JP3945510B2 - In-cylinder charged air amount estimation device for internal combustion engine - Google Patents

Description

  The present invention relates to an in-cylinder charged air amount estimation device for an internal combustion engine.

  In order to optimize the air-fuel ratio of the air-fuel mixture burned in the combustion chamber of the internal combustion engine, the amount of air filled in the combustion chamber when the intake valve is closed (hereinafter referred to as “cylinder charged air amount”). It is necessary to estimate accurately. For this reason, an in-cylinder charged air amount estimation device that estimates the in-cylinder charged air amount from the pressure in the intake pipe or the like using a numerical calculation model obtained from a law of conservation of mass, a state equation of gas, or the like is known.

  In the in-cylinder charged air amount estimation device described in Patent Literature 1, the intake pipe interior is determined via the throttle valve based on the law of conservation of mass for the intake pipe from the throttle valve to the intake valve and the state equation for the air in the intake pipe. The amount of air charged in the cylinder using a mathematical formula established between the flow rate of air passing through the throttle valve flowing into the cylinder and the flow rate of air charged in the cylinder from the intake pipe to each cylinder through the intake valve by opening the intake valve Thus, the cylinder air charge amount can be estimated with relatively high accuracy.

JP 2002-70633 A JP 2001-234798 A

  When estimating the cylinder air filling amount using a mathematical formula, if the mathematical formula obtained based on the law of conservation of mass or the equation of state is used as it is, the mathematical formula becomes complicated and the calculation load becomes large. The mathematical formula is used in a simplified manner.

  By the way, if the intake valve opening / closing valve timing is set to the retard side, the intake valve is opened even after the intake bottom dead center. In this case, since the intake valve is kept open even when the piston starts to rise, there is a possibility that the air taken into the cylinder will flow back into the intake pipe. However, if the mathematical expression is simplified and used in estimating the cylinder air charge amount as described above, the back flow of such air is not taken into consideration, and thus the calculated cylinder air charge amount is calculated. Will cause an error.

  Accordingly, an object of the present invention is to provide an in-cylinder charged air amount estimation device that can estimate the in-cylinder charged air amount in consideration of the backflow of air from the cylinder into the intake pipe.

In order to solve the above-described problem, in the first invention, an in-cylinder charged air amount estimation device for an internal combustion engine having a plurality of cylinders and a plurality of intake valves, the in-cylinder charged air amount to each cylinder, Divided into a basic air amount and an excess air amount that flows into the cylinder from the intake passage portion exceeding the throttle valve passing air flow rate by opening the intake valve, and flows into the intake passage portion via the throttle valve Basic air amount calculation means for calculating the basic air amount based on the flow rate of air passing through the throttle valve and the opening time of each intake valve, and the excess air amount is calculated based on the amount of decrease in intake pressure due to the opening of the intake valve. In-cylinder charged air amount estimation comprising: an excess air amount calculating means for calculating the amount of in-cylinder charged air for each cylinder by adding the basic air amount and the excess air amount. In the apparatus, the basic air amount calculating means includes The average air flow rate to the cylinder to calculate a virtual intake valve opening time such as to be equal to the throttle-passing air flow rate, using the virtual intake valve opening time as the valve opening time of the intake valve.
According to the first invention, the virtual intake valve opening time is such that the average air flow rate to all cylinders is equal to the throttle passage air flow rate. For this reason, if there is a backflow of air from the cylinder to the intake pipe, the virtual intake valve opening time is shorter than the actual intake valve opening time, and this virtual intake valve opening time is used. If the basic air amount is calculated by the basic air amount calculating means, the basic air amount can be accurately calculated.

  According to a second aspect, in the first aspect, the basic air amount calculation means is configured so that the virtual air amount is calculated when a backflow of air to the intake passage portion occurs near the intake valve opening timing or the intake valve closing timing. A typical intake valve opening time is used as the intake valve opening time.

  According to the present invention, the basic air amount can be accurately calculated even if there is a backflow of air from the cylinder into the intake pipe. Therefore, the cylinder charge air amount can be accurately calculated by the cylinder charge air amount calculation means. can do.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a case where the present invention is applied to a direct injection spark ignition type internal combustion engine. The present invention can also be applied to other spark ignition internal combustion engines and compression self-ignition internal combustion engines.

