JP2012154245A - Control system of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control system of an internal combustion engine which includes a 2-system EGR consisting of a high pressure EGR and a low pressure EGR and can monitor concentration distribution of a specific substance in piping including the EGR pipes such that the internal combustion engine is controlled with high performance.SOLUTION: Each of an intake pipe 3, an exhaust pipe 4, a low pressure EGR pipe 6, and a high pressure EGR pipe 5 is equally divided in volume, to thereby set such piping areas as L1 and the like, H1 and the like, I1 and the like, and E1 and the like. A storage area to which an oxygen concentration of each piping area is written is set in a memory 70. A volumetric flow rate and an oxygen concentration of each pipe are calculated every 1-cycle of the engine 2, according to which a value of the oxygen concentration stored in the storage area of the memory 70 is updated. Openings of a low pressure EGR valve 60 and a high pressure EGR valve 50 are controlled such that an amount of oxygen flown into the engine 2 in each cycle is optimized on the basis of the stored value.

Description

  The present invention relates to a control device for an internal combustion engine.

  For example, in a diesel engine, a technique called EGR (Exhaust Gas Recirculation) in which exhaust gas is recirculated (recirculated) from an exhaust pipe to an intake pipe in order to suppress the amount of NOx in the exhaust is known. When performing EGR, it is required to control the valve opening of the EGR pipe so that the amount of oxygen taken into the engine is optimized. For this purpose, Patent Document 1 below discloses a method of estimating the oxygen concentration distribution in the EGR pipe and using the information.

  Specifically, in Patent Document 1, in order to accurately grasp the oxygen concentration in the EGR gas recirculated to the intake pipe, the recirculation delay of the EGR gas is obtained from the length of the EGR recirculation path and the EGR gas flow rate, and EGR The technical contents for sequentially storing and reading out the oxygen concentration in the path are disclosed.

Japanese Patent No. 3329711

  In the technique described in Patent Document 1, the return delay is obtained from the EGR gas flow rate and the EGR path length, and only simple piping is assumed. However, since the actual piping is not uniform in thickness, there is a possibility that the accuracy of oxygen concentration calculation is low with the method of Patent Document 1.

  Moreover, although only 1 system EGR is considered in patent document 1, two systems, high voltage | pressure EGR and low voltage | pressure EGR, may be equipped today. Therefore, development of a calculation method corresponding to two systems of EGR is required. Furthermore, this technique need not be limited to oxygen concentration. If the distribution of the concentration of a specific substance in the pipe can be grasped, a technique that leads to high-performance control of the engine can be developed.

  Therefore, in view of the above problems, the problem to be solved by the present invention is that each EGR pipe is controlled so that a high-performance internal combustion engine can be controlled in a state where two systems of EGR of high pressure EGR and low pressure EGR are equipped. It is another object of the present invention to provide a control device for an internal combustion engine that grasps the distribution of the concentration of a specific substance in a pipe including

  In order to achieve the above object, an internal combustion engine control apparatus according to the present invention includes an intake passage through which intake air from an internal combustion engine flows, an exhaust passage through which exhaust from the internal combustion engine flows, and the exhaust passage to the intake passage. A recirculation passage for recirculating exhaust gas, a storage section having a plurality of storage areas one-to-one associated with a plurality of piping areas obtained by dividing the recirculation passage, the intake passage, and the exhaust passage by equal volumes, and the internal combustion engine First calculation means for calculating a volume flow rate of gas flowing into the return passage, the intake passage, and the exhaust passage for each cycle of the engine; and the return passage, the intake passage, and the exhaust for each cycle of the internal combustion engine. A second calculation means for calculating the concentration of the specific substance in the gas flowing into the passage, a volume flow rate calculated by the first calculation means for each cycle of the internal combustion engine, and a calculation by the second calculation means. The And storage control means for storing the concentration of the specific substance in the piping region corresponding to the storage area on a one-to-one basis in each storage area of the storage unit. It is characterized by.

  As a result, the control apparatus for an internal combustion engine according to the present invention has a recirculation passage for recirculating exhaust gas from the exhaust passage to the intake passage, and has a piping region in which each pipe is divided by an equal volume, and a memory corresponding to it in the storage unit. An area is set, the volume flow rate of the gas flowing into each pipe and the concentration of the specific substance are calculated every cycle, and the concentration of the specific substance is stored in each storage area. Accordingly, the concentration of the specific substance for each piping region divided into equal volumes can be stored for each cycle in an appropriate manner even for piping having a uniform thickness. Therefore, a control device that accurately calculates and stores the concentration distribution of the specific substance in each pipe and controls the internal combustion engine is realized.

