JP2009203941A - Device for controlling internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device for controlling that is contributable to precise driving control of an internal combustion engine, by preventing erroneous estimation. <P>SOLUTION: A lower limit clip value ALCest_eOCL is formed based on an E0 assumption alcohol concentration estimate value ALCest_e0 arithmetically operated by assuming that the whole is an oil kind of the low concentration, and an upper limit clip value ALCest_e85CL is formed based on the E0 assumption alcohol concentration estimate value ALCest_e0 arithmetically operated by assuming that the whole is an oil kind of the high concentration, to be set as the upper and lower limit clip values of an alcohol concentration estimate value ALCest estimated based on a measured value of the air-fuel ratio. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine, and is particularly useful when applied to estimation of alcohol concentration based on an air-fuel ratio in a vehicle (flexible fuel vehicle, hereinafter referred to as FFV) that can use both gasoline fuel and alcohol fuel. Is.

  Recently, alcohol such as ethanol has attracted attention as a low-pollution fuel, and the development of FFV using this alcohol as fuel by mixing it with gasoline is advancing. Also in this type of FFV, an oxygen sensor or LAFS (linear air-fuel ratio sensor) is provided to detect the air-fuel ratio from the oxygen concentration in the exhaust, and during operation, the fuel supply amount is fed back so that the air-fuel ratio approaches the target air-fuel ratio. Control to correct. At this time, in the FFV, it is necessary to appropriately control the fuel injection amount in consideration of the difference in characteristics of both fuels, such as the difference in the theoretical air-fuel ratio between gasoline and alcohol. That is, it is necessary to accurately grasp the alcohol concentration of the alcohol-mixed fuel and perform accurate fuel supply amount control according to the alcohol concentration. Here, it is known that the alcohol concentration can be estimated based on data representing the state of the exhaust gas. Therefore, instead of the method of directly detecting the alcohol concentration with the alcohol sensor, a method of estimating the alcohol concentration in the FFV based on the output signal of the oxygen sensor or LAFS that is an air-fuel ratio sensor for detecting the exhaust air-fuel ratio has been proposed. ing. In this case, the fuel injection amount is controlled so that a predetermined air-fuel ratio is obtained based on the estimated alcohol value.

  When the alcohol concentration is estimated based on the air-fuel ratio as described above, it is important to accurately reflect the change in the fuel mixture ratio in the tank due to refueling in the estimation. Therefore, Patent Documents 1 and 2 disclose this kind of technology. In Patent Document 1, it is assumed that the alcohol concentration contributing to the increase in the remaining fuel amount is 100%, and the remaining fuel amount and alcohol concentration before the change and the fuel amount contributing to the increase in the increase amount Based on the above, the alcohol concentration in the mixed fuel is calculated. Further, in Patent Document 2, there is provided means for switching the upper and lower limit values for limiting the air-fuel ratio correction amount depending on whether or not the single composition concentration of the mixed fuel has been changed.

JP 2007-9903 A JP 2004-293349 A

  However, in Patent Document 1, all changes in fuel to the increase side are considered to be 100% alcohol concentration. Therefore, when gasoline is actually refueled, the injection amount becomes more than necessary, and exhaust gas performance due to over-rich or It may lead to a deterioration in drivability, which may lead to misfire and engine stall. On the other hand, Patent Document 2 merely expands the range of the air-fuel ratio correction amount that can correct the fuel injection amount, and is not an appropriate upper and lower limit clip that can be considered from the amount of fuel supplied. Accordingly, there is a concern that exhaust gas performance or drivability deteriorates due to overestimation of air / fuel ratio due to erroneous estimation, overlean, or engine stall.

  An object of the present invention is to provide a control device that can prevent erroneous estimation in the case of estimating an alcohol concentration based on an air-fuel ratio and contribute to accurate operation control of an internal combustion engine in view of the above-described conventional technology. .

