Method for controlling internal combustion engine and control device of internal combustion engine

Abstract

In a method for controlling an internal combustion engine and a control device of an internal combustion engine according to the present invention, normally, an intake air volume (A1) directly measured by an air flow meter (19) is selected as the air volume to serve as the basis for air-fuel ratio control, but when in a transient state in a condition in which the opening area (St) of a throttle valve (14) is smaller than the opening area (Sn) of a negative pressure-generating valve (18), the air flow meter (19) is not relied upon and, for example, an intake air volume (A2) computed by estimation on the basis of the throttle opening ratio is selected as the air volume to serve as the basis for air-fuel ratio control. This suppresses a response delay in the detection of the intake air volume, making it possible to supply the intake air volume (A) in accordance with the engine torque (T) required by the internal combustion engine (1), and an improvement in the accuracy of air-fuel ratio control can be attained.

Description

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

[0001] The present invention relates to a control method for an internal combustion engine and a control device for an internal combustion engine.

[0002] Generally, in a control method for an internal combustion engine, as described in Patent Document 1 below, the intake air amount is directly detected by an air flow meter, and also the internal combustion engine is controlled by estimating the intake air amount based on predetermined parameters without relying on the air flow meter.

[0003] For example, in a turbocharged engine, it may be difficult to accurately detect the intake air volume using an air flow meter in the surge region of the turbocharger, the pulsation region at low speed and high load, etc. Therefore, when it is difficult to accurately detect the intake air volume using an air flow meter, such as in the surge region or pulsation region, a method is adopted in engine control to estimate the intake air volume based on predetermined parameters without using the detection value of the air flow meter.

[0004] Furthermore, some engines recirculate a portion of the exhaust gas (blow-by gas and EGR) back into the intake. In this case, a vacuum generating valve that assists in generating vacuum is disposed upstream of the turbocharger to efficiently recirculate the blow-by gas and EGR. In such systems, in a sudden transient state, a delay occurs in the detection of the intake air volume by the air flow meter, making it difficult to accurately detect the intake air volume, and there is still room for improvement.

[0005] Japanese Patent Application Laid-Open No. 2021-050632

[0006] One aspect of the present invention is a control method for an internal combustion engine including a throttle valve provided in an intake passage, a supercharger provided upstream of the throttle valve, a negative pressure generation valve provided upstream of the supercharger, and an air flow meter provided upstream of the negative pressure generation valve, wherein the intake air amount that forms the basis of air-fuel ratio control is measured based on the output of the air flow meter, and when the opening area of ​​the throttle valve is smaller than the opening area of ​​the negative pressure generation valve and the internal combustion engine is in a predetermined transient state, an intake air amount estimation calculation is performed that does not rely on the air flow meter.

[0007] In this way, the intake air amount is normally measured directly by the air flow meter, and when the internal combustion engine is in a predetermined transient state, an intake air amount is estimated without relying on the air flow meter. This suppresses the delay in detecting the intake air amount based on the air flow meter measurement that occurs in the transient state, and enables the intake air amount that serves as the basis for air-fuel ratio control of the internal combustion engine to be output with high accuracy.

[0008] It is a schematic diagram of an internal combustion engine according to the present invention. It is a control block diagram of an ECU according to a first embodiment of the present invention. It is a flowchart of air-fuel ratio control of the ECU shown in Figure 1. It is a time chart related to air-fuel ratio control of the ECU shown in Figure 1. It is a control block diagram of an ECU according to a second embodiment of the present invention.

[0009] Hereinafter, embodiments of a method for controlling an internal combustion engine and a control device for an internal combustion engine according to the present invention will be described in detail with reference to the drawings. Note that in each of the following embodiments, an embodiment in which the method for controlling an internal combustion engine and the control device for an internal combustion engine according to the present invention are applied to a gasoline engine with a supercharger will be described.

[0010] (Configuration of Internal Combustion Engine) FIG. 1 shows a schematic diagram of a gasoline engine with a supercharger according to this embodiment.

[0011] For example, as shown in FIG. 1, the internal combustion engine 1 is a spark ignition engine equipped with a turbocharger as a supercharger, and includes a cylinder 2 having a combustion chamber 2 a therein, and a crankcase 3 .

