JP2005098166A - Air-fuel ratio control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase an air-fuel ratio control accuracy by performing air-fuel ratio control while reflecting the dynamic characteristics of an air-fuel ratio sensor. <P>SOLUTION: This air-fuel ratio control device of an internal combustion engine is formed such that an air-fuel ratio sensor 32 is disposed in the exhaust pipe 24 of the engine 10. An ECU 40 calculates an air-fuel ratio correction amount for matching a detected air-fuel ratio value from air-fuel ratio sensor signals to a target value, and controls the air-fuel ratio by using the air-fuel ratio correction amount. Also the ECU calculates the varied amounts of the air-fuel ratio detected value to rich side and lean side, calculates data on the varied amount of the air-fuel ratio correction amounts to rich side and lean side, and based on the data on the varied amounts of the calculated air-fuel ratio detected values to rich side and lean side and the data on the varied amounts of the calculated air-fuel ratio correction amounts to rich side and lean side, data on responsiveness in a variation to rich side and a variation in lean side can be calculated. In this device, control parameters on the air-fuel ratio control are corrected by using the data on the responsiveness calculated. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

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

  Conventionally, an air-fuel ratio sensor is provided in an exhaust pipe of an internal combustion engine, and an air-fuel ratio detector (exhaust air-fuel ratio) of exhaust gas discharged from the internal combustion engine is detected by a detection signal of the air-fuel ratio sensor. Has been put to practical use. In the air-fuel ratio control system using this air-fuel ratio detection apparatus, air-fuel ratio feedback control is performed so that the detected air-fuel ratio is stabilized at the target value.

  In such a case, during the air-fuel ratio control, the air-fuel ratio varies to the rich side or the lean side with respect to the target air-fuel ratio (for example, the theoretical air-fuel ratio). On the other hand, for the purpose of improving the purification efficiency of the catalytic converter disposed in the exhaust pipe, a technique for forcibly changing the exhaust air-fuel ratio to the rich side and the lean side in the vicinity of the theoretical air-fuel ratio has been proposed. (For example, Patent Document 1).

  However, when the air-fuel ratio fluctuates to the rich side or the lean side as described above, the response when the output of the air-fuel ratio sensor changes to the rich side is different from the response when the output changes to the lean side. Thus, there is a problem that the average value of the detected air-fuel ratio deviates from the true average air-fuel ratio (for example, 14.7), leading to deterioration of exhaust emission. In other words, as is generally known, an air-fuel ratio sensor has a solid electrolyte body such as zirconia and a pair of electrodes arranged so as to sandwich the solid electrolyte body, and exhaust gas according to the amount of oxygen ions conducted between the electrodes. The oxygen concentration (ie, air / fuel ratio) is detected. In this case, if the reaction speed differs between the electrodes due to factors such as individual sensor differences and changes over time, the sensor responsiveness will differ between when the air-fuel ratio changes to the rich side and when it changes to the lean side. This causes the above problem.

In Patent Document 2, a linear A / F sensor is disposed upstream of the three-way catalyst in the exhaust system of the internal combustion engine, and a λO 2 sensor is disposed downstream of the three-way catalyst. The control variable and the air-fuel ratio correction coefficient of the linear A / F sensor are corrected while monitoring the output of the above. This makes it possible to perform highly accurate air-fuel ratio control. However, even when such a technique is used, if the sensor response is different between when the air-fuel ratio changes to the rich side and when it changes to the lean side as described above, the convergence speed to the theoretical air-fuel ratio varies. As a result, the control accuracy of the air-fuel ratio may be lowered.
Japanese Patent Publication No. 7-33793 JP-A-2-67443

  The main object of the present invention is to provide an air-fuel ratio control device for an internal combustion engine that can improve the control accuracy of the air-fuel ratio by performing air-fuel ratio control reflecting the dynamic characteristics of the air-fuel ratio sensor. Is.

