Detecting device of intake air quantity

Description: TECHNICAL FIELD [Detailed description of the invention]

[Industrial application field] The present invention relates to an intake air amount detecting device for detecting the intake air amount of an internal combustion engine, and in particular, the intake air for detecting the intake air amount of a so-called independent intake type internal combustion engine in which the internal combustion engine is provided with a throttle valve in an intake pipe for each cylinder. It relates to a quantity detection device.

[Conventional technology] Conventionally, the optimum amount of fuel is supplied to the internal combustion engine to operate the internal combustion engine at a desired air-fuel ratio, and the combustion timing is controlled at the optimum ignition timing. Is calculated after detecting the negative pressure of the intake pipe using a pressure sensor as the average value of all cylinders, or is detected by an air flow meter. However, in recent years, a so-called independent cylinder type internal combustion engine has been proposed in which a throttle valve is provided for each cylinder of the internal combustion engine in order to further improve the operating performance of the internal combustion engine and improve the response such as acceleration response. The control technology for the internal combustion engine has been researched and developed. That is, since the independent intake type internal combustion engine has a throttle valve for each cylinder, not only the responsiveness is improved, but also the pressure interference between the cylinders is eliminated and the internal combustion engine can be operated more efficiently. .. On the other hand, in order to detect the intake air amount of each cylinder, it is necessary to provide an air flow meter, a pressure sensor, etc. for each cylinder, and the structure is complicated. Therefore, as a device for detecting the amount of intake air for controlling an independent cylinder type internal combustion engine, a simple air flow meter system having a structure in which an air flow meter is provided at a place where each intake pipe is gathered upstream of the throttle valve is the mainstream. Further, as a method of detecting the intake pipe pressure, a method of detecting the averaged pressure by newly providing a communication pipe leading to each cylinder has been proposed.

[Problems that the invention tries to solve] However, the above technology also has the following problems and is not yet sufficient. That is, the greatest advantage of the independent cylinder type internal combustion engine is the improvement of the response, but in the case where the air flow meter is provided at the gathering part of each intake pipe, the air flow meter acts as the resistance of the intake air. It works to reduce the benefits. Therefore, in order to control the independent cylinder type internal combustion engine, it is a more preferable technique to accurately detect the intake air amount from the negative pressure of the intake pipe. However, in the conventional technique in which a communication pipe is provided in each cylinder to detect the intake air pressure, pressure interference between the cylinders occurs as a new problem through the communication pipe, and the structure is not sufficient. There was also a problem in terms of cost due to the complexity. The present invention has been made to solve the above problems, and even in an independent cylinder type internal combustion engine, the structure is simple while taking advantage of the characteristics of the independent cylinder type, and even the influence of atmospheric pressure is taken into consideration. It is an object of the present invention to provide an excellent intake air amount detecting device capable of accurately detecting the intake air amount of an internal combustion engine.

