JP2011069262A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device for an internal combustion engine controlling EGR (Exhaust Gas Recirculation) quantity with certain accuracy even when a pressure sensor downstream of an intake throttle valve has a failure. <P>SOLUTION: A learning value of a feedback coefficient of LPL (Low Pressure Loop) throttle valve opening is calculated beforehand. If a target value calculation part detects a failure of the pressure sensor 301 installed downstream of an LPL throttle valve 204, the LPL throttle valve opening is calculated by multiplying target LPL throttle valve opening by the calculated feedback coefficient. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present embodiment relates to a technology of a control device for an internal combustion engine.

There is EGR (Exhaust Gas Recirculation) as a technique for reducing the emission amount of nitrogen oxide (NO _X ) discharged from the engine. In EGR, by returning the exhaust gas to the intake system, the combustion temperature in the combustion chamber can be lowered, combustion of nitrogen in the air-fuel mixture can be prevented, and NO _X generation can be suppressed. Hereinafter, the exhaust gas returned to the intake system is referred to as EGR gas, and the amount of EGR gas is referred to as EGR amount.

The EGR has an LPL (Low Pressure Loop) that returns exhaust gas to the intake system by connecting the exhaust passage downstream of the turbocharger exhaust turbine and the intake passage upstream of the turbocharger compressor through a low pressure EGR passage. ) -EGR (low pressure EGR) is known. Hereinafter, the low pressure EGR passage is referred to as an LPL-EGR passage.
In general, in an internal combustion engine having a supercharger such as a turbocharger, intake pulsation occurs when the rotational speed of the compressor is low, such as during deceleration or when stopped. In LPL-EGR, the amount of EGR gas is controlled by the differential pressure between the upstream and downstream of the LPL-EGR passage. Therefore, when the intake pulsation occurs, the exhaust gas flows backward toward the air flow meter, causing the air flow meter to be contaminated by the exhaust gas.

  In order to solve such a problem, a technique for forcibly driving a supercharger under conditions where intake pulsation occurs is disclosed (for example, see Patent Document 1). In addition, the amount of EGR can be accurately controlled before and after switching between a region where high pressure EGR (HPL (High Pressure Loop) -EGR) and low pressure EGR (LPL-EGR) are used together and a region where only low pressure EGR is used. A technique is disclosed (for example, see Patent Document 2).

JP 2008-261257 A JP 2007-315371 A

In the techniques described in Patent Document 1 and Patent Document 2, it is possible to suppress the air flow meter from being contaminated and the intake system parts from corroding under the condition that intake pulsation occurs. It is not considered that the suppression of the intake pulsation becomes insufficient due to the responsiveness of the supercharger and the responsiveness of the LPL throttle valve when the state shifts from the non-existing state to a state where intake pulsation can occur.
Under such conditions, the exhaust gas may flow backward in the intake passage and the air flow meter may be contaminated or the intake system parts may be corroded, which is insufficient.

  Further, in the techniques described in Patent Document 1 and Patent Document 2, it is not considered to accurately supply the required EGR amount by using the pressure detection means at the downstream position of the intake throttle valve. No consideration is given to the failure of the pressure sensing means downstream of the valve.

  Accordingly, an object of the present invention is to provide an internal combustion engine that accurately supplies the required EGR amount using the pressure detection means downstream of the intake throttle valve, even when the pressure detection means downstream of the intake throttle valve fails. An object of the present invention is to provide a control device for an internal combustion engine capable of controlling EGR.

