JP2008208740A - Air-fuel ratio control device for internal combustion engine with supercharger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce influence exerted on accuracy of air-fuel ratio control by operation of a waste gate valve in an air-fuel ratio control device for an internal combustion engine with a supercharger. <P>SOLUTION: An output signal from an exhaust gas sensor 16 disposed at a position downstream of a turbine 10 of the supercharger and upstream of an exhaust emission control catalyst 14 is fed back to a calculation of a fuel injection amount, and a steady component of a feedback value is learned. The predetermined state of the waste gate valve 12 during execution of learning is either one of an open state or a closed state. The waste gate valve 12 is fixed to the predetermined state until learning of the control amount regarding the air-fuel ratio control is completed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an air-fuel ratio control device for an internal combustion engine with a supercharger, and in particular, an internal combustion engine with a supercharger having a wastegate valve and an exhaust gas sensor disposed downstream of the turbine of the supercharger. The present invention relates to an air-fuel ratio control apparatus.

  Conventionally, an air-fuel ratio control apparatus is known in which an exhaust gas sensor is arranged in an exhaust passage of an internal combustion engine, and its output signal is fed back to calculation of a fuel injection amount. However, an error may be included in the output signal of the exhaust gas sensor due to various causes. When an error is included in the output signal of the exhaust gas sensor, even the error is fed back to the calculation of the fuel injection amount, and the accuracy of the air-fuel ratio control is lowered. Therefore, for example, in the technique described in Patent Document 1, the output signal of the exhaust gas sensor is corrected based on the exhaust pressure, so that an error due to the exhaust pressure fluctuation is excluded from the output signal of the exhaust gas sensor.

Air-fuel ratio control based on the output signal of the exhaust gas sensor is also performed in an internal combustion engine with a supercharger. As the position of the exhaust gas sensor in the internal combustion engine with a supercharger, the exhaust gas sensor can be disposed not only upstream of the turbocharger turbine as described in Patent Document 1, but also downstream of the turbine.
Japanese Patent Laid-Open No. 2006-9694 JP 2001-263084 A JP 2006-104978 A

  However, when the supercharger is equipped with a wastegate valve, the flow of exhaust gas downstream of the turbine varies greatly depending on whether the wastegate valve is open or closed. In the structure in which the exhaust gas sensor is disposed downstream of the turbine, there is a difference in the degree of exhaust gas hitting the exhaust gas sensor depending on whether the waste gate valve is open or closed.

  Usually, since an exhaust purification catalyst is arranged in the immediate vicinity of the turbine, there are restrictions on the selection of the position of the exhaust gas sensor downstream of the turbine. For this reason, if the exhaust gas sensor is arranged in accordance with the flow of the exhaust gas when the wastegate valve is in the closed state, the contact of the exhaust gas in the open state is not good. On the contrary, if the exhaust gas sensor is arranged in accordance with the flow of the exhaust gas when the wastegate valve is in the open state, the exhaust gas hit in the closed state is no longer good.

  The exhaust gas sensor has a structure in which a sensor element is provided inside the cover. The exhaust gas sensor outputs a signal corresponding to the ambient atmosphere of the sensor element, that is, the air-fuel ratio of the gas inside the cover. For this reason, if the exhaust gas hit is not good, gas exchange inside the cover is not promoted, and a deviation occurs between the air-fuel ratio indicated by the output signal of the exhaust gas sensor and the actual air-fuel ratio of the exhaust gas. .

  As described above, when the supercharger is equipped with a wastegate valve and an exhaust gas sensor is disposed downstream of the turbine, the operation of the wastegate valve affects the accuracy of air-fuel ratio control. However, in the conventional air-fuel ratio control, it has not been taken into account that the exhaust gas contact with the exhaust gas sensor changes depending on the open / close state of the waste gate valve.

  The present invention has been made to solve the above-described problems, and is an air-fuel ratio control device for an internal combustion engine with a supercharger that can reduce the influence of the operation of a wastegate valve on the accuracy of air-fuel ratio control. The purpose is to provide.

In order to achieve the above object, a first invention provides an air-fuel ratio control apparatus for an internal combustion engine with a supercharger having a wastegate valve,
An exhaust gas sensor disposed downstream of the turbocharger turbine and upstream of the exhaust purification catalyst;
Feedback means for feeding back the output signal of the exhaust gas sensor to the calculation of the fuel injection amount;
Learning means for learning a stationary component of a feedback value calculated by the feedback means;
A wastegate valve control means for controlling the operation of the wastegate valve;
The waste gate valve is in a predetermined state at the time of learning execution by the learning means in one of an open state and a closed state, and the waste gate valve control means until the learning by the learning means is completed. Is characterized in that the wastegate valve is fixed in the predetermined state.

According to a second invention, in the first invention,
A second exhaust gas sensor disposed downstream of the exhaust purification catalyst;
Second feedback means for feeding back an output signal of the second exhaust gas sensor to calculation of a fuel injection amount;
Second learning means for learning a stationary component of the feedback value calculated by the second feedback means;
The waste gate valve control means fixes the waste gate valve in the predetermined state until learning by the second learning means is completed.

According to a third invention, in the first or second invention,
The predetermined state is an open state, and the wastegate valve control means releases the fixation of the wastegate valve when a torque increase request for the internal combustion engine is detected.

4th invention is 1st or 2nd invention,
The predetermined state is a closed state, and the waste gate valve control means releases the fixation of the waste gate valve when a torque reduction request for the internal combustion engine is detected.

In order to achieve the above object, a fifth aspect of the present invention provides an air-fuel ratio control apparatus for an internal combustion engine with a supercharger having a wastegate valve.
An exhaust gas sensor disposed downstream of the turbocharger turbine and upstream of the exhaust purification catalyst;
A second exhaust gas sensor disposed downstream of the exhaust purification catalyst;
Feedback means for feeding back the output signal of the exhaust gas sensor to the calculation of the fuel injection amount;
Second feedback means for feeding back an output signal of the second exhaust gas sensor to calculation of a fuel injection amount;
Learning means for learning a stationary component of a feedback value calculated by the second feedback means;
A wastegate valve control means for controlling the operation of the wastegate valve;
The waste gate valve is in a predetermined state at the time of learning execution by the learning means in one of an open state and a closed state, and the waste gate valve control means until the learning by the learning means is completed. Is characterized in that the wastegate valve is fixed in the predetermined state.

