JP2010121596A - Exhaust emission control system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To hold a catalyst device at a proper temperature state while restraining exhaust of NOx and smoke. <P>SOLUTION: The exhaust emission control system is equipped with: a plurality of air intake superchargers which is arranged in series and includes a motor-driven supercharger (217) capable of supercharging intake air in a positively rotating state corresponding to one rotative direction of a motor (400); EGR passages (301, 302, 311, 312) capable of feeding an EGR gas to an air intake system; an EGR supercharger (307) which is arranged on the same shaft as the motor-driven supercharger and is capable of supercharging or exhausting the EGR gas depending on the positively rotating state or a negatively rotating state, respectively; a blocking means (403) capable of blocking the supply of driving force for accelerating the negative rotation of the motor-driven supercharger, a discriminating means (100) for discriminating whether the catalyst device (500) is in a prescribed OT state or not, and a control means (100) for controlling the motor so that the EGR supercharger becomes the negative rotating state when it has been discriminated that the catalyst device is in the OT state. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a technical field of an exhaust purification device capable of purifying exhaust discharged from an internal combustion engine.

  As this type of apparatus, an apparatus including an EGR gas compressor that pressurizes EGR gas and recirculates it to an intake passage has been proposed (see, for example, Patent Document 1). According to the supercharged engine EGR device disclosed in Patent Document 1 (hereinafter referred to as “prior art”), the EGR gas compressor and the exhaust passage turbine are detachably connected via a clutch. By ensuring a sufficient amount of intake air into the cylinder, it is possible to perform EGR efficiently while preventing the occurrence of smoke and deterioration of fuel consumption, and the amount of NOx emissions in the exhaust gas in the entire operating range of the engine It is supposed that it becomes possible to reduce.

  A technique for preventing the recirculated exhaust gas from entering the supercharger in a configuration having the EGR means and the supercharger has also been proposed (see, for example, Patent Document 2).

  In addition, when the fuel addition required by the exhaust gas purification catalyst is executed, there is also proposed one that prevents the cooling performance of the EGR cooler from being lowered by selecting a bypass line that bypasses the EGR cooler by the flow path switching means. (For example, refer to Patent Document 3).

  Also disclosed is a technique for preventing the backflow of exhaust gas and intake air by connecting the exhaust manifold and the upstream side of the compressor intake port through an EGR passage (see, for example, Patent Document 4).

  Further, a technique has been proposed in which the exhaust manifold is divided and an EGR passage is formed in a part of the exhaust manifold (for example, see Patent Document 5).

  Furthermore, an exhaust gas recirculation device provided with a mechanical supercharger that is driven when the actual recirculation exhaust amount is smaller than the target recirculation exhaust amount has also been proposed (see, for example, Non-Patent Document 1).

JP-A-11-62715 JP-A-8-319873 JP 2006-233947 A JP 2004-245117 A JP-A-9-151805 Japanese Utility Model Publication No. 5-1843

  According to the above conventional technique, although the NOx emission amount can be reduced by the large amount of EGR, the smoke emission amount is likely to increase due to the decrease in the intake air amount. On the other hand, in order to deal with such a problem, it is well known that a plurality of superchargers are arranged in series with each other for the purpose of securing a new air amount.

  However, when a plurality of intake superchargers are arranged in series with each other, a plurality of turbines work at the same time in the exhaust region, which causes a decrease in exhaust temperature compared to the case where a single supercharger is employed. . For this reason, in the catalyst device that can be arranged on the downstream side of these superchargers, the temperature rise is hindered, and the exhaust purification efficiency itself decreases.

  On the other hand, the catalytic device is not limited to such a low temperature region, but can affect the exhaust purification efficiency even in a high temperature region. For example, in the catalyst device, when the process related to various exhaust purifications such as regeneration of PM (Particulate Matter) (that is, oxidation combustion) or oxidation of HC or CO proceeds excessively, the temperature of the catalyst device is increased. May rise rapidly. Such excessive temperature rise (that is, OT (Over Temperature)) of the catalyst device may cause damage to the catalyst device due to a heat load and may cause the catalyst device to be melted in some cases. Damage caused by such a heat load eventually reduces the purification efficiency of exhaust gas in the catalyst device. As described above, it is difficult for the conventional technology to sufficiently contribute to the purification of exhaust gas by reducing NOx and smoke emission due to the difficulty of maintaining the catalyst device at an appropriate temperature state. There are technical problems.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide an exhaust emission control device capable of maintaining the catalyst device at an appropriate temperature state while suppressing the emission of NOx and smoke.

  In order to solve the above-described problems, an exhaust emission control device according to the present invention is an exhaust emission control device for an internal combustion engine having a catalyst device in an exhaust system, and is rotationally driven by a driving force supplied from a motor. A plurality of intake superchargers disposed in series with each other in the intake system of the internal combustion engine, including a motor-driven supercharger configured to be able to supercharge intake air in a positive rotation state corresponding to the rotation direction; An EGR passage that branches from the exhaust system upstream of the catalyst device and that can supply a part of the exhaust gas flowing through the exhaust system to the intake system as EGR gas, and is driven to rotate by a driving force supplied from the motor; The motor-driven supercharger is uniaxially arranged in the exhaust system upstream of the EGR passage or the catalyst device, and the forward rotation state and the reverse rotation corresponding to the one rotation direction of the motor The EGR supercharger is capable of supercharging and exhausting the EGR gas in a state, and is provided between the motor-driven supercharger and the motor, and the motor-driven supercharger from the motor to the motor-driven supercharger is provided. A shut-off means capable of shutting off transmission of driving force for encouraging reverse rotation of the feeder; a discriminating means for judging whether or not the catalyst device is in a predetermined OT state; and that the catalyst device is in the OT state. And control means for controlling the motor so that the EGR supercharger is in the reverse rotation state when it is determined.

  The internal combustion engine according to the present invention has one or a plurality of cylinders, and in each of the cylinders, a fuel such as gasoline, light oil or various alcohols, or a mixture of the fuel and intake air. It is a concept that encompasses an engine that can extract the force generated when the air-fuel mixture burns, for example, through mechanical transmission paths such as pistons, connecting rods, and crankshafts. For example, it means a 2-cycle or 4-cycle reciprocating engine.

  According to the exhaust emission control device of the present invention, fresh air is supplied to the internal combustion engine through an intake system that can include, for example, an intake passage and an intake manifold, by a plurality of intake air superchargers that are arranged in series with each other. Is done. For this reason, it is possible to obtain a relatively high supercharging pressure as compared with, for example, a case where supercharging is performed by a single intake supercharger. The “intake supercharger” according to the present invention is a device that can supply (that is, supercharge) in a state where the pressure of the intake air, which is the air sucked from the outside, is increased to an atmospheric pressure or higher. Thus, for example, as a preferred form, at least a part uses exhaust energy (exhaust pressure as a simple form) (that is, at least a part of the rotational driving force of the turbine corresponding to the exhaust pressure is used for the compressor). It may be configured as a so-called turbocharger or the like used as a rotational driving force).

  On the other hand, the exhaust gas discharged from the combustion chamber and guided to the outside through the exhaust system is purified by various exhaust purification processes in various catalyst devices installed in the exhaust system with appropriate installation modes. Although this catalyst device can preferably exhibit a suitable exhaust purification effect in a temperature range equal to or higher than the catalyst activation temperature, the thermal energy of the exhaust is exclusively used for the temperature rise. That is, the composition is such that the heat energy of the exhaust gas is supplied to the catalyst device by heat exchange or the like generated in the process in which the high-temperature exhaust gas discharged from the combustion chamber passes through the catalyst device, and the temperature of the catalyst device is promoted.

