JP2012132406A - Control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device of an internal combustion engine which can properly control an EGR gas quantity even when an operation state of the internal combustion engine changes.SOLUTION: The control device includes a first exhaust gas recirculating means and a second exhaust gas recirculating means, and when revealing that an absolute value of a deviation in a first recirculating gas quantity to a target quantity of a first recirculating gas quantity is larger than a predetermined threshold value deviation, compensation for the deviation by a second recirculating gas quantity is started, and when revealing that the absolute value of the deviation is the threshold value deviation or less in a period of making the compensation by the second recirculating gas quantity, the compensation by the second recirculating gas quantity is finished. A recirculating gas quantity control means determines a transition pattern of expressing a transition of the second recirculating gas quantity on and after compensation finishing time being time when finishing the compensation by the second recirculating gas quantity based on a first response time length-related parameter related to the response time length of the first recirculating gas quantity, and changes the second recirculating gas quantity on and after the compensation finishing time according to the transition pattern.

Description

  The present invention relates to a control device applied to an internal combustion engine that performs exhaust gas recirculation (so-called external EGR; hereinafter also simply referred to as “EGR”) that recirculates a part of the exhaust gas of the internal combustion engine from the exhaust passage to the intake passage. About.

  Exhaust gases from internal combustion engines such as spark ignition internal combustion engines and diesel engines include harmful substances (hereinafter also referred to as “emissions”) such as nitrogen oxides (NOx) and particulate matter (PM). It is desirable to reduce emissions as much as possible. As a method of reducing the emission amount of emission, for example, a method of reducing the NOx amount by introducing exhaust gas (EGR gas) recirculated from the exhaust passage to the intake passage into the combustion chamber together with fresh air has been proposed.

  On the other hand, as is well known, there is a trade-off relationship between the amount of NOx contained in exhaust gas and the amount of PM. That is, when the internal combustion engine is controlled to decrease the NOx amount (for example, when the EGR gas amount in the above example is increased), the PM amount increases and the internal combustion engine is controlled to decrease the PM amount. Then (for example, when the amount of EGR gas in the above example is decreased), the amount of NOx increases. Therefore, it is desirable to control the internal combustion engine in consideration of both the NOx amount and the PM amount from the viewpoint of comprehensively reducing the emission amount of emissions. For example, in the above example, it is desirable that the EGR gas amount is controlled so that the NOx amount matches a predetermined target amount according to the performance of the exhaust gas purifying catalyst.

  Therefore, one of the conventional control devices (hereinafter also referred to as “conventional device”) includes a supercharger having a compressor and a turbine, and a passage (high pressure EGR) for returning exhaust gas from the upstream side of the turbine to the downstream side of the compressor. A passage), a control valve provided in the high pressure EGR passage, a passage for returning the exhaust gas from the downstream side of the turbine to the upstream side of the compressor, and a control valve provided in the low pressure EGR passage; It is applied to the internal combustion engine provided with. This conventional apparatus adjusts the opening degree of each control valve in accordance with the operating state of the internal combustion engine, whereby the amount of exhaust gas (high pressure EGR gas) passing through the high pressure EGR passage and the exhaust gas passing through the low pressure EGR passage (low pressure EGR). Change the amount of gas). Thus, the conventional apparatus controls the total amount of exhaust gas to be recirculated (that is, the EGR gas amount) (see, for example, Patent Document 1). Thus, conventionally, it has been desired to control the amount of EGR gas so as to coincide with an appropriate amount according to the operating state of the internal combustion engine.

JP 2008-115780 A

  As described above, when exhaust gas recirculation (external EGR) is performed, generally, exhaust gas (EGR gas) moves from the exhaust passage to the intake passage via a predetermined flow path. For this reason, in general, a time length corresponding to the length of the flow path through which the EGR gas travels after the EGR gas amount starts to change toward the predetermined target amount until the EGR gas amount reaches the target amount. Cost. As a result, when the EGR gas amount is changed, a period in which the EGR gas amount (actual amount) does not match the target amount may occur.

  If the difference between the EGR gas amount and its target amount is sufficiently small (for example, if the steady state where the rate of change of the load of the internal combustion engine is sufficiently small is continued), the amount of emission emissions It is considered to be short enough to be ignored from the viewpoint of reducing the amount of light. However, if the difference between the EGR gas amount and its target amount is large (for example, in a transient state where the load of the internal combustion engine increases or decreases), the length of the period has a substantial effect on the emission amount of emissions. It may be long enough to give.

  Thus, if the operating state of the internal combustion engine changes during exhaust gas recirculation (for example, in the transient state), the EGR gas amount may not be controlled appropriately. In this case, there is a possibility that the emission amount is not sufficiently reduced.

  In view of the above problems, an object of the present invention is to provide a control device for an internal combustion engine that can appropriately control the amount of EGR gas even when the operating state of the internal combustion engine changes.

  A control device according to the present invention for achieving the above object is applied to an internal combustion engine having a plurality of means for recirculating exhaust gas from an exhaust passage to an intake passage.

Specifically, the internal combustion engine is
"First exhaust gas recirculation means" for recirculating exhaust gas discharged from the combustion chamber of the internal combustion engine to the exhaust passage from the exhaust passage to the intake passage through the first passage;
"Second exhaust gas recirculation means" for recirculating exhaust gas discharged from the combustion chamber to the exhaust passage from the exhaust passage to the intake passage through a second passage that is "different" from the first passage;
Is provided.

  Thus, in the internal combustion engine to which the control device of the present invention is applied, both the first exhaust gas recirculation means and the second exhaust gas recirculation means can recirculate the exhaust gas from the exhaust passage to the intake passage.

  The control device of the present invention may include three or more exhaust gas recirculation means. When the control device includes three or more exhaust gas recirculation means, the first exhaust gas recirculation means and the second exhaust gas recirculation means may be any two of the three or more exhaust gas recirculation means.

  Further, in the present invention, “refluxing exhaust gas from the exhaust passage to the intake passage” means returning at least a part of exhaust gas discharged from the combustion chamber of the internal combustion engine from the exhaust passage to the intake passage. It does not mean that all exhaust gas is recirculated from the exhaust passage to the intake passage.

The control device of the present invention applied to an internal combustion engine having the above-described configuration is
While changing the “first reflux gas amount” which is the amount of exhaust gas recirculated by the first exhaust gas recirculation means and introduced into the combustion chamber, it is recirculated by the second exhaust gas recirculation means and introduced into the combustion chamber. A recirculation gas amount control means is provided for controlling the total amount of exhaust gas introduced into the combustion chamber by changing the “second recirculation gas amount”, which is the amount of the exhaust gas.

  As the “first recirculation gas amount” and the “second recirculation gas amount”, for example, the amount (mass or volume, etc.) of exhaust gas per unit time introduced into the combustion chamber can be adopted. Further, as the “first recirculation gas amount” and the “second recirculation gas amount”, for example, the same combustion chamber with respect to the total amount of gas introduced into the combustion chamber (amount of mixed gas of fresh air and exhaust gas). The ratio of the amount of exhaust gas contained in the gas introduced into (ie, the EGR rate) can be adopted. Thus, in the control device of the present invention, the “first recirculation gas amount” may be an amount representing the degree of the amount of exhaust gas recirculated by the first exhaust gas recirculation means and introduced into the combustion chamber. The “second recirculation gas amount” may be an amount representing the degree of the amount of exhaust gas recirculated by the second exhaust gas recirculation means and introduced into the combustion chamber.

Hereinafter, the control of the first reflux gas amount and the second reflux gas amount performed by the reflux gas amount control means will be described in the order of the following 1-4.
1. 1. Basic concept of control of reflux gas volume 2. Transition of the second reflux gas amount when the compensation of the reflux gas amount ends. 3. Response time length of reflux gas Others The explanation is continued below.

1. Basic concept of control of recirculation gas amount The recirculation gas amount control means of the present invention takes into account the magnitude of the difference between the first recirculation gas amount (actual amount) and its target amount, and uses the difference as the second recirculation amount. The second reflux gas amount is controlled so as to compensate by the gas amount.

Specifically,
The recirculation gas amount control means sets the deviation when the “absolute value of the deviation of the first recirculation gas amount with respect to the target amount of the first recirculation gas amount” is larger than a predetermined threshold deviation. 2. “Start” to compensate by the amount of reflux gas.
Further, the recirculation gas amount control means is configured to reduce a deviation of the first recirculation gas amount with respect to a target amount of the first recirculation gas amount during a period in which the deviation is compensated by the second recirculation gas amount. When the absolute value is found to be less than or equal to the threshold deviation, “end” the compensation of the deviation by the second reflux gas amount.

  The “target amount” of the first recirculation gas amount is not particularly limited as long as it is set to an appropriate value according to the operating state of the internal combustion engine. For example, as the target amount of the first recirculation gas amount, an amount for reducing the emission emission amount as much as possible (for example, for matching the NOx amount in the exhaust gas with a predetermined target amount) can be adopted. Furthermore, as the target amount of the first recirculation gas amount, for example, an amount for making the total amount of the first recirculation gas amount and the second recirculation gas amount a predetermined target total amount may be employed. In addition, for example, when a target total amount is defined as an amount for reducing the emission emission amount as much as possible, an amount that can achieve the target total amount can be adopted as the target amount of the first reflux gas amount.

  Hereinafter, for convenience, the exhaust gas recirculated by the first exhaust gas recirculation means is also referred to as “first recirculation gas”, and the exhaust gas recirculated by the second exhaust gas recirculation means is also referred to as “second recirculation gas”.

  The first reflux gas has a predetermined composition, density, viscosity, and the like, and the first reflux gas is refluxed through the first passage. Therefore, it takes a predetermined length of time for the first recirculation gas to move (return from the exhaust passage to the intake passage). Therefore, when the first recirculated gas amount is changed, a predetermined time length is required from when the first recirculated gas amount starts to be changed until the exhaust gas having the changed first recirculated gas amount is introduced into the combustion chamber. It takes a long time. Therefore, when the first recirculation gas amount is changed, the predetermined time length after the first recirculation gas amount (actual amount) does not coincide with the target amount (that is, after the first recirculation gas amount starts to be changed). Period of time) may occur. In particular, when the difference between the first recirculation gas amount and the target amount is large (for example, in the transient state), the length of the “period in which the first recirculation gas amount and the target amount do not match” is the emission emission. May be long enough to have a substantial effect on the amount.

  Therefore, when the difference between the first recirculation gas amount and the target amount (that is, the absolute value of the deviation) is larger than the threshold deviation, the recirculation gas amount control means of the present invention calculates the deviation by the second recirculation gas amount. To compensate.