  According to the first aspect of the present invention, the variation data of the air-fuel ratio detection value detected from the air-fuel ratio sensor signal to the rich side and the lean side are calculated, respectively, and the air-fuel ratio correction amount to the rich side and the lean side are calculated. Change amount data is calculated respectively. Further, based on the change amount data of the calculated air-fuel ratio detection value to the rich side and the lean side and the change amount data of the calculated air-fuel ratio correction amount to the rich side and the lean side, The response data of the air-fuel ratio sensor is calculated for each of the change time and the change time to the lean side. Then, the control parameter relating to the air-fuel ratio control is corrected using the calculated response data.

  According to the above configuration, response data when the air-fuel ratio sensor changes on the rich side and on the rich side change can be obtained individually. Therefore, the dynamic characteristics of the air-fuel ratio sensor can be known from the response data, and the control parameters relating to the air-fuel ratio control can be corrected by reflecting the dynamic characteristics. Thereby, the control accuracy of the air-fuel ratio can be improved.

  Here, the change to the rich side and the change to the lean side express the change direction of the air-fuel ratio detection value and the air-fuel ratio correction amount, and are interpreted as the change in the rich direction or the change in the lean direction. It is what is done. Therefore, the present invention is not limited to the case of changing to the rich side or the lean side across the theoretical air-fuel ratio. Changes on the rich side and lean side of the air-fuel ratio correction amount refer to changes for increasing or decreasing the fuel amount, for example, in accordance with changes in the air-fuel ratio detection value.

  In the second aspect of the present invention, since the control parameter is corrected according to the difference between the responsiveness data when changing to the rich side and when changing to the lean side, the response of the rich change / lean change Air-fuel ratio control that matches the difference can be realized.

  In the third aspect of the present invention, the responsiveness parameter that equalizes the responsiveness data at the time of the change to the rich side and the change to the lean side is calculated, and the control parameter is corrected using the responsiveness parameter. Is done. In this case, by using the response parameter, even if there is a difference between the response to the rich side and the response to the lean side of the air-fuel ratio sensor, the difference is eliminated, and the control accuracy of the air-fuel ratio can be improved. It becomes.

  Examples of control parameters to be corrected include the following. That is, in the invention described in claim 4, the air-fuel ratio correction amount as the control parameter is corrected. In the invention according to claim 5, the air-fuel ratio target value as the control parameter is corrected. In the invention described in claim 6, the control gain as the control parameter is corrected. Any of these can realize suitable air-fuel ratio control suitable for sensor response. It should be noted that at least two of the air-fuel ratio correction amount, the air-fuel ratio target value, and the control gain can be corrected.

  According to the seventh aspect of the present invention, the responsiveness data is obtained from the ratio between the change amount data of the air-fuel ratio detection value and the change amount data of the air-fuel ratio correction amount for each of the change to the rich side and the change to the lean side. Is calculated. In this case, since the response data is obtained by comparing the change in the air-fuel ratio detection value with the change in the air-fuel ratio correction amount, the reliability of the response data is increased. Therefore, the control parameter can be corrected more preferably.

  In the invention according to claim 8, since the control parameter is corrected when the air-fuel ratio deviation changes so as to increase, it is possible to eliminate the state where the change in the air-fuel ratio deviation becomes large. .

  As described in claim 9, as the change amount data of the air-fuel ratio detection value and the change amount data of the air-fuel ratio correction amount, their change speed or change acceleration may be calculated. Particularly in this case, the change speed or the change acceleration may be calculated by a smoothing calculation.

  In the invention according to claim 10, the air-fuel ratio is forcibly changed to the rich side and the lean side, and when the air-fuel ratio detection value changes to the rich side as the air-fuel ratio changes, or the air-fuel ratio The control parameter is corrected based on change amount data when the detected value changes to the lean side. In this case, sufficient amount of change data can be obtained when the air-fuel ratio changes to the rich side or the lean side, and highly reliable control parameter correction can be realized. When the air-fuel ratio is forcibly changed in this way, the cycle and amplitude of the air-fuel ratio change should be specified in advance.

