JP5287529B2 - Engine intake control device - Google Patents

Description

  The present invention relates to an engine intake control device that performs intake control of an engine provided with an EGR pipe for returning a part of exhaust gas to an intake system.

  The EGR amount in a diesel engine is not controlled by detecting the EGR amount by any means, but indirectly by controlling the intake air amount (also referred to as intake air flow rate, MAF, Maf). It is common to control.

  Conventionally, an intake air amount sensor (MAF sensor) mounted on an intake pipe is used to adjust an EGR amount by controlling an EGR valve and an intake throttle valve so that the target intake air amount and the MAF sensor output value coincide with each other. (For example, refer to Patent Document 1).

JP 2003-166445 A JP 11-159404 A

  In order to cope with the recent tightening of exhaust gas regulations, it is necessary to accurately control the EGR rate or the intake oxygen concentration. Therefore, it is difficult to cope with the intake air amount control using the MAF sensor which has been conventionally performed.

  During the transition, the behavior of the intake air measured by the MAF sensor and the intake oxygen concentration in the cylinder or the intake manifold changes due to the delay in reflux of the EGR gas. Further, in response to changes in the intake pressure and the intake air temperature, the gas density changes and the oxygen concentration taken into the cylinder changes.

  Therefore, in the conventional MAF control, the responsiveness may be improved by correcting the target intake air amount according to the amount of change in the engine speed or the fuel injection amount during the transition. In addition, a correction table (correction map) based on intake pressure and intake air temperature is provided to cope with the problem.

  Instead of indirectly controlling the EGR amount with the intake air amount (detected by the MAF sensor), control has been proposed in which the intake oxygen concentration and the EGR rate are set as target values (see Patent Document 2). .

  In Patent Document 2, the intake oxygen concentration and the EGR rate are obtained by calculation (or can be detected by a sensor), and feedback controlled according to a predetermined target value.

  However, since the volumetric efficiency changes depending on the exhaust pressure, the ambient temperature, etc., there is a problem that the accuracy of the intake control deteriorates.

  In recent years, a flow sensor that directly measures the EGR gas flow rate has been proposed. If this sensor is used, the EGR rate or the intake oxygen concentration can be obtained without obtaining the cylinder intake gas amount. There is no effect.

  As a sensor that directly measures the EGR gas flow rate, a hot-wire flow meter can be used. Although it can be realized by diverting the technology of the MAF sensor, it is difficult to realize a high response by taking measures for improving the environmental resistance and temperature dependency characteristics.

  Accordingly, an object of the present invention is to provide an intake control device for an engine that can solve the above-described problems and improve the accuracy of intake control.

In order to achieve the above object, the present invention provides an engine including an intake throttle valve provided in an intake pipe of an engine and an EGR valve provided in an EGR pipe for communicating the exhaust pipe of the engine with the intake pipe. The intake oxygen concentration or the EGR rate in the intake control is determined based on at least the volume efficiency of the engine, and the volume efficiency is a volume in which the volume efficiency for each operating state of the engine is stored in advance. An engine intake control device that reads from an efficiency table, the EGR flow rate detecting means provided in the EGR pipe for detecting the flow rate of gas passing through the EGR pipe, and when the engine operating state is in a steady state A learning supplement that learns and corrects the volumetric efficiency of the volumetric efficiency table based on the detection value of the EGR flow rate detection means. Means obtains a volumetric efficiency from the volumetric efficiency table based on the operating state of the engine, based on the determined volumetric efficiency, and converts the intake oxygen concentration of the target to the intake air amount as a target, and its transformation Control means for controlling the intake throttle valve and the EGR valve to match the actual intake air amount with the intake air amount .

  Preferably, intake air amount detection means for detecting the flow rate of intake air flowing through the intake pipe upstream of the supercharger, and intake air for detecting the temperature in the intake manifold provided at the downstream end of the intake pipe A temperature detection means; and an intake pressure detection means for detecting the pressure in the intake manifold, wherein the learning correction means is the intake temperature detection means, the intake pressure detection means, the intake air amount detection means, The volumetric efficiency in the steady state is calculated based on the detected value with the EGR flow rate detection means, and the volumetric efficiency in the volumetric efficiency table is corrected with the calculated volumetric efficiency.

