JP4254504B2 - Internal combustion engine - Google Patents

Description

  The present invention relates to an internal combustion engine.

A technique for controlling pre-ignition by controlling the closing timing of the intake and exhaust valves (for example, refer to Patent Document 1) and a technique for controlling pre-ignition by adjusting the EGR amount according to the NOx concentration of the exhaust (for example, Patent Document 2) is known.
JP 2000-120457 A (page 2-3, FIG. 1) JP 2001-152853 A (Page 5-11, FIG. 1) Japanese Utility Model Publication No. 6-58147 Japanese Utility Model Publication No. 6-58148 Japanese Utility Model Publication No. 6-58149 Japanese Utility Model Publication No. 5-187326

  For example, in an internal combustion engine that performs premixed compression ignition at a high load, heat is released from the wall surface of the cylinder and the temperature is lowered, but the temperature is hardly lowered at the center of the cylinder. As a result, pre-ignition easily occurs at the center of the cylinder.

The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a technique that can optimize the ignition timing and the combustion speed in an internal combustion engine.

In order to achieve the above object, the internal combustion engine according to the present invention employs the following means. That is,
The exhaust gas is provided with an exhaust introduction hole in the exhaust inflow direction so that the exhaust gas introduced into the cylinder has a predetermined concentration distribution, and only the exhaust gas is introduced from the exhaust introduction hole.

The greatest feature of the present invention resides in that a part of exhaust gas is directly introduced into the cylinder and combustion control is performed by generating a predetermined exhaust concentration distribution in the cylinder.
In the internal combustion engine configured as described above, a part of the exhaust gas can be directly introduced into the cylinder separately from the intake air. Unlike exhaust gas recirculation (EGR), where intake and exhaust are mixed and introduced into the cylinder, the exhaust is directly introduced into the cylinder, so the intake and exhaust are less likely to mix and the concentration of exhaust is high And a thin part. If the exhaust gas concentration distribution can be created in this way, it is possible to intentionally change the ignition timing and combustion speed of the air-fuel mixture.

In the present invention, an operating state detecting means for detecting an operating state of the internal combustion engine,
An exhaust inflow direction control means for controlling an inflow direction of exhaust flowing into the cylinder from the exhaust introduction hole based on a detection value of the operating state detection means;
Can be provided.

  In the internal combustion engine configured as described above, the exhaust inflow direction control means controls the exhaust inflow direction into the cylinder based on the operating state to change the exhaust gas concentration distribution, and changes the ignition timing and combustion speed depending on the location. It becomes possible to make it.

In the present invention, air-fuel ratio detection means for detecting the air-fuel ratio distribution in the cylinder,
An exhaust inflow direction control means for controlling an inflow direction of exhaust flowing into the cylinder from the exhaust introduction hole based on a detection value of the air-fuel ratio detection means;
Can be provided.

In the internal combustion engine thus configured, it is possible to change the exhaust gas concentration distribution based on the air-fuel ratio distribution in the cylinder and change the ignition timing and combustion speed in the cylinder depending on the location.
In the present invention, inflow exhaust gas temperature lowering means for lowering the temperature of exhaust gas flowing into the cylinder from the introduction hole,
Inflow exhaust gas temperature control means for controlling the temperature of the exhaust gas flowing into the cylinder from the exhaust gas introduction hole according to the operating state of the internal combustion engine;
Can be provided.

In the internal combustion engine configured as described above, it is possible to change the ignition timing and the combustion speed in the cylinder by changing the exhaust gas concentration distribution and the temperature distribution.
In the present invention, when the internal combustion engine is a premixed compression ignition internal combustion engine and pre-ignition does not occur, the inflow exhaust gas temperature control means prohibits a decrease in the exhaust gas temperature by the inflow exhaust gas temperature reduction means. be able to.

  Here, premature ignition means ignition earlier than usual, and is ignition at a time exceeding the allowable range. If uncooled EGR gas is introduced, premature ignition is likely to occur due to temperature rise. However, in an operating state where premature ignition is not likely to occur, ignition is achieved by introducing this uncooled EGR gas. The timing is advanced and it is possible to approach the optimal ignition timing.

In the present invention, inflow exhaust speed increasing means for increasing the inflow speed of exhaust flowing into the cylinder from the exhaust introduction hole,
Inflow exhaust speed control means for controlling the degree of increase in inflow speed by the inflow exhaust speed increase means based on the operating state of the internal combustion engine;
Can be provided.

  By changing the speed of the exhaust gas flowing into the cylinder, it is possible to form a gas distribution suitable for each operation state. It is also possible to change the rotational speed of the swirl.

  In the internal combustion engine according to the present invention, the distribution and temperature distribution of the exhaust gas introduced into the cylinder can be changed, the ignition timing and the combustion speed can be made appropriate, and the combustion noise can be reduced.

  Hereinafter, specific embodiments of an internal combustion engine according to the present invention will be described with reference to the drawings. Here, a case where the internal combustion engine according to the present invention is applied to a premixed compression ignition internal combustion engine for driving a vehicle will be described as an example.

<First Embodiment>
FIG. 1 is a diagram showing a schematic configuration of an engine according to the present embodiment.
An engine 1 shown in FIG. 1 is a water-cooled four-cycle diesel engine having four cylinders 2. The four cylinders 2 are arranged in the order of the second cylinder (# 2), the third cylinder (# 3), and the fourth cylinder (# 4) in order from the first cylinder (# 1) on the left side of the drawing.

The engine 1 is configured by connecting a cylinder head 1a and a cylinder block 1b.
An intake port 4 and an exhaust port 5 are formed in the cylinder head 1a, and an intake valve 6 and an exhaust valve 7 that move up and down are provided at the boundary between the intake port 4 and the exhaust port 5 and the inside of the cylinder 2. ing. The cylinder head 1 a is provided with an in-cylinder fuel injection valve 3 that directly injects fuel into the cylinder 2. On the other hand, the intake port 4 is provided with an in-intake fuel injection valve 8 that injects fuel during intake air flowing through the intake port 4.

  High pressure fuel is supplied to the cylinder fuel injection valve 3 and the intake fuel injection valve 8. When a drive current is applied to the in-cylinder fuel injection valve 3, the in-cylinder fuel injection valve 3 opens, and as a result, fuel is injected from the in-cylinder fuel injection valve 3 into the cylinder 2. On the other hand, when a drive current is applied to the intake fuel injection valve 8, the intake fuel injection valve 8 is opened, and as a result, fuel is injected from the intake fuel injection valve 8 into the intake port 4. The fuel injected into the intake port 4 forms an air-fuel mixture with the intake air and is sucked into the cylinder 2. Thereby, premixed combustion becomes possible.

  The premix combustion can also be performed by injecting fuel from the cylinder fuel injection valve 3 during the intake stroke or the compression stroke. Further, the amount of fuel injected from the in-cylinder fuel injection valve 3 and the in-intake fuel injection valve 8 is calculated from a map from the engine speed and the load. Further, the basic fuel injection timing is also calculated from the engine speed and load using a map. These maps are obtained in advance by experiments or the like.

  An intake branch pipe 20 is connected to the intake port 4, and an exhaust branch pipe 9 is connected to the exhaust port 5. The intake branch pipe 20 is provided with an intake temperature sensor 21 that outputs a signal corresponding to the temperature of the intake air flowing through the intake branch pipe.

The cylinder block 1 b includes a piston 10 inserted into the cylinder 2.
Further, the exhaust branch pipe 9 and each cylinder 2 communicate with each other via an exhaust gas recirculation passage (hereinafter referred to as an EGR passage) 11 that recirculates a part of the exhaust gas flowing through the exhaust branch pipe 9 to the cylinder 2. Has been. Hereinafter, the exhaust gas flowing through the EGR passage 11 will be referred to as EGR gas. One end of the EGR passage 11 is connected to the exhaust branch pipe 9, and the other end is branched and connected to each cylinder 2. Further, the EGR passage 11 branches into a first EGR passage 11 a in which the EGR cooler 12 is interposed and a second EGR passage 11 b that bypasses the EGR cooler 12. A part of the cooling water for cooling the engine 1 circulates in the EGR cooler 12, and heat exchange is performed between the EGR gas flowing in the first EGR passage 11a and the cooling water, thereby cooling the EGR gas. .

  Further, in the middle of the first EGR passage 11a closer to the cylinder 2 than the EGR cooler 12, a flow rate of EGR gas, which is constituted by an electromagnetic valve or the like and circulates in the first EGR passage 11a according to the magnitude of applied power, is set. A flow rate adjusting valve (hereinafter referred to as a first EGR valve) 13a to be changed is provided. On the other hand, in the middle of the second EGR passage 11b closer to the cylinder 2 than the EGR cooler 12, the flow rate of EGR gas that is configured by an electromagnetic valve or the like and circulates in the second EGR passage 11b is changed according to the magnitude of applied power. A flow rate adjusting valve (hereinafter referred to as a second EGR valve) 13b is provided. The first EGR passage 11a and the second EGR passage 11b merge on the downstream side of the first EGR valve 13a and the second EGR valve 13b. An EGR temperature sensor 14 for detecting the temperature of the EGR gas flowing through the EGR passage 11 is provided in the EGR passage 11 between the junction point of the first EGR passage 11a and the second EGR passage 11b and the branch point of each cylinder 2. ing.