  A first aspect of the present invention that achieves the above object is a control device for an internal combustion engine operable with an alcohol-containing fuel, the air-fuel ratio detection means for detecting an air-fuel ratio of an exhaust system of the internal combustion engine, Feedback control means for performing feedback control so that the air-fuel ratio detected by the fuel-fuel ratio detection means approaches the target air-fuel ratio, and alcohol concentration estimation for estimating the alcohol concentration of the alcohol-containing fuel based on the air-fuel ratio detected by the air-fuel ratio detection means Means, parameter control means for controlling operating parameters of the internal combustion engine in accordance with the air-fuel ratio feedback correction amount and the alcohol concentration, and fuel supply determination means for detecting that fuel has been supplied into the tank, and the alcohol The concentration estimating means determines that the fuel increase when the oil supply determining means determines that the fuel has been supplied is relatively alcohol-rich. A first computing means for computing a first hypothetical alcohol concentration estimated value, which is an estimated alcohol concentration value when it is assumed that the fuel is a first fuel having a small first concentration, and the fuel increase amount A second calculation for calculating a second hypothetical alcohol concentration estimated value, which is an alcohol concentration estimated value when assuming that the fuel is a second concentration fuel having a relatively high alcohol concentration, based on the estimated alcohol concentration value. And when the feedback correction amount of the feedback control means changes to correct the air-fuel ratio in the lean direction, the first hypothetical alcohol concentration estimated value is selected while the air-fuel ratio is corrected in the rich direction. In such a case, the lean / rich determination means for selecting the second hypothesized alcohol concentration estimate and the lean / rich determination means Clip setting means for setting the first assumed alcohol concentration estimated value thus made as a lower limit clip value and further setting the second assumed alcohol concentration estimated value selected by the lean / rich determination means as an upper limit clip value. The control apparatus for an internal combustion engine is characterized by being configured as described above.

  According to this aspect, it is possible to set an accurate upper / lower limit clip value at the time of alcohol concentration estimation in the alcohol concentration estimation means, so an accurate upper / lower limit clip value is set even when the alcohol concentration of the fuel changes due to fueling. Thus, erroneous estimation can be prevented in advance.

  As a result, it is possible to satisfactorily suppress deterioration of exhaust gas performance and drivability due to over-rich or over-lean of the air-fuel ratio due to erroneous estimation of the alcohol concentration. This can also solve problems such as misfire and engine stall of the internal combustion engine.

  According to a second aspect of the present invention, in the control device for an internal combustion engine described in the first aspect, the clip value setting means sets a value obtained by subtracting a predetermined margin from the first assumed alcohol concentration estimated value as the lower limit. The internal combustion engine control apparatus is characterized in that a clip value and a value obtained by adding a predetermined margin to the second hypothesized alcohol concentration estimated value are set as the upper limit clip value.

  According to this aspect, it is possible to set a more appropriate upper / lower limit clip value by removing variations in hardware performance of the air / fuel ratio detection system, etc., so that the air / fuel ratio is over-rich or over-lean due to erroneous estimation of the alcohol concentration. The deterioration of exhaust gas performance and drivability due to can be better suppressed.

  According to the present invention, the first hypothetical alcohol concentration estimated value when the fuel increase amount is all assumed to be a low alcohol concentration fuel is set as the lower limit clip value, and the second hypothesis when all the fuel is assumed to be a high alcohol concentration fuel. The upper and lower alcohol concentration estimates are assumed to be the upper clip value and the upper and lower alcohol concentration estimates are clipped. Therefore, in the alcohol concentration estimation process after refueling, a concentration that exceeds a possible concentration or a concentration that is less than the above concentration Is not erroneously estimated as an alcohol concentration estimated value.