[0012] An intake passage 11 of the internal combustion engine 1 has an air cleaner 12 at its inlet, which is the upstream end, and a turbocharger compressor 13 located midway through the passage. A throttle valve 14, which controls the amount of intake air into the internal combustion engine 1, is located downstream of the compressor 13, is equipped with an electric actuator such as a motor, and is a so-called electronically controlled throttle valve whose opening is controlled by an engine controller 15. An intercooler 16 is located 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 an intake collector 17, which is a collector of the intake manifold, from which multiple intake branch pipes 17a branch out, leading to each cylinder. The intake collector 17 is also equipped with a boost pressure sensor 20 for detecting the intake air pressure (boost pressure).

[0013] A vacuum generating valve 18 is provided in the intake passage 11 upstream of the compressor 13 to generate vacuum in the region between the compressor 13 and the intake passage 11. The vacuum generating valve 18 has a butterfly valve-type configuration similar to the throttle valve 14, and its opening is controlled by the engine controller 15 via an electric actuator so as to generate the vacuum required depending on the operating conditions of the internal combustion engine 1. The provision of the vacuum generating valve 18 makes it possible to generate the vacuum required depending on the operating conditions of the internal combustion engine 1, thereby contributing to the appropriate recirculation of blow-by gas or EGR (Exhaust Gas Recirculation), as described below. An air flow meter 19 is provided upstream of the vacuum generating valve 18, i.e., between the vacuum generating valve 18 and the air cleaner 12, to detect the amount of intake air 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 meter may also be used.

[0014] In an internal combustion engine, gas containing unburned components, i.e., blow-by gas, leaks from the combustion chamber 2a of each cylinder into the crankcase 3. This blow-by gas is guided to a first oil separator chamber 6 provided at 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 formed at the top of the cylinder head cover 5, and the second oil separator chamber 7 communicates with the space inside the cylinder head, which is connected to the crankcase 3.

[0015] The internal combustion engine 1 is also provided with a blow-by gas return system that recirculates blow-by gas by returning it to the intake passage 11. This blow-by gas return system has a fresh air introduction pipe 21 that introduces fresh air into the crankcase 3, a first blow-by gas pipe 22 that guides the blow-by gas to the upstream side of the compressor 13 in the intake passage 11, and a second blow-by gas pipe 23 that guides the blow-by gas to the downstream side of the throttle valve 14 in the intake passage 11.

[0016] One end of the fresh air introduction pipe 21, which is the upstream end in the flow of fresh air, is connected upstream of the negative pressure generating valve 18 of the intake passage 11, and the other end, which is the downstream end in the flow of fresh air, is connected to the second oil separator chamber 7 of the internal combustion engine 1. Here, the air flow meter 19 is located upstream of the connection position of the upstream end of the fresh air introduction pipe 21 in the intake passage 11, and measures the gas flow rate including the fresh air flowing into the fresh air introduction pipe 21 as the intake air amount.

[0017] The first blow-by gas pipe 22 has one end, which is the upstream end in the flow of blow-by gas, connected to the first oil separator chamber 6 of the internal combustion engine 1, and the other end, which is the downstream end in the flow of blow-by gas, connected between the negative pressure generating valve 18 and the compressor 13 in the intake passage 11. A one-way valve 25 is provided at the connection between the first blow-by gas pipe 22 and the first oil separator chamber 6, and allows only gas to flow from the crankcase 3 (first oil separator chamber 6) to the intake passage 11. The one-way valve 25 is a mechanical check valve having, for example, an umbrella-shaped valve element that opens and closes in response to a pressure difference, and the one-way valve 25 prevents backflow from the intake passage 11 side toward the crankcase 3.

[0018] The second blow-by gas pipe 23 has one end, which is the upstream end in the flow of blow-by gas, connected to the first oil separator chamber 6 of the internal combustion engine 1, and the other end, which is the downstream end in the flow of blow-by gas, connected to the downstream side of the throttle valve 14 of the intake passage 11, specifically to the intake collector 17. A PCV valve 26 that mechanically adjusts the flow rate of blow-by gas in accordance with the pressure difference is provided at the connection between the second blow-by gas pipe 23 and the first oil separator chamber 6. The PCV valve 26 also functions as a check valve that blocks the flow of gas from the intake collector 17 side toward the first oil separator chamber 6 side.

