Direct-injection spark-ignition engine

The This invention relates to a cylinder injection engine with Spark ignition, a having combustion chamber formed by a cylinder wall of a cylinder block, a cylinder, has a bottom surface of a cylinder head, mounted on the cylinder block and a piston crown of a piston provided in the cylinder, a spark plug, placed substantially in the center of the combustion chamber, an intake system for the Introducing the intake air into the combustion chamber and generating a normal tumble flow of the intake air in the combustion chamber, wherein the inlet system comprises two inlet openings includes to the combustion chamber and a partial shut-off valve, which is essentially the lower half of each the two inlet openings closes; a fuel Ritzer valve provided at a side wall portion the combustion chamber and disposed between opening ends of the two inlet openings for the direct injection of fuel into the combustion chamber at a compression; and a piston bowl cavity formed in the Piston crown and receiving the normal tumble flow upright.

On such a direct injection spark ignition engine is z. B. in the JP Reference 8-296 463A taken.

In addition, different spark-ignition proposed and developed internal combustion engines with direct been injected into the fuel directly into the engine cylinder has been. In general, with such spark-ignited internal combustion engines direct a combustion mode between a homogeneous Combustion (a burn operation with early injection) wherein the fuel injection is carried out early in the suction stroke and a homogeneous air / fuel mixture produced, and a stratified Charge combustion engine can be switched (a burn operation with later Injection), in which a late Fuel injection this moment delayed until near the end of the compression stroke to to produce a stratified air / fuel mixture. As is well it is known to switch between these two combustion modes is dependent on determined by the engine operating conditions such as engine speed and load. Such stratified or stratified combustion mode is effective under operating conditions of low engine load, where the Amount of the injected fuel is relatively low. In contrast this is while operation under high engine load conditions where the amount of fuel the sprayed out is, due to the demands for greater engine power and larger engine output torque is relatively large, a lower requirement for a stratified charge and, instead, it is necessary uniform air / fuel mixture layers to form, in particular in order to avoid that the engine knocks. Such spark-ignition Internal combustion engine with direct injection is in Japanese Provisional Patent publication No. 8-35429 or in the interim Japanese Patent Publication No. 6-81651 shown. The preliminary Japanese Patent Publication No. 8-35429 teaches the use of a swirl control valve, the turbulent flow produced by modulating the gas into the cylinder movement and the education of the air / fuel mixture modulated. On the other hand teaches Japanese Provisional Patent publication No. 6-81651 the use of upright, straight intake ports, which serve to effect the intake air into the combustion chamber is drawn in a direction of a curved piston head top to steer and the intake air stream in a strict reverse tumble flow stable for a divert combustion.

Also teaches the <patcit><text>DE 196 19 782 A1</text></patcit> providing a nozzle inside an intake port for influencing of the intake air flow.