  As shown in FIG. 1, in this embodiment, for example, an engine body 1 having eight cylinders is fixed on a cylinder block 2, a piston 3 that reciprocates in the cylinder block 2, and the cylinder block 2. And a cylinder head 4. A combustion chamber 5 is formed between the piston 3 and the cylinder head 4. In the cylinder head 4, an intake valve 6, an intake port 7, an exhaust valve 8, and an exhaust port 9 are arranged for each cylinder. Further, as shown in FIG. 1, a spark plug 10 is disposed at the center of the inner wall surface of the cylinder head 4, and a fuel injection valve 11 is disposed around the inner wall surface of the cylinder head 4. Further, a cavity 12 extending from the lower side of the fuel injection valve 11 to the lower side of the spark plug 10 is formed on the top surface of the piston 3.

  The intake port 7 of each cylinder is connected to a surge tank 14 via an intake branch pipe 13, and the surge tank 14 is connected to an air cleaner 16 via an intake pipe 15. A throttle valve 18 driven by a step motor 17 is disposed in the intake pipe 15. In this specification, the portion of the intake passage composed of the intake pipe 15 downstream of the throttle valve 18, the surge tank 14, the intake branch pipe 12, and the intake port 7, that is, the portion of the intake passage from the throttle valve 18 to the intake valve 6. Is referred to as an “intake pipe portion IM”. On the other hand, the exhaust port 9 of each cylinder is connected to a catalytic converter 21 containing an exhaust purification device 20 via an exhaust branch pipe and an exhaust pipe 19, and this catalytic converter 21 communicates with the atmosphere via a muffler (not shown). Is done.

  The intake valve 6 of each cylinder is driven to open and close by an intake valve drive device 22. The intake valve driving device 22 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, as shown by AD in FIG. 2, the valve opening timing VO and the valve closing timing VC of the intake valve 6 are advanced, and accordingly the opening / closing valve 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. In this case, the phase angle (valve opening timing) 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.

  Referring to FIG. 1, an electronic control unit (ECU) 31 comprises a digital computer, and is connected to each other via a bidirectional bus 32, a RAM (random access memory) 33, a ROM (read only memory) 34, a CPU ( A microprocessor) 35, an input port 36, and an output port 37. An air flow meter 40 for detecting the flow rate of air (intake gas) passing through the intake pipe 15 is disposed in the intake pipe 15 upstream of the throttle valve 18. The surge tank 14 is provided with a pressure sensor 41 for detecting an air pressure (hereinafter referred to as “intake pressure”) Pm in the intake pipe portion IM. Further, a load sensor 43 that generates an output voltage proportional to the amount of depression of the accelerator pedal 42 is connected to the accelerator pedal 42, and a throttle opening sensor for detecting the opening of the throttle valve 18 (see FIG. Not shown). The output signals of these sensors 40, 41 and 43 are input to the input port 36 via corresponding AD converters 38, respectively. Further, the input port 36 is connected to a crank angle sensor 44 that generates an output pulse every time the crankshaft rotates, for example, 30 °. The CPU 35 calculates the engine speed based on the output pulse of the crank angle sensor 44. On the other hand, the output port 37 is connected to the spark plug 10, the fuel injection valve 11, the step motor 17, and the intake valve drive device 22 through corresponding drive circuits 39, which are based on the output from the electronic control unit 31. Be controlled.

Incidentally, in the internal combustion engine of the present embodiment, the fuel injection amount (fuel injection time) TAUi of the i-th cylinder (i = 1, 2,..., 8) is calculated based on, for example, the following equation (1).
TAUi = TAUb · ηi · k (1)
Here, TAUb represents a basic fuel injection amount, ηi represents an air amount variation correction coefficient of the i-th cylinder, and k represents another correction coefficient.