  Specifically, when the absolute value of the deviation is larger than the threshold deviation at a predetermined time point (hereinafter, also referred to as “first time point” for convenience) (for example, when the state of the internal combustion engine is in a transient state) ), Compensation by the second reflux gas amount is “started”. For example, if the first recirculation gas amount is less than the target amount at the first time point (that is, if the first recirculation gas amount is insufficient), the second recirculation gas amount is increased, and the first recirculation gas amount is the target amount. If it is greater than the amount (ie, if the first reflux gas amount is excessive), the second reflux gas amount is reduced. Then, the absolute value of the deviation becomes equal to or less than the threshold deviation at a time point after the compensation by the second recirculation gas amount is continued for a predetermined time length (hereinafter also referred to as “second time point” for convenience). In the case (for example, when the state of the internal combustion engine approaches a steady state through a transient state), the compensation by the second recirculation gas amount is “finished”. Note that, during the period in which the compensation by the second recirculation gas amount is performed, the first recirculation gas amount may or may not be changed toward the target amount.

  From the viewpoint of performing compensation by the second recirculation gas amount as described above, the “threshold deviation” is set. That is, the “threshold deviation” of the first recirculation gas amount is “the length of the period during which the first recirculation gas amount and the target amount do not match” if the deviation of the first recirculation gas amount is equal to or less than the threshold deviation. It is not particularly limited as long as it is set to an appropriate value that can be determined to be short enough to be ignored in terms of appropriately controlling the amount of one reflux gas. As the threshold deviation, for example, the configuration of the internal combustion engine to which the control device is applied, the characteristics of the exhaust gas (composition, density, viscosity, etc.), the first reflux gas amount changed from the time when the first reflux gas amount starts to change An appropriate value can be adopted in consideration of the length of time required until the exhaust gas is introduced into the combustion chamber, the accuracy of control of the EGR gas amount required for the control device, and the allowable emission emission amount. The threshold deviation may be a value greater than zero or zero.

  The degree of compensation by the second recirculation gas amount (for example, the amount of increase or decrease of the second recirculation gas amount) is an amount (for example, insufficient) that can appropriately compensate for the deviation of the first recirculation gas amount. The amount is not particularly limited as long as it is an amount that compensates for the amount or an amount that compensates for the excess amount.

  As described above, in the internal combustion engine, both the first exhaust gas recirculation means and the second exhaust gas recirculation means can recirculate the exhaust gas from the exhaust passage to the intake passage. Therefore, when the absolute value of the deviation of the first recirculation gas amount is larger than the threshold deviation, the total amount of the first recirculation gas amount and the second recirculation gas amount is obtained by compensating the deviation with the second recirculation gas amount. 2 The total amount when the first recirculation gas amount matches the target amount can be made closer to the total amount than when the recirculation gas amount is not increased or decreased.

Therefore, the control device of the present invention appropriately controls the total amount of the first reflux gas amount and the second reflux gas amount (that is, the EGR gas amount) even during the period in which the first reflux gas amount is changed. can do. Thereby, the control device of the present invention can appropriately control the amount of EGR gas even when the operating state of the internal combustion engine changes (for example, even in the transient state described above).
The above is the basic concept of the control of the reflux gas amount in the present invention.

2. Transition of the second recirculation gas amount when the compensation of the recirculation gas amount is completed As described above, the recirculation gas amount control means determines that the absolute value of the deviation of the first recirculation gas amount is larger than the threshold deviation (that is, the above-mentioned Compensation by the amount of the second recirculation gas is started (at the first time point), and the compensation is terminated when the absolute value of the deviation of the first recirculation gas is equal to or less than the threshold deviation (that is, at the second time point). In other words, the EGR gas is changed by changing the “second recirculation gas amount (or both the second recirculation gas amount and the first recirculation gas amount)” during the period in which the compensation by the second recirculation gas amount is performed. After the amount (total amount) is controlled and the compensation is completed, the “first reflux gas amount” is changed to control the EGR gas amount (total amount). Hereinafter, such a change in the type of the recirculation gas (first recirculation gas and / or second recirculation gas) for controlling the amount of EGR gas is also referred to as “switching of recirculation gas”.

  When the compensation by the second recirculation gas amount is “finished”, the EGR gas amount may not be appropriately controlled unless the “recirculation gas switching” is performed smoothly. For example, when the change of the first recirculation gas amount is started when the compensation by the second recirculation gas amount ends, the exhaust gas of the first recirculation gas amount changed from the time when the first recirculation gas amount starts to be changed. At the time point before introduction into the combustion chamber, the first recirculation gas amount does not match the target amount. As a result, the amount of EGR gas at the time immediately before the switching of the reflux gas is different from the amount of EGR gas at the time immediately after the switching has a substantial influence on the emission amount of emissions. There is a possibility that. That is, when the reflux gas is switched, the EGR gas amount may fluctuate considerably.

Therefore, in the control device of the present invention, when compensation by the second recirculation gas amount ends (that is, after the second time point), the second recirculation gas amount is changed according to a predetermined “transition pattern”. Specifically, the reflux gas amount control means is:
“It is related to a first response time length that is a time length required from the time when the first recirculated gas amount starts to be changed to the time when the exhaust gas having the changed first recirculated gas amount is introduced into the combustion chamber. “Transition pattern” representing a transition of the second reflux gas amount after the compensation end time, which is a time point when the compensation of the deviation is completed by the second reflux gas amount based on the “first response time length related parameter” And the second recirculation gas amount is changed after the end of compensation according to the transition pattern.

  As the “first response time length related parameter”, for example, the response time constant of the first recirculation gas amount when the first recirculation gas amount is changed, and the deviation of the first recirculation gas amount at the second time point is large. The length of the flow path through which the first recirculation gas travels, the internal combustion engine member existing on the flow path of the first recirculation gas, the pressure loss generated in the flow path of the first recirculation gas, the characteristics of the exhaust gas (composition, density and One or more of parameters such as viscosity) and the difference between the pressure of the gas present in the exhaust passage and the pressure of the gas present in the intake passage may be employed.

  The “transition pattern” may be “an increase or decrease pattern of the second reflux gas amount that can suppress fluctuations in the total amount after the second time point (that is, when the reflux gas is switched)”. There is no particular limitation. For example, the transition pattern is determined based on a model (map) determined in consideration of the first response time length-related parameter, such as “the increase or decrease of the second recirculation gas amount, the time The relationship between the course and the “course” can be adopted. Furthermore, as the “relationship between the increase or decrease of the second recirculation gas amount and the passage of time”, for example, “the increase or decrease of the second recirculation gas amount with respect to the passage of time from the second time point” is represented. “Profile”, “a function in which the elapsed time length from the second time point is an input value and the increase or decrease in the second reflux gas amount is the output value”, and “increase in the second reflux gas amount The combination of the target value for the minute or the reduced amount and the length of time for which the increased or decreased amount of the second recirculation gas amount is matched with the target value. The above-mentioned “relationship between the increment or decrement of the second recirculation gas amount and the passage of time” may include “setting the second recirculation gas amount to zero at the second time point”.

If the second reflux gas amount is changed according to the transition pattern after the second time point, the change in the EGR gas amount when such a change is made is compared with the same change when such a change is not made. Smaller. Thus, in the control device of the present invention, when the compensation by the second recirculation gas amount is completed (when the recirculation gas is switched), the second recirculation gas amount is changed according to the transition pattern, Furthermore, the amount of EGR gas can be controlled appropriately.
The above is the transition of the second reflux gas amount when the compensation of the reflux gas amount in the present invention is completed.

3. By the way, as described above, the “first response time length” is required to introduce the changed amount of the first reflux gas into the combustion chamber. Similarly, a “second response time length” is required from the time when the second recirculation gas amount starts to be changed to the time when the exhaust gas having the changed second recirculation gas amount is introduced into the combustion chamber.

  Here, it is preferable that the second response time length is shorter than the first response time length. Thereby, the circulating gas amount control means can more quickly compensate for the deviation of the first circulating gas amount.

  The “second response time length” is, for example, the response time constant of the second reflux gas amount when the second reflux gas amount is changed, the length of the flow path through which the second reflux gas moves, Internal combustion engine members present on the recirculation gas flow path, pressure loss generated in the second recirculation gas flow path, exhaust gas characteristics (composition, density, viscosity, etc.), and gas pressure and intake air present in the exhaust passage It depends on one or more of the differences from the pressure of the gas present in the passage.

  Even if the second response time length is not shorter than the first response time length, the deviation of the first circulating gas amount is at least partially compensated. That is, even in this case, the circulating gas amount control means can make the deviation of the first circulating gas amount smaller than “the same deviation when compensation by the second circulating gas amount is not performed”.

4). Others Several aspects of the control device of the present invention are listed below.

First, during the period in which compensation by the second recirculation gas amount is performed, as described above, the first recirculation gas amount may or may not be changed toward the target amount. Therefore, for example, as one aspect of the control device of the present invention,
The recirculation gas amount control means performs compensation when the deviation of the first recirculation gas amount with respect to the target amount of the first recirculation gas amount is larger than the threshold deviation (that is, compensation by the second recirculation gas amount). In some cases, the first reflux gas amount may not be changed.

Furthermore, in the control device of the present invention, as described above, the transition pattern of the second reflux gas amount is determined based on the first response time length related parameter. In another aspect of the invention,
As the first response time length-related parameter, a response time constant of the first recirculation gas amount when the first recirculation gas amount changes can be adopted.

As described above, the target amount of the first recirculation gas amount may be set to an appropriate value according to the operating state of the internal combustion engine. Therefore, for example, in another aspect of the control device of the present invention,
The target amount of the first recirculation gas amount is a first oxygen concentration related parameter related to the oxygen concentration of exhaust gas (first recirculation gas) recirculated by the first exhaust gas recirculation means, and a target amount of the total amount. It may be configured to be determined based on at least one of the deviation of the total amount with respect to the target total amount.

  Of course, the target amount of the first recirculation gas amount is not limited to at least one of the first oxygen concentration related parameter and the deviation of the total amount, but includes a plurality of parameters including at least one of them and other predetermined parameters. It may be determined based on.

Further, the first oxygen concentration related parameter may be the oxygen concentration itself of the first recirculation gas or the oxygen concentration of the mixed gas of the first recirculation gas and the fresh air in the intake passage. Therefore, for example, in another aspect of the control device of the present invention,
As the first oxygen concentration related parameter, the gas in the intake passage (ie, the first recirculation gas and the fresh air) in the vicinity of the connection portion downstream of the connection portion between the first passage and the intake passage. The oxygen concentration of the mixed gas) can be employed.