  According to the present invention, an excellent effect that the accuracy of intake control can be improved is exhibited.

FIG. 1 is a schematic configuration diagram of an intake air control device according to an embodiment of the present invention. FIG. 2 is a diagram illustrating an example of the volumetric efficiency table. FIG. 3 is a diagram for explaining the transient model. FIG. 4 is a block diagram of intake oxygen concentration feedback control. FIG. 5 is a diagram for explaining a comparison between MAF control and intake oxygen concentration control, and shows experimental results. FIG. 6 is an example of a control flowchart for performing control related to volumetric efficiency learning. FIG. 7 is an example of a control flowchart for performing control according to the volumetric efficiency table learning condition. FIG. 8 is a block diagram of MAF substitution type intake oxygen concentration control. FIG. 9 is an example of a control flowchart for performing control relating to calculation of the EGR valve operation amount.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  The engine intake control device (hereinafter referred to as an intake control device) of the present embodiment is directed to, for example, a diesel engine mounted on a vehicle.

  A schematic structure of the intake control device and the engine will be described with reference to FIG.

  As shown in FIG. 1, the intake control device 1 is provided in an intake throttle valve 4 provided in an intake pipe 5 of the engine 2 and an EGR pipe 6 for communicating the exhaust pipe 3 of the engine 2 with the intake pipe 5. The EGR valve 7 controls the intake air of the engine 2 and determines the intake oxygen concentration or EGR rate in the intake air control based on at least the volume efficiency of the engine 2. The volume efficiency is determined for each operating state of the engine 2. The volumetric efficiency is read from a volumetric efficiency table stored in advance, and an EGR flow sensor 8 that is provided in the EGR pipe 6 and detects the flow rate of gas passing through the EGR pipe 6, and a detection value of the EGR flow sensor 8 And an engine control unit (hereinafter referred to as ECU) 9 serving as learning correction means for learning and correcting the volumetric efficiency of the volumetric efficiency table.

  More specifically, the engine 2 discharges exhaust gas from the engine body 11 having a plurality of cylinders 16, the intake pipe 5 for supplying intake air to the cylinders 16 of the engine body 11, and the cylinder 16. Exhaust pipe 3, an exhaust gas recirculation device (EGR device) 12 that extracts a part of the exhaust gas from the exhaust pipe 3, returns it to the intake pipe 5 and recirculates, and intake air (new air) supplied to the cylinder 16. A turbocharger 13 for pressure and compression and an ECU 9 for controlling the engine 2 are provided.

  The engine body 11 has an injector 18 that injects and supplies fuel to each cylinder 16. The injectors 18 control the fuel injection amount and injection timing by the ECU 9. In the illustrated example, high pressure fuel stored in the common rail 17 is supplied to the injector 18. The engine body 11 is provided with a crank sensor 21 and a cam sensor 22. The sensors 21 and 22 constitute detection means for detecting the engine speed, and the detected value of the sensor 21 (or 22) is transmitted to the ECU 9, and the ECU 9 calculates the engine speed based on the detected value. .

  The intake pipe 5 is provided with a MAF sensor (intake air amount sensor) 26, an intercooler 27, a compressor 28 of the turbocharger 13, and an intake throttle valve 4 in order from the upstream side.

  The MAF sensor 26 detects the flow rate (mass flow rate) of the intake air flowing through the intake pipe 5 and transmits the detected value to the ECU 9. The intake throttle valve 4 is for adjusting the flow rate of the intake air passing through the intake pipe 5, and the valve opening degree is continuously controlled by the ECU 9.

  An intake manifold 29 that communicates with each cylinder 16 of the engine body 11 is provided at the downstream end of the intake pipe 5. The intake manifold 29 is provided with a temperature sensor (hereinafter referred to as an intake air temperature sensor) 31 serving as an intake air temperature detecting means and a pressure sensor (hereinafter referred to as an intake air pressure sensor) 32 serving as an intake pressure detecting means. The intake temperature sensor 31 detects the temperature (gas temperature) in the intake manifold 29, the intake pressure sensor 32 detects the pressure (gas pressure) in the intake manifold 29, and the detected values of these sensors 31, 32 are transmitted to the ECU 9. Is done.