  In the invention according to claim 11, since the control parameter is corrected when the average value of the air-fuel ratio detection value is a predetermined value or more away from the target value average, the average value of the air-fuel ratio detection value is the target value. It is possible to eliminate a state that deviates greatly from the average.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings. In the present embodiment, an engine control system is constructed for an in-vehicle multi-cylinder gasoline engine that is an internal combustion engine. In the control system, an electronic control unit (hereinafter referred to as ECU) is used as a center to control the fuel injection amount. And control of ignition timing. First, an overall schematic configuration diagram of the engine control system will be described with reference to FIG.

  In the engine 10 shown in FIG. 1, an air cleaner 12 is provided at the most upstream portion of the intake pipe 11, and an air flow meter 13 for detecting the intake air amount is provided downstream of the air cleaner 12. A throttle valve 14 whose opening is adjusted by an actuator such as a DC motor and a throttle opening sensor 15 for detecting the throttle opening are provided on the downstream side of the air flow meter 13. A surge tank 16 is provided downstream of the throttle valve 14, and an intake pipe pressure sensor 17 for detecting the intake pipe pressure is provided in the surge tank 16. The surge tank 16 is connected to an intake manifold 18 that introduces air into each cylinder of the engine 10. In the intake manifold 18, an electromagnetically driven fuel injection that injects fuel near the intake port of each cylinder. A valve 19 is attached.

  An intake valve 21 and an exhaust valve 22 are respectively provided in the intake port and the exhaust port of the engine 10, and an air / fuel mixture is introduced into the combustion chamber 23 by the opening operation of the intake valve 21, and the exhaust valve 22. By the opening operation, the exhaust gas after combustion is discharged to the exhaust pipe 24. A spark plug 27 is attached to the cylinder head of the engine 10 for each cylinder, and a high voltage is applied to the spark plug 27 at a desired ignition timing through an ignition device (not shown) including an ignition coil. By applying this high voltage, a spark discharge is generated between the opposing electrodes of each spark plug 27, and the air-fuel mixture introduced into the combustion chamber 23 is ignited and used for combustion.

  The exhaust pipe 24 is provided with a catalyst 31 such as a three-way catalyst for purifying CO, HC, NOx and the like in the exhaust gas, and the air-fuel ratio of the air-fuel mixture is detected on the upstream side of the catalyst 31 with exhaust gas as a detection target. An air-fuel ratio sensor 32 (linear A / F sensor or the like) is provided for detecting the above. Further, the cylinder block of the engine 10 includes a coolant temperature sensor 33 that detects the coolant temperature, and a crank angle sensor 34 that outputs a rectangular crank angle signal for each predetermined crank angle of the engine (for example, at a cycle of 30 ° CA). It is attached.

  The outputs of the various sensors described above are input to the ECU 40 that controls the engine. The ECU 40 is configured mainly by a microcomputer including a CPU, a ROM, a RAM, and the like, and executes various control programs stored in the ROM, so that the fuel injection amount and ignition of the fuel injection valve 19 according to the engine operating state. The ignition timing by the plug 27 is controlled. In particular, in the fuel injection amount control, an air-fuel ratio correction coefficient FAF is calculated as an air-fuel ratio correction amount based on the deviation between the air-fuel ratio (detected air-fuel ratio) detected by the air-fuel ratio sensor 32 and the target air-fuel ratio. The air-fuel ratio F / B control using the correction coefficient FAF is performed.

  Here, the configuration of the air-fuel ratio sensor 32 will be described with reference to FIG. The air-fuel ratio sensor 32 has a sensor element 50 having a laminated structure, and FIG. 8 shows a cross-sectional configuration of the sensor element 50. Actually, the sensor element 50 has a long shape extending in a direction orthogonal to the paper surface of FIG. 8, and the entire element is accommodated in a housing or an element cover.

