JP2005036726A - Exhaust temperature rising device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust temperature rising device of an internal combustion engine capable of rising an exhaust gas temperature while insulating so that an aftertreatment device may not be cooled at idle running stop time even slow running and idle running stop are intermittently repeated due to a traffic congestion, etc. <P>SOLUTION: The exhaust temperature rising device of the internal combustion engine which raises an exhaust temperature if needed so that a temperature which is needed with a particulate filter 12 (aftertreatment device) of catalyst regeneration type on the mid-way of an exhaust tube 11 (exhaust gas channel) can be assured, includes a controller 17 (fuel injection control means) altered into setting which are altered to fuel injection pattern and a raised idle running number of revolutions from a usual idle running number of revolutions in order to perform retarding combustion of the fuel to timing later than a compressing top dead center, when a rise in the exhaust temperature is required. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an exhaust gas temperature raising device for an internal combustion engine.

  Particulate matter (particulate matter) discharged from a diesel engine is mainly composed of soot composed of carbonaceous matter and SOF content (Soluble Organic Fraction) composed of high-boiling hydrocarbon components. Although it has a composition containing a small amount of sulfate (mist-like sulfuric acid component), as a measure to reduce this kind of particulates, a particulate filter is installed in the middle of the exhaust passage through which exhaust gas flows. Has been performed conventionally.

  This type of particulate filter has a porous honeycomb structure made of a ceramic such as cordierite, and the inlets of the flow paths partitioned in a lattice pattern are alternately sealed, and the inlets are not sealed. About the flow path, the exit is sealed, and only the exhaust gas which permeate | transmitted the porous thin wall which divides each flow path is discharged | emitted downstream.

  Then, the particulates in the exhaust gas are collected and deposited on the inner surface of the porous thin wall, so that the particulates are appropriately burned and removed before the exhaust resistance increases due to clogging. It is necessary to regenerate, but in normal diesel engine operating conditions, there are few opportunities to obtain exhaust temperatures that are high enough for the particulates to self-combust. For example, an appropriate amount for alumina loaded with platinum A catalyst regeneration type particulate filter in which an oxidation catalyst formed by adding rare earth elements such as cerium is integrally supported on a particulate filter, or an oxidation catalyst is arranged separately in the previous stage of the particulate filter. Adoption is under consideration.

  That is, if such a catalyst regeneration type particulate filter is employed, the oxidation reaction of the collected particulates is promoted to lower the ignition temperature, and the particulates can be burned and removed even at an exhaust temperature lower than the conventional one. It becomes possible.

  In addition to the particulate filter described above, it has also been proposed to equip the exhaust passage with a NOx selective reduction catalyst or NOx occlusion reduction catalyst for the purpose of removing NOx in the exhaust gas as a post-treatment device. Particularly in recent years, an aftertreatment device in which a particulate filter is combined with a NOx storage reduction catalyst has been developed.

However, even if any of these after-treatment devices is adopted, a relatively high exhaust temperature higher than a predetermined temperature is required in order to obtain reliable combustion removal of particulates and sufficient catalytic activity. If the low temperature operation state (generally, the region where the exhaust temperature is low extends to the light load operation region) continues, there is a problem that the aftertreatment device cannot function sufficiently. It has been proposed that the exhaust gas temperature is positively increased by fuel injection control or intake throttle as appropriate in a low operating state (see, for example, Patent Document 1).
JP 2003-83139 A

  However, especially in the case of vehicles that travel only on congested roads such as city buses in Tokyo, slow driving and idling stop are repeated intermittently, so idling stops when the accelerator is off. During this time, the exhaust gas temperature and flow rate drastically decrease, causing the post-processing device to cool down, and the post-processing device is required no matter how much fuel injection control or intake air temperature control is performed during the next slow speed restart. There was a problem that the temperature could not be raised.

  The present invention has been made in view of the above-mentioned circumstances, and even when slow running and idling stop are repeated intermittently due to traffic jams or the like, exhaust is performed while keeping the post-processing device warm so as not to cool down when idling stops. An object of the present invention is to provide an exhaust gas temperature raising device for an internal combustion engine that can increase the temperature of gas.