  The exhaust pipe 3 is provided with an exhaust manifold 36 at its upstream end, and in order from the upstream side downstream of the exhaust manifold 36, an exhaust throttle valve 37, a turbine 38 of the turbocharger 13, and an exhaust gas purifier. A post-processing device 39 is provided.

  The EGR device 12 includes an EGR pipe 6, an EGR valve 7, and an EGR cooler provided in the EGR pipe 6.

  One end (upstream end) of the EGR pipe 6 is connected to the exhaust pipe 3 between the exhaust manifold 36 and the exhaust throttle valve 37, and the other end (downstream end) is an intake air between the intake pipe 5 and the intake throttle valve 4. Connected to tube 5. The exhaust gas in the exhaust pipe 3 flows into the intake pipe 5 through the EGR pipe 6 and is mixed with fresh air, and the mixed gas is sucked into the cylinder 16 of the engine body 11.

  The EGR valve 7 is for adjusting the flow rate of exhaust gas (EGR gas) passing through the EGR pipe 6, and the valve opening degree is continuously controlled by the ECU 9.

  An EGR flow sensor 8 is provided in the EGR pipe 6 on the downstream side of the EGR valve 7. The EGR flow rate sensor 8 detects the flow rate of EGR gas flowing through the EGR pipe 6 and transmits the detected value to the ECU 9. The EGR flow sensor 8 and the MAF sensor 26 described above are composed of, for example, a hot wire flow meter.

  The sensors 9, 21-22, 26, 31-32 and the actuators 4, 7, 18, 37 are connected to the ECU 9 so as to communicate with each other. The ECU 9 has storage means (hereinafter referred to as ECU memory) 42 for storing various data and programs. The ECU memory 42 stores the above-described volumetric efficiency table and the like.

  As will be described in detail later, the ECU 9 determines the volume in the steady state based on the detection values of the intake air temperature sensor 31, the intake pressure sensor 32, the MAF sensor 26, and the EGR flow sensor 8 when the engine 2 is in a steady state. The efficiency is calculated, and the volume efficiency of the volume efficiency table is corrected by the calculated volume efficiency.

  Further, the ECU 9 obtains the volume efficiency from the volume efficiency table based on the operating state of the engine 2, obtains the intake oxygen concentration (or EGR concentration) based on the obtained volume efficiency, and obtains the target intake oxygen concentration (or EGR). The intake throttle valve 4 and the EGR valve 7 are controlled (for example, feedback control) so as to match the calculated intake oxygen concentration (or EGR concentration) with (concentration).

  Here, the intake control device 1 of the present embodiment uses the EGR flow sensor 8 for learning correction of the volumetric efficiency table during steady operation, and performs control using a simple intake model, which will be described later, at the time of transition, thereby improving the volumetric efficiency. The problem of the influence of variation and the responsiveness of the EGR flow sensor 8 is solved.

The intake oxygen concentration is calculated from the detected values of the MAF sensor 26, the intake pressure sensor 32, and the intake air temperature sensor 31, and the fuel injection amount. The fuel injection amount needs to match the instruction value (instruction injection amount) from the ECU 9 to the injector 18 and the actual value (actual injection amount) that the injector 18 actually injects. In this case, it is desirable to correct in advance from an exhaust O ₂ sensor (not shown) provided in the exhaust pipe 3.

  In the transient state, the intake and exhaust are regarded as a simple volume and expressed by approximating with a first-order lag. The cylinder intake gas amount is described by a state equation based on the speed density method, and a volume efficiency table obtained experimentally in advance is stored in the ECU 9 as an initial value, and the volume calculated from information of the EGR flow sensor 8 and the like. Learn sequentially with efficiency.

  These points will be described in detail below.

1. Steady data fit 1.1 Intake oxygen concentration calculation formula Assuming that the engine 2 is in a steady state, the intake oxygen concentration is calculated by the mass per cylinder and stroke.

The intake gas flow rate M _CYL of the cylinder 16 is calculated by Equation 1. This formula 1 is used in the control of a gasoline engine.

The volumetric efficiency η _VOL is table data of intake pressure and engine speed. Alternatively, the pressure ratio between intake and exhaust may be used.

Since EGR gas mass M _EGR is in a steady state,

It becomes.