  The basic fuel injection amount TAUb is a fuel injection amount necessary to make the air-fuel ratio coincide with the target air-fuel ratio. This basic fuel injection amount TAUb is obtained in advance as a function of parameters relating to the engine operation state (for example, engine load and engine speed NE, etc., hereinafter referred to as “operation parameters”), and is stored in the ROM 32 in the form of a map. Or calculated by mathematical formulas based on operating parameters. The correction coefficient k is a collective representation of an air-fuel ratio correction coefficient, an acceleration increase correction coefficient, etc., and is set to 1.0 when there is no need for correction.

When the amount of air that is filled in the cylinder when the intake valve is closed in the i-th cylinder is referred to as the in-cylinder charged air amount Mci (g), the air amount variation correction coefficient ηi is between the cylinders with the in-cylinder charged air amount Mci. This is to compensate for variations. The air amount variation correction coefficient ηi of the i-th cylinder is calculated based on the following equation (2), for example.
ηi = Mci / Mcave (2)
Here, Mcave represents the average value (= ΣMci / 8, “8” represents the number of cylinders) of the cylinder air charge amount Mci of all cylinders.

  Here, for example, if a deposit mainly made of carbon is formed on the inner peripheral surface of the intake pipe portion IM or the outer peripheral surface of the intake valve 6, the deposit adhesion amount varies from cylinder to cylinder. There is a risk of variation between cylinders. In addition, there may be a manufacturing error between the cylinders in the volume of the combustion chamber 5 and the like. In this case as well, there is a possibility that the in-cylinder charged air amount Mci may vary between the cylinders. If the cylinder charge air amount Mci varies among the cylinders and the fuel injection amount is kept equal for all the cylinders, the air-fuel ratio and the output torque will vary among the cylinders. Therefore, in the present embodiment, an air amount variation correction coefficient ηi is introduced to compensate for the variation between cylinders in the in-cylinder charged air amount.

  In consideration of the fact that the timing at which the fuel injection is actually performed is a certain time ahead of the calculation timing of the fuel injection amount TAUi, the basic fuel injection amount TAUb in equation (1) is the fuel injection by equation (1). The predicted value may be a certain time ahead of the calculation timing of the amount TAUi.

Alternatively, the fuel injection amount TAUi of the i-th cylinder can be calculated based on the following equation (3).
TAUi = Mci · k / AFt (3)
Here, AFt is a target air-fuel ratio.

  As described above, whether the fuel injection amount TAUi is calculated based on the formula (1) or the formula (3), the air-fuel ratio is made to coincide with the target air-fuel ratio for all the cylinders, and the output torque is calculated. In order to eliminate the variation between the cylinders, it is necessary to accurately obtain the in-cylinder charged air amount Mci.

  In the present embodiment, the in-cylinder charged air amount Mci is calculated based on the intake pressure decrease amount ΔPmdwni that is the decrease amount of the intake pressure Pm generated by opening the intake valve 6 of the i-th cylinder. Next, the intake pressure decrease amount ΔPmdwni will be described first with reference to FIGS.

  FIG. 3 shows the intake pressure Pm detected by the pressure sensor 41 over, for example, a 720 ° crank angle at regular time intervals. The intake order in the internal combustion engine shown in FIG. 3 is # 1- # 8- # 4- # 3- # 6- # 5- # 7- # 2. In FIG. 3, OPi (i = 1, 2,..., 8) represents the opening / closing valve timing of the intake valve 6 of the i-th cylinder, and the 0 ° crank angle represents the intake top dead center of the # 1 cylinder # 1. ing. As can be seen from FIG. 3, when intake into 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 when the intake valve 6 of the i-th cylinder is opened 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 Pmmaxi, and the intake pressure Pm at the downward peak DNi is referred to as a minimum value Pmmini, the intake pressure to the i-th cylinder is performed. Pm decreases from the maximum value Pmmaxi to the minimum value Pmmini. Therefore, the intake pressure decrease amount ΔPmdwni in this case is expressed by the following equation (4).
ΔPmdwni = Pmmaxi−Pmmini (4)

  On the other hand, as shown in FIG. 4, when the intake valve 6 is opened, the cylinder intake air flow rate mci (g / g), which is the flow rate of air that flows out of the intake pipe IM and is sucked into the cylinder CYL of the i-th cylinder. sec, see FIG. 5) 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, when air flows into the intake pipe IM through the throttle valve 17 by the throttle valve passage air flow rate mt and intake into the i-th cylinder is performed, air is sucked into the cylinder from the intake pipe IM through the intake valves 6. Considering that the air flow rate mci flows out, the in-cylinder intake air flow rate mci, which is the outflow amount, temporarily exceeds the throttle valve passing air flow rate mt, which is the inflow amount, and therefore, the intake pressure that is the pressure in the intake pipe IM. The atmospheric pressure Pm decreases by the intake pressure decrease amount ΔPmdwni.