  As a result, it is possible to satisfactorily suppress deterioration of exhaust gas performance and drivability due to over-rich or over-lean of the air-fuel ratio due to erroneous estimation of the alcohol concentration. This can also solve problems such as misfire and engine stall of the internal combustion engine.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram showing an FFV engine and its control apparatus according to an embodiment of the present invention. As shown in the figure, an ignition plug 3 is attached to each cylinder in a cylinder head 2 of an engine 1 that is an internal combustion engine mounted on an FFV, and an ignition coil 4 that outputs a high voltage is connected to the ignition plug 3. ing. An intake port 5 is formed in the cylinder head 2 for each cylinder, and an intake valve 7 is provided on the intake port 5 on the combustion chamber 6 side. The intake valve 7 is opened and closed following the cam of the camshaft 8 that rotates in accordance with the engine rotation, and communicates and shuts off the intake port 5 and the combustion chamber 6.

  One end of an intake manifold 9 is connected to and communicated with the intake port 5. An electromagnetic fuel injection valve 10 is attached to the intake manifold 9 corresponding to each cylinder, and the fuel injection valve 10 is connected to a fuel pipe 11. The fuel pipe 11 is connected to a fuel supply device (not shown), and a mixed fuel containing alcohol (ethanol) and gasoline is supplied from the fuel tank 14. The amount of fuel in the fuel tank 14 is detected by a fuel sensor 21.

  An intake pipe upstream of the intake manifold 9 is provided with a throttle valve 12 that opens and closes an intake passage, and a throttle position sensor 13 that detects a valve opening (throttle opening) of the throttle valve 12.

  On the other hand, an exhaust port 15 is formed in each cylinder head 2 for each cylinder, and an exhaust valve 17 is provided on the combustion chamber 6 side of the exhaust port 15. The exhaust valve 17 is opened and closed following the cam of the camshaft 18 that rotates in accordance with the engine rotation, and communicates and shuts off the exhaust port 15 and the combustion chamber 6. One end of an exhaust manifold 16 is connected to the exhaust port 15, and the exhaust manifold 16 communicates with the exhaust port 15.

  An exhaust pipe (exhaust passage) 20 is connected to the other end of the exhaust manifold 16, and an exhaust purification catalyst 23 is provided in the exhaust pipe 20. An oxygen sensor 22 is provided in the exhaust pipe 20 upstream of the exhaust purification catalyst 23.

  An electronic control unit I (hereinafter referred to as ECUI), which is a control device, performs comprehensive control including the engine 1, and on its input side, a throttle position sensor 13, a fuel sensor 21, an oxygen sensor 22, Various sensors such as a crank angle sensor 25 for detecting the crank angle of the engine 1 are connected, and detection information from these sensors is input. On the other hand, various output devices such as the fuel injection valve 10, the ignition coil 4, and the throttle valve 12 are connected to the output side of the ECUI. These various output devices output operation parameters such as fuel injection time, ignition timing, and throttle opening calculated by ECUI based on detection information from various sensors. That is, based on detection information from various sensors, the air-fuel ratio corresponding to the alcohol concentration of the mixed fuel is set to an appropriate target air-fuel ratio (target A / F), and feedback control is performed based on information from the oxygen sensor 22. The

  FIG. 2 is a block diagram showing the detailed configuration of the ECU I according to this embodiment (note that the sensors only show the oxygen sensor 22 and the fuel sensor 21). As shown in the figure, the ECU I in this embodiment includes an air-fuel ratio detection unit 51, a feedback correction amount setting unit 52, a target air-fuel ratio setting unit 53, an alcohol concentration estimation unit 54, an operation parameter control unit 55, and an oil supply determination unit 56. Have.

  Among these, the air-fuel ratio detection unit 51 processes the output signal of the oxygen sensor 22 to detect the air-fuel ratio, and outputs this air-fuel ratio to the feedback correction amount setting unit 52. The feedback correction amount setting unit 52 compares the measured air-fuel ratio with the target air-fuel ratio preset in the target air-fuel ratio setting unit 53, and sets the air-fuel ratio feedback correction amount FB to the operation parameter control unit 55 so as to reach the target air-fuel ratio. Output to.