The ratio of air in the exhaust manifold 36 is obtained. Combustion, considering that the amount of air stoichiometric ratio times the amount of fuel is consumed, the ratio AR _EXH air exhaust gas,

It becomes.

  Here, considering the input to the system including EGR,

It becomes.

The air ratio AR _INM in the intake manifold 29 is

It becomes.

Inspiratory oxygen concentration O _2INM is

It becomes.

  The steady-state intake oxygen concentration can be calculated by these calculation formulas 1-6.

1.2 Correction of Instructed Injection Amount and Actual Injection Amount The above-mentioned “1.1 Intake oxygen concentration calculation formula” is based on the premise that the instruction injection amount and the actual injection amount are the same. However, actually, the command injection amount and the actual injection amount change due to product variations and changes with time. The correction is necessary to use it in the actual machine.

Using the above equation 4, the actual injection amount can be calculated from the intake air amount and the exhaust oxygen concentration (AR _EXH ).

In order to correct the fuel injection amount on the actual machine, an exhaust O ₂ sensor (not shown) mounted on the exhaust pipe 3 is used. The exhaust O ₂ sensor may be mounted for the main control or may be mounted for the post-processing control and can be used. It is determined whether or not the operating state of the engine 2 is steady. When the engine 2 is steady, the fuel injection amount is calculated by Expression 7, and the command injection amount and the actual injection amount are corrected.

  The characteristics of the injector 18 (injection valve) depend on the pressure in the common rail 17 (common rail pressure), and individual differences and secular changes also depend on it. Characteristic data for each injector 18 is presented from the injection system manufacturer and incorporated in the ECU 9. However, the fuel injection amount on the actual machine may be calculated according to Equation 7 and may be adapted before shipment.

  After shipment to the market, the estimated injection amount calculated in the steady state of the engine is learned from the command injection amount and common rail pressure table to update the correction table.

1.3 Creation of volumetric efficiency table data Volumetric efficiency (initial value) is calculated using steady data. The engine speed and the combustion injection amount (engine output) are changed, and the volumetric efficiency steady data in various states is measured.

  FIG. 2 shows an example of data (volumetric efficiency) measured during steady operation of the engine 2. Volumetric efficiency is organized with respect to engine speed and intake pressure. The pressure ratio between the intake pressure and the exhaust pressure may be used instead of the intake pressure. The circles in FIG. 2 are experimental data.

  The grid of the volumetric efficiency table data is set at an appropriate interval. The intermediate value is linearly complemented according to the size of the table data. Higher-order interpolation may be used instead of linear interpolation.

2. Transient Model FIG. 3 schematically shows an intake or exhaust system (system) 45. Based on the following formula 8-15, the intake system and the exhaust system are expressed by a simple model of first order delay + dead time.

  From the energy conservation law, when there is no heat transfer, the volume balance of the system 45 shown in FIG. 3 can be expressed by the following formula 8 (general formula). Equation 8 is

It becomes. When V is constant and temperature T is constant, h ₁ = h ₂ = c _p T

Since the volume of the intake manifold 29 is constant,

From Equation (2), κ = c _p / c _ν

It becomes.

  Here, the cylinder intake gas amount per unit time can be expressed by the following equation 12 assuming that the engine speed Ne, the volumetric efficiency η, and the gas constant R. The volume efficiency η is data of the volume efficiency table described above.

Therefore,

  This results in a first-order differential equation such as

  Therefore, since the time constant T of this system is T = 1 / a,

It becomes.

  Here, the intake system volume Vinm is substituted for V to calculate Tinm. A first-order lag filter with a time constant Tinm is added to the intake air amount (Maf) in the above-mentioned “1.1 Intake oxygen concentration calculation formula”. Further, the first-order lag filter of the time constant Texm is calculated by substituting the exhaust system + EGR system volume Vexm into V, and the first-order lag filter of the time constant Texm is added to the aforementioned air mass ratio FrAirExh of the exhaust gas.

3. Learning of the volumetric efficiency table The volumetric efficiency _{ηVOL_M} is calculated by the mass per cylinder and stroke. The above formulas 1 and 2 are used. From these formulas 1 and 2, the volume efficiency η _{VOL_M} is _expressed by the following formula 16.

