JP2009079527A - Egr device for multi-cylinder engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To promote cost reduction and fuel economy improvement without requiring the installation of a smoke filter in an EGR passage in an EGR device for a multi-cylinder engine having the EGR passage introducing exhaust gas discharged from an EGR gas forming cylinder to an intake passage of an normal cylinder by dividing a plurality of cylinder engine bodies into the EGR gas forming cylinder and the other normal cylinder. <P>SOLUTION: The plurality of cylinder engine bodies 2 are divided into the EGR gas forming cylinder 2a and the other normal cylinder 2b. The device has the EGR passage 4 introducing exhaust gas discharged from the EGR gas forming cylinder 2a to the suction passage 3 of the normal cylinder 2b, and a fuel injection map exclusive for the EGR gas forming cylinder 2a separately from a fuel injection map for the normal cylinder 2b. In the fuel injection map exclusive for the EGR gas forming cylinder 2a, a fuel injection quantity and timing not generating smoke are always set irrespective of operation states of the engine bodies 2. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention divides an engine body of a plurality of cylinders into an EGR gas generating cylinder and another normal cylinder, and guides exhaust gas discharged from the EGR gas generating cylinder to an intake passage of the normal cylinder. About.

  An EGR device provided in a diesel engine or the like is intended to reduce the combustion temperature by circulating a part of the exhaust gas to the intake passage of the engine and suppress the generation of NOx.

  As an EGR device for a multi-cylinder diesel engine, an EGR passage that divides a multi-cylinder engine body into an EGR gas generation cylinder and another normal cylinder and introduces exhaust gas discharged from the EGR gas generation cylinder into an intake passage of the normal cylinder What is provided is known (patent document 1).

  In this EGR device, soot that collects smoke components (soot, etc.) in exhaust gas flowing in the EGR passage in the middle of the EGR passage that guides exhaust gas discharged from the EGR gas generation cylinder to the intake passage of the normal cylinder A filter is provided.

JP-A-7-54715 JP 2006-46252 A

  However, the necessity of a smoke filter that removes smoke components from the exhaust gas discharged from the EGR gas generation cylinder means that non-burning fuel that causes smoke is injected into the EGR gas generation cylinder. This means that there is room for improvement in fuel economy.

  Moreover, providing the smoke filter in the EGR passage leads to an increase in manufacturing cost of the entire apparatus. In addition, clogging of the soot filter due to aging is inevitable, so it is necessary to perform maintenance periodically to eliminate clogging, and the running cost is also improved.

  An object of the present invention, which was created in view of the above circumstances, is to provide an EGR device for a multi-cylinder engine that does not require a smoke filter in an EGR passage and can promote cost reduction and fuel efficiency improvement.

  In order to achieve the above object, the present invention divides a multi-cylinder engine body into an EGR gas generating cylinder and another normal cylinder, and introduces exhaust gas discharged from the EGR gas generating cylinder into the intake passage of the normal cylinder. An EGR device for a multi-cylinder engine having an EGR passage that includes a fuel injection map dedicated to the EGR gas generation cylinder provided separately from the fuel injection map for the normal cylinder, and the fuel dedicated to the EGR gas generation cylinder The injection map is set with a fuel injection amount and timing at which smoke does not always occur regardless of the operating state of the engine body.

  In the fuel injection map dedicated to the EGR gas generating cylinder, the fuel injection timing may be advanced from the fuel injection map for the normal cylinder.

  An EGR valve provided in the EGR passage and having a variable passage sectional area; an exhaust pressure adjustment passage having one end connected to the EGR passage and the other end connected to an exhaust passage of the normal cylinder; and the exhaust pressure adjustment passage An exhaust pressure control valve having a variable passage area, an engine rotation speed sensor for detecting the rotation speed of the engine body, an engine throttle sensor for detecting a load of the engine body, and an opening degree of the EGR valve And a controller for controlling the opening of the exhaust pressure control valve, the controller based on the detected value of the engine speed sensor and the detected value of the engine throttle sensor, and the opening of the EGR valve and the controller It may control the opening of the exhaust pressure control valve.

