JP2008128118A - Control system of compression ignition type internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology capable of quickly transferring an internal combustion engine to a premixed combustion operation state from a fuel cut operation state, in a control system of a compression ignition type internal combustion engine for performing premixed combustion operation by introducing an EGR gas quantity of a predetermined quantity or more into a cylinder. <P>SOLUTION: This invention is the control system of the compression ignition type internal combustion engine for performing the premixed combustion operation by introducing EGR gas of the predetermined quantity or more into the cylinder, and shortens a transport delay in the EGR gas, by enabling a first opening-closing valve to perform pulse supercharging operation, when the internal combustion engine transfers to the premixed combustion operation state from the fuel cut operation state, by arranging the first opening-closing valve in an intake passage on the upstream side of an intake valve of the internal combustion engine. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a control system for a compression ignition type internal combustion engine, and more particularly to a control system for a compression ignition type internal combustion engine capable of a premixed combustion operation.

  As an internal combustion engine mounted on a vehicle or the like, a compression ignition type internal combustion engine capable of switching between a premixed combustion operation and a diffusion combustion operation is known.

  When a compression ignition type internal combustion engine is operated by premix combustion, it is necessary to introduce a larger amount of EGR gas into the combustion chamber than during diffusion combustion operation in order to prevent pre-ignition of fuel (or premixed gas). . However, when the internal combustion engine shifts from the diffusion combustion operation state or the fuel cut operation state to the premixed combustion operation state, the EGR gas amount cannot be increased immediately.

In contrast, a method has been proposed in which EGR gas is stored during premixed combustion operation or diffusion combustion operation, and the stored EGR gas is appropriately supplied to the combustion chamber (see, for example, Patent Document 1).
JP 2005-325811 A JP 2000-248946 A

  By the way, the above-described conventional technique requires a large specification change in order to store the EGR gas.

  An object of the present invention is to provide a control system for a compression ignition type internal combustion engine that performs a premixed combustion operation by introducing an EGR gas amount of a predetermined amount or more into a cylinder, and the internal combustion engine is changed from a fuel cut operation state to a premixed combustion operation state. It is to provide technology that can be quickly transferred to.

  The present invention employs the following means in order to solve the above-described problems. That is, the present invention provides a control system for a premixed compression ignition internal combustion engine having an on / off valve for pulse supercharging, when the internal combustion engine transitions from a fuel cut operation state to a premix combustion operation state. By delaying the first on-off valve arranged upstream of the intake valve by pulse supercharging, the transport delay of EGR gas is shortened.

  Specifically, the present invention relates to a control system for a compression ignition type internal combustion engine that performs a premixed combustion operation by introducing a predetermined amount or more of EGR gas into a cylinder, and to the intake passage upstream of the intake valve of the internal combustion engine. A first on-off valve provided; and control means for performing a pulse supercharging operation of the first on-off valve when the internal combustion engine shifts from a fuel cut operation state to a premixed combustion operation state.

  In recent years, an internal combustion engine has been proposed in which an open / close valve is provided in an intake passage upstream of the intake valve, and the open / close valve is pulse-supercharged when a sudden increase in intake air amount is required, such as during acceleration operation. Pulse supercharging is a supercharging method that increases the inertial supercharging effect of intake air by making the valve opening period of the on-off valve different from the valve opening period of the intake valve, and is sometimes called impulse supercharging.

The operation of the on-off valve in pulse supercharging (pulse supercharging operation) is, for example, an operation that closes before the opening of the intake valve starts and opens before the intake valve starts to close.

  According to such a pulse supercharging operation, during the period from the opening timing of the intake valve to the opening timing of the on-off valve (hereinafter referred to as “first period”), the on-off valve and the intake valve The intake passage (hereinafter referred to as “valve passage”) in the meantime becomes negative pressure by the downward movement of the piston. For this reason, when the on-off valve is opened, the gas upstream from the on-off valve rapidly flows into the valve passage and the cylinder. As a result, the inertial supercharging effect of intake air is increased, and the gas charging efficiency in the cylinder is improved.

  The above-described pulse supercharging is mainly used to compensate for turbocharger supercharging delay (turbo lag) during acceleration operation of an internal combustion engine equipped with a turbocharger. In the present invention, the internal combustion engine is premixed from a fuel cut operation state. Pulse supercharging is now performed when shifting to the combustion operation state.