In the exhaust gas recirculation mechanism configured as described above, when the first EGR valve 13a or the second EGR valve 13b is opened, the EGR passage 11 becomes conductive, and a part of the exhaust gas flowing in the exhaust branch pipe 9 is part of the exhaust gas recirculation mechanism. It flows into the EGR passage 11. When the first EGR valve 13a is opened, the EGR gas flows through the first EGR passage 11a and is guided to the cylinder 2 through the EGR cooler 12. On the other hand, when the second EGR valve 13b is opened, the EGR gas flows through the second EGR passage 11b and is guided to the cylinder 2 at a high temperature. When both the first EGR valve 13a and the second EGR valve 13b are opened, the EGR gas cooled by the EGR cooler 12 and the EGR gas kept at a high temperature are mixed. The temperature of the EGR gas introduced into the cylinder 2 can be adjusted by adjusting the opening degree of the first EGR valve 13a and the second EGR valve 13b at this time. Here, feedback control for controlling the opening degrees of the first EGR valve 13a and the second EGR valve 13b based on the output signal of the EGR temperature sensor 14 can be performed.

  The cylinder 2 is provided with an EGR introduction hole 15 that is above the upper surface of the piston 10 and is in a communicating state when the piston 10 is located at the bottom dead center. When the piston 10 is located at a position other than the bottom dead center, the EGR introduction hole 15 is covered with the side surface of the piston 10 and is in a non-communication state. The other end of the EGR passage 11 is connected to the EGR introduction hole 15. The EGR introduction holes 15 are provided at two positions on the diameter axis of the cylinder 2 and symmetrical.

  EGR gas is introduced into the cylinder (the first cylinder in FIG. 1) in which the piston 10 is located at the bottom dead center of the intake stroke. At this time, EGR is introduced in the cylinder where the piston 10 is located at the compression top dead center (the second cylinder in FIG. 1) or the cylinder located at the exhaust top dead center (the third cylinder in FIG. 1). Since the hole 15 is covered with the piston 10, the EGR gas is not introduced into the cylinder 2. Further, in the cylinder (fourth cylinder in FIG. 1) located at the bottom dead center of the expansion stroke, the backflow of EGR gas is prevented by a check valve 17 described later.

  FIG. 2 is a cross-sectional view of the engine at the EGR introduction hole 15. On the outer periphery of the cylinder 2, an EGR introduction pipe 16 is provided that can be rotated around the cylinder outer peripheral surface by a link mechanism or the like to change the introduction angle of the EGR gas. Further, the EGR introduction pipe 16 is provided with a check valve 17 for preventing the backflow of EGR gas. The cylinder head 1a includes a first air-fuel ratio sensor 18a at the center of the cylinder and a second air-fuel ratio sensor 18b at the outer periphery of the cylinder.

  FIG. 3 is a view showing the mounting positions of the first air-fuel ratio sensor 18a and the second air-fuel ratio sensor 18b. The first air-fuel ratio sensor 18a and the second air-fuel ratio sensor 18b output a signal corresponding to the air-fuel ratio.

  The engine 1 configured as described above is provided with an electronic control unit (ECU) 19 for controlling the engine 1. The ECU 19 is a unit that controls the operating state of the engine 1 in accordance with the operating conditions of the engine 1 and the driver's request.

  Various sensors are connected to the ECU 19 via electric wiring, and output signals of the various sensors described above are input to the ECU 19. On the other hand, the in-cylinder fuel injection valve 3, the intake-air fuel injection valve 8, the first EGR valve 13a, the second EGR valve 13b, and the like are connected to the ECU 19 via electric wiring and can be controlled. The ECU 19 stores various application programs and various control maps.

Next, an introduction mode of EGR gas according to the present embodiment will be described.
FIG. 4 is a diagram showing the EGR gas introduction direction from the cylinder wall surface and the distribution of EGR gas at that time. In FIG. 4, black dots indicate EGR gas, and the larger the dot size, the deeper the EGR gas concentration.

  FIG. 4A is a diagram in which the EGR introduction pipe 16 is arranged so that the center line of the EGR introduction pipe 16 coincides with the cylinder diameter line. With this arrangement, EGR gas flows toward the center of the cylinder. Further, when a swirl is generated in the cylinder 2, the EGR introduction pipe 16 may be arranged so that the EGR gas is introduced in a direction opposite to the swirl rotation direction.

  Here, since the cylinder center is away from the cylinder wall surface, the temperature drop due to the cooling water is small. Accordingly, the temperature in the center of the cylinder becomes high, and pre-ignition is likely to occur. In particular, pre-ignition tends to occur when the load is high, when the intake air temperature is high, when the boost pressure is high, or when the rotational speed is low.

  In such a case, as shown in FIG. 4A, when the EGR gas cooled by the EGR cooler 12 is introduced, the air-fuel mixture temperature after compression is lowered due to a decrease in the specific heat ratio. Thereby, it becomes possible to suppress premature ignition.

  On the other hand, when the EGR gas cooled by the EGR cooler 12 is introduced, the temperature of the air-fuel mixture may decrease and ignition may not be achieved, or the ignition timing may be delayed. However, pre-ignition may occur if EGR gas is not introduced. Further, if the amount of EGR gas is decreased, combustion noise may occur. Thus, when high-temperature EGR gas that is not cooled by the EGR cooler 12 is introduced, the high temperature EGR gas can compensate for the decrease in temperature rise. Here, by introducing a high-temperature EGR gas, it is possible to slow down the combustion by reducing the oxygen concentration and extending the combustion period. Therefore, it is possible to suppress premature ignition at the center of the cylinder and to suppress the occurrence of misfire or delay in ignition timing by excessively lowering the temperature, thereby reducing combustion noise by slow combustion.

  In FIG. 4B, the EGR introduction pipe 16 is arranged at a shallow angle so that the EGR gas rotates at the center of the cylinder, and the two EGR introduction pipes 16 are symmetrical with respect to the cylinder center. FIG.

  FIG. 5 is a graph showing the relationship between the distance from the cylinder center and the EGR gas concentration when EGR gas is introduced in the direction shown in FIGS. 4 (A) and 4 (B). 5A corresponds to FIG. 4A, and FIG. 5B corresponds to FIG. 4B. When the EGR gas is introduced in the direction shown in FIG. 4B, the EGR gas concentration at the center of the cylinder is lighter than that in the case where the EGR gas is introduced in the direction shown in FIG. On the other hand, EGR gas is also distributed at locations far from the cylinder center (close to the cylinder outer periphery). Thus, the EGR gas concentration distribution differs between the arrangement of the EGR introduction pipe 16 shown in FIGS. 4A and 4B. In FIG. 4B, since the EGR gas is introduced at an angle, swirl is generated in the cylinder, or the rotational speed of the swirl in the cylinder can be increased. Due to this swirl, the gas having a large specific gravity moves toward the cylinder outer peripheral side, and the gas having a small specific gravity moves toward the cylinder center side.

  When the EGR gas cooled by the EGR cooler 12 is introduced as shown in FIG. 4B, the temperature in the cylinder at the compression top dead center can be lowered on average, and premature ignition can be suppressed. In addition, the swirl promotes cooling of the air-fuel mixture on the cylinder wall surface, and the in-cylinder temperature is lowered, so that pre-ignition can be suppressed.

By the way, when the EGR gas cooled by the EGR cooler 12 is introduced, the temperature in the cylinder 2 does not rise and the ignition may not be performed or the ignition timing may be delayed. However, pre-ignition may occur if EGR gas is not introduced. In such a case, hot EGR gas that does not pass through the EGR cooler 12 is introduced as shown in FIG. Here, since the oxygen concentration is low when ignition is performed on the cylinder center side, the pressure increase during ignition is small. However, since the combustion gas on the center side that has been ignited first compresses the gas having a low EGR concentration on the cylinder outer peripheral side, the combustion is completed in a short time. Thereby, combustion noise is reduced, and deterioration of fuel consumption due to a long combustion period can be suppressed.

FIG. 4C is a diagram in which the EGR introduction pipe 16 is arranged so as to introduce EGR gas along the cylinder outer periphery at a further angle than in FIG. 4B.
By the way, when the air-fuel mixture in the cylinder 2 is simultaneously ignited, the pressure in the cylinder 2 is rapidly increased and the combustion noise is increased. In such a case, when the EGR gas cooled by the EGR cooler 12 is introduced to the cylinder outer peripheral side, the temperature of the air-fuel mixture at the compression top dead center can be lowered, and the temperature on the cylinder central side can be reduced to the cylinder outer peripheral side. The temperature can be higher. Therefore, the air-fuel mixture at the cylinder center side is ignited first, and the ignition timing is delayed as it approaches the cylinder outer periphery. As a result, the gas in the central portion becomes high temperature and expands, while the unburned gas is compressed and the temperature rises to ignite. Thus, a distribution can be created at the time of ignition, and combustion noise can be reduced. For example, under low load, high rotation, low temperature, and low supercharging, pre-ignition is unlikely to occur, so that under such conditions, the cylinder center can be ignited first.

