JP2016205283A - Engine control device with turbo supercharger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly switch a detection value and a calculation value of suction air amount.SOLUTION: A control portion 7 is equipped with a suction air amount calculating portion 71 which calculates suction air amount on the basis of an operation state of an engine 2; and a suction air amount setting portion 72 which set either one of a detection value L of suction air amount detected by an air flow sensor 51 or a calculation value D of the suction air amount calculated by the suction air amount calculating portion 71 as suction air amount. The suction air amount setting portion 72 makes switch speed at which the suction air amount is switched from the calculation value D to the detection value L, lower than switch speed at which the suction air amount is switched from the detection value L to the calculation value D.SELECTED DRAWING: Figure 8

Description

  The technology disclosed herein relates to a control device for an engine with a turbocharger.

  In the turbocharged engine, the turbine is disposed in the exhaust passage and the compressor is disposed in the intake passage. When the turbine is rotationally driven by the exhaust discharged from the combustion chamber of the engine, the compressor directly connected to the turbine is rotationally driven, and the amount of intake air into the combustion chamber is increased. In this type of turbocharger, it is known that surging occurs during deceleration.

  Surging reduces the intake air volume when the throttle valve is closed during deceleration, while maintaining the intake air pressure (supercharging pressure) between the compressor and the throttle valve for a turbine that continues to rotate for a while. Caused by being. Conventionally, in order to suppress surging, a bypass passage that bypasses the upstream and downstream sides of the compressor and a bypass valve that opens and closes the bypass passage are provided, and the bypass valve is opened during deceleration, so that the compressor is connected via the bypass passage. It is known to release the supercharging pressure upstream of the engine.

  In that case, since the intake air is recirculated to the upstream side of the compressor through the bypass passage during deceleration, the detection accuracy of the intake air amount by the airflow sensor arranged on the upstream side of the compressor is deteriorated. Therefore, for example, in Patent Document 1, when it is determined that the recirculation of the intake air to the airflow sensor occurs, the intake air amount based on the engine speed and the opening degree of the throttle valve is used instead of the detection value by the airflow sensor. A control device that employs the calculated value is disclosed.

JP 2009-97490 A

  By the way, even when the bypass valve is closed, the intake air amount can be obtained by calculation. However, in normal times, that is, in a situation where the intake air does not recirculate to the upstream side of the compressor, the accuracy of detection of the intake air amount by the airflow sensor is more accurate than the calculation accuracy of the intake air amount based on the opening of the throttle valve. Is also expensive.

  That is, it is necessary to properly use the detected value and the calculated value of the intake air amount depending on the situation. However, there is a case where the detected value and the calculated value of the intake air amount do not coincide with each other. In this case, the intake air amount changes in a step shape when switching between the detected value and the calculated value. Since the intake air amount is used for controlling the fuel injection amount, if the intake air amount changes stepwise, vibration may occur due to torque fluctuations, or the emission performance may be temporarily deteriorated. The technology disclosed herein has been made in view of such a point, and an object thereof is to appropriately perform switching between a detected value and a calculated value of the intake air amount.

  The technology disclosed herein includes a turbocharger having a compressor disposed in an intake passage, a bypass passage provided in the intake passage and bypassing the compressor, and a bypass passage provided in the bypass passage. A control device for an engine with a turbocharger provided with a bypass valve for opening and closing the engine. The control device includes an intake air amount sensor that is provided upstream of the compressor in the intake passage and detects an intake air amount, and an intake air amount calculation unit that calculates an intake air amount based on an operating state of the engine And an intake air amount that is set as one of the intake air amount detected by the intake air amount sensor and the intake air amount calculated by the intake air amount calculation unit. A setting unit, wherein the intake air amount setting unit makes a switching speed for switching the intake air amount from the calculated value to the detected value slower than a switching speed for switching the intake air amount from the detected value to the calculated value.

  According to this configuration, the intake air amount setting unit selectively uses the detected value by the intake air amount sensor and the calculated value by the intake air amount calculation unit as the intake air amount. Basically, the detected value is more accurate than the calculated value, but the accuracy of the detected value may deteriorate when the intake air that has passed through the compressor is recirculated through the bypass passage. For example, the intake air amount setting unit normally sets the detected value as the intake air amount, and sets the calculated value as the intake air amount when the accuracy of the detected value deteriorates.

  Here, the detected value may not match the calculated value. In such a case, if the value set as the intake air amount is switched between the detected value and the calculated value, the set intake air amount varies. obtain.

  Therefore, the intake air amount setting unit makes the switching speed for switching the intake air amount from the calculated value to the detected value slower than the switching speed for switching the intake air amount from the detected value to the calculated value. Thus, when the intake air amount is switched from the calculated value to the detected value, the intake air amount gradually changes from the calculated value to the detected value. For this reason, even if the calculated value and the detected value are different, rapid fluctuations in the intake air amount are suppressed. Control of the engine using the intake air amount is stabilized by suppressing rapid fluctuations in the intake air amount. As a result, vibration due to torque fluctuation is reduced, and temporary deterioration of emission performance is reduced.

  The intake air amount setting unit sets the detected value as an intake air amount when the bypass valve is closed, and calculates the intake air amount from the detected value when the bypass valve is opened. You may switch to a value.

