JP4338660B2 - engine - Google Patents

Description

  The present invention includes a combustion chamber having an ignition plug at an upper portion, an intake passage through which fresh air taken into the combustion chamber flows, an exhaust passage through which exhaust gas discharged from the combustion chamber flows, and a branch from the exhaust passage And an EGR path connected to the exhaust gas supply section of the intake path, and the exhaust gas flowing into the EGR path from the exhaust path flows into the intake path from the exhaust gas supply section.

  As a method for suppressing the generation of NOx (nitrogen oxide) in the engine, an EGR path connecting the exhaust path and the intake path is provided, and exhaust gas discharged from the combustion chamber to the exhaust path is recirculated to the intake path through the EGR path. An exhaust gas recirculation method (hereinafter referred to as EGR) is known, and by performing this EGR, exhaust gas having a relatively large specific heat is mixed with fresh air sucked into the combustion chamber, thereby reducing the heat capacity of the fresh air. The increase in combustion temperature can be suppressed.

  As an engine for performing EGR as described above, the intake passage is divided into two passages, and the exhaust gas is supplied by connecting the EGR passage to only one of the passages so that the exhaust gas is stratified in the combustion chamber. The engine (for example, refer to Patent Document 1) and a mixing mechanism for accelerating mixing by rotating fresh air and exhaust gas in the intake passage, respectively, and homogenizing the exhaust gas in the combustion chamber An engine configured as described above (for example, see Patent Document 2) is known.

  In a so-called stratified combustion engine in which fuel is biased near the upper spark plug in the combustion chamber and burned, EGR is performed in a form in which the exhaust gas is stratified in the combustion chamber. In this case, the amount of exhaust gas supplied is increased to suppress the excessive increase in the combustion speed and combustion temperature, thereby suppressing the generation of NOx. The combustion state achieved can be realized, and the production of CO (carbon monoxide) and THC (unburned hydrocarbon) can be suppressed.

  On the other hand, in an engine that homogeneously burns a mixture with a high equivalence ratio in the combustion chamber as a whole, exhaust gas is locally supplied excessively by executing EGR in a form in which the exhaust gas is homogenized in the combustion chamber. While suppressing the instability of the combustion state, a large amount of exhaust gas is recirculated to the combustion chamber, so that the generation of NOx can be significantly suppressed.

JP 2002-106419 A Japanese Patent Laid-Open No. 10-8965

  However, the engines described in Patent Documents 1 and 2 employ a very complicated structure in order to stratify or homogenize exhaust gas in the combustion chamber, which may lead to an increase in cost and size. .

  Further, for example, it is not configured to switch between a state in which the exhaust gas is stratified and a state in which the exhaust gas is homogenized in the combustion chamber in accordance with the operating state of the engine. It is necessary to adopt the structure of the intake passage.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to stratify or homogenize exhaust gas in a combustion chamber with a simple configuration in an engine that implements EGR, and further to operation. By appropriately stratifying or homogenizing the exhaust gas in the combustion chamber according to the state, a sufficient amount of exhaust gas is recirculated while reliably maintaining the combustion state in the combustion chamber, and NOx generation is reliably suppressed. The point is to provide an engine that can.

In order to achieve the above object, an engine according to the present invention includes a combustion chamber having an ignition plug at an upper portion, an intake passage through which fresh air sucked into the combustion chamber flows, and exhaust gas discharged from the combustion chamber flows. And an EGR path branched from the exhaust path and connected to the exhaust gas supply section of the intake path, and exhaust gas flowing from the exhaust path into the EGR path flows into the intake path from the exhaust gas supply section The first characteristic configuration of the engine is that the volume from the exhaust gas supply unit to the inlet of the combustion chamber in the intake passage is defined as the exhaust gas mixing path volume, and the intake volume per cycle in the combustion chamber is defined as one cycle intake. The ratio of the volume and the exhaust gas mixing path volume to the one-cycle intake volume is defined as the exhaust gas mixing path ratio,
As the exhaust gas supply section, a stratification exhaust gas supply section in which the exhaust gas mixing path ratio is in a range of 0.5 or more and less than 1.0 or in a range of 1.5 or more and less than 2.0, the stratification is performed. The exhaust gas is supplied into the intake passage from the exhaust gas supply unit, and the exhaust gas is stratified in the upper part of the combustion chamber.

  In an engine that implements EGR that recirculates exhaust gas to the intake passage using the back pressure of the exhaust passage through the EGR passage that connects the exhaust passage and the intake passage, the intake passage has a new A concentration distribution consisting of a concentrated exhaust gas portion having a high concentration of exhaust gas relative to the air and a light exhaust gas portion having a low concentration of exhaust gas relative to fresh air is formed.

  That is, when exhaust gas is supplied from the exhaust gas supply unit to the intake passage at a time when the flow of fresh air is stopped in the intake passage, that is, at a time other than the intake stroke, the concentration of exhaust gas with respect to fresh air increases. On the other hand, when exhaust gas is supplied from the exhaust gas supply unit to the intake passage at the time when fresh air is flowing in the intake passage, that is, during the intake stroke, the concentration of the exhaust gas with respect to the fresh air decreases. Thus, the light exhaust gas part is formed. As a result, in the intake passage, a concentration distribution consisting of the concentrated exhaust gas portion and the light exhaust gas portion appears at intervals corresponding to the intake volume per cycle in the combustion chamber.

