JP5842795B2 - Control device for an internal combustion engine with a supercharger - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine with a supercharger that operates a supercharging pressure control actuator so that the supercharging pressure becomes a target supercharging pressure, and more specifically, a function for self-diagnosis of abnormality related to supercharging pressure control It is related with the control apparatus provided with.

  2. Description of the Related Art Conventionally, as disclosed in, for example, Japanese Patent Application Laid-Open No. 2008-25529, an internal combustion engine with a supercharger including an actuator used for supercharging pressure control such as a waste gate valve, an air bypass valve, and a variable flap is known. If a valve opening failure occurs that sticks to any of these actuators at the valve opening position, a desired supercharging pressure cannot be obtained and the function of the supercharger is impaired. Therefore, in the above-described conventional apparatus, a delay (delay coefficient) until the pressure ratio before and after the compressor reaches a pressure ratio to be reached after shifting to a steady state is calculated, and the delay coefficient is compared with the abnormality determination value. Thus, the occurrence of valve opening failure of these actuators is detected.

JP 2008-25529 A

  In the above-described conventional technology, it is possible to detect that an abnormality has occurred in any of the actuators used for supercharging pressure control. For example, a waste gate valve abnormality and an air bypass valve abnormality are detected separately. It is not possible. For this reason, even if an abnormality has occurred in the wastegate valve, there has been a risk of erroneous detection that the air bypass valve is abnormal.

  The present invention has been made in view of the above-described problems. In an internal combustion engine with a supercharger including an air bypass valve and a wastegate valve, the abnormality of the air bypass valve is distinguished from the abnormality of the wastegate valve. It is an object of the present invention to provide a control device for an internal combustion engine with a supercharger that can be detected easily.

In order to achieve the above object, a first invention provides a wastegate valve for flowing exhaust gas by bypassing a turbine provided in an exhaust passage of an internal combustion engine, and a compressor provided in an intake passage of the internal combustion engine. An air bypass valve for recirculating air from the downstream side to the upstream side of the compressor, and configured to operate the wastegate valve so that the supercharging pressure becomes the target supercharging pressure In the control device for an internal combustion engine with a turbocharger,
Means for obtaining a measured air flow rate that is a measured value of the air flow rate in the intake passage;
An acquisition means for acquiring a target opening correlation value having a correlation with a target opening of the waste gate valve;
Calculation means for calculating an estimated air flow rate based on the measured boost pressure obtained by a boost pressure sensor and the target opening correlation value;
The air bypass when the measured supercharging pressure is larger than the first threshold and the difference between the measured air flow and the estimated air flow is larger than the second threshold for a predetermined time. Air bypass valve abnormality detection means for detecting valve abnormality;
It is characterized by having.

According to a second invention, in the first invention,
The wastegate valve is a diaphragm type valve,
The acquisition means is a means for acquiring a target diaphragm pressure for realizing the target opening as the target opening correlation value.

According to a third invention, in the first or second invention,
The calculation means calculates the estimated air flow rate when the target opening degree correlation value is a value corresponding to a fully closed state of the waste gate valve.

A fourth invention is any one of the first to third inventions,
The second threshold value is set such that the larger the measured supercharging pressure is, the larger the value is.

According to a fifth invention, in any one of the first to fourth inventions,
When an abnormality of the air bypass valve is detected, control means for performing control for reducing the rotational speed of the turbine is further provided.

According to a sixth invention, in the fifth invention,
The control means is a means for operating the opening degree of the waste gate valve in the opening direction.

According to a seventh invention, in the fifth invention,
The control means is means for operating the throttle of the internal combustion engine in a closing direction.

  According to the first aspect of the invention, the estimated air flow rate is calculated based on the measured boost pressure obtained by the boost pressure sensor and the correlation value between the target opening of the wastegate valve. The measured supercharging pressure is larger than the first threshold, and the difference between the measured value (measured air flow rate) of the air flow rate in the intake passage of the internal combustion engine and the estimated air flow rate is larger than the second threshold value. When the state continues for a predetermined time, an abnormality of the air bypass valve is detected. When an open failure occurs in which the wastegate valve is stuck in an open state, the supercharging pressure tends to be less likely to increase than when an open failure occurs in the air bypass valve. Therefore, according to the present invention, when the measured supercharging pressure is larger than the first threshold value, the air bypass valve abnormality is self-diagnosed to accurately distinguish the air bypass valve abnormality from the waste gate valve abnormality. Can be detected.

