JP3945509B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine.

  With multiple cylinders, air flows into the intake pipe from the throttle valve to the intake valve through the throttle valve by the amount of air passing through the throttle valve, and when the intake stroke is performed, the air passes through each intake valve from the intake pipe In an internal combustion engine that flows out by the amount of charge air and is filled in each cylinder, the cylinder charge air in each cylinder is calculated using a formula obtained from the mass conservation law for the intake pipe and the state equation for the air in the intake pipe. An internal combustion engine in which the amount is calculated is known (see Patent Document 1).

JP 2002-70633 A JP 2001-234798 A

  In order to calculate the in-cylinder charged air amount using this mathematical formula, for example, the temperature of the air in the intake pipe and the volume of the intake pipe must be obtained. However, in order to obtain the air temperature, for example, a temperature sensor is required, and considering the response delay, it is difficult to obtain the air temperature accurately even if the temperature sensor is used. Further, since there is a manufacturing error in the intake pipe, the volume of the intake pipe cannot be considered to be equal to, for example, a design value. It is not practical to measure the volume of the intake pipe one by one.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a control device for an internal combustion engine that can easily and accurately calculate the in-cylinder charged air amount.

  In order to solve the above-described problem, according to the first invention, a plurality of cylinders are provided, and air flows into the intake passage portion from the throttle valve to the intake valve through the throttle valve by the amount of air passing through the throttle valve, and the intake stroke In the internal combustion engine in which air flows out from the intake passage portion through the respective intake valves by the amount of in-cylinder charged air and is filled in each cylinder, the in-cylinder charged air amount is changed to the first air amount and the second air amount. The first air amount is an excess of the in-cylinder charged air amount with respect to the throttle valve passing air amount generated by the intake stroke, and the intake air pressure generated by the intake stroke is calculated. An intake pressure decrease amount detecting means for detecting an intake pressure decrease amount which is a decrease amount for each cylinder, a first air amount calculating means for calculating a first air amount of each cylinder based on each intake pressure decrease amount, and a throttle Valve passing air Throttle valve passing air amount detecting means for detecting the second air amount calculating means for calculating the second air amount of each cylinder based on the throttle valve passing air amount, and the first air amount and the second air amount, respectively. In-cylinder charged air amount calculating means for calculating the in-cylinder charged air amount of each cylinder by summing, and a control means for performing engine control based on the in-cylinder charged air amount of each cylinder. The one air amount calculating means sets a set crank angle range so that the intake strokes of at least two cylinders for which the in-cylinder charged air amount is to be calculated, and the cylinder in which the intake stroke is performed within the set crank angle range A control device is provided that calculates a total value of intake air pressure decrease amounts, and calculates a first air amount based on each intake pressure decrease amount and the total intake pressure decrease amount.

  Further, according to the second invention, in the first invention, when the backflow of air from the cylinder to the intake passage portion occurs at the end of the intake stroke, the second air amount calculating action is prohibited by the second air amount calculating means. is doing.

  The in-cylinder charged air amount can be calculated easily and accurately.

  FIG. 1 shows a case where the present invention is applied to a four-stroke spark ignition type internal combustion engine. However, the present invention can also be applied to a compression ignition type internal combustion engine.

  Referring to FIG. 1, 1 is an engine body having, for example, 8 cylinders, 2 is a cylinder block, 3 is a cylinder head, 4 is a piston, 5 is a combustion chamber, 6 is an intake valve, 7 is an intake port, and 8 is an exhaust. A valve, 9 is an exhaust port, and 10 is a spark plug. The intake port 7 is connected to a surge tank 12 via a corresponding intake branch pipe 11, and the surge tank 12 is connected to an air cleaner 14 via an intake duct 13. A fuel injection valve 15 is disposed in each intake branch pipe 11, and a throttle valve 17 driven by a step motor 16 is disposed in the intake duct 14. In the present specification, an intake passage portion including the intake duct 14, the surge tank 13, the intake branch pipe 12, and the intake port 7 downstream of the throttle valve 17 is referred to as an intake pipe IM.

