JP2009221991A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device for internal combustion engine capable of detecting abnormality of a fuel system even in a process for estimating concentration of alcohol based on an air-fuel ratio. <P>SOLUTION: A lower limit concentration limit value ALCest_e0(n) is formed by performing a primary delay processing twice based on an E0 supposition alcohol concentration limit value ALCest_e0 computed by supposing that all the oil is a kind of oil which has a low concentration and an alcohol concentration estimation value ALCest, and an upper limit concentration limit value ALCest_e85(n) is formed by performing the primary delay processing twice based on an E85 supposition alcohol concentration limit value ALCest_e85 computed by supposing that all the oil is a kind of oil which has a high concentration and the alcohol concentration estimation value ALCest. Abnormality is detected based on magnitude relation between the lower limit concentration limit value ALCest_e0(n) and the alcohol concentration estimation value ALCest, and between the upper limit concentration limit value ALCest_e85(n) and the alcohol concentration estimation value ALCest. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine, and is particularly useful when applied to a vehicle that can use either gasoline fuel or alcohol fuel (hereinafter referred to as FFV).

  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 as to achieve a predetermined air-fuel ratio based on the estimated alcohol concentration value.

  Patent Document 1 discloses a technique for estimating an alcohol concentration in FFV. Patent Document 1 discloses a technique for accurately reflecting, for example, a change in a fuel mixture ratio in a tank due to refueling in estimating an alcohol concentration based on an air-fuel ratio.

JP 2007-9903 A

  Conventionally, when the alcohol concentration is estimated, the fuel system monitoring is prohibited during this period because a predetermined estimation is performed based on the output of the air-fuel ratio sensor. Therefore, it is impossible to detect a failure due to an abnormality in the fuel system during the process of estimating the alcohol concentration.

  In view of the above prior art, the present invention provides an internal combustion engine control apparatus that can detect an abnormality in a fuel system even during an alcohol concentration estimation process based on an air-fuel ratio and can contribute to accurate operation control of the internal combustion engine. With the goal.

  The configuration of the present invention that achieves the above object is based on the following knowledge and principle. FIG. 1 is a graph showing the relationship between fuel consumption and alcohol concentration when refueling over time along the horizontal axis, where (a) shows the characteristics on the rich side and (b) shows the characteristics on the lean side. Each is shown. As shown in the figure, the alcohol concentration estimated value ALTest from the air-fuel ratio sensor converges toward a predetermined value while changing stepwise. At this time, the alcohol concentration estimated value ALEST hardly changes until a predetermined time T1 elapses immediately after refueling, and thereafter changes stepwise every time the alcohol concentration estimating process is executed, and reaches a predetermined value after time T2. It has converged. That is, until the fuel consumption integrated value reaches the threshold value D, the alcohol concentration estimated value ALTest does not change. Similarly, after the time T2, that is, after the fuel consumption integrated value exceeds the threshold value E, the alcohol concentration estimated value ALTest changes. You can see that they are not. The former is considered to be because the replacement of fuel around the injector is started at the time of the threshold value D, and the replacement is almost completed at the time of the threshold value E in the latter.

  Therefore, the threshold value D ≧ the fuel consumption amount integrated value, D <the fuel consumption amount integrated value ≦ the threshold value E, and the threshold value E <the fuel consumption amount integrated value are divided into three regions, that is, the initial region A, the transient region B, and the saturation region C. An optimum estimation result is obtained when the estimated alcohol concentration is obtained.

  Of these, paying attention to the transition region B in particular, the change in the alcohol concentration estimated value ALTest in the transition region B is linear on the rich side with respect to the alcohol concentration estimated value ALTest at the time of refueling and the E85 hypothetical alcohol concentration estimated value ALTest_e85. It was found that the value obtained by performing the delay process twice can be approximated well (this characteristic is indicated by a thin solid line in the figure). Here, the E85 assumed alcohol concentration estimated value ALTest_e85 is an alcohol when it is assumed that the fuel increase amount at the time of refueling is a fuel having a relatively high alcohol concentration, for example, E85 (15% gasoline / 85% ethanol). The concentration can be obtained by calculation (the calculation formula will be described later).

  Therefore, as described above, the value calculated by performing the first-order lag process twice can be considered as the upper limit value of the alcohol concentration estimated value ALTest on the rich side. Therefore, this value is set as the upper limit density limit value ALTest_e85 (n).