During fuel cut operation of the internal combustion engine, fuel is not combusted in the cylinder, so that the only gas discharged from the internal combustion engine is air. For this reason, the EGR gas circulation path (that is, the path starting from the inside of the cylinder of the internal combustion engine through the exhaust passage, the EGR passage, and the intake passage and returning to the cylinder again. This circulation path is hereinafter referred to as “EGR circulation path”. Gas in which the concentration of air is high and the concentration of burned gas components (for example, carbon dioxide (CO ₂ ) and water (H ₂ O) generated when the fuel burns) is low. . Further, there is a gas transport delay before the gas discharged from the internal combustion engine is taken into the internal combustion engine again through the EGR circulation path.

  Therefore, immediately after the internal combustion engine shifts from the fuel cut operation state to the premixed combustion operation state, most of the gas introduced into the cylinder is air. As a result, immediately after the internal combustion engine shifts to the premixed combustion operation state, the burned gas component concentration in the cylinder is excessively low and the oxygen concentration is excessively high. If the burned gas component concentration in the cylinder is excessively low and the oxygen concentration is excessively high, if the internal combustion engine is operated in a premixed combustion mode, the fuel may ignite prematurely and increase vibration and noise. It was.

  Therefore, the compression ignition type internal combustion engine control system according to the present invention is configured to cause the first on-off valve to perform a pulse supercharging operation when the internal combustion engine shifts from the fuel cut operation state to the premixed combustion operation state.

  In this case, the EGR gas flowing from the EGR passage to the intake passage is assisted by the negative pressure generated in the inter-valve passage, and the flow rate and flow rate of the EGR gas flowing from the EGR passage to the intake passage are increased. As a result, the transport delay of EGR gas as described above is shortened.

  When the transport delay of EGR gas is shortened, the burned gas component concentration in the cylinder rapidly increases after the fuel cut operation ends, and at the same time, the oxygen concentration in the cylinder quickly decreases. Therefore, the internal combustion engine can quickly shift from the fuel cut operation state to the premixed combustion operation state.

  In addition, the 1st on-off valve concerning this invention may be arrange | positioned in the intake passage upstream from the connection part of an EGR passage. In such a configuration, it is preferable that the EGR valve is in an open state during a first period from the opening start timing of the intake valve to the opening start timing of the first on-off valve. In this case, although it is difficult for a negative pressure to be generated in the inter-valve passage, EGR gas flows from the EGR passage through the inter-valve passage into the cylinder. That is, the first period is a period in which only fresh EGR gas flows into the cylinder without fresh air (air) flowing into the cylinder.

Therefore, the transport delay of EGR gas is shortened and the EGR rate in the cylinder can be increased. As a result, the internal combustion engine can shift more rapidly from the fuel cut operation state to the premixed combustion operation state.

  In the control system for a compression ignition type internal combustion engine according to the present invention, when the first on-off valve is disposed in the intake passage upstream of the connection portion of the EGR passage, the control means is configured to premix the internal combustion engine from the fuel cut operation state. You may make it retard the valve opening start time of the 1st on-off valve at the time of transfer to a combustion operation state from a prescribed valve opening start time.

  In normal pulse supercharging, when the opening timing of the first on-off valve becomes excessively late, the negative pressure generated in the inter-valve passage increases (the pressure decreases), but the first on-off valve opens. Since the period until the intake valve closes (hereinafter referred to as “second period”) is shortened, the amount of fresh air (air) introduced into the cylinder is reduced.

  Therefore, in normal pulse supercharging, the opening start timing of the first on-off valve is limited to a time when the amount of fresh air (air) introduced into the cylinder reaches a peak or before that. In contrast, when the internal combustion engine shifts from the fuel cut operation state to the premixed combustion operation state, the amount of fresh air (air) introduced into the cylinder decreases and the amount of EGR gas introduced into the cylinder decreases. As the number increases, a quicker transition becomes possible.

  Therefore, the control means of the present invention delays the opening timing of the first on-off valve from a specified timing (opening timing when performing normal pulse supercharging), thereby extending the first period. The second period was shortened. In this case, the amount of fresh air (air) introduced into the cylinder decreases and the amount of EGR gas introduced into the cylinder increases. As a result, when the internal combustion engine shifts from the fuel cut operation state to the premixed combustion operation state, the EGR rate in the cylinder rapidly increases.

  Next, in the control system for the compression ignition type internal combustion engine according to the present invention, the control means defines the closing timing of the first on-off valve when the internal combustion engine shifts from the fuel cut operation state to the premixed combustion operation state. You may make it advance from the valve closing timing.