In order to achieve the above object, a sixth aspect of the invention provides an air-fuel ratio control apparatus for an internal combustion engine with a supercharger having a wastegate valve.
An exhaust gas sensor disposed downstream of the turbocharger turbine and upstream of the exhaust purification catalyst;
Feedback means for feeding back the output signal of the exhaust gas sensor to the calculation of the fuel injection amount;
A wastegate valve control means for controlling the operation of the wastegate valve;
The waste gate valve control means fixes the waste gate valve in a closed state in a specific operation region in which the air-fuel ratio of the exhaust gas varies between cylinders.

A seventh invention is the sixth invention, wherein
Learning means for learning a stationary component of a feedback value calculated by the feedback means;
The waste gate valve control means fixes the waste gate valve in a closed state when the internal combustion engine is operated in the specific operation region in a state where learning by the learning means is not completed. .

In an eighth aspect based on the sixth aspect,
A second exhaust gas sensor disposed downstream of the exhaust purification catalyst;
Second feedback means for feeding back an output signal of the second exhaust gas sensor to calculation of a fuel injection amount;
Second learning means for learning a stationary component of the feedback value calculated by the second feedback means;
The waste gate valve control means fixes the waste gate valve in a closed state when the internal combustion engine is operated in the specific operation region in a state where learning by the second learning means is not completed. It is a feature.

In order to achieve the above object, a ninth aspect of the invention provides an air-fuel ratio control apparatus for an internal combustion engine with a supercharger having a wastegate valve.
An exhaust gas sensor disposed downstream of the turbocharger turbine and upstream of the exhaust purification catalyst;
Feedback means for feeding back the output signal of the exhaust gas sensor to the calculation of the fuel injection amount;
Correction means for correcting the calculation of the feedback value in the feedback means according to the open / closed state of the waste gate valve;
It is characterized by having.

In order to achieve the above object, a tenth aspect of the invention is an air-fuel ratio control apparatus for an internal combustion engine with a supercharger having a wastegate valve.
An exhaust gas sensor disposed downstream of the turbocharger turbine and upstream of the exhaust purification catalyst;
A second exhaust gas sensor disposed downstream of the exhaust purification catalyst;
Feedback means for feeding back the output signal of the exhaust gas sensor to the calculation of the fuel injection amount;
Second feedback means for feeding back an output signal of the second exhaust gas sensor to calculation of a fuel injection amount;
Correction means for correcting the calculation of the feedback value in the second feedback means according to the open / closed state of the waste gate valve;
It is characterized by having.

  According to the first aspect of the invention, the wastegate valve is fixed to the predetermined state at the time of learning until the learning is completed, so that the exhaust gas sensor hits the exhaust gas sensor during learning based on the output signal of the exhaust gas sensor. Can be prevented, and early completion of learning and improvement of learning accuracy can be realized.

  According to the second invention, the wastegate valve is fixed in the predetermined state until learning based on the output signal of the exhaust gas sensor downstream of the catalyst (second learning) is completed. It is possible to prevent an error included in the output signal due to a change in exhaust gas hit, that is, a learning target of the second learning from fluctuating, and to achieve the early completion of the second learning and improvement of the learning accuracy. Can be realized.

  According to the third aspect of the invention, even when the wastegate valve is fixed in the open state, the wastegate valve is unlocked when there is a request for an increase in torque. The torque can be increased quickly.

  According to the fourth aspect of the invention, even when the wastegate valve is fixed in the closed state, the wastegate valve is released when the torque reduction is requested. The torque can be quickly reduced.

  According to the fifth invention, the wastegate valve is fixed to a predetermined state at the time of learning until learning is completed, so that the output signal is included in the output signal due to a change in exhaust gas hitting the exhaust gas sensor upstream of the catalyst. It is possible to prevent the error, that is, the learning target of learning based on the output signal of the exhaust gas sensor downstream of the catalyst from fluctuating, thereby realizing early completion of learning and improvement of learning accuracy.

  According to the sixth aspect of the invention, even in an operation region where the air-fuel ratio of the exhaust gas varies between cylinders, the exhaust gas is agitated by the turbine by fixing the wastegate valve in the closed state. Can promote mixing. As a result, even if the air-fuel ratio of the exhaust gas varies between cylinders, the air-fuel ratio of the exhaust gas flowing through the exhaust gas sensor can be made uniform, and in which operating region the internal combustion engine is operated However, air-fuel ratio control based on the output signal of the exhaust gas sensor can be performed with high accuracy.

  According to the seventh aspect, since the wastegate valve is fixed to the closed state on the condition that learning based on the output signal of the exhaust gas sensor is not completed, early completion of learning and improvement of learning accuracy are achieved. While realizing, the situation where the operation of the wastegate valve is limited can be minimized.

  According to the eighth aspect of the invention, the waste gate valve is fixed to the closed state on the condition that learning based on the output signal of the exhaust gas sensor downstream of the catalyst (second learning) is not completed. The situation where the operation of the wastegate valve is restricted is minimized while realizing the early completion of the second learning and the improvement of the learning accuracy for the error included in the output signal to the exhaust gas sensor. Can do.

  According to the ninth aspect of the invention, the correction of the feedback value based on the output signal of the exhaust gas sensor is corrected depending on whether the waste gate valve is in the open state or the open state. Even when the gas contact state changes, the air-fuel ratio control can be performed with high accuracy.

  Further, according to the tenth aspect of the invention, the correction of the feedback value based on the output signal of the exhaust gas sensor downstream of the catalyst is corrected depending on whether the waste gate valve is in the open state or the open state. The air-fuel ratio control can be performed with high accuracy even when the degree of exhaust gas hitting the exhaust gas sensor changes.