  On the other hand, on the lean side as well, the change in the alcohol concentration estimated value ALTest is good at a value calculated by performing the first-order lag process twice with respect to the alcohol concentration estimated value ALTest at the time of refueling and the E0 hypothetical alcohol concentration estimated value ALTest_e0. (This characteristic is indicated by a thin solid line in the figure). Here, the E0 assumed alcohol concentration estimated value ALTest_e0 is calculated by calculating the alcohol concentration when it is assumed that the fuel increase amount at the time of refueling is a fuel having a relatively low alcohol concentration, for example, E0 (100% gasoline). (A calculation formula will be described later).

  Therefore, as described above, the value calculated by performing the first-order lag process twice can be considered as the lower limit value of the alcohol concentration estimated value ALTest on the lean side. Therefore, this value is set as the lower limit concentration limit value ALTest_e0 (n).

  The first-order lag processing described above is preferably performed in the transition region B every predetermined fuel consumption or every predetermined time. By doing so, the alcohol concentration can be estimated with higher accuracy.

  Therefore, as described above, the value calculated by performing the first-order lag process twice can be considered as the lower limit value of the alcohol concentration estimated value ALTest on the lean side. Therefore, this value is set as the lower limit concentration limit value ALTest_e0 (n).

  If the upper limit concentration limit value ALTest_e85 (n) and the lower limit concentration limit value ALTest_e0 (n) are determined as described above, an abnormality in the alcohol concentration estimated value ALTest is detected by comparison with the alcohol concentration estimated value ALTest based on these. obtain. That is, the estimated alcohol concentration value ALTest enclosed by broken lines a and b in FIG. 1 exceeds the upper limit concentration limit value ALTest_e85 (n), and the estimated alcohol concentration value ALTest enclosed by broken lines c and d is the lower limit concentration limit value. Since it is less than ALTest_e0 (n), it may be determined that it is basically abnormal.

  However, in order to eliminate variations in hardware performance of the air-fuel ratio sensor or the like, the upper limit limit value ALTest_e85CL (n) and a predetermined margin are expected in the upper limit concentration limit value ALTest_e85 (n) and the lower limit concentration limit value ALTest_e0 (n), and It is more preferable to use the lower limit limit value ALTest_e0CL (n) and the abnormality determination value added to these. Here, the upper limit value ALTest_e85CL (n) is a value obtained by adding a margin α to the upper limit density limit value ALTest_e85 (n), and the lower limit value ALTest_e0CL (n) is subtracted from the lower limit density limit value ALTest_e0 (n). It is the value. In FIG. 1, the upper limit limit value ALTest_e85CL (n) to the lower limit limit value ALTest_e0 (n) CL with the margin α taken into account is indicated by a thick dotted line along the upper limit density limit value ALTest_e85 (n) to the lower limit density limit value ALTest_e0 (n). ing. Thus, when the margin α is provided, the alcohol concentration estimated value ALTest deviates from the upper limit value ALTest_e85CL (n) (the upper limit concentration limit value ALTest_e85 (n) + α) exceeding the predetermined abnormality determination value β. If so, it is determined that the fuel system is abnormal on the rich side. Further, if the alcohol concentration estimated value ALTest deviates from the lower limit value ALTest_e0CL (n) (lower limit concentration limit value ALTest_e0 (n) −α) below the abnormality determination value β, it indicates that there is an abnormality in the fuel system on the lean side. Can be determined.

  Here, if such an abnormal state is detected even once, it can be immediately determined that the fuel system is abnormal. However, considering the case where the abnormal state occurs accidentally, it is determined that the fuel system is abnormal when an abnormal state is detected a plurality of times (twice in the case shown in FIG. 1) in the same driving cycle. It seems more appropriate to do.

  Here, it is of course possible to directly use the upper limit density limit value ALTest_e85 (n) and the lower limit density limit value ALTest_e0 (n) as the upper and lower limit limits in this case without providing a margin α. Thus, abnormality in the fuel system can be detected while executing the process for estimating the alcohol concentration.

  The embodiment of the present invention based on such knowledge and principle is as follows.

