JP2023068251A - Control device and control method for internal combustion engine - Google Patents

Abstract

To provide a control device and a control method for an internal combustion engine each of which enables materialization of the target torque of the internal combustion engine even if environmental change occurs,.SOLUTION: A control device and a control method for an internal combustion engine are provided each of which is configured to: calculate a target EGR gas flow volume which passes through an EGR valve (18) of an internal combustion engine (1) on the basis of an operation state of the internal combustion engine (1); convert the target EGR gas flow volume to a target EGR valve opening; calculate a target EGR flow volume upper limit value on the basis of a target pressure ratio being a pressure ratio of the target pressure of the inside of an intake manifold (8) of the internal combustion engine (1) and atmospheric pressure or the throttle upstream-side pressure of the internal combustion engine; calculate an upper limit value of the target EGR valve opening on the basis of at least the target EGR flow volume upper limit value and an acoustic velocity of EGR gas passing through the EGR valve; limit the target EGR gas flow volume by the upper limit value of the target EGR valve opening; and control the opening of the EGR valve (18) on the basis of the limited target EGR valve opening.SELECTED DRAWING: Figure 2

Description

The present application relates to a control device and control method for an internal combustion engine.

In general, internal combustion engines have an important technical problem of improving fuel efficiency. Conventionally, by using an EGR (Exhaust Gas Recirculation) control device that recirculates the exhaust gas that has been burned in the internal combustion engine to the intake side and mixes and burns the fresh air and the exhaust gas that are taken into the internal combustion engine, the pumping loss is reduced. Technologies for improving fuel efficiency have been proposed, such as reduction of , and ignition advance control using knock suppression due to a decrease in combustion temperature.

However, in the EGR control device described above, the recirculated exhaust gas (hereinafter referred to as EGR gas) generally cannot be reburned, and the torque of the internal combustion engine is reduced by the amount of fresh air sucked into the internal combustion engine. based on quantity. Therefore, in order to achieve the target internal combustion engine torque, the necessary amount of fresh air is secured within the limited intake capacity of the internal combustion engine, and the amount of EGR gas is reduced as much as possible within a range that does not cause poor combustion. It is important to increase fuel efficiency by increasing fuel consumption.

2. Description of the Related Art Conventionally, a technique disclosed in Patent Document 1, for example, is known as a control device for an internal combustion engine using an EGR control device. In this conventional technique, a target EGR rate is stored in advance in a map according to the target internal combustion engine torque, and the opening of the EGR valve is controlled based on the stored target EGR rate.

Japanese Patent No. 4061971

In the conventional technique disclosed in Patent Document 1, the target EGR rate is set in advance in a map corresponding to the rotational speed of the internal combustion engine and the target internal combustion engine torque, and the target EGR rate is determined based on this map. However, when the environment changes, for example, when the outside air temperature drops, the air density generally increases. lower. Such a situation can be dealt with by increasing the target EGR rate and further increasing the flow rate of EGR gas. Therefore, even when the EGR flow rate can be increased, it is possible to increase the EGR flow rate by the amount of fresh air volume required to achieve the target internal combustion engine torque, for example, when the outside air temperature drops. However, there is still room for improvement in fuel efficiency.

The present application discloses a technique for solving the above-described problems. Even when an environmental change occurs, the target internal combustion engine torque is achieved, and EGR gas is reduced as much as possible within a range in which poor combustion does not occur. It is an object of the present invention to provide a control device and control method for an internal combustion engine that increases the volume.

The control device for an internal combustion engine disclosed in the present application includes:
a throttle that controls the amount of intake air flowing into the internal combustion engine;
an EGR passage that connects an exhaust pipe of the internal combustion engine and an intake manifold downstream of the throttle and returns part of exhaust gas of the internal combustion engine to the intake manifold;
an EGR valve provided in the EGR passage for controlling the flow rate of EGR gas in the EGR passage;
an operating state detection means for detecting an operating state of the internal combustion engine;
a first means for calculating a target EGR gas flow rate based on the operating state of the internal combustion engine;
a second means for converting the target EGR gas flow rate into a target EGR valve opening;
a third means for calculating a target EGR gas flow rate upper limit value based on a target pressure ratio, which is a pressure ratio between the target pressure inside the intake manifold and the atmospheric pressure or the throttle upstream pressure;
fourth means for calculating a target EGR valve opening upper limit based on at least the target EGR gas flow rate upper limit and the sound velocity of the EGR valve passage gas passing through the EGR valve;
fifth means for limiting the target EGR valve opening degree calculated by the first means by the target EGR valve opening upper limit value calculated by the fourth means;
with
configured to control the opening of the EGR valve based on the target EGR valve opening limited by the fifth means,
It is characterized by