  According to the second invention, in the diaphragm type wastegate valve, the target diaphragm pressure can be used as the target opening degree correlation value.

  According to the third invention, the estimated air flow rate is calculated when the target opening degree correlation value is a value corresponding to the fully closed state of the waste gate valve. For this reason, according to the present invention, the relationship between the target opening degree correlation value and the estimated air flow rate can be further simplified, so that a more accurate estimated air flow rate can be calculated.

  According to the fourth invention, the second threshold value is set to a larger value as the measured supercharging pressure is larger. The air flow rate when the air bypass valve is fully opened with respect to the supercharging pressure tends to be almost linear with the air flow rate when the air bypass valve is fully closed. For this reason, according to the present invention, by setting the second threshold value corresponding to the supercharging pressure, the self-diagnosis of the abnormality of the air bypass valve can be accurately performed regardless of the supercharging pressure.

  According to the fifth aspect, when an abnormality of the air bypass valve is detected, control for reducing the rotational speed of the turbine is executed. For this reason, according to this invention, it becomes possible to suppress effectively the situation where a rotational speed rises more than the turbine rotational speed corresponding to the achievable supercharging pressure.

  According to the sixth aspect of the invention, by operating the wastegate valve in the opening direction, a part of the exhaust gas can be bypassed from the turbine and the turbine speed can be easily reduced.

  According to the seventh aspect, by operating the throttle in the closing direction, the intake air amount can be limited and the turbine rotational speed can be reduced easily.

It is the schematic which shows the structure of the internal combustion engine with a supercharger in which the control apparatus which concerns on Embodiment 1 of this invention is used. It is a block diagram which shows the structure of the control apparatus which concerns on Embodiment 1 of this invention. It is a figure which shows the supercharging characteristic of the supercharger which concerns on Embodiment 1 of this invention. It is a flowchart which shows the routine for the abnormality diagnosis performed by the control apparatus which concerns on Embodiment 1 of this invention.

Embodiment 1 FIG.
Embodiment 1 of the present invention will be described with reference to the drawings.

  An internal combustion engine (hereinafter also referred to as “engine”) in which the control device according to the present embodiment is used is a supercharged engine having a wastegate valve (hereinafter also referred to as “WGV”), and more specifically, by a throttle. This is a four-cycle reciprocating engine that can control torque by adjusting the amount of air. FIG. 1 is a schematic diagram illustrating a configuration of a supercharged engine in which a control device according to the present embodiment is used. The supercharged engine according to the present embodiment includes a turbocharger 30 including a compressor 32 provided in the intake passage 10 and a turbine 34 provided in the exhaust passage 20. The intake passage 10 is connected to an intake manifold 18 attached to the engine body 2. An air cleaner 12 is provided at the inlet of the intake passage 10, and an air flow meter 42 for measuring the air flow rate is disposed downstream of the air cleaner 12 and upstream of the compressor 32. An intercooler 14 is provided between the compressor 32 and the throttle 16 in the intake passage 10. A supercharging pressure sensor 44 for measuring the pressure in the upstream portion of the throttle 16, that is, the supercharging pressure, is attached to the outlet of the intercooler 14. The intake passage 10 is provided with an air bypass valve (hereinafter also referred to as “ABV”) 36 for bypassing the compressor 32 from the downstream side to the upstream side of the compressor 32 to recirculate the air. For example, the air bypass valve 36 is opened when the throttle 16 is suddenly closed to suppress the occurrence of surge and protect the compressor 32. The exhaust passage 20 is connected to an exhaust manifold 22 attached to the engine body 2. The exhaust passage 20 is provided with a waste gate valve 38 for allowing the exhaust gas to flow by bypassing the turbine 34. This waste gate valve 38 is a diaphragm type waste gate valve corresponding to active control that realizes an arbitrary opening degree by controlling the diaphragm pressure by driving an E-VRV (Electric Vacuum Regulating Valve).