  According to a first aspect of the present invention, there is provided a control device for an internal combustion engine operable with an alcohol-containing fuel, the air-fuel ratio detection means for detecting the air-fuel ratio of the exhaust system of the internal combustion engine, and the air-fuel ratio detection means When it is determined that the alcohol concentration estimating means for estimating the alcohol concentration of the alcohol-containing fuel based on the air-fuel ratio, an oil supply determining means for detecting that fuel has been supplied into the tank, and the oil supply determining means being supplied The assumed alcohol concentration estimating means for estimating the assumed alcohol concentration according to this assumption and the assumed alcohol concentration estimated by the assumed alcohol concentration estimating means are used to limit the alcohol concentration. Limit value setting means for setting a value, and an abnormality determination for determining an abnormality in a fuel supply system that supplies the alcohol-containing fuel to the internal combustion engine And an alcohol concentration estimated value estimated by the alcohol concentration estimating means during the alcohol concentration change period after it is determined that the oil supply determining means has been refueled, and the limit value setting means is set by the limit value setting means. And a failure determination unit that determines a failure of the fuel supply system based on the set limit value and the failure determination value set by the failure determination value setting unit.

  According to this aspect, it is assumed that the fuel type for the increased amount of fuel is assumed, and the limit value of the alcohol concentration estimated value is set using the assumed alcohol concentration estimated value associated with this assumption to detect an abnormality in the alcohol concentration estimated value. As a result, it is possible to detect an abnormality in the fuel system even during the process of estimating the alcohol concentration.

  According to a second aspect of the present invention, in the control apparatus for an internal combustion engine described in the first aspect, the hypothetical alcohol concentration estimating means includes a fuel having a first concentration of alcohol having a relatively low alcohol concentration as the fuel type. Assuming a second concentration fuel having a relatively high alcohol concentration, the first and second hypothetical alcohol concentration estimated values are calculated for the first and second concentration fuels, respectively, and the limit value is set. The means sets the first limit value using the first hypothetical alcohol concentration estimated value, sets the second limit value using the second hypothetical alcohol concentration estimated value, and sets the abnormality determination value. The setting means is the control device for an internal combustion engine, wherein the abnormality determination value is set in a range below the first limit value and / or in a range above the second limit value.

  According to this aspect, the first alcohol concentration limit value when all fuel increases are assumed to be low alcohol concentration fuel and the second alcohol concentration limit value when all fuel increases are assumed to be high alcohol concentration fuel. Thus, the abnormality of the estimated alcohol concentration value is detected, so that the abnormality of the fuel system can be detected more accurately.

  According to a third aspect of the present invention, in the control apparatus for an internal combustion engine according to the second aspect, there is provided 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. The limit value setting means sets the first limit value when the feedback correction amount of the feedback back control means changes so as to correct the air-fuel ratio in the lean direction, while setting the air-fuel ratio in the rich direction. In the control apparatus for the internal combustion engine, the second limit value is set when the change is made so as to be corrected.

  According to this aspect, since the abnormality of the alcohol concentration estimation value is detected in consideration of the lean direction or the rich direction, the abnormality of the fuel system is more accurately detected even during the process of estimating the alcohol concentration. Can be detected.

  According to a fourth aspect of the present invention, in the control apparatus for an internal combustion engine according to the third aspect, the limit value setting means determines that the oil supply determination means has been refueled during the alcohol concentration change period. From the predetermined alcohol concentration estimated value estimated by the alcohol concentration estimating means, a first-order lag process is performed twice for the first or second hypothetical alcohol concentration estimated value, and the first limit value and / or the The control apparatus for an internal combustion engine is characterized in that a second limit value is set.

  According to this aspect, it is possible to form a limit value that accurately follows the change in alcohol concentration during the alcohol concentration change period, and it is possible to accurately detect an abnormality in the fuel system based on this limit value.

  According to a fifth aspect of the present invention, in the control apparatus for an internal combustion engine according to the fourth aspect, the fuel consumption amount detecting means for detecting the fuel consumption amount of the internal combustion engine is provided, and the limit value setting means is After the fuel supply determining means determines that the fuel has been supplied, a second amount greater than the first predetermined fuel consumption is detected from the time when the fuel consumption detection means detects that the first predetermined fuel consumption is consumed. The first limit value and / or the second limit value is set by performing the first-order lag process twice for each predetermined fuel consumption amount within a period until it is detected that the predetermined fuel consumption amount is consumed. The control apparatus for an internal combustion engine is characterized by the above.

  According to this aspect, the limit value that accurately follows the change in alcohol concentration during the alcohol concentration change period can be formed by performing the first-order lag process twice for each predetermined fuel consumption.

  According to a sixth aspect of the present invention, in the control apparatus for an internal combustion engine according to the fourth aspect, the fuel consumption amount detecting means for detecting the fuel consumption amount of the internal combustion engine is provided, and the limit value setting means is After the fuel supply determining means determines that the fuel has been supplied, a second amount greater than the first predetermined fuel consumption is detected from the time when the fuel consumption detection means detects that the first predetermined fuel consumption is consumed. The first limit value and / or the second limit value is set by performing the first-order lag process twice at predetermined time intervals within a period until it is detected that the predetermined fuel consumption is consumed. The control apparatus for an internal combustion engine is characterized.