  The recirculation passage includes a first recirculation passage that recirculates exhaust gas from an upstream side of a turbine equipped in the exhaust passage to a downstream side of a compressor equipped in the intake passage, and a downstream side of the turbine than the compressor. A second recirculation passage for recirculating exhaust gas upstream, wherein the first calculation means calculates a volume flow rate of a gas flowing into each of the first recirculation passage and the second recirculation passage, and the second calculation The means may calculate the concentration of the specific substance in the gas flowing into each of the first reflux passage and the second reflux passage.

  According to the present invention, the exhaust gas recirculation passage includes two systems, a first recirculation passage that recirculates from the turbine upstream to the compressor downstream, and a second recirculation passage that recirculates from the turbine downstream to the compressor upstream. The volume flow rate of each reflux passage and the concentration of a specific substance are calculated. Therefore, in a high-performance exhaust gas recirculation system that recirculates exhaust gas in two systems, it is possible to realize a control device that controls the internal combustion engine with high performance by accurately calculating the volume flow rate and the concentration of a specific substance for each pipe.

  Further, it comprises a third calculation means for calculating the concentration of the specific substance in the gas exhausted from the internal combustion engine for each cycle of the internal combustion engine, and the storage control means stores the specific information stored in each of the storage areas. A storage movement unit may be provided to move the concentration of the substance to another storage area on the downstream side in accordance with the volume flow rate calculated by the first calculation unit after one cycle of the internal combustion engine.

  According to this invention, since the means for calculating the concentration of the specific substance discharged from the internal combustion engine for each cycle and the means for moving the numerical value stored in the storage area according to the volume flow rate in the storage unit, When storing the concentration distribution of a specific substance in a pipe, it is reasonable to calculate the concentration of the specific substance in the exhaust from the internal combustion engine, and the concentration value in each pipe will move to the downstream side in order. Adopt a different method. Therefore, a control device that can grasp the concentration of the specific substance in the pipe by a rational method and controls the internal combustion engine with high performance can be realized.

  Further, for each cycle of the internal combustion engine, according to the volume flow rate calculated by the first calculation means, the concentration of the specific substance stored in the storage area for the gas flowing out from the reflux passage is used. A fourth calculating means for calculating the amount of the specific substance in the gas flowing into the internal combustion engine may be provided.

  According to this invention, for each cycle, the amount of the specific substance flowing into the internal combustion engine is determined using the concentration of the specific substance stored in the storage area corresponding to the gas flowing out from the reflux passage according to the volume flow rate. calculate. Therefore, a storage area corresponding to the piping area is set, and the concentration value of the specific substance stored in each storage area is transferred to the internal combustion engine with high accuracy using a model that moves according to the volumetric flow rate of each cycle. The amount of the specific substance to be calculated can be calculated, and a control device for controlling the internal combustion engine with high performance can be realized.

  The first calculation means is calculated by fifth calculation means for calculating the mass flow rate of the gas flowing into the recirculation passage, the intake passage, and the exhaust passage for each cycle of the internal combustion engine, and the fifth calculation means. Conversion means for converting the mass flow rate into volume flow rate by pressure and temperature in the reflux passage, the intake passage, and the exhaust passage may be provided.

  According to the present invention, the mass flow rate in each pipe is first calculated, and then the mass flow rate is converted into the volume flow rate by the temperature value and the pressure value. First, it can be converted into a volume flow rate suitable for grasping the spatial distribution of concentration in each pipe. Therefore, it is possible to realize a control device that stores the concentration of the specific substance by a calculation procedure in a rational order and controls the internal combustion engine with high performance.

  The specific substance is oxygen, and has valve control means for controlling the opening degree of the valve provided in the reflux passage using the oxygen concentration in each of the storage areas stored by the storage control means. It is good.

  According to the present invention, in the configuration including the recirculation passage for recirculating the exhaust gas from the exhaust passage to the intake passage, the piping region in which each piping is divided by an equal volume, and the storage region corresponding to the piping region are set in the storage unit, The volume flow rate of gas flowing into each pipe and the oxygen concentration in the gas are calculated every cycle, and the oxygen concentration is stored in each storage area. Based on this information, the valve of the reflux passage is opened. Adjust the degree. Therefore, corresponding to pipes that are not uniform in thickness, the oxygen concentration of each pipe area divided into equal volumes is stored for each cycle, and the opening degree of the valve of the reflux passage is adjusted based on this. can do. Therefore, the oxygen concentration distribution in each pipe is accurately calculated and stored. For example, the amount of oxygen flowing into the internal combustion engine is controlled with high accuracy, and the amount of NOx and PM discharged from the internal combustion engine is controlled with high accuracy. A control device is realized.

The block diagram of the control apparatus of the internal combustion engine in one Example of this invention. The flowchart which shows the example of control processing. The flowchart which shows the example of the calculation process of mass flow rate. The figure which shows the example of the memory | storage process in memory.

  Embodiments of the present invention will be described below with reference to the drawings. First, FIG. 1 is a schematic diagram of an apparatus configuration in an embodiment of a control apparatus 1 (hereinafter, apparatus 1) according to the present invention.