  According to the first characteristic configuration, the stratification exhaust gas supply unit having the exhaust gas mixing path ratio as described above is provided in the intake passage, and the EGR is performed from the stratification exhaust gas supply unit when the EGR is performed. By supplying exhaust gas to the passage, while maintaining a good distribution of exhaust gas concentration with respect to fresh air in the intake passage, the fresh exhaust gas is placed in the combustion chamber in a state where the concentrated exhaust gas portion is unevenly distributed in the ignition region at the upper part of the combustion chamber. Can inhale.

That is, when exhaust gas is supplied to the intake passage from the exhaust gas supply unit for stratification in which the exhaust gas mixing path ratio is in the range of 0.5 or more and less than 1.0 or in the range of 1.5 or more and less than 2.0. During the period other than the intake stroke, most of the concentrated exhaust gas portion in the concentration distribution of the exhaust gas formed near the exhaust gas supply portion is sucked into the combustion chamber at the later stage of the intake stroke where the influence of the new airflow is relatively small Therefore, it is possible to inhale the fresh air into the combustion chamber while suppressing the diffusion of the concentrated exhaust gas portion, and to distribute the concentrated exhaust gas portion sucked into the combustion chamber in the later stage of the intake stroke in the ignition region at the upper portion of the combustion chamber. it can.
Therefore, in the ignition region, the air-fuel mixture is slowly burned with a large amount of exhaust gas to suppress the generation of NOx, and in regions other than the ignition region, the exhaust gas is suppressed from being excessively supplied to the air-fuel mixture, Stable combustion can be realized, and CO and THC emissions can be suppressed.

  Further, if the exhaust gas mixing path ratio of the stratification exhaust gas supply part is within the range of 0.5 or more and less than 1.0, most of the concentrated exhaust gas part formed in the vicinity of the stratification exhaust gas supply part Since the combustion chamber can be sucked into the combustion chamber in a very short time of the intake stroke, it is possible to further suppress the diffusion of the concentrated exhaust gas in the intake passage and realize a good combustion state.

In addition to the first characteristic configuration, the second characteristic configuration of the engine according to the present invention is configured to perform stratified combustion in which fuel is stratified and burned in an upper portion of the combustion chamber,
In the case of performing the stratified combustion, the exhaust gas is caused to flow into the intake passage from the stratified exhaust gas supply section to stratify the exhaust gas in the upper part of the combustion chamber.

  According to the second characteristic configuration, for example, when so-called stratified combustion is performed in which fuel is stratified and burned in the form of biasing fuel near the upper spark plug in the combustion chamber, the intake air is supplied from the stratification exhaust gas supply unit. By letting the exhaust gas flow into the road and stratify the exhaust gas in the upper part of the combustion chamber, in the ignition region, the rich mixture is slowly burned by many exhaust gases to suppress the generation of NOx, and in the region other than the ignition region In addition, it is possible to suppress the exhaust gas from being supplied excessively with respect to the light mixture, to realize stable combustion, and to suppress the emission of CO and THC. Therefore, for example, even when the air-fuel mixture having a low equivalent ratio is stratified in the combustion chamber, a stable combustion state can be realized.

According to a third characteristic configuration of the engine of the present invention, the volume from the exhaust gas supply unit to the inlet of the combustion chamber in the intake passage is defined as the exhaust gas mixing path volume, and the intake volume per cycle in the combustion chamber is defined as the one-cycle intake volume. The ratio of the exhaust gas mixing path volume to the one-cycle intake volume is defined as the exhaust gas mixing path ratio,
The exhaust gas supply unit includes a homogenization exhaust gas supply unit in which the exhaust gas mixing path ratio is in a range of less than 0.5, in a range of 1.0 or more and less than 1.5, or in a range of 2.0 or more. The exhaust gas is supplied from the homogenization exhaust gas supply section into the intake passage so that the exhaust gas is homogenized in the combustion chamber.

  According to the third characteristic configuration, in the intake passage, the exhaust gas supply section for homogenization having the exhaust gas mixing path ratio as described above is provided, and when performing EGR, the exhaust gas is supplied from the homogenization exhaust gas supply section to the intake passage. By supplying, fresh air can be sucked into the combustion chamber in a state in which the concentration distribution of exhaust gas with respect to fresh air in the intake passage is eliminated and homogenized.