  According to this configuration, when the bypass valve is closed, the detected value is set as the intake air amount. This is because when the bypass valve is closed, there is no recirculation of the intake air, and if there is no recirculation of the intake air, the detected value is more accurate than the calculated value. On the other hand, when the bypass valve is opened, the intake air flows back to the upstream side of the compressor through the bypass passage, and the detection accuracy of the intake air amount sensor may deteriorate. Therefore, when the bypass valve is opened, the intake air amount is switched from the detected value to the calculated value. Thereby, a decrease in the accuracy of the intake air amount is suppressed.

  According to this configuration, the intake air amount is switched from the detected value to the calculated value when the detection accuracy of the intake air amount sensor is deteriorated. At this time, the switching speed from the detected value to the calculated value is faster than the switching speed from the calculated value to the detected value. Thereby, the intake air amount can be quickly switched to a calculated value with higher accuracy. That is, the accuracy of the intake air amount is prioritized over the fluctuation of the intake air amount.

  Further, the intake air amount setting unit switches between the detected value and the calculated value by adjusting a reflection degree of the detection value and a reflection degree of the calculated value, and the intake air amount is set to the intake air amount. The change rate of the reflection degree when switching from the calculated value to the detected value may be slower than the change speed of the reflection degree when switching the intake air amount from the detected value to the calculated value.

  According to this configuration, the switching speed from the calculated value to the detected value and the switching speed from the detected value to the calculated value are adjusted by adjusting the changing speed of the reflected degree of the detected value and the changing speed of the reflected degree of the calculated value. Change it.

  Specifically, when switching the intake air amount from the detected value to the calculated value, the intake air amount setting unit immediately switches the calculated value to the detected value, while changing the intake air amount to the calculated value. When switching from the detected value to the detected value, the reflected value of the detected value may be gradually increased while the reflected value of the calculated value is gradually decreased.

  According to this configuration, switching from the detected value to the calculated value is performed immediately, and a decrease in the accuracy of the intake air amount is immediately suppressed. On the other hand, switching from the calculated value to the detected value is gradually performed, and fluctuations in the intake air amount are suppressed.

  Further, the intake air amount setting unit slows down the switching speed for switching the intake air amount from the calculated value to the detected value as the pressure difference or pressure ratio before and after the throttle valve provided in the intake passage becomes smaller. Also good.

  If the pressure difference or pressure ratio before and after the throttle valve is large, the intake air amount is small. Even if there is a deviation between the detected value and the calculated value, the amount of deviation is small because the amount of intake air itself is small. That is, even if the detected value does not match the calculated value and the intake air amount fluctuates during switching, the fluctuation amount is small. On the other hand, when the pressure difference or pressure ratio before and after the throttle valve is small and the intake air amount is large, the amount of deviation between the detected value and the calculated value also increases. Therefore, the switching speed from the calculated value to the detected value is decreased as the pressure difference or pressure ratio before and after the throttle valve decreases. As a result, the greater the influence of fluctuations in the intake air amount at the time of switching, the slower the switching speed from the calculated value to the detected value, and the fluctuation in the intake air amount is effectively suppressed.

  According to the engine control device with the turbocharger, switching between the detected value and the calculated value of the intake air amount can be appropriately executed.

It is a block diagram which shows schematic structure of the engine system of an engine with a turbocharger. It is a block diagram of a control part. It is a compressor performance map. 4A is a timing chart of opening and closing of the bypass valve, and FIG. 4B is a timing chart of the detected value and the calculated value of the intake air amount. It is a flowchart of a process of the intake air amount setting unit when the detected value is set to the intake air amount. It is a flowchart of a process of the intake air amount setting unit when the calculated value is set to the intake air amount. It is a block diagram of an intake air amount setting unit. It is a graph which shows the change aspect of a 1st reflection coefficient. 9A is a timing chart of the intake air amount, FIG. 9B is a timing chart of the fuel injection amount, and FIG. 9C is the air-fuel ratio detected by the O ₂ sensor 56. FIG. 9D is a timing chart, and FIG. 9D is a timing chart of the fuel injection amount feedback correction amount.

<Engine system configuration>
Hereinafter, exemplary embodiments will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of the engine system 100.

  As shown in FIG. 1, the engine system 100 includes an engine 2, an intake system 10, an exhaust system 30, a turbocharger 4, an accelerator pedal device 6, and a control unit 7.

  The engine 2 is a gasoline engine. An intake system 10 is connected to the combustion chamber 21 of the engine 2 via an intake port 22, and an exhaust system 30 is connected via an exhaust port 23. The engine 2 ignites an intake valve 24 that opens and closes the intake port 22, a fuel injection valve 25 that injects fuel toward the combustion chamber 21, and a mixture of intake air and fuel supplied into the combustion chamber 21. It has an ignition plug 26, a piston 27 that reciprocates by combustion of the air-fuel mixture in the combustion chamber 21, and an exhaust valve 28 that opens and closes the exhaust port 23.

  The intake system 10 includes an intake passage 11, an air cleaner 16, a compressor 41 of the turbocharger 4, an intercooler 15, a throttle valve 14, and an intake manifold 13. The air cleaner 16, the compressor 41, the intercooler 15, the throttle valve 14 and the intake manifold 13 are arranged in the intake passage 11 in this order. The air cleaner 16 takes in external air from the air intake port 16a. The air taken into the air cleaner 16 passes through the filter 16 b and flows to the compressor 41. This air is supercharged by the compressor 41, cooled by the intercooler 15, the flow rate is adjusted by the throttle valve 14, and supplied to the combustion chamber 21 of each cylinder via the intake manifold 13.