  However, when each of the plurality of intake superchargers constituting the exhaust purification device is configured as a so-called turbocharger or the like that drives a turbine by exhaust pressure, the exhaust pressure decreases according to the number of intake superchargers. Therefore, it is preferable that the catalyst device is located downstream of the plurality of turbines (which may be located upstream of some turbines, but in that case, the turbine becomes difficult to drive sufficiently, and the supercharger In the case where there is a possibility of hindering the original supercharging operation), the heat load supplied per unit time is reduced with the decrease in the exhaust pressure, and the temperature rise is hindered. As a result, the purification efficiency of the exhaust gas decreases, and the amount of smoke or NOx in the exhaust gas (so-called engine output gas) discharged from the combustion chamber can be reduced. There may be a problem that the purification of the catalyst output gas) does not always proceed properly.

  Therefore, the exhaust emission control device of the present invention is configured to include a motor-driven supercharger as at least a part of the plurality of intake air superchargers. The “motor-driven supercharger” according to the present invention refers to, for example, a rotation shaft such as a motor output shaft and the rotation shaft directly or indirectly from a motor that uses power storage means such as a vehicle-mounted battery. Or a motor driven by a driving force supplied as appropriate through a rotating shaft or the like that is connected in a limited manner when various physical, mechanical, electrical, or magnetic conditions are satisfied. The intake air can be supercharged in a normal rotation state corresponding to one rotation direction (in this case, “normal rotation” only means one rotation direction of the motor-driven supercharger). The apparatus is preferably a fluid compression means such as a compressor that compresses the gas on the inlet side by forward rotation of the rotating shaft and guides the gas to the outlet side.

  When the motor-driven supercharger performs supercharging of the intake air, the exhaust pressure does not decrease. Therefore, in the exhaust gas purification apparatus according to the present invention, a desirable supercharging effect is achieved by a plurality of intake superchargers. In obtaining, it is possible to suppress a decrease in the thermal load supplied to the catalyst device. Therefore, the temperature rise of the catalyst device is obviously promoted as compared with the case where all of the plurality of intake superchargers are driven to exhaust, and the reduction of exhaust purification efficiency in the catalyst device is suppressed.

On the other hand, the exhaust gas purification apparatus according to the present invention branches from an exhaust system of an internal combustion engine that may include, for example, an exhaust port, an exhaust manifold, an exhaust passage, and the like, and supplies a part of the exhaust gas flowing through the exhaust system to the intake system as EGR gas. A possible EGR passage is further provided. For example, the EGR passage is directly or indirectly connected to the intake system of the internal combustion engine, or an EGR valve or the like such as a valve device that can control the flow rate of EGR gas (hereinafter simply referred to as “EGR amount” or the like). The exhaust system is configured to communicate in a limited manner depending on the state, and a part of the exhaust gas led to the EGR passage and discharged to the exhaust system is an intake system as EGR gas containing a relatively large amount of inert CO _2. It is configured to be refluxed. The EGR gas is mixed with the intake air supplied to the intake system to form intake air that is sucked into the cylinder, so that, for example, the generation of NOx or the like is suppressed at least somewhat.

  However, in view of the fact that a relatively high supercharging pressure can be realized by a plurality of intake superchargers as described above, the exhaust pressure (so-called so-called part of the exhaust manifold) between the EGR passage and the exhaust system (so-called exhaust manifold). , The engine back pressure), and the pressure deviation between the EGR passage and the intake pressure at the merging position of the intake system (for example, a part of the intake manifold) tends to be small. For this reason, in the configuration in which the EGR gas is pushed into the intake system using this pressure deviation, there may be a case where it is difficult to recirculate sufficient EGR gas to the intake system.

  Therefore, an EGR supercharger is provided in the EGR passage or the exhaust system of the internal combustion engine. The EGR supercharger satisfies various conditions, such as a rotating shaft such as the motor output shaft described above, and the rotating shaft directly, indirectly, or physically, mechanically, electrically or magnetically. In this case, the motor is rotationally driven by a driving force supplied through an appropriately connected rotating shaft or the like, and the motor is in a normal rotation state corresponding to the one rotation direction described above (in this case, "Normal rotation" means an apparatus configured to be able to supercharge EGR gas in only one rotation direction of the EGR supercharger). It is a fluid compression means such as a compressor that compresses the inlet side gas and forwards it to the outlet side by forward rotation. By supercharging EGR gas by the EGR supercharger, even if the pressure deviation is relatively small, it is possible to supply a practically sufficient amount of EGR gas to the intake system. Therefore, according to the configuration of the exhaust gas purification apparatus according to the present invention having the plurality of intake air superchargers and the EGR supercharger in this way, the generation amounts of smoke and NOx can be simultaneously reduced.

  Moreover, in the exhaust emission control device according to the present invention, the EGR supercharger is uniaxially arranged with the motor-driven supercharger described above. Here, “uniaxial arrangement” means that the rotation axis is substantially shared. Therefore, the EGR supercharger and the motor-driven supercharger can be rotated synchronously or integrally with the rotation of the motor, but the EGR supercharger and the motor-driven supercharger can be “substantially”. The strict connection between the feeder and the motor is not limited in any way. For example, the motor output shaft may be used as both rotary shafts, or the motor output shaft may be used as one rotary shaft and under various modes (directly, indirectly or limited). May be connected to each other), or both of them may individually have a rotating shaft and may be connected to the motor output shaft under various modes. In any case, this uniaxial arrangement ensures good mountability when the EGR supercharger and the motor-driven supercharger are mounted on the vehicle. It is also possible to efficiently use a motor as a driving force source for the motor-driven supercharger.

  At this time, various engaging means such as an electromagnetic clutch, a mechanical clutch or a fluid clutch are interposed between the motor and the EGR supercharger, and the motor and the EGR supercharger are selectively connected. It may be configured to obtain. In this case, it is possible to perform only supercharging of intake air without supercharging of EGR gas. Therefore, an area that requires a relatively large amount of fresh air or an exhaust drive type intake supercharger is sufficient. This is effective in a low rotation area where the motor does not operate normally.

  By the way, in order to suitably purify the exhaust gas in the catalyst device, it is not sufficient to ensure the heat load described above. For example, when the catalyst device has a filter that can capture various PMs, such as DPF (Diesel Particulate Filter), so-called PM regeneration can be performed as a process of exhaust purification, but the progress of this PM regeneration is precisely controlled. In general, it belongs to a difficult category. For this reason, excessive regeneration of the catalyst device, so-called catalyst OT, may occur as a result of excessive PM regeneration in the catalyst device. Since the catalyst OT can cause thermal deterioration of the catalyst device, melting of the catalyst device, and the like, it is necessary to prevent or quickly avoid the catalyst device. That is, in order to suitably maintain the exhaust purification efficiency, a measure for maintaining the catalyst device in a suitable temperature range is required.

  Here, in the present invention, the motor that drives the EGR supercharger may rotate in either the forward or reverse rotational direction, unlike an exhaust drive type gas turbine or the like in which the rotational direction is substantially uniquely defined. Is possible. Since the EGR supercharger exhibits the supercharging action of the EGR gas in the normal rotation state as described above, the reverse rotation state (“reverse rotation” is a rotation direction opposite to the normal rotation described above. On the contrary, it has the effect of guiding the gas in the EGR passage to the exhaust system. At this time, it is possible to easily introduce relatively low-temperature air into the EGR passage from the intake system through not only high-temperature exhaust but also, for example, opening the throttle and opening the EGR valve. Thus, by operating the EGR supercharger in the reverse rotation state in this way, relatively low-temperature air that does not undergo the combustion process can be used as secondary air for cooling the catalyst device.