  The invention according to claim 1 of the present invention that solves the above-mentioned problems is a turbocharger that is driven by exhaust gas discharged from an internal combustion engine to supercharge intake air, and an exhaust gas downstream of an exhaust turbine of the supercharger. A part of the exhaust gas from the passage is taken in as EGR gas, and the EGR gas is recirculated to the intake passage on the upstream side of the compressor of the supercharger, and the low pressure EGR passage is provided in the low pressure EGR passage. An EGR valve that changes the road area, an intake throttle valve that is provided in the intake passage of the internal combustion engine and that can change the amount of intake air taken into the internal combustion engine, and detects the pressure at a downstream position of the intake throttle valve A first means for determining a target pressure at a downstream position of the intake throttle valve in accordance with a rotational speed and a load of the internal combustion engine; Based on the second means for determining the value according to the rotational speed and load of the internal combustion engine, the pressure at the downstream position of the intake throttle valve obtained from the pressure detection means, and the target pressure, the intake throttle A third means for correcting the intake throttle valve opening based on the calculated feedback coefficient and the basic value of the intake throttle valve opening; and a feedback coefficient of the intake throttle valve. The fourth means for calculating the learning value, the fifth means for detecting the failure of the pressure detection means, and the basic value of the intake throttle valve opening and the learning value when the pressure detection means fails. And a sixth means for calculating the intake throttle valve opening degree.

  According to the first aspect of the present invention, the intake throttle valve opening degree can be calculated based on the learning value calculated in advance even when the pressure detection means downstream of the intake throttle valve fails. As a result, EGR can be controlled even when the pressure detection means downstream of the intake throttle valve fails.

  According to a second aspect of the present invention, there is provided a supercharger that is driven by exhaust discharged from an internal combustion engine to supercharge intake air, and a part of the exhaust from an exhaust passage downstream of the supercharger at an exhaust turbine. An EGR valve that takes in as EGR gas and recirculates the EGR gas to an intake passage upstream of the compressor of the supercharger, and an EGR valve that is provided in the low pressure EGR passage and changes the flow area of the low pressure EGR passage And an intake throttle valve provided in the intake passage of the internal combustion engine and capable of changing an intake air amount sucked into the internal combustion engine, and a pressure detection means for detecting a pressure at a downstream position of the intake throttle valve. A first means for determining a target pressure at a position downstream of the intake throttle valve in accordance with a rotational speed of the internal combustion engine and an intake air flow rate acquired from an air flow meter; Based on second means for obtaining a basic value of the valve opening according to the rotational speed and load of the internal combustion engine, the pressure at the downstream position of the intake throttle valve obtained from the pressure detection means, and the target pressure. And a third means for correcting the intake throttle valve opening based on the calculated feedback coefficient and a basic value of the intake throttle valve opening, and the intake throttle valve A fourth means for calculating a learning value of the feedback coefficient of the valve; a fifth means for detecting a failure of the pressure detection means; and a basic value of the intake throttle valve opening when the pressure detection means is faulty. And a sixth means for calculating the intake throttle valve opening based on the learned value.

  According to the invention according to claim 2, in addition to the effect of the invention according to claim 1, the target pressure at the downstream position of the intake throttle valve is more accurately determined according to the change in the intake air flow rate and the engine speed. Can be set.

  According to the present invention, in an internal combustion engine that accurately supplies the required EGR amount using the pressure detection means downstream of the intake throttle valve, even when the pressure detection means downstream of the intake throttle valve fails, A control device for an internal combustion engine capable of controlling EGR can be provided.

It is a schematic diagram of the intake system and the exhaust system in the LPL-EGR system. 1 is a schematic diagram of an LPL-EGR system according to a first embodiment. It is a functional block diagram of ECU which concerns on 1st Embodiment. It is explanatory drawing which shows the structural example of the target pressure value map which concerns on 1st Embodiment. It is explanatory drawing which shows the structural example of the target LPL throttle valve opening degree map which concerns on 1st Embodiment. It is a flowchart which shows the flow of the EGR control process which concerns on 1st Embodiment. It is a flowchart which shows the flow of the target pressure value and target LPL throttle valve opening calculation process which concern on 1st Embodiment. It is a flowchart which shows the flow of the LPL throttle valve opening degree calculation process which concerns on 1st Embodiment. It is a schematic diagram of the LPL-EGR system which concerns on 2nd Embodiment. It is explanatory drawing which shows the structural example of the exhaust pressure value map which concerns on 2nd Embodiment. It is a flowchart which shows the flow of the target pressure value and target LPL throttle valve opening calculation process which concern on 2nd Embodiment.

  Next, modes for carrying out the present invention (referred to as “embodiments”) will be described in detail with reference to the drawings as appropriate.

<< First Embodiment >>
First, a first embodiment of the present invention will be described with reference to FIGS.

