JP2007092618A - Internal combustion engine with supercharger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform recovery process of an EGR cooler without influencing the operation performance of an internal combustion engine, with regard to an internal combustion engine with a supercharger. <P>SOLUTION: In an EGR passage 24 connecting an upstream of a turbine 14b of the supercharger 14 in an exhaust gas passage 10 and a downstream of a compressor 14a in an intake air passage 8, the EGR cooler 26 is arranged in an upstream of an EGR valve 28. A bypass passage 50 branching off from the downstream of the compressor 14a in the intake air passage 8 is connected to the EGR passage 24 between the EGR cooler 26 and the EGR valve 28. The bypass passage 50 can be opened and closed by the bypass valve 18. Also, the compressor 14a can be forcibly driven by a drive means 14c without depending on an operation condition of the internal combustion engine. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an internal combustion engine with a supercharger, and particularly to an internal combustion engine with a supercharger provided with an EGR device with an EGR cooler.

  2. Description of the Related Art An EGR device that recirculates part of exhaust gas from an exhaust passage to an intake passage is known that includes an EGR cooler that cools the recirculated exhaust gas (EGR gas). According to the EGR device with the EGR cooler, the density of the EGR gas can be increased by cooling the EGR gas, and the EGR rate can be improved while ensuring a sufficient amount of fresh air.

  However, since the EGR gas contains moisture, soot and the like, when the EGR gas is cooled by the EGR cooler, soot and the like adhere to the condensed moisture, and the deposits accumulate in the EGR cooler. There is a possibility. Accumulation of deposits causes a decrease in cooling efficiency of the EGR cooler and an increase in pressure loss.

Patent Document 1 discloses a technique for preventing the efficiency of the EGR cooler from being reduced due to deposits. The technique disclosed here introduces intake air into an EGR cooler, and thereby blows away and removes deposits in the EGR cooler. Also disclosed here is a technique in which a supercharger is provided in the intake passage, and supercharged air from the supercharger is introduced into the EGR cooler.
JP-A-11-257167 JP 2000-328950 A

  When the intake air is introduced into the EGR cooler as described in Patent Document 1, the amount of air sucked into the internal combustion engine decreases due to the pressure loss when the intake air passes through the EGR cooler. A decrease in the intake air amount may cause a decrease in the output of the internal combustion engine and a deterioration in exhaust emission. The same applies to the case where supercharged air from the supercharger is introduced into the EGR cooler, and the supercharging pressure decreases due to pressure loss when passing through the EGR cooler, which may adversely affect the operation performance of the internal combustion engine. .

  The present invention has been made to solve the above-described problems, and provides an internal combustion engine with a supercharger capable of performing EGR cooler recovery processing without affecting the operation performance of the internal combustion engine. The purpose is to do.

In order to achieve the above object, a first invention is an internal combustion engine with a supercharger,
A supercharger that is disposed in an intake passage of the internal combustion engine, and that supercharges air sucked into a combustion chamber of the internal combustion engine;
Drive means capable of forcibly driving the supercharger without depending on the operating state of the internal combustion engine;
An EGR device that connects an exhaust passage of the internal combustion engine and a downstream of the supercharger in the intake passage, and recirculates a part of the exhaust gas to the intake passage;
An EGR cooler provided in the EGR device;
A bypass passage branched from the downstream of the supercharger in the intake passage and introducing a part of the air supercharged by the supercharger to the EGR cooler;
A bypass control means for controlling a bypass ratio of the bypass air amount with respect to an amount of bypass air flowing into the bypass passage or an intake air amount based on an operating state of the internal combustion engine;
Drive control means for controlling the forced drive amount of the supercharger by the drive means based on the operating state of the internal combustion engine and the operating state of the bypass control means;
It is characterized by having.

According to a second invention, in the first invention,
The bypass control means controls the bypass air amount or the bypass ratio based on an index value indicating the efficiency of the EGR cooler.

According to a third invention, in the first invention,
The bypass control means controls the bypass air amount or the bypass ratio based on an index value indicating a surge state of the supercharger.

According to a fourth invention, in the first invention,
The bypass control means controls the bypass air amount or the bypass ratio based on an index value indicating a deceleration request to the internal combustion engine.

