JP2011111904A - Engine fuel injection control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent an air-fuel ratio from tending to be over rich due to delay in correction value updating process by O2 feedback when engine rotation speed rushes into an idling ranged rapidly. <P>SOLUTION: A correction amount determination part 25 determines, based on an oxygen concentration in exhaust gas, a correction amount KO2 for correcting a basic injection time of fuel so that the air-fuel ratio of an engine converges on a stoichiometric air-fuel ratio. A correction part 26 calculates a fuel injection time by using the correction amount KO2. The correction amount KO2 is calculated by addition or subtraction of a correction term to or from a reference correction amount. An operation range determination part 20 determines whether engine rotation speed Ne is in an A range (idling range) lower than a predetermined rotation speed or in a B range equal to or higher than the predetermined rotation speed. The correction amount determination part 25 calculates the correction amount KO2 by using, as a correction term in the A range, a first correction term larger than a second correction term in the B range for a predetermined time after transition of the engine rotation speed range from the B range to the A range. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an engine fuel injection control apparatus, and more particularly to an engine fuel injection control apparatus including feedback control for converging an intake air-fuel mixture to a stoichiometric air-fuel ratio based on an oxygen concentration in exhaust gas.

  Conventionally, from the viewpoint of fuel efficiency and exhaust gas component regulations (emission regulations), the oxygen concentration in the exhaust gas is detected by an oxygen sensor provided in the exhaust system, and the intake air-fuel mixture is reduced by the correction amount obtained based on the detected value. Feedback control is performed to converge to an appropriate air-fuel ratio, that is, the stoichiometric air-fuel ratio. In general, such feedback control is performed in the vicinity of the idling engine speed in which the fuel injection amount is determined by the intake negative pressure of the engine and the engine speed, that is, in the low engine speed region. For example, Patent Document 1 discloses a technique for prohibiting feedback control until the engine speed decreases to a predetermined value during deceleration in an air-fuel ratio control apparatus that performs air-fuel ratio feedback control based on a detection value of an oxygen concentration sensor. ing.

JP 61-81533 A

  By the way, when the engine decelerates, control is performed to reduce the correction amount so as to reduce the fuel injection amount. However, when the engine is suddenly decelerating while traveling and enters the vicinity of the idle speed, the engine speed is reduced. The process by feedback control for reducing the correction amount cannot be followed with respect to the rapid decrease, and the air-fuel ratio tends to be in an overrich state.

  Also, during sudden deceleration as described above, the air-fuel mixture may be blown back from the combustion chamber into the intake pipe due to the gap generated when the intake valve is fully closed due to the influence of carbon generated during engine combustion. In the case where it overlaps with the entry to the vicinity of the idle speed, the condition that the air-fuel ratio becomes an over-rich state is more likely to be created.

  In the air-fuel ratio control device described in Patent Document 1, during deceleration, feedback control is prohibited until the engine speed drops to a predetermined value, and feedback control is performed after the engine speed drops below a predetermined value. Therefore, when the engine is rapidly decelerating at the start of the feedback control, the feedback control process cannot catch up with the rapid decrease in the engine speed, and the air-fuel ratio tends to become rich. Further, when the valve gap due to carbon is generated as described above, the possibility of over-riching is further increased, so that there is a problem that a region where appropriate feedback control can be performed is reduced.

  The object of the present invention is to solve the above problems by increasing the follow-up performance of feedback control against a sudden decrease in engine speed and expanding the area where appropriate feedback control can be performed, as described above. It is an object of the present invention to provide an engine fuel injection control device capable of preventing the air-fuel ratio from becoming over-rich even if the influence of the above occurs.

  In order to achieve the above object, the present invention is based on the basic injection time for determining the injection amount of fuel supplied to the engine so that the air-fuel ratio of the engine converges to the stoichiometric air-fuel ratio based on the oxygen concentration in the exhaust gas. A correction amount determining means for determining a correction amount; and a fuel injection amount calculating means for calculating a fuel injection time for the engine using the correction amount and the basic injection time. The correction amount is a reference correction amount. In the engine fuel injection control apparatus calculated by adding and subtracting the correction term, an operation for determining whether the engine speed is in a first region less than a predetermined speed or in a second region not less than the predetermined speed. An area determination means, wherein the correction amount determination means is a predetermined time after the engine speed area shifts from the second area to the first area, and is used in the second area as a correction term in the first area. Greater than the second correction term There is a first feature in that it is configured to calculate the correction amount by using the first correction term. Further, the present invention has a second feature in that the predetermined rotational speed of the engine used by the operation region determination means is a value for determining whether or not the engine is in an idle operation region.