  The sensor element 50 includes a solid electrolyte layer 51, a diffusion resistance layer 52, a shielding layer 53, and an insulating layer 54, which are stacked on the upper and lower sides of the drawing. A protective layer (not shown) is provided around the element 50. The rectangular plate-shaped solid electrolyte layer 51 is made of a partially stabilized zirconia sheet, and a pair of upper and lower electrodes 55 and 56 are arranged opposite to each other with the solid electrolyte layer 51 interposed therebetween. The electrodes 55 and 56 are made of platinum Pt or the like. The diffusion resistance layer 52 is composed of a porous sheet for introducing exhaust gas into the electrode 55, and the shielding layer 53 is composed of a dense layer for suppressing permeation of exhaust gas. Each of these layers 52 and 53 is made of a ceramic such as alumina or zirconia by a sheet forming method or the like, but has different gas permeability due to the difference in the average pore diameter and porosity of the porosity.

  The insulating layer 54 is made of ceramics such as alumina and zirconia, and an air duct 57 is formed at a portion facing the electrode 56. In addition, a heater 58 made of platinum Pt or the like is embedded in the insulating layer 54. The heater 58 is a heating element that generates heat when energized from a battery power source, and the entire element is heated by the generated heat. In the following description, the electrode 55 is also referred to as a diffusion layer side electrode, and the electrode 56 is also referred to as an atmosphere side electrode.

  In the sensor element 50, the surrounding exhaust gas is introduced from the side portion of the diffusion resistance layer 52 and reaches the diffusion layer side electrode 55. When the exhaust gas is lean, oxygen in the exhaust gas is decomposed by the diffusion layer side electrode 55 by applying a voltage between the electrodes 55 and 56, ionized and passes through the solid electrolyte layer 51, and then is passed from the atmosphere side electrode 56 to the atmosphere duct 57. Discharged. At this time, a current flows in the direction from the atmosphere side electrode 56 to the diffusion layer side electrode 55, and a sensor signal corresponding to the current level is output. On the other hand, when the exhaust gas is rich, oxygen in the atmosphere duct 57 is decomposed by the atmosphere side electrode 56, ionized and passes through the solid electrolyte layer 51 and then discharged from the diffusion layer side electrode 55. And it reacts with unburned components such as HC and CO in the exhaust gas. At this time, a current flows in the direction from the diffusion layer side electrode 55 to the atmosphere side electrode 56, and a sensor signal corresponding to the current level is output.

  As described above, in the air-fuel ratio sensor 32 (sensor element 50), the oxygen decomposition reaction or the like is performed by the diffusion layer side electrode 55 and the atmosphere side electrode 56. Sensor response is different at each lean. This difference in responsiveness is caused by individual sensor differences and changes over time. If the sensor responsiveness is different, it is considered that the air-fuel ratio control is adversely affected. Therefore, in the air-fuel ratio control apparatus of the present embodiment, in order to improve the control accuracy of the air-fuel ratio, the air-fuel ratio correction coefficient FAF as a control parameter relating to the air-fuel ratio control is changed to the sensor response and the lean side when changing to the rich side. Correction will be made based on the sensor responsiveness at the time of the change to, and the details will be described below.

  FIG. 2 is a functional block diagram showing the configuration of the air-fuel ratio control apparatus by function, and each of these functions will be briefly described. In the air-fuel ratio adjustment unit M1, an air-fuel ratio correction coefficient FAF is calculated based on the deviation between the detected air-fuel ratio φsig calculated from the air-fuel ratio sensor signal and the target air-fuel ratio, and parameters taken in from a response detection unit M4 described later The air-fuel ratio correction coefficient FAF is corrected by α. The air-fuel ratio correction coefficient storage unit M2 stores at least the current value and the previous value of the air-fuel ratio correction coefficient FAF, and the detected air-fuel ratio storage unit M3 stores at least the current value and the previous value of the detected air-fuel ratio φsig. . The responsiveness detection unit M4 calculates a responsiveness parameter (parameter α) representing the responsiveness of the air-fuel ratio sensor 32 to the rich side and the lean side based on the air-fuel ratio correction coefficient FAF and the detected air-fuel ratio φsig. Here, the air-fuel ratio will be described as an excess fuel ratio (fuel amount / air amount), but there is no problem even if a configuration using an excess air ratio is used instead.

