JP2006242074A - Premix combustion compression ignition internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent adhesion of injected fuel on an inner wall surface of an intake port and an intake branch pipe in a premix combustion compression ignition internal combustion engine performing fuel injection for forming air fuel premixture by an injection valve provided on an intake port and an intake branch pipe. <P>SOLUTION: The premix combustion compression ignition internal combustion engine includes the premix combustion injection valve 3 for injecting fuel on the intake branch pipe 7 or the intake port 7b of the compression ignition internal combustion engine, injects fuel from the premix combustion injection valve 3 at timing earlier than timing close to compression stroke top dead center, and forms air fuel premixture in a cylinder and performs premix combustion. The premix combustion injection valve 3 is provided with an atomization means atomizing injected fuel, and a high temperature EGR device introducing EGR gas generated during premix combustion to an EGR gas introduction port near an injection valve installation section of the intake branch pipe 7 and the intake port 7b on which the premix combustion injection valve is provided. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a compression ignition internal combustion engine that performs premixed combustion.

  In a compression ignition internal combustion engine, when premixed combustion is performed for the purpose of suppressing NOx and smoke, as the operation state of the compression ignition internal combustion engine becomes a high load operation state and the engine load and the engine speed increase, The possibility of premature ignition increases. Therefore, a technique for performing premixed combustion at low and medium loads and performing normal combustion (diffusion combustion) at high loads based on the operating state of the compression ignition internal combustion engine is disclosed (for example, Patent Document 1). See). In this technique, switching from premixed combustion to normal combustion is performed via multistage injection in which both premixed combustion and normal combustion are performed during one cycle. As a result, it is intended to facilitate combustion switching.

In addition, a compression ignition internal combustion engine that performs premixed combustion, and a technique that includes a premixed combustion injection valve for forming a premixed air in its intake port is disclosed. (For example, see Patent Documents 2 and 3.) As a result, fuel is injected from the premixed combustion injection valve at an earlier stage to form a premixed gas in the cylinder, thereby further promoting the mixing of the intake air and the injected fuel and improving emissions. Is.
JP-A-11-324964 JP 2004-197593 A JP 2004-197599 A Japanese Utility Model Publication No. 64-34434 Japanese Utility Model Publication No. 5-92469 JP-A-9-96256 JP 2002-327653 A

  In a compression ignition internal combustion engine that performs premixed combustion, fuel injection for forming premixed fuel is performed by an injection valve provided in an intake port or an intake branch pipe, thereby enabling a period from fuel injection to self-ignition. And a uniform premixed gas that is more mixed with the intake air is formed to improve the emission.

  However, in the above-mentioned compression ignition internal combustion engine, even if the engine fuel to be used, such as light oil, is injected, the premixed gas is formed well in the intake port or the intake branch pipe due to the low evaporability of the fuel. Without being attached to the inner wall surface. Then, the adhering fuel enters the cylinder later, and smoke is generated when the air-fuel ratio in the cylinder is lowered, or the lubricating oil is diluted by mixing the fuel into the lubricating oil from the inner wall surface of the cylinder. There is a risk that.

  In the present invention, in view of the above problems, in a premixed combustion compression ignition internal combustion engine in which fuel injection for forming a premixed gas is performed by an injection valve provided in an intake port or an intake branch pipe, It aims at avoiding adhering to the inner wall surface of an intake branch pipe.

In order to solve the above-described problems, the present invention makes it possible to atomize injected fuel and to inject EGR gas generated by premixed combustion in fuel injection from an injection valve provided in an intake port or an intake branch pipe. By spraying the injected fuel from the valve, evaporation of the injected fuel forming the premixed gas is promoted. Thereby, it is possible to avoid the fuel from adhering to the inner wall surface of the intake port or the intake branch pipe.

  More specifically, the present invention has a premixed combustion injection valve for injecting fuel into an intake branch pipe or intake port of a compression ignition internal combustion engine, and near the top dead center of the compression stroke from the premixed combustion injection valve. A premixed combustion compression ignition internal combustion engine in which fuel injection is performed earlier than this time to form a premixed gas in a cylinder and premixed combustion is performed, and the premixed combustion injection valve contains finely injected fuel. The EGR gas generated by the premixed combustion is led to the intake branch pipe provided with the premixed combustion injection valve or the EGR gas inlet near the injection valve installation site of the intake port. A premixed combustion compression ignition internal combustion engine further comprising a high temperature EGR device.

  When premixed combustion is performed in the compression ignition internal combustion engine described above, fuel injection from the premixed combustion injection valve is performed at a time earlier than the time near the top dead center of the compression stroke. A mixture is formed. As a result, NOx and smoke are suppressed. Note that the premixed combustion in the present invention is not limited to the case where the premixed fuel is injected by a single fuel injection, but a plurality of times of fuel injection for reasons such as avoiding the fuel from adhering to the inner wall surface of the cylinder. This includes the case where the premixed fuel is injected.

