JP4906887B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention optimizes the fuel injection amount in an automobile called a so-called flexible fuel vehicle (hereinafter abbreviated as “FFV”) that can run even with a mixed fuel of alcohol (single component) and gasoline in any ratio. The present invention relates to a control device for an internal combustion engine.

  Currently, in addition to gasoline, there is a so-called FFV automobile that can run on mixed fuels of various compositions of alcohol and gasoline.

  Usually, a three-way catalyst that simultaneously purifies HC, CO, and NOx in exhaust gas is installed in an exhaust passage of an internal combustion engine of an automobile. This three-way catalyst has a characteristic that the purification efficiency of HC, CO, and NOx in the exhaust gas becomes the highest when the air-fuel ratio is near the stoichiometric air-fuel ratio.

  Since alcohol has different contents of carbon (C) atoms and oxygen (O) atoms than ordinary gasoline, the theoretical air-fuel ratio of alcohol and gasoline also differs. Therefore, when supplying a mixed fuel of alcohol and gasoline to the internal combustion engine, it is necessary to calculate the theoretical air-fuel ratio in accordance with the change in the alcohol concentration in the mixed fuel and correct the air-fuel ratio supplied to the internal combustion engine.

  Therefore, as a conventional technique for solving the above-described problems, an internal combustion engine that estimates the alcohol concentration based on the correlation between the air-fuel ratio correction amount by feedback control and the alcohol concentration and improves control performance such as air-fuel ratio control. Control devices have been proposed. Specifically, the deviation of the air-fuel ratio from the stoichiometric air-fuel ratio is detected from the oxygen concentration in the exhaust gas detected by the oxygen concentration sensor provided upstream of the three-way catalyst, and the air-fuel ratio is feedback-controlled. As a result, the air-fuel ratio is automatically corrected in the vicinity of the theoretical air-fuel ratio that varies depending on the alcohol concentration (see, for example, Patent Document 1).

  However, the hydrogen concentration in the exhaust gas increases in proportion to the alcohol concentration. Moreover, since the molecular weight of hydrogen is smaller than the molecular weight of oxygen, it is easy to diffuse into the zirconia element of the oxygen concentration sensor. Therefore, in the conventional technique as shown in Patent Document 1, the output of the oxygen concentration sensor slightly shifts to the rich (small) side. For this reason, the air-fuel ratio shifts slightly from the stoichiometric air-fuel ratio to the lean side (large), resulting in a problem that the catalyst purification efficiency is reduced and HC, CO, and NOx emissions are increased. .

  Therefore, as a conventional technique for solving the above problems, the air-fuel ratio is slightly changed from the stoichiometric air-fuel ratio by shifting the air-fuel ratio to the rich side in proportion to the alcohol concentration estimated by the air-fuel ratio correction amount of the feedback control. Control devices for internal combustion engines that prevent shifting to the lean side have been proposed (see, for example, Patent Documents 2 and 3).

JP 2004-245097 A JP-A-1-244133 JP 62-294739 A

  However, in the conventional techniques as shown in Patent Documents 2 and 3, when an error occurs in the alcohol concentration estimated by the air-fuel ratio correction amount of feedback control using the upstream oxygen concentration sensor, control performance such as air-fuel ratio control is achieved. Gets worse. Furthermore, with this prior art, the compensation accuracy of the lean shift due to hydrogen is reduced with the deterioration of the control performance, and the fuel injection amount cannot be optimized.

  Here, the factors of the estimation error of the alcohol concentration described above include the setting error of the estimation period set after the fuel supply determination to the fuel tank, and the air-fuel ratio caused by the characteristic fluctuation of the fuel supply device (for example, fuel injector, air flow sensor). Examples include correction amount fluctuations.

  The present invention has been made to solve the above-described problems, and can estimate the alcohol concentration more accurately and optimize the fuel injection amount based on the estimated alcohol concentration. An object of the present invention is to obtain a control device for an internal combustion engine.

An internal combustion engine control apparatus according to the present invention includes a fuel supply device that supplies fuel in a fuel tank to an internal combustion engine, a catalyst that is disposed in an exhaust system of the internal combustion engine, purifies exhaust gas from the internal combustion engine, An upstream oxygen concentration sensor that is provided on the upstream side and detects the oxygen concentration in the upstream exhaust gas before being purified by the catalyst, and a downstream exhaust gas that is provided on the downstream side of the catalyst and has been purified by the catalyst An upstream air-fuel ratio that adjusts the air-fuel ratio supplied to the internal combustion engine so that the detected value by the upstream oxygen concentration sensor matches the downstream target oxygen concentration sensor and the upstream target value An internal combustion engine comprising feedback control means and downstream air-fuel ratio feedback control means for adjusting the upstream target value so that the detection value by the downstream oxygen concentration sensor matches the downstream target value A downstream side concentration estimated value calculating means for calculating a concentration estimated value for a single composition of fuel in the fuel tank based on an adjustment amount of the upstream target value by the downstream air-fuel ratio feedback control means; A fuel supply amount adjusting means for adjusting the fuel supply amount to the internal combustion engine based on the concentration estimated value calculated by the downstream concentration estimated value calculating means, and using the upstream oxygen concentration sensor The fuel supply amount is corrected and controlled based on the concentration estimated value calculated by the downstream concentration estimated value calculating means so as to suppress the concentration estimation error as compared with the case of calculating the concentration estimated value of the composition .

  According to the control device for an internal combustion engine according to the present invention, by calculating the alcohol concentration estimated value for a single composition in the fuel tank based on the adjustment amount of the upstream target value by the downstream air-fuel ratio feedback control means, It is possible to obtain a control device for an internal combustion engine that can estimate the alcohol concentration more accurately and can optimize the fuel injection amount based on the estimated alcohol concentration value.