  In addition, in the control device of the present invention, a specific method for changing the first reflux gas amount and the second reflux gas amount is not particularly limited. For example, the first exhaust gas recirculation means may be configured to have a first control valve that changes the amount of exhaust gas passing through the first passage. Furthermore, the second exhaust gas recirculation means may be configured to have a second control valve that changes the amount of exhaust gas passing through the second passage.

  In the above configuration, for example, when the first control valve is instructed to change the opening, the first circulating gas amount is changed (for example, changed toward the target amount). Further, for example, when the second control valve is instructed to change its opening, the second circulating gas amount is changed (for example, increased or decreased so as to compensate for the deviation of the first reflux gas amount). )

1 is a schematic view of an internal combustion engine to which a control device according to an embodiment of the present invention is applied. It is a schematic flowchart which shows the outline | summary of the action | operation of the control apparatus which concerns on embodiment of this invention. It is the schematic which shows the relationship between the engine speed which the control apparatus which concerns on embodiment of this invention employs, the target amount of fuel injection quantity, and EGR mode. 6 is a time chart showing the relationship between the low-pressure EGR valve opening degree and the oxygen concentration of the gas in the exhaust manifold in a representative engine. It is a time chart which shows transition of the deviation of EGR gas amount, low pressure EGR gas amount, high pressure EGR valve opening, low pressure EGR valve opening, and transition pattern in a reference example. It is a time chart which shows transition of an EGR gas amount, a deviation of a low pressure EGR gas amount, a high pressure EGR valve opening, a low pressure EGR valve opening, and a transition pattern in an embodiment of the present invention. It is a time chart which shows transition of the deviation of EGR gas amount, low pressure EGR gas amount, high pressure EGR valve opening, low pressure EGR valve opening, and transition pattern in a reference example. It is a time chart which shows transition of an EGR gas amount, a deviation of a low pressure EGR gas amount, a high pressure EGR valve opening, a low pressure EGR valve opening, and a transition pattern in an embodiment of the present invention. It is the flowchart which showed the routine which CPU of the control apparatus which concerns on embodiment of this invention performs. It is the flowchart which showed the routine which CPU of the control apparatus which concerns on embodiment of this invention performs.

<Outline of device>
FIG. 1 shows a schematic configuration of a system in which a control device according to an embodiment of the present invention (hereinafter also referred to as “implementation device”) is applied to an internal combustion engine 10. The internal combustion engine 10 is a four-cylinder diesel engine having four cylinders, a first cylinder to a fourth cylinder. Hereinafter, for convenience, the “internal combustion engine 10” is also simply referred to as “engine 10”.

  As shown in FIG. 1, the engine 10 includes an engine main body 20 including a fuel injection system, an intake system 30 for introducing air into the engine main body 20, and gas discharged from the engine main body 20 to the outside of the engine 10. An exhaust system 40 for performing the operation, a supercharger 50 for compressing air that is driven by the energy of the exhaust gas and introduced into the engine body 20, and an EGR device 60 for recirculating the exhaust gas from the exhaust system 40 to the intake system 30; It has.

  The engine body 20 includes a cylinder head 21 to which an intake system 30 and an exhaust system 40 are connected. The cylinder head 21 has a plurality of fuel injection devices (for example, solenoid injectors) 22 provided at the upper part of each cylinder so as to correspond to each cylinder. Each of the fuel injection devices 22 is connected to a fuel tank (not shown), and supplies fuel into the combustion chamber of each cylinder in response to an instruction signal from the electric control device 90.

  The intake system 30 includes an intake port (not shown) formed in the cylinder head 21, an intake manifold 31 communicated with each cylinder via the intake port, an intake pipe 32 connected to a collective portion on the upstream side of the intake manifold 31, A first throttle valve 33 provided in the pipe 32 and capable of changing an opening area in the intake pipe 32; a throttle valve actuator 33a for rotating the first throttle valve 33 according to an instruction signal from the electric control device 90; An intercooler 34 provided in the intake pipe 32 on the upstream side of the first throttle valve 33, a supercharging device 50 provided on the upstream side of the intercooler 34 (details of this device will be described later), and a supercharging device. The intake pipe 32 is provided on the upstream side of 50 and the opening area in the intake pipe 32 is changed. A second throttle valve 35, a throttle valve actuator 35 a that rotates the second throttle valve 35 in response to an instruction signal from the electric control device 90, and an intake pipe 32 provided upstream of the second throttle valve 35. An air cleaner 36. The intake manifold 31 and the intake pipe 32 constitute an intake passage.

  The exhaust system 40 includes an exhaust port (not shown) formed in the cylinder head 21, an exhaust manifold 41 communicated with each cylinder via the exhaust port, an exhaust pipe 42 connected to a downstream portion of the exhaust manifold 41, an exhaust A supercharging device 50 (details of this device will be described later) provided in the pipe 42, and an exhaust gas purifying catalyst (for example, DPNR) provided in the exhaust pipe 42 downstream of the supercharging device 50 43. The exhaust manifold 41 and the exhaust pipe 42 constitute an exhaust passage.

  The supercharger 50 includes a compressor 51 provided in the intake passage (intake pipe 32) and a turbine 52 provided in the exhaust passage (exhaust pipe 42). The compressor 51 and the turbine 52 are connected so as to be coaxially rotatable by a rotor shaft (not shown). Therefore, when the turbine 52 is rotated by the energy of the exhaust gas, the compressor 51 also rotates. Thereby, the air introduced into the compressor 51 is compressed using the energy of the exhaust gas (that is, supercharging is performed).

  The EGR device 60 includes a low pressure EGR mechanism 62, which is a “first means” for recirculating exhaust gas from the exhaust system 40 (exhaust passage) to the intake system 30 (intake passage), and “second” for recirculating exhaust gas in the same manner. It has a high pressure EGR mechanism 61 which is means. The names “high pressure EGR mechanism” and “low pressure EGR mechanism” are derived from the fact that the pressure of exhaust gas recirculated by the “high pressure” EGR mechanism is higher than the pressure of exhaust gas recirculated by the “low pressure” EGR mechanism. To do.

  One end of the high-pressure EGR mechanism 61 is connected to the exhaust pipe 42 (point A in the figure) upstream of the turbine 52 and the other end of the intake pipe 32 (point B in the figure) downstream of the compressor 51. A high pressure EGR passage 61a connected to the high pressure EGR passage 61a, a high pressure EGR gas cooling device 61b provided in the high pressure EGR passage 61a, and a high pressure EGR control valve provided in the high pressure EGR passage 61a and capable of changing an opening area of the high pressure EGR passage 61a 61c. The high-pressure EGR control valve 61c changes the amount of exhaust gas (high-pressure EGR gas amount) that passes through the high-pressure EGR passage 61a and circulates from the exhaust passage to the intake passage in accordance with an instruction signal from the electric control device 90. ing. This instruction signal is a signal for instructing the opening degree of the high pressure EGR control valve 61c (high pressure EGR valve opening degree) Ohplv.

  One end of the low pressure EGR mechanism 62 is connected to the exhaust pipe 42 (point C in the figure) downstream of the turbine 52, and the other end of the intake pipe 32 (point D in the figure) upstream of the compressor 51. A low pressure EGR passage 62a connected to the low pressure EGR passage 62a, a low pressure EGR gas cooling device 62b provided in the low pressure EGR passage 62a, and a low pressure EGR control valve provided in the low pressure EGR passage 62a and capable of changing an opening area of the low pressure EGR passage 62a 62c. The low-pressure EGR control valve 62c changes the amount of exhaust gas (low-pressure EGR gas amount) that passes through the low-pressure EGR passage 62a and circulates from the exhaust passage to the intake passage according to an instruction signal from the electric control device 90. ing. This instruction signal is a signal for instructing the opening degree of the low pressure EGR control valve 62c (low pressure EGR valve opening degree) Olplv.

  Thus, the high pressure EGR mechanism 61 is configured to recirculate the exhaust gas through the exhaust gas path (high pressure EGR path 61 a) different from the exhaust gas path (low pressure EGR path 62 a) in the low pressure EGR mechanism 62. In other words, in the engine 10, “both” of the high pressure EGR mechanism 61 and the low pressure EGR mechanism 62 can recirculate exhaust gas from the exhaust passage to the intake passage. Needless to say, “both” of the high pressure EGR mechanism 61 and the low pressure EGR mechanism 62 do not always need to recirculate the exhaust gas from the exhaust passage to the intake passage, and the high pressure EGR mechanism 61 and the “Only one” of the low pressure EGR mechanism 62 may recirculate the exhaust gas from the exhaust passage to the intake passage.

  Hereinafter, for convenience, the total amount of the high-pressure EGR gas amount and the low-pressure EGR gas amount is also simply referred to as “EGR gas amount”.

  Further, an accelerator pedal 71 for inputting an acceleration request and a required torque to the engine 10 is provided outside the engine 10. The accelerator pedal 71 is operated by an operator of the engine 10.

  In addition, the implementation device includes a plurality of sensors. Specifically, the implementation apparatus includes an intake air amount sensor 81, a first oxygen concentration sensor 82, an intake air temperature sensor 83, a supercharging pressure sensor 84, a crank position sensor 85, a second oxygen concentration sensor 86, and an accelerator opening. A degree sensor 87 is provided.

  The intake air amount sensor 81 is provided in the intake pipe 32 upstream of the second throttle valve 35. The intake air amount sensor 81 outputs a signal corresponding to the intake air amount that is the mass flow rate of air flowing through the intake pipe 32 (that is, the mass of air sucked into the engine 10). Based on this signal, the intake air amount is acquired.

  The first oxygen concentration sensor 82 is provided on the downstream side of the position (point D in the figure) where the low pressure EGR passage 62a and the intake pipe 32 are connected and in the vicinity of the same position. The first oxygen concentration sensor 82 is a known limiting current type oxygen concentration sensor. The first oxygen concentration sensor 82 outputs a signal corresponding to the oxygen concentration of the mixed gas of low-pressure EGR gas and fresh air. Based on this signal, the oxygen concentration of the mixed gas is acquired.

  The intake air temperature sensor 83 is provided in the intake pipe 32 on the downstream side of the intercooler 34. The intake air temperature sensor 83 outputs a signal corresponding to the intake air temperature that is the temperature of the air flowing through the intake pipe 32. Based on this signal, the intake air temperature is acquired.

  The supercharging pressure sensor 84 is provided in the intake pipe 32 downstream of the compressor 51 and downstream of the first throttle valve 33. The supercharging pressure sensor 84 outputs a signal representing the pressure of the gas in the intake pipe 32 (that is, the pressure of the gas compressed by the supercharging device 50). Based on this signal, the supercharging pressure is acquired.