  The alcohol concentration estimation unit 54 estimates the alcohol concentration in the alcohol-containing fuel based on the air-fuel ratio feedback correction amount FB, generates an alcohol concentration estimated value ALTest, and outputs this to the operation parameter control unit 55. Here, the alcohol concentration estimation unit 54 according to the present embodiment prevents the erroneous estimation of the alcohol concentration by performing an accurate clipping process based on the estimated upper and lower limit values of the alcohol concentration. A specific configuration of the alcohol concentration estimation unit 54 including such clipping processing will be described in detail later.

  The operation parameter control unit 55 controls parameters related to the operation of the engine 1 such as a fuel supply amount to the fuel injection valve 10 based on the air-fuel ratio feedback correction amount FB and the alcohol concentration estimated value ALTest.

  The fuel supply determination unit 56 detects the current fuel amount Vold based on the output of the fuel sensor 21 that detects the fuel level in the fuel tank 14 (see FIG. 1). Then, it is determined that refueling has been performed when an increase in the fuel amount equal to or greater than a predetermined amount is detected from the fuel amount Vold in the current fuel tank (immediately before refueling). When refueling is performed, the refueling amount Vnew is added to the fuel amount Vold in the fuel tank immediately before refueling, and the information is output to the alcohol concentration estimation unit 54.

  The alcohol concentration estimation unit 54 in this embodiment includes an estimation processing unit 60, first and second calculation units 61 and 62, a lean / rich determination unit 63, and a clip unit 64. Here, the estimation processing unit 60 estimates the alcohol concentration based on the feedback correction amount FB based on the actually measured value of the air-fuel ratio, and generates the alcohol concentration estimated value ALTest. Based on the alcohol concentration estimated value ALTest and the output of the refueling determination unit 56, the first arithmetic unit 61 is an oil type having a relatively low alcohol concentration, for example, the first concentration, for all fuel increases during refueling. An E0 assumed alcohol concentration estimated value ALC_e0, which is a first alcohol concentration estimated value when it is assumed that E0 (gasoline 100%), is calculated. Based on the alcohol concentration estimated value ALTest and the output of the refueling determination unit 56, the second computing unit 62 is an oil type with a relatively high alcohol concentration, for example, the second concentration, for all fuel increases during refueling. An E85 assumed alcohol concentration estimated value ALC_e85, which is a second estimated alcohol concentration value when it is assumed that E85 (gasoline 15% / ethanol 85 percent), is calculated. Specifically, the first calculation unit 61 performs the calculation represented by the following formula (1), and the second calculation unit 62 performs the calculation represented by the following formula (2).

1) When newly refueled fuel is assumed to be “E0” ALEST_e0 = (Vold × ALCest ÷ 100) / (Vold +
Vnew) (1)
2) When the newly refueled fuel is assumed to be “E85” ALEST_e85 = (Vold × ALEST ÷ 100 + Vnew × 0.
85) / (Vold + Vnew) (2)
However, in the above formulas (1) and (2), Vold: Fuel amount in tank immediately before refueling, Vnew; Refueling amount, ALTest; Alcohol concentration estimated value immediately before refueling, ALTest_e0; E0 assumed alcohol concentration estimated value, ALTest_e85; E85 This is an estimated alcohol concentration estimate.

  The lean / rich determination unit 63 inputs the E0 assumed alcohol concentration estimated value ALTest_e0 if the movement of the air-fuel ratio feedback correction amount FB is in the lean direction, and inputs the E85 assumed alcohol concentration estimated value ALTest_e85 if the movement is in the rich direction. 64 is controlled. That is, the lean / rich determination unit 63 performs control for selecting any one of the E0 assumed alcohol concentration estimated value ALTest_e0 to the E85 assumed alcohol concentration estimated value ALTest_e85 via the clip unit 64.

