JP2008208784A - Control system for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide technology suitably raising temperature of insides of an intake passage and/or a cylinder during start period in a control system of an internal combustion engine provided with an EGR mechanism. <P>SOLUTION: Temperature in the intake passage, the cylinder, and exhaust gas is raised while inhibiting big drop of torque and excessive stall of engine rotation speed or the like by increasing quantity of EGR gas introduced into the internal combustion engine than specified quantity when inertia energy of the internal combustion engine is higher than predetermined value during a start period of the internal combustion engine. Exhaust emission during start period can be suitably reduced and a catalyst arranged in an exhaust passage of the internal combustion engine can be activated at an early stage. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a control technique for an internal combustion engine having an EGR mechanism.

Conventionally, in order to improve the startability of an internal combustion engine and reduce exhaust emissions, a technique has been disclosed in which a throttle valve and an idle speed control valve are closed and an EGR valve is opened when the internal combustion engine is started ( For example, see Patent Document 1).
JP-A-11-200907 Japanese Utility Model Publication No. 7-35747 JP-A-8-121259

  By the way, in consideration of reducing the exhaust emission discharged from the internal combustion engine into the atmosphere, the temperature in the intake passage and / or the cylinder is increased as much as possible to reduce the fuel adhering to the wall in the intake passage and / or the cylinder. It is effective to reduce it.

  On the other hand, a method of increasing the temperature in the intake passage and / or the cylinder by introducing a large amount of EGR gas into the cylinder during the start-up period of the internal combustion engine is conceivable. However, if a large amount of EGR gas is introduced into the cylinder during the start-up period of the internal combustion engine, the combustion stability of the air-fuel mixture is reduced, leading to a reduction in torque, a stall in engine speed, and the like.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to suitably control the temperature of the intake passage and / or the cylinder during the start-up period in an internal combustion engine control system equipped with an EGR mechanism. The provision of technology to enhance.

  In order to solve the above-described problems, the present invention increases the amount of EGR gas as much as possible on the condition that the inertial energy of the internal combustion engine is sufficiently high during the start-up period of the internal combustion engine having the EGR mechanism. I did it.

  Specifically, an internal combustion engine control system according to the present invention includes an EGR mechanism that introduces EGR gas into a cylinder of the internal combustion engine, an acquisition unit that acquires inertial energy of the internal combustion engine during the startup period of the internal combustion engine, Control means for executing a large amount of EGR processing for increasing the amount of EGR gas introduced into the cylinder by the EGR mechanism when the inertial energy acquired by the acquisition unit exceeds a predetermined value. It is characterized by.

  The “specified amount” here corresponds to the maximum amount of EGR gas that does not impair the combustion stability during the start-up period. Further, the “starting period” here is a concept including a period from the start of cranking to the convergence of the engine speed to the target idle speed.

  The control system for an internal combustion engine according to the present invention executes the mass EGR process only when the inertial energy of the internal combustion engine is higher than a predetermined value during the start-up period of the internal combustion engine. When the amount of EGR gas introduced into the cylinder exceeds the specified amount due to the execution of a large amount of EGR processing, the temperature in the cylinder rises rapidly.

As a result, the fuel adhering to the inner wall surface of the cylinder and the top surface of the piston (wall surface adhering fuel) decreases.
When the fuel adhering to the wall surface decreases, the fuel component (for example, hydrocarbon (HC)) discharged from the cylinder without being burned also decreases.

  As an EGR mechanism according to the present invention, a mechanism (hereinafter referred to as “external EGR”) that includes an EGR passage that guides a part of exhaust gas from an exhaust passage of an internal combustion engine to an intake passage, and an EGR valve that changes a passage sectional area of the EGR passage. Called "mechanism"). In this case, the temperature in the intake passage can be rapidly increased in addition to the temperature in the cylinder by the mass EGR process. As a result, in addition to the wall-attached fuel in the cylinder, the wall-attached fuel in the intake passage can also be reduced.

  As an EGR mechanism according to the present invention, a variable valve mechanism that changes the opening and closing timing of an intake valve and / or an exhaust valve so that a part of gas burned in a cylinder (burned gas) remains in the cylinder. (Hereinafter referred to as “internal EGR mechanism”) can also be used. In this case, the fuel attached to the wall surface in the cylinder can be reduced by the mass EGR process using the internal EGR mechanism.

  When the opening / closing timing of the intake valve and / or the exhaust valve is changed so that a part of the burned gas once flows back into the intake passage and is again sucked into the cylinder when the large-scale EGR process is executed, In addition to the adhering fuel, the wall adhering fuel in the intake passage can also be reduced.

  Further, when a large amount of EGR processing is performed by the EGR mechanism as described above, the combustion of the air-fuel mixture becomes slow. When the combustion of the air-fuel mixture becomes slow, the exhaust temperature of the internal combustion engine rises. As a result, the catalyst disposed in the exhaust passage of the internal combustion engine is activated early.

  Therefore, if a large amount of EGR processing is performed during the start-up period of the internal combustion engine, exhaust emission of the internal combustion engine can be reduced and early activation of the catalyst can be achieved.

  By the way, if the amount of EGR gas is larger than the specified amount, the combustion stability of the air-fuel mixture may be reduced, resulting in a significant reduction in torque and excessive stalling of the engine rotational speed. However, since the control system for an internal combustion engine according to the present invention performs a large amount of EGR processing only when the inertial energy of the internal combustion engine is sufficiently high, it is possible to suppress a reduction in torque and a stall in engine speed. Therefore, it is possible to reduce the fuel adhering to the wall surface and to activate the catalyst early without significantly reducing the torque or excessively stalling the engine speed during the start-up period of the internal combustion engine.

