JP2006200362A - Exhaust gas purification device for hybrid vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the exhaust gas purification performance by improving the reduction efficiency of a NOx catalyst for occluding unpurified NOx and a reducing agent while preventing flowing out thereof in an exhaust emission purification device in a hybrid vehicle. <P>SOLUTION: The exhaust emission purification device 50 is provided with a first catalyst 51 and a second catalyst 52 capable of being reduced by occluding NOx in the exhaust emission in an exhaust pipe 46, and a fuel addition valve 61 to feed fuel as the reducing agent to each catalyst 51, 52. At EV running by MGs 12, 13 in stopping DE 11 when fuel is injected from the fuel addition valve 61 into an exhaust port 33, while a low pressure EGR valve 59 is opened and a shutter valve 68 is closed, an electrically assisted turbosupercharger is actuated, the NOx and fuel flowed out from the first catalyst 51 and the second catalyst 52 are returned into a suction pipe 37 through an low pressure EGR passage 58, and circulated into the first catalyst 51 and the second catalyst 52. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an exhaust emission control device in which an NOx storage reduction catalyst is provided in an exhaust passage of an internal combustion engine in a hybrid vehicle that can travel using an internal combustion engine and an electric motor as power sources.

  An NOx storage reduction catalyst that stores NOx in the exhaust gas when the exhaust air-fuel ratio is lean, releases the NOx stored when the oxygen concentration in the exhaust gas decreases, and reduces it with the added reducing agent. Is already known. That is, in such an exhaust purification device having a storage reduction type NOx catalyst, when the internal combustion engine is operated at a lean air-fuel ratio, NOx in the exhaust gas is stored by the storage reduction type NOx catalyst, and this storage reduction type When the NOx occlusion amount of the NOx catalyst reaches a predetermined value, the reducing agent is injected into the upstream exhaust passage. Then, the reducing agent is supplied together with the exhaust gas to the NOx storage reduction catalyst, and the NOx stored in the NOx storage reduction catalyst is released by reducing the oxygen concentration in the exhaust gas due to the oxidation reaction, and the released NOx and The reducing agent reacts and reduces, and the exhaust gas is purified.

  By the way, in the NOx storage reduction catalyst described above, the reducing agent is supplied when the NOx storage amount reaches a predetermined value, and the reducing agent reacts with the NOx released as the oxygen concentration in the exhaust gas decreases. To be reduced. In this case, the NOx release rate released from the NOx storage reduction catalyst is not constant, and a relatively large amount of NOx is rapidly released immediately after the reducing agent is supplied and the oxygen concentration is lowered. NOx is released at a relatively low release rate. Therefore, when NOx is released, a relatively large amount of NOx is released from the NOx storage reduction catalyst, but most of the NOx reacts with the reducing agent and is reduced, but a part of the NOx remains appropriately due to the remaining oxygen. It is not reduced, but exudes from the NOx storage reduction catalyst as unpurified NOx, and the NOx purification rate decreases.

  The NOx storage reduction catalyst has a temperature range in which the released NOx can be effectively reduced, and the NOx storage reduction catalyst is heated to the activation temperature in advance. However, when a reducing agent is supplied to the NOx storage reduction catalyst, NOx stored by the oxidation reaction is released, and the NOx storage reduction catalyst is heated to a temperature higher than the activation temperature, effectively reducing NOx. It deviates from the temperature range that can be reduced. Then, the NOx storage reduction catalyst cannot reliably reduce the released NOx by the reducing agent, and part of the NOx is discharged from the storage reduction NOx catalyst as unpurified NOx, resulting in a decrease in the NOx purification rate. End up.

  As what solves such a problem, there exists a thing described in the following patent document 1, for example. The exhaust purification device for an internal combustion engine described in Patent Document 1 below has a storage reduction type NOx catalyst disposed in the exhaust passage of the internal combustion engine, stores NOx in the exhaust gas during lean air-fuel ratio operation, and has a storage amount of When the judgment value is reached, the reducing agent is injected into the exhaust passage to release and reduce NOx from the NOx storage reduction catalyst, and this judgment value is obtained from the NOx storage reduction catalyst immediately after the supply of the reducing agent. The amount of unpurified NOx released due to the discharge of NOx or the amount of purified NOx released due to exudation during NOx occlusion is set to a predetermined low value.

JP 2000-240428 A

  In the above-described exhaust purification device of Patent Document 1, when the NOx storage reduction catalyst is reduced, the determination value is determined based on the amount of unpurified NOx released by discharging from the NOx storage reduction catalyst and the purified NOx release by seepage during NOx storage. The amount is set in consideration of the amount, and the NOx purification rate can be improved by suppressing the discharge amount of the unpurified NOx due to the discharge and the seepage due to the increase in the NOx occlusion amount to a low value. In this case, the relationship between the NOx occlusion amount of the NOx storage reduction catalyst, the amount of unpurified NOx released due to discharge, and the amount of purified NOx released due to exudation during NOx occlusion is obtained by a prior experiment. The maximum value of the NOx occlusion amount at which the purification NOx release amount becomes a predetermined value or less is obtained, and this is used as the determination value. However, in such an exhaust purification device, high-precision control is required for the NOx reduction treatment, resulting in an increase in cost. Even with this method, it is not possible to completely eliminate the amount of unpurified NOx released due to discharge or seepage.

  Further, the above-described exhaust purification device reacts by contacting with the noble metal supported on the surface when the reducing agent passes through the space of the NOx storage reduction catalyst when the storage capacity is reduced, and the stored NOx. Therefore, when the reducing agent and the NOx storage reduction catalyst come into efficient contact with each other, the NOx reduction efficiency, that is, the exhaust gas purification efficiency is improved. However, when the exhaust gas to which the reducing agent is added flows into the NOx storage reduction catalyst, a part of the reducing agent does not react with the NOx storage reduction catalyst due to the flow rate, and is exhausted to the outside.

  The present invention is intended to solve such problems, and has attempted to improve exhaust purification efficiency by improving the reduction efficiency of the stored NOx catalyst by preventing the outflow of unpurified NOx and reducing agent. An object of the present invention is to provide an exhaust emission control device for a hybrid vehicle.

  In order to solve the above-described problems and achieve the object, an exhaust emission control device for a hybrid vehicle according to the present invention is provided in an exhaust passage of the internal combustion engine in a hybrid vehicle that can run using an internal combustion engine and an electric motor as power sources. A NOx storage reduction catalyst that can store and reduce NOx in the exhaust gas, a reducing agent supply means that supplies a reducing agent to the NOx storage reduction catalyst, and the reducing agent when the vehicle is driven by the electric motor. When the reducing agent is supplied from the supply means to the NOx storage reduction catalyst, the NOx flowing out of the NOx storage reduction catalyst and the reducing agent that has passed through the NOx storage reduction catalyst are returned to the NOx storage reduction catalyst. It is characterized by comprising means.