  In the present embodiment, the air-fuel ratio adjustment unit M1 corresponds to “correction amount calculation unit” and “control parameter correction unit”, and the responsiveness detection unit M4 includes “air-fuel ratio detection value change calculation unit” and “correction amount change calculation”. Means ”,“ responsiveness data calculation means ”and“ parameter calculation means ”.

  Each of the above functions is realized by a control program executed by the ECU 40, and the processing procedure of the air-fuel ratio adjusting unit M1 and the responsiveness detecting unit M4 will be described.

  FIG. 3 is a flowchart showing FAF calculation processing in the air-fuel ratio adjustment unit M1. In FIG. 3, first, in step S101, it is determined whether or not an air-fuel ratio F / B condition is satisfied. The air-fuel ratio F / B condition includes, for example, that the coolant temperature is equal to or higher than a predetermined temperature, is not in a high rotation / high load state, and that the air-fuel ratio sensor 32 is in an active state. If the condition is satisfied, the process proceeds to step S102, and an air-fuel ratio deviation err is calculated from the target air-fuel ratio φref and the detected air-fuel ratio φsig (err = φref−φsig). Thereafter, in step S103, the deviation change amount Δerr is calculated from the difference between the current value err (k) of the air-fuel ratio deviation and the previous value err (k−1), and in step S104, the deviation change amount Δerr is greater than zero. Determine whether it is larger.

  When Δerr ≦ 0, the process proceeds to step S105, and an air-fuel ratio correction coefficient FAF is calculated by the following equation based on a known PI control method.

FAF = KFp · err + KFi · Σerr
KFp is a proportional constant, and KFi is an integral constant.

  If Δerr> 0, the process proceeds to step S106, and an air-fuel ratio correction coefficient FAF is calculated by the following equation using a parameter α described later. That is, in this case, the air-fuel ratio correction coefficient FAF is corrected by the parameter α with respect to the normal FAF calculation value.

FAF = α (KFp · err + KFi · Σerr)
The method for calculating the air-fuel ratio correction coefficient FAF is not limited, and the FAF value is calculated using a model that reflects the past FAF value and calculates the current value of the FAF value, or a model that represents the dynamic behavior of the engine 10. Anything can be applied arbitrarily.

  If the air-fuel ratio F / B condition is not satisfied, the process proceeds to step S107, and the air-fuel ratio correction coefficient FAF is set to 1.

  Next, FIGS. 4 to 6 are flowcharts showing calculation processing in the responsiveness detection unit M4, and FIG. 4 is a flowchart showing FAF change rate calculation processing for calculating the change rate of the air-fuel ratio correction coefficient FAF. FIG. 5 is a flowchart showing the φsig change rate calculation process for calculating the change rate of the detected air-fuel ratio φsig, and FIG. 6 is a flowchart showing the parameter α calculation process.

  First, in the FAF change speed calculation process of FIG. 4, in step S201, it is determined whether or not the air-fuel ratio correction coefficient FAF is currently being calculated, and the process proceeds to step S202 on condition that the FAF calculation is being performed. In step S202, the change amount ΔFAF is calculated from the difference between the current value FAF (k) and the previous value FAF (k−1) of the air-fuel ratio correction coefficient. Thereafter, in step S203, it is determined whether or not the change amount ΔFAF of the air-fuel ratio correction coefficient is larger than zero. Here, ΔFAF> 0 means that the fuel injection amount by the fuel injection valve 19 is corrected to the increase side, and accordingly the air-fuel ratio changes to the rich side.

  When ΔFAF> 0, the process proceeds to step S204, and the change rate ΔFAFR of the air-fuel ratio correction coefficient when changing to the rich side is calculated by the following equation.

ΔFAFR (k) = ΔFAFR (k−1) + ksm1 (ΔFAF (k) −ΔFAF (k−1))
In the above equation, ksm1 is an annealing rate.

  If ΔFAF ≦ 0, the process proceeds to step S205, and the change rate ΔFAFL of the air-fuel ratio correction coefficient when changing to the lean side is calculated by the following equation.