  On the other hand, depending on the operating state, fuel may be injected during the intake stroke or the compression stroke. In such a case, the fuel adheres to the cylinder wall surface and is discharged together with the exhaust gas without being burned, or so-called bore flushing that dilutes engine oil for lubricating the cylinder wall surface and induces oil film breakage occurs. To do. In addition, at low speed, low load, low temperature, etc., the fuel is difficult to ignite, so it must be ignited first in the center of the cylinder where the temperature is high and easy to ignite. Will increase. Further, at low rotation, low load, low temperature, etc., the temperature of the gas decreases at the outer periphery of the cylinder, so that the combustion state deteriorates, and extinguishing (misfire) and increasing HC emissions occur. In such a case, hot EGR gas that does not pass through the EGR cooler 12 is introduced as shown in FIG. The swirl and the high temperature EGR gas promote the evaporation of the fuel adhering to the cylinder wall surface. Further, by disposing the EGR gas having a low oxygen concentration on the cylinder outer peripheral side, combustion at the cylinder outer peripheral part can be slowed down, and combustion noise can be reduced. Furthermore, by introducing a high temperature EGR gas, it is possible to suppress a temperature drop on the cylinder outer peripheral side.

  FIG. 4D is a diagram in which the EGR introduction pipe 16 is arranged so as to be symmetric with respect to the cylinder diameter line orthogonal to the line connecting the two EGR introduction holes 15. By introducing the EGR gas from the EGR introduction pipe 16 arranged in this manner, the EGR gas collides on the cylinder outer peripheral side, and the EGR gas can be drifted in the vicinity where the EGR gas collides.

  Here, when the EGR gas cooled by the EGR cooler 12 is introduced as shown in FIG. 4D, a gas cooled at the outer periphery of the cylinder is generated. Further, it is possible to produce a gas having a wide temperature range such as a gas cooled by EGR, a gas having a high temperature at the center of the cylinder, or a gas having a temperature between these. Thereby, ignition timing can be disperse | distributed and it becomes possible to reduce a combustion noise. Furthermore, EGR gas can also be disposed at the center of the cylinder, and combustion noise can be reduced while suppressing premature ignition at the center of the cylinder.

By the way, when the EGR gas cooled by the EGR cooler 12 is introduced, the air-fuel mixture may not ignite due to a decrease in temperature. In such a case, hot EGR gas that does not pass through the EGR cooler 12 is introduced as shown in FIG. The high temperature EGR gas can suppress the temperature at the compression top dead center from excessively decreasing. As a result, a gas having a low temperature on the outer periphery side of the cylinder, a gas having a low oxygen concentration due to EGR, a gas having a high temperature in the center of the cylinder, a gas having a high temperature and a low oxygen concentration, a wide range of temperatures, EGR gas concentration, oxygen concentration, etc. Gas can be produced and combustion noise can be reduced. On the cylinder outer periphery side, the temperature of the gas decreases due to heat exchange, but ignition starts from a location where the oxygen concentration is high, and the unburned portion is compressed or supplied with heat, so the temperature rises and ignition occurs.

FIG. 6 is a diagram showing the effects of EGR gas introduction direction, EGR gas temperature, and EGR introduction.
Thus, by controlling the inflow direction of the EGR gas into the cylinder and the EGR gas temperature, it is possible to suppress premature ignition and the like. Here, since the optimum EGR gas introduction direction and EGR gas temperature differ depending on the operation state, the target EGR gas introduction direction and EGR gas temperature are determined according to the operation state, and further feedback control of the EGR gas temperature is performed. I do.

Next, EGR gas introduction control according to the present embodiment will be described.
FIG. 7 is a flowchart showing a flow of EGR gas introduction control according to the present embodiment.

  In step S101, it is determined whether or not the air-fuel ratio at the center of the cylinder detected by the first air-fuel ratio sensor 18a is smaller than 25. In the present embodiment, it is determined that pre-ignition is performed when the air-fuel ratio is smaller than 25.

If an affirmative determination is made in step S101, the process proceeds to step S102. On the other hand, if a negative determination is made, this routine is terminated.
In step S102, the arrangement of the EGR introduction pipe 16 is changed. The EGR introduction pipe 16 is arranged at the position shown in FIG.

  In step S103, the opening degree EGRc of the first EGR valve 13a and the opening degree EGRh of the second EGR valve 13b are determined. Here, the first EGR valve opening degree EGRc and the second EGR valve opening degree EGRh are determined from the engine speed and the fuel injection amount (load) using a map.

  FIG. 8 is a diagram showing the relationship among the rotational speed, the fuel injection amount, and the EGR valve opening. The EGR valve opening is a value obtained by combining the first EGR valve opening EGRc and the second EGR valve opening EGRh. The higher the rotational speed and the greater the fuel injection amount, the greater the EGR valve opening degree. This map is obtained in advance by experiments or the like and stored in the ECU. At the same time, an estimated value of the EGR amount introduced at this valve opening is obtained from a map.

  FIG. 9 is a diagram showing the relationship among the rotational speed, the fuel injection amount, and the EGR amount. The higher the rotation speed and the greater the fuel injection amount, the greater the EGR amount. This map is obtained in advance by experiments or the like and stored in the ECU.

  In step S104, the EGR gas temperature Tegr is calculated. What is calculated at this time is the target EGR gas temperature that satisfies the condition of not prematurely igniting and not misfiring.

  FIG. 10 is a graph showing the relationship between the EGR amount, the air-fuel ratio A / Fc at the center of the cylinder detected by the first air-fuel ratio sensor 18a, and the EGR gas temperature Tegr. The EGR gas temperature Tegr decreases as the amount of EGR decreases and as the air-fuel ratio A / Fc detected by the first air-fuel ratio sensor 18a decreases. This map is obtained in advance by experiments or the like and stored in the ECU. A target EGR gas temperature is calculated based on this map.

In step S105, the actual EGR gas temperature is the target EG calculated in step S104.
The first EGR valve opening EGRc and the second EGR valve opening EGRh are feedback controlled so that the R gas temperature Tegr is reached. That is, when the actual EGR gas temperature is higher than the target EGR gas temperature Tegr, the first EGR valve is opened and the second EGR valve is closed to lower the EGR gas temperature. On the other hand, when the actual EGR gas temperature is lower than the target EGR gas temperature Tegr, the first EGR valve is closed and the second EGR valve is opened to increase the EGR gas temperature. The actual EGR gas temperature uses the output signal of the EGR temperature sensor 14.

In this way, by controlling the EGR temperature, it is possible to suppress pre-ignition at the center of the cylinder.
As described above, according to the present embodiment, the inflow direction of the EGR gas can be changed based on the operation state, and the temperature of the EGR gas can be changed. Thereby, the distribution of EGR gas concentration and the temperature distribution in the cylinder can be made, and the ignition timing such as suppression of premature ignition in the center of the cylinder can be controlled, and the combustion noise can be reduced.

<Second Embodiment>
In the present embodiment, premature ignition due to an increase in intake air temperature is suppressed.
In this embodiment, although the EGR introduction control method is different from that in the first embodiment, the basic configuration of the engine and other hardware to be applied is the same as that in the first embodiment. The explanation is omitted because it is common.

  Here, when the intake air temperature rises, the final temperature reached when the air-fuel mixture is compressed becomes high, and premature ignition is likely to occur. Therefore, in the present embodiment, in order to suppress the occurrence of premature ignition, the EGR introduction pipe 16 is arranged at the position shown in FIG. 4B, and the EGR gas cooled by the EGR cooler in the cylinder is supplied. Introduce. Thereby, the temperature rise in a cylinder can be suppressed and generation | occurrence | production of premature ignition can be suppressed.

Next, EGR gas introduction control according to the present embodiment will be described.
FIG. 11 is a flowchart showing a flow of EGR gas introduction control according to the present embodiment.

  In step S201, it is determined whether or not the intake air temperature Tb detected by the intake air temperature sensor 21 is higher than 45 ° C. In the present embodiment, it is determined that pre-ignition occurs when the intake air temperature Tb is higher than 45 ° C.

If an affirmative determination is made in step S201, the process proceeds to step S202. On the other hand, if a negative determination is made, this routine is terminated.
In step S202, the arrangement of the EGR introduction pipe 16 is changed. The EGR introduction pipe 16 is disposed at the position shown in FIG.

  In step S203, the opening degree of the EGR valve is determined. Here, the opening degree EGRc of the first EGR valve 13a and the opening degree EGRh of the second EGR valve 13b are determined from the engine speed and the fuel injection amount (load) using a map. In the same manner as in the first embodiment, it is obtained from the relationship among the rotational speed, the fuel injection amount, and the EGR valve opening shown in FIG. At the same time, an estimated value of the EGR amount introduced at this valve opening is obtained from a map. Similarly to the first embodiment, this is obtained from the relationship among the rotational speed, the fuel injection amount, and the EGR amount shown in FIG.

In step S204, the EGR gas temperature is calculated. What is calculated at this time is the EGR gas temperature that satisfies the condition that the pre-ignition does not occur and the misfire does not occur.
FIG. 12 is a diagram showing the relationship between the EGR amount, the intake air temperature Tb, and the EGR gas temperature Tegr. The EGR gas temperature Tegr decreases as the EGR amount decreases or as the intake air temperature Tb increases. This map is obtained in advance by experiments or the like and stored in the ECU. Based on this map, the EGR gas temperature is calculated.

  In step S205, the first EGR valve opening degree EGRc and the second EGR valve opening degree EGRh are feedback-controlled so that the actual EGR gas temperature becomes the target EGR gas temperature Tegr calculated in step S204. That is, when the actual EGR gas temperature is higher than the target EGR gas temperature Tegr, the first EGR valve 13a is opened and the second EGR valve 13b is closed to lower the EGR gas temperature. On the other hand, when the actual EGR gas temperature is lower than the target EGR gas temperature Tegr, the first EGR valve 13a is closed and the second EGR valve 13b is opened to increase the EGR gas temperature.