  Therefore, when the traveling by the internal combustion engine is switched to the traveling by the electric motor, when the reducing agent is supplied from the reducing agent supply means to the NOx storage reduction catalyst, the reducing agent reacts with the NOx storage reduction catalyst. NOx is reduced and some unpurified NOx and reducing agent flow out of the NOx storage reduction catalyst. However, when the internal combustion engine is stopped, NOx or NOx storage outflowed from the NOx storage reduction catalyst by the circulation means. Since the reducing agent slipped from the NOx catalyst is returned to the NOx storage reduction catalyst, the unpurified NOx that has flowed out is purified again by the NOx storage reduction catalyst by the slipping reducing agent, so the NOx storage reduction catalyst There is no need to provide an auxiliary catalyst on the downstream side, and as a result, the reduction efficiency of the stored NOx catalyst can be improved and the exhaust purification efficiency can be improved.

  In the exhaust emission control device for a hybrid vehicle of the present invention, the circulation means includes an intake passage and an electrically assisted turbocharger provided in the exhaust passage, the exhaust passage downstream of the NOx storage reduction catalyst, and the electric drive. An exhaust gas recirculation passage connecting the intake passage upstream of the assist turbocharger, an exhaust gas recirculation valve provided in the exhaust gas recirculation passage, and the NOx storage reduction catalyst in the exhaust passage A shutter valve provided on the downstream side of the engine, and the exhaust gas recirculation passage is opened by the exhaust gas recirculation valve, and the exhaust assist passage is closed by the shutter valve. By driving the feeder, NOx and the reducing agent are returned to the NOx storage reduction catalyst.

  Therefore, when the traveling by the internal combustion engine is switched to the traveling by the electric motor, the shutter valve is closed and the electric assist turbocharger is driven, so that the NOx flowing out of the NOx storage reduction catalyst or the NOx storage reduction type is driven. The exhaust gas containing the reducing agent that has passed through the NOx catalyst is returned to the intake passage through the exhaust gas recirculation passage, and the exhaust gas is repeatedly purified by the NOx storage reduction catalyst, so that the stored NOx catalyst is reduced. Efficiency can be improved and exhaust purification efficiency can be improved.

  In the exhaust gas purification apparatus for a hybrid vehicle of the present invention, the circulation means includes a circulation passage that connects an upstream exhaust passage and a downstream exhaust passage of the NOx storage reduction catalyst, and an electric motor provided in the circulation passage. A switching valve that shuts off an upstream exhaust passage and a downstream exhaust passage of the NOx storage reduction catalyst and communicates the NOx storage reduction catalyst with the circulation passage; and The NOx and the reducing agent are returned to the NOx storage reduction catalyst by driving the electric pump with the exhaust passage blocked and the circulation passage communicated.

  Accordingly, when the traveling by the internal combustion engine is switched to the traveling by the electric motor, the switching valve shuts off the upstream exhaust passage and the downstream exhaust passage of the NOx storage reduction catalyst and also stores the NOx storage reduction catalyst and the circulation passage. The exhaust gas containing NOx flowing out from the NOx storage reduction catalyst and the reducing agent slipped through the NOx storage reduction catalyst is returned to the NOx storage reduction catalyst through the circulation passage. Thus, the purification process is repeated, and the reduction efficiency of the stored NOx catalyst can be improved to improve the exhaust purification efficiency.

  In the exhaust emission control device for a hybrid vehicle according to the present invention, when the reducing agent is supplied from the reducing agent supply means to the NOx storage reduction catalyst while the electric motor is running on the vehicle, the reducing agent is stored in the NOx storage reduction catalyst. The passage time estimation means for estimating the passage time is provided, and at the passage time of the reducing agent estimated by the passage time estimation means, the electric assist turbocharger or the electric pump is set at a predetermined low rotational speed set in advance. On the other hand, the electric assist turbocharger or the electric pump is driven at a predetermined high rotation speed at a time other than the passage time.

  Accordingly, when the reducing agent passes through the NOx storage reduction catalyst, the space velocity at that time is reduced by driving the electric assist turbocharger or the electric pump at a low speed, and the reducing agent stores the NOx catalyst. The NOx released from the reduced NOx catalyst can be efficiently reduced. On the other hand, when the reducing agent passes through other than the NOx storage reduction catalyst, the electric assist turbocharger or the electric pump is operated at a high speed. By driving, the reducing agent can be transferred to the NOx storage reduction catalyst at an early stage, the reduction efficiency of the stored NOx catalyst can be improved, and the exhaust purification efficiency can be improved.

  According to the exhaust emission control device for a hybrid vehicle of the present invention, the unpurified NOx and the reducing agent that have flowed out of the NOx storage reduction catalyst when the internal combustion engine is stopped and the electric motor is running can be traveled by the internal combustion engine or the electric motor. Since it is returned to the NOx storage reduction catalyst by the circulation means, the flow of unpurified NOx and the reducing agent can be surely prevented without providing an auxiliary catalyst downstream of the NOx storage reduction catalyst. The exhaust gas purification efficiency can be improved by improving the reduction efficiency of the NOx catalyst.

  Hereinafter, an embodiment of an exhaust emission control device in a hybrid vehicle according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

  FIG. 1 is a schematic configuration diagram of an exhaust purification device in a hybrid vehicle according to a first embodiment of the present invention, FIG. 2 is a flowchart showing a NOx reduction process by the exhaust purification device in the hybrid vehicle of the first embodiment, and FIG. It is a schematic block diagram showing the hybrid vehicle to which the exhaust emission control device of Example 1 is applied.

  The vehicle on which the exhaust emission control device according to the first embodiment is mounted is a hybrid vehicle having a power train that uses a combination of two types of power sources, that is, an internal combustion engine and an electric motor. First, a description will be given of a hybrid vehicle equipped with the exhaust purification device of the first embodiment.

  In the hybrid vehicle of the first embodiment, as shown in FIG. 3, the vehicle is equipped with a diesel engine (DE) 11 as an internal combustion engine and a motor generator (MG) 12 as an electric motor as power sources. The vehicle is also equipped with a motor generator (MG) 13 that receives the output of the DE 11 and generates electric power. These DE11, MG12, and MG13 are connected by a power split mechanism 14. The power split mechanism 14 distributes the output of the DE 11 to the MG 13 and the drive wheel 15 and transmits the output from the MG 12 to the drive wheel 15 or to the drive wheel 15 via the speed reducer 16 and the drive shaft 17. It functions as a transmission related to the driving force.

