JP2008297933A - Fuel injection quantity control device and fuel injection quantity control system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection quantity control device and a fuel injection quantity control system suppressing fluctuation of output torque during a catalyst warming up operation period during which ignition timing is delayed. <P>SOLUTION: This device is provided with a rotation speed calculation means calculating rotary crankshaft rotation speed caused by each combustion in cylinder during the catalyst warming up operation period during which ignition timing is retarded as compared to ignition timing during normal operation in order to warm up a catalyst device, a rotation speed calculation means calculating rotary crankshaft rotation speed caused by each combustion in cylinder, a fluctuation quantity calculation means calculating fluctuation quantity of each crankshaft rotation speed based on crankshaft rotation speed of each cylinder calculated by the rotation speed calculation means, and means for correction between cylinders S42, S43 correcting injection quantity to each cylinder to suppress a fluctuation quantity calculated by the fluctuation quantity calculation means. Fuel injection quantity is controlled based on the injection quantity for each cylinder corrected by the means for correction between cylinders during the catalyst warm up operation period. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel injection amount control device applied to an internal combustion engine composed of a plurality of cylinders, and a control system including the device.

2. Description of the Related Art Conventionally, it has been known that a catalyst device that purifies exhaust from an engine (internal combustion engine) does not sufficiently perform a purification function when the catalyst is at a low temperature such as when the engine is started. Conventionally, as a countermeasure, when the catalyst is at a low temperature, the ignition timing is retarded (for example, 10 to 20 ° C. A retarded from TDC), thereby raising the temperature of the catalyst and warming up the catalyst device ( Patent Document 1).
JP 2002-357136 A

  By the way, when the engine is composed of a plurality of cylinders, even if the conditions such as the fuel injection amount for each cylinder are the same, the torque applied to the crankshaft during the expansion stroke is different due to the individual difference of each cylinder. . As a result, the output torque of the crankshaft varies. The inventors have obtained the knowledge that when the ignition timing is retarded to warm up the catalyst as described above, the output torque fluctuations appear remarkably as the combustion state deteriorates.

  The present invention has been made in order to solve the above-described problems, and an object of the present invention is to provide a fuel injection amount control device and a fuel injection device that suppress output torque fluctuation during a catalyst warm-up operation period that retards the ignition timing. It is to provide a quantity control system.

  Hereinafter, means for solving the above-described problems and the operation and effects thereof will be described.

  The invention according to claim 1 includes an injection amount calculation means for calculating an injection amount for each cylinder of fuel injected into each cylinder of the multi-cylinder internal combustion engine, and the injection amount for each cylinder calculated by the injection amount calculation means is calculated. A fuel injection amount control device for controlling a fuel injection amount based on a catalyst warm-up operation period in which an ignition timing is retarded compared to an ignition timing during normal operation in order to warm up a catalyst device for purifying exhaust gas A rotation speed calculation means for calculating a crankshaft rotation speed resulting from the combustion of each of the cylinders, and a crankshaft rotation speed for each cylinder based on the crankshaft rotation speed for each cylinder calculated by the rotation speed calculation means. A variation amount calculation unit for calculating a variation amount; and an inter-cylinder correction unit for correcting the cylinder specific injection amount so as to suppress the variation amount calculated by the variation amount calculation unit; During machine operation period, and controlling the injection amount of fuel based on the cylinder injection amount corrected by the inter-cylinder correction means.

  According to this, during the catalyst warm-up operation period in which the ignition timing is retarded, the cylinder-by-cylinder injection amount is corrected so as to suppress the variation amount of the crankshaft rotation speed, so that the variation of the crankshaft rotation speed can be suppressed, It is possible to suppress output torque fluctuation during the catalyst warm-up operation period. As a specific example, for cylinders with a high crankshaft rotation speed, correction is made to reduce the injection amount by cylinder, and for cylinders with a low crankshaft rotation speed, correction is made to increase the injection amount by cylinder. Thus, the cylinder specific injection amount can be corrected so as to suppress the variation amount.

  The invention according to claim 2 is characterized in that the inter-cylinder correction means increases the correction amount for the cylinder specific injection amount as the variation amount calculated by the variation amount calculation means increases. According to this, the variation amount of the crankshaft rotation speed can be further reduced as compared with the case where the correction amount for the cylinder-by-cylinder injection amount is made uniform regardless of the variation amount.

  According to a third aspect of the present invention, the variation amount calculating means includes a target rotational speed set to a common value for all the cylinders of the multi-cylinder internal combustion engine, and a cylinder rotational speed calculated by the rotational speed calculating means. The difference from the crankshaft rotation speed is calculated for each of the cylinders as the variation amount.

  According to a fourth aspect of the present invention, the target rotational speed is an average value of crankshaft rotational speeds for each cylinder calculated by the rotational speed calculating means.