  Here, the premixed combustion injection valve is provided with atomization means so that the injected fuel is atomized. The main atomization of the fuel is to quickly evaporate the injected fuel for forming the premixed gas. Further, the atomization of the injected fuel by the atomizing means is caused by the fact that the nozzle diameter of the premixed combustion injection valve is smaller than a predetermined size, the injection pressure in the premixed combustion injection valve is larger than the predetermined injection pressure, or This can be achieved by providing at least one of collision members for colliding the fuel injected from the premixed combustion injection valve. The predetermined size and the predetermined injection pressure are the size of the injection hole and the injection pressure so that the particle size of the injected fuel becomes a particle size suitable for promoting evaporation. As the injection hole size decreases and the injection pressure increases, atomization of the injected fuel is promoted. The collider is a device that reduces the particle size of the fuel when the injected fuel collides. Moreover, you may atomize injected fuel combining these. Further, the atomization may be performed by raising the temperature of the injected fuel.

  Then, the EGR gas generated by the premixed combustion is directly sprayed on the atomized fuel injected from the premixed combustion injection valve by the high temperature EGR device. That is, the high temperature EGR gas introduced from the EGR gas inlet to the intake branch pipe or the intake port is mixed with the injected fuel from the premixed combustion injection valve, so that the surface area of the injected fuel is increased by atomization. Evaporation is further promoted. As a result, the adhesion of the injected fuel to the inner wall surface of the intake branch pipe or the intake port is avoided.

  Here, in the premixed combustion compression ignition internal combustion engine, the EGR gas inlet may be positioned downstream in the intake flow of the injection valve installation site. That is, the fuel is injected from the premixed combustion injection valve toward the high-temperature EGR gas existing in the intake branch pipe or the intake port, thereby evaporating the injected fuel. Further, because of the positional relationship between the EGR gas inlet and the premixed combustion injection valve, the EGR gas does not directly hit the premixed combustion injection valve. Therefore, it is possible to avoid soot in the EGR gas from adhering to the premixed combustion injection valve and carbonization of the fuel in the injection valve.

Furthermore, in the premixed combustion compression ignition internal combustion engine described above, the high temperature EGR device may be provided inside a cylinder head of the premix compression compression ignition internal combustion engine. By providing the high temperature EGR device inside the cylinder head, the length of the path for recirculating EGR gas to the intake system can be shortened as much as possible. As a result, it is possible to suppress the temperature drop of the EGR gas and introduce high-temperature EGR gas suitable for evaporation of the injected fuel into the intake branch pipe or the intake port.

  Furthermore, in the premixed combustion compression ignition internal combustion engine described above, the EGR gas inlet is directed to a predetermined adhesion portion of the intake branch pipe or the intake port to which the fuel injected from the premixed combustion injection valve adheres. You may make it open. This predetermined part means a part where the injected fuel from the premixed combustion injection valve easily adheres in the intake branch pipe or the intake port. Therefore, by setting the opening direction of the EGR gas inlet so that the high-temperature EGR gas hits the predetermined portion, the adhesion of the injected fuel to the intake branch pipe or the inner wall surface of the intake port can be avoided. Is possible.

  Here, conversely, in the premixed combustion compression ignition internal combustion engine, when the EGR gas introduction port is located upstream in the intake flow of the injection valve installation site, the intake branch pipe extends from the EGR gas introduction port. Or you may make it further provide the EGR gas introduction apparatus which introduces EGR gas from this EGR gas introduction port by projecting in the said intake port and opening toward the said premixed combustion injection valve.

  When the EGR gas introduction port is located on the upstream side of the injection valve installation site, the EGR gas temperature may be lowered by mixing with fresh air before the EGR gas is mixed with the injected fuel. Therefore, by providing the EGR gas introduction device, it is possible to mix the EGR gas with the fuel injected from the premixed combustion injection valve while avoiding the EGR gas from being mixed with fresh air as much as possible. Thereby, it becomes possible to avoid adhesion of the injected fuel to the inner wall surface of the intake branch pipe or the intake port.

  Here, in the premixed combustion compression ignition internal combustion engine described above, the EGR cooler that cools at least a part of the EGR gas generated by the premixed combustion, and the EGR gas cooled by the EGR cooler are converted into the premixed combustion compression ignition. A low-temperature EGR device that leads to the intake passage of the internal combustion engine, and an EGR adjustment device that adjusts the respective EGR gas flow rates flowing through the high-temperature EGR device and the low-temperature EGR device based on the operating state of the premixed combustion compression ignition internal combustion engine , May be further provided.

  By installing a low temperature EGR device and adjusting the flow rate of EGR gas flowing into the high temperature EGR device and the low temperature EGR device by the EGR adjustment device, the temperature inside the cylinder is finally suitable for the operating state of the premixed combustion compression ignition internal combustion engine Temperature can be controlled. At this time, since the evaporation of the injected fuel from the premixed combustion injection valve is sufficiently ensured by the high temperature EGR device, during the premixed combustion, the adhesion of fuel to the intake branch pipe or the inner wall of the intake port is avoided. On the other hand, it becomes possible to control the in-cylinder temperature to a temperature at which premature ignition can be avoided.

  Further, in the premixed combustion compression ignition internal combustion engine, the EGR adjustment device may cause the EGR gas flow rate flowing through the high temperature EGR device to be a predetermined flow rate or higher when premixed combustion is performed in the premixed combustion compression ignition internal combustion engine. In this state, the flow rate of the EGR gas flowing through the low temperature EGR device may be increased as the engine load of the premixed combustion compression ignition internal combustion engine increases.