  MG12 is an AC synchronous motor and is driven by AC power. The inverter 18 converts the electric power stored in the battery 19 from DC to AC and supplies it to the MG 12, and converts the electric power generated by the MG 13 from AC to DC and stores it in the battery 19. The MG 13 has basically the same configuration as the MG 12 described above, and has a configuration as an AC synchronous motor. In this case, the MG 12 mainly outputs the driving force, whereas the MG 13 mainly receives the output of the DE 11 and generates power.

  The MG 12 mainly generates a driving force, but can also generate electric power (regenerative power generation) by using the rotation of the driving wheels 15 and can also function as a generator. At this time, a brake (regenerative brake) acts on the drive wheel 15, and the vehicle can be braked by using this together with the foot brake or the engine brake. On the other hand, the MG 13 mainly receives the output of the DE 11 and generates power, but can also function as an electric motor that receives and drives the power of the battery 19 via the inverter 18.

  The crankshaft 20 of DE11 is provided with a crank position sensor 21 that detects the piston position and the engine speed. The crank position sensor 21 is connected to the engine ECU 22 and outputs a detection result. The drive shafts 23 and 24 of the MG 12 and MG 13 are provided with rotation speed sensors 25 and 26 for detecting the respective rotation positions and rotation speeds. Each rotation speed sensor 25, 26 is connected to a motor ECU 27 and outputs a detection result.

  The power split mechanism 14 described above is constituted by a planetary gear unit. That is, the power split mechanism (planetary gear unit) 14 includes a sun gear, a planetary gear arranged around the sun gear, a ring gear arranged on the outer periphery of the planetary gear, and a gear carrier holding the planetary gear, although not shown. It is composed of The crankshaft 20 of the DE 11 is coupled to the gear carrier via the central axis, and the output of the DE 11 is input to the gear carrier of the planetary gear unit 14. The MG 12 has a stator and a rotor inside, and the rotor is coupled to the ring gear, and the rotor and the ring gear are coupled to the speed reducer 16. The speed reducer 16 transmits the output input from the MG 12 to the ring gear of the planetary gear unit 14 to the drive shaft 17, and the MG 12 is always connected to the drive shaft 17.

  Similarly to MG12, MG13 has a stator and a rotor inside, and this rotor is coupled to the sun gear. That is, the output of the DE 11 is divided by the planetary gear unit 14 and input to the rotor of the MG 13 via the sun gear. The output of the DE 11 is divided by the planetary gear unit 14 and can be transmitted to the drive shaft 17 via a ring gear or the like.

  The entire planetary gear unit 14 can be used as a non-transmission transmission by controlling the amount of power generated by the MG 13 to control the rotation of the sun gear. That is, the output of DE 11 or MG 12 is output to the drive shaft 17 after being shifted by the planetary gear unit 14. Further, the rotational speed of the DE 11 can be controlled by controlling the power generation amount of the MG 13 (power consumption when it functions as a motor). Note that when the rotational speeds of the MG12 and MG13 are controlled, the motor ECU 27 controls the inverter 18 with reference to the outputs of the rotational sensors 25 and 26, whereby the rotational speed of the DE11 can also be controlled. is there.

  The various controls described above are controlled by a plurality of electronic control units (ECUs). The driving by DE11 and the driving by MG12 and MG13, which are characteristic as a hybrid vehicle, are comprehensively controlled by the main ECU. That is, the distribution of the output of DE 11 and the output of MG 12 and MG 13 is determined by main ECU 28, and control commands are output to engine ECU 22 and motor ECU 27 to control DE 11, MG 12, and MG 13.

  Further, the engine ECU 22 and the motor ECU 27 also output information on the DE 11, MG 12, and MG 13 to the main ECU 28. The main ECU 28 is also connected to a battery ECU 29 that controls the battery 19 and a brake ECU 30 that controls the brake. The battery ECU 29 monitors the state of charge of the battery 19 and outputs a charge request command to the main ECU 28 when the amount of charge is insufficient. Receiving the charge request, the main ECU 28 controls the MG 13 to generate power so that the battery 19 is charged. The brake ECU 30 controls the vehicle and controls the regenerative braking by the MG 12 together with the main ECU 28.

  Since the hybrid vehicle of the present embodiment is configured as described above, by distributing the necessary output required for the entire vehicle to DE11 and MG12 (MG13) while operating the hybrid vehicle, DE11 It is possible to satisfy the output required for the entire vehicle while controlling the driving state to a desired driving state.

  Next, the exhaust emission control device for the hybrid vehicle of the first embodiment will be described. In the exhaust gas purification apparatus for a hybrid vehicle according to the first embodiment, as shown in FIG. 1, a diesel engine (DE) 11 as an internal combustion engine is not shown, but a cylinder head is fastened on a cylinder block, and a plurality of cylinder bores are connected. The pistons are respectively fitted to be freely movable up and down. A crankcase is fastened to the lower part of the cylinder block, a crankshaft is rotatably supported in the crankcase, and each piston is connected to the crankshaft via a connecting rod.

  A plurality of combustion chambers 31 are constituted by a cylinder block, a cylinder head, and pistons, and the combustion chamber 31 is formed with an intake port 32 and an exhaust port 33 facing each other at the upper portion. The lower end portions of the intake valve 34 and the exhaust valve 35 are positioned with respect to 33. The intake valve 34 and the exhaust valve 35 are supported by the cylinder head so as to be movable along the axial direction, and are urged and supported in a direction to close the intake port 32 and the exhaust port 33. An intake cam shaft and an exhaust cam shaft are rotatably supported by the cylinder head, and the intake cam and the exhaust cam are in contact with upper end portions of the intake valve 32 and the exhaust valve 33 via a roller rocker arm.

  Therefore, when the intake camshaft and the exhaust camshaft rotate in synchronization with DE11, the intake cam and the exhaust cam operate the roller rocker arm, and the intake valve 34 and the exhaust valve 35 move up and down at a predetermined timing. 32 and the exhaust port 33 can be opened and closed to allow the intake port 32 and the combustion chamber 31 to communicate with the combustion chamber 31 and the exhaust port 33, respectively.

