JP2006266169A - Auxiliary chamber type internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an auxiliary chamber type internal combustion engine capable of suitably controlling concentration of fresh air fuel mixture in an auxiliary chamber even when stratified combustion is performed in a main combustion chamber. <P>SOLUTION: The auxiliary chamber type internal combustion engine 1 is provided with the main combustion chamber 63, the auxiliary combustion chamber 61, a communication passage 61d, a fuel injection valve 27, a compressed air injection valve 28 and an ECU 40. The auxiliary combustion chamber adjoins the main combustion chamber. The communication passage keeps communication between the main combustion chamber and the auxiliary combustion chamber. The fuel injection valve supplies first fuel and second fuel to the auxiliary combustion chamber. The first fuel is fuel for forming stratified air fuel mixture in the main combustion chamber and the second fuel is fuel burned in the auxiliary combustion chamber. The compressed air injection valve supplies compressed air to the auxiliary combustion chamber to push out first fuel from the auxiliary combustion chamber to the main combustion chamber via the communication hole. The ECU controls the compressed air injection valve and the fuel injection valve to make the fuel injection valve supply second fuel to the auxiliary combustion chamber further after the compressed air injection valve pushes out the first fuel from the auxiliary combustion chamber to the main combustion chamber. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a sub-chamber internal combustion engine.

Conventionally, a sub-combustion type internal combustion engine including a main combustion chamber and a sub-combustion chamber provided adjacent to the main combustion chamber has been proposed (see, for example, Patent Document 1).
11-500510 (page 1-28, Fig.1-11)

  However, when stratified combustion is performed in the main combustion chamber, a part of the fuel supplied to the sub-combustion chamber is pushed out from the sub-combustion chamber to the main combustion chamber via the communication path, and an air-fuel mixture is formed. The air-fuel mixture existing in the vicinity of the passage may flow back to the auxiliary combustion chamber. For this reason, since the concentration of the fresh air mixture in the auxiliary combustion chamber tends to vary from cycle to cycle, the concentration of the fresh air mixture in the auxiliary combustion chamber may not be suitably controlled.

  The subject of this invention is providing the subchamber internal combustion engine which can control suitably the density | concentration of the fresh air mixture of a subcombustion chamber also when stratified combustion is performed in a main combustion chamber.

  The sub-chamber internal combustion engine according to the present invention includes a main combustion chamber, a sub-combustion chamber, a communication path, a fuel supply unit, an air supply unit, and a control unit. The auxiliary combustion chamber is adjacent to the main combustion chamber. The communication passage communicates the main combustion chamber and the sub-combustion chamber. The fuel supply unit supplies the first fuel and the second fuel to the auxiliary combustion chamber. The first fuel is a fuel for forming a stratified mixture in the main combustion chamber. The second fuel is a fuel for burning in the auxiliary combustion chamber. The air supply unit supplies compressed air to the auxiliary combustion chamber in order to push the first fuel from the auxiliary combustion chamber to the main combustion chamber via the communication passage. The control unit includes the air supply unit and the fuel supply unit so that the fuel supply unit further supplies the second fuel to the sub-combustion chamber after the air supply unit pushes the first fuel from the sub-combustion chamber to the main combustion chamber. Control.

  In this sub-chamber internal combustion engine, the air supply unit supplies compressed air to the sub-combustion chamber in order to push the first fuel from the sub-combustion chamber to the main combustion chamber via the communication path. For this reason, substantially all of the first fuel can be pushed out from the auxiliary combustion chamber to the main combustion chamber. In addition, the control unit may supply the air supply unit and the fuel supply so that the fuel supply unit further supplies the second fuel to the sub-combustion chamber after the air supply unit pushes the first fuel from the sub-combustion chamber to the main combustion chamber. Control part. For this reason, the concentration of the fresh air mixture in the auxiliary combustion chamber can be controlled by the amount that the fuel supply unit supplies the second fuel to the auxiliary combustion chamber without returning the stratified mixture in the main combustion chamber to the auxiliary combustion chamber. it can.

  In the sub-chamber internal combustion engine according to the present invention, the concentration of the fresh air mixture in the sub-combustion chamber can be controlled by the amount that the fuel supply unit supplies the second fuel to the sub-combustion chamber. For this reason, even when stratified combustion is performed in the main combustion chamber, the concentration of the fresh air mixture in the auxiliary combustion chamber can be suitably controlled.

<Configuration and Operation of Sub-chamber Internal Combustion Engine as Premise of the Present Invention>
The configuration and operation of the sub-chamber internal combustion engine 1 which is the premise of the present invention will be described with reference to FIGS.

(Schematic configuration of sub-chamber internal combustion engine)
FIG. 1 shows a cross-sectional view of the sub-chamber internal combustion engine 1.

  The sub-chamber internal combustion engine 1 mainly includes a main combustion chamber 63, an intake / exhaust mechanism, a fuel injection valve (fuel supply unit) 27, a compressed air injection valve (air supply unit) 28, a sub-combustion chamber 61, a spark plug 29, and a piston. 3 and an ECU (control unit) 40.

  The main combustion chamber 63 is a chamber surrounded by the cylinder head 20, the cylinder block 10 and the piston 3. The cylinder head 20 is formed with an intake port 23 for supplying fresh air to the main combustion chamber 63 and an exhaust port 24 for discharging burned gas from the main combustion chamber 63 as exhaust gas.

  An intake valve 21 is provided downstream of the intake port 23 as an intake / exhaust mechanism. On the other hand, an exhaust valve 22 is disposed upstream of the exhaust port 24. The intake cam shaft 21b / exhaust cam shaft 22b fixed to the intake cam shaft 21b / exhaust cam shaft 22b rotating in conjunction with the rotation of the crankshaft are arranged above the intake valve 21 / exhaust valve 22. Then, the intake valve 21 / exhaust valve 22 are opened and closed.

  The auxiliary combustion chamber 61 is a chamber provided adjacent to the main combustion chamber 63 and is surrounded by the auxiliary combustion chamber wall 61c. Specifically, a sub-combustion chamber wall 61 c is formed in the space formed between the intake port 23 and the exhaust port 24 in the cylinder head 20, and the sub-combustion chamber wall 61 c is formed. In addition, a communication passage 61d that connects the main combustion chamber 63 and the sub-combustion chamber 61 is formed on the bulged hemispherical bottom surface of the sub-combustion chamber wall 61c.

  The fuel injection valve 27 is a valve that injects fuel into the auxiliary combustion chamber 61. The fuel injection valve 27 is provided so as to penetrate the auxiliary combustion chamber wall 61c. The tip of the fuel injection valve 27 protrudes into the auxiliary combustion chamber 61.

  The compressed air injection valve 28 is a valve that injects compressed air into the auxiliary combustion chamber 61. The compressed air injection valve 28 is provided so as to penetrate the auxiliary combustion chamber wall 61c. The tip of the compressed air injection valve 28 is located in the vicinity of the cylinder axis CA and protrudes into the auxiliary combustion chamber 61.

  The spark plug 29 is a plug for igniting the fresh air mixture in the auxiliary combustion chamber 61. The spark plug 29 is provided so as to penetrate the auxiliary combustion chamber wall 61c. A tip end portion 29 a (ignition part) of the spark plug 29 is provided so as to protrude into the auxiliary combustion chamber 61.

  The piston 3 is provided with a cavity 3 a for forming a stratified mixture in the main combustion chamber 63 at the approximate center of the crown surface. The cavity 3a has a substantially circular shape when viewed in a vertical cross section of the cylinder axis CA. The center of volume of the cavity 3a is on the cylinder axis CA.

  The ECU 40 is electrically connected to the fuel injection valve 27, the compressed air injection valve 28, the spark plug 29, and the like.