ここで、ｔｍａｘｉはｉ番気筒への吸気により吸気圧Ｐｍに上向きのピークが発生する時刻である上向きピーク発生時刻を、ｔｍｉｎｉはｉ番気筒への吸気により吸気圧Ｐｍに下向きのピークが発生する時刻である下向きピーク発生時刻を、Δｔｄｗｎｉは上向きピーク発生時刻ｔｍａｘｉから下向きピーク発生時刻ｔｍｉｎｉまでの時間間隔（ｓｅｃ）を、Δｔｏｃは吸気弁開弁時間（ｓｅｃ）を、それぞれ表している（図４参照）。 The in-cylinder charged air amount Mci is obtained by integrating the in-cylinder intake air flow rate mci with time. Accordingly, if the influence of the overlap of the intake valve opening / closing valve timing OPi (see FIG. 3) on the cylinder filling air amount Mci or the air quantity variation correction coefficient ηi can be ignored, the cylinder filling air amount Mci is expressed by the following equation (5). Can be expressed as:

Here, tmaxi is an upward peak generation time, which is a time when an upward peak occurs in the intake pressure Pm due to intake into the i-th cylinder, and tmini is a downward peak generated in the intake pressure Pm due to intake into the i-th cylinder. The downward peak occurrence time, which is the time, Δtdwni represents the time interval (sec) from the upward peak occurrence time tmaxi to the downward peak occurrence time tmini, and Δtoc represents the intake valve opening time (sec) (FIG. 4). reference).

  In Expression (5), the first term on the right side is a portion indicated by T1 in FIG. 4 (hereinafter referred to as “region T1”), that is, a portion surrounded by the cylinder intake air flow rate mci and the throttle valve passing air flow rate mt. The second term on the right side is a portion indicated by T2 in FIG. 4 (hereinafter referred to as “region T2”), that is, the cylinder intake air flow rate mci, the throttle valve passing air flow rate mt, and the straight line mci. The area of the portion surrounded by = 0 is approximated by a trapezoid.

  As described above, the intake air flow rate mci in the cylinder temporarily exceeds the throttle valve passing air flow rate mt due to intake. Therefore, during this period, the cylinder charge air amount Mci obtained by time integration of the cylinder intake air flow rate mci exceeds the time integral value of the throttle valve passage air flow rate mt. The region T1 thus represents an excess of the cylinder charge air amount Mci with respect to the integral value of the throttle valve passage air flow rate mt generated by intake.

  Therefore, in general terms, the in-cylinder charged air amount is divided into a basic air amount represented by the area of the region T1 and an excess air amount represented by the area of the region T2, and the excess air amount is determined by intake air. This is the excess of the in-cylinder charged air amount with respect to the throttle valve passing air amount generated by the engine, and the in-cylinder charged air amount of each cylinder is calculated by summing the basic air amount and the excess air amount for each cylinder. It turns out that.

ここで、Ｖｍは吸気管ＩＭの容積（ｍ³）を、Ｒａは気体定数を空気の平均分子量で除算した値（以下、単に「気体定数」と称す）を、Ｔｍは吸気管ＩＭ内の空気の温度（Ｋ）をそれぞれ表している（図５参照）。式（６）は、Ｖｍ／ＲａをパラメータＫｍとして表すと、次式（７）のように変形される。

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 is the volume (m ³ ) of the intake pipe IM, Ra is a value obtained by dividing the gas constant by the average molecular weight of air (hereinafter simply referred to as “gas constant”), and Tm is the air in the intake pipe IM. The temperature (K) of each is expressed (refer FIG. 5). Expression (6) is transformed into the following expression (7) when Vm / Ra is expressed as a parameter Km.