In the spark ignition Internal combustion engines with direct injection according to the Japanese provisional Patent Publications No. 8-35429 and 6-81651 is a deep piston bowl cavity combustion chamber in a piston top (or a piston head) formed. The Fuel injection while performed the compression stroke, the aforementioned case flow or counter-case flow maintain the cylinder and then transmits the vortex flow (or the tumble flow) the air / fuel mixture in the vicinity of the spark plug. As a result, the rich mixture (an easily ignitable concentrated mixture) around the spark plug and the concentration of the rich mixture is during the Compression ignited first. Second, the surrounding air layers (lean or ultra-lean Mixture layers of an air / fuel ratio close to a lean misfire limit) ignited the little fuel included. To get a good stratified combustion to ensure (or at effectively the easily ignitable mixture in the vicinity of the spark plug to concentrate), it is not preferred, the fuel injection, injected from the fuel injection nozzle during the compression stroke, inner half of the combustion chamber during a certain time period distribute widely, while the fuel spray, injected, in the vicinity the spark plug will be carried. From the above-mentioned establish in conventional spark ignition Internal combustion engines with direct injection, the piston bowl cavity combustion chamber in the piston crown is formed so that the center axis of the piston-bowl cavity far from&lt;?page 3?&gt;to the center axis of the piston in the direction to is offset to the intake valve, such that the piston bowl cavity as a relatively deep and greater Cavity is formed. also is shown in the engines of the prior art in Japanese provisional Patent Publications No. 8-35429 and 6-81651, a spray angle of the fuel, which is injected through the injection valve, closely or smaller. Due to such a small fuel spray angle tends the focus of the sprayed fuel to the side to be concentrated so that an undesirably increased Sprühbenetzung (Sprühversatz) occurs. Due to the excessively increased Sprühpenetrierung , the fuel that impinges on the piston head or with this collides (ie with the piston bowl cavity Verbrennungskammerwandung or the wall of the bowl cavity combustion chamber) and that is reflected from this, secondary to the cylinder wall during the homogeneous combustion impinge on the intake stroke. As such Impingement of the fuel injection with a narrow angle to the Piston bowl cavity, there is an increased Orientation for the incoming fuel, on the wall of the piston bowl cavity combustion chamber to adhere in the form of a fuel film and as a result could be a rapid carbonization occur so that the exhaust emission control performance by increased Exhaust emissions, such as smoke and particulate matter, and by the formation of unburned hydrocarbons (HC) are affected can. It is possible, that the increased Sprühpenetration undesirable Deposits in the engine performs. The deep and wide Piston bowl cavity combustion chamber leads to an increase in the total surface area of ​​the combustion chamber and thus increased thermal losses. also impaired the eccentric Piston bowl cavity a Piston balance of the piston-type open-burning. especially while the cold start operation is a large difference between a thermal expansion efficiency of the engine cylinder and a thermal Expansion efficiency of the spool and thus the piston often suffers from a undesirable Clamping movement. The clamping movement of the piston during the Cold start operation occurs, noise and an unbalanced causing piston wear.

Regarding such a direct injection spark-ignition engine, it is an object of the invention improve stable stratified combustion stability of such a motor and thereby enhance the engine performance.

For one Engine of the above-mentioned type, this object is in an inventive Way solved that a fuel mist sprayed from the Kraftstoffeinspritzerventil while of the compression stroke is executed in the normal case and a flow in the vicinity of Tip through the spark plug the normal tumble flow supplied is, and the piston bowl two opposite flat side walls un has d a curved, rounded bottom wall portion formed along the streamlines the normal tumble flow, so that relatively strong normal tumble flow masses within a controllable Fallströmungs- area between the two opposite sidewalls are formed.

More Preferred embodiments are in the subclaims resigned.

in the Following the invention in greater detail by means regarding the accompanying drawings explained, in which:

<figref idrefs="S18">1</figref> is a longitudinal sectional view, a cylinder of spark ignition Internal combustion engine with direct injection shows that having a piston with a spherical, bowl-like Piston cavity (the part of the invention forms) is provided;

<figref idrefs="S19">2</figref> is a plan view of the piston of the engine of <figref idrefs="S18">1</figref>, the one improved spherical bowl-like formed in the piston combustion chamber arrangement;

<figref idrefs="S19">3</figref> is a perspective view of the piston head portion Motor according to the <figref idrefs="S18">1</figref> shows;

<figref idrefs="S20">4</figref> is a graph showing the relationship between combustion stability and a ratio (d / D) an inner diameter (d) of the circular opening of the piston bowl cavity to a cylinder bore (D) shows;

<figref idrefs="S20">5</figref> is a diagram of the relationship between a thickness case flow near the top dead center (ie a downflow maintenance performance) and a ratio (R / D) of the radius of curvature (R) of the curved, recessed Section of the piston bowl cavity to the cylinder bore (D) shows:

<figref idrefs="S21">6</figref> is a graph showing the relationship between combustion stability and a spray angle a cone-shaped Fuel jet which is injected, shows:

<figref idrefs="S22">7</figref> is a longitudinal sectional view, an embodiment a spark-ignition internal combustion engine direct shows that has a piston with a scheibenfedernutartigen piston bowl cavity in accordance with the Invention is provided is provided;

&lt;?page 4?&gt;

<figref idrefs="S23">8</figref> is a plan view of a piston of the engine of the embodiment, the improved scheibenfedernutartige, the piston bowl-like having trained combustion chamber structure.

<figref idrefs="S23">9</figref> is a perspective view of the piston head portion Motor of the embodiment shows.