Further, the control method for an internal combustion engine disclosed in the present application includes:
a first step of calculating a target EGR gas flow rate passing through an EGR valve of the internal combustion engine based on an operating state of the internal combustion engine;
a second step of converting the target EGR gas flow rate into a target EGR valve opening;
a third step of calculating a target EGR flow rate upper limit value based on a target pressure ratio, which is a pressure ratio between the target pressure inside the intake manifold of the internal combustion engine and the atmospheric pressure or the throttle upstream pressure of the internal combustion engine;
a fourth step of calculating an upper limit value of the target EGR valve opening based on at least the target EGR flow rate upper limit value and the speed of sound of EGR gas passing through the EGR valve;
a fifth step of limiting the target EGR gas flow rate by an upper limit value of the target EGR valve opening;
has
controlling the opening of the EGR valve based on the restricted target EGR valve opening;
It is characterized by

According to the internal combustion engine control apparatus and control method disclosed in the present application, even when an environmental change occurs, the internal combustion engine can increase the amount of EGR gas as much as possible within a range where poor combustion does not occur while achieving a target internal combustion engine torque. An engine control apparatus and control method are provided.

1 is a configuration diagram showing a control system of an internal combustion engine to which the control device and control method for an internal combustion engine according to Embodiment 1 are applied; FIG. 1 is a block configuration diagram showing a control device for an internal combustion engine according to Embodiment 1; FIG. FIG. 3 is a functional block diagram showing processing in a target EGR valve opening calculation section in the control device for an internal combustion engine according to Embodiment 1; 4 is a functional block diagram showing processing in a target EGR gas flow rate basic value calculation section in the control device for an internal combustion engine according to Embodiment 1; FIG. 3 is a functional block diagram showing processing in a target volumetric efficiency calculation section in the control device for an internal combustion engine according to Embodiment 1; FIG. 3 is a functional block diagram showing processing in EGR gas dimensionless flow rate calculation means in the control device for an internal combustion engine according to Embodiment 1; FIG. FIG. 3 is a functional block diagram showing processing in a target EGR valve opening basic value calculation section in the control device for an internal combustion engine according to Embodiment 1;

A control device and a control method for an internal combustion engine according to Embodiment 1 of the present application will be described below with reference to the drawings. In each figure, the same or corresponding parts are denoted by the same reference numerals.
Embodiment 1.
FIG. 1 is a configuration diagram showing a control system of an internal combustion engine to which an internal combustion engine control device and control method according to Embodiment 1 are applied. In FIG. 1, an air flow sensor 2 for measuring the intake air flow rate Qa to the internal combustion engine 1 and an intake air temperature (hereinafter referred to as "intake air temperature") are provided upstream of an intake passage 6 constituting an intake system of the internal combustion engine 1. An intake air temperature sensor 3 for measuring AT) is provided.

Instead of using the airflow sensor 2 that directly measures the intake air amount Qa, the intake air amount Qa may be estimated from other sensor information. Further, the intake air temperature sensor 3 may be configured integrally with the airflow sensor 2 or may be configured separately from the airflow sensor 2 . Furthermore, instead of using the intake air temperature sensor 3 that directly measures the intake air temperature AT, the intake air temperature AT may be estimated and calculated from other sensor information.

In the intake system of the internal combustion engine 1, a throttle 4 having a valve capable of electronically adjusting the opening area of the intake passage 6 is provided downstream of the airflow sensor 2. As shown in FIG. Further, the throttle 4 is provided with a throttle position sensor 5 for measuring the opening of the valve.

A surge tank 7 that equalizes the pressure inside the intake passage 6 and an intake manifold (hereinafter referred to as "intake manifold") 8 are connected to the downstream side of the throttle 4 . The intake manifold 8 is provided with an intake manifold pressure sensor 9 for measuring the pressure inside the intake manifold (hereinafter referred to as "intake manifold pressure"). The intake manifold pressure may be estimated and calculated from other sensor information instead of the intake manifold pressure sensor 9 that directly measures the intake manifold pressure.