  In the control system for an internal combustion engine according to the present invention, the predetermined value is greater than an inertia energy (hereinafter referred to as “reference inertia energy”) when the rotation speed of the internal combustion engine converges to a target idle rotation speed. It may be set.

  In this case, the mass EGR process is executed when the inertial energy of the internal combustion engine exceeds the reference inertial energy. As a result, even if the combustion stability of the internal combustion engine is reduced due to the execution of a large amount of EGR processing, the engine speed is difficult to fall below the target idle speed.

  When the EGR mechanism according to the present invention is an external EGR mechanism, the execution time of the mass EGR process may be changed in consideration of the flow rate (flow rate) of the EGR gas flowing through the EGR passage.

  Specifically, the control system for an internal combustion engine according to the present invention further includes first estimation means for estimating a flow rate (flow rate) of EGR gas flowing through the EGR passage, and the control means sets the estimated value of the first estimation means. Accordingly, the execution time of the mass EGR process may be changed. The “execution time” here is a time when the control means gives an instruction to the EGR valve.

  The flow rate of the EGR gas is a pressure difference (hereinafter referred to as “EGR”) between the pressure at the inlet of the EGR passage (the connection between the EGR passage and the exhaust passage) and the pressure at the outlet of the EGR passage (the connection between the EGR passage and the intake passage). Referred to as “passage differential pressure”). That is, as the EGR passage differential pressure increases, the flow rate of EGR gas increases. On the other hand, the operating speed of the EGR valve is substantially constant.

  Therefore, as the flow rate of the EGR gas increases, the EGR gas introduced into the internal combustion engine during the operation period of the EGR valve (the period from the time when the EGR valve receives the instruction of the control means to the time when the operation as instructed is completed). Will increase.

  For this reason, when a large amount of EGR processing is terminated under the condition that the flow rate of EGR gas is high, there is a situation in which more EGR gas than the prescribed amount is introduced into the internal combustion engine even after the inertial energy has decreased below a predetermined value. Can occur.

  On the other hand, if the execution time of the mass EGR process is advanced as the flow rate of the EGR gas is increased, the above-described situation is less likely to occur.

  The control means changes the target EGR gas amount at the time of execution of the mass EGR process according to the estimated value of the first estimation means instead of changing the execution time of the mass EGR process according to the estimated value of the first estimation means. May be.

  The operation period of the EGR valve becomes longer as the operation amount of the EGR valve increases. For this reason, the operation period of an EGR valve becomes short, so that the target EGR gas amount at the time of execution of mass EGR processing decreases.

  Therefore, as the flow rate of the EGR gas estimated by the first estimation unit increases, the same effect as when the execution time of the large-scale EGR process is changed when the target EGR gas amount during the large-volume EGR process is reduced. Obtainable.

  Next, when the EGR mechanism according to the present invention is an internal EGR mechanism, even if the execution time of the large-scale EGR processing is changed in consideration of the operating speed of the variable valve mechanism instead of considering the flow rate of the EGR gas. Good.

  Specifically, the control system for an internal combustion engine according to the present invention further includes second estimation means for estimating the operating speed of the variable valve mechanism, and the control means performs a large amount of EGR processing according to the estimated value of the second estimation means. You may make it change the execution time of.

  The operating speed of the variable valve mechanism changes depending on the following conditions. That is, when the variable valve mechanism is driven by hydraulic pressure, the operation speed decreases as the oil temperature decreases. In addition, when the variable valve mechanism is a mechanism driven by electric power, the operation speed decreases as the battery voltage decreases.

  For this reason, when a large amount of EGR processing is terminated under the condition that the operating speed of the variable valve mechanism is low, EGR gas exceeding the specified amount is introduced into the internal combustion engine even after the inertial energy has decreased below a predetermined value. Things can happen.

  On the other hand, if the execution time of the large-volume EGR processing is advanced as the operation speed of the variable valve mechanism decreases, the above-described situation becomes difficult to occur.

  Note that the control means changes the target EGR gas amount at the time of executing the mass EGR process according to the estimated value of the second estimating means instead of changing the execution time of the mass EGR process according to the estimated value of the second estimating means. May be.

  The operation period of the variable valve mechanism (the period from the time when the variable valve mechanism receives an instruction from the control means to the time when the operation as instructed is completed) becomes longer as the operation amount of the variable valve mechanism increases. For this reason, the operation period of the variable valve mechanism becomes shorter as the target EGR gas amount at the time of execution of the large-scale EGR process decreases.

  Therefore, when the target EGR gas amount at the time of execution of the large-scale EGR process is reduced as the operation speed estimated by the second estimation unit becomes lower, the same effect as when the execution time of the large-scale EGR process is changed can be obtained. Can do.

  The control system for an internal combustion engine according to the present invention includes detection means for detecting EGR passage pressure difference, oil temperature, or battery voltage instead of the first estimation means or the second estimation means, and the control means is the detection means. Depending on the detected value, the execution time of the mass EGR process or the target EGR gas amount when the mass EGR process is executed may be changed.

  According to the present invention, in an internal combustion engine provided with an EGR mechanism, the temperature in the intake passage and / or the cylinder can be suitably increased during the start period.