  According to a fifth aspect of the present invention, the inter-cylinder correction unit corrects the cylinder-by-cylinder injection amount so that a sum of correction amounts for the cylinders by the inter-cylinder correction unit becomes a preset set value. It is characterized by. Note that the “correction amount” is a value set by reversing the sign of plus and minus in the case of decreasing and in the case of increasing.

According to this, as the cylinder-by-cylinder correction means corrects the cylinder-by-cylinder injection amount so that the variation amount is suppressed, the air-fuel ratio after the injection amount correction changes compared to the air-fuel ratio before the injection amount correction. Can eliminate concerns. For example, when the correction amount for the first cylinder by the inter-cylinder correction means is minus 10 mm ³ and the correction amount for the second cylinder is plus 8 mm ³ , the sum of the correction amounts becomes minus 2 mm ³ and the air-fuel ratio is lean. However, according to the above invention, such a concern can be solved.

  The invention according to claim 6 is characterized in that the set value is zero, so that the air-fuel ratio after the injection amount correction can be made the same as the air-fuel ratio before the injection amount correction. Therefore, it can be avoided that the actual air-fuel ratio in the catalyst warm-up operation period becomes different from the actual air-fuel ratio in the previous period.

  According to a seventh aspect of the present invention, an air-fuel ratio calculating means for acquiring a detection value from a detection sensor for detecting an exhaust state, calculating an actual air-fuel ratio based on the acquired detection value, and a target for calculating a target air-fuel ratio. Air-fuel ratio calculating means, and the inter-cylinder correcting means is arranged so that the actual air-fuel ratio calculated by the air-fuel ratio calculating means approaches the target air-fuel ratio calculated by the target air-fuel ratio calculating means. It is characterized by correcting the injection amount for each cylinder. According to this, the actual air-fuel ratio can be brought close to the suitably set target air-fuel ratio.

  According to an eighth aspect of the present invention, after the catalyst warm-up operation period ends with the end of warming-up of the catalyst device, the injection amount calculation means does not perform correction by the inter-cylinder correction means. The fuel injection amount is controlled based on the calculated cylinder specific injection amount.

The invention according to claim 9 includes any one of the fuel injection amount control devices described above, and at least one of a fuel injection device that injects fuel and a catalyst device that purifies exhaust gas. System. According to this fuel injection amount control system, the various effects described above can be exhibited in the same manner.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings.

  FIG. 1 is a schematic system configuration diagram showing an in-cylinder injection internal combustion engine (engine 1) according to the present embodiment and an electronic control unit (ECU 10) that controls the operating state of the engine 1. The engine 1 is mounted on a vehicle and functions as a travel drive source. Further, the engine 1 according to the present embodiment is assumed to be a multi-cylinder spark ignition type reciprocating engine, but in FIG. 1, only one cylinder is shown for convenience of explanation.

Detection signals are input to the ECU 10 from various sensors such as an air flow meter 11, a crank angle sensor 12, an A / F sensor 13, and an O ₂ sensor 14. The ECU 10 controls the operation of the fuel injection valve 21, the throttle valve 22, and the ignition device 23 based on the values of these detection signals.

  The fuel injection valve 21 is provided for each of a plurality of cylinders, and the opening / closing operation of the injection valve is controlled based on a command signal from the ECU 10. The fuel supplied from the fuel tank (not shown) to the fuel injection valve 21 is directly injected into the combustion chamber 1 a by opening the fuel injection valve 21. The fuel injection amount by each fuel injection valve 21 is controlled independently for each combustion chamber 1a.

The ECU 10 also relates to the fuel injection amount based on the engine speed calculated from the detected value of the crank angle sensor 12, the intake pressure of the intake pipe 2, the detected values of the A / F sensor 13 and the O ₂ sensor 14, and the like. A command signal is output. Incidentally, if it is determined that the air-fuel mixture is lean based on the detection values of the A / F sensor 13 and the O ₂ sensor 14, the fuel injection amount is increased and corrected. On the other hand, if it is determined that the air-fuel mixture is rich, the fuel injection amount is corrected to decrease.

  Incidentally, the crank angle sensor 12 outputs a sampling signal to the ECU 10 every 30 ° C. The ECU 10 calculates the engine rotation speed based on the time interval at which the sampling signal is acquired.

  The throttle valve 22 is a valve that controls the amount of intake air by adjusting the air passage area in the intake pipe 2 and is an electronic control type that is driven by an electric motor. Then, the intake air amount is controlled by controlling the operation of the electric motor based on a command signal from the ECU 10. In this embodiment, one throttle valve 22 is provided for a plurality of cylinders. However, a throttle valve 22 may be provided for each cylinder. The intake air amount may be controlled independently for each combustion chamber 1a.

  Further, the ECU 10 outputs a command signal related to the intake air amount based on the accelerator operation amount by the driver, the engine speed calculated from the detected value of the crank angle sensor 12, the values of the air flow meter 11, and the like.