The cylinder head of the internal combustion engine 1 includes an intake valve 11 for adjusting the amount of combustible air-fuel mixture introduced into the cylinder 10 from the intake passage 6, and an exhaust valve for adjusting the amount of exhaust gas discharged from the cylinder 10 to the exhaust passage 12. A valve 13 is provided. The intake valve 11 is provided with an intake valve variable timing mechanism 14 (hereinafter referred to as “IVT”) that changes the opening/closing timing of the intake valve 11 . The exhaust valve 13 is provided with an exhaust valve variable timing mechanism 15 (hereinafter referred to as “EVT”) that changes the opening/closing timing of the exhaust valve 13 .

A cylinder head of the internal combustion engine 1 is provided with an ignition coil (not shown) that drives an ignition plug that generates sparks in the cylinder. In addition, an exhaust manifold downstream of the cylinder and an exhaust pipe downstream of it (hereinafter collectively referred to as "exhaust manifold") are equipped with an O2 sensor 16 for measuring the air-fuel ratio of the exhaust gas and a toxic substance in the exhaust gas. A catalyst (not shown) is provided to purify the A linear A/F sensor may be provided instead of the O2 sensor 16 .

The intake manifold 8 and the exhaust manifold are connected to each other by an EGR passage 17, and the EGR passage 17 is provided with an EGR valve 18 for controlling the EGR gas flow rate. Further, the crankshaft of the internal combustion engine 1 has a crankangle plate 19 that rotates integrally with the crankshaft, and a crank angle plate 19 that detects the period between edges of the crankangle plate 19 in order to calculate the crank angle and the rotation speed of the internal combustion engine. A sensor 20 is provided.

Further, although not shown, various sensors including an atmospheric pressure sensor for detecting atmospheric pressure, a throttle upstream pressure sensor for detecting throttle upstream pressure, and a water temperature sensor for detecting the cooling water temperature of the internal combustion engine are provided.

FIG. 2 is a block configuration diagram showing a control device for an internal combustion engine according to Embodiment 1. As shown in FIG. 2, various sensors 30 include the aforementioned air flow sensor 2, intake air temperature sensor 3, throttle position sensor 5, intake manifold pressure sensor 9, O2 sensor 16, crank angle sensor 20, and a large sensor (not shown in FIG. 1). An atmospheric pressure sensor 31, an upstream pressure sensor 32, and a water temperature sensor 33 are included. The various sensors 30 correspond to operating state detection means for detecting the operating state.

An electronic control unit (hereinafter referred to as "ECU") 21 includes an input interface (hereinafter referred to as "input I/F") 21a, an arithmetic processing section 21b, and an output interface (hereinafter referred to as "output I/F"). ) 21c.

The input I/F 21a of the ECU 21 receives the intake air amount Qa from the air flow sensor 2 in various sensors 30, the intake air temperature AT from the intake air temperature sensor 3, the throttle opening Th from the throttle position sensor 5, and the intake manifold pressure sensor 9. Along with the intake manifold pressure Pb, the air-fuel ratio AF from the O2 sensor 16, the internal combustion engine speed Ne calculated from the cycle between edges from the crank angle sensor 20, the atmospheric pressure Pa from the atmospheric pressure sensor 31, and the throttle from the upstream pressure sensor 32. Detection signals including the upstream pressure P1 and the water temperature WT of the internal combustion engine from the water temperature sensor 33 are input.

For the atmospheric pressure Pa, the output of means for estimating and calculating the atmospheric pressure Pa from other sensor information may be used instead of using the output of the atmospheric pressure sensor 31 for direct measurement. Alternatively, instead of using the output of the upstream pressure sensor 32 for directly measuring the throttle upstream pressure P1, the output of means for estimating and calculating the throttle upstream pressure P1 from other sensor information may be used.

The arithmetic processing unit 21b in the ECU 21 includes throttle opening degree control means and EGR valve opening degree control means. The throttle opening degree control means calculates a target intake air amount tQc for realizing a target internal combustion engine torque, and calculates a target throttle opening degree for realizing the target intake air amount tQc. The EGR valve opening degree control means calculates an EGR valve opening degree that achieves the target intake air amount tQc and does not cause poor combustion.

The arithmetic processing unit 21b also calculates control command values for other actuators included in the various actuators 40, such as the injector of the fuel injection device and the ignition coil of the ignition device provided in the combustion chamber of the internal combustion engine 1. .

The output I/F 21c in the ECU 21 outputs a drive control signal based on the calculation result of the calculation processing section 21b to various actuators 40 including actuators for driving the throttle 4 and the EGR valve 18.