  The throttle valve 14 is an electronically controlled valve that adjusts the amount of air supplied to the combustion chamber 21 by changing the intake passage area in the intake passage 11. The throttle valve 14 is opened and closed by a control signal from the control unit 7 in response to a pedal depression operation on the accelerator pedal device 6 by the driver.

  Further, the intake passage 11 is provided with an intake air recirculation device 17 that recirculates a part of the intake air supercharged by the compressor 41 to the upstream side of the compressor 41. The intake air recirculation device 17 has a bypass passage 17a and a bypass valve 17b.

  One end of the bypass passage 17 a is connected to a portion of the intake passage 11 between the airflow sensor 51 and the compressor 41, and the other end of the bypass passage 17 a is between the compressor 41 and the intercooler 15 of the intake passage 11. Connected to the part. The bypass valve 17 b is an electronically controlled valve that is provided in the bypass passage 17 a and is opened and closed by a control signal from the control unit 7.

  The exhaust system 30 includes an exhaust passage 31, an exhaust manifold 32, a turbine 42 of the turbocharger 4, and an exhaust purification catalyst 33. The exhaust manifold 32, the turbine 42, and the exhaust purification catalyst 33 are disposed in the exhaust passage 31 in this order.

  The turbocharger 4 includes a compressor 41, a turbine 42, and a waste gate valve 43. When the turbine 42 is rotationally driven by the exhaust gas discharged from the engine 2, the compressor 41 connected to the turbine 42 by a shaft is rotationally driven, and the intake air is supercharged.

  The waste gate valve 43 is configured to allow part of the exhaust discharged from the engine 2 to escape downstream by bypassing the turbine 42 via an exhaust bypass passage 44 communicating with the upstream and downstream of the turbine 42.

  The engine system 100 shown in FIG. 1 is provided with various sensors. Specifically, in the intake system 10, an airflow sensor 51 is provided in a portion of the intake passage 11 between the air cleaner 16 and the compressor 41. The airflow sensor 51 detects the amount of intake air taken into the intake passage 11 via the air cleaner 16. As the airflow sensor 51, for example, a hot wire type or Karman vortex type airflow sensor can be adopted. The airflow sensor 51 is an example of an intake air amount detection sensor.

  A pressure sensor 52 is provided in a portion of the intake passage 11 between the intercooler 15 and the throttle valve 14. The pressure sensor 52 detects the pressure in the intake passage 11 between the intercooler 15 and the throttle valve 14, that is, the supercharging pressure. The throttle valve 14 is provided with a throttle valve opening sensor 53 for detecting the opening of the throttle valve 14. Furthermore, a pressure sensor 54 and a temperature sensor 55 are arranged in the intake manifold 13. The pressure sensor 54 detects the pressure in the intake manifold 13, that is, the intake manifold pressure. The temperature sensor 55 detects the temperature in the intake manifold 13.

In the exhaust system 30, an O ₂ sensor 56 that detects the oxygen concentration in the exhaust gas is provided in the exhaust passage 31 (specifically, the exhaust passage 31 between the turbine 42 and the exhaust purification catalyst 33) on the downstream side of the turbine 42. ing.

The airflow sensor 51 supplies a detection signal corresponding to the detected intake air amount to the control unit 7. The pressure sensor 52 supplies a detection signal corresponding to the detected supercharging pressure to the control unit 7. The throttle valve opening sensor 53 supplies a detection signal corresponding to the detected opening of the throttle valve 14 to the control unit 7. The pressure sensor 54 supplies a detection signal corresponding to the detected intake manifold pressure to the control unit 7. The temperature sensor 55 supplies a detection signal corresponding to the detected temperature to the control unit 7. The O ₂ sensor 56 supplies a detection signal corresponding to the detected oxygen concentration to the control unit 7. The control unit 7 is supplied with a detection signal from an accelerator pedal opening sensor 57 of the accelerator pedal device 6.

  The control unit 7 stores a CPU, various programs executed on the CPU (including a basic control program such as an OS and an application program that is activated on the OS and realizes a specific function), and various data. It is comprised by the computer provided with internal memories, such as ROM and RAM. The control unit 7 performs various controls and processes based on the detection signals supplied from the various sensors described above. For example, the control unit 7 opens and closes the throttle valve 14, the bypass valve 17b, and the waste gate valve 43, determines whether or not recirculation of the intake air to the air flow sensor 51 occurs, and based on the determination result, the air flow sensor One of the calculated air amount calculated by the detected air amount and the intake air amount calculating means 51 is set as the intake air amount.

  FIG. 2 is a block diagram of the control unit 7. Functionally, the control unit 7 includes an intake air amount calculation unit 71, an intake air amount setting unit 72, a fuel injection amount control unit 73, a bypass valve control unit 74, and a storage unit 75. .

  The intake air amount calculation unit 71 includes the opening degree of the throttle valve 14 detected by the throttle valve opening degree sensor 53, the intake manifold pressure detected by the pressure sensor 54, and the intake air amount 13 detected by the temperature sensor 55. The amount of intake air supplied to the combustion chamber 21 is calculated based on the temperature. That is, the intake air amount calculation unit 71 obtains the intake air amount by the so-called D Jetronic method. The intake air amount obtained by the intake air amount calculation unit 71 is hereinafter referred to as “calculated value”.