  An intake pipe (intake passage) 37 is connected to the intake port 32 via an intake manifold 36, and an air cleaner 38 is attached to an air intake port of the intake pipe 37. A throttle valve 39 is provided on the downstream side of the air cleaner 38. Each cylinder head is provided with an injector 41 capable of injecting light oil as fuel into each combustion chamber 31 at a high pressure. Each injector 41 is connected to a fuel pump 44 via a delivery pipe 42 and a fuel supply pipe 43, and the fuel pump 44 is driven by the DE 11. On the other hand, an exhaust pipe (exhaust passage) 46 is connected to the exhaust port 33 via an exhaust manifold 45.

  The intake pipe 37 and the exhaust pipe 46 are provided with an electric assist turbocharger (MAT) 47. In the electric assist turbocharger 47, a compressor 47a provided in an intake pipe 37 and a turbine 47b provided in an exhaust pipe 46 are integrally connected by a drive shaft 47c, and are forcibly driven by a drive motor 48. can do. An intercooler 49 is provided in the intake pipe 37 on the downstream side of the compressor 47a in the electric assist turbocharger 47 to cool the intake air that has been supercharged by the compressor 47a and whose temperature has risen.

  The exhaust pipe 46 is provided with an exhaust purification device 50 that purifies harmful substances contained in the exhaust gas. In the exhaust purification device 50, a first catalyst 51 and a second catalyst 52 are arranged in series. Has been configured. The first catalyst 51 is a NOx storage reduction catalyst that stores NOx in the exhaust gas when the exhaust air-fuel ratio is lean, and releases the stored NOx when the oxygen concentration in the exhaust gas decreases, The fuel is reduced by the added fuel (reducing oil in this embodiment) as a reducing agent. The second catalyst 52 is a NOx storage reduction catalyst having a particulate filter, which collects particulates (PM: particulates) in exhaust gas, particularly black smoke, and when the exhaust air-fuel ratio is lean. The NOx in the exhaust gas is occluded, and the occluded NOx is released when the oxygen concentration in the exhaust gas decreases, and is reduced by the added fuel.

  The DE 11 is provided with a high-pressure exhaust gas recirculation (EGR) device 53 that returns high-pressure exhaust gas to the intake system, and a low-pressure exhaust gas recirculation (EGR) device 54 that returns low-pressure exhaust gas to the intake system. The high-pressure EGR device 53 connects the exhaust manifold 45 and the intake pipe 37 immediately before the intake manifold 36 to recirculate a part of the high-pressure exhaust gas to the intake system, and the high-pressure EGR passage 55 The high pressure EGR valve 56 is provided, and the EGR cooler 57 is provided in the high pressure EGR passage 55 and cools the high pressure exhaust gas. The low pressure EGR device 54 connects the exhaust pipe 46 on the downstream side of the exhaust purification device 51 and the intake pipe 37 on the upstream side of the compressor 47a in the electrically assisted turbocharger 47 on the downstream side of the throttle valve 39, thereby reducing the low pressure exhaust gas. A low pressure EGR passage 58 for recirculating a part of the gas to the intake system, a low pressure EGR valve 59 provided in the low pressure EGR passage 58, and an EGR cooler 60 provided in the low pressure EGR passage 58 for cooling the low pressure exhaust gas. It consists of and.

  Further, the first catalyst 51 and the second catalyst 52 release the stored NOx when the oxygen concentration in the exhaust gas is reduced, and the released NOx is reduced by the fuel. A fuel addition valve 61 for injecting fuel (reducing agent) is provided in the cylinder head. The fuel addition valve 61 is connected to the fuel pump 44 via a fuel supply pipe 62, and an open / close valve 63 is provided in the fuel supply pipe 62.

  By the way, the engine ECU 22 can control various devices of the DE 11. In other words, the crank angle detected by the crank position sensor 21 is input to the engine ECU 22, and the engine ECU 22 determines each stroke of intake, compression, expansion (explosion), and exhaust in each cylinder based on the crank angle. In addition, the engine speed is calculated. Further, the accelerator opening detected by the accelerator position sensor 64 is inputted to the engine ECU 22, and the engine ECU 22 determines the fuel injection amount based on the accelerator opening and the engine speed. The engine ECU 22 controls the fuel pump 44 to maintain the fuel pressure in the delivery pipe 42 at a predetermined value, and controls the injector 41 to inject a predetermined amount of fuel into the combustion chamber 31 at a predetermined injection timing. can do.

  Further, the engine ECU 22 controls the drive of the electrically assisted turbocharger 47 based on the accelerator opening so that the output of the DE 11 can be adjusted. Further, the engine ECU 22 drives and controls the high pressure EGR device 53 and the low pressure EGR device 54 in accordance with the engine operating state. That is, by opening and closing the EGR valves 56 and 59 in a predetermined operation state, high-pressure exhaust gas or low-pressure exhaust gas is circulated as EGR gas to the intake system through the EGR passages 55 and 58, and the combustion temperature is lowered. Suppresses the generation of NOx.

  Furthermore, the engine ECU 22 regenerates the first catalyst 51 and the second catalyst 52 that constitute the exhaust purification device 50 at a predetermined time. That is, a first temperature sensor 65 that measures the temperature of the exhaust gas is provided on the downstream side of the first catalyst 51, and a second temperature sensor that measures the temperature of the exhaust gas on the downstream side of the second catalyst 52. 66 is provided. Further, a differential pressure sensor 67 that detects a differential pressure between the pressure of the exhaust gas flowing into the exhaust purification device 50 and the pressure of the exhaust gas discharged from the exhaust purification device 50 is provided.

  Accordingly, when the DE 11 is operated at a lean air-fuel ratio, the first catalyst 51 and the second catalyst 52 occlude NOx in the exhaust gas. When the NOx occlusion amounts of the first catalyst 51 and the second catalyst 52 reach a predetermined value, the engine ECU 22 controls the fuel addition valve 61 and injects a predetermined amount of fuel into the exhaust port 33 as a reducing agent. Then, when fuel is supplied to the first catalyst 51 and the second catalyst 52 through the exhaust pipe 46, the oxygen concentration in the exhaust gas is reduced by the oxidation reaction, so that the NOx stored in each of the catalysts 51 and 52 is released. The released NOx and the fuel react to be reduced, and the exhaust gas is purified, whereby the first catalyst 51 and the second catalyst 52 are regenerated.