  In the conventional pulse supercharging, the closing timing of the first on-off valve is set after the intake valve is closed in order to reduce the amount of internal EGR gas (burned gas remaining in the cylinder at the end of the exhaust stroke). . On the other hand, when the valve closing timing of the first on-off valve is advanced, the internal EGR gas amount increases. As a result, when the internal combustion engine shifts from the fuel cut operation state to the premixed combustion operation state, the oxygen concentration in the cylinder can be immediately reduced.

  When the first opening / closing valve is disposed in the intake passage downstream of the connection portion of the EGR passage, the closing timing of the first opening / closing valve may be advanced from the closing timing of the intake valve. In this case, since the inside of the valve passage is kept at a negative pressure even after the first on-off valve is closed, the intake valve opening period of the next cycle (specifically, the opening periods of the intake valve and the exhaust valve overlap) During the valve overlap period), the exhaust gas flows backward and the amount of internal EGR gas increases. As a result, the oxygen concentration in the cylinder can be rapidly reduced when the internal combustion engine shifts from the fuel cut operation state to the premixed combustion operation state.

  In the control system for the compression ignition type internal combustion engine according to the present invention, the control means defines the opening timing of the first on-off valve when the internal combustion engine shifts from the fuel cut operation state to the premixed combustion operation state. The valve opening timing may be retarded from the valve opening timing, and the valve closing timing of the first on-off valve may be advanced from the specified valve closing timing.

In this case, the EGR gas transportation delay period is shortened by delaying the opening timing of the first on-off valve, and the internal E is increased by advancing the closing timing of the first on-off valve.
The amount of GR gas increases. Therefore, due to their synergistic effect, the oxygen concentration in the cylinder immediately decreases to a concentration at which pre-ignition can be suppressed after completion of the fuel cut operation.

  The control system for a compression ignition type internal combustion engine according to the present invention further includes a second on-off valve provided in the EGR passage, and the above-mentioned control system is used when the internal combustion engine shifts from the fuel cut operation state to the premixed combustion operation state. In addition to the pulse supercharging operation of the first on-off valve, the second on-off valve may be operated by pulse supercharging.

  Specifically, the second on-off valve repeats the operation of opening when the negative pressure wave of the intake pulsation reaches the second on-off valve and closing when the positive pressure wave reaches the second on-off valve. May be. According to such a configuration, the transport delay of EGR gas can be further shortened.

  According to the present invention, in a control system for a compression ignition internal combustion engine that performs a premixed combustion operation by introducing an EGR gas amount of a predetermined amount or more into a cylinder, the internal combustion engine is in a premixed combustion operation state from a fuel cut operation state. Can be quickly transferred to.

  Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

<Example 1>
First, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a diagram showing the configuration of a control system for a compression ignition internal combustion engine according to the present invention.

  The internal combustion engine shown in FIG. 1 is a compression ignition type internal combustion engine (diesel engine) capable of appropriately switching between a premixed combustion operation and a diffusion combustion operation. The internal combustion engine 1 includes a fuel injection valve 3 that can inject fuel directly into each cylinder 2 and an intake passage 4 that guides air into each cylinder 2. A compressor housing 50 and an intercooler 6 of a centrifugal supercharger (turbocharger) 5 are disposed in the intake passage 4.

  The intake air supercharged by the compressor housing 50 is guided to each cylinder 2 after being cooled by the intercooler 6. The intake air introduced into each cylinder 2 is ignited and burned in the cylinder 2 together with the fuel injected from the fuel injection valve 3.

  The gas burned in each cylinder 2 is discharged to the exhaust passage 7. The exhaust discharged into the exhaust passage 7 is released into the atmosphere via the turbine housing 51 and the exhaust purification device 8 disposed in the middle of the exhaust passage 7.

  As the exhaust purification device 8, a NOx storage reduction catalyst having oxidation ability and NOx storage capacity, a particulate filter having oxidation ability and PM trapping capacity, a particulate filter carrying a storage reduction type NOx catalyst, or the like is used. It can be illustrated.

  The intake passage 4 and the exhaust passage 7 described above are connected to each other by a high-pressure EGR passage 9. Specifically, the exhaust passage 7 upstream from the turbine housing 51 and the intake passage 4 downstream from the intercooler 6 are connected to each other by a high-pressure EGR passage 9.