  The crank position sensor 85 is provided in the vicinity of a crankshaft (not shown). The crank position sensor 85 outputs a signal having a pulse corresponding to the rotation of the crankshaft. Based on this signal, the number of revolutions of the crankshaft per unit time (hereinafter simply referred to as “engine speed NE”) is acquired.

  The second oxygen concentration sensor 86 is provided in the exhaust pipe 42 upstream of the catalyst 43. The second oxygen concentration sensor 86 is a known limiting current type oxygen concentration sensor. The second oxygen concentration sensor 86 outputs a signal corresponding to the oxygen concentration of the exhaust gas introduced into the catalyst 43. Based on this signal, the oxygen concentration of the exhaust gas (in other words, the air-fuel ratio) is acquired.

  The accelerator opening sensor 87 is provided in the vicinity of the accelerator pedal 71. The accelerator opening sensor 87 outputs a signal corresponding to the opening of the accelerator pedal 71. Based on this signal, the accelerator pedal opening degree Accp is acquired.

  Further, the implementation apparatus includes an electric control device 90. The electric control device 90 includes a CPU 91, a ROM 92 in which a program executed by the CPU 91, a table (map), constants, and the like are stored in advance, a RAM 93 in which the CPU 91 temporarily stores data as necessary, and data when the power is turned on. And a backup RAM 94 that holds the stored data while the power is shut off, and an interface 95 including an AD converter. The CPU 91, ROM 92, RAM 93, backup RAM 94, and interface 95 are connected to each other via a bus.

  The interface 95 is connected to the plurality of sensors described above and transmits signals output from the sensors to the CPU 91. Further, the interface 95 is connected to the fuel injection device 22, the actuators 33a and 35a, the high pressure EGR control valve 61c, the low pressure EGR control valve 62c, and the like, and sends an instruction signal to them according to an instruction from the CPU 91. .

<Outline of device operation>
Hereinafter, an outline of the operation of the implementation apparatus applied to the engine 10 will be described with reference to FIG. FIG. 2 is a “schematic flowchart” showing an outline of the operation of the implementation apparatus.

  When the low-pressure EGR gas amount is changed, the execution device matches the target amount (target total amount) with the EGR gas amount (that is, the total amount of the low-pressure EGR gas amount and the high-pressure EGR gas amount) as quickly as possible. “Compensation by high-pressure EGR gas amount” is performed as necessary. Furthermore, when the compensation by the high-pressure EGR gas amount is “finished”, the implementation apparatus changes the high-pressure EGR gas amount according to a predetermined “transition pattern” in order to suppress the fluctuation of the EGR gas amount as much as possible.

  Specifically, the implementation apparatus determines a target amount of the low pressure EGR gas amount in step 210 of FIG. This target amount is determined based on, for example, the operating state of the engine 10. Next, in step 220, the execution apparatus determines the absolute value of the deviation of the actual amount of the low-pressure EGR gas amount from the target amount of the low-pressure EGR gas amount (hereinafter also simply referred to as “deviation of the low-pressure EGR gas amount”). It is determined whether or not it is equal to or less than the threshold deviation. When the absolute value of the deviation is equal to or smaller than the threshold deviation (for example, when the state of the engine 10 is a steady state, or when the engine 10 is in a transient state but close to a steady state), the execution apparatus goes to step 230. Advancing and changing the low pressure EGR gas amount toward the target amount. In this case, the “compensation based on the high-pressure EGR gas amount” described above is not performed.

  On the other hand, when it is found that the absolute value of the deviation of the low pressure EGR gas amount is larger than the threshold deviation (for example, when the state of the engine 10 is in a transient state), the execution apparatus proceeds to step 240 and The deviation is compensated by the amount of high-pressure EGR gas. This compensation is performed, for example, by increasing or decreasing the high pressure EGR gas amount according to the deviation of the low pressure EGR gas amount. In this case, since the process of step 230 is not executed, the low-pressure EGR gas amount is not changed.

  Then, when it is found that the absolute value of the deviation of the first recirculation gas amount is equal to or less than the threshold deviation during the period when the compensation by the high pressure EGR gas amount is performed (for example, the state of the engine 10 goes through a transient state). When approaching a steady state), the execution apparatus proceeds to Step 230 via Step 200 to Step 220 and starts changing the low-pressure EGR gas amount toward the target amount. In this case, since the process of step 240 is not executed, the compensation by the high pressure EGR gas amount is terminated. Thus, in this case, the compensation by the high pressure EGR gas amount is finished and the low pressure EGR gas amount starts to be changed. Hereinafter, such a change in the type of the reflux gas for controlling the amount of EGR gas is also referred to as “switching of the reflux gas”.

Next, since the current time is immediately after the compensation by the high pressure EGR gas amount is completed, the implementation apparatus proceeds to step 260 via step 250 to determine a “transition pattern” of the high pressure EGR gas amount. This transition pattern is, for example, the length of time required from when the low-pressure EGR gas amount starts to be changed until the exhaust gas with the changed low-pressure EGR gas amount is introduced into the combustion chamber (hereinafter referred to as “response of low-pressure EGR gas amount”). Also referred to as “time length”)). In step 270, the execution apparatus changes the high-pressure EGR gas amount according to the transition pattern.
The above is the outline of the operation of the implementation apparatus.

<Determining EGR mode>
Next, an operation mode of the EGR device 60 in the implementation apparatus (hereinafter also referred to as “EGR mode”) and a determination method thereof will be described with reference to FIG. FIG. 3 is a schematic diagram showing a map for determining the EGR mode.

  The execution device is configured to use the high pressure EGR mechanism 61 and the low pressure EGR mechanism 62 properly based on the operating state of the engine 10. Specifically, the implementation apparatus preferentially uses the high-pressure EGR mechanism 61 when the load on the engine 10 is small. Thereby, for example, it is possible to improve the ignitability of the fuel by recirculating exhaust gas having high energy (exhaust gas before passing through the turbine 52). On the other hand, the implementation device preferentially uses the low pressure EGR mechanism 62 when the load on the engine 10 is large. Thereby, for example, even when a sufficient amount of EGR gas cannot be recirculated by the high pressure EGR mechanism 61 due to an increase in the supercharging pressure (pressure of the gas downstream of the compressor 51), A sufficient amount of EGR gas can be refluxed by the low pressure EGR mechanism 62. The implementation apparatus uses both the high pressure EGR mechanism 61 and the low pressure EGR mechanism 62 when the load on the engine 10 is medium.

  More specifically, the execution device adjusts the amount of high-pressure EGR gas by adjusting the opening of the first throttle valve 33 and the opening of the high-pressure EGR control valve 61c based on the operating state of the engine 10. Further, the execution device adjusts the amount of low-pressure EGR gas by adjusting the opening of the second throttle valve 35 and the opening of the low-pressure EGR control valve 62c based on the operating state of the engine 10. In other words, the execution device is configured to allow the high-pressure EGR control valve 61c, the low-pressure EGR control valve 62c, the first throttle valve 33, and the second throttle valve 35 (hereinafter, referred to as “exhaust gas”) to circulate an appropriate amount of exhaust gas from the exhaust passage to the intake passage. (Also collectively referred to as “each control valve”).

  In order to execute the control described above, the execution apparatus divides the operating state of the engine 10 into three regions and determines the operating state of each control valve suitable for each of the three regions. The operating state of each control valve is determined based on the EGR mode.

  More specifically, the implementation apparatus is shown in FIG. 3 as “EGR mode table MapEM (NE, Qtgt) in which the relationship among the engine rotational speed NE, the target value Qtgt of the fuel injection amount, and the EGR mode EM is predetermined. Is stored in the ROM 92. “HPL” shown in FIG. 3 represents that the high pressure EGR mechanism 61 is preferentially operated (HPL mode), and “HPL + LPL” is that both the high pressure EGR mechanism 61 and the low pressure EGR mechanism 62 are operated ( MPL mode), and “LPL” represents that the low pressure EGR mechanism 62 is operated preferentially (LPL mode).

The implementation apparatus determines the EGR mode by applying the actual engine speed NE and the target value Qtgt of the fuel injection amount to the EGR mode table MapEM (NE, Qtgt). And the implementation apparatus operates each control valve according to the determined EGR mode. That is, the implementation apparatus controls the opening degree of each control valve.
The above is the EGR mode and its determination method in the implementation apparatus.

<Response time length of low pressure EGR gas amount>
The implementation apparatus employs a response time constant when the low-pressure EGR gas amount is changed as one of the parameters related to the “response time length of the low-pressure EGR gas amount”. This response time constant is acquired based on the results of experiments conducted using a typical internal combustion engine (hereinafter also referred to as “representative engine”) having the same configuration as the engine 10. Hereinafter, an example of a method for obtaining the response time constant will be described with reference to the time chart shown in FIG.

  FIG. 4 is a time chart showing the relationship between the opening degree of the low pressure EGR control valve 62c (low pressure EGR valve opening degree) and the oxygen concentration of the gas in the exhaust manifold 41. In FIG. 4, in order to facilitate understanding, a waveform of each value is schematically shown. At time t0 in this time chart, standard operation suitable for obtaining the response time constant of the low pressure EGR gas amount is performed. In the example shown in FIG. 4, the low pressure EGR valve opening at time t0 is a predetermined opening between the minimum value (fully closed) and the maximum value (fully opened), and the oxygen concentration at time t0 is the predetermined opening. It is assumed that it is a predetermined value according to the degree.

  At time t1, control for acquiring a response time constant is started. More specifically, the implementation apparatus controls the low pressure EGR control valve 62c so that the low pressure EGR valve opening becomes the maximum value (fully opened) at time t1. At this time, the oxygen concentration starts to decrease after a predetermined time length related to the configuration of the representative engine and the characteristics of the exhaust gas has elapsed since the low-pressure EGR valve opening has reached the maximum value (fully opened). That is, the oxygen concentration starts to decrease at time t2 after a predetermined time length has elapsed from time t1. Furthermore, it takes a predetermined length of time from when the oxygen concentration starts to decrease until the oxygen concentration reaches a value (minimum value Ox1) corresponding to the opening degree (fully opened). Therefore, the oxygen concentration reaches the minimum value Ox1 after a predetermined time length has elapsed from time t2.