  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 a schematic configuration of a control system for an internal combustion engine according to the present invention.

  An internal combustion engine 1 shown in FIG. 1 is a four-stroke cycle spark ignition type internal combustion engine (gasoline engine) having a plurality of cylinders 2. The cylinder 2 of the internal combustion engine 1 is connected to the intake passage 30 through the intake port 3 and is connected to the exhaust passage 40 through the exhaust port 4.

  The intake port 3 is provided with a fuel injection valve 5 that injects fuel into the cylinder 2. The intake passage 30 is provided with a throttle valve 6 that controls the amount of air flowing through the intake passage 30. An intake pressure sensor 7 that measures the pressure in the intake passage 30 is disposed in the intake passage 30 downstream of the throttle valve 6. An air flow meter 8 that measures the amount of air flowing through the intake passage 30 is provided in the intake passage 30 upstream of the throttle valve 6.

  On the other hand, an exhaust purification device 9 is disposed in the exhaust passage 40. The exhaust purification device 9 includes a three-way catalyst, an NOx storage reduction catalyst, and the like, and purifies exhaust when it is in a predetermined activation temperature range. An exhaust pressure sensor 10 that measures the pressure in the exhaust passage 40 is disposed in the exhaust passage 40 upstream of the exhaust purification device 9.

  The internal combustion engine 1 is also provided with an intake valve 11 that opens and closes an open end of the intake port 3 facing the cylinder 2 and an exhaust valve 12 that opens and closes the open end of the exhaust port 4 facing the cylinder 2. The intake valve 11 and the exhaust valve 12 are opened and closed by an intake camshaft 13 and an exhaust camshaft 14, respectively.

  A spark plug 15 for igniting the air-fuel mixture in the cylinder 2 is disposed above the cylinder 2. A piston 16 is slidably inserted into the cylinder 2. The piston 16 is connected to a crankshaft 18 via a connecting rod 17.

  A crank position sensor 19 that detects the rotation angle of the crankshaft 18 is disposed in the vicinity of the crankshaft 18. Further, the internal combustion engine 1 is provided with a water temperature sensor 20 that measures the temperature of the cooling water circulating through the internal combustion engine 1.

  The internal combustion engine 1 includes an external EGR mechanism. The external EGR mechanism includes an EGR passage 50 and an EGR valve 51. The EGR passage 50 connects the exhaust passage 40 upstream of the exhaust purification device 9 and the intake passage 30 downstream of the throttle valve 6. The EGR passage 50 is a passage that guides a part of the exhaust gas flowing through the exhaust passage 40 to the intake passage 30. The EGR valve 51 is disposed in the middle of the EGR passage 50. The EGR valve 51 adjusts the amount of EGR gas flowing through the EGR passage 50 by changing the passage cross-sectional area of the EGR passage 50.

  The internal combustion engine 1 configured as described above is provided with an ECU 21. The ECU 21 is an electronic control unit that includes a CPU, a ROM, a RAM, and the like. The ECU 21 is electrically connected to various sensors such as the intake pressure sensor 7, the air flow meter 8, the exhaust pressure sensor 10, the crank position sensor 19, and the water temperature sensor 20 described above, and the measurement values of the various sensors can be input. ing.

  The ECU 21 electrically controls the fuel injection valve 5, the throttle valve 6, the spark plug 15, and the EGR valve 51 based on the measurement values of the various sensors described above. For example, the ECU 21 performs temperature increase control for increasing the temperature in the cylinder 2 during the start-up period of the internal combustion engine 1.

  Hereinafter, the temperature rise control in this embodiment will be described.

  During the cold start of the internal combustion engine 1 and / or immediately after the cold start, the fuel injected from the fuel injection valve 5 tends to adhere to the inner wall surface of the cylinder 2 and the inner wall surface of the intake port 3. Most of the fuel adhering to the inner wall surface of the cylinder 2 or the intake port 3 (wall surface adhering fuel) is discharged from the internal combustion engine 1 without being burned. At that time, if the exhaust gas purification device 9 is not activated, the unburned fuel described above is released into the atmosphere without being purified.

  In order to reduce the exhaust emission during the cold start of the internal combustion engine 1 and / or immediately after the cold start, the reduction of the fuel adhering to the wall surface and the early activation of the exhaust purification device 9 are effective. As a method for reducing the fuel adhering to the wall surface, a method of circulating a large amount of EGR gas using an external EGR mechanism is conceivable.

  When a large amount of EGR gas is circulated, the inner wall surface of the intake port 3 and the inner wall surface of the cylinder 2 are warmed by the heat of the EGR gas. In this case, vaporization of the fuel adhering to the intake wall 3 and the inner wall surface of the cylinder 2 and / or vaporization of the fuel before adhering to the intake port 3 and the inner wall surface of the cylinder 2 are promoted. As a result, the fuel adhering to the wall surface is reduced.

  Further, when a large amount of EGR gas is circulated, the combustion rate of the air-fuel mixture decreases. When the combustion speed of the air-fuel mixture decreases, the exhaust temperature of the internal combustion engine 1 increases. As a result, the exhaust gas purification device 9 receives the heat of the exhaust gas and quickly rises in temperature.

  Therefore, if a large amount of EGR gas is circulated during the start-up period of the internal combustion engine 1, it becomes possible to reduce the fuel adhering to the wall surface and to activate the exhaust purification device 9 early. As a result, exhaust emission during the cold start of the internal combustion engine 1 and / or immediately after the cold start is reduced.