  On the other hand, the exhaust port 11 is connected to a catalytic converter 20 via an exhaust manifold 18 and an exhaust pipe 19, and this catalytic converter 20 is communicated to the atmosphere via a muffler (not shown). The intake stroke order of the internal combustion engine shown in FIG. 1 is # 1- # 8- # 4- # 3- # 6- # 5- # 7- # 2.

  The intake valve 6 of each cylinder is driven to open and close by an intake valve drive device 21. The intake valve drive device 21 includes a camshaft and a switching mechanism for selectively switching the rotation angle of the camshaft with respect to the crank angle between the advance side and the retard side. When the rotation angle of the camshaft is advanced, the valve opening timing VO and the valve closing timing VC of the intake valve 6 are advanced as shown by AD in FIG. 2, and therefore the valve opening timing is advanced. On the other hand, when the rotation angle of the camshaft is retarded, the valve opening timing VO and the valve closing timing VC of the intake valve 6 are retarded as shown by RT in FIG. Horned. In this case, the valve opening timing (phase) is changed while the lift amount and the operating angle (valve opening period) of the intake valve 6 are maintained. In the internal combustion engine shown in FIG. 1, the rotation angle of the camshaft is switched to the advance side or the retard side according to the engine operating state. Note that the present invention can also be applied when the valve opening timing of the intake valve 6 is continuously changed or when the lift amount or the operating angle is changed.

  The electronic control unit 30 is composed of a digital computer, and is connected to each other by a bidirectional bus 31. A ROM (Read Only Memory) 32, a RAM (Random Access Memory) 33, a CPU (Microprocessor) 34, an input port 35 and an output port 36. It comprises. An air flow meter 39 for detecting the flow rate of intake air flowing through the engine intake passage is attached to the intake duct 13 upstream of the throttle valve 17. The surge tank 12 is attached with a pressure sensor 40 for sequentially detecting the intake pressure Pm (kPa) that is the pressure in the intake pipe IM, for example, at intervals of 10 msec. Further, a load sensor 43 for detecting the depression amount ACC of the accelerator pedal 42 is connected to the accelerator pedal 42. The output signals of these sensors 39, 40, and 43 are input to the input port 35 via corresponding AD converters 37, respectively. Further, a crank angle sensor 44 that generates an output pulse every time the crankshaft rotates, for example, 30 ° is connected to the input port 35. The CPU 34 calculates the engine speed NE based on the output pulse of the crank angle sensor 44. On the other hand, the output port 36 is connected to the spark plug 10, the fuel injection valve 15, the step motor 16, and the intake valve drive device 21 through corresponding drive circuits 38, which are based on output signals from the electronic control unit 30. Controlled.

  The fuel injection time TAUi of the i-th cylinder (i = 1, 2,..., 8) is calculated based on the following equation (1), for example.

TAUi = TAUb · kDi · kk (1)
Here, TAUb represents a basic fuel injection time, kDi represents an air amount variation correction coefficient of the i-th cylinder, and kk represents another correction coefficient.

  The basic fuel injection time TAUb is a fuel injection time required to make the air-fuel ratio coincide with the target air-fuel ratio. The basic fuel injection time TAUb is obtained in advance as a function of the engine operating state, for example, the depression amount ACC of the accelerator pedal 42 and the engine speed NE, and is stored in the ROM 32 in the form of a map. The correction coefficient kk collectively represents an air-fuel ratio correction coefficient, an acceleration increase correction coefficient, and the like, and is set to 1.0 when correction is not necessary.