  In the middle of the high-pressure EGR passage 9, a high-pressure EGR valve 10 that adjusts the cross-sectional area of the high-pressure EGR passage 9 and a high-pressure EGR cooler 11 that cools the gas (EGR gas) flowing through the high-pressure EGR passage 9 are arranged. Has been. A first intake throttle valve 12 is disposed in a portion of the intake passage 4 downstream of the intercooler 6 and upstream of the connecting portion of the high pressure EGR passage 9. The amount of EGR gas flowing through the high pressure EGR passage 9 is adjusted by the opening degrees of the high pressure EGR valve 10 and the first intake throttle valve 12.

  The intake passage 4 downstream from the connecting portion of the high pressure EGR passage 9 is branched into the same number (four in this case) of branch pipes 40 as the number of cylinders of the internal combustion engine 1. Each branch pipe 40 communicates with the cylinder 2 of the internal combustion engine 1 (hereinafter, the four branch pipes are collectively referred to as “intake manifolds”). Each branch pipe of the intake manifold 40 is provided with a first on-off valve 18 that opens and closes the passage of each branch pipe.

  The fuel injection valve 3, the high pressure EGR valve 10, the first intake throttle valve 12, and the first on-off valve 18 are electrically controlled by the ECU 13. The ECU 13 is attached to the internal combustion engine 1, the measured value of the air flow meter 14 disposed in the intake passage 4, the measured value of the air-fuel ratio sensor (A / F sensor) 15 disposed in the exhaust passage 7 downstream of the exhaust purification device 8. The fuel injection valve 3, the high pressure EGR valve 10, the first intake throttle valve 12, and the first on-off valve 18 are controlled using the measured value of the crank position sensor 16 and the measured value of the accelerator position sensor 17 as parameters.

  For example, the ECU 13 causes the internal combustion engine 1 to perform a premixed combustion operation when the engine operating state determined from the load (accelerator opening) Accp and the engine speed Ne of the internal combustion engine 1 is in the premixed combustion region shown in FIG. On the other hand, when the engine operating state is in the diffusion combustion operation region of FIG. 2, the ECU 13 causes the internal combustion engine 1 to perform the diffusion combustion operation.

  When the internal combustion engine 1 is operated in a premixed combustion mode, the ECU 13 sets the pilot injection amount to zero (stops pilot injection) and sets the main injection timing earlier than the compression top dead center (see FIG. 3). Set at the beginning or middle of the compression stroke.

  On the other hand, when the internal combustion engine 1 is operated by diffusion combustion, as shown in FIG. 4, the ECU 13 sets the pilot injection amount to an amount larger than zero (executes pilot injection) and compresses the main injection timing. Set near the point.

  If the internal combustion engine 1 is operated in a premixed combustion mode and the oxygen concentration in the cylinder 2 becomes high, the fuel injected from the fuel injection valve 3 may ignite prematurely before forming the premixed gas. . For this reason, during the premixed combustion operation of the internal combustion engine 1, it is necessary to introduce a larger amount of EGR gas into the cylinder 2 than during the diffusion combustion operation to lower the oxygen concentration.

  By the way, during the fuel cut operation of the internal combustion engine 1, fuel is not combusted in the cylinder 2, so that the EGR circulation path (the exhaust passage 7, the high-pressure EGR passage 9, and the intake passage 4 starting from the combustion chamber of the internal combustion engine 1 sequentially) The path returning to the combustion chamber again is filled with a gas having a high air concentration and a low concentration of burned gas components. Further, after completion of the fuel cut operation, a transport delay occurs until the gas burned in the first combustion cylinder reaches the cylinder 2 of the internal combustion engine 1 through the EGR circulation path.

  Therefore, during the period from the end of the fuel cut operation to the elimination of the transport delay, the amount of burned gas component introduced into the cylinder 2 is minimal or zero. For this reason, if the internal combustion engine 1 is premixed and burned immediately after the end of the fuel cut operation, the oxygen concentration in the cylinder 2 becomes excessively high. As a result, the fuel injected from the fuel injection valve 3 may ignite prematurely and increase vibration and noise.

  On the other hand, a method of causing the internal combustion engine 1 to perform a diffusion combustion operation during a period from the end of the fuel cut operation until the transportation delay is eliminated can be considered. However, all the cylinders 2 of the internal combustion engine 1 do not restart the combustion at the same time when the fuel cut operation ends, but sequentially restart the combustion according to the fuel injection sequence.