<figref idrefs="S24">10</figref> is is a perspective view showing a modification of a case flow amplification device or mechanism shows.

reference Referring now to the drawings, and in particular <figref idrefs="S18">1</figref> to <figref idrefs="S19">3</figref>. is the spark-ignition Internal combustion engine according to the invention using a four-valve spark ignition gasoline engine shown. Like in the<figref idrefs="S18">1</figref> is shown, wherein the spark-ignition internal combustion engine with direct injection, which does not form part of the invention is the spark plug <figref>11</figref> in the Substantially in the center of the combustion chamber <figref>4</figref> arranged. The cylinder head <figref>2</figref> is on a cylinder block <figref>1</figref>. of an engine cylinder, mounted. A piston <figref>3</figref> is received in the cylinder to slide along a stroke to be movable in the cylinder. The combustion chamber<figref>4</figref> is the cylinder wall of the cylinder block <figref>1</figref>, The bottom surface of the cylinder head <figref>2</figref> and the top surface (or the piston crown or the piston head) of the piston <figref>3</figref> limited. The motor is provided with two inlet openings (<figref>7</figref>. <figref>7</figref>) Equipped, the opposite the axial center line of the cylinder in the cylinder block <figref>1</figref> drilled is displaced. As clearly shown in<figref idrefs="S19">2</figref> to see is, is the cylinder head <figref>2</figref> with two intake valve openings (<figref>7</figref>. <figref>7</figref>) Equipped, the opposite the axial center line of the cylinder in a cylinder block <figref>1</figref> educated is displaced, and with two gas valve openings (<figref>8</figref>. <figref>8</figref>) the opposite the axial center line of the cylinder in the opposite or opposing Direction are offset to the positions of the inlet openings. As made in <figref idrefs="S18">1</figref> and <figref idrefs="S19">2</figref> It can be seen, the motor has so-called cross-flow aperture arrangement. Two intake valves (<figref>5</figref>. <figref>5</figref>) Are in the respective inlet apertures (<figref>7</figref>. <figref>7</figref>) Arranged in order to open and close, while two exhaust valves (<figref>6</figref>. <figref>6</figref>) In the respective outlet ports (<figref>8</figref>. <figref>8</figref>) Are arranged in order to open and close. Each of the intake ports (<figref>7</figref>. <figref>7</figref>) Is contoured to easily a can cause sufficient turbulent effect, ie a strong case flow can provide the air / fuel mixture, in the form of a vertical vortex tumble flow (tumble flow in Cylinder) but within the combustion chamber <figref>4</figref>. as shown in the arrow a in <figref idrefs="S18">1</figref> indicated. As in the motor is shown, a case flow strengthening means or a case flow strengthening mechanism <figref>9</figref> also in each of the intake ports (<figref>7</figref>. <figref>7</figref>) Contained in the intake system, provided for the purpose of forcibly introducing a strong case action (tumbling action) on the air / fuel mixture, in particular during a Burn operation with stratified charge (a burn operation with later Injection), in which a late fuel-injection the event delayed until near the end of the compression stroke to to produce a stratified air / fuel mixture and the combustion flame in a small very rich air / fuel mixture layer around the tip of the spark plug <figref>11</figref> starts and after the ignition, to the leaner mixture, the rest of the combustion chamber <figref>4</figref> fills spreads. As seen from <figref idrefs="S18">1</figref> and <figref idrefs="S19">2</figref> apparent is (an embodiment the invention is later completely described) and from the <figref idrefs="S22">7</figref> and <figref idrefs="S23">8</figref> (A second embodiment) the full later is explained) is a part-closing valve <figref>10</figref> as the case flow strengthening mechanism <figref>9</figref> used. The Partial shut-off valve <figref>10</figref> is in its closed position moved to substantially the lower half of each of the intake ports (<figref>7</figref>. <figref>7</figref>) while shut the stratified combustion mode to a strong case flow generating in the combustion chamber. The partial shut-off valve<figref>10</figref> becomes in its open Position moves to a full flow connection while therethrough a homogeneous combustion mode (a combustion mode with early injection) ensure, wherein the fuel injection at an early stage in the intake stroke produces a homogeneous air / fuel mixture and then subsequently the mixture evenly on an air / fuel ratio is mixed as near as possible to the stoichiometric (14.6: 1 air / fuel ratio (AFR)). A fuel injection valve <figref>12</figref> is in a side wall portion the combustion chamber <figref>4</figref> and in the vicinity of the substantially central Portion of the downstream opening ends of the intake ports (<figref>7</figref>. <figref>7</figref>) Arranged so as to direct fuel into the combustion chamber <figref>4</figref> inject or spray out.