  When the amount of air that is filled in the cylinder at the completion of the intake stroke in the i-th cylinder is referred to as in-cylinder charged air amount Mci (g), the air amount variation correction coefficient kDi indicates the variation in the cylinder filled air amount Mci between cylinders. It is for compensation. The air amount variation correction coefficient kDi of the i-th cylinder is calculated based on the following equation (2), for example.

kDi = Mci / Mciave (2)
Here, Mciav represents an average value of the cylinder air charge amount Mci (= ΣMci / 8, where “8” represents the number of cylinders).

  For example, if a deposit mainly made of carbon is formed on the inner peripheral surface of the intake pipe IM or the outer peripheral surface of the intake valve 6, the deposit adhesion amount varies from cylinder to cylinder, so that there is a variation between cylinders in the in-cylinder charged air amount Mci. May occur. If there is a cylinder-to-cylinder variation in the cylinder charge air amount Mci, the output torque will have a cylinder-to-cylinder variation.

  Therefore, in the embodiment according to the present invention, the air amount variation correction coefficient kDi is introduced to compensate for the variation between cylinders in the in-cylinder charged air amount.

  Alternatively, the fuel injection time TAUi of the i-th cylinder can be calculated based on the following equation (3).

TAUi = Mci · kAF · kk (3)
Here, kAF is a correction coefficient for making the air-fuel ratio coincide with the target air-fuel ratio.

  Considering that the timing at which the fuel injection is actually performed is a certain time ahead of the calculation timing of the fuel injection time TAU, the in-cylinder charged air amount Mci in the equation (3) is set to the fuel injection time TAU. The predicted value may be a certain time ahead of the calculation timing.

  Whether the fuel injection time TAU is calculated based on the formula (1) or based on the formula (3), it is necessary to accurately obtain the in-cylinder charged air amount Mci.

  In the embodiment according to the present invention, the in-cylinder charged air amount Mci is calculated based on the intake pressure decrease amount ΔPmdi, which is the decrease amount of the intake pressure Pm generated by the intake stroke of the i-th cylinder. Next, the intake pressure decrease amount ΔPmdi will be described first with reference to FIGS.

  FIG. 3 shows the intake pressure Pm detected by the pressure sensor 40 over a 720 ° crank angle at regular time intervals, for example. In FIG. 3, OPi (i = 1, 2,..., 8) represents the intake valve opening period of the i-th cylinder, and the 0 ° crank angle represents the intake top dead center of the 1st cylinder # 1. . As can be seen from FIG. 3, when the intake stroke of a certain cylinder is started, the intake pressure Pm that has increased starts to decrease, and thus an upward peak occurs in the intake pressure Pm. The intake pressure Pm further decreases and then increases again, so that a downward peak occurs in the intake pressure Pm. As described above, an upward peak and a downward peak are alternately generated in the intake pressure Pm. In FIG. 3, the upward peak generated in the intake pressure Pm due to the intake stroke of the i-th cylinder is indicated by UPi, and the downward peak is indicated by DNi.

  As shown in FIG. 4, when the intake pressure Pm at the upward peak UPi is referred to as a maximum value PmMi and the intake pressure Pm at the downward peak DNi is referred to as a minimum value Pmmi, the intake pressure of the i-th cylinder is performed, whereby the intake pressure is increased. Pm decreases from the maximum value PmMi to the minimum value Pmmi. Therefore, the intake pressure decrease amount ΔPmdi in this case is expressed by the following equation (4).

ΔPmdi = PMMi-Pmmi (4)
On the other hand, as shown in FIG. 4, when the intake valve 6 opens, the in-cylinder intake air flow rate mci (g / sec, FIG. 5), which is the flow rate of the air that flows out of the intake pipe IM and is sucked into the in-cylinder CYL. See) begins to increase. Next, when the in-cylinder intake air flow rate mci becomes larger than the throttle valve passage air flow rate mt (g / sec, see FIG. 5), which is the flow rate of air passing through the throttle valve 17 and flowing into the intake pipe IM, The atmospheric pressure Pm begins to decrease. Next, when the in-cylinder intake air flow rate mci decreases and becomes smaller than the throttle valve passage air flow rate mt, the intake pressure Pm starts to increase.