(Schematic operation of sub-chamber internal combustion engine)
In the sub-chamber internal combustion engine 1, fresh air is introduced into the intake port 23. In the intake stroke, the intake valve 21 is opened by the intake cam 21 a, and fresh air is introduced from the intake port 23 into the main combustion chamber 63.

  Here, when controlled in a homogeneous combustion mode described later, pressurized fuel is supplied to the fuel injection valve 27. The fuel injection valve 27 injects the third fuel into the auxiliary combustion chamber 61 with the injection amount Q3. The third fuel is a fuel that is supplied to form a homogeneous mixture in the main combustion chamber 63. The compressed air injection valve 28 injects compressed air into the sub-combustion chamber 61 at a pressure P3, whereby a part of the third fuel in the sub-combustion chamber 61 is main-combusted from the sub-combustion chamber 61 via the communication passage 61d. Extrude into chamber 63. The pressure P3 is higher than the pressure Pm of the main combustion chamber 63. As a result, a fresh air mixture (homogeneous mixture) is formed in the main combustion chamber 63.

  In the compression stroke, the fresh air mixture in the main combustion chamber 63 is compressed in the main combustion chamber 63.

  Here, when controlled in the stratified combustion mode described later, the fuel injection valve 27 receives supply of pressurized fuel. The fuel injection valve 27 injects the first fuel into the auxiliary combustion chamber 61 with the injection amount Q1. The first fuel is supplied to form a stratified mixture in the main combustion chamber 63. The compressed air injection valve 28 injects compressed air into the auxiliary combustion chamber 61 at a pressure P1, thereby main combustion of a part of the first fuel in the auxiliary combustion chamber 61 from the auxiliary combustion chamber 61 through the communication passage 61d. Extrude into chamber 63. The pressure P1 is higher than the pressure Pm of the main combustion chamber 63. As a result, a fresh air mixture (stratified mixture) is formed in the main combustion chamber 63.

  A part of the fresh air mixture in the main combustion chamber 63 is introduced from the main combustion chamber 63 to the sub-combustion chamber 61 via the communication passage 61d.

  By the spark plug 29, the fresh air mixture in the auxiliary combustion chamber 61 is ignited and burned at a predetermined timing. The combustion gas (flame) in the auxiliary combustion chamber 61 is radiated to the main combustion chamber 63 through the communication passage 61d in a torch shape, and the fresh air-fuel mixture in the main combustion chamber 63 is ignited and burned.

  In the expansion stroke, the piston 3 is pushed down by the combustion pressure generated by burning the fresh air mixture in the main combustion chamber 63.

  In the exhaust stroke, the exhaust valve 22 is opened by the exhaust cam 22a, and the burned gas burned in the main combustion chamber 63 is discharged to the exhaust port 24 as exhaust gas.

  The ECU 40 performs various controls by supplying control signals to the fuel injection valve 27, the compressed air injection valve 28, the spark plug 29, and the like. The ECU 40 executes logic for performing various controls. For example, the ECU 40 executes predetermined logic in an electric circuit, software, or both.

(Detailed configuration of ECU)
The ECU 40 mainly includes a load calculation unit 41, a fuel injection control unit 42, an air injection control unit 43, an ignition timing control unit 44, and a storage unit 45. The load calculation unit 41, the fuel injection control unit 42, the air injection control unit 43, and the ignition timing control unit 44 are a CPU or the like. The storage unit 45 is a ROM, a RAM, or the like, and stores programs, map information, and the like.

  The ECU 40 not only executes logic for performing various controls but also executes logic for controlling the fuel injection valve 27 and the compressed air injection valve 28.

(Detailed operation of ECU)
The ECU 40 includes a crank angle signal detected by a crank angle sensor (not shown), a coolant temperature signal detected by a water temperature sensor (not shown), and an accelerator opening detected by an accelerator opening sensor (not shown). A degree signal is input. The load calculation unit 41 receives these signals. The load calculation unit 41 calculates the engine load based on these signals.

  The fuel injection control unit 42 receives information on the engine load from the load calculation unit 41. Further, the fuel injection control unit 42 refers to the storage unit 45 and receives map information from the storage unit 45. The fuel injection control unit 42 determines a control mode based on engine load information, map information, and the like, and generates a fuel injection period control signal. When the control mode is the homogeneous combustion mode, the fuel injection valve 27 injects the third fuel of the injection amount Q3 into the auxiliary combustion chamber 61 in the intake stroke based on the fuel injection period control signal. Alternatively, when the control mode is the stratified combustion mode, the fuel injection valve 27 injects the first fuel of the injection amount Q1 into the auxiliary combustion chamber 61 in the compression stroke based on the fuel injection period control signal.

  The air injection control unit 43 receives engine load information from the load calculation unit 41. Further, the air injection control unit 43 refers to the storage unit 45 and receives map information from the storage unit 45. The air injection control unit 43 determines a control mode based on the engine load information and map information, and generates an air injection period control signal. When the control mode is the homogeneous combustion mode, the compressed air injection valve 28 injects a predetermined amount of compressed air into the auxiliary combustion chamber 61 at the pressure P3 in the intake stroke based on the air injection period control signal. Alternatively, when the control mode is the stratified combustion mode, the compressed air injection valve 28 injects a predetermined injection amount of compressed air into the auxiliary combustion chamber 61 at the pressure P1 in the compression stroke based on the air injection period control signal.

  The ignition timing control unit 44 receives engine load information from the load calculation unit 41 and generates an ignition timing control signal based on the engine load information and the like. Thereby, the spark plug 29 generates a spark at a predetermined timing based on the ignition timing control signal.

(Detailed operation of fuel in sub-chamber internal combustion engine)
The detailed operation of the fuel in the sub-chamber internal combustion engine 1 will be described with reference to FIGS. 2 to 4 show the operation of the fuel when the control mode is the stratified combustion mode.

  As shown in FIG. 2, the compressed air injection valve 28 is configured to inject an injection amount (injection period) such that a part of the first fuel F1 is pushed from the auxiliary combustion chamber 61 to the main combustion chamber 63 based on the air injection period control signal. ) Is injected into the auxiliary combustion chamber 61 at a pressure P1. The fuel injection valve 27 injects the first fuel F1 into the auxiliary combustion chamber 61 with the injection amount Q1 based on the fuel injection period control signal. As a result, the pressure Ps of the auxiliary combustion chamber 61 becomes higher than the pressure Pm of the main combustion chamber 63 (Ps−Pm> 0), and a part of the first fuel F1 becomes the auxiliary combustion chamber 61 as the fuel F2 and the fuel F3. To the main combustion chamber 63 through the communication passage 61d.

  Then, as shown in FIG. 3, the fuel F2 and the fuel F3 are mixed with fresh air in the main combustion chamber 63, respectively, to become a stratified mixture M2 and a stratified mixture M3.

  Further, the first fuel F 1 remaining in the auxiliary combustion chamber 61 is mixed with fresh air in the auxiliary combustion chamber 61. Then, after the compressed air injection valve 28 finishes injecting the compressed air, the pressure Ps of the sub-combustion chamber 61 becomes equal to the pressure Pm of the main combustion chamber 63 (Ps−Pm≈0) after a lapse of a predetermined period. At this time, the stratified mixture M2 and the stratified mixture M3 in the vicinity of the communication passage 61d are pushed by the piston 3 and flow backward from the main combustion chamber 63 to the auxiliary combustion chamber 61 through the communication passage 61d. Further, the stratified mixture M2 and the stratified mixture M3 in the vicinity of the communication passage 61d flow backward from the main combustion chamber 63 to the sub-combustion chamber 61 through the communication passage 61d, so that the fuel F2 and the fuel remaining in the communication passage 61d F3 also flows back into the auxiliary combustion chamber 61. As a result, the fresh air in the auxiliary combustion chamber 61, the first fuel F1 remaining in the auxiliary combustion chamber 61, the fuel F2 and the fuel F3 remaining in the communication passage 61d, and the stratified mixing in the vicinity of the communication passage 61d The gas M2 and the stratified mixture M3 are mixed to form a fresh air mixture M1 in the auxiliary combustion chamber 61. Here, the amount of the stratified mixture M2 and the stratified mixture M3 flowing back to the auxiliary combustion chamber 61 tends to vary from cycle to cycle due to the influence of the in-cylinder flow of the main combustion chamber 63. For this reason, the concentration of the fresh air mixture M1 in the auxiliary combustion chamber 61 may not be suitably controlled.