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

  FIG. 1 is a diagram showing a configuration of an exhaust system of an internal combustion engine (hereinafter referred to as an engine) to which an air-fuel ratio control apparatus according to Embodiment 1 of the present invention is applied. The engine 2 according to the present embodiment is a multi-cylinder engine (a four-cylinder engine is shown in FIG. 1), and an inlet of an exhaust manifold 6 is connected to each cylinder 4 of the engine 2. An exhaust pipe 8 is connected to the outlet of the exhaust manifold 6. The engine 2 according to this embodiment is an engine with a supercharger (specifically, a turbocharger), and a turbocharger turbine 10 is attached to the exhaust pipe 8. Further, a wastegate valve (hereinafter referred to as WGV) 12 is attached to the exhaust pipe 8 so as to bypass the turbine 10.

An exhaust gas purification catalyst 14 for purifying harmful substances (HC, CO, NOx) in the exhaust gas is disposed in the exhaust pipe 8. A catalyst upstream sensor 16 is attached upstream of the exhaust purification catalyst 14 and downstream of the turbine 10. The catalyst upstream sensor 16 is an exhaust gas sensor (so-called A / F sensor) that outputs a signal linearly corresponding to the air-fuel ratio of the exhaust gas. A catalyst downstream sensor 18 is attached downstream of the exhaust purification catalyst 14. The catalyst downstream sensor 18 is an exhaust gas sensor (so-called O ₂ sensor) having an output characteristic in which the output suddenly changes between the rich side and the lean side with respect to the air / fuel ratio with reference to the stoichiometric air / fuel ratio.

  The engine 2 includes an ECU (Electronic Control Unit) 20 as its control device. The ECU 20 performs air-fuel ratio control for adjusting the fuel injection amount so that the air-fuel ratio of the exhaust gas becomes the target air-fuel ratio as control of the engine 2. More specifically, the air-fuel ratio control includes main feedback control based on the output signal of the catalyst upstream sensor 16 and sub-feedback control based on the output signal of the catalyst downstream sensor 18. The main feedback control is a process for making the output signal of the catalyst upstream sensor 16 coincide with the target air-fuel ratio, and the sub feedback control is a process for compensating for a steady error included in the output signal of the catalyst upstream sensor 16. It is.

  In the main feedback control, a deviation between the actual air-fuel ratio of the exhaust gas measured by the catalyst upstream sensor 16 and the target air-fuel ratio is calculated, and a correction value (hereinafter referred to as a main value) fed back to the calculation of the fuel injection amount by PI control of the deviation. FB correction value) is calculated. In addition, a steady component included in the main FB correction value is learned as a learning value (hereinafter referred to as a main FB learning value). In the main feedback control, a fuel injection amount correction coefficient is calculated using the main FB correction value and the main FB learning value, and the final fuel injection amount is calculated by multiplying the basic value of the fuel injection amount by the correction coefficient. Is done. The basic value of the fuel injection amount is calculated from the measured value of the intake air amount and the target air-fuel ratio.

  The main FB learning value is learned as follows, for example. First, at the start of learning, the main FB learning value is set to a predetermined initial value (for example, zero). After the start of learning, a predetermined update value is added (or subtracted) to the main FB learning value at a constant cycle. As learning progresses, the steady component included in the main FB correction value is gradually transferred to the main FB correction value, and eventually the vibration center of the main FB correction value converges to zero. When the vibration center of the main FB correction value converges to zero, the learning of the main FB learning value is completed. In FIG. 3, each operation of the main FB learning value and the main FB correction value from the start to the completion of learning is illustrated by a time chart.

  On the other hand, in the sub-feedback control, the deviation between the output signal of the catalyst downstream sensor 18 and a predetermined reference signal is calculated. The reference signal is a signal corresponding to the stoichiometric value. Then, a correction value (hereinafter referred to as a sub FB correction value) to be fed back to the calculation of the fuel injection amount is calculated by PI control of the deviation. In addition, a steady component included in the sub FB correction value is learned as a learning value (hereinafter referred to as a sub FB learning value). The sub FB correction value and the sub FB learning value are respectively added to the output signal of the catalyst upstream sensor 16 as a correction signal.

  The sub FB learning value is learned as follows, for example. First, the sub FB learning value is set to zero at the start of learning. After the start of learning, the integral term of the sub FB correction value (I term of PI control) is added to the sub FB learning value at a constant period, and at the same time, the integral term of the sub FB correction value is reset to zero. Thereby, as the learning progresses, the steady component included in the sub FB correction value is gradually transferred to the sub FB learning value, and the integral term of the sub FB correction value eventually converges to zero. The learning of the sub FB learning value is completed when the integral term of the sub FB correction value converges to zero. In FIG. 4, each operation of the sub FB learning value and the sub FB correction value from the start to the completion of learning is illustrated in a time chart.

  The accuracy of the air-fuel ratio control described above depends on the reliability of the output signals of the exhaust gas sensors 16 and 18. However, the internal combustion engine with a supercharger as in the present embodiment has a feature that the reliability of the output signal of the catalyst upstream sensor 16 depends on the open / close state of the WGV 12. This is because the reliability of the output signal of the catalyst upstream sensor 16 changes depending on how the exhaust gas hits the catalyst upstream sensor 16, and the flow of the exhaust gas in the vicinity of the catalyst upstream sensor 16 changes depending on the open / close state of the WGV 12.

  In FIG. 1, the flow of exhaust gas is shown by a curve with an arrow. The exhaust gas flow indicated by a solid line in FIG. 1 is an exhaust gas flow when the WGV 12 is closed, and the exhaust gas flow indicated by a broken line in FIG. 1 is an exhaust gas flow when the WGV 12 is open. is there. The exhaust gas flow shown in FIG. 1 is merely schematic, but actually, the exhaust gas flow downstream of the turbine 10 varies depending on the open / close state of the WGV 12. At the position of the catalyst upstream sensor 16 shown in FIG. 1, the exhaust gas hitting condition is good when the WGV 12 is open, but the exhaust gas hitting condition gets worse when the WGV 12 is closed. Therefore, there is a high possibility that a highly reliable output signal cannot be obtained when the WGV 12 is in the closed state.