[0019] In addition to the air flow meter 19, the engine controller 15 receives detection signals from various sensors, such as a throttle position sensor 31 indicating the throttle opening, a crank angle sensor 32 indicating the rotational speed of the internal combustion engine 1, an air-fuel ratio sensor 33 detecting the exhaust air-fuel ratio in an exhaust passage (not shown), a water temperature sensor 34 indicating the coolant temperature, a throttle upstream pressure sensor 35 which is a pressure sensor indicating the throttle upstream pressure which is the pressure upstream of the throttle valve 14, a collector pressure sensor 36 which is a pressure sensor indicating the pressure in the intake collector 17, a cam angle sensor 37 which indicates valve timing, and an intake air temperature sensor 38 which indicates the intake air temperature. The engine controller 15 then executes various controls of the internal combustion engine 1, such as control of the fuel injection amount and injection timing by a fuel injection valve (not shown) of the internal combustion engine 1, control of ignition timing by a spark plug (not shown), control of the opening amount of the throttle valve 14, the vacuum generating valve 18, etc., control of the boost pressure of a turbocharger, etc.

[0020] [First Embodiment] A first embodiment of a method for controlling an internal combustion engine and a control device for an internal combustion engine according to the present invention will be described below with reference to Figs.

[0021] (Configuration of Control Device for Internal Combustion Engine) FIG. 2 shows a control block diagram relating to the air-fuel ratio control of the engine controller 15 according to this embodiment, where (a) is an overall control block diagram, (b) shows an output mode of the intake air amount based on measurement by an air flow meter, and (c) shows an output mode of the intake air amount based on an estimated calculation.

[0022] 2A, the engine controller 15 according to this embodiment includes an AFM signal-to-physical quantity converter B1, a throttle position-based air volume estimation controller B2, a throttle-passing air volume switching determiner B3, a collector pressure calculator B4, and a cylinder intake air volume calculator B5. The AFM signal-to-physical quantity converter B1 corresponds to the intake air volume measuring unit of the present invention and converts the AFM signal, which is the output signal from the air flow meter 19, to measure the intake air volume. The throttle position-based air volume estimation controller B2 corresponds to the intake air volume estimation calculator of the present invention and performs an intake air volume estimation calculation to estimate the intake air volume based on the throttle position obtained from the output signal of the throttle position sensor 31, the engine speed obtained from the output signal of the crank angle sensor 32, and the throttle upstream pressure obtained from the output signal of the throttle upstream pressure sensor 35. A throttle-passing air amount switching determination unit B3 determines whether to switch the measurement method for the amount of air passing through the throttle valve 14 (intake air amount) depending on, for example, the driver's setting or the operating state of the internal combustion engine 1. A collector pressure calculation unit B4 calculates the internal pressure (collector pressure) of the intake collector 17 based on the output signal of the AFM signal-to-physical quantity conversion unit B1 or the throttle opening-based air amount estimation control unit B2 input via the throttle-passing air amount switching determination unit B3. A cylinder intake air amount calculation unit B5 calculates the amount of intake air introduced into the cylinder 2 based on the ENG rotation speed obtained from the output signal of the crank angle sensor 32 and the valve timing obtained from the output signal of the cam angle sensor 37.

[0023] In this embodiment, when the throttle-passing air amount switching determination unit B3 determines that the current state is not in a "rapid transient state," as will be described later with reference to FIG. 3, the intake air amount obtained by converting the output signal (AFM signal) of the air flow meter 19, i.e., the intake air amount A1 directly measured by the air flow meter 19, is output as the air amount serving as the basis for air-fuel ratio control, as shown in FIG. 2(b). Note that this intake air amount A1 is the amount of air that has passed through the air flow meter 19 and does not include the amount of blow-by gas. Next, the collector pressure is calculated based on this intake air amount A1, and the intake air amount A calculated based on this collector pressure, the engine speed obtained from the output signal of the crank angle sensor 32, and the valve timing obtained from the output signal of the cam angle sensor 37 is output.

[0024] On the other hand, when the throttle-passing air volume switching determination unit B3 determines that the current state corresponds to a "sudden transient state" (described later with reference to FIG. 3), as shown in FIG. 2C, the throttle-opening-based air volume estimation control unit B2 estimates an intake air volume A2 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 crank angle sensor 32, and the throttle upstream pressure obtained from the output signal of the throttle upstream pressure sensor 35, and outputs the estimated intake air volume A2 as the air volume serving as the basis for air-fuel ratio control. Note that this intake air volume A2 is estimated based on the throttle opening, and the intake air volume A1 does not include the amount of blow-by gas. Next, the collector pressure is calculated based on this intake air volume A2, and the intake air volume A calculated based on this collector pressure, the ENG speed obtained from the output signal of the crank angle sensor 32, and the valve timing obtained from the output signal of the cam angle sensor 37 is output.

[0025] (Control Method of Internal Combustion Engine) FIG. 3 shows a control flowchart of air-fuel ratio control in the engine controller 15. As shown in FIG.