According to a fifth invention, in any one of the first to fourth inventions,
The drive control means controls the forced drive amount of the supercharger so that the supercharging pressure becomes a target supercharging pressure corresponding to an operating state of the internal combustion engine.

A sixth invention is any one of the first to fifth inventions,
The bypass control means includes a bypass valve that opens and closes the bypass passage, and controls the bypass air amount or the bypass ratio according to an opening degree of the bypass valve.

A seventh invention is the invention according to any one of the first to sixth inventions,
An intercooler is disposed downstream of the supercharger in the intake passage,
The bypass passage is branched from the upstream side of the intercooler in the intake passage.

According to an eighth invention, in any one of the first to seventh inventions,
The supercharger has a turbine disposed in the exhaust passage, and is a turbocharger that supercharges air using energy of exhaust gas received by the turbine,
The bypass passage communicates with the upstream of the turbine via the EGR cooler.

A ninth invention is an internal combustion engine with a supercharger in order to achieve the above object,
A supercharger for supercharging air sucked into a combustion chamber of the internal combustion engine using energy of exhaust gas discharged from the internal combustion engine;
Drive means capable of forcibly driving the compressor of the supercharger without depending on the operating state of the internal combustion engine;
An EGR passage branched from the upstream of the turbine of the supercharger in the exhaust passage of the internal combustion engine and connected to the downstream of the compressor in the intake passage;
An EGR valve for opening and closing the EGR passage;
An EGR cooler disposed upstream of the EGR valve in the EGR passage;
A bypass passage branched from the compressor downstream in the intake passage and connected between the EGR cooler and the EGR valve in the EGR passage;
A bypass valve for opening and closing the bypass passage;
It is characterized by having.

A tenth invention is the ninth invention,
An intercooler is disposed downstream of the compressor in the intake passage,
The bypass passage is branched from the upstream side of the intercooler in the intake passage.

  According to the first invention, the supercharged air is controlled by controlling the forced drive amount of the supercharger based on the operating state of the internal combustion engine and the operating state of the bypass control means for controlling the bypass air amount or the bypass ratio. It is possible to compensate for a decrease in supercharging pressure associated with bypassing the engine. Thus, the supercharged air can be supplied to the EGR cooler and the EGR cooler recovery process can be performed without affecting the operation performance of the internal combustion engine.

  According to the second aspect of the invention, by controlling the bypass air amount or the bypass ratio according to the efficiency of the EGR cooler, the EGR cooler can be quickly recovered when the efficiency of the EGR cooler decreases.

  According to the third aspect of the present invention, the bypass air amount or the bypass ratio is controlled according to the surge state of the supercharger, thereby increasing the air amount passing through the supercharger and avoiding the occurrence of a surge. The recovery process of the EGR cooler can be performed by introducing the supercharged air to the EGR cooler.

  According to the fourth invention, by controlling the amount of bypass air or the bypass ratio according to the deceleration request, effectively using the supercharged air at the time of deceleration that will be discharged without contributing to combustion, The recovery process of the EGR cooler can be performed efficiently.

  According to the fifth aspect of the invention, the supercharging pressure is maintained at the target supercharging pressure corresponding to the operating state of the internal combustion engine by the forced driving of the supercharger by the drive means, so that the internal combustion engine before and after bypassing the supercharged air It is possible to prevent the driving performance of the vehicle from changing.

  According to the sixth invention, since the bypass air amount or the bypass ratio is determined by the opening degree of the bypass valve, it is indirectly controlled by controlling the opening degree of the bypass valve without actually measuring the bypass air amount or the bypass ratio. Thus, the amount of bypass air or the bypass ratio can be controlled.

  According to the seventh aspect of the invention, high-temperature and high-pressure supercharged air that is not cooled by the intercooler and that does not cause pressure loss due to the passage of the intercooler can be supplied to the EGR cooler. The recovery process can be performed more effectively.

  According to the eighth aspect of the invention, the supercharged air used for the recovery process of the EGR cooler is supplied to the turbine of the supercharger and reused for rotational driving of the turbine. Thereby, a part of work done by the supercharger can be recovered, and waste of energy can be reduced.