That is, when exhaust gas is supplied to the intake passage from the exhaust gas supply section for homogenization in which the exhaust gas mixing path ratio is within a range of less than 0.5 or within a range of 1.0 or more and less than 1.5, a period other than the intake stroke In addition, most of the rich exhaust gas part in the concentration distribution of exhaust gas formed near the exhaust gas supply part is sucked into the combustion chamber at the beginning of the intake stroke where the influence of the new air current is relatively large. The diffusion of the concentrated exhaust gas part is promoted, and the fresh air can be sucked into the combustion chamber in a state where the exhaust gas is homogenized.
Further, when exhaust gas is supplied to the intake passage from the homogenization exhaust gas supply part in which the exhaust gas mixing path ratio is in the range of 2.0 or more, most of the concentrated exhaust gas part formed in the vicinity of the homogenization exhaust gas supply part, Since the combustion chamber can be sucked into the combustion chamber in an extremely long time of three or more cycles ahead, the exhaust gas is supplied in a state in which the exhaust gas is further homogenized by further promoting the diffusion of the concentrated exhaust gas portion in the intake passage. Fresh air can be sucked into the combustion chamber.
Therefore, it is possible to remarkably suppress the generation of NOx by recirculating a large amount of exhaust gas to the combustion chamber while suppressing the combustion state from becoming unstable due to excessive supply of exhaust gas locally.

In addition to the third characteristic configuration, the fourth characteristic configuration of the engine according to the present invention is configured to perform homogeneous combustion in which the fuel is homogenized and burned in the combustion chamber,
When performing the homogeneous combustion, the exhaust gas is caused to flow from the homogenization exhaust gas supply section into the intake passage to homogenize the exhaust gas in the combustion chamber.

  According to the fourth characteristic configuration, when so-called homogeneous combustion is performed in which the fuel is homogenized and burned as a whole in the combustion chamber, the exhaust gas is caused to flow into the intake passage from the homogenization exhaust gas supply unit, and the exhaust gas is discharged in the combustion chamber. By homogenizing, it is possible to achieve a stable combustion state by uniformly mixing exhaust gas with fuel in the entire combustion chamber. Therefore, even when a high-equivalence ratio air-fuel mixture is burned in the combustion chamber, a large amount of exhaust gas can be recirculated to the combustion chamber, and NOx production can be greatly suppressed.

According to a fifth characteristic configuration of the engine of the present invention, the volume from the exhaust gas supply unit to the inlet of the combustion chamber in the intake passage is defined as the exhaust gas mixing path volume, and the intake volume per cycle in the combustion chamber is defined as the one-cycle intake volume. The ratio of the exhaust gas mixing path volume to the one-cycle intake volume is defined as the exhaust gas mixing path ratio,
As the exhaust gas supply section, a stratification exhaust gas supply section in which the ratio of the exhaust gas mixing path is 0.5 or more and less than 1.0 or 1.5 or more and less than 2.0, and the exhaust gas mixing path An exhaust gas supply unit for homogenization within a range of less than 0.5, 1.0 or more and less than 1.5 or 2.0 or more,
An exhaust gas stratification operation mode in which exhaust gas flows into the intake passage from the stratification exhaust gas supply unit and stratifies the exhaust gas in an upper portion of the combustion chamber, and exhaust gas flows into the intake passage from the homogenization exhaust gas supply unit An operation mode switching means for switching between the exhaust gas homogenization operation mode for homogenizing the exhaust gas in the combustion chamber,
There exists a control means which controls the said operation mode switching means based on a driving | running state.

  According to the fifth feature configuration, since the stratification exhaust gas supply unit and the homogenization exhaust gas supply unit are provided, the same effects as the first or third feature configuration can be exhibited, Further, the control means controls the operation mode switching means based on the operation state such as fuel distribution in the combustion chamber to switch between the exhaust gas stratification operation mode and the exhaust gas homogenization operation mode, thereby reducing NOx. In addition, the operation can be performed in an appropriate operation mode capable of realizing stable combustion.

The sixth characteristic configuration of the engine according to the present invention includes, in addition to the fifth characteristic configuration, stratified combustion in which fuel is stratified and burned in the combustion chamber, and homogeneous combustion in which fuel is homogenized and burned in the combustion chamber. Is configured to do alternatively,
When the control means performs stratified combustion in the combustion chamber, the operation mode switching means is set to the exhaust gas stratification operation mode, and when the control means performs homogeneous combustion in the combustion chamber, the operation mode switching means is set to the exhaust gas homogeneous. It is in the point to set to the operation mode.

  According to the sixth feature, when the equivalence ratio of the air-fuel mixture combusted in the combustion chamber is lower than a set value, for example, when the air-fuel mixture is stratified combustion, the control means uses the operation mode switching means. By switching to the exhaust gas stratification operation mode, NOx generation in the ignition region and stable combustion in regions other than the ignition region can be realized. On the other hand, when the equivalence ratio of the air-fuel mixture burned in the combustion chamber is higher than, for example, a set value and the air-fuel mixture burns homogeneously, the control means switches to the exhaust gas homogenization operation mode by the operation mode switching means. Thus, while realizing a stable combustion state, a large amount of exhaust gas can be recirculated to the combustion chamber, so that the generation of NOx can be significantly suppressed.

Embodiments of the present invention will be described with reference to the drawings.
As shown in FIG. 1 and the like, the engine is defined by an inner surface of a cylinder 3, a lower surface of a cylinder head 4, and a top surface of a piston 5, and a combustion chamber 1 having a spark plug 2 at the upper portion and an intake valve 6. And an intake passage 8 through which fresh air I drawn into the combustion chamber 1 flows, and an exhaust passage 9 connected to the combustion chamber 1 through an exhaust valve 7 through which the exhaust gas E discharged from the combustion chamber 1 flows. And are provided.

