JPH102224A - Fuel cylinder injection type spark ignition engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure good ignitability without slowing the initial combustion at stratified combustion time, in a fuel cylinder injection type spark ignition engine generating a tumble flow in a cylinder. SOLUTION: A rising part for deflecting a tumble flow upward is provided in a top surface of a piston 5, a tumble flow passing surface 5b and an air flow stagnation surface 5c are formed, in a compression stroke, by a fuel injection valve 6, fuel is injected in an air flow stagnation side region 9b of a combustion chamber formed by the air flow stagnation surface 5c and a combustion chamber upper wall surface. The air flow stagnation surface is tilted so as to face a spark plug 7 after a latter period of the compression stroke, in a surface part 8a of the combustion chamber upper wall surface opposed to the tumble passing surface, in the compression stroke latter period, adjacent to the tumble flow passing surface, an air flow toward inside the air flow stagnation side region is generated. The air flow stagnation side region has a shape deflected so as to advance this air flow to the spark plug along the air flow stagnation surface, fuel injected in the air flow stagnation side region by the deflected air flow is guided in the vicinity of the spark plug.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a direct injection type spark ignition engine in which fuel is directly injected into a combustion chamber and ignited by a spark plug.

[0002]

2. Description of the Related Art In such a direct injection type spark ignition engine, fuel is concentrated near an ignition plug,
It is known to achieve stratified combustion which ensures ignitability and enables combustion of a lean mixture as a whole. Even in such stratified combustion, if turbulence occurs in the combustion chamber,
It has been proposed to generate a tumble flow in a combustion chamber by a structure of an intake system in order to increase a combustion speed and improve combustion.

[0003] However, such a tumble flow may cause the fuel concentrated near the spark plug to diverge and deteriorate the ignitability. to solve this problem,
Japanese Patent Application Laid-Open No. 5-33650 discloses a direct injection type spark ignition engine in which a tumble flow is generated, in which a spark plug is arranged above a side wall of a combustion chamber and a fuel injection valve for injecting fuel near the spark plug is provided. There is disclosed an apparatus provided with a reflector on the top surface of the piston to prevent the tumble flow from rising along the side wall of the combustion chamber on the side of the ignition plug.

[0004]

According to the above-mentioned prior art, the fuel concentrated near the ignition plug during stratified combustion is:
Since the tumble flow is deflected by the reflector and does not arrive near the spark plug, the tumble flow is not diverged by the tumble flow, and a reliable ignitability can be guaranteed. However, on the other hand, at the time of stratified charge combustion, since no turbulence due to the tumble flow occurs in the vicinity of the spark plug, the initial combustion becomes slow, and good combustion utilizing the tumble flow cannot be realized.

Accordingly, an object of the present invention is to provide a cylinder injection type spark ignition engine in which a tumble flow is generated in a combustion chamber.
It is to ensure good ignitability without slowing down initial combustion during stratified combustion.

[0006]

According to a first aspect of the present invention, there is provided an in-cylinder injection spark ignition engine according to the present invention, wherein a raised portion for deflecting a tumble flow generated in a combustion chamber upward on a top surface of a piston is provided. A tumble flow passage surface and an airflow stagnation surface are formed on the top surface of the piston with the top of the bulge as a boundary. In a direct injection type spark ignition engine in which fuel is injected into an airflow stagnation side region of a combustion chamber formed by a wall surface and is ignited by a spark plug arranged on the combustion chamber upper wall surface, the airflow stagnation surface is compressed. In the late stage of the stroke, the surface portion of the upper wall surface of the combustion chamber facing the tumble flow passage surface is inclined toward the spark plug, and the surface portion of the upper wall surface of the combustion chamber faces the tumble flow passage surface in the late compression stroke. The airflow stagnation side region is deflected such that the airflow travels along the airflow stagnation surface to the spark plug. The fuel is injected into the airflow stagnation side region by the deflected airflow, and is guided to the vicinity of the ignition plug.