  In this case, the first catalyst 51 and the second catalyst 52 release the stored NOx, and an active temperature range is set in which the NOx can be reduced by the fuel. When each of the catalysts 51 and 52 is in this active temperature region The engine ECU 22 performs regeneration control. That is, when the exhaust gas temperature detected by the first temperature sensor 65 is in this activation temperature region, the engine ECU 22 injects a predetermined amount of fuel by the fuel addition valve 61 and regenerates the first catalyst 51 and the second catalyst 52. Execute control. On the other hand, when the exhaust gas temperature detected by the first temperature sensor 65 is not in the activation temperature region, the engine ECU 22 performs temperature increase control of the first catalyst 51 and the second catalyst 52. In this temperature rise control, for example, fuel is injected for raising the catalyst temperature by the fuel addition valve 61, and the exhaust gas temperature is raised by the oxidation reaction in each catalyst 51, 52 to raise the temperature of each catalyst 51, 52. The first catalyst 51 and the second catalyst 52 have a deterioration temperature at which the catalyst function deteriorates, and the engine ECU 22 determines whether the exhaust gas temperature detected by the second temperature sensor 66 does not exceed the deterioration temperature. Is monitoring. Further, the NOx occlusion amount occluded in the first catalyst 51 and the second catalyst 52 is estimated from the continued engine operating state.

  On the other hand, when the DE 11 is operated at a lean air-fuel ratio, the second catalyst 52 collects PM in the exhaust gas. When the PM collection amount of the second catalyst 52 reaches a predetermined value, the engine ECU 22 controls the fuel addition valve 61 to inject a predetermined amount of fuel into the exhaust port 33. Then, when fuel is supplied to the first catalyst 51 and the second catalyst 52 through the exhaust pipe 46, the catalyst temperature rises due to the oxidation reaction, so that the PM collected in the second catalyst 52 is burned and regenerated. Is done. In this case, when the exhaust gas pressure difference detected by the differential pressure sensor 67 exceeds a predetermined value, the engine ECU 22 generates a pressure loss in the second catalyst 52 and the PM trapping amount is saturated. The fuel addition valve 61 injects a predetermined amount of fuel and executes the regeneration control of the second catalyst 52.

  The fuel contains a sulfur (S) component, and this S component reacts with oxygen to become sulfur oxide (SOx), and this SOx is replaced with NOx instead of NOx in the first catalyst 51 and the second catalyst 52. Occluded. Therefore, when the PM collected by the second catalyst 52 is burned and regeneration control is executed, the engine ECU 22 adjusts the amount of fuel injected by the fuel addition valve 61 and is stored in the first catalyst 51 and the second catalyst 52. Reproduce after removing the SOx.

  By the way, in the 1st catalyst 51 and the 2nd catalyst 52 which have the function to occlude and reduce NOx, since a relatively large amount of NOx is suddenly released when fuel is supplied and regenerated, a part of NOx is residual oxygen. As a result, the first catalyst 51 and the second catalyst 52 ooze out as unpurified NOx without being properly reduced. Further, when the fuel flows into the first catalyst 51 and the second catalyst 52 together with the exhaust gas, a part of the fuel slips through without reacting with the first catalyst 51 and the second catalyst 52 due to the flow velocity.

  Therefore, in the exhaust emission control device in the hybrid vehicle of the first embodiment, when a predetermined amount of fuel is injected as a reducing agent from the fuel addition valve 61 to the exhaust port 33 during EV traveling consisting of MG12 and MG13, the first catalyst 51 and NOx and fuel flowing out from the second catalyst 52 are returned to the first catalyst 51 and the second catalyst 52 (circulation means). In this case, in this embodiment, the electric assist turbocharger 47 and the low pressure EGR device 54 are applied as the circulation means, and the exhaust pipe 46 on the downstream side of the first catalyst 51, the second catalyst 52, and the low pressure EGR device 54. Is provided with a shutter valve 68.

  Accordingly, when the DE 11 is stopped and the hybrid vehicle is driven only by the MG 12 and MG 13, a predetermined amount of fuel is injected from the fuel addition valve 61, while the low pressure EGR valve 59 of the low pressure EGR device 54 is opened and the shutter valve 68 is opened. In this state, by driving the electrically assisted turbocharger 47, the exhaust gas containing NOx and fuel flowing out from the first catalyst 51 and the second catalyst 52 passes through the low pressure EGR passage 58 to the intake pipe 37. return. As a result, the NOx flowing out from each of the catalysts 51 and 52 and the NOx flowing out are reliably purified by the fuel in the first catalyst 51 and the second catalyst 52 while preventing the fuel from flowing out to the outside.

  When the hybrid vehicle is driven only by MG12 and MG13 with DE11 stopped, when exhaust gas is returned from the exhaust system to the intake system and returned to the respective catalysts 51 and 52 through the combustion chamber 31, any cylinder in DE11 is It is desirable to stop the DE 11 at a position where an overlap period in which the latter half of the exhaust stroke and the first half of the intake stroke overlap each other for a predetermined period. In this case, the engine ECU 22 determines the strokes of intake, compression, expansion (explosion), and exhaust in each cylinder based on the crank angle detected by the crank angle sensor 21, and based on this detection signal, the cylinder overrun It is only necessary to grasp the lap period and stop fuel injection at a predetermined time.

  Here, the control of the NOx reduction process by the exhaust emission control device in the hybrid vehicle of the first embodiment will be described in detail based on the flowchart of FIG.

  In the control of the NOx reduction process by the exhaust purification device in the hybrid vehicle of the first embodiment, as shown in FIG. 2, it is determined in step S11 whether the start condition of the NOx reduction processing in the exhaust purification device 50 is satisfied. In this case, the engine ECU 22 detects the NOx occlusion amount of each of the catalysts 51 and 52 in the exhaust emission control device 50 based on the engine operating state after the DE 11 starts operation. By determining whether or not the determination value set based on the NOx saturation amounts 51 and 52 has been exceeded, it is determined whether or not the start condition for the NOx reduction process of the exhaust purification device 50 is satisfied. If the current NOx occlusion amount exceeds the determination value in step S11, it is determined that the NOx reduction processing of the exhaust purification device 50 should not be started yet, and this routine is exited without doing anything.

  In step S11, if the current NOx occlusion amount exceeds the determination value, the NOx reduction process of the exhaust purification device 50 should be started and the process proceeds to step S12. In this step S12, it is determined whether or not the EV traveling condition by the hybrid vehicle only by MG11 and MG12 is satisfied. Here, if the EV traveling condition is not satisfied, the process proceeds to step S13, where NOx reduction processing control in engine traveling is executed.

  On the other hand, if the EV traveling condition of the hybrid vehicle is satisfied in step S12, the NOx reduction process control is executed in the EV traveling in which DE11 is stopped after step S14. In step S14, it is determined whether the exhaust gas temperature T detected by the first temperature sensor 65 is higher than the catalyst activation temperature Tg. If the exhaust gas temperature T is equal to or lower than the catalyst activation temperature Tg, the catalyst is detected in step S15. Execute temperature rise control. That is, a predetermined amount of fuel is injected by the fuel addition valve 61, and the exhaust gas temperature is raised by the oxidation reaction in the first catalyst 51 and the second catalyst 52 to raise the temperature of each catalyst 51, 52.