In this way, by controlling the EGR temperature, it is possible to suppress pre-ignition due to an increase in intake air temperature.
As described above, according to the present embodiment, when the intake air temperature rises, EGR gas is introduced to the cylinder center side, and the occurrence of premature ignition on the cylinder center side can be suppressed.

<Third Embodiment>
In the present embodiment, the occurrence of knocking and combustion noise is suppressed.
In this embodiment, although the EGR introduction control method is different from that in the first embodiment, the basic configuration of the engine and other hardware to be applied is the same as that in the first embodiment. The explanation is omitted because it is common.

  Here, if the air-fuel ratio in the cylinder is uniform, the air-fuel mixture may be ignited all at once and knock or combustion noise may be generated. Therefore, in the present embodiment, in order to suppress the occurrence of premature ignition, the EGR introduction pipe 16 is disposed at the position shown in FIG. 4C or 4D to introduce EGR gas into the cylinder. Thereby, simultaneous ignition of the air-fuel mixture can be suppressed, and knocking and combustion noise can be suppressed.

Next, EGR gas introduction control according to the present embodiment will be described.
FIG. 13 is a flowchart showing a flow of EGR gas introduction control according to the present embodiment.

  In step S301, it is determined whether or not the engine is in an operating state where combustion noise increases. In the present embodiment, it is determined that the combustion noise increases as the output difference between the first air-fuel ratio sensor 18a at the cylinder center and the second air-fuel ratio sensor 18b at the cylinder outer periphery decreases.

  FIG. 14 is a diagram showing the relationship between the outputs of both air-fuel ratio sensors, knocking and combustion noise increase regions. The shaded portion in this figure is the knock and combustion noise increase region. This relationship is obtained in advance by experiments or the like.

If an affirmative determination is made in step S301, the process proceeds to step S302. On the other hand, if a negative determination is made, this routine is terminated.
In step S302, the arrangement of the EGR introduction pipe 16 is changed. The EGR introduction pipe 16 is arranged at the position shown in FIG. 4 (C) or (D).

  FIG. 15 is a diagram showing a relationship among the engine speed, the fuel injection amount, and the arrangement of the EGR introduction pipe 16. When the rotational speed is low and the fuel injection amount is large, the arrangement shown in FIG. 4D is used to suppress premature ignition. Based on this relationship, the arrangement of the EGR introduction pipe 16 is determined. This relationship is obtained in advance by experiments or the like and stored in the ECU.

  In step S303, the opening degree of the EGR valve is determined. Here, the first EGR valve opening degree EGRc and the second EGR valve opening degree EGRh are determined from the engine speed and the fuel injection amount (load) using a map. In the same manner as in the first embodiment, it is obtained from the relationship among the rotational speed, the fuel injection amount, and the EGR valve opening shown in FIG. At the same time, an estimated value of the EGR amount introduced at this valve opening is obtained from a map. Similarly to the first embodiment, this is obtained from the relationship among the rotational speed, the fuel injection amount, and the EGR amount shown in FIG.

  In step S304, the EGR gas temperature is calculated. What is calculated at this time is the EGR gas temperature that satisfies the condition that the pre-ignition does not occur and the misfire does not occur. Similar to the first embodiment, it is obtained from the relationship between the EGR amount, the intake air temperature Tb, and the EGR temperature Tegr shown in FIG.

  In step S305, the opening degree EGRc of the first EGR valve 13a and the opening degree EGRh of the second EGR valve 13b are feedback-controlled so that the actual EGR gas temperature becomes the target EGR gas temperature Tegr calculated in step S304. That is, when the actual EGR gas temperature is higher than the target EGR gas temperature Tegr, the first EGR valve 13a is opened and the second EGR valve 13b is closed to lower the EGR gas temperature. On the other hand, when the actual EGR gas temperature is lower than the target EGR gas temperature Tegr, the first EGR valve 13a is closed and the second EGR valve 13b is opened to increase the EGR gas temperature.

In this way, by controlling the EGR temperature, knocking can be prevented and combustion noise can be reduced.
As described above, according to the present embodiment, when the output difference between the first air-fuel ratio sensor 18a and the second air-fuel ratio sensor 18b is small, the EGR gas is moved to the position shown in FIG. Can be introduced to make the air-fuel ratio distribution in the cylinder non-uniform so that knocking can be prevented or combustion noise can be reduced.

<Fourth embodiment>
In the present embodiment, an apparatus for supplying EGR is different from the above-described embodiment.

FIG. 17 is a diagram showing a schematic configuration of the engine according to the present embodiment. FIG. 17A is a longitudinal sectional view, and FIG. 17B is a transverse sectional view.
Here, the engine 1 shown in FIG. 17 is a water-cooled four-cycle diesel engine having cylinders 2.

The engine 1 is configured by connecting a cylinder head 1a and a cylinder block 1b.
An intake port 4 and an exhaust port 5 are formed in the cylinder head 1a, and an intake valve 6 and an exhaust valve 7 that move up and down are provided at the boundary between the intake port 4 and the exhaust port 5 and the inside of the cylinder 2. ing. The cylinder head 1 a is provided with an in-cylinder fuel injection valve 3 that directly injects fuel into the cylinder 2.

An EGR introduction hole 15 is provided in the side wall of the cylinder 2, and an EGR chamber 100 having a predetermined volume is connected to the cylinder 2 through the EGR introduction hole 15. The EGR introduction hole 15 is located above the upper surface of the piston 10 when the piston 10 is located at the bottom dead center. At this time, the EGR chamber 100 and the cylinder 2 are communicated with each other. The EGR introduction hole 15 is blocked by the side surface of the piston 10 when the piston 10 moves upward from the bottom dead center. The EGR chamber 100 is a space in which an air-fuel mixture combusted in a cylinder (hereinafter referred to as burned gas) can be temporarily stored. The EGR introduction holes 15 are provided at two positions on the diameter axis of the cylinder 2 and symmetrical.

  Here, FIG. 18 is a diagram showing an EGR gas introduction state when the engine is operated at the normal intake / exhaust valve opening / closing timing. FIG. 18A shows the first stage of the expansion stroke, FIG. 18B shows the second stage of the expansion stroke, FIG. 18C shows the second stage of the exhaust stroke and the first stage of the intake stroke, and FIG. 18D shows the second stage of the intake stroke. .

In the first half of the expansion stroke (see FIG. 18A), the fuel burns in the cylinder 2 and the pressure rises. Thereby, the piston 10 moves downward.
In the latter stage of the expansion stroke (see FIG. 18B), the EGR introduction hole 15 is opened, and the EGR chamber 100 and the cylinder 2 are communicated with each other. At this time, since the pressure of the burned gas is high, a part of the burned gas flows into the EGR chamber 100.

  Next, the exhaust valve 7 is opened, and the exhaust stroke starts (see FIG. 18C). As the piston 10 rises, the EGR introduction hole 15 is closed, and the burned gas is stored in the EGR chamber 100 in a high pressure state. As the burned gas in the cylinder 2 is discharged to the exhaust port 5, the pressure in the cylinder 2 decreases.

  In the intake stroke in which the exhaust valve 7 is closed and the intake valve 6 is opened, the pressure in the cylinder 2 further decreases due to the inflow of intake air. Then, in the later stage of the intake stroke (see FIG. 18D), the EGR introduction hole 15 opens. At this time, since the pressure in the EGR chamber 100 is higher than the pressure in the cylinder 2, the burned gas stored in the EGR chamber 100 flows into the cylinder 2 vigorously.

  In this way, the burnt gas having a high temperature generated in the previous cycle is stored in the EGR chamber 100, and the burnt gas having a high temperature can be introduced into the cylinder 2 as the EGR gas at the next cycle. . Thereby, the area | region in which premix compression ignition is possible at the time of low load can be expanded. Further, it is possible to improve the ignitability at low load, high speed rotation, and low temperature of the engine, and to suppress the release of unburned combustion components into the atmosphere. Furthermore, warm-up can be completed promptly.

Further, as compared with the engine shown in FIG. 1, the EGR passage 11 can be omitted, and a simple structure can be achieved.
The burned gas having a high temperature introduced from the EGR chamber 100 into the cylinder 2 is hereinafter referred to as internal EGR gas.

  In the present embodiment, the case where the EGR introduction hole 15 is formed so as to face the center of the cylinder has been described as an example. However, as shown in FIG. Thus, the opening direction of the EGR introduction hole 15 may be formed. Thereby, since the inflow direction of the burned gas is changed, the distribution of the EGR gas can be formed in the cylinder 2. Then, the same effect as the “uncooled EGR gas” shown in FIG. 6 can be obtained. Further, as described in a later embodiment, the direction in which the internal EGR gas is introduced into the cylinder 2 may be variable.

<Fifth embodiment>
This embodiment is different from the fourth embodiment in that the pressure of burned gas stored in the EGR chamber 100 is increased by retarding the valve opening timing of the exhaust valve 7. Therefore, the engine 1 according to the present embodiment includes a variable valve mechanism that can change the opening / closing timing of the exhaust valve 7. The other configuration is the same as that of the fourth embodiment, and therefore, different points will be mainly described in the present embodiment.

  Here, as the pressure of the burned gas stored in the EGR chamber 100 increases, the amount of the burned gas stored in the EGR chamber 100 increases. Therefore, it becomes possible to supply more EGR gas.