  Further, the penetration of the fuel F2 and the fuel F3 becomes long, and as shown in FIG. 4, the stratified mixture M2a and the stratified mixture M3a may bounce off the cavity 3a and reach the communication path 61d. At this time, when the pressure Ps of the auxiliary combustion chamber 61 becomes equal to the pressure Pm of the main combustion chamber 63 (when Ps−Pm≈0), the stratified mixture M2a and a part of the stratified mixture M3a are pushed to the piston 3. Then, it flows backward from the main combustion chamber 63 to the auxiliary combustion chamber 61 through the communication passage 61d. As a result, the fresh air mixture M1 in the auxiliary combustion chamber 61 and the stratified mixture M2a and the stratified mixture M3a that have flowed back to the auxiliary combustion chamber 61 are mixed to become the fresh air mixture M1a in the auxiliary combustion chamber 61. Here, the amount of the stratified mixture M2a and the stratified mixture M3a flowing back to the auxiliary combustion chamber 61 tends to vary from cycle to cycle due to the influence of the in-cylinder flow of the main combustion chamber 63. For this reason, the concentration of the fresh air mixture M1a in the auxiliary combustion chamber 61 may not be suitably controlled.

  When the intake pressure Pi is low, the penetration of the fuel F2 and the fuel F3 tends to be longer than when the intake pressure Pi is high. Here, the intake pressure Pi is the pressure of fresh air introduced from the intake port 23 into the main combustion chamber 63. Further, when the compressed air pressure P1 is high, the penetration of the fuel F2 and the fuel F3 tends to be longer than when the compressed air pressure P1 is low.

  As described above, since the concentration of the fresh air mixture M1, M1a in the auxiliary combustion chamber 61 may not be suitably controlled, the secondary combustion generated by the ignition of the fresh air mixture M1, M1a in the auxiliary combustion chamber 61 may occur. The combustion gas (flame) in the chamber 61 may not be sufficient for stratified combustion in the main combustion chamber 63 when it is radiated to the main combustion chamber 63 via the communication passage 61d in a torch shape. For this reason, there is a tendency that stratified combustion cannot be performed in the main combustion chamber 63.

<Configuration and Operation of Sub-chamber Internal Combustion Engine According to Embodiment of the Present Invention>
A sub-chamber internal combustion engine 100 according to an embodiment of the present invention will be described focusing on differences from the internal combustion engine 1 which is the premise of the present invention, with reference to FIGS. In addition, the same component as the internal combustion engine 1 which is the premise of the present invention is indicated by the same member number, and the description is omitted.

(Schematic configuration of sub-chamber internal combustion engine)
FIG. 5 shows a sectional view of the sub-chamber internal combustion engine 100.

  The sub-chamber internal combustion engine 100 includes an ECU (control unit) 140 instead of the ECU 40. Other points are the same as those of the sub-chamber internal combustion engine 1 which is the premise of the present invention.

(Schematic operation of sub-chamber internal combustion engine)
In the compression stroke, when controlled in the stratified combustion mode, the fuel injection valve 27 injects the first fuel into the auxiliary combustion chamber 61 with the injection amount Q101. When controlled in the stratified combustion mode, the compressed air injection valve 28 injects the compressed air A101 into the auxiliary combustion chamber 61 at the pressure P101, so that a part of the first fuel in the auxiliary combustion chamber 61 is injected into the auxiliary combustion chamber 61. 61 is pushed out to the main combustion chamber 63 through the communication passage 61d. Here, the pressure P101 is higher than the pressure Pm of the main combustion chamber 63.

  In addition, instead of a part of the stratified mixture in the main combustion chamber 63 being introduced from the main combustion chamber 63 to the sub-combustion chamber 61 via the communication passage 61d, the fuel injection valve 27 causes the second fuel to flow into the sub-combustion chamber 61. Is further injected at an injection amount Q102 to generate a fresh air mixture in the auxiliary combustion chamber 61. Here, the second fuel is a fuel for burning in the auxiliary combustion chamber 61.

  Other points are the same as those of the sub-chamber internal combustion engine 1 which is the premise of the present invention.

(Detailed configuration of ECU)
The ECU 140 includes a fuel injection control unit 142 instead of the fuel injection control unit 42, an air injection control unit 143 instead of the air injection control unit 43, and a storage unit 145 instead of the storage unit 45. Other points are the same as those of the sub-chamber internal combustion engine 1 which is the premise of the present invention.

(Detailed operation of ECU)
The fuel injection control unit 142 receives engine load information from the load calculation unit 41. Further, the fuel injection control unit 142 refers to the storage unit 145 and receives map information from the storage unit 145. The fuel injection control unit 142 determines a control mode based on engine load information, map information, and the like, and generates a fuel injection period control signal. When the control mode is the homogeneous combustion mode, the fuel injection valve 27 injects the third fuel of the injection amount Q3 into the auxiliary combustion chamber 61 in the intake stroke based on the fuel injection period control signal. Alternatively, when the control mode is the stratified combustion mode, the fuel injection valve 27 injects the first fuel of the injection amount Q101 into the sub-combustion chamber 61 in the compression stroke based on the fuel injection period control signal, and injects in the compression stroke. An amount Q102 of the second fuel is injected into the auxiliary combustion chamber 61.

  The air injection control unit 143 receives engine load information from the load calculation unit 41. The air injection control unit 143 refers to the storage unit 145 and receives map information from the storage unit 145. The air injection control unit 143 determines a control mode based on the engine load information and map information, and generates an air injection period control signal. When the control mode is the homogeneous combustion mode, the compressed air injection valve 28 injects a predetermined injection amount of compressed air A101 into the auxiliary combustion chamber 61 at the pressure P3 in the intake stroke based on the air injection period control signal. . Alternatively, when the control mode is the stratified combustion mode, the compressed air injection valve 28 injects a predetermined injection amount of compressed air A101 into the auxiliary combustion chamber 61 at the pressure P101 in the compression stroke based on the air injection period control signal. .

  Other points are the same as those of the sub-chamber internal combustion engine 1 which is the premise of the present invention.

(Control of sub-chamber internal combustion engine)
Control of the sub-chamber internal combustion engine 100 will be described with reference to FIG.

  FIG. 6 shows the control of the sub-chamber internal combustion engine 100 when the control mode is the stratified combustion mode when the required injection amount Q101 is small and when the required injection amount Q101 is large. In FIG. 6, Ps indicates the pressure in the auxiliary combustion chamber 61, Pm indicates the pressure in the main combustion chamber 63, and Ps−Pm (pressure difference) indicates the pressure difference between the auxiliary combustion chamber 61 and the main combustion chamber 63. Further, Ps−Pm (pressure difference) when the required injection amount Q101 is small is indicated by a one-dot chain line, and Ps−Pm (pressure difference) when the required injection amount Q101 is large is indicated by a solid line. Ps-Pm (pressure difference) is shown only for the compression stroke.

((When the required injection amount is small))
When the required injection amount Q101 is small, the fuel injection control unit 142 of the ECU 140 determines the injection time of the first fuel as FT1 (corresponding to the injection amount Q101), and sets the injection time of the second fuel as FT3 (injection amount Q102). Equivalent) The fuel injection control unit 142 of the ECU 140 controls the fuel injection valve 27 as follows, and the air injection control unit 143 of the ECU 140 controls the compressed air injection valve 28 as follows.