  Incidentally, an air cleaner 4 is provided in the upstream portion of the throttle valve 22 in the intake pipe 2, and the air flow meter 11 is a sensor for detecting the amount of fresh air sucked through the air cleaner 4.

  The exhaust pipe 3 is provided with an upstream side catalyst device 5 and a downstream side catalyst device 6 provided with a three-way catalyst for purifying CO, HC, NOx and the like in the exhaust gas. The upstream side catalyst device 5 is installed on the upstream side of the downstream side catalyst device 6 in the exhaust pipe 3, and the downstream side catalyst device 6 is activated until the catalyst of the downstream side catalyst device 6 rises in temperature and is activated. It is a device for assisting the purification action by.

The A / F sensor 13 described above is installed on the upstream side of the upstream catalyst device 5, and the O ₂ sensor 14 described above is installed on the downstream side of the upstream catalyst device 5 and on the upstream side of the downstream catalyst device 6. . Incidentally, the A / F sensor 13 is an oxygen concentration sensor that can linearly detect the air-fuel ratio of the air-fuel mixture by outputting an oxygen concentration detection signal corresponding to the oxygen concentration in the exhaust gas. The O ₂ sensor 14 detects whether the air-fuel mixture is rich or lean with respect to the predetermined value by detecting whether the oxygen concentration in the exhaust gas is higher or lower than the predetermined value. It is.

  The ECU 10 includes a known microcomputer (not shown), and controls the engine 1 by driving the various actuators based on detection signals sequentially input from the various sensors. The microcomputer mounted on the ECU 10 basically includes a CPU (basic processing device) that performs various calculations, a RAM as a main memory, a ROM (read only storage device) as a program memory, and a data storage memory. Are composed of various arithmetic devices and storage devices such as an EEPROM (electrically rewritable nonvolatile memory). The ROM stores various programs and control maps related to engine control including programs related to fuel injection amount control, intake air amount control, ignition timing control, and the like, and the data storage memory (EEPROM) stores engine 1 Various data including the diagnostic data is stored in advance.

  Next, a processing procedure for catalyst warm-up control according to the present embodiment will be described with reference to FIG. The catalyst warm-up control process is started by the microcomputer of the ECU 10 as a trigger when the ignition switch is turned on, and is repeatedly executed at a predetermined cycle, for example.

  In this series of processes, first, in step S10, it is determined whether or not an execution condition for the catalyst warm-up operation is satisfied. Here, the catalyst warm-up operation is an operation for activating the catalyst of the upstream side catalyst device 5 by increasing the temperature. In step S10, based on the value acquired by the catalyst temperature detection sensor 15 for detecting the catalyst temperature of the upstream side catalyst device 5, it is determined that the catalyst temperature is lower than a preset threshold value. It is said.

  When it is determined that the catalyst warm-up operation execution condition is satisfied (S10: YES), the catalyst warm-up operation is executed in step S11, and when it is determined that the catalyst warm-up operation is not satisfied (S10: In (NO), a series of processes is once terminated. In the catalyst warm-up operation in step S11, the ignition timing by the ignition device 23 is retarded compared to the ignition timing during normal operation. The ignition timing during normal operation is controlled to a timing that is advanced from the timing (TDC) when the piston of the engine 1 reaches top dead center to the extent that knocking does not occur. Further, the ignition timing during the catalyst warm-up operation is controlled to a timing delayed from the TDC (for example, a timing retarded by 10 to 20 ° C. from the TDC).

  By retarding the ignition timing in this manner, the combustion period is retarded. As a result, the temperature of the catalyst rises due to the flame in the combustion chamber 1a or the exhaust pipe 3, and the warm-up operation for the upstream side catalyst device 5 is performed. Made. Regarding the fuel injection timing by the fuel injection valve 21, when performing the catalyst warm-up operation, the additional fuel is injected in the combustion chamber 1a or the exhaust pipe 3 by injecting the additional fuel in the expansion stroke or the exhaust stroke. It may be burned to further increase the catalyst temperature.

  When the catalyst warm-up operation in step S11 is executed, the temperature of the catalyst rises. When the catalyst temperature becomes higher than the threshold value, the warm-up operation execution condition in step S10 is not satisfied (S10: NO). That is, it is considered that the catalyst warm-up operation has ended, and the series of processes is ended.

  By the way, even if the conditions such as the fuel injection amount for each cylinder are the same, the torque applied to the crankshaft 1b during the expansion stroke is different due to the individual difference of each cylinder. As a result, the output torque of the crankshaft 1b varies. When the ignition timing is retarded so as to warm up the catalyst as described above, the aforementioned output torque fluctuations remarkably appear as the combustion state deteriorates.

  In addition, the catalyst warm-up fuel injection amount control described below is to suppress the occurrence of significant output torque fluctuations due to the catalyst warm-up operation that retards the ignition timing in this way. Control.