A spherical, dished piston Schüsselhohlraum- Combustion chamber (or a spherical cup-shaped piston bowl cavity combustion chamber) <figref>13</figref> is in the center portion of the piston head <figref>3</figref> educated. The spherical, dished piston cavity <figref>13</figref> is in the central portion of the piston head formed so that the maximum cup depth of the cavity <figref>13</figref> in the center of the cavity is obtained, so that the central deepest Point of the cavity with the central axis of the piston <figref>3</figref> matches and the spherical, cup-like cavity <figref>13</figref> is coaxial with respect to the central axis the piston <figref>3</figref> arranged. In addition, a spherical curved, recessed inner concave peripheral wall surface (or &lt;?page 5?&gt;a concave bottom wall surface) of the cavity <figref>13</figref> so sized or contoured to the recessed inner peripheral wall surface of the cavity <figref>13</figref> in a direction of a flow line the previously explained case flow bent or is rounded, indicated by the arrow a in <figref idrefs="S18">1</figref>, In the piston assembly of the engine, as best seen in <figref idrefs="S19">3</figref> appreciated is the piston bowl cavity combustion chamber <figref>13</figref> as a spherical recessed, bowl-shaped cavity educated. For the reasons the following with reference to the <figref idrefs="S20">4</figref> and <figref idrefs="S20">5</figref> are explained, is the top end of the circular opening (easy the circular opening) the spherically-recessed, bowl-like Combustion chamber space <figref>13</figref> dimensioned such that the ratio (d / D) the inner diameter (d) of the circular opening of the dish-like Hohlraumverbrennungskarnmer <figref>13</figref> to the cylinder bore (D) within a range of 40% to 80% (see <figref idrefs="S20">4</figref>) set, and such that the ratio (R / D) of the radius of curvature (R) to the cylinder bore (D) within a range of 20 % Is 65%. additionally to the aforementioned is in the embodiment shown a wide-angle injector as a fuel injector <figref>12a</figref> of Injector <figref>12</figref> used a wide fuel spray angle ensure that ranges from 70 degrees to 90 degrees and to correspondingly the spray characteristics to improve, for example, the peak penetration (fuel-spray penetration) the spray Wandungs-hitting, the air / fuel mixing and the formation of a controlled Air / fuel mixture layer.