ΔFAFL (k) = ΔFAFL (k−1) + ksm1 (ΔFAF (k) −ΔFAF (k−1))
As described above, the change rates ΔFAFR and ΔFAFL of the air-fuel ratio correction coefficient are calculated as change amount data of the air-fuel ratio correction amount at the time of rich change and lean change.

  Next, in the φsig change speed calculation process of FIG. 5, in step S301, it is determined whether or not the detected air-fuel ratio φsig is currently being calculated, and the process proceeds to step S302 on condition that φsig is being calculated. In step S302, the amount of change Δφsig is calculated from the difference between the current value φsig (k) of the detected air-fuel ratio and the previous value φsig (k−1). Thereafter, in step S303, it is determined whether or not the change amount Δφsig of the detected air-fuel ratio is greater than zero. Here, Δφsig> 0 means that the excess fuel ratio increases and the air-fuel ratio changes to the rich side.

  When Δφsig> 0, the process proceeds to step S304, and the change rate ΔφsigR of the detected air-fuel ratio when changing to the rich side is calculated by the following equation.

ΔφsigR (k) = ΔφsigR (k−1) + ksm2 (Δφsig (k) −Δφsig (k−1))
In the above equation, ksm2 is an annealing rate.

  If Δφsig ≦ 0, the process proceeds to step S305, and the change rate ΔφsigL of the detected air-fuel ratio when changing to the lean side is calculated by the following equation.

ΔφsigL (k) = ΔφsigL (k−1) + ksm2 (Δφsig (k) −Δφsig (k−1))
As described above, the change rates ΔφsigR and ΔφsigL of the detected air-fuel ratio are calculated as the change amount data of the sensor signal at the time of rich change and lean change.

  In the parameter α calculation process of FIG. 6, in step S401, the ratio compR (= ΔφsigR (k) between the change rate ΔφsigR of the detected air-fuel ratio and the change rate ΔFAFR of the air-fuel ratio correction coefficient when the air-fuel ratio changes to the rich side. / ΔFAFR (k)) and the ratio compL (= ΔφsigL (k) / ΔFAFL (k) between the change rate ΔφsigL of the detected air-fuel ratio and the change rate ΔFAFL of the air-fuel ratio correction coefficient when the air-fuel ratio changes to the lean side )) Is calculated.

Thereafter, in step S402, a ratio compRL between the calculated compR and compL is calculated. In subsequent step S403, a parameter α is calculated using a PI compensator for setting compRL to a target value (= 1). That is,
e = compRL-1
α = 1 + kp · e + ki (Σe)
The parameter α is calculated as follows. Note that kp is a proportionality constant and ki is an integration constant.

  Thus, compR and compL are calculated as responsiveness data of the air-fuel ratio sensor 32 at the time of rich change and lean change, and the parameter α is calculated as a responsiveness parameter. The parameter α calculated as described above is used for calculating the air-fuel ratio correction coefficient FAF in step S106 of FIG.

  FIG. 7 is a time chart showing the behavior of the air-fuel ratio φ and the air-fuel ratio correction coefficient FAF. In FIG. 7, the target air-fuel ratio is forcibly changed to the rich side and the lean side with respect to the theoretical air-fuel ratio (φ = 1) in a predetermined cycle, and the detected air-fuel ratio φsig and the air-fuel ratio correction coefficient FAF change accordingly. It shows how to do. The air-fuel ratio fluctuation is carried out for the purpose of, for example, early activation of the catalytic converter at the cold start of the engine 10 and improvement of catalyst purification efficiency (functional regeneration) during normal operation. The air-fuel ratio fluctuates toward the rich side and the lean side with a period of about several Hz.

  In (a), the waveform of the detected air-fuel ratio φsig is shifted to the lean side as a whole, and the average value of the actual air-fuel ratio (actual air-fuel ratio) is shifted to the lean side by the average air-fuel ratio deviation in the figure. Yes. This is considered to be because the response is higher when the air-fuel ratio changes to the lean side than when the air-fuel ratio changes to the rich side. On the other hand, in (b), the air-fuel ratio correction coefficient FAF is corrected from the dotted line to the solid line based on the response difference between the rich change and the lean change. This eliminates the average air-fuel ratio deviation as seen in (a).