  Hereinafter, the processing procedure of the catalyst warm-up fuel injection amount control according to the present embodiment will be described with reference to FIGS. Note that the process shown in FIG. 3 is started by the microcomputer of the ECU 10 as a trigger when the ignition switch is turned on, and is repeatedly executed, for example, at a predetermined cycle.

  In this series of processing, first, in step S20, it is determined whether or not the ignition retard control in step S11 described above is being performed. If it is determined that the ignition retard control is being performed (S11: YES), an inter-cylinder variation correction amount for suppressing the torque fluctuation is calculated in steps S22 to S25 described later, and the ignition retard is performed. If it is determined that the control is not being performed (S11: NO), the process proceeds to step S21, the inter-cylinder variation correction amount is set to zero, and the series of processes is terminated.

  In step S22 (variation amount calculating means), an error amount w_err (n) of the angular velocity (rotational speed) of the crankshaft 1b resulting from the combustion of each cylinder is calculated by the subroutine processing shown in FIG. That is, first, in step S30, the angular velocity w (n) of each cylinder is calculated. Note that (n) indicates the cylinder number n. For example, in the case of a four-cylinder engine 1, the angular velocity of the first cylinder is w (1), the angular velocity of the second cylinder is w (2), 3 The angular velocity of the numbered cylinder is expressed as w (3), and the angular velocity of the numbered cylinder is expressed as w (4).

  Here, as described above, the output torque of the crankshaft 1b fluctuates due to individual differences among the cylinders, and therefore the rotational speed of the crankshaft 1b also fluctuates (see FIG. 5). The peak value of the first rotation speed appearing in FIG. 5 is the peak value resulting from the combustion of the first cylinder, and the second peak value is attributed to the combustion of the cylinder that burns next (for example, the third cylinder). It is a peak value, and is a peak value resulting from the combustion of cylinders that burn sequentially thereafter.

  In step S30, the angular velocity of the crankshaft 1b is calculated based on the detected value of the crank angle sensor 12 in a predetermined period T1 including the time when the peak value appears in the 180 ° C. A period. The angular velocity calculated for the value is calculated as the angular velocity w (n) of each cylinder.

  Next, the process proceeds to step S31, in which it is determined whether or not a predetermined detection time T2 (sampling period) has elapsed since the start of ignition retard control. If it is determined that the elapsed time T2 has elapsed (S31: YES), the process proceeds to step S32. If it is determined that the elapsed time T2 has not elapsed (S31: NO), a series of steps shown in FIG. The process is temporarily terminated. That is, until the elapsed time T2 elapses, the angular velocity w (n) detection processing of each cylinder in step S30 is performed.

  In the subsequent step S32, the average angular velocity w_avg (n) of each cylinder is calculated for the angular velocity w (n) of each cylinder detected during the elapsed time T2. Then, the overall average value w_allavg of the average angular velocity w_avg (n) of each cylinder is calculated. That is, the average value w_allavg for all cylinders is calculated by the equation Σw_avg (n) / n.

  In the subsequent step S33, an error w_err (n) that is an average angular velocity w_avg (n) of each cylinder with respect to the average value w_allavg of all the cylinders is calculated (see FIG. 6). When the average angular velocity w_avg (n) of each cylinder is larger than the average value w_allavg for all cylinders, the value of the error w_err (n) is positive, and the average angular velocity w_avg (n) is smaller than the average value w_allavg for all cylinders. The value of the error w_err (n) is set as negative. For example, in the case of the # 2 cylinder shown in FIG. 6, the error w_err (2) = w_allavg−w_avg (2) is expressed, and the value of the error w_err (2) is negative. For example, in the case of the # 3 cylinder shown in FIG. 6, the error w_err (3) = w_allavg−w_avg (3) is expressed, and the value of the error w_err (3) is positive. In this way, the error w_err (n) of each cylinder is calculated by the process of step S33.

  Next, in step S23 shown in FIG. 3, the presence / absence of rotational variation for each cylinder is determined based on the value of the error w_err (n) of each cylinder calculated in the process of step S33. Specifically, it is determined whether or not the value of the error w_err (n) exceeds a preset upper limit value w_max or lower limit value w_min. If it is determined that the value of the error w_err (n) exceeds the upper limit value w_max or the lower limit value w_min, it is determined that there is variation for the cylinder, and the process proceeds to step S25. For example, in the case of the # 2 cylinder shown in FIG. 6, since the absolute value of the error w_err (2) exceeds the upper limit value w_max, it is determined that there is variation. In the case of the # 3 cylinder shown in FIG. 6, the absolute value of the error w_err (3) is larger than the lower limit value w_min, so it is determined that there is variation.