  At time t3 after a predetermined length of time has elapsed from the time when the oxygen concentration reaches the minimum value Ox1, the implementation apparatus sets the low pressure EGR control valve 62c so that the low pressure EGR valve opening becomes the minimum value (fully closed). To control. Thus, the oxygen concentration starts to increase at time t4 after a predetermined time length has elapsed from time t3. Furthermore, a predetermined time length is required from when the oxygen concentration starts to increase until the oxygen concentration reaches the maximum value Ox2 (in order to increase by the change amount A from the minimum value Ox1 to the maximum value Ox2). Therefore, the oxygen concentration reaches the maximum value Ox2 after a predetermined time length has elapsed from time t4. Here, the implementation apparatus states that “the length of time until the oxygen concentration reaches a value (Ox1 + γ · A) corresponding to a predetermined ratio γ (for example, γ = 0.632) of the change amount A (that is, FIG. 4). Time length from time t4 to time t5) ”is acquired as the response time constant TCup on the increasing side.

  Next, at a time t6 after a predetermined length of time has elapsed from the time when the oxygen concentration reaches the maximum value Ox2, the implementation device operates the low pressure EGR control valve so that the low pressure EGR valve opening becomes the maximum value (fully opened). 62c is controlled. Thus, the oxygen concentration starts to decrease at time t7 after a predetermined time length has elapsed from time t6. Furthermore, a predetermined time length is required from when the oxygen concentration starts to decrease until the oxygen concentration reaches the minimum value Ox1 (in order to decrease by the change amount A). Therefore, the oxygen concentration reaches the minimum value Ox1 after a predetermined time length has elapsed from time t7. Here, the implementation apparatus states that “the length of time until the oxygen concentration reaches a value (Ox2−γ · A) corresponding to a predetermined ratio γ of the variation A (for example, γ = 0.632 as described above). (That is, the time length from time t7 to time t8 in FIG. 4) ”is acquired as the response time constant TCdown on the decreasing side.

The execution apparatus acquires the average value of the response time constant TCup on the increase side and the response time constant TCdown on the decrease side acquired as described above as the response time constant TC of the low pressure EGR gas amount. The response time constant TC is stored in the ROM 92.
The above is the method for obtaining the response time constant of the low pressure EGR gas amount in the present invention.

<Control method of EGR gas amount>
As described above, the implementation apparatus controls the low-pressure EGR gas amount according to the operating state of the engine 10, and takes into account the deviation of the low-pressure EGR gas amount, the response time length of the low-pressure EGR gas amount, and the like. Control the amount. Hereinafter, such a control method for the low-pressure EGR gas amount and the high-pressure EGR gas amount will be described separately for the case where the low-pressure EGR gas amount “increases” and the case where the low-pressure EGR gas amount “decreases”. .

1. When the low-pressure EGR gas amount increases In the following, a time chart shown in FIGS. 5 and 6 shows a control method of the EGR gas amount (that is, the total amount) when the low-pressure EGR gas amount “increases” toward a predetermined target amount. Will be described with reference to FIG. FIG. 5 is a time chart showing an example of the case where “the high-pressure EGR gas amount is not changed according to the transition pattern” when the recirculation gas is switched, and FIG. It is a time chart which shows the example in the case of "the high pressure EGR gas amount is changed." That is, FIG. 5 is a time chart showing control performed by a reference example for comparison with the implementation apparatus, and FIG. 6 is a time chart showing control performed by the implementation apparatus. In FIG. 5 and FIG. 6, the actual waveform of each value is schematically shown for easy understanding.

  FIG. 5 shows the EGR gas amount (high pressure EGR gas amount HPL, low pressure EGR gas amount LPL, and their total amount HPL + LPL), and the deviation ΔLPL of the actual amount of low pressure EGR gas amount from the target amount of low pressure EGR gas amount The opening pattern of the high-pressure EGR control valve 61c (high-pressure EGR valve opening degree), the opening degree of the low-pressure EGR control valve 62c (low-pressure EGR valve opening degree), and the transition pattern for increasing or decreasing the high-pressure EGR gas amount HPL It is a time chart showing the relationship of.

  In the example shown in FIG. 5, the operating state of the engine 10 changes at time t1, and the target amount LPLtgt of the low pressure EGR gas amount LPL is determined so as to increase the low pressure EGR gas amount LPL. On the other hand, in this example, for easy understanding, the target amount HPLtgt of the high pressure EGR gas amount HPL does not change even when the operating state of the engine 10 changes (that is, the target amount HPLtgt of the high pressure EGR gas amount HPL does not change). , And maintained at the target amount before the operating state is changed.)

  In this example, the absolute value of the deviation ΔLPL (= LPL−LPLtgt) of the low pressure EGR gas amount LPL with respect to the target amount LPLtgt at time t1 is larger than the predetermined threshold deviation ΔLPLth. Therefore, the implementation apparatus does not change the low pressure EGR gas amount LPL at time t1 (that is, maintains the amount before the time t1), and starts compensating for the deviation ΔLPL by the high pressure EGR gas amount HPL.

  Specifically, since the target amount LPLtgt at time t1 is larger than the low pressure EGR gas amount LPL at time t1, deviation ΔLPL at time t1 is a negative value. In other words, the low pressure EGR gas amount LPL is insufficient at the time t1. Therefore, the execution apparatus gives an instruction to “increase the high-pressure EGR gas amount HPL by an amount capable of compensating for the deviation ΔLPL” to the high-pressure EGR control valve 61c at time t1. In response to this instruction, at time t1, the high-pressure EGR valve opening degree Ohplv increases by a predetermined opening degree difference.

  Hereinafter, for the sake of convenience, the change amount of the high pressure EGR gas amount HPL that can compensate for the deviation ΔLPL is also referred to as “compensation amount”, and the change amount of the high pressure EGR valve opening Ohplv for changing the high pressure EGR gas amount HPL by the compensation amount. Is also referred to as “compensation opening difference”.

  Here, as shown in FIG. 1, the exhaust gas (high pressure EGR gas) that has passed through the high pressure EGR control valve 61c reaches the combustion chamber via the point B and the intake manifold 31 in the figure in this order. Therefore, after the high-pressure EGR valve opening Ohplv increases by the compensation opening difference, it takes a very long time until the high-pressure EGR gas amount HPL corresponding to the increased opening reaches the combustion chamber ( That is, no response time length is required. Therefore, at the time immediately after time t1, the high pressure EGR gas amount HPL is increased by the compensation amount.

  As time elapses after the compensation by the high pressure EGR gas amount HPL is started, the absolute value of the deviation ΔLPL gradually decreases (in other words, approaches zero). This is because, for example, when the operating state of the engine 10 changes (time t1), the fuel injection amount, the engine rotational speed, and the like greatly vary from predetermined steady values (that is, in a transient state). Although the target amount LPLtgt is set to a large value in relation, the fuel injection amount, the engine speed, etc. gradually approach the steady values as time elapses from the simultaneous point (time t1) (that is, the steady state is reached). This is because the target amount LPLtgt is set to a small value in relation to the approaching). In addition, this is because, for example, the target amount LPLtgt is gradually set to a small value in connection with an increase in the ratio of the inert gas in the exhaust gas due to compensation by the high pressure EGR gas amount HPL. caused by.

  Actually, after the compensation by the high pressure EGR gas amount HPL is started, the total amount HPL + LPL, the compensation amount of the high pressure EGR gas amount HPL, and the target amount LPLtgt of the low pressure EGR gas amount LPL are decreased. It is considered that the compensation opening degree difference of the high pressure EGR valve opening degree Ohplv may also decrease. However, in this example, it is assumed that the total amount HPL + LPL, the compensation amount of the high-pressure EGR gas amount HPL, and the compensation opening difference of the high-pressure EGR valve opening Ohplv do not change even after time t1 for easy understanding. To do.

  Referring to FIG. 5 again, the deviation ΔLPL matches the threshold deviation ΔLPLth at time t2 after a predetermined length of time has elapsed from time t1. Therefore, at time t2, the implementation apparatus ends the compensation by the high pressure EGR gas amount HPL and starts changing the low pressure EGR gas amount LPL toward the target amount LPLtgt. Specifically, at time t2, the execution apparatus gives an instruction to “set the compensation amount of the high pressure EGR gas to zero” to the high pressure EGR control valve 61c and “increases the low pressure EGR gas amount LPL to the target amount LPLtgt”. An “instruction” is given to the low pressure EGR control valve 62c. In response to these instructions, at time t2, the high-pressure EGR valve opening Ohplv returns to the opening before the compensation is performed, and the low-pressure EGR valve opening increases by a predetermined opening difference (the target opening Olplvtgt). Match.)

  As a result, the high pressure EGR gas amount HPL is reduced to the amount before the compensation is started immediately after time t2. As described above, in this example, the high-pressure EGR gas amount HPL is not changed according to the transition pattern when the recirculation gas is switched. Therefore, for convenience, in FIG. 5, the transition pattern is maintained in a state where neither increase nor decrease is performed (that is, a state where the increase and decrease are zero with respect to the high pressure EGR gas amount HPL before the compensation is started). Yes.

  On the other hand, as shown in FIG. 1, the exhaust gas (low pressure EGR gas) that has passed through the low pressure EGR control valve 62c is a point D in the figure, a compressor 51, an intercooler 34, a first throttle valve 33, a point B in the figure, And, it reaches the combustion chamber via the intake manifold 31 in this order. Therefore, after the low-pressure EGR valve opening Olplv has increased by the opening difference, a considerable amount of time is required until the low-pressure EGR gas amount LPL corresponding to the increased opening reaches the combustion chamber. (Response time length) is required. In this example, the response time length of the low pressure EGR gas amount LPL is longer than the response time length of the high pressure EGR gas amount HPL. Therefore, the low pressure EGR gas amount LPL does not coincide with the target amount LPLtgt at time t2, and starts increasing toward the target amount LPLtgt at time t3 after a predetermined time length has elapsed from time t2, and from time t3 This also coincides with the target amount LPLtgt at a later time t4. Hereinafter, the difference between the low pressure EGR gas amount LPL and the target amount LPLtgt during the period from time t2 to time t4 is also referred to as “response delay-induced deviation”.

  As a result, as shown in FIG. 5, in the period from time t2 to time t4, the total amount HPL + LPL does not coincide with the target total amount SUMTgt. That is, during this period, the amount of EGR gas varies.

  In order to suppress such fluctuations in the EGR gas amount as much as possible, when the compensation by the high-pressure EGR gas amount HPL is completed (that is, when the recirculation gas is switched), the implementation apparatus increases the pressure according to a predetermined transition pattern. EGR gas amount HPL is changed.

  A case where the high pressure EGR gas amount HPL is changed according to the transition pattern will be described with reference to FIG. FIG. 6 is a time chart showing the relationship between the EGR gas amount, the deviation ΔLPL, the high pressure EGR valve opening, the low pressure EGR valve opening, and the transition pattern, as in FIG. 5.