  The present invention relates to an exhaust temperature raising device for an internal combustion engine that raises an exhaust temperature as necessary so as to ensure a temperature required for a post-treatment device in the middle of an exhaust passage, and when the exhaust temperature needs to be raised. A fuel injection control means is provided for changing the fuel injection pattern so that fuel is delayed burned at a timing later than the compression top dead center and changing the idling speed to a setting higher than the normal idling speed. It is.

  Thus, even in an operation state where the exhaust temperature is low, such as during a light load operation of the internal combustion engine, the fuel injection pattern is appropriately changed by the fuel injection control means, and the fuel is delayed burned at a timing later than the compression top dead center. By doing so, the delayed combustion amount is burned at a timing when it is difficult to convert it to output, thereby reducing the thermal efficiency of the internal combustion engine, increasing the amount of heat not used for power in the heat generation amount of the fuel and raising the exhaust temperature. .

  On the other hand, even if idling is present while the temperature of the exhaust gas is raised in this way, the idling speed is changed to a higher setting than usual by the fuel injection control means, so that the aftertreatment device is circulated. When the temperature and flow rate of the exhaust gas is raised to a predetermined level and the aftertreatment device is kept warm so as not to cool down, and then the non-idling operation is resumed, the aftertreatment device is caused by the rise in exhaust temperature due to delayed combustion. The temperature is easily raised to the required level.

  Further, in the present invention, an intake throttle means for appropriately reducing the intake flow rate may be provided. If the intake flow rate is reduced by the intake throttle means when the exhaust temperature needs to be raised, the amount of working air in the cylinder is reduced. As the pumping loss increases, the driver further depresses the accelerator to compensate for the torque drop due to the increased pumping loss, the exhaust temperature rises due to the increase in the fuel injection amount, and the intake flow rate is reduced, so that the inside of the cylinder The amount of exhaust gas generated during combustion decreases, the flow rate of exhaust gas flowing through the aftertreatment device decreases, and the exhaust gas temperature rises even when the heat capacity of the exhaust gas decreases.

  Further, in the present invention, an exhaust throttle means for appropriately reducing the exhaust flow rate may be provided. If the exhaust flow rate is reduced by the exhaust throttle means when the exhaust gas temperature needs to be raised, the exhaust gas upstream of the exhaust throttle means. As the exhaust gas pressure is raised, the exhaust temperature rises, and the exhaust resistance of the internal combustion engine increases, making it difficult for intake air having a relatively low temperature to flow into the cylinder, resulting in a residual amount of exhaust gas having a relatively high temperature. The exhaust temperature is further increased by increasing the air in the cylinder containing a large amount of the exhaust gas having a relatively high temperature and compressing it in the next compression stroke to reach the explosion stroke.

  Here, it is possible to employ a variable geometry turbocharger as the exhaust throttle means. By doing this, the opening of each nozzle vane on the turbine side is narrowed down to reduce the channel cross-sectional area. The exhaust flow rate is narrowed down, the same effect as described above is generated, the exhaust temperature is raised, and the exhaust resistance is increased to increase the friction equivalent to the exhaust brake and to compensate for the torque decrease due to this. The exhaust gas temperature can be further increased by increasing the fuel injection amount by further depressing the accelerator by the driver.

  Further, when the variable geometry turbocharger is used in this way, a bypass flow path that guides a part of the exhaust gas discharged from the internal combustion engine to the outlet side of the turbine by bypassing the turbine of the variable geometry turbocharger. And an opening / closing valve that opens and closes the bypass channel appropriately.

  That is, if the opening of each nozzle vane on the turbine side is narrowed down to reduce the cross-sectional area of the passage, and the bypass passage is opened by opening the on-off valve as appropriate, the exhaust gas from the internal combustion engine is converted into the turbine. As a result, the temperature of the exhaust gas led without performing work in the turbine is maintained higher than usual, and the exhaust gas bypasses the turbine. As a result, the turbine drive force is reduced, which reduces the efficiency of the turbocharger and increases the intake resistance on the compressor side. The temperature of the exhaust gas can be increased.

  According to the exhaust temperature raising apparatus for an internal combustion engine of the present invention described above, various excellent effects as described below can be obtained.