  First, at the second start time (CA1) before the first start time (CA3), the compressed air injection valve 28 starts to inject the compressed air A101 into the auxiliary combustion chamber 61 at the pressure P101. Thereby, the pressure difference (Ps−Pm) starts to increase from 0 to a positive value.

  Then, at the first start time (CA3), the fuel injection valve 27 starts to inject the first fuel into the auxiliary combustion chamber 61. At this time, the pressure difference (Ps−Pm) is a positive value, and the pressure (Ps) in the auxiliary combustion chamber 61 is larger than the pressure (Pm) in the main combustion chamber 63. Accordingly, the first fuel injected into the auxiliary combustion chamber 61 is pushed out from the auxiliary combustion chamber 61 to the main combustion chamber 63 via the communication passage 61d. The pressure difference (Ps−Pm) is increased by the supply of the compressed air A101 from the compressed air injection valve 28, and the first fuel is transferred from the auxiliary combustion chamber 61 to the main combustion chamber 63 via the communication passage 61d. As a result of the balance with the decrease caused by the extrusion, the positive fixed value Pa is stabilized.

  The fuel injection valve 27 finishes injecting the first fuel into the auxiliary combustion chamber 61 at the first end time (CA4) after the elapse of the injection time FT1 from the first start time (CA3). At this time, the first fuel remains in the auxiliary combustion chamber 61, and the compressed air injection valve 28 continues to inject the compressed air A101 into the auxiliary combustion chamber 61 at the pressure P101. Further, the pressure difference (Ps−Pm) continues to be stable at a positive constant value Pa.

  The compressed air injection valve 28 finishes injecting the compressed air A101 into the sub-combustion chamber 61 at the second end timing (CA2) after the predetermined time ΔT has elapsed from the first end timing (CA4). At this time, the pressure difference (Ps−Pm) starts to decrease from the positive constant value Pa to 0. The predetermined time ΔT is obtained in advance as a time sufficient to push substantially all of the first fuel from the auxiliary combustion chamber 61 to the main combustion chamber 63 via the communication passage 61d. The injection time of the compressed air A101 is AT1, and includes the injection time FT1 of the first fuel.

  At the third start time (CA5) after the second end time (CA2), the fuel injection valve 27 starts to inject the second fuel into the auxiliary combustion chamber 61. The fuel injection valve 27 finishes injecting the second fuel into the auxiliary combustion chamber 61 at the third end timing (CA6) after the injection time FT3 has elapsed from the third start timing (CA5). At this time, in the auxiliary combustion chamber 61, the second fuel injected by the fuel injection valve 27 is mixed with fresh air, and a fresh air mixture is formed. Here, the pressure difference (Ps−Pm) becomes substantially zero after the decay time (DTa) has elapsed from the second end time (CA2). That is, the time from the second end time (CA2) to the third start time (CA5) is longer than the decay time (DTa). Therefore, in a state where the second fuel hardly leaks from the auxiliary combustion chamber 61 to the main combustion chamber 63 via the communication passage 61d (a state where Ps−Pm≈0), the fuel injection valve 27 causes the second fuel to flow into the auxiliary combustion chamber. 61 is sprayed. In addition, a sufficient time (CA6 to CA9) for forming a fresh air mixture is secured, and the concentration of the fresh air mixture in the auxiliary combustion chamber 61 depends on the injection time FT3 (corresponding to the injection amount Q102). To be controlled. For this reason, the concentration of the fresh air mixture in the sub-combustion chamber 61 is reduced and fluctuated for each cycle, and is suitably controlled.

  At a timing (CA9) after the third start timing (CA5), the tip portion 29a of the spark plug 29 ignites the fresh air mixture in the auxiliary combustion chamber 61.

((When the required injection amount is large))
When the required injection amount Q101 is large, the fuel injection control unit 142 of the ECU 140 determines the injection time of the first fuel as FT2 (corresponding to the injection amount Q101), and sets the injection time of the second fuel as FT3 (injection amount Q102). Equivalent) The fuel injection control unit 142 of the ECU 140 controls the fuel injection valve 27 as follows, and the air injection control unit 143 of the ECU 140 controls the compressed air injection valve 28 as follows.

  First, at the second start time (CA7) before the first start time (CA8), the compressed air injection valve 28 starts to inject the compressed air A101 into the auxiliary combustion chamber 61 at the pressure P101. Thereby, the pressure difference (Ps−Pm) starts to increase from 0 to a positive value.

  Then, at the first start time (CA8), the fuel injection valve 27 starts to inject the first fuel into the auxiliary combustion chamber 61. At this time, the pressure difference (Ps−Pm) is a positive value, and the pressure (Ps) in the auxiliary combustion chamber 61 is larger than the pressure (Pm) in the main combustion chamber 63. Accordingly, the first fuel injected into the auxiliary combustion chamber 61 is pushed out from the auxiliary combustion chamber 61 to the main combustion chamber 63 via the communication passage 61d. The pressure difference (Ps−Pm) is increased by the supply of the compressed air A101 from the compressed air injection valve 28, and the first fuel is transferred from the auxiliary combustion chamber 61 to the main combustion chamber 63 via the communication passage 61d. As a result of the balance with the decrease caused by the extrusion, the positive fixed value Pa is stabilized.

  The fuel injection valve 27 finishes injecting the first fuel into the auxiliary combustion chamber 61 at the first end timing (CA4) after the injection time FT2 has elapsed from the first start timing (CA8). At this time, the first fuel remains in the auxiliary combustion chamber 61, and the compressed air injection valve 28 continues to inject the compressed air A101 into the auxiliary combustion chamber 61 at the pressure P101. Further, the pressure difference (Ps−Pm) continues to be stable at a positive constant value Pa.

  The compressed air injection valve 28 finishes injecting the compressed air A101 into the sub-combustion chamber 61 at the second end timing (CA2) after the predetermined time ΔT has elapsed from the first end timing (CA4). At this time, the pressure difference (Ps−Pm) starts to decrease from the positive constant value Pa to 0. The predetermined time ΔT is obtained in advance as a time sufficient to push substantially all of the first fuel from the auxiliary combustion chamber 61 to the main combustion chamber 63 via the communication passage 61d. The injection time of the compressed air A101 is AT2, and includes the injection time FT2 of the first fuel.

  At the third start time (CA5) after the second end time (CA2), the fuel injection valve 27 starts to inject the second fuel into the auxiliary combustion chamber 61. The fuel injection valve 27 finishes injecting the second fuel into the auxiliary combustion chamber 61 at the third end timing (CA6) after the injection time FT3 has elapsed from the third start timing (CA5). At this time, in the auxiliary combustion chamber 61, the second fuel injected by the fuel injection valve 27 is mixed with fresh air, and a fresh air mixture is formed. Here, the pressure difference (Ps−Pm) becomes substantially zero after the decay time (DTa) has elapsed from the second end time (CA2). That is, the time from the second end time (CA2) to the third start time (CA5) is longer than the decay time (DTa). Therefore, in a state where the second fuel hardly leaks from the auxiliary combustion chamber 61 to the main combustion chamber 63 via the communication passage 61d (a state where Ps−Pm≈0), the fuel injection valve 27 causes the second fuel to flow into the auxiliary combustion chamber. 61 is sprayed. In addition, a sufficient time (CA5 to CA9) for the formation of the fresh air mixture is secured, and the concentration of the fresh air mixture in the auxiliary combustion chamber 61 depends on the injection time FT3 (corresponding to the injection amount Q102). To be controlled. For this reason, the concentration of the fresh air mixture in the sub-combustion chamber 61 is reduced and fluctuated for each cycle, and is suitably controlled.