  That is, air flows into the intake pipe IM through the throttle valve 17 by the throttle valve passage air flow rate mt, and when the intake stroke is performed, the air flows out from the intake pipe IM through the intake valves 6 by the in-cylinder intake air flow rate mci. Therefore, the in-cylinder intake air flow rate mci that is an outflow component temporarily exceeds the throttle valve passage air flow rate mt that is an inflow component, and therefore the intake pressure Pm that is the pressure in the intake pipe IM is the intake pressure. Decrease by the reduction amount ΔPmdi.

  The in-cylinder charged air amount Mci is obtained by integrating the in-cylinder intake air flow rate mci with time. Therefore, assuming that the influence of the overlap of the intake valve opening period OPi (see FIG. 3) on the in-cylinder charged air amount Mci or the air amount variation correction coefficient kDi can be ignored, the in-cylinder charged air amount Mci is expressed by the following equation (5). Can be expressed as:

Here, tMi is an upward peak generation time that is a time when an upward peak occurs in the intake pressure Pm, tmi is a downward peak generation time that is a time when a downward peak occurs in the intake pressure Pm, and Δtdi is an upward peak generation. The time interval (sec) from the time tMi to the downward peak occurrence time tmi, Δtop represents the intake valve opening time (sec), respectively (see FIG. 4).

  In the equation (5), the first term on the right side represents the area of the portion indicated by T1 in FIG. 4, that is, the portion surrounded by the cylinder intake air flow rate mci and the throttle valve passing air flow rate mt. The second term represents the area of the portion indicated by T2 in FIG. 4, that is, the portion surrounded by the cylinder intake air flow rate mci, the throttle valve passing air flow rate mt, and the straight line mci = 0 in a trapezoidal form. is there.

  As described above, the in-cylinder intake air flow rate mci temporarily exceeds the throttle valve passing air flow rate mt by performing the intake stroke. Accordingly, the in-cylinder charged air amount Mci obtained by time-integrating the in-cylinder intake air flow rate mci exceeds the time integrated value of the throttle valve passage air flow rate mt. The portion T1 thus represents an excess of the in-cylinder charged air amount Mci with respect to the integral value of the throttle valve passage air flow rate mt generated by the intake stroke.

  Therefore, in general terms, the in-cylinder charged air amount is divided into a first air amount represented by the area of the portion T1 and a second air amount represented by the area of the portion T2, and the first air amount is This is an excess of the in-cylinder charged air amount with respect to the throttle valve passing air amount generated by the intake stroke, and the in-cylinder charged air amount of each cylinder is obtained by summing the first air amount and the second air amount. Is calculated.

  On the other hand, the law of conservation of mass for the intake pipe IM is expressed by the following equation (6) using the equation of state for the air in the intake pipe IM.

Here, Vm represents the volume (m ³ ) of the intake pipe IM, Ra represents the gas constant per mole of air, and Tm represents the temperature (K) of the air in the intake pipe IM (see FIG. 5). ).

  Between time tMi and time tmi, the intake pressure Pm decreases by the intake pressure decrease amount ΔPmdi. Therefore, when Vm / (Ra · Tm) is expressed collectively by the parameter Km, and the throttle valve passing air flow rate mt is expressed by the average value mtave, the expression (5) is expressed by the following expression (7) using the expression (6). Can be rewritten as

  Then, the intake pressure Pm is detected by the pressure sensor 39 to calculate the intake pressure decrease amount ΔPmdi, the above-described parameter Km is obtained, the throttle valve passing air flow rate mt is detected by the air flow meter 39, and the average value mtave is calculated. If the time interval Δtdi (= tmi−tMi) is calculated by detecting the times tMi, tmi from the intake pressure Pm and the throttle valve passing air flow rate average value mtave, the in-cylinder charged air amount Mci is calculated using the equation (7). It can be calculated. The intake valve opening time Δtop is stored in the ROM 32 in advance.

