Control method of internal combustion engine and control device of internal combustion engine

Abstract

The present application relates to a control method of an internal combustion engine and a control device of an internal combustion engine, in which an intake air amount (A1) directly measured by an air flow meter (19) is selected as an air amount that becomes a basis of an air-fuel ratio control at normal times, and in a state in which an opening area (St) of a throttle valve (14) is smaller than an opening area (Sn) of a negative pressure generation valve (18), an intake air amount (A2) that is not dependent on the air flow meter (19), for example, an intake air amount that is estimated and calculated based on a throttle opening degree, is selected as an air amount that becomes a basis of an air-fuel ratio control at a prescribed transition state. Thus, a response delay of detection of the intake air amount can be suppressed, an intake air amount (A) corresponding to a requested engine torque (T) of the internal combustion engine (1) can be supplied, and an improvement in precision of the air-fuel ratio control can be achieved.

Description

Technical Field

[0001] This invention relates to a control method and a control device for an internal combustion engine. Background Technology

[0002] Typically, in the control methods of internal combustion engines, as described in Patent Document 1 below, in addition to directly detecting the intake air volume by means of an air flow meter, the internal combustion engine can also be controlled by estimating the intake air volume based on prescribed parameters without using the air flow meter.

[0003] For example, in turbocharged engines, it can be difficult to accurately detect the intake air volume using a flow meter in areas such as the turbocharger surge region or the low-speed, high-load pulsation region. Therefore, in situations where it is difficult to accurately detect the intake air volume using a flow meter, such as the surge or pulsation region, a method is used in engine control to estimate the intake air volume based on prescribed parameters instead of using the flow meter's measured value.

[0004] Furthermore, depending on the engine, some engines recirculate a portion of the exhaust gas (blow-through gas and EGR) back to the intake. In such engines, to ensure efficient recirculation of blow-through gas or EGR, a negative pressure generating valve is installed upstream of the turbocharger to assist in generating negative pressure. In such systems, during rapid transitions, the detection of the intake air volume in the airflow meter is delayed, making it difficult to accurately detect the intake air volume; however, there is room for improvement in this regard.

[0005] Patent Document 1: Japanese Patent Application Publication No. 2021-050632 Summary of the Invention

[0006] In one aspect of the present invention, there is a control method for an internal combustion engine having a throttle valve disposed in an intake passage, a turbocharger disposed upstream of the throttle valve, a negative pressure generating valve disposed upstream of the turbocharger, and an air flow meter disposed upstream of the negative pressure generating valve. In this control method, the intake air volume, which forms the basis for air-fuel ratio control, is measured based on the output of the air flow meter. Furthermore, when the opening area of ​​the throttle valve is smaller than the opening area of ​​the negative pressure generating valve, and the internal combustion engine is in a predetermined transition state, an estimation calculation of the intake air volume independent of the air flow meter is performed.

[0007] In this way, under normal conditions, the intake air volume is directly measured by an air flow meter. When the internal combustion engine is in a specified transition state, an estimation calculation of the intake air volume is performed independently of the air flow meter. As a result, the detection delay of the intake air volume based on the air flow meter measurement that occurs in the transition state can be suppressed, and the intake air volume that becomes the basis for the air-fuel ratio control of the internal combustion engine can be output with high accuracy. Attached Figure Description

[0008] Figure 1 This is a schematic diagram of the internal combustion engine involved in the present invention.

[0009] Figure 2 This is a control module diagram of the ECU according to the first embodiment of the present invention.

[0010] Figure 3 yes Figure 1 The flowchart shown is for the air-fuel ratio control of the ECU.

[0011] Figure 4 Is with Figure 1 The timing diagram shown is related to the air-fuel ratio control of the ECU.

[0012] Figure 5 This is a control module diagram of the ECU according to the second embodiment of the present invention. Detailed Implementation

[0013] Hereinafter, embodiments of the control method and control device for an internal combustion engine according to the present invention will be described in detail based on the accompanying drawings. Furthermore, in the following embodiments, the method of applying the control method and control device for an internal combustion engine according to the present invention to a turbocharged gasoline engine will be described.