  The control device according to the present embodiment is realized as part of the function of an ECU (Electronic Control Unit) 100 that controls the supercharged engine. In addition to the air flow meter 42 and the supercharging pressure sensor 44, the ECU 100 includes various sensors such as a throttle opening sensor 46, an engine speed sensor 48, an accelerator opening sensor 50, and the like regarding various engine operating conditions and operating conditions. Information and signals are input. The ECU 100 operates various actuators such as the throttle 16 and the waste gate valve 38 based on the information and signals.

  The block diagram of FIG. 2 shows a configuration of ECU 100 as a control device according to the present embodiment. According to the configuration shown in FIG. 2, the ECU 100 includes a target boost pressure calculation unit 102, a boost pressure control unit 104, an air flow rate estimation unit 110, and an abnormality diagnosis unit 112. However, these elements 102, 104, 110, and 112 are expressed by a diagram focusing on only elements relating to the supercharging pressure control and abnormality diagnosis among various functions of the ECU 100. Therefore, FIG. 2 does not mean that the ECU 100 includes only these elements. The ECU 100 is an automobile computer, and each element is virtually realized when software stored in the memory is executed by the CPU.

  The target boost pressure calculation unit 102 calculates a target boost pressure Pict for boost pressure control. For calculating the target supercharging pressure Pict, the engine speed NE measured by the engine speed sensor 48 and the accelerator pedal opening AP measured by the accelerator opening sensor 50 are used. The target boost pressure calculation unit 102 determines a target air amount based on these pieces of information, and determines a target boost pressure Pict according to the target air amount.

  The supercharging pressure control unit 104 is for determining an operation amount of the wastegate valve 38 for realizing the target supercharging pressure Pict, and is configured by a target diaphragm pressure calculating unit 106 and a control duty ratio calculating unit 108. ing. The target diaphragm pressure calculation unit 106 determines a target diaphragm pressure Pdft as a physical quantity used for opening degree control of the wastegate valve 38 based on the target supercharging pressure Pict. Here, a known physical model in which the behavior of air in the supercharged engine is physically modeled is used. Based on the target diaphragm pressure Pdft calculated by the target diaphragm pressure calculation unit 106, the control duty ratio calculation unit 108 determines the control duty ratio Dvrv of E-VRV that is the operation amount of the waste gate valve 38.

  The ECU 100 extracts the target diaphragm pressure Pdft calculated by the target diaphragm pressure calculation unit 106 among the various parameters calculated by the supercharging pressure control unit 104 as an opening correlation value of the waste gate valve 38. When the air bypass valve 36 is closed, the air flow rate estimation unit 110 is based on the target diaphragm pressure Pdft calculated by the target diaphragm pressure calculation unit 106 and the measured boost pressure Picm measured by the boost pressure sensor 44. An estimated air flow rate mafe, which is an estimated value of the air flow rate, is calculated. The estimated air flow rate mafe is calculated by using a supercharging characteristic as shown in FIG. 3, for example. FIG. 3 is a diagram showing a supercharging characteristic of the supercharger according to the first embodiment of the present invention. As shown in this figure, the air flow rate with respect to the supercharging pressure when the air bypass valve 36 is closed has different characteristics depending on the magnitude of the diaphragm pressure. Therefore, the ECU 100 stores the characteristics of the diaphragm pressure, the supercharging pressure, and the air flow rate as shown in FIG. 3 using a map or the like, so that the estimated air corresponding to the target diaphragm pressure Pdft and the measured supercharging pressure Picm is stored. Calculate the flow rate mafe. When the waste gate valve 38 is opened, the estimated air flow rate mafe corresponding to the measured supercharging pressure Picm may not be uniquely determined. For this reason, the calculation of the estimated air flow rate mafe in the air flow rate estimation unit 110 is preferably based on the premise that the waste gate valve 38 is closed.

  The abnormality diagnosis unit 112 diagnoses an abnormality of the air bypass valve 36 which is a device related to supercharging pressure control. If there is an abnormality in the air bypass valve 36, the abnormality diagnosis unit 112 sets an abnormality flag FLG (sets the value of the flag FLG to 1). For abnormality diagnosis by the abnormality diagnosis unit 112, the estimated air flow rate mafe calculated by the air flow rate estimation unit 110, the measured boost pressure Picm measured by the boost pressure sensor 44, and the air flow rate measured by the air flow meter 42 are used. mafm is used. Hereinafter, an abnormality diagnosis method using these pieces of information will be described with reference to FIG.