<Configuration>
FIG. 1 is a schematic diagram of an intake system and an exhaust system in an LPL-EGR system.
In FIG. 1, the intake gas is indicated by a white arrow, and the exhaust gas is indicated by a black arrow. Further, the intake gas mixed with the exhaust gas returned through the LPL-EGR passage 212 (low pressure EGR passage) is indicated by a dotted arrow.
Note that the internal combustion engine in the present embodiment includes a supercharger 205. The supercharger 205 is an exhaust turbocharger system, and includes an exhaust turbine 205b and a compressor 205a driven by the exhaust turbine 205b.
In the LPL-EGR system 10, the air taken in from outside air is purified by the air cleaner 201, and then the flow rate is adjusted by the LPL throttle valve (intake throttle valve) 204. The flow rate of the intake air is measured by an air flow meter 202 installed immediately after the air cleaner 201.
Thereafter, the intake air is mixed with the exhaust gas returned through the LPL-EGR passage 212 communicating with the exhaust passage 209 on the downstream side of the three-way catalyst 211 described later, and the supercharger is the intake gas. Compressed by the 205 compressor 205a.
Since the compressed intake gas has a high temperature, it is cooled by an intercooler 206 installed in the intake passage 203 and then the flow rate is adjusted by a throttle valve 207 to the intake port of an engine (internal combustion engine) 208. Sent.

Exhaust gas exhausted from the exhaust port of the engine 208 is sent to the exhaust turbine 205 b of the supercharger 205 via the exhaust passage 209. The exhaust gas is sent to the three-way catalyst 211 after rotating the exhaust turbine 205b. The exhaust gas purified by the three-way catalyst 211 is discharged to the outside through a muffler (not shown), but a part of the exhaust gas is an LPL-EGR passage connected downstream of the three-way catalyst 211. It is returned to the intake system via 212. The exhaust gas returned to the intake system via the LPL-EGR passage 212 is referred to as EGR gas.
The hot EGR gas that has entered the LPL-EGR passage 212 is first cooled by the EGR cooler 213, and then the EGR valve (EGR valve) 214 adjusts the EGR amount by changing the flow path area of the LPL-EGR passage 212. And returned to the intake passage 203.

  The EGR amount is also adjusted by adjusting the opening of the LPL throttle valve 204. That is, by adjusting the opening of the LPL throttle valve 204, the differential pressure between the upstream and downstream sides of the LPL-EGR passage 212 is controlled to adjust the EGR amount.

FIG. 2 is a schematic diagram of the LPL-EGR system according to the first embodiment.
In the LPL-EGR system 10, the same elements as those in FIG. Further, the flow of the intake gas and the exhaust gas is the same as that in FIG. In FIG. 2, as in FIG. 1, the intake air is indicated by a white arrow, the exhaust gas is indicated by a black arrow, and the intake gas mixed with the exhaust gas by EGR is indicated by a dotted arrow. .

The LPL throttle valve 204 and the EGR valve 214 are controlled by an EGR control signal output from an ECU (Engine Control Unit) 1.
The ECU 1 acquires the engine rotation speed and the net effective pressure value as a load from the engine 208, acquires the atmospheric pressure value from the atmospheric pressure value sensor 302, the LPL throttle valve 204, the intake passage 203 of the LPL-EGR passage 212, The actual pressure value on the suction side of the compressor 205a is acquired from a pressure sensor (pressure detecting means) 301 installed between the connecting portion of the compressor 205a. The ECU 1 calculates the LPL throttle valve opening based on these acquired values, and uses the LPL throttle valve opening control signal, which is information on the LPL throttle valve opening, and the information on the opening of the EGR valve 214. An EGR control signal including a certain EGR valve control signal is generated and output to the LPL throttle valve 204, the EGR valve 214, and the like.
Thereby, the opening degree of the LPL throttle valve 204 can be controlled based on the actual pressure value downstream of the LPL throttle valve 204.