Since the fuel injection amount increases as the engine load of the premixed combustion compression ignition internal combustion engine increases, the possibility of premature ignition in premixed combustion increases. Therefore, in order to supply more EGR gas into the cylinder, the flow rate of the EGR gas flowing through the low temperature EGR device is increased by the EGR adjustment device. However, in order to ensure sufficient evaporation of the fuel injected from the premixed combustion injection valve, the EGR adjustment device maintains the EGR gas flow rate flowing through the high temperature EGR device at a predetermined flow rate or higher. That is, while increasing the amount of low-temperature EGR gas to avoid premature ignition, the flow rate of EGR gas flowing through each of the high-temperature EGR device and the low-temperature EGR device is adjusted for EGR so that the injected fuel is sufficiently evaporated. Adjusted by the device. Accordingly, the predetermined flow rate is a high-temperature EGR gas flow rate for ensuring the evaporation of the injected fuel from the premixed combustion injection valve.

  Further, when the premixed combustion compression ignition internal combustion engine includes a diffusion combustion injection valve that injects fuel into the cylinder, the EGR adjustment device performs diffusion combustion by fuel injection from the diffusion combustion injection valve. The EGR gas may be blocked from flowing into the high temperature EGR device.

  In the above-mentioned premixed combustion compression ignition internal combustion engine, for example, when the engine load of the internal combustion engine increases and it becomes difficult to avoid pre-ignition when premixed combustion is performed, diffusion combustion instead of premixed combustion is performed. Is done. This diffusion combustion is performed by fuel injection at a time near the top dead center of the compression stroke. In such a case, since fuel injection from the premixed combustion injection valve is not performed, it is not necessary to flow EGR gas through the high temperature EGR device. As a result, since the EGR gas is recirculated only by the low temperature EGR device, a large amount of EGR gas can be efficiently supplied into the cylinder.

  In a premixed combustion compression ignition internal combustion engine in which fuel injection for forming a premixed gas is performed by an injection valve provided in an intake port or intake branch pipe, the injected fuel adheres to the inner wall surface of the intake port or intake branch pipe Can be avoided.

  Here, an embodiment of a premixed combustion compression ignition internal combustion engine according to the present invention will be described based on the drawings.

  FIG. 1 is a block diagram showing a schematic configuration of a compression ignition internal combustion engine (hereinafter simply referred to as “internal combustion engine”) 1 to which the present invention is applied. FIG. 2 is a cross-sectional view of the internal combustion engine 1 centering mainly on the intake system. The internal combustion engine 1 is a compression ignition type internal combustion engine having four cylinders 2. Further, a premixed combustion injection valve 3 for injecting fuel into the intake branch pipe 7 and a normal combustion injection valve 11 for injecting fuel directly into the combustion chamber of the cylinder 2 are provided. The premixed combustion injection valve 3 is provided in the intake branch pipe 7, and the penetrating force applied to the injected fuel is smaller than that of the normal combustion injection valve 11. The fuel injected from the premixed combustion injection valve 3 diffuses into the intake branch pipe 7 to form a premixed gas for premixed combustion. The normal combustion injection valve 11 is provided in the cylinder head 30 and injects fuel directly into the cylinder 2. The fuel injected from the normal combustion injection valve 11 has a relatively strong penetration force, and injects fuel that becomes an ignition source of the premixed gas formed by the premixed combustion injection valve 3. When premixed combustion is not performed in the internal combustion engine 1, diffusion combustion is performed by fuel injection from the normal combustion injection valve 3.

  The premixed combustion injection valve 3 and the normal combustion injection valve 11 are connected to a pressure accumulation chamber 4 that stores fuel pressurized to a predetermined pressure. Light oil, which is engine fuel stored in the fuel tank 5, is supplied to the pressure accumulation chamber 4 by a fuel pump 6. The driving source of the fuel pump 6 is a part of the engine output of the internal combustion engine 1. Further, each branch pipe of the intake branch pipe 7 of the internal combustion engine 1 is connected to the combustion chamber via an intake port 7b. Similarly, an exhaust branch pipe 12 is connected to the internal combustion engine 1, and each branch pipe of the exhaust branch pipe 12 is connected to a combustion chamber via an exhaust port. Here, the intake port and the exhaust port are provided with an intake valve and an exhaust valve, respectively.

The intake branch pipe 7 is connected to the intake pipe 8. Further, an intake throttle valve 10 that adjusts the flow rate of the intake air flowing through the intake pipe 8 is located in a portion of the intake pipe 8 that is located immediately upstream of the intake branch pipe 7. An air flow meter 9 for detecting the amount of intake air flowing through the pipe 8 is provided. On the other hand, the EGR device 21 is provided in the internal combustion engine 1. The EGR device 21 recirculates a part of the exhaust gas flowing through the exhaust branch pipe 12 to each branch pipe of the intake branch pipe 7. The EGR device 21 includes an EGR passage 22 extending from the exhaust branch pipe 12 (upstream side) to the intake branch pipe 7 (downstream side), and an EGR valve 24 for adjusting the flow rate of EGR gas.

  An intake pipe 8 positioned between the air flow meter 9 and the intake throttle valve 10 is provided with a compressor side of a supercharger 16 that operates using exhaust energy as a drive source. A turbine side is provided. Here, the supercharger 16 is a so-called variable displacement centrifugal supercharger, and it is possible to finely adjust the finally reached supercharging pressure by adjusting the opening of the variable nozzle. Become. The intake pipe 8 downstream of the supercharger 16 is provided with an intercooler 15 for cooling the intake air that has been pressurized by the supercharger 16 and has reached a high temperature. Further, the turbine side of the supercharger 16 is connected to an exhaust pipe 13, and the exhaust pipe 13 is connected to a muffler downstream. An exhaust purification catalyst 14 that purifies exhaust from the internal combustion engine 1 is provided in the middle of the exhaust pipe 13.