  Then, if the opening timing of the exhaust valve 7 is retarded and the exhaust valve 7 is opened after the EGR introduction hole 15 is blocked by the piston 1010 at the beginning of the exhaust stroke, the exhaust gas is stored in the EGR chamber 100. The pressure of burnt gas can be increased. That is, if the exhaust valve 7 is opened before the EGR introduction hole 15 is closed by the piston 1010, the pressure in the cylinder 2 and the EGR chamber 100 is reduced, and therefore the amount of burned gas remaining in the EGR chamber 100 is reduced. To do. Therefore, if the valve opening timing of the exhaust valve 7 is adjusted so that the exhaust valve 7 is opened after the EGR introduction hole 15 is blocked by the piston 1010, the burned gas having a high pressure remains in the EGR chamber 100. A lot of burned gas can be stored.

  In the present embodiment, the valve opening timing of the exhaust valve 7 is adjusted according to the operating state of the engine 1. As a result, it is possible to supply an amount of internal EGR gas corresponding to the operating state of the engine 1.

  Here, FIG. 19 is a diagram showing the relationship between the engine speed, the fuel injection amount, and the exhaust valve opening timing. The fuel injection amount may be an engine load or an accelerator opening. In the high rotation high load region (the upper right region in FIG. 19), the exhaust valve 7 is opened at 50 degrees before bottom dead center, that is, at the end of the expansion stroke. Then, the valve opening timing of the exhaust valve 7 is retarded as the engine speed becomes low or the load is low, and the exhaust valve 7 is closed after the EGR introduction hole 15 is closed in the low engine speed and low load area (lower left area in FIG. 19). Open the valve.

  In this way, the supply amount (mass) of EGR gas can be changed steplessly, and an amount of EGR gas corresponding to the operating state of the engine 1 at that time can be supplied. In particular, when a variable valve mechanism that changes the valve opening timing of the exhaust valve 7 by electromagnetic drive or hydraulic drive is employed, the responsiveness of the exhaust valve 7 is high, and the internal EGR amount can be changed quickly.

<Sixth Embodiment>
The present embodiment is different from the fifth embodiment in that the pressure of burned gas stored in the cylinder EGR chamber 100 is changed by changing the timing at which the EGR introduction hole 15 is closed by the piston 10. To do. Therefore, the engine 1 according to the present embodiment includes a mechanism for changing the closing time of the EGR introduction hole 15.

  FIG. 20 is a schematic configuration diagram of an engine according to the present embodiment. The engine according to the present embodiment is the same as the engine according to the fourth embodiment except that the EGR introduction hole 15 is provided with a closing timing variable mechanism 101 and the variable valve mechanism is not necessarily required. Therefore, the same components as those of the engine shown in FIG.

  The closing timing variable mechanism 101 rotates around the point a in the direction indicated by the arrow in FIG. 20 to change the opening area of the EGR introduction hole 15. That is, when the closing timing variable mechanism 101 moves from the upper side to the lower side in FIG. 20, the EGR introduction hole 15 is reduced from the upper side. Thereby, the time when the EGR introduction hole 15 is completely closed by the piston 10 is advanced. That is, when the opening area of the EGR introduction hole 15 is small, the EGR introduction hole 15 is closed early, and as the opening area is increased, the time when the EGR introduction hole 15 is completely closed is delayed.

Here, in the early stage of the exhaust stroke, as the piston 1010 rises, the exhaust flows out from the exhaust valve 7 and the pressure in the cylinder 2 decreases. Therefore, if the EGR introduction hole 15 is closed with the piston 10 at an early stage, the burned gas can be stored in the EGR chamber 100 while the pressure in the EGR chamber 100 is high. And the pressure of the burned gas stored in the EGR chamber 100 becomes lower as the timing for closing the EGR introduction hole 15 becomes later. Thus, the earlier the timing for closing the EGR introduction hole 15, the higher the pressure of burned gas is stored in the EGR chamber 100, and a larger amount (mass) of burned gas can be stored in the EGR chamber 100. it can.

  Further, in the fifth embodiment in which the amount of burned gas stored is increased by retarding the valve opening timing of the exhaust valve 7, the burned gas is compressed in the early stage of the exhaust stroke, so the pump loss There is a risk that the fuel consumption will deteriorate. In this respect, in the present embodiment, such a situation does not occur and deterioration of fuel consumption can be suppressed.

  Further, a larger amount of burned gas can be stored in the EGR chamber 100 by combining with the increase in the amount of burned gas stored using the variable valve mechanism described in the fifth embodiment.

  FIG. 21 is a diagram showing the relationship among the engine speed, the fuel injection amount, and the closing timing of the EGR introduction hole. Here, the fuel injection amount may be an engine load or an accelerator opening. In the high rotation high load region (the upper right region in FIG. 21), the closing timing variable mechanism 101 is controlled so that the EGR introduction hole 15 is closed at 50 degrees after the bottom dead center. Then, the closing timing of the EGR introduction hole 15 is advanced as the rotation speed or load is reduced, and the EGR introduction hole 15 is closed at 10 degrees after the bottom dead center in the low rotation low load area (lower leftmost area in FIG. 21). Thus, the closing timing variable mechanism 101 is controlled.

In this way, the supply amount (mass) of EGR gas can be changed steplessly, and an amount of EGR gas corresponding to the operating state of the engine 1 at that time can be supplied.
<Seventh embodiment>
FIG. 22 is a schematic configuration diagram of an engine according to the present embodiment.

  The present embodiment is different from the fourth embodiment in that a second EGR chamber 102 is further connected to the EGR chamber 100. In the engine 1 in the present embodiment, the first valve 103 is provided between the cylinder 2 and the EGR chamber 100, and the second valve 104 is provided between the EGR chamber 100 and the second EGR chamber 102. The other configuration is the same as that of the fourth embodiment, and therefore, different points will be mainly described in the present embodiment.

  The first valve 103 and the second valve 104 are valves that are opened and closed by a signal from the ECU. In a state where the first valve 103 is opened and the second valve 104 is closed, the burned gas can be introduced only into the EGR chamber 100. Thereby, the internal EGR gas for the volume of the EGR chamber 100 can be introduced. Further, when the first valve 103 and the second valve 104 are opened, the burned gas can be introduced into the EGR chamber 100 and the second EGR chamber 102. Thereby, the internal EGR gas for the volume of the EGR chamber 100 and the second EGR chamber 102 can be introduced. Furthermore, in the state where the first valve 103 is closed, the introduction of the internal EGR gas from the EGR chamber 100 and the second EGR chamber 102 can be stopped.

  Here, FIG. 23 is a diagram showing the relationship among the engine speed, the fuel injection amount, and the open / close states of the first valve and the second valve. Here, the fuel injection amount may be an engine load or an accelerator opening. In the high rotation high load region (the upper right region in FIG. 23), both the first valve 103 and the second valve 104 are closed. Further, when the engine speed or the load is lower than that, the first valve 103 is opened and the second valve 104 is closed. When the engine speed or load further decreases to enter a low rotation / low load region (lower left region in FIG. 23), both the first valve 103 and the second valve 104 are opened.

  In this way, the amount of the burned gas stored can be increased in stages as the engine speed or load decreases, so that the amount of internal EGR gas can be increased in stages. Thereby, the amount of internal EGR gas corresponding to the operating state of the engine can be supplied.

<Eighth Embodiment>
FIG. 24 is a schematic configuration diagram of an engine according to the present embodiment.
In the present embodiment, unlike the fourth embodiment, an EGR chamber piston 105 is provided in the EGR chamber 100, and the volume of the EGR chamber 100 is changed by the movement of the EGR chamber piston 105. Thereby, the quantity of internal EGR gas is adjusted. The EGR chamber piston 105 is moved by a signal from the ECU. The other configuration is the same as that of the fourth embodiment, and therefore, different points will be mainly described in the present embodiment.

  Here, FIG. 25 is a diagram showing the relationship between the engine speed, the fuel injection amount, and the volume of the EGR chamber 100. Here, the fuel injection amount may be an engine load or an accelerator opening. In the high rotation high load region (the upper right region in FIG. 25), the EGR chamber piston 105 is moved so that the volume of the EGR chamber 100 is minimized. The volume of the EGR chamber 100 is increased as the rotation or load becomes lower, and the EGR chamber piston 105 is set so that the volume of the EGR chamber 100 is maximized in the low rotation and low load region (lower left region in FIG. 25). To control.

  In this way, the amount of internal EGR gas can be increased as the engine speed or load decreases. Further, the amount of internal EGR gas can be adjusted steplessly. Thereby, the amount of internal EGR gas corresponding to the operating state of the engine can be supplied.

<Ninth embodiment>
In the present embodiment, the inflow speed of the internal EGR gas from the EGR chamber 100 into the cylinder 2 is increased by advancing the valve closing timing of the intake valve 6. Therefore, the engine 1 according to the present embodiment includes a variable valve mechanism that can change the opening / closing timing of the intake valve 6. The other configuration is the same as that of the fourth embodiment, and therefore, different points will be mainly described in the present embodiment.

  Here, as the pressure of the burned gas stored in the EGR chamber 100 becomes relatively higher than the pressure in the cylinder 2, the inflow rate of the burned gas from the EGR chamber 100 into the cylinder 2 increases. Then, as described in the first embodiment, by changing the inflow speed of the internal EGR gas, the distribution of the EGR gas in the cylinder 2 can be changed according to the operating state of the engine, or the swirl rotation It is possible to change the speed.