As from the foregoing, Clearly, in the engine is the spherical bowl-like piston bowl cavity combustion chamber <figref>13</figref>centrally formed in the central portion of the piston crown, so formed, to the most deeply recessed, inner peripheral wall section has at the center of the piston crown and is the spherical, recessed, inner circumferential wall surface the cavity is contoured to the spherically recessed inner peripheral wall surface is substantially along a flow line the tumble flow (see the arrow A of <figref idrefs="S18">1</figref>) Of the intake air is curved. This suppresses or avoids occurrence of an undesired disturbance in the flow case. in the A result, a downflow maintaining power can be increased. Therefore , the fuel jet (denoted by F in the <figref idrefs="S18">1</figref> and <figref idrefs="S19">2</figref>) the of the injector <figref>12</figref> in the compression stroke during stratified charge combustion safely and reliably the tumble flow worn and in the vicinity the tip of the spark plug <figref>11</figref> are fed, to a richer air / fuel mixture layer around the spark plug for easy ignition to form. Accordingly, the combustion stability can stratified greatly increased combustion will. How vorerläutert, is the form of the arrangement (training) of the spherical, bowl-like Piston cavity <figref>13</figref> effective to build a strong case to flow produce and undesirable disorder in terms of the case flow to suppress. also eliminated the right set of conditions d / D and R / D the need for an excessively and deep unfounded Piston bowl cavity. Therefore, it is possible the piston Schüsselhohlraum- combustion chamber <figref>13</figref> as small as possible form. As a result, which can be the total surface area the combustion chamber <figref>4</figref> be reduced, so that hereby effective thermal losses are reduced and whereby the engine power output while the homogeneous combustion as well as during the stratified combustion mode elevated can be. Due to the high downflow maintaining performance, obtained by the unique shape and arrangement of the spherical, bowl-like Piston cavity combustion chamber <figref>13</figref> , the fuel the rate of the injector <figref>12a</figref> injected and throughout the combustion chamber <figref>4</figref> is distributed, effectively through the full cooperation of the controlled strong tumble flow (see the arrow A of <figref idrefs="S18">1</figref>) And the reason-curved, recessed inner circumferential wall surface the cavity <figref>13</figref> raised and simultaneously transmits the strong Tumble to a forcible separation of the fuel film, the the on the inner wall cavity <figref>13</figref> adheres in. This avoids that, due to the fuel film an undesirable Carbonization occurs and increases a total combustion stability (including a stability homogeneous combustion as well as a stability of a stratified combustion) with remarkable decrease of Exhaust emissions such as smoke, particulate matter (PM), unburnt Hydrocarbon (HCs) and the suppression of the formation of deposits. also is the spherical bowl-like Piston cavity <figref>13</figref> substantially in the central portion of the formed piston crown and thus is a balance of the piston <figref>3</figref>. the upward and down moved well. The good dynamic piston balance that centrally from the trained, spherical, bowl-like cavity <figref>13</figref> formed, eliminates or reduces noise and unsymmetrical piston wear during Operation of the motor and extended in this way the life of the engine. Specifically, the piston bowl cavity combustion chamber<figref>13</figref> as a spherical recessed, cup-shaped formed portion and thus the entire maintenance performance for the Downflow components in all fluid flow directions the air drawn into the air flow included are increased (or the intake air flow, which enters through the inlet port). These improved overall downflow maintaining performance realized a sta&lt;?page 6?&gt;bilere combustion during the combustion mode stratified charge. Also, in the inlet opening<figref>7</figref> the Case flow strengthening mechanism <figref>9</figref> (eg Part-closing valve <figref>16</figref> in the first and second embodiment) provided. As mentioned above, is the case flow strengthening mechanism <figref>9</figref> to, forced a strong tumble flow and to provide the air / fuel mixture a strong case action to rent. The creation of the case flow strengthening mechanism<figref>9</figref> increased a Operating Range the stratified charge combustion. As in the<figref idrefs="S18">1</figref> and <figref idrefs="S22">7</figref> shown, is the part-closing valve <figref>10</figref> as the downflow amplification device <figref>9</figref> used so that the part-closing valve <figref>10</figref> closes to the bottom half of the flow channel cross-section the inlet opening <figref>7</figref> during stratified to seal combustion and opens completely, a complete flow connection the inlet opening <figref>7</figref> during the to establish homogeneous combustion. The partial closure valve<figref>10</figref> is simple in structure and easy in the inlet opening <figref>7</figref> to install, so that a case flow strengthening mechanism is provided with a low cost.