  The internal combustion engine 1 is also provided with an electronic control unit (hereinafter referred to as “ECU”) 20 for controlling the internal combustion engine 1. The ECU 20 includes a CPU, a ROM, a RAM, and the like for storing various programs and maps to be described later, and controls the operating conditions of the internal combustion engine 1 according to the operating conditions of the internal combustion engine 1 and the driver's request. Unit.

  Here, the premixed combustion injection valve 3 and the normal combustion injection valve 11 are opened and closed by a control signal from the ECU 20. That is, according to a command from the ECU 20, the fuel injection timing and the fuel injection amount from the premixed combustion injection valve 3 and the normal combustion injection valve 11 depend on the operating state of the internal combustion engine 1 such as the engine load and the engine speed. Control is performed for each injection valve, so that premixed combustion and normal combustion are performed in the internal combustion engine 1. The combustion control performed in the internal combustion engine 1 will be described later. Further, the opening and closing of the EGR valve 24 and the opening of the variable nozzle of the supercharger 16 are also controlled in accordance with commands from the ECU 20.

  Further, an accelerator opening sensor 26 is electrically connected to the ECU 20, and the ECU 20 receives a signal corresponding to the accelerator opening and calculates an engine load required for the internal combustion engine 1 based on the signal. The crank position sensor 25 is electrically connected to the ECU 20, and the ECU 20 receives a signal corresponding to the rotation angle of the output shaft of the internal combustion engine 1, and the engine rotational speed of the internal combustion engine 1, the engine rotational speed and the gear. The vehicle speed or the like of the vehicle on which the internal combustion engine 1 is mounted is calculated from the ratio or the like.

  Here, in the internal combustion engine 1, premixed combustion and normal combustion (diffusion combustion) are selectively performed based on the operating state of the internal combustion engine 1 represented by the engine speed and the engine load. FIG. 3 shows the relationship between the combustion region to which the operating state of the internal combustion engine 1 belongs and the combustion performed in the internal combustion engine 1. 3, the horizontal axis represents the engine speed of the internal combustion engine 1, and the vertical axis represents the engine load of the internal combustion engine 1. Here, the operating state of the internal combustion engine 1 is represented by the engine rotational speed and the engine load, and belongs to one of the combustion regions of the premix combustion region R1 on the low load side and the normal combustion region R2 on the high load side.

When the engine load of the internal combustion engine 1 increases and the amount of fuel supplied to the combustion chamber increases, or when the engine rotation speed increases and the substantial time for forming the premixed gas in the combustion chamber decreases, it is formed in the combustion chamber. The premixed gas mixture is not uniform and pre-ignition tends to occur. Therefore, when the operating state of the internal combustion engine 1 belongs to the premixed combustion region R1 in which premature ignition can be avoided, premixed combustion is performed to improve emissions and reduce combustion noise. Further, when the internal combustion engine 1 belongs to the normal combustion region R2 where it is difficult to avoid premature ignition, high engine output is achieved by performing normal combustion which is so-called diffusion combustion instead of premixed combustion.

  As described above, premixed combustion or normal combustion is performed according to the combustion region to which the operating state of the internal combustion engine 1 belongs, but at the time of premixed combustion, the fuel injection timing is earlier than the timing near the top dead center of the compression stroke. Then, fuel is injected from the premixed combustion injection valve 11 into the intake branch pipe 7, and the premixed gas is introduced into the cylinder 2 when the intake valve is opened, so that a uniform premixed gas is formed in the cylinder 2. . In order to suppress premature ignition at the time of premixed combustion, when the operating state of the internal combustion engine 1 belongs to the premixed combustion region R1, the opening degree of the EGR valve 24 is set by the ECU 20 and the operating state of the internal combustion engine 1 is normally set. The EGR gas is controlled to be opened more than when belonging to the combustion region R2, and more EGR gas is supplied into the cylinder 2 through the intake branch pipe 7. That is, when premixed combustion and normal combustion are performed, the opening degree of the EGR valve 24 is controlled to an opening degree suitable for each combustion.

  Further, when premixed combustion is performed in the internal combustion engine 1, a relatively high supercharging pressure is required to introduce intake air into the cylinder 2. Therefore, during premixed combustion, the opening of the variable nozzle of the supercharger 16 is adjusted to increase the supercharging pressure in the internal combustion engine 1. On the other hand, during normal combustion, the opening degree of the variable nozzle is adjusted in order to avoid deterioration of the combustion state due to an excessive increase in exhaust pressure in the exhaust branch pipe 12 due to a relatively large engine load. Is done.

  Here, returning to FIG. 2, the formation of the premixed gas in the internal combustion engine 1 will be described in detail. The recirculation of the EGR gas to the intake branch pipe 7 by the EGR device 21 is performed via the EGR gas inlet 22a through which the EGR passage 22 communicates with each branch pipe. The EGR device 21 is not provided with a special device for cooling the EGR gas, and the EGR gas generated by the premixed combustion in the internal combustion engine 1 is in a relatively high temperature state, and the intake branch pipe 7 Will be recycled. Here, the positional relationship between the EGR inlet 22a and the premixed combustion injection valve 3 in this embodiment is such that the EGR gas inlet 22a is positioned downstream of the premixed combustion injection valve 3 in the flow of intake air. Yes. Therefore, the fuel injected from the premixed combustion injection valve 3 is mixed with the intake air while being exposed to the relatively high temperature EGR gas to form a premixed gas.