  According to the embodiment described above in detail, the following excellent effects can be obtained.

  Since the responsiveness when the air-fuel ratio sensor 32 changes on the rich side and the responsiveness when the lean-side change changes are individually detected, the dynamic characteristics of the air-fuel ratio sensor 32 can be known from the responsiveness data. The air-fuel ratio correction coefficient FAF can be corrected reflecting the characteristics. Thereby, the control accuracy of the air-fuel ratio is improved, and inconveniences such as deterioration of exhaust emission can be suppressed. In this case, in particular, a parameter α that makes the responsiveness to the rich side and the responsiveness to the lean side of the air-fuel ratio sensor 32 equal is calculated, and the air-fuel ratio correction coefficient FAF is corrected using the parameter α. Therefore, even if there is a difference between the responsiveness to the rich side and the responsiveness to the lean side of the air-fuel ratio sensor 32, the air-fuel ratio correction can be performed so that the difference is eliminated. Therefore, an unexpected air-fuel ratio shift to the rich side or the lean side can be eliminated, and as a result, the control accuracy of the air-fuel ratio can be improved.

  Further, from the ratio between the change amount data (ΔφsigR, ΔφsigL) of the detected air-fuel ratio φsig and the change amount data (ΔFAFR, ΔFAFL) of the air-fuel ratio correction coefficient FAF for each of the change to the rich side and the change to the lean side. Since the responsiveness data (compR, compL) is calculated, the responsiveness data is obtained by comparing the change in the detected air-fuel ratio φsig with the change in the air-fuel ratio correction coefficient FAF. Therefore, the reliability of the responsiveness data is increased, and the FAF correction can be performed more suitably.

  Further, in the configuration in which the air-fuel ratio is forcibly fluctuated to the rich side and the lean side, the deviation of the air-fuel ratio average can be eliminated. Therefore, when the air-fuel ratio fluctuates, the center of the fluctuation can always be a desired air-fuel ratio (for example, the theoretical air-fuel ratio).

  In addition, this invention is not limited to the content of description of the said embodiment, For example, you may implement as follows.

  In the above embodiment, the air-fuel ratio correction coefficient FAF is corrected using the parameter α set so as to eliminate the response to the rich side and the lean side, but this configuration is changed. For example, the air-fuel ratio correction coefficient FAF is corrected using the response data (compR, compL) to the rich side and lean side of the air-fuel ratio sensor 32 individually. In this case, the correction may be performed using at least one of the response data to the rich side and the response data to the lean side, and the proper use may be performed according to the state of the response change.

  In the above embodiment, the detected air-fuel ratio change rate ΔφsigR, ΔφsigL, and the change rate ΔFAFR, ΔFAFL of the air-fuel ratio correction coefficient are used as the air-fuel ratio detection value and the change amount data of the air-fuel ratio correction amount to the rich side or lean side. However, instead of this, it is possible to use a change acceleration of the detected air-fuel ratio and a change acceleration of the air-fuel ratio correction coefficient.

  In the above embodiment, the FAF correction is performed with the parameter α when the deviation change amount Δerr is larger than 0 in the processing of FIG. 3, but the average value of the detected air-fuel ratio φsig when the air-fuel ratio varies is the target value. A configuration may be adopted in which the air-fuel ratio correction coefficient FAF is corrected when a predetermined value or more is deviated from the value average.

  The control parameter to be corrected may be an air-fuel ratio target value or a feedback gain (control gain) other than the air-fuel ratio correction coefficient FAF. It should be noted that at least two of the air-fuel ratio correction coefficient FAF, the air-fuel ratio target value, and the feedback gain can be corrected.

It is a block diagram which shows the outline of the engine control system in embodiment of invention. It is a functional block diagram which shows the structure of an air fuel ratio detection apparatus. It is a flowchart which shows FAF calculation processing. It is a flowchart which shows the calculation process of FAF change speed. It is a flowchart which shows the calculation process of (phi) sig change speed. It is a flowchart which shows the calculation process of parameter (alpha). It is a time chart which shows the behavior of an air fuel ratio and an air fuel ratio correction coefficient. It is sectional drawing which shows the structure of a sensor element.