  By the way, if a large amount of EGR gas is circulated during the start-up period of the internal combustion engine 1, the combustion stability of the air-fuel mixture is impaired, and there is a risk that the torque will be reduced or the engine will be excessively stalled.

  FIG. 2 is a diagram illustrating the magnitude of torque fluctuation and the change in the amount of heat of EGR gas with respect to the change in the amount of EGR gas. The amount of heat of the EGR gas increases as the amount of EGR gas increases, and decreases after reaching the peak value EGRmax.

  EGR gas amount when the amount of heat of EGR gas reaches the peak value EGRmax (hereinafter referred to as “peak EGR gas amount”) EGRmax is a region in which the magnitude of torque fluctuation is greater than the allowable limit value (torque fluctuation deterioration area) Belonging to.

  Accordingly, when the EGR gas amount increases to the peak EGR gas amount EGRmax during the start-up period of the internal combustion engine 1, the magnitude of torque fluctuation exceeds the allowable limit value due to a significant decrease in torque, and a significant stall of the engine rotation speed occurs. As a result, engine rotation fluctuations may become excessive.

  On the other hand, a method of limiting the amount of EGR gas within a range where the combustion stability of the air-fuel mixture is not impaired can be considered. For example, in FIG. 2, a method of setting an EGR gas amount (hereinafter referred to as “specified EGR gas amount”) EGRtrg at which the torque fluctuation value is equal to the allowable limit value to a target EGR gas amount during the start-up period is conceivable.

  However, if the amount of EGR gas during the start-up period is limited to the specified EGR gas amount EGRtrg, the amount of heat of the EGR gas decreases, so it becomes difficult to reduce the fuel adhering to the wall surface and to activate the exhaust purification device 9 early. .

  Therefore, the ECU 21 performs a process of increasing the EGR gas amount to the peak EGR gas amount EGRmax (mass EGR process) only when the inertial energy of the internal combustion engine 1 is sufficiently large during the start-up period of the internal combustion engine 1. did.

  FIG. 3 is a diagram showing a transition of the inertial energy Ee during the start-up period of the internal combustion engine 1. In FIG. 3, the inertia energy Ee is very small during the period (cranking period) from the start of the internal combustion engine 1 to the occurrence of the first explosion. For this reason, it is preferable that the EGR gas amount during the cranking period is limited to a specified EGR gas amount EGRtrg or less.

  In the continuous explosion period after the first explosion, the inertial energy Ee gradually increases. However, the ignitability and combustion stability of the air-fuel mixture are low during the continuous explosion period. For this reason, it is preferable that the amount of EGR gas during the continuous explosion period is also limited to the specified EGR gas amount EGRtrg or less.

  Immediately after the complete explosion of the internal combustion engine 1, the inertial energy Ee becomes excessive, and the engine speed exceeds the target idle speed (in this case, the target value of the first idle speed) and excessively rises. For this reason, when a large amount of EGR processing is performed immediately after the complete explosion of the internal combustion engine 1, a decrease in torque and a stall of the engine rotational speed due to the large amount of EGR processing are offset by excess inertia energy.

  Therefore, even if a large amount of EGR processing is executed when the inertial energy Ee immediately after the internal combustion engine 1 is completely exploded, the above-described problems do not occur, and the reduction of the fuel adhering to the wall surface and the early stage of the exhaust purification device 9 can be achieved. It becomes possible to aim at activity. Further, since the excessive increase in the engine speed is reduced by executing the large-scale EGR process, it is possible to reduce the increase in vibration and noise due to the excessive increase in the engine speed.

As a method for determining the time when the internal combustion engine 1 has completely exploded, a method for determining that the internal combustion engine 1 has completed the complete explosion on condition that the inertial energy Ee of the internal combustion engine 1 has exceeded a predetermined value can be exemplified. As the predetermined value at that time, inertia energy (hereinafter referred to as “target inertia energy”) Ebase when the engine speed has converged to the target idle speed can be used. The target inertia energy Ebase may be obtained experimentally in advance.

  By the way, the amount of EGR gas introduced into the internal combustion engine 1 during the operation period of the EGR valve 51 varies depending on the flow rate of the EGR gas. That is, the amount of EGR gas introduced into the internal combustion engine 1 during the operation period of the EGR valve 51 increases as the flow rate of the EGR gas increases.

  For this reason, when the ECU 21 performs a large amount of EGR processing without considering the flow rate of the EGR gas, a situation may occur where the EGR gas amount exceeds the specified EGR gas amount EGRtrg when the inertial energy Ee is equal to or less than the target inertial energy Ebase.

  For example, when the ECU 21 terminates the large-scale EGR process, if an instruction signal is output from the ECU 21 to the EGR valve 51 triggered by a decrease in the inertia energy Ee below the target inertia energy Ebase, the inertia energy Ee becomes the target inertia. A period in which the EGR gas amount becomes larger than the prescribed EGR gas amount EGRtrg after the energy Ebase or less is reached.

  On the other hand, in the temperature increase control of this embodiment, according to the flow rate of the EGR gas, the execution time of the large-scale EGR process (that is, the instruction to change the EGR gas amount from the peak EGR gas amount EGRmax to the specified EGR gas amount EGRtrg). The time when the signal is output from the ECU 21) is changed.