Here, if the values measured by the sensors 8, 26, 31, 32 are given to the temperature T _{INM of} the intake manifold 29, the pressure P _INM of the intake manifold 29, the intake air amount M _AIR , and the EGR flow rate M _EGR , the volume efficiency η _{VOL_M} is calculated.

When the volume efficiency obtained experimentally in advance in “1.3 Creation of Volume Efficiency Table Data” is η _VOL , the error e _VOL is expressed by the following Expression 17 or Expression 18.

  Or

May be indicated.

When the predetermined learning condition is _satisfied , the error e _VOL is stored in the ECU memory 42 prepared in advance. The error e _VOL is stored in the ECU memory 42 as a correction coefficient table.

  Table 1 below shows the table.

As shown in Table 1, the initial value of the correction coefficient e _VOL is 1.0. The table can be in the form of Equation 19 below. As shown in Equation 19, the table of the correction coefficient e _{VOL is} a table of the engine speed Ne and the fuel injection amount Q _FIN or a table of the intake manifold pressure _PINM. If the exhaust pressure sensor can be used, the intake / exhaust pressure ratio You may refer to it with _PINM / _PEXM .

That is, the correction coefficient as a parameter of e _VOL table, the combination of the combination of the engine speed Ne and fuel injection quantity Q _FIN, or the engine speed Ne and the intake manifold pressure P _INM or the engine speed Ne and Hai吸, A combination with the exhaust pressure ratio P _INM / P _EXM is conceivable. The ECU 9 corrects the volumetric efficiency of the volumetric efficiency table according to Expression 17 or Expression 18 based on the correction coefficient read from the correction coefficient table.

  Next, the operation of the intake control device 1 of the present embodiment will be described.

  First, FIG. 4 shows an example of intake oxygen concentration feedback control based on the calculated intake oxygen concentration. The feedback controller can be realized by PID control, for example. This intake oxygen concentration feedback control is executed by the ECU 9.

  As shown in FIG. 4, the ECU 9 is detected by the engine speed calculated from the detection value of the crank sensor 21 or the cam sensor 22, the calculated fuel injection amount (for example, the above-mentioned injection amount estimated value), and a water temperature sensor (not shown). Based on the measured water temperature, the target intake oxygen concentration is read from the target intake oxygen concentration map stored in advance in the ECU memory 42.

  Further, the ECU 9 determines the engine speed, the fuel injection amount, the intake pressure detected by the intake pressure sensor 32, the intake air temperature detected by the intake temperature sensor 31, and the intake air amount detected by the MAF sensor 26. On the basis of the above, the intake oxygen concentration is calculated by the above formula 1-6.

  Next, the ECU 9 calculates the difference between the target intake oxygen concentration and the calculated intake oxygen concentration, and obtains the target opening degrees of the intake throttle valve 4 and the EGR valve 7 based on the difference. Further, the ECU 9 outputs control signals to the intake throttle valve 4 and the EGR valve 7 so that the obtained target opening is obtained. In this way, the ECU 9 functions as a feedback controller that performs feedback control of the intake oxygen concentration.

  FIG. 5 shows a comparison between intake air amount control (MAF control) and intake oxygen concentration control. FIG. 5 shows, as an example, the behavior of intake air when switching from diesel premixed combustion (low oxygen concentration) to diesel premixed combustion (low oxygen concentration) again through conventional combustion.

  In FIG. 5, the horizontal axis represents time, the upper vertical axis represents the intake oxygen concentration, and the lower vertical axis represents the intake air amount (MAF). In FIG. 5, the behavior during MAF control is indicated by a dotted line M, and the behavior during intake oxygen concentration control is indicated by a thick solid line C. The target value of the intake oxygen concentration is indicated by a thin solid line T1, and the target value of MAF is indicated by a thin solid line T2.

  At the time of MAF control, as indicated by the dotted line M, the target MAF converges quickly and is controlled, but the behavior of the intake oxygen concentration is delayed due to the influence of the EGR recirculation delay or the like.

  On the other hand, as shown by the solid line C, the behavior at the time of intake oxygen concentration control can be quickly converged to the target intake oxygen concentration, and the period of inappropriate combustion state at the time of switching is reduced compared to the time of MAF control. it can. Looking at the state of the MAF at that time, overshoot and undershoot have occurred. In MAF control, overshoot and undershoot have occurred, so it cannot be said that the control is good. However, in terms of the intake oxygen concentration that contributes to actual combustion, the target value can be quickly converged.