Next, arithmetic processing executed by the arithmetic processing unit 21b of the ECU 21 will be described. In the control device and control method for an internal combustion engine according to Embodiment 1, the target EGR gas flow rate basic value Qveegr as the target EGR gas flow rate used for calculation of the upper limit value described later is the flow rate passing through the nozzle in compressible fluid dynamics. Based on the calculation formula, using the EGR valve effective opening area Segr, the EGR gas sound velocity αegr, the EGR gas dimensionless flow rate _σegr , and the EGR gas density ρegr, the following formula (1) can be used. can.

なお、式（２）におけるＥＧＲガス温度Ｔｅｇｒ、および、以降述べる全てのＥＧＲガス温度Ｔｅｇｒに代えて、排気温度Ｔｅｘを用いてもよい。 Here, the EGR gas sound velocity αegr is obtained by using the EGR gas specific heat ratio κegr, which is the ratio of the constant pressure heat capacity to the constant volume heat capacity of the EGR gas, the EGR gas constant Regr, and the EGR gas temperature Tegr passing through the EGR valve. It can be calculated by the following formula (2).

The exhaust gas temperature Tex may be used in place of the EGR gas temperature Tegr in Equation (2) and all EGR gas temperatures Tegr described below.

Next, the EGR gas dimensionless flow rate σegr can be calculated by the following equation (3) using the intake manifold pressure Pb and the exhaust pressure Pex, which is the pressure inside the exhaust passage 12 .

Also, the EGR gas density ρegr can be calculated by the following formula (4).

The internal combustion engine control apparatus and control method according to Embodiment 1 will be specifically described below based on the above-described formulas (1) to (4). FIG. 3 is a functional block diagram showing processing in a target EGR valve opening computing section in the internal combustion engine control apparatus according to the first embodiment. In FIG. 3, the target EGR valve opening calculation unit 100 includes a target EGR gas flow rate basic value calculation unit 110 as a first means for calculating the target EGR gas flow rate basic value Qveegr, and a sonic velocity of the EGR gas passing through the EGR valve. EGR valve passage gas sonic velocity calculation means 101 for calculating the EGR gas sonic velocity αegr, an EGR gas dimensionless flow rate calculator 130 for calculating the EGR gas dimensionless flow rate σegr, and a target EGR valve effective opening area limit value LimSegr and target EGR valve effective opening area limit value calculation means 102 .

Further, the target EGR valve opening calculation unit 100 includes a target EGR valve opening limit value calculation unit 103 for calculating a target EGR valve opening limit value LimPSTM, and a misfire request upper limit target EGR rate for calculating a misfire request upper limit target EGR rate Regrex. a misfire request upper limit target EGR valve effective opening area calculation means 105 for calculating the misfire request upper limit target EGR valve effective opening area RegSegr; and a misfire request upper limit target EGR valve opening degree RegPTSM for calculating the misfire request upper limit target EGR valve opening RegPTSM. A valve opening calculating means 106, a target EGR valve opening basic value calculating section 140 for calculating a target EGR valve opening basic value PSTMb, and a first minimum value calculating means 145 for calculating an EGR valve opening upper limit value UprPTSM. , and a second minimum value calculating means 146 for calculating the target EGR valve opening PSTM.

Here, the aforementioned target EGR gas flow rate basic value calculation section 110 will be described in further detail. FIG. 4 is a functional block diagram showing processing in a target EGR gas flow rate basic value calculation section in the internal combustion engine control apparatus according to the first embodiment. In FIG. 4, a target EGR gas flow rate basic value calculation unit 110 includes target intake manifold pressure calculation means 111 that calculates a target intake manifold pressure tPb, a target volumetric efficiency calculation unit 120 that calculates a target volumetric efficiency tKv, and a target EGR gas flow rate basic value calculation unit 111 that calculates a target intake manifold pressure tPb. and a target EGR gas flow rate basic value calculation means 147 for calculating the value Qveegr. The target EGR gas flow rate basic value calculation means 147 corresponds to a third means for calculating the target EGR gas flow rate upper limit value.

The target EGR gas flow rate basic value calculator 110 configured as described above calculates the target intake manifold pressure tPb calculated by the target intake manifold pressure calculator 111, the target volumetric efficiency tKv calculated by the target volumetric efficiency calculator 120, the target intake Using air amount tQc, EGR valve passage gas density ρegr, intake manifold internal temperature Tim, internal combustion engine speed Ne, EGR gas constant Regr, and cylinder stroke volume Vc, target EGR gas flow rate basic value calculation means 147 Then, the target EGR gas flow rate basic value Qveegr is calculated using the following equation (5).