  According to this aspect, the limit value that accurately follows the alcohol concentration change during the alcohol concentration change period can be formed by performing the first-order lag process twice for each predetermined time.

  According to a seventh aspect of the present invention, in the control device for an internal combustion engine according to the fourth, fifth or sixth aspect, the limit value setting means is a value obtained by subtracting a predetermined margin from the first limit value. Is set as the lower limit value, and / or a value obtained by adding a predetermined margin to the second limit value is set as the upper limit value.

  According to this aspect, since a margin is anticipated at the time of abnormality determination, accurate determination can be performed by removing the influence of variations in performance of hardware systems such as an air-fuel ratio sensor.

  According to an eighth aspect of the present invention, in the control device for an internal combustion engine according to the seventh aspect, the abnormality determining means is configured such that the alcohol concentration estimated value estimated by the alcohol concentration estimating means is the limit value setting means. A value obtained by adding the abnormality determination value to the upper limit value set by the limit value setting means when the value is less than the value obtained by subtracting the abnormality determination value from the lower limit value set in When it exceeds, the control apparatus for an internal combustion engine determines that the fuel supply system is abnormal.

  According to this aspect, abnormality determination of the fuel system can be performed in consideration of the abnormality determination value.

  According to a ninth aspect of the present invention, in the control device for an internal combustion engine according to the seventh aspect, the abnormality determining means is configured such that the estimated alcohol concentration value estimated by the alcohol concentration estimating means is set by the limit value setting means. The number of times below the value obtained by subtracting the abnormality determination value from the lower limit value, and / or the number of times the alcohol concentration estimated value exceeds the value obtained by adding the abnormality determination value to the upper limit value set by the limit value setting means. In the control apparatus for an internal combustion engine, the fuel supply system is determined to be abnormal when the predetermined number of times is exceeded.

  According to this aspect, fuel system abnormality determination can be performed based on the number of abnormal states with the abnormality determination value taken into account.

  According to the present invention, since the alcohol concentration estimated value is determined to be abnormal using the assumed alcohol concentration estimated value when all the increased amount of fuel is assumed to be a specific fuel type, the alcohol concentration estimating process is performed. It is possible to detect an abnormality in the fuel system even during the operation.

  As a result, inconveniences such as excessive fuel injection can be prevented, and deterioration of exhaust gas performance and drivability can be satisfactorily suppressed. In addition, problems such as misfire and engine stall of the internal combustion engine due to abnormality in the fuel system can be solved.

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

  FIG. 2 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 (hereinafter referred to as ECU) I, 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. 3 is a block diagram showing a detailed configuration of the ECU according to the present embodiment (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 oil supply determination unit 56, an alcohol concentration estimation unit 60, and a first assumed alcohol concentration. Estimation unit 61, second hypothetical alcohol concentration estimation unit 62, lean / rich determination unit 63, limit value setting unit 64, abnormality determination unit 65, abnormality determination value setting unit 66, fuel consumption amount determination unit 67, and operation parameter control unit 55.

  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 60 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.

  The operation parameter control unit 55 controls parameters related to the operation of the engine 1 such as the fuel injection time for 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 fuel amount of a predetermined amount or more is detected from the fuel amount Vold in the 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 first hypothetical alcohol concentration estimation unit 61 and the second hypothetical alcohol concentration estimation unit 62. To do.

  The first hypothetical alcohol concentration estimator 61 is based on the alcohol concentration estimated value ALTest at the time of refueling and the output of the refueling determination unit 56, and all of the fuel increase amount at the time of refueling is an oil type having a relatively low alcohol concentration, For example, the E0 assumed alcohol concentration estimated value ALTest_e0 when it is assumed that the first concentration is E0 (gasoline 100%) is calculated. Specifically, the calculation shown in the following formula (1) is performed.

ALTest_e0 = (Vold × ALCest ÷ 100 + 0 × Vnew) /
(Vold + Vnew) (1)
In the above formula (1), Vold is the amount of fuel in the tank immediately before refueling, and Vnew is the amount of refueling.