  In step S25, the fuel injection amount Atau (n) as the amount injected per combustion cycle is calculated for each cylinder by the subroutine processing shown in FIG. 7A. That is, first, in step S40, it is determined whether or not the A / F sensor 13 is activated. That is, since the A / F sensor 13 cannot output an accurate detection value in a low temperature state, it is determined in step S40 whether or not it is activated to the extent that an accurate detection value can be output. If the temperature of the A / F sensor 13 is equal to or higher than a preset temperature, it is determined that the A / F sensor 13 is activated (S40: YES), and the process proceeds to step S41.

<About Steps S41 and S42>
In step S41, the fuel correction amount Aaf for each cylinder is calculated based on the deviation (A / F-α) between the actual air-fuel ratio A / F and the target air-fuel ratio α calculated by the detection value of the A / F sensor 13. That is, the fuel correction amount Aaf is calculated by the equation Kaf (A / F−α). As shown in FIG. 7B, Kaf is a fuel correction gain for air-fuel ratio control, and Kaf may be set to a different value according to the value of the deviation (A / F-α). Kaf may be set to a fixed value regardless of the value of the deviation (A / F−α).

  In the following step S42, the fuel injection amount Atau (n) for each cylinder is changed to the previous value Atau0 (n) of the fuel injection amount for each cylinder, the error amount w_err (n) calculated in step S33, and in step S41. Calculation is performed based on the calculated fuel correction amount Aaf. That is, the fuel injection amount Atau (n) for each cylinder is calculated by the equation Atau0 (n) + (Ktau × w_err (n)) + Aaf. As shown in FIG. 7B, Ktau is a fuel correction gain for controlling the angular velocity, and this correction gain Ktau has different values depending on the error amount w_err (n) as shown in FIG. 7C. It is set.

  Specifically, when w_err (n) is a positive value, the larger the value of w_err (n), the larger the correction gain Ktau is set, and when w_err (n) is a negative value, The smaller the value of w_err (n), the larger the correction gain Ktau is set. Incidentally, a map used for calculating the fuel correction gain Kaf for air-fuel ratio control and a map shown in FIG. 7C used for calculating the fuel correction gain Ktau for angular velocity control are stored in the ROM.

  And since the calculation formula in step S42 has a term of (Ktau × w_err (n)), the angular velocity variation amount between the cylinders is suppressed. For example, in the case of the # 2 cylinder shown in FIG. 6, the fuel injection amount Atau (2) is corrected from the value of w_allavg + w_err (2) to the value of w_allavg by the term (Ktau × w_err (2)). It becomes. In the case of the # 3 cylinder shown in FIG. 6, the fuel injection amount Atau (3) is corrected from the value of w_allavg + w_err (3) to the value of w_allavg according to the term (Ktau × w_err (3)). It becomes.

  Therefore, step S42 functions as an inter-cylinder correction means that corrects the fuel injection amount Atau (n) for each cylinder so as to suppress the amount of variation in angular velocity between cylinders by having the term (Ktau × w_err (n)). Will be.

  By the way, if the Aaf term is deleted in the calculation formula in step S42, the variation amount is suppressed. However, as a result of correction by the term (Ktau × w_err (n)), the fuel injection amount for all the cylinders increases or It can be reduced. For example, as shown in FIG. 6, when the variation correction is performed to reduce the injection amount for the # 2 cylinder and the variation correction is performed to increase the injection amount for the # 3 cylinder, the amount of reduction correction applied to the # 2 cylinder is If the amount is larger than the amount of increase correction applied to the # 3 cylinder, there is a concern that the overall average value w_allavg decreases to the value indicated by β in FIG. When the overall average value w_allavg changes in this way, there is a concern that the air-fuel ratio fluctuates as a result of the variation correction.

  In view of this point, the calculation formula in step S42 has the term of the fuel correction amount Aaf for air-fuel ratio control. Therefore, even if the overall average value w_allavg decreases to β as described above, the A / F sensor in step S41. As a result of adding the fuel correction amount Aaf calculated based on the detected value of 13, the actual air-fuel ratio A / F is feedback-controlled so as to approach the target air-fuel ratio α.

  Accordingly, the steps S41 and S42 have the term of the fuel correction amount Aaf for air-fuel ratio control, thereby correcting the fuel injection amount Atau (n) for each cylinder so that the actual air-fuel ratio A / F approaches the target air-fuel ratio α. Therefore, it functions as an air-fuel ratio correcting means.

<About Steps S43, S44, S45>
On the other hand, if the temperature of the A / F sensor 13 is lower than the preset temperature, it is determined that the A / F sensor 13 is not activated (S40: NO), and the process proceeds to step S43. The following steps S43, S44, and S45 are processes for exhibiting a function equivalent to the above-described air-fuel ratio correcting means without using the detection value of the A / F sensor 13.