  The device 1 is an embodiment of a control device configured for an internal combustion engine (engine) of an automobile vehicle. The apparatus 1 includes an engine 2, an intake pipe 3, an exhaust pipe 4, a high-pressure EGR pipe 5, a low-pressure EGR pipe 6, and an electronic control unit 7 (ECU: Electronic Control Unit).

  Air is supplied to the engine 2 through the intake pipe 3. Exhaust gas from the engine 2 is discharged outside the vehicle through the exhaust pipe 4. The high pressure EGR pipe 5 and the low pressure EGR pipe 6 are pipes for exhaust gas recirculation (EGR) from the exhaust pipe to the intake pipe. The exhaust gas recirculation through the EGR pipe 5 lowers the combustion temperature in the engine and reduces the amount of NOx emitted from the engine. The ECU 7 has a normal computer structure and controls various controls described later.

  The high pressure EGR pipe 5 circulates the exhaust gas from the upstream side of the turbine 42 of the turbocharger to the downstream side of the compressor 34. The low pressure EGR pipe 6 circulates the exhaust gas from the downstream side of the turbine 42 to the upstream side of the compressor 34. The reason why two EGR systems are provided in this way is as follows.

  By providing two EGR systems, the intake air pressure due to turbocharger supercharging may not be secured at high loads because the amount of EGR that can be recirculated from the exhaust passage may not be secured with high pressure EGR due to the increase in intake air pressure due to turbocharger turbocharging. In order not to be affected by the rise, EGR is executed with a low pressure EGR communicating with the upstream side of the intake passage from the compressor. As a result, a sufficient EGR amount can be ensured even under conditions where the intake pressure is supercharged in a high load range.

  The engine 2 is a diesel engine, for example, and injects fuel from the injector 20 into the cylinder. The intake pipe 3 is equipped with an air flow meter 30, an intake throttle 31, a pressure sensor 32, a temperature sensor 33, a turbocharger compressor 34, and an intercooler 35.

  The air flow meter 30 measures the mass flow rate of intake air. The intake air amount is adjusted by adjusting the opening degree of the intake throttle 31. The pressure sensor 32 and the temperature sensor 33 measure the pressure and temperature in the intake manifold, respectively. The compressor 34 of the turbocharger is supplied with driving force from the turbine on the exhaust pipe 4 side, compresses the intake air, and sends more air to the engine 2. The intercooler 35 cools the intake air and allows more air to be sent to the engine 2.

  The exhaust pipe 4 is equipped with a pressure sensor 40, a temperature sensor 41, a turbocharger turbine 42, and a DPF 43 (Diesel Particulate Filter). The pressure sensor 40 and the temperature sensor 41 detect the pressure and temperature in the exhaust manifold. The turbine 42 is rotated by the exhaust gas discharged from the engine 2, and sends the driving force generated thereby to the compressor 34.

  For example, the DPF 43 may have a structure in which the inlet side and the outlet side are alternately clogged in a so-called honeycomb structure. Exhaust gas discharged during operation of the engine 2 contains PM (particulate matter), and this PM is collected inside or on the surface of the DPF wall when the exhaust gas passes through the DPF wall having the above structure of the DPF 43. Is done. The DPF 43 may be a DPF with an oxidation catalyst on which an oxidation catalyst is supported.

  Whenever the estimated value of the PM amount accumulated in the DPF 43 is considered to exceed a predetermined value, the DPF 43 is burned by raising the temperature of the DPF 43 by post injection after main injection in the engine cylinder, for example. Just replay it. At that time, for example, a differential pressure sensor for measuring a pressure difference (front-rear differential pressure) between the inlet side and the outlet side of the DPF 43 is equipped, and from the measured value and a map showing the relationship between the differential pressure and the PM deposition amount, PM What is necessary is just to estimate the amount of accumulation.

  The high pressure EGR pipe 5 and the low pressure EGR pipe 6 are provided with a high pressure EGR valve 50 and a low pressure EGR valve 60, respectively, and the amount of exhaust gas recirculated is adjusted by their opening degrees. Further, the high pressure EGR pipe 5 and the low pressure EGR pipe 6 are provided with EGR coolers 51 and 52 to cool the recirculated exhaust gas, thereby enabling more exhaust gas recirculation. The apparatus 1 also includes an accelerator opening sensor 80 and an engine speed sensor 81. The degree of depression of the accelerator of the vehicle by the driver is detected by the accelerator opening sensor 80. The engine speed is detected by the engine speed sensor 81.

  In the apparatus 1, the amount of oxygen flowing into the engine 2 is controlled with high accuracy every cycle in order to set the NOx or PM emission amount from the engine 2 to an appropriate value. For this purpose, the oxygen concentration distribution in each pipe in the apparatus configuration shown in FIG. 1 is calculated and stored for each cycle of the engine 2.