[Means to solve the problem] The present invention made to achieve such an object is as illustrated in FIG. In the intake air amount detection device that detects the intake air amount of an internal combustion engine having a throttle valve for each intake pipe of each cylinder. It is provided on the downstream side of the throttle valve of the intake pipe of a specific cylinder, and for each cycle of the internal combustion engine, the pressure inside the intake pipe when the cylinder is performing intake and the pressure inside the intake pipe when the cylinder is not performing intake. Intake pipe pressure detecting means for detecting the pressure inside the intake pipe, respectively, A rotation speed detecting means for detecting the rotation speed of the internal combustion engine, and Throttle opening detection means for detecting the opening degree of the throttle valve in a cycle shorter than at least one cycle of the internal combustion engine, and A reference intake that calculates a reference intake air amount based on the pressure inside the intake pipe when the cylinder is performing intake intake detected by the intake pipe pressure detecting means and the rotation speed detected by the rotation speed detecting means. Air volume calculation means and A first atmospheric pressure correction that takes in the pressure inside the intake pipe when the cylinder is not executing intake as the atmospheric pressure detected by the intake pipe pressure detecting means and corrects the reference intake air amount based on the atmospheric pressure. Means and A correction intake air amount calculation means that calculates a correction intake air amount based on the throttle valve opening degree detected by the throttle opening detection means and the rotation speed detected by the rotation speed detection means. A second atmospheric pressure that takes in the pressure inside the intake pipe when the cylinder is not executing intake as atmospheric pressure detected by the intake pipe pressure detecting means and corrects the amount of intake air for correction based on the atmospheric pressure. Correction means and Every time the correction intake air amount is corrected by the second atmospheric pressure correction means, the amount of change in the correction intake air amount after the atmospheric pressure correction is obtained, and the change amount is used as the intake air amount. The increase / decrease value setting means to be set as the increase / decrease value, and When the reference intake air amount is atmospherically corrected by the first atmospheric pressure correction means, the correction result is set as the intake air amount of the internal combustion engine, and then the first atmospheric pressure correction means is used. Until the reference intake air amount is corrected to the atmospheric pressure, each time the increase / decrease value is set by the increase / decrease value setting means, the increase / decrease value is sequentially added to the set intake air amount to take in air. Intake air amount setting means to update the amount, It is characterized by being equipped with.

[Action] In the intake air amount detecting device of the present invention configured as described above, the intake pipe pressure detecting means is provided on the downstream side of the throttle valve of the intake pipe of the specific cylinder in the intake pipe of each cylinder. The intake pipe pressure detecting means detects the pressure inside the intake pipe when the cylinder is performing intake and the pressure inside the intake pipe when the cylinder is not performing intake, for each cycle of the internal combustion engine. Further, the throttle opening degree detecting means detects the opening degree of the throttle valve in a cycle shorter than one cycle of the internal combustion engine, and the rotation speed detecting means detects the rotation speed of the internal combustion engine. Then, when the intake pipe pressure detecting means detects the pressure inside the intake pipe when the intake pipe is executing the intake air, the reference intake air amount calculating means detects the detected pressure inside the intake pipe and the rotation speed detecting means of the internal combustion engine. The reference intake air amount is calculated based on the number of rotations, and the first atmospheric pressure correction means is inside the intake pipe when the intake pipe pressure detecting means detects the calculated reference intake air amount. Atmospheric pressure is corrected based on the pressure. That is, since the intake air amount of the internal combustion engine is proportional to the pressure inside the intake pipe on the downstream side of the throttle valve of the cylinder in the intake stroke and inversely proportional to the rotation speed of the internal combustion engine, the intake pipe pressure detecting means is used in the present invention. Then, the pressure inside the intake pipe when the specific cylinder is performing intake is detected, and the reference intake air amount calculation means is used to calculate the reference intake air amount, which is the reference value of the intake air amount from the detection result and the rotation