1 is a configuration diagram illustrating an internal combustion engine according to a first embodiment of the present invention. It is a graph which shows the relationship between the alcohol concentration of the mixed fuel of gasoline and ethanol, and a theoretical air fuel ratio. It is a block diagram which shows the principal part of a binary type oxygen concentration sensor. It is a block diagram which shows the principal part of a linear type oxygen concentration sensor. It is a graph which shows the result of having detected the exhaust gas before purification when the upstream oxygen concentration sensor is a binary oxygen concentration sensor. It is a graph which shows the result of having detected exhaust gas before purification when the upstream oxygen concentration sensor was a linear type oxygen concentration sensor. It is a graph which shows the result of having detected exhaust gas before purification when the downstream oxygen concentration sensor is a binary type oxygen concentration sensor. It is a graph which shows the result of having detected the exhaust gas before purification, when the downstream oxygen concentration sensor is a linear oxygen concentration sensor. It is explanatory drawing which shows an example of the two-dimensional map of the engine speed and load in ECU which concerns on Embodiment 1 of this invention. It is a flowchart which shows the setting operation | movement of the upstream air-fuel ratio feedback control by ECU which concerns on Embodiment 1 of this invention. It is explanatory drawing which shows the two-dimensional map of the output voltage and excess air ratio in ECU which concerns on Embodiment 1 of this invention. It is explanatory drawing which shows the two-dimensional map of the target excess air ratio and alcohol concentration in ECU which concerns on Embodiment 1 of this invention. It is explanatory drawing which shows the two-dimensional map of the alcohol concentration correction coefficient and alcohol concentration in ECU which concerns on Embodiment 1 of this invention. It is a flowchart which shows the setting operation | movement of the downstream air fuel ratio feedback control by ECU which concerns on Embodiment 1 of this invention. It is a flowchart which shows the setting operation | movement of the alcohol concentration estimated value by ECU which concerns on Embodiment 1 of this invention. It is explanatory drawing which shows the two-dimensional map of (DELTA) AFobj_flt and alcohol concentration estimated value error (DELTA) AL in ECU which concerns on Embodiment 1 of this invention.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

Embodiment 1 FIG.
FIG. 1 is a configuration diagram illustrating an internal combustion engine control apparatus according to Embodiment 1 of the present invention. The internal combustion engine shown in FIG. 1 is an internal combustion engine that uses a fuel containing alcohol. Further, this internal combustion engine is provided with a plurality of cylinders, but FIG. 1 shows only one of them.

  In FIG. 1, an engine 1 that is an internal combustion engine is provided with an intake port 2, an exhaust port 3, and a water jacket 4 that cools the engine 1. An intake pipe 5 is connected to the intake port 2. An exhaust pipe 6 is connected to the exhaust port 3. A water temperature sensor 7 for detecting the cooling water temperature is attached to the water jacket 4. The rotational speed of the engine 1 is detected by the frequency of the pulse signal output at every predetermined crank angle from the crank angle sensor 8.

  The intake pipe 5 has an air cleaner storage portion 9 and a surge tank 10. An air cleaner 11 for purifying air from an intake duct (not shown) is provided in the air cleaner storage unit 9. An intake air temperature sensor 12 for detecting the intake air temperature is provided in the surge tank 10.

  An air flow meter 13 and a throttle valve 14 are provided between the air cleaner housing 9 and the surge tank 10 in the intake pipe 5. The air flow meter 13 detects the amount of intake air to the engine 1. A throttle body 15 is provided above the throttle valve 14. A throttle valve 14 can be housed in the throttle body 15, and the throttle body 15 includes an idle speed control valve 16 that adjusts the air intake amount and an intake pipe pressure that detects the pressure of the intake pipe 5. A sensor 17 is provided.

  On the other hand, the exhaust pipe 6 is provided with an upstream oxygen concentration sensor 18 and a downstream oxygen concentration sensor 19. Further, a three-way catalyst 20 for purifying exhaust gas is provided between the upstream oxygen concentration sensor 18 and the downstream oxygen concentration sensor 19 in the exhaust pipe 6. The upstream oxygen concentration sensor 18 detects the oxygen concentration in the exhaust gas before being purified by the three-way catalyst 20. The downstream oxygen concentration sensor 19 detects the oxygen concentration in the exhaust gas after being purified by the three-way catalyst 20.

  A fuel injection valve (injector) 21 for injecting fuel is provided in the vicinity of the intake port 2 of each cylinder. The fuel injection valve 21 is provided in the intake air in the intake pipe 5 so as to have a predetermined air-fuel ratio in accordance with a driving condition according to a fuel injection command signal from an engine control unit 40 (hereinafter abbreviated as “ECU 40”). Then, the fuel supplied from the fuel tank 22 is injected.

  Although not shown, the ECU 40 includes a backup RAM (Random Access Memory) or EEPROM (Electrically Erasable and Programmable Read Only Memory) that stores data used for various arithmetic processes described later, and a ROM that stores an arithmetic control program. And have. The ECU 40 receives detection signals from various sensors (not shown) provided in the engine 1 and its periphery.

  The ECU 40 according to the first embodiment includes an upstream air-fuel ratio feedback control means 41, a downstream air-fuel ratio feedback control means 42, an upstream alcohol concentration estimated value calculation means 43 (corresponding to an upstream concentration estimation means), The downstream alcohol concentration estimated value calculating means 44 (corresponding to the downstream concentration estimating means), the upstream target excess air ratio calculating means 45 (corresponding to the upstream target value calculating means), and the fuel supply amount adjusting means 46 Have.

  Although details will be described later, each means in the ECU 40 generally functions as follows. Further, the control device for an internal combustion engine in the present invention may be configured not to include the upstream alcohol concentration estimated value calculating means 43 and the upstream target excess air ratio calculating means 45.

  The upstream air-fuel ratio feedback control means 41 adjusts the air-fuel ratio supplied to the internal combustion engine so that the value detected by the upstream oxygen concentration sensor 18 matches an upstream target excess air ratio (upstream target value) described later. To do.

  The downstream air-fuel ratio feedback control means 42 adjusts the upstream target excess air ratio so that the value detected by the downstream oxygen concentration sensor 19 matches the downstream target value described later.

  The upstream alcohol concentration estimated value calculating means 43 calculates an alcohol concentration estimated value for a single composition of the fuel in the fuel tank 22 based on the adjustment amount of the air / fuel ratio by the upstream air / fuel ratio feedback control means 41.

  The downstream alcohol concentration estimated value calculation means 44 calculates an alcohol concentration estimated value for a single composition of fuel in the fuel tank 22 based on the adjustment amount of the upstream target excess air ratio by the downstream air-fuel ratio feedback control means 42. calculate.

  The upstream target excess air ratio calculating means 45 calculates the upstream target excess air ratio based on the alcohol concentration estimated value calculated by the upstream alcohol concentration estimated value calculating means 43.

  The fuel supply amount adjusting means 46 adjusts the fuel supply amount to the internal combustion engine based on the alcohol concentration estimated value calculated by the upstream alcohol concentration estimated value calculating means 43 and the downstream alcohol concentration estimated value calculating means 44.

  In the fuel tank 22, the mixed fuel is stored. Examples of the mixed fuel include a mixed fuel of gasoline and ethanol.