[0014] (Structure of an internal combustion engine)

[0015] Figure 1 A schematic diagram of a turbocharged gasoline engine according to this embodiment is shown.

[0016] For example, such as Figure 1 As shown, the internal combustion engine 1 is a spark-ignition internal combustion engine with a turbocharger as a supercharger, and has a cylinder 2 and a crankcase 3, wherein the cylinder 2 has a combustion chamber 2a inside.

[0017] The intake passage 11 of the internal combustion engine 1 has an air filter 12 at its upstream inlet and a compressor 13 with a turbocharger in the middle of the passage. A throttle valve 14, which controls the amount of air intake into the internal combustion engine 1, is located downstream of the compressor 13 and has an electric actuator such as an electric motor; it is an electronically controlled throttle valve whose opening is controlled by the engine controller 15. An intercooler 16 is arranged between the compressor 13 and the throttle valve 14 to cool the intake air compressed by the compressor 13. The throttle valve 14 is located upstream of the intake manifold main pipe, i.e., the intake header 17, from which multiple intake manifolds 17a branch off to each cylinder. Furthermore, the intake header 17 has a boost sensor 20 for detecting intake pressure (boost).

[0018] A negative pressure generating valve 18 is provided upstream of the compressor 13 in the intake passage 11. This valve generates negative pressure in the region between the compressor 13 and the negative pressure generating valve 18. The negative pressure generating valve 18 has a butterfly valve-type structure similar to the throttle valve 14, and its opening is controlled by the engine controller 15 via an electric actuator to generate the required negative pressure according to the operating conditions of the internal combustion engine 1. That is, by providing this negative pressure generating valve 18, the required negative pressure can be generated according to the operating conditions of the internal combustion engine 1, contributing to the proper backflow of leaking gas or EGR (described later). Furthermore, an air flow meter 19 is arranged further upstream of the negative pressure generating valve 18, between the negative pressure generating valve 18 and the air filter 12, to detect the amount of air intake into the internal combustion engine 1. The air flow meter 19 is, for example, a hot-wire air flow meter, but other types of air flow meters are also possible.

[0019] Furthermore, in the internal combustion engine, gas containing unburned components leaks from the combustion chamber 2a of each cylinder into the crankcase 3, which is called blow-by gas. This blow-by gas is guided to the first oil separator chamber 6 provided on the top of the cylinder head cover 5 via a blow-by gas passage 4 formed vertically inside the internal combustion engine 1. In addition to the first oil separator chamber 6, a second oil separator chamber 7 is also formed on the top of the cylinder head cover 5, and the second oil separator chamber 7 communicates with the space inside the cylinder head that connects to the crankcase 3.

[0020] Additionally, the internal combustion engine 1 is equipped with a blow-by gas recirculation system for recirculating the blow-by gas back to the intake passage 11. This blow-by gas recirculation system includes a fresh air inlet pipe 21 that introduces fresh air into the crankcase 3, a first blow-by gas pipe 22 that guides the blow-by gas upstream of the compressor 13 in the intake passage 11, and a second blow-by gas pipe 23 that guides the blow-by gas downstream of the throttle valve 14 in the intake passage 11.

[0021] Regarding the fresh air inlet duct 21, one end, which becomes the upstream end when fresh air flows, is connected to the intake passage 11 at a location further upstream than the negative pressure generating valve 18, while the other end, which becomes the downstream end when fresh air flows, is connected to the second oil separator chamber 7 of the internal combustion engine 1. Here, the air flow meter 19 is located further upstream in the intake passage 11 than at the upstream connection point of the fresh air inlet duct 21, and measures the gas flow rate, including the fresh air flowing to the fresh air inlet duct 21, as the intake air volume.

[0022] Regarding the first leaky gas pipe 22, one end, which is upstream when leaky gas flows, is connected to the first oil separator chamber 6 of the internal combustion engine 1, and the other end, which is downstream when leaky gas flows, is connected between the negative pressure generating valve 18 of the intake passage 11 and the compressor 13. At the connection between the first leaky gas pipe 22 and the first oil separator chamber 6, a one-way valve 25 is provided that only allows the flow of gas from the crankcase 3 (first oil separator chamber 6) towards the intake passage 11. This one-way valve 25 is, for example, a check valve with a mechanical structure having an umbrella-shaped valve body that opens and closes based on pressure difference; the backflow from the intake passage 11 side towards the crankcase 3 is prevented by this one-way valve 25.