  At a timing (CA9) after the third start timing (CA5), the tip portion 29a of the spark plug 29 ignites the fresh air mixture in the auxiliary combustion chamber 61.

  Here, compared with the case where the required injection amount Q101 is small, the first end timing (CA4) at which the fuel injection valve 27 finishes injecting is the same, and the compressed air injection valve 28 transfers the compressed air A101 to the auxiliary combustion chamber 61. The second end time (CA2) at which the injection is finished is the same. On the other hand, the second start time (CA7) at which the fuel injection valve 27 starts to be injected is advanced from the second start time (CA1) when the required injection amount Q101 is small. As a result, the fuel injection valve 27 injects the first fuel according to the required injection amount Q101. Further, the first start time (CA8) at which the compressed air injection valve 28 starts to inject the compressed air A101 into the auxiliary combustion chamber 61 is also advanced from the first start time (CA3) when the required injection amount Q101 is small. ing. That is, the predetermined time ΔT is secured, and the injection times AT1 and AT2 of the compressed air injection valve 28 include the injection times FT1 and FT2 of the fuel injection valve 27. Therefore, depending on the required fuel injection amount. Accordingly, it is possible to prevent the first fuel from remaining in the auxiliary combustion chamber 61.

(Detailed operation of fuel in sub-chamber internal combustion engine)
The detailed operation of the fuel in the sub-chamber internal combustion engine 100 will be described with reference to FIGS. 7 to 12 show the operation of the fuel when the control mode is the stratified combustion mode.

  As shown in FIG. 7, the compressed air injection valve 28 is configured to inject an injection amount (injection period) such that substantially all of the first fuel F101 is pushed out from the auxiliary combustion chamber 61 to the main combustion chamber 63 based on the air injection period control signal. The compressed air A101 of AT1, AT2) is started to be injected into the auxiliary combustion chamber 61 at the pressure P101. Then, the fuel injection valve 27 injects the first fuel F101 into the auxiliary combustion chamber 61 with the injection amount Q101 based on the fuel injection period control signal. As a result, the pressure Ps of the auxiliary combustion chamber 61 becomes higher than the pressure Pm of the main combustion chamber 63 (Ps−Pm> 0), and the first fuel F101, as shown in FIG. The auxiliary combustion chamber 61 is pushed out to the main combustion chamber 63 through the communication passage 61d.

  The compressed air injection valve 28 continues to inject the compressed air A101 into the auxiliary combustion chamber 61 at the pressure P101 until a predetermined time (ΔT) has elapsed after the fuel injection valve 27 has finished injecting the first fuel F101. As a result, as shown in FIG. 9, substantially all of the first fuel F101 is pushed out from the sub-combustion chamber 61 to the main combustion chamber 63 via the communication passage 61d to become the fuel F102 and the fuel F103.

  As shown in FIG. 10, the fuel F102 and the fuel F103 are mixed with fresh air in the main combustion chamber 63, respectively, and become a stratified mixture M102 and a stratified mixture M103. Then, after the compressed air injection valve 28 finishes the injection of the compressed air A101 and the decay time (DTa) has elapsed, the pressure Ps of the auxiliary combustion chamber 61 becomes equal to the pressure Pm of the main combustion chamber 63 (Ps−Pm≈0). Becomes). At this time, since almost all of the first fuel F101 is pushed out from the auxiliary combustion chamber 61 to the main combustion chamber 63 via the communication passage 61d, the stratified mixture M102 and the stratified mixture M103 exist in the vicinity of the communication passage 61d. The fuel F102 and the fuel F103 stay in the communication path 61d is reduced. On the other hand, in a state where the second fuel F104 hardly leaks from the auxiliary combustion chamber 61 to the main combustion chamber 63 via the communication passage 61d (a state where Ps−Pm≈0), the fuel injection valve 27 performs the auxiliary combustion of the second fuel F104. It injects with the injection quantity Q102 to the chamber 61. FIG. As a result, as shown in FIG. 11, the fresh air in the auxiliary combustion chamber 61 and the second fuel F104 injected by the fuel injection valve 27 into the auxiliary combustion chamber 61 are mixed, and the fresh air mixing in the auxiliary combustion chamber 61 is performed. I feel like M104. Here, the injection amount Q102 of the second fuel F104 injected into the auxiliary combustion chamber 61 by the fuel injection valve 27 is not easily affected by the in-cylinder flow of the main combustion chamber 63, and does not easily change from cycle to cycle. For this reason, the concentration of the fresh air mixture M104 in the auxiliary combustion chamber 61 is suitably controlled.

  Further, the penetration of the fuel F102 and the fuel F103 has an appropriate length (see FIG. 9), and as shown in FIG. 11, even if the stratified mixture M102 and the stratified mixture M103 bounce back in the cavity 3a, the vicinity of the communication path 61d is reached. Not reached. For this reason, even if the pressure Ps of the auxiliary combustion chamber 61 becomes equal to the pressure Pm of the main combustion chamber 63 (even if Ps−Pm≈0), the stratified mixture M102 and the stratified mixture M103 remain in the main combustion chamber. Backflow from 63 to the auxiliary combustion chamber 61 through the communication passage 61d is reduced. As a result, the fresh air mixture M104 in the auxiliary combustion chamber 61 is less affected by the stratified mixture M102 and the stratified mixture M103. For this reason, the concentration of the fresh air mixture M104 in the auxiliary combustion chamber 61 is less likely to fluctuate from cycle to cycle and is suitably controlled.

  Note that the intake pressure Pi and the pressure P101 of the compressed air A101 are adjusted so that the penetrations of the fuel F102 and the fuel F103 have an appropriate length.

  As described above, since the concentration of the fresh air mixture M104 in the auxiliary combustion chamber 61 is suitably controlled, the combustion gas in the auxiliary combustion chamber 61 (generated by igniting the fresh air mixture M104 in the auxiliary combustion chamber 61) ( As shown in FIG. 12, the flame (B104) is sufficient to cause stratified combustion in the main combustion chamber 63 when it is radiated to the main combustion chamber 63 through the communication passage 61d as a flame B105 and a flame B106. It will be something. For this reason, it becomes easy to perform stratified combustion in the main combustion chamber 63. In the main combustion chamber 63, since the stratified mixture M102 and the stratified mixture M103 are formed in the region where the flame B105 and the flame B106 are emitted, stratified combustion is easily performed.

(Characteristics of sub-chamber internal combustion engine)
(1)
Here, the compressed air injection valve 28 supplies the compressed air A101 to the auxiliary combustion chamber 61 in order to push the first fuel F101 from the auxiliary combustion chamber 61 to the main combustion chamber 63 via the communication passage 61d. For this reason, substantially all of the first fuel F <b> 101 is pushed out from the auxiliary combustion chamber 61 to the main combustion chamber 63. Further, the ECU 140 causes the fuel injection valve 27 to further supply the second fuel F104 to the auxiliary combustion chamber 61 after the compressed air injection valve 28 pushes the first fuel F101 from the auxiliary combustion chamber 61 to the main combustion chamber 63. The compressed air injection valve 28 and the fuel injection valve 27 are controlled. For this reason, the fuel injection valve 27 does not return the stratified mixture M102 and the stratified mixture M103 in the main combustion chamber 63 to the subcombustion chamber 61, and the sub-combustion chamber 61 supplies the second fuel F104 to the subcombustion chamber 61 by the injection amount Q102. The concentration of the fresh air mixture in the combustion chamber 61 is controlled.

  In this way, the concentration of the fresh air mixture in the auxiliary combustion chamber 61 is controlled by the injection amount Q102 that the fuel injection valve 27 supplies the second fuel F104 to the auxiliary combustion chamber 61. For this reason, even when stratified combustion is performed in the main combustion chamber 63, the concentration of the fresh air mixture in the auxiliary combustion chamber 61 is suitably controlled.