  The piston 5 is swingably connected to a connecting rod (not shown), and the reciprocating motion of the piston 5 is obtained as a rotational motion of one crankshaft (not shown) by the connecting rod. Such a configuration is no different from a normal engine.

  The fresh air I flowing through the intake passage 8 is appropriately supercharged by a supercharger or the like and then sucked into the combustion chamber 1, and is naturally supplied by a fuel supply unit (not shown) provided in the intake passage 8 or the combustion chamber 1. Gaseous fuel such as gas is supplied to form an air-fuel mixture, and the air-fuel mixture burns in the combustion chamber 1.

  In the combustion chamber 1, the air-fuel mixture is compressed by the rise of the piston 5, and then spark-ignited by the spark plug 2 and burned.

An EGR path 15 is provided that branches from the exhaust path 9 and is connected to the exhaust gas supply unit 11 of the intake path 8. Through this EGR path 15, the exhaust gas E enters the intake path 8 using the back pressure of the exhaust path 9. So-called EGR supplied from the exhaust gas supply unit 11 is performed.
An EGR valve 16 is provided in the EGR path 15, and the EGR amount that is the supply amount of the exhaust gas E to the intake path 8 can be controlled by adjusting the opening degree of the EGR valve 16.

Hereinafter, the supply state of the exhaust gas E to the intake passage 8 by the exhaust gas supply passage 11 will be described.
The distribution state of the fresh air I flowing through the intake passage 8 periodically varies with the cycle period as the intake valve 6 is opened and closed. That is, in the intake path 8, during the intake stroke in which the intake valve 6 is opened, fresh air I is sucked into the combustion chamber 1 and the pressure decreases, and in other strokes, the fresh air I is not sucked. Pulsation occurs that the pressure does not decrease.

  Therefore, the pressure in the vicinity of the exhaust gas supply unit 11 changes in synchronization with the pulsation of the fresh air I in the intake passage 8, and specifically, the exhaust gas supply in the middle stage of the intake stroke where the flow velocity of the fresh air I is the highest. The pressure in the vicinity of the portion 11 is the lowest.

  Then, the supply amount of the exhaust gas E from the exhaust gas supply unit 11 to the intake passage 8 periodically changes in the cycle period due to the pulsation of the fresh air I as described above. In particular, at the moment when the flow of the fresh air I in the intake passage 8 stops when the intake valve 6 is closed, a large amount of the exhaust gas E is supplied to the fresh air I due to the inertia in the flow of the exhaust gas E. . Therefore, the intake passage 8 includes a rich exhaust gas portion R in which the exhaust gas E is darker than other portions in the intake passage 8 and a light exhaust gas portion L in which the exhaust gas E is thinner than the rich exhaust gas portion R along the flow direction. Thus, fresh air I having a so-called exhaust gas concentration distribution that alternately appears at intervals corresponding to the intake volume per cycle in the combustion chamber 1 is formed. Then, one concentrated exhaust gas portion R is unevenly distributed in a part of the intake region IA where the fresh air I sucked into the combustion chamber 1 in the next intake stroke of the intake passage 8 exists.

Further, this engine will be described in detail later, but as an exhaust gas supply unit 11, a stratification exhaust gas supply unit 11A and a homogenization exhaust gas supply unit 11B appropriately disposed in the intake passage 8 are provided to perform stratification. The exhaust gas E is supplied from the exhaust gas supply unit 11A to the intake passage 8 to stratify the exhaust gas E in the combustion chamber 1, or the exhaust gas E is supplied from the homogenization exhaust gas supply unit 11B to the intake passage 8 to The exhaust gas E is configured to be homogenized.
Hereinafter, the first and second embodiments as the engine configuration when stratifying the exhaust gas, and the third and fourth embodiments as the engine configuration when performing homogenization of the exhaust gas will be described.
In the following description, the volume from the exhaust gas supply unit 11 to the inlet of the combustion chamber 1 in the intake passage 8 is the exhaust gas mixing path volume (VL), and the intake volume per cycle in the combustion chamber 1 is the one-cycle intake volume (VG). ), The ratio of the exhaust gas mixing path volume (VL) to the one-cycle intake volume (VG) is called the exhaust gas mixing path ratio (VL / VG). The one-cycle intake volume (VG) corresponds to the volume of the intake region IA in which fresh air I is taken into the combustion chamber 1 in the next intake stroke of the intake passage 8, and the engine displacement (combustion chamber) (The difference between the maximum volume and the minimum volume) and the filling efficiency.

[First Embodiment]
As a first embodiment, an engine configuration when stratifying the exhaust gas E shown in FIG. 1 will be described.

  The engine shown in FIG. 1 includes, as an exhaust gas supply unit 11, a stratification exhaust gas supply unit 11A in which an exhaust gas mixing path ratio (VL / VG) is in a range of 0.5 or more and less than 1.0. The exhaust gas E is supplied from the exhaust gas supply unit 11A to the intake passage 8 to form a density distribution of the exhaust gas E in the intake passage 8.