  In the example shown in FIG. 6, similarly to the above, at time t1, compensation of the deviation ΔLPL by the high pressure EGR gas amount HPL is started. Further, at time t2, the compensation by the high pressure EGR gas amount HPL is completed, and the low pressure EGR gas amount LPL starts increasing toward the target amount LPLtgt.

  At this time t2, the implementation apparatus determines the “transition pattern” of the high-pressure EGR gas amount HPL. In this example, as shown in FIG. 6, the transition pattern is “in the period from time t2 to time t4, the high pressure EGR gas amount HPL is increased by an amount corresponding to the response delay caused by the low pressure EGR gas amount LPL. " Then, the execution device changes the high pressure EGR gas amount HPL according to the transition pattern after time t2.

  The transition pattern is obtained by, for example, using a model designed in consideration of the response time constant of the low pressure EGR gas amount, for example, a predetermined parameter (for example, a difference between the low pressure EGR gas amount LPL and the target amount LPLtgt at time t2). Can be determined by applying.

  If the high pressure EGR gas amount HPL is changed according to the above transition pattern after time t2, the high pressure EGR gas amount HPL is increased from time t2 to time t4. ) Is supplemented. As a result, the total amount HPL + LPL matches the target total amount SUMTgt even during the period from time t2 to time t4. That is, the fluctuation of the EGR gas amount during this period is suppressed.

2. When the Low Pressure EGR Gas Amount is Reduced Next, a method for controlling the EGR gas amount when the low pressure EGR gas amount “decreases” toward the target amount will be described with reference to the time charts shown in FIGS. FIG. 7 is a time chart showing an example of the case where the amount of high-pressure EGR gas is not changed according to the transition pattern when the reflux gas is switched, and FIG. It is a time chart which shows the example in the case of "the high pressure EGR gas amount is changed." 7 is a time chart showing the control performed by the reference example, and FIG. 8 is a time chart showing the control performed by the implementation apparatus. In FIGS. 7 and 8, the actual waveform of each value is schematically shown for easy understanding.

  FIG. 7 is a time chart showing the relationship between the EGR gas amount, the deviation ΔLPL, the high pressure EGR valve opening, the low pressure EGR valve opening, and the transition pattern, as in FIGS. 5 and 6.

  In the example shown in FIG. 7, the operating state of the engine 10 changes at time t1, and the target amount LPLtgt of the low pressure EGR gas amount LPL is determined so as to reduce the low pressure EGR gas amount LPL. On the other hand, in this example as well, it is assumed that the target amount HPLtgt of the high pressure EGR gas amount HPL does not change even if the operating condition of the engine 10 changes so as to facilitate understanding.

  In this example, the absolute value of the deviation ΔLPL (= LPL−LPLtgt) of the low pressure EGR gas amount LPL with respect to the target amount LPLtgt at time t1 is larger than the predetermined threshold deviation ΔLPLth. Therefore, the implementation apparatus does not change the low pressure EGR gas amount LPL at time t1, and starts compensating for the deviation ΔLPL by the high pressure EGR gas amount HPL.

  Specifically, since the target amount LPLtgt at time t1 is smaller than the low pressure EGR gas amount LPL at time t1, the deviation ΔLPL at time t1 is a positive value. In other words, the low pressure EGR gas amount LPL is excessive at time t1. Therefore, the execution apparatus gives an instruction to the high pressure EGR control valve 61c to “decrease the high pressure EGR gas amount HPL by an amount that can compensate for the deviation ΔLPL” (ie, a correction amount) at time t1. In response to this instruction, at time t1, the high-pressure EGR valve opening degree Ohplv decreases by a predetermined opening degree difference (that is, a compensation opening degree difference). As in the case of “the low pressure EGR gas amount LPL increases”, the high pressure EGR gas amount HPL is decreased by the correction amount at the time immediately after time t1.

  As time elapses after the compensation by the high pressure EGR gas amount HPL is started, the absolute value of the deviation ΔLPL gradually decreases for the same reason as described above. Then, at time t2 after a predetermined time length has elapsed from time t1, the deviation ΔLPL of the low pressure EGR gas amount LPL matches the threshold deviation ΔLPLth. Therefore, at time t2, the implementation apparatus ends the compensation by the high pressure EGR gas amount HPL and starts changing the low pressure EGR gas amount LPL toward the target amount LPLtgt. Specifically, at time t2, the execution device gives an instruction to “set the compensation amount of the high pressure EGR gas to zero” to the high pressure EGR control valve 61c and “decreases the low pressure EGR gas amount LPL to the target amount LPLtgt”. An “instruction” is given to the low pressure EGR control valve 62c. In response to these instructions, at time t2, the high pressure EGR valve opening Ohplv returns to the opening before the compensation is performed, and the low pressure EGR valve opening Olplv decreases by a predetermined opening difference.

  As a result, the high pressure EGR gas amount HPL coincides with the amount before the compensation is started immediately after time t2. On the other hand, the low pressure EGR gas amount LPL does not coincide with the target amount LPLtgt at time t2, starts to decrease toward the target amount LPLtgt at time t3 after a predetermined time length has elapsed from time t2, and starts from time t3. This also coincides with the target amount LPLtgt at a later time t4. That is, a response delay caused deviation occurs.

  As a result, during the period from time t2 to time t4, the total amount HPL + LPL does not match the target total amount SUMTgt. That is, during this period, the amount of EGR gas varies.

  Therefore, when the compensation by the high pressure EGR gas amount HPL is completed, the implementation apparatus changes the high pressure EGR gas amount HPL according to a predetermined transition pattern. A case where the high-pressure EGR gas amount HPL is changed according to the transition pattern will be described with reference to FIG. FIG. 8 is a time chart showing the relationship between the EGR gas amount, the deviation ΔLPL, the high pressure EGR valve opening, the low pressure EGR valve opening, and the transition pattern, as in FIG.

  In the example shown in FIG. 8, as described above, at time t1, compensation of the deviation ΔLPL by the high pressure EGR gas amount HPL is started. Further, at time t2, the compensation by the high pressure EGR gas amount HPL is completed, and the low pressure EGR gas amount LPL starts to decrease toward the target amount LPLtgt.

  At this time t2, the implementation apparatus determines the “transition pattern” of the high-pressure EGR gas amount HPL. In this example, as shown in FIG. 8, the transition pattern is “in the period from time t2 to time t4, the high pressure EGR gas amount HPL is decreased by an amount corresponding to the response delay caused by the low pressure EGR gas amount LPL. " Then, the execution device changes the high pressure EGR gas amount HPL according to the transition pattern after time t2. The transition pattern can be determined based on a predetermined model or the like as in the case where “the low pressure EGR gas amount LPL is increased”.

  If the high pressure EGR gas amount HPL is changed according to the above transition pattern after time t2, the high pressure EGR gas amount HPL is reduced from time t2 to time t4. ) Is offset. As a result, the total amount HPL + LPL matches the target total amount SUMTgt even during the period from time t2 to time t4. That is, the fluctuation of the EGR gas amount during this period is suppressed.

In the above description with reference to FIGS. 5 to 8, as described above, when the operating state of the engine 10 changes, only the target amount LPLtgt of the low pressure EGR gas amount LPL changes and the target amount of the high pressure EGR gas amount HPL changes. HPLtgt is assumed not to change. On the other hand, in practice, when the operating state of the engine 10 changes, both the target amount LPLtgt of the low pressure EGR gas amount LPL and the target amount HPLtgt of the high pressure EGR gas amount HPL may change. However, as understood from the above description, even if the target amount HPLtgt of the high pressure EGR gas amount HPL changes, if the transition pattern is determined in consideration of the change of the target amount HPLtgt, the low pressure EGR gas It is possible to appropriately compensate for the deviation ΔLPL of the amount LPL and the response delay-induced deviation of the low pressure EGR gas amount LPL (see, for example, the routine of FIG. 10 described later).
The above is the EGR gas amount control method in the implementation apparatus.

<Actual operation>
Hereinafter, the actual operation of the implementation apparatus will be described.
In the implementation apparatus, the CPU 91 is configured to repeatedly execute each routine shown in the flowcharts of FIGS. 9 and 10 at predetermined timings.

  The CPU 91 uses the compensation execution flag XHPL in these routines. When the value of the compensation execution flag XHPL is “1”, the compensation execution flag XHPL indicates that compensation by the high pressure EGR gas amount HPL is being performed (or immediately after being performed). On the other hand, when the compensation execution flag XHPL and its value is “0”, it indicates that compensation by the high pressure EGR gas amount HPL is not performed (or not immediately after it is performed).

Hereinafter, each routine will be described in detail.
First, it is assumed that the current value of the compensation execution flag XHPL is set to “0”. Hereinafter, for the sake of convenience, this assumption is also referred to as “initial setting assumption”.

  Each time the CPU 91 matches the crank angle of an arbitrary cylinder with a predetermined crank angle before the intake stroke (for example, 90 ° crank angle before exhaust top dead center) θf, the “fuel injection control routine” shown in the flowchart of FIG. "Is repeatedly executed. The CPU 91 determines the target amount Qtgt of the fuel injection amount by this routine, and causes the fuel injection device 22 to inject the fuel of the target amount Qtgt into the cylinder. Hereinafter, the cylinder before the intake stroke whose crank angle coincides with the crank angle θf is also referred to as “fuel injection cylinder”.

  Specifically, the CPU 91 starts processing from step 900 in FIG. 9 at a predetermined timing and proceeds to step 910. In step 910, the CPU 91 sets a predetermined fuel injection amount table MapQtgt (NE, Accp) to “a relationship between the engine speed NE, the accelerator pedal opening Accp, and the fuel injection amount target amount Qtgt”. The target amount Qtgt of the fuel injection amount is determined by applying the engine speed NE and the accelerator pedal opening degree Accp at the present time.

  In the fuel injection amount table MapQtgt (NE, Accp), the target amount Qtgt of the fuel injection amount is determined so as to be an appropriate value in consideration of the output required for the engine 10, the fuel consumption, the emission amount of emission, and the like.

  Next, the CPU 91 proceeds to step 920. In step 920, the CPU 91 gives an instruction to inject fuel of the target amount Qtgt to the fuel injection device 22 provided in the fuel injection cylinder. Thereby, the target amount Qtgt of fuel is injected into the fuel injection cylinder. Thereafter, the CPU 91 proceeds to step 995 to end the present routine tentatively.

  Further, the CPU 91 repeatedly executes the “EGR amount control routine” shown by the flowchart in FIG. 10 every time a predetermined time elapses. By this routine, the CPU 91 considers the operating state of the engine 10, the deviation ΔLPL of the low pressure EGR gas amount LPL, the response delay cause deviation of the low pressure EGR gas amount LPL, and the like, and the low pressure EGR gas amount LPL and the high pressure EGR gas amount. Control HPL.