  Specifically, the distribution of the oxygen concentration is obtained by dividing each pipe into equal volume areas (pipe areas) and obtaining the oxygen concentration for each pipe area. At that time, it is not considered that the value of oxygen concentration in each piping region changes due to the mixing of gas between adjacent piping regions, and the amount of gas newly entering the upstream piping region in each cycle is divided into each piping. Consider a model in which the value of oxygen concentration in the region shifts downstream. In other words, if the volumetric flow velocity in the current cycle in each pipe is a numerical value for N pipe areas, the numerical value of the oxygen concentration in each pipe area simply shifts to the downstream side by N, thereby causing the upstream upstream The N piping regions become regions with new oxygen concentrations.

  FIG. 1 shows an example of the piping region. In this example, the low pressure EGR pipe 6 is divided into 20 parts with an equal volume, and 20 pipe regions L1 to L20 are set. Similarly, the high-pressure EGR pipe 5 is divided into ten pipe regions of equal volume H1 to H10. A region from the outlet position of the low pressure EGR pipe 6 to the outlet position of the high pressure EGR pipe 5 in the intake pipe 3 is divided into five piping areas of equal volumes I1 to I5. The area from the inlet position of the high pressure EGR pipe 5 to the inlet position of the low pressure EGR pipe 6 in the exhaust pipe 4 is divided into five piping areas E1 to E5 with an equal volume.

  L1 to L20 are equal volumes, H1 to H10 are equal volumes, I1 to I5 are equal volumes, and E1 to E5 are equal volumes. In addition, L1, H1, I1, and E1 do not need to be this volume. Since the EGR coolers 51 and 61, the intercooler 35, the DPF 43, and the like are arranged, the cross-sectional areas through which exhaust flows in each pipe of the intake pipe 3, the exhaust pipe 4, the high-pressure EGR pipe 5, and the low-pressure EGR pipe 6 are constant. Absent. Therefore, the exhaust gas flow direction lengths of L1 to L20 (H1 to H10, I1 to I5, E1 to E5) are not constant. Naturally, the larger the flow cross-sectional area, the shorter the flow direction length.

  In order to store the numerical value of the oxygen concentration in each piping area and rewrite every cycle, as shown in FIG. 4, the memory area in the ECU 7 has a storage area corresponding to each piping area on a one-to-one basis. Is set.

  As described above, the distribution of the oxygen concentration in each pipe is constituted by the numerical values of the oxygen concentration for each pipe region of L1 to L20, H1 to H10, I1 to I5, and E1 to E5. A (1)... A (20), b (1),..., B (10), c (1),..., C (5), d (1),. , D (5) is the numerical value of the oxygen concentration in each piping region.

  Then, for each cycle, the oxygen concentration values in the number of piping regions in accordance with the volume flow velocity on the upstream side of each piping become new numerical values (indicated by ax, bx, cx, dx in FIG. 4), and downstream thereof. Then, the numerical value of the oxygen concentration shifts to the downstream side by the number of the piping regions that have become new numerical values. Details of the rewriting process in the memory 70 will be described later.

  In this embodiment, the opening degree of the high pressure EGR valve 50 and the low pressure EGR valve 60 is controlled by the ECU 6 so that the amount of NOx discharged from the engine 2 becomes an appropriate amount under the configuration of FIG. The processing procedure is shown in FIG. 2 (and FIG. 3). The processing of FIG. 2 (and FIG. 3) is stored in, for example, the memory 70 in the ECU 7, and is performed every cycle of the engine 2 (that is, in a 4-stroke / 1-cycle engine during the period from the start to the stop of the engine 2). Can be processed automatically by the ECU 7 every 4 strokes and every 2 strokes in a 2 stroke / 1 cycle engine).

  In the process of FIG. 2, first, in step S <b> 10, the ECU 7 acquires detection values and the like of each sensor. Specifically, the accelerator opening detected by the accelerator opening sensor 80, the engine speed detected by the engine speed sensor 81, the intake air amount (fresh air amount) detected by the air flow meter 30, and the intake air detected by the pressure sensor 32 Pressure value in manifold, temperature value in intake manifold detected by temperature sensor 33, pressure value in exhaust manifold detected by pressure sensor 40, temperature value in exhaust manifold detected by temperature sensor 41, pressure sensor 62 detects Each numerical value such as the pressure value in the low-pressure EGR pipe 6 and the temperature value in the low-pressure EGR pipe 6 detected by the temperature sensor 41 is acquired.

  Next, in S20, the ECU 7 calculates the fuel injection amount Q from the injector 20. Specifically, for example, a map indicating the optimal injection amount according to the operating condition of the engine 2 consisting of the accelerator opening and the engine speed is stored in advance in, for example, the memory 70, and the map and obtained in S10 are obtained. The fuel injection amount Q may be calculated from the accelerator opening and the actual value of the engine speed.