(2)
Here, the concentration of the fresh air mixture in the auxiliary combustion chamber 61 is controlled by the injection amount Q102 that the fuel injection valve 27 supplies the second fuel F104 to the auxiliary combustion chamber 61. The spark plug 29 ignites a fresh air mixture formed in the auxiliary combustion chamber 61 by the second fuel F104.

  In this manner, the fresh air mixture in the auxiliary combustion chamber 61 is ignited in a state where the concentration of the fresh air mixture in the auxiliary combustion chamber 61 is suitably controlled. As a result, the combustion gas (flame) B104 in the auxiliary combustion chamber 61 generated by igniting the fresh air mixture M104 in the auxiliary combustion chamber 61 becomes the main combustion chamber 63 via the communication passage 61d as the flame B105 and flame B106. When radiating in the form of a torch, it becomes sufficient for stratified combustion in the main combustion chamber 63. For this reason, it becomes easy to perform stratified combustion in the main combustion chamber 63.

(3)
Here, the ECU 140 retards the second end time (CA2) from the first end time (CA4). Here, the first end timing (CA4) is a timing at which the fuel injection valve 27 finishes injecting the first fuel F101 into the auxiliary combustion chamber 61. The second end timing (CA2) is a timing at which the compressed air injection valve 28 finishes injecting the compressed air A101 into the auxiliary combustion chamber 61.

  Specifically, the second end time (CA2) is a timing after a predetermined time ΔT has elapsed from the first end time (CA4). Here, the predetermined time ΔT is obtained in advance as a time sufficient to push out substantially all of the first fuel F101 from the auxiliary combustion chamber 61 to the main combustion chamber 63 via the communication passage 61d.

  In this way, sufficient time is secured to push substantially all of the first fuel F101 from the sub-combustion chamber 61 to the main combustion chamber 63 via the communication passage 61d, so that the first fuel F101 enters the sub-combustion chamber 61. It is prevented from remaining. For this reason, the concentration of the fresh air mixture in the auxiliary combustion chamber 61 is easily controlled.

(4)
Here, the ECU 140 retards the third start time (CA5) from the second end time (CA2). Here, the third start timing (CA5) is a timing at which the fuel injection valve 27 starts to inject the second fuel F104 into the auxiliary combustion chamber 61.

  Specifically, the third start time (CA5) is the time when the decay time (DTa) or more has elapsed from the second end time (CA2). Here, the decay time (DTa) is the time required for the pressure difference (Ps−Pm) to decay from Pa to substantially zero.

  Thus, sufficient time is secured for the second fuel F104 to be in a state in which it is difficult for the second fuel F104 to leak from the auxiliary combustion chamber 61 to the main combustion chamber 63 via the communication passage 61d (a state where Ps−Pm≈0). The second fuel F104 injected by the fuel injection valve 27 into the auxiliary combustion chamber 61 is less likely to flow out of the auxiliary combustion chamber 61 into the main combustion chamber 63 via the communication passage 61d. For this reason, the concentration of the fresh air mixture in the auxiliary combustion chamber 61 is easily controlled.

(5)
Here, the ECU 140 advances the first start timing (CA3, CA8) when the injection amount Q101 of the first fuel F101 is large compared to when the injection amount Q101 of the first fuel F101 is small. As a result, the fuel injection valve 27 injects the first fuel according to the required injection amount Q101. On the other hand, the ECU 140 does not change the first end timing (CA4) when the injection amount Q101 of the first fuel F101 is large compared to when the injection amount Q101 of the first fuel F101 is small.

  As described above, the ECU 140 performs control so that the first start time (CA3, CA8) is changed according to the required injection amount Q101 and the first end time (CA4) is not changed. For this reason, it is easy to set the period from the first end time (CA4) to the second end time (CA2) as the predetermined time ΔT. As a result, the first fuel F101 is prevented from remaining in the auxiliary combustion chamber 61 regardless of the required injection amount Q101.

(6)
Here, the compressed air injection valve 28 injects the compressed air A101 into the auxiliary combustion chamber 61 at the pressure P101. Here, the pressure P101 is higher than the pressure Pm of the main combustion chamber 63. For this reason, the pressure Ps of the auxiliary combustion chamber 61 becomes higher than the pressure Pm of the main combustion chamber 63.

  Thus, since the pressure Ps of the auxiliary combustion chamber 61 becomes higher than the pressure Pm of the main combustion chamber 63 by the compressed air A101 injected by the compressed air injection valve 28, substantially all of the first fuel F101 is discharged from the auxiliary combustion chamber 61. It is pushed out to the main combustion chamber 63 through the communication passage 61d. Further, pushing out the first fuel F101 from the auxiliary combustion chamber 61 to the main combustion chamber 63 via the communication passage 61d is performed in a desired period (CA1 to CA2, CA7 to CA2).

(7)
Here, the compressed air injection valve 28 supplies the compressed air A101 to the auxiliary combustion chamber 61 in order to push the first fuel F101 from the auxiliary combustion chamber 61 to the main combustion chamber 63 via the communication passage 61d in the compression stroke. . For this reason, since almost all of the first fuel F101 is pushed out from the auxiliary combustion chamber 61 to the main combustion chamber 63 in the compression stroke, a stratified mixture is easily formed in the main combustion chamber 63. The ECU 140 also includes the second fuel F104 after the compressed air injection valve 28 pushes the first fuel F101 from the auxiliary combustion chamber 61 to the main combustion chamber 63 and before the tip portion 29a of the spark plug 29 is ignited. The fuel injection valve 27 is controlled so as to be further supplied to the auxiliary combustion chamber 61. For this reason, the fuel injection valve 27 does not return the stratified mixture M102 and the stratified mixture M103 in the main combustion chamber 63 to the subcombustion chamber 61, and the sub-combustion chamber 61 supplies the second fuel F104 to the subcombustion chamber 61 by the injection amount Q102. The concentration of the fresh air mixture in the combustion chamber 61 is controlled.

  Thus, the stratified mixture M102 and the stratified mixture M103 are formed in the main combustion chamber 63, and the fuel injection valve 27 supplies the second fuel F104 to the subcombustion chamber 61, and the fresh air in the subcombustion chamber 61 is supplied by the injection amount Q102. The concentration of the gas mixture is controlled. For this reason, the concentration of the fresh air mixture in the auxiliary combustion chamber 61 is suitably controlled when stratified combustion is performed in the main combustion chamber 63.

(Modification of the embodiment)
(A) When the control mode is the stratified combustion mode, the period during which the first fuel F101 is pushed out from the auxiliary combustion chamber 61 to the main combustion chamber 63 via the communication path 61d (CA1 to CA2, CA7 to CA2) It is preferable that it is before the timing at which the flame B105 and the flame B106 are emitted (timing immediately after CA9) and in the latter half of the compression stroke. This is because the fresh air mixture is stratified in the main combustion chamber 63 when the timing at which the flame B105 and the flame B106 are emitted (timing immediately after CA9) and the period during which the flame B105 and the flame B106 are pushed out (CA1 to CA2, CA7 to CA2) are closer. It is because it is easy to be ignited in a hot state. However, the period from the second end time (CA2) to the third start time (CA5) needs to be secured for the attenuation period (DTa) or more. In addition, the period from the third end timing (CA6) to the ignition timing (CA9) needs to be secured for a period sufficient for a fresh air mixture to be formed in the auxiliary combustion chamber 61.

  The local air-fuel ratio of the stratified mixture M102 and the stratified mixture M103 may be leaner than the stoichiometric air-fuel ratio. This is because, in the main combustion chamber 63, the stratified mixture M102 and the stratified mixture M103 are ignited by the flame B105 and the flame B106, so that lean compared to the case where the stratified mixture M102 and the stratified mixture M103 are ignited by spark. This is because ignition is easy at a high air-fuel ratio.