  In addition, in the premixed combustion injection valve 3, the injection pressure is increased so that the injected fuel is atomized. In this embodiment, the injection pressure of the premixed combustion injection valve 3 is set to 100 MPa. As a result, the atomized fuel is exposed to a relatively high temperature EGR gas, and the evaporation of the fuel is promoted. As a result, most of the injected fuel contributes to the formation of the premixed gas, and it is avoided that the injected fuel adheres to the inner wall surfaces of the intake branch pipe 7 and the intake port 7b.

  Here, FIG. 4 shows the relationship between the intake air temperature when the fuel injected from the premixed combustion injection valve 3 forms a premixed gas and the dilution rate of the lubricating oil of the internal combustion engine 1. In this dilution of the lubricating oil, the fuel injected from the premixed combustion injection valve 3 enters the cylinder 2 through the inner wall surface of the intake branch pipe 7 and the intake port 7b, and mixes with the lubricating oil from the inner wall surface of the cylinder 2. Is caused. As shown in FIG. 4, when the intake air temperature for forming the premixed gas becomes high, the oil dilution rate decreases, that is, the injected fuel from the premixed combustion injection valve 3 becomes the inner wall surface of the intake branch pipe 7 or the intake port 7b. It can be seen that the amount attached to the surface decreases. Further, when the injection pressure in the premixed combustion injection valve 3 is set high and atomization of the injected fuel is performed, the injected fuel from the mixed combustion injection valve 3 is dramatically supplied to the intake branch pipe 7 and the intake port 7b. It can be understood that the amount attached to the inner wall surface decreases.

Accordingly, in the internal combustion engine 1 of the present embodiment shown in FIGS. 1 and 2, the fuel is atomized by the premixed combustion injection valve 3 and the evaporation of the fuel is accelerated by exposing the injected fuel to the high-temperature EGR gas. Further, it becomes possible to sufficiently prevent the fuel injected from the mixed combustion injection valve 3 from adhering to the inner wall surfaces of the intake branch pipe 7 and the intake port 7b. The premixed combustion injection valve 3 is attached to the intake branch pipe 7 by attaching the premixed combustion injection valve 3 so that the spray direction is directed to the EGR gas flowing out from the EGR introduction port 22a. Can be fully extracted.

  Further, since the EGR gas introduction port 22a is located downstream of the premixed combustion injection valve 3, the EGR gas does not directly hit the premixed combustion injection valve 3. Therefore, there is no possibility that the injection port of the premixed combustion injection valve 3 is clogged with soot in the EGR gas or the fuel in the injection valve is carbonized.

  Here, regarding atomization of the injected fuel of the premixed combustion injection valve 3, in the above embodiment, the fuel is atomized by setting the injection pressure high. The nozzle diameter of the injection valve 3 is made smaller, a colliding element for colliding the fuel injected from the nozzle hole is provided, the temperature of the fuel stored in the pressure accumulating chamber 4 is increased, or these are performed in combination. Or the atomization of the fuel may be performed.

  FIG. 5 shows a second embodiment of a compression ignition internal combustion engine 1 that performs premixed combustion according to the present invention. The internal combustion engine 1 shown in FIG. 5 is a modification of the internal combustion engine 1 shown in FIG. 1 and has the same function as the engine elements of the internal combustion engine 1 shown in FIG. 1 among the engine elements of the internal combustion engine 1 shown in FIG. The same reference numerals are assigned to the items, and detailed description of the function is omitted. The feature of the internal combustion engine 1 in the present embodiment is that an EGR passage 22 constituting the EGR device 21 is provided inside the cylinder head 30, and the premixed combustion injection valve 3 and the EGR gas inlet described in the first embodiment. This is the point where the positional relationship 22a is maintained. Specifically, the premixed combustion injection valve 3 is provided in the intake branch pipe 7 on the upstream side, and the EGR gas inlet 22a opens to the intake port 7b on the downstream side.

  By providing the EGR passage 22 inside the cylinder head 30, the length of the path through which the EGR gas flows from the exhaust branch pipe 12 to the intake branch pipe 7 is shortened and recirculated to the intake branch pipe 7. It becomes possible to suppress the temperature drop of the EGR gas at the time as much as possible. As a result, the atomized fuel injected by the premixed combustion injection valve 3 can be exposed to a higher-temperature EGR gas, so that the injected fuel is more reliably contained in the intake branch pipe 7 and the intake port 7b. It is possible to avoid adhesion to the wall surface.

  FIG. 6 shows a third embodiment of a compression ignition internal combustion engine 1 that performs premixed combustion according to the present invention. The internal combustion engine 1 shown in FIG. 6 is a variation of the internal combustion engine 1 shown in FIG. 1 and has the same function as the engine elements of the internal combustion engine 1 shown in FIG. 1 among the engine elements of the internal combustion engine 1 shown in FIG. The same reference numerals are assigned to the components, and detailed description of the function is omitted. A feature of the internal combustion engine 1 in the present embodiment is that an EGR passage 22 constituting the EGR device 21 is provided in the cylinder head 30, and the premixed combustion injection valve 3 and the EGR gas inlet described in the first embodiment. This is that the positional relationship 22a is maintained. Specifically, in the intake port 7b in the cylinder head 30, the premixed combustion injection valve 3 is provided on the upstream side, and the EGR gas introduction port 22a is opened on the downstream side.