  The reliability of the output signal of the catalyst upstream sensor 16 affects not only the main feedback control but also the sub feedback control. In particular, the influence of each learning value on the learning speed and learning accuracy is great. Specifically, since the main FB learning value is learned based on the output signal of the catalyst upstream sensor 16, the reliability of the output signal of the catalyst upstream sensor 16 directly affects the learning accuracy of the main FB learning value. Further, the learning target related to the sub FB learning value is a steady error included in the output signal of the catalyst upstream sensor 16, but the learning target is not stable in a situation where the reliability of the output signal of the catalyst upstream sensor 16 is low. Inaccurate learning is not possible.

  Therefore, in the present embodiment, when the air-fuel ratio control is performed, the open / close state of the WGV 12 is controlled as described below. FIG. 2 is a flowchart showing a routine of the opening / closing control of the WGV 12 executed in the present embodiment. The opening / closing control of the WGV 12 is performed by the ECU 20 together with the air-fuel ratio control.

  In the first step S100 of the routine shown in FIG. 2, the learning state of the main FB learning value and the sub FB learning value is confirmed. The learning state of these learning values can be confirmed by ON / OFF of each flag indicating that learning is in progress and learning is completed. FIG. 3 illustrates the relationship between the progress status of the main FB learning, the learning execution flag, and the learning completion flag. FIG. 4 illustrates the relationship between the progress status of the sub FB learning, the learning execution flag, and the learning completion flag.

  In step S102, it is determined whether learning is being executed based on the confirmation result in step S100. If the learning execution flag of either the main FB learning value or the sub FB learning value is on, it is determined that learning is being executed. When learning is not being executed, that is, after learning of both the main FB learning value and the sub FB learning value is completed, the process of step S110 is selected. In step S110, the control of the open / close state of the WGV 12 is performed according to the situation. That is, opening / closing control of the WGV 12 is performed in accordance with a normal routine related to supercharger control.

  If it is determined in step S102 that learning is being performed, the determination in step S104 is performed. In step S104, it is determined whether there is a torque increase request from the driver to the engine 2. The torque increase request is detected from the accelerator opening and the rate of change. When there is no torque increase request, the process of step S106 is selected. In step S <b> 106, a signal requesting to fix the WGV 12 to the open state (WGV opening / fixing request signal) is output to the driver that drives the WGV 12. FIG. 3 illustrates the relationship between the progress status of the main FB learning and the WGV opening / fixing request signal. FIG. 4 illustrates the relationship between the progress of the sub FB learning and the WGV opening / fixing request signal.

  The WGV opening / fixing request signal is output and the WGV 12 is fixed in the open state, whereby the exhaust gas flow indicated by the broken line in FIG. 1 is realized. As a result, the exhaust gas hitting state to the catalyst upstream sensor 16 can be kept good, and the learning of each learning value is completed early and learned while ensuring the reliability of the output signal of the catalyst upstream sensor 16 at the time of learning execution. It is possible to achieve improvement in accuracy.

  On the other hand, when there is a torque increase request, the process of step S108 is selected and the WGV 12 is released from being fixed to the open state. That is, while the learning is being executed, the WGV 12 is basically fixed in the open state, but when there is a torque increase request, the WGV 12 is released from being fixed until the torque increase request disappears. As a result, the WGV 12 can be closed and the torque can be quickly increased. For example, the acceleration response can be improved during acceleration.

  Even after the completion of learning of the main FB learning value and the sub FB learning value, even if the degree of exhaust gas hitting the catalyst upstream sensor 16 changes, the effect of this on the accuracy of air-fuel ratio control is compared to when learning is not completed. small. Therefore, by controlling the open / closed state of the WGV 12 according to the routine shown in FIG. 2 and thereby quickly learning each learning value with high accuracy, the influence of the operation of the WGV 12 on the accuracy of the air-fuel ratio control is reduced. be able to.

  By the way, in the present embodiment, the open / close state of the WGV 12 is controlled based on the learning states of both the main FB learning value and the sub FB learning value. However, the WGV 12 may be controlled based on only one of the learning states. it can. For example, if the degree of exhaust gas hitting the catalyst upstream sensor 16 significantly affects the main FB learning value rather than the sub FB learning value, the open / close state of the WGV 12 is controlled based only on the learning state of the main FB learning value. You may do it. Conversely, the open / close state of the WGV 12 may be controlled based only on the learning state of the sub FB learning value.

  Further, in the present embodiment, when there is a torque increase request, the torque increase request is prioritized over learning, but learning may be prioritized. That is, even when there is a torque increase request from the driver, the WGV 12 remains fixed in the open state if learning is being executed. According to this, learning accuracy is not lowered even temporarily, and learning can be completed earlier.

  In the present embodiment, the ECU 20 performs main feedback control, thereby realizing the “feedback means” according to the first and fifth aspects of the invention, and learning the main FB learning value in the main feedback control. The “learning means” according to the first invention is realized. Further, the “sub-feedback means” according to the second and fifth inventions is realized by the ECU 20 performing the sub-feedback control, and the sub-FB learning value is learned in the sub-feedback control. The “second learning means” and the “learning means” according to the fifth invention are realized. Then, when the ECU 20 executes the routine shown in FIG. 2, the “waist gate valve control means” according to the first, second, third and fifth inventions is realized.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to the drawings.

  FIG. 5 is a diagram showing a configuration of an engine exhaust system to which the air-fuel ratio control apparatus according to the second embodiment of the present invention is applied. In the configuration shown in FIG. 5, the same parts or portions as those in the configuration shown in FIG. The difference between the configuration of the exhaust system according to the present embodiment and the configuration of the exhaust system according to the first embodiment is in the attachment position of the catalyst upstream sensor 16.

  In FIG. 5, the flow of the exhaust gas is shown by a curve with an arrow. The exhaust gas flow indicated by the solid line in FIG. 5 is the exhaust gas flow when the WGV 12 is closed, and the exhaust gas flow indicated by the broken line in FIG. 5 is the exhaust gas flow when the WGV 12 is open. is there. At the position of the catalyst upstream sensor 16 shown in FIG. 5, the exhaust gas hitting condition is good when the WGV 12 is closed, but the exhaust gas hitting condition is worsened when the WGV 12 is opened. Therefore, in the configuration of the exhaust system according to the present embodiment, there is a high possibility that a highly reliable output signal cannot be obtained when the WGV 12 is open.