speed of the internal combustion engine. Calculate the amount. However, since the intake air amount of the internal combustion engine is large when the atmospheric pressure is large and decreases when the atmospheric pressure is small, it is necessary to correct the reference intake air amount obtained in this way. Further, in order to correct the atmospheric pressure, it is necessary to detect the atmospheric pressure, but if the atmospheric pressure sensor is used for the atmospheric pressure detection, the device configuration becomes complicated. Therefore, in the present invention, paying attention to the fact that the pressure inside the intake pipe of a cylinder that is not performing intake is substantially equal to the atmospheric pressure, the pressure inside the intake pipe at this time is detected by using the intake pipe pressure detecting means to obtain the atmospheric pressure. Is detected, and further, the first atmospheric pressure correction means corrects the reference intake air amount based on the detection result. As a result, the reference intake air amount corrected by the first atmospheric pressure correction means becomes the true intake air amount actually sucked into the internal combustion engine. Next, in the intake air amount detecting device of the present invention, the correction intake air amount calculating means is the opening degree of the throttle valve detected by the throttle opening degree detecting means and the rotation of the internal combustion engine detected by the rotation speed detecting means. The amount of intake air for correction is calculated based on the number, and the second atmospheric pressure correction means corrects the amount of intake air for correction at atmospheric pressure in the same manner as the first atmospheric pressure correction means, and the increase / decrease value setting means. However, every time the second atmospheric pressure correction means corrects the intake air amount for correction, the amount of change in the intake air amount for correction after the atmospheric pressure correction is obtained, and this is set as an increase / decrease value of the intake air amount. To do. Then, the intake air amount setting means once sets the reference intake air amount corrected by the first atmospheric pressure correction means as the intake air amount of the internal combustion engine, and then the first atmospheric pressure correction means. True until the reference intake air amount is corrected to atmospheric pressure, each time the increase / decrease value is set by the increase / decrease value setting means, the increase / decrease value is sequentially added to the once set intake air amount to increase the intake air amount. By updating, the intake air amount of the internal combustion engine is set. That is, the reference intake air amount corrected by the first atmospheric pressure correction means is based on the pressure in the intake pipe when the specific cylinder detected in each cycle of the internal combustion engine is performing intake. Therefore, immediately after executing a series of detection operations such as detection of the pressure in the intake pipe calculation of the reference intake air amount atmospheric pressure correction, the true intake air amount is obtained as described above, but after this atmospheric pressure correction. If the reference intake air amount is set as the intake air amount of the internal combustion engine as it is, the driver operates the accelerator until the next series of detection operations is executed, and the throttle valve opening is extended. When the intake air amount changes, it becomes impossible to set the intake air amount corresponding to the change. Therefore, in the present invention, the throttle valve opening degree is detected by using the throttle opening degree detecting means in a cycle shorter than one cycle of the internal combustion engine (that is, a cycle shorter than the detection cycle of the intake pipe pressure by the intake pipe pressure detecting means). By calculating the amount of intake air for correction from the detection result and the rotation speed of the internal combustion engine, the amount of intake air for correction is calculated in a cycle shorter than the calculation cycle of the reference intake air amount, and further, the intake for correction is calculated. The amount of air is corrected to atmospheric pressure, the amount of change in the amount of intake air for correction after the correction of atmospheric pressure is obtained, and this value is set as an increase / decrease value of the amount of intake air. Therefore, in the intake air amount setting means, the intake air amount is truly set by the reference intake air amount immediately after the atmospheric pressure correction for each cycle of the internal combustion engine, and the driver operates the accelerator during that time to operate the throttle valve. When the opening degree changes, the intake air amount is accurately corrected accordingly, and the accurate intake air amount is always set. Hereinafter, the present invention will be described in detail with reference to examples in order to explain the present invention more specifically.