  As in the second embodiment, the EGR passage 22 is provided in the cylinder head 30 in this way, so that the length of the path through which the EGR gas flows from the exhaust branch pipe 12 to the intake branch pipe 7 is further increased. It becomes shorter and it becomes possible to suppress the temperature drop of EGR gas at the time of recirculation to the intake branch pipe 7 as much as possible. As a result, the atomized fuel injected by the premixed combustion injection valve 3 can be exposed to a higher-temperature EGR gas, so that the injected fuel is more reliably contained in the intake branch pipe 7 and the intake port 7b. It is possible to avoid adhesion to the wall surface.

FIG. 7 shows a fourth embodiment of a compression ignition internal combustion engine 1 that performs premixed combustion according to the present invention. The internal combustion engine 1 shown in FIG. 7 is a variation of the internal combustion engine 1 shown in FIGS. 1 and 5, and of the engine elements of the internal combustion engine 1 shown in FIG. 7, the engine elements of the internal combustion engine 1 shown in FIGS. Components having the same functions are denoted by the same reference numerals, and detailed description thereof is omitted. The feature of the internal combustion engine 1 in the present embodiment is that an EGR passage 22 constituting the EGR device 21 is provided inside the cylinder head 30, and the premixed combustion injection valve 3 and the EGR gas inlet described in the first embodiment. This is the point where the positional relationship 22a is maintained. Specifically, the premixed combustion injection valve 3 is provided in the intake branch pipe 7 on the upstream side, and the EGR gas inlet 22a opens to the intake port 7b on the downstream side. Furthermore, the opening direction of the EGR gas introduction port 22a is directed to the inner portion R3 of the intake port 7b. This back portion R3 is a place where intake (including fuel injected from the premixed combustion injection valve 3) is easy to hit due to the shape of the intake port 7b. Easy to adhere.

  Therefore, by directing the opening direction of the EGR gas introduction port 22a toward the back portion R3 in this way, the EGR gas M1 hits the back portion R3, and the temperature is always maintained at a high temperature, thereby suppressing fuel adhesion thereto. it can. Even if the injected fuel adheres to the inner portion R3, the attached fuel immediately evaporates. Further, from the positional relationship between the EGR gas inlet 22a and the premixed combustion injection valve 3, as described above, the atomized fuel injected by the premixed combustion injection valve 3 is exposed to a higher temperature EGR gas. Therefore, it is possible to more reliably prevent the injected fuel from adhering to the inner wall surfaces of the intake branch pipe 7 and the intake port 7b. Further, the EGR passage 22 is provided inside the cylinder head 30, whereby the length of the path through which the EGR gas flows from the exhaust branch pipe 12 to the intake branch pipe 7 becomes shorter, and recirculation is performed in the intake branch pipe 7. It is possible to suppress the temperature drop of the EGR gas at the time of being performed as much as possible.

  FIG. 8 shows a fifth embodiment of a compression ignition internal combustion engine 1 that performs premixed combustion according to the present invention. The internal combustion engine 1 shown in FIG. 8 is a variation of the internal combustion engine 1 shown in FIG. 1, and has the same function as the engine elements of the internal combustion engine 1 shown in FIG. 1 among the engine elements of the internal combustion engine 1 shown in FIG. The same reference numerals are assigned to the items, and detailed description of the function is omitted. The premixed combustion injection valve 3 is provided in the intake branch pipe 7. The characteristic point of the internal combustion engine 1 in this embodiment is that the EGR gas inlet 22a is located upstream of the premixed combustion injection valve 3, and the EGR gas from the EGR gas inlet 22a is fed by the EGR gas inlet 32. The premixed combustion injection valve 3 is led to the vicinity of the injection hole. That is, the EGR gas recirculated through the EGR passage 22 is supplied into the intake branch pipe 7 by the EGR gas introduction device 32 opened toward the injection port of the premixed combustion injection valve 3.

  With this configuration, the high-temperature EGR gas is mixed with the fresh air flowing through the intake branch pipe 7 and mixed with the fuel injected from the premixed combustion injection valve 3 before the temperature is lowered. As a result, the atomized injected fuel can be exposed to a higher temperature EGR gas, and thus the injected fuel can be more reliably avoided from adhering to the inner wall surfaces of the intake branch pipe 7 and the intake port 7b. It becomes possible.

  FIG. 9 shows a sixth embodiment of a compression ignition internal combustion engine 1 that performs premixed combustion according to the present invention. The internal combustion engine 1 shown in FIG. 9 is a variation of the internal combustion engine 1 shown in FIG. 1, and has the same function as the engine elements of the internal combustion engine 1 shown in FIG. 1 among the engine elements of the internal combustion engine 1 shown in FIG. The same reference numerals are assigned to the items, and detailed description of the function is omitted. The difference between the internal combustion engine 1 shown in FIG. 1 and the internal combustion engine 1 shown in FIG. 9 is the configuration of the EGR device 21.