  However, as described at the beginning, it is difficult to accurately obtain the intake pipe volume Vm and the intake pipe temperature Tm. Therefore, in the embodiment according to the present invention, the parameter Km is obtained without obtaining the intake pipe volume Vm and the intake pipe temperature Tm. Next, a method for calculating the parameter Km according to the embodiment of the present invention will be described with reference to FIG.

  In the embodiment according to the present invention, the amount of air flowing into the intake pipe IM and the intake pipe within the set crank angle range set so as to include the intake strokes of at least two cylinders for calculating the cylinder charge air amount Mci. We focus on the amount of air flowing out of IM.

  FIG. 6 shows a case in which the 720 ° crank angle range from the intake top dead center of the first cylinder to the intake top dead center of the next first cylinder is set as the set crank angle range, including the intake stroke of all cylinders. Is shown.

The total amount of air flowing into the intake pipe IM within this 720 ° crank angle range is the area of the portion indicated by hatching in FIG. 6A, and the average value of the air flow rate through the throttle valve in this 720 ° crank angle range. and mtave, crankshaft is represented by a product of the required time t ₇₂₀ taken to rotate by 720 ° crank angle (mtave · t _720). On the other hand, the total amount of air that flows out of the intake pipe IM and fills the cylinder within the 720 ° crank angle range is the area of the portion indicated by hatching in FIG. It is represented by ΣMci.

  If the intake pressure Pm hardly changes between the start point and the end point of the 720 ° crank angle range, the total amount of air that flows into the intake pipe IM during this 720 ° crank angle, The total amount of air charged in the cylinder should be approximately equal to each other. Therefore, in this case, the following equation (8) is established.

  When formula (7) is substituted into the right side of formula (8) and rearranged, the parameter Km can be expressed as the following formula (9).

That is, to calculate the throttle valve passage air flow rate average mtave from the throttle valve passage air flow rate mt that has been detected by the air flow meter 39, and calculates the required time t ₇₂₀ from the output of the crank angle sensor 44, the time interval Derutatdi (see FIG. 4 ) Total value ΣΔtdi or a sum value Σ (Δtdi + Δtop) of the sum of the time interval Δtdi and the intake valve opening time Δtop (see FIG. 4), and the total value ΣΔPmdi of the intake pressure decrease amount ΔPmdi is calculated. Km can be calculated. In this way, the parameter Km can be easily obtained without obtaining the intake pipe volume Vm and the intake pipe temperature Tm, and therefore the in-cylinder charged air amount Mci can be obtained easily and accurately.

  As shown in FIG. 7, for example, a 360 ° crank angle range including the intake strokes of four cylinders can be set as the set crank angle range. In the example shown in FIG. 7, the first 360 ° crank angle range from the intake top dead center of the first cylinder to the intake top dead center of the sixth cylinder, and the next No. 1 from the intake top dead center of the sixth cylinder. A second 360 ° crank angle range up to the intake top dead center of the cylinder is set.

For the first 360 ° crank angle range, the average value of the air flow rate through the throttle valve mtave in the first 360 ° crank angle range and the time required for the crankshaft to rotate by the first 360 ° crank angle range. From t ₃₆₀ and the sum ΣMcj (j = 1, 2, 3, 4) of the in-cylinder charged air amount Mcj of the cylinder in which the intake stroke is performed within the first 360 ° crank angle range, the following equation (10) is obtained. To establish. Here, j represents the intake stroke order. Similarly, for the second 360 ° crank angle range, the throttle valve passing air flow rate average value mave ′ in the second 360 ° crank angle range and the crankshaft rotate by the second 360 ° crank angle range. From the required time t ′ ₃₆₀ and the total ΣMcj (j = 5, 6, 7, 8) of the cylinder charge air amount Mcj of the cylinder in which the intake stroke is performed within the second 360 ° crank angle range, Formula (11) is materialized.