  Specifically, the execution start timing and the execution end timing of the large-scale EGR process are determined when the inertial energy Ee becomes equal to the determination reference value Ecr. The determination reference value Ecr is a value (= Ebase + α) obtained by adding a predetermined amount α to the target inertial energy Ebase.

  The predetermined amount α is increased or decreased according to the flow rate of the EGR gas. Since the flow rate of EGR gas increases as the EGR passage differential pressure increases, the predetermined amount α may be set to a larger value as the EGR passage differential pressure ΔP increases as shown in FIG.

  FIG. 5 is a diagram illustrating an example of the execution time of the large-scale EGR process. In FIG. 5, the determination reference value Ecr1 (= Ecr + α1) at the execution start time (t1 in FIG. 5) of the large-scale EGR process is different from the determination reference value Ecr2 (= Ecr + α2) at the execution end time (t2 in FIG. 5). However, immediately after the complete explosion of the internal combustion engine 1 (when the engine speed exceeds the target idle speed) and the EGR passage pressure difference ΔP is in a transient state, the predetermined amount α is set accordingly. Because it changes.

  When the execution time of the large-scale EGR processing is determined in this way, the EGR gas amount can be returned to the specified EGR gas amount EGRtrg or less before the inertial energy Ee becomes equal to or less than the target inertia energy Ebase.

  Next, the execution procedure of the temperature increase control in the present embodiment will be described along the flowchart of FIG. FIG. 6 is a flowchart showing a temperature increase control routine in this embodiment. The temperature increase control routine is stored in advance in the ROM of the ECU 21 and is periodically executed by the ECU 21.

  In the temperature increase control routine, the ECU 21 first determines in S101 whether or not the internal combustion engine 1 is in the starting period. As this determination method, for example, a method of using a flag that is set to “0” at the start of start of the internal combustion engine 1 (at the start of cranking) and rewritten to “1” when the start of the internal combustion engine 1 is completed is exemplified. be able to.

If a negative determination is made in S101, the ECU 21 ends the execution of this routine. On the other hand, when a positive determination is made in S101, the ECU 21 proceeds to S102.

  In S102, the ECU 21 calculates a target idle speed. Specifically, the ECU 21 calculates the target idle speed based on the measured value (cooling water temperature thw) of the water temperature sensor 20 and the map shown in FIG. In FIG. 7, the target idle speed is fixed to a constant value in a region where the coolant temperature thw is equal to or higher than the predetermined temperature thw1 (warm-up completion region). On the other hand, in the region where the coolant temperature thw is lower than the predetermined temperature thw1 (warm-up operation region), the target idle speed is set higher as the coolant temperature thw is lower. The predetermined temperature thw1 is a cooling water temperature at which it can be considered that the internal combustion engine 1 has been warmed up.

  Here, returning to FIG. 6, in S103, the ECU 21 calculates the target inertia energy Ebase based on the target idle speed determined in S102. The relationship between the target idle speed and the target inertia energy Ebase may be obtained experimentally in advance.

  In S104, the ECU 21 calculates the peak EGR gas amount EGRmax. The peak EGR gas amount EGRmax changes according to the combustion stability of the air-fuel mixture. Since the combustion stability of the air-fuel mixture changes according to the temperature in the cylinder 2, the peak EGR gas amount EGRmax may be calculated using the temperature in the cylinder 2 as a parameter. At that time, since the temperature in the cylinder 2 correlates with the coolant temperature thw, the ECU 21 is based on a map (for example, see FIG. 8) that defines the relationship between the coolant temperature thw and the peak EGR gas amount EGRmax. The peak EGR gas amount EGRmax may be calculated.

  In S105, the ECU 21 calculates a predetermined amount (hereinafter referred to as “first predetermined amount”) α1 used for determining the execution start timing of the large-scale EGR process. Specifically, the ECU 21 first calculates the EGR passage differential pressure ΔP by subtracting the measured value of the intake pressure sensor 7 from the measured value of the exhaust pressure sensor 10. Subsequently, the ECU 21 calculates the first predetermined amount α1 based on the EGR passage pressure difference ΔP and the map shown in FIG.

In S <b> 106, the ECU 21 calculates the current inertial energy Ee of the internal combustion engine 1. The inertial energy Ee can be calculated based on the following equation.
F = 1/2 * I * ω

  In the above formula, I is the inertial mass of the movable part of the internal combustion engine 1, and ω is the angular velocity of the crankshaft 18.

  In S107, the ECU 21 has the inertia energy Ee calculated in S106 equal to or greater than the sum of the target inertia energy Ebase calculated in S103 and the first predetermined amount α1 calculated in S105 (= Ebase + α1 = Ecr1). It is determined whether or not.

  If a negative determination is made in S107 (Ee <Ecr1), the ECU 21 returns to S105. If an affirmative determination is made in S107 (Ee ≧ Ecr1), the ECU 21 proceeds to S108.

  In S108, the ECU 21 starts execution of the mass EGR process. That is, the ECU 21 outputs an instruction signal to the EGR valve 51 in order to increase the EGR gas amount introduced into the internal combustion engine 1 to the peak EGR gas amount EGRmax determined in S104.

In this routine, the execution start timing of the large-scale EGR process is determined based on the EGR passage pressure difference ΔP. Also good.