  The limit value setting unit 64 calculates the lower limit concentration limit value ALTest_e0 (n) by performing the first-order lag process twice with respect to the alcohol concentration estimated value ALTest at the time of refueling and the E0 assumed alcohol concentration estimated value ALTest_e0. Specifically, the calculations shown in the following equations (2) and (3) are performed.

ALTest_ds0 (n) = K_ds × ALCest_ds0 (n−1)
+ (1-K_ds) × ALCest_e0 (2)
ALTest_e0 (n) = K × ALTest_e0 (n−1)
+ (1-K) × ALTest_ds0 (n) (3)

  Similarly, in the limit value setting unit 64, based on the alcohol concentration estimated value ALTest at the time of refueling and the output of the refueling determination unit 56, all of the fuel increase amount at the time of refueling is an oil type having a relatively high alcohol concentration, for example, The E85 hypothetical alcohol concentration estimated value ALTest_e85 when it is assumed that the second concentration is E85 (gasoline 15% / ethanol 85%) is calculated. Specifically, the calculation shown in the following equation (4) is performed.

ALTest_e85 = (Vold × ALCest ÷ 100 + 85 × Vnew) /
(Vold + Vnew) (4)

  Further, the limit value setting unit 64 calculates the upper limit concentration limit value ALTest_e85 (n) by performing the first-order lag process twice on the alcohol concentration estimated value ALTest at the time of refueling and the E85 assumed alcohol concentration estimated value ALTest_e85. Specifically, the calculations shown in the following equations (5) and (6) are performed.

ALTest_ds85 (n) = K_ds × ALCest_ds85 (n−1)
+ (1−K_ds) × ALCest_e85 (5)
ALTest_e85 (n) = K × ALTest_e85 (n−1)
+ (1-K) × ALTest_ds85 (n) (6)

  FIG. 4 schematically shows two first-order lag processes represented by the above equations (2) and (3) and the above equations (5) and (6). In the figure, the left half block is a portion corresponding to the first primary processing, and the right half block is a portion corresponding to the second primary processing. Further, “1 / Z” means processing for returning to the previous value.

  The two first-order lag processes shown by the above formulas (2), (3) and the above formulas (5), (6) are performed every predetermined fuel consumption or every predetermined time in the transient region B shown in FIG. Here, the fuel consumption amount determination unit 67 detects the fuel consumption amount based on the output signal of the fuel sensor 21, and sends a signal representing this fuel consumption amount to the limit value setting unit 64. Further, the alcohol concentration estimated value ALTest is obtained based on the following equation (7) in the initial region A and the following equations (8) and (9) in the saturated region C.

1) Initial region A (D ≧ fuel consumption integrated value)
ALTest (n) = ALCest (n−1) (7)
Since there is no change in the estimated value in this area, the previous value is used as it is.
2) Saturation region C (E <Fuel consumption integrated value)
ALTest (n) = ALCest_e0 (lean side) (8)
ALTest (n) = ALCest_e85 (rich side) (9)

  The lean / rich determination unit 63 shown in FIG. 3 detects whether the movement of the air-fuel ratio feedback correction amount FB is in the lean direction or the rich direction. Further, the limit value setting unit 64 shown in FIG. 3 indicates the lower limit concentration limit value ALTest_e0 (n) if the detection result of the lean / rich determination unit 63 is in the lean direction, and the upper limit concentration limit value ALTest_e85 ( n) is selected. As a result, the lower limit concentration limit value ALTest_e0 (n) is supplied to the abnormality determination unit 65 in the lean direction, and the upper limit concentration limit value ALTest_e85 (n) is supplied to the abnormality determination unit 65 in the rich direction.

  Here, as described above, the reason why the lower limit concentration limit value ALTest_e0 (n) is selected if the movement of the air-fuel ratio feedback correction amount FB is in the lean direction, and the upper limit concentration limit value ALTest_e85 (n) is selected if the movement is in the rich direction. Keep it.

  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, which means that 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.

  The abnormality determination unit 65 compares the current alcohol concentration estimated value ALTest (n) with the lower limit concentration limit value ALTest_e0 (n) or the upper limit concentration limit value ALTest_e85 (n) output from the limit value setting unit 64. The abnormality of the alcohol concentration estimated value ALTest (n) is detected.