  Therefore, in the present embodiment, when the air-fuel ratio control is performed, the open / close state of the WGV 12 is controlled as described below. FIG. 6 is a flowchart showing a routine of the opening / closing control of the WGV 12 executed in the present embodiment. The opening / closing control of the WGV 12 is performed by the ECU 20 together with the air-fuel ratio control.

  In the first step S200 of the routine shown in FIG. 6, the learning state of the main FB learning value and the sub FB learning value is confirmed. In the next step S202, it is determined whether learning is being executed based on the confirmation result in step S200. When learning is not being executed, that is, after learning of both the main FB learning value and the sub FB learning value is completed, the process of step S210 is selected. In step S210, the opening / closing control of the WGV 12 is performed according to a normal routine related to supercharger control.

  If it is determined in step S202 that learning is being performed, the determination in step S204 is performed. In step S204, it is determined whether or not there is a torque reduction request from the driver to the engine 2. The torque reduction request is detected from the accelerator opening and its changing speed. If there is no torque reduction request, the process of step S206 is selected. In step S206, a signal (WGV closing / fixing request signal) for requesting the WGV 12 to be closed is output to the driver that drives the WGV 12.

  By outputting the WGV closing / fixing request signal and fixing the WGV 12 to the closed state, the exhaust gas flow indicated by the solid line in FIG. 5 is realized. As a result, the exhaust gas hitting state to the catalyst upstream sensor 16 can be kept good, and the learning of each learning value is completed early and learned while ensuring the reliability of the output signal of the catalyst upstream sensor 16 at the time of learning execution. It is possible to achieve improvement in accuracy.

  On the other hand, if there is a torque reduction request, the process of step S208 is selected and the WGV 12 is released from being closed. That is, while the learning is being executed, the WGV 12 is basically fixed in the closed state, but when there is a torque reduction request, the WGV 12 is released from being fixed until the torque reduction request disappears. As a result, it becomes possible to quickly reduce the torque by opening the WGV 12, and for example, the deceleration response can be improved during deceleration.

  By the way, in the present embodiment, the open / close state of the WGV 12 is controlled based on the learning states of both the main FB learning value and the sub FB learning value. However, the WGV 12 may be controlled based on only one of the learning states. it can.

  Further, in this embodiment, when there is a torque reduction request, the torque reduction request is given priority over learning, but learning may be given priority. That is, even when there is a torque reduction request from the driver, the WGV 12 remains fixed in the closed state if learning is being executed. According to this, learning accuracy is not lowered even temporarily, and learning can be completed earlier.

  In the present embodiment, the ECU 20 performs main feedback control, thereby realizing the “feedback means” according to the first and fifth aspects of the invention, and learning the main FB learning value in the main feedback control. The “learning means” according to the first invention is realized. Further, the “sub-feedback means” according to the second and fifth inventions is realized by the ECU 20 performing the sub-feedback control, and the sub-FB learning value is learned in the sub-feedback control. The “second learning means” and the “learning means” according to the fifth invention are realized. The ECU 20 executes the routine shown in FIG. 6 to realize the “waist gate valve control means” according to the first, second, fourth and fifth inventions.

Embodiment 3 FIG.
Next, a third embodiment of the present invention will be described with reference to the drawings.

  The air-fuel ratio control apparatus as the third embodiment of the present invention is applied to an engine having an exhaust system having the configuration shown in FIG. In the multi-cylinder engine 2 as shown in FIG. 5, the air-fuel ratio of the exhaust gas may vary among the cylinders depending on the operating region. This variation in the air-fuel ratio between the cylinders is caused by variations in the intake air amount between the cylinders due to operating conditions, changes in the injector characteristics of each cylinder, and the like. The variation in the intake air amount is mainly due to the intake pulsation, which is greatly influenced by the engine speed.

  FIG. 7 illustrates the relationship between the engine speed and the degree of variation in the air-fuel ratio between cylinders. The degree of variation here refers to calculating the difference in air-fuel ratio between cylinders by calculating the air-fuel ratio difference between the cylinder with the largest air-fuel ratio or the cylinder with the smallest air-fuel ratio, or the dispersion of the air-fuel ratio between cylinders. It is what became. As shown in FIG. 7, the variation in the air-fuel ratio between the cylinders rapidly increases in a specific operation region.

  When the variation in the air-fuel ratio between the cylinders is large, the exhaust gas discharged from the exhaust manifold 9 may have uneven air-fuel ratio. When exhaust gas having a large air-fuel ratio irregularity flows to the catalyst upstream sensor 16, a deviation occurs between the air-fuel ratio indicated by the output signal of the catalyst upstream sensor 16 and the average air-fuel ratio of the actual exhaust gas. The accuracy of control will deteriorate. In particular, when the learning of the main FB learning value and the sub FB learning value is not completed, the influence of the reliability of the output signal of the catalyst upstream sensor 16 on the accuracy of the air-fuel ratio control is great.

  Therefore, in the present embodiment, when the air-fuel ratio control is performed, the open / close state of the WGV 12 is controlled as described below. FIG. 8 is a flowchart showing a routine of the opening / closing control of the WGV 12 executed in the present embodiment. The opening / closing control of the WGV 12 is performed by the ECU 20 together with the air-fuel ratio control.

  In the first step S300 of the routine shown in FIG. 8, it is determined whether or not the current or future operating region of the engine 2 is a specific operating region in which the variation in the air-fuel ratio between the cylinders is large. If the operation is not in the specific operation region, the process in step S308 is selected. In step S308, the opening / closing control of the WGV 12 is performed according to a normal routine related to supercharger control.

  When the engine 2 is operated in the specific operation region, the process of step S302 is executed. In step S302, the learning state of the main FB learning value and the sub FB learning value is confirmed. In the next step S304, it is determined whether learning is being executed based on the confirmation result in step S302. When learning is not being executed, that is, when learning of both the main FB learning value and the sub FB learning value has already been completed, the process of step S308 is selected, and the opening / closing control of the WGV 12 is performed in a random manner.