  On the other hand, the airflow sensor 51 detects the amount of intake air actually flowing through the intake passage 11 and obtains the amount of intake air by the so-called L-Jetronic method. Hereinafter, the intake air amount obtained based on the detection result of the airflow sensor 51 is referred to as a “detected value”.

  The intake air amount setting unit 72 sets either the calculated value or the detected value as the intake air amount used for controlling the engine 2. This setting method will be described later. The intake air amount is used for various controls of the engine 2. For example, the intake air amount is used for control of the following fuel injection amount.

The fuel injection amount control unit 73 controls the fuel injection amount injected from the fuel injection valve 25 using the intake air amount set by the intake air amount setting unit 72. Specifically, the fuel injection amount control unit 73 determines the fuel injection amount with respect to the intake air amount so that the air-fuel ratio in the combustion chamber 21 becomes a desired air-fuel ratio. Further, the fuel injection amount control unit 73 feedback-controls the fuel injection amount so that the air-fuel ratio becomes a desired air-fuel ratio based on the oxygen concentration in the exhaust gas detected by the O ₂ sensor 56.

  The bypass valve control unit 74 controls the opening degree of the bypass valve 17 b according to the operating state of the engine 2. For example, the control unit 7 controls the intake air amount by adjusting the opening of the throttle valve 14 based on the accelerator opening detected by the accelerator pedal opening sensor 57.

<Control of bypass valve>
Hereinafter, the control of the bypass valve 17b by the bypass valve control unit 74 will be described in detail.

  The turbocharger 4 has a compressor performance map as shown in FIG. The compressor performance map includes a compressor passage flow rate that is a flow rate of intake air that passes through the compressor 41, a compressor pressure ratio (supercharging pressure / atmospheric pressure) that is a ratio of the intake pressure between the upstream side and the downstream side of the compressor 41, the compressor The relationship with the compressor speed which is the speed of 41 is defined. Such a compressor performance map is stored in the storage unit 75.

  The compressor performance map has a so-called surge region in a region where the compressor passage flow rate is smaller than the broken line in FIG. 3 (hereinafter referred to as “surge line L”). The surge region is expanded to the side where the flow rate through the compressor is larger as the compressor pressure ratio is larger. In this surge region, the compressor pressure ratio is too high with respect to the compressor passage flow rate, so that the intake air supercharged by the compressor 41 can flow back to the compressor 41.

  Therefore, the bypass valve control unit 74 includes the operating state of the compressor 41 estimated based on the accelerator opening detected by the accelerator pedal opening sensor 57 in the normal region on the side where the compressor passage flow rate is higher than the surge line L. In this case, the bypass valve 17b is fully closed. On the other hand, the bypass valve control unit 74 includes the operating state of the compressor 41 estimated based on the accelerator opening detected by the accelerator pedal opening sensor 57 in the surge region where the compressor passage flow rate is smaller than the surge line L. If it is indicated (indicated by a broken line arrow in the figure), the bypass valve 17b is opened. When the bypass valve 17b is opened, the intake air supercharged to the compressor 41 is returned to the downstream side of the compressor 41 through the bypass passage 17a. As a result, the compressor pressure ratio is rapidly reduced, and the operation state of the compressor 41 does not enter the surge region, and the compressor passage flow rate is reduced. Thus, the compressor 41 is protected.

  The operating state of the compressor 41 tends to enter the surge region, for example, when the engine 2 is decelerated. In particular, when the vehicle is decelerated from a state where the intake air is supercharged, the compressor pressure ratio is high, so the operating state of the compressor 41 tends to enter the surge region. Since the compressor 41 continues to rotate due to inertia for a while, the supercharging of the intake air continues for a while, while the opening of the throttle valve 14 is reduced. As a result, surging can occur because the intake air amount is throttled while the compressor pressure ratio is high. On the other hand, when the bypass valve 17b is opened, the supercharged intake air does not flow backward to the compressor 41 but is returned to the upstream side of the compressor 41 through the bypass passage 17a.

<Switching intake air amount>
Subsequently, switching between the detected value and the calculated value of the intake air amount will be described in detail.

  The intake air amount setting unit 72 sets the detected value as the intake air amount when the bypass valve 17b is closed, and sets the calculated value as the intake air amount when the bypass valve 17b is opened.

  FIG. 4A shows a timing chart of opening and closing of the bypass valve 17b, and FIG. 4B shows a timing chart of the detected value and the calculated value of the intake air amount.

  FIG. 4A shows an operation in which the engine 2 is decelerated, the bypass valve 17b is switched from the closed state to the open state, and then the bypass valve 17b is returned from the open state to the closed state. At this time, as shown in FIG. 4 (B), the detected value and the calculated value of the intake air amount decrease as the engine 2 decelerates, and become a minute value when the bypass valve 17b is opened. . While the bypass valve 17b is open, and even after the bypass valve 17b is closed, the detected value and the calculated value change with a minute value.

  Since the airflow sensor 51 actually measures the intake air amount, normally, the detected value has higher accuracy of the intake air amount than the calculated value. As shown in FIG. 4B, the detected value may slightly deviate from the calculated value. However, when the bypass valve 17b is closed, the detected value is more accurate than the calculated value. In particular, when the intake air amount is small, the pressure difference before and after the throttle valve 14 is large, so that the calculated value is easily affected by errors. Also in this point, the detected value is more accurate than the calculated value.