  According to the ninth invention, the supercharged air supercharged by the compressor of the supercharger is caused to flow in the reverse direction from the outlet side of the EGR cooler to the inlet side by closing the EGR valve and opening the bypass valve. The deposits such as soot accumulated in the EGR cooler can be discharged to the exhaust passage. Further, since the supercharged air used for the recovery process of the EGR cooler is supplied to the turbine of the supercharger and reused for the rotational drive of the turbine, a part of the work done by the supercharger is driven by the turbine. It can be recovered as energy, and energy waste can be reduced. Furthermore, according to the ninth aspect, since the compressor can be forcibly driven without depending on the operating state of the internal combustion engine, even if the supercharged air is bypassed, the necessary excess is required. The supply pressure can be obtained, and the operation performance of the internal combustion engine and the recovery process of the EGR cooler can be made compatible.

  According to the tenth aspect of the invention, high-temperature and high-pressure supercharged air that is not cooled by the intercooler and that does not cause pressure loss due to the passage of the intercooler can be supplied to the EGR cooler. The recovery process can be performed more effectively.

Hereinafter, embodiments of the present invention will be described with reference to FIGS.
FIG. 1 is a schematic configuration diagram of an internal combustion engine with a supercharger as an embodiment of the present invention. In the present embodiment, the present invention is applied to a diesel engine having a turbocharger with an electric motor (motor-assisted turbocharger, also referred to as MAT for short).

  As shown in FIG. 1, the diesel engine has an engine body 2 having a plurality of cylinders (four cylinders in FIG. 1). The engine body 2 is provided with an in-cylinder injector 32 for directly injecting fuel into the combustion chamber. The in-cylinder injector 32 is provided for each cylinder and is connected to the common rail 34. That is, this diesel engine is configured as a common rail type diesel engine. Fuel stored in a fuel tank (not shown) is pumped up by a supply pump 36, compressed to a predetermined fuel pressure, and supplied to the common rail 34. Although not shown in the drawing, the supply pump 36 includes a low-pressure pump and a high-pressure pump.

  An exhaust manifold 6 that collects exhaust gas discharged from each cylinder is connected to the exhaust side of the engine body 2. An exhaust pipe 10 is connected to the outlet of the exhaust manifold 6. The exhaust manifold 6 and the exhaust pipe 10 constitute an “exhaust passage” according to the present invention. In the middle of the exhaust pipe 10, a catalyst 30 such as a NOx catalyst, DPF, or DPNR is disposed.

  An intake manifold 4 for distributing intake air to each cylinder is connected to the intake side of the engine body 2. An intake pipe 8 is connected to the inlet of the intake manifold 4 for taking air from the atmosphere and guiding it to the intake manifold 4. The intake manifold 4 and the intake pipe 8 constitute an “intake passage” according to the present invention. An air cleaner 12 is attached to the inlet of the intake pipe 8. An intake throttle valve 22 is provided upstream of the intake manifold 4. The intake throttle valve 22 is normally opened fully.

  A compressor 14 a of a turbocharger 14 with an electric motor is provided upstream of the intake throttle valve 22 in the intake pipe 8. The turbocharger with electric motor 14 includes a compressor 14a, a turbine 14b, and an electric motor 14c disposed between the compressor 14a and the turbine 14b. The turbine 14 b is provided in the middle of the exhaust pipe 10 extending from the exhaust manifold 6 to the catalyst 30. The compressor 14a and the turbine 14b are integrally connected by a connecting shaft, and the compressor 14a is rotationally driven by the exhaust energy of the exhaust gas input to the turbine 14b. The connecting shaft is also a rotor of the electric motor 14c, and the compressor 14a can be forcibly driven by operating the electric motor 14c. An intercooler 16 for cooling the air supercharged by the compressor 14a is provided downstream of the compressor 14a in the intake pipe 8.

  An EGR pipe 24 is connected to the intake pipe 8 from the intake throttle valve 22 to the intake manifold 4. The opposite end of the EGR pipe 24 is connected to the exhaust manifold 6, and a part of the exhaust gas (EGR gas) is introduced into the intake pipe 8 through the EGR pipe 24. By introducing EGR gas, which has a higher specific heat than that of air and a small amount of oxygen, into the intake pipe 8, the combustion temperature in the cylinder can be lowered and the amount of NOx produced can be reduced. An EGR valve 28 that opens and closes the EGR pipe 24 is provided in the middle of the EGR pipe 24. Further, an EGR cooler 26 for cooling the EGR gas flowing inside is provided upstream (exhaust side) of the EGR valve 28 in the EGR pipe 24. Cooling increases the density of the EGR gas, and it is possible to improve the EGR rate while securing the intake air amount.