  First, in step S43 (inter-cylinder correction means), a fuel correction amount Atau1 (n) for suppressing rotational variation is calculated based on the error amount w_err (n) calculated in step S33. That is, the fuel correction amount Atau1 (n) is calculated by the equation Ktau × w_err (n). As shown in FIG. 7B, Ktau is a fuel correction gain for controlling the angular velocity, and this correction gain Ktau is similar to step S42 described above, as shown in FIG. Different values are set according to n).

  In the subsequent step S44, the fuel correction amount Aaf for air-fuel ratio control is calculated by dividing the sum of all cylinders of Atau1 (n) calculated in step S43 by the number of cylinders n. That is, the fuel correction amount Aaf for air-fuel ratio control is calculated by the equation ΣAtau1 (n) / n.

For example, in the case shown in FIG. 6, the fuel correction amount Atau1 (2) for the # 2 cylinder is minus 10 mm ³ , the fuel correction amount Atau1 (3) for the # 3 cylinder is plus 8 mm ³ , and the fuel correction amounts for the # 1, # 4 cylinders When Atau1 (1) and Atau1 (4) are 0 mm ³ and a 4-cylinder engine (n = 4), ΣAtau1 (n) / n = (− 10 + 8) /4=−0.5. Therefore, the fuel correction amount Aaf for air-fuel ratio control is −0.5 (mm ³ ) common to each cylinder.

  In the subsequent step S45, the fuel injection amount Atau (n) for each cylinder is changed to the previous value Atau0 (n) of the fuel injection amount for each cylinder, and the fuel correction amount Atau1 (n) for suppressing the rotational variation calculated in step S43. And the fuel correction amount Aaf for air-fuel ratio control calculated in step S44. That is, the fuel injection amount Atau (n) for each cylinder is calculated by the equation Atau0 (n) + Atau1 (n) −Aaf.

  Since the calculation formula in step S45 has the term of the fuel correction amount Atau1 (n) for suppressing rotational variation calculated by the calculation formula having the term of (Ktau × w_err (n)), the same as in step S42. Thus, the variation in angular velocity between cylinders is suppressed. Therefore, steps S43 and S45 function as an inter-cylinder correction unit that corrects the cylinder specific fuel injection amount Atau (n) so as to suppress the angular velocity variation amount between the cylinders.

  Further, since the calculation formula in step S45 has the term of the fuel correction amount Aaf for air-fuel ratio control, it is possible to suppress the overall average value w_allavg from decreasing to β as described above. Therefore, steps S44 and S45 have the term of the fuel correction amount Aaf for air-fuel ratio control, thereby correcting the cylinder specific fuel injection amount Atau (n) so that the actual air-fuel ratio approaches the target air-fuel ratio α. It will function as correction means.

  On the other hand, if it is determined in step S23 in FIG. 3 that there is no rotational variation, the process proceeds to step S24 in FIG. 3, and the previous value Atau0 (n) of the fuel injection amount for each cylinder is maintained and this value Atau (n) is maintained. To do.

  As described above, when the process for calculating the cylinder specific fuel injection amount Atau (n) is performed in step S42 or step S45, the series of processes in FIG. Then, the ECU 10 controls the operation of the fuel injection valve 21 by other processing (not shown) based on the cylinder-by-cylinder fuel injection amount Atau (n) thus calculated.

  FIGS. 8A and 8B illustrate one mode when the operation of the fuel injection valve 21 is controlled based on the fuel injection amount Atau (n) for each cylinder.

  FIG. 8A is a timing chart showing a change in the rotational speed of the crankshaft 1b and a change in the ignition timing. Until the time point t1, the ignition timing is controlled in the normal operation. In other words, as described above, the timing is controlled so that the TDC is advanced to such an extent that knock does not occur. As the catalyst warm-up operation is executed at the time t1, the ignition timing is retarded to a timing that is retarded (for example, 10 to 20 ° C. from TDC).

  FIG. 8B is a timing chart showing the rotation speed, torque change, and actual air-fuel ratio change of the crankshaft 1b after time t1 in FIG. 8A. In the period T2 from the time point t1 to the time point t2, the process of FIG. 4 for detecting the angular velocity w (n) of each cylinder is performed. Further, as shown in FIG. 8 (b), due to the catalyst warm-up operation being executed, the rotational speed and torque greatly fluctuate from the time t1 to the time t2. Incidentally, the actual air-fuel ratio fluctuates due to hunting when feedback control is performed by the A / F sensor 13 so that the target air-fuel ratio is achieved.

  Then, when the process of detecting the angular velocity w (n) is finished and the time point t2 is reached, fuel injection based on the cylinder fuel injection amount Atau (n) calculated by the process of FIG. 7 is performed. Here, the solid lines indicated by reference signs NE and TK in FIG. 8B show the rotational speed and torque test results when fuel injection based on the cylinder specific fuel injection amount Atau (n) is performed. The solid line indicated by “, TK” indicates the rotational speed and torque when the fuel injection is performed when the air-fuel ratio correction by the fuel correction amount Aaf for air-fuel ratio control and the variation correction by the error amount w_err (n) are not performed. The test results are shown.