Since the intake pressure Pm decreases by the intake pressure decrease amount ΔPmdwni from the time tmaxi to the time tmini, the equation (5) can be rewritten as the following equation (8) using the equation (7).

  Then, the intake pressure Pm is detected by the pressure sensor 41, the intake pressure decrease amount ΔPmdwni is calculated, the above-described parameter Km is obtained, the throttle valve passing air flow rate mt is detected by the air flow meter 40, and the average value mtave is calculated. If the time interval Δtdwni (= tmini−tmaxi) is calculated by detecting the times tmaxi and tmini from the intake pressure Pm, the in-cylinder charged air amount Mci can be calculated using the equation (8). Note that the intake valve opening time Δtoc is an instruction value from the ECU 31 to the intake valve driving device 22, and is therefore the time during which the intake valve 6 is actually opened.

  However, as described above, if the in-cylinder charged air amount is calculated as described above due to the backflow of the air sucked into the cylinder into the intake pipe or other factors, there is an error in the in-cylinder charged air amount. Will occur. That is, the second term on the right side of Equation (8) approximates the region T2 in FIG. 4 with a trapezoid. However, when air backflow or the like occurs, the value approximately calculated by the second term on the right side of Equation (8) is larger than the region T2 by the amount indicated by the oblique lines in FIG. As a result, a large amount of air filled in the cylinder is calculated, and an error occurs. In other words, if the intake valve opening time Δtoc is set to a value equal to the time during which the intake valve 6 is actually opened, an error occurs in the value approximately calculated by the second term on the right side of Equation (8). End up.

  Therefore, in the present invention, even if air backflow or the like occurs by adjusting the intake valve opening time Δtoc to an appropriate value instead of the actual opening time of the intake valve 6, the region T2 Can be calculated with high accuracy. Hereinafter, a method for calculating the cylinder air charge amount in the present invention will be described with reference to FIGS. 7 and 8.

  FIG. 7 shows an in-cylinder charge air flow rate mci and an average air flow rate through the throttle valve for all cylinders between a crank angle of 720 ° from the intake top dead center of the first cylinder to the intake top dead center of the next cylinder. The value mave is shown.

The total amount of air flowing into the intake pipe IM during this crank angle 720 ° is the area of the portion indicated by hatching in FIG. 7A, and the average air flow rate through the throttle valve during this crank angle 720 ° value mtave, crankshaft is represented by a product of the required time t ₇₂₀ taken to rotate by the crank angle _{720 ° (mtave · t 720)} . On the other hand, the total amount of air that flows out of the intake pipe IM and is filled in the cylinder during the crank angle 720 ° is the area of the portion indicated by hatching in FIG. 7B, and is the in-cylinder charged air amount Mci. It is represented by ΣMci.

If the intake pressure Pm hardly changes between the start point and the end point of the crank angle 720 °, the total amount of air flowing into the intake pipe IM during the crank angle 720 ° and the cylinders flowing out of the intake pipe IM The total amount of air filled inside should be approximately equal to each other. Therefore, in this case, the following equation (9) is established.

ここで、Ｔｍａｖｅは、クランク角７２０°の間における吸気管ＩＭ内の空気温度平均値を表している。 Then, when Expression (8) is substituted into the right side of Expression (9) and rearranged, it can be expressed as the following Expression (10).

Here, Tmave represents an air temperature average value in the intake pipe IM during a crank angle of 720 °.

  However, equation (10) may not actually hold. As described above, this is a value approximately calculated by the second term on the right side of Expression (8) by setting the intake valve opening time Δtoc to a value equal to the time during which the intake valve 6 is actually opened. This is because an error occurs.

Therefore, in the present invention, the variable x is used for the above equation (10) instead of the intake valve opening time Δtoc. In this case, the above formula (10) is expressed as the following formula (11).

Then, when formula (11) is arranged for variable x, it can be expressed as the following formula (12).