  If it is determined in step S304 that learning is being executed, the determination in step S306 is performed. In step S306, a signal (WGV closing / fixing request signal) for requesting the WGV 12 to be closed is output to the driver that drives the WGV 12. FIG. 9 is a time chart showing an example of ON / OFF operation of the WGV closing / fixing request signal with respect to changes in the engine speed.

  When the WGV closing / fixing request signal is output and the WGV 12 is fixed in the closed state, the exhaust gas discharged from each cylinder to the exhaust manifold 6 passes through the turbine 10 and flows into the exhaust pipe 6. At that time, the exhaust gas is agitated by the turbine 10 to promote mixing. Thereby, even if the air-fuel ratio of the exhaust gas varies among the cylinders, the air-fuel ratio of the exhaust gas flowing through the catalyst upstream sensor 16 can be made uniform. By eliminating irregularities in the air-fuel ratio of the exhaust gas, the reliability of the output signal of the catalyst upstream sensor 16 can be ensured, and early learning completion of each learning value and improvement in learning accuracy can be realized. Become.

  In the present embodiment, the WGV 12 is fixed in a closed state on the condition that learning of either the main FB learning value or the sub FB learning value is not completed. Regardless of completion, the WGV 12 may always be closed and fixed in the specific operation region. This is because the reliability of the output signal of the catalyst upstream sensor 16 affects the accuracy of the air-fuel ratio control even when learning is completed. However, by setting learning incomplete as a condition for closing and fixing the WGV 12, it is possible to minimize the situation in which the operation of the WGV 12 is restricted while realizing early completion of learning and improvement of learning accuracy.

  In the present embodiment, the “feedback means” according to the sixth aspect of the present invention is realized by the ECU 20 performing the main feedback control, and the main FB learning value is learned in the main feedback control. The “learning means” according to the seventh invention is realized. Further, the “sub-feedback means” according to the eighth invention is realized by the ECU 20 performing the sub-feedback control, and the sub-FB learning value is learned in the sub-feedback control. Second learning means "is realized. Then, when the ECU 20 executes the routine shown in FIG. 8, the “waist gate valve control means” according to the sixth, seventh and eighth inventions is realized.

Embodiment 4 FIG.
Next, a fourth embodiment of the present invention will be described with reference to the drawings.

  It is known that there is a difference between the stoichiometric point on the output characteristics of the A / F sensor and the true stoichiometric point. The deviation of the stoichiometric point varies depending on the composition of the exhaust gas, but also varies depending on how the exhaust gas hits the A / F sensor. Therefore, in the configuration shown in FIG. 1 or the configuration shown in FIG. 5, there is a difference in the deviation of the stoichiometric point depending on whether the WGV 12 is open or closed.

  FIG. 10 shows the output characteristics of the catalyst upstream sensor 16 with respect to stoichiometry when the WGV 12 is in an open state and a closed state. The output characteristics shown in FIG. 10 apply to the output characteristics of the catalyst upstream sensor 16 in the configuration shown in FIG. With the configuration shown in FIG. 5, the output characteristics of the catalyst upstream sensor 16 show opposite characteristics when the WGV 12 is in an open state and a closed state. In the configuration shown in FIG. 1, when the WGV 12 is closed and the exhaust gas hit condition is good, the deviation between the stoichiometric point and the true stoichiometric point on the output characteristics of the catalyst upstream sensor 16 is small. However, when the WGV 12 opens and the exhaust gas contact condition deteriorates, the deviation between the stoichiometric point and the true stoichiometric point on the output characteristics of the catalyst upstream sensor 16 increases.

  The air-fuel ratio control apparatus according to the fourth embodiment of the present invention corrects the calculation of the feedback value in the main feedback control in accordance with the open / close state of the WGV 12, and thereby outputs the output characteristics of the catalyst upstream sensor 16 according to the open / close state of the WGV 12. This is characterized by compensating for the difference between the two. Specifically, the target air-fuel ratio setting is changed depending on whether the WGV 12 is in an open state or a closed state.

  FIG. 11 shows an example of setting the target air-fuel ratio according to the open / close state of the WGV 12. When the true stoichiometric point is shifted to the lean side from the stoichiometric point on the output characteristics of the catalyst upstream sensor 16 (as shown in FIG. 10), the target air-fuel ratio is the catalyst upstream sensor 16 as shown in FIG. Is set to a richer side than the stoichiometric point on the output characteristics. Further, in the closed state of the WGV 12 where the deviation between the stoichiometric point and the true stoichiometric point on the output characteristics of the catalyst upstream sensor 16 is large, the target air-fuel ratio is set to a richer side than the open state of the WGV 12. The relationship between the target air-fuel ratio, the intake air amount, and the open / closed state of the WGV 12 shown in FIG. 11 is mapped and stored in the ECU 20.

  As described above, in the present embodiment, the setting of the target air-fuel ratio is changed depending on whether the WGV 12 is open or closed. Since the difference in the output characteristics of the catalyst upstream sensor 16 due to the open / closed state of the WGV 12 is compensated for by changing the setting of the target air-fuel ratio, the operation of the WGV 12 changes the degree of exhaust gas hitting the catalyst upstream sensor 16. However, the actual air-fuel ratio of the exhaust gas can be controlled with high accuracy toward the original target air-fuel ratio (for example, stoichiometry).

  The air-fuel ratio control according to the present embodiment can be combined with any of the air-fuel ratio control apparatuses of the first to third embodiments.

  In the present embodiment, the “feedback means” according to the ninth aspect of the present invention is realized by the ECU 20 performing the main feedback control. The ECU 20 changes the setting of the target air-fuel ratio related to the main feedback control according to the map shown in FIG. 11, thereby realizing the “correction means” according to the ninth aspect of the invention.

Embodiment 5. FIG.
Next, a fifth embodiment of the present invention will be described with reference to the drawings.

  The air-fuel ratio control apparatus according to the fifth embodiment of the present invention corrects the calculation of the feedback value in the sub-feedback control according to the open / close state of the WGV 12, and thereby outputs the output characteristics of the catalyst upstream sensor 16 according to the open / close state of the WGV 12. This is characterized by compensating for the difference between the two. Specifically, a learning correction value corresponding to the open / close state of the WGV 12 is added to the sub FB learning value, and this is used as a correction signal for correcting the output signal of the catalyst upstream sensor 16.