  Then, when the temperature of the first catalyst 51 and the second catalyst 52 is raised and it is determined in step S14 that the exhaust gas temperature T is higher than the catalyst activation temperature Tg, in step S16, first, the catalyst is added by the fuel addition valve 61. An amount of fuel that can reduce the NOx occluded by 51 and 52 is injected. Next, in step S17, after stopping DE11 by stopping fuel injection from each injector 41 in DE11, in step S18, the low pressure EGR valve 59 in the low pressure EGR device 54 is opened, while the throttle valve 39 and Shutter valve 68 is closed, and EV travel is started in step S19.

  Subsequently, in step S20, the electrically assisted turbocharger 47 is driven. In step S21, the reduction process timer starts counting up, and in step S22, the fuel addition valve 61 injects into the exhaust port 33. The arrival position of the spent fuel is estimated. In this case, the engine ECU (passage timing estimation means) 22 estimates the flow rate of the injected fuel based on the passage volume and length of the intake system and exhaust system, the driving force of the electric assist turbocharger 47, etc. The time of passing through the device 50 is estimated. Therefore, in step S23, when the fuel arrival position (passage time) is not in the exhaust purification device 50, in step S24, the electric assist turbocharger 47 is driven at a high speed, while the fuel arrival position (passage time). Is in the vicinity of the exhaust emission control device 50, the electric assist turbocharger 47 is driven at a low speed in step S25.

  When the DE 11 is operated at a lean air-fuel ratio, the first catalyst 51 and the second catalyst 52 occlude NOx in the exhaust gas. When the NOx occlusion amounts of the first catalyst 51 and the second catalyst 52 reach a predetermined value, a predetermined amount of fuel is injected into the exhaust port 33 by the fuel addition valve 61 with the DE 11 stopped. Then, the fuel is supplied to the first catalyst 51 and the second catalyst 52 through the exhaust pipe 46, and the NOx occluded in each of the catalysts 51 and 52 is released by the reduction of the oxygen concentration in the exhaust gas due to the oxidation reaction. The NOx and fuel that have been reacted react and reduce, and the exhaust gas is purified.

  In this case, a small amount of NOx and fuel flow out from the first catalyst 51 and the second catalyst 52, but this outflowed NOx and fuel is because the downstream end of the exhaust pipe 46 is closed by the shutter valve 68. It is not discharged to the outside, but is returned to the intake pipe 37 by the low pressure EGR passage 58 by the driving force of the electric assist turbocharger 47, and circulates through the intake system and the exhaust system for a predetermined time. At this time, as described above, when the position where the fuel injected by the fuel addition valve 61 does not reach the exhaust purification device 50, the electric assist turbocharger 47 is driven at a high speed and is in the vicinity of the exhaust purification device 50. Sometimes, the electrically assisted turbocharger 47 is driven at a low speed, so that the space velocity at which the fuel moves through the exhaust purification device 50 is reduced, and the NOx reduction processing time can be lengthened to improve the processing efficiency. Therefore, the NOx stored in the first catalyst 51 and the second catalyst 52 is reliably purified using the fuel while preventing the NOx and fuel flowing out from the first catalyst 51 and the second catalyst 52 from being discharged to the outside.

  In step S26, it is determined whether the count time of the reduction process timer has passed a preset process time. If the count time of the reduction process timer has passed this process time, in step S27, the electric assist is performed. The turbocharger 47 is stopped, the low pressure EGR valve 59 is closed in step S28, and the throttle valve 39 and the shutter valve 68 are opened. In step S29, the count of the reduction process timer is cleared. The processing time described in step S26 is a time during which the first catalyst 51 and the second catalyst 52 that have become saturated due to occlusion of NOx can be completely regenerated with fuel, and is obtained in advance through experiments or the like.

  As described above, in the exhaust purification device for the hybrid vehicle of the first embodiment, the exhaust purification device 50 including the first catalyst 51 and the second catalyst 52 that can store and reduce NOx in the exhaust gas in the exhaust pipe 46 is provided. In addition, a fuel addition valve 61 for supplying fuel as a reducing agent to each of the catalysts 51 and 52 is provided, and a predetermined amount of fuel is supplied from the fuel addition valve 61 to the exhaust port 33 during EV traveling by the MG 12 and MG 13 that have stopped the DE 11. When injected, the low-pressure EGR valve 59 in the low-pressure EGR device was opened and the shutter valve 68 was closed, and the electric assist turbocharger was driven to flow out of the first catalyst 51 and the second catalyst 52. NOx and fuel are returned to the intake pipe 37 through the low pressure EGR passage 58 and are circulated through the first catalyst 51 and the second catalyst 52.

  Accordingly, when the DE 11 is stopped and a predetermined amount of fuel is injected from the fuel addition valve 61 when the hybrid vehicle is driven only by the MG 12 and MG 13, NOx is released from the respective catalysts 51 and 52 due to a decrease in the oxygen concentration. The released NOx reacts with the fuel and is reduced. At this time, a part of the unpurified NOx and the reducing agent flows out from the catalysts 51 and 52. The exhausted NOx and the exhaust gas containing the fuel are Then, the electric assist turbocharger 47 returns to the intake pipe 37 through the low pressure EGR passage 58 and returns to the catalysts 51 and 52 again. As a result, the unpurified NOx and fuel that have flowed out of the catalysts 51 and 52 are not discharged to the outside, and the catalyst 51 and 52 are again purified by the fuel that has passed through the unpurified NOx that has flowed out. Further, an auxiliary catalyst for treating the unpurified NOx and the fuel that has passed through is not required on the downstream side of the catalysts 51 and 52, and the reduction efficiency of the stored NOx catalyst can be improved and the exhaust purification efficiency can be improved.

  Further, after the fuel is injected, the low pressure EGR valve 59 is opened and the shutter valve 68 is closed, and the electric assist turbocharger is driven to reduce the NOx and fuel flowing out from the first catalyst 51 and the second catalyst 52 to a low pressure. When returning to the intake pipe 37 through the EGR passage 58 and circulating again to the first catalyst 51 and the second catalyst 52, the engine ECU 22 estimates the arrival position of the injected fuel, and the arrival position of the fuel reaches the exhaust purification device 50. When not, the electric assist turbocharger 47 is driven at a high speed, while when the fuel arrival position is in the vicinity of the exhaust purification device 50, the electric assist turbocharger 47 is driven at a low speed.