  In the fuel tank 22, a fuel pump 23 for pumping up the mixed fuel and a fuel level gauge 24 for detecting the liquid level of the mixed fuel are provided. A pressure regulator 26 is connected to the fuel pump 23 via a fuel supply pipe 25. A fuel filter 27 is connected to the pressure regulator 26 via a fuel supply pipe 25. A delivery pipe 28 for supplying fuel to the fuel injection valve 21 of each cylinder is connected to the fuel filter 27 via the fuel supply pipe 25.

  The back pressure chamber of the pressure regulator 26 is open to the atmosphere. As a result, surplus fuel sent from the fuel pump 23 to the pressure regulator 26 is returned from the fuel return port 26 a of the pressure regulator 26 into the fuel tank 22.

  In addition, a canister 29 that adsorbs the vaporized gas generated from the mixed fuel is connected to the fuel tank 22. The canister 29 is connected to the surge tank 10 via the valve 30. The valve 30 is opened when the vaporized gas is introduced based on a control signal from the ECU 40. As a result, the vaporized gas adsorbed by the canister 29 is introduced into the engine 1 through the intake pipe 5.

  FIG. 2 is a graph showing the relationship between the alcohol concentration of the mixed fuel of gasoline and ethanol and the theoretical air-fuel ratio. The three-way catalyst 20 can purify NOx, HC, and CO in the exhaust gas with maximum purification efficiency when the air-fuel ratio is near the stoichiometric air-fuel ratio. However, fuels having different single component concentration (alcohol concentration) in the fuel have different C (carbon) atom contents compared to ordinary gasoline, so that the theoretical air-fuel ratios of gasoline and alcohol are also different.

  Therefore, upstream air-fuel ratio feedback control using the upstream oxygen concentration sensor 18 is used as a method of maintaining the air-fuel ratio in the three-way catalyst 20 at the stoichiometric air-fuel ratio even for fuels having different single composition component concentrations in the fuel. Generally known.

  Here, conventional upstream air-fuel ratio feedback control using the upstream oxygen concentration sensor 18 will be described.

  The ECU 40 detects the amount of deviation of the air-fuel ratio from the stoichiometric air-fuel ratio based on the oxygen concentration in the exhaust gas detected by the upstream oxygen concentration sensor 18, and feedback-controls the air-fuel ratio supplied to the engine 1 to the stoichiometric air-fuel ratio. . As a result, the air-fuel ratio is automatically corrected in the vicinity of the theoretical air-fuel ratio that varies depending on the alcohol concentration.

  However, the control accuracy for maintaining the air-fuel ratio in the three-way catalyst 20 at the stoichiometric air-fuel ratio is not sufficient only by the upstream air-fuel ratio feedback control using the upstream oxygen concentration sensor 18.

  Therefore, the upstream oxygen concentration sensor 18 and the downstream oxygen concentration sensor 19 are used to detect the deviation of the air-fuel ratio in the three-way catalyst 20 from the stoichiometric air-fuel ratio, and to maintain the air-fuel ratio at the stoichiometric air-fuel ratio. A double concentration sensor system that performs downstream air-fuel ratio feedback control that corrects the control constant of the upstream air-fuel ratio feedback control and adjusts the upstream air-fuel ratio is generally known.

  Here, the configuration and function of the upstream oxygen concentration sensor 18 and the downstream oxygen concentration sensor 19 will be mainly described below. FIG. 3 is a block diagram showing the main part of the binary oxygen concentration sensor, and FIG. 4 is a block diagram showing the main part of the linear oxygen concentration sensor.

  The upstream oxygen concentration sensor 18 and the downstream oxygen concentration sensor 19 in the first embodiment are binary oxygen concentration sensors having binary output characteristics with the stoichiometric air-fuel ratio as a boundary, but are not necessarily limited thereto. Instead, a linear oxygen concentration sensor that linearly detects the amount of deviation of the air-fuel ratio from the stoichiometric air-fuel ratio may be used.

  First, as shown in FIG. 3, a zirconia element is provided inside the binary oxygen concentration sensor. The binary oxygen concentration sensor guides air having a high oxygen concentration inside the zirconia element and guides exhaust gas having a low oxygen concentration outside the zirconia element.

  Thus, when a difference in oxygen concentration occurs between both ends of the zirconia element, oxygen ions pass through the zirconia element, and an electromotive force represented by the Nernst equation is generated. For example, when the air-fuel ratio in the exhaust gas that passes outside the zirconia element is smaller than the stoichiometric air-fuel ratio, the difference in oxygen concentration increases, so the electromotive force also increases. On the contrary, when the air-fuel ratio in the exhaust gas that passes outside the zirconia element is larger than the stoichiometric air-fuel ratio, the difference in oxygen concentration is small, so the electromotive force is also small.

  Further, platinum is used for the electrodes at both ends of the zirconia element in order to extract an electromotive force. This is because, in addition to the role of the electrode, the catalytic action of platinum is used to obtain a sufficient electromotive force and a characteristic that abruptly changes the oxygen concentration in the vicinity of the outer electrode with the theoretical air-fuel ratio as a boundary.

  On the other hand, as shown in FIG. 4, a zirconia element and an oxygen pump element are provided inside the linear oxygen concentration sensor. When the exhaust gas introduced into the measurement chamber is leaner than the stoichiometric air-fuel ratio, the oxygen pump element releases oxygen in the measurement chamber into the outer exhaust gas. On the contrary, the oxygen pump element takes in oxygen in the outer exhaust gas when the exhaust gas introduced into the measurement chamber is richer than the stoichiometric air-fuel ratio.

  The oxygen pump element is controlled by a control unit (not shown) of a linear oxygen concentration sensor. The control unit outputs a voltage indicating an air-fuel ratio deviation amount of the exhaust gas with respect to the stoichiometric air-fuel ratio. Therefore, the linear oxygen concentration sensor can linearly detect the deviation amount of the air-fuel ratio with respect to the stoichiometric air-fuel ratio based on the current value of the oxygen pump element generated by the release and intake of oxygen.

  FIG. 5 is a graph showing a result of detecting exhaust gas before purification when the upstream oxygen concentration sensor 18 is a binary oxygen concentration sensor, and FIG. 6 is a graph showing the upstream oxygen concentration sensor 18 being a linear oxygen sensor. It is a graph which shows the result of having detected exhaust gas before purification when it is a concentration sensor. The excess air ratio (λ) shown on the horizontal axis in FIGS. 5 and 6 is defined by the air / fuel ratio / theoretical air / fuel ratio.