  Further, according to the present invention, the correction amount is calculated using a fixed value as the correction term for a predetermined time after starting the engine regardless of whether the engine speed is in the first region or the second region. There is a third feature.

  According to the present invention, the correction term is switched from the first correction term to the second correction term after a predetermined time has elapsed since the engine speed range has shifted from the second region to the first region. There is a fourth feature.

  In addition, the present invention maintains the second correction term as a correction term until the engine speed reaches the second region after switching from the first correction term to the second correction term. There is a fifth feature.

  In addition, the present invention is characterized in that, when switching from the first correction term to the second correction term, the first correction term is gradually reduced and converged to the second correction term. There are 6 features.

  Further, according to the present invention, when switching from the first correction term to the second correction term, the first correction term is gradually decreased by a predetermined amount to converge to the second correction term. There is a seventh feature in the point of letting it go.

  Further, the present invention further includes deviation calculating means for calculating a deviation amount between the latest value of the intake negative pressure of the engine and the negative pressure value of the previous stroke, and the basic injection time is determined by the engine speed and the intake negative pressure. The first correction amount that is determined as a function of pressure and that is larger than the second correction amount in the first region is used when the deviation amount calculated by the deviation calculating means is larger than a predetermined deviation amount. Thus, there is an eighth feature in that the correction amount is calculated.

  According to the present invention having the first feature, in the first region where the engine speed is low, the correction amount is calculated by using a larger correction term than that used in the second region where the engine speed is high. Therefore, the basic injection time, that is, the amount by which the basic injection amount is corrected (feedback amount) can be increased in one feedback control. Therefore, for example, when the engine is suddenly decelerated and enters the first region, the air-fuel ratio can be made to follow the theoretical air-fuel ratio (target air-fuel ratio) in a short time by increasing the change in the feedback correction amount. In addition, the range in which feedback control can be performed can be widened, and even when the influence of carbon occurs as described above, it is possible to prevent overrich and improve fuel consumption and emissions. Furthermore, since the time during which the correction term is increased is limited, it is possible to prevent the engine speed from fluctuating due to a large feedback amount by continuing to use the large correction term. In addition, according to the present invention having the second feature, the above-described effect becomes prominent when the first region is set in an idle operation region that is particularly likely to be over-rich and requires attention.

  According to the present invention having the third feature, since the process using the large correction term is not performed for a predetermined time after the engine is started, it is possible to prevent the engine speed from fluctuating immediately after the engine is started. And startability can be improved.

  According to the present invention having the fourth feature, since the second correction term smaller than the first correction term is used after a predetermined time has elapsed, it is possible to prevent the engine speed from fluctuating due to a large feedback amount. it can.

  According to the present invention having the fifth feature, after the first correction term is switched from the first correction term to the second correction term in the first region, the small second correction term is changed until the second region where the engine speed is high. As a result, the engine speed is stabilized by the correction term used after the lapse of a predetermined time, and the fluctuation of the engine speed can be avoided from increasing.

  According to the present invention having the sixth feature, it is possible to reduce the engine shock that accompanies the rapid switching of the correction term, and therefore it is possible to suppress fluctuations in the engine speed.

  According to the present invention having the seventh feature, the correction term is gradually reduced to the target second correction term with accuracy in a stepwise manner when switching from the first correction term to the second correction term. Can do.

  According to the present invention having the eighth feature, the correction term is switched by determining the intake negative pressure in addition to the determination based on the engine speed. Thus, over-rich caused by a decrease in intake negative pressure and an increase in basic injection time determined as a function of intake negative pressure can be prevented.