  Here, as described above, the reason why the E0 assumed alcohol concentration estimated value ALTest_e0 is selected if the movement of the air-fuel ratio feedback correction amount FB is in the lean direction, and the E85 assumed alcohol concentration estimated value ALTest_e85 is selected if the movement is in the rich direction. deep.

  The fact that the movement of the air-fuel ratio feedback correction amount FB when the estimation of the alcohol concentration after refueling is in the lean direction means that the actual fuel may be smaller. That is, less fuel is required to maintain the stoichiometric state, and in this case, the alcohol concentration of the current fuel is smaller. On the other hand, if the movement of the air-fuel ratio feedback correction amount FB is in the rich direction, it indicates that the alcohol concentration of the current fuel is higher for the opposite reason.

  Therefore, if the movement of the air-fuel ratio feedback correction amount FB is in the lean direction, the E0 hypothetical alcohol concentration estimated value ALTest_e0, which is a calculation value when assuming that E0 having a small alcohol concentration is all supplied, is set to the lower limit value of the clip unit 64. To the unit 65. On the other hand, if the movement of the air-fuel ratio feedback correction amount FB is in the rich direction, the E85 hypothetical alcohol concentration estimated value ALTest_e85, which is a calculated value when it is assumed that E85 having a high alcohol concentration has been supplied, is set to the upper limit value of the clip unit 64. The data is output to the unit 66. The lower limit setting unit 65 and the upper limit setting unit 66 obtain the lower limit clip value ALTest_e0CL and the upper limit clip value ALTest_e85CL of the alcohol concentration estimated value ALTest by a predetermined calculation.

  Specifically, the lower limit clip value ALTest_e0CL is obtained by the calculation of the following equation (3) with the margin α added to the E0 assumed alcohol concentration estimated value ALTest_e0, and the following equation (4) with the margin α added to the E85 assumed alcohol concentration estimated value ALTest_e85: The upper limit clip value ALTest_e85CL is obtained by the above calculation.

1) Calculation of lower limit clip value ALTest_e0CL ALTest_e0CL = (Vold × ALEST ÷ 100) /
(Vold + Vnew) −α ≧ 0% (3)
Here, ALCS_e0CL ≧ 0 is set because the alcohol concentration in this case does not become less than 0% even when all of the oil types E0 are supplied.
2) Calculation of upper limit clip value ALTest_e85CL ALTest_e85CL = (Vold × ALCest ÷ 100 + Vnew ×
0.85) / (Vold + Vnew) + α ≦ 85% (4)

  Here, ALCS_e85CL ≦ 85% is set because the alcohol concentration in this case does not exceed 85% even when fuel of all E85 oil types is supplied.

  The comparison unit 67 is set with an alcohol concentration estimated value ALTest which is an output of the estimation processing unit 60. Further, the comparison unit 67 compares the set alcohol concentration estimated value ALTest with any one selected from the lower limit clip value ALTest_e0CL to the upper limit clip value ALTest_e85CL output from the lower limit value setting unit 65 to the upper limit value setting unit 66. . As a result, when ALEST <ALCest_e0CL or ALEST> ALCest_e85CL, the lower limit clip value ALTest_e0CL or the upper limit clip value ALTest_e85CL is set as the alcohol concentration estimated value ALTest, and the alcohol concentration estimated value ALTest in this case is output to the operation parameter control unit 55. To do. This is because the actual alcohol concentration does not become lower than the lower limit clip value ALTest_e0CL, and does not exceed the upper limit clip value ALTest_e85CL. That is, in these cases, it is determined that the alcohol concentration is erroneously estimated, and the alcohol concentration estimated value ALEST is clipped to the lower limit clip value ALTest_e0CL to the upper limit clip value ALTest_e85CL.