According to a second aspect of the present invention, there is provided an in-cylinder injection spark ignition engine according to the present invention, wherein a ridge for deflecting a tumble flow generated in a combustion chamber upward is provided on a top surface of a piston, and the ridge portion is provided on the top surface of the piston. A tumble flow passage surface and an intake stagnation surface are formed at the boundary of the top of the portion, and when performing stratified combustion, the intake stagnation surface and the combustion chamber upper wall surface are formed by the fuel injection valve in the compression stroke. In a cylinder injection type spark ignition engine in which fuel is injected into an airflow stagnation side region of a combustion chamber and is ignited by an ignition plug disposed on the upper wall surface of the combustion chamber, the airflow stagnation surface includes the ignition plug in a later stage of a compression stroke. A part of the surface portion of the upper wall surface of the combustion chamber facing the intake stagnation surface,
In the latter half of the compression stroke, the squish flow has a shape that approaches the intake stagnation surface and generates a squish flow that proceeds to the spark plug along the air stagnation surface, and is injected into the air flow stagnation side region by the squish flow. The fuel is guided to the vicinity of the ignition plug.

[0008]

FIG. 1 is a schematic longitudinal sectional view through an intake / exhaust port showing a first embodiment of a direct injection type spark ignition engine according to the present invention at an early stage of a compression stroke. In the figure, reference numeral 1 denotes an intake port which opens to the upper wall of the combustion chamber,
Is an intake valve that can open and close this opening. Reference numeral 3 denotes an exhaust port that opens on the upper wall surface of the combustion chamber, and reference numeral 4 denotes an exhaust valve that can open and close this opening. Reference numeral 5 denotes a piston that slides in the cylinder. The intake port 1 has a structure that generates a tumble flow that descends along the side wall on the exhaust port side and rises along the side wall on the intake port side in the combustion chamber during the intake stroke. The fuel injection valve 6 is arranged on the upper part of the side wall of the combustion chamber on the intake port 1 side.

FIG. 2 is a plan view showing the top surface of the piston 5. Referring to FIGS. 1 and 2, on the top surface of the piston 5,
A raised portion is formed to deflect the tumble flow upward so that the tumble flow does not rise along the side wall on the intake port side of the combustion chamber. Thus, the top surface of the piston 5 has a tumble flow passage surface 5b on the exhaust port 3 side where the tumble flow passes through the top 5a of the raised portion, and an air flow stagnation surface on the intake port 1 side where the tumble flow does not pass. 5c are formed.

The tumble flow passage surface 5b on the top surface of the piston 5
Have a smooth, slightly concave inclined surface shape so as to not significantly attenuate the tumble flow. On the other hand, the airflow stagnation surface 5c on the top surface of the piston 5 also has a smooth concave slope shape, and a partially spherical depression 5d is formed at a substantially central portion of the surface 5c.

FIG. 3 is a schematic longitudinal sectional view showing the first embodiment of the direct injection type spark ignition engine according to the present invention in the latter half of the compression stroke, passing through the center of the cylinder. As shown in the figure, the ignition plug 7 is disposed substantially at the center of the upper wall surface of the combustion chamber, and in the latter half of the compression stroke, the above-mentioned airflow stagnation surface 5c is
It is supposed to go to.

The fuel injection valve 6 is directed to inject fuel into a depression 5d formed in the airflow stagnation surface 5c during the middle stage of the compression stroke. The surface portion 8a of the upper wall of the combustion chamber facing the tumble flow passage surface 5b is shaped so as to approach the tumble flow passage surface 5b in the latter half of the compression stroke. A flow region 9a is formed.

On the other hand, a surface portion 8b of the upper wall surface of the combustion chamber facing the air stagnation surface 5c has a substantially horizontal surface and an arc-shaped surface that smoothly connects this surface to the side wall of the combustion chamber. The stagnation surface 5c is not so closely approached. Therefore, in the latter stage of the compression stroke, the tumble flow is crushed in the tumble flow region 9a of the combustion chamber, and a large number of small vortices are generated. In addition, the tumble flow including the small vortex flows in the airflow stagnation region 9b of the combustion chamber. The airflow along the surface 5b flows in from the tumble flow region 9a.