  Accordingly, the space velocity at which the fuel moves through the exhaust purification device 50 is reduced, the NOx reduction treatment time in the catalysts 51 and 52 is lengthened, and the treatment efficiency can be improved. As a result, the first catalyst 51 and the second catalyst 51 The NOx occluded in the first catalyst 51 and the second catalyst 52 can be reliably purified using this fuel while preventing the NOx and fuel flowing out from the catalyst 52 from flowing out.

  FIG. 4 is a schematic configuration diagram of an exhaust emission control device in a hybrid vehicle according to Embodiment 2 of the present invention. In addition, the same code | symbol is attached | subjected to the member which has the same function as what was demonstrated in the Example mentioned above, and the overlapping description is abbreviate | omitted.

  In the exhaust emission control device in the hybrid vehicle of the second embodiment, as shown in FIG. 4, the exhaust pipe 46 is provided with an exhaust emission control device 50 including a first catalyst 51 and a second catalyst 52, and the first catalyst. 51 is an NOx storage reduction catalyst, and the second catalyst 52 is an NOx storage reduction catalyst having a particulate filter. A fuel addition valve 61 for injecting fuel (reducing agent) into the exhaust port 33 is provided in the cylinder head. When the NOx occlusion amounts of the first catalyst 51 and the second catalyst 52 become saturated, this fuel is supplied. By injecting fuel with the addition valve 61, the oxygen concentration in the exhaust gas is reduced to release the stored NOx, and the released NOx is reduced by the fuel.

  Further, in the exhaust emission control device in the hybrid vehicle of the second embodiment, when the predetermined amount of fuel is injected as the reducing agent from the fuel addition valve 61 to the exhaust port 33 during EV traveling consisting of MG12 and MG13, the first catalyst 51 and NOx and fuel flowing out from the second catalyst 52 are returned to the first catalyst 51 and the second catalyst 52 (circulation means). In this case, in the present embodiment, as the circulation means, a circulation passage 71 is provided that connects the exhaust passage upstream of the exhaust purification device 50 in the exhaust pipe 46 and the exhaust passage downstream, and the exhaust purification device 50 and the exhaust pipe. 46 and switching valves 72 and 73 communicating with the circulation passage 71 are provided, and an electric pump 74 is provided in the circulation passage 71.

  That is, the exhaust pipe 46 is provided with a circulation passage 71 so as to bypass the exhaust purification device 50, and the first switching valve is provided at the upstream side of the exhaust purification device 50 and the upstream end of the circulation passage 71 in the exhaust pipe 46. 72 is provided on the downstream side of the exhaust purification device 50 in the exhaust pipe 46 and the downstream end of the circulation passage 71. An electric pump 74 is provided in the circulation passage 71. Each of the switching valves 72 and 73 and the electric pump 74 can be driven and controlled by the engine ECU 22, and normally the exhaust pipe 46 and the exhaust purification device 50 are opened by the switching valves 72 and 73. By operating the switching valves 72 and 73, the exhaust pipe 46 and the exhaust purification device 50 are shut off, and the exhaust purification device 50 and the circulation passage 71 are communicated with each other, and the electric pump 74 is driven to exhaust the exhaust gas. It can be circulated in a loop passage formed by the purification device 50 and the circulation passage 71.

  Therefore, when it is estimated that a predetermined amount of fuel is injected from the fuel addition valve 61 and the injected fuel reaches the exhaust purification device 50 when the DE 11 is stopped and the hybrid vehicle is driven by EV only by the MG 12 and the MG 13. The switching valves 72 and 73 shut off the exhaust pipe 46 and the exhaust purification device 50, and communicate the exhaust purification device 50 and the circulation passage 71 to form a loop passage. Then, the fuel reaches the first catalyst 51 and the second catalyst 52, and the NOx occluded in each of the catalysts 51 and 52 is released due to a decrease in the oxygen concentration in the exhaust gas due to the oxidation reaction, and the released NOx and The fuel reacts and is reduced, and the exhaust gas is purified.

  In this case, a small amount of unpurified NOx and fuel flow out from the first catalyst 51 and the second catalyst 52, and this outflowed NOx and fuel are circulated by the switching valve 73 downstream of the exhaust purification device 50 in the exhaust pipe 46. Since it communicates with the passage 71, it is not discharged to the outside. Since the switching passages 72 and 73 form a loop passage formed by the exhaust purification device 50 and the circulation passage 71, the electric pump 74 is driven to flow out of the first catalyst 51 and the second catalyst 52. The exhaust gas containing NOx and fuel is returned to the first catalyst 51 and the second catalyst 52 through the circulation passage 71 again. Therefore, the NOx flowing out from the respective catalysts 51 and 52 and the NOx flowing out by the fuel are reliably purified by the first catalyst 51 and the second catalyst 52 while preventing the fuel from flowing out to the outside.

  Similarly to the first embodiment, when the fuel circulates in the exhaust purification device 50 and the circulation passage 71, when the fuel reaching position is not in the exhaust purification device 50, the electric pump 74 is driven at a high speed, When it is in the vicinity of the exhaust purification device 50, the electric pump 74 is driven at a low speed, so that the space velocity at which the fuel moves through the exhaust purification device 50 is reduced, and the NOx reduction processing time is lengthened to improve the processing efficiency. it can. Therefore, the NOx stored in the first catalyst 51 and the second catalyst 52 is reliably purified using the fuel while preventing the NOx and fuel flowing out from the first catalyst 51 and the second catalyst 52 from being discharged to the outside.

  As described above, in the exhaust emission control device in the hybrid vehicle according to the second embodiment, the exhaust emission control device 50 including the first catalyst 51 and the second catalyst 52 that can store and reduce NOx in the exhaust gas in the exhaust pipe 46 is provided. And a fuel addition valve 61 for supplying fuel as a reducing agent to each of the catalysts 51 and 52, and a circulation passage for connecting the upstream exhaust passage and the downstream exhaust passage of the exhaust purification device 50 in the exhaust pipe 46. 71 is provided, the exhaust purification device 50 and the exhaust pipe 46 are shut off, and switching valves 72 and 73 communicating with the circulation passage 71 are provided, and an electric pump 74 is provided in the circulation passage 71.