reference Referring now to <figref idrefs="S20">4</figref> and <figref idrefs="S20">5</figref> are in these variations in a stable stratified combustion shown, influenced by the size of an area of ​​the circular opening of the spherically-recessed, bowl-like Cavity combustion chamber <figref>13</figref> and the depth of the cavity <figref>13</figref>, The test data in the <figref idrefs="S20">4</figref> and <figref idrefs="S20">5</figref> shown are, are experimentally assured by the inventors of the invention. As out <figref idrefs="S20">4</figref> It can be seen, when the ratio d / D the diameter (d) of the circular opening to that of the cylinder bore (D) set to 60%, showing the engine the highest combustion stability the stratified combustion. If the ratio (d / D) is set to near 30%, is the opening area the spherical bowl-like Piston bowl cavity <figref>13</figref> excessively tight and the excessively narrow cavity opening has the difficulty to receive the injected fuel jet or capture. This allows the fuel Einsprühstrahl, undesirably distribute or within the combustion chamber <figref>4</figref> to diffuse, so that from this unstable combustion results. In contrast, when the opening area the spherical, cup-like piston bowl cavity is excessively large, eg. For example, when the opening area the cavity is set to nearly 90%, a tendency of fuel Einsprühstrahl to be easily within the cavity combustion chamber <figref>13</figref> distributed to be,. due to the excessively large cavity opening in addition, as shown from the characteristic curve in <figref idrefs="S20">5</figref> apparent is changed the strength the tumble flow (or the Fallströmungs- Maintaining power) as a function of the ratio (R / D) the radius of curvature R of the curved the recessed portion of the spherical cup-like piston bowl cavity <figref>13</figref> to that of the cylinder bore D. As from <figref idrefs="S20">5</figref> apparent is, if the ratio R / D to about 40% is set, the highest Downflow maintaining performance are obtained. The downflow maintaining performance is at a relatively high maintained level when the ratio R / D is within the range of 20% to 65%. In contrast this, when the ratio R / D is less than 20%, or when the ratio R / D is more than 70%, there is a tendency in that the downflow maintenance performance decreases. Based on the test results in the<figref idrefs="S20">4</figref> and <figref idrefs="S20">5</figref> illustrated are, the diameter D of the circular opening of the spherical cup-like Piston bowl cavity set so that the relationship he d / D is in a range of 40% to 80%, wherein the radius of curvature R of the spherical, cup-like piston bowl cavity <figref>13</figref> established is he the ratio R / D is sufficient in a range of 20% to 65%, and whereby the engine power output due to both the increased stability coated combustion, as well as the increased downflow maintenance performance elevated is.

reference Referring now to <figref idrefs="S21">6</figref> in this, the spray angle / combustion stability characteristic curve shown. As from<figref idrefs="S21">6</figref> is apparent when the Fuel spray angle is below 70 degrees, there is a tendency that the Recast or insertion effect for the air / fuel mixture, of the strong tumble flow is generated while the combustion mode with stratified charge decreases. In addition, a leading relatively narrow Spray angle (under 70 degrees) to a reduced air / fuel mixture homogenization penetration due to the increased Sprühdurch while the combustion mode with homogeneous combustion (during Operation with earlier Fuel injection in the suction stroke) and also leads to an adhesion the fuel film on the piston crown. With a spray angle below 70 degrees tends both the combustion stability during the homogeneous combustion as well as during the stratified combustion to diminish. In contrast, it is when the spray angle is set to be larger than 90 degrees is a tendency that the fuel Einspritzsprühstrahl excessively within the combustion chamber dispersed, namely due to the excessively wide spray angle (Above 90 degrees). Such a far-dispersed fuel spray resulting in an undesirable Adhesion of the fuel film at the spark plug and cause sooty carbon deposits on the insulator around the electrode of &lt;?page 7?&gt;spark plug <figref>11</figref>, This deteriorates stability the stratified combustion. To both in terms of coated Combustion and homogeneous combustion stable combustion characteristics to obtain, the spray angle is within a predetermined angular range of 70 to 90 degrees set. By the predetermined spray angle in the range of 70 to set 90 degrees, using the spark-ignition internal combustion engine with Direct injection according to the embodiment a wide-angle injector. Therefore, a stability the stratified combustion to a greater extent be increased. It should also the use of the wide-angle injection nozzle which is capable of a Sprühwinkelbereich to achieve from 70 to 90 degrees, effective to homogenization of the mixture during to promote the mode with homogeneous combustion and thus suppresses Formation of smoke, unburned hydrocarbons, sooty carbon deposits.

reference Referring to the <figref idrefs="S22">7</figref> to <figref idrefs="S23">9</figref> is in this motor structure according to one embodiment of the invention shown. The engine configuration of the embodiment of<figref idrefs="S22">7</figref> to <figref idrefs="S23">9</figref> is similar of the motor according to the <figref idrefs="S18">1</figref> to <figref idrefs="S19">3</figref> with the Except. that the shape of the piston bowl cavity of the embodiment of the invention from that of the engine described in conjunction with the <figref idrefs="S18">1</figref> - <figref idrefs="S19">3</figref> different is.