  In addition, when ALTest_e85CL ≧ ALCest ≧ ALCest_e0CL, the alcohol concentration estimated value ALTest that is the output of the estimation processing unit 60 is output as it is.

  Here, the concept of alcohol concentration estimation will be described with reference to FIG. FIG. 3 is an explanatory diagram showing a time-series relationship among the alcohol concentration estimation, the fuel injection amount correction value, and the fuel injection amount reference value in this embodiment. As shown in FIG. 6A, the estimation process is executed at the rising timing of the measurement pulses P1, P2, and P3 in the measurement periods T1, T2, and T3 assigned at predetermined intervals. As a result, the fuel injection amount reference value changes as shown in the figure to operate the engine 1 at a predetermined air-fuel ratio, as indicated by the stepped dotted line in FIG. Although this example is a case where it increases in a staircase pattern, of course, such a change does not always occur.

  On the other hand, the fuel injection amount correction value, which is the average value of the FB integral values reflecting the air-fuel ratio feedback correction amount FB, rises and falls in a state deviating from the injection amount reference value as shown by the solid line in FIG. To change. In FIG. 5B, the injection amount correction value that deviated by a large value in the initial stage becomes smaller each time the concentration estimation is performed with the passage of time, and finally almost matches the injection amount reference value. It shows that it is in a state. Thus, it is considered that the alcohol concentration estimated value ALTest in a state where the deviation amount of the injection amount correction value, which is an actually measured value with respect to the injection amount reference value, converges to a predetermined value or less reflects the true alcohol concentration.

  4A and 4B are diagrams conceptually illustrating alcohol concentration estimation in relation to the upper and lower limit clips. FIG. 4A is a processing timing of alcohol concentration estimation processing, and FIG. 4B is an alcohol concentration estimated value ACLest on the rich side and an upper limit clip. The relationship with the value ALTest_e85CL, (c) shows the relationship between the estimated alcohol concentration on the lean side and the lower limit clip value ALTest_e0CL. As shown in FIG. 6A, the estimation process is executed at the rising timing of the measurement pulses P1, P2, and P3, as in the case shown in FIG. FIGS. 7B and 7C show how the alcohol concentration estimated value ALTest changes in a stepped manner every time the estimation process is executed at the rising timing of the measurement pulses P1, P2, and P3. At this time, on the rich side shown in FIG. 6B, the upper limit clip value ALTest_e85CL obtained by adding the margin α to the E85 assumed alcohol concentration estimated value ALTest_e85 is used to prevent erroneous estimation of the alcohol concentration estimated value ALTest. On the lean side, the lower limit clip value ALTest_e0CL obtained by subtracting the margin α from the E0 assumed alcohol concentration estimated value ALTest_e0 is used to prevent erroneous estimation of the alcohol concentration estimated value ALTest. Although not shown in FIG. 4, in this estimation process, the alcohol concentration of 85% is an absolute upper limit value and the alcohol concentration of 0% is an absolute lower limit value for the reasons described above.

  In principle, it is possible to prevent erroneous estimation even when the E0 assumed alcohol concentration estimated value ALTest_e0 itself is set as the lower limit clip value ALTest_e0CL and the E85 assumed alcohol concentration estimated value ALTest_e85 itself is set as the upper limit clip value ALTest_e85CL without considering the margin α. Is possible. However, there is a variation in hardware performance in the feedback system that generates the air-fuel ratio feedback correction amount FB. Therefore, it is preferable to allow for the margin α as described above in view of such variation. This is because the margin α absorbs variations in hardware performance of the feedback system.

  In this embodiment, when refueling is performed, the first calculation unit 61 of the alcohol concentration estimation unit 54 assumes that all of the fuel increase during refueling is E0 (gasoline 100%). Assuming that the E0 assumed alcohol concentration estimated value ALTest_e0, which is a value, is calculated, the second calculating unit 62 assumes that all of the fuel increase during refueling is E85 (15% gasoline / 85% ethanol). An E85 hypothetical alcohol concentration estimated value ALTest_e85, which is a concentration estimated value, is calculated.