Explanation of symbols

10 ... Engine,
24 ... exhaust pipe,
32 ... Air-fuel ratio sensor,
40: ECU, M1: Air-fuel ratio adjusting unit, M4: Responsiveness detecting unit.

Claims (11)

An air-fuel ratio sensor installed in the exhaust passage of the internal combustion engine;
An internal combustion engine comprising: a correction amount calculating means for calculating an air-fuel ratio correction amount for making the air-fuel ratio detection value detected from the air-fuel ratio sensor signal coincide with a target value, and controlling the air-fuel ratio using the air-fuel ratio correction amount In the air-fuel ratio control apparatus of
Air-fuel ratio detection value change calculation means for calculating change data of the air-fuel ratio detection value to the rich side and lean side, respectively;
Correction amount change calculation means for calculating change amount data of the air-fuel ratio correction amount to the rich side and lean side, respectively;
Based on the change amount data of the calculated air-fuel ratio detection value to the rich side and the lean side and the change amount data of the calculated air-fuel ratio correction amount to the rich side and the lean side, when changing to the rich side, the lean Responsiveness data calculating means for calculating responsiveness data of the air-fuel ratio sensor for each of the changes to the side;
Control parameter correction means for correcting control parameters relating to air-fuel ratio control using the calculated response data;
An air-fuel ratio control apparatus for an internal combustion engine, comprising: 2. The air-fuel ratio control apparatus for an internal combustion engine according to claim 1, wherein the control parameter correction unit corrects the control parameter according to a difference between the responsiveness data when changing to the rich side and when changing to the lean side. A parameter calculating means for calculating a responsiveness parameter that equalizes each responsiveness data at the time of change to the lean side at the time of change to the rich side calculated by the responsiveness data calculation means;
The air-fuel ratio detection apparatus for an internal combustion engine according to claim 1, wherein the control parameter correction means corrects the control parameter using the responsiveness parameter. The air-fuel ratio control apparatus for an internal combustion engine according to any one of claims 1 to 3, wherein the control parameter correction means corrects an air-fuel ratio correction amount as the control parameter. The air-fuel ratio control apparatus for an internal combustion engine according to any one of claims 1 to 3, wherein the control parameter correction means corrects an air-fuel ratio target value as the control parameter. The air-fuel ratio control apparatus for an internal combustion engine according to any one of claims 1 to 3, wherein the control parameter correction means corrects a control gain as the control parameter. The responsiveness data calculating means is responsive from a ratio between the change amount data of the air-fuel ratio detection value and the change amount data of the air-fuel ratio correction amount for each of the change to the rich side and the change to the lean side. The air-fuel ratio control apparatus for an internal combustion engine according to any one of claims 1 to 6, wherein data is calculated. The air-fuel ratio control apparatus for an internal combustion engine according to any one of claims 1 to 7, wherein the control parameter is corrected when the air-fuel ratio deviation changes so as to increase. The change speed or change acceleration is calculated as change amount data of the air-fuel ratio detection value, and the change speed or change acceleration is calculated as change amount data of the air-fuel ratio correction amount. An air-fuel ratio detection device for an internal combustion engine. Air-fuel ratio changing means for forcibly changing the air-fuel ratio to the rich side and the lean side, and when the air-fuel ratio detection value changes to the rich side as the air-fuel ratio changes by the air-fuel ratio changing means, or the air-fuel ratio detection value is The air-fuel ratio control apparatus for an internal combustion engine according to any one of claims 1 to 9, wherein the control parameter is corrected based on change amount data when changing to a lean side. 11. The internal combustion engine according to claim 10, further comprising means for calculating an average value of the detected air-fuel ratio, wherein the control parameter is corrected when the average value of the detected air-fuel ratio is more than a predetermined value from the target value average. Engine air-fuel ratio control device.

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