  For this reason, the amount of burned gas components introduced into the cylinder 2 at the time when the transport delay is eliminated is extremely small relative to the amount capable of suppressing the pre-ignition of the fuel. Therefore, it is difficult to quickly shift the internal combustion engine 1 from the diffusion combustion operation to the premixed combustion operation after the transportation delay is eliminated.

  Therefore, in the control system for the compression ignition internal combustion engine in the present embodiment, the ECU 13 causes the first on-off valve 18 to perform a pulse supercharging operation when the internal combustion engine 1 shifts from the fuel cut operation state to the premixed combustion operation state. I made it.

  As shown in FIG. 5, the pulse supercharging operation of the first on-off valve 18 is closed before the intake valve is opened (specifically, after the intake valve is closed in the immediately preceding cycle). This is an operation that is opened before the start of closing.

  According to such a pulse supercharging operation, an inter-valve passage from the first on-off valve 18 to the intake valve is formed in the first period from the opening start timing of the intake valve to the opening start timing of the first on-off valve 18. Negative pressure. When the first on-off valve 18 is opened, the gas upstream from the first on-off valve 18 rapidly flows into the cylinder 2 due to the negative pressure in the valve passage. As a result, the inertial supercharging effect of the intake air is increased and the gas charging efficiency in the cylinder 2 is improved.

  The above-described pulse supercharging is performed mainly to compensate for the supercharging delay (turbo lag) of the turbocharger 5 at the start of acceleration operation of the internal combustion engine 1, but in this embodiment, the internal combustion engine 1 is preliminarily moved from the fuel cut operation state. The first on-off valve 18 is also pulse-supercharged when shifting to the mixed combustion operation state.

  If the first on-off valve 18 performs a pulse supercharging operation when the internal combustion engine 1 shifts from the fuel cut operation state to the premixed combustion operation state, the EGR gas in the high pressure EGR passage 9 is caused by the negative pressure generated in the intervalve passage. It is drawn into the inter-passage and the cylinder vigorously. That is, the flow of EGR gas flowing in the high pressure EGR passage 9 is assisted by the negative pressure described above. As a result, the transport delay of the EGR gas described above is shortened.

  When the transport delay of EGR gas is shortened after the fuel cut operation of the internal combustion engine 1 is completed, the burned gas component concentration in the cylinder 2 rapidly increases and the oxygen concentration rapidly decreases. For this reason, the internal combustion engine 1 can start the premixed combustion operation without premature ignition at an early time after the end of the fuel cut operation.

  By the way, in the conventional pulse supercharging, as shown in FIG. 5 described above, the closing timing of the first on-off valve 18 is set later than the closing timing of the intake valve. This is to reduce the amount of burnt gas (internal EGR gas) remaining in the cylinder 2 even after the exhaust stroke ends.

  On the other hand, as shown in FIG. 6, the ECU 13 of this embodiment advances the closing timing of the first on-off valve 18 at the same time as or before the closing timing of the intake valve. In this case, since the pressure in the valve passage decreases after the intake valve is closed, the burned gas in the cylinder 2 is once drawn into the valve passage during the valve overlap period of the next cycle, and the valve is closed after the exhaust valve is closed. The air is re-inhaled into the cylinder 2 from the intermediate passage. As a result, the amount of burned gas (internal EGR gas) remaining in the cylinder 2 increases.

When the amount of the internal EGR gas is increased in this way, the burned gas component concentration in the cylinder 2 immediately increases after the fuel cut operation of the internal combustion engine 1 is finished due to a synergistic effect with the shortening of the transport delay described above. The oxygen concentration begins to drop immediately. As a result, even if the internal combustion engine 1 starts the premixed combustion operation immediately after the fuel cut operation is completed, it is possible to suppress the occurrence of premature ignition.

  Hereinafter, the control procedure of the present embodiment will be described with reference to FIG. FIG. 7 is a flowchart showing a control routine when the internal combustion engine 1 shifts from the fuel cut operation state to the premixed combustion operation state. This control routine is stored in advance in the ROM of the ECU 13 and is periodically executed by the ECU 13.

  In the control routine of FIG. 7, the ECU 13 first determines whether or not the fuel cut control execution condition is satisfied in S101. Conventionally known conditions are used as fuel cut control execution conditions. For example, the accelerator opening degree Accp is zero, the engine speed Ne is equal to or higher than a predetermined speed, and the cooling water temperature of the internal combustion engine 1 is a constant temperature. The conditions such as the above can be exemplified.