  Therefore, when the DE 11 stops and a predetermined amount of fuel is injected from the fuel addition valve 61 and reaches the exhaust purification device 50 during EV travel of the hybrid vehicle using only the MG 12 and MG 13, the exhaust pipe 46 is driven by the switching valves 72 and 73. And the exhaust purification device 50 are cut off, and the exhaust purification device 50 and the circulation passage 71 are communicated to form a loop passage to drive the electric pump 74. Then, the fuel reaches the first catalyst 51 and the second catalyst 52, and the NOx occluded in each of the catalysts 51 and 52 is released due to a decrease in the oxygen concentration in the exhaust gas due to the oxidation reaction. At this time, a part of the unpurified NOx and the reducing agent flow out from the catalysts 51 and 52, and the exhausted NOx and the exhaust gas containing the fuel are circulated by the electric pump 74. 71 is returned to each catalyst 51 and 52 again. As a result, the unpurified NOx and fuel that have flowed out of the catalysts 51 and 52 are not discharged to the outside, and the catalyst 51 and 52 are again purified by the fuel that has passed through the unpurified NOx that has flowed out. Further, an auxiliary catalyst for treating the unpurified NOx and the fuel that has passed through is not required on the downstream side of the catalysts 51 and 52, and the reduction efficiency of the stored NOx catalyst can be improved and the exhaust purification efficiency can be improved.

  In each of the above-described embodiments, the fuel addition valve 61 as the reducing agent supply means is provided in the cylinder head and the fuel is injected into the exhaust port 33. However, the mounting position is not limited to this, and the exhaust purification device 50 is not limited thereto. As long as it is an exhaust system on the upstream side. In the case of the second embodiment described above, the first catalyst 51 and the second catalyst 51 are provided by providing the exhaust pipe 46 on the upstream side of the exhaust purification device 50 and the upstream end of the circulation passage 71 at substantially the same position as the first switching valve 72. When regenerating the catalyst 52, by switching the switching valves 71 and 72 and then injecting the fuel as the reducing agent, it is not necessary to estimate the arrival position of the injected fuel, and the purification efficiency can be further improved. .

  In each of the embodiments, the exhaust purification device 50 includes the first catalyst 51 as the NOx storage reduction catalyst and the second catalyst 52 as the NOx storage reduction catalyst having the particulate filter. The catalyst may be an oxidation catalyst.

  As described above, the exhaust emission control device for a hybrid vehicle according to the present invention circulates NOx and the reducing agent flowing out from the NOx storage reduction catalyst again and stores them in the NOx storage reduction catalyst. It is useful when applied to a hybrid vehicle that can run using a motor as a power source.

1 is a schematic configuration diagram of an exhaust emission control device in a hybrid vehicle according to a first embodiment of the present invention. 3 is a flowchart showing NOx reduction processing by the exhaust purification device in the hybrid vehicle of the first embodiment. 1 is a schematic configuration diagram illustrating a hybrid vehicle to which an exhaust emission control device according to a first embodiment is applied. It is a schematic block diagram of the exhaust gas purification apparatus in the hybrid vehicle which concerns on Example 2 of this invention.

Explanation of symbols

11 Diesel engine, DE (internal combustion engine)
12, 13 Motor generator, MG (electric motor)
14 Power distribution mechanism (planetary gear unit)
19 Battery 22 Engine ECU (passing time estimation means)
27 Motor ECU
28 Main ECU
29 Battery ECU
37 Intake pipe (intake passage)
39 Throttle valve 46 Exhaust pipe (exhaust passage)
47 Electric assist turbocharger (circulation means)
50 Exhaust purification device 51 First catalyst (NOx storage reduction catalyst)
52 2nd catalyst (NOx storage reduction catalyst)
54 Low pressure recirculation (EGR) device 58 Low pressure recirculation (EGR) passage (circulation means)
59 Low pressure recirculation (EGR) valve (circulation means)
61 Fuel addition valve (reducing agent supply means)
68 Shutter valve (circulation means)
71 Circulation passage (circulation means)
72, 73 switching valve (circulation means)
74 Electric pump (circulation means)

Claims (4)

  In a hybrid vehicle capable of running using an internal combustion engine and an electric motor as a power source, a storage reduction type NOx catalyst provided in an exhaust passage of the internal combustion engine and capable of storing and reducing NOx in exhaust gas, and the storage reduction type A reducing agent supply means for supplying a reducing agent to the NOx catalyst; and from the NOx storage reduction catalyst when the reducing agent is supplied from the reducing agent supply means to the NOx storage reduction catalyst when the vehicle is driven by the electric motor. An exhaust emission control device for a hybrid vehicle, comprising: circulating means for returning the NOx that has flowed out and the reducing agent that has passed through the NOx storage reduction catalyst to the NOx storage reduction catalyst.   2. The exhaust gas purification apparatus for a hybrid vehicle according to claim 1, wherein the circulation means includes an intake passage and an electrically assisted turbocharger provided in the exhaust passage, and the exhaust passage downstream of the NOx storage reduction catalyst. And an exhaust gas recirculation passage that connects the intake passage upstream of the electrically assisted turbocharger, an exhaust gas recirculation valve provided in the exhaust gas recirculation passage, and the occlusion reduction in the exhaust passage A shutter valve provided on the downstream side of the NOx catalyst, the exhaust gas recirculation passage is opened by the exhaust gas recirculation valve, and the exhaust passage is closed by the shutter valve. By driving the assist turbocharger, NOx and the reducing agent are returned to the NOx storage reduction catalyst. Exhaust purification system in the vehicle.   2. The exhaust gas purification apparatus for a hybrid vehicle according to claim 1, wherein the circulation means is provided in the circulation passage, a circulation passage that connects an upstream exhaust passage and a downstream exhaust passage of the NOx storage reduction catalyst, and the circulation passage. And a switching valve that shuts off the upstream exhaust passage and the downstream exhaust passage of the NOx storage reduction catalyst and communicates the NOx storage reduction catalyst with the circulation passage, Exhaust gas purification in a hybrid vehicle, wherein the exhaust passage is blocked by a switching valve and the electric pump is driven in a state where the circulation passage is communicated to return NOx and a reducing agent to the NOx storage reduction catalyst. apparatus. 4. The exhaust gas purification apparatus for a hybrid vehicle according to claim 2, wherein when the reducing agent is supplied from the reducing agent supply means to the storage-reduction NOx catalyst during vehicle travel by the electric motor, the reducing agent is A passage timing estimating means for estimating the passage time of the NOx storage reduction catalyst is provided, and the electric assist turbocharger or the electric pump is set in advance at a passage time of the reducing agent estimated by the passage timing estimation means; The exhaust gas purification in a hybrid vehicle is characterized in that the electric assist turbocharger or the electric pump is driven at a predetermined high rotational speed at a time other than the passage time while being driven at a low rotational speed. apparatus.

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