  FIG. 12 shows an example of setting a learning correction value (sub FB learning correction value) according to the open / close state of the WGV 12. Here, it is assumed that a predetermined sub FB learning correction value is added to the sub FB learning value when the WGV 12 is in the closed state with the WGV 12 in the closed state. When the true stoichiometric point shifts to the lean side with respect to the stoichiometric point on the output characteristics in the closed state of the WGV 12 (as shown in FIG. 10), as shown in FIG. 12, the sub FB learning correction value Is set to correct the sub FB learning value to the increase side. The relationship between the sub FB learning correction value and the intake air amount shown in FIG. 12 is mapped and stored in the ECU 20.

  As described above, in the present embodiment, correction is added to the calculation of the sub FB learning value depending on whether the WGV 12 is in an open state or a closed state. The correction applied to the calculation of the sub FB learning value compensates for the difference in the output characteristics of the catalyst upstream sensor 16 depending on the open / close state of the WGV 12, so that the exhaust gas hitting the catalyst upstream sensor 16 changes due to the operation of the WGV 12. Even in this case, the actual air-fuel ratio of the exhaust gas can be controlled to the original target air-fuel ratio (for example, stoichiometric) with high accuracy.

  The air-fuel ratio control according to the present embodiment can be combined with any of the air-fuel ratio control apparatuses of the first to third embodiments.

  In the present embodiment, the “feedback means” according to the tenth invention is realized by the ECU 20 performing the main feedback control, and the sub-feedback control according to the tenth invention. "Second feedback means" is realized. Then, the “correcting means” according to the tenth aspect of the present invention is realized by the ECU 20 correcting the sub FB learning value related to the sub feedback control according to the map shown in FIG.

Embodiment 6 FIG.
Finally, Embodiment 6 of the present invention will be described with reference to the drawings.

  The air-fuel ratio control apparatus as the sixth embodiment of the present invention corrects the calculation of the feedback value in the sub-feedback control according to the open / close state of the WGV 12 as in the fifth embodiment, and thereby depends on the open / close state of the WGV 12. It is characterized by compensating for the difference in the output characteristics of the catalyst upstream sensor 16. However, in the present embodiment, a method of changing the setting of the reference signal related to the sub feedback control is adopted. Specifically, the reference signal is a signal corresponding to the stoichiometric value, and sub-feedback control is performed using a signal obtained by adding a stoichiometric correction value corresponding to the open / closed state of the WGV 12 to this signal.

  FIG. 13 shows an example of setting the stoichiometric correction value (catalyst stoichiometric correction value) according to the open / closed state of the WGV 12. When the true stoichiometric point deviates further toward the lean side than the stoichiometric point on the output characteristics of the catalyst upstream sensor 16 (as shown in FIG. 10), the catalyst stoichiometric correction value is the reference signal as shown in FIG. Is set to be corrected to the increase side. Further, in the closed state of the WGV 12 where the deviation between the stoichiometric point and the true stoichiometric point on the output characteristics of the catalyst upstream sensor 16 is large, the catalyst stoichiometric correction value is set to a larger value than in the open state of the WGV 12. The relationship between the catalyst stoichiometric correction value, the intake air amount, and the open / closed state of the WGV 12 shown in FIG. 13 is mapped and stored in the ECU 20.

  As described above, in the present embodiment, the setting of the reference signal for sub feedback control is changed depending on whether the WGV 12 is in an open state or a closed state. Since the difference in the output characteristics of the catalyst upstream sensor 16 due to the open / close state of the WGV 12 is compensated for by the change of the reference signal setting, even when the exhaust gas hits the catalyst upstream sensor 16 changes due to the operation of the WGV 12. Thus, it becomes possible to control the actual air-fuel ratio of the exhaust gas to the original target air-fuel ratio (for example, stoichiometry) with high accuracy.

  The air-fuel ratio control according to the present embodiment can be combined with any of the air-fuel ratio control apparatuses of the first to third embodiments.

  In the present embodiment, the “feedback means” according to the tenth invention is realized by the ECU 20 performing the main feedback control, and the sub-feedback control according to the tenth invention. "Second feedback means" is realized. Then, the “correction means” according to the tenth aspect of the present invention is realized by the ECU 20 correcting the sub FB learning value for the sub feedback control according to the map shown in FIG.

Others.
Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, the following modifications may be made.

  In the configuration shown in FIG. 1 and the configuration shown in FIG. 5, exhaust gas sensors are provided upstream and downstream of the exhaust purification catalyst. However, the catalyst downstream sensor is not always essential in applying the present invention. The first, third, fourth, sixth, seventh and ninth inventions can be applied to an engine which does not have a catalyst downstream sensor but has only a catalyst upstream sensor.

In the configuration shown in FIG. 1 and the configuration shown in FIG. 5, the catalyst upstream sensor is an A / F sensor, but this may be an O ₂ sensor. Conversely, an A / F sensor can be used as the catalyst downstream sensor.

1 is a diagram showing a configuration of an exhaust system of an internal combustion engine to which an air-fuel ratio control apparatus as Embodiment 1 of the present invention is applied. It is a flowchart which shows the routine of the opening / closing control of WGV performed in Embodiment 1 of this invention. It is a figure which shows the relationship with the progress of the main FB learning in main feedback control, and the operation | movement of WGV with a time chart. It is a figure which shows the relationship between the progress of sub FB learning in sub feedback control, and operation | movement of WGV with a time chart. It is a figure which shows the structure of the exhaust system of the internal combustion engine to which the air fuel ratio control apparatus as Embodiment 2 of this invention is applied. It is a flowchart which shows the routine of the opening / closing control of WGV performed in Embodiment 2 of this invention. It is a figure which shows the relationship between an engine speed and the dispersion | variation in the air fuel ratio between cylinders. It is a flowchart which shows the routine of the opening / closing control of WGV performed in Embodiment 3 of this invention. It is a time chart which shows an example of ON / OFF operation | movement of the WGV closing fixation request signal with respect to the change of the engine speed implement | achieved in Embodiment 3 of this invention. It is a figure for demonstrating the influence which the opening-and-closing state of WGV has on the output characteristic of a catalyst upstream sensor. It is a figure for demonstrating the change of the setting of the target air fuel ratio according to the opening / closing state of WGV performed in Embodiment 4 of this invention. It is a figure for demonstrating correction | amendment of the sub FB learning correction amount according to the opening / closing state of WGV performed in Embodiment 5 of this invention. It is a figure for demonstrating the change of the setting of the catalyst stoichiometric correction amount according to the opening / closing state of WGV performed in Embodiment 6 of this invention.