In this embodiment, the EGR device 21 includes a low temperature EGR passage 41 and an EGR cooler 40 in addition to the EGR passage 22 and the EGR valve 24. The low temperature EGR passage 41 is a passage branched from the EGR valve 24 and connected to the intake pipe 8 on the downstream side of the intake throttle valve 10. An EGR cooler 40 that cools the EGR gas flowing therethrough is provided in the middle of the low-temperature EGR passage 41. Further, the EGR valve 24 in the present embodiment is a valve that controls the flow rates of the EGR gas flowing into the EGR passage 22 and the low temperature EGR passage 41.

  The EGR gas is cooled by the EGR cooler 40 by flowing the EGR gas into the low temperature EGR passage 41. As a result, the temperature of the intake air supplied into the cylinder 2 decreases, and more EGR gas can be supplied into the cylinder 2 so that premature ignition in premixed combustion can be efficiently avoided. It is possible to improve the emission in diffusion combustion. Therefore, in the internal combustion engine 1 according to the present embodiment, the opening degree of the EGR valve 24 is adjusted based on the operating state, and the EGR gas flow rate flowing through the EGR passage 22 and the EGR gas flow rate flowing through the low temperature EGR passage 41 are controlled. The

  The control of the EGR gas flow rate will be described with reference to FIG. The horizontal axis of the graph in FIG. 10 represents the engine load of the internal combustion engine 1, and the vertical axis represents the amount of intake gas supplied into the cylinder 2. This intake gas amount flows through the EGR passage 22 and is recirculated to the intake branch pipe 7, and the relatively high temperature EGR gas amount (hereinafter referred to as “high temperature EGR gas amount”) and the low temperature EGR passage 41 flow through the EGR. The sum of the relatively low temperature EGR gas amount cooled by the cooler 40 and recirculated to the intake pipe 8 (hereinafter referred to as “low temperature EGR gas amount”) and the amount of fresh air supercharged by the supercharger 16. is there.

  Here, when the engine load of the internal combustion engine 1 is small and its operating state belongs to the premixed combustion region R1, premixed combustion is performed by fuel injection from the premixed combustion injection valve 3. At this time, the opening degree of the EGR valve 24 is adjusted so that the high-temperature EGR gas amount is always equal to or greater than the predetermined amount G1. This predetermined amount G1 is the amount of high-temperature EGR gas necessary for evaporating the atomized fuel injected from the premixed combustion injection valve 3 during premixed combustion, as shown in the first embodiment. . Further, since the fuel injection amount from the premixed combustion injection valve 3 increases as the engine load of the internal combustion engine 1 increases, the possibility of premature ignition increases. Therefore, as the engine load increases, the amount of low-temperature EGR gas is increased, and the substantial amount of EGR gas in the cylinder 2 is maintained at an amount that can suppress pre-ignition.

  Further, when the engine load of the internal combustion engine 1 increases and the operation state belongs to the normal combustion region R2, the fuel injection from the premixed combustion injection valve 3 is stopped, and the fuel from the normal combustion injection valve 3 is stopped. Diffusion combustion is performed by injection. Therefore, when this diffusion combustion is performed, the opening degree of the EGR valve 24 is adjusted, the amount of EGR gas flowing through the EGR passage 22 is shut off, and all of the EGR gas flows through the low temperature EGR passage 41. In this way, an amount of EGR gas necessary for improving the emission during diffusion combustion is efficiently supplied into the cylinder 2. When the engine load of the internal combustion engine 1 further increases, the EGR gas recirculation by the EGR device 21 is interrupted to accommodate the engine load, and a sufficient amount of fresh air is secured in the cylinder 2.

  As described above, in the internal combustion engine 1 according to this embodiment, by adjusting the opening degree of the EGR valve 24, it is possible to avoid the injection fuel from adhering to the intake branch pipe 7 and the intake port during premixed combustion. Thus, it becomes possible to supply an amount of EGR gas suitable for combustion performed according to the operating state into the cylinder 2.

  FIG. 11 shows a seventh embodiment of a compression ignition internal combustion engine 1 that performs premixed combustion according to the present invention. The internal combustion engine 1 shown in FIG. 11 is a variation of the internal combustion engine 1 shown in FIG. 9 and has the same function as the engine elements of the internal combustion engine 1 shown in FIG. 9 among the engine elements of the internal combustion engine 1 shown in FIG. The same reference numerals are assigned to the items, and detailed description of the function is omitted. The difference between the internal combustion engine 1 shown in FIG. 9 and the internal combustion engine 1 shown in FIG. 11 is the configuration of the EGR device 21.

  In the present embodiment, the EGR device 21 includes an EGR passage 22, EGR valves 24 a and 24 b, a low temperature EGR passage 41, and an EGR cooler 40. The EGR gas flow rate flowing through the EGR passage 22 is controlled by the EGR valve 24b, and the EGR gas flow rate flowing through the low temperature EGR passage 41 is controlled by the EGR valve 24a based on commands from the ECU 20, respectively. The control of each EGR valve is performed so that the high temperature EGR gas amount and the low temperature EGR gas amount in the sixth embodiment described above are supplied into the cylinder 2.