  Next, in S30, the ECU 7 calculates the basic opening degree SBShp of the high pressure EGR valve 50 and the basic opening degree SBSlp of the low pressure EGR valve 60. As for the basic openings SBShp and SBSlp, a map indicating an appropriate basic opening according to the engine speed and the fuel injection amount is stored in the memory 70 in advance, and the map and the engine speed obtained in S10 and S20 are stored. What is necessary is just to obtain | require from the actual value of the fuel injection quantity Q calculated | required by (4).

  Next, in S40, the ECU 7 calculates the current value GTT of the target value of the amount of oxygen sucked into the cylinder of the engine 2 (in-cylinder intake oxygen amount) every cycle. The target value GTT for the in-cylinder intake oxygen amount is stored in advance in the memory 70 as a target value for the in-cylinder intake oxygen amount in accordance with the engine speed and the fuel injection amount. What is necessary is just to obtain | require from the engine rotational speed calculated | required by (4) and the actual value of the fuel injection quantity Q calculated | required by S20.

  Next, in S50, the ECU 7 calculates the mass flow rate of the gas flowing through each of the intake pipe 3, the exhaust pipe 4, the high pressure EGR pipe 5, and the low pressure EGR pipe 6. Here, the gas flowing through the intake pipe 3 is a gas that passes through the intake throttle 31 in particular. The gas flowing through the exhaust pipe 4 is particularly a gas passing through the turbine 42. The mass flow rates of the gas flowing through the intake pipe 3 (intake throttle 31), the exhaust pipe 4 (turbine 42), the high pressure EGR pipe 5, and the low pressure EGR pipe 6 are denoted as Mdth, Mtb, Mhp, and Mlp, respectively. Details of the calculation processing in S50 are shown in FIG.

  In the process of FIG. 3, first, in S200, the ECU 7 detects the intake mass flow rate Mail. This may be detected by the air flow meter 30.

Next, in S <b> 210, the ECU 7 calculates the mass flow rate Mcld of the gas sucked into the cylinder of the engine 2. Specifically, this Mcld is calculated by the following equation (e1). Note that * indicates multiplication and / indicates division.
Mcld = {η * Pim * Vcld} / {R * Tim} (e1)

  Expression (e1) is a well-known gas state equation, Pim and Tim are the pressure value and temperature value in the intake manifold detected by the pressure sensor 32 and the temperature sensor 33, respectively, Vcld is the cylinder volume of the engine 2, and R is Gas constant. η is the charging efficiency of the gas sucked into the cylinder of the engine 2, and may be set to an appropriate value in advance, for example.

Next, in S220, the ECU 7 calculates the current value Mhp of the gas mass flow rate for one cycle in the high-pressure EGR pipe 5. Specifically, Mhp is calculated by the following equation (e2). Expression (e2) is a well-known Bernoulli theorem, where Pex is the pressure value in the exhaust manifold detected by the pressure sensor 40, Pim is the pressure value in the intake manifold detected by the pressure sensor 32, and M is the high pressure EGR valve 50. The gas flow path cross-sectional area of the high-pressure EGR pipe 5 when the opening is SBShp obtained in S30 above, α is a proportional coefficient, and ^ (1/2) is a square root.
Mhp = α * M * (Pex−Pim) ^ (1/2) (e2)

Next, in S230, the ECU 7 calculates the current value Mdth of the mass flow rate of the gas for one cycle passing through the intake throttle 31. Mdth is calculated by the following equation (e3) from the law of conservation of mass at the portion where the high pressure EGR pipe 5 joins the intake pipe 3.
Mdth = Mcld−Mhp (e3)

Next, in S240, the ECU 7 calculates the current value Mlp of the mass flow rate of the gas for one cycle in the low pressure EGR pipe 6. Mlp is calculated by the following equation (e4) from the law of conservation of mass at the portion where the low pressure EGR pipe 6 joins the intake pipe 3.
Mlp = Mdth-Mair (e4)

Next, in S250, the ECU 7 calculates the current value Mtb of the mass flow rate of the gas for one cycle passing through the turbine 42. Since the increase in the mass of gas from the intake pipe 3 to the exhaust pipe 4 is the mass of fuel injected in the cylinder, Mtb is calculated by the following equation (e5). The above is the processing procedure of FIG. The above processing is executed in S50 of FIG.
Mtb = Q + Mdth (e5)

Returning to FIG. 2, next, in S60, the ECU 7 converts the mass flow rate calculated in S50 into a volume flow rate. Volume flow rates converted from Mdth, Mtb, Mhp, and Mlp are expressed as Vdth, Vtb, Vhp, and Vlp, respectively. Specifically, Vdth, Vtb, Vhp, and Vlp are calculated by the following equations (e6) to (e9). Here, Ddth, Dtb, Dhp, and Dlp are the densities of the gas that passes through the intake throttle 31, the gas that passes through the turbine 42, the gas that flows through the high-pressure EGR pipe 5, and the gas that flows through the low-pressure EGR pipe 6, respectively.
Vdth = Mdth / Ddth (e6)
Vtb = Mtb / Dtb (e7)
Vhp = Mhp / Dhp (e8)
Vlp = Mlp / Dlp (e9)