[0023] Regarding the second leaky gas pipe 23, one end, which is upstream when leaky gas flows, is connected to the first oil separator chamber 6 of the internal combustion engine 1, and the other end, which is downstream when leaky gas flows, is connected to the downstream side of the throttle valve 14 of the intake passage 11, specifically the intake manifold 17. At the connection between the second leaky gas pipe 23 and the first oil separator chamber 6, a PCV valve 26 is provided to mechanically regulate the flow rate of the leaky gas based on the pressure difference. The PCV valve 26 also functions as a check valve to prevent the flow of gas from the intake manifold 17 side towards the first oil separator chamber 6 side.

[0024] In addition, the engine controller 15 receives detection signals from various sensor groups, including the air flow meter 19, as well as the throttle position sensor 31 (indicating throttle opening), the crankshaft angle sensor 32 (indicating the rotational speed of the internal combustion engine 1), the air-fuel ratio sensor 33 (detecting the exhaust air-fuel ratio in the exhaust passage other than those shown), the coolant temperature sensor 34 (indicating coolant temperature), the upstream pressure sensor 35 (indicating the upstream pressure of the throttle valve 14), the manifold pressure sensor 36 (indicating the pressure in the intake manifold 17), the cam angle sensor 37 (indicating valve timing), and the intake temperature sensor 38 (indicating intake air temperature). Furthermore, the engine controller 15 performs various controls of the internal combustion engine 1, such as the control of fuel injection quantity or injection timing implemented by fuel injection valves other than those shown in the diagram of the internal combustion engine 1, the control of ignition timing implemented by spark plugs other than those shown in the diagram, the control of the opening amount of throttle valve 14 or negative pressure generating valve 18, and the control of turbocharger boost.

[0025] [First Implementation]

[0026] The following is based on Figures 2-4 The first embodiment of the control method and control device for an internal combustion engine involved in the present invention will be described.

[0027] (Structure of the control device for an internal combustion engine)

[0028] Figure 2 The diagram shows a control module related to the air-fuel ratio control of the engine controller 15 according to this embodiment. (a) shows an overall view of the control module. (b) shows an output method based on the intake air volume measured by an air flow meter. (c) shows an output method based on the intake air volume calculated by estimation.

[0029] like Figure 2As shown in (a), the engine controller 15 according to this embodiment includes an AFM signal physical quantity conversion unit B1, an air volume estimation control unit B2 based on throttle opening, a throttle air volume switching determination unit B3, a manifold pressure calculation unit B4, and a cylinder intake air volume calculation unit B5. Furthermore, the AFM signal physical quantity conversion unit B1 corresponds to the intake air volume measurement unit of this invention, converting the output signal from the air flow meter 19, i.e., the AFM signal, to measure the intake air volume. The air volume estimation control unit B2 based on throttle opening corresponds to the intake air volume estimation calculation unit of this invention, performing an intake air volume estimation calculation based on the throttle opening obtained from the output signal of the throttle position sensor 31, the ENG speed obtained from the output signal of the crankshaft angle sensor 32, and the upstream pressure of the throttle obtained from the output signal of the upstream pressure sensor 35, to estimate the intake air volume. The throttle body air volume switching determination unit B3 determines the switching method of measuring the air volume (intake air volume) through the throttle valve 14 based on, for example, the driver's settings or the operating state of the internal combustion engine 1. The manifold pressure calculation unit B4 calculates the internal pressure (manifold pressure) of the intake manifold 17 based on the output signal of the AFM signal physical quantity conversion unit B1 input via the throttle body air volume switching determination unit B3 or the output signal of the air volume estimation control unit B2 based on the throttle opening. The cylinder intake air volume calculation unit B5 calculates the intake air volume introduced into the cylinder 2 based on the ENG speed obtained from the output signal of the crankshaft angle sensor 32 and the valve timing obtained from the output signal of the cam angle sensor 37.