  However, when the bypass valve 17 b is opened and a part of the intake air is recirculated to the upstream side of the compressor 41, a part of the intake air can flow back through the air flow sensor 51. However, although the airflow sensor 51 can detect the amount of air passing therethrough, it cannot determine the direction in which the airflow sensor 51 passes, and therefore the accuracy of the detection value decreases. As shown in FIG. 4B, when the bypass valve 17b is open, the fluctuation amount of the detected value is larger than the fluctuation amount of the calculated value. This indicates that the detection accuracy of the airflow sensor 51 is lowered.

  Therefore, when the bypass valve 17b is closed, the detected value is set as the intake air amount, and when the bypass valve 17b is opened, the calculated value is set as the intake air amount.

  Specifically, the intake air amount setting unit 72 sets the intake air amount according to the flowcharts shown in FIGS. FIG. 5 is a flowchart of processing of the intake air amount setting unit 72 when the detected value is set to the intake air amount. FIG. 6 is a flowchart of processing of the intake air amount setting unit 72 when the calculated value is set to the intake air amount.

  When the detected value is set as the intake air amount, the intake air amount setting unit 72 determines whether or not the bypass valve 17b is opened in step S110, that is, whether or not the closed state is switched to the open state. Determine. When the detected value is set to the intake air amount, the bypass valve 17b is closed as described above. The intake air amount setting unit 72 determines whether or not the bypass valve 17b has been opened based on the control content of the bypass valve 17b by the bypass valve control unit 74.

  When the bypass valve 17b is opened, the intake air amount setting unit 72 changes the intake air amount from the detected value to the calculated value in step S120. On the other hand, when the bypass valve 17b remains closed, the intake air amount setting unit 72 maintains the detected value as the intake air amount.

  On the other hand, when the calculated value is set as the intake air amount, the intake air amount setting unit 72 determines whether or not the bypass valve 17b is closed in step S210, that is, whether or not the open air state is switched to the closed state. Determine whether or not. When the calculated value is set to the intake air amount, the bypass valve 17b is opened as described above. The intake air amount setting unit 72 determines whether or not the bypass valve 17b is closed based on the control content of the bypass valve 17b by the bypass valve control unit 74.

  When the bypass valve 17b is closed, the intake air amount setting unit 72 changes the intake air amount from the calculated value to the detected value in step S220. On the other hand, when the bypass valve 17b remains open, the intake air amount setting unit 72 maintains the calculated value as the intake air amount.

  Here, the intake air amount setting unit 72 changes the switching speed when switching the intake air amount from the detection value to the calculated value and the switching speed when switching the intake air amount from the calculated value to the detection value. .

  FIG. 7 is a block diagram of the intake air amount setting unit 72. The intake air amount setting unit 72 includes a reflection coefficient setting unit 76 and an intake air amount switching unit 77.

  The reflection coefficient setting unit 76 sets a first reflection coefficient K1 that is a reflection coefficient of the detection value L. The first reflection coefficient K1 is a value between 0 and 1. On the other hand, the second reflection coefficient K2, which is the reflection coefficient of the calculated value D, is K2 = 1−K1 (K2 = 0 to 1), and the sum of the first reflection coefficient K1 and the second reflection coefficient K2 is 1. That is, the reflection coefficient setting unit 76 sets the first reflection coefficient K1 and also sets the second reflection coefficient K2. The first reflection coefficient K1 is an example of the reflection degree of the detection value L, and the second reflection coefficient K2 is an example of the reflection degree of the calculated value D.

  The intake air amount switching unit 77 calculates the intake air amount by adding a value obtained by multiplying the detection value L by the first reflection coefficient K1 and a value obtained by multiplying the calculated value D by the second reflection coefficient K2.

  When the first reflection coefficient K1 is 1, the second reflection coefficient K2 is 0, and the detection value L is the intake air amount. On the other hand, when the first reflection coefficient K1 is 0, the second reflection coefficient K2 is 1, and the calculated value D is the intake air amount. When the first reflection coefficient K1 is a value between 0 and 1, the second reflection coefficient K2 is a value satisfying (1−K1) and a value between 0 and 1. In this case, the intake air amount is set to a value in which the detection value L is reflected at a rate according to the first reflection coefficient K1 and the calculated value D is reflected at a rate according to the second reflection coefficient K2.

  That is, when the reflection coefficient setting unit 76 changes the values of the first reflection coefficient K1 and the second reflection coefficient K2, the value set as the intake air amount is switched between the detected value L and the calculated value D. The switching speed between the detection value L and the calculated value D is adjusted by adjusting the speed at which the reflection coefficient setting unit 76 changes the values of the first reflection coefficient K1 and the second reflection coefficient K2.

  Specifically, FIG. 8 shows how the first reflection coefficient K1 is changed. The reflection coefficient setting unit 76 immediately changes the first reflection coefficient K1 from 1 to 0 when switching from the detected value L to the calculated value D, that is, when changing the first reflection coefficient K1 from 1 to 0. On the other hand, the reflection coefficient setting unit 76 gradually changes the first reflection coefficient K1 from 0 to 1 when switching from the calculated value D to the detection value L, that is, when changing the first reflection coefficient K1 from 0 to 1. .