The densities Ddth, Dtb, Dhp, and Dlp are calculated by the following equations (e10) to (e13).
Ddth = 1.293 * (273 + T1) /273*P1/101.3 (e10)
Dtb = 1.293 * (273 + T2) /273*P2/101.3 (e11)
Dhp = 1.293 * (273 + T3) /273*P3/101.3 (e12)
Dlp = 1.293 * (273 + T4) /273*P4/101.3 (e13)

  Expressions (e10) to (e13) are expressions for correcting the air density (1.293 kg per cubic meter) at 0 degrees Celsius (absolute temperature 273 degrees) and 1 atmosphere (101.3 kPa) with temperature and pressure. . T1, T2, T3, and T4 are temperatures in the intake pipe 3, exhaust pipe 4, high-pressure EGR pipe 5, and low-pressure EGR pipe 6, respectively. P1, P2, P3, and P4 are intake pipe 3, exhaust pipe 4, and high-pressure, respectively. This is the pressure in the EGR pipe 5 and the low pressure EGR pipe 6.

  For example, T1 may be the temperature in the intake manifold detected by the temperature sensor 33. T2 may be the temperature in the exhaust manifold detected by the temperature sensor 41. T3 may be an average value of the detected temperature value of the temperature sensor 33 and the detected temperature value of the temperature sensor 41. T4 may be a detected temperature value of the temperature sensor 63.

  P1 may be the pressure in the intake manifold detected by the pressure sensor 32. P2 may be the pressure in the exhaust manifold detected by the pressure sensor 40. P3 may be an average value of the detected pressure value of the pressure sensor 32 and the detected pressure value of the pressure sensor 40. P4 may be a detected pressure value of the pressure sensor 62.

Next, in S70, the ECU 7 calculates the memory movement amount of each pipe. As described above, the present embodiment employs a model in which the numerical value of the oxygen concentration in each piping region moves downstream when a new gas flows in every cycle. The number of areas to move. The memory movement amounts of the low-pressure EGR pipe 6, high-pressure EGR pipe 5, intake pipe 3, and exhaust pipe 4 are N1, N2, N3, and N4, respectively. N1, N2, N3, and N4 are calculated by the following equations (e14) to (e17).
N1 = Vlp / V1 (e14)
N2 = Vhp / V2 (e15)
N3 = Vdth / V3 (e16)
N4 = Vtb / V4 (e17)

  In equations (e14) to (e17), V1 is the volume (volume) of the piping region L1 (to L20), V2 is the volume (volume) of the piping region H1 (to H10), and V3 is the volume of the piping region I1 (to I5). (Volume), V4 is the volume (volume) of the piping region E1 (from E5). In N1 to N4, the numbers after the decimal point may be rounded off (or rounded down or rounded up), for example.

  Next, in S80, the ECU 7 calculates the current value of the oxygen concentration in the gas flowing out from each pipe in one cycle. Oxygen concentrations in the gas flowing out in one cycle from the low pressure EGR pipe 6, the high pressure EGR pipe 5, the intake pipe 3, and the exhaust pipe 4 are expressed as Clp, Chp, Cdth, and Ctb, respectively.

In the current cycle, the gas for N1, N2, N3, and N4 piping regions obtained in S70 flows out from each piping. Therefore, the oxygen concentration of the outflowing gas may be an average value of the oxygen concentration in the piping region. Therefore, Clp, Chp, Cdth, and Ctb are calculated from (e18) to (e21) below.
Clp = {a (20) +... + A (21−N1)} / N1 (e18)
Chp = {b (10) +... + B (11−N2)} / N2 (e19)
Cdth = {c (5) +... + C (6-N3)} / N3 (e20)
Ctb = {d (5) +... + D (6-N4)} / N4 (e21)

  Next, in S90, the ECU 7 calculates (estimates) the current value of the oxygen amount (in-cylinder inhaled oxygen amount) taken into the cylinder of the engine 2 in one cycle. The in-cylinder intake oxygen amount is expressed as GTO2. The oxygen flowing into the cylinder of the engine 2 is composed of oxygen flowing from the high-pressure EGR pipe 5 and oxygen flowing from the intake pipe 3 side. The gas flowing out from the high pressure EGR pipe 5 has a volume flow rate of Vhp and an oxygen concentration of Chp, and the product of Vhp and Chp is the amount of oxygen flowing out of the high pressure EGR pipe 5 in the current cycle.