More specifically, when the lean / rich determination unit 63 first determines that it is in the lean direction, the limit value setting unit 64 selects the lower limit density limit value ALTest_e0 (n) and determines that it is in the rich direction. The upper limit density limit value ALTest_e85 (n) is selected. Then, a predetermined margin α is subtracted or added. That is, the margin α is subtracted from the lower limit density limit value ALTest_e0 (n), and the margin α is added to the upper limit density limit value ALTest_e85 (n). As a result, the lower limit value ALTest_e0CL (n) and the upper limit value ALTest_e85CL (n) are obtained. Further, the abnormality determination value β set in the abnormality determination value setting unit 66 is subtracted from the lower limit value ALTest_e0CL (n), and the abnormality determination value β is added to the upper limit value ALTest_e85CL (n) to estimate the alcohol concentration. Compare with the value ALTest. As a result,
When ALTest (n) <ALCest_e0CL (n) −β, or ALTest (n)> ALCest_e85CL (n) + β, the alcohol concentration estimated value ALTest (n) is regarded as abnormal, and a failure counter (not shown) No.) is set to the number of abnormal states (once). When this count reaches a predetermined value (for example, twice), it is determined that the fuel system is abnormal. Here, the predetermined value of the count number is set in the abnormality determination value setting unit 66.

  When an abnormality in the fuel system is detected in this way, the abnormality display unit 68 displays that the abnormality is present. As a result of the above comparison, when an abnormality in the alcohol concentration estimated value ALTest (n) is detected, the lower limit concentration limit value ALTest_e0 (n) to the upper limit concentration limit value ALTest_e85 (n) are changed to the alcohol concentration estimated value ALTest ( n) is output to the operation parameter control unit 55.

  In this embodiment, when refueling, the first hypothetical alcohol concentration estimation unit 61 assumes an alcohol concentration estimation value when it is assumed that all of the fuel increase during refueling is E0 (gasoline 100%). The alcohol when the E0 assumed alcohol concentration estimated value ALTest_e0 is calculated and the second assumed alcohol concentration estimating unit 62 assumes that all of the fuel increase during refueling is E85 (gasoline 15% / ethanol 85%). An E85 hypothetical alcohol concentration estimated value ALTest_e85, which is a concentration estimated value, is calculated. Thereafter, the limit value setting unit 64 performs predetermined first-order lag processing based on the E0 hypothetical alcohol concentration estimated value ALTest_e0, the E85 hypothetical alcohol concentration estimated value ALTest_e85, and the alcohol concentration estimated value ALTest, and the lower limit concentration limit value ALTest_e0 (n) and the upper limit A density limit value ALTest_e85 (n) is obtained.

  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. As a result, in the lean direction, the lower limit concentration limit value ALTest_e0 (n) based on the E0 assumed alcohol concentration estimated value ALTest_e0 is selected. Then, the abnormality determination unit 65 compares the alcohol concentration estimated value ALTest (n) estimated by the alcohol concentration estimating unit 60 with the lower limit limiting value ALTest_e0CL (n) that allows for the margin α in the lower limit concentration limiting value ALTest_e0 (n). If the former is less than the latter, it is determined as abnormal.

  On the other hand, if it is in the rich direction, the upper limit concentration limit value ALTest_e85 (n) based on the E85 assumed alcohol concentration estimated value ALTest_e85 is selected. Thereafter, the alcohol concentration estimation value ALTest (n) estimated by the alcohol concentration estimation unit 60 is compared with the upper limit concentration limit value ALTest_e85 (n) and the upper limit limit value ALTest_e85CL (n) that allows for the margin α. If it exceeds, it is judged as abnormal.

  Thus, the abnormality of the fuel system is also detected simultaneously with the alcohol concentration estimated value ALTest.

  5 to 7 are flowcharts showing a processing procedure in the ECU according to the present embodiment. As shown in FIG. 5A, at the time of key-off, the fuel amount Vold in the tank and the current estimated concentration ALTest are stored (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 determination flag is turned OFF (Step S4). (See S5 and S6).
4) After the refueling determination flag = ON, the lower limit concentration limit value ALTest_e0 (n) and the upper limit concentration limit value ALTest_e85 (n) are calculated (see step S7). Specifically, the calculations of the formulas (1) and (4) are performed. At this time, since the lower limit concentration limit value ALTest_e0 (n) does not become less than 0%, the lower limit concentration limit value ALTest_e0 (n) ≧ 0. Further, since the upper limit density limit value ALTest_e85CL (n) does not exceed 85%, the upper limit density limit value ALTest_e85 (n) ≦ 85.