  On the other hand, in view of the fact that the EGR supercharger corresponds to the one rotation direction of the motor and the reverse rotation state of the EGR supercharger corresponds to the reverse rotation direction of the motor, the EGR supercharger is uniaxial. Similar effects can occur in the motor-driven supercharger that is arranged. That is, since the normal rotation state of the motor-driven supercharger corresponds to one rotation direction of the motor, the reverse rotation state of the motor-driven supercharger corresponds to the reverse rotation direction of the motor. That is, the motor-driven supercharger exhibits an action of discharging the intake air from the intake system in the reverse rotation state. Such a reverse flow of the intake air causes a significant decrease in the amount of fresh air sucked into the cylinder, which in turn causes a decrease in the fuel injection amount that is regulated by the smoke generation limit and affects the power performance of the vehicle. give. Even if the folding EGR supercharger is driven in the reverse rotation state, if this type of intake air backflow occurs in the intake system, it is difficult to guide the low-temperature intake air from the intake system.

  Therefore, it is necessary to take measures to prevent the motor-driven supercharger from going into the reverse rotation state in the technical idea that the catalyst device is cooled by the EGR supercharger arranged in a single axis with the motor-driven supercharger. obtain. Therefore, the exhaust emission control device according to the present invention is provided with a shut-off means such as a one-way clutch that can cut off the transmission of the driving force that promotes reverse rotation of the motor-driven supercharger from the motor to the motor-driven supercharger. ing. By this action of the shut-off means, cooling of the catalyst device is realized by operating the EGR supercharger in the reverse rotation state at least without backflow of the intake air.

  In particular, it is not a good idea to perform cooling of this type of catalyst device without any guideline in view of the required frequency of supercharging of EGR gas that should be the original operation of the EGR supercharger. In that respect, the exhaust emission control device according to the present invention is configured to efficiently cool the catalyst device as follows. That is, according to the exhaust emission control device of the present invention, during its operation, for example, discrimination that can take the form of various processing units such as an ECU (Electronic Control Unit), various controllers or various computer systems such as a microcomputer device, etc. The means determines whether or not the catalyst device is in the OT state.

  Here, the “OT state” means a state in which the catalyst device is excessively heated, a state in which it is possible to predict, estimate or determine that the catalyst device will be exposed to an excessive heat load due to excessive temperature increase in the near future. Including the state in which the catalyst device requires cooling. Whether or not the catalyst device is in the OT state is determined, for example, when the temperature of the exhaust system in the vicinity of the catalyst device or the catalyst device, the operating condition of the internal combustion engine (for example, when the operating condition of high rotation and high load continues) The exhaust temperature becomes high, the catalyst temperature also becomes high and the catalyst OT is likely to occur), or the trap state of PM in the catalyst device (for example, if the trap amount is large, the PM chain is likely to be regenerated more easily). It is possible to carry out at least within a practical range based on the fact that the temperature rise is easy to proceed).

  On the other hand, when it is determined by the determining means that the catalyst device is in the OT state, the control means that can take the form of various processing units such as an ECU, various controllers or various computer systems such as a microcomputer device, for example, The motor is controlled so that the EGR supercharger is in the above-described reverse rotation state through an appropriate drive system or drive member control that can appropriately include a switching circuit, a PWM control circuit, an inverter circuit, and the like. In other words, the motor is driven to rotate in the direction of rotation opposite to the one direction of rotation described above. As a result, the cooling gas is supplied from the EGR passage to the catalyst device, and the catalyst device is cooled, so that the OT of the catalyst device can be prevented efficiently and reliably. That is, according to the exhaust emission control device of the present invention, it is possible to maintain the catalyst device at an appropriate temperature state while suppressing NOx and smoke emission.

  In one aspect of the exhaust emission control device according to the present invention, the shut-off means converts the driving force that promotes reverse rotation of the motor-driven supercharger into driving force that promotes forward rotation of the motor-driven supercharger. Including means.

  According to this aspect, the shut-off means includes a conversion means that can take the form of, for example, a reverse gear or a back gear as a suitable form, or is configured as such conversion means, and is the reverse of the motor-driven supercharger. By converting the driving force that encourages rotation into the driving force that encourages forward rotation, transmission of the driving force that encourages reverse rotation of the motor-driven supercharger from the motor to the motor-driven supercharger is cut off. ing.

  As described above, when the motor-driven supercharger enters the normal rotation state as a result of the transmission of the driving force for promoting the normal rotation to the motor-driven supercharger, as described above, the intake air from the motor-driven supercharger Supercharging action occurs. For this reason, on the one hand, the intake air is actively supplied to the intake system, and on the other hand, at least a part of the actively supplied intake air can be used for cooling the catalyst device. According to this aspect, the driving force that promotes the reverse rotation of the motor-driven supercharger is thus converted into the driving force that promotes the forward rotation, that is, the transmission is more actively interrupted. Can be controlled more appropriately, which is extremely useful in practice.

  Such an operation and other advantages of the present invention will become apparent from the embodiments described below.

<Embodiment of the Invention>
Various preferred embodiments of the present invention will be described below with reference to the drawings.

<Configuration of Embodiment>
First, the configuration of an engine system 10 according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic configuration diagram conceptually showing the configuration of the engine system 10.

  In FIG. 1, an engine system 10 is mounted on a vehicle (not shown), and includes an ECU 100, an engine 200, an EGR device 300, a motor 400, and a catalyst device 500.

  The ECU 100 is an electronic control unit that includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like and is configured to be able to control the entire operation of the engine 200. The ECU 100 is configured to execute OT avoidance control, which will be described later, according to a control program stored in the ROM. The ECU 100 is an example of a “discriminating unit” and “control unit” according to the present invention.

  The engine 200 is an in-line four-cylinder diesel engine that is an example of an “internal combustion engine” according to the present invention that uses light oil as fuel. The outline of the engine 200 will be described. The engine 200 has a configuration in which four cylinders 202 are arranged in parallel in a cylinder block 201. The thermal energy generated when the air-fuel mixture containing fuel is compressed and ignited in each cylinder causes a reciprocating motion of a piston (not shown), and is connected to the piston via a connecting rod (both (Not shown). Below, the principal part structure of the engine 200 is demonstrated with a part of the operation | movement.

  The engine 200 according to this embodiment is an in-line four-cylinder diesel engine in which four cylinders 202 are arranged in parallel in a direction perpendicular to the paper surface in FIG. 1, but the configuration of the individual cylinders 202 is equal to each other. Here, only one cylinder 202 will be described.

  Upon combustion of the air-fuel mixture in the cylinder 202, the intake air as the air sucked from the outside is guided to the intake manifold 203 that is installed in common for each cylinder, and then the intake port (not connected) provided independently for each cylinder. The intake port is drawn into the cylinder 202 when the intake valve (not shown) configured to allow communication between the intake port and the inside of the cylinder is opened. In the cylinder 202, light oil as fuel is injected from an in-cylinder direct injection injector 204, and the injected fuel is a gas (hereinafter referred to as “intake air”) that is sucked into the cylinder inside each cylinder. Is abbreviated as “)” to obtain the above-mentioned air-fuel mixture.

  In engine 200, fuel is stored in a fuel tank (not shown). The fuel stored in the fuel tank is pumped out of the fuel tank by the action of a feed pump (not shown) and is pumped to a high pressure pump (not shown) through a low pressure pipe (not shown). The high pressure pump is configured to be able to supply fuel to the common rail 205. The high-pressure pump can take various known modes, and the details thereof will be omitted here.