The reason why the reflection coefficient setting unit 76 changes the changing speed of the first reflection coefficient K1 in this way will be described with reference to the timing chart of FIG. 9A is a timing chart of the intake air amount, FIG. 9B is a timing chart of the fuel injection amount, and FIG. 9C is the air-fuel ratio detected by the O ₂ sensor 56. FIG. 9D is a timing chart, and FIG. 9D is a timing chart of the fuel injection amount feedback correction amount.

  Here, a case where the intake air amount is switched from the calculated value D to the detected value L will be described. FIG. 9A shows a detection value L (dashed line) and a calculated value D (solid line). In the example of FIG. 9A, the detection value L is a value smaller than the actual intake air amount, and the calculated value D is a value larger than the actual intake air amount. Further, the fluctuation of values as shown in FIG. 4B is omitted. Therefore, originally, when the calculated value D is set as the intake air amount, the fluctuation amount of the detection value L is relatively large, but this is not shown.

  Here, for convenience of explanation, it is assumed that the fuel injection amount control unit 73 starts control of the fuel injection amount at time t0. At this time, the calculated value D is set as the intake air amount. The fuel injection amount control unit 73 determines the fuel injection amount corresponding to the calculated value D so that the air-fuel ratio becomes the target air-fuel ratio (here, the target air-fuel ratio is the stoichiometric air-fuel ratio), and the fuel An injection amount of fuel is supplied through the fuel injection valve 25 (FIG. 9B).

However, since the calculated value D is a value larger than the actual intake air amount as shown in FIG. 9A, the fuel injection amount determined by the fuel injection amount control unit 73 becomes the stoichiometric air-fuel ratio. More than the value. Therefore, as shown in FIG. 9C, the detection signal of the O ₂ sensor 56 indicates that the actual air-fuel ratio is richer than the stoichiometric air-fuel ratio.

Then, as shown in FIG. 9D, the fuel injection amount control unit 73 sets the feedback correction amount for the fuel injection amount to a value corresponding to lowering the actual air-fuel ratio to the target air-fuel ratio at time t1. Set. That is, a negative feedback correction amount is set. Accordingly, as shown in FIG. 9B, the fuel injection amount supplied from the fuel injection valve 25 is reduced. As a result, as shown in FIG. 9C, the detection signal of the O ₂ sensor 56 is It shows that the actual air-fuel ratio substantially matches the stoichiometric air-fuel ratio.

  Thereafter, at time t2, the intake air amount is switched from the calculated value D to the detected value L as the bypass valve 17b is closed.

  At this time, it is assumed that the intake air amount is immediately switched from the calculated value D to the detected value L as indicated by a thick broken line in FIG. As a result, the intake air amount decreases stepwise from the calculated value D to the detected value L.

  Then, as shown in FIG. 9B, the fuel injection amount control unit 73 reduces the fuel injection amount in accordance with the decrease in the intake air amount. However, since the detected value L is slightly smaller than the actual intake air amount, the actual air-fuel ratio shifts to the lean side from the theoretical air-fuel ratio (FIG. 9C).

  On the other hand, as shown in FIG. 9D, the fuel injection amount control unit 73 sets the feedback correction amount for the fuel injection amount to a value corresponding to the actual air-fuel ratio rising to the target air-fuel ratio at time t3. Set to. As a result, as shown in FIG. 9B, the fuel injection amount supplied from the fuel injection valve 25 is increased, and as a result, the actual air-fuel ratio substantially matches the stoichiometric air-fuel ratio (FIG. 9 ( C)).

  However, in such control, as shown in FIG. 9C, when the calculated value D is switched to the detected value L, the actual air-fuel ratio changes stepwise. As a result, torque fluctuations can occur and vibrations can occur. Further, when the air-fuel ratio temporarily shifts to the lean side, the performance of the exhaust purification catalyst 33 can be lowered, and the emission performance can be lowered.

  On the other hand, the intake air amount setting unit 72 does not immediately switch from the calculated value D to the detected value L, but gradually switches from the calculated value D to the detected value L as shown by a thick solid line in FIG. . Specifically, the intake air amount setting unit 72 linearly changes the first reflection coefficient K1 from 0 to 1 as shown in FIG. As a result, the set intake air amount gradually decreases linearly from the calculated value D to the detected value L.

The fuel injection amount set by the fuel injection amount control unit 73 is not reduced stepwise from the amount corresponding to the calculated value D to the amount corresponding to the detected value L, but as shown in FIG. 9B. The amount is gradually reduced according to the amount of intake air that gradually decreases. Corresponding to such a change in the fuel injection amount, the actual air-fuel ratio detected by the O ₂ sensor 56 gradually changes to the lean side as shown in FIG. 9C. The feedback correction amount set by the fuel injection amount control unit 73 is also increased by an amount corresponding to a slight decrease in the intake air amount, as shown in FIG. 9D.

  While the intake air amount is gradually switched from the calculated value D to the detected value L, such feedback control is repeated. For this reason, the actual air-fuel ratio does not return to the stoichiometric air-fuel ratio again after being reduced stepwise, but gradually decreases to the stoichiometric air-fuel ratio although it decreases slightly as shown in FIG. 9C. . Thereby, the step-like change of the actual air-fuel ratio is suppressed. As a result, torque fluctuations are suppressed, vibrations are reduced, deviation of the air-fuel ratio from the target air-fuel ratio is reduced, and deterioration in emission performance is suppressed.