That is, as shown in FIG. 1 (a), at the start time (TDC) of the intake stroke, the position of the concentrated exhaust gas portion R is the position of the stratified exhaust gas supply portion 11A set as described above, that is, This is the position on the rear end side of the intake area IA where the fresh air I inhaled in the next intake stroke exists.
Then, as shown in FIG. 1B, the concentrated exhaust gas portion R is not yet drawn into the combustion chamber 1 at the intermediate time (90 ° ATDC) of the intake stroke where the flow of the fresh air I becomes strong. As shown in (c), the combustion chamber 1 is inhaled at a time slightly before the end time (BDC) of the intake stroke at which the flow of the fresh air I becomes weak.
Therefore, the diffusion of the concentrated exhaust gas portion R is suppressed, and the fresh air I is sucked into the combustion chamber 1 in a state where the concentrated exhaust gas portion R is unevenly distributed in the ignition region above the combustion chamber 1.
That is, even when the overall equivalence ratio of the air-fuel mixture in the combustion chamber 1 is lowered, the exhaust gas E is stratified in the upper portion of the combustion chamber 1, so that in the ignition region at the upper portion of the combustion chamber 1, The temperature rise can be sufficiently suppressed by the high-concentration exhaust gas E, and the generation of NOx can be suppressed. On the other hand, in the region other than the ignition region, combustion of the air-fuel mixture is prevented from being inhibited by the exhaust gas E. And a stable combustion state can be realized.

[Second Embodiment]
As a second embodiment, an engine configuration when stratifying the exhaust gas E shown in FIG. 2 will be described.
The engine shown in FIG. 2 includes, as the exhaust gas supply unit 11, a stratification exhaust gas supply unit 11A in which the exhaust gas mixing path ratio (VL / VG) is in a range of 1.5 or more and less than 2.0. The exhaust gas E is supplied from the exhaust gas supply unit 11A to the intake passage 8 to form a density distribution of the exhaust gas E in the intake passage 8.

  That is, as shown in FIG. 2A, at the start time (TDC) of the intake stroke, the position of the concentrated exhaust gas portion R becomes the position of the stratified exhaust gas supply portion 11A set as described above. From the start of the intake stroke two cycles ahead, as in the first embodiment, the exhaust gas mixing path ratio (VL / VG) is within a range of 0.5 or more and less than 1.0, that is, That is, it is the position on the rear end side of the intake area IA.

  Therefore, also in the engine shown in FIG. 2, the diffusion of the rich exhaust gas portion R is suppressed, and the fresh air I is sucked into the combustion chamber 1 in a state where the rich exhaust gas portion R is unevenly distributed in the ignition region above the combustion chamber 1. It will be.

  Further, comparing the engine of the first embodiment with the engine of the second embodiment, the engine of the first embodiment is closer to the combustion chamber 1 because the position of the stratification exhaust gas supply unit 11A is closer to the combustion chamber 1. It is considered that the diffusion of the part R can be further suppressed.

  Further, the opening degree of the EGR valve 16A provided in the EGR passage 15A connected to the stratification exhaust gas supply unit 11A is adjusted to control the EGR amount from the stratification exhaust gas supply unit 11A to the intake passage 8. be able to.

  Further, in the first and second embodiments, the overall equivalence ratio of the air-fuel mixture in the combustion chamber 1 is lowered, and fuel is stratified in the upper portion of the combustion chamber 1, that is, the ignition region, and the rich mixing in the ignition region is performed. When performing so-called stratified combustion in which the spark is ignited by the spark plug 2 and burned, the exhaust gas E is supplied from the stratification exhaust gas supply section 11A to the intake passage 8 and the exhaust gas E is stratified in the upper part of the combustion chamber 1. Thus, in the ignition region, the temperature rise due to the combustion of the rich mixture is sufficiently suppressed by the high-concentration exhaust gas E, and the generation of NOx is suppressed. On the other hand, in the regions other than the ignition region, It is suppressed that combustion is inhibited by the exhaust gas E, and a stable combustion state is realized.

  As a structure for stratifying the fuel in the upper part of the combustion chamber 1, a known method can be adopted, for example, directly in the ignition region of the combustion chamber 1 at the later stage of the intake stroke or at the beginning of the compression process. The fuel supply method and the fuel supply part for supplying fuel gas in the intake passage 8 are arranged in the same manner as the stratified exhaust gas supply part 11A described so far, and the air-fuel mixture formed in the intake passage 8 is For example, a method of sucking the combustion chamber 1 may be employed.

[Third Embodiment]
As a third embodiment, an engine configuration when the exhaust gas E shown in FIG. 3 is homogenized will be described.
The engine shown in FIG. 3 includes, as the exhaust gas supply unit 11, a homogenization exhaust gas supply unit 11B having an exhaust gas mixing path ratio (VL / VG) within a range of 2.0 or more, and the homogenization exhaust gas supply unit 11B. The exhaust gas E is supplied to the intake passage 8 to form a density distribution of the exhaust gas E in the intake passage 8.