Similarly, the gas flowing into the engine 2 from the intake pipe 3 has a volume flow rate of Vtdh and an oxygen concentration of Cdth, and the product of Vdth and Cdth is the amount of oxygen flowing into the engine 2 from the intake pipe 3 side in the current cycle. It becomes. Therefore, GTO2 is calculated by the following equation (e22) after all.
GTO2 = Chp * Vhp + Cdth * Vdth (e22)

Next, in S100, the ECU 7 calculates a deviation ΔGT between the estimated value of the cylinder intake oxygen amount and the target value. ΔGT is a difference between GTO2 calculated in S90 and GTT calculated in S40, and is calculated by the following equation (e23).
ΔGT = GTO2-GTT (e23)

  Next, in S110, the ECU 7 calculates opening correction amounts of the high pressure EGR valve 50 and the low pressure EGR valve 60. The opening correction amounts of the high pressure EGR valve 50 and the low pressure EGR valve 60 are denoted as SKhp and SKlp, respectively. As a method for calculating SKhp and SKlp, for example, a map showing the optimum SKhp and SKlp according to ΔGT may be stored in the memory 70 in advance, and calculated from this map and the value of ΔGT obtained in S100.

Next, in S120, the ECU 7 calculates final openings (openings used in the current cycle) of the low pressure EGR valve 60 and the high pressure EGR valve 50. The final openings of the low pressure EGR valve 60 and the high pressure EGR valve 50 are denoted as SEDlp and SEDhp, respectively. These are the sum of SBSlp and SBShp obtained in S30 and SKlp and SKhp obtained in S110, and are calculated by the following equations (e24) and (e25).
SEDlp = SBSlp + SKlp (e24)
SEDhp = SBShp + SKhp (e25)

  Next, in S <b> 130, the ECU 7 controls the opening degrees of the low pressure EGR valve 60 and the high pressure EGR valve 50. That is, the ECU 7 controls the openings of the low pressure EGR valve 60 and the high pressure EGR valve 50 to the openings SEDlp and SEDhp obtained in S120, respectively.

Next, in S140, the ECU 7 calculates the oxygen concentration Cex in the gas discharged from the engine 2 in one cycle at the current time point. Cex is calculated by the following equation (e26).
Cex = {GTO2-1.5 * Q} / {Mcld + 0.5 * Q} (e26)

The meaning of the formula (e26) is as follows. The denominator of the equation (e26) is the amount of gas discharged from the engine 2 in one cycle, and the numerator is the amount of oxygen discharged from the engine 2 in one cycle. Normally, the combustion reaction in the engine cylinder is considered as 1 mol of CH ₂ (fuel) and 3/2 mol of O ₂ react to produce 1 mol of CO ₂ and 1 mol of H ₂ O. It is.

  Accordingly, combustion of 1 mole of fuel increases the gas by 0.5 moles, so that the denominator of equation (e26) is obtained. Since 1 mol of fuel reduces oxygen by 3/2 mol, a numerator of formula (e26) is obtained. GTO2 and Mcld in the formula (e26) may be values obtained by converting the mass into the number of moles.

  Next, in S150, the ECU 7 calculates the current value of the oxygen concentration in the gas flowing into each pipe in one cycle. Oxygen concentrations in the gas that flows into each pipe of the low pressure EGR pipe 6, the high pressure EGR pipe 5, the exhaust pipe 4, and the intake pipe 3 in one cycle are expressed as ax, bx, cx, and dx, respectively.

  The gas flowing into the low pressure EGR pipe 6 is a gas flowing out from the exhaust pipe 4. The oxygen concentration of the gas flowing out from the exhaust pipe 4 is the above-described Ctb. The gas flowing into the high pressure EGR pipe 5 and the exhaust pipe 4 is a gas discharged from the engine 2. The oxygen concentration of the gas discharged from the engine 2 is the above-described Cex. The gas flowing into the intake pipe 3 (downstream portion from the outlet of the low pressure EGR pipe 6) is a mixture of air flowing from the outside of the vehicle and gas flowing out of the low pressure EGR pipe 6.

As is known, the oxygen concentration in the air flowing from the outside of the vehicle is 0.23 in mass ratio, and the oxygen concentration of the gas discharged from the low-pressure EGR pipe 6 is the above-described Clp. As described above, ax, bx, cx, and dx are calculated by the following equations (e27) to (e30).
ax = Ctb (e27)
bx = Cex (e28)
cx = Cex (e29)
dx = (0.23 * Mair + Clp * Mlp) / (Mair + Mlp) (e30)

  Next, in S160, the ECU 7 rewrites the stored contents in the memory 70 using the oxygen concentration obtained in S160. An example of this process is shown in FIG. As described above, when new gas flows into the low-pressure EGR pipe 6, the high-pressure EGR pipe 5, the intake pipe 3, and the exhaust pipe 4 in the current cycle, the oxygen concentration in each of the piping regions is increased by N1, N2, N3, and N4, respectively. It moves downstream (moves to the right in FIG. 4).