  Here, the intake air amount setting unit 72, specifically the reflection coefficient setting unit 76, changes the switching speed for switching from the calculated value D to the detected value L so that the pressure difference before and after the throttle valve 14 (upstream pressure−downstream pressure) is small. I'm late. That is, the reflection coefficient setting unit 76, as shown by the two-dot chain line in FIG. 8, decreases as the pressure difference between the supercharging pressure detected by the pressure sensor 52 and the intake manifold pressure detected by the pressure sensor 54 decreases. The change speed of the reflection coefficient K1 from 0 to 1 is reduced. When the pressure difference before and after the throttle valve 14 is large, the amount of intake air is small, so that the amount of fluctuation when the intake air amount switches from the calculated value D to the detected value L is also small. For this reason, the influence of fluctuations in the intake air amount on the vibration and emission performance of the engine 2 is small. On the other hand, when the pressure difference before and after the throttle valve 14 is small, the amount of intake air is large, and therefore the amount of fluctuation when the intake air amount switches from the calculated value D to the detected value L is also large. Therefore, the influence of fluctuations in the intake air amount on the vibration and emission performance of the engine 2 is large. Therefore, by reducing the switching speed as the pressure difference before and after the throttle valve 14 becomes smaller, fluctuations in the intake air amount are further reduced, and the influence on the vibration and emission performance of the engine 2 is reduced. The switching speed may be adjusted based on the pressure ratio (upstream pressure / downstream pressure) instead of the pressure difference before and after the throttle valve 14. That is, the switching speed is set slower as the pressure ratio before and after the throttle valve 14 becomes smaller.

  On the other hand, the switching speed when the intake air amount is switched from the detected value L to the calculated value D is relatively high. In the first place, the reason why the detected value L and the calculated value D are properly used according to the opening and closing of the bypass valve 17b is that the accuracy of the detected value L deteriorates when the bypass valve 17b is opened. That is, the reason for switching from the detected value L to the calculated value D is that if the detected value L is continuously used as the intake air amount, the influence on the vibration and emission performance of the engine 2 is large. Therefore, when switching from the detected value L to the calculated value D, the intake air amount setting unit 72 increases the switching speed. As a result, the accuracy of the intake air amount is prioritized and improved over the suppression of sudden fluctuations in the intake air amount. Specifically, the detection value L is immediately switched to the calculated value D. As described above, the control unit 7 includes the intake air amount calculation unit 71 that calculates the intake air amount based on the operating state of the engine 2, the detected value L of the intake air amount detected by the airflow sensor 51, and the intake air An intake air amount setting unit 72 that sets one of the calculated intake air amount values D calculated by the air amount calculation unit 71 as an intake air amount, and the intake air amount setting unit 72 calculates the intake air amount The switching speed for switching from the value D to the detection value L is made slower than the switching speed for switching the intake air amount from the detection value L to the calculated value D.

  According to this configuration, it is possible to suppress sudden fluctuations in the intake air amount when switching from the calculated value D to the detected value L, and thus it is possible to suppress vibrations of the engine 2 and a decrease in emission performance. The accuracy of the calculated value D is lower than the accuracy of the normal detection value L, but not so low. For this reason, priority is given to suppressing sudden fluctuations in the intake air amount, rather than switching to the detection value L and increasing the accuracy of the intake air amount as much as possible. On the other hand, when switching from the detected value L to the calculated value D, the accuracy of the detected value L is lowered so that the calculated value D is lower than the detected value L. In such a case, priority is given to improving the accuracy of the intake air amount over suppression of sudden fluctuations in the intake air amount, and the detection value L is quickly switched to the calculated value D. As described above, the detection value L and the calculated value D are appropriately switched depending on the situation, and the switching speed at that time should be given priority on suppression of sudden fluctuations in the intake air amount, It is set appropriately depending on whether improvement should be prioritized.

  More specifically, the intake air amount setting unit 72 sets the detected value L as the intake air amount when the bypass valve 17b is closed, and detects the intake air amount when the bypass valve 17b is opened. Switch from L to calculated value D.

  That is, when the bypass valve 17b is normally closed, the detection value L that is inherently highly accurate is set as the intake air amount. When the bypass valve 17b is opened, the intake air is recirculated to the upstream side of the compressor 41 and the detection accuracy of the airflow sensor 51 is lowered, so that the intake air amount is switched from the detected value L to the calculated value D. Thereby, a decrease in the accuracy of the intake air amount is suppressed.

  The intake air amount setting unit 72 switches between the detected value L and the calculated value D by adjusting the first reflection coefficient K1 of the detected value L and the second reflection coefficient K2 of the calculated value D, and The change rate of the first reflection coefficient K1 and the second reflection coefficient K2 when the air amount is switched from the calculated value D to the detected value L, and the first reflection coefficient K1 when the intake air amount is switched from the detected value L to the calculated value D and It is slower than the changing speed of the second reflection coefficient K2.

  According to this configuration, the intake air amount setting unit 72 can adjust the switching speed between the detected value L and the calculated value D by adjusting the changing speed of the first reflection coefficient K1 and the second reflection coefficient K2. it can.

  Further, the intake air amount setting unit 72 decreases the switching speed at which the intake air amount is switched from the calculated value D to the detected value L as the pressure difference or pressure ratio before and after the throttle valve 14 provided in the intake passage 11 decreases. .