  The common rail 205 is electrically connected to the ECU 100, and is configured to store high pressure fuel supplied from the upstream side (that is, the high pressure pump side) up to a target rail pressure set by the ECU 100. It is. The common rail 205 is provided with a rail pressure sensor capable of detecting the rail pressure and a pressure limiter for limiting the amount of fuel accumulated so that the rail pressure does not exceed the upper limit value. The illustration is omitted. The injector 204 described above is mounted for each cylinder 202, and each is connected to the common rail 205 via the high-pressure delivery 206.

  Here, to supplement the configuration of the injector 204, the injector 204 includes an electromagnetic valve that operates based on a command supplied from the ECU 100, and a nozzle (both not shown) that injects fuel when the solenoid valve is energized. Prepare. The solenoid valve is configured to be able to control the communication state between the pressure chamber to which the high-pressure fuel of the common rail 205 is applied and the low-pressure side low-pressure passage connected to the pressure chamber. The pressurizing chamber and the low pressure passage are communicated with each other, and the pressurizing chamber and the low pressure passage are shut off from each other when energization is stopped.

  On the other hand, the nozzle has a built-in needle for opening and closing the nozzle hole, and the fuel pressure in the pressure chamber urges the needle in the valve closing direction (direction in which the nozzle hole is closed). Accordingly, when the pressure chamber and the low-pressure passage are connected by energization of the electromagnetic valve and the fuel pressure in the pressure chamber decreases, the needle rises in the nozzle and opens (opens the nozzle hole), so that the common rail 205 is opened. The high-pressure fuel supplied more can be injected from the injection hole. In addition, when the energization of the solenoid valve is stopped, the pressurization chamber and the low pressure passage are cut off from each other and the fuel pressure in the pressure chamber rises, and the needle is lowered in the nozzle to close the valve, thereby terminating the injection. It has become.

  In addition, the fuel corresponding to the target injection amount is injected into each cylinder 202 via the injector 204, and a small amount of pilot injection for preventing a rapid temperature rise in the combustion chamber, and the target injection amount and the pilot injection amount. The main injection corresponding to the difference between and the main injection is divided and injected.

  The above-described air-fuel mixture burns by self-ignition in the compression process, and opens an exhaust valve (not shown) that opens and closes in conjunction with opening and closing of the intake valve as a burned gas or a partially unburned air-fuel mixture The structure is sometimes led to the exhaust manifold 207 via an exhaust port (not shown). The exhaust manifold 207 communicates with the exhaust passage 208, and most of the exhaust gas is guided to the exhaust passage 208.

  On the other hand, the LP side turbine 210 is installed in the exhaust passage 208 so as to be accommodated in an LP (Low Pressure) side turbine housing 209. The LP-side turbine 210 is configured to be rotatable about a predetermined rotation axis by the pressure of the exhaust led to the exhaust passage 208. The rotation axis of the LP-side turbine 210 is shared with the LP-side compressor 212 installed in the intake passage 213 so as to be accommodated in the LP-side compressor housing 211, and when the LP-side turbine 210 rotates due to exhaust pressure, The side compressor 212 is also configured to rotate about the rotation axis. The intake passage 213 and the intake manifold 203 constitute an example of the “intake system” according to the present invention. The LP-side compressor 212 is configured to be able to pump (i.e., supercharge) the intake air guided from the outside to the intake passage 213 via a cleaner (not shown) to the intake manifold 203 by the pressure accompanying the rotation. 1 is an example of an “intake supercharger” according to the present invention.

  The LP-side turbine 210 is provided with a VN (Variable Nozzle: variable nozzle) 214 capable of adjusting the exhaust pressure for driving the LP-side turbine 210 in accordance with the opening degree of the nozzle vane.

  On the other hand, HP (High Pressure) side intake passage 215 (HP side intake passage 215 which branches from the downstream branch position of LP side compressor 212 in intake passage 213 is also an “intake system” according to the present invention. In one example, the HP-side compressor 217 is installed in a form housed in the HP-side compressor housing 216. The HP-side compressor 217 is configured to be capable of further supercharging the intake air guided to the HP-side intake passage 215 (that is, the intake air supercharged by the LP-side compressor 212) according to the present invention. This is another example of the “intake supercharger”, and is arranged in series with the LP-side compressor 212. The intake air supercharged by the HP-side compressor 217 is returned to the intake passage 213 again at the downstream side of the branch position via the HP-side compressor outlet 218 which is a part of the HP-side intake passage 215. Yes. As described above, the engine 200 according to the present embodiment has a configuration in which so-called two-stage supercharging can be performed by the LP-side compressor 212 and the HP-side compressor 217.

  The HP-side compressor outlet 218 and the LP-side compressor outlet 219 that is the outlet of the LP-side compressor 212 (a part of the intake passage 213 and set downstream of the branch position described above) The switching valve 220 is connected. The intake air switching valve 220 includes a valve body whose opening is binary variable between a fully opened opening and a fully closed opening, and is configured to be able to switch the intake air supply path according to the opening. It is an electromagnetic on-off valve. The intake air switching valve 220 is electrically connected to the ECU 100, and the opening degree thereof is controlled by the ECU 100 via an appropriate drive system.

  Supplementally, when the communication between the LP-side compressor outlet 219 and the HP-side compressor outlet 218 is blocked by the intake air switching valve 220 (that is, a state corresponding to a fully closed opening), the LP-side compressor 212 The entire amount of the intake air supercharged by is supplied to the HP-side compressor 217. Further, in a state where the LP-side compressor outlet 219 and the HP-side compressor outlet 218 are communicated with each other by the intake air changeover valve 220 (that is, a state corresponding to the fully opened opening degree), the HP-side compressor will be described later. When 217 is stopped, the intake air supercharged by the LP-side compressor 212 is hardly supplied to the HP-side compressor 217 (that is, passes through the LP-side compressor outlet 219 having a lower flow path resistance). And) is supplied to the intake manifold 203 on the downstream side. The intake air switching valve 220 may have a structure whose opening degree is continuously variable.

  The motor 400 is a DC brushless motor that is an example of a “motor” according to the present invention that is configured to be driven in the forward rotation direction and the reverse rotation direction by electric power supplied from a battery (not shown). One end of a motor shaft 401 that is a motor output shaft that passes through the rotor of the motor 400 is connected to the rotary shaft of the HP-side compressor 217 described above via a one-way clutch 403 and a reverse gear 404 described later. For this reason, according to the rotational speed of the motor shaft 401, the rotational speed of the HP side compressor 217 also changes, and the supercharging pressure of the HP side compressor 217 changes. That is, the HP side compressor 217 is an example of the “motor drive supercharger” according to the present invention.

  The motor 400 is configured such that a drive system (not shown) is electrically connected to the ECU 100 and the drive state is controlled by the ECU 100. That is, the supercharging state of the HP side compressor 217 can be adjusted as appropriate by the ECU 100. The HP-side compressor 217 is installed so that when the motor 400 rotates in the forward direction (that is, an example of “one direction of rotation of the motor” according to the present invention), the HP-side compressor 217 enters the forward rotation state and can supercharge intake air. Has been. That is, the normal rotation state of the HP-side compressor 217 corresponds to the normal rotation state of the motor 400.

  A diesel throttle valve 221 capable of adjusting the amount of intake air is disposed in the intake passage 213. The diesel throttle valve 221 is a rotary valve that is electrically connected to the ECU 100 and is configured to be rotatable by a driving force supplied from a throttle valve motor 222 that is controlled by the ECU 100. The diesel throttle valve 221 serves as a boundary. The rotational position is continuously controlled from the fully closed position where the upstream portion and the downstream portion of the intake passage 213 are substantially blocked to the fully opened position where the intake passage 213 communicates almost entirely. Engine 200 is a diesel engine, and its output is controlled through injection amount increase / decrease control, unlike air-fuel ratio control (intake air amount control) in an engine using gasoline or the like as fuel. Therefore, the diesel throttle valve 221 is basically controlled to the fully open position (the position of the illustrated diesel throttle valve 221 corresponds to the fully open position) during the operation period of the engine 200. In the intake passage 213, an intercooler ("I / C" in the figure) 223 capable of cooling the supercharged intake air is installed.