Explanation of symbols

2 Internal combustion engine 4 Cylinder 6 Exhaust manifold 8 Exhaust pipe 10 Turbine 12 Wastegate valve 14 Exhaust purification catalyst 16 Catalyst upstream sensor (A / F sensor)
18 Catalyst downstream sensor (O ₂ sensor)
20 ECU
32 A / F sensor

Claims (10)

In the air-fuel ratio control device for an internal combustion engine with a supercharger having a wastegate valve,
An exhaust gas sensor disposed downstream of the turbocharger turbine and upstream of the exhaust purification catalyst;
Feedback means for feeding back the output signal of the exhaust gas sensor to the calculation of the fuel injection amount;
Learning means for learning a stationary component of a feedback value calculated by the feedback means;
A wastegate valve control means for controlling the operation of the wastegate valve;
The waste gate valve is in a predetermined state at the time of learning execution by the learning means in one of an open state and a closed state, and the waste gate valve control means until the learning by the learning means is completed. An air-fuel ratio control apparatus for an internal combustion engine with a supercharger, wherein the wastegate valve is fixed in the predetermined state. A second exhaust gas sensor disposed downstream of the exhaust purification catalyst;
Second feedback means for feeding back an output signal of the second exhaust gas sensor to calculation of a fuel injection amount;
Second learning means for learning a stationary component of the feedback value calculated by the second feedback means;
2. The internal combustion engine with a supercharger according to claim 1, wherein the waste gate valve control means fixes the waste gate valve in the predetermined state until learning by the second learning means is completed. Air-fuel ratio control device.   The predetermined state is an open state, and the wastegate valve control means releases the fixation of the wastegate valve when a torque increase request for the internal combustion engine is detected. 3. An air-fuel ratio control device for an internal combustion engine with a supercharger according to 2.   The predetermined state is a closed state, and the wastegate valve control means releases the fixation of the wastegate valve when a torque reduction request for the internal combustion engine is detected. 3. An air-fuel ratio control device for an internal combustion engine with a supercharger according to 2. In the air-fuel ratio control device for an internal combustion engine with a supercharger having a wastegate valve,
An exhaust gas sensor disposed downstream of the turbocharger turbine and upstream of the exhaust purification catalyst;
A second exhaust gas sensor disposed downstream of the exhaust purification catalyst;
Feedback means for feeding back the output signal of the exhaust gas sensor to the calculation of the fuel injection amount;
Second feedback means for feeding back an output signal of the second exhaust gas sensor to calculation of a fuel injection amount;
Learning means for learning a stationary component of a feedback value calculated by the second feedback means;
A wastegate valve control means for controlling the operation of the wastegate valve;
The waste gate valve is in a predetermined state at the time of learning execution by the learning means in one of an open state and a closed state, and the waste gate valve control means until the learning by the learning means is completed. An air-fuel ratio control apparatus for an internal combustion engine with a supercharger, wherein the wastegate valve is fixed in the predetermined state. In the air-fuel ratio control device for an internal combustion engine with a supercharger having a wastegate valve,
An exhaust gas sensor disposed downstream of the turbocharger turbine and upstream of the exhaust purification catalyst;
Feedback means for feeding back the output signal of the exhaust gas sensor to the calculation of the fuel injection amount;
A wastegate valve control means for controlling the operation of the wastegate valve;
The wastegate valve control means fixes the wastegate valve in a closed state in a specific operation region where the air-fuel ratio of the exhaust gas varies between cylinders. Control device. Learning means for learning a stationary component of a feedback value calculated by the feedback means;
The waste gate valve control means fixes the waste gate valve in a closed state when the internal combustion engine is operated in the specific operation region in a state where learning by the learning means is not completed. The air-fuel ratio control apparatus for an internal combustion engine with a supercharger according to claim 6. A second exhaust gas sensor disposed downstream of the exhaust purification catalyst;
Second feedback means for feeding back an output signal of the second exhaust gas sensor to calculation of a fuel injection amount;
Second learning means for learning a stationary component of the feedback value calculated by the second feedback means;
The waste gate valve control means fixes the waste gate valve in a closed state when the internal combustion engine is operated in the specific operation region in a state where learning by the second learning means is not completed. The air-fuel ratio control apparatus for an internal combustion engine with a supercharger according to claim 6 or 7. In the air-fuel ratio control device for an internal combustion engine with a supercharger having a wastegate valve,
An exhaust gas sensor disposed downstream of the turbocharger turbine and upstream of the exhaust purification catalyst;
Feedback means for feeding back the output signal of the exhaust gas sensor to the calculation of the fuel injection amount;
Correction means for correcting the calculation of the feedback value in the feedback means according to the open / closed state of the waste gate valve;
An air-fuel ratio control apparatus for an internal combustion engine with a supercharger. In the air-fuel ratio control device for an internal combustion engine with a supercharger having a wastegate valve,
An exhaust gas sensor disposed downstream of the turbocharger turbine and upstream of the exhaust purification catalyst;
A second exhaust gas sensor disposed downstream of the exhaust purification catalyst;
Feedback means for feeding back the output signal of the exhaust gas sensor to the calculation of the fuel injection amount;
Second feedback means for feeding back an output signal of the second exhaust gas sensor to calculation of a fuel injection amount;
Correction means for correcting the calculation of the feedback value in the second feedback means according to the open / closed state of the waste gate valve;
An air-fuel ratio control apparatus for an internal combustion engine with a supercharger.

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