It is a block diagram which shows the function of the fuel-injection control apparatus which concerns on one Embodiment of this invention. It is a figure which shows an example of the correction | amendment term preset in the correction amount determination part. It is a conceptual diagram which shows the relationship between the correction | amendment term and the area | region classified according to engine speed. It is a figure which shows a response | compatibility with the change of the output of O2 sensor, and the correction | amendment term selected. It is a timing chart at the time of the deceleration which shows the outline | summary of the control concerning this embodiment. It is a flowchart concerning O2 feedback control. It is a flowchart of feedback control start determination. It is a flowchart which shows the process of a correction term setting. It is a conceptual diagram of stepwise return of a correction term. It is a principal part enlarged view of FIG. FIG. 4 is a functional block diagram of an abnormality detection device for intake negative pressure PB due to carbon adhering to the intake valve.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a system configuration of a fuel injection control apparatus according to an embodiment of the present invention, and in particular, shows a configuration related to control in an idle rotation region that is a low rotation region. In FIG. 1, a fuel injection control device 1 is provided in an internal combustion engine, that is, an engine, which is a drive source of a motorcycle or the like. The fuel injection control device 1 is provided in a control unit 2 that functions as a fuel injection amount determining unit, an engine speed sensor (hereinafter referred to as “Ne sensor”) 3 that detects an engine speed Ne, and an engine exhaust system. And an oxygen concentration sensor (hereinafter referred to as “O2 sensor”) 4 that functions as an oxygen concentration detection means, and a negative pressure sensor (hereinafter referred to as “PB sensor”) 5 that detects the intake negative pressure PB of the engine. . The fuel injection amount determined by the control unit 2 (that is, an instruction of the fuel injection time indicating the fuel injection amount) is input to the injection valve driving unit 6, and the injection valve driving unit 6 performs fuel injection according to the input fuel injection time instruction. The injection valve 7 is driven.

  The Ne sensor 3, the O2 sensor 4, and the PB sensor 5 all have a known configuration, and the attachment position to the engine may be any known location. Omitted.

  The control unit 2 includes an operation region determination unit 20, a basic injection time calculation unit 21, a basic injection time correction unit 22, and a PB-Ne control map 23. Further, the basic injection time correction unit 22 includes an air-fuel ratio determination unit 24, a correction amount determination unit 25, and a correction unit 26. The function of each part of the control unit 2 can be realized by a computer program executed by a microcomputer.

  The PB-Ne control map 23 outputs the engine speed Ne and the intake negative so that the basic injection time T0 is output by the engine speed Ne input from the Ne sensor 3 and the intake negative pressure PB input from the PB sensor 5. The storage means stores the basic injection time T0 as a function of the pressure PB, and can be constituted by a memory of a microcomputer.

  The PB-Ne control map 23 is used to supply the basic injection time T0 in a low rotation range determined from the engine speed Ne and the throttle opening. In a region of medium speed or higher determined from the engine speed Ne and the throttle opening, a Ne-TH control map that supplies the basic injection time T0 based on the engine speed Ne and the throttle opening is used. Since control in the region of medium speed or higher is controlled by a well-known method, a specific description is omitted.

  The operation area determination unit 20 compares the engine speed Ne input from the Ne sensor 3 with the rotation speed value for area determination, or is an idle area (hereinafter referred to as “A area”) or other area other than the idle area ( Hereinafter, it is referred to as “B region”). The determined operation region is input to the correction amount determination unit 25 as data indicating whether the region is an A region or a B region.

  The air-fuel ratio determination unit 24 determines whether the air-fuel ratio A / F is rich (lean) or lean (thin) with respect to the theoretical air-fuel ratio based on the oxygen concentration detection data input from the O2 sensor 4. Alternatively, data indicating lean is input to the correction amount determination unit 25.

  Corresponding to the A region or the B region, the correction amount determination unit 25 has a value used immediately after the air-fuel ratio A / F is reversed from one of the rich side and the lean side to the other, and the other values. A correction term (PI correction term) consisting of a value used while changing within one of the rich side and the lean side is set. Therefore, the correction amount determination unit 25 selects according to the data indicating whether the region is the A region or the B region, and whether the air-fuel ratio A / F is immediately after the rich side and the lean side are reversed from one to the other, or at other timings. The correction amount KO2 is determined by adding or subtracting the corrected term. The correction amount KO2 is determined as “reference correction amount (1.0) ± correction term”. The correction term is negative on the rich side and positive on the lean side.

  The correction unit 26 calculates the fuel injection time Ti by multiplying the basic injection time T0 by the correction amount KO2, and inputs the fuel injection time Ti to the injection valve drive unit 6.