  On the other hand, the lean / rich determination unit 63 detects whether the movement of the air-fuel ratio feedback correction amount FB is in the lean direction or the rich direction, and if it is in the lean direction, the lower limit clip value based on the E0 assumed alcohol concentration estimated value ALTest_e0. ALCS_e0CL is selected and compared with the alcohol concentration estimated value ALTest estimated by the estimation processing unit 60. On the other hand, in the rich direction, the upper limit clip value ALTest_e85CL based on the E85 hypothetical alcohol concentration estimated value ALTest_e85 is selected and compared with the alcohol concentration estimated value ALTest estimated by the estimation processing unit 60.

  As a result, only when ALTest_e85CL ≧ ALCest ≧ ALCest_e0CL, the alcohol concentration estimated value ALTest which is the output of the estimation processing unit 60 is output as it is. Otherwise, the lower limit clip value ALTest_e0CL to the upper limit clip value ALTest_e85CL are the alcohol concentration estimated value ALTest. Is output as In this way, it is possible to generate an alcohol concentration estimated value ALTest that accurately prevents erroneous estimation of the alcohol concentration estimated value ALTest.

  FIG. 5 is a flowchart showing a processing procedure in the ECU I according to this embodiment. As shown in FIG. 5A, the fuel amount Vold in the tank and the current estimated concentration ALTest are stored at the time of key-off (see step S1).

On the other hand, the upper and lower limit clip values are calculated according to the following processing procedure as shown in FIG.
1) Input the current fuel amount V (see step S2).
2) Calculate the amount of oil supply Vnew = V-Vold (see step S3).
3) Next, it is determined whether or not the oil supply amount Vnew is equal to or greater than a predetermined value. If Yes, the oil supply determination flag is turned on, and if No, the oil supply flag is turned off (steps 4 and 5). , 6).
4) After the refueling flag = ON, the upper / lower limit clip value is calculated. Specifically, the lower limit clip value ALTest_e0CL and the upper limit clip value ALTest_e85CL are obtained by the calculations of the equations (3) and (4) (see step S7).

  Further, the alcohol concentration estimation using the upper and lower limit values obtained by the procedure shown in FIG. 5B is performed by the following processing procedure as shown in FIG.

1) The alcohol concentration estimation process is performed to update the alcohol concentration estimated value ALTest (see step S8).
It is determined whether or not the movement of the air-fuel ratio feedback correction amount AF / FB is in the lean direction (see step S9).
2) As a result of the determination process in step S9, when it is determined that the vehicle is in the lean direction, the alcohol concentration estimated value ALTest updated in step S8 is compared with the lower limit clip value ALTest_e0CL set in step S7, and ALTest <ALCest_e0CL In this case, the lower limit clip value ALTest_e0CL is set as the alcohol concentration estimated value ALTest in this case (see Step S10 and Step S11).
3) If it is determined in step S9 that the direction is not the lean direction, it is determined whether the movement of the correction amount AF / FB is in the rich direction (see step S12).
4) As a result of the determination process in step S12, when it is determined that the direction is rich, the alcohol concentration estimated value ALTest updated in step S8 is compared with the upper limit clip value ALTest_e85CL set in step S7, and ALTest> ALTest_e85CL. In this case, the upper limit clip value ALTest_e85CL is set as the alcohol concentration estimated value ALTest in this case (see Step S13 and Step S14).

  Thus, in the case of ALTest <ALCest_e0CL or ALEST> ALCest_e85CL, which is considered to be an erroneous estimation of the alcohol concentration, the lower limit clip value ALTest_e0CL or the upper limit clip value ALTest_e85CL is set as the alcohol concentration estimated value ALTest. On the other hand, when ALTest_e85CL ≧ ALCest ≧ ALCest_e0CL, the alcohol concentration estimated value ALTest is set as it is.