1 is a diagram illustrating a schematic configuration of a premixed combustion compression ignition internal combustion engine according to a first embodiment of the present invention. It is a figure showing the schematic structure of the intake system vicinity of the premixed combustion compression ignition internal combustion engine which concerns on Example 1 of this invention. In the premixed combustion compression ignition internal combustion engine which concerns on the Example of this invention, it is a figure which shows the combustion area to which the operating state belongs. In the premixed combustion compression ignition internal combustion engine according to the embodiment of the present invention, it is a diagram showing the relationship between the intake air temperature and the dilution rate of the lubricating oil for each injection pressure from the premixed combustion injection valve. It is a figure showing the schematic structure of the intake system vicinity of the premixed combustion compression ignition internal combustion engine which concerns on Example 2 of this invention. It is a figure showing schematic structure of the intake system vicinity of the premixed combustion compression ignition internal combustion engine which concerns on Example 3 of this invention. It is a figure showing schematic structure of the intake system vicinity of the premixed combustion compression ignition internal combustion engine which concerns on Example 4 of this invention. It is a figure showing the schematic structure of the intake system vicinity of the premixed combustion compression ignition internal combustion engine which concerns on Example 5 of this invention. It is a figure showing schematic structure of the premixed combustion compression ignition internal combustion engine which concerns on Example 6 of this invention. In the compression ignition internal combustion engine which concerns on Example 6 of this invention, it is a figure which shows the relationship between the engine load, the high temperature EGR gas amount supplied in a cylinder, and the low temperature EGR gas amount. It is a figure showing schematic structure of the premixed combustion compression ignition internal combustion engine which concerns on Example 7 of this invention.

Explanation of symbols

1. Compression compression internal combustion engine (internal combustion engine)
2 ... Cylinder 3 ... Premixed combustion injection valve 7 ... Intake branch pipe 7b ... Intake port 8 ... Intake pipe 11 ... Normal combustion injection valve 12 .... Exhaust branch pipe 20 ... ECU
21 ... EGR device 22 ... EGR passage 22a ... EGR gas inlet 24 ... EGR valve 24a ... EGR valve 24b ... EGR valve 25 ... crank Position sensor 26 ... Accelerator opening sensor 30 ... Cylinder head 32 ... EGR gas introduction device 40 ... EGR cooler 41 ... Low temperature EGR passage R1 ... Premixed combustion Region R2 ... Normal combustion region R3 ... Back

Claims (9)

A premixed combustion injection valve for injecting fuel into an intake branch pipe or intake port of a compression ignition internal combustion engine, and fuel injection from the premixed combustion injection valve at a time earlier than the time near the top dead center of the compression stroke A premixed combustion compression ignition internal combustion engine that performs premixed combustion by forming a premixed gas in a cylinder,
The premixed combustion injection valve is provided with atomization means for atomizing the injected fuel,
A high-temperature EGR device that further guides EGR gas generated by premixed combustion to the intake branch pipe provided with the premixed combustion injection valve or the EGR gas inlet near the injection valve installation site of the intake port; A premixed combustion compression ignition internal combustion engine.   The atomizing means may be configured such that the nozzle diameter of the premixed combustion injection valve is smaller than a predetermined size, the injection pressure in the premixed combustion injection valve is larger than a predetermined injection pressure, or from the premixed combustion injection valve 2. The premixed combustion compression ignition internal combustion engine according to claim 1, wherein at least one of collisions for colliding the injected fuel is provided.   3. The premixed combustion compression ignition internal combustion engine according to claim 1, wherein the EGR gas introduction port is located downstream in the intake flow of the injection valve installation site. 4.   4. The premixed combustion compression ignition internal combustion engine according to claim 1, wherein the high temperature EGR device is provided inside a cylinder head of the premix compression ignition internal combustion engine. 5.   The said EGR gas inlet is open toward the predetermined attachment site | part of the said intake branch pipe or the said intake port to which the injection fuel from the said premix combustion injection valve adheres. Item 5. A premixed combustion compression ignition internal combustion engine according to any one of Items 4 to 6. The EGR gas inlet is located on the upstream side in the intake flow of the injection valve installation site,
An EGR gas introduction device for introducing EGR gas from the EGR gas introduction port by projecting from the EGR gas introduction port to the intake branch pipe or the intake port and opening toward the premixed combustion injection valve; The premixed combustion compression ignition internal combustion engine according to claim 1 or 2, further comprising: An EGR cooler that cools at least part of the EGR gas generated by the premixed combustion;
A low-temperature EGR device that guides EGR gas cooled by the EGR cooler to an intake passage of the premixed combustion compression ignition internal combustion engine;
The EGR adjusting device that adjusts the flow rate of each EGR gas flowing through the high temperature EGR device and the low temperature EGR device based on the operating state of the premixed combustion compression ignition internal combustion engine is further provided. A premixed combustion compression ignition internal combustion engine according to any one of claims 1 to 6.   When the premixed combustion is performed in the premixed combustion compression ignition internal combustion engine, the EGR adjusting device maintains the EGR gas flow rate flowing through the high temperature EGR device at a predetermined flow rate or higher, and the premixed combustion compression ignition internal combustion engine. The premixed combustion compression ignition internal combustion engine according to claim 7, wherein the flow rate of the EGR gas flowing through the low temperature EGR device is increased as the engine load increases. A diffusion combustion injection valve for injecting fuel into the cylinder;
The premixing according to claim 8, wherein the EGR adjusting device blocks the flow of EGR gas into the high temperature EGR device when diffusion combustion is performed by fuel injection from the diffusion combustion injection valve. Combustion compression ignition internal combustion engine.

Images