set to so that the distance from the fuel injection valve to the predetermined inner surface, fuel injection
At the injection timing, the injection injected from the fuel injection valve
Be longer than the breakup length of the propellant
An in-cylinder fuel injection engine , which is set .