The ECU 1 according to the first embodiment will be described along FIG. 3 with reference to FIG.
FIG. 3 is a functional block diagram of the ECU according to the first embodiment.
The ECU 1 includes an input unit 121 for inputting information, a processing unit 100 for processing information, a storage unit 110 for storing information, and an output unit 122 for outputting information.
The information input to the input unit 121 includes the engine rotation speed input from the engine 208 and the net effective pressure value as a load, the atmospheric pressure value input from the atmospheric pressure sensor 302, and the pressure sensor as described above with reference to FIG. There is an actual pressure value input from 301.

The storage unit 110 stores a target pressure value map 111, a target LPL throttle valve opening map 112, and an EGR amount map 113.
The target pressure value map 111 is associated with the atmospheric pressure value, the rotational speed of the engine 208, and the net effective pressure value, and is a target pressure value (target pressure) that is an optimum pressure downstream of the LPL throttle valve 204. Is stored. The target LPL throttle valve opening map 112 is associated with the atmospheric pressure value, the rotational speed of the engine 208, and the net effective pressure value, and causes the aforementioned target pressure value to be generated downstream of the LPL throttle valve 204. The target LPL throttle valve opening (the basic value of the opening of the intake throttle valve) that is the opening of the LPL throttle valve 204 is stored. In the EGR amount map 113, for example, the EGR amount is calculated with reference to the engine speed and the net effective pressure value.
The target pressure value map 111 will be described later with reference to FIG. 4, and the target LPL throttle valve opening map 112 will be described later with reference to FIG.

The processing unit 100 includes a target value calculation unit (first means, second means) 102 and an LPL throttle valve opening calculation unit (third means, fourth means, fifth means, sixth means). ) 103, an EGR control unit 104, and an EGR amount calculation unit 101.
The target value calculation unit 102 calculates the target pressure value from the target pressure value map 111 based on the engine speed, the net effective pressure value, and the atmospheric pressure value among the input information, and the target LPL throttle valve opening degree. A target LPL throttle valve opening is calculated from the map 112.
The LPL throttle valve opening calculator 103 calculates the LPL throttle valve opening by feedback control using the target pressure value calculated by the target value calculator 102, the target LPL throttle valve opening, and the actual pressure value of the input information.
The EGR control unit 104 generates an EGR control signal including the LPL throttle valve opening calculated by the LPL throttle valve opening calculation unit 103, and outputs the EGR control signal to the LPL throttle valve 204 via the output unit 122. , LPL throttle valve 204 is controlled.
Note that the EGR control unit 104 also controls the EGR valve 214.
The EGR amount calculation unit 101 calculates the EGR amount with reference to the EGR amount map 113 based on the engine rotation speed and the net effective pressure value.
In the processing unit 100 and each of the units 101 to 104, a program stored in a ROM (Read Only Memory) or HD (Hard Disk) (not shown) is expanded in a RAM (Random Access Memory) and executed by a CPU (Central Processing Unit). To be realized.

<Map>
FIG. 4 is an explanatory diagram illustrating a configuration example of a target pressure value map according to the first embodiment, and FIG. 5 is an explanatory diagram illustrating a configuration example of a target LPL throttle valve opening map according to the first embodiment. .
As shown in FIGS. 4 and 5, each map stores the target pressure value and the target LPL throttle valve opening in association with the net effective pressure value and the engine speed.
Further, as shown in FIGS. 4 and 5, the target pressure value map 111 and the target LPL throttle valve opening map 112 are stored as a set for each atmospheric pressure value.
Although shown in the form of a graph in FIGS. 4 and 5, the target pressure value map 111 and the target LPL throttle valve opening map 112 are actually tables corresponding to the engine speed and the net effective pressure value. The configuration is stored for each atmospheric pressure value.
The atmospheric pressure value, the engine speed, the net effective pressure value, and the like are described as discrete values. When a value between these values is input, the target value calculation unit 102 performs an interpolation process. The target pressure value and the target LPL throttle valve opening are calculated.
The map is an example, and may be a function, for example.