  Since the ECU 100 performs supercharging pressure control by the supercharging pressure control unit 104, if both the air bypass valve 36 and the wastegate valve 38 are normal, the measured air flow rate mafm measured by the air flow meter 42 is estimated air. It should almost match the flow rate mafe.

  However, if the wastegate valve 38 is stuck in the opened state due to some abnormality and does not operate according to the indicated opening, the actual supercharging pressure cannot be matched with the target supercharging pressure Pict. As a result, the measured supercharging pressure Picm corresponding to the actual supercharging pressure becomes smaller than the target supercharging pressure Pict, and the estimated air flow rate mafe deviates in a small direction from the measured air flow rate mafm.

  When the air bypass valve 36 is stuck in an open state due to some abnormality, the air on the downstream side of the compressor 32 passes through the air bypass valve 36 and is recirculated to the upstream side. As a result, the measured supercharging pressure Picm corresponding to the actual supercharging pressure is smaller than the target supercharging pressure Pict under the operating conditions where the air bypass valve 36 should be closed. It will deviate from mafm in a small direction.

  As can be seen from the above example, when there is an abnormality in either the air bypass valve 36 or the waste gate valve 38, a difference in magnitude occurs between the measured air flow rate mafm and the estimated air flow rate mafe.

  Here, as shown in FIG. 3, the larger the opening degree of the wastegate valve 38, that is, the smaller the diaphragm pressure (negative pressure), the lower the actual supercharging pressure with respect to the air flow rate. In particular, when the wastegate valve 38 is fully open (for example, a line with a diaphragm pressure of 30 kPa in FIG. 3), even if the air flow rate increases, the actual supercharging pressure does not increase beyond a certain pressure. . On the other hand, when the air bypass valve 36 is open (for example, the dotted line in FIG. 3), the actual supercharging pressure is lower than when the air bypass valve 36 is closed, but the air The actual supercharging pressure continues to rise as the flow rate increases.

  For this reason, the air bypass valve 36 is closed in a region of the supercharging pressure that cannot be reached when the wastegate valve 38 is open but can be reached when the air bypass valve 36 is open. When there is a difference in size between the measured air flow rate mafm and the estimated air flow rate mafe regardless of the operating conditions, it is determined that the air bypass valve 36 is stuck in an open state due to some abnormality. Can do.

Therefore, the abnormality diagnosis unit 112 of the control device according to the first embodiment operates when the air bypass valve 36 is closed when the measured boost pressure Picm is larger than the predetermined threshold β in the steady state of the engine. Calculate the estimated air flow rate mafe under the conditions. When the difference between the measured air flow rate mafm and the estimated air flow rate mafe is larger than the threshold value α for a predetermined time, the value of the abnormality flag FLG is set to 1 because the air bypass valve 36 is open and has a failure. To.

  The values of the threshold values α and β are determined by adaptation using an actual engine. Specifically, for example, as shown in FIG. 3, the difference between the air flow rate when the air bypass valve 36 is closed and the air flow rate when the air bypass valve 36 is opened increases as the boost pressure increases. Tend to be. Therefore, it is preferable to set the threshold value α so as to increase as the supercharging pressure increases. Thereby, since the suitable threshold value (alpha) according to the measurement supercharging pressure Picm can be set, the precision of self-diagnosis can be improved.

  The abnormality diagnosis method described above is implemented by the ECU 100 executing the routine shown in the flowchart of FIG. The abnormality diagnosis routine is executed by the ECU 100 every control cycle. In the first step S100 of the abnormality diagnosis routine, it is determined whether or not it is in a steady state and whether or not the measured supercharging pressure Picm measured by the supercharging pressure sensor 44 is equal to or greater than a threshold value β. If the determination result is negative, it can be determined that there is a possibility that the wastegate valve 38 is abnormal. Therefore, when the determination result of step S100 is negative, the value of the flag FLG is held as zero.