  The variable x calculated in this way is a value corresponding to the intake valve opening time Δtoc, and the total amount of air that has flowed into the intake pipe IM during the crank angle of 720 ° and the outflow from the intake pipe IM. This value is determined when it is assumed that the total amount of air charged in each cylinder is equal (hereinafter referred to as “virtual intake valve opening time”). In other words, the virtual intake valve opening time x is a trapezoid with a portion surrounded by a dotted line in FIG. 8 (that is, a trapezoid in which the upper base is Δtdwni, the lower base is the virtual intake valve opening time x, and the height is mtave. The area of the portion is determined to be equal to the area of the portion (region T2) surrounded by the in-cylinder intake air flow rate mci, the throttle valve passage air flow rate mave, and the straight line mci = 0. However, although FIG. 8 shows one cylinder, the virtual intake valve opening time x is actually the total value of all cylinders in the area surrounded by the dotted line is the total area of the region T2. It is determined to be equal to the total value of the cylinders.

On the other hand, when Expression (8) is expressed using a variable x instead of Δtoc, Expression (13) is obtained.

  Then, by substituting the value of the variable x calculated by Expression (12) into Expression (13), the in-cylinder charged air amount to each cylinder is accurately calculated.

  That is, according to the present invention, a virtual intake valve opening time is calculated such that the average air flow rate to all cylinders is equal to the throttle passage air flow rate, and the virtual intake valve opening time is calculated as the intake valve opening time. By calculating the region T2 using the valve opening time, it is possible to accurately calculate the in-cylinder charged air amount for each cylinder.

  FIG. 9 shows a routine for calculating the fuel injection amount 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 101, the basic fuel injection amount TAUb is calculated based on the engine load, engine speed, etc. detected by the load sensor 43, the crank angle sensor 44, and the like. Next, at step 102, a routine for calculating the cylinder charge air amount Mci shown in FIG. 10 is executed, whereby the cylinder charge air amount Mci for each cylinder is calculated. Next, in step 103, the i-th cylinder air is calculated using equation (2) based on the in-cylinder charged air amount Mci calculated in step 102 and the average value Mcave of all the cylinders in the in-cylinder charged air amount. A quantity variation correction coefficient ηi is calculated (i = 1, 2,..., 8). Next, at step 104, a correction coefficient k is calculated. In step 105, the fuel injection amount TAUi is calculated using equation (1) based on the basic fuel injection amount TAUb, the air amount variation correction coefficient ηi, and the correction coefficient k calculated in steps 101, 103, and 104. The fuel injection valve 11 of the i-th cylinder injects fuel by the fuel injection amount 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 121, the throttle valve passing air flow rate mt is detected from the output of the air flow meter 40 or the like. Next, at step 122, the upward peak occurrence time tmaxi and the downward peak occurrence time tmini due to the opening of the intake valve 6 of the i-th cylinder are detected from the output of the pressure sensor 41 (i = 1, 2,...). , 8). Next, at step 123, the time interval Δtdwni of the i-th cylinder is calculated based on the peak occurrence times tmaxi and tmini detected at step 122 (Δtdwni = tmini−tmaxi). Next, at step 124, the variable x calculated by the virtual intake valve opening time x calculation routine shown in FIG. 11 is acquired.

  In step 125, the maximum value Pmmaxi and the minimum value Pmmini of the intake pressure due to the opening of the intake valve 6 of the i-th cylinder are detected from the output of the pressure sensor 41. Next, at step 126, the intake pressure decrease amount ΔPmdwni of the i-th cylinder is calculated using equation (4) based on the maximum value Pmmaxi and the minimum value Pmmini detected at step 125. In step 127, the temperature Tm in the intake pipe portion IM is detected based on the output of a temperature sensor (not shown) or the like. In step 128, the in-cylinder charged air amount Mci for each cylinder is calculated using equation (13) based on mt, Δtdwni, x, ΔPmdwni, and Tm calculated in steps 121, 123, 124, 126, and 127. Calculated. The calculated in-cylinder charged air amount Mci for each cylinder is used to calculate the fuel injection amount TAUi for each cylinder shown in FIG.

  FIG. 11 shows a variable x calculation routine according to an embodiment of the present invention. This calculation routine is performed every time the crankshaft rotates 720 °.