  An exhaust pressure sensor provided in the exhaust passage of the EGR gas generation cylinder; and an intake pressure sensor provided in the intake passage of the EGR gas generation cylinder. The controller has a detection value of the exhaust pressure sensor described above. The opening degree of the exhaust pressure control valve may be controlled so as to be equal to the detected value of the intake pressure sensor.

  A charge tank for storing EGR gas may be provided in the EGR passage.

  An EGR cooler that cools the EGR gas may be provided in the EGR passage so as to be positioned upstream of the EGR gas flow from the charge tank.

  According to the EGR device of a multi-cylinder engine according to the present invention, it is not necessary to provide a smoke filter in the EGR passage, and cost reduction and fuel efficiency improvement can be promoted.

  A preferred embodiment of the present invention will be described with reference to the accompanying drawings.

  As shown in FIG. 1, an EGR device 1 for a multi-cylinder engine according to the present embodiment divides an engine body 2 of a plurality of cylinders into an EGR gas generation cylinder 2a and another normal cylinder 2b, and discharges from the EGR gas generation cylinder 2a. The EGR passage 4 for guiding the exhaust gas to the intake passage 3 of the normal cylinder 2b is provided.

  In the present embodiment, the inline 6-cylinder engine body 2 is divided into a right-end 1-cylinder EGR gas generating cylinder 2a and a left-side 5-cylinder normal cylinder 2b. It may be divided into three cylinders and three cylinders. The engine type is not limited to the in-line type, and may be a V type, a horizontally opposed type, and the like. The number of cylinders is not limited to six cylinders, and any number of cylinders (for example, eight cylinders) may be used as long as there are two or more cylinders.

  The EGR device 1 includes a fuel injection map dedicated to the EGR gas generation cylinder 2a provided separately from the fuel injection map for the normal cylinder 2b. The fuel injection map dedicated to the EGR gas generating cylinder 2a is always set with the fuel injection amount and timing at which smoke does not occur regardless of the operating state of the engine body 2 (the amount of operation of the accelerator pedal and the engine speed at that time, etc.). Has been. Specifically, in the fuel injection map dedicated to the EGR gas generation cylinder 2a, the fuel injection timing is advanced than the fuel injection map for the normal cylinder 2b.

  That is, in the fuel injection map for the normal cylinder 2b, depending on the operating state of the engine body 2, the fuel injection timing of the normal cylinder 2b is delayed in order to keep the NOx emission amount discharged from the engine body 2 below the regulation value. There is a region to be cornified (retarded), but even in the operating state of such a region, the fuel injection map dedicated to the EGR gas generation cylinder 2a does not retard the fuel injection timing of the EGR gas generation cylinder 2a. For this reason, smoke is not discharged from the EGR gas generation cylinder 2a even in an operation state where smoke is discharged from the normal cylinder 2b.

  The smoke discharged from the normal cylinder 2b is collected and removed by an unshown post-processing device (filter, catalyst, etc.) disposed on the downstream side of the turbine T in the exhaust passage 5 of the normal cylinder 2b. The so-called common rail type is used for the fuel injection system of the engine body 2, and the fuel injection amount and timing of each cylinder are controlled by controlling the energization signal to the solenoid valve of the injector provided in each cylinder. Easy to control.

  An exhaust passage 5 having an exhaust manifold 4 is connected to the exhaust side of each normal cylinder 2b, and an intake passage 3 having an intake manifold 6 is connected to the intake side of each normal cylinder 2b. A turbine T that is rotationally driven by exhaust gas is disposed in the middle of the exhaust passage 5, and a compressor C that is rotationally driven by the turbine T and pressurizes the intake air to the engine body 2 is disposed in the middle of the intake passage 3. It is installed. The compressor C and the turbine T constitute a turbocharger.

  The EGR device 1 includes an EGR passage 4 that communicates the exhaust passage 7 of the EGR gas generating cylinder 2a and the intake passage 3 of the normal cylinder 2b, an EGR valve 8 that is provided in the EGR passage 4 and has a variable passage sectional area. An exhaust pressure adjusting passage 9 (PC passage 9: pressure control passage) having one end connected to the EGR passage 4 and the other end connected to the exhaust passage 5 of the normal cylinder 2b, and a passage area provided in the PC passage 9. A variable exhaust pressure control valve 10 (PC valve 10: pressure control valve) is provided.