  If a negative determination is made in S101, the ECU 13 once ends the execution of this routine. On the other hand, if an affirmative determination is made in S101, the ECU 13 proceeds to S102.

  In S102, the ECU 13 stops the fuel injection from the fuel injection valve 3 and closes the intake throttle valve 12 and the high pressure EGR valve 10 in order to prevent an excessive increase in the engine speed.

  In S103, the ECU 13 determines whether or not a fuel cut control execution end condition is satisfied. The fuel cut control execution end condition is that the above-described fuel cut execution condition is not satisfied.

  If a negative determination is made in S103, the ECU 13 repeatedly executes the process of S103 until the fuel cut control execution end condition is satisfied. On the other hand, if an affirmative determination is made in S103, the ECU 13 proceeds to S104.

  In S104, the ECU 13 calculates the engine speed Ne from the measured value of the crank position sensor 16, and reads the measured value (accelerator opening) Accp of the accelerator position sensor 17, and from the engine speed Ne and the accelerator opening Accp. It is determined whether or not the determined engine operating state belongs to the above-described premixed combustion operation region shown in FIG.

  If a negative determination is made in S104 (when the engine operation state belongs to the diffusion combustion operation region), the ECU 13 proceeds to S108 and resumes the pilot injection and the main injection near the compression top dead center from the fuel injection valve 3. As a result, the execution of the fuel cut control is completed, and the high-pressure EGR valve 10 and the intake throttle valve 12 are returned to the normal opening.

  On the other hand, when an affirmative determination is made in S104 (when the engine operating state belongs to the premixed combustion operation region), the ECU 13 proceeds to S105 and opens the high pressure EGR valve 10 and the first intake throttle valve 12. In addition, the first on-off valve 18 is pulse-supercharged according to the timing shown in FIG.

  In this case, since the transport delay of EGR gas is shortened and the amount of internal EGR gas is increased, the burned gas component concentration in the cylinder 2 is rapidly increased, and at the same time, the oxygen concentration in the cylinder 2 is rapidly decreased.

Next, the ECU 13 determines in S106 whether or not the oxygen concentration (O ₂ concentration) in the cylinder 2 has decreased to a target oxygen concentration (target O ₂ concentration) or less. The oxygen concentration (O ₂ concentration) in the cylinder 2 can be estimated and calculated based on the EGR rate.

If a negative determination is made in S106 (O ₂ concentration> target O ₂ concentration), the ECU 13 continues until the oxygen concentration (O ₂ concentration) in the cylinder 2 falls below the target oxygen concentration (target O ₂ concentration). The process of S106 is repeatedly executed.

On the other hand, when a positive determination is made in S106 (O ₂ concentration ≦ target O ₂ concentration), the ECU 13 proceeds to S107. In S107, the ECU 13 stops the pulse supercharging operation of the first on-off valve 18, and keeps the first on-off valve 18 in the open state.

  Thus, when the ECU 13 executes the combustion control routine, the control means according to the present invention is realized. Therefore, according to the present embodiment, when the internal combustion engine 1 shifts from the fuel cut operation state to the premixed combustion operation state, it is possible to realize a rapid transition while suppressing premature ignition.

  In the control routine of FIG. 7 described above, the internal combustion engine 1 may be operated in the diffusion combustion operation during the period in which the processing of S105 to S107 is performed, or the premixed combustion operation is performed while retarding the main injection timing. You may be made to do. In this case, it is possible to shift the operating state while reliably suppressing the occurrence of premature ignition.

  In this embodiment, an example in which the present invention is applied to an internal combustion engine having a high pressure EGR mechanism including a high pressure EGR passage 9, a high pressure EGR valve 10, a high pressure EGR cooler 11, and a first intake throttle valve 12 will be described. However, it is also possible to apply to an internal combustion engine provided with a low pressure EGR mechanism.

  As shown in FIG. 8, the low pressure EGR mechanism includes a low pressure EGR passage 19, a low pressure EGR valve 20, a low pressure EGR cooler 21, and a second intake throttle valve 22.