  (I) According to the first aspect of the present invention, even when the internal combustion engine is in an operation state where the exhaust temperature is low, such as during light load operation, the fuel is delayed by the fuel injection control means so that the internal combustion engine It is possible to raise the exhaust temperature by lowering the heat efficiency of the fuel and increasing the amount of heat that is not used for motive power of the fuel, and idling is intervening while raising the temperature of the exhaust gas in this way However, the idling speed can be increased more than usual by the fuel injection control means, and the temperature and flow rate of the exhaust gas flowing through the aftertreatment device can be raised to a predetermined level to keep the aftertreatment device cool. Even in an operation state where the light load operation and idling are repeated intermittently, the temperature of the exhaust gas can be raised efficiently while keeping the temperature of the aftertreatment device not to cool during idling. The temperature required in the post-processing apparatus can Rukoto can be reliably ensured.

  (II) According to the invention described in claim 2 of the present invention, the pumping loss can be increased by reducing the amount of working air in the cylinder by narrowing the intake air flow rate by the intake throttle means, and this decreases. The exhaust gas temperature can be increased by increasing the fuel injection amount to compensate for the torque, and the exhaust gas temperature can also be reduced by suppressing the amount of exhaust gas generated in the in-cylinder combustion and reducing the heat capacity of the exhaust gas. Further rise can be realized.

  (III) According to the invention described in claim 3 of the present invention, the exhaust gas flow rate can be reduced by the exhaust throttle means to increase the exhaust gas upstream of the exhaust throttle means to increase the exhaust temperature, In addition, since the exhaust resistance of the internal combustion engine increases, intake of relatively low temperature does not easily flow into the cylinder, and the residual amount of exhaust gas with relatively high temperature increases. The exhaust temperature can be further increased by compressing the air in the cylinder including the cylinder in the next compression stroke to reach the explosion stroke.

  (IV) According to the invention described in claim 4 of the present invention, the exhaust flow rate can be narrowed down by narrowing the opening of each nozzle vane on the turbine side of the variable geometry turbocharger to reduce the cross-sectional area of the passage. As a result, the same operational effects as in (III) can be obtained, and the exhaust resistance can be increased to increase the friction in the same manner as the exhaust brake, so that fuel injection can be made up to compensate for the reduced torque. The exhaust gas temperature can be further increased by increasing the amount.

  (V) According to the invention described in claim 5 of the present invention, the opening of each nozzle vane on the turbine side is narrowed down to reduce the cross-sectional area of the flow path, and then the on-off valve is appropriately opened to open the bypass flow path. By opening the engine, exhaust gas from the internal combustion engine can be sent out at a high pressure by bypassing the turbine, so that the temperature of the exhaust gas introduced without performing work in the turbine can be maintained higher than usual. In addition, the efficiency of the turbocharger can be reduced, the intake resistance on the compressor side can be increased, and the intake throttle action can also be obtained at the same time. Can do.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIGS. 1 and 2 show an example of an embodiment of the present invention. In FIG. 1, reference numeral 1 in FIG. 1 denotes a vehicle diesel engine equipped with a variable geometry turbocharger as a turbocharger 2, which is led from an air cleaner 3. The intake air 4 is sent to the compressor 2 a of the turbocharger 2 through the intake pipe 5, and the intake air 4 pressurized by the compressor 2 a is sent to the intercooler 6 to be cooled, and further from the intercooler 6 to the intake manifold The intake air 4 is guided to 7 and distributed to each cylinder 8 of the diesel engine 1 (the case of in-line 6 cylinders is illustrated in FIG. 1).

  Further, the exhaust gas 9 discharged from each cylinder 8 of the diesel engine 1 is sent to the turbine 2b of the turbocharger 2 through the exhaust manifold 10, and the exhaust gas 9 that has driven the turbine 2b is discharged to the exhaust pipe 11 (exhaust gas). It is discharged to the outside of the vehicle through the flow path).

  Further, in the middle of the exhaust pipe 11, a catalyst regeneration type particulate filter 12 integrally supporting an oxidation catalyst is provided as a post-processing device. As shown in an enlarged view in FIG. The curate filter 12 has a porous honeycomb structure made of ceramic, and the inlets of the respective flow paths 12a partitioned in a lattice pattern are alternately sealed, and the flow paths 12a that are not sealed are as follows. The outlet is sealed, and only the exhaust gas 9 that has permeated through the porous thin wall 12b partitioning each flow path 12a is discharged downstream.