  The PC passage 9 guides a part of the exhaust gas discharged from the EGR gas generation cylinder 2a (exhaust gas not passing through the EGR passage 4 to the intake passage 3 of the normal cylinder 2b) to the exhaust passage 5 of the normal cylinder 2b. Is. The PC valve 10 provided in the middle of the PC passage 9 adjusts the flow rate of the exhaust gas discharged from the EGR gas generation cylinder 2 a from the exhaust passage 7 through the PC passage 9 to the exhaust passage 5, so that the exhaust passage 7 The exhaust pressure inside is adjusted.

  A charge tank 11 for storing EGR gas is provided in the middle of the EGR passage 4, and an EGR cooler 12 for cooling the EGR gas is provided upstream of the charge tank 11 in the flow of EGR gas. It has been. The charge tank 11 is an exhaust gas (EGR gas) discharged from the EGR gas generation cylinder 2a and directed to the intake passage 3 of the normal cylinder 2b, and then led to the intake passage 3 of the normal cylinder 2b. It functions as a buffer for uniformly guiding the EGR gas to each cylinder of the cylinder 2b.

  If the charge tank 11 is omitted, the intake air in the plurality of normal cylinders 2b is discharged at the timing when the EGR gas generating cylinder 2a becomes an exhaust stroke and the exhaust pressure (dynamic pressure) is discharged from the EGR cooler 12. A large amount of EGR gas is introduced only into the cylinders that are in the stroke, and variations in the EGR rate among the cylinders of the plurality of normal cylinders 2b are large, so that appropriate NOx reduction cannot be performed. For this reason, a charge tank 11 for temporarily storing the EGR gas discharged from the EGR cooler 12 is provided, and this is functioned as a buffer.

  The capacity of the charge tank 11 is a capacity capable of buffering and absorbing the exhaust pressure (dynamic pressure) due to the exhaust stroke of the EGR gas generating cylinder 2a without being directly transmitted to the intake passage 3 of the normal cylinder 2b. The capacity is set according to the required EGR amount calculated from the cylinder volume of 2b and the target NOx value. The EGR cooler 12 has a large capacity (capacity for containing EGR gas), and the EGR cooler 12 itself has a buffer function to absorb the influence of the exhaust pressure (dynamic pressure) due to the exhaust stroke of the EGR gas generation cylinder 2a. If so, the charge tank 11 is unnecessary.

  There is no need to provide a soot filter in the middle of the EGR passage 4. This is because the exhaust gas of the EGR gas generation cylinder 2a flows through the EGR passage 4 and the exhaust gas of the EGR gas generation cylinder 2a does not always contain a smoke component as described above. That is, the fuel injection amount and timing of the EGR gas generation cylinder 2a are determined by a fuel injection map dedicated to the EGR gas generation cylinder provided separately from the fuel injection map for the normal cylinder 2b. In the fuel injection map, as described above, the fuel injection amount and timing at which smoke is not always generated are set regardless of the operating state of the engine body 2.

  Thus, since it is not necessary to provide a smoke filter in the EGR passage 4, cost reduction can be promoted. That is, providing the soot filter in the EGR passage 4 leads to an increase in the manufacturing cost of the entire apparatus. However, in this embodiment, the soot filter is unnecessary, and the manufacturing cost is reduced accordingly. In addition, if a soot filter is provided in the EGR passage 4, clogging of the soot filter due to aging is unavoidable, so it is necessary to perform maintenance periodically to eliminate clogging, and the running cost is also improved. However, since the soot filter is unnecessary in this embodiment, the running cost can be reduced. Moreover, since the inside of the EGR cooler 12 is not contaminated by smoke components (soot and the like), the heat exchange efficiency of the EGR cooler 12 does not deteriorate.

  Further, the fuel injection amount and timing of the EGR gas generation cylinder 2a are controlled by a fuel injection map dedicated to the EGR gas generation cylinder 2a provided separately from the fuel injection map for the normal cylinder 2b. Fuel consumption can be improved. That is, in the fuel injection map dedicated to the EGR gas generation cylinder 2a, the fuel injection amount and timing at which smoke is not generated is always set regardless of the operating state of the engine body 2, so that the EGR gas generation cylinder 2a burns. Excess fuel that causes the remaining fuel is not supplied, and the EGR gas generation cylinder 2a has improved fuel efficiency compared to the normal cylinder 2b. Therefore, the fuel efficiency of the engine body 2 as a whole is improved.