[Example] FIG. 2 is a schematic view of a control system of a 4-cylinder independent intake internal combustion engine equipped with the intake air amount detection device of the embodiment. In the figure, 10 indicates a 4-cylinder engine, and the intake pipe 11 of each cylinder is connected to a throttle valve 12 linked to an accelerator pedal (not shown) and a fuel tank (not shown) to inject fuel toward the intake pipe. An injection valve 13 is provided. The cylinders are arranged in the order of the first cylinder, the second cylinder, the third cylinder, and the fourth cylinder from the upper part of the drawing. Further, the spark plug 14 provided for each cylinder is appropriately supplied with a high voltage by the distributor 15 to determine the ignition timing. Reference numeral 16 denotes a throttle opening sensor that detects the opening degree of the throttle valve 12, and outputs an analog output proportional to the opening degree of the throttle valve 12. In this embodiment, an intake pressure sensor 17 including a pressure sensor for detecting the negative pressure of the intake pipe is provided on the downstream side of the throttle valve 12 of the intake pipe 11 of the first cylinder. Further, 18 represents a water temperature sensor that detects the cooling water temperature of the internal combustion engine 10, 19 represents an oxygen sensor that detects the oxygen concentration in the exhaust gas of the internal combustion engine 10, and 20 represents an intake air temperature sensor that detects the intake air temperature. The output of these various sensors and the operating state of various devices are centrally processed by the electronic control device 30. As shown in the figure, the electronic control device 30 is composed of a logical operation circuit centered on a microcomputer, and operates by receiving electric power from an in-vehicle battery 21 via a key switch 22. 31 is the central part of the computer, which is a CPU that executes various operations, and performs processing according to the control program and map stored in ROM 32, which will be described later. 33 is RAM for temporary storage of data. 34 corresponds to the outputs from the various sensors, the throttle opening sensor 16, the intake pressure sensor 17, the water temperature sensor 18, the oxygen sensor 19, and the intake temperature sensor 20, the cylinder discrimination signal from the distributor 15, and the rotation angle of the crank angle. It is an input port that inputs the rotation angle signal, including an A / D converter, waveform shaper, etc., and outputs necessary information to the CPU 31 as appropriate. Reference numeral 35 denotes an output port, which outputs the opening timing and time to the fuel injection valve 13 of each cylinder according to the calculation result of the CPU 31, and also outputs a signal for determining the ignition timing of the spark plug 14 to the distributor 15. .. Each component of the electronic control device 30 is connected by a data and an address bus 36. FIGS. 3 (A), 3 (B) and 4 show a flowchart of an intake air amount detection program stored in the ROM 32. FIGS. 3A and 3B show a flowchart of a routine for determining the timing of capturing the output of the sensor. (A) The figure shows the timing of two times in one cycle (two rotations of the crankshaft) that takes in the output of the intake pressure sensor 17 in a routine that is repeatedly executed by the CPU 31 in synchronization with the crank angle of the internal combustion engine 10. ing. First, when the crank angle becomes a predetermined value and the CPU 31 enters the processing of this routine, it is determined in step 100 whether or not it is the timing to take in the intake pipe pressure PS. The PS intake timing is the intake process of the first cylinder when the intake pressure sensor 17 takes the crank angle with respect to the TDC of the first cylinder as the horizontal axis as shown in the timing chart (A) of Fig. 5. It is the timing when the output indicating the negative pressure condition in the middle is generated and the timing when the intake pipe pressure becomes equal to the atmospheric pressure below the intake stroke. Therefore, as is clear from the timing chart in Fig. 5 (A), the period during which the negative pressure of the intake pipe of the first cylinder, which is shown by the solid line, is greatly depressed (about 0 ° CA to 360 ° CA) and At any time during the period of continuous output of a constant value (about 360 ° CA to 720 ° CA), in this embodiment, the capture of the output PS of the sensor is started at about 160 ° CA and 680 ° CA. If it is determined in this step 100 that the crank angle of the internal combustion engine 10 is about 160 ° CA or 680 ° CA, the A / D conversion process of the output of the intake pressure sensor 17 is started in the next step 110, and the suction is started. The output of the pressure sensor 17 is A / D converted at the input port 34, and its values PSAD1 (PS value at 160 ° CA) and PSAD2 (PS value at 680 ° CA) (Fig. 5 (B), (C)). ) Is temporarily stored in the buffer, and a series of processes are started. If the crank angle is other than about 160 ° CA or 680 ° CA, this routine is terminated and other routines are