ここでＴｃｒｋは定数であり、内燃機関１が、３気筒の場合は「４０」、４気筒の場合は「３０」、６気筒の場合は「２０」となる。

Here, Tcrk is a constant, and is "40" if the internal combustion engine 1 has three cylinders, "30" if it has four cylinders, and "20" if it has six cylinders.

The intake manifold internal temperature Tim may be detected using a sensor for direct measurement, or may be estimated from other sensor information and calculated. In the first embodiment, in consideration of the heat received from the internal combustion engine 1 with respect to the intake air temperature AT, a value calculated from a correspondence map with the water temperature WT of the internal combustion engine is added to the detected value or calculated value to obtain the intake manifold internal temperature Tim. is calculated.

The EGR valve passing gas density ρegr can be calculated using the above-described formula (4). The cylinder stroke volume Vc can be calculated from [total displacement/number of cylinders] of the internal combustion engine 1 .

The target intake manifold pressure calculation means 111 first uses a pre-adapted map centered on the internal combustion engine speed Ne to calculate a target pressure ratio tPb/Pa, which is the pressure ratio between the target intake manifold pressure tPb and the atmospheric pressure Pa, or , the target pressure ratio tPb/P1, which is the pressure ratio between the target intake manifold pressure tPb and the throttle upstream pressure P1, is calculated. Next, the target intake manifold pressure calculation means 111 calculates the product of the aforementioned target pressure ratio tPb/Pa (or tPb/P1) and the atmospheric pressure Pa from the atmospheric pressure sensor (or throttle upstream pressure P1). , the target intake manifold pressure tPb is calculated.

Here, the aforementioned target pressure ratio tPb/Pa (or tPb/P1) is a pressure ratio for the purpose of setting the target value unaffected by atmospheric pressure. A target intake manifold pressure tPb using a map may be set and used. However, since the target intake manifold pressure tPb is the target intake manifold pressure at the normal pressure of "101.3" [kPa], the target intake manifold pressure tPb is subjected to atmospheric pressure correction in consideration of the influence of the atmospheric pressure. It is necessary to calculate the target intake manifold pressure.

Next, the target volumetric efficiency calculator 120 in FIG. 4 will be described. FIG. 5 is a functional block diagram showing processing in the target volumetric efficiency calculation section in the internal combustion engine control apparatus according to the first embodiment. In FIG. 5, the target volumetric efficiency basic value calculation means 121 uses the target pressure ratio tPb/Pa (or tPb/P1), the internal combustion engine speed Ne, the target IVT phase angle, and the target EVT phase angle. Calculates the target volumetric efficiency basic value Kvb.

The target volumetric efficiency basic value Kvb is set for each of the target IVT phase angle and the target EVT phase angle using a map centered on the internal combustion engine speed Ne and the target pressure ratio tPb/Pa (or tPb/P1). is calculated by the target volumetric efficiency basic value calculation means 121.

なお、目標体積効率Ｋｖの算出時に入力する目標体積効率基本値Ｋｖｂには、フィルタ処理を入れるようにしても良い。 Next, the target volumetric efficiency calculation means 122 calculates the target volumetric efficiency Kv using the following equation (6) based on the target volumetric efficiency basic value Kvb and the intake manifold internal temperature Tim.

Note that the target volumetric efficiency basic value Kvb input when calculating the target volumetric efficiency Kv may be filtered.

As described above, the target intake air amount tQc is obtained by subtracting the target intake air amount tQc from the total air amount (fresh air amount + EGR valve passing gas amount) that provides the target pressure ratio tPb/Pa (or tPb/P1). While realizing the target pressure ratio tPb/Pa (or tPb/P1), the target EGR gas flow rate basic value Qveegr can be calculated by the above equation (5).

Next, returning to FIG. 3 , the EGR valve passing gas sonic velocity calculation means 101 calculates the EGR valve passing gas sonic velocity αegr based on the EGR gas temperature Tegr, and inputs it to the target EGR valve effective opening area limit value calculating means 102 .

Here, the EGR gas temperature Tegr may use a sensor detection value, or may be estimated from other sensor information. Alternatively, the exhaust gas temperature Tex may be used as the EGR gas temperature Tegr. The exhaust gas temperature Tex is calculated by matching the measured relationship between the internal combustion engine speed Ne and the charging efficiency Ec to a map with axes. Note that the exhaust temperature Tex may be filtered as necessary.