  An intake manifold pressure sensor 224 is installed in the intake passage 213. The intake manifold pressure sensor 224 is a sensor configured to detect the intake manifold pressure Pb (substantially equivalent to the supercharging pressure of the engine 200 as a whole), which is the intake air pressure in the intake manifold 203. The intake manifold pressure sensor 224 is electrically connected to the ECU 100, and the detected intake manifold pressure Pb is referred to by the ECU 100 at a constant or indefinite timing.

  Further, an exhaust manifold pressure sensor 225 is installed in the exhaust manifold 207. The exhaust manifold pressure sensor 225 is a sensor configured to be able to detect an exhaust manifold pressure P4 (so-called engine back pressure) as exhaust pressure in the exhaust manifold 207. The exhaust manifold pressure sensor 225 is electrically connected to the ECU 100, and the detected exhaust manifold pressure P4 is referred to by the ECU 100 at a constant or indefinite timing.

  A catalyst device 500 including a DPF (Diesel Particulate Filter) (not shown) is installed on the downstream side of the exhaust passage 208. This DPF is a so-called ceramic wall flow filter configured to collect and purify PM discharged from the engine 200, and captures PM in countless pores formed on the surface of the carrier. In a predetermined regeneration process, exhausted gas can be purified by oxidizing and burning captured PM. Supplementally, in this catalyst device 500, an oxidation catalyst is installed in front of this DPF, and NO, CO and HC in the exhaust are oxidized by this oxidation catalyst, and the regeneration of PM is promoted in the DPF. It has become. The catalyst device 500 may include other catalyst devices such as an NSR (Nox Strage Reduction) catalyst.

  A water jacket (not shown) for circulating and supplying cooling water such as LLC is provided on the outer peripheral portion of the cylinder 202 in the cylinder block 201 that accommodates the cylinder 202, and the entire engine 200 including the cylinder 202 is cooled. It is configured to be possible.

  In the engine system 10, the ECU 100 includes various index values that define the operating conditions of the engine 200 or the vehicle on which the engine 200 is mounted, in addition to the illustration. It is configured to be electrically input via a sensor (not shown). For example, the ECU 100 is configured to be able to acquire the engine rotational speed NE of the engine 200 from the NE sensor and the accelerator pedal opening (that is, the accelerator opening) from the accelerator position sensor.

  In the present embodiment, the engine 200 is configured as a diesel engine, but the internal combustion engine according to the present invention can be similarly applied to an engine using gasoline or alcohol as fuel. Furthermore, the cylinder arrangement may be varied.

  Next, the EGR device 300 will be described. The EGR device 300 includes an EGR introduction passage 301, an EGR passage 302, an EGR cooler 303, an EGR cooler bypass valve 304, an EGR valve 305, an EGR compressor housing 306, an EGR compressor 307, a first switching valve 308, a second switching valve 309, EGR. A compressor outlet pressure sensor 310, a first passage 311 and a second passage 312 are provided, and a part of the exhaust gas can be circulated to the intake manifold 203 as EGR gas.

  The EGR introduction passage 301 is a tubular member that allows the exhaust passage 208 and the first passage 311 to communicate with each other, and is configured to branch from the exhaust passage 208 upstream of the LP-side turbine housing 209. Further, an end portion of the EGR introduction passage 301 opposite to the exhaust passage 208 is connected to the EGR compressor housing 306, and the EGR introduction passage 301 is configured to communicate with the EGR compressor housing 306 therein.

  The first passage 311 is a hollow and metallic tubular member having one end connected to the EGR compressor housing 306 and the other end connected to the EGR passage 302. The first passage 311 and the EGR passage 302 may be formed integrally with each other, welded, or kept airtight by an appropriate connecting member (for example, a flange, a gasket, or a coupler). May be connected.

  The EGR passage 302 has one end connected to the first passage 311 and the other end connected to the intake passage 213 at a connection position on the upstream side of the intake manifold 203, the EGR introduction passage 301, the first passage 311 and This is a hollow and metallic tubular member that constitutes an example of the “EGR passage” according to the present invention together with the second passage 312.

  The EGR cooler 303 is an EGR gas cooling device provided in the EGR passage 302. The EGR cooler 303 has a configuration in which the cooling water piping of the engine 200 is stretched around the outer periphery, and the EGR gas that is guided to the EGR passage 302 and passes through the EGR cooler 303 is cooled by heat exchange with the cooling water. In this configuration, it is guided to the downstream side (that is, the intake passage 213 side). The EGR cooler 303 is connected to an inlet pipe and an outlet pipe (both not shown) each communicating with the water jacket described above, and the cooling water flows from the inlet pipe into the cooling water pipe, and the outlet It is discharged out of the cooling water pipe through the pipe. The discharged cooling water is returned to the cooling water circulation system of the engine 200, and is supplied again from the inlet pipe through a predetermined path.

  In the EGR passage 302, a bypass passage (not shown) that connects the upstream side and the downstream side of the EGR cooler 303 is formed. When EGR gas is led to the bypass passage, the EGR gas returns to the intake system without passing through the EGR cooler 303 installed in the bypassed section of the EGR passage 302 bypassed by the bypass passage. It has become.

  The EGR cooler bypass valve 304 is installed in the EGR passage 302 in the vicinity of the upstream end (that is, the exhaust manifold side) of the EGR cooler 303 (this configuration is merely an example, and the EGR cooler bypass valve 304 is in the vicinity of the downstream end. In other words, the valve device can switch the EGR gas supply path in the EGR passage 302 in a binary manner by controlling the position of the valve body. The EGR cooler bypass valve 304 is electrically connected to the ECU 100, and the valve body position is controlled by the ECU 100 to the upper level.

  More specifically, the position of the EGR cooler bypass valve 304 is such that the position of the valve body shuts off the inflow of EGR gas into the bypassed section described above and guides the EGR gas only to the bypass passage, Contrary to this, the configuration is such that the inflow of EGR gas to the bypass passage is blocked and the valve position on the cooler side that guides the EGR gas only to the bypassed section can be switched in a binary and selective manner. .

  The configuration of the bypass passage and the EGR cooler bypass valve 304 is not limited to the form described here. For example, the EGR cooler bypass valve 304 can change the amount of EGR gas that bypasses the EGR cooler 303 stepwise or continuously by stepwise or continuous control of the open / close state of one or more valve bodies. It may be configured.

  The EGR valve 305 is installed in the EGR passage 302 upstream of the connection position with the intake passage 213 described above, and changes the amount of EGR gas (that is, the amount of EGR) by controlling the opening / closing state of the valve body. This is an electromagnetic on-off valve configured to be capable of. The EGR valve 305 is electrically connected to the ECU 100, and its driving state is controlled by the ECU 100 to the upper level. Supplementally, the EGR gas guided to the EGR passage 302 will eventually have this valve body position of the EGR cooler bypass valve 304 described above, regardless of which of the two types of valve body positions described above. An amount corresponding to the opening of the EGR valve 305 (that is, the degree of valve opening, which can be expressed as a numerical value standardized as 100 (%) for full opening, 0 (%) for full closing, etc.) It is supplied to the manifold 203.