  Next, an example of a control flowchart will be described based on FIGS.

  A control flowchart of volumetric efficiency learning will be described based on FIG. This control flowchart is executed by the ECU 9 and is called at a constant time period after the engine 2 is started.

  In step S71, volume efficiency is obtained from the volume efficiency table obtained in “1.3 Creation of Volume Efficiency Table” by referring to the engine speed and intake manifold pressure under the operating conditions at that time.

In step S72, the volume efficiency η _{VOL_M} is calculated from Equation 16.

In step S73, it performs error calculation (using Equation 17 in FIG example) based on the volumetric efficiency eta _{VOL_M} calculated in volumetric efficiency eta _VOL and step S72 obtained in step S71.

In step S74, if the learning condition flag calculated in another routine (volume efficiency table learning condition described later) is 1 (learning valid), the error e _VOL obtained in step S73 is converted to the learning table (correction coefficient value). Table) (step S75). The value of the grid portion of the operating conditions (engine speed, intake pressure) at that time is updated. During learning, it may be updated sequentially, or may be stored in another buffer memory (not shown) of the ECU 9 for statistical processing (such as averaging).

  A control flowchart of the volumetric efficiency table learning condition will be described with reference to FIG. This control flowchart is also executed by the ECU 9, and is called at a constant time period after the engine 2 is started.

  In step S81, it is determined whether the EGR control on flag is 1 or not. If 1 (EGR control is valid), the process proceeds to step S82. The condition for flag = 1 is determined from the engine speed, fuel injection amount, water temperature, and the like.

  In step S82, it is determined whether or not the engine speed is within a certain threshold range. If it is within the threshold range, the process proceeds to step S83.

  In step S83, it is determined whether or not the fuel injection amount falls within a certain threshold range. If it is within the threshold range, the process proceeds to step S84.

  In step S84, it is determined whether or not there is an absolute value of the rate of change of the fuel injection amount or less than a threshold value. Here, the change rate of the engine speed and the accelerator opening may be calculated and determined from them.

  From these steps S82 to S84, it is determined whether or not the operating state of the engine 2 is in a steady state, and the process proceeds to step S85 when in a steady state.

  In step S85, the learning condition flag is set to 1. This learning condition flag is referred to in the volumetric efficiency learning control described above (step 74 in FIG. 6). When the learning condition flag is 1, learning control is performed.

  On the other hand, if it is determined in steps S82 to S84 that the engine 2 is in a transient state (for example, at high engine load, high engine speed, or acceleration of the vehicle), the learning condition flag is set to 0 in step S86. As a result, the learning control of the volume efficiency becomes invalid.

  As described above, according to the present embodiment, the volumetric efficiency variation can be corrected by learning the volumetric efficiency table with the EGR flow sensor 8. As a result, the accuracy of intake control can be improved.

  Further, the low response of the EGR flow sensor 8 is not affected by the steady use. In addition, a calculation formula for estimating the intake oxygen concentration can be realized by a simple method.

  As another form, a configuration in which the intake oxygen concentration of the estimation calculation result is not feedback-controlled with respect to the target intake oxygen concentration, but is replaced with the target MAF value from the target intake oxygen concentration.

  Another embodiment will be described with reference to FIGS.

  In this embodiment, the calculation formula and its adaptation are basically the same as the configuration of the above-described embodiment, and only the calculation configuration is changed, but the advantage that the MAF feedback controller of the prior art can be used as it is There is.

  The intake control device of the present embodiment performs intake control by replacing the target intake oxygen concentration with the target MAF. That is, the ECU 9 obtains the volume efficiency from the volume efficiency table based on the operation state of the engine 2, converts the target intake oxygen concentration into the target intake air amount based on the obtained volume efficiency, and converts the conversion. Control means for controlling (for example, feedback control) the intake throttle valve 4 and the EGR valve 7 so as to make the actual intake air amount coincide with the target intake air amount.

  First, conversion from the target intake oxygen concentration to the target MAF will be described.

  The target MAF is derived as shown in Equation 20 below. From the above formulas 2, 5, and 6, when formulas 2, 5, and 6 are arranged, the following formula 20 is obtained.