  A bypass pipe 50 is connected midway in the intake pipe 8 from the compressor 14 a to the intercooler 16. The bypass pipe 50 is connected at the opposite end between the EGR cooler 26 and the EGR valve 28 in the EGR pipe 24. A bypass valve 18 that opens and closes the bypass pipe 50 is provided in the middle of the bypass pipe 50. By opening the bypass valve 18, a part of the air supercharged by the compressor 14 a can flow to the EGR pipe 24.

  According to the configuration shown in FIG. 1, the flow of gas in the diesel engine can be controlled by a combination of opening / closing of the EGR valve 28 and opening / closing of the bypass valve 18, for example, as shown in FIGS. 2 and 3. First, FIG. 2 shows a gas flow when the bypass valve 18 is closed and the EGR valve 28 is opened. By closing the bypass valve 18, all of the supercharged air supercharged by the compressor 14 a does not flow to the bypass pipe 50 but is supplied to the engine body 2 through the intake pipe 8. Further, by opening the EGR valve 28, an amount of EGR gas corresponding to the opening degree is introduced from the EGR pipe 24 into the intake pipe 8. During normal operation, the gas flow in the diesel engine is controlled to the flow shown in FIG.

  FIG. 3 shows the gas flow when the bypass valve 18 is opened and the EGR valve 28 is closed. By opening the bypass valve 18, a part of the supercharged air (bypass air) supercharged by the compressor 14 a flows into the EGR pipe 24 through the bypass pipe 50. The flow rate of bypass air (bypass air amount) flowing through the bypass pipe 50 and the ratio (bypass ratio) of the bypass air amount to the flow rate of air sucked into the intake pipe 8 (intake air amount) depend on the opening of the bypass valve 18. Can be controlled. Further, since the EGR valve 28 is closed, the bypass air that has flowed into the EGR pipe 24 flows backward from the outlet side of the EGR cooler 26 to the inlet side and flows to the exhaust manifold 6.

  According to the gas flow shown in FIG. 3, the deposits such as soot accumulated in the EGR cooler 26 can be blown off by the bypass air, and the blown-off deposits can be discharged to the exhaust side instead of the intake side. it can. The bypass air supplied to the EGR cooler 26 is high-temperature and high-pressure supercharged air that is not cooled by the intercooler 16 and that does not cause a pressure loss due to the passage of the intercooler 16. The deposits can be effectively removed. Further, the bypass air used for the recovery process of the EGR cooler 26 then flows through the exhaust pipe 10 to the turbine 14b and is reused for driving the turbine 14b. Thereby, a part of work done by the compressor 14a can be recovered as driving energy of the turbine 14b, and waste of energy can be reduced.

  Note that if a part of the supercharged air is bypassed, there is a concern that the supercharging pressure will decrease, but this diesel engine may forcibly drive the compressor 14a by the electric motor 14c without depending on the operating state of the engine body 2. it can. Thereby, even when the supercharged air is bypassed, the necessary supercharging pressure can be obtained when necessary, and both the operation performance of the engine body 2 and the recovery process of the EGR cooler 26 can be made compatible. it can.

  In this diesel engine, when a predetermined condition is satisfied, the operation state of the bypass valve 18, the EGR valve 28 and the electric motor 14c is controlled, and the gas flow shown in FIG. The flow of gas in the diesel engine is switched to the flow. The operating states of the bypass valve 18, the EGR valve 28, and the electric motor 14c are controlled by an ECU (Electronic Control Unit) 70. The ECU 70 is a control device that comprehensively controls the entire diesel engine, and various sensors listed below are connected to the input side of the ECU 70.