Subsequently, based on the EGR gas temperature Tegr passing through the EGR valve 18, the sound velocity αegr of the gas passing through the EGR valve 18 is calculated using the above equation (2). Note that the EGR valve passing gas sonic velocity αegr may be calculated by previously adapting a map centered on the EGR gas temperature Tegr, which is the temperature of the EGR gas passing through the EGR valve 18 .

Next, the EGR gas dimensionless flow rate calculator 130 will be described. FIG. 6 is a functional block diagram showing processing in the EGR gas dimensionless flow rate calculating means in the internal combustion engine control apparatus according to Embodiment 1. In FIG. In FIG. 6 , the EGR gas dimensionless flow rate calculator 130 includes target intake manifold pressure calculation means 111 , EGR gas dimensionless flow rate basic value calculation means 131 , and ripple correction coefficient calculation means 132 .

The target intake manifold pressure calculation means 111 calculates the target intake manifold pressure tPb as described above. The EGR gas dimensionless flow rate basic value calculation means 131 calculates the EGR gas dimensionless flow rate basic value σegrb based on the target intake manifold pressure tPb and the exhaust pressure Pex using the above-described formula (3). Alternatively, a map centered on the exhaust pressure ratio tPb/Pex, which is the pressure ratio between the target intake manifold pressure tPb and the exhaust pressure Pex, may be adapted in advance to calculate the EGR gas dimensionless flow rate basic value σegrb.

The ripple correction coefficient calculation means 132 calculates the EGR gas passage flow rate due to superimposition of intake and exhaust pulsations in a state where the exhaust pressure ratio between the target intake manifold pressure tPb and the EGR valve passage EGR gas pressure Pegr is [tPb/Pegr≈1.0]. A ripple correction coefficient Kripple for correcting the change is calculated. That is, even at the exhaust pressure ratio described above, when the superimposition of intake and exhaust pulsations is large, the EGR gas flows in the reverse direction compared to when the superimposition is small. Corrected by The ripple correction coefficient Kripple can be calculated by adapting in advance a map centered on the internal combustion engine speed Ne, the exhaust pressure ratio tPb/Pegr, and the EVT phase angle.

The EGR valve passing EGR gas pressure Pegr may use the output value of a sensor that is directly measured, or may be estimated and calculated from other sensor information such as the exhaust pressure Pex, and furthermore, the exhaust pressure Pex may be used directly. You may do so.

Finally, the EGR gas dimensionless flow rate σegr is calculated by correcting the EGR gas dimensionless flow rate basic value σegrb with the aforementioned ripple correction coefficient Kripple.

Returning to FIG. 3, the target EGR valve effective opening area limit value calculation means 102 calculates the following formula ( 7) is used to calculate the target EGR valve effective opening area limit value LimSegr. The target EGR valve effective opening area limit value calculation means 102 corresponds to a second means for converting the target EGR gas flow rate into the target EGR valve opening.

Next, the target EGR valve opening limit value LimPSTM is calculated by the target EGR valve opening limit value calculation means 103 using the aforementioned target EGR valve effective opening area limit value LimSegr. Specifically, the target EGR valve opening limit value LimPSTM is calculated by previously adapting a map centered on the target EGR valve effective opening area limit value LimSegr. The target EGR valve opening limit value calculation means 103 corresponds to fourth means for calculating the target EGR valve opening upper limit value.

Here, a method for limiting the target EGR valve opening degree limit value LimPSTM to an opening degree at which poor combustion does not occur will be described. First, the misfire request upper limit target EGR rate calculation means 104 calculates the misfire request upper limit target EGR rate Regrex. This is calculated by pre-storing in a map centered on the target charging efficiency tEc and the internal combustion engine speed Ne. Generally, the EGR rate is represented by [EGR gas amount/(fresh air amount + EGR gas amount)], but here, for ease of calculation, [EGR gas amount/fresh air amount] is used as the EGR rate for convenience. .

Next, based on the misfire request upper limit target EGR rate Regrex, the misfire request upper limit target EGR valve effective opening area calculation means 105 calculates the misfire request upper limit target EGR valve effective opening area RegSegr. Specifically, by taking the product of the misfire request upper limit target EGR rate Regrex and the target intake air amount tQc, it is converted into an EGR gas flow rate, and this is replaced with the Qveegr part of the above equation (7) to calculate do.