The alcohol concentration is estimated according to the procedure shown in FIG.
1) Accumulate fuel consumption after refueling (see step S8).
2) It is determined whether or not the fuel integrated value is equal to or less than a predetermined amount 2 (threshold E) (see step S9).
3) If the determination result in step S9 is No, the value is in the saturation region C, so a value based on the above equation (8) (in the case of the lean side) or a value based on the above equation (9) (in the case of the rich side) is set. (See step S10).
4) If the determination result in step S9 is Yes, since it is in the transition region B or the initial region A, it is determined whether or not the fuel integrated value is equal to or less than a predetermined amount 1 (threshold value D) (see step S11). .
5) If the determination result in step S11 is No, the value is based on the above equation (7) because it is in the initial region A (see step S12).
6) If the determination result in step S11 is Yes, the transition region B exists, so the lower limit or the upper limit of the estimated alcohol concentration value is calculated. Whether this is executed by performing the first-order lag processing by the formulas (2) and (3) based on the calculation result based on the above formula (1) (in the case of the lean side), or the calculation result based on the above formula (4) Is executed by performing the first-order lag processing twice by the equations (5) and (6) (rich side). As a result, the lower limit density limit value ALTest_e0 (n) to the upper limit density limit value ALTest_e85 (n) are generated (see step S13).
7) The alcohol concentration estimated value ALTest (n) is updated by a normal calculation (see step S14).
8) Finally, the alcohol concentration estimated value ALTest (n) generated in step S14 is verified (see step S15).

FIG. 7 is a flowchart showing the details of the extracted step S15. A procedure for verifying the alcohol concentration estimated value ALTest will be described with reference to FIG.
1) It is determined whether or not the movement of the air-fuel ratio feedback correction amount FB is in the lean direction (see step S16).
2) If it is determined that the direction is lean as a result of the determination process in step S16, the margin α and the abnormality determination are made based on the alcohol concentration estimated value ALTest (n) and the lower limit concentration limit value ALTest_e0 (n) calculated in step S13. Compare with the value obtained by subtracting the value β,
ALTest (n) <ALCest_e0 (n) − (α + β)
In this case, since the alcohol concentration estimated value ALTest (n) in this case is abnormal, one fail counter is added (see steps S17 and S18).
3) Next, it is determined whether or not the count number of one fail counter A exceeds a predetermined value (for example, twice). If it exceeds, it is determined that the fuel system is abnormal and the alcohol concentration estimated value ALTest ( The lower limit concentration limit value ALTest_e0 (n) is set to n) (see steps S19 and S20).
4) As a result of the determination in step S16, when it is determined that the movement of the air-fuel ratio feedback correction amount FB is not in the lean direction, such as when the determination result in steps S16, S17, and S19 is No, whether or not the rich direction is determined. Is determined (see step S21).
5) As a result of the determination process in step S21, when it is determined that the direction is rich, the margin α and the abnormality determination are performed on the alcohol concentration estimated value ALTest (n) and the upper limit concentration limit value ALTest_e85 (n) calculated in step S13. Compare the value added with β,
ALTest (n)> ALCest_e85 (n) + (α + β)
In this case, since the alcohol concentration estimated value ALTest (n) in this case is abnormal, another fail counter is added (see steps S22 and S23).
6) Next, it is determined whether or not the count value of the other fail counter B exceeds a predetermined value (for example, twice), and if it exceeds, it is determined that the fuel system is abnormal, and the alcohol concentration estimated value ALTest ( The upper limit density limit value ALTest_e85 (n) is set in n) (see steps S24 and S25).

  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 figure which shows temporally the relationship between the fuel consumption at the time of refueling, and alcohol concentration along the time axis which is a horizontal axis, (a) shows the characteristic of the rich side, (b) shows the characteristic of the lean side, respectively. Yes. 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 embodiment of this invention. It is explanatory drawing which shows typically the 2nd time primary delay process in embodiment of this invention. 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 embodiment of this invention (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 embodiment of this invention. It is a flowchart which shows the verification procedure of the alcohol concentration estimated value which concerns on embodiment of this invention.

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 55 Operation parameter control part 56 Oil supply determination part 60 Alcohol concentration estimation part 61 1st assumption alcohol concentration estimation part 62 2nd Assumed alcohol concentration estimation unit 63 Lean / rich determination unit 64 Limit value setting unit 65 Abnormality determination unit 66 Abnormality determination value setting unit 67 Fuel consumption determination unit

Claims (9)