  These test results demonstrate that variation in rotational speed and torque is suppressed by performing variation correction with the error amount w_err (n). In addition, since the change in the actual air-fuel ratio does not change after the time t2 when the variation correction is started, the air-fuel ratio does not change before and after the variation correction is performed by the air-fuel ratio correction based on the fuel correction amount Aaf. It is proved that.

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

  (1) During the catalyst warm-up period, the angular velocity w (n) of each cylinder is detected, the angular velocity error amount w_err (n) is calculated from the detection result, and the rotation according to the error amount w_err (n) Calculate the correction amount (Ktau x w_err (n)) for variation suppression, and correct the previous value Atau0 (n) of the fuel injection amount by cylinder based on the correction amount (Ktau x w_err (n)). The injection amount Atau (n) is calculated. As a result, even during the catalyst warm-up operation period in which the ignition timing is retarded, variations in the rotational speed of the crankshaft 1b can be suppressed. As a result, the crankshafts 1 and TK in FIG. Variations in the rotational speed and torque of the shaft 1b can be suppressed.

  (2) If the A / F sensor 13 is activated during the catalyst warm-up operation period, the air-fuel ratio control is performed based on the deviation (A / F-α) between the actual air-fuel ratio A / F and the target air-fuel ratio α. The fuel correction amount Aaf is calculated, the previous value Atau0 (n) of the cylinder specific fuel injection amount is corrected based on the correction amount Aaf, and the cylinder specific fuel injection amount Atau (n) is calculated. As a result, it is possible to prevent the air-fuel ratio after the correction by the correction amount for suppressing rotational variation (Ktau × w_err (n)) from changing compared to the air-fuel ratio before the injection amount correction.

  (3) If the A / F sensor 13 is not activated during the catalyst warm-up operation period, a fuel correction amount Atau1 (n) for suppressing rotational variation is calculated based on the error amount w_err (n), and the correction amount A value obtained by dividing the sum of all cylinders of Atau1 (n) by the number of cylinders n is calculated as a fuel correction amount Aaf for air-fuel ratio control. Then, the cylinder-by-cylinder fuel injection amount Atau (n) is calculated by correcting the previous value Atau0 (n) of the cylinder-by-cylinder fuel injection amount based on the correction amount Aaf. According to this, even when the A / F sensor 13 is not activated, the air-fuel ratio after the correction by the rotation variation suppression correction amount (Ktau × w_err (n)) is the pre-injection amount correction. It can suppress that it changes compared with the air fuel ratio.

  (4) The absolute value of the correction amount (Ktau × w_err (n)) for suppressing the rotational variation is set to a larger value as the absolute value of the angular velocity error amount w_err (n) is larger. The larger the value, the larger the correction amount for the previous value Atau0 (n) of the fuel injection amount by cylinder. Therefore, the variation in the rotational speed of the crankshaft 1b can be further reduced as compared with the case where the correction amount for suppressing the rotational variation is uniform regardless of the amount of variation.

  (5) The error w_err (n) as the variation amount of each cylinder is calculated based on the average angular velocity w_avg (n) of each cylinder. Therefore, compared with the case where the error w_err (n) is calculated based on the angular velocity w (n) of each cylinder, it is possible to suppress the value of the error w_err (n) from fluctuating greatly. It can suppress that (Ktau × w_err (n)) fluctuates greatly.

  (6) The error w_err (n) is calculated based on the overall average value w_allavg of the average angular velocity w_avg (n) of each cylinder. Therefore, the sum of the correction amounts (Ktau × w_err (n)) for each cylinder can be made closer to zero compared to the case where the calculation is based on other values. Therefore, it can be suppressed that the air-fuel ratio after the correction by the correction amount for suppressing rotational variation (Ktau × w_err (n)) is changed compared to the air-fuel ratio before the injection amount correction.

(Other embodiments)
The above embodiments may be implemented with the following modifications. Further, the characteristic structures of the respective embodiments may be arbitrarily combined.

  -Depending on the retard amount of the ignition timing in the catalyst warm-up operation, the correction amount for suppressing rotational variation may be set to a different value. For example, the fuel correction gain Ktau for controlling the angular velocity may be set to be larger or smaller as the retard amount is larger, or the map shown in FIG. 7C is set according to the retard amount of the ignition timing. You may change the inclination of.

  The correction amount for suppressing rotational variation may be set to different values depending on whether the error amount w_err (n) is positive or negative. For example, when w_err (n) is positive, the fuel correction gain Ktau may be set to be increased or decreased, or, as shown in FIG. You may change the inclination of the map.

  The error w_err (n) as the variation amount of each cylinder may be calculated based on the angular velocity w (n) of each cylinder instead of calculating based on the average angular velocity w_avg (n) of each cylinder. .