As best of <figref idrefs="S23">9</figref> apparent, the motor according to the invention is of the described embodiment only in slightly of the motor of the <figref idrefs="S18">1</figref> - <figref idrefs="S19">3</figref> differently, that the piston used in the engine according to the embodiment; with a scheibenfedernutförmigen Piston bowl cavity <figref>113</figref> provided is. Thus, the same reference numerals have been used are to the elements shown in the engine according to the embodiment in the <figref idrefs="S18">1</figref> to <figref idrefs="S19">3</figref>To designate, on applied corresponding elements that, in the engine of the embodiment shown in <figref idrefs="S22">7</figref> to <figref idrefs="S23">9</figref>, used are, for purposes of comparison.

Just the piston structure to scheibenfedernutartigen piston bowl cavity <figref>113</figref> having, will be described in detail with reference to the accompanying drawings explained, while a detailed description of the other elements will be omitted here is because the aforementioned description the same self-explanatory appears with respect to the first embodiment. As seen from <figref idrefs="S22">7</figref> to <figref idrefs="S23">9</figref> clearly is the scheibenfedernutartige piston bowl cavity <figref>113</figref> by two opposite, parallel side wall portions and a rounded bottom wall portion defined. The aforementioned two square opposite parallel essentially flat side walls of the crescent cavity <figref>113</figref> are formed in such a manner that is taken on case flow extend, as shown by serving a case in <figref idrefs="S22">7</figref> implied and is substantially parallel to the direction of the tumble flow, indicated extend by the arrow A. The aforementioned rounded bottom wall portion the cavity <figref>113</figref> is given in the direction of the tumble flow , Some designed by the arrow a. The radius of curvature R of the piston scheibenfedernutartigen bowl cavity <figref>113</figref> is parallel by one level to the aforementioned two opposite flat side walls cut. As seen from<figref idrefs="S22">7</figref> to <figref idrefs="S23">9</figref> apparent is, has the rounded bottom wall portion of the cavity <figref>113</figref> the same radius of curvature in the direction perpendicular to the two opposite parallel, crescent substantially Side walls of the cavity <figref>113</figref>, A square opening (a substantially regular square opening) the scheibenfedernutartigen piston bowl cavity <figref>113</figref> becomes by two parallel, obtuse edge limited sections the rounded bottom wall portion and the two parallel, perpendicular edge limited portions of the two opposing flat side walls limited. In the same manner as the cavity<figref>13</figref> of the first embodiment is to provide a stable stability the stratified combustion to create, the length d of each of the four sides of the square opening the scheibenfedernutartigen piston bowl cavity <figref>113</figref> so dimensioned such that the ratio (D / D) to the diameter of the cylinder bore within 40% to 80%. in addition, the Fallströmungs- to enhance maintenance performance, the radius of curvature R of the rounded bottom wall portion of the cavity <figref>113</figref> so dimensioned such that the ratio (R / D) of the radius of curvature R of the rounded bottom wall portion to that of the cylinder bore D is within the range of 20% to 65%. Thus, the engine can For example, after the second execution the same effects as those in the first embodiment cause. It should also the rounded bottom wall portion of the cavity <figref>113</figref> along the direction (or the flow line) the case flow (See the arrow A, shown in <figref idrefs="S22">7</figref>) effective recessed and also are the two opposite flat side walls the cavity <figref>113</figref> substantially parallel to the flow line the case flow educated. Thus, securing the two opposite flat side walls and the smoothly curved, rounded bottom wall portion of the cavity <figref>113</figref> a good Converging effect and an increased Flow straightening effect on the case flow. As a result, the downflow maintaining performance in higher be increased and enlarged dimensions. Accordingly, the stability of stratified Ver&lt;?page 8?&gt;combustion are further increased.