[0030] According to this structure, in this embodiment, in the throttle body air volume switching determination unit B3, the reference... Figure 3 In cases where it is determined not to fall under the category of "abrupt transitional states" described later, such as Figure 2 As shown in (b), the intake air volume obtained by converting the output signal (AFM signal) of the air flow meter 19, i.e., the intake air volume A1 directly measured by the air flow meter 19, is output as the air volume that forms the basis for air-fuel ratio control. Furthermore, this intake air volume A1 is obtained by measuring the amount of air passing through the air flow meter 19, and it does not include any leakage gas. Next, based on this intake air volume A1, the manifold pressure is calculated, and the intake air volume A is output. This intake air volume A is calculated based on the manifold pressure, the ENG speed obtained from the output signal of the crankshaft angle sensor 32, and the valve timing obtained from the output signal of the cam angle sensor 37.

[0031] On the other hand, in the throttle body air volume switching determination unit B3, in reference Figure 3 In cases where it is determined to belong to the "abrupt transitional state" described later, such as Figure 2 As shown in (c), the intake air volume A2, estimated in the throttle opening-based air volume estimation control unit B2, is used as the air volume for air-fuel ratio control, based on the throttle opening obtained from the output signal of the throttle position sensor 31, the ENG speed obtained from the output signal of the crankshaft angle sensor 32, and the upstream throttle pressure obtained from the output signal of the upstream throttle pressure sensor 35. Furthermore, since this intake air volume A2 is estimated based on the throttle opening, it does not include any leakage gas. Next, based on this intake air volume A2, the manifold pressure is calculated, and the intake air volume A is output. This intake air volume A is calculated based on the manifold pressure, the ENG speed obtained from the output signal of the crankshaft angle sensor 32, and the valve timing obtained from the output signal of the camshaft angle sensor 37.

[0032] (Control methods for internal combustion engines)

[0033] Figure 3 The control flowchart of air-fuel ratio control in engine controller 15 is shown.

[0034] Regarding the engine controller 15 according to this embodiment, in Figure 2 The throttle valve shown is based on the air volume switching determination unit B3. Figure 3 The control flow shown determines the switching of the intake air volume measurement method. Specifically, first, it determines whether the opening area St of the throttle valve 14 is less than the opening area Sn of the negative pressure generating valve 18 (St < Sn) (step S1). If the determination in step S1 is "No", that is, the opening area St of the throttle valve 14 is greater than the opening area Sn of the negative pressure generating valve 18 (St > Sn), the process proceeds to step S4, and the switching determination flag Fc is deactivated (Fc = 0).

[0035] On the other hand, if the determination in step S1 is "Yes", that is, in the state where the opening area St of the throttle valve 14 is less than the opening area Sn of the negative pressure generating valve 18 (St < Sn), then it is determined whether the operating state of the internal combustion engine 1 belongs to the specified "abrupt transition state", that is, whether it is in the state where the transition determination flag is set (Ft=1) (step S2). If the determination in step S2 is "No", that is, in the state where the transition determination flag is released (Ft=0), the process proceeds to step S4, and the switching determination flag Fc is released (Fc=0).

[0036] On the other hand, if the result in step S2 is "Yes", that is, in the state where the transition determination flag is set (Ft=1), in the next step S3, the switching determination flag Fc is set (Fc=1), and this control flow ends.

[0037] Figure 4 A timing diagram related to the air-fuel ratio control of engine controller 15 is shown. Furthermore, in Figure 4 In order to simplify the following explanation, the opening area of ​​the negative pressure generating valve 18 is set to be constant and is shown in the figure. However, the opening area of ​​the negative pressure generating valve 18 will of course vary according to the operating state of the internal combustion engine 1, that is, the negative pressure generation request of the internal combustion engine 1.