  Further, in the EGR device 1 according to the present embodiment, the EGR gas generation cylinder 2a has a fuel injection map dedicated to the EGR gas generation cylinder 2a that is provided separately from the fuel injection map for the normal cylinder 2b, than the normal cylinder 2b. However, since the fuel injection timing is advanced, the exhaust gas temperature of the EGR gas generation cylinder 2a is lower than the exhaust gas temperature of the normal cylinder 2b. Therefore, the capacity of the EGR cooler 12 and the amount of cooling water flowing through the EGR cooler 12 can be reduced as compared with those not including the fuel injection map dedicated to the EGR gas generation cylinder 2a. Since this cooling water is cooled by the engine fan driven by the engine body 2, reducing the amount of this cooling water to the EGR cooler 12 can reduce the work amount of the engine fan. Fuel consumption is improved.

  The EGR device 1 also includes an engine rotation speed sensor 13 that detects a rotation speed Ne of the engine body 2 and an engine throttle sensor 14 that detects a load L of the engine body 2. The engine rotation speed sensor 13 detects the rotation speed of the crankshaft of the engine body 2, and the engine throttle sensor 14 detects the opening degree of the accelerator pedal.

  The EGR device 1 is a controller that controls the opening of the EGR valve 8 based on the detected value Ne of the engine rotation speed sensor 13 and the fuel injection amount Q of the normal cylinder 2b determined by the detected value L of the engine throttle sensor 14. 15 (ECU15: Electronic control unit). The ECU 15 stores a standard EGR valve opening map (Ne, Q) in which the target opening of the EGR valve 8 corresponding to the engine operating state, that is, the engine rotation speed Ne and the fuel injection amount Q is written. ing.

  The ECU 15 inputs the detected value Ne of the engine speed sensor 13 and the fuel injection amount Q of the normal cylinder 2b determined by the detected value L of the engine throttle sensor 14 to the standard EGR valve opening map (Ne, Q). Thus, the target opening of the EGR valve 8 is obtained, a command is transmitted to an actuator 8a (such as an electromagnetic solenoid) that adjusts the opening of the EGR valve 8, and the opening of the EGR valve 8 is controlled to the target opening.

  However, sufficient EGR gas cannot be led to the intake passage 3 of the normal cylinder 2b only by such opening degree control of the EGR valve 8, and a desired EGR rate and EGR amount may not be obtained. . In recent diesel engines, there is an operation region in which the fuel injection timing is retarded in order to satisfy strict NOx emission regulations. In this embodiment as well, the fuel injection timing is retarded for the normal cylinder 2b depending on the operating state of the engine body 2. ing.

  As described above, when the fuel injection timing is retarded for the normal cylinder 2b, the combustion deteriorates, so-called post-combustion combustion occurs frequently, the exhaust temperature rises, and the exhaust pressure rises. On the other hand, with respect to the EGR gas generation cylinder 2a, the fuel injection timing is advanced from the normal cylinder by the fuel injection map dedicated to the EGR gas generation cylinder 2a as described above, so that the combustion is improved compared to the normal cylinder 2b. As a result, the exhaust temperature is lowered, and the exhaust pressure is lower than that of the normal cylinder 2b. Further, in the engine operating region where the turbocharger has high turbo efficiency, the intake pressure (boost pressure) of the normal cylinder 2b of the engine body 2 may be higher than the exhaust pressure.

  This relationship can be expressed as “exhaust pressure of EGR gas generating cylinder 2a” <“exhaust pressure of normal cylinder 2b” <“intake pressure of normal cylinder 2b”. In this case, the exhaust gas from the EGR gas generation cylinder 2a cannot be guided to the intake passage 3 of the normal cylinder 2b. Therefore, in the EGR device 1 according to the present embodiment, the PC passage 9 is provided between the EGR passage 4 and the exhaust passage 5 of the normal cylinder 2b, the PC valve 10 is provided in the middle of the PC passage 9, and the PC valve 10 The exhaust gas in the exhaust passage 7 of the EGR gas generation cylinder 2a is clogged by controlling so that the opening of the EGR gas is reduced, and the “exhaust pressure of the EGR gas generation cylinder 2a” is set to “intake pressure of the normal cylinder 2b”. I tried to increase it.