[0026] In the engine controller 15 according to this embodiment, the throttle passing air amount switching determination section B3 shown in Fig. 2 determines whether or not the metering method for the intake air amount should be switched based on the control flow shown in Fig. 3. Specifically, first, it is determined (step S1) whether the opening area St of the throttle valve 14 is smaller than the opening area Sn of the vacuum generation valve 18 (St<Sn). If the result of step S1 is "No," that is, if it is determined that the opening area St of the throttle valve 14 is larger than the opening area Sn of the vacuum generation valve 18 (St>Sn), the process proceeds to step S4, where the switching determination flag Fc is reset (Fc=0).

[0027] On the other hand, if step S1 returns "Yes," that is, if it is determined that the opening area St of the throttle valve 14 is smaller than the opening area Sn of the vacuum generating valve 18 (St<Sn), then it is determined (step S2) whether the operating state of the internal combustion engine 1 corresponds to a predetermined "sudden transient state," that is, whether the transient determination flag is set (Ft=1). If step S2 returns "No," that is, if it is determined that the transient determination flag is cleared (Ft=0), the process proceeds to step S4, where the switching determination flag Fc is cleared (Fc=0).

[0028] On the other hand, if the answer in step S2 is "Yes", that is, if it is determined that the transient determination flag is set (Ft = 1), then in the next step S3, the switching determination flag Fc is set (Fc = 1), and this control flow ends.

[0029] 4 shows a time chart relating to the air-fuel ratio control in the engine controller 15. Note that in FIG. 4, for the sake of simplicity of the explanation that will be given later, the opening area of ​​the negative pressure generating valve 18 is shown as being constant, but it goes without saying that the opening area of ​​the negative pressure generating valve 18 varies depending on the operating state of the internal combustion engine 1, i.e., the negative pressure generation requirement of the internal combustion engine 1.

[0030] 3 will be explained based on a time chart. For example, as shown in Figure 4, from time t0 to time t1, the required engine torque (engine load) of the internal combustion engine 1 does not fluctuate significantly, and the transient determination flag Ft is cleared (Ft = 0). Therefore, the intake air amount A1 directly measured by the air flow meter 19 is selected as the air amount that forms the basis of the air-fuel ratio control (see Figure 2(b)).

[0031] In the time period from t1 to t3, the rate of change of the engine torque (engine load) increases to or exceeds a predetermined value, which is called a "sudden transient state," and the transient determination flag Ft is set (Ft = 1). Furthermore, during the time period from t1 to t2 during which the transient determination flag Ft is set, the opening area St of the throttle valve 14 is smaller than the opening area Sn of the vacuum generating valve 18 (St < Sn), and the switching determination flag Fc is set (Fc = 1).

[0032] Therefore, in the section t1 to t2, the switching determination flag Fc is set, and the intake air amount A2 estimated based on the throttle opening is selected as the air amount that serves as the basis for air-fuel ratio control (see FIG. 2(c)). This allows the intake air amount A to be supplied in accordance with the required engine torque (engine load) T of the internal combustion engine 1 (see the solid line in FIG. 4(e)), whereas direct measurement using the air flow meter 19 would result in a response delay in detecting the intake air amount (see the dashed line in FIG. 4(e)). As a result, large fluctuations in the air-fuel ratio A / F, shown by the dashed line in FIG. 4(f), are suppressed, and the air-fuel ratio A / F, shown by the solid line in FIG. 4(f), can be appropriately maintained.

[0033] Subsequently, after time t2, the opening area St of the throttle valve 14 becomes larger than the opening area Sn of the vacuum generating valve 18 (see FIG. 4A), and the switching determination flag Fc is cleared (Fc=0) (see FIG. 4D). As a result, the intake air amount A1 directly measured by the air flow meter 19 is selected as the air amount used as the basis for air-fuel ratio control, as usual (see FIG. 4E). Since the opening area St of the throttle valve 14 is larger than the opening area Sn of the vacuum generating valve 18 (St>Sn) after time t2, no significant response delay occurs in the detection of the intake air amount by the air flow meter 19, and the intake air amount A corresponding to the required engine torque (engine load) T of the internal combustion engine 1 can be supplied (see the solid line in FIG. 4E).

[0034] (Effects of the Present Embodiment) The conventional control method for an internal combustion engine does not take into consideration the method for measuring the intake air amount in the above-mentioned "sudden transient state." As a result, a response delay occurs in the detection of the intake air amount by the air flow meter, making it difficult to accurately detect the intake air amount, and there is still room for improvement.