  -The error w_err (n) as the variation amount of each cylinder is calculated based on other preset values instead of being calculated based on the overall average value w_allavg of the average angular velocity w_avg (n) of each cylinder. May be. The other value may be calculated based on, for example, the engine speed, the target air-fuel ratio, or the like.

  The internal combustion engine (engine 1) to which the present invention is applied is not limited to a direct injection engine that directly injects fuel into the combustion chamber 1a, but is a port injection engine that injects fuel into the intake pipe 2, for example. May be.

BRIEF DESCRIPTION OF THE DRAWINGS The system schematic block diagram which shows the engine concerning one Embodiment of this invention, and ECU which controls the driving | running state of an engine. The flowchart which shows the process sequence of the catalyst warm-up control by ECU concerning the embodiment. The flowchart which shows the process sequence of fuel injection amount control at the time of catalyst warming-up by ECU concerning the embodiment. The flowchart which shows the process sequence which calculates the angular velocity error between cylinders which is a subroutine process of the flowchart shown in FIG. Explanatory drawing which shows the detection period which detects the angular velocity w (n) of each cylinder. Explanatory drawing which shows average angular velocity w_avg (n) of all cylinders, all-cylinder average value w_allavg, error w_err (n), etc. The flowchart which shows the fuel injection amount calculation process procedure which is the subroutine process of the flowchart shown in FIG. 6 is a timing chart as one aspect when the operation of the fuel injection valve is controlled based on the cylinder specific fuel injection amount Atau (n) according to the same embodiment;

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Engine, 1b ... Crankshaft, 5 ... Sub catalyst apparatus, 6 ... Main catalyst apparatus, 10 ... ECU (fuel injection amount control apparatus), S22 ... Variation amount calculation means, S25 ... Inter-cylinder correction means.

Claims (9)

An injection amount calculating means for calculating the amount of fuel injected into each cylinder of a multi-cylinder internal combustion engine is provided, and the fuel injection amount is controlled based on the cylinder specific injection amount calculated by the injection amount calculating means. A fuel injection amount control device,
The crankshaft rotational speed resulting from the combustion of each of the cylinders is calculated during the catalyst warm-up operation period in which the ignition timing is retarded relative to the ignition timing during normal operation in order to warm up the catalyst device that purifies the exhaust gas. Rotation speed calculating means;
Variation amount calculating means for calculating a variation amount of the crankshaft rotation speed for each cylinder based on the crankshaft rotation speed for each cylinder calculated by the rotation speed calculation means;
An inter-cylinder correction unit that corrects the cylinder specific injection amount so as to suppress the variation amount calculated by the variation amount calculation unit;
With
During the catalyst warm-up operation period, the fuel injection amount control device controls the fuel injection amount based on the cylinder specific injection amount corrected by the inter-cylinder correction means.   2. The fuel injection amount control device according to claim 1, wherein the inter-cylinder correction unit increases the correction amount with respect to the cylinder-by-cylinder injection amount as the variation amount calculated by the variation amount calculation unit increases. .   The variation amount calculating means calculates a difference between a target rotational speed set to a common value for all cylinders of the multi-cylinder internal combustion engine and a crankshaft rotational speed for each cylinder calculated by the rotational speed calculating means. The fuel injection amount control device according to claim 1, wherein the variation amount is calculated for each of the cylinders.   4. The fuel injection amount control device according to claim 3, wherein the target rotation speed is an average value of a crankshaft rotation speed for each cylinder calculated by the rotation speed calculation means.   2. The inter-cylinder correction unit corrects the cylinder-by-cylinder injection amount so that a total sum of correction amounts for the cylinders by the inter-cylinder correction unit becomes a preset set value. 5. The fuel injection amount control device according to any one of 4 above.   6. The fuel injection amount control device according to claim 5, wherein the set value is zero. An air-fuel ratio calculating means for acquiring a detection value from a detection sensor for detecting an exhaust state and calculating an actual air-fuel ratio based on the acquired detection value;
Target air-fuel ratio calculating means for calculating the target air-fuel ratio;
With
The inter-cylinder correction unit corrects the cylinder specific injection amount so that the actual air-fuel ratio calculated by the air-fuel ratio calculation unit approaches the target air-fuel ratio calculated by the target air-fuel ratio calculation unit. The fuel injection amount control device according to claim 1, wherein the fuel injection amount control device is a fuel injection amount control device.   After the catalyst warm-up operation period ends with the end of warming-up of the catalyst device, the cylinder-by-cylinder injection amount calculated by the injection amount calculating means without performing correction by the inter-cylinder correcting means. 8. The fuel injection amount control device according to claim 1, wherein the fuel injection amount is controlled based on the fuel injection amount. The fuel injection amount control device according to any one of claims 1 to 8,
At least one of a fuel injection device for injecting fuel and a catalyst device for purifying exhaust;
A fuel injection amount control system comprising:

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