  In the above embodiment, the oil type having a low relative alcohol concentration is E0, and the oil type having a high relative concentration is E85. However, the present invention is not limited to these. If there is a relative concentration difference between the two types of oil, the present invention can be applied without limitation, and similar actions and effects can be expected. Incidentally, in the case of E100, the part related to E85 in the above embodiment may be replaced with E100.

  The present invention can be effectively used in the automotive industry, particularly in the industrial field related to FFV.

It is a block diagram which shows the engine of FFV which concerns on embodiment of this invention, and its control apparatus. It is a block diagram which shows the detailed structure of ECU which concerns on the said embodiment. It is explanatory drawing which shows the time-sequential relationship of alcohol concentration estimation in the said embodiment, fuel injection amount correction value, and fuel injection amount reference value. It is explanatory drawing which shows notionally alcohol concentration estimation in the relationship with the upper / lower limit clip in the said embodiment. It is a flowchart which shows the procedure (b) of the calculation process of the time of key-off in the ECU which concerns on the said embodiment (a), and an upper / lower limit clip value. It is a flowchart which shows the procedure of the alcohol concentration estimation process in ECU which concerns on the said embodiment.

Explanation of symbols

I ECU
DESCRIPTION OF SYMBOLS 1 Engine 10 Fuel injection valve 21 Fuel sensor 22 Oxygen sensor 51 Air-fuel ratio detection part 52 Feedback correction amount setting part 54 Alcohol concentration estimation part 55 Operation parameter control part 56 Refueling determination part 60 Estimation processing part 61 1st calculating part 62 2nd Calculation unit 63 Lean / rich determination unit 64 Clip unit

Claims (2)

A control device for an internal combustion engine operable with an alcohol-containing fuel,
Air-fuel ratio detection means for detecting an air-fuel ratio of the exhaust system of the internal combustion engine;
Feedback control means for performing feedback control so that the air-fuel ratio detected by the air-fuel ratio detection means approaches the target air-fuel ratio;
Alcohol concentration estimation means for estimating the alcohol concentration of the alcohol-containing fuel based on the air-fuel ratio detected by the air-fuel ratio detection means;
Parameter control means for controlling operating parameters of the internal combustion engine in accordance with the air-fuel ratio feedback correction amount and the alcohol concentration;
Refueling determination means for detecting that fuel has been refueled in the tank,
The alcohol concentration estimation means includes
A first hypothetical alcohol concentration estimate that is an alcohol concentration estimate when it is assumed that the fuel increase when the fuel supply determining means determines that the fuel has been supplied is a fuel having a relatively low alcohol concentration. First computing means for computing a value based on the estimated alcohol concentration value;
A second hypothetical alcohol concentration estimated value that is an alcohol concentration estimated value when the fuel increase amount is assumed to be a second concentration fuel having a relatively high alcohol concentration is calculated based on the alcohol concentration estimated value. Two computing means;
When the feedback correction amount of the feedback control means changes so as to correct the air-fuel ratio in the lean direction, the first hypothetical alcohol concentration estimated value is selected, while changing so as to correct the air-fuel ratio in the rich direction. A lean / rich determination means for selecting the second hypothetical alcohol concentration estimate,
The first hypothetical alcohol concentration estimated value selected by the lean / rich determining means is a lower limit clip value, and the second hypothetical alcohol concentration estimated value selected by the lean / rich determining means is the upper limit clip value. A control apparatus for an internal combustion engine, characterized by comprising clip setting means for setting. The control apparatus for an internal combustion engine according to claim 1,
The clip value setting means sets a value obtained by subtracting a predetermined margin from the first hypothetical alcohol concentration estimated value as the lower limit clip value, and further adds a predetermined margin to the second hypothetical alcohol concentration estimated value. A control apparatus for an internal combustion engine, wherein the control value is set as the upper limit clip value.

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