  The low-pressure EGR passage 19 is a passage that guides exhaust gas from the exhaust passage 7 downstream of the turbine housing 51 (downstream of the exhaust purification device 8 in the example of FIG. 8) to the intake passage 4 upstream of the compressor housing 50. The low-pressure EGR valve 20 is a valve that adjusts the cross-sectional area of the low-pressure EGR passage 19. The low pressure EGR cooler 21 is a heat exchanger for cooling the gas flowing through the low pressure EGR passage 19. The second intake throttle valve 22 is disposed in the intake passage 4 upstream of the connection portion of the low pressure EGR passage 19, and cooperates with the low pressure EGR valve 20 to allow EGR gas flowing from the low pressure EGR passage 19 to the intake passage 4. It is a valve that adjusts the amount.

  The EGR circulation path of the internal combustion engine 1 equipped with the low pressure EGR mechanism (the path returning to the combustion chamber again through the exhaust passage 7, the low pressure EGR passage 19, and the intake passage 4 in this order from the combustion chamber of the internal combustion engine 1). It becomes longer than an internal combustion engine equipped with a mechanism. Further, an intercooler 6 and an intake manifold 40 having a larger capacity than the intake passage 4 exist in the intake passage 4 downstream of the connection portion of the low pressure EGR passage 19. For this reason, the transport delay period of EGR gas is significantly longer than that of an internal combustion engine equipped with a high pressure EGR mechanism.

On the other hand, when the first on-off valve 18 performs a pulse supercharging operation according to the timing shown in FIG. 6 at the end of the fuel cut operation of the internal combustion engine 1, the gas flow speed in the intake passage 4 and the low pressure EGR passage 19 increases. Therefore, the response delay of the EGR gas is greatly shortened. Further, since the amount of internal EGR gas increases due to the pulse supercharging operation of the first on-off valve 18, the burned gas component in the cylinder 2 when the internal combustion engine 1 shifts from the fuel cut operation state to the premixed combustion operation. The concentration can be increased rapidly and the oxygen concentration can be decreased rapidly. As a result, a significant shortening of the transition period from the fuel cut operation state to the premixed combustion operation state can be expected.

<Example 2>
Next, a second embodiment of the present invention will be described with reference to FIGS. Here, a configuration different from that of the first embodiment will be described, and description of the same configuration will be omitted.

  In the first embodiment described above, the high pressure EGR passage 9 is connected to the intake passage 4 upstream of the first opening / closing valve 18. In this embodiment, the high pressure EGR passage 9 is downstream of the first opening / closing valve 18. Connected to.

  In this case, the high pressure EGR passage 9 is branched into four downstream from the high pressure EGR valve 10 and connected to each of the four branch pipes of the intake manifold 40.

  In this configuration, the ECU 13 opens the high-pressure EGR valve 10 and causes the first on-off valve 18 to perform a pulse supercharging operation when the internal combustion engine 1 shifts from the fuel cut operation state to the premixed combustion operation state.

  At that time, since the high pressure EGR passage 9 is connected in the middle of the valve passage, fresh air (air) upstream from the first on-off valve 18 does not flow into the valve passage and the cylinder 2 in the first period. In addition, only the EGR gas from the high pressure EGR passage 9 flows into the valve passage and the cylinder 2.

  As a result, the transport delay of EGR gas can be greatly reduced, and the amount of EGR gas introduced into the cylinder 2 immediately after the fuel cut operation of the internal combustion engine 1 can be rapidly increased.

  In addition, when EGR gas flows into the intervalve passage during the first period described above, since the inside of the intervalve passage does not become negative pressure, fresh air (air) that flows into the cylinder 2 after the first on-off valve 18 is opened. The amount of decreases.

  As a result, the oxygen concentration in the cylinder 2 can be rapidly reduced immediately after the internal combustion engine 1 ends the fuel cut operation.

  Therefore, according to the control system for the compression ignition type internal combustion engine according to the present embodiment, the EGR rate in the cylinder 2 is rapidly increased immediately after the fuel cut operation of the internal combustion engine 1 is finished. It becomes possible to immediately start the premixed combustion operation later.

  The first on-off valve 18 may perform the pulse supercharging operation in accordance with the timing of FIG. 6 described above, but as shown in FIG. You may make it be retarded from time.

  In this case, the amount of fresh air (air) flowing into the cylinder 2 is further reduced, and the amount of EGR gas flowing into the cylinder 2 is further increased.

<Example 3>
Next, a third embodiment of the present invention will be described with reference to FIG. Here, a configuration different from that of the first embodiment will be described, and description of the same configuration will be omitted.