  Usually, the hydrogen (H2) concentration in the exhaust gas before purification increases as the alcohol concentration increases. Further, hydrogen having a molecular weight smaller than that of oxygen (O 2) easily diffuses into the zirconia element of the upstream oxygen concentration sensor 18. For this reason, the detected oxygen concentration becomes lower than the actual oxygen concentration, and the electromotive force of the upstream oxygen concentration sensor 18 also increases.

  Therefore, as shown in FIGS. 5 and 6, in the alcohol fuel, the actual air-fuel ratio is the theoretical air-fuel ratio (excess air ratio (λ) = 1), whereas the electromotive force of the binary oxygen concentration sensor is large. Becomes rich output. Further, since the linear oxygen concentration sensor detects the air-fuel ratio with reference to the oxygen concentration detected by the zirconia element, the output is similarly rich.

  As described above, the air-fuel ratio by the upstream air-fuel ratio feedback control using the upstream binary oxygen concentration sensor or the upstream linear oxygen concentration sensor is slightly leaner than the stoichiometric air-fuel ratio in proportion to the alcohol concentration. Sneak away. Accordingly, the purification rate of the three-way catalyst 20 decreases, and the amount of NOx, HC, and CO emissions increases.

  FIG. 7 is a graph showing the result of detecting the exhaust gas before purification when the downstream oxygen concentration sensor 19 is a binary oxygen concentration sensor, and FIG. 8 is a graph showing the downstream oxygen concentration sensor 19 being a linear oxygen sensor. It is a graph which shows the result of having detected exhaust gas before purification when it is a concentration sensor.

  As shown in FIGS. 7 and 8, the hydrogen concentration in the exhaust gas is almost zero regardless of the alcohol concentration because the hydrogen is oxidized by being purified by the three-way catalyst 20. Further, in the vicinity of the stoichiometric air-fuel ratio and on the lean side of the stoichiometric air-fuel ratio, the oxidation effect of the three-way catalyst 20 increases, so that the hydrogen concentration becomes almost zero. Furthermore, on the richer side than the stoichiometric air-fuel ratio, the oxidizing action of the three-way catalyst 20 decreases, so the hydrogen concentration increases. Therefore, in the downstream oxygen concentration sensor 19, the output shift due to the alcohol concentration change near the stoichiometric air-fuel ratio is greatly reduced.

  The lean shift of the air-fuel ratio by the upstream oxygen concentration sensor 18 can be detected by the downstream oxygen concentration sensor 19. For this reason, the double oxygen concentration sensor system that corrects the upstream air-fuel ratio by downstream air-fuel ratio feedback control is also effective for increasing hydrogen in alcohol fuel.

  Furthermore, a change in alcohol concentration can be detected based on the correction amount of the upstream air-fuel ratio by the downstream air-fuel ratio feedback control.

  Therefore, in the first embodiment of the present invention, the downstream concentration estimated value calculating means for calculating the alcohol concentration estimated value based on the upstream air / fuel ratio correction amount by the downstream air / fuel ratio feedback control, and this downstream side A control apparatus for an internal combustion engine provided with fuel supply amount adjusting means 46 for adjusting the fuel supply amount to the internal combustion engine based on the alcohol concentration estimated value calculated by the concentration estimated value calculating means will be described below.

  First, the upstream air-fuel ratio feedback control using the upstream oxygen concentration sensor 18 will be described.

The fuel injection amount Qfuel1 supplied from the fuel injection valve 21 to the engine 1 includes a basic injection amount Qfuel0 when the alcohol concentration is 0%, an alcohol concentration correction coefficient KAL, an air-fuel ratio feedback correction coefficient KFB, a learning correction coefficient KLRN, Using the transpiration gas introduction correction coefficient KPRG, the following equation (1) is set.
Qfuel1 = Qfuel0 × KAL × KFB × KLRN × KPRG (1)

The basic injection amount Qfuel0 in the above equation (1) is calculated using the following equation (2) using the supply air amount Qacyl to the engine 1 calculated from the intake air amount qa detected by the air flow meter 13 and the target air-fuel ratio AF0. ).
Qfuel0 = Qacyl / AF0 (2)

  The target air-fuel ratio AF0 in the above equation (2) is an air-fuel ratio when the alcohol concentration is 0%, and a three-dimensional map of engine speed and load (for example, intake air amount qa) as shown in FIG. Is set based on

  In FIG. 9, when the engine speed or the load is large, the target air-fuel ratio AF0 (= 12 to 13) for enrichment control is set. When the engine speed or load is in the intermediate operating range, the target air-fuel ratio AF0 (≈14.5) for the theoretical air-fuel ratio control is set. Further, when the engine speed is in the intermediate operating range and the load is small, the target air-fuel ratio AF0 (= 16) for lean control or the target air-fuel ratio AF0 (= ∞) for fuel cut is set.

  Here, the alcohol concentration correction coefficient KAL, the air-fuel ratio feedback correction coefficient KFB, the learning correction coefficient KLRN, and the transpiration gas introduction correction coefficient KPRG will be described below.

  The alcohol concentration correction coefficient KAL is a correction coefficient for correcting a change in the theoretical air-fuel ratio that changes depending on the alcohol concentration. The alcohol concentration correction coefficient KAL is calculated based on the air-fuel ratio feedback correction coefficient KFB and the downstream air-fuel ratio feedback control.

  The air-fuel ratio feedback correction coefficient KFB is a correction coefficient for upstream air-fuel ratio feedback control that is performed based on the output of the upstream oxygen concentration sensor 18 so as to achieve an upstream target air excess ratio AFobj described later.

  The learning correction coefficient KLRN is a correction coefficient that corrects characteristic variation due to aging of the fuel supply apparatus (for example, the fuel injection valve 21). Further, the learning correction coefficient KLRN is calculated based on the air-fuel ratio feedback correction coefficient KFB.

  The transpiration gas introduction correction coefficient KPRG is a correction coefficient for correcting fluctuations in the air-fuel ratio due to the introduction of transpiration gas. The transpiration gas introduction correction coefficient KPRG is calculated based on the air-fuel ratio feedback correction coefficient KFB.

  FIG. 10 is a flowchart showing the setting operation of the upstream air-fuel ratio feedback control by the ECU 40 according to the first embodiment of the present invention. This is an upstream air-fuel ratio feedback control routine for correcting the air-fuel ratio supplied to the internal combustion engine based on the output of the upstream oxygen concentration sensor 18, and is executed every predetermined time, for example, every 5 ms.

  In FIG. 10, the symbols “Y” and “N” of the branching portions from the respective determination processes indicate “Yes” and “No”, respectively.