Referring to FIG. 11, in step 141, a time t ₇₂₀ required for the crankshaft to rotate 720 ° is detected based on the output of the crank angle sensor 44 and the like. Next, at step 142, an average value mave of the throttle passage air flow rate while the crankshaft rotates 720 ° is calculated from the output of the air flow meter 40 and the like. Next, in step 143, ΣΔtdwni is calculated by adding the time intervals Δtdwni calculated in step 123 of FIG. 10 for all the cylinders. In step 144, ΣΔPmdwni is calculated by adding the intake pressure decrease amount ΔPmdwni calculated in step 125 of FIG. 10 for all the cylinders. Next, at step 145, the average value Tmave of the temperature in the intake pipe portion IM is calculated based on the output of the temperature sensor. Next, in step 146, the value of the variable x is calculated using equation (12) based on t ₇₂₀ , mtave, ΣΔtdwni, ΣΔPmdwni and Tmave calculated in steps 141, 142, 143, 144 and 145.

  As described above, equation (12) is established on the condition that the intake pressure Pm is almost changed between the start point and the end point of the crank angle of 720 °. Therefore, the cylinder charge air amount Mci is calculated only during the steady operation. In the transient operation in which the intake pressure Pm is likely to fluctuate between the start point and the end point of the crank angle of 720 °, it is preferable to stop calculating the in-cylinder charged air amount Mci. Here, the steady operation means, for example, an operation in which the engine load and the engine speed are substantially constant, and the transient operation means, for example, an operation in which the engine load and the engine speed fluctuate.

  In the above description, the intake valve opening / closing valve timing is set to the retard side, and the intake valve opens even after the intake bottom dead center, so that the air sucked into the cylinder flows back into the intake pipe The present invention is applied. However, the present invention is not limited to the above case. For example, the intake valve opening / closing valve timing is set to the advance side, and the intake valve opens before the intake top dead center. The present invention can also be applied to a case where the air does not flow into the intake pipe.

1 is an overall view of an internal combustion engine to which the present invention is applied. It is a figure which shows the intake valve opening timing. It is a figure which shows the detection result of the intake pressure Pm. It is a time chart for demonstrating intake pressure fall amount (DELTA) Pmdwni. It is a figure for demonstrating the calculation method of the cylinder filling air amount Mci. It is a time chart for demonstrating the error in approximation. 6 is a time chart for explaining a method of calculating a virtual intake valve opening time x. 6 is a time chart for explaining a method of calculating a virtual intake valve opening time x. It is a flowchart which shows the calculation routine of the fuel injection amount TAUi. It is a flowchart which shows the calculation routine of the cylinder filling air amount Mci. It is a flowchart which shows the calculation routine of the value of the variable x.

Explanation of symbols

1 Engine Body 6 Intake Valve 10 Fuel Injection Valve 18 Throttle Valve 31 ECU
22 Intake valve drive device 40 Air flow meter 41 Pressure sensor IM Intake pipe

Claims (2)

An in-cylinder charged air amount estimation device for an internal combustion engine having a plurality of cylinders and a plurality of intake valves,
The in-cylinder charged air amount to each cylinder is divided into two parts: a basic air amount and an excess air amount that flows into the cylinder from the intake passage portion exceeding the throttle valve passage air flow rate when the intake valve opens,
A basic air amount calculating means for calculating a basic air amount based on a throttle valve passing air flow rate flowing into the intake passage portion via the throttle valve and a valve opening time of each intake valve;
Excess air amount calculating means for calculating an excess air amount based on the amount of decrease in intake pressure due to the opening of the intake valve;
In-cylinder charged air amount estimation device comprising: cylinder-filled air amount calculating means for calculating the cylinder-filled air amount for each cylinder by adding the basic air amount and the excess air amount,
The basic air amount calculating means calculates a virtual intake valve opening time such that an average air flow rate to all cylinders is equal to a throttle passing air flow rate, and the virtual intake valve opening time is calculated as the intake valve opening time. The in-cylinder charged air amount estimation device used as the valve opening time.   The basic air amount calculating means calculates the virtual intake valve opening time of the intake valve when a backflow of air to the intake passage portion occurs near the intake valve opening timing or the intake valve closing timing. The in-cylinder charged air amount estimation device according to claim 1, which is used as a valve opening time.

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