  (B) When the intake pressure Pi is low, the ECU 140 may retard the first start time (CA3) and the second start time (CA1) compared to when the intake pressure Pi is high.

  That is, when the intake pressure Pi is low, the density of fresh air in the main combustion chamber 63 tends to be lower than when the intake pressure Pi is high. For this reason, when the intake pressure Pi is low, the penetration when the first fuel is pushed out from the auxiliary combustion chamber 61 to the main combustion chamber 63 tends to be longer than when the intake pressure Pi is high.

  Even in this case, as shown in FIG. 13, the ECU 140 determines the first start time (CA11) and the second start time (CA10) when the intake pressure Pi is low, and the first start time when the intake pressure Pi is high. The angle is retarded compared to (CA3) and the second start time (CA1). Here, since the required injection amount Q101 does not change, the injection period FT3 of the first fuel when the intake pressure Pi is low has substantially the same length as the injection period FT1 of the first fuel when the intake pressure Pi is high. is there. Therefore, the ECU 140 also determines the first end time (CA12) and the second end time (CA13) when the intake pressure Pi is low, and the first end time (CA4) and the second end time when the intake pressure Pi is high. The angle is retarded similarly to the end time (CA2).

  As described above, since the timing at which the first fuel is pushed out from the sub-combustion chamber 61 to the main combustion chamber 63 is delayed, the timing at which the first fuel pushed into the main combustion chamber 63 is reflected by the cavity 3a and reaches the communication path 61d is also reached. Be late. For this reason, the stratified mixture in the main combustion chamber 63 is prevented from returning to the sub-combustion chamber 61.

  In FIG. 13, Ps−Pm (pressure difference) when the intake pressure Pi is high is indicated by a one-dot chain line, and Ps−Pm (pressure difference) when the intake pressure Pi is low is indicated by a solid line. Ps-Pm (pressure difference) is shown only for the compression stroke. Further, the period from the second end time (CA13) to the third start time (CA5) is longer than the decay time (DTc) when the intake pressure Pi is low. The injection time of the compressed air A101 when the intake pressure Pi is low is AT3, and includes the injection time FT3 of the first fuel.

  (C) The ECU 140 retards the first start time (CA3) and the second start time (CA1) when the pressure P101 of the compressed air A101 is high compared to when the pressure P101 of the compressed air A101 is low. May be.

  That is, the pressure difference (Ps−Pm) becomes larger when the pressure P101 of the compressed air A101 is high (pressure difference Pb) than when the pressure P101 of the compressed air A101 is low (pressure difference Pa) (Pb> Tends to be Pa). For this reason, when the pressure P101 of the compressed air A101 is high, the penetration when the first fuel is pushed out from the auxiliary combustion chamber 61 to the main combustion chamber 63 tends to be longer than when the pressure P101 of the compressed air A101 is low. There is.

  Even in this case, as shown in FIG. 14, the ECU 140 performs the first start time (CA19) and the second start time (CA18) when the pressure P101 of the compressed air A101 is high, and the pressure P101 of the compressed air A101 is low. The first start time (CA3) and the second start time (CA1) are retarded. Here, since the required injection amount Q101 does not change, the first fuel injection period FT5 when the pressure P101 of the compressed air A101 is high is the first fuel injection period FT1 when the pressure P101 of the compressed air A101 is low. Is approximately the same length. For this reason, the ECU 140 also determines the first end time (CA20) and the second end time (CA21) when the pressure P101 of the compressed air A101 is high, and the first end time when the pressure P101 of the compressed air A101 is low. The angle is similarly retarded as compared with (CA4) and the second end time (CA2).

  As described above, since the timing at which the first fuel is pushed out from the sub-combustion chamber 61 to the main combustion chamber 63 is delayed, the timing at which the first fuel pushed into the main combustion chamber 63 is reflected by the cavity 3a and reaches the communication path 61d is also reached. Be late. For this reason, the stratified mixture in the main combustion chamber 63 is prevented from returning to the sub-combustion chamber 61.

  In FIG. 14, Ps−Pm (pressure difference) when the pressure P101 of the compressed air A101 is low is indicated by a one-dot chain line, and Ps−Pm (pressure difference) when the pressure P101 of the compressed air A101 is high is indicated by a solid line. ing. Ps-Pm (pressure difference) is shown only for the compression stroke. Further, the decay time (DTb) when the pressure P101 of the compressed air A101 is high is longer than the decay time (DTa) when the pressure P101 of the compressed air A101 is low. However, even when the pressure P101 of the compressed air A101 is high, the period from the second end time (CA21) to the third start time (CA5) is the decay time (DTb) when the pressure P101 of the compressed air A101 is high. ) Is longer than When the pressure P101 of the compressed air A101 is high, the injection time of the compressed air A101 is AT5, and includes the injection time FT5 of the first fuel.

  (D) The ECU 140 may control the compressed air injection valve 28 so that the pressure P101 of the compressed air A101 at the time of cooling is higher than the pressure P101 of the compressed air A101 at the time of warming up.

  That is, the first fuel is less likely to vaporize when cold, compared to when warm. For this reason, the first fuel tends to adhere to the wall surface 61 a (see FIG. 5) of the auxiliary combustion chamber 61 and remain in the auxiliary combustion chamber 61 when cold.

  Even in this case, the ECU 140 controls the compressed air injection valve 28 so that the pressure P101 of the compressed air A101 is higher when the engine is cold than when the engine is warm. For this reason, the flow of the first fuel pushed out from the auxiliary combustion chamber 61 to the main combustion chamber 63 via the communication passage 61d becomes strong at the time of cold machine in which the first fuel is hard to vaporize. As a result, since the vaporization of the first fuel is promoted at the time of cold machine in which the first fuel is difficult to vaporize, the adhesion of the first fuel to the wall surface 61a of the auxiliary combustion chamber 61 is reduced.

  Further, the ECU 140 may retard the first start time (CA3, CA15) and the second start time (CA1, CA14) when the engine is cold compared to when warming up.

  That is, the pressure difference (Ps−Pm) tends to become larger (Pb> Pa) when cold (pressure difference Pb) than when warm (pressure difference Pa). For this reason, the penetration when the first fuel is pushed out from the sub-combustion chamber 61 to the main combustion chamber 63 during cold operation tends to be longer than that during warm-up.

  Even in this case, as shown in FIG. 15, the ECU 140 sets the first start time (CA15) and the second start time (CA14) at the time of cooling, and the first start time (CA3) and the second start at the time of warming up. The angle is retarded compared to the timing (CA1). Here, since the required injection amount Q101 does not change, the injection period FT4 of the first fuel at the time of cool-down is substantially the same length as the injection period FT1 of the first fuel at the time of warm-up. For this reason, the ECU 140 also sets the first end time (CA16) and the second end time (CA17) at the time of cool-down to the first end time (CA4) and the second end time (CA2) at the time of warm-up. Compare and retard as well.

  As described above, since the timing at which the first fuel is pushed out from the sub-combustion chamber 61 to the main combustion chamber 63 is delayed, the timing at which the first fuel pushed into the main combustion chamber 63 is reflected by the cavity 3a and reaches the communication path 61d is also reached. Be late. For this reason, the stratified mixture in the main combustion chamber 63 is prevented from returning to the sub-combustion chamber 61.

  In FIG. 15, Ps−Pm (pressure difference) at the time of warming is indicated by a one-dot chain line, and Ps−Pm (pressure difference) at the time of cooling is indicated by a solid line. Ps-Pm (pressure difference) is shown only for the compression stroke. Further, the decay time (DTb) at the time of cooling is longer than the decay time (DTa) at the time of warming up. However, even during cold, the period from the second end time (CA17) to the third start time (CA5) is longer than the decay time (DTb). The injection time of the compressed air A101 at the time of cold is AT4, and includes the injection time FT4 of the first fuel.