  Specifically, the CPU 91 starts processing from step 1000 in FIG. 10 at a predetermined timing and proceeds to step 1005. In step 1005, the CPU 91 applies the target engine speed NEt and the target value Qtgt of the fuel injection amount to the EGR mode table MapEM (NE, Qtgt) described above, thereby referring to the EGR mode EM (see FIG. 3). ).

  Next, the CPU 91 proceeds to step 1010. In step 1010, the CPU 91 pre-defines the low pressure EGR valve target opening in which the “relationship between the EGR mode EM, the engine speed NE, the accelerator opening Accp, and the target opening Olplvgt of the low pressure EGR control valve 62 c” is determined. By applying the current EGR mode EM, the engine speed NE, and the accelerator opening Accp to the degree table MapOlplvtgt (EM, NE, Accp), the target opening Olplvgt of the low pressure EGR control valve 62c is determined.

  In the low pressure EGR valve target opening table MapOlplvtgt (EM, NE, Accp), the target opening Olplvtgt is determined so as to be an appropriate value considering the emission amount, the output required for the engine 10, and the like. .

  Next, the CPU 91 proceeds to step 1015. In step 1015, the CPU 91 pre-defines the high-pressure EGR valve target opening in which “the relationship among the EGR mode EM, the engine speed NE, the accelerator opening Accp, and the target opening Ohplvtgt of the high-pressure EGR control valve 61c” is determined. The target opening Ohplvtgt of the high-pressure EGR control valve 61c is determined by applying the current EGR mode EM, the engine speed NE and the accelerator opening Accp to the degree table MapOhplvtgt (EM, NE, Accp).

  In the high pressure EGR valve target opening table MapOhplvtgt (EM, NE, Accp), the target opening Ohplvtgt is determined so as to be an appropriate value in consideration of the emission amount of emissions, the output required for the engine 10, and the like.

  Next, the CPU 91 proceeds to step 1020. In step 1020, the CPU 91 calculates a deviation ΔLPLv of the low pressure EGR valve opening by subtracting the target opening Olplvtgt from the current opening Olplv of the low pressure EGR control valve 62c.

  Next, the CPU 91 proceeds to step 1025. In step 1025, the CPU 91 determines whether or not the absolute value of the deviation ΔLPLv is equal to or smaller than a predetermined threshold deviation ΔLPLvth.

  If the deviation ΔLPLv of the low-pressure EGR valve opening is equal to or less than the threshold deviation ΔLPLvth (for example, if the steady state is maintained), “the low-pressure EGR valve opening Olplv and the target opening Olplvtgt match It is determined so that “the length of the period not to be performed” becomes an appropriate value that can be determined to be short enough to be ignored from the viewpoint of appropriately controlling the amount of EGR gas. Such a threshold deviation ΔLPLvth can be determined by taking into account the configuration of the engine 10 and the characteristics of the exhaust gas.

  If the absolute value of the deviation ΔLPLv at the current time is equal to or smaller than the threshold deviation ΔLPLvth, the CPU 91 determines “Yes” in step 1025 and proceeds to step 1030. In step 1030, the CPU 91 gives an instruction to the low pressure EGR control valve 62c so that the opening degree of the low pressure EGR control valve 62c matches the target opening degree Ollplvgt.

  Next, the CPU 91 proceeds to step 1035. In step 1035, the CPU 91 determines whether or not the value of the compensation execution flag XHPL is “1”. If the initial setting assumption is followed, the current value of the compensation execution flag XHPL is “0”, so the CPU 91 determines “No” in step 1035. Thereafter, the CPU 91 proceeds to step 1095 to end the present routine tentatively.

  As described above, when the absolute value of the deviation ΔLPLv of the low pressure EGR valve opening at the current time is equal to or smaller than the threshold deviation ΔLPLvth, an instruction to make the low pressure EGR valve opening Olplv coincide with the target opening Olplvgt is made at this time. On the other hand, in this case, compensation by the high pressure EGR gas amount HPL is not performed.

  On the other hand, when the absolute value of the deviation ΔLPLv at the current time is larger than the threshold deviation ΔLPLvth (for example, when the engine 10 is in a transient state by changing the EGR mode from the HPL mode to the LPL mode), the CPU 91 In step 1025, it is determined as “No”, and the process proceeds to step 1040. In step 1040, the CPU 91 obtains (updates) the target opening Ohplvtgt by subtracting the deviation ΔLPLv from the target opening Ohplvtgt of the high pressure EGR control valve 61c. That is, if the deviation ΔLPLv is a positive value (the low pressure EGR gas amount is excessive), the target opening Ohplvtgt of the high pressure EGR control valve 61c is decreased, and if the deviation ΔLPLv is a negative value (the low pressure EGR gas amount is insufficient). The target opening degree Ohplvtgt of the high pressure EGR control valve 61c is increased. By updating the target opening Ohplvtgt of the high pressure EGR control valve 61c in this way, the high pressure EGR gas amount HPL corresponding to the updated target opening Ohplvtgt becomes an amount that can compensate for the deviation ΔLPLv.

  Next, the CPU 91 proceeds to step 1045. In step 1045, the CPU 91 gives an instruction to the high-pressure EGR control valve 61c so that the opening degree of the high-pressure EGR control valve 61c matches the updated target opening degree Ohplvtgt. Note that the time point at which the process of step 1045 is executed corresponds to “time t1” in FIGS.

  As a result, as shown in FIGS. 5 to 8, the deviation of the low pressure EGR gas amount LPL in the period from time t1 to time t2 is compensated by the high pressure EGR gas amount HPL.

  Next, the CPU 91 proceeds to step 1050. In step 1050, the CPU 91 stores “1” as the value of the compensation execution flag XHPL. Thereafter, the CPU 91 proceeds to step 1095 to end the present routine tentatively.

  As described above, when the absolute value of the deviation ΔLPLv of the low pressure EGR valve opening at the present time is larger than the threshold deviation ΔLPLvth, the high pressure EGR valve opening is set as “target opening Ohplvtgt (updated to compensate for deviation ΔLPLv”). Is instructed to match. That is, compensation by the high pressure EGR gas amount HPL is performed. In this case, since the process of step 1030 is not executed, the low-pressure EGR valve opening is not changed.

  Thereafter, it is assumed that the deviation ΔLPLv of the low pressure EGR valve opening is equal to or less than the threshold deviation ΔLPLvth during the period in which the compensation by the high pressure EGR gas amount HPL is performed. At this time, when the CPU 91 starts processing from step 1000, the process proceeds to step 1025 via steps 1005 to 1020. According to the above assumption, the CPU 91 determines “Yes” in step 1025 and proceeds to step 1030 to instruct the low pressure EGR control valve 62c to make the opening of the low pressure EGR control valve 62c coincide with the target opening Olplvgt. give. It should be noted that the time point at which the process of step 1030 is executed corresponds to “time t2” in FIGS.

  Thereafter, the CPU 91 proceeds to step 1035. Since the current value of the compensation execution flag XHPL is “1”, the CPU 91 determines “Yes” in step 1035 and proceeds to step 1055.

  In step 1055, the CPU 91 determines that “the target opening Olplvgt of the low pressure EGR control valve 62c, the current opening Olplv of the low pressure EGR control valve 62c, the target opening Ohplvtgt of the high pressure EGR control valve 61c, and the high pressure EGR control valve. Transition pattern table MapTP (Olplvtgt, Olplv, Ohplvtgt, Ohplv, TC) that predetermines the relationship between the current opening degree Ohplv of 61c, the response time constant TC of the low pressure EGR gas amount, and the transition pattern TP (t) In addition, the target opening degree Olplvgt of the low pressure EGR control valve 62c, the opening degree Olplv of the low pressure EGR control valve 62c at the present time, the target opening degree Ohplvtgt of the high pressure EGR control valve 61c, the opening degree Ohplv of the high pressure EGR control valve 61c, and The transition pattern TP (t) is determined by applying the response time constant TC stored in the ROM 92.

  In the transition pattern table MapTP (Olplvtgt, Olplv, Ohplvtgt, Ohplv, TC), the transition pattern TP (t) is an appropriate value that can appropriately compensate for the response delay caused by the low pressure EGR gas amount LPL. It is determined. In the implementation apparatus, the transition pattern TP (t) is determined as “a profile representing an increase or decrease in the high pressure EGR gas amount HPL over time”.

  Next, the CPU 91 proceeds to step 1060. In step 1060, the CPU 91 adds a transition pattern TP (t) to the target opening degree Ohplvtgt of the high pressure EGR control valve 61c, thereby representing a target transition Opplgtgt (t representing the actual transition of the opening degree of the high pressure EGR control valve 61c. ).

  Next, the CPU 91 proceeds to step 1065. In step 1065, the CPU 91 gives an instruction to the high pressure EGR control valve 61c so as to change the opening degree of the high pressure EGR control valve 61c in accordance with the target transition Ohplvtgt (t). Note that the time point at which the process of step 1065 is executed corresponds to “time t2” in FIGS. That is, the process of step 1030 and the process of step 1065 are executed at substantially the same timing.

  Next, the CPU 91 proceeds to step 1070. In step 1070, the CPU 91 stores “0” as the value of the compensation execution flag XHPL. Thereafter, the CPU 91 proceeds to step 1095 to end the present routine tentatively.

  As described above, when the low pressure EGR valve opening degree is changed, the CPU 91 compensates the deviation ΔLPLv by increasing or decreasing the high pressure EGR valve opening degree based on the deviation ΔLPLv of the low pressure EGR valve opening degree ( Step 1045). Further, when the compensation of the deviation ΔLPLv is completed, the CPU 91 compensates for the response delay caused deviation of the low pressure EGR gas amount LPL by changing the high pressure EGR valve opening according to the transition pattern TP (t) (step 1065).

  Thereby, the implementation apparatus can appropriately control the EGR gas amount (total amount HPL + LPL) even during the period in which the low pressure EGR gas amount LPL is changed. Furthermore, the implementation apparatus can appropriately control the EGR gas amount even when the compensation by the high pressure EGR gas amount HPL is terminated (when the reflux gas is switched). As a result, the execution apparatus can appropriately control the amount of EGR gas even when the operating state of the engine 10 changes (for example, even during a period from the transient state to the steady state).