  The EGR compressor 307 is a supercharger that is an example of an “EGR supercharger” according to the present invention that is installed in a form that is accommodated in the EGR compressor housing 306. The EGR compressor 307 pumps a part of the exhaust gas (that is, EGR gas) guided through the EGR introduction passage 301 to the first passage 311 connected to the downstream side according to the rotation speed of the rotation shaft. This is possible, and the EGR gas is supercharged by pumping the EGR gas. The rotating shaft of the EGR compressor 307 is connected to the other end portion of the motor shaft 401 described above via an electromagnetic clutch 402 described later. That is, the EGR compressor 307 substantially shares the rotation axis with the HP-side compressor 217 for fresh air supercharging, and an example of “one-shaft arrangement” according to the present invention is realized.

  Similar to the HP-side compressor 217, the EGR compressor 307 is accommodated in the EGR compressor housing 306 so that EGR gas is supercharged when the motor 400 rotates forward. That is, the normal rotation state of the EGR compressor 307 corresponds to the normal rotation state of the motor 400.

  Further, since the EGR compressor 307 can supercharge EGR gas in the forward rotation state, when the motor 400 is in the reverse rotation state rotated in the reverse direction, the gas is exhausted through the EGR passage 302 on the contrary. Can lead to. At this time, if the EGR valve 305 and the diesel throttle valve 221 are open, relatively low-temperature intake air that is not used for combustion can be directly supplied from the intake passage 213 to the exhaust passage 208 as secondary air.

  The second passage 312 is a hollow and metallic tubular member having one end connected to the exhaust manifold 207 and the other end connected to the EGR passage 302. The second passage 312 can supply the exhaust gas staying in the exhaust manifold 207 as EGR gas to the EGR passage 302 without passing through the EGR compressor 307 (that is, bypassing). The second passage 312 and the EGR passage 302 may be formed integrally with each other, welded, or kept airtight by an appropriate connecting member (for example, a flange, a gasket, or a coupler). May be connected.

  The first switching valve 308 is an electromagnetic on-off valve provided with a valve body that can binaryly control the open / close state between fully closed and fully open. The first switching valve 308 is installed in the first passage 311 and can change the communication state of the first passage 311 and the EGR passage 302 in a binary manner according to the open / close state of the valve element. That is, when the valve body is in the fully open state, the first passage 311 and the EGR passage 302 communicate with each other, and when the valve body is in the fully closed state, the communication between the first passage 311 and the EGR passage 302 is Blocked.

  Similar to the first switching valve 308, the second switching valve 309 is an electromagnetic switching valve including a valve element that can binaryly control the open / close state between fully closed and fully opened. The second switching valve 309 is installed in the second passage 312 and can binaryly change the communication state between the second passage 312 and the EGR passage 302 according to the open / close state of the valve element. That is, when the valve body is in the fully open state, the second passage 312 and the EGR passage 302 communicate with each other, and when the valve body is in the fully closed state, the communication between the second passage 312 and the EGR passage 302 is Blocked.

  Therefore, the EGR gas passes through the exhaust manifold 207, the EGR introduction passage 301, the EGR compressor 307, the first passage 311 and the EGR passage 302 in a state where the first switching valve 308 is opened and the second switching valve 209 is closed. The intake manifold 203 is guided to the intake manifold 203 via the exhaust manifold 207, the second passage 312 and the EGR passage 302 in a state where the first switching valve 308 is closed and the second switching valve 209 is opened. Led. Hereinafter, the former route (route passing through the EGR compressor 307) will be referred to as the first route, and the latter route (route bypassing the EGR compressor 307) will be referred to as the second route as appropriate.

  The EGR compressor outlet pressure sensor 310 is a sensor that is installed in the first passage 311 and configured to detect the EGR compressor outlet pressure Pegr, which is the pressure of EGR gas in the first passage 311. The EGR compressor outlet pressure sensor 310 is electrically connected to the ECU 100, and the detected EGR compressor outlet pressure Pegr is referred to by the ECU 100 at a constant or indefinite timing. The pressure of the EGR gas in the second passage 312 is replaced by the exhaust manifold pressure P4 detected by the exhaust manifold pressure sensor 225.

  On the other hand, the engine system 10 includes an electromagnetic clutch 402. The electromagnetic clutch 402 has metal clutch plates (not shown) opposed to each other, and has a structure in which electromagnetic force is appropriately generated by energization control with respect to a solenoid driving device (not shown) to couple or separate both clutch plates. An electromagnetically driven clutch device. The electromagnetic clutch 402 is electrically connected to the ECU 100, and the driving state of the electromagnetic clutch 402 (here, the energization state of the solenoid driving device) is configured to be controlled by the ECU 100.

  Here, the rotating shaft of the HP side compressor 217 and the rotating shaft of the EGR compressor 307 are connected to both ends of the motor shaft 401 which is the rotating shaft of the motor 400. The clutch plate is fixed to an end portion of the motor shaft 401 facing the rotation shaft of the EGR compressor 307 and an end portion of the rotation shaft of the EGR compressor 307 facing the motor shaft 401. Therefore, in a coupled state in which both clutch plates are coupled to each other, the motor 400 and the EGR compressor 307 rotate integrally or synchronously with a rotation shaft that can be regarded as an integral body in which both shaft bodies are coupled. On the other hand, in the separated state where both clutch plates are separated from each other, the EGR compressor 307 loses its rotational driving force and stops.

  The engine system 10 includes a one-way clutch 403 and a reverse gear 404 between the motor shaft 401 and the rotation shaft of the HP-side compressor 217.

  The one-way clutch 403 is a known one-way clutch device in which a large number of cams are arranged between an outer ring portion and an inner ring portion. When the motor 400 is rotated forward, the cam stretches between the outer ring portion and the inner ring portion. As a result, the driving force of the motor 400 is transmitted to the rotating shaft of the HP-side compressor 217, and the rotating shaft of the HP-side compressor 217 is rotationally driven in the positive rotation direction described above. On the other hand, when the motor 400 rotates in the reverse direction, the inner ring rotates idly with a very low torque due to the cam falling in the circumferential direction, so that the driving force of the motor 400 is hardly transmitted to the rotating shaft of the HP side compressor 217. That is, the one-way clutch 403 is an example of the “blocking means” according to the present invention that transmits the driving force from the motor 400 so as to rotate the HP-side compressor 217 only in the forward rotation direction.

  The reverse gear 404 is installed closer to the motor 400 than the one-way clutch 403, and is configured to transmit the rotation of the motor shaft 401 to the rotation shaft of the HP-side compressor 217 with reversal of the rotation direction. It is a metal gear device as an example of the “conversion means” according to the invention. According to the reverse gear 404, when the motor 400 is in the reverse rotation state, the HP-side compressor 217 is in the normal rotation state, so that the intake air is supercharged when the secondary air is supplied to the exhaust passage 208 described above. be able to.

  However, when the reverse gear 404 is completely fixed to the motor shaft 401, rotation in the reverse rotation direction is transmitted to the rotation shaft of the HP-side compressor 217 when the motor 400 is driven in the forward rotation state. Therefore, transmission of the driving force to the HP-side compressor 217 is interrupted by the action of the one-way clutch 403.

  Therefore, in the present embodiment, the reverse gear 404 is accommodated in a gear box (not shown) together with a forward gear (not shown) and various engagement devices. The gear box is further configured to be interposed between the motor shaft 401 and the one-way clutch 403. The motor shaft 401 and the one-way clutch 403 are engaged with an engagement device housed in the gear box. In accordance with the combination state, the reverse gear 404 and the forward gear are always coupled via a selected one. The engagement device is electrically connected to the ECU 100, and the engagement state is controlled by the ECU 100. In such a configuration, the ECU 100 selects the reverse gear 404 when the motor 400 is in the reverse rotation state, and selects the forward gear when the motor 400 is in the normal rotation state. For this reason, the HP-side compressor 217 is configured to be in a normal rotation state regardless of which direction the motor 400 rotates, and the intake air can be supercharged.