executed without starting the process of step 110 as described above. FIG. 3B shows a routine for capturing the output (TA) of the throttle opening sensor 16 which is repeatedly processed by the CPU 31 every time a predetermined time elapses. First, when the processing of the CPU 31 shifts to this routine, it is determined in step 200 whether or not a predetermined time (T [ms]) has elapsed after the previous processing of this routine. Then, step 210 is processed only when it is determined that T [ms] has elapsed, and this routine is terminated otherwise. This step 210 AD-converts the output TA of the throttle opening sensor 16 and controls the start of a series of processes for storing the value (TAAD) at a predetermined address, and the intake of TAAD is started. FIG. 5 (E) is a timing chart for capturing the output of the throttle opening sensor TA. As shown in the figure, the value TAAD obtained by AD-converting TA is executed every predetermined cycle T [ms]. This predetermined period T [ms] is a value smaller than the period during which the AD conversion value PSAD of the intake pipe negative pressure is taken in, and TAAD is taken in at a frequency higher than the PSAD uptake frequency. FIG. 4 shows the main routine of this embodiment, and calculates the intake air amount Q of the internal combustion engine 10. This routine is repeatedly executed by the CPU 31 at predetermined time intervals. When the CPU 31 enters the processing of this routine, the A / D conversion of the output PS of the intake pressure sensor 17 (the series of processing started in step 110 described above) is completed in step 300, and the latest PS value is calculated. Judgment is made as to whether or not the capture has been made. If it is determined in this step that the latest PS A / D conversion has not been completed, the process proceeds to step 380 described later, and if the A / D conversion is completed, the next step 310 is processed. In step 310, the A / D conversion value PSAD of the output PS of the intake pressure sensor 17 is calculated in the CPU 31. Then, it is determined whether this A / D conversion value PSAD value is detected in synchronization with either 160 ° CA or 680 ° CA of the crank angle (step 320), and if it is the data at 160 ° CA. The reference intake air amount QPMC is calculated by the processing of steps 330 to 350, and 680 If the data is at the time of CA, the atmospheric pressure correction coefficients KPM and KTA of QPM and QTA, which will be described later, are calculated by the processing of steps 360 and 370. First, the calculation of QPMC will be described. The PSAD value calculated in step 310 is set in the variable PSAD1 as a value indicating the negative pressure status of the intake air (step 330), and the intake air amount QPM is calculated from the value PSAD1 and the rotation speed NE of the internal combustion engine 10. Be done (step 340). This calculation is no different from the conventional calculation of the intake air amount Q, and can be obtained by calculation by the CPU 31 or by searching the map prepared in the ROM 32 in advance. The intake air amount QPM thus obtained is multiplied by the atmospheric pressure correction coefficient KPM in the subsequent step 350 to calculate the reference intake air amount QPMC. On the other hand, the atmospheric pressure correction coefficient KTA used when calculating this reference intake air amount QPMC and the atmospheric pressure correction coefficient KTA of the intake air increase / decrease QTA calculated based on the throttle opening TA described later are executed. Are steps 360 and 370. First, in step 360, the PSAD value calculated in step 310 is set in the variable PSAD2, and in the following step 370, two atmospheric pressure correction coefficients KPM and KTA are calculated. These two atmospheric pressure correction coefficients KPM and KTA are also obtained by the calculation of CPU31 or by the search of each map prepared in ROM32. When the atmospheric pressure changes, the intake air amount changes even under the same intake pipe pressure or throttle opening. Therefore, this change is corrected by the calculation of the CPU 31 by formulating the degree of this change in advance, or by executing the search by preparing it as a map. It is obtained by the calculation of U31 or by the search of each map prepared in ROM32. When the atmospheric pressure changes, the intake air amount changes even under the same intake pipe pressure or throttle opening. Therefore, this change is corrected by the calculation of the CPU 31 by formulating the degree of this change in advance, or by executing the search by preparing it as a map. It is obtained by the calculation of U31 or by the search of each map prepared in ROM32. When the atmospheric pressure changes, the intake air amount changes even under the same intake pipe pressure or throttle opening. Therefore, this change is corrected by the calculation of the CPU 31 by formulating the degree of this change in advance, or by executing the search by preparing it as a map. When the QPMC, KPM, or KTA is obtained in this way, step 380 is then executed. Here, the same process as in step 300 described above is executed, and it is determined whether or not the latest TA value