  The opening degree of the PC valve 10 is controlled by the ECU 15 based on the detected value Ne of the engine speed sensor 13 and the fuel injection amount Q of the normal cylinder 2b determined by the detected value L of the engine throttle sensor 14. The ECU 15 stores a standard PC valve opening map (Ne, Q) in which the target opening of the PC valve 10 corresponding to the engine operating state, that is, the engine rotation speed Ne and the fuel injection amount Q is written. ing.

  The ECU 15 inputs the detected value Ne of the engine speed sensor 13 and the fuel injection amount Q of the normal cylinder 2b determined by the detected value L of the engine throttle sensor 14 to the standard PC valve opening map (Ne, Q). Thus, the target opening of the PC valve 10 is obtained, a command is transmitted to an actuator 10a (such as an electromagnetic solenoid) that adjusts the opening of the PC valve 10, and the opening of the PC valve 10 is controlled to the target opening.

  When the ECU 15 controls the EGR valve 8 to open (control in the opening direction), the ECU 15 basically controls the PC valve 10 to close (control in the closing direction). When the EGR valve 8 is controlled to open, it is necessary to increase the EGR rate and the EGR amount. At this time, the PC valve 10 is closed and the “exhaust pressure of the EGR gas generating cylinder 2a” is set to “intake pressure of the normal cylinder 2b” This is because it is necessary to raise it. However, when the opening degree of the EGR valve 8 is controlled, the opening degree of the PC valve 10 at that time is “exhaust pressure of the EGR gas generating cylinder 2a”> “intake pressure of the normal cylinder 2b”, and the desired EGR If there is a pressure difference from which the rate and the EGR amount are obtained, the opening degree of the PC valve 10 is kept as it is, and only the opening degree of the EGR valve 8 is controlled.

  As described above, the ECU 15 controls the opening degree of the EGR valve 8 on the basis of the standard EGR valve opening degree map and also controls the PC valve 10 on the basis of the standard PC valve opening degree map. With respect to 2b, it is possible to accurately control the desired EGR rate after securing a large amount of EGR. Therefore, regardless of the operating state of the engine body 2, an appropriate EGR rate and EGR amount corresponding to the operating state can be realized. When the EGR valve 8 is fully opened and the PC valve 10 is fully closed, an EGR rate of about 20% can be realized.

  By the way, the standard EGR valve opening map and the standard PC valve opening map described above are created from steady test data (data after the transient response has converged), but the transient mode is the state before the transient response has converged. In the opening control of the EGR valve 8 and the PC valve 10 based on the above maps based on the steady test data, a large amount of EGR gas is circulated and SM (smoke) deteriorates, and conversely, the exhaust pressure decreases. A case where EGR is impossible is conceivable.

  Therefore, in the EGR device 1 according to the present embodiment, the exhaust pressure sensor 16 is provided in the exhaust passage 7 of the EGR gas generation cylinder 2a, the intake pressure sensor 18 is provided in the intake passage 17 of the EGR gas generation cylinder 2a, and the intake passage 3 is provided. A MAF sensor 19 (mass air flow sensor) is provided, and a detection value of the exhaust pressure sensor 16 (exhaust pressure Po), a detection value of the intake pressure sensor 18 (intake pressure Pi), a detection value of the MAF sensor 19 (intake air amount MAF), etc. Based on the above, the ECU 15 feedback-controls the opening degree of the EGR valve 8 and the opening degree of the PC valve 10.

  In particular, the opening degree of the PC valve 10 is feedback-controlled by the ECU 15 so that the detected value Po of the exhaust pressure sensor 16 and the detected value Pi of the intake pressure sensor 18 are equal. This is because by this control, the exhaust pressure Po and the intake pressure Pi of the EGR gas generation cylinder 2a are equalized, so that EGR can be performed efficiently without deteriorating the fuel consumption.