<Flowchart>
Next, the EGR control method according to the first embodiment will be described with reference to FIGS. 6 to 8 with reference to FIGS.
FIG. 6 is a flowchart showing a flow of EGR control processing according to the first embodiment.
First, the EGR amount calculation unit 101 performs an EGR amount calculation process with reference to the EGR amount map 113 based on the engine rotation speed and the net effective pressure value (S101).
Next, the target value calculation unit 102 calculates the target pressure value and the target LPL throttle valve opening based on the input engine speed, net effective pressure value (load), and atmospheric pressure value (S102). . Details of the processing in step S102 will be described later with reference to FIG.
Next, the LPL throttle valve opening calculation unit 103 performs feedback control based on the actual pressure value input from the pressure sensor 301 in addition to the target pressure value and the target LPL throttle valve opening calculated in step S102. An LPL throttle valve opening calculation process is performed (S103). The process of step S103 will be described later with reference to FIG.
Then, the EGR control unit 104 generates an LGR throttle valve opening calculated in step S103 and an EGR control signal for controlling the EGR valve 214, and based on the control of the LPL throttle valve 204 and the EGR amount. EGR control is performed by performing valve opening control of the EGR valve 214 (S104). Details of the processing in step S104 are known techniques, and thus detailed description thereof is omitted.
Then, the processing unit 100 determines whether or not the engine 208 has been stopped (S105).
When the engine 208 is not stopped as a result of step S105 (S105 → No), the processing unit 100 returns the process to step S101.
As a result of step S105, when the engine 208 is stopped (S105 → Yes), the processing unit 100 stops the processing.

(Target pressure value and target LPL throttle valve opening calculation processing)
FIG. 7 is a flowchart showing the flow of the calculation process (S102) of the target pressure value and the target LPL throttle valve opening according to the first embodiment.
The target value calculation unit 102 searches the target pressure value map 111 (FIG. 4) in the storage unit 110 with reference to the input engine speed, net effective pressure value (load), and atmospheric pressure value, and the corresponding target. A pressure value is calculated (S201).
Next, the target value calculation unit 102 refers to the input engine rotation speed, net effective pressure value (load), and atmospheric pressure value, and reads the target LPL throttle valve opening map 112 (FIG. 5) in the storage unit 110. Search is performed, the corresponding target LPL throttle valve opening is calculated (S202), and the process returns to step S102 in FIG.

(LPL throttle valve opening calculation process)
FIG. 8 is a flowchart showing the flow of the LPL throttle valve opening calculation process (S103) according to the first embodiment.
In the first embodiment, an example using PID (Proportional Integration and Differential) control is shown as an example of feedback control. However, the present invention is not limited to this, and other feedback control such as PI (Proportional and Integration) is used. Also good.
The LPL throttle valve opening calculation unit 103 determines whether or not the pressure sensor 301 has failed (S301). Whether or not the pressure sensor 301 has failed is determined by determining whether or not the signal from the pressure sensor 301 has been interrupted for a certain period of time and whether or not an abnormal value continues to be output. Is performed by determining.

If a failure is detected as a result of step S301 (S301 → Yes), the LPL throttle valve opening calculation unit 103 calculates in step S315, which will be described later, and the learning value stored in the storage unit 110 is changed to the step of FIG. By multiplying the target LPL throttle valve opening acquired in S202, the LPL throttle valve opening is calculated (S320), and the process returns to step S102 of FIG.
If no failure is detected as a result of step S301 (S301 → No), the LPL throttle valve opening calculation unit 103 reads a P-term coefficient, an I-term coefficient, and a D-term coefficient set in advance in the storage unit 110. (S302, S303, S304). The P-term coefficient, the I-term coefficient, and the D-term coefficient need only be read once.
Next, the LPL throttle valve opening calculation unit 103 calculates the current deviation by subtracting the actual pressure value acquired from the pressure sensor 301 (FIG. 2) from the target pressure value acquired in step S201 of FIG. (S305).

Then, the LPL throttle valve opening calculation unit 103 subtracts the previous deviation temporarily stored in the storage unit 110 from the current deviation calculated in step S305, and further multiplies the P term coefficient acquired in step S302. Thus, the P term in the PID control is calculated (S306).
Next, the LPL throttle valve opening calculation unit 103 calculates the I term in the PID control by multiplying the current deviation calculated in step S305 by the I term coefficient acquired in step S303 (S307).
Subsequently, the LPL throttle valve opening calculation unit 103 subtracts twice the previous deviation temporarily stored in the storage unit 110 from the current deviation calculated in step S <b> 305, and further temporarily stores it in the storage unit 110. The D term in the PID control is calculated by multiplying the previous deviation added by the D term coefficient acquired in step S304 (S308).