has been obtained by completing the process of capturing the throttle opening TA in step 210 in FIG. 3 (B). If it is not completed, step 450 described later is executed, and only when it is completed, a series of processes from step 390 to step 440 is executed. The process of steps 390 to 440 shows the process for calculating the increase / decrease value ΔQTA of the reference intake air amount QPMC calculated in step 350 described above. First, in step 390, the AD conversion value TAAD of the throttle opening TA is calculated and used for the processing of the CPU 31. Then, the intake air amount QTA calculated from the throttle opening TA is calculated from this value TAAD and the rotation speed NE of the internal combustion engine 10 (step 400). The calculation of this QTA is also performed by the process of directly calculating the QPM as described above, or by searching the map. In the following step 410, the correction coefficient KAT obtained from the latest atmospheric pressure detection result (PSAD2) calculated in step 370 is multiplied by this QTA, and the intake air amount obtained from the throttle opening TA obtained by atmospheric pressure correction. QTAC is calculated. In the next step 420, it is determined whether or not the TAAD calculated in step 390 is the timing immediately before the A / D conversion of PSAD1 is executed, that is, the timing immediately before the crank angle of 160 ° CA. As shown in Fig. 5 (B) and (E), PSAD1 has a crank angle of 720. For each CA, TAAD is calculated for each predetermined time T [ms], and the TAAD calculation frequency is always set higher than the PSAD calculation frequency. Therefore, in the calculation of PSAD1, the calculation of TAAD is always executed very close to the timing (within a small time difference). Therefore, in this step, it is determined whether or not QTAC is calculated by TAAD at the timing immediately before the timing of PSAD1. Then, step 430 is executed only when this QTAC is the timing immediately before PSAD1, the value of QTAC is set in the variable QTAB, and the process proceeds to step 440 otherwise. Figure 5 (E) shows the relationship between QTAC and QTAB. Step 440 is a step for calculating the increase / decrease value ΔQTA of the intake air amount, and the ΔQTA is calculated from the latest QTAC value and the QTAB value by the following equation. ΔQTA = QTAC-QTAB As described above, QTAB was calculated immediately before the calculation of QPMC, and the effect (QTAB) of this throttle opening TA on the intake air amount is already reflected in the value of QPMC. However, when the throttle valve 12 is controlled to open and close from the time of this QPMC calculation, the intake air amount and the rotation speed NE naturally change, but the change in the intake air amount at this time is up to the next predetermined crank angle (160 ° CA). Cannot be calculated. Therefore, when information on the intake air amount of the internal combustion engine 10 is required within the undetectable time of the intake air amount, the difference between QTAC and QTAB calculated from the throttle opening TA and the rotation speed NE at that time, that is, , It is calculated how much the intake air amount changes based on the changes in the throttle opening TA and the rotation speed NE compared to the time when the QPMC is calculated. Then, by adding this value (ΔQTA) to the QPMC (step 450), the intake air amount Q (FIG. 5 (F)) of the internal combustion engine 10 is constantly calculated. The shaded area in FIG. 5 (E) represents the correction width (ΔQTA) of the intake air amount based on the throttle opening TA and the rotation speed NE. The intake air amount Q calculated in this way is then used for various existing controls. For example, it can be widely used for calculating the fuel injection amount for keeping the air-fuel ratio of the internal combustion engine 10 at a desired value, calculating the ignition timing for controlling the output torque and emissions of the internal combustion engine 10. In this embodiment, the crank angle synchronization process of FIG. 3 (A) is used for the intake pipe pressure detecting means, the time synchronization process of FIG. 3 (B) is used for the throttle opening detection means, and the step of FIG. The process of 340 is the reference intake air amount detecting means, the process of step 350 in FIG. 4 is the first atmospheric pressure correction means, the process of step 400 in FIG. 4 is the correction intake air amount calculation means, and the fourth. The process of step 410 in FIG. 4 corresponds to the second atmospheric pressure correction means, the process of step 440 in FIG. 4 corresponds to the increase / decrease value setting means, and the process of step 450 in FIG. 4 corresponds to the intake air amount setting means. FIG. 6 shows an application example in which the ignition timing of the internal combustion engine 10 is determined by using the intake air amount Q detected by the intake air amount detection device of this embodiment. FIG. 6 is a flowchart for determining the ignition timing. The ignition advance calculation routine shown in Fig. 6 is repeatedly executed as a part of the main routine that executes the control of the internal combustion engine 10 or