  In other words, if the exhaust pressure Po of the EGR gas generation cylinder 2a is higher than the intake pressure Pi, the exhaust gas of the EGR gas generation cylinder 2a becomes clogged, so that pump work occurs in the EGR gas generation cylinder 2a and fuel efficiency is improved. It will get worse. On the other hand, if the exhaust pressure Po of the EGR gas generating cylinder 2a is lower than the intake pressure Pi, EGR may be impossible. Therefore, if the exhaust pressure Po and the intake pressure Pi of the EGR gas generation cylinder 2a are equal, EGR can be performed efficiently without deteriorating fuel consumption.

  The upstream end of the intake passage 17 of the EGR gas generation cylinder 2a is connected to the intake passage 3 of the normal cylinder 2b downstream of the compressor C and upstream of the connection portion of the EGR passage 4.

  FIG. 2 shows a control flow of the ECU 15.

  In step 1, the engine speed Ne is detected by the engine speed sensor 13, and in step 2, the accelerator opening degree L, that is, the engine load L is detected by the engine throttle sensor 14. In step 3, based on the accelerator opening L and the engine speed Ne, the fuel injection amount Q of the normal cylinder 2b is determined from the fuel injection map stored in the ECU 15. The fuel injection amount Q may be finely corrected based on water temperature, hydraulic pressure, or the like.

  In step 4, based on the engine speed Ne and the fuel injection amount Q, the opening degree of the EGR valve 8 that matches the engine operating state at that time is obtained from the standard EGR valve opening degree map stored in the ECU 15. . In step 5, based on the engine speed Ne and the fuel injection amount Q, the opening degree of the PC valve 10 that matches the engine operating state at that time is obtained from the standard PC valve opening degree map stored in the ECU 15. .

  In step 6, the opening of the EGR valve 8 and the opening of the PC valve 10 are the opening obtained in steps 4 and 5, respectively. The actuator 10a for adjusting the opening is operated. As described above, the standard EGR valve opening map and the standard PC valve opening map are created based on the steady test data. Therefore, the EGR (EGR rate, EGR amount) when the engine is in a steady state can be appropriately matched with the engine operating state by the control in steps 1 to 6.

  The EGR control when the engine is in a transient state is performed by step 7 and subsequent steps.

  In step 7, the intake pressure sensor 18 provided in the intake passage 17 of the EGR gas generation cylinder 2a detects the intake pressure (supercharging pressure) Pi of the EGR gas generation cylinder 2a. In step 8, the exhaust gas of the EGR gas generation cylinder 2a is detected. An exhaust pressure sensor 16 provided in the passage 7 detects the exhaust pressure Po of the EGR gas generation cylinder 2a. In step 9, the actual EGR rate and EGR amount are detected based on the intake air amount obtained by the MAF sensor 19 provided in the intake passage 3 on the upstream side of the compressor C.

  As shown in FIG. 1, a first flow rate sensor 20 is provided in the intake passage 3 of the normal cylinder 2 b downstream from the portion to which the EGR passage 4 is connected, and the second flow rate in the EGR passage 4 downstream from the EGR valve 8. The flow rate sensor 21 may be provided, the EGR rate may be obtained based on the output values of the first and second flow rate sensors 20, 21, and the EGR amount may be obtained based on the output value of the second flow rate sensor 21. Here, EGR rate = cylinder inflow exhaust gas amount / (cylinder inflow air amount + cylinder inflow exhaust gas amount), and this EGR rate is obtained by dividing the output value of the second flow rate sensor 21 by the output value of the first flow rate sensor 20. It is obtained by.

  In step 10, it is determined whether the boost pressure Pi obtained by the intake pressure sensor 18 and the exhaust pressure Po obtained by the exhaust pressure sensor 16 match the pressure target map. The pressure target map describes a relationship in which the exhaust pressure Po is equal to the supercharging pressure Pi. When this relationship is not satisfied, that is, when step 10 is no, the routine returns to step 6 to open the opening of the PC valve 10 ( Alternatively, feedback control is performed so that the opening degree of the EGR valve 8 and the opening degree of the PC valve 10) satisfy the above relationship.

  By this control, the exhaust pressure Po becomes equal to the supercharging pressure Pi, and as described above, the exhaust gas in the EGR gas generation cylinder 2a is not clogged and pump work does not occur in the EGR gas generation cylinder 2a. Thus, appropriate EGR control (EGR rate control, EGR amount control) can be performed efficiently without deteriorating fuel consumption. If step 10 is yes, go to step 11.