This air flow is generated by the surface portion 8b of the upper wall of the combustion chamber.
Travels along this surface to reach an arcuate surface, deflects and deflects to the air stagnation surface 5c, and is further deflected to ignite along the air stagnation surface 5c to collide with the substantially horizontal surface at Proceeds to the plug 7, the airflow stagnation region 9b
This forms a flow in the opposite direction to the tumble flow.

The in-cylinder injection spark ignition engine of the present embodiment
The stratified combustion is performed when the engine is under a low load, and the stratified combustion can make the overall air-fuel ratio leaner than the stoichiometric air-fuel ratio, so that fuel consumption can be reduced. When such stratified combustion is performed, the depression 5d of the airflow stagnation surface 5c is caused by the fuel injection valve 6 in the middle stage of the compression stroke.
Fuel is injected inside. This fuel is vaporized in the depression 5d by the latter stage of the compression stroke, is guided to the vicinity of the ignition plug 7 by the above-described airflow, and forms a relatively rich mixture near the ignition plug 7.

The air-fuel mixture thus formed is reliably ignited by the spark plug 7, and thereafter, the flame propagates to the intake air in the combustion chamber to realize stratified combustion. In this stratified combustion, since the turbulence is formed in the vicinity of the spark plug 7 by the above-described airflow including a small vortex, an initial combustion with a high combustion speed is realized, and further, the tumble flow region 9a of the combustion chamber is provided. As described above, a small vortex is generated, and a small vortex is carried in the airflow stagnation region 9b by the above-described airflow. Therefore, a small vortex is generated throughout the combustion chamber. The combustion speed can be increased, and very good stratified combustion can be realized.

At high engine load, as shown in FIG. 4, if fuel is injected during the intake stroke, a uniform mixture can be formed in the cylinder by the late stage of the compression stroke by the tumble flow. Due to the turbulence near the plug 7 and the small eddy current in the entire combustion chamber, good uniform combustion with a high combustion speed is realized, and a high engine output can be obtained. Of course, when the engine is under a medium load, a part of the required fuel amount is injected into the intake stroke to form a lean homogeneous mixture in the cylinder, and the remaining fuel is injected into the compression stroke to produce a relatively rich mixture near the ignition plug 7. By forming an appropriate air-fuel mixture, it is also possible to perform stratified combustion that can obtain a relatively high engine output.

FIG. 5 is a schematic longitudinal sectional view showing a second embodiment of the direct injection spark ignition engine according to the present invention in the latter half of the compression stroke, passing through the center of the cylinder. Only the differences from the first embodiment will be described below. The in-cylinder injection spark ignition engine according to the present embodiment includes a surface portion 8a 'facing the tumble flow passage surface 5b on the upper wall surface of the combustion chamber and an airflow stagnation surface 5c on the upper wall surface of the cylinder.
The surface portion 8b 'which faces the piston 5 approaches the surface of the piston 5 to the same extent. Thereby, the first
As in the embodiment, the airflow stagnation region 9b ′ of the combustion chamber includes:
No airflow flows in from the tumble flow region 9a '.

The airflow stagnation surface 5c 'of the piston 5 has a substantially horizontal portion around it, and the peripheral portion of the upper wall surface of the combustion chamber opposed to this portion is very close to the squish in the latter half of the compression stroke. An area 10 is formed so that the squish flow generated thereby travels to the spark plug 7 along the airflow stagnation surface 5c.

When performing stratified charge combustion, the fuel injected into the depression 5d of the piston 5 is guided to the vicinity of the ignition plug 7 by this squish flow, and a relatively rich mixture is formed near the ignition plug 7. In addition to the above, turbulence due to the squish flow can be generated in the vicinity of the ignition plug 7, and good ignitability and initial combustion can be realized as in the first embodiment.