  FIG. 2 is a diagram illustrating an example of correction terms preset in the correction amount determination unit 25. In FIG. 2, the correction term is selected to be larger than the other timing immediately after the air-fuel ratio A / F is reversed. In the example shown in FIG. 2, in the B region where the engine speed Ne is large, the correction terms (+ PR and −PL) used immediately after the reversal of the air-fuel ratio A / F is “0.01”. The correction terms (+ IR and −IL) used in the timing are “0.001”.

  On the other hand, in the A region where the engine speed Ne is less than 2500 rpm, the correction terms (+ PR and −PL) used immediately after the reversal of the air-fuel ratio A / F is “0.1” and used at other timings. The correction terms (+ IR and −IL) to be performed are “0.02”. Thus, in the A area, extremely large values of 10 times and 20 times are selected as compared with the B area, respectively. That is, when the engine speed Ne is in the A region, the maximum correction term is selected from the preset correction terms.

FIG. 3 is a conceptual diagram showing the relationship between correction terms and regions. As shown in FIG. 3, in the A region where the engine speed Ne is less than 2500 rpm, an extremely large correction term is set as compared with the B region where the engine speed Ne is higher. However, if the engine speed Ne remains in the A region, for example, for 10 seconds, it is returned to the same correction term value as in the B region. This is because it can be estimated that the air-fuel ratio has approached the stoichiometric air-fuel ratio by feedback control using the correction term KO2 used in the A region while the engine speed Ne remains temporarily in the A region.

  FIG. 4 is a diagram showing the correspondence between the change in the output of the O2 sensor 4 and the selected correction term. In FIG. 4, the horizontal axis is the time axis, and the vertical axis is the output VO2 of the O2 sensor 4 and the value of the correction term. Whether the air-fuel ratio A / F is rich or lean is determined according to whether the output VO2 of the O2 sensor 4 is equal to or higher than a threshold (rich / lean determination voltage) for determining whether the air is rich or lean. Then, a correction term selected depending on whether the determination result is processing on the rich side or the lean side, or processing immediately after reversal from one of the rich side and the lean side to the other is used.

  For example, immediately after the timing t1 when the air-fuel ratio A / F is reversed from the rich side to the lean side, a large positive correction term (+ PR) is used, and the correction term (+ PR) is a small correction term (+ PR) at the timing t2. The correction term (+ IR) is maintained until timing t3 when the air-fuel ratio A / F is reversed from the lean side to the rich side. Therefore, the correction amount KO2 updated every predetermined time is increased stepwise from “1.0”.

  Immediately after the timing t3 when the air-fuel ratio A / F is reversed to the rich side, a large negative correction term (-PL) is used, and the correction term (-PL) is a small correction term (-PL) at the timing t4. IL), and the correction term (-IL) is maintained until timing t5 when the air-fuel ratio is reversed from the rich side to the lean side.

  FIG. 5 is a timing chart at the time of deceleration showing an outline of the control according to the present embodiment. In FIG. 5, at the timing T1, the Ne-TH control map for outputting the fuel injection time is switched to the PB-Ne control map for low rotation, where the engine speed Ne and the throttle opening are reduced to a predetermined value or less. Here, feedback control based on the output of the O2 sensor 4 is started, and the correction amount KO2 is controlled in order to converge the air-fuel ratio A / F determined by the air-fuel ratio determination unit 24 to the theoretical air-fuel ratio.

  After switching from the Ne-TH control map to the PB-Ne control map, the correction term is switched from the value for the B region to the value for the A region (see FIG. 2) at a timing T2 when the engine speed Ne is reduced to 2500 rpm. . The correction term for area A is maintained until timing T3 when a predetermined time (for example, 10 seconds) elapses. That is, the correction amount KO2 changes greatly compared to before the engine speed Ne drops below 2500 rpm. Therefore, the O2 feedback control is performed at a high response speed, and can follow even in the case of sudden deceleration.

  Then, at timing T3 after the lapse of a predetermined time, the correction term is switched to a value for the B area that is an area other than the A area (see FIG. 2). This is because the air-fuel ratio can be estimated to have stabilized after the elapse of a predetermined time since entering the A region, so that the O2 feedback speed is returned to the normal time rather than the sudden deceleration.

  FIG. 6 is a flowchart according to O2 feedback control. In FIG. 6, in step S1, it is determined whether or not the O2 feedback control start condition is satisfied. This determination condition will be described later in detail with reference to FIG. If the O2 feedback control start condition is satisfied, the process proceeds to step S2. In step S <b> 2, the function of the operation region determination unit 20 determines whether the region based on the engine speed Ne is the A region or the B region. If the area is the A area, the process proceeds to step S3, and if the area is the B area, the process proceeds to step S4.