[0038] Based on time sequence diagrams, for those based on Figure 3 The air-fuel ratio control of the engine controller 15, as previously described, will be explained, for example, Figure 4 As shown, until time t0 to t1, the requested engine torque (engine load) of internal combustion engine 1 does not change significantly, thus deactivating the transition judgment flag Ft (Ft=0). Therefore, the air volume, which forms the basis for air-fuel ratio control, is selected as the intake air volume A1 directly measured by the air flow meter 19 (refer to...). Figure 2 (b)).

[0039] Furthermore, within the time interval t1 to t3, a so-called "abrupt transition state" occurs where the rate of change of engine torque (engine load) increases to a value greater than or equal to a predetermined value, and this state is marked with a transition determination flag Ft (Ft=1). Additionally, within the time interval t1 to t2 of the time interval marked with transition determination flag Ft, if the opening area St of the throttle valve 14 is less than the opening area Sn of the negative pressure generating valve 18 (St<Sn), this state is marked with a switching determination flag Fc (Fc=1).

[0040] Therefore, within the interval t1 to t2, by switching the setting of the judgment flag Fc, the intake air volume A2 (as calculated based on the throttle opening) is selected for the air volume that forms the basis of air-fuel ratio control. Figure 2 (c) This results in a response delay when detecting the intake air volume, compared to the direct measurement achieved by the air flow meter 19 (see [reference]). Figure 4 (e) relative to the dashed line, the intake air volume A (refer to) that can be supplied with respect to the requested engine torque (engine load) T of the internal combustion engine 1. Figure 4 (e) solid line). As a result, it can suppress Figure 4 (f) The large variation in the air-fuel ratio A / F, indicated by the dashed line, should be appropriately maintained. Figure 4 The air-fuel ratio A / F is shown by the solid line in (f).

[0041] Then, after time t2, the opening area St of the throttle valve 14 becomes greater than the opening area Sn of the negative pressure generating valve 18 (refer to...). Figure 4(a) The state of the switching decision flag Fc has been cleared (Fc=0) (refer to Figure 4 (d)). Therefore, the air volume that forms the basis for air-fuel ratio control is, as is usually the intake air volume A1 directly measured by the air flow meter 19 (refer to...). Figure 4 (e)). After time t2, the opening area St of the throttle valve 14 is greater than the opening area Sn of the negative pressure generating valve 18 (St>Sn), so the detection of the intake air volume by the air flow meter 19 will not produce a large response delay, and the intake air volume A corresponding to the requested engine torque (engine load) T of the internal combustion engine 1 (refer to) Figure 4 (e) solid line).

[0042] (Effects of this implementation method)

[0043] In the aforementioned conventional control methods for internal combustion engines, no consideration was given to the measurement of intake air volume under the "abrupt transition state" described above. Therefore, the air flow meter experiences a response delay in detecting the intake air volume, making it difficult to accurately detect the intake air volume; there is room for improvement in this regard.

[0044] In contrast, the internal combustion engine control method of this embodiment, under normal circumstances, selects the intake air volume A1 directly measured by the air flow meter 19 as the air volume based on air-fuel ratio control. When the opening area St of the throttle valve 14 is less than the opening area Sn of the negative pressure generating valve 18, and during a predetermined transition state, i.e., a "sharp transition state," it selects the intake air volume A2, which is not dependent on the air flow meter 19, but is calculated based on, for example, the throttle opening, as the air volume based on air-fuel ratio control. This suppresses the response delay in detecting the intake air volume, supplies the intake air volume A corresponding to the requested engine torque (engine load) T of the internal combustion engine 1, and improves the accuracy of air-fuel ratio control.

[0045] Furthermore, in the aforementioned calculation of the intake air volume A2, in this embodiment, it is preferable that the intake air volume is calculated in the throttle-opening-based air volume estimation control unit B2 based on the throttle opening obtained from the output signal of the throttle position sensor 31 and the ENG speed obtained from the output signal of the crankshaft angle sensor 32. In other words, in the aforementioned calculation of the intake air volume A2, the throttle opening obtained from the output signal of the throttle position sensor 31 and the ENG speed obtained from the output signal of the crankshaft angle sensor 32 are necessary parameters related to the aforementioned calculation of the intake air volume A2, while the upstream throttle pressure obtained from the output signal of the upstream throttle pressure sensor 35 is any parameter that contributes to improving the accuracy of the calculation of the intake air volume A2.