Here, by substituting the target intake oxygen concentration (O _2SETP) to O _2INM, the exhaust oxygen concentration calculated from equation 3 in O _2EXM, the M _CYL Substituting cylinder intake gas amount calculated from equation 1 For example, the intake air amount (M _AIRSETP ) necessary for achieving the target intake oxygen concentration is calculated (Formula 21). O _2EXM calculated from Equation 3 substitutes a value to which a delay element is applied.

  Next, the operation of the intake control device of this embodiment will be described.

  As shown in FIG. 8, the ECU 9 reads the target intake oxygen concentration from the target intake oxygen concentration map based on the engine speed, the fuel injection amount, and the water temperature, as in the above-described embodiment.

  The ECU 9 of the present embodiment further converts the read target intake oxygen concentration into the target MAF by the above equation 21 based on the engine speed, fuel injection amount, intake pressure, intake temperature, and intake air amount. The ECU 9 feedback-controls the intake throttle valve 4 and the EGR valve 7 so that the detected value of the MAF sensor 26 matches the converted target MAF.

  Next, an example of a control flowchart for calculating the EGR valve operation amount will be described with reference to FIG. This control flowchart is also executed by the ECU 9, and is called at a constant time period after the engine 2 is started.

  FIG. 9 shows an example of intake oxygen concentration control by the EGR valve 7. Note that not only the EGR valve 7 but also the intake throttle valve 4 and the supercharger (for example, the nozzle vane of the variable turbocharger) may be simultaneously controlled.

  In step S101, the target MAF is calculated from the above equation 21.

  In step S102, a difference between the target MAF (Maf_target_calc) calculated in step S101 and the intake air amount (Maf) measured by the MAF sensor 26 is calculated.

  In step S103, the target EGR valve opening is calculated by PID control based on the difference calculated in step S102.

More specifically, the difference calculated in step S102 and e, the K _P is a proportional gain, the K _I is an integration gain, when the K _D and the differential gain, the target EGR valve opening EGRV _POS,

It becomes. When the EGR control is valid according to the calculated target EGR valve opening, the position control of a motor (not shown) of the EGR valve 7 is performed.

  Also in this embodiment, the same effect as the above-described embodiment can be obtained.

  The present invention is not limited to these embodiments, and various modifications and applications can be considered.

DESCRIPTION OF SYMBOLS 1 Intake control apparatus 2 Engine 3 Exhaust pipe 4 Intake throttle valve 5 Intake pipe 6 EGR pipe 7 EGR valve 8 EGR flow sensor (EGR flow detection means)
9 ECU (learning correction means, control means)

Claims (2)

Intake control of the engine is performed by an intake throttle valve provided in an intake pipe of the engine and an EGR valve provided in an EGR pipe for communicating the exhaust pipe of the engine with the intake pipe. Engine intake control in which oxygen concentration or EGR rate is determined based on at least the volumetric efficiency of the engine, and the volumetric efficiency is read from a volumetric efficiency table in which the volumetric efficiency for each operating state of the engine is stored in advance. A device,
EGR flow rate detection means provided in the EGR pipe for detecting the flow rate of gas passing through the EGR pipe;
Learning correction means for learning and correcting the volumetric efficiency of the volumetric efficiency table based on the detection value of the EGR flow rate detection means when the engine is in a steady state ;
The volume efficiency is obtained from the volume efficiency table based on the operating state of the engine, the target intake oxygen concentration is converted into the target intake air amount based on the obtained volume efficiency, and the converted intake air amount is converted. And an intake air control apparatus for controlling the intake throttle valve and the EGR valve so that the actual intake air amounts coincide with each other . Intake air amount detection means for detecting the flow rate of intake air flowing through the intake pipe;
An intake air temperature detection means for detecting the temperature in the intake manifold provided at the downstream end of the intake pipe;
An intake pressure detecting means for detecting the pressure in the intake manifold,
The learning correction means calculates the volume efficiency in the steady state based on detection values of the intake air temperature detection means, the intake pressure detection means, the intake air amount detection means, and the EGR flow rate detection means, and calculates The engine intake control device according to claim 1, wherein the volumetric efficiency of the volumetric efficiency table is corrected by volumetric efficiency.