  Therefore, the parameter Km for the first crank angle range can be expressed as the following equation (12), and the parameter Km for the second crank angle range can be expressed as the following equation (13).

  In this case, the in-cylinder charged air amount Mcj (j = 1, 2, 3, 4) of the cylinder in which the intake stroke is performed within the first crank angle range is calculated using the parameter Km calculated by the following equation (12). The in-cylinder charged air amount Mcj (j = 5, 6, 7, 8) of the cylinder in which the intake stroke is performed within the second crank angle range is calculated by the following equation (13). It is calculated by the equation (7) using the parameter Km.

  Therefore, in general terms, the set crank angle range is set so as to include the intake strokes of at least two cylinders for which the cylinder air charge amount should be calculated, and the intake stroke is performed within this set crank angle range. The total value ΣΔPmdi of the intake pressure decrease amount ΔPmdi of the cylinder is calculated, and the above-described first air amount is calculated based on the respective intake pressure decrease amount ΔPmdi and the intake pressure decrease amount total value ΣΔPmdi. Alternatively, the intake pressure decrease amount ΔPmdi, the intake pressure decrease amount total value ΣΔPmdi, the throttle valve passing air flow rate mt or its average value mtave, the time required for the crankshaft to rotate within the set crank angle range, and the intake pressure Pm The first air amount is determined based on the time interval Δtdi from the occurrence of the upward peak UPi (see FIG. 4) to the occurrence of the downward peak DNi or its total value ΣΔtdi, or the intake valve opening time Δtop or the total value ΣΔtop. You can also see that it is calculated.

  By the way, for example, when the intake valve opening period is set to the retarded side RT (see FIG. 2), the intake valve closing timing VC is after the intake bottom dead center. In this case, since the intake valve 6 is held in the open state even when the piston starts to rise, the air sucked into the cylinder may flow back into the intake pipe IM. When such a backflow occurs, the in-cylinder intake air flow rate mci temporarily becomes a negative value as indicated by X in FIG. 8, and the portion T2 can no longer be approximated by a trapezoid. That is, when the backflow of air from the cylinder to the intake pipe IM occurs at the end of the intake stroke, the cylinder charge air amount Mci cannot be accurately calculated from the equation (7).

  Therefore, in the embodiment according to the present invention, when the intake valve opening period is set to the retarded side RT, the operation of calculating the in-cylinder charged air amount Mci according to the equation (7) is prohibited. In this case, the in-cylinder charged air amount Mci is not updated, and the air amount variation correction coefficient kDi is calculated from the in-cylinder charged air amount Mci calculated in the previous calculation cycle.

  FIG. 9 shows a routine for calculating the fuel injection time TAUi of the i-th cylinder according to the embodiment of the present invention. This routine is executed by interruption every predetermined crank angle.

  Referring to FIG. 9, in step 100, a basic fuel injection time TAUb is calculated. In the following step 101, a routine for calculating the cylinder air charge amount Mci is executed. This routine is illustrated in FIG. In the subsequent step 102, the air amount variation correction coefficient kDi of the i-th cylinder is calculated using equation (2) (i = 1, 2,..., 8). In the subsequent step 103, a correction coefficient kk is calculated. In the following step 104, the fuel injection time TAUi is calculated using the equation (1). The fuel injection valve 15 of the i-th cylinder injects fuel for the fuel injection time TAUi.

  FIG. 10 shows a routine for calculating the in-cylinder charged air amount Mci of the i-th cylinder according to the embodiment of the present invention.