Next, the LPL throttle valve opening calculation unit 103 calculates the current change in the PID term by adding each of the P term, I term, and D term calculated in steps S306 to S308 (S309).
Further, the LPL throttle valve opening calculation unit 103 adds the current PID term change calculated in step S309 to the previous PID term temporarily stored in the storage unit 110, thereby obtaining the current PID term ( (Feedback coefficient) is calculated (S310).

Next, the LPL throttle valve opening calculation unit 103 determines whether or not the current PID term calculated in step S310 is greater than a preset upper limit value (S311).
If the result of step S311 is that the current PID term is larger than the upper limit value (S311 → Yes), the LPL throttle valve opening calculation unit 103 updates the current PID term to the set upper limit value (S312), step S311 The process proceeds to S315.

If the result of step S311 is that the current PID term is less than or equal to the upper limit (S311 → No), the LPL throttle valve opening calculation unit 103 determines whether or not the current PID term is smaller than a preset lower limit. Determination is made (S313).
As a result of step S313, when the current PID term is smaller than the lower limit value (S313 → Yes), the LPL throttle valve opening calculation unit 103 updates the current PID term to the set lower limit value (S314), and step The process proceeds to S315.
If the result of step S313 is that the current PID term is equal to or greater than the lower limit (S313 → No), the LPL throttle valve opening calculation unit 103 advances the process to step S315.

  In step S315, the LPL throttle valve opening calculation unit 103 calculates a learning value. The learning value is calculated in the following procedure. First, the LPL throttle valve opening calculation unit 103 acquires a preset learning coefficient from the storage unit 110. Next, the LPL throttle valve opening calculation unit 103 adds the value obtained by multiplying the calculated current PID term by the learning coefficient and the value obtained by multiplying the previous learning value by (1−learning coefficient). A learning value is calculated. The LPL throttle valve opening calculation unit 103 stores the calculated current learning value in the storage unit 110. This learning value is held in the storage unit 110 even when the ignition is OFF. Note that the initial value of the learning value is, for example, 1.0.

Then, the LPL throttle valve opening calculation unit 103 updates the previous PID term with the current PID term (S316), and temporarily stores the updated previous PID term in the storage unit 110.
Next, the LPL throttle valve opening calculation unit 103 updates the previous deviation with the previous deviation (S317), and temporarily stores the updated previous deviation in the storage unit 110.
Furthermore, the LPL throttle valve opening calculation unit 103 updates the previous deviation with the current deviation calculated in step S305 (S318), and temporarily stores the updated previous deviation in the storage unit 110.
Subsequently, the LPL throttle valve opening calculation unit 103 calculates the LPL throttle valve opening by multiplying the target LPL throttle valve opening acquired in step S202 of FIG. 7 by the calculated current PID term (S319). Return to step S103 in FIG.

(Summary)
According to the first embodiment, the pressure downstream of the LPL throttle valve 204 can be maintained at an optimum pressure (target pressure value) according to the engine speed and the engine load (net effective pressure value). Can be suppressed. For example, when intake pressure pulsation does not occur and the actual pressure value is high, that is, when the pressure at the downstream position of the LPL throttle valve 204 is increased, the LPL throttle valve 204 is closed to prevent backflow. can do. Further, if a differential pressure is generated between the upstream and downstream sides of the LPL-EGR passage 212 in a state where the amount of EGR is small, EGR gas remaining in the LPL-EGR passage 212 enters the intake passage 203. By controlling the LPL throttle valve 204 to reduce the differential pressure, it is possible to prevent EGR gas from entering the intake passage 203. For this reason, it is possible to prevent the air flow meter 202 from being contaminated and to prevent corrosion of other intake system components.