  (E) The ECU 140 stratifies the main combustion chamber 63 after the compressed air injection valve 28 pushes the first fuel from the sub-combustion chamber 61 to the main combustion chamber 63 in a high load state in an operation state where stratified combustion is performed. The compressed air injection valve 28 and the fuel injection valve 27 may be controlled so that a part of the air-fuel mixture flows into the auxiliary combustion chamber 61 via the communication passage 61d.

  That is, the ECU 140 controls the compressed air injection valve 28 so that the pressure P101 of the compressed air A101 becomes high and does not supply the second fuel to the sub-combustion chamber 61 in the high load state in the operation state where stratified combustion is performed. Thus, the fuel injection valve 27 is controlled. As a result, the first fuel supplied to the auxiliary combustion chamber 61 is vigorously pushed out to the main combustion chamber 63 via the communication passage 61d, reflected by the cavity 3a, and returned to the vicinity of the communication passage 61d. Then, when the stratified mixture in the main combustion chamber 63 is pushed by the piston 3, the stratified mixture in the vicinity of the communication passage 61d is introduced into the sub-combustion chamber 61 through the communication passage 61d. It becomes an air-fuel mixture. The fresh air mixture in the auxiliary combustion chamber 61 is ignited and burned at a predetermined timing by the spark plug 29. The combustion gas (flame) in the sub-combustion chamber 61 is radiated in a torch shape to the main combustion chamber 63 through the communication passage 61d, and the stratified mixture in the main combustion chamber 63 is combusted.

  Here, stratified combustion tends to be easily performed in the main combustion chamber 63 during a high load state in an operation state where stratified combustion is performed. For this reason, in this high load state, stratified combustion is easily performed in the main combustion chamber 63 even if the concentration of the fresh air mixture in the sub-combustion chamber 61 is not suitably controlled. That is, according to the operating state, the second fuel is not further supplied to the sub-combustion chamber 61, but combustion in the sub-combustion chamber 61 is performed, and the stratified mixture can be combusted in the main combustion chamber 63. ing.

  The sub-chamber internal combustion engine according to the present invention can perform stratified combustion in the main combustion chamber, and has an effect that the concentration of the fresh air mixture in the sub-combustion chamber can be suitably controlled. Useful as an internal combustion engine or the like.

1 is a cross-sectional view of a sub-chamber internal combustion engine that is a premise of the present invention. The figure which shows the operation | movement of the fuel in a subchamber internal combustion engine. The figure which shows the operation | movement of the fuel in a subchamber internal combustion engine. The figure which shows the operation | movement of the fuel in a subchamber internal combustion engine. 1 is a cross-sectional view of a sub-chamber internal combustion engine according to a first embodiment of the present invention. The figure which shows control of a subchamber internal combustion engine. The figure which shows the operation | movement of the fuel in a subchamber internal combustion engine. The figure which shows the operation | movement of the fuel in a subchamber internal combustion engine. The figure which shows the operation | movement of the fuel in a subchamber internal combustion engine. The figure which shows the operation | movement of the fuel in a subchamber internal combustion engine. The figure which shows the operation | movement of the fuel in a subchamber internal combustion engine. The figure which shows the operation | movement of the fuel in a subchamber internal combustion engine. The figure which shows control of a subchamber internal combustion engine (modification). The figure which shows control of a subchamber internal combustion engine (modification). The figure which shows control of a subchamber internal combustion engine (modification).

Explanation of symbols

1,100 Sub-chamber internal combustion engine 27 Fuel injection valve (fuel supply unit)
28 Compressed air injection valve (air supply part)
29 Spark plug 29a Tip part (ignition part)
40,140 ECU (control unit)
61 Subcombustion chamber 61d Communication path 63 Main combustion chamber

Claims (11)

A main combustion chamber;
A secondary combustion chamber adjacent to the main combustion chamber;
A communication passage communicating the main combustion chamber and the sub-combustion chamber;
A fuel supply section for supplying a first fuel, which is a fuel for forming a stratified mixture in the main combustion chamber, and a second fuel, which is a fuel for burning in the subcombustion chamber, to the subcombustion chamber; ,
An air supply section for supplying compressed air to the sub-combustion chamber to push the first fuel from the sub-combustion chamber to the main combustion chamber via the communication path;
After the air supply unit pushes the first fuel from the sub-combustion chamber to the main combustion chamber, the air supply unit and the air supply unit further supply the second fuel to the sub-combustion chamber. A control unit for controlling the fuel supply unit;
With
Sub-chamber internal combustion engine. An ignition unit for igniting a fresh air mixture formed in the auxiliary combustion chamber by the second fuel;
The sub-chamber internal combustion engine according to claim 1. The control unit finishes supplying the compressed air to the sub-combustion chamber from a first end timing when the fuel supply unit finishes supplying the first fuel to the sub-combustion chamber. Delay the second end time, which is the time,
The sub-chamber internal combustion engine according to claim 1 or 2. The control unit retards a third start time, which is a time when the fuel supply unit starts supplying the second fuel to the sub-combustion chamber, relative to the second end time;
The sub-chamber internal combustion engine according to claim 3. The control unit sets a first start time, which is a time when the fuel supply unit starts supplying the first fuel to the sub-combustion chamber, when the injection amount of the first fuel is large. Advancing compared to the case where the amount is small,
The sub-chamber internal combustion engine according to any one of claims 1 to 4. The control unit includes a first start time when the fuel supply unit starts supplying the first fuel to the sub-combustion chamber, and a time when the air supply unit starts supplying compressed air to the sub-combustion chamber. The second start timing is delayed when the intake pressure, which is the pressure of fresh air sucked into the main combustion chamber, is low compared to when the intake pressure is high,
The sub-chamber internal combustion engine according to any one of claims 1 to 5. The air supply unit supplies the compressed air having a pressure higher than the pressure of the main combustion chamber to the sub-combustion chamber.
The sub-chamber internal combustion engine according to any one of claims 1 to 6. The control unit includes a first start time when the fuel supply unit starts supplying the first fuel to the sub-combustion chamber, and a time when the air supply unit starts supplying compressed air to the sub-combustion chamber. The second start time is retarded when the pressure of the compressed air is high compared to when the pressure of the compressed air is low,
The sub-chamber internal combustion engine according to claim 7. The control unit controls the air supply unit so that the pressure of the compressed air at the time of cooling is higher than the pressure of the compressed air at the time of warming up.
The sub-chamber internal combustion engine according to claim 7 or 8. The control unit is configured to perform the stratification of the main combustion chamber after the air supply unit pushes the first fuel from the sub-combustion chamber to the main combustion chamber in a high load state in an operation state where stratified combustion is performed. Controlling the air supply unit and the fuel supply unit so that a part of the air-fuel mixture flows into the sub-combustion chamber via the communication path;
The sub-chamber internal combustion engine according to any one of claims 1 to 9. A main combustion chamber;
A secondary combustion chamber adjacent to the main combustion chamber;
A communication passage communicating the main combustion chamber and the sub-combustion chamber;
A fuel supply unit that supplies, to the sub-combustion chamber, a first fuel that is a fuel supplied to form a fresh air mixture in the main combustion chamber and a second fuel that is burned in the sub-combustion chamber When,
An air supply for supplying compressed air to the sub-combustion chamber in order to push out the first fuel from the sub-combustion chamber to the main combustion chamber through the communication path in a compression stroke;
After the air supply unit pushes the first fuel from the sub-combustion chamber to the main combustion chamber, the air supply unit further supplies the second fuel to the sub-combustion chamber before ignition. A control unit for controlling the supply unit and the fuel supply unit;
With
Sub-chamber internal combustion engine.

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