Further, the misfire request upper limit target EGR valve opening RegPTSM is calculated by the misfire request upper limit target EGR valve opening calculation means 106 based on the misfire request upper limit target EGR valve effective opening area RegSegr. Since the target EGR valve opening limit value calculation means 103 and the misfire request upper limit target EGR valve opening calculation means 106 share the relationship between the effective opening area of the EGR valve and the EGR valve opening, the same map is used. good.

The misfire request upper limit target EGR valve opening degree RegPTSM described above is calculated from the misfire request upper limit target EGR rate Regrex calculated from a map based on the target charging efficiency tEc and the internal combustion engine speed Ne. The misfire request upper limit target EGR valve opening degree RegPTSM may be directly calculated using a map based on the target charging efficiency tEc and the internal combustion engine speed Ne.

Next, the first minimum value calculating means 145 calculates the EGR valve opening upper limit value UprPTSM, which is the minimum value between the aforementioned target EGR valve opening limit value LimPSTM and the misfire request upper limit target EGR valve opening value RegPTSM. calculate. The EGR valve opening upper limit value UprPTSM indicates the EGR valve opening at which the target intake air amount tQc is achieved and combustion failure does not occur.

Finally, the second minimum value calculating means 146 calculates the above-described EGR valve opening upper limit UprPTSM and the target EGR valve opening basic value PSTMb calculated by the target EGR valve opening basic value calculator 140 described later. is calculated as the target EGR valve opening degree PSTM. Based on this target EGR valve opening PSTM, an opening instruction is given to the actuator that controls the EGR valve 18 . The first minimum value calculation means 145 and the second minimum value calculation means 146 calculate the target EGR valve opening degree calculated by the above-described first means as the target EGR valve opening degree calculated by the above-described fourth means. This corresponds to the fifth means for limiting by the upper limit value.

Here, the target EGR valve opening basic value calculator 140 will be described with reference to FIG. FIG. 7 is a functional block diagram showing processing in a target EGR valve opening basic value calculation section in the internal combustion engine control apparatus according to the first embodiment. In FIG. 7, a target EGR valve opening basic value calculation unit 140 includes pre-correction target EGR valve opening calculation means 141, target EGR valve opening temperature correction coefficient calculation means 148, and target EGR valve opening pressure ratio correction coefficient. a calculation means 149;

First, by storing in advance a map centered on the target charging efficiency tEc and the internal combustion engine speed Ne, the pre-correction target EGR valve opening calculation means 141 can be used to calculate the pre-correction target EGR valve opening Calculate BPSTMb.

Next, for the pre-correction target EGR valve opening BPSTMb, the target EGR valve opening temperature correction coefficient calculated by the target EGR valve opening temperature correction coefficient calculating means 148 and the target EGR valve opening pressure ratio correction coefficient calculating means A target EGR valve opening basic value PSTMb is calculated by performing correction using the target EGR valve opening pressure ratio correction coefficient calculated by 149 .

More specifically, the target EGR valve opening temperature correction coefficient can be calculated from a pre-stored map with the water temperature WT and the intake air temperature AT as axes. The target pressure ratio EGR valve opening pressure ratio correction coefficient is a target pressure ratio calculated from a pre-stored map with the internal combustion engine speed Ne and the throttle opening Th as axes, and the internal combustion engine speed Ne. can be calculated from a pre-stored map with .

According to the internal combustion engine control apparatus and control method according to Embodiment 1 described above, it is possible to obtain an internal combustion engine control apparatus and control method that can achieve the target internal combustion engine torque even when an environmental change occurs. Further, it is possible to introduce the maximum EGR flow rate within a range in which poor combustion does not occur while ensuring the target intake air amount tQc required to achieve the target internal combustion engine torque. Furthermore, even if the environment changes with respect to when the map of the target EGR flow rate is set, the target EGR flow rate is calculated based on the target pressure ratio, which is the ratio between the target value of the intake manifold pressure, which is the pressure in the intake manifold, and the throttle upstream pressure. By calculating the upper limit value of and limiting the target EGR flow rate based on the calculation result, in an internal combustion engine that performs EGR control, it is possible to increase the EGR flow rate as much as possible within a range that does not cause poor combustion, thereby improving fuel efficiency. can.

Although the present application has described exemplary embodiments, the various features, aspects, and functions described in the embodiments are not limited to application of particular embodiments, alone or Various combinations are applicable to the embodiments. Therefore, countless modifications not illustrated are envisioned within the scope of the technology disclosed in the present application. For example, the modification, addition, or omission of at least one component shall be included.