  First, in step S101, the ECU 40 takes in and outputs the output V1 from the upstream oxygen concentration sensor 18 by A / D conversion, and outputs an output voltage (V) and an excess air ratio (λ) of 2 as shown in FIG. Using the dimension map, the output V1 is converted into the detected excess air ratio AF1.

In step S102, the ECU 40 sets the upstream target air excess ratio AFobj based on a target air excess ratio reference value AFobj0, which will be described later, and a target air excess ratio correction value ΔAFobj as shown in the following equation (3). To calculate.
AFobj ← AFobj0 + ΔAFobj (3)

  The reference value AFobj0 of the upstream target excess air ratio in the above equation (3) compensates for the lean shift of the upstream oxygen concentration sensor 18 caused by the hydrogen concentration that increases in proportion to the alcohol concentration. Therefore, the reference value AFobj0 of the upstream target excess air ratio is set according to the change in the alcohol concentration AL using a two-dimensional map as shown in FIG.

  Further, the correction value ΔAFobj of the upstream target excess air ratio in the above equation (3) is calculated by downstream air-fuel ratio feedback control described later, and a reference value of the upstream target excess air ratio due to an alcohol concentration estimated value error ΔAL described later. The setting error of AFobj0 is compensated.

  Here, the two-dimensional map as shown in FIG. 12 is set for each operation condition delimited by the engine speed and the load because the amount of increase in the hydrogen concentration varies depending on the engine speed and the load. This is because as the engine speed or load increases, the hydrogen concentration change due to the alcohol concentration change tends to decrease, and the lean shift of the upstream oxygen concentration sensor 18 tends to decrease.

  The reference value AFobj0 of the upstream target excess air ratio is not necessarily set according to the change in alcohol concentration, and the lean shift of the upstream oxygen concentration sensor 18 caused by the hydrogen concentration is compensated by the downstream air-fuel ratio feedback control. May be.

Next, in step S103, the ECU 40 calculates a deviation ΔAF1 between the detected excess air ratio AF1 and the upstream target excess air ratio AFobj as in the following equation (4).
ΔAF1 ← AF1-AFobj (4)

  Next, in step S104, the ECU 40 determines whether the upstream air-fuel ratio feedback condition by the upstream oxygen concentration sensor 18 is satisfied.

  At this time, for example, in the case of the air-fuel ratio control condition of the stoichiometric air-fuel ratio control and in the active state of the upstream oxygen concentration sensor 18 (that is, Yes), it is determined that the upstream air-fuel ratio feedback condition is satisfied, and step S105 The process moves to.

  However, when it is determined that the open loop control described later is prohibited, it is determined that the upstream air-fuel ratio feedback condition is satisfied even in the air-fuel ratio control condition other than the theoretical air-fuel ratio control.

In step S105, the ECU 40 performs proportional calculation (hereinafter referred to as “P”) and integral calculation (hereinafter referred to as “I”), which are PI control processes, in accordance with the deviation ΔAF1, and eliminates the deviation ΔAF1. The output is calculated as in the following equations (5) to (7). Note that the air-fuel ratio feedback correction coefficient KFB is calculated by a general PI controller.
KFB ← 1.0 + KI + KP (5)
KI ← KI + GI x ΔAF1 (6)
KP ← GP × ΔAF1 (7)

  In the above equations (5) and (6), KI is an integral calculation value on the upstream side. In addition, KP in the above formulas (5) and (7) is an upstream proportional calculation value. Further, GI in the above equation (6) is an upstream integral gain. Furthermore, GP in the above equation (7) is an upstream proportional gain. GI and GP are set for each operation condition so that the feedback controllability is good.

  Here, when the detected excess air ratio AF1 of the upstream oxygen concentration sensor 18 is smaller (lean) than the upstream target excess air ratio AFobj, the fuel supply amount is reduced so that the air-fuel ratio feedback correction coefficient KFB decreases. Set to. Accordingly, the detected excess air ratio AF1 is set to be the upstream target excess air ratio AFobj.

  On the other hand, if the air-fuel ratio control condition other than the stoichiometric air-fuel ratio control, the upstream oxygen concentration sensor 18 is in an inactive state, or is in a failure state (ie, No), it is determined that the upstream feedback condition is not satisfied. Then, the process proceeds to step S106.

  Here, as the air-fuel ratio control conditions other than the theoretical air-fuel ratio control, for example, during the enrichment control when the cooling water temperature is low, during the enrichment control of the high load power increase, during the lean control for improving fuel efficiency, For example, during lean control after starting and during fuel cut.

  In step S106, the ECU 40 resets the air-fuel ratio feedback correction coefficient KFB to 1.0. That is, KI and KP are reset to 0.

  Next, in step S107, the ECU 40 determines whether or not it is an update condition for the alcohol concentration correction coefficient KAL.

  At this time, if the update condition of the alcohol concentration correction coefficient KAL is satisfied (that is, Yes), the process proceeds to step S108.

  Here, during the estimation of the alcohol concentration, it is necessary to prohibit the introduction of the transpiration gas, which will be described later, and it is necessary to prohibit the open loop control, so that other air-fuel ratio control functions are deteriorated. Therefore, the alcohol concentration update period is set to a period during which the alcohol concentration is likely to change due to refueling.

  The alcohol concentration update period is, for example, a predetermined period after it is determined that fuel has been supplied to the fuel tank 22 based on a change in the detection signal of the fuel level gauge 24 in the fuel tank 22, or a predetermined period after the engine is started. For example, a predetermined period after the storage value such as the alcohol concentration correction coefficient KAL stored in the backup RAM is initialized by the period or the reset process of the ECU 40 may be used. In addition, the alcohol concentration update period is managed by time, integrated fuel injection amount, and the like.

In step S108, the ECU 40 updates the alcohol concentration correction coefficient KAL from the air-fuel ratio feedback correction coefficient KFB as the following expression (8).
KAL ← KAL × KFB (8)

  “KAL × KFB” in the above equation (8) is a multiplication of the current alcohol concentration correction coefficient KAL and the air-fuel ratio feedback correction coefficient KFB, and the current alcohol concentration is based on the theoretical air-fuel ratio of 0% alcohol concentration. This corresponds to a true alcohol concentration correction coefficient KAL for compensating the theoretical air-fuel ratio.

  Further, the ECU 40 updates the estimated alcohol concentration value based on a characteristic map of the alcohol concentration correction coefficient KAL and the alcohol concentration AL as shown in FIG. This estimated alcohol concentration value is used for various air-fuel ratio control and ignition timing control.

  Here, examples of the air-fuel ratio control include fuel control at the time of engine start. Further, examples of the ignition timing control include calculation of a control constant related to ignition timing calculation and knock control.