  According to this configuration, the intake air amount setting unit 72 adjusts the switching speed from the intake calculation value D to the detection value L according to the intake air amount. Specifically, when the pressure difference before and after the throttle valve 14 is small and the intake air amount is large, the switching speed from the calculated value D to the detected value L is set slower. The greater the amount of intake air, the greater the effect of sudden fluctuations in the amount of intake air on the vibration and emission performance of the engine 2. Therefore, by adjusting the switching speed in this way, it is possible to more effectively reduce the influence of sudden fluctuations in the intake air amount on the vibration and emission performance of the engine 2.

<< Other Embodiments >>
As described above, the embodiment has been described as an example of the technique disclosed in the present application. However, the technology in the present disclosure is not limited to this, and can also be applied to an embodiment in which changes, replacements, additions, omissions, and the like are appropriately performed. Moreover, it is also possible to combine each component demonstrated by the said embodiment and it can also be set as new embodiment. In addition, among the components described in the accompanying drawings and detailed description, not only the components essential for solving the problem, but also the components not essential for solving the problem in order to exemplify the above technique. May also be included. Therefore, it should not be immediately recognized that these non-essential components are essential as those non-essential components are described in the accompanying drawings and detailed description.

  About the said embodiment, it is good also as following structures.

  The configuration of the engine system 100 is an example, and is not limited to this configuration.

  The intake air amount setting unit 72 determines whether the bypass valve 17b is opened or closed based on the control content of the bypass valve control unit 74, but the intake air amount setting unit 72 uses other methods to determine whether the bypass valve 17b is open or closed. It may be determined whether to open or close. For example, the intake air amount setting unit 72 determines that the bypass valve 17b is opened when the absolute value of the change amount or the absolute value of the change rate of at least one of the detected value L and the calculated value D exceeds a predetermined threshold value. You may judge. That is, when the bypass valve 17b is opened, the amount of intake air decreases, so that changes in the detected value L and the calculated value D increase. Therefore, it is possible to determine whether the bypass valve 17b is open based on the absolute value of the change amount or the absolute value of the change rate of at least one of the detected value L and the calculated value D.

  The intake air amount setting unit 72 switches the intake air amount from the calculated value D to the detected value L when the bypass valve 17b is closed, but the switching timing from the calculated value D to the detected value L is It is not limited to this. For example, the intake air amount setting unit 72 may switch the intake air amount from the calculated value D to the detected value L when the fluctuation amount of the detected value L falls below a predetermined threshold. That is, the reason why the calculated value D is used is that the amount of change in the detected value L increases due to recirculation of the intake air. Therefore, the calculated value D may be switched to the detected value L if the fluctuation amount of the detected value L becomes small. Alternatively, the intake air amount setting unit 72 may reset the detection value L as the intake air amount after a predetermined time has elapsed after setting the calculated value D as the intake air amount. Here, the predetermined time can be set to a time estimated that the fluctuation of the detection value L is settled.

  As described above, the technology disclosed herein is useful for a control device for a turbocharged engine.

DESCRIPTION OF SYMBOLS 100 Engine system 11 Intake passage 17a Bypass passage 17b Bypass valve 2 Engine 4 Turbocharger 41 Compressor 51 Air flow sensor (intake air amount sensor)
7 Control unit (control device)
71 Intake air amount calculation unit 72 Intake air amount setting unit

Claims (5)

A turbocharger having a compressor disposed in an intake passage, a bypass passage provided in the intake passage and bypassing the compressor, and a bypass valve provided in the bypass passage and opening and closing the bypass passage. A turbocharged engine control device,
An intake air amount sensor that is provided upstream of the compressor in the intake passage and detects an intake air amount;
An intake air amount calculation unit for calculating an intake air amount based on an operating state of the engine;
An intake air amount setting unit that sets either the detected value of the intake air amount detected by the intake air amount sensor or the calculated value of the intake air amount calculated by the intake air amount calculation unit as the intake air amount And
The intake air amount setting unit is configured to reduce a switching speed at which the intake air amount is switched from the calculated value to the detected value slower than a switching speed at which the intake air amount is switched from the detected value to the calculated value. Control device for engine with a feeder. The control device for an engine with a turbocharger according to claim 1,
The intake air amount setting unit sets the detected value as an intake air amount when the bypass valve is closed, and changes the intake air amount from the detected value to the calculated value when the bypass valve is opened. A control device for an engine with a turbocharger, characterized by switching. In the control device for an engine with a turbocharger according to claim 1 or 2,
The intake air amount setting unit includes:
By adjusting the reflection degree of the detection value and the reflection degree of the calculated value, switching between the detection value and the calculated value is performed,
The rate of change in the degree of reflection when switching the intake air amount from the calculated value to the detected value is made slower than the rate of change in the degree of reflection when switching the intake air amount from the detected value to the calculated value. Control device for turbocharged engine. The engine control device with a turbocharger according to claim 3,
The intake air amount setting unit includes:
When switching the intake air amount from the detected value to the calculated value, while immediately switching the calculated value to the detected value,
A turbocharger characterized in that, when the intake air amount is switched from the calculated value to the detected value, the reflected degree of the calculated value is gradually increased while the reflected degree of the detected value is gradually increased. Engine control unit. The control device for an engine with a turbocharger according to any one of claims 1 to 4,
The intake air amount setting unit slows the switching speed at which the intake air amount is switched from the calculated value to the detected value as the pressure difference or pressure ratio before and after the throttle valve provided in the intake passage decreases. An engine control device with a turbocharger.

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