<Summary of Embodiment>
As described with reference to FIGS. 1 to 10, the control device (implementing device) according to the embodiment of the present invention is
A first exhaust gas recirculation means (low pressure EGR mechanism) 62 for recirculating exhaust gas discharged from the combustion chamber of the engine 10 to the exhaust passage 42 from the exhaust passage 42 to the intake passage 32 via a first passage (low pressure EGR passage) 62a; The second exhaust gas recirculation for recirculating the exhaust gas discharged from the combustion chamber to the exhaust passage 42 from the exhaust passage 42 to the intake passage 32 via a second passage (high pressure EGR passage) 61a different from the first passage 62a. The engine 10 is provided with a means (high pressure EGR mechanism) 61.

This implementation device is
The first recirculation gas amount (low pressure EGR gas amount) LPL, which is the amount of the exhaust gas recirculated by the first exhaust gas recirculation means 62 and introduced into the combustion chamber, is changed and recirculated by the second exhaust gas recirculation means 61. By changing the second recirculation gas amount (high pressure EGR gas amount) HPL that is the amount of exhaust gas introduced into the combustion chamber, the recirculation gas amount that controls the total amount of exhaust gas HPL + LPL introduced into the combustion chamber Control means.

Specifically,
The first exhaust gas recirculation means 62 includes a first control valve (low pressure EGR control valve) 62c that changes the amount of exhaust gas passing through the first passage 62a, and the second exhaust gas recirculation means 61 includes the second passage 61a. A second control valve (high pressure EGR control valve) 61c that changes the amount of exhaust gas passing through the cylinder is provided. However, the first exhaust gas recirculation means 62 and the second exhaust gas recirculation means 61 do not necessarily have a control valve, and have some means capable of controlling the first recirculation gas amount LPL and the second recirculation gas amount HPL. It only has to be.

The reflux gas amount control means includes:
When it is found that the absolute value of the deviation ΔLPLv of the first reflux gas amount LPL with respect to the target amount of the first reflux gas amount LPL (for example, the target amount at time t1 in FIG. 6) is larger than a predetermined threshold deviation ΔLPLvth (For example, at time t1 in FIG. 6), the compensation of the deviation ΔLPLv by the second reflux gas amount HPL is started.

Further, the reflux gas amount control means includes:
During the period when the deviation ΔLPLv is compensated by the second reflux gas amount HPL (for example, after time t1 in FIG. 6), the first reflux gas with respect to the target amount of the first reflux gas amount LPL. When the absolute value of the deviation ΔLPLv of the amount LPL is found to be equal to or smaller than the threshold deviation ΔLPLvth (for example, time t2 in FIG. 6), the compensation of the deviation ΔLPLv with the second reflux gas amount HPL is terminated. It ’s like that.

In the implementation device,
The target amount of the first recirculation gas amount LPL is determined based on several parameters related to the operating state of the engine 10 (see step 1010 in FIG. 10). However, the target amount of the first recirculation gas amount LPL is not necessarily determined based on the parameters exemplified in the implementation apparatus. For example, this target amount corresponds to the first oxygen concentration related parameter related to the oxygen concentration of the exhaust gas recirculated by the first exhaust gas recirculation means 62 and the target total amount HPL + LPL which is the target amount of the total amount HPL + LPL. It may be determined based on at least one of the deviation ΔLPLv of the total amount HPL + LPL. That is, the target amount of the first recirculation gas amount LPL may be set to an appropriate value according to the operating state of the internal combustion engine.

  In the implementation apparatus, when the compensation by the second recirculation gas amount HPL described above is completed, the second recirculation gas amount is changed in consideration of the response delay-induced deviation of the first recirculation gas amount LPL.

Specifically, the reflux gas amount control means includes:
The time (for example, time of FIG. 6) when the exhaust gas of the changed first recirculation gas amount (LPL) is introduced into the combustion chamber from the time when the first recirculation gas amount (LPL) starts to change (for example, time t2 in FIG. 6) Based on the first response time length related parameter (see also below) related to the first response time length which is the time length required until t4), the deviation ΔLPLv is compensated by the second reflux gas amount HPL. A transition pattern TP (t) representing a transition of the second recirculation gas amount HPL after a compensation end time (for example, time t2 in FIG. 6), which is a time when the process ends, is determined, and the transition pattern TP (t) Accordingly, the second reflux gas amount HPL is changed after the compensation end point (same as above).

In the implementation device,
As the first response time length related parameter, several parameters including a response time constant TC of the first recirculation gas amount LPL when the first recirculation gas amount LPL is changed are adopted (FIG. 10). (See Step 1055 of the above).

  However, the first response time length-related parameter does not necessarily need to include the response time constant TC of the first recirculation gas amount LPL. For example, as the first response time length related parameter, the first response time length related parameter includes the magnitude of the deviation ΔLPLv of the first recirculation gas amount LPL, the length of the flow path through which the first recirculation gas moves, the first Internal combustion engine members existing on the flow path of the recirculation gas, pressure loss generated in the flow path of the first recirculation gas, exhaust gas characteristics (composition, density, viscosity, etc.), pressure of the gas existing in the exhaust passage and the intake passage One or more of the parameters such as the difference from the pressure of the gas present in the can be employed. Further, for example, as a first response time length-related parameter, oxygen of the gas in the intake passage 32 on the downstream side of the connection portion between the first passage 62a and the intake passage 32 and in the vicinity of the connection portion. The concentration (for example, the output value of the first oxygen concentration sensor 82 in FIG. 1 or the like) may be employed.

  That is, the first response time length-related parameter is the length of time required from the time when the first recirculation gas amount LPL starts to be changed to the time when the exhaust gas having the changed first recirculation gas amount LPL is introduced into the combustion chamber. Any parameter can be used as long as it is related to

By the way, in the implementation device,
Rather than the first response time length, the time required from the time when the second recirculation gas amount HPL starts to be changed to the time when the exhaust gas having the changed second recirculation gas amount HPL is introduced into the combustion chamber. A certain second response time length is short. However, the control device of the present invention can also be applied to an internal combustion engine in which the second response time length is not shorter than the first response time length.

Furthermore, in the implementation device:
When the deviation ΔLPLv of the first recirculation gas amount LPL with respect to the target amount of the first recirculation gas amount LPL is larger than the threshold deviation ΔLPLvth, the first recirculation gas amount LPL is not changed (steps 1025 and 1030 in FIG. 10). See). However, in the control device of the present invention, in this case, the change of the first recirculation gas amount LPL is not necessarily prohibited, and the first recirculation gas amount is compensated during the period when the compensation by the second recirculation gas amount HPL is performed. The LPL may be changed toward the target amount.

<Other aspects>
The present invention is not limited to the above embodiments, and various modifications can be adopted within the scope of the present invention.

  For example, in the implementation apparatus, when the deviation ΔLPLv is larger than the threshold deviation ΔLPLvth, compensation is performed using the high-pressure EGR gas amount (see step 1025 in FIG. 10). However, the control device of the present invention can be configured to perform compensation by the amount of high-pressure EGR gas regardless of the magnitude of the deviation (that is, by setting the threshold deviation to zero).

  Further, for example, the implementation device is applied to the diesel engine 10. However, the control device of the present invention can also be applied to a spark ignition engine.

  DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 32 ... Intake pipe, 42 ... Exhaust pipe, 61 ... High pressure EGR mechanism, 61a ... High pressure EGR passage, 61c ... High pressure EGR control valve, 62 ... Low pressure EGR mechanism, 62a ... Low pressure EGR passage, 62c ... Low pressure EGR Control valve, 90 ... Electronic control unit

Claims (7)

First exhaust gas recirculation means for recirculating exhaust gas discharged from the combustion chamber of the internal combustion engine to the exhaust passage from the exhaust passage to the intake passage through the first passage;
Second exhaust gas recirculation means for recirculating exhaust gas discharged from the combustion chamber to the exhaust passage from the exhaust passage to the intake passage via a second passage different from the first passage;
Applied to an internal combustion engine with
The amount of exhaust gas recirculated by the first exhaust gas recirculation means and the amount of exhaust gas introduced into the combustion chamber is changed, and the exhaust gas recirculated by the second exhaust gas recirculation means and introduced into the combustion chamber is changed. Recirculation gas amount control means for controlling the total amount of exhaust gas introduced into the combustion chamber by changing the amount of the second recirculation gas,
When the absolute value of the deviation of the first recirculation gas amount with respect to the target amount of the first recirculation gas amount is found to be larger than a predetermined threshold deviation, the deviation is compensated by the second recirculation gas amount. And the absolute value of the deviation of the first recirculation gas amount with respect to the target amount of the first recirculation gas amount is not more than the threshold deviation during the period when the deviation is compensated by the second recirculation gas amount. Recirculation gas amount control means for ending compensation of the deviation by the second recirculation gas amount when it is found to be present;
An internal combustion engine control apparatus comprising:
The reflux gas amount control means includes:
A first response time length related to a first response time length which is a time length required from the time when the first recirculation gas amount starts to be changed to the time when the exhaust gas having the changed first recirculation gas amount is introduced into the combustion chamber. Based on one response time length related parameter, a transition pattern representing a transition of the second reflux gas amount after the compensation end time, which is a time point when the compensation of the deviation by the second reflux gas amount is finished, is determined. A control device for an internal combustion engine that changes the second recirculation gas amount after the end of compensation according to the transition pattern. The control device according to claim 1,
The time length required from the time when the second recirculation gas amount starts to be changed to the time when the exhaust gas having the changed second recirculation gas amount is introduced into the combustion chamber is longer than the first response time length. 2. A control device for an internal combustion engine having a short response time length. In the control device according to claim 1 or 2,
The control apparatus for an internal combustion engine, wherein the recirculation gas amount control means does not change the first recirculation gas amount when a deviation of the first recirculation gas amount with respect to a target amount of the first recirculation gas amount is larger than the threshold deviation. . In the control device according to any one of claims 1 to 3,
The control apparatus for an internal combustion engine, wherein a response time constant of the first recirculation gas amount when the first recirculation gas amount is changed is adopted as the first response time length related parameter. In the control device according to claim 1 to claim 4,
The target amount of the first recirculation gas amount is the first oxygen concentration related parameter related to the oxygen concentration of the exhaust gas recirculated by the first exhaust gas recirculation means, and the total amount relative to the target total amount which is the target amount of the total amount. A control device for an internal combustion engine, which is determined based on at least one of the deviations. In the control device according to any one of claims 1 to 5,
As the first oxygen concentration-related parameter, an internal combustion engine in which an oxygen concentration of gas in the intake passage in the vicinity of the connection portion downstream of the connection portion between the first passage and the intake passage is employed. Control device. In the control device according to any one of claims 1 to 6,
The first exhaust gas recirculation means has a first control valve that changes the amount of exhaust gas passing through the first passage, and the second exhaust gas recirculation means is a second that changes the amount of exhaust gas that passes through the second passage. A control device for an internal combustion engine having a control valve.

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