  In this diesel engine, an intake manifold pressure sensor 72, an exhaust manifold pressure sensor 74, an air flow meter 76, an EGR cooler outlet temperature sensor 80, an EGR cooler inlet temperature sensor 82, and a crank angle sensor 78 are used as sensors for acquiring information related to the operation state. , An accelerator opening sensor 84 and the like are provided. The intake manifold pressure sensor 72 is attached to the intake manifold 4 and outputs a signal corresponding to the pressure (intake manifold pressure) in the intake manifold 4. The exhaust manifold pressure sensor 74 is attached to the exhaust manifold 6 and outputs a signal corresponding to the pressure (exhaust manifold pressure) in the exhaust manifold 6. The air flow meter 76 is disposed near the downstream of the air cleaner 12 in the intake pipe 8 and outputs a signal corresponding to the intake air amount. The EGR cooler outlet temperature sensor 80 is disposed at the outlet of the EGR cooler 26 and outputs a signal corresponding to the outlet temperature of the EGR cooler 26. The EGR cooler inlet temperature sensor 82 is disposed at the inlet of the EGR cooler 26 and outputs a signal corresponding to the inlet temperature of the EGR cooler 26. The crank angle sensor 78 is a sensor that outputs a signal corresponding to the rotation angle of the crankshaft, and the accelerator opening sensor 84 is a sensor that outputs a signal corresponding to an accelerator opening (not shown).

  The ECU 70 controls the operating states of the bypass valve 18, the EGR valve 28, and the electric motor 14c in accordance with a predetermined control program based on the output of each sensor. The control of the electric motor 14 c by the ECU 70 is performed via the motor controller 60. The motor controller 60 is a device that supplies electric power to the electric motor 14c and controls the rotation of the compressor 14a.

  Switching from the gas flow shown in FIG. 2 to the gas flow shown in FIG. 3 is performed in the following three cases. The first case is a case where the cooling efficiency of the EGR cooler 26 is lowered. In this case, the ECU 70 controls the operating state of each device according to the routine shown in the flowchart of FIG.

  In the first step S100 of the routine shown in FIG. 4, it is determined whether or not the efficiency (cooling efficiency) of the EGR cooler 26 is lower than the efficiency required for realizing the desired EGR rate. The index value indicating the efficiency of the EGR cooler 26 includes a temperature difference between the inlet temperature of the EGR cooler 26 measured by the EGR cooler inlet temperature sensor 82 and the outlet temperature of the EGR cooler 26 measured by the EGR cooler outlet temperature sensor 82. Can be used. The smaller the temperature difference, the lower the EGR cooler efficiency. While the EGR cooler efficiency is maintained above the required efficiency, the following processing is skipped and this routine is executed from the beginning.

  As a result of the determination, if the EGR cooler efficiency is lower than the required efficiency, it is next determined whether or not the EGR valve 28 is closed (step S102). The ECU 70 controls the opening degree of the EGR valve 28 based on the rotational speed and load of the engine body 2 by a routine different from this routine. In the other routine, when the flag for closing the EGR valve 28 is turned on, the determination result in step S102 is switched from No to Yes. While the EGR valve 28 is open, the following processing is skipped, and this routine is executed from the beginning.

  When the EGR valve 28 is closed, the intake manifold pressure measured by the intake manifold pressure sensor 72 is compared with the exhaust manifold pressure measured by the exhaust manifold pressure sensor 74 (step S104). When the exhaust manifold pressure is higher than the intake manifold pressure, the supercharged air cannot flow from the intake pipe 8 toward the exhaust manifold 6 even if the bypass valve 18 is opened. Accordingly, in this case, the following processing is skipped and this routine is executed from the beginning.

  When the intake manifold pressure is higher than the exhaust manifold pressure, the bypass valve 18 is opened (step S106). The opening degree of the bypass valve 18 is determined from the operation state of the diesel engine such as the rotational speed and the load. As a result, the intake pipe 8 and the exhaust manifold 6 are in communication with each other via the bypass pipe 50 and the EGR pipe 24, and bypass air, which is part of the supercharged air, bypasses the engine body 2 from the intake pipe 8 to the exhaust manifold 6. Then flow into. At this time, in the EGR cooler 26, bypass air flows from the outlet side to the inlet side, and soot and deposits accumulated in the EGR cooler 26 are blown off toward the exhaust manifold 6.

  In the next step S108, it is determined whether the supercharging pressure (intake manifold pressure measured by the intake manifold pressure sensor 72) is lower than the target supercharging pressure. When the bypass valve 18 is opened and a part of the supercharged air is bypassed, the supercharging pressure of the supercharged air supplied to the engine body 2 decreases. If the supercharging pressure is maintained above the target supercharging pressure even after the bypass valve 18 is opened, the following processing is skipped and this routine is executed from the beginning.