That is, as shown in FIG. 3A, at the start time (TDC) of the intake stroke, the position of the concentrated exhaust gas portion R is the position of the homogenization exhaust gas supply portion 11B set as described above, that is, the combustion. The position is sufficiently separated from the chamber 1.
Then, the concentrated exhaust gas portion R is sufficiently diffused to reach the intake area IA in the intake passage 8 by the start time of the intake stroke that is three cycles or more ahead. A relatively homogeneous exhaust gas E is present. Therefore, as shown in FIG. 3B and FIG. 3C, fresh air I can be sucked into the combustion chamber 1 with the exhaust gas E homogenized in the combustion chamber 1.
That is, even when the equivalent ratio of the air-fuel mixture in the combustion chamber 1 is increased, the exhaust gas E mixed with a part of the air-fuel mixture becomes excessively thin by homogenizing the exhaust gas E in the combustion chamber 1. It is possible to prevent the exhaust gas E mixed with a part of the air-fuel mixture from becoming excessively thick and to suppress the exhaust of CO and THC while suppressing the NOx emission.

[Fourth Embodiment]
As a fourth embodiment, an engine configuration when the exhaust gas E shown in FIG. 4 is homogenized will be described.
The engine shown in FIG. 4 includes, as the exhaust gas supply unit 11, a homogenization exhaust gas supply unit 11B having an exhaust gas mixing path ratio (VL / VG) within a range of less than 0.5, and the homogenization exhaust gas supply unit 11B. The exhaust gas E is supplied to the intake passage to form a density distribution of the exhaust gas E in the intake passage 8.

  That is, as shown in FIG. 4A, at the start time (TDC) of the intake stroke, the position of the concentrated exhaust gas portion R is the position of the homogenization exhaust gas supply portion 11B set as described above, that is, This is the position on the front end side of the intake area IA.

  Then, as shown in FIG. 4B, the concentrated exhaust gas portion R is sucked into the combustion chamber 1 at an intermediate time (90 ° ATDC) of the intake stroke where the flow of the fresh air I becomes strong, and the fresh air I As shown in FIG. 4C, the fresh air I can be sucked into the combustion chamber 1 with the exhaust gas E homogenized as shown in FIG. 4C.

  Further, the exhaust gas supply unit 11 includes a homogenization exhaust gas supply unit 11B having an exhaust gas mixing path ratio (VL / VG) in the range of 1.0 or more and less than 1.5, and the homogenization exhaust gas supply unit 11B. Even when the exhaust gas E is supplied to the intake passage to form a concentration distribution of the exhaust gas E in the intake passage 8, the start timing of the intake stroke two cycles ahead is the same as in the fourth embodiment. Since the position of the rich exhaust gas portion R is the position on the front end side of the intake region IA, the fresh air I can be sucked into the combustion chamber 1 while the exhaust gas E is homogenized in the combustion chamber 1.

  Further, when the engine of the third embodiment is compared with the engine of the fourth embodiment, the engine of the third embodiment is more concentrated because the position of the exhaust gas supply unit 11B for homogenization is far from the combustion chamber 1. It is considered that the diffusion of the part R can be further promoted.

  Further, the opening degree of the EGR valve 16B provided in the EGR passage 15B connected to the homogenization exhaust gas supply unit 11B is adjusted to control the EGR amount from the homogenization exhaust gas supply unit 11B to the intake passage 8. be able to.

  In the third and fourth embodiments, the overall equivalence ratio of the air-fuel mixture in the combustion chamber 1 is increased, the fuel is homogenized throughout the combustion chamber 1, and the homogeneous air-fuel mixture is spark-ignited. When so-called homogeneous combustion is performed, exhaust gas E is supplied from the homogenization exhaust gas supply section 11B to the intake passage 8 to homogenize the exhaust gas E in the combustion chamber 1. Thus, the exhaust gas E is homogeneously mixed and a stable combustion state is realized. For example, when a large amount of exhaust gas is recirculated to the combustion chamber 1, the generation of NOx due to combustion of the high-equivalence ratio air-fuel mixture is greatly suppressed. .

  As a configuration for homogenizing the fuel in the upper portion of the combustion chamber 1, a known method can be adopted. For example, the fuel is directly fueled in the combustion chamber 1 at the initial stage of the intake stroke, and the fuel is generated by a new air flow. The fuel supply unit that supplies fuel gas in the intake passage 8 is disposed in the same manner as the exhaust gas supply unit 11B for homogenization described so far, and the air-fuel mixture formed in the intake passage 8 is disposed. For example, a method of sucking the combustion chamber 1 may be employed.

  In the above embodiment, the engine is configured to perform either stratification or homogenization of the exhaust gas E in the combustion chamber 1, but the engine is configured to perform both stratification and homogenization alternatively. It doesn't matter. Hereinafter, a fifth embodiment will be described as an engine configuration configured to selectively perform both stratification and homogenization of the exhaust gas E in the combustion chamber 1 as described above.

[Fifth Embodiment]
In the engine shown in FIG. 5, the exhaust gas supply unit 11 is stratified so that the exhaust gas mixing path ratio (VL / VG) is in the range of 0.5 or more and less than 1.0, as in the engine of the first embodiment. Exhaust gas supply unit 11A and a homogenization exhaust gas supply unit 11B having an exhaust gas mixing path ratio (VL / VG) in the range of 2.0 or more, as in the engine of the third embodiment.
The stratification exhaust gas supply section 11A is formed as an opening to the intake path 8 of the stratification EGR path 15A branched from the EGR path 15, while the homogenization exhaust gas supply section 11B is an EGR path. 15 is formed as an opening for the intake passage 8 of the homogenizing EGR passage 15B branched from the passage 15.