  Then, the closing timing of the intake valve 6 is advanced, and after the intake valve 6 is closed at the end of the intake stroke, the EGR chamber 100 and the cylinder 2 communicate with each other via the EGR introduction hole 15. The pressure difference between the EGR chamber 100 and the cylinder 2 during this communication can be increased. That is, if the closing timing of the intake valve 6 is advanced to close the intake valve 6 while the piston 10 is being lowered, the pressure in the cylinder 2 is reduced while the piston 10 is lowered to the bottom dead center thereafter. descend. As a result, the pressure difference between the EGR chamber 100 and the cylinder 2 can be increased.

In the present embodiment, the closing timing of the intake valve 6 is adjusted according to the operating state of the engine 1. As a result, it is possible to supply the internal EGR gas at an inflow speed corresponding to the operating state of the engine 1. Here, the flow rate of the internal EGR gas from the EGR chamber 100 into the cylinder 2 can be changed by changing the timing of closing the intake valve 6. That is, as the closing timing of the intake valve 6 is earlier, the pressure difference between the cylinder 2 and the EGR chamber 100 is increased, and the inflow speed of the internal EGR gas is increased. As a result, it is possible to obtain an EGR gas distribution and a swirl rotational speed commensurate with the operating state of the engine 1 at that time.

  Here, by increasing the inflow speed of the internal EGR gas, for example, the following effects can be obtained. That is, when the internal EGR gas is introduced in the direction shown in FIG. 4A, the internal EGR gas can be concentrated at the center of the cylinder 2. When the internal EGR gas is introduced in the direction shown in FIG. 4B, the rotational speed of the swirl can be increased and the distribution of EGR gas and fuel can be made more uniform. When the internal EGR gas is introduced in the direction shown in FIG. 4C, the internal EGR gas can be concentrated around the cylinder side wall. Further, when the internal EGR gas is introduced in the direction shown in FIG. 4D, the internal EGR gas is more distributed on the cylinder center side.

<Tenth Embodiment>
This embodiment is different from the ninth embodiment in that the inflow speed of the internal EGR gas is changed by changing the opening area of the EGR introduction hole 15. Therefore, the engine 1 according to the present embodiment includes a mechanism for changing the opening area of the EGR introduction hole 15. Since other configurations are the same as those of the above-described embodiment, the differences will be mainly described in the present embodiment.

FIG. 26 is a schematic configuration diagram of an engine according to the present embodiment.
The engine is the same as the engine according to the ninth embodiment except that the EGR introduction hole 15 includes an opening area variable mechanism 106 and a variable valve mechanism is not always necessary.

  The opening area variable mechanism 106 rotates around the point b in the direction indicated by the arrow in FIG. 26 to change the opening area of the EGR introduction hole 15. That is, when the opening area variable mechanism 106 moves from the lower side to the upper side in FIG. 26, the opening area of the EGR introduction hole 15 is reduced from the lower side.

  Thus, according to the opening area variable mechanism 106, the opening area of the EGR introduction hole 15 can be reduced. The inflow rate of burned gas from the EGR chamber 100 into the cylinder 2 can be increased as the opening area of the EGR introduction hole 15 is reduced.

  Further, the advancement of the closing timing of the intake valve 6 increases the difference between the pressure in the EGR chamber 100 and the pressure in the cylinder 2 to increase the inflow speed of the internal EGR gas. In the embodiment, since the intake air is expanded at the end of the intake stroke, there is a possibility that the pump loss increases and the fuel consumption deteriorates. In this respect, in the present embodiment, such a situation does not occur and deterioration of fuel consumption can be suppressed.

Furthermore, the inflow speed of the burned gas into the cylinder 2 can be increased as compared with the ninth embodiment.
Further, by combining the variable valve mechanism described in the ninth embodiment, the inflow speed of the burned gas into the cylinder 2 can be further increased.

  Note that the inflow speed of the internal EGR gas can be increased in the same manner by an engine including the closing timing variable mechanism 101 shown in FIG. In this case, the inflow speed of the internal EGR gas can be increased as the time when the EGR introduction hole 15 is completely closed is advanced.

<Eleventh embodiment>
FIG. 27 is a schematic configuration diagram of an engine according to the present embodiment. 27A is a cross-sectional view of the engine, and FIG. 27B is a vertical cross-sectional view when the engine is cut along a cutting line XX. In addition, about the structure similar to above-described embodiment, the same symbol is attached | subjected and description is abbreviate | omitted.

  FIG. 28A is an enlarged cross-sectional view of a portion indicated by Y in FIG. FIG. 28B is an enlarged vertical cross-sectional view in which a portion indicated by Y in FIG. 27A is cut along a cutting line XX.

  The engine according to the present embodiment includes a closing timing variable mechanism 101 (or an opening area variable mechanism 106), an EGR chamber piston 105, an EGR introduction direction regulating plate 107, and a variable valve mechanism for intake and exhaust valves. Yes. The EGR introduction direction restricting plate 107 is connected to an axis C parallel to the cylinder axis and rotates around a point c. Two EGR introduction direction restricting plates 107 are provided for each EGR introduction hole 15.

  In the engine configured as described above, the inflow direction of the internal EGR gas can be changed by rotating the EGR introduction direction regulating plate 107. In addition, with respect to the closing timing variable mechanism 101, the EGR chamber piston 105, and the variable valve operating mechanism of the intake / exhaust valve, the functions and effects described in the above-described embodiments can be obtained.

Next, the flow of internal EGR gas introduction control according to this embodiment will be described.
FIG. 29 is a flowchart showing a flow of internal EGR gas introduction control according to the present embodiment.

This flow is carried out at each specified time.
In step S401, an EGR amount required from the engine operating state (hereinafter referred to as a required internal EGR amount) is calculated. The ECU reads the engine rotational speed and the fuel injection amount, and substitutes the relationship among the engine rotational speed, the fuel injection amount, and the required internal EGR amount into a map that is obtained in advance, thereby obtaining the required internal EGR amount.

  In step S402, the orientation of the EGR introduction direction regulating plate 107 is calculated. Here, FIG. 30 is a diagram showing the engine speed, the fuel injection amount, and the direction of the EGR introduction direction restricting plate 107. 30 correspond to (A) to (D) in FIG. 4 or FIG. 16, respectively. Therefore, the ECU can obtain the direction of the EGR introduction direction regulating plate 107 by substituting the engine speed and the fuel injection amount into the map shown in FIG.

  In step S403, the inflow speed of the burned gas from the EGR chamber 100 into the cylinder 2 is calculated. Here, FIG. 31 is a diagram showing the engine speed, the fuel injection amount, and the EGR introduction speed. The higher the engine speed, the higher the internal EGR gas introduction speed. As a result, even when the engine speed increases, the amount of internal EGR gas introduced per crank angle can be kept substantially constant.

  In step S404, in order to obtain the state calculated in steps S401 to S403, the position of the closing timing variable mechanism 101 (EGR amount, EGR introduction speed), the position of the EGR chamber piston 105 (EGR amount), the EGR introduction direction regulating plate The position 107 (EGR introduction direction) and the intake / exhaust valve opening / closing timing (EGR amount, EGR introduction speed) are determined and adjusted to that state.

In this way, it is possible to control the introduction of internal EGR gas in accordance with the operating state of the engine at that time.
<Twelfth embodiment>
In the present embodiment, the mixing ratio of the internal EGR gas and the exhaust gas (hereinafter referred to as external EGR gas) supplied from the exhaust pipe to the intake pipe is changed depending on the operating state of the engine.

FIG. 32 is a schematic configuration diagram of an engine according to the present embodiment.
The engine 1 shown in FIG. 32 is a water-cooled four-cycle diesel engine having four cylinders 2.

Each cylinder 2 is provided with an in-cylinder fuel injection valve 3 that directly injects fuel into the cylinder 2.
An exhaust branch pipe 9 and an intake branch pipe 20 are connected to the engine 1. Further, the engine 1 is provided with an exhaust gas recirculation device 22 (hereinafter referred to as an EGR device 22) that recirculates part of the exhaust gas flowing through the exhaust gas branch tube 9 to the intake air branch tube 20. The EGR device 22 includes an exhaust gas recirculation passage 23 (hereinafter referred to as an EGR passage 23) that communicates the exhaust branch pipe 9 and the intake branch pipe 20, and exhaust gas that flows through the EGR passage 23 (hereinafter referred to as external EGR gas). The EGR cooler that cools the external EGR gas that circulates in the EGR passage 23 on the upstream side of the EGR valve 24, that is, on the exhaust branch pipe 9 side. 25.

  Further, the exhaust branch pipe 9 is provided with an exhaust temperature sensor 26 for detecting the temperature of the exhaust gas in the exhaust branch pipe 9. Furthermore, a crank position sensor 27 that detects the rotational speed of the engine 1 is attached to the engine 1. Moreover, in this Embodiment, the accelerator opening sensor 28 which detects an accelerator opening is provided. And the output signal of these sensors is input into ECU19 which is a control apparatus.

  In the present embodiment, the mechanism shown in FIG. 27 is provided in each cylinder 2, and all of the closing timing variable mechanism 101, the EGR chamber piston 105, the EGR introduction direction regulating plate 107, and the variable valve mechanisms for intake and exhaust valves are provided. The cylinder 2 operates in conjunction with each other.

  In the engine 1 configured as described above, the external EGR gas supplied into the cylinder 2 via the EGR device 22 is cooled by the EGR cooler 25 and thus has a low temperature. On the other hand, the internal EGR gas supplied from the EGR chamber 100 into the cylinder 2 is introduced into the cylinder 2 at a relatively high temperature.