  However, if the supercharging pressure does not reach the target supercharging pressure determined from the rotational speed and load of the engine body 2, the diesel engine cannot obtain a desired operating performance, for example, the torque decreases. Therefore, in step S110, if the supercharging pressure is lower than the target supercharging pressure as a result of the determination, the compressor 14a is forcibly driven by the electric motor 14c (MAT operation). If the compressor 14a is already forcibly driven by the electric motor 14c, the output of the electric motor 14c is increased.

  As specific control methods of the electric motor 14c in step S110, for example, the following two methods are conceivable. Here, the motor 14c is controlled by any one of the methods described below. The first method is a method of feeding back the deviation between the target boost pressure and the boost pressure to the rotational speed of the electric motor 14c. The number of rotations of the motor 14c is increased in accordance with the magnitude of the deviation until the deviation becomes zero or less than a predetermined value.

  The second method is a method of controlling the electric motor 14c according to a map that defines a correspondence relationship between the target supercharging pressure and the rotation speed of the electric motor 14c. A map is prepared for each set opening degree of the bypass valve 18. For example, if the opening degree control of the bypass valve 18 is 1/0 control between open (on) and closed (off), an open map when the bypass valve 18 is open and a close map when the bypass valve 18 is closed Prepare two types of. In this case, when the bypass valve 18 is opened in step S106, the map to be referenced is switched from the closed map to the open map, and while the bypass valve 18 is open, the rotational speed of the motor 14c is based on the open map. Be controlled.

  According to the above routine, when the cooling efficiency of the EGR cooler 26 decreases, the cooling efficiency of the EGR cooler 26 can be recovered while maintaining the supercharging pressure at the target supercharging pressure. The ECU 70 executes the processes of steps S100, S102, S104, and S106, thereby realizing the “bypass control means” according to the present invention. Further, the “drive control means” according to the present invention is realized by the ECU 70 executing the processing of steps S108 and S110.

  Next, a second case in which the gas flow in the diesel engine is switched to the flow shown in FIG. 3 will be described. The second case is when the compressor 14a reaches the surge limit. In this case, the ECU 70 controls the operating state of each device according to the routine shown in the flowchart of FIG.

  In the first step S200 of the routine shown in FIG. 5, it is determined whether or not the compressor 30a has reached the surge limit. The turbocharger 14 with an electric motor can achieve a high supercharging pressure by forcibly driving the compressor 14a by the electric motor 14c, but tends to exceed the surge limit of the compressor 14a. As the index value indicating the surge state of the compressor 30a, the pressure ratio between the outlet pressure (intake manifold pressure) and the inlet pressure (atmospheric pressure) of the compressor 14a and the intake air amount measured by the air flow meter 76 can be used. When the relationship between the pressure ratio and the intake air amount exceeds a predetermined surge line, it is determined that the compressor 14a has reached the surge limit.

  If the result of determination in step S200 is that the compressor 14a has reached the surge limit, the bypass valve 18 is opened (step S202). At this time, the opening degree of the EGR valve 28 is controlled by the ECU 70 by a routine different from this routine, but the EGR valve 28 is closed in an operation region where a surge can occur. In the vicinity of the surge limit, the intake manifold pressure is higher than the exhaust manifold pressure due to forced supercharging by the electric motor 14c. Therefore, when the bypass valve 18 is opened, the intake pipe 8 and the exhaust manifold 6 are in communication with each other via the bypass pipe 50 and the EGR pipe 24, and a part of the supercharged air (bypass air) is exhausted from the intake pipe 8. The engine body 2 is bypassed and flows into the manifold 6.

  Thereby, the flow rate of the air passing through the compressor 14a is increased, and the surge of the compressor 14a is avoided. At this time, in the EGR cooler 26, bypass air flows from the outlet side to the inlet side, and soot and other deposits accumulated in the EGR cooler 26 are blown off toward the exhaust manifold 6.