In the present embodiment, in the latter half of the compression stroke,
Since the surface portion 8a 'of the upper wall surface of the combustion chamber facing the tumble flow passage surface 5b is not so close to the tumble flow passage surface 5b, the tumble flow region 9a' of the combustion chamber has a tumble flow region as in the first embodiment. Are not crushed and the tumble flow is maintained. However, the squish flow collides with the tumble flow, so that a large number of small vortices are generated in the squish flow region 9a ', and turbulence is generated in the airflow stagnation region 9b by the squish flow. As a result, good combustion with a high combustion rate can be realized even after the initial combustion.

In the above-described two embodiments, the ignition plug 7 can be disposed substantially at the center of the upper wall surface of the combustion chamber, whereby the flame spreads uniformly throughout the combustion chamber, so that good combustion is achieved. Can be something. Also,
As compared with the case where the ignition plug 7 is arranged on the exhaust port side of the upper wall surface of the combustion chamber, the temperature of the arrangement position is lower, and abnormal combustion such as knocking and pre-ignition can be prevented. Since the fuel injection valve 6 is disposed near the intake port having a relatively low temperature in the combustion chamber, it is possible to prevent problems such as generation of vapor.

In the first embodiment, the surface portion 8b of the upper wall surface of the combustion chamber facing the airflow stagnation surface 5c of the piston 5
Was constituted by a substantially horizontal surface and an arc-shaped surface,
This is not a limitation of the present invention, and the airflow flowing out of the tumble flow region 9a of the combustion chamber is reduced by the airflow stagnation region 9b.
In this case, the air may be deflected along the air flow stagnation surface of the piston 5 toward the spark plug 7. For example, if the air flow flowing out of the tumble flow region 9a collides at an acute angle, even if the air flow is not a substantially horizontal surface, It may be an inclined surface.

In the first and second embodiments, the depression 5d formed on the airflow stagnation surface 5c of the piston 5 does not limit the present invention. For example, when the depression is omitted, stratified combustion is not performed. At the time of implementation, the fuel may be injected toward the airflow or the squish flow immediately before ignition.

[0025]

As described above, according to the in-cylinder injection type spark ignition engine according to the present invention, the ridge for deflecting the tumble flow generated in the combustion chamber upward is provided on the top surface of the piston. A tumble flow passage surface and an intake stagnation surface are formed on the top surface of the piston with the top of the ridge as a boundary, and when performing stratified combustion, the intake stagnation surface and the upper wall surface of the combustion chamber by the fuel injection valve in the compression stroke. In the in-cylinder injection-type spark ignition engine in which fuel is injected into the airflow stagnation side region of the combustion chamber formed by the ignition plug arranged on the upper wall surface of the combustion chamber, the airflow stagnation surface is in the late stage of the compression stroke. The surface portion of the upper wall surface of the combustion chamber, which is inclined toward the spark plug and faces the tumble flow passage surface, approaches the tumble flow passage surface in the latter half of the compression stroke and moves toward the airflow stagnation side region. The airflow stagnation-side region has a shape that generates a flow, and the airflow stagnation-side region has a shape in which the airflow is deflected so as to proceed to the spark plug along the airflow stagnation surface, and is deflected by the deflected airflow. At the time of ignition, because the fuel injected into the
In the vicinity of the spark plug, fuel is concentrated and turbulence is generated by the air flow, so that good ignitability and initial combustion in stratified combustion can be realized. The entire combustion chamber is disturbed by the tumble flow, and the combustion after the initial combustion is also good.