  On the other hand, if the determination result in step S100 is affirmative, it can be determined that there is no abnormality in the wastegate valve 38. In this case, the process by the ECU 100 proceeds to the next step S102. In step S102, an estimated air flow rate mafe when the air bypass valve 36 is closed is calculated based on the measured supercharging pressure Picm and the target diaphragm pressure Pdft. Next, in step S104, it is determined whether or not the magnitude of the difference between the air flow rate mafm measured by the air flow meter 42 and the estimated air flow rate mafe calculated in step S102 is greater than a threshold value α. If the determination result is negative, it can be determined that no abnormality has occurred in the air bypass valve 36. Therefore, when the determination result of step S102 is negative, the value of the flag FLG is held as zero.

  On the other hand, if the determination result of step S102 is affirmative, it can be determined that the air bypass valve 36 is open. In this case, the processing by the ECU 100 proceeds to step S106, and the value of the abnormality flag FLG indicating that an abnormality has occurred in the air bypass valve 36 is set to 1.

  When the flag FLG is set, the ECU 100 turns on a lamp indicating an abnormality provided on the instrument panel and records an abnormality code indicating an abnormality of the air bypass valve 36 in the memory. The recorded abnormality code is read by the diagnostic device at the time of inspection of the vehicle, and the vehicle mechanic looks at the abnormal code displayed on the diagnostic device and identifies where the abnormality is occurring.

  Further, when the flag FLG is set, in order to suppress the air leakage from the air bypass valve 36, control for reducing the supercharging pressure is performed. As a method for reducing the supercharging pressure, for example, control for increasing the opening of the waste gate valve 38 to reduce the turbo rotation speed, or limiting the intake air amount by reducing the opening of the throttle 16. Thus, it is possible to perform control to reduce the turbo rotation speed.

Others.
The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, in the first embodiment, the target diaphragm pressure Pdft is used as the opening correlation value of the waste gate valve 38, but other opening correlation values such as the control duty ratio Dvrv may be used.

2 Engine body 10 Intake passage 20 Exhaust passage 30 Turbocharger 32 Compressor 34 Turbine 38 Wastegate valve 42 Air flow meter 44 Supercharging pressure sensor 100 ECU (control device)
102 Target supercharging pressure calculation unit 104 Supercharging pressure control unit 106 Target diaphragm pressure calculation unit 108 Control duty ratio calculation unit 110 Air flow rate estimation unit 112 Abnormality diagnosis unit

Claims (7)

A wastegate valve for bypassing the turbine provided in the exhaust passage of the internal combustion engine to flow exhaust gas, and the compressor bypassing the compressor from the downstream side to the upstream side of the compressor provided in the intake passage of the internal combustion engine A control device for an internal combustion engine with a supercharger configured to operate the wastegate valve so that a supercharging pressure becomes a target supercharging pressure.
Means for obtaining a measured air flow rate that is a measured value of the air flow rate in the intake passage;
An acquisition means for acquiring a target opening correlation value having a correlation with a target opening of the waste gate valve;
Calculation means for calculating an estimated air flow rate based on the measured boost pressure obtained by a boost pressure sensor and the target opening correlation value;
The air bypass when the measured supercharging pressure is larger than the first threshold and the difference between the measured air flow and the estimated air flow is larger than the second threshold for a predetermined time. Air bypass valve abnormality detection means for detecting valve abnormality;
A control device for an internal combustion engine with a supercharger. The wastegate valve is a diaphragm type valve,
2. The control device for an internal combustion engine with a supercharger according to claim 1, wherein the acquisition means is means for acquiring a target diaphragm pressure for realizing the target opening as the target opening correlation value. .   The supercharging according to claim 1 or 2, wherein the calculation means calculates the estimated air flow rate when the target opening degree correlation value is a value corresponding to a fully closed state of the waste gate valve. Control device for internal combustion engine with a machine.   The internal combustion engine with a supercharger according to any one of claims 1 to 3, wherein the second threshold value is set so as to increase as the measured supercharging pressure increases. Control device.   5. The control device according to claim 1, further comprising a control unit that executes control for reducing the rotational speed of the turbine when an abnormality of the air bypass valve is detected. 6. Control device for an internal combustion engine with a supercharger.   6. The control device for an internal combustion engine with a supercharger according to claim 5, wherein the control means is means for operating the opening degree of the waste gate valve in an opening direction.   6. The control apparatus for an internal combustion engine with a supercharger according to claim 5, wherein the control means is means for operating a throttle of the internal combustion engine in a closing direction.

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