  FIG. 11 is a diagram showing a schematic configuration of a control system for a compression ignition type internal combustion engine in the present embodiment. In FIG. 11, a second opening / closing valve 23 is disposed upstream of the high pressure EGR valve 10 in the high pressure EGR passage 9.

  In this configuration, the ECU 13 causes the first on-off valve 18 to perform a pulse supercharging operation and also causes the second on-off valve 23 to perform a pulse supercharging operation when the internal combustion engine 1 shifts from the fuel cut operation state to the premixed combustion operation state. .

  Specifically, the ECU 13 quickly opens the second on-off valve 23 when a negative pressure wave due to the intake pulsation reaches the second on-off valve 23, and the ECU 13 The operation of closing the second on-off valve 23 is repeated.

  Thus, when the second on-off valve 23 performs a pulse supercharging operation, the flow of the EGR gas flowing through the high-pressure EGR passage 9 is assisted by the pulse supercharging operation of the first on-off valve 18, and the pulse of the second on-off valve 23. It is also assisted by the supercharging operation.

  Therefore, when the internal combustion engine 1 shifts from the fuel cut operation state to the premixed combustion operation, the EGR gas transport delay is further reduced. As a result, when the internal combustion engine 1 shifts from the fuel cut operation state to the premixed combustion operation state, it is possible to realize a quicker transition while suppressing premature ignition.

  Needless to say, the pulse supercharging operation using the second on-off valve 23 may be combined with the second embodiment described above.

It is a figure which shows the structure of the control system of the compression ignition type internal combustion engine in a 1st Example. It is a figure which shows the map for switching a premix combustion operation and a diffusion combustion operation. It is a timing chart which shows the fuel injection timing at the time of a premix combustion operation. It is a timing chart which shows the fuel injection timing at the time of diffusion combustion operation. FIG. It is a figure which shows the pulse supercharging operation | movement of the conventional 1st on-off valve. It is a figure which shows the pulse supercharging operation | movement of the 1st on-off valve in a 1st Example. It is a flowchart which shows the control routine when an internal combustion engine transfers to a premix combustion operation state from a fuel cut operation state. It is a figure which shows the other structural example of the control system of the compression ignition type internal combustion engine in a 1st Example. It is a figure which shows the structure of the control system of the compression ignition type internal combustion engine in a 2nd Example. It is a figure which shows the pulse supercharging operation | movement of the 1st on-off valve in a 2nd Example. It is a figure which shows schematic structure of the control system of the compression ignition type internal combustion engine in a 3rd Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... Cylinder 3 ... Fuel injection valve 4 ... Intake passage 7 ... Exhaust passage 9 ... High pressure EGR passage 10 .... High pressure EGR valve 11 .... High pressure EGR cooler 12 .... First intake throttle valve 13 .... ECU
18 .... First open / close valve 19 .... Low pressure EGR passage 20 .... Low pressure EGR valve 21 ... Low pressure EGR cooler 22 .... Second intake throttle valve 23 ...... Second On-off valve 40 ... Intake manifold

Claims (4)

In a control system for a compression ignition internal combustion engine that performs a premixed combustion operation by introducing a predetermined amount or more of EGR gas into a cylinder,
A first on-off valve provided in an intake passage upstream of the intake valve of the internal combustion engine;
Control means for causing the first on-off valve to perform a pulse supercharging operation when the internal combustion engine shifts from a fuel cut operation state to a premixed combustion operation state;
A control system for a compression ignition type internal combustion engine. In Claim 1, the first on-off valve is disposed in the intake passage upstream of the connection portion of the EGR passage,
When the internal combustion engine shifts from the fuel cut operation state to the premixed combustion operation state, the control means delays the valve opening start timing of the first on-off valve in the pulse supercharging operation from a specified valve opening start timing. A control system for a compression ignition type internal combustion engine characterized in that the angle is made to be square.   3. The control means according to claim 1, wherein the control means defines a valve closing start timing of the first on-off valve in the pulse supercharging operation when the internal combustion engine shifts from a fuel cut operation state to a premixed combustion operation state. A control system for a compression ignition type internal combustion engine, which is advanced from the valve closing start timing of the engine. The EGR passage according to any one of claims 1 to 4, wherein the exhaust passage and the intake passage of the internal combustion engine communicate with each other;
A second on-off valve provided in the EGR passage,
A control system for a compression ignition type internal combustion engine, wherein the control means causes the second on-off valve to perform a pulse supercharging operation when the internal combustion engine shifts from a fuel cut operation state to a premixed combustion operation state.

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