  In S109, the ECU 21 calculates a predetermined amount (hereinafter referred to as “second predetermined amount”) α2 used to determine the execution end timing of the large-scale EGR process. Specifically, the ECU 21 first calculates the EGR passage differential pressure ΔP by subtracting the measured value of the intake pressure sensor 7 from the measured value of the exhaust pressure sensor 10. Subsequently, the ECU 21 calculates the second predetermined amount α2 based on the EGR passage differential pressure ΔP and the above-described map of FIG.

  In S110, the ECU 21 calculates the inertial energy Ee of the internal combustion engine 1 at the current time again.

  In S111, the ECU 21 has the inertia energy Ee calculated in S110 equal to or less than the sum of the target inertia energy Ebase determined in S103 and the second predetermined amount α2 calculated in S109 (= Ebase + α2 = Ecr2). It is determined whether or not.

  If a negative determination is made in S111 (Ee> Ecr2), the ECU 21 returns to S109. If an affirmative determination is made in S111 (Ee ≦ Ecr2), the ECU 21 proceeds to S112.

  In S112, the ECU 21 ends the execution of the mass EGR process. That is, the ECU 21 outputs an instruction signal to the EGR valve 51 so as to reduce the EGR gas amount to the specified EGR gas amount EGRtrg.

  In this case, the EGR valve 51 starts to operate before the inertial energy Ee of the internal combustion engine 1 drops below the target inertial energy Ebase. As a result, before the inertial energy Ee of the internal combustion engine 1 drops below the target inertial energy Ebase, the EGR gas amount decreases to the specified EGR gas amount EGRtrg.

  As described above, when the ECU 21 executes the temperature increase control routine of FIG. 6, the acquisition means, control means, and first estimation means according to the present invention are realized.

  Therefore, according to the control system for the internal combustion engine of the present embodiment, the temperature in the cylinder 2 and the intake passage 30 are not accompanied during the start-up period of the internal combustion engine 1 without a significant decrease in torque or excessive stall of the engine speed. The internal temperature and the exhaust temperature can be raised. As a result, the fuel adhering to the wall surface in the intake passage 30 and the cylinder 2 decreases, and the exhaust purification device 9 rapidly rises in temperature, thereby reducing exhaust emissions and early activation of the exhaust purification device 9.

  In this embodiment, the execution time of the large-scale EGR process is changed according to the flow rate of the EGR gas, but the target EGR gas amount at the time of executing the large-scale EGR process may be changed according to the flow rate of the EGR gas. .

  The operation period of the EGR valve 51 becomes longer as the operation amount of the EGR valve 51 increases. For this reason, the operation period of the EGR valve 51 becomes shorter as the target EGR gas amount at the time of execution of the large-scale EGR process decreases.

  Therefore, if the target EGR gas amount at the time of executing the large-scale EGR process is reduced as the flow rate of the EGR gas is increased, the same effect as when the execution timing of the large-scale EGR process is changed according to the flow rate of the EGR gas is obtained. be able to.

<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 example in which the EGR gas amount is adjusted by the external EGR mechanism has been described. In this embodiment, an example in which the EGR gas amount is adjusted by the internal EGR mechanism will be described.

  FIG. 9 is a diagram showing a schematic configuration of an internal combustion engine control system in the present embodiment. In FIG. 9, the same components as those in the first embodiment are denoted by the same reference numerals.

  A variable valve mechanism 120 for changing the rotational phase of the intake camshaft 13 relative to the crankshaft 18 is attached to the intake camshaft 13 of the internal combustion engine 1 shown in FIG.

  In the internal combustion engine 1 configured as described above, EGR gas can be introduced into the internal combustion engine 1 using the variable valve mechanism 120.

  For example, the ECU 21 increases the valve overlap period of the intake valve 11 and the exhaust valve 12 by controlling the variable valve mechanism 120 to advance the valve opening timing of the intake valve 11.

  When the valve overlap period of the intake valve 11 and the exhaust valve 12 increases, a part of the burned gas in the cylinder 2 once flows back to the intake port 3 and then is re-inhaled into the cylinder 2. The burned gas re-inhaled into the cylinder 2 acts as EGR gas at the time of combustion in the next cycle.

  According to the above method, the EGR gas amount of the internal combustion engine 1 can be changed immediately. However, since the operation speed of the variable valve mechanism 120 is not stable during the start-up period of the internal combustion engine 1, it is preferable to adjust the execution time of the large-scale EGR process according to the operation speed of the variable valve mechanism 120.

  If the ECU 21 executes a large amount of EGR processing without considering the operating speed of the variable valve mechanism 120, a situation may occur in which the EGR gas amount exceeds the specified EGR gas amount EGRtrg when the inertial energy Ee is equal to or less than the target inertial energy Ebase.

  In particular, when the ECU 20 ends the mass EGR process, if an instruction signal is output from the ECU 20 to the variable valve mechanism 120 triggered by a decrease in the inertia energy Ee below the target inertia energy Ebase, the inertia energy Ee is A period in which the EGR gas amount becomes less than the specified EGR gas amount EGRtrg after the target inertial energy Ebase or less is reached.

  On the other hand, in the temperature increase control of this embodiment, the execution time of the large-scale EGR process is changed according to the operating speed of the variable valve mechanism 120.

  Specifically, as shown in FIG. 10, the execution end time of the large-scale EGR process is set to a time (t3 in FIG. 10) when the inertial energy Ee becomes equal to or less than the determination reference value Ecr. The determination reference value Ecr value is a value obtained by adding a predetermined amount β to the target inertial energy Ebase (= Ebase + β), and the predetermined amount β is increased or decreased according to the operating speed of the variable valve mechanism 120.