  In step S3, the correction term corresponding to the region A is selected using the correction term map (see FIG. 2). In step S4, “0” is set to a time flag that is set to “1” when the timer for measuring the time for holding the correction term for the A area is set. In step S5, the correction term corresponding to the region B is selected using the correction term map (see FIG. 2).

  FIG. 7 is a flowchart of the feedback control start determination. In step S10, it is determined whether or not the warm-up is completed depending on whether or not the engine coolant temperature TW is equal to or higher than a predetermined warm-up completion temperature (for example, 40 ° C.). If step S10 becomes affirmative, it will progress to step S11 and it will be judged whether a control area | region is an area | region which uses a PB-Ne control map. The determination in step S11 can be made based on whether the throttle opening and the engine speed Ne are equal to or less than predetermined values.

  If step S11 becomes affirmative, it will progress to step S12 and it will be judged whether the O2 sensor 4 was activated. Whether or not the O2 sensor 4 is activated is generally determined based on the elapsed time from the engine start or the temperature or water temperature of the O2 sensor 4. The elapsed time from the start of the engine is the time required until the O2 sensor 4 is activated, and is set in advance based on experimental results and the like.

  If step S12 is affirmative, the process proceeds to step S13 to determine whether or not the engine speed Ne is within a value indicating the O2 feedback execution region. The engine speed Ne indicating the O2 feedback execution region is, for example, in the range of 1200 rpm to 8000 rpm.

  In this way, if all the determinations in steps S10 to S13 are affirmative, the process proceeds to step S2 in FIG. Therefore, until the O2 sensor 4 is activated after a predetermined time has elapsed after the engine is started, the O2 feedback control is started even when the engine state is in the A region based on the engine speed Ne. Since the process does not proceed to step S2 in FIG. 6, the engine is operated with a fixed value (correction term 0) that does not increase the correction term even if the engine state is the A region.

  FIG. 8 is a flowchart showing details of step S3. In FIG. 8, in step S30, it is determined whether or not the time flag is “1”. Immediately after entering the A area, since the time flag has an initial value “0”, the process proceeds to step S31, and the correction term corresponding to the A area is used as the correction amount KO2 calculation unit (function of the correction amount determination unit 25). set. Accordingly, the correction amount determination unit 25 calculates “reference correction amount (1.0) ± correction term” to determine the correction amount.

  In step S32, the time for holding the correction term for the A area (10 seconds) is set in the timer TA. In step S33, “1” is set in the time flag to indicate that the timer TA has been set. In step S34, it is determined whether or not the time set in the timer TA has elapsed.

  The process returns to the flowchart of FIG. 6 until the time set in the timer TA elapses. If the time set in the timer TA has elapsed, the process proceeds to step S35, and the correction term for the A region is gradually returned to the correction term for the B region. Set the correction term. In step S36, a preset correction term subtraction value is subtracted from the current correction term. This is because the correction term is gradually returned to the value for the B region.

  In step S37, it is determined whether or not the current correction term calculated in step S36 is less than the target value of the correction term. If step S37 is positive, the process proceeds to step S38, and the correction term for the B region is maintained as the correction term. That is, after the correction amount determination unit 25 switches from a large correction term to a small correction term, this small correction term is maintained as a correction term until the engine speed reaches the B region. If step S37 is negative, that is, if the correction term has not yet returned to the correction term for the B region, the process proceeds to step S39, and the current correction term calculated in step S36 is set in the calculation unit for the correction amount KO2.

  FIG. 9 is a conceptual diagram of the stepwise return of the correction term described with reference to FIG. FIG. 9 shows the relationship among the air-fuel ratio A / F, the engine speed Ne, and the correction amount KO2 over time. The correction term is increased to the maximum value that can be set for the area A at time T2 when the engine speed Ne decreases and becomes less than the predetermined speed. As a result, the correction amount KO2 is switched to the maximum value KO2max. This maximum value KO2max is maintained for a predetermined time TA while the engine speed Ne is in the A region, the correction term is gradually reduced from the timing T3a, and the correction amount KO2 gradually decreases. Then, after the timing T3b when the correction term is reduced to the target value, the correction term is maintained at the value for the B region that is the target value. The air-fuel ratio A / F is gradually converged to a small amplitude from a large fluctuation state according to the change of the correction amount KO2.