According to a second aspect of the present invention, there is provided a direct injection type spark ignition engine according to the present invention, wherein the piston top surface is provided with a raised portion for deflecting the tumble flow generated in the combustion chamber upward. A tumble flow passage surface and an intake stagnation surface are formed around the top of the ridge, and when performing stratified charge combustion, the fuel injection valve forms the intake stagnation surface and the combustion chamber upper wall surface during the compression stroke. In a direct injection type spark ignition engine in which fuel is injected into an airflow stagnation side region of a combustion chamber to be ignited by an ignition plug arranged on the upper wall surface of the combustion chamber, the airflow stagnation surface has a spark plug in a later stage of the compression stroke. Part of the surface of the upper wall of the combustion chamber that faces the intake stagnation surface approaches the intake stagnation surface in the latter half of the compression stroke and proceeds to the spark plug along the airflow stagnation surface. Since the fuel injected into the airflow stagnation side region is guided by the squish flow to the vicinity of the ignition plug, the fuel is concentrated near the ignition plug at the time of ignition. At the same time, turbulence is generated by the airflow, and good ignitability and initial combustion in stratified combustion can be realized. The entire combustion chamber is disturbed by the tumble flow, and the combustion after the initial combustion is also good.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view of a direct injection type spark ignition engine according to a first embodiment of the present invention passing through an intake / exhaust port at an early stage of a compression stroke.

FIG. 2 is a plan view showing a top surface of the piston of FIG. 1;

FIG. 3 is a schematic vertical cross-sectional view passing through the center of the cylinder showing the first embodiment of the direct injection spark ignition engine according to the present invention in the latter half of the compression stroke.

FIG. 4 is a schematic vertical cross-sectional view passing through the center of the cylinder, showing the first embodiment of the direct injection spark ignition engine according to the present invention in the intake stroke.

FIG. 5 is a schematic vertical cross-sectional view passing through the center of a cylinder, showing a second embodiment of the direct injection spark ignition engine according to the present invention in the latter half of the compression stroke.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Intake port 3 ... Exhaust port 5 ... Piston 5b ... Tumble flow passage surface 5c, 5c '... Airflow stagnation surface 6 ... Fuel injection valve 7 ... Spark plug 9a, 9a' ... Tumble flow region 9b, 9b '... Airflow stagnation region 10 ... Squish area

Continuing from the front page (72) Inventor Hiroyuki Kitahi 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Eiki 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation

Claims (2)

[Claims] 1. A ridge for deflecting a tumble flow generated in a combustion chamber upward on a top surface of a piston, and a tumble flow passage surface and an airflow stagnation surface are formed on the top surface of the piston with the top of the ridge as a boundary. When performing stratified combustion, fuel is injected into the airflow stagnation side region of the combustion chamber formed by the airflow stagnation surface and the upper wall surface of the combustion chamber by the fuel injection valve during the compression stroke, In a direct injection type spark ignition engine ignited by an ignition plug disposed on a room upper wall, the airflow stagnation surface is inclined toward the ignition plug in a later stage of a compression stroke, and faces the tumble flow passage surface. The surface portion of the upper wall surface of the combustion chamber has a shape that generates an airflow that approaches the tumble flow passage surface in the late stage of the compression stroke and flows toward the airflow stagnation side region. The airflow stagnation side region has a shape that is deflected so that the airflow proceeds along the airflow stagnation surface to the spark plug, and the fuel injected into the airflow stagnation side region by the deflected airflow. Is directed to the vicinity of the spark plug. 2. A ridge for deflecting a tumble flow generated in a combustion chamber upward on a top surface of a piston, and a tumble flow passage surface, an intake stagnation surface and a stagnation surface are formed on the top surface of the piston with the top of the ridge being a boundary. When performing stratified combustion, fuel is injected into the airflow stagnation side region of the combustion chamber formed by the intake stagnation surface and the combustion chamber upper wall surface by the fuel injection valve during the compression stroke, In a direct injection type spark ignition engine ignited by an ignition plug disposed on a chamber upper wall, the airflow stagnation surface is inclined toward the ignition plug in a later stage of a compression stroke, and the combustion opposing the intake stagnation surface. A part of the surface portion of the upper chamber wall surface may generate a squish flow that approaches the intake stagnation surface and travels along the airflow stagnation surface to the ignition plug in a later stage of the compression stroke. A direct injection type spark ignition engine, wherein the fuel injected into the airflow stagnation side region by the squish flow is guided to the vicinity of the spark plug.