The operating speed of the variable valve mechanism 120 can be estimated by the following method. That is, when the variable valve mechanism 120 is a mechanism driven by hydraulic pressure, the operating speed of the variable valve mechanism 120 becomes lower (slower) as the oil temperature becomes lower, as shown in FIG. The higher the temperature, the higher (faster). When the variable valve mechanism 120 is a mechanism driven by an electric motor, the operating speed of the variable valve mechanism 120 becomes lower (slower) as the battery voltage becomes lower, as shown in FIG. The higher the battery voltage, the higher (faster).

  Therefore, the predetermined amount β used for determining the execution timing of the large-scale EGR process becomes larger as the operation speed of the variable valve mechanism 120 estimated based on FIG. 11 or FIG. It is preferable to set a smaller value as the speed increases (see FIG. 13).

  This means that the determination reference value Ecr becomes larger as the operation speed of the variable valve mechanism 120 becomes lower, and the determination reference value Ecr becomes smaller as the operation speed of the variable valve mechanism 120 becomes higher.

  As a result, the execution end timing of the mass EGR processing is earlier as the operation speed of the variable valve mechanism 120 is lower, and is later as the operation speed of the variable valve mechanism 120 is higher.

  When the execution end timing of the large-scale EGR process is adjusted in this way, the EGR gas amount can be returned to the specified EGR gas amount EGRtrg or less before the inertial energy Ee becomes equal to or less than the target inertia energy Ebase.

  In the example shown in FIG. 10, the execution start timing of the large-scale EGR process is fixed at a timing when the inertia energy Ee exceeds the target inertia energy Ebase. It may be changed using

  However, it is preferable that the execution start time of the large-scale EGR process is set as early as long as the inertial energy Ee exceeds the target inertial energy Ebase. Therefore, in the present embodiment, the execution start time of the large-scale EGR process is fixed to the time when the inertia energy Ee exceeds the target inertia energy Ebase.

  In the present embodiment, the predetermined amount β is determined using the operating speed of the variable valve mechanism 120 as a parameter, but may be determined using the oil temperature or the battery voltage as a parameter. That is, the predetermined amount β may be set to a larger value as the oil temperature or the battery voltage becomes lower, and may be set to a smaller value as the oil temperature or the battery voltage becomes higher.

  Next, the execution procedure of the temperature increase control in the present embodiment will be described along the flowchart of FIG. FIG. 14 is a flowchart showing a temperature increase control routine in this embodiment. In FIG. 14, the same reference numerals are assigned to the same processes as those in the temperature raising control routine of the first embodiment described above.

  In the temperature increase control routine of FIG. 14, when the ECU 21 calculates the peak EGR gas amount EGRmax in S104, the process proceeds to S201. In S201, the ECU 21 calculates the inertial energy Ee at the current time.

  Subsequently, the ECU 21 proceeds to S202, and determines whether or not the inertial energy Ee calculated in S201 is larger than the target inertial energy Ebase calculated in S103. If a negative determination is made in S202, the ECU 21 returns to S201. If an affirmative determination is made in S202, the ECU 21 proceeds to S108.

  In S108, the ECU 21 starts execution of the mass EGR process. Specifically, the ECU 21 controls the variable valve mechanism 120 to advance the valve opening timing of the intake valve 11, whereby the EGR gas amount introduced into the internal combustion engine 1 is the peak EGR calculated in S104. The gas amount is increased to EGRmax.

  When the ECU 21 finishes executing the process of S108, the ECU 21 proceeds to S203. In S203, the ECU 21 calculates a predetermined amount β used to determine the execution end time of the large-scale EGR process. Specifically, the ECU 21 calculates the operating speed of the variable valve mechanism 120 based on the oil temperature or battery voltage and the map of FIG. 11 or FIG. Subsequently, the ECU 21 calculates a predetermined amount β based on the operating speed of the variable valve mechanism 120 and the map of FIG.

  When the ECU 21 finishes executing the process of S203, the ECU 21 proceeds to S110 and calculates the inertial energy Ee at the present time again.

  Subsequently, in S204, the ECU 21 has the inertia energy Ee calculated in S110 equal to or less than the sum of the target inertia energy Ebase calculated in S103 and the predetermined amount β calculated in S203 (= Ebase + β = Ecr). It is determined whether or not.

  If a negative determination is made in S204 (Ee> Ecr), the ECU 21 returns to S203. If an affirmative determination is made in S204 (Ee ≦ Ecr), the ECU 21 proceeds to S112 and ends the execution of the large-volume EGR process. That is, the ECU 21 controls the variable valve mechanism 120 to retard the valve opening timing of the intake valve 11 to the normal valve opening timing.

  In this case, the variable valve mechanism 120 starts to operate before the inertial energy Ee of the internal combustion engine 1 drops below the target inertial energy Ebase. As a result, before the inertial energy Ee of the internal combustion engine 1 drops below the target inertial energy Ebase, the EGR gas amount decreases to the specified EGR gas amount EGRtrg.

  As described above, when the ECU 21 executes the temperature increase control routine of FIG. 14, the acquisition means, control means, and second estimation means according to the present invention are realized.