  Next, an error in the alcohol concentration estimated value will be described. The error in the estimated alcohol concentration value is caused by a setting error in the alcohol concentration update period.

  In addition, as the setting error of the alcohol concentration update period, for example, when the fuel supply determination omission occurs and the variation in the air-fuel ratio feedback correction coefficient caused by the characteristic variation of the fuel supply device is not reflected in the learning correction coefficient KLRN, the alcohol concentration For example, it is reflected in the correction coefficient KAL.

  In order to reduce the influence of short-term fluctuations in the air-fuel ratio feedback correction coefficient KFB due to upstream air-fuel ratio feedback control, the air-fuel ratio feedback correction coefficient KFB may be subjected to filter processing or moving average processing. However, when the alcohol concentration correction coefficient KAL is updated, since the change in the air-fuel ratio feedback correction coefficient KFB due to the change in alcohol concentration is reflected in the alcohol concentration correction coefficient KAL, the air-fuel ratio feedback correction coefficient KFB is reset to 1.0. That is, KP and KI are reset to zero.

  Also, the alcohol concentration correction coefficient KAL may be calculated based on the downstream alcohol concentration described later using a characteristic map (see FIG. 13).

  On the other hand, if the update condition of the alcohol concentration correction coefficient KAL is not satisfied (that is, No), the process proceeds to step S109.

  Next, in step S109, the ECU 40 determines whether or not it is a condition for introducing a transpiration gas.

  At this time, if it is the condition for introducing the transpiration gas (that is, Yes), the transpiration gas is introduced, and the process proceeds to step S110.

In step S110, the ECU 40 updates the transpiration gas introduction correction coefficient KPRG that compensates for changes in the air-fuel ratio due to changes in the concentration of the transpiration gas introduced into the intake pipe 5, as shown in the following equation (9).
KPRG ← KPRG × KFB (9)

  “KPRG × KFB” in the above equation (9) is a multiplication of the current transpiration gas introduction correction coefficient KPRG and the air-fuel ratio feedback correction coefficient KFB, and corresponds to a true transpiration gas correction coefficient that compensates for the introduced transpiration gas concentration. To do.

  On the other hand, if it is not the condition for introducing the transpiration gas (determined as the alcohol concentration update period in Step S107) (that is, No), the introduction of the transpiration gas is prohibited, and the process proceeds to Step S111. Thereby, the fluctuation of the air-fuel ratio feedback correction coefficient KFB due to the introduction of the transpiration gas is prevented, and the accuracy of the alcohol concentration estimated value is improved.

  In step S111, the ECU 40 resets the transpiration gas introduction correction coefficient KPRG to 1.0.

  Next, in step S112, the ECU 40 determines whether or not the learning value update prohibition condition of the learning correction coefficient KLRN of the air-fuel ratio feedback correction coefficient KFB is satisfied.

  At this time, when it is not during the alcohol concentration update period and when the transpiration gas is introduced (that is, Yes), it is determined that the learning value update prohibition condition of the learning correction coefficient KLRN is not satisfied, and the process proceeds to step S113.

In step S113, the ECU 40 updates the learning correction coefficient KLRN as in the following equation (10).
KLRN ← KLRN × KFB (10)

  “KRLN × KFB” in the above equation (10) is a multiplication of the current learning correction coefficient KLRN and the air-fuel ratio feedback correction coefficient KFB, and corresponds to a true learning correction coefficient.

  On the other hand, when it is during the alcohol concentration update period and when the transpiration gas is introduced (that is, No), it is determined that the learning value update prohibition condition of the learning correction coefficient KLRN is satisfied, and updating of the learning value of the learning correction coefficient KLRN is prohibited. To do. This prevents fluctuations in the air-fuel ratio feedback correction coefficient KFB caused by alcohol concentration changes and transpiration gas concentration changes from being reflected in the update of the learning correction coefficient KLRN, and the learning value of the learning correction coefficient KLRN, alcohol concentration correction The calculation accuracy of the coefficient KAL and the transpiration gas introduction correction coefficient KPRG is improved.

  Here, the update of the learning value of the learning correction coefficient KLRN (hereinafter referred to as “learning control”) in the first embodiment will be described.

  The learning control compensates for a secular change and individual difference (production variation) of the fuel supply device (for example, the fuel injection valve 21). Examples of the secular change of the fuel supply device include a change in the injection amount characteristic of the fuel injection valve 21. Further, the individual difference includes an error in the amount of air detected by the air flow meter 13.

  When there is no change in these characteristics, the center of the air-fuel ratio feedback correction coefficient KFB is designed (set) to be 1.0. However, when there is a characteristic change, the center of the air-fuel ratio feedback correction coefficient KFB is deviated from 1.0.

  Therefore, the learning control has an effect of compensating the deviation of the center of the air-fuel ratio feedback correction coefficient KFB from 1.0 by the learning value and the learning correction coefficient KLRN and keeping the center of the air-fuel ratio feedback correction coefficient KFB at 1.0. is there.

  Next, in step S114, the ECU 40 determines whether or not the air-fuel ratio open loop control is prohibited.

  At this time, if the air-fuel ratio open loop control prohibition condition is satisfied (the alcohol concentration update period in step S107) (that is, Yes), the process proceeds to step S115.

  In step S115, the ECU 40 prohibits air-fuel ratio open loop control. Thereby, the accuracy of the alcohol concentration estimated value is improved by reliably performing the upstream air-fuel ratio feedback control and calculating the air-fuel ratio feedback correction coefficient KFB.

  As air-fuel ratio open loop control, for example, rich control for increasing high load power, which is air-fuel ratio control other than stoichiometric air-fuel ratio control, lean control for fuel improvement, rich control at low cooling water temperature And lean control after starting.

  FIG. 14 is a flowchart showing the setting operation of the downstream air-fuel ratio feedback control by the ECU 40 according to the first embodiment of the present invention. This is a calculation routine for downstream air-fuel ratio feedback control that calculates the correction value ΔAFobj of the upstream target excess air ratio based on the output of the downstream oxygen concentration sensor 19, and is executed every predetermined time, for example, every 5 ms. The

  First, in step S201, the ECU 40 reads the output V2 from the downstream oxygen concentration sensor 19.

  Next, in step S202, the ECU 40 sets a downstream target value VR2 that is a target value for the output V2 of the downstream oxygen concentration sensor 19. Note that the predetermined output value of the downstream oxygen concentration sensor 19 near the theoretical air-fuel ratio is set to, for example, around 0.45V.