Further, fluctuations in the EGR amount due to intake pulsation or the like can be suppressed, and the controllability of the LPL-EGR system 10 can be improved.
Furthermore, since the pressure (target pressure value) downstream of the LPL throttle valve 204 is set according to the atmospheric pressure value, an accurate EGR amount can be obtained even if an environmental change occurs. Further, even if the environment changes, the air flow meter 202 can be prevented from being contaminated, and corrosion of other intake system components can be prevented.
Furthermore, since intake pulsation can be prevented, fresh air can be prevented from flowing into the exhaust passage 209 via the LPL-EGR passage 212, and malfunction of the O ₂ sensor provided downstream of the three-way catalyst 211 can be prevented. Can do.

Even if the LPL throttle valve 204 is closed in a state where a pumping loss occurs, the pressure downstream of the LPL throttle valve 204 is maintained at an optimum pressure (target pressure value), thereby preventing the occurrence of a pumping loss. be able to.
Furthermore, since the opening degree of the LPL throttle valve 204 is adjusted in accordance with the pressure downstream of the LPL throttle valve 204, when the state changes from a state where there is no intake pulsation to a state where intake pulsation can occur, The intake pulsation can be suppressed regardless of the responsiveness or the responsiveness of the LPL throttle valve 204.

  Furthermore, according to the present embodiment, a learning value of the feedback coefficient (PID term in the present embodiment) is calculated, and when the pressure sensor 301 fails, the opening degree of the LPL throttle valve 204 is determined based on this learning value. Since it can be calculated, the LPL-EGR system 10 can be controlled even if the pressure sensor 301 fails. As a result, it is possible to prevent an extremely low fuel consumption and drivability.

<< Second Embodiment >>
Next, a second embodiment of the present invention will be described with reference to FIGS. In the second embodiment, the same elements as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.

<Configuration>
FIG. 9 is a schematic diagram of an LPL-EGR system according to the second embodiment.
The LPL-EGR system 10a is different from the LPL-EGR system 10 shown in FIG. 2 in that the intake air flow rate is added from the air flow meter 202 as input information to the ECU 1a.
Note that the ECU 1a has an exhaust pressure value map 111a, which will be described later in FIG. 10, instead of the target pressure value map 111 (FIG. 3), and that the target value calculation unit 102 has an engine rotation speed and an intake air flow rate. 3 except that the exhaust pressure value (exhaust pressure) is estimated from the exhaust pressure value map 111a based on the atmospheric pressure value and the target pressure value is calculated from the estimated exhaust pressure value. Illustration and description are omitted.

<Map>
FIG. 10 is an explanatory diagram of a configuration example of an exhaust pressure value map according to the second embodiment.
As described above, the ECU 1a stores the exhaust pressure value map 111a as shown in FIG. 10 in the storage unit 110 (FIG. 3) instead of the target pressure value map 111 shown in FIG.
In the exhaust pressure value map 111a, the exhaust pressure value is associated with the intake air flow rate acquired from the air flow meter 202 and the engine rotation speed, and further stored for each atmospheric pressure value.

<Flowchart>
Next, the target pressure value and target LPL throttle valve opening calculation processing (step S102 in FIG. 6) according to the second embodiment will be described with reference to FIG.
The other processes (step S101, step S103, and step S104 in FIG. 6) are the same as those in the first embodiment, and thus illustration and description thereof are omitted.

(Target pressure value and target LPL throttle valve opening calculation processing)
FIG. 11 is a flowchart showing a flow of target pressure value and target LPL throttle valve opening calculation processing (S102) according to the second embodiment.
The target value calculation unit 102 searches the exhaust pressure value map 111a (FIG. 10) in the storage unit 110 using the input engine speed, intake air flow rate, and atmospheric pressure as keys, and estimates the corresponding exhaust pressure value. (S201a).
Next, the target value calculation unit 102 calculates the target pressure value by subtracting the required differential pressure value (preset) from the estimated exhaust pressure value (S202a).
Next, the target value calculation unit 102 searches the target LPL throttle opening map 112 (FIG. 5) in the storage unit 110 using the input engine speed, net effective pressure value, and atmospheric pressure as keys, and the corresponding values are obtained. The target LPL throttle valve opening is calculated (S203a), and the process returns to step S102 in FIG.