  In view of the fact that the presence of the reverse gear 404 makes it difficult for the HP-side compressor 217 to reversely rotate within the normal operating range, the one-way clutch 403 is not necessarily required, but the one-way clutch 403 is provided. As a result, regardless of the direction of rotation of the motor 400 and the mode of selection of the gear in the gear box, the reverse rotation of the HP-side compressor 217 is physically prevented, so that high reliability is ensured.

<Operation of Embodiment>
The engine system 10 can perform two-stage supercharging of intake air using the LP side compressor 212 and the HP side compressor 217, and can realize a relatively high supercharging pressure (substantially equivalent to the intake manifold pressure Pb). It is. For this reason, the discharge | emission of smoke is suppressed suitably. Moreover, high power performance (for example, acceleration performance) by two-stage supercharging is secured. On the other hand, in view of the fact that the supercharging pressure can be increased in this way, the deviation between the intake manifold pressure Pb and the exhaust manifold pressure P4 is relatively easy to reduce, and the EGR gas is guided to the intake manifold 203 using this pressure difference. With only the configuration, it is difficult to ensure a sufficient amount of EGR. In that respect, the engine system 10 is provided with an EGR compressor 307, which can supercharge EGR gas. For this reason, it is possible to avoid a decrease in the amount of EGR that accompanies an increase in the supercharging pressure, and it is also possible to suitably reduce NOx by EGR (which means that EGR gas is circulated through the intake system). That is, according to the engine system 10, it is possible to simultaneously reduce smoke and NOx emissions.

  The HP-side compressor 217 is a motor-driven supercharger that operates by receiving a driving force supplied from the motor 400, and does not require exhaust energy for driving. For this reason, it is the structure by which the fall of exhaust temperature is suppressed compared with the case where all the superchargers which supercharge intake air are exhaust drive type. That is, according to the engine system 10, when reducing the smoke and NOx emission, the thermal load supplied to the catalyst device 500 does not decrease, and the temperature rise of the catalyst device 500 is promoted. There is no problem that the purification efficiency itself is lowered. That is, it is possible to achieve a suitable purification of exhaust gas while reducing the smoke and NOx emission.

  On the other hand, if the temperature of the catalyst device 500 is suitably increased in this way, the catalyst device 500 adds unburned fuel (that is, unburned HC) to the exhaust passage 208, or such unburned HC or When the PM is forcedly regenerated in the catalyst device 500 by temporarily increasing the CO emission amount, etc., the OT of the catalyst device 500 due to excessive continuous regeneration of PM is not necessarily prevented. Such a problem is not limited to the case where a PM capture and regeneration unit such as a DPF is provided, but may similarly occur in S regeneration control or the like in an NSR catalyst or the like.

  On the other hand, the EGR compressor 307 uses the motor 400 as a driving force source, similarly to the HP-side compressor 217. As described above, the motor 400 can rotate in either the forward or reverse rotation direction. Therefore, the EGR compressor 307 can also rotate in either the forward or reverse rotation direction. The engine system 10 is configured such that OT avoidance control is executed by the ECU 100 using this characteristic, and OT of the catalyst device 500 is suitably prevented. Here, the details of the OT avoidance control will be described with reference to FIG. FIG. 2 is a flowchart of the OT avoidance control.

  In FIG. 2, the ECU 100 determines whether or not the catalyst device 500 is in the OT state (step S101). Here, the “OT state” includes, of course, a state in which OT has already occurred at present, but if anything, it is estimated that this type of OT is likely to occur so that it is difficult to overlook in practice. Refers to the state to obtain. In step S101, the ECU 100 determines that the temperature of the catalyst device 500 (so-called catalyst bed temperature) measured by a temperature sensor (not shown) installed in or near the catalyst device 500 is in such an OT state. It is determined whether or not (or exceeds) a reference value defined based on the definition. Here, it is configured that the determination that the catalyst device 500 is in the OT state is made when the temperature of the catalyst device 500 is equal to or higher than the reference value. However, the temperature increase rate of the catalyst device 500 is equal to or higher than the reference value. In some cases, it may be determined that the catalyst device 500 is in the OT state. Alternatively, instead of or in addition to the temperature of the catalyst device 500, the PM accumulation state in the catalyst device 500 is determined based on the operation history of the engine system 10 (preferably, the history of the rotation state and load state of the engine 200). It may be estimated and used as an index for such discrimination.

  If it is determined in step S101 that the catalyst device 500 is not in the OT state (step S101: NO), the ECU 100 ends the OT avoidance control. However, the execution state of the OT avoidance control is controlled so as to be repeatedly executed at a predetermined timing, and the process is repeated again from step S101 after an appropriate time has elapsed. On the other hand, when it is determined that the catalyst device 500 is in the OT state (step S101: YES), the ECU 100 shifts the process to step S102.

  In step S102, the ECU 100 determines whether or not unburned HC or CO for PM regeneration is being supplied to the catalyst device 500 due to, for example, a situation that corresponds to a PM forced regeneration condition (step S102). S102). When unburned HC or CO is supplied to the catalyst device 500 (step S102: YES), the ECU 100 stops the supply of unburned HC or CO (step S103), and shifts the processing to step S104. On the other hand, when unburned gas HC or CO is not supplied to the catalyst device 500 (step S102: NO), the ECU 100 skips step S103 and advances the process to step S104.

  In step S104, the ECU 100 executes an OT avoidance process. The OT avoidance processing refers to a series of processing processes for controlling the operating state of each part of the engine system 10 such as the engine 200, the EGR device 300, and the motor 400 in order to protect the catalyst device 500 from OT.

  In the OT avoidance process, the ECU 100 first drives the motor 400 in the reverse rotation state. At this time, the ECU 100 starts energization of the electromagnetic clutch 402 to connect the clutch plates to each other and controls the electromagnetic clutch 402 to the connected state described above. When the driving force accompanying the reverse rotation of the motor 400 is transmitted from the motor 400 to the EGR compressor 307 via the electromagnetic clutch 402, the EGR compressor 307 enters a reverse rotation state. Accordingly, as already described, gas is discharged from the EGR passage 302 to the exhaust passage 208 by the EGR compressor 307.

  Further, in the OT avoidance process, the ECU 100 further opens the first switching valve 308 and closes the second switching valve 309, thereby selecting the first path described above as the gas discharge path. Further, the ECU 100 opens the intake air switching valve 220 and controls the EGR valve 305 and the diesel throttle valve 221 to be fully opened. As a result, low-temperature intake air that is not used for combustion is introduced from the intake passage 213 to the EGR passage 302 as secondary air, and is supplied to the catalyst device 500 through the first passage 311, the EGR introduction passage 301, and the exhaust passage 208 in order. The As a result, the catalytic device 500 in a relatively high temperature state is actively cooled by the secondary air, and the occurrence of OT is prevented.

  In view of the fact that by rotating the motor 400 in the reverse direction, secondary air is supplied to the catalytic device 500 and the temperature of the catalytic device 500 can be reduced, OT can be avoided. The rotational speed of 400 is not particularly limited. For example, the rotation speed of the motor 400 may be a fixed value set in advance for supplying secondary air, or the temperature state of the catalyst device 500 at that time (can be specified in association with the execution of step S101). ), Etc., and may be a variable value, and the secondary air is supplied quickly enough not to reveal a drop in power performance based on experiments, experience, theory, or simulation. However, it may be set so that power consumption accompanying reverse rotation of the motor 400 can be suppressed as much as possible.