[0035] In contrast, in the control method for an internal combustion engine according to this embodiment, the intake air amount A1 measured directly by the air flow meter 19 is normally selected as the air amount on which air-fuel ratio control is based, but when the engine is in a predetermined transient state, i.e., a "rapid transient state," with the opening area St of the throttle valve 14 smaller than the opening area Sn of the negative pressure generating valve 18, an intake air amount A2 estimated and calculated, for example, based on the throttle opening, without relying on the air flow meter 19 is selected as the air amount on which air-fuel ratio control is based. This suppresses response delays in the detection of the intake air amount, making it possible to supply an intake air amount A corresponding to the required engine torque (engine load) T of the internal combustion engine 1, and improving the accuracy of air-fuel ratio control.

[0036] In addition, in this embodiment, when estimating the intake air amount A2, it is desirable that the throttle opening-based air amount estimation control unit B2 calculates the intake air amount based on the throttle opening obtained from the output signal of the throttle position sensor 31 and the ENG rotation speed obtained from the output signal of the crank angle sensor 32. In other words, when estimating the intake air amount A2, the throttle opening obtained from the output signal of the throttle position sensor 31 and the ENG rotation speed obtained from the output signal of the crank angle sensor 32 are essential parameters for estimating the intake air amount A2, and the throttle upstream pressure obtained from the output signal of the throttle upstream pressure sensor 35 is an optional parameter that contributes to improving the accuracy of the estimation of the intake air amount A2.

[0037] Furthermore, throttle opening-based air amount estimation control section B2 calculates intake air amount A2 based on the throttle opening obtained from the output signal of throttle position sensor 31 and the ENG rotation speed obtained from the output signal of crank angle sensor 32, so that intake air amount A2 does not include the amount of blow-by gas, and intake air amount estimation calculation can be performed at the same control level as intake air amount A1 directly measured by air flow meter 19. This makes it possible to simplify the control structure related to the intake air amount estimation calculation.

[0038] [Second Embodiment] Figure 5 shows a second embodiment of the control method for an internal combustion engine and the control device for an internal combustion engine according to the present invention, which estimates and controls the intake air amount using a method different from that of the first embodiment. Note that the basic configuration other than the above changes is the same as that of the first embodiment. Therefore, the same components as those of the first embodiment are denoted by the same reference numerals, and a description thereof will be omitted.

[0039] (Configuration of Control Device for Internal Combustion Engine) FIG. 5 shows a control block diagram relating to the air-fuel ratio control of the engine controller 15 according to this embodiment, where (a) is an overall control block diagram, (b) shows the output mode of the intake air amount based on measurement by an air flow meter, and (c) shows the output mode of the intake air amount based on an estimated calculation.

[0040] 5A, the engine controller 15 according to this embodiment includes an AFM signal-to-physical quantity converter B1, a model-based air amount estimation controller B6, a collector pressure calculator B4, a cylinder intake air amount switching determination unit B7, and a cylinder intake air amount calculator B5. The model-based air amount estimation controller B6 corresponds to the intake air amount estimation unit according to the present invention and performs an intake air amount estimation calculation to estimate the intake air amount based on the collector pressure obtained from the output signal of the collector pressure sensor 36, the engine speed obtained from the output signal of the crank angle sensor 32, the valve timing obtained from the output signal of the cam angle sensor 37, and the exhaust pressure determined by the estimation calculation. The cylinder intake air amount switching determination unit B7 determines whether to switch the measurement method for the amount of air introduced into the cylinder 2 (intake air amount) depending on, for example, the driver's settings or the operating state of the internal combustion engine 1.

[0041] In this embodiment, when the cylinder intake air amount switching determination unit B7 determines that the current state is not in the "abrupt transient state (see step S2 in FIG. 3)," the intake air amount obtained by converting the output signal (AFM signal) of the air flow meter 19, i.e., the intake air amount A1 directly measured by the air flow meter 19, is output as the air amount serving as the basis for air-fuel ratio control, as shown in FIG. 5(b). Note that this intake air amount A1 is the amount of air that has passed through the air flow meter 19 and does not include the amount of blow-by gas. Next, the collector pressure is calculated based on this intake air amount A1, and the intake air amount A calculated based on this collector pressure, the engine speed obtained from the output signal of the crank angle sensor 32, and the valve timing obtained from the output signal of the cam angle sensor 37 is output.