Referring to FIG. 10, in step 110, it is determined whether or not the opening timing of the intake valve 6 is set to the advance side AD (see FIG. 2). When the opening timing of the intake valve 6 is set to the advance side AD, the routine proceeds to step 111 where the throttle valve passage air flow average value mave is calculated. In the following step 112, the required time _t720 is calculated. In the following step 113, the upward peak occurrence time tMi and the downward peak occurrence time tmi for the i-th cylinder are detected (i = 1, 2,..., 8). In the following step 114, the time interval Δtdi of the i-th cylinder is calculated (Δtdi = tmi−tMi). In the following step 115, Σ (Δtdi + Δtop) is calculated. In the following step 116, the maximum value PmMi and the minimum value Pmmi for the i-th cylinder are detected. In the following step 117, the intake pressure decrease amount ΔPmdi of the i-th cylinder is calculated using equation (4). In the following step 118, the total intake pressure decrease amount ΣΔPmdi is calculated. In the following step 119, the parameter Km is calculated using equation (9). In the following step 120, the cylinder charge air amount Mci of the i-th cylinder is calculated using equation (7). On the other hand, when the opening timing of the intake valve 6 is set to the retard side RT in step 110, the processing cycle is ended. Therefore, calculation of the cylinder air charge amount Mci is prohibited.

  In the embodiment described so far, the portion T2 shown in FIG. 4 is approximated to a trapezoid whose upper and lower sides are Δtdi and Δtop, respectively. However, the portion T2 can be approximated to a rectangle with one side of, for example, Δtdi. In this case, the above-described equations (7) and (9) are respectively expressed by the following equations (14) and (15).

1 is an overall view of an internal combustion engine. It is a figure which shows the intake valve opening timing. It is a figure which shows the detection result of the intake valve Pm. It is a time chart for demonstrating intake pressure fall amount (DELTA) Pmdi. It is a figure for demonstrating the calculation method of the cylinder filling air amount Mci. It is a time chart for demonstrating the calculation method of the parameter Km. It is a time chart for demonstrating another example of the calculation method of the parameter Km. 6 is a time chart for illustrating a cylinder intake air flow rate mci when the intake valve opening timing is set to the retard side. It is a flowchart which shows the calculation routine of fuel injection time TAUi. It is a flowchart which shows the calculation routine of the cylinder filling air amount Mci.

Explanation of symbols

1 Engine Body 6 Intake Valve 17 Throttle Valve 40 Pressure Sensor IM Intake Pipe

Claims (2)

  A plurality of cylinders are provided, and air flows into the intake passage portion from the throttle valve to the intake valve through the throttle valve by the amount of air passing through the throttle valve, and when the intake stroke is performed, the intake passage portion passes through the intake valves through the respective intake valves. In an internal combustion engine in which air flows out by the amount of in-cylinder charged air and is filled in each cylinder, the in-cylinder charged air amount is divided into a first air amount and a second air amount, and the first air amount This is an excess of the in-cylinder charged air amount with respect to the amount of air passing through the throttle valve caused by the stroke, and the intake pressure reduction amount, which is a reduction amount of the intake pressure caused by the intake stroke, is detected for each cylinder. Air pressure decrease amount detection means, first air amount calculation means for calculating the first air amount of each cylinder based on the respective intake pressure decrease amounts, throttle valve passage air amount detection means for detecting the throttle valve passage air amount, , Second air amount calculating means for calculating the second air amount of each cylinder based on the amount of air passing through the Lottle valve, and adding the respective first air amount and second air amount to thereby add cylinder in-cylinder air for each cylinder. In-cylinder charged air amount calculating means for calculating the amount, and control means for performing engine control based on the in-cylinder charged air amount of each cylinder, the first air amount calculating means comprising: The crank angle range is set so that the intake strokes of at least two cylinders to be calculated are included, and the total value of the intake pressure decrease amounts of the cylinders in which the intake stroke is performed within the set crank angle range is calculated, A control device that calculates a first air amount based on each intake pressure decrease amount and the total intake pressure decrease amount.   2. The control device for an internal combustion engine according to claim 1, wherein when the backflow of air from the cylinder to the intake passage portion occurs at the end of the intake stroke, the second air amount calculation operation by the second air amount calculation means is prohibited.

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