  Further, in the example shown in FIG. 1, an EGR pipe 13 connects between one end portion of the exhaust manifold 10 in the arrangement direction of the cylinders 8 and one end portion of the intake pipe 5 connected to the intake manifold 7. A part of the exhaust gas 9 extracted from the exhaust manifold 10 is recirculated to the intake pipe 5 through the water-cooled EGR cooler 14 and the EGR valve 15 and recirculated from the exhaust side to the intake side. The generation of NOx can be reduced by suppressing the combustion of fuel in each cylinder 8 by the exhaust gas 9 and lowering the combustion temperature.

  A temperature sensor 16 for measuring the temperature of the exhaust gas 9 is provided on the outlet side of the particulate filter 12, and a detection signal 16a of the temperature sensor 16 forms an engine control computer (ECU: Electronic Control Unit). On the other hand, in this control device 17 (fuel injection control means), fuel is injected toward a fuel injection device 18 that injects fuel into each cylinder 8 of the diesel engine 1. A fuel injection signal 18a for commanding the timing and the injection amount is output.

  Here, the fuel injection device 18 is composed of a plurality of injectors (not shown) provided for each cylinder 8, and the electromagnetic valves of these injectors are appropriately controlled to open by the fuel injection signal 18a. The injection timing (injection start timing) and the injection amount (valve opening time) are appropriately controlled.

  Further, the accelerator of the driver's seat (not shown) is provided with an accelerator sensor 19 (load sensor) for detecting the accelerator opening as a load of the diesel engine 1, and the rotational speed is set at an appropriate position of the diesel engine 1. A rotation sensor 20 for detection is provided, and an accelerator opening signal 19a and a rotation speed signal 20a from the accelerator sensor 19 and the rotation sensor 20 are also input to the control device 17.

  Further, in the control device 17, opening command signals 21a, 15a for commanding the opening degree to the intake throttle valve 21 provided in the intake pipe 5 downstream of the intercooler 6 and the EGR valve 15 of the EGR pipe 13 respectively. Is output.

  Here, the intake throttle valve 21 may be functionally used as an intake shutter used together with an idling stop device, a noise suppressor used together with an auxiliary brake, or the like. In this embodiment, such an intake throttle valve is used. By instructing the valve 21 and the EGR valve 15 to perform another operation independent of the original operation, the valve 21 and the EGR valve 15 are used as intake throttle means for raising the exhaust temperature as will be described later.

  And in the said control apparatus 17, while the fuel injection signal 18a of normal mode is determined based on the accelerator opening signal 19a and the rotation speed signal 20a, when it becomes necessary to raise exhaust gas temperature, The normal mode is switched to the exhaust gas temperature raising mode, and the fuel injection signal 18a is determined so that the fuel is delayed and burned at a timing later than the compression top dead center (crank angle 0 °).

  In other words, the fuel injection is performed near the compression top dead center, and then the injection control is performed such that the post injection is performed at a timing at which ignition is possible later than the compression top dead center. The temperature mode is used during light load operation where the exhaust temperature is low, such as when slowing down a congested road, and does not require a large output, so the injection amount in the main injection is kept to a light level. Thus, the injection pattern is mainly post-injection (an injection pattern in which main injection itself is delayed from the compression top dead center is also possible).

  However, since it becomes difficult to connect stable combustion to the post-injection because the injection amount in the main injection becomes small, it is preferable to employ a three-stage injection in which a pilot injection is added prior to the main injection.

  Moreover, in the control device 17, when the exhaust gas temperature raising mode is adopted, the idling speed is changed to a setting higher than the normal idling speed. More specifically, The injection amount per one time read from the injection amount map at idling is increased.

  When the exhaust temperature raising mode is executed by the control device 17, the intake throttle valve 21 of the intake pipe 5 and the EGR valve 15 of the EGR pipe 13 are used as temperature raising means for raising the exhaust temperature. More specifically, the intake throttle valve 21 and the EGR valve 15 are throttled by the opening command signals 21a and 15a in the exhaust gas temperature raising mode.

  Further, the turbocharger 2 composed of the variable geometry turbocharger employed in this embodiment, as is conventionally known, tilts the nozzle vane on the turbine 2b side by the actuator 22 to open each nozzle pane. However, when the control device 17 enters the exhaust gas temperature raising mode, an opening degree command signal 22a for reducing the opening degree of each nozzle pane to the actuator 22 is output. The turbocharger 2 is utilized as an exhaust throttle means for raising the exhaust temperature as will be described later.