[0046] Furthermore, in the throttle opening-based air volume estimation control unit B2, the intake air volume A2 is calculated based on the throttle opening obtained from the output signal of the throttle position sensor 31 and the ENG speed obtained from the output signal of the crankshaft angle sensor 32. Therefore, this intake air volume A2 does not include the amount of leaked gas, and the intake air volume estimation calculation can be performed at the same control level as the intake air volume A1 directly measured by the air flow meter 19. As a result, the control structure related to this intake air volume estimation calculation can be simplified.

[0047] [Second Implementation]

[0048] Figure 5 This invention illustrates a second embodiment of the control method and control device for an internal combustion engine, which performs estimated control of the intake air volume in a manner different from the first embodiment described above. Furthermore, the basic structure, except for this point of change, is the same as in the first embodiment. Therefore, descriptions of structures identical to those in the first embodiment are omitted by using the same reference numerals.

[0049] (Structure of the control device for an internal combustion engine)

[0050] Figure 5 The diagram shows a control module related to the air-fuel ratio control of the engine controller 15 according to this embodiment. (a) shows an overall view of the control module. (b) shows an output method based on the intake air volume measured by an air flow meter. (c) shows an output method based on the intake air volume calculated by estimation.

[0051] like Figure 5 As shown in (a), the engine controller 15 according to this embodiment includes an AFM signal physical quantity conversion unit B1, a model-based air quantity estimation control unit B6, a manifold pressure calculation unit B4, a cylinder intake air quantity switching determination unit B7, and a cylinder intake air quantity calculation unit B5. Here, the model-based air quantity estimation control unit B6 performs intake air quantity estimation calculation relative to the intake air quantity estimation calculation unit of the present invention. This intake air quantity estimation calculation estimates the intake air quantity based on the manifold pressure obtained from the output signal of the manifold pressure sensor 36, the ENG speed obtained from the output signal of the crankshaft angle sensor 32, the valve timing obtained from the output signal of the cam angle sensor 37, and the exhaust pressure obtained through estimation calculation. The cylinder intake air quantity switching determination unit B7 determines the switching method of the measurement of the air quantity (intake air quantity) introduced into the cylinder 2, for example, according to the driver's settings or the operating state of the internal combustion engine 1.

[0052] According to this structure, in this embodiment, when the cylinder intake air volume switching determination unit B7 determines that it does not belong to the aforementioned "abrupt transition state" (see reference...) Figure 3 In the case of step S2), such as Figure 5 As shown in (b), the intake air volume obtained by converting the output signal (AFM signal) of the air flow meter 19, i.e., the intake air volume A1 directly measured by the air flow meter 19, is output as the air volume that forms the basis for air-fuel ratio control. Furthermore, this intake air volume A1 is obtained by measuring the amount of air passing through the air flow meter 19, and it does not include any leakage gas. Next, the manifold pressure is calculated based on this intake air volume A1, and the intake air volume A calculated based on the manifold pressure, the ENG speed obtained from the output signal of the crankshaft angle sensor 32, and the valve timing obtained from the output signal of the cam angle sensor 37 is output.

[0053] On the other hand, when the cylinder intake air volume switching determination unit B7 determines that it belongs to the aforementioned "abrupt transition state", such as Figure 5 As shown in (c), the intake air volume A3, estimated in the model-based air volume estimation control unit B6 based on the manifold pressure obtained from the output signal of the manifold pressure sensor 36, the ENG speed obtained from the output signal of the crankshaft angle sensor 32, the valve timing obtained from the output signal of the camshaft angle sensor 37, and the exhaust pressure calculated according to the estimation, is output as the air volume that forms the basis for air-fuel ratio control. Furthermore, this intake air volume A3 is calculated taking into account the manifold pressure, and includes not only the intake air volume of fresh air but also the amount of leaked gas. Next, the intake air volume A, which is calculated based on the intake air volume A3, the ENG speed obtained from the output signal of the crankshaft angle sensor 32, and the valve timing obtained from the output signal of the camshaft angle sensor 37, is output.