as an independent routine, and is the best when the ignition timing of each cylinder is set. Calculate whether the internal combustion engine can be operated. First, in step 500, it is determined whether or not the current ignition timing should be calculated. Whether or not any of the cylinders of the internal combustion engine 10 is approaching the time when ignition is required is determined from the crank angle and the like. Then, the processes of steps 510 to 530 are executed only when it is determined that it is the ignition timing calculation time, and this routine is terminated otherwise. In step 510, the current rotation speed NE and intake air amount Q of the internal combustion engine 10 are detected. It detects the operating status of the internal combustion engine 10 required to calculate the ignition timing. Here, the rotation speed NE can always be detected by the rotation angle signal from the distributor 15, and the calculation result of the above-described embodiment is used as the intake air amount Q. Therefore, the routine shown in FIG. 4 of the embodiment is executed immediately before the execution of this routine, and the intake air amount Q of the internal combustion engine 10 is obtained. Next, in step 520, a known map for calculating the ignition timing (not shown) is searched from the above two values of NE and Q, and the ignition timing is calculated. After that, in step 530, the map search result is stored in the RAM 33, and ignition is performed according to the information in the RAM 33 by an ignition execution routine (not shown). As described above, the intake air amount Q calculated in the above-described embodiment is not different from the intake air amount as a control parameter of the internal combustion engine 10 from the conventional method, and can be widely used as a parameter for all existing controls. is there.

[Effect of the invention] As described in detail above, in the intake air amount detecting device of the present invention, the intake pipe pressure detecting means is provided in a specific cylinder among the plurality of cylinders of the internal combustion engine, and the intake pipe pressure detecting means is used to specify. The pressure inside the intake pipe when the cylinder is performing intake and the pressure inside the intake pipe when not performing intake are detected, respectively, and the reference intake is based on the pressure inside the intake pipe when intake is executed and the rotation speed of the internal combustion engine. The amount of air is calculated, and the calculation result is corrected to atmospheric pressure by the pressure inside the intake pipe when intake is not being executed, and the value is temporarily set as the amount of intake air of the internal combustion engine. The reference intake air amount corrected for atmospheric pressure corresponds to the actual intake air amount immediately after the calculation, but since the reference intake air amount can be calculated only for each cycle of the internal combustion engine, during that one cycle. In order to correct the change in the intake air amount of the internal combustion engine, the opening degree of the throttle valve is detected in a cycle shorter than one cycle of the internal combustion engine, and the correction intake air amount is calculated from the detection result and the rotation speed of the internal combustion engine. Then, this correction intake air amount is corrected to atmospheric pressure by the pressure inside the intake pipe when intake is not being executed, and the amount of change in the correction intake air amount after the atmospheric pressure correction is set as an increase / decrease value of the intake air amount. Then, the intake air amount is updated by adding this increase / decrease value to the reference intake air amount after atmospheric pressure correction once set as the intake air amount of the internal combustion engine. Therefore, according to the intake air amount detecting device of the present invention, the intake air amount of the independent cylinder type internal combustion engine can always be accurately detected without being affected by the change in atmospheric pressure. Further, since no device such as an air flow meter that acts as a resistance to the intake air is used for the detection, the characteristics of the independent cylinder type internal combustion engine can be fully exhibited, and the intake pipe pressure detecting means. Is only required to be provided in a specific cylinder, so that pressure interference between the cylinders does not occur, and the intake air amount detection device is extremely excellent.

[Simple explanation of drawings]

FIG. 1 is a basic configuration diagram of the present invention, FIG. 2 is a schematic configuration diagram of an embodiment, FIGS. 3 (A), (B) and 4 are control flowcharts thereof, and FIG. 5 is a timing chart thereof. Fig. 6 shows the application order of the intake air amount obtained in the examples. 10 ...... Internal combustion engine, 11 ...... Intake pipe 12 ...... Throttle valve, 14 ...... Spark plug 16 ...... Throttle opening sensor 17 ...... Intake pressure sensor, 30 ...... Electronic control device 31 ...... CPU, 32 ...... ROM