  Here, in the engine system 10, a one-way clutch 403 is provided between the motor shaft 401 and the rotation shaft of the HP-side compressor 217. Therefore, even if the motor 400 is driven in the reverse rotation state in the OT avoidance process, the driving force accompanying the reverse rotation of the motor 400 is not transmitted to the HP side compressor 217. For this reason, when the HP compressor 217 falls into the reverse rotation state, there is no case where the intake air that is supercharged from the intake passage 213 is discharged by the same principle as the supply of the secondary air by the EGR compressor 307. That is, even if the forward gear is selected for power transmission between the motor shaft 401 and the one-way clutch 403 in the gear box described above (that is, in this case, the motor 400 itself is in the reverse rotation state, and the forward gear is Thus, the driving force in the reverse rotation direction is input to the one-way clutch 403 without reversing the rotation direction), and the HP-side compressor 217 does not act in a direction that inhibits at least the supply of secondary air to the catalyst device 500.

  On the other hand, in the OT avoidance process, the transmission gear in the gear box may be switched from the forward gear to the reverse gear 404. In this case, the driving force accompanying the reverse rotation of the motor 400 is transmitted to the one-way clutch 403 as a driving force in the forward rotation direction by the action of the reverse gear 404. For this reason, the driving force is transmitted by the one-way clutch 403, and the HP-side compressor 217 is driven in the normal rotation state by the driving force of the motor 400. That is, in this case, the secondary air is supercharged, and a larger amount of secondary air can be supplied to the catalyst device 500 than when the secondary air is not supercharged. As a result, the cooling of the catalyst device 500 can proceed with higher efficiency.

  Whether or not the reverse gear 404 can be selected may be determined in any way in view of at least the reverse rotation of the HP-side compressor 217 being avoided by the action of the one-way clutch 403. For example, as a preferred embodiment, when the catalyst device 500 is exposed to a higher heat load, the reverse gear 404 is selected, and a sufficient catalyst cooling effect can be obtained only by supplying secondary air by the EGR compressor 307. If the heat load is moderate, the drive energy may be saved without switching the gear from the forward gear to the reverse gear 404. Alternatively, from the viewpoint of ending the cooling of the catalyst device 500 as quickly as possible, the reverse gear 404 may always be selected when the OT avoidance process is performed. In any case, the control of the heat load on the catalyst device 500 is greatly improved by the supply of the secondary air.

  When the OT avoidance process is started in step S104, the ECU 100 determines whether or not the temperature of the catalyst device 500 is less than a reference value (step S105). Here, the reference value according to step S105 may be equal to the reference value according to step S101, but is preferably set to a value lower than the reference value according to step S101. As a preferred embodiment, the reference value is low enough to determine that the catalytic device 500 does not fall into the OT state for a while after the execution of the OT avoidance process, and to a value that ensures sufficient catalytic activity. Is set. The reference value according to step S105 is a value that defines the end condition of the OT avoidance process.

  If the temperature of the catalyst device 500 is equal to or higher than the reference value (step S105: NO), the ECU 100 waits for the process in step S105 and continues the OT avoidance process. On the other hand, when the temperature of the catalyst device 500 is lower than the reference value (step S105: YES), the ECU 100 determines that the occurrence of OT is avoided and ends the OT avoidance control.

  As described above, according to the engine system 10 according to the present embodiment, when the catalyst device 500 is in the OT state by the OT avoidance control, the OT avoidance process is executed and the EGR compressor 307 is rotated in the reverse rotation state. By driving the secondary air having a temperature lower than that of the high-temperature exhaust gas passing through the cylinder to the exhaust passage 208, the catalyst device 500 can be suitably cooled. At this time, by appropriately selecting a reverse gear 404 provided between the motor shaft 401 and the one-way clutch 403, the HP-side compressor 217 can be used as a supercharger for secondary air supercharging. Thus, the catalyst device 500 can be cooled more quickly.

  That is, according to the engine system 10 according to the present embodiment, (1) high boost pressure is realized by two-stage supercharging using the LP side compressor 207 and the HP side compressor 217, and smoke is increased by increasing the amount of fresh air. The EGR amount can be suitably secured by supercharging the EGR gas realized by the EGR compressor 307, and (2) the motor drive type in which the HP compressor 217 is driven by the motor 400. By being configured as a supercharger, it is possible to suppress a decrease in the exhaust gas temperature, promote a temperature rise of the catalyst device 500, and purify the exhaust gas appropriately on the downstream side of the catalyst. (3) The EGR compressor 307 After realizing a simplified system configuration by being uniaxially arranged with the HP side compressor 217, (4) the one-way described above While preventing reverse rotation of the HP side compressor 217 by the action of the latch 403 and reverse gear 404 an appropriate amount of secondary air becomes possible to cool the catalytic converter 500 by feeding to the catalyst device 500. That is, it is possible to maintain the catalyst device at an appropriate temperature state while suppressing the discharge of NOx and smoke.

  The present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the spirit or idea of the invention that can be read from the claims and the entire specification, and an exhaust emission control device with such a change is also included. Moreover, it is included in the technical scope of the present invention.

1 is a schematic configuration diagram conceptually showing a configuration of an engine system according to an embodiment of the present invention. 2 is a flowchart of OT avoidance control executed by an ECU in the engine system of FIG. 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Engine system, 100 ... ECU, 200 ... Engine, 209 ... LP side turbine housing, 210 ... LP side turbine, 211 ... LP side compressor housing, 212 ... LP side compressor, 216 ... HP side compressor housing, 217 ... HP side Compressor, 220 ... intake switching valve, 224 ... intake manifold pressure sensor, 225 ... exhaust manifold pressure sensor, 300 ... EGR device, 301 ... EGR introduction passage, 302 ... EGR passage, 303 ... EGR cooler, 304 ... EGR cooler bypass valve, 305 ... EGR valve, 306 ... EGR compressor housing, 307 ... EGR compressor, 308 ... first switching valve, 309 ... second switching valve, 310 ... EGR compressor outlet pressure sensor, 311 ... first path, 312 ... second path, 400 ... Motor, 4 1 ... motor shaft, 402 ... electromagnetic clutch 403 ... one-way clutch, 404 ... reverse gear, 500 ... catalyzer.

Claims (2)

An exhaust gas purification device for an internal combustion engine comprising a catalyst device in an exhaust system,
The intake system of the internal combustion engine includes a motor-driven supercharger that is rotationally driven by a driving force supplied from a motor and configured to be able to supercharge intake air in a normal rotation state corresponding to one rotation direction of the motor. A plurality of intake superchargers arranged in series with each other;
An EGR passage branching from the exhaust system upstream of the catalyst device and capable of supplying a part of the exhaust gas flowing through the exhaust system as EGR gas to the intake system;
It is rotationally driven by the driving force supplied from the motor, and is uniaxially arranged with the motor drive supercharger in the exhaust system on the upstream side of the EGR passage or the catalyst device, and corresponds to the one rotation direction of the motor. An EGR supercharger capable of supercharging and exhausting the EGR gas in a normal rotation state and a reverse rotation state, respectively,
A shut-off means provided between the motor-driven supercharger and the motor, and capable of interrupting transmission of a driving force that promotes reverse rotation of the motor-driven supercharger from the motor to the motor-driven supercharger;
Discriminating means for discriminating whether or not the catalyst device is in a predetermined OT state;
And a control means for controlling the motor so that the EGR supercharger is in the reverse rotation state when it is determined that the catalyst device is in the OT state. . The said interruption | blocking means contains the conversion means which converts the driving force which encourages reverse rotation of the said motor drive supercharger into the drive force which encourages normal rotation of the said motor drive supercharger. Exhaust purification equipment.

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