  Therefore, it is possible to change the temperature of the EGR gas in the cylinder 2 by changing the supply ratio of the external EGR gas and the internal EGR gas. Thereby, EGR gas having a temperature corresponding to the operating state of the engine 1 can be introduced into the cylinder 2.

Next, the flow of EGR gas supply control according to this embodiment will be described.
FIG. 33 is a flowchart showing a flow of internal EGR gas and external EGR gas introduction control according to the present embodiment.

This flow is carried out at each specified time.
In step S501, a target average temperature in the cylinder at the compression top dead center (hereinafter referred to as a target in-cylinder average compression end temperature (T_TDC_ave)) is calculated. Here, FIG. 34 is a diagram showing the relationship among the engine speed, the fuel injection amount, and the target in-cylinder average compression end temperature (T_TDC_ave). The target in-cylinder average compression end temperature (T_TDC_ave) increases as the engine speed increases and as the fuel injection amount decreases. The ECU can obtain the target in-cylinder average compression end temperature (T_TDC_ave) by substituting the engine speed and the fuel injection amount into the map shown in FIG.

In step S502, the internal EGR gas temperature (T_hot_egr) is calculated. The internal EGR gas temperature (T_hot_egr) is a temperature detected by the exhaust temperature sensor 26 (
It is calculated by adding a temperature correction coefficient (K_hot_egr) to Tex). That is, the temperature of the burned gas discharged from the cylinder 2 is lower than that of the internal EGR gas before the temperature is detected by the exhaust temperature sensor 26 through the exhaust port. By adding the temperature drop to the temperature (Tex) detected by the exhaust temperature sensor 26, the internal EGR gas temperature (T_hot_egr) can be obtained. That is, the internal EGR gas temperature (T_hot_egr) is calculated by the following equation.

T_hot_egr = Tex + K_hot_egr
Here, the temperature correction coefficient (K_hot_egr) can be obtained by using a map obtained in advance by experiments or the like from the relationship between the engine speed and the load.

  In step S503, the external EGR gas temperature (T_cool_egr) is calculated. The external EGR gas temperature (T_cool_egr) is calculated by subtracting the temperature (K_cool_egr) that is decreased by the EGR cooler 25 from the temperature (Tex) detected by the exhaust temperature sensor 26. That is, the external EGR gas temperature (T_cool_egr) is calculated by the following equation.

T_cool_egr = Tex−K_cool_egr
Here, the temperature (K_cool_egr) that is lowered by the EGR cooler 25 can be obtained by using a map that is obtained in advance through experiments or the like from the relationship between the engine speed and the load.

  In step S504, the EGR amount required from the operating state of the engine 1, that is, the total of the internal EGR amount and the external EGR amount (hereinafter referred to as the total EGR amount (G_EGR_total)) is calculated. Here, FIG. 35 is a diagram showing the relationship between the engine speed, the fuel injection amount, and the total EGR amount (G_EGR_total). The total EGR amount (G_EGR_total) increases as the engine speed increases and the fuel injection amount increases. The ECU can obtain the total EGR amount (G_EGR_total) by substituting the engine speed and the fuel injection amount into the map shown in FIG.

  In step S505, an internal EGR amount (G_EGR_hot) and an external EGR amount (G_EGR_cool) are calculated. The sensible heat generated when the internal EGR gas is cooled is used to warm the external EGR gas as it is, and the total of the internal EGR gas amount (G_EGR_hot) and the external EGR gas amount (G_EGR_cool) is the total EGR amount. Since (G_EGR_total), it can be obtained by solving the following equation.

T_TDC_ave = (G_EGR_cool × C_EGR_cool × T_cool_egr + G_EGR_hot × C_EGR_hot × T_hot_egr) / (G_EGR_cool × C_EGR_cool + G_EGR_hot_TGR_hot_GTR_hot_GTR_hot_GTR_hot_GTR_hot_GTR_hot_GTR
G_EGR_total = G_EGR_cool + G_EGR_cool
Here, C_EGR_cool is the specific heat of the internal EGR gas and is a function of the internal EGR gas temperature (T_hot_egr). C_EGR_hot is a specific heat of the external EGR gas and is a function of the external EGR gas temperature (T_cool_egr).

  In step S506, the closing timing variable mechanism 101, the EGR chamber piston 105, and the variable valve operating mechanism of the intake and exhaust valves are controlled so that the internal EGR amount (G_EGR_hot) and the external EGR amount (G_EGR_cool) calculated in step S505 are obtained.

In this way, the total EGR amount and the ratio between the internal EGR gas and the external EGR gas can be changed in accordance with the operating state of the engine at that time. Therefore, it is possible to supply EGR gas corresponding to the operating state of the engine.

<Thirteenth embodiment>
FIG. 36 is a schematic configuration diagram of an engine according to the present embodiment.
In the present embodiment, the EGR introduction hole 15 of the first cylinder and the EGR introduction hole 15 of the fourth cylinder are connected, and the EGR introduction hole 15 of the second cylinder and the EGR introduction hole 15 of the third cylinder are connected. Yes. The second embodiment is different from the first embodiment in that EGR gas is directly supplied from the cylinder in the expansion stroke to the cylinder in the intake stroke. Since other configurations are the same as those of the first embodiment, the description will focus on differences from the present embodiment.

  The engine 1 shown in FIG. 36 is a water-cooled four-cycle diesel engine having four cylinders 2. The four cylinders 2 are arranged in the order of the second cylinder (# 2), the third cylinder (# 3), and the fourth cylinder (# 4) in order from the first cylinder (# 1) on the left side of FIG.

The engine 1 is configured by connecting a cylinder head 1a and a cylinder block 1b.
Each cylinder 2 is provided with an EGR introduction hole 15 that is located above the upper surface of the piston 10 and opens to the side wall of the cylinder 2 when the piston 10 is located at the bottom dead center. The EGR introduction hole 15 is closed by the side surface of the piston 10 when the piston 10 moves upward. Further, two EGR introduction holes 15 are provided on the diameter axis of each cylinder 2 at symmetrical positions.

  One end of the third EGR passage 11c is branched and connected to the two EGR introduction holes 15 provided in the first cylinder. The other end of the third EGR passage 11c is branched and connected to two EGR introduction holes 15 provided in the fourth cylinder. On the other hand, one end of the fourth EGR passage 11d is branched and connected to the two EGR introduction holes 15 provided in the second cylinder. The other end of the fourth EGR passage 11d is branched and connected to two EGR introduction holes 15 provided in the third cylinder.

  In the middle of the third EGR passage 11c, a flow rate adjusting valve (hereinafter referred to as third EGR) is configured with an electromagnetic valve or the like, and changes the flow rate of the EGR gas flowing through the third EGR passage 11c according to the magnitude of applied power. 13c is provided. Similarly, in the middle of the fourth EGR passage 11d, a flow rate adjustment valve (hereinafter referred to as a fourth EGR passage) is configured with an electromagnetic valve or the like, and changes the flow rate of the EGR gas flowing through the fourth EGR passage 11d in accordance with the magnitude of applied power. 13d is provided.

  Here, FIG. 37 is a diagram showing the supply state of the EGR gas between the cylinders with arrows. The uppermost arrow (1) indicates that EGR gas is introduced from the fourth cylinder to the first cylinder. That is, when the piston 10 of the first cylinder is located at the intake bottom dead center (that is, when the intake stroke is shifted to the compression stroke), the piston 10 of the fourth cylinder is located at the expansion bottom dead center ( That is, the expansion stroke shifts to the exhaust stroke.) In this case, the pressure in the first cylinder is lower than the pressure in the fourth cylinder. When the third EGR valve 13c is opened at this time, the burned gas in the fourth cylinder can be introduced into the first cylinder as EGR gas due to the pressure difference between the cylinders.

  On the other hand, by opening the third EGR valve 13c when the first cylinder is at the expansion bottom dead center and the fourth cylinder is at the intake bottom dead center (see the third arrow (3) from the top in FIG. 37), The burned gas in the number cylinder can be introduced into the number four cylinder.

Similarly, by opening the fourth EGR valve 13d when the second cylinder is at the expansion bottom dead center and the third cylinder is at the intake bottom dead center (see the second arrow (2) from the top in FIG. 37). The burned gas in the second cylinder can be introduced into the third cylinder. Further, when the second cylinder is at the intake bottom dead center and the third cylinder is at the expansion bottom dead center (refer to the fourth arrow (4) from the top in FIG. 37), the fourth EGR valve 13d is opened to open 3 The burned gas in the number cylinder can be introduced into the number two cylinder.

By supplying EGR gas between the cylinders in this way, more EGR gas having a higher temperature can be introduced.
In the present embodiment, a four-cylinder engine has been described. However, the present invention can also be applied to other multi-cylinder engines. In this case, the EGR introduction hole of the cylinder that is in the intake stroke is connected to the EGR introduction hole of the cylinder that is in the expansion stroke.

<Other embodiments>
In the above-described embodiment, the EGR introduction holes 15 are provided at two locations per cylinder, and the EGR gas is introduced from two locations. Instead, the EGR introduction holes 15 are provided at four locations per cylinder. And EGR gas may be introduced from four locations.