  Furthermore, in the example shown here, a bypass flow path 23 is provided that guides part of the exhaust gas 9 discharged from the diesel engine 1 to the outlet side of the turbine 2b by bypassing the turbine 2b of the turbocharger 2. In the middle of the bypass flow path 23, an open / close valve 24 that can be opened and closed is provided. When the control device 17 enters the exhaust gas temperature raising mode, the valve opening command signal is sent to the open / close valve 24. 24a is output, and the turbocharger 2 composed of this variable geometry turbocharger is utilized as a temperature raising means for raising the exhaust temperature as described later.

  Note that switching from the normal mode to the exhaust temperature raising mode in the control device 17 described above is based on the accelerator opening signal 19a and the rotation speed signal 20a from the accelerator sensor 19 and the rotation sensor 20, and the current operation state is low in the exhaust temperature. It may be performed when it is determined that the vehicle is in the light load operation region and the current exhaust gas temperature is below the required temperature by the particulate filter 12 based on the detection signal 16a of the temperature sensor 16. However, instead of executing the mode switching every time under this condition, the collection state of the particulate filter 12 is judged from the differential pressure before and after, or the amount of collection is estimated from the past operation state. What is necessary is just to perform mode switching in the stage estimated that the collection amount of the curate filter 12 has increased.

  Thus, for example, even during light load operation where the exhaust temperature is low, such as when traveling slowly on a congested road and repeating idling stops, the control device 17 normally The mode is switched from the mode to the exhaust gas temperature raising mode, the fuel injection pattern is changed appropriately, and the fuel from the post injection is delayed burned at a timing later than the compression top dead center, so that the delayed combustion amount is not easily converted to the output. By burning at the timing, the thermal efficiency of the diesel engine 1 decreases, and the amount of heat not used for power in the calorific value of the fuel increases, and the exhaust temperature rises.

  On the other hand, even if idling stops while the temperature of the exhaust gas 9 is raised in this way, the idling speed is changed to a higher setting than usual by the control device 17, so the particulate filter 12 is When the temperature and flow rate of the flowing exhaust gas 9 are raised to a predetermined level and the particulate filter 12 is kept warm so that it does not cool down, and then the slow drive is restarted, the exhaust gas temperature rises due to delayed combustion. The temperature of the curate filter 12 is easily raised to a necessary level.

  Further, in the present embodiment, when the control device 17 is switched from the normal mode to the exhaust gas temperature raising mode, the intake throttle valve 21 and the EGR valve 15 are throttled by the opening command signals 21a and 15a from the control device 17. Therefore, the working gas amount in the cylinder 8 decreases and the pumping loss increases, and the accelerator is further depressed by the driver to compensate for the torque decrease due to the increase in pumping loss, and the exhaust temperature increases due to the increase in the fuel injection amount. In addition, since the intake flow rate is reduced, the amount of exhaust gas 9 generated by combustion in the cylinder 8 is reduced, the flow rate of the exhaust gas 9 flowing through the particulate filter 12 is reduced, and the heat capacity of the exhaust gas 9 is increased. Lowering the exhaust temperature also increases.

  The controller 17 also outputs an opening command signal 22a to the actuator 22 of the turbocharger 2 to narrow down the opening of each nozzle pane of the turbine 2b. Is reduced, the exhaust flow rate is narrowed, and the upstream exhaust gas 9 is boosted to increase the exhaust temperature, and the exhaust resistance of the diesel engine 1 is increased, so that the temperature in the cylinder 8 is relatively low. It becomes difficult for the intake air 4 to flow in and the residual amount of the exhaust gas 9 having a relatively high temperature increases, and the air in the cylinder 8 containing a large amount of the exhaust gas 9 having a relatively high temperature is compressed in the next compression stroke and exploded. The exhaust temperature can be further increased by reaching the stroke, and the friction increases as the exhaust resistance increases, resulting in a decrease in torque. Accelerator by the driver will be further depressed is also increased further exhaust temperature by the fuel injection amount is increased is achieved in order to compensate.