  As the stratification exhaust gas supply section 11A, as in the engine of the second embodiment, the stratification exhaust gas supply in which the exhaust gas mixing path ratio (VL / VG) is in the range of 1.5 or more and less than 2.0. The unit 11A may be provided. Moreover, as the exhaust gas supply unit 11B for homogenization, the exhaust gas supply unit 11B for homogenization in which the exhaust gas mixing path ratio (VL / VG) is in the range of 0 or more and less than 0.5, as in the engine of the fourth embodiment. May be provided.

  Furthermore, the stratification EGR valve 16A provided in the stratification EGR passage 15A leading to the stratification exhaust gas supply unit 11A is configured to be able to intermittently supply the exhaust gas E to the stratification exhaust gas supply unit 11A. On the other hand, the homogenization EGR valve 16B provided in the homogenization EGR passage 15B leading to the homogenization exhaust gas supply unit 11B is configured to be able to intermittently supply the exhaust gas E to the homogenization exhaust gas supply unit 11B. Yes.

  Then, an engine control unit (hereinafter referred to as ECU) 30 comprising a computer opens the stratification EGR valve 16A and closes the homogenization EGR valve 16B to the intake passage from the stratification exhaust gas supply section 11A. 8 is set to an exhaust gas stratification operation mode in which the exhaust gas E is supplied to the combustion chamber 1 to stratify the exhaust gas E, while the stratification EGR valve 16A is closed and the homogenization EGR valve 16B is opened. The exhaust gas stratification operation mode and the exhaust gas homogenization operation mode are configured in an exhaust gas homogenization operation mode in which the exhaust gas E is supplied from the gasification exhaust gas supply unit 11B to the intake passage 8 to homogenize the exhaust gas E in the combustion chamber 1. Further, the operation mode switching means 31 is controlled, and the operation mode switching means 31 is controlled based on the combustion state of the air-fuel mixture in the combustion chamber 1. It is configured to function as a control unit 32 that.

  That is, the control means 32 detects the overall equivalence ratio of the air-fuel mixture burned in the combustion chamber 1 from the measurement result of the oxygen concentration sensor 20 that measures the oxygen concentration of the exhaust gas E flowing through the exhaust passage 9. When the equivalence ratio is as low as less than a predetermined set value, the air-fuel mixture is stratified and combusted in the combustion chamber 1 by a known method, and the operation mode switching means 31 switches to the exhaust gas stratification operation mode. When the exhaust gas E is stratified and the equivalent ratio is as high as the set value or more, the air-fuel mixture is homogeneously combusted in the combustion chamber 1 by a known method and the exhaust gas is homogenized by the operation mode switching means 31. By switching to the operation mode and homogenizing the exhaust gas E in the combustion chamber 1, the distribution of the exhaust gas E in the combustion chamber 1 is changed according to the combustion state of the combustion chamber 1 to reduce the NO. And to realize the stabilization of the combustion state.

  In the above embodiment, the exhaust gas stratification operation mode and the exhaust gas homogenization operation mode are switched based on the equivalence ratio of the air-fuel mixture in the combustion chamber 1, but the switching is performed based on another state such as the temperature of the combustion chamber 1. It doesn't matter. For example, when the temperature of the combustion chamber 1 is low, the combustion chamber 1 is switched to the exhaust gas stratification operation mode to achieve a stable combustion state in the entire combustion chamber 1 while suppressing the generation of NOx as slow combustion in the ignition region, When the temperature of the combustion chamber 1 is high, switching to the exhaust gas stratification operation mode can suppress the generation of NOx in the entire combustion chamber 1.

  Further, at the time of transition between the exhaust gas stratification operation mode and the exhaust gas homogenization operation mode, for example, the opening ratio between the stratification EGR valve 16A and the homogenization EGR valve 16B is adjusted to supply the stratification exhaust gas. The supply amount of the exhaust gas E from the part 11A and the supply amount of the exhaust gas E from the homogenization exhaust gas supply part 11B may be appropriately adjusted.

  In the above embodiment, the stratification exhaust gas supply unit 11A and the homogenization exhaust gas supply unit 11B are provided as separate exhaust gas supply units 11, but by adjusting the position of one exhaust gas supply unit 11, The exhaust gas supply unit 11 may be configured to function alternatively to the stratification exhaust gas supply unit 11A and the homogenization exhaust gas supply unit 11B.

  In the above embodiment, the natural gas city gas is used as the fuel. However, a gaseous fuel other than the natural gas city gas may be used as the fuel.