[0054] (Effects of this implementation method)

[0055] As described above, in this embodiment, when the opening area St of the throttle valve 14 is less than the opening area Sn of the negative pressure generating valve 18 (St < Sn), during the aforementioned "abrupt transition state," instead of the intake air volume A2 estimated based on the throttle opening described in the first embodiment, the intake air volume A3 estimated based on the manifold pressure, ENG speed, valve timing, and exhaust pressure is selected as the air volume that forms the basis for air-fuel ratio control. Therefore, the response delay in detecting the intake air volume can be suppressed, and the intake air volume A corresponding to the requested engine torque (engine load) T of the internal combustion engine 1 is supplied. In the model-based air volume estimation control described in this embodiment, higher measurement accuracy than the throttle opening-based air volume estimation control described in the first embodiment can be ensured.

[0056] Furthermore, in the aforementioned calculation of the intake air volume A3, in this embodiment, it is preferable that the intake air volume is calculated in the model-based air volume estimation control unit B6 based on the manifold pressure obtained from the output signal of the manifold pressure sensor 36 and the ENG speed obtained from the output signal of the crankshaft angle sensor 32. In other words, in the aforementioned calculation of the intake air volume A3, the manifold pressure obtained from the output signal of the manifold pressure sensor 36 and the ENG speed obtained from the output signal of the crankshaft angle sensor 32 are necessary parameters related to the aforementioned calculation of the intake air volume A3. The valve timing obtained from the output signal of the cam angle sensor 37 and the exhaust pressure obtained through the estimation calculation are arbitrary parameters that contribute to improving the accuracy of the calculation of the intake air volume A3.

[0057] The present invention is not limited to the structures illustrated in the foregoing embodiments, and can be freely modified according to the specifications of the internal combustion engine to which the present invention is applied.

[0058] In summary, the foregoing embodiments illustrate the application of the internal combustion engine control method and control device of the present invention to an internal combustion engine having a blow-by gas reduction device. However, the present invention can also be applied to an internal combustion engine having an EGR system that recirculates a portion of the exhaust gas as EGR. When applied to an internal combustion engine having such an EGR system, the same effect is achieved as when applied to an internal combustion engine having the aforementioned blow-by gas reduction device.

Claims

1. A control method for an internal combustion engine, the internal combustion engine comprising a throttle valve disposed in an intake passage, a turbocharger disposed upstream of the throttle valve, a negative pressure generating valve disposed upstream of the turbocharger, and an air flow meter disposed upstream of the negative pressure generating valve. In this control method for internal combustion engines, Based on the output of the air flow meter, the amount of intake air, which forms the basis for air-fuel ratio control, is measured. Furthermore, when the opening area of ​​the throttle valve is smaller than the opening area of ​​the negative pressure generating valve, and the internal combustion engine is in a specified transition state, an estimation calculation of the intake air volume is performed independently of the air flow meter.

2. The control method for an internal combustion engine according to claim 1, wherein, The estimated intake air volume is calculated based on the opening degree of the throttle valve and the speed of the internal combustion engine.

3. The control method for an internal combustion engine according to claim 1, wherein, The estimated intake air volume is calculated based on the pressure inside the main pipe of the intake manifold connected to the intake passage and the rotational speed of the internal combustion engine.

4. The control method for an internal combustion engine according to any one of claims 1 to 3, wherein, The negative pressure generating valve is controlled to open and close to allow for the return of leaked gas or EGR.

5. A control device for an internal combustion engine, the internal combustion engine comprising a throttle valve disposed in an intake passage, a turbocharger disposed upstream of the throttle valve, a negative pressure generating valve disposed upstream of the turbocharger, and an air flow meter disposed upstream of the negative pressure generating valve. The control device of this internal combustion engine has: The intake air volume measurement unit measures the intake air volume, which forms the basis for air-fuel ratio control, based on the output of the air flow meter; and The intake air volume estimation unit performs intake air volume estimation calculations independent of the air flow meter when the opening area of ​​the throttle valve is smaller than the opening area of ​​the negative pressure generating valve and the internal combustion engine is in a specified transition state.

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