Next, in step S203, the ECU 40 calculates a deviation ΔV2 between the output V2 of the downstream oxygen concentration sensor 19 and the downstream target value VR2 as in the following equation (11).
ΔV2 ← V2-VR2 (11)

  Next, in step S <b> 204, the ECU 40 determines whether the downstream feedback condition by the downstream oxygen concentration sensor 19 is satisfied.

  At this time, when the downstream oxygen concentration sensor 19 is in an active state and the upstream feedback condition is satisfied and the theoretical air-fuel ratio control is performed (that is, Yes), the downstream feedback condition is satisfied. Determination is made, and the process proceeds to step S205.

In step S205, the ECU 40 performs P (proportional calculation) and I (integral calculation), which are PI control processes, in accordance with the deviation ΔV2, and outputs such that the deviation ΔV2 is eliminated by the following equations (12) to (14). Calculate as follows. The correction value ΔAFobj for the upstream target excess air ratio is calculated by a general PI controller.
ΔAFobj ← KI2 + KP2 (12)
KI2 ← KI2 + GI2 × ΔV2 (13)
KP2 ← GP2 × ΔV2 (14)

  KI2 in the above equations (12) and (13) is a downstream integral calculation value. Further, KP2 in the above equations (12) and (14) is a downstream proportional calculation value. Furthermore, GI2 in the above equation (13) is an integral gain on the downstream side. Furthermore, GP2 in the above equation (14) is a downstream proportional gain. GI2 and GP2 are set for each operating condition so that the downstream air-fuel ratio feedback control is good.

  Since P generates an output in proportion to the deviation ΔV2, it exhibits fast response and can rapidly reduce the deviation ΔV2. In addition, I integrates the deviation ΔV2 to generate an output, so that it operates relatively slowly and is stationary in the downstream oxygen concentration sensor 19 due to characteristic fluctuations of the upstream oxygen concentration sensor 18 due to hydrogen or the like. Deviation ΔV2 can be eliminated.

  Here, when the output V2 of the downstream oxygen concentration sensor 19 is smaller (lean) than the downstream target value VR2, the upstream target excess air ratio AFobj uses the output V2 of the downstream oxygen concentration sensor 19 as the downstream target. Correction is made to be larger (rich) than the value VR2, and the output V2 of the downstream oxygen concentration sensor 19 is set to the downstream target value VR2.

  On the other hand, when the downstream oxygen concentration sensor 19 is in an inactive state and the upstream feedback condition is not satisfied and the theoretical air-fuel ratio control is not performed (that is, No), it is determined that the downstream feedback condition is not satisfied. Then, the process proceeds to step S206.

  In step S206, the ECU 40 stops updating P and stores the integral calculation value KI2 in the backup RAM.

  Here, since the hydrogen concentration in the exhaust gas changes depending on the engine speed and the operating condition of the load, the characteristic fluctuation of the upstream oxygen concentration sensor 18 also changes depending on the engine speed and the operating condition of the load.

  Therefore, the downstream integral calculation value KI2 is stored in the backup RAM provided for each operation condition divided by the engine speed and the load, and the backup RAM to be updated is switched every time the operation condition changes. In addition, by using the backup RAM, the downstream integral calculation value KI2 is reset every time the engine is stopped and restarted, thereby preventing a decrease in control performance.

  FIG. 15 is a flowchart showing the setting operation of the estimated alcohol concentration value on the downstream side by the ECU 40 according to the first embodiment of the present invention. This is a calculation routine of the downstream alcohol concentration estimated value calculating means 44 that corrects the alcohol concentration estimated value and the alcohol concentration correction coefficient KAL based on the correction value ΔAFobj of the target excess air ratio calculated by the downstream air-fuel ratio feedback control. Therefore, it is executed every predetermined time, for example, every 5 ms.

  Here, the upstream target excess air ratio AFobj is set in a feed-forward manner according to the estimated alcohol concentration value calculated by the upstream air-fuel ratio feedback control. However, when an alcohol concentration estimated value error ΔAL occurs, it is compensated in a feedback manner by the downstream air-fuel ratio feedback control.

  Therefore, it is possible to determine whether or not an estimation error ΔAL of the alcohol concentration estimation value has occurred due to a change in the correction value ΔAFobj of the target excess air ratio calculated by the downstream air-fuel ratio feedback control. When it is determined that the estimation error ΔAL of the alcohol concentration estimated value has occurred, the alcohol concentration estimated value can be corrected.

  First, the ECU 40 filters ΔAFobj_flt that is obtained by filtering the correction value ΔAFobj of the target excess air ratio in order to reduce the influence of temporary fluctuations in the output of the downstream oxygen concentration sensor 19 caused by excessive operation such as acceleration and deceleration of the engine. Is calculated (step S301).

  ΔAFobj_flt is stored in a backup RAM provided for each operating condition divided by the engine speed and load, and switches the backup RAM to be updated each time the operating condition changes. This is because the characteristic fluctuation amount of the upstream oxygen concentration sensor 18 due to the alcohol concentration change changes depending on the engine speed and the operating condition of the load.

  Note that the integral calculation value KI2 of the downstream air-fuel ratio feedback control stored for each operating condition may be used instead of ΔAFobj_flt. This is because the integral calculation value KI2 has an effect of compensating for the characteristic variation of the upstream oxygen concentration sensor 18.

  Next, in step S302, the ECU 40 calculates an estimation error of the alcohol concentration estimated value calculated by the downstream air-fuel ratio feedback control. At this time, the ECU 40 calculates ΔAFobj_flt and the alcohol concentration estimated value error ΔAL using a two-dimensional map as shown in FIG.

  Next, in step S303, the ECU 40 determines whether or not the alcohol concentration estimated value error ΔAL is large by determining whether or not an average value ΔALAVE of an alcohol concentration estimated value error ΔAL described later is larger than a predetermined threshold value. To do.

  The ECU 40 calculates an average value ΔALAVE of the alcohol concentration estimated value error ΔAL under a specific operating condition. This is because the alcohol concentration estimated value is calculated by calculating the average value ΔALAVE of the alcohol concentration estimated value error ΔAL of the operating condition in which the characteristic variation becomes large or the average value ΔALAVE of the alcohol concentration estimated value error ΔAL of the operating condition having a high operating frequency The calculation accuracy of the error ΔAL can be improved.

  In step S303, when the average value ΔALAVE of the alcohol concentration estimated value error ΔAL is larger than the predetermined threshold (that is, Yes), the ECU 40 determines that the alcohol concentration estimated value error ΔAL is also large, and the process proceeds to step S304. .