Schematic which shows the state in the intake stroke of the engine of 1st Embodiment. Schematic which shows the state in the intake stroke of the engine of 2nd Embodiment. Schematic which shows the state in the intake stroke of the engine of 3rd Embodiment. Schematic which shows the state in the intake stroke of the engine of 4th Embodiment. Schematic showing the engine configuration of the fifth embodiment

Explanation of symbols

1: Combustion chamber 2: Spark plug 6: Intake valve 8: Intake passage 11: Exhaust gas supply section 11A: Stratified exhaust gas supply section 11B: Homogenization exhaust gas supply section 15A, 15B: EGR path 31: Operation mode switching means 32 : Control means I: Fresh air E: Exhaust gas

Claims (6)

A combustion chamber having an ignition plug at an upper portion; an intake passage through which fresh air taken into the combustion chamber flows; an exhaust passage through which exhaust gas discharged from the combustion chamber flows; and an intake passage branched from the exhaust passage An exhaust gas supply section connected to the exhaust gas supply section, and an exhaust gas flowing from the exhaust path into the EGR path into the intake path from the exhaust gas supply section,
In the intake passage, the volume from the exhaust gas supply unit to the inlet of the combustion chamber is the exhaust gas mixing path volume, the intake volume per cycle in the combustion chamber is the one cycle intake volume, and the one cycle intake volume of the exhaust gas mixing path volume is The ratio to the exhaust gas mixing path ratio,
As the exhaust gas supply section, a stratification exhaust gas supply section in which the exhaust gas mixing path ratio is in a range of 0.5 or more and less than 1.0 or in a range of 1.5 or more and less than 2.0, the stratification is performed. An engine configured to cause exhaust gas to flow from the exhaust gas supply unit into the intake passage and stratify the exhaust gas in the upper portion of the combustion chamber. It is configured to perform stratified combustion in which fuel is stratified and burned at the upper part of the combustion chamber,
2. The engine according to claim 1, wherein when performing the stratified combustion, the exhaust gas is flowed into the intake passage from the stratified exhaust gas supply unit to stratify the exhaust gas in an upper portion of the combustion chamber. A combustion chamber having an ignition plug at an upper portion; an intake passage through which fresh air taken into the combustion chamber flows; an exhaust passage through which exhaust gas discharged from the combustion chamber flows; and an intake passage branched from the exhaust passage An exhaust gas supply section connected to the exhaust gas supply section, and an exhaust gas flowing from the exhaust path into the EGR path into the intake path from the exhaust gas supply section,
In the intake passage, the volume from the exhaust gas supply unit to the inlet of the combustion chamber is the exhaust gas mixing path volume, the intake volume per cycle in the combustion chamber is the one cycle intake volume, and the one cycle intake volume of the exhaust gas mixing path volume is The ratio to the exhaust gas mixing path ratio,
The exhaust gas supply unit includes a homogenization exhaust gas supply unit in which the exhaust gas mixing path ratio is in a range of less than 0.5, in a range of 1.0 or more and less than 1.5, or in a range of 2.0 or more. An engine configured to cause exhaust gas to flow into the intake passage from the homogenization exhaust gas supply unit so as to homogenize the exhaust gas in the combustion chamber. It is configured to perform homogeneous combustion in which fuel is homogenized and burned in the combustion chamber,
The engine according to claim 3, wherein, when performing the homogeneous combustion, the exhaust gas is flowed into the intake passage from the homogenization exhaust gas supply unit to homogenize the exhaust gas in a combustion chamber. A combustion chamber having an ignition plug at an upper portion; an intake passage through which fresh air taken into the combustion chamber flows; an exhaust passage through which exhaust gas discharged from the combustion chamber flows; and an intake passage branched from the exhaust passage An exhaust gas supply section connected to the exhaust gas supply section, and an exhaust gas flowing from the exhaust path into the EGR path into the intake path from the exhaust gas supply section,
In the intake passage, the volume from the exhaust gas supply unit to the inlet of the combustion chamber is the exhaust gas mixing path volume, the intake volume per cycle in the combustion chamber is the one cycle intake volume, and the one cycle intake volume of the exhaust gas mixing path volume is The ratio to the exhaust gas mixing path ratio,
As the exhaust gas supply section, a stratification exhaust gas supply section in which the ratio of the exhaust gas mixing path is 0.5 or more and less than 1.0 or 1.5 or more and less than 2.0, and the exhaust gas mixing path An exhaust gas supply unit for homogenization within a range of less than 0.5, 1.0 or more and less than 1.5 or 2.0 or more,
An exhaust gas stratification operation mode in which exhaust gas flows into the intake passage from the stratification exhaust gas supply unit and stratifies the exhaust gas in an upper portion of the combustion chamber, and exhaust gas flows into the intake passage from the homogenization exhaust gas supply unit An operation mode switching means for switching between the exhaust gas homogenization operation mode for homogenizing the exhaust gas in the combustion chamber,
An engine comprising control means for controlling the operation mode switching means based on an operating state. Stratified combustion in which fuel is stratified and burned in the combustion chamber, and homogeneous combustion in which fuel is homogenized and burned in the combustion chamber are alternatively performed,
When the control means performs stratified combustion in the combustion chamber, the operation mode switching means is set to the exhaust gas stratification operation mode, and when the control means performs homogeneous combustion in the combustion chamber, the operation mode switching means is set to the exhaust gas homogeneous. The engine according to claim 5, wherein the engine is in an operation mode.

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