1 internal combustion engine, 2 airflow sensor, 3 intake air temperature sensor, 4 throttle,
5 throttle position sensor, 6 intake passage, 7 surge tank, 8 intake manifold,
9 intake manifold pressure sensor, 10 cylinder, 11 intake valve, 12 exhaust path,
13 exhaust valve, 14 IVT, 15 EVT, 16 O2 sensor,
17 EGR passage, 18 EGR valve, 19 crank angle plate,
20 crank angle sensor, 21 ECU, 21a input I/F, 21b arithmetic processing section,
21c output I/F, 30 various sensors, 31 atmospheric pressure sensor, 32 upstream pressure sensor,
33 water temperature sensor, 40 various actuators, 100 target EGR valve opening calculation unit,
101 EGR valve passing gas sound velocity calculation means,
102 target EGR valve effective opening area limit value calculation means;
103 target EGR valve opening limit value calculation means;
104 misfire request upper limit target EGR rate calculation means;
105 misfire request upper limit target EGR valve effective opening area calculation means;
106 misfire request upper limit target EGR valve opening calculation means;
110 target EGR gas flow rate basic value calculator, 111 target intake manifold pressure calculator,
120 target volumetric efficiency calculation unit, 121 target volumetric efficiency basic value calculation means,
122 target volumetric efficiency calculation means, 130 EGR gas dimensionless flow rate calculator,
131 EGR gas dimensionless flow rate basic value calculation means, 132 ripple correction coefficient calculation means,
140 target EGR valve opening basic value calculator;
141 pre-correction target EGR valve opening calculation means;
145 first minimum value calculation means, 146 second minimum value calculation means,
147 target EGR gas flow rate basic value calculation means;
148 target EGR valve opening temperature correction coefficient calculation means;
149 target EGR valve opening pressure ratio correction coefficient calculation means

Claims (5)

a throttle that controls the amount of intake air flowing into the internal combustion engine;
an EGR passage that connects an exhaust pipe of the internal combustion engine and an intake manifold downstream of the throttle and returns part of exhaust gas of the internal combustion engine to the intake manifold;
an EGR valve provided in the EGR passage for controlling the flow rate of EGR gas in the EGR passage;
an operating state detection means for detecting an operating state of the internal combustion engine;
a first means for calculating a target EGR gas flow rate based on the operating state of the internal combustion engine;
a second means for converting the target EGR gas flow rate into a target EGR valve opening;
a third means for calculating a target EGR gas flow rate upper limit value based on a target pressure ratio, which is a pressure ratio between the target pressure inside the intake manifold and the atmospheric pressure or the throttle upstream pressure;
fourth means for calculating a target EGR valve opening upper limit based on at least the target EGR gas flow rate upper limit and the sound velocity of the EGR valve passage gas passing through the EGR valve;
fifth means for limiting the target EGR valve opening degree calculated by the first means by the target EGR valve opening upper limit value calculated by the fourth means;
with
configured to control the opening of the EGR valve based on the target EGR valve opening limited by the fifth means,
A control device for an internal combustion engine, characterized by: The target EGR valve opening upper limit includes an upper limit for the EGR valve opening that avoids misfiring of the internal combustion engine,
The control device for an internal combustion engine according to claim 1, characterized in that: The target EGR valve opening upper limit includes an upper limit based on an EGR rate that avoids misfiring of the internal combustion engine,
The control device for an internal combustion engine according to claim 1, characterized in that: The target pressure ratio is calculated from a pre-fitted map,
The map is set for each rotation speed of the internal combustion engine,
The control device for an internal combustion engine according to claim 1, characterized in that: a first step of calculating a target EGR gas flow rate passing through an EGR valve of the internal combustion engine based on an operating state of the internal combustion engine;
a second step of converting the target EGR gas flow rate into a target EGR valve opening;
a third step of calculating a target EGR flow rate upper limit value based on a target pressure ratio, which is a pressure ratio between the target pressure inside the intake manifold of the internal combustion engine and the atmospheric pressure or the throttle upstream pressure of the internal combustion engine;
a fourth step of calculating an upper limit value of the target EGR valve opening based on at least the target EGR flow rate upper limit value and the speed of sound of EGR gas passing through the EGR valve;
a fifth step of limiting the target EGR gas flow rate by an upper limit value of the target EGR valve opening;
has
controlling the opening of the EGR valve based on the restricted target EGR valve opening;
A control method for an internal combustion engine, characterized by:

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