reference Referring to <figref idrefs="S24">10</figref> shall provide for the modification of the case flow strengthening mechanism <figref>9</figref> shown. In the above-described first and second embodiments, as a Example of the case flow strengthening mechanism Part-closing valve <figref>10</figref> used. In contrast, according to the modification in <figref idrefs="S24">10</figref> on Downflow reinforcing agents with the inlet valve <figref>5</figref> even connected. As in<figref idrefs="S24">10</figref> shown is, has the intake valve <figref>5</figref> a valve head <figref>5a</figref> and a valve stem portion <figref>5b</figref> on. The free end of valve stem <figref>5b</figref> with a slotted portion provided with a projection portion of a control arm <figref>14</figref> to Preventing rotational movement of the valve stem <figref>5b</figref> coupled is. A curved, a tumble effect producing, partly a collar educated, upright wall portion <figref>15</figref> is on the back of the valve head portion <figref>5a</figref> so connected thereto that it's over in the circumferential direction the lower half of the valve head portion <figref>5a</figref> extends. Therefore, by the tumble flow Shutting off the sucked air flow passing through the opening space the lower half side of the intake valve <figref>5</figref> flows, are amplified. In such a case, the case flow strengthening means or device only by the structural change the valve head portion of the intake valve <figref>5</figref> be achieved. To a downflow amplifying means to create or device with a low manufacturing cost, it is advantageous to generating the tumble flow effect neck-shaped wall portion <figref>15</figref> one piece with the inlet valve <figref>5</figref> perform or integral with this to connect. As stated above, when the case flow strengthening means or device <figref>9</figref> is provided a method of operation easily be extended by stratified combustion. In the shown embodiments is the fundamental Concept (main feature) of the invention by way of example as the solitary piston bowl cavity structure clarifies that generates proper case flow (The vertical vortex airflow movement, which is generated in the vertical direction, as indicated by the Arrow A in <figref idrefs="S18">1</figref> and <figref idrefs="S22">7</figref> illustrated is). As clearly the concept of the invention may also a piston bowl cavity structure be applied, which produces a so-called reverse-tumble flow (vertical Eddy current movement, in the opposite case the flow direction in relation to the Direction as is indicated by the arrow A, generated).

As already explained above, , the bowl-like the piston formed combustion chamber arrangement a scheibenfedernutartigen have cavity a square opening and the deepest portion in a cavity center thereof has.

Of the scheibenfedernutartige cavity is opposed by two, parallel, substantially semi-circular flat side wall portions and a rounded bottom wall portion formed.

Preferably the ratio the length of each of the four sides of the square opening of the scheibenfedernutartigen Cavity to the cylinder bore is within a range of 40% to 80% set, and also the ratio of a radius of curvature of the rounded bottom wall portion of the scheibenfedernutartigen Cavity to the cylinder bore is within a range 20% fixed and 65%. More specifically, the direct injection engine may spark-ignition also a downflow amplification device exhibit that is provided in a single-line system. The Fallströmungs- amplifying device may have a teilabschaltbares valve closed in a Position is movable to a lower half of the inlet port during the disable stratified charge combustion mode, and in a open position to the full Fluid communication therethrough during the homogeneous combustion mode secure.

In This mode generates the fuel injection early in an Intake a homogeneous air-fuel mixture.

alternative can Fallströmungs- amplifying device a collar-like wall section, connected to the rear of the valve head portion of the intake valve, so that the collar-like wall section in the circumferential direction on the lower half of the Valve head portion extends. Moreover, the different spray characteristics reinforce namely the peak penetration (the fuel spray mist penetration), the spray mist / wall abutment, the air / fuel mixing and the formation of a controlled air / fuel mixture layer, it is preferred that the fuel injection valve, a breitwinklige injection a Kraftstoffsprühwinkels has the from 70 ° to 90 ° is sufficient.

Again, the direct injection spark-ignition engine between a stratified Charge combustion mode where the fuel injection into a Compression is carried out, while the introduction of a vertical vortex flow in case an air introduced, which is einsogen into the combustion chamber through an intake port, and a homogeneous combustion mode where fuel injection early in the Intake a homogeneous air-fuel mixture produced, has &lt;?page 9?&gt;on a cylinder block having a cylinder, a piston movable by a stroke in the cylinder, and a centrally-formed bowl-like formed in the piston combustion chamber assembly in its piston head has a cylinder head mounted on the cylinder block, a center arranged spark plug and a fuel injection valve in the vicinity of the intake valve for the direct injection of the fuel is provided in the combustion chamber. The bowl-like formed in the piston combustion chamber is formed so that the deepest portion of the bowl-like get trained in the piston combustion chamber in the middle of the piston head is, and the concave inner wall surface of the cavity combustion chamber is designed to be curved in a direction of a flow line of the vertical vortex tumble flow.