(Summary)
According to the second embodiment, the target pressure value at the downstream position of the intake throttle valve can be set more accurately according to the change in the intake air flow rate and the engine rotation speed.

1,1a ECU (control device)
10, 10a LPL-EGR system 100 processing unit 102 target value calculation unit (first means, second means)
103 LPL throttle valve opening calculation section (third means, fourth means, fifth means, sixth means)
DESCRIPTION OF SYMBOLS 104 EGR control part 110 Storage part 111 Target pressure value map 111a Exhaust pressure value map 112 Target LPL throttle valve opening degree map 201 Air cleaner 202 Air flow meter 203 Intake passage 204 LPL throttle valve (intake throttle valve)
205 Supercharger 205a Compressor 205b Exhaust turbine 206 Intercooler 208 Engine (internal combustion engine)
209 Exhaust passage 211 Three-way catalyst 212 LPL-EGR passage (low pressure EGR passage)
213 EGR cooler 214 EGR valve (EGR valve)
301 Pressure sensor (pressure detection means)

Claims (2)

A supercharger that is driven by exhaust gas discharged from the internal combustion engine to supercharge intake air;
A low pressure EGR passage that takes in a part of exhaust gas as an EGR gas from an exhaust passage downstream of the supercharger exhaust turbine and recirculates the EGR gas to an intake passage upstream of the compressor of the supercharger;
An EGR valve that is provided in the low pressure EGR passage and changes a flow area of the low pressure EGR passage;
An intake throttle valve provided in the intake passage of the internal combustion engine and capable of changing an intake amount taken into the internal combustion engine;
Pressure detecting means for detecting the pressure at the downstream position of the intake throttle valve;
An internal combustion engine comprising:
First means for determining a target pressure at a downstream position of the intake throttle valve in accordance with a rotational speed and a load of the internal combustion engine;
A second means for obtaining a basic value of the intake throttle valve opening according to the rotational speed and load of the internal combustion engine;
Based on the pressure at the downstream position of the intake throttle valve acquired from the pressure detection means and the target pressure, a feedback coefficient of the intake throttle valve is calculated, and the calculated feedback coefficient and the intake throttle valve opening are calculated. A third means for correcting the intake throttle valve opening by the basic value of the degree;
A fourth means for calculating a learning value of the feedback coefficient of the intake throttle valve;
Fifth means for detecting a failure of the pressure detecting means;
A sixth means for calculating the intake throttle valve opening from the basic value of the intake throttle valve opening and the learning value at the time of failure of the pressure detection means;
A control apparatus for an internal combustion engine, comprising: A supercharger that is driven by exhaust gas discharged from the internal combustion engine to supercharge intake air;
A low pressure EGR passage that takes in a part of exhaust gas as an EGR gas from an exhaust passage downstream of the supercharger exhaust turbine and recirculates the EGR gas to an intake passage upstream of the compressor of the supercharger;
An EGR valve that is provided in the low pressure EGR passage and changes a flow area of the low pressure EGR passage;
An intake throttle valve provided in the intake passage of the internal combustion engine and capable of changing an intake amount taken into the internal combustion engine;
Pressure detecting means for detecting the pressure at the downstream position of the intake throttle valve;
An internal combustion engine comprising:
First means for determining a target pressure at a downstream position of the intake throttle valve in accordance with a rotational speed of the internal combustion engine and an intake air flow rate acquired from an air flow meter;
A second means for obtaining a basic value of the intake throttle valve opening according to the rotational speed and load of the internal combustion engine;
Based on the pressure at the downstream position of the intake throttle valve acquired from the pressure detection means and the target pressure, a feedback coefficient of the intake throttle valve is calculated, and the calculated feedback coefficient and the intake throttle valve opening are calculated. A third means for correcting the intake throttle valve opening by the basic value of the degree;
A fourth means for calculating a learning value of the feedback coefficient of the intake throttle valve;
Fifth means for detecting a failure of the pressure detecting means;
A sixth means for calculating the intake throttle valve opening from the basic value of the intake throttle valve opening and the learning value at the time of failure of the pressure detection means;
A control apparatus for an internal combustion engine, comprising:

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