  Further, in the exhaust gas temperature raising mode, as described above, the opening of each nozzle vane on the turbine 2b side is narrowed down to reduce the cross-sectional area of the flow path, and the open / close valve is operated by the valve opening command signal 24a from the control device 17. 24 is opened and the bypass passage 23 is opened, so that the exhaust gas 9 from the diesel engine 1 bypasses the turbine 2b and is sent out at a high pressure, and is exhausted without performing work in the turbine 2b. As a result, the temperature of the gas 9 is maintained higher than usual, and the exhaust gas 9 flows around the turbine 2b to reduce the turbine driving force, thereby reducing the efficiency of the turbocharger 2. As the intake resistance on the compressor 2a side increases, the intake throttle action can be obtained at the same time. Noboru Yutakaka gas 9 can be achieved.

  Therefore, according to the above embodiment, even when the diesel engine 1 is in an operation state where the exhaust temperature is low, the fuel is delayed by the control device 17 to reduce the thermal efficiency of the diesel engine 1. The amount of heat that is not used for power in the generated heat can be increased to raise the exhaust gas temperature, and even if idling is interposed while the temperature of the exhaust gas 9 is being raised in this way, the control device 17 As a result, the idling speed can be increased more than usual, and the temperature and flow rate of the exhaust gas 9 flowing through the particulate filter 12 can be raised to a predetermined level to keep the particulate filter 12 cool. Even when the engine is idling, the particulate filter during idling The temperature required 2 is efficiently raising Yutakaka exhaust gas 9 can be achieved with thermal insulation to avoid cold in the particulate filter 12 side can be reliably secured.

  In particular, in the present embodiment, the intake throttle valve 21 and the EGR valve 15 are used to throttle the intake flow rate and the recirculation gas amount, or the opening amount of each nozzle vane on the turbine 2b side of the turbocharger 2 is reduced to reduce the exhaust flow rate. Or by exhausting the exhaust gas 9 from the diesel engine 1 while bypassing the turbine 2b at a high pressure, it is possible to achieve an extremely effective increase in exhaust temperature in the exhaust gas temperature raising mode as described above. .

  The exhaust gas temperature raising device for an internal combustion engine according to the present invention is not limited to the above-described embodiment. In addition to the catalyst regeneration type particulate filter, the post-treatment device can remove NOx in the exhaust gas. The intended NOx selective reduction catalyst, NOx occlusion reduction catalyst, etc. may be adopted, the fuel injection control means may be configured independently of the engine control computer, and the variable throttle geometry is used for the exhaust throttle means. Of course, it is possible to employ an exhaust brake, an exhaust throttle valve, or the like in addition to the turbocharger, and other various modifications can be made without departing from the scope of the present invention.

It is the schematic which shows an example of the form which implements this invention. It is sectional drawing which shows the detail of the particulate filter of FIG.

Explanation of symbols

1 Diesel engine (internal combustion engine)
2 Turbocharger (Variable geometry turbocharger: Exhaust throttle means)
2a Compressor 2b Turbine 4 Intake 5 Intake pipe 8 Cylinder 9 Exhaust gas 11 Exhaust pipe (exhaust flow path)
12 Particulate filter (post-processing device)
17 Control device (fuel injection control means)
18 Fuel Injection Device 18a Fuel Injection Signal 21 Intake Throttle Valve (Intake Throttle Means)
21a Opening command signal 22 Actuator 22a Opening command signal 23 Bypass passage 24 Open / close valve 24a Opening command signal

Claims (5)

  An exhaust temperature raising device for an internal combustion engine that raises the exhaust temperature as needed to ensure the temperature required by the aftertreatment device in the middle of the exhaust flow path, and compresses the fuel when the exhaust temperature needs to be raised. A fuel injection control means is provided for changing the fuel injection pattern so as to cause delayed combustion at a timing later than the dead center and changing the idling speed to a setting higher than the normal idling speed. Temperature device.   2. The exhaust gas temperature raising device for an internal combustion engine according to claim 1, further comprising an intake throttle means for appropriately reducing an intake flow rate.   The exhaust temperature raising device for an internal combustion engine according to claim 1, further comprising exhaust throttle means for appropriately reducing an exhaust flow rate.   4. The exhaust gas temperature raising device for an internal combustion engine according to claim 3, further comprising a variable geometry turbocharger as the exhaust throttle means.   Provided with a bypass passage for bypassing a part of the exhaust gas discharged from the internal combustion engine to the outlet of the turbine by bypassing the turbine of the variable geometry turbocharger, and an opening / closing valve for opening and closing the bypass passage appropriately The exhaust gas temperature raising device for an internal combustion engine according to claim 4, wherein

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