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;
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;
Refueling determination means for detecting that fuel has been refueled in the tank;
Assuming the fuel type for the fuel increase when it is determined that the fuel supply determining means has been supplied, and assuming alcohol concentration estimating means for estimating the assumed alcohol concentration according to this assumption,
Limit value setting means for setting the limit value of the alcohol concentration using the assumed alcohol concentration estimated by the assumed alcohol concentration estimation means;
An abnormality determination value setting means for setting an abnormality determination value for determining an abnormality of a fuel supply system for supplying the alcohol-containing fuel to the internal combustion engine;
The alcohol concentration estimated value estimated by the alcohol concentration estimating means, the limit value set by the limit value setting means, and the abnormality determination value setting during the alcohol concentration change period after determining that the oil supply determining means has been refueled An abnormality determination means for determining an abnormality of the fuel supply system based on an abnormality determination value set by the means;
A control apparatus for an internal combustion engine, comprising: The control apparatus for an internal combustion engine according to claim 1,
The assumed alcohol concentration estimation means includes:
As the fuel type, a first concentration fuel with a relatively low alcohol concentration and a second concentration fuel with a relatively high alcohol concentration are assumed, and the first and second concentration fuels are the first. Calculating the first and second hypothetical alcohol concentration estimates respectively;
The limit value setting means includes:
Using the first hypothetical alcohol concentration estimate to set a first limit value, while using the second hypothetical alcohol concentration estimate to set a second limit value;
The abnormality determination value setting means includes
The control apparatus for an internal combustion engine, wherein the abnormality determination value is set in a range below the first limit value and / or in a range above the second limit value. The control apparatus for an internal combustion engine according to claim 2,
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,
The limit value setting means includes:
When the feedback correction amount of the feedback back control means changes so as to correct the air-fuel ratio in the lean direction, the first limit value is set, whereas when it changes so as to correct the air-fuel ratio in the rich direction. A control apparatus for an internal combustion engine, wherein the second limit value is set. The control device for an internal combustion engine according to claim 3,
The limit value setting means includes:
During the alcohol concentration change period, from the predetermined alcohol concentration estimated value estimated by the alcohol concentration estimating means after determining that the oil supply determining means has been refueled, the first or second hypothetical alcohol concentration estimated value Then, the first-order delay process is performed twice to set the first limit value and / or the second limit value. The control apparatus for an internal combustion engine according to claim 4,
Fuel consumption detecting means for detecting the fuel consumption of the internal combustion engine;
The limit value setting means includes:
A second predetermined amount greater than the first predetermined fuel consumption amount from the time when the fuel consumption amount detecting means detects that the first predetermined fuel consumption amount has been consumed after the fuel supply determining portion determines that the fuel has been supplied. The first limit value and / or the second limit value is set by performing the first-order lag process twice for each predetermined fuel consumption amount within a period until it is detected that the fuel consumption amount is consumed. A control device for an internal combustion engine. The control apparatus for an internal combustion engine according to claim 4,
Fuel consumption detecting means for detecting the fuel consumption of the internal combustion engine;
The limit value setting means includes:
A second predetermined amount greater than the first predetermined fuel consumption amount from the time when the fuel consumption amount detecting means detects that the first predetermined fuel consumption amount has been consumed after the fuel supply determining portion determines that the fuel has been supplied. The first limit value and / or the second limit value is set by performing the first-order lag process twice at predetermined time intervals within a period until it is detected that the fuel consumption is consumed. A control device for an internal combustion engine. The control device for an internal combustion engine according to claim 4, 5 or 6,
The limit value setting means includes:
A value obtained by subtracting a predetermined margin from the first limit value is set as a lower limit value, and / or a value obtained by adding a predetermined margin to the second limit value is set as an upper limit value. Control device for internal combustion engine. The control apparatus for an internal combustion engine according to claim 7,
The abnormality determining means includes
When the alcohol concentration estimated value estimated by the alcohol concentration estimating means falls below a value obtained by subtracting the abnormality determination value from the lower limit value set by the limit value setting means, and / or the alcohol concentration estimated value is the limit A control apparatus for an internal combustion engine, characterized in that the fuel supply system is determined to be abnormal when exceeding a value obtained by adding the abnormality determination value to an upper limit value set by a value setting means. The control apparatus for an internal combustion engine according to claim 7,
The abnormality determining means includes
The number of times that the alcohol concentration estimated value estimated by the alcohol concentration estimating means falls below a value obtained by subtracting the abnormality determination value from the lower limit value set by the limit value setting means, and / or the alcohol concentration estimated value is the limit. A control apparatus for an internal combustion engine, wherein the fuel supply system is determined to be abnormal when the number of times exceeding the value obtained by adding the abnormality determination value to the upper limit value set by the value setting means is a predetermined number or more. .

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