  According to the above routine, it is possible to prevent the cooling efficiency of the EGR cooler 26 from being lowered while avoiding the surge of the compressor 14a. In addition, the “bypass control means” according to the present invention is realized by the ECU 70 executing the processes of steps S200 and S202. Although not shown in the above routine, the ECU 70 feeds back the deviation between the target supercharging pressure and the supercharging pressure to the rotation speed of the electric motor 14c, thereby reducing the supercharging pressure due to the bypass of the supercharging air. It is preventing. However, in order to prevent the turbocharger 14 from being damaged due to excessive rotation, an upper limit value is set for the rotation speed of the electric motor 14c. The “drive control means” according to the present invention is realized by the ECU 70 controlling the electric motor 14 c as described above.

  Next, a third case in which the gas flow in the diesel engine is switched to the flow shown in FIG. 3 will be described. The third case is when the accelerator is turned off. In this case, the ECU 70 controls the operating state of each device according to the routine shown in the flowchart of FIG.

  In the first step S300 of the routine shown in FIG. 6, it is determined whether or not the accelerator opening measured by the accelerator opening sensor 84 is zero. Here, the accelerator opening is used as an index value indicating a deceleration request to the diesel engine. When the accelerator opening is not zero, that is, when there is no driver's deceleration request, the following processing is skipped and this routine is executed from the beginning.

  If the accelerator opening is zero as a result of the determination, it is next determined whether or not the EGR valve 28 is closed (step S302). The ECU 70 controls the opening degree of the EGR valve 28 based on the rotational speed and load of the engine body 2 by a routine different from this routine. In the other routine, when the flag for closing the EGR valve 28 is turned on, the determination result in step S302 is switched from No to Yes. While the EGR valve 28 is open, the following processing is skipped, and this routine is executed from the beginning.

  If the EGR valve 28 is closed, the bypass valve 18 is opened (step S304). As a result, the intake pipe 8 and the exhaust manifold 6 are in communication with each other via the bypass pipe 50 and the EGR pipe 24.

  Further, in the next step 306, the compressor 14a is forcibly driven by the electric motor 14c (MAT operation) so that the supercharging pressure becomes the target supercharging pressure at the time of deceleration. As a method for controlling the electric motor 14c in step S306, the same method as the method for controlling the electric motor 14c in step S110 described above can be used. When the compressor 14a is forcibly driven, the supercharging pressure increases greatly, and a part of the supercharging air (bypass air) flows from the intake pipe 8 to the exhaust manifold 6 by bypassing the engine body 2. At this time, in the EGR cooler 26, bypass air flows from the outlet side to the inlet side, and soot and deposits accumulated in the EGR cooler 26 are blown off toward the exhaust manifold 6.

  When the accelerator is off, the supercharged air supplied to the engine body 2 is discharged as it is without contributing to combustion. However, according to the above routine, the supercharged air is used effectively, and the EGR cooler is used. The decrease in the cooling efficiency of 26 can be effectively prevented. Note that the ECU 70 executes the processes of steps S300, S302, and S304, thereby realizing the “bypass control means” according to the present invention. Further, the “drive control means” according to the present invention is realized by the ECU 70 executing the process of step S306.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, the following modifications may be made.

  In the configuration of FIG. 1, the EGR cooler 26 is arranged upstream (exhaust side) of the EGR valve 28, but the EGR cooler 26 is arranged downstream (intake side) of the EGR valve 28, and the EGR cooler 26 and the EGR valve 28 are arranged. A bypass pipe 50 may be connected between the two. According to this, the bypass air used for the recovery process of the EGR cooler 26 is supplied to the engine body 2 through the EGR pipe 24. Although the pressure loss occurs in the supercharged air supplied to the engine body 2 through the EGR cooler 26, the compressor 14a is forcibly driven by the electric motor 14c to compensate for the decrease in the supercharging pressure due to the pressure loss. Can do.

  In the configuration of FIG. 1, a turbocharger with an electric motor is used as a supercharger. However, in the present invention, the supercharger may be an electric compressor that drives a compressor only by the electric motor. The means for forcibly driving the compressor is not limited to the electric motor.

1 is a schematic configuration diagram of an internal combustion engine with a supercharger as an embodiment of the present invention. FIG. 2 is a diagram showing a gas flow when the bypass valve is closed and the EGR valve is opened in the configuration shown in FIG. 1. In the structure shown in FIG. 1, it is a figure which shows the flow of gas when a bypass valve is opened and an EGR valve is closed. It is a flowchart which shows the routine of control implemented in embodiment of this invention. It is a flowchart which shows the routine of control implemented in embodiment of this invention. It is a flowchart which shows the routine of control implemented in embodiment of this invention.