[0042] On the other hand, if the cylinder intake air amount switching determination unit B7 determines that the current state corresponds to the aforementioned "sudden transient state," as shown in FIG. 5C, the model-based air amount estimation control unit B6 estimates an intake air amount A3 based on the collector pressure obtained from the output signal of the collector pressure sensor 36, the ENG speed obtained from the output signal of the crank angle sensor 32, the valve timing obtained from the output signal of the cam angle sensor 37, and the exhaust pressure obtained by estimation calculation, and outputs the estimated intake air amount A3 as the air amount serving as the basis for air-fuel ratio control. Note that this intake air amount A3 is calculated taking into account the collector pressure, and includes not only the amount of fresh intake air but also the amount of blow-by gas. Next, the intake air amount A calculated based on this intake air amount A3, the ENG speed obtained from the output signal of the crank angle sensor 32, and the valve timing obtained from the output signal of the cam angle sensor 37 is output.

[0043] (Effects of the Present Embodiment) As described above, in the present embodiment, when the opening area St of the throttle valve 14 is smaller than the opening area Sn of the negative pressure generating valve 18 (St<Sn) and the engine is in the "sudden transient state," the intake air amount A3 estimated based on the collector pressure, ENG speed, valve timing, and exhaust pressure is selected as the air amount serving as the basis for air-fuel ratio control, instead of the intake air amount A2 estimated and calculated based on the throttle opening according to the first embodiment. This not only suppresses response delays in intake air amount detection and makes it possible to supply the intake air amount A corresponding to the required engine torque (engine load) T of the internal combustion engine 1, but also ensures higher measurement accuracy with the model-based air amount estimation control according to the present embodiment than with the throttle opening-based air amount estimation control according to the first embodiment.

[0044] In this embodiment, when estimating the intake air amount A3, it is desirable that the model-based air amount estimation control unit B6 calculates the intake air amount based on the collector pressure obtained from the output signal of the collector pressure sensor 36 and the ENG rotation speed obtained from the output signal of the crank angle sensor 32. In other words, when estimating the intake air amount A3, the collector pressure obtained from the output signal of the collector pressure sensor 36 and the ENG rotation speed obtained from the output signal of the crank angle sensor 32 are essential parameters for estimating the intake air amount A3, and the valve timing obtained from the output signal of the cam angle sensor 37 and the exhaust pressure determined by the estimation calculation are optional parameters that contribute to improving the accuracy of the estimation calculation of the intake air amount A3.

[0045] The present invention is not limited to the configurations exemplified in the above-described embodiments, but can be freely modified according to, for example, the specifications of the internal combustion engine to which the present invention is applied.

[0046] In particular, in each of the above embodiments, an example has been given of the application of the internal combustion engine control method and internal combustion engine control device of the present invention to an internal combustion engine having a blow-by gas reduction device, but the present invention can also be applied to an internal combustion engine having, for example, an EGR system that recirculates a portion of the exhaust gas as EGR, and even when applied to an internal combustion engine having such an EGR system, the same effects can be achieved as when applied to an internal combustion engine having the blow-by gas reduction device.

Claims

1. A control method for an internal combustion engine equipped with a throttle valve provided in an intake passage, a turbocharger provided upstream of the throttle valve, a negative pressure generating valve provided upstream of the turbocharger, and an air flow meter provided upstream of the negative pressure generating valve, comprising the steps of: measuring an intake air volume that forms the basis of air-fuel ratio control based on the output of the air flow meter; and performing an intake air volume estimation calculation that does not rely on 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 predetermined transient state.

2. A method for controlling an internal combustion engine as claimed in claim 1, wherein said intake air amount estimation calculation estimates said intake air amount based on the opening of said throttle valve and the rotation speed of said internal combustion engine.

3. A method for controlling an internal combustion engine as claimed in claim 1, wherein the intake air volume estimation calculation estimates the intake air volume based on the pressure inside a collector of an intake manifold connected to the intake passage and the rotation speed of the internal combustion engine.

4. A method for controlling 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 for the recirculation of blow-by gas or EGR.

5. A control device for an internal combustion engine comprising a throttle valve provided in an intake passage, a turbocharger provided upstream of the throttle valve, a negative pressure generating valve provided upstream of the turbocharger, and an air flow meter provided upstream of the negative pressure generating valve, comprising: an intake air amount measuring unit that measures the intake air amount serving as the basis for air-fuel ratio control based on the output of the air flow meter; and an intake air amount estimating unit that performs an intake air amount estimation calculation without relying on 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 predetermined transient state.

Images