  Therefore, according to the control system for the internal combustion engine of the present embodiment, the temperature in the cylinder 2 and the intake passage 30 are not accompanied during the start-up period of the internal combustion engine 1 without a significant decrease in torque or excessive stall of the engine speed. The internal temperature and the exhaust temperature can be raised. As a result, the fuel adhering to the wall surface in the intake passage 30 and the cylinder 2 decreases, and the exhaust purification device 9 rapidly rises in temperature, thereby reducing exhaust emission and early activation of the exhaust purification device 9.

  In this embodiment, the execution time of the large-volume EGR process is changed according to the operating speed of the variable valve mechanism 120, but the target EGR at the time of executing the large-volume EGR process is changed according to the operating speed of the variable valve mechanism 120. The gas amount may be changed.

  The operation period of the variable valve mechanism 120 becomes longer as the operation amount of the variable valve mechanism 120 increases. For this reason, the operation period of the variable valve mechanism 120 becomes shorter as the target EGR gas amount at the time of executing the large volume EGR process decreases.

  Therefore, if the target EGR gas amount at the time of executing a large amount of EGR processing is reduced as the operating speed of the variable valve mechanism 120 becomes lower, the increase / decrease in the operating speed due to the oil temperature or the battery voltage is offset by the increase / decrease in the operating amount. Is done. As a result, the same effect as when the execution time of the large-scale EGR process is changed according to the operating speed of the variable valve mechanism 120 can be obtained.

It is a figure which shows schematic structure of the control system of the internal combustion engine in a 1st Example. It is a figure which shows the torque fluctuation | variation with respect to the change of EGR gas amount, and the change of the calorie | heat amount of EGR gas. It is a figure which shows transition of the inertia energy in the starting period of an internal combustion engine. It is a figure which shows the relationship between predetermined amount (alpha) and EGR channel | path differential pressure (DELTA) P. It is a figure which shows the execution time of mass EGR processing in a 1st Example. It is a flowchart which shows the temperature rising control routine in a 1st Example. It is a figure which shows the relationship between target idle speed and cooling water temperature. It is a figure which shows the relationship between peak EGR gas amount and cooling temperature. It is a figure which shows schematic structure of the control system of the internal combustion engine in a 2nd Example. It is a figure which shows the execution time of mass EGR process in a 2nd Example. It is a figure which shows the relationship between the operating speed of a variable valve mechanism, and oil temperature. It is a figure which shows the relationship between the operating speed of a variable valve mechanism, and a battery voltage. It is a figure which shows the relationship between predetermined amount (beta) and the operating speed of a variable valve mechanism. It is a flowchart which shows the temperature rising control routine in a 2nd Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... Cylinder 3 ... Intake port 4 ... Exhaust port 5 ... Fuel injection valve 6 ... Throttle valve 7.・ ・ ・ ・ Intake pressure sensor 8 ・ ・ ・ Air flow meter 9 ・ ・ ・ Exhaust gas purification device 10 ・ ・ ・ Exhaust pressure sensor 11 ・ ・ ・ Intake valve 12 ・ ・ ・ Exhaust valve 13 · Intake side camshaft 14 ··· exhaust side camshaft 15 ··· spark plug 16 ··· piston 17 · · · connecting rod 18 · · · crankshaft 19 · · · crank position sensor 20 .... Water temperature sensor 21 ... ECU
30 ... Air intake passage 40 ... Exhaust passage 50 ... EGR passage 51 ... EGR valve 120 ... Variable valve mechanism

Claims (8)

An EGR mechanism for introducing EGR gas into the cylinder of the internal combustion engine;
Acquisition means for acquiring inertial energy of the internal combustion engine during a start-up period of the internal combustion engine;
Control means for executing large-scale EGR processing for increasing the amount of EGR gas introduced into the cylinder by the EGR mechanism from a prescribed amount when inertial energy acquired by the acquisition means exceeds a predetermined value;
An internal combustion engine control system comprising:   2. The internal combustion engine according to claim 1, wherein the EGR mechanism includes an EGR passage that communicates an exhaust passage and an intake passage of the internal combustion engine, and an EGR valve that changes a cross-sectional area of the EGR passage. Control system. The first estimation means for estimating the flow rate of EGR gas flowing through the EGR passage according to claim 2, further comprising:
The control system for an internal combustion engine, wherein the control means changes an execution timing of the mass EGR processing in accordance with an estimated value of the first estimation means. The first estimation means for estimating the flow rate of EGR gas flowing through the EGR passage according to claim 2, further comprising:
The control system for an internal combustion engine, wherein the control means changes a target EGR gas amount at the time of execution of the large-scale EGR processing according to an estimated value of the first estimation means.   2. The variable valve mechanism according to claim 1, wherein the EGR mechanism changes the opening / closing timing of the intake valve and / or the exhaust valve so that a part of the gas burned in the cylinder of the internal combustion engine remains in the cylinder. An internal combustion engine control system. In Claim 4, further comprising a second estimating means for estimating the operating speed of the variable valve mechanism,
The control system for an internal combustion engine, wherein the control means changes an execution timing of the large-scale EGR process according to an estimated value of the second estimation means. In Claim 4, further comprising a second estimating means for estimating the operating speed of the variable valve mechanism,
The control system for an internal combustion engine, wherein the control means changes a target EGR gas amount at the time of execution of the large-scale EGR processing in accordance with an estimated value of the second estimation means.   8. The internal combustion engine according to claim 1, wherein the predetermined value is equal to or greater than an inertial energy when the rotational speed of the internal combustion engine is converged to a target idle rotational speed. Control system.

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