Explanation of symbols

2 Engine body 4 Intake manifold 6 Exhaust manifold 8 Intake pipe 10 Exhaust pipe 12 Air cleaner 14 Turbocharger with electric motor (MAT)
14a Compressor 14b Turbine 14c Electric motor 16 Intercooler 18 Bypass valve 24 EGR pipe 26 EGR cooler 28 EGR valve 50 Bypass pipe 60 Motor controller 70 ECU
72 Intake manifold pressure sensor 74 Exhaust manifold pressure sensor 76 Air flow meter 78 Crank angle sensor 80 EGR cooler outlet temperature sensor 82 EGR cooler inlet temperature sensor 84 Accelerator opening sensor

Claims (10)

A supercharger disposed in an intake passage of the internal combustion engine, for supercharging air sucked into a combustion chamber of the internal combustion engine;
Drive means capable of forcibly driving the supercharger without depending on the operating state of the internal combustion engine;
An EGR device that connects an exhaust passage of the internal combustion engine and a downstream of the supercharger in the intake passage, and recirculates a part of the exhaust gas to the intake passage;
An EGR cooler provided in the EGR device;
A bypass passage branched from the downstream of the supercharger in the intake passage and introducing a part of the air supercharged by the supercharger to the EGR cooler;
A bypass control means for controlling a bypass ratio of the bypass air amount with respect to an amount of bypass air flowing into the bypass passage or an intake air amount based on an operating state of the internal combustion engine;
Drive control means for controlling the forced drive amount of the supercharger by the drive means based on the operating state of the internal combustion engine and the operating state of the bypass control means;
An internal combustion engine with a supercharger.   2. The internal combustion engine with a supercharger according to claim 1, wherein the bypass control means controls the bypass air amount or the bypass ratio based on an index value indicating the efficiency of the EGR cooler.   The internal combustion engine with a supercharger according to claim 1, wherein the bypass control means controls the bypass air amount or the bypass ratio based on an index value indicating a surge state of the supercharger.   2. The internal combustion engine with a supercharger according to claim 1, wherein the bypass control means controls the bypass air amount or the bypass ratio based on an index value indicating a deceleration request to the internal combustion engine.   The said drive control means controls the forced drive amount of the said supercharger so that a supercharging pressure may become the target supercharging pressure according to the driving | running state of the said internal combustion engine. An internal combustion engine with a supercharger according to any one of the above.   The bypass control means includes a bypass valve that opens and closes the bypass passage, and controls the bypass air amount or the bypass ratio according to an opening degree of the bypass valve. An internal combustion engine with a supercharger as described in 1. An intercooler is disposed downstream of the supercharger in the intake passage,
The internal combustion engine with a supercharger according to any one of claims 1 to 6, wherein the bypass passage is branched from the upstream side of the intercooler in the intake passage. The supercharger has a turbine disposed in the exhaust passage, and is a turbocharger that supercharges air using energy of exhaust gas received by the turbine,
The supercharged internal combustion engine according to any one of claims 1 to 7, wherein the bypass passage communicates with the upstream of the turbine via the EGR cooler. A supercharger for supercharging air sucked into a combustion chamber of the internal combustion engine using energy of exhaust gas discharged from the internal combustion engine;
Drive means capable of forcibly driving the compressor of the supercharger without depending on the operating state of the internal combustion engine;
An EGR passage branched from the upstream of the turbine of the supercharger in the exhaust passage of the internal combustion engine and connected to the downstream of the compressor in the intake passage;
An EGR valve for opening and closing the EGR passage;
An EGR cooler disposed upstream of the EGR valve in the EGR passage;
A bypass passage branched from the compressor downstream in the intake passage and connected between the EGR cooler and the EGR valve in the EGR passage;
A bypass valve for opening and closing the bypass passage;
An internal combustion engine with a supercharger. An intercooler is disposed downstream of the compressor in the intake passage,
The internal combustion engine with a supercharger according to claim 9, wherein the bypass passage is branched from the upstream side of the intercooler in the intake passage.

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