  In this way, by gradually reducing the correction amount KO2, it is possible to prevent an air-fuel ratio bias immediately after the correction amount is switched. That is, the correction amount is always up and down since the correction term is added and subtracted around “1.0”. Therefore, for example, when the correction amount KO2 is returned to a small correction term for the B region at the timing when the fluctuation range of the correction amount KO2 is at the maximum value, the air-fuel ratio is once greatly biased in the rich direction. Further, for example, if the correction amount KO2 is returned to a small correction term for the B region at a timing when the fluctuation range of the correction amount KO2 is at the lower maximum value, immediately after that, the air-fuel ratio is once largely biased in the lean direction. By performing the control shown in FIG. 8 and FIG. 9, the deviation of the air-fuel ratio can be suppressed.

  The effect by this embodiment is demonstrated with reference to FIG. 10 which expanded the principal part of FIG. It should be noted that the correction amount KO2 and the air-fuel ratio A / F are shown as being shifted up and down for distinction. In FIG. 10, when the O2 feedback control is started at the timing T1 during deceleration, the correction amount KO2 is reduced according to the output of the O2 sensor 4, the fuel injection time is shortened, and the engine rotation speed Ne is reduced. The air / fuel ratio is controlled to be A / F. However, if the decrease in the engine speed Ne is abrupt, the correction amount KO2 in each feedback control is small, so that it takes time for the correction amount KO2 to become small as shown by the dotted line. The fuel ratio A / F may decrease and become over-rich as described by the dotted line in the figure.

  Therefore, at the timing T2 when the engine speed Ne is reduced to 2500 rpm, the correction term in the feedback control for each time is increased to increase the degree of reduction of the correction amount KO2. As a result, immediately after the timing T2, the correction amount KO2 becomes smaller than before, and as a result, the air-fuel ratio A / F becomes small as shown by the dotted line from the timing T2, and the over-rich condition is rapidly suppressed. Then, as shown by the solid line, it is converged to the stoichiometric air-fuel ratio in a short time.

  The effect of increasing the O2 feedback speed so that the correction term can be increased to follow the rapid decrease in the engine speed Ne in the low engine speed range is that carbon generated during engine combustion adheres to the intake valve. Even in such a case, it is more effective.

  If carbon generated in the combustion chamber adheres to the intake valve, the intake valve may not close completely. In this case, the intake negative pressure PB decreases compared to the normal time. As a result, in the control in which the basic injection time is calculated using the PB-Ne control map, a long basic injection time is read from the map, and the air-fuel ratio A / F tends to be over-rich.

  Therefore, if the fuel injection amount control of this embodiment is applied, it is possible to prevent the air-fuel ratio A / F from becoming over-rich.

  FIG. 11 is a functional block diagram of the abnormality detection device for the intake negative pressure PB due to carbon adhering to the intake valve. In FIG. 11, the stroke detection unit 10 detects a section from the compression stroke to the exhaust stroke of the engine, and outputs a stroke detection signal at a predetermined interval during the section. Each stroke of the engine cycle can be determined by a well-known method. The PB detection unit 11 takes in the intake negative pressure PB detected by the PB sensor 5 in response to the stroke detection signal, and inputs an average value in that section to the deviation detection unit 12. This average value is stored in the previous value storage unit 13. The previous value storage unit 13 is updated with the current value every time the PB detection unit 11 calculates and outputs the current average value of the intake negative pressure PB.

  The deviation detection unit 12 calculates a difference between the current value input from the PB detection unit 11 and the previous value read from the previous value storage unit 13 and inputs the difference to the abnormality detection unit 14. The abnormality detection unit 14 determines whether the intake negative pressure PB is abnormal depending on whether the difference calculated by the deviation calculation unit 12 exceeds a preset value. When an abnormality is detected, a PB abnormality signal is output.

  This PB abnormality signal can be added as one of the determination criteria in the feedback control start determination process described with reference to FIG. For example, a processing step for determining the presence or absence of a PB abnormality signal is provided immediately before step S10 in FIG. 7, and the process proceeds to step S10 when it is determined that there is a PB abnormality signal. As a result, an abnormal drop in the intake negative pressure PB that occurs when carbon is caught in the intake valve is detected, and the air-fuel ratio A / F becomes overrich during sudden deceleration when such an abnormality occurs. Can be prevented.