  Note that the characteristic variation of the oxygen concentration sensor due to hydrogen can be separated from the characteristic variation of the oxygen concentration sensor due to factors such as secular change by utilizing the fact that there is a tendency difference depending on the operating conditions. Therefore, when the average value ΔALAVE of the alcohol concentration estimated value error ΔAL under a predetermined operating condition is large and the average value ΔALAVE of the alcohol concentration estimated value error ΔAL under other operating conditions is small, the alcohol concentration estimated value error ΔAL is large. It may be determined that it has become.

  Further, when the deviation between the average value ΔALAVE of the alcohol concentration estimated value error ΔAL at the previous engine stop and the average value ΔALAVE of the alcohol concentration estimated value error ΔAL during the current engine operation becomes large, the alcohol concentration estimated value It may be determined that the error ΔAL has increased. This is because fuel supply is highly likely to be performed while the engine is stopped, and therefore an alcohol concentration estimated value error ΔAL may occur for each fuel supply.

In step S304, the ECU 40 corrects the alcohol concentration estimated value based on the current alcohol concentration estimated value and the average value ΔALAVE of the alcohol concentration estimated value error ΔAL as shown in the following equation (15).
AL ← AL + ΔALAVE (15)

  Further, the ECU 40 updates the alcohol concentration correction coefficient KAL based on the corrected alcohol concentration estimated value using the characteristic map (see FIG. 13). At this time, the ECU 40 resets ΔAFobj_flt or KI2 stored for each operating condition to zero.

  Note that the upstream target air excess ratio AFobj (AFobj + ΔAFobj) after the downstream air-fuel ratio feedback control is a true upstream target air excess ratio. For this reason, you may make it calculate downstream alcohol concentration estimated value AL2 using a characteristic map (refer FIG. 12). At this time, AFobj0 may not be changed according to the upstream alcohol concentration. In this case, if the difference between the downstream alcohol concentration estimated value AL2 and the upstream alcohol concentration estimated value becomes large, it is determined that an alcohol concentration estimated value error ΔAL has occurred, and the upstream alcohol concentration estimated value is The downstream alcohol concentration estimated value AL2 may be substituted.

  As described above, the control device for an internal combustion engine according to the first embodiment calculates the alcohol concentration estimated value for a single composition in the fuel tank based on the adjustment amount of the upstream target value by the downstream air-fuel ratio feedback control means. Calculated. Further, the fuel supply amount to the internal combustion engine is adjusted based on the calculated alcohol concentration estimated value. As a result, the alcohol concentration can be estimated more accurately, and the fuel injection amount can be optimized based on the estimated alcohol concentration value.

  In the above description, the downstream concentration estimated value calculating means for calculating the alcohol concentration estimated value for a single composition in the fuel tank based on the adjustment amount of the upstream target value by the downstream air / fuel ratio feedback control means 42. However, the present invention is not limited to such a configuration. An upstream-side concentration estimated value calculating means for calculating an alcohol concentration estimated value for a single composition in the fuel tank based on the adjustment amount of the air-fuel ratio by the upstream-side air-fuel ratio feedback control means 41 may be provided. It is. In this case, the fuel supply amount to the internal combustion engine can be adjusted according to the estimated values by the downstream concentration estimated value calculating means and the upstream concentration estimated value calculating means.

  Further, the upstream target value can be calculated based on the estimated value by the upstream concentration estimated value calculating means. In this case, the upstream target value is set in a feedforward manner according to the alcohol concentration estimated value calculated by the upstream air-fuel ratio feedback control, and when the alcohol concentration estimated value error ΔAL occurs, It is compensated in a feedback manner by the downstream air-fuel ratio feedback control.

  Reference Signs List 1 engine (internal combustion engine), 18 upstream oxygen concentration sensor, 19 downstream oxygen concentration sensor, 20 three-way catalyst, 21 fuel injection valve (fuel supply device), 22 fuel tank, 41 upstream air-fuel ratio feedback control means, 42 Downstream air-fuel ratio feedback control means, 43 Upstream alcohol concentration estimation value calculation means (upstream concentration estimation means), 44 Downstream alcohol concentration estimation value calculation means (downstream concentration estimation means), 45 Upstream target air excess ratio calculation Means (upstream target value calculating means), 46 fuel supply amount adjusting means.

Claims (3)

A fuel supply device for supplying the fuel in the fuel tank to the internal combustion engine;
A catalyst disposed in the exhaust system of the internal combustion engine for purifying exhaust gas from the internal combustion engine;
An upstream oxygen concentration sensor that is provided upstream of the catalyst and detects an oxygen concentration in the upstream exhaust gas before being purified by the catalyst;
A downstream oxygen concentration sensor that is provided on the downstream side of the catalyst and detects the oxygen concentration in the downstream exhaust gas after being purified by the catalyst;
Upstream air-fuel ratio feedback control means for adjusting the air-fuel ratio supplied to the internal combustion engine so that the detected value by the upstream oxygen concentration sensor matches the upstream target value;
A control device for an internal combustion engine, comprising: a downstream air-fuel ratio feedback control unit that adjusts the upstream target value so that a detection value by the downstream oxygen concentration sensor matches a downstream target value. ,
A downstream concentration estimated value calculating means for calculating a concentration estimated value for a single composition of the fuel in the fuel tank based on an adjustment amount of the upstream target value by the downstream air-fuel ratio feedback control means;
Fuel supply amount adjusting means for adjusting the fuel supply amount to the internal combustion engine based on the concentration estimated value calculated by the downstream concentration estimated value calculating means ;
Based on the concentration estimated value calculated by the downstream concentration estimated value calculating means so as to suppress the concentration estimation error as compared with the case of calculating the concentration estimated value of the single composition by using the upstream oxygen concentration sensor. And a control device for the internal combustion engine , wherein the fuel supply amount is corrected and controlled . The control apparatus for an internal combustion engine according to claim 1,
An upstream side concentration estimated value calculating means for calculating a concentration estimated value of a single composition of the fuel in the fuel tank based on the adjustment amount of the air / fuel ratio by the upstream side air / fuel ratio feedback control;
The fuel supply amount adjusting means adjusts the fuel supply amount to the internal combustion engine based on the respective estimated concentration values calculated by the upstream concentration estimated value calculating means and the downstream concentration estimated value calculating means. A control device for an internal combustion engine. The control apparatus for an internal combustion engine according to claim 2,
The control apparatus for an internal combustion engine, further comprising an upstream target value calculation means for calculating the upstream target value based on the concentration estimated value calculated by the upstream concentration estimated value calculation means.

Images