  The oxygen concentrations of the gas newly flowing into the low pressure EGR pipe 6, the high pressure EGR pipe 5, the intake pipe 3, and the exhaust pipe 4 are ax, bx, cx, and dx obtained in S150. In the example of FIG. 4, the case where N1 is 3, N2 is 2, N3 is 2, and N4 is 3 is shown. The above is the processing procedure of FIG. 2 and FIG.

  In the above embodiment, an example of calculating the oxygen concentration is shown. However, the present invention is not limited to the oxygen concentration, and may be used for calculating the concentration of a specific substance related to the control of the engine 2. In the above example, the low-pressure EGR pipe 6 is divided into 20 parts, the high-pressure EGR pipe is divided into 10 parts, the intake pipe is divided into 5 parts, and the exhaust pipe is divided into 5 parts. In addition, the portion using the mass may be changed to the number of moles, and in that case, the conservation law in the branching and merging portion of the pipe is established.

  In S70, the memory movement amounts N1 to N4 are obtained as integer values by rounding off the decimal part, but this may be a non-integer value. In that case, the oxygen (specific substance) concentration value in each piping region after one cycle may be calculated by weighted averaging the two mixed concentration values according to the respective volume ratios. Also in the calculation in S80, when the memory movement amount is a non-integer, the weighted average of density values according to the volume ratio may be used. If the memory movement amount is set to a non-integer in this way, calculation with higher accuracy becomes possible.

1 control device 2 engine (internal combustion engine)
3 Intake pipe (intake passage)
4 Exhaust pipe (exhaust passage)
5 High pressure EGR pipe (reflux passage, first reflux passage)
6 Low pressure EGR pipe (reflux passage, second reflux passage)
7 ECU
70 Memory (storage unit)

Claims (6)

An intake passage through which the intake air of the internal combustion engine flows;
An exhaust passage through which exhaust from the internal combustion engine circulates;
A recirculation passage for recirculating exhaust gas from the exhaust passage to the intake passage;
A storage unit having a plurality of storage areas one-to-one associated with a plurality of piping areas obtained by dividing the recirculation passage, the intake passage, and the exhaust passage by equal volumes;
First calculation means for calculating a volume flow rate of gas flowing into the recirculation passage, the intake passage, and the exhaust passage for each cycle of the internal combustion engine;
Second calculation means for calculating a concentration of a specific substance in the gas flowing into the recirculation passage, the intake passage, and the exhaust passage for each cycle of the internal combustion engine;
For each cycle of the internal combustion engine, using the volume flow rate calculated by the first calculation unit and the concentration of the specific substance calculated by the second calculation unit, the individual storage areas of the storage unit Storage control means for storing the concentration of the specific substance in the piping region corresponding to the storage region on a one-to-one basis;
A control apparatus for an internal combustion engine, comprising: The recirculation passage includes a first recirculation passage that recirculates exhaust gas from an upstream side of a turbine equipped in the exhaust passage to a downstream side of a compressor equipped in the intake passage, and a downstream side of the turbine and upstream of the compressor. A second recirculation passage for recirculating exhaust gas to
The first calculation means calculates a volume flow rate of gas flowing into each of the first reflux passage and the second reflux passage,
2. The control device for an internal combustion engine according to claim 1, wherein the second calculation unit calculates the concentration of the specific substance in the gas flowing into each of the first return passage and the second return passage. Third calculation means for calculating the concentration of a specific substance in the gas discharged from the internal combustion engine for each cycle of the internal combustion engine;
The storage control means determines the concentration of the specific substance stored in each of the storage areas after another cycle of the internal combustion engine according to the volume flow rate calculated by the first calculation means. The control apparatus for an internal combustion engine according to claim 1 or 2, further comprising a storage movement means for moving the storage area.   For each cycle of the internal combustion engine, the internal combustion engine uses the concentration of the specific substance stored in the storage area for the gas flowing out from the recirculation passage according to the volume flow rate calculated by the first calculation means. The control device for an internal combustion engine according to any one of claims 1 to 3, further comprising a fourth calculation means for calculating the amount of the specific substance in the gas flowing into the engine. The first calculation means includes
Fifth calculation means for calculating a mass flow rate of gas flowing into the recirculation passage, the intake passage, and the exhaust passage for each cycle of the internal combustion engine;
A conversion means for converting the mass flow rate calculated by the fifth calculation means into a volume flow rate by the pressure and temperature in the reflux passage, the intake passage and the exhaust passage;
The control apparatus for an internal combustion engine according to any one of claims 1 to 4, further comprising: The specific substance is oxygen;
6. The valve control unit according to claim 1, further comprising: a valve control unit configured to control an opening degree of a valve provided in the reflux passage by using an oxygen concentration in each of the storage areas stored by the storage control unit. The control apparatus for an internal combustion engine according to the item.