  In step 11, the actual EGR (EGR amount, EGR rate) obtained by using the MAF sensor 19, the first flow sensor 20, the second flow sensor 21, etc. is described in the EGR target map, and the engine operation at that time It is determined whether the target EGR (EGR amount, EGR rate) corresponding to the state (fuel injection amount Q, engine rotation speed Ne) matches. When they do not match, that is, when step 11 is NO, the routine returns to step 6, and the opening degree of the EGR valve 8 and the opening degree of the PC valve 10 are feedback-controlled so that the actual EGR matches the target EGR.

  With the above control, it is possible to always realize appropriate EGR control (EGR amount control, EGR rate control) suitable for the operating state of the engine regardless of the steady state or the transient state. Further, as described above, it is not necessary to provide a smoke filter in the EGR passage 4.

It is the schematic of the EGR apparatus of the multicylinder engine which concerns on one Embodiment of this invention. It is explanatory drawing which shows the control flow of the controller (ECU) of the EGR apparatus of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 EGR apparatus of multi-cylinder engine 2 Engine main body 2a EGR gas generation cylinder 2b Normal cylinder 3 Intake passage of normal cylinder 2b 4 EGR passage 5 Exhaust passage of normal cylinder 2b 7 Exhaust passage of EGR gas generation cylinder 2a 8 EGR valve 9 Exhaust pressure Adjustment passage (PC passage)
10 Exhaust pressure control valve (PC valve)
11 Charge tank 12 EGR cooler 13 Engine rotation speed sensor 14 Engine throttle sensor 15 Controller (ECU)
16 Exhaust pressure sensor 17 Intake passage of EGR gas generation cylinder 2a 18 Intake pressure sensor Ne Detected value of engine rotation speed sensor 13 Detected value of engine throttle sensor 14 Q Fuel injection amount Po Detected value of exhaust pressure sensor 16 Pi Intake pressure sensor 18 detected values

Claims (6)

An EGR device for a multi-cylinder engine having an EGR passage that divides an engine body of a plurality of cylinders into an EGR gas generation cylinder and another normal cylinder and introduces exhaust gas discharged from the EGR gas generation cylinder into the intake passage of the normal cylinder Because
A fuel injection map dedicated to the EGR gas generating cylinder provided separately from the fuel injection map for the normal cylinder;
The EGR device for a multi-cylinder engine is characterized in that the fuel injection map dedicated to the EGR gas generating cylinder is set with a fuel injection amount and timing at which smoke is not always generated regardless of the operating state of the engine body.   2. The EGR device for a multi-cylinder engine according to claim 1, wherein the fuel injection map dedicated to the EGR gas generating cylinder has a fuel injection timing advanced relative to the fuel injection map for the normal cylinder. 3. An EGR valve provided in the EGR passage and having a variable passage sectional area;
An exhaust pressure adjusting passage having one end connected to the EGR passage and the other end connected to the exhaust passage of the normal cylinder;
An exhaust pressure control valve provided in the exhaust pressure adjusting passage and having a variable passage area;
An engine rotation speed sensor for detecting the rotation speed of the engine body;
An engine throttle sensor for detecting the load of the engine body;
A controller for controlling the opening of the EGR valve and the opening of the exhaust pressure control valve,
2. The controller according to claim 1, wherein the controller controls the opening of the EGR valve and the opening of the exhaust pressure control valve based on a detection value of the engine rotation speed sensor and a detection value of the engine throttle sensor. 2. An EGR device for a multi-cylinder engine according to 2. An exhaust pressure sensor provided in an exhaust passage of the EGR gas generating cylinder;
An intake pressure sensor provided in the intake passage of the EGR gas generating cylinder,
4. The EGR device for a multi-cylinder engine according to claim 3, wherein the controller controls the opening of the exhaust pressure control valve so that a detection value of the exhaust pressure sensor becomes equal to a detection value of the intake pressure sensor.   The EGR device for a multi-cylinder engine according to claim 3 or 4, wherein a charge tank for storing EGR gas is provided in the EGR passage.   6. The EGR device for a multi-cylinder engine according to claim 5, wherein an EGR cooler that cools the EGR gas is provided in the EGR passage so as to be positioned upstream of the flow of EGR gas from the charge tank.

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