  As described above, according to the present embodiment, when the engine speed is suddenly decelerated during traveling and the engine speed enters the vicinity of the idle speed, the correction amount KO2 is reduced with respect to the sudden decrease in the engine speed. It is possible to prevent the phenomenon that the process does not catch up and causes over-richness. In particular, it is possible to better cope with over-rich caused by a decrease in the intake negative pressure PB due to the biting of carbon into the intake valve.

  DESCRIPTION OF SYMBOLS 1 ... Fuel injection control apparatus, 2 ... Control part (fuel injection amount determination part), 3 ... Ne sensor, 4 ... O2 sensor, 5 ... PB sensor, 6 ... Injection valve drive part, 7 ... Fuel injection valve, 10 ... Stroke Detection unit, 11 PB detection unit, 12 Deviation detection unit, 20 Operation region determination unit, 21 Basic injection time calculation unit, 22 Basic injection time correction unit, 23 PB-Ne control map, 24 Air-fuel ratio Determination unit, 25 ... correction amount determination unit, 26 ... correction unit,

Claims (8)

An oxygen concentration detection sensor (4) for detecting the oxygen concentration in the exhaust gas discharged from the engine, and the air-fuel ratio of the engine is the stoichiometric air-fuel ratio based on the oxygen concentration detected by the oxygen concentration detection sensor (4). Correction amount determining means (25) for determining a correction amount (KO2) for correcting the basic injection time for determining the injection amount of fuel supplied to the engine so as to converge to the correction amount, the correction amount (KO2) and the basic amount Fuel injection amount calculation means (26) for calculating the fuel injection time to the engine using the injection time, and the correction amount (KO2) is calculated by adding and subtracting a correction term to the reference correction amount. In the engine fuel injection control device
An operation region determination means (20) is provided for determining whether the engine speed is in a first region (A region) less than a predetermined number of revolutions or in a second region (B region) greater than the predetermined number of rotations. ,
The correction amount determining means (25) uses a second time in the second region as a correction term in the first region for a predetermined time after the engine speed region shifts from the second region to the first region. An engine fuel injection control apparatus configured to calculate the correction amount (KO2) using a first correction term larger than the correction term.   The engine fuel injection control according to claim 1, wherein the predetermined engine speed used by the operation region determination means is a value for determining whether or not the engine is in an idle operation region. apparatus.   The correction amount determining means (25) uses a fixed value as the correction term for a predetermined time after engine startup, regardless of whether the engine speed is in the first region or the second region. The engine fuel injection control device according to claim 1 or 2, wherein the correction amount (KO2) is calculated.   The correction amount determining means (25) changes the correction term from the first correction term to the second correction after a predetermined time has elapsed since the engine speed range has shifted from the second region to the first region. The fuel injection control device for an engine according to any one of claims 1 to 3, wherein the engine fuel injection control device is configured to switch to the item.   After the correction amount determining means (25) switches from the first correction term to the second correction term, the second correction term is used as a correction term until the engine speed reaches the second region. The fuel injection control device for an engine according to claim 4, wherein the fuel injection control device is configured to maintain the above.   When the correction amount determining means (25) switches from the first correction term to the second correction term, the correction amount determining means (25) gradually reduces the first correction term and converges it to the second correction term. 6. The fuel injection control device for an engine according to claim 4 or 5, wherein the fuel injection control device for the engine is configured as described above.   When the correction amount determining means (25) performs switching from the first correction term to the second correction term, the first correction term is gradually decreased by a predetermined amount step by step. 6. The fuel injection control device for an engine according to claim 4, wherein the fuel injection control device is configured to converge to a correction term. A negative pressure sensor (5) for detecting an intake negative pressure (PB) of the engine;
Deviation calculation means (12) for calculating a deviation amount between the latest negative pressure value detected by the negative pressure sensor and the negative pressure value one stroke before,
The basic injection time is determined as a function of engine speed (Ne) and intake negative pressure (PB),
The first correction larger than the second correction amount in the first region when the correction amount determining means (25) is larger than a predetermined deviation amount when the deviation amount calculated by the deviation calculating means (12) is larger than a predetermined deviation amount. 8. The engine fuel injection control device according to claim 1, wherein the correction amount (KO2) is calculated using a quantity.

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