FIG. 16 is a diagram showing the EGR gas introduction direction and the distribution of EGR gas when EGR introduction holes 15 are provided at four locations per cylinder and EGR gas is introduced from four locations.
The four EGR introduction holes 15 are respectively provided on two axes orthogonal to the cylinder central axis. These two axes are also orthogonal to the cylinder center axis. The arrangement of the EGR introduction pipe 16 shown in FIGS. 16A to 16D corresponds to that of FIGS. 4A to 4D, respectively.

  In the first to fourth embodiments, the EGR gas introduction method shown in FIG. 4 (C) or FIG. 16 (C) can be used for one or three EGR introduction sites.

It is a figure which shows schematic structure of an engine. It is a cross-sectional view of an engine at an EGR introduction hole. It is the figure which showed the attachment position of the 1st air fuel ratio sensor and the 2nd air fuel ratio sensor. It is the figure which showed EGR gas introduction direction from the cylinder wall surface, and distribution of EGR gas at that time. FIG. 4A is a diagram in which the EGR introduction pipe is arranged so that the center line of the EGR introduction pipe coincides with the cylinder diameter line. FIG. 4B is a diagram in which the EGR introduction pipe is arranged so that the EGR gas rotates at a shallow angle at the center of the cylinder and the two EGR introduction pipes are symmetrical with respect to the center of the cylinder. is there. FIG. 4C is a diagram in which the EGR introduction pipe is arranged so as to introduce the EGR gas along the cylinder outer periphery at a further angle than in FIG. 4B. FIG. 4D is a diagram in which the EGR introduction pipe is arranged so as to be symmetric with respect to the cylinder diameter line orthogonal to the line connecting the two EGR introduction holes. FIG. 5 is a diagram showing the relationship between the distance from the cylinder center and the EGR gas concentration when EGR gas is introduced in the directions of FIGS. 4 (A) and 4 (B). It is the figure which showed the relationship of the effect by the introduction direction of EGR gas, EGR gas temperature, and EGR introduction. It is the flowchart figure which showed the flow of EGR gas introduction control by 1st Embodiment. It is the figure which showed the relationship between a rotation speed, fuel injection amount, and an EGR valve opening degree. It is the figure which showed the relationship between a rotation speed, fuel injection amount, and EGR amount. FIG. 6 is a diagram showing a relationship between an EGR amount, an air-fuel ratio A / Fc at the center of a cylinder detected by a first air-fuel ratio sensor, and an EGR temperature. It is the flowchart figure which showed the flow of EGR gas introduction control by 2nd Embodiment. It is the figure which showed the relationship between the amount of EGR, intake air temperature Tb, and EGR temperature Tegr. It is the flowchart figure which showed the flow of EGR gas introduction control by 3rd Embodiment. It is the figure which showed the relationship between the output of both air fuel ratio sensors, a knock, and a combustion noise increase area | region. It is the figure which showed the relationship between an engine speed, fuel injection amount, and arrangement | positioning of an EGR introduction pipe. It is the figure which showed EGR gas introduction | transduction direction and distribution of EGR gas when EGR introduction holes are provided in four places per cylinder and EGR gas is introduced from four places. FIGS. 16A to 16D correspond to FIGS. 4A to 4D. It is a figure which shows schematic structure of the engine by 4th Embodiment. FIG. 17A is a longitudinal sectional view, and FIG. 17B is a transverse sectional view. It is the figure shown about the introduction state of EGR gas in case the engine is drive | operated by the normal intake / exhaust valve opening / closing timing. FIG. 18A shows the first stage of the expansion stroke, FIG. 18B shows the second stage of the expansion stroke, FIG. 18C shows the second stage of the exhaust stroke and the first stage of the intake stroke, and FIG. 18D shows the second stage of the intake stroke. . It is the figure which showed the relationship between engine speed, fuel injection amount, and exhaust valve opening timing. It is a schematic block diagram of the engine by 6th Embodiment. It is the figure which showed the relationship between an engine speed, fuel injection quantity, and the closing time of an EGR introduction hole. It is a schematic block diagram of the engine by 7th Embodiment. It is the figure which showed the relationship between an engine speed, fuel injection amount, and the opening-and-closing state of a 1st valve and a 2nd valve. It is a schematic block diagram of the engine by 8th Embodiment. It is the figure which showed the relationship between an engine speed, fuel injection amount, and the volume of an EGR chamber. It is a schematic block diagram of the engine by 10th Embodiment. It is a schematic block diagram of the engine by 11th Embodiment. 27A is a cross-sectional view of the engine, and FIG. 27B is a vertical cross-sectional view when the engine is cut along a cutting line XX. FIG. 28A is an enlarged cross-sectional view of a portion indicated by Y in FIG. FIG. 28B is an enlarged vertical cross-sectional view in which a portion indicated by Y in FIG. 27 is cut along a cutting line XX. It is the flowchart figure which showed the flow of internal EGR gas introduction control by 11th Embodiment. It is the figure which showed the engine speed, the fuel injection quantity, and the direction of the EGR introduction direction regulating plate. It is the figure which showed the engine speed, the fuel injection quantity, and the EGR introduction speed. It is a schematic block diagram of the engine by 12th Embodiment. It is the flowchart figure which showed the flow of introduction control of internal EGR gas and external EGR gas by 12th Embodiment. It is the figure which showed the relationship between engine speed, fuel injection amount, and target cylinder average compression end temperature (T_TDC_ave). It is the figure which showed the relationship between engine speed, fuel injection amount, and total EGR amount (G_EGR_total). It is a schematic block diagram of the engine by 13th Embodiment. It is the figure which showed the supply state of the EGR gas between cylinders with the arrow.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Engine 1b ... Cylinder block 1a ... Cylinder head 2 ... Cylinder 3 ... In-cylinder fuel injection valve 4 ... Intake port 5 ... Exhaust port 6 ... intake valve 7 ... exhaust valve 8 ... intake fuel injection valve 9 ... exhaust branch pipe 10 ... piston 11 ... EGR passage 11a ... first EGR passage 11b ... 2nd EGR passage 11c, 3rd EGR passage 11d, 4th EGR passage 12 ... EGR cooler 13a, 1st EGR valve 13b, 2nd EGR valve 13c, 3rd EGR valve 13d, 4th EGR valve 14 ... EGR Temperature sensor 15... EGR introduction hole 16... EGR introduction pipe 17... Check valve 18 a .. First air-fuel ratio sensor 18 b.
20 ... Intake branch pipe 21 ... Intake temperature sensor 22 ... Exhaust gas recirculation device (EGR device)
23 ... Exhaust gas recirculation passage (EGR passage)
24 ... Flow control valve (EGR valve)
25 ... EGR cooler 26 ... exhaust temperature sensor 27 ... crank position sensor 28 ... accelerator opening sensor 100 ... EGR chamber 101 ... closing timing variable mechanism 102 ... second EGR chamber 103 ... 1 valve 104, second valve 105, EGR chamber piston 106, opening area variable mechanism 107, EGR introduction direction regulating plate

Claims (6)

An exhaust introduction hole having an exhaust inflow direction in which exhaust gas introduced into the cylinder has a predetermined concentration distribution is provided in a wall surface in the cylinder, and the exhaust inflow direction is a passage connected to the exhaust introduction hole. An internal combustion engine which is changed by changing an angle with respect to a cylinder wall surface and introduces only exhaust gas from the exhaust introduction hole. An operating state detecting means for detecting an operating state of the internal combustion engine;
A storage device for storing a relationship between an operating state of the internal combustion engine and an inflow direction of the exhaust;
An exhaust inflow direction control means for changing an inflow direction of exhaust flowing into the cylinder from the exhaust introduction hole based on a detected value of the operating state detection means and a relationship stored in the storage device ;
The internal combustion engine according to claim 1, further comprising: Air-fuel ratio detecting means for detecting the air-fuel ratio distribution in the cylinder;
A storage device for storing a relationship between an air-fuel ratio distribution in the cylinder and an inflow direction of the exhaust;
An exhaust inflow direction control means for changing an inflow direction of exhaust flowing into the cylinder from the exhaust introduction hole based on a detected value of the air-fuel ratio detection means and a relationship stored in the storage device ;
The internal combustion engine according to claim 1, further comprising: Inflow exhaust gas temperature lowering means for lowering the temperature of exhaust gas flowing into the cylinder from the introduction hole;
Inflow exhaust gas temperature control means for controlling the temperature of the exhaust gas flowing into the cylinder from the exhaust gas introduction hole according to the operating state of the internal combustion engine;
The internal combustion engine according to any one of claims 1 to 3, further comprising: The internal combustion engine is a premixed compression ignition internal combustion engine, and when the ignition timing is within an allowable range, the inflow exhaust gas temperature control unit prohibits a decrease in exhaust gas temperature by the inflow exhaust gas temperature reduction unit. The internal combustion engine according to claim 4. An EGR chamber connected to the exhaust introduction hole and storing the burned gas in the cylinder;
Increasing the inflow speed of the exhaust gas flowing into the cylinder from the exhaust introduction hole by changing the valve opening timing of the exhaust valve when the burned gas in the cylinder is taken into the EGR chamber, or Or an inflow exhaust speed increasing means for increasing by changing the opening area of the exhaust introduction hole ;
A storage device for storing a relationship between an operating state of the internal combustion engine and an inflow speed of the exhaust;
Inflow / exhaust speed control means for changing the degree of increase in the inflow speed by the inflow / exhaust speed increase means based on the operating state of the internal combustion engine and the relationship stored in the storage device ;
The internal combustion engine according to any one of claims 1 to 5, further comprising:

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