JP2008309138A - Air fuel ratio control system for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To more securely perform feedback control of an air fuel ratio of each of first and second cylinder blocks to a target air fuel ratio, in an internal combustion engine wherein a first exhaust passage connected to the first cylinder block and a second exhaust passage connected to the second cylinder block are communicated with each other by a communication pipe. <P>SOLUTION: This air fuel ratio control system for the internal combustion engine is provided with a first air fuel ratio sensor arranged in a connection part between the first exhaust passage and the communication pipe; a second air fuel ratio sensor arranged in a connection part between the second exhaust passage and the communication pipe; a means for detecting an exhaust gas amount ratio which is a ratio between the amount of exhaust gas flowing inside the first exhaust passage on the downstream side of the connection part with the communication pipe and the amount of exhaust gas flowing inside the second exhaust passage on the downstream side of the connection part with the communication pipe; and a correction coefficient calculating means for calculating a feedback correction coefficient and learning correction coefficient suitable for performing air fuel ratio control of each of the first and second cylinder blocks, based on the air fuel ratios detected by the respective air fuel ratio sensors and the exhaust gas amount ratio. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an air-fuel ratio control apparatus for an internal combustion engine.

  A plurality of cylinders, and the cylinders are divided into a first cylinder group and a second cylinder group, and a first exhaust passage connected to the first cylinder group and a second cylinder group connected to the second cylinder group; The two exhaust passages are connected to each other by a communication pipe, whereby at least a part of the exhaust gas of the first cylinder group flows into the second exhaust passage through the communication pipe, and the exhaust gas of the second cylinder group Or at least a part of the exhaust gas of the second cylinder group flows into the first exhaust passage through the communication pipe and can merge with the exhaust gas of the first cylinder group. The flow of exhaust gas flowing in the first exhaust passage downstream of the connecting portion and the flow of exhaust gas flowing in the second exhaust passage downstream of the connecting portion of the connecting pipe are controlled by a control valve according to the engine operating state. Internal combustion engines that are controlled are known (for example, Patent Document 1, Patent Document 2 and Patent) Document reference 3).

JP-A-8-121153 Japanese Patent Publication No. 1-227246 Japanese Utility Model Publication 1-173423

  By the way, in a general internal combustion engine, when it is necessary to control the air-fuel ratio to the target air-fuel ratio, an air-fuel ratio sensor is provided in the exhaust passage, and the air-fuel ratio is controlled based on the output of the air-fuel ratio sensor. ing. Specifically, the fuel injection amount is feedback-controlled so that the air-fuel ratio becomes the target air-fuel ratio with a feedback correction coefficient calculated based on the output of the air-fuel ratio sensor.

  In addition, if the amount of fuel actually injected from the fuel injection valve, the amount of intake air, etc. deviate from the normal amount due to individual variations in the fuel injection valve, throttle valve, etc. or changes over time, the feedback correction coefficient deviates greatly from zero. There is a fear. However, it is preferable in terms of control that the feedback correction coefficient varies around zero. Therefore, a correction coefficient that returns the feedback correction coefficient to almost zero (hereinafter referred to as a learning correction coefficient) when the feedback correction coefficient greatly deviates from zero is statistically learned, and the learning correction coefficient is reflected in feedback control. Control is performed.

  However, when such feedback control is applied to an internal combustion engine provided with the above-described communication pipe, the air-fuel ratio may not be properly feedback controlled. For example, when a part of the exhaust gas of the first cylinder group flows into the second exhaust passage through the communication pipe and merges with the exhaust gas of the second cylinder group, the exhaust gas is disposed in the second exhaust passage. The air-fuel ratio detected by the air-fuel ratio sensor is not detected by the individual air-fuel ratio of the second cylinder group due to the interference of exhaust gas from the first cylinder group. Therefore, there is a problem that it may be difficult to perform feedback control so that the air-fuel ratio of the second cylinder group matches the target air-fuel ratio.

  In view of the above problems, the present invention provides an internal combustion engine in which a first exhaust passage connected to a first cylinder group and a second exhaust passage connected to a second cylinder group are connected to each other by a communication pipe. An object of the present invention is to provide an air-fuel ratio control apparatus for an internal combustion engine that can more reliably feedback-control the air-fuel ratios of the first cylinder group and the second cylinder group to a target air-fuel ratio.

  According to the first aspect of the present invention, a first exhaust passage that includes a plurality of cylinders, divides the cylinders into a first cylinder group and a second cylinder group, and is connected to the first cylinder group. And the second exhaust passage connected to the second cylinder group are connected to each other by a communication pipe, so that at least a part of the exhaust gas of the first cylinder group enters the second exhaust passage through the communication pipe. It flows in and merges with the exhaust gas of the second cylinder group, or at least a part of the exhaust gas of the second cylinder group flows into the first exhaust passage through the communication pipe and is exhausted from the first cylinder group. The amount of exhaust gas flowing in the first exhaust passage downstream of the connecting portion with the communication pipe and the amount of exhaust gas flowing in the second exhaust passage downstream of the connecting portion of the communication pipe In the internal combustion engine in which the exhaust gas amount ratio, which is the ratio, is controlled, the connecting portion between the first exhaust passage and the communication pipe A first air-fuel ratio sensor, a second air-fuel ratio sensor disposed at a connection portion between the second exhaust passage and the communication pipe, means for detecting an exhaust gas amount ratio, When a part of the exhaust gas flows into the second exhaust passage and merges with the exhaust gas of the second cylinder group, the output of the first air-fuel ratio sensor that contacts only the exhaust gas of the first cylinder group is used. A first feedback correction coefficient is calculated based on the first feedback correction coefficient, a first learning correction coefficient is calculated based on the first feedback correction coefficient, and the first cylinder group exhaust gas and the second cylinder group exhaust gas contact each other. A second feedback correction coefficient is calculated based on the output of the second air-fuel ratio sensor, and the second air-fuel ratio when it is assumed that only the exhaust gas of the second cylinder group is in contact with the second air-fuel ratio sensor. The assumed output, which is the sensor output, is output from the first air-fuel ratio sensor. And the second air-fuel ratio sensor output and the detected exhaust gas amount ratio, the second learning correction coefficient is calculated based on the calculated assumed output, and the exhaust gas of the second cylinder group When a part of the gas flows into the first exhaust passage and merges with the exhaust gas of the first cylinder group, the exhaust gas of the first cylinder group and the exhaust gas of the second cylinder group come into contact with each other. The first feedback correction coefficient is calculated based on the output of the air-fuel ratio sensor, and the first air-fuel ratio sensor when it is assumed that only the exhaust gas of the first cylinder group is in contact with the first air-fuel ratio sensor. A hypothetical output that is an output is calculated based on the output of the first air-fuel ratio sensor, the output of the second air-fuel ratio sensor, and the detected exhaust gas amount ratio, and the first output based on the calculated hypothetical output. The learning correction coefficient is calculated and the exhaust gas of the second cylinder group A correction coefficient calculating means for calculating a second feedback correction coefficient based on the output of the second air-fuel ratio sensor that only contacts, and calculating a second learning correction coefficient based on the second feedback correction coefficient; The first air-fuel ratio control means for controlling the air-fuel ratio of the first cylinder group with the first feedback correction coefficient and the first learning correction coefficient so as to match the fuel ratio, and the first air-fuel ratio control means so as to match the target air-fuel ratio. There is provided an air-fuel ratio control apparatus for an internal combustion engine, comprising: a second air-fuel ratio control means for controlling an air-fuel ratio of a second cylinder group with a feedback correction coefficient of 2 and a second learning correction coefficient.

  That is, in the first aspect of the invention, the first air-fuel ratio sensor disposed at the connection portion between the first exhaust passage and the communication pipe and the connection portion between the second exhaust passage and the communication pipe are disposed. The second air-fuel ratio sensor, the amount of exhaust gas flowing in the first exhaust passage downstream of the connection portion between the communication pipe and the amount of exhaust gas flowing in the second exhaust passage downstream of the connection portion of the communication pipe; Means for detecting an exhaust gas amount ratio which is a ratio of Then, the correction coefficient calculation means is suitable for controlling the air-fuel ratio of each of the first cylinder group and the second cylinder group based on the air-fuel ratio detected by each air-fuel ratio sensor and the exhaust gas amount ratio. The feedback correction coefficient and the learning correction coefficient can be calculated, and by performing the air-fuel ratio control using the calculated feedback correction coefficient and the learning correction coefficient, the first cylinder group and the second cylinder group are controlled. Each air-fuel ratio can be more reliably feedback-controlled to the target air-fuel ratio.

  According to the second aspect of the present invention, the means for detecting the exhaust gas amount ratio is disposed downstream of the connection portion of each of the first exhaust passage and the second exhaust passage with the communication pipe. A pressure sensor for detecting a back pressure of each of the first exhaust passage and the second exhaust passage, and based on the back pressure detected by each pressure sensor, the downstream of the connecting portion with the communication pipe The exhaust gas amount ratio, which is a ratio between the amount of exhaust gas flowing through the first exhaust passage and the amount of exhaust gas flowing through the second exhaust passage downstream of the connecting portion of the communication pipe, is calculated. An air-fuel ratio control apparatus for an internal combustion engine as described in 1 is provided.

  According to the third aspect of the present invention, the first exhaust passage and the second exhaust passage are connected to the first connecting portion downstream of the connecting portion with the connecting tube downstream of the connecting portion with the connecting tube. An exhaust control valve for controlling the amount of exhaust gas flowing in the exhaust passage and the amount of exhaust gas flowing in the second exhaust passage downstream of the connecting portion between the communication pipes is provided to detect the exhaust gas amount ratio Means for detecting the valve opening degree of the exhaust control valve, and based on the valve opening degree of the exhaust control valve detected by the valve opening degree detection means, An exhaust gas amount ratio, which is a ratio of the amount of exhaust gas flowing in the first exhaust passage downstream of the connecting portion and the amount of exhaust gas flowing in the second exhaust passage downstream of the connecting portion of the connecting pipe, An air-fuel ratio control apparatus for an internal combustion engine according to claim 1 for calculating is provided.

  According to a fourth aspect of the present invention, the exhaust control valve disposed in the first exhaust passage is completely closed, and all the exhaust gas of the first cylinder group is in the second exhaust passage. When the exhaust gas flows into and merges with the exhaust gas of the second cylinder group, the exhaust gas of the first cylinder group and the exhaust gas of the second cylinder group come into contact with each other based on the output of the second air-fuel ratio sensor. First and second feedback correction coefficients are calculated, the exhaust control valve disposed in the second exhaust passage is completely closed, and all of the exhaust gas of the second cylinder group is the first The first air-fuel ratio sensor that contacts the exhaust gas of the first cylinder group and the exhaust gas of the second cylinder group when flowing into the exhaust passage and joining the exhaust gas of the first cylinder group Calculating the first and second feedback correction coefficients based on the output of Air-fuel ratio control system for an internal combustion engine according to claim 3 is provided.

  According to the invention described in each claim, the internal combustion engine in which the first exhaust passage connected to the first cylinder group and the second exhaust passage connected to the second cylinder group are connected to each other by the communication pipe. In the engine, there is a common effect that the air-fuel ratios of the first cylinder group and the second cylinder group can be more reliably feedback-controlled to the target air-fuel ratio.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals.

  FIG. 1 is an overall configuration diagram for explaining an air-fuel ratio control apparatus for an internal combustion engine according to an embodiment of the present invention. The internal combustion engine in one embodiment shown in FIG. 1 is a V-type 6-cylinder gasoline engine with a supercharger. Although a gasoline engine is described here as an example, the present invention is not limited to this, and a diesel engine may be used in other embodiments.

  In FIG. 1, reference numeral 10 denotes an engine body. The engine body includes a first cylinder group 100 including a first cylinder (# 1), a second cylinder (# 2), and a third cylinder (# 3), and a fourth cylinder ( # 4), a fifth cylinder (# 5), and a second cylinder group 200 including a sixth cylinder (# 6). The engine body 10 also includes an opening / closing timing changing device for changing the opening / closing timing of the intake valve and the exhaust valve of each cylinder, and a valve lift amount changing device for changing the valve lift amount of the intake valve and the exhaust valve of each cylinder. It has.

  As shown in FIG. 1, an intake manifold 101 connected to each cylinder of the first cylinder group 100 is an exhaust-driven supercharger 103 that is driven by an exhaust gas flow through an intake pipe 102. The compressor 103 a is connected to the outlet of the compressor 103 a, and the inlet of the compressor 103 a is connected to the air cleaner 104. Between the air cleaner 104 and the compressor 103a, an air flow meter 105 that detects the intake air amount of the cylinders of the first cylinder group 100 and the second cylinder group 200 is provided. A throttle valve 106 driven by a step motor is arranged in the intake pipe 102, and a cooling device (intercooler) 107 for cooling the intake air flowing in the intake pipe 102 is arranged around the intake pipe 102. Is done. In the embodiment shown in FIG. 1, the engine cooling water is guided into the intercooler 107, and the intake air is cooled by the engine cooling water.

  In the internal combustion engine of the present embodiment, the intake air passage to the cylinders of the first cylinder group 100 and the intake air passage to the cylinders of the second cylinder group 200 are common up to just above the throttle valve 106, and supercharging is performed. Air from the machine 103 is supplied to both the cylinders of the first cylinder group 100 and the cylinders of the second cylinder group 200.

  The exhaust manifold 110 of the first cylinder group 100 is connected to the inlet of the exhaust turbine 103b of the supercharger 103 via the exhaust pipe 111, and the outlet of the exhaust turbine 103b is connected to the first exhaust gas purification via the exhaust pipe 112. Connected to the catalyst 113. Further, the exhaust manifold 210 of the second cylinder group 200 is connected to the second exhaust purification catalyst 213 via the exhaust pipe 212. As a result, a first exhaust passage having an exhaust pipe 111 and an exhaust pipe 112 and the like and leading exhaust gas to the first exhaust purification catalyst 113 is formed, and an exhaust pipe 212 and the like are provided in the second exhaust purification catalyst 213. A second exhaust passage for guiding the exhaust gas is configured.

  The first exhaust passage and the second exhaust passage include a communication pipe connecting the first exhaust passage and the second exhaust passage, specifically, the exhaust pipe 111 and the second exhaust pipe constituting the first exhaust passage. A communication pipe 310 connecting the exhaust pipe 212 constituting the exhaust passage is provided. A first exhaust control valve 114 is disposed in the downstream exhaust passage immediately after the first exhaust purification catalyst 113, and a second exhaust is provided in the downstream exhaust passage immediately after the second exhaust purification catalyst 213. A control valve 214 is provided. The first exhaust control valve 114 and the second exhaust control valve 214 are connected to an ECU 50, which will be described later, and the opening degree of each valve is independently controlled by a signal from the ECU 50 according to the operating state.

  Accordingly, at least a part of the exhaust gas of the first cylinder group 100 flows into the second exhaust passage via the communication pipe 310 and merges with the exhaust gas of the second cylinder group 200 or the second cylinder. At least a part of the exhaust gas of the group 200 flows into the first exhaust passage via the communication pipe 310 so as to be merged with the exhaust gas of the first cylinder group 100, and the second downstream of the connecting portion with the communication pipe 310. It is possible to control an exhaust gas amount ratio that is a ratio of the amount of exhaust gas flowing through one exhaust passage and the amount of exhaust gas flowing through the second exhaust passage downstream of the connecting portion of the communication pipe 310.

  The electronic control unit (hereinafter referred to as ECU) 50 includes a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), and a known digital computer in which input / output ports are connected by a bidirectional bus. In addition, the air flow meter 105 described above and various types including an air-fuel ratio sensor, a pressure sensor, a valve opening degree detection means, a correction coefficient calculation means, a first air-fuel ratio control means, a second air-fuel ratio control means, etc., which will be described later. By exchanging signals with sensors and various means, parameters necessary for controlling engine speed, intake air amount, etc. are obtained, and air-fuel ratio control (fuel injection amount control) and ignition timing control are performed based on the obtained parameters. Various controls related to engine operation are performed.

  The opening / closing timing change device and the valve lift amount changing device described above are also connected to the ECU 50, and the opening / closing timing and valve lift amount of each intake / exhaust valve are controlled by a signal from the ECU 50. The throttle valve 106 described above is also connected to the ECU 50, and the opening degree of the throttle valve 106 is controlled by a signal from the ECU 50.

  As can be understood from the above description of each component, the internal combustion engine of the present embodiment includes a plurality of cylinders, which are divided into a first cylinder group 100 and a second cylinder group 200, and the first The first exhaust passage connected to the second cylinder group 100 and the second exhaust passage connected to the second cylinder group 200 are connected to each other by the communication pipe 310, whereby the exhaust gas of the first cylinder group 100 is connected. At least a part of the exhaust gas flows into the second exhaust passage through the communication pipe 310 and merges with the exhaust gas of the second cylinder group 200 or at least a part of the exhaust gas of the second cylinder group 200 communicates with the communication pipe. The amount of exhaust gas flowing into the first exhaust passage through the first exhaust passage through the first exhaust passage of the first cylinder group 100 and flowing through the first exhaust passage downstream of the connecting portion with the communication pipe 310; In the second exhaust passage downstream of the connecting portion with the communication pipe 310 Which is the ratio of the amount of exhaust gas that flows is configured to control the exhaust gas amount ratio.

  In such an internal combustion engine, for example, a part of the exhaust gas of the first cylinder group 100 flows into the second exhaust passage via the communication pipe 310 and merges with the exhaust gas of the second cylinder group 200. In this case, the air-fuel ratio detected by the air-fuel ratio sensor disposed in the second exhaust passage receives the interference of the exhaust gas from the first cylinder group, and the individual air-fuel ratio of the second cylinder group 200 is reduced. It may not be detected. In such a case, there is a problem that it is difficult to perform feedback control so that the air-fuel ratio of the second cylinder group 200 matches the target air-fuel ratio.

  In the air-fuel ratio control apparatus in FIG. 1 showing an embodiment of the present invention, even in such an internal combustion engine, the air-fuel ratios of the first cylinder group 100 and the second cylinder group 200 are more reliably set to the target sky. In order to perform feedback control to the fuel ratio, the first air-fuel ratio sensor 120 disposed at the connection portion between the first exhaust passage and the communication pipe 310 and the connection portion between the second exhaust passage and the communication pipe 310 are disposed. Further, the amount of exhaust gas flowing in the first exhaust passage downstream of the connection portion between the second air-fuel ratio sensor 220 and the communication pipe 310 and the second exhaust passage downstream of the connection portion of the communication pipe 310 are distributed. Pressure sensors 121 and 221 for detecting an exhaust gas amount ratio that is a ratio to the exhaust gas amount and valve opening degree detection means 51 are provided. In the present embodiment, the pressure sensors 121 and 221 are disposed downstream of the connecting portions of the first exhaust passage and the second exhaust passage with the respective communication pipes 310, and the first exhaust passage and the second exhaust passage. The valve opening degree detection means 51 detects the valve opening degree of each of the first exhaust control valve 114 and the second exhaust control valve 214.

  When a part of the exhaust gas of the first cylinder group 100 flows into the second exhaust passage and merges with the exhaust gas of the second cylinder group 200, only the exhaust gas of the first cylinder group 100 is present. The first feedback correction coefficient is calculated based on the output of the contacting first air-fuel ratio sensor 120, the first learning correction coefficient is calculated based on the first feedback correction coefficient, and the exhaust gas of the first cylinder group 100 is calculated. And a second feedback correction coefficient is calculated based on the output of the second air-fuel ratio sensor 220 with which the exhaust gas of the second cylinder group 200 comes into contact, and the exhaust of the second cylinder group 200 is sent to the second air-fuel ratio sensor 220. The assumed output, which is the output of the second air-fuel ratio sensor 220 when it is assumed that only the gas is in contact, is output as well as the output of the first air-fuel ratio sensor 120 and the output of the second air-fuel ratio sensor 220. Exhaust gas A second learning correction coefficient is calculated based on the calculated assumed output, and a part of the exhaust gas of the second cylinder group 200 flows into the first exhaust passage and is calculated based on the quantity ratio. When merging with the exhaust gas of the first cylinder group 100, the first feedback is based on the output of the first air-fuel ratio sensor 120 in contact with the exhaust gas of the first cylinder group 100 and the exhaust gas of the second cylinder group 200. A correction coefficient is calculated, and an assumed output, which is an output of the first air-fuel ratio sensor 120 when it is assumed that only the exhaust gas of the first cylinder group 100 is in contact with the first air-fuel ratio sensor 120, Calculating based on the output of the first air-fuel ratio sensor 120 and the output of the second air-fuel ratio sensor 220 and the detected exhaust gas amount ratio, and calculating a first learning correction coefficient based on the calculated assumed output; Second cylinder group 20 Correction coefficient calculation means for calculating a second feedback correction coefficient based on the output of the second air-fuel ratio sensor 220 with which only the exhaust gas contacts, and calculating a second learning correction coefficient based on the second feedback correction coefficient 52.

  Further, a first air-fuel ratio control means 53 for controlling the air-fuel ratio of the first cylinder group 100 with the first feedback correction coefficient and the first learning correction coefficient so as to coincide with the target air-fuel ratio, and the target air-fuel ratio And a second air-fuel ratio control means 54 for controlling the air-fuel ratio of the second cylinder group 200 with the second feedback correction coefficient and the second learning correction coefficient.

  The air-fuel ratio control in the air-fuel ratio control apparatus for the internal combustion engine of the embodiment shown in FIG. 1 having the above-described components will be described below.

In the air-fuel ratio control in the present embodiment, the air-fuel ratio of the first cylinder group 100 and the second cylinder group 200 is controlled to a common target air-fuel ratio, and the fuel injection time TAU1 and the first fuel injection time TAU1 of the first cylinder group 100 are controlled. It is assumed that the fuel injection time TAU2 of the second cylinder group 200 is calculated based on the following equations (1) and (2).
TAU1 = TB · (1 + FAF1 + KG1) (1)
TAU2 = TB · (1 + FAF2 + KG2) (2)
Here, TB is the basic fuel injection time, FAF1 and FAF2 are feedback correction coefficients for the first cylinder group 100 and the second cylinder group 200, and KG1 and KG2 are the first cylinder group 100 and the second cylinder group 200. The learning correction coefficient is shown respectively.

  The basic fuel injection time TB is a fuel injection time required for setting the air-fuel ratio of the first cylinder group 100 and the second cylinder group 200 to a common target air-fuel ratio, and is, for example, a map as a function of the engine operating state. Is stored in the ECU 50 in advance.

  The feedback correction coefficients FAF1 and FAF2 are for making the air-fuel ratios of the corresponding cylinder groups coincide with a common target air-fuel ratio, and are set to zero when correction is not necessary. Both the first feedback correction coefficient FAF1 and the second feedback correction coefficient FAF2 vary around zero.

  The learning correction coefficients KG1 and KG2 are for correcting the corresponding feedback correction coefficients FAF1 and FAF2, respectively, and are set to zero when there is no need for correction.

  When the amount of fuel actually injected from the fuel injection valve, the amount of intake air, etc. deviates from the normal amount due to individual variations in the fuel injection valve, throttle valve, etc. or changes over time, the feedback correction coefficients FAF1, FAF2 deviate greatly from zero. There is a risk. However, it is preferable in terms of control that the feedback correction coefficients FAF1, FAF2 vary around zero. Therefore, in this embodiment, when the feedback correction coefficients FAF1, FAF2 deviate greatly from zero, the feedback correction coefficients FAF1, FAF2 are returned to almost zero, and the learning correction coefficients KG1, KG2 are changed accordingly.

Hereinafter, the air-fuel ratio control in the present embodiment will be described in detail.
In the air-fuel ratio control by the air-fuel ratio control apparatus of the present invention, when a part of the exhaust gas of the first cylinder group 100 flows into the second exhaust passage and merges with the exhaust gas of the second cylinder group 200 The first feedback correction coefficient is calculated based on the output of the first air-fuel ratio sensor 120 that contacts only the exhaust gas of the first cylinder group 100, and the exhaust gas and the second cylinder group of the first cylinder group 100 are calculated. A second feedback correction coefficient is calculated based on the output of the second air-fuel ratio sensor 220 with which 200 exhaust gases come into contact.

  Further, when a part of the exhaust gas of the second cylinder group 200 flows into the first exhaust passage and merges with the exhaust gas of the first cylinder group 100, the exhaust gas of the first cylinder group 100 and the The first feedback correction coefficient is calculated based on the output of the first air-fuel ratio sensor 120 with which the exhaust gas of the second cylinder group 200 contacts, and the second air-fuel ratio with which only the exhaust gas of the second cylinder group 200 contacts. Based on the output of the sensor 220, a second feedback correction coefficient is calculated.

  However, in the present embodiment, the first exhaust control valve 114 is completely closed, and all the exhaust gas of the first cylinder group 100 flows into the second exhaust passage, and the second cylinder group 200 When merging with the exhaust gas, the first and second feedback correction coefficients are calculated based on the output of the second air-fuel ratio sensor 220 in contact with the exhaust gas of the first cylinder group 100 and the exhaust gas of the second cylinder group 200. Try to calculate. Further, when the second exhaust control valve 214 is completely closed and all the exhaust gas of the second cylinder group 200 flows into the first exhaust passage and merges with the exhaust gas of the first cylinder group 100. The first and second feedback correction coefficients are calculated based on the output of the first air-fuel ratio sensor 120 in contact with the exhaust gas of the first cylinder group 100 and the exhaust gas of the second cylinder group 200.

  For example, when the first exhaust control valve 114 and the second exhaust control valve 214 are switched from the opened state to the state where the first exhaust control valve 114 is completely closed, Since the exhaust gas flows only into the second exhaust purification catalyst 213 disposed in the exhaust passage of the exhaust gas, the exhaust gas that flows into only the second exhaust purification catalyst 213 is exhausted in terms of purification of the exhaust gas. What is necessary is just to optimally control the fuel ratio. In the air-fuel ratio control apparatus of the present invention, the second air-fuel ratio sensor 220 disposed in the second exhaust passage is disposed at a connection portion between the second exhaust passage and the communication pipe 310, and The air-fuel ratio of the exhaust gas into which the exhaust gas from the first cylinder group 100 and the exhaust gas from the second cylinder group 200 merge, that is, the air-fuel ratio of the exhaust gas flowing into the second exhaust purification catalyst 213 is detected.

  Therefore, the first and second feedback correction coefficients are calculated based on the output of the second air-fuel ratio sensor 220, and the air-fuel ratios of the first cylinder group 100 and the second cylinder group 200 are controlled using the feedback correction coefficients. By doing so, the air-fuel ratio of the exhaust gas flowing into the second exhaust purification catalyst 213 can be optimally controlled. Further, according to such control, even when there is a time delay from the change of the exhaust control valve state to the change of the exhaust gas flow, the air-fuel ratio of the exhaust gas flowing into the second exhaust purification catalyst 213 is reduced. Optimal control can be achieved.

  FIG. 2 is a diagram showing an embodiment of a control routine for determining an air-fuel ratio sensor used for calculation of a feedback correction coefficient. In the control routine in FIG. 2, the open / closed states of the first exhaust control valve 114 and the second exhaust control valve 214 are determined according to the operating state of the internal combustion engine, and are used to calculate the feedback correction coefficient according to this state. Determine the air-fuel ratio sensor.

  Referring to FIG. 2, in step 501, it is determined whether or not a feedback control execution condition is satisfied. In the present embodiment, it is determined that the feedback control execution condition is satisfied when the air-fuel ratio sensor is activated and the engine warm-up operation is completed, and it is determined that the other conditions are not satisfied. When it is determined that the feedback control execution condition is not satisfied, the routine proceeds to step 506, where the feedback control is prohibited.

  In contrast, when it is determined that the feedback control execution condition is satisfied, the routine proceeds to step 502, where the current engine operating state is supercharged based on the load region of the engine operating state determined from the intake air amount, the engine speed, and the like. It is determined whether or not it is in a state that requires operation by the machine.

  When it is determined that the current engine operating state is not required to be operated by the supercharger, that is, in the low load region, the routine proceeds to step 507 and step 508. In step 507, the first exhaust control valve 114 provided in the first exhaust passage having the supercharger 103 is closed, and the first exhaust control valve 114 provided in the second exhaust passage not having the supercharger 103 is closed. The second exhaust control valve 214 is opened. Next, at step 508, based on the output of the second air-fuel ratio sensor 220 in contact with the exhaust gas of the first cylinder group 100 and the exhaust gas of the second cylinder group 200, the first cylinder group 100 and the second cylinder. It is determined to calculate both first and second feedback correction factors for the group 200.

  On the other hand, when it is determined that the current engine operating state is a state where it is necessary to perform the operation by the supercharger 103, the routine proceeds to step 503, and whether or not the intake air amount and the engine speed are within a predetermined range. Is determined.

  When it is determined that the intake air amount and the engine speed are not within the predetermined range and it is determined that the engine operating state is in the high load range, the routine proceeds to step 509 and step 510. In step 509, the first exhaust control valve 114 provided in the first exhaust passage having the supercharger 103 is opened, and the first exhaust control valve 114 provided in the second exhaust passage not having the supercharger 103 is opened. The second exhaust control valve 214 is also opened. Next, at step 510, a first feedback correction coefficient for the first cylinder group 100 is calculated based on the first air-fuel ratio sensor 120 disposed in the first exhaust passage, and is disposed in the second exhaust passage. Further, it is determined to calculate the second feedback correction coefficient for the second cylinder group 200 based on the second air-fuel ratio sensor 220.

  On the other hand, when it is determined that the intake air amount and the engine speed are within the predetermined range and the engine operating state is determined to be within the medium load range, the routine then proceeds to step 504 and step 505. In step 504, the first exhaust control valve 114 provided in the first exhaust passage having the supercharger 103 is opened, and the first exhaust control valve 114 provided in the second exhaust passage not having the supercharger 103 is opened. The second exhaust control valve 214 is closed. Next, at step 505, the first cylinder group 100 and the second cylinder are based on the output of the first air-fuel ratio sensor 120 in contact with the exhaust gas of the first cylinder group 100 and the exhaust gas of the second cylinder group 200. It is determined to calculate both first and second feedback correction factors for the group 200.

  Next, a method for calculating the feedback correction coefficient in the air-fuel ratio control of the present embodiment will be described. FIG. 3 is a diagram illustrating an embodiment of a feedback correction coefficient calculation routine. In the calculation routine in FIG. 3, the target in-cylinder fuel injection amount and the actual in-cylinder fuel injection amount are calculated from the air-fuel ratio detected by the first air-fuel ratio sensor 120 and the second air-fuel ratio sensor 220. A deviation is calculated, and a feedback correction coefficient is calculated based on the deviation.

  Referring to FIG. 3, in step 601, it is determined whether or not a feedback control execution condition is satisfied. In the present embodiment, it is determined that the feedback control execution condition is satisfied when the air-fuel ratio sensor is activated and the engine warm-up operation is completed, and it is determined that the other conditions are not satisfied. When it is determined that the feedback control execution condition is not satisfied, the routine proceeds to step 610, where the feedback correction coefficient is fixed to zero.

  On the other hand, when it is determined that the feedback control execution condition is satisfied, the routine proceeds to step 602, where the respective air-fuel ratios are detected from the first air-fuel ratio sensor 120 and the second air-fuel ratio sensor 220. Specifically, the output voltage from the first air-fuel ratio sensor 120 and the second air-fuel ratio sensor 220 is a map in which the air-fuel ratio can be calculated from the output voltage of the air-fuel ratio sensor, and is stored in the ECU 50 in advance. The map is converted to an air-fuel ratio, and the air-fuel ratio is detected from the first air-fuel ratio sensor 120 and the second air-fuel ratio sensor 220.

  In step 603 following step 602, the actual in-cylinder fuel injection amounts of the first cylinder group 100 and the second cylinder group 200 are calculated. In the present embodiment, the actual in-cylinder fuel injection amount of each cylinder group is calculated in consideration of the distance from the exhaust gas outlet of each cylinder group to the corresponding air-fuel ratio sensor. Specifically, the distance from the exhaust gas outlet of the first cylinder group 100 to the first air-fuel ratio sensor 120 corresponds to the M stroke of the engine process, and the exhaust gas of the second cylinder group 200 Assume that the distance from the outlet to the second air-fuel ratio sensor 220 corresponds to the N stroke of the engine process. In the first cylinder group 100, the actual in-cylinder fuel injection amount before the M stroke is calculated, and the second In the cylinder group 200, an actual in-cylinder fuel injection amount before N strokes is calculated. If the distance from the exhaust gas outlet of the first cylinder group 100 to the first air-fuel ratio sensor 120 is the same as the distance from the exhaust gas outlet of the second cylinder group 200 to the second air-fuel ratio sensor 220. Both of them correspond to the same engine process stroke, and the actual in-cylinder fuel injection amounts of the first cylinder group 100 and the second cylinder group 200 are calculated.

  In the present embodiment, the actual in-cylinder fuel injection amount before the M stroke of the first cylinder group 100 is calculated based on the intake air amount in the first cylinder group before the M stroke by the first air-fuel ratio sensor 120 this time. It is calculated by dividing (dividing) by the detected air-fuel ratio. Similarly, the actual in-cylinder fuel injection amount before the N stroke of the second cylinder group 200 is detected by the second air-fuel ratio sensor 220 this time as the second cylinder group intake air amount before the N stroke. It is calculated by dividing (dividing) by the air-fuel ratio. The intake air amount in the first cylinder group and the intake air amount in the second cylinder group are the same as the intake air amount in the first cylinder group 100 and the second cylinder group 200, and the air flow meter 105 is used. It is assumed that half of the intake air amount detected from the air is sucked into each of the first cylinder group 100 and the second cylinder group 200. However, the present invention is not limited to this, and an air flow meter may be provided in each intake port of the first cylinder group 100 and the second cylinder group 200 to detect the intake air amount.

  In Step 604 following Step 603, the target in-cylinder fuel injection amount before the M stroke of the first cylinder group 100 is calculated, and the target in-cylinder fuel injection amount before the N stroke of the second cylinder group 200 is calculated. calculate. In the present embodiment, the target in-cylinder fuel injection amount before the M stroke of the first cylinder group 100 is calculated based on the intake air amount in the first cylinder group before the M stroke by the first air-fuel ratio sensor 120. It is calculated by dividing (dividing) by the previously detected air-fuel ratio. Similarly, the target in-cylinder fuel injection amount before the N stroke of the second cylinder group 200 is detected by the second air-fuel ratio sensor before the N stroke. It is calculated by dividing (dividing) by the air-fuel ratio.

  In step 605 following step 604, the in-cylinder fuel injection amount deviation before the M stroke of the first cylinder group 100 is calculated, and the in-cylinder fuel injection amount deviation of the second cylinder group 200 before the N stroke is calculated. calculate. In the present embodiment, the in-cylinder fuel injection amount deviation before the M stroke of the first cylinder group 100 is the first in-cylinder fuel injection amount of the first cylinder group 100 before the M stroke. This is calculated by subtracting the actual in-cylinder fuel injection amount of the cylinder group 100. Similarly, the in-cylinder fuel injection amount deviation before the N stroke of the second cylinder group 200 is the second cylinder group 200 before the N stroke from the target in-cylinder fuel injection amount of the second cylinder group 200 before the N stroke. This is calculated by subtracting the actual in-cylinder fuel injection amount.

  In step 606 and step 607 following step 605, the in-cylinder fuel injection amount deviation before the M stroke of the first cylinder group 100 and the in-cylinder fuel injection amount deviation of the second cylinder group 200 before the N stroke are processed with a high-pass filter. The first cylinder group 100 and the first cylinder group 100 based on the in-cylinder fuel injection amount deviation after processing, the time integral value of the in-cylinder fuel injection amount deviation, and a predetermined proportional constant and integral constant, etc. Each feedback correction coefficient for the second cylinder group 200 is calculated. In step 608 following step 607, the time integral value of the in-cylinder fuel injection amount deviation is updated by adding the current in-cylinder fuel injection amount deviation.

  In the air-fuel ratio control of the present embodiment, the first exhaust control valve 114 is completely closed, and all the exhaust gas of the first cylinder group 100 flows into the second exhaust passage and the second cylinder group. When merging with the exhaust gas of 200, the first and second feedback corrections are performed based on the output of the second air-fuel ratio sensor 220 in contact with the exhaust gas of the first cylinder group 100 and the exhaust gas of the second cylinder group 200. The coefficient is calculated. Further, when the second exhaust control valve 214 is completely closed and all the exhaust gas of the second cylinder group 200 flows into the first exhaust passage and merges with the exhaust gas of the first cylinder group 100. The first and second feedback correction coefficients are calculated based on the output of the first air-fuel ratio sensor 120 in contact with the exhaust gas of the first cylinder group 100 and the exhaust gas of the second cylinder group 200.

  Based on this, in step 609 following step 608, the feedback correction coefficient is selectively changed when either one of the first exhaust control valve 114 and the second exhaust control valve 214 is completely closed. . That is, when the first exhaust control valve 114 is completely closed and all of the exhaust gas of the first cylinder group 100 flows into the second exhaust passage and merges with the exhaust gas of the second cylinder group 200. The feedback correction coefficient for the second cylinder group 200 calculated in step 607 is changed to be applied as the feedback correction coefficient for both the first cylinder group 100 and the second cylinder group 200. . Further, when the second exhaust control valve 214 is completely closed and all the exhaust gas of the second cylinder group 200 flows into the first exhaust passage and merges with the exhaust gas of the first cylinder group 100. The feedback correction coefficient for the first cylinder group 100 calculated in step 607 is changed to be applied as the feedback correction coefficient for both the first cylinder group 100 and the second cylinder group 200. .

  Next, a method for calculating the air-fuel ratio used for calculating the learning correction coefficient will be described. FIG. 4 is a diagram showing an embodiment of a calculation routine for calculating the air-fuel ratio used for calculating the learning correction coefficient. In the calculation routine in FIG. 4, the opening / closing states of the first exhaust control valve 114 and the second exhaust control valve 214 are determined according to the operating state of the internal combustion engine, and are used to calculate the learning correction coefficient according to this state. Calculate the air-fuel ratio.

  Referring to FIG. 4, in step 701, it is determined whether or not a feedback control execution condition is satisfied. In the present embodiment, it is determined that the feedback control execution condition is satisfied when the air-fuel ratio sensor is activated and the engine warm-up operation is completed, and it is determined that the other conditions are not satisfied. When it is determined that the feedback control execution condition is not satisfied, the calculation routine ends.

  On the other hand, when it is determined that the feedback control execution condition is satisfied, the routine proceeds to step 702, where the current engine operating state is supercharged based on the load region of the engine operating state determined from the intake air amount, the engine speed, and the like. It is determined whether or not it is in a state that requires operation by the machine.

  A first exhaust control valve 114 disposed in a first exhaust passage having a supercharger 103 is determined that the current engine operation state is in a state where it is not necessary to perform operation by the supercharger, that is, in a low load region. Is closed, and when the second exhaust control valve 214 provided in the second exhaust passage without the supercharger 103 is opened, the routine proceeds to step 705. In step 705, the first exhaust control valve 114 disposed in the first exhaust passage having the supercharger 103 is closed and disposed in the second exhaust passage not having the supercharger 103. The air-fuel ratio used for calculating the respective learning correction coefficients of the first cylinder group 100 and the second cylinder group 200, which is suitable when the second exhaust control valve 214 is opened, is calculated.

  The first exhaust control valve 114 disposed in the first exhaust passage having the supercharger 103 is closed, and the second exhaust control disposed in the second exhaust passage not having the supercharger 103. When the valve 214 is opened, the air-fuel ratio detected from the first air-fuel ratio sensor 120 arranged at the connection portion between the first exhaust passage and the communication pipe 310 is the first cylinder group 100. Corresponds to air-fuel ratio. On the other hand, the air-fuel ratio detected from the second air-fuel ratio sensor 220 arranged at the connection portion between the second exhaust passage and the communication pipe 310 is the air-fuel ratio of the first cylinder group 100 and the second cylinder group 200. The average value of the air-fuel ratio is detected.

  Based on this, in the calculation routine in the present embodiment, the first exhaust control valve 114 disposed in the first exhaust passage having the supercharger 103 is closed, and the second not having the supercharger 103. When the second exhaust control valve 214 disposed in the exhaust passage is opened, the air-fuel ratio used to calculate the learning correction coefficient for the first cylinder group 100 is the first air-fuel ratio. It is assumed that the air-fuel ratio detected from the fuel ratio sensor 120 is used. On the other hand, the air-fuel ratio used for calculating the learning correction coefficient for the second cylinder group 200 is obtained by doubling the air-fuel ratio detected by the second air-fuel ratio sensor 220 and doubling the air-fuel ratio. By subtracting the air-fuel ratio detected from the first air-fuel ratio sensor 120, the second air-fuel ratio when it is assumed that only the exhaust gas of the second cylinder group 200 is in contact with the second air-fuel ratio sensor 220. Assume that an assumed output that is an output of the air-fuel ratio sensor is calculated, and the calculated air-fuel ratio of the assumed output is used. By doing in this way, the air fuel ratio used for calculation of the appropriate learning correction coefficient with respect to each of the first cylinder group 100 and the second cylinder group 200 can be calculated.

  On the other hand, when it is determined in step 702 that the current engine operation state is in a state where it is necessary to perform the operation by the supercharger 103, the process proceeds to step 703, where the intake air amount and the engine speed are within a predetermined range. Is determined.

  When it is determined that the intake air amount and the engine speed are not within the predetermined range and it is determined that the engine operating state is within the high load range, the routine proceeds to step 706. In step 706, the amount of exhaust gas flowing in the first exhaust passage downstream of the connecting portion with the communication pipe 310 and the amount of exhaust gas flowing in the second exhaust passage downstream of the connecting portion of the communication pipe 310 are calculated. The exhaust gas amount ratio as a ratio is detected by at least one of the pressure sensors 121 and 221 and the valve opening means 51. Then, it is determined whether or not the detected exhaust gas amount ratio is 5 to 5.

  When it is determined that the detected exhaust gas amount ratio is 5 to 5, the routine proceeds to step 707, where the first cylinder group 100 and the second cylinder group are suitable when the exhaust gas amount ratio is 5 to 5. The air-fuel ratio used for calculation of each learning correction coefficient of 200 is calculated. When the exhaust gas amount ratio is 5 to 5, the exhaust gas is not flowing through the communication pipe 310 except in a specific state, and the first exhaust passage and the communication pipe 310 are connected to each other. The air-fuel ratio detected from the first air-fuel ratio sensor 120 disposed at the connection portion corresponds to the air-fuel ratio of the first cylinder group 100 and is disposed at the connection portion between the second exhaust passage and the communication pipe 310. The air-fuel ratio detected from the second air-fuel ratio sensor 220 corresponds to the air-fuel ratio of the second cylinder group 200.

  Based on this, in the calculation routine in the present embodiment, when the exhaust gas amount ratio is 5 to 5, the air-fuel ratio used to calculate the learning correction coefficient for the first cylinder group 100 is the first The air-fuel ratio detected from the second air-fuel ratio sensor 120 is used, and the air-fuel ratio used to calculate the learning correction coefficient for the second cylinder group 200 is the air-fuel ratio detected from the second air-fuel ratio sensor 220. The fuel ratio shall be used. By doing in this way, the air fuel ratio used for calculation of the appropriate learning correction coefficient with respect to each of the first cylinder group 100 and the second cylinder group 200 can be calculated.

  On the other hand, when it is determined that the detected exhaust gas amount ratio is not 5 to 5, the routine proceeds to step 708, where the first cylinder group 100 and the second cylinder suitable for when the exhaust gas amount ratio is not 5 to 5 are used. The air-fuel ratio used to calculate the learning correction coefficient for each of the cylinder groups 200 is calculated. When the exhaust gas amount ratio is not 5 to 5, a part of the exhaust gas of the first cylinder group 100 flows into the second exhaust passage via the communication pipe 310 and the exhaust gas of the second cylinder group 200 Or a part of the exhaust gas of the second cylinder group 200 flows into the first exhaust passage via the communication pipe 310 and merges with the exhaust gas of the first cylinder group 100. . Therefore, from one of the first air-fuel ratio sensor 120 and the second air-fuel ratio sensor 220, the exhaust gas from either the first cylinder group 100 or the second cylinder group 200 is removed. The air-fuel ratio that has received the interference is detected.

  Based on this, in the calculation routine according to the present embodiment, when it is determined that the detected exhaust gas amount ratio is not 5 to 5, the first cylinder group 100 and the second cylinder group 100 are controlled according to the exhaust gas amount ratio. The air-fuel ratio used to calculate the respective learning correction coefficients for the cylinder group 200 is calculated.

  For example, the ratio of the amount of exhaust gas flowing through the first exhaust passage downstream of the connection portion with the communication pipe 310 to the amount of exhaust gas flowing through the second exhaust passage downstream of the connection portion with the communication pipe 310 is 4 In the case of pair 6, that is, a part of the exhaust gas of the first cylinder group 100 flows into the second exhaust passage through the communication pipe 310 and merges with the exhaust gas of the second cylinder group 200. In this case, the air-fuel ratio used to calculate the learning correction coefficient for the first cylinder group 100 is the air-fuel ratio detected from the first air-fuel ratio sensor 100. On the other hand, the air-fuel ratio used to calculate the learning correction coefficient for the second cylinder group 200 is calculated in consideration of the amount of exhaust gas that circulates into the second exhaust passage via the communication pipe 310. Specifically, based on the output of the first air-fuel ratio sensor 120, the output of the second air-fuel ratio sensor 220, and the amount of exhaust gas that circulates into the second exhaust passage via the communication pipe 310, the second air-fuel ratio. Assuming that only the exhaust gas of the second cylinder group 200 is in contact with the sensor 220, an assumed output that is an output of the second air-fuel ratio sensor 220 is calculated, and the calculated assumed output is calculated as the second output. The air-fuel ratio used to calculate the learning correction coefficient for the cylinder group 200 is assumed. Note that the amount of exhaust gas that circulates in the second exhaust passage via the communication pipe 310 is the amount of the exhaust gas that circulates in the first exhaust passage downstream of the connection section with the communication pipe 310 and the connection section between the communication pipe 310. It is calculated based on an exhaust gas amount ratio that is a ratio with the exhaust gas amount flowing through the downstream second exhaust passage. That is, when it is assumed that only the exhaust gas of the second cylinder group 200 is in contact with the second air-fuel ratio sensor 220, the assumed output which is the output of the second air-fuel ratio sensor 220 is the first air-fuel ratio. It is calculated based on the output of the sensor 120, the output of the second air-fuel ratio sensor 220, and the exhaust gas amount ratio.

An embodiment of an air-fuel ratio calculation method used for calculating the learning correction coefficient for the second cylinder group 200 in the above case will be described below.
The air-fuel ratio (A) detected by the second air-fuel ratio sensor 220 is considered to correspond to the following equation (3).
A = (B × C + D × E) ÷ (C + E) (3)
Here, A is the air-fuel ratio detected by the second air-fuel ratio sensor 220, B is the air-fuel ratio of only the second cylinder group 200, C is the intake air amount of the second cylinder group 200, and D is the first air-fuel ratio. The air-fuel ratio of only the cylinder group 100, E, indicates the amount of exhaust gas that circulates into the second exhaust passage via the communication pipe 310, respectively.

Then, if the air-fuel ratio detected by the second air-fuel ratio sensor 220 is obtained, the air-fuel ratio (B) of only the second cylinder group 200, which is the above-mentioned hypothetical output, is calculated from this equation (1). be able to. That is, the air-fuel ratio (B) of only the second cylinder group 200 can be calculated from the following equation (4).
B = (A × (C + E) − (D × E)) ÷ C (4)
Then, the air-fuel ratio (B) of only the second cylinder group calculated in this way is used to calculate the learning correction coefficient for the second cylinder group 200.

  By applying the above-described method for calculating the air-fuel ratio used for calculating the learning correction coefficient for each of the first cylinder group 100 and the second cylinder group 200 according to the exhaust gas amount ratio, the first cylinder A part of the exhaust gas of the group 100 flows into the second exhaust passage through the communication pipe 310 and merges with the exhaust gas of the second cylinder group 200 or a part of the exhaust gas of the second cylinder group 200. Flows into the first exhaust passage via the communication pipe 310 and merges with the exhaust gas of the first cylinder group 100, even for the first cylinder group 100 and the second cylinder group 200. The air-fuel ratio used for calculating an appropriate learning correction coefficient can be calculated.

  If it is determined in step 703 that the intake air amount and the engine speed are within the predetermined range and the engine operating state is determined to be in the medium load range, then the routine proceeds to step 704. In step 704, the first exhaust control valve 114 disposed in the first exhaust passage having the supercharger 103 is opened and disposed in the second exhaust passage not having the supercharger 103. The air-fuel ratio used for calculating the respective learning correction coefficients of the first cylinder group 100 and the second cylinder group 200, which is suitable when the second exhaust control valve 214 is closed, is calculated.

  The first exhaust control valve 114 disposed in the first exhaust passage having the supercharger 103 is opened, and the second exhaust control disposed in the second exhaust passage not having the supercharger 103. When the valve 214 is closed, the air-fuel ratio detected from the second air-fuel ratio sensor 220 disposed at the connection portion between the second exhaust passage and the communication pipe 310 is that of the second cylinder group 200. Corresponds to air-fuel ratio. On the other hand, the air-fuel ratio detected from the first air-fuel ratio sensor 120 disposed at the connection portion between the first exhaust passage and the communication pipe 310 is the air-fuel ratio of the first cylinder group 100 and the second cylinder group 200. The average value of the air-fuel ratio is detected.

  Based on this, in the calculation routine in the present embodiment, the first exhaust control valve 114 disposed in the first exhaust passage having the supercharger 103 is opened, and the second not having the supercharger 103. When the second exhaust control valve 214 disposed in the exhaust passage is closed, the air-fuel ratio used to calculate the learning correction coefficient for the second cylinder group 200 is the second air-fuel ratio. It is assumed that the air-fuel ratio detected from the fuel ratio sensor 220 is used. On the other hand, the air-fuel ratio used to calculate the learning correction coefficient for the first cylinder group 100 is doubled from the air-fuel ratio detected by the first air-fuel ratio sensor 120 and doubled. By subtracting the air-fuel ratio detected from the second air-fuel ratio sensor 220, the first air-fuel ratio when it is assumed that only the exhaust gas of the first cylinder group 100 is in contact with the first air-fuel ratio sensor 120. Assume that an assumed output that is an output of the air-fuel ratio sensor is calculated, and the calculated air-fuel ratio of the assumed output is used. By doing in this way, the air fuel ratio used for calculation of the appropriate learning correction coefficient with respect to each of the first cylinder group 100 and the second cylinder group 200 can be calculated.

  According to such a calculation method, the amount of exhaust gas flowing in the first exhaust passage downstream of the connection portion with the communication pipe 310 and the exhaust gas flowing in the second exhaust passage downstream of the connection portion of the communication pipe 310. In accordance with the gas amount ratio, it is possible to calculate an appropriate air-fuel ratio that is used to calculate the respective learning correction coefficients for the first cylinder group 100 and the second cylinder group 200. Then, a learning correction coefficient is calculated using the calculated appropriate air-fuel ratio, and air-fuel ratio control is performed using the learning correction coefficient and the feedback correction coefficient as described above, whereby the first cylinder group It becomes possible to feedback control the air-fuel ratios of 100 and the second cylinder group 200 to the target air-fuel ratio more reliably.

1 is an overall configuration diagram for illustrating an air-fuel ratio control apparatus for an internal combustion engine according to an embodiment of the present invention. It is a figure which shows one Embodiment of the control routine for determining the air fuel ratio sensor used for calculation of a feedback correction coefficient. It is a figure which shows one Embodiment of the calculation routine of a feedback correction coefficient. It is a figure which shows one Embodiment of the calculation routine for calculating the air fuel ratio used for calculation of a learning correction coefficient.

Explanation of symbols

51 Valve opening degree detection means 52 Correction coefficient calculation means 53 First air-fuel ratio control means 54 Second air-fuel ratio control means 100 First cylinder group 114 First exhaust control valve 121 Pressure sensor 200 Second cylinder group 214 Second exhaust control valve 221 Pressure sensor 310 Communication pipe

Claims (4)

With multiple cylinders,
These cylinders are divided into a first cylinder group and a second cylinder group,
The first exhaust passage connected to the first cylinder group and the second exhaust passage connected to the second cylinder group are connected to each other by a communication pipe, whereby at least the exhaust gas of the first cylinder group is connected. Part of the exhaust gas flows into the second exhaust passage through the communication pipe and merges with the exhaust gas of the second cylinder group, or at least part of the exhaust gas of the second cylinder group passes through the communication pipe to the first Allowing it to flow into the exhaust passage and merge with the exhaust gas of the first cylinder group,
Exhaust gas amount ratio which is a ratio of the amount of exhaust gas flowing in the first exhaust passage downstream of the connecting portion with the communication pipe and the amount of exhaust gas flowing in the second exhaust passage downstream of the connecting portion of the communication pipe In an internal combustion engine designed to control
A first air-fuel ratio sensor disposed at a connection portion between the first exhaust passage and the communication pipe, and a second air-fuel ratio sensor disposed at a connection portion between the second exhaust passage and the communication pipe;
Means for detecting the exhaust gas amount ratio;
When a part of the exhaust gas of the first cylinder group flows into the second exhaust passage and merges with the exhaust gas of the second cylinder group,
Calculating a first feedback correction coefficient based on the output of the first air-fuel ratio sensor in contact with only the exhaust gas of the first cylinder group;
Calculating a first learning correction coefficient based on the first feedback correction coefficient;
Calculating a second feedback correction coefficient based on the output of the second air-fuel ratio sensor in contact with the exhaust gas of the first cylinder group and the exhaust gas of the second cylinder group;
Assuming that only the exhaust gas of the second cylinder group is in contact with the second air-fuel ratio sensor, the assumed output that is the output of the second air-fuel ratio sensor is the output of the first air-fuel ratio sensor and the second output of the first air-fuel ratio sensor. 2 based on the output of the air / fuel ratio sensor 2 and the detected exhaust gas amount ratio, and calculating a second learning correction coefficient based on the calculated assumed output,
When a part of the exhaust gas of the second cylinder group flows into the first exhaust passage and merges with the exhaust gas of the first cylinder group,
Calculating a first feedback correction coefficient based on the output of the first air-fuel ratio sensor in contact with the exhaust gas of the first cylinder group and the exhaust gas of the second cylinder group;
Assuming that only the exhaust gas of the first cylinder group is in contact with the first air-fuel ratio sensor, the assumed output which is the output of the first air-fuel ratio sensor is the output of the first air-fuel ratio sensor and the first output of the first air-fuel ratio sensor. 2 based on the output of the air-fuel ratio sensor 2 and the detected exhaust gas amount ratio, and calculating a first learning correction coefficient based on the calculated assumed output,
Calculating a second feedback correction coefficient based on the output of the second air-fuel ratio sensor in contact with only the exhaust gas of the second cylinder group;
Correction coefficient calculating means for calculating a second learning correction coefficient based on the second feedback correction coefficient;
First air-fuel ratio control means for controlling the air-fuel ratio of the first cylinder group with the first feedback correction coefficient and the first learning correction coefficient so as to coincide with the target air-fuel ratio;
Second air-fuel ratio control means for controlling the air-fuel ratio of the second cylinder group with a second feedback correction coefficient and a second learning correction coefficient so as to coincide with the target air-fuel ratio;
An air-fuel ratio control apparatus for an internal combustion engine comprising:   The means for detecting the exhaust gas amount ratio is disposed downstream of the first exhaust passage and the second exhaust passage connected to the communication pipe, and the first exhaust passage and the second exhaust passage. Exhaust gas having pressure sensors for detecting the respective back pressures of the exhaust passages and flowing in the first exhaust passages downstream of the connecting portions with the communication pipes based on the back pressures detected by the pressure sensors. 2. The air-fuel ratio control apparatus for an internal combustion engine according to claim 1, wherein an exhaust gas amount ratio, which is a ratio between an amount of exhaust gas and an exhaust gas amount flowing through the second exhaust passage downstream of the connecting portion of the communication pipe, is calculated. . The amount of exhaust gas flowing in the first exhaust passage downstream of the connection portion with the communication pipe downstream of the connection portion with the communication pipe of the first exhaust passage and the second exhaust passage; An exhaust control valve for controlling the amount of exhaust gas flowing in the second exhaust passage downstream of the connecting portion with the communication pipe is disposed;
The means for detecting the exhaust gas amount ratio has valve opening degree detecting means for detecting the valve opening degree of the exhaust control valve, and the valve opening degree of the exhaust control valve detected by the valve opening degree detecting means is determined. Based on the ratio between the amount of exhaust gas flowing in the first exhaust passage downstream of the connecting portion with the communication pipe and the amount of exhaust gas flowing in the second exhaust passage downstream of the connecting portion with the communication pipe The air-fuel ratio control apparatus for an internal combustion engine according to claim 1, wherein an exhaust gas amount ratio is calculated. The exhaust control valve disposed in the first exhaust passage is completely closed, and all of the exhaust gas of the first cylinder group flows into the second exhaust passage, and the second cylinder group The first and second feedback correction coefficients are calculated based on the output of the second air-fuel ratio sensor in contact with the exhaust gas of the first cylinder group and the exhaust gas of the second cylinder group. And
The exhaust control valve disposed in the second exhaust passage is completely closed, and all of the exhaust gas of the second cylinder group flows into the first exhaust passage, and the first cylinder group The first and second feedback correction coefficients based on the output of the first air-fuel ratio sensor in contact with the exhaust gas of the first cylinder group and the exhaust gas of the second cylinder group. The